Role of Interfacial Water in Improving the Activity and Stability of Lattice‐Oxygen‐Mediated Acidic Oxygen Evolution on RuO ₂

Although RuO₂-based electrocatalysts have been widely studied for acidic oxygen evolution reaction (OER), triggering the conventional adsorbate evolution mechanism to suppress kinetically favorable lattice oxygen mechanism (LOM) pathway at the expense of activity is the state-of-the-art strategy. To date, approaches to simultaneously achieve remarkable activity and stability of RuO₂-based electrocatalysts through the kinetically favorable LOM pathway toward acidic OER are still elusive. Herein, we report that RuS_0.45O_x catalyst with the synergetic regulation of asymmetric S-Ru-O microstructure and Ru-SO₄ local environments can simultaneously boost the lattice-oxygen-mediated OER activity and stability under acidic electrolyte. Experimental results, including operando attenuated total reflectance surface-enhanced infrared absorption spectroscopy, operando X-ray photoelectron spectroscopy, and theoretical studies, indicate the dynamic evolution of interfacial water structure from hydrogen-bond water to free-H₂O on the surface of RuS_0.45O_x. The generated continuous free-H₂O-enriched local environment is in favor of accelerating the sluggish kinetics of interfacial water dissociation and facilitating the replenishment of lattice oxygen vacancies generated during the lattice-oxygen-mediated OER process, thereby significantly enhancing the stability. Consequently, the obtained RuS_0.45O_x displays remarkable acidic OER performance with 160 mV to reach 10 mA cm^-2, and robust stability with negligible activity decay over 500 h at 100 mA cm^-2.