Beyond configurational entropy: Investigating the local atomic and electronic structures in Zr-content-modulated compositionally complex FeCoNiMoZr oxides for efficient and stable oxygen evolution

A mechanistic design paradigm beyond the conventional high-entropy effect is established. • Short-range ordering and electronic redistribution synergistically optimize OER kinetics. • Element-specific functional assignment enables efficient and stable oxygen evolution. The development of non-noble metal electrocatalysts with high intrinsic activity and long-term durability for the oxygen evolution reaction (OER) remains a major challenge. Herein, we report a series of FeCoNiMoZr high-entropy oxides (HEOs) synthesized via a sol-gel method, and systematically investigate the synergistic effects of high-valent Zr incorporation and sintering temperature on the structural, electronic, and catalytic properties. Comprehensive characterization reveals that the optimal HEO-Zr 1.5 -T 600 achieves a unique local optimization window where localized nanocrystalline domains coexist with a disordered matrix. It exhibits exceptional OER performance in 1.0 M KOH, with low overpotentials of 219/279 mV at 10/100 mA cm −2 , a small Tafel slope of 48.3 mV dec −1 , and an 18-fold enhancement in turnover frequency compared to its counterparts. Furthermore, it demonstrates remarkable long-term stability (4.7% current decay over 100 h) and a high Faradaic efficiency of 90.7%. Results suggest distinct functional roles for the constituent elements, Zr and Mo primarily regulate macroscopic structural distortions, framework stability, and electronic redistribution, while Fe, Co, and Ni serve as the principal active centers. This work moves beyond the generic high-entropy effect to establish a design paradigm: rational enhancement in HEOs arises from an element-specific, functionally complementary catalytic architecture within a compositionally and thermally defined local optimization window. Download: Download high-res image (166KB) Download: Download full-size image