Enhanced photo-reduction and removal of Cr(VI) on reduced graphene oxide decorated with TiO2 nanoparticles.

Reduced graphene oxide decorated with TiO2 nanoparticles (TiO2-RGO) was synthesized and characterized by scanning and transmission electron microscopy, powder X-ray diffraction, ultraviolet-visible spectroscopy, photoluminescence excitation and emission spectroscopy, and X-ray photoelectron spectroscopy. Photo-reduction and removal of Cr(VI) from an aqueous solution using the material were investigated under visible light irradiation. Compared to pure TiO2, the TiO2-RGO exhibited an improved photocatalytic performance in the reduction of Cr(VI) under visible light irradiation, with a maximum removal of 86.5% vs 54.2% due to the increased light absorption intensity and wavelength range as well as the reduction in electron-hole pair recombination in TiO2 with the addition of RGO. The adsorption and photocatalytic reduction of Cr(VI) decreased with increasing pH, due to the decrease in the electrostatic attraction between anionic Cr(VI) and TiO2-RGO and the decrease in the thermodynamic driving force of Cr(VI) reduction to Cr(III).