JP5581884B2 - Method for producing catalyst-supported powder for fuel cell, method for producing electrode for fuel cell - Google Patents

Description

  The present invention relates to a method for producing a fuel cell catalyst-supporting powder, a method for producing a fuel cell electrode, and a fuel cell electrode.

  Fuel cells are attracting attention as power generation systems that have little negative impact on the environment. In particular, a polymer electrolyte fuel cell using an ion exchange membrane as an electrolyte is considered promising as an in-vehicle power source because it has a low operating temperature and can be miniaturized.

Such an electrode used for a fuel cell includes an ion exchange resin, a catalyst metal, and a support of the catalyst metal. When a gas containing hydrogen and a gas containing oxygen are respectively supplied to the anode and cathode of a fuel cell equipped with this electrode on both sides of the polymer electrolyte membrane, the following reaction proceeds at the anode and cathode to generate power. can get.
Anode: 2H ₂ → 4H ⁺ + 4e ⁻
Cathode: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O
Overall: 2H ₂ + O ₂ → 2H ₂ O

  The above reaction mainly occurs at a site formed on a contact surface between a proton conduction path called a cluster part of an ion exchange resin and a carrier made of a conductive material. In order to promote the above reaction, it is necessary to efficiently support a catalytic metal having a high catalytic activity at the site.

  Therefore, in Patent Document 1, after obtaining a mixture having a cation exchange resin on the surface of carbon particles, a cation containing a counter ion of the cation exchange resin and a catalytic metal element (hereinafter also referred to as “catalytic metal ion”). Cation exchange by adsorbing catalytic metal ions to the cation exchange resin (adsorption process) and then chemically reducing the catalytic metal ions with hydrogen gas (reduction process). It has been proposed to increase the utilization rate of the catalyst metal supported on the surface of the carbon particles in contact with the proton conduction path of the resin.

In order to promote the above-described reaction in the fuel cell, it is also important to improve the catalytic activity. As a method for improving the activity (catalytic activity), it is conceivable to increase the catalytic activity per unit mass of the catalytic metal by reducing the particle diameter of the catalytic metal.
In the method proposed in Patent Document 1, it is possible to increase the amount of catalytic metal supported on the carbon particles by repeating the adsorption step and the reduction step after the adsorption step and the reduction step. However, there is a problem that the particle diameter of the catalyst metal becomes large due to repetition of the adsorption step and the reduction step.

  As a method of supporting a metal having a small particle diameter on a carrier that is a conductive material, for example, in a solution in which a catalyst metal ion and a carrier on which metal fine particles generated by reduction of the catalyst metal ion are supported are dispersed. Patent Document 2 proposes a method in which carbon monoxide coexists and the catalytic metal ions are reduced with a reducing agent such as sodium borohydride, followed by filtration and drying.

Japanese Patent No. 3649085 JP-A-6-106076

Therefore, it was examined that the catalyst metal is supported on the carbon support according to the method proposed in Patent Document 2. Specifically, a method was investigated in which carbon monoxide coexists in a solution (dispersion) in which catalytic metal ions, carbon, and a cation exchange resin are dispersed, and reduction is performed with sodium borohydride. According to this method, the particle size of the catalyst metal supported on carbon could be made smaller than that produced by the method described in Patent Document 1, but could not be made sufficiently small.
The present invention has been completed based on the above circumstances, and a method for producing a catalyst-supporting powder for a fuel cell in which the particle diameter of the catalyst metal to be supported is reduced, a method for producing an electrode for a fuel cell, and a fuel It aims at providing the electrode for batteries.

  The particle size of the catalyst metal supported on the carbon can also be obtained by the method in which carbon monoxide coexists in the dispersion in which the catalyst metal ion, carbon, and cation exchange resin are dispersed and reduced with sodium borohydride. It was thought that the reason why the catalyst metal could not be made sufficiently small was that the catalyst metal aggregated during the filtration and drying after the catalyst metal was precipitated in the dispersion.

As a result of intensive studies to solve the above problems, the present invention has been found. That is, the present invention provides an ion-exchange reaction of carbon having an ion-exchange group or a solid mixture containing carbon and a cation-exchange resin with a cation containing a platinum group catalytic metal element by an ion-exchange reaction. A first step of adsorbing to an ion exchange group of a group or a cation exchange resin, and the cation adsorbed by executing the first step to carbon monoxide, sulfur oxide, and nitrogen oxide at least one with a reducing agent consisting of the poison gas 1ppm~100ppm and hydrogen, and a second step of reduction by the following reduction temperature 100 ° C. or higher 0.99 ° C., characterized in that through the said platinum of family of catalysts cation containing a metal element is a platinum ammine complex ions are _{^{[Ru (NH 3) 4]}} 2+, or _{^{[Ru (NH 3) 6]}} 4+, before The poison gas is method for producing a catalyst-supporting powder for a fuel cell is for the catalytic metal particles.
Is found, the present invention includes carbon having an ion-exchange group, or a mixture of solid containing carbon and a cation exchange resin, the ion exchange reaction a cation containing a catalytic metal element of the platinum group, with carbon A first step of adsorbing an ion exchange group or an ion exchange group of a cation exchange resin, and the cation adsorbed by executing the first step, carbon monoxide, sulfur oxide, and nitrogen And a second step of reducing at a reduction temperature of 100 ° C. or more and 150 ° C. or less using a reducing agent composed of 1 ppm to 100 ppm of at least one poison gas of oxide and hydrogen , the platinum group cation containing a catalytic metal element is platinum ammine complex ions are _{^{[Ru (NH 3) 4]}} 2+, or _{^{[Ru (NH 3) 6]}} 4+, wherein Poison gas is the fuel cell electrode manufacturing method is directed against the catalytic metal particles.

In the production method of the present invention (a method for producing a fuel cell catalyst-supported powder and a method for producing a fuel cell electrode), the catalytic metal ion is at least one of carbon monoxide, sulfur oxide, and nitrogen oxide. Since the reducing agent includes the reducing agent, at least one of carbon monoxide, sulfur oxide, and nitrogen oxide contained in the reducing agent is adsorbed on the generated catalytic metal particles by the reducing agent, The activity is reduced to suppress the growth (large particle size) of the catalyst metal particles.
Further, in the production method of the present invention, in order to increase the supported amount of catalyst metal particles, even if adsorption and reduction of catalyst metal ions are repeated, carbon monoxide, sulfur oxide, and nitrogen oxidation contained in the reducing agent are performed. Since at least one of the materials suppresses the growth of the catalytic metal particles, it is possible to carry a large amount of small catalytic metal particles on the carbon.
In the production method of the present invention, after catalytic metal ions are adsorbed by an ion exchange reaction to carbon having ion exchange groups or a solid mixture containing carbon and a cation exchange resin, Reduction with a reducing agent causes catalyst metal to precipitate. That is, in the present invention, since a solid mixture containing carbon having an ion exchange group or carbon and a cation exchange resin is previously in a solid state, catalyst metal ions are adsorbed, and then catalyst metal particles are deposited. Unlike the case where the catalyst metal particles are precipitated in a solution in which cation exchange resin, carbon, and catalyst metal ions are dispersed, the aggregation of the catalyst metal particles does not occur.
As a result, according to the present invention, the particle diameter of the catalytic metal supported on the carrier can be remarkably reduced, and thereby the catalytic activity can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the catalyst support powder for fuel cells which made the particle diameter of the catalyst metal supported small, the manufacturing method of the electrode for fuel cells, and the electrode for fuel cells can be provided.

Graph showing the relationship between the number of times platinum (catalyst metal) is supported and the particle size of platinum supported on the catalyst-supported powder Graph showing the relationship between the amount of carbon monoxide in the reducing agent (hydrogen) used in Example 3 and the reduction time Graph showing the relationship between the concentration of carbon monoxide (CO) contained in the reducing agent and the particle size of platinum supported on the catalyst-supported powder Graph showing the relationship between the reduction temperature and the particle size of platinum supported on catalyst-supported powder

  The method for producing a catalyst-supporting powder for a fuel cell according to the present invention and the method for producing an electrode for a fuel cell according to the present invention comprise a catalyst metal element in a solid mixture containing carbon having an ion exchange group or carbon and a cation exchange resin. A step of adsorbing a cation containing oxygen by an ion exchange reaction (first step), an ion adsorbed by executing the first step is at least one of carbon monoxide, sulfur oxide, and nitrogen oxide And a step of reducing using a reducing agent containing one kind (second step). Hereinafter, the first step and the second step will be described in order.

(First step: adsorption step)
In the first step, catalytic metal ions are subjected to an ion exchange reaction with carbon having an ion exchange group or a solid mixture containing carbon and an ion exchange resin (hereinafter also simply referred to as “solid mixture”). Ions containing the catalytic metal are adsorbed on an ion exchange resin.
Carbon having an ion exchange group can be produced by a known method such as oxidation treatment of carbon with KMnO ₄ or HNO ₃ . A solid mixture can be prepared by mixing an ion exchange resin solution dissolved in carbon, an ion exchange resin, and a solvent (such as ethanol, 2-propanol, and water) by a known method, and then removing the solvent.

Examples of the method for removing the solvent include a method for drying the solvent. Examples of the method for drying the solvent include standing drying, air drying, warm air drying, infrared heat drying, far infrared heat drying, reduced pressure drying, and spray drying.
When it is desired to prepare a powdery solid mixture, it is preferable to perform spray drying among the methods described above because it is simple. The solid mixture or the carbon having an ion exchange group may be in the form of a powder or a sheet.
In addition, when the shape of carbon having a solid mixture or an ion exchange group is a sheet shape, the catalyst metal particles are supported by executing the first step and the second step, and used directly as a fuel cell electrode. This is preferable because the manufacturing process can be simplified.

  As carbon, a material having high electron conductivity and high corrosion resistance can be used. As such carbon, for example, carbon black such as acetylene black and furnace black, activated carbon, and the like can be used. Preferably, Denka Black [manufactured by Denki Kagaku Kogyo Co., Ltd.], Vulcan XC-72 (manufactured by Cabot Corp.), Black Peal 2000 (manufactured by Cabot Corp.) or Ketjenblack EC [manufactured by Ketjenblack International Co., Ltd.] Use carbon black. In addition to this, carbon having a high graphitization degree can be used. As carbon having a high degree of graphitization, Tokablack # 3855 [manufactured by Tokai Carbon Co., Ltd.], Denkaback FX-35 [Electrochemical Industry Co., Ltd.], or by baking carbon black at a high temperature, the degree of graphitization is increased. Can be used. By using carbon with a high degree of graphitization, a highly durable fuel cell catalyst can be obtained even at a high electrode potential.

Any cation exchange resin may be used as long as it has proton conductivity, for example, a perfluorocarbon sulfonic acid type, a styrene-divinylbenzene sulfonic acid type cation exchange resin, or a carboxylic acid form of those resins is used. It is preferable.
In the present invention, a cation exchange resin solution in which a cation exchange resin is dissolved in a solvent can be used as a raw material for the cation exchange resin. As the solvent, it is preferable to use a liquid containing water and alcohol (such as ethanol) in an arbitrary ratio, but only water may be used as a solvent.

A method of adsorbing metal ions by an ion exchange reaction between a solid mixture containing carbon and a cation exchange resin and catalytic metal ions (adsorption process) will be described.
In the adsorption step, first, a compound containing a catalytic metal element (for example, [Pt (NH ₃ ) ₄ ] Cl ₂ ) is dissolved in a liquid containing water to prepare a solution containing catalytic metal ions. Subsequently, by immersing the solid mixture in a solution containing catalytic metal ions, the catalytic metal ions are adsorbed on the cation exchange resin contained in the solid mixture containing carbon and cation exchange resin. The adsorption of the catalytic metal ion is based on an ion exchange reaction between the counter ion of the cation exchange resin and the catalytic metal ion.

In the present invention, as a catalyst metal ion, it is difficult to adsorb on the surface of carbon (conductive material) exposed without being coated with the cation exchange resin, and ion exchange reaction with ions of the cation exchange resin. Thus, those that adsorb preferentially to the cluster part (proton conduction path) of the cation exchange resin are preferred.
As the catalytic metal ion having such adsorption characteristics, for example, a cation containing a platinum group metal or a complex ion of a platinum group metal can be used. Specifically, platinum complex metal ions such as [Pt (NH ₃ ) ₄ ] ²⁺ , [Pt (NH ₃ ) ₆ ] ⁴⁺ , or [Ru (NH ₃ ) ₄ ] ²⁺ and [Ru (NH ₃ ) ₆ ] ⁴⁺ can be suitably used. In the present invention, in addition to the ammine complex ion, a platinum group metal complex ion coordinated with a nitrate group or a nitroso group can also be used.
Even when carbon having an ion exchange group is used in place of the above-mentioned solid mixture, the catalyst metal ion can be adsorbed on the carbon surface by an ion exchange reaction between the ion exchange group and the catalyst metal ion.

(Second step: reduction step)
In the second step, the catalytic metal ions adsorbed by executing the first step are converted into a reducing agent comprising at least one poison gas and hydrogen among carbon monoxide, sulfur oxide, and nitrogen oxide. The catalyst metal particles are supported on the surface of the carbon particles in contact with the proton conduction path of the cation exchange resin.
At least one of carbon monoxide, sulfur oxide, and nitrogen oxide (poison gas) contained in the reducing agent is adsorbed on the catalyst metal particles to suppress the growth of the catalyst metal particles.

As the sulfur oxide, sulfur monoxide (SO), sulfur dioxide (SO ₂ ), or the like can be used, and as the nitrogen oxide, nitrogen monoxide (NO), nitrogen dioxide (NO ₂ ), or the like can be used. it can. These reducing agents can be used with hydrogen.

  The amount of poisoning gas contained in the reducing agent is preferably 1 to 100 ppm because the effect of suppressing the growth of metal particles is sufficiently exhibited. If the amount of poisoning gas is less than 1 ppm, the effect of adsorbing to the catalyst metal particles and suppressing growth may not be sufficiently exhibited. Moreover, when the amount of poisoning gas is higher than 100 ppm, there is a concern about the danger to the human body.

  The reduction step is preferably performed at 100 ° C. or more and 200 ° C. or less, and particularly preferably 100 ° C. or more and 150 ° C. or less because the catalyst metal particles can be further reduced. When the reduction temperature exceeds 200 ° C., the poisoning gas may be decomposed, so that the effect of the present invention may be reduced.

  In the production method of the present invention, the catalyst metal ions are adsorbed by immersing the powder carrying the catalyst metal particles obtained through the second step (catalyst support powder) again in a solution containing the catalyst metal ions. Thereafter, the adsorbed catalytic metal ions may be reduced. By repeating the adsorption / reduction process of adsorbing and reducing catalyst metal ions, the amount of catalyst metal supported can be increased.

  Even with the production method of the present invention, the particle size of the catalyst metal is slightly larger than before the adsorption / reduction step by repeating the adsorption / reduction step, but the adsorption / reduction step is repeated as compared with the conventional method. The increase in the particle size of the catalyst metal due to this is very gradual. The particle diameter of the catalyst metal can be controlled by adjusting the number of adsorption / reduction processes for adsorbing and reducing the catalyst metal ions.

In the present invention, the catalyst-supported powder obtained through the first step and the second step is allowed to stand for about 1 to 6 hours in a hydrogen gas atmosphere containing a poisoning gas (leaving step). -You may perform a reduction | restoration process. When the leaving step is executed, the growth of the catalytic metal particles can be sufficiently suppressed even when a reducing agent that does not contain poisonous gas is used in the adsorption / reduction step after the leaving step.
Further, in the reduction step (second reduction step after the first step) after the first step and the second step, hydrogen gas that does not contain poisonous gas may be used as the reducing agent. The amount of poisoning gas may be less than the previous reduction process. Further, the amount of poisoning gas may be reduced with the passage of time of the reduction process.
By reducing the amount of poisoning gas used in this way, it is possible to reduce the effect on the person (person) who handles the reducing agent containing the poisoning gas.

  An example of the manufacturing method of the electrode containing the catalyst carrying | support powder obtained by the manufacturing method of this invention is demonstrated. The catalyst-supported powder obtained by the production method of the present invention is dispersed in, for example, N-methyl-2-pyrrolidone and applied as a slurry to a base material (for example, titanium foil) and dried to form a sheet-like catalyst layer. To do. The catalyst layer thus produced is transferred to both surfaces of the cation exchange membrane, and the substrate is removed to obtain a cation exchange membrane (membrane / catalyst layer assembly) having catalyst layers on both surfaces. The fuel cell electrode can be formed on both sides of the cation exchange membrane by stacking carbon paper (gas diffusion layer) on both sides of the cation exchange membrane having the catalyst layers on both sides and applying heat pressure bonding.

<Examples and Comparative Examples>
The invention is further illustrated by examples embodying the invention.
1. Examination of the relationship between the number of catalyst metal loadings and the particle size of the supported catalyst metal particles

Example 1
(1) Production of catalyst metal-supported powder 1 g of carbon powder (manufactured by Cabot, Vulcan XC-72), 8.6 g of cation exchange resin solution (manufactured by Aldrich, 5% by mass Nafion solution), 1 g of water, and 1 g of ethanol Are mixed to prepare a mixed solution, and the mixed solution is granulated by spray drying (120 ° C.), whereby a powder containing a cation exchange resin and a carbon powder (solid mixture, cation exchange resin compounding ratio 30) Mass%).
A powder containing a cation exchange resin and a carbon powder is impregnated in a 50 mmol / liter [Pt (NH ₃ ) ₄ ] Cl ₂ aqueous solution for 6 hours, and [Pt (NH ₃ ) ₄ ] ²⁺ ions are impregnated with the cation exchange resin. After being adsorbed by the ion exchange reaction, it was washed with purified water and dried (first step).
The powder obtained after drying is placed in a reaction vessel, and adsorbed [Pt (NH ₃ ) ₄ ] ²⁺ ions are reduced to Pt while introducing hydrogen containing 10 ppm of carbon monoxide into the reaction vessel. Step 2, reduction conditions: 110 ° C., 4 hours), a catalyst metal-supported powder was obtained. The catalyst metal-supported powder is supported once with Pt.
Next, XRD analysis of the catalyst metal-supported powder was performed using an X-ray diffractometer [RINT TTR-III, manufactured by Rigaku Corporation], and the particle diameter (nm) of Pt particles supported on carbon was calculated.

(2) Adsorption / Reduction Step The catalyst metal-supported powder obtained in (1) is impregnated with 50 mmol / liter of [Pt (NH ₃ ) ₄ ] Cl ₂ aqueous solution for 6 hours, and [Pt (NH ₃ ) ₄ ]. After adsorbing ²⁺ ions, it was washed with purified water and dried (adsorption process). The powder obtained after drying was placed in a reaction vessel, and while adsorbing hydrogen containing 10 ppm of carbon monoxide into the reaction vessel, adsorbed [Pt (NH ₃ ) ₄ ] ²⁺ ions were reduced to Pt [ Reduction step, reduction conditions (110 ° C., 4 hours)], catalyst metal-supported powder was prepared. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in (1), and the particle diameter (nm) of Pt particles supported on carbon was calculated.

(3) Preparation and XRD analysis of catalyst metal-supported powder with 3-10 support times The catalyst-supported powder obtained through the adsorption / reduction process of (2) is subjected to the same adsorption / reduction process as (2). Then, XRD analysis of the catalyst metal-supported powder obtained each time the adsorption / reduction process was performed was performed, and the particle diameter of Pt particles supported on carbon was calculated.
The particle diameter (nm) of Pt particles supported on carbon is shown in Table 1 for each number of supported Pt, and the relationship between the number of supported Pt particles and the particle diameter (nm) of Pt particles is shown in the graph of FIG. It was. The vertical axis in FIG. 1 indicates the particle diameter (nm) of Pt, and the horizontal axis indicates the number of times Pt is supported. In FIG. 1, the data of Example 1 is indicated by ◯.

(Example 2)
(1) Preparation of catalyst metal-supported powder A catalyst metal-supported powder was prepared by the same method as in (1) of Example 1, and XRD analysis of this catalyst metal-supported powder was performed in the same manner as in Example 1 and supported on carbon. The particle size of the Pt particles was calculated.

(2) Adsorption / reduction process (hydrogen is used as the reducing agent in the second and subsequent reduction processes)
After impregnating [Pt (NH ₃ ) ₄ ] ²⁺ ions by impregnating the catalyst metal-supported powder obtained in (1) with 50 mmol / liter of [Pt (NH ₃ ) ₄ ] Cl ₂ aqueous solution for 6 hours. Washed with purified water and dried (adsorption process). The powder obtained after drying is placed in a reaction vessel, and while adsorbing hydrogen into the reaction vessel, adsorbed [Pt (NH ₃ ) ₄ ] ²⁺ ions are reduced to Pt [reduction step, reduction condition (110 C., 4 hours)], a catalyst metal-supported powder was produced. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in (1), and the particle diameter (nm) of Pt particles supported on carbon was calculated.

(3) Preparation and XRD analysis of catalyst metal-supported powder with 3-10 support times The catalyst-supported powder obtained through the adsorption / reduction process of (2) is subjected to the same adsorption / reduction process as (2). Then, XRD analysis of the catalyst metal-supported powder obtained each time the adsorption / reduction process was performed was performed, and the particle diameter of Pt particles supported on carbon was calculated.
The particle diameter (nm) of the Pt particles supported on the carbon is shown in Table 1 for each number of supported Pt and is shown in the graph of FIG. In FIG. 1, the data of Example 2 are indicated by ●.

(Example 3)
(1) Production of catalyst metal-supported powder 1 g of carbon powder (manufactured by Cabot, Vulcan XC-72), 8.6 g of cation exchange resin solution (manufactured by Aldrich, 5% by mass Nafion solution), 1 g of water, and 1 g of ethanol Are mixed to prepare a mixed solution, and the mixed solution is granulated by spray drying (120 ° C.), whereby a powder containing a cation exchange resin and a carbon powder (solid mixture, cation exchange resin compounding ratio 30) Mass%).
A powder containing a cation exchange resin and carbon powder is impregnated in 50 mmol / liter of an aqueous solution [Pt (NH ₃ ) ₄ ] Cl ₂ for 6 hours, and [Pt (NH ₃ ) ₄ ] ²⁺ ions are ^added to the cation exchange resin. After adsorbing to the cluster part by ion exchange reaction, it was washed with purified water and dried (first step).
The powder obtained after drying was placed in a reaction vessel, and adsorbed [Pt (NH ₃ ) ₄ ] ²⁺ ions were introduced into the reaction vessel while introducing hydrogen containing a predetermined amount of carbon monoxide (described in detail later). The catalyst metal-supported powder was obtained by reducing to Pt (second step, reducing condition: 110 ° C., 4 hours). The catalyst metal-supported powder is supported once with Pt. XRD analysis of the obtained catalyst metal-supported powder was performed in the same manner as in Example 1, and the particle diameter of Pt particles supported on carbon was calculated.
The amount (ppm) of carbon monoxide in the reducing agent (hydrogen) used in the second step was controlled as shown in FIG. Specifically, the amount of carbon monoxide in hydrogen is set to 10 ppm at the start of the reduction process (0 hr) and is reduced as the reduction time elapses. At the end of the reduction process (after 4 hours from the start of reduction) : 4hrs) was set to 0 ppm.

(2) Adsorption / Reduction Step The catalyst metal-supported powder obtained in (1) is impregnated with 50 mmol / liter of [Pt (NH ₃ ) ₄ ] Cl ₂ aqueous solution for 6 hours, and [Pt (NH ₃ ) ₄ ]. After adsorbing ²⁺ ions, it was washed with purified water and dried (adsorption process). The powder obtained after drying is placed in a reaction vessel, and adsorbed [Pt (NH ₃ ) ₄ ] ²⁺ ions are reduced to Pt while introducing hydrogen containing a predetermined amount of carbon monoxide into the reaction vessel. [Reduction step, reduction conditions (110 ° C., 4 hours)], a catalyst metal-supported powder was produced. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in (1), and the particle diameter of Pt particles supported on carbon was calculated.
The amount of carbon monoxide in the reducing agent (hydrogen) used in the reduction step was controlled in the same manner as in the second step (1).

(3) Preparation and XRD analysis of catalyst metal-supported powder with 3-10 support times The catalyst-supported powder obtained through the adsorption / reduction process of (2) is subjected to the same adsorption / reduction process as (2). Then, XRD analysis of the catalyst metal-supported powder obtained each time the adsorption / reduction process was performed was performed, and the particle diameter of Pt particles supported on carbon was calculated.
The particle diameter (nm) of the Pt particles supported on the carbon is shown in Table 1 for each number of supported Pt and is shown in the graph of FIG. In FIG. 1, the data of Example 3 is indicated by ♦.

(Comparative Example 1)
(1) Preparation of catalyst metal-supported powder A catalyst metal-supported powder was prepared in the same manner as in (1) of Example 1 except that hydrogen was used instead of hydrogen containing 10 ppm of carbon monoxide used in the second step. Obtained. The catalyst metal-supported powder is supported once with Pt. Similarly to Example 1, XRD analysis of the catalyst metal-supported powder was performed, and the particle diameter of the Pt particles supported on carbon was calculated.

(2) Adsorption / Reduction Step The catalyst metal-supported powder obtained in (1) is impregnated with 50 mmol / liter of [Pt (NH ₃ ) ₄ ] Cl ₂ aqueous solution for 6 hours, and [Pt (NH ₃ ) ₄ ]. After adsorbing ²⁺ ions, it was washed with purified water and dried (adsorption process). The powder obtained after drying is placed in a reaction vessel, and while introducing hydrogen into the reaction vessel, the adsorbed [Pt (NH ₃ ) ₄ ] ²⁺ ions are reduced to Pt (reduction step), and the catalyst metal is supported. A powder was prepared. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in (1), and the particle diameter of Pt particles supported on carbon was calculated.

(3) Preparation and XRD analysis of catalyst metal-supported powder with 3-10 support times The catalyst-supported powder obtained through the adsorption / reduction process of (2) is subjected to the same adsorption / reduction process as (2). Then, XRD analysis of the catalyst metal-supported powder obtained each time the adsorption / reduction process was performed was performed, and the particle diameter of Pt particles supported on carbon was calculated.
The particle diameter (nm) of the Pt particles supported on the carbon is shown in Table 1 for each number of supported Pt and is shown in the graph of FIG. In FIG. 1, the data of Comparative Example 1 is indicated by Δ.

(Results and discussion)
When the catalyst metal-supported powders of Examples 1 to 3 produced by the production method of the present invention and the catalyst metal-supported powder of Comparative Example 1 produced using hydrogen as a reducing agent were compared between those having the same number of times supported, In Examples 1-3, the result that the particle diameter of Pt particle | grains carry | supported was smaller than the comparative example 1 was obtained. Further, as the number of loadings increases, the particle diameter of the Pt particles is significantly increased in Comparative Example 1, whereas in Examples 1 to 3, the particle diameter of the Pt particles is not easily increased even when the number of loadings is increased. was gotten.
From these results, according to the production method of the present invention, the supported catalyst metal particles (platinum particles) can be reduced in size, and in order to increase the amount of supported catalyst metal particles, It has been found that when the reduction is repeated, the growth of catalytic metal particles can be remarkably suppressed.
In Comparative Example 1 in which hydrogen is used as the reducing agent, the particle diameter of the Pt particles grows larger as the number of supported particles increases. It is done.
Among Examples 1 to 3, even in the second and subsequent reduction steps, in Example 1 using hydrogen containing carbon monoxide as a reducing agent, the particle diameter of the platinum particles is particularly small, and even if the number of loadings increases, almost no matter The particle size did not increase. From this result, it was found that the growth of catalytic metal particles can be remarkably suppressed when hydrogen containing carbon monoxide is used as a reducing agent in the second and subsequent reduction steps.

2. Study on relationship between poison gas concentration in reducing agent and particle diameter of catalytic metal particles (Example 1-1)
Example 1-1 is the same as Example 1-1 except that hydrogen containing 1 ppm of carbon monoxide was used instead of hydrogen containing 10 ppm of carbon monoxide used in the second step. A catalytic metal-supported powder was obtained. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in Example 1, and the particle diameter (nm) of Pt particles supported on carbon was calculated. The results are shown in Table 2 and FIG.
In FIG. 3, the vertical axis represents the particle diameter (nm) of Pt, and the horizontal axis represents the CO concentration (ppm) in the reducing agent. In FIG. 3, the data of Example 1-1, Example 1-2, and Example 1-2 are indicated by ◯. Examples 1-2 and 1-3 will be described below.

(Example 1-2)
The catalytic metal-supported powder obtained in (1) of Example 1 was referred to as Example 1-2. The particle diameters of Pt particles supported on carbon in the catalyst metal-supported powder of Example 1-2 are shown in Table 2 and FIG. 3 (using data of the catalyst metal-supported powder with the number of times of support of Example 1). .

(Example 1-3)
Example 1-3 is the same as Example (1) except that hydrogen containing 100 ppm of carbon monoxide is used instead of hydrogen containing 10 ppm of carbon monoxide used in the second step. A catalytic metal-supported powder was obtained. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in Example 1, and the particle diameter (nm) of Pt particles supported on carbon was calculated. The results are shown in Table 2 and FIG.

(Comparative Example 2-0)
5 ml of a 50 mmol / liter [Pt (NH ₃ ) ₄ ] Cl ₂ aqueous solution, 1 g of carbon powder (Cabot, Vulcan XC-72), 8 cation exchange resin solution (Aldrich, 5% Nafion solution) After adding 32 ml of 5% by mass of sodium borohydride to the solution obtained by mixing 1.6 g of ethanol and 1 g of ethanol while blowing nitrogen as an inert gas (adding 8 ml four times per minute) Filtration and drying gave catalyst metal-supported powder. The mixing ratio of the solid content of the cation exchange resin excluding the catalyst metal was set to 30% by mass. The obtained catalyst metal-supported powder was subjected to XRD analysis in the same manner as in Example 1, and the particle diameter (nm) of Pt particles supported on carbon was calculated and shown in Table 2.

(Comparative Example 2-1)
A catalyst metal-supported powder of Comparative Example 2-1 was obtained in the same manner as Comparative Example 2-0 except that nitrogen gas containing 1 ppm of carbon monoxide was used instead of nitrogen. The obtained catalyst metal-supported powder was subjected to XRD analysis in the same manner as in Example 1, and the particle diameter (nm) of Pt particles supported on carbon was calculated. The results are shown in Table 2 and FIG.
In FIG. 3, the data of Comparative Example 2-1, Comparative Example 2-2, and Comparative Example 2-2 are indicated by Δ. Comparative Example 2-2 and Comparative Example 2-3 will be described below.

(Comparative Example 2-2)
A catalyst metal-supported powder of Comparative Example 2-2 was obtained in the same manner as Comparative Example 2-0 except that nitrogen gas containing 10 ppm of carbon monoxide was used instead of nitrogen. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in Example 1, and the particle diameter (nm) of Pt particles supported on carbon was calculated. The results are shown in Table 2 and FIG.

(Comparative Example 2-3)
A catalyst metal-supported powder of Comparative Example 2-3 was obtained in the same manner as Comparative Example 2-0 except that nitrogen gas containing 100 ppm of carbon monoxide was used instead of nitrogen. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in Example 1, and the particle diameter (nm) of Pt particles supported on carbon was calculated. The results are shown in Table 2 and FIG.

(Comparative Example 3-1)
1 g of carbon powder (Cabot Co., Vulcan XC-72) was immersed in an ethanol aqueous solution of 50 mmol / liter of H ₂ PtCl ₆ , dried, and physically adsorbed using hydrogen containing 1 ppm of carbon monoxide as a reducing agent. ₂ PtCl ₆ was reduced to Pt to obtain catalyst metal-supported powder. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in Example 1, and the particle diameter (nm) of Pt particles supported on carbon was calculated. The results are shown in Table 2 and FIG.
In FIG. 3, the data of Comparative Example 3-1, Comparative Example 3-2 and Comparative Example 3-2 are indicated by □. Comparative Example 3-2 and Comparative Example 3-3 will be described below.

(Comparative Example 3-2)
A catalytic metal-supported powder of Comparative Example 3-2 was obtained in the same manner as Comparative Example 3-1, except that hydrogen containing 10 ppm of carbon monoxide was used instead of hydrogen containing 1 ppm of carbon monoxide. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in Example 1, and the particle diameter (nm) of Pt particles supported on carbon was calculated. The results are shown in Table 2 and FIG.

(Comparative Example 3-3)
A catalytic metal-supported powder of Comparative Example 3-3 was obtained in the same manner as Comparative Example 3-1, except that hydrogen containing 100 ppm of carbon monoxide was used instead of hydrogen containing 1 ppm of carbon monoxide. This catalyst metal-supported powder was subjected to XRD analysis in the same manner as in Example 1, and the particle diameter (nm) of Pt particles supported on carbon was calculated. The results are shown in Table 2 and FIG.

(Results and discussion)
In the catalyst metal-supported powders (Examples 1-1, 1-2, and 1-3) obtained by the method of the present invention, the catalyst metal-supported powders (Comparative Examples 2-1 and 2-2) obtained by the comparative method. The particle diameter of platinum particles (catalyst metal particles) supported on carbon was significantly smaller than that of 2-3, 3-1, 3-2, 3-3).
Further, even if the CO concentration in the reducing agent is increased in Comparative Examples 2-1 to 2-3, the effect of reducing the particle diameter of the Pt particles is slight. In Comparative Examples 3-1 to 3-3, the reducing agent is Even when the CO concentration in the medium was increased, the particle diameter of the Pt particles was almost the same. On the other hand, in the method of the present invention (Examples 1-1 to 1-3), the particle diameter of the Pt particles was reduced by increasing the CO concentration in the reducing agent.
From these results, according to the method of the present invention, the catalytic metal particles supported on carbon can be reduced in size, and the catalytic metal particles can be reduced in size by increasing the CO concentration in the reducing agent. I understood that I could do it.
Although the method of Comparative Examples 2-1 to 2-3 was able to reduce the particle diameter of platinum particles supported on carbon as compared with the methods of Comparative Examples 3-1 to 3-3, it was not sufficient. In the methods in Comparative Examples 2-1 to 2-3, it is considered that platinum particles aggregate when the platinum particles are precipitated in the dispersion and then filtered and dried.
In the methods of Comparative Examples 3-1 to 3-3, there was almost no effect of reducing the particle size of the Pt particles even when the CO concentration was increased. Since the compound (H ₂ PtCl ₆ ) for adsorbing carbon on the carbon is adsorbed on the carbon surface, the Pt particles that form the core of growth are large aggregates even if they are reduced with hydrogen gas containing CO. For this reason, it is presumed that even if the concentration of CO is increased, the effect of reducing the particle size of the Pt particles hardly appears.

3. Examination about relationship between reduction temperature and particle diameter of supported catalyst metal particles (Example 1-4)
The catalyst metal-supported powder obtained in Example 1 (3) and having a Pt support count of 10 was used as the catalyst metal-supported powder of Example 1-4. The particle diameter of Pt particles supported on carbon in the catalyst metal-supported powder of Example 1-4 is shown in Table 3 and FIG. 4 (using data of catalyst metal-supported powder of 10 support times in Example 1). .
In FIG. 4, the vertical axis indicates the particle diameter (nm) of Pt, and the horizontal axis indicates the reduction temperature (° C.). In FIG. 4, the data of Example 1-4, Example 1-5, and Reference Example 1 are indicated by ◯. Examples 1-5 and Reference Example 1 will be described below.

(Example 1-5)
A catalyst metal-supported powder was obtained in the same manner as (1) of Example 1 except that the reduction condition was 150 ° C. in the second step (the number of times of Pt support was one).
For the catalyst metal-supported powder with one Pt support, the adsorption / reduction process was repeated nine times in the same manner as in (2) of Example 1 except that the reduction condition was 150 ° C. A powder was prepared (Pt was loaded 10 times).
For the produced catalyst metal-supported powder with 10 Pt-supported times, XRD analysis was performed in the same manner as in (1) of Example 1 to calculate the particle size (nm) of Pt particles supported on carbon, and Table 3 and This is shown in FIG.

( Reference Example 1 )
A catalytic metal-supported powder was obtained in the same manner as (1) of Example 1 except that the reducing condition was 200 ° C. in the second step (the number of times Pt was supported).
For the catalyst metal-supported powder with one Pt support, the adsorption / reduction process was repeated nine times in the same manner as in (2) of Example 1 except that the reduction condition was 200 ° C. A powder was prepared (Pt was loaded 10 times).
For the produced catalyst metal-supported powder with 10 Pt-supported times, XRD analysis was performed in the same manner as in (1) of Example 1 to calculate the particle size (nm) of Pt particles supported on carbon, and Table 3 and This is shown in FIG.

(Comparative Example 1-1)
The catalyst metal-supported powder having a Pt support count of 10 obtained in (3) of Comparative Example 1 was used as the catalyst metal-supported powder of Comparative Example 1-1. The particle diameters of the Pt particles supported on carbon in the catalyst metal-supported powder of Comparative Example 1-1 are shown in Table 3 and FIG. 4 (using data of the catalyst metal-supported powder of Comparative Example 1 with 10 support times). .
In FIG. 4, the data of Comparative Example 1-1, Comparative Example 1-2, and Comparative Example 1-3 are indicated by Δ. Comparative Example 1-2 and Comparative Example 1-3 will be described below.

(Comparative Example 1-2)
A catalytic metal-supported powder was obtained in the same manner as in (1) of Comparative Example 1 except that the reduction condition was 150 ° C. in the second step (the number of times Pt was supported).
For the catalyst metal-supported powder with one Pt support, the adsorption / reduction process was repeated nine times in the same manner as (2) of Comparative Example 1 except that the reduction condition was 150 ° C. A powder was prepared (Pt was loaded 10 times).
For the produced catalyst metal-supported powder with 10 Pt-supported times, XRD analysis was performed in the same manner as in (1) of Example 1 to calculate the particle size (nm) of Pt particles supported on carbon, and Table 3 and This is shown in FIG.

(Comparative Example 1-3)
A catalytic metal-supported powder was obtained in the same manner as (1) of Comparative Example 1 except that the reduction condition was 200 ° C. in the second step (the number of times Pt was supported).
For the catalyst metal-supported powder with one Pt support, the adsorption / reduction process was repeated nine times in the same manner as (2) of Comparative Example 1 except that the reduction condition was 200 ° C. A powder was prepared (Pt was loaded 10 times).
For the produced catalyst metal-supported powder with 10 Pt-supported times, XRD analysis was performed in the same manner as in (1) of Example 1 to calculate the particle size (nm) of Pt particles supported on carbon, and Table 3 and This is shown in FIG.

(Results and discussion)
In the catalyst metal-supported powder obtained by the method of the present invention (Examples 1-4 and 1-5, Reference Example 1 ), the catalyst metal-supported powder obtained by the comparative method (Comparative Examples 1-1 and 1-2). The particle diameter of platinum particles (catalyst metal particles) supported on carbon was significantly smaller than that of 1-3).
Among those produced by the method of Example, in Example 1-4 where the reduction temperature was low, the particle diameter of platinum particles supported on carbon was particularly small. This is probably because CO is more easily adsorbed to the platinum particles when the reduction temperature is lower. When the reduction temperature reaches 200 ° C., CO adsorbed on the platinum particles decreases due to CO changing to CO ₂ and the like, and the effect of reducing the particle diameter of the platinum particles is considered to decrease.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the above embodiment, CO is exemplified as the poison gas, but sulfur monoxide (SO), sulfur dioxide (SO ₂ ), nitrogen monoxide (NO), nitrogen dioxide (NO ₂ ), etc. may be used. . Even when hydrogen containing these poisoning gases is used as a reducing agent, the same effect as when using hydrogen containing CO is obtained.

Claims (2)

Ion exchange group or cation exchange resin possessed by carbon by ion exchange reaction of cation containing catalytic metal element of platinum group to carbon having ion exchange group or solid mixture containing carbon and cation exchange resin A first step of adsorbing to an ion exchange group possessed by:
The cation adsorbed by executing the first step is used using a reducing agent comprising at least one poison gas of 1 ppm to 100 ppm of carbon monoxide, sulfur oxide, and nitrogen oxide and hydrogen. And a second step of reducing at a reduction temperature of 100 ° C. or higher and 150 ° C. or lower ,
The platinum group cation containing a catalytic metal element is platinum ammine complex ions are _{^{[Ru (NH 3) 4]}} 2+, or _{^{[Ru (NH 3) 6]}} 4+,
A method for producing a catalyst-supporting powder for a fuel cell , wherein the poisoning gas is for catalyst metal particles . Ion exchange group or cation exchange resin possessed by carbon by ion exchange reaction of cation containing catalytic metal element of platinum group to carbon having ion exchange group or solid mixture containing carbon and cation exchange resin A first step of adsorbing to an ion exchange group possessed by:
The cation adsorbed by executing the first step is used using a reducing agent comprising at least one poison gas of 1 ppm to 100 ppm of carbon monoxide, sulfur oxide, and nitrogen oxide and hydrogen. And a second step of reducing at a reduction temperature of 100 ° C. or higher and 150 ° C. or lower ,
The platinum group cation containing a catalytic metal element is platinum ammine complex ions are _{^{[Ru (NH 3) 4]}} 2+, or _{^{[Ru (NH 3) 6]}} 4+,
A method for producing an electrode for a fuel cell , wherein the poisoning gas is for catalytic metal particles .

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