Phtotocatalytic Degradation of Methyelene Blue by Cu Doped TiO2 Thin Films under Visible Light Irradiation

Abstract

Pure TiO2 and Copper doped TiO2 thin films of various concentrations (0.02–0.05 mol %) have been successfully deposited onto glass substrate by sol-gel dip coating technique and annealed at 400oC for 3 hours. The XRD results showed the presence of anatase phase for all the films and the crystallite size decreases with increasing doping concentrations. The morphological observations and compositional analysis were recorded with SEM and EDX. The UV-Visible study showed that the optical band gap energy decreases with increasing Cu content. It was also found that copper doping shifted the absorption edge of TiO2 toward a visible regime depicting the possible modification in the electronic band structure. The photocatalytic activity was evaluated by monitoring the degradation of methyelene blue under visible light illumination. It was found that the percentage of degradation was higher in 0.05mol% Cu-TiO2 when compared with other films. The efficiency of the Cu-TiO2 thin film was preserved even after the extended usage of the films which sustains the reusability nature of Cu-TiO2 films. Introduction. Titanium dioxide (TiO2) has been extensively studied because of its excellent phtotocatalytic activity, chemical stability, non toxicity, optoelectronic property and low cost. However, the wide band gap and intense electron-hole pair recombination limit its efficiency in photo electro chemical applications. Tailoring the band structure of TiO2 is an effective method for widening its optical absorption range and improving its visible light phtotocatalytic activity [1, 2]. Catalytic activity of TiO2 is dependent on its phase structure, crystallite size, specific surface area and pore structure. Doping additives were found successful in altering the photo electrochemical properties of TiO2 [3, 4]. In particular, doping metal impurity in TiO2 matrix has been found remarkable as the way it exploits the better photo catalytic activity [5, 6]. Cu is a potential metal dopant for phtotocatalytic mechanism since the visible light absorption of TiO2 can be enhanced by the adding Cu [7]. Here the efforts have been made to prepare Cu doped TiO2 film because the film shaped photocatalysts are convenient to use and recyclable. There are numerous methods to prepare Cu doped TiO2 thin film but the sol-gel method shows more advantages over other methods [8]. By carrying out this method in solution, we can modify the few desired structural characteristics like compositional homogeneity, grain size, surface morphology and porosity is possible with this technique. Methyelene blue is a harmful material existing in liquid coming from industries. Exposure to methyelene blue causes various health issues such as increased heart beat rate, vomiting, shock, jaundice and tissue necrosis in human being. Cu doped TiO2 thin film can be used to photo degrade the methyelene blue in waste water. In this work, pure TiO2 and Copper doped TiO2 thin films with various Cu concentrations (0.02-0.05 mol %) were prepared by sol-gel technique. The structural and optical properties of the samples were reported. The phtotocatalytic activity of prepared films was evaluated by methyelene blue degradation under visible light irradiation.