Enhanced Performance of a Monolayer MoS2/WSe2 Heterojunction as a Photoelectrochemical Cathode

Transition-metal dichalcogenide(TMD) semiconductors have attracted interest as photoelectrochemical(PEC) electrodes due to their novel band-gap structures,optoelectronic properties, and photocatalytic activities.However, the photo-harvesting efficiency still requires improvement. In this study, A TMD stacked heterojunction structure was adopted to further enhance the performance of the PEC cathode. A P-type WSeand an N-type Mo Smonolayer were stacked layer-by-layer to build a ultrathin vertical heterojunction using a micro-fabrication method.In situ measurement was employed to characterize the intrinsic PEC performance on a single-sheet heterostructure.Benefitting from its built-in electric field and type II band alignment, the MoS/WSebilayer heterojunction exhibited exceptional photocatalytic activity and a high incident photo-to-current conversion efficiency(IPCE). Comparing with the monolayer WSecathode, the PEC current and the IPCE of the bilayer heterojunction increased by a factor of 5.6 and enhanced 50%, respectively. The intriguing performance renders the MoS/WSeheterojunction attractive for application in high-performance PEC water splitting.