Oxygen exchange reaction on mixed conducting oxides: (Ba,Sr)(Co,Fe)O3-δ and (Bi,Sr)(Co,Fe)O3-δ SOFC cathode materials

A. Wedig, L. Wang, R. Merkle

Perovskites with electronic and ionic conductivity (oxygen vacancies) are used as cathode materials in solid oxide fuel cells. To understand more about the mechanism of the surface reaction (comprising steps such as adsorption, dissociation, incorporation), effective rate constants k are measured (e.g. by microcontact impedance spectroscopy) as function of pO2, T, DC-bias. Their variation with the perovskite's cation composition and related bulk properties (conductivity - see fig 1(a) and (b), defect concentrations and mobilities) gives further evidence about point defects involved in the rate-determining step. In particular the correlation with ionic conductivity (Fig. 1(b)) indicates that oxygen vacancies and their migration are involved in the rate determining step. DFT calculations on intermediates and transition states also help to elucidate the reaction mechanism.

see also Poster  and annual report 2011  www.fkf.mpg.de/88262/IV_03_02.pdf


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Journal of Materials Research 27(15), 2000-2008 (2012) DOI: 10.1557/jmr.2012.186

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Phys. Chem. Chem. Phys. 13 (2011) 16530 DOI: 10.1039/C1CP21684H

A. Wedig, R. Merkle, J. Maier
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J. Electrochem. Soc. (2013) accepted DOI: 10.1149/2.017401jes

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