Heterophase RuO ₂ oxygen evolution catalyst for durable proton exchange membrane water electrolysis

Dissolution of ruthenium (Ru) species under harsh anode operating conditions severely impedes the commercialization of non–iridium (Ir) proton exchange membrane water electrolyzers (PEMWEs). Here, we propose a catalyst design strategy that engineers phases beyond conventional atomic ordering, constructing a heterophase MoRuO x catalyst (AC-MoRuO x ). This catalyst achieves 10 milliamperes per square centimeter in an acidic oxygen evolution reaction with merely 180-millivolt overpotential while operating stably for >3000 hours. In PEMWE devices, AC-MoRuO x delivers record durability at industrial current densities: ≥2000 hours at 1.0 ampere per square centimeter and 1000 hours at 1.5 amperes per square centimeter. We demonstrate that heterophase architecture and atomic arrangements reconfigure electronic structures and phase distribution, simultaneously optimizing active-site density and structural integrity. This breakthrough resolves the long-standing activity-stability trade-off in ruthenium-based catalysts.