Unraveling the Surface Hydroxyl Network on In2O3 Nanoparticles with High-Field Ultrafast Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy
Unraveling the Surface Hydroxyl Network on In2O3 Nanoparticles with High-Field Ultrafast Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy
复制标题
利用高场超快魔角旋转核磁共振波谱揭示 In2O3 纳米粒子的表面羟基网络
DOI：
10.1021/acs.analchem.1c02759
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发表时间：
2021
影响因子：
7.4
通讯作者：
Hou Guangjin
中科院分区：
文献类型：
--
作者：
Han Qiao;Gao Pan;Liang Lixin;Chen Kuizhi;Dong Aiyi;Liu Zhengmao;Han Xiuwen;Fu Qiang;Hou Guangjin
羟基是金属氧化物的主要活性表面位点之一。然而，由于分辨率有限，它们的光谱表征一直具有挑战性，特别是在存在强羟基网络的富含羟基的表面上。在这里，以纳米结构 In2O3 为例，由于在高磁场 (18.8 T) 和高达 60 kHz 的快速魔角旋转 (MAS) 下进行的高分辨率 1 H NMR 光谱，我们显示出对表面羟基的显着增强的辨别力。总共区分了九种羟基，并借助 17 O NMR 进一步确定了它们的归属（μ1、μ2 和μ3）。通过二维 (2D)1H-1H 同核相关实验进一步探索了这些羟基的空间分布，在原子水平上揭示了复杂的表面羟基网络。此外，以如此高分辨率对这些羟基进行定量分析可以进一步研究这些羟基的物理化学性质和催化性能表征（在二氧化碳还原中）。这项工作提供了对 In2O3 纳米粒子的表面结构/性质的深刻理解，重要的是，可能会促进高场超快 MAS NMR 技术在其他金属氧化物材料上富含羟基表面的研究中的普遍应用。
Hydroxyl groups are among the major active surface sites over metal oxides. However, their spectroscopic characterizations have been challenging due to limited resolutions, especially on hydroxyl-rich surfaces where strong hydroxyl networks are present. Here, using nanostructured In2O3as an example, we show significantly enhanced discrimination of the surface hydroxyl groups, owing to the high-resolution1H NMR spectra performed at a high magnetic field (18.8 T) and a fast magic angle spinning (MAS) of up to 60 kHz. A total of nine kinds of hydroxyl groups were distinguished and their assignments (μ1, μ2, and μ3) were further identified with the assistance of17O NMR. The spatial distribution of these hydroxyl groups was further explored via two-dimensional (2D)1H-1H homonuclear correlation experiments with which the complex surface hydroxyl network was unraveled at the atomic level. Moreover, the quantitative analysis of these hydroxyl groups with such high resolution enables further investigations into the physicochemical property and catalytic performance characterizations (in CO2reduction) of these hydroxyl groups. This work provides insightful understanding on the surface structure/property of the In2O3nanoparticles and, importantly, may prompt general applications of high-field ultrafast MAS NMR techniques in the study of hydroxyl-rich surfaces on other metal oxide materials.