Molten Salt Synthesis of Core-Shell Heterostructure Cathode Materials for Solid Oxide Fuel Cells

Abstract

Core-shell La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) – La0.8Sr0.2MnO3 (LSM) heterostructure crystalline materials have been synthesized in a simple, one-step feeding method via a KNO3 molten salt solvent. Two-phase perovskite composites can be synthesized in times as short as 10 minutes, and is demonstrated for the first time in a molten salt. A combination of X-ray diffraction and S/TEM energy dispersive X-ray spectroscopy has been utilized to confirm the formation of an LSM shell on LSCF cores in all samples when adjusting dwell time, core size, weight ratio between core and shell precursors, and weight ratio of powder to salt. Specifically, decreasing the LSCF core size increases core-shell yield. Smaller cores introduce a greater density of facets on the crystal surface, and provide more favorable sites for LSM heterogeneous nucleation. Decreasing the weight ratio of shell precursor to core decreases shell thickness, reduces the number of homogeneously nucleated LSM nanoparticles, and increases core-shell yield. Increasing the amount of salt relative to powder decreases supersaturation in the melt and results in less uniform, isolated shell deposition on the cores. Overall, the molten salt synthesis of core-shell perovskite oxides is investigated and demonstrated as an expeditious method to synthesize core-shell composites for energy applications. Considering the parameters of molten salt synthesized LSCF-LSM, optimized core-shell cathodes are then fabricated and used as electrodes in symmetric cells as a preliminary insight into their efficacy for solid oxide fuel cells.