Water electrolyzers are the key technology for splitting water with renewable electricity to produce green hydrogen and oxygen. Over several decades, the technology has evolved into four main types, each with distinct advantages and disadvantages. The development of cell materials has been central to this evolution, improving the efficiency and durability of these systems. Continued material advancements are vital for boosting efficiency and lowering energy consumption, which in turn reduces the operating costs of green hydrogen plants. In this article, IDTechEx explores key developments in cell materials across these four main electrolyzer technologies.
For a comprehensive analysis of this evolving materials landscape, including detailed market forecasts and key industry players, further details can be found in the IDTechEx report, "Materials for Green Hydrogen Production 2026-2036: Technologies, Players, Forecasts". This report covers innovations across Alkaline (AEL), Proton Exchange Membrane (PEMEL), Anion Exchange Membrane (AEMEL), and Solid Oxide (SOEC) electrolyzer technologies.
Alkaline Electrolyzer (AEL): Innovations in Electrodes and Diaphragms
As the most established electrolyzer technology, AEL benefits from mature component design and manufacturing. However, significant innovation continues, particularly in electrode catalysts and diaphragms.
The industry standard for most AEL systems is nickel-based electrodes. State-of-the-art systems typically use:
- Cathode Catalysts: Nickel-molybdenum (Ni-Mo) or nickel-cobalt (Ni-Co) alloys, and Raney nickel.
- Anode Catalysts: Nickel-iron (Ni-Fe) hydroxides and oxyhydroxides.
To better compete with PEM electrolyzers on efficiency, some manufacturers enhance these electrodes with platinum group metals (PGMs) and rare earth oxides. For example, platinum can be added to the cathode formulation, while mixed metal oxides containing ruthenium or iridium can be used for anodes, as showcased by products from De Nora.
Beyond catalyst composition, innovation is also occurring in electrode substrates and manufacturing. Nickel foams and felts are being explored as alternatives to conventional porous plates and meshes.
A major trend is the adoption of advanced electrode coating processes. Jolt Solutions, for instance, has developed the Sparkfuze process, which uses exothermic reactions to form the catalyst from precursors in just one or two cycles. This method is faster, more energy-efficient, and less costly than the conventional "coat-and-bake" technique, which requires multiple coating and high-temperature drying steps.
Diaphragms are also a key area of innovation. While Zirfon (a zirconia-polysulfone composite) remains the industry standard, new production methods are emerging. Novamem, for instance, has developed a process where nanoparticles are embedded within a polymer and then dissolved, leaving behind a highly optimized porous network for electrolyte flow.
PEM Electrolyzer (PEMEL): Reducing Precious Metal Content and Addressing PFAS Concerns
As the second most established technology, the proton exchange membrane electrolyzer (PEMEL) benefits from innovations in the related PEM fuel cell field. Its solid polymer electrolyte makes it highly responsive and ideal for pairing with intermittent renewables like wind and solar. While component design is relatively standard nowadays, significant R&D continues.
Catalysis in PEMELs relies on precious metals: platinum on carbon at the cathode and iridium oxide at the anode. These are typically dispersed in a catalytic ink with an ionomer binder and coated onto the membrane to create a catalyst-coated membrane (CCM). Improving CCM manufacturing to minimize precious metal waste is a major R&D focus for companies and research institutes alike.
Reducing the quantity of iridium is critical for long-term supply chain resilience. Soaring demand for PEMELs is expected to strain the global iridium market, potentially leading to shortages. To mitigate this, catalyst manufacturers like Heraeus are commercializing alternatives such as iridium-ruthenium (Ir-Ru) mixed oxides and supported iridium catalysts, which offer similar performance with less iridium. However, the ultimate goal remains developing entirely iridium-free catalysts.
Growing concerns over potential per- and poly-fluoroalkyl substance (PFAS) regulations are driving R&D into PFAS-free, hydrocarbon-based proton exchange membranes. Companies like Ionomr Innovations are developing new membrane formulations using sulfonated hydrocarbon materials for proton transport. IDTechEx’s Ion Exchange Membrane report provides detailed coverage of this emerging market.
A separate, fundamental challenge in membrane design is balancing conductivity with durability and safety. Thinner membranes improve proton conductivity but are less durable and more susceptible to hydrogen crossover. Key strategies to manage this trade-off include reinforcing the membrane with materials like ePTFE and PEEK while ensuring sufficient thickness to maintain safety. Established manufacturers like Chemours, Gore, Syensqo, and AGC are actively working to solve these challenges.
AEM Electrolyzers (AEMEL): Bypassing PFAS and Developing Optimal Electrode Systems
The anion exchange membrane electrolyzer (AEMEL) is an emerging hybrid technology aiming to combine the low-cost materials of AEL with the responsiveness of PEMEL. While historically challenged by membrane instability, several manufacturers – including established players like AGC and Fumatech and newer entrants like Versogen and Ionomr Innovations – are now commercializing stable AEM membranes.
Most AEM membranes use hydrocarbon backbones (based on polymers like PBI and PAP) doped with quaternary ammonium sidechains to transport hydroxide (OH−) ions. The primary R&D goals are to optimize conductivity and long-term stability while scaling up manufacturing. A key advantage of this approach is the complete avoidance of PFAS materials, which is possible due to the less harsh operating conditions compared to PEMELs.
A critical design choice in AEMEL is the "wet" versus "dry" cathode configuration, which dictates component selection:
- Dry cathode systems: the cathode is not supplied with a liquid electrolyte. Components are similar to PEMELs, using carbon gas diffusion layers and a catalyst coated directly onto the membrane.
- Wet cathode systems: the electrolyte is fed to both the anode and cathode. This design uses nickel-based porous transport layers on both sides, with catalysts coated either on the transport layers or the membrane.
Solid Oxide Electrolyzers (SOEC): Lowering Temperatures and Improving Cell Design
The solid oxide electrolyzer (SOEC) is an emerging technology defined by its high operating temperatures (600-900 °C). This high-temperature operation boosts electrical efficiency and allows for the use of industrial waste heat in the process. SOEC technology has benefited significantly from parallel developments in solid oxide fuel cells (SOFCs).
Conventional SOEC designs are "electrode-supported" or "electrolyte-supported," where one layer provides structural integrity. A key trend is the shift towards "metal-supported" cells, where the active layers are coated onto a porous stainless-steel support. This design, commercialized by Ceres Power, allows for thinner cell layers while gaining the structural durability of stainless steel.
Another significant trend is the push towards lower operating temperatures to reduce energy requirements. This has led to the adoption of alternative electrolytes like gadolinia-doped ceria (GDC), which can operate at 600 °C compared to the 800 °C needed for traditional yttria-stabilized zirconia (YSZ). This shift requires adapting the electrode materials to the new electrolyte. Topsoe is a key developer that has successfully commercialized SOEC systems based on this lower-temperature GDC technology.
Summary & Outlook: A Multi-Billion Dollar Component Market Fueled by Continuous Innovation
IDTechEx projects the annual market for water electrolyzer components to surpass US$10 billion by 2036. This significant growth is driven by the anticipated surge in demand for electrolyzer systems as green hydrogen projects gain momentum and achieve commercial maturity. The electrolyzer sector has a long history of benefiting from continuous innovation, and this trend is set to continue. As this article illustrates, even in relatively mature component areas, there is still substantial room for improvement. For more detailed insights into these innovations, key players, company case studies, and 10-year component market forecasts, please see the full report: "Materials for Green Hydrogen Production 2026-2036: Technologies, Players, Forecasts".