Dual-Anion Entropy Engineering of Se-P High-Entropy Interfaces in HEAs for Optimized H^* Binding and Accelerated...

High-entropy alloys (HEAs) offer unique catalytic advantages due to their multielement composition and severe lattice distortion. However, most HEA-based electrocatalysts rely on a single-anionic component, limiting interfacial electronic tunability and active-site optimization. Herein, we report an entropy-driven dual-anion interface strategy that integrates both selenium (Se) and phosphorus (P) into a multimetallic NiCoFeMnMo (HEA) catalyst supported on Ni foam. A hydrothermal process yields the HEA precursor, followed by solid-state phosphorization to establish a conductive phosphide backbone. Subsequent hydrothermal selenization generates Se-rich surface domains, creating synergistic P-in-bulk and Se-on-surface dual-anion architecture. This configuration preserves the high configurational entropy of the NiCoFeMnMo cationic framework while introducing heterogeneous Se-P coordination environments and interfacial electronic disorder that modulate electron distribution. The resulting HEA-Se-P electrode exhibits markedly enhanced hydrogen evolution reaction (HER) activity in 1.0 M KOH, delivering an overpotential of 17 mV at 10 mA·cm^-2, and outstanding long-term durability. DFT calculations confirm that dual-anion engineering produces an optimized interfacial ensemble with near-thermoneutral hydrogen adsorption, enabling balanced H^* adsorption energetics and enhanced catalytic turnover. This work demonstrates that dual-anion entropy engineering is a powerful and generalizable strategy to design highly efficient HER catalysts for sustainable hydrogen production.