Hierarchically Structured Cu-Based Electrocatalysts with Nanowires Array for Water Splitting

We report here the fabrication of CuO nanowires and their use as efficient electrocatalyst for the oxygen evolution reaction (OER) or as precursor for preparation of Cu3P nanowires for the hydrogen evolution reaction (HER). The surface-bound Cu(OH)2 nanowires are in situ grown on a three-dimensional copper foam (CF) by anodic treatment, which are then converted to CuO nanowires by calcination in air. The direct growth of nanowires from the underlying conductive substrate can eliminate the use of any conductive agents and binders, which ensures good electrical contact between the electrocatalyst and the conductive substrate. The hierarchically nanostructured Cu-based electrode exhibits excellent catalytic performance toward OER in 1 M KOH solution. Phosphorization of the CuO/CF electrode generates the Cu3P/CF electrode, which can act as an excellent electrocatalyst for HER in 1 M KOH. An alkaline electrolyzer is constructed using CuO and Cu3P nanowires coated copper foams as anode and cathode, which can realize overall water splitting with a current density of 102 mA/cm2 at an applied cell voltage of 2.2 V.