Development of planar potentiometric gas sensors for automotive exhaust application

International audience; In the past, we have deeply investigated the development of a Bêta-alumina potentiometric sensor with two coplanar metallic electrodes. Recently, many papers have demonstrated an interest for similar non-Nernstian devices based on stabilised zirconia (YSZ) electrolyte. The common particularity of such sensors is related to the use a dissymmetry of electrodes on an electrolyte and to work in a single gas cell. Our main experimental results obtained with Bêta-alumina sensors are reported with the special attention to develop gas sensors for exhaust applications. The sensors are evaluated under CO, HC and NO, CO. The selectivity depends on the sensor temperatures. The performances appear sufticient to satisfy in the future automotive applications like the control of NOxTrap or DeNOx devices. The measure of NH3 concentrations seems also possible. The comparison of performances of sensors replacing bêta-alumina electrolyte by YSZ is also presented. Similar behaviours are obtained for both types of sensors. These comparisons reinforce our proposal of a capacitive model mainly based on the difference of reactivity of the electrodes. It is pointed out that mixed potentials cannot explain the behaviour of our sensors under oxygen. Very good agreements are obtained between this capacitive model and the experimental results, not only versus oxygen, but also with mixture of oxygen and CO.