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

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.