Doping of TiO2-GO and TiO2-rGO with noble metals: synthesis, characterization and photocatalytic performance for azo dye discoloration.

The nanocomposites of titania coupled with graphene oxide (GO) and reduced graphene oxide (rGO), respectively, were prepared by homogeneous hydrolysis with urea. Graphene was obtained by effect of high-intensity cavitation field on natural graphite in the presence of strong aprotic solvents in pressurized ultrasonic reactor. The morphology of TiO2-GO and TiO2-rGO composites was assessed by scanning electron microscopy and atomic force microscopy. The nitrogen adsorption-desorption was used for determination of surface area (BET) and porosity. Raman and IR spectroscopy were used for qualitative analysis and diffuse reflectance spectroscopy was employed to estimate band-gap energies. Further enhancement of the photocatalytic activity was attained by codoping of composites with noble metals--Au, Pd and Pt. The photocatalytic activity of TiO2-GO and TiO2-rGO were assessed by photocatalytic decomposition of Orange II dye in an aqueous slurry under UV and visible light irradiation. The photocatalytic activity of noble metals codoped samples was determined with decomposition of Reactive Black 5 azo dye.