Ppb-Level Hydrogen Sulfide Gas Sensor Based on the Nanocomposite of MoS₂ Octahedron/ZnO-Zn₂SnO₄ Nanoparticles

Hydrogen sulfide (H₂S) detection is extremely necessary due to its hazardous nature. Thus, the design of novel sensors to detect H₂S gas at low temperatures is highly desirable. In this study, a series of nanocomposites based on MoS₂ octahedrons and ZnO-Zn₂SnO₄ nanoparticles were synthesized through the hydrothermal method. Various characterizations such as X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectrum (XPS) have been used to verify the crystal phase, morphology and composition of synthesized nanocomposites. Three gas sensors based on the nanocomposites of pure ZnO-Zn₂SnO₄ (MS-ZNO-0), 5 wt% MoS₂-ZnO-Zn₂SnO₄ (MS-ZNO-5) and 10 wt% MoS₂-ZnO-Zn₂SnO₄ (MS-ZNO-10) were fabricated to check the gas sensing properties of various volatile organic compounds (VOCs). It showed that the gas sensor of (MS-ZNO-5) displayed the highest response of 4 to 2 ppm H₂S and fewer responses to all other tested gases at 30 °C. The sensor of MS-ZNO-5 also displayed humble selectivity (1.6), good stability (35 days), promising reproducibility (5 cycles), rapid response/recovery times (10 s/6 s), a limit of detection (LOD) of 0.05 ppm H₂S (R_a/R_g = 1.8) and an almost linear relationship between H₂S concentration and response. Several elements such as the structure of MoS₂, higher BET-specific surface area, n-n junction and improvement in oxygen species corresponded to improving response.