JP5582092B2 - Fuel cell - Google Patents

Description

  The present invention relates to a catalyst used for a fuel cell or the like.

  Patent Document 1 is configured to increase the porosity of at least one of the catalyst layers arranged on both sides of the solid polymer electrolyte membrane from the inlet side to the outlet side of the gas flow path, Describes a polymer electrolyte fuel cell in which the power generation performance is improved by improving the drainage performance.

JP 2007-26783 A

In Patent Document 1, the amount of platinum (Pt) used as a catalyst is relatively large at 0.35 mg / cm ² (hereinafter referred to as “high Pt”), and the secondary particle radius of the catalyst is also 0.6 μm to 2.5 μm. And it was relatively big. With such a high Pt catalyst, it is difficult for oxygen to be deficient in a high current density region. Therefore, even if the secondary particle radius of the catalyst is relatively large, the performance of the fuel cell can be maintained. However, from the viewpoint of cost reduction and effective use of resources, when trying to reduce the amount of platinum used as a catalyst, if the secondary particle radius of the conventional catalyst is relatively large, the performance of the fuel cell will be reduced. It has become difficult to maintain.

  The present invention has been made to solve at least a part of the above-described problems, and an object thereof is to provide a catalyst for improving the efficiency of a fuel cell.

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 an embodiment of the present invention, a fuel cell is provided. The fuel cell includes an electrolyte membrane and a catalyst layer formed on both surfaces of the electrolyte membrane, and the catalyst layer is a secondary formed by a plurality of primary particles made of carbon carrying a platinum catalyst. Particles, and an ionomer that penetrates the inside of the secondary particles and covers the outside of the secondary particles, and the radius of the secondary particles is in the range of 105 nm to 200 nm, and the catalyst layer The ratio (I / C) of the mass I of the ionomer and the mass C of the carbon is 0.95 to 1.35. According to this embodiment, the efficiency of the fuel cell can be improved.

[Application Example 1]
A fuel cell comprising an electrolyte membrane and a catalyst layer formed on both surfaces of the electrolyte membrane, wherein the catalyst layer is formed by aggregating a plurality of primary particles made of carbon carrying a platinum catalyst. A fuel cell comprising: a secondary particle; and an ionomer that penetrates into the secondary particle and covers the outside of the secondary particle, wherein a radius of the secondary particle is in a range of 105 nm to 200 nm. .
According to this application example, the efficiency of the fuel cell can be improved.

[Application Example 2]
The fuel cell according to Application Example 1, wherein the ratio (I / C) of the mass I of the ionomer in the catalyst layer to the mass C of the carbon is 0.65 to 1.35.
According to this application example, the efficiency of the fuel cell can be further improved.

[Application Example 3]
The fuel cell according to Application Example 2, wherein the porosity, which is a ratio not occupied by the secondary particles and the ionomer in the catalyst layer, is 0.33 to 0.58.
According to this application example, the efficiency of the fuel cell can be further improved.

[Application Example 4]
In the fuel cell according to Application Example 1 or 2, the secondary particle radius is 105 nm to 135 nm, and the ratio (I / C) of the mass I of the ionomer and the mass C of the carbon in the catalyst layer is 0.95 to 1.25, a fuel cell.
According to this application example, the efficiency of the fuel cell can be further improved.

[Application Example 5]
The fuel cell according to Application Example 4, wherein the porosity, which is a ratio not occupied by the secondary particles and the ionomer in the catalyst layer, is 0.38 to 0.48.
According to this application example, the efficiency of the fuel cell can be further improved.

  The present invention can be realized in various forms. For example, the present invention can be realized in various forms such as a fuel cell catalyst in addition to a fuel cell.

It is explanatory drawing which shows the structure of the membrane electrode gas diffusion layer assembly of the fuel cell of one Embodiment of this invention. It is explanatory drawing which expands and shows the catalyst layer vicinity on the cathode side. It is explanatory drawing which compares the mass ratio of an ionomer and carbon, and the structure of a secondary particle. It is explanatory drawing which compares the magnitude of the porosity. It is explanatory drawing which compares a secondary particle diameter. It is explanatory drawing which shows the relationship between the magnitude | size of a secondary particle, and the ratio of the platinum currently used. It is explanatory drawing which shows the manufacturing process of a catalyst layer. It is a graph which shows the relationship between ionomer / carbon mass ratio and porosity. It is explanatory drawing which shows the model of a catalyst. It is explanatory drawing which shows the parameter of a sample in a present Example, and the measurement result of a current density. It is a graph which shows the relationship between a secondary particle radius and an electric current density. It is a graph which shows the relationship between an ionomer / carbon mass ratio and a current density. It is a graph which shows the relationship between a porosity and a current density.

  FIG. 1 is an explanatory diagram showing a configuration of a membrane electrode gas diffusion layer assembly of a fuel cell according to an embodiment of the present invention. The membrane electrode gas diffusion layer assembly 10 includes an electrolyte membrane 100, a catalyst layer 200, and a gas diffusion layer 300. The electrolyte membrane 100 is formed using, for example, a proton conductive ion exchange membrane made of a fluorine resin such as perfluorosulfonic acid polymer or a hydrocarbon resin. The catalyst layer 200 is formed on both surfaces of the electrolyte membrane 100. The configuration of the catalyst layer will be described later. The electrolyte membrane 100 and the catalyst layer 200 are collectively referred to as a membrane electrode assembly 20. The gas diffusion layer 300 is disposed so as to sandwich the membrane electrode assembly 20. As the gas diffusion layer 300, a carbon non-woven fabric or carbon paper formed using carbon fibers can be used. Further, as the gas diffusion layer 300, an expanded metal or a metal porous body can be used.

  FIG. 2 is an explanatory diagram showing an enlarged view of the vicinity of the catalyst layer on the cathode side. The catalyst layer 200 includes secondary particles 120, an ionomer 130, a water film 140, and voids 150. The secondary particles 120 include carbon (primary particles) 110 and platinum (Pt) 115. Here, platinum 115 is supported on carbon 110 and functions as a catalyst. In this embodiment, platinum is used as a catalyst, but a platinum alloy catalyst made of platinum and another metal may be used instead of the platinum catalyst. Note that the secondary particles 120 include a plurality of carbons 110. The ionomer 130 covers around the secondary particles 120. Here, the ionomer means “ion + polymer” and means an ionic polymer resin. As the ionomer 130, it is preferable to use a perfluorosulfonic acid polymer that is the same component as the ion exchange membrane (resin) that forms the electrolyte membrane 100 (FIG. 1). The ionomer 130 covers the periphery of the secondary particles 120, but part of the ionomer 130 penetrates into the interior of the secondary particles 120 and fills between the plurality of carbons 110. A water film 140 is formed outside the ionomer 130 covering the secondary particles 120. The void 150 is a portion other than the portion occupied by the secondary particles 120, the ionomer 130, and the water film 140 in the catalyst layer 200. The porosity refers to the proportion of voids in the total volume of the catalyst layer 200.

During operation of the fuel cell, air (oxygen) is supplied from the gas diffusion layer 300 to the gap 150. Oxygen dissolves in the ionomer 130 covering the periphery of the secondary particle 120, further moves to the ionomer inside the secondary particle 120, and is supplied to the platinum 115. Here, when the amount of platinum 115 on the cathode side is reduced to 0.1 mg / cm ² (low Pt), the number of secondary particles 120 is reduced. The amount of oxygen to be supplied per secondary particle is larger than that of 115 (0.35 mg / cm ² ). As described above, oxygen is supplied to the platinum 115 via the ionomer 130. Here, since the amount of oxygen that can enter the ionomer 130 is limited, the diffusion of oxygen becomes the rate-limiting factor for improving the efficiency of the fuel cell.

  FIG. 3 is an explanatory diagram comparing the mass ratio of ionomer and carbon and the structure of secondary particles. Here, the ionomer that has entered the interior of the secondary particle 120 is referred to as an “ionomer 131” in distinction from the ionomer 130 that covers the secondary particle 120. In the catalyst layer 200 (FIG. 1), as shown in FIG. 3A, as the mass ratio of the ionomer 130 to the mass of the carbon 110 increases, the thickness of the ionomer 130 surrounding the secondary particles 120 increases. In addition, the amount of ionomer 131 inside the secondary particle 120 increases. On the other hand, in the catalyst layer 200 (FIG. 1), as shown in FIG. 3B, the smaller the ratio of the mass of the ionomer 130 to the mass of the carbon 110, the smaller the thickness of the ionomer 130 surrounding the secondary particles 120. Further, the amount of ionomer 131 inside the secondary particle 120 is reduced.

  If the ionomer / carbon mass ratio is too large, the amount of ionomer 131 in the secondary particle 120 increases, so that the diffusion of oxygen in the secondary particle 120 is improved, but the thickness of the ionomer 130 surrounding the secondary particle 120 is increased. As the thickness increases, the diffusion distance from the void 150 (FIG. 2) to the platinum 115 increases, and the diffusion of oxygen in the ionomer 130 deteriorates. Moreover, when there are many ionomers 130, IR loss of the whole catalyst layer 200 (FIG. 1) will become small.

  On the other hand, if the ionomer / carbon mass ratio is too small, the thickness of the ionomer 130 surrounding the secondary particle 120 becomes thin, so that the diffusion of oxygen in the ionomer 130 is improved, but the ionomer 131 in the secondary particle 120 Since the amount is reduced, the diffusion of oxygen in the secondary particles 120 becomes worse. Moreover, since there are few ionomers 130, the IR loss of the whole catalyst layer 200 (FIG. 1) becomes large. In this way, that is, if the mass ratio (ionomer / carbon mass ratio, or I / C ratio) between the ionomers 130 and 131 and the carbon 110 is too large or too small, the performance of the fuel cell is lowered. An ionomer / carbon mass ratio is preferable.

  FIG. 4 is an explanatory diagram comparing the size of the porosity. As shown in FIG. 4A, when the porosity in the catalyst layer 200 (FIG. 1) is too small, the amount of ionomer 130 used in the void 150 is reduced, so that the ionomer 131 inside the secondary particle 120 The amount increases and the diffusion of oxygen in the ionomer 131 improves, but the diffusion of oxygen in the voids 150 worsens. On the other hand, as shown in FIG. 4B, when the porosity in the catalyst layer 200 (FIG. 1) is too large, the diffusion of oxygen in the void 150 is improved, but the ionomer 130 is more in the coating inside the void 150. Since it is used, the amount of ionomer 131 in the secondary particles is reduced, and the diffusion of oxygen in the ionomer 131 of the secondary particles 120 is deteriorated. Thus, since the performance of the fuel cell is lowered if the void is too large or too small, it is preferable that the void has an appropriate porosity.

  FIG. 5 is an explanatory diagram for comparing secondary particle diameters. As shown in FIG. 5A, when the radius of the secondary particle 120 is large, the surface area of the carbon 110 becomes small, so that the thickness of the ionomer 130 around the secondary particle 120 becomes thick, and oxygen is contained in the ionomer 130. Difficult to diffuse into. On the other hand, as shown in FIG. 5B, when the radius of the secondary particle 120 is small, the surface area of the carbon 110 is increased, so that the thickness of the ionomer 130 around the secondary particle 120 is reduced. It becomes easy to diffuse into the platinum 115 and improve the voltage performance.

  FIG. 6 is an explanatory diagram showing the relationship between the size of secondary particles and the proportion of platinum used. As shown in FIG. 6A, when the radius of the secondary particle 120 is relatively large, the number of primary particles 110 included in the secondary particle 120 is large. In such a case, a part of the primary particles 110 are surrounded by the other primary particles 110 and do not face the ionomer 130 around the secondary particles 120. Oxygen may not be sufficiently supplied to the platinum 115 carried on the primary particles 110 inside the secondary particles 120, and oxygen may be insufficient. Therefore, it is difficult to increase the voltage performance as compared with the amount of platinum. On the other hand, as shown in FIG. 6B, when the radius of the secondary particles 120 is relatively small, the number of primary particles 110 included in the secondary particles 120 is small. In such a case, since the primary particles 110 face the ionomer 130 around the secondary particles 120, sufficient oxygen is supplied to the platinum 115 supported on the primary particles 110 inside the secondary particles 120. Therefore, the voltage performance can be improved as compared with the amount of platinum. Therefore, it can be said that the smaller the radius of the secondary particles 120, the easier it is to improve the voltage performance of the fuel cell.

  However, if the size of the secondary particles 120 is too small, the gap between the secondary particles 120 becomes small, and the generated water is easily clogged in the gap. If the gap between the secondary particles 120 is small, the ionomer 130 in the gap between the secondary particles 120 swells with water and further narrows the gap. As a result, it becomes difficult to suppress the diffusion of oxygen and the discharge of water and improve the voltage performance. That is, the size of the secondary particles 120 may not be too small, and is preferably an appropriate size.

  From the above, it is considered that the voltage performance of the fuel cell is influenced by the size of the secondary particles 120, the ionomer / carbon mass ratio, and the porosity. Hereinafter, a catalyst layer in which the size of the secondary particles 120, the ionomer / carbon mass ratio, and the porosity were changed was created, and the performance of the fuel cell was measured.

FIG. 7 is an explanatory view showing a manufacturing process of the catalyst layer. First, in the step (A), a catalyst solution is prepared. First, carbon on which a commercially available platinum catalyst is supported is prepared. As the carbon material on which the platinum catalyst is supported, for example, Ketchin Black made by Tanaka Kikinzoku Metal can be used. This ketchin black has a carbon particle size of 30 nm and carries platinum having a particle size of 2 to 3 nm. In the step (A), Kettin Black, Nafion (Nafion is a registered trademark), water, and alcohol (ethanol, 1-propanol) are mixed to prepare a catalyst. In addition, the mass ratio of each component is as follows.
Component Range Example Platinum (Pt) 0.1-0.7 0.4
Carbon 0.3-0.9 0.6
Nafion 0.1-0.7 0.66
Water 5-15 8
Alcohols 1-12 4
Here, as will be described later, the mass ratio of carbon and Nafion affects the porosity. That is, the porosity can be adjusted by changing the mass ratio of carbon and Nafion.

  In the step (B), the catalyst solution is put in a beaker and pulverized by applying ultrasonic waves for about 2 minutes using an ultrasonic homogenizer. Since the catalyst solution contains Nafion (ionomer) and has a high viscosity, it generates heat by ultrasonic grinding. Next, in step (C), a beaker is placed in the cooled water and cooled for about 5 minutes. Next, in a process (D), a rotor is put into a beaker and it stirs for about 5 minutes using a rotator. The stirring by the rotator and the rotor is preferably stirred so strongly that the catalyst solution does not spill from the beaker. From the step (B) to the step (D), that is, a series of steps of ultrasonic pulverization, cooling and stirring is taken as one cycle, this cycle is repeated a plurality of times. The size of the secondary particles 120 (FIG. 2) can be adjusted by the number of repetitions of this cycle. That is, the size of the secondary particles 120 can be reduced as the number of ultrasonic grinding, cooling, and stirring is repeated. For example, if the size of the secondary particles 120 is to be about 100 nm in diameter, the number of ultrasonic grinding, cooling, and stirring may be repeated about 30 times, and the size of the secondary particles 120 is to be about 200 nm in diameter. The number of repetitions of ultrasonic grinding, cooling, and stirring may be about 2 to 7 times. The number of repetitions of sonication, cooling and stirring described above is an example. The number of repetitions of specific ultrasonic pulverization, cooling, and stirring for making the size of the secondary particles 120 a desired size may slightly vary depending on the strength of the ultrasonic pulverization and other conditions. The secondary particles 120 can be made smaller as the number of repetitions of ultrasonic grinding, cooling, and stirring is increased. A method for measuring the size of the secondary particles 120 will be described later.

  In the step (E), a catalyst solution in which the size of the secondary particles is adjusted is formed into a thin film (thickness: about 11 μm) by the doctor blade method. In this embodiment, the catalyst thin film is formed by the doctor blade method, but other than the doctor blade method, a screen printing method, a gravure coating method, a spray coating method, or the like may be used. In the next step (F), the formed thin film is placed on a hot plate and rapidly dried at a temperature of 80 ° C. for 5 to 15 minutes, and then dried at a temperature of 100 ° C. for 2 to 3 hours using a vacuum drying furnace. In the next step (G), the membrane electrode assembly 20 shown in FIG. 7G is formed by press-bonding the thin film dried at 130 ° C. using a hot press to the electrolyte membrane 100.

  In step (A), a pore forming agent may be added to the catalyst solution. The pore-forming agent is not particularly limited as long as it generates bubbles by heating or the like. Examples of pore-forming agents include foaming agents such as azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), p, p-oxybisbenzenesulfonyl hydrazide (OBSH), paraffin that generates bubbles by thermal decomposition, poly Resins such as lactic acid can be used. When the pore-forming agent is added, in the step (F), the step of heating the pore-forming agent at a temperature equal to or higher than the decomposition temperature (for example, 200 ° C. to 210 ° C. if the pore forming agent is azodicarbonamide). By adding, bubbles can be generated by thermal decomposition, and the pore-forming agent traces can be made into voids. That is, the ratio of voids can be adjusted by the amount of pore former in addition to the ionomer / carbon mass ratio.

FIG. 8 is a graph showing the relationship between the ionomer / carbon mass ratio and the porosity. FIG. 9 is an explanatory diagram showing a catalyst model. As can be seen from the graph of FIG. 8, as the ionomer / carbon mass ratio (I / C ratio) increases, the porosity decreases. The reason for this is considered to be that when the ionomer / carbon mass ratio (I / C ratio) is increased as shown in FIG. 9, the amount of ionomer 130 outside the secondary particles 120 is increased, so that the voids 150 are blocked. The applicant examined the relationship between the ionomer / carbon mass ratio and the porosity with various samples, and found that the porosity can be expressed by the following approximate expression (1).
Porosity = −0.2 × Z + 0.5833 (1)
In the formula (1), Z is an ionomer / carbon mass ratio (I / C ratio).

  Regarding the size of the voids and the size (radius) of the secondary particles, cross-sectional images of the catalyst layers of various samples were taken using a transmission electron microscope, and the secondary particles 120 and the voids 150 were confirmed from the cross-sectional images. And their sizes were measured. Regarding the radius of the secondary particle 120, the area of the secondary particle 120 was calculated from the cross-sectional image, and the radius of the circle having the same area as that area was calculated. The average value of the radii of the circles was defined as the radius of the secondary particles 120. The number of secondary particles 120 measured is several or more per sample, and the larger the number of measurements, the better. Note that the volume of the secondary particles may be calculated from the area of the secondary particles 120, and the radius of the sphere having the same volume as the area may be calculated. About the ratio of the space | gap 150, since a magnitude | size is not as uniform as a secondary particle, the magnitude | size of the space | gap 150 was totaled and the ratio of the total magnitude | size of the space | gap with respect to the volume of the catalyst layer 200 was computed.

FIG. 10 is an explanatory diagram showing the measurement results of sample parameters and current density in this example. The current density was measured under the following conditions. A fuel cell having a catalyst layer size of 20 cm ² was prepared. To this fuel cell, pure hydrogen and air were supplied as reaction gases at a pressure of 0.1 MPa. The stoichiometric ratio of pure hydrogen to air was 5 for all. That is, 5 times the reaction gas was supplied with respect to the amount of reaction gas required for power generation of the fuel cell. The temperature of the fuel cell was set to 80 ° C., and the bubbler temperature on the anode side was set to 90 ° C. and the bubbler temperature on the cathode side was set to 80 ° C. in order to humidify the reaction gas. The bubbler temperature is the dew point temperature of each reaction gas. Under the above conditions, the current density of the fuel cell at an output voltage of 0.6 V was measured.

FIG. 11 is a graph showing the relationship between secondary particle radius and current density. When the diameter of the secondary particles 120 is 105 nm (Sample Nos. 4 to 7, 22 to 25), the value of the current density is 1.25 A / cm ^{2 to} 1.85 A / cm ^2. Is 135 nm (sample No. 26 to 29), the value of current density is 1.75 A / cm ^{2 to} 1.95 A / cm ² , and the secondary particle 120 has a diameter of 200 nm (sample NO. 8 to 11) The value of the current density was 1.05 A / cm ^{2 to} 1.2 A / cm ² . Further, when the diameter of the secondary particles 120 is increased to 250 nm (sample No. 12), the current density is 0.49 A / cm ² , and when the diameter of the secondary particles 120 is decreased to 80 nm (sample NO. 1), the current is increased. The density was 0.75 A / cm ² . From the above results, the diameter of the secondary particles 120 is preferably an appropriate size, and it is difficult to improve the efficiency of the fuel cell, whether it is larger or smaller. The diameter of the secondary particles is preferably in the range of 105 nm to 200 nm, more preferably in the range of 105 nm to 135 nm, and 135 nm is a good result.

FIG. 12 is a graph showing the relationship between the ionomer / carbon mass ratio and the current density. When the ionomer / carbon mass ratio value is 0.65 (sample Nos. 4, 5, 8, 9, 17, 19), the current density value is 1.05 A / cm ^{2 to} 1.25 A / cm ² . Yes, when the ionomer / carbon mass ratio value is 0.95 (Sample Nos. 22, 23, 26, 27), the current density value is 1.6 A / cm ^{2 to} 2.05 A / cm ² , When the ionomer / carbon mass ratio value is 1.25 (samples No. 24, 25, 28, 29), the current density value is 1.6 A / cm ^{2 to} 1.85 A / cm ² , and the ionomer / when the value of the carbon mass ratio of 1.35 (sample NO.6,7,10,11), the value of the current density was ^{1.1A / cm 2 ~1.4A / cm 2} . Further, when the ionomer / carbon mass ratio value increases to 1.5 (sample No. 13), the current density becomes 0.67 A / cm ² , and the ionomer / carbon mass ratio value decreases to 0.4 ( Sample No. 2), the current density was 0.49 A / cm ² . From the above results, the value of the ionomer / carbon mass ratio is preferably an appropriate value, and it is difficult to improve the efficiency of the fuel cell, whether it is larger or smaller. In addition, it turned out that the range of 0.65-1.35 is preferable as a value of ionomer / carbon mass ratio, and the range of 0.95-1.25 is still more preferable. In addition, when the diameter of the secondary particles is in the range of 105 nm to 135 nm and the ionomer / carbon mass ratio is 0.95 to 1.25, the current density value is 1.6 A / cm ^2. It became -2.05 A / cm < ² >, and it became a more preferable result.

FIG. 13 is a graph showing the relationship between porosity and current density. When the porosity is 0.33, the current density value is 1.05 A / cm ^{2 to} 1.35 A / cm ² , and when the porosity is 0.38, the current density value is 1.6 A / cm ^2. a ~1.95A / cm ^2, when the porosity is 0.48, the value of the current density was ^{1.7A / cm 2 ~2.05A / cm 2} , when the porosity is 0.58, the current The density value was 1.05 / cm ^{2 to} 1.4 A / cm ² . Further, when the porosity was increased to 0.7, the current density was 0.64 A / cm ² , and when the porosity was decreased to 0.3, the current density was 0.78 A / cm ² . That is, it was found that the porosity is preferably within a range of 0.33 to 0.58, and more preferably 0.38 to 0.48.

  As mentioned above, according to the present Example, the favorable result was obtained by making secondary particle radius into 105 nm-200 nm. Furthermore, the more preferable result was obtained by setting it as the range of 105 nm-135 nm. Moreover, when the secondary particle radius was 105 nm to 200 nm, good results were obtained by setting the value of the ionomer / carbon mass ratio in the range of 0.65 to 1.35. Furthermore, more preferable results were obtained when the secondary particle radius was in the range of 105 nm to 135 nm and the ionomer / carbon mass ratio value was 0.95 to 1.25. As for the porosity, good results were obtained within the range of 0.33 to 0.58, and more preferable results were obtained when the rate was 0.38 to 0.48.

  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 ... Membrane electrode gas diffusion layer assembly 20 ... Membrane electrode assembly 100 ... Electrolyte membrane 110 ... Carbon 115 ... Platinum 120 ... Secondary particle 130 ... Ionomer 131 ... Ionomer 140 ... Water film 150 ... Void 300 ... Gas diffusion layer

Claims (4)

A fuel cell,
An electrolyte membrane;
A catalyst layer formed on both surfaces of the electrolyte membrane;
With
The catalyst layer is
Secondary particles formed by collecting a plurality of primary particles of carbon carrying a platinum catalyst;
An ionomer that penetrates into the interior of the secondary particles and covers the exterior of the secondary particles,
Radius of the secondary particles is state, and are within the scope of 105Nm～200nm,
Wherein the ratio of the mass I of the ionomer in the catalyst layer and the mass C of the carbon (I / C) is, Ru der 0.95 to 1.35, the fuel cell. The fuel cell according to claim 1 , wherein
The fuel cell whose porosity which is the ratio which the said secondary particle and the said ionomer in the said catalyst layer do not occupy is 0.33-0.58. The fuel cell according to claim 1 , wherein
The secondary particle radius is from 105 nm to 135 nm,
The fuel cell, wherein a ratio (I / C) of a mass I of the ionomer in the catalyst layer to a mass C of the carbon is 0.95 to 1.25. The fuel cell according to claim 3 , wherein
The fuel cell whose porosity which is the ratio which the said secondary particle and the said ionomer in the said catalyst layer do not occupy is 0.38-0.48.

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