Pd single atoms guided proton transfer along an interfacial hydrogen bond network for efficient electrochemical hydrogenation.

Electrochemical hydrogenation (ECH) of unsaturated carbon-heteroatom bonds is essential for chemical transformations but is often limited by a barrier-intensive surface hydrogen transfer process. The interfacial hydrogen bond (HB) network offers a promising pathway for proton transfer but requires addressing the challenge of nondirectional proton shuttling in three-dimensional space. Here, we create hydrophilic CuO_x islands on Cu foam (CF) and load electron-enriched Pd (Pd^δ-) single atoms as proton traps (Pd₁-CuO_x/CF) to guide a fast proton transfer along a modified HB network to enhance ECH efficiency. During ECH, hydrophilic CuO_x islands dissociate H₂O into protons and reconstruct the interfacial HB network for facile proton transfer, while the Pd^δ- single atoms reorient H₂O molecules to electrostatically attract and reduce protons to active hydrogen, enabling efficient substrate hydrogenation. With guided proton transfer, Pd₁-CuO_x/CF achieves 99% hydrogenation efficiency for C─Cl bonds, outperforming Pd₁-CF (69%) and CuO_x/CF (57%), and demonstrates high selectivity and Faradaic efficiency in hydrogenating C═O and C≡N bonds to produce valuable chemicals.