Method for producing graphene oxide gel

Abstract

A method of reversibly forming a graphene oxide gel by reacting graphene oxide dispersed in an aqueous solution with an organic amine or a quaternary phosphonium salt. A method of forming an anhydrous graphene oxide dispersion is also provided.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 502,320, filed May 5, 2017, the entire contents of which are incorporated herein by reference. background

[0003] Graphene is a two-dimensional (2D) material that can be viewed as a single monomolecular sheet of graphite. Since its initial isolation and characterization, graphene has emerged as a material with surprisingly unique and versatile properties. The potential applications of graphene are numerous and include polymer composites, drug delivery, and energy storage, to name a few.

[0004] Graphene oxide hydrogels are important for bulk processing, purification, transportation and storage. These are concentrated, greater than 10 g / L aqueous gels. Previous methods for forming graphene oxide hydrogels require the addition of hydrochloric acid at a concentration of 1 M or higher and result in graphene oxide hydrogels containing too many foreign impurities. The resulting pH makes the graphene oxide gels unsuitable for applications requiring controlled pH or non-corrosive conditions.

[0005] Another problem that has so far hindered the development of graphene in many applications is aggregation. The formation of aggregates blocks the surface area of ​​the graphene, thereby reducing the performance of the material.

[0006] Graphene functionalization has become a hot area of ​​research in recent years. Georgakilas et al. "Functionalization of Graphene: Covalent and Non-Covalent Approaches, Derivatives and Applications" (Chem. Rev. 2012, 112, 6156) is a 59-page review article cited more than 450 times, which specifically discusses the non-covalent interaction of graphene and graphene oxide and the application of such materials. However, despite the large number of citations, it is noted that there are still many challenges, including limited production, poor material quality, limited ability to customize electronic properties, and energy conversion challenges in, for example, batteries and other related applications.

[0007] Despite all the work being done in this area, it is clear that there remains a need for improved graphene and graphene oxide materials suitable for a variety of applications. In particular, it would be quite advantageous to have a graphene oxide functionalization platform that could be used to generate graphene oxide gels and related materials with tunable properties suitable for a range of uses.

[0008] It would be additionally advantageous to have new methods of making graphene oxide gels with fewer impurities. It would be further advantageous to form graphene oxide gels under milder, less corrosive or non-corrosive conditions in order to develop new uses that were previously unavailable due to the corrosive conditions in which graphene oxide gels exist.

[0009] It would be further advantageous if graphene oxide gels could be reversibly formed, thereby providing the ability to form graphene oxide dispersions under anhydrous conditions, thereby opening new avenues for reactions requiring anhydrous conditions, including surface modifications using methods that cannot be performed under aqueous conditions, and the preparation of nanocomposites with hydrophobic polymers and nanoparticles.

[0010] It would further be advantageous to be able to vary the polarity of graphene oxide, thereby allowing both hydrophobic and hydrophilic forms of graphene oxide to be obtained.

[0011] Overview

[0012] Provided herein is a method of forming a graphene oxide hydrogel, the method comprising the steps of providing an acidic aqueous dispersion of graphene oxide, adding a reactant selected from an organic amine and a phosphonium salt, and stirring the mixture to form the graphene oxide hydrogel.

[0013] In various embodiments, the reactant is an organic amine. The organic amine can be a primary amine, a secondary amine, a tertiary amine or a quaternary amine, or / and a combination thereof. The organic amine can be, for example, an alkylamine, an arylamine, a heterocyclic amine, a polymeric amine, a spirotetramine and a combination thereof. In other embodiments, the reactant can be a phosphonium ion or a phosphonium salt. In a specific embodiment, the reactant is selected from triethylamine, diisopropylethylamine, tetrabutylammonium hydroxide, 6-aminocaproic acid, HEPES, N,N-dimethyldodecylamine, diisopropylamine, hexylamine, hexadecylamine, 4,4'-bipyridine, tris(2-aminoethyl)amine, benzyltriphenylphosphonium chloride, methyltrioctyl ammonium chloride, dodecyltrimethylammonium chloride, 1,12-diaminododecane, tetra(4-aminophenyl)methane and a combination thereof.

[0014] The method may further comprise the step of isolating the resulting graphene oxide gel, which may be achieved by filtration or by centrifugation.

[0015] In certain embodiments of the methods described herein, the ratio of reactants to graphene oxide is from about 0.9 mmol reactants / gram of graphene oxide to about 400 mmol reactants / gram of graphene oxide. In certain embodiments, the aqueous dispersion of graphene oxide has a graphene oxide concentration in the range of about 0.1 g / L to about 5 g / L, and the reactants have a total amine concentration or a total phosphonium concentration in the range of about 0.05 mM to about 100 mM. In further embodiments, the total amine concentration or the total phosphonium concentration is in the range of about 10 mM to about 70 mM. In still further embodiments, the total amine concentration or the total phosphonium concentration is about 40 mM.

[0016] The aqueous solution is acidified using an inorganic acid, which is added to give a concentration in the range of about 0.004 M to about 2 M, and a pH of less than 7, and preferably in the range of 6.5 to 1, and more preferably in the range of 6 to 1.5. In a preferred embodiment, the acidic aqueous dispersion of graphene oxide comprises sulfuric acid. In a preferred embodiment, the sulfuric acid has a concentration in the range of about 0.004 M to about 2 M. In another embodiment, the acidic aqueous dispersion of graphene oxide comprises hydrochloric acid. In those embodiments, the hydrochloric acid has a concentration in the range of about 0.004 M to about 2 M.

[0017] In some embodiments, the graphene oxide gel can be freeze-dried to obtain a graphene oxide aerogel. The graphene oxide aerogel can be reduced to form a graphene aerogel. In some embodiments, such reduction can be accomplished by thermal reduction or by chemical reduction.

[0018] In another embodiment provided herein, a method for forming a graphene oxide gel comprises the steps of: mixing an aqueous dispersion of graphene oxide having a pH of less than 7 with a mixture of formula (I): XR a R 1 R 2 R 3 (I) wherein X is selected from N and P; wherein a is 0 or 1; wherein R, R 1 , R 2 and R 3 may be the same or different and are selected from H, alkyl, cycloalkyl, cycloheteroalkyl, aryl, heteroaryl, or wherein R, R 1 , R 2 and R 3 Two of them may form a five-membered ring or a six-membered ring, wherein the five-membered ring or the six-membered ring may be saturated or unsaturated and may contain one or more heteroatoms; provided, however, that when X is N and a is 0, R 1 , R 2 and R 3No more than 2 of them are H; when X is N and a is 1, R, R 1 , R 2 and R 3 No more than 3 of them are H, and when X is P and a is 1, R, R 1 , R 2 and R 3 neither is H; and reacting the graphene oxide with a compound of formula I to form a graphene oxide gel; and optionally, isolating the graphene oxide gel.

[0019] In some embodiments of the method, there is a further step of freeze-drying the graphene oxide gel to form a graphene oxide aerogel. In still other embodiments, the method further comprises a step of reducing the graphene oxide aerogel to form a graphene aerogel.

[0020] Further provided is a method of forming an anhydrous graphene oxide dispersion in an organic solvent, comprising the steps of: providing an isolated graphene gel, removing water from the isolated graphene gel; and dispersing the isolated graphene gel in an organic solvent to form a graphene oxide dispersion in the organic solvent. In preferred embodiments, the organic solvent is an anhydrous organic solvent. In some embodiments of the method, the dispersing step is accomplished by sonicating the isolated graphene gel in the organic solvent.

[0021] Also provided are applications using the graphene oxide gel and aerogel. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A method of making a graphene oxide hydrogel as described herein is illustrated.

[0023] Figure 2 A method for making a graphene oxide dispersion in toluene is illustrated.

[0024] Figure 3 The reversible formation of graphene oxide hydrogels according to the methods described herein is demonstrated.

[0025] Details

[0026] Graphene oxide (GO) hydrogels are important for bulk processing, purification, transportation, and storage. These are concentrated, greater than 10 g / L, aqueous gels.

[0027] Methods of forming graphene oxide gels are provided herein. Graphene oxide gels prepared by the methods provided herein have fewer impurities than graphene oxide gels prepared by conventional methods. Advantageously, graphene oxide gels prepared by the methods described herein are prepared under less corrosive conditions, which allows for a wider range of applications than previously available. The graphene oxide hydrogels can be used in applications requiring controlled pH or non-corrosive conditions.

[0028] The hydrogels produced by the methods described herein can be further processed by freeze drying to obtain graphene oxide aerogels. In addition, the graphene oxide aerogels can be thermally reduced to form graphene aerogels, which are the lowest density solid materials known.

[0029] Without being limited by theory, it is believed that the graphene oxide gel produced by the methods described herein is formed by electrostatic interactions of the graphene oxide surface with the ionic ends of the ammonium or phosphonium salts. Advantageously, this can be used to reversibly change the polarity of the graphene oxide. Using the methods described herein, graphene oxide can be made hydrophobic, even though it is normally hydrophilic.

[0030] Another advantage of the methods described herein is that by using the reversal of the polarity of graphene oxide, it is possible to make anhydrous graphene oxide dispersions in organic solvents.

[0031] The term gel as used herein refers to a jelly-like colloid or flocculated material held together by, for example, crosslinking, intermolecular forces, electrostatic forces, and the like. Graphene oxide hydrogels are gel compositions of graphene oxide in water or in aqueous solution. The graphene oxide gels described herein can be separated by methods such as filtration or centrifugation. The graphene oxide gels or graphene oxide hydrogels manufactured by the methods described herein are advantageously reversible. Also provided herein is a graphene oxide aerogel, which is an extremely low density solid formed by the methods described herein.

[0032] The term reversible as applied to the formation of the graphene oxide gel prepared by the method described herein means that the graphene oxide flocculates to form a gel that can be separated by filtration or centrifugation. Graphene oxide prepared by conventional methods cannot be separated in this way. Therefore, the test to determine that the graphene oxide is no longer a hydrogel is that it cannot be separated from water by centrifugation at 4000 rpm, and that it cannot be separated by vacuum filtration, thereby behaving like a graphene oxide dispersion that has not been treated with ammonium or phosphonium salts.

[0033] As used herein, the term alkyl includes C1 to C 20Straight or branched chain alkyl, examples include methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, etc. The alkyl group may be substituted with other functional groups at one or more positions, as long as such substitution does not render the alkyl group unusable for the methods described herein. The alkyl group may further include cycloalkyl and heterocycloalkyl groups.

[0034] The term aryl, used alone or in combination with other terms (e.g., alkylaryl, halogenated aryl, or halogenated alkylaryl), includes aromatic groups such as phenyl, biphenyl, and benzyl, and fused aryl groups such as naphthyl, anthracenyl, phenanthrenyl, fluorenyl, and indenyl, etc. The term aryl also includes heteroaryl, which is an aryl having carbon and one or more heteroatoms (e.g., O, N, or S) in the aromatic ring. Examples of heteroaryl include indolyl, pyrrolyl, etc. Aryl further includes substituted aryl, such as alkyl-substituted aryl and halogen-substituted aryl. Alkyl-substituted aryl includes, but is not limited to, for example, butylphenyl, propylphenyl, ethylphenyl, methylphenyl, 3,5-dimethylphenyl, tert-butylphenyl, etc. Halogen-substituted aryl or halogenated aryl refers to an aryl in which one or more substitutable positions have been substituted by a halogen group, examples of which include fluorophenyl, 4-chlorophenyl, 2,5-dichlorophenyl, etc. Halogenated alkylaryl refers to an aryl with a haloalkyl substituent. Examples of haloalkylaryl groups include groups such as bromomethylphenyl, 4-bromobutylphenyl, and the like.

[0035] The organic amine described herein can be a primary amine, a secondary amine, a tertiary amine or a quaternary amine. The organic amine described herein can include a linear, branched or cyclic functional group. The organic amine can be a diamine, a triamine, a tetramine or a polyamine. In some preferred embodiments, the organic amine includes 1-4 alkyl C1 to C 30 alkyl chains, wherein the alkyl chains may be the same or different; in some embodiments, the organic amine may have 1-4 C1-C 20 Alkyl; in some embodiments, C 10 -C 20 Primary alkylamines are preferred; in other embodiments, amines having one C 10 -C 20 Secondary amines having two C 10 -C 20 Tertiary amines having three C 10 -C 20The quaternary amine of alkyl and one methyl is preferred. Other similar alkylamines may be preferred in other applications. In some embodiments, the amine can be a polymeric amine, such as polylysine, polyethyleneimine, polyacrylamide, poly (allylamine) and the like. The amine can also be a cyclic amine, also referred to as a heterocyclic amine. Cyclic amines include both aromatic cyclic amines and non-aromatic cyclic amines. Some non-limiting examples of cyclic amines include: pyrrolidine, methylpyrrolidine, imidazole, picoline, piperidine, piperazine, pyrimidine, quinolone, acridine, 1,8-diazabicyclo (5.4.0) undec-7-ene (DBU).

[0036] In certain embodiments, the amine may be hydrophobic or very hydrophobic. In other embodiments, the amine may be hydrophilic. In still other embodiments, the amine may be amphiphilic.

[0037] According to some embodiments described herein, particularly preferred amines include triethylamine, diisopropylethylamine, tetrabutylammonium hydroxide, 6-aminocaproic acid, HEPES, N,N-dimethyldodecylamine, diisopropylamine, hexylamine, hexadecylamine, methyltrioctylammonium chloride, dodecyltrimethylammonium chloride, 4,4'-bipyridine, tris(2-aminoethyl)amine, benzyltriphenylphosphonium chloride, methyltrioctylammonium chloride, dodecyltrimethylammonium chloride, 1,12-diaminododecane, tetrakis(4-aminophenyl)methane, and 1-4 C 10 -C 30 Alkyl and 0-1 methyl alkylamine.

[0038] In some embodiments, phosphonium salts are used instead of amines. Particularly preferred are quaternary phosphonium salts. In a preferred embodiment, the phosphonium salt is benzyltriphenylphosphonium chloride.

[0039] The functional groups described herein may be substituted at one or more positions with other functional groups, provided that such substitution does not render the alkyl group unusable for the methods described herein. Suitable substituents will be known to those of ordinary skill in the art and may include functional groups such as olefins, alkynes, halides, alcohols, ethers, aldehydes, ketones, carbonyls, carboxylic acids, esters, amino acids, amines, amides, imines, thiols, disulfides, aryls, heteroaryls, and the like.

[0040] The graphene oxide hydrogel is formed in an acidic aqueous solution. Inorganic acids are preferably used in the methods described herein. Exemplary inorganic acids that can be used for these methods include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and the like. The acid concentration in the aqueous solution is preferably in the range of about 0.004M to about 2M. The pH is preferably in the range of about 6.5 to about 1, and more preferably in the range of about 6 to about 1.5. In yet other embodiments, the pH is in the range of about 5 to about 2. In most embodiments, it is preferred to maintain the pH below 7 after adding the organic amine or phosphonium salt.

[0041] method

[0042] Procedure for making graphene oxide hydrogel. An amine or phosphonium salt is added to a dispersion of graphene oxide in water with a graphene oxide concentration of 1-5 g / L and a sulfuric acid concentration between 2 and 0.004 M under stirring. The amount of amine added is preferably at least sufficient to make a 0.004 M solution of an amine containing a shorter alkyl group, such as triethylamine. If the amine contains multiple amine functional groups on the same molecule or has very hydrophobic alkyl, aryl or heterocyclic groups, the molecular concentration can be reduced so that the total amine content is not less than 0.9 (mmol amine) / (g graphene oxide). Alternatively, sufficient aqueous solution of alkylammonium hydrogen sulfate can be added to make a solution with a total concentration of ammonium salts equal to 0.004 M. The graphene oxide gel can be isolated by centrifugation or filtration.

[0043] Some non-limiting examples of organic amines (all available from Sigma-Aldrich, St. Louis, Missouri) include: primary, secondary, tertiary and quaternary alkyl amines, wherein the alkyl groups may be the same or different, cyclic amines such as piperidine and piperazine, cyclic aromatic amines such as pyrrolidine, methylpyrrolidine, imidazole, methylpyridine, etc. Some exemplary organic amines for use in the methods described herein include triethylamine, diisopropylethylamine, tetrabutylammonium hydroxide, 6-aminocaproic acid, HEPES, N,N-dimethyldodecylamine, diisopropylamine, hexylamine, hexadecylamine, 4,4'-bipyridine; 4,4'-trimethylenedipyridine; tris(2-aminoethyl)amine and piperidine.

[0044] In some embodiments, phosphonium salts may be used, with quaternary phosphonium salts being particularly preferred. A preferred phosphonium salt for use in the methods described herein is benzyltriphenylphosphonium chloride.

[0045] Procedure for making graphene oxide aerogel. The graphene oxide hydrogel formed in the above method was frozen in a round bottom flask in a dry ice bath at -78°C. The flask was placed under a vacuum of 9 mbar and allowed to warm to ambient temperature under active vacuum.

[0046] Procedure for making graphene aerogel. Graphene oxide aerogel was placed under vacuum and heated above 150 °C for 4 hours under active vacuum.

[0047] Procedure for making graphene oxide dispersions in anhydrous solvents. This method is best used to prepare graphene oxide dispersions in anhydrous solvents such as toluene, dichloromethane, anhydrous ethanol, and the like. The reactant (i.e., the organic amine or phosphonium salt) is hydrophobic, and most preferably highly hydrophobic. Some non-limiting examples of suitable reactants include C 10 To C 20Primary, secondary, tertiary and quaternary amines, and similar phosphonium salts. Some preferred amines include C 16 H 33 NH3Cl, C 11 H 23 N(CH3)2HCl and (C 10 H 21 )3N(CH3)Cl. Depending on the end use of the dispersion being prepared, the reagent is preferably selected so as to be inert toward the particular reagents that may be used.

[0048] The four-necked round bottom flask was then placed in a plastic bucket, equipped with an overhead stirrer, a nitrogen inlet, an addition funnel with a nitrogen outlet, and a thermometer, and then purged with nitrogen for 20 minutes. 4 L of a 2 mg / mL aqueous dispersion of graphene oxide (Aldrich product catalog number 763705) was added to the flask. 0.75 L of toluene and 0.75 L of ethanol were then added to the reaction mixture.

[0049] The organic amine or phosphonium salt reactant is added and dissolved in 0.75 L of ethanol in the above molar ratio and the mixture is added streamwise under very rapid stirring. A thick gel will form and it will separate from the aqueous portion. The reaction mixture is stirred for 30 minutes.

[0050] Solid materials are separated by centrifugation, for example, 15 minutes at 3500 rpm should be sufficient. The liquid supernatant is decanted into a collection bottle, using a scraper to retain any solids. All solid materials are collected in a large container. All clear liquids are collected in a waste container set aside for the reaction.

[0051] Ethanol was added to the solid mixture to a total volume of 4.0 L. The mixture was stirred well until all materials were dispersed and a thick homogeneous product / ethanol mixture was obtained. More ethanol may be added to obtain a homogeneous dispersion.

[0052] The solid material was separated by centrifugation. The clear liquid supernatant was decanted into a collection bottle and the solid material was collected in a large container. The supernatant was added to the collected waste stream.

[0053] Ethanol is added to the solid material to a total volume of 4.0 L and stirred thoroughly until uniform, 30 minutes is usually sufficient for this step. The solid material is separated by centrifugation. The clarified liquid supernatant is decanted into a collection bottle. The solid material is placed in a large rotary evaporation bottle. The clarified liquid ethanol mixture is added to the collected waste stream.

[0054] A preferred anhydrous solvent (e.g., toluene, dichloromethane, anhydrous ethanol or other) is added to the solid material to a total volume of 4 L and mixed until homogeneous. Volatiles are removed on a rotary evaporator to a total volume of 1 L. This step is repeated twice. The product can be dried to dryness on a rotary evaporator and then placed under high vacuum for 4 hours.

[0055] The anhydrous hydrophobic solid graphene oxide was dispersed into 4 L of an anhydrous solvent by stirring to obtain an anhydrous dispersion of graphene oxide.

[0056] Graphene oxide was reversibly flocculated to form hydrogels by adding alkylammonium salts. 1.8 mmol (NEt3) or 1.0 mmol [N(Me2)C 12 H 25 ] was added to 5 mL 1M HCl to prepare a solution of ammonium hydrochloride. This ammonium salt solution was added to 40 mL of graphene oxide dispersion having a concentration of 3 g / L and a pH of 6-1.5 to make the final pH below 7. The mixture was filtered by vacuum filtration (polypropylene filter pad or The graphene oxide hydrogel was separated by centrifugation (10 min at 3500 rpm).

[0057] The gel was then transferred to a reaction vessel and 40 mL of 2M HCl was added followed by thorough mixing. The hydrogel was isolated by vacuum filtration or centrifugation as described above. These steps were repeated.

[0058] Water was added to the gel to a total volume of 40 mL and mixed thoroughly until homogeneous. Saturated sodium bicarbonate solution was slowly added with stirring until a homogeneous dispersion or pH 8 was obtained.

[0059] Thus, according to this method, the flocculation of graphene oxide to form a gel that can be separated by filtration or centrifugation is reversible.

[0060] Applications. The tunable properties of graphene oxide gels and graphene oxide aerogels produced by the methods described herein make them particularly suitable for a variety of applications. Specifically, by selecting reactants (i.e., organic amines or phosphonium salts) with specific properties such as hydrophobicity, redox activity, compatibility with related systems, the properties of the produced graphene oxide gels, graphene oxide aerogels, or graphene aerogels can be effectively and reversibly changed.

[0061] Energy storage. Supercapacitors are energy storage devices similar to batteries. Each consists of two electrodes - an anode and a cathode, an electrolyte, and a separator between the anode and cathode. Batteries use electrochemical reactions to provide electrical energy to devices, while supercapacitors use the electrostatic accumulation of charge in the anode and cathode to store energy. Supercapacitors currently have lower energy density than batteries, but higher charge and discharge rates. An important factor affecting the energy storage capacity of supercapacitors is the specific surface area of ​​the electrode material. Activated carbon, reduced graphene oxide, and reduced graphene oxide aerogels have all been used previously as anode and cathode materials in capacitors with some success due to their high specific surface areas.

[0062] The graphene oxide hydrogels described herein prepared using ammonium and phosphonium salts can be used to make reduced graphene oxide aerogels by freeze drying followed by thermal reduction as previously described. Advantageously, this procedure for making reduced graphene oxide aerogels provides a unique ability to design reduced graphene oxide aerogels using ammonium and phosphonium salts of varying size and polarity to affect the specific surface area and energy storage capacity of supercapacitors.

[0063] When selecting reactants (i.e., organic amines or phosphonium salts), the first consideration is that supercapacitors will benefit from reactants that can prevent stacking, thereby increasing the specific surface area. Particularly suitable reagents include very hydrophobic or polymeric amines. Some examples of particularly suitable amines include spirotetramine, 1,12-diaminododecane, and tetrakis(4-aminophenyl)methane. Second, considering increasing capacity, redox-active amines, such as polyaniline, can be used. In some embodiments, a combination of two or more amines can be used together to improve a variety of properties.

[0064] A supercapacitor is provided, comprising an anode and a cathode, an electrolyte ionically connecting the anode and the cathode; and an ion permeable membrane physically separating the anode and the cathode, wherein at least one of the anode and the cathode comprises a graphene aerogel prepared by the method described herein. In a particularly preferred embodiment, both the anode and the cathode comprise a graphene aerogel prepared by the method described herein.

[0065] The supercapacitor is suitable for both aqueous electrolytes and organic electrolytes. Some exemplary aqueous electrolytes include inorganic acids, bases and salts, especially including but not limited to acids such as sulfuric acid, potassium hydroxide, quaternary phosphonium salts, sodium perchlorate, lithium perchlorate and lithium hexafluoroarsenate. Some exemplary organic electrolytes include but are not limited to acetonitrile, propylene carbonate, tetrahydrofuran, diethyl carbonate, γ-butyrolactone and solutions containing quaternary ammonium salts or alkylammonium salts such as tetraethylammonium tetrafluoroborate and triethylmethyl tetrafluoroborate (NMe(Et)).

[0066] The ion permeable membrane is an electrically insulating material; some non-limiting examples of membranes include capacitor paper, cellulose paper, non-woven porous polymers, woven glass fibers, and porous woven ceramic fibers. In certain preferred embodiments, the ion permeable membrane is a non-woven porous polymer selected from polyamide, polypropylene, polyethylene, polytetrafluoroethylene, polyvinyl chloride, and combinations thereof. In certain embodiments, the electrolyte and the membrane are a single material selected from solid electrolytes and gel electrolytes.

[0067] More generally, electrodes having a conductive substrate and a graphene oxide aerogel or graphene aerogel produced by the methods described herein can be used in many applications. The high specific surface area, improved purity, and tunable properties make the aerogels described herein ideal for many applications.

[0068] Batteries: Similar to supercapacitors, for battery applications, amines are selected to prevent restacking and allow room for expansion when charging and filling with lithium. Exemplary amines for preparing graphene oxide hydrogels and final graphene aerogels for battery applications according to the methods provided herein include those listed above as being useful for supercapacitors. Particularly preferred amines include 1,12-diaminododecane and tetrakis(4-aminophenyl)methane.

[0069] Air-Sensitive Reactions: As discussed in the methods above and as shown in the examples below, the methods described herein can advantageously provide graphene oxide hydrogels and aerogels and graphene aerogels, and graphene oxide dispersions in anhydrous solvents. Although the hydrophilic nature of graphene oxide makes its use in air-sensitive applications very challenging, the flexibility of the methods described herein provides an effective approach to materials tailored for such uses. Preferred amines for these applications include highly hydrophobic quaternary or tertiary ammonium salts, which are inert to a variety of highly reactive reagents and facilitate the dispersion of GO into organic solvents. Some particularly preferred amines include N,N-dimethyldodecylamine, methyltrioctylammonium chloride, and dodecyltrimethylammonium chloride, although other amines can be determined by one skilled in the art.

[0070] The anhydrous graphene oxide dispersion is particularly suitable for use in reactions involving, for example, organolithium, Grignard reagents, acid chlorides, etc. Many other applications requiring the use of graphene oxide under anhydrous conditions can also be achieved by using the methods provided herein.

[0071] Hydrophobic composites. Another application that can be obtained using the graphene oxide gels provided herein is the preparation of hydrophobic composites. The composites can be made using an anhydrous dispersion of graphene oxide prepared by the methods described herein by adjusting the properties of the anhydrous graphene oxide dispersion by selecting reactants (i.e., organic amines or phosphonium salts) having properties that are compatible with the other materials in the composite to be formed. Long chain amines are suitable for forming many composites.

[0072] In one embodiment, anhydrous graphene oxide dispersions can be used to make composite materials containing quantum dots, the anhydrous graphene oxide dispersions being formed using primary amines with longer alkyl groups (e.g., 1-decylamine or higher amines). Such anhydrous graphene oxide dispersions will also be compatible with other nanoparticles. In another embodiment, the anhydrous graphene oxide dispersion is combined with a hydrophobic polymer to form a composite material.

[0073] Inks. The graphene oxide dispersions prepared by the methods described herein can also be used to prepare inks for coating or printing methods (including but not limited to spin coating, dip coating, blade coating, inkjet printing, screen printing, gravure printing, etc.). In these embodiments, the graphene oxide inks are formulated with amine-modified graphene oxide, non-aqueous solvents, and additives. Using the methods described herein, the amines used with graphene oxide can be selected to provide specific properties.

[0074] In one embodiment, a graphene oxide gel is prepared wherein the reactant is selected from amines having an organic group that matches the polarity of the solvent used for the ink formulation. In a preferred embodiment, N,N-dimethyldodecylamine is used.

[0075] Purification. Another advantage of the methods described herein is that the methods produce graphene oxide gels with fewer extraneous impurities than graphene oxide gels formed using conventional methods. In addition, it has been found that these methods, especially the gelling effect of amine or phosphonium salt reactants, can be used to provide improved methods for purifying graphene oxide. For purification applications, preferred reactants include organic amines that are water-soluble in acidic or neutral water and contain at least one very hydrophobic group or multiple amine functional groups. Some preferred amines include, but are not limited to, N,N-dimethyldodecylamine, tris(2-aminoethyl)amine, and tris[2-(dimethylamino)ethyl]amine.

[0076] In one embodiment, the purification method comprises the following steps: dispersing the graphene oxide to be purified in an aqueous solution having a pH in the range of 6 to 1.5; adding a reactant, i.e. an organic amine or phosphonium salt, which preferably has a very hydrophobic group or multiple amine functional groups; stirring the mixture to form a graphene oxide hydrogel; isolating the graphene oxide gel by filtration or centrifugation; washing the gel with water, which may be neutral or acidic, at a pH of 7-1, until excess amine or phosphonium salt is removed, resulting in a purified graphene oxide gel, which is ready for storage, use or further processing.

[0077] In some embodiments, the pH of the purified graphene oxide can be acidified with a volatile acid (e.g., hydrochloric acid or acetic acid), or it can be retained in neutral pH water. In other embodiments, the volatiles can be removed to dryness and the purified graphene oxide can be redispersed in neutral water. In still other embodiments, the pH of the purified graphene oxide can be adjusted with a base, such as, in particular, ammonia, hydroxides, or carboxylates.

[0078] Since many different properties, i.e., tunable graphene oxide hydrogels, aerogels, and graphene aerogels, can be achieved using the methods disclosed herein by varying the amine or phosphonium salt used, a kit containing suitable components, including a graphene starting material, a suitable acid, and one or more suitable reactants, can be envisioned to enable others to readily use the described methods.

[0079] Examples. The following methods were used to prepare a variety of graphene oxide hydrogels using various amines.

[0080] Formation of graphene oxide hydrogel. An amine is added to a dispersion of graphene oxide in water (having a graphene oxide concentration in the range of 1-5 g / L and a sulfuric acid concentration between 2 and 0.004 M) under stirring. The amount of amine added is at least sufficient to make a 0.04 M solution (based on amine). The graphene oxide gel is isolated by centrifugation at 4000 rpm for 10 minutes. The graphene oxide gel is then analyzed or further processed as outlined below.

[0081] A variety of amines were tested (all from Sigma-Aldrich (St. Louis, Missouri)), including the following, each listed as a Sigma-Aldrich product number: triethylamine (T0886), diisopropylethylamine (387649), tetrabutylammonium hydroxide (178780), 6-aminocaproic acid (07260), HEPES (H3784), N,N-dimethyldodecylamine (284386), diisopropylamine (471224), hexylamine (219703), hexadecylamine (445312), 4,4'-bipyridine (289426); 4,4'-trimethylenedipyridine (121193); tris(2-aminoethyl)amine (225630). Each of these amines produced graphene oxide hydrogels, and the properties of each graphene oxide hydrogel varied with the properties of the specific amine used.

[0082] This shows that the method provided herein can be used to form graphene oxide hydrogels using a wide range of organic amines as reactants. In addition, this shows that the method provides an effective way to adjust the properties of graphene oxide gels for different applications, because the method does work for a wide range of amines with different properties.

[0083] Comparative Example. The method for forming a graphene oxide aerogel outlined above was carried out using ammonia as the amine reactant. No graphene oxide gel was formed.

[0084] Formation of graphene oxide aerogel. The graphene oxide hydrogel formed above was frozen in a round bottom flask in a dry ice bath at -78°C. The flask was placed under a vacuum of 9 mbar and allowed to warm to ambient temperature under active vacuum to provide graphene oxide aerogel.

[0085] The graphene oxide aerogel prepared by the above method can be converted into graphene aerogel as follows. The graphene oxide aerogel is added to a flask and placed under vacuum. The flask is heated at 200° C. for 4 hours under active vacuum.

[0086] Graphene oxide dispersion in toluene. A four-necked round-bottom flask was equipped with an overhead stirrer, a nitrogen inlet, a nitrogen outlet, and a thermometer, and purged with nitrogen; all additions were made through a funnel under a stream of nitrogen. Sulfuric acid (290 mL) was added to the flask. Graphite (Aldrich, 7.0 g) was added under slow stirring and under a stream of nitrogen. The reaction mixture was cooled with a water bath cooled to 10-15° C. Potassium permanganate (12.5 g) was added to the reaction mixture under slow stirring, followed by replacing the funnel with a stopper. Nitrogen was introduced through a pressure equalizing bubbler. The temperature was maintained at 30° C. or less, and the reaction mixture was stirred for 1 hour. Potassium permanganate (12.5 g) was added to the reaction mixture through a funnel under a stream of nitrogen under slow stirring. The funnel was replaced with a Teflon-lined glass stopper, and the reaction mixture was slowly stirred at ambient temperature for 4 days. Ice and water were added to the quenching vessel, followed by the reaction mixture and stirring to quench the reaction. The quenching mixture was diluted with water to a total volume of 3.0 L. To the quench vessel was added 30% aqueous hydrogen peroxide (23 mL) and bubbling was observed. The mixture was stirred slowly until the purple color dissipated and a yellow suspension remained.

[0087] Solid material is separated by centrifugation.Solid product is transferred to a large container and about 4L water is added to obtain a cumulative volume of 4.50 L.The mixture is fully stirred to obtain a uniform brown / orange dispersion.Any residual larger heavy solid material is removed by centrifugation.Liquid supernatant portion is carefully decanted in a four-necked round-bottomed flask, which is equipped with an overhead stirrer, a nitrogen inlet, a feed funnel with a nitrogen outlet and a thermometer and then purged with nitrogen.Toluene (0.75L) and ethanol (0.75L) are added to the reaction mixture. Hexadecane (12.0g) is added to ethanol (0.75L), and the mixture is added downstream to the feed funnel under rapid stirring.The thick paste separated from the water-containing portion is formed.The reaction is stirred for 30 minutes, and solid material is separated by centrifugation subsequently.

[0088] The liquid was decanted and all solid material was collected in a large container. Ethanol was then added to the solid mixture to a total volume of 4 L. It was stirred until the material was dispersed, resulting in a thick homogeneous product / ethanol mixture. The solids were separated by centrifugation and collected in a large container. Ethanol was added again to a total volume of 4 L. The mixture was stirred again until uniform and the solid material was separated by centrifugation.

[0089] The solid material was transferred to a large rotary evaporation bottle and toluene was added to a total volume of 4 L. Volatiles were removed on the rotary evaporator to a total volume of approximately 1.5 L, taking care not to completely dry the material. The rotary evaporation procedure was repeated twice, and the product was subsequently diluted to the desired concentration with anhydrous toluene. The graphene oxide aerogel in the anhydrous solution can be further processed as shown below, or used as is for applications requiring anhydrous conditions.

[0090] Preparation of carboxylic acid functionalized graphene oxide from toluene dispersion.Replace primary amine hexadecylamine with non-nucleophilic tertiary amine N, N-dimethyl dodecylamine, prepare dispersion of graphene oxide (0.16g) in toluene (40mL) as above.Remove toluene to dryness, and keep it under vacuum for 3 hours.Dissolve the obtained solid in dichloromethane (50mL).In the case of stirring under nitrogen, add adipoyl chloride (0.56mL) through diaphragm by syringe.In the case of stirring under nitrogen, add pyridine (0.63mL) dropwise through diaphragm by syringe.Make reaction mixture stir overnight at ambient temperature for 16 hours.Add water (80mL) to reaction mixture and mix thoroughly.Separate obtained solid by centrifugation at 4000rpm for 10 minutes.Decant two layers of solvent to separate from the solid appearing between the two layers.Wash obtained solid with acetic acid aqueous solution (1.5g acetic acid in 150mL water), separate the solid again by centrifugation. The solid was washed with acetic acid in ethanol (1.0 g acetic acid in 150 mL ethanol) and isolated by centrifugation. The solid was washed again with ethanol (150 mL) and isolated by centrifugation. The resulting solid paste was dried under high vacuum for analysis.

[0091] The embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the claims.

[0092] The present invention relates to the following embodiments:

[0093] 1. A method for forming a graphene oxide gel, comprising the following steps:

[0094] Providing an aqueous dispersion of graphene oxide, wherein the aqueous solution is acidic;

[0095] adding a reactant selected from an organic amine and a phosphonium salt; and

[0096] The mixture is stirred to form the graphene oxide hydrogel.

[0097] 2. The method of embodiment 1, wherein the reactant is an organic amine selected from primary amines, secondary amines, tertiary amines, quaternary amines and combinations thereof.

[0098] 3. The method according to embodiment 2, wherein the organic amine is selected from alkyl amines, aromatic amines, heterocyclic amines, polymeric amines, spirotetramines and combinations thereof.

[0099] 4. The method of embodiment 2, wherein the reactant is selected from triethylamine, diisopropylethylamine, tetrabutylammonium hydroxide, 6-aminocaproic acid, HEPES, N,N-dimethyldodecylamine, diisopropylamine, hexylamine, hexadecylamine, 4,4'-bipyridine, tris(2-aminoethyl)amine, benzyltriphenylphosphonium chloride, methyltrioctylammonium chloride, dodecyltrimethylammonium chloride, 1,12-diaminododecane, tetrakis(4-aminophenyl)methane, and combinations thereof.

[0100] 5. The method of embodiment 1 further comprises the step of isolating the obtained graphene oxide hydrogel.

[0101] 6. The method of embodiment 5, wherein the graphene oxide hydrogel is separated by filtration.

[0102] 7. The method of embodiment 5, wherein the graphene oxide hydrogel is separated by centrifugation.

[0103] 8. The method of embodiment 1, wherein the ratio of the reactant to graphene oxide is from about 0.9 mmol reactant / gram graphene oxide to about 400 mmol reactant / gram graphene oxide.

[0104] 9. The method of embodiment 1, wherein the aqueous dispersion of graphene oxide has a graphene oxide concentration in the range of about 0.1 g / L to about 5 g / L, and the reactants have a total organic amine concentration or a total phosphonium salt concentration in the range of about 0.05 mM to about 100 mM.

[0105] 10. The method of embodiment 8, wherein the total organic amine concentration or the total phosphonium salt concentration is in the range of about 10 mM to about 70 mM.

[0106] 11. The method of embodiment 9, wherein the total organic amine concentration or the total phosphonium salt concentration is about 40 mM.

[0107] 12. The method of embodiment 1, wherein the aqueous solution further comprises an inorganic acid.

[0108] 13. The method of embodiment 12, wherein the concentration of the inorganic acid is in the range of about 0.004 to about 2M.

[0109] 14. The method of embodiment 12, wherein the inorganic acid is selected from sulfuric acid and hydrochloric acid.

[0110] 15. The method of embodiment 5, further comprising the step of freeze-drying the graphene oxide to form a graphene oxide aerogel.

[0111] 16. The method of embodiment 15, further comprising the step of reducing the graphene oxide aerogel to form a graphene aerogel.

[0112] 17. The method of embodiment 16, wherein the reducing step comprises thermal reduction.

[0113] 18. The method of embodiment 16, wherein the reducing step comprises chemical reduction.

[0114] 19. A method for forming a graphene oxide gel, comprising the following steps:

[0115] mixing an aqueous dispersion of graphene oxide with a compound of formula (I), said aqueous dispersion having a pH of less than 7,

[0116] XR a R1R2R3 (I)

[0117] wherein X is selected from N and P;

[0118] Where a is 0 or 1;

[0119] wherein R, R1, R2 and R3 may be the same or different and are selected from H, alkyl, cycloalkyl, cycloheteroalkyl, aryl, heteroaryl, or wherein two of R, R1, R2 and R3 may form a five-membered ring or a six-membered ring, wherein the five-membered ring or the six-membered ring may be saturated or unsaturated and may contain one or more heteroatoms; provided, however, that when X is N and a is 0, no more than 2 of R1, R2 and R3 are H; when X is N and a is 1, no more than 3 of R, R1, R2 and R3 are H, and when X is P and a is 1, none of R, R1, R2 and R3 are H; and

[0120] reacting the graphene oxide with the compound of formula I to form a graphene oxide gel; and optionally, isolating the graphene oxide gel.

[0121] 20. The method of embodiment 19, further comprising the step of freeze-drying the graphene oxide hydrogel to form a graphene oxide aerogel.

[0122] 21. The method of embodiment 20, further comprising the step of reducing the graphene oxide aerogel to form a graphene aerogel.

[0123] 22. The method of embodiment 19, wherein the compound of formula (I) reacts with the graphene oxide through electrostatic interaction.

[0124] 23. A method for forming an anhydrous graphene oxide dispersion comprising the steps of:

[0125] Providing an aqueous dispersion of graphene oxide, wherein the aqueous solution is acidic;

[0126] adding a hydrophobic amine to the aqueous dispersion of graphene oxide;

[0127] stirring the mixture to form a graphene oxide hydrogel;

[0128] separating the graphene oxide hydrogel;

[0129] removing water from the isolated graphene hydrogel; and

[0130] The separated graphene hydrogel is dispersed in an anhydrous organic solvent to form an anhydrous graphene oxide dispersion.

[0131] 24. The method of embodiment 23, wherein the hydrophobic amine is selected from N,N-dimethyldodecylamine, methyltrioctylammonium chloride and dodecyltrimethylammonium chloride.

[0132] 25. An anhydrous dispersion of graphene oxide formed by the method of embodiment 23.

[0133] 26. A method for forming a graphene oxide aerogel, comprising the steps of:

[0134] providing an aqueous dispersion of graphene oxide, wherein the aqueous dispersion has a pH of less than 7;

[0135] adding a reactant comprising an organic amine or a phosphonium salt;

[0136] stirring the mixture to form a graphene oxide hydrogel;

[0137] isolating the graphene oxide hydrogel; and

[0138] The graphene oxide is freeze-dried to form the graphene oxide aerogel.

[0139] 27. The method of embodiment 26, wherein the reactant is a compound of formula I

[0140] XR a R1R2R3 (I)

[0141] wherein X is selected from N and P;

[0142] Where a is 0 or 1;

[0143] wherein R, R1, R2 and R3 may be the same or different and are selected from H, alkyl, cycloalkyl, cycloheteroalkyl, aryl, heteroaryl, or wherein two of R, R1, R2 and R3 may form a five-membered ring or a six-membered ring, wherein the five-membered ring or the six-membered ring may be saturated or unsaturated and may contain one or more heteroatoms; but with the proviso that when X is N and a is 0, no more than 2 of R1, R2 and R3 are H; when X is N and a is 1, no more than 3 of R, R1, R2 and R3 are H, and when X is P and a is 1, none of R, R1, R2 and R3 is H.

[0144] 28. The method of embodiment 26, wherein the reactant reacts with graphene oxide via electrostatic interaction.

[0145] 29. The method of embodiment 26, wherein the reactant is an organic amine selected from the group consisting of hydrophobic amines, polymeric amines, and spirotetramines.

[0146] 30. The method of embodiment 29, wherein the organic amine is selected from 1,12-diaminododecane and tetrakis(4-aminophenyl)methane.

[0147] 31. The method of embodiment 26, further comprising the step of reducing the graphene oxide aerogel to form a graphene aerogel.

[0148] 32. A graphene aerogel prepared by the method described in embodiment 31.

[0149] 33. A supercapacitor comprising:

[0150] Anode and cathode,

[0151] an electrolyte ionically connecting the anode and the cathode; and

[0152] an ion-permeable membrane physically separating the anode from the cathode;

[0153] Wherein at least one of the anode and the cathode comprises the graphene aerogel of embodiment 32.

[0154] 34. The supercapacitor of embodiment 33, wherein the electrolyte is selected from aqueous electrolytes and organic electrolytes.

[0155] 35. The supercapacitor of embodiment 33, wherein the ion-permeable separator is an electrically insulating material.

[0156] 36. The supercapacitor of embodiment 35, wherein the ion permeable separator is selected from capacitor paper, cellulose paper, non-woven porous polymer, woven glass fiber, and porous woven ceramic fiber.

[0157] 37. The supercapacitor of embodiment 36, wherein the ion permeable membrane is a non-woven porous polymer selected from the group consisting of polyamide, polypropylene, polyethylene, polytetrafluoroethylene, polyvinyl chloride, and combinations thereof.

[0158] 38. The supercapacitor of embodiment 33, wherein the electrolyte and the separator are a single material selected from a solid electrolyte and a gel electrolyte.

[0159] 39. The supercapacitor of embodiment 33, wherein both the anode and the cathode comprise graphene aerogel.

[0160] 40. An electrode comprising a conductive substrate and the graphene aerogel of embodiment 32.

[0161] 41. A battery comprising the electrode of embodiment 40.

[0162] 42. A method for purifying graphene oxide, comprising the following steps:

[0163] dispersing the graphene oxide to be purified in an aqueous solution having a pH in the range of 6 to 1.5;

[0164] Add the reactant of formula (I)

[0165] XR a R1R2R3 (I)

[0166] wherein X is selected from N and P;

[0167] Where a is 0 or 1;

[0168] wherein R, R1, R2 and R3 may be the same or different and are selected from H, alkyl, cycloalkyl, cycloheteroalkyl, aryl, heteroaryl, or wherein two of R, R1, R2 and R3 may form a five-membered ring or a six-membered ring, wherein the five-membered ring or the six-membered ring may be saturated or unsaturated and may contain one or more heteroatoms; provided, however, that when X is N and a is 0, no more than 2 of R1, R2 and R3 are H; when X is N and a is 1, no more than 3 of R, R1, R2 and R3 are H, and when X is P and a is 1, none of R, R1, R2 and R3 is H;

[0169] stirring the mixture to form a graphene oxide hydrogel;

[0170] isolating the graphene oxide hydrogel; and

[0171] The graphene oxide hydrogel is washed to produce purified graphene oxide.

[0172] 43. The method of embodiment 42, wherein the reactant is a hydrophobic amine.

[0173] 44. The method of embodiment 43, wherein the hydrophobic amine is selected from N,N-dimethyldodecylamine, methyltrioctylammonium chloride and dodecyltrimethylammonium chloride.

[0174] 45. The method of embodiment 42, wherein the washing step is performed using water or an acidic aqueous solution.

[0175] 46. ​​The method of embodiment 42 further comprises the step of acidifying the graphene oxide after the washing step.

[0176] 47. The method of embodiment 42 further comprises the step of dispersing the purified graphene oxide in a solvent, wherein the solvent is selected from the group consisting of water, an acidic solution, and an alkaline solution.

Claims

1. A method for forming an anhydrous graphene oxide dispersion, comprising the following steps: Providing an aqueous dispersion of graphene oxide, wherein the aqueous dispersion is acidic; adding a hydrophobic amine to the aqueous dispersion of graphene oxide; stirring the mixture to form a graphene oxide hydrogel; separating the graphene oxide hydrogel; removing water from the isolated graphene hydrogel; and The separated graphene hydrogel is dispersed in an anhydrous organic solvent to form an anhydrous graphene oxide dispersion.

2. The method of claim 1, wherein the hydrophobic amine is selected from the group consisting of hexadecylamine, N,N-dimethyldodecylamine, methyltrioctylammonium chloride, and dodecyltrimethylammonium chloride.

3. The method of claim 1, wherein the anhydrous organic solvent is selected from toluene, methylene chloride and anhydrous ethanol.

4. A method for forming a graphene oxide aerogel, comprising the following steps: providing an aqueous dispersion of graphene oxide, wherein the aqueous dispersion has a pH of less than 7; adding a reactant comprising an organic amine or a phosphonium salt; stirring the mixture to form a graphene oxide hydrogel; separating the graphene oxide hydrogel; and freeze-drying the graphene oxide to form the graphene oxide aerogel, Wherein the reactant is a compound of formula I XR a R1R2R3(I) wherein X is selected from N and P; Where a is 0 or 1; wherein R, R1, R2 and R3 may be the same or different and are selected from H, alkyl, cycloalkyl, cycloheteroalkyl, aryl, heteroaryl, or wherein two of R, R1, R2 and R3 may form a five-membered ring or a six-membered ring, wherein the five-membered ring or the six-membered ring may be saturated or unsaturated and may contain one or more heteroatoms; but provided that when X is N and a is 0, no more than 2 of R1, R2 and R3 are H; when X is N and a is 1, no more than 3 of R, R1, R2 and R3 are H, and when X is P and a is 1, none of R, R1, R2 and R3 is H.

5. The method of claim 4, wherein the reactant reacts with graphene oxide via electrostatic interaction.

6. The method of claim 4, wherein the reactant is an organic amine selected from the group consisting of hydrophobic amines, polymeric amines, and spirotetramines.

7. The method of claim 6, wherein the organic amine is selected from 1,12-diaminododecane and tetrakis(4-aminophenyl)methane.

8. The method of claim 4, further comprising the step of reducing the graphene oxide aerogel to form a graphene aerogel.

9. A graphene aerogel prepared by the method according to claim 8.

10. A supercapacitor, comprising: Anode and cathode, an electrolyte ionically connecting the anode and the cathode; and an ion-permeable membrane physically separating the anode from the cathode; At least one of the anode and the cathode comprises the graphene aerogel of claim 9.

11. The supercapacitor of claim 10, wherein the electrolyte is selected from aqueous electrolytes and organic electrolytes.

12. The ultracapacitor of claim 10, wherein the ion-permeable separator is an electrically insulating material.

13. The supercapacitor of claim 12, wherein the ion permeable separator is selected from the group consisting of capacitor paper, cellulose paper, nonwoven porous polymer, woven glass fiber, and porous woven ceramic fiber.

14. The supercapacitor of claim 13, wherein the ion permeable separator is a nonwoven porous polymer selected from the group consisting of polyamide, polypropylene, polyethylene, polytetrafluoroethylene, polyvinyl chloride, and combinations thereof.

15. The supercapacitor of claim 10, wherein the electrolyte and the separator are a single material selected from a solid electrolyte and a gel electrolyte.

16. The ultracapacitor of claim 10, wherein the anode and the cathode both comprise graphene aerogel.

17. An electrode comprising a conductive substrate and the graphene aerogel of claim 9.

18. A battery comprising the electrode of claim 17.

19. A method for purifying graphene oxide, comprising the following steps: dispersing the graphene oxide to be purified in an aqueous solution having a pH in the range of 6 to 1.5; Add the reactant of formula (I) XR a R1R2R3(I) wherein X is selected from N and P; Where a is 0 or 1; wherein R, R1, R2 and R3 may be the same or different and are selected from H, alkyl, cycloalkyl, cycloheteroalkyl, aryl, heteroaryl, or wherein two of R, R1, R2 and R3 may form a five-membered ring or a six-membered ring, wherein the five-membered ring or the six-membered ring may be saturated or unsaturated and may contain one or more heteroatoms; provided, however, that when X is N and a is 0, no more than 2 of R1, R2 and R3 are H; when X is N and a is 1, no more than 3 of R, R1, R2 and R3 are H, and when X is P and a is 1, none of R, R1, R2 and R3 is H; stirring the mixture to form a graphene oxide hydrogel; isolating the graphene oxide hydrogel; and The graphene oxide hydrogel is washed to produce purified graphene oxide.

20. The method of claim 19, wherein the reactant is a hydrophobic amine.

21. The method of claim 20, wherein the hydrophobic amine is selected from N,N-dimethyldodecylamine, methyltrioctylammonium chloride, and dodecyltrimethylammonium chloride.

22. The method of claim 19, wherein the washing step is performed using water or an acidic aqueous solution.

23. The method of claim 19, further comprising the step of acidifying the graphene oxide after the washing step.

24. The method of claim 19, further comprising the step of dispersing the purified graphene oxide in a solvent, wherein the solvent is selected from the group consisting of water, an acidic solution, and an alkaline solution.

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