Advent Technologies (ADN) 10-Q 15 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 15, 2021
Entity Listings [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Document Transition Report	false
Entity File Number	001-38742
Entity Registrant Name	Advent Technologies Holdings, Inc.
Entity Central Index Key	0001744494
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-0982969
Entity Address, Address Line One	200 Clarendon Street
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02116
City Area Code	617
Local Phone Number	655-6000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		51,253,591
Common Stock [Member]
Entity Listings [Line Items]
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	ADN
Security Exchange Name	NASDAQ
Warrants [Member]
Entity Listings [Line Items]
Title of 12(b) Security	Warrants
Trading Symbol	ADNWW
Security Exchange Name	NASDAQ

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 92,492,367	$ 515,734
Accounts receivable	5,569,801	421,059
Due from related parties	0	67,781
Contract assets	936,259	85,930
Inventories	5,598,574	107,939
Prepaid expenses and Other current assets	3,767,096	496,745
Total current assets	108,364,097	1,695,188
Non-current assets:
Goodwill and intangibles, net	54,281,798	0
Property and equipment, net	7,883,042	198,737
Other non-current assets	2,155,156	136
Deferred tax assets	1,279,969	0
Total non-current assets	65,599,965	198,873
Total assets	173,964,062	1,894,061
Current liabilities:
Trade and other payables	5,522,624	881,394
Due to related parties	30,000	1,114,659
Deferred income from grants, current	1,098,019	158,819
Contract liabilities	28,832	167,761
Other current liabilities	7,595,619	904,379
Income tax payable	1,135,199	201,780
Total current liabilities	15,410,293	3,428,792
Non-current liabilities:
Warrant liability	17,282,987	0
Deferred tax liabilities	3,756,859	0
Deferred income from grants, non-current	171,995	182,273
Other long-term liabilities	1,209,336	76,469
Total non-current liabilities	22,421,177	258,742
Total liabilities	37,831,470	3,687,534
Commitments and contingent liabilities
Stockholders' equity / (deficit)
Common stock ($0.0001 par value per share; Shares authorized: 110,000,000 at September 30, 2021 and December 31, 2020; Issued and outstanding: 51,253,591 and 25,033,398 at September 30, 2021 and December 31, 2020, respectively)	5,125	2,503
Preferred stock ($0.0001 par value per share; Shares authorized: 1,000,000 at September 30, 2021 and December 31, 2020; nil issued and outstanding at September 30, 2021 and December 31, 2020	0	0
Additional paid-in capital	161,263,673	10,993,762
Accumulated other comprehensive (loss) / income	(717,328)	111,780
Accumulated deficit	(24,418,878)	(12,901,518)
Total stockholders' equity / (deficit)	136,132,592	(1,793,473)
Total liabilities and stockholders' equity / (deficit)	$ 173,964,062	$ 1,894,061

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Stockholders' equity / (deficit)
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	110,000,000	110,000,000
Common stock, shares issued (in shares)	51,253,591	25,033,398
Common stock, shares outstanding (in shares)	51,253,591	25,033,398
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Revenue, net	$ 1,673,998	$ 225,412	$ 4,166,754	$ 526,032
Cost of revenues	(1,645,781)	(90,477)	(2,662,476)	(374,430)
Gross profit	28,217	134,934	1,504,278	151,602
Income from grants	507,606	16,076	631,787	159,182
Research and development expenses	(893,215)	(37,640)	(1,561,049)	(81,273)
Administrative and selling expenses	(13,040,649)	(886,629)	(27,558,242)	(1,641,063)
Amortization of intangibles	(309,734)	0	(467,447)	0
Operating loss	(13,707,773)	(773,258)	(27,450,673)	(1,411,552)
Finance costs	(13,542)	(1,712)	(26,961)	(4,749)
Fair value change of warrant liability	2,421,874	0	15,833,334	0
Foreign exchange differences, net	(15,256)	(8,005)	(2,141)	(26,584)
Other (expenses) / income, net	(15,960)	31,058	78,146	24,848
Loss before income tax	(11,330,657)	(751,917)	(11,568,295)	(1,418,037)
Income tax	50,935	3,101	50,935	0
Net loss	$ (11,279,722)	$ (748,816)	$ (11,517,360)	$ (1,418,037)
Net loss per share
Basic loss per share (in dollars per share)	$ (0.23)	$ (0.03)	$ (0.26)	$ (0.07)
Basic weighted average number of shares (in shares)	48,325,164	23,182,817	43,982,039	21,180,639
Diluted loss per share (in dollars per share)	$ (0.23)	$ (0.03)	$ (0.26)	$ (0.07)
Diluted weighted average number of shares (in shares)	48,325,164	23,182,817	43,982,039	21,180,639

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME / (LOSS) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME / (LOSS) [Abstract]
Net loss	$ (11,279,722)	$ (748,816)	$ (11,517,360)	$ (1,418,037)
Other comprehensive income / (loss), net of tax effect:
Foreign currency translation adjustment	(540,871)	(2,042)	(829,108)	(13,544)
Total other comprehensive loss	(540,871)	(2,042)	(829,108)	(13,544)
Comprehensive loss	$ (11,820,594)	$ (750,858)	$ (12,346,468)	$ (1,431,581)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY / (DEFICIT) - USD ($)		Preferred Stock [Member]Series A [Member]	Preferred Stock [Member]Series Seed [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated OCI [Member]	Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 315	$ 2,108	$ 888	$ 8,811,647	$ (9,767,619)	$ 118,859	$ (833,802)
Beginning balance (in shares)		314,505	2,108,405	888,184
Retroactive application of recapitalization		$ (315)	$ (2,108)	$ 503	1,920	0	0	0
Retroactive application of recapitalization (in shares)		(314,505)	(2,108,405)	13,026,925
Adjusted balance, beginning of period at Dec. 31, 2019		$ 0	$ 0	$ 1,392	8,813,567	(9,767,619)	118,859	(833,802)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of preferred stock	[1]	$ 0	$ 0	$ 223	1,429,782	0	0	1,430,005
Issuance of preferred stock (in shares)	[1]	0	0	2,225,396
Issuance of non-vested stock awards	[1]	$ 0	$ 0	$ 914	20,822	0	0	21,736
Issuance of non-vested stock awards (in shares)	[1]	0	0	9,135,138
Repurchase of shares	[1]	$ 0	$ 0	$ (24)	(139,910)	(12,857)	0	(152,792)
Repurchase of shares (in shares)	[1]	0	0	(242,245)
Recognition of stock grant plan		$ 0	$ 0	$ 0	413,396	0	0	413,396
Net loss		0	0	0	0	(1,418,037)	0	(1,418,037)
Other comprehensive loss		0		0	0	0	(13,544)	(13,544)
Ending balance at Sep. 30, 2020		$ 0	$ 0	$ 2,503	10,537,657	(11,198,513)	105,315	(553,039)
Ending balance (in shares) at Sep. 30, 2020		0	0	25,033,398
Adjusted balance, beginning of period (in shares) at Dec. 31, 2019		0	0	13,915,109
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 0	$ 0	$ 2,133	10,314,200	(10,436,840)	107,357	(13,150)
Beginning balance (in shares)		0	0	21,332,235
Issuance of non-vested stock awards	[1]	$ 0	$ 0	$ 376	8,559	0	0	8,935
Issuance of non-vested stock awards (in shares)	[1]	0	0	3,755,010
Repurchase of shares	[1]	$ 0	$ 0	$ (5)	(21,730)	(12,857)	0	(34,593)
Repurchase of shares (in shares)	[1]	0	0	(53,848)
Recognition of stock grant plan		$ 0	$ 0	$ 0	236,628	0	0	236,628
Net loss		0	0	0	0	(748,816)	0	(748,816)
Other comprehensive loss		0	0	0	0	0	(2,042)	(2,042)
Ending balance at Sep. 30, 2020		$ 0	$ 0	$ 2,503	10,537,657	(11,198,513)	105,315	(553,039)
Ending balance (in shares) at Sep. 30, 2020		0	0	25,033,398
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 845	$ 2,096	$ 3,017	10,990,307	(12,901,518)	111,780	(1,793,473)
Beginning balance (in shares)		844,037	2,095,592	3,017,057
Retroactive application of recapitalization		$ (845)	$ (2,096)	$ (514)	3,455	0	0	0
Retroactive application of recapitalization (in shares)		(844,037)	(2,095,592)	22,016,341
Adjusted balance, beginning of period at Dec. 31, 2020		$ 0	$ 0	$ 2,503	10,993,762	(12,901,518)	111,780	(1,793,473)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Business combination and PIPE financing		$ 0	$ 0	$ 2,107	108,005,876	0	0	108,007,984
Business combination and PIPE financing (in shares)		0	0	21,072,549
Share capital increase from warrants exercise		$ 0	$ 0	$ 2	262,175	0	0	262,177
Share capital increase from warrants exercise (in shares)		0	0	22,798
Share capital increase		$ 0	$ 0	$ 512	37,923,348	0	0	37,923,860
Share capital increase (in shares)		0	0	5,124,846
Stock based compensation expense		$ 0	$ 0	$ 0	4,078,513	0	0	4,078,513
Net loss		0	0	0	0	(11,517,360)	0	(11,517,360)
Other comprehensive loss		0		0	0	0	(829,108)	(829,108)
Ending balance at Sep. 30, 2021		$ 0	$ 0	$ 5,125	161,263,673	(24,418,878)	(717,328)	136,132,592
Ending balance (in shares) at Sep. 30, 2021		0	0	51,253,591
Adjusted balance, beginning of period (in shares) at Dec. 31, 2020		0	0	25,033,398
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 0	$ 0	$ 4,613	119,964,708	(13,139,155)	(176,457)	106,653,709
Beginning balance (in shares)		0	0	46,128,745
Share capital increase		$ 0	$ 0	$ 512	37,923,348	0	0	37,923,860
Share capital increase (in shares)		0	0	5,124,846
Stock based compensation expense		$ 0	$ 0	$ 0	3,375,616	0	0	3,375,616
Net loss		0	0	0	0	(11,279,722)	0	(11,279,722)
Other comprehensive loss		0	0	0	0	0	(540,871)	(540,871)
Ending balance at Sep. 30, 2021		$ 0	$ 0	$ 5,125	$ 161,263,673	$ (24,418,878)	$ (717,328)	$ 136,132,592
Ending balance (in shares) at Sep. 30, 2021		0	0	51,253,591
[1]	The amounts have been retroactively restated to give effect to the recapitalization transaction.

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS [Abstract]
Net Cash used in Operating Activities	$ (24,690,329)	$ (1,045,004)
Cash Flows from Investing Activities:
Purchases of property and equipment	(2,658,584)	(89,123)
Advances for the acquisition of property and equipment	(1,917,856)	0
Acquisition of subsidiaries, net of cash acquired	(19,425,378)	0
Net Cash used in Investing Activities	(24,001,818)	(89,123)
Cash Flows from Financing Activities:
Business Combination and PIPE financing, net of issuance costs paid	141,120,851	0
Proceeds of issuance of preferred stock	0	1,430,005
Proceeds from issuance of non-vested stock awards	0	21,736
Repurchase of shares	0	(69,430)
Proceeds of issuance of common stock and paid-in capital from warrants exercise	262,177	0
State loan proceeds	113,377	0
Repayment of convertible promissory notes	0	(500,000)
Net Cash provided by Financing Activities	141,496,405	882,311
Net increase / (decrease) in cash and cash equivalents	92,804,258	(251,815)
Effect of exchange rate changes on cash and cash equivalents	(827,624)	(17,918)
Cash and cash equivalents at the beginning of the period	515,734	1,199,015
Cash and cash equivalents at the end of the period	92,492,367	929,283
Non-cash Operating Activities:
Recognition of stock grant plan	$ 4,078,513	$ 413,396

Basis of presentation

Basis of presentation	9 Months Ended
	Sep. 30, 2021
Basis of presentation [Abstract]
Basis of presentation	1. Basis of presentation (a) Overview On February 4, 2021 (“Closing Date”), AMCI Acquisition Corp. (“AMCI”), consummated the previously announced business combination (the “Business Combination”) pursuant to that certain merger agreement (the “Agreement and Plan of Merger”), dated October 12, 2020, by and among AMCI, AMCI Merger Sub Corp., a Delaware corporation and newly formed wholly-owned subsidiary of AMCI (“Merger Sub”), AMCI Sponsor LLC (the “Sponsor”), solely in the capacity as the representative from and after the effective time of the Business Combination for the stockholders of AMCI (the “Purchaser Representative”), Advent Technologies, Inc., a Delaware corporation (“Legacy Advent”), and Vassilios Gregoriou, solely in his capacity as the representative from and after the effective time for the Legacy Advent stockholders (the “Seller Representative”), as amended by Amendment No. 1 and Amendment No. 2 to the Agreement and Plan of Merger, dated as of October 19, 2020 and December 31, 2020, respectively, by and among AMCI, Merger Sub, Sponsor, Legacy Advent, and Seller Representative. In connection with the closing of the Business Combination (the “Closing”), AMCI acquired 100% of the stock of Legacy Advent (as it existed immediately prior to the Closing) and its subsidiaries. On the Closing Date, and in connection with the closing of the Business Combination, AMCI changed its name to Advent Technologies Holdings, Inc. (the "Company" or "Advent"). Legacy Advent was deemed the accounting acquirer in the Business Combination based on an analysis of the criteria outlined in Accounting Standards Codification ("ASC") 805. This determination was primarily based on Legacy Advent's stockholders prior to the Business Combination having a majority of the voting interests in the combined company, Legacy Advent's operations comprising the ongoing operations of the combined company, Legacy Advent's board of directors comprising a majority of the board of directors of the combined company, and Legacy Advent's senior management comprising the senior management of the combined company. Accordingly, for accounting purposes, the Business Combination was treated as the equivalent of Legacy Advent issuing stock for the net assets of AMCI, accompanied by a recapitalization. The net assets of AMCI are stated at historical cost, with no goodwill or other intangible assets recorded. While AMCI was the legal acquirer in the Business Combination, because Legacy Advent was deemed the accounting acquirer, the historical financial statements of Legacy Advent became the historical financial statements of the combined company, upon the consummation of the Business Combination. As a result, the unaudited condensed consolidated financial statements included in this report reflect (i) the historical operating results of Legacy Advent prior to the Business Combination; (ii) the results of the Company (combined results of AMCI and Legacy Advent) following the closing of the Business Combination; (iii) the assets and liabilities of Legacy Advent at their historical cost; and (iv) Company’s equity structure for all periods presented. In accordance with guidance applicable to these circumstances, the equity structure has been restated in all comparative periods up to the Closing Date, to reflect the number of shares of the Company's common stock, $0.0001 par value per share ("Common Stock") issued to Legacy Advent's stockholders in connection with the recapitalization transaction. As such, the shares and corresponding capital amounts and earnings per share related to Legacy Advent Preferred Stock (“Preferred Series A” and “Preferred Series Seed”) and Legacy Advent common stock prior to the Business Combination have been retroactively restated as shares reflecting the exchange ratio established in the Business Combination Agreement. Activity within the statement of changes in stockholders' equity / (deficit) for the issuances of Legacy Advent's Preferred Stock, were also retroactively converted to Legacy Advent common stock. (Note 3). On February 18, 2021, the Company, entered into a Membership Interest Purchase Agreement with Bren-Tronics, Inc. (“Seller”) and UltraCell, LLC, a Delaware limited liability company and a direct wholly-owned subsidiary of Seller (“UltraCell”) (the “Purchase Agreement”). See Note 3 “Business Combination” accompanying the unaudited condensed consolidated financial statements for additional information. On June 25, 2021, the Company entered into a Share Purchase Agreement (the “Purchase Agreement”), with F.E.R. fischer Edelstahlrohre GmbH, a limited liability company incorporated under the Laws of Germany (the “Seller”) to acquire (the “Acquisition”) all of the issued and outstanding equity interests in SerEnergy A/S, a Danish stock corporation and a wholly-owned subsidiary of the Seller (“SerEnergy”) and fischer eco solutions GmbH, a German limited liability company and a wholly-owned subsidiary of the Seller (“FES” and together with SerEnergy, the “Target Companies”) together with certain outstanding shareholder loan receivables. See Note 3 “Business Combination” accompanying the unaudited condensed consolidated financial statements for additional information. (b) Unaudited Condensed Consolidated Financial Statements The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. Generally Accepted Accounting Principles (“GAAP”) and pursuant to the regulations of the U.S. Securities and Exchange Commission (“SEC”). The unaudited financial information reflects, in the opinion of management, all adjustments, consisting of normal recurring adjustments, considered necessary for a fair statement of the Company's financial position, results of operations and cash flows for the periods indicated. The results reported for the interim period presented are not necessarily indicative of results that may be expected for the full year. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company's audited consolidated financial statements as of and for the year ended December 31, 2020 included in the Current Report on Form 8-K filed with the SEC on February 9, 2021 (the “Original Form 8-K”), as amended by Amendment No. 1 to Form 8-K, filed with the SEC on February 9, 2021 (“Amendment No. 1”), as further amended by Amendment No. 2 to Form 8-K, filed with the SEC on March 26, 2021 (“Amendment No. 2”) and as further amended by Amendment No 3 to Form 8-K, filed with the SEC on May 20, 2021 (“Amendment No. 3,” and, the Original Form 8-K, as so amended by Amendment No. 1, Amendment No. 2 and Amendment No. 3, the “Super Form 8-K”). The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. Intercompany accounts and transactions have been eliminated. Certain prior period balances have been reclassified to conform to the current period presentation in the unaudited condensed consolidated financial statements and the accompanying notes. Share and per share amounts are presented on a post-conversion basis for all periods presented, unless otherwise specified. (c) Going Concern The unaudited condensed consolidated financial statements have been prepared by management in accordance with GAAP, assuming that the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. Accordingly, these financial statements do not include any adjustments that may result in the event the Company is unable to continue as a going concern. Beginning in March 2020, the COVID-19 pandemic and the measures imposed to contain this pandemic have disrupted and are expected to continue to impact the Company’s business. The magnitude of the impact of the COVID-19 pandemic on the Company’s productivity, results of operations and financial position, and its disruption to the Company’s business (fuel cells sales timeline, realization of income from grants received) will depend in part, on the length and severity of these restrictions and on the Company’s ability to conduct business in the ordinary course. As of the date of this Quarterly Report on Form 10-Q, the Company’s existing cash resources are sufficient to support planned operations for the next 12 months. As a result, management believes that the Company's existing financial resources are sufficient to continue operating activities for at least one year past the issuance date of the unaudited condensed consolidated financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies: There have been no significant changes from the significant accounting policies disclosed in Note 2 of the “Notes to Consolidated Financial Statements” included in the Super Form 8-K. The Company is an “emerging growth company,” as defined in Section 2(a) of the Securities Act, as modified by the Jumpstart our Business Startups Act of 2012, (the “JOBS Act”). As an emerging growth company (“EGC”), the JOBS Act allows the Company to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are applicable to private companies. The Company elected to use this extended transition period under the JOBS Act until such time the Company is no longer considered to be an EGC. The Company applied the following new accounting policies: (a) Business acquisitions, Goodwill and Intangible Assets The Company allocates the fair value of purchase consideration transferred in a business acquisition to the tangible assets acquired, liabilities assumed, and intangible assets acquired based on their estimated fair values. The excess of the fair value of purchase consideration transferred over the fair values of these identifiable assets and liabilities is recorded as goodwill. In case the fair value of purchase consideration transferred is below fair values of these identifiable assets and liabilities, the Company recognizes a gain from a bargain purchase. Such valuations require management to make significant estimates and assumptions, especially with respect to intangible assets. Significant estimates in valuing certain intangible assets include, but are not limited to, future expected cash flows from acquired licenses, trade names, in process research and development ("R&D"), useful lives and discount rates, patents, customer clientele, customer contracts and know-how. Management's estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. During the measurement period, the Company may record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Upon the conclusion of the measurement period, any subsequent adjustments are recorded in the consolidated statement of operations. For significant acquisitions, the Company obtains independent appraisals and valuations of the intangible (and certain tangible) assets acquired and certain assumed liabilities. The Company analyzes each acquisition individually and all acquisitions within each reporting period in aggregate to determine if those are material acquisitions in the context of ASC 805-10-50. The estimated fair values and useful lives of identified intangible assets are based on many factors, including estimates and assumptions of future operating performance and cash flows of the acquired business, estimates of cost avoidance, the nature of the business acquired, the specific characteristics of the identified intangible assets and our historical experience and that of the acquired business. The estimates and assumptions used to determine the fair values and useful lives of identified intangible assets could change due to numerous factors, including product demand, market conditions, regulations affecting the business model of our operations, technological developments, economic conditions and competition. We conduct a goodwill impairment analysis annually in the fourth fiscal quarter, as of October 1, and as necessary if changes in facts and circumstances indicate that the fair value of our reporting units may be less than their carrying amounts. When indicators of impairment do not exist and certain accounting criteria are met, we are able to evaluate goodwill impairment using a qualitative approach. When necessary, our quantitative goodwill impairment test consists of two steps. The first step requires that we compare the estimated fair value of our reporting units to the carrying value of the reporting unit’s net assets, including goodwill. If the fair value of the reporting unit is greater than the carrying value of its net assets, goodwill is not considered to be impaired and no further testing is required. If the fair value of the reporting unit is less than the carrying value of its net assets, we would be required to complete the second step of the test by analyzing the fair value of its goodwill. If the carrying value of the goodwill exceeds its fair value, an impairment charge is recorded. Currently, we identify one reporting unit. (b) Warrants The Company may issue or assume common stock warrants with debt, equity or as standalone financing instruments that are recorded as either liabilities or equity in accordance with the respective accounting guidance. Warrants recorded as equity are recorded at their relative fair value or fair value determined at the issuance date and remeasurement is not required. Warrants recorded as liabilities are recorded at their fair value, within warrant liability on the consolidated balance sheets, and remeasured on each reporting date with changes recorded in revaluation of warrant liability on the Company's consolidated statements of operations. (c) Fair Value of Financial Instruments As a result of the Business Combination, the Company assumed a warrant liability (the "Warrant Liability") related to previously issued 3,940,278 warrants, each exercisable to purchase one share of common stock at an exercise price of $11.50 per share, originally sold to AMCI Sponsor LLC (the “Sponsor”) in a private placement consummated in connection with AMCI’s Initial Public Offering (the “Private Placement Warrants”) and the 400,000 warrants, each exercisable to purchase one share of common stock at an exercise price of $11.50 per share, converted from the Sponsor’s non-interest bearing loan to the Company of $400,000 in connection with the closing of the Business Combination (the “Working Capital Warrants”) (Note 12). The Private Placement Warrants and the Working Capital Warrants have substantially the same terms as the 22,029,279 warrants, each exercisable to purchase one share of common stock at an exercise price of $11.50 per share, issued by AMCI in its Initial Public Offering (the “Public Warrants”). The Warrant Liability is remeasured to its fair value at each reporting period and upon settlement. The change in fair value is recognized in revaluation of warrant liability on the consolidated statements of operations. The change in fair value of the warrant liability is as follows: Warrant Liability Estimated fair value at February 4, 2021 $ 33,116,321 Change in estimated fair value $ (15,833,334 ) Estimated fair value at September 30, 2021 $ 17,282,987 The estimated fair value of the Private Placement Warrants and the Working Capital Warrants (each as defined below) is determined using Level 3 inputs by using the Black-Scholes model. The application of the Black-Scholes model requires the use of a number of inputs and significant assumptions including volatility. Significant judgment is required in determining the expected volatility of our common stock. Due to the limited history of trading of our common stock, we determined expected volatility based on a peer group of publicly traded companies. The following table provides quantitative information regarding Level 3 fair value measurement inputs as of their measurement date September 30, 2021: Stock price $ 8.70 Exercise price (strike price) $ 11.50 Risk-free interest rate 0.83 % Volatility 67.30 % Remaining term (in years) 4.34 The Company performs routine procedures such as comparing prices obtained from independent source to ensure that appropriate fair values are recorded. (d) Earnings / (Loss) Per Share Earnings / (Loss) Per Share is computed by dividing earnings / (loss) by the weighted average number of common shares outstanding during the period. Diluted earnings / (loss) per share reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted at the beginning of the periods presented, or issuance date, if later. The treasury stock method is used to compute the dilutive effect of warrants. (e) Stock-based Compensation Stock-based compensation consists of stock options and restricted stock units (“RSUs”). Stock options and restricted stock units are equity classified and are measured at the fair market value of the underlying stock at the grant date. Under ASC 718, an entity may recognize compensation cost for an award with only a service condition that has a graded vesting schedule on either (1) an accelerated basis as though each separately vesting portion of the award was, in substance, a separate award or (2) a straight-line basis over the total requisite service period for the entire award. An entity’s use of either a straight-line or an accelerated attribution method represents an accounting policy election and thus should be applied consistently to all similar awards. The Company has elected to recognize compensation cost on a straight-line basis over the total requisite service period for the stock options and restricted stock units. This election does not affect the Company’s previous year results since the Restricted Stock Awards granted in the prior period did not have a service requirement and therefore the stock compensation expense was recognized immediately. The Company has also a policy of accounting for forfeitures when they occur. (f) Recent Accounting pronouncements Recently issued accounting pronouncements not yet adopted In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02, Leases (Topic 842), to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. In July 2018, ASU 2018-10, Codification Improvements to Topic 842, Leases, was issued to provide more detailed guidance and additional clarification for implementing ASU 2016-02. Furthermore, in July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements, which provides an optional transition method in addition to the existing modified retrospective transition method by allowing a cumulative effect adjustment to the opening balance of retained earnings in the period of adoption. Additionally, ASU 2019-01, Codification Improvements to Topic 842, Leases and ASU 2020-02, Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 119 and Update to SEC Section on Effective Date Related to Accounting Standards Update No. 2016-02, Leases (Topic 842), provided additional clarifications for implementing ASU 2016.02. The new lease standard was originally effective for private entities on January 1, 2021, with early adoption permitted. Following the issuance of ASU 2020-05, Effective Dates for Certain Entities (Topic 842), the effective date of Leases was deferred for private entities (the “all other” category) to fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early application continues to be permitted which means that an entity may choose to implement Leases before those deferred effective dates. The Company is currently evaluating the effect of the adoption of this guidance on the consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses of Financial Instruments, which, amends the requirement on the measurement and recognition of expected credit losses for financial assets held. Furthermore, amendments, ASU 2019-10 and ASU 2019-11 provided additional clarification for implementing ASU 2016-13. ASU 2016-13 is effective for the Company beginning January 1, 2023, with early adoption permitted. The Company is currently in the process of evaluating the effect of this guidance on the consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which is intended to simplify various aspects related to accounting for income taxes. The pronouncement is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2020 for public entities, with early adoption permitted. ASU 2019-12 is effective for the Company beginning January 1, 2022, taking the exemption allowed for the “emerging growth companies”

Business Combination

Business Combination	9 Months Ended
	Sep. 30, 2021
Business Combination [Abstract]
Business Combination	3. Business Combination (a) AMCI Acquisition Corp. As detailed in Note 1 on February 4, 2021, the Company and AMCI consummated the Business Combination pursuant to the terms of the merger agreement, with Advent Legacy surviving the merger as a wholly-owned subsidiary of AMCI. Immediately prior to the closing of the Business Combination, all shares of outstanding preferred stock Series A and preferred stock Series Seed of Legacy Advent were automatically converted into shares of the Legacy Advent's common stock. Upon the consummation of the Business Combination, each share of Legacy Advent common stock issued and outstanding was canceled and converted into the right to receive the amount of shares as determined based on the merger consideration of $250 million minus the estimated consolidated indebtedness of Legacy Advent and its subsidiaries as of the consummation of the Business Combination, net of their estimated consolidated cash and cash equivalents (“Closing Net Indebtedness”) divided by $10.00. The Closing Net Indebtedness was based solely on estimates determined shortly prior to the closing and was not subject to any post-closing true-up or adjustment. Upon the closing of the Business Combination, AMCI's certificate of incorporation was amended and restated to, among other things, authorize the issuance of 111,000,000 shares, of which 110,000,000 shares are shares of common stock, par value $0.0001 per share and 1,000,000 shares are shares of undesignated preferred stock, par value $0.0001 per share. In connection with the execution of the Business Combination Agreement, AMCI entered into separate subscription agreements (each, a "Subscription Agreement") with a number of investors (each a "Subscriber"), pursuant to which the Subscribers agreed to purchase, and AMCI agreed to sell to the Subscribers, an aggregate of 6,500,000 shares of common stock (the "PIPE Shares"), for a purchase price of $10.00 per share and an aggregate purchase price of $65.0 million, in a private placement pursuant to the subscription agreements (the "PIPE"). The PIPE investment closed simultaneously with the consummation of the Business Combination. The Business Combination is accounted for as a reverse recapitalization in accordance with GAAP. Under this method of accounting, AMCI was treated as the "acquired" company for financial reporting purposes. See Note 1 "Basis of Presentation" in the accompanying unaudited condensed consolidated financial statements for further details. Accordingly, for accounting purposes, the Business Combination was treated as the equivalent of Legacy Advent issuing stock for the net assets of AMCI, accompanied by a recapitalization. The net assets of AMCI are stated at historical cost, with no goodwill or other intangible assets recorded. The following table reconciles the elements of the Business Combination to the consolidated statement of cash flows and the consolidated statement of changes in equity for the nine months ended September 30, 2021: Recapitalization Cash- AMCI’s trust and cash (net of redemptions) $ 93,310,599 Cash – PIPE plus interest 65,000,118 Less transaction costs and advisory fees paid (17,188,519 ) Less non-cash warrant liability assumed (33,116,321 ) Net Business Combination and PIPE financing $ 108,005,877 The number of shares of common stock issued immediately following the consummation of the Business Combination: Recapitalization Class A Common A stock of AMCI, outstanding prior to Business Combination 9,061,136 Less Redemption of AMCI shares (1,606 ) Class B Common Stock of AMCI, outstanding prior to Business Combination 5,513,019 Shares issued in PIPE 6,500,000 Business Combination and PIPE financing shares 21,072,549 Legacy Advent Shares 25,033,398 Total shares of Common Stock immediately after Business Combination 46,105,947 (b) UltraCell, LLC On February 18, 2021 (the “acquisition date”), pursuant to the terms and conditions of the Purchase Agreement, the Company acquired 100% of the issued and outstanding membership units of UltraCell from Bren-Tronics, Inc. The results of UltraCell’s operations have been included in the unaudited condensed consolidated financial statements since the acquisition date. The Company has assessed provisions in ASC 805 and concluded that the UltraCell acquisition should be accounted as an acquisition of a business. The Company evaluated whether substantially all the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets and concluded that it is not. Since the “substantially all” threshold is not met, the Company further assessed whether the set acquired includes an input and a substantive process that together significantly contribute to the ability to create outputs. Following its assessment, the Company concluded that the minimum requirements to define UltraCell as a business are met. UltraCell is an entity specialized in lightweight fuel cells for the portable power market with mature products and cutting-edge technology. The acquisition consideration transferred totaled $6.0 million, of which $4.0 million was cash and $2 million was the fair value of the contingent consideration. The contingent consideration arrangement required the Company to pay $2 million of additional cash to UltraCell’s former holders of membership interests, if UltraCell entered into certain customer arrangements for sales of products prior to June 30, 2021. On April 16, 2021 Advent paid the additional consideration based on UltraCell achieving completion of the terms of the contingent consideration. Assets and liabilities at acquisition The assets acquired and liabilities assumed at the date of acquisition were as follows: Current assets Cash and cash equivalents $ 77,129 Other current assets 658,332 Total current assets $ 735,461 Non-current assets 9,187 Total assets $ 744,649 Current liabilities 110,179 Non-current liabilities - Total liabilities $ 110,179 Net assets acquired $ 634,469 Goodwill arising on acquisition Cost of investment $ 6,000,000 Net assets value 634,469 Consideration to be allocated $ 5,365,531 Fair value adjustment - New intangibles Trade name "UltraCell" 405,931 Patented technology 4,328,228 Total intangibles acquired $ 4,734,159 Remaining Goodwill $ 631,372 The fair value of the assets acquired and liabilities assumed was based on a Purchase Price Allocation of UltraCell LLC conducted by an independent third party. The intangible assets recognized are the Trade Name “UltraCell” and the Patented Technology. The fair value measurement of the intangible assets has been performed by applying a combination of market, cost and income approach methods. The Trade Name was valued with the Relief-from-royalty method, which combines market & income approaches. The royalty rate used for the valuation of the Trade Name was 1.3%, which was determined from the market using databases from completed transactions at a global level while the discount rate used was 12.6%. The Patented Technology was valued with the multi period excess earnings method, which is an income approach. The discount rate used for the valuation of the Patented Technology was 11.6%. The Trade Name has an indefinite useful life while the Patented Technology has a useful life of 10 years. Included in goodwill is the value of assembled workforce, which under FASB ASC topic 805, does not meet either the contractual-legal or the separability criterion in order to be separately valued as an intangible asset. As part of the acquisition, the Company acquired fully trained personnel thereby avoiding the expenditure that would have been required to hire and train equivalent personnel. Therefore, the assemblage cost avoided method was considered the most appropriate method for the valuation of the assembled workforce. The assembled workforce was valued at $0.19 million and has been included in goodwill. (c) Acquisition of SerEnergy and FES Effective on August 31, 2021, pursuant to the previously announced Share Purchase Agreement (the “Purchase Agreement”), dated as of June 25, 2021, by and between Advent Technologies Holdings Inc. (the “Buyer”) and F.E.R. fischer Edelstahlrohre GmbH, a limited liability company incorporated under the Laws of Germany (the “Seller”), the Company acquired (the “Acquisition”) all of the issued and outstanding equity interests in SerEnergy A/S, a Danish stock corporation and a wholly-owned subsidiary of the Seller (“SerEnergy”) and fischer eco solutions GmbH, a German limited liability company and a wholly-owned subsidiary of the Seller (“FES” and together with SerEnergy, the “Target Companies”) together with certain outstanding shareholder loan receivables. The shareholder loans became intercompany at closing and were eliminated in consolidation. The Company has assessed provisions in ASC 805 and concluded that the SerEnergy and FES acquisition should be accounted as an acquisition of a business. The Company evaluated whether substantially all the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets and concluded that it is not. Since the “substantially all” threshold is not met, the Company further assessed whether the set acquired includes an input and a substantive process that together significantly contribute to the ability to create outputs. Following its assessment, the Company concluded that the minimum requirements to define SerEnergy and FES as a business are met. The results of the SerEnergy’s and FES’s operations have been included in the unaudited condensed consolidated financial statements since the acquisition date. The revenues associated to SerEnergy and FES for the one-month period ended September 30, 2021 (acquisition date to September 30, 2021) was $791,626. The net loss associated to SerEnergy and FES for the one-month period ended September 30, 2021 (acquisition date to September 30, 2021) was $834,944. If the acquisition had been consummated as of January 1, 2020, the Company’s pro-forma revenues and net loss for the nine months ended September 30, 2021 would have been $13.1 million and $(20.3) million, respectively, and for the nine months ended September 30, 2020 would have been $2.4 million and $(11.6) million, respectively. Similarly, pro-forma revenues and net loss for the three months ended September 30, 2021 would have been $3.9 million and $(13.1) million, respectively, and for the three months ended September 30, 2020 would have been $0.5 million and $(2.5) million, respectively. The unaudited pro forma results are for comparative purposes only and do not purport to be indicative of the results that would have actually been obtained if the acquisition had occurred at the beginning of the period presented. In addition, these results are not intended to be a projection of future results and do not reflect any synergies that might be achieved from the combined operations. Pursuant to the Purchase Agreement, the Company acquired SerEnergy and FES, the fuel cell systems business of fischer Group. SerEnergy is a leading manufacturer of high-temperature polymer electrolyte membrane HT-PEM fuel cells and operates facilities in Aalborg, Denmark and in Manila, Philippines. FES operates in Achern, Germany and provides fuel-cell stack assembly and testing as well as the production of critical fuel cell components, including membrane electrode assemblies, bipolar plates and reformers. As consideration for the transactions contemplated by the Purchase Agreement, the Company paid to the Seller $17,869,309 (€15,000,000) in cash (the “Cash Consideration”) and on August 31, 2021, the Company issued to the Seller 5,124,846 shares of common stock of the Company with a par value $0.0001 per share (the “Share Consideration”). The Share Consideration was capped to shares representing 9.999% of the Company’s common stock outstanding as of the completion (taking into account the common stock issued as Share Consideration, the “Cap”). An additional amount of $4,366,802, representing cash on the balance sheet of the acquired businesses at closing, will be paid to F.E.R. fischer Edelstahlrohre GmbH to complete the acquisition of SerEnergy and FES and is included in “Other current liabilities” (Note 10). Transaction costs amounted to $889,716 and have been expensed in the condensed consolidated statement of operations under the caption “Administrative and selling expenses” in the accompanying condensed consolidated statement of operations. Assets and liabilities at acquisition The assets acquired and liabilities assumed at the date of acquisition were as follows: Current assets Cash and cash equivalents $ 4,366,802 Other current assets 10,454,864 Total current assets $ 14,821,665 Non-current assets 5,434,180 Total assets $ 20,255,845 Current liabilities 5,818,170 Non-current liabilities 1,179,618 Total liabilities $ 6,997,788 Net assets acquired $ 13,258,057 Goodwill arising on acquisition Cost of investment Cash consideration $ 22,236,111 Share consideration 37,923,860 Total cost of investment 60,159,971 Less: Net assets value 13,258,057 Original excess purchase price $ 46,901,914 Fair value adjustments Real Property 76,000 New intangibles: Patents 17,275,000 Process know-how (IPR&D) 2,599,000 Order backlog 247,000 Total intangibles acquired $ 20,121,000 Deferred tax liability arising from the recognition of intangibles and real property valuation (4,444,000 ) Deferred tax assets on tax losses carried forward 1,915,000 Remaining Goodwill $ 29,233,914 The fair value of the assets acquired and liabilities assumed was based on a Purchase Price Allocation of SerEnergy and FES conducted by an independent third party. The acquired businesses specialize in the manufacturing of hydrogen fuel cell systems and align with Advent’s ability to provide clean power in the stationary, remote, portable and off-grid markets under the “Any Fuel. Anywhere.” value proposition. The Company’s ability to deliver hydrogen through liquid fuels allows it to have immediate market opportunity today, without having to wait for the global hydrogen infrastructure to develop. The acquisitions also accelerate the Company’s strategy to cover the full vertical supply chain with its products and puts the Company in a competitive position to deliver reliable, efficient and cost-effective fuel cell systems with a new product portfolio of the latest high temperature-PEM fuel cells covering a range of 25W to 90kW systems. The acquisitions also make Advent a leading manufacturer of high temperature fuel cells across Europe and Asia. Expanding the business in Europe and Asia is a strategic move and allows the Company to have well-placed production capabilities and market penetration. Included in goodwill is the value of assembled workforce, which under FASB ASC topic 805, does not meet either the contractual-legal or the separability criterion in order to be separately valued as an intangible asset. As part of the acquisition, the Company acquired fully trained personnel thereby avoiding the expenditure that would have been required to hire and train equivalent personnel. The assembled workforce included in goodwill was valued at $2.4 million applying the cost approach. Goodwill is not expected to be deductible for tax purposes. Intangible assets The intangible assets recognized on the acquisition of SerEnergy and FES are as follows: Patents Two groups of patents are assumed to be the most significant drivers of future cash flows. The patents relate to improvements in gaskets, bipolar plates and cooling plates for fuel cells. The fair value of patents was determined by applying the multi-period excess earnings method which is an income approach. The discount rate used for the valuation of patents was 7.2%. Patents are amortized over 10 years since management assumes, that these groups of patents will continue to drive cash flows for 10 years, after which new patents will be of more relevance. Process know-how (IPR&D) SerEnergy and FES are currently developing cost reduction initiatives (unpatented know-how) related to membrane electrode assembly, bipolar plates, gaskets, burner/reformer and electronics. This IPR&D is evaluated as a significant asset for the business as it will allow significant cost reduction leading to higher profits in the future. These cost reductions are expected to be introduced beginning in 2022. The multi-period excess earnings method was applied to calculate the fair value of this asset. The discount rate used for the valuation of IPR&D was 10.1%. IPR&D is amortized over its useful life of 6 years, being the average timespan of a generation of fuel cell modules. Order backlogs Order backlogs recognized are in respect of two main customers of SerEnergy. The assessment of this asset was based on the total amount of order backlog attributable to these customers. The fair value was determined applying the income approach. Resulting cash flows after tax were discounted to present value by a minimal discount rate as the backlog’s timespan is less than a year.

Related party disclosures

Related party disclosures	9 Months Ended
	Sep. 30, 2021
Related party disclosures [Abstract]
Related party disclosures	4. Related party disclosures: The amounts included in the accompanying consolidated balance sheets and consolidated statements of operations are as follows: September 30, 2021 (Unaudited) December 31, 2020 Due to related parties Unpaid compensation cost Unpaid compensation cost Vassilios Gregoriou $ - $ 613,971 Emory Sayre De Castro - 425,528 Christos Kaskavelis - 75,160 Charalampos Antoniou 30,000 - Total $ 30,000 $ 1,114,659 September 30, 2021 (Unaudited) December 31, 2020 Due from related parties Prepayment Prepayment Charalampos Antoniou $ - $ 67,781 Total $ - $ 67,781 The outstanding balances as of December 31, 2020 due to/from the Company’s executives and officers relating to unpaid compensation and prepaid services were settled during the first quarter of 2021. The Company executives, Vassilios Gregoriou, Christos Kaskavelis, Emory Sayre De Castro, James Coffey and William Hunter, each received a signing bonus and transaction bonus upon the consummation of the merger in an aggregate amount of $5.6 million, which is included in administrative and selling expenses in the statement of operations for the nine months period ended September 30, 2021.

Inventories

Inventories	9 Months Ended
	Sep. 30, 2021
Inventories [Abstract]
Inventories	5. Inventories: Inventories consist of the following: September 30, 2021 (Unaudited) December 31, 2020 Raw materials and supplies $ 5,598,574 $ 107,939 Total $ 5,598,574 $ 107,939

Prepaid expenses and Other curr

Prepaid expenses and Other current assets	9 Months Ended
	Sep. 30, 2021
Prepaid expenses and Other current assets [Abstract]
Prepaid expenses and Other current assets	6. Prepaid expenses and other current assets: Prepaid expenses and other current assets are analyzed as follows: September 30, 2021 (Unaudited) December 31, 2020 VAT receivable $ 826,973 $ 259,831 Grants receivable 597,155 95,064 Other current assets 520,007 140,126 Prepaid expenses 1,822,962 1,724 Total $ 3,767,096 $ 496,745 Prepaid expenses as of September 30, 2021 mainly include prepayments to insurers for directors’ and officers’ insurance services for liabilities that may arise in their capacity as directors and officers of a public entity.

Property and equipment, net

Property and equipment, net	9 Months Ended
	Sep. 30, 2021
Property and equipment, net [Abstract]
Property and equipment, net	7. Property and equipment, net: During the nine-month period ended September 30, 2021, additions to property, plant and equipment of $2.7 million include leasehold improvements, machinery, office and other equipment. Additionally, upon acquisition of UltraCell LLC, the Company acquired property and equipment with a net book value of $0.01 million. Upon acquisition of SerEnergy and FES, the Company acquired property and equipment with a net book value of $5.4 million. There are no collaterals or other commitments on the Company’s property and equipment.

Other non-current assets

Other non-current assets	9 Months Ended
	Sep. 30, 2021
Other non-current assets [Abstract]
Other non-current assets	8. Other non-current assets: Other non-current assets as of September 30, 2021 include mainly advances to suppliers for the acquisition of fixed assets of $1,917,856 and guarantees paid as a security for the rental of premises of $167,626.

Trade and other payables

Trade and other payables	9 Months Ended
	Sep. 30, 2021
Trade and other payables [Abstract]
Trade and other payables	9. Trade and other payables: September 30, 2021 (Unaudited) December 31, 2020 Trade payables and other payables $ 5,522,624 $ 881,394 Total $ 5,522,624 $ 881,394 Trade payables include balances of suppliers and consulting service providers. Other payables include $1.8 million for executive severance as of September 30, 2021.

Other current liabilities

Other current liabilities	9 Months Ended
	Sep. 30, 2021
Other current liabilities [Abstract]
Other current liabilities	10. Other current liabilities: Other current liabilities are analyzed as follows: September 30, 2021 (Unaudited) December 31, 2020 Accrued expenses for legal and consulting fees $ 1,110,587 $ 814,965 Other accruals and short-term payables 6,485,032 89,414 Total $ 7,595,619 $ 904,379 Other accruals and short-term payables as of September 30, 2021 include an amount of $4,366,802, which is payable to F.E.R. fischer Edelstahlrohre GmbH to complete the acquisition of SerEnergy and FES, as discussed in Note 3(c). Other accruals and short-term payables as of September 30, 2021 also include an amount of $127,104, being the current portion of the accrued warranty reserve discussed in Note 11.

Other long-term liabilities

Other long-term liabilities	9 Months Ended
	Sep. 30, 2021
Other long-term liabilities [Abstract]
Other long-term liabilities	11. Other long-term liabilities: Other long-term liabilities as of September 30, 2021 mainly include an amount of $940,972, being the non-current portion of a total accrued warranty reserve of $1,068,076. We accrue a warranty reserve of 8% of the sale price of the fuel cells sold. Warranty reserve is released when repairs or replacements are carried out in relation to items under warranties or when the warranty period for the fuel cell expires. The portion of the warranty reserve expected to be incurred within the next 12 months is included within Other current liabilities (Note 10), while the remaining balance is included within Other long-term liabilities on the consolidated balance sheets.

Private Placement Warrants and

Private Placement Warrants and Working Capital Warrants	9 Months Ended
	Sep. 30, 2021
Private Placement Warrants and Working Capital Warrants [Abstract]
Private Placement Warrants and Working Capital Warrants	12. Private Placement Warrants and Working Capital Warrants: In connection with the Business Combination, the Company has assumed 3,940,278 Private Placement Warrants issued upon AMCI’s Initial Public Offering. In addition, upon the closing of the Business Combination, the working capital loan provided by AMCI’s Sponsor to AMCI was converted into 400,000 Working Capital Warrants, which were also assumed. The terms of the Working Capital Warrants are the same as those of the Private Placement Warrants. As of September 30, 2021, the Company had 4,340,278 Private Placement Warrants and Working Capital Warrants outstanding. Each Private Placement Warrant and Working Capital Warrant entitles the registered holder to purchase one share of Common Stock at a price of $11.50 per share, subject to adjustment, at any time commencing 30 days after the completion of the Business Combination. The Public Warrants will expire five years after the completion of a Business Combination or earlier upon redemption or liquidation. The Private Placement Warrants and Working Capital Warrants are identical to the Public Warrants, except that the Private Placement Warrants and Working Capital Warrants and the common stock issuable upon the exercise of those warrants will not be transferable, assignable or salable until 30 days after the completion of a Business Combination, subject to certain limited exceptions. Additionally, the Private Placement Warrants and Working Capital Warrants will be exercisable on a cashless basis and be non-redeemable so long as they are held by the initial purchasers or their permitted transferees. If those warrants are held by someone other than the initial purchasers or their permitted transferees, they will be redeemable by the Company and exercisable by such holders on the same basis as the Public Warrants. As of September 30, 2021, the Private Placement Warrants and Working Capital Warrants are held by its initial purchasers. According to the provisions of the Private Placement Warrants and Working Capital Warrants warrant agreements, the exercise price and number of shares of common stock issuable upon exercise of those warrants may be adjusted in certain circumstances including in the event of a stock dividend, or recapitalization, reorganization, merger or consolidation. Private Placement Warrants and Working Capital Warrants are classified as liabilities in accordance with the Company’s evaluation of the provisions of ASC 815- 40-15, which provides that a warrant is not indexed to the issuer’s common stock if the terms of the warrant require an adjustment to the exercise price upon a specified event and that event is not an input to the fair value of the warrant with a fixed exercise price and fixed number of underlying shares.

Stockholders' Equity _ (Deficit

Stockholders' Equity / (Deficit)	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity / (Deficit) [Abstract]
Stockholders' Equity / (Deficit)	13. Stockholders’ Equity / (Deficit): Shares Authorized As of September 30, 2021, the Company had authorized a total of 111,000,000 shares for issuance with 110,000,000 shares designated as common stock, par value $0.0001 per share and 1,000,000 shares designated as preferred stock, par value $0.0001 per share. Common Stock On April 9, 2021, 22,798 common shares were issued in connection with the exercise of public warrants discussed below. On August 31, 2021, 5,124,846 common shares were issued in connection with the share consideration for the acquisition of SerEnergy and FES discussed in Note 3(c). As of September 30, 2021, the Company’s issued and outstanding common shares were 51,253,591. Public Warrants In connection with the Business Combination, the Company has assumed Public Warrants issued upon AMCI’s Initial Public Offering. As of March 31, 2021, the Company had 22,052,077 Public Warrants outstanding. Each Public Warrant entitles the registered holder to purchase one share of Common Stock at a price of $11.50 per share, subject to adjustment, at any time commencing 30 days after the completion of the Business Combination. The Public Warrants will expire five years after the completion of a Business Combination or earlier upon redemption or liquidation. During the second quarter of 2021, certain warrant holders exercised their option to purchase an additional 22,798 shares at $11.50. These exercises generated $262,177 additional proceeds to the Company and increased our shares outstanding by 22,798 shares. Following these exercises, as of September 30, 2021, the Company’s Public Warrants amounted to 22,029,279. Once the warrants become exercisable, the Company may redeem the Public Warrants: – in whole and not in part; – at a price of $0.01 per warrant; – upon not less than 30 days’ prior written notice of redemption; – if, and only if, the reported last sale price of the Company’s common stock equals or exceeds $18.00 per share for any 20 trading days within a 30-trading day period ending three business days before the Company sends the notice of redemption to the warrant holders; and – if, and only if, there is a current registration statement in effect with respect to the shares of common stock underlying such warrants. If the Company calls the Public Warrants for redemption, management will have the option to require all holders that wish to exercise the Public Warrants to do so on a “cashless basis,” as described in the warrant agreement. The exercise price and number of shares of common stock issuable upon exercise of the warrants may be adjusted in certain circumstances including in the event of a stock dividend, or recapitalization, reorganization, merger or consolidation. However, the warrants will not be adjusted for issuance of common stock at a price below its exercise price. In addition, the warrant agreement provides that in case of a tender offer or exchange that involves 50% or more of the Company’s stockholders, the Public Warrants may be settled in cash, equity securities or other assets depending on the kind and amount received per share by the holders of the common stock in such consolidation or merger that affirmatively make such election. Public Warrants are classified in equity in accordance with the Company’s evaluation of the provisions of ASC 480 and ASC 815. The Company analyzed the terms of the Public Warrants and concluded that there are no terms that provide that the warrant is not indexed to the issuer’s common stock. The Company also analyzed the tender offer provision discussed above, and considering that upon the Closing of the Business Combination the Company has a single class of common shares, concluded that the exception discussed in ASC 815-40-25 applies, and thus equity classification is not precluded. Compensation Plans The Company’s Board of Directors and shareholders previously approved the 2021 Equity Incentive Plan (the “Plan”) to reward certain employees and directors of the Company. The Plan has been established to advance the interests of the Company by providing for the grant to Participants of Stock and Stock-based Awards. The maximum number of shares of Stock that may be delivered in satisfaction of Awards under the Plan is 6,915,892 shares (the “Initial Share Pool”). Stock Options Pursuant to and subject to the terms of the 2021 Equity Incentive Plan the Company entered into separate Stock Option Agreements with each participant according to which each participant is granted an option (the “Stock Option”) to purchase up to a specific number of shares of Stock set forth in each agreement with an exercise price equal to the market price of Company’s stock at the date of grant. Stock options have been granted as follows: Grant date Number of shares Strike price June 11, 2021 1,959,500 $ 10.36 August 24, 2021 230,529 $ 7.62 August 31, 2021 457,133 $ 7.40 The Stock Options are granted to each Participant in connection with their employment with the Company. The Stock Options vest on a graded basis over four years. The Company has a policy of recognizing compensation cost on a straight-line basis over the total requisite service period for the stock options. The Company has recognized compensation cost of $1,218,532 in respect of Stock Options granted, which is included in administrative and selling expenses in the statement of operations for the nine months ended September 30, 2021. The Company has also a policy of accounting for forfeitures when they occur. The following table presents the assumptions used to estimate the fair value of the stock options as of the Grant Date: Assumptions Stock options granted on June 11, 2021 Stock options granted on August 24, 2021 Stock options granted on August 31, 2021 Expected volatility 50.0 % 60.7 % 65.7 % Risk-free rate 1.0 % 1.0 % 1.0 % Time to maturity 6.075 years 6.25 years 6.25 years The following table summarizes the activities for our unvested stock options for the nine months ended September 30, 2021: Unvested Shares Number of Shares Grant Date Fair Value Unvested as of December 31, 2020 - $ Granted on June 11, 2021 1,959,500 $ 5.04 Granted on August 24, 2021 230,529 $ 4.32 Granted on August 31, 2021 457,133 $ 4.45 Unvested as of September 30, 2021 2,647,162 As of September 30, 2021, there was $11.7 million of unrecognized compensation cost related to unvested stock options. This amount is expected to be recognized over the remaining vesting period of stock options. Restricted Stock Units Pursuant to and subject to the terms of the 2021 Equity Incentive Plan the Company entered into separate Restricted Stock Units (“RSUs”) with each participant. On the Grant Date of RSUs, the Company grants to each participant a specific number of RSUs as set forth in each agreement, giving each participant the conditional right to receive without payment one share of Stock. The RSUs are granted to each participant in connection with their ongoing employment with the Company. The Company has in place Restricted Stock Unit Agreements that vest within 1 year and Restricted Stock Unit Agreements that vest on a graded basis over four years. The Company has a policy of recognizing compensation cost on a straight-line basis over the total requisite service period. The Company has recognized compensation cost of $2,790,176 in respect of RSUs, which is included in administrative and selling expenses in the statement of operations for the nine months ended September 30, 2021. The Company has also a policy of accounting for forfeitures when they occur. The following table summarizes the activities for our unvested restricted stock units ("RSUs") for the nine months ended September 30, 2021: Unvested Restricted Stock Units Number of Shares Grant Date Fair Value Unvested as of December 31, 2020 - Granted on June 11, 2021 2,036,716 $ 10.36 Granted on August 24, 2021 230,529 $ 7.62 Granted on August 31, 2021 457,122 $ 7.40 Unvested as of September 30, 2021 2,724,367 As of September 30, 2021, there was $23.4 million of unrecognized compensation cost related to unvested RSUs. This amount is expected to be recognized over the remaining vesting period of Restricted Stock Unit Agreements. Stock Grant Plans On March 26, 2020, the Company’s Board of Directors and shareholders approved the 2018-2020 Stock Grant Plan (the “2018-2020 Plan”) to reward certain employees and directors of the Company. The maximum aggregate number of shares that was able to be issued under the Plan was 1,280,199 common shares. The Company entered into separate Restricted Stock Award Agreements with each participant according to which awards for 1,280,199 shares of common stock were granted with a purchase price of $0.01 per share. Under the Plan, if the employee ceased to be employed with the Company for any reason prior to December 31, 2020, the Company had a limited repurchase period to repurchase the granted shares at a price of $0.01 per share. If the Company did not exercise such repurchase option and unless the Company declined in writing to exercise its repurchase option prior to such time, the repurchase option was automatically deemed exercised at the end of the repurchase window. This limited repurchase right lapsed upon the occurrence of a liquidation event. The repurchase feature was deemed equivalent to a forfeiture (vesting) provision. The shares vested over a period ending December 31, 2020. The stock-based compensation was recognized to administrative and selling expenses over the vesting period and based on the fair value of the shares on the grant date. As of September 9, 2020, the Company’s Board of Directors and shareholders approved the 2020-2023 Stock Grant Plan (the “2020-2023 Plan”) to reward certain employees and directors of the Company. The maximum aggregate number of shares that was able to be issued under this plan was 893,503 common shares. The Company entered into separate Restricted Stock Award Agreements with each participant according to which awards for 893,503 shares of common stock were granted with a purchase price of $0.01 per share. If the Company did not exercise such repurchase option and unless the Company declined in writing to exercise its repurchase option prior to such time, the repurchase option was automatically deemed exercised at the end of the repurchase window. This limited repurchase right lapsed upon the occurrence of a liquidation event. The repurchase feature was deemed equivalent to a forfeiture (vesting) provision. The shares vested over a period ending December 31, 2020. The stock-based compensation was recognized to administrative and selling expenses over the vesting period and based on the fair value of the shares on the grant date. The Company recognized compensation cost of $413,396 in respect of the Restricted Stock Awards granted, which is included in administrative and selling expenses in the statement of operations for the nine months ended September 30, 2020. The following table summarizes the activities for our unvested restricted stock awards for the nine months ended September 30, 2020: Unvested Restricted Stock Awards Number of Shares Grant Date Fair Value Unvested as of December 31, 2019 - $ - Granted 2,173,702 $ 0.40 Unvested as of September 30, 2020 2,173,702 $ 0.40 As of September 30, 2020, there was $0.2 million of unrecognized compensation cost related to unvested restricted stock awards granted under the 2018-2020 Plan and $0.3 million of unrecognized compensation cost related to unvested restricted stock awards granted under the 2020-2023 Plan. The amount of $0.5 million, in aggregate from both plans, was recognized through December 31, 2020.

Revenue, net

Revenue, net	9 Months Ended
	Sep. 30, 2021
Revenue, net [Abstract]
Revenue, net	14. Revenue, net: Revenue, net is analyzed as follows: Three months ended September 30, (Unaudited) Nine months ended September 30, (Unaudited) 2021 2020 2021 2020 Sales of goods $ 1,673,998 $ 225,412 $ 4,166,754 $ 526,032 Total revenue from contracts with customers $ 1,673,998 $ 225,412 $ 4,166,754 $ 526,032 As of September 30, 2021 and December 31, 2020 contract assets were $936,259 and $85,930, respectively. Also, the Company has recognized contract liabilities of $28,832 and $167,761 as of September 30, 2021 and December 31, 2020, respectively.

Fair value measurement

Fair value measurement	9 Months Ended
	Sep. 30, 2021
Fair value measurement [Abstract]
Fair value measurement	15. Fair value measurement: The carrying amounts reflected in the consolidated balance sheets of cash and cash equivalents, accounts receivables, net, other current assets, trade and other payables, due from/to related parties, other current liabilities and income tax payable approximate their respective fair values due to the short maturity of these instruments.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Taxes [Abstract]
Income Taxes	16. Income Taxes To calculate the interim tax provision, at the end of each interim period the Company estimates the annual effective tax rate and applies that to its ordinary quarterly earnings. The effect of changes in the enacted tax laws or rates is recognized in the interim period in which the change occurs. The computation of the annual estimated effective tax rate at each interim period requires certain estimates and judgments including, but not limited to, the expected operating income for the year, projections of the proportion of income earned and taxed in foreign jurisdictions, permanent differences between book and tax amounts, and the likelihood of recovering deferred tax assets generated in the current year. The accounting estimates used to compute the provision for income taxes may change as new events occur, additional information is obtained, or the tax environment changes.

Commitments and contingencies

Commitments and contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and contingencies [Abstract]
Commitments and contingencies	17. Commitments and contingencies: 17.1 Litigation The Company is subject to legal and regulatory actions that arise from time to time in the ordinary course of business. The assessment as to whether a loss is probable or reasonably possible, and as to whether such loss or a range of such loss is estimable, often involves significant judgment about future events. There is no material pending or threatened litigation against the Company that remains outstanding as of September 30, 2021. 17.2 Guarantee letters The Company has contingent liabilities in relation to performance guarantee letters and other guarantees provided to third parties that arise from its normal business activity and from which no substantial charges are expected to arise. As of September 30, 2021, issued letters of guarantee amount to $2,776,164. 17.3 Operating Leases On February 5, 2021, the Company entered into a lease agreement by and among the Company, in its capacity as Tenant, and BP Hancock LLC, a Delaware limited liability company, in its capacity as Landlord. The lease provides for the rental by the Company of office space at 200 Clarendon Street, Boston, MA 02116 for use as the Company’s executive offices. Under the terms of the lease, the Company leases 6,041 square feet at an initial fixed annual rent of $456,095. The term of the lease is for five years (unless terminated as provided in the lease) and commenced on April 1, 2021. The Company provided security in the form of a security deposit in the amount of $114,023 which is included in Other non-current assets. On March 8, 2021, the Company entered into a lease for 21,401 square feet as a product development and manufacturing center at Hood Park in Charlestown, MA. Under the terms of the lease, the Company will pay an initial fixed annual rent of $1,498,070. The lease has a term of eight years and five months, with an option to extend for five years, and is expected to commence in May 2022. The Company is obliged to provide security in the form of a security deposit in the amount of $750,000 before commencement of the lease. On August 31, 2021, the Company through its wholly owned subsidiary, FES, entered into a lease agreement by and among the Company, in its capacity as lessee, and fischer group SE & Co. KG, having its registered seat in Achern, in its capacity as lessor. The lease provides for the rental by the Company of office space, workspace and outdoor laboratory at 77855 Achern, Im Gewerbegebiet 7 for use by FES. Under the terms of the lease, the Company leases 1,017 square feet at a monthly basic rate of Euros 7,768 plus VAT. The Company provided security in the form of a parent guarantee for a maximum amount of Euro 30,000. Additionally, the Company’s subsidiaries Advent Technologies S.A. and UltraCell LLC have in place rental agreements for the lease of office and factory spaces

Net income _ (loss) per share

Net income / (loss) per share	9 Months Ended
	Sep. 30, 2021
Net income / (loss) per share [Abstract]
Net income / (loss) per share	18. Net income / (loss) per share Net income (loss) per share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period. The following table sets forth the computation of the basic and diluted net income / (loss) per share for the three months ended September 30, 2021 and 2020 and the nine months ended September 30, 2021 and 2020. Three months ended September 30, (Unaudited) Nine months ended September 30, (Unaudited) 2021 2020 2021 2020 Numerator: Net loss $ (11,279,722 ) $ (748,816 ) $ (11,517,360 ) $ (1,418,037 ) Denominator: Basic weighted average number of shares 48,325,164 23,182,817 43,982,039 21,180,639 Diluted weighted average number of shares 48,325,164 23,182,817 43,982,039 21,180,639 Net loss per share: Basic $ (0.23 ) $ (0.03 ) $ (0.26 ) $ (0.07 ) Diluted $ (0.23 ) $ (0.03 ) $ (0.26 ) $ (0.07 ) Basic net income / (loss) per share is computed by dividing net income / (loss) for the periods presented by the weighted-average number of common shares outstanding during these periods. Diluted As

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	19. Subsequent Events The Company evaluated subsequent events and transactions that occurred after the balance sheet date up to the date that the financial statements were issued. Based upon this review, the Company did not identify any subsequent events that would have required adjustment or disclosure in the financial statements.

Basis of presentation (Policies

Basis of presentation (Policies)	9 Months Ended
	Sep. 30, 2021
Basis of presentation [Abstract]
Overview	(a) Overview On February 4, 2021 (“Closing Date”), AMCI Acquisition Corp. (“AMCI”), consummated the previously announced business combination (the “Business Combination”) pursuant to that certain merger agreement (the “Agreement and Plan of Merger”), dated October 12, 2020, by and among AMCI, AMCI Merger Sub Corp., a Delaware corporation and newly formed wholly-owned subsidiary of AMCI (“Merger Sub”), AMCI Sponsor LLC (the “Sponsor”), solely in the capacity as the representative from and after the effective time of the Business Combination for the stockholders of AMCI (the “Purchaser Representative”), Advent Technologies, Inc., a Delaware corporation (“Legacy Advent”), and Vassilios Gregoriou, solely in his capacity as the representative from and after the effective time for the Legacy Advent stockholders (the “Seller Representative”), as amended by Amendment No. 1 and Amendment No. 2 to the Agreement and Plan of Merger, dated as of October 19, 2020 and December 31, 2020, respectively, by and among AMCI, Merger Sub, Sponsor, Legacy Advent, and Seller Representative. In connection with the closing of the Business Combination (the “Closing”), AMCI acquired 100% of the stock of Legacy Advent (as it existed immediately prior to the Closing) and its subsidiaries. On the Closing Date, and in connection with the closing of the Business Combination, AMCI changed its name to Advent Technologies Holdings, Inc. (the "Company" or "Advent"). Legacy Advent was deemed the accounting acquirer in the Business Combination based on an analysis of the criteria outlined in Accounting Standards Codification ("ASC") 805. This determination was primarily based on Legacy Advent's stockholders prior to the Business Combination having a majority of the voting interests in the combined company, Legacy Advent's operations comprising the ongoing operations of the combined company, Legacy Advent's board of directors comprising a majority of the board of directors of the combined company, and Legacy Advent's senior management comprising the senior management of the combined company. Accordingly, for accounting purposes, the Business Combination was treated as the equivalent of Legacy Advent issuing stock for the net assets of AMCI, accompanied by a recapitalization. The net assets of AMCI are stated at historical cost, with no goodwill or other intangible assets recorded. While AMCI was the legal acquirer in the Business Combination, because Legacy Advent was deemed the accounting acquirer, the historical financial statements of Legacy Advent became the historical financial statements of the combined company, upon the consummation of the Business Combination. As a result, the unaudited condensed consolidated financial statements included in this report reflect (i) the historical operating results of Legacy Advent prior to the Business Combination; (ii) the results of the Company (combined results of AMCI and Legacy Advent) following the closing of the Business Combination; (iii) the assets and liabilities of Legacy Advent at their historical cost; and (iv) Company’s equity structure for all periods presented. In accordance with guidance applicable to these circumstances, the equity structure has been restated in all comparative periods up to the Closing Date, to reflect the number of shares of the Company's common stock, $0.0001 par value per share ("Common Stock") issued to Legacy Advent's stockholders in connection with the recapitalization transaction. As such, the shares and corresponding capital amounts and earnings per share related to Legacy Advent Preferred Stock (“Preferred Series A” and “Preferred Series Seed”) and Legacy Advent common stock prior to the Business Combination have been retroactively restated as shares reflecting the exchange ratio established in the Business Combination Agreement. Activity within the statement of changes in stockholders' equity / (deficit) for the issuances of Legacy Advent's Preferred Stock, were also retroactively converted to Legacy Advent common stock. (Note 3). On February 18, 2021, the Company, entered into a Membership Interest Purchase Agreement with Bren-Tronics, Inc. (“Seller”) and UltraCell, LLC, a Delaware limited liability company and a direct wholly-owned subsidiary of Seller (“UltraCell”) (the “Purchase Agreement”). See Note 3 “Business Combination” accompanying the unaudited condensed consolidated financial statements for additional information. On June 25, 2021, the Company entered into a Share Purchase Agreement (the “Purchase Agreement”), with F.E.R. fischer Edelstahlrohre GmbH, a limited liability company incorporated under the Laws of Germany (the “Seller”) to acquire (the “Acquisition”) all of the issued and outstanding equity interests in SerEnergy A/S, a Danish stock corporation and a wholly-owned subsidiary of the Seller (“SerEnergy”) and fischer eco solutions GmbH, a German limited liability company and a wholly-owned subsidiary of the Seller (“FES” and together with SerEnergy, the “Target Companies”) together with certain outstanding shareholder loan receivables. See Note 3 “Business Combination” accompanying the unaudited condensed consolidated financial statements for additional information.
Unaudited Condensed Consolidated Financial Statements	(b) Unaudited Condensed Consolidated Financial Statements The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. Generally Accepted Accounting Principles (“GAAP”) and pursuant to the regulations of the U.S. Securities and Exchange Commission (“SEC”). The unaudited financial information reflects, in the opinion of management, all adjustments, consisting of normal recurring adjustments, considered necessary for a fair statement of the Company's financial position, results of operations and cash flows for the periods indicated. The results reported for the interim period presented are not necessarily indicative of results that may be expected for the full year. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company's audited consolidated financial statements as of and for the year ended December 31, 2020 included in the Current Report on Form 8-K filed with the SEC on February 9, 2021 (the “Original Form 8-K”), as amended by Amendment No. 1 to Form 8-K, filed with the SEC on February 9, 2021 (“Amendment No. 1”), as further amended by Amendment No. 2 to Form 8-K, filed with the SEC on March 26, 2021 (“Amendment No. 2”) and as further amended by Amendment No 3 to Form 8-K, filed with the SEC on May 20, 2021 (“Amendment No. 3,” and, the Original Form 8-K, as so amended by Amendment No. 1, Amendment No. 2 and Amendment No. 3, the “Super Form 8-K”). The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. Intercompany accounts and transactions have been eliminated. Certain prior period balances have been reclassified to conform to the current period presentation in the unaudited condensed consolidated financial statements and the accompanying notes. Share and per share amounts are presented on a post-conversion basis for all periods presented, unless otherwise specified.
Going Concern	(c) Going Concern The unaudited condensed consolidated financial statements have been prepared by management in accordance with GAAP, assuming that the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. Accordingly, these financial statements do not include any adjustments that may result in the event the Company is unable to continue as a going concern. Beginning in March 2020, the COVID-19 pandemic and the measures imposed to contain this pandemic have disrupted and are expected to continue to impact the Company’s business. The magnitude of the impact of the COVID-19 pandemic on the Company’s productivity, results of operations and financial position, and its disruption to the Company’s business (fuel cells sales timeline, realization of income from grants received) will depend in part, on the length and severity of these restrictions and on the Company’s ability to conduct business in the ordinary course. As of the date of this Quarterly Report on Form 10-Q, the Company’s existing cash resources are sufficient to support planned operations for the next 12 months. As a result, management believes that the Company's existing financial resources are sufficient to continue operating activities for at least one year past the issuance date of the unaudited condensed consolidated financial statements.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Summary of Significant Accounting Policies [Abstract]
Business acquisitions, Goodwill and Intangible Assets	(a) Business acquisitions, Goodwill and Intangible Assets The Company allocates the fair value of purchase consideration transferred in a business acquisition to the tangible assets acquired, liabilities assumed, and intangible assets acquired based on their estimated fair values. The excess of the fair value of purchase consideration transferred over the fair values of these identifiable assets and liabilities is recorded as goodwill. In case the fair value of purchase consideration transferred is below fair values of these identifiable assets and liabilities, the Company recognizes a gain from a bargain purchase. Such valuations require management to make significant estimates and assumptions, especially with respect to intangible assets. Significant estimates in valuing certain intangible assets include, but are not limited to, future expected cash flows from acquired licenses, trade names, in process research and development ("R&D"), useful lives and discount rates, patents, customer clientele, customer contracts and know-how. Management's estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. During the measurement period, the Company may record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Upon the conclusion of the measurement period, any subsequent adjustments are recorded in the consolidated statement of operations. For significant acquisitions, the Company obtains independent appraisals and valuations of the intangible (and certain tangible) assets acquired and certain assumed liabilities. The Company analyzes each acquisition individually and all acquisitions within each reporting period in aggregate to determine if those are material acquisitions in the context of ASC 805-10-50. The estimated fair values and useful lives of identified intangible assets are based on many factors, including estimates and assumptions of future operating performance and cash flows of the acquired business, estimates of cost avoidance, the nature of the business acquired, the specific characteristics of the identified intangible assets and our historical experience and that of the acquired business. The estimates and assumptions used to determine the fair values and useful lives of identified intangible assets could change due to numerous factors, including product demand, market conditions, regulations affecting the business model of our operations, technological developments, economic conditions and competition. We conduct a goodwill impairment analysis annually in the fourth fiscal quarter, as of October 1, and as necessary if changes in facts and circumstances indicate that the fair value of our reporting units may be less than their carrying amounts. When indicators of impairment do not exist and certain accounting criteria are met, we are able to evaluate goodwill impairment using a qualitative approach. When necessary, our quantitative goodwill impairment test consists of two steps. The first step requires that we compare the estimated fair value of our reporting units to the carrying value of the reporting unit’s net assets, including goodwill. If the fair value of the reporting unit is greater than the carrying value of its net assets, goodwill is not considered to be impaired and no further testing is required. If the fair value of the reporting unit is less than the carrying value of its net assets, we would be required to complete the second step of the test by analyzing the fair value of its goodwill. If the carrying value of the goodwill exceeds its fair value, an impairment charge is recorded. Currently, we identify one reporting unit.
Warrants	(b) Warrants The Company may issue or assume common stock warrants with debt, equity or as standalone financing instruments that are recorded as either liabilities or equity in accordance with the respective accounting guidance. Warrants recorded as equity are recorded at their relative fair value or fair value determined at the issuance date and remeasurement is not required. Warrants recorded as liabilities are recorded at their fair value, within warrant liability on the consolidated balance sheets, and remeasured on each reporting date with changes recorded in revaluation of warrant liability on the Company's consolidated statements of operations.
Fair Value of Financial Instruments	(c) Fair Value of Financial Instruments As a result of the Business Combination, the Company assumed a warrant liability (the "Warrant Liability") related to previously issued 3,940,278 warrants, each exercisable to purchase one share of common stock at an exercise price of $11.50 per share, originally sold to AMCI Sponsor LLC (the “Sponsor”) in a private placement consummated in connection with AMCI’s Initial Public Offering (the “Private Placement Warrants”) and the 400,000 warrants, each exercisable to purchase one share of common stock at an exercise price of $11.50 per share, converted from the Sponsor’s non-interest bearing loan to the Company of $400,000 in connection with the closing of the Business Combination (the “Working Capital Warrants”) (Note 12). The Private Placement Warrants and the Working Capital Warrants have substantially the same terms as the 22,029,279 warrants, each exercisable to purchase one share of common stock at an exercise price of $11.50 per share, issued by AMCI in its Initial Public Offering (the “Public Warrants”). The Warrant Liability is remeasured to its fair value at each reporting period and upon settlement. The change in fair value is recognized in revaluation of warrant liability on the consolidated statements of operations. The change in fair value of the warrant liability is as follows: Warrant Liability Estimated fair value at February 4, 2021 $ 33,116,321 Change in estimated fair value $ (15,833,334 ) Estimated fair value at September 30, 2021 $ 17,282,987 The estimated fair value of the Private Placement Warrants and the Working Capital Warrants (each as defined below) is determined using Level 3 inputs by using the Black-Scholes model. The application of the Black-Scholes model requires the use of a number of inputs and significant assumptions including volatility. Significant judgment is required in determining the expected volatility of our common stock. Due to the limited history of trading of our common stock, we determined expected volatility based on a peer group of publicly traded companies. The following table provides quantitative information regarding Level 3 fair value measurement inputs as of their measurement date September 30, 2021: Stock price $ 8.70 Exercise price (strike price) $ 11.50 Risk-free interest rate 0.83 % Volatility 67.30 % Remaining term (in years) 4.34 The Company performs routine procedures such as comparing prices obtained from independent source to ensure that appropriate fair values are recorded.
Earnings / (Loss) Per Share	(d) Earnings / (Loss) Per Share Earnings / (Loss) Per Share is computed by dividing earnings / (loss) by the weighted average number of common shares outstanding during the period. Diluted earnings / (loss) per share reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted at the beginning of the periods presented, or issuance date, if later. The treasury stock method is used to compute the dilutive effect of warrants.
Stock-based Compensation	(e) Stock-based Compensation Stock-based compensation consists of stock options and restricted stock units (“RSUs”). Stock options and restricted stock units are equity classified and are measured at the fair market value of the underlying stock at the grant date. Under ASC 718, an entity may recognize compensation cost for an award with only a service condition that has a graded vesting schedule on either (1) an accelerated basis as though each separately vesting portion of the award was, in substance, a separate award or (2) a straight-line basis over the total requisite service period for the entire award. An entity’s use of either a straight-line or an accelerated attribution method represents an accounting policy election and thus should be applied consistently to all similar awards. The Company has elected to recognize compensation cost on a straight-line basis over the total requisite service period for the stock options and restricted stock units. This election does not affect the Company’s previous year results since the Restricted Stock Awards granted in the prior period did not have a service requirement and therefore the stock compensation expense was recognized immediately. The Company has also a policy of accounting for forfeitures when they occur.
Recent Accounting Pronouncements	(f) Recent Accounting pronouncements Recently issued accounting pronouncements not yet adopted In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02, Leases (Topic 842), to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. In July 2018, ASU 2018-10, Codification Improvements to Topic 842, Leases, was issued to provide more detailed guidance and additional clarification for implementing ASU 2016-02. Furthermore, in July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements, which provides an optional transition method in addition to the existing modified retrospective transition method by allowing a cumulative effect adjustment to the opening balance of retained earnings in the period of adoption. Additionally, ASU 2019-01, Codification Improvements to Topic 842, Leases and ASU 2020-02, Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 119 and Update to SEC Section on Effective Date Related to Accounting Standards Update No. 2016-02, Leases (Topic 842), provided additional clarifications for implementing ASU 2016.02. The new lease standard was originally effective for private entities on January 1, 2021, with early adoption permitted. Following the issuance of ASU 2020-05, Effective Dates for Certain Entities (Topic 842), the effective date of Leases was deferred for private entities (the “all other” category) to fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early application continues to be permitted which means that an entity may choose to implement Leases before those deferred effective dates. The Company is currently evaluating the effect of the adoption of this guidance on the consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses of Financial Instruments, which, amends the requirement on the measurement and recognition of expected credit losses for financial assets held. Furthermore, amendments, ASU 2019-10 and ASU 2019-11 provided additional clarification for implementing ASU 2016-13. ASU 2016-13 is effective for the Company beginning January 1, 2023, with early adoption permitted. The Company is currently in the process of evaluating the effect of this guidance on the consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which is intended to simplify various aspects related to accounting for income taxes. The pronouncement is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2020 for public entities, with early adoption permitted. ASU 2019-12 is effective for the Company beginning January 1, 2022, taking the exemption allowed for the “emerging growth companies”

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
Summary of Significant Accounting Policies [Abstract]
Change in Fair Value of Warrant Liability	The Warrant Liability is remeasured to its fair value at each reporting period and upon settlement. The change in fair value is recognized in revaluation of warrant liability on the consolidated statements of operations. The change in fair value of the warrant liability is as follows: Warrant Liability Estimated fair value at February 4, 2021 $ 33,116,321 Change in estimated fair value $ (15,833,334 ) Estimated fair value at September 30, 2021 $ 17,282,987
Fair Value Measurements Input	The following table provides quantitative information regarding Level 3 fair value measurement inputs as of their measurement date September 30, 2021: Stock price $ 8.70 Exercise price (strike price) $ 11.50 Risk-free interest rate 0.83 % Volatility 67.30 % Remaining term (in years) 4.34

Business Combination (Tables)

Business Combination (Tables)	9 Months Ended
	Sep. 30, 2021
Business Acquisition [Line Items]
Reconciles the Elements of Business Combination to Consolidated Statements	The following table reconciles the elements of the Business Combination to the consolidated statement of cash flows and the consolidated statement of changes in equity for the nine months ended September 30, 2021: Recapitalization Cash- AMCI’s trust and cash (net of redemptions) $ 93,310,599 Cash – PIPE plus interest 65,000,118 Less transaction costs and advisory fees paid (17,188,519 ) Less non-cash warrant liability assumed (33,116,321 ) Net Business Combination and PIPE financing $ 108,005,877
Common Stock Issued Following the Consummation of Business Combination	The number of shares of common stock issued immediately following the consummation of the Business Combination: Recapitalization Class A Common A stock of AMCI, outstanding prior to Business Combination 9,061,136 Less Redemption of AMCI shares (1,606 ) Class B Common Stock of AMCI, outstanding prior to Business Combination 5,513,019 Shares issued in PIPE 6,500,000 Business Combination and PIPE financing shares 21,072,549 Legacy Advent Shares 25,033,398 Total shares of Common Stock immediately after Business Combination 46,105,947
UltraCell LLC [Member]
Business Acquisition [Line Items]
Assets Acquired and Liabilities Assumed	The assets acquired and liabilities assumed at the date of acquisition were as follows: Current assets Cash and cash equivalents $ 77,129 Other current assets 658,332 Total current assets $ 735,461 Non-current assets 9,187 Total assets $ 744,649 Current liabilities 110,179 Non-current liabilities - Total liabilities $ 110,179 Net assets acquired $ 634,469 Goodwill arising on acquisition Cost of investment $ 6,000,000 Net assets value 634,469 Consideration to be allocated $ 5,365,531 Fair value adjustment - New intangibles Trade name "UltraCell" 405,931 Patented technology 4,328,228 Total intangibles acquired $ 4,734,159 Remaining Goodwill $ 631,372
SerEnergy and FES [Member]
Business Acquisition [Line Items]
Assets Acquired and Liabilities Assumed	The assets acquired and liabilities assumed at the date of acquisition were as follows: Current assets Cash and cash equivalents $ 4,366,802 Other current assets 10,454,864 Total current assets $ 14,821,665 Non-current assets 5,434,180 Total assets $ 20,255,845 Current liabilities 5,818,170 Non-current liabilities 1,179,618 Total liabilities $ 6,997,788 Net assets acquired $ 13,258,057 Goodwill arising on acquisition Cost of investment Cash consideration $ 22,236,111 Share consideration 37,923,860 Total cost of investment 60,159,971 Less: Net assets value 13,258,057 Original excess purchase price $ 46,901,914 Fair value adjustments Real Property 76,000 New intangibles: Patents 17,275,000 Process know-how (IPR&D) 2,599,000 Order backlog 247,000 Total intangibles acquired $ 20,121,000 Deferred tax liability arising from the recognition of intangibles and real property valuation (4,444,000 ) Deferred tax assets on tax losses carried forward 1,915,000 Remaining Goodwill $ 29,233,914

Related party disclosures (Tabl

Related party disclosures (Tables)	9 Months Ended
	Sep. 30, 2021
Related party disclosures [Abstract]
Related Party Transactions	The amounts included in the accompanying consolidated balance sheets and consolidated statements of operations are as follows: September 30, 2021 (Unaudited) December 31, 2020 Due to related parties Unpaid compensation cost Unpaid compensation cost Vassilios Gregoriou $ - $ 613,971 Emory Sayre De Castro - 425,528 Christos Kaskavelis - 75,160 Charalampos Antoniou 30,000 - Total $ 30,000 $ 1,114,659 September 30, 2021 (Unaudited) December 31, 2020 Due from related parties Prepayment Prepayment Charalampos Antoniou $ - $ 67,781 Total $ - $ 67,781

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2021
Inventories [Abstract]
Inventories	Inventories consist of the following: September 30, 2021 (Unaudited) December 31, 2020 Raw materials and supplies $ 5,598,574 $ 107,939 Total $ 5,598,574 $ 107,939

Prepaid expenses and Other cu_2

Prepaid expenses and Other current assets (Tables)	9 Months Ended
	Sep. 30, 2021
Prepaid expenses and Other current assets [Abstract]
Prepaid expenses and Other current assets	Prepaid expenses and other current assets are analyzed as follows: September 30, 2021 (Unaudited) December 31, 2020 VAT receivable $ 826,973 $ 259,831 Grants receivable 597,155 95,064 Other current assets 520,007 140,126 Prepaid expenses 1,822,962 1,724 Total $ 3,767,096 $ 496,745

Trade and other payables (Table

Trade and other payables (Tables)	9 Months Ended
	Sep. 30, 2021
Trade and other payables [Abstract]
Trade and Other Payables	September 30, 2021 (Unaudited) December 31, 2020 Trade payables and other payables $ 5,522,624 $ 881,394 Total $ 5,522,624 $ 881,394

Other current liabilities (Tabl

Other current liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Other current liabilities [Abstract]
Other Current Liabilities	Other current liabilities are analyzed as follows: September 30, 2021 (Unaudited) December 31, 2020 Accrued expenses for legal and consulting fees $ 1,110,587 $ 814,965 Other accruals and short-term payables 6,485,032 89,414 Total $ 7,595,619 $ 904,379

Stockholders' Equity _ (Defic_2

Stockholders' Equity / (Deficit) (Tables)	9 Months Ended
	Sep. 30, 2021
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assumptions Used to Estimate the Fair Value of Stock Options	The following table presents the assumptions used to estimate the fair value of the stock options as of the Grant Date: Assumptions Stock options granted on June 11, 2021 Stock options granted on August 24, 2021 Stock options granted on August 31, 2021 Expected volatility 50.0 % 60.7 % 65.7 % Risk-free rate 1.0 % 1.0 % 1.0 % Time to maturity 6.075 years 6.25 years 6.25 years
Activities for Unvested Stock	The following table summarizes the activities for our unvested stock options for the nine months ended September 30, 2021: Unvested Shares Number of Shares Grant Date Fair Value Unvested as of December 31, 2020 - $ Granted on June 11, 2021 1,959,500 $ 5.04 Granted on August 24, 2021 230,529 $ 4.32 Granted on August 31, 2021 457,133 $ 4.45 Unvested as of September 30, 2021 2,647,162
Stock Options [Member] | 2021 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Activities for Unvested Stock	Stock options have been granted as follows: Grant date Number of shares Strike price June 11, 2021 1,959,500 $ 10.36 August 24, 2021 230,529 $ 7.62 August 31, 2021 457,133 $ 7.40
Unvested Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Activities for Unvested Stock	The following table summarizes the activities for our unvested restricted stock units ("RSUs") for the nine months ended September 30, 2021: Unvested Restricted Stock Units Number of Shares Grant Date Fair Value Unvested as of December 31, 2020 - Granted on June 11, 2021 2,036,716 $ 10.36 Granted on August 24, 2021 230,529 $ 7.62 Granted on August 31, 2021 457,122 $ 7.40 Unvested as of September 30, 2021 2,724,367
Unvested Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Activities for Unvested Stock	The following table summarizes the activities for our unvested restricted stock awards for the nine months ended September 30, 2020: Unvested Restricted Stock Awards Number of Shares Grant Date Fair Value Unvested as of December 31, 2019 - $ - Granted 2,173,702 $ 0.40 Unvested as of September 30, 2020 2,173,702 $ 0.40

Revenue, net (Tables)

Revenue, net (Tables)	9 Months Ended
	Sep. 30, 2021
Revenue, net [Abstract]
Revenue, Net	Revenue, net is analyzed as follows: Three months ended September 30, (Unaudited) Nine months ended September 30, (Unaudited) 2021 2020 2021 2020 Sales of goods $ 1,673,998 $ 225,412 $ 4,166,754 $ 526,032 Total revenue from contracts with customers $ 1,673,998 $ 225,412 $ 4,166,754 $ 526,032

Net income _ (loss) per share (

Net income / (loss) per share (Tables)	9 Months Ended
	Sep. 30, 2021
Net income / (loss) per share [Abstract]
Computation of Basic and Diluted Net Loss Per Share	The following table sets forth the computation of the basic and diluted net income / (loss) per share for the three months ended September 30, 2021 and 2020 and the nine months ended September 30, 2021 and 2020. Three months ended September 30, (Unaudited) Nine months ended September 30, (Unaudited) 2021 2020 2021 2020 Numerator: Net loss $ (11,279,722 ) $ (748,816 ) $ (11,517,360 ) $ (1,418,037 ) Denominator: Basic weighted average number of shares 48,325,164 23,182,817 43,982,039 21,180,639 Diluted weighted average number of shares 48,325,164 23,182,817 43,982,039 21,180,639 Net loss per share: Basic $ (0.23 ) $ (0.03 ) $ (0.26 ) $ (0.07 ) Diluted $ (0.23 ) $ (0.03 ) $ (0.26 ) $ (0.07 )

Basis of presentation (Details)

Basis of presentation (Details) - $ / shares	Sep. 30, 2021	Feb. 04, 2021	Dec. 31, 2020
Basis of Presentation [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001		$ 0.0001
AMCI Acquisition Corp. [Member]
Basis of Presentation [Abstract]
Acquired percentage		100.00%
Common stock, par value (in dollars per share)		$ 0.0001

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details)	8 Months Ended	9 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2021USD ($)Reportingunit$ / sharesshares	Mar. 31, 2021shares
Summary of Significant Accounting Policies [Abstract]
Number of reporting units | Reportingunit		1
Warrant [Member]
Fair Value Measurements [Abstract]
Remaining term	4 years 4 months 2 days	4 years 4 months 2 days
Stock Price [Member] | Warrant [Member]
Fair Value Measurements [Abstract]
Measurement input | $	8.70	8.70
Exercise Price [Member] | Warrant [Member]
Fair Value Measurements [Abstract]
Measurement input | $	11.50	11.50
Risk-free interest rate [Member] | Warrant [Member]
Fair Value Measurements [Abstract]
Measurement input	0.0083	0.0083
Volatility [Member] | Warrant [Member]
Fair Value Measurements [Abstract]
Measurement input | $	0.6730	0.6730
Warrant Liabilities [Member]
Warrants [Abstract]
Warrants issued (in shares)		3,940,278
Changes in Fair Value of Warrant Liabilities [Roll Forward]
Estimated fair value at beginning balance | $	$ 33,116,321
Change in estimated fair value | $	(15,833,334)
Estimated fair value at ending balance | $	$ 17,282,987	$ 17,282,987
Common Stock [Member]
Warrants [Abstract]
Number of shares called by each warrant (in shares)			1
Common Stock [Member] | Warrant Liabilities [Member]
Warrants [Abstract]
Number of shares called by each warrant (in shares)	1	1
Exercise price (in dollars per share) | $ / shares	$ 11.50	$ 11.50
Private Placement Warrants [Member]
Warrants [Abstract]
Warrants issued (in shares)		22,029,279
Number of shares called by each warrant (in shares)	1	1
Exercise price (in dollars per share) | $ / shares	$ 11.50	$ 11.50
Fair Value Measurements [Abstract]
Remaining term	5 years	5 years
Private Placement Warrants [Member] | Common Stock [Member]
Warrants [Abstract]
Number of shares called by each warrant (in shares)	1	1
Exercise price (in dollars per share) | $ / shares	$ 11.50	$ 11.50
Working Capital Warrants [Member]
Warrants [Abstract]
Warrants issued (in shares)		400,000
Number of shares called by each warrant (in shares)	1	1
Exercise price (in dollars per share) | $ / shares	$ 11.50	$ 11.50
Fair Value Measurements [Abstract]
Remaining term	5 years	5 years
Working Capital Warrants [Member] | Common Stock [Member]
Warrants [Abstract]
Number of shares called by each warrant (in shares)	1	1
Exercise price (in dollars per share) | $ / shares	$ 11.50	$ 11.50
Sponsor [Member]
Warrants [Abstract]
Non-interest bearing loan | $		$ 400,000

Business Combination, AMCI Acqu

Business Combination, AMCI Acquisition Corp (Details) - USD ($)	Feb. 04, 2021	Sep. 30, 2021	Dec. 31, 2020
Business Combination, Description [Abstract]
Common stock, shares authorized (in shares)		110,000,000	110,000,000
Common stock, par value (in dollars per share)		$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)		1,000,000	1,000,000
Preferred stock, par value (in dollars per share)		$ 0.0001	$ 0.0001
Consummation of Business Combination [Abstract]
Common stock, shares outstanding (in shares)		51,253,591	25,033,398
AMCI Acquisition Corp. [Member]
Business Combination, Description [Abstract]
Merger consideration	$ 250,000,000
Purchase price (in dollars per share)	$ 10
Authorized issuance of shares (in shares)	111,000,000
Common stock, shares authorized (in shares)	110,000,000
Common stock, par value (in dollars per share)	$ 0.0001
Preferred stock, shares authorized (in shares)	1,000,000
Preferred stock, par value (in dollars per share)	$ 0.0001
Goodwill	$ 0
Intangible assets	$ 0
Business Combination to consolidated statements [Abstract]
Proceeds from issuance of common stock		$ 93,310,599
Less transaction costs and advisory fees paid		(17,188,519)
Less non-cash warrant liability assumed		$ (33,116,321)
Consummation of Business Combination [Abstract]
Common stock, shares outstanding (in shares)		46,105,947
Less Redemption of AMCI shares (in shares)		(1,606)
AMCI Acquisition Corp. [Member] | Legacy [Member]
Consummation of Business Combination [Abstract]
Common stock, shares outstanding (in shares)		25,033,398
AMCI Acquisition Corp. [Member] | PIPE [Member]
Business Combination, Description [Abstract]
Purchase price (in dollars per share)	$ 10
Business Combination to consolidated statements [Abstract]
Proceeds from issuance of common stock		$ 65,000,118
Net Business Combination and PIPE financing		$ 108,005,877
Consummation of Business Combination [Abstract]
Common stock, shares outstanding (in shares)		21,072,549
Common stock, shares issued (in shares)		6,500,000
AMCI Acquisition Corp. [Member] | Class A Common Stock [Member]
Consummation of Business Combination [Abstract]
Common stock, shares outstanding (in shares)		9,061,136
AMCI Acquisition Corp. [Member] | Class B Common Stock [Member]
Consummation of Business Combination [Abstract]
Common stock, shares outstanding (in shares)		5,513,019

Business Combination, UltraCell

Business Combination, UltraCell LLC (Details) - UltraCell LLC [Member]	Feb. 18, 2021USD ($)
Business Combination, Description [Abstract]
Acquired percentage	100.00%
Merger consideration	$ 6,000,000
Payments to acquire business combination	4,000,000
Fair value of contingent consideration	2,000,000
Additional cash required to pay contingent consideration	2,000,000
Current Assets [Abstract]
Cash and cash equivalents	77,129
Other current assets	658,332
Total current assets	735,461
Non-current assets	9,187
Total assets	744,649
Current liabilities	110,179
Non-current liabilities	0
Total liabilities	110,179
Net assets acquired	634,469
Goodwill Arising on Acquisition [Abstract]
Cost of investment	6,000,000
Net assets value	634,469
Consideration to be allocated	5,365,531
Intangibles acquired	4,734,159
Remaining Goodwill	631,372
Trade Name [Member]
Goodwill Arising on Acquisition [Abstract]
Intangibles acquired	$ 405,931
Trade Name [Member] | Royalty Rate [Member]
Goodwill Arising on Acquisition [Abstract]
Intangible assets, measurement input	0.013
Trade Name [Member] | Discount Rate [Member]
Goodwill Arising on Acquisition [Abstract]
Intangible assets, measurement input	0.126
Patented Technology [Member]
Goodwill Arising on Acquisition [Abstract]
Intangibles acquired	$ 4,328,228
Useful lives of assets	10 years
Patented Technology [Member] | Discount Rate [Member]
Goodwill Arising on Acquisition [Abstract]
Intangible assets, measurement input	0.116
Assembled Workforce [Member]
Goodwill Arising on Acquisition [Abstract]
Remaining Goodwill	$ 190,000

Business Combination, SerEnergy

Business Combination, SerEnergy and FES (Details)	Aug. 31, 2021USD ($)GroupCustomer$ / sharesWkWshares	Aug. 31, 2021EUR (€)CustomerWkWshares	Sep. 30, 2021USD ($)$ / shares	Sep. 30, 2021USD ($)$ / shares	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)$ / shares	Sep. 30, 2020USD ($)	Dec. 31, 2020$ / shares
Business Combination, Description [Abstract]
Revenue, net				$ 1,673,998	$ 225,412	$ 4,166,754	$ 526,032
Net loss				$ (11,279,722)	(748,816)	$ (11,517,360)	(1,418,037)
Common stock, par value (in dollars per share) | $ / shares			$ 0.0001	$ 0.0001		$ 0.0001		$ 0.0001
Cost of Investment [Abstract]
Share consideration				$ 37,923,860		$ 37,923,860
SerEnergy and FES [Member]
Business Combination, Description [Abstract]
Revenue, net			$ 791,626
Net loss			$ (834,944)
Pro-forma revenues				3,900,000	500,000	13,100,000	2,400,000
Pro-forma net loss				$ (13,100,000)	$ (2,500,000)	$ (20,300,000)	$ (11,600,000)
Consideration paid	$ 17,869,309	€ 15,000,000
Issued to the seller shares of common stock (in shares) | shares	5,124,846	5,124,846
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001
Percentage of share consideration	9.999%	9.999%
Transaction costs	$ 889,716
Current Assets [Abstract]
Cash and cash equivalents	4,366,802
Other current assets	10,454,864
Total current assets	14,821,665
Non-current assets	5,434,180
Total assets	20,255,845
Current liabilities	5,818,170
Non-current liabilities	1,179,618
Total liabilities	6,997,788
Net assets acquired	13,258,057
Cost of Investment [Abstract]
Cash consideration	22,236,111
Share consideration	37,923,860
Cost of investment	60,159,971
Net assets value	13,258,057
Original excess purchase price	46,901,914
Fair value adjustment of Real Property	76,000
Intangibles acquired	20,121,000
Deferred tax liability arising from the recognition of intangibles and real property valuation	(4,444,000)
Deferred tax assets on tax losses carried forward	1,915,000
Remaining Goodwill	$ 29,233,914
SerEnergy and FES [Member] | Minimum [Member]
Cost of Investment [Abstract]
High temperature-PEM fuel cells coverage | W	25	25
SerEnergy and FES [Member] | Maximum [Member]
Cost of Investment [Abstract]
High temperature-PEM fuel cells coverage | kW	90	90
SerEnergy and FES [Member] | Assembled Workforce [Member]
Cost of Investment [Abstract]
Remaining Goodwill	$ 2,400,000
SerEnergy and FES [Member] | Patents [Member]
Cost of Investment [Abstract]
Intangibles acquired	$ 17,275,000
Number of group patents | Group	2
Intangible assets, measurement input	0.072
Useful lives of assets	10 years	10 years
Period of drive cash flows after new patents will be more relevance	10 years	10 years
Number of main customers | Customer	2	2
SerEnergy and FES [Member] | Process know-how (IPR&D) [Member]
Cost of Investment [Abstract]
Intangibles acquired	$ 2,599,000
Intangible assets, measurement input	0.101
Useful lives of assets	6 years	6 years
SerEnergy and FES [Member] | Order Backlog [Member]
Cost of Investment [Abstract]
Intangibles acquired	$ 247,000

Related party disclosures (Deta

Related party disclosures (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Due to Related Parties [Abstract]
Unpaid compensation cost	$ 30,000	$ 1,114,659
Due from Related Parties [Abstract]
Prepayment	0	67,781
Related Party Transaction [Abstract]
Related party transaction amount	5,600,000
Vassilios Gregoriou [Member]
Due to Related Parties [Abstract]
Unpaid compensation cost	0	613,971
Christos Kaskavelis [Member]
Due to Related Parties [Abstract]
Unpaid compensation cost	0	75,160
Emory Sayre De Castro [Member]
Due to Related Parties [Abstract]
Unpaid compensation cost	0	425,528
Charalampos Antoniou [Member]
Due to Related Parties [Abstract]
Unpaid compensation cost	30,000	0
Due from Related Parties [Abstract]
Prepayment	$ 0	$ 67,781

Inventories (Details)

Inventories (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Inventories [Abstract]
Raw materials and supplies	$ 5,598,574	$ 107,939
Total	$ 5,598,574	$ 107,939

Prepaid expenses and Other cu_3

Prepaid expenses and Other current assets (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Prepaid expenses and Other current assets [Abstract]
VAT receivable	$ 826,973	$ 259,831
Grants receivable	597,155	95,064
Other current assets	520,007	140,126
Prepaid expenses	1,822,962	1,724
Total	$ 3,767,096	$ 496,745

Property and equipment, net (De

Property and equipment, net (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Property, Plant and Equipment, Net, by Type [Abstract]
Addition to property and equipment	$ 2,700
UltraCell LLC [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment with net book value	10
SerEnergy and FES [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment with net book value	$ 5,400

Other non-current assets (Detai

Other non-current assets (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Other Assets, Noncurrent [Abstract]
Other Assets, Noncurrent	$ 2,155,156	$ 136
Fixed Assets [Member]
Other Assets, Noncurrent [Abstract]
Other Assets, Noncurrent	1,917,856
Rental Premises [Member]
Other Assets, Noncurrent [Abstract]
Other Assets, Noncurrent	$ 167,626

Trade and other payables (Detai

Trade and other payables (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Trade and other payables [Abstract]
Trade payables and other payables	$ 5,522,624	$ 881,394
Total	5,522,624	$ 881,394
Executive severance payable	$ 1,800,000

Other current liabilities (Deta

Other current liabilities (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Other current liabilities [Abstract]
Accrued expenses for legal and consulting fees	$ 1,110,587	$ 814,965
Other accruals and short-term payables	6,485,032	89,414
Total	7,595,619	$ 904,379
Consideration payables for acquisition	4,366,802
Accrued warranty reserve, current	$ 127,104

Other long-term liabilities (De

Other long-term liabilities (Details)	Sep. 30, 2021USD ($)
Other long-term liabilities [Abstract]
Accrued warranty reserve, non-current	$ 940,972
Total accrued warranty reserve	$ 1,068,076
Percentage of accrued warranty reserve on sale price of fuel cells sold	8.00%

Private Placement Warrants an_2

Private Placement Warrants and Working Capital Warrants (Details)	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Private Placement Warrant [Member]
Private Placement Warrants [Abstract]
Warrants issued (in shares)	22,029,279
Warrants outstanding (in shares)	4,340,278
Number of shares called by each warrant (in shares)	1
Exercise price (in dollars per share) | $ / shares	$ 11.50
Period to exercise warrants after business combination	30 days
Warrants expiration period	5 years
Period not to transfer, assign or sell warrants	30 days
Working Capital Warrants [Member]
Private Placement Warrants [Abstract]
Warrants issued (in shares)	400,000
Warrants outstanding (in shares)	4,340,278
Number of shares called by each warrant (in shares)	1
Exercise price (in dollars per share) | $ / shares	$ 11.50
Period to exercise warrants after business combination	30 days
Warrants expiration period	5 years
Period not to transfer, assign or sell warrants	30 days
Initial Public Offering [Member] | Private Placement Warrant [Member]
Private Placement Warrants [Abstract]
Warrants issued (in shares)	3,940,278

Stockholders' Equity _ (Defic_3

Stockholders' Equity / (Deficit), Shares Authorized and Common Stock, Public Warrants (Details) - USD ($)	3 Months Ended	9 Months Ended
	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Aug. 31, 2021	Aug. 09, 2021	Mar. 31, 2021	Dec. 31, 2020
Stockholders' Equity (Deficit) [Abstract]
Shares authorized (in shares)		111,000,000
Common stock, shares authorized (in shares)		110,000,000					110,000,000
Common stock, par value (in dollars per share)		$ 0.0001					$ 0.0001
Preferred stock, shares authorized (in shares)		1,000,000					1,000,000
Preferred stock, par value (in dollars per share)		$ 0.0001					$ 0.0001
Common Stock [Abstract]
Common stock, shares issued (in shares)		51,253,591		5,124,846			25,033,398
Common stock, shares outstanding (in shares)		51,253,591					25,033,398
Warrants [Abstract]
Proceeds from exercise of warrants		$ 262,177	$ 0
Common Stock [Member]
Warrants [Abstract]
Number of shares called by each warrant (in shares)						1
Increase in shares outstanding (in shares)		22,798
Public Warrants [Member]
Common Stock [Abstract]
Common stock, shares issued (in shares)					22,798
Warrants [Abstract]
Warrants outstanding (in shares)		22,029,279				22,052,077
Exercise price of warrant (in dollars per share)	$ 11.50					$ 11.50
Period to exercise warrants after business combination		30 days
Expiration period of warrants		5 years
Warrant holders exercised options to purchase additional shares (in shares)	22,798
Proceeds from exercise of warrants	$ 262,177
Increase in shares outstanding (in shares)	22,798
Warrant redemption price (in dollars per share)		$ 0.01
Notice period to redeem warrants		30 days
Share price (in dollars per share)		$ 18
Threshold trading days		20 days
Threshold consecutive trading days		30 days
Public Warrants [Member] | Minimum [Member]
Warrants [Abstract]
Percentage of company's stockholders		50.00%

Stockholders' Equity _ (Defic_4

Stockholders' Equity / (Deficit), Compensation Plans (Details)	Jun. 11, 2021shares
2021 Equity Incentive Plan [Member]
Compensation Plans [Abstract]
Maximum number of shares of stock (in shares)	6,915,892

Stockholders' Equity _ (Defic_5

Stockholders' Equity / (Deficit), Stock Options (Details) - Stock Options [Member]	9 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares
Share-based Payment Arrangement, Additional Disclosure [Abstract]
Vesting on graded basis	4 years
Compensation cost | $	$ 1,218,532
Number of Shares [Roll Forward]
Unvested, beginning of period (in shares)	0
Unvested, ending of period (in shares)	2,647,162
Grant Date Fair Value [Abstract]
Unrecognized compensation cost | $	$ 11,700,000
Stock Options Granted on June 11, 2021 [Member]
Grant Date of Stock Options [Abstract]
Number of shares (in shares)	1,959,500
Strike price (in dollars per share) | $ / shares	$ 10.36
Fair Value of Options Granted [Abstract]
Expected volatility	50.00%
Risk-free rate	1.00%
Time to maturity	6 years 27 days
Number of Shares [Roll Forward]
Granted (in shares)	1,959,500
Grant Date Fair Value [Abstract]
Granted (in dollars per share) | $ / shares	$ 5.04
Stock Options Granted on August 24, 2021 [Member]
Grant Date of Stock Options [Abstract]
Number of shares (in shares)	230,529
Strike price (in dollars per share) | $ / shares	$ 7.62
Fair Value of Options Granted [Abstract]
Expected volatility	60.70%
Risk-free rate	1.00%
Time to maturity	6 years 3 months
Number of Shares [Roll Forward]
Granted (in shares)	230,529
Grant Date Fair Value [Abstract]
Granted (in dollars per share) | $ / shares	$ 4.32
Stock Options Granted on August 31, 2021 [Member]
Grant Date of Stock Options [Abstract]
Number of shares (in shares)	457,133
Strike price (in dollars per share) | $ / shares	$ 7.40
Fair Value of Options Granted [Abstract]
Expected volatility	65.70%
Risk-free rate	1.00%
Time to maturity	6 years 3 months
Number of Shares [Roll Forward]
Granted (in shares)	457,133
Grant Date Fair Value [Abstract]
Granted (in dollars per share) | $ / shares	$ 4.45

Stockholders' Equity _ (Defic_6

Stockholders' Equity / (Deficit), Restricted Stock Units and Stock Grant Plans (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 11, 2021	Dec. 31, 2020	Sep. 09, 2020
2021 Equity Incentive Plan [Member]
Share-based Payment Arrangement, Additional Disclosure [Abstract]
Maximum number of shares of stock (in shares)			6,915,892
Unvested Restricted Stock Units [Member] | 2021 Equity Incentive Plan [Member]
Share-based Payment Arrangement, Additional Disclosure [Abstract]
Number of shares, right to receive (in shares)	1
Restricted Stock Unit Agreement vesting term	1 year
Vesting on graded basis	4 years
Compensation cost	$ 2,790,176
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested, beginning of period (in shares)	0
Unvested, ending of period (in shares)	2,724,367
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Unrecognized compensation cost	$ 23,400,000
Unvested Restricted Stock Units [Member] | 2021 Equity Incentive Plan [Member] | Stock Options Granted on June 11, 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted in number of share (in shares)	2,036,716
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Granted in fair value (in dollars per share)	$ 10.36
Unvested Restricted Stock Units [Member] | 2021 Equity Incentive Plan [Member] | Stock Options Granted on August 24, 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted in number of share (in shares)	230,529
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Granted in fair value (in dollars per share)	$ 7.62
Unvested Restricted Stock Units [Member] | 2021 Equity Incentive Plan [Member] | Stock Options Granted on August 31, 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted in number of share (in shares)	457,122
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Granted in fair value (in dollars per share)	$ 7.40
Unvested Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Unrecognized compensation cost		$ 200,000
Unvested Restricted Stock Awards [Member] | 2018-2020 Stock Grant Plan [Member]
Share-based Payment Arrangement, Additional Disclosure [Abstract]
Maximum number of shares of stock (in shares)	1,280,199
Granted (in shares)	1,280,199
Purchase price (in dollars per share)	$ 0.01			$ 0.01
Compensation cost	$ 413,396
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested, beginning of period (in shares)		0
Granted in number of share (in shares)		2,173,702
Unvested, ending of period (in shares)		2,173,702
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Unvested as of beginning of period (in dollars per share)		$ 0
Granted in fair value (in dollars per share)		0.40
Unvested as of ending of period (in dollars per share)		$ 0.40
Unrecognized compensation cost		$ 300,000
Unvested Restricted Stock Awards [Member] | 2020-2023 Stock Grant Plan [Member]
Share-based Payment Arrangement, Additional Disclosure [Abstract]
Maximum number of shares of stock (in shares)					893,503
Granted (in shares)	893,503
Purchase price (in dollars per share)					$ 0.01
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Unrecognized compensation cost		$ 500,000

Revenue, net (Details)

Revenue, net (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Abstract]
Revenue from contracts with customers		$ 1,673,998	$ 225,412	$ 4,166,754	$ 526,032
Contract assets	$ 936,259	936,259		936,259		$ 85,930
Contract liabilities	28,832	28,832		28,832		$ 167,761
SerEnergy and FES [Member]
Disaggregation of Revenue [Abstract]
Revenue from contracts with customers	$ 791,626
Sales of Goods [Member]
Disaggregation of Revenue [Abstract]
Revenue from contracts with customers		$ 1,673,998	$ 225,412	$ 4,166,754	$ 526,032

Commitments and contingencies (

Commitments and contingencies (Details)	Aug. 31, 2021EUR (€)ft²	Sep. 30, 2021USD ($)	Mar. 08, 2021USD ($)ft²	Feb. 04, 2021USD ($)ft²
Guarantees Letters [Abstract]
Issued letters of guarantee		$ 2,776,164
Operating Leases [Abstract]
Area of leased space | ft²	1,017		21,401	6,041
Annual rent			$ 1,498,070	$ 456,095
Lease contract term			8 years 5 months	5 years
Security deposit			$ 750,000
Monthly basic rate plus VAT | €	€ 7,768
Term of option to extend lease			5 years
Maximum [Member]
Operating Leases [Abstract]
Security deposit | €	€ 30,000
Other Non-current Assets [Member]
Operating Leases [Abstract]
Security deposit				$ 114,023

Net income _ (loss) per share_2

Net income / (loss) per share (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator [Abstract]
Net loss	$ (11,279,722)	$ (748,816)	$ (11,517,360)	$ (1,418,037)
Denominator [Abstract]
Basic weighted average number of shares (in shares)	48,325,164	23,182,817	43,982,039	21,180,639
Diluted weighted average number of shares (in shares)	48,325,164	23,182,817	43,982,039	21,180,639
Net loss per share [Abstract]
Basic (in dollars per share)	$ (0.23)	$ (0.03)	$ (0.26)	$ (0.07)
Diluted (in dollars per share)	$ (0.23)	$ (0.03)	$ (0.26)	$ (0.07)