SWCNTs AS ELECTRON WITHDRAWERS IN NANOCRYSTALLINE ANATASE PHOTOCATALYSTS

Abstract

Single-walled carbon nanotube (SWCNT)/anatase TiO2 composite materials were prepared by successive sol–gel and hydrothermal processes. The composites contained thin SWCNT bundles embedded in aggregates of ~ 12 nm anatase crystallites. A series of SWCNT/ TiO2 photocatalysts was prepared with various SWCNT contents; a SWCNT content of ~ 8 wt.% was found to be optimal for methylene blue (MB) degradation under combined UV/visible radiation. The optimized SWCNT/ TiO2 composite demonstrated substantially higher photocatalytic activity than pure nanocrystalline anatase (5.2 times) and Degussa P-25 TiO2 powder (2.7 times). The MB degradation and mineralization processes were separately evaluated and complete decomposition of MB was shown to take place. The presence of SWCNTs caused an increase in the visible light absorbance of TiO2 ; however, SWCNT/ TiO2 composites did not show any photocatalytic activity when the UV part of the UV/visible light source was filtered. Therefore SWCNTs worked as acceptors for the TiO2 photoexcited electrons, but did not act as sensitizers for TiO2 .