Upgrading TiO2 Photoactivity under Visible Light by Synthesis of MWCNT/TiO2 Nanocomposite

Abstract

Nanocomposites of multi-walled carbon nanotubes and titanium dioxide (MWCNT/TiO2) were synthesized by the sol-gel method. Regarding hydrophobicity of carbon nanotubes (CNTs), benzyl alcohol was used as the linking agent between CNT powder and TiO2 gel which was prepared from the precursor of titanium tetraisopropoxide. The prepared samples were treated under thermal treatments. A part of the samples was heated to prepare MWCNT/TiO2 nanocomposite with anatase TiO2 and the other parts were heated until burning CNTs and prepare pseudo-tube TiO2 (PT-TiO2). The aterials were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), thermo gravimetric analysis (TGA), Brunauer-Emmet-Teller (BET) measurement and UV-vis diffuse reflectance spectra (DRS). The hotocatalytic activity of MWCNT/TiO2 nd PT-TiO2 was studied for degradation of acetaldehyde under UV-visible and visible light irradiation. The Photocatalytic reaction was examined in a gaseous stirred flow reactor equipped with 80W Hg lamp and the concentration–time results were compared with commercial TiO2 (P25-TiO2). Considerable reduction of acetaldehyde concentration was achieved under visible irradiation by the MWCNT/TiO2 nanocomposite, whereas none of the PT-TiO2 and typical P25-TiO2 showed activity under visible light. An optimal fraction of 30 wt% MWCNT in anatase TiO2 was found to have the highest activity under visible light irradiation.