An effective strategy to enhancing tolerance to contaminants poisoning of solid oxide fuel cell cathodes

Highlights: • The mechanism of LSCF cathode poisoning was unraveled using in situ/operando SERS. • SERS study of the contaminated LSCF indicates a preferential poisoning on boundary. • Surface coating of conformal film with exsolved particles is applied on LSCF surface. • The coating is active to oxygen reduction but inert to contaminant poisoning. • The coating enhanced the Cr-tolerance of LSCF under accelerated testing conditions. Commercialization of solid oxide fuel cells (SOFCs) is impeded by severe cathode degradation from the poisoning effect of contaminants commonly encountered in air (such as H₂O and CO₂) and from other cell components (e.g., Cr species from chromium-containing interconnector). Here we report our findings in unraveling the mechanism of Cr poisoning of La_.6Sr_.4Co_.2Fe_.8O₃ (LSCF) cathodes using our unique in situ/operando surface enhanced Raman spectroscopy. Further, we present an effective strategy to enhancing the tolerance to contaminants poisoning of LSCF cathode through infiltration of a hybrid catalyst coating, which is composed of a conformal film of perovskite PrNi_.5Mn_.5O₃ (PNM) and exsoluted PrO_x nano-particles. The coating is catalytically active to oxygen reduction reaction but inert to contaminant poisoning. When subjected to an accelerated Cr-poisoning test, the cells with a hybrid catalyst-coated LSCF cathode show excellent peak power density (P_max of 0.71 Wcm⁻²) and significantly enhanced durability (degradation rate of 0.0434% h⁻¹ at 0.7 V), much better than those of cells with a bare LSCF cathode (P_max of ~0.46 Wcm⁻² and degradation rate of 0.4% h⁻¹ at 0.7 V). The results suggest that surface modification of electrodes with a coating of rationally designed catalysts is a cost-effective approach to dramatically reducing electrode degradation caused by contaminations.