CN101214954A - Preparation method of conductive single-layer graphite sheet modified with ionic liquid cationic group - Google Patents

Abstract

The invention provides a preparation method of a conductive single-layer graphite sheet modified with an ionic liquid cationic group. It uses ionic liquid and water as the electrolyte, and graphite rods as electrodes. In the reaction, the cationic organic groups of the ionic liquid can be connected to the graphite flakes, and the graphite flakes will be exfoliated. The obtained single-layer graphite flakes have Organic groups, and have not been oxidized, so it has good oil solubility and polymer miscibility, and has good conductivity, and can be used to prepare conductive composite materials with excellent performance.

Description

Preparation method of conductive single-layer graphite sheet modified with ionic liquid cationic group

technical field

The invention relates to a preparation method of a self-conducting single-layer graphite sheet modified with an ionic liquid cationic group, which does not require reduction.

Background technique

Carbon-based composite materials are being widely concerned by scientists due to their light weight, high strength, and good electronic conductivity. For example, they can be used in aerospace and military fields. (Kotov, A.N.Carbon sheet solutions. Nature 442, 254-255(2006).) At present, carbon-based composite materials are mostly filled with single-walled carbon nanotubes, but single-walled carbon nanotubes are easy to agglomerate; Nanotubes formed by curling sheets have limitations such as difficulty in controlling their diameter and high cost. (Price, B.K.Hudson, J.L.Tour, J.M.Green Chemical Functionalization of Single-Walled Carbon Nanotubes in Ionic Liquids.J.Am.Chem.Soc.127, 14867-14870(2005).) For the above reasons, scientists will Invested in single-layer graphite flakes as an ideal candidate. In recent years, since single-layer graphite sheets have the same large surface area as single-walled carbon nanotubes, with a large number of π electrons on the surface, they have excellent electronic properties, and compared with single-walled carbon nanotubes, they have no chirality and The price is low, and it is concerned by scientists. At present, the only known way to prepare single-layer graphite flakes is the oxide of exfoliated carbon, but the single-layer graphite flakes made of oxides of exfoliated carbon are due to the presence of hydroxyl and epoxy compounds on the flakes. In addition, carbonyl and carboxyl groups appear on the edge of the sheet, so there are many defects: first, it is hydrophilic, not lipophilic, so it cannot be miscible with polymers; second, it is insulating, so it is in the preparation of conductive composites. There are also many limitations in application. To address this problem Stankovich et al. (Dikin, D.A.Dommett, G.H.B.Kohlhaas, K.M.Zimney, E.J.Stach, E.A.Piner, R.D.Nguyen, S.T. & Ruoff, R.S.Stankovich, S.Graphene-based compositematerials. Nature 442, 282-286 (2006)) used phenylisocyanate to modify the surface characteristics of carbon nanosheets prepared from exfoliated carbon oxides, making the formed isocyanate-modified carbon oxides no longer hydrophilic, and Stable dispersion in polar aprotic solution (N,N-dimethylformamide), so it can form polymer composites with many polymers. But the composite material prepared in this way is an insulator, and it is necessary to add a small amount of reducing agent dimethylhydrazine to restore the conductivity of graphite. The carbon-based composite material obtained by the method of Stankovich et al. has obtained a good conductive effect: the seepage point (0.1 volume percent content), the maximum conductivity 1S/m (Siemens per meter). However, it takes a long time to add chemical modifiers and reducing agents, and Stankovich et al. need to use a large amount of methanol in the process of agglomerating the composite material, thus causing environmental pollution and waste of time.

Contents of the invention

In order to overcome the negative impact caused by chemical modification and reduction of carbon oxides, the invention provides a preparation method of a conductive single-layer graphite sheet modified with ionic liquid cationic groups. The single-layer graphite sheet prepared by the method not only has lipophilic properties and high molecular polymer mutual solubility, but also has good electrical conductivity, and can be used to prepare conductive composite materials with excellent performance.

The technical scheme that the present invention adopts is: be (1-20) with the volume ratio: 1 water and ionic liquid as electrolytic solution, graphite rod as electrode, electrolysis 5-10 hour under 5-25 volt voltage, anode graphite rod will Like an onion skin, the cations on the ionic liquid interact with the π bonds on the graphite sheet to exfoliate. After the reaction, the obtained exfoliated single-layer graphite sheet is washed with absolute ethanol and placed in a drying oven. Dry at 50-60°C for 2-10 hours to obtain a conductive single-layer graphite sheet modified with ionic liquid cationic groups;

The ionic liquid is 1-butyl-3 methylimidazolium tetrafluoroborate, 1-pentyl-3 methylimidazolium tetrafluoroborate, 1-hexyl-3 methylimidazolium tetrafluoroborate, 1-heptyl-3 methylimidazolium tetrafluoroborate, 1-octyl-3 methylimidazolium tetrafluoroborate, 1-butyl-3 methylimidazolium hexafluorophosphate, 1-pentyl-3 Methylimidazolium hexafluorophosphate, 1-hexyl-3 methylimidazolium hexafluorophosphate, 1-heptyl-3 methylimidazolium hexafluorophosphate, 1-octyl-3 methylimidazolium hexafluorophosphate, chlorine 1-butyl-3 methylimidazole chloride, 1-pentyl-3 methylimidazole chloride, 1-hexyl-3 methylimidazole chloride, 1-heptyl-3 methylimidazole chloride or 1- Octyl-3 methylimidazole.

The invention has the beneficial effects of inventing a method for preparing conductive single-layer graphite sheets modified with ionic liquid cationic groups in only one step. The method is simple, fast in response and friendly to the environment. The single-layer graphite sheet prepared by the method not only has lipophilic properties and high molecular polymer mutual solubility, but also has good electrical conductivity, and can be used to prepare conductive composite materials with excellent performance.

It can be seen from the electron microscope image of Figure 2 that the length of the conductive single-layer graphite sheet modified with ionic liquid cationic groups is about 700nm, the width is 500nm, the average thickness is about 1.1nm, and there are wrinkles or folds, so it has a large surface area. Fig. 4 is a photo of a conductive single-layer graphite sheet modified with ionic liquid cationic groups prepared by different ratios of water and ionic liquid dissolved in N, N-dimethylformamide. 1, 2, 3, 4, 5, 6, 7 are 1: 0, 1: 1, 1: 3, 1 : 5, 1: 8, 1: 15, and 1: 20 prepared conductive single-layer graphite sheet with ionic liquid cationic group modification, 8, 9, and 10 were prepared with hydrophobic ionic liquid 1-octyl -3-methylimidazolium hexafluorophosphorus, 1-octyl-3-methylimidazolium tetrafluoroboron, 1-butyl-3-methylimidazolium hexafluorophosphorus and water in a ratio of 1:1 Conductive monolayer graphite flakes modified with ionic liquid cationic groups. As can be seen from the figure, except that the No. 1 conductive single-layer graphite sheet prepared by using only hydrophilic ionic liquid as the electrolyte cannot be dissolved in N, N-dimethylformamide, the graphite sheet prepared under the remaining conditions It has good compatibility in N,N-dimethylformamide, and can keep for several months without sedimentation. Fig. 5 is a diagram of the electrical conductivity of four kinds of composite materials prepared by mixing conductive single-layer graphite flakes with ionic liquid cationic groups and high molecular polymers through liquid phase mixing. Conductivity of four composites of conductive single-layer graphite flakes and polystyrene with ionic liquid cationic groups modified using a standard four-probe method. Among them, the composite material with conductive single-layer graphite sheet and polystyrene modified by No. 8 ionic liquid cationic group reaches the seepage point when the volume percentage is 0.1, and reaches the maximum when the volume percentage reaches 4.19. It is 13.84S/m. Compared with the single-wall carbon nanotube polystyrene composite material reported in the literature, the conductivity is 3-15 times higher. Also, in contrast to their method, the present invention uses standard industrial methods.

Description of drawings

Figure 1 is a schematic diagram of the reaction and anode exfoliation of a conductive single-layer graphite sheet modified with ionic liquid cationic groups. In the figure, there are constant-voltage and steady-current power supply 1, graphite electrode 2, electrolyte solution 3 and ionic liquid 4, and mixed solution 5 of water and ionic liquid (the hydrophobic ionic liquid has an interface with water, and the hydrophilic one has no interface. ); 6 is a schematic diagram of the exfoliation of the anode graphite rod, and the conductive single-layer graphite sheet is obtained due to the corrosion of the anode graphite rod.

Fig. 2 is a micrograph of a conductive single-layer graphite sheet modified with ionic liquid cationic groups. Among them, a is a transmission electron microscope image, b is a field emission scanning electron microscope image, and c is an atomic force electron microscope image. The table shows the thickness of a conductive single-layer graphite sheet modified with ionic liquid cationic groups.

Fig. 3 is a comparative spectrogram of pristine graphite (1) and a conductive single-layer graphite sheet (2) modified with ionic liquid cationic groups. Wherein, a is the X-ray photoelectron spectrum, b is the Raman spectrum, c is the infrared spectrum, and d is the X-ray diffraction spectrum.

Fig. 4 is a photo of solubility in N, N-dimethylformamide of a conductive single-layer graphite sheet modified with ionic liquid cationic groups prepared by different ratios of water and ionic liquid.

Fig. 5 is a diagram of the electrical conductivity of four kinds of composite materials prepared by mixing conductive single-layer graphite flakes with ionic liquid cationic groups and polymers through liquid phase mixing.

Detailed ways

Example 1

Use 1-octyl-3 methylimidazolium hexafluorophosphate and water with a volume ratio of 1:1 as the electrolyte, graphite rods as electrodes, and a constant voltage and current power supply to provide a voltage of 15 volts for 10 hours of electrolysis. After the reaction is completed, the The exfoliated single-layer graphite flake obtained was washed with absolute ethanol, and dried in a drying oven at 55° C. for 6 hours to obtain a conductive single-layer graphite flake modified with 1-octyl-3 methylimidazole ;

Example 2

Use 1-octyl-3-methylimidazolium tetrafluoroborate and water with a volume ratio of 1:1 as the electrolyte, graphite rods as electrodes, and a constant-voltage and stable-current power supply to provide 15 volts for 8 hours of electrolysis. After the reaction is complete Wash the exfoliated single-layer graphite sheets obtained with absolute ethanol, and dry them in a drying oven at 55° C. for 6 hours to obtain a conductive single-layer graphite modified with 1-octyl-3 methylimidazole piece;

Example 3

Use 1-octyl-3 methylimidazole chloride and water with a volume ratio of 1:5 as the electrolyte, graphite rods as electrodes, and a constant voltage and current power supply to provide a voltage of 10 volts for 6 hours of electrolysis. After the reaction is completed, the obtained The exfoliated single-layer graphite sheet was washed with absolute ethanol, and dried in a drying oven at 55°C for 6 hours to obtain a conductive single-layer graphite sheet modified with 1-octyl-3 methylimidazole;

Example 4

Use 1-butyl-3 methylimidazolium tetrafluoroborate and water with a volume ratio of 1:1 as the electrolyte, graphite rods as electrodes, and a constant-voltage and stable-current power supply to provide 15 volts for 6 hours of electrolysis. After the reaction is complete Wash the exfoliated single-layer graphite sheets obtained with absolute ethanol, and dry them in a drying oven at 55°C for 6 hours to obtain conductive single-layer graphite modified with 1-butyl-3 methylimidazole piece;

Example 5

Use 1-butyl-3 methylimidazolium hexafluorophosphate and water with a volume ratio of 1:1 as the electrolyte, graphite rods as electrodes, and a constant voltage and current power supply to provide a voltage of 15 volts for 6 hours of electrolysis. After the reaction is completed, the The exfoliated single-layer graphite sheet obtained was washed with absolute ethanol, and dried in a drying oven at 55°C for 6 hours to obtain a conductive single-layer graphite sheet modified with 1-butyl-3 methylimidazole .

Example 6

Use 1-octyl-3 methylimidazolium tetrafluoroborate and water with a volume ratio of 1:20 as the electrolyte, other conditions are the same as in Example 1, and dry at 55°C for 2 hours in a drying oven, and other conditions are the same as in Example 1 1.

Example 7

1-butyl-3-methylimidazolium hexafluorophosphate and water with a volume ratio of 1:1 were used as the electrolyte, graphite rods were used as electrodes, and a constant voltage and constant current power supply provided a voltage of 5 volts. Other conditions were the same as in Example 6.

Claims (1)

1. a kind of preparation method with conductive single-layer graphite sheet is characterized in that, step and condition are as follows: be (1-20) with volume ratio: 1 water and ionic liquid as electrolyte, graphite rod as electrode, in After electrolysis at 5-25 volts for 5-10 hours, the anode graphite rod will peel off like an onion skin through the interaction between the cations on the ionic liquid and the π bonds on the graphite sheet, and the obtained flakes will be peeled off after the reaction is completed. The single-layer graphite sheet was washed with absolute ethanol, and dried in a drying oven at 50-60°C for 2-10 hours to obtain a conductive single-layer graphite sheet modified with ionic liquid cationic groups; The ionic liquid is 1-butyl-3 methylimidazolium tetrafluoroborate, 1-pentyl-3 methylimidazolium tetrafluoroborate, 1-hexyl-3 methylimidazolium tetrafluoroborate, 1-heptyl-3 methylimidazolium tetrafluoroborate, 1-octyl-3 methylimidazolium tetrafluoroborate, 1-butyl-3 methylimidazolium hexafluorophosphate, 1-pentyl-3 Methylimidazolium hexafluorophosphate, 1-hexyl-3 methylimidazolium hexafluorophosphate, 1-heptyl-3 methylimidazolium hexafluorophosphate, 1-octyl-3 methylimidazolium hexafluorophosphate, chlorine 1-butyl-3 methylimidazole chloride, 1-pentyl-3 methylimidazole chloride, 1-hexyl-3 methylimidazole chloride, 1-heptyl-3 methylimidazole chloride or 1- Octyl-3 methylimidazole.

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