Interactions of Oxide Surfaces with Water Revealed with Solid-State NMR Spectroscopy
Interactions of Oxide Surfaces with Water Revealed with Solid-State NMR Spectroscopy
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DOI：
10.1021/jacs.0c03760
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发表时间：
2020-06-24
影响因子：
15
通讯作者：
Peng, Luming
中科院分区：
文献类型：
--
作者：
Chen, Junchao;Hope, Michael A.;Peng, Luming
含水材料在自然环境中是普遍存在的，并且在理论建模和显微镜技术的帮助下，先前已经努力研究含水表面的结构和动力学，以了解其在各种化学和物理应用中的关键作用。然而，一个整体的原子尺度的水-固体界面的理解，包括水对表面离子的影响，仍然缺乏。在此，我们以含有不同水量的二氧化铈纳米棒为例，结合固体核磁共振和密度泛函理论，展示了一种探索水与表面相互作用的新方法。NMR位移和弛豫时间分析提供了氧离子的局部结构和表面上水运动性质的详细信息：分子吸附水的量随着温度的升高（从室温到150摄氏度）迅速减少，而羟基在150摄氏度以下是稳定的，动态水分子被发现与表面氧离子瞬间配位。动态核极化选择性检测表面氧物种的适用性相比，传统的NMR与表面选择性同位素标记：最佳的方法取决于富集的可行性和样品中质子的浓度。这些结果为水合氧化物纳米结构的界面结构提供了新的见解，这对于提高各种应用的性能非常重要。
Hydrous materials are ubiquitous in the natural environment and efforts have previously been made to investigate the structures and dynamics of hydrated surfaces for their key roles in various chemical and physical applications, with the help of theoretical modeling and microscopy techniques. However, an overall atomic-scale understanding of the water-solid interface, including the effect of water on surface ions, is still lacking. Herein, we employ ceria nanorods with different amounts of water as an example and demonstrate a new approach to explore the water-surface interactions by using solid-state NMR in combination with density functional theory. NMR shifts and relaxation time analysis provide detailed information on the local structure of oxygen ions and the nature of water motion on the surface: the amount of molecularly adsorbed water decreases rapidly with increasing temperature (from room temperature to 150 degrees C), whereas hydroxyl groups are stable up to 150 degrees C, and dynamic water molecules are found to instantaneously coordinate to the surface oxygen ions. The applicability of dynamic nuclear polarization for selective detection of surface oxygen species is also compared to conventional NMR with surface selective isotopic-labeling: the optimal method depends on the feasibility of enrichment and the concentration of protons in the sample. These results provide new insight into the interfacial structure of hydrated oxide nanostructures, which is important to improve performance for various applications.