A novel strategy of entropy engineering at the A-site in spinel oxides for developing high-performance SOFC cathodes

Abstract

Developing high-performance cathode materials for intermediate-temperature solid oxide fuel cells (SOFCs) is crucial to advance SOFC technology. This study explores the application of an entropy engineering strategy to the A-site of ferrite spinel oxides to develop high-performance cathode materials. We synthesized a high-entropy spinel oxide, (Mg_0.2Fe_0.2Co_0.2Ni_0.2Cu_0.2)Fe₂O₄, and compared its performance with its lower-entropy counterparts, CoFe₂O₄ and (Mg_0.333Co_0.333Ni_0.333)Fe₂O₄. Experimental results and density functional theory (DFT) calculations revealed that (Mg_0.2Fe_0.2Co_0.2Ni_0.2Cu_0.2)Fe₂O₄ exhibits superior electrochemical performance owing to its suitable electronic structure, diverse surface metal cations, and abundant surface oxygen vacancies. When applied as the cathode in an anode-supported SOFC, the cell achieves a peak power density of 787.15 mW cm⁻² at 800 °C and demonstrates excellent long-term stability over 100 hours of operation. These findings highlight the potential of A-site entropy engineering as a promising approach to enhance the performance and stability of SOFC spinel oxide cathodes.