Electrochemical fluorination of graphite in 47% HF aqueous solution

Electrochemical fluorination of graphite sheet in 47% HF aqueous solution using galvanostatic and potential sweep methods were performed and the structure of the products were investigated in detail. When graphite sheet was oxidized by potential sweep method up to 2.4 V vs. Cu/CuF2 couple, three current peaks were observed in voltammogram and single phase of stage 1 type CxF was obtained after 10 cycles of potential sweep. Furthermore, galvanostatic fluorination under various current densities, 3–100 mA/cm2 yielded a semi-covalent stage 2 CxF with Ic = 0.89–0.9 nm and pure stage 1 bi-intercalation phase of CxF with Ic = 1.14–1.18 nm. The saturated compositions calculated from the weight change of the samples were C4.1F for the semi-covalent stage 2 CxF and C2.8F for stage 1 bi-intercalation phase. For the semi-covalent stage 2 CxF, a structure model was proposed and based on this model, the calculated X-ray diffraction intensity showed good agreement with the observed one. Stage 1 bi-intercalation phase was formed as the result of the intercalation of fluoride ion into the vacant carbon layer in the semi-covalent stage 2 CxF.