JP2006318707A - Electrode structure of solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode structure of a solid polymer fuel cell with high power generating performance and excellent high-potential durability and fuel shortage durability. <P>SOLUTION: In the electrode structure of the solid polymer fuel cell equipped with an anode electrode, a cathode electrode, and a polymer electrolyte film arranged between the electrodes, a carbon carrier with a specific surface area of 800 m<SP>2</SP>/g or more and 900 m<SP>2</SP>/g or less is used as a catalyst layer of the both electrodes. With this, the electrode structure of the solid polymer fuel cell can be provided with high power generating performance and excellent high-potential durability and fuel shortage durability. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrode structure of a polymer electrolyte fuel cell, and particularly relates to an electrode structure of a polymer electrolyte fuel cell having high power generation performance and excellent high potential durability and fuel shortage durability.

  In recent years, fuel cells are highly expected as a means for suppressing global warming and environmental destruction, and as a next-generation power generation system. A fuel cell generates energy by an electrochemical reaction between hydrogen and oxygen. For example, a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid electrolyte fuel cell, a solid polymer fuel cell, etc. Can be mentioned. Among these, the polymer electrolyte fuel cell has been attracting attention as a power source for automobiles (two-wheeled and four-wheeled) and portable power sources because it can be started from room temperature and has a small size and high output.

  A general polymer electrolyte fuel cell is a single cell in which an electrode structure (MEA), which is a basic structural unit of a fuel cell, is sandwiched between separators, and a stack in which several tens to several hundreds are combined ( Used as an assembled battery). An electrode structure, which is a basic structural unit of the stack, is formed of two electrodes, an anode electrode (fuel electrode) and a cathode electrode (air electrode), and a polymer electrolyte membrane disposed between these electrodes. The electrode is formed of a catalyst layer that performs an oxidation / reduction reaction in contact with the polymer electrolyte membrane and a gas diffusion layer in contact with the catalyst layer.

  The polymer electrolyte fuel cell having such a configuration generates power by supplying a fuel containing hydrogen to the anode electrode side and supplying oxygen or air to the cathode electrode side. In the fuel gas supplied to the anode electrode, hydrogen is ionized on the electrode catalyst, moves to the cathode electrode side through the electrolyte membrane, and electrons generated in the meantime are taken out to the external circuit and used as direct current electric energy. Is done.

  By the way, when the fuel cell described above is mounted on an automobile or the like, a rapid output change is caused according to the acceleration fluctuation of the automobile, and thus high durability that can withstand this change in operating conditions is required.

In particular, when the fuel cell is stopped, air is purged to remove both the anode electrode side and the cathode electrode side to remove residual water, so that both the anode electrode side and the cathode electrode side are filled with Air after the stop. become. Therefore, when starting the fuel cell, even if hydrogen is supplied to the anode electrode side, Air that has been filled at the time of stoppage remains, so an interface between hydrogen and residual Air is formed. Thus, the fuel cell reaction occurs in the _{Air-H 2} interface on the anode electrode side, electromotive force is generated in the _{Air-H 2} interface. When such a partial high potential state occurs, it is necessary to supply protons for power generation, but there is no hydrogen on the cathode electrode side and only Air. Therefore, on the cathode electrode side, electrolysis of water and corrosion of carbon occur to supply protons, and protons generated by the reaction are supplied. Such deterioration of the power generation performance of the cathode electrode due to the corrosion of carbon is considered to be a factor that reduces the power generation performance of the entire fuel cell.

  Moreover, the figure showing the change of the electric current value with respect to the driving | running condition of a fuel cell is shown in FIG. A region surrounded by a broken line in FIG. 1 is a transitional time due to a change in driving conditions due to acceleration fluctuation of the automobile, and fuel supply delay is likely to occur in this region. For such acceleration fluctuations in automobiles, it is necessary to flexibly supply hydrogen on the anode electrode side in response to output changes corresponding to the acceleration fluctuations, but hydrogen supplied as fuel is in a gaseous state. In addition, it is difficult to respond flexibly to changes in output due to poor responsiveness when controlling the supply amount. For this reason, the supply of fuel gas is delayed, and a shortage of fuel temporarily occurs in the electrode structure.

  Along with this fuel shortage, the cathode electrode undergoes electrolysis of water as a proton supply source in order to maintain current, and a so-called reverse voltage is generated. In the situation where the electrolysis of water proceeds, when the fuel shortage further proceeds, the oxidation of carbon and the deterioration of metal progress. That is, in a fuel-deficient state, carbon as a support in the catalyst layer constituting the cathode electrode is corroded and power generation performance is degraded. Then, when the performance of the cathode electrode is deteriorated, the power generation performance of the entire fuel cell is lowered.

  On the other hand, Patent Document 1 discloses an invention in which corrosion resistance is improved by heat-treating the support carbon at a high temperature to graphitize the carbon that is the catalyst support. This is a method for improving the corrosion resistance performance of the material used for the electrode, and improves the durability by slowing the progress of the corrosion of the carbon.

Patent Document 2 discloses an invention relating to a fuel cell provided with a water splitting layer that promotes water electrolysis reaction preferentially. Thus, water electrolysis is preferentially performed when reverse voltage is generated due to fuel shortage, and the progress of corrosion of the catalyst carrier can be delayed.
JP 2004-172107 A JP 2004-22503 A

  However, since the invention disclosed in Patent Document 1 is obtained by increasing the crystallinity by graphitization of carbon which is a catalyst carrier, the specific surface area is reduced and the dispersion state of the noble metal is lowered. The surface area is also reduced. As a result, the reaction area is reduced, resulting in a decrease in reactivity and a decrease in power generation performance.

  Further, in the invention disclosed in Patent Document 2, an effect is seen in a temporary fuel shortage situation by providing a water splitting layer. However, in actual operating conditions, rapid speed fluctuations are repeatedly performed, and in a situation where a part of the electrode structure continues to run out of fuel due to flattening or the like, the corrosion reaction of carbon proceeds. As a result, the power generation performance is degraded.

  The present invention has been made in view of the problems as described above, and provides an electrode structure for a polymer electrolyte fuel cell having high power generation performance and excellent high-potential durability and fuel shortage durability. Objective.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have achieved a power generation performance by making the specific surface area of the carbon support used for the catalyst of both electrodes 800 m ² / g or more and 900 m ² / g or less. The present inventors have found that an electrode structure for a polymer electrolyte fuel cell that is high and has high potential durability and excellent fuel shortage durability can be provided, and the present invention has been completed. More specifically, the present invention provides an electrode structure for a polymer electrolyte fuel cell as follows.

(1) An electrode structure of a polymer electrolyte fuel cell comprising an anode electrode, a cathode electrode, and a polymer electrolyte membrane disposed between these electrodes, wherein both electrodes are the polymer The catalyst layer has a catalyst layer in contact with the electrolyte membrane, and the catalyst layer contains an ion conductive material and a catalyst in which a catalyst metal is supported on carbon, and the specific surface area of the carbon is 800 m ² / g or more and 900 m ^2. / G or less of a polymer electrolyte fuel cell electrode structure.

In the electrode structure of (1), the specific surface area of carbon of the catalyst carrier used in the catalyst layers of both electrodes is set to 800 m ² / g or more and 900 m ² / g or less. More specifically, by setting the specific surface area of carbon to 800 m ² / g or more, a constant terminal voltage can be secured even in a fuel-deficient state, and excellent durability is achieved. In addition, by setting the specific surface area of carbon to 900 m ² / g or less, it has excellent durability in a high potential state generated at the time of startup. Therefore, according to the electrode structure of (1), it is possible to provide an electrode structure of a polymer electrolyte fuel cell having high power generation performance and excellent high potential durability and fuel shortage durability.

  (2) The electrode structure for a polymer electrolyte fuel cell according to (1), wherein an average lattice spacing of the [002] plane of the carbon is 0.340 nm or more and 0.360 nm or less.

  In the electrode structure (2), the average lattice spacing of the [002] plane of carbon of the catalyst carrier used in the catalyst layers of both electrodes is set to 0.340 nm or more and 0.360 nm or less. Such carbon is considered to be partially graphitized. Therefore, by setting the average lattice spacing of the [002] plane of carbon to 0.340 nm or more, pores are formed between primary particles in the carbon secondary particles, and excellent water discharge properties and gas Introduces and discharges. Further, when the average lattice spacing of the [002] plane of carbon is 0.360 nm or less, excellent strength and corrosion resistance can be obtained. Therefore, according to the electrode structure of (2), it is possible to provide an electrode structure for a polymer electrolyte fuel cell having high power generation performance and excellent high-potential durability and fuel shortage durability.

  (3) The catalyst metal of the catalyst contained in the catalyst layer of the anode electrode is a Pt—Ru alloy, and the particle diameter of the Pt—Ru alloy is 3 nm or more and 10 nm or less (1) or (2) The electrode structure of the polymer electrolyte fuel cell described.

  The electrode structure (3) uses a Pt—Ru alloy having a particle diameter of 3 nm or more and 10 nm or less as the catalyst metal of the catalyst contained in the catalyst layer of the anode electrode. The Pt—Ru catalyst having this Pt—Ru alloy supported on a carrier is excellent in catalytic activity and stability, and has excellent high potential durability when the particle size is 3 nm or more. Moreover, when it is 10 nm or less, the Pt—Ru alloy is easily supported. For this reason, excellent high potential durability can be effectively obtained by setting the particle diameter range of the Pt—Ru alloy to 3 nm or more and 10 nm or less. Therefore, according to the electrode structure of (3), it is possible to provide an electrode structure for a polymer electrolyte fuel cell that is superior in power generation performance, high potential durability, and fuel shortage durability.

  (4) The catalyst metal of the catalyst contained in the catalyst layer of the cathode electrode is a Pt—Co alloy, and the molar ratio of Pt to Co is 1 or more and 3 or less, and any one of (1) to (3) The electrode structure of the polymer electrolyte fuel cell described.

  A Pt—Co catalyst in which an alloy of platinum and cobalt is supported on a carrier has a higher catalytic activity than the platinum catalyst that has been generally used conventionally, and has excellent power generation performance. Furthermore, when the molar ratio of platinum to cobalt is 1 or more, the elution amount of cobalt is suppressed, and the corrosion resistance is excellent. Further, when the molar ratio of platinum to cobalt is 3 or less, the catalytic activity can be maintained. For this reason, by setting the range of the molar ratio of platinum to cobalt to 1 or more and 3 or less, excellent corrosion resistance and high catalytic activity can be ensured. Therefore, according to the electrode structure of (4), it is possible to provide an electrode structure of a polymer electrolyte fuel cell that is further excellent in power generation performance, high potential durability, and fuel shortage durability.

  According to the present invention, it is possible to provide an electrode structure for a polymer electrolyte fuel cell having high power generation performance, excellent high potential durability and fuel shortage durability.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[overall structure]
FIG. 2 shows a cross-sectional view of the electrode structure 1 of the polymer electrolyte fuel cell according to this embodiment. As shown in FIG. 2, the electrode structure 1 includes an anode electrode 3, a cathode electrode 4, and a polymer electrolyte membrane 2 disposed between these electrodes. The anode electrode 3 is formed of a catalyst layer 32 in contact with the polymer electrolyte membrane 2 and a gas diffusion layer 31 in contact with the catalyst layer 32. The cathode electrode 4 is formed of a catalyst layer 42 in contact with the polymer electrolyte membrane 2 and a gas diffusion layer 41 in contact with the catalyst layer 42.

  Here, the polymer electrolyte fuel cell according to the present invention includes an electrode structure composed of an anode electrode and a cathode electrode, and a polymer electrolyte membrane disposed therebetween, and the electrode structure sandwiched between separators, Laminated. The separator is preferably one in which individual electrode structures are arranged on both the anode electrode side and the cathode electrode side, but one separator has a shape facing the anode electrode and the cathode electrode of the adjacent electrode structure. It may be taken.

[Polymer electrolyte membrane]
The polymer electrolyte membrane 2 is formed from a polymer electrolyte. Specifically, it is a fluorinated polymer in which all or at least a part of the polymer skeleton is fluorinated, or a hydrocarbon-based polymer that does not contain fluorine in the polymer skeleton, and has an ion exchange group. preferable. The kind of ion exchange group is not particularly limited, and can be arbitrarily selected according to the application. For example, a polymer electrolyte having at least one of ion exchange groups such as sulfonic acid, carboxylic acid, and phosphonic acid can be used.

  Fluoropolymer in which all or at least a part of the polymer skeleton is fluorinated, and as a polymer electrolyte having an ion exchange group, specifically, a perfluorocarbon sulfonic acid polymer such as Nafion (registered trademark), Examples include perfluorocarbon phosphonic acid polymers, trifluorostyrene sulfonic acid polymers, and ethylenetetrafluoroethylene-g-styrene sulfonic acid polymers. Of these, Nafion is preferably used.

  Examples of polymer electrolytes that are hydrocarbon-based polymers that do not contain fluorine in the polymer skeleton and have ion exchange groups include polysulfonic acid, polyaryletherketonesulfonic acid, polybenzimidazolealkylsulfonic acid, Examples thereof include benzimidazole alkylphosphonic acid. Further, polyarylene having a sulfonic acid group can also be used as the polymer electrolyte. Specifically, for example, a polyarylene copolymer having a sulfonic acid group to which a quinone compound is added, a polyarylene having a sulfonic acid group and an ozone-treated carbon material, sulfonic acid The thing etc. which the polyarylene which has group, and the carbon atom which comprises a fullerene molecule couple | bonded can be used.

[Catalyst layer of cathode electrode]
The catalyst layer 42 of the cathode electrode 4 contains a catalyst in which a metal is supported on an electrically conductive material, an ion conductive material, and a crystalline carbon fiber as a pore forming agent.

  As the electrically conductive substance, carbon having a low electric resistance and low cost is preferably used. Examples of carbon include acetylene black, furnace black, and ketjen black.

The carbon support used for the catalyst layer of the cathode electrode in the present embodiment has a specific surface area of 800 m ² / g or more and 900 m ² / g or less. In addition, the specific surface area as used in the field of this invention means the specific surface area by BET method. Here, the relationship between the BET surface area of carbon and the terminal voltage is shown in FIGS. 3 and 4 show that the applied current was set to 0.1 A / cm ² under conditions where the operating temperature was 95 ° C., the relative humidity was 50% for both electrodes, and the utilization was 70% for both electrodes. This is a result of performing a time operation, measuring a terminal voltage (V) at 0.1 A / cm ^2, and determining a performance drop (V) after high potential endurance.

FIG. 4 is a partially enlarged view of FIG. 3. As shown in FIG. 4, when the BET surface area of carbon is 800 m ² / g or more, a certain terminal voltage is obtained. Moreover, when the BET surface area of carbon is 900 m ² / g or more, the performance degradation (V) after high potential durability is large. Therefore, desired performance can be obtained by setting the range of the BET surface area of carbon to 800 m ² / g or more and 900 m ² / g or less.

  The carbon support preferably has an average lattice spacing of [002] plane of 0.340 nm or more and 0.360 nm or less. The average lattice spacing of the [002] plane of the carbon support can be measured by, for example, an X-ray diffraction method.

  Note that the specific surface area and average lattice spacing of the carbon support used in the catalyst layer of the cathode electrode in this embodiment can be controlled by adjusting the firing temperature and reaction time of the carbon particles.

As the catalyst, a Pt—Co catalyst in which an alloy of platinum and cobalt is supported on carbon is preferably used, and the molar ratio of platinum to cobalt in the Pt—Co catalyst is preferably 1 or more and 3 or less. Further, the loading rate of the noble metal is 40 wt% or more and 75 wt% or less, and the CO adsorption surface area of the noble metal by the pulse method is 45 m ² / g. metal above 100 m ² / g. It is preferable that it is below metal.

  The ion conductive substance is preferably formed of a polymer electrolyte, and a polymer electrolyte similar to that of the polymer electrolyte membrane 2 is preferably used.

In addition, the crystalline carbon fiber used as the pore-forming agent may be a whisker-like fiber having high integrity as a crystal, for example, a concept including carbon nanotubes in addition to single-crystal intrinsic whisker and polycrystalline non-intrinsic whisker. It is. In particular, the crystalline carbon fiber used in the present embodiment has a fiber diameter of 0.1 μm or more and 0.3 μm or less, a fiber length of 10 μm or more and 50 μm or less, and a bulk density of 0.03 g / cm ³ or more and 0.0. The physical properties are 06 g / cm ³ or less, the specific surface area is 12 m ² / g or more and 18 m ² / g or less, the lattice spacing of the [002] plane is 0.339 nm or less, and the specific resistance is 0.025 Ωcm or less. Crystalline carbon fibers having the following are preferably used.

[Anode electrode catalyst layer]
The catalyst layer 32 of the anode electrode 3 contains an ion conductive material and a catalyst in which a metal is supported on a carrier such as carbon. The ion conductive material is preferably formed of a polymer electrolyte, and a polymer electrolyte similar to that used in the polymer electrolyte membrane 2 or the catalyst layer 42 of the cathode electrode 4 is preferably used.

  As the catalyst, in addition to a catalyst in which platinum is supported on carbon, a Pt—Ru catalyst in which an alloy of platinum and ruthenium is supported on carbon is preferably used, and the particle diameter of the Pt—Ru alloy is 3 nm or more and 10 nm or less. It is preferable. As the carbon, the same carbon as that used for the cathode electrode can be used.

[Gas diffusion layer]
The gas diffusion layer 31 on the anode electrode 3 side and the gas diffusion layer 41 on the cathode electrode 4 side may have the same configuration as a conventional general gas diffusion layer. In the anode electrode 3 side and the cathode electrode 4 side, The same configuration may be used. On the anode electrode 3 side, it is preferable that the hydrogen gas of the fuel can reach the catalyst layer 32 evenly. On the cathode electrode 4 side, air containing oxygen gas is evenly distributed in the catalyst layer 42. It is preferable that it can be reached. Specifically, as shown in FIG. 2, the gas diffusion layer 31 on the anode electrode 3 side includes a carbon Teflon (registered trademark) layer 311 in contact with the catalyst layer 32 and a carbon paper layer 312 in contact with the carbon Teflon layer 311. Formed from. The gas diffusion layer 41 on the cathode electrode 4 side is formed of a carbon / Teflon layer 411 in contact with the catalyst layer 42 and a carbon paper layer 412 in contact with the carbon / Teflon layer 411. These gas diffusion layers can be obtained, for example, by applying a mixture of Teflon dispersion and carbon black powder onto carbon paper that has been subjected to water repellency treatment with Teflon dispersion or the like in advance.

<Manufacturing method>
The manufacturing method of the electrode structure 1 according to the present embodiment is as follows. First, an anode catalyst and a polymer electrolyte are mixed to obtain an anode catalyst paste. Similarly, a cathode catalyst, a crystalline carbon fiber, and a polymer electrolyte are mixed to obtain a cathode catalyst paste. Each of the obtained anode catalyst paste and cathode catalyst paste is applied to a Teflon sheet or the like. Thereby, an anode electrode sheet and a cathode electrode sheet are obtained. Next, the polymer electrolyte membrane 2 is placed between the well-dried anode electrode sheet and cathode electrode sheet, and transferred by a decal method (transfer method), so that the joined body of the polymer electrolyte membrane 2 and the catalyst layer is obtained. can get. Finally, separately, a polymer electrolyte membrane 2 and a catalyst are placed between a pair of gas diffusion layer sheets prepared by applying and drying a paste obtained by mixing polytetrafluoroethylene or the like and carbon black in a solvent on carbon paper. After arrange | positioning the conjugate | zygote with a layer, the electrode structure 1 is obtained by integrating by 130 degreeC-160 degreeC hot press. In addition, a solid polymer fuel cell can be obtained by alternately laminating the electrode structure 1 and the separator. The separator has a groove and is used as a reaction gas supply passage. Carbon or metal materials can be used in appropriate combination.

  Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

<Example 1>
[Creation of cathode electrode sheet]
First, Pt-Co-supported carbon particles (trade name, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), in which a catalytic metal composed of an alloy of platinum and cobalt is supported on acetylene black having a BET specific surface area of 850 m ² / g and d / 2 of 0.345 nm. “TEC36F52”, Pt: Co = 3: 1 (molar ratio)) was prepared. The Pt—Co-supported carbon particles had a mass ratio of acetylene black and catalyst metal of 48:52. Mix 10g of Pt-Co-supported carbon particles, 50g of ion conductive polymer (DuPont, trade name "Nafion DE2020") and 2.5g of crystalline carbon fiber (Showa Denko, trade name "VGCF") A cathode catalyst paste was obtained. The obtained catalyst paste was applied onto a FEP (tetrafluoroethylene-hexafluoropropylene copolymer) sheet so that the amount of the catalyst alloy was 0.50 mg / cm ² and dried to obtain a cathode electrode sheet.

[Creation of anode electrode sheet]
Ion conductive polymer (DuPont, trade name “Nafion DE2021”) 5 g, carbon black powder (Cabot, trade name “Ketjen Black”) 1 g and catalyst powder Pt—Ru alloy powder (Tanaka Kikinzoku Kogyo Co., Ltd.) Product, product name “TEC90110”, 9 g of Pt: Ru = 1: 1 (molar ratio), 5 g of pure water and 10 g of 1-propanol were mixed to obtain an anode electrode paste. The obtained catalyst paste was applied onto an FEP sheet so that the amount of catalyst alloy was 0.30 mg / cm ² and dried to obtain an anode electrode sheet.

[Preparation of joined body of polymer electrolyte membrane and catalyst layer]
An ion conductive polymer (manufactured by DuPont, trade name “Nafion DE2021”) was prepared as a polymer electrolyte membrane. The polymer electrolyte membrane was disposed between the anode electrode sheet and the cathode electrode sheet obtained above. Subsequently, it was transferred by a decal method (transfer method) to obtain a joined body of a polymer electrolyte membrane and a catalyst layer.

[Create gas diffusion layer]
A foundation layer paste A was obtained by mixing 12.0 g of Teflon dispersion (trade name “L170J” manufactured by Asahi Glass Co., Ltd.) and 18.0 g of carbon black powder (trade name “Vulcan XC75” manufactured by Cabot Corp.). 25 g of ion-conducting polymer (trade name “Nafion DE2021” manufactured by DuPont) and 5 g of carbon black powder (trade name “Ketjen Black” manufactured by Cabot) and crystalline carbon fiber (manufactured by Showa Denko KK, product name) “VGCF”) 2.5 g was mixed to obtain a base layer paste B. This base layer paste A was applied on a carbon paper (trade name “TGP060” manufactured by Toray Industries, Inc., product name “TGP060”) which had been subjected to water repellency treatment in advance using a Teflon dispersion (trade name “FEP120J” manufactured by Mitsui DuPont Chemicals) The paste A was applied and dried so as to be 2.0 mg / cm ^2, and then the base layer paste B was applied and dried so that the dry weight was 0.30 mg / cm ^2. Obtained.

[Create electrode structure]
Between the two gas diffusion layer sheets obtained above, a joined body of the polymer electrolyte membrane and the catalyst layer was disposed and integrated by hot pressing to obtain an electrode structure.

<Example 2>
[Creation of cathode electrode sheet]
First, Pt—Co-supported carbon particles obtained by supporting a catalytic metal made of an alloy of platinum and cobalt on acetylene black having a BET surface area of 850 m ² / g and d / 2 of 0.345 nm (made by Tanaka Kikinzoku Kogyo Co., Ltd., trade name “ TEC36F62 ", Pt: Co = 3: 1 (molar ratio)). The Pt—Co-supported carbon particles had a mass ratio of acetylene black and catalyst metal of 38:62. Mix 10g of Pt-Co-supported carbon particles, 50g of ion conductive polymer (DuPont, trade name "Nafion DE2020") and 2.5g of crystalline carbon fiber (Showa Denko, trade name "VGCF") A cathode catalyst paste was obtained. The obtained catalyst paste was applied onto a FEP (tetrafluoroethylene-hexafluoropropylene copolymer) sheet so that the amount of the catalyst alloy was 0.50 mg / cm ² and dried to obtain a cathode electrode sheet.

  Using this cathode electrode sheet and the anode electrode sheet prepared in Example 1, an electrode structure was obtained in the same manner as in Example 1.

<Comparative Example 1>
[Creation of cathode electrode sheet]
First, Pt—Co-supported carbon particles in which a catalyst metal made of an alloy of platinum and cobalt is supported on furnace black graphitized at 2800 ° C. with a BET surface area of 140 m ² / g and d / 2 of 0.348 nm (Tanaka Kikinzoku) A trade name “TEC36EA52” manufactured by Kogyo Co., Ltd., Pt: Co = 3: 1 (molar ratio)) was prepared. The Pt—Co-supported carbon particles had a mass ratio of furnace black to catalyst metal of 48:52. Mix 10g of Pt-Co-supported carbon particles, 50g of ion conductive polymer (DuPont, trade name "Nafion DE2020") and 2.5g of crystalline carbon fiber (Showa Denko, trade name "VGCF") A cathode catalyst paste was obtained. The obtained catalyst paste was applied onto an FEP (tetrafluoroethylene-hexafluoropropylene copolymer) sheet so that the amount of platinum was 0.50 mg / cm ² and dried to obtain a cathode electrode sheet.

  Using this cathode electrode sheet and the cathode electrode sheet prepared in Example 1, an electrode structure was obtained in the same manner as in Example 1.

<Comparative Example 2>
[Creation of anode electrode sheet]
36.8 g of ion-conducting polymer (trade name “Nafion DE2021”, manufactured by DuPont), and Pt—Ru-supported carbon particles having a mass ratio of carbon black to catalyst of 46:54 (trade name, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) “TEC61E54” and 10 g of Pt: Ru = 1: 1 (molar ratio) were mixed to obtain an anode catalyst paste. The obtained catalyst paste was applied onto the FEP sheet so that the amount of the catalyst alloy was 0.15 mg / cm ² and dried to obtain an anode electrode sheet.

[Preparation of joined body of polymer electrolyte membrane and catalyst layer]
An ion conductive polymer (manufactured by DuPont, trade name “Nafion DE2021”) was prepared as a polymer electrolyte membrane. This polymer electrolyte membrane was disposed between the anode electrode sheet obtained above and the cathode electrode sheet obtained in Example 1. Subsequently, it was transferred by a decal method (transfer method) to obtain a joined body of a polymer electrolyte membrane and a catalyst layer.

[Create gas diffusion layer]
25.0 g of ion-conducting polymer (manufactured by DuPont, trade name “Nafion DE2021”) and precious metal alloy catalyst powder (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., trade name “TEC61E54”) and crystalline carbon fiber (manufactured by Showa Denko, product) The base layer paste C was obtained by mixing 2.5 g of the name “VGCF”). Base layer paste obtained in Example 1 on carbon paper (trade name “TGP060”, manufactured by Toray Industries, Inc.) that has been subjected to water repellent treatment in advance using a Teflon dispersion (trade name “FEP120J” manufactured by Mitsui DuPont Chemical Co., Ltd.). Gas diffusion is achieved by applying and drying A so that the dry weight is 2.0 mg / cm ^2, and then applying and drying the base layer paste C so that the amount of platinum is 0.05 mg / cm ² during drying. A layer sheet was obtained.

[Create electrode structure]
The gas diffusion layer sheet obtained above is disposed on the anode electrode side, the gas diffusion layer sheet obtained in Example 1 is disposed on the cathode electrode side, and the assembly of the polymer electrolyte membrane and the catalyst layer is disposed therebetween. Then, an electrode structure was obtained by integration by hot pressing.

<Comparative Example 3>
An ion conductive polymer (manufactured by DuPont, trade name “Nafion DE2021”) was prepared as a polymer electrolyte membrane. The polymer electrolyte membrane was disposed between the cathode electrode sheet prepared by the same method as in Example 1 and the anode electrode sheet prepared by the same method as in Comparative Example 2. Subsequently, it was transferred by a decal method (transfer method) to obtain a joined body of a polymer electrolyte membrane and a catalyst layer. This joined body was placed between gas diffusion layer sheets prepared by the same method as in Example 1, and integrated by hot pressing to obtain an electrode structure.

<Comparative example 4>
Pt-Co-supported carbon particles (trade name “TEC36E52”, trade name “TEC36E52”, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), in which a catalytic metal made of an alloy of platinum and cobalt is supported on carbon black (product of Lion, trade name “Ketjen Black EC”) : Co = 3: 1 (molar ratio)). The Pt—Co-supported carbon particles had a mass ratio of the carrier to the catalyst metal of 48:52. 10 g of this Pt-Co-supported carbon particle, 36 g of ion conductive polymer (trade name “Nafion DE2020” manufactured by DuPont) and 2.5 g of crystalline carbon fiber (trade name “VGCF” manufactured by Showa Denko KK) are mixed. A cathode catalyst paste was obtained. The obtained catalyst paste was applied onto an FEP (tetrafluoroethylene-hexafluoropropylene copolymer) sheet so that the amount of platinum was 0.50 mg / cm ² and dried to obtain a cathode electrode sheet.

  A polymer electrolyte membrane (manufactured by DuPont, trade name “Nafion DE2021”) is placed between this cathode electrode sheet and the cathode electrode sheet prepared in the same manner as in Example 1, and transferred by a decal method (transfer method). A joined body of the polymer electrolyte membrane and the catalyst layer was obtained. This joined body was placed between gas diffusion layer sheets prepared by the same method as in Example 1, and integrated by hot pressing to obtain an electrode structure.

<Evaluation>
First, each of the electrode structures obtained in Examples 1 and 2 and Comparative Examples 1 to 4 was placed between a pair of separators to form a single cell, and then assumed to be in a normal use state under the following operating conditions. The terminal voltage at the time of the acceleration test assuming the test and the overload state was confirmed. The durability test assuming a normal use state used an applied current of 0.1 A / cm ² , and the acceleration test assuming an overload state used an applied current of 1.0 A / cm ² .
[Operating conditions] Operating temperature: 80 ℃
Humidification conditions: anode = cathode = 60%
Pressure: Anode / cathode = 130/100 kPa
Utilization rate (consumption / supply): anode = cathode = 50%

[Transient durability test]
After confirming the performance of the terminal voltage, an endurance test at the time of transition was performed as an evaluation of the performance deterioration in the fuel shortage state. FIG. 5 is a graph showing the conditions of the transient durability test. Specifically, it was performed under the following conditions.
[Transient durability test operating conditions] Electrode area: 35 cm ²
OCV → 1 A / cm ² → OCV (repeated 100 times with 100 sec as one cycle)

[Start / stop durability test]
After confirming the current / voltage performance, an endurance test at the time of starting and stopping was performed as an evaluation of performance degradation in a high potential state. FIG. 6 is a graph showing the conditions of the start / stop durability test. Specifically, it was performed under the following conditions.
[Start / stop durability conditions] Stop → Start → Stop (This was repeated 10 times as one cycle)

  Table 1 shows the results after the transient durability test and the start / stop durability test.

  From the results of Table 1, Comparative Example 1 had already low terminal voltage and low power generation performance in the performance before endurance. Further, Comparative Examples 2 and 3 showed a significant decrease in performance after the transient durability test, and Comparative Example 4 had a significant decrease in performance after the start / stop durability test. On the other hand, it was confirmed that the present example had high power generation performance and was excellent in high potential durability and fuel shortage durability.

It is a figure showing the change of the electric current value with respect to the driving | running condition of a fuel cell. It is sectional drawing which shows the whole structure of an electrode structure. It is the figure which showed the relationship of the performance fall after BET surface area of carbon, terminal voltage, and high potential endurance. It is the figure which showed the relationship of the performance fall after BET surface area of carbon, terminal voltage, and high potential endurance. It is the figure which showed the conditions of the transient durability test. It is the figure which showed the conditions of the start / stop durability test.

Explanation of symbols

1 Electrode Structure 2 Polymer Electrolyte Membrane 3 Anode Electrode 31 Diffusion Layer 311 Carbon Teflon Layer 312 Carbon Paper Layer 32 Catalyst Layer 4 Cathode Electrode 41 Diffusion Layer 411 Carbon Teflon Layer 412 Carbon Paper Layer 42 Catalyst Layer

Claims (4)

An electrode structure of a polymer electrolyte fuel cell comprising an anode electrode, a cathode electrode, and a polymer electrolyte membrane disposed between these electrodes,
Both electrodes have a catalyst layer in contact with the polymer electrolyte membrane,
The catalyst layer contains an ion conductive material and a catalyst in which a catalytic metal is supported on carbon,
The carbon specific surface area is an electrode structure of a polymer electrolyte fuel cell having a specific surface area of 800 m ² / g or more and 900 m ² / g or less.   2. The electrode structure for a polymer electrolyte fuel cell according to claim 1, wherein an average lattice spacing of the [002] plane of the carbon is 0.340 nm or more and 0.360 nm or less. The catalyst metal of the catalyst contained in the catalyst layer of the anode electrode is a Pt—Ru alloy,
The electrode structure for a polymer electrolyte fuel cell according to claim 1 or 2, wherein the particle diameter of the Pt-Ru alloy is 3 nm or more and 10 nm or less. The catalyst metal of the catalyst contained in the catalyst layer of the cathode electrode is a Pt—Co alloy,
4. The electrode structure for a polymer electrolyte fuel cell according to claim 1, wherein the molar ratio of Pt to Co is 1 or more and 3 or less.

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