Bi1.78Ca2Co1.63O6.65 cathode with low thermal expansion coefficient for intermediate temperature-solid oxide fuel cells

Abstract

The misfit compound Bi1.78Ca2Co1.63O6.65 was successfully synthesized and evaluated as a novel cathode material for intermediate temperature solid oxide fuel cells exhibiting good thermal stability, as well as chemical and thermal compatibility with the Ce0.9Gd0.1O2−γ electrolyte. The thermal expansion coefficient was found to be approximately 11.8×10−6K−1 from 100°C to 800°C, which highlighted the main advantage of this material compared to other cobaltite based perovskite cathodes. The maximum power densities of the NiO/Ce0.9Gd0.1O2−γ anode-supported button cells fabricated with a Ce0.9Gd0.1O2−γ electrolyte and Bi1.78Ca2Co1.63O6.65 cathode reached 551.2mW·cm−2 at 704°C with around 10% loss of activity during the 72h test. The thermal compatibility with the electrolyte, along with the encouraging electrochemical performance, allows us to propose Bi1.78Ca2Co1.63O6.65 as a potential novel cathode material for intermediate temperature-solid oxide fuel cells.