The theoretical calculation and analysis of the chemical equilibrium in the synthetic process and its effect on hydrogen production performance for sulfide catalysts

In the present study, the authors found that the growth of sulfide catalyst crystals involved the dissolution-recrystallization process, resulting in the formation of stacking fault structured homojunctions through the theoretical calculation and analysis of the chemical equilibrium in the synthetic process for sulfide catalysts. It was also revealed that, compared with the alkali solution, using an alkaline ammonia solution as the hydrothermal solvent could promote more NiS cocatalysts to be distributed on the surface of the sulfide catalysts, leading to the formation of more p-n junctions. Both the p-n junctions and the stacking fault structures effectively promoted the separation of photogenerated charges, leading to a quantum efficiency at 420 nm of up to 74.6%, which is the highest efficiency reported to date among visible-light-driven photocatalysts without noble metal cocatalysts. Research of chemical equilibrium in the synthetic process for the CdZnS solid solution, it was revealed that certain amounts of CdS and ZnS may exist, thus forming a three-phase detached catalyst (CdS and ZnS single-phases and CdZnS solid solution phase). In this way, the structure could improve the hydrogen production performance of the CdZnS solid solution. The results were also confirmed by characterization of the catalysts.