In-situ synthesis of self Ti3+ doped TiO2/RGO nanocomposites as efficient photocatalyst to remove organic dyes from wastewater under direct sunlight irradiation

Abstract

Reduced graphene oxide modified titania nanocomposite is successfully synthesized using an inorganic precursor of titania and graphite through a controlled hydrolysis method. Modified Hummers’ method is adopted to synthesize the graphene oxide. XRD analysis indicates that the synthesized anatase titania nanocrystals have crystallite size within the range of 3–10 nm. Microstructural and Raman study confirms the TiO2 nanocrystals are closely packed and in interfacial contacts with graphene oxide sheets respectively. It has been observed that small percentage of graphene oxide loading (5 wt%) on TiO2, some extent influences the textural properties; like, crystallite size, specific surface area, pore volume, etc. The low intense photoluminescence spectra of the nanocomposite reveal slower rate of radiative recombination of the charge carriers. UV-Vis absorption and DRS-spectra illustrates a red shift in absorption peak and a reduced band gap in the nanocomposite, respectively. The existence of Ti3+ and oxygen vacancies into lattice is observed from the XPS analysis. Electrical conductivity in the nanocomposite is found to be higher compared to reference TiO2, as evident from the CIS analysis. Therefore, the combination of reduced graphene oxide and titania in the nanocomposites significantly increases the adsorption aptitude towards organic pollutants (e.g. dyes) which is related to their typical surface properties. Moreover, the incorporation of graphene oxide in the nanocomposites exerts a significant combined effect on the charge transfer dynamics and adsorption, which together provide them with better photocatalytic activity toward rhodamine B and other organic dyes in aqueous solution.