Synthesis of nanostructured spinel (NiFeCrZnMg)3O4 as potential cathode material for solid oxide fuel cells via a high entropy strategy

High-entropy design has emerged as a groundbreaking material synthesis strategy, enabling the preparation of high-entropy materials that often surpass the performance of traditional individual component materials. Here, a five-component high-entropy spinel cathode material, (NiFeCrZnMg)3O4 (FNCZM), for solid oxide fuel cells (SOFC) is synthesized via a simple solution combustion method. FNCZM shows a typical spinel structure similar to that of two-component NiFe2O4. Microstructural studies demonstrate that the high-entropy design stimulates the development of oxygen vacancies in spinel materials and results in a range of different surface metal valence states. Density functional theory analysis shows that implementing a high-entropy design leads to a significant boost in the oxygen adsorption performance of cathode materials. Compared with NiFe2O4, FNCZM cathode exhibits excellent oxygen reduction activity. Electrochemical impedance spectroscopy (EIS) and relaxation time distribution (DRT) studies suggest that the transfer and interaction of surface species, such as electrons and oxygen atoms, represent the rate-limiting step in the oxygen reduction reaction occurring at the FNCZM cathode. This research illustrates that the high-entropy engineering of spinel oxides is a viable approach to boost the performance of cathodes in SOFC.