Enhanced Oxygen Reduction Activity on Ruddlesden-Popper Phase Decorated La0.8Sr0.2FeO3-δ 3D Heterostructured Cathode for Solid Oxide Fuel Cells.

A new heterostructured (La,Sr)2FeO4-δ (LSF214)-La0.8Sr0.2FeO3-δ (LSF113) electrode has been synthesized to improve the oxygen reduction reaction (ORR). This new materials system was fabricated by the deposition of Sr(NO3)2 into the LSF113 framework followed by subsequent heat treatment, resulting in a new three-dimensional (3D) LSF214-LSF113 heterostructured electrode. This material system consists of a with Ruddlesden-Popper (R-P) LSF214 phase formed on the surface of the LSF113 framework. The ORR activity has been enhanced by 1 order of magnitude using the LSF214-LSF113 heterostructured electrode. The ORR enhancement was the result of higher catalytic activity of the LSF214 phase and a mismatch in the lattice parameter between LSF214 and LSF113 regions which results in oxygen molecule adsorption and oxygen vacancy formation become more favered. Impedance spectroscopy measurements revealed that the presence of LSF214 reduced the polarization resistance of the LSF113 electrode on a ceria-based electrolyte. The high frequency resistance (RH) and low frequency resistance (RL) decreased substantially due to the enhanced oxygen transport process and accelerated oxygen incorporation rate in the LSF214-LSF113 heterostructured electrode. The heterostructured LSF214-LSF113 electrode provides a promising new approach to improve the oxygen reduction reaction activity through multiphase materials systems with tailored microstructures.