Dual-Site Cobalt-Doped RuO2/TiO2 Electrocatalyst Enables Stable and Cost-Efficient Acidic Oxygen Evolution for PEM Water Electrolysis

Developing efficient, cost-effective, and durable electrocatalysts for proton exchange membrane water electrolysis (PEMWE) remains a significant challenge, requiring the stabilization and enhancement of catalyst activity under harsh conditions. Here, we present cobalt-doped ruthenium dioxide (Co0.3Ru0.7O2) on TiO2 as an electrocatalyst toward an acidic oxygen evolution reaction. The Co0.3Ru0.7O2–TiO2 achieves an impressive overpotential of 322 mV at 1 A cm–2 and demonstrates stable operation for over 1000 h at 500 mA cm–2 in a PEMWE device. Comprehensive experimental and theoretical calculation results demonstrate that the doping of Co atoms into the rutile RuO2 lattice optimizes the geometric configuration. Moreover, the lattice-matched interface between Co0.3Ru0.7O2 and TiO2 promotes interfacial electron redistribution and stabilizes active centers under oxidative conditions. This facilitates a dual-site fully parallel oxidation (DFO) pathway in which intermediates are synchronously adsorbed and desorbed at Ru and Co sites, enabling direct O–O coupling. This work highlights the synergistic effect of the Ru–Co dual sites and TiO2 support in establishing a stable, self-regulating electronic environment that drives efficient intermediate transformation via the DFO mechanism.