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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Surface reconstruction of Pt nanocrystals interacting with gas atmosphere. Bridging the pressure gap with in situ diffraction
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Surface reconstruction of Pt nanocrystals interacting with gas atmosphere. Bridging the pressure gap with in situ diffraction

机译：Pt纳米晶体与气体气氛相互作用的表面重建。用原位衍射弥合压力差

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摘要

A carefully designed in situ XRD experiment when guided by atomistic simulations can provide data on the atomistic structure of a surface layer of platinum nanoclusters. Even the adsorption process for a strongly bonded adsorbate can be monitored and interpreted, providing data that are not available from other techniques. The data reported here present the first observation of surface reconstruction of nanocrystals by X-ray diffraction known to the authors. We were able to observe repeatable in situ evolution of Pt nanocrystal diffraction peak positions on exchange of gas atmosphere from hydrogen to helium. Experiments at room temperature and at 373 K shows various hydrogen desorption rate in He atmosphere but a very similar rate of an average lattice constant change with clearly separated desorption and reconstruction phases. The hydrogen desorption rate has been shown to be controlled by a slower process-hydrogen spillover and its activation energy was estimated. Diffraction peaks of Pt on exposition to O2 shift at various degree to lower angles due to surface relaxation-the effect being particle-size-dependent and illustrating elongation of surface Pt-Pt bonds caused by adsorption. The results show the possibility for XRD to become a nanosurface science tool enabling the combination of structure analysis with adsorption/desorption measurements within the pressure gap and material gap.
机译：在原子模拟的指导下，精心设计的原位XRD实验可以提供有关铂纳米团簇表面层的原子结构的数据。甚至可以监控和解释强结合吸附物的吸附过程，从而提供其他技术无法获得的数据。本文报道的数据是作者已知的通过X射线衍射对纳米晶体进行表面重建的第一个观察结果。我们能够观察到从氢气到氦气交换气体气氛时Pt纳米晶体衍射峰位置的可重复原位演化。室温和373 K下的实验表明，He气氛中的氢气解吸速率各不相同，但平均晶格常数的变化速率却非常相似，且解吸和重建阶段明显分开。氢的解吸速率已显示出受较慢的过程氢溢出控制，并估计了其活化能。暴露于O2时，Pt的衍射峰由于表面松弛而以不同程度移至较低角度-该效果取决于颗粒大小，并说明了吸附引起的表面Pt-Pt键的伸长。结果表明，XRD可能成为纳米表面科学工具，使结构分析与压力间隙和材料间隙内的吸附/解吸测量相结合。

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