Oxygen vacancy and interface effect dual modulation of SnS2/SnO2 heterojunction for boosting formaldehyde detection at low temperature.

Formaldehyde (HCHO) is a harmful volatile organic pollutant, which is commonly found in interior decoration and furniture products. Therefore, it is necessary to develop a gas sensor that can quickly and accurately detect formaldehyde for human health and environmental protection. In order to achieve this goal, in this work, SnS₂/SnO₂ heterostructure was synthesized by in-situ sulfurization process on the basis of SnO₂ nanospheres, and its formaldehyde sensing performance was studied. After testing, it was found that the gas sensor based on SnS₂/SnO₂ heterojunction has more excellent gas sensing performance than pure SnO₂ gas sensor at the same operating temperature (100 °C). Specifically, SnS₂/SnO₂-2 (Sn:S = 3:2) has the advantages of high sensitivity (4.01 at 0.1 ppm), excellent selectivity, low theoretical detection limit (13.26 ppb), good humidity resistance and long-term stability. The excellent sensing performance of SnS₂/SnO₂ sensors for formaldehyde detection is mainly attributed to the n-n heterojunction formed by SnS₂ and SnO₂, which generates a built-in electric field to accelerate the electron transport in the material, the higher oxygen vacancy sites adsorb a large number of reactive gas molecules to promote the oxidation of formaldehyde molecules, and the unique porous structure to promote the transmission and diffusion of gases and increase the surface area to provide more adsorption sites and reactive centers for gas molecules. Therefore, the construction of SnS₂/SnO₂ heterostructures will be an effective way to develop next-generation formaldehyde gas sensors with higher sensing performance.