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Electronic structure of fluorinated multiwalled carbon nanotubes studied using x-ray absorption and photoelectron spectroscopy

机译：使用X射线吸收和光电子能谱研究氟化多壁碳纳米管的电子结构

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This paper presents the results of combined investigation of the chemical bond formation in fluorinated multiwalled carbon nanotubes (MWCNTs) with different fluorine contents (10-55 wt %) and reference compounds (highly oriented pyrolytic graphite crystals and "white" graphite fluoride) using x-ray absorption and photoelectron spectroscopy at C 1s and F 1s thresholds. Measurements were performed at BESSY II (Berlin, Germany) and MAX-laboratory (Lund, Sweden). The analysis of the soft x-ray absorption and photoelectron spectra points to the formation of covalent chemical bonding between fluorine and carbon atoms in the fluorinated nanotubes. It was established that within the probing depth (～15 nm) of carbon nanotubes, the process of fluorination runs uniformly and does not depend on the fluorine concentration. In this case, fluorine atoms interact with MWCNTs through the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton (phase 1) and this bonding is accompanied by a change in the hybridization of the 2s and 2p valence electron states of the carbon atom from the trigonal (sp~2) to tetrahedral (sp~3) hybridization and by a large electron transfer between carbon an fluorine atoms. In the MWCNT near-surface region the second fluorine-carbon phase with weak electron transfer is formed; it is located mainly within two or three upper graphene monolayers, and its contribution becomes much poorer as the probing depth of fluorinated multiwalled carbon nanotubes (F-MWCNTs) increases. The defluorination process of F-MWCNTs on thermal annealing has been investigated. The conclusion has been made that F-MWCNT defluorination without destruction of graphene layers is possible.
机译：本文介绍了使用x联合研究在不同氟含量（10-55 wt％）的氟化多壁碳纳米管（MWCNT）和参考化合物（高取向热解石墨晶体和“白色”氟化石墨）中化学键形成的结果。 C 1s和F 1s阈值处的X射线吸收和光电子能谱。在BESSY II（德国柏林）和MAX-laboratory（瑞典隆德）进行测量。对软X射线吸收和光电子光谱的分析表明，氟化纳米管中的氟和碳原子之间形成了共价化学键。已经确定，在碳纳米管的探测深度（〜15 nm）内，氟化过程均匀地进行，并且与氟的浓度无关。在这种情况下，氟原子通过氟原子与石墨骨架（相1）的石墨烯层的共价键合与MWCNT相互作用，并且该键伴随碳原子2s和2p价电子态的杂化变化从三方（sp〜2）到四面体（sp〜3）杂交并通过碳原子之间的大电子转移得到一个氟原子。在MWCNT近表面区域中，形成了具有弱电子转移的第二氟碳相。它主要位于两个或三个上层石墨烯单层内，并且随着氟化多壁碳纳米管（F-MWCNT）探测深度的增加，其作用变得更差。研究了F-MWCNT在热退火条件下的脱氟过程。已经得出结论，在不破坏石墨烯层的情况下进行F-MWCNT脱氟化是可能的。

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