Microwave-assisted synthesis of an RGO/CdS/TiO step-scheme with exposed TiO {001} facets and enhanced visible photocatalytic activity.

Semiconductor-based heterojunction photocatalysts with a special active crystal surface act as an essential part in environmental remediation and renewable energy technologies. In this study, an RGO/CdS/TiO step-scheme with high energy {001} TiO facets was successfully fabricated a microwave-assisted solvothermal method. The photocatalytic performance of as-prepared samples was assessed by degrading methylene blue under visible light irradiation. We found that the photocatalytic activity of the RGO/CdS/TiO step-scheme heterojunction was related to the proportion of TiO. A ternary sample with a TiO content of 10 wt% exhibited superior photocatalytic performance, and approximately 99.7% of methylene blue was degraded during 50 min of visible illumination which was much higher than the percentages found for TiO, CdS, RGO/TiO, and RGO/CdS. The greatly improved photocatalytic performance is due to the exposure of the reactive {001} surface of TiO and the formation of a CdS/TiO heterojunction step-scheme, which effectively inhibits the recombination of charge carriers at the heterogeneous interfaces. Moreover, the incorporation of graphene further enhances the visible light harvesting and serves as an electron transport channel for rapidly separating photogenerated carriers. Based on the PL, XPS, photoelectrochemical properties and the free radical capturing experiment results, a possible photodegradation mechanism was proposed.