Concentration-dependent regulation of RuO2 by Ta doping for enhanced acidic oxygen evolution

The activity-stability trade-off of RuO 2 -based catalysts remains a key challenge for acidic oxygen evolution reaction (OER) in proton exchange membrane water electrolyzes. Here, a series of Ta 5+ -doped RuO 2 catalysts (Ta-RuO 2 -x, 6–41 at.%) was constructed to elucidate the effect of Ta concentration on structural evolution and OER performance, revealing a clear non-monotonic dependence on dopant content. An optimal Ta doping level was identified, delivering an overpotential of 187 mV to achieve 10 mA cm −2 in 0.5 M H 2 SO 4 , together with a Tafel slope of 88.3 mV dec −1 and stable operation for over 160 h. Structural analysis indicates that moderate Ta incorporation regulates the RuO 2 lattice and modulates the electronic structure of Ru sites, accompanied by oxygen-vacancy formation, thereby optimizing Ru O interactions. Furthermore, combined pH-dependent kinetic analysis and density functional theory (DFT) calculations suggest that Ta doping favors an adsorbate evolution mechanism (AEM)-dominated pathway and lowers the energy barrier of the rate-determining step. This work highlights dopant concentration as a key parameter governing the structure–activity relationship of RuO 2 catalysts in acidic OER.