Morphological control of anodic crystalline TiO2 nanochannel films for use in size-selective photocatalytic decomposition of organic molecules

Abstract

We report the size-selective photocatalytic decomposition of organic molecules using crystalline anodic TiO2 nanochannel films as the photocatalyst. The porous TiO2 films were formed by anodizing titanium at 20V in glycerol electrolyte containing various amounts of K3PO4, K2HPO4, and KH2PO4 at 433K. Regardless of the electrolyte composition, the as-formed TiO2 films had a crystalline anatase structure. The basicity of the electrolyte markedly influenced the morphology of the TiO2 nanochannel films; more regular nanochannels developed with increasing basicity of the electrolyte. Because the diameter of the nanochannels in the films formed in a basic electrolyte was as small as ∼10nm, the anodic TiO2 nanochannel films with a thickness of 5μm revealed a selective photocatalytic decomposition of methylene blue (MB) in a mixture of MB and direct red 80 (DR) kept under UV irradiation. The importance of the diameter of the nanochannels and their uniformity for size-selective decomposition of organic molecules were investigated.