In situ addition of Ni salt on skeletal Cu7S4 integrated CdS nanorods photocatalyst for efficient production of H2 under solar light irradiation

Development of earth-abundant, low cost, skeletal-type copper sulfide superstructures plays a prominent role in various potential applications, owing to the properties of superstructures such as excellent permeability of charge and mass. In this study, we synthesized the hollow superstructures of crystallinity-controlled polyhedral skeletal-type copper sulfide (Cu7S4), which were integrated with cadmium sulfide (CdS) nanorods. The photocatalytic hydrogen production by water splitting was investigated under solar light irradiation with lactic acid as a hole scavenger. The Cu7S4/CdS composites exhibited the H2 production rate of 6.25 μmol h-1, which was 3 times higher than CdS. Moreover, the addition of small amount of nickel salts to the reaction solution significantly improved the activity of Cu7S4/CdS for H2 production (45 μmol h-1), which was 20 times higher than CdS and 7 times higher than Cu7S4/CdS. The enhancement of activity in Ni-Cu7S4/CdS (Cu7S4/CdS with Ni salts in reaction solution) was attributed to the effective separation of charge carriers due to the unique properties of the skeletal-type Cu7S4 cages and the superior charge transportation of Ni salts in the reaction solution. The Cu7S4/CdS system containing Ni salts in the reaction solution is reported in photocatalytic hydrogen production for the first time, to the best of our knowledge, which promises new and inspiring research for the development of photocatalytic water splitting applications.