Roadmap toward next-generation proton exchange membrane water electrolyzers

Green hydrogen production via proton exchange membrane water electrolyzers (PEMWEs) is crucial for achieving carbon neutrality, enabling large-scale renewable energy integration. By potentially lowering hydrogen production costs to under $2/kg H 2 by 2030, PEMWEs are poised to become central to the hydrogen economy. However, scalability from MW to GW levels presents significant challenges, particularly in catalytic overpotentials and transport resistances. This perspective outlines critical issues in catalytic overpotential, electron and proton transport resistance, and mass-transport limitations. We propose a comprehensive roadmap to advance PEMWE technology through improved catalyst designs, reduced transport resistances, and innovative manufacturing techniques, such as catalyst-coated substrates (CCSs). Achieving the ambitious target of 1.6 V at 3 A/cm 2 with reduced catalyst loading will require breakthroughs in materials science, cell architecture, and scalable production processes. This analysis emphasizes collaborative efforts and technological innovations to achieve a sustainable hydrogen future.