Controlling Au–Pd Surface on Au Nanocubes for Selective Catalytic Alkyne Semihydrogenation

The heterogeneous nanocatalyst based on palladium (Pd) is one of the most preferable choices for catalytic hydrogenation reactions as the adsorption and dissociation of hydrogen molecules (H 2 ) are almost spontaneous on Pd surface to form the adsorbed H atoms (H ad ). However, in terms of alkyne semihydrogenation, it remains a grand challenge to optimize both the activity and selectivity of reactions using bare Pd catalysts as the case is largely complicated by the excessive H ad produced from rapid H 2 dissociation and the strong Pd-H binding. In this communication, a well-designed model is developed for seeking a selective semihydrogenation catalyst based on surface lattice engineering. In the proposed model, the ultrathin atomic layer of AuPd shell is grown on the Au nanocubes. The Au nanocubes provide specific facets as substrates for hosting catalytic sites, which can also provide information for further lattice engineering design. While Pd atoms are the active centers for hydrogenation reactions in the nanostructures, alloying Pd atoms with Au in the shells can significantly alter the binding of H ad to metals. As such, the activity and selectivity in catalytic alkyne semihydrogenation can be substantially maneuvered by tailoring the atomic arrangement of Pd and Au on surface. As a proof of concept, the Au@AuPd nanocatalyst with a surface Pd/Au ratio of 1:4 achieves a 98.9% semihydrogenation selectivity with a conversion of 98.2% in the 2-methyl-3-butyn-2-ol (MBY) hydrogenation reaction.