Graphene-metal-oxide composites for the degradation of dyes under visible light irradiation

Reduced graphene oxide (RGO) was respectively modified with tin dioxide (SnO2) and titanium dioxide (TiO2) via a direct redox reaction between the graphene oxide (GO) and the reactive cations Sn2+ and Ti3+, forming RGO-SnO2 and RGO-TiO2 composites. During this redox reaction, GO was reduced to RGO while Sn2+ and Ti3+ were oxidized to SnO2 and TiO2, depositing on the surface of the RGO. The composite materials were found to exhibit very interesting photocatalytic properties for degrading Rhodamine B under visible light irradiation. First, their photocatalytic activities were higher than that of P25 (a commercial TiO2 as a benchmark photocatalyst). Second, the reaction mechanism catalyzed by the composite materials was different from that of semiconductor photocatalysis. Characterization data showed that the excellent photocatalytic performance of the composite materials was associated with the good electrical conductivity and effective charge separation because of the presence of RGO. The present work opens up a new avenue to preparing RGO-based composite materials and provides new insights into the photocatalytic degradation of dyes under visible light irradiation.