用高场超快魔角自旋核磁共振光谱解开 In2O3 纳米粒子的表面羟基网络,Analytical Chemistry

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用高场超快魔角自旋核磁共振光谱解开 In2O3 纳米粒子的表面羟基网络
Analytical Chemistry ( IF 6.7 ) Pub Date : 2021-12-08 , DOI: 10.1021/acs.analchem.1c02759
Qiao Han _{1,

2} , Pan Gao ₁ , Lixin Liang _{1,

2} , Kuizhi Chen ₁ , Aiyi Dong _{1,

3} , Zhengmao Liu _{1,

2} , Xiuwen Han ₁ , Qiang Fu ₁ , Guangjin Hou ₁

Affiliation

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，尤其是在存在强羟基网络的富含羟基的表面上。在这里，以纳米结构的 In ₂ O ₃为例，由于在高磁场 (18.8 T) 和快速魔角旋转下进行的高分辨率¹ H NMR 光谱，我们显示出对表面羟基的显着增强的辨别力。MAS) 高达 60 kHz。总共九种羟基被区分及其分配（μ ₁，μ ₂，μ ₃）用的协助下进一步确定¹⁷核磁共振。这些羟基的空间分布通过二维 (2D) ¹ H- ¹ H 同核相关实验进一步探索，其中复杂的表面羟基网络在原子水平上被解开。此外，以如此高的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特征（在 CO ₂还原中）。这项工作提供了对 In ₂ O ₃的表面结构/性质的深刻理解纳米粒子，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的富羟基表面研究中的普遍应用。

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Unraveling the Surface Hydroxyl Network on In2O3 Nanoparticles with High-Field Ultrafast Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

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 In₂O₃ as an example, we show significantly enhanced discrimination of the surface hydroxyl groups, owing to the high-resolution ¹H 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 of ¹⁷O 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 CO₂ reduction) of these hydroxyl groups. This work provides insightful understanding on the surface structure/property of the In₂O₃ nanoparticles 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.

更新日期：2021-12-21

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