Strain engineering for C2N/Janus monochalcogenides van der Waals heterostructures: Potential applications for photocatalytic water splitting

A type-II van der Waals (vdW) heterostructure that can inhibit carrier recombination and improve the photocatalytic efficiency of water splitting has received much attention for photocatalytic water splitting. In this work, two-dimensional Janus monochalcogenides, In2SSe(In2STe, In2SeTe) and C2N, are designed to type-II vdW heterostructures for photocatalytic water splitting. First-principles calculation results show that C2N/In2SSe and C2N/In2STe heterostructures have a type-I band alignment, and that C2N/In2SeTe have a unique type-II band alignment. Under biaxial strain, both C2N/In2SSe and C2N/In2STe heterostructures can have a type-I to type-II band alignment and an indirect-direct band-gap transition. Systematically electronic structure and band alignment results show that C2N/In2SSe and C2N/In2SeTe vdW heterostructures are more suitable for photocatalytic water splitting under strain than C2N/In2STe heterostructure. In addition, the optical absorption of C2N/In2SSe and C2N/In2SeTe vdW heterostructures can be significantly improved under biaxial strain. Detailed strain engineering results show that C2N is more sensitive to strain than Janus monochalcogenides due to the planar properties of sp2 hybrization of C2N, which dominate the band gap and band transition in heterostructures under strain. These results indicate that C2N/In2SSe and C2N/In2SeTe vdW heterostructures can be used as photocatalytic water splitting materials, providing a motivation for further research on Janus heterostructures.