Fabrication and electrochemical properties of copper oxide (CuO) nanowire–cobalt oxide (Co3O4) nanoparticle heterostructures for oxygen evolution reaction

Abstract

Nanoscale heterostructures of metal oxides with controlled morphology, interface and phase purity have been considered of great importance for efficient and cost-effective water splitting process. Here, we report the fabrication of CuO nanowire–Co3O4 nanoparticle heterostructures for the oxygen evolution reaction in the electrocatalytic water splitting process. The synthesis was achieved in a facile and surfactant-free two-step thermal growth process, where free-standing CuO nanowires were first produced by directly annealing a piece of copper foil in the air. This was followed by dip-coating of cobalt salt on the surface of CuO nanowires and subsequent thermal treatment in air to result in the uniform formation of Co3O4 nanoparticles on the CuO nanowires. The morphology and structure of the heterostructures were characterised by the microscopic and diffraction methods. CuO nanowires or the heterostructures were further coated onto a glassy carbon electrode for oxygen evolution in the electrochemical water splitting. The effective surface areas of the electrodes were measured using the Randles–Sevcik equation. Their electrocatalytic activity was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel methods.