JP2007188768A - Polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte fuel cell excelling in durability, and capable of exerting sufficient power generation performance by keeping an excellent gas diffusion property for electrode catalyst layers even in a high humidification operation. <P>SOLUTION: This polymer electrolyte fuel cell is provided, on both sides of an electrolyte membrane 10 made of a solid polymer, with the electrode catalyst layers 12 and 22 formed with an electrode catalyst with catalyst particles supported to a carbon support, and a proton conducting electrolyte, and also provided, between the electrolyte membrane 10 and at least one of the electrode catalyst layers 12 and 22, with water retention layers 11 and 22 each containing a carbon support and a proton conducting electrolyte, and having water retentivity higher than those of the electrode catalyst layers 12 and 22. Power generation performance and durability are improved by smoothly moving water in the electrode catalyst layers to the water retention layers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid polymer fuel cell that uses an electrolyte membrane made of a solid polymer and obtains electric energy by an electrochemical reaction.

  A polymer electrolyte fuel cell comprises a single cell as a power generation element with an electrolyte membrane made of a solid polymer sandwiched between a pair of catalyst electrode layers, and the fuel electrode (anode) of the pair of electrodes contains hydrogen And an oxidizing gas (air) containing oxygen to the air electrode (cathode) of the pair of electrodes, and an electrochemical reaction of the following formula on the surface of each electrode on the electrolyte layer side It is made to take out electric energy from an electrode.

Fuel electrode reaction: H2 → 2H ++ 2e− (1)
Air electrode reaction: 2H + + 2e− + (1/2) O 2 → H 2 O (2)

  For supplying fuel gas to the fuel electrode, a method of directly supplying a fuel gas that is pure hydrogen from a hydrogen storage device, or a method of reforming a fuel containing hydrogen and supplying it as a fuel gas is known. . The hydrogen storage device includes a high-pressure gas tank, a liquefied hydrogen tank, a hydrogen storage alloy tank, and the like, and the fuel containing hydrogen includes natural gas, methanol, gasoline, and the like. On the other hand, air is generally used as the oxidizing gas supplied to the air electrode.

  Furthermore, in the polymer electrolyte fuel cell, it is necessary to keep the electrolyte membrane in a wet state, and in order to fully extract the performance of the electrolyte membrane and improve the power generation efficiency, it is necessary to keep the moisture content of the electrolyte membrane optimal. There is. For this reason, in the polymer electrolyte fuel cell, the fuel gas and the oxidizing gas to be introduced are sufficiently humidified in advance.

  The polymer electrolyte fuel cell described above has been researched and developed as a power source for automobiles and stationary use. In order to efficiently extract the electric energy generated at the fuel electrode and the oxygen electrode over a long period of time, low humidification is required. In addition to exhibiting stable power generation performance in the range from high to high humidity, it is necessary to make it excellent in durability.

In a conventional polymer electrolyte fuel cell, an ion in the electrode catalyst layer is formed by disposing a layer containing an inorganic compound having a water contact angle of 10 degrees or less between the electrolyte membrane and the electrode catalyst layer. Prevents deterioration of properties due to drying of exchange resin, makes it difficult for output voltage to drop, especially during low humidification operation and non-humidification operation of oxidizing gas, and enables high battery output to be obtained stably over a long period of time ( Patent Document 1) and by placing a water retention layer between the electrode catalyst layer and the gas diffusion layer, the gas diffusion layer has high water retention, and performance degradation is suppressed even in a fuel shortage situation. (Patent Document 2) has been proposed.
JP 2003-288915 A JP 2004-146305 A

  However, in the conventional solid oxide fuel cell as described above, the one described in Patent Document 1 has a water contact angle of 10 degrees as a water retention layer disposed between the electrolyte membrane and the electrode catalyst layer. Although the layer containing the inorganic compound as described below is used, there is a problem that the durability of the material constituting the catalyst layer is not sufficient. On the other hand, the material described in Patent Document 2 is particularly highly humidified. During operation, there is a problem in that the gas diffusion path to the electrode catalyst layer is blocked by the water retention layer, resulting in insufficient power generation performance, and it has been a problem to solve these problems.

  The present invention has been made paying attention to the above-mentioned conventional problems, and is excellent in durability and maintains good gas diffusibility with respect to the electrode catalyst layer under all operating conditions from low humidification to high humidification. An object of the present invention is to provide a polymer electrolyte fuel cell capable of exhibiting sufficient power generation performance.

  The solid polymer fuel cell of the present invention comprises an electrode catalyst having catalyst particles supported on a carbon carrier, which is a conductive carrier, and an electrode catalyst layer formed of a proton conductive electrolyte on both sides of an electrolyte membrane made of a solid polymer. I have. In addition, a water retention layer that includes a carbon carrier and a proton conductive electrolyte and has higher water retention than the electrode catalyst layer is provided between the electrolyte membrane and at least one electrode catalyst layer of the fuel electrode and the air electrode. The above configuration is a means for solving the conventional problems.

  In the polymer electrolyte fuel cell of the present invention, a water retention layer containing a carbon support and a proton conductive electrolyte and having higher water retention than the electrode catalyst layer is disposed between the electrolyte membrane and the electrode catalyst layer. The water in the catalyst layer moves smoothly to the water retention layer, so that the catalyst elution resistance of the electrode catalyst layer, the corrosion resistance of the carbon support and the good gas diffusibility to the electrode catalyst layer are obtained. In all operating conditions leading to humidification, stable power generation performance can be exhibited over a long period of time, and excellent durability can be obtained.

  FIG. 1 is a cross-sectional view illustrating an embodiment of a solid polymer fuel cell of the present invention. The illustrated solid electrolyte fuel cell includes an anode side (fuel electrode side) water retention layer 11, an anode side electrode catalyst layer 12, an anode side gas diffusion layer 13, and a fuel on one surface of an electrolyte membrane 10 made of a solid polymer. Separator plates 15 forming the gas flow path 14 are sequentially stacked.

  Further, the solid oxide fuel cell has a cathode side (air electrode side) water retention layer 21, a cathode side electrode catalyst layer 22, a cathode side gas diffusion layer 23, and an oxidizing gas flow path 24 on the other surface of the electrolyte membrane 10. The separator plates 25 to be formed are laminated in order, and the membrane electrode assembly 1 is constituted by the electrolyte membrane 10, the water retention layers 11, 21, the electrode catalyst layers 12, 22, and the gas diffusion layers 13.23. ing.

  The electrode catalyst layers 12 and 22 include an electrode catalyst in which catalyst particles are supported on a conductive carrier and a proton conductive electrolyte, and a carbon carrier is used as the conductive carrier. The water retention layers 11 and 21 include a carbon carrier and a proton conductive electrolyte, and have higher water retention than the electrode catalyst layers 12 and 22.

  The gas diffusion layers 13 and 23 include base material layers 13a and 23a on the separator plates 15 and 25 side, and carbon particle layers 13b and 23b on the electrode catalyst layers 12 and 22 side. These gas diffusion layers 13 and 23 are mainly conductive porous bodies made of, for example, carbon paper, carbon cloth, carbon non-woven fabric, and the like, and supply fuel gas and oxidizing gas to the electrode catalyst layers 12 and 22 by diffusion. In addition to having a function to achieve this, it desirably has water repellency and is also used as a current collector.

  Separator plates 15 and 25 are made of carbon such as dense carbon graphite or carbon plate, or made of metal such as stainless steel, and form flow paths 14 and 24 for fuel gas and oxidizing gas, and are electrically conductive by themselves. It can also be used as an external terminal by providing a suitable or appropriate energization path.

  Here, in the polymer electrolyte fuel cell, hydrogen contained in the fuel gas supplied to the fuel electrode side (anode side) is oxidized by the catalyst particles in the electrode catalyst layer 12, thereby generating protons and electrons. Protons reach the electrode catalyst layer 22 on the air electrode side (cathode side) through the proton conductive electrolyte and the electrolyte membrane 10 in the electrode catalyst layer 12.

  On the other hand, the electrons pass through the carbon carrier in the electrode catalyst layer 12, the gas diffusion layer 13, the separator plate 15 and the external circuit, and further pass through the separator plate 25 and the gas diffusion layer 23 on the air electrode side to pass through the cathode side electrode catalyst layer. 22 is reached.

  The protons and electrons that have reached the cathode-side electrode catalyst layer 22 react with oxygen contained in the oxidizing gas (air) supplied to the air electrode side to generate water. Such an electrochemical reaction enables the fuel cell to extract electricity to the outside.

  In the above solid oxide fuel cell, in order to improve the power generation performance, it is important to support the catalyst particles in the electrode catalyst layers 12 and 22 on the carbon support with good dispersibility. In order to use it, it is necessary to efficiently contact the catalyst particles and the proton conductive electrolyte.

  In order to improve the power generation performance, it is necessary to satisfactorily reach the respective electrode catalyst layers 12 and 22 with the fuel gas and the oxidizing gas supplied to the anode side and the cathode side. In order to generate water, the generated water is discharged from the cathode-side electrode catalyst layer 22 to prevent water clogging in the electrode catalyst layer 22 and the gas diffusion layer 23 and to ensure gas diffusibility to the electrode catalyst layer 22. It is important to.

  Furthermore, in the polymer electrolyte fuel cell, in order to improve the durability, not only a material having high durability is used as the material forming the electrode catalyst layers 12 and 22, but also the electrode catalyst layers 12 and 22 are used. Since the deterioration of the carbon support and the electrode catalyst forming the film occurs through the water, it is also effective and important to sufficiently discharge water from the electrode catalyst layers 12 and 22.

  Therefore, the polymer electrolyte fuel cell has a configuration in which the water retention layers 11 and 12 having high water retention containing the carbon support and the proton conductive electrolyte are disposed between the electrolyte membrane 10 and the electrode catalyst layers 12 and 22. Thus, the water in the electrode catalyst layers 12 and 22, that is, the water that causes deterioration of the gas diffusibility and the deterioration of the carbon support and the electrode catalyst is quickly moved to the water retention layers 11 and 21, in other words, the electrodes Water is quickly discharged from the electrode catalyst layers 12 and 22 without impairing the gas diffusibility, catalyst elution resistance, and carbon carrier corrosion resistance of the catalyst layers 12 and 22, thereby providing excellent power generation performance and durability. Will be obtained.

  Further, the polymer electrolyte fuel cell of the present invention, as a more preferred embodiment, the mass ratio of the carbon support and the proton conductive electrolyte in the water retention layer to the mass ratio of the carbon support and the proton conductive electrolyte in the electrode catalyst layer. Can be larger.

  As described above, by changing the composition ratio of the carbon carrier and the proton conductive electrolyte in the electrode catalyst layer and the water retention layer, the movement of water from the electrode catalyst layer to the water retention layer, that is, the discharge of water from the electrode catalyst layer is promoted. In addition, it is possible to provide a polymer electrolyte fuel cell excellent in power generation performance and durability by ensuring gas diffusibility with respect to the electrode catalyst layer and durability of the electrode catalyst layer.

  Furthermore, as a more preferred embodiment, the polymer electrolyte fuel cell of the present invention has a pore diameter in the water retention layer as compared with the pore diameter in the electrode catalyst layer (the diameter of the pores that transmit gas or water). Can be small.

  As described above, if the pore diameters in the electrode catalyst layer and the water retention layer are made different, the water moves from the larger pore diameter to the smaller one in the hydrophilic portion. Discharge of water from the electrode catalyst layer is promoted, and gas diffusibility with respect to the electrode catalyst layer and durability of the electrode catalyst layer are ensured to provide a polymer electrolyte fuel cell excellent in power generation performance and durability it can.

  Furthermore, in the polymer electrolyte fuel cell of the present invention, as a more preferred embodiment, the carbon carrier and the proton conductive electrolyte in the electrode catalyst layer, and the carbon carrier and the proton conductive electrolyte in the water retention layer are the electrode catalyst layer and the water retention layer. The proton conductive electrolyte and the electrolyte membrane in the water retention layer can be continuous at the interface between the water retention layer and the electrolyte membrane. In addition, the electrons move smoothly, and good power generation performance can be obtained.

  The proton conductive electrolyte is not particularly limited, and a known one can be used, but any member having at least high proton conductivity may be used. The proton-conducting electrolyte that can be used in this case is roughly classified into a fluorine-based electrolyte containing fluorine atoms in all or part of the polymer skeleton and a hydrocarbon-based electrolyte not containing fluorine atoms in the polymer skeleton.

  Specific examples of the fluorine-based electrolyte include perfluorocarbon sulfonic acids such as Nafion (registered trademark: manufactured by DuPont), Aciplex (registered trademark: manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark: manufactured by Asahi Glass Co., Ltd.), etc. Polymer, polytrifluorostyrene sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene copolymer, and poly A suitable example is vinylidene fluoride-perfluorocarbon sulfonic acid polymer.

  Specific examples of the hydrocarbon electrolyte include polysulfone sulfonic acid, polyaryl ether ketone sulfonic acid, polybenzimidazole alkyl sulfonic acid, polybenzimidazole alkyl phosphonic acid, polystyrene sulfonic acid, polyether ether ketone sulfonic acid, and poly A suitable example is phenylsulfonic acid.

  Since the polymer electrolyte is excellent in heat resistance and chemical stability, it preferably contains a fluorine atom. Among them, Nafion (registered trademark: manufactured by DuPont), Aciplex (registered trademark: manufactured by Asahi Kasei Co., Ltd.) Fluorine electrolytes such as Flemion (registered trademark: manufactured by Asahi Glass Co., Ltd.) are preferred.

  Further, the electrolyte membrane is not particularly limited, and examples thereof include a membrane made of an electrolyte having proton conductivity. For example, perfluorosulfonic acid membranes represented by various Nafion (registered trademark) and Flemion (registered trademark) manufactured by DuPont, ion exchange resins manufactured by Dow Chemical Company, ethylene-tetrafluoroethylene copolymer resin membranes, Fluoropolymer electrolyte membranes such as resin membranes based on trifluorostyrene, hydrocarbon resin membranes having sulfonic acid groups, and other commercially available polymer electrolyte membranes such as polytetrafluoroethylene ( A membrane in which a polymer microporous membrane made of PTFE) or polyvinylidene fluoride (PVDF) is impregnated with a liquid electrolyte such as phosphoric acid or ionic liquid, a membrane in which a porous body is filled with a polymer electrolyte, etc. May be used. The electrolyte used for the electrolyte membrane and the electrolyte used for each catalyst layer and water retention layer may be the same or different.

  Specific examples of the carbon carrier include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite, and the like. The carbon black is not particularly limited as long as it is a conventional one, but preferred examples include channel black, furnace black, thermal black, ketjen black, and acetylene black. Carbon black may be a commercially available product, such as Cabot Vulcan XC-72, Vulcan P, Black Pearls 880, Black Pearls 1100, Black Pearls 1300, Black Pearls 2000, Regal 400, Ketjen Black manufactured by Lion. EC, oil furnace black such as # 3150 and # 3250 manufactured by Mitsubishi Chemical Corporation; acetylene black such as Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd. and the like. Furthermore, from the viewpoint of corrosion resistance, a carbon support such as carbon black graphitized by heat treatment at 2000 to 3000 ° C. in an inert atmosphere may be used.

  Furthermore, in the polymer electrolyte fuel cell of the present invention, as a more preferred embodiment, the carbon support in the water retention layer may have lower corrosion resistance than the carbon support in the electrode catalyst layer.

  Here, since the carbon carrier forming the electrode catalyst layer plays an important role in power generation, it must be protected for a long time, and its deterioration is suppressed by discharging water from the electrode catalyst layer. can do. Therefore, by using a carbon carrier having a lower corrosion resistance than the carbon carrier of the electrode catalyst layer as the carbon carrier of the water retention layer, water is discharged from the electrode catalyst layer and the carbon carrier of the water retention layer is preferentially corroded. Thereby, the carbon support | carrier of an electrode catalyst layer can be protected, As a result, the polymer electrolyte fuel cell excellent in electric power generation performance and durability can be provided.

  Furthermore, in the polymer electrolyte fuel cell of the present invention, as a more preferred embodiment, the specific surface area of the carbon support in the electrode catalyst layer can be smaller than the specific surface area of the carbon support in the water retention layer. .

  More specifically, the carbon support in the electrode catalyst layer has a specific surface area of 100 to 500 m 2 / g and an average lattice spacing of 0.341 to 0.355 nm, and the carbon support in the water retention layer has a specific surface area of 500. It can be ˜1500 m 2 / g.

  As described above, by varying the specific surface area of the carbon support in the water retention layer and the electrode catalyst layer, the corrosion resistance of the carbon support in the water retention layer can be reduced with respect to the carbon support in the electrode catalyst layer. Discharges water from the electrode catalyst layer and preferentially corrodes the carbon support in the water retention layer, promotes a sacrificial corrosion reaction that protects the carbon support in the electrode catalyst layer, and as a result, solids with excellent power generation performance and durability. A molecular fuel cell can be provided.

  In the carbon support of the electrode catalyst layer, the specific surface area was set to 100 to 500 m 2 / g. If the specific surface area was less than 100 2 / g, the dispersibility of the catalyst component on the carbon support was lowered and sufficient power generation was achieved. This is because performance may not be obtained, and if the specific surface area is larger than 5002 / g, sufficient corrosion resistance may not be obtained. The specific surface area of the conductive carrier is a value measured by the BET method using nitrogen.

  Moreover, in the carbon support of the electrode catalyst layer, the average lattice spacing was set to 0.341 to 0.355 nm because when the average lattice spacing was smaller than 0.341 nm, the catalyst component was similar to the specific surface area of the carbon support. This is because if the average lattice spacing is larger than 0.355 nm, sufficient corrosion resistance may not be obtained.

The lattice spacing (d ₀₀₂ ) of the carbon support is the face spacing of the hexagonal mesh plane based on the graphite structure of the carbon support, and is the ½ interlayer distance of the lattice constant in the c-axis direction that is the vertical direction of the hexagonal mesh plane. Mean value. The heat-treated carbon support has a graphitized layer consisting of a three-dimensional crystal lattice resembling the graphite structure on the surface. As graphitization proceeds, the fine voids between the crystal lattices decrease, and the crystal structure of the carbon support is reduced. It approaches the crystal structure of graphite. In the present invention, the lattice spacing d ₀₀₂ is a value measured by the Gakushin method using the X-ray diffraction method (Michio Inagaki, carbon No. 36, 25-34 (1963)).

  Furthermore, in the carbon carrier of the water retaining layer, the specific surface area is set to 500 to 1500 m2 / g, and if the specific surface area is smaller than 5002 / g, there is a possibility that the corrosion resistance becomes high and sufficient sacrificial corrosion effect cannot be obtained. This is because if the specific surface area is larger than 15002 / g, the corrosion resistance is lowered, the sacrificial corrosion effect period is shortened, and sufficient durability may not be obtained.

  Furthermore, in a polymer electrolyte fuel cell of the present invention, as a more preferable embodiment, the catalyst particles of the electrode catalyst in the electrode catalyst layer exhibit a catalytic action in either one of hydrogen oxidation reaction and oxygen reduction reaction. Specifically, platinum, gold, silver, copper, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and these Preferred is at least one selected from the group consisting of alloys containing.

  As described above, in the electrode catalyst of the electrode catalyst layer, a solid polymer fuel cell that provides high power generation efficiency by supporting catalyst particles having catalytic action on either one of hydrogen oxidation and oxygen reduction on a carbon carrier. Can be provided.

  Hereinafter, examples of the polymer electrolyte fuel cell of the present invention will be described more specifically. The polymer electrolyte fuel cell of the present invention is not limited to the following examples.

Example 1
1. Preparation of Gas Diffusion Layer A diffusion layer substrate was prepared by punching carbon paper (Carbon Paper TGP-H-060, thickness: about 190 μm, manufactured by Toray Industries, Inc.) into a 7 cm square. Subsequently, the following water repellent treatment was performed on the diffusion layer base material. After immersing the diffusion layer base material for 5 minutes in a solution in which a polytetrafluoroethylene (PTFE) dispersion (D-1E made by Daikin Industries, Ltd., containing 60% by mass of PTFE) is adjusted to a predetermined concentration with pure water, the same The diffusion layer substrate was pulled up and drained. Thereafter, the diffusion layer substrate was dried in an oven at 60 ° C. for 1 hour.

  Next, in order to form a carbon particle layer on the surface of the diffusion layer substrate subjected to the above water repellent treatment, carbon black (VULCAN XC-72R manufactured by CABOT), a PTFE dispersion similar to the water repellent treatment, and a pure Water was mixed and dispersed in a homogenizer for 3 hours to form a slurry.

  And the said slurry was uniformly apply | coated to one side of the diffusion layer base material after a water repellent process using the doctor blade method. Thereafter, it was similarly dried in an oven at 60 ° C. for 30 minutes, and further fired at 350 ° C. for 30 minutes in order to weld and fix the water repellent. Thereby, a gas diffusion layer in which a carbon particle layer (thickness: about 50 μm) was formed on the diffusion layer base material was obtained.

2. Electrocatalyst layer preparation Carbon black (Mitsubishi Chemical Co., Ltd. Ketjen Black EC, specific surface area 800 m2 / g) is used as a carbon support (conductive support), and this carbon support has a catalytic action for oxidation of hydrogen and reduction of oxygen. As particles to be shown, an electrode catalyst carrying 40 wt% of platinum particles having an average particle diameter of 2 to 3 nm was prepared.

  Electrocatalyst, pure water, and proton conductive electrolyte solution (Nafion solution DE520 manufactured by DuPont) with a mass ratio of carbon support and proton conductive electrolyte of the electrode catalyst (mass of proton conductive electrolyte / mass of carbon support) of 0.90 Electrocatalyst slurry was prepared by mixing, stirring, and degassing the electrolyte content of 5 wt%.

  And said electrode catalyst slurry was apply | coated by the screen-printing method on the Teflon (trademark: DuPont company make) sheet | seat, and the electrode catalyst layer was produced. At this time, the application conditions of the electrode catalyst slurry were adjusted so that the Pt mass per unit area was 0.4 mg / cm 2, the area of the electrode catalyst layer was 5 cm × 5 cm, and the thickness of the electrode catalyst layer was 10 μm.

3. Preparation of water retention layer The carbon ratio of the carbon support and the proton conductive electrolyte (proton conductive electrolyte mass / carbon mass) was 1.10, and the same carbon black (Kitsubishi Chemical Co., Ltd. A water retention layer slurry was prepared by mixing, stirring, and defoaming a chain black EC specific surface area of 800 m <2> / g), pure water and a proton conductive electrolyte solution (Nafion solution DE520 manufactured by DuPont, electrolyte content 5 wt%). And said water retention layer slurry was apply | coated to the surface of the electrode catalyst layer produced previously by the screen-printing method, and the water retention layer was produced.

4). Assembly of membrane electrode assembly A Teflon sheet coated with a water retention layer and an electrode catalyst layer is disposed on both sides of an electrolyte membrane (Dafon Nafion 112, thickness 50 μm, area 10 cm × 10 cm). At this time, the electrolyte membrane and the water retention layer are It arrange | positions so that it may contact, Then, it hot-pressed by the pressure of 2.0 MPa for 10 minutes at 150 degreeC, and produced the electrolyte membrane with a water retention layer and an electrode catalyst layer by peeling a Teflon sheet.

  Next, the gas diffusion layer prepared previously was arranged on both surfaces of the water retention layer and the electrolyte membrane with an electrode catalyst layer so that the carbon particle layer was on the electrode catalyst layer side to obtain a membrane electrode assembly. And a sealing material and a separator board were arrange | positioned on both surfaces of said membrane electrode assembly, and it clamped in the lamination direction so that it might become a predetermined surface pressure, and obtained the polymer electrolyte fuel cell (refer FIG. 1).

  In this embodiment, the water retention layer is provided on both the anode side and the cathode side, but a water retention layer may be provided on either the anode side or the cathode side. Further, the carbon particle layer of the gas diffusion layer may be provided on either the anode side or the cathode side, or may not be provided.

(Example 2)
An electrode catalyst layer was formed on the surface of the carbon particle layer of the gas diffusion layer by screen printing, and then the electrode catalyst layer was dried to produce a gas diffusion layer with an electrode catalyst layer.

  The water retention layer used was a water retention layer slurry having a mass ratio of the carbon support and the proton conductive electrolyte of 0.90, and the water retention layer slurry was applied on the Teflon sheet by screen printing to form a water retention layer. .

  Then, a Teflon sheet coated with a water retention layer is placed on both surfaces of the electrolyte membrane so that the water retention layer is in contact, hot pressed at 150 ° C. for 10 minutes at a pressure of 3.0 MPa, and then the Teflon sheet is peeled off. An electrolyte membrane with a water retention layer was produced. At this time, by performing hot pressing at a pressure higher than that of Example 1, a water retention layer having a pore diameter smaller than that of the water retention layer of Example 1 was produced.

  Thereafter, a gas diffusion layer with an electrode catalyst layer is disposed on both surfaces of the electrolyte membrane with a water retention layer. At this time, the water retention layer and the electrode catalyst layer are disposed in contact with each other, and the pressure is 2.0 MPa at 150 ° C. for 10 minutes. A membrane / electrode assembly was produced by hot pressing. Then, a polymer electrolyte fuel cell was produced in the same manner as in Example 1.

(Example 3)
A polymer electrolyte fuel cell was produced in the same manner as in Example 1 except that VULCAN XC-72R manufactured by CABOT was used as the carbon black for the electrode catalyst layer, and an electrode catalyst carrying 40 wt% platinum on a carbon support was used. did.

Example 4
As carbon black of the electrode catalyst layer, acetylene black manufactured by Denki Kagaku Kogyo Co., Ltd., specific surface area: 260 m 2 / g, lattice spacing: 0.345 nm was used, and platinum particles having an average particle diameter of 2 to 3 nm were added to this carbon support at 50 wt%. A polymer electrolyte fuel cell was produced in the same manner as in Example 1 except that the supported electrode catalyst was used and an electrode catalyst slurry was prepared at a mass ratio of the carbon support to the proton conductive electrolyte of 0.65.

(Example 5)
As the carbon black of the electrode catalyst layer, graphitized carbon black obtained by heat-treating the carbon black of Example 1 (graphitized Ketjen black specific surface area: 110 m 2 / g, lattice spacing: 0.344 nm) was used. An electrode catalyst slurry was prepared by setting the mass ratio of the carrier to the proton conductive electrolyte to 0.65.

  In addition, as a carbon black for the water retention layer, BLACK PEARLS 2000 (specific surface area: 1475 m 2 / g) manufactured by CABOT was used, and a water retention layer slurry was prepared with a mass ratio of carbon to proton conductive electrolyte of 1.20. Otherwise, a polymer electrolyte fuel cell was produced in the same manner as in Example 1.

(Comparative Example 1)
A polymer electrolyte fuel cell was produced in the same manner as in Example 2, except that the surface of the electrolyte membrane was coated with the SiO2 fine particle dispersion using a spray coating apparatus, and this SiO2 fine particle layer was produced instead of the water retention layer.

(Performance evaluation)
About the polymer electrolyte fuel cell of Examples 1-5 and Comparative Example 1, the performance evaluation test by the following method was implemented.

  The temperature of the polymer electrolyte fuel cell was adjusted to 80 ° C., hydrogen (dew point 80 ° C.) was supplied as a fuel gas to the anode side, and air (dew point 60 ° C.) was supplied as an oxidizing gas to the cathode side. The pressure on the exhaust side of the fuel cell was atmospheric pressure.

  Then, after generating power for 1 minute at a current density of 1 A / cm 2 (hydrogen utilization rate 70%, air utilization rate 40%), power generation was stopped. Next, the supply of hydrogen and air was stopped, the atmosphere inside the battery was replaced with nitrogen gas, and the system was on standby for 1 minute. Then, again, the fuel gas was supplied to the anode side, and the oxidizing gas was supplied to the cathode side, and electric power was generated at a current density of 1 A / cm 2 for 1 minute.

  The above power generation / stop operation was repeated, and the number of cycles from the initial voltage to the 20% decrease in performance was determined and used as the durability evaluation. Table 1 shows the production conditions and results of durability evaluation of the polymer electrolyte fuel cells of Examples 1 to 5 and Comparative Example 1.

  As is apparent from Table 1, the polymer electrolyte fuel cells of Examples 1 to 5 have higher performance than Comparative Example 1, and in particular, the polymer electrolyte fuel cells of Examples 3 to 5 As compared with Comparative Example 1, the performance was greatly improved.

It is sectional drawing explaining one Embodiment of the polymer electrolyte fuel cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electrolyte membrane 11 Anode side water retention layer 12 Anode side electrode catalyst layer 13 Anode side gas diffusion layer 21 Cathode side water retention layer 22 Cathode side electrode catalyst layer 23 Cathode side gas diffusion layer

Claims (8)

  On both sides of an electrolyte membrane made of a solid polymer, an electrode catalyst having catalyst particles supported on a carbon support and an electrode catalyst layer formed of a proton conductive electrolyte are provided, and a carbon is provided between the electrolyte membrane and at least one of the electrode catalyst layers. A solid polymer fuel cell comprising a water retention layer containing a carrier and a proton conductive electrolyte and having higher water retention than the electrode catalyst layer.   2. The solid polymer type according to claim 1, wherein the mass ratio of the carbon support and the proton conductive electrolyte in the water retention layer is larger than the mass ratio of the carbon support and the proton conductive electrolyte in the electrode catalyst layer. Fuel cell.   3. The polymer electrolyte fuel cell according to claim 1, wherein the pore diameter in the water retention layer is smaller than the pore diameter in the electrode catalyst layer.   The carbon carrier and proton conductive electrolyte in the electrode catalyst layer and the carbon carrier and proton conductive electrolyte in the water retention layer are continuous at the interface between the electrode catalyst layer and the water retention layer, and the proton conductive electrolyte and electrolyte membrane in the water retention layer are The polymer electrolyte fuel cell according to any one of claims 1 to 3, which is continuous at the interface between the water retention layer and the electrolyte membrane.   The solid polymer fuel cell according to any one of claims 1 to 4, wherein the carbon support in the water retention layer has lower corrosion resistance than the carbon support in the electrode catalyst layer.   6. The polymer electrolyte fuel cell according to claim 1, wherein the specific surface area of the carbon support in the electrode catalyst layer is smaller than the specific surface area of the carbon support in the water retention layer. The carbon support in the electrode catalyst layer has a specific surface area of 100 to 500 m ² / g and an average lattice spacing of 0.341 to 0.355 nm, and the carbon support in the water retention layer has a specific surface area of 500 to 1500 m ² / g. The polymer electrolyte fuel cell according to claim 6, wherein   The catalyst particles catalyze one of hydrogen oxidation reaction and oxygen reduction reaction, and Pt, Au, Ag, Cu, Ru, Ir, Rh, Pd, Os, W, Pb, Fe, Cr, The solid polymer according to any one of claims 1 to 7, wherein the polymer is at least one of Co, Ni, Mn, V, Mo, Ga, and Al, or an alloy containing at least one of them. Type fuel cell.

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