Tetrahexahedral Pt–Pd alloy nanocatalysts with high-index facets: an atomistic perspective on thermodynamic and shape stabilities
Tetrahexahedral Pt–Pd alloy nanocatalysts with high-index facets: an atomistic perspective on thermodynamic and shape stabilities
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DOI：
10.1039/c3ta14085g
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发表时间：
2014
影响因子：
--
通讯作者：
Y. Wen;Rao Huang;Xiang-Ming Zeng;G. Shao;Shigang Sun
中科院分区：
文献类型：
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作者：
Y. Wen;Rao Huang;Xiang-Ming Zeng;G. Shao;Shigang Sun
具有高折射率晶面的金属纳米粒子由于其表面低配位点的高密度而表现出优异的电催化活性，因此在过去几年中引起了人们的极大兴趣。合金化可以通过高折射率晶面和组分电子结构的协同作用进一步提高其催化活性。采用原子模拟方法，研究了{210}和{310}晶面结合的四面体Pt-Pd合金纳米粒子的热力学和形状稳定性。通过蒙特卡罗模拟的能量最小化表明，最外层由Pd原子占主导地位，而Pt原子优先占据纳米颗粒的次最外层。分子动力学模拟的加热过程表明，{210}面的纳米粒子具有更好的热力学和形状稳定性比{310}面的。利用表面原子的配位数探讨了不同稳定性的可能来源。此外，高Pt比率将有助于增强它们的稳定性。对于这两种多面纳米颗粒，熔化已经从表面均匀地发展到核心，并且在整体熔化之前，四面体最终演变成球形形状。这些结果有助于理解高折射率刻面纳米颗粒的组成和热力学性质，对合金纳米催化剂的开发也具有实际意义。
Metallic nanoparticles with high-index facets exhibit exceptional electrocatalytic activity owing to the high density of low coordination sites at the surface, thus they have attracted intense interest over the past few years. Alloying could further improve their catalytic activity by the synergy effects of high-index facets and electronic structures of components. Using atomistic simulations, we have investigated thermodynamic and shape stabilities of tetrahexahedral Pt–Pd alloy nanoparticles respectively bound by {210} and {310} facets. Energy minimization through Monte Carlo simulations has indicated that the outermost layer is predominated by Pd atoms while Pt atoms preferentially occupy the sub-outermost layer of nanoparticles. Molecular dynamics simulations of the heating process have shown that the {210} faceted nanoparticles possess better thermodynamic and shape stabilities than the {310} faceted ones. The coordination numbers of surface atoms were used to explore the potential origin of the different stabilities. Furthermore, a high Pt ratio will help enhance their stabilities. For both faceted nanoparticles, the melting has homogeneously developed from the surface into the core, and the tetrahexahedra have finally evolved into sphere-like shape prior to the overall melting. These results are helpful for understanding the composition and thermodynamic properties of high-index faceted nanoparticles, and are also of practical importance to the development of alloy nanocatalysts.