On the Impact of the Degree of Fluorination on the ORR Limiting Processes within Iron Based Catalysts: A Model Study on Symmetrical Films of Barium Ferrate
| Autor: | Wollstadt, Stephan, Clemens, Oliver |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Technology
impedance spectroscopy lcsh:QH201-278.5 thin film fluorination lcsh:T lcsh:Technology Article ORR catalysts lcsh:TA1-2040 oxyfluorides barium ferrate lcsh:Descriptive and experimental mechanics lcsh:Electrical engineering. Electronics. Nuclear engineering lcsh:Engineering (General). Civil engineering (General) lcsh:Microscopy ddc:600 lcsh:TK1-9971 lcsh:QC120-168.85 |
| Zdroj: | Materials, Vol 13, Iss 2532, p 2532 (2020) Materials Volume 13 Issue 11 Materials, 13 (11), Art. Nr.: 2532 |
| ISSN: | 1996-1944 |
| DOI: | 10.5445/ir/1000123636 |
| Popis: | In this study, symmetrical films of BaFeO2.67, BaFeO2.33F0.33 and BaFeO2F were synthesized and the oxygen uptake and conduction was investigated by high temperature impedance spectroscopy under an oxygen atmosphere. The data were analyzed on the basis of an impedance model designed for highly porous mixed ionic electronic conducting (MIEC) electrodes. Variable temperature X-ray diffraction experiments were utilized to estimate the stability window of the oxyfluoride compounds, which yielded a degradation temperature for BaFeO2.33F0.33 of 590 ° C and a decomposition temperature for BaFeO2F of 710 ° C. The impedance study revealed a significant change of the catalytic behavior in dependency of the fluorine content. BaFeO2.67 revealed a bulk-diffusion limited process, while BaFeO2.33F0.33 appeared to exhibit a fast bulk diffusion and a utilization region &delta larger than the electrode thickness L (8 &mu m). In contrast, BaFeO2F showed very area specific resistances due to the lack of oxygen vacancies. The activation energy for the uptake and conduction process of oxygen was found to be 0.07/0.29 eV (temperature range-dependent), 0.33 eV and 0.67 eV for BaFeO2.67, BaFeO2.33F0.33 and BaFeO2F, respectively. |
| Databáze: | OpenAIRE |
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