Folded nanosheet-like Co0.85Se array for overall water splitting

Active, stable, and earth-abundant bifunctional electrocatalyst for overall water splitting is pivotal to actualize large-scale water splitting via electrolysis. In this work, the hierarchical folded nanosheet-like Co0.85Se array on Ni foam is constructed by liquid-phase chemical conversion with cobalt precursor nanorod array. It can serve as an efficient bifunctional electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolyte, with a current density of 10 mA cm−2 at overpotential of 232 mV for OER and 129 mV for HER and Tafel slope of 78.9 mV dec−1 for OER and 95.0 mV dec−1 for HER, respectively. The two-electrode alkaline water electrolyzer utilizing this folded nanosheet-like Co0.85Se array as both anode and cathode toward overall water splitting offered a current of 10 mA cm−2 at a cell voltage of 1.60 V. This work explores an efficient and low-cost electrocatalyst for overall water splitting application in alkaline electrolytes.