Black phosphorus quantum dots facilitate carrier separation for enhancing hydrogen production over hierarchical Cu7S4/ZnIn2S4 composites

Abstract

At present, inefficient charge separation is considered to be one of the most important factors, limiting the photocatalytic hydrogen production. To solve this problem, herein, hierarchical Cu₇S₄/ZnIn₂S₄ decorated with black phosphorus quantum dots (BPQDs) was rationally designed and its photocatalytic hydrogen evolution was investigated under visible light. The structural characterization proved the wrapped morphology of ZnIn₂S₄ grown on the Cu₇S₄ nanocrystals and BPQDs were uniformly dispersed on the surface of ZnIn₂S₄. Moreover, the close hierarchical structure of Cu₇S₄ with ZnIn₂S₄ and carrier separation facilitator of BPQDs were synergistically beneficial for boosting charge separation and transfer. The hydrogen production results showed that the ternary BPQDs@10% Cu₇S₄/ZnIn₂S₄ yielded the highest H₂ evolution rate of 885 μmol g⁻¹ h⁻¹, about 6.8 times higher than that of the pristine ZnIn₂S₄, indicating its promising application in hydrogen production. In addition, the possible working mechanism was deeply explored using photo-electrochemistry, and the results illustrated that the enhanced photocatalytic hydrogen evolution can be attributed to the efficient charge separation caused by the formation of the hierarchical interface structure and increased carrier transfer efficiency of BPQDs. This study demonstrates that the regulation of interfacial charge transfer can positively facilitate photocatalytic activity and the ternary BPQDs@10% Cu₇S₄/ZnIn₂S₄ can be employed as an efficient candidate for hydrogen production.