CO2 sensing properties and mechanism of ZnMn2O4 nanotubes under air and inert conditions

Abstract

With the increasing usages of fossil fuels, CO₂ is excessively produced and brings serious greenhouse effects. It is important to detect the concentrations of CO₂ in many application fields such as environmental monitoring and health care. Herein, ZnMn₂O₄ nanotubes have been successfully synthesized and used as a sensing material for CO₂ detection. The mean diameter of the ZnMn₂O₄ nanotubes is measured as approximately 100 nm and the wall thickness was measured as 41 nm. By loading the ZnMn₂O₄ nanotubes onto a lab-made micro-hotplate, a MEMS sensor for CO₂ detection was fabricated. The sensing experiments indicate that the ZnMn₂O₄ nanotubes exhibit a good sensing response to CO₂ gas with concentrations in the range of 2.5–100% under both air and N₂ atmospheres. The ZnMn₂O₄ also shows good repeatability and reversible responses to CO₂ gas. According to the XRD, in situ Raman, and XPS characterization results, the ZnMn₂O₄ nanotubes react with CO₂ molecules based on a disproportionation reaction mechanism, since the MnCO₃ and ZnMnO₃ are generated and can be identified during the detection process. Our results indicate that the ZnMn₂O₄ nanotubes show great application potentials for CO₂ sensing in both air and inert atmospheres.