Effect of successive incorporation of tungstophosphoric acid into TiO2 on the activity of photocatalysts for the degradation of methylene blue

The effect of incorporation of different amounts of tungstophosphoric acid (TPA) into TiO2 to alter its photocatalytic activity was studied. Varying amounts of TPA (10%–50% in weight) were introduced into TiO2 synthesis gel for hydrothermal preparation of TPA–TiO2 photocatalysts. The produced photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis (EDX), UV–vis diffuse reflectance spectroscopy, FTIR, N2 adsorption and surface charge measurements. XRD data shows a pure anatase crystalline phase for all the TPA-containing TiO2 samples. The effective band gap (Egeff), calculated from the diffuse reflectance spectra, and the pH at point of zero charge (pHpzc) are lower for the samples with higher amounts of TPA. The EDX analysis and FTIR spectra of TPA–TiO2 samples reveal sound incorporation of TPA into TiO2. The activity of the photocatalysts for the degradation of methylene blue correlates with the TPA contents of the samples.