Fabrication, characterization and photocatalytic activity of ternary ZnWO4/In2O3/ZnO nanocomposite photocatalyst for organic dye pollutant remediation

A ternary ZnWO₄/In₂O₃/ZnO nanocomposite photocatalyst was prepared by wet impregnation to include ZnWO₄ contents of 5, 10 and 15 %. The ZnWO₄/In₂O₃/ZnO nanocomposites were characterized by thermogravimetric analysis, powder X-ray diffractometry, Fourier transform infrared spectrometry, X-ray photoelectron spectrometry, scanning electron microscopy, energy dispersive X-ray spectrometry and transmission electron microscopy. These characterization techniques confirmed the successful formation of ZnWO₄/In₂O₃/ZnO nanocomposites. The Rietveld refinement confirmed a presence of In₂O₃, ZnWO₄ and ZnO in ZnWO₄/In₂O₃/ZnO nanocomposite. The SEM and TEM images of ZnWO₄/In₂O₃/ZnO nanocomposite showed spherical nanoparticle of In₂O₃, irregular shape of ZnO and nanoplatelet of ZnWO₄. The optical behavior of the nanocomposites was investigated by ultraviolet-visible diffuse reflectance spectroscopy. The bandgap values of ZnO, In₂O₃ and ZnWO₄ powders were 3.08, 2.90 and 3.22 eV, respectively. The 10 %ZnWO₄/In₂O₃/ZnO nanocomposite was the most effective photocatalyst, degrading almost 100 % of methylene blue in the presence of 50 μL of H₂O₂. The 10 %ZnWO₄/In₂O₃/ZnO nanocomposite was effective for five cycles of photocatalysis. A mechanism was proposed to describe the roles of the hydroxyl radical, hole and superoxide anion radical in degradation on the 10 %ZnWO₄/In₂O₃/ZnO photocatalyst.