Coverage Layer Phase Composition-Dependent Photoactivity of One-Dimensional TiO2-Bi2O3 Composites

Abstract

TiO2-Bi2O3 composite rods were synthesized by combining hydrothermal growth of rutile TiO2 rod templates and sputtering deposition of Bi2O3 thin films. The TiO2-Bi2O3 composite rods with beta-Bi2O3 phase and alpha/beta-Bi2O3 dual-phase decoration layers were designed, respectively, via in situ radio-frequency magnetron sputtering growth and post-annealing procedures in ambient air. The crystal structure, surface morphology, and photo-absorption performances of the pristine TiO2 rods decorated with various Bi2O3 phases were investigated. The crystal structure analysis reveals that the crystalline TiO2-Bi2O3 rods contained beta-Bi2O3 and alpha/beta-Bi2O3 crystallites were separately formed on the TiO2 rod templates with different synthesis approaches. The morphology analysis demonstrates that the beta-Bi2O3 coverage layer on the crystalline rutile TiO2 rods showed flat layer morphology; however, the surface morphology of the alpha/beta-Bi2O3 dual-phase coverage layer on the TiO2 rods exhibited a sheet-like feature. The results of photocatalytic decomposition towards methyl orange dyes show that the substantially improved photoactivity of the rutile TiO2 rods was achieved by decorating a thin sheet-like alpha/beta-Bi2O3 coverage layer. The effectively photoinduced charge separation efficiency in the stepped energy band configuration in the composite rods made from the TiO2 and alpha/beta-Bi2O3 explained their markedly improved photoactivity. The TiO2-alpha/beta-Bi2O3 composite rods are promising for use as photocatalysts and photoelectrodes.