Adjacent-Site Proximity as a Dominant Activity Descriptor in Single-Atom Pt Catalysts for Hydrogen Evolution Reaction

Site-specific underpotential deposition strategy enables precise spatial control over atomic-level active sites, enriching adjacent Pt sites while tuning oxidation states Adjacent-site proximity dominates hydrogen evolution reaction (HER) activity, with adjacent Pt sites deliver a 41-fold higher mass activity than isolated Pt sites. Pt–H–Pt bridge intermediate at adjacent sites lowers the H–H coupling barrier and accelerates HER kinetics.