In-situ constructing of one-dimensional SnIn₄S₈-CdS core-shell heterostructure as a direct Z-scheme photocatalyst with enhanced photocatalytic oxidation and reduction capabilities

Incorporating heterojunctions and constructing structures are reliable strategies to solve the problem of inefficient intrinsic charge generation in semiconductors. In this study, a direct Z-scheme heterojunction was formed ingeniously, via the intimate coaxial contact of SnIn4S8-CdS (SISCS) core-shell nanostructure. The prepared coreshell SISCS composites exhibited more superior photocatalytic oxidation and reduction capabilities in comparison with bare CdS and SnIn4S8. Significantly, the SISCS2 sample could reduce 98.9% of Cr (VI) (20 mg/L) and degrade almost all methyl orange (MO) (15 mg/L) within 24 min. The apparent rate constants of Cr (VI) and MO photodegradation over SISCS2 were 3.52 and 7.52 times than those of bare CdS nanomds, 4.57 and 5.59 folds as those of pure SnIn4S8, respectively. The intimate coaxial contact between CdS and SnIn4S8 efficiently enhanced the charge transfer, and the redox ability of the CdS and SnIn4S8 could be maintained crediting to the Z-scheme system heterojunction. Moreover, the enlarged specific surface area and the super-hydrophilic surface could both ensure excellent photocatalytic activity of SISCS composites. Furthermore, the Z-Scheme photocatalytic mechanism and the degradation pathways of MO were also discussed in depth.