JPH10334922A - Solid high polymer fuel cell and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-performance solid high polymer fuel cell by arranging a hydrogen electrode and an oxygen electrode made of a gas diffusion layer and a catalyst layer across an electrolyte film made of a solid high polymer material, and containing a proton shift acceleration power generation initial stage characteristic increasing agent at least in the catalyst layer on the oxygen electrode side. SOLUTION: An electrolyte film 1 made of a solid high polymer material is pinched from both faces by a hydrogen electrode 2 and an oxygen electrode 3 laminated with a gas diffusion layer and a catalyst layer on the catalyst layer side respectively, collectors 4 having gas feed grooves 4a are arranged on the outer faces, and gas seal bodies 5 are provided and sealed to obtain a solid high polymer fuel cell. At least a catalyst layer on the oxygen electrode side contains a power generation initial stage characteristic increasing agent which accelerates the proton shift in it and increasing the power generation initial stage characteristic or a water holding agent capable of holding moisture of 1-10 mg/cm<2> . Sulfuric acid, phosphoric acid, or their compounds are preferably used for increasing an agent or water-holding agent, and at least the oxygen electrode 3 can be impregnated and contained with it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell and a method for manufacturing the same, and more particularly, to a polymer electrolyte hydrogen-oxygen fuel cell.

[0002]

2. Description of the Related Art A typical example of a conventional polymer electrolyte fuel cell is a hydrogen-oxygen fuel cell. This fuel cell is composed of two current collectors and an electrolyte membrane made of a solid polymer material. (Hereinafter, referred to as a solid polymer electrolyte membrane or an electrolyte membrane), two electrodes sandwiching the electrolyte membrane, and means for supplying hydrogen and oxygen as fuel. Both electrodes are a catalyst, a carrier supporting the catalyst, a proton conductor made of the same solid polymer material as the electrolyte membrane,
And a binder for solidifying them. And
At the two electrodes, a hydrogen electrode and an oxygen electrode, an electrochemical reaction represented by the following chemical formula is performed.

[0003] That is, in the hydrogen electrode, hydrogen molecules are ionized from hydrogen gas supplied to the hydrogen electrode to generate protons.
(Hydrogen ions H ⁺ ) and emit electrons.
^{_{H 2 ⇒ 2H + + 2e -}} ( Formula 1) protons is conducted through the gas diffusion layer and the catalyst layer of the hydrogen electrode side, to reach the electrolyte membrane, further, by moving the electrolyte membrane,
Move to the opposite oxygen electrode side. On the other hand, the emitted electrons are
Move to oxygen electrode through external circuit.
In the catalyst layer in the oxygen electrode, the oxygen gas supplied to the oxygen electrode, the internally transferred protons, and the externally transferred electrons react as shown in the following formula to obtain (1/2) O ₂ + 2H ⁺ + 2e ^−. ⇒ H ₂ O (Chemical formula 2) Finally, water is generated.

[0004] The reaction process of the above fuel cell mainly comprises the following four steps. That is, (A) diffusion of hydrogen and oxygen to the catalyst surface, (B) reaction in the catalyst layer (catalyst surface) in the hydrogen electrode and oxygen electrode, (C) conduction of protons inside both electrodes and inside the electrolyte membrane, and (D) Water release. It has been found that the degree of diffusion of the fuel gas and the degree of the reaction rate at each stage greatly affect the battery output characteristics. Japanese Patent Application Laid-Open No. Sho 60-35472 discloses a technique that employs a corrugated current collector for efficiently supplying and diffusing fuel to the catalyst surface in the step (A). Also, JP-A-3-102774 and JP-A-2-102.
86071 proposes to use a carbon plate having rectangular grooves. These corrugated current collectors or carbon plates having rectangular grooves are brought into contact with the electrodes to create a space on the contact surface, and fuel is diffused through the space to the electrode surface to produce a certain amount of output.

Usually, the above-mentioned structure is employed in a polymer electrolyte fuel cell, and protons passing through the electrolyte membrane are subjected to the above formula (2) at the interface between the electrolyte membrane and the oxygen electrode. Then, water is generated at the oxygen electrode interface. The generated water makes it easy for the protons to reach the active components inside the oxygen electrode catalyst layer.

[0006]

However, in the above prior art, even if the proton conductor is sufficiently present in the catalyst layer, the water content in the initial stage of power generation in the oxygen electrode (catalyst layer) becomes a bottleneck, There is a problem to be solved in that the battery performance does not appear in the early stage of power generation. Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a high-performance polymer electrolyte fuel cell and a method for manufacturing the polymer electrolyte fuel cell.

[0007]

A feature of the polymer electrolyte fuel cell according to the present invention that achieves the above object is that each of the polymer electrolyte fuel cells comprises an electrolyte membrane made of a solid polymer material, a gas diffusion layer and a catalyst layer. In a polymer electrolyte fuel cell including a hydrogen electrode and an oxygen electrode sandwiching the electrolyte membrane on the catalyst layer side, and the respective current collectors, at least the catalyst layer on the oxygen electrode side includes the catalyst layer The present invention is characterized by containing a power generation initial characteristic improving agent which promotes proton transfer in the inside and increases power generation initial characteristics. Another feature is that at least the catalyst layer on the oxygen electrode side contains a water retention agent capable of holding a water content in the range of 1 to 10 (mg / cm ² ).

On the other hand, a method for producing a polymer electrolyte fuel cell according to the present invention, which achieves the object, comprises a hydrogen electrode and an oxygen electrode formed by laminating a gas diffusion layer and a catalyst layer on the respective catalyst layer sides. A method for manufacturing a polymer electrolyte fuel cell manufactured by sandwiching an electrolyte membrane made of a solid polymer material, wherein at least the oxygen electrode promotes proton transfer in the catalyst layer to increase initial power generation characteristics. It is impregnated with a raising agent or a water retention agent capable of holding a water content in the range of 1 to 10 (mg / cm ² ).

According to the present invention, since a predetermined amount of water for promoting proton transfer in the early stage of power generation is contained in the catalyst layer in advance, shortage of proton transfer in the early stage of power generation due to shortage of water is avoided, and the amount of water is increased from the initial stage of power generation. High performance battery characteristics can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing a polymer electrolyte fuel cell according to one embodiment of the present invention. 1 shows a cross section of a basic battery structure. FIG.
It is an enlarged view of the electrolyte membrane and each electrode part of FIG. Figure 1
This will be described with reference to FIG. In the figure, a polymer electrolyte fuel cell according to the present embodiment has an electrolyte membrane 1 made of a solid polymer material, and a hydrogen electrode 2 and an oxygen electrode 3 as two electrodes provided so as to sandwich the electrolyte membrane 1 from both sides. And a stacked body of the two current collectors 4 disposed outside the respective electrodes and the gas seal body 5. Each of the current collectors 4 has a plurality of gas supply grooves 4a, and a hydrogen gas and an oxygen gas corresponding to each electrode are supplied to the gas supply grooves 4a. Further, the current collectors 4 sandwiching the electrolyte membrane 1, the hydrogen electrode 2 and the oxygen electrode 3 are in contact with each other at their ends, and a gas seal body 5 is provided at the corresponding contact portion to prevent leakage of each gas. It is a configuration that prevents it.

FIG. 2 shows a stacked arrangement relationship of the hydrogen electrode 2, the electrolyte membrane 1, and the oxygen electrode 3 in this embodiment. The hydrogen electrode 2 includes a catalyst layer 6 on the hydrogen electrode side and a gas diffusion layer 7 (acting as an electron conductor), and the oxygen electrode 3 includes a catalyst layer 8 on the oxygen electrode side and a gas diffusion layer 9 (electron conductor). Act as). The gas diffusion layers 7 and 9 can be obtained, for example, by molding and sintering carbon fibers. Each of the catalyst layers 6 and 8 includes an active component that functions as a catalyst that promotes a reaction with the supplied hydrogen gas and oxygen gas, a carrier that supports the active component, and a proton conductor that conducts protons. , A power generation initial property improving agent or a water retention agent, which will be described later, and a binder for solidifying these. Further, the gas diffusion layer 7, the catalyst layer 6, the electrolyte membrane 1, the catalyst layer 8, and the gas diffusion 9 are laminated and integrated.

That is, the polymer electrolyte fuel cell according to the present invention is characterized in that the catalyst layer of the oxygen electrode or both of the catalyst layers of the oxygen electrode and the hydrogen electrode contain an agent for increasing initial power generation properties or a water retention agent. Is to be. In other words, since the catalyst layer 6 on the hydrogen electrode 2 side and the catalyst layer 8 on the oxygen electrode 3 side of the present embodiment contain a later-described power generation initial property improving agent or a water retention agent, proton transfer at the hydrogen electrode 2 is performed. Is promoted,
By facilitating the transfer of protons from the electrolyte membrane 1 at the oxygen electrode 3 and effectively using the catalytic function of the active component of the oxygen electrode 3, the proton transfer at both electrodes is improved, and the initial power generation characteristics are improved. This aims to stabilize battery performance.

Next, the content of the power generation initial property improving agent and the water retention agent according to the present invention will be described. In addition, in this specification, the power generation initial characteristic increasing agent and the water retention agent are referred to as a water retention agent and the like. First,
With respect to the method of containing the water retention agent and the like, a method of adsorbing (impregnating) the water retention agent and the like into the catalyst layer is effective (that is, the current manufacturing process can be used as it is and effective in terms of productivity). Points to consider in this adsorption method are the time for adsorption to the catalyst layer,
Examples include the concentration of the water retention agent and the like, and the strength of the water repellency of the catalyst layer. Among these, a simple adsorption method is one in which the concentration of the binder (water repellency) and the concentration of the water retention agent and the like are kept constant and adjusted only by the adsorption time to perform the adsorption. Further, from the viewpoint of productivity, the material such as a water retention agent is the same material as the electrolyte membrane,
For example, it is effective that the material of the water retention agent and the like and the electrolyte membrane also serve as the material by using sulfuric acid or a sulfate compound having a sulfonic acid group.

The concentration of the water retention agent is 1M (mol) to 3M.
(Mol) range is good, the content of water such as a water retention agent is 1 to
A range of 10 (mg / cm ² ) is good. Preferably 3 for practical reasons
It was found that the range of ６6 (mg / cm ² ) was good. That is, 1 (m
g / cm ² ) or less, the power generation initial characteristics are not improved, and if it exceeds 10 (mg / cm ² ), the pores of the catalyst layer are closed, and the characteristics are not improved. . And 3 (m
This is because if it is at least g / cm ² ), the initial power generation characteristics will surely be improved, and if it is at most 6 (mg / cm ² ), anxiety of pore blockage will be avoided. Since the catalyst layer of the prior art has a high water repellency, its water content is small, and the content exceeding 1 (mg / cm ² ) has not been observed at present.

Next, the relationship between the inclusion of a water retention agent or the like in the catalyst layer and the water repellency of the catalyst layer will be described. The method of controlling the strength of water repellency includes a method of changing the absolute amount of the binder having water repellency to be added to the catalyst layer and a method of changing the mixing ratio of each binder having different strength of water repellency. . The former is characterized in that the water repellency can be controlled without changing the pore structure of the catalyst layer. The latter is characterized in that it is simple and practical although it slightly changes the pore structure of the catalyst layer. As the water-repellent binder, polytetrafluoroethylene (hereinafter, PTFE)
), Fluorinated graphite represented by (CF) n, or a mixture thereof.

However, the water-repellent binder cannot be contained in a large amount because it is an electrical resistor. For example, when the water-repellent binder is PTFE, the amount is 10 to 40 (% by weight), preferably 10 to 40% by weight with respect to the total amount of the respective catalyst layers of the hydrogen electrode and the oxygen electrode.
30 (% by weight).
(% By weight), preferably 20 to 40 (% by weight). It has been found that the amount of the water-repellent binder at the hydrogen electrode is desirably greater than the amount of the water-repellent binder at the oxygen electrode by at least 10% by weight. It is also assumed that other water-repellent binders have the same range as above.

Incidentally, the ion exchange group of the proton conductor is hydrophilic, but the other parts are not necessarily hydrophilic, and differ depending on the selected material. Therefore, the effect of adding the proton conductor is not so great as to surpass the binder. Moreover, as the amount of addition increases, the hydrophilic groups increase and the hydrophilicity surely increases. However, since the proton conductor exists as a membrane inside the catalyst layer, adding a large amount of the proton conductor closes the catalyst pores. There is a risk of doing so. Therefore, much cannot be added, and it is necessary to appropriately select the material of the proton conductor, and it is difficult to control the water repellency by the amount of the proton conductor. The proton conductor, which is added to the catalyst layer to increase the effective reaction surface area, is exposed to oxidizing and reducing atmospheres, so that it is used under severe operating conditions. It can be said that an acid resin or the like is particularly preferable.

On the other hand, a coating method is suitable for producing an electrode. That is, an active component as a catalyst, carbon as a carrier supporting the active component, a proton conductor,
A water-repellent binder is mixed in advance to prepare a coating agent for the catalyst layer, and the catalyst layer is applied to the gas diffusion layer, and the gas diffusion layer and the catalyst layer are laminated to form a hydrogen electrode and an oxygen electrode, respectively. This is a method for producing Therefore, when the electrode according to the present invention is produced by diverting this method, the water repellency of the electrode is arbitrarily selected by adjusting the amount of the water-repellent binder as described above, Is determined according to the strength of the water repellency of the electrode, which depends on the amount of the water repellent binder.

In other words, when it is desired to increase the content of the water retention agent or the like (that is, the impregnation amount), the addition amount of the binder is reduced to weaken the water repellency of the catalyst layer. On the other hand, when it is desired to reduce the content of the water retention agent or the like, the amount of the binder added is increased to increase the water repellency of the catalyst layer. That is, it can be said that the content of the water retention agent and the like can be adjusted arbitrarily by the addition amount of the water-repellent binder, and the current manufacturing process can be used as it is. Hereinafter, a few examples of typical ones studied by the inventors will be shown, and the details of the present invention will be described. However, the embodiments are not limited to only these. That is, the present invention is widely applied to configurations of the disclosed technology and the like.

[0020]

Embodiments Hereinafter, specific embodiments will be described. [Example 1] The catalyst layer and gas diffusion layer of the hydrogen electrode and the oxygen electrode of Example 1 were manufactured as follows, using substantially the same structure and material for both electrodes. That is, the catalyst layer was formed of platinum as an active ingredient, carbon powder as a carrier supporting the platinum, and a perfluorosulfonic acid-based cation exchange resin (Nafion liquid, manufactured by Aldrich Chemical Co.) as a proton conductor. An aqueous suspension of PTFE as a water-repellent binder was sufficiently kneaded and prepared to prepare a catalyst layer paste. The gas diffusion layer has a pore diameter of about 100 (μm) and a thickness of 1
An aqueous suspension of PTFE was applied to 00 (μm) carbon paper at a PTFE application amount of 12 (mg / cm ² ),
(° C.).

Then, the above-mentioned catalyst layer paste was applied to the gas diffusion layer, laminated, and dried at 80 (° C.) to produce a two-electrode substrate. Then, with respect to the total of those two electrode substrate (electrode area 9cm ^2), an aqueous solution of sulfuric acid 1M (mol), 5 impregnated at a rate of (mg / cm ^2), i.e., the catalyst layer water retention agent To form a hydrogen electrode and an oxygen electrode. As described above, in this example, the active component, the carrier, the proton conductor, and the binder were kneaded and prepared to form a paste-like catalyst layer once, and then the carbon as a gas diffusion layer was formed. The catalyst layer is applied to paper or the like to form a solidified electrode substrate, and the electrode substrate of the gas diffusion layer and the catalyst layer is immersed in sulfuric acid, and a water retention agent, etc. Agent). In other words, it can be said that this is a “method of indirectly containing water in the catalyst layer” in which the catalyst layer (mainly the proton conductor) retains water. The above method can be said to be an effective method because the current production process can be used as it is.

That is, the method of manufacturing a polymer electrolyte fuel cell according to the present invention is characterized in that a hydrogen diffusion layer and a catalyst layer are formed on a hydrogen electrode and an oxygen electrode, respectively. In a method for manufacturing a polymer electrolyte fuel cell manufactured by sandwiching an electrolyte membrane made of a polymer material, at least an oxygen electrode, a power generation initial property improving agent that promotes proton transfer in a catalyst layer and increases power generation initial properties, or 1 to 10 (mg /
cm ² ) in order to impregnate a water retention agent capable of retaining a water content in the range.

The specific composition of the hydrogen electrode is platinum 0.3 (mg / cm
² ), carbon powder 0.97 (mg / cm ² ), proton conductor 30
(% By weight) and PTFE 30 (% by weight). The composition of the oxygen electrode was platinum 0.3 (mg / cm ² ), carbon powder 0.97 (mg / cm ² ), proton conductor 20 (% by weight), and PTFE 20 (% by weight).
In addition, an electrolyte membrane made of a solid polymer material includes Du Pon
Nafion 117 manufactured by t company was used. Then, the electrolyte membrane is disposed so as to be sandwiched between the catalyst layers of the hydrogen electrode and the oxygen electrode, and hot pressing is performed, that is, at a pressure of 100 (kg / cm ² ), at a temperature of 120 (° C.), and at 15 ° C. A single cell was created by pressing and gluing for a minute. On the other hand, for comparison with this example, both the hydrogen electrode and the oxygen electrode were platinum 0.3 (mg / cm ² ).
And carbon powder 0.97 (mg / cm ² ) and proton conductor 2
0 (wt%) and the same composition of PTFE 20 (wt%), and both electrodes were made without impregnation with sulfuric acid, that is, without containing a water retention agent, etc. It was created.

Each single cell prepared as described above is incorporated as a battery, and the current density-voltage characteristics of each
The measurement was performed under the conditions of 1 ° C. and 1 atm. The result is shown in FIG.
FIG. 3 is a diagram showing the relationship between the elapsed time and the voltage of the fuel cell according to one embodiment of the present invention. The initial performance of the battery using the electrode of the conventional example shown in the figure shows an initial voltage of 0.52 V (average) at a current density of 500 (mA / cm ² ). On the other hand, in the initial performance of the battery using the electrode of this example, it was found that the initial voltage was 0.62 V (average) at a current density of 500 (mA / cm ² ). As described above, the initial power generation characteristics of the polymer electrolyte fuel cell can be improved by adopting a configuration as in this embodiment in which the oxygen electrode and the hydrogen electrode contain a water retention agent or the like in advance.

[Embodiment 2] The construction of Embodiment 2 is almost the same as that of Embodiment 1, except that the amount of impregnation with a water retention agent and the like is different. The substrate was impregnated with a 3M (molar) sulfuric acid solution 5 (mg / cm ² ). The relationship between the elapsed time indicating the battery performance of Example 2 and the voltage was almost the same as the result of Example 1 shown in FIG. In the case of the second embodiment, the initial performance of the battery is as follows.
The characteristic that the initial voltage at the time of cm ² ) exceeded 0.60 V was exhibited. Even when the concentration of the water retention agent or the like was increased as in Example 2, the battery performance could be significantly improved by impregnating the oxygen electrode and the hydrogen electrode in advance.

[Embodiment 3] The configuration of Embodiment 3 is such that the porosity of the oxygen electrode is higher than that of the hydrogen electrode. That is, electrodes having different porosity were produced in the respective catalyst layers between the gas diffusion layers of the hydrogen electrode and the oxygen electrode and the electrolyte membrane. In addition, the catalyst layer of both electrodes was made into two layers, respectively.
On the other hand, the paste of the first layer on the gas diffusion layer side of the catalyst layer of the hydrogen electrode supports a platinum catalyst on a carbon carrier having an average particle size of 3 (μm), and has a 30 (wt%) ion exchange resin. (Perfluorosulfonic acid resin) and 40% by weight of PTFE
Was obtained by kneading. The paste of the second layer on the electrolyte membrane side of the catalyst layer of the hydrogen electrode was the same as in Example 1. Then, these pastes were applied to two layers of carbon paper as a gas diffusion layer, and dried at 80 (° C.) to produce a hydrogen electrode.

On the other hand, the paste of the first layer on the side of the gas diffusion layer of the catalyst layer of the oxygen electrode supports a platinum catalyst on a carbon carrier having an average particle diameter of 6 (μm), and comprises 20% by weight. Ion exchange resin (perfluorosulfonic acid resin) and 30 (% by weight)
Of PTFE was kneaded. The paste of the second layer on the electrolyte membrane side of the catalyst layer of the oxygen electrode was the same as in Example 1. Then, paste these pastes onto carbon paper for 2 hours.
It was applied to the layer and dried at 80 (° C.) to produce an oxygen electrode. Other than the above configuration and the subsequent manufacturing steps are the same as those in the first embodiment.

FIG. 4 is a diagram showing the relationship between current density and voltage of a fuel cell according to Embodiment 3 of the present invention. In the figure,
Compared with the current density of 500 (mA / cm ² ), the battery voltage of the conventional example was about 0.60 V, whereas the battery performance of the present example was about 0.65 V. . In addition, it was also found that the battery performance of this example was superior to the conventional example in terms of current density over a wide range. In other words, it can be said that an output with a high current density can be obtained at the same voltage. With the configuration in which the porosity of the oxygen electrode is higher than that of the hydrogen electrode, battery performance can be improved. As described above, the polymer electrolyte fuel cell according to the present invention can activate the oxygen electrode and the hydrogen electrode more than the conventional one, and as a result, it is possible to greatly improve the cell output.

The above is summarized as follows. That is,
The polymer electrolyte fuel cell according to the present invention supplies a polymer electrolyte membrane and a hydrogen electrode and an oxygen electrode which are electrodes provided so as to sandwich the electrolyte membrane, and supplies hydrogen gas and oxygen gas to the hydrogen electrode and the oxygen electrode, respectively. The electrode comprises a catalyst layer comprising a carbon support, an active component carried thereon, a proton conductor, and a water-repellent binder, and an electron outside the catalyst layer serving also as a gas diffusion layer. In a polymer electrolyte fuel cell comprising a conductor, a water retention agent or the like is previously added to the catalyst layer to make it wet.

According to the present invention, the cell performance of the polymer electrolyte fuel cell can be improved by controlling the water retention agent and the like of the catalyst layer of each electrode under certain specific conditions. Furthermore, according to the present invention, since the content of the water retention agent and the like differs depending on the water repellency of the electrode, when the hydrogen electrode side has a higher water repellency than the oxygen electrode side, the oxygen electrode is more water repellent than the hydrogen electrode. Increasing the content of the like, and, in both the oxygen electrode and the hydrogen electrode, if the water retention agent and the like are sufficient, the water retention agent and the like can also serve as the proton conductor, so that the proton conductor may be omitted. I can say.

Further, the catalyst layers of both the hydrogen electrode and the oxygen electrode of the present embodiment comprise a carbon carrier, an active component (catalyst) carried on the carbon carrier, a proton conductor, and a water-repellent binder. The active component is preferably platinum or a platinum group metal, for example, rhodium, ruthenium, palladium and iridium, and the material of the proton conductor may be the same solid polymer electrolyte as the electrolyte membrane or may be different. .
As the water-repellent binder, a fluorine resin such as polytetrafluoroethylene, fluorinated graphite represented by a chemical molecular formula (CF) n, or a mixture thereof is effective. It can be said that sulfuric acid and a sulfate compound having a sulfonic acid group, which can also serve as a material for the electrolyte membrane, are good as the water retention agent from the viewpoint of productivity and the like. The electrolyte membrane applied to the present invention is generally in the form of a membrane, and its material is generally used, such as solid polymer electrolyte resin such as perfluorosulfonic acid resin and perfluorocarboxylic acid resin. Are preferred.

The supplementary explanation is as follows. In a conventional polymer electrolyte fuel cell, water is added to the hydrogen electrode in order to prevent the electrolyte membrane from drying and to promote the transfer of protons. As for the oxygen electrode, the catalyst layer is water-repellent, but is humidified. Even when humidified, the catalyst layer of the prior art has a high water repellency, and therefore has a low water content, and no water content exceeding 1 (mg / cm ² ) has been observed at present. That is, both the hydrogen electrode and the oxygen electrode must have a certain amount of water to promote the transfer of protons necessary for the electrode reaction in the catalyst layer. However, the diffusion of hydrogen gas on the hydrogen electrode side promotes the association between protons and moisture, so that the water dependence on the oxygen electrode side is smaller than that on the oxygen electrode side. The water retention amount becomes a bottleneck, and the movement of protons is impaired, so that the battery performance exhibiting high initial power generation characteristics cannot be exhibited.

On the other hand, in the polymer electrolyte fuel cell according to the present invention, proton transfer in the catalyst layer is promoted in advance in the catalyst layer of the oxygen electrode or both of the catalyst layers of the hydrogen electrode and the oxygen electrode to improve the initial power generation characteristics. By containing a water retention agent or the like capable of holding a predetermined amount of water for raising (that is, by containing a power generation initial property increasing agent that promotes proton transfer in the catalyst layer and raises power generation initial characteristics), This facilitates the transfer of protons due to a shortage of water in the early stage of operation, and achieves the desired battery performance. And after various investigations, the water content of the water retention agent that retains water is 1 to
It has been found that the range is preferably 10 (mg / cm ² ).

The requirements for the power generation initial property enhancer are as follows: (1) Dissociation of protons (hydrogen ions H ⁺ );
(2) not to attack active ingredients (platinum, ruthenium, etc.),
(3) Do not block the pores in the catalyst layer (they do not exist as a solid), and include sulfuric acid or a sulfuric acid compound, phosphoric acid or a phosphoric acid compound. Even with acids having the same (1) and (3) functions, it can be said that hydrochloric acid is unsuitable because it attacks the active ingredient.

Further, the flexibility of the electrode absorbed with the water retention agent and the like is improved, so that the contact resistance is further reduced by disposing the electrolyte membrane and the catalyst layer more densely when the electrode is formed as an integrated electrode. , The internal resistance can be reduced. As a result, battery performance is improved. Further, the transfer of protons from the hydrogen electrode is facilitated, and the electrode performance is stabilized. That is, by previously containing a water retention agent and the like, the hydrogen electrode and the oxygen electrode also have flexibility, so that the affinity with the electrolyte membrane is improved, and the catalyst layer and the electrolyte membrane are more densely integrated, and hydrogen The transfer of protons from the electrode is facilitated, and the electrode reaction proceeds at the oxygen electrode.

As for the water retention agent, if it has the same properties as the electrolyte membrane, rather than using a simple water retention agent or the like,
Sulfonic acid compounds are preferred because they are advantageous not only in the electrode reaction but also in terms of productivity. There is an optimum range for containing a water retention agent and the like in the electrode catalyst layer, and when a large amount is contained, gas diffusivity is impaired, so that porosity contributing to the electrode reaction must be ensured. In other words, when a water retention agent or the like is contained, if the proportion of the pores in the electrode catalyst layer increases, gas diffusivity is impaired and performance is reduced, so there is a limit from itself. When the water retention agent or the like was sulfuric acid, the value was 10 (mg / cm ² ).

Regarding the porosity, hydrogen supplied to the hydrogen electrode has a small molecular size and is well diffused. Therefore, even if the porosity is lower than that of the oxygen electrode, the gas can be easily diffused and the gas supply becomes poor. Never. Since the oxygen electrode has low oxygen diffusivity and low reactivity, it is important to increase the porosity and supply a sufficient amount. However, the porosity of the electrode has an appropriate range. If the porosity is too low, gas diffusivity is reduced, and the electrode reaction does not proceed. On the other hand, if the porosity is too high, the electric resistance of the electrode catalyst layer increases, and further, the catalyst layer is easily dried by the supplied gas, and it becomes difficult to maintain an effective area of the reaction field, and the electrode performance is not exhibited. Therefore,
The porosity has an appropriate range. According to the results of the study, the hydrogen electrode has a good porosity of 35 to 60 (%) and the oxygen electrode has a good porosity of about 40 to 65 (%). Rate 5 (%)
A higher value is more effective in water balance between the two electrodes, but a value of 10% or more is suitable for improving electrode performance.

[0038]

According to the present invention, the activity of the air (oxygen) electrode of the solid polymer electrolyte type hydrogen-air (oxygen) fuel cell can be greatly improved as compared with the conventional one, so that the cell performance is dramatically improved. To improve. Therefore, there is an effect that a polymer electrolyte fuel cell having high performance in the early stage of power generation can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a polymer electrolyte fuel cell according to one embodiment of the present invention.

FIG. 2 is an enlarged view of an electrolyte membrane and respective electrode portions of FIG.

FIG. 3 is a diagram showing a relationship between elapsed time and voltage of a fuel cell according to one embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between current density and voltage of a fuel cell according to Embodiment 3 of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... electrolyte membrane, 2 ... hydrogen electrode, 3 ... oxygen electrode, 4 ... current collector,
4a: gas supply groove, 5: gas seal, 6, 8: catalyst layer, 7, 9: gas diffusion layer.

Claims (5)

[Claims] 1. An electrolyte membrane made of a solid polymer material, a hydrogen electrode and an oxygen electrode which are formed by laminating a gas diffusion layer and a catalyst layer and sandwich the electrolyte membrane on each of the catalyst layer sides, And a current collector, wherein at least the catalyst layer on the oxygen electrode side contains a power generation initial property improving agent that promotes proton transfer in the catalyst layer and increases power generation initial properties. Characteristic polymer electrolyte fuel cell. 2. An electrolyte membrane made of a solid polymer material, a hydrogen electrode and an oxygen electrode which are formed by laminating a gas diffusion layer and a catalyst layer, and sandwich the electrolyte membrane on each catalyst layer side, And a current collector, wherein at least the catalyst layer on the oxygen electrode side is 1 to 10 (mg /
A polymer electrolyte fuel cell comprising a water retention agent capable of holding a water content in the range of cm ² ). 3. The polymer electrolyte fuel cell according to claim 1, wherein the power generation initial characteristic increasing agent or the water retention agent is sulfuric acid, a sulfuric acid compound, phosphoric acid, or a phosphoric acid compound. 4. A solid polymer produced by sandwiching an electrolyte membrane made of a solid polymer material on each of the catalyst layer side of a hydrogen electrode and an oxygen electrode formed by laminating a gas diffusion layer and a catalyst layer, respectively. In the method for producing a fuel cell, at least to the oxygen electrode, a power generation initial property enhancer that promotes proton transfer in the catalyst layer and increases power generation initial properties, or 1 to 10 (mg / cm
² ) A method for producing a polymer electrolyte fuel cell, characterized by impregnating a water retention agent capable of holding a water content in the range of ² ). 5. The solid polymer type according to claim 4, wherein the impregnation amount of the power generation initial characteristic increasing agent or the water retention agent is adjusted according to the water repellency of the catalyst layer. A method for manufacturing a fuel cell.