Design Rule for Highly Stable Efficient High-Entropy Metal Oxide Electrocatalysts: Complementary Roles of 3d Transition Metal Ions

The diversification of chemical composition has sparked significant research interest owing to its effectiveness in developing versatile functional high-entropy materials. To develop highly stable, efficient metal oxide electrocatalysts, fundamental principles for the selection of efficient metal components must be established. In this study, the complementary roles of 3d transition metal components in enhancing the performance and stability of metal oxide electrocatalysts are systematically investigated. By examining the effects of single-metal substitution on the electronic configuration and crystal morphology of MnO₂ nanowires, V, Fe, Co, and Ni ions are identified as effective elements for improving electrocatalytic activity. The resulting quinary-metal-based α-MnVFeCoNiO₂ nanowires exhibited superior activity and stability for the oxygen evolution reaction (OER) over the unsubstituted α-MnO₂ and binary/ternary/quaternary-metal-based homologs. In situ Raman and density functional theory calculations demonstrated that multi-metal substitution promoted the adhesion of the reaction intermediate during the OER. The improvements in OER performance can be attributed to the suppression of lattice oxygen occupation, the provision of diverse surface-active sites, the enhancement of charge/mass transport, and the acceleration of electrocatalysis kinetics. Design factors are identified to be crucial for optimizing the electrocatalytic performance of high-entropy MnO₂ nanowires.