Chemical synthesis of graphite perfluorooctanesulfonate using K2MnF6 in hydrofluoric acid or mixed acid solutions

Graphite intercalation compounds (GICs) of nominal composition CxC8F17SO3. yF are prepared under ambient conditions in 48% hydrofluoric acid, using the oxidant K2MnF6. The product compositions are evaluated by mass uptake, TGA, DSC, and elemental analysis. PXRD analysis indicates that the stable product after 3-4 day reaction (x congruent to 18, y congruent to 4) is a GIC comprised of a solid solution of stage 2 and stage 3. A similar product, although containing a greater graphite fluor ide impurity, can be obtained within 1 h using this method at 50 degrees C. Longer reactions at elevated temperature lead to product degradation and other impurities. The addition of up to 83 vol % concentrated HNO3 or 17% fuming H2SO4 produces a stage 2 intercalation compound within hours. One-dimensional structural modeling for the stage 2 GIC provides refined values for the graphene carbon/intercalant mole ratio, distance between graphene and sulfonate oxygen planes, position of additional intercalated fluoride, and the chain takeoff angle, The products obtained by this synthetic method and the observed staging phenomena are related to previous reports on graphite fluorometalates and an energetic model for graphite intercalation.