Structure and Photocatalytic Property of Zinc Oxide Film Prepared by Anodizing

Abstract

Formation of anodic porous zinc oxide (ZnO) films with high specific surface area was investigated in various electrolytes such as oxalic acid, ammonium borate, and sodium hydroxide solutions. Composition of the anodic film formed in oxalic acid, which was composed of an outer rock-like structure and an inner granular structure, was mainly Zn(OH)₂ containing a small amount of ZnO. In contract, crystalline porous ZnO film with a straight cellular structure was formed in a sodium hydroxide solution. At low anodizing voltage of 9 V, formation of thicker films of more than 30 μm was achieved through suppression of extensive gas evolution. Photocatalytic activity of the ZnO films assessed using photodegradation of methylene blue under UV irradiation was comparable with that of TiO₂ nanoparticle film (P25).