Turning bad into good: A medium-entropy double perovskite oxide with beneficial surface reconstruction for active and robust cathode of solid oxide fuel cells.

The cathodes of solid oxide fuel cells (SOFCs) often suffer from detrimental cation segregations and associated impurities poisoning, leading to insufficient electroactivity and poor stability. Here we developed a medium-entropy double perovskite GdBa(Co1.2Mn0.2Fe0.2Ni0.2Cu0.2)O5-δ (ME-GBCO) for promising SOFC cathode. The increased configuration entropy can effectively tailor the surface composition with in situ formed active BaCoO3-δ (BCO) species, rather than inert and deleterious BaOx segregation on parent GdBaCo2O5-δ (GBCO) surface. Accordingly, the layered ME-GBCO cathode with beneficial surface reconstruction exhibited not only high oxygen reduction activity but excellent durability against CO2 impurity, enabling it a very attractive cathode for intermediate temperature SOFCs (IT-SOFCs). Our study provides a new idea for development of efficient and durable cathodes via configurational entropy induced rational surface reconstruction.