Photoelectrochemical water splitting on a delafossite CuGaO2 semiconductor electrode

Abstract

A pellet of polycrystalline CuGaO2 with a delafossite structure was prepared from Ga2O3 and CuO by high-temperature solid-state synthesis. The CuGaO2 pellet was a p-type semiconductor for which the electrical conductivity, carrier density, carrier mobility and Seebeck coefficient were 5.34 × 10-2 Ω-1cm-1, 3.5 × 1020 cm-3, 9.5 × 10-4 cm2V-1s-1 at room temperature, and +360 μV/K, respectively. It also exhibited two optical transitions at about 2.7 and 3.6 eV. The photoelectrochemical properties of the CuGaO2 pellet electrode were investigated in aqueous electrolyte solutions. The flat-band potential of this electrode, determined using a Mott-Schottky plot, was +0.18 V vs SCE at pH 4.8 and followed the Nernst equation with respect to pH. Under UV light illumination, a cathodic photocurrent developed, and molecular hydrogen simultaneously evolved on the surface of the electrode due to the direct reduction of water without deposition of any metal catalyst.