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 (Ov) concentration in RuO2, enabling the controllable modulation of the atomic local coordination structures of RuO2. At the optimal Ov level, the RuO2-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. Operando 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.