Sulfur vacancy, p-n-type heterojunction and ohmic contact to synergistically improve the hydrogen evolution activity of CoS/Sv-ZnIn2S4/Ni(OH)2 composites

The sluggish charge-carrier kinetics for conventional photocatalysts severely limit the photogenerated charge utilization and result in unfavorable hydrogen evolution efficiency. To address these challenges, CoS/S v -ZnIn 2 S 4 /Ni(OH) 2 photocatalysts, containing sulfur vacancy, p-n-type heterojunction and Ohmic contact, were successfully constructed via an in-situ technique. Defect-mediated enrichment of photogenerated electrons at sulfur vacancies achieved fast charge transfer and inhibited the carrier recombination. The interfacial electric field (IEF) due to p-n-type heterojunction enhanced the carrier separation and transfer. Ohmic contact rapidly extracted the photogenerated charges and accelerated the hydrogen reduction reaction dynamics. As expected, CoS/S v -ZnIn 2 S 4 /Ni(OH) 2 catalysts reached an impressive hydrogen evolution rate of 19.45 mmol g −1  h −1 , which was 8.61 times higher than that of pure ZIS. This work demonstrates that the synergistic effect between sulfur vacancies and IEF effects may establish a new paradigm for designing high-efficiency multi-component sulfide-based photocatalysts.