Breaking the out-of-plane symmetry of Janus WSSe bilayer with chalcogen substitution for enhanced photocatalytic overall water-splitting

Stacking the Janus transition metal dichalcogenides monolayer into bilayer is predicted to be a promising path to improve the photocatalytic water-splitting performance. However, the recovery of out-of-plane symmetry, caused by the energetically stacking pattern, makes the photocatalytic performance of bilayer disappointing. In this work, in order to break the out-of-plane symmetry, we choose selenium and tellurium to replace the surface sulphur of Janus WSSe bilayer, constructing the spatially asymmetric configurations. The first principles calculation results show that, the substitution strengthens the light absorption capacity, and promote the spatial separation of photogenerated carriers. Furthermore, the design of WSSe-WSeTe heterostructure, formed with tellurium substitution, improve the solar-to-hydrogen conversion efficiency and driving force of photo-induced carriers. Its solar-to-hydrogen conversion efficiency is up to 10.71%, and the photocatalytic water-splitting reactions on it could operate spontaneously, indicating an ideal water-splitting photocatalyst. Our study sheds light on a hopeful way to improve the photocatalytic performance for Janus transition metal dichalcogenides bilayers.