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

• WS 2 decorated Mn 0.5 Cd 0.5 S/CuInS 2 p-n heterojunction synthesized for H 2 -production. • Multichannel charge-carrier transfer between Mn 0.5 Cd 0.5 S, CuInS 2 and WS 2 discussed. • High H 2 -production rate achieved over composite, 3.98-fold higher than Mn 0.5 Cd 0.5 S. Effective charge separation and sufficient light harvesting are crucial for photocatalytic water splitting into renewable and storable hydrogen energy. Employing WS 2 as cocatalyst and CuInS 2 as p-type semiconductor and photosensitizer, a novel WS 2 /Mn 0.5 Cd 0.5 S/CuInS 2 hierarchical tandem p-n heterostructure was constructed based on the energy band engineering theory. In this tandem p-n heterostructure, Mn 0.5 Cd 0.5 S nanoparticles adhere closely to CuInS 2 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 WS 2 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 WS 2 cocatalyst and the p-n junction charge transfer channels, the smartly designed ternary WS 2 /Mn 0.5 Cd 0.5 S/CuInS 2 heterostructure displays the optimal photoactivity toward hydrogen production (681.7 μmol h −1 ), more 3.98-fold enhancement than individual Mn 0.5 Cd 0.5 S under simulated sunlight irradiation. This research provides a new avenue for constructing multi-hierarchical systems with remarkably boosted charge separation and light-harvesting abilities for high-efficiency solar energy conversion.