Detection of propylene under oxidizing conditions using zirconia-based potentiometric sensor

A sensor device detecting propylene under oxidizing conditions at high temperatures has been fabricated using a yttria-stabilized zirconia (YSZ) as the solid electrolyte. When the sample gas containing 0-500 ppm propylene and 10 vol.% O-2 was fed to various metal electrodes at 600 degrees C, the Pt, Pd and Ni electrodes had a small or negligible EMF response, but the Au electrode had a large EMF response, which was based on a mixed potential. The mixed potentials of the Au electrode for H-2, CO and CH4 were very small and that for propylene was independent of the presence of water vapor and CO2. However, since this sensor was an oxygen concentration cell, the mixed potential for propylene was affected by changing the O-2 concentration. This problem was appreciably solved using a one-compartment cell attached with the Au and Pt electrodes, where their sensitivities to O-2 were compensated by each other. In addition, the mechanism of the mixed potential for propylene was discussed by measuring the polarization curve of the Au electrode and its catalytic activity. (C) 1998 Elsevier Science S.A. All rights reserved.