Department of Polymer Engineering, University of Akron, Akron, Ohio 44325, USA.
Phys Chem Chem Phys. 2013 Apr 21;15(15):5488-92. doi: 10.1039/c3cp00135k.
Surfactant-stabilized metal nanoparticles have shown promise as catalysts although specific surface features and their influence on catalytic performance have not been well understood. We quantify the thermodynamic stability, the facet composition of the surface, and distinct atom types that affect rates of atom leaching for a series of twenty near-spherical Pd nanoparticles of 1.8 to 3.1 nm size using computational models. Cohesive energies indicate higher stability of certain particles that feature an approximate 60/20/20 ratio of {111}, {100}, and {110} facets while less stable particles exhibit widely variable facet composition. Unique patterns of atom types on the surface cause apparent differences in binding energies and changes in reactivity. Estimates of the relative rate of atom leaching as a function of particle size were obtained by the summation of Boltzmann-weighted binding energies over all surface atoms. Computed leaching rates are in good qualitative correlation with the measured catalytic activity of peptide-stabilized Pd nanoparticles of the same shape and size in Stille coupling reactions. The agreement supports rate-controlling contributions by atom leaching in the presence of reactive substrates. The computational approach provides a pathway to estimate the catalytic activity of metal nanostructures of engineered shape and size, and possible further refinements are described.
表面活性剂稳定的金属纳米粒子作为催化剂表现出了良好的前景，尽管其表面的具体特征及其对催化性能的影响还没有被很好地理解。我们使用计算模型定量地描述了一系列二十个近球形 Pd 纳米粒子的热力学稳定性、表面的晶面组成以及影响原子浸出速率的不同原子类型，这些纳米粒子的尺寸为 1.8 至 3.1nm。内聚能表明，具有约 60/20/20 的{111}、{100}和{110}晶面比例的某些颗粒具有更高的稳定性，而稳定性较低的颗粒表现出广泛变化的晶面组成。表面上独特的原子类型模式导致结合能和反应性的明显差异。通过对所有表面原子的玻尔兹曼加权结合能进行求和，得到了原子浸出率作为粒子尺寸函数的相对速率的估计。计算出的浸出速率与相同形状和尺寸的肽稳定 Pd 纳米粒子在 Stille 偶联反应中的催化活性的测量结果具有良好的定性相关性。这种一致性支持了在有反应性底物存在的情况下，原子浸出对速率的控制作用。该计算方法为估计具有工程形状和尺寸的金属纳米结构的催化活性提供了一条途径，并描述了可能的进一步改进。
