| Design of precious metal (PM) catalysts featured by both high PM dispersion and definite surface atom arrangement was a challengeable topic for innovating more efficient PM catalysts .Herein, a series of "Pd on Cu" nanostructures (denoted as Pdm^Cu, m was Pd:Cu molar ratio) were prepared by employing PdCl42- to chemically sculpture Cu nanoparticles (ca.5.0 nm), and their catalytic performance were investigated through hydrogenation of nitrobenzene compounds. It was demonstrated by synthetic characterizations (UV-vis, XRD,XPS and HRTEM) and catalytic measurements that the strategy was functional to confine the surface deposited Pd atoms as ordered (200) atom arrangement on Cu nanoparticles at properly controlled Pd:Cu atomic ratio (m?0.3), resulting in the remarkable enhancements in both Pd utilization (mass-specific activity of Pd increased to one order of magnitude) and selectivity (beyond 95% versus 62%) compared to conventional Pd nanocatalysts with Pd(111)surface, which suggested that Pd(200) formed in Pdm^Cu nanostructures was a desired atom arrangement to control the selectivity of Pd catalyst.For selective hydrogenation of p-Chloronitrobenzene to p-Chloroamine, DFT simulations disclosed the by-way dechlorination on Pd(200) would be significantly suppressedby the weaker steric effect compared to Pd(111),providing the insight for the observed Pd(200) arrangement induced selectivity enhancements on our samples. These findings indicated that manipulating of precious metal as the surface with desired atom arrangement was feasible from a controlled chemical sculpturing process on alive transition metal template, the consequent nanostructures mimic Pd^Cu samples could present comprehensive catalytic advantages in both high utilization and outstanding selectivity for important heterogeneous catalysis, which could also be functional for other advanced applications upon cost-saving and surface-defined precious metal materials. |
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