Recent Progress in LaNi1-xFexO3-δ Perovskite Oxides for SOFC Cathodes and Energy Catalysis: The Role of the Ni/Fe Ratio

LaNi1-xFexO3-δ (LNF) perovskite oxides are promising Sr- and Co-free materials for solid oxide fuel cell (SOFC) cathodes and energy-related catalytic applications. The Ni/Fe ratio strongly influences their electronic structure, defect chemistry, transport properties, reducibility, and structural stability. This review examines how these composition-dependent properties affect LNF synthesis and performance across different applications. For SOFC cathodes, LaNi0.6Fe0.4O3 is an important reference composition because of its favorable balance of conductivity, thermal compatibility, and stability. In oxygen evolution electrocatalysis and other applications, however, the preferred Ni/Fe ratio varies substantially with the required reaction properties and operating conditions. Synthesis, microstructure, surface reconstruction, reduction, and exsolution further affect the functional state of LNF. Therefore, no universally optimal Ni/Fe ratio exists. Composition should instead be selected for the intended application, followed by appropriate synthesis and surface/interface engineering to further improve performance.