JP2003201417A - Carbon black, electrode catalyst carrier formed from the carbon black, electrode catalyst using carrier and electrochemical device using carrier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide carbon black useful as a carrier for electrode catalysts, to provide an electrode catalyst using the carrier and having excellent electrode performances, and to provide an electrochemical device using the carrier and having excellent electrode performances. <P>SOLUTION: The carbon black is characterized by having a DBP oil absorption of 170 to 300 cm<SP>3</SP>/100 g, a specific surface area of 250 to 400 m<SP>2</SP>/100 g by BET method, a primary particle diameter of 10 to 17 nm, a surface opening radius of 10 to 30 nm, and a fine pore total volume of 0.40 to 2.0 cm<SP>3</SP>/g. The electrode catalyst is used for electrochemical devices such as solid polymer type fuel batteries. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

The present invention relates to a novel carbon black, a carrier for an electrode catalyst comprising the carbon black, an electrode catalyst using the carrier, and an electrochemical device such as a solid polymer electrolyte fuel cell using the electrode catalyst. .

[0002]

2. Description of the Related Art A solid polymer electrolyte fuel cell is a portable power source, because a high current density can be obtained at a low temperature.
Development is underway as a drive power source for electric vehicles and as a cogeneration power source.

A solid polymer electrolyte fuel cell has a structure in which an ion exchange membrane which is a solid polymer electrolyte is arranged between a fuel electrode (anode) and an air electrode (cathode). Both the fuel electrode and the air electrode are made of a mixture of a catalyst carrying a noble metal and a polymer electrolyte.

In this structure, when hydrogen is used as a fuel, in the fuel electrode, hydrogen gas passes through the pores in the electrode and reaches the catalyst, and the catalyst releases electrons to become hydrogen ions. Hydrogen ions reach the air electrode through the electrolyte in the electrode and the solid polymer electrolyte membrane between both electrodes. The emitted electrons flow to the external circuit through the catalyst carrier in the electrode and reach the air electrode from the external circuit. On the other hand, when oxygen is used as an oxidant,
At the air electrode, oxygen passes through the pores in the electrode and reaches the catalyst,
It reacts with hydrogen ions and electrons that arrive from the fuel electrode to produce water.

In the solid polymer electrolyte fuel cell, in order to promote the electrode reaction and improve the cell characteristics, it is required that the catalyst constituting the electrode has a high catalytic activity. Therefore, a catalyst in which a highly active noble metal, particularly platinum or a platinum alloy, is supported on a carrier made of carbon black is used as the catalyst.

Further, in order to effectively use the expensive noble metal catalyst, it is necessary to increase the contact area between the catalyst in the electrode and the polymer electrolyte, and the noble metal catalyst existing at a position far from the gas flow channel is required. Gases (hydrogen, oxygen) used for electrode reaction to reduce concentration overvoltage due to gas supply delay
Is required to have high diffusivity.

For this reason, many studies have been conducted on a method for supporting a noble metal and a catalyst carrier. In order to improve the contact property between the electrode catalyst and the polymer electrolyte, for example, JP-A-9-16
7622 discloses that the volume occupied by pores with a diameter of 8 nm or less
A method is described in which the adsorption of noble metal particles to the pores in which the polymer electrolyte cannot be distributed is controlled by supporting a noble metal with carbon black of 500 cm ³ / g or less as a carrier. From the same viewpoint, it is effective in JP-A-2000-100448 to use carbon black having 6 nm or less pores of 20% or less of all pores as a carrier for improving the catalyst utilization rate. Is listed.

In order to improve the diffusivity of the reaction gas in the electrode, JP-A-6-203840 describes that it is effective to set the porosity in the electrode layer to 65 to 90% by volume. There is. Japanese Unexamined Patent Publication No. 9-92293 discloses a diameter of 0.04 to 1
The electrode volume of pores is 0.06 cm ³ / g or more in the [mu] m, similar to the JP-A-9-283154, the volume of the larger pores than 0.1μm is 0.4 cm ³ / g or more It is described that the characteristic electrode improves the characteristics of the solid polymer electrolyte fuel cell.

Further, Japanese Patent Laid-Open No. 6-203852 describes a method of ensuring pores for diffusion of a reaction gas in the electrode by adding a pore-forming agent when preparing the electrode. In addition, J. Appl. Electrochem., Vol.28 (1998) pp.277,
Gas diffusion at the air electrode is improved by adding a pore-forming agent,
It has been reported that the characteristics of the solid polymer electrolyte fuel cell are improved.

[0010]

However, when the reaction gas reaches the catalyst through the pores in the electrode, it is not enough to control the pores on the surface of the primary particles as in the above-mentioned conventional disclosure. is there. Carbon black is generally composed of secondary particles fused with primary particles. In order for a reaction gas to reach a noble metal supported on a carrier made of carbon black, pores formed in the secondary particles are required. Since it is necessary to pass through the inside, it is expected that the diffusivity of the reaction gas greatly changes depending on the pore structure of the secondary particles.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems, and to improve the diffusivity of a reaction gas into a catalyst in an electrode used in an electrochemical device such as a solid polymer electrolyte fuel cell. It is to provide a novel carbon black having a pore structure most suitable for the above purpose and suitable as a catalyst carrier.

[0012] Another object of the present invention is to further provide an electrocatalyst carrier comprising the carbon black, an electrocatalyst using the carrier, and an electrochemical such as a solid polymer electrolyte fuel cell using the electrocatalyst. To provide an intelligent device.

[0013]

In order to solve the above-mentioned problems, the present inventors have proposed the above-mentioned fine pores that function as a route through which a reaction gas reaches a noble metal when a noble metal is supported on carbon black as a carrier. As a result of intensive studies on the structure, the present invention has been completed.

[0014] Namely, the present invention is primarily in the DBP oil absorption 170~300cm ³ / 100g, BET specific surface area is at 250~400m ² / g, a primary particle size of 10～17Nm, and , The total volume of pores with a radius of 10-30 nm is 0.
Provided is a carbon black having a content of 40 cm ³ / g or more. This carbon black has a pore structure suitable as a carrier for an electrode catalyst, and provides a good path for the reaction gas as described above.

Then, the present invention secondly provides an electrode catalyst carrier comprising the above carbon black. Further, the present invention thirdly, an electrode catalyst comprising the above carrier and platinum supported on the carrier, wherein the amount of platinum is 5 to 70% by mass based on the whole electrode catalyst. An electrode catalyst is provided. Fourthly, an electrochemical device provided with the above-mentioned electrode catalyst is provided.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

-Carbon Black and Carrier-The carbon black of the present invention may be any one as long as it can obtain predetermined physical properties, and the kind thereof is not particularly limited, but furnace black is preferable and pores having a radius of 10 to 30 nm. total volume of 0.40 cm ³ / g or more, preferably 0.50 cm ³ /
It has more than g.

First, in the carbon black of the present invention, the total volume of pores having a radius of 10 to 30 nm (hereinafter referred to as “specific pore volume”) is 0.40 cm ³ / g or more. For example, when the carbon black is used as a carrier for an electrode catalyst of an air electrode of a solid polymer electrolyte fuel cell, the reaction field functions as a reaction gas in the pores where oxygen as a reaction gas easily diffuses. It is considered to be the interface where the noble metal that promotes the reduction reaction, the polymer electrolyte that supplies hydrogen ions from the fuel electrode necessary for the reaction, and the conductive carrier carbon black that transfers the electron generated as a result of the reaction . Of the pores, those having a too small radius are not suitable as reaction gas supply passages because the polymer electrolyte is difficult to penetrate and the gas diffusivity is low.

The pores of the carrier carbon black assumed by the present inventor as the reaction gas supply passage have a larger pore diameter as the reaction gas supply passage provided in the electrode of the solid polymer electrolyte fuel cell. The reaction gas functions as an end path from the pores to the noble metal supported on the carrier carbon black.

The larger the specific pore volume formed by the carrier carbon black, the more efficiently the reaction gas can reach the noble metal catalyst supported on the carrier carbon black. Therefore, the specific pore volume is 0.40 cm. It is necessary to be ³ / g or more, preferably 0.50 cm ³ / g or more. If the specific pore volume is too small, the absolute volume of the pores functioning as a reaction gas supply channel will be insufficient, making it difficult to obtain the desired effect. However, the specific pore volume is usually 2.0 cm ³ / g or less for production reasons, and it is difficult to produce carbon black exceeding this.

[0021] In the carbon black of the present invention, DBP oil absorption amount 170~300cm ³ / 100g, preferably 180~250c
m is a ³ / 100g. The DBP oil absorption amount is an index showing the amount of pores formed secondarily when carbon black composed of primary particles having no pores is assumed. However, as the amount of pores of the primary particles increases, the amount of pores of the primary particles is also counted in the measured DBP oil absorption amount, and the DBP oil absorption amount apparently increases. The DBP oil absorption in the carbon black of the present invention is greater than 300 cm ^3/100 g is undesirable meant that there too the pores of primary particles is not effective as a supply path for the reaction gas. On the other hand, D
If BP oil absorption is less than 170cm 3 ^/ 100g, the amount of secondary-formed pores serving as a supply path of the reaction gas is too small.

Further, in the carbon black of the present invention,
The primary particle size is 10 to 17 nm, preferably 13 to 16 nm
Is. When an electrocatalyst is produced by supporting platinum and optionally other metal on a carrier made of carbon black of the present invention, it is secondarily formed in order to improve the catalytic activity per supported metal unit mass. It is desirable to carry the metal particles in a higher dispersed state on the inner wall surface of the fine pores, that is, on the surface of the primary particles of carbon black. Further, in the electrode of the solid polymer electrolyte fuel cell, since the carrier carbon black functions as an electron conductor as described above, the primary particles of the carrier carbon black are in good contact with each other to form an electron conductive path. Is desirable. In the present invention, when carbon black is used as a carrier, if the primary particle diameter of the carbon black exceeds 17 nm, the activity of the obtained electrode catalyst is likely to decrease. Further, when the primary particle size is less than 10 nm, the specific surface area becomes too large and industrially most of the raw material oil used is gasified, resulting in extremely low productivity and difficult handling of the resulting powder. It will be unrealistic.

The carbon black of the present invention has a BET specific surface area of 250 to 400 m ² / g, preferably 250 to 400 m ² / g.
It is 350 m ² / g. Generally, when carbon black having a larger specific surface area is used as a carrier, the noble metal particles can be supported in a higher dispersed state. However, even if carbon black having a specific surface area of more than 400 m ² / g is used as a carrier, the volume of the fine pores of the primary particles, which cannot function as a reaction gas supply passage, is excessively increased, which is disadvantageous. Furthermore, as the specific surface area increases, the conductive carbon black becomes more susceptible to electrochemical corrosion. When carbon black having a too small BET specific surface area is used as a carrier, the precious metal fine particles cannot be supported in a highly dispersed state, and the catalytic activity per unit mass of supported metal tends to decrease.

The method for producing the carbon black of the present invention is not particularly limited, but for example, it can be produced by the following method. Generally, there is furnace black as a carbon black having the physical properties of the present invention, which is industrially manufactured by an oil furnace method. In the oil furnace method, fuel and air such as gas and oil are introduced into a special reaction section lined with bricks that can withstand high temperatures up to about 2000 ° C, and completely burned to form a high temperature atmosphere of 1400 ° C or higher. The above liquid feedstock oil is continuously sprayed and pyrolyzed. In the downstream region of the furnace, water is sprayed on the produced high temperature gas containing carbon black to stop the reaction, and then carbon black and exhaust gas are separated by a bag filter. Furnace black is generally obtained by spraying raw material oil such as creosote oil, EHE, and tar into a complete combustion air stream. Its quality, physical properties such as secondary particle pore structure, particle size, etc. It is controlled by selecting various conditions such as the flow rate of fuel, air, and raw materials, the kind and amount of additives such as alkali metal salts to the reaction system, combustion conditions, cooling rate and the like.

An example of the apparatus used is shown in FIG. 1 and its details will be described below. This apparatus is an apparatus for producing carbon black by the oil furnace method, which burns fuel to generate high-temperature gas, is connected to the first zone A, the downstream thereof, and introduces the raw material, the second zone B, and further downstream thereof. The third zone C is formed by connecting and quenching the produced carbon black with a water spray.

First, heavy fuel oil is introduced as a spray from the fuel introduction nozzle F, and this is mixed with the combustion air introduced from the combustion air introduction nozzle G and burned. As the fuel used here, in addition to heavy oil, liquid fuel such as light oil, gasoline, kerosene, and gaseous fuel such as natural gas, propane and hydrogen can be used. The diameter of the combustion chamber (D
1) is 1100 mm.

The generated combustion gas is passed through a gradually convergent tapered device, and is designed to increase the gas flow velocity in the furnace and increase the turbulent flow energy in the furnace. Second
In zone B, the upstream side as seen from the downstream end (that is, the boundary between the second zone B and the third zone C) of the narrowed portion (the diameter (D2) of that portion is 175 mm) having the smallest diameter in the device. The carbon black raw material is introduced from six raw material introduction pipes provided at the position of the distance D (raw oil introduction position) on the side. As the raw material introduced here, coal-based hydrocarbons such as creosote oil and petroleum-based hydrocarbons such as ethylene bottom oil are generally used. The particle diameter (primary particle diameter) and the degree of particle connection (secondary particle structure) can be adjusted by setting the raw material introduction position and adjusting the amount of raw material oil. The distance between the end of the combustion chamber and the downstream end of the throttle (L1)
Is 3300 mm.

In the third zone C, the throttle portion is connected to the reaction stopping pipe portion via the tapered portion. From the cooling water introduction pipe provided at the position of the distance E (reaction stop position) on the downstream side when viewed from the downstream end of the throttle portion of the reaction stop pipe portion,
By spraying the introduced water and quenching it, the carbon black production reaction is stopped. The length (L2) of the tapered portion is 1800 mm, and the diameter (D3) of the reaction stopping pipe portion is 400 mm. The third zone C is followed by a collection device such as a bag filter and a cyclone, where gas and carbon black are separated.

The greatest feature of the carbon black of the present invention is that it has a specific DBP oil absorption and a specific surface area, and that the specific pore volume is 0.40 cm ³ / g or more. Such a special pore distribution has a wide distribution of primary particle diameters, that is, in the state where large-sized particles and small-sized particles are mixed, these particles are bonded like grapes to form carbon black with many voids. It is presumed that it has formed.

In order to produce such carbon black, it is preferable that the raw material introducing section of the second zone B is in an atmosphere having a wide temperature distribution and residence time distribution. By doing so, it becomes a carbon black in which large and small primary particles are mixed, and by increasing the streamline distribution of the raw material flow in the furnace, various primary particles and secondary particles are It is presumed that carbon black with large voids can be obtained by complex fusion.

-Electrocatalyst-The present invention relates to an electrode catalyst comprising a carrier made of carbon black having the above-mentioned specific physical properties and platinum supported on the carrier, wherein the amount of platinum with respect to the entire electrode catalyst is 5
It also relates to an electrocatalyst characterized by being ~ 70% by mass.

In addition to platinum, other metal may be supported on the carrier, as the case may be. Other metals include
Palladium, rhodium, iridium, ruthenium, gold,
Silver, iron, zinc, nickel, molybdenum, cobalt, tin,
At least one metal selected from the group consisting of chromium, manganese, rhenium, tungsten and copper can be mentioned.

In the electrocatalyst, platinum may exist alone in a metal state, an oxide state or a hydroxide state, or may exist in an alloy state with the other metal or a complex oxide state. Good. Furthermore, these may exist in a mixed state. Preferred states of platinum present are the metallic state and the oxide state.

In this electrode catalyst, the optimum amount of platinum is 5 to 70% by mass, preferably 10 to 60% by mass, based on the total amount of the electrode catalyst. When the amount of platinum is less than 5% by mass, the number of platinum particles present in the secondary pores of the furnace black, which is a carrier, (here, "platinum particles" means platinum is the above-mentioned metal state, (Including the case of being in an alloy state or a compound state) is too small and the diffusion process of the reaction gas to reach the platinum particles becomes large, so that the supply of the reaction gas to the platinum particles tends to be insufficient and the performance of the electrode deteriorates. on the other hand,
When the amount of platinum exceeds 70% by mass, the diameter of platinum particles tends to be large, and the catalytic activity per unit mass of platinum decreases, so that the performance of the electrode deteriorates.

When other metal is supported in addition to platinum,
The amount is preferably 0.05 to 4 moles, and more preferably 0.25 to 2 moles, relative to 1 mole of platinum supported in order to further improve the catalytic activity.

In the production of the electrode catalyst of the present invention, for example, a predetermined amount of the carbon black is suspended in water to form a slurry, and a hexachloroplatinic acid (IV) aqueous solution containing a predetermined amount of platinum is added to the slurry. After reduction treatment with 10 times equivalent of hydrazine hydrate, filtration, washing, drying, and pulverization are performed. In this way, the electrode catalyst is obtained in a powder state. When other metals such as ruthenium mentioned above are supported in addition to platinum, a predetermined amount of the catalyst powder in which Pt is supported on carbon black prepared in advance as described above is suspended in water to prepare a slurry. Ruthenium trichloride (III) containing a certain amount of ruthenium
After adding an aqueous solution and neutralizing it with a sodium hydroxide solution in an amount of 3 times the ruthenium content, the mixture is filtered, dried and dried at 500 ° C.
Hydrogen reduction is performed to obtain an electrode catalyst powder.

As described above, according to the present invention, the secondary pores of the carbon black used as the carrier are used as a supply path for the reaction gas to reach the active metal carried on the carrier. By paying attention, the optimum range of various properties of the carrier was found. By supporting platinum with the carbon black of the present invention as a carrier,
It is possible to obtain an electrode catalyst having high performance.

-Electrochemical device-The electrode catalyst of the present invention is not only suitable for a solid polymer electrolyte fuel cell, but also useful as an electrode catalyst for any electrochemical device using an electrode. . Other electrochemical devices include, for example, electrolyzers and sensors.

[0039]

EXAMPLES The present invention will be specifically described below with reference to preparation examples and examples, but the present invention is not limited to these examples.

[Production of carbon black] [Example 1] (Production of furnace black A) Carbon black was produced under the production conditions shown in Table 1 according to the above production method using the apparatus shown in FIG. This is designated as "furnace black A". This furnace black A has a specific surface area, a DBP oil absorption amount and a primary particle diameter shown in Table 1, is bulky, has a large internal space, and has a large gas permeation amount. Moreover, the specific pore volume is 0.40 cm ³ from FIG.
/ G or more.

[Comparative Example 1] (Production of furnace black B (for comparison)) In the apparatus shown in FIG. 1, two cooling water introducing pipes are mainly provided in the reaction stopping pipe portion of the third zone C. Carbon black was produced under the production conditions shown in Table 1 according to the above production method except that the carbon black was changed. This is designated as "furnace black B". This furnace black B is shown in Table 1.
It has the specific surface area, the DBP oil absorption amount, and the primary particle diameter as described above, has a smaller specific surface area than the furnace black A of Example 1, and has a small pore volume, so that the gas permeation amount is small.

[Comparative Example 2] (Production of furnace black C (for comparison)) Mainly potassium carbonate (K ₂ C) which is a secondary structure controlling agent.
Carbon black was produced under the production conditions shown in Table 1 according to the above production method using the apparatus shown in FIG. 1 except that O ₃ ) was added to the feedstock oil. This is designated as "furnace black C". It should be noted that potassium carbonate (K ₂ CO ₃ ) has an action of preventing primary particles from aggregating to form secondary particles. This furnace black C has a specific surface area, a DBP oil absorption amount and a primary particle diameter shown in Table 1, has a smaller DBP oil absorption amount and a smaller pore volume than the furnace black A of Example 1, and therefore has a small gas permeation rate. The amount is small.

[Comparative Examples 3 and 4] In Table 1, commercially available carbon black "Ketjen Black EC" (trade name, manufactured by Ketjen Black International) (Comparative Example 3) and "Vulcan XC-72R" are shown. The physical property values of (commercial name, manufactured by Cabot Corporation) (Comparative Example 4) are shown. Both have a small pore volume,
Compared to the furnace black A of Example 1, the amount of gas permeation is small.

[Evaluation Method of Carbon Black] <Measurement of Pore Distribution> BJ was measured using a nitrogen adsorption measuring device TriStar 3000 manufactured by Micromeritics.
It was measured by the H method. FIG. 2 shows the results of pore distribution by the BJH method of the furnace black A of the above-mentioned Example 1, the furnace black B of the above-mentioned Comparative Examples 1 and 2, the furnace black C, and the two commercial products of the above-mentioned Comparative Examples 3 and 4. .

<Measurement of DBP oil absorption> 1 at 150 ° C ± 1 ° C
20.00 g (A) of the sample dried for 2 hours was used as an absorber meter (manufactured by Brabender, spring tension 2.68 kg).
/ Cm) into the mixing chamber and rotate the rotating machine in the mixing chamber with the limit switch set in advance to the predetermined position (the limit switch is set to a position of about 70% of the maximum torque). At the same time, DBP (specific gravity 1.
045 to 1.050) at a rate of 4 ml / min. The torque rapidly increases near the end point and the limit switch is turned off. From the DBP amount (Bml) added until then, D
The BP oil absorption (Dml / 100g) was calculated by the formula: D = B / A × 100.

<Measurement of Specific Surface Area> Micromerit
BE using Flow-sorb 2300 manufactured by ics
It was measured by the one-point method based on the T method. <Measurement of primary particle diameter> Electron microscope JSM manufactured by JEOL Ltd.
-6300F has a small spherical shape (having a contour of microcrystals) forming a carbon black aggregate (secondary particle),
Components that could not be separated) were photographed and the average diameter was calculated.

[0047]

[Table 1]

[Preparation of Electrode Catalyst Powder] [Example 2] 35.0% of Furnace Black A of Example 1 was prepared.
g was weighed and suspended in water to obtain a slurry. Next, Pt 15.0g
Hexachloroplatinic acid (IV) aqueous solution containing Pt was added, then reduced with 10 times equivalent of hydrazine hydrate with respect to Pt, and then filtered, washed, dried and pulverized to prepare a powder of Pt 30% electrode catalyst. . The powder had a Pt analysis value of 30.8
% By mass, BET specific surface area of 185 m ² / g, surface area of Pt based on CO adsorption amount of 93 m ² / g-Pt (surface area per unit weight of Pt. The same applies hereinafter), Pt crystallite diameter is 3.1 nm there were.

[Example 3] The same as Example 2 except that the amount of furnace black A used in Example 2 was changed to 25.0 g and the amount of Pt contained in the hexachloroplatinic acid (IV) aqueous solution was changed to 25.0 g. Similarly, a powder of Pt 50% electrocatalyst was prepared. The powder had a Pt analysis value of 47.8% by mass, BET
Specific surface area of 146 m ² / g, surface area of Pt by CO adsorption 74
The crystallite diameter of m ² / g-Pt and Pt was 1.7 nm.

Example 4 30% P prepared in Example 2
21.7 g of t-electrode catalyst was weighed and suspended in water to obtain a slurry. Next, an aqueous solution of ruthenium (III) trichloride containing 3.3 g of Ru was added, and the mixture was neutralized with a sodium hydroxide solution in an amount of 3 times equivalent to Ru, filtered off, dried and subjected to hydrogen reduction at 500 ° C. The powder had a Pt analysis value of 27.1% by mass and R
u analysis value 12.1% by mass, BET specific surface area 188 m ² / g, Pt
Had a crystallite diameter of 4.2 nm.

Comparative Example 5 An electrode catalyst powder containing 30% Pt was prepared in the same manner as in Example 2 except that the furnace black A used in Example 2 was changed to the Ketjen black EC of Comparative Example 3. The powder had a Pt analysis value of 29.7% by mass, a BET specific surface area of 434 m ² / g, and a Pt based on a CO adsorption amount.
Surface area of 128 m ² / g-Pt, and the crystallite diameter of Pt was 1.5 nm.

[Comparative Example 6] Furnace Black A used in Example 2 was replaced with Vulcan XC-72R of Comparative Example 4.
An electrode catalyst powder containing 30% Pt was prepared in the same manner as in Example 2 except that The powder had a Pt analysis value of 30.2% by mass, a BET specific surface area of 153 m ² / g and a P value based on the CO adsorption amount.
The surface area of t is 95 m ² / g-Pt, and the crystallite diameter of Pt is 1.6 nm.
Met.

Comparative Example 7 A powder of Pt 30% electrode catalyst was prepared in the same manner as in Example 2 except that the furnace black A used in Example 2 was changed to the furnace black B of Comparative Example 1. The powder has a Pt analysis value of 30.3% by mass,
The BET specific surface area was 127 m ² / g, the surface area of Pt according to the amount of CO adsorption was 85 m ² / g-Pt, and the crystallite diameter of Pt was 3.2 nm.

Comparative Example 8 A Pt 30% electrode catalyst powder was prepared in the same manner as in Example 2 except that the furnace black A used in Example 2 was changed to the furnace black C of Comparative Example 3. The powder had a Pt analysis value of 30.9% by mass, a BET specific surface area of 241 m ² / g, and a Pt based on the amount of CO adsorbed.
Surface area was 85 m ² / g-Pt, and the crystallite diameter of Pt was 3.8 nm.

Comparative Example 9 An electrode catalyst powder containing 50% Pt was prepared in the same manner as in Example 3 except that the furnace black A used in Example 3 was changed to the Ketjenblack EC of Comparative Example 3. The powder had a Pt analysis value of 49.6% by mass, a BET specific surface area of 320 m ² / g, and a Pt based on a CO adsorption amount.
Surface area of 102 m ² / g-Pt, and the crystallite diameter of Pt was 2.3 nm.

Comparative Example 10 30% prepared in Comparative Example 6
21.7 g of the Pt electrode catalyst was weighed and suspended in water to obtain a slurry. Next, an aqueous solution of ruthenium (III) trichloride containing 3.3 g of Ru was added, and the mixture was neutralized with a sodium hydroxide solution in an amount of 3 times the amount of Ru, filtered, dried, and hydrogen reduced at 500 ° C. The powder had a Pt analysis value of 26.0% by mass and R
u analysis value 13.1% by mass, BET specific surface area 148 m ² / g, Pt
Had a crystallite diameter of 4.8 nm.

[Preparation of Electrolyte Membrane-Electrode Assembly] PTFE
(Polytetrafluoroethylene, manufactured by Mitsui Fluorochemicals: Teflon 30J) water repellent treatment 50 x 50 mm, thickness 6
0 μm porous carbon paper (Toray: TGP-H-
060) was prepared as an electrode substrate. Each of the platinum-supported or platinum-ruthenium-supported carbon powder catalysts obtained in Examples 2 to 4 and Comparative Examples 5 to 10 had a mass ratio of catalyst / Teflon powder (Kitamura: KTL-4N) = 7/3. And mixed with alcohol and further mixed until a paste was formed. The paste thus formed was uniformly applied to the entire one surface of the porous carbon paper and baked to form a catalyst layer. next,
A 5 wt% Nafion solution (manufactured by Aldrich) was uniformly applied to the surface of the catalyst layer so that the geometric area of the electrode was 0.02 ml / cm ^2, and dried at 80 ° C. for 1 hour. In this way, electrodes were prepared using the platinum-supporting carbon powder or the platinum-ruthenium-supporting carbon powder of each of the examples and the comparative examples.

Next, a commercial product Pt 27% -R which will be the anode
u13% / Carbon (trade name: SA27-13RC,
An electrode using NCE Chemcat) and an electrode obtained by using the platinum-supporting carbon powder of Example 2 as a cathode are provided on both sides of a perfluorosulfonic acid electrolyte membrane (DuPont, trade name: Nafion 112). On top of each other so that the catalyst layer side of each electrode is in contact with the electrolyte and thermocompression-bonded by hot pressing to form an electrolyte membrane-electrode assembly M.
EA-1 was obtained.

Next, except that the electrode using the platinum-supporting carbon powder of Comparative Examples 5 to 8 was used as the cathode, the above M was used.
Electrolyte membrane-electrode assemblies MEA-2, MEA-3, MEA-4, and MEA- were prepared in the same manner as in the preparation of EA-1.
5 were produced respectively.

Next, the above MEA-1 was prepared except that the electrode using the platinum-supporting carbon powder of Comparative Example 9 was used as the anode and the electrode using the platinum-supporting carbon powder of Example 3 was used as the cathode. Electrolyte membrane in the same way as
An electrode assembly MEA-6 was produced.

Next, except that the electrodes using the platinum-supporting carbon powder of Comparative Example 9 were used on both sides of the electrolyte membrane, the above ME was used.
Electrolyte membrane-electrode assembly ME in the same manner as in the preparation of A-1
A-7 was produced.

Next, except that the electrode using the platinum-supporting carbon powder of Comparative Example 9 was used as the anode and the platinum-ruthenium-supporting carbon powder of Example 4 was used as the cathode, the MEA-1 was used. An electrolyte membrane-electrode assembly MEA-8 was produced in the same manner as in the above production. next,
An electrolyte was prepared in the same manner as in the above MEA-1, except that an electrode using the platinum-supporting carbon powder of Comparative Example 9 as the anode and an electrode using the platinum-ruthenium-supporting carbon powder of Comparative Example 10 as the cathode were used. A membrane-electrode assembly MEA-9 was prepared.

<Performance Evaluation Test> Each MEA produced as described above was evaluated by a fuel cell single cell evaluation device (Scriber Associates).
Manufactured by model: 890), the cell temperature was set to 80 ° C., the anode was hydrogenated with saturated steam at 90 ° C. or hydrogen containing 100 ppm CO, and the cathode was 5
The unit cell was operated by increasing the flow rate of air or oxygen humidified at 0 ° C. so that the utilization rate of each gas was always 50%.

In FIG. 3, as the evaluation of the cathode performance, the amount of platinum used per electrode geometric area in the anode was 0.45 mg.
/ Cm ² , MEA-1 to MEA-5 in which the amount of platinum used per electrode geometric area in the cathode was 0.3 mg / cm ^2.
2 shows a current density-voltage curve in the case of using air as a cathode gas. The cell voltage drops sharply on the high current density side because the air supplied to the cathode diffuses the material to the electrode surface at a rate-determining rate. The higher the limiting current density at this time, the better the gas diffusivity. It can be said to be a structure. Comparing with this limiting current density, the electrode catalyst of Example 2
MEA-1 using the cathode using (support: Furnace Black A) showed the highest value, and then MEA-1 using the cathode using the electrode catalyst of Comparative Example 5 (support: Ketjen Black EC). 2 and the electrode catalyst of Comparative Example 7
MEA-4 using a cathode using (carrier: Furnace Black B) is almost the same, and then MEA-3 using a cathode using the electrode catalyst of Comparative Example 6 (carrier: Vulcan XC-72R), comparison. It became the rank order of MEA-5 using the cathode using the electrocatalyst of Example 8 (support: Furnace Black C). The diffusion limit current density in each MEA of the above results is plotted on the vertical axis, and the radius in FIG.
The total volume of pores having a size of 10 to 30 nm is shown on the horizontal axis in FIG. As a result, the electrode catalyst of Example 2 having a specific pore volume of 0.40 cm ³ / g or more (support: furnace black A)
It can be seen that the MEA-1 using the cathode using is the highest performance.

As an evaluation of the cathode in FIG. 5, the amount of platinum used per electrode geometric area in the anode was 0.45 mg / c.
m ² , MEA-1, MEA-3, M in which the amount of platinum used per electrode geometric area in the cathode was 0.4 mg / cm ^2.
7 shows a current density-voltage curve when EA-5 is used and oxygen is used as a cathode gas. From these results, MEA using the cathode using the electrode catalyst of Example 2 (support: furnace black A) in all current density regions
1 has the highest cell voltage, and then the electrode catalyst of Comparative Example 6
MEA-3 using a cathode using (carrier: Vulcan XC-72R), MEA using a cathode using the electrode catalyst of Comparative Example 8 (carrier: furnace black C)
The order of -5 is obtained, and the cell voltage difference becomes large in the high current density region where the influence of the substance diffusion becomes remarkable.

As an evaluation of the cathode in FIG. 6, the amount of platinum used per electrode geometric area in the anode was 0.7 mg / c.
m ² , the current density when oxygen was used as the cathode gas with MEA-6 and MEA-7 in which the amount of platinum used per electrode geometric area in the cathode was 0.7 mg / cm ^2.
The voltage curve is shown. From these results, the cell voltage of MEA-6 using the cathode using the electrocatalyst of Example 3 (carrier: Furnace Black A) was the same as that of Comparative Example 9 (carrier: Ketjen Black) in all current density regions. E
C) The value was higher than that of MEA-7 using a cathode, and the cell voltage difference was large in the high current density region where the effect of material diffusion was particularly remarkable.

As an evaluation of the cathode in FIG. 7, the amount of platinum used per electrode geometric area in the anode was 0.7 mg / c.
m ^{2 is} the current density-voltage curve when oxygen is used as the cathode gas, using MEA-8 and MEA-9 in which the amount of platinum used per electrode geometric area in the cathode is 0.45 mg / cm ² . From these results, MEA-8 using the cathode using the electrode catalyst of Example 4 (support: furnace black A) was obtained in almost all current density regions.
The cell voltage of Comparative Example 10 (Vulcan XC-
72R) has a higher value than that of MEA-9 using a cathode, and in the high current density region where the influence of material diffusion is particularly remarkable, the cell voltage difference becomes large, and furnace black is also used in alloy-based catalysts. The superiority of using A was confirmed.

FIG. 8 shows the above ME as the evaluation of the anode.
The current density-voltage curve at the time of reversing an anode and a cathode about A-8 and MEA-9 and using hydrogen containing 100 ppmCO as an anode gas and oxygen as a cathode is shown. From these results, the cell voltage of MEA-8 using the anode using the electrode catalyst of Example 4 (support: furnace black A) was almost the same as that of Comparative Example 10 (Vulcan XC-72R) in almost all current density regions. The value was higher than that of MEA-9 using No. 2, and the superiority of using Furnace Black A was confirmed also in CO resistance performance.

[0069]

EFFECTS OF THE INVENTION By adopting the furnace black having specific physical properties according to the present invention as a carrier for an electrode catalyst for a polymer electrolyte fuel cell, a gas used for an electrode reaction due to its pore structure ( (Hydrogen, oxygen, etc.) can be sufficiently secured to diffuse into the catalyst, the platinum-based catalytic activity is improved, and even if carbon monoxide is mixed in the fuel hydrogen gas as a catalyst poison, the platinum-based catalytic activity is It is possible to exhibit high battery characteristics with little deterioration.

[Brief description of drawings]

FIG. 1 is a schematic view of a carbon black production apparatus.

FIG. 2 is a diagram showing a relationship between a pore radius of carbon black used in Example 2 and Comparative Examples 5 to 8 and a total pore volume thereof.

FIG. 3 is an electrolyte-electrode composite body (ME prepared using the electrode catalyst powder according to Example 2 and Comparative Examples 5 to 8).
It is a figure which shows the evaluation of A-1 to MEA-5).

FIG. 4 shows the pore volume of carbon black used in Example 2 and Comparative Examples 5 to 8 at a pore radius of 10 to 30 nm and the electrode catalyst powders of Example 2 and Comparative Examples 5 to 8. Electrolyte-electrode composite (MEA-1) produced by using
~ MEA-5) is a diagram showing the relationship with the diffusion limit current density.

FIG. 5 is prepared by using the electrode catalyst powders according to Example 2 and Comparative Examples 6 and 8 in which the amounts of platinum used in the anode and the cathode are changed, and the amounts of platinum used in the anode and the cathode are changed. It is a figure which shows evaluation of electrolyte-electrode composite_body | complex (MEA-1, MEA-3, MEA-5).

FIG. 6 is an electrolyte-electrode composite (MEA-) produced using the electrode catalyst powders of Example 3 and Comparative Example 9.
It is a figure which shows the evaluation of 6, MEA-7).

FIG. 7 is an electrolyte-electrode composite (MEA) produced by using the electrode catalyst powder according to Example 4 and Comparative Example 10.
It is a figure which shows evaluation of -8, MEA-9).

FIG. 8 shows 100 ppm CO as an anode gas.
It is a figure which shows the evaluation of the electrolyte electrode complex (MEA-8, MEA-9) produced using the electrode catalyst powder which concerns on Example 4 and the comparative example 10 when mixed hydrogen is used.

Continued front page    (72) Inventor Masamichi Ueda             3-19-3 Chugoku, Ichikawa, Chiba Prefecture             ー Chemcat Co., Ltd. Ichikawa Laboratory (72) Inventor Mitsuo Suzuki             1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa             Within Mitsubishi Chemical Corporation (72) Inventor Shuchi Yoshimura             2-5-3 Marunouchi 2-chome, Chiyoda-ku, Tokyo             Ryo Chemical Co., Ltd. (72) Inventor Shinichi Kanamaru             1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Corporation             Inside the company F term (reference) 4J037 AA02 BB15 CA03 DD05 DD06                       DD07 DD17 FF11                 5H018 AA06 EE02 EE03 EE08 HH00                       HH01 HH02 HH04                 5H026 AA06 EE02 EE05 HH01 HH02                       HH04

Claims (9)

[Claims] In 1. A DBP oil absorption 170~300cm ³ / 100g,
The BET method has a specific surface area of 250 to 400 m ² / g, a primary particle diameter of 10 to 17 nm, and a total volume of pores having a radius of 10 to 30 nm of 0.40 cm ³ / g or more. And carbon black. 2. The carbon black according to claim 1, wherein the carbon black is furnace black. 3. A carrier for an electrode catalyst, comprising the carbon black according to claim 1 or 2. 4. The carrier for an electrode catalyst according to claim 3, wherein the carbon black is furnace black. 5. The carrier for an electrode catalyst according to claim 3, wherein the electrode catalyst is for a polymer electrolyte fuel cell. 6. An electrode catalyst comprising the carrier according to claim 3 or 4 and platinum supported on the carrier, wherein the amount of platinum based on the whole electrode catalyst is 5 to 70% by mass. Characteristic electrode catalyst. 7. In addition to platinum, palladium, rhodium, iridium, ruthenium, gold, silver, iron,
Zinc, nickel, molybdenum, cobalt, tin, chromium,
The electrode catalyst according to claim 6, which carries at least one metal selected from the group consisting of manganese, rhenium, tungsten, and copper. 8. An electrochemical device comprising the electrocatalyst according to claim 6 or 7. 9. The electrochemical device according to claim 8, which is a solid polymer electrolyte fuel cell, an electrolyzer, or a sensor.