Hierarchically Structured CuCo2S4 Nanowire Arrays as Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Hydrogen produced from water splitting offers a green alternative to conventional energy such as fossil fuels. Herein, CuCo2S4 nanowire arrays were synthesized on a nickel foam substrate by a two-step hydrothermal approach and utilized as highly efficient bifunctional electrocatalyst for overall water splitting. The CuCo2S4 nanowire arrays were identified as an exceptionally active catalyst for the hydrogen evolution reaction (HER) in a basic solution with an extremely low overpotential of 65 mV to reach a current density of 10 mA/cm2. The hierarchically structured CuCo2S4 electrode was also highly active toward the oxygen evolution reaction (OER), achieving a high current density of 100 mA/cm2 at an overpotential of only 310 mV. Consequently, an alkaline electrolyzer constructed using CuCo2S4 nanowire arrays as both anode and cathode can realize overall water splitting with a current density of 100 mA/cm2 at a cell voltage of 1.65 V, suggesting a promising bifunctional electrocatalyst for efficient overall water splitting.