Localization of High-Entropy Metal Oxide in Iron Oxide Nanoparticles for Efficient Oxygen Evolution Reaction

Abstract

The development of efficient, durable and cost-effective oxygen evolution reaction (OER) electrocatalysts is essential for advancing renewable energy technologies. Herein, we report a novel strategy that spatially confines a nanoscale localized high-entropy oxide (LHEO) consisting of Fe, Co, Ni, Zn and Mn within α-Fe₂O₃, forming a unique α-Fe₂O₃@LHEO nanoarchitecture. The catalyst exhibits outstanding OER performance for alkaline water splitting, achieving a current density of 10 mA cm^-2 at a low overpotential of 229 mV with a small Tafel slope of 34.4 mV dec^-2, significantly outperforming commercial RuO₂ (326 mV, 118.8 mV dec^-1). It also shows excellent long-term stability over 1000 h at 100 mA cm^-2 without notable activity degradation. Applied in rechargeable zinc-air batteries with natural seawater, the α-Fe₂O₃@LHEO cathode delivers a high power density of 88.3 mW cm^-2 and stable operation over 600 cycles, substantially surpassing the benchmark Ru-Pt electrocatalyst (74.7 mW cm^-2, 170 cycles). Combined experimental and theoretical studies reveal that LHEO induces lattice strain in α-Fe₂O₃, modulates its electronic structure and lowers the crystal field splitting energy to stabilize high-spin Fe³⁺. These effects enhance metallic character for efficient charge transfer and optimize the adsorption/desorption of key oxygen reaction intermediates, thus shifting the OER pathway from the conventional adsorbate evolution mechanism (AEM) to the more energetically favorable lattice oxygen mechanism (LOM) with the energy barrier reduced from 1.85 eV to 1.71 eV. Overall, this work proposes a novel localized high-entropy engineering approach that overcomes key bottlenecks in designing efficient and durable OER electrocatalysts based on earth-abundant materials.

Keywords

Localized high-entropy engineering / Earth-abundant oxygen evolution reaction electrocatalysts / Lattice oxygen mechanism / Seawater Splitting / Zinc-air battery

RIGHTS & PERMISSIONS

Higher Education Press 2026

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