Electrochemical promotion of CO combustion over Pt/YSZ under high vacuum conditions

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 °C while only electrochemical oxidation was observed at 400 °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 O2 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.

Oxygen evolution and catalytic rate measurements under high vacuum conditions show that electrochemical promotion is related to PtOx, which is stable at 300 °C but thermodynamically unstable at 400 °C. 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.Figure optionsDownload as PowerPoint slideHighlights
► EPOC of CO oxidation is investigated under high vacuum conditions.
► O2 evolution and catalytic reveal that EPOC is related to stable PtOx.
► Polarization time and O2 pressure strongly influence the oxygen storage.
► O2 is released after polarization and acts as sacrificial promoter.