摘要
The fabrication of ultrathin alloy shells as heterogeneous catalysts to increase the utilization efficiency and enhance the catalytic activity of metal atoms has been recognized as an effective method for the construction of efficient metal nanocatalysts, particularly noble-metal nanocatalysts. In this study, we demonstrate the successful formation of Pd-M （M = Ni, Ag, Cu） alloy shells with a tunable thickness on preformed nanoscale Pd seeds. The success of this synthesis mainly relies on the combination of the slow reduction of ＂M＂ ions and the subsequent diffusion of M ad-atoms into the surface lattice of Pd seeds. The composition of the Pd-M alloy shell is easily tuned by changing the type and amount of the added precursor, and the shell thickness is manipulated according to the reaction time. More significantl the surface structure of these alloy shells is maintained after the reaction, implying that any desired surface structure of Pd-M alloy shells can be prepared by using the appropriate starting materials. Further catalytic evaluation of the hydrogenation of chloronitrobenzenes shows that these alloy surfaces exhibit significantly improved selectivity compared to the Pd seeds. The Pd-Ni alloy surfaces exhibit much better catalytic selectivity （as high as 〉 99%） than Pd catalysts.
The fabrication of ultrathin alloy shells as heterogeneous catalysts to increase the utilization efficiency and enhance the catalytic activity of metal atoms has been recognized as an effective method for the construction of efficient metal nanocatalysts, particularly noble-metal nanocatalysts. In this study, we demonstrate the successful formation of Pd-M （M = Ni, Ag, Cu） alloy shells with a tunable thickness on preformed nanoscale Pd seeds. The success of this synthesis mainly relies on the combination of the slow reduction of ＂M＂ ions and the subsequent diffusion of M ad-atoms into the surface lattice of Pd seeds. The composition of the Pd-M alloy shell is easily tuned by changing the type and amount of the added precursor, and the shell thickness is manipulated according to the reaction time. More significantl the surface structure of these alloy shells is maintained after the reaction, implying that any desired surface structure of Pd-M alloy shells can be prepared by using the appropriate starting materials. Further catalytic evaluation of the hydrogenation of chloronitrobenzenes shows that these alloy surfaces exhibit significantly improved selectivity compared to the Pd seeds. The Pd-Ni alloy surfaces exhibit much better catalytic selectivity （as high as 〉 99%） than Pd catalysts.
