Physico-Chemical nanomaterials science

Novel fluoroalkylated and chlorofluorinated nanoporous carbons: synthesis and surface properties
Chernenko S. I.1, Zaderko A. N.1, Diyuk V. E.1, Afonin S.2, Mariychuk R.3, Grishchenko L. M.1, Boldyrieva O. Yu.1, Lisnyak V. V.1
1 Faculty of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska Street, 64/13, Kyiv 01601, Ukraine.
E-mail: sofiiachernenko@ukr.net; lisnyak@chem.univ.kiev.ua
2 Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology, POB 3640, Karlsruhe, 76021, Germany.
3 Presov Universirty in Presov, Ul. 17 novembra, 1, Presov 15 080 01, Slovakia.

This decade has witnessed a significant increase in the buying of energy storage devices, including super-capacitors. The obstacle to the widespread use of recharging devices is their low energetic capacity. It depends mostly on electrode material. The easy way to solve the problem is the use of fluorinated carbons. Such solid carbons show a limited degree of surface oxidation and high hydrophobicity. 
In this work, we conducted chlorination and fluoroalkylation and functionalized the inner surface of nanoscale porous nanocarbons. Here, we reported the reactions of nanoporous ACs, CFs, and MWCNTs heated in the temperature range of 400–800 °С with 1,1,1,2-tetrafluoroethane, pentafluoroethane, and dichloro-difluoromethane diluted in argon. The resulting samples were examined by TGA, ATR, XPS, N2 adsorption, and 19F MAS NMR. Typically, the fluorinated and chlorinated carbons contain 0.11–1.96 mmol g–1 of fluorine and 0.60–2.87 mmol g–1 of chlorine. Treatment at 400 °C and 500 °C caused the formation of a small concentration (up to 0.5 mmol g–1) of fluoroalkyl groups and 0.90–2.41 mmol g–1 of chlorine groups on the surface. The optimal temperature range is ranged from 600 to 700 °C. At this temperature range, the maximum fluorine content of 2–3 mmol g–1 was obtained. 19F NMR spectroscopy shows the presence of CF3, CF2, CH2F, and –CF2–CF2 groups. The 1,1,1,2-tetrafluoroethane is a more effective fluorinating reagent than pentafluoroethane for fluorine chemisorption. Fluorinated and chlorinated carbons can serve as very efficient precursors for producing superacids containing –CF2SO3H groups. Such carbon materials are analogs of the classic Nafion® H super acid material used to produce proton exchange membranes. The prepared carbon materials are effective solid acids for catalysis.