FABRICATION OF NANOSTRUCTURED ZINC OXIDE VIA ELECTRODEPOSITION AND HEAT TREATMENT

Abstract

Zinc oxide is a promising material used as a photocatalyst to treat organic contaminants in water. To obtain good photocatalytic activity in the film, porosity and high surface area are often promoted. In this work, a systematic study of the fabrication process of nanostructured zinc oxide thin film via electrodeposition and heat treatment is carried out. The process-structure-property relationship of both zinc and zinc oxide films are investigated. This research is divided into three parts. In the first part, the effects of current density and additives on the structure and property of zinc film are studied. Both current density and additives play an important role in controlling the structure of the zinc film and also in the formation of zinc oxide. Additives influence the texture development of the deposits and in turn influence the corrosion resistance in the coatings. Upon applying a direct current of 2 A/dm2 with no additive, sub-micron zinc rods that are intertwined and formed clusters of granules is observed. In the second part, the effect of heat treatment temperature on the structure and surface morphology of zinc oxide thin films are analyzed. The oxidation reaction both below and above the melting point of zinc metal are studied. For temperature below the melting point, ZnO nanoneedle is formed and grown using the zinc deposit structure as a template. However, spherical ZnO particles agglomerate as parts of the rod structure for temperature above the melting point. In the third part, ZnO thin film with different surface morphologies is tested for the photocatalytic property. ZnO thin film annealed at 500°C shows the best photocatalytic activity in degrading MB dyes under UV light irradiation. This may be attributed to the higher surface area of the film. In conclusion, nanostructured ZnO thin film with good photocatalytic property can be synthesized from electrodeposition and heat treatment method.