Oxygen Vacancies in Shape Controlled Cu₂O/Reduced Graphene Oxide/In₂O₃ Hybrid for Promoted Photocatalytic Water Oxidation and Degradation of Environmental Pollutants

Abstract

A novel shape controlled Cu₂O/reduced graphene oxide/In₂O₃ (Cu₂O/RGO/In₂O₃) hybrid with abundant oxygen vacancies was prepared by a facile, surfactant-free method. The hybrid photocatalyst exhibits an increased photocatalytic activity in water oxidation and degradation of environmental pollutants (methylene blue and Cr⁶⁺ solutions) compared with pure In₂O₃ and Cu₂O materials. The presence of oxygen vacancies in Cu₂O/RGO/In₂O₃ and the formation of heterojunction between In₂O₃ and Cu₂O induce extra diffusive electronic states above the valence band (VB) edge and reduce the band gap of the hybrid consequently. Besides, the increased activity of Cu₂O/RGO/In₂O₃ hybrid is also attributed to the alignment of band edge, a process that is assisted by different Fermi levels between In₂O₃ and Cu₂O, as well as the charge transfer and distribution onto the graphene sheets, which causes the downshift of VB of In₂O₃ and the significant increase in its oxidation potential. Additionally, a built-in electric field is generated on the interface of n-type In₂O₃ and p-type Cu₂O, suppressing the recombination of photoinduced electron-hole pairs and allowing the photogenerated electrons and holes to participate in the reduction and oxidation reactions for oxidizing water molecules and pollutants more efficiently.