JP2002134123A - Catalyst for fuel cell, its manufacturing method, and electrode for the fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for a fuel cell, made from carbon powder on which platinum base transition metal fine particles dispersed with a silicone base polymer compound are carried. SOLUTION: The carbon powder coated with the silicone base polymer, in which the platinum base transition metal is dispersed, can be obtained in a simple, rapid process. The carbon powder can be used in a catalyst electrode as the catalyst for the fuel cell, which has high efficiency and high durability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalyst for a fuel cell, a method for producing the same, and an electrode for a fuel cell.

[0002]

2. Description of the Related Art A fuel cell has a high energy efficiency of 30 to 40% as compared with an internal combustion engine and emits only water using hydrogen and oxygen as fuel. It is considered as one of the ultimate battery candidates in the 21st century that could revolutionize the world. Above all, a solid oxide fuel cell that operates at a low temperature of 70 to 90 ° C., has a high energy density, and has a small capacity has attracted much attention as a power source for electric vehicles or homes.

A fuel cell has a structure in which hydrogen and oxygen are supplied from both sides of an outermost separator with a membrane / electrode assembly interposed therebetween, and a plurality of such cells are connected in series. Consists of connected stacks. This membrane-electrode assembly is composed of electrodes having two catalyst layers called a hydrogen electrode and an oxygen electrode on both sides of an ion exchange membrane. At the hydrogen electrode, the hydrogen gas of the fuel becomes protons (H ⁺ ) by the action of a catalyst and passes through the ion exchange membrane toward the oxygen electrode. At the oxygen electrode, oxygen in the sent air reacts with protons by the action of a catalyst to form water. This series of reactions produces electricity. As a catalyst at such a hydrogen electrode or an oxygen electrode, a catalyst made of platinum is usually used.

A platinum catalyst is generally prepared by impregnating a carbon simple substance such as activated carbon or carbon black with a platinum ion-containing solvent such as chloroplatinic acid, and then impregnating the solvent with a protective colloid such as polyvinyl alcohol. It is prepared by depositing platinum colloid on carbon alone by the action of a reducing agent such as sodium borohydride or hydrogen.

However, this catalyst has the following demands.
There is a problem. (1) Since platinum metal is expensive, it is desired to reduce the amount used and to increase the activity. (2) If impurities such as carbon monoxide and sulfur enter and cover the catalyst surface, the catalytic activity is reduced (poisoning). (3) With the passage of time, the platinum particles adhere to each other and the surface area decreases, and the activity decreases.

As a solution to this problem, (1) platinum metal is used as fine particles to increase the surface area to increase the activity, and (2) measures such as adding a metal other than platinum such as ruthenium, rhodium and palladium are taken. I have.

However, regarding (3), the compounding ratio of the amount of the protective colloid and the reducing agent to be used for the main material of platinum and carbon alone, the selection of the reaction conditions for platinum fine particles, the temperature, time and atmosphere Although the settings were complicated and complicated, they could not be solved. In particular, when calcined in the final step to make a catalyst electrode, polyvinyl alcohol, polymethyl vinyl ether, polyvinylpyrrolidone, gelatin, etc., which have been conventionally used as protective colloids, are decomposed, and platinum can be stably held. It was not possible to prevent the aggregation of platinum when used as an electrode material. For this reason, the high catalytic activity of platinum has not been able to be exhibited with a long life of 5,000 hours for automobiles and 50,000 hours for home use.

[0008] The present invention has been made in view of the above circumstances, and is a simple and rapid process for dispersing and dispersing platinum fine particles.
A carbon powder coated with a stabilized silicon-based polymer compound can be obtained, a fuel cell catalyst which can be used as a catalyst having high efficiency and excellent durability, a method for producing the same, and a fuel using the catalyst. It is intended to provide a battery electrode.

[0009]

Means for Solving the Problems and Embodiments of the Invention As a result of intensive studies, the present inventor has found that a reducing silicon-based polymer thin film formed on carbon powder is converted into a salt of a platinum-based transition metal. A carbon powder coated with a silicon-based polymer compound in which platinum fine particles are dispersed and stabilized by a simple and quick process by contacting with, a fuel that can be used as a highly efficient and durable catalyst It was found that a battery catalyst was obtained.

By the way, silicon-based polymer compounds have high heat resistance, which has not been obtained by organic resins, since silicon has a higher metallicity than carbon and silicon oxide has high oxidation resistance. It is a very interesting material that can be used at a wide range of temperatures, showing flexibility at low temperatures and good film-forming properties by introducing organic groups on silicon. In addition, certain silicon-based polymer compounds, for example, polysilane as a precursor of a silicon carbide ceramic material, and polysiloxane as a precursor of a silicon oxide ceramic material, can become a material having extremely excellent heat resistance by heat treatment or the like. Well known. Further, a silicon-based polymer compound having a Si-Si bond and / or a Si-H bond, particularly a polysilane or a polymer having a hydrogen atom directly bonded to a Si atom,
It is known that it has a reducing property and forms a metal colloid from a metal salt.

In the present invention, a highly dispersed platinum colloid is required for manifesting the catalytic function of the fuel cell. Therefore, the present inventor has proposed that by using the above-mentioned silicon-based polymer compound, platinum does not act on protective colloids such as polyvinyl alcohol or reducing agents such as sodium borohydride or hydrogen at all and can stably form platinum at high temperatures. It has been found that a carbon carrier coated with a polymer in which a colloid is dispersed can be obtained.

That is, when a platinum-based transition metal salt among metal salts is brought into contact with a reducing silicon-based polymer compound, the silicon-based polymer compound reduces the platinum-based transition metal salt and stabilizes its colloid. It has been found that since two tasks can be performed at the same time, the process and the control are simplified. Furthermore, when polysilane is used as the reducing silicon-based polymer compound, when polysilane and a platinum-based transition metal salt react,
At the same time that the platinum salt is reduced to platinum colloid, the polysilane is oxidized to polysiloxane and retains platinum in a fine colloidal state. Can be
The present inventors have found that a fuel cell electrode material having long-term durability can be obtained, and have accomplished the present invention.

Accordingly, the present invention provides a fuel cell catalyst comprising a carbon powder carrying platinum-based transition metal fine particles stably dispersed in a silicon-based polymer compound, and a reducing silicon-based polymer compound. A catalyst for a fuel cell comprising a carbon powder carrying platinum-based transition metal particles stably dispersed by a silicon-based polymer compound, comprising contacting a surface-coated carbon powder with a platinum-based transition metal salt. And a fuel cell electrode containing a calcined product of the above catalyst.

Hereinafter, the present invention will be described in more detail.
As the carbon powder used in the present invention, spherical carbon black, flaky graphite, fibrous carbon fiber, hollow carbon balun and the like can be used. As the carbon black, many varieties characterized by particle diameter, specific surface area, DBP oil absorption and the like can be used, and examples thereof include Ketjen black, furnace black, acetylene black, Vulcan, SRF carbon, and activated carbon. As the carbon fiber, any of carbon fibers roughly classified into an isotropic pitch type, a liquid crystal pitch type, and a PAN type can be used. And those marketed under the name of Tonen).

In the production method of the present invention, the carbon powder is treated with a reducing silicon-based polymer compound to form a layer of the reducing silicon-based polymer compound on the outermost surface of the carbon powder.

In this case, as the silicon-based polymer compound for treating the powder, a compound having a reducing action is used. Silicon-based polymer compounds having a reducing action include Si-S
Polysilane having i-bond or Si-H bond, polycarbosilane, polysiloxane, and polysilazane can be selected. Among them, polysilane or polysiloxane having a hydrogen atom directly bonded to Si atom is preferable. Used.

Here, the molecule has a Si—Si bond.
As the silicon-based polymer compound, polysilane is preferable.
The polysilane represented by the following general formula (1) is preferably used.
Suitable. (R¹ _mR^Two _nX_pSi)_q (1) (where R¹, R^TwoIs a hydrogen atom or a substituted or unsubstituted
A monovalent hydrocarbon group, X is R ¹, Alkoxy group, halogen source
Represents an atom, an oxygen atom or a nitrogen atom, and m is 0.1 ≦ m ≦
2, n is 0 ≦ n ≦ 1, p is 0 ≦ p ≦ 0.5, and
It is a number that satisfies 1 ≦ m + n + p ≦ 2.5. q is 4 ≦
It is an integer satisfying q ≦ 100,000. )

In the polysilane of the above formula (1),
R ¹ and R ² are a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, and R ¹ and R ² may be the same or different from each other; Is an aliphatic, alicyclic or aromatic hydrocarbon group. In the case of an aliphatic or alicyclic hydrocarbon, it has 1 to 12, preferably 1 to 6 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclopentyl group, and a cyclohexyl group. Is mentioned. The aromatic hydrocarbon group preferably has 6 to 14, more preferably 6 to 10 carbon atoms, and examples thereof include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a benzyl group, and a phenethyl group. . In addition, as the substituted hydrocarbon group,
Examples of the unsubstituted hydrocarbon groups exemplified above in which part or all of the hydrogen atoms have been substituted with halogen atoms, alkoxy groups, amino groups, aminoalkyl groups, etc., for example, monofluoromethyl groups, trifluoromethyl groups, m- And a dimethylaminophenyl group. X is the same group as R ¹ , an alkoxy group, a halogen atom, an alkoxy group having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, an isopropoxy group, a halogen atom is a fluorine atom,
Examples thereof include a chlorine atom and a bromine atom. Usually, a methoxy group and an ethoxy group are used.

M is 0.1 ≦ m ≦ 2, especially 0.5 ≦ m ≦
1, n is 0 ≦ n ≦ 1, especially 0.5 ≦ n ≦ 1, and p is 0 ≦ p
≦ 0.5, especially 0 ≦ p ≦ 0.2 and 1 ≦ m + n
+ P ≦ 2.5, especially 1.5 ≦ m + n + p ≦ 2, and q is 4 ≦ q ≦ 100,000, especially 10 ≦ q
It is an integer in the range of ≦ 10,000.

The silicon-based polymer compound having a hydrogen atom (Si-H group) directly bonded to a silicon atom includes the following general compounds having a Si-H group in a side chain and a Si-O-Si bond in a main chain. The polysiloxane represented by the formula (2) is preferably used. (R ³ _a R ⁴ _{b Hc} SiO _d ) _e (2) (wherein, R ³ and R ⁴ represent a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group, an alkoxy group or a halogen atom,
a is 0.1 ≦ a ≦ 2, b is 0 ≦ b ≦ 1, and c is 0.01 ≦
c ≦ 1, d is 0.5 ≦ d ≦ 1.95, and 2 ≦ a
+ B + c + d ≦ 3.5. e is 2 ≦ e
It is an integer satisfying ≦ 100,000. )

In the polysiloxane of the above formula (2),
R ³ and R ⁴ are a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, and may be the same or different from R ³ and R ^4. And an aliphatic, alicyclic or aromatic hydrocarbon group. In the case of an aliphatic or alicyclic hydrocarbon, it has 1 to 12, preferably 1 to 6 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclopentyl group, and a cyclohexyl group. Is mentioned. The aromatic hydrocarbon group preferably has 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms, such as phenyl, tolyl, xylyl, naphthyl, benzyl and phenethyl. Can be In addition, as the substituted hydrocarbon group,
Examples of the unsubstituted hydrocarbon groups exemplified above in which part or all of the hydrogen atoms have been substituted with halogen atoms, alkoxy groups, amino groups, aminoalkyl groups, etc., for example, monofluoromethyl groups, trifluoromethyl groups, m- And a dimethylaminophenyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, and an isopropoxy group.
To 4, and the halogen atom includes a fluorine atom, a chlorine atom, and a bromine atom.

A is 0.1 ≦ a ≦ 2, especially 0.5 ≦ a ≦
1, b is 0 ≦ b ≦ 1, especially 0.5 ≦ b ≦ 1, and c is 0.0
1 ≦ c ≦ 1, especially 0.1 ≦ c ≦ 1, d is 0.5 ≦ d ≦
1.95, especially 1 ≦ d ≦ 1.5 and 2 ≦ a + b
+ C + d ≦ 3.5, preferably 2 ≦ a + b + c + d ≦
It is a number that satisfies 3.2. e is 2 ≦ e ≦ 100,00
0, preferably an integer in the range of 10 ≦ e ≦ 10,000.

In the present invention, the step of treating the powder with a silicon-based polymer compound to form a layer of the silicon-based polymer compound on the powder surface includes dissolving the silicon-based polymer compound in an organic solvent, By adding the powder into the solution or by mixing the solution into the powder and then removing the organic solvent, a layer of the silicon-based polymer compound can be formed on the surface of the powder.

In this step, examples of the organic solvent in which the silicon-based polymer compound is dissolved include aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as hexane, octane and cyclohexane, and tetrahydrofuran. , Ether solvents such as dibutyl ether, esters such as ethyl acetate, dimethylformamide, dimethyl sulfoxide, aprotic polar solvents such as hexamethylphosphoric triamide,
In addition, nitromethane, acetonitrile and the like are preferably used.

The concentration of the silicon-based polymer compound-containing solution is as follows:
0.01 to 50% (wt%, the same applies hereinafter), preferably 0.1 to 30%, particularly 0.1 to 10% is suitable. When the concentration is too low, the silicon-based polymer compound layer becomes thin. In some cases, it is difficult to form the powder uniformly on the surface of the powder, and the use of a large amount of solvent may increase the cost. On the other hand, if the concentration is too high, the silicon-based polymer compound layer becomes thick and may easily cause agglomeration of the powder.

Next, the solvent is distilled off by raising the temperature or reducing the pressure. Usually, at a temperature equal to or higher than the boiling point of the solvent, for example, under reduced pressure of 1 to 100 mmHg,
It is effective to stir at a temperature of about 200 ° C. Then, for a while under a dry atmosphere or under reduced pressure, 40 to 2
By leaving the mixture at a temperature of about 00 ° C., the solvent is effectively distilled off and dried, whereby a silicon-based polymer compound-treated powder can be produced.

The thickness of the silicon-based polymer compound layer is 0.0
The thickness is preferably from 01 to 1.0 μm, and more preferably from 0.01 to 0.1 μm. When the thickness is less than 0.001 μm, it is difficult to form a silicon-based polymer compound layer uniformly on the powder surface. On the other hand, if the thickness is more than 1.0 μm, the silicon-based polymer compound layer becomes thicker, which tends to cause agglomeration of the powder, and the amount of the silicon-based polymer compound increases, which becomes expensive and may be disadvantageous economically. is there.

Next, the powder obtained by forming a silicon-based polymer compound layer on the surface of the obtained carbon powder is treated with a solution containing a metal salt composed of a platinum-based transition metal. A step of precipitating the metal colloid is performed. In this treatment, the surface of the silicon-based polymer compound-treated powder is brought into contact with a solution containing a metal salt. And a metal film is formed.

As the platinum-based transition metal used in the present invention, one of platinum, Ir, Pd, and Rh or a mixture thereof is preferable, and among these, platinum is particularly preferable.

Pt ²⁺ , Pt ³⁺ , or Pt ²⁺
t4 ⁺ , PtX ₂ , PtX ₃ , Pt
_{X 4, [PtA 6] X} 2, M I 2 [PtX 4], M I 2 [PtX
^{_{2 Y 2], M I [}} PtX 3 Y], M I [PtX 2 Y 2], M I 2
[PtX ₆ ] (X and Y are each F ⁻ , Cl ⁻ , Br ⁻ ,
^{I -, OH -, CN -} , NO 3 -, N 3 -, CH 3 COO -, S
CN, acetylacetonate, 1 / 2SO ₄ ^2- , 1/2
An anion such as CO ₃ ^2- , M ^I is a monovalent cation such as K, Na or H, and A is NH ₃ or amines. ). Specifically, PtCl ₂ , PtBr ₂ , PtI ₂ , Pt (CN) ₂ ,
Pt (SCN) ₂ , PtCl ₃ , PtBr ₃ , PtI ₃ , P
tF ₄ , PtCl ₄ , PtBr ₄ , PtI ₄ , K ₂ [PtC
l ₂ (acac) ₂ ], H ₂ PtCl _{6 and the} like.

The iridium salts include Ir ⁺ , Ir ²⁺ ,
IrX, IrX comprising Ir ^{3 +} or Ir ^{4 +}
₂ , IrX ₃ , IrX ₄ , [IrX ₆ ] M ^I ₃ , M ^I [Ir
X _4] (X is, Cl, an anion of halogen, such as SO ₄ Br, etc., M ^I is, K, Na, Rb, is a monovalent cation such as Cs or H.) Forms, such as Can be represented by Specifically, KIr (SO ₄ ) ₂ , RbIr (S
O ₄ ) ₂ , CsIr (SO ₄ ) _{2 and the} like.

The palladium salt contains Pd ^{2+ and} can usually be represented in the form of Pd-Z ₂ . Z
Is a salt such as halogen such as Cl, Br, I, etc., acetate, trifluoroacetate, acetylacetonate, carbonate, perchlorate, nitrate, sulfate, oxide and the like. Specifically, PdCl ₂ , Pd
Br ₂ , PdI ₂ , Pd (OCOCH ₃ ) ₂ , Pd (OCO
CF ₃ ) ₂ , PdSO ₄ , Pd (NO ₃ ) ₂ , PdO and the like.

The rhodium salt contains Rh ^{3 +,} and includes RhX ₃ , Rh ₂ X ₆ , [RhA ₆ ] X ₃ , M
^I ₃ [RhX ₆ ], M ^I [RhX ₄ ] (X is a halogen such as F or Cl, an anion such as CN or SO ₄ , and M ^I is
A is a monovalent cation such as K, Na or H, and A is N
H ₃ or amines. ). Specifically, Rh ₂ (SO ₄ ) ₃ , Rh (NO ₃ ) ₃ ,
RhCl ₃ , RhF ₃ , RhCN ₃ , KRh (SO ₄ ) ₂ ,
Examples include NaRh (SO ₄ ) ₂ and HRh (SO ₄ ) ₂ .

As a method of treating the powder with a platinum-based transition metal salt solution, a platinum-based transition metal salt is dissolved using a solvent which does not dissolve the silicon-based polymer compound and can dissolve or disperse the platinum-based transition metal salt. A solution method in which a solution containing a metal salt is prepared, and a powder coated with a silicon-based polymer compound film is charged into the solution and brought into contact with a platinum-based transition metal salt is preferred.
By such treatment, the platinum-based transition metal salt is adsorbed on the surface of the silicon-based polymer compound film of the powder coated with the silicon-based polymer compound, and at the same time, the metal-coated powder supported as a reduced colloid. A body is formed.

As the solvent which does not dissolve the silicon-based polymer compound and can dissolve or disperse the metal salt, it cannot be said unconditionally because the solubility differs depending on the type of the side chain group. And acetone, ketones such as methyl ethyl ketone, esters such as ethyl acetate, alcohols such as methanol and ethanol, aprotic polar solvents such as dimethylformamide, dimethyl sulfoxide, hexamethylphosphoric amide, and nitromethane , Acetonitrile and the like. In particular, in the case of phenylmethylpolysilane, a hydrophilic organic solvent such as water or an alcohol or ketone mixed with water can be suitably used.

The concentration of the metal salt varies depending on the solvent in which the salt is dissolved, but may be from 0.01% to a saturated solution of the salt. If it is less than 0.01%, the amount of metal colloid serving as a plating catalyst is not sufficient, and if it exceeds a saturated solution, solid salts are precipitated, which is not preferable. 0.01 when the solvent is water
-20%, more preferably 0.1-5% is often used.

The silicon-based polymer compound-treated powder may be immersed in a metal salt solution at a temperature from room temperature to 70 ° C. for 0.1 to 120 minutes, more preferably about 1 to 15 minutes. Thus, a powder in which a metal colloid is deposited on the surface of the silicon-based polymer compound on the carbon powder can be produced.

The treatment of the solution containing the metal salt is carried out in the presence or absence of a surfactant, but is particularly preferably carried out in the presence of a surfactant. That is, the powder is
It is made hydrophobic by treatment with a silicon-based polymer compound.
For this reason, the affinity with the solution in which the metal salt is dissolved is reduced, and the metal salt is not dispersed in the solution, so that the efficiency of the metal colloid formation reaction may be reduced. In this case, it is preferable to add a surfactant to improve the viscosity, and thereby the silicon-based polymer compound-treated powder can be dispersed in a solution containing a metal salt in a short time.

As the surfactant, those which do not cause foaming and lower only the surface tension are desirable. Surfynol 104, 420, 504 (Nissin Chemical Industry Co., Ltd.)
Non-ionic surfactants such as those manufactured by Toshiba Corporation can be suitably used.

When a surfactant is added, the amount of the surfactant is such that the silicon-based polymer compound-coated powder is uniformly dispersed in the surfactant solution or the metal salt solution containing the surfactant. It is preferable to use 0.0001 to 10 parts by weight, preferably 0.001 to 1 part by weight, particularly 0.01 to 0.5 part by weight based on 100 parts by weight of the metal salt solution. If the amount of the surfactant is too small, the effect may be poor.

As a treatment method, first, a silicon-based polymer compound-treated powder is brought into contact with a surfactant or a surfactant diluted with water, stirred and dispersed, and then brought into contact with a solution containing a metal salt. Thus, the reaction of forming a metal colloid on the surface of the film by the reducing action of the silicon-based polymer compound can be promptly advanced. Further, if necessary, heat treatment at a temperature of 50 to 60 ° C. promotes adsorption of a metal salt on the surface of the silicon-based polymer compound film and formation of a metal colloid from the metal salt.

When the surfactant is not used, it is preferable that the silicon-based polymer compound-treated powder is brought into contact with a solvent and sufficiently stirred to be dispersed.

After such treatment, the powder is treated with the same solvent containing no metal salt as described above to remove the metal salt which has not been reduced and is merely adsorbed on the powder. By removing, a metal colloid-coated powder can be obtained.

The silicon-based polymer compound-treated powder may be immersed in a metal salt solution at a temperature from room temperature to 70 ° C. for 0.1 to 120 minutes, more preferably about 1 to 15 minutes. As a result, a powder in which a metal colloid is deposited on the surface of the silicon-based polymer compound can be produced.

Thereafter, by heating, if necessary, the formation of metal colloid from the platinum-based transition metal salt on the surface of the silicon-based polymer compound is promoted, and the powder coated with the polymer in which the platinum-based transition metal is dispersed well. You can get the body. The heating conditions are usually room temperature to 150 ° C. for 1 minute to 10 hours,
It is preferable to carry out at normal pressure or reduced pressure.

The amount of the platinum-based transition metal carried by the silicon-based polymer compound-treated powder used as a fuel cell catalyst is generally 1 to 50%.
3 to 25% is desirable.

Thereafter, the fuel cell catalyst is mixed with a water-repellent agent such as Teflon (registered trademark) or an admixture such as alcohol or a surfactant in accordance with a conventional method to form a conductive porous material such as carbon paper. An electrode for a fuel cell can be manufactured by coating and molding on a porous substrate and finally firing the obtained molded body.

The calcination can be performed in an atmosphere of a reducing gas such as an oxidizing gas, argon-hydrogen, or ammonia, or an inert gas such as argon, helium, or nitrogen. The heat treatment temperature is 150 ° C. to 350 ° C. in the case of an oxidizing gas atmosphere.
In the case of an atmosphere of a reducing gas or an inert gas, the temperature is preferably from 150 ° C. to 1000 ° C., and more preferably the heat treatment is performed at a temperature of 200 ° C. or higher. The processing time is preferably 0.5 to 8 hours, more preferably 1 to 4 hours. In this manner, a part or all of the reducible silicon-based polymer compound between the powder and the metal is ceramicized to suitably produce a fuel cell electrode having higher heat resistance, insulation and adhesion. be able to.

[0049]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Synthesis Example 1]Method for producing polysilane  Phenyl hydrogen polysilane (hereinafter abbreviated as PPHS)
Was produced by the following method. Replace with argon
Bis (cyclopentadienyl) dichloro
Diethyl methyllithium in THF solution of zirconium
After adding an ether solution and reacting at room temperature for 30 minutes,
The catalyst was prepared in the system by distilling off the agent under reduced pressure.
To this, phenyltrihydrosilane was added to the catalyst at 10,000
0-fold molar addition, 100-150 ° C. for 3 hours, then 2
The mixture was heated and stirred at 00 ° C. for 8 hours. Product in toluene
Dissolve and wash with hydrochloric acid to deactivate and remove the catalyst.
Was. Magnesium sulfate is added to this toluene solution to remove water.
Was removed and filtered. This makes it almost quantitative
PPHS with an average molecular weight of 1,200 and a glass transition point of 65 ° C
Obtained.

[Example 1]Polysilane treatment of carbon powder  Use commercially available acetylene black as carbon powder
Was. Dissolve 1 g of PPHS in 200 g of toluene.
Solution to 100 g of acetylene black and stirred for 1 hour
did. At a rotary evaporator, at a temperature of 60 ° C,
At a pressure of 45 mmHg, toluene is distilled off and dried.
Was. A 1% polysilane treated powder was obtained.

[0052]Production of platinum colloid deposited powder  The polysilane-treated powder is hydrophobized.
It comes to float on the surface. Surfino as a surfactant
No. 504 (surfactant manufactured by Nissin Chemical Industry Co., Ltd.).
10 g of this treated powder is put into 200 g of a 5% aqueous solution,
It was dispersed in water by stirring using sound waves.

The platinum treatment was carried out using 210 g of the above powder-water dispersion.
Then, 50 g (1 g of chloroplatinic acid, 0.48 g of platinum) of a 2% H ₂ PtCl ₆ aqueous solution was added thereto, and the mixture was stirred for 30 minutes, filtered, and washed with water. By these treatments, a powder having platinum colloid adhered to the powder surface was obtained. This powder was isolated by filtration, washed with water and dried, and then heated at 250 ° C. for 1 hour in air.

[0054]Analysis of colloidal platinum powder  When this catalyst was observed with an electron microscope, 1 to 5 n
m colloidal platinum is retained on the carrier in the form of primary particles
And heated in air at 250 ° C for 1 hour.
However, it was confirmed that the particles were uniformly dispersed on the carrier.

Comparative Example 1 For comparison, 10 g of acetylene black not subjected to polysilane treatment was added to 200 g of a 0.5% aqueous solution of Surfynol 504, and the mixture was similarly stirred and dispersed in water.

The platinum treatment was carried out using 210 g of the above powder-water dispersion.
Then, 50 g of a 2% H ₂ PtCl ₆ aqueous solution was added thereto, and the mixture was treated under the same conditions as in Example 1. In these treatments, no platinum colloid was generated, and a powder having platinum ions attached to the powder surface was obtained. This powder did not allow platinum ions to be distilled out and supported by washing with water.

Comparative Example 2 A conventional general preparation method of polyvinyl alcohol (2 g) was prepared by mixing methanol / water with 50 / 50V.
/ V% aqueous solution 400 g, stirred and dissolved.
5 g of acetylene black not treated with polysilane
Was added to 400 g of the methanol aqueous solution, and the mixture was ultrasonically stirred and dispersed in water.

For the platinum treatment, 405 g of the above powder-water dispersion was used.
50 g of a 2% H ₂ PtCl ₆ aqueous solution was added to
The mixture was vigorously stirred while heating at 0 ° C. under reflux. After 8 hours, the mixture was filtered and washed with water. In these treatments, a powder having platinum colloid adhered to the powder surface was obtained. When this catalyst was observed with an electron microscope, it was confirmed that the platinum colloid aggregated into secondary particles having a size of 10 to 50 nm was uniformly dispersed on the carrier. Upon heating, it was confirmed that the material was unevenly distributed on the carrier in a large lump having a size of μm or more.

1 g of the catalyst prepared in Example 1 and Comparative Example 2
The mixture was weighed, and a 25 V / V% aqueous ethanol solution and a Teflon dispersion liquid were added to the catalyst at 25 wt% and sufficiently kneaded, followed by coating on carbon paper. After air-drying at room temperature all day and night, it was dried at 150 ° C. for 2 hours and further calcined at 350 ° C. for 2 hours in air to form a catalyst electrode.

The performance of these electrodes was evaluated in phosphoric acid at 190 ° C. as the monopolar potential of the oxygen electrode with respect to the standard hydrogen electrode. Table 1 shows the results.

[0061]

[Table 1]

As shown in Table 1, in comparison with the performance of the electrode manufactured in Comparative Example 2, according to the method of the present invention, platinum was finely dispersed and uniformly dispersed, and even after thermal history. Since the state was maintained, it was found that the electrode performance was greatly improved, and the life was greatly improved.

[0063]

According to the present invention, a carbon powder coated with a silicon-based polymer in which a platinum-based transition metal is dispersed can be obtained by a simple and rapid process, which has high efficiency and excellent durability. It can be used as a catalyst electrode that can be used as a catalyst for a fuel cell.

Claims (11)

[Claims] 1. A fuel cell catalyst comprising a carbon powder carrying platinum-based transition metal fine particles dispersed by a silicon-based polymer compound. 2. The catalyst according to claim 1, wherein the platinum transition metal is platinum, Ir, Pd or Rh. 3. The silicon polymer compound having a reducing property is selected from polysilane, polycarbosilane, polysiloxane and polysilazane having a Si—Si bond and / or a Si—H bond. 3. The catalyst according to 1 or 2. 4. The polysilane is represented by the following formula (1).
The catalyst according to claim 3, which is a catalyst. (R¹ _mR^Two _nX_pSi)_q (1) (where R¹, R^TwoIs a hydrogen atom or a substituted or unsubstituted
A monovalent hydrocarbon group, X is R ¹, Alkoxy group, halogen source
Represents an atom, an oxygen atom or a nitrogen atom, and m is 0.1 ≦ m ≦
2, n is 0 ≦ n ≦ 1, p is 0 ≦ p ≦ 0.5, and
Number satisfying 0.1 ≦ m + n + p ≦ 2.5, q is 4 ≦ q
It is an integer satisfying ≦ 100,000. ) 5. The catalyst according to claim 3, wherein the polysiloxane is represented by the following formula (2). (R ³ _a R ⁴ _{b Hc} SiO _d ) _e (1) (wherein R ³ and R ⁴ represent a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group, an alkoxy group or a halogen atom,
a is 0.1 ≦ a ≦ 2, b is 0 ≦ b ≦ 1, and c is 0.01 ≦
c ≦ 1, d is 0.5 ≦ d ≦ 1.95, and 2 ≦ a
+ B + c + d ≦ 3.5, e is 2 ≦ e ≦ 10
It is an integer satisfying 0000. ) 6. The method for producing a catalyst for a fuel cell according to claim 1, wherein the carbon powder whose surface is coated with a silicon-based polymer compound having a reducing property is brought into contact with a salt of a platinum-based transition metal. . 7. The method according to claim 6, wherein the platinum-based transition metal is platinum, Ir, Pd or Rh. 8. The silicon-based polymer compound having a reducing property is selected from polysilane, polycarbosilane, polysiloxane, and polysilazane having a Si—Si bond and / or a Si—H bond. 8. The method according to 6 or 7. 9. The polysilane is represented by the following formula (1).
9. The method of claim 8, wherein the method comprises: (R¹ _mR^Two _nX_pSi)_q (1) (where R¹, R^TwoIs a hydrogen atom or a substituted or unsubstituted
A monovalent hydrocarbon group, X is R ¹, Alkoxy group, halogen source
Represents an atom, an oxygen atom or a nitrogen atom, and m is 0.1 ≦ m ≦
2, n is 0 ≦ n ≦ 1, p is 0 ≦ p ≦ 0.5, and
Number satisfying 0.1 ≦ m + n + p ≦ 2.5, q is 4 ≦ q
It is an integer satisfying ≦ 100,000. ) 10. The method according to claim 8, wherein the polysiloxane is represented by the following formula (2). (R ³ _a R ⁴ _{b Hc} SiO _d ) _e (1) (wherein R ³ and R ⁴ represent a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group, an alkoxy group or a halogen atom,
a is 0.1 ≦ a ≦ 2, b is 0 ≦ b ≦ 1, and c is 0.01 ≦
c ≦ 1, d is 0.5 ≦ d ≦ 1.95, and 2 ≦ a
+ B + c + d ≦ 3.5, e is 2 ≦ e ≦ 10
It is an integer satisfying 0000. ) 11. An electrode for a fuel cell containing the calcined product of the catalyst according to claim 1. Description: