JP5636631B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to a catalyst layer for a fuel cell.

A catalyst layer for promoting an electrochemical reaction is formed on both surfaces of the electrolyte membrane of the fuel cell. Here, a fuel cell is known in which the volume of pores having a diameter of 60 to 1000 nm in the catalyst is 0.15 to 0.25 cm ³ / g as the catalyst layer (for example, Patent Document 1).

JP 2003-151564 A

  However, when cathode gas with low humidity is supplied to the fuel cell and the cell temperature of the fuel cell is operated at about 100 ° C., which is the boiling point of water, the generated water generated at the cathode evaporates in large quantities from the catalyst layer. To do. Therefore, there is a problem that the fuel cell is easily dried up and it is difficult to continue the power generation of the fuel cell.

  An object of the present invention is to solve at least one of the above problems and to make it difficult to dry up the fuel cell even when the cell temperature during operation of the fuel cell is close to the boiling point of water.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
According to one embodiment of the present invention, a fuel cell that can be operated by supplying a non-humidified reaction gas under a condition of 100 ° C. is provided. The fuel cell includes an electrolyte membrane, and an anode catalyst layer and a cathode catalyst layer that are respectively disposed on the surface of the electrolyte membrane. The cathode catalyst layer has a gap, and the amount of the gap is 1.0 mL / m. More than ² and 5.6 mL / m ² or less, and the water permeability of the electrolyte membrane is larger than 0.10 mg / (min · cm ² · kPa). According to the fuel cell of this embodiment, it is possible to make it difficult to dry up the fuel cell even when the cell temperature during operation of the fuel cell is 100 ° C. (boiling point of water).

[Application Example 1]
4. A fuel cell, comprising an electrolyte membrane and a catalyst layer disposed on the surface of the electrolyte membrane, wherein the catalyst layer has voids, and the amount of voids is more than 1.0 mL / m ² . A fuel cell having a water permeability of not more than 6 mL / m ² and greater than 0.1 mg / (min · cm ² · kPa) of the electrolyte membrane.
According to this application example, it is possible to make it difficult to dry up the fuel cell even when the cell temperature during operation of the fuel cell is close to the boiling point of water.

[Application Example 2]
The fuel cell according to Application Example 1, wherein the fuel cell is operated near the boiling point of water.

[Application Example 3]
The fuel cell according to application example 1 or 2, the amount of the gap is 1.7 mL / m ² or more 5.6 mL / m ² or less, the fuel cell.
According to the conditions of this application example, it is possible to make dry-up less likely.

[Application Example 4]
The fuel cell according to any one of Application Examples 1 to 3, wherein the water permeability of the electrolyte membrane is 0.15 mg / (min · cm ² · kPa) or more.
According to the conditions of this application example, it is possible to make dry-up less likely.

[Application Example 5]
The fuel cell according to any one of claims 1 to 4, wherein the amount of the gap is adjusted to the value by filling the gap with a fiber.

  The present invention can be realized in various forms. For example, in addition to a fuel cell, the present invention can be realized in various forms such as a fuel cell system, a fuel cell catalyst layer, and a manufacturing method thereof.

It is explanatory drawing which shows typically the cross section of the fuel cell used for the Example of this invention. It is explanatory drawing which shows typically the structure of the catalyst layer vicinity. It is explanatory drawing which shows the effect of a present Example typically. An example of a method for reducing the size of the gap is shown. It is a table | surface which shows the characteristic of the samples 1-17, and the performance of each sample. It is explanatory drawing which shows an electrolyte membrane measuring apparatus typically. It is explanatory drawing which shows a power generation continuation evaluation apparatus typically. It is explanatory drawing which shows the quantity of the space | gap calculated | required using the mercury intrusion method. It is explanatory drawing which shows distribution of the diameter of the colloid particle contained in the ink for cathode catalyst layers. It is explanatory drawing explaining the amount of space | gap per unit area of a catalyst layer, the permeation | transmission performance of the water in an electrolyte membrane, and the presence or absence of power generation maintenance.

    FIG. 1 is an explanatory view schematically showing a cross section of a fuel cell used in an embodiment of the present invention. The fuel cell 10 includes an electrolyte membrane 20, a catalyst layer 30, a gas diffusion layer 35, a separator 40, and a gasket 45. The electrolyte membrane 20 is a membrane for moving protons generated on the anode side to the cathode side. The electrolyte membrane 20 is also used to move water between the cathode and the anode. As the electrolyte membrane 20, for example, a proton conductive ion exchange membrane made of a fluorine resin such as perfluorocarbon sulfonic acid polymer or a hydrocarbon resin can be used.

  The catalyst layer 30 is formed on the surface of the electrolyte membrane 20. As the catalyst of the catalyst layer 30, for example, a platinum catalyst or a platinum alloy catalyst made of platinum and another metal can be used. The catalyst is supported on, for example, carbon particles and applied to the surface of the electrolyte membrane 20 to form the catalyst layer 30.

  The gas diffusion layer 35 is disposed on both surfaces of the electrolyte membrane 20. As the gas diffusion layer 35, carbon cloth or carbon paper using a carbon non-woven fabric can be used. Further, as the gas diffusion layer 35, a porous body made of metal or resin can be used. The separator 40 is disposed outside the gas diffusion layer 35. As the separator 40, for example, a metallic flat plate can be used. The frame 45 is formed on the outer edge of the electrolyte membrane 20 and supports the electrolyte membrane 20. The frame 45 is formed of, for example, resin or rubber.

  FIG. 2 is an explanatory view schematically showing a configuration in the vicinity of the catalyst layer. The catalyst layer 30 includes catalyst particles 100 and an electrolyte 200. The catalyst particles 100 are obtained by supporting a catalyst such as platinum (Pt) on a carrier such as carbon particles. The electrolyte 200 is made of, for example, a fluorine resin or a hydrocarbon resin such as perfluorocarbon sulfonic acid polymer, and has proton conductivity. The electrolyte 200 is different from the electrolyte membrane 20 in that the catalyst particles 100 are included therein. Further, the electrolyte 200 and the electrolyte membrane 20 may have different ion exchange capacities. The electrolyte 200 has a large number of pores 300 (also referred to as “voids 300”). The reaction gas is supplied to the catalyst particles 100 through the gap 300.

  In the gap 300 in the electrolyte 200, the water 400 generated by the electrochemical reaction of the fuel cell evaporates. The amount of the gap 300 greatly affects the evaporation rate of the water 400. That is, if the amount of the gap 300 is large, the water 400 is easily evaporated. Therefore, if the amount of the gap 300 is large, the fuel cell is easily dried up, and the efficiency of the fuel cell is reduced. In particular, when the fuel cell 10 is operated near the boiling point of water, it is preferable that the amount of the gap 300 is small.

  FIG. 3 is an explanatory view schematically showing the effect of the present embodiment. In FIG. 3, the same hatching is applied to the catalyst particles 100 and the electrolyte 200 as solid phases. In this embodiment, the amount of the gap 300 is reduced to suppress the evaporation of the water 400 and prevent the fuel cell from drying up.

The applicant of the present application created membrane electrode assemblies under various conditions, and examined the void volume, porosity, and water permeability. Furthermore, the continuity of power generation of the fuel cell was examined using the produced membrane electrode assembly. As a result, the amount of voids 300 is greater than 1.0 mL / m ^2, if 5.6 mL / m ² or less, with the proviso that the "operating temperature of the fuel cell is not humidified boiling point of water, and the reaction gas" The power generation of the fuel cell can be continued for a long time. A more preferred conditions, the amount of voids is 1.7 mL / m ² or more 5.6 mL / m ² or less. The unit of “amount of voids” is the volume of voids per 1 m ^{2 of} the catalyst layer.

  There are various methods for reducing the amount of the gap 300. As an example, the formation conditions of the catalyst layer 30, that is, the method of adjusting the amount of the voids 300 by changing the composition and generation conditions of the catalyst particles 100 and the electrolyte 200, or the fibers in the voids 300 after the catalyst layer 30 is formed. Can be used to adjust the amount of the gap 300.

FIG. 4 shows an example of a method for reducing the size of the gap. In this embodiment, the voids 300 are filled with carbon nanotube 500 fibers. As a result, a part of the gap 300 is filled with the carbon nanotubes 500, so that the amount of the gap 300 can be reduced. Thus, by filling the voids with fibers such as carbon nanotubes, the amount of voids 300 is greater than 1.0 mL / m ² and in the range of 5.6 mL / m ² or less, or 1.7 mL / m ^2. Even if it adjusts to the range below 5.6 mL / m < ² > above, it is possible to continue the electric power generation of the fuel cell 10 for a long time.

Further, the applicant of the present application has found that the water permeability of the electrolyte membrane 20 has an influence on the continuity of power generation of the fuel cell. That is, in this embodiment, since the amount of the gap 300 is reduced, on the contrary, there is a tendency that flooding is likely to occur. Therefore, it is preferable to move water to the anode side through the electrolyte membrane 20. If the water permeability of the electrolyte membrane 20 is larger than 0.10 mg / (min · cm ² · kPa) (= 1.0 mg / (min · m ² · Pa)), the power generation of the fuel cell is continued for a long time. Is possible. A more preferable condition is that the water permeability of the electrolyte membrane 20 is 0.15 mg / (min · cm ² · kPa) or more.

[Experimental example]
FIG. 5 is a table showing the characteristics of samples 1 to 17 and the performance of each sample. In addition, preparation and performance test of each sample were performed as follows.

[Sample 1]
(1) Preparation of electrolyte solution L1 A perfluorocarbon polymer having a sulfonic acid group was dissolved in a mixed solvent of water and alcohol to prepare an electrolyte solution L1. At this time, the ion exchange capacity of the electrolyte was 1.45 meq / g. It adjusted so that it might become.

(2) Formation of electrolyte membrane M1 The electrolyte solution L1 was applied on a flat plate and dried to obtain an electrolyte membrane M1.

(3) Evaluation of water permeability of electrolyte membrane FIG. 6 is an explanatory view schematically showing an electrolyte membrane measuring apparatus. The electrolyte membrane measurement device 50 includes an electrolyte membrane installation unit 60, a liquid water pressurization unit 70, and a permeated water amount measurement unit 80. The electrolyte membrane installation unit 60 includes an electrolyte membrane 20 and a liquid water container 65. A pipe 90 is connected between the liquid water container 65 and the liquid water pressurizing unit 70 and between the liquid water container 65 and the permeated water amount measuring unit 80. The electrolyte membrane 20 is disposed in the liquid water container 65 and separated into the liquid water pressurizing unit 70 side and the permeated water amount measuring unit 80 side. In the electrolyte membrane measuring device 50, when pressurized using the liquid water pressurizing unit 70, the liquid water passes through the electrolyte membrane 20 and moves to the permeated water amount measuring unit 80 side. The amount of water that has moved is measured using the permeated water amount measuring unit 80.

The procedure for measuring the water permeation rate is as follows.
(A) The temperature of the liquid water in the electrolyte membrane installation part 60 and the liquid water container 65 was set to 90 ° C.
(B) Next, a constant pressure was applied to the liquid water pressurizing unit 70 side of the electrolyte membrane 20 using the liquid water pressurizing unit 70.
(C) In this state, using the permeated water measuring unit 80, the increase in liquid water of the permeated water measuring unit 80 of the electrolyte membrane 30 was measured at regular intervals.
(D) The permeation speed of the liquid water was determined using the change over time of the increase in liquid water thus obtained.
(E) The pressure applied by using the liquid water pressurizing unit 70 was changed, and (b) to (d) were repeated.
(F) Permeability (rate of change in speed) of liquid water with respect to pressure was determined using the permeation speed of liquid water at each pressure (“water permeation performance” in the table of FIG. 5).

(4) Preparation of cathode catalyst layer ink C1 Electrolyte solution L1 and carbon black supporting a Pt catalyst (weight ratio of Pt to the total weight 50%) were mixed to prepare cathode catalyst layer ink C1. The weight ratio between the electrolyte and the catalyst-supported carbon black was adjusted to 25:75.

(5) Preparation of anode catalyst layer ink A1 The electrolyte solution L1 and carbon black carrying a Pt catalyst (50% by weight of Pt with respect to the total weight) were mixed to prepare an anode catalyst ink A1. The weight ratio of the electrolyte and the carbon black carrying the catalyst was adjusted to 33:67.

(6) Preparation of Membrane / Electrode Assembly MEA1 Cathode catalyst layer ink C1 and anode catalyst ink A1 were applied on the electrolyte membrane M1 to form a membrane / electrode assembly MEA1 in which the catalyst layer 30 was formed. At this time, the cathode electrode was applied so that the amount of Pt per unit area was 0.5 mg / cm ² (= 5 g / m ² ). Further, the anode electrode was applied so that the amount of Pt per unit area was 0.2 mg / cm ² (= 2 g / m ² ).

(7) Gas diffusion layer G1
As the gas diffusion layer G1, a water-repellent carbon paper packed with a water-repellent carbon powder layer (a mixture of carbon black and polytetrafluoroethylene) was used. The thickness of the gas diffusion layer G1 was 300 μm. Moreover, the water permeation start pressure (pressure at which water permeation is started) was 150 kPa.

(8) Power Generation Continuity Evaluation Device FIG. 7 is an explanatory diagram schematically showing a power generation continuation evaluation device. The power generation continuation evaluation apparatus 600 includes an evaluation cell 650, an LCR meter 680, a fuel gas supply unit 700, and an oxidizing gas supply unit 800. The evaluation cell 650 includes a membrane electrode assembly MEA1, a gas diffusion layer G1, and a current collector plate 670. The gas diffusion layer G1 is disposed on both sides of the membrane electrode assembly MEA1, and the current collector plate 670 is disposed outside the gas diffusion layer G1. An LCR meter 680 is connected to the current collector plate 670. The LCR meter 680 measures the voltage generated in the membrane electrode assembly MEA1.

  The fuel gas supply unit 700 includes a fuel gas tank 710, a gas flow rate control unit 720, a humidifier 730, a pipe 740 connecting them, and a three-way valve 750. The fuel gas supply unit 700 is connected to the anode side of the evaluation cell 650 by a pipe 740. The humidifier 730 is connected to the pipe 740 by two three-way valves 750. By switching these two three-way valves 750, it is possible to supply humidified fuel gas to the membrane electrode assembly MEA1 or supply unhumidified 0% humidity fuel gas.

  The oxidizing gas supply unit 800 includes an oxidizing gas tank 810, a gas flow rate control unit 820, a humidifier 830, a pipe 840 connecting them, and a three-way valve 850. Since the configuration of the oxidizing gas supply unit 800 is the same as the configuration of the fuel gas supply unit 700, a reference numeral obtained by adding 100 to the reference numeral indicating each configuration of the fuel gas supply unit 700 is assigned to each configuration, and description thereof is omitted.

(9) Evaluation of power generation maintenance 1
(A) The temperature of the evaluation cell 650 is set to 100 ° C., and air having a stoichiometric ratio of 150% and a gauge pressure of 100 kPa is supplied as an oxidizing gas so that the current density is 1.0 A / cm ^2. As a result, hydrogen gas having a stoichiometric ratio of 250% and a gauge pressure of 100 kPa was supplied to generate electric power. At this time, the humidity of the oxidizing gas and the fuel gas was adjusted so that the dew point of both electrodes was 80 ° C. Α = 250% shown in FIG. 5 indicates the stoichiometric ratio of the fuel gas.
(B) After power generation was stabilized under this humidity, the three-way valves 750 and 850 were switched to switch the reaction gas supplied to both electrodes to dry gas.
(C) After switching to dry gas, evaluation was performed based on whether or not continuous power generation (about 1 hour) could be maintained.

(10) Evaluation of power generation maintenance 2
The stoichiometric ratio of the fuel gas was set to 200%, and other conditions were the same as those in Evaluation 1 for maintaining power generation. Α = 200% shown in FIG. 5 indicates the stoichiometric ratio of the fuel gas.

(11) Measurement of void volume, average pore diameter, and porosity of catalyst layer The void volume of the catalyst layer 30 was measured by a mercury intrusion method. When using the mercury intrusion method, it is expressed by the Washburn equation.
D = −4γcos θ / P
There is a relationship. Here, P is the applied pressure, γ is the surface tension of mercury (= 480 mN / m), θ is the contact angle (= 140 degrees) between mercury and the pore wall, and D is the diameter of the pore. When a certain pressure P is applied, mercury enters a hole having a pore diameter of D or more. If the penetration volume at this time is measured and integrated, the amount of pores (voids) can be determined. Further, from the pore diameter D and the mercury intrusion volume, the pores were regarded as spheres, the number of pores at each diameter was determined, and the average pore diameter was determined from this value. Further, the weight of the electrolyte and catalyst particles contained in the portion excluding the voids of the catalyst layer 30 and the volume of the portion excluding the voids of the catalyst layer 30 from the density of the electrolyte and catalyst particles are obtained, and the voids in the catalyst layer 30 are obtained. A ratio of 300 (porosity) was determined.

  FIG. 8 is an explanatory diagram showing the amount of voids determined using the mercury intrusion method. The part indicated by hatching indicates the total amount of the gap 300.

Samples 2 to 17 in which the production conditions of the sample 1 and the electrolyte membrane were changed were prepared and evaluated in the same manner as the sample 1.
[Sample 2]
(1) Preparation of electrolyte solution L2 A perfluorocarbon polymer having a sulfonic acid group was dissolved in a mixed solvent of water and alcohol to prepare an electrolyte solution L2. At this time, the ion exchange capacity of the electrolyte was 0.90 meq / g. It adjusted so that it might become.
(2) Preparation of cathode catalyst layer ink C2 Electrolyte solution L2 and Pt catalyst-supported carbon black (50% by weight of Pt with respect to the total weight) were mixed to prepare cathode catalyst layer ink C2. The weight ratio of the electrolyte to the catalyst-supporting carbon was adjusted to 25:75.
(3) Other conditions Other conditions are the same as those of Sample 1.

[Sample 3]
(1) Preparation of electrolyte solution L3 A perfluorocarbon polymer having a sulfonic acid group was dissolved in a mixed solvent of water and alcohol to prepare an electrolyte solution L3. At this time, the ion exchange capacity of the electrolyte was 1.33 meq / g. It adjusted so that it might become.
(2) Preparation of Cathode Catalyst Layer Ink C3 Electrolyte solution L3 and carbon black carrying Pt catalyst (50% by weight of Pt with respect to the total weight) were mixed to prepare cathode catalyst layer ink C3. The weight ratio of the electrolyte to the catalyst-supporting carbon was adjusted to 25:75.
(3) Other conditions Other conditions are the same as those of Sample 1.

[Sample 4]
(1) Preparation of Membrane / Electrode Assembly MEA2 Cathode catalyst layer ink C1 and anode catalyst ink A1 were applied on the electrolyte membrane M1 to form a membrane / electrode assembly MEA2 in which the catalyst layer 30 was formed. At this time, the cathode electrode was applied so that the amount of Pt per unit area was 1.0 mg / cm ² (10 g / m ² ). The anode electrode was coated so that the amount of Pt per unit area was 0.2 mg / cm ² (2 g / m ² ).
(2) Other conditions Other conditions are the same as those of Sample 1.

[Sample 5]
(1) Formation of electrolyte membrane M2 Electrolyte solution L3 was applied onto a flat plate and dried to obtain electrolyte membrane M2.
(2) Other conditions Other conditions are the same as those of Sample 1.

[Sample 6]
(1) Formation of electrolyte membrane M3 The electrolyte solution L2 was applied on a flat plate and dried to obtain an electrolyte membrane M3.
(2) Other conditions Other conditions are the same as those of Sample 1.

[Sample 7]
(1) Formation of electrolyte membrane M1 ′ The electrolyte solution L1 was applied on a flat plate and dried to obtain an electrolyte membrane M1 ′. At this time, the thickness of the electrolyte membrane M1 ′ was adjusted so that the thickness of the electrolyte membrane M1 ′ was twice that of the electrolyte membrane M1 of the sample 1.
(2) Other conditions Other conditions are the same as those of Sample 1.

[Sample 8]
(1) Preparation of cathode catalyst layer ink C4 Electrolyte solution L1 and carbon black supporting a Pt catalyst (weight ratio of Pt to the total weight 50%) were mixed to prepare cathode catalyst layer ink C4. The weight ratio of the electrolyte to the catalyst-supported carbon was adjusted to be 30:70.
(2) Other conditions Other conditions are the same as those of Sample 1.

[Sample 9]
(1) Formation of electrolyte membrane M2 Electrolyte solution L3 was applied onto a flat plate and dried to obtain electrolyte membrane M2.
(2) Other conditions Other conditions are the same as those of Sample 8.

[Sample 10]
(1) Preparation of Cathode Catalyst Layer Ink C5 Electrolyte solution L3 and Pt catalyst-supported carbon black (Pt weight ratio to the total weight 50%) were mixed to prepare a cathode catalyst layer ink. The weight ratio of electrolyte to catalyst-carrying carbon was 25:75. The cathode catalyst layer ink contains ink particles. The ink particles are colloidal particles, and have carbon particles supporting a catalyst and an electrolyte surrounding the carbon particles. The colloidal particles were pulverized to about 0.1 μm using ultrasonic waves, and allowed to stand for 2 days after pulverization to prepare cathode catalyst layer ink C5. FIG. 9 is an explanatory diagram showing the distribution of the diameters of colloidal particles contained in the cathode catalyst layer ink. A part of the crushed colloidal particles aggregated, and the distribution of the diameters of the colloidal particles contained in the cathode catalyst layer ink C5 was about 0.1 μm and about 0.4 μm, and peaks were observed. .
(2) Other conditions Other conditions are the same as those of Sample 1.

[Sample 11]
(1) Preparation of cathode catalyst layer ink C6 Electrolyte solution L3 and carbon black carrying a Pt catalyst (50% by weight of Pt with respect to the total weight) were mixed to prepare an ink for cathode catalyst layer. The weight ratio of electrolyte to catalyst-carrying carbon was 20:80. Thereafter, the carbon particles carrying the catalyst were pulverized using ultrasonic waves, and allowed to stand for 2 days after pulverization to prepare cathode catalyst layer ink C6.
(2) Other conditions Other conditions are the same as those of Sample 1.

[Sample 12]
(1) Preparation of cathode catalyst layer ink C7 Electrolyte solution L2 and carbon black carrying Pt catalyst (80% by weight of Pt with respect to the total weight) were mixed to prepare cathode catalyst layer ink. In addition, it prepared so that the weight ratio of electrolyte and catalyst carrying | support carbon might be set to 10:90.
(2) Other conditions Other conditions are the same as those of Sample 1.

[Sample 13]
(1) Formation of electrolyte membrane M2 Electrolyte solution L3 was applied onto a flat plate and dried to obtain electrolyte membrane M2.
(2) Other conditions Other conditions are the same as those of the sample 12.

[Sample 14]
(1) Preparation of cathode catalyst layer ink C8 Electrolyte solution L1 and carbon black carrying a Pt catalyst (80% by weight of Pt with respect to the total weight) were mixed to prepare cathode catalyst layer ink C8. The weight ratio of electrolyte to catalyst-carrying carbon was 25:75.
(2) Other conditions Other conditions are the same as those of the sample 12.

[Sample 15]
(1) Preparation of cathode catalyst layer ink C8 Electrolyte solution L1 and platinum black were mixed to prepare cathode catalyst layer ink C9. In addition, it prepared so that the weight ratio of electrolyte and platinum might be set to 5:95.
(2) Other conditions Other conditions are the same as those of Sample 1.

[Sample 16]
(1) Preparation of carbon nanotubes While supporting a carbon nanotube purification catalyst (for example, nickel, iron) on carbon paper and supplying a raw material gas (for example, acetylene), while carbon nanotubes are vertically aligned on carbon paper, Generated.
(2) Preparation of Membrane / Electrode Assembly MEA3 A cathode / catalyst layer ink C2 and an anode catalyst ink A1 were applied on the electrolyte membrane M1 to form a membrane / electrode assembly MEA3 having the catalyst layer 30 formed thereon. At this time, the cathode electrode was applied so that the amount of Pt per unit area was 0.5 mg / cm ² (5 g / m ² ). The anode electrode was coated so that the amount of Pt per unit area was 0.2 mg / cm ² (2 g / m ² ).
(3) Insertion of carbon nanotubes into the membrane electrode assembly MEA3 A carbon paper with carbon nanotubes oriented is pressed against the catalyst layer 30 on the cathode side of the membrane electrode assembly MEA3 with a load of 1 MPa, and the voids in the catalyst layer 30 on the cathode side Carbon nanotubes were inserted into the.
(4) Other conditions Other conditions are the same as those of Sample 1.

[Sample 17]
(1) Formation of electrolyte membrane M2 ′ The electrolyte solution L3 was applied on a flat plate and dried to obtain an electrolyte membrane M2 ′. At this time, the thickness of the electrolyte membrane M2 ′ was adjusted to be ½ times that of the electrolyte membrane M1 of Sample 1.
(2) Other conditions Other conditions are the same as those of Sample 1.

  FIG. 5 shows the evaluation results of each sample. Whether the power generation at 100 ° C. can be maintained for a long time depends on the amount of voids per unit area of the catalyst layer and the water permeation performance of the electrolyte membrane, and the size of the pores (voids) It was found that the porosity had no effect.

FIG. 10 is an explanatory diagram for explaining the void amount per unit area of the catalyst layer, the water permeation performance in the electrolyte membrane, and whether or not power generation can be maintained. In the region where power generation can be maintained, the amount of the gap 300 is more than 1.0 mL / m ² and 5.6 mL / m ² or less, and the water permeability of the electrolyte membrane 20 is 0.10 mg / (min · cm ² · kPa). More preferably 1.7 mL / m ² or more 5.6 mL / m ² or less of the range for the range of air gap 300. Further, the water permeability range of the electrolyte membrane 20 is more preferably 0.15 mg / (min · cm ² · kPa) or more.

When the amount of voids is larger than 5.6 mL / m ² , at a temperature of 100 ° C., the water evaporation rate is fast, so that it is easy to dry up and power generation may not be maintained. In addition, when the amount of voids is 1.0 mL / m ² or less, the reaction gas necessary for the reaction is not sufficiently supplied, and thus power generation may not be maintained. In the present specification, the amount of voids is defined by the volume of voids per unit area of the catalyst layer. When this is defined by the volume of the voids per unit volume of the catalyst layer, the absolute amount of the voids 300 included in the catalyst layer 30 varies depending on the thickness of the catalyst layer 30. That is, if the catalyst layer 30 is thickened, the absolute amount of the voids 300 is increased, so that the evaporation rate is increased and it is easy to dry up. As a unit of the void amount of the catalyst layer, a unit having a high correlation with the evaporation rate of water in the entire catalyst layer is preferably adopted. For that purpose, the amount of the void 300 per unit area of the catalyst layer 30 is defined. Is reasonable.

  There are various ways to adjust the amount of void 300. For example, as can be seen from the results of Samples 1 to 3, it can be prepared by adjusting the ion exchange capacity of the electrolyte 200. When the ion exchange capacity of the electrolyte 200 is increased, the amount of voids is reduced. Further, the particle size of the ink particles may be adjusted (comparison of samples 3 and 10). In this case, the amount of voids decreases when the ink particles are finely crushed. Here, the ink particles are those in which the catalyst particles 100 and the electrolyte 200 are aggregated.

  Further, the amount of the voids 300 may be prepared not only by preparing the catalyst particles 100 and the electrolyte 200 (FIG. 2) but also by filling fibers such as carbon nanotubes in the voids 300 as shown in FIG.

In the present embodiment, water evaporation is suppressed in the catalyst layer 30. Therefore, the cathode tends to be in a state of water. For this reason, it is necessary to quickly move the produced water generated by the electrochemical reaction at the cathode to the anode. For that purpose, the water permeability of the electrolyte membrane 20 needs to be high. From the results of this example, it is sufficient that the water permeability of the electrolyte membrane 20 is larger than 0.10 mg / (min · cm ² · kPa), and is 0.15 mg / (min · cm ² · kPa) or more. More preferred.

  The embodiments of the present invention have been described above based on some examples. However, the above-described embodiments of the present invention are for facilitating the understanding of the present invention and limit the present invention. It is not a thing. The present invention can be changed and improved without departing from the spirit and scope of the claims, and it is needless to say that the present invention includes equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 20 ... Electrolyte membrane 30 ... Catalyst layer 35 ... Gas diffusion layer 40 ... Separator 45 ... Frame 50 ... Electrolyte membrane measuring device 60 ... Electrolyte membrane installation part 65 ... Liquid water container 70 ... Liquid water pressurization part 80 ... Permeation | transmission Water quantity measuring unit 90 ... pipe 100 ... catalyst particle 150 ... stoichiometric ratio 200 ... electrolyte 250 ... stoichiometric ratio 300 ... hole (void)
400 ... Water 500 ... Carbon nanotube 600 ... Power generation continuation evaluation device 650 ... Evaluation cell 670 ... Current collector 700 ... Fuel gas supply unit 710 ... Fuel gas tank 720 ... Gas flow rate control unit 730 ... Humidifier 740 ... Piping 800 ... Oxidation gas supply 810 ... Oxidizing gas tank 820 ... Gas flow rate control unit 830 ... Humidifier 840 ... Piping

Claims (4)

A fuel cell that can be operated by supplying a non-humidified reaction gas at 100 ° C. ,
An electrolyte membrane;
An anode catalyst layer and a cathode catalyst layer respectively disposed on the surface of the electrolyte membrane;
With
The cathode catalyst layer has voids;
The amount of the void is more than 1.0 mL / m ² and 5.6 mL / m ² or less,
A fuel cell, wherein the water permeability of the electrolyte membrane is greater than 0.10 mg / (min · cm ² · kPa). The fuel cell according to claim 1 , wherein
Wherein the amount of the gap is 1.7 mL / m ² or more 5.6 mL / m ² or less, the fuel cell. The fuel cell according to claim 1 or 2 ,
A fuel cell, wherein the water permeability of the electrolyte membrane is 0.15 mg / (min · cm ² · kPa) or more. The fuel cell according to any one of claims 1 to 3 , wherein
The amount of the voids is a fuel cell that is adjusted to the above value by filling the voids with fibers.

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