Use of cobalt oxide CoOOH in a carbon monoxide sensor operating at low temperatures

Cobalt oxide CoOOH was prepared from a Co(NO3)2 solution via a precipitation with NaOH and oxidation in air. The prepared samples were characterized by X-ray diffraction (XRD), temperature program reduction (TPR), and thermo-gravimetric/differential thermal analysis (TG/DTA) techniques. The resulting CoOOH was used as a sensing material in a semiconductor type CO sensor. The optimum CO detection working temperature was found to be 80 °C (S = 6.7) in this study, while the response time was short (∼1 min). CoOOH has better response than Co3O4 at low temperatures and can detect CO concentration of 1 ppm. CoOOH offers high CO detection selectivity relative to H2 (SCO/SH2∼4SCO/SH2∼4) and good linearity (R2 = 0.9903) for CO concentrations ranging from 1 to 1000 ppm. A probable explanation of the CO sensing characteristics of CoOOH is proposed.