Fabricating WS2/Mn0.5Cd0.5S/CuInS2 hierarchical tandem p-n heterojunction for highly efficient hydrogen production

Effective charge separation and sufficient light harvesting are crucial for photocatalytic water splitting into renewable and storable hydrogen energy. Employing WS2 as cocatalyst and CuInS2 as p-type semiconductor and photosensitizer, a novel WS2/Mn0.5Cd0.5S/CuInS2 hierarchical tandem p-n heterostructure was constructed based on the energy band engineering theory. In this tandem p-n heterostructure, Mn0.5Cd0.5S nanoparticles adhere closely to CuInS2 nanosheets to form a p-n junction along with the strong and monodirectional inner-built electric field, which can regulate the directional transfer/migration of photoinduced electrons-hole pairs and significantly boost the charge separation. Furthermore, the WS2 cocatalyst employed in the ternary heterostructure further expedites the spatial charge separation and directional migration of photoexcited electrons, as well as simultaneously provides plentiful reaction active sites to decrease the activation barrier for hydrogen generation reaction. Benefiting from the synergetic cooperation of WS2 cocatalyst and the p-n junction charge transfer channels, the smartly designed ternary WS2/Mn0.5Cd0.5S/CuInS2 heterostructure displays the optimal photoactivity toward hydrogen production (681.7 mu mol h-1), more 3.98-fold enhancement than individual Mn0.5Cd0.5S under simulated sunlight irradiation. This research provides a new avenue for constructing multihierarchical systems with remarkably boosted charge separation and light-harvesting abilities for highefficiency solar energy conversion.