Z-scheme SnC/HfS2 van der Waals heterojunction increases photocatalytic overall water splitting

Abstract

Designing a direct Z-scheme system is one of the effective ways to develop a high-efficient photocatalyst. In this paper, we designed the SnC/HfS2 heterojunction and explored its electronic structure and photocatalytic properties for water splitting based on first-principles calculations. Our results suggest that SnC/HfS2 heterostructure is a typical direct Z-scheme heterojunction, which can effectively separate carriers and possesses strong oxidation and reduction capabilities. The valence band maximum of SnC is close to the conduction band minimum of HfS2, which is in favor of the recombination of inter-layer carriers. The very small interlayer band gap and appropriate built-in electric field direction make the migration of electrons and holes along the Z-path. The photo-generated electrons on SnC make the hydrogen evolution reaction happen continuously, while the photo-generated holes on HfS2 make the oxygen evolution reaction happen continuously. The calculation of the reaction energy barrier indicates that the procedure of photocatalytic water splitting on the SnC/HfS2 heterojunction can be spontaneous. Our results show that SnC/HfS2 heterojunction is a potential direct Z-scheme photocatalyst for the overall decomposition of water.