Interstitial-Carbon-Triggered p-d-p Orbital Hybridization in Pd ₃ BiC _x Metallene for Electrocatalytic Alkynol Semi-Hydrogenation

Electrocatalytic alkynol semihydrogenation (EASH) represents a promising alternative to conventional alkenol production. However, it is plagued by severe overhydrogenation and a competitive hydrogen evolution reaction (HER). In this work, we synthesize a Pd 3 BiC x intermetallic carbide metallene (Pd 3 BiC x ene) as a high-performance electrocatalyst for the selective semihydrogenation of 2-methyl-3-butyn-2-ol (MBY). At −0.3 V vs RHE, the catalyst system achieves 94.1% conversion, 95.3% selectivity, and 90.4% Faradaic efficiency while maintaining long-term stability over 70 h. Mechanistic studies demonstrate that carbon doping induces synergistic p-d-p orbital hybridization among Pd, Bi, and C. This electronic structure modulation optimizes the adsorption energy of MBY while facilitating the desorption of 2-methyl-3-buten-2-ol (MBE). Furthermore, carbon doping kinetically hinders overhydrogenation by eliminating subsurface hydrogen species and increasing the energy barrier for the overhydrogenation step. Concurrently, this p-d-p hybridization stabilizes surface adsorbed hydrogen (H* ads ), thereby promoting the hydrogenation pathway and suppressing the HER. This work establishes an effective catalyst design strategy for fabricating p-d-p orbital-hybridized intermetallic catalysts, offering an innovative approach for high-efficiency EASH.