Mitigating the Activity−Stability Trade-Off in In-Doped RuO2 for Acidic Oxygen Evolution via Electronic Regulation of Lattice Oxygen Chemistry

The practical deployment of Ru-based catalysts for the acidic oxygen evolution reaction (OER) is fundamentally constrained by the reciprocal relationship between catalytic turnover and structural integrity. Herein, we report an indium-doped RuO2 (In−RuO2) catalyst, in which indium incorporation disrupts the Ru−O−Ru symmetry and modulates the local electronic structure, thereby tuning Ru−O covalency and promoting lattice oxygen participation in the OER process. The optimized In0.15Ru0.85O2 delivers a low overpotential of 177 mV at 10 mA cm−2 and maintains stable operation for over 320 h at 100 mA cm−2 in 0.5 M H2SO4. Moreover, in a proton exchange membrane (PEM) water electrolyzer, it operates steadily for 800 h at 500 mA cm−2 with a low decay rate of 37.5 μV h−1. Operando studies, including isotope-labeling and isotope-switching differential electrochemical mass spectrometry (DEMS), TMA+ probing, and pH-dependent analysis, reveal the coexistence of the adsorbate evolution mechanism (AEM) and lattice oxygen mechanism (LOM), with LOM becoming more prominent upon indium incorporation. Density functional theory (DFT) calculations show that indium incorporation induces Ru−O−In charge redistribution, narrows the energy gap between Ru 4d and O 2p bands, modulates the Ru−O bonding, and stabilizes Ru oxidation states, collectively facilitating LOM activity while suppressing Ru overoxidation and dissolution. This work provides atomic-level mechanistic insights into electronic regulation of lattice oxygen chemistry and establishes indium doping as a robust strategy for simultaneously enhancing activity and stability of RuO2 in acidic OER.