JP2002184427A - Proton conductive substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate many disadvantages of a proton conductive substance usable in a polymer solid electrolyte of a fuel cell that proton conductivity of a conventional fluoride hydrocarbon polymer electrolyte material is markedly reduced in low humidity atmosphere or at a temperature of 100 deg.C, the suppression of the permeation property of fuel such as methanol, namely, crossover is difficult, and the proton conductive substance is very expensive. SOLUTION: The inventor of this invention finds that the proton conductive substance has a boron containing part, the dissociation property of sulfonic acid of a sulfo group containing part is promoted, and as a result, proton conductivity is improved. Moreover, this invention relates to a fuel cell constituted by the proton conductive substance and the proton conductive substance composed of polymer stable under acid condition and a film composed of the proton conductive substance and having a thickness of 10 to 500 μm by nipping and holding the film between a fuel electrode and an oxidant electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proton conductive substance, and more particularly to a proton conductive substance which can be used for a polymer solid electrolyte of a fuel cell.

[0002]

2. Description of the Related Art Fluorohydrocarbon-based polymer electrolyte materials, which are typical proton-conductive polymer electrolyte membranes, exhibit a significant decrease in proton conductivity in a low-humidity atmosphere or at a high temperature of 100 ° C. or higher, and require a fuel such as methanol. Have many drawbacks, such as difficulty in suppressing the permeability, that is, crossover, and being extremely expensive. On the other hand, a sulfonated product of a normal hydrocarbon polymer (T. Kobayashi,
M. Rikukawa, K. Sanui, and N. Ogata, Solid State Io
nics, Vol. 106, 219 (1998)) and a siloxane polymer having a sulfonylbenzyl group on silicon as an organic / inorganic hybrid proton conductive material (I. Gautier,
A. Denoyelle, JY Sanchez, and C. Poinsignon, El
ectrochimica Acta, Vol. 37, 1615 (1992)) and an organic-inorganic hybrid polymer obtained by polymerizing a siloxane and an organic polymer through a urethane bond (I. Honma, S. Hirakaw)
a, K. Yamada, and JM Bae, Solid State Ionics, V
ol. 118, 29 (1999)), but there are problems that the synthesis method is complicated and the proton conductivity is somewhat low. An organic-inorganic hybrid material having a borosiloxane structure having a methyl group on silicon has been reported (GD Soraru, N. Dallabona, C. Gervais, and F. Ba
bonneau, Chem. Mater. Vol. 11, 910 (1999)), not proton conductive.

[0003] A fuel cell, which is one of the applications of the proton conductive polymer, is a battery that utilizes energy generated from an electrochemical reaction between fuel and oxygen, and has a proton conductive property between a fuel electrode and an oxidation electrode. Known structures sandwiching an electrolyte membrane (JP-A-2000-277123 and JP-A-2000-277123)
-285933, JP-A-11-45733, JP-A-6-1994
251780 etc.). These generally have a thickness of 50-20.
By constructing a fuel cell by stacking multiple layers of cells in which electrodes such as platinum are closely attached to both sides of an electrolyte membrane of about 0 μm, flowing oxygen from one side and hydrogen from the other side and applying an appropriate back pressure at an appropriate temperature. This makes this function as a battery. However, as in the publications cited herein, this electrolyte membrane is generally used as a perfluorocarbon polymer having a sulfonic acid group (for example, Nafion (EID).
The above problem is caused by the use of a trademark of Upon Inc.)).

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolyte material having high proton conductivity and a simple method for producing the same in order to solve the above problems. In order to obtain high proton conductivity, the present invention focuses on the borosiloxane skeleton as a structure that promotes the dissociation of sulfonic acid,
As a result of studying the preparation of a borosiloxane polymer by a hydrolysis-condensation method and its sulfonation method, an organic-inorganic hybrid proton conductor having high proton conductivity was obtained.

[0005]

Means for Solving the Problems The present inventors have proposed a proton
When the conductive material is a boron-containing portion (BO_3/2Having)
To form a sulfonic acid group-containing portion (Si (X-SO₃H)
_xO_{(4-x) / 2}) The dissociation of sulfonic acid is promoted
Found that the proton conductivity improved as a result.
Thus, the present invention has been completed. That is, the eye of the present invention
The target is given by the following formula (SiR¹ _xO_{(4-x) / 2})_a(BO_3/2)_b(S
iR² _yO_{(4-y) / 2})_c  (In the formula, R¹Is -X-S
O₃Represents H (wherein X is a divalent carbon having 2 to 18 carbon atoms)
Represents a hydride group. ), R²Is a monovalent of 1 to 18 carbon atoms
Represents a hydrocarbon group, x is greater than 0 and 2 or less, y is 0 or more
Above 2 or less, a and b are each 10% or less with respect to a + b
Above 90% or less, c is 0% or more with respect to a + b + c
80% or less. ). This professional
Tons of conductive materials can improve performance by doping phosphoric acid.
Improvement can be achieved. Another object of the present invention is to
These proton conductive materials and stable
It is an object of the present invention to provide a proton conductive material composed of protons.
Still another object of the present invention is to provide a proton conductive material
And a membrane having a thickness of 10 to 500 μm, and
A fuel cell sandwiched between the electrode and the oxidant electrode
To provide.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The proton conductive substance of the present invention (or
Is an organic / inorganic hybrid proton conductor)
Having a siloxane structure and a sulfonic acid group, and having the following formula (SiR¹ _xO_{(4-x) / 2})_a(BO_3/2)_b(S
iR² _yO_{(4-y) / 2})_c  It is represented by These essential components (SiR¹ _xO
_{(4-x) / 2}) Part and (BO)_3/2) Part and optional
Component (SiR² _yO_{(4-y) / 2}) Part is applicable
There is no need to construct blocks in the order of the expressions,
The polymer may be dispersed. That is, the above equation is simply a configuration
It merely shows the components and their ratios. Proton conductivity
In order to improve the boron content, a boron-containing portion (BO_3/2)
And a sulfonic acid group-containing portion (SiR
¹ _xO_{(4-x) / 2}) Is closer to the polymer
It is considered that the above is more preferable.

In the above formula, R ¹ represents -X-SO ₃ H, and X represents a divalent hydrocarbon group having 2 to 18 carbon atoms, preferably 2 to 8 carbon atoms. There are no other restrictions. R ² has 1 to 18 carbon atoms, preferably 1 to 8 carbon atoms;
More preferably, it represents a monovalent hydrocarbon group of 2 to 6, and there is no particular limitation as long as it is a monovalent hydrocarbon group. That is, X and R ² may be linear or branched, or may have an unsaturated bond, and may have an aromatic ring or an alicyclic ring. When these carbon numbers are large, for example, the compatibility when mixed with a polymer is increased, which is advantageous in producing a film or the like, but on the other hand, the proton conductivity is reduced, so depending on the purpose. What is necessary is just to select suitably.

X is greater than 0 and less than or equal to 2, preferably 0.
01 or more and 1.5 or less, more preferably 0.1 or more and 1.1 or less
Y is 0 or more and 2 or less, preferably 0.01 or more and 1.5 or less, and more preferably 0.1 or more and 1.1 or less. A and b are each 10% or more and 90% or less, preferably 30% or more and 70% or less, and more preferably 40% or more and 60% or less with respect to a + b. C is a +
0% or more and 80% or less, preferably 10% with respect to b + c
Not less than 60% and not less than 20% and not more than 50%. These figures indicate that the sulfonic acid group in the proton conductive substance is 0.1%.
It is preferable that the amount is appropriately selected so as to be 1 to 20 milliequivalents / g, particularly 1 to 5 milliequivalents / g. The proton conductive material of the present invention is doped with phosphoric acid,
High temperature (about 100 to about 180 ° C, especially about 100 to about 150
C) can be improved. The preferred phosphoric acid doping amount is 0.1 to 50 mmol / g, particularly 1 to 10 mmol / g, based on the proton conductive substance.
It is.

The method for producing the proton conductive substance of the present invention is not particularly limited, and may be prepared by a known method. An example of the production method is shown in FIG. 1 (reaction mechanism 1) and FIG. 2 (reaction mechanism 2). The compounds shown in these figures are merely examples, and the present invention is not limited thereto. In reaction mechanism 1,
A polymer is produced by a hydrolysis reaction between an alkoxysilane derivative having a thiol group and a borate ester, and a borosiloxane polymer having a sulfonic acid group is produced by oxidizing the thiol group. Also,
In the reaction mechanism 2, a polymer is formed by a hydrolysis reaction of an alkoxysilane derivative having a hydrocarbon group and a borate ester, and the borosiloxane polymer having a sulfonic acid group is formed by sulfonating the hydrocarbon group. Is generated. That is, the proton conductive substance of the present invention can be easily produced by hydrolysis of an alkoxysilane derivative and a borate ester, followed by sulfonation, followed by sulfonation. Higher proton conductivity can be obtained by employing reaction conditions. That is, in the reaction mechanism 1, the temperature at the time of the oxidation reaction is preferably 90 ° C. or less, particularly 70 ° C.
± 5 ° C is preferred.

The blend system in which the proton conductor of the present invention is dispersed in a suitable polymer can form a good film. As long as this polymer is stable under acidic conditions, that is, it does not cause degradation such as decomposition, other characteristics are not particularly limited. These polymers may be thermoplastic polymers or thermosetting polymers, and include organic polymers and inorganic polymers. For example,
Suitable examples include addition polymerization polymers such as polystyrene and polyolefin, and some of the polycondensation polymers are unstable under acidic conditions. Preferred polymers include, for example, polystyrene sulfonic acid, cross-linked polystyrene sulfonic acid, or a non-proton conductive polymer such as polyethylene oxide, styrene isoprene.
Styrene block copolymer, polyvinylidene fluoride, silicon resin and the like can be mentioned. These polymers function as structural materials. These polymers may be appropriately selected for a purpose, for example, a polymer suitable for the production of a film if a film is prepared. The proton conductor may be mixed with these polymers by a known method, or the polymer may be polymerized after dispersing the proton conductor in a monomer.

Further, a perfluorocarbon polymer having a sulfonic acid group (for example, Nafion) which is a proton conductive polymer may be used as a structural material. By mixing the proton conductive substance of the present invention with the perfluorocarbon polymer, the proton conductivity can be further improved, and therefore, the amount of expensive perfluorocarbon polymer used can be reduced. The content of the proton conductive substance of the present invention in the polymer depends on the type of the polymer to be used.In general, the higher the content is, the higher the proton conductivity is. It is better to increase the ratio. In view of this, 50 to 90% is preferable. When a polymer having a sulfonic acid group is used, the content may be 50%, and for a polymer having no sulfonic acid group, the content may be 70 to 90%. In addition, it is also possible to introduce a cross-linking structure according to requirements such as methanol crossover control and dimensional stability.

Since the proton conductive substance of the present invention has excellent proton conductivity, it can be used as an electrolyte membrane for a fuel cell. This film may be composed of the proton conductive substance and the polymer of the present invention as described above, and has a thickness of usually 10 to 500 μm, preferably 50 to 20 μm.
0 μm. A cell in which a fuel electrode such as platinum and an oxidation electrode are adhered to both sides of this membrane is laminated as necessary to form a fuel cell, and a fuel such as oxygen and a fuel such as hydrogen are poured from one of them and the other at an appropriate temperature. By applying an appropriate back pressure, the battery can function as a battery.

[0013]

The following examples illustrate the present invention but are not intended to limit the invention.
The proton conductivity was measured by an AC impedance method. The sample is 100 borosiloxane polymer
This was prepared by heating at 1 ° C. for 1 hour, and was controlled to have a square shape with an area of 1.0 × 1.0 cm ² and a thickness of 0.4 mm by a spacer. A platinum plate was used as an electrode. FIG. 3 shows a schematic diagram of the apparatus used for the measurement. An alternating current of 10 mV was applied thereto, the frequency was changed from 8 MHz to 0.0001 Hz, and the bulk resistance ( _Rb ) was obtained from the obtained Cole-Cole plot by curve fitting using an equivalent circuit. . The ion conductivity σ (S / cm) is obtained by changing the distance d (cm) between the electrodes to the cross-sectional area S (c
m ² ) and the product of the resistance (S ⁻¹ (= Ω)). σ = d / R _b S The proton conductivity is preferably as large as possible, and the proton conductivity of a general sulfonic acid group-containing perfluorocarbon polymer is about 0.1 S / cm. It is said that a proton conductivity of 0.1 S / cm or more is preferable.

[0014]Example 1  According to the reaction mechanism 1 shown in FIG.
It was created. 3-mercaptotriethoxysilane 4.9
6 g (25.3 mmol), triisopropyl borate
4.77 g (25.3 mmol), n-hexyl trime
10.3 g (49.9 mmol) of toxic silane
Dissolved in 100 ml. 0.04N in the solution
 An aqueous HCl solution (3.59 g, 199 mmol) was added, and the
After stirring at temperature for 24 hours, stirring at 60 ° C. for 48 hours,
Further, heating and refluxing were performed for 5 hours. Solvent removed under reduced pressure at room temperature
And further dried under reduced pressure at 90 ° C. for 24 hours,
A soft solid polymer was obtained (yield 10.4 g).
In a flask containing 1.04 g of the prepared polymer,
30% H₂O₂Add 5 ml of the solution, and add
Temperature) for 1 hour. After completion of stirring, the solvent is removed under reduced pressure
The mixture was further dried at room temperature under reduced pressure for 24 hours. This product
Called “sample 70”. Set the oxidation reaction temperature to 90 ° C
The same operation was repeated, and the obtained product was designated as “Sample 90”.
Call. The obtained polymer was a powder. Get more
Of sulfuric acid generated during oxidation of part of the polymer
6 times ultrasonic cleaning and filtration with diethyl ether
Performed to obtain a borosiloxane electrolyte. Before and after cleaning
The yield and yield are shown in Table 1. 4 and 5 described later.
In this context, a washed sample refers to a sample after washing,
The sample indicates a sample before washing.

[0015]

[Table 1]

In addition, 3-mercaptotriethoxysila
Hexane starting with triisopropyl borate
Borosiloxane electrolyte containing no hydroxyl group
And 10 ^-1 Scm^-1On the order of proton conductivity
As shown, attempts to form film by blending with polymer
And the film forming property was low, and there was deliquescence. Sample 9
0 and sample 70, proton conductivity before and after washing
Rate σ, relative humidity at 25 ° C. and proton conductivity
FIG. 4 shows the relationship between proton conductivity and relative humidity at 95%.
FIG. 5 shows the temperature dependence of the ratio. You can see from these figures
When oxidized at 90 ° C, the thiol group is converted to sulfonic acid.
Is not oxidized and partially oxidized to sulfuric acid.
The sulfuric acid is removed by washing,
A significant drop was observed. However, it oxidized at 70 ° C
The proton conductivity of the sample was reduced by washing.
Did not decrease. That is, the oxidation reaction temperature is 70 ° C.
Obviously it is appropriate. In addition, the prototype of the present invention
Proton conductivity of conductive materials is shown to be quite high
Was.

[0017]Example 2  4.91 g of 3-mercaptotriethoxysilane (25
Rimole), 4.73 g of triisoproyl borate (25.
1 mmol), n-hexyltrimethoxysilane
4 g (50.5 mmol) in 2-propanol 50 ml
Dissolved in. 0.04N HCl aqueous solution
Liquid, tetraethylammonium tetrafluoroborate
0.25 g (1.15 mmol) and phosphoric acid (0.5 mol
/ L) and add 100 ml (50 mmol) at room temperature
The mixture was stirred for 24 hours. The solvent was removed under reduced pressure at room temperature and 140
Heat treatment was performed at 2 ° C. for 2 hours. After heat treatment, 2 at 90 ° C
It dried under reduced pressure for 4 hours. Powder the obtained polymer in a mortar
After crushed into a shape, it is transferred to a flask, and 30% H₂O₂Dissolution
50 ml of the liquid was added, and the mixture was stirred at 70 ° C. for 1 hour. End of stirring
Thereafter, the solvent was removed under reduced pressure, and further dried under reduced pressure at room temperature for 24 hours.
And borosiloxane electrolysis of white powder doped with phosphoric acid
Got the quality. Diagram of temperature dependence of proton conductivity in air
6 is shown. 100 ° C (1000 / T = about 2.68) or higher
However, the decrease in proton conductivity is small,
As a result, a high proton conductivity at a high temperature could be achieved.

[0018]Example 3  Sulfonation on silicon according to reaction scheme 2 shown in FIG.
Synthesis of borosiloxane polymer having phenyl group
Was. 6.29 g of trimethoxyphenylsilane (31.7
Mmol), 5.87 g of triisopropyl borate (3
1.2 mmol) and water (0.1 N HCl) 1.92
g (96 mmol) was placed in a 30 ml flask. solvent
100 ml of acetonitrile was added as the
Stirred. Next, raise the temperature to 60 ° C and stir for 65 hours
The mixture was refluxed at 85 ° C. for 3 hours. Solvent in vacuum
And removed by drying at 80 ° C for 24 hours.
A xane polymer was obtained. Synthesized borosiloxane polymer
Crushed and 0.202 g of crushed polymer in 10 ml
Transfer to flask and add N₂While flowing dichloromethane
Dissolved in 3 ml. Then slowly add chlorosulfuric acid (C
lSO₃H) 0.1 ml was added for sulfonation. mixture
Was stirred at 0 ° C. for 3 hours. After the solvent was distilled off, unreacted sulfuric acid was removed.
Ultrasonic washing several times with diethyl ether to wash away
It was washed using a purifier. And at room temperature in a vacuum for 24 hours
Drying to obtain a sulfonated borosiloxane electrolyte
Was. Although details are not shown, trimethoxyphenylsilane
Using trimethoxybenzylsilane instead of orchid
Have the same properties by repeating the same operation
A borosiloxane electrolyte was obtained.

[0019]Example 4  6.27 g of trimethoxyphenylsilane (31.6 mm
Mol), 5.91 g of triisopropyl borate (31.4
Mmol) and 1.287 g of styrene (12.36
Lmol) into a 300 ml flask, and the solvent
100 ml of nitrile was used. Further, water (0.1N H
(Cl) 2.51 g (139.4 mmol)
0.64 g (3.90 mmol) of AIBN was added, and room temperature was added.
For 5 hours. Then raise the temperature to 60 ° C for one week
The mixture was stirred for another 3 hours and refluxed for 3 hours. Solvent in vacuum
Removed by drying at 80 ° C for 24 hours, yellow uniform
Was obtained as a solid polymer. This solid polymer is borosiloki
Interpenetrating Network Structure of Sun Polymer and Polystyrene (I
PN). Synthesized polymer
And crushed polymer (0.501 g) in 10 ml
Transfer to Lasco and dilute dichloromethane 5 with flowing nitrogen gas.
Dissolved in ml. Then, slowly add chlorosulfuric acid (Cl
SO₃H) 0.3 ml was added for sulfonation. The mixture
Stir at 0 ° C for 3 hours, evaporate the solvent and wash unreacted sulfuric acid.
Several times ultrasonic cleaning with diethyl ether to flush
It was washed using a vessel. Dried in vacuum at room temperature for 24 hours,
Hybrid of borosiloxane electrolyte and polystyrene
A polymer was obtained. In addition, the sample which changed the ratio of styrene,
Polices crosslinked by adding divinylbenzene (DVB)
Hybrid of Tylenesulfonic acid and Borocitoxane
System, adding tetraethoxysilane (TEOS)
Therefore, a system in which borosiloxane was crosslinked was also prepared.

FIG. 7 shows the proton conductivity of the borosiloxane electrolytes obtained in Examples 3 and 4. In FIG.
“A” is a structural formula of a: b: c: m = 1: 1: 1: 0:
4, a hybrid electrolyte of polystyrene sulfonic acid and borosiloxane, “B” is a structural formula of a: b:
c: m = 1: 1: 0: 0: a hybrid electrolyte of polystyrenesulfonic acid and borosiloxane, where “C” is
A hybrid electrolyte of polystyrenesulfonic acid and borosiloxane having a: b: c: m = 1: 1: 1: 0: 1 in the structural formula of “DVB-10” is a: b: c:
m = 1: 1: 1: 0: 4% of divinylbenzene (DVB) 10%
Electrolyte and TEOS-0.2 are chemical formula 1
Represents an electrolyte material cross-linked with 20% of tetraethoxysilane (TEOS) with a: b: c: m = 1: 1: 0.2: 4.

Embedded image FIG. 7 shows that the proton conductive material of the present invention shows a considerably high proton conductivity.

[0021]Example 5  Hexyl-free borosiloxa prepared in Example 1
10% by weight of styrene-isoprene
-Blend styrene block copolymer (SIS)
The electrolyte was prepared in the following manner. SIS 0.036g
Dissolve in toluene solvent (1 ml) until a homogeneous solution is obtained.
Was. Borosiloxane electrolyte while stirring on a mortar
0.324 g of a SIS toluene solution was added. Frass
Transfer to a glass and dried under reduced pressure at room temperature for 24 hours.
A solid blend electrolyte was obtained. Borosiloxane electrolyte
Fig. 8 shows the proton conductivity of the blend system of
You. Shows fairly high proton conductivity under high humidity conditions
I understand. Although details are not shown, instead of SIS
Polyethylene oxide, polypropylene oxide,
Using a polymer such as fion or vinylidene fluoride
By repeating these operations, the borosiloxa
Thus, a blend-type electrolyte with the electrolyte was obtained. These are likewise
Excellent proton conductivity was shown.

[0022]

The proton conductive substance of the present invention has high proton conductivity because the dissociation of the sulfonic acid group is promoted by the introduction of Lewis acidic boron. Further, by doping with phosphoric acid, a high temperature (about 100 to about 180 ° C., particularly about 10 ° C.) can be obtained.
0 to about 150 ° C.). The proton conductive substance of the present invention can be easily synthesized from an organosilicon alkoxide and a borate. Furthermore, the proton conductive substance of the present invention can be easily prepared as a blend system with another polymer, and by appropriately selecting the hydrocarbon group introduced into the proton conductive substance, the compatibility with the polymer is improved, and the membrane is improved. Can be easily generated. It is also possible to introduce a bridge structure. Further, the formed membrane can be used as an electrolyte membrane for a fuel cell.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a reaction for producing a proton conductive substance of the present invention (reaction mechanism 1).

FIG. 2 is a diagram showing another example of the reaction for producing a proton conductive substance of the present invention (reaction mechanism 2).

FIG. 3 is a diagram showing an apparatus for measuring proton conductivity.

FIG. 4 is a diagram showing the relative humidity dependence of proton conductivity at 25 ° C.

FIG. 5 is a diagram showing temperature dependence of proton conductivity under a relative humidity of 95%.

FIG. 6 is a diagram showing the temperature dependence of proton conductivity in air of a borosiloxane electrolyte doped with phosphoric acid.

FIG. 7 is a diagram showing the relative humidity dependence of proton conductivity in air of a borosiloxane electrolyte having a benzenesulfonyl group.

FIG. 8 is a graph showing relative humidity dependence of proton conductivity at 25 ° C. of a blend system of a borosiloxane electrolyte and ISI.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 8/10 H01M 8/10 (72) Inventor Yang Yunmatsu International House 413 F-Term (Reference) 4F071 AA01 AA12X AA22 AA22X AA26 AA51 AA67 AA68 AA75 AA78 AB25 AH15 BC01 BC12 4J002 BB00X BC03X BC12X BD14X BP01X CH02X CP03X CP19W DH026BA04 BA04 BA04 BA04 BA04 G04 BA00 EE18 HH03

Claims (5)

[Claims] 1. The following formula (SiR)¹ _xO_{(4-x) / 2})_a(BO_3/2)_b(S
iR² _yO_{(4-y) / 2})_c  (In the formula, R¹Is -X-S
O₃Represents H (wherein X is a divalent carbon having 2 to 18 carbon atoms)
Represents a hydride group. ), R²Is a monovalent of 1 to 18 carbon atoms
Represents a hydrocarbon group, x is greater than 0 and 2 or less, y is 0 or more
Above 2 or less, a and b are each 10% or less with respect to a + b
Above 90% or less, c is 0% or more with respect to a + b + c
80% or less. ). 2. The proton conductive substance according to claim 1, doped with phosphoric acid. 3. A proton conductive substance comprising the proton conductive substance according to claim 1 and a polymer stable under acidic conditions. 4. A membrane having a thickness of 10 to 500 μm, comprising the proton conductive substance according to claim 3. 5. A fuel cell comprising the membrane according to claim 4 interposed between a fuel electrode and an oxidant electrode.