Electrocatalytic Semi-Hydrogenation of Alkynes to Alkenes Over Pd2B 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 Pd2B 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 Pd2B 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 Pd2B 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.