Enhanced overall water splitting under visible light of MoSSe∣WSSe heterojunction by lateral interfacial engineering

Abstract

Photocatalytic splitting water is a promising method to obtain hydrogen energy. While design and synthesis of efficient and economical photocatalysts is one of the important contents. Janus MoSSe and WSSe monolayers are efficient and wide sunlight harvesting photocatalysts due to their intrinsic vertical electric fields. So how is the photocatalytic performance of lateral MoSSe∣WSSe heterojunctions, which possesses an intra-plane interface and intrinsic vertical electric field? In the present work, the structural property, electronic characteristic, optical property, and photocatalytic application of MoSSe∣WSSe lateral heterojunctions are systematically investigated. It is found that both zigzag and armchair configurations are semiconductors with suitable bandgaps of ∼1.60 eV. Besides, they possess a type-II band alignment where electrons tend to accumulate at the coupling interface of MoSSe side and holes at WSSe side, giving rise to a paralleled electric field in heterojunctions, which can largely promote the separation of photo-generated carriers. More remarkably, these heterojunctions exhibit pronounced solar-spectrum absorption efficiency, proper valence, and conduction band positions by initializing the redox reactions of H2O and high carrier mobility. Intriguingly, the zigzag MoSSe∣WSSe heterojunction has a better photocatalytic performance in an acidic environment, and the armchair MoSSe∣WSSe prefers to produce H2 and O2 in a neutral environment. These fascinating properties render the intra-plane MoSSe∣WSSe heterojunctions as the wide solar harvesting photocatalysts in further overall water splitting.