Synergizing Pd₁Sb₂ Site with Neighboring Near-Surface Pd Site to Break the Trade-Off between Selectivity and Activity of Alkyne Semihydrogenation

Catalytic hydrogenation of trace alkynes in excess alkenes is essential for producing polymer-grade olefins from steam cracking and alkane dehydrogenation, but achieving high selectivity without sacrificing activity remains a significant challenge. Herein, we report a catalyst design that synergistically integrates computationally proposed surface Pd1Sb2 trimer sites with near-surface Pd sites (Pdns) on the P63/mmc PdSb intermetallic catalyst to achieve the semihydrogenation of alkynes with both high activity and selectivity. Alkynes can be readily activated through strong σ-bonding on the Pd1Sb2 trimer sites, whereas alkenes are only weakly adsorbed via π-interactions due to their matched electronic structures and spatial configurations. Moreover, the neighboring Pdns cooperates with the Pd1Sb2 sites to achieve spontaneous dissociation of H2 for subsequent hydrogenation. Consequently, the fabricated PdSb intermetallic catalyst exhibits ethylene and propylene selectivities of 96.50% and 98.65%, respectively, at nearly complete conversions of acetylene and propyne, under industrially relevant conditions, outperforming state-of-the-art catalysts. This study demonstrates a promising strategy that synergizes near-surface and surface ensemble sites to spatially and energetically match with the target reaction pathway, enabling the overcoming of the trade-off between activity and selectivity in hydrogenation.