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Matei F.,Petroleum Gas University of Ploiesti | Ciuparu D.,Petroleum Gas University of Ploiesti | Jimenez-Borja C.,Avda. Camilo Jose Cela | Dorado F.,Avda. Camilo Jose Cela | And 2 more authors.
Applied Catalysis B: Environmental | Year: 2012

The microstructure and electrochemical promotion of thin Pd catalyst-electrodes deposited on yttria-stabilized zirconia (YSZ) prepared either by sputter-deposition or wet impregnation has been studied for the complete oxidation of methane using XRD, XPS and steady state catalytic measurements in conjunction to electrochemical studies at temperatures 350-460°C under various CH 4 to O 2 ratios. As prepared sputtered catalyst electrodes, which consist mainly of a Pd metal phase are able to electrochemically promote the CH 4 oxidation, while impregnated films, which mainly consist of a PdO phase, can be electropromoted only after in situ reduction. On both types of catalyst-electrodes the reaction exhibits electrophobic behavior under all experimental conditions of this study, i.e. the rate increases moderately with anodic polarization. For sputtered samples, negative current application causes a decrease of the catalytic rate which remains lower than the initial open circuit rate after current interruption. This is a new type of permanent electrochemical promotion and a poisoning index, β, is introduced to quantify the magnitude of this effect. © 2012 Elsevier B.V..

Jimenez-Borja C.,Avda. Camilo Jose Cela | Souentie S.,University of Patras | Gonzalez-Cobos J.,Avda. Camilo Jose Cela | Dorado F.,Avda. Camilo Jose Cela | Valverde J.L.,Avda. Camilo Jose Cela
Journal of Applied Electrochemistry | Year: 2013

Cyclic voltammetry and steady state polarization measurements were performed for the electrochemical characterization of the O2(g), Pd/YSZ system. The effect of oxygen partial pressure was investigated in the temperature range of 350-400 °C and it was found that under polarization phase transformations can take place. Application of negative potential values, lower than a threshold value of -0.6 V, can result in the decomposition of PdO, while the reduced species can be re-oxidized during a linear anodic potential scan. The results suggested that during the first minutes of cathodic polarization, the PdO reduction reaction dominated versus the oxygen reduction reaction, while it becomes more significant as the oxygen concentration in the gas phase increased within the range 0-6 kPa. © Springer Science+Business Media Dordrecht 2013.

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