Preparation and Characterization of Semiconductor Oxide Thin Films for Hydrogen Photogeneration by Splitting of Water

Abstract

The semiconductor thin films of ZnO and CU2O were prepared by simple and low cost techniques and characterized for determining the photogeneration of Hydrogen by splitting water. Semiconductor thin film and a Cu plate were used as two electrodes in photoelectrochemical cell and Fe2+/Fe3+ redox couple was used as the electrolyte. ZnO thin films with different thicknesses have been prepared on cleaned glass substrates by a spray pyrolysis technique using Zinc Hydroxide precursor at the temperature between 250 - 300 6C. Optical properties of the prepared ZnO thin films have been studied by using UV-Visible spectroscopy and electrical resistance of thin film was measured. The photocurrent densities of the ZnO thin film were carried out in a photoelectrochemical cell under 60W light irradiation. Variations of absorbance, band gap, conductivity and photocurrent density with film thickness were investigated. The effective optical band gap and conductivity for ZnO thin films having film thickness ~2 pm were found to be 2.9 ev and 1.9xl0'7 (ficm)' respectively. Significant amount of photocurrent was observed and photocurrent density was found to be increased with film thickness. Higher photocurrent density was observed film thickness with ~2 pm. CU2O thin films have been prepared by heating Cu plates in air. The photoelectrochemical properties of the prepared thin films were investigated as a function of Fe2+/Fe3+ redox couple concentration. Time duration for decreasing photocurrent to dark current after turning off light source was studied. 0.04 M Fe2+/Fe5+ redox couple concentration was identified as optimum concentration of electrolyte in photoelectrochemical cell using CU2O thin film.