Ceria-based materials for solid oxide fuel cells

This paper is focused on the comparative analysis of data on electronic and ionic conduction in gadolinia-doped ceria (CGO) ceramics as well as on the electrochemical properties of various oxide electrodes in contact with ceria-based solid electrolytes. Properties of electrode materials, having thermal expansion compatible with that of doped ceria, are briefly reviewed. At temperatures below 1000 K, Ce_0.90Gd_0.10O_2– (CGO10) was found to possess a better stability at reduced oxygen pressures than Ce_0.80Gd_0.20O_2– (CGO20). Incorporation of small amounts of praseodymium oxide into Ce_0.80Gd_0.20O_2– leads to a slight improvement of the stability of CGO20 at intermediate temperatures, but the difference between electrolytic domain boundaries of the Pr-doped material and CGO10 is insignificant. Since interaction of ceria-based ceramis with electrode materials, such as lanthanum-strontium manganites, may result in the formation of low-conductive layers at the electrode/electrolyte interface, optimization of electrode fabrication conditions is needed. A good electrochemical activity in contact with CGO20 electrolyte was pointed out for electrodes of perovskite-type La_0.8Sr_0.2Fe_0.8Co_0.2O_3– and LaFe_0.5Ni_0.5O_3–, and LaCoO_3–/La₂Zr₂O₇ composites; surface modification of the electrode layers with praseodymium oxide results in considerable decrease of cathodic overpotentials. Using highly-dispersed ceria for the activation of SOFC anodes significantly improves the fuel cell performance.