Investigation of CO2 reaction with copper oxide nanoparticles for room temperature gas sensing

Abstract

The sensing of CO₂ at room temperature enables the prospects towards low power and low cost CO₂ gas sensors and has a high demand in both industrial and domestic applications. In this work we report a detailed work function read out (Kelvin probe) based analysis on copper oxide nanoparticles (CuO-NPs) as a new CO₂ gas sensitive material. The reversible interactions of CO₂ with the thick CuO-NPs layer result in a work function change of about 42 mV for dry air and approximately 97 mV for humid conditions (r.h. = 20%), at a CO₂ concentration step of 400 to 4000 ppm. The CO₂ gas sensing mechanism at room temperature is studied by Fourier transform infrared (FTIR) spectroscopy and explained by thermodynamical calculations. The correlation found between the FTIR spectrum and thermodynamical studies suggest the reversible formation of hydroxocarbonates (malachite, azurite) which is responsible for the gas sensing effect. Moreover, the results concerning long term signal stability over time present suitability towards indoor gas sensing applications. The results indicated in this paper give a new direction to metal oxide based nanoparticles as sufficiently fast and sensitive ambient CO₂ detecting materials.