AVS 57th International Symposium & Exhibition
    Energy Frontiers Topical Conference Friday Sessions
       Session EN+SS-FrM

Paper EN+SS-FrM6
Enhancement of Visible-Light Photocatalytic Efficiency of TiO2 Nanopowder by Anatase/Rutile Interface Formation

Friday, October 22, 2010, 10:00 am, Room Mesilla

Session: Photocatalysis and Solar Fuels
Presenter: Y.J. Chen, National Dong Hwa University, Taiwan, Republic of China
Authors: Y.J. Chen, National Dong Hwa University, Taiwan, Republic of China
C.S. Lin, National Dong Hwa University, Taiwan, Republic of China
Correspondent: Click to Email
In this article we report that the presence of anatase/rutile interface is essential on realization of visible-light photocatalytic ability of TiO2 produced by the novel flat-flame chemical vapor condensation (FFCVC) method. Previous study shows that when nitrogen is replaced by argon as precursor carrier gas as well as quench gas in the FFCVC process, the synthesized TiO2 nanopowder changes from anatase/rutile duel phases to anatase single phase. The UV-vis absorption spectra suggest that the synthesized TiO2 with single anatase phase may still possess visible light absorption capability when the process parameters are carefully chosen. However, the photocatalytic efficiency drops to minimal value for the single-phase TiO2 compared with that for dual-phase TiO2. To confirm that the photocatalytic efficiency difference is caused by the formation of anatase/rutile interface, we synthesize the TiO2 nanopowder using argon as carrier gas while using either nitrogen or argon as quench gas for comparison. Results show that when using nitrogen as quench gas, the TiO2 powder is mostly anatase phase with minor rutile content, while when using argon as quench gas, the TiO2 powder is almost anatase phase with hardly any rutile content. From the x-ray diffraction analysis, the grain size of anatase from both processes is similar, indicating that the choice of quench gas does not influence significantly on the nucleation process of the TiO2 nanopowder. On the other hand, the use of nitrogen as quench gas does promote the formation of rutile phase, even though the rutile content is still minimal. This observation indicates that the nitrogen as quench gas does have some effect, although weak, on TiO2 nanopowder during its final coalescence and growth stage. The visible-light photocatalytic experiment shows that even two powder samples are similar, the photocatalytic efficiency of TiO2 with minor rutile content is significant while that of TiO2 with single anatase phase is insignificant. Since the anatase from both processes is considered the same, the photocatalytic efficiency difference must be due to that minor rutile formation. Since the photocatalytic reaction occurs mostly on the anatase surface, the enhancement of photocatalytic efficiency by the formation of rutile phase leads to the conclusion that the anatase/rutile interface is the major cause for the efficiency enhancement. We will show the XPS, EPR, and XRD characterization of powders and discuss the materials science behind the phenomenon.