Photocatalytic Activity of Defective TiO2-x for Water Treatment/Methyl Orange Dye Degradation

This study is designed to highlight photocatalytic activity of TiO2 nanoparticles in methyl orange (MO) dye degradation. Titanium dioxide TiO2 nanopowder was synthesized by conventional sol-gel method and calcined in air atmosphere at different temperatures 350C, 550C and 850C. The prepared TiO2 nanoparticles then were subjected to a solid state reaction with calcium hydride (CaH2) at the same temperatures but calcined in argon atmosphere. X-Ray Diffraction (XRD) measurements used for phase and crystalline size identification showed that the obtained samples have the same TiO2 anatase phase, but the crystalline size decreased after reduction treatment. The electronic properties obtained via UV spectroscopy showed the decrease in calculated energy gap from 3.3 eV for prepared TiO2-550 to 2.65 eV for reduced TiO2-CaH2-550, which extend the absorption spectra toward visible light region. Energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM) measurements revealed that the particle size decreased after reduction treatment similar to the XRD crystalline size. EDS results indicated that the deficient in oxygen content relates to formation oxygen vacancies responsible for nonstoichiometric TiO2-x oxides formation. The synthesized reduced TiO2 showed an excellent photo-catalytic activity in methyl orange dye degradation under optimum condition: pH 4.5, 40 mg catalyst loading and 10 ppm initial dye concentration.