In-Sb Covalent Bonds over Sb₂Se₃/In₂Se₃ Heterojunction for Enhanced Photoelectrochemical Water Splitting

Antimony selenide is a promising P-type photocatalyst, but it has a large number of deep energy level defects, leading to severe carrier recombination. The construction of a heterojunction is a common way to resolve this problem. However, the conventional heterojunction system inevitably introduces interface defects. Herein, we employ in situ synthesis to epitaxially grow In₂Se₃ nanosheets on Sb₂Se₃ nanorods and form In-Sb covalent interfacial bonds. This petal-shaped heterostructure reduced interface defects and enhanced the efficiency of carrier separation and transport. In this work, the photocurrent density in the proposed Sb₂Se₃/In₂Se₃ photocathode is 0.485 mA cm^-2 at 0 V_RHE, which is 30 times higher than that of pristine Sb₂Se₃ and it has prominent long-term stability for 24 h without obvious decay. The results reveal that the synergy of the bidirectional built-in electric field constructed between In₂Se₃ and Sb₂Se₃ and the solid In-Sb interfacial bonds together build a high-efficiency transport channel for the photogenerated carriers that display enhanced photoelectrochemical (PEC) water-splitting performance. This work provides efficient guidance for reducing interface defects via the in situ synthesis and construction of interfacial bonds.