摘要
[Display omitted]
High-entropy-alloy (HEA) catalysts have attracted considerable interest for a wide range of catalytic applications. However, the development of high-index faceted HEA catalysts remains rare, due to the synthetic challenge of achieving both atomic-level mixing and precise control over surface facets and atomic arrangements. Here, we report a kinetically controlled two-step synthesis of high-index faceted HEA atomic layers, including {210}, {310}, and {320} facets, epitaxially grown on concave nanocubes with a PtIrRuRhAu composition. Synchrotron X-ray absorption spectroscopy (XAS) confirms inter-element bonding, indicating an atomically mixed multimetallic surface. In situ microscopy analysis demonstrates thermal stability of the high-index faceted HEA atomic layers up to 500 °C. Importantly, they also show excellent hydrogen evolution reaction (HER) activity in 0.5 M H2SO4, requiring an overpotential of only 41 mV to reach a current density of −10 mA cm−2 (normalized to the geometric electrode area). Operando XAS analysis reveals electronic modulation under applied potential, with electron gain at Ir sites and loss at Au sites. Density functional theory calculations identify that incorporating weakly hydrogen-binding Au into platinum-group-metal-based HEA surfaces creates sites with near-optimal hydrogen adsorption free energy, effectively tuning adsorption energetics and enabling well-balanced hydrogen binding for enhanced HER activity.