Self-assembly of snowflake-like CuS with ultrathin ZnInS nanosheets to form S-scheme heterojunctions for photocatalytic hydrogen production.

Step-scheme (S-scheme) heterojunction has attracted much attention in the design of heterostructures for photocatalysts. In this study, we successfully utilized the principle of electrostatic self-assembly to load ultrathin ZnInS nanosheets onto snowflake-like CuS using a simple grinding method, and synthesized CuS/ZnInS S-scheme heterojunctions according to the different work functions (Φ). At the optimal CuS loading ratio (5 wt%), the hydrogen yield of the CuS/ZnInS composites reaches 5.58 mmol·h·g, which is 5.12 times higher than that of pure ZnInS (1.09 mmol·h·g). The apparent quantum efficiency (AQE) of the CuS/ZnInS composites reaches 5.8 % (λ = 370 nm), which is an improvement compared to pure ZnInS (2.7 %). The AQE of pure ZnInS is 0.4 %, while the AQE of CuS/ZnInS composites is enhanced to 1.0 % at λ = 456 nm. The heterojunction interface of CuS and ZnInS builds a built-in electric field (IEF), which greatly reduces the recombination rate of photogenerated electrons and holes, retains highly reduced photoelectrons in the conduction band (CB) of ZnInS. The snowflake structure of CuS effectively increases the active sites and specific surface area, and improves the light absorption. This work opens a new avenue for designing photocatalysts, synergizing energy development and protecting the environment.