Coupling of W-Doped SnO2and TiO2for Efficient Visible-Light Photocatalysis

Five mol % tungsten-doped tin oxide ( W0.05Sn0.95O₂ , TTO5) was prepared by co-precipitation of SnCl₄·5H₂O and WCl₄ , followed by calcination at 1000∘C . The as-prepared TTO5 was in the pure cassiterite phase with a particle size of ~50 nm and optical bandgap of 2.51 eV. Herein it was applied for the formation of TTO5/ TiO₂ heterojunctions by covering the TTO5 surface with TiO₂ by sol-gel method. Under visible-light irradiation ( λ≥420 nm), TTO5/ TiO₂ showed a significantly high photocatalytic activity in removing gaseous 2-propanol (IP) and evolving CO₂ . It is deduced that its high visible-light activity is caused by inter-semiconductor holetransfer between the valence band (VB) of TTO5 and TiO₂ , since the TTO5 nanoparticle (NP) exhibits the absorption edge at ~450 nm and its VB level is located more positive side than that of TiO₂ . The evidence for the hole-transport mechanism between TTO5 and TiO₂ was also investigated by monitoring the holescavenging reaction with 1,4-terephthalic acid (TA).