Effect of V2O5-content on electrode catalytic layer morphology and mixed potential ammonia sensor performance

SCR catalysts V2O5-WO3-TiO2 (VWT) with various V2O5 content (0-5 wt.%) were prepared by impregnation method in this work. Crystalline structures of the synthesized powder were analyzed by X-ray powder diffraction. Different VWT catalysts were used as sensing materials to prepare mixed potential ammonia sensors based on 5YSZ (ZrO2 doped 5 mol% Y2O3) solid electrolyte. The sensing electrodes were characterized by XRD and environmental scanning electron microscopy. NH3 sensitivity was tested at 550 °C for the sensors with different V2O5 content sensing electrodes. With the increment of V-content, the slope of semi-logarithmic characteristic curves increased but began to fall when V-content was more than 2 wt.%. High-contented V2O5 promoted anatase TiO2 grains growing up to be rod-shaped and block-shaped morphology in sintering, leading to the reduction of specific surface area. The decreased dispersion of V2O5, resulting from the growing up of the carrier TiO2, was responsible for the reduced activity of sensing electrode catalytic. The suitable content of V2O5 in VWT catalysts for NH3 sensors is 1-2 wt.% based on various factors.