Bi₂S₃/ZnS heterostructures for H₂S sensing in the dark: the synergy of increased surface-adsorbed oxygen and charge transfer

Bismuth sulfide (Bi₂S₃) is a promising sensing material owing to its unique properties like a narrow bandgap, a large number of surface-adsorption sites, and excellent electrical properties. However, the unsatisfactory sensitivity precludes its application in high-performance sensors to detect H₂S. Herein, a Bi₂S₃/ZnS heterostructure was constructed as a sensing material to further improve its sensitivity toward H₂S by modulating light or dark conditions. The sensor based on the Bi₂S₃/ZnS heterostructure exhibited an ultrahigh response (1027%) when exposed to 500 ppb H₂S in the dark, roughly 4 times higher than that of pristine Bi₂S₃ under indoor light. Besides, pristine ZnS has almost no H₂S sensing response. Such a distinctive enhancement is mainly attributed to the effective separation of electron-hole pairs and charge transfer by the heterostructures, as well as more surface-adsorbed oxygen under dark conditions, which is conducive to H₂S sensing. Moreover, the Bi₂S₃/ZnS-based sensor has excellent selectivity, repeatability, long-term stability, and humidity tolerance, which lays a good foundation for its practical production and application in dark and humid environments, such as tunnels.