JP3997304B2 - Solid electrolyte membrane, process for producing the same, and fuel cell using the solid electrolyte membrane - Google Patents

Description

  The present invention relates to a solid electrolyte membrane having proton conductivity, a method for producing the same, and a fuel cell using the solid electrolyte membrane.

Currently, fluorine-containing ion exchange membranes (commercially available under trade names such as “Nafion” and “Flemion”), which are widely used as materials for fuel cells, are organic polymer membranes, so they have sufficient heat resistance. In addition, it is difficult to use at high temperatures above 80 ℃. Considering the improvement in the energy efficiency of the entire fuel cell system, 100% can be used to effectively use the waste heat generated during power generation.
Development of materials that can be used at temperatures up to ~ 150 ° C is eagerly desired.

SiO ₂ —P ₂ O ₅ glass has been proposed as an inorganic solid electrolyte that can be used at high temperatures (Non-Patent Document 1). However, since this solid electrolyte is composed only of an inorganic substance, it has a drawback that it lacks flexibility and is brittle.

Patent Document 1 proposes a mixed member of (1) an inorganic proton conductive material and (2) at least one selected from polyvinylpyrrolidone, polyethylene glycol, polyoxazoline and polydimethylsiloxane as a proton conductive member in a fuel cell. ing. However, this proton conductive member is basically a glass-based material mainly composed of a vitreous inorganic material in which a polymer exists in a mixed state. Therefore, although the flexibility is improved as compared with the case of the inorganic material alone, it is not sufficient when considering use as a self-supporting film.

  Further, a method is described in which a silica mesoporous thin film is formed from silicon alkoxide and a surfactant, and then the surfactant is removed therefrom to obtain a silica mesoporous thin film (Patent Document 2). However, this silica mesoporous thin film does not have proton conductivity.

In recent years, a surface modification method has been reported in which mesoporous silica is prepared by a synthesis method of MCM-41, which is crystalline porous silica, and -SH groups, -SO ₃ H groups and the like are introduced on the silica surface. (Non-Patent Documents 2 to 5). However, these mesoporous silicas are all powders and not thin films.
JP 2002-15742 A JP 2001-130911 A Industrial materials, Vol.49, No.1, pp56-59 J. Am. Chem. Soc., 124, 15176 (2002) Chem. Comm., 317 (1998) J. Am. Chem. Soc., 124, 9694 (2002) Chemistry and Industry 56, 239 (2003)

  The main object of the present invention is to provide a solid electrolyte membrane having proton conductivity, a method for producing the same, and a fuel cell using the solid electrolyte membrane.

The present inventor has conducted research while considering the current problems of the technology as described above, and as a result, after creating an organic-inorganic hybrid film by the sol-gel method, the organic porous film is removed by removing organic molecules. The present invention succeeds in producing a solid electrolyte membrane having proton conductivity by introducing a functional group showing proton conductivity into the surface of the inorganic porous membrane and modifying the surface, thereby completing the present invention. It came.

That is, this invention provides the following solid electrolyte membrane, its manufacturing method, and a fuel cell using this solid electrolyte membrane.
Item 1. A first step of producing an inorganic-organic hybrid membrane by a sol-gel method, a second step of producing an inorganic porous membrane by removing organic molecules from the inorganic-organic hybrid membrane, and a fine process of the inorganic porous membrane. A method for producing a proton conductive solid electrolyte membrane comprising a third step of introducing a proton conductive group into the pores and on the surface ,
After the third step, the inorganic porous membrane is surface-modified by reacting a silane coupling agent containing a group that can be converted into a proton conductive group in and on the pores of the inorganic porous membrane. , A step of chemically converting the proton-conducting group into a proton-conducting group.
A silane coupling agent containing a group that can be converted into the proton conductive group has the formula (I):
_{X j R k Si [(CH} 2) n -Y] m (I)
Wherein X is an alkoxy group or a halogen atom, R is an alkyl group, Y is a group that can be converted into a proton conductive group, j is 1, 2 or 3, k is 0, 1 or 2, m is 1, 2. Or 3 and satisfies j + k + m = 4, and n represents an integer of 2 to 11)
A method for producing a proton conductive solid electrolyte membrane, which is a compound represented by the formula:
Item 2. Item 2. The process according to Item 1, wherein the first step is a step of producing an inorganic-organic hybrid film by mixing and solidifying tetraalkoxysilane and a surfactant under acidic conditions.
Item 3. Item 2. The process according to Item 1, wherein the second step is a step of heating the inorganic-organic hybrid membrane to produce an inorganic porous membrane.
Item 4. Item 4. The method according to Item 3, wherein the inorganic porous membrane has a thickness of 1000 μm or less, a center pore diameter of 1 to 50 nm, a specific surface area of 200 to 800 m ² / g, and a pore volume of 0.1 to 1.0 cm ³ / g.
Item 5 . A silane coupling agent containing a group that can be converted into a proton conductive group is represented by the formula (II)
:
_{X 3 Si- (CH 2) n} -Y (II)
(Wherein X is an alkoxy group having 1 to 6 carbon atoms or a halogen atom, Y is —SH, —P (O) (OR ¹ ) (OR ² ) or —COOR ³ , R ¹ , R ² and R ³ are The same or different alkyl group, aryl group or aralkyl group, n represents an integer of 2 to 8)
The manufacturing method of claim | item 1 which is a compound represented by these.
Item 6 . 6. A proton conductive solid electrolyte membrane produced by the production method according to any one of items 1 to 5 .
Item 7 . Item 7. The proton conductive solid electrolyte membrane according to Item 6 , having a thickness of 1000 μm or less, a center pore diameter of 1 to 50 nm, a specific surface area of 200 to 800 m ² / g, and a pore volume of 0.1 to 1.0 cm ³ / g.

The proton conductive solid electrolyte membrane of the present invention is basically composed of a first step of producing an inorganic-organic hybrid membrane by a sol-gel method, an inorganic porous material by removing organic molecules from the inorganic-organic hybrid membrane. It consists of a second step for producing a membrane and a third step for introducing a functional group exhibiting proton conductivity into the pores and on the surface of the inorganic porous membrane. Hereinafter, each step will be specifically described.
I. First Step In this step, specifically, an inorganic-organic hybrid film is formed by mixing and solidifying tetraalkoxysilane and a surfactant under acidic conditions. The raw materials used in this step, the sol-gel method, and the resulting inorganic-organic hybrid film will be specifically described.

Tetraalkoxysilane In the present invention, at least one tetraalkoxysilane is used as the inorganic porous raw material (silica source). Examples of tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetra n-propoxysilane, tetraisopropoxysilane, and tetra n-butoxysilane.

Surfactant As the surfactant used in the present invention, for example, a triblock copolymer composed of three polyalkylene oxide chains can be used. Among the triblock copolymers, triblock copolymers represented by polyethylene oxide (EO) chain-polypropylene oxide (PO) chain-polyethylene oxide (EO) chain are preferable. When the number of EO chain repeats is x and the number of PO chain repeats is y, this triblock copolymer can be represented as (EO) x (PO) y (EO) x. The x and y of the triblock copolymer that can be used in the present invention are not particularly limited, but x is preferably 5 to 110, y is preferably 15 to 70, x is 15 to 20, and y is 50 to 60. More preferably.

  Furthermore, a triblock copolymer ((PO) x (EO) y (PO) x) of polypropylene oxide (PO) chain-polyethylene oxide (EO) chain-polypropylene oxide (PO) chain can also be preferably used. Here, x and y are not particularly limited, but x is preferably 5 to 110, and y is preferably 15 to 70, more preferably 15 to 20, and y is 50 to 60.

Examples of the triblock copolymer include (EO) ₅ (PO) ₇₀ (EO) ₅ , (EO) ₁₃ (PO) ₃₀ (EO) ₁₃ , (EO) ₂₀ (PO) ₃₀ (EO) ₂₀ , (EO). ₂₆ (PO) ₃₉ (EO) ₂₆ , (EO) ₁₇ (PO) ₅₆ (EO) ₁₇ , (EO) ₁₇ (PO) ₅₈ (EO) ₁₇ , (EO) ₂₀ (PO) ₇₀ (EO) ₂₀ , ( EO) ₈₀ (PO) ₃₀ (EO) ₈₀ , (EO) ₁₀₆ (PO) ₇₀ (E
O) ₁₀₆ , (EO) ₁₀₀ (PO) ₃₉ (EO) ₁₀₀ , (EO) ₁₉ (PO) ₃₃ (EO) ₁₉ , (E
O) ₂₆ (PO) ₃₆ (EO) ₂₆ . Among these, (EO) ₁₇ (PO) ₅₆ (EO) ₁₇ and (EO) ₁₇ (PO) ₅₈ (EO) ₁₇ are preferably used. These triblock copolymers are available from BASF, etc., and triblock copolymers having desired x and y values can be obtained at a small scale production level. The above triblock copolymers can be used singly or in combination of two or more.

As other surfactants, for example, compounds (salts) having an ammonium group at the terminal, such as alkyltriethylammonium, alkyltrimethylammonium, dimethyldialkylammonium, alkylammonium, and benzyltrimethylammonium can be used. Alternatively, a terminal is a sulfone group (—O—SO ₃ —; sulfate), a carboxyl group (—CO
A compound (salt) or the like having O—; carboxylate), a phosphate group (—O—PO ₃ —; phosphate) or the like may be used. These surfactants may be used alone or in combination of two or more.

  The surfactant is preferably used in such an amount that the mixing ratio with tetraalkoxysilane is tetraalkoxysilane / surfactant = 1/1 to 10/1 (molar ratio). It is more preferable to use it so that alkoxysilane / surfactant = 2/1 to 5/1 (molar ratio).

As the acid component involved in the sol-gel reaction, nitric acid, sulfuric acid, hydrochloric acid, acetic acid, phosphoric acid and the like can be used. The use ratio of the acid is about 0.01 to 0.5 mol, more preferably about 0.01 to 0.1 mol, per 1 mol of tetraalkoxysilane.

As a reaction solvent in the sol-gel method, alcohols such as ethanol, methanol, and propanol are used. The usage-amount of a reaction solvent is about 2-20 mol with respect to 1 mol of tetraalkoxysilane, More preferably, it is about 5-10 mol.

Production of Inorganic-Organic Hybrid Membrane The sol-gel reaction performed using the above raw materials can be carried out according to a known method except that a surfactant is present in the reaction system. That is, each of the above materials is mixed at a predetermined ratio to form a sol, then solidified into a film shape in a predetermined container, and then dried to obtain a desired inorganic-organic hybrid material. it can. For example, an acidic component and tetraalkoxysilane may be added to an alcohol solution of a surfactant and stirred at about 10 to 50 ° C. (preferably about 30 to 45 ° C.) for about 5 to 40 hours. Then the solution was 0-100 ° C
Solidify to a certain degree to obtain an inorganic-organic hybrid film.

The inorganic-organic hybrid film produced by the method of the present invention comprises an inorganic matrix phase composed of silica (SiO ₂ ) and an organic polymer phase composed of a surfactant uniformly dispersed in the inorganic matrix phase. . In this film, it is considered that the surfactant is dispersed on the molecular order in the inorganic matrix.

  The film thickness of the inorganic-organic hybrid film containing the surfactant obtained in the first step is preferably 1000 μm or less, and more preferably 1 μm to 800 μm. When the film thickness exceeds 1000 μm, the uniformity of the pore arrangement of the hybrid film tends to deteriorate.

As described above, in the present invention, the tetraalkoxysilane is partially polymerized in an acidic solvent, mixed with a surfactant, and then thinned while suppressing the condensation reaction of the tetraalkoxysilane partial polymer under acidic conditions. Therefore, it becomes possible to make a thin film with low viscosity. As a result, the thickness of the resulting inorganic-organic hybrid film can be made very small. Further, since the thinning is possible while suppressing the condensation reaction, the viscosity change of the liquid containing the tetraalkoxysilane partial polymer is reduced during the thinning, and the thinning can be performed uniformly.
II. Second Step In this step, the method for removing the surfactant from the inorganic-organic hybrid film obtained in the first step is not particularly limited, but for example, a method by firing or a method of treating with a solvent such as water or alcohol Can be used. Thereby, an inorganic porous membrane is manufactured.

In the case of the method by firing, the firing condition is not particularly limited as long as the surfactant part is removed from the inorganic-organic hybrid film, and is appropriately selected depending on the decomposition temperature of the surfactant to be used. Usually, it may be heated at about 150 to 600 ° C. for about 1 to 5 hours. In order to completely remove the surfactant component, it is preferable to heat for 2 hours or more. For example, when a triblock copolymer is used as the surfactant, it may be heated at about 160 to 220 ° C. for about 2 to 5 hours. Firing can be performed in the air, but since a large amount of combustion gas is generated, it may be performed by introducing an inert gas such as nitrogen.

When removing the surfactant from the inorganic-organic hybrid film using a solvent, for example, a silica mesoporous thin film containing a surfactant is immersed in a solvent having a high solubility of the surfactant. As the solvent, water, ethanol, methanol, acetone or the like can be used.

When a cationic surfactant is used, a silica mesoporous thin film containing a surfactant can be immersed in ethanol or water with a small amount of hydrochloric acid and heated at 50 to 70 ° C. Thereby, a cationic surfactant is ion-exchanged and extracted by protons. When an anionic surfactant is used, the surfactant can be extracted in a solvent to which an anion has been added. In addition, when a nonionic surfactant is used, extraction can be performed only with a solvent. In addition, it is preferable to apply an ultrasonic wave at the time of extraction.

The inorganic porous membrane from which the surfactant has been removed has hydroxyl groups on the surface and in the pores. The inorganic porous film has silica (SiO ₂ ) as a main component, and the film thickness is 1000 μm or less, preferably 20 to 800 μm, and more preferably 100 to 800 μm. When the film thickness exceeds 1000 μm, the uniformity of the pore arrangement of the inorganic porous film tends to deteriorate.

The center pore diameter of the inorganic porous membrane from which the surfactant has been removed is about 1 to 50 nm, preferably about 2 to 20 nm, more preferably about 2 to 10 nm, and its specific surface area is 200 to 800 m ² / About g, preferably about 300 to 700 m ² / g, and the pore volume is about 0.1-1.0 cm ³ / g, preferably about 0.1-0.6 cm ³ / g.

  Here, the center pore diameter is a curve (pore diameter distribution curve) in which a value (dV / dD) obtained by differentiating the pore volume (V) with respect to the pore diameter (D) is plotted against the pore diameter (D). ) At the maximum peak.

The pore size distribution curve can be obtained by the method described below. That is, the silica mesoporous thin film is cooled to liquid nitrogen temperature (−196 ° C.), nitrogen gas is introduced, the adsorption amount is obtained by a constant volume method or a gravimetric method, and then the pressure of the introduced nitrogen gas is gradually increased. Then, the adsorption amount of nitrogen gas with respect to each equilibrium pressure is plotted, and an adsorption isotherm is obtained. Using this adsorption isotherm, a pore size distribution curve can be obtained by a calculation method such as Cranston-Inklay method, Pollimore-Heal method, BJH method.
III. Third step In this step, the surface of the inorganic porous membrane obtained in the second step and -OH groups present in the pores are reacted with a silane coupling agent having a group that can be converted into a proton conductive group, Then, the proton conductive solid electrolyte membrane of the present invention is manufactured by chemically converting a group that can be converted into a proton conductive group into a proton conductive group.

Reaction with Silane Coupling Agent In the present invention, a silane coupling agent having a group that can be converted into a proton conductive group means a reactive group (alkoxy group, halogen atom, etc.) and a proton conductive group on silicon. It means a silicon compound containing an alkyl group having such a group. For example, the following formula (I):
_{X j R k Si [(CH} 2) n -Y] m (I)
Wherein X is an alkoxy group or a halogen atom, R is an alkyl group, Y is a group that can be converted into a proton conductive group, j is 1, 2 or 3, k is 0, 1 or 2, m is 1, 2. Or 3 and satisfies j + k + m = 4, and n represents an integer of 2 to 11)
The compound represented by these is mentioned.

  The alkyl moiety in the alkoxy group represented by X is not particularly limited, and examples thereof usually include linear or branched alkyl having 1 to 6 carbon atoms. Specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl and the like. Preferably, it is C1-C4 linear or branched alkyl, More preferably, C1-C3 linear or branched alkyl is mentioned.

  Examples of the halogen atom represented by X include F, Cl, Br, and I. Of these, Cl and Br are preferable, and Cl is particularly preferable.

  The alkyl group represented by R is exemplified by the alkyl moiety in the alkoxy group represented by X described above. A methyl group is preferred.

In the present invention, the proton conductive group means a group having a proton (hydrogen ion) that is easily dissociated and thereby having conductivity, such as —SO ₃ H, —PO ₃ H, —COOH, and the like. Can be mentioned. The group that can be converted into a proton conductive group represented by Y means a group that can be converted into the proton conductive group by chemical conversion (oxidation reaction, hydrolysis reaction, etc.), and includes, for example, —SH and —P, respectively. (O) (OR ¹ ) (OR ² ) (wherein R ¹ and R ² are the same or different and are an alkyl group, an aryl group or an aralkyl group), —COOR ³ (wherein R ³ is an alkyl group) A group, an aryl group or an aralkyl group).

The alkyl groups represented by R ¹ , R ² and R ³ are the same or different and have 1 to
6 linear or branched alkyl groups are preferable, and examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl and the like. Of these, methyl and ethyl are preferable. Examples of the aryl group represented by R ¹ , R ² and R ³ are the same or different and include phenyl, toluyl, naphthyl, anthryl, phenanthryl and the like. Examples of the aralkyl group represented by R ¹ , R ² and R ³ are the same or different and include benzyl, phenethyl and the like.

  It is preferable that j is 2 or 3, k is 0 or 1, m is 1 and j + k + m = 4 is satisfied, and j is 3, k is 0, m is 1 and j + k + m = 4 is more preferable.

  N is preferably an integer of 2 to 8, more preferably an integer of 2 to 5, and particularly preferably 2 or 3.

Of the compounds represented by formula (I), preferred are those represented by formula (II):
_{X 3 Si- (CH 2) n} -Y (II)
(However, X, Y and n are the same as above)
The compound represented by these is mentioned.

In the formula (II), more preferably, X is methoxy, ethoxy, isopropoxy, n-propoxy, n-butoxy, Cl, Br, Y is —SH, —P (O) (OCH ₃ ) ₂ , —P ( O) (OCH ₂ CH ₃ ) ₂ , —COOCH ₃ , —COOCH ₂ CH ₃ , where n is 2 or 3.

  Preferable specific examples of the compound represented by the formula (I) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2- (dimethoxyphosphoryl) ethyltriethoxysilane, 2- (diethoxy Phosphoryl) ethyltriethoxysilane, 2- (methoxycarbonyl) ethyltriethoxysilane, 2- (ethoxycarbonyl) ethyltriethoxysilane, 3-mercaptopropyltrichlorosilane, 2-trichlorosilylethyl acetate and the like. Among these, 3-mercaptopropyltrimethoxysilane is preferable.

  Any of these silane coupling agents is commercially available or can be easily produced by a known method.

The reaction between the silane coupling agent and the inorganic porous membrane can be performed by immersing the inorganic porous membrane in a solution of the silane coupling agent. The solvent is not particularly limited as long as it can dissolve the silane coupling agent, and benzene, toluene, xylene, tetrahydrofuran and the like can be employed. The concentration of the silane coupling agent in the solution may be about 20 to 25 g / L. The conditions for the immersion are not particularly limited, but can be appropriately selected within a temperature range from room temperature (about 10 to 35 ° C) to the boiling point of the solvent. From the viewpoint of reactivity, it is preferably refluxed in a solvent. Although the reflux temperature depends on the boiling point of the solvent used, it is usually about 30 to 200 ° C., preferably about 50 to 150 ° C., and the reflux time is usually about 5 to 24 hours, preferably about 10 to 20 hours. is there. Thus, a group that can be converted into a proton conductive group can be introduced and modified on the surface of the inorganic porous membrane, and then the group is converted into a proton conductive group.

Production of Proton Conductive Solid Electrolyte Membrane The above surface-modified inorganic porous membrane is converted into an inorganic porous membrane having a proton conductive group. That is, the group (Y) that is introduced into the surface and pores of the inorganic porous membrane and can be converted into a proton conductive group is chemically converted into a proton conductive group.

Specifically, when the group (Y) that can be converted into a proton conductive group is —SH, it is converted into —SO ₃ H by a known oxidation reaction. For example, in the oxidation reaction, nitric acid, hydrogen peroxide (water), oxygen, peracid (eg, formic acid, peracetic acid, perbenzoic acid, mCPBA) or the like can be used as an oxidizing agent.

When the group (Y) that can be converted into a proton conductive group is -P (O) (OR ¹ ) (OR ² ), it is converted into -PO ₃ H by a known hydrolysis reaction. For example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution can be used.

When the group (Y) that can be converted into a proton conductive group is —COOR ³ , it is converted to —CO ₂ H by a known hydrolysis reaction. For example, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, hydrochloric acid, trifluoromethanesulfonic acid, formic acid, etc. can be used.

  In the solid electrolyte membrane of the present invention thus obtained, the hydrogen atom of the hydroxyl group in the surface and pores of the inorganic porous membrane is substituted with a group having a proton conductive group. Specifically, it is substituted with a group represented by any of the following formulas (III) to (V).

_{-Si (CH 2) n -SO 3} H (III)
_{-Si (CH 2) n -PO 3} H (IV)
_{-Si (CH 2) n -COOH (} V)
(Where n is the same as above)
In the solid electrolyte membrane of the present invention, proton conductive groups (—SO ₃ H, —PO ₃ H, —CO ₂ H, etc.) are bonded to the inorganic porous material via a covalent bond or the like. In contrast, it has high stability and high proton conductivity.

The thickness of the solid electrolyte membrane of the present invention is about 100 μm to 1000 μm, preferably about 100 to 800 μm, the center pore diameter is about 1 to 50 nm, preferably about ^{2 to 20} nm, and the specific surface area is 200 to 800 m ^2. / g, preferably about 300 to 600 m ² / g, and the pore volume is about 0.1 to 1.0 cm ³ / g, preferably about 0.1 to 0.6 cm ³ / g.

Specifically, the solid electrolyte membrane of the present invention is on the order of 10 ⁻⁴ to 10 ⁻² S / cm, specifically 1 × 10 ⁻⁴ to 1 × under conditions of a temperature of 85 ° C. and a relative humidity of 95%. 10 ^-2 S / cm or so, preferably a high degree ^{5 × 10 -4 ~10 -2 S /} cm proton conductivity. Therefore, the solid electrolyte membrane of the present invention is widely used as a proton conductive material, and can be suitably used as, for example, a solid electrolyte membrane, a water electrolysis membrane, a sensor electrolyte membrane in a fuel cell or the like.

The solid electrolyte membrane of the present invention achieves high proton conductivity by the above-described novel surface modification method. In addition, since the substrate of the solid electrolyte membrane of the present invention is an inorganic compound, it has heat resistance and chemical resistance (corrosion resistance), and can be used at high temperatures. Therefore, the solid electrolyte membrane of the present invention is useful as, for example, a solid electrolyte membrane, a water electrolysis membrane, a sensor electrolyte membrane in a fuel cell or the like.

  Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof.

The proton conductivity test in the following examples was performed using an impedance analyzer with the sample sandwiched between the electrodes by a two-terminal method in an environmental test machine (an apparatus capable of keeping temperature and humidity variable and constant).

Example 1
Dissolve 2.0g of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) conjugated polymer in 15 g of ethanol, then solution 1.487 in 70% nitric acid / water (0.01 / 4 mol ratio) g was added. Further, 4.25 g of tetraethoxysilane was added and stirred at 35-40 degrees for 20 hours. The obtained solution was placed in a petri dish and then solidified by removing the solvent at room temperature to obtain an organic-inorganic hybrid film. A porous membrane was obtained by firing 0.497 g of an organic-inorganic hybrid membrane at 190 degrees for 3 hours.

A solution is prepared by adding 4.5 mL of dehydrated toluene to 0.12 g of 3-mercatopropyltrimethoxysilane. Using this solution, 0.12 g of the porous membrane was immersed and refluxed (refluxed) at 100 ° C. for 20 hours to introduce thiol groups into the inner surface of the porous glass pores, thereby modifying the porous glass membrane. Furthermore, an oxidation reaction was performed using a 70% nitric acid solution to convert the functional group from thiol to sulfonic acid. The used porous glass film A has a 10 mm square, a thickness of 0.6 mm, and an average pore diameter of 5.8 nm. The proton conductivity of this membrane at 85 ° C. and relative humidity of 95% was 2.7 × 10 ⁻³ S / cm. Thus, a film having high proton conductivity was obtained by this surface modification method.

Example 2
Dissolve 2.0g of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) conjugated polymer in 15 g of ethanol, then solution 1.487 in 70% nitric acid / water (0.01 / 4 mol ratio) g was added. Further, 4.25 g of tetraethoxysilane was added and stirred at 35-40 degrees for 20 hours. The obtained solution was placed in a petri dish and solidified by removing the solvent at 40 degrees to obtain an organic-inorganic hybrid film. A porous membrane was obtained by firing 0.31 g of an organic-inorganic hybrid membrane at 190 ° C. for 3 hours.

A solution is prepared by adding 5.5 mL of dehydrated toluene to 0.14 g of 3-mercaptopropyltrimethoxysilane. Using this solution, 0.14 g of the porous membrane was immersed and refluxed (refluxed) at 100 ° C. for 20 hours to introduce thiol groups into the inner surface of the porous glass pores, thereby modifying the porous glass membrane. Furthermore, an oxidation reaction was performed using a 70% nitric acid solution to convert the functional group from thiol to sulfonic acid. The used porous glass film A has a size of 7 mm square, a thickness of 0.4 mm, and an average pore diameter of 5.2 nm. The proton conductivity of this membrane at 80 ° C. and 95% relative humidity was 6.9 × 10 ⁻⁴ S / cm. Thus, a film having high proton conductivity was obtained by this surface modification method.

Example 3
Dissolve 2.0g of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) conjugated polymer in 15 g of ethanol, then solution 1.487 in 70% nitric acid / water (0.01 / 4 mol ratio) g was added. Further, 4.25 g of tetraethoxysilane was added and stirred at 35-40 degrees for 20 hours. The obtained solution was placed in a petri dish and solidified by removing the solvent at 80 degrees to obtain an organic-inorganic hybrid film. A porous membrane was obtained by baking 0.525 g of an organic-inorganic hybrid membrane at 190 degrees for 3 hours.

A solution is prepared by adding 5.5 mL of dehydrated toluene to 0.14 g of 3-mercaptopropyltrimethoxysilane. Using the solution, 0.15 g of the porous membrane was immersed and refluxed (refluxed) at 100 ° C. for 20 hours to introduce thiol groups into the inner surface of the porous glass pores, thereby modifying the porous glass membrane. Furthermore, an oxidation reaction was performed using a 70% nitric acid solution to convert the functional group from thiol to sulfonic acid. The used porous glass membrane A has an 8 mm square, a thickness of 0.64 mm, and an average pore diameter of 4.4 nm. The proton conductivity of this membrane at 85 ° C. and 95% relative humidity was 7.0 × 10 ⁻⁴ S / cm. Thus, a film having high proton conductivity was obtained by this surface modification method.

Claims (8)

A first step of producing an inorganic-organic hybrid membrane by a sol-gel method, a second step of producing an inorganic porous membrane by removing organic molecules from the inorganic-organic hybrid membrane, and a fine process of the inorganic porous membrane. A method for producing a proton conductive solid electrolyte membrane comprising a third step of introducing a proton conductive group into the pores and on the surface ,
After the third step, the inorganic porous membrane is surface-modified by reacting a silane coupling agent containing a group that can be converted into a proton conductive group in and on the pores of the inorganic porous membrane. , A step of chemically converting the proton-conducting group into a proton-conducting group.
A silane coupling agent containing a group that can be converted into the proton conductive group has the formula (I):
_{X j R k Si [(CH} 2) n -Y] m (I)
Wherein X is an alkoxy group or a halogen atom, R is an alkyl group, Y is a group that can be converted into a proton conductive group, j is 1, 2 or 3, k is 0, 1 or 2, m is 1, 2. Or 3 and satisfies j + k + m = 4, and n represents an integer of 2 to 11)
A method for producing a proton conductive solid electrolyte membrane, which is a compound represented by the formula: The process according to claim 1, wherein the first step is a step of producing an inorganic-organic hybrid film by mixing and solidifying tetraalkoxysilane and a surfactant under acidic conditions. The method according to claim 1, wherein the second step is a step of heating the inorganic-organic hybrid membrane to produce an inorganic porous membrane. The thickness of the inorganic porous membrane is 1000 μm or less, the center pore diameter is 1 to 50 nm, and the specific surface area is 200 to 800 m ² / g
The process according to claim ³ , wherein the pore volume is 0.1 to 1.0 cm ³ / g. A silane coupling agent containing a group that can be converted into a proton conductive group has the formula (II):
_{X 3 Si- (CH 2) n} -Y (II)
(Wherein X is an alkoxy group having 1 to 6 carbon atoms or a halogen atom, Y is —SH, —P (O) (OR ¹ ) (OR ² ) or —COOR ³ , R ¹ , R ² and R ³ are The same or different alkyl group, aryl group or aralkyl group, n represents an integer of 2 to 8)
The process according to claim 1 , wherein the compound is represented by the formula: Claim 1-5 proton conducting solid electrolyte membrane produced by the method according to any one of. The proton conductive solid electrolyte membrane according to claim 6 , having a thickness of 1000 µm or less, a central pore diameter of 1 to 50 nm, a specific surface area of 200 to 800 m ² / g, and a pore volume of 0.1 to 1.0 cm ³ / g. . A fuel cell using the proton conductive solid electrolyte membrane according to claim 6 or 7 .