WO 3 Doping Effects on the Photoelectrocatalytic Activity of TiO 2 Nanotube Film Prepared by an Anodization Process
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1258-Q05-06
WO3 Doping Effects on the Photoelectrocatalytic Activity of TiO2 Nanotube Film Prepared by an Anodization Process Hei Lok Tsai, Micheal K.H. Leung, Gui Sheng Li, Dennis C.Y. Leung Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China ABSTRACT WO3 doped TiO2 nanotube(WO3-doped TNT) thin film was fabricated by anodizing the TiO2 nanotube (TNT) film in an NH4F electrolyte containing WO4- ions. The sample was characterized by Field Emission Scanning Electron Microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–Vis diffuse reflectance spectroscopy (DRS). The results show that WO3 was successfully doped into TiO2 nanotubes and the absorption edge of WO3 doped TNT appeared to be red shifted. The photoelectrocatalytic (PEC) activity of WO3 doped TNT electrode was evaluated through the PEC degradation of aqueous Acid Blue 80. The experimental results demonstrated that the PEC degradation rate of WO3 doped TNT is increased by 48% and by 167% over that of non-doped TNT under UVA light irradiation and visible-light irradiation, respectively, at an applied potential of 1.54V. The degradation rates of WO3 doped TNT under photocatalytic (PC), electrochemical (EC), and PEC processes were compared. The results reveal the synergetic effect of PC and EC processes. INTRODUCTION TiO2 is regarded as one of the best photocatalysts for environmental applications, such as photocatalytic degradation of pollutants (Adachi, Murata et al. 2000; Zhang, Yuan et al. 2008) , solar cell (Macak, Tsuchiya et al. 2005; Rattanavoravipa, Sagawa et al. 2008) , and gas sensor (Rella, Spadavecchia et al. 2007; Seo, Yuasa et al. 2009) due to its high level of photocatalytic activity, photo-stability, cost effectiveness and non-toxicity. However, the efficiency of photocatalytic reaction is limited by the wide band gap of TiO2 (3.2 eV) which causes a high recombination rate of photo-generated electrons and holes. Such a wide band gap also limits the utilization of sunlight since TiO2 only absorbs UV irradiation (λ
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