| Summary: | A new solid-state <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>19</mn></msup></semantics></math></inline-formula>F magic-angle spinning NMR signal at an isotropic <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>19</mn></msup></semantics></math></inline-formula>F chemical shift of −53 ppm is measured from graphite fluoride synthesized by reaction of graphite with F<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> at temperatures above 750 K with no catalyst. Two-dimensional NMR suggests the −53 ppm <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>19</mn></msup></semantics></math></inline-formula>F NMR signal originates from covalent fluoromethanetriyl groups belonging to ordered (C<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mi>y</mi></msub></semantics></math></inline-formula>F)<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mi>n</mi></msub></semantics></math></inline-formula> bulk domains composited with the major (CF)<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mi>n</mi></msub></semantics></math></inline-formula> domains. Quantitative <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>19</mn></msup></semantics></math></inline-formula>F and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>13</mn></msup></semantics></math></inline-formula>C NMR find <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>y</mi><mo>=</mo><mn>4.32</mn><mo>±</mo><mn>0.64</mn></mrow></semantics></math></inline-formula>. DFT calculations of NMR chemical shifts for unsaturated fluorographene models show that a (C<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>4</mn></msub></semantics></math></inline-formula>F)<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mi>n</mi></msub></semantics></math></inline-formula> 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 (C<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>4</mn></msub></semantics></math></inline-formula>F)<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mi>n</mi></msub></semantics></math></inline-formula> structure, which constitutes up to 15% of the carbon in our graphite fluoride composites. The (C<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>4</mn></msub></semantics></math></inline-formula>F)<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mi>n</mi></msub></semantics></math></inline-formula> 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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