Bismuth Sulfide Nanorod/Vanadium Carbide MXene as Nitrogen Dioxide Gas Sensor Operating at Room Temperature under Ultraviolet-Assisted Recovery

Endowed with a narrow bandgap and relatively high carrier mobility, bismuth sulfide (Bi2S3) has attracted attention in the field of gas sensors. However, pristine Bi2S3 still has limitations on the suboptimal sensitivity and recovery performance at room temperature. Herein, we engineered Bi2S3/vanadium-based MXene (V2CTx) Schottky heterojunctions by introducing V2CTx MXene, which has unique electrical properties, a large specific surface area, and abundant functional groups. Bi2S3 nanorod (NR)/V2CTx nanosheet (NS) 1D/2D heterostructure demonstrates an improved response (∼190%) to 20 ppm of nitrogen dioxide (NO2) at room temperature (25 °C), which is 6.7 times that of the pristine Bi2S3 sensor. The optimized Bi2S3 NR/V2CTx NS sensors exhibit a fully recoverable response, with outstanding repeatability and a short recovery time of 103 s to 20 ppm of NO2 under 365 nm ultraviolet illumination. In addition, Bi2S3/V2CTx heterostructures possess desirable sensing performances, including high selectivity, outstanding long-term stability, and reliability at various humidity conditions for NO2 detection at room temperature. The photosensitive property of Bi2S3 and the construction of Bi2S3/V2CTx Schottky junctions improve the gas sensing performance and facilitate electron transfer. The photogenerated holes recombine with the adsorbed NO2– ionized molecules on the surface to neutralize and release NO2 by the UV-cleaning effect. In addition, the photogenerated electrons combine with the adsorbed oxygen molecules to form the oxygen species O2– (ads). This work provides significant research potential for developing high-performance metal sulfide/MXene-based sensing materials at room temperature.