Facile synthesis of ZnIn2S4@ZnS composites for efficient photocatalytic hydrogen precipitation

Abstract

It has been demonstrated that compounding of semiconductor materials with appropriate energy band structures can effectively increase the separation efficiency of photogenerated carriers and, consequently, the activity of hydrogen synthesis. In this work, ZnIn₂S₄@ZnS composites were synthesized through a two-step process in order to investigate the influence of ZnS addition on the rate of hydrogen production of the composites. XRD and TEM measurements confirmed the effective synthesis of ZnIn₂S₄@ZnS composites. ZnIn₂S₄@ZnS-0.3 exhibited the best photocatalytic performance with a hydrogen production rate of 2.873 mmol g⁻¹ h⁻¹, approximately 12.5 times that of pure phase ZnIn₂S₄. The XPS measurement indicates that there is a strong interfacial interaction between ZnS and ZnIn₂S₄, indicating more than simple mechanical mixing had occurred. The fluorescence spectrum demonstrates that the electron–hole recombination in ZnIn₂S₄@ZnS-0.3 is significantly reduced and that efficient interface charge transfer and separation have been accomplished. Based on the Mott–Schottky diagram, an interfacial electron transfer mechanism for the ZnIn₂S₄@ZnS composite was hypothesized. This work sheds light on the interfacial electron transfer between the composite semiconductor materials, which promotes the separation of photogenerated carriers and, as a result, enhances photocatalytic hydrogen production activity.