Mixed-potential type NH3 sensor based on stabilized zirconia and Ni3V2O8 sensing electrode

A mixed-potential type gas sensor using stabilized zirconia (YSZ) and a sensing electrode (SE) that consists of the new type composite oxide Ni3V2O8 was developed for ammonia (NH3) detection at elevated temperature, such as 650 °C. The Ni3V2O8 materials were synthesized from Ni(NO3)2·6H2O and NH4VO3 through the sol–gel method. Ni3V2O8 sintered at different temperatures was also characterized using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The present study mainly focused on the effect of sintering temperature of SE materials (800 °C, 1000 °C, 1200 °C) on NH3 sensing characteristics. Results showed that the Ni3V2O8 calcined at 1000 °C exhibited the largest sensitivity in an NH3 concentration range of 50–500 ppm at 650 °C. The response for the sensor attached with a Ni3V2O8-SE sintered at 1000 °C to 100 ppm of NH3 was approximately −62 mV. Moreover, ΔV almost varied linearly with the logarithm of NH3 concentration in the range of 50–500 ppm, which the slope was −96 mV/decade. Furthermore, the present sensor also displayed small drifts over 30 days and cross-sensitivities in the presence of various interfering gases. The high-sensing characteristics of the sensor attached with a Ni3V2O8-SE sintered at 1000 °C to NH3 are explained in terms of the micro-structure of the SE and the high electrocatalytic activities induced by the beneficial effect of the interaction between the Ni and V two metal oxides.