RMG Acquisition Corp. III 8K November 2023 H2B2 Electrolysis Technologies Investor Presentation | RMGCF 3 Nov 23

Exhibit 99.1

November 2023 H2B2 Electrolysis Technologies Investor Presentation

Disclaimer This presentation has been prepared for use by H2B2 Electrolysis Technologies, Inc. (together with its subsidiaries and affiliates, the “Company”) and RMG Acquisition Corp. III (“RMG III”) in connection with their proposed business combination (the “Business Combination”). This presentation is intended to provide a general overview of the business and operations of the Company and does not purport to deal with all aspects and details in respect thereof. This presentation is being delivered for informational purposes only and is being provided to you solely in your capacity as a potential investor considering an investment in the Company or RMG III. 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The risks and uncertainties described in such filings as well as other factors may cause actual events, results or performance to be materially different from those contained in the forward-looking statements, the Company’s estimates and beliefs or the estimates prepared by independent parties, and the Company may not actually achieve the plans, intentions or expectations disclosed in the forward-looking statements, including but not limited to the matters referred to as part of the Company's pipeline and projections. You should review this presentation completely and with the understanding of the foregoing and should not place undue reliance on the forward-looking statements. 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Accordingly, there can be no assurance that the projected results are indicative of the future performance of the Company, or that actual results will not differ materially from those presented in the projected information. Inclusion of the projected information in this presentation should not be regarded as a representation by any person that the results contained in the projected information will be achieved. Intellectual Property All rights to the trademarks, service marks, trade names, copyrights, logos and other intellectual property listed herein are the property of their respective owners and are used for reference purposes only. Such use should not be construed as and does not imply an affiliation with, or endorsement by the owners of such trademarks, service marks, trade names copyrights, logos and other intellectual property. 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Executive summary 1

4 Today’s presenters H2B2 Electrolysis Technologies RMG Acquisition Corp. III Bob Mancini CEO and Director Anselmo Andrade CEO Felipe Benjumea CIO Florencio Ferrera COO Javier Brey CTO

H2B2 at a glance A leading green hydrogen company with a unique positioning across the entire value chain, offering clients complete solutions Operating KPIs Business model and major highlights Source: Company information (1) PEM: Proton Exchange Membrane; SOEC: Solid Oxide Exchange Cells; AEM: Anion Exchange Membrane A technological leader in PEM, SOEC, and AEM with references worldwide Demonstrated success with flagship project SoHyCal and ~2.8 GW in pipeline Selected by the European Commission to develop PEM, SOEC & AEM technology under the Important Project of Common European Interest (IPCEI) program Ability to retain minority stakes through construction and operations phase, showcasing commitment to clients Ability to offer LTSAs, making projects financeable Ability to integrate with renewables, offering clients full solutions 5 Green H2 Technology agnostic focused on PEM, SOEC and AEM electrolyzers(1) 5.6 GW Total pipeline, of which ~73 MW is under construction or awarded ~$35mm awarded R&D grants from IDEA, CDTI, EU and IPCEI driving R&D new electrolysis technology ~200+ Green H2 projects identified in pipeline through 2024E Electrolyzers EPC O&M Investments and Asset Management Development of Green Hydrogen Facilities R&D

Source: Company Information 6 H2B2 electrolysis technologies overview A leading green hydrogen company providing end-to-end solutions, with a pipeline of over 200 projects Founded in 2016, H2B2 designs, builds, and operates H2 production facilities, including the transport, storage and sale of green H2 H2B2 has a extraordinary development, best-in-class management team, with experience in H2 and energy project that has been delivering outstanding performance together for over 20 years Global strategy, co-locating electrolyzer manufacturing facilities next to major customers Existing 200MW manufacturing facilities in Sevilla (Spain) and potentially adding facilities in US, India, Colombia, and Northern Spain Under H2B2’s GreenH joint venture, they also have leased a manufacturing facility in India with an expected manufacturing capacity of 100 MW Strategy built around 6 business units (Labs, Project Development, Electrolyzers, EPC, O&M, and Asset Management) offering integrated solutions H2B2 utilizes proven PEM technology and is developing in-house, next generation SOEC and AEM stacks and electrolyzers – H2B2 has the flexibility to integrate any third-party technologies, including alkaline at the EPC level 1 2 3 4 5

Source:, Company information (1) BloombergNEF New Energy Outlook 2021; (2) The first 3MW (Phase I) is operational, with an additional 6MW (Phase II) under FID Key investment highlights A leader in green hydrogen across the entire value chain, backed by a highly experienced management team with successful project track record Strategy developed and delivered by industry leading team H2B2’s top management team has 150+ years of combined experience in the H2 sector 60+ employees covering R&D, manufacturing, EPC and O&M across the US, Europe, LatAm and India 6 Green H2 expected to drive the decarbonization of the global economy The green hydrogen energy market has potential to reach ~$10 trillion value by 2030(1) United States’ IRA direct incentives and EU’s Green Industrial Plan are making large projects viable 1 100% owner of SoHyCal, one of the largest green H2 electrolysis plants in the US Large 9MW(2) green H2 off-grid plant directly supply hydrogen refueling stations in California Ability to provide full production guarantees for SoHyCal, facilitating long-term offtake agreements 5 H2B2, a leading global platform in the green H2 space End-to-end value chain expertise: R&D, proprietary electrolyzer tech, project lifecycle, manufacturing, EPC, O&M, and green H2 production, storage, delivery 2 Patented and proprietary electrolyzer technology Currently utilizing proven PEM technology in the supply of its manufactured electrolyzers Developing next generation technologies (AEM & SOEC) 4 Client-centric business model One-stop-shop approach with tailor-made and scalable solutions, offering development/design, EPC, electrolyzers, offtake agreements, financing and O&M services 3 7

8 Overview of RMG III management team Founder and CEO of Riverside Management Group Former CEO of Horsehead Industries (renamed American Zinc Recycling), the Largest Zinc Recycler and Producer in the U.S Co-Founder of Mohegan Energy, Leading Capital Formation for the Acquisition of Met Resources D. James Carpenter • Founding Investor & Board Member of Allied Resource Corp. Chairman of the Board Robert S. Mancini CEO and Director Former Partner, Founder & Co-Head of Power Investment Business at Carlyle (NASDAQ:CG) Former Managing Director of Goldman Sachs (NYSE:GS) Co-Founder & Head of Power Investment Business, Founder & Head of Commodities Principal Investment Business at Goldman Sachs (NYSE:GS) Former Chairman & CEO of Cogentrix Energy Philip Kassin President, COO and Director Former Senior Managing Director of Evercore (NYSE:EVR) Former Head of M&A & Financing at Access Industries Former Board Member and Chairman of the Finance & Investment Committee at LyondellBasell (NYSE:LYB) Senior Investment Banking Roles at Morgan Stanley, Goldman Sachs, Merrill Lynch and AIG Wesley Sima CFO Former Chief Financial Officer of RMG Acquisition Corp. II Former Vice President of M-III Partners and M-III Acquisition Corp. (acquisition of IEA) Former member of ING Capital LLC’s Natural Resource Project Finance, Corporate Finance and Advisory deal teams in New York City Formerly a member of both the finance and corporate development teams at Entegra Power Group, formerly an independent power producer and owner/operator of multiple natural gas related assets, based in Tampa, FL RMG Acquisition Corp. III Overview RMG Acquisition Corp. III (“RMG III”) is a NASDAQ listed SPAC which completed its $483mm IPO on February 9, 2021 RMG III management team has significant public company board experience (NYSE, NASDAQ, and TSX) The team successfully consummated SPAC transactions for RMG Acquisition Corp I and RMG Acquisition Corp II Supported by Riverside Management Group, a leading merchant bank with ~25 years of experience in M&A advisory and principal investing Previous Experience Highly Experienced RMG III Management Team

Source: Company information (1) SoHyCal Phase I has an electrolysis capacity of 1,290 kg per day of hydrogen, and once Phase II is completed, SoHyCal is expected to have an electrolysis capacity of 3,000 kg or more of hydrogen per day; (2) Important Projects of Common European Interest; (3) Hydrogen Refueling Stations Proven track-record throughout the years in the H2 space Since its foundation in 2016, H2B2 has proven its execution capabilities, successfully developing multiple H2 projects 9 2020 Divestment of Giner ELX (current Plug Power) for ~$14.3mm, allowing H2B2 to focus on the development of SOEC-AEM technologies 2017 Contract with CEPSA, for the supply of a PEM electrolyzer, to produce ultra-pure H2 Corporate milestones Commercial milestones 2016 H2B2 Electrolysis Technologies is founded with the mission to design, build and operate H2 production facilities, including the transport and sale of hydrogen Opening of offices in Spain and California 2021 $10mm capital raise, to reinforce growth and strengthen R&D capabilities 2022 JV with GRIL to develop hydrogen projects in India EU selected H2B2 as an IPCEI(2) and awarded €25mm in grants H2B2 was selected among 80 companies as Ecopetrol’s tech partner 2018 Electrolyzer supplied to CEU University, one of the leading Spanish universities, for investigation uses in domestic clean heat 2019 Involved in an EU-led trigeneration project seeking to improve energy efficiency through H2 Unit supplied to VTT; a leading research laboratory 2020 Supply contract of 2 PEM electrolyzers to be applied in a CCPP in the UAE 2021 Supply of an HRS(3), including H2 production to FM Logistic Construction start of SoHyCal plant, a world pioneer green H2 production plant in California (expected 3Tn/day, 100% renewable) 2022 Supply of electrolyzers to Serveo (1MW), GP Joule (10MW), and Ecopetrol, among others Development of a H2 self-supply energy system for a hospital in the Netherlands 2023 Electrolyzer supply contracts with Puerto de Vigo (1MW) and Redexis (2.5MW) Selected bidder for an 18MW project in Norway and a 30MW project in the US MoU signed with Enel 1 MW electrolyzer and train HRS under construction in India 2017 Strategic investment (25% stake) in Giner ELX, developer and manufacturer of PEM stacks technology 2018 The California Energy Commission awarded H2B2 a 1.29Tn/day(1) hydrogen plant (SoHyCal) 1MW PEM stack tested in NREL 2023 Signed a business combination agreement with RMG III with the intention of becoming listed on the NASDAQ

Green hydrogen plant in Rørvik Norway 18 MW Selected bidder (cooperation period) Maritime fuel India 1 MW, 420 kg / day HRS Under Construction Mobility Highlighted projects H2B2 has a highly visible project pipeline with several projects under construction or executable in the near-term Green hydrogen plant in California (SoHyCal) Source: Company information (1) 3MW in Phase I (operational as of September 2023), and additional 6MW in Phase II HRS and Electrolyzer in India United States 9 MW(1) Phase I: Operational Phase II: Under FID Mobility Green hydrogen plant in California United States 30 MW Selected bidder Mobility 10 Hydrogenation Plant for Biofuel Production in Italy Italy 3 MW Selected bidder Industrial Electrolyzer for Mobility in Spain Spain 2.5 MW Under Construction Mobility California Energy Commission Medha GreenStat & NTE Dynamis Energy Greenswitch Redexis

Source: Company information, ARUP Electrolysis technologies Technology agnostic with focus on technologies best suited for renewables Electrolyzer Technology Overview Most mature technology, used over the past ~30 years The hydrogen evolution reaction takes place in a liquid alkaline electrolyte solution Growing technology, usually developed with a renewable energy installation Employs a conductive membrane that encapsulates the electrolyte and separate the gases Runs in regenerative mode to achieve the electrolysis of water Takes place at high temperatures, using steam allows for a superior kinetics performance Less mature technology with a high potential It integrates a solid, non-porous polymer electrolyte to enhance the kinetics Pros Most mature and commercially available technology Ability to run at high pressure Relatively easy to manufacture Lower Capex per MW relative to PEM Can be connected to renewable energy sources (PV, wind) Fast start-up, shutdown More efficient at a high current density Higher purity H2 gas than alkaline High conversion efficiency (up to 25% less electrical energy consumption) Can be used with high-temperature heat sources Ability to operate at high current densities Fast start-up, shutdown Use of non-precious-metal catalysts reduces cell cost Ability to run at different pressure  Requires high input of electrical energy × Relatively low current density × High maintenance costs × Not appropriate for operation using transient power sources  Requires high input of electrical energy and a power source  High system costs due to platinum- based family catalysts and a proton exchange membrane  High system cost  Need for constant operation  Long start-up and break-in times  Requires high input of electrical energy  Stability problems Technology Readiness Level (TRL) Cons Commercialization phase Commercialization phase R&D phase R&D phase Solid Oxide (SOEC) Anion Exchange Membrane (AEM) Alkaline Water Electrolysis (AWE) Proton Exchange Membrane (PEM) Diversified supplier base (Plug Power, Hystar, Bosch, Schaeffler) In-house In-house In-house In-house In-house Stack Supply Electrolyzer Supply 11

Source: Company information SoHyCal, one of the largest operating green hydrogen plants in the US H2B2’s flagship project is a successful example of an operational, off-grid project, key for the energy transition Location California, US Sponsor California Energy Commission Installed capacity Phase I: 3 MW Phase II: 6 MW Total: 9 MW Completion status Phase I: Operational Phase II: Under FID Green H2 capacity Phase I: 1,290 kg / day Phase II: >1,710 kg / day Total: >3,000 kg / day Phase I Operational start date September 2023 Understanding SoHyCal’s importance H2B2 has a “first mover advantage”, as it expects to lead the supply of renewable hydrogen to major offtakers present in the region to fill unmet demand The project, 100% developed by H2B2, is serving as a blueprint for future projects involving connection with renewables, gas pipeline, permitting, hydrogen dispensing and transport, etc., giving a significant competitive advantage vs others who have yet to develop and deliver a completed project To accelerate the development and deployment of renewable hydrogen in the U.S., the U.S. Department of Energy has reserved up to $1.2bn to invest into green H2 projects in California. H2B2’s SoHyCal project may be eligible for a portion of these funds One of the largest operating off-grid renewable energy hydrogen projects in the United States, using a 15 MW PV plant and biogas fed engine, supplied by a co-located dairy farm 12

Source: Company information, Ecopetrol, World Economic Forum, Government of Colombia 13 Leveraging partnerships to access global markets H2B2 seeks to scale globally through strategic partnerships and joint ventures H2B2 has been selected as technological partner by Ecopetrol in connection with its decarbonization strategy Ecopetrol is the largest and primary petroleum company in Colombia and the second largest oil & gas company in Latin America In May 2022, H2B2 was selected by Ecopetrol as technological partner to help the company in the decarbonization of its activities through green hydrogen facilities – H2B2 was after a very competitive selection process that included 80+ companies from 16 countries As part of the partnership, H2B2 will lead the construction of a manufacturing facility in Colombia to supply Ecopetrol’s South American market, as well as provide maintenance services and HRS once completed Ecopetrol: technological partner for decarbonization GreenH: JV to grow the hydrogen economy in Asia In 2023, H2B2 launched GreenH, a joint venture with GR Promoter Group (“GR”) to develop the hydrogen economy in Asia – GR is an India-based listed company, that develops, constructs and operates all types of infrastructure related projects (highways, power lines, substations, railways, multimodal logistic centers, etc.) The JV is based in India, and H2B2 owns 50% Through GreenH, H2B2 expects to manufacture electrolyzers and develop, construct, and operate green hydrogen generation plants for all sectors GreenH expects to build and operate 10-500 MW green hydrogen production plants in key Asian countries Under H2B2’s GreenH joint venture, they also have leased a manufacturing facility in India with an expected manufacturing capacity of 100 MW Potentially provide O&M and associated services for these production plants Key H2B2 responsibilities include the development and transfer of technology, supply of the stacks (PEM, SOEC and AEM) and ensuring projects are up to date with any technological upgrades

Industry overview 2 13

H 2 Introduction to green hydrogen Hydrogen is broadly applicable to multiple end markets, and can be obtained as a gas through fossil fuels (Grey, Blue), nuclear power (Pink H2) or renewable sources (Green H2) What is hydrogen? Main types by source of energy utilized Applications and end markets Hydrogen (H ) is a clean, chemical energy carrier 2 alternative to methane (natural gas) On the planet, vast numbers of hydrogen atoms are contained in water, plants, animals and humans – It's the most abundant chemical element in the universe, contributing ~75% of total mass – However, despite being present in nearly all molecules in living things, it’s very scarce as a gas (less than one part per million by volume) Hydrogen can be produced from a variety of energy sources, such as natural gas, nuclear power, biogas and renewable power like solar and wind Hydrogen can be obtained through a process called electrolysis, which consists of using electricity to split water into oxygen and hydrogen H2O Electrolysis O2 Oxygen Hydrogen H2 O2 H2 - Grey hydrogen Hydrogen produced from natural gas using steam methane reforming (SMR) Natural gas CO2 H2 Blue hydrogen Grey hydrogen, but with carbon capture utilization and storage techniques applied Green hydrogen “Clean hydrogen,” generated from renewable energy, using water as a feedstock for electrolysis Natural gas H2 CO 2 Carbon capture (CCS) O2 Water H2 Renewable energy Hydrogen H2 Mobility Used as a substitute for fossil fuels in fuel cell cars, trucks, planes, trains, etc. Heat and power Power generation for grid, power buffering and heat for residential and industrial uses Agriculture Converted to ammonia and used in fertilizers and crop nutrients Source: Hydrogen Council, US Department of Energy, McKinsey, Bloomberg Industrial applications Used for steel production, hydrocracking, hydrogenation and synthetic gas Hydrogen is compressed and stored underground in tanks or caverns, to be used in the future Seasonal storage Pink hydrogen Hydrogen produced using electrolysis powered by nuclear energy O2 Water Nuclear energy 13

Regulatory support schemes Strong regulatory support worldwide (focus on H2B2’s core markets) United States Bipartisan Infrastructure Law includes $9.5bn for clean H2 initiatives ($8bn earmarked for Regional Clean H2 Hubs) Inflation Reduction Act (IRA) provides green H2 with substantial investment or production tax credits $3/kg green hydrogen tax credit supporting H2 production Europe REPowerEU sets a target of 10mm tons of domestic green H2 production and 10mm tons of imports by 2030 European Commission (EC) announced the creation of a €3bn European H2 bank in September 2022 EC has also proposed an upper subsidies capped at €4/kg for green hydrogen projects Target of 50% of all H2 demand in industry from renewable origin by 2030 Latin America Colombia: target of 1-3GW of electrolysis capacity (40% low-carbon) by 2030 Chile: 21% of its 2050 carbon neutrality target using green hydrogen (25GW by 2030) Uruguay: target of 1mm tons per annum of green H2 production by 2040 India Adopted net zero by 2070 in 2021 Committed to non-fossil energy capacity of 500GW by 2030 155GW new non-hydro capacity for green hydrogen production by 2030 25-year waiver on transmission charges for renewable power used by electrolyzers Japan In April 2023, the government of Japan published a draft to revise the Basic Hydrogen Strategy The draft includes a target of 12mm tons hydrogen supply by 2040 The plan also mentions JPY 15tn government and private investments to drive the adoption of the hydrogen economy Source: ARUP, Infrastructure Investment and Jobs Act Public Law No. 117-58, Inflation Reduction Act Public Law No. 117-169 16

Global electrolyzer market Driven by tremendous hydrogen demand, the electrolyzer market is expected to experience solid growth over the next decade, with PEM gaining significant market share versus alkaline installations Installed electrolyzer capacity (GW) Annual electrolyzer capacity in Europe and North America (GW) Annual electrolyzer installations by technology (GW) Annual investment in electrolyzer deployment ($bn) 2 5 11 21 39 63 100 157 242 2022 2023E 2024E 2025E 2026E 2027E 2028E 2029E 2030E 1 2 5 9 13 16 21 27 36 2022 2023E 2024E 2025E 2026E 2027E 2028E 2029E 2030E 4 24 35 51 5 12 8 16 13 21 34 1 3 6 10 7 17 24 37 56 85 2022 2023E 2024E 2025E 2026E Alkaline PEM 2027E 2028E 2029E 2030E Total 82% CAGR 57% CAGR 2 3 7 11 18 27 1 3 3 5 4 6 7 7 0.3 0.7 2.5 5.5 8 11 17 25 34 2028E 2029E 2030E Europe 2022 2023E 2024E 2025E 2026E 2027E US + Canada 81% CAGR 74% CAGR Source: BloombergNEF 2023 17

Source: Company information, ARUP (1) Arup working under its capacity as vendor due diligence provider to H2B2 Electrolysis Technologies H2B2 addresses challenges to development of green hydrogen There has been industry-wide attrition in green hydrogen projects due to difficulties regarding securing external funding. H2B2 is positively situated to secure project financing where others are not. Green hydrogen is a relatively expensive energy compared to many alternative energy sources. This can be a limiting factor for near-term demand and investment Governments and regulatory bodies recognize the importance of hydrogen in the energy transition and have been increasing hydrogen-specific targets globally since 2016. These targets have been supported with regulatory incentives (e.g., US IRA, EU Green Industrial Plan, among others) that have made green hydrogen economically competitive Regulation and government incentives As the near- and medium-term demand grows rapidly due to regulatory drivers and improving economics, electrolyzer supply must increase commensurately to avoid industry wide shortages and project delays Supply Chain Security Securing an offtake agreement is key to obtaining funding for green hydrogen projects. Some past projects in the industry have stalled due difficulty securing offtake agreements to support project financing Potential offtakers are concerned about investing projects where there is uncertainty regarding the consistent production of hydrogen, given the relatively new technology and largely unproven execution capabilities of most EPC providers Most players are focused either on technology (electrolyzers) or EPC, creating a technology gap/risk for financing institutions and offtakers Execution Risk H2B2 has the ability to provide production guarantees, which facilitates long-term offtake contracts. H2B2 is able to provide this due to its extensive project execution experience and vertical integration H2B2 has the necessary capacity to complete the business plan. Electrolyzer technology agnosticism and current in- house supply further insulate H2B2 from supply chain risk Green hydrogen production costs are expected to decline due to technological advancements and economies of scale. Further, Arup substantiated that H2B2 has potential to be a relatively low-cost provider of quality green hydrogen products(1) Challenge How H2B2 addresses 18

Business overview 3 H2B2 Manufacturing Facility Sevilla Spain

Strategy developed and delivered by industry leading team Management team with a solid track record and working together in hydrogen and renewables projects Blanca Benjumea CFO and HR manager Founding member of H2B2 Last 5 years focused on hydrogen, holding top executive positions in H2B2 Past experience in public company auditing and strategic consulting at KPMG in Spain and New York BSc in Business Administration from Fordham University in New York Javier Brey CTO Founding member of H2B2 25+ years of experience in the H2 sector Chairman of the Spanish Hydrogen Association since 2009 Former CEO of Abengoa Hydrogen Former CEO of Hynergreen PhD with thesis on Hydrogen Economy Antonio Vázquez Chairman 40+ years in management roles Joined H2B2 in Dec-2022 Former chairman of listed- IAG (Iberia, British Airways) Former Board Member of Telefónica Internacional and Aldeasa Former CEO of listed-Altadis at the time of the ~$17 billion acquisition (enterprise value) by Imperial Tobacco Anselmo Andrade CEO Founding member of H2B2 Last 7 years focused on hydrogen holding top executive positions in H2B2 Previously acted as CFO and Business Development Officer of H2B2 Past experience in strategic consulting MSc in Finance from London School of Economics (LSE) Felipe Benjumea CIO Founding member of H2B2 Last 7 years focused on hydrogen holding top executive positions in H2B2 Previously acted as Head of Investor Relations & Capital Markets Past experience in corporate and investment banking BSc in Business Administration from Saint Louis University ~20 years working together and delivering outstanding performance Florencio Ferrera COO 27+ years in the energy sector across multiple EPC projects Joined H2B2 in July 2021 Several senior positions in Abengoa (Energy Operations Director, Energy General Director and Project Manager) África Castro Head of Business Development Founding member of H2B2 20+ years dedicated to hydrogen Vice-Chairman of the Spanish Hydrogen Technology Platform Former Head of Business Dev. at Abengoa Hydrogen Asdrúbal Lupi Head of Engineering 35+ years of experience in infrastructure and power engineering Joined H2B2 in December 2021 as Project Manager of SoHyCal Power Plant I&C engineering at Abengoa Energy José Luis Márquez Procurement Director & Construction Lead Former CEO of Abeinsa (Abengoa) in the US 20+ years in EPC project management in the energy industry globally Joined H2B2 in January 2023 Manuel Rodríguez Electrolyzers Business Unit Manager Founding member of H2B2 as Project Engineer Past experience as Engineer at Abengoa Hydrogen Past experience as development and production manager Antonio Zamora O&M Business Unit Manager 22+ years of experience in asset management of energy assets in multiple technologies Joined H2B2 in October 2022 Industrial Technical Engineer specialized in Power Plants Source: Company information 20

Business model Electrolyzers (Electrolyzers & Refueling Stations manufacturing) EPC (Construction & related services) O&M (O&M services) Integrated product and services offering, with tailor-made solutions across the hydrogen value chain H2B2 Business Model (full coverage of value chain) across H value 2 chain) R&D (R&D development Development of Green Hydrogen Facilities (Project development services) Investments and Asset Management (Minority equity investments) Present in some of the largest projects by installed capacity worldwide Source: Company information 20 Hub-and-spoke manufacturing of PEM electrolyzers Electrolyzers with top- tier technology Several patents filed, and additional exclusive licensed patents already granted Proven EPC capabilities End-to-end solutions from power generation to dispensing/injection of green H2 Could offer different levels of guarantees to include coverage for costs, delays and/or potential performance variances Technology agnostic, with the ability to integrate PEM, ALK, SOEC and AEM Once a project is commissioned, H2B2 offers a variety of services for operations and maintenance to fit client requirements, including: Preventive Maintenance Long Term Service Agreement (LTSA) Production guarantees To keep minority equity stakes in project SPVs at financial close Expected to generate sustainable dividends from these investments Providing the services required to set up a green hydrogen production facility Includes all pre- construction phase tasks: identifying opportunities, carrying out the feasibility analysis, permitting, ensuring offtake and sourcing of financing Development of efficient and durable electrolysis technologies, allowing cost reductions in Capex and Opex for the production of green hydrogen Partnered with leading research institutions and universities to support its R&D activities

Client-centric business model Two differentiated, scalable business models providing bespoke services across the green hydrogen value chain Conventional product Integrated product Self- developed Third parties Product Business Model Overview Selected example Equipment, plant and services provided to projects developed by third parties, including manufacturing, installation of electrolyzers and/or construction Usually contracted through a competitive bidding process R&D Project Dev. Electrol. EPC O&M Asset Mgmt. R&D Project Dev. Electrol. EPC O&M Asset Mgmt. R&D Project Dev. Electrol. EPC O&M Asset Mgmt. Projects developed by H2B2 and funded by third parties, where H2B2 can invest a minority stake Sole developer or partner with other co- developers to create synergies Focused in regulated markets (US & Europe) H2B2 positions itself as a technological partner for a third party that is interested in developing green hydrogen projects H2B2 to provide turnkey solutions for third party investors The first 3 MW (Phase I) of SoHyCal in California is operational, with an additional 6 MW (Phase II) under FID Technological partner for the supply of electrolyzers and refueling stations Supply GP Joule with 10MW of electrolyzer capacity GP Joule Source: Company information 20 California Energy Commission EcoPetrol

Business model | R&D Under R&D, H2B2 is developing revolutionary technologies for PEM, AEM and SOEC electrolysis Overview H2B2 Labs is the business unit focused on R&D, and its fundamental objective is the development of more efficient and durable electrolysis technologies to allow a reduction in costs in both capital and operating expenditures in the production of hydrogen H2B2’s R&D strategy is structured around the continuous improvement (efficiency and cost reduction) of PEM electrolyzers, and the development of SOEC and AEM technologies for stacks and electrolyzers Partnering with leading institutions to develop particular parts of their SOEC and AEM electrolyzers, including CIEMAT and CSIC H2B2 has licensing arrangements with third parties for patents related to electrolysis technologies, and has filed another 6 patents related to PEM Balance of Plant (BoP) and SOEC stacks > 25 external collaborators for R&D within prominent institutions R&D Grants H2B2 objectives and cost down strategy PEM SOEC AEM Objectives Cost-down strategy BoP simplification, improve heat and water management, In-house design of purification systems, integration with batteries Improvement of BoP for modular units. Development and BoP improvement of large facilities (>10MW) Development of 100kW electrolyzers in the near-term, and up to 1MW in the medium- term Development of 100kW electrolyzers in the near-term, and up to 1MW in the medium- term Focused on dry membrane- electrode assembly manufacturing technique Manufacture of ceramic electrolytes by 3D printing (increase stack energy density, and simplifies manufacturing) ~$35mm Awarded in R&D grants across 3 primary institutions (IPCEI(1), CDTI(2), IDAE(3)) IPCEI CDTI IDAE Awarded by the IPCEI, an Awarded through an R&D Awarded to support R&D EU subsidy program to support program from a program Spanish support development and sponsored by the Spanish program which aims to construction of Ministry of Energy. promote innovation and manufacturing facilities for technological development. AEM and SOEC stacks. Source: Company information (1) Important Projects of Common European Interest; (2) Center for Technological Development and Innovation; (3) Institute for Energy Diversification and Saving 23

Source: Company information Business model | Electrolyzers Since 2016, H2B2 has manufactured and installed electrolyzers, with a unique product offering in the industry Medium-scale Capacity of 50-300 kW per container Hydrogen production of 10-60 Nm3/h Integrated within a container Overview Product portfolio Highlighted projects H2B2 is focused on the manufacturing, assembly and installation of electrolyzers and hydrogen refueling stations H2B2 has two main types of electrolyzer solutions: Containerized solutions for those units up to 15-20MW (“plug-and-play” electrolyzers) Skid mounted solutions for those plants greater than 20 MW, skids are installed on-site and interconnected by H2B2 H2B2 has a wide range of electrolyzers under commercialization, with 1-4 stacks, with a total maximum output of approximately 1,726kg of green hydrogen per day Apart from manufacturing and installation, this business unit also covers start up and testing works H2B2 supplies electrolyzers with CE marking(1) and, if necessary, ETL stamp(2) (priced separately), as well as required safety studies (HAZOP by default) Leading renewables company Supply of 5 EL400N units totaling 10MW capacity for HRS, producing 860 kg/day Supporting Indian Railways’ carbon neutrality Supply of 1MW EL200N electrolyzer and HRS Leading gas distribution company Supply of 2.5MW electrolyzer to Redexis Large-scale Capacity of 0.5-5 MW per container Hydrogen production of 100-1,000 Nm3/h Integrated into 40ft containers Large Scale Skid mounted solutions For projects greater than 20 MW (e.g. 100MW), H2B2 can execute on-site installation of the electrolyzers H2B2 Focus GP Joule 24 (1) Conformité Européenne, meaning that have been assessed to meet high safety, health, and environmental protection requirements; (2) ETL Mark is proof of product compliance to North American safety standards Medha Redexis

Business model | EPC H2B2 has full construction capabilities, from engineering to commissioning, including extensive experience in integration with renewable energy Overview Main divisions within EPC Illustrative H2B2 project timeline H2B2 performs engineering, procurement, construction and commissioning services required for the construction of hydrogen plants Necessary capabilities to build tailor-made hydrogen plants in less than 20 months from engineering to commissioning Main steps include Engineering, Procurement and Construction & Commissioning Leading the construction of a green hydrogen plant in California (SoHyCal), and the electrical and mechanical installations of other projects Extensive experience in the integration of renewable energy installations (mainly PV and wind), being key in the construction of green hydrogen plants Months 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Engineering Procurement Construction Commissioning H2B2 is capable of building a full hydrogen plant in 20 months, 10 if excluding engineering and procurement Source: Company information 25 Engineering Starts as soon as a project is awarded Includes geotechnical testing, full permitting, areas classification, technical support, tabulations, etc. If needed, H2B2 may collaborate with local engineering firms to ensure full code compliance Procurement Starts at the 2nd month of the project Purchasing all material and equipment needed, including contract negotiations, in parallel with the engineering team Building long-term relationships with key suppliers Construction & Commissioning On-site activities mainly targeted at the installation and construction of the plant, as well as the integration with third-party equipment This stage includes performance tests until provisional acceptance and the plant reaches COD status Division Overview Illustrative Duration ~12 months ~13 months ~10 months

Geographic commercial and manufacturing footprint H2B2 is present in multiple countries, and with current or planned manufacturing facilities in Europe, America and Asia Current manufacturing plant Planned manufacturing plant North America Europe Strategic partners 200 MW Current manufacturing capacity Market coverage of the plant Latin America Asia-Pacific 100 MW Expected capacity for leased manufacturing facility, under GreenH Joint Venture Strategic partners Arches H2 California Energy Commission Enel Strategic partners Ecopetrol Strategic partners GRIL H2B2 Manufacturing Facility, Sevilla Spain Source: Company information 25

Financials & pipeline 4 27

2023E 2024E 2025E 2023E-2025E revenue projections(1) Strong growth supported by both highly visible pipeline and proven track record H2B2 has a strong and achievable Business Plan, supported by specific identified opportunities and management’s proven track record of successful execution. Breakeven (at Adj. EBITDA level) will be achieved by 2025E Revenue ($ millions) $206.6 $78.6 $12.0 553% Growth 163% Growth Source: Company Information (1) Projections assume the SoHyCal project will be deconsolidated from H2B2 for accounting purposes in 2024 28

Summary financial projections(1) Source: Company Information (1) Projections assume the SoHyCal project will be deconsolidated from H2B2 for accounting purposes in 2024 28 310%+ Revenue CAGR generated primarily from projects under construction, awarded projects or projects currently in the pipeline ~$35mm Historical and projected grant funding for R&D to increase electrolyzer efficiency and breadth of product portfolio (next-generation SOEC and AEM technologies) ~45% Of 2024 revenue expected to be generated from Integrated Products, providing a more fulsome / integrated suite of services for clients $m 2023E 2024E 2025E Net Income (Loss) ($20.9) ($16.3) $3.9 (+) Income tax expense - - 0.2 (+) Interest and other expense, net - 0.1 0.3 (-) Other income (0.7) (1.7) (2.9) (+) Depreciation of long-lived assets 0.3 1.9 3.7 Adjusted EBITDA ($21.2) ($16.0) $5.2 (+) Grant funding 7.2 10.2 11.5 (+) One-off expenses 6.2 - - (-) Dividends from Minority Interest Projects - - 0.1 Further Adjusted EBITDA ($7.9) ($5.8) $16.7

H2B2’s robust pipeline(1) Robust pipeline of ~5.6 GW of identified potential projects, of which ~73MW either under construction (~16 MW) or awarded pending FID (~57 MW) Potential pipeline projects Includes projects that have not been awarded yet but are at varying stages of the process, including those that (i) we have bids out for, (ii) are at the budgetary or technological partner stage, (iii) are at the technical economical proposal or expected RFQ stage or (iv) are at the tender process or early development stage Installed ~5.5 GW Potential pipeline projects ~57 MW Awarded projects ~3 MW Installed ~16 MW Under construction ~5.6 GW Pipeline + awarded + under construction + installed ~76 MW Award / Contracted / Installed Under construction Projects to be executed in 2023 & 2024 Source: Company Information (1) Pipeline assumes the SoHyCal project will be deconsolidated from H2B2 for accounting purposes in 2024 30 Awarded projects Projects awarded or named preferred bidder, subject to client obtaining financial close, including Phase II of SoHyCal Dynamis Energy NTE California Greenswitch Energy Commission Medha Serveo Puerto de Vigo GP Joule Redexis California Energy Commission Ecopetrol Cepsa Esenttia FM Logistics VTT Tecnicas Reunidas PowiDian Universitat De Valencia

Thank you For Further Inquiries Please Contact Investor Contacts: Anselmo Andrade Fernandez de Mesa Chief Executive Officer anselmo.andrade@h2b2.es Roberto Wilson Fernandez del Castillo Investor Relations roberto.wilson@h2b2.es

RMG Acquisition Corp. III (RMGCF) 8-KNovember 2023 H2B2 Electrolysis Technologies Investor Presentation