Durability and Performance of High Performance Infiltration Cathodes

The performance and durability of solid oxide fuel cell (SOFC) cathodes consisting of a porous Ce_0.9Gd_0.1O_1.95 (CGO) infiltrated with nitrates corresponding to the nominal compositions La_0.6Sr_0.4Co_1.05O_3-δ (LSC), LaCoO_3-δ (LC), and Co₃O₄ are discussed. At 600°C, the polarization resistance, R_p, varied as: LSC (0.062Ωcm²)<LC (0.079Ωcm²)<Co₃O₄ (0.27Ωcm²). High temperature X-ray diffraction revealed a number of different phases in LSC and LC. The electrochemical performance of the LSC-infiltrated CGO cathode was found to depend on the infiltrate firing temperature and is suggested to originate from a complex interplay between the formation, percolation, and surface area of electronically conducting and catalytically active phases. Simplified models that predict the R_p of LSC-infiltrated CGO were applied and showed that the performance is not only characterized by the nanoscale size of the infiltrate but also from a better surface exchange property. A 450h test of an LSC-infiltrated CGO cathode showed an R_p with final degradation rate of only 11mΩcm²kh^-1. An SOFC with an LSC-infiltrated CGO cathode tested for 1,500h at 700°C and 0.5Acm^-2 (60% fuel, 20% air utilization) revealed no measurable degradation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.