Modulating the atomic local structure of ruthenium oxide for enhanced oxygen evolution reaction

Developing low-cost, highly active and robust electrocatalysts for acidic oxygen evolution reaction (OER) is a critical challenge facing the hydrogen-based energy delivery system. As a cheaper alternative to the benchmark IrO₂, RuO₂ possesses higher OER catalytic activity but suffers from intrinsically low stability arising from Ru dissolution and lattice oxygen overoxidation. Herein, we report a high-vacuum annealing strategy to regulate the oxygen vacancy (O_v) concentration in RuO₂, enabling the controllable modulation of the atomic local coordination structures of RuO₂. At the optimal O_v level, the RuO_2-x-2 catalyst forms stable metallic Ru-Ru bonds while maintaining oxidized Ru-O moieties, achieving an ultralow overpotential of 169 mV at 10 mA cm⁻² and exceptional stability with 400-hour stable operation in 0.5 M H₂SO₄. <em>Operando</em> X-ray absorption fine structure (XAFS) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) results reveal that the Ru-Ru and adjacent Ru-O sites synergistically activate the oxide pathway mechanism, circumventing the scaling relationship and minimizing the structural distortion during the OER. This work provides not only a facile approach to controllable modulate local structure of RuO₂ but also insights into the synergistic effects between multiple active centers, which would greatly promote the further development of high-performance RuO₂-based OER electrocatalysts.