Photoelectrochemical Water Splitting on a Delafossite CuGaO2Semiconductor Electrode

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 5.34×10⁻²Ω⁻¹cm⁻¹ , 3.5×10²⁰cm⁻³ , 9.5×10⁻⁴cm²V⁻¹s⁻¹ at room temperature, and +360μV/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.