Abstract
Herein we report simple, low-cost and scalable preparation of reduced graphene oxide (rGO) supported surfactant-free Cu2O-TiO2 nanocomposite photocatalysts by an ultrasound assisted wet impregnation method. Unlike the conventional preparation techniques, simultaneous reduction of Cu2+ (in the precursor) to Cu+ (Cu2O), and graphene oxide (GO) to rGO is achieved by an ultrasonic method without the addition of any external reducing agent; this is ascertained by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. UV-visible diffused reflectance spectroscopy (DRS) studies (Tauc plots) provide evidence for the loading of Cu2O tailoring the optical band gap of the photocatalyst from 3.21 eV to 2.87 eV. The photoreactivity of the as-prepared Cu2O-TiO2/rGO samples is determined via H-2 evolution from water in the presence of glycerol as a hole (h(+)) scavenger under visible light irradiation. Very interestingly, the addition of rGO augments the carrier mobility at the Cu2O-TiO2 p-n heterojunction, which is evidenced by the significantly reduced luminescence intensity of the Cu2O-TiO2/rGO photocatalyst. Hence rGO astonishingly enhances the photocatalytic activity compared with pristine TiO2 nanoparticles (NPs) and Cu2O-TiO2, by factors of similar to 14 and similar to 7, respectively. A maximum H-2 production rate of 110 968 mu mol h(-1) g(cat)(-1) is obtained with a 1.0% Cu and 3.0% GO photocatalyst composition; this is significantly higher than previously reported graphene based photocatalysts. Additionally, the present H-2 production rate is much higher than those of precious/noble metal (especially Pt) assisted (as co-catalysts) graphene based photocatalysts. Moreover, to the best of our knowledge, this is the highest H-2 production rate (110 968 mu mol h(-1) g(cat)(-1)) achieved by a graphene based photocatalyst through the splitting of water under visible light irradiation.