Enhanced Oxygen Reduction Activity on Ruddlesden-Popper Phase Decorated La_0.8Sr_0.2FeO_3-δ 3D Heterostructured Cathode...

A new heterostructured (La,Sr)₂FeO_4-δ (LSF₂₁₄)-La_0.8Sr_0.2FeO_3-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 (R_H) and low frequency resistance (R_L) 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.