Enhanced photoelectrochemical activity of Ce doped ZnO nanocomposite thin films under visible light

Ce-doped ZnO and pure ZnO nanocomposite thin films with different Ce/Zn ratios (0, 2, 5, 10, 15, 20, and 30 at.%) have been prepared by sol-gel method at optimum annealing temperature of 500 degrees C. The synthesized samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis spectrophotometry. According to our XPS data analysis, there are three major metal ions namely Ce3+, Ce4+ and Zn2+ that coexist on the surface. The XRD measurements indicate that the ZnO thin films have a hexagonal wurtzite structure, and CeO2 crystallites formed in the Ce-doped ZnO nanocomposite thin films. Photoelectrochemical property of the samples was studied by three electrode galvanostat/potentiostat system. The addition of Ce to ZnO thin film increased photocurrent density to about double amount at applied potential of 0.6 V as compared to undoped ZnO film in photoelectrochemical water splitting reaction. It was also observed that adding cerium to ZnO nanocomposite thin films resulted in enhancement of the photoresponsivity of the layers. Among different Ce/Zn ratios examined, the optimum doping concentration at 10 at.% demonstrated the highest photocurrent density as compared to other investigated ratios under similar experimental conditions. (C) 2011 Elsevier B.V. All rights reserved.