Jia Haili, Wang Canhui, Wang Chao, Clancy Paulette
Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218, United States of America.
Nanotechnology. 2021 Jun 7;32(35). doi: 10.1088/1361-6528/ac027d.
Electron energy loss spectroscopy (EELS) has recently been applied to probe chemisorbed molecules on metal nanostructures, but a fundamental understanding of the correlation between these spectra and the electronic structures of the adsorbates has been limited. We report here on the insights afforded by time-dependent density functional theory to decipher the energy loss near edge structure (ELNES) of EELS spectra associated with chemisorption. These first-principles calculations simulate the ELNES-EELS spectra for chemisorbed CO on various facets of Au and Pt. Computational predictions of key signatures such as the 'red shift' and reductions in the peak intensity of the 2* and 6* peaks, as compared to free CO in the gas phase, are validated in comparison to experimentally collected EELS spectra. These signatures are revealed to arise from changes in the electronic structure in terms of unoccupied density of states associated with the chemisorption process. They are consistent with a Blyholder model that incorporates donation and back-donation of electrons. They are also characteristic of the chemisorption process, such as the choice of metal, site of adsorption and the coverage and distribution of adsorbates. Our simulations thus provide guidelines for the use of ELNES-EELS to characterize the atomic structure and adsorption property of nanostructured surfaces and facilitate the development of advanced nanomaterials for catalytic applications.
电子能量损失谱（EELS）最近已被用于探测金属纳米结构上的化学吸附分子，但对这些光谱与被吸附物电子结构之间的相关性的基本理解一直有限。我们在此报告了含时密度泛函理论所提供的见解，以解读与化学吸附相关的EELS光谱的能量损失近边结构（ELNES）。这些第一性原理计算模拟了化学吸附在金和铂的各个晶面上的一氧化碳的ELNES-EELS光谱。与气相中的自由一氧化碳相比，对诸如“红移”以及2和6峰的峰强度降低等关键特征的计算预测，通过与实验收集的EELS光谱进行比较得到了验证。这些特征被揭示是由于与化学吸附过程相关的未占据态密度方面的电子结构变化而产生的。它们与包含电子给予和反馈给予的布莱霍尔德模型一致。它们也是化学吸附过程的特征，例如金属的选择、吸附位点以及被吸附物的覆盖度和分布。因此，我们的模拟为使用ELNES-EELS来表征纳米结构表面的原子结构和吸附特性提供了指导，并促进了用于催化应用的先进纳米材料的开发。
