JP4813218B2 - Proton conducting electrolyte and fuel cell - Google Patents

Description

  The present invention relates to a proton conductive electrolyte suitable as a fuel cell material and a fuel cell using the same.

As electrolytes for fuel cells, fluorinated polyethylene sulfonic acid membranes, which are also used in applications such as salt electrolysis, seawater desalination, and water treatment, are widely used for reasons such as excellent proton conductivity and chemical stability. ing. For example, a Nafion film, a Flemion film, an Aciplex film, a Dow film (all of which are trade names) are commercially available. However, since these electrolyte membranes contain fluorine, they are not preferable from an environmental viewpoint and are expensive.
As electrolyte membranes not containing fluorine, polystyrene sulfonic acid for water treatment ion exchange resins and ion exchange membranes, and sulfonated aromatic polymers for fuel cells have been proposed (Patent Document 1, Non-Patent Document 1). . However, these have insufficient heat resistance and chemical stability for practical use as a fuel cell.

In addition, from the viewpoint of power generation efficiency and system efficiency of the fuel cell and long-term durability of the constituent members, in particular, at an operating temperature of about 100 ° C. to 200 ° C., operating conditions of no humidification or low humidity of 50% or less relative humidity. However, there is a demand for a fuel cell in which good power generation performance can be stably obtained over a long period of time. However, even when the above material is used for the electrolyte membrane, it is difficult to obtain stable performance.
Japanese National Patent Publication No. 11-502245 T.A. Kobayashi, M .; Rikukawa, K .; Sanui, N .; Ogata, Solid State Ionics, 106, 1998, p. 219

  In order to improve the power generation performance of the fuel cell, there is a method of improving proton conductivity by increasing the introduction rate of functional groups into the aromatic polymer used for the material of the electrolyte membrane. However, the higher the functional group introduction rate, the lower the flexibility when forming an electrolyte membrane, resulting in a fragile membrane.

  The present invention has been made in view of the above circumstances, is excellent in proton conductivity and flexibility after film formation, and can stably obtain good power generation performance for a long period of time even under the above operating conditions. An object of the present invention is to provide a proton conductive electrolyte suitable as a material for a polymer electrolyte fuel cell, and a fuel cell using the same.

  As a result of intensive studies to solve the above problems, the present inventor obtained a high molecular weight polymer capable of film formation, and a polyamic acid that maintains flexibility after film formation even when a sulfamide group is introduced at a high introduction rate. As a precursor, it was found that a polyamic acid derivative having excellent proton conductivity and flexibility was obtained, and the present invention was completed.

That is, the proton conductive electrolyte of the present invention is characterized in that it contains a polyamic acid derivative in which a carboxylic acid or a sulfamic acid group is introduced as a side chain in a polyamide containing an alkylene group in the main chain.

  The proton conductive electrolyte of the present invention is preferably the polyamic acid derivative represented by the following general formula (1).

（但し、一般式（１）中、Ａｒは芳香族環又は芳香族環を含む基であり、Ｒはアルキレン基であり、ａ，ｂは、０≦ａ≦２，０≦ｂ≦２，且つａ＋ｂ＝２を満たす数であり、ｎは平均重合度であって１００〜３０００００の整数である。）

(In the general formula (1), Ar is an aromatic ring or a group containing an aromatic ring, R is an alkylene group , a and b are 0 ≦ a ≦ 2, 0 ≦ b ≦ 2, and (It is a number satisfying a + b = 2, and n is an average degree of polymerization and is an integer of 100 to 300,000.)

Moreover, the proton conductive electrolyte of this invention can be set as the structure by which R in the polyamic-acid derivative shown by the said General formula (1) was made into the alkylene group whose carbon number is 3-12.

  In addition, the proton conductive electrolyte of the present invention can be configured such that the polyamic acid derivative is a compound in which all or part of the side chain carboxylic acid group of the polyamic acid is sulfamidated.

  In the proton conductive electrolyte of the present invention, the polyamic acid derivative may be reacted with a triethylamine salt of amidosulfuric acid after all or part of the side chain carboxylic acid group of the polyamic acid is acid chlorideed, and further subjected to cation exchange. What is obtained is preferable.

  The proton conductive electrolyte of the present invention can be configured by mixing the polyamic acid derivative of the present invention and polyvinyl sulfamic acid represented by the following general formula (2).

（但し、一般式（２）中、Ｒ_１はＨ，ＣＯＯＨ，ＣＯＮＨＳＯ_３Ｈ，芳香族基であり、Ｒ_２はＨ，ＣＨ_３であり、Ｒ_３，はそれぞれＣＯＯＨ，アルコキシ基，ハロゲン基，エステル基，芳香族基を示し、ｍ，ｎはそれぞれ平均重合度であって１００〜１００００００の整数である。）

(In the general formula (2), R ₁ is H, COOH, CONHSO ₃ H, an aromatic group, R ₂ is H, CH ₃ , and R ₃ is COOH, an alkoxy group, a halogen group, An ester group and an aromatic group are shown, m and n are average degrees of polymerization, respectively, and are integers of 100 to 1000000.)

  Further, the proton conductive electrolyte of the present invention has a mass ratio of 9/1 to 1/1 / of the polyamic acid derivative of the present invention and the polyvinylsulfamic acid represented by the general formula (2). A range of 1 is preferable.

The fuel cell of the present invention comprises a pair of electrodes and an electrolyte membrane disposed between the electrodes, and the electrolyte membrane is composed of the proton conductive electrolyte of the present invention.
Further, the fuel cell of the present invention may be configured such that the proton conductive electrolyte of the present invention is contained in a part of the electrode.

  According to the present invention, a proton-conducting electrolyte excellent in proton conductivity and flexibility after film formation can be realized by adopting a configuration containing the polyamic acid derivative. Further, by using the proton conductive electrolyte of the present invention as an electrolyte membrane for a fuel cell, the current density is high even when the operating temperature is 100 ° C. or higher and 200 ° C. or lower and no relative humidity is 50% or less, A high-power, long-life polymer electrolyte fuel cell can be provided.

  Hereinafter, the proton conductive electrolyte and the fuel cell of the present invention will be described in detail.

[Proton conducting electrolyte]
"First example (polyamic acid derivative)"
The proton conductive electrolyte of the present invention is characterized in that it includes a polyamic acid derivative in which a carboxylic acid or a sulfamic acid group is introduced as a side chain in a polyamide containing an alkylene group in the main chain.

In the present invention, by including an alkylene group in the main chain of the polyamide, excellent flexibility can be obtained when forming as an electrolyte membrane, and a sulfamic acid group is introduced at a high introduction rate as a side chain of the polyamide. In some cases, a polyamic acid derivative having high proton conductivity is obtained. By comprising such a polyamic acid derivative, a proton conductive electrolyte having excellent proton conductivity and flexibility after film formation can be obtained.

  As the polyamic acid derivative of the present invention, a compound represented by the following general formula (1) is particularly preferable in terms of excellent proton conductivity and flexibility.

上記一般式（１）中、Ａｒは芳香族環又は芳香族環を含む基であり、Ｒはアルキレン基であり、ａ，ｂは、０≦ａ≦２，０≦ｂ≦２，且つａ＋ｂ＝２を満たす数であり、ｎは平均重合度であって１００〜３０００００の整数である。
芳香族環、又は芳香族環を含む基としては、フェニル基、ナフチル基等が挙げられるが、何ら限定されるものでは無い。

In the general formula (1), Ar is an aromatic ring or a group containing an aromatic ring, R is an alkylene group , a and b are 0 ≦ a ≦ 2, 0 ≦ b ≦ 2, and a + b = 2, n is an average degree of polymerization and is an integer of 100 to 300,000.
Examples of the aromatic ring or the group containing an aromatic ring include a phenyl group and a naphthyl group, but are not limited thereto.

R in the polyamic acid derivative (1) is preferably an alkylene group having 3 to 12 carbon atoms.

In the present invention, the polyamic acid derivative is preferably a compound in which all or part of the side chain carboxylic acid group of the polyamic acid is sulfamidated.
Further, as the polyamic acid derivative, a polyamic acid derivative obtained by subjecting all or a part of the side chain carboxylic acid group of the polyamic acid to acid chloride, reacting with amidosulfuric acid triethylamine salt, and further cation exchange should be preferably used. Can do.

The functional group introduction rate: a / a + b of the polyamic acid derivative represented by the general formula (1) is preferably in the range of 80% to 100%. Introduction rate of functional group: If a / a + b is less than 80%, sufficient proton conductivity cannot be obtained.

In the proton conductive electrolyte as described above, when a sulfamic acid group is introduced as a side chain of polyamide at a high introduction rate, flexibility when forming as an electrolyte membrane is lowered, and there is a possibility that a brittle membrane is formed.
In the present invention, because the polyamide main chain contains an alkylene group in the polyamic acid derivative, even when a sulfamic acid group is introduced as a side chain of the polyamide at a high introduction rate, it is formed as an electrolyte membrane. Since the film is excellent in flexibility, it is possible to prevent the film from becoming brittle. Therefore, a proton conductive electrolyte having both excellent proton conductivity and flexibility after film formation can be obtained.
As described above, the proton conductive electrolyte of the present invention can be suitably used as an electrolyte membrane of a fuel cell even when a polyamic acid derivative is used alone.

"Second example (polyamic acid + polyvinylsulfamic acid)"
The proton conductive electrolyte of the present invention can be configured by mixing the polyamic acid derivative of the present invention and polyvinyl sulfamic acid represented by the following general formula (2).

上記一般式（２）中、Ｒ_１はＨ，ＣＯＯＨ，ＣＯＮＨＳＯ_３Ｈ，芳香族基であり、Ｒ_２はＨ，ＣＨ_３であり、Ｒ_３，はそれぞれＣＯＯＨ，アルコキシ基，ハロゲン基，エステル基，芳香族基を示し、ｍ，ｎはそれぞれ平均重合度であって１００〜１００００００の整数である。
芳香族基としては、フェニル基、ナフチル基等が挙げられるが、何ら限定されるものでは無い。

In the general formula (2), R ₁ is H, COOH, CONHSO ₃ H, an aromatic group, R ₂ is H, CH ₃ , and R ₃ is COOH, an alkoxy group, a halogen group, and an ester group, respectively. , Represents an aromatic group, and m and n each represent an average degree of polymerization and an integer of 100 to 1,000,000.
Examples of the aromatic group include a phenyl group and a naphthyl group, but are not limited in any way.

The polyvinylsulfamic acid in the present invention has good solubility by introducing a methylene group as shown in the above general formula (2). Thereby, the introduction rate of the functional group of polyvinylsulfamic acid is increased, and proton conductivity is improved.
Moreover, since polyvinyl sulfamic acid (2) is easy to synthesize | combine with a higher molecular weight, the high molecular weight polyvinyl sulfamic acid which can be formed into a film as a proton-conductive electrolyte film can be obtained.

  The proton conductive electrolyte of the present invention is excellent in that the polyamic acid derivative having excellent proton conductivity and flexibility after film formation is mixed with the polyvinylsulfamic acid (2). In addition to proton conductivity, the flexibility when forming an electrolyte membrane is further improved.

  In the proton conductive electrolyte of the present invention, the ratio of the average degree of polymerization of the polyvinylsulfamic acid copolymer represented by the general formula (2): n / m is in the range of 3/7 to 7/3. Preferably there is. Average polymerization degree: When the ratio of n / m is less than 3/7, sufficient proton conductivity cannot be obtained, and when the ratio of n / m exceeds 7/3, the polymer is dissolved in water.

  Moreover, in this invention, the mixing ratio of the polyamic acid of the said invention and the polyvinyl sulfamic acid represented by the said General formula (2) is the range of 9/1-1/1 by mass ratio. Is preferred. By setting the mixing ratio within the above range, the proton conductivity of the proton conductive electrolyte and the flexibility after film formation can be further improved.

[Proton Producing Electrolyte Manufacturing Method]
(Polyamide acid derivative)
When synthesizing the polyamic acid derivative represented by the general formula (1) used in the proton conductive electrolyte of the present invention, for example, the following method can be used.

When the polyamic acid derivative is synthesized as a sulfamidated polyamide sulfamic acid, it is preferable to carry out by a method of sulfamidating the side chain carboxylic acid of the polyamic acid from the viewpoint of ease of synthesis.
In particular, it is preferable that the side chain carboxylic acid group of the polyamic acid is converted to an acid chloride, reacted with an amidosulfuric acid triethylamine salt, and further subjected to cation exchange.
An example of a synthesis scheme of this polyamidesulfamic acid is shown below.

  As shown in the above synthesis scheme, the polyamic acid of the general formula (5) used as the starting polymer is, for example, a polymer of an aromatic tetraacetic acid dianhydride of the general formula (3) and an aromatic diamine of the general formula (4). It can be produced by condensation. Ar, R, and n in the general formulas (3) to (5) are the same as those in the general formula (1) (target product).

By mixing the polyamic acid (5) and thionyl chloride (SOCl ₂ ) in an amide solvent with stirring at room temperature or low temperature for several hours to 24 hours, the polyamic acid (5) has a side chain carboxylic acid. All or at least a part is converted to an acid chloride group (acid chloride). In the example shown in the general formula (6), only one of the side chain carboxylic acids of the polyamic acid (5) is converted into an acid chloride group and the other remains as a carboxylic acid. Can also be converted to acid chloride groups. Examples of the amide solvent used at this time include N, N′-dimethylacetamide, N, N′-dimethylformamide and the like. After completion of the reaction, the reaction solution is poured into methanol or the like, and the precipitate is filtered and washed to separate the produced polymer (6).

The obtained polymer (6) and amidosulfuric acid triethylamine salt (NH ₂ SO ₃ H · N (C ₂ H ₅ ) ₃ ) were stirred and mixed in an amide solvent at room temperature or low temperature for several hours to 24 hours. By doing so, the polyamide sulfamic acid triethylamine salt of the general formula (7) is synthesized. In the example shown in the general formula (7), only one of the side chains of the polyamic acid (5) that has been converted to an acid chloride by the above reaction is converted to a sulfamate, but as described above, the other side chain If the carboxylic acid is converted to an acid chloride, the other side chain can be converted into a sulfamate. As the amide-based solvent used in this case, the same amide solvent as that used in the acid chloride reaction is used. After completion of the reaction, the reaction solution is poured into methanol or the like, and the precipitate is filtered and washed to separate the produced polymer (7).

  Finally, the resulting solution of the polyamidesulfamic acid triethylamine salt (7) (for example, N, N′-dimethylacetamide solution, etc.) is passed through a cation exchange resin to convert the cation exchange (sulfamide acid salt). Converted to sulfamic acid) and protonated. The treatment liquid is poured into methanol, dichloromethane, chloroform or the like, and the precipitate is filtered and washed to obtain the target polyamic acid derivative represented by the general formula (1).

The polyamic acid derivative (1) of this example has a structure in which a sulfamic acid group is introduced only in a part of the side chain of the polyamic acid as a result of the above reactions. Since each reaction form of the side chain is not limited, it is possible to convert not only a part of the side chain of the polyamic acid but also the entire side chain into a sulfamic acid group, for example.
Further, as described above, a and b in the polyamic acid derivative represented by the general formula (1) are 0 ≦ a ≦ 2, 0 ≦ b ≦ 2, and a + b = 2, and each functional group is Exist in different proportions.

(Polyvinylsulfamic acid)
Examples of the method for synthesizing the polyvinylsulfamic acid represented by the general formula (2) used in the proton conductive electrolyte of the present invention include a method of synthesizing a raw material polymer by sulfamidation.
When the raw material polymer is synthesized by sulfamidation, for example, it can be synthesized by the following method.

First, a raw material polymer having at least COOH as a starting polymer, such as polyacrylic acid, is dissolved in dehydrated N, N′-dimethylformamide (DMF), and then thionyl chloride is gradually added dropwise under a nitrogen atmosphere. The polymer solution is stirred at room temperature for 24 hours.
Next, dehydrated dichloromethane is mixed with a predetermined amount of amidosulfuric acid and triethylamine to form an amidosulfuric acid triethylamine salt. This solution is gradually added dropwise to the polymer solution under a nitrogen atmosphere and stirred at room temperature for 16 hours.
Subsequently, after distilling off the solvent in the reaction solution under reduced pressure at a temperature of 50 ° C., pure water is added to the viscous material, followed by stirring at room temperature for 1 hour. Then, the precipitate is filtered off, washed with pure water, and then heated and vacuum dried at a temperature of 70 ° C. for 24 hours to obtain a light brown powdered polyvinyl sulfamic acid triethylamine salt. This powder of polyvinyl sulfamic acid triethylamine salt is dissolved in DMF and passed through a cation exchange resin for proton exchange. Then, the treatment liquid is concentrated, dropped into pure water to filter out precipitates, washed with pure water, and then heated and dried at 70 ° C. for a whole day and night. Famic acid can be obtained.

  The method for synthesizing polyvinylsulfamic acid used for the proton conductive electrolyte of the present invention is not limited to the above method. For example, a method may be used in which a vinyl monomer is used as a raw material, and a sulfamic acid group is previously introduced into the vinyl monomer before polymerization.

The proton conductive electrolyte of the present invention may contain components other than polyvinyl sulfamic acid and polyamide sulfamic acid as necessary within a range not departing from the gist of the present invention.
For example, in order to increase the strength of the obtained film, a fluorine-containing polymer such as polytetrafluoroethylene can be used in combination as a reinforcing agent.
In addition, a basic nitrogen-containing polymer, oxygen-containing polymer, sulfur-containing polymer, and the like can be used in combination as an ion complex electrolyte.
Further, ortho-phosphoric acid, metaphosphoric acid, polyphosphoric acid and the like can be used together to form a gel electrolyte.

  According to the proton conductive electrolyte of the present invention, a proton conductive electrolyte excellent in proton conductivity and flexibility after film formation can be realized by including the above-described polyamic acid derivative.

"Fuel cell"
In FIG. 1, the schematic diagram of the single cell which comprises the fuel cell of this embodiment is shown. A single cell (fuel cell) 1 shown in FIG. 1 includes an oxygen electrode (electrode) 2, a fuel electrode (electrode) 3, and a proton conductive electrolyte of the present embodiment sandwiched between the oxygen electrode 2 and the fuel electrode 3. A membrane 4 (hereinafter may be referred to as an electrolyte membrane 4), an oxidant distribution plate 5 having an oxidant flow path 5a disposed outside the oxygen electrode 2, and a fuel disposed outside the fuel electrode 3. It is composed of a fuel distribution plate 6 having a flow path 6a, and operates under conditions of an operating temperature of 100 ° C. to 200 ° C. and a humidity of no humidification or a relative humidity of 50% or less.
Further, in the fuel cell of the present embodiment, in the above configuration, the electrolyte membrane 4 is the above-described proton conductive electrolyte of the present invention. Moreover, it can be set as the structure by which the proton conductive electrolyte of this invention contained in the oxygen electrode 2 and a part of fuel electrode 3. FIG.

  The fuel electrode 3 and the oxygen electrode 2 are each generally composed of porous catalyst layers 2a and 3a and porous carbon sheets (carbon porous bodies) 2b and 3b that hold the catalyst layers 2a and 3a, respectively. The catalyst layers 2a and 3a contain an electrode catalyst (catalyst), a hydrophobic binder for solidifying and molding the electrode catalyst, and a conductive material.

  The catalyst is not particularly limited as long as it is a metal that promotes a hydrogen oxidation reaction and an oxygen reduction reaction. For example, lead, iron, manganese, cobalt, chromium, gallium, vanadium, tungsten, ruthenium, iridium, palladium, platinum, There may be mentioned rhodium or an alloy thereof. An electrode catalyst can be constituted by supporting such a metal or alloy on activated carbon.

  As the hydrophobic binder, it is preferable to use the proton conductive electrolyte according to the present invention, but other resins can be used, for example, a fluororesin having hydrophobicity can be used. Among the fluororesins, those having a melting point of 400 ° C. or less are preferable. Examples of such fluororesins include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride, tetrafluoroethylene / hexafluoroethylene copolymer. A resin excellent in hydrophobicity and heat resistance such as a polymer and perfluoroethylene can be used. By adding the hydrophobic binder, it is possible to prevent the catalyst layers 2a and 3a from being wetted excessively by the water generated in response to the power generation reaction, and the fuel gas and oxygen in the fuel electrode 3 and the oxygen electrode 2 can be prevented. Can be prevented.

  Further, the conductive material may be any material as long as it is an electrically conductive material, and examples thereof include various metals and carbon materials. Examples thereof include carbon black such as acetylene black, activated carbon and graphite, and these are used alone or in combination.

  As described above, the catalyst layers 2a and 3a may be configured to contain the proton conductive electrolyte according to the present invention instead of the hydrophobic binder or together with the hydrophobic binder. By adding the proton conductive electrolyte according to the present invention, the proton conductivity in the fuel electrode 3 and the oxygen electrode 2 can be improved, and the internal resistance of the fuel electrode 3 and the oxygen electrode 2 can be reduced.

The oxidant distribution plate 5 and the fuel distribution plate 6 are made of a conductive metal or the like, and function as a current collector by joining to the oxygen electrode 2 and the fuel electrode 3 respectively. Oxygen and fuel gas are supplied to the fuel electrode 3. That is, the fuel electrode mainly containing hydrogen is supplied to the fuel electrode 3 through the fuel flow path 6 a of the fuel flow distribution plate 6, and the oxidant flow path 5 a of the oxidant flow distribution plate 5 is supplied to the oxygen electrode 2. Through this, oxygen as an oxidizing agent is supplied.
The hydrogen supplied as fuel may be supplied by hydrogen generated by reforming hydrocarbon or alcohol, and oxygen supplied as oxidant is supplied in a state of being contained in air. Also good.

  In this single cell 1, hydrogen is oxidized on the fuel electrode 3 side to generate protons, which are conducted through the electrolyte membrane 4 to reach the oxygen electrode 2, and protons and oxygen are electrochemically connected to the oxygen electrode 2. It reacts to produce water and generates electrical energy.

  According to the fuel cell, even in an operating temperature range of 100 ° C. or higher and 200 ° C. or lower with no humidification or a relative humidity of 50% or lower, the current density is high, the output is high, and the life is long. A polymer electrolyte fuel cell that stably exhibits power generation performance for a long period of time can be obtained, and can be suitably used for automobiles, home power generation, or portable devices.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited by the following example.

[Example 1]
"Synthesis of polyamic acid"
As the polyamic acid which is a precursor of the polyamic acid derivative, the target product was Ar: benzene, R: (CH ₂ ) ₁₀ in the general formula (1), and the precursor was synthesized as shown below.
First, 3.45 g (20 mmol) of 1,10-diaminodecane was dissolved in 170 mL of dehydrated N, N′-dimethylformamide (DMF), and 4.36 g (20 mmol) of pyromellitic anhydride recrystallized from acetone / hexane was gradually added. In addition, the mixture was stirred at 700 rpm for 1 hour at 15 ° C, 60 hours at 25 ° C, and reacted. Next, the reaction solution was precipitated in 4 L of acetone / hydrochloric acid (1/4), recovered by filtration, washed with 1 mol / L hydrochloric acid aqueous solution and acetone, and heated and vacuum dried at 60 ° C. for 36 hours to obtain the following general solution. Polyamic acid represented by the formula (8) was obtained as white powder 7.65 g (yield 98%).

¹ H-NMR spectrum (DMSO-d ₆ , 500 MHz) of the obtained white powder was 1.20-1.38 (br, —CH ₂ —), 1.43-1.57 (br, —CH ₂ —). _{), 3.13-3.24 (br, -CH 2} -), 7.34,7.68,8.08 (s, Ph), the spectrum of 8.39,8.44 (m, NH) Furthermore, the absorption (1719,1655 cm < ^-1 > (vC _{= O} )) derived from the carbonyl group in IR spectrum was shown.

  The above polymer is soluble in DMF, N, N′-dimethylacetamide (DNAc), N-methylpyrrolidine (NMP), dimethylsulfoxide (DMSO), etc., and insoluble in water, methanol, chloroform, hexane, benzene and toluene. there were.

"Synthesis of polyamic acid derivatives"
1.17 g (3 unit mmol) of the polyamic acid (8) synthesized as described above was dissolved in 100 mL of dehydrated DMF, and 1.78 g (15 mmol) of thionyl chloride was gradually added dropwise under a nitrogen atmosphere, and the mixture was stirred at room temperature for 6 hours. Stir. Next, 2.91 g (30 mmol) of amidosulfuric acid (manufactured by Kishida Chemical Co., Ltd.) and 3.03 g (30 mmol) of triethylamine were mixed with 15 mL of dehydrated dichloromethane to form an amidosulfuric acid triethylamine salt, and then gradually added to the polymer solution under a nitrogen atmosphere. And stirred at room temperature for 16 hours. After the solvent in the reaction solution was distilled off under reduced pressure at 50 ° C., 100 mL of pure water was added to the viscous body, and the mixture was stirred at room temperature for 1 hour. Thereafter, the solution was centrifuged at 4000 rpm for 10 minutes, the supernatant was removed, and the remaining solid was filtered. The recovered product was dissolved in 100 mL of DMF and passed through 250 mL of a cation exchange resin (Amberlyst 15JWET manufactured by Organo) to exchange protons. Then, the treatment liquid is concentrated to 10 mL, dropped into 200 mL of pure water, and the precipitate is filtered off, and dried by heating and vacuuming at 70 ° C. overnight to obtain a polyamide sulfamic acid represented by the following general formula (9). As a light brown powder, 0.68 g (yield 42%) was obtained.

¹ H-NMR spectrum (DMSO-d ₆ , 500 MHz) of the obtained light brown powder was 1.20-1.35 (br, —CH ₂ —), 1.49-1.65 (br, —CH _2). -), 3.20-3.30 (m, -CH _2- ), 3.52-3.64 (m, -CH _2- ) spectra, and further absorption from carbonyl group in IR spectrum (1716) , and _{^{1635cm -1 (v C = O)}} ), showed an absorption derived from a sulfonic acid group _{(1192,1055cm-1 (v S =} O)).

The polymer was soluble in DMF, DMAc, NMP, DMSO, etc., and insoluble in water, methanol, chloroform, hexane, benzene, and toluene.
Further, when elemental analysis of sulfur of the polymer was performed, the functional group in the general formula (9) had an introduction ratio a: b = 9: 1.
The polyamide sulfamic acid (9) obtained as described above was dissolved in DMAc, cast on a glass plate, and heated and dried at 60 ° C. to obtain a light brown transparent film.

"Proton conductivity measurement"
The proton conductive electrolyte membrane of Example 1 was sandwiched between disc-shaped platinum electrodes having a diameter of 13 mm, and the ionic conductivity was determined by measuring complex impedance. The graph of FIG. 2 shows the temperature dependence of proton conductivity.
As shown in Table 1, the proton conductive electrolyte membrane of Example 1 had an ionic conductivity at 150 ° C. of 3.2 × 10 ⁻³ Scm ⁻¹ .

"Fuel cell evaluation"
Next, carbon powder carrying 50% by mass of platinum was added to the DMAc solution of the electrolyte membrane prepared in Example 1 and sufficiently stirred to obtain a suspension. At this time, the weight ratio of the platinum-supported carbon powder and the proton conductive electrolyte was adjusted to 2: 1 by the weight ratio of the solid content. This suspension was applied onto a carbon porous body (porosity 75%) and dried to obtain a porous electrode for a fuel cell.
The electrolyte membrane obtained in Example 1 was sandwiched between the pair of porous electrodes to form a single cell. Hydrogen was supplied to the fuel and air was supplied to the oxidant, and a power generation test was conducted at 150 ° C. As a result, the open circuit voltage was 0.985 V and a voltage of 0.524 V was obtained at a current density of 100 mA / cm ² . .

[Examples 2 to 7]
"Other examples of electrolyte membrane"
Instead of the polyamic acid (8) used in Example 1, the polymers shown in Table 1 below were used as raw materials, and the polymers synthesized by the same method as in Example 1 were mixed in the proportions shown in Table 1 below. Using the electrolyte membrane produced by the same method as in Example 1, proton conductivity measurement and evaluation of the fuel cell were performed.
In addition, as for A component shown in Examples 1-3, a and b in a formula are a: b = 1.8: 0.2, A component shown in Examples 4 and 5 is a in formula. , B is a: b = 1.7: 0.3, and the components A shown in Examples 6 and 7 are such that a and b in the formula are a: b = 1.9: 0.1. It was.

  A list of raw materials and electrolyte components in each of the above examples is shown in Table 1, and a list of evaluation measurement results is shown in Table 2.

As shown in Table 2, the electrolyte membrane using the proton conductive electrolyte obtained in Examples 2 to 7 also has a proton conductivity of 1.7 × 10 ⁻³ Scm ^{−1 at} 150 ° C. (Example 7). It became the range of -2.8 * 10 < ^-3 > Scm < ^-1 > (Example 3), and favorable proton conductivity was obtained. Further, as in Example 1, a high-quality fuel cell was obtained by using these proton conductive electrolytes.

[Comparative example]
In the same manner as in Example 1, a sulfonated polyetheretherketone was dissolved in N-methylpyrrolidone to prepare a solution, which was cast on a glass plate and heat-dried at 60 ° C. to obtain a light yellow transparent film. It was. Proton conductivity was measured at 150 ° C. using the membrane thus prepared, but no conductivity was exhibited.

  The proton conductive electrolyte of the present invention is excellent in proton conductivity and flexibility after film formation, and is preferably used for an electrolyte membrane and an electrode of a fuel cell. By using the proton conductive electrolyte of the present invention, a solid polymer having a high current density, high output, and long life even when the operating temperature is 100 ° C. or higher and 200 ° C. or lower and no humidification or relative humidity is 50% or less. A fuel cell of the type can be provided.

It is a figure which illustrates typically an example of the fuel cell using the proton-conductive electrolyte of this invention, and is the schematic which shows the cross section of a single cell. It is a figure explaining an example of the proton conductive electrolyte of this invention, and is a graph which shows the temperature dependence of proton conductivity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Single cell (fuel cell), 2 ... Oxygen electrode (electrode), 3 ... Fuel electrode (electrode), 4 ... Proton conductive electrolyte membrane (proton conductive electrolyte)

Claims (7)

A proton conductive electrolyte comprising a polyamide having an alkylene group in the main chain represented by the following general formula (1) and a polyamic acid derivative in which a carboxylic acid or a sulfamic acid group is introduced as a side chain.

(In the general formula (1), R is an alkylene group having 3 to 12 carbon atoms, Ar is an aromatic ring or a group containing an aromatic ring, and a 1 and b are 0 ≦ a ≦ (2, 0 ≦ b ≦ 2, and a + b = 2), a / a + b is in the range of 80% to 100%, and n is the average degree of polymerization and is an integer of 100 to 300,000.)   2. The proton conductive electrolyte according to claim 1, wherein the polyamic acid derivative is a compound in which all or a part of the side chain carboxylic acid group of the polyamic acid is sulfamidated. 3.   The polyamic acid derivative is obtained by acid chloride of all or a part of the side chain carboxylic acid group of the polyamic acid, and then reacting with an amidosulfuric acid triethylamine salt, followed by cation exchange. The proton conductive electrolyte according to claim 2. A proton conductive electrolyte comprising the polyamic acid derivative according to any one of claims 1 to 3 and a polyvinylsulfamic acid represented by the following general formula (2).

(In the general formula (2), R ₁ is H, COOH, CONHSO ₃ H, an aromatic group, R ₂ is H, CH ₃ , and R ₃ is COOH, an alkoxy group, a halogen group, An ester group and an aromatic group are shown, m and n are average degrees of polymerization, respectively, and are integers of 100 to 1000000, and the ratio of n / m is in the range of 3/7 to 7/3.)   The mixing ratio of the polyamic acid derivative according to any one of claims 1 to 3 and the polyvinylsulfamic acid represented by the general formula (2) is in a range of 9/1 to 1/1 by mass ratio. The proton conducting electrolyte according to claim 4, wherein the proton conducting electrolyte is provided.   A fuel cell comprising a pair of electrodes and an electrolyte membrane disposed between the electrodes, wherein the electrolyte membrane comprises the proton conductive electrolyte according to any one of claims 1 to 5. .   The fuel cell according to claim 6, wherein the proton-conducting electrolyte according to claim 1 is contained in a part of the electrode.

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