JP3596773B2 - Polymer electrolyte fuel cell - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polymer electrolyte fuel cell of the present invention, and more particularly to a gas diffusion layer of an electrode, that is, a gas diffusion electrode, which is a constituent element thereof.
[0002]
[Prior art]
A polymer electrolyte fuel cell supplies a fuel gas such as hydrogen and an oxidant gas such as air (generally, the fuel gas supply side is called an anode electrode, and the oxidant gas supply side is called a cathode electrode). It reacts electrochemically on a catalyst such as platinum, and generates electricity and heat simultaneously. The required ionic conductivity of the polymer electrolyte used in the polymer electrolyte fuel cell is maintained when the polymer electrolyte is sufficiently wetted with water. On the other hand, the electrode reaction as a battery is a reaction of generating water at a three-phase interface of a catalyst, a polymer electrolyte, and a reaction gas.If water vapor in a supplied gas and water generated by the electrode reaction are not quickly discharged, Water accumulates in the electrodes and the gas diffusion layer, resulting in poor gas diffusion and poor battery characteristics.
[0003]
From such a viewpoint, for the electrodes used in the polymer electrolyte fuel cell, measures are taken to promote moisturization of the polymer electrolyte and discharge of water. As a general electrode, an electrode obtained by forming a carbon powder supporting a noble metal serving as a catalyst layer, that is, carbon particles, on a porous carbon support serving as a gas diffusion layer is used.
[0004]
As the porous carbon support, a carbon nonwoven fabric such as carbon paper made of carbon fiber, a carbon cloth, or the like is used. These porous carbon supports are subjected to a water-repellent treatment using a dispersion of a polytetrafluoroethylene-based material in advance, so that the water produced by the electrode reaction is promptly discharged, and a polymer electrolyte is used. In general, the polymer electrolyte in the membrane or the electrode is made to be in an appropriate wet state. In addition, as another method, a countermeasure for mixing water-repellent carbon particles into the electrode catalyst layer to discharge excess water generated in the electrode catalyst layer has been taken.
[0005]
In Japanese Patent Application Laid-Open Nos. 8-124581 and 6-262562, the current collector is made of carbon cloth, and the mesh is gradually roughened in the direction from the gas inlet to the gas outlet. An example with improved diffusivity is disclosed.
[Patent Document 1]
JP-A-8-124583
[Patent Document 2]
JP-A-6-262562
[0006]
[Problems to be solved by the invention]
As described above, the electrode used in the conventional polymer electrolyte fuel cell uses a porous carbon support serving as a gas diffusion layer, and the porous carbon support includes a carbon paper made of carbon fiber or the like. Carbon nonwoven fabric, carbon cloth, or the like is used. Generally, the gas permeability of carbon nonwoven cloth is isotropic, whereas the gas permeability of carbon cloth in the thickness direction is larger than that in the in-plane direction due to pores derived from the mesh. For this reason, in general, carbon cloth is more excellent in discharging excess water generated in the catalyst layer, whereas water retention of water is better in carbon nonwoven cloth.
[0007]
As described above, there is a trade-off between the water discharge property and the water retention property of the gas diffusion layer, and it is difficult to achieve both the water discharge property and the water retention property of the catalyst layer in the gas diffusion layer, making it optimal under certain operating conditions. In this state, a suitable porous carbon support is selected.
Therefore, when the discharge current changes, or when the flow rate or humidification amount of the supplied gas changes, the catalyst layer may be in a state of insufficient moisture or a gas blocking state due to excessive moisture, and the battery characteristics may deteriorate. there were. This problem cannot be solved by the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-124583, in which the mesh is gradually roughened in the direction from the gas inlet to the gas outlet to improve the gas diffusibility.
Further, it is necessary that the supplied gas sufficiently reaches the polymer electrolyte membrane while maintaining a good balance between the water discharging property and the water retention.
[0008]
That is, moisture generated in the catalyst layer is quickly sucked into the gas diffusion layer, evaporated in the gas diffusion layer and efficiently discharged out of the battery, so that excessive water does not stay in the electrode catalyst, and the polymer electrolyte There is a demand for a high-performance electrode designed to maintain a suitable wet state and allow the supplied gas to sufficiently reach the polymer electrolyte membrane.
[0009]
Further, gradually changing the roughness of the mesh of the carbon cloth in the plane direction involves difficulties in manufacturing the carbon cloth and causes an increase in cost.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized in that a carbon support of a gas diffusion layer is provided with a porous density distribution. In addition, two methods are proposed for providing the density distribution of the porosity.
[0011]
A polymer electrolyte fuel cell based on the first method of the present invention is an electrolyte membrane comprising a hydrogen ion conductive polymer electrolyte membrane and a pair of electrodes arranged so as to sandwich the hydrogen ion conductive polymer electrolyte membrane. A fuel cell comprising: an electrode assembly; and a pair of separator plates having a gas flow path arranged so as to sandwich the electrolyte membrane-electrode assembly, wherein each of the electrodes is the hydrogen ion conductive polymer electrolyte. A catalyst layer in contact with the membrane, and a gas diffusion layer in contact with the catalyst layer, wherein the gas diffusion layer includes a carbon support containing carbon cloth, and the carbon support is at least a carbon support on the catalyst layer side. A plurality of carbon support layers, and a second carbon support layer laminated on the first carbon support layer on the side opposite to the catalyst layer, wherein the first carbon support layer and the second carbon support layer Second Pore distribution of Bon support layer, the first carbon support layer is finer, the second carbon support layer is rough, and the first carbon support layer and the second carbon support layer are integratedWherein the first carbon support layer includes at least a first weft layer having a small inter-weft spacing, and the second carbon support layer includes at least a second weft layer having a wide inter-weft spacing. The first carbon support layer and the second carbon support layer are made of carbon cloth knitted with a common warp yarn.It is characterized by the following. That is, the pore distribution is such that there are more smaller pores on the catalyst layer side and fewer smaller pores on the opposite side of the catalyst layer.
[0012]
Also,PreviousIt is effective that the mesh of the carbon cloth of the first carbon support layer is fine and the mesh of the carbon cloth of the second carbon support layer is coarse..
[0013]
Further, it is effective that the carbon support comprises a carbon cloth formed by knitting a yarn having a small thickness and a carbon cloth formed by knitting a yarn having a large thickness.
Further, it is effective that the carbon support is formed by laminating a carbon nonwoven cloth and the carbon cloth.
[0014]
Preferably, the gas diffusion layer has a polymer-containing conductive layer containing carbon powder and a fluororesin on the catalyst layer side.
Preferably, the carbon support is subjected to a water-repellent treatment.
[0015]
Further, a polymer electrolyte fuel cell based on the second method of the present invention includes a hydrogen ion conductive polymer electrolyte membrane and a pair of electrodes arranged so as to sandwich the hydrogen ion conductive polymer electrolyte membrane. A fuel cell comprising: an electrolyte membrane-electrode assembly; and a pair of separator plates having a gas flow path arranged so as to sandwich the electrolyte membrane-electrode assembly, wherein each of the electrodes has a high hydrogen ion conductivity. It has a catalyst layer in contact with a molecular electrolyte membrane, and a gas diffusion layer in contact with the catalyst layer, wherein the gas diffusion layer includes carbon cloth, and the carbon cloth has intermittent meshes of different sizes in a plane direction. Is characterized in that
[0016]
Further, it is effective that the carbon cloth has a plurality of yarns having different thicknesses arranged periodically in a plane direction.
In the carbon cloth, it is effective that the interval between the weft yarns changes periodically in the surface direction.
[0017]
Preferably, the gas diffusion layer has a polymer-containing conductive layer containing carbon powder and a fluororesin on the catalyst layer side.
Preferably, the carbon cloth has been subjected to a water-repellent treatment.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 schematically shows the configuration of a polymer electrolyte fuel cell which is the basis of the present invention.
In FIG. 1, on both surfaces of a polymer electrolyte membrane 11 for selectively transporting hydrogen ions, a catalyst layer 12 mainly composed of a carbon powder carrying a platinum-based metal catalyst is disposed so as to be in close contact with and contact with the polymer layer. Further, on the outer surface of the catalyst layer 12, a pair of gas diffusion layers 13 composed of a porous carbon support having pores are arranged so as to be in close contact with the catalyst layer 12. The electrode 14 is constituted by the gas diffusion layer 13 and the catalyst layer 12. This electrode can also be called a gas diffusion electrode.
[0019]
Outside the electrode 14, a polymer electrolyte membrane-electrode assembly (hereinafter, MEA) 15 formed of the electrode 14 and the polymer electrolyte membrane 11 is mechanically fixed, and adjacent MEAs are electrically connected to each other. A separator plate 17 which is connected in series, further supplies a reaction gas to the electrode, and has a gas flow path 16 formed on one surface for carrying away water and excess gas generated by the reaction is arranged. Although the gas flow path can be provided separately from the separator plate 17, a method in which a groove is provided on the surface of the separator plate to form a gas flow path is generally used. Further, a gasket 18 is sandwiched between the polymer electrolyte membrane 11 and the separator plate 17 to prevent leakage of the reaction gas.
[0020]
During battery operation, oxygen or air, which is a reaction active material, is diffused from the gas flow path to the catalyst layer through the gas diffusion layer at the cathode electrode, and is generated by the reaction, and from the catalyst layer to the gas diffusion layer by a permeation effect. Excess moisture that has permeated is removed from the pores of the gas diffusion layer to the outside of the battery together with excess gas.
[0021]
The gas diffusion layer constituting the polymer electrolyte fuel cell based on the first method of the present invention has a porous carbon support, and its pore distribution is inclined so as to be fine on the catalyst layer side and coarse on the separator plate side. ing. That is, the pore distribution differs in the thickness direction of the gas diffusion layer. More specifically, the pore distribution is such that on the catalyst layer side, there are a larger number of smaller pores and on the opposite side of the catalyst layer, a smaller number of larger pores. By providing such an inclination, it is possible to achieve both the water discharging property and the water retention of the catalyst layer.
[0022]
That is, the water in the catalyst layer is held in the catalyst layer by the gas diffusion layer having a fine pore distribution, but when excess water is generated and the water overflows from the catalyst layer and reaches the gas diffusion layer, The water is guided to a layer having a coarser pore distribution and is quickly discharged from the catalyst layer. At that time, in the layer having a coarse pore distribution, the water and the gas are in a phase-separated state, and the water discharge path and the gas passage are separated, so that both the water discharge property and the water retention property to the catalyst layer can be achieved. .
[0023]
Further, the carbon cloth contained in the porous carbon support which is a component of the gas diffusion layer of the polymer electrolyte fuel cell based on the second method of the present invention has meshes of different sizes intermittently distributed in the plane direction. ing. That is, the pore distribution differs in the plane direction of the carbon cloth. That is, the large pores and the small pores are arranged intermittently, more preferably periodically, so as to achieve both the water discharging property of the gas diffusion layer and the gas diffusing property to the catalyst layer. Can be.
Excess water generated from the catalyst layer is guided to large pores and is quickly discharged from the catalyst layer. At that time, the gas diffuses from the small pores, so that the water discharge passage and the gas passage are separated, so that both water discharge and gas diffusion to the catalyst layer can be achieved.
[0024]
The gas diffusion layer constituting the polymer electrolyte fuel cell based on the first and second methods of the present invention preferably has a polymer-containing conductive layer containing carbon powder and a fluororesin on the catalyst layer side. . This has the effect of efficiently discharging excess water from the catalyst layer and preventing the electrodes from being short-circuited due to the porous carbon support sinking into the proton conductive polymer membrane.
[0025]
In order to form a gas diffusion layer in which the pore distribution is fine on the catalyst layer side and coarse on the separator plate side as in the polymer electrolyte fuel cell based on the first method of the present invention, (1) the mesh A method of laminating a plurality of cloths having different roughnesses, or (2) knitting a plurality of weft layers having different spacings between weft yarns with a common warp yarn, or (3) laminating a carbon nonwoven cloth and a carbon cloth. Good.
[0026]
The roughness of the mesh of the carbon cloth can be easily changed by using yarns having different thicknesses. By using a thicker thread, the mesh of the carbon cloth can be coarsened, i.e., the number per unit cross section is reduced, and as a result, the number of pores is reduced, and the average size of the pores is reduced. Can be made larger.
[0027]
This is more specifically expressed by the number of weft yarns or warp yarns crossing a cross section parallel to the longitudinal direction of either the warp yarns or the weft yarns of the carbon cloth as follows. That is, for example, when yarns having a thickness of 200 μm, 300 μm, and 600 μm, which are made by twisting fibers having a thickness of 10 μm, are used, the number of the yarns is per inch of a cut end (that is, in a cross section of 1 inch × cloth thickness). ), 70, 60 and 40 respectively. Further, in the case of using a band-shaped yarn having a width of 1 mm, the number of the yarns is 12 per inch of a cut end.
[0028]
In order to change the pore distribution of the carbon nonwoven fabric, the bulk density is changed. Specifically, the pore distribution of the carbon nonwoven fabric can be easily changed by using a carbon nonwoven fabric having a desired bulk density among carbon nonwoven fabrics such as carbon paper having different bulk densities. By using a carbon nonwoven fabric having a higher bulk density, the number of pores in the carbon nonwoven fabric can be increased, and the average size of the pores can be reduced. Although a carbon nonwoven fabric may be separately manufactured, it may be selected from commercially available carbon nonwoven fabrics.
[0029]
As a commercially available carbon nonwoven fabric, for example, in the case of carbon paper (product number MFG-070, MFV4-120) manufactured by Mitsubishi Rayon Co., the bulk density is 0.44 g / cm.³And 0.49 g / cm³In the case of carbon paper (product number TGP-H-060) manufactured by Toray Industries, the bulk density is 0.42 to 0.46 g / cm.³It is. Furthermore, in the case of carbon nonwoven fabric (manufactured by Ballard Material Products) (product number AvCarb P50T) and carbon nonwoven fabric (manufactured by Nippon Carbon Co., Ltd. (product number GF-20-N05)), the bulk density is 0.28 g / cm, respectively.³And 0.06 g / cm³It is.
[0030]
Next, as in the polymer electrolyte fuel cell based on the second method of the present invention, a carbon cloth in which meshes of different sizes are intermittently distributed in the plane direction, more preferably periodically, is formed. In order to configure, a method of (1) intermittently or periodically arranging a plurality of yarns having different thicknesses, or (2) intermittently or periodically changing an interval between weft yarns may be adopted. . In the above (1) and (2), the distribution of the mesh does not necessarily have to be periodic, but if the distribution is random, the characteristics will vary in the plane, and the battery voltage tends to decrease. For this reason, it is preferable that the distribution of meshes is periodic in order to ensure uniform characteristics in the plane.
[0031]
The size of the mesh can be defined by the interval between adjacent parallel yarns, and by arranging a thicker yarn, the mesh adjacent to the yarn can be enlarged. Further, by changing the interval between the yarns, the size of the mesh sandwiched between the yarns can be changed.
This can be expressed more specifically as the interval between adjacent parallel yarns of either the warp yarn or the weft yarn of the carbon cloth as follows. That is, for example, the interval between adjacent yarns of carbon cloth made by arranging 600 μm thick yarns every 300 μm yarns made by twisting 10 μm thick fibers is 300 μm thick yarns. Is about 0.42 mm, but the distance between a 300 μm thick yarn and a 600 μm thick yarn is about 0.53 mm.
[0032]
Further, the interval between adjacent yarns of the carbon cloth made by thinning out several yarns of 300 μm in thickness made by twisting fibers of 10 μm in thickness is about 0. It is 42 mm, but it is about 0.84 mm in the thinned part.
[0033]
The carbon cloth or the carbon support of the polymer electrolyte fuel cell based on the first and second systems of the present invention is desirably subjected to a water-repellent treatment when operating at a high current density. This is to enhance the water discharge property and prevent water from staying in the gas diffusion layer even when discharging at a high current density. As such a water-repellent treatment, there is a method in which a dispersion in which polytetrafluoroethylene is dispersed is impregnated into a carbon cloth or a carbon support and heat-treated.
[0034]
Carbon cloth can be made by knitting carbon fiber yarns. However, if a complicated mesh must be formed, knitting yarns made of PAN (polyacrylonitrile) fiber or the like to make a woven fabric. An effective method is to make it by heat treatment in an inert gas. Generally, nitrogen is used as the inert gas. The heat treatment temperature is generally from 1000 ° C. to 2000 ° C.
Hereinafter, embodiments will be specifically described.
[0035]
【Example】
<< Example 1 >>
First, as schematically shown in FIG. 2, a carbon cloth 20 was prepared in which the mesh roughness was fine so as to be fine on the catalyst layer side and coarse on the separator plate side.
A yarn having a thickness of about 300 μm made by twisting PAN-based fibers having a thickness of about 10 μm is referred to as a first layer weft yarn 20a, and a yarn having a thickness of about 600 μm obtained by twisting PAN-based fibers having a thickness of about 10 μm. As the second layer weft yarn 20b, a fabric was prepared in which a yarn having a thickness of about 600 μm was knitted as a warp yarn 20c of the second layer, and a yarn having a thickness of about 300 μm was formed as a warp yarn 20d connecting the first and second layers.
[0036]
This cloth was heated at 2000 ° C. for 24 hours in a nitrogen atmosphere to be graphitized to prepare a carbon cloth. FIG. 1 shows a cross section of the carbon cloth 20 and a surface viewed from the second layer side.
[0037]
The carbon cloth was impregnated with a dispersion of polytetrafluoroethylene (Rublon LDW-40 manufactured by Daikin Industries, Ltd.) at a dry weight of 10% by weight, and then heated at 350 ° C. using a hot air dryer. Water repellency treatment was performed.
Further, a polymer-containing conductive layer made of carbon powder and a fluororesin was formed. That is, a dispersion of polytetrafluoroethylene as a fluororesin (Rublon LDW-40, manufactured by Daikin) was mixed with Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd. as carbon powder at a dry weight of 30% by weight. The dispersion was applied to the fine side of the mesh of the water-repellent carbon cloth, and heated at 350 ° C. using a hot air drier to form a gas diffusion layer including a polymer-containing conductive layer.
[0038]
Next, an electrolyte membrane-electrode assembly (MEA) was prepared by the following method. 10 g of water was added to 10 g of a conductive carbon powder carrying 50% by weight of platinum particles having an average particle diameter of about 30 ° (manufactured by Tanaka Kikinzoku Kogyo KK: TEC10E50E), and 9% by weight of the hydrogen ion conductive polymer electrolyte was added. 55 g of an ethanol solution (Flemion, manufactured by Asahi Glass Co., Ltd.) was mixed to prepare a catalyst paste. This paste was applied on a polypropylene film by bar coating using a wire bar, and dried to form an oxidant electrode-side catalyst layer. The coating amount of the catalyst layer is such that the platinum content is 1 cm.²It was adjusted to be 0.3 mg per unit.
[0039]
To 10 g of a conductive carbon powder carrying a platinum-ruthenium alloy (Tanaka Kikinzoku Kogyo KK: TEC61E54), 10 g of water was added, and a 9% ethanol solution of a hydrogen ion conductive polymer electrolyte (manufactured by Asahi Glass Co., Ltd.) : Flemion) to prepare a catalyst paste. This paste was applied on a polypropylene film by bar coating using a wire bar, and dried to form a fuel electrode side catalyst layer. The coating amount of the catalyst layer is such that the platinum content is 1 cm.²It was adjusted to be 0.3 mg per unit.
[0040]
This polypropylene film with a catalyst layer was cut into 6 cm squares, and a hydrogen ion conductive polymer electrolyte membrane (manufactured by Japan Gore-Tex Co., Ltd .: Gore-Select, film thickness: 30 μm) was formed into two sets of the above-described catalyst layer-attached layers. After sandwiching the catalyst layer with a polypropylene film on the inside and hot pressing at 130 ° C. for 10 minutes, the polypropylene film was removed to obtain a polymer electrolyte membrane with a catalyst layer.
[0041]
An MEA was formed by sandwiching the gas diffusion layers 13 on both sides of the polymer electrolyte membrane with a catalyst layer such that the first layer was on the inside. Using the MEA, a fuel cell characteristic measuring cell (single cell) shown in FIG. 1 was assembled and tested.
[0042]
The temperature of the single cell was set to 70 ° C., and as an active material, hydrogen gas was humidified on the negative electrode side at a dew point of 70 ° C., and the utilization was 80%. When prepared and subjected to a discharge test while passing a current of 0 to 800 mA / cm 2, a good discharge voltage was shown regardless of the current density. FIG. 3 shows the current density-voltage characteristics of the cell. This is because the balance between the drainage performance and the water retention performance in the cell of the polymer electrolyte fuel cell could be well maintained, and a sufficient supply of supply gas to the polymer electrolyte membrane could be ensured.
[0043]
《referenceAn example1》
As schematically shown in FIG. 4, a first cloth in which a yarn having a thickness of about 300 μm is formed by twisting PAN-based fibers of about 10 μm into a plain weave, and a PAN-based fiber of about 10 μm in thickness are combined. Each of the second cloths having a thickness of about 600 μm and having a plain weave was heated at 2000 ° C. for 24 hours in a nitrogen atmosphere to be graphitized to prepare a carbon cloth 50.
[0044]
These carbon cloths 50 are subjected to a water-repellent treatment in the same manner as in Example 1, and a carbon cloth 50a made of the first cloth and a carbon cloth 50b made of the second cloth are overlapped to form a carbon cloth made of the first cloth. A layer made of carbon powder and a fluororesin was formed on the cloth side in the same manner as in Example 1 to form a gas diffusion layer. FIG. 4 shows a cross section of the carbon cloth and a surface viewed from the second cloth side.
[0045]
Using this gas diffusion layer, a cell for measuring fuel cell characteristics was assembled in the same manner as in Example 1, and a discharge test was performed. As a result, a good discharge voltage was exhibited regardless of the current density. FIG. 3 shows the current density-voltage characteristics of the cell.
[0046]
"Example2》
As schematically shown in FIG. 5, using a yarn having a thickness of about 300 μm by twisting PAN-based fibers having a thickness of about 10 μm and a yarn having a thickness of about 600 μm, a thick yarn 1 is used for every three thin yarns. The warp yarns 60b and the weft yarns 60a were arranged so as to form a book, and the plain woven cloth was heated at 2000 ° C. for 24 hours in a nitrogen atmosphere to be graphitized, thereby producing the carbon cloth 60.
This carbon cloth 60 was subjected to a water-repellent treatment and the formation of a layer composed of carbon powder and a fluororesin in the same manner as in Example 1 to form a gas diffusion layer.
FIG. 5 shows a cross section and a surface of the carbon cloth.
[0047]
Using this gas diffusion layer, a cell for measuring fuel cell characteristics was assembled in the same manner as in Example 1, and a discharge test was performed. As a result, a good discharge voltage was exhibited regardless of the current density. FIG. 3 shows the current density-voltage characteristics of the cell.
[0048]
"Example3》
As schematically shown in FIG. 6, a warp yarn is formed by twisting PAN-based fibers having a thickness of about 10 μm to a thickness of about 300 μm so that a gap of one yarn is opened for every three yarns. 70b and the weft 70a were arranged, respectively, and the plain-woven cloth was heated at 2000 ° C. for 24 hours in a nitrogen atmosphere to be graphitized to prepare a carbon cloth.
This carbon cloth 70 was subjected to a water-repellent treatment and the formation of a layer made of carbon powder and a fluororesin in the same manner as in Example 1 to form a gas diffusion layer.
FIG. 6 shows a cross section and a surface of the carbon cloth.
[0049]
Using this gas diffusion layer, a cell for measuring fuel cell characteristics was assembled in the same manner as in Example 1, and a discharge test was performed. As a result, a good discharge voltage was exhibited regardless of the current density. FIG. 8 shows the current density-voltage characteristics of the cell.
[0050]
"Example4》
A gas diffusion layer was formed in the same manner as in Example 1 except that a polymer-containing conductive layer made of carbon powder and a fluororesin was not formed on the gas diffusion layer.
Using this gas diffusion layer, a cell for measuring fuel cell characteristics was assembled in the same manner as in Example 1, and a discharge test was performed. As a result, although the voltage was low at a low current density, a high discharge voltage was exhibited at a high current density. . FIG. 8 shows the current density-voltage characteristics of the cell.
[0051]
"Example5》
A gas diffusion layer was formed in the same manner as in Example 1 except that the carbon cloth was not subjected to the water-repellent treatment.
A cell for measuring fuel cell characteristics was assembled using this gas diffusion layer in the same manner as in Example 1, and a discharge test was performed. As a result, the voltage was low at a high current density, but a high discharge voltage was exhibited at a low current density. . FIG. 8 shows the current density-voltage characteristics of the cell.
[0052]
"Example6》
A gas diffusion layer was formed in the same manner as in Example 1 except that a polymer-containing conductive layer made of carbon powder and a fluororesin was not formed on the gas diffusion layer, and a water-repellent treatment of carbon cloth was not performed.
A cell for measuring fuel cell characteristics was assembled using this gas diffusion layer in the same manner as in Example 1, and a discharge test was performed. As a result, the voltage was low at a high current density, but a high discharge voltage was exhibited at a low current density. . FIG. 8 shows the current density-voltage characteristics of the cell.
[0053]
《referenceAn example2》
As schematically shown in FIG. 9, a plain weave of a yarn having a thickness of about 300 μm made by twisting PAN-based fibers of about 10 μm is heated in a nitrogen atmosphere at 2000 ° C. for 24 hours to be graphitized. Thus, a carbon cloth 101 was produced.
A carbon paper 102 (TGP-H-060, thickness 180 μm, manufactured by Toray Industries, Inc.) was overlaid on the carbon cloth 101 to form a porous carbon support.
A layer made of carbon powder and a fluororesin was formed on the carbon paper side of the carbon support in the same manner as in Example 1 to form a gas diffusion layer. FIG. 9 shows the cross section of the carbon support and the surface viewed from the carbon paper side.
[0054]
Using this gas diffusion layer, a cell for measuring fuel cell characteristics was assembled in the same manner as in Example 1, and a discharge test was performed. As a result, a good discharge voltage was exhibited regardless of the current density. FIG. 8 shows the current density-voltage characteristics of the cell.
[0055]
These Examples 2 to6 and Reference Examples 1 and 2The reason why a good discharge voltage was obtained in Example 1 was that the balance between the drainage performance and the water retention performance in the cell of the polymer electrolyte fuel cell could be well maintained, and the supply gas This is because the supply to the polymer electrolyte membrane could be secured.
[0056]
As in some of the above embodiments, (1) an example of combining fine mesh carbon cloth on the catalyst layer side and a coarse mesh carbon cloth on the separator plate side, and (2) small pores on the catalyst layer side Various attempts were made to combine a large number of carbon nonwoven fabrics and a coarse mesh carbon cloth on the separator plate side. As a result, in the case of (1), the preferable current-voltage characteristic of the final cell was obtained by using a fine mesh carbon cloth having a number of 40 to 70 pieces per one inch of a cut, and using a coarse cloth. As the carbon cloth of the mesh, a carbon cloth having a number of 12 to 60 pieces per 1 inch of cut is used, and the ratio between the number of the fine carbon cloth and the number of the coarse carbon cloth is 1.2 times or more. Was the case.
[0057]
In the case of (2), the preferable current-voltage characteristics of the final cell were obtained because the carbon nonwoven fabric had a bulk density of 0.06 to 0.49 g / cm.³(That is, all of the commercially available carbon nonwoven fabrics exemplified above could be effectively used), and when using a coarse mesh carbon cloth having 12 to 60 wires per inch of cut end Met.
[0058]
Further, in the above embodiment, the two-layer structure of the first carbon support layer having many small pores and the second carbon support layer having many large pores has been exemplified. Even if it is changed to a multi-layer structure, the multi-layer structure has many small pores on the carbon support layer on the catalyst layer side and few large pores on the opposite side (separator plate side). For example, it was separately confirmed that the effects of the present invention were exhibited.
[0059]
<< Comparative Example >>
As schematically shown in FIG. 7, a PAN-based fiber having a thickness of about 300 μm made by twisting fibers of about 10 μm in thickness and plain-woven is heated in a nitrogen atmosphere at 2000 ° C. for 24 hours to be graphitized. Thus, a carbon cloth 80 was produced.
This carbon cloth 80 was subjected to a water-repellent treatment and the formation of a polymer-containing conductive layer made of carbon powder and a fluororesin in the same manner as in Example 1, thereby forming a gas diffusion layer.
FIG. 7 shows a cross section and a surface of the carbon cloth gas diffusion layer.
[0060]
A cell for measuring fuel cell characteristics was assembled using this gas diffusion layer in the same manner as in Example 1, and a discharge test was performed. As the current density increased, the discharge voltage decreased. FIG. 3 shows the current density-voltage characteristics of the cell.
[0061]
【The invention's effect】
As described above, according to the present invention, the balance between drainage performance and water retention performance in a cell of a polymer electrolyte fuel cell can be well maintained, and sufficient supply of a supply gas to a polymer electrolyte membrane can be ensured. As a result, the output performance of the fuel cell could be improved.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a polymer electrolyte fuel cell according to an embodiment and an example of the present invention.
FIG. 2 is a partial cross-sectional perspective view schematically illustrating a carbon cloth according to the first embodiment of the present invention.
FIG. 3 is a first embodiment of the present invention.andExample2, Reference Example 1, andFIG. 7 is a diagram illustrating current density-voltage characteristics of a single cell of a comparative example.
FIG. 4 of the present invention.referenceAn example1FIG. 2 is a partial cross-sectional perspective view schematically showing a carbon cloth in FIG.
FIG. 5 shows an embodiment of the present invention.2FIG. 2 is a partial cross-sectional perspective view schematically showing a carbon cloth in FIG.
FIG. 6 shows an embodiment of the present invention.3FIG. 2 is a partial cross-sectional perspective view schematically showing a carbon cloth in FIG.
FIG. 7 is a partial cross-sectional perspective view schematically showing a carbon cloth in a comparative example for comparison with the example of the present invention.
FIG. 8 shows an embodiment of the present invention.3From Example6 and Reference Example 2FIG. 4 is a diagram showing current density-voltage characteristics of the single cell of FIG.
FIG. 9 of the present invention.referenceAn example2FIG. 2 is a partial cross-sectional perspective view schematically showing a carbon cloth support in FIG.

Claims (11)

A hydrogen ion conductive polymer electrolyte membrane, an electrolyte membrane-electrode assembly comprising a pair of gas diffusion electrodes arranged so as to sandwich the hydrogen ion conductive polymer electrolyte membrane, and the electrolyte membrane-electrode assembly A fuel cell comprising: a pair of separator plates each having a gas flow path interposed therebetween, wherein each of the gas diffusion electrodes is a catalyst layer in contact with the hydrogen ion conductive polymer electrolyte membrane; and A gas diffusion layer in contact with the gas diffusion layer, the gas diffusion layer includes a carbon support containing carbon cloth, the carbon support is at least a first carbon support layer on the catalyst layer side, and the catalyst layer side And a second carbon support layer laminated on the first carbon support layer on a side opposite to the first carbon support layer, and a pore distribution of the first carbon support layer and the second carbon support layer. Is Serial first carbon backing layer finely the second carbon support layer is rough, and the first carbon support layer and the second carbon support layer are integrated, the first carbon support layer, The second carbon support layer includes at least a first weft layer with a narrow inter-weft spacing, the second carbon support layer includes a second weft layer with at least a wide inter-weft spacing, and the first carbon support layer and the second carbon support. A polymer electrolyte fuel cell , wherein the layers are made of carbon cloth knitted with a common warp . Before SL carbon cloth mesh is finer the first carbon support layer, a polymer electrolyte fuel cell of the mesh is coarse claim 1, wherein the carbon cloth of the second carbon support layer. 2. The polymer electrolyte fuel cell according to claim 1, wherein the carbon support comprises a carbon cloth formed by knitting a yarn having a small thickness and a carbon cloth formed by knitting a yarn having a large thickness. The polymer electrolyte fuel cell according to claim 1, wherein the carbon support is formed by laminating a carbon nonwoven fabric and the carbon cloth. The polymer electrolyte fuel cell according to claim 1, wherein the gas diffusion layer has a polymer-containing conductive layer containing conductive carbon powder and a fluororesin on the catalyst layer side. The polymer electrolyte fuel cell according to claim 1, wherein the carbon support is subjected to a water-repellent treatment. A hydrogen ion conductive polymer electrolyte membrane, an electrolyte membrane-electrode assembly comprising a pair of gas diffusion electrodes arranged so as to sandwich the hydrogen ion conductive polymer electrolyte membrane, and the electrolyte membrane-electrode assembly A fuel cell comprising: a pair of separator plates each having a gas flow path interposed therebetween; wherein each of the gas diffusion electrodes is a catalyst layer in contact with the proton conductive polymer electrolyte membrane; and A gas diffusion layer in contact with the gas diffusion layer, wherein the gas diffusion layer comprises a carbon support containing carbon cloth, wherein the gas diffusion layer comprises carbon cloth, A polymer electrolyte fuel cell characterized by being intermittently distributed in a cell. 8. The polymer electrolyte fuel cell according to claim 7 , wherein a plurality of yarns having different thicknesses are periodically arranged in the carbon cloth. The polymer electrolyte fuel cell according to claim 7 , wherein the weft of the carbon cloth changes periodically. The polymer electrolyte fuel cell according to claim 7 , wherein the gas diffusion layer has a polymer-containing conductive layer containing a conductive carbon powder and a fluororesin on the catalyst layer side. The polymer electrolyte fuel cell according to claim 7 , wherein the carbon cloth is subjected to a water-repellent treatment.

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