Nanoscaled ( La0.5Sr0.5 ) CoO3 − δ Thin Film Cathodes for SOFC Application at 500 ° C < T < 700 ° C

Abstract

Nanoscaled and nanoporous (LSC) thin film cathodes (film thickness ranging from 200 to , grain and pore size in the range of ) were electrochemically characterized to determine their potential for intermediate and low-temperature solid oxide fuel cells (SOFCs). Chemically homogeneous, large area , and nanoporous LSC thin films were derived from metallorganic precursors (metallorganic deposition) and deposited on yttria-doped zirconia [(YSZ) “design 1”] and gadolinia-doped ceria [(GCO) “design 2”]. The area-specific polarization resistance of both designs was evaluated on symmetrical cells with special emphasis on constancy, depending on temperature and time by means of electrochemical impedance spectroscopy. For both designs, we report the capability of low polarization resistances, e.g., at , (LSC/YSZ), respectively, (LSC/GCO). Oxygen reduction reaction was facilitated by a substantial inner surface area of the porous thin-film cathode, as suggested by the application of Adler’s model. Nanoporous LSC thin-film cathodes from this study were compared to alternative design concepts for high-performance porous cathodes and with dense thin-film cathodes. Furthermore, the aim of our study was (i) to find a temperature regime with a perspective for chemical durability of an LSC/YSZ interface. We could prove that at a temperature of and for , polarization resistance of the LSC/YSZ interface remains constant, and at unreported low values, which reopens LSC/YSZ for micro-SOFC application; (ii) to estimate the structural durability of nanoscaled and nanoporous LSC thin-film cathodes. We have been able to demonstrate stable and unreported low polarization resistance for LSC/GCO in the temperature range between 500 and , which is of technical interest for auxiliary-power-unit application.