Redirecting dynamic structural evolution of nickel-contained RuO2 catalyst during electrochemical oxygen evolution reaction

Abstract

Electrochemical oxygen evolution reaction (OER) is a main efficiency bottleneck of water electrolysis. Commercial ruthenium oxide (RuO2) catalyst displays remarkable activities but poor stability for OER. The instability stems from lattice oxygen oxidation, resulting in the oxidation of Ru4+ to soluble Rux+ (x > 4) species. Herein, we redirect dynamic structural evolution of Ru-based catalysts through introducing oxidized nickel (Ni) components. By virtue of comprehensive structural characterizations, such as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), operando Raman and so forth, it is demonstrated that when the atomic content of Ni exceeds that of ruthenium (Ru), the Ni components can efficiently inhibit the Ru4+ oxidation and structural collapse. Density functional theory (DFT) calculations suggest that the introduction of Ni component hinders the formation of oxygen vacancies, and makes lattice oxygen mediated mechanism turn to adsorbate evolution mechanism, which eventually improves the stability. The optimized nickel-contained RuO2 catalyst delivers an effective reactivity with an overpotential of less than 215 mV to attain 10 mA cm−2 and remarkable stability with only 5 mV increment after 5000 potential cycles. This work provides insights into the origin of dynamic structural evolution of transition-metal-modified RuO2 electrocatalysts.