Coupling of W-Doped SnO2 and TiO2 for efficient visible-light photocatalysis

Abstract

Five mol % tungsten-doped tin oxide (W0.05Sn0.95O2, TTO5) was prepared by co-precipitation of SnCl4·5H 2O 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 (γ ≥ 420 nm), TTO5/TiO 2 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).