Reduced graphene oxide as a solid-state mediator in TiO2/In0.5WO3 S-scheme photocatalyst for hydrogen production

Abstract

Photocatalytic H2 evolution has been proven to be one of the promising methods for tackling global energy and environmental issues. In this work, rGO supported TiO2/In0.5WO3 S-scheme heterojunction photocatalyst was prepared by using the hydrothermal and wet impregnation methods. The crystallinity and morphology of synthesized photocatalysts were ascertained by XRD, FESEM, and TEM. The results showed high crystallinity and distribution of TiO2/In0.5WO3 on rGO sheets. The photocatalytic activity of synthesized photocatalyst was evaluated towards photocatalytic H2 production. It was noted that compared to bare TiO2 (24.15 ± 1.8 μmol/h/g), TiO2/In0.5WO3 (132.6 ± 5.1 μmol/h/g) and rGO supported TiO2/In0.5WO3 (309.98 ± 11.4 μmol/h/g) photocatalysts showed ~ 5 and ~ 12 folds enhanced photocatalytic H2 production activity. Further, 5.2, 11.3 and 15.6% AQE was achieved at 365 nm for TiO2, TiO2/In0.5WO3 and rGO supported TiO2/In0.5WO3. This was mainly attributed to improved light absorption by TiO2/In0.5WO3 and rapid charge carrier separation characteristics of rGO as revealed by UV–vis DRS, Photoluminescence spectroscopy and Photocurrent studies. Based on photoelectrochemical results, a direct S-scheme heterojunction charge transfer mechanism was proposed to explain the significantly enhanced photocatalytic performance of rGO supported TiO2/In0.5WO3 photocatalyst. This work stipulates new comprehensions into the construction of S-scheme heterostructure through rGO as a solid-state mediator.