Highly Exposed Ultra‐Small High‐Entropy Sulfides with d‐p Orbital Hybridization for Efficient Oxygen Evolution

Abstract Precise regulation of electronic structure and nanoscale geometry represents a transformative strategy for breaking the activity‐stability trade‐off in oxygen evolution electrocatalysts. Here, highly exposed ultra‐small high‐entropy sulfides (HES, 5.2 nm) confined in porous carbon nanofibers are designed. This structure involves a dual‐engineering synergistic effect combining d‐p orbital hybridization and nanoconfinement. X‐ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations reveal hybridization between transition metal 3d orbitals and sulfur 3p orbitals. This orbital interaction induces a d‐band center shift toward the Fermi level and facilitates interfacial charge redistribution, endowing HES with superior electron‐donating capability to accelerate proton‐coupled electron transfer kinetics. Such electronic modulation significantly optimizes the adsorption of oxygen evolution reaction (OER) intermediates ( * OH, * O, * OOH). Experimentally, the HES demonstrates exceptional OER performance, exhibiting a low overpotential of 200 mV at 10 mA cm −2 and remarkable durability with negligible current decay during 300 h operation across current densities ranging from 10 to 100 mA cm −2 . This work establishes a dual optimization strategy leveraging orbital hybridization engineering and size engineering for advanced electrocatalyst design, providing a new design approach in energy conversion technologies.