Review of experimental and modelling developments for ceria-based solid oxide fuel cells free from internal short circuits

Ceria-based solid oxide fuel cells (SOFCs) are the promising candidates for the low- and intermediate-temperature SOFCs. However, the Ce 4+ in the ceria-based electrolyte materials is likely reduced to Ce 3+ under low oxygen partial pressure, leading to high electronic conductivity. Therefore, ceria-based SOFCs commonly show low open-circuit voltage and low efficiency due to the leakage current. While extensive studies of the electron transport mechanism and the methods for the prevention of leakage current in ceria-based electrolytes have been conducted, systematic reviews of the relevant literature have been notably rare. In this review, the formation mechanism and factors affecting electronic conductivity in doped ceria are clearly described. Additionally, two kinds of methods including the optimization of the single ceria-doped electrolyte and the use of the various electron blocking layers (e.g., ZrO 2 -based, doped BaCeO 3 /SrCeO 3 and doped Bi 2 O 3 materials) are systematically summarized. Finally, mathematical models describing the electrochemical characteristics of ceria-based SOFCs based on different assumptions are reviewed. This review can provide useful guidance for the further development and application of internal short-circuit-free ceria-based SOFCs.