JP2006054176A - Electrode for polymer electrolyte fuel cell, manufacturing method of electrode for polymer electrolyte fuel cell, and polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a polymer electrolyte fuel cell capable of obtaining the polymer electrolyte fuel cell which is superior in heat resistance and chemical resistance, and which functions stably even in a high temperature humidification state, and to provide a manufacturing method of the electrode for the polymer electrolyte fuel cell, and the polymer electrolyte fuel cell. <P>SOLUTION: This is the electrode for the polymer electrolyte fuel cell which has a porous conductor (A), a catalyst layer (B), and a gas diffusion layer (C). The catalyst layer (B) is composed of a proton conductor (B1), an electron conductive carbon (B2) which carries the catalyst, and the electron conductive carbon (B3), and in which the proton conductor (B1) is composed of a cross-linked structural body (a) consisting of a metal-oxygen bond, and an acid group containing structural body (b) having the acid group bonded by a covalent bond to the cross-linked structural body consisting of the metal-oxygen bond. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention provides an electrode for a polymer electrolyte fuel cell, which is excellent in heat resistance and chemical resistance, and can obtain a polymer electrolyte fuel cell that functions stably even in a high-temperature humidified state, and for a polymer electrolyte fuel cell The present invention relates to an electrode manufacturing method and a polymer electrolyte fuel cell.

Since fuel cells have high power generation efficiency and excellent environmental characteristics, in recent years, fuel cells have attracted attention as next-generation power generation devices that can contribute to solving environmental problems and energy problems that have become major social issues. Among these, solid polymer fuel cells are characterized by the fact that ion exchange resins and the like used as electrolytes are solid and polymer, and have been actively developed in recent years. Such a polymer electrolyte fuel cell has a structure in which both electrodes of a negative electrode and a positive electrode are arranged with an electrolyte interposed therebetween. For example, fuel hydrogen is supplied to the negative electrode side, and oxygen or air is supplied to the positive electrode side. Causes an electrochemical reaction to generate electricity.
Therefore, in order to maximize the performance of the polymer electrolyte fuel cell, an electrode structure that easily conducts protons and electrons and a highly functional catalyst for enhancing the electrode reaction are important issues. .

For such a problem, Patent Document 1 discloses a method of depositing a catalytic noble metal on the inner surface of an ion exchange membrane resin and then growing a catalytic metal layer on the surface. As the metal component used, platinum and other platinum group metals are shown.
In Non-Patent Document 1, Nafion 117 (registered trademark: manufactured by Du Pont), which is a kind of sulfonated fluororesin, is used as a solid polymer electrolyte, and an electrode is formed using this material and an electronic conductor. Discloses a method for improving the working area by making the reaction site of the catalyst layer three-dimensional. By using such a method, not only the contact surface between the electrolyte and the membrane but also the catalyst inside the catalyst layer can be used, and the utilization rate of platinum can be dramatically improved by this catalyst layer. . Furthermore, by dropping the ion exchange resin onto the platinum-supported carbon highly dispersed in the solution to form a catalyst layer that coats the ion-exchange resin on the surface of the platinum-supported carbon, the output can be further improved and the platinum utilization rate can be improved. It is illustrated.

However, when a thermoplastic fluoropolymer such as Nafion (registered trademark) is used as the proton conductor for the electrode, irreversible structural changes or partial dissolution occur in high-temperature humidified conditions or in the presence of chemicals such as methanol. There was a case. Therefore, a polymer electrolyte fuel cell having a catalyst-containing electrode using such a resin cannot obtain a stable output when operated at high temperature or when methanol is used as a fuel, and has heat resistance, chemical resistance, etc. The durability was also inferior. For this reason, there has been a need for a proton conductor capable of maintaining proton conductivity and the binding function of the catalyst-supporting carbon without causing irreversible structural changes even in the presence of chemicals such as high-temperature humidification or methanol. .

Japanese Patent Publication No.58-47471 M.M. Uchida, Y. et al. Fukuoka, Y. et al. Sugawara, H .; Ohta, and A.A. Ohta: J.M. Electrochem. Soc. , 145, 3708 (1998)

The present invention provides an electrode for a polymer electrolyte fuel cell, which is excellent in heat resistance and chemical resistance, and can obtain a polymer electrolyte fuel cell that functions stably even in a high-temperature humidified state, and for a polymer electrolyte fuel cell An object of the present invention is to provide an electrode manufacturing method and a polymer electrolyte fuel cell.

The present invention is an electrode for a polymer electrolyte fuel cell having a porous conductor (A), a catalyst layer (B), and a gas diffusion layer (C), wherein the catalyst layer (B) is a proton conductor ( B1), an electron conductive carbon (B2) carrying a catalyst, and an electron conductive carbon (B3). The proton conductor (B1) is a cross-linked structure (a ) And an acid group-containing structure (b) having an acid group covalently bonded to a crosslinked structure composed of a metal-oxygen bond.
Hereinafter, the present invention will be described in detail.

As a result of diligent research, the present inventors have found that a proton conductor constituting the catalyst layer of a polymer electrolyte fuel cell electrode includes a crosslinked structure composed of metal-oxygen bonds and a crosslinked structure composed of metal-oxygen bonds. By using a three-dimensional cross-linked structure comprising an acid group-containing structure having an acid group covalently bonded, no structural change occurs in the presence of a chemical such as high temperature or methanol, and a high temperature of 100 ° C. or higher. However, it has been found that an electrode for a polymer electrolyte fuel cell that exhibits stable performance can be obtained. Further, in addition to the electron conductive carbon carrying the catalyst in the catalyst layer, the electron conductive carbon not carrying the catalyst is added to the anode side by adding the electron conductive carbon not carrying the catalyst. In the present invention, it has been found that a polymer electrolyte fuel cell with good power generation performance can be realized by functioning as a gas channel for supplying reaction gas to the catalyst and functioning as a channel for draining reaction product water on the cathode side. It came to complete.

By using the polymer electrolyte fuel cell electrode of the present invention, it has excellent heat resistance and chemical resistance, and functions stably even in the presence of chemicals such as high-temperature humidification and methanol, so that the operating temperature is 100 ° C. or higher. It is possible to obtain a polymer electrolyte fuel cell that can be As a result, it is possible to improve the power generation efficiency and reduce the CO non-poisoning of the catalyst. In addition, the operating temperature can be expanded to a cogeneration system using heat, which can lead to a dramatic improvement in energy efficiency.

The electrode for a polymer electrolyte fuel cell of the present invention has a porous conductor (A), a catalyst layer (B), and a gas diffusion layer (C).
Here, the polymer electrolyte fuel cell electrode refers to a member that undergoes an oxidation reaction of hydrogen and a reduction reaction of oxygen. Such an electrode for a polymer electrolyte fuel cell is referred to as a proton conductive solid high electrode. A polymer electrolyte fuel cell is formed by connecting a pair of separators arranged on both sides of a molecular film and having a structure for supplying fuel to both sides as unit cells. Can be used.

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of the polymer electrolyte fuel cell electrode of the present invention. As shown in FIG. 1, an electrode 1 for a polymer electrolyte fuel cell is composed of (A) a porous conductor 2 and (C) a gas diffusion layer 4 and (B) a catalyst layer 3 laminated in three layers. It consists of a structure. However, (C) the gas diffusion layer 4 may be formed simultaneously with (A) the porous conductor 2 or (B) the catalyst layer 3 and integrated.

The porous conductor (A) is one constituent layer of the polymer electrolyte fuel cell electrode of the present invention, and plays a role as a current collector and gas diffusion.

A preferable upper limit of the resistance value in the thickness direction of the porous conductor (A) is 50 mΩ · cm ² . When it exceeds 50 mΩ · cm ² , an ohmic loss occurs at a high current density, and the output may decrease due to the influence.
Moreover, the minimum with the preferable gas transmission rate of the said porous conductor (A) is 100 mL * mm / (cm < ² > * hr * mmAg). If it is less than 100 mL · mm / (cm ² · hr · mmAg), hydrogen and oxygen may not be smoothly conveyed to the catalyst layer (B). In addition, in order to make the said gas permeation rate into the said range, it is preferable that the porosity (ratio of the whole volume and the volume of a pore part) of the said porous conductor (A) is 50% or more.

The porous conductor (A) is preferably water repellent. In the fuel cell reaction, hydrogen is oxidized and protons and electrons are generated on the anode side, while oxygen is reduced and water is generated on the cathode side. In this way, the electrode, particularly the cathode side electrode, is affected by the generated water, and water may enter the fine pores formed by the electrode, causing flooding (clogging by the generated water). is there. However, by making the porous conductor (A) water repellent, generated water can be eliminated and flooding can be effectively prevented.

Examples of a method of making the porous conductor (A) water-repellent include a method of impregnating the porous conductor (A) with a fluororesin such as polytetrafluoroethylene (PTFE), or a porous conductor (A ) The method of fluorinating itself may be mentioned, but the method of impregnating with a fluororesin is more preferred.
As the fluororesin used in the method for impregnating the fluororesin, a tetrafluoroethylene-hexafluoropropylene copolymer (FEP resin) having a low melt viscosity is particularly suitable. When the porous conductor (A) is water-repellent by impregnating the FEP resin, the FEP resin may be impregnated within a range of 5 to 40% by weight with respect to the porous conductor (A). preferable.

The polymer electrolyte fuel cell of the present invention has a gas diffusion layer (C). By having the gas diffusion layer (C), it is possible to improve the gas diffusion performance and enable appropriate electronic conductivity and moisture management. The gas diffusion layer (C) is preferably formed between the porous conductor (A) and the catalyst layer (B). However, the gas diffusion layer (C) may be formed simultaneously with the porous conductor (A) or the catalyst layer (B).

The gas diffusion layer (C) is preferably water repellent. As described above, in the electrode, particularly the cathode side electrode, flooding may occur due to the generated water, but the generated water is eliminated by making the gas diffusion layer (C) water repellent. And flooding can be effectively prevented. Therefore, the gas diffusion layer (C) is preferably a mixture of polytetrafluoroethylene (PTFE) as a water repellent material and carbon black as an electron conductor. In this case, the mixing ratio of carbon black and polytetrafluoroethylene (PTFE) is preferably 3: 7 to 7: 3, more preferably 5: 5. Since polytetrafluoroethylene (PTFE) is a non-conductor, adding a large amount may increase resistance.

Moreover, the preferable upper limit of the thickness of a gas diffusion layer (C) is 0.1 mm. If it exceeds 0.1 mm, the resistance value increases and the output may decrease. Moreover, carbon black used in the gas diffusion layer (C) can be appropriately free materials can be used, particularly preferably not less than a specific surface area of 10 m 2 / ^g.

The electrode for a polymer electrolyte fuel cell of the present invention has a catalyst layer (B).
The catalyst layer (B) combines (i) a reaction that decomposes hydrogen on the fuel side into protons (hydrogen ions) and electrons, and (ii) a combination of protons, electrons, and oxygen on the oxygen side. It is a layer that performs a reaction to form water.

In the catalyst layer (B) of the polymer electrolyte fuel cell electrode arranged on the anode (fuel electrode) side, when hydrogen is supplied as the fuel, H ₂ → 2H ⁺ + 2e ⁻ The reaction is promoted to generate protons and electrons, and the protons pass through the proton conductive membrane in contact with the electrodes, and the catalyst layer (B) of the polymer electrolyte fuel cell electrode disposed on the cathode (oxygen electrode) side. To be supplied. Electrons are collected by the polymer electrolyte fuel cell electrode on the fuel electrode side, used as electricity, and then supplied to the oxygen electrode side.
On the other hand, the oxygen electrode side catalyst layer receives supplied oxygen, protons passing through the proton conductive membrane, and electrons used as electricity, and a reaction of 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O occurs. It becomes. At this time, the catalyst in the catalyst layer (B) functions to promote the reaction of 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O.

The catalyst layer (B) is composed of a proton conductor (B1), an electron conductive carbon (B2) carrying a catalyst, and an electron conductive carbon (B3).
The proton conductor (B1) has a function of conducting protons generated by the catalyst to the proton conductive membrane, and the proton conductor (B1) is a crosslinked structure (a) composed of a metal-oxygen bond. And an acid group-containing structure (b) having an acid group bonded by a covalent bond and a crosslinked structure consisting of a metal-oxygen bond. By having such a structure, the proton conductor (B1) is not easily deformed or altered by heat, and the three-phase interface is not destroyed or modified. In addition, the polymer electrolyte fuel cell having such a proton conductor (B1) can operate at a high temperature, increases energy efficiency, reduces catalyst poisoning, simplifies a cooling device by improving cooling efficiency, etc. You can enjoy great benefits. The three-phase interface means an interface formed between the catalyst-fuel gas or oxygen gas, the catalyst-proton conductor, and the catalyst-electron conductive material (carbon black).

The proton conductor (B1) has a crosslinked structure (a) formed of a metal-oxygen bond formed by a sol-gel reaction and an acid group covalently bonded to the crosslinked structure formed of a metal-oxygen bond. A three-dimensional cross-linked structure composed of the acid group-containing structure (b) is preferable. By forming a three-dimensional crosslinked structure composed of metal-oxygen bonds by the sol-gel reaction, the proton conductivity of the proton conductor (B1) is improved, and the battery performance is improved, such as an increase in power generation output. be able to.
Here, the sol-gel reaction refers to a reaction that forms a three-dimensional crosslinked structure by a metal-oxygen bond by hydrolysis or condensation reaction of a metal alkoxide such as an alkoxysilyl group or a metal halide with an acid or water. A typical example is a reaction for forming a three-dimensional cross-linking structure composed of a metal-oxygen bond composed of metal elements such as silicon, titanium, zirconium, and aluminum and oxygen. The sol-gel reaction is a hydrolysis or condensation reaction of a metal compound (precursor) having an alkoxy group or a halogen. As the metal compound, a three-dimensional cross-linked structure with a metal-oxygen bond is obtained by hydrolysis or condensation reaction. Can be used.

As the cross-linked structure (a) composed of the metal-oxygen bond, a cross-linked structure composed of a silicon-oxygen bond is preferable, and among them, a structure having the structure represented by the following chemical formula (1) is preferable.

式（１）中、Ｘは架橋に関与する−Ｏ−結合又はＯＨ基であり、Ｒ^１はメチル基、エチル基、プロピル基、ブチル基又はフェニル基を表し、ｎは０〜３の整数である。

In Formula (1), X is an —O— bond or OH group involved in crosslinking, R ¹ represents a methyl group, an ethyl group, a propyl group, a butyl group, or a phenyl group, and n is an integer of 0 to 3. is there.

In the crosslinked structure (a) having the structure represented by the chemical formula (1), n is preferably 0. When n is 0, the number of —O— bonds involved in crosslinking with respect to one silicon atom is maximized, and the three-dimensional crosslinked structure formed of the crosslinked structure (a) can be made stronger. A catalyst layer (B) that is excellent in heat resistance and chemical resistance and that functions stably even in a high-temperature humidified state or in the presence of chemicals such as methanol can be obtained.

Moreover, as a precursor in the case of forming the crosslinked structure which consists of a silicon- oxygen bond by sol-gel reaction, alkoxysilane compounds, such as tetraethoxysilane and tetramethoxysilane, are mentioned, for example. These are preferable because they are available in large quantities and at low cost, and the reaction control is easy. Moreover, as the alkoxysilane compound, a compound partially substituted with an alkyl group or a phenyl group may be used.

The proton conductor (B1) includes an acid group-containing structure having an acid group covalently bonded to a crosslinked structure composed of a metal-oxygen bond in addition to the crosslinked structure (a) composed of a metal-oxygen bond ( b)
By having the acid group, a sufficient proton concentration of the proton conductor (B1) can be secured, and a decrease in proton conductivity of the proton conductor (B1) can be prevented. In addition, as a method of fixing the acid group to the catalyst layer, a method of holding the acid group in the catalyst layer by ionic interaction or the like may be considered. However, in such a method, water supplied to the fuel cell, fuel cell operation, It may be extracted and dissipated from the catalyst layer due to water generated at times. However, in the present invention, since the acid group-containing structure (b) is covalently bonded to the crosslinked structure composed of metal-oxygen bonds, the acid groups are not easily separated, and the proton conduction is performed. The proton conductivity of the body (B1) can be stably maintained.

The acid group-containing structure (b) is not particularly limited as long as it has an acid group and is covalently bonded to a crosslinked structure composed of a metal-oxygen bond. It preferably has a crosslinked structure composed of the same kind of metal-oxygen bond as the crosslinked structure (a) composed of a bond. The acid group-containing structure (b) preferably has the following general formula (2).

In the formula (2), X is an —O— bond or OH group involved in crosslinking, R ² is a methyl group, ethyl group, propyl group, butyl group or phenyl group, and R ³ is carbon number 1 containing an acid group. Represents an organic group of ˜50, and m is an integer of 0˜2.

R ³ has at least one acid group and is bonded to a crosslinked structure composed of a metal-oxygen bond by a covalent bond. Examples of the acid group include a sulfonic acid group, a phosphonic acid group, a carboxylic acid group, a sulfuric acid group, a phosphoric acid group, and a boric acid group. Among these, it is preferable to use a sulfonic acid group because the pKa is particularly low, the proton concentration in the catalyst layer can be sufficiently secured, and it is thermally stable.
The acid group may be covalently bonded to a crosslinked structure composed of a metal-oxygen bond via an alkylene group, and the alkylene group is not particularly limited. For example, a methylene group, Examples thereof include an ethylene group, a trimethylene group, a tetramethylene group, a hexamethylene group, and an octamethylene group.
Moreover, in the said acid group containing structure (b), since the one where there are many metal-oxygen bonds can hold | maintain a three-dimensional crosslinked structure, and there is little performance deterioration, in the said General formula (2), m is preferably 0.

Furthermore, it is preferable that R ³ of the acid group-containing structure (b) has a structure represented by the following general formula (3).

式（３）中、ｎは１〜２０の整数である。

In formula (3), n is an integer of 1-20.

Examples of the raw material of the acid group-containing structure (b) in which n in the general formula (3) is 3 include trihydroxysilylpropyl sulfonic acid. The trihydroxysilylpropylsulfonic acid is commercially available from Gelest, and is easily available and can be used particularly preferably. In addition, a synthesis method using allyl bromide as a raw material has been established and is easily available.

The proton conductor (B1) is an acid group-containing oligomer comprising the crosslinked structure (a) and an acid group-containing structure (b), or a crosslinked structure (a) and an acid group-containing structure (b). It is preferable that it consists of. By using the acid group-containing oligomer, the crosslinking control with the crosslinked structure (a) becomes easier than in the case where the acid group-containing structure (b) is used alone, and more stably in the catalyst layer (B). Acid groups can be present. That is, when the acid group-containing structure (b) is used alone, it becomes a homostructure (a state where each is independently crosslinked and exists as a mixture), and the proton conductor (B1) is converted into metal-oxygen. It may not be possible to obtain a strong three-dimensional crosslinked structure by bonding. Moreover, even if it is a case where a three-dimensional crosslinked structure can be obtained by combination with a specific crosslinked structure (a), the crosslinked structure is combined under the restriction of the type of crosslinking structure and crosslinking reaction conditions, If the crosslinking reaction conditions are not preferred, a three-dimensional crosslinked structure may not be obtained, resulting in a homostructure or the like, or the acid group-containing structure (b) may be dissipated.

On the other hand, when an acid group-containing oligomer is used, since the crosslinking group in the oligomer can be freely controlled, the degree of freedom of the crosslinked structure to be combined or the crosslinking reaction conditions is remarkably improved. Furthermore, by adjusting the composition and degree of polymerization of the acid group-containing oligomer, the reaction rate, polarity, etc. can be adjusted, the process window is widened, and it becomes easy to form a three-dimensional crosslinked structure. Furthermore, an efficient proton conduction path (ion channel) can be formed by previously arranging a plurality of acid groups in an acid group-containing oligomer.
For example, as a means for increasing proton conductivity, there is a method of introducing an acid group in a large amount, but the acid group is introduced even to a portion where it does not become an ion path, and as a result, the electrode becomes extremely hydrophilic, Due to this contact, the electrode cracks or dissolves in water. On the other hand, when an acid group-containing oligomer is used, an acid group can be introduced efficiently along the ion path, so that sufficient physical properties (durability, heat resistance, water resistance, etc.) of the electrode are not degraded and sufficient protons are obtained. It becomes possible to ensure conductivity.

Examples of the method for producing the acid group-containing oligomer include, for example, polycondensation of a mercapto group-containing alkoxysilane alone or copolycondensation of the mercapto group-containing alkoxysilane with another hydrolyzable silyl compound or the like. And a method of substituting a mercapto group with a sulfonic acid group. The mercapto group-containing alkoxysilane is not particularly limited as long as it has at least one mercapto group and at least one alkoxysilyl group, but a compound having a structure represented by the following general formula (4) is used. Is preferred.

式（４）中、Ｒ^４はＣＨ_３、Ｃ_２Ｈ_５、Ｃ_３Ｈ_７、Ｃ_４Ｈ_９又はＣ_６Ｈ_５、Ｒ^５はＯＣＨ_３、ＯＣ_２Ｈ_５、ＯＣ_３Ｈ_７又はＯＣ_４Ｈ_９であり、ｍは２〜３の整数、ｔは０〜１の整数であり、ｍ＋ｔは３である。また、ｎは１〜２０の整数である。

In formula (4), R ⁴ is CH ₃ , C ₂ H ₅ , C ₃ H ₇ , C ₄ H ₉ or C ₆ H ₅ , and R ⁵ is OCH ₃ , OC ₂ H ₅ , OC ₃ H ₇ or OC _4. is H _9, m is 2-3 integer, t is an integer from 0 to 1, m + t is 3. Moreover, n is an integer of 1-20.

R ⁴ is not particularly limited as long as it is a non-reactive group that does not react with an alkoxysilyl group, and an alkyl group having 4 or less carbon atoms, a phenyl group, or the like is preferably used in consideration of stability, cost, and the like.

The R ⁵ is not particularly limited as long as it can undergo a condensation reaction or can generate a group that can be condensed by hydrolysis, and examples thereof include a hydroxy group, an alkoxy group, an acetoxy group, and chlorine. Among these, an alkoxy group is most preferable, and an alkoxy group having 4 or less carbon atoms that is easily available is particularly preferable.

In the compound having the structure represented by the general formula (4), m is 2 to 3. When m is 1, the reaction stops when the polycondensation reaction is performed, and a preferable mercapto group-containing oligomer cannot be formed or the reactivity of the mercapto group-containing oligomer may be extremely reduced. It is difficult to use as. It is possible to adjust the molecular weight of the mercapto group-containing oligomer by adding a small amount.

Examples of mercapto group-containing alkoxysilanes in which m is 3 include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltripropoxysilane, 3-mercaptopropyltributoxysilane, 2-mercapto. Examples include ethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 2-mercaptoethyltripropoxysilane, 2-mercaptoethyltributoxysilane, and mercaptomethyltrimethoxysilane. Among these, those in which R ⁵ is OCH ₃ or OC ₂ H ₅ are preferable, and in particular, 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane in which t is 0, m is 3, and n is 3 are , Commercially available from Gelest, and can be preferably used. Among these, 3-mercaptopropyltrimethoxysilane having R ⁵ of OCH ₃ is a general-purpose product and can be preferably used because it is available in large quantities and at a low price.

Examples of mercapto group-containing alkoxysilanes in which m is 2 and t is 1 include 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-mercaptopropylmethyldipropoxysilane, and 3-mercaptopropylmethyl. Examples include dibutoxysilane, 3-mercaptopropylethyldimethoxysilane, 3-mercaptopropylbutyldiethoxysilane, 3-mercaptopropylphenyldimethoxysilane, mercaptomethylmethyldiethoxysilane, and the like. Among these, compounds in which R ⁵ is OCH ₃ or OC ₂ H ₅ and R ⁴ is CH ₃ are preferred, and 3-mercaptopropylmethyldimethoxysilane in which n is 3 is commercially available from Gelest. Are preferably used.

In addition, the mercapto group-containing alkoxysilane is obtained by hydrosilylation reaction using a platinum complex catalyst in the double bond portion of a linear hydrocarbon compound having 20 or less carbon atoms having a double bond and a halogen group. A method of introducing an alkoxysilyl group and reacting sodium hydrosulfide with the halogen group, or when there are two double bonds, an alkoxysilyl group is introduced into one double bond by a hydrosilylation reaction, and the other It can also be obtained by a method of hydrolyzing after adding thiosulfuric acid or the like to the double bond. In this case, when a compound having an alkoxysilyl group in advance and having a halogen group or a double bond is used as a raw material, the reaction can be completed in one step, which is preferable.

Moreover, as a hydrolysable silyl compound used when manufacturing the said acid group containing oligomer, the compound which has a structure shown in following General formula (5) can be used.

式（５）中、Ｒ^６はＣｌ、ＯＨ、ＯＣＨ_３、ＯＣ_２Ｈ_５、ＯＣ_３Ｈ_７、ＯＣ_４Ｈ_９又はＯＣＯＣＨ_３である。

In the formula (5), R ⁶ is Cl, OH, OCH ₃ , OC ₂ H ₅ , OC ₃ H ₇ , OC ₄ H ₉ or OCOCH ₃ .

Examples of the hydrolyzable silyl compound represented by the general formula (5) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane. Among these, tetramethoxysilane and tetraethoxysilane are general-purpose products, are inexpensive, and are easily available in large quantities, and therefore can be particularly preferably used. In the hydrolyzable silyl compound represented by the general formula (5), as R ⁵ , an alkoxy group is most preferable, and an alkoxy group having 4 or less carbon atoms that is easily available is particularly preferable.

Furthermore, as a hydrolysable silyl compound used when manufacturing the said acid group containing oligomer, the compound which has a structure shown to following General formula (6) can be used.

式（６）中、Ｒ^７はＣｌ、ＯＨ、ＯＣＨ_３、ＯＣ_２Ｈ_５、ＯＣ_３Ｈ_７、ＯＣ_４Ｈ_９又はＯＣＯＣＨ_３であり、Ｒ^８はＣＨ_３、Ｃ_２Ｈ_５、Ｃ_３Ｈ_７、Ｃ_４Ｈ_９、Ｃ_６Ｈ_１３、Ｃ_８Ｈ_１７、Ｃ_１１Ｈ_２３、Ｃ_１２Ｈ_２５、Ｃ_１６Ｈ_３３、Ｃ_１８Ｈ_３７又はＣ_６Ｈ_５であり、ｍは２〜３の整数、ｎは１〜２の整数である。但し、ｍ＋ｎ＝４である。

In the formula (6), R ⁷ is Cl, OH, OCH ₃ , OC ₂ H ₅ , OC ₃ H ₇ , OC ₄ H ₉ or OCOCH ₃ , and R ⁸ is CH ₃ , C ₂ H ₅ , C ₃ H ₇ , C ₄ H ₉ , C ₆ H ₁₃ , C ₈ H ₁₇ , C ₁₁ H ₂₃ , C ₁₂ H ₂₅ , C ₁₆ H ₃₃ , C ₁₈ H ₃₇ or C ₆ H ₅ , m is 2 to 3 An integer, n is an integer of 1 to 2. However, m + n = 4.

In the hydrolyzable silyl compound having the structure represented by the general formula (6), m is 2 to 3. When m is 1, the end may be blocked when the polycondensation reaction is performed, or the reactivity of the oligomer may be extremely reduced, as in the case of mercapto group-containing alkoxysilane. Although it is difficult to use as a main component, it is possible to adjust the molecular weight of the mercapto group-containing oligomer by adding a small amount.

As R ⁷ , any compound that can undergo a condensation reaction or that generates a group that can be condensed by hydrolysis may be used. Examples thereof include a hydroxy group, an alkoxy group, an acetoxy group, and chlorine. Among these, an alkoxy group is most preferable, and an alkoxy group having 4 or less carbon atoms that is easily available is particularly preferable.

Examples of the hydrolyzable silyl compound represented by the general formula (6) include methyltrimethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, phenylmethyldimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, i Examples include methoxy compounds such as -propyltrimethoxysilane and n-butyltrimethoxysilane, and ethoxy compounds, isopropoxy compounds, and butoxy compounds thereof. In particular, when R ⁷ is methoxy or ethoxy, reaction control and availability are easy to use.

A method for producing a mercapto group-containing oligomer having a plurality of mercapto groups using the mercapto group-containing alkoxysilane or, if necessary, a hydrolyzable silyl compound as a raw material is not particularly limited. For example, JP-A-9-40911 Publication, JP-A-8-134219, JP-A-2002-30149, Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 33, pp. 751-754, 1995, Journal of Polymer Science: Partner A: Party 37, pages 1017-1026, 1999, etc., can be used.

By oxidizing the mercapto group of the mercapto group-containing oligomer produced by the above-mentioned method to form a sulfonic acid group to form a sulfonic acid group-containing oligomer, the acid group-containing oligomer can be used. The method for oxidizing the mercapto group is not particularly limited, and for example, hydrogen peroxide, peracetic acid, performic acid, nitric acid, plasma, light, active oxygen, ozone, or the like can be used. In addition, about the thing of aqueous solution, since the produced | generated acid group containing oligomer may become a three-dimensional crosslinked structure with the produced | generated sulfonic acid and water, in such a case, what does not contain water, such as ozone Is preferably used.

The mass ratio between the crosslinked structure (a) and the acid group-containing structure (b) in the proton conductor (B1) of the present invention is such that the catalyst layer (B) satisfies heat resistance, flexibility, and proton conductivity. If it is, it will not specifically limit, Although it changes also with each structure and manufacturing method, the range of 1: 9-9: 1 is preferable. When there are too few crosslinked structures (a), a softness | flexibility and heat resistance may fall. On the other hand, when there are too few acid group containing structures (b), proton conductivity may become very low.

The catalyst layer (B) includes, in addition to the proton conductor (B1), an electron conductive carbon (B2) and an electron conductive carbon (B3) formed by supporting a catalyst. Thereby, in the said catalyst layer (B), the said proton conductor (B1) takes the form formed in the pore which the electron conductive carbon (B2) formed by carrying | supporting a catalyst, A polymer electrolyte fuel cell electrode having high heat resistance and chemical resistance and functioning stably even at high temperatures can be obtained.

Examples of the catalyst used in the electron conductive carbon (B2) carrying the catalyst include platinum, a noble metal alloy containing platinum, and other known catalysts. Examples of the noble metal alloy having platinum include a platinum-ruthenium alloy and a platinum-iron alloy. In a direct methanol fuel cell, it is preferable to use a platinum-ruthenium alloy having a platinum: ruthenium ratio of 1: 1. .

A preferable lower limit of the amount of the catalyst supported is 10% by weight with respect to the carbon black of the carrier. If it is less than 10% by weight, the amount of catalyst supported is small, and the output of the obtained polymer electrolyte fuel cell may be lowered. A more preferred lower limit is 30% by weight.

In the present invention, the catalyst needs to be in direct contact with fuel (hydrogen gas, methanol, etc.). If it is not in direct contact with the fuel, it cannot act to decompose hydrogen into protons and electrons. Further, the catalyst needs to be in contact with a conductive material (electron conductive carbon) capable of conducting electrons (electricity). Electrons generated on the surface of the catalyst are transmitted to the conductive material (electron conductive carbon) or electrode in contact with the catalyst through the catalyst itself, and are induced to the outside. Furthermore, the catalyst needs to be in contact with the proton conductor in the catalyst layer. That is, it is necessary to transmit the proton generated on the catalyst surface to the proton conductor in the catalyst layer, and further to transmit the proton to the oxygen electrode side through the proton conductive electrolyte membrane.

The carbon black suitably used for the electron-conducting carbon (B2) carrying the catalyst carries the function as a carrier carrying the catalyst and conducts electrons (electricity) generated by the catalyst to an external conductor. It has a function as a conductor for the purpose. The carbon black generally exists in a state where particles are fused. These particles are called primary particles or aggregates, and the aggregates of these aggregates are called agglomerates (aggregates). The gap between the agglomerates serves as a reaction gas or water vapor diffusion passage or a generated water drainage passage (gas channel) (for example, J. Electrochem. Soc Vol. 142, No. 2, page 463). A part of the agglomerate in the carbon black on the catalyst layer is buried in the electrolyte membrane by hot pressing or the like and is firmly bonded.

In the electron conductive carbon (B2) formed by supporting the catalyst, a preferable lower limit of the specific surface area evaluated by the BET method is 100 m ² / g, and a preferable upper limit is 1500 m ² / g. Since the region where the electrode reaction occurs is limited to the vicinity of the interface between the electrolyte membrane and the electrode and a thin portion of about 10 to 50 μm from the surface of the membrane, a catalyst layer having a catalyst density as high as possible can be formed in this region. This is an indispensable condition for improving electrode performance. For this purpose, it is preferable to support a large amount of catalyst using carbon black having a large surface area. If it is less than 100 m ² / g, the catalyst may not be supported in a highly dispersed state. If it exceeds 1500 m ² / g, the carbon black becomes brittle and tends to collapse, which is not preferable. Therefore, in order to realize high dispersion support while maintaining the strength, about 200 to 1000 m ² / g is more preferable. The specific surface area of the BET method is determined by immersing degassed carbon black in liquid nitrogen in accordance with JIS K 6217, measuring the amount of nitrogen adsorbed on the carbon black surface at equilibrium, and calculating the specific surface area from the value. (M ² / g) is a calculated value.

The preferable lower limit of the DBP oil absorption amount of the electron conductive carbon (B2) formed by supporting the catalyst is 50 ml / 100 g. If the DBP oil absorption amount is outside the above range, the reaction gas and water vapor diffusion passages or the generated water drainage passages are reduced, and it is difficult to form a three-phase interface. The DBP oil absorption is an amount (ml / 100 g) of carbon black absorbed with dibutyl phthalate (DBP) and is a value correlated with the agglomerate volume in the carbon black.

The catalyst layer (B) has electron conductive carbon (B3).
Since the electron conductive carbon (B2) formed by supporting the catalyst has a step of supporting the catalyst in the production process, the types of usable carbon are limited. Also, carbon having good catalyst supportability is not necessarily advantageous for gas channel formation, and the catalyst layer (B) having only the electron conductive carbon (B2) formed by supporting the catalyst has a gas channel structure. Formation may be insufficient.
Therefore, in the present invention, it is not necessary to pursue catalyst supportability, and by using electron conductive carbon (B3) advantageous for gas channel formation, it becomes easy to prevent an increase in concentration overvoltage, and a good three-phase interface. Thus, an electrode for a polymer electrolyte fuel cell capable of realizing good power generation performance can be realized.

In the electron conductive carbon (B3), a preferable lower limit of the specific surface area evaluated by the BET method is 10 m ² / g. If it is less than 10 m ² / g, it may be difficult to form a gas channel.

In the electron conductive carbon (B3), a preferable lower limit of the DBP oil absorption is 50 ml / 100 g. If it is less than 50 ml / 100 g, it may be difficult to form a gas channel.

The preferable lower limit of the content of the electron conductive carbon (B3) is 1% by weight in terms of the carbon weight ratio with respect to the electron conductive carbon (B2) formed by supporting the catalyst, and the preferable upper limit is 100% by weight. If it is less than 1% by weight, the effect of adding the electron conductive carbon (B3) cannot be sufficiently exhibited, and if it exceeds 100% by weight, the thickness of the catalyst layer (B) becomes too thick. In some cases, the ohmic loss increases due to an increase in the proton transfer path, and the gas diffusion performance deteriorates due to a longer gas path.

A preferable upper limit of the thickness of the catalyst layer (B) is 30 μm. If it exceeds 30 μm, an increase in ohmic loss due to an increase in the proton transfer path and a decrease in gas diffusion performance due to a longer gas path may occur.

FIG. 2 is a schematic view showing a state of the electron conductive carbon (B2) and the electron conductive carbon (B3) formed by supporting the catalyst in the catalyst layer (B). (1) in FIG. 2 is a schematic view of a conventional electrode including only an electron conductive carbon (B2) formed by supporting a catalyst on a catalyst layer, and (2) is an electron conductive carbon formed by supporting a catalyst ( It is the schematic of the electrode for polymer electrolyte fuel cells of this invention containing both B2) and electron conductive carbon (B3).
In the electrode shown in FIG. 2 (1), the proton conductor (B1) is formed in the pores formed by the electron conductive carbon (B2) formed by supporting the catalyst. While the proton network function, which is the ability to carry oxygen, is improved, the proton conductor (B1) closes the pores formed by the electron-conductive carbon (B2) that supports the catalyst, so the material supply in electrochemistry is insufficient As a result, the concentration overvoltage may increase. However, in the electrode shown in FIG. 2 (2), since the electron conductive carbon (B3) functions as a gas channel, even if the amount of the proton conductor (B1) in the electrode is large, an increase in concentration overvoltage is prevented. Can do. On the cathode side, the gas channel may be further blocked by the reaction product water. However, since the electron conductive carbon (B3) functions as a drain channel for the reaction product water, the gas channel can be secured.

Thus, in the catalyst layer (B), a cross-linked structure (a) composed of a metal-oxygen bond and an acid group-containing structure having an acid group covalently bonded to the cross-linked structure composed of a metal-oxygen bond ( The proton conductor (B1) composed of b) is formed in the pores formed by the electron conductive carbon (B2) formed by supporting the catalyst, and has heat resistance and chemical resistance. In addition, it is possible to construct an electrode that is high and that functions stably even at high temperatures. Further, in the present invention, it is not necessary to pursue catalyst supportability, and by using electron conductive carbon (B3) advantageous for gas channel formation, it becomes easy to prevent an increase in concentration overvoltage, and a good three-phase interface. Therefore, it is possible to realize a polymer electrolyte fuel cell electrode capable of realizing power generation performance.

The electrode for a polymer electrolyte fuel cell of the present invention can be produced by providing the porous conductor (A) with the gas diffusion layer (C) and then laminating the catalyst layer (B).
Here, the proton conductor (B1) constituting the catalyst layer (B) is preferably produced by a sol-gel reaction. However, since the sol-gel reaction is an extremely fast reaction, when the crosslinked structure (a) and the acid group-containing structure (b) are mixed at the same time in the production of the catalyst layer (B), the viscosity gradually increases. Since it rises and gels rapidly, for example, Step 1 for preparing a slurry by mixing an electron conductive carbon (B2) carrying a catalyst and an acid group-containing structure (b), Step 2 for mixing a cross-linked structure (a) composed of metal-oxygen bonds to prepare a paste, Step 3 for adding electron conductive carbon (B3) to the paste, and adding the electron conductive carbon (B3) The applied paste is applied onto a porous conductor with a gas diffusion layer and then pressed to form a catalyst layer (B) 4, and the catalyst layer (B) is dried and the entire electrode is hot-pressed Step 5 The Ukoto, it is possible to produce a polymer electrolyte fuel cell electrode. Such a method for producing an electrode for a polymer electrolyte fuel cell is also one aspect of the present invention.

In step 1, the electron conductive carbon (B2) formed by supporting the catalyst and the acid group-containing structure (b) are mixed to prepare a slurry, and the electron conductive carbon formed by supporting the catalyst as a carrier. This is a step of modifying the acid group-containing compound on the surface of (B2). In addition, you may use an acid group containing oligomer as said acid group containing structure (b).

The electron-conducting carbon (B2) formed by supporting the catalyst has strong agglomeration and is present not as primary particles but as an aggregate of primary particles (aggregates). Then, after pulverizing the electron conductive carbon (B2) formed by supporting the agglomerated catalyst to reduce the agglomerate size, protons are formed on the surface of the electron conductive carbon (B2) formed by supporting the catalyst. The acid group-containing structure (b) that is a raw material of the conductor is adsorbed.
As a method for pulverizing the electron conductive carbon (B2) formed by supporting the agglomerated catalyst, for example, a ball mill method, an ultrasonic dispersion method, or the like can be used. From the viewpoint, the ultrasonic dispersion method is preferable.

When the electron conductive carbon (B2) formed by supporting the catalyst and the acid group-containing structure (b) are mixed, a solvent may be used. The solvent is not particularly limited as long as it can be used for dissolving and mixing organic substances and metal alkoxides. For example, alcohols such as methanol, ethanol, isopropanol, n-butanol and t-butanol, tetrahydrofuran, dioxane and the like Ethers, glycol alkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, water, and the like. The content of the solvent is not particularly limited, and usually the solid content is preferably about 10 to 80% by weight.

In Step 2, the slurry obtained in Step 1 was mixed with a crosslinked structure (a) composed of a metal-oxygen bond, and adsorbed on the surface of the electron conductive carbon (B2) carrying the catalyst. In this step, a sol-gel reaction is caused between the acid group-containing structure (b) and the crosslinked structure (a) to produce a paste.

In step 2, it is preferable to cause a sol-gel reaction by ultrasonic dispersion. In Steps 1 and 2, since the viscosity of the reaction mixture may increase rapidly due to the progress of the sol-gel reaction, the viscosity of the paste is maintained at a viscosity that can be applied in a later step. It is preferable to do. Here, the preferable lower limit of the coatable viscosity is 500 cp, and the preferable upper limit is 10,000 cp. If it is out of the above range, the coating in the next step may not be performed smoothly. Moreover, in order to maintain the said viscosity in the said range, it is preferable to perform the process of maintaining a mixture at 0-40 degreeC. Specifically, for example, a method of adjusting the temperature to a room temperature state, a method of holding in a constant temperature and humidity chamber, and the like can be mentioned.

In the above step 1 or 2, the particle size control of the proton conductor (B1) obtained from the crosslinked structure (a) and the acid group-containing structure (b), the bond control between the particles, and the accompanying particle gap For the purpose of controlling, it is preferable to add a polarity control agent.

The polarity control agent is an organic liquid and is preferably water-soluble. When it is water-soluble, it is possible to adjust the solubility of the crosslinked structure (a) and the acid group-containing structure (b) in the solvent, and it is possible to control the particle diameter of the particles and the gap between the particles. Become. Furthermore, there is an advantage that it can be easily extracted by washing with water from the obtained electrode for a polymer electrolyte fuel cell.

Examples of the polar control agent include those having a polar substituent such as a hydroxyl group, an ether group, an amide group and an ester group, an acid group such as a carboxylic acid group and a sulfonic acid group, or a salt thereof. And those having a base such as an amine or a salt thereof. Of these, acids, bases and salts thereof are preferably nonionic since it is necessary to pay attention to the interaction with these catalysts when using catalysts in the hydrolysis and condensation. Specifically, for example, glycerin and derivatives thereof, ethylene glycol and derivatives thereof, diethylene glycol, triethylene glycol, tetraethylene glycol, ethylene glycol polymers such as polyethylene glycol of various molecular weights, glucose, fructose, mannitol, sorbit, sucrose Sugars, polyhydric hydroxyl compounds such as pentaerythritol, water-soluble resins such as polyoxyalkylene, polyvinyl alcohol, polyvinyl pyrrolidone, and acrylic acid, carbonates such as ethylene carbonate and propylene carbonate, and alkyl sulfur oxides such as dimethyl sulfoxide Amides such as dimethylformamide, and polyoxyethylene alkyl ethers such as ethylene glycol monomethyl ether.

In addition, ethylene glycol (mono / di) alkyl ethers in which a part or all of the terminal OH of the ethylene glycol is an alkyl ether can also be suitably used. Specifically, for example, ethylene glycol monomethyl ether, dimethyl ether, monoethyl ether, diethyl ether, monopropyl ether, dipropyl ether, monobutyl ether, dibutyl ether, monopentyl ether, dipentyl ether, monodicyclopentenyl ether, mono Examples thereof include glycidyl ether, diglycidyl ether, monophenyl ether, diphenyl ether, monovinyl ether divinyl ether, and the like. Further, part or all of the terminal OH of ethylene glycols may be an ester. Specific examples include monoacetates and diacetates of the ethylene glycols.
In addition, when an acid and a salt thereof may be used, an acid such as acetic acid, propionic acid, dodecyl sulfuric acid, dodecyl sulfonic acid, benzene sulfonic acid, dodecyl benzene sulfonic acid, toluene sulfonic acid and the like, and the like, When a base and a salt thereof may be used, ammonium salts such as trimethylbenzylammonium chloride, amines such as N, N-dimethylbenzylamine, and salts thereof may be used. Furthermore, zwitterionic compounds such as amino acids such as sodium glutamate can also be used.

Although it is possible to use an inorganic salt or the like as the polarity control agent, generally, the inorganic salt has a strong cohesive force (high melting point) and includes a crosslinked structure (a) and an acid group-containing structure (b). Even if it is added to the mixture, it is difficult to finely disperse it at the molecular level, resulting in large crystals and amorphous solids, and there is a high possibility of forming large aggregates that are disadvantageous to the physical properties of the electrode.

As the polarity control agent, other ionic surfactants can be suitably used, and anionic, cationic, amphoteric surfactants and the like can also be used in consideration of interaction with the catalyst.
Of these, polyoxyalkylene which is a liquid water-soluble organic substance and has appropriate compatibility and incompatibility with the crosslinked structure (a) and the acid group-containing structure (b) is preferable. These polymers can be preferably used. As the polyoxyalkylene, for example, a polyoxyalkylene represented by the following general formula (7) can be used.

式（７）中、ｎは１〜１４の整数である。

In formula (7), n is an integer of 1-14.

Polymers of ethylene glycol as represented by the above general formula (7) are commercially available from dimers (diethylene glycol) to polyethylene glycols of various molecular weights, and compatibility, viscosity, molecular size, etc. can be appropriately selected. Therefore, it can be preferably used. In particular, in the present invention, diethylene glycol having a molecular weight of about 100 to polyethylene glycol having an average molecular weight of 600 can be more preferably used, and tetraethylene glycol or polyethylene glycol having a molecular weight of around 200 can be particularly preferably used.

The particle diameter of the proton conductor (B1) obtained and the size of the gap between the particles are compatible with the crosslinked structure (a) and the acid group-containing structure (b), and an electrode forming raw material system including a solvent and an additive. It is determined by the compatibility balance with the whole and the molecular weight and blending amount of the polar controlling agent. In the case of the present invention, there is a correlation between the average molecular weight of the polarity control agent and the diameter of the gap between the particles, and when polyethylene glycol having a molecular weight of more than 600 is used, the diameter becomes large and the physical properties deteriorate or the electrode becomes brittle. On the other hand, if the molecular weight is less than 100, a dense three-dimensional crosslinked structure may be formed, and sufficient particle gaps may not be formed.

The polar control agent has a preferred lower limit of boiling point of 100 ° C and a preferred upper limit of melting point of 25 ° C. When the boiling point is less than 100 ° C., it volatilizes during the condensation reaction performed when forming the electrode, and the particle diameter control of the particles and the particle gap control become insufficient, and the desired proton conductivity cannot be ensured. A more preferred lower limit is 150 ° C., and a more preferred lower limit is 200 ° C. or more. In addition, when the intermolecular interaction of the polarity control agent is too large, the polarity control agent may solidify to form a large domain other than the gap between the particles. In this case, the strength of the electrode may be reduced. is there.
Moreover, the magnitude of the intermolecular interaction of the polarity control agent is substantially correlated with the melting point, and the melting point can be used as an index. Therefore, when the melting point exceeds 25 ° C., an appropriate intermolecular interaction cannot be expected. A more preferred upper limit is 15 ° C.

The amount of the polarity control agent added depends on the type and molecular weight of the polarity control agent, the structure of the polymer electrolyte fuel cell electrode, etc., but in general, the acid group-containing structure (b) and the crosslinked structure A preferred lower limit is 3 parts by weight and a preferred upper limit is 150 parts by weight with respect to 100 parts by weight of the mixture of (a). When the amount is less than 3 parts by weight, the effect of controlling the particle diameter and particle gap is hardly observed. When the amount exceeds 150 parts by weight, the particle gap becomes too large and the resulting polymer electrolyte fuel cell electrode is brittle. And various physical properties may deteriorate.

Step 3 is a step of adding electron conductive carbon (B3) to the paste obtained in Step 2.
By adding the above-mentioned electron conductive carbon (B3), it is advantageous for gas channel formation, and it becomes easy to prevent the increase of concentration overvoltage, realizing a good three-phase interface, and in turn realizing good power generation performance. Possible solid polymer fuel cell electrodes can be realized.

Step 4 is a step of forming the catalyst layer (B) by applying a paste to which the electron conductive carbon (B3) is added on the porous conductor with a gas diffusion layer and then pressing.
Examples of the method for applying the paste include a screen printing method, a gravure coating method, a doctor blade method, and a spray coating method. Of these, the doctor blade method and the spray coating method are preferable. In addition, since the unevenness | corrugation may be formed in the electrode surface for obtained polymer electrolyte fuel cells when it apply | coats by the said doctor blade method, the cold press which presses with a roll after coating may be performed. preferable. The doctor blade method is preferably performed using a bar coater or a knife coater.

Step 5 is a step of drying the catalyst layer (B) and hot pressing the entire electrode.
Examples of the process for drying the catalyst layer (B) and hot pressing the entire electrode include, for example, a solvent drying process for drying the solvent, and a hot pressing process for accelerating and completing the crosslinking reaction consisting of metal-oxygen bonds by applying temperature. And the like.

The said hot press process is a process of advancing the positive crosslinking reaction of the acid group containing structure (b) in a mixed state in a paste, and a crosslinked structure (a) by heating at high temperature.
The hot pressing step is preferably performed by a method in which the entire electrode including the catalyst layer (B) is sandwiched and pressed. By using such a method, the escape route of the vaporized solvent is ensured, and cracks and cracks on the electrode surface due to pressure expansion due to rapid vaporization of the solvent can be prevented.
As conditions for the hot pressing step, it is preferable that the temperature is 130 to 200 ° C., the pressure is 0.5 to 30 kg / cm ² , and the time is 3 seconds to 30 minutes. In particular, if the temperature and pressure are excessively high, the obtained polymer electrolyte fuel cell electrode itself may be shattered.

Moreover, you may perform the cold press process for the purpose of thickness adjustment between a solvent drying process and a hot press process. The cold pressing step is performed to improve the surface roughness by applying force from above and below and to remove the solvent contained in the porous conductor with a gas diffusion layer.
The cold pressing step is preferably performed in a state where a porous material (for example, filter paper, PTFE membrane filter) or the like that absorbs the solvent is placed on the applied paste. As the porous material, it is preferable to use a material having a water-repellent surface. Thereby, a uniform electrode sheet can be formed without the formed paste adhering to the porous material. In addition, since the cold press process is performed for the purpose of solvent removal and thickness adjustment, the temperature is 0 to 50 ° C., the pressure is 5 to 20 kg / cm ² , and the time is set so as not to increase the temperature actively. Is preferably 10 to 60 seconds.

As another embodiment of the method for producing a polymer electrolyte fuel cell electrode of the present invention, for example, a crosslinked structure (a) composed of a metal-oxygen bond and an acid group-containing structure (b) are mixed. Step 1 for preparing a slurry, mixing the electron conductive carbon (B2) carrying the catalyst with the slurry, Step 2 for preparing a paste, and adding the electron conductive carbon (B3) to the paste Step 3, applying the paste to which the electron conductive carbon (B3) is added on the porous conductor with a gas diffusion layer, and then pressing to produce a catalyst layer (B), and The manufacturing method which has the process 5 which dries a catalyst layer (B) and heat-presses the whole electrode is mentioned. Such a method for producing an electrode for a polymer electrolyte fuel cell according to another aspect of the present invention is also one aspect of the present invention.

In another aspect of the method for producing an electrode for a polymer electrolyte fuel cell of the present invention, first, as step 1, a crosslinked structure (a) comprising a metal-oxygen bond and an acid group-containing structure (b) are prepared. The solid polymer fuel cell of the present invention described above is that a slurry is prepared by mixing, and in Step 2, the paste is prepared by mixing the slurry with electron conductive carbon (B2) carrying a catalyst. This is different from the manufacturing method of the electrode for a vehicle.
By performing such a process, the acid group-containing structure (b) is more firmly incorporated into the three-dimensional crosslinked structure, and therefore the acid group-containing structure (b) is less likely to dissipate.

A polymer electrolyte fuel cell can be obtained by using the electrode for a polymer electrolyte fuel cell of the present invention as an electrode and using a proton conductive solid polymer membrane or the like as an electrolyte. Such a polymer electrolyte fuel cell is also one aspect of the present invention. Here, the solid polymer fuel cell is a fuel cell characterized by using a proton conductive solid polymer membrane (hereinafter also simply referred to as an electrolyte membrane) as an electrolyte.

The proton conductive solid polymer membrane is not particularly limited, but a heat resistant electrolyte membrane is preferably used in order to make use of the characteristics of the electrode of the present invention. As the above heat-resistant electrolyte membrane, for example, engineering plastics having an aromatic ring such as polybenzimidazole in the main chain into which sulfonic acid or phosphoric acid is introduced, acid-doped silica glass, and acid are used. Examples include doped organic-inorganic composites. Further, a film containing a metal-oxygen bond in the film, for example, a film containing a metal oxide such as silica, alumina, or titanium oxide can be used. Specific examples include those obtained by adding silica or the like to a sulfonated fluororesin such as Nafion (registered trademark). Further, it is also possible to use a film in which the film itself is cross-linked by a metal-oxygen bond, particularly a silicon-oxygen bond.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Production of water-repellent carbon paper Water-repellent carbon paper was produced according to the procedure shown in FIG. Specifically, carbon paper (TGP-H-120, manufactured by Toray Industries, Inc.), which has been weighed in advance, is added to a tetrafluoroethylene-hexafluoropropylene copolymer (FEP resin) aqueous solution (manufactured by Daikin Industries, Ltd., NEOFRON (registered trademark) ND). -1) and the solvent was evaporated to dryness. And this operation was repeated until 10 weight% FEP resin was added with respect to the weight of carbon paper. Next, ultrasonic cleaning was performed in isopropanol (hereinafter also referred to as IPA) to remove the contained surfactant, followed by baking at 300 ° C. for 30 minutes to prepare a water-repellent carbon paper.

(2) Preparation of Gas Diffusion Layer First, a 35 wt% Triton (registered trademark) solution (Rohm and Haas, Triton (registered trademark)) in carbon black (manufactured by Denki Black AB12 (registered trademark)) X-100) was added and mixed for 30 minutes using a ball mill (manufactured by FRITSCH, P-7) to prepare a carbon paste. Next, this carbon paste and water repellent material polytetrafluoroethylene (PTFE) dispersion (Mitsui / DuPont Fluorochemical Co., Ltd., 30-J) were added so that the carbon black: PTFE ratio was 6: 4. Using a ball mill, mixing was performed for 30 minutes to obtain a gas diffusion layer paste. The obtained gas diffusion layer paste was coated on the water-repellent carbon paper obtained in (1) with a bar coater (manufactured by PK PRINT-COAT INSTRUMENT, K CONTROL COATER) and dried at 60 ° C. for 1 hour. After drying, a cold press (10 kgf / cm ² , 30 seconds) is performed, and further, triton (registered trademark) contained therein is removed by immersion in IPA, and then hot press (360 ° C., 2.5 kN, 3 seconds), and water-repellent carbon paper with a gas diffusion layer was prepared by quenching in water.

(3) Production of polymer electrolyte fuel cell electrode (i) Production of carbon paste (cp-1) Ketchen Black EC (Ketchenen) having a BET specific surface area of 800 m ² / g and DBP oil absorption of 365 ml / 100 g 2.0 g of platinum catalyst-supported carbon black (platinum-supported 50% by weight) using Black International as a carrier, 3- (trihydroxysilyl) -1-propanesulfonic acid aqueous solution (concentration 18.5% by weight, manufactured by Gelest) , THS (pro) SO ₃ H / CB) = 0.25) 3.0 g and 15 g of water were mixed for 3 minutes using an ultrasonic homogenizer (Viracell, manufactured by SONICS), and carbon paste (cp-1) Was made.

(Ii) Preparation of carbon paste (cp-2) The temperature of carbon paste (cp-1) obtained was adjusted to room temperature (25 ° C.), and a solution obtained by dissolving 1.6 g of tetraethoxysilane in 1.6 g of IPA was added thereto. In addition, mixing with an ultrasonic homogenizer produced a carbon paste (cp-2).

(Iii) Preparation of carbon paste (cp-3) Carbon black (BET specific surface area: 68 m ² / g, DBP oil absorption: 175 ml / 100 g) as an electron conductor component was added to the obtained carbon paste (cp-2). 0.5 g was added. Then, it mixed with the ultrasonic homogenizer and produced the carbon paste (cp-3).

(Iv) Carbon paste coating process Knife coater (manufactured by Matsuo Sangyo Co., Ltd.) so that the obtained carbon paste (cp-3) has a thickness of 20 μm on the water-repellent carbon paper with gas diffusion layer obtained in (2). Coating was performed, and roll press was further performed. At that time, the temperature of the coated plate was set to 25 ° C.

(V) Preparation of electrode for polymer electrolyte fuel cell After coating, it was dried in an oven at 60 ° C. for 1 hour. Thereafter, a cold press (10 kgf / cm ² ) was performed at 20 ° C. for 30 seconds, followed by a hot press (20 kgf / cm ² ) at 150 ° C. for 5 minutes to form a catalyst layer (B). At the time of hot pressing, a fluororesin sheet (thickness: 100 μm) was pressed between the upper and lower sides of the electrode and pressed to manufacture an electrode made of water-repellent carbon paper with catalyst layer / gas diffusion layer. The electrode had the layer configuration shown in FIG. 1, the catalyst layer (B) had a thickness of 20 μm, and the porous conductor (A) + gas diffusion layer (C) had a thickness of 0.36 mm.

(Example 2)
A polymer electrolyte fuel cell electrode was produced in the same manner as in Example 1 except that the following operation was performed in (iii) of Example 1 (3).
(Iii) Preparation of carbon paste (cp-4)
0.5 g of carbon black (BET specific surface area: 290 m ² / g, DBP oil absorption: 98 ml / 100 g) as an electron conductor component was added to the obtained carbon paste (cp-2). Then, it mixed with the ultrasonic homogenizer and produced the carbon paste (cp-4).

(Example 3)
(1) Production of water-repellent carbon paper Water-repellent carbon paper was produced according to the procedure shown in FIG. Specifically, carbon paper (TGP-H-60, manufactured by Toray Industries, Inc.), which has been previously weighed, is added to an aqueous tetrafluoroethylene-hexafluoropropylene copolymer (FEP resin) aqueous solution (manufactured by Daikin Industries, Ltd., NEOFRON (registered trademark) ND). -1) and the solvent was evaporated to dryness. This was repeated until 10 wt% FEP resin was added relative to the weight of the carbon paper. Furthermore, the surfactant contained therein was removed by ultrasonic cleaning in IPA, followed by baking at 300 ° C. for 30 minutes to produce a water-repellent carbon paper.

(2) Production of polymer electrolyte fuel cell electrode (i) Production of carbon paste (cp-5) Ketchen Black EC (Ketchen Black) having a BET specific surface area of 800 m ² / g and DBP oil absorption of 365 ml / 100 g 1.5 g of platinum catalyst-supported carbon black (platinum supported 50% by weight) using Black International as a carrier, 3- (trihydroxysilyl) -1-propanesulfonic acid aqueous solution (concentration 30.0% by weight: manufactured by Gelest) 1.5 g and 20 g of water were mixed for 30 minutes using an ultrasonic homogenizer (manufactured by SONICS, Viracell) to prepare a carbon paste (cp-5).

(Ii) Preparation of carbon paste (cp-6) The temperature of carbon paste (cp-5) obtained was adjusted to room temperature (25 ° C), and a solution obtained by dissolving 0.9 g of tetraethoxysilane in 5.0 g of IPA was added thereto. In addition, the mixture was mixed with an ultrasonic homogenizer to prepare a carbon paste (cp-6).

(Iii) Preparation of carbon paste (cp-7) 0.5 g of carbon black (BET specific surface area: 68 m ² / g, DBP oil absorption: 175 ml / 100 g) as an electron conductor component was added to carbon paste (cp-6). Added. Then, it mixed with the ultrasonic homogenizer and produced the carbon paste (cp-7).

(Iv) Preparation of carbon paste (cp-8) 1.5 g of polytetrafluoroethylene (PTFE) aqueous solution (PTFE30-J, Mitsui DuPont Fluorochemical Co., Ltd.) and 10 g of water were added to carbon paste (cp-7). Then, it mixed with the ultrasonic homogenizer and produced the carbon paste (cp-8).

(V) On the water-repellent carbon paper obtained in the carbon paste coating step (1), coating was performed with a knife coater (manufactured by Matsuo Sangyo Co., Ltd.) so as to have a thickness of 20 μm, followed by roll pressing. At that time, the temperature of the coated plate was set to 25 ° C.

(Vi) Preparation of electrode for polymer electrolyte fuel cell After coating, it was dried in an oven at 60 ° C. for 5 minutes. Thereafter, cold pressing (10 kgf / cm ² ) at 20 ° C. was performed for 30 seconds, followed by hot pressing (150 kgf / cm ² ) at 150 ° C. for 20 minutes to form a catalyst layer (B). At the time of hot pressing, a fluororesin sheet (thickness: 100 μm) was pressed between the top and bottom of the electrode and pressed to produce an electrode made of catalyst layer / water-repellent carbon paper. The electrode had the layer configuration shown in FIG. 1, the catalyst layer (B) had a thickness of 20 μm, and the porous conductor (A) had a thickness of 0.19 mm.

(Comparative Example 1)
A polymer electrolyte fuel cell electrode was produced in the same manner as in Example 1 except that the following operation was performed in (3) of Example 1.
(I) Preparation of carbon paste (cp-9) Platinum catalyst-supported carbon using Ketchen Black EC (manufactured by Ketchen Black International) having a BET specific surface area of 800 m ² / g and DBP oil absorption of 365 ml / 100 g as a carrier Black (platinum-supported 20% by weight) 5.0 g, 3- (trihydroxysilyl) -1-propanesulfonic acid aqueous solution (manufactured by Gelest) 3.0 g and water 15 g, an ultrasonic homogenizer (manufactured by SONICS, Viracell) And mixed for 3 minutes to prepare a carbon paste (cp-9).

(Ii) Preparation of carbon paste (cp-10) The temperature of carbon paste (cp-9) obtained was adjusted to room temperature (25 ° C), and a solution obtained by dissolving 1.6 g of tetraethoxysilane in 1.6 g of IPA was added thereto. In addition, a carbon paste (cp-10) was prepared by mixing for 3 minutes using an ultrasonic homogenizer (Vircell, manufactured by SONICS).

(Iii) Carbon paste coating process After the carbon paste (cp-10) is held for 30 minutes in a constant temperature and humidity chamber (ESPESHSH-240) adjusted to 10 ° C., the repellent property with the gas diffusion layer obtained in (2) Coating was performed on water carbon paper with a knife coater (manufactured by Matsuo Sangyo Co., Ltd.) so as to have a thickness of 50 μm, and then roll pressing was performed. At that time, the temperature of the coated plate was set to 25 ° C.

(Iv) Preparation of electrode for polymer electrolyte fuel cell After coating, it was dried in an oven at 60 ° C. for 1 hour. Thereafter, cold pressing (10 kgf / cm ² ) at 20 ° C. was performed for 30 seconds, followed by hot pressing (150 kgf / cm ² ) at 150 ° C. for 5 minutes to form a catalyst layer (B). At the time of hot pressing, a fluororesin sheet (thickness: 100 μm) was pressed between the upper and lower sides of the electrode and pressed to manufacture an electrode made of water-repellent carbon paper with catalyst layer / gas diffusion layer. The electrode has the layer structure shown in FIG. 1, the catalyst layer (B) has a thickness of 50 μm, and the porous conductor (A) + gas diffusion layer (C) has a thickness of 0.36 mm.

(Evaluation)
(1) Power generation performance As shown in FIG. 4, the polymer electrolyte fuel cell electrode obtained in Example 1 is disposed on both sides of a proton conductive electrolyte membrane (Nafion 112 (registered trademark: manufactured by Du Pont)). Further, separators are arranged on both sides of the separator, sandwiched between current collector plates, and a single cell for evaluation fuel cell is produced by tightening with a bolt. An electronic load device (“890B” manufactured by US Scribner Co., Ltd.) and a gas supply device (Toyo The power generation performance at 80 ° C. was evaluated using “FC-GAS-1” manufactured by Technica. The gas used was oxygen and hydrogen, and the gas flow rates were 200 ml / min for both hydrogen and oxygen.
The results are shown in FIG. The current-potential curve in FIG. 5 shows the performance during fuel cell power generation. A load is applied so that the current density is constant, the voltage at that time is measured, and the current density ( A / cm ² ), and the voltage (mV) is plotted on the vertical axis.

(2) Maximum Output, Limiting Current Density For the polymer electrolyte fuel cell electrodes obtained in Examples and Comparative Examples, a single cell for evaluation fuel cell similar to (1) was prepared, and the maximum output density and limit The current density was measured. The maximum output density is the maximum value of the power generation output (mW / cm ² ) obtained by multiplying the current density (A / cm ² ) and the voltage (mV). The larger the value, the better the performance as a fuel cell. It shows that it is excellent. The limit current density is the maximum current density (A / cm ² ) that can be applied during measurement, and the larger the value, the better the performance as a fuel cell.

(3) Maximum output after immersion in heat-resistant water The maximum output of the single cell for fuel cell used in (2) was measured after being immersed in hot water at 120 ° C. under saturated steam and impregnated with an autoclave for 24 hours.
The results are shown in Table 1.

As shown in Table 1, it can be seen that the fuel cells using the polymer electrolyte fuel cell electrodes obtained in Examples 1 to 3 show excellent values even in the maximum output density and the limit current density. .

ADVANTAGE OF THE INVENTION According to this invention, the polymer electrolyte fuel cell electrode which can obtain the polymer electrolyte fuel cell which is excellent in heat resistance and chemical resistance, and functions stably also in a high temperature humidification state, a polymer electrolyte fuel A battery electrode manufacturing method and a polymer electrolyte fuel cell can be provided.

1 is a schematic cross-sectional view showing an example of an electrode for a polymer electrolyte fuel cell of the present invention. (1) is a schematic diagram showing the configuration of a conventional polymer electrolyte fuel cell electrode, and (2) is a schematic diagram showing the configuration of the polymer electrolyte fuel cell electrode of the present invention. It is a figure which shows the preparation procedures of the water repellent carbon paper in an Example. It is a figure which shows the evaluation method of the electric power generation performance of the electrode for polymer electrolyte fuel cells. 2 is a graph showing the power generation performance at 80 ° C. of the fuel cell configured with the electrodes of Example 1. FIG.

Explanation of symbols

1 Electrode for polymer electrolyte fuel cell 2 Porous conductor (A)
3 Catalyst layer (B)
4 Gas diffusion layer (C)

Claims (16)

An electrode for a polymer electrolyte fuel cell having a porous conductor (A), a catalyst layer (B), and a gas diffusion layer (C),
The catalyst layer (B) comprises a proton conductor (B1), an electron conductive carbon (B2) carrying a catalyst, and an electron conductive carbon (B3).
The proton conductor (B1) includes a crosslinked structure (a) composed of a metal-oxygen bond, and an acid group-containing structure (b) having an acid group covalently bonded to the crosslinked structure composed of a metal-oxygen bond. An electrode for a polymer electrolyte fuel cell, comprising: The electrode for a polymer electrolyte fuel cell according to claim 1, wherein the crosslinked structure (a) has a structure represented by the following general formula (1).

In Formula (1), X is an —O— bond or OH group involved in crosslinking, R ¹ represents a methyl group, an ethyl group, a propyl group, a butyl group, or a phenyl group, and n is an integer of 0 to 3. is there. 3. The polymer electrolyte fuel cell electrode according to claim 2, wherein n is 0. 4. The polymer electrolyte fuel cell electrode according to claim 1, wherein the acid group-containing structure (b) has a structure represented by the following chemical formula (2).

In formula (2), X is an —O— bond or OH group involved in crosslinking, R ² is a methyl group, ethyl group, propyl group, butyl group or phenyl group, and R ³ is a carbon number containing an acid group. The organic group of 1-50 is represented, m is an integer of 0-2. 5. The polymer electrolyte fuel cell electrode according to claim 4, wherein m is 0. 6. The polymer electrolyte fuel cell electrode according to claim 4, wherein R ³ has a structure represented by the following general formula (3).

In formula (3), n is an integer of 1-20. 7. The polymer electrolyte fuel cell electrode according to claim 6, wherein n is 3. The acid group-containing structure (b), or the crosslinked structure (a) and the acid group-containing structure (b) are acid group-containing oligomers. 6. An electrode for a polymer electrolyte fuel cell according to 6 or 7. The electron conductive carbon (B2) formed by supporting a catalyst has a specific surface area of 100 to 1500 m ² / g evaluated by a BET method. 7. An electrode for a polymer electrolyte fuel cell according to 7 or 8. 10. The electron conductive carbon (B2) formed by supporting a catalyst has a DBP oil absorption of 50 ml / 100 g or more, 10, 9, 9, 9 or 9. Electrode for solid polymer fuel cell. The electron conductive carbon (B3) has a specific surface area evaluated by the BET method of 10 m ² / g or more, characterized in that the electron conductive carbon (B3) is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 11. The electrode for a polymer electrolyte fuel cell according to 10. The solid according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein the electron conductive carbon (B3) has a DBP oil absorption of 50 ml / 100 g or more. Polymer fuel cell electrode. The electron conductive carbon (B3) containing the catalyst is contained in an amount of not more than 1 time in terms of carbon weight with respect to the electron conductive carbon (B2). 6. An electrode for a polymer electrolyte fuel cell according to claim 6, 7, 8, 9, 10, 11 or 12. A method for producing an electrode for a polymer electrolyte fuel cell having a porous conductor (A), a catalyst layer (B), and a gas diffusion layer (C),
Step 1 for preparing a slurry by mixing the electron conductive carbon (B2) carrying the catalyst and the acid group-containing structure (b),
Step 2 in which the slurry is mixed with a crosslinked structure (a) composed of a metal-oxygen bond to produce a paste,
Step 3 of adding electron conductive carbon (B3) to the paste,
Step 4 of forming the catalyst layer (B) by applying a paste after applying the paste containing the electron conductive carbon (B3) on the porous conductor with a gas diffusion layer, and
Step 5 of drying the catalyst layer (B) and hot pressing the entire electrode
A method for producing an electrode for a polymer electrolyte fuel cell, comprising: A method for producing an electrode for a polymer electrolyte fuel cell having a porous conductor (A), a catalyst layer (B), and a gas diffusion layer (C),
Step 1 in which a crosslinked structure (a) composed of a metal-oxygen bond and an acid group-containing structure (b) are mixed to produce a slurry,
Step 2 in which the slurry is mixed with an electron conductive carbon (B2) formed by supporting a catalyst to produce a paste.
Step 3 of adding electron conductive carbon (B3) to the paste,
Step 4 of forming the catalyst layer (B) by applying a paste after applying the paste containing the electron conductive carbon (B3) on the porous conductor with a gas diffusion layer, and
Step 5 of drying the catalyst layer (B) and hot pressing the entire electrode
A method for producing an electrode for a polymer electrolyte fuel cell, comprising: A solid polymer type comprising the electrode for a polymer electrolyte fuel cell according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13. Fuel cell.

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