Gu Sasa, Lu Yan, Kaiser Julian, Albrecht Martin, Ballauff Matthias
EM-ISFM Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
Phys Chem Chem Phys. 2015 Nov 14;17(42):28137-43. doi: 10.1039/c5cp00519a. Epub 2015 Mar 19.
We present a detailed study of the catalytic activity of Au/Pd nanoalloys with Au : Pd molar ratio 75 : 25 synthesized using spherical polyelectrolyte brushes (SPB) as carrier system. The reduction of 4-nitrophenol (Nip) by sodium borohydride (BH4(-)) has been used as a model reaction. This reaction proceeds in two steps: 4-nitrophenol is first reduced to 4-hydroxylaminophenol which in a second step is reduced to the final product 4-aminophenol. Both steps of the reaction proceed on the surface of the nanoparticles (Langmuir-Hinshelwood-mechanism). We use this model to analyze the experimental data obtained by catalysis with the Au/Pd-nanoalloys. Good agreements between theory and experiments were found up to 30% conversion of Nip. The kinetic parameters were compared with the data derived from neat Au and Pd nanoparticles immobilized in the same SPB carrier system. The addition of 25% molar ratio of Pd to the nanoalloys increases the reaction rate of the first step nearly 10 times compared with that of SPB-Au and 60 times compared with that of SPB-Pd. Analysis of the nanoalloy by high-resolution transmission electron microscopy suggests that the surface defects of the nanoalloys play an important role for the enhanced catalytic activity.
我们对以球形聚电解质刷（SPB）为载体系统合成的金钯摩尔比为75:25的金/钯纳米合金的催化活性进行了详细研究。以硼氢化钠（BH4(-)）还原4-硝基苯酚（Nip）作为模型反应。该反应分两步进行：4-硝基苯酚首先被还原为4-羟基氨基苯酚，第二步再被还原为最终产物4-氨基苯酚。反应的两个步骤均在纳米颗粒表面进行（朗缪尔-欣谢尔伍德机理）。我们使用该模型来分析金/钯纳米合金催化获得的实验数据。在Nip转化率达到30%之前，理论与实验结果吻合良好。将动力学参数与固定在相同SPB载体系统中的纯金和钯纳米颗粒得到的数据进行了比较。与SPB-Au相比，向纳米合金中添加25%摩尔比的钯使第一步反应速率提高了近10倍，与SPB-Pd相比提高了60倍。通过高分辨率透射电子显微镜对纳米合金的分析表明，纳米合金的表面缺陷对增强催化活性起着重要作用。
