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

Spinel oxide Zn 2 SnO 4 with cubic structure was synthesized by solid state reaction method. A NH 3 sensor based on mixed potential mechanism were fabricated with 8% yttria stabilized zirconia electrolyte with bi-layered and Zn 2 SnO 4 sensing electrode (SE). The influence of Zn 2 SnO 4 -SE thickness and sintering temperature on the response performance of the sensor was evaluated. The results display that the sensor using Zn 2 SnO 4 -SE with a thickness of 17 µm and sintered at 1100 °C displays better performance, which is closely related to the microstructure of the Zn 2 SnO 4 -SE. The response signals are linearly related to the logarithm of the NH 3 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 CO 2 and H 2 is hardly observed; the NH 3 sensitivity decreases with the increasing of O 2 content to some extent; relative humidity and NO or NO 2 cause serious interference. In order to eliminate NO or NO 2 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 NO 2 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.