Promotive effect of CNT on Co3O4–SnO2 in a semiconductor-type CO sensor working at room temperature

Sensing materials of Co3O4–SnO2 system were prepared from CoOOH and tin(II) 2-ethylhexanoate in air. The prepared samples were characterized using X-ray diffraction (XRD), temperature program reduction (TPR), and thermo-gravimetric/differential thermal analysis (TG/DTA) techniques. The resulting Co3O4–SnO2 material was used as a semiconductor p-type CO sensor. The maximum sensor response to CO in the working temperature range from 25 to 100 °C was found at 25 °C. The mixture with a Co3O4–SnO2 ratio of 1:4 had the highest sensor response among various ratios of Co3O4–SnO2 at the working temperature. Doping 0.1% CNT into Co3O4–SnO2 enhanced the CO response of undoped Co3O4–SnO2. The sensor response varied under CO concentrations ranging from 20 to 1000 ppm. An explanation for the CO sensing characteristics of the sensor was proposed by referring to the adsorption and desorption processes of CO.