NMR Chemical Shifts of 15N-Bearing Graphene

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• 作者：Xianlong Wang ; Zhufeng Hou ; Takashi Ikeda ; Kiyoyuki Terakura
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：June 26, 2014
• 年：2014
• 卷：118
• 期：25
• 页码：13929-13935
• 全文大小：427K
• ISSN：1932-7455

文摘

The <sup>15sup>N NMR chemical shifts of possible nitrogen-containing moieties at edges and defects of graphene are investigated by using the first-principles method. Our computational results show that pyridine-like and graphite-like N can be rather easily identified using the <sup>15sup>N NMR technique, in agreement with experiment. On the other hand, pyridinium-like <sup>15sup>N is hardly distinguished from the pyrrole-like one using the NMR, because these <sup>15sup>N nuclei give nearly overlapping signals. However, our simulations suggest that <sup>1sup>H NMR is useful to discriminate between them; the NMR chemical shifts of <sup>1sup>H directly bonded with pyridinium-like and pyrrole-like N along the armchair edge are estimated to be 0.8 and 10.1 ppm, respectively, while the corresponding chemical shift for pyridinium-like N along the zigzag edge is located between them. The <sup>15sup>N NMR signals for various moieties at edges we considered are found to be similar to the corresponding ones at defects except for pyridine-like nitrogens. Conversely, the <sup>15sup>N NMR chemical shifts are altered sensitively by the degree of aggregation of pyridine-like <sup>15sup>N atoms both along armchair edges and at defect sites. Interestingly, the graphite-like <sup>15sup>N doped along zigzag edges, which was attributed in our previous work to an active configuration for oxygen reduction reaction at the cathode of fuel cells, is identifiable via NMR irrespective of the details of samples such as edge terminations, dopant distributions, and graphene sizes.