Exploring the CO₂ sensing capabilities of MWCNT-SnO₂ composites at moderate temperatures

Multi-walled carbon nanotubes supported tin dioxide (MWCNT−SnO2) composites were successfully prepared using microwave-assisted synthesis and evaluated for their gas sensing properties using carbon dioxide gas (CO2). The morphology, structural and surface analyses of the composites were characterized by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) surface area analysis, respectively. The composites exhibited uniform dispersion of SnO2 nanoparticles on the MWCNTs, with particle size of 3−5 nm. The XRD analysis confirmed the crystalline structure of the composites, while BET surface area analysis demonstrated a high specific surface area of 119.01 m2/g, complimented by enhanced electrical conductivity of 3.23 S/cm, indicating excellent material properties for sensing application. Gas sensing measurements were evaluated at moderate temperature of 50 °C. The composites exhibited measurable and reproducible responses to CO2 with sensitivities ranging from 1.87% to 5.56%, which was evaluated across various concentrations of 20−160 ppm. Notably, the sensitivity showed an inverse concentration dependence, increasing at low CO2 concentrations but decreasing at higher concentrations, a trend likely attributed to diffusion limitations. This study highlights a significant advancement towards energy efficient sensing materials by achieving a detectable CO2 response at a low operating temperature of 50 °C, a condition that is typically challenging for conventional SnO2−based sensors. These findings demonstrate that the prepared MWCNT−SnO2 composites are effective and promising candidates for the developemnt of low-temperature gas sensing materials.