Photocatalytic activity for H-2 evolution of TiO2 with tuned surface crystalline phase

Two methods, which is high temperature calcination method and doping La2O3 method, were used to prepare TiO2 with an adjustable surface crystalline structure. It has been shown that TiO2 powders with a tunable surface phase were obtained by carefully controlling the calcination temperature and calcination time. Compared with calcination method, it is difficult to prepare TiO2 with variable surface anatase-rutile ratio by La2O3 doping. UV Raman spectra and XRD clearly indicate that La2O3 can act as a stabilizer for the development of rutile phase from the bulk to surface region of La2O3-TiO2 sample, even after high temperature calcination. The rate of H-2 production from methanol-water solution was used as an indicator for the photocatalytic activity of the TiO2 and La2O3-TiO2 samples. It is evident that enhanced activity of TiO2 is observed when the surface region is in the mixed phase, in comparison of the sample with pure surface anatase or pure surface rutile. The notable effect of surface phase on the photocatalytic activity of TiO2 is also observed in the La2O3-TiO2 sample. The rate of H-2 production shows similar photocatalytic activities although their bulk rutile contents are greatly different in the La2O3-TiO2 samples, which is similar to that of undoped TiO2. (C) 2013 Elsevier B.V. All rights reserved