Highly selective NO2 sensing for mobile on-site monitoring enabled by a dual-sensitization mechanism in palladium sulfide-based nanocomposites

A sulfur vacancy-rich PdS/MoS 2 hierarchical heterostructures were synthesized via in-situ microwave-assisted method. • A dual-sensitization mechanism of synergistic enhancement of sulfur vacancy and heterojunction was proposed. • A mobile monitoring system is developed for on-site NO 2 tracking, enabling excessive NO 2 concentration warning. Developing high-selectivity and high-sensitivity nitrogen dioxide (NO 2 ) gas sensors, and explaining the complex underlying sensitization mechanisms remain critical challenges. Herein, we propose a dual-sensitization mechanism of synergistic enhancement of sulfur vacancy and heterojunction at composite interface to develop a high-performance NO 2 gas sensor at room temperature. A novel sulfur vacancy-rich palladium sulfide (PdS) nanocluster is synthesized via a microwave-assisted method, and it is further in situ decorated on molybdenum disulfide (MoS 2 ) nanoflowers to construct hierarchical heterostructure. The high selectivity of PdS/MoS 2 gas sensor is verified via experiment and density functional theory calculation. The PdS/MoS 2 composite system shows the highest adsorption energy (−1.89 eV) to NO 2 among various interfering gases, which further decreases to −2.11 eV after introducing sulfur vacancies. Meanwhile, the proposed dual-sensitization mechanism is based on “targeted electron-reflux” effect resulting from the synergistic action of sulfur vacancies and the p-p heterojunction, which modulates the interfacial carrier migration behaviors. Furthermore, a mobile NO 2 monitoring system is developed for on-site NO 2 tracking, which is equipped with the PdS/MoS 2 gas sensor, universal serial bus module, and smart phone, enabling real-time monitoring and excessive NO 2 concentration warning. This work proposes a research approach for complicated gas sensing mechanism, and provides an avenue for portable and intelligent gas detection. Download: Download high-res image (162KB) Download: Download full-size image