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.