Synthesis of Cu2O-CuO two layer as photocathode and investigation of its photoelectrochemical properties

Production of hydrogen through photoelectrochemical water splitting using a semiconductor is a promising method for production of clean and renewable energy. Cu2O is a positive semiconductor that its conduction band position is suitable for photoelectrochemical reduction of water. In this study, Cu2O was synthesized using electrochemical deposition and it was heat treated at 450 °C for 30 min to obtain two layer Cu2O-CuO and improve its photoelectrochemical property. Oxidation of Cu2O resulted in two layer Cu2O-CuO. The x-ray pattern of the electrodeposited layer showed a pure Cu2O layer. Scanning electron microscopy showed a microstructure change after heat treatment and the particle size was in nanometer scale. Photocurrent density was measured using linear sweep voltammetry under chopped illumination and it was concluded that the photocurrent density of the heat treated sample at 450 °C was increased to 731 μA.cm-2. Electrochemical impedance spectroscopy at constant potential and frequency range of 0.1-105 Hz and also at fixed frequency and potential range of -0.3V up to 0.5V was performed to study charge transfer characteristic of the photocathode and to determine the flat band potential and carrier density. Carrier density of Cu2O and Cu2O-CuO was determined to be 1.3×1018 cm-3 and 3.05×1018 cm-3, respectively and the flat bend potential of Cu2O and Cu2O-CuO was determined to be 0.19V and 0.23V, respectively.