Electrocatalytic Semi‐Hydrogenation of Alkynes to Alkenes Over Pd ₂ B Using Water as the Hydrogen Source

Highly selective electrocatalytic semi‐hydrogenation of alkynes to alkenes using water as the hydrogen source over Pd‐based electrocatalysts is of great significance but remains challenging because Pd‐based catalysts tend to promote overhydrogenation. In this study, we demonstrate the incorporation of boron into the Pd lattice to form an ordered Pd 2 B intermetallic phase. The interstitial B atoms regulate the electronic structure of Pd, strengthening alkyne adsorption while weakening alkene binding and suppressing subsurface hydrogen formation, thereby enhancing selectivity toward alkyne semi‐hydrogenation. As a result, the Pd 2 B catalyst achieves highly efficient (97%) conversion of 4‐ethynylaniline (4‐EA) to 4‐vinylaniline (4‐VA) with over 93% alkene selectivity and excellent cycling stability. In situ Raman characterization further reveals that Pd 2 B exhibits stronger adsorption and activation of the alkyne triple (C≡C) bond than pure Pd, facilitating directional alkyne‐to‐alkene conversion and efficient utilization of water‐derived hydrogen species. This work presents an ultrafast strategy for the synthesis of noble‐metal based intermetallic compounds via Joule heating and demonstrates their potential in selective electrocatalytic alkyne semi‐hydrogenation.