Improvement of NO2 sensing characteristic for mixed potential type gas sensor based on YSZ and Rh/Co3V2O8 sensing electrode

The NO2 sensing performance of a stabilized zirconia (YSZ)-based mixed potential type gas sensor utilizing a Co3V2O8 sensing electrode (SE) was improved by the addition of a noble metal. Among the different types of noble metal (Au, Pt, Pd and Rh), the sensor attached with Co3V2O8-SE loaded with Rh exhibited a noticeable improvement in NO2 response and the maximum response value was obtained when the loading mass fraction of Rh was 3 wt%. Results showed that the response for the sensor utilizing 3 wt% Rh/Co3V2O8-SE was 113.5 mV to 50 ppm NO2 and the sensitivity to 10-300 ppm NO2 was 85 mV per decade at the operating temperature of 650 degrees C, which were enhanced by 77.5 mV and 39 mV per decade compared to those of a sensor attached with Co3V2O8-SE, respectively. It is noteworthy that the response for each of sensor displayed a good linear relationship to the logarithm of NO2 concentration in the ranges of 10-300 ppm at 650 degrees C. Additionally, the sensor attached with 3 wt% Rh/Co3V2O8-SE also exhibited a low detection limit of 500 ppb and good selectivity to NO2 at 650 degrees C. The improvement of sensing characteristics for a sensor using 3 wt% Rh/Co3V2O8-SE may be attributed to enhanced electrochemical catalytic reaction activity to NO2 and a mixed potential mechanism was further verified by polarization curve.