A mixed-potential type NH3 sensors based on spinel Zn2SnO4 sensing electrode

Abstract

Spinel oxide Zn2SnO4 with cubic structure was synthesized by solid state reaction method. A NH3 sensor based on mixed potential mechanism were fabricated with 8% yttria stabilized zirconia electrolyte with bi-layered and Zn2SnO4 sensing electrode (SE). The influence of Zn2SnO4-SE thickness and sintering temperature on the response performance of the sensor was evaluated. The results display that the sensor using Zn2SnO4-SE with a thickness of 17 µm and sintered at 1100 °C displays better performance, which is closely related to the microstructure of the Zn2SnO4-SE. The response signals are linearly related to the logarithm of the NH3 concentrations over the operating temperature range and at 600 °C the sensor shows the highest sensitivity of − 61.8 mV/decade. The cross-sensitivity experiment results show that the cross-sensitivity of the sensor towards CO2 and H2 is hardly observed; the NH3 sensitivity decreases with the increasing of O2 content to some extent; relative humidity and NO or NO2 cause serious interference. In order to eliminate NO or NO2 interference, CuO was chosen to replace Pt as the reference electrode, and the results show that the cross-sensitivity of the sensor to NO or NO2 was significantly reduced, but the sensitivity slightly decreases. The sensor also shows a relatively good long-term stability. The polarization curve and Tafel plots verify that the sensor complies with mixed potential model.