JP4506165B2 - Membrane electrode assembly and method of using the same - Google Patents

Description

The present invention is a membrane electrode assembly: methods of using (MEA Membrane Electrode Assembly)及 benefactor.

  Conventionally, a fuel cell system using a membrane electrode assembly 90 as shown in FIG. 12 is known. The membrane electrode assembly 90 includes an electrolyte layer 91 made of an ion exchange membrane, an air electrode 93 formed integrally on one surface of the electrolyte layer 91, and a hydrogen electrode 92 formed integrally on the other surface of the electrolyte layer 91. And have.

  The air electrode 93 is joined to the air electrode reaction layer 93a joined to one surface of the electrolyte layer 91, the air diffusion layer 93b joined to the non-electrolyte layer side of the air electrode reaction layer 93a, and diffuses air into the air electrode reaction layer 93a. Consists of.

  Further, the hydrogen electrode 92 is bonded to the hydrogen electrode reaction layer 92a bonded to the other surface of the electrolyte layer 91 and the non-electrolyte layer side of the hydrogen electrode reaction layer 92a, and hydrogen diffusion for diffusing hydrogen into the hydrogen electrode reaction layer 92a. Layer 92b.

The membrane electrode assembly 90 is sandwiched between separators to form a cell as a minimum power generation unit, and a large number of cells are stacked to form a fuel cell stack. Hydrogen is supplied to the hydrogen electrode reaction layer 92a by a hydrogen supply means, and air is supplied to the air electrode reaction layer 93a by an air supply means. Thus, the fuel cell system is configured.

  In this membrane electrode assembly 90, hydrogen ions and electrons are generated from hydrogen of the fuel by an electrochemical reaction in the hydrogen electrode reaction layer 92a. The hydrogen ions move with water in the electrolyte layer 91 toward the air electrode reaction layer 93a. Further, the electrons flow through the load connected to the fuel cell system and flow into the air electrode reaction layer 93a. On the other hand, in the air electrode reaction layer 93a, water is generated from oxygen, hydrogen ions, and electrons contained in the air. By such a reaction occurring continuously, the fuel cell system can continuously generate an electromotive force.

  However, in the conventional membrane electrode assembly 90, when the fuel cell system is started below the freezing point, the water remaining inside and the generated water accompanying power generation are frozen, and the gas passage is blocked, and the output There is a problem that the voltage drops and cannot start. The relationship between the time in this case and the output voltage and temperature of the fuel cell system is shown in FIG. In FIG. 13, G91 is a graph showing the relationship between time and the output voltage of the fuel cell system (voltage per cell), and G92 is a graph showing the relationship between time and the temperature of the fuel cell system. Further, t91 is the time when the start of the fuel cell system is started, and t92 is the time when the load is connected and power generation is started.

  When this fuel cell system is started at time t91, an output voltage (open circuit voltage) of about 1 V per cell is generated. When the load is connected and power generation is started at time t92, the reaction between the hydrogen ions and air is an exothermic reaction, so the temperature of the fuel cell system slightly increases.

  However, generated water is generated with power generation, and the generated water is frozen below freezing point. For this reason, the supply path of hydrogen and air in the membrane electrode assembly 90 is blocked, which inhibits the reaction between new hydrogen ions and oxygen, and the output voltage is suddenly lowered to generate power. It becomes impossible. Further, since the reaction between hydrogen ions and oxygen, which is an exothermic reaction, is not maintained, the temperature of the fuel cell system hardly increases. For this reason, in this fuel cell system, the continuous reaction is interrupted and cannot be activated.

  On the other hand, the fuel cell system provided with the heating apparatus of patent document 1 is proposed. In this fuel cell system, when starting below freezing, the membrane electrode assembly 90 is first heated by a heating device and then started. Therefore, in this fuel cell system, the water remaining in the membrane electrode assembly 90 and the generated water accompanying power generation are not frozen, and a desired output can be obtained.

JP-A-7-94202

  However, in the fuel cell system of Patent Document 1 described above, when starting below freezing, as long as a normal membrane electrode assembly is used, the water remaining inside the membrane electrode assembly and the generated water accompanying power generation are prevented from freezing. It requires a lot of energy to do. In addition, as long as such a membrane electrode assembly is used, it takes time to warm up and the startup time becomes long.

The present invention, said was made in view of the conventional circumstances, resolution to provide the use of a membrane electrode assembly及 patron that can be under low-temperature environment to activate the fuel cell system easily It is an issue that should be done.

The membrane electrode assembly of the present invention is bonded to the electrolyte layer, the air electrode reaction layer bonded to one surface of the electrolyte layer, the non-electrolyte layer side of the air electrode reaction layer, and air is supplied to the air electrode reaction layer. An air diffusion layer that diffuses, a hydrogen electrode reaction layer bonded to the other surface of the electrolyte layer, and a hydrogen diffusion layer bonded to the non-electrolyte layer side of the hydrogen electrode reaction layer and diffusing hydrogen into the hydrogen electrode reaction layer In a membrane electrode assembly having
The air electrode reaction layer, pore material having a pore, electrically conductive particles, coated on the catalyst and the electrolyte solution base air electrode paste is having conductivity composed of, it is dried,
The hydrogen electrode reaction layer is formed by applying a hydrogen electrode paste comprising the conductive particles, the catalyst, and the electrolyte solution to the base material, and drying the substrate.
The air electrode reaction layer has a pore volume larger than that of the hydrogen electrode reaction layer due to the pore material.

The membrane electrode assembly of the present invention, an air electrode reaction layer, the air electrode paste is applied to a substrate having conductivity, including a pore material having a pore. The air electrode reaction layer has a pore volume larger than that of the hydrogen electrode reaction layer due to the pore material. Thus, in the fuel cell system using this membrane electrode assembly, water in the gas passage of the air electrode reaction layer is dispersed in the pores, thereby freezing the gas passage of the air electrode reaction layer during low temperature operation. Can be prevented. For this reason, in the fuel cell system using this membrane electrode assembly, even during low temperature operation, the gas passage can be prevented from being blocked for a long time, and power generation can be continued for a long time. . Further, even when warming up the fuel cell system, the warm-up time is shortened, and the time until startup is shortened.

Therefore, according to the membrane electrode assembly of the present invention, the fuel cell system can be easily started even in a low temperature environment.

The membrane electrode assembly of the present invention is bonded to the electrolyte layer, the air electrode reaction layer bonded to one surface of the electrolyte layer, the non-electrolyte layer side of the air electrode reaction layer, and air is supplied to the air electrode reaction layer. An air diffusion layer that diffuses, a hydrogen electrode reaction layer bonded to the other surface of the electrolyte layer, and a hydrogen diffusion layer bonded to the non-electrolyte layer side of the hydrogen electrode reaction layer and diffusing hydrogen into the hydrogen electrode reaction layer In a membrane electrode assembly having
The air electrode reaction layer is applied to a conductive substrate with an air electrode paste composed of conductive particles, a catalyst and an electrolyte solution, and a water dispersion layer paste composed of a pore material having a pore and a binder, Become dried,
The hydrogen electrode reaction layer is formed by applying a hydrogen electrode paste comprising the conductive particles, the catalyst, and the electrolyte solution to the base material, and drying the substrate.
The air electrode reaction layer is characterized by integrally having a water dispersion layer made of the water dispersion layer paste . The air electrode reaction layer may have a plurality of water dispersion layers. Thereby, water in the gas passage of the air electrode reaction layer can be further dispersed in the pores, and freezing in the gas passage of the air electrode reaction layer during low temperature operation can be further prevented. For this reason, the effect of this invention can be exhibited more reliably.

The water dispersion layer may be provided between a portion of the air electrode reaction layer other than the water dispersion layer and the electrolyte layer or the air diffusion layer. As a result, the water in the gas passage in the portion other than the water dispersion layer in the air electrode reaction layer can be further dispersed in the pores, and the gas passage in the portion other than the water dispersion layer in the air electrode reaction layer during low temperature operation Freezing inside can be further prevented. For this reason, the effect of this invention can be exhibited more reliably.

In the membrane electrode assembly of the present invention, the water dispersion layer preferably contains a water repellent material and a hydrophilic material. Since water is repelled in the water repellent material portion, the pores are hardly filled with water. In the hydrophilic material portion, water repelled by the water repellent material is absorbed. As a result, a gas passage is ensured and air is smoothly supplied to the air electrode reaction layer.

Aqueous dispersion layer, as water repellent, water repellent-treated carbon black, activated carbon, and at least one carbon aerogels and carbon nanotube, as a hydrophilic material may be composed of a least one carbon black electrolytes and hydrophilic treatment . If it is these, while being able to ensure a pore volume, electrical conductivity can be hold | maintained.

The membrane electrode assembly of the present invention is obtained by the following production method. This manufacturing method includes an electrolyte layer, an air electrode reaction layer bonded to one surface of the electrolyte layer, and an air diffusion that is bonded to the non-electrolyte layer side of the air electrode reaction layer and diffuses air into the air electrode reaction layer. film having a layer, and the hydrogen electrode reaction layer bonded to the other surface of the electrolyte layer is bonded to a non-electrolyte layer side of the water Motokyoku reaction layer, the hydrogen diffusion layer for diffusing hydrogen into aqueous Motokyoku reaction layer In the method for producing an electrode assembly,
The pore material and conductive particles and a catalyst having a pore by mixing the electrolyte solution to produce an air electrode paste, after coating the air electrode paste for the electrically conductive certain substrate, the dried A first step of forming an air electrode reaction layer;
A conductive electrode, a catalyst, and an electrolyte solution are mixed to prepare a hydrogen electrode paste. The hydrogen electrode paste is applied to a conductive substrate and then dried to form the hydrogen electrode reaction layer. Two steps,
A third step of obtaining the membrane electrode assembly by bonding the electrolyte layer between the air electrode reaction layer and the hydrogen electrode reaction layer and bonding them together.

In this manufacturing method, in the first step, an air electrode paste in which a pore material, conductive particles, a catalyst, and an electrolyte solution are mixed is applied to a substrate, and then dried to form an air electrode reaction layer. The base material has conductivity and gas permeability such as carbon cloth, carbon paper, carbon felt and the like. This substrate is preferably water-repellent. In order to have water repellency, a water repellent material can be applied to a substrate such as carbon cloth.

In the second step, a hydrogen electrode paste in which conductive particles, a catalyst, and an electrolyte solution are mixed is applied to a substrate, and then dried to form a hydrogen electrode reaction layer. In the third step, an electrolyte layer is sandwiched between the air electrode reaction layer and the hydrogen electrode reaction layer, and these are joined to obtain a membrane electrode assembly. Therefore, expensive equipment and strict management are not required.

  Moreover, in this manufacturing method, since the air electrode reaction layer containing the pore material is formed in the first step, the membrane electrode assembly obtained has a large pore volume of the air electrode reaction layer. Thereby, in the fuel cell system using this membrane electrode assembly, freezing in the gas passage of the air electrode reaction layer during low temperature operation can be prevented by dispersing generated water accompanying power generation in the pores. .

  Japanese Patent Laid-Open No. 2001-338654 discloses a fuel cell system in which an air electrode reaction layer is divided into two layers. However, this publication does not disclose any method for manufacturing a membrane electrode assembly.

The membrane electrode assembly of the present invention can also be obtained by the following production method. The manufacturing method includes an electrolyte layer, an air electrode reaction layer bonded to one surface of the electrolyte layer, and an air diffusion layer bonded to the non-electrolyte side of the air electrode reaction layer and diffusing air into the air electrode reaction layer. A hydrogen electrode reaction layer bonded to the other surface of the electrolyte layer, and a hydrogen diffusion layer bonded to the non-electrolyte side of the hydrogen electrode reaction layer and diffusing hydrogen into the hydrogen electrode reaction layer In the manufacturing method of the body,
By mixing the pore material and a binder with a pore to form a water-dispersible layer paste, after coating the aqueous dispersion layer paste on one electrically conductive certain substrate, the aqueous dispersion layers dried A first step of forming;
An electroconductive particle, a catalyst, and an electrolyte solution are mixed to prepare an air electrode paste, and the air electrode paste is applied to the aqueous dispersion layer side of the substrate obtained in the first step, and then dried. A second step of forming the air electrode reaction layer,
Conductive particles, a catalyst, and an electrolyte solution are mixed to prepare a hydrogen electrode paste. The hydrogen electrode paste is applied to the aqueous dispersion layer side of the substrate obtained in the first step, and then dried. A third step of forming the hydrogen electrode reaction layer,
A fourth step of obtaining the membrane electrode assembly by bonding the electrolyte layer between the air electrode reaction layer and the hydrogen electrode reaction layer and bonding them together.

In this manufacturing method, in a first step, after the pore material, a binder and a mixed aqueous dispersion layer paste was coated fabric on one surface of the electrically conductive certain substrates, aqueous dispersion on one side of the diffusion layer was dried Form a layer. The substrate is the same.

In the second step, an air electrode paste in which conductive particles, a catalyst, and an electrolyte solution are mixed is applied to the aqueous dispersion layer side of the base material obtained in the first step, and then dried to obtain an air electrode reaction layer. Form. Further, in the third step, after applying the conductive particles and catalyst and the electrolyte solution and the mixture was hydrogenated electrode paste to the substrate, to form formed the hydrogen electrode reaction layer and dried. In the fourth step, an electrolyte layer is sandwiched between the air electrode reaction layer and the hydrogen electrode reaction layer, and these are joined to obtain a membrane electrode assembly. Therefore, expensive equipment and strict management are not required.

  In this manufacturing method, the water dispersion layer is formed in the first step, and the water dispersion layer is formed on the air electrode reaction layer side in the fourth step. The pore volume on the reaction layer side increases. Thereby, in the fuel cell system using this membrane electrode assembly, freezing in the gas passage of the air electrode reaction layer during low temperature operation can be prevented by dispersing generated water accompanying power generation in the pores. .

  JP 2003-92112 A discloses a fuel cell system in which a water evaporation control porous layer is formed between an oxidant catalyst layer (air electrode reaction layer) and an oxidant gas diffusion layer (air diffusion layer). Is disclosed. However, this publication does not disclose any method for manufacturing a membrane electrode assembly.

In the above manufacturing method, in the fourth step, with sandwiching the electrolyte layer between the air electrode reaction layer and the hydrogen electrode reaction layer, water dispersed between the portion and the air diffusion layer other than the water-dispersible layer of the air electrode reaction layer These can be bonded with a layer interposed therebetween to obtain a membrane electrode assembly.

In the above manufacturing method, in the fourth step, water during with sandwiching the electrolyte layer between the air electrode reaction layer and the hydrogen electrode reaction layer, a portion other than the water-dispersible layer of the air electrode reaction layer and the electrolyte layer These can be bonded with a dispersion layer interposed therebetween to obtain a membrane electrode assembly.

Further, in the manufacturing method of the membrane electrode assembly, in the fourth step, it is also preferred that the air electrode reaction layer and plural layers of aqueous dispersion layer. Thereby, the membrane electrode assembly can further disperse the water in the gas passage of the air electrode reaction layer into the pores, and further prevent freezing in the gas passage of the air electrode reaction layer during low temperature operation. Can do. For this reason, the effect of this invention can be exhibited more reliably.

In the above manufacturing method, Hosoanazai preferably contains a parent aqueous. The parent Mizuzai portion, the water repelled by the water repellent material is absorbed. As a result, a gas passage is ensured and air is smoothly supplied to the air electrode reaction layer.

  The pore material may be composed of at least one of water-repellent treated carbon black, activated carbon, carbon aerogel, carbon nanotube, electrolyte, and hydrophilic treated carbon black. If it is these, while being able to ensure a pore volume, electrical conductivity can be hold | maintained.

The method of using the membrane electrode assembly of the present invention includes an electrolyte layer, an air electrode reaction layer bonded to one surface of the electrolyte layer, and a non-electrolyte layer side of the air electrode reaction layer. An air diffusion layer for diffusing air, a hydrogen electrode reaction layer bonded to the other surface of the electrolyte layer, and a non-electrolyte layer side of the hydrogen electrode reaction layer to diffuse hydrogen into the hydrogen electrode reaction layer In the method of using a membrane electrode assembly having a hydrogen diffusion layer,
The air electrode reaction layer contains a pore material having pores,
Dispersing water in the gas passage of the air electrode reaction layer into the pores of the pore material of the air electrode reaction layer to prevent freezing in the gas passage of the air electrode reaction layer during low temperature operation It is characterized by.

In the method of use of the present invention, even during low temperature operation, the gas passage can be prevented from being blocked for a long time, and power generation can be continued for a long time. Further, even when warming up the fuel cell system, the warm-up time is shortened, and the time until startup is shortened. Further, since the generated water accompanying power generation is generated on the air electrode reaction layer side, increasing the pore volume of the air electrode reaction layer is effective in dispersing the generated water.

Therefore, according to the method of using the membrane electrode assembly of the present invention, the fuel cell system can be easily started even in a low temperature environment.

The air electrode reaction layer preferably contains 0.71 μl / cm ² or more of pores having a pore diameter of 1 nm to 1 μm . Thus, in the fuel cell system using this membrane electrode assembly, water in the gas passage of the air electrode reaction layer is dispersed in the pores, thereby freezing the gas passage of the air electrode reaction layer during low temperature operation. Can be prevented. For this reason, in the fuel cell system using this membrane electrode assembly, even during low temperature operation, the gas passage can be prevented from being blocked for a long time, and power generation can be continued for a long time. . Further, even when warming up the fuel cell system, the warm-up time is shortened, and the time until startup is shortened.

Examples 1-3 the use of a membrane electrode assembly及 originator of the present invention embodying be described with reference to the drawings.
Example 1

  As shown in FIG. 1, a membrane electrode assembly 10 of Example 1 includes an electrolyte layer 1 made of an ion exchange membrane, an air electrode 3 integrally formed on one surface of the electrolyte layer 1, and other electrolyte layers 1. And a hydrogen electrode 2 integrally formed on the surface.

  The air electrode 3 is provided on the electrolyte layer 1 side, and is integrally formed on the surface side of the air electrode reaction layer 3a having water absorption and the air electrode reaction layer 3a opposite to the electrolyte layer 1, and can diffuse air. It consists of the air diffusion layer 3b.

  The hydrogen electrode 2 is integrally formed on the surface side of the hydrogen electrode reaction layer 2a provided on the electrolyte layer 1 side and the hydrogen electrode reaction layer 2a on the opposite side of the electrolyte layer 1, and is a hydrogen diffusion layer capable of diffusing hydrogen. 2b.

  Next, the manufacturing method of the membrane electrode assembly 10 having the above configuration will be described. First, a diffusion layer paste made of a mixture of carbon black as conductive particles and PTFE particles as water repellent particles is prepared.

  And the carbon cloth as a base material is prepared, and after apply | coating the paste for diffusion layers on both surfaces of a base material, it is made to dry. Thereby, the air diffusion layer 3b or the hydrogen diffusion layer 2b that repels water and easily passes through the gas is formed on both surfaces of the base material.

  In the first step, Pt as a catalyst is previously supported on carbon black to obtain a Pt-supported carbon catalyst (Pt support density 30 to 60%). Then, a Nafion (registered trademark) solution (5% by mass) as an electrolyte solution was added to the Pt supported carbon catalyst so that the mass ratio of the Pt supported carbon catalyst and Nafion (registered trademark) was about 0.1 to 0.5. Solution). Furthermore, carbon black (Vulcan XC72, manufactured by Cabot Corporation) as a pore material is added to this so as to be 10 to 70% by mass with respect to the whole. And this is mixed well and the paste for air electrodes is produced. The air electrode paste is applied to a substrate and then dried to form the air electrode reaction layer 3a.

  Next, in the second step, Pt as a catalyst is previously supported on carbon black to obtain a Pt-supported carbon catalyst (Pt support density 30 to 60%). Then, a Nafion (registered trademark) solution (5% by mass) as an electrolyte solution was added to the Pt supported carbon catalyst so that the mass ratio of the Pt supported carbon catalyst and Nafion (registered trademark) was about 0.1 to 0.5. Solution). And this is mixed well and the paste for hydrogen electrodes is produced. The hydrogen electrode paste is applied to a substrate and then dried to form the hydrogen electrode reaction layer 2a.

In the third step, an electrolyte layer (thickness: about 50 μm) 1 made of Nafion 112 (registered trademark) is interposed between the air electrode reaction layer 3a and the hydrogen electrode reaction layer 2a. And thermocompression bonding by hot pressing is performed under conditions of a temperature of 140 to 160 ° C. and a surface pressure of 70 to 100 kg / cm ² . Thus, the membrane electrode assembly 10 can be obtained without requiring an expensive apparatus or strict management.

  In the manufacturing method of Example 1, since the air electrode reaction layer 3a containing carbon black as the pore material is formed in the first step, the obtained membrane electrode assembly 10 is formed of the air electrode reaction layer 3a. The pore volume increases. Thereby, in the fuel cell system using this membrane electrode assembly 10, the generated water accompanying power generation is dispersed in the pores to prevent freezing in the gas passage of the air electrode reaction layer 3a during low temperature operation. Can do. For this reason, in the fuel cell system using the membrane electrode assembly 10, even during low temperature operation, the gas passage can be prevented from being blocked for a long time, and power generation can be continued for a long time. Become. Further, even when warming up the fuel cell system, the warm-up time is shortened, and the time until startup is shortened.

Therefore, according to the manufacturing method of the first embodiment, it is possible to manufacture the membrane electrode assembly 10 that can easily start the fuel cell system even in a low temperature environment. Moreover, according to the method of using the membrane electrode assembly 10 of Example 1, the fuel cell system can be easily started even in a low temperature environment.
(Test 1)

  A test for confirming the effect of Example 1 was conducted.

  First, in addition to the membrane electrode assembly 10 (1) and 10 (2) of Example 1, a conventional membrane electrode assembly 90 was prepared as a comparative example. The membrane electrode assembly 90 is manufactured by the same manufacturing method as in this example. However, in the manufacturing method of the membrane electrode assembly 90, no pore material is added to the air electrode paste.

The pore distribution with respect to the pore diameter of the air electrode reaction layers 3a and 93a of these membrane electrode assemblies 10 (1), 10 (2), and 90 was examined. The result is shown in the graph of FIG. In FIG. 2, D10 (1) is a graph of the membrane electrode assembly 10 (1), and D10 (2) is a graph of the membrane electrode assembly 10 (2). D90 is a graph of the membrane electrode assembly 90. However, the pore diameter range for examining the pore distribution was 1 nm to 1 μm. The pores having a pore diameter of 30 nm to 1 μm were measured by a mercury intrusion method using a pore sizer 9320 (manufactured by Micromeritics). In addition, pores having a pore diameter of 30 nm or less were measured by a nitrogen adsorption method using Omnisoap 360 (manufactured by Coulter). In the nitrogen adsorption method, a pore of the following ranges pore diameter 2nm from the adsorption isotherm by the MP method, a pore in the range of pore diameter 2Nm～30n m was determined by calculation from desorption isotherm by the BJH method .

  Table 1 shows the pore volumes of the air electrode reaction layers 3a and 93a of the membrane electrode assemblies 10 (1), 10 (2), and 90.

Next, these membrane electrode assemblies 10 (1), 10 (2), 90 were sandwiched between separators to form cells. Then, while cooling the cell at −10 ° C., power generation was performed at a current density of 0.1 A / cm ² , and the voltage at that time was measured. The result is shown in FIG. In FIG. 3, V10 (1) is a graph of the membrane electrode assembly 10 (1), and V10 (2) is a graph of the membrane electrode assembly 10 (2). V90 is a graph of the membrane electrode assembly 90. FIG. 4 shows the relationship between the pore volume of the air electrode reaction layer and the power generation time. In FIG. 4, T90 indicates the power generation time of the membrane electrode assembly 90, and T10 (2) indicates the power generation time of the membrane electrode assembly 10 (2). Further, T10 (1) indicates the power generation time of the membrane electrode assembly 10 (1). 3 and 4 show that the power generation time increases in proportion to the pore volume of the air electrode reaction layer. This is because the larger the pore volume of the air electrode reaction layer, the larger the amount of generated water that accompanies power generation can be dispersed in the pores, and the longer the time it takes for the air gas supply path to be blocked by freezing of the generated water. It is thought to be. When a pore material is added to the air electrode reaction layer 3a, the reaction layer pore volume includes 1 μl / cm ² of pores having a pore diameter of 1 nm to 1 μm.
(Example 2)

  As shown in FIG. 5, the membrane / electrode assembly 20 of Example 2 includes an electrolyte layer 1 made of an ion exchange membrane, an air electrode 13 integrally formed on one surface of the electrolyte layer 1, and other electrolyte layers 1. And a hydrogen electrode 2 integrally formed on the surface.

The air electrode 13 is formed integrally with the air electrode reaction layer 13a ( including the water dispersion layer 13c provided integrally on the side opposite to the electrolyte layer 1 ) provided on the electrolyte layer 1 side and the surface side of the water dispersion layer 13c . And an air diffusion layer 13b capable of diffusing air.

  The hydrogen electrode 2 is integrally formed on the surface side of the hydrogen electrode reaction layer 2a provided on the electrolyte layer 1 side and the hydrogen electrode reaction layer 2a on the opposite side of the electrolyte layer 1, and is a hydrogen diffusion layer capable of diffusing hydrogen. 2b.

  Next, the manufacturing method of the membrane electrode assembly 20 having the above configuration will be described. First, a diffusion layer paste made of a mixture of carbon black as conductive particles and PTFE particles as water repellent particles is prepared.

  And the carbon cloth as a base material is prepared, and after apply | coating the paste for diffusion layers on both surfaces of a base material, it is made to dry. Thereby, the air diffusion layer 13b or the hydrogen diffusion layer 2b that repels water and easily passes gas is formed on both surfaces of the base material.

  In the first step, carbon black (Vulcan XC72, manufactured by Cabot Corporation) as a pore material is added to a Nafion (registered trademark) solution (5% by mass solution) as a hydrophilic material and binder, and carbon black and Nafion (registered trademark) are added. ) And the mass ratio of about 0.1 to 0.5. And this is mixed well and the paste for water dispersion layers is produced. The aqueous dispersion layer paste is applied to a substrate and then dried to form the aqueous dispersion layer 13c.

  Next, Pt as a catalyst is previously supported on carbon black to obtain a Pt-supported carbon catalyst (Pt support density 30 to 60%). Then, a Nafion (registered trademark) solution (5% by mass) as an electrolyte solution was added to the Pt supported carbon catalyst so that the mass ratio of the Pt supported carbon catalyst and Nafion (registered trademark) was about 0.1 to 0.5. Solution). And this is mixed well and the paste for air electrodes is produced. After apply | coating this paste for air electrodes to the water dispersion layer 13c side of the base material which consists of the air diffusion layer 12b and the water dispersion layer 13c obtained at the 1st process, it is made to dry and the air electrode reaction layer 13a is formed.

  Further, in the second step, Pt as a catalyst is previously supported on carbon black to obtain a Pt-supported carbon catalyst (Pt support density 30 to 60%). Then, a Nafion (registered trademark) solution (5% by mass) as an electrolyte solution was added to the Pt supported carbon catalyst so that the mass ratio of the Pt supported carbon catalyst and Nafion (registered trademark) was about 0.1 to 0.5. Solution). And this is mixed well and the paste for hydrogen electrodes is produced. The hydrogen electrode paste is applied to the water dispersion layer 23c side of the base material composed of the hydrogen diffusion layer 22b and the water dispersion layer 23c obtained in the first step, and then dried to form the hydrogen electrode reaction layer 2a.

Then, in the third step, the sandwich Nafion 112 electrolyte layer made of (R) (thickness of about 50 [mu] m) 1 between the air electrode reaction layer 13a and the hydrogen electrode reaction layer 2a, the air diffusion layer 13b It arrange | positions so that the water dispersion layer 13c of the air electrode reaction layer 13a may be pinched | interposed between them. And thermocompression bonding by hot pressing is performed under conditions of a temperature of 140 to 160 ° C. and a surface pressure of 70 to 100 kg / cm ² . In this way, the membrane electrode assembly 20 can be obtained without requiring expensive equipment or strict management.

In the manufacturing method of Example 2, the water dispersion layer 13c was formed in the first step, and the water dispersion layer 13c was formed on the air electrode reaction layer 13a side in the fourth step. No. 20 has a larger pore volume on the air electrode reaction layer 13a side. As a result, in the fuel cell system using the membrane electrode assembly 20, the generated water accompanying power generation is dispersed in the water dispersion layer 13c, thereby preventing freezing in the gas passage of the air electrode reaction layer 13a during low temperature operation. can do. For this reason, also in the fuel cell system using this membrane electrode assembly 20, the same operation effect as Example 1 can be produced.
(Test 2)

  A test for confirming the effect of Example 2 was performed.

  First, in addition to the membrane electrode assembly 20 (1), 20 (2), 20 (3) of Example 2, a conventional membrane electrode assembly 90 was prepared as a comparative example. The membrane electrode assembly 90 is manufactured by the same manufacturing method as in Example 1.

  The pore volume of the aqueous dispersion layer 13c of these membrane electrode assemblies 20 (1), 20 (2), 20 (3), 90 was measured in the same manner as in Example 1. The results are shown in Table 2.

Next, these membrane electrode assemblies 20 (1), 20 (2), 20 (3), and 90 were sandwiched between separators to form cells. Then, while cooling the cell at −10 ° C., power generation was performed at a current density of 0.1 A / cm ² , and the voltage at that time was measured. The result is shown in FIG. In FIG. 6, V20 (1) is a graph of the membrane electrode assembly 20 (1), and V20 (2) is a graph of the membrane electrode assembly 20 (2). Further, V20 (3) is a graph of the membrane electrode assembly 20 (3), and V90 is a graph of the membrane electrode assembly 90. FIG. 7 shows the relationship between the pore volume of the water dispersion layer 13c and the power generation time. In FIG. 7, T90 indicates the power generation time of the membrane electrode assembly 90, and T20 (3) indicates the power generation time of the membrane electrode assembly 20 (3). T20 (2) indicates the power generation time of the membrane electrode assembly 20 (2), and T20 (1) indicates the power generation time of the membrane electrode assembly 20 (1). According to FIGS. 6 and 7, in the range where the pore volume of the water dispersion layer 13c is about 0.45 μl / cm ² or less, the power generation time increases in proportion to the pore volume, and 0.45 μl / cm ^2. It can be seen that the power generation time is substantially constant in the range exceeding the degree. This is because, in the range where the pore volume of the water dispersion layer 13c is about 0.5 μl / cm ² or less, the larger the pore volume of the water dispersion layer 13c, the more the generated water accompanying power generation is dispersed in the pores. This is thought to be because the time until the supply path of the air gas is blocked due to the freezing of the generated water becomes longer.
(Example 3)

  As shown in FIG. 8, the membrane electrode assembly 30 of Example 3 includes an electrolyte layer 1 made of an ion exchange membrane, an air electrode 23 integrally formed on one surface of the electrolyte layer 1, and other electrolyte layers 1. And a hydrogen electrode 2 integrally formed on the surface.

Air electrode 23, an empty Kikyoku reaction layer 23a that will be formed integrally with the electrolyte layer 1 (. Containing an electrolyte layer 1 side of the water-dispersible layer 23d and the surface of the water-dispersible layer 23c), an air electrode reaction layer 23a The air diffusion layer 23b is integrally formed on the surface side and can diffuse air.

  The hydrogen electrode 2 is integrally formed on the surface side of the hydrogen electrode reaction layer 2a provided on the electrolyte layer 1 side and the hydrogen electrode reaction layer 2a on the opposite side of the electrolyte layer 1, and is a hydrogen diffusion layer capable of diffusing hydrogen. 2b.

  Next, the manufacturing method of the membrane electrode assembly 30 having the above configuration will be described. First, a diffusion layer paste made of a mixture of carbon black as conductive particles and PTFE particles as water repellent particles is prepared.

  And the carbon cloth as a base material is prepared, and after apply | coating the paste for diffusion layers on both surfaces of a base material, it is made to dry. Thereby, the air diffusion layer 23b or the hydrogen diffusion layer 2b that repels water and easily passes gas is formed on both surfaces of the base material.

  In the first step, carbon black (Vulcan XC72, manufactured by Cabot Corporation) as a pore material is added to a Nafion (registered trademark) solution (5% by mass solution) as a hydrophilic material and binder, and carbon black and Nafion (registered trademark) are added. ) And the mass ratio of about 0.1 to 0.5. And this is mixed well and the paste for water dispersion layers is produced. The aqueous dispersion layer paste is applied to a substrate and then dried to form the aqueous dispersion layer 23c. Further, this water dispersion layer paste is applied to a carbon cloth as a base material and then dried to form a water dispersion layer 23d.

  Next, Pt as a catalyst is previously supported on carbon black to obtain a Pt-supported carbon catalyst (Pt support density 30 to 60%). Then, a Nafion (registered trademark) solution (5% by mass) as an electrolyte solution was added to the Pt supported carbon catalyst so that the mass ratio of the Pt supported carbon catalyst and Nafion (registered trademark) was about 0.1 to 0.5. Solution). And this is mixed well and the paste for air electrodes is produced. The air electrode paste is applied to a carbon cloth as a base material and then dried to form the air electrode reaction layer 23a.

  Further, in the second step, Pt as a catalyst is previously supported on carbon black to obtain a Pt-supported carbon catalyst (Pt support density 30 to 60%). Then, a Nafion (registered trademark) solution (5% by mass) as an electrolyte solution was added to the Pt supported carbon catalyst so that the mass ratio of the Pt supported carbon catalyst and Nafion (registered trademark) was about 0.1 to 0.5. Solution). And this is mixed well and the paste for hydrogen electrodes is produced. The hydrogen electrode paste is applied to a substrate and then dried to form the hydrogen electrode reaction layer 2a.

In the third step, an electrolyte layer (thickness: about 50 μm) 1 made of Nafion 112 (registered trademark) is sandwiched between the water dispersion layer 23d and the hydrogen electrode reaction layer 2a, and between the air diffusion layer 23b. The air electrode reaction layer 23a (including the water dispersion layer 23d and the water dispersion layer 23c ) is disposed so as to be sandwiched therebetween. And thermocompression bonding by hot pressing is performed under conditions of a temperature of 140 to 160 ° C. and a surface pressure of 70 to 100 kg / cm ² . Thus, the membrane electrode assembly 30 can be obtained without requiring an expensive apparatus or strict management.

In the manufacturing method of Example 3, water dispersible layer 23c in the first step, 23d is formed, in the fourth step, since the both surfaces of the air electrode reaction layer 23a are formed aqueous dispersion layer 23c, the 23d, obtained The obtained membrane electrode assembly 30 has a large pore volume on the air electrode reaction layer 23a side. As a result, in the fuel cell system using the membrane electrode assembly 30, the generated water accompanying power generation is dispersed in the water dispersion layers 23c and 23d, thereby freezing the gas passage in the air electrode reaction layer 23a during low temperature operation. Can be prevented. For this reason, also in the fuel cell system using this membrane electrode assembly 30, the same operation effect as Example 1 can be produced.
(Test 3)

  A test for confirming the effect of Example 3 was performed.

  First, in addition to the membrane electrode assembly 30 of Example 3, a conventional membrane electrode assembly 90 was prepared as a comparative example. The membrane electrode assembly 90 is manufactured by the same manufacturing method as in Example 1.

The pore volume of the water dispersion layers 23c and 23d in the air electrode reaction layers 23a and 93a of the membrane electrode assemblies 30 and 90 was measured in the same manner as in Example 1. The results are shown in Table 3.

Next, a cell was constructed by sandwiching these membrane electrode assemblies 30 and 90 with separators. Then, while cooling the cell at −10 ° C., power generation was performed at a current density of 0.1 A / cm ² , and the voltage at that time was measured. The result is shown in FIG. In FIG. 9, V30 is a graph of the membrane electrode assembly 30, and V90 is a graph of the membrane electrode assembly 90. According to FIG. 9, it can be seen that the membrane electrode assembly 30 having a larger total pore volume has a longer power generation time than the membrane electrode assembly 90. This is because the membrane electrode assembly 30 having a large total pore volume can disperse a large amount of generated water accompanying power generation in the pores, and the time until the air gas supply path is blocked by freezing of the generated water. It is thought to be longer.
(Modification 1)

  As a modification of the membrane electrode assembly of Example 3, a membrane electrode assembly 40 shown in FIG. 10 can be considered. The membrane electrode assembly 40 includes an electrolyte layer 1 made of an ion exchange membrane, an air electrode 33 integrally formed on the other surface of the electrolyte layer 1, and a hydrogen electrode 2 integrally formed on one surface of the electrolyte layer 1. And have.

The air electrode 33 is composed of, and diffusible air diffusion layers 33b of air (. An electrolyte layer 1 side of the water-dispersible layer 33c) Check Kikyoku reaction layer 33a that will be formed integrally with the electrolyte layer 1.

  The hydrogen electrode 2 is integrally formed on the surface side of the hydrogen electrode reaction layer 2a provided on the electrolyte layer 1 side and the hydrogen electrode reaction layer 2a on the opposite side of the electrolyte layer 1, and is a hydrogen diffusion layer capable of diffusing hydrogen. 2b.

The manufacturing method of this membrane electrode assembly 40 is substantially the same as that of Example 3. However, in the fourth step, an electrolyte layer (thickness: about 50 μm) 1 made of Nafion 112 (registered trademark) is sandwiched between the water dispersion layer 33c and the hydrogen electrode reaction layer 2a, and the water dispersion of the air electrode reaction layer 33a is performed. the layers 33c arranged so as to go seen sandwiched between the air diffusion layer 33b. And thermocompression bonding by hot pressing is performed under conditions of a temperature of 140 to 160 ° C. and a surface pressure of 70 to 100 kg / cm ² . Thus, the membrane electrode assembly 40 can be obtained without requiring an expensive apparatus or strict management. Other operations and effects are the same as those of the third embodiment.
(Modification 2)

  Further, as a modified example of the membrane electrode assembly of Example 3, a membrane electrode assembly 50 shown in FIG. 11 is also conceivable. The membrane electrode assembly 50 includes an electrolyte layer 1 made of an ion exchange membrane, an air electrode 43 formed integrally on one surface of the electrolyte layer 1, and a hydrogen electrode 2 formed integrally on the other surface of the electrolyte layer 1. And have.

The air electrode 43 includes a mixed layer 43a formed integrally with the electrolyte layer 1 and an air diffusion layer 43b formed integrally on the surface side of the mixed layer 43a and capable of diffusing air. Mixing layer 43a is for air electrode reaction layer has a plurality of water-dispersible layer.

  The hydrogen electrode 2 is integrally formed on the surface side of the hydrogen electrode reaction layer 2a provided on the electrolyte layer 1 side and the hydrogen electrode reaction layer 2a on the opposite side of the electrolyte layer 1, and is a hydrogen diffusion layer capable of diffusing hydrogen. 2b.

The manufacturing method of this membrane electrode assembly 50 is substantially the same as that of Example 3. However, in the fourth step, an electrolyte layer (thickness: about 50 μm) 1 made of Nafion 112 (registered trademark) is sandwiched between the mixed layer 43a and the hydrogen electrode reaction layer 2a, and the electrolyte layer 1 and the air diffusion layer 43b The mixed layer 43a is sandwiched between the layers. And thermocompression bonding by hot pressing is performed under conditions of a temperature of 140 to 160 ° C. and a surface pressure of 70 to 100 kg / cm ² . In this way, the membrane electrode assembly 50 can be obtained without requiring an expensive apparatus or strict management. Other operations and effects are the same as those of the third embodiment.

  The present invention can be used for a moving power source for an electric vehicle or the like, or a stationary power source.

1 is a schematic diagram of a membrane electrode assembly according to Example 1. FIG. 4 is a graph showing the pore distribution with respect to the pore diameter of the air electrode reaction layer according to Example 1. 6 is a graph illustrating a relationship between a power generation time and a cell voltage according to Example 1; 6 is a graph showing the relationship between the pore volume of the air electrode reaction layer and the power generation time according to Example 1. FIG. 6 is a schematic diagram of a membrane electrode assembly according to Example 2. It is a graph which concerns on Example 2 and shows the relationship between electric power generation time and a cell voltage. It is a graph which concerns on Example 2 and shows the relationship between the pore volume of a water dispersion layer, and electric power generation time. 6 is a schematic diagram of a membrane electrode assembly according to Example 3. FIG. It is a graph which concerns on Example 3 and shows the relationship between electric power generation time and a cell voltage. It is a schematic diagram of a membrane electrode assembly according to Modification 1. It is a schematic diagram of a membrane electrode assembly according to Modification 2. It is related and is a schematic diagram of a membrane electrode assembly. It is a graph which shows the relationship between the time and voltage of a membrane electrode assembly conventionally.

DESCRIPTION OF SYMBOLS 10, 20, 30, 40, 50 ... Membrane electrode assembly 1 ... Electrolyte layer 3a, 13a, 23a, 33a ... Air electrode reaction layer 3b, 13b, 23b, 33b, 43b ... Air diffusion layer 13c, 23c, 23d, 33c ... water diffusion layer 2a ... hydrogen electrode reaction layer 2b ... hydrogen diffusion layer

Claims (7)

An electrolyte layer, an air electrode reaction layer bonded to one surface of the electrolyte layer, an air diffusion layer bonded to the non-electrolyte layer side of the air electrode reaction layer and diffusing air into the air electrode reaction layer, and the electrolyte In a membrane electrode assembly having a hydrogen electrode reaction layer bonded to the other surface of the layer and a hydrogen diffusion layer bonded to the non-electrolyte layer side of the hydrogen electrode reaction layer and diffusing hydrogen into the hydrogen electrode reaction layer,
The air electrode reaction layer is formed by applying and drying a paste for an air electrode comprising a pore material having pores, conductive particles, a catalyst and an electrolyte solution on a conductive substrate,
The hydrogen electrode reaction layer is formed by applying a hydrogen electrode paste comprising the conductive particles, the catalyst, and the electrolyte solution to the base material, and drying the substrate.
The air electrode reaction layer has a pore volume larger than that of the hydrogen electrode reaction layer due to the pore material. The membrane electrode assembly according to claim 1, wherein the air electrode reaction layer contains 0.71 µl / cm ² or more of pores having a pore diameter of 1 nm to 1 µm. An electrolyte layer, an air electrode reaction layer bonded to one surface of the electrolyte layer, an air diffusion layer bonded to the non-electrolyte layer side of the air electrode reaction layer and diffusing air into the air electrode reaction layer, and the electrolyte In a membrane electrode assembly having a hydrogen electrode reaction layer bonded to the other surface of the layer and a hydrogen diffusion layer bonded to the non-electrolyte layer side of the hydrogen electrode reaction layer and diffusing hydrogen into the hydrogen electrode reaction layer,
The air electrode reaction layer is applied to a conductive substrate with an air electrode paste composed of conductive particles, a catalyst and an electrolyte solution, and a water dispersion layer paste composed of a pore material having a pore and a binder, Become dried,
The hydrogen electrode reaction layer is formed by applying a hydrogen electrode paste comprising the conductive particles, the catalyst, and the electrolyte solution to the base material, and drying the substrate.
The membrane electrode assembly, wherein the air electrode reaction layer integrally has a water dispersion layer made of the water dispersion layer paste. 4. The membrane / electrode assembly according to claim 3, wherein the aqueous dispersion layer contains pores having a pore diameter of 1 nm to 1 μm in an amount of 0.3 μl / cm ² or more.   The membrane electrode assembly according to claim 3 or 4, wherein the air electrode reaction layer has a plurality of the water dispersion layers.   6. The water dispersion layer is provided between a portion of the air electrode reaction layer other than the water dispersion layer and the electrolyte layer or the air diffusion layer. 2. The membrane electrode assembly according to item 1. An electrolyte layer, an air electrode reaction layer bonded to one surface of the electrolyte layer, an air diffusion layer bonded to the non-electrolyte layer side of the air electrode reaction layer and diffusing air into the air electrode reaction layer, and the electrolyte Use of a membrane electrode assembly having a hydrogen electrode reaction layer bonded to the other surface of the layer and a hydrogen diffusion layer bonded to the non-electrolyte layer side of the hydrogen electrode reaction layer and diffusing hydrogen into the hydrogen electrode reaction layer In the method
The air electrode reaction layer contains a pore material having pores,
Dispersing water in the gas passage of the air electrode reaction layer into the pores of the pore material of the air electrode reaction layer to prevent freezing in the gas passage of the air electrode reaction layer during low temperature operation A method of using a membrane electrode assembly characterized by

Images