Boosting photocatalytic hydrogen evolution: Orbital redistribution of ultrathin ZnIn2S4 nanosheets via atomic defects

Defect engineering, inducing photo-excited electrons and holes to different surfaces of semiconductor photocatalyst, is an efficient strategy to improve the photocatalytic activity. A rapid heating-up hydrothermal technique is developed to regulate ZnIn2S4 crystal growth, then, ultrathin ZnIn2S4 nanosheets with In defect-rich [InS]6 interlayer but perfect [InS]4 and [ZnS]4 surface layers are successfully prepared (ultra-ZIS-VIn). Interestingly, the In defect, inducing the redistribution of the orbitals near the valence band maximum, separates the oxidation and reduction sites on the opposite sides of the ultra-ZIS-VIn nanosheets. Simultaneously, In defects increase the density of states (near the valence band maximum and conduction band minimum) and delocalize the electron around In defects. Accordingly, the photocatalytic hydrogen evolution rate is optimized to 13.4 mmol h−1 g−1, which is 8.9 times higher than that of defect-free ZnIn2S4 (pristine-ZIS).