通过介观模型研究粒径对多孔碳中扩散离子NMR谱的影响
Investigating particle size effects on NMR spectra of ions diffusing in porous carbons through a mesoscopic model
AI总结：
本研究调整了粒径对多孔碳中扩散离子NMR谱的影响，改进介观模型纳入颗粒与本体电解质的动态交换，揭示磁环境分布、交换速率及孔径分布等因素对NMR谱的作用规律。
摘要：
表征多孔碳中的离子吸附与扩散，对于理解这类材料在储能、电容去离子等一系列关键技术中的性能至关重要。核磁共振（NMR）波谱法是研究这类体系的有力技术，它能够区分本体物种与吸附物种，且对动态现象具有敏感性。然而，由于影响NMR谱的影响因素众多，有时难以对实验结果做出清晰解读。本研究对一种用于预测碳颗粒中扩散离子NMR谱的介观模型进行了调整，纳入了颗粒内部空间与颗粒周围本体电解质之间的动态交换过程。针对多孔碳中不同磁环境分布的情况，系统研究了粒径对NMR谱的影响。该模型表明，要预测符合实际的NMR谱，必须考虑一定范围的磁环境（而非对应吸附物种的单一化学位移值），同时纳入一系列（颗粒内外的）一系列交换速率（而非单一时间尺度）。根据碳颗粒的孔径分布以及本体物种与吸附物种的比例，NMR谱的线宽和峰位都会受到粒径的显著影响。
英文摘要：
Characterizing ion adsorption and diffusion in porous carbons is essential to understand the performance of such materials in a range of key technologies such as energy storage and capacitive deionisation. Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful technique to get insights in these systems thanks to its ability to distinguish between bulk and adsorbed species and to its sensitivity to dynamic phenomena. Nevertheless, a clear interpretation of the experimental results is sometimes rendered difficult by the various factors affecting NMR spectra. A mesoscopic model to predict NMR spectra of ions diffusing in carbon particles is adapted to include dynamic exchange between the intra-particle space and the bulk electrolyte surrounding the particle. A systematic study of the particle size effect on the NMR spectra for different distributions of magnetic environments in the porous carbons is conducted. The model demonstrates the importance of considering a range of magnetic environments, instead of a single chemical shift value corresponding to adsorbed species, and of including a range of exchange rates (between in and out of the particle), instead of a single timescale, to predict realistic NMR spectra. Depending on the pore size distribution of the carbon particle and the ratio between bulk and adsorbed species, both the NMR linewidth and peak positions can be largely influenced by the particle size.
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