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V 2 O 5 -WO 3 -TiO 2 mixed metal oxide catalyst was synthesized by impregnation method for fabricating sensing electrodes of potentiometric ammonia sensor in this paper. The sensing electrodes were sintered from 650 °C to 900 °C to obtain different electrode microstructures. Crystalline structures of the sensing materials were analyzed by X-ray powder diffraction, and the sensing electrode microstructures were characterized by environmental scanning electron microscopy. Sintering temperature strongly affects the microstructure and the sensitivity of the sensing electrode. With the increment of sintering temperature, the slope of semi-logarithmic characteristic curves increased but began to fall when temperature was more than 750 °C. The effect of sintering temperature on the response and recovery property has similarities, the sensors sintered at 750 °C and 700 °C show the shortest response/recovery times. The increase of the sintering temperature is beneficial for a stronger bond between sensing electrode and YSZ electrolyte, and this could increase the amount of three-phase boundary, and improve the sensor performance. High temperature promotes the V 2 O 5 volatilization, anatase TiO 2 grains growing up and the anatase to rutile phase transition, further cause the reduction of the electrode specific surface area. The volatilization of V 2 O 5 and the destruction of high dispersion V 2 O 5 resulted from the growing up of the carrier TiO 2 , are responsible for the degraded properties of sensing electrode. The suitable operating temperature for this type NH 3 sensor is 550 °C based on the compromise of various factors which could influence the sensor performance. [ABSTRACT FROM AUTHOR]

• InVO 4 was first applied to the sensing electrode for potentiometric ammonia sensor. • The sensor has considerable sensitivity of -86.7 mV/decade and response value of −143 mV to 320 ppm NH 3 at 600 °C. • The sensor with InVO 4 electrode exhibits good NH 3 sensitivity, selectivity and durability. Orthorhombic InVO 4 powder was synthesized by precipitation method and sintered at 900, 1000 and 1100 °C to prepare the sensing electrodes for potentiometric ammonia sensors. The influence of sintering temperature on electrode morphology and NH 3 sensing properties was investigated at 600 °C operating temperature. With the increase of sintering temperature, the layer thickness decreases and porosity increases for InVO 4 electrode. The resulting reduction of gas-phase consumption of NH 3 and the increment of three-phase boundary (TPB) enhance the NH 3 sensitivity from −79.9 mV/decade of 900 °C to −86.7 mV/decade of 1000 °C. The 1100 °C-sintered sensor has the lowest sensitivity of −25.9 mV/decade due to the TPB reduction caused by over-loosened electrode from more intense sintering. The response and recovery times decrease from 68 s and 151 s for 900 °C-sintered sensor to 19 s and 29 s for 1100 °C-sintered sample. The highest NH 3 response is obtained at 600 °C with the response values of −143 mV to 320 ppm and −13 mV to 10 ppm NH 3. The recovery rate accelerates with increase of operating temperature from 550 to 650 °C, but response rate slows down. The low cross-sensitivity to various gases especially NO x indicates good NH 3 selectivity of the sensor due to the outstanding electrocatalytic activity of InVO 4 for NH 3 oxidation electrode reaction. Considered the good NH 3 sensitivity, selectivity, repeatability, durability and resistance to oxygen/vapor interference, it is believed that InVO 4 is a promising ammonia sensing electrode material. [ABSTRACT FROM AUTHOR]