JP2018514371A - Anion exchange membrane and method for producing the same - Google Patents

Abstract

The anion exchange membrane includes oxidized carbon having an oxygen-containing functional group. At least some of the hydrogen cations of the oxygen-containing functional group are replaced with alkali or alkaline earth metal cations so that the membrane has anion conductivity. The alkali or alkaline earth metal cation preferably comprises Li + and / or K +, and the oxidized carbon suitably comprises single or multiple layers of graphene oxide. [Selection] Figure 2

Description

  The present invention relates to an anion exchange membrane and a method for producing the same. In particular, the present invention has high ionic conductivity, high mechanical strength, and high gas barrier properties, and is a polymer electrolyte membrane fuel cell (PEMFC) (Polymer Electrolyte Fuel Cell). The present invention also relates to an oxidized carbon-based anion exchange membrane that can be used in an electrolytic cell (or electrolytic cell), a battery, a humidifier, and the like, and a method for producing the same.

  Fuel cells have high efficiency and power density, and when hydrogen is used as fuel, the only exhaust gas is water, which is a promising energy supply technology in the future. Alkaline fuel cells (AFC) have several advantages over proton-conducting acid-based fuel cells (eg, Nafion-based fuel cells (Nafion is a registered trademark of EI du Pont de Nemours & Co., Inc.)) There is a point. The reaction rate at the cathode is much faster, thus allowing the use of inexpensive non-noble metal catalysts (eg, nickel for the anode and silver for the cathode). In addition, the alkaline environment hardly corrodes the catalyst and promotes oxidation of methanol. AFC has less fuel crossover than Nafion-based solid polymer electrolyte membrane fuel cells (PEMFC). Furthermore, higher alcohols such as ethanol and propanol can be used as fuel, thereby improving the energy density of the system.

However, AFC can be problematic because it mainly uses a liquid electrolyte. Aqueous electrolyte liable to be poisoned by CO _2, therefore, AFC is usually driven by pure O _2, the cost is increased thereby. Another problem is gas electrode flooding. Accordingly, there is great interest in replacing liquid electrolytes with anion exchange membranes (or anion conducting electrolyte membranes) with good mechanical and chemical stability and good ionic conductivity. Although several anion exchange membranes are available, their main problem is somewhat lower conductivity and mechanical strength compared to the proton conducting membranes Nafion or other proton conducting electrolyte membranes.

  On the other hand, JP-A-2014-216059 (Patent Document 1) proposes to use graphene oxide as a solid electrolyte of a secondary battery. As schematically shown in FIG. 1A, graphene oxide is a single layer of graphite covered with oxygen-containing functional groups (sometimes referred to as oxygen functional groups or oxygen groups) containing carboxylic acid groups, hydroxyl groups, epoxy groups, and the like. Made of carbon. Graphene oxide can be produced in large quantities, can be dispersed in water, and has a high mechanical strength film that exhibits high impermeability to anything other than water (see scanning electron microscope image shown in FIG. 1B) ) Can be formed. Surface oxygen functional groups can be used to further chemically functionalize the surface to form new compounds. These characteristics make graphene oxide an ideal film for use in film technology.

  However, Patent Document 1 only discloses graphene oxide having proton conductivity, and Patent Document 1 has no description about modifying graphene oxide so as to have anion conductivity.

  U.S. Pat. No. 8,715,610 (Patent Document 2) discloses a method for producing a stable graphene dispersion, which includes reducing a graphene oxide dispersion by adding a reducing agent in the presence of a base. It is disclosed. However, Patent Document 2 does not disclose anything about the process of modifying graphene oxide so as to have anion conductivity.

JP 2014-216059 A US Pat. No. 8,715,610

  In light of these prior art problems, the main object of the present invention is to provide a carbon oxide based anion exchange membrane and a method for easily forming such an anion exchange membrane.

  The second object of the present invention is to provide an anion exchange membrane having high ion conductivity, high mechanical strength and / or high gas barrier properties, and a method for easily forming such an anion exchange membrane. is there.

  In order to achieve the above object, according to one aspect of the present invention, an oxygenated carbon having an oxygen-containing functional group is included, and at least a part of the hydrogen cation of the oxygen-containing functional group is substituted with an alkali or alkaline earth metal cation. An anion exchange membrane is provided. This provides an oxidized carbon-based anion exchange membrane.

Preferably, at least a part of the hydrogen cation of the oxygen-containing functional group is substituted with an alkali metal cation, and the alkali metal cation preferably contains at least one of Li ⁺ and K ⁺ . These cations are easy to replace the hydrogen cation of the oxygen-containing functional group of oxidized carbon, and contribute to the realization of an oxidized carbon-based anion exchange membrane having high ionic conductivity.

  According to another aspect of the present invention, there is provided a method for producing an anion exchange membrane comprising treating an oxidized carbon having an oxygen-containing functional group with a basic solution. According to this method, an oxidized carbon-based anion exchange membrane can be easily formed.

  Preferably, the base of the basic solution is at least one selected from the group consisting of alkali and alkaline earth metal hydroxides, oxides, hydrides, and carbonates, and more preferably alkali metal water. It is at least one selected from the group consisting of oxides, oxides, hydrides and carbonates. The alkali metal preferably contains at least one of Li and K. The cation contained in such a basic solution easily replaces the hydrogen cation of the oxygen-containing functional group of the oxidized carbon, and contributes to the realization of an oxidized carbon-based anion exchange membrane having high ionic conductivity.

  According to still another aspect of the present invention, there is provided an anion exchange membrane comprising oxidized carbon having an oxygen-containing functional group, wherein the oxidized carbon is treated with a basic solution. Oxidized carbon treated with a basic solution has anion conductivity and thus provides an oxidized carbon-based anion exchange membrane.

  Preferably, the base of the basic solution is at least one selected from the group consisting of alkali and alkaline earth metal hydroxides, oxides, hydrides, and carbonates, and more preferably alkali metal water. It is at least one selected from the group consisting of oxides, oxides, hydrides and carbonates. The alkali metal preferably contains at least one of Li and K. The cation contained in such a basic solution easily replaces the hydrogen cation of the oxygen-containing functional group of the oxidized carbon, and contributes to the realization of an oxidized carbon-based anion exchange membrane having high ionic conductivity.

  In a preferred embodiment of the present invention, the oxidized carbon in the anion exchange membrane or the manufacturing method thereof includes at least one of graphene oxide, graphite oxide, oxidized carbon nanotube, and oxidized fullerene, and particularly preferably a single layer or a plurality of layers. The layer contains graphene oxide. Since such oxidized carbon has high mechanical strength and high gas barrier properties, the anion exchange membrane formed from them also has high mechanical strength and high gas barrier properties. Furthermore, by replacing the hydrogen cation with an alkali metal or alkaline earth metal, the gas barrier properties of oxidized carbon are improved.

  The oxygen-containing functional group usually includes at least one of a carboxylic acid group, a hydroxyl group, and an epoxy group.

FIG. 1A is a diagram schematically illustrating a chemical structure of graphene oxide having various functional groups including a carboxylic acid functional group. FIG. 1B is a scanning electron microscope image of a cross section of the graphene oxide film. FIG. 2 is a diagram schematically illustrating cation exchange that occurs in the graphene oxide reforming process according to an embodiment of the present invention. 3A is a graph showing a wide span X-ray photoelectron spectrum of graphene oxide after potassium cation exchange in Example 1. FIG. FIG. 3B is a graph showing an X-ray photoelectron spectrum with an electronic binding energy in the range of 280 to 292 eV, showing the C1s signal. FIG. 3C is a graph showing an X-ray photoelectron spectrum with an electronic binding energy in the range of 526 to 538 eV, and shows an O1s signal. FIG. 3D is a graph showing an X-ray photoelectron spectrum with an electronic binding energy in the range of 290 to 298 eV, and shows a K2p signal. FIG. 4A is a graph showing the dependence of the anion conductivity of the graphene oxide film obtained in Example 1 on humidity with respect to various temperatures. FIG. 4B is an Arrhenius plot showing the activation energy of the graphene oxide film obtained in Example 1 with respect to various relative humidity. FIG. 4C is a graph showing the dependency of the activation energy of the graphene oxide film obtained in Example 1 on humidity. FIG. 5A shows gas chromatography-thermal conductivity detection of hydrogen permeated through four different types of membranes (15 and 40 μm thick conventional graphene oxide and 15 and 40 μm thick graphene oxide modified by cation exchange). It is a graph which shows a device (GC-TCD) signal. FIG. 5B is a bar chart showing the permeability and permeance of hydrogen through four different types of membranes. FIG. 6 is a graph showing the relationship between the potassium content of the graphene oxide film obtained in Example 1 and the stirring time. FIG. 7A is a graph showing the dependence of the anion conductivity of the graphene oxide film obtained in Example 2 on humidity with respect to various temperatures. FIG. 7B is an Arrhenius plot showing the activation energy of the graphene oxide film obtained in Example 2 with respect to various relative humidity. FIG. 7C is a graph showing the dependency of the activation energy of the graphene oxide film obtained in Example 2 on humidity. FIG. 8 is a graph showing the ionic conductivity of the graphene oxide film modified with LiOH obtained in Example 3 with respect to various temperatures and humidity. FIG. 9A is a schematic diagram showing an anion conductive membrane device (alkaline fuel cell) using a treated graphene oxide-based membrane as an electrolyte. FIG. 9B is a graph showing polarization curves and power density data of an alkaline fuel cell formed using a graphene oxide anion exchange membrane. FIG. 10A is a schematic diagram showing an alkaline membrane electrolytic cell to which the anion exchange membrane of the present invention can be applied. FIG. 10B is a schematic diagram showing an alkaline membrane redox flow battery to which the anion exchange membrane of the present invention can be applied. FIG. 10C is a schematic diagram showing an alkaline membrane wastewater treatment apparatus to which the anion exchange membrane of the present invention can be applied. FIG. 10D is a schematic diagram showing an alkaline membrane seawater desalination apparatus to which the anion exchange membrane of the present invention can be applied.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In a preferred embodiment of the present invention, graphene oxide is treated in a basic solution containing alkali and / or alkaline earth cations (eg, but not limited to Li ⁺ , K ⁺ , Na ⁺ , Ca ²⁺ ). Thus, an anion exchange membrane is synthesized. As described above with reference to FIG. 1A, graphene oxide has oxygen-containing functional groups such as carboxylic acid functional groups or hydroxyl functional groups bonded to the surface. When graphene oxide is treated with a basic solution, cation exchange occurs in the basic solution in some of the oxygen-containing functional groups of graphene oxide. That is, the hydrogen cation contained in the oxygen-containing functional group of graphene oxide is replaced by an alkali or alkaline earth metal cation in the basic solution, and an oxygen-alkali metal (or alkaline earth metal) bond is formed.

As is well known, for example, when a carboxylic acid is reacted with an alkali in an aqueous solution, for example, the following spontaneous neutralization reaction occurs:
HCO ₂ H (aq) + NaOH (aq)-> HCO ₂ Na (aq) + H ₂ O (l)
CH ₃ CO ₂ H (aq) + KOH (aq)-> CH ₃ CO ₂ K (aq) + H ₂ O (l)

That is, a cation exchange reaction occurs, and a hydrogen cation in the carboxylic acid functional group is replaced with an alkali cation (for example, Li ⁺ , K ⁺ , Na ⁺ ) to form a carboxylate. The same or similar cation exchange reaction occurs for the oxygen-containing functional groups of graphene oxide in the presence of a strong base.

In an example in which graphene oxide having carboxylic acid groups (and hydroxyl functional groups) immobilized on the surface thereof is treated with a basic solution containing an alkali cation having a pH of 12, for example, a similar neutralization reaction occurs. That is, the alkali cation in the basic solution reacts with the carboxylic acid group, whereby the hydrogen cation in the carboxylic acid group is replaced with the alkali cation to form a new compound. FIG. 2 is a schematic diagram exemplarily showing cation exchange in a carboxylic acid group of graphene oxide (carbon oxide), in which the base is LiOH and the alkali cation is Li ⁺ .

When a film is formed from graphene oxide treated with a basic solution and dried, alkali cations (or alkaline earth cations) become relatively immobile and improve the mobility of OH ⁻ ions in a basic environment. . In this way, by treating the graphene oxide in a basic solution to cause cation exchange in the graphene oxide, the graphene oxide has anion conductivity, and the membrane formed therefrom is an anion exchange membrane. Become.

  The graphene oxide-based anion exchange membranes formed in this way exhibit higher mechanical strength and higher gas barrier properties and are comparable (potentially) compared to currently commercially available anion exchange membranes. Higher conductivity), lower cost and higher workability.

  In the above-described process, graphene oxide having various oxygen concentrations can be used (for example, but not limited to, 1 to 50 atomic percent (at%)). In addition, graphene oxide can be dispersed in a solvent (for example, but not limited to, water, ethanol, and the like), and graphene oxide dispersions with various graphene oxide concentrations can be used. The graphene oxide concentration is preferably greater than about 0.1 mg / ml, more preferably from about 1 to about 10 mg / ml. If the graphene oxide concentration is too low, it will take too much time for industrial processing to evaporate or filter a large amount of solvent to obtain a graphene oxide-based anion exchange membrane, or excessive energy consumption will be required. On the other hand, if the concentration is too high, the viscosity of the graphene oxide dispersion becomes too high, and it becomes difficult to stir, spray, print, apply, and filter the graphene oxide dispersion, or anion exchange obtained from the graphene oxide dispersion The film pressure of the film tends to be non-uniform.

  In embodiments of the present invention, alkali and alkaline earth metal salts (or bases) that can be used in a basic solution for cation exchange are, for example, without limitation, lithium, sodium, potassium, rubidium. , Hydroxides, oxides, hydrides or carbonates of alkali or alkaline earth metals such as cesium, beryllium, magnesium, calcium, strontium, barium and radium. A mixture of these may be used.

  In the embodiment of the present invention, a graphene oxide dispersion (for example, a graphene oxide concentration of 5 mg / ml and an oxygen content of 20 at%) is used. The anion exchange membrane is formed by a chemical reaction between graphene oxide in an aqueous dispersion and a basic solution such as an aqueous potassium hydroxide solution.

  Basic solutions containing various concentrations of alkali or alkaline earth metal salts (eg, hydroxide) may be mixed with the graphene oxide dispersion at various temperatures for various times. During the mixing process, alkali (or alkaline earth) cation exchange occurs and the surface functional groups of graphene oxide are modified to include alkali or alkaline earth cations. At this time, if a reducing agent such as hydrazine is used, most of the oxygen-containing functional group contained in graphene oxide is removed (see Patent Document 2), so it is desirable not to use a reducing agent.

  The graphene oxide anion exchange membrane can be produced by filtering the alkali-treated graphene oxide dispersion with, for example, a polycarbonate filter. Various thicknesses of electrolyte layers (or anion exchanges) can be sprayed, printed, or applied to various substrates (for example, but not limited to, carbon paper, silicon wafers, glass, or plastics). It is also possible to form a film. In a preferred embodiment of the present invention, the membrane is formed by vacuum filtration over a polycarbonate filter. After filtration, the membrane is dried, for example for 48 hours at room temperature, and peeled off the filter.

  The thickness of the anion exchange (or electrolyte) membrane formed from the modified graphene oxide can be easily changed based on the concentration and volume of the dispersion. For example, although not limited, an electrolyte membrane having a thickness in the range of 5 μm to 80 μm is usually used. In one embodiment of the present invention, the thickness of the electrolyte membrane used for the fuel cell is, for example, 15 μm.

<Example>
The following examples are intended to illustrate the present invention and should not be construed as limiting.

  The ionic conductivity (mS / cm) of the sample membrane obtained in each example was obtained as follows.

Through-plane ionic conductivity was determined using a membrane test apparatus (Scribner Associates Inc. MTS 740) with an impedance analyzer (Solatron SI1260). Measured in a frequency range of 30 MHz to 10 Hz with an AC amplitude of 100 mV with a setting of 2 electrodes / 4 terminals (the latter is for reducing lead wire resistance) for a 10 × 30 mm ² thick film of about 40 μm thickness Went. Gas diffusion electrode (E-TEK, ELAT for high temperature, 140E-W, 18 × 5mm ² ) was attached to platinum electrode using conductive carbon paint (SPI Supplies, colloidal graphite, Part # 05006-AB), A graphene oxide-based film sample was placed between the electrodes. The cell was compressed at a pressure of 1.074 MPa in order to obtain good electrode contact. The impedance was measured at a temperature of 30 ° C. to 80 ° C. while isothermally changing at a relative humidity (RH) of 100 to 0%. Prior to impedance measurements, the samples were pretreated with 100% RH for 4 hours, and also pretreated for 1 hour between measurements for different RH. From the obtained film resistance R (Ω), thickness L (cm), and effective measurement area A (0.55 cm ² ) between overlapping electrodes, the conductivity (usually represented by the Greek letter σ) is expressed using the following equation: Calculated.
σ = L / (R · A)

<Example 1: Graphene oxide film modified with KOH>
210.8 mg of potassium hydroxide (KOH) was dissolved in 43.01 ml of a graphene oxide aqueous dispersion (graphene oxide concentration 5 mg / ml, oxygen content 20 at%), and conditions were set at 500 rpm for 24 hours at room temperature using a magnetic stirrer. And stirred. The resulting dispersion (ie basic solution) had a pH of 12.5. This was vacuum filtered on a polycarbonate filter, dried, and peeled to obtain a membrane. The film used for the conductivity measurement had a thickness of about 40 μm. The membranes for the hydrogen permeability test were about 15 and 40 μm thick, respectively, and were measured against two unmodified graphene oxide membranes of about 15 and 40 μm thick, respectively.

  According to X-ray photoelectron spectroscopy (XPS) (FIGS. 3A-3D), the carbon content is 81.6 at%, the oxygen content is 16.5 at%, and the potassium content is 5.7 at%, and the ionic conductivity (anion conductivity) ) Showed a strong increasing tendency with increasing humidity and temperature (FIG. 4A). The highest conductivity was 6.1 mS / cm at 70 ° C. The activation energy decreased with decreasing humidity, ranging from 0.44 eV at 100% RH to 0.01 eV at 0% RH (FIGS. 4B and 4C). The activation energy at 100% RH was close to the activation energy of the commercially available Tokuyama A201 anion exchange membrane (Tokuyama Corporation, Japan).

  In order to confirm the gas barrier characteristics of the modified graphene oxide film obtained as described above, a hydrogen permeability test was performed. The two modified graphene oxide films prepared for the hydrogen permeability test were 15 and 40 μm thick, respectively. For comparison, they were compared with two unmodified graphene oxide films having thicknesses of 15 and 40 μm, respectively.

Using a dry gas barrier analyzer (GTR-11A / 31A, GTR Tech, Japan), dry hydrogen permeation rate (gas permeation unit (GPU)) passing through these membranes (diameter 1 cm, area 0.785 cm ² ). And measured at a constant temperature of 30 ° C. This device has an automatic gas sampling unit connected to a gas chromatograph equipped with a thermal conductivity detector. The total pressure difference between the feed side and the sweep side of the membrane was 200 kPa. The sample collection time after evacuating the sweep side of the membrane was 30 minutes. The hydrogen permeability (or permeation rate) of a graphene oxide film functionalized by KOH treatment is about one-fifth that of a pure (ie, unmodified) graphene oxide film. It shows that the gas barrier properties were improved by the treatment (FIGS. 5A and 5B). In FIG. 5B, the permeability does not depend on the pressure but depends on the thickness, and the transmittance does not ideally depend on the thickness.

  Further, the potassium content of the film formed from the modified graphene oxide after 10 minutes, 30 minutes and 24 hours of alkaline cation exchange reaction time was measured using XPS (FIG. 6). There is no trend of potassium content with increasing reaction time, indicating that the cation exchange reaction occurs spontaneously very rapidly at room temperature, as reported in the literature. Therefore, depending on various conditions such as the amount of graphene oxide dispersion, the amount of alkali or alkaline earth metal salt dissolved in it (or the pH of the basic solution), the stirring speed, etc., the treatment with the basic solution of graphene oxide It can be considered that the cation exchange reaction process can be completed in a few seconds even when the process is carried out on a mass production scale. In addition, the value (about 5.0 thru | or 7.5 at%, FIG. 6) of the potassium content measured here was a value close | similar to the potassium content (5.7 at%) observed by the previous film | membrane.

Example 2: KOH-modified graphene oxide film
98.6 mg of potassium hydroxide (KOH) was dissolved in 40.24 ml of graphene oxide dispersion (graphene oxide concentration 5 mg / ml, oxygen content 20 at%). This corresponds to about half the KOH concentration compared to Example 1. This was stirred at 500 rpm for 24 hours at room temperature. The resulting dispersion had a pH of 11.3. Six membranes were formed from this modified graphene oxide dispersion by vacuum filtration (four 5 ml dispersions and two 10 ml dispersions). The thickness of the film used for ion conductivity measurement was 40 μm. The potassium content measured by XPS was 1.9 at%.

  Ionic conductivity increased with humidity and temperature (FIG. 7A). The highest conductivity was 5.3 mS / cm at 70 ° C. This value is comparable to a commercially available anion exchange membrane currently on the market (for example, a thickness direction conductivity of 8-12 mS / cm for Tokuyama A201 membrane). The activation energy decreased with decreasing humidity, ranging from 0.38 eV at 100% RH to 0.04 eV at 0% RH (FIGS. 7B and 7C).

  The ionic conductivity of Example 1 is higher than that of Example 2, indicating that the ionic conductivity depends on the concentration of KOH used in the cation exchange reaction. In order to achieve sufficient ion (anion) conductivity in the modified graphene oxide film, the concentration of KOH in the graphene oxide dispersion in which KOH is dissolved is preferably greater than about 1 mM, more preferably from about 10 mM to About 1M. In other words, the pH of the graphene oxide dispersion in which KOH is dissolved is preferably about 11, more preferably about 12 to about 14. The reaction between graphene oxide and KOH is saturated at a KOH concentration at which all oxygen-containing functional groups on the graphene oxide react and no further reaction occurs. Therefore, it is considered preferable that the concentration of KOH does not greatly exceed such a concentration.

<Example 3: LiOH-modified graphene oxide film>
In Example 3, potassium hydroxide (KOH) was replaced with lithium hydroxide (LiOH) to show that the alkali cation exchange method can be widely applied regardless of the specific cation involved in the reaction. LiOH was reacted with graphene oxide in the dispersion for 24 hours. In the modified graphene oxide sample, 0.55 at% Li was present as measured by XPS. This value is slightly lower than that of KOH, but can be explained by the fact that LiOH is a weaker base than KOH. The ionic conductivity of graphene oxide modified with Li was lower than that observed with graphene oxide treated with KOH at all temperatures (about one third at 30 ° C.) (FIG. 8). This can be attributed to a change in activation energy of OH ⁻ ions due to differences in alkalinity between two different alkali salts, or differences in electronegativity of alkali cations. Thus, the anion exchange membrane based on embodiment of this invention can be formed using not only KOH but various alkali metal (or alkaline-earth metal) salts.

<Example 4: Fuel cell>
A membrane treated electrode assembly (MEA) was formed using a base-treated graphene oxide based anion exchange membrane having a thickness of 15 μm obtained by the process described in Example 1. Also, Pt / C electrocatalyst (Tanaka Kikinzoku Kogyo Co., Ltd., 46.2 wt% Pt) is mixed with 5 wt% anion conductive polymer electrolyte solution (Tokuyama Co., Ltd.), ethanol (Chameleon), and deionized water. A catalyst ink was prepared. The catalyst ink was stirred for 10 hours and then subjected to ultrasonic treatment for 30 minutes before use (Ultrasonic Disperser UH-600 manufactured by SMT). This catalyst ink is sprayed onto a modified graphene oxide film having anion conductivity with a spray device (spray apparatus C-3J manufactured by Nordson Co., Ltd.) using a mask, and 0.5 cm ^{2 on} both sides of the graphene oxide film. A size electrode was formed. The catalyst filling amount of each electrode was 0.3 mg Pt / cm ² . A water repellent carbon paper (EC-TP1-060T) gas diffusion layer (GDL) was precisely placed on the electrocatalyst layer. As a result, a graphene oxide-membrane electrode assembly (GO-MEA) as shown in FIG. 9A is formed. The formed GO-MEA was placed in a single cell test holder (1 cm ² ) and placed in a homemade fuel cell test device. The alkaline fuel cell thus obtained was placed in an oven and heated to 30 ° C. Hydrogen and air were allowed to flow at 100 ml / min and 100% RH, and the performance of the cell was examined using a potentiostat (Solartron SI 1287). As a result, the open circuit voltage was 0.88 V, and the maximum power density was 1.13 mW / cm ² at a current density of 2.6 mA / cm ² (FIG. 9B). As described above, the graphene oxide-based anion exchange membrane according to the embodiment of the present invention can be suitably used as an electrolyte of an alkaline fuel cell.

<Example 5: Other uses>
In addition to its use as an electrolyte in alkaline fuel cells, the graphene oxide based anion exchange membrane according to the present invention can be used in other membrane utilization technologies. For example, graphene oxide-based anion exchange membranes include anion conducting electrolytes in microbial fuel cells or enzyme fuel cells, anion exchange membranes (AEM) in alkaline polymer electrolyte electrolytic cells (FIG. 10A), ion exchange membranes in redox flow batteries ( IEM) (FIG. 10B), an ion exchange membrane (FIG. 10C) of an alkaline membrane wastewater treatment apparatus, and an AEM (FIG. 10D) of an alkaline membrane seawater desalination apparatus. Furthermore, the graphene oxide-based anion exchange membrane according to the present invention can be used for reverse electrodialysis batteries, alkaline batteries, metal-air batteries, gas barrier applications, humidification applications, and the like.

  Although the present invention has been described with reference to preferred embodiments thereof, it is to be understood by those skilled in the art that the present invention is not limited to these embodiments and that various modifications can be made without departing from the scope of the present invention. It is self-explanatory.

  For example, although graphene oxide is used in the above embodiment, other oxidized carbon such as graphite oxide, oxidized carbon nanotube, or oxidized fullerene, preferably having high mechanical strength and / or high gas barrier properties, is used instead of graphene oxide. It can also be used.

  Moreover, in the said embodiment, the anion exchange membrane was produced by filtering the base-processed graphene oxide dispersion liquid on a polycarbonate filter. However, an anion exchange membrane can also be formed by printing, pouring, compressing or spraying a dispersion, ink or paint containing base-treated graphene oxide. Furthermore, the anion exchange membrane may be a complex with a polymer, fullerene, nanotube, or the like. Such a composite can be obtained by mixing an alkali-modified graphene oxide dispersion with these materials before film formation. Furthermore, you may perform the further chemical surface functionalization process suitably with respect to the base-treated graphene oxide as needed.

Claims (20)

  An anion exchange membrane comprising an oxidized carbon having an oxygen-containing functional group, wherein at least a part of hydrogen cations of the oxygen-containing functional group are substituted with an alkali or alkaline earth metal cation.   The anion exchange membrane according to claim 1, wherein at least a part of the hydrogen cations of the oxygen-containing functional group is substituted with an alkali metal cation. The anion exchange membrane according to claim 2, wherein the alkali metal cation includes at least one of Li ⁺ and K ⁺ .   The anion exchange membrane according to claim 1, wherein the oxidized carbon includes at least one of graphene oxide, graphite oxide, oxidized carbon nanotube, and oxidized fullerene.   The anion exchange membrane according to claim 1, wherein the carbon oxide includes a single layer or a plurality of layers of graphene oxide.   The anion exchange membrane according to claim 1, wherein the oxygen-containing functional group includes at least one of a carboxylic acid group, a hydroxyl group, and an epoxy group.   A method for producing an anion exchange membrane, comprising treating oxidized carbon having an oxygen-containing functional group with a basic solution.   The anion exchange membrane according to claim 7, wherein the base of the basic solution is at least one selected from the group consisting of hydroxides, oxides, hydrides and carbonates of alkali and alkaline earth metals. Method.   The method for producing an anion exchange membrane according to claim 7, wherein the base of the basic solution is at least one selected from the group consisting of alkali metal hydroxides, oxides, hydrides, and carbonates.   The method for producing an anion exchange membrane according to claim 9, wherein the alkali metal contains at least one of Li and K.   The method for producing an anion exchange membrane according to claim 7, wherein the oxidized carbon includes at least one of graphene oxide, graphite oxide, oxidized carbon nanotube, and oxidized fullerene.   The method for producing an anion exchange membrane according to claim 7, wherein the oxidized carbon includes a single layer or a plurality of layers of graphene oxide.   The method for producing an anion exchange membrane according to claim 7, wherein the oxygen-containing functional group includes at least one of a carboxylic acid group, a hydroxyl group, and an epoxy group.   An anion exchange membrane comprising oxidized carbon having an oxygen-containing functional group, wherein the oxidized carbon is treated with a basic solution.   The anion exchange membrane according to claim 14, wherein the base of the basic solution is at least one selected from the group consisting of hydroxides, hydrides, oxides and carbonates of alkali and alkaline earth metals.   The anion exchange membrane according to claim 14, wherein the base of the basic solution is at least one selected from the group consisting of alkali metal hydroxides, oxides, hydrides, and carbonates.   The anion exchange membrane according to claim 16, wherein the alkali metal contains at least one of Li and K.   The anion exchange membrane according to claim 14, wherein the oxidized carbon includes at least one of graphene oxide, graphite oxide, oxidized carbon nanotube, and oxidized fullerene.   The anion exchange membrane according to claim 14, wherein the carbon oxide includes a single layer or a plurality of layers of graphene oxide.   The anion exchange membrane according to claim 14, wherein the oxygen-containing functional group includes at least one of a carboxylic acid group, a hydroxyl group, and an epoxy group.