Chemical Tuning of Specific Capacitance in Functionalized Fluorographene

Abstract

Owing to its high surface area and excellent conductivity, graphene is considered an efficient electrode material for supercapacitors. However, its restacking in electrolytes hampers its broader utilization in this field. Covalent graphene functionalization is a promising strategy for providing more efficient electrode materials. The chemistry of fluorographene is particularly attractive as it allows scalable chemical production of useful graphene derivatives. Nevertheless, the influence of chemical composition on the capacitance of graphene derivatives is a largely unexplored field in nanomaterials science, limiting further development of efficient graphene-based electrode materials. In the present study, we obtained well-defined graphene derivatives differing in chemical composition but with similar morphologies by controlling the reaction time of 5-aminoisophthalic acid with fluorographene. The gravimetric specific capacitance ranged from 271 to 391 F g –1 (in 1 M Na 2 SO 4 ), with the maximum value achieved by a delicate balance between the amount of covalently grafted functional groups and density of the sp 2 carbon network governing the conductivity of the material. Molecular dynamics simulations showed that covalent grafting of functional groups with charged and ionophilic/hydrophilic character significantly enhanced the ionic concentration and hydration due to favorable electrostatic interactions among the charged centers and ions/water molecules. Therefore, conductive and hydrophilic graphitic surfaces are important features of graphene-based supercapacitor electrode materials. These findings provide important insights into the role of chemical composition on capacitance and pave the way toward designing more efficient graphene-based supercapacitor electrode materials.

One‐Step Synthesis of Janus Fluorographene Derivatives

“…In order to elucidate the nature of the graphene surface as well as the type of bonds, the deconvolution of C 1s high‐resolution spectra and water contact angle measurements of pristine FG, JFG‐OH(T) and JFG‐OH(W) derivatives prepared at 60 °C are presented in Figure . As is observed, when JFG‐OH is dispersed in H 2 O (Figure B), the peak assigned to C−F species at 289.75 eV is significantly lower, with C−C at 285.02 eV and C=C at 284.35 eV peaks being dominant in the spectrum. However, when JFG‐OH is dispersed in toluene (Figure A), the arrangement of nanosheets is directed by the hydrophobic nature of the C−F bonds.…”

Basicity‐Engineered Graphite Fluoride Functionalization and Beyond: An Unusual Reaction between Ultraweak Nucleophile and Ultrastrong CF Bonds

“…More powerful than FT‐IR, XPS can identify elemental valence states, quantify elemental composition and multidimensionally provide insights into the structural information of bGF and its derivative. First, in the survey XPS spectra of bGF, very prominent peaks of C 1s at ≈286 eV and F 1s at ≈690 eV were of clear visibility (Figure b) . As predicted, N 1s and O 1s had their signatures at ≈401 and ≈533 eV, respectively, and F 1s peak was substantially reduced and seemed negligible.…”

“…After solvothermal treatment with aqueous ammonia, the C–F peak disappeared completely, while the signature of CF 2 moieties was almost negligible. Accordingly, new, strong and broadened peaks associated with N–H/O–H, C–N, and C–O components emerged around 3500–3100, 1387, and 1236 cm −1 , respectively (Figure a) . These results demonstrated the covalent coupling of NH 2 and OH functionalities with graphene scaffolds by nucleophilic substitution toward CF bonds.…”

“…Recently, a new tactic of graphene functionalization has attracted increasing interest. That is, very inactive bulk graphite fluoride (bGF, CF x ) was chemically transformed and modified with organic addends by the reactions between ultrastrong C–F units and nucleophilic compounds . The underlying reason is that bGF is much more integrated in hexagonal honeycomb texture than the popular GO.…”

Graphite fluoride and fluorographene as a new class of solid lubricant additives for high‐performance polyamide 66 composites with excellent mechanical and tribological properties

“…Similar to the relationship between graphite and graphene, the GrF platelets also can be exfoliated to fluorographene (FG) nanosheets with several layers. FG, as the youngest graphene based derivative and the thinnest transparent insulator, exhibits similar properties to GrF but has a smaller size and larger specific surface area compared with GrF, which makes FG an excellent advanced material in many areas, such as solid lubricants, super hydrophobic oleophobic coatings, optoelectronic and thermoelectric devices, electrode materials and so on. The unique properties of FG are caused by the fluoride atoms introduced on the surface of carbon, which changes the hybridization of carbon from sp 2 to sp 3 and increases the interlamellar space in the FG nanosheets .…”