Electrochemical processes at interfaces and mixed conductor development
- Pacific Northwest Lab., Richland, WA (United States)
Rates of oxygen reduction at the cathode/electrolyte interface of an electrochemical cell that simulated an operating solid oxide fuel cell were assessed for a variety of cathode materials. Using complex impedance with an unbonded interface cell design and dc polarization methods, the relative contributions of charge transfer, oxygen dissociation and diffusional processes could be distinguished. This experimental approach yielded intrinsic electrocatalytic activities for cathode materials as a function of temperature and oxygen partial pressure, independent of interfacial morphology. Electrocatalytic activities for substituted lanthanum manganites and yttrium manganites varied considerably depending on composition, but all showed intrinsic activities substantially higher than platinum. Ceramics that conduct both ions and electrons (mixed conductors) are technologically important materials, with applications as semipermeable membranes in gas separation, as electrodes in solid oxide fuel cells, and as electrocatalysts. Oxygen transport can occur under open circuit conditions in such materials, driven only by a gradient in the chemical potential of oxygen. An increase in the rate of charge transfer reactions and a reduction in polarization effects are among the advantages of the use of mixed conductors as electrode materials in solid oxide fuel cells. Predominantly ionically-conducting ceria-zirconia compositions were doped with multivalent rare earth oxides to introduce extrinsic electronic conductivity. Electronic conduction was further enhanced by partial reduction.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 140116
- Report Number(s):
- ORNL/FMP-93/1; CONF-9305135-; ON: DE94001091; TRN: 93:003927-0010
- Resource Relation:
- Conference: 7. annual conference on fossil energy materials, Oak Ridge, TN (United States), 11-13 May 1993; Other Information: PBD: Jul 1993; Related Information: Is Part Of Proceedings of the Seventh Annual Conference on Fossil Energy Materials; Fossil Energy AR and TD Materials Program; Cole, N.C.; Judkins, R.R. [comps.]; PB: 402 p.
- Country of Publication:
- United States
- Language:
- English
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