NiFe Layered Double Hydroxides with Unsaturated Metal Sites via Precovered Surface Strategy for Oxygen Evolution Reaction

The oxygen evolution reaction (OER) plays an important role for multiple energy conversion devices, such as electrochemical water splitting, yet it suffers from high overpotential due to its sluggish kinetics. As one of the most promising OER catalysts, NiFe layered double hydroxides (LDHs) can be rationally tailored via defect engineering to achieve enhanced catalytic performance. Herein, we report a fluoride precovered surface strategy to manipulate the coordinatively unsaturated metal sites of NiFe LDH catalysts. The adsorption of fluoride is introduced during the crystallization process with flexible amount, and the precovered fluoride can be easily removed by electrochemical treatment, leaving a controllable density of unsaturated metal sites with high activity toward OER. Specifically, NiFe LDH with an optimized amount of fluoride precovered demonstrates an overpotential of 243 mV to achieve the current density of 10 mA cm(-2) for OER, with a reduced Tafel slope of 50 mV dec(-1), exhibiting enhanced catalytic performance than pristine NiFe LDH. Such a precovered surface strategy can effectively manipulate the density of coordinatively unsaturated metal sites and has great potential in catalyst design with high performance via defect engineering.