Monodisperse Ni/Pd core/shell nanoparticles （NPs） have been synthesized by sequential reduction of nickel（II） acetate and palladium（II） bromide in oleylamine （OAm） and trioctylphosphine （TOP）. The Ni/Pd NPs ...Monodisperse Ni/Pd core/shell nanoparticles （NPs） have been synthesized by sequential reduction of nickel（II） acetate and palladium（II） bromide in oleylamine （OAm） and trioctylphosphine （TOP）. The Ni/Pd NPs have a narrow size distribution with a mean particle size of 10 nm and a standard deviation of 5% with respect to the particle diameter. Mechanistic studies showed that the presence of TOP was essential to control the reductive decomposition of Ni-TOP and Pd-TOP, and the formation of Ni/Pd core/shell NPs. Using the current synthetic protocol, the composition of the Ni/Pd within the core/shell structure can be readily tuned by simply controlling the initial molar ratio of the Ni and Pd salts. The as-synthesized Ni/Pd core/shell NPs were supported on graphene （G） and used as catalyst in Suzuki-Miyaura cross-coupling reactions. Among three different kinds of Ni/Pd NPs tested, the Ni/Pd （Ni/Pd = 3/2） NPs were found to be the most active catalyst for the Suzuki-Miyaura cross-coupling of arylboronic acids with aryl iodides, bromides and even chlorides in a dimethylformamide/water mixture by using K2CO3 as a base at 110 ℃. The G-Ni/Pd was also stable and reusable, providing 98% conversion after the 5th catalytic run without showing any noticeable Ni/Pd composition change. The G-Ni/Pd structure reported in this paper combines both the efficiency of a homogeneous catalyst and the durability of a heterogeneous catalyst, and is promising catalyst candidate for various Pd-based catalytic applications.展开更多
文摘Monodisperse Ni/Pd core/shell nanoparticles （NPs） have been synthesized by sequential reduction of nickel（II） acetate and palladium（II） bromide in oleylamine （OAm） and trioctylphosphine （TOP）. The Ni/Pd NPs have a narrow size distribution with a mean particle size of 10 nm and a standard deviation of 5% with respect to the particle diameter. Mechanistic studies showed that the presence of TOP was essential to control the reductive decomposition of Ni-TOP and Pd-TOP, and the formation of Ni/Pd core/shell NPs. Using the current synthetic protocol, the composition of the Ni/Pd within the core/shell structure can be readily tuned by simply controlling the initial molar ratio of the Ni and Pd salts. The as-synthesized Ni/Pd core/shell NPs were supported on graphene （G） and used as catalyst in Suzuki-Miyaura cross-coupling reactions. Among three different kinds of Ni/Pd NPs tested, the Ni/Pd （Ni/Pd = 3/2） NPs were found to be the most active catalyst for the Suzuki-Miyaura cross-coupling of arylboronic acids with aryl iodides, bromides and even chlorides in a dimethylformamide/water mixture by using K2CO3 as a base at 110 ℃. The G-Ni/Pd was also stable and reusable, providing 98% conversion after the 5th catalytic run without showing any noticeable Ni/Pd composition change. The G-Ni/Pd structure reported in this paper combines both the efficiency of a homogeneous catalyst and the durability of a heterogeneous catalyst, and is promising catalyst candidate for various Pd-based catalytic applications.
