Band Alignment Tunning via the Facets of CdS Nanocrystals with g‐C₃N₄ for Unveiling Their Enhanced Photocatalytical Property

Abstract The heterojunction is a great approach to profit the photogenerated electrons and holes separation and then enhance the photoelectric current for the photochemical reactions, such as the hydrogen evolution reaction. The intrinsic of the enhanced electrons and hole separation is ascribed to the appropriate band alignment between the two contact materials and plenty of research has reported the different band alignments formed by the different contacted bulk nanomaterials. Few studies focus on the precious crystal structure‐related band alignment. Here, the polyheptazine structured g‐C₃N₄ together with the wurtzite CdS is investigated, and different band alignments are formed through the different exposed crystal planes of CdS. It is found that along with the annealing temperature, the CdS will dominantly expose with the (110) facets and then form the S‐scheme heterojunction with the g‐C₃N₄. The formed built‐in electric field between the valence band of CdS and the conductive band of g‐C₃N₄ accelerates the recombination between the photogenerated electrons from CdS and holes from g‐C₃N₄. Meanwhile, it promotes the separation of the photogenerated electrons with holes from g‐C₃N₄, resulting in the superior photocatalytic HER performance. The study supplies a new venue for preciously tunneling the band alignments between the heterogeneous catalysts for optimizing the photoelectric properties.