Co/Cu-modified NiO film grown on nickel foam as a highly active and stable electrocatalyst for overall water splitting

The development and utilization of low-cost and efficient electrocatalysts for overall water splitting is of great significance for future energy supplies. Herein, the Co-doped NiCu mixed oxide films on Ni foam as a bifunctional electrocatalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are synthesized by a facile solvothermal method using methanol as a reactant and followed by annealing in air, which exhibits a remarkably enhanced HER and OER activity. The well-constructed surface and porous skeleton structure with large volume provides a large number of catalytically active sites during the electrochemical reaction. Notably, CuO plays an important role in improving the catalytic activity of electrodes, meanwhile, Co doping is beneficial to increase the conductivity and activate the Ni sites at the lower overpotentials via charge transfer effect. Accordingly, the optimized CuO-NiO/Ni foam electrode exhibits comparatively low overpotential of 38 mV and 172 mV at 10 mA/cm2 for HER and OER in 1.0 M KOH, respectively. Moreover, the electrode shows excellent long-term stability for 1000 cyclic voltammetric cycles in both HER and OER. The self-assembled overall water splitting device using the electrode as both the anode and cathode achieves the current density of 10mA/cm2 at a low cell voltage 1.51V. This study is promising as a simple method for depositing multimetal mixed oxide on metal substrate as an efficient bifunctional electrocatalyst, holding great significance in future energy application.