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

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 = similar to 1.3 at 50 ppb and similar to 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, H-2, 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.