Tuning C-F Bonding of Graphite Fluoride by Applying High Pressure: Experimental and Theoretical Study

C2F graphite fluoride has a unique mutable structure when subjected to external applied pressure. In the present study, we examine C2F using X-ray Raman scattering (XRS) up to 6.5 GPa coupled with theoretical simulations. Using the XRS technique, we follow the in situ high-pressure evolution of the energy loss corresponding to the C and F K-edge. Significant variations occur at 2.9 GPa, remain up to 6.5 GPa, and persist at ambient conditions after decompression. The permanent changes are related to an increased planarity of the graphitic layers and a modulation of the fluorine configuration. The all-electron density of a C2F-sp(3) slab obtained from the DFT simulation and the quantum theory of atoms in molecules reveals the appearance of bond-critical points between in-plane and out-of-plane F-F, suggesting an increasingly ionic character of the structure under biaxial isotropic strain. Pressure can be used as an alternative to chemical synthesis for tuning C-F bonding and metastabilizing new intercalated fluorine compounds with potentially improved electrochemical properties.