Room-temperature sensing performance of binary Co–Zn doped MoS2/graphite composites toward ppb-level NO2

Abstract

Molybdenum disulfide (MoS₂), a transition metal dichalcogenide (TMD), is conventionally regarded as a promising room-temperature sensing material due to its unique physical and chemical properties. However, the gas sensors based on pure MoS₂ films do not seem to achieve the expectation. In this study, we fabricated the unique structure of dispersed Co and Zn atoms doped on the MoS₂/graphite (Co–Zn/MG) composite and investigated the gas-sensing properties. We find that the sensor based on the Co–Zn/MG composite shows high responses toward NO₂ gas (R_a/R_g = ∼1.3 at 50 ppb and ∼5.5 at 5 ppm) at room temperature, which is significantly higher than that of the pristine MoS₂ sensor in our work. In addition, the Co–Zn/MG sensor has a low limit of detection of 6.2 ppb, fast response–recovery time (118/383 s toward 1 ppm NO₂), and long-term stability. Compared with other gases, including NO, NH₃, H₂, CO, and ethanol, the sensor exhibits good selectivity toward NO₂ due to its lower activation energy. Furthermore, the enhanced gas-sensing mechanism can be attributed to the modulation of Schottky barrier height, enriched oxygen adsorption, and catalysis. This work may open a new avenue to achieve NO₂ sensors with absolutely competitive performance at room temperature.