Photocatalytic degradation of various toxic organic pollutants on surface of ZnO - TiO2 nanoparticles doped with some transition elements prepared by sol-gel and microwave methods

Abstract

ZnO, TiO2 and ZnO-TiO2 nanoparticles possess high photocatalytic reactivity in degrading various organic pollutants; however, the law surface area, wide band gap energy and the photocorrosion severely hinder its industrial application. One of the recent challenges is concerned with manipulation of novel mesoporous photocatalyst with high surface area and good photocatalytic stability. In this research work, a novel series of mesoporous Au/ZnO, Au/TiO2 and Au/ZnO-TiO2 nanoparticles containing 0-10 wt% Au was prepared by microwave facile sol-gel route using PVP as pore and structure directing agent. The structural, crystalline, optical and the nanostructure features were investigated by X-ray diffraction [XRD], N2-adsorption-desorption isotherm, Diffuse reflectance spectra [DRS], Photoluminescence (PL), Field emission scanning electron microscope [FESEM] and high resolution transmission electron microscopy [HRTEM]. It is clear from FESEM and HRTEM that gold nanoparticles are incorporated uniformly on the surface of ZnO and TiO2 filling theirs pores. DRS analysis confirms the pronounced reduction of band gap energy upon addition of gold nanoparticles revealing the positive shift of the photocatalytic response to visible region. It is obvious to notice that the photocatalytic reactivity of Au/ZnO and Au/TiO2 nanoparticles in degrading methylene blue is nearly twice of that of ZnO which can be attributed to the greater ability of Au to accept electron from ZnO and TiO2 conduction band, which in turn reducing the recombination of photoinduced electron–hole couples. Various scavengers as KI, isopropanol, benzoquinone and methyl viologen are performed in degradation of methylene blue dye to