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

Abstract

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 °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 °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 °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.