Insight into the photoelectric characteristic and photocatalytic water splitting in van der Waals heterostructures Cs 2 PbI 4 /MX 2 (M=Mo, W; X=Se, S)

Abstract

The photoelectric characteristic and photocatalytic water splitting in van der Waals heterostructures Cs2PbI4/MX2 (M=Mo,W; X=Se, S) were carried out based on first principle calculations. Four stable heterostructures were obtained with indirect narrow gaps. Among them, Cs2PbI4/MoSe2, Cs2PbI4/MoS2 and Cs2PbI4/WSe2 belong to type-II heterostructures, and Cs2PbI4/WS2 is type-I heterostructure. High optical absorption efficiency and high carrier mobility imply that type-I heterostructure Cs2PbI4/WS2 has a broad potential application prospect in light-emitting devices. Moreover, the optical absorption efficiency up to 10-5cm-1, the spatial separation interval of photogenerated electron-hole (~3.30), and type-II band edge alignment mean that heterostructures are easy to realize electron-hole separation and transfer, reduce the recombination probability of electron and holes, and thus enabling solar energy conversion and highly efficient photocatalytic water splitting. Especially, Cs2PbI4/MoSe2 heterostructure can trigger HER and OER reaction spontaneously at pH=0 under equilibrium potential 1.23 V with a limiting reaction barrier of 1.16 eV for OER, which is close to 1.128 eV in WSe2/MoSe2 heterojunction reported recently, implying that its may be an excellent photocatalyst. In addition, the limiting reaction barrier of Cs2PbI4/WSe2 heterostructure is 1.27 V, low overpotential for OER is 0.31 V, and high power conversion efficiency indicating that it may have a potential applications in both solar cells and photocatalytic water splitting.