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 islands on Cu foam (CF) and load electron-enriched Pd (Pd) single atoms as proton traps (Pd-CuO/CF) to guide a fast proton transfer along a modified HB network to enhance ECH efficiency. During ECH, hydrophilic CuO islands dissociate HO into protons and reconstruct the interfacial HB network for facile proton transfer, while the Pd single atoms reorient HO molecules to electrostatically attract and reduce protons to active hydrogen, enabling efficient substrate hydrogenation. With guided proton transfer, Pd-CuO/CF achieves 99% hydrogenation efficiency for C─Cl bonds, outperforming Pd-CF (69%) and CuO/CF (57%), and demonstrates high selectivity and Faradaic efficiency in hydrogenating C═O and C≡N bonds to produce valuable chemicals.