Engineering a Proton-Regulating Interfacial Microenvironment for Durable RuO2 Electrocatalysis in PEM Water Electrolysis

Abstract Proton exchange membrane (PEM) water electrolysis is a technology for hydrogen production, but its deployment is limited by the cost and durability of acidic oxygen evolution reaction (OER) catalysts. RuO2 exhibits intrinsic OER activity yet degrades rapidly under high-current-density operation and start–stop cycles. Sluggish interfacial proton dissipation may contribute to this instability by promoting proton accumulation and local acidification. Here, we report an atomic-level microenvironment engineering strategy via aliovalent strontium incorporation into rutile RuO2. Modified RuO2 features a structurally distorted and electronically polarized interface that, according to calculations, alters interfacial water organization and may favor oxygen-end-oriented water configurations near the Sr-modified regions. This modified interfacial environment is associated with alleviated local acidification, facilitated proton-transfer-related processes, suppressed lattice oxygen participation, and favored surface-confined oxygen coupling. Operando characterization in a PEM membrane–electrode assembly further supports dynamic interfacial water reorganization and enhanced proton-transfer kinetics under device-relevant conditions. Modified RuO2 delivers 10 mA cm–2 at 197 mV in acidic electrolyte and, in a PEM electrolyzer, achieves 1 A cm–2 at 1.686 V, operates for over 400 h with Ru dissolution suppressed to 5.79 ng h–1, and withstands 3102 start–stop cycles. These findings support interfacial microenvironment regulation as a strategy for improving the durability of Ru-based acidic OER catalysts.