B-site substitution in NaCo1−2xFexNixF3 perovskites for efficient oxygen evolution

The oxygen evolution reaction (OER) has slow chemical dynamics in the electrochemical decomposition of water. Herein, we demonstrate that B-site substitution engineering on ABF3 is an efficient strategy to boost the OER activity due to the modified electronic structure. A series of perovskite fluorides with the formula NaCo1−2xFexNixF3 were fabricated via a simple hydrothermal process, in which Co was partially substituted by both Fe and Ni. The optimized perovskite fluoride exhibited a low overpotential of 265 mV at a current density of 10 mA cm−2 and outstanding electrochemical stability after 100 h continuous electrocatalysis for the OER. These results are superior to the state-of-the-art perovskite-based OER catalysts. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) results showed that the dual-substitution of Fe and Ni atoms not only produced higher valence Co3+ ions but also generated the more active species Fe3+. In addition, the produced metal oxyhydroxides (MOOH, M = Co, Fe, Ni) on the catalyst surface during OER activation could contribute both excellent catalytic activity and ultralong stability.