FABRICATION AND CHARACTERIZATION OF COBALT PIGMENTED ANODIZED ZINC FOR PHOTOCATALYTIC APPLICATION

Abstract

Population growth and urbanization have led to water scarcity and pollution which is a health hazard not only to human but also the ecosystem in general. This has necessitated coming up with ways of treating water before consumption. Photocatalysis has proved to be one of the most promising cheap techniques, which involve chemical utilization of solar energy. TiO2 widely used in photocatalysis absorbs a narrow range of the solar spectrum compared to ZnO. In this regard, this study aimed at preparing and optimizing Cobalt pigmented ZnO which is applicable in photocatalytic water treatment. The objectives in this study were to fabricate zinc oxide (ZnO) thin films by anodization, pigment the fabricated films with varying Cobalt concentrations, characterize the fabricated films optically and to investigate the Cobalt pigmented ZnO performance in the methylene blue degradation under UV light irradiation. Mirror polished Zinc plates were sonicated in ethanol and rinsed. Anodization was done at room temperature in 0.5M oxalic acid at a constant voltage of 10V for 60 minutes and Cobalt electrodeposited in the films. Post deposition treatment was done at 2500C. Optical properties of the films were studied using a UV-VIS- NIR spectrophotometer in the solar range of 300nm-2500nm. The photocatalytic activity of the fabricated films was studied in Methylene Blue solution degradation in the presence of UV light irradiation for 5 hours. Cobalt pigmenting was observed to reduce reflectance and optical band gap from 3.34eV to 3.10eV indicating good photocatalytic properties. In this study, ZnO film pigmented with Cobalt for 20s was found to be the most photocatalytic with a rate constant of 0.0317hr-1 hence had the optimum Cobalt concentration for photocatalytic water treatment. This can be applied in small scale water purification.