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

State Key Laboratory of Materials Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, PR China

^a Corresponding author: jzxiao@mail.hust.edu.cn

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.