Novel Zn–M–O (M = Sn, Co) sensing electrodes for selective mixed potential CO/C3H8 sensors

The sensing performance of the Zn–Sn–O and ZnCo2O4 oxide electrodes to carbon monoxide and propane at 600 °C was investigated. The planar-type mixed-potential sensor coupled with Zn2SnO4 + SnO2 as sensing electrode indicated a linear relationship between the responses of the sensor and the logarithm of CO concentrations within a range from 60 ppm to 1500 ppm. The sensor showed good signal reproducibility at 600 °C while some interference from NO2 and C3H8 were also observed. On the other hand, the sensor using the ZnCo2O4 sensing electrode indicated a higher response to propane and excellent selectivity to NO2 and CO at 600 °C. These two new sensing electrodes demonstrated a significant potential to be employed for the selective mixed-potential CO/C3H8 sensors for online monitoring automobile gas emissions.