JP2011044299A - Method of manufacturing electrode material for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of carrying out surface adjustment by uniformly introducing a defect in a catalyst carrying body face made of a carbon plate with high crystallinity, and of making a failure part on a surface of this surface-adjusted plate-shape carrying body uniformly carry metal catalyst particles when fabricating a plate electrode material of a fuel cell. <P>SOLUTION: By irradiating a plasma gas 13G on the surface of the catalyst carrying plate W with high crystallinity, lattice failure is uniformly introduced into the face of the catalyst carrying plate W, and by reacting the catalyst carrying plate W in which the lattice failure is introduced, a material in which an organic metal compound (including metal molecule to become conductive metal catalyst) is dissolved in an organic solvent, and the material dissolved in an supercritical CO<SB>2</SB>, the conductive metal catalyst particles are carried by the catalyst carrying body W. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a material used for a fuel cell electrode material, typically a catalyst layer (catalyst electrode).

A typical fuel cell electrode material is a catalyst layer (catalyst electrode). The catalyst layer is produced not only by using a metal catalyst particle supported on carbon particles, but also on a catalyst carrier comprising a carbon plate (for example, a graphene sheet). There is a demand to produce a material for a catalyst layer (catalyst electrode) by supporting a platinum particle).
In such a case, it is preferable to support as many platinum particles as possible on the carbon plate in a uniform and dense manner in order to make the catalyst capacity suitable.
And it is preferable to make the specific surface area of many platinum particles carry | supported on a carbon plate as large as possible, and to carry | support the platinum particle of nano order size smaller than the platinum particle of the micron order until now on a carbon plate.

However, if lattice defects (also referred to as lattice defects or simply defects) exist on the carbon plate non-uniformly, platinum particles are preferentially supported by the lattice defects as a supporting site, and the platinum particles are uniformly supported on the carbon plate surface. The state cannot be formed.
Therefore, in order to uniformly support nano-order sized platinum particles on a carbon plate, a carbon plate with high crystallinity (for example, made of a single crystal free of lattice defects) is prepared, and platinum is provided on the surface of the carbon plate. In order to uniformly support the carbon particles, it is preferable to form the platinum particles uniformly over the entire surface of the carbon plate by intentionally using lattice defects as platinum particle support sites. For this purpose, it is necessary to adjust the surface of the carbon plate.

  In other words, a carbon plate having a flat surface with high crystallinity is prepared, and a carbon plate that supports nano-order sized platinum particles is formed on the surface of a carbon plate that is formed by lattice-deficient recesses having a uniform nano-order size. A method for adjusting the surface of the plate is required.

  For example, as a nano-order surface adjustment method for such a highly crystalline carbon plate, Patent Document 1 discloses a method of creating lattice defects on the surface of carbon nanotubes using a strong acid such as nitric acid or sulfuric acid.

JP 2006-334527 A

  However, it has been found that even when wet etching is subjected to surface adjustment with a strong acid (wet acid treatment) on a material having high crystallinity, lattice defects are hardly generated uniformly. Also, if a stronger acid is used to lower the pH in order to facilitate the generation of lattice defects, recesses on the order of microns will be created rather than lattice defects, making it difficult to uniformly introduce defects on the order of nanometers. Become.

  In view of such circumstances, the present invention provides a carbon plate (typical) having a high crystallinity and a basically flat surface when producing an electrode material for fuel cells (typically an electrode material for a catalyst layer). Prepare a graphene sheet. Then, the defects are uniformly introduced (damaged) on the surface of the carbon plate to adjust the surface, and the defects on the surface of the surface-adjusted plate-shaped carrier are used as supporting sites to form a metal catalyst. An object is to provide a suitable method for uniformly supporting particles.

(Aspect of the Invention)
Hereinafter, embodiments of the invention will be shown and described. The items (1) to (5) correspond to the claims 1 to 5.
(1) preparing a flat catalyst-carrying plate having high crystallinity, irradiating plasma on the surface of the catalyst-carrying plate, and introducing lattice defects uniformly on the surface of the catalyst-carrying plate; Comprising the step of reacting the catalyst-carrying plate into which is introduced, an organic metal compound (including a metal molecule serving as a conductive metal catalyst) dissolved in an organic solvent, and supercritical CO _2. A method for producing a catalyst electrode material by supporting the conductive metal catalyst particles on the catalyst carrier.

  The catalyst support plate having high crystallinity described in this section is preferably basically composed of a single crystal, and also needs conductivity because it is an electrode material for a fuel cell. Typically, it is a carbon plate or a graphite plate typified by a graphene sheet, and is preferably flat.

  The plasma irradiation is preferably performed by a plasma processing apparatus provided with a so-called parallel plate capacitively coupled plasma generation mechanism described later. That is, according to the apparatus, a plasma gas is introduced in a high vacuum, and a high voltage is applied to two parallel electrode plates. Then, the plasma gas is struck against the surface of the catalyst support plate to cause damage to create lattice defects (lattice defects), and nano-order concave portions (support sites) are uniformly formed on the catalyst support plate. In particular, since a carbon plate or a graphite plate represented by a graphene sheet has a flat surface, it can be fixed in close contact with the susceptor surface of the apparatus, and the apparatus is suitable for plasma treatment of these plate materials.

On the other hand, the supercritical CO ₂ treatment was introduced for the following reasons. Platinum catalysts typically used in fuel cells have low reserves on the earth and are expensive, so there is a problem in cost to disseminate them to the public, for example, for fuel cells in fuel cell vehicles. Therefore, it is necessary to realize high efficiency and low cost. As a measure for this, it is desired that the effective area of the supported platinum is large. More specifically, in order to increase the effective catalytic area of the platinum catalyst, there is a demand for increasing the specific surface area of platinum by making the platinum finer and increasing the supported amount.

However, it is known that a catalyst-supporting base material made of carbon having a high crystallinity whose surface has been adjusted by the above-described method exhibits water repellency when the crystallinity is high. Therefore, in the conventional liquid phase platinum supporting method, it was not possible to support more platinum particles uniformly and over the entire catalyst supporting substrate.
Therefore, a supercritical fluid has been used as a reaction solvent used during loading. In general, a supercritical fluid has a property of dissolving a substance like a liquid and entering a narrow gap or a minute uneven portion like a gas. In particular, supercritical CO ₂ has low toxicity and reactivity, is nonflammable, has a low critical point, and is easy to handle.

By reacting supercritical CO ₂ with a platinum-containing organic solution in which an organometallic compound is dissolved in a certain organic solvent, a large number of nano-order-sized recesses whose surface is uniformly adjusted by the plasma processing apparatus 1 described above The inventors of the present application have found a method for uniformly supporting nano-order size platinum particles on the catalyst supporting substrate W of the carbon plate while using as a supporting site.
That is, according to the item (1), a large number of catalyst metal particles can be uniformly supported on the catalyst support plate.

(2) The catalyst electrode material for a fuel cell according to (1), wherein the flat catalyst-carrying plate having high crystallinity is made of a carbon plate, a metal plate, a metal oxide plate, or a nitride. Manufacturing method.

  The carbon plate is a so-called graphite plate (graphene sheet). The width (vertical and horizontal dimensions) is determined according to the power generation capacity of the fuel cell used. It is also possible to use a large size, cut last and processed into an appropriate size.

(3) The conductive metal catalyst particles are made of a nano-order size transition metal such as platinum, cobalt, palladium, iridium, or an alloy of any combination thereof (1) or (2 ) For producing a catalyst electrode material for a fuel cell.

  This section exemplifies the type of the conductive metal catalyst particles.

(4) The plasma source gas used during the plasma irradiation is made of Ar, Ne, Xe, CO ₂ , H ₂ O, H ₂ , O ₂ , N ₂ , Cl ₂ , or CF ₄ , or these The method for producing a fuel cell catalyst carrier material according to any one of items (1) to (3), wherein the gas is a rare gas or a mixed gas thereof.
This section exemplifies the plasma source gas species used during plasma irradiation.

(5) The radical source gas used at the time of plasma irradiation is composed of H ₂ , CO ₂ , H ₂ O, O ₂ , N ₂ , Cl ₂ , or CF ₄ , or these rare gases or these The method for producing a fuel cell catalyst carrier material according to any one of items (1) to (3), wherein the mixed gas is any combination.
This section exemplifies radical source gas species used during plasma irradiation.
(6) The organometallic compound is trimethyl (methylcyclopentadienyl) platinum, platinum acetylacetonate, chloroplatinic acid, or an organometallic compound containing the conductive metal catalyst particles (1) A method for producing a catalyst carrier material for a fuel cell according to any one of items 5 to 5.
In this section, the organometallic compound contains a platinum molecule of a catalytic metal, and exemplifies it.
(7) The method according to any one of (1) to (6), including a step of heating the catalyst-carrying plate into which the lattice defects are introduced to a temperature equal to or higher than a decomposition temperature of the organometallic compound. A method for producing a catalyst carrier material for a fuel cell.
This section exemplifies that the catalyst metal is easily fixed to the catalyst support plate by the above process.

  According to the present invention, in order to support metal catalyst particles (for example, platinum particles) on a conductive support (for example, carbon plate) made of a highly crystalline material (material close to a single crystal), the surface of the support is adjusted. As preferred, nano-order lattice defects are formed. According to the present invention, nano-sized metal catalyst particles can be uniformly and abundantly supported on the surface-adjusted conductive support, and as a result, the catalytic ability of the fuel cell electrode material is increased. be able to.

It is sectional drawing of the plasma processing apparatus for introduce | transducing a defect | deletion into a support body surface (damage process). The CO ₂ supercritical solvent containing dissolved metal catalyst particles to CO ₂ supercritical is a perspective view of a device for supporting the metal catalyst particles to a defect of the bearing surface (hereinafter referred to as "supercritical CO ₂ processing apparatus"). 3 is an SEM observation image of a platinum-supported carbon plate obtained in Example 1. FIG. 3 is an SEM observation image of a platinum-supported carbon plate obtained in Example 2. 4 is an SEM observation image of a platinum-supported carbon plate obtained in Example 3. FIG. 6 is an SEM observation image of a platinum-supported carbon plate obtained in Example 4. 6 is an SEM observation image of a platinum-supported carbon plate obtained in Example 5. 6 is an SEM observation image of a platinum-supported carbon plate obtained in Example 5. It is a SEM observation image of the carbon plate damaged excessively obtained by the comparative example.

Hereinafter, an embodiment of the present invention (referred to as “this embodiment”) will be described by dividing it into a defect introduction plasma processing step and a supercritical CO ₂ processing step.

<Defect introduction plasma treatment process>
The defect-introducing plasma processing step uses the plasma processing apparatus 1 shown in FIG. 1 to perform plasma processing on a flat surface of a conductive substrate having high crystallinity, so that many nano-order defects are formed on the carbon plate surface. It is a step of forming a support site that is uniformly formed and is easy to support nano-sized metal catalyst particles (hereinafter referred to as “platinum particles”) on the carbon plate surface.

FIG. 1 is a schematic cross-sectional view of the plasma processing apparatus 1. The plasma processing apparatus 1 will be described with reference to FIG.
The plasma processing apparatus 1 has a chamber 6 surrounded by a substantially cylindrical metal wall 6W, and the chamber 6 is grounded for safety. Since the internal space 8 of the chamber 6 is in a high vacuum atmosphere, the metal wall portion 6W needs to have a certain mechanical strength. Therefore, it consists of a stainless steel plate, for example. An insulating plate 9 made of ceramic, for example, is laid on the bottom 6B inside the chamber 6, and a cylindrical susceptor support 10 is provided on the insulating plate 9. A susceptor 3S that also serves as the lower electrode 3 is provided on the susceptor support 10.

  The susceptor support 10 is preferably provided with a refrigerant chamber (not shown) therein. A refrigerant is introduced into the refrigerant chamber via a refrigerant introduction pipe (not shown), and is discharged from a discharge pipe (not shown) and circulated. Then, the cold heat is transferred to the processing substrate W through the susceptor 3S. Thus, by utilizing the heat transfer action, it is possible to maintain the processing surface of the processing substrate W at a desired temperature (for example, 600 ° C. or lower if the processing substrate W is made of graphite).

  A gas passage 12, which is a through passage for supplying a heat transfer medium (He gas or the like) to the back surface of the processing substrate W, is formed in the insulating plate 9, the susceptor support 10, the susceptor 3 </ b> S, and the electrostatic chuck. Yes. The cold heat of the susceptor 3S is transmitted to the processing substrate W through this heat transfer medium, and thus the processing substrate W can be maintained at a predetermined temperature.

  Moreover, it is preferable to provide an electrostatic chuck (not shown) on the lower electrode 3 so that the bottom of the processing substrate W placed thereon is fixed during the plasma processing. The electrostatic chuck fixes the processing substrate W on the susceptor 3S by electrostatic force.

  For example, an upper electrode 2 made to contain a Si material is provided so as to face the upper surface of the susceptor 3S. The upper electrode 2 is fixed and supported by a lid-like upper part 14 for vacuum-sealing the chamber 8 via an insulating material 2E. The upper electrode 2 is supported by an electrode support 22 having many gas discharge holes 13. The electrode support 22 also serves as a gas shower for injecting plasma processing gas. A gas supply pipe P is connected to the gas discharge port 13 so that the plasma processing gas 13G strikes the processing substrate W on average. A valve 15, a gas flow controller 16, and a processing gas supply source 17 are connected to the gas supply pipe P. The processing gas supply source 17 is supplied with a mixed gas of a plasma source gas and a radical source gas, which is a processing gas for plasma processing, and the processing gas is controlled in the chamber 8 while being controlled at a constant mixing ratio by the gas flow controller 16. To be supplied.

Regarding the processing gas, the plasma source gas may be, for example, Ar, Xe, He, N ₂ , CO ₂ , H ₂ O, H ₂ , O ₂ , N ₂ , Cl ₂ , or CF ₄ , or rare A gas or a mixed gas of any combination thereof is preferable, and the radical source gas is composed of H ₂ , CO ₂ , H ₂ O, H ₂ , O ₂ , N ₂ , Cl ₂ , or CF _4. A gas or a rare gas or a mixed gas thereof is preferable.

Further, an exhaust pipe 18 is connected to the chamber 6. An exhaust device (not shown) is connected to the exhaust pipe 18. As the exhaust device (not shown), it is preferable to use a high vacuum pump such as a diffusion pump, a turbo molecular pump, or a cryopump (a rotary pump for roughing is also used if necessary). This is because the internal space (internal atmosphere) 8 of the chamber 6 can be set to a high vacuum atmosphere suitable for plasma processing. A gate valve 20 is provided on the side wall 6 </ b> W of the chamber 6 through a conduit 19. With the gate valve 20 opened, the inside of the chamber 6 is made equal to the atmospheric pressure, and the processing base material W is carried into and out of a load lock chamber (not shown) adjacent to the plasma processing apparatus 1. Although not shown, the load lock chamber (not shown) is at a position perpendicular to the paper surface of FIG. 1 and has a conveyance port at substantially the same height as the processing substrate W shown in FIG. Is preferred. After the processing substrate W is transferred, the transfer port is closed with a vacuum valve so that the plasma processing apparatus 1 is vacuum-sealed. Further, it is preferable to communicate with the supercritical CO ₂ processing apparatus 100 via the load lock chamber and to carry the processing substrate W from the plasma processing apparatus 1 to the supercritical CO ₂ processing apparatus 100 without contacting the outside air. This is to prevent the processing substrate W from being contaminated with dust and oil during conveyance between both apparatuses.

  A first high frequency power supply 4 is connected to the upper electrode 2. A matching box 19 is provided between the first high-frequency power source 4 and the upper electrode 14. When the plasma is formed in the chamber 6 by the matching box 19, the impedance of the plasma is matched with the impedance of the transmission line 23 having the coaxial structure extending from the high frequency power source 4 to prevent the alternating current from being rebounded and applied. Plasma is generated while efficiently using electric power (RF power). The first high-frequency power supply 4 may have a frequency in the range of 100 kH to 200 MHz, and has a frequency of 60 MHz, for example. By applying such high frequency power, high density plasma can be formed.

  A second high frequency power source 5 is connected to the lower electrode 3. A capacitor 24 is interposed in the power supply line. The second high-frequency power source 5 draws ions into the processing substrate W and gives an appropriate ion action without damaging the processing substrate W. The frequency may be in the range of 100 kH to 13.56 MHz, and is preferably 2 MHz, for example.

A manufacturing method for performing plasma processing on the processing substrate W using the plasma processing apparatus 1 having the above configuration will be described below.
[Processing substrate preparation process]
First, the processing base material W is prepared. For example, the treatment substrate W is a carbon plate (graphite) having a thickness of about several millimeters and having high crystallinity (preferably single crystal) and having high flatness. As pretreatment, it is preferable to sufficiently degrease with an organic solvent while applying ultrasonic waves, wash with pure water, and dry.

[Process base material installation process]
Next, the processing substrate W is carried into the plasma processing apparatus 1 from a load lock chamber (not shown) and placed on the susceptor support 10. Then, a DC voltage is applied to the electrostatic chuck (not shown) to generate a Coulomb force (electrostatic force) between the susceptor support 10 and the processing substrate W. In this way, the processing substrate W is electrostatically adsorbed and fixed on the susceptor support 10.

[Vacuum drawing process]
Thereafter, the chamber interior 8 is brought into an airtight state with respect to the outside by closing a vacuum valve (not shown) so that gas does not enter from the outside. Next, roughing is performed by a roughing pump (not shown) such as a rotary pump until a certain degree of vacuum (for example, about 100 Pa) is reached. Thereafter, vacuuming is further performed with a high vacuum pump (not shown). In this way, the degree of vacuum in the plasma processing apparatus 1 is increased, and the internal atmosphere is changed from 0.1 Pa to 100 Pa.

[Process gas supply process]
Next, the vacuum valve 15 is opened and a mixed gas such as Ar gas (plasma source gas) is supplied from the processing gas supply source 17 to the chamber interior 8 via the gas flow controller 16, for example, a 2: 1 ratio. Hydrogen gas (radical source gas) is introduced. The gas flow controller 16 always monitors and controls the gas flow. Further, the gas flow controller 16 is communicated with an Ar gas cylinder, a hydrogen gas cylinder (not shown), and necessary valves so as to maintain the above gas ratio.

[High voltage application process]
Thereafter, RF power for applying a voltage of several V to several hundred V, for example, a high frequency voltage (high frequency power) of any frequency from 100 kHz to 200 MHz between the upper electrode 2 and the lower electrode 3 is: For example, it is set to 400W to 500W.

[Plasma treatment process]
Under such conditions, the gas introduced into the plasma processing apparatus 1 (chamber internal space 8) is turned into plasma. In this plasma state, gas molecules are accelerated by a high voltage applied between the upper electrode 2 and the lower electrode 3. Then, the surface of the treated substrate W is struck to cause the carbon lattice of the treated substrate W to be lost (damage the carbon lattice). When this treatment is continued for a certain time, for example, 15 seconds to 30 seconds, the defects of the carbon lattice are uniformly created on the upper surface of the treated substrate W. In particular, in the plasma processing apparatus 1, since the gas shower head 22 is used, the processing gas spreads uniformly over the entire upper surface of the processing substrate W.
In this way, the surface of the carbon substrate treated substrate W having uniform defects is uniformly surface-adjusted, and a large number of nano-order-sized concave portions are supported on platinum (catalyst metal) particle support sites described below. Built as

<Supercritical CO ₂ treatment equipment>
Furthermore, by using the supercritical CO ₂ processing apparatus 100 (FIG. 2) described below, the catalyst supporting substrate W supported on the surface using the plasma processing apparatus 1 described above is used as a starting point for nano- An order metal catalyst (typically a platinum catalyst) is suitably supported. Hereinafter, the supercritical CO ₂ treatment will be described.

FIG. 2 is a perspective view for explaining the supercritical CO ₂ processing apparatus 100. For convenience, the two tanks in FIG. 2 are shown in perspective views partially broken so that the internal structure of the two tanks can be seen.
As shown in FIG. 2, the supercritical CO ₂ processing apparatus 100 includes a cylindrical reaction tank 25 and a susceptor 26 including a support column on which a processing substrate W can be placed substantially horizontally in the reaction layer 25. The first conduit 28 that can communicate with the inside of the reaction tank 25 and can introduce critical CO _2, and is spaced apart from the reaction tank 25 by a certain width, and can be shut off and communicated by the reaction tank 25 and the valve 29. The stirring tank 30, the _second tank 31 that communicates with the stirring tank 30, and can introduce critical CO ₂ into the stirring tank 30, and also communicates with the stirring tank 30 and introduces an organometallic solution in which an organic platinum compound is dissolved. A possible third conduit 32. A heater 27 capable of adjusting the temperature is inserted inside the susceptor 26. The supercritical CO ₂ treatment apparatus 100 includes a propeller 33 capable of mixing and stirring the critical CO ₂ and the organic metal solution with a motor in the stirring tank 30.

Regarding the operation of the supercritical CO ₂ processing apparatus 100 described above, a method of supporting platinum particles on the base material (carbon substrate) W that has been plasma-processed by the plasma processing apparatus 1 will be described below.
As shown in FIG. 2, the processing substrate W is disposed and fixed on the horizontal surface of the susceptor 26. Then, the inside of the reaction vessel 25 is filled with supercritical CO ₂ (temperature 100 ° C. to 200 ° C., pressure 7 MPa to 15 MPa).

Next, an organometallic solution (platinum organometallic compound solution) in which an appropriate amount of trimethyl (methylcyclopentadienyl) platinum (organometallic compound) is dissolved in a stirring vessel 30 by means of a valve (not shown) from the third conduit 32. Introduce into the stirring layer 30. At the same time, supercritical CO ₂ is introduced into the stirring layer 30 from the second conduit 31 [In addition to trimethyl (methylcyclopentadienyl), conductive metal catalyst particles such as platinum acetylacetonate and chloroplatinic acid are added. Organic metal compounds containing can also be used]. And after setting the internal pressure of the stirring tank 30 larger than the internal pressure of the reaction tank 25, the valve | bulb 29 is opened. Due to the internal pressure difference, a mixture of the organometallic solution prepared in the stirring tank 30 and the supercritical CO ₂ is introduced into the reaction tank 25, and a large number of times formed by the plasma treatment of the processing substrate W for a predetermined time. Nano-sized platinum particles are supported and fixed using the recess as a supporting site.
In addition,

As described above, according to the present embodiment, using the supercritical CO ₂ processing apparatus 100, the processing substrate W is already uniformly formed on the processing substrate W typified by a highly crystalline carbon plate. Nano-order platinum particles can be supported on the nano-order defects.

  The platinum-supported carbon substrate produced in this way can be used as a catalyst layer as it is. Alternatively, a large number of nano-order holes may be opened from the back surface of the platinum supporting surface of the carbon substrate until reaching the platinum supporting portion, and then bonded to both surfaces of the electrolyte membrane. Also, the surface layer of the starting carbon substrate has a carbon structure with high crystallinity, a pore forming agent is included in the carbon component under the surface layer, and when the treatment is completed, the pore forming agent is dissolved from the platinum-supporting carbon substrate. A large number of holes may be formed and then bonded to both surfaces of the electrolyte membrane.

  The electrode material for a fuel cell according to the present invention can also be used for fuel cells other than PEFC. For example, the electrode material can be used for a direct methanol fuel cell (abbreviated as “DMFC”). it can.

<Examples 1, 2 and 3>
Hereinafter, using the RF power applied between the upper electrode 2 and the lower electrode 3 as a variable, a carbon substrate is prepared as a processing substrate W, and according to the following plasma processing conditions, the RF power is set as 250 W, 500 W, and 750 W as parameters. The results of carrying platinum in Example 1, Example 2, and Example 3 in which defects were introduced into the carbon substrate surface by performing plasma treatment on the carbon substrate will be described.
Referring to Table 1 and Table 2, the amount of platinum particles supported was evaluated by the number of platinum fine particles per unit area (m ² ), and see FIGS. 4, 5, and 6 (SEM observation images). Then, the uniformity of the platinum particles on the carbon plate was visually evaluated (for comparison, FIG. 3 shows an SEM observation image of the carbon plate without any plasma treatment).

Plasma processing conditions:
Ar gas: 100 sccm [standard cc / min]
・ Hydrogen gas: 50 sccm [standard cc / min]
RF power: 250 W (Example 1), 500 W (Example 2), 750 W (Example 3)
・ Bias power: 500W
-Chamber pressure: 5.3 Pa
・ Plasma treatment time: 30 seconds

Supercritical CO ₂ treatment conditions:
・ Pressure: 10MPa
-Substrate heating temperature: 170 ° C
・ Processing time: 30 minutes

[Evaluation] Regarding the amount of platinum particles supported on the carbon plate, from Tables 1 and 2, carbon was applied as RF power was 250 W (Example 1), 500 W (Example 2), and 750 W (Example 3). It was found that the number of platinum particles supported on the plate increased almost proportionally.
On the other hand, as for the uniformity of the loading state of the platinum particles on the carbon plate, the RF powers of 250 W (Example 1) and 500 W (Example 2) were good from FIGS. 4 and 5. When 750 W (Example 3) in FIG. 6 was obtained, the platinum carrying amount increased as described above, but the carbon plate was damaged in the depth direction, and the uniformity of the platinum carrying state was not good.
From the above, it was found that the platinum loading depends on the RF power when the platinum particles are loaded on the carbon plate. Overall, Example 2 gave the best results.

<Example 4, Example 5, and Comparative Example>
Next, the optimum RF power (500 W) shown in Example 2 was applied according to the following plasma processing conditions, and the plasma processing time was used as a parameter for 15 seconds (Example 4), 30 seconds (Example 5), Supercritical CO ₂ treatment was performed on three points for 60 seconds (comparative example), and the results were examined.
[Plasma treatment conditions]
Ar gas: 100 sccm [standard cc / min]
・ Hydrogen gas: 50 sccm [standard cc / min]
・ RF power: 500W
・ Bias power: 500W
-Chamber pressure: 5.3 Pa
Plasma treatment time: 15 seconds (Example 4), 30 seconds (Example 5), 60 seconds (Comparative Example)

[Evaluation] From Tables 3 and 4, when the plasma treatment time was set to 15 seconds and 30 seconds, the amount of platinum supported on the carbon plate increased substantially proportionally. However, when the plasma treatment time was 60 seconds, platinum particles could not be confirmed on the carbon plate. When the plasma processing time is increased to 60 seconds in this way, in the plasma processing apparatus 1 described above with reference to FIG. 1, Si contained in the electrode member of the upper electrode 2 is sputtered on the surface of the carbon plate (graphite). As a result, it is considered that platinum particle support sites could not be formed, and thereafter the platinum particles were not supported on the carbon plate.

From the above embodiment, using the plasma processing apparatus 1 and the supercritical CO ₂ processing apparatus 100, platinum particles are supported on a highly crystalline carbon plate uniformly and densely as much as possible, and a catalyst layer (catalyst electrode). It was found that materials for use can be produced.

  It should be noted that the present invention is not limited to the above-described embodiments and examples, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

W: catalyst support plate, 13G: plasma gas, 31: supercritical CO ₂

Claims (5)

A step of preparing a flat catalyst carrier plate with high crystallinity;
Performing plasma irradiation on the surface of the catalyst-carrying plate to uniformly introduce lattice defects on the surface of the catalyst-carrying plate;
A step of reacting the catalyst-carrying plate into which the lattice defects have been introduced, an organic metal compound dissolved in an organic solvent, and supercritical CO ₂ ;
A method for producing a catalyst electrode material by supporting conductive metal catalyst particles on the catalyst carrier.   The method for producing a catalyst electrode material for a fuel cell according to (1), wherein the flat catalyst-carrying plate having high crystallinity is a carbon plate, a metal plate, a metal oxide plate, or a nitride. .   3. The conductive metal catalyst particle is made of a transition metal such as platinum, cobalt, palladium, iridium, or an alloy of any combination thereof having a nano-order size. The manufacturing method of the catalyst electrode material for fuel cells. The plasma source gas used in the plasma irradiation is made of Ar, Ne, Xe, CO ₂ , H ₂ O, H ₂ , O ₂ , N ₂ , Cl ₂ , or CF ₄ , or a rare gas thereof. The method for producing a fuel cell catalyst carrier material according to any one of claims 1 to 3, wherein the gas is a mixed gas thereof. The radical source gas used at the time of plasma irradiation is composed of H ₂ , CO ₂ , H ₂ O, O ₂ , N ₂ , Cl ₂ , or CF ₄ , or these rare gases or any one of these The method for producing a fuel cell catalyst carrier material according to any one of claims 1 to 3, wherein the mixed gas is a mixed gas of any of the above.