Chemo — Resistive CO2 gas sensor based on CuO-SnO2 heterojunction nanocomposite material

Heterojunction nanocomposites were realized between p-type CuO and n-type SnO₂ by simple hydrothermal route, further incorporation with 0.5wt.% silver showed an efficient sensor response of 72.02% towards carbon dioxide at a comparably low operating temperature of 300°C. The synthesized samples were characterized extensively by XRD and UV-DRS. Morphological evaluations carried out using transmission electron microscope not only provided information on the size and shape of the materials but also revealed that the hierarchical assembly remained intact for CuO-SnO₂ nanocomposite. Furthermore, carbon dioxide gas sensing properties (sensitivity, sensor response, and recovery time) of the as-synthesized nanocomposites were investigated to demonstrate the ability of p-n heterojunction. Owing to the porous structure and large surface area, the nanocomposite exhibited superior sensitivity with short response/recovery times at concentrations of 10,000 ppm of CO₂ gas balanced in air. Finally, it was concluded that embellishing 0.5wt.% silver on the surface activated these nanocomposites. This surface activation reduced the operating temperature and also promoted excellent sensitivity, selectivity, recovery time towards carbon dioxide. A detailed insight into sensing mechanism based on UV-DRS spectroscopy studies was presented.