MoS ₂ –PdS ₂ Heterostructure for NO ₂ Sensing under Ambient Conditions: An Experimental and Computational Study

To protect the human environment, it is crucial to develop gas sensors that can effectively detect harmful gases at room temperature (RT). Even small traces of harmful gases like nitrogen dioxide (NO₂) are challenging to detect at RT. To resolve this issue, the van der Waals (vdWs) junction of 2D transition metal dichalcogenides (TMDCs) and novel metal dichalcogenides (NMDCs) holds significant potential for sensing devices because of intriguing properties at the junction. This study presents an efficient NO₂ gas sensor based on the vdW junction of PdS₂ and MoS₂ material working at RT (30 °C). Compared with pristine PdS₂, the conductivity of the vdW junction improved significantly. The MoS₂/PdS₂ heterojunction sensor demonstrates remarkable response and selectivity toward NO₂ at RT, which are inaccessible in PdS₂ and MoS₂ as individual sensors. The heterojunction sensor exhibits a relative response of ∼25% to 20 ppm of NO₂ as compared to pristine PdS₂ (∼7%) and pristine MoS₂ (∼12%) sensors and has a significantly lower limit of detection (LOD) of 1.4 ppb. The sensor demonstrates reasonably good response and recovery time, excellent stability, and long-term durability. Also, density functional theory (DFT) calculations indicate that the p-p junction of MoS₂/PdS₂ provides more favorable sites for NO₂ adsorption. This is due to the more negative adsorption energy, which improves charge transfer during the adsorption of NO₂ and boosts the electrical response of the gas sensors. This study offers a prospective framework for the development of gas sensors based on 2D vdW heterojunctions, which demonstrate enhanced sensing performance at RT conditions.