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

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 Co³⁺ ions are generated on the pore wall of nanosheets, and the unique atomic structure around Co³⁺ ions leads to appropriate electronic structure and adsorption energy of intermediates, thus accelerating hydrogen and oxygen evolution.