Full-spectrum-responsive Bi2S3@CdS S-scheme heterostructure with intimated ultrathin RGO toward photocatalytic Cr(VI) reduction and H2O2 production: Experimental and DFT studies

Abstract Heterostructure-based photocatalysis offers significant potential for developing ultraviolet–visible (UV–Vis) to near-infrared (NIR) light-responsive catalysts with abundant beneficial physicochemical properties to boost environmental remediation upon solar-light irradiation. In this study, for the first time a novel ternary heterostructure photocatalysts containing Bi2S3@CdS@RGO (BCG) were rationally constructed using the hydrothermal approach. The resultant ternary composite with 5 wt% of CdS and 20 wt% of reduced graphene oxide (RGO) contents (BCG-5) was adopted as an optimal sample for photo-reduction of Cr(VI) under simulated solar-light irradiation. The apparent rate constant of the photo-reduction process over BCG-5 was ~ 13, 4, and 3 times higher than those of Bi2S3, CdS, and BC-5, respectively, within 150 min. The enhanced photocatalytic activity of ternary composite could be linked predominantly to the formation of heterostructural, synergistic behavior between the components, hierarchical morphology, the formation of n-n type high-low junctions, efficient interfacial charge-transfer capability, large specific surface area, full-spectrum light-absorption, and outstanding photo-stability. Electron spin resonance and reactive radical-scavenging results demonstrated that the hydroxyl and superoxide active species were primarily responsible for Cr(VI) removal. Furthermore, the photocatalytic activity of BCG-5, as an optimal sample, was further assessed regarding the photocatalytic production of H2O2, with 1.37 and 15.14 times higher efficiency than binary and bare samples, respectively. Assisted by the density functional theory calculations, ultraviolet photoelectron spectroscopy analyses, the charge-carriers pathway and possible photocatalytic mechanism were systematically discussed in S-scheme heterojunction. We expect that our findings will open new horizons for significant applications of bismuth-rich-based heterostructures under both visible- and NIR-light irradiation to address environmental and energy issues.