Earth-Abundant Copper-Based Bifunctional Electrocatalyst for Both Catalytic Hydrogen Production and Water Oxidation

The production of hydrogen through water splitting via electrolysis/photocatalysis seems a promising and appealing pathway for clean energy conversion and storage. Herein we report for the first time that a series of water-soluble copper complexes can be used as catalyst precursors to generate the copper-based bifunctional catalyst composite for both hydrogen production and water oxidation reactions. Under an applied cathodic potential, a thin catalyst film was grown on a fluorine-doped tin oxide (FTO) electrode, accompanied by the production of a large amount of hydrogen gas bubbles. Scanning electron microscopy shows the presence of nanoparticulate material on the FTO. Powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicated that the materials consist of amorphous cuprous oxide mixed copper hydroxide (H-2-CuCat), which can catalyze water reduction in a copper-free aqueous solution (pH = 9.2) under a low overpotential. Remarkably, under an applied anodic potential, the material can also efficiently catalyze water oxidation to evolve oxygen. The present robust, bifunctional, switchable, and noble-metal-free catalytic material has potential applications in solar water-splitting devices.