JP2018181570A - Solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer fuel cell which enables the enhancement of a power generation performance and the prevention of drying up and flooding.SOLUTION: A solid polymer fuel cell 1 comprises: a solid polymer electrolyte film 2; a catalyst layer 3 provided on each face of the solid polymer electrolyte film 2; a gas diffusion layer 4 provided on each of the catalyst layers 3, 3; and water-management porous layers 5 provided between one catalyst layer 3 and one gas diffusion layer 4, and between the other catalyst layer 3 and the other gas diffusion layer 4. In the solid polymer fuel cell 1, a thickness t[μm] of the water-management porous layer 5, a concentration c[%] of a water-repellent material included in the water-management porous layer 5, and a value k determined from a molecular weight m of the water-repellent material are set according to the following formula: k=t*c/log m, where 15≤k≤200.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polymer electrolyte fuel cell in which a solid polymer membrane is used as an electrolyte layer, electrodes are provided on both sides thereof, and fuel gas and oxidant gas are supplied to each electrode to obtain electric energy by an electrochemical reaction. In particular, the present invention relates to a polymer electrolyte fuel cell in which the configuration and material of both electrodes are improved.

  The polymer electrolyte fuel cell has a structure in which a polymer electrolyte membrane is used as an electrolyte layer and electrodes are disposed on both sides thereof. The electrolyte membrane is required to have properties such as ion exchange properties, mechanical strength and gas barrier properties, and each electrode is also required to have good gas diffusivity in addition to good electrode reactivity. Generally, each electrode is mainly composed of a catalyst layer and a gas diffusion layer, but in order to improve the water retention of the catalyst layer, a microporous layer between the catalyst layer and the gas diffusion layer Or a water management layer may be provided.

  The inventors of the present invention have previously provided a solid for which a porous layer for controlling water evaporation is provided between an oxidant catalyst layer and an oxidant gas diffusion layer as disclosed in Patent Document 1 below in order to ensure water retention. A polymer fuel cell is proposed. In order to make the humidity of the oxidant catalyst layer uniform over the entire cell surface, the porous layer for water evaporation control of this polymer electrolyte fuel cell is as follows from the inlet side to the outlet side of the gas as follows: It is inclined. For example, the pore diameter is distributed from the gas inlet side to the gas outlet side, the water repellency and the hydrophilicity are graded, and the surface tension is graded.

  Patent Document 2 discloses a gas diffusion electrode used in a fuel cell, in which a microporous layer containing conductive fine particles and a water repellent resin is formed on at least one side of a conductive porous substrate. It is disclosed. In this gas diffusion electrode, the sliding angle of the conductive porous substrate is 70 ° or less, the porosity of the conductive porous substrate is 80% or more, and the thickness of the microporous layer is 10 μm to 50 μm, fine The porosity of the porous layer is 60% or more and 95% or less.

The porous electrode substrate disclosed in Patent Document 3 has a pore distribution when measured by the mercury intrusion method satisfies the following conditions, and is composed of carbon powder and a water repellent on one side and / or both sides thereof. A coating layer is provided.
<Condition>
A pore distribution curve whose abscissa is a normal logarithm display, and at least a section of 1 to 100 μm in diameter consists of 80 measurement points at regular intervals in a common logarithm display, and a narrow axis in which the abscissa is logarithmic In the pore distribution, the skewness S of the pore distribution at a diameter of 1 to 100 μm is −1.0 <S <−0.5, the kurtosis K is 3.0 <K <4.5, and 1 to 20 μm There is one peak in the pore size range of 1, and also one peak in the pore size range of 20 to 100 μm, and the peak in the pore size range of 1 to 20 μm is higher than the peak in the pore size range of 20 to 100 μm.

JP 2003-92112 A JP, 2016-6799, A Unexamined-Japanese-Patent No. 2016-91996

  Although the inventions described in any of the patent documents are provided with the above-mentioned microporous layer and water management layer, the inventors of the present invention have made intensive studies for their specific configurations. Then, it was found that the thickness of the microporous layer and the water management layer, and the concentration and molecular weight of the water repellent material contained in them are related to the power generation performance of the fuel cell and the prevention of the flooding, and the present invention The result is

  The present invention has been made in view of such circumstances, and its main object is to provide a polymer electrolyte fuel cell capable of improving power generation performance and preventing flooding.

The polymer electrolyte fuel cell according to the present invention for achieving the above object is provided with a solid polymer electrolyte membrane, a catalyst layer provided on both sides of the solid polymer electrolyte membrane, and both catalyst layers. A water containing a water repellent material provided between a gas diffusion layer, one of the catalyst layer and one of the gas diffusion layers, and / or between the other of the catalyst layer and the other of the gas diffusion layers And a control porous layer, wherein a thickness k of the water management porous layer, a concentration c of the water repellent material c [%], and a value k obtained from the molecular weight m of the water repellent material are set by the following equation It is characterized in that 15 ≦ k ≦ 200.
k = t · c / log m

  In the polymer electrolyte fuel cell according to the present invention, the thickness t of the water management porous layer is 10 μm to 100 μm, and the concentration c of the water repellent material is 1% to 30%. It features.

  Furthermore, the polymer electrolyte fuel cell according to the present invention is characterized in that the molecular weight m of the water repellent material is 100 or more and 100 million or less.

  According to the polymer electrolyte fuel cell according to the present invention, the value k obtained from the thickness t of the water management porous layer, the concentration c of the water repellent material and the molecular weight m of the water repellent material is 15 ≦ k ≦ 200. , Improvement in power generation performance and prevention of dry-up and flooding.

  In addition, according to the polymer electrolyte fuel cell according to the present invention, the power generation performance can be improved, the dry-up and the prevention of the flooding can be more surely achieved, and the battery can be made compact.

  Furthermore, according to the polymer electrolyte fuel cell according to the present invention, the improvement of the power generation performance and the prevention of the dry-up and the flooding can be further surely achieved.

FIG. 1 is a conceptual view showing an embodiment of a polymer electrolyte fuel cell of the present invention. It is a table | surface which shows the specification of MEA used for this test. It is a schematic block diagram of the electric power generation evaluation apparatus used for this test. It is a table | surface which shows the measurement conditions of this test. FIG. 16 is a graph showing a current density-cell voltage curve when testing the power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM at a utilization rate of 20% and a humidification temperature of 40 ° C. to 60 ° C. a) is the case where the mixing ratio of the low molecular weight fluororesin (molecular weight is 332) of the water management porous layer is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² (b (C) is the water management porous layer when the low molecular weight fluorocarbon resin mixing ratio of the water management porous layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² ). The case is shown in which the low-molecular-weight fluororesin mixing ratio is 7.8% and the coating amount of the water management porous layer to the gas diffusion layer is 6.0 mg / cm ² . 14 is a graph showing a current density-cell voltage curve when a test of power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM is performed at a utilization rate of 20% and a humidification temperature of 65 ° C. to 85 ° C. a) When the low molecular weight fluorocarbon resin mixing ratio of the water management porous layer is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the water management porous (C) is the low molecular weight fluorocarbon resin of the water management porous layer when the low molecular weight fluorocarbon resin mixing ratio of the layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² It shows the case where the mixing ratio is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 6.0 mg / cm ² . 14 is a graph showing a current density-cell voltage curve when a test of power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM is performed at a utilization rate of 40% and a humidification temperature of 40 ° C. to 60 ° C. a) When the low molecular weight fluorocarbon resin mixing ratio of the water management porous layer is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the water management porous (C) is the low molecular weight fluorocarbon resin of the water management porous layer when the low molecular weight fluorocarbon resin mixing ratio of the layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² It shows the case where the mixing ratio is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 6.0 mg / cm ² . FIG. 16 is a graph showing a current density-cell voltage curve when testing the power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM at a utilization rate of 40% and a humidification temperature of 65 ° C. to 85 ° C. a) When the low molecular weight fluorocarbon resin mixing ratio of the water management porous layer is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the water management porous (C) is the low molecular weight fluorocarbon resin of the water management porous layer when the low molecular weight fluorocarbon resin mixing ratio of the layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² It shows the case where the mixing ratio is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 6.0 mg / cm ² . 14 is a graph showing a current density-cell voltage curve when a test of power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM is performed at a utilization rate of 70% and a humidification temperature of 40 ° C. to 60 ° C. a) When the low molecular weight fluorocarbon resin mixing ratio of the water management porous layer is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the water management porous (C) is the low molecular weight fluorocarbon resin of the water management porous layer when the low molecular weight fluorocarbon resin mixing ratio of the layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² It shows the case where the mixing ratio is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 6.0 mg / cm ² . FIG. 16 is a graph showing a current density-cell voltage curve when testing the power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM at a utilization rate of 70% and a humidification temperature of 65 ° C. to 85 ° C. a) When the low molecular weight fluorocarbon resin mixing ratio of the water management porous layer is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the water management porous (C) is the low molecular weight fluorocarbon resin of the water management porous layer when the low molecular weight fluorocarbon resin mixing ratio of the layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² It shows the case where the mixing ratio is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 6.0 mg / cm ² . It is a graph which shows the current density-cell voltage curve at the time of testing the power generation performance of the polymer electrolyte fuel cell of this example, and shows the case of a humidification temperature of 40 ° C. to 60 ° C. at a utilization rate of 20%. . It is a graph which shows the current density-cell voltage curve at the time of testing the power generation performance of the polymer electrolyte fuel cell of this example, and shows the case of a humidification temperature of 65 ° C. to 85 ° C. at a utilization rate of 20%. . It is a graph which shows the current density-cell voltage curve at the time of testing the power generation performance of the polymer electrolyte fuel cell of this example, and shows the case where the humidification temperature is 40 ° C. to 60 ° C. at a utilization rate of 40%. . It is a graph which shows the current density-cell voltage curve at the time of testing the power generation performance of the polymer electrolyte fuel cell of this example, and shows the case of a humidification temperature of 65 ° C. to 85 ° C. at a utilization rate of 40%. . It is a graph which shows the current density-cell voltage curve at the time of testing the power generation performance of the polymer electrolyte fuel cell of this example, and shows the case of a humidification temperature of 40 ° C. to 60 ° C. at a utilization rate of 70%. . It is a graph which shows the current density-cell voltage curve at the time of testing the power generation performance of the polymer electrolyte fuel cell of this example, and shows the case of a humidification temperature of 65 ° C. to 85 ° C. with 70% utilization . It is a graph which shows the relationship of the fluorine content of the water management porous layer of the polymer electrolyte fuel cell used for this test, application amount, and thickness. It is explanatory drawing of the effect of a water management porous layer, (a) is a case without a water management porous layer, (b) has shown the case with a water management porous layer.

  Hereinafter, specific examples of the polymer electrolyte fuel cell of the present invention will be described in detail based on the drawings.

  FIG. 1 is a conceptual view showing one embodiment of the polymer electrolyte fuel cell of the present invention. The polymer electrolyte fuel cell 1 of this embodiment comprises a solid polymer electrolyte membrane 2 as an electrolyte membrane, a catalyst layer 3 provided on both sides of the solid polymer electrolyte membrane 2, and both catalyst layers 3, 3 And a water management porous layer 5 provided between one catalyst layer 3 and one gas diffusion layer 4 and between the other catalyst layer 3 and the other gas diffusion layer 4 , And the separator 6 provided in each of the two gas diffusion layers 4, 4.

  The solid polymer electrolyte membrane 2 is formed in a substantially rectangular shape in a side view, and is an electrolyte membrane having proton conductivity. In the present embodiment, as the solid polymer electrolyte membrane 2, perfluorocarbon sulfonic acid (for example, Nafion membrane manufactured by DuPont, USA), which is a proton exchange membrane, is used.

  Each catalyst layer 3 is formed in a substantially rectangular shape in a side view, and is a layer including a substance having catalytic activity, a support of the substance, and an ionomer. The substance having catalytic activity is, for example, platinum. Also, the support is, for example, carbon particles. Furthermore, the ionomer is, for example, a fluorine-based polymer electrolyte. As shown in FIG. 1, one gas diffusion layer 4 is formed on the surface (left surface) opposite to the surface (right surface) in contact with the solid polymer electrolyte membrane 2 in the one (left) catalyst layer 3. Provided. The other (right side) catalyst layer 3 is provided with the other gas diffusion layer 4 on the side (right side) opposite to the side (left side) in contact with the solid polymer electrolyte membrane 2.

  Each gas diffusion layer 4 is formed in a substantially rectangular shape in a side view, and is a porous layer that promotes the diffusion of the reaction gas to the catalyst layer 3. In the present embodiment, each gas diffusion layer 4 is a cloth-like or plate-like one containing carbon fibers.

  Each water management porous layer 5 is formed in a substantially rectangular shape in a side view, and is a layer containing a water repellent material. Generally, PTFE (polytetrafluoroethylene (molecular weight of several million to 10,000,000)) is used as the water repellent material, but in the present embodiment, a material having a smaller molecular weight, for example, a low molecular weight of 332 is used. A fluorine resin is used. In the present embodiment, each water management porous layer 5 is formed of a mixture of a carbon material and a low molecular weight fluororesin water repellent material.

  The low molecular weight fluorine resin used in each water management porous layer 5 has a molecular weight of 332, has an amorphous structure different from existing fluorine resins, is soluble in a special perfluoro solution, and is 100 ° C. The thin film coating can be applied by evaporating the solvent. Moreover, water repellent treatment is possible in the same manner as conventional Teflon (registered trademark). Furthermore, since the diameter of the low molecular weight fluorocarbon resin is much smaller than that of PTFE, it can be coated so as to wrap the particles of Vulcan Black described later in particle units. Therefore, better water repellent performance can be expected as compared with the conventional PTFE water repellent.

  Each separator 6 is formed in a substantially rectangular shape in a side view, and for example, a metal plate subjected to corrosion resistance treatment, a high density carbon plate, a composite plate of carbon and a resin, or the like is used. As shown in FIG. 1, one separator 6 is provided on one gas diffusion layer 4 on the opposite side to the surface in contact with one water management porous layer 5. In one of the separators 6 is formed a fuel gas flow channel 7 which is a flow path of the fuel gas. As a fuel gas, for example, a hydrogen-containing gas obtained by reforming a hydrocarbon fuel is used. The other separator 6 is provided on the other side of the other gas diffusion layer 4 opposite to the side in contact with the other water management porous layer 5. In the other separator 6, an oxidant gas flow groove 8 which is a flow path of oxidant gas is formed. As the oxidant gas, for example, air is used.

  Thus, one catalyst layer 3, one water management porous layer 5, one gas diffusion layer 4 and one separator 6 are provided sequentially from the solid polymer electrolyte membrane 2 disposed in the center toward one side. Be The other catalyst layer 3, the other water management porous layer 5, the other gas diffusion layer 4 and the other separator 6 are provided in order from the solid polymer electrolyte membrane 2 to the other. Thereby, the polymer electrolyte fuel cell 1 which is a unit cell is comprised.

  In the polymer electrolyte fuel cell, when the dischargeability of the generated water in the gas diffusion layer is poor, the generated water is accumulated in the gas diffusion layer to clog the pores, and the flooding which inhibits the passage of the gas occurs. On the other hand, when the water content in the battery is insufficient, the ion conductivity of the electrolyte membrane may be reduced, or a dry up may occur. Therefore, it is extremely important to control the water produced by the reaction between the fuel and the oxidant and the moisture by humidifying the gas supplied into the battery.

  Therefore, in the present embodiment, by providing the water management porous layer 5 containing a water repellent material between the gas diffusion layer 4 and the catalyst layer 3, the wettability of the gas diffusion layer 4 or the solid polymer electrolyte membrane 2 is obtained. To be appropriate. Specifically, in the polymer electrolyte fuel cell 1 of this example, the thickness t [μm] of the water management porous layer 5, the concentration c [%] of the water repellent material contained in the water management porous layer 5, and The value k determined from the molecular weight m of the water repellent material is set by the following equation, and 15 ≦ k ≦ 200. Therefore, according to the polymer electrolyte fuel cell 1 of the present embodiment, it is possible to improve power generation performance and prevent dry-up and flooding.

    [Equation 1] k = t · c / log m

  In the polymer electrolyte fuel cell 1 of this example, the thickness t of the water management porous layer 5 is 10 μm to 100 μm, and the concentration c of the water repellent material is 1% to 30%. preferable. As a result, in addition to the fact that the improvement of the power generation performance and the prevention of dry-up and flooding can be achieved more reliably, the battery can be made compact. Further, in the polymer electrolyte fuel cell 1 of the present embodiment, the water-repellent material preferably has a molecular weight m of 100 or more and 100 million or less. Thereby, the improvement of the power generation performance, and the prevention of the dry-up and the flooding can be further surely achieved. Furthermore, in the polymer electrolyte fuel cell 1 of the present embodiment, a low molecular weight fluorocarbon resin is used, so the water management porous layer 5 can be made thinner than before, and the amount of use of the water repellent material can be reduced. it can. Therefore, the cost of the stack (for example, a fuel cell automobile and a home use fuel cell) on which the polymer electrolyte fuel cell 1 of this embodiment is mounted can be reduced, and a wide range of operation from low humidity to high humidity. It is possible to operate the stack in the area.

  Next, a test of the power generation performance of the polymer electrolyte fuel cell 1 of the present embodiment will be described.

  The water management porous layer 5 is formed in the polymer electrolyte fuel cell 1 used in the present test as follows. First, a mixture of carbon material and water repellent material is manufactured. In this test, carbon black Vulcan black (made by Cabot Co., Ltd.) is placed in a beaker, a 9% solution of low molecular weight resin (molecular weight is 32) and a solvent for low molecular weight fluorocarbon resin (molecular weight is 332) are added. Mix well with. Next, the mixture is dried in a drying oven (manufactured by Toyo Seisakusho Co., Ltd.) at 60 ° C. for 1 hour. Thereafter, when the mixture is in the form of a fine powder, the mixture is transferred from the beaker to a stirring mixer, a blender (type: WB-1 (Osaka Chemical Co., Ltd.)), and stirred for about 20 seconds. This stirring is repeated a total of three times. And finally, put powdered PTFE into a blender and stir for about 20 seconds. In this way, a mixture of carbon material and low molecular weight fluorocarbon resin is produced.

  The powdery mixture thus prepared is applied by suction onto a carbon paper (24 cm × 14 cm square) which has been previously subjected to water repellent treatment with a low molecular weight fluorine resin 1% solution by a dry coating apparatus. The carbon paper used was 280 μm in thickness manufactured by Toray Industries, Inc. The carbon paper coated with the mixture is fired at 355 ° C. for 15 minutes in a firing furnace (manufactured by Toyo Seisakusho Co., Ltd.). Thereafter, using a roller, the mixture is fixed on carbon paper while making the thickness of the applied mixture uniform. Here, the firing in the firing furnace and the fixing by the roller are repeated twice. Thus, the water management porous layer 5 is provided on the gas diffusion layer 4.

  FIG. 2 is a table showing the specifications of MEA (Membrane Electrode Assembly) used in this test. In this test, first, using a preliminary test CCM (Catalyst Coated Membrane) and a gas diffusion layer to be described later, the low molecular weight fluororesin mixing ratio of the water management porous layer and the application amount of the water management porous layer to the gas diffusion layer The power generation test was carried out under the conditions described later by changing. Here, preliminary test CCM uses a 25 μm-thick fluorine-based electrolyte membrane as the electrolyte membrane 2 and uses a carbon-supported platinum catalyst manufactured by Tanaka Kikinzoku Co., Ltd. as the cathode and anode catalyst layers 3. Then, from the test results, the mixing ratio and the coating amount having the most excellent power generation performance are found, and the water management porous layer 5 under the found conditions, the hydrocarbon-based film as the electrolyte membrane 2, and the ionomer The power generation test was performed by combining the catalyst layer 3 containing the fluorine-based polymer electrolyte and the gas diffusion layer described later. In addition, in this test, carbon paper KP (made by Mitsubishi Rayon Co., Ltd.) having a thickness of 120 μm, which is considered to be highly resistant to flooding, is used for the gas diffusion layer, Water treatment is applied. A water management porous layer is applied to the gas diffusion layer. An MEA is formed of the above materials, and this MEA is incorporated into a cell holder to form a single cell (unit cell). The cell holder is, for example, a carbon material machined by machining 16 linear channels having a rib width of 1 mm, a groove width of 1 mm, and a groove depth of 0.5 mm.

  FIG. 3 is a schematic configuration diagram of a power generation evaluation device used in the present test. The power generation evaluation device 9 includes two humidifiers 10 and 11, an electronic load device 12, and a data recording device (not shown). One humidifier 10 is provided in a fuel gas supply passage 14 for supplying a fuel gas to the anode 13 of the unit cell. In the fuel gas supply passage 14, a pressure reducing valve 15 and a flow meter 16 are provided on the upstream side of the humidifier 10 in order from the upstream side. The other humidifier 11 is provided in an oxidant gas supply passage 18 that supplies oxidant gas to the cathode 17 of the unit cell. A pressure reducing valve 19 and a flow meter 20 are provided in the oxidant gas supply passage 18 on the upstream side of the humidifier 11 in order from the upstream side. Moreover, it is also possible to set the current and voltage obtained by power generation to arbitrary values by the electronic load device 12 incorporated in the power generation evaluation device. The data acquisition system (model number: DELL LATITUDE D510 (the evaluation software is manufactured by NFU Inc. and the As510 fuel cell evaluation system is used)) follows the preset program, and the humidification temperature of the fuel gas and the oxidant gas The operation of the evaluation device such as the cell temperature, gas utilization, load voltage, and presence or absence of gas supply to the cell can be fully automatically controlled. In addition, the data acquisition device can automatically acquire cell voltage, current density, cell internal resistance, cell temperature, and the like. With such a configuration, the power generation evaluation device 9 can supply the fuel cell and the oxidant gas at an arbitrary flow rate previously humidified to the unit cell which is the test object, and the cell temperature and the gas humidification temperature can be arbitrarily selected. It can be set to

FIG. 4 is a table showing measurement conditions of this test. As shown in this figure, in this test, the cell temperature was kept at 75 ° C. throughout all the tests described later, and the humidification temperature of the fuel and the oxidant was changed from 40 ° C. to 85 ° C. Moreover, in this test, with the fuel utilization fixed at 70%, the oxidant utilization was performed in three patterns of 20%, 40% and 70%. Furthermore, in this test, the flow direction of the fuel gas and the flow direction of the oxidant gas were made to face each other. In the power generation evaluation apparatus used in this test, the maximum flow rate at the oxidant side mass flow controller is 3.0 L / min, so the maximum current densities at 20%, 40% and 70% utilization rates are respectively The values are 800 mA / cm ² , 1600 mA / cm ² and 2400 mA / cm ² .

FIG. 5 is a graph showing a current density-cell voltage curve when testing the power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM, wherein (a) is a low molecular weight fluororesin of the water management porous layer When the mixing ratio is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8 %, And when the coating amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (c) is 7.8% of the low molecular weight fluororesin mixing ratio of the water management porous layer and the water management porous The case where the application amount to the gas diffusion layer of the layer is 6.0 mg / cm ² is shown. In FIG. 5, the utilization rate is 20%, and the humidification temperature is 40 ° C. to 60 ° C.

As can be seen from FIG. 5, the cell with the low molecular weight fluororesin mixing ratio of the water management porous layer at 2.1% and the application amount of the water management porous layer to the gas diffusion layer at 2.0 mg / cm ² is the most power generating It has been confirmed that the performance is excellent. On the other hand, in the cell in which the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 6.0 mg / cm ² , the humidification temperature is 40 ° C. in particular. The cell voltage tended to decrease with the increase of the current density in the range from 50 ° C. to 50 ° C.

FIG. 6 is a graph showing a current density-cell voltage curve when testing the power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM, wherein (a) is a low molecular weight fluororesin of the water management porous layer When the mixing ratio is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8 %, And when the coating amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (c) is 7.8% of the low molecular weight fluororesin mixing ratio of the water management porous layer and the water management porous The case where the application amount to the gas diffusion layer of the layer is 6.0 mg / cm ² is shown. In FIG. 6, the utilization rate is 20%, and the humidification temperature is 65 ° C. to 85 ° C.

As can be seen from FIG. 6, the power generation performance is most excellent when the mixing ratio of the low molecular weight fluororesin in the water management porous layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 2. It could be confirmed that the cell was at 0 mg / cm ² . Moreover, in this cell, since the same power generation performance is exhibited in all the humidified temperature regions, it can be inferred that no flooding is caused at all. On the other hand, in the case of a cell in which the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 6.0 mg / cm ² , the humidification temperature is 65 ° C. Cell performance is greatly disturbed, and it is presumed that flooding has occurred. In cells in which the low molecular weight fluorocarbon resin mixing ratio of the water management porous layer is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , the power generation performance is increased as the humidification temperature increases. Tended to decrease.

FIG. 7 is a graph showing a current density-cell voltage curve when testing the power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM, wherein (a) is a low molecular weight fluororesin of the water management porous layer When the mixing ratio is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8 %, And when the coating amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (c) is 7.8% of the low molecular weight fluororesin mixing ratio of the water management porous layer and the water management porous The case where the application amount to the gas diffusion layer of the layer is 6.0 mg / cm ² is shown. In FIG. 7, the utilization rate is 40%, and the humidification temperature is 40 ° C. to 60 ° C.

As can be seen from FIG. 7, the power generation performance itself is such that the low molecular weight fluororesin mixing ratio of the water management porous layer is 2.1%, and the coating amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² Of the water management porous layer, the mixture ratio of the low molecular weight fluorocarbon resin in the water management porous layer is 7.8%, and the coating amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² It could be confirmed that the cell was excellent.

FIG. 8 is a graph showing a current density-cell voltage curve when testing the power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM, wherein (a) is a low molecular weight fluororesin of the water management porous layer When the mixing ratio is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8 %, And when the coating amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (c) is 7.8% of the low molecular weight fluororesin mixing ratio of the water management porous layer and the water management porous The case where the application amount to the gas diffusion layer of the layer is 6.0 mg / cm ² is shown. In FIG. 8, the utilization rate is 40%, and the humidification temperature is 65 ° C. to 85 ° C.

As can be seen from FIG. 8, the power generation performance was most excellent when the mixing ratio of the low molecular weight fluororesin in the water management porous layer was 7.8% and the application amount of the water management porous layer to the gas diffusion layer was 2. It could be confirmed that the cell was at 0 mg / cm ² . In addition, it was confirmed that this cell was almost uniform in power generation performance at all humidification temperatures of 65 ° C. to 85 ° C., and could generate power up to the measurement limit of 1600 mA / cm ² .

FIG. 9 is a graph showing a current density-cell voltage curve when testing the power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM, wherein (a) is a low molecular weight fluororesin of the water management porous layer When the mixing ratio is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8 %, And when the coating amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (c) is 7.8% of the low molecular weight fluororesin mixing ratio of the water management porous layer and the water management porous The case where the application amount to the gas diffusion layer of the layer is 6.0 mg / cm ² is shown. In FIG. 9, the utilization rate is 70%, and the humidification temperature is 40 ° C. to 60 ° C.

As can be seen from FIG. 9, the cell with the water management porous layer containing 7.8% of low-molecular-weight fluororesin and a coating amount of 2.0 mg / cm ² for the water management porous layer on the gas diffusion layer is the most power-generating It has been confirmed that the performance is excellent. It was also confirmed that this cell can generate power up to about 1500 mA / cm ² and 0.09 V even at 60 ° C. humidification. On the other hand, in the cell in which the low molecular weight fluorocarbon resin mixing ratio of the water management porous layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 6.0 mg / cm ² , the power generation performance decreases significantly. It can be seen that power can be generated only up to about 800 mA / cm ² .

FIG. 10 is a graph showing a current density-cell voltage curve when testing the power generation performance of a polymer electrolyte fuel cell having a preliminary test CCM, wherein (a) is a low molecular weight fluororesin of the water management porous layer When the mixing ratio is 2.1% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (b) is the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8 %, And when the coating amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² , (c) is 7.8% of the low molecular weight fluororesin mixing ratio of the water management porous layer and the water management porous The case where the application amount to the gas diffusion layer of the layer is 6.0 mg / cm ² is shown. In FIG. 10, the utilization rate is 70%, and the humidification temperature is 65 ° C. to 85 ° C.

As can be seen from FIG. 10, the cell in which the mixing ratio of the low molecular weight fluororesin in the water management porous layer is 7.8% and the application amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ² is the most Although the power generation performance was high, it was confirmed that the higher the current density, the more likely the flooding occurred. In addition, the cell with the water management porous layer containing 7.8% of low-molecular-weight fluorocarbon resin and an application amount of 6.0 mg / cm ² for the water management porous layer to the gas diffusion layer has the lowest power generation performance. From the fact that the cell performance is largely disturbed by the humidification at 65 ° C., it can be understood that the flooding has occurred.

Thus, as a result of conducting a preliminary test using the solid polymer fuel cell 1 having a preliminary test CCM, the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8%, and the gas diffusion of the water management porous layer It was shown that when the coating amount to the layer was 2.0 mg / cm ² , the best power generation performance could be obtained. Therefore, based on this result, the mixing ratio of the low molecular weight fluororesin of the water management porous layer 5 is 7.8%, and the application amount of the water management porous layer 5 to the gas diffusion layer 4 is 2.0 mg / cm ² . The test of the power generation performance of the polymer electrolyte fuel cell 1 of this example was conducted, and comparative evaluation was performed with the polymer electrolyte fuel cell 1 having the preliminary test CCM. The polymer electrolyte fuel cell 1 of this example, as shown in FIG. 2, has a water management porous layer 5 having the conditions found by the preliminary test, a hydrocarbon-based membrane as an electrolyte membrane, and fluorine which is an ionomer. A catalyst layer 3 containing a polymer electrolyte and a gas diffusion layer 4 are provided.

The following FIGS. 11 to 16 show a book in which the low molecular weight fluororesin mixing ratio of the water management porous layer is 7.8% and the coating amount of the water management porous layer to the gas diffusion layer is 2.0 mg / cm ^2. It is a figure which shows the test result of the electric power generation performance of the polymer electrolyte fuel cell 1 of an Example. Here, FIGS. 11 to 16 are graphs showing a current density-cell voltage curve when testing the power generation performance of the polymer electrolyte fuel cell of this example, and FIG. 11 shows a utilization rate of 20%. When the humidification temperature is 40 ° C to 60 ° C, Fig. 12 shows a utilization rate of 20% and the humidification temperature of 65 ° C to 85 ° C. Fig. 13 shows the utilization rate of 40% at a humidification temperature of 40 ° C to 60 ° C. When the humidification temperature is 65 ° C to 85 ° C at 40% rate, Fig. 15 shows the case of 70% utilization rate at 40% to 60 ° C, and Fig. 16 shows 70% utilization rate at 65 ° C to 85 ° C. It shows.

  As can be seen from these figures, the polymer electrolyte fuel cell 1 of this example is compared with the polymer electrolyte fuel cell 1 having the preliminary test CCM at the utilization rates of 20%, 40% and 70%. The improvement of the power generation performance has been confirmed in the low humidification area where the humidification temperature is 40 ° C to 60 ° C. In addition, the polymer electrolyte fuel cell 1 of the present example exhibits substantially the same power generation performance as the polymer electrolyte fuel cell 1 having the preliminary test CCM under high humidification conditions of a humidification temperature of 65 ° C. to 85 ° C. That was confirmed.

  Here, FIG. 17 is a graph showing the relationship between the fluorine resin content, the amount of application, and the thickness of the water management porous layer 5 of the polymer electrolyte fuel cell 1 used in the present test. That is, each of the above-described water management porous layers 5 of the solid polymer fuel cell 1 having the preliminary test CCM and the solid polymer fuel cell 1 having the hydrocarbon film and the catalyst layer 3 containing the fluorine-based polymer electrolyte. It shows the relationship of values. In FIG. 17, the conditions (a), (b) and (c) indicate the mixing ratio and the application amount of the low molecular weight fluororesin of the water management porous layer 5 described above (a), (b) and (c) Respectively. As can be seen from this figure, the polymer electrolyte fuel cell 1 used in this test has a value of k in the range of 15 ≦ k ≦ 200.

  If the mixing ratio of the low molecular weight fluorocarbon resin in the water management porous layer is increased through this test, the power generation performance on the high humidity side is generally improved, and the coating amount of the water management porous layer to the gas diffusion layer is increased. In general, there was a tendency for the power generation performance to decline. This is considered to be due to the following reasons.

  FIG. 18 is an explanatory view for explaining the effect of the water management porous layer, in which (a) shows the case without the water management porous layer and (b) shows the case with the water management porous layer. As shown in this figure, normally, by forming the water management porous layer 5, the retention and discharge of generated water on the cathode side are appropriately performed, and the cell in a low humidified atmosphere which tends to be in a dry state Power generation performance will be improved. On the other hand, in a highly humidified atmosphere, the amount of generated water held in the water management porous layer 5 is large, and flooding easily occurs. Therefore, by mixing a low molecular weight fluorocarbon resin having hydrophobicity with the water management porous layer 5, the dischargeability of generated water from the water management porous layer 5 to the gas diffusion layer can be improved.

  From this, also in the present test, as the mixing ratio of the low molecular weight fluorine resin increases, the retention and discharge properties of the generated water of the water management porous layer 5 can be optimized, and in particular, the highly humidified atmosphere which becomes highly wet. Below, it can be inferred that the larger effect was exhibited. That is, the water repellency is further improved as the amount of the low molecular weight fluorine resin is increased, and the inside of the cell becomes highly wet, and in addition, the generated water can be rapidly generated even in the highly humidified state where the dischargeability of the produced water is deteriorated. It is presumed that water can be discharged out of the cell.

  When the coating amount of the water management porous layer 5 to the gas diffusion layer 4 is increased, the permeation of the fuel gas and the oxidant gas to the catalyst layer 3 is inhibited by the increase of the thickness of the water management porous layer 5, and the catalyst layer The dischargeability of the generated water from 3 to the gas diffusion layer 4 is reduced. Therefore, it is presumed that the deterioration of the power generation performance of the polymer electrolyte fuel cell 1 and the flooding were caused.

By the way, the conditions under which the power generation performance was most excellent in the above-mentioned preliminary test (the low molecular weight fluororesin mixing ratio of water management porous layer is 7.8%, and the coating amount of water management porous layer to gas diffusion layer is 2.0 mg / cm ^In the case of ² ), in the power generation test this time, the solid polymer fuel cell 1 of the present example using the hydrocarbon membrane as the electrolyte membrane in the low utilization rate condition and the low humidification region has a solid high with preliminary test CCM. It was found that the power generation performance, the dry-up resistance and the anti-flooding resistance were further superior to those of the molecular fuel cell 1. In addition, the polymer electrolyte fuel cell 1 of this example exhibited substantially the same performance as the polymer electrolyte fuel cell 1 having the preliminary test CCM in the high humidification region. This is due to the effect of the low molecular weight fluorine resin mixed in the water management porous layer 5 in addition to the dry-up resistance under a low humidity atmosphere and the flooding resistance performance in a high humidity atmosphere, which are characteristic of hydrocarbon-based membranes. It is considered that the generated water can be easily discharged even in the high humidification area.

  The polymer electrolyte fuel cell of the present invention is not limited to the constitution of the above embodiment, and can be appropriately modified. For example, in the above embodiment, the water management porous layer 5 is provided between one catalyst layer 3 and one gas diffusion layer 4 and between the other catalyst layer 3 and the other gas diffusion layer 4. However, it may be provided between one catalyst layer 3 and one gas diffusion layer 4 or between the other catalyst layer 3 and the other gas diffusion layer 4.

  The present invention can be suitably used for a polymer electrolyte fuel cell.

1 solid polymer electrolyte fuel cell 2 solid polymer electrolyte membrane 3 catalyst layer 4 gas diffusion layer 5 water management porous layer

Claims (3)

Solid polymer electrolyte membrane,
Catalyst layers respectively provided on both sides of the solid polymer electrolyte membrane;
Gas diffusion layers respectively provided to the two catalyst layers;
A water management porous layer provided between one of the catalyst layer and one of the gas diffusion layers and / or between the other of the catalyst layer and the other of the gas diffusion layers and containing a water repellent material; Equipped
A value k obtained from the thickness t [μm] of the water management porous layer, the concentration c [%] of the water repellent material, and the molecular weight m of the water repellent material is set by the following equation, 15 ≦ k ≦ 200 A polymer electrolyte fuel cell characterized in that
k = t · c / log m The solid polymer fuel according to claim 1, wherein the thickness t of the water management porous layer is 10 μm to 100 μm, and the concentration c of the water repellent material is 1% to 30%. battery. The molecular weight m of the said water repellent material is 100-100 million. The polymer electrolyte fuel cell of Claim 1 or Claim 2 characterized by the above-mentioned.

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