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

Abstract

C 2 F graphite fluoride has a unique mutable structure when subjected to external applied pressure. In the present study, we examine C 2 F 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 C 2 F-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.

Liquid-phase exfoliation of F-diamane-like nanosheets

“…The calculated values of the binding energies are given in Table 4. From these results we can see that the C atoms are bonded only to other C atoms (C1s-C) as the C-1s values are smaller than the case where they are attached to fluorine (C1s-F), a similar situation previously observed in a study on a C2F-sp 3 slab supercell [53]. The higher energy values of the core level obtained for the "F-diamane" monolayer can be related to the more covalent character of the C-F bonds than in the slab model (which is also supported by the calculated values of the Laplacian at the BCP).…”

Liquid-Phase Exfoliation of Poly(Dicarbon Monofluoride) (C2F)n

“…From these results we can see that the C atoms are bonded only to other C atoms (C1s-C) as the C-1s values are smaller than if they were attached to fluorine (C1s-F), a similar situation as previously observed in a study on a C 2 F-sp 3 slab supercell. [36] The higher energy values of the core level obtained for the "F-diamane" monolayer can be related to the more covalent character of the C-F bonds than in the slab model (which is also supported by the calculated values of the Laplacian at the BCP). Our DFT results are in fair agreement with the experimental values of the core level.…”

Pushing capacities and energy densities beyond theoretical limits of lithium primary batteries using active CFx nanocapsules with x > 1

“…In fact, the energetic F ions brought the interconnections among the overlapped layers to produce disordered sp 3 structures, hence confirming a complete structural change. 36 The FT-IR spectra were obtained to further reveal the chemical structures of CFNCs (Fig. 1h).…”

“…5b), which showed slight differences; therefore, PBE is followed for the rest of the calculations and considered the most reliable one. Typically, F atoms prefer to bond with the edge carbon atoms of the chair-type graphene edge plane (e-) and basal plane (b-); hence, e-C 24 F 36 Specifically, when the Li atom is 10 Å away from the edge and basal planes, the absorbing energy is 2.37 and 3.26 eV for e-C 24 F 36 Li (black line) and b-C 24 F 36 Li (red line) systems, respectively, showing that F atoms bonded to the basal plane take more energy than the edge plane ones for the C 24 F 36 structure. Similarly, for a larger structure (C 32 F 46 ), the binding energy of Li + is 2.73 eV and 4.22 eV for e-C 32 F 46 Li (blue line) and b-C 32 F 46 Li ( pink line) systems, respectively, showing that increasing system size required more energy.…”