JP2006185855A - Method of producing electrode catalyst ink and electrode catalyst layer obtained from the electrode catalyst ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing an electrode catalyst ink for forming a catalyst layer in which platinum black is highly dispersed. <P>SOLUTION: The temperature of a mixture comprising a polymer electrolyte and a fluorine compound is controlled to 40 to 70°C, and the platinum black is added to the mixture. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing an electrode catalyst ink, and more particularly to a method for producing an electrode catalyst ink using platinum black.

  A fuel cell is a clean power generation system in which the product of an electrode reaction is water in principle. Among them, a polymer electrolyte fuel cell operates at a lower temperature than other fuel cells. Expected to be a power source for moving objects.

  However, in fuel cells, the main component is carbon in the electrode catalyst layer as the potential of the fuel (anode) electrode and oxygen (cathode) electrode changes due to various causes such as long-term continuous operation and start / stop. There is a point to be improved in that corrosion of the catalyst carrier occurs and the electrode performance deteriorates. For example, when the electrode is in a noble potential environment (> about 1.0 V) at the fuel electrode and oxygen electrode of the polymer electrolyte fuel cell, the electrochemical oxidation reaction of carbon in the electrode catalyst layer, that is, carbon Corrosion progresses. As the corrosion of the carbon progresses, the platinum peeled off from the carbon aggregates with other platinum, thereby reducing the surface area of the platinum and reducing the amount of the catalyst that is effectively used, thereby reducing the battery performance. As shown in the following chemical formula 1, the carbon corrosion reaction is considered to be a reaction in which carbon dioxide is generated using water as an oxidizing agent.

Therefore, in the past, an attempt was made to produce an electrocatalyst layer that was not affected by carbon corrosion by using platinum black in which platinum was formed in a very fine spongy form instead of a carrier and catalyst mainly composed of carbon. There is an attempt. In Patent Document 1, a solution containing a fluorine-containing ion exchange resin and a fluorine-containing compound solvent is prepared, platinum black having an average particle size of 3 μm is then dispersed in the solution, and the viscosity of the resulting mixture is 100 to 20000 cP. A method for producing an electrode catalyst layer using the mixed liquid prepared as described above as an electrode catalyst ink is disclosed.
JP 2002-151088 A

  However, in the conventional method, platinum black particles are remarkably agglomerated in the process of preparing the electrocatalyst ink, and it is difficult to obtain an electrocatalyst layer excellent in catalyst utilization and gas diffusibility. In the method described in Patent Document 1, it is difficult to apply the obtained electrocatalyst ink on the substrate because platinum black particles are aggregated and settled at the same time as platinum black is added. Therefore, an electrode catalyst layer in which platinum black is highly dispersed cannot be obtained.

  An object of the present invention is to provide a method for producing an electrode catalyst ink for producing an electrode catalyst layer in which platinum black is highly dispersed.

  As a result of examining the production method of the electrocatalyst ink in detail, the present inventor has found that the above problem can be solved by adjusting the temperature of the mixed liquid when adding platinum black. That is, the present invention provides a method for producing an electrocatalyst ink characterized by adjusting the temperature of a mixed solution containing a polymer electrolyte and a fluorine compound to 40 to 70 ° C. and adding platinum black to the mixed solution. To solve.

  According to the present invention, an electrocatalyst ink having a high degree of dispersion of platinum black can be obtained.

  The first of the present invention is a method for producing an electrocatalyst ink containing a polymer electrolyte, a fluorine compound and platinum black. The temperature of the mixed liquid comprising the polymer electrolyte and the fluorine compound is set to 40 to 70 ° C. It is a manufacturing method of the electrode catalyst ink which adds platinum black.

  In the method of the present invention, the temperature of the mixed solution when adding platinum black is 40 to 70 ° C, preferably 50 to 65 ° C. Thereby, an electrode catalyst ink in which platinum black is highly dispersed is obtained. Although the mechanism by which the dispersibility of platinum black is improved by adjusting the temperature of the mixed solution to the above range is not clear, increasing the temperature of the mixed solution changes the structure of the fluorine compound molecular chain to a sufficiently elongated structure. These are expected to be the result of suppressing the aggregation and sedimentation of platinum black by spatially arranging these three-dimensionally. It is preferable that the temperature of the mixed solution is within the above range because the added platinum black is less likely to aggregate in the mixed solution and has excellent coating properties. Moreover, when it exceeds 70 degreeC, there exists a possibility that an electrode catalyst ink may gelatinize. In order to adjust the mixed solution to the predetermined temperature, a water bath, an oil bath or the like may be used.

  The stirring time after adding platinum black to the mixed solution can be appropriately determined depending on the degree of dispersion of platinum black, the volatility of the solvent, etc., but it is preferable because mixing and stirring for 60 minutes or more improves the dispersibility of platinum black. . A homogenizer or the like may be used as the stirring means, and in addition to the stirring means, a ball mill, a bead mill, a jet mill, an ultrasonic device, or the like may be used. At this time, the electrode catalyst ink temperature needs to be maintained at the predetermined temperature.

  The viscosity of the electrode catalyst ink is preferably 1 to 20 Pa · s (1,000 to 20,000 cps), more preferably 1.2 to 18 Pa · s (1,200 to 18,000 cps), and still more preferably. Is 1.5 to 15 Pa · s (1,500 to 15,000 cps). It is preferable that the viscosity of the electrode catalyst ink is 1 Pa · s (1,000 cps) or more because platinum black is less likely to aggregate in the mixed solution and is excellent in the application property of the electrode catalyst ink, and is 20 Pa · s (20,000 cps) or less It is preferable that the polymer electrolyte and platinum black can be uniformly mixed, and the viscosity is not too high and the coating property is excellent. The above-mentioned viscosity is a value when the temperature of the electrode catalyst ink is 40 to 70 ° C. The viscosity can be adjusted as appropriate by changing the ratio of the constituent elements of the electrode catalyst ink, and can also be adjusted as appropriate by using a viscosity modifier. Viscosity can be measured using a B type viscometer, a TV-10 type viscometer, a TV-20 type viscometer, or the like.

  Next, components of the electrode catalyst ink will be described in detail.

(Platinum black)
The average particle diameter of platinum black used in the present invention is preferably 2 to 20 nm, more preferably 2 to 18 nm, and still more preferably 2 to 15 nm. It is preferable that the average particle diameter of platinum black is 2 nm or more because platinum black does not easily dissolve and dissolve even when an electrode catalyst layer prepared using an electrode catalyst ink is exposed to a noble potential environment. It is preferable because a desired catalytic activity can be obtained.

  The average particle size is calculated by calculating the average value based on the crystallite size determined from the half-value width of the diffraction peak of platinum in X-ray diffraction or the particle size obtained from the observation result in a transmission electron microscope. can get.

(Fluorine compound)
The fluorine compound is preferably at least one selected from the group consisting of a fluorine-containing alcohol having 1 to 6 carbon atoms, a fluorine-containing ether having 1 to 6 carbon atoms, and a fluorine-containing alkane having 1 to 6 carbon atoms. By using the above-mentioned fluorine compound, the dispersibility of platinum black in the electrode catalyst ink can be enhanced, and the dispersion state can be stabilized.

  As the fluorine-containing alcohol having 1 to 6 carbon atoms, 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoropropanol, 2,2,3,4,4,4-hexafluorobutanol , And 1,1,1,3,3,3-hexafluoro-2-propanol. Examples of the fluorinated ether having 1 to 6 carbon atoms include 2,2,3,3,3-pentafluoropropyl methyl ether, 2,2,3,3,3-pentafluoropropyl fluoromethyl ether, and 1,1 , 3,3,3-pentafluoro-2-trifluoromethylpropyl methyl ether and the like. 1,3-dichloro-1,1,2,2,3-pentafluoropropane, 1,1-dichloro-2,2,3,3,3-pentafluoropropane as a fluorine-containing alkane having 1 to 6 carbon atoms 1,1,1,2,3,4,4,5,5,5-decafluoropentane, 1,1,1-trichloro-2,2,3,3,3-pentafluoropropane, etc. It is done.

  The fluorine compound preferably has a trifluoromethyl group and / or chlorodifluoromethyl group, a hydroxyl group and / or hydrogen in the molecule. By using the above-mentioned fluorine compound having a functional group, the viscosity of the mixed solution can be adjusted to an appropriate range.

  The mass ratio of platinum black and fluorine compound in the electrode catalyst ink is preferably 1:10 to 1: 500, more preferably 1:25 to 1: 350. When the mass ratio of platinum black and fluorine compound is within the above range, the viscosity of the mixed liquid can be maintained within a preferable range, and as a result, the electrode catalyst having excellent dispersibility of platinum black and excellent coating properties. This is preferable because an ink can be produced. The fluorine compound leaves fluorine atoms in the electrode catalyst layer when the electrode catalyst ink is dried, and most of the other is volatilized. When the fuel cell is operated for a long time, excessive moisture is accumulated in the electrode catalyst layer, which may cause flooding. Since the fluorine atoms remain in the electrode catalyst layer, the ability to remove excess water can be improved.

(Polymer electrolyte)
The polymer electrolyte is not particularly limited and known ones can be used, but those having high proton conductivity are preferable. Polymer electrolytes having high proton conductivity include perfluorocarbon polymers having a sulfonic acid group, those obtained by doping a hydrocarbon polymer compound with an inorganic acid such as phosphoric acid, and some proton-conducting functional groups And an organic / inorganic hybrid polymer substituted with a proton conductor in which a polymer matrix is impregnated with a phosphoric acid solution or a sulfuric acid solution. Examples of the perfluorocarbon polymer having a sulfonic acid group include NAFION (registered trademark) manufactured by DuPont Co., Ltd., FLEMION (registered trademark) manufactured by Asahi Glass Co., Ltd., and ACIPLEX (registered trademark) manufactured by Asahi Kasei Chemicals Corporation.

  The mass ratio of platinum black and polymer electrolyte in the electrode catalyst ink is preferably 1: 0.1 to 1:10, more preferably 1: 0.5 to 1: 5. When the mass ratio of the polymer electrolyte to platinum black is 0.1 or more, an electrode catalyst layer in which the polymer electrolyte is sufficiently coated with platinum black can be obtained, so that sufficient performance can be obtained at the initial stage of the battery. On the other hand, when the mass ratio of the polymer electrolyte is 10 or less, pores necessary for the diffusion of the reaction gas can be secured in the obtained electrode catalyst layer, and flooding can be prevented. On the other hand, when the mass ratio of the polymer electrolyte exceeds 10, the layer of the polymer electrolyte covering platinum black in the obtained electrode catalyst layer becomes thick, and the reaction gas diffusion rate may decrease.

  In mixing the polymer electrolyte and the fluorine compound, the polymer electrolyte may be used as a solution in which the solid polymer electrolyte is mixed with water and / or methanol, ethanol, propanol alcohol solvent.

  If the desired viscosity is not obtained even after adjusting the mixing ratio of the constituent elements of the electrode catalyst ink, methanol, ethanol, n-propanol, 2-propanol, 1-butanol, 2-butanol, 1, An organic solvent such as 4-dioxane, n-propyl ether, or dimethyl sulfoxide may be further added to the mixed solution or the electrode catalyst ink to adjust the viscosity.

  The electrode catalyst ink may contain a water repellent such as PTFE, polyvinylidene fluoride (PVDF), or perfluoroalkoxy resin (PFA). By including these water repellents, the ability to remove excess water can be further improved.

  The median diameter of the particle size distribution of the platinum black aggregate contained in the electrocatalyst ink obtained by the conventional method was in the range of 5 to 30 μm. In the present invention, the median diameter is in the range of 0.1 to 2 μm. Thus, platinum black can be dispersed, and platinum black can be highly dispersed. Furthermore, when the median diameter is in the range of 0.1 to 2 μm, the film thickness of the electrode catalyst layer can be set to a preferable range described later.

  A second aspect of the present invention is an electrode catalyst ink obtained by the above-described production method.

  The electrode catalyst ink of the present invention is excellent in platinum black dispersibility and coatability. The electrode catalyst ink can be stored in a highly dispersed state of platinum black by maintaining the ink temperature at 40 to 70 ° C. and continuing stirring. In addition, the electrocatalyst ink obtained by the above-described method can make the precipitated platinum black into a highly dispersed state again by stirring at 40 to 70 ° C. even when the ink temperature is 39 ° C. or lower. .

  The third of the present invention is an electrode catalyst layer obtained from the above-mentioned electrode catalyst ink.

  In the electrode catalyst layer of the present invention, platinum black is highly dispersed, so that the catalyst utilization rate is high and the gas diffusibility is excellent, and the battery performance is not easily lowered even when exposed to a noble potential environment. The electrode catalyst layer of the present invention can be produced by a conventionally known method in which the above-described electrode catalyst ink is applied and dried on a solid polymer electrolyte membrane or the like.

  The electrode catalyst ink can be applied by a die coater method, a screen printing method, a doctor blade method, a spray method, a curtain coater method, or the like. The electrode catalyst layer may be formed on the gas diffusion layer in addition to the solid polymer electrolyte membrane. In addition, when formed on a base material such as a polytetrafluoroethylene (PTFE) sheet, the PTFE sheet on which the electrode catalyst layer is formed is brought into contact with the solid polymer electrolyte membrane and the electrode catalyst layer. After lamination and hot pressing, only the PTFE sheet may be peeled off. The thickness of the electrode catalyst layer is preferably 1 to 40 μm, more preferably 5 to 35 μm. When the thickness of the electrode catalyst layer is 1 μm or more, a uniform film can be formed, and when the thickness is 40 μm or less, flooding can be suppressed.

  The electrode catalyst layer is excellent in platinum black dispersibility by using the electrode catalyst ink obtained by the first method of the present invention.

  In addition, in a part of a conventional general electrode catalyst layer composed of an electrode catalyst in which catalyst particles are supported on a conductive carrier and a solid polymer electrolyte, particularly in a portion where corrosion of the conductive carrier is likely to occur, An electrode catalyst layer may be disposed. This also provides an electrode catalyst layer with excellent durability.

  A fourth aspect of the present invention is a fuel cell membrane-electrode assembly (also simply referred to as “MEA”) having the above-described electrode catalyst layer. According to the electrode catalyst layer in which platinum black of the present invention is highly dispersed, an MEA excellent in durability and power generation performance can be obtained.

  The structure of the MEA is not particularly limited, but the anode side electrode catalyst layer and the anode side gas diffusion layer, and the cathode side electrode catalyst layer and the cathode side gas diffusion layer are opposed to each other on both sides of the solid polymer electrolyte membrane. It has an arranged configuration.

  In the MEA of the present invention, the above-described electrode catalyst layer may be used for at least one of the anode side electrode catalyst layer and the cathode side electrode catalyst layer, but it is used for the cathode side electrode catalyst layer in which corrosion of the carbon support is likely to occur. preferable. When the above-described electrode catalyst layer is used for the cathode-side electrode catalyst layer, a conventionally known anode electrode catalyst layer used for MEA may be applied to the anode-side electrode catalyst layer in addition to the above-described electrode catalyst layer. However, it is more preferable that the above-described electrode catalyst layer of the present invention is used for both the anode-side electrode catalyst layer and the cathode-side electrode catalyst layer because of excellent durability and the like.

  The MEA is characterized by using the above-mentioned third electrode catalyst layer of the present invention, and other solid polymer electrolyte membranes, gas diffusion layers and the like are generally used in conventionally known MEAs. If it is used, it can be used without particular limitation. Therefore, detailed description of the solid polymer electrolyte membrane, the gas diffusion layer, and the like is omitted.

  A fifth aspect of the present invention is a fuel cell having the above-described MEA. As described above, since the electrode catalyst layer of the present invention is excellent in each characteristic, a fuel cell having high power generation performance can be obtained by using these.

  As the type of the fuel cell, a polymer electrolyte fuel cell that is small in size and capable of high density and high output is preferably exemplified.

  The configuration of the fuel cell is not particularly limited, and a conventionally known technique may be used as appropriate. Generally, the fuel cell has a structure in which an MEA is sandwiched between separators. As the separator for sandwiching the MEA, any conventionally known separator such as a carbon made of dense carbon graphite, a carbon plate, or a metal such as stainless steel can be used without limitation. The separator has a function of separating air and fuel gas, and a channel groove for securing the channel may be formed. The thickness and size of the separator, the shape of the flow channel, and the like are not particularly limited, and may be appropriately determined in consideration of the output characteristics of the obtained fuel cell.

  Furthermore, a stack in which a plurality of MEAs are stacked via a separator and connected in series may be formed so that the fuel cell can obtain a desired voltage or the like. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited only to the following Example.

Example 1
[Production of gas diffusion layer]
Carbon paper (TGP-H-060 manufactured by Toray Industries, Inc., 180 μm thick) is punched into a 55 × 55 mm square, and then an aqueous dispersion solution of PTFE (D1 manufactured by Daikin Industries, Ltd., containing 60% by mass of PTFE) is purified water. Then, the carbon paper was dipped in a solution diluted to a predetermined concentration for 2 minutes and then dried in an oven at 60 ° C. for 10 minutes to give the carbon paper a water repellent treatment. At this time, the PTFE content in the carbon paper was 25% by mass.

Next, carbon black (Valcan XC72R manufactured by Cabot, specific surface area 220 m ² / g) and polytetrafluoroethylene (manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) and 2-propanol (on one side of the water repellent treated carbon paper) A slurry solution uniformly dispersed in Wako Pure Chemical Industries, Ltd. (special grade reagent) was applied by a spray method. Next, it was dried to obtain a gas diffusion layer in which a carbon layer (film thickness 50 μm) was formed on carbon paper. The gas diffusion layer was further heat-treated at 350 ° C. for 5 minutes in an inert gas atmosphere. The mass ratio of carbon to polytetrafluoroethylene (PTFE) in the carbon layer was 50:50.

[Production of electrode catalyst layer]
To a glass container in a water bath set to be kept at 20 ° C., 2.0 g of a polymer electrolyte solution (Nafion solution DE520 manufactured by DuPont, polymer electrolyte content 5 mass%) is added, and then 2, 2, 3, 8.0 g of 3,3-pentafluoropropanol (manufactured by Aldrich Co., Ltd.) was gradually added dropwise and mixed and stirred for 10 minutes using a homogenizer. Next, the temperature of the water bath was raised to 50 ° C., and mixing and stirring were performed for 30 minutes. Next, 80 mg of a commercially available platinum black catalyst (manufactured by Johnson Matthey, HISPEC 1000, average particle size 10 nm) was added to this solution, and the mixture was stirred and stirred at 50 ° C. for 3 hours to obtain an electrode catalyst ink. The viscosity of the electrode catalyst ink at this time was 10 Pa · s (10,000 cps). The viscosity was 50 ° C., and measurement was performed using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd., model number B-8L). This electrode catalyst ink was applied to both surfaces of a solid polymer electrolyte membrane (trade name Nafion 112, manufactured by DuPont Co., Ltd., film thickness 50 μm) by a die coater method and air-dried to obtain an electrode catalyst layer. The obtained fuel electrode and oxygen electrode electrode catalyst layers each have a platinum black loading of 0.50 mg / cm ² , an electrode catalyst layer thickness of 20 μm, a coating area of 50 × 50 mm, and a mass of the solid polymer electrolyte and platinum black. The ratio (solid polymer electrolyte / platinum black) was 1.25.

[Assembly of MEA and single cell]
A solid polymer electrolyte membrane having a fuel electrode electrode catalyst layer and an oxygen electrode electrode catalyst layer formed on both sides was sandwiched between two gas diffusion layers prepared in advance. Thereafter, an MEA was produced by hot pressing for 3 minutes at 120 ° C. and 20 kgf / cm ² , and this was sandwiched between graphite separators and further sandwiched between gold-plated stainless steel current collector plates. A cell.

[Evaluation of initial characteristics and durability]
The initial characteristics and durability of the fuel cell were evaluated by atmospheric pressure, a cell temperature of 70 ° C., hydrogen gas as a fuel, and air gas as an oxidant. Both gases were humidified at 60 ° C. and supplied to the cell. Under this condition, the cell voltage at a current density of 0.5 A / cm ² was measured. On the other hand, as durability evaluation, after performing continuous power generation for 10 minutes under the same conditions as described above, power generation is terminated, and at the end of time, gas supply to the single cell is stopped for both the fuel electrode and the oxygen electrode, The operation was continued again under the same conditions. This operation is performed as a start / stop condition, and is performed 5,000 times. The cell voltage holding ratio after start / stop with respect to the initial cell voltage {(cell voltage after 5,000 start / stop / initial cell voltage) × 100 (%)} Was defined as durability evaluation. The initial cell voltage at that time was 0.70 V, and the cell voltage holding ratio was 97%.

(Example 2)
A fuel cell single cell was assembled in the same manner as in Example 1 except that the electrode catalyst layer was prepared by changing the weight of 2,2,3,3,3-pentafluoropropanol of Example 1 from 8.0 g to 4.0 g. And evaluated. The initial cell voltage was 0.72 V, and the cell voltage holding ratio was 92%.

(Example 3)
A fuel cell single cell was assembled and evaluated in the same manner as in Example 1 except that the electrode catalyst layer was prepared by changing the weight of 2,2,3,3,3-pentafluoropropanol of Example 1 from 8.0 g to 20 g. Went. At this time, the viscosity of the electrode catalyst ink measured at 50 ° C. was 10 Pa · s (10,000 cps). The initial cell voltage was 0.67 V, and the cell voltage holding ratio was 94%.

Example 4
Except that a 2,2,3,3,3-pentafluoropropanol of Example 1 was changed to 2,2,3,4,4,4-hexafluorobutanol and an electrode catalyst layer was prepared, the same as in Example 1 A fuel cell single cell was assembled and evaluated. At this time, the viscosity of the electrode catalyst ink measured at 50 ° C. was 10 Pa · s (10,000 cps). The initial cell voltage was 0.70 V, and the cell voltage holding ratio was 97%.

(Example 5)
A fuel cell single cell was assembled and evaluated in the same manner as in Example 1 except that the electrode catalyst layer was prepared by changing the weight of the polymer electrolyte solution of Example 1 from 2.0 g to 3.0 g. At this time, the viscosity of the electrode catalyst ink measured at 50 ° C. was 10 Pa · s (10,000 cps). The initial cell voltage was 0.72 V, and the cell voltage holding ratio was 92%.

(Example 6)
A fuel cell single cell was assembled and evaluated in the same manner as in Example 1 except that the electrode catalyst layer was prepared by changing the weight of the polymer electrolyte solution of Example 1 from 2.0 g to 5.0 g. At this time, the viscosity of the electrode catalyst ink measured at 50 ° C. was 10 Pa · s (10,000 cps). The initial cell voltage was 0.73 V, and the cell voltage holding ratio was 91%.

(Example 7)
A fuel cell single cell was assembled and evaluated in the same manner as in Example 1 except that the electrode catalyst layer was produced by changing the temperature of the water bath of Example 1 from 50 ° C to 65 ° C. At this time, the viscosity of the electrode catalyst ink as measured at 65 ° C. was 14 Pa · s (14,000 cps). The initial cell voltage was 0.67 V, and the cell voltage holding ratio was 94%.

(Example 8)
The temperature of the water bath in Example 1 was changed from 50 ° C. to 65 ° C., and the viscosity of the electrode catalyst ink measured at 65 ° C. using 2-propanol was adjusted to 10 Pa · s (10,000 cps). A fuel cell single cell evaluation was performed in the same manner as in Example 1 except that the catalyst layer was prepared. The initial cell voltage was 0.70 V, and the cell voltage holding ratio was 97%.

(Comparative Example 1)
An electrode catalyst ink was prepared in the same manner as in Example 1 except that the temperature of the water bath was maintained at 20 ° C., but platinum black aggregated and settled in the electrode catalyst ink in the glass container at the same time as platinum black was added. did. For this reason, coating by the die coater method could not be performed and coating by the doctor blade method was attempted, but platinum black was agglomerated and settled so that coating could not be performed. For this reason, the electrode catalyst ink of Comparative Example 1 could not form a desired electrode catalyst layer, and a membrane / electrode assembly could not be obtained.

(Comparative Example 2)
An electrode catalyst ink was prepared in the same manner as in Example 1 except that ethanol of the same mass was used instead of 2,2,3,3,3-pentafluoropropanol. Platinum black aggregated and settled in the electrode catalyst ink. For this reason, coating by the die coater method could not be performed and coating by the doctor blade method was attempted, but platinum black was agglomerated and settled so that coating could not be performed. For this reason, the electrode catalyst ink of Comparative Example 2 could not form a desired electrode catalyst layer, and a membrane / electrode assembly could not be obtained.

(Comparative Example 3)
A copolymer comprising a polymerized unit based on tetrafluoroethylene having an ion exchange capacity of 1.1 meq / g and a polymerized unit based on CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₃ H in ethanol Dissolved. By setting the concentration of the copolymer in the obtained mixed solution to 9.0 wt%, a polymer electrolyte solution was obtained. To this solution, 40.4 g of 2,2,3,3,3-pentafluoropropanol was added to prepare a solution. Next, 0.4 g of platinum black was added to 11.1 g of this solution maintained at 20 ° C., and at the same time as the addition, aggregation and sedimentation proceeded in the solution. The viscosity of the electrode catalyst ink when measured at 20 ° C. was 24 Pa · s (24,000 cps). Since this electrode catalyst layer ink could not be applied to both sides of the solid polymer electrolyte membrane by the die coater method, an electrode catalyst layer was obtained by the doctor blade method. As for other conditions, a membrane / electrode assembly was prepared according to Example 1, and a single fuel cell evaluation was performed. The initial cell voltage was 0.62 V, and the cell voltage holding ratio was 84%.

  Table 1 shows the results of Examples 1 to 8 and Comparative Examples 1 to 3. In Table 1, the fluorine compound referred to in the present application is described in the column of the solvent.

Claims (11)

A method for producing an electrocatalyst ink comprising a polymer electrolyte, a fluorine compound and platinum black,
Adjusting the temperature of the mixed solution containing the polymer electrolyte and the fluorine compound to 40 to 70 ° C .;
A method for producing an electrocatalyst ink, comprising adding platinum black to the mixed solution.   The method for producing an electrocatalyst ink according to claim 1, wherein the platinum black has an average particle diameter of 2 to 20 nm.   The method for producing an electrode catalyst ink according to claim 1, wherein the electrode catalyst ink has a viscosity of 1 to 20 Pa · s.   The fluorine compound comprises at least one selected from the group consisting of a fluorine-containing alcohol having 1 to 6 carbon atoms, a fluorine-containing ether having 1 to 6 carbon atoms, and a fluorine-containing alkane having 1 to 6 carbon atoms. The method for producing an electrode catalyst ink according to claim 1.   The method for producing an electrocatalyst ink according to claim 1, wherein the fluorine compound has a trifluoromethyl group and / or a chlorodifluoromethyl group, and a hydroxyl group and / or a hydrogen atom. .   The method for producing an electrode catalyst ink according to claim 1, wherein a mass ratio of the platinum black to the fluorine compound is 1:10 to 1: 500.   The method for producing an electrocatalyst ink according to claim 1, wherein a mass ratio of the platinum black to the polymer electrolyte is 1: 0.1 to 1:10.   An electrode catalyst ink obtained by the production method according to claim 1.   An electrode catalyst layer obtained from the electrode catalyst ink according to claim 8.   An MEA having the electrode catalyst layer according to claim 9.   A fuel cell comprising the MEA according to claim 10.