2D NiCo2S4 decorated on ZnIn2S4 formed S-scheme heterojunction for photocatalytic hydrogen production

The hydrothermal preparation of NiCo2S4/ZnIn2S4 photocatalysts with different mass ratios is studied. Ni-cobalt bimetallic sulfide nanosheets are grown on zinc-indium bimetallic sulfide to form a compact heterojunction. First, both NiCo2S4 and ZnIn2S4 exhibit N-type semiconductor characteristics, a heterojunction formed by both can reduce the surface reaction energy barrier and use its synergy, strengthening the charge self-diffusion between the two semiconductors, it means the formation of a strong electric field. From the electron transfer path and band structure, NiCo2S4/ZnIn2S4 has S-scheme heterojunction characteristics. NiCo2S4 is a reducing photocatalyst (RP), and ZnIn2S4 is an oxidative photocatalyst (OP). Under the action of built-in electric field (BIEF), strong photogenic electrons and holes exist in CB of RP (NiCo2S4) and VB of OP (ZnIn2S4). Thus, the overall redox capacity of the NiCo2S4/ZnIn2S4 heterojunction is enhanced. Using visible light, the composite material can be used for photocatalytic hydrogen production. It is further shown that the composite material has a good effect in photocatalytic hydrogen production under the sensitizer eosin Y (EY) system. The optimal hydrogen production is about 221.75 mmol when the mass ratios of NiCo2S4/ZnIn2S4 is 20%, and the photocatalytic activity of the composite is about 47 times that of ZnIn2S4. Notably, the stability of the composites is the better. A reasonable photo-catalytic mechanism is proposed based on the band gap and photoelectrochemical properties of heterojunction. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The hydrothermal synthesis of NiCo2S4/ZnIn2S4 photocatalysts with different mass ratios was investigated. The growth of Ni-cobalt bimetallic sulfide nanosheets on zinc-indium bimetallic sulfide resulted in a compact heterojunction. The heterojunction exhibited N-type semiconductor characteristics and facilitated charge self-diffusion between the two semiconductors, leading to the formation of a strong electric field.