Active site diversity of near-equiatomic PtCoNiFeCr high-entropy alloy: A site-resolved DFT study of hydrogen adsorption

High-entropy alloys (HEAs) offer a chemically diverse surface landscape in which local coordination, rather than the nominal bulk composition, governs electrocatalytic activity. Here we combine density functional theory (DFT) with a special quasirandom structure (SQS) model to map hydrogen adsorption thermodynamics on a near-equiatomic PtCoNiFeCr HEA. Bulk calculations confirm the intrinsic mechanical robustness of the fcc solid solution, revealing high stiffness (B₀=181GPa) and intrinsic ductility (B/G=2.15) essential for electrode durability. A representative set of threefold hollow sites (38 symmetrically distinct configurations) was investigated to evaluate adsorption behavior. Calculated adsorption free energies ΔGH_* span −1.18 to +1.14 eV, demonstrating a broad distribution of binding strengths across the HEA surface. Among the sampled ensembles, the Co–Cr–Ni^c hollow site exhibits near-thermoneutral binding(ΔGH_*=0.014eV), comparable to Pt(111) (ΔGH_*=−0.09eV). Electronic structure analysis indicates that this favorable behavior is associated with a combination of local electronic contribution and moderate charge transfer to adsorbed hydrogen (Bader Q_H = −0.706 e), rather than a single governing descriptor. Analysis across representative adsorption environments further indicates that no single descriptor fully explains the observed adsorption energetics, highlighting the role of local coordination and subsurface effects . This study focuses on adsorption thermodynamics and does not include kinetic barriers or full electrochemical effects. By linking local coordination motifs to ΔGH_*, ε_d, and Q_H, this work provides a framework to rationalize HEA electrocatalysis, highlighting that ensemble heterogeneity enables the emergence of near-optimal adsorption sites within a broader distribution of local chemical environments.