Energetics of defects on graphene through fluorination

Experimental Realization of Fluoroborophene

Borophene, an anisotropic metallic Dirac material exhibits superlative physical and chemical properties. While the lack of bandgap restricts its electronic chip applications, insufficient charge carrier density and electrochemical/catalytically active sites, restricts its energy storage and catalysis applications. Fluorination of borophene can induce bandgap and yield local electron injection within its crystallographic lattice. Herein, a facile synthesis of fluoroborophene with tunable fluorine content through potassium fluoride-assisted solvothermal-sonochemical combinatorial approach is reported. Fluoroborophene monolayers with lateral dimension 50 nm-5 µm are synthesized having controlled fluorine content (12-35%). Fluoroborophene exhibits inter-twinned crystallographic structure, with fluorination-tunable visible-range bandgap ≈1.5-2.5 eV, and density functional theory calculations also corroborate it. Fluoroborophene is explored for electrocatalytic oxygen evolution reaction in an alkaline medium and bestow a good stability. Tunable bandgap, electrophilicity and molecular anchoring capability of fluoroborophene will open opportunities for novel electronic/optoelectronic/spintronic chips, energy storage devices, and in numerous catalytic applications.

Fluorination of MXene by Elemental F2 as Electrode Material for Lithium-Ion Batteries

The transformation of MXene sheets into TiOF₂ 2D sheets with superior electrochemical performance was developed. MXene synthesized from Ti₃ AlC₂ was fluorinated for 3, 6, and 24 h, respectively, by means of a direct fluorination process. Exposure of MXene powder to elemental fluorine for 3 h induced the formation of CF₂ groups and TiF₃ on the surface, which have beneficial effects on the electrochemical performance. X-ray photoelectron spectroscopy suggested that after fluorinating the MXene sample for 6 h Ti²⁺ and Ti³⁺ were not present on the surface but only Ti⁴⁺ , indicating the formation of TiOF₂ . XRD indicated that TiOF₂ was present after fluorinating for 3 h, and after 24 h the MXene had transformed to TiOF₂ with minor impurities remaining, maintaining its 2D layer morphology. The 24 h fluorinated sample with its TiOF₂ phase showed superior capacity that increased with cycle number. It also had a better rate capability than non-2D-layered TiOF₂ , indicating the advantage of the 2D-layered morphology derived from the parent MXene phase.

Do defects enhance fluorination of graphene?

Graphene reactivity can be modulated by creating intentional defects.

Synergistic Amination of Graphene: Molecular Dynamics and Thermodynamics

Functionalization of graphene using organic moieties constitutes an affordable way to modulate its physical and chemical properties. Finding an exact structural formula of functionalized graphene using experimental approaches is challenging. We studied in detail the thermal stability and thermodynamics of amino- and ethylamino-graphene and found a surprising synergistic effect: more amino groups stabilize functionalized graphene favoring further amination, whereas a small concentration of amino groups is unstable in many cases. The functional groups can be attached either on the same side or simultaneously on different sides of the graphene sheet. Deformation of functionalized graphene is proportional to the number of amino groups. Complete amination leading to formation of the ultimate product, Cx(NH2)x, is hindered sterically. Our study assists in the determination of the structure of chemically modified graphene and makes specific predictions that can be tested and validated experimentally.

Acid induced fluorinated graphene oxide

Brown graphene oxide was interestingly tuned into nearly white fluorinated graphene oxide with rich oxygen groups under hydrothermal treatment with nitric and hydrofluoric acid.