YSZ-based sensor using Cr-Fe-based spinel-oxide electrodes for selective detection of CO

A selective carbon monoxide (CO) sensor was developed by the use of both of CuCrFeO₄ and CoCrFeO₄ as the sensing electrode (SE) for yttria-stabilized zirconia (YSZ)-based potentiometric sensor. The sensing-characteristic examinations of the YSZ-based sensors using each of spinel oxides as the single-SE sensor showed that CuCrFeO₄-SE had the ability to detect CO, hydrocarbons and NO_x gases, while CoCrFeO₄-SE was sensitive to hydrocarbons and NO_x gases. Thus, when both SEs were paired as a combined-SEs sensor, the resulting sensor could generate a selective response to CO at 450 °C under humid conditions. The sensor was also capable of detecting CO in the concentration range of 20-700 ppm. Its sensing mechanism that was examined via polarization-curve measurements was confirmed to be based on mixed-potential model. The CO response generated by the combined-SEs sensor was unaffected by the change of water vapor concentration in the range of 1.3-11.5 vol% H₂O. Additionally, the sensing performance was stable during 13 days tested.