Enhanced photocatalytic activities of low-bandgap TiO2-reduced graphene oxide nanocomposites

In this study, a hydrothermal method was successfully used to prepare a reduced graphene oxide (RG)-titanium dioxide (TiO2) hybrid in 10-20 nm, starting from commercial TiO2 P25 nanoparticles and liquid-exfoliated graphene oxide (GO). Compared to TiO2, an obvious red shift of light absorption (from 3.1 to 2.6 eV) of the as-prepared RG-TiO2 was observed by UV-Vis analysis, and an enhanced photocatalytic degradation of the Rhodamine B (Rh. B) was also observed under Xe lamp exposure test by using the as-prepared RG-TiO2. Multiple characterizations of this RG-TiO2 nanocomposite confirmed that its photocatalytic enhancement could be ascribed to two approaches. Firstly, RG extended the mean free path and photogenerated electrons' lifetime of TiO2, which minimized electron-hole pairs' recombination. Secondly, RG expanded the light absorption spectrum of TiO2 from UVrange to UV and visible light range. The explication of these improvements was concluded as the energy gap changing and a likelihood of up-conversion photoluminescence mechanism (UCPL). Due to the low-cost, nonpoisonous and excellent photocatalytic properties of RG-TiO2, this material can be applied well in sewage treatment and other related fields.