2D/1D CaIn2S4/TiO2 S-scheme heterojunction: In-situ hydrothermal synthesis and enhanced photocatalytic H2 evolution

Abstract

Constructing S-scheme heterojunction between TiO₂ and other reduction semiconductors can effectively enhance the intrinsically low carrier separation efficiency and increase the reduction ability of single TiO₂ photocatalyst. In this work, a hydrothermally synthesized 2D CaIn₂S₄ nanosheets, possessing the merits of narrow bandgap and strong reduction ability, have been developed to construct S-scheme heterojunction with TiO₂ nanofiber. It is found that the 2D CaIn₂S₄ nanosheets can be in-situ assembled onto the surface of 1D TiO₂ nanofiber to form a 2D/1D CaIn₂S₄/TiO₂ S-scheme heterojunction, which then presents an extremely reinforced H₂-evolution rate (ca. 564.66 μmol·g^–1·h^–1), about 3- and 7-fold higher than that of the single TiO₂ and CaIn₂S₄, respectively. Finally, the in-situ XPS, DFT calculations, steady and transient-state spectrum results indicate that the formation of S-scheme heterojunctions between CaIn₂S₄ and TiO₂. This work may deliver a novel and insightful inspiration for the development of high-efficiency S-scheme heterojunction photocatalysts.