Improving Visible Light-Absorptivity and Photoelectric Conversion Efficiency of a TiO ₂ Nanotube Anode Film by Sensitization with Bi ₂O ₃ Nanoparticles

Abstract

This study presents a novel visible light-active TiO ₂ nanotube anode film by sensitization with Bi ₂O ₃ nanoparticles. The uniform incorporation of Bi ₂O ₃ contributes to largely enhancing the solar light absorption and photoelectric conversion efficiency of TiO ₂ nanotubes. Due to the energy level difference between Bi ₂O ₃ and TiO ₂, the built-in electric field is suggested to be formed in the Bi ₂O ₃ sensitized TiO ₂ hybrid, which effectively separates the photo-generated electron-hole pairs and hence improves the photocatalytic activity. It is also found that the photoelectric conversion efficiency of Bi ₂O ₃ sensitized TiO ₂ nanotubes is not in direct proportion with the content of the sensitizer, Bi ₂O ₃, which should be carefully controlled to realize excellent photoelectrical properties. With a narrower energy band gap relative to TiO ₂, the sensitizer Bi ₂O ₃ can efficiently harvest the solar energy to generate electrons and holes, while TiO ₂ collects and transports the charge carriers. The new-type visible light-sensitive photocatalyst presented in this paper will shed light on sensitizing many other wide-band-gap semiconductors for improving solar photocatalysis, and on understanding the visible light-driven photocatalysis through narrow-band-gap semiconductor coupling.