Bifunctional gas sensor based on Bi2S3/SnS2 heterostructures with improved selectivity through visible light modulation

Abstract

The effective monitoring of hazardous gases at room temperature is extremely indispensable in the “Internet of things” application; however, developing bifunctional gas sensors for advanced sensing platforms still remains a challenge. Herein, we demonstrate a visible-light-modulated strategy to realize the bifunctional detection of NO₂ and H₂S by using Bi₂S₃/SnS₂ heterostructures as sensing materials. The sensor based on Bi₂S₃/SnS₂ exhibited superior sensitivity toward NO₂ under light irradiation and high selectivity to H₂S in the dark at room temperature; additionally, it achieved ultrahigh responses (14.0 (R_g/R_a) towards 500 ppb NO₂ and 12.3 (R_a/R_g) towards 500 ppb H₂S). Such distinctive light-dependent sensing behavior is mainly attributed to the different gas-sensing mechanisms of Bi₂S₃/SnS₂ toward NO₂ (physisorption model) and H₂S (oxygen absorbate-mediated model). As confirmed by in situ XPS characterization, the decrease in surface-adsorbed oxygen on Bi₂S₃/SnS₂ under light illumination offers the opportunity to modulate the number of active adsorption sites and consequently obtain bifunctional gas-sensing characteristics. In addition, the heterojunction effect, which is beneficial for interfacial charge transfer, also contributes to the improved sensing performance. Moreover, the Bi₂S₃/SnS₂ sensor presented rapid response–recovery speed, outstanding repeatability, and reliable stability to ppb-level target gases. This work offers an alternative strategy to designing bifunctional gas sensors through light modulation, which might significantly encourage the development of other smart sensing materials and further expand their potential applications.