S‐Scheme Photocatalytic Mechanism of Type‐I Band Alignment in α‐In2Se3/g‐C3N4 Heterostructure

The energy band alignment and photocatalytic performance of α‐In 2 Se 3 /g‐C 3 N 4 heterojunctions of two configurations (A and B) are studied through first‐principles calculations. The spontaneous out‐of‐plane electric polarization of α‐In 2 Se 3 points away from g‐C 3 N 4 for configuration A, in which the layer spacing and formation energy are lower than those of configuration B. Configuration A of α‐In 2 Se 3 /g‐C 3 N 4 is characteristic of the I‐type energy band alignment and S‐scheme heterojunction for photocatalytic performance, which is different from the II‐type band alignment characteristic of the previous traditional Z‐scheme heterojunctions with a larger built‐in electric field. The existence of a stronger intrinsic electric field of α‐In 2 Se 3 causes the photogenerated electrons in α‐In 2 Se 3 to migrate across the interface region of α‐In 2 Se 3 /g‐C 3 N 4 to reach the valence band maximum (VBM) of g‐C 3 N 4 for configuration A. The recombination of the photogenerated electrons from the conduction band minimum (CBM) of α‐In 2 Se 3 with holes from the VBM of g‐C 3 N 4 reduces the number of photogenerated holes in the VBM of g‐C 3 N 4 . The photogenerated electrons in the CBM of g‐C 3 N 4 due to the absence of holes move toward the surface of g‐C 3 N 4 and play a significant role in the hydrogen generation activity.