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Electrochemical promotion of CO combustion over Pt/YSZ was investigated under high vacuum conditions. A galvanostatic step was coupled to mass spectrometric gas analysis using an electrochemical mass spectrometric monitoring device. Non-Faradaic electrochemical promotion of catalysis took place at 300 degrees C while only electrochemical oxidation was observed at 400 degrees C. Oxygen evolution measurements revealed that electrochemical promotion is related to the thermodynamically stable PtOx species over the Pt/gas interface. The polarization time and O-2 pressure show strong influence on the relaxation transient upon current interruption. We propose that during anodic polarization, PtOx is first formed at the Pt/YSZ interface. With prolonged polarization time, the formed PtOx either migrates over the Pt/gas interface inducing electrochemical promotion or diffuses into the Pt bulk leading to the oxygen storage. After polarization, the stored O species is released and acts as sacrificial promoter causing the persistent electrochemical promotion effect. (C) 2011 Elsevier B.V. All rights reserved.
Jan Van Herle, Davide Ferri, Oliver Kröcher, Hossein Madi, Andre Heel