Cu2S/TiO2 heterojunction applied to visible light Orange II degradation

We report on the study of some physical properties of Cu2S and their effects toward the photoactivity of the Cu2S/TiO2 heterojunction. Transport properties of Cu2S, i.e. thermoelectric power and electrical conductivity were studied and correlated to the photoelectrochemical characterization to establish the energetic diagram of the Cu2S/TiO2 heterosystem. Corrosion tests of Cu2S and Cu2S/TiO2 electrodes were carried out by plotting the polarization curves in Orange II solution in the dark and under illumination to simulate the photoactive environment. We evaluate the performance of Cu2S and Cu2S/TiO2 by determining the fill factor and the energy conversion efficiency. Electrical Impedance Spectroscopy (EIS) is used for investigation of charge carrier dynamics in these photocatalytic devices. The valence and the conduction bands were estimated to be respectively of -0.3 and of -1.5 V, which enable electron injection from activated Cu2S to an activated TiO2. The p-Cu2S/n-TiO2 is optimized by its application to Orange II degradation under visible light. The best configuration Cu2S(60%)/TiO2 shows its maximum degradation rate (R-initial = 9 x 10(-2) mg l(-1) min(-1)) at 15 mg l(-1) of Orange II (pH similar to 6.8). The ideal irradiation intensity is estimated to be 18.88 x 10(-6) kW which results in an electrical energy consumption per order of magnitude (EE/O) of 20.95 kWh m(-3). (C) 2012 Elsevier B.V. All rights reserved.