Green Hydrogen in Europe: Where Are We Now?

Abstract: Green hydrogen, produced via electrolysis using renewable energy, is a critical pathway to decarbonizing energy systems. This study compares key electrolysis technologies, including Alkaline (AE), Proton Exchange Membrane (PEM), Solid Oxide (SOE), and Anion Exchange Membrane (AEM) systems. SOE demonstrates the highest efficiency ranging from 80% to 90% which operates at elevated temperatures ranging from 700°C to 900°C, and has higher capital costs per Kilowatt which ranged from $2,000 to $3,000 per kW. PEM offers rapid response times ranging from 10 s to 30s and high hydrogen purity of 99.99% but suffers from shorter lifespans ranging from 40,000 to 60,000 hours. Material advancements, such as Nafion™ membranes and Iridium Oxide catalysts, enhance efficiency by up to 10%. Hydrogen storage methods reveal compressed hydrogen as suitable for short-term applications, while ammonia carriers and LOHC excel in long-term storage due to their safety and cost efficiency. Distribution technologies vary, with pipelines having cost-effective of $0.05/kg H₂/km over long distances, while trucks offer flexibility for shorter ranges. Environmental analysis highlights the carbon intensity disparity, with green hydrogen emitting 0 to 0.5 kg CO₂/kg H₂ compared to grey hydrogen’s which emits 10 to 12 kg CO₂/kg H₂. Lifecycle water consumption ranges from 7 to 12 L/kg H₂, with SOE being the most water-efficient. Global hydrogen projects, such as Saudi Arabia's NEOM with 650,000 tons per year and Europe’s HyDeal Ambition with 1,500,000 tons per year, illustrate the large-scale adoption of hydrogen technologies. Policy frameworks, including the EU Hydrogen Strategy and the USA Clean Hydrogen Plan, emphasize subsidies and infrastructure investments. This comprehensive analysis underscores the potential of green hydrogen, provided technological, environmental, and policy challenges are addressed effectively.

<p indent="0mm">Green hydrogen has gained much interest due to its low cost, sustainability, and environmental friendliness, especially when combined with water electrolysis technology powered by renewable energy resources. It has been recognized as one of the perfect solutions to achieve the goal of near-zero carbon emissions. According to the type of materials used to separate the anode and cathode and the ionic species it conduct, the electrolyzers can be divided into several categories, i.e., alkaline water electrolyzer (AWE) that involve the use of liquid electrolyte, proton exchange membrane water electrolyzer (PEMWE), solid oxide electrolyzer (SOE), and anion exchange membrane water electrolyzer (AEMWE). As the key component in different water electrolysis technologies, polymeric membrane materials, including proton exchange membrane (PEM), anion exchange membrane (AEM), and ion-solvating membranes (ISM), are of great importance, which serve as the ionic conductor and gas separator. Thus, the efficiency and durability of water electrolyzers are mainly determined by the properties of membranes, such as ionic conductivity, chemical stability, and mechanical properties. However, these unfavorable performance parameters of membranes still limited the worldwide commercialization of water electrolysis for the production of green hydrogen. In a typical AWE, a porous diaphragm made of asbestos or composite ceramic (or asbestos)/polymer materials (Zirfon, a state-of-the-art diaphragm) is used to separate the gas product and transport hydroxide ions. Although the mature AWE technology shows higher durability, low capital cost, and high compatibility with non-noble metal catalysts, they operate at low current densities lying between <sc>0.3−0.4 A cm⁻²,</sc> owning to the high ionic resistance and high gas permeation of the non-ionic separator membranes. The replacement of porous diaphragm with ionic polymeric membranes, such as PEM, AEM, and ISM based on polybenzimidazoles have attracted increasing attention in water electrolysers, due to their effectiveness of ion transport and gas tightness of the dense membrane. The acidic PEM allow the operation of water splitting with higher efficiency and current densities <sc>(500−2000 A cm⁻²).</sc> However, large-scale implementation of PEMWE technology is limited by the expensive PEM and precious platinum group metal (PGM) catalysts. When working under basic environment, the AWE using solid AEM and ISM combines the merits of traditional AWE and PEMWE, i.e., an alkaline working environment allows for the use of PGM-free catalysis and the solid hydroxide ion conducting membrane reduce the ionic resistance of the cells. Thus, the design of AEM and ISM materials plays a crucial role in the overall performance and durability of electrolytic cells. Currently, compared with PEMWE, the AEMs and ISMs with sufficient conductivity and satisfactory stability are still highly needed, due to the well-recognized vulnerable functional cations and polymer backbones in hot and alkali aqueous solutions. Thus, numerous chemical designs on AEMs are carried out. In this review, we summarized the research progress of polymeric membranes in water electrolysis for hydrogen production. We first compared the properties of membranes and electrolyzer device performance using different types of membranes, and analyzed the relationship between polymer structure and device performance; then, after analyzing the development and the technical advantages and disadvantages of PEM, AEM, and ISMs, the technical limitations and future developing trends of these technical routes were discussed. Finally, we also give a brief prospect on how to guide and encourage the future development of various technical pathways through the policy guidance, so as to realize the large-scale market penetration of water electrolysis technology for green hydrogen production.

1. Introduction Content: Hydrogen stands at the forefront of alternative energy solutions, offering a versatile and powerful approach to achieving a sustainable energy future. As the lightest and most abundant element in the universe, hydrogen can be produced from various resources and utilized in diverse applications—from fueling vehicles to storing excess renewable energy. Embracing hydrogen technology is critical for reducing global dependence on fossil fuels, minimizing environmental impact, and enhancing energy resilience. This clean energy vector plays a pivotal role in integrating renewable sources into the energy grid, facilitating a smooth transition to low-carbon energy systems worldwide. Visuals: Use an image of Earth, emphasizing areas where hydrogen production and usage are prominent, illustrated with symbols like hydrogen pumps, refineries, and transport vehicles. Highlight key regions with advanced hydrogen infrastructure and potential growth areas, effectively showcasing hydrogen's role in powering a cleaner, more sustainable planet.2. Section on Fuel Cells Sub-Title: "Harnessing Chemical Energy Directly from Hydrogen" Content:Explanation of how fuel cells work.Types of fuel cells (PEM, SOFC, etc.).Applications (transport, stationary power, etc.). Visuals: Diagrams of fuel cell operation, photos of fuel cell vehicles or power systems.3. Section on Electrolyzers Sub-Title: "Splitting Water to Power the Future" Types of Electrolyzers: PEM (Proton Exchange Membrane): Delivers high-purity hydrogen, ideal for dynamic energy inputs. Alkaline: Traditional technology, cost-effective for steady, large-scale hydrogen output. Solid Oxide Electrolyzer (SOE): Operates at high temperatures, increasing efficiency by using heat to assist electrolysis. Anion Exchange Membrane (AEM): Combines advantages of PEM and alkaline, with potential for lower costs and improved durability. Membrane-Free Electrolyzer: Employs bipolar membranes, potentially reducing costs and complexity in certain applications.4. Section on Energy Conversion Sub-Title: "Efficient Energy Use and Storage" Content:Role of energy conversion in renewable energy.Methods of storing and converting energy (batteries, mechanical systems, etc.). Visuals: Charts comparing energy storage methods, images of large-scale energy storage facilities.5. Case Studies Hydrogen Buses in California, USA: Overview: California has pioneered the adoption of hydrogen fuel cell buses in public transportation systems across several cities. Impact: These buses significantly reduce urban air pollution and carbon emissions, contributing to cleaner city air and sustainable urban transport. Visuals: Map of California showing cities with hydrogen bus fleets, infographics of emission reductions, and passenger statistics. Green Hydrogen in Neom, Saudi Arabia: Overview: The Neom project aims to build a hydrogen-based economy, planning one of the world's largest green hydrogen plants. Impact: This initiative is set to position Saudi Arabia as a leader in green hydrogen production, diversifying its economy and reducing its dependence on oil exports. Visuals: Illustrative map of the Neom area, diagrams of the hydrogen production process, and projected economic impacts. Hydrogen Energy Storage in Germany: Overview: Germany's Energiewende (energy transition) includes investments in hydrogen technology for storing excess renewable energy. Impact: Enhances grid stability and maximizes the use of renewable energy sources, reducing reliance on fossil fuel-based power plants. Visuals: German national grid map with key hydrogen storage sites, charts showing energy storage capacity, and utilization rates. Hydrogen Trains in Germany: Overview: Introduction of the world’s first hydrogen-powered passenger trains in Lower Saxony. Impact: Provides a more sustainable alternative to diesel engines with zero emissions, showcasing the practical application of hydrogen in rail transport. Visuals: Routes of hydrogen trains, operational data, and comparisons with traditional diesel train emissions. Conclusion These case studies demonstrate hydrogen technology's versatility and capacity to support sustainable energy goals across transportation and energy storage sectors. By implementing similar technologies, nations can achieve significant environmental and economic benefits.6. Future Outlook and Challenges Content:Potential advancements in technology.Current challenges facing scalability and cost. Visuals: Future-oriented imagery, possibly futuristic cityscapes.7. Conclusion Content: Hydrogen technologies have the potential to revolutionize the energy landscape by providing a sustainable, clean, and versatile energy solution. As technological advancements continue and infrastructure develops, hydrogen can play a pivotal role in achieving a sustainable energy future. With strong policy support and global collaboration, the transition to a hydrogen economy can significantly contribute to reducing carbon emissions, enhancing energy security, and promoting economic growth. Visuals: Inspirational quote or image that highlights innovation. Figure 1

Patent analysis on green hydrogen technology for future promising technologies

For decades, proton-exchange membrane (PEM) water electrolysis (WE) has been used mainly for oxygen generation in anaerobic environments. Over the past two decades, however, it has been increasingly used for hydrogen generation in the industrial sector at various and increasing scale. The PEMWE technology is also considered as a key one in the frame of the ongoing energy transition if the process of hydrogen generation by means of WE is linked to renewable energy sources, such as wind, solar, etc.Among other existing water electrolysis technologies, such as alkaline, solid oxide, the technology based on proton-exchange membranes has received a great deal of interest in South Africa. One of the reasons is endowment of South Africa with its PGM resources, such as platinum (Pt) and iridium (Ir) that are used in PEM water electrolysis (WE) catalytic components. As it is known, PEMWE technology is very well suited to accommodate intermittency of energy supply associated with renewables. PEMWE technology can also deliver relatively high-pressure hydrogen gas of high purity. South Africa has also superior endowment of both onshore wind and solar. It is known thar renewable energy (RE) is one of the largest operational cost components in the production of green hydrogen. Other factors contributing to the interest in green hydrogen water electrolysis technology in South Africa that are not obvious, but important, include large tracts of sparsely populated land with little alternative use, which can be dedicated for RE production. South Africa also has a suitable geographical position with deep water ports for the potential export of large quantity of hydrogen and its derivatives such as ammonia.Approximately 15 years ago South African Government approved national program HySA: Hydrogen South Africa that resulted in developing expertise and capacity to conduct research, development, and earlier commercial activities around green hydrogen production by means of water electrolysis. These activities include development of local IP at the components, stack and system levels. Recently, a number of “catalytic” projects have been identified in order to increase a demand in green hydrogen and stimulate investments.Recently, an international R&D project between South Africa and Japan was launched to develop further expertise in both green hydrogen and ammonia technologies [1]. Most recently, large companies, such as SASOL, made commitments to lead green hydrogen production at a large scale for the variety of applications, aiming at decarbonisation of mining and petrochemical sectors [2]. On the Governmental level, South Africa recently has approved its national hydrogen road map [3].This talk will provide a comprehensive update on the research, technology, and commercialisation activities in South Africa in the area of green hydrogen production.

Hydrogen energy, as an important green energy source, is a crucial guarantee for achieving carbon neutrality and peak carbon emissions. The anion exchange membrane electrolysis cell combines the advantages of alkaline electrolysis cell and proton exchange membrane electrolysis cell, and can use non precious metal catalysts combined with renewable energy, which is expected to break through the bottleneck of high production cost of green hydrogen. Anion exchange membrane electrolysis of water for hydrogen production combines the advantages of alkaline electrolysis of water and proton exchange membrane electrolysis of water for hydrogen production. It has the characteristics of high electrolysis efficiency, fast response rates, and low cost, and is considered one of the most promising renewable green energy hydrogen production technologies at present. Anion exchange membrane (AEM) is a key component that provides OH– ion conduction and blocks gas crossover, which directly affects the performance and service life of the anion exchange membrane electrolysis water system. However, current AEM membranes face issues of low ion conductivity and poor stability. This review introduces the role of AEM in electrolytic cells, the performance requirements and evaluation parameters that high-performance AEM should meet, and focuses on the transport mechanism and influencing factors of OH– in AEM. Furthermore, this review provides an overview of the structural composition of AEM, as well as common cationic groups and polymer backbone types; The degradation mechanism of different cationic groups and the characteristics of polymer main chains were elaborated, with a focus on the strategies for designing the stability of cationic functional groups, the methods for modifying and preparing polymer main chains, and the performance of AEM. Finally, the future challenges and potential research directions of AEM membranes were discussed, and it was pointed out that high-performance AEM membranes that meet practical application needs should be constructed and prepared through strategies such as crosslinking, block copolymerization, side chain grafting, and composite membrane technology based on the design of alkali resistant and stable AEM membranes, providing reference and guidance for the further development of AEM.

Advancements in Electrolyzer Materials for Green Hydrogen Production

Hydrogen farm concept: A Perspective for Turkey

The demand to reduce fossil fuel dependence has received unprecedented attention due to the generation of greenhouse gases and increase in energy consumption. Hydrogen is considered an ideal energy carrier for building a global renewable energy system owing to its numerous benefits, such as high energy efficiency and nontoxicity. However, more than 95% of hydrogen is produced by reformation of natural gas, which is a nonrenewable energy source with high carbon emissions that predominantly consists of methane. To realize hydrogen as a true alternative to fossil fuels, it must be produced in an environmentally friendly and sustainable manner, which is also known as green hydrogen. One approach to generating green hydrogen is by water electrolysis to split water, which is an essentially unlimited resource.Current approaches to water electrolysis currently use proton exchange membranes, but anion exchange membranes (AEMs) operate under alkaline conditions and thus allow the use of platinum group metal (PGM)-free metals as electrocatalysts, which makes them a more cost-effective alternative. However, AEM water electrolysis (AEMWE) is limited by unsatisfactory cell durability and performance due to the poor physicochemical stability under alkaline conditions and low hydroxide conductivity of the AEM. Therefore, AEMs need to be improved in terms of their mechanical properties, dimensional stability, and alkaline stability to ensure cell durability and in terms of their hydroxide conductivity to ensure cell performance.For AEMs, an important step in improving the efficiency and durability of the cell is to enhance the ion conductivity and chemical stability of these materials, which are vulnerable to hydroxide. The stable operation of AEMWE under high alkaline conditions and elevated temperatures is necessary; hence, the spacer-type cation groups anchored from the backbone and aryl ether-free based polymers are a promising candidate for tolerating harsh alkaline conditions.Thus, we newly designed various type of aryl ether-free poly(fluorene)-based AEMs with interstitial alkyl chains in the conducting groups and a polymer backbone for water electrolysis. The rationally designed AEMs not only demonstrated excellent mechanical properties, high alkaline stability and satisfactory hydroxide conductivity, making them excellent cell performance and durability of the AEMWE. The resulting single AEMWE cell using synthesized AEM demonstrates a voltage decay rate of 2 mV kh− 1 at 1.0 A cm− 2, significantly lower than those reported for AEMWEs and Nafion-based PEMWEs. Additionally, a large-sized 1-cell AEMWE stack utilizing PFPBPF-4-QA with an active area of 63.6 cm2 acheived an energy conversion efficiency of 80.2% and a voltage decay rate of 1.5 mV kh−1 for 2,000 h,with over 90% of the initial efficiency maintained for over 49,095 h through exponential fitting calculation.

Design and analysis of negative CO2 emission methanol synthesis process incorporating green hydrogen and blue hydrogen

Will blue hydrogen lock us into fossil fuels forever?

Green hydrogen produced from wind, solar or hydro power is a suitable electricity storage medium. Hydrogen is typically employed as mid- to long-term energy storage, whereas batteries cover short-term energy storage. Green hydrogen can be produced by any available electrolyser technology [alkaline electrolysis cell (AEC), polymer electrolyte membrane (PEM), anion exchange membrane (AEM), solid oxide electrolysis cell (SOEC)] if the electrolysis is fed by renewable electricity. If the electrolysis operates under elevated pressure, the simplest way to store the gaseous hydrogen is to feed it directly into an ordinary pressure vessel without any external compression. The most efficient way to generate electricity from hydrogen is by utilizing a fuel cell. PEM fuel cells seem to be the most favourable way to do so. To increase the capacity factor of fuel cells and electrolysers, both functionalities can be integrated into one device by using the same stack. Within this article, different reversible technologies as well as their advantages and readiness levels are presented, and their potential limitations are also discussed.

The impact of offshore energy hub and hydrogen integration on the Faroe Island’s energy system

Water splitting via electrocatalysis and photocatalysis: Engineering stumbling blocks and advancements

Water electrolysis processes play a crucial role in transitioning to a climate-friendly society. They facilitate the integration of renewable energy, offer a clean and versatile energy carrier, decarbonize industries, improve energy storage and grid stability, and support the development of sustainable transportation solutions. As technology advances and economies of scale are realized, electrolysis is expected to play an increasingly significant role in the clean energy landscape, contributing to a more sustainable and resilient future.Various water-splitting electrolysis processes currently exist, including alkaline, solid oxide, proton exchange membrane (PEM), anion exchange (AEM), acidic-alkaline amphoteric, microbial, and photoelectrochemical methods [1]. In our research group, we are actively involved in membrane development for both PEM and AEM water electrolysis.In PEM electrolysis membrane development, our group explores several approaches, such as (a) aromatic main-chain block copolymers[2],(b) acid-base blend membranes using sulfonated and partially fluorinated aromatic polyether, polybenzimidazole, and a PSU-derived basic polymer[2], (c) poly(fluorene)-based sulfonated ionomers, (d) sulfonated and phosphonated poly(pentafluorostyrene) polymers with flexible side groups, and (d) nanophase-separated block copolymers based on phosphonated[3] or sulfonated pentafluorostyrene and octylstyrene. Additionally, we investigate (e) H+-conductive fiber-mat reinforced perfluorosulfonic acid (PFSA) polymers[4].The development of anion exchange membranes in our research group includes (a) polystyrene-based side chain anion exchange polymers and their blends with polybenzimidazole[5], (b) polynorbornene-based optionally ionically and covalently crosslinked anion exchange polymers and membranes, (c) side chain anion exchange polymers and membranes prepared by polyhydroxyalkylation[6], and (d) anion exchange blend membranes made from polydiallyldimethylammonium salts and polybenzimidazole.This contribution highlights the application of two polymer types in PEM and AEM membrane water electrolysis, respectively:(A) PEM Water Electrolysis (PEMWE): Membranes from PEM types (a) and (b) demonstrated good performance. PEM (a) achieved 2.2 V@6 A/cm2, and PEM (b) reached 2.26 V@6 A/cm2 (compared to Nafion212: 2.26 V@6 A/cm2)[2]. These performances were accomplished with non-optimized membrane-electrode assemblies using Nafion as the electrode ionomer. Further performance improvements are expected with optimized electrodes containing the same ionomers as used in the membrane.(B) AEM Water Electrolysis (AEMWE): Blend membranes from AEM type (a) exhibited excellent alkali stability (no conductivity decrease after 1000 hrs of storage in 1M KOH@85°C) and good AEMWE performance (CuCo anode catalyst, 1M KOH, 70°C, 2 V@3 A/cm2)[5]. Type (c) AEMs were applied to a seawater electrolysis cell at 60°C, achieving a performance of 2 V@1 A/cm2 using completely noble metal-free catalysts in both the anode and cathode[6].[1] M. F. Ahmad Kamaroddin, N. Sabli, T. A. Tuan Abdullah, S. I. Siajam, L. C. Abdullah, A. Abdul Jalil, A. Ahmad, Membranes 2021, 11.[2] J. Bender, B. Mayerhöfer, P. Trinke, B. Bensmann, R. Hanke-Rauschenbach, K. Krajinovic, S. Thiele, J. Kerres, Polymers 2021, 13.[3] S. Auffarth, M. Wagner, A. Krieger, B. Fritsch, L. Hager, A. Hutzler, T. Böhm, S. Thiele, J. Kerres, ACS Materials Lett. 2023, 5, 2039.[4] M. S. Mu'min, M. Komma, D. Abbas, M. Wagner, A. Krieger, S. Thiele, T. Böhm, J. Kerres, Journal of Membrane Science 2023, 685, 121915.[5] L. Hager, M. Hegelheimer, J. Stonawski, A. T. S. Freiberg, C. Jaramillo-Hernández, G. Abellán, A. Hutzler, T. Böhm, S. Thiele, J. Kerres, J. Mater. Chem. A 2023.[6] M. L. Frisch, T. N. Thanh, A. Arinchtein, L. Hager, J. Schmidt, S. Brückner, J. Kerres, P. Strasser, ACS Energy Lett. 2023, 8, 2387.