RuO2 emerges as a promising alternative to IrO2 for acidic oxygen evolution reaction (OER) due to its relatively low cost. But its practical application remains hindered by stability issues originating from the oxidation of lattice oxygen. Here, we report a low Ru-content solid solution oxide (Ru0.32Ta0.66Mn0.02O2) for efficient acidic OER. The Ru0.32Ta0.66Mn0.02O2 catalyst possesses a low overpotential of 175 mV@10 mA cm-2 in 0.5 M H2SO4 and achieves current densities of 0.5/1 A cm-2 at cell voltages of 1.539/1.660 V in a proton exchange membrane water electrolyzer with stable response for over 1000 h@0.5 A cm-2. X-ray absorption spectroscopy (XAS) reveals that Ta and Mn effectively modulates the distance between the active sites, thereby promoting the direct O─O coupling. Moreover, Mn increases the surface coverage of *OH, facilitating the oxide pathway mechanism (OPM) for OER. In situ infrared spectroscopy and 18O-labeled mass spectrometry confirm the formation of *O─O* intermediate on Ru0.32Ta0.66Mn0.02O2 via OPM. Density functional theory calculation demonstrates that TaO2 matrix weakens the d-p orbital hybridization and attenuate the Ru─O covalency, thereby inhibiting the oxidation of lattice oxygen. In addition, the doped Mn reduces the OER free energy barrier by triggering the OPM, breaking the linear scaling relationship of OER.
Liu et al. (2026) studied this question.