WO2017081910A1

WO2017081910A1 - Catalyst for gas electrodes and battery

Info

Publication number: WO2017081910A1
Application number: PCT/JP2016/074858
Authority: WO
Inventors: 裕輝名古; 峻園田; 横田　博
Original assignee: デンカ株式会社
Priority date: 2015-11-10
Filing date: 2016-08-25
Publication date: 2017-05-18
Also published as: JP2019008864A

Abstract

Provided is a catalyst for gas electrodes, which is capable of elongating the service life of a battery that uses a gas as a reactant by suppressing corrosion deterioration of a carbon material, and which enables the achievement of excellent output characteristics. A catalyst for gas electrodes, which is composed of: a carrier that is obtained by covering a part or the whole of the surface of a conductive carbon with an inorganic oxide; and metal fine particles that adhere to the surface of the carrier and have catalytic activity. This catalyst for gas electrodes is characterized in that the volume of pores having a pore radius of from 10 Å to 40 Å (inclusive) of the conductive carbon as determined by a nitrogen adsorption method is 0.3 mL/g or less.

Description

Gas electrode catalyst and battery

The present invention relates to a gas electrode catalyst and a battery.

A battery using gas as a reactant is useful as a device capable of obtaining electric energy larger than the volume of the battery itself. In particular, fuel cells are considered promising as clean power generators that consume hydrogen and air and discharge only water. Among them, polymer electrolyte fuel cells (PEFC) that use polymer electrolytes as ion conductors have room temperature. From the advantages of being able to operate in the vicinity and being relatively easy to downsize, it is promising as a new power generator for home use or automobile use.

In a battery using a gas such as PEFC as a reactant, a gas electrode catalyst is generally used to promote the reaction of the reactant gas and efficiently extract a current. As one form of the gas electrode catalyst, there is a form in which a substance having catalytic activity is attached and supported on a porous carrier having conductivity. In PEFC, metal particles such as platinum are widely used as a substance having catalytic activity, and carbon materials such as carbon black are widely used as a porous carrier having conductivity. PEFC is designed to form three types of conduction paths of gas, ions and electrons for each metal fine particle by coating this type of gas electrode catalyst with a thin film of polymer electrolyte. Yes.

In PEFC, there is a problem that the power generation performance gradually decreases because the carbon material as a support is corroded. In particular, since oxygen and moisture in the air promote the corrosion of the carbon material, the corrosion deterioration of the air electrode is one factor that determines the life performance of the PEFC.

In order to suppress the corrosion deterioration of the carbon material in the air electrode and improve the life performance of the PEFC, for example, in Patent Document 1, a metal oxide or metal nitride having conductivity that is less susceptible to corrosion by oxygen or moisture than the carbon material is disclosed. A method of using as a carrier is disclosed. However, metal oxides and metal nitrides are not necessarily stable in the entire potential range in the battery usage environment, and there is a problem that they are easily corroded when the potential varies greatly.

For example, Patent Document 2 discloses a method using a carbon material coated with a silicon-based polymer as a carrier. However, as a result of the inventor's examination, the method according to the prior art described in Patent Document 2 does not improve the corrosion resistance depending on the pore distribution of the carbon material, or may result in a decrease in output performance. .

JP 2014-1112569 A Japanese Patent No. 3613330

In view of the above problems and circumstances, the present invention provides a gas electrode catalyst that suppresses corrosion deterioration of a carbon material and realizes high catalytic activity in a battery using a gas such as PEFC as a reactant, and uses the same. The purpose is to provide a battery having excellent life performance and output performance.

That is, the present invention employs the following means in order to solve the above problems.

(1) A gas electrode catalyst comprising a support having a form in which a part or all of the surface of conductive carbon is coated with an inorganic oxide and metal fine particles having catalytic activity attached to the surface of the support, A catalyst for a gas electrode, wherein a pore volume having a pore radius of 10 to 40 mm measured by a nitrogen adsorption method of the conductive carbon is 0.3 mL / g or less.

(2) The gas electrode catalyst according to (1), wherein the inorganic oxide is silica.

(3) The gas electrode catalyst as set forth in (1) or (2), wherein the surface coverage of the conductive carbon by the inorganic oxide is 20 area% or more and 80 area% or less.

(4) In any one of (1) to (3), the pH measured at 25 ° C. is 3.0 or more and 6.5 or less after the carrier is dispersed in ion-exchanged water. The catalyst for gas electrodes as described.

(5) A battery using a gas electrode catalyst according to any one of (1) to (4) and using a gas as a reactant.

As a result of intensive studies, the present inventors have found that corrosion deterioration of carbon materials can be suppressed by using a support in which a part or all of the surface of conductive carbon is coated with an inorganic oxide. Furthermore, it discovered that high catalytic activity was implement | achieved by using the thing with small pore volume of a specific radius as electroconductive carbon. In addition, it has been found that even higher catalytic activity can be realized by using an inorganic oxide having an appropriate acidity. A battery using a gas produced using these as a reactant has excellent life performance and output performance.

FIG. 1 is a schematic view of a gas electrode catalyst of the present invention. FIG. 2 is a diagram illustrating a state in which a thin-film inorganic oxide covers the surface of conductive carbon. FIG. 3 is a diagram for explaining a state in which the particulate inorganic oxide covers the surface of the conductive carbon. FIG. 4 is a view for explaining a state in which oxygen or moisture penetrates into pores having a pore radius of not less than 10 and not more than 40. FIG. 5 is a diagram for explaining a state in which a reaction gas cannot enter a closed pore having a radius of 10 to 40 mm. FIG. 6 is a diagram for explaining a state in which the path of hydrogen ions is interrupted at a position where the polymer electrolyte is interrupted. FIG. 7 is a diagram for explaining a mode of mediating a hydrogen ion pathway when an acidic functional group is present at a position where the polymer electrolyte is interrupted.

Hereinafter, the present invention will be described in detail. A gas electrode catalyst comprising a support having a form in which a part or all of the surface of conductive carbon is coated with an inorganic oxide, and fine metal particles having catalytic activity attached to the surface of the conductive carbon. A catalyst for a gas electrode, wherein a pore volume having a pore radius of 10 to 40 mm measured by a nitrogen adsorption method is 0.3 mL / g or less. The pore volume measured by the nitrogen adsorption method in the present invention with a pore radius of 10 to 40 mm is measured by the measurement method defined in JIS Z 8831-2: 2010, and is 14.3. 2 In the pore size distribution calculated based on the mesopore size distribution determination method (BJH method) by Barrett, Joyner and Halenda, it means the cumulative pore volume in the range of 10 to 40 pores.

The gas electrode catalyst in the present invention comprises a carrier having a form in which a part or all of the surface of conductive carbon is coated with an inorganic oxide, and metal fine particles having catalytic activity attached to the surface. Here, the inorganic oxide covers part or all of the surface of the conductive carbon, as shown in FIG. 2 and FIG. An inorganic oxide in the form of particles that is sufficiently smaller than the surface contacts with a part or all of the surface of the conductive carbon by chemical bonding or physical adsorption, and the other surface of the surface of the conductive carbon It means that a solid, liquid, gas or the like is in a state where it cannot substantially contact. In addition, the metal fine particles adhere to the surface of the carrier means that the metal fine particles come into contact with the carrier surface (which may be a region coated with an inorganic oxide or a region not coated) by chemical bonding or physical adsorption. Means that the electrons are held at positions where mutual movement is possible.

The inorganic oxide in the present invention is one or more selected from solid oxides such as silica, phosphorus oxide, titanium oxide, and alumina among oxides of various typical elements or transition elements. Among these, silica is particularly preferable from the viewpoints of stability and acidity. Inorganic oxides are less susceptible to corrosion by oxygen and moisture than conductive carbon, and this coats the surface of the carbon material, making it difficult for the conductive carbon to come into contact with oxygen and moisture and suppressing the corrosion deterioration of the conductive carbon. can do.

The conductive carbon in the present invention is selected from carbon black, carbon nanotubes, carbon nanofibers, graphite, graphene, carbon fibers, elemental carbon, glassy carbon and the like, as in the case of a general gas electrode catalyst carrier. is there. Among these, carbon black is preferable from the viewpoints of electronic conductivity, specific surface area that greatly affects the amount of metal fine particles attached, porosity that greatly affects gas transport, and among them, acetylene black or furnace black is more preferable.

In the conductive carbon in the present invention, the pore volume having a pore radius of 10 to 40 mm measured by the nitrogen adsorption method is 0.3 mL / g or less, and more preferably 0.25 mL / g or less. As shown in FIG. 4, when the entrance of the conductive carbon has a pore radius of 10 to 40 mm, the inner surface of the pore may be in direct contact with oxygen or moisture. Therefore, the effect of suppressing the corrosion deterioration of the present invention is reduced. In addition, as shown in FIG. 5, when the inlet is blocked by an inorganic oxide, the metal fine particles attached to the inner surface of the pore cannot contact the reactant gas, and thus cannot function as a catalyst. The catalytic activity of the gas electrode catalyst as a whole is reduced. In any case, it is not preferable that the pore volume having a pore radius of 10 to 40 mm is large, and conversely, it is preferable that the pore volume is small because both the effect of suppressing corrosion deterioration and the catalytic activity are increased.

The metal fine particles having catalytic activity in the present invention are metal fine particles having a function of catalyzing a chemical reaction (electrode reaction) that oxidizes or reduces a reactant gas to generate a flow of electrons and ions, that is, an electric current. Particularly when used in PEFC applications, an electrode reaction that oxidizes a fuel gas (typically hydrogen) to extract electrons and hydrogen ions, and an electrode reaction that consumes electrons and hydrogen ions to reduce oxygen gas are used. Metal fine particles that catalyze seed electrode reactions are each required. From the standpoint of stability and activity, platinum fine particles, platinum fine particles, alloy fine particles of platinum and different metals (iron, cobalt, nickel, ruthenium, rhodium, palladium, gold, etc.), platinum and foreign elements (titanium) are used for any electrode reaction. , Vanadium, chromium, manganese, iron, cobalt, nickel, ruthenium, rhodium, palladium, lead, bismuth, etc.) fine particles or platinum and different metals (iron, cobalt, nickel, ruthenium, rhodium, palladium, gold, etc.) particles It is preferable that it is 1 or more types chosen from the microparticles | fine-particles which phase-separate and exist in the inside.

In the present invention, the smaller the particle diameter of the metal fine particles having catalytic activity, the larger the contact area with the reactant gas, which is preferable. Specifically, the number average diameter is preferably 5 nm or less, and more preferably 3 nm or less. In addition, it is preferable from the viewpoint of stability that the particle diameter is uniform rather than a mixture of large and small particle diameters.

The surface coverage of the conductive carbon by the inorganic oxide in the present invention is preferably 20 area% or more and 80 area% or less, and more preferably 40 area% or more and 70 area% or less. By setting the surface coverage to 20% by area or more, the portion where the conductive carbon can directly contact oxygen or moisture is reduced, so that the effect of suppressing corrosion deterioration is enhanced. Further, by setting the surface coverage to 80 area% or less, there is a portion where the hydrophobic conductive carbon is exposed, so that liquid water accumulates inside the gas electrode, and a gas path as a reactant Since the phenomenon (flooding) that clogs the battery is less likely to occur, the output performance as a battery is improved.

After dispersing the carrier in the present invention in ion-exchanged water, the pH measured at 25 ° C. is preferably 3.0 or more and 6.5 or less, and more preferably 4.0 or more and 6.0 or less. When the gas electrode catalyst is used in applications such as PEFC, the electrode is manufactured by coating the surface of the gas electrode catalyst with a polymer electrolyte thin film in order to deliver hydrogen ions to the metal fine particles. At this time, as shown in FIG. 6, the polymer electrolyte rarely completely covers the surface of the gas electrode catalyst, and a portion in which the path of hydrogen ions is partially interrupted is generally generated. At this time, as shown in FIG. 7, if an inorganic oxide having an acidic functional group is present in the interrupted portion, the path of hydrogen ions can be mediated. By dispersing the support in ion-exchanged water and setting the pH measured at 25 ° C. to 6.5 or less, the amount of acidic functional groups necessary to mediate the hydrogen ion pathway can be obtained, and the entire catalyst for gas electrodes As a result, the catalytic activity increases. On the other hand, when there are too many acidic functional groups, since the acidic functional groups are hydrophilic, moisture is easily trapped on the surface of the carrier, and flooding is likely to occur. From this viewpoint, the pH measured at 25 ° C. after dispersing the carrier in ion-exchanged water is preferably 3.0 or more.

When producing a battery using a gas as a reactant using the gas electrode catalyst of the present invention, the gas electrode catalyst is mixed with a binder and formed into a flat plate to form a gas electrode, which is an ion conductor. The battery is brought into contact with one or two surfaces of the electrolyte. When contacting only one surface, another type of gas electrode or an electrode that is not a gas electrode is brought into contact with the opposite surface.

When the battery using gas as a reactant is PEFC, the electrolyte that is an ionic conductor is a solid polymer electrolyte, and the ions that are conducted are typically hydrogen ions. The solid polymer electrolyte may be any one that conducts hydrogen ions or other desired ions. From the viewpoint of oxidation-reduction stability and ionic conductivity, a sulfonic acid-modified polyfluorinated olefin (for example, Nafion®) Etc.) is particularly preferred. Moreover, it is preferable to use a solid polymer electrolyte as a binder used when manufacturing a gas electrode, and to make the solid polymer electrolyte coat | cover the surface of the catalyst for gas electrodes.

Hereinafter, the gas electrode catalyst of the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

<Example 1>
(Measurement of pore volume)
In this example, acetylene black (manufactured by Denka Co., BET specific surface area of 740 m ² / g) was used as the conductive carbon. The pore volume of acetylene black having a pore radius of 10 to 40 mm was measured by the nitrogen adsorption method described below. After 0.03 g of the sample was vacuum degassed at 100 ° C. for 14 hours, a fully automatic gas adsorption / desorption measuring device OMISORP360CX (manufactured by Beckman Coulter) was used, and adsorption / desorption curves by a continuous capacity method using nitrogen as an adsorption gas. Got. Using this, the pore size distribution was calculated based on the BJH method, and the cumulative pore volume in the range of the pore radius of 10 to 40 cm was calculated to be 0.219 mL / g.

(Manufacture of carrier)
A carrier was produced in the following manner. A precision dispersion emulsifier (M Technique Co., Ltd., Claremix) is added to 1 kg of a mixed solvent of water / ethanol = 1/1 (mass ratio) of 2.0 g of the acetylene black and 90 mg of hexadecyltrimethylammonium chloride (Kanto Chemical Co., Ltd.). Then, 1N ammonia water (manufactured by Kanto Chemical Co., Inc.) was added to adjust the pH to 11. While stirring this dispersion with a magnetic stirrer, 80 g of tetraethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise at room temperature over 10 hours, and the mixture was further stirred for 2 hours to be reacted. Thereafter, the reaction solution was suction filtered, washed with pure water, and dried to obtain 2.1 g of a carrier having a carbon black surface coated with silica as a black powder.

(Evaluation of carrier)
The produced carrier was evaluated in the following manner. The results are shown in Table 1.

[Surface coverage]
Using a field emission scanning electron microscope MERLIN (manufactured by Carl Zeiss), a sample in which the carrier is spread on a carbon adhesive tape is bonded under the conditions of an acceleration voltage of 0.8 kV and an observation magnification of 50,000 times. A backscattered electron composition image was obtained in which the entire area was occupied by the carrier. When the average value of the maximum value and the minimum value of the lightness of the reflected electron composition image was used as a threshold value, and the area ratio of the portion where the lightness was not less than the threshold value was calculated as the surface coverage, it was 11 area%.

[PH]
0.2 g of the carrier was mixed with 100 mL of ion exchanged water, allowed to stand in a constant temperature room at 25 ° C. for 24 hours, and then measured for pH using a desktop pH meter F-71 (manufactured by Horiba, Ltd.). .9.

(Manufacture of gas electrode catalyst)
0.22 g of the carrier was mixed with 100 g of ultrapure water together with 0.12 g of chloroplatinic acid (IV) and 0.13 g of sodium carbonate, and 20 mL of 0.07 mol / L formaldehyde aqueous solution was added in an 80 ° C. water bath for 5 minutes. The mixture was stirred while dropping, and further stirred for 4 hours. The stirred liquid was suction filtered to take out a solid, and vacuum dried at 60 ° C. for 1 hour to obtain a black powder. This black powder was heat-treated at 120 ° C. in a nitrogen atmosphere to obtain 0.20 g of a gas electrode catalyst as a black powder. When the platinum loading was measured using ICP, it was Pt / C = 0.11 (mass ratio). Moreover, it was 112 m < ² > / g when the specific surface area of platinum was measured using the CO pulse method.

(Evaluation of catalyst for gas electrode)
The produced gas electrode catalyst was evaluated in the following manner. The results are shown in Table 1.

[Production of electrodes]
An ink obtained by mixing 18.5 mg of the gas electrode catalyst and 100 μL of 5% Nafion (registered trademark) dispersion in a mixed solution of 19 mL of ultrapure water and 6 mL of 2-propanol was used as a rotating electrode (0.196 cm ² ) made of glassy carbon. 10 μL of the solution was dropped on the substrate and dried at 60 ° C. for 15 minutes to obtain a catalyst evaluation electrode.

[Catalytic activity]
The following operations were all carried out in a constant temperature room at 25 ° C. A half cell was prepared using the catalyst evaluation electrode as a working electrode, platinum as a counter electrode, a standard hydrogen electrode as a reference electrode, and a 0.1 M perchloric acid aqueous solution as an electrolyte. First, nitrogen bubbling was performed on the electrolyte solution for 30 minutes, and cyclic voltammetry was performed for 5 cycles under the conditions of 0.05 to 1.20 V and 50 mV / s for pretreatment in a state where the number of rotations of the working electrode was zero. Next, oxygen bubbling was performed on the electrolyte solution for 30 minutes, and convection voltammetry was performed under the conditions of 0.05 to 1.20 V and 10 mV / s, respectively, with the working electrode rotation speed set to 400, 900, 1600, and 2500 rpm. The current value at the time of 0.9 V was recorded. The value (unit: A / g) obtained by dividing the value (unit: A) obtained by mass transfer correction of the obtained current value by the Koutecky-Levic equation by the mass of platinum (unit: g) was defined as the catalytic activity. . In this example, it was 301 A / g.

[durability]
The following operations were all carried out in a constant temperature room at 25 ° C. The cell in which the catalytic activity was measured was subjected to nitrogen bubbling again for 30 minutes, and maintained at 1.0 V for 30 seconds with the working electrode rotating at zero, then 1.0 to 1.5 V, 0 1000 cycles of cyclic voltammetry were performed under the condition of 5 V / s. Next, oxygen bubbling was performed on the electrolytic solution for 30 minutes, and the catalytic activity was measured in the same manner as the measurement of the catalytic activity. The ratio (unit:%) of the obtained catalyst activity value to the initial catalyst activity was defined as durability. In this example, it was 79%.

(Manufacturing PEFC)
50 μL of an ink prepared by mixing 18.5 mg of the gas electrode catalyst and 100 μL of 5% Nafion (registered trademark) dispersion in a mixed solution of 19 mL of ultrapure water and 6 mL of 2-propanol was dropped onto 1 cm × 1 cm carbon paper. The electrode for evaluation was dried at 15 ° C. for 15 minutes. As a counter electrode, an electrode produced in the same manner as the evaluation electrode was used except that the gas electrode catalyst was changed to a commercially available catalyst (TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.). An electrolyte membrane (Nafion (registered trademark) NR211, manufactured by DuPont) is cut into 1 cm × 1 cm, and an evaluation electrode is provided on one side, a counter electrode is provided on the opposite side, and the surface on which the ink is dropped is attached to the electrolyte membrane side. The membrane electrode assembly was obtained by hot pressing at 120 ° C. This was attached to a standard cell (manufactured by Japan Automobile Research Institute) to obtain PEFC.

(Evaluation of PEFC)
The manufactured PEFC was evaluated in the following manner. The results are shown in Table 1.

[Output characteristics]
The PEFC temperature is adjusted to 80 ° C., and as a pre-treatment, 100% relative humidity oxygen is introduced into the gas electrode catalyst side (cathode) and 100% relative humidity hydrogen is introduced into the gas electrode catalyst side (anode). And aging was performed for 30 minutes. Next, after blocking only oxygen on the cathode side and allowing to stand until the open circuit voltage was stabilized at around 0 V, oxygen was introduced and the open circuit potential was measured for 2 minutes. The potential was measured for 15 minutes at 0, 0.2, 0.1, 0.08, 0.06, 0.04, and 0.02 A / cm ² , respectively. The obtained potential value was plotted against the current, and a current value (unit: A / cm ² ) at a potential of 0.9 V was obtained by extrapolation, and this value was used as output characteristics. In this example, it was 1.30 A / cm ² .

[Cycle characteristics]
The temperature of the PEFC where the output characteristics were measured was adjusted to 80 ° C., nitrogen with a relative humidity of 100% was introduced into the cathode, and hydrogen with a relative humidity of 100% was introduced into the anode, and maintained at 1.0 V for 30 seconds. 1000 cycles of cyclic voltammetry were performed under the conditions of 0 to 1.5 V and 0.5 V / s. Subsequently, only nitrogen on the cathode side was cut off and allowed to stand until the open circuit voltage was stabilized, oxygen was introduced, and the output characteristics were measured in the same manner as the measurement of the output characteristics. The ratio (unit:%) of the obtained output characteristic value to the initial output characteristic was defined as the cycle characteristic. In this example, it was 72%.

<Examples 2 to 5>
A support was produced and evaluated in the same manner as in Example 1 except that the amount of hexadecyltrimethylammonium chloride added in Example 1 was changed to 180 mg, 450 mg, 900 mg, and 1800 mg. In addition, a gas electrode catalyst, PEFC, was prepared and evaluated. The results are shown in Table 1.

<Example 6>
A carrier was produced and evaluated in the same manner as in Example 1 except that acetylene black in Example 1 was changed to acetylene black (Denka Co., BET specific surface area 750 m ² / g). In addition, a gas electrode catalyst, PEFC, was prepared and evaluated. The results are shown in Table 1.

<Examples 7 to 8>
A carrier was produced and evaluated in the same manner as in Example 6 except that the amount of hexadecyltrimethylammonium chloride added in Example 6 was changed to 450 mg and 1800 mg. In addition, a gas electrode catalyst, PEFC, was prepared and evaluated. The results are shown in Table 1.

<Example 9>
Example 1 The same as Example 1 except that 80 g of tetraethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was changed to 60 g of trimethyl phosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) and the amount of hexadecyltrimethylammonium chloride added was changed to 900 mg. The carrier was produced by the method described above and evaluated. In addition, a gas electrode catalyst, PEFC, was prepared and evaluated. The results are shown in Table 1.

<Example 10>
A carrier was produced in the same manner as in Example 1 except that 80 g of tetraethoxysilane of Example 1 was changed to 80 g of tetraethoxytitanium (manufactured by Tokyo Chemical Industry Co., Ltd.) and the addition amount of hexadecyltrimethylammonium chloride was changed to 900 mg. And evaluated. In addition, a gas electrode catalyst, PEFC, was prepared and evaluated. The results are shown in Table 1.

<Example 11>
The carrier was prepared in the same manner as in Example 1 except that 80 g of tetraethoxysilane of Example 1 was changed to 110 g of aluminum triisopropoxide (manufactured by Tokyo Chemical Industry Co., Ltd.) and the addition amount of hexadecyltrimethylammonium chloride was changed to 900 mg. Manufactured and evaluated. In addition, a gas electrode catalyst, PEFC, was prepared and evaluated. The results are shown in Table 1.

<Comparative Example 1>
A support was produced and evaluated in the same manner as in Example 1 except that 80 g of tetraethoxysilane in Example 1 was changed to 80 g of ethanol. In addition, a gas electrode catalyst, PEFC, was prepared and evaluated. The results are shown in Table 1.

<Comparative Example 2>
A support was produced in the same manner as in Example 1 except that the acetylene black of Example 1 was changed to Ketjen Black EC600JD (manufactured by Lion Corporation, specific surface area 1190 m ² / g), and 80 g of tetraethoxysilane was changed to 80 g of ethanol. And evaluated. In addition, a gas electrode catalyst, PEFC, was prepared and evaluated. The results are shown in Table 1.

<Comparative Example 3>
A carrier was produced and evaluated in the same manner as in Example 1 except that the acetylene black in Example 1 was changed to Ketjen Black EC600JD. In addition, a gas electrode catalyst, PEFC, was prepared and evaluated. The results are shown in Table 1.

From the results shown in Table 1, it was found that the gas electrode catalysts of the examples of the present invention were excellent in catalytic activity and durability, and the PEFC produced using the catalyst was excellent in output characteristics and cycle characteristics.

The above results were the same for the PEFC anodes produced in the same manner as the PEFC cathodes used in the examples, and also for the electrodes of methanol direct fuel cells.

By using the gas electrode catalyst of the present invention, in a battery using gas as a reactant, it is possible to achieve both suppression of corrosion deterioration of the carbon material and excellent catalytic activity. Thereby, a battery using a gas excellent in output characteristics and life performance as a reactant can be obtained.

DESCRIPTION OF SYMBOLS 1 Conductive carbon 2 Inorganic oxide 2a Thin-film-like inorganic oxide 2b Particulate inorganic oxide 3 Metal fine particle which has catalytic activity 3a Metal fine particle which cannot contact with reaction gas 4 Gas electrode catalyst 5 Liquid or gas 6 Oxygen or moisture 7 Pore with a pore radius of 10 to 40 mm 8 Reactive gas 9 Polymer electrolyte 10 Path of hydrogen ion 10a Path of hydrogen ion mediated by acidic functional group 11 Acid functional group

Claims

A gas electrode catalyst comprising a support having a form in which a part or all of the surface of conductive carbon is coated with an inorganic oxide and metal fine particles having catalytic activity attached to the surface of the support, A catalyst for a gas electrode, wherein a pore volume having a pore radius of 10 to 40 mm measured by a nitrogen adsorption method of carbon is 0.3 mL / g or less.
The catalyst for a gas electrode according to claim 1, wherein the inorganic oxide is silica.
The gas electrode catalyst according to claim 1 or 2, wherein a surface coverage of the conductive carbon by the inorganic oxide is 20 area% or more and 80 area% or less.
The gas electrode according to any one of claims 1 to 3, wherein the carrier measured at 25 ° C after dispersing the carrier in ion-exchanged water has a pH of 3.0 to 6.5. catalyst.
A battery using the gas electrode catalyst according to any one of claims 1 to 4 as a reactant.