Cross-plane iridium-based filaments sap efficiency in proton exchange membrane electrolyzers

Proton exchange membrane electrolysis cells (PEMECs) are key to producing green hydrogen. The success of the green hydrogen economy depends on the technical maturity and scalability of water electrolysis systems. However, achieving energy-efficient and long-term operation requires a thorough understanding of aging mechanisms. While PEMECs have been extensively studied under laboratory conditions, data derived from industrial-scale operations are scarce. Our study addresses aging in an industry-oriented PEMEC operated under realistic conditions for 5,000 h, revealing systematic parasitic current pathways from cross-plane iridium filaments within the membrane, correlated with the anode/porous transport layer (PTL) interface. Experiments and computational models confirm that these parasitic currents do not impede system operation but do reduce system efficiency. This filament formation associated with the anode/PTL interface represents a hitherto unreported source of aging within PEMECs. Our findings will help optimize PEMEC design, effectively improving system performance and lifetime on an industrial scale, thus advancing the green hydrogen economy.