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) 2 FeO 4−δ (LSF 214 )-La 0.8 Sr 0.2 FeO 3−δ (LSF 113 ) electrode has been synthesized to improve the oxygen reduction reaction (ORR). This new materials system was fabricated by the deposition of Sr(NO 3 ) 2 into the LSF 113 framework followed by subsequent heat treatment, resulting in a new three-dimensional (3D) LSF 214 -LSF 113 heterostructured electrode. This material system consists of a with Ruddlesden–Popper (R–P) LSF 214 phase formed on the surface of the LSF 113 framework. The ORR activity has been enhanced by 1 order of magnitude using the LSF 214 -LSF 113 heterostructured electrode. The ORR enhancement was the result of higher catalytic activity of the LSF 214 phase and a mismatch in the lattice parameter between LSF 214 and LSF 113 regions which results in oxygen molecule adsorption and oxygen vacancy formation become more favered. Impedance spectroscopy measurements revealed that the presence of LSF 214 reduced the polarization resistance of the LSF 113 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 LSF 214 -LSF 113 heterostructured electrode. The heterostructured LSF 214 -LSF 113 electrode provides a promising new approach to improve the oxygen reduction reaction activity through multiphase materials systems with tailored microstructures.