Concavity Tuning of Intermetallic Pd–Pb Nanocubes for Selective Semihydrogenation Catalysis

Although considerable studies on pursuing high-performance Pd-based catalysts for the semihydrogenation of alkynes have been carried out, the creation of catalyst with high activity, selectivity and stability simultaneously toward semihydrogenation reactions remains a significant challenge. Herein, for the first time we report a facile synthetic strategy to realize the intermetallic Pd–Pb nanocubes with different concave degree by selectively utilizing small molecules. These obtained Pd–Pb nanocrystals exhibit high activity in the semihydrogenation of alkynes, where their performances are highly shape- and composition-dependent with Pd–Pb concave nanocubes showing the optimized alkene selectivity of 94.6% and activity of 179.2 h^–1, much higher than those of 10% Pd/C. Detailed X-ray photoelectron spectroscopy results show that the higher ratio of metallic Pd results in the higher activity for semihydrogenation of phenylacetylene and the higher ratio of Pb²⁺ and Pb/Pd contribute to higher styrene selectivity. The density functional theory calculations further reveal that the favorable adsorption energy of phenylacetylene and desirable desorption energy of styrene on the Pd₃Pb surface are critical for the phenylacetylene semihydrogenation with excellent activity and high selectivity. Furthermore, the Pd–Pb concave nanocube can endure at least five cycles with very limited conversion and selectivity decays, representing an efficient Pd-based catalyst for selective hydrogenation and beyond.