Electrochemically Exfoliation Of Graphene Sheets In Deep Eutectic Ionic Liquids

Graphene, a one-atom-thick planar sheet of sp2-bonded carbon with a two-dimensional hexagonal latticestructure, has drawn tremendous attention during recent years. On the basis of its novel properties such asintrinsically superior electrical conductivity, high specific surface area, excellent mechanical strength andremarkable thermal conductivity, graphene has been viewed as one of the most promising materials in thefields of electronics and photonics, energy storage and conversion.These deep eutectic ionic liquids have unique solvent properties and high electrochemical conductivity.They possess several characteristics, including wide potential electrochemical windows, low-volatility andgood conductivity, which render them attractive alternatives as electrochemical solvents.Here we illustrate a simple and fast electrochemical method to exfoliate graphite cathode intohigh-quality few-layer graphene flakes (≤7layers) in deep eutectic solvent. The graphene flakes detachedfrom cathodic graphite received a defect healing. The atom layers, crumpled morphology and scroll thatconcerned with structure defect of FFG were found through transmission electron microscope (TEM).Themain research contents and results are as follows:(1). Factors affect electrochemically exfoliation of grapheme sheets in deep eutectic ionic liquids: we usedseveral low cost eutectic liquid, such as zinc chloride-urea, choline chloride-urea, and cholinechloride-glycerol as effects of electrolyte. The effect factors on the graphite foil exfoliation, such asthe composition of electrolyte, the test voltage and the temperature of the reaction system were investigated.(2). Test conditions on the electrochemical exfoliation effect: an appropriate amount of deionized water wasadded into the selected choline and glycerol eutectic ionic liquid used in our study, the electrochemicalintercalation exfoliation tests were done by adjusting the pH value, changing the applied voltagemethods and adding long chain auxiliary surfactants under the same temperature conditions.The microscopic morphology, chemical structure and crystal structure of the product were studied byusing scanning electron microscopy, field emission scanning electron microscopy, transmission electronmicroscopy, infrared spectroscopy and X-ray diffraction. The effect of different conditions on theexfoliation result was investigated on the macro level according to the settlement of graphene dispersionsolution as well as the UV-Vis absorbance of the grapheme dispersion after settlement. The optimumresearch conditions and results are as follows: the optimum volume ratio of DES/H2O is1:1, the best pulseintensity is [+4V~5s, OV~2s] and pH=12.0. Meanwhile, the appropriate concentration of cationicsurfactant cetyltrimethylammonium chloride (CTAC) was added which significantly improved theproductivity without affecting the output of the electrochemical exfoliation quality. Studies determine thebest concentration of CTAC is0.16mg/ml. The various characterization and ultimately determine that theyield of grapheme in the system is about12.7%, and the majority of graphene contained six layers.