Bi₂S₃–In₂S₃ Heterostructures for Efficient Photoreduction of Highly Toxic Cr⁶⁺ Enabled by Facet-Coupling and Z-Scheme Structure

The construction of Z-scheme photocatalyst materials mimicking the natural photosynthesis system provides many advantages, including increased light harvesting, spatially separated reductive and oxidative active sites and strong redox ability. Here, a novel Bi₂S₃ nanorod@In₂S₃ nanoparticle heterojunction photocatalyst synthesized through one-pot hydrothermal method for Cr⁶⁺ reduction is reported. A systematic investigation of the microstructural and compositional characteristics of the heterojunction catalyst confirms an intimate facet coupling between (440) crystal facet of In₂S₃ and (060) crystal facet of Bi₂S₃, which provides a robust heterojunction interface for charge transfer. When tested under visible-light irradiation, the Bi₂S₃–In₂S₃ heterojunction photocatalyst with 15% Bi₂S₃ loading content achieves the highest Cr⁶⁺ photoreduction efficiency of nearly 100% with excellent stability, which is among the best-reported performances for Cr⁶⁺ removal. Further examination using optical, photoelectrochemical, impedance spectroscopy, and electron spin resonance spectroscopy characterizations reveal greatly improved photogenerated charge separation and transfer efficiency, and confirm Z-scheme electronic structure of the photocatalyst. The Z-scheme Bi₂S₃–In₂S₃ photocatalyst demonstrated here presents promise for the removal of highly toxic Cr⁶⁺, and could also be of interest in photocatalytic energy conversion.