Direct Observations of Oxygen-induced Platinum Nanoparticle Ripening Studied by In Situ TEM
Direct Observations of Oxygen-induced Platinum Nanoparticle Ripening Studied by In Situ TEM
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DOI：
10.1021/ja910094r
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发表时间：
2010-06-16
影响因子：
15
通讯作者：
Helveg, Stig
中科院分区：
文献类型：
--
作者：
Simonsen, Soren B.;Chorkendorff, Ib;Helveg, Stig
本研究探讨了铂纳米粒子在平面非晶态氧化铝载体上的烧结机理，作为汽车尾气净化催化剂的模型体系。通过原位电子显微镜观察了催化剂在650℃、10mbar空气中的反应过程。时间分辨图像序列明确地揭示了铂纳米颗粒的烧结是由Ostwald熟化过程引起的。对一组铂纳米粒子的统计分析表明，其粒度分布从初始的高斯分布、对数正态分布转变为Lifshitz-Slyosov-Wagner(LSW)分布。此外，还确定了系综平均颗粒尺寸和颗粒密度的时间依赖性。平均场动力学描述捕捉到了观察到的行为的主要趋势。然而，在单个纳米颗粒水平上，观察到了与模型的偏差，这在一定程度上表明局部环境影响原子交换过程。
This study addresses the sintering mechanism of Pt nanoparticles dispersed on a planar, amorphous Al2O3 support as a model system for a catalyst for automotive exhaust abatement. By means of in situ transmission electron microscopy (TEM), the model catalyst was monitored during the exposure to 10 mbar air at 650 degrees C. Time-resolved image series unequivocally reveal that the sintering of Pt nanoparticles was mediated by an Ostwald ripening process. A statistical analysis of an ensemble of Pt nanoparticles shows that the particle size distributions change shape from an initial Gaussian distribution via a log-normal distribution to a Lifshitz-Slyozov-Wagner (LSW) distribution. Furthermore, the time-dependency of the ensemble-averaged particle size and particle density is determined. A mean field kinetic description captures the main trends in the observed behavior. However, at the individual nanoparticle level, deviations from the model are observed suggesting in part that the local environment influences the atom exchange process.