New CUSIP Number. After the Effective Time, the post-Reverse Stock Split shares of Common Stock would have a new CUSIP number, which is a number used to identify our equity securities.

Effectiveness of Reverse Stock Split. The Reverse Stock Split, if approved by stockholders, would become effective upon the date determined by the Board and, if required by law or otherwise deemed advisable by the Board, upon the filing of a Certificate of Amendment to our Certificate of Incorporation with the Secretary of State of the State of Delaware. It is expected that this filing will take place promptly following the Special Meeting, assuming the stockholders approve the Reverse Split Proposal. However, the exact timing of the filing of the Certificate of Amendment will be determined by the Board based on its evaluation as to when such action will be the most advantageous to the Company and our stockholders. In addition, the Board reserves the right, notwithstanding stockholder approval and without further action by the stockholders, to elect not to proceed with the Reverse Split Proposal if, at any time before the Effective Time, the Board, in its sole discretion, determines that it is no longer in our and our stockholders’ best interests to proceed with the Reverse Split Proposal.

Effect on the Company’s Stock Plans. As of February 2, 2021, we reserved approximately 6,915,892 shares of Common Stock in connection with our Plans and equity awards. Under the terms of the Plan, in the event of a stock split, the Compensation Committee of the Board (the “Compensation Committee”), acting as Administrator of the Plan, shall make appropriate adjustments to the maximum number of shares of stock specified in Section 4(a) therein that may be delivered under the Plan, and will make appropriate adjustments to the number and kind of shares of stock or securities underlying equity awards then outstanding or subsequently granted, any exercise or purchase prices (or base values) relating to equity awards and any other provision of the equity awards affected by such change. In accordance with such provision, upon implementation of the Reverse Split Proposal, the Compensation Committee has determined to make certain equitable adjustments to the number of shares issuable upon the vesting of outstanding restricted stock units, per share exercise price and the number of shares issuable upon the exercise of stock options under the Plans and proportionately adjust the aggregate number of shares reserved for issuance and the aggregate number of shares that may be issued pursuant to incentive stock options based on the Final Ratio determined by the Board. In addition, pursuant to the authority provided under the Plans, the Compensation Committee, or the Board, as applicable, is expected to authorize the Company to effect any other changes necessary, desirable, or appropriate to give effect to the Reverse Split Proposal, including any applicable technical, conforming changes to our Plans. The Compensation Committee or the Board will also determine the treatment of fractional shares subject to stock options and other outstanding awards under the Plans.

Effect on Authorized but Unissued Shares of Common Stock. Currently, we are authorized in our Certificate of Incorporation to issue up to a total of 500,000,000 shares of Common Stock. The total number of authorized shares of Common Stock will not change as a result of the Reverse Stock Split. As of the Record Date, we had 77,618,716 shares of Common Stock outstanding and no shares of Common Stock held in treasury. As described above, the Reverse Stock Split would have the effect of reducing the number of issued and outstanding shares of Common Stock, the number of shares of Common Stock held in treasury, and the number of shares of Common Stock reserved for issuance pursuant to our stock plans. Therefore, because the total number of authorized shares of Common Stock will not change as a result of the Reverse Stock Split, upon the effectiveness of the Reverse Stock Split, the number of authorized shares of Common Stock that are not issued or reserved for issuance would increase. All authorized but unissued shares that are not reserved for issuance would remain available for issuance by the Board for general corporate purposes at any time, at its discretion, without stockholder approval. If the Board were to authorize the issuance of any such shares, such issuances could dilute the ownership interests of holders of Common Stock and may also cause a decline in the trading price of our Common Stock.

Effect on Warrants. If the Reverse Stock Split is effected, proportionate adjustments are generally required to be made to the per share exercise price and the number of shares issuable upon the exercise of Warrants to Purchase Common Stock into shares of Common Stock. This will result in approximately the same aggregate price being required to be paid under such securities upon exercise or conversion, and approximately the same value of shares of Common Stock being delivered upon such exercise immediately following the Reverse Stock Split as was the case immediately preceding the Reverse Stock Split. The number of shares reserved for issuance pursuant to these securities will be proportionately adjusted based on the Final Ratio, subject to our treatment of fractional shares.

Potential Anti-Takeover Effect. This proposal, if adopted and implemented, will result in a relative increase in the number of authorized but unissued shares of Common Stock vis-à-vis the outstanding shares of Common Stock and could, under certain circumstances, have an anti-takeover effect. For example, the issuance of a large block of Common Stock could dilute the stock ownership of a person seeking to effect a change in the composition of the Board or contemplating a tender offer or other transaction for the combination of the Company with another company. However, the Reverse Split Proposal providing for the Reverse Stock Split is not being proposed in response to any effort of which the Company is aware to accumulate shares of Common Stock or obtain control of the Company, nor is it part of a plan by management to recommend to the Board and stockholders a series of amendments to the Certificate of Incorporation. Other than the Reverse Split Proposal for the Reverse Stock Split, the Board does not currently contemplate recommending the adoption of any other amendments to the Certificate of Incorporation that could be construed to reduce or interfere with the ability of third parties to take over or change the control of the Company.

Fractional Shares. Stockholders will not receive fractional post-Reverse Stock Split shares in connection with the Reverse Stock Split. Instead, we will pay to each registered stockholder, in cash, the value of any fractional share interest in our Common Stock arising from the Reverse Stock Split. The cash payment would equal the fraction to which the stockholder would otherwise be entitled multiplied by the closing sales price of the common stock as reported on Nasdaq, as of the effective date of the Reverse Stock Split.

Effect on Par Value; Reduction in Stated Capital. The Reverse Stock Split will not affect the par value of our Common Stock, which will remain at $0.0001 per share of Common Stock. As a result, the stated capital on our balance sheet attributable to our Common Stock, which consists of the par value per share of Common Stock multiplied by the aggregate number of shares of Common Stock issued (including treasury shares), will be reduced in proportion to the Final Ratio selected by the Board. Correspondingly, our additional paid-in capital account, which consists of the difference between our stated capital and the aggregate amount paid to the Company upon issuance of all currently outstanding shares of the Common Stock, will be increased by the amount by which the stated capital is reduced. Our stockholders’ equity, in the aggregate, will remain unchanged.

No Going Private Transaction. Notwithstanding the decrease in the number of outstanding shares of Common Stock following the proposed Reverse Stock Split, the Board does not intend for this transaction to be the first step in a “going private transaction” within the meaning of Rule 13e-3 of the Exchange Act.

No Appraisal or Dissenter’s Rights. Under Delaware law, holders of Common Stock will not be entitled to dissenter’s rights or appraisal rights with respect to the Reverse Split Proposal.

Effect on Registered and Beneficial Holders. If the Reverse Stock Split is effected, we intend to treat beneficial holders (i.e., stockholders who hold their shares in “street name” through a bank, broker or other nominee) in the same manner as registered stockholders whose shares are registered in their names. Banks, brokers or other nominees will be instructed to effect the Reverse Stock Split for their beneficial holders holding shares in “street name.” However, these banks, brokers or other nominees may have different procedures than registered stockholders for processing the Reverse Stock Split. Stockholders who hold shares of our Common Stock with a smaller reporting companybank, broker, or other nominee and who have questions in this regard are encouraged to contact their banks, brokers or other nominees.

Effect on Registered Book-Entry Holders. Some of our registered stockholders may hold some or all of their shares electronically in book-entry form under the direct registration system for securities. These stockholders do not have stock certificates evidencing their ownership of Common Stock. Instead, they are provided with a statement reflecting the number of shares registered in their accounts. If you hold shares in book-entry form, you do not need to take any action following the Effective Time in order for your shares to be adjusted to reflect the Reverse Stock Split, subject to the treatment of fractional shares, if applicable. If you are entitled to post-Reverse Stock Split shares, a transaction statement will automatically be sent to your address of record indicating the number of shares you hold following the Effective Time.

Reservation of Right to Abandon the Reverse Split Proposal

The Board reserves the right to abandon the Reverse Split Proposal without further action by our stockholders at any time before the Effective Time, even if stockholders approve such amendment at the time we cease to be an emerging growth company, we may continue to rely on exemptions from certain disclosure requirements that are available to smaller reporting companies. Specifically, as a smaller reporting company we may choose to present only the two most recent fiscal years of audited financial statementsSpecial Meeting. By voting in our Annual Report on Form 10-K and, similar to emerging growth companies, smaller reporting companies have reduced disclosure obligations regarding executive compensation.

Interests of Directors and Executive Officers

Certain of our officers and directors have an interest in the Reverse Split Proposal as a result of their ownership of shares of Common Stock. However, we do not believe that our officers or directors have interests in the Reverse Split Proposal that are different than or greater than those of any of our other stockholders.

Material U.S. Federal Income Tax Consequences of the Reverse Stock Split

The following discussion is a summary of the material U.S. federal income tax consequences of the proposed Reverse Stock Split to us and to U.S. Holders (as defined below) that hold shares of Common Stock as capital assets for U.S. federal income tax purposes (generally, property held for investment). This discussion is based on the Internal Revenue Code of 1986, as amended, which we refer to as the Code, U.S. Treasury Regulations promulgated thereunder, judicial decisions, and published rulings and administrative pronouncements of the U.S. Internal Revenue Service, which we refer to as the IRS, in each case in effect as of the date of this proxy statement. These authorities may change or be subject to differing interpretations. Any such change or differing interpretation may be applied retroactively in a manner that could adversely affect us or a U.S. Holder. We have not sought and will not seek any rulings from the IRS regarding the matters discussed below and there can be no assurance that the person should be re-electedIRS or electeda court will not take a contrary position to that discussed below regarding the tax consequences of the proposed Reverse Stock Split.

For purposes of this discussion, a “U.S. Holder” is a beneficial owner of Common Stock that, for U.S. federal income tax purposes, is or is treated as (i) an individual who is a citizen or resident of the United States; (ii) a corporation (or any other entity or arrangement treated as a directorcorporation) created or organized under the laws of the Company.

In addition, it does not address consequences relevant to U.S. Holders that are subject to special rules, including, without limitation, financial institutions, insurance companies, real estate investment trusts, regulated investment companies, grantor trusts, tax-exempt organizations, dealers or traders in securities, commodities or currencies, stockholders who hold Common Stock as part of a position in a straddle or as part of a hedging, conversion or integrated transaction for U.S. federal income tax purposes, persons whose functional currency is not the U.S. dollar, or U.S. Holders who actually or constructively own 10% or more of our Board, namely our audit, compensation and nominating and corporate governance committees. The directors serving on each committee are listedvoting stock.

If a partnership (or other entity treated as a partnership for U.S. federal income tax purposes) is the beneficial owner of Common Stock, the U.S. federal income tax treatment of a partner in the descriptions below. Our directorspartnership will generally depend on the status of the partner and the activities of the partnership. Accordingly, partnerships (and other entities treated as partnerships for U.S. federal income tax purposes) holding Common Stock and the partners in such entities should consult their own tax advisors regarding the U.S. federal income tax consequences of the proposed Reverse Stock Split to them.

In addition, the following discussion does not address the U.S. federal estate and gift tax, alternative minimum tax, or state, local and non-U.S. tax law consequences of the proposed Reverse Stock Split. Furthermore, the following discussion does not address any tax consequences of transactions effectuated before, after or at the same time as the proposed Reverse Stock Split, whether or not they are in connection with the proposed Reverse Stock Split. This discussion should not be considered as tax or investment advice, and the tax consequences of the proposed Reverse Stock Split may also servenot be the same for all stockholders.

Each stockholder should consult his, her or its own tax advisors concerning the particular U.S. federal tax consequences of the Reverse Stock Split, as well as the consequences arising under the laws of any other taxing jurisdiction, including any state, local or foreign tax consequences.

Tax Consequences to the Company. The proposed Reverse Stock Split is intended to be treated as a “recapitalization” pursuant to Section 368(a)(1)(E) of the Code. As a result, we should not recognize taxable income, gain or loss in connection with the proposed Reverse Stock Split.

Tax Consequences to U.S. Holders. Assuming the Reverse Stock Split qualifies as a “recapitalization” pursuant to Section 368(a)(1)(E) of the Code, except as described below with respect to cash received in lieu of a fractional share, a U.S. Holder generally should not recognize gain or loss upon the proposed Reverse Stock Split for U.S. federal income tax purposes. A U.S. Holder’s aggregate adjusted tax basis in the shares of Common Stock received pursuant to the proposed Reverse Stock Split should equal the aggregate adjusted tax basis of the shares of Common Stock exchanged therefor. The U.S. Holder’s holding period in the shares of Common Stock received pursuant to the proposed Reverse Stock Split (excluding the portion of the tax basis that is allocable to any fractional share) should include the holding period in the shares of Common Stock exchanged therefor. U.S. Treasury Regulations provide detailed rules for allocating the tax basis and holding period of shares of Common Stock surrendered in a recapitalization to shares received in the recapitalization. U.S. Holders of shares of Common Stock acquired on other committeesdifferent dates and at different prices should consult their tax advisors regarding the allocation of the tax basis and holding period of such shares.

As noted above, we will not issue fractional shares of Common Stock in connection with the Reverse Stock Split. Instead, we will pay to each registered stockholder, in cash, the value of any fractional share interest in our Common Stock arising from the Reverse Stock Split. Those registered stockholders who hold their shares in certificate form will receive a cash payment for their fractional interest, if applicable, following the surrender of their pre- Reverse Stock Split stock certificates for post- Reverse Stock Split shares. The cash payment would equal the fraction to which the stockholder would otherwise be entitled multiplied by the closing sales price of the common stock as reported on Nasdaq, as of the effective date of the Reverse Stock Split.

In general, a U.S. Holder who receives a cash payment in lieu of a fractional share will recognize capital gain or loss equal to the difference between the amount of cash received in lieu of the fractional share and the portion of the U.S. Holder’s tax basis of the Common Stock surrendered in the Reverse Stock Split that is allocable to the fractional share. Such gain or loss generally will be long-term capital gain or loss if the U.S. Holder’s holding period in its Common Stock surrendered in the Reverse Stock Split is more than one year as of the date of the Reverse Stock Split. The deductibility of net capital losses by individuals and corporations is subject to limitations.

U.S. Holders that have acquired different blocks of our BoardCommon Stock at different times or at different prices are urged to consult their own tax advisors regarding the allocation of their aggregated adjusted basis among, and the boardholding period of, directors of the Company’s subsidiaries that are notour Common Stock.

Information returns generally will be required to be describedfiled with the IRS with respect to the payment of cash in lieu of a fractional share made pursuant to the Reverse Stock Split unless such U.S. Holder is an exempt recipient and timely and properly establishes the exemption. In addition, payments of cash in lieu of a fractional share made pursuant to the Reverse Stock Split may, under certain circumstances, be subject to backup withholding, unless a U.S. Holder timely provides proof of an applicable exemption or a correct taxpayer identification number, and otherwise complies with the applicable requirements of the backup withholding rules. Any amounts withheld under the backup withholding rules are not additional tax and may be refunded or credited against the U.S. Holder’s U.S. federal income tax liability, provided that the U.S. Holder timely furnishes the required information to the IRS. U.S. Holders should consult their tax advisors regarding their qualification for an exemption from backup withholding and the procedures for obtaining such an exemption.

The U.S. federal income tax discussion set forth above does not discuss all aspects of U.S. federal income taxation that may be relevant to a particular stockholder in light of such stockholder’s circumstances and income tax situation and our view regarding the U.S. federal income tax consequences of the Reverse Stock Split is not binding on the Internal Revenue Service or the courts. Accordingly, we urge you to consult with your own tax advisor with respect to all of the potential U.S. federal, state, local and foreign tax consequences to you of the Reverse Stock Split.

Required Vote

The Reverse Split Proposal requires the affirmative vote of a majority of the outstanding shares of Common Stock entitled to vote at the Special Meeting.

PROPOSAL 2

AMENDMENT TO THE ADVENT TECHNOLOGIES HOLDINGS, INC.

2021 EQUITY INCENTIVE PLAN

The Board has unanimously adopted, and is submitting for stockholder approval, an amendment to the Advent Technologies Holdings, Inc. 2021 Equity Incentive Plan (as amended by this proxy statement and which are therefore not identified in the information below.

As of March 8, 2024, there were approximately 823,585 shares of Common Stock available for issuance under the Plan. Accordingly, the Board has determined that there are not sufficient shares of Common Stock available under the Plan to support the Company’s intended compensation programs over the next several years.

On February 2, 2024, subject to stockholder approval, the Board approved the Plan Amendment described in this Proposal 2, and the Board is now submitting the Plan Amendment attached to this Proxy Statement as providedAnnex B for stockholder approval. As proposed for approval, the Plan Amendment will increase the number of shares of our Common Stock issuable under the Plan by 10,163,296 shares. As described more fully below, we consider equity compensation to be a key component of our compensation structure.

The closing sale price of our Common Stock quoted on The Nasdaq Capital Market on March 15, 2024, was $0.1811 per share.

Description of the Plan Amendment

The following is a summary of the Plan Amendment:

Section 4(a) of the Plan is amended to include an additional 10,163,296 shares of Common Stock authorized for issuance under the Plan.

Description of the Plan

The following is a summary of the material terms of the Plan. This summary is not complete and is qualified in its entirety by reference to the full text of the Plan, as modified by the Delaware General Corporation Law (the “DGCL”),Plan Amendment attached to this Proxy Statement as Annex B, and conductsit assumes that this Proposal 2 is approved.

Purpose

The purpose of the Plan is to advance our interests by providing for the grant to our employees, directors, consultants, and advisors of stock and stock-based awards.

Administration

The Plan is administered by the Compensation Committee, except with respect to matters that are not delegated to the Compensation Committee by the Board. The Compensation Committee (or Board, as applicable) has the discretionary authority to interpret the Plan and any awards granted under it, determine eligibility for and grant awards, determine the exercise price, base value from which appreciation is measured or purchase price, if any, applicable to any award, determine, modify, accelerate and waive the terms and conditions of any award, determine the form of settlement of awards, prescribe forms, rules and procedures

relating to the Plan and awards, determine the time or times of receipt, type of and number of shares of Common Stock covered by awards and otherwise do all things necessary or desirable to carry out the purposes of the Plan or any award. The Compensation Committee may delegate such of its business through meetingsduties, powers, and responsibilities as it may determine to one or more of its members, members of the Board and, three standing committees:to the Audit Committee,extent permitted by law, the Company’s officers, and may delegate to employees and other persons such ministerial tasks as it deems appropriate. As used in this description, the term “Administrator” refers to the Compensation Committee and its authorized delegates, as applicable.

Eligibility

Company employees, directors, consultants, and advisors are eligible to participate in the NominatingPlan. Eligibility for stock options intended to be incentive stock options, or ISOs, is limited to our employees or employees of certain of our affiliates. Eligibility for stock options, other than ISOs, and Governance Committee.

Authorized Shares

Subject to adjustment as described below, the maximum number of shares of our Common Stock that may be delivered in satisfaction of awards under the Plan is currently 6,915,892 shares. If the Plan Amendment is approved by the stockholders, the maximum number of shares of our Common Stock that may be delivered in satisfaction of awards under the Plan will increase to 17,079,188. The number of shares of our Common Stock delivered in satisfaction of awards under the Plan is determined (i) by including shares withheld by us in payment of the exercise price or purchase price of the award or in satisfaction of tax withholding requirements with respect to the award, (ii) by including the full number of shares covered by any portion of a SAR which is settled in shares of our Common Stock, and (iii) by excluding any shares underlying awards settled in cash or that expire, become unexercisable, terminate or are forfeited to us without the delivery (or retention, in the case of restricted stock or unrestricted stock) of shares of our Common Stock. The number of shares available for delivery under the Plan will not be increased by any shares that have been delivered under the Plan and are subsequently repurchased using proceeds directly attributable to stock option exercise. Shares that may be delivered under the Plan may be authorized but unissued shares, treasury shares or previously issued shares acquired by the Company.

Director Limits

The aggregate value of all compensation granted or paid to any of our non-employee directors with respect to any calendar year, including awards under the Plan, for his or her services as a director during such calendar year, may not exceed $500,000 with the value of any awards under the Plan calculated based on their grant date fair value and assuming maximum payout.

Types of Awards

The Plan provides for the grant of stock options, SARs, restricted and unrestricted stock and stock units, performance awards and other awards that are convertible into or otherwise based on our Common Stock. Dividend equivalents may also be provided in connection with certain awards under the Plan, provided that any dividend equivalents will be subject to the same risk of forfeiture, if any, as applies to the underlying award.

Stock options and SARs. The Administrator may grant stock options, including ISOs, and SARs. A stock option is a right entitling the holder to acquire shares of our Common Stock upon payment of the applicable exercise price. A SAR is a right entitling the holder upon exercise to receive an amount (payable in cash or shares of equivalent value) equal to the excess of the fair market value of the shares subject to the right over the base value from which appreciation is measured. The exercise price per share of each stock option, and the base value of each SAR, granted under the Plan shall be no less than 100% of the fair market value of a share on the date of grant (110% in the case of certain ISOs). Other than in connection with certain corporate governance policiestransactions or changes to our capital structure, stock options and SARs granted under the Plan may not be repriced, amended, or substituted for with new stock options or SARs having a lower exercise price or base value, nor may any consideration be paid upon the cancellation of any stock options or SARs that have a per share exercise or base price greater than the fair market value of a share on the date of such cancellation, in each case, without stockholder approval. Each stock option and SAR will have a maximum term of not more than ten years from the date of grant (or five years, in the case of certain ISOs).

Restricted and unrestricted stock and stock units. The Administrator may grant awards of stock, stock units, restricted stock, and restricted stock units. A stock unit is an unfunded and unsecured promise, denominated in shares, to deliver shares or cash measured by the value of shares in the future, and a restricted stock unit is a stock unit that is subject to the satisfaction of specified performance or other vesting conditions. Restricted stock are shares subject to restrictions requiring that they be forfeited, redelivered, or offered for sale to us if specified performance or other vesting conditions are not satisfied.

Performance awards. The Administrator may grant performance awards, which are awards subject to the achievement of performance criteria.

Other share-based awards. The Administrator may grant other awards that are convertible into or otherwise based on shares of our Common Stock, subject to such terms and conditions as it determines.

Substitute awards. The Administrator may grant substitute awards in connection with certain corporate transactions, which may have terms and conditions that are inconsistent with the terms and conditions of the Plan.

Vesting; Terms of Awards

The Administrator determines the terms and conditions of all awards granted under the Plan, including the time or times an award vests or becomes exercisable, the terms and conditions on which an award remains exercisable, and the effect of termination of a participant’s employment or service on an ongoing basisaward. The Administrator may at any time accelerate the vesting or exercisability of an award. The Administrator may cancel, rescind, withhold, or otherwise limit or restrict any award if a participant is not in compliance with all applicable provisions of the Plan and/or any award agreement evidencing the grant of an award, or if the participant breaches any restrictive covenants.

Transferability of Awards

Except as the Administrator may otherwise determine, awards may not be transferred other than by will or by the laws of descent and distribution.

Effect of Certain Transactions

In the event of certain covered transactions (including the consummation of a view towards maintainingconsolidation, Business Combination or similar transaction, the best corporate governance practicessale of all or substantially all of our assets or shares of our Common Stock, or our dissolution or liquidation), the Administrator may, with respect to outstanding awards, provide for (in each case, on such terms and subject to such conditions as it deems appropriate):

Except as the Administrator may otherwise determine, each award will automatically terminate or be forfeited immediately upon the consummation of the covered transaction, other than awards that are substituted for, assumed, or that continue following the covered transaction.

Adjustment Provisions

As noted above, in the contextevent of certain corporate transactions, including a stock dividend, stock split, or combination of shares (including the Reverse Stock Split), recapitalization or other change in our capital structure, the Administrator shall make appropriate adjustments to the maximum number of shares that may be delivered under the Plan, the individual award limits, the number and kind of securities subject to, and, if applicable, the exercise or purchase prices (or base values) of outstanding awards, and any other provisions affected by such event.

Clawback

The Administrator may provide that any outstanding award, the proceeds of any award or shares acquired thereunder and any other amounts received in respect of any award or shares acquired thereunder will be subject to forfeiture and disgorgement to us, with interest and other related earnings, if the participant to whom the award was granted is not in compliance with any provision of the Company’s current business environmentPlan or any award, any non-competition, non-solicitation, no-hire, non-disparagement, confidentiality, invention assignment or other restrictive covenant, or any company policy that relates to trading on non-public information and aligning our governance practices closelypermitted transactions with the interestrespect to shares of our stockholders. Our BoardCommon Stock or provides for forfeiture, disgorgement, or clawback, or as otherwise required by law or applicable stock exchange listing standards.

Amendments and management valueTermination

The Administrator may at any time amend the perspective of our stockholdersPlan or any outstanding award and encourage stockholdersmay at any time suspend or terminate the Plan as to communicate with the Boardfuture grants. However, except as described under “Communication with Directors” below.

Term

No awards shall be granted under the Merger.

Material U.S. Federal Income Tax Consequences of Awards Granted Under the Plan

The following is a summary of U.S. federal income tax consequences associated with awards granted under the Plan. The summary does not purport to cover federal employment tax or other compensatory fee fromU.S. federal tax consequences that may be associated with the listed companyPlan, nor does it cover state, local, or anynon-U.S. taxes, except as may be specifically noted. The Plan is not subject to the Employee Retirement Income Security Act of its subsidiaries or (2)1974, as amended, and is not intended to be qualified under Section 401(a) of the Internal Revenue Code of 1986, as amended (the “Code”).

Stock Options (other than ISOs). In general, a participant has no taxable income upon the grant of a stock option that is not intended to be an affiliated personISO (an “NSO”) but realizes income in connection with the exercise of the listed company or anyNSO in an amount equal to the excess (at the time of its subsidiaries.

ISOs. In general, a participant realizes no taxable income upon the grant or exercise of an ISO. However, the exercise of an ISO may result in an alternative minimum tax liability to the caseparticipant. With some exceptions, a disposition of allshares purchased pursuant to an ISO within two years from the membersdate of our compensation committee,grant or within one year after exercise produces ordinary income to the independence criteriaparticipant (and generally a deduction to us, subject to the limitations set forth in Rule 10C-1the Code) equal to the value of the shares at the time of exercise less the exercise price. Any additional gain recognized in the disposition is treated as a capital gain for which we are not entitled to a deduction. If the participant does not dispose of the shares until after the expiration of these one and two-year holding periods, any gain or loss recognized upon a subsequent sale of shares purchased pursuant to an ISO is treated as a long-term capital gain or loss for which we are not entitled to a deduction.

SARs. The grant of a SAR does not itself result in taxable income, nor does taxable income result merely because a SAR becomes exercisable. In general, a participant who exercises a SAR for shares of stock or receives payment in cancellation of a SAR will have ordinary income equal to the amount of any cash and the fair market value of any stock received upon such exercise. A corresponding deduction is generally available to us, subject to the limitations set forth in the Code.

Unrestricted Stock Awards. A participant who purchases or is awarded unrestricted stock generally has ordinary income equal to the excess of the fair market value of the shares at that time over the purchase price, if any, and a corresponding deduction is generally available to us, subject to the limitations set forth in the Code.

Restricted Stock Awards. A participant who is awarded or purchases shares subject to a substantial risk of forfeiture generally does not have income until the risk of forfeiture lapses. When the risk of forfeiture lapses, the participant has ordinary income equal to the excess of the fair market value of the shares at that time over the purchase price, if any, and a corresponding deduction is generally available to us, subject to the limitations set forth in the Code. However, a participant may make an election under Section 83(b) of the Code to be taxed on restricted stock when it is acquired rather than later, when the substantial risk of forfeiture lapses. A participant who makes an effective 83(b) election will realize ordinary income equal to the fair market value of the shares as of the time of acquisition less any price paid for the shares. A corresponding deduction will generally be available to us, subject to the limitations set forth in the Code. If a participant makes an effective 83(b) election, no additional income results by reason of the lapsing of the restrictions.

For purposes of determining capital gain or loss on a sale of shares awarded under the Exchange Act. In making such determination, our board of directors consideredPlan, the relationships that each such non-employee director has with our Company and all other facts and circumstances that our board of directors deemed relevant in determining his or her independence, including the beneficial ownership of our capital stock by each non-employee director. Dr. Gregoriou is not an independent director under these rules because he is our Chief Executive Officer. Emory De Castro is not an independent director under these rules because he is our Chief Technology Officer. Christos Kaskavelis is not an independent director under these rules because he is our Chief Marketing Officer.

Restricted Stock Units. The grant of a range of diversity perspectives, including butrestricted stock unit does not limiteditself generally result in taxable income. Instead, the participant is taxed upon vesting (and a corresponding deduction is generally available to professional experience, skills, knowledge and length of service.

Application of directors, Advent Technologies Holdings, Inc., 200 Clarendon Street, Boston, MA 02116, Attention: Corporate Secretary. All such letters willSection 409A of the Code

Section 409A of the Code imposes an additional 20% tax and interest on an individual receiving non-qualified deferred compensation under a plan that fails to satisfy certain requirements.

While the awards that have been granted and that are to be promptly forwardedgranted pursuant to the appropriate members of our Board, the appropriate committee chairperson or individual directors, as applicable, by the Secretary. The mailing envelope should contain a clear notation that the enclosed letter is a “Stockholder-Board Communication” or “Stockholder-Director Communication.” All such letters should clearly state whether the intended recipientsPlan are all members of our Board or certain specified individual directors.

Required Vote

The Plan Amendment Proposal requires the affirmative vote of a majority of the outstanding shares of Common Stock entitled to vote at the time, attended the 2021 annual meeting of stockholders.

The following table sets forth information known to the Company regarding the beneficial ownership of our common stock as of April 13, 2022March 15, 2024, by:

Beneficial ownership is determined according to the rules of the SEC, which generally provide that a person has beneficial ownership of a security if he, she or it possesses sole or shared voting or investment power over that security, including options and warrants that are currently exercisable or exercisable within 60 days. Stock issuable upon exercise of options and warrants currently exercisable within 60 days are deemed outstanding solely for purposes of calculating the percentage of total voting power of the beneficial owner thereof.

The beneficial ownership of Company common stock is based on 51,253,59177,658,141 shares of common stockCommon Stock outstanding as of April 13, 2022.

Unless otherwise indicated, the Company believes that each person named in the table below has sole voting and investment power with respect to all shares of Company common stock beneficially owned by them.

There have been no transactions since January 1, 20212023, to which we have been a participant in which the amount involved, exceeded or will exceed $120,000, and in which any of our directors, executive officers, or holders of more than 5% of our capital stock, or any members of their immediate family, had or will have a direct or indirect material interest, other than compensation arrangements which are described under “Executive OfficerCompensation” and Director Compensation.”

U.S. Securities and Exchange Commission rules concerning the delivery of annual disclosure documents allow us or your broker to send a single set of our proxy materials to any household at which two or more of our stockholders reside, if we or your broker believe that the stockholders are members of the same family, unless we have received contrary instructions from one or more of the stockholders. This practice, referred to as “householding,” benefits both you and us. It reduces the volume of duplicate information received at your household and helps to reduce our expenses. The rule applies to our notices, annual reports, proxy statements and information statements.

We will undertake to deliver promptly, upon written or oral request, a separate copy to a stockholder at a shared address to which a single copy of proxy materials was delivered. You may make a written or oral request by sending a notification to our Corporate Secretary at the address above, providing your name, your shared address, and the address to which we should direct the additional copy of proxy materials. Multiple stockholders sharing an address who have received one copy of a mailing and would prefer us to mail each stockholder a separate copy of future mailings should contact us at our principal executive offices. Additionally, if current stockholders with a shared address received multiple copies of a mailing and would prefer us to mail one copy of future mailings to stockholders at the shared address, notification of that request may also be made through our principal executive offices. Stockholders who participate in householding will continue to have access to and utilize separate proxy voting instructions.

OTHER BUSINESS

The Board of Directors does not know of any other matter to be acted upon at the Special Meeting. However, if any other matter shall properly come before the Special Meeting, the proxy holders named in the proxy accompanying this proxy statement will have authority to vote all proxies in accordance with their discretion.

Annex A

Certificate of Amendment

of the

Second Amended and Restated

Certificate of Incorporation

of

Advent Technologies Holdings, Inc.

Advent Technologies Holdings, Inc. (hereinafter called the “Corporation”), organized and existing under and by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify as follows:

FIRST: The name of the Corporation is Advent Technologies Holdings, Inc. The original Certificate of Incorporation of the Corporation was filed with the Secretary of the State of Delaware on June 18, 2018; an Amended and Restated Certificate of Incorporation of the Corporation was filed on November 15, 2018; a Certificate of Amendment to such Amended and Restated Certificate of Incorporation of the Corporation was filed on May 19, 2020; and a further Certificate of Amendment to such Amended and Restated Certificate of Incorporation of the Corporation was filed on October 16, 2020. The Second Amended and Restated Certificate of Incorporation of the Corporation was filed on February 4, 2021 (together with this amendment, the “Current Certificate”), as amended by that certain Certificate of Amendment to such Second Amended and Restated Certificate of Amendment filed on June 20, 2023.

SECOND: Pursuant to Section 242 of the DGCL the Board of Directors of the Corporation has duly adopted, and the stockholders of the Corporation have approved the amendments to the Current Certificate set forth in this Certificate of Amendment.

THIRD: Pursuant to Section 242 of the General Corporation Law, Article IV is hereby amended by deleting subsection (a) in its entirety and replacing it with the following:

“(a) Authorized Shares. The total number of shares of stock which the Corporation shall have authority to issue is 501,000,000 shares, consisting of 500,000,000 shares of Common Stock, par value $0.0001 per share (“Common Stock”), and 1,000,000 shares of Preferred Stock, par value $0.0001 per share (“Preferred Stock”). Upon the filing and effectiveness (the “Effective Time”), pursuant to the DGCL, of this Certificate of Amendment to the Second Amended and Restated Certificate of Incorporation of the Corporation, each [number to be determined from 2 to 30] shares of Common Stock and either issued and outstanding or held by the Corporation in treasury stock immediately prior to the Effective Time shall, automatically and without any action on the part of the respective holders thereof, be combined and converted into one share of Common Stock (the “Reverse Stock Split”). No fractional shares shall be issued in connection with the Reverse Stock Split. Holders of Common Stock who otherwise would be entitled to receive fractional shares of Common Stock because they hold a number of shares not evenly divisible by the Reverse Stock Split ratio will automatically be entitled to receive, in cash, the value of any fractional share interest in Common Stock arising from the Reverse Stock Split equal to the fraction to which such stockholder would otherwise be entitled multiplied by the closing sales price of the Common Stock as reported on The Nasdaq Stock Market as of the Effective Time.”

FOURTH: This Certificate of Amendment shall be effective upon filing with the Secretary of State of the State of Delaware.

[Remainder of Page Intentionally Left Blank; Signature Page to Follow]

IN WITNESS WHEREOF, the Corporation has caused this Certificate of Amendment to be executed by its Chief Executive Officer this ___ day of __________, 2024.