Abstract
20 systematically doped ceria samples: strong dependence of oxygen exchange rate on dopant concentration, even steeper for redox-active dopants (Pr).
Highlights
Ceria (CeO2) based materials nd an extremely wide range of application, e.g., exhaust emission control and soot oxidation in automotive, catalyst for steam reforming, water gas shi and oxidation reactions, solid electrolyte in solid oxide fuel cells (SOFC)
Isolated studies of the oxygen exchange kinetics were performed on Gd, Pr, Tb, and Nb doped ceria by oxygen isotope exchange line pro ling (IELP),[7,8,9,10,11,12,13] isothermal isotope exchange (IIE),[14] isotope exchange gas analysis (IEGA)[15] pulsed isotope exchange (PIE),[16,17] electrochemical impedance spectroscopy
Results obtained at temperatures above 800 C should be interpreted with care, since in this regime the Al2O3 reactor itself showed oxygen exchange activity (Fig. 4, close symbols), mainly by isotopic scrambling at the surface as indicated by the high 34O2 fraction
Summary
Ceria (CeO2) based materials nd an extremely wide range of application, e.g., exhaust emission control and soot oxidation in automotive, catalyst for steam reforming, water gas shi and oxidation reactions, solid electrolyte in solid oxide fuel cells (SOFC) (see, e.g., ref. 1–6). 28 indicate that even for a superoxide adsorbed in an oxygen vacancy still a perceptible dissociation barrier must be overcome Point defects such as oxygen vacancies or redox-active dopants naturally represent catalytically active centers for surface reactions Journal of Materials Chemistry A exchange:[37] the sample is exposed to an isotope enriched oxygen pulse, and the resulting mixture of 32O2, 16O18O, and 36O2 isotopologues quanti ed by mass spectroscopy This technique enables a fast screening of the oxygen incorporation reaction rate as a function of dopant content and oxygen partial pressure in the absence of any precious metals, and yields additional mechanistic information compared to IELP.[37,38,39,40,41]
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