Solids (Apr 2022)

Composites of (C<sub>4</sub>F)<sub><i>n</i></sub> and (CF)<sub><i>n</i></sub> Synthesized by Uncatalyzed Fluorination of Graphite

  • Brennan J. Walder,
  • Noah B. Schorr,
  • Lyle B. Brunke,
  • Michael P. Siegal,
  • Todd M. Alam,
  • Keith J. Fritzsching,
  • Timothy N. Lambert

DOI
https://doi.org/10.3390/solids3020017
Journal volume & issue
Vol. 3, no. 2
pp. 237 – 257

Abstract

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A new solid-state 19F magic-angle spinning NMR signal at an isotropic 19F chemical shift of −53 ppm is measured from graphite fluoride synthesized by reaction of graphite with F2 at temperatures above 750 K with no catalyst. Two-dimensional NMR suggests the −53 ppm 19F NMR signal originates from covalent fluoromethanetriyl groups belonging to ordered (CyF)n bulk domains composited with the major (CF)n domains. Quantitative 19F and 13C NMR find y=4.32±0.64. DFT calculations of NMR chemical shifts for unsaturated fluorographene models show that a (C4F)n phase with fluorine bound covalently to a single side of the carbon layer best explains the observed NMR chemical shifts. We assign the new phase to this (C4F)n structure, which constitutes up to 15% of the carbon in our graphite fluoride composites. The (C4F)n content of the composite affects bulk electrochemical properties in a manner similar to graphite fluorides produced by conventional, catalyzed fluorination processes.

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