JP2007265734A - Catalyst electrode for fuel cell, its manufacturing method, polymer electrolyte membrane/electrode assembly for fuel cell, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell equipped with a catalyst electrode having a high effective utilization factor of a platinum catalyst while being easy to manufacture. <P>SOLUTION: A suspension containing a platinum catalyst particle and a hydrogen ion conductive polymer electrolyte as solid contents is sprayed to the surfaces of the electrode base materials 21, 41 of a fuel cell by using ultrasonic vibration while resonating a spray nozzle. The catalyst electrode manufactured by making it adhere to the surfaces of the electrode base materials 21, 41 has high porosity, and the effective utilization factor of the platinum catalyst increases. In addition, the platinum utilization factor can be further increased by making the catalyst layers 22, 42 of the catalyst electrode have inclined structures, this solid polymer type fuel cell having excellent battery performance can be manufactured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a catalyst electrode for a fuel cell that is easy to produce and has a high effective utilization rate of a platinum catalyst, a method for producing the same, a polymer electrolyte membrane / electrode assembly for a fuel cell using the catalyst electrode, and a fuel cell.

  A fuel cell using hydrogen and oxygen is attracting attention as a power generation system that has almost no adverse environmental impact because its reaction product is essentially only water. In recent years, a polymer electrolyte fuel cell using an ion exchange membrane having hydrogen ion conductivity as an electrolyte among fuel cells has a low operating temperature, a high output density, and can be easily downsized. It is expected to be used for in-vehicle power sources and household stationary power sources.

  A polymer electrolyte fuel cell is formed by stacking a large number of single cells. As shown in FIG. 2, the single cell is composed of an anode-side separator 1, an anode-side catalyst electrode 2, a hydrogen ion conductive polymer electrolyte membrane 3, a cathode-side catalyst electrode 4 and a cathode-side separator 5 stacked in this order. Configured. The anode side catalyst electrode 2 is composed of an electrode base material 21 and a catalyst layer 22 laminated on the surface, and the cathode side catalyst electrode 4 is composed of an electrode base material 41 and a catalyst layer 42 laminated on the surface. It consists of The anode side electrode base material 21 and the cathode side electrode base material 41 are both made of a material having gas diffusibility and conductivity. For example, carbon paper or carbon cloth is used. The anode-side catalyst layer 22 and the cathode-side catalyst layer 42 are both formed into particles by supporting a platinum catalyst on carbon particles and fixed to the electrode base materials 21 and 41 with a hydrogen ion conductive polymer electrolyte. Configured.

  The anode-side separator 1 is provided with a reaction gas flow path to supply hydrogen gas. On the other hand, the reaction gas flow path is also provided in the cathode-side separator 5 to supply oxygen gas. An electromotive force is generated between the electrodes 2 and 4 by reacting these hydrogen gas and oxygen gas in the presence of a platinum catalyst.

  By the way, as the polymer electrolyte fuel cell becomes widespread, reduction of the amount of the platinum catalyst used is an important issue. The reason is that the amount of platinum reserves in the entire earth is limited. For example, if the current number of automobiles is replaced by a fuel cell vehicle from a gasoline vehicle, the current amount of platinum used per unit area may exceed the reserves of the earth.

  In order to reduce the amount of platinum catalyst used, it is important to increase the effective utilization rate of the platinum catalyst. However, when the catalyst layers 22 and 42 are formed by a general wet coating method such as a die coater or screen printing, the solvent is gradually dried. Aggregation proceeds. For this reason, the porosity in the catalyst layers 22 and 42 is reduced, and the path of the fuel gas is easily blocked, and the three-phase interface formed from the catalyst and the hydrogen ion conductive polymer electrolyte in the catalyst layers 22 and 42 is sufficiently provided. It becomes difficult to form. As a result, it is difficult to increase the effective utilization rate of the platinum catalyst, and there is a drawback that the battery performance obtained per unit platinum amount is lowered. In particular, when used in a vehicle, since a large current is required instantly, the diffusibility of fuel gas tends to be insufficient and battery performance tends to be lower than when used for cogeneration.

  Therefore, it has been proposed to form an electrode catalyst layer using a general high-pressure spray (see Patent Document 1). When high-pressure spray is used, the drying speed of the catalyst ink can be increased, the catalyst can be prevented from agglomerating, and more three-phase interfaces can be formed, which tends to improve battery performance. However, the porosity of the catalyst layer formed using high-pressure spray is about 30%, and sufficient battery performance cannot be achieved with a low platinum content. Further, in high pressure spraying, since spray is applied with pressure, spraying becomes strong, and overspray and secondary scattering are likely to occur. Therefore, unless a device such as establishing a collection cycle of the sprayed ink is established, the catalyst ink application efficiency is as low as 15 to 20%, and the effective utilization rate of the platinum catalyst in the deposited catalyst layer is also 5 to 50%. There is a drawback that it becomes lower and lower. Furthermore, there is a drawback that film thickness unevenness is likely to occur due to overspray and secondary scattering.

  In order to improve battery performance, catalyst electrodes having various inclined structures have been proposed. For example, paying attention to the relatively high gas concentration on the gas diffusion electrode side and the relatively high concentration of ionized ions and electrons on the hydrogen ion conductive electrolyte membrane side, changing the composition in the thickness direction of the catalyst electrode layer, A technique for increasing the reaction site by increasing the amount of catalyst supported on the hydrogen ion conductive electrolyte membrane side (see, for example, Patent Document 2), and changing the hydrogen ion conductive electrolytic mass in the thickness direction for the purpose of controlling the diffusion of the reaction gas. A technique (for example, refer to Patent Document 3), a technique for changing proton conductivity or electron conductivity in the thickness direction (for example, refer to Patent Document 4), and the like.

JP-A-8-115726 JP-A-9-180730 JP 2001-319663 A JP 2005-259525 A

  However, any of the above techniques is an inclined structure manufactured using a general wet method such as a die coater or screen printing, or a high-pressure spray. In the case of a die coater, screen printing, or the like, it is extremely difficult to manufacture if an inclined gradient that continuously changes is applied to the inclined structure. Even when high-pressure spray is used, it is difficult to control the inclination of the inclined structure because film thickness unevenness is likely to occur due to overspray and secondary scattering.

  The present invention has been made under the technical background as described above. By sufficiently forming a three-phase interface and increasing the utilization ratio of the platinum catalyst, the amount of the platinum catalyst used is reduced and the power generation characteristics are excellent. It aims at providing the catalyst electrode for fuel cells, its manufacturing method, the polymer electrolyte membrane electrode assembly for fuel cells, and a fuel cell.

According to the first aspect of the present invention, a suspension containing platinum catalyst particles and a hydrogen ion conductive polymer electrolyte as a solid content is resonated with a spray nozzle on the surface of a fuel cell electrode substrate using ultrasonic vibration. The fuel cell catalyst electrode is produced by spraying while allowing the suspension to adhere to the surface of the electrode substrate to form a catalyst layer.
The invention according to claim 2 has an inclined structure in which the content of the platinum catalyst particles and the hydrogen ion conductive polymer electrolyte in the catalyst electrode changes in the thickness direction of the catalyst electrode. 1. The fuel cell catalyst electrode according to 1.
According to a third aspect of the present invention, the catalyst electrode is provided between the hydrogen ion conductive polymer electrolyte membrane and the gas diffusion electrode, and the inclined structure is formed from the hydrogen ion conductive polymer electrolyte membrane to the gas diffusion electrode. The catalyst electrode for a fuel cell according to claim 2, wherein the catalyst electrode for a fuel cell according to claim 2 has an inclined structure in which the content of the platinum catalyst particles increases and the content of the hydrogen ion conductive polymer electrolyte decreases. It is.
The invention according to claim 4 is the suspension, wherein the platinum catalyst particle content is 10 mass% to 40 mass%, and the hydrogen ion conductive polymer electrolyte content is 20 mass% to 20 mass%. It is 80 mass%, It is a catalyst electrode for fuel cells in any one of Claims 1-3 characterized by the above-mentioned.
A fifth aspect of the present invention is the catalyst electrode for a fuel cell according to any one of the first to fourth aspects, wherein a resonance frequency of the ultrasonic vibration is 10 kHz to 500 kHz.
The invention according to claim 6 is the catalyst electrode for a fuel cell according to any one of claims 1 to 5, wherein the porosity of the catalyst layer in the catalyst electrode is 30 to 90%.
The invention described in claim 7 uses two fuel cell catalyst electrodes according to any one of claims 1 to 6, and sandwiches a hydrogen ion conductive polymer electrolyte membrane between the two catalyst electrodes. A polymer electrolyte membrane / electrode assembly (MEA) for fuel cells, characterized in that
The invention according to claim 8 is a fuel cell comprising the polymer electrolyte membrane / electrode assembly for fuel cell according to claim 7 sandwiched between two separators each having a reaction gas flow path. is there.
According to the ninth aspect of the present invention, a suspension containing platinum catalyst particles and a hydrogen ion conductive polymer electrolyte as a solid content is made to resonate a spray nozzle on the surface of a fuel cell electrode substrate using ultrasonic vibration. A method of producing a catalyst electrode for a fuel cell, comprising: a step of spraying while adhering and adhering the suspension to the surface of the electrode substrate to form a catalyst layer.

  In the present invention, since the suspension is sprayed while resonating the spray nozzle using ultrasonic vibration, the suspension is applied with ultrasonic energy to release the solid content from the cohesive energy. For this reason, the particle size distribution of the fine particles in the sprayed suspension becomes sharp, and the average particle size also becomes small. For this reason, the porosity of the formed catalyst layer is increased, gas diffusibility is improved, and a three-phase interface can be sufficiently formed. The porosity of the catalyst layer is a ratio of the volume of the pores to the product of the electrode area and the thickness of the catalyst layer, and is measured with a pore distribution measuring device Pore Sizer 9320 (manufactured by Shimadzu Corporation). Is possible.

  In addition, an inclined structure can be imparted to the catalyst electrode by spraying the suspension while resonating the spray nozzle using ultrasonic vibration. In particular, the spray method using ultrasonic vibration can suppress overspray and secondary scattering, improve the coating efficiency, reduce the amount of platinum catalyst used, and continuously change the gradient. An inclined structure can be formed. As a result, it is possible to manufacture a catalyst electrode that further increases the three-phase interface and improves the battery performance.

  Therefore, according to the present invention, by sufficiently forming a three-phase interface and increasing the utilization rate of the platinum catalyst, the catalyst electrode for a fuel cell which has reduced the amount of platinum catalyst used and has excellent power generation characteristics, a method for producing the same, a fuel cell A polymer electrolyte membrane / electrode assembly for use and a fuel cell can be provided.

  In the present invention, a suspension (catalyst ink) containing platinum catalyst particles and a hydrogen ion conductive polymer electrolyte as a solid content is sprayed on the surface of an electrode substrate while resonating a spray nozzle using ultrasonic vibration. Then, fine particles obtained by coating the periphery of the platinum catalyst particles with a hydrogen ion conductive polymer electrolyte are attached to the surface of the electrode base material to form a catalyst layer.

  As the platinum catalyst particles used in the present invention, platinum alone or platinum-supported carbon particles can be used. In addition, an alloy of platinum, ruthenium, and the like and platinum, or carbon particles supporting the alloy may be used. The hydrogen ion conductive polymer electrolyte is preferably a fluorine-based cation exchange resin such as Nafion (manufactured by DuPont; registered trademark). It is necessary to disperse the platinum catalyst particles and the hydrogen ion conductive polymer electrolyte after mixing. The catalyst ink can be dispersed with a ball mill or an ultrasonic homogenizer. This hydrogen ion conductive polymer electrolyte adheres to the periphery of the platinum catalyst particles during the dispersion treatment or spray treatment, and forms fine particles as a whole.

  The solvent used in the catalyst ink is not particularly limited, and preferably includes a volatile liquid organic solvent that does not react with the platinum catalyst particles or the hydrogen ion conductive polymer electrolyte. desirable. Water having high affinity with the hydrogen ion conductive polymer electrolyte may be included.

  Further, in the present invention, spray sprayed while resonating using ultrasonic vibration transmits ultrasonic waves generated by piezoceramics and the like to the spray nozzle part to resonate, and ultrasonic waves are applied to the catalyst ink passing therethrough. By applying energy and releasing from the cohesive energy that the ink itself tries to gather together, it is atomized and sprayed (ultrasonic spray).

  The vibration frequency of such an ultrasonic spray is desirably 10 kHz to 500 kHz. When the vibration frequency is less than 10 kHz, the ultrasonic energy is insufficient, and the constraint due to the cohesive energy of the catalyst ink cannot be fully released, so that the liquid cannot be in a mist state. In addition, when the vibration frequency exceeds 500 kHz, the ratio of the catalyst ink that cannot follow the given ultrasonic vibration and cannot resonate increases, and the sharp particle distribution of the fog fine particles is impaired. .

  In the present invention, the catalyst layer of the catalyst electrode desirably has an inclined structure. The inclined structure is a structure in which the content of platinum catalyst particles and hydrogen ion conductive polymer electrolyte in the catalyst electrode changes in the thickness direction of the catalyst electrode, for example, gas from the hydrogen ion conductive polymer electrolyte membrane. The gradient structure is such that the platinum catalyst particle content increases and the hydrogen ion conductive polymer electrolyte content decreases toward the diffusion electrode. By giving such a tilted structure to the catalyst layer, compared to the case of a uniform single layer, the gas supplied from the gas diffusion layer side is easily transported to the reaction site, and the platinum catalyst particles easily react. In addition, the hydrogen ions generated by the reaction can easily flow to the hydrogen ion conductive polymer electrolyte membrane side. Further, the reaction between electrons supplied from the external circuit and the oxidizing gas also proceeds smoothly. As a result, the internal resistance of the fuel cell is reduced and the power generation performance can be improved.

  The inclined structure may be a plurality of layers of two or more layers. As the multilayer structure is formed, the reaction and the movement of ions proceed more smoothly, and the power generation performance is easily improved and the stability is also improved. In order to make the inclined structure into a plurality of layers, a plurality of nozzles filled with catalyst inks having different compositions may be prepared and sprayed. When it is desired to carry out spraying online, nozzles can be continuously prepared on the line and sprayed. In the case of ultrasonic spraying, overspray and secondary scattering are unlikely to occur, so productivity can be dramatically improved.

  The content of platinum catalyst particles in the catalyst ink is desirably 10% by mass to 40% by mass. If the amount is less than 10% by mass, the catalyst becomes insufficient and it is difficult to sufficiently exhibit the power generation characteristics. If the amount is 40% by mass or more, the number of platinum catalysts that are not reacted and is wasted increases.

  Moreover, as for content of a hydrogen ion conductive polymer electrolyte, 20 mass%-80 mass% are desirable. If the amount is less than 20% by mass, the hydrogen ion conductive polymer electrolyte is insufficient and it is difficult to sufficiently exhibit power generation characteristics. If the amount is 80% by mass or more, platinum catalyst particles are embedded too much and the three-phase interface is reduced. It is.

  When the porosity of the catalyst layer in the catalyst electrode is less than 30%, the supply of the reaction gas is insufficient and the battery performance is deteriorated. On the other hand, when the porosity exceeds 90%, the electrical conductivity is lowered and the direct current resistance is increased, and the mechanical strength as the catalyst layer is lowered and becomes insufficient.

  Next, in the present invention, the electrode base material to be sprayed is an electrode base material for a polymer electrolyte fuel cell, and is generally made of a material having gas diffusibility and conductivity. A gas diffusion electrode (gas diffusion layer) For example, carbon paper or carbon cloth can be used. The spray layer may be formed in advance on the electrode substrate before spraying. The eye-catching layer is a layer that prevents the catalyst ink from penetrating into the electrode, and even if the spray amount is small, it does not soak into the electrode, and deposits on the electrode to form a film to form a three-phase. Form an interface. Such a sealing layer can be formed, for example, by kneading carbon and a fluororesin and sintering at a temperature equal to or higher than the melting point of the fluororesin. As the fluororesin, polytetrafluoroethylene (PTFE) or the like can be used.

  Moreover, it is desirable to spray in the state which heated the surface of this electrode base material at 60-120 degreeC. By spraying on the surface of the electrode base material heated to 60 to 120 ° C., the solvent in the catalyst ink is instantly dried to prevent aggregation of platinum catalyst particles after landing, and the porosity of the catalyst layer Can be improved. If the electrode substrate surface is less than 60 ° C., the effect of instantly drying the solvent is low. Further, when the electrode substrate surface exceeds 120 ° C., drying unevenness may occur. This effect can be further conspicuous by managing and controlling the atmospheric gas during ultrasonic spraying.

  Next, the spray speed in the ultrasonic spray may be such that the catalyst ink passes at a rate of about 0.01 ml / min to 10 ml / min. In the case of this level of spraying speed, natural falling spraying is highly possible. The nozzle diameter of the ultrasonic spray can be selected according to the spraying pressure and the spraying speed, and is generally about several mm.

  Moreover, when spraying by such an ultrasonic spray, you may send the gas which conveys this microparticles | fine-particles in the range of the low pressure which does not interfere with the natural fall spray of the sprayed microparticles | fine-particles. The pressure of the carrier gas is preferably about 0.005 to 0.02 MPa. Further, although the spray angle may be slightly affected by sending the carrier gas, there is no particular problem in forming the catalyst layer. The type of gas may be compressed air or nitrogen, and is not particularly limited as long as it is inexpensive and safe.

  What was obtained by forming the catalyst layer on the surface of the electrode substrate in this way can be used as an anode side catalyst electrode or a cathode side catalyst electrode of a polymer electrolyte fuel cell. That is, first, as shown in FIG. 1, the catalyst layers 22 and 42 are formed on the electrode base materials 21 and 41 to form an anode side catalyst electrode and a cathode side catalyst electrode, respectively. Next, the MEA can be manufactured by sandwiching the hydrogen ion conductive polymer electrolyte membrane 3 between the catalyst electrodes and joining them by hot pressing or the like.

  A fuel cell can be formed by sandwiching the MEA with two separators having a reaction gas flow path. Although a single fuel cell functions as a fuel cell, a large electromotive force can be obtained by stacking a large number of fuel cells.

  Hereinafter, the present invention will be further described by way of examples.

Example 1
2.0 g of a commercially available platinum-supported carbon catalyst having a platinum loading of 30% by mass and 5.0 g of a commercially available hydrogen ion conductive polymer electrolyte 20% by mass solution (Nafion solution), 20.0 g of water and 23.0 g of isopropanol. The catalyst ink 1 was prepared by stirring for 30 minutes using an ultrasonic homogenizer in a mixed solvent (platinum catalyst particle solid content ratio 20 mass%, hydrogen ion conductive polymer electrolyte solid content ratio 33 mass%).

  1.5 g of a commercially available platinum supported carbon catalyst having a platinum loading of 30% by mass and 7.5 g of a commercially available hydrogen ion conductive polymer electrolyte 20% by mass (Nafion solution), 20.0 g of water and 23.0 g of isopropanol. The catalyst ink 2 was prepared by stirring for 30 minutes using an ultrasonic homogenizer in a mixed solvent (platinum catalyst particle solid content ratio 15 mass%, hydrogen ion conductive polymer electrolyte solid content ratio 50 mass%).

  1.0 g of a commercially available platinum-supported carbon catalyst with a platinum loading of 30% by mass and 10.0 g of a commercially available hydrogen ion conductive polymer electrolyte 20% by mass solution (Nafion solution), 20.0 g of water and 23.0 g of isopropanol The catalyst ink 3 was prepared by stirring for 30 minutes using an ultrasonic homogenizer in a mixed solvent (platinum catalyst particle solid content ratio 10 mass%, hydrogen ion conductive polymer electrolyte solid content ratio 67 mass%).

The prepared catalyst ink 1 is put into a syringe, and the target layer is formed by an ultrasonic spray having an inner diameter of the nozzle of about 2 mm and a vibration frequency of 100 kHz at a spray pressure of 0.01 MPa and a liquid feeding speed of 0.15 ml / min. Ultrasonic spraying was performed on attached carbon paper (manufactured by E-Tek). Then, the catalyst ink 2 was sprayed ultrasonically at a spraying pressure of 0.01 MPa and a liquid feed speed of 0.15 ml / min. Further thereon, the catalyst ink 3 was ultrasonically sprayed by an ultrasonic spray having an inner diameter of the nozzle of about 2 mm at a spraying pressure of 0.01 MPa and a liquid feeding speed of 0.15 ml / min. Platinum content in the catalyst layer was produced on the anode side 0.10 mg / cm ^2, the cathode side so that the 0.15 mg / cm ^2. At that time, the anode-side catalyst layer and the cathode-side catalyst layer both had a porosity of 55%.

The obtained catalyst electrode was cut into a predetermined area and joined to a hydrogen ion conductive polymer electrolyte membrane (Nafion membrane manufactured by DuPont) to prepare an MEA. The joining was performed using a hot press under conditions of 150 ° C., 50 kg / cm ² and 5 minutes. Next, the MEA was sandwiched between two separators having a reaction gas flow path to manufacture a fuel cell as shown in FIG.

(Example 2)
The catalyst ink 1 is carbon paper (E-) with an eye layer at an atomizing pressure of 0.01 MPa and a liquid feed rate of 0.15 ml / min by ultrasonic spraying with an inner diameter of the nozzle of about 2 mm and a vibration frequency of 100 kHz. Ultrasonic spraying was performed on Tek). Then, the catalyst ink 3 is ultrasonically sprayed at an atomizing pressure of 0.01 MPa and a liquid feeding speed of 0.15 ml / min by ultrasonic spraying with an inner diameter of the nozzle of about 2 mm and a vibration frequency of 100 kHz. It was. Platinum content in the catalyst layer was produced on the anode side 0.10 mg / cm ^2, the cathode side so that the 0.15 mg / cm ^2. At that time, both the anode-side catalyst layer and the cathode-side catalyst layer had a porosity of 50%.

The obtained catalyst electrode was cut into a predetermined area and joined to a hydrogen ion conductive polymer electrolyte membrane (Nafion membrane manufactured by DuPont) to prepare an MEA. The joining was performed using a hot press under conditions of 150 ° C., 50 kg / cm ² and 5 minutes. Next, the MEA was sandwiched between two separators having a reaction gas flow path to manufacture a fuel cell as shown in FIG.

(Example 3)
The catalyst ink 2 is carbon paper (E-) with an eye layer at an atomizing pressure of 0.01 MPa and a liquid feed rate of 0.15 ml / min by ultrasonic spraying with an inner diameter of the nozzle of about 2 mm and a vibration frequency of 100 kHz. Ultrasonic spraying was performed on Tek). Platinum content in the catalyst layer was produced on the anode side 0.10 mg / cm ^2, the cathode side so that the 0.15 mg / cm ^2. At that time, both the anode-side catalyst layer and the cathode-side catalyst layer had a porosity of 45%.

(Comparative Example 1)
Example 1 is the same as Example 1 except that the ultrasonic spray used in Example 1 is changed to air spray.

The obtained catalyst electrode was cut into a predetermined area and joined to a hydrogen ion conductive polymer electrolyte membrane (Nafion membrane manufactured by DuPont) to prepare an MEA. The joining was performed using a hot press under conditions of 150 ° C., 50 kg / cm ² and 5 minutes. Next, the MEA was sandwiched between two separators having a reaction gas flow path to manufacture a fuel cell as shown in FIG.

(Measurement of fuel cell performance)
The battery performance was measured by supplying hydrogen gas humidified and heated at 80 ° C. so that the hydrogen flow rate was 400 ml / min and the oxygen flow rate was 200 ml / min, and oxygen gas that was not humidified. The results are shown in Table 1. It was found that the battery performance was improved when the catalyst electrodes of Example 1 and Example 2 were used as compared with the case of using the catalyst electrode of Comparative Example 1.

(Electrochemical measurement of platinum surface area)
According to a well-known electrochemical measurement method, the amount of hydrogen desorption electricity of the catalyst electrode is measured, and this value is divided by the electrode area to obtain the amount of hydrogen desorption electricity per electrode unit area, and then divided by 210 μC / cm ² . Further, the active surface area per unit weight of platinum was measured by dividing this value by the amount of platinum supported per unit area of electrode. Measurement was performed by supplying hydrogen gas to the anode electrode side and nitrogen gas to the cathode electrode side in a humidified condition of 40 ° C.

As a result of the measurement, the electrochemically active surface area on the cathode electrode side in Example 1 was 910 cm ² / mg. The electrochemically active surface area on the cathode side in Example 2 was 840 cm ² / mg. The electrochemically active surface area of the cathode side in Example 3 was 770 cm ² / mg. On the other hand, the electrochemically active surface area of the cathode side of (Comparative Example 1) was 480 cm ² / mg. Assuming that the size of the platinum catalyst is about 2 nm, the surface area when all of the platinum catalyst is effectively used is about 1400 cm ² / mg. Using this value, the effective utilization rate of the platinum catalyst was found to be 65% in Example 1, 60% in Example 2, 55% in Example 3, and 34% in Comparative Example 1.

  From the above measurement results, it was confirmed that the catalyst electrodes of Examples 1 to 3 had a higher platinum effective utilization rate and superior battery performance as compared with the catalyst electrode of Comparative Example 1.

  The catalyst electrode for a fuel cell of the present invention has a high effective utilization rate of a platinum catalyst even when the amount of platinum is low, has excellent power generation performance, can be manufactured at low cost, and has a solid polymer fuel having excellent power generation performance Since the battery can be manufactured, application in the field of polymer electrolyte fuel cells can be expected.

It is explanatory drawing of the manufacturing process of a membrane electrode assembly. It is a disassembled perspective view of a fuel cell.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Anode side separator, 2 ... Anode side catalyst electrode, 21 ... Anode side electrode base material, 22 ... Anode side catalyst layer, 3 ... Hydrogen ion conductive polymer electrolyte membrane, 4 ... Cathode side Catalyst electrode 41... Cathode side electrode base material 42... Cathode side catalyst layer 5.

Claims (9)

  By spraying a suspension containing platinum catalyst particles and a hydrogen ion conductive polymer electrolyte as a solid content on the electrode substrate surface of a fuel cell while resonating a spray nozzle using ultrasonic vibration, the electrode A catalyst electrode for a fuel cell, which is produced by adhering the suspension to the surface of a substrate to form a catalyst layer.   2. The catalyst electrode for a fuel cell according to claim 1, wherein the catalyst electrode has an inclined structure in which the content of the platinum catalyst particles and the hydrogen ion conductive polymer electrolyte in the catalyst electrode changes in the thickness direction of the catalyst electrode. .   The catalyst electrode is provided between the hydrogen ion conductive polymer electrolyte membrane and the gas diffusion electrode, and the inclined structure contains the platinum catalyst particles from the hydrogen ion conductive polymer electrolyte membrane toward the gas diffusion electrode. The catalyst electrode for a fuel cell according to claim 2, wherein the catalyst electrode for a fuel cell has an inclined structure in which the amount increases and the content of the hydrogen ion conductive polymer electrolyte decreases.   In the suspension, the platinum catalyst particle content is 10% by mass to 40% by mass, and the hydrogen ion conductive polymer electrolyte content is 20% by mass to 80% by mass. The fuel cell catalyst electrode according to any one of claims 1 to 3.   5. The fuel cell catalyst electrode according to claim 1, wherein a resonance frequency of the ultrasonic vibration is 10 kHz to 500 kHz.   The catalyst electrode for a fuel cell according to any one of claims 1 to 5, wherein the porosity of the catalyst layer in the catalyst electrode is 30 to 90%.   7. A fuel comprising two fuel cell catalyst electrodes according to claim 1 and a hydrogen ion conductive polymer electrolyte membrane sandwiched between the two catalyst electrodes. Battery polymer electrolyte membrane / electrode assembly.   A fuel cell comprising the polymer electrolyte membrane / electrode assembly according to claim 7 sandwiched between two separators each having a reaction gas flow path. A suspension containing platinum catalyst particles and a hydrogen ion conductive polymer electrolyte as a solid content is sprayed on the surface of the electrode substrate of the fuel cell while resonating a spray nozzle using ultrasonic vibration, and the electrode substrate A method for producing a catalyst electrode for a fuel cell, comprising the step of depositing the suspension on a surface to form a catalyst layer.

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