Interfacial Mediation by Sn And S Vacancies of p-SnS/n-ZnIn₂S₄ for Enhancing Photocatalytic Hydrogen Evolution with New Scheme of Type-I Heterojunction

The construction of interfacial electric field (IEF) in semiconductor heterojunction is of great significance in boosting photocatalytic hydrogen evolution through efficient separation of photogenerated charge-carriers. However, the exploitation of IEF in type-I heterojunction has not been proposed for designing photocatalysts. Herein, based on the density functional theory prediction, p-SnS with different work functions modulated by Sn-vacancy are compounded with n-ZnIn₂S₄ containing S-vacancy to form type-I heterojunction. The optimized SnS/ZnIn₂S₄ photocatalyst without co-catalysts exhibits an impressive hydrogen evolution rate of 22.75 mmol g⁻¹ h⁻¹, 6.23 times of ZnIn₂S₄. Systematic investigations reveal that the interfacial Sn-S bond acts as a transport channel that accelerates the interface charge-carriers transfer under the promotion of IEF originating from the significant Fermi level difference. A large difference in the surface photovoltage signal of SnS/ZnIn₂S₄ and ZnIn₂S₄ is achieved from effective photogenerated charge-carriers separation by IEF. The new p-n type-I scheme of SnS/ZnIn₂S₄ induced by the interfacial mediation can separate the photogenerated charge-carriers, and retain the highly reductive electrons of ZnIn₂S₄ for hydrogen evolution, overcoming the disadvantage of reduction potential decline in the typical type-I scheme. This study will afford a new theoretical basis for the achievement of high-efficiency photocatalytic hydrogen evolution through interface modulation.