KR20140045160A - Low-oxidized graphene oxide and preparation method thereof - Google Patents

Abstract

Graphene oxide obtained by oxidizing graphite, introducing alkyl ammonium among layers for expanding gaps among layers, and peeling the layers: minimizes the destruction of a pi electron structure of graphene due to a mild oxidizing condition compare to regular conditions; prevents the destruction of a carbon-carbon bond since alkyl ammonium stops the oxidation; and is easily peeled in low energy, thereby enabling users to produce the large area and high quality graphene oxide. [Reference numerals] (AA) Oxidation

Description

LOW-OXIDIZED GRAPHENE OXIDE AND PREPARATION METHOD THEREOF

The present invention relates to a low oxidized large-area high-quality graphene oxide, and a method for preparing the same using alkylammonium.

Graphene is an allotrope of carbon. It is a two-dimensional structure of a single atomic layer in which carbon atoms are connected by sp ² bonds, and benzene-type carbon rings are connected to form a honeycomb structure.

There are four known methods for producing graphene, such as mechanical exfoliation, chemical vapor deposition (CVD), organic solvent method, and graphite redox-reduction method. It is most preferred in terms of ease of production.

The oxidation-reduction method of graphite reduces the van der Waals attraction by reducing the pi electron density between layers by inducing oxygen-based functional groups to facilitate the peeling between layers, and the method of oxidizing graphite has been used to date. ) Method, the Steudenmaier method, the Brodie method and the like are mainly known.

However, since the oxidation process combines a strong acid and a strong oxidizer to oxidize to extreme conditions, not only does not restore the original graphene structure after reduction, but also oxygen remains after the reduction process, so that mass production of graphene is performed. There is a disadvantage in that it is easy but cannot produce high quality graphene.

In general, in the oxidation of graphite layers, the first hydroxyl group and epoxy group are formed, and as the oxidation reaction proceeds continuously, the carboxyl group is finally formed through ether, etc. Defects occur due to breakage of carbon bonds, which are not fully restored even after reduction.

Also, in general, high energy such as ultrasonic waves is used to exfoliate graphite oxide after preparation, and defects induced by oxidation reactions act as weak points under high energy such as ultrasonic waves. As a result, the graphene breaks down, which causes the cross-sectional area to decrease.

Recent studies (Spanu, Charkarova-Kack et al.) Have shown that the graphite van der Waals attraction completely disappears when the graphite interlayer spacing is more than 5Å.

Accordingly, it is an object of the present invention to minimize the defects due to oxidation and to facilitate the exfoliation of graphite oxide, which is an intermediate material, to produce large-scale high-quality graphene oxide.

In accordance with the above object, the present invention provides a graphene oxide formed by interlayer exfoliation of graphite oxide having 5 to 20 oxygen atoms per 100 carbon atoms and alkylammonium intercalated and bonded between layers to expand the interlayer spacing.

In another aspect, the present invention comprises the steps of reacting graphite with a solution containing an oxidizing agent and an alkylammonium compound to obtain a graphite oxide having an interlaminar spacing expanded by alkylammonium intercalation and bonding between the layers; And it provides a method for producing graphene oxide, comprising the step of exfoliating the graphite oxide.

The present invention also provides a graphite oxide having 5 to 20 oxygen atoms per 100 carbon atoms and having an interlayer spacing of 10 to 25 mm 3.

According to the graphene oxide manufacturing method according to the present invention, due to the mild oxidation conditions than the conventional oxidation method minimizes the destruction of the graphene native pi electronic structure (prevents further oxidation progress after the introduction of hydroxyl and epoxy groups in the oxidation process In addition, it is possible to prevent carbon-carbon bond breakage), and the interlayer distance of graphite oxide, which is an intermediate material, is increased, so that peeling is easy under low energy, and a large-scale high-quality graphene oxide can be manufactured.

1 is a schematic diagram illustrating a step-by-step process for producing low-oxidized graphene oxide according to an example of the present invention.
FIG. 2 compares XRD results of graphite oxide (A) having an alkylammonium intercalated in accordance with an example of the present invention and graphite oxide (B) prepared by a conventional human method.
Figure 3 shows an AFM image (a) of the graphene oxide prepared according to an example of the present invention and the results of the partial further analysis (b).

Low Oxidized Graphene Oxide

The graphene oxide of the present invention is a graphite oxide having 5 to 20 oxygen atoms per 100 carbon atoms and having an alkylammonium intercalated and bonded between layers to expand the interlayer spacing, and is formed by interlayer peeling.

In this case, the graphite oxide having the interlayer spacing expanded may be 5 to 30 GPa, and may be, for example, 10 to 25 GPa, more specifically 15 to 25 GPa.

The graphene oxide of the present invention may have an area of 10 μm ² or more, for example, may have an area of 10 μm ² to 100 μm ² .

In addition, the alkylammonium may have 1 to 4 alkyl groups, and at least one of these alkyl groups may have a linear main chain having a length of 2.5 Å or more. More specifically, the alkylammonium is 3,6-diamino-10-methylacridin-10-inium, methyl-trialkylammonium, alkyldimethylbenzylammonium, benzyl-alkyl-dimethylammonium, benzyl-alkyl-bis ( 2-hydroxyethyl) ammonium, benzyl-trialkylammonium, 2-butannoyloxyethyl-trimethyl-azanibine, (1-ethoxy-1-oxoalkan-2-yl) -triketylazanibane, alkyl-trimethyl -Ammonium, dialkyl-dimethylammonium, N, N-dimethyl-N-alkyl-ammonium, choline phosphate, tetraalkylammonium, and mixtures thereof. These alkyl groups may have 5 or more carbon atoms, for example, 5 to 15 carbon atoms.

Figure 3 shows an AFM image (a) of the graphene oxide prepared in accordance with an example of the present invention and the results of the partial analysis further (b), which shows that any graph produced by the conventional redox method It can be seen that a uniform single layer of graphene oxide was prepared compared to fin oxide.

The low oxidized graphene oxide of the present invention may have from 1 to 50 oxygen atoms per 100 carbon atoms, more specifically from 5 to 20 oxygen atoms per 100 carbon atoms.

The low oxidized graphene oxide of the present invention has a high C / O ratio and a large area even after reduction, and can be utilized as a heat dissipating material, an electromagnetic shielding material, an antistatic material, and a super capacitor electrode material, as well as conventional graphene. It can also be used in the field of transparent electrode materials that were not possible with oxides.

Manufacturing method

Graphene oxide of the present invention comprises the steps of (a) reacting graphite with a solution containing an oxidizing agent and an alkylammonium compound to obtain a graphite oxide having an interlaminar spacing expanded by alkylammonium intercalation and bonding between the layers; And (b) delaminating the graphite oxide.

An example of a reaction mechanism for preparing graphene oxide according to the present invention will be described with reference to FIG. 1 as follows:

(R1) An oxidizing agent (KMnO ₄ , H ₂ SO _4, etc.) was added to graphite (about 0.34 nm between layers).

(R2) oxidant anion (MnO ₄ ⁻ ) between the layers of graphite Etc.)

(R3) Oxidizer anions (MnO ₄ ^- at carbon atoms between graphite layers) Etc.)

(R4) Carbon between graphite layers bonds to oxygen atoms of oxidant anions (MnO ₄ ⁻ ).

(R5) OH group is substituted on the carbon atom between the graphite layers.

(R6) Alkyl ammonium ion reacts with OH group substituted by a carbon atom.

(R7) Oxygen atoms of OH groups and nitrogen atoms of alkylammonium ions are bonded by electrostatic attraction to expand the interlayer spacing of graphite oxide.

(R8) Graphene oxide was obtained by delamination of graphite oxide having expanded interlayer spacing.

According to the method of the present invention, the oxidation reaction is carried out in a milder condition than before, thereby minimizing the destruction of graphene's native pi electronic structure, and after the hydroxyl group and the epoxy group are introduced through the oxidation reaction, the alkylammonium is electrostatically charged. By binding to hydroxy and epoxy groups by attraction or chemical bonding to prevent the oxidation of hydroxy and epoxy groups to ether, it is possible to prevent the breakdown of carbon-carbon bonds of graphene in graphite, Since the distance between the graphite layers is greatly increased by the alkylammonium intercalated therein, the peeling is facilitated even under low energy, or the peeling is induced during the reaction, so that a large-area high-quality graphene oxide can be easily produced.

Hereinafter, the method for producing graphene oxide will be described in more detail step by step.

Preparation of Graphite

Graphite used as a starting material may be used natural graphite, kish graphite (synthetic graphite), expandable graphite (expandable graphite or expanded graphite), or a mixture thereof.

Preparation of Solution Containing Oxidizer and Alkyl Ammonium Compound

The oxidizing agent used in the present invention is not particularly limited, but may include, for example, a component selected from the group consisting of permanganate, chlorate, peroxide and combinations thereof. Among these, it is preferable to include permanganate, chlorate, or a combination thereof.

More specific examples of the oxidizing agent include potassium permanganate, calcium permanganate, ammonium permanganate, sodium permanganate, potassium chlorate, sodium chlorate, ammonium chlorate, manganese heptoxide and mixtures thereof. Can be. Of these, preference is given to using potassium permanganate, potassium chlorate, sodium chlorate or mixtures thereof.

The alkylammonium compound used as the intercalant in the present invention may have 1 to 4 alkyl groups.

In addition, at least one of the alkyl groups of the alkylammonium compound may have a linear main chain having a length of 2.5 Å or more, for example, the length may be 2.5 to 20 Å, and more specifically 6 to 20 Å. .

In addition, the alkylammonium compound may have at least one alkyl group having 5 or more carbon atoms in the linear main chain, for example, 5 to 15 carbon atoms.

Examples of the alkylammonium compound include 3,6-diamino-10-methylacridin-10-inium compound, methyl-trialkylammonium compound, alkyldimethylbenzylammonium compound, benzyl-alkyl-dimethylammonium compound, benzyl- Alkyl-bis (2-hydroxyethyl) ammonium compound, benzyl-trialkylammonium compound, 2-butannoyloxyethyl-trimethyl-azanicin compound, (1-ethoxy-1-oxoalkan-2-yl) -tri Ketylazanibine compounds, alkyl-trimethyl-ammonium compounds, dialkyl-dimethylammonium compounds, N, N-dimethyl-N-alkyl-ammonium compounds, choline phosphate compounds, tetraalkylammonium compounds, and mixtures thereof are possible. The alkyl group of these exemplary compounds may have 5 or more carbon atoms, for example, 5 to 15 carbon atoms.

Specific examples of when the alkylammonium compound is a quaternary alkylammonium compound include N, N, N-trisdecyl-1-decaneammonium bromide chloride; N, N-didodecyl-N-methyl-1-dodecaneammonium chloride; N, N, N-trihexadecyl-1-hexadecaneammonium chloride; N-methyl-N, N-dioctadecyl-1-octadecaneammonium chloride; N-benzyl-N, N-dimethyl-1-decanammonium chloride; N-benzyl-N, N-dimethyl-1-tetradecaneammonium chloride; N-benzyl-N, N-dimethyl-1-tetradecaneammonium chloride dihydrate; N-benzyl-N, N-dimethyl-1-dodecaneammonium bromide; N-benzyl-N, N-dimethyl-1-hexadecaneammonium bromide; N-benzyl-N, N-dimethyl-1-octadecaneammonium chloride; Benzyldimethylhexadecylammonium dichromate; N-benzyl-1-methoxy-N, N-dimethyl-1-oxo-2-dodecaneammonium chloride; N-benzyl-1-ethoxy-N, N-dimethyl-1-oxo-2-dodecaneammonium chloride; N-benzyl-1- (hexyloxy) -N, N-dimethyl-1-oxo-2-dodecaneammonium chloride; N-benzyl-N, N-dimethyl-1- (octyloxy) -1-oxo-2-dodecaneammonium chloride; N-benzyl-N, N-dimethyl-2- {2- [4- (2,4,4-trimethylpentan-2-yl) phenoxy] ethoxy} ethaneammonium chloride; Benzyl-dodecyl-dimethylammonium bromide; N-benzyl-N, N-bis (2-hydroxyethyl) dodecane-1-ammonium chloride; N-benzyl-N, N-dimethyl-2-phenoxyethaneammonium 3-hydroxynaphthalene-2-carboxylate; 2- (carbamoyloxy) -N, N, N-trimethylpropane-1-ammonium; 2- (carbamoyloxy) -N, N, N-trimethylpropane-1-ammonium; (1-ethoxy-1-oxohexadecan-2-yl) -trimethylazanium bromide; Hexadecyl-trimethyl-ammonium chloride; Hexadecyl-trimethyl-ammonium bromide; 1-hexadecylpyridinium chloride; 4- (4-chlorophenyl) butyl-diethyl-heptylammonium; {[3- (dodecanoylamino) propyl] (dimethyl) ammonio} acetate; Cocamidopropyl hydroxide; Complanine; 1,1'-decane-1,10-diylbis (4-amino-2-methylquinolinium) decyl] -2-methyl-4-quinolin-1- 윰 amine dichloride; Didecyl-dimethylammonium chloride; N, N-dimethyl-N-octadecyloctadecane-1-ammonium chloride; N, N-dimethyl-N- (2-phenoxyethyl) dodecane-1-ammonium bromide; 10-methyl-9- (10-methylacridin-10-VII-9-yl) acridin-10-VII dinitrate; 1,1 '-[oxybis (methylene)] bis {4-[(E)-(hydroxyimino) methyl] pyridinium}; 2- (3-carboxy-1-oxo-propoxy) ethyl-trimethyl-ammonium; 2,2 '-[(1,4-dioxobutane-1,4-diyl) bis (oxy)] bis (N, N, N-trimethylethaneammonium); Tetra-n-butylammonium bromide; Tetra-n-butylammonium fluoride; Tetra-n-butylammonium hydroxide; Tetra-n-butylammonium tribromide; Tetraoctylammonium bromide; Tetrapropylammonium perruthenate; N- {2-[(4-methoxybenzyl) (pyrimidin-2-yl) amino] ethyl} -N, N-dimethylhexadecane-1-ammonium bromide; Poly [bis (2-chloroethyl) ether-alt-1,3-bis [3- (dimethylamino) propyl] urea]; Hydroxyethyl cellulose dimethyl diallylammonium chloride copolymer; Diallyldimethylammonium chloride-hydroxyethyl cellulose copolymer; Copolymers of acrylamide and quaternary dimethylammoniumethyl methacrylate; Poly (diallyldimethylammonium chloride); Quaternary hydroxyethyl cellulose; Copolymers of vinylpyrrolidine and quaternary dimethylaminoethyl methacrylate; Acrylamide-dimethylaminoethyl methacrylate methyl chloride copolymer; Acrylamide-dimethylaminoethyl methacrylate methyl chloride copolymer; Copolymers of acrylic acid and diallyldimethylammonium chloride; Copolymers of vinylpyrrolidine and methacrylamidopropyl trimethylammonium; Poly (acrylamide 2-methacryloxyethyltrimethyl ammonium chloride); Poly (2-methacryloxyethyltrimethylammonium chloride); Terpolymers of acrylic acid, acrylamide and diallyldimethylammonium chloride; Poly [oxyethylene (dimethylimino) ethylene (dimethylimino) ethylene dichloride]; Terpolymers of vinylcaprolactam, vinylpyrrolidine and quaternary vinylimidazoles; Terpolymers of acrylic acid, methacrylamidopropyl trimethyl ammonium chloride and methyl acrylate; And mixtures thereof.

Since the reaction between the graphite and the alkylammonium compound is preferably performed in the presence of an acid, the oxidizing agent and the alkylammonium compound-containing solution may include sulfuric acid, nitric acid, phosphoric acid, carboxylic acid, and the like. As these acids, lower concentrations of acid solutions can be used as compared to the prior art, for example, when sulfuric acid is used, 70% to 85% of sulfuric acid solutions of 95% to 98% concentration are used in the conventional human method. This is also possible in sulfuric acid solutions in% concentration.

Preparation of Expanded Graphite Oxide by Inserting and Bonding Alkyl Ammonium Between Layers

This step is a step of reacting the previously prepared solution by mixing with graphite. As described above, in the present invention, only one mixing reaction process is required without oxidizing graphite to prepare graphite oxide, extracting / cleaning, and reacting it with an intercalating agent, and thus, time and cost are required. Efficient at The mixing reaction time is not particularly limited, but may be, for example, 6 hours or more, or 6 to 24 hours.

The oxidant reacted with graphite in this step is possible in very small amounts. More specifically, the oxidant may be adjusted to react in an amount of 18.9 mmol or less per 1 g of graphite. In addition, the oxidizing agent may be reacted in an amount of 0.6 to 18.9 mmol per 1 g of graphite, and more specifically, in an amount of 3.15 to 9.5 mmol.

In addition, the alkylammonium compound may be reacted in an amount of 0.028 to 8.28 mmol per gram of graphite, more specifically 0.28 to 2.8 mmol Can be reacted in an amount of.

Summarizing the reaction mechanism in this step, the hydroxy group and the epoxy group are introduced between the graphite layers, and then the alkylammonium is bonded by the electrostatic attraction or chemical bond to the hydroxy group and the epoxy group, so that the interlayer spacing is It can be summarized as expanding. As such, alkylammonium is bonded to the hydroxy and epoxy groups to inhibit the progress of the oxidation reaction to functional groups such as carbonyl and carboxyl groups, which are the next step after the formation of the hydroxyl and epoxy groups. As a result, the alkylammonium not only functions to prevent further oxidation after the formation of the hydroxyl group and the epoxy group, but also binds the hydroxyl group and the epoxy group by an electrostatic attraction or chemical bond and is bonded by van der Waals attraction. The interlayers can be expanded to facilitate exfoliation even under low energy.

Graphite oxides in which the interlayer spacing is expanded by alkylammonium may have an interlayer spacing of 5 to 30 GPa, for example 10 to 25 GPa, more specifically 15 to 25 GPa.

2 XRD pattern (A) of graphite oxide prepared using alkylammonium according to the present invention and XRD pattern (B) of graphite oxide prepared by a human method, which is a general method of preparing graphite oxide, which is alkyl The (002) peak of graphite oxide prepared using ammonium exhibits 2θ at about 4.2 °, which corresponds to an interlayer spacing of 18.79Å, and the (002) peak of graphite oxide prepared by the human method at about 11.2 °. This corresponds to an interlaminar spacing of 9.9 ms.

The graphite oxide thus produced, in which the alkylammonium is bonded between layers to expand the interlayer space, may have 1 to 50 oxygen atoms per 100 carbon atoms, and more specifically 5 to 20 oxygen atoms per 100 carbon atoms. Can have

Preparation of Graphene Oxide by Delamination

The graphite oxide obtained through the previous step is easy to peel even under low energy (eg shear stress) because of the large interlayer spacing. In addition, peeling may be induced during the previous reaction because of the large interlayer spacing.

Such delamination can be carried out using an apparatus selected from the group consisting of homogenizers, Kuet Taylor reactors, high pressure homogenizers, and combinations thereof.

After the above peeling step, the washing and separating step of the graphene oxide may be further performed. The washing and separating may be performed using an apparatus selected from the group consisting of filter presses, centrifuges, decants, and combinations thereof.

In addition, after washing and separating the graphene oxide, if necessary, the step of removing the alkylammonium bonded between the layers may be carried out. For example, when the reduction process is carried out, oxygen-based functional groups are removed and bound between the layers. Alkylammonium can be removed.

The present invention has been described above by way of specific examples, which are only examples, and the present invention has various modifications and other equivalent embodiments apparent to those skilled in the art, and the following claims are attached to the present invention. It should be understood that it can be done within.

Claims (11)

Graphite oxide having 5 to 20 oxygen atoms per 100 carbon atoms and a graphite oxide having an intercalation of alkylammonium intercalated and bonded between layers to form an interlayer exfoliation.
The method according to claim 1,
Graphene oxide, characterized in that the expanded interlayer spacing of the graphite oxide is 10 to 25 mm 3.
3. The method according to claim 1 or 2,
Graphene oxide, characterized in that having an area of 10 ㎛ ² to 100㎛ ² , graphene oxide.
The method according to claim 1,
Graphene oxide, characterized in that the alkylammonium has 1 to 4 alkyl groups, at least one of these alkyl groups has a linear main chain length of 2.5 Å or more.
The method according to claim 1 or 4,
The alkylammonium is 3,6-diamino-10-methylacridin-10-inium, methyl-trialkylammonium, alkyldimethylbenzylammonium, benzyl-alkyl-dimethylammonium, benzyl-alkyl-bis (2-hydroxy Ethyl) ammonium, benzyl-trialkylammonium, 2-butannoyloxyethyl-trimethyl-azanidyl, (1-ethoxy-1-oxoalkan-2-yl) -triketylazanidyl, alkyl-trimethyl-ammonium, di Alkyl-dimethylammonium, N, N-dimethyl-N-alkyl-ammonium, Graphene oxide, characterized in that it is selected from the group consisting of tetraalkylammonium, and mixtures thereof.
(a) reacting the graphite with a solution comprising an oxidizing agent and an alkylammonium compound to obtain an graphite ammonium having an interlayer spacing expanded by alkylammonium intercalation and bonding between the layers; And
(b) comprising the step of exfoliating the graphite oxide, a method for producing graphene oxide (graphene oxide).
The method according to claim 6,
The method of producing a graphene oxide, characterized in that the oxidant comprises a component selected from the group consisting of potassium permanganate, potassium chlorate, sodium chlorate and mixtures thereof.
8. The method according to claim 6 or 7,
The interlayer gap is expanded graphite oxide
With an interlayer spacing of 10 to 25 mm 3
A method for producing graphene oxide, characterized in that it has 5 to 20 oxygen atoms per 100 carbon atoms.
The method according to claim 6,
The solution of step (a), characterized in that it further comprises a sulfuric acid solution of 70% to 85% concentration, the method for producing graphene oxide.
The method according to claim 6,
In the reaction of the step (a), by introducing the hydroxy group and the epoxy group between the graphite layer by the oxidant, and then the alkylammonium bonds to the hydroxy group and the epoxy group by electrostatic attraction or chemical bond, A method for producing graphene oxide, characterized in that graphite oxide having an interlayer spacing is expanded while further oxidation reaction of hydroxyl group and epoxy group is suppressed.
Graphite oxide having 5 to 20 oxygen atoms per 100 carbon atoms and having an interlayer spacing of 10 to 25 microns.

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