Survey of materials selection for ceramic fuel cells II. Cathodes and anodes

• Published in: Solid state ionics 1996, Vol.86, p.1223-1234
• Main Author: Steele, Brian C.H.
• Format: Article
• Language: English
• Subjects: Anodes; Applied sciences; Cathodes; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Oxygen self diffusion; Oxygen surface exchange; Solid oxide fuel cell
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/0167-2738(96)00291-3

By assigning target values (0.15 Ω cm 2) for the performance of the individual components in a single SOFC cell it has been possible to propose a very simple model which relates experimentally accessible parameters, such as, oxygen surface exchange coefficients ( k cm · s −1) and self diffusion coefficients ( D ∗ cm 2 · s −1 ) to the behaviour of porous oxide cathodes. Characteristic lengths including a collection length ( l c ), and a maximum length ( l l ) for bulk diffusion of oxygen ions, have been defined and calculated for La 0.8Sr 0.2O 3 + x , La 0.8Sr 0.2Co 0.2Fe 0.8O 3 − x , Sm 0.6Ca 0.4CoO 3 − x . These characteristic lengths have been used to interpret the reported behaviour of the oxide electrocalalysts and to suggest modifications which could improve their performance. Although a similar model has not yet been developed to interpret the behaviour of anodes, appropriate comments have been made about the selection and optimisation of anodes for intermediate temperature (500–750 °C) SOFC operation.