Enhancement of La0.6Sr0.4Co0.2Fe0.8O3-δ durability and surface electrocatalytic activity by La0.85Sr0.15MnO3±δ investigated using a new test electrode platform

Abstract

A carefully designed test cell platform with a new electrode structure is utilized to determine the intrinsic surface catalytic properties of an electrode. With this design, the electrocatalytic activity and stability of an La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) cathode is enhanced by a dense thin La_0.85Sr_0.15MnO_3±δ (LSM) coating, suggesting that an efficient electrode architecture has been demonstrated that can make effective use of desirable properties of two different materials: fast ionic and electronic transport in the backbone (LSCF) and facile surface kinetics on the thin-film coating (LSM). Theoretical analyses suggest that the enhanced electrocatalytic activity of LSM-coated LSCF is attributed possibly to surface activation under cathodic polarization due to the promotion of oxygen adsorption and/or dissociation by the surface layer and the dramatically increased oxygen vacancy population in the surface film. Further, the observed time-dependent activation over a few hundreds of hours and durability are likely associated with the formation of a favorable hybrid surface phase intermediate between LSM and LSCF. This efficient electrode architecture was successfully applied to the state-of-the-art LSCF-based cathodes by a simple solution infiltration process, achieving reduced interfacial resistance and improved stability under fuel cell operating conditions.