Porous Cobalt–Nickel Hydroxide Nanosheets with Active Cobalt Ions for Overall Water Splitting

Abstract

Abstract Low‐cost and high‐performance catalysts are of great significance for electrochemical water splitting. Here, it is reported that a laser‐synthesized catalyst, porous Co 0.75 Ni 0.25 (OH) 2 nanosheets, is highly active for catalyzing overall water splitting. The porous nanosheets exhibit low overpotentials for hydrogen evolution reaction (95 mV@10 mA cm −2 ) and oxygen evolution reaction (235 mV@10 mA cm −2 ). As both anode and cathode catalysts, the porous nanosheets achieve a current density of 10 mA cm −2 at an external voltage of 1.56 V, which is much lower than that of commercial Ir/C‐Pt/C couple (1.62 V). Experimental and theoretical investigations reveal that numerous Co 3+ ions are generated on the pore wall of nanosheets, and the unique atomic structure around Co 3+ ions leads to appropriate electronic structure and adsorption energy of intermediates, thus accelerating hydrogen and oxygen evolution.