The effect of V2O5-WO3-TiO2 electrode thickness on ammonia sensing properties for potentiometric sensor

Abstract

SCR catalyst V2O5-WO3-TiO2 was synthesized for fabricating sensing electrodes of potentiometric ammonia sensor in this work. As an important sensing electrode structural parameter, the influence of the electrode thickness on sensor properties was investigated. The VWT electrodes with the thickness of 9.8, 15.2 and 24.5μm were made by different screen printing frequency. As the thickness increased, the NH3 sensitivity of the sensor decreased from 71.9 to 17.0 mV/decade, and the response/recovery rates also slowed down rapidly. Considering the EIS results, it is believed that with the increase of electrode thickness, more NH3 molecules are consumed by catalytic reactions in VWT electrode, which reduces the concentration of NH3 involved in the electrode reaction at the three phase boundary. The weakened reaction reduces the NH3 sensitivity and increases the interface resistance of the TPB. The increased VWT thickness retards the diffusion of NH3 molecules, and finally prolongs the response/recovery times.