Direct Z-scheme arsenene/HfS2 van der Waals heterojunction for overall photocatalytic water splitting: First-principles study

Abstract

In this paper, the electronic structure and photocatalytic mechanism of arsenene/HfS2 heterojunction with the stable structure are explored systematically based on first-principles calculations. The calculated projected band structure shows that arsenene/HfS2 junction has intrinsic type-II staggered band alignment characteristics, with a bandgap of 0.79 eV, which is much smaller than that of the bandgap on both sides. The small inter-layer bandgap and the built-in electric field induced by the charge transfer at the interface can accelerate the transfer of photo-generated electrons and holes along the Z-scheme path. The appropriate band edge position and efficient charge carriers separation qualify arsenene/HfS2 heterojunction to be an excellent photocatalyst for water splitting. Moreover, the Gibbs free energy diagram indicates that solar energy can effectively drive water splitting on arsenene/HfS2 junction. The influence of the bi-axial strain and pH value of water are discussed. Our calculations predict that the arsenene/HfS2 van der Waals heterojunction can be a promising candidate for direct Z-scheme photocatalyst for overall water splitting.