Synthesis, characterization and mechanism of enhanced visible light photocatalytic activity of TiO2-WO3 nanocomposites

Titanium dioxide (TiO2) is a wide bandgap semiconductor which shows excellent photocatalytic activity under UV irradiation. To extend the light absorption efficiency to visible region, TiO2 can be coupled with other semiconductors to form nanocomposites. In the present study, photocatalytic efficiency of TiO2-WO3 nanocomposites against methylene blue dye was investigated. TiO2-WO3 nanocomposites with different W/Ti ratio were synthesized by sol–gel method. The samples were characterized using X-ray diffraction (XRD), High resolution transmission spectroscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Brunauer, Emmett and Teller surface area analyzer (BET), UV–Vis diffuse reflectance spectra (DRS) and zeta potential analyzer. XRD and HR-TEM analysis confirmed the crystallinity of nanocomposites. XPS analysis confirmed the phase purity of the nanocomposite. The specific surface area and pore radius were calculated from BET analysis. The energy bandgap of all the samples were calculated from UV–Vis DRS analysis. The optical band gap of the nanocomposites was less compared to that of pure TiO2. This decrease in band gap has resulted in extending the photocatalytic activity to visible range. Optimum W/Ti ratio for obtaining maximum photocatalytic efficiency was arrived at and its mechanism was studied in detail using zeta potential measurements and scavenging tests. Reusability of the catalyst was also confirmed.