Active Hydrogen Reservoir Enabled by p – d Orbital Hybridization in PdSb Metallene for Electrocatalytic Alkynol Semi‑Hydrogenation at Large Current Densities

ABSTRACT Electrocatalytic semi‐hydrogenation reaction (ESHR) represents a promising sustainable production route, making the electrocatalytic synthesis of alkenol from alkynol at near‐industrial current densities particularly significant. However, large current densities readily promote the competing hydrogen evolution reaction (HER), which consequently reduces the overall reaction efficiency. Here, we report a PdSb metallene (PdSb ene) electrocatalyst that overcomes this limitation by functioning as an efficient “active hydrogen reservoir”. The p – d orbital hybridization induced by Sb incorporation modulates the electronic structure of Pd, which facilitates water dissociation, stabilizes H* intermediates, and steers the hydrogenation pathway toward thermodynamic favorability. Operating at a current density of −200 mA cm −2 , the PdSb ene catalyst achieved the semi‐hydrogenation of 2‐methyl‐3‐butyn‐2‐ol (MBY) to 2‐methyl‐3‐buten‐2‐ol (MBE) with a 92% conversion, 96% selectivity, and 88% Faradaic efficiency, while maintaining stable performance for over 400 h. This work demonstrates that constructing an orbital‑hybridization‑driven “active hydrogen reservoir” is a viable strategy for efficient electrosynthesis under demanding conditions.