Factors affecting the nucleus-independent chemical shift in NMR studies of microporous carbon electrode materials
Factors affecting the nucleus-independent chemical shift in NMR studies of microporous carbon electrode materials
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DOI：
10.1016/j.ensm.2019.05.010
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发表时间：
2019-09
影响因子：
20.4
通讯作者：
L. Cervini;Olivia Lynes;Geoffrey R Akien;A. Kerridge;N. Barrow;J. Griffin
中科院分区：
文献类型：
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作者：
L. Cervini;Olivia Lynes;Geoffrey R Akien;A. Kerridge;N. Barrow;J. Griffin
NMR光谱学最近已成为研究电容储能装置中使用的微孔碳电极中的电解质物质的有力方法。这种方法的关键是核独立的化学位移（NICS），使吸附的物种，以区分从那些在散装电解质。众所周知，NICS的大小取决于吸附物质与碳表面的距离，因此已在几项研究中用作碳孔径的探针。然而，NICS也可能受到许多其他结构和化学因素的影响，这些因素并不总是被考虑在内。为了研究这一点，我们已经进行了系统的研究的影响因素的NICS的水性电解质物种吸附在聚合物衍生的活性炭在没有施加的电位。我们发现，从碳结构以及电解质的行为和化学性质所产生的一些影响可以有助于观察到的NICS。反过来，这些影响的测量提供了有关离子行为的重要信息，并揭示了在没有施加电位的情况下不同离子的吸附行为的显着差异。根据几个计算研究，我们发现实验证据表明，自发吸附的碱离子的局部浓度随孔径的减小。这对于理解电容性器件中电荷存储的分子水平机制具有潜在的意义。
NMR spectroscopy has recently emerged as a powerful method for studying electrolyte species in microporous carbon electrodes used in capacitive energy storage devices. Key to this approach is the nucleus-independent chemical shift (NICS) which enables adsorbed species to be distinguished from those in the bulk electrolyte. The magnitude of the NICS is well known to be dependent on the distance of the adsorbed species from the carbon surface, and has therefore been used in several studies as a probe of the carbon pore size. However, the NICS can also be influenced by a number of other structural and chemical factors which are not always taken into account. To investigate this, we have carried out a systematic study of the factors influencing the NICS of aqueous electrolyte species adsorbed on polymer-derived activated carbon in the absence of an applied potential. We find that a number of effects arising from both the carbon structure as well as the behaviour and chemical properties of the electrolyte species can contribute to the observed NICS. In turn, the measurement of these effects provides important information about ion behaviour and reveals significant differences in the adsorption behaviour of different ions in the absence of an applied potential. In accordance with several computational studies, we find experimental evidence that the local concentration of spontaneously adsorbed alkali ions decreases with the pore size. This has potential implications for understanding the molecular-level mechanism of charge storage in capacitive devices.