Coupling of W-Doped SnO2 and TiO2 for Efficient Visible-Light Photocatalysis

Five mol % tungsten-doped tin oxide (W0.05Sn0.95O2, TTO5) was prepared by co-precipitation of SnCl4 center dot 5H(2)O and WCl4, followed by calcination at 1000 degrees C. The as-prepared TTO5 was in the pure cassiterite phase with a particle size of similar to 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 (lambda >= 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 hole-transfer between the valence band (VB) of TTO5 and TiO2, since the TTO5 nanoparticle (NP) exhibits the absorption edge at similar to 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 hole-scavenging reaction with 1,4-terephthalic acid (TA).