Electrochemical promotion of methane oxidation on Pd catalyst-electrodes deposited on Y2O3-stabilized-ZrO2

The catalytic activity of Pd/YSZ and Pd-CeO2/YSZ catalysts prepared via organometallic paste calcination or via wet impregnation has been investigated under conditions of excess in oxygen and at temperatures from 250 to 450 degrees C. The catalyst-electrodes were characterized via XRD. SEM, in situ electrical conductivity measurements, electrochemical current-potential curves and catalytic kinetic measurements. The impregnated Pd films were found to be more active with light-off temperatures of 270 degrees C vs. 320 degrees C for metal paste catalysts. Only the impregnated catalyst could be electropromoted at temperatures above 320 degrees C. The Pd-CeO2/YSZ catalyst exhibited high catalytic activity but could not be electropromoted. Co-feeding of ethylene or pre treatment in oxidizing ethylene-oxygen gas mixtures enhances the rate of methane conversion in comparison to non-treated samples and allows electrochemical promotion of the methane oxidation at temperatures as low as 320 degrees C. The reason for this behavior is discussed in view of detailed pre and post surface characterization and in situ electrochemical measurements. (C) 2012 Elsevier B.V. All rights reserved.