Modulating Coordinate Site Occupancy in High-entropy Spinel Electrocatalysts

High-entropy spinel oxides (HESOs) allow for tunable electronic structures and improved electrocatalytic properties through multi-cation engineering, yet understanding and controlling site-specific cation distributions remains a key challenge. Here, we modulate cationic coordination site occupancy between tetrahedral and octahedral sites in a Co–Fe–Cr–Mn–Ni framework by adding a sixth cation with a different site preference energy (e.g., Zn, Ga, Mg, or Al). Zn preferentially occupies tetrahedral sites, which increases octahedral occupancy of Co. Such site modification is confirmed by density functional theory, synchrotron X-ray absorption spectroscopy, and magnetic circular dichroism. Particularly, Zn-HESO shows the highest occupancy of Co3+ and Co2+ in octahedral sites, leading to more active sites for oxygen evolution reaction, increased electrical conductivity, and greater catalytic activity and stability among different HESOs. Adding a selected cation effectively tunes coordination site occupation in spinels, showing a clear structure-property relationship and providing a clue for the development of next-generation multicomponent catalysts.