Doped ceria interlayer is ubiquitously used between the cathode and electrolyte in solid oxide fuel cells to prevent the cathode/electrolyte interaction and offer a better thermal expansion match. The mechanism on how the interlayer influences the durability and activity of the cathode still remains elusive. This is particularly true in the nickelate cathode (e.g. Pr2NiO4) since the nickelate does go through a phase transition during operation. Traditional Gd-doped ceria was found to substantially accelerate the phase transition in Pr2NiO4 cathode, leading to faster cell degradation in performance. In this work, several new designs of the interlayer are adopted, including various approaches to add Pr into ceria. The addition of Pr in the ceria layer can suppress the phase decomposition of nickelate cathode and increase the performance. As a result, the cell performance exhibits zero degradation over 500 hours. Electrochemical impedance spectroscopy data and its distribution of relation times were obtained to understand the mechanism for this unique observation.

Key words: Doped ceria, interlayer, zero degradation, nickelate