F-I2 Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
Phys Chem Chem Phys. 2012 May 14;14(18):6487-95. doi: 10.1039/c2cp23974d. Epub 2012 Mar 28.
We present a quantitative study of the catalytic activity of well-defined faceted gold-palladium nanoalloys which are immobilized on cationic spherical polyelectrolyte brushes. The spherical polyelectrolyte brush particles used as carriers for the nanoalloys consist of a solid polystyrene core onto which cationic polyelectrolyte chains of 2-aminoethyl methacrylate are attached. Au/Pd nanoalloy particles with sizes in the range from 1 to 3 nm have been generated which are homogeneously distributed on the surface of the spherical polyelectrolyte brushes. The reduction of 4-nitrophenol has been chosen as a well-controlled model reaction allowing us to determine the catalytic activity of the nanoalloys as a function of the Au/Pd composition. The adsorption behavior was studied by Langmuir-Hinshelwood kinetics. We find a pronounced maximum of the catalytic activity at 75 molar % Au. A comparison of gold, platinum, palladium and gold-palladium alloy nanoparticles is made in terms of Langmuir-Hinshelwood kinetics. Density functional calculations for Au/Pd clusters with up to 38 atoms show that the density of states at the Fermi level increases with increasing Pd content, and that the highest occupied orbitals are associated with Pd atoms. The calculations confirm that small changes in the atomic arrangement can lead to pronounced changes in the particles' electronic properties, indicating that the known importance of surface effects is further enhanced in nanoalloys.
我们提出了一种定量研究固定在阳离子球形聚电解质刷上的具有明确面心结构的金钯纳米合金的催化活性的方法。用作纳米合金载体的球形聚电解质刷颗粒由固体聚苯乙烯核组成，其上连接有 2-氨基乙基甲基丙烯酸酯的阳离子聚电解质链。已经生成了尺寸在 1 至 3nm 范围内的 Au/Pd 纳米合金颗粒，它们均匀地分布在球形聚电解质刷的表面上。选择 4-硝基苯酚的还原作为一个很好控制的模型反应，使我们能够确定纳米合金的催化活性作为 Au/Pd 组成的函数。通过 Langmuir-Hinshelwood 动力学研究了吸附行为。我们发现 Au 的摩尔含量为 75%时，催化活性有明显的最大值。根据 Langmuir-Hinshelwood 动力学，比较了金、铂、钯和金钯合金纳米颗粒。对于最多 38 个原子的 Au/Pd 团簇的密度泛函计算表明，费米能级处的态密度随 Pd 含量的增加而增加，并且最高占据轨道与 Pd 原子有关。这些计算证实，原子排列的微小变化会导致颗粒电子性质的显著变化，这表明表面效应的已知重要性在纳米合金中进一步增强。
