Stabilized zirconia-based planar sensor using coupled oxide(+Au) electrodes for highly selective CO detection

A mixed-potential-type yttria-stabilized zirconia (YSZ)-based planar sensor utilizing coupled oxide(+Au) electrodes was developed with aspirations of highly selective and sensitive carbon monoxide (CO) detection. The combination of a Nb2O5(+Au)-sensing electrode (SE) and a NiO(+Au)-SE′ in one sensor at an operational temperature of 450 °C was found to be capable of cancelling out high responses to NOx and unsaturated hydrocarbons (HCs), while maintaining CO sensitivity. The present combined-type sensor demonstrated a linear relationship of CO sensitivity on a logarithmic scale of CO concentration over the range of 10–400 ppm, providing a rather high response, even down to 10 ppm CO. The polarization curves obtained for the combined-type sensor indicated that the sensing mechanism involved a mixed potential at both of the composite electrodes; Nb2O5(+Au)-SE and NiO(+Au)-SE′. In addition, the CO sensitivity of the combined-type sensor was invariant to changes in water vapor concentration in the range of 2–11 vol.%.