Kinetics-assisted identification and regulation of active sites for Pd-catalyzed propyne selective hydrogenation

Identification and regulation of active sites are significant for guiding the design and optimization of hydrogenation catalysts toward the target product but remain a great challenge. Herein, we demonstrate a kinetics-assisted identification method combined with theoretical calculations for identifying and further regulating the dominant active sites of Pd catalysts for propyne hydrogenation. Kinetics analysis and model calculations based on the cuboctahedron shape of Pd nanoparticles in the catalysts indicate the Pd(111) sites as the dominant active sites for the propyne conversion and propylene formation while the Pd(100) sites as those for the propane formation, which are further rationalized by theoretical calculations. Moreover, the Pd catalyst with electron-rich properties exhibits relatively higher activity and selectivity, guided by which the SiO2 support with abundant electron-donating hydroxyl groups is employed to increase the Pd electron density. Such electronic regulation for the Pd catalyst clearly enhances the selective hydrogenation of propyne.