Janus MoSSe/WSeTe heterostructures: a direct Z-scheme photocatalyst for hydrogen evolution

Inspired by natural photosynthesis, direct Z-scheme heterostructures are considered as promising photocatalysts for solar-driven water splitting and attract ever-growing interest. Herein, based on density functional theory and nonadiabatic molecular dynamics calculations, we predict a Janus MoSSe/WSeTe heterostructure as a potential direct Z-scheme photocatalyst for hydrogen evolution. Our calculations show that photogenerated carriers can transfer at the interface via a traditional type II path or Z-scheme path depending on stacking configurations. Surprisingly, introducing surface chalcogen vacancies can not only effectively switch the charge transfer path from type II to Z-scheme, but also increase the time difference between electron (hole) transfer and interlayer carrier recombination with a time scale of 25 ps (37.4 ps), one order of magnitude longer than that of 2595 fs (1531 fs) in intrinsic Z-scheme. This is ascribed to the introduced defect trap states strongly modulating the competition between charge separation and interlayer e-h recombination. These properties make MoSSe/WSeTe heterostructures a compelling direct Z-scheme candidate for photocatalytic hydrogen evolution.