A highly efficient room-temperature NO2 gas sensor based on three-dimensional core–shell structured CoS2 bridged Co3O4@MoS2

Abstract

In recent years, two-dimensional transition metal dihalides have emerged as a subject of growing research interest in the field of gas sensing. This heightened attention can be attributed to their notable characteristics of high surface area ratios, customizable electronic properties of the layers, and a wide range of catalytic capabilities. These unique features make them promising candidates for gas sensing applications and warrant further investigation and exploration in this area. Practical applications of the original TMD (MoS₂) gas sensors are limited by their poor gas sensing performance at room temperature (RT), including less-than-full recovery, long response times, and low response speeds. Addressing these challenges is crucial for improving their real-world usability. In this study, we synthesized three-component heterojunctions (Co₃O₄–CoS₂@MoS₂) with a controlled morphology and composition using different mass ratios of raw materials. The Co₃O₄–CoS₂@MoS₂-2 gas sensor demonstrated exceptional sensitivity to NO₂ gas (R_a/R_g = 39.6 in 100 ppm) at room temperature, achieving an ultra-fast response time of merely 3.4 seconds in ambient air. This sensing behavior first benefits from Co₃O₄'s high specific surface area and abundant oxygen vacancy concentration. The second is the synergistic effect of the heterogeneous structure between MoS₂ and Co₃O₄. And finally, the electron holding capacity of the S atom in CoS₂. The synergistic effect of the three factors promotes the gas-sensing performance of the sensor. The results we obtained show that this approach is viable to improve the sensing performance of metal oxides under RT conditions and can also be scaled up to include other 2D transition metal dihalide-based materials.