A Novel Strategy to Synthesize Cathode Heterostructures at the Nanoscale for Solid Oxide Fuel Cells (SOFCs) Using a Molten Salt Solvent

Abstract

In the last three decades, solid oxide fuel cells (SOFCs) have garnered significant interest for viable alternative energy systems owing to their high electrical efficiency and fuel flexibility. In this work, we introduce a novel synthesis of cathodes in SOFCs. Conventional cathode materials, strontium-doped lanthanum manganite (LSM) and strontium-doped cobalt iron oxide (LSCF), both individually lack the optimal characteristics to maximize oxygen reduction rates. Furthermore, the accumulation of chromium on SOFC cathodes is known to significantly hinder the performance of the cells. Incorporating cathodes with core-shell structures in SOFCs could alleviate this problem: effectively combining the functionalities of both materials and providing a nanoscale protection from Cr poisoning with a shell such as Cr-doped LSM (LSCM), which has been shown to have stable polarization resistances compared to LSM. However, synthesizing core-shell composites previously has proved difficult requiring multiple steps, resulting in non-uniform structures. In this work, we propose a two-step molten salt synthesis process to create core-shell heterostructures with precise composition with relative ease. In doing so, we have synthesized LSM and LSCF using a LiCl-KCl eutectic melt and a LaCrO3-LaMnO3 heterostructure at 550 ºC and dwell times as low as 10 minutes. This result provides a strong motivation to further explore LSCM as a shell for core-shell cathodes to ensure protection from chromium poisoning as well as LSCF-LSM for enhanced cathode functionality. In essence, this work demonstrates an inexpensive, sustainable method to synthesize core-shell cathodes that can potentially provide high power densities and lower rates of degradation arising from Cr-poisoning.