Photo-electro-catalysis enhancement on carbon nanotubes/titanium dioxide (CNTs/TiO2) composite prepared by a novel surfactant wrapping sol-gel method

In this paper, we describe the feasibility of a novel method for coating a uniform and well-defined nanometer-scale titania (TiO2) layer on individual CNTs (multi-walled), producing a mesoporous nanocomposite film. The surfactant wrapping technique, carried out in the presence of sodium dodecylbenzesulfonate, was introduced to modify a conventional sol-gel method for the synthesis of these nanocomposites. The bare CNTs and the composites were characterized by a range of analytical techniques including transmission electron microscopy (TEM), fleld-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), energy dispersive X-ray (EDX) and thermogravinnetric and differential scanning calorimetry analysis (TGA-DSC). The results show the successful covering of the CNTs with a uniform metal oxide layer of 5-10 nm in thickness which after annealing at 500 degrees C led to a mesoporous and well-crystallized TiO2 film (anatase). Photo-electro-catalysis was investigated in 50 ml solution of methylene blue (MB) model substrate (5 mg/l) and NaCl (supporting electrolyte, 0.1 mol/l) under ambient conditions. Irradiation of the composite or the TiO2-coated electrode at a sufficiently positive potential resulted in enhanced MB degradation. However, CNTs/TiO2 degraded MB at greater rates than TiO2 alone, suggesting that synergistic photo-electro-effects took place in the composite catalyst. The increase in the degradation rates of MB in the presence of nanocomposites was attributed to the CNTs supported porous conductive structure which favours electron-hole separation and the removal of photo-generated electrons from the TiO2 nanolayers. (c) 2008 Elsevier B.V. All rights reserved.