Especially popular in Europe, the PEMEL stands out for its high energy efficiency and compatibility with intermittent renewable energy sources.
The PEM electrolyzer shares many materials and components with the PEM fuel cell (PEMFC), greatly benefiting from advancements in the fuel cell sector. Initiated by NASA, PEMFC technology has evolved significantly, leading to both the PEMEL and PEMFC becoming relatively well-established technologies. However, they still face numerous challenges.
The burgeoning green hydrogen market is driving demand for electrolyzer systems, which in turn is generating demand for electrolyzer materials and components. This boom presents a significant opportunity for material and component suppliers, along with various industry players, to capitalize on this growth, innovate, and introduce new products.
Simplified diagram of the components of a proton exchange membrane electrolyzer (PEMEL) cell. Source: IDTechEx
Proton exchange membrane (PEM)
The proton exchange membrane (PEM) is the backbone of the electrolyzer, located between the cathode and the anode. PEMs facilitate the transfer of protons (H+ ions) from the anode to the cathode. They also provide electrical insulation between the electrodes and ensure that the hydrogen and oxygen evolution reactions occur separately, resulting in the production of high-purity hydrogen and preventing the mixing of gases, especially hydrogen and oxygen.
The membranes are made of perfluorinated sulfonic acid (PFSA) ionomers. Nafion, a Chemours brand (originally developed by DuPont), is the best-known and most widely used material in PEMELs and PEMFCs. The market is dominated by established companies such as Chemours and WL Gore & Associates. However, these companies continue to innovate their products to achieve better performance.
The main challenge in improving PEMs is balancing performance, safety, and durability. This is because increasing performance requires thinner membranes to improve conductivity; however, this leads to greater hydrogen-to-oxygen gas cross-pollination and faster membrane degradation. A common mitigation tactic explored in the industry is the use of a reinforcing layer, such as expanded polytetrafluoroethylene (PTFE), over which the PFSA ionomer is coated.
Addressing the challenges of improving membrane performance with new composite materials will be key to advancing the technology. Despite these challenges, PFSA membranes will remain the dominant material due to a lack of suitable, readily available alternatives. Consequently, a significant market exists for these membranes in the electrolyzer and fuel cell industries.
Platinum group metal catalysts and catalyst-coated membrane (CCM)
Platinum (Pt) and iridium (Ir) catalyze the electrochemical reactions of hydrogen and oxygen evolution that take place in the electrolyzer, respectively. The latest generation materials used are platinum supported on carbon black (Pt/C) for the cathode and iridium black (Ir) or iridium oxide (IrOx) for the anode.
The catalysts are combined with PFSA ionomer resins in the form of an ink, which is then coated onto the membrane, producing the catalyst-coated membrane (CCM). CCM production is a key research area, as electrolyzer performance depends heavily on its properties. A crucial aspect is the development of efficient, continuous roll-to-roll processes for CCM production that can ensure consistent throughput, minimal loss of catalytic inks, and highly automated, large-scale production.
The most important research objective is the need to reduce the iridium loading on anodes. Current loadings of 1 to 2.5 g/kW in PEM electrolyzers are problematic, as future demand for this equipment could put significant pressure on the global iridium supply. To address this issue, catalyst manufacturers such as Heraeus Precious Metals are introducing new products that reduce the iridium loading. These include iridium ruthenium oxide (IrRuOx), which is already beginning to be used commercially. However, over time, new supported iridium catalysts (a concept similar to platinum supported on carbon) will be needed to reduce dependence on iridium supply. Therefore, significant opportunities exist to develop and market new catalyst products that offer competitive performance compared to current Ir and IrOx catalysts, while simultaneously reducing the total iridium loading to less than 1 g/kW.
Gas diffusion layers (GDL)
Gas diffusion layers (GDLs), also known as porous transport layers (PTLs), are another key component of PEMEL cells. These components are present on both sides of the electrodes and facilitate water transfer to the membrane, the removal of product gases (H2 and O2) from the electrodes, and the flow of electrons through the cell.
Carbon paper, composed of carbon fibers, PTFE, and carbon black, is used as the cathode material. The anode is based on titanium felt coated with a thin layer of platinum. Titanium is necessary for its corrosion resistance on the anode side, while platinum provides greater electrical conductivity and additional stability. These materials are here to stay and will be used in all PEMEL batteries.
The carbon paper was developed through the efforts of the PEM fuel cell industry and is now quite mature. Therefore, the main focus of development is on the anode side to reduce the thickness of the titanium felt, optimize porosity, and decrease the amount of platinum required. The platinum loading is particularly important and can be reduced using advanced coating technologies, such as physical vapor deposition (PVD).
Bipolar plates
The bipolar plates act as a physical barrier to separate the cells. More importantly, these plates conduct electrons from the anode of one cell to the cathode of another, and also provide channels for the flow of water and gas within the cells. Unlike PEM fuel cells, which can use graphite bipolar plates, PEM electrolyzers use titanium plates, which are more resistant to corrosion. Gold and platinum coatings are required on the cathode and anode faces, respectively, to increase corrosion resistance and reduce electrical contact resistance, similar to the platinum used in titanium DOFs.
Once again, these components benefit from the manufacturing of highly developed metallic bipolar plates in the PEM fuel cell sector. Companies offering plate manufacturing technologies include Dana Inc., Schuler, Elcon Precision, and many more. Each manufacturer utilizes different technologies, each with its own advantages and disadvantages. Despite the high level of development, manufacturers can still optimize production by reducing material waste and speeding up production lines.
The coating of bipolar plates is an area that could benefit most from new concepts. For example, more advanced coating technologies, such as PVD, can reduce the use of precious metals. Alternatives to titanium could also be found to lower the overall manufacturing cost. This requires experimenting with various metal alloys and material combinations, such as titanium-coated stainless steel. The latter is considered a promising option, but it still needs to undergo extensive testing in commercial operations.
Gaskets and sealing materials
Gaskets or seals are often overlooked when designing electrolyzer stacks, but these components are equally vital. They serve as sealing elements, creating an interface between different components, such as the bipolar plates and the separator. These precisely engineered barriers ensure that gases, water, and cell components remain contained and separated as needed. Gaskets typically take the form of thin sheets or tapes sandwiched between the bipolar plates.
Gasket materials are typically chosen to provide low hydrogen gas permeability to prevent leaks, as well as chemical resistance to the acidic and oxidizing conditions of the electrolyzer. They must also have adequate compressibility and mechanical properties to withstand compressive forces. Typical materials used include ethylene propylene diene monomer (EPDM) rubber, fluorinated rubber (FKM), PTFE, and silicone.
Preformed gaskets are the most common type. They are injection molded to fit the electrolyzer stack. The intricate designs of bipolar plates require meticulous sealing, so gasket manufacturers often partner with electrolyzer or bipolar plate suppliers. This allows the manufacturer to deposit the gaskets directly onto the customer's components and ship them to the customer. Gasket innovation strategies focus on optimizing the material and manufacturing process, as well as eliminating the application phase by supplying resins that customers can apply and cure themselves.
Market outlook and strategic perspectives
The electrolyzer component market is poised for significant expansion, with IDTechEx projecting its market value to reach an impressive $31.7 billion by 2034. This growth is primarily driven by the rapid evolution of the green hydrogen industry. As this article demonstrates, there are substantial opportunities for component supply and innovation within this market.
The IDTechEx report, "Materials for Green Hydrogen Production 2024-2034: Technologies, Players, Forecasts," also provides similar information on the materials and components used in alkaline water electrolyzers (AWE), anion exchange membrane electrolyzers (AEMEL), and solid oxide electrolyzers (SOEC). Comprehensive lists of electrolyzer stack suppliers, components, and materials are offered, along with case studies of key commercial innovations in the sector.
Furthermore, the report provides granular 10-year market forecasts, quantifying the demand for materials and components in tons, square meters (m2), and millions of dollars annually. Refer to the report for in-depth insights into current trends and key opportunities in the water electrolyzer components market.
Author: Chingis Idrissov, Technology Analyst at IDTechEx
