Promoting Oxide Pathway Mechanism on Low‐Ruthenium‐Content Oxides for Enhanced Oxygen Evolution in Proton Exchange Membrane Water Electrolyzer

ABSTRACT RuO 2 emerges as a promising alternative to IrO 2 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 (Ru 0.32 Ta 0.66 Mn 0.02 O 2 ) for efficient acidic OER. The Ru 0.32 Ta 0.66 Mn 0.02 O 2 catalyst possesses a low overpotential of 175 mV@10 mA cm −2 in 0.5 M H 2 SO 4 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 18 O‐labeled mass spectrometry confirm the formation of *O─O* intermediate on Ru 0.32 Ta 0.66 Mn 0.02 O 2 via OPM. Density functional theory calculation demonstrates that TaO 2 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.