An new catalyst monitoring sensor for gasoline engine using YSZ-Al2O3 as solid electrolyte and gas diffusion barrier

A new sensor to monitor the degradation of three-way catalyst was designed by stacking three layers of the same YSZ (Yttria Stabilized Zirconia)-Al2O3 porous composite with two Pt electrodes being inserted in between. Each co mposite layer could serve as an oxide-ionic conductor as well as a gas diff usion barrier. Under an appropriate polarization voltage (0.4 V) applied be tween the Pt electrodes, the central layer attached with the electrodes, Pt \YSZ-Al2O3\ Pt, worked as an oxygen pumping cell, while the upper or lower YSZ-Al2O3 layer worked as a gas diffusion barrier to provide the limiting current with respect to excess O-2 in the fuel-lean atmosphere or that with respect to excess reducing gases like CO, H-2, and CmHn in the fuel-rich c ondition. The amperometric signal was well proportional to the deviation of air/fuel ratio from the stoichiometric one so that a wide range of catalys t degradation could be monitored very well by this sensor. This sensor has advantages of simple operating algorithm, easy fabrication, and high therma l shock resistance. (C) 1999 Elsevier Science S.A. All rights reserved.