JP2013020843A - Gas diffusion electrode and fuel cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas diffusion electrode having a high drainage function of water produced during power generation and an excellent water-retention function for preventing dry-up of a polymer electrolytic membrane, and to provide a fuel cell using the same.SOLUTION: The gas diffusion electrode for solid polymer fuel cell using a carbonaceous porous body is provided with trenches in the contact surface with a separator. The gas diffusion electrode for solid polymer fuel cell using a carbonaceous porous body is provided with trenches having a width of 0.1-2.0 mm and a depth of 5-100 μm in the contact surface with a separator, at a pitch of 0.5-2.0 mm. The trenches are formed by applying the water jet punching method to a paper body.

Description

  The present invention relates to a gas diffusion electrode used for a polymer electrolyte fuel cell and a fuel cell using the same.

  A polymer electrolyte fuel cell is an apparatus that obtains an electromotive force by electrochemically reacting a fuel gas such as hydrogen and an oxidizing gas such as oxygen. The polymer electrolyte fuel cell includes a hydrogen ion (proton). And a polymer electrolyte membrane that selectively conducts. Further, two sets of gas diffusion electrodes each having a catalyst layer mainly composed of carbon powder carrying a noble metal catalyst and a gas diffusion electrode substrate are joined to both surfaces of the polymer electrolyte membrane.

  Such a joined body composed of a polymer electrolyte membrane and two sets of gas diffusion electrodes is called a membrane-electrode assembly (MEA). Further, on both outer sides of the MEA, separators are provided in which gas flow paths for supplying fuel gas or oxidizing gas and for discharging generated gas and excess gas are formed.

  The gas diffusion electrode mainly requires the following three functions. The first function is a function of uniformly supplying the fuel gas or the oxidizing gas to the noble metal-based catalyst in the catalyst layer from the gas flow path formed in the separator disposed outside the first function. The second function is a moisture management function that achieves both a function of discharging water generated by the reaction in the catalyst layer and a water retention function for preventing the electrolyte membrane from drying. The third function is a function of conducting electrons necessary for the reaction in the catalyst layer or electrons generated by the reaction in the catalyst layer to the separator. As a base material satisfying these functions, a base material having a porous structure made of a carbonaceous material is usually used.

  The base material having a porous structure is made of a paper-like carbon / carbon composite obtained by making a short carbon fiber, binding it with an organic polymer, and firing it at a high temperature to carbonize the organic polymer. Things are known. Moreover, in order to prevent the voltage drop which arises by the retention of the produced water during electric power generation, it is known to use together the porous material from which a pore diameter differs (refer patent document 1).

JP 2009-234851

  However, the fuel cell using the porous carbon sheet disclosed in Patent Document 1 is excellent in drainage of generated water, but has no water retention function, and therefore, depending on operating conditions such as low humidity inside the battery, the polymer The electrolyte membrane was dried, and there was a tendency that a sufficient electromotive force could not be obtained.

  The present invention overcomes the above-described problems, and provides a gas diffusion electrode having a high drainage function of generated water during power generation and an excellent water retention function that prevents drying of the polymer electrolyte membrane, and a fuel cell using the gas diffusion electrode The purpose is to do.

  The above problems are solved by the following inventions [1] to [6].

  [1] A gas diffusion electrode for a polymer electrolyte fuel cell using a carbonaceous porous body, wherein a groove is provided on a contact surface with the separator.

  [2] The gas diffusion electrode according to [1], wherein grooves having a width of 0.1 to 2.0 mm and a depth of 5 to 100 μm are provided on the contact surface with the separator at a pitch of 0.5 to 2.0 mm. .

  [3] The gas diffusion electrode according to [1] or [2], wherein the groove is formed by applying a water jet punching method to the paper body.

  [4] The gas diffusion electrode according to any one of [1] to [3], wherein the groove has a sine wave shape.

  [5] A polymer electrolyte fuel cell using the gas diffusion electrode according to any one of [1] to [4].

  [6] A polymer electrolyte fuel cell in which the gas diffusion electrode according to any one of [1] to [4] is disposed so that a surface having a groove faces a separator.

  According to the present invention, it is possible to manufacture a gas diffusion electrode that has a high drainage function of generated water during power generation and an excellent water retention function that prevents drying of the polymer electrolyte membrane, and a fuel cell using the gas diffusion electrode.

It is a block diagram of a solid polymer type fuel cell of the present invention. It is a gas diffusion electrode for polymer electrolyte fuel cells obtained in an example, and is a view showing a groove provided on the gas diffusion electrode. It is the figure which showed arrangement | positioning at the time of assembling | attaching the gas diffusion electrode for polymer electrolyte fuel cells obtained in the Example to a fuel cell.

  The present invention relates to a gas diffusion electrode for a polymer electrolyte fuel cell using a carbonaceous porous body, in which a groove is provided on a contact surface with a separator to form a flow path for controlling the flow of a reaction gas. It is a gas diffusion electrode for molecular fuel cells. Details will be described below.

  Examples of the carbonaceous porous body held in the gas diffusion electrode of the polymer electrolyte fuel cell include a carbonaceous porous body in which short carbon fibers are bound by carbon. Here, the carbon short fiber is a carbon fiber cut into an arbitrary fiber length. The length of the short carbon fiber is preferably 2 to 12 mm, and more preferably 3 to 9 mm. Within this range, dispersibility during papermaking and mechanical strength as a gas diffusion electrode are increased.

  The short carbon fiber can be used regardless of the raw material, but one or more selected from polyacrylonitrile (hereinafter abbreviated as PAN) carbon fiber, pitch carbon fiber, rayon carbon fiber, and phenolic carbon fiber. It is preferable that the carbon fiber is included, and it is more preferable that the PAN-based carbon fiber or the pitch-based carbon fiber is included.

  The average diameter of the short carbon fibers is preferably about 3 to 30 μm, more preferably 4 to 20 μm, and still more preferably 4 to 8 μm. Within this range, the surface smoothness and conductivity as a gas diffusion electrode are good.

  Examples of the carbon material for binding the short carbon fibers to each other include a carbon material obtained by carbonizing a resin and a carbon material obtained by carbonizing an organic fiber. As the resin to be carbonized, a known resin that can bind the carbon fiber of the gas diffusion electrode at the stage of carbonization can be appropriately selected and used. From the viewpoint of easily remaining as a conductive substance after carbonization, a phenol resin, an epoxy resin, a furan resin, pitch, and the like are preferable, and a phenol resin having a high carbonization rate is particularly preferable when carbonized by heating. As the organic fiber to be carbonized, a carbon fiber precursor short fiber obtained by cutting a long carbon fiber precursor fiber into an appropriate length, or a fibrous trunk having a diameter of 100 μm or less, for example, a diameter of several μm or less ( For example, carbon precursor fibers (b′-1) having a structure in which a large number of fibrils of 0.1 to 3 μm are branched (hereinafter sometimes referred to simply as “fibers (b′-1)”), or fibrillation by beating. Carbon fiber precursor short fibers (b′-2) (hereinafter simply referred to as “fibers (b′-2)”) and the like fibrillated carbon precursor fibers (b ′).

  Carbonization of the carbon material can be performed by firing at 1500 to 2200 ° C. in an inert gas.

  The carbonaceous porous body of the present invention is a gas diffusion electrode for a polymer electrolyte fuel cell in which a groove is provided on a contact surface with a separator. The groove provided on the contact surface of the carbonaceous porous body with the reaction gas serves as a flow path for controlling the flow of the reaction gas. Here, the flow path means not only the flow of fuel gas and oxidant gas (collectively referred to as “reaction gas”) in general fuel cells, but also the flow of reaction gas is controlled efficiently. In addition to reacting, it plays a role such as discharge of generated water generated during power generation. Accordingly, the flow path (groove) needs to be formed on the contact surface of the gas diffusion electrode with the separator.

  In order to manufacture a gas diffusion electrode having a flow path, there is a method of forming a flow path by providing grooves by fine machining or the like in the gas diffusion electrode after carbonization. When providing the groove, the groove may be formed by providing a concave portion on the gas diffusion electrode, the groove may be formed by providing a convex, or the groove is formed by providing the concave and convex portions. May be. Specifically, a high-pressure liquid injection method such as a water jet punching method performed during paper making when the substrate has flexibility, a high-pressure gas injection method such as a steam jet punching method, a water jet punching method performed by striking high-pressure water, A mechanical entanglement method such as a steam jet method or a needle punching method performed by high-pressure steam, or a combination of these methods can be used.

  In the method of performing machining after carbonization, the gas diffusion electrode has a problem that carbon powder is generated at the time of cutting, and in the needle punching method, the carbon short fibers may be broken. On the other hand, if the water jet punching method and the steam jet method using high-pressure steam are used, not only the above-mentioned problems will occur, but also various shapes of flow paths can be continuously formed, and a three-dimensional entanglement structure can be formed on the paper body. As a result, the strength of the paper body is improved. It is suitable to strike a liquid rather than a gas on a paper body to form a deeper flow path. From this viewpoint, it is preferable to use a water jet punching method. In the water jet method, the width of the flow channel to be formed can be changed by changing the hole diameter of the water jet nozzle, and the interval between the flow channels can be changed by changing the pitch between the nozzles. When a sinusoidal flow path is formed, the amplitude and period of the formed flow path can be changed depending on the change of the amplitude and the amplitude period of the nozzle. As described above, according to the water jet punching method, it is possible to manufacture gas diffusion electrodes having various flow channel shapes.

  In the present invention, “controlling the flow of the reaction gas” means adjusting the flow of the reaction gas in the same direction or making it meander according to the purpose. For example, in order to react efficiently by controlling the flow of the reaction gas, the flow of the reaction gas may be meandered.

  The shape of the groove (flow path) in the gas diffusion electrode of the present invention may be either a straight line or a curved line. However, even if the shape of the groove (channel) is linear or curved, if the groove (channel) has a non-uniform channel distribution in the surface direction of the gas diffusion electrode, such as a quadratic curve, Depending on the direction of the flow path shape, the water retention and drainage properties change greatly, and as a result, the power generation performance changes greatly. Therefore, care must be taken when assembling the gas diffusion electrode to the fuel cell. If a gas diffusion electrode having a flow path shape with a substantially uniform groove (flow path) distribution in the surface direction of the gas diffusion electrode is used, the direction of the flow path may be changed by 90 degrees when the gas diffusion electrode is assembled to the fuel cell. The water retention and drainage properties are not significantly changed, and favorable power generation performance is obtained, which is preferable. As a gas diffusion electrode having a groove (channel) shape in which the groove (channel) distribution is almost uniform in the surface direction of the gas diffusion electrode, (1) the groove (channel) shape is zigzag and the zigzag is the same pattern Gas diffusion electrode in which the zigzag groove (flow path) is uniformly arranged on the electrode surface, and (2) the groove (flow path) has a sine wave shape, and the sine wave shape groove. A gas diffusion electrode in which (flow path) is uniformly arranged on the electrode surface can be mentioned.

The sine wave shape here refers to a curved shape having a constant period defined by a sine function. By oscillating the nozzle used in the water jet punching method at a constant frequency perpendicular to the sheet flow direction, a sinusoidal groove (flow path) can be formed in the sheet. The nozzle used in the water jet punching method may be a single row nozzle, but it is more preferable to use a plurality of rows of nozzles from the viewpoint of uniformly forming grooves (flow paths) on the entire surface of the sheet. Details are given below.
<Water jet punching>
The water jet punching method will be described below.

  In water jet punching, a high-pressure liquid jet nozzle having nozzle holes arranged in one or a plurality of rows that vibrate in a direction perpendicular to the sheet conveying direction is used, and a sinusoidal groove having a period of 20 to 100 mm and an amplitude of 1 to 3 mm. A (flow path) is formed on the sheet surface. If no vibration is applied to the high-pressure liquid jet nozzle, a linear flow path along the flow direction of the sheet can be formed.

  In water jet punching, a sinusoidal trajectory can be uniformly imparted to the sheet surface by vibrating the water jet nozzles arranged in one or more rows in a direction perpendicular to the sheet conveyance direction.

  The locus of water jet punching formed on the sheet surface is determined by the relationship between the sheet conveyance speed, the nozzle vibration speed, and the nozzle swing width. As a nozzle frequency, it is practical to control with about 1 to 1000 rpm and a swing width of about 6 mm. When the sheet conveyance speed is set to 1 to 10 m / min, the cycle is 20 to 100 mm and the amplitude is 1 to 3 mm. A sinusoidal shape can be formed on the sheet.

  In order to further strengthen the groove (flow path) forming process and the sheet entanglement, it is possible to repeatedly perform the process using the water jet nozzle. For example, the pitch between rows of nozzles can be set to 30 cm, and two nozzles can be fixed and vibration can be applied by a single nozzle vibration device.

  The diameter of the nozzle hole for generating a high-pressure water flow of the high-pressure liquid jet nozzle is preferably 0.05 to 0.3 mm. When the diameter is 0.05 mm or more, the hitting force of water jet punching is suitable, and groove (flow path) formation and entanglement processing can be performed efficiently. If the diameter is 0.3 mm or less, it is possible to easily prevent the water jet punching water amount from increasing and the striking force to become strong, and it is possible to easily prevent the surface from becoming rough due to thick trajectories remaining on the sheet surface.

  The pitch between the nozzle holes of the high-pressure liquid jet nozzle is not particularly limited. The narrower the pitch between holes, the higher the density of the entanglement treatment is possible. 3 mm is preferred.

  The pressure of the high-pressure water flow of the high-pressure liquid jet nozzle is preferably 0.1 to 6 MPa. When the pressure is 0.1 MPa or more, it is easy to improve the formation state of the grooves (flow paths) and the entanglement of the fibers. When the pressure is 6 MPa or less, it is possible to easily prevent the form of the gas diffusion electrode precursor sheet from collapsing and breaking.

  The sine wave shape in the present invention does not need to be strictly a sine wave shape, and includes a substantially sine wave shape. From the viewpoint of power generation performance, it is preferable that the groove (channel) distribution on the surface of the gas diffusion electrode is more uniform, so it is preferable to be closer to the sine wave shape, and most preferably in the sine wave shape in a strict sense. is there.

  The gas diffusion electrode having a groove (flow path) in the fuel cell is preferably arranged so that the surface of the gas diffusion electrode having the groove (flow path) faces the separator. By arranging in this way, gas and moisture flowing through the groove (flow path) of the separator can be efficiently transported.

  As shown in FIG. 1, the solid polymer fuel cell is composed of a polymer electrolyte membrane, a catalyst layer, a gas diffusion electrode, and a current collector. Generally, each structural unit is arranged vertically and stacked in the horizontal direction.

  In the polymer electrolyte fuel cell in which the structural units are arranged vertically as described above, when the shape of the groove (flow path) of the gas diffusion electrode of the present invention is a zigzag shape or a sinusoidal shape, the present invention When this gas diffusion electrode is used as a fuel electrode (hydrogen electrode), it is effective in terms of moisture retention by arranging a zigzag shape or a sine wave shape in a direction perpendicular to the vertical direction. Further, when used as an oxidant electrode (oxygen electrode), it is preferable to provide a zigzag shape or a sine wave shape in the vertical direction to provide a drainage function.

  The width of the groove provided in the gas diffusion electrode of the present invention is preferably 0.1 to 2.0 mm, more preferably 0.2 to 1.5 mm. When the width of the groove is too narrow, the function as the flow path is not sufficiently exhibited, and when it is too wide, the roughness of the surface of the gas diffusion electrode cannot be kept good. Moreover, it is preferable that the depth of a groove | channel is 2-100 micrometers, More preferably, it is 5-50 micrometers. If the depth of the groove is too shallow, it will not show good drainage as a flow path, and if it is too deep, the strength of the gas diffusion electrode cannot be kept good. Furthermore, the pitch between the grooves is preferably in the range of 0.5 to 2.0 mm, more preferably 0.5 to 1.5 mm. If the pitch between the grooves is too narrow, the grooves cannot be formed with high accuracy, and if it is too wide, the ratio of the groove area in the surface cannot be kept large. In order to maximize the function as a groove and make the distribution of the groove in the plane of the gas diffusion electrode uniform, it is also effective to form the groove flow path in an overlapping manner.

<Example 1>
As the carbon short fiber (A), a PAN-based carbon fiber having an average fiber diameter of 7 μm and an average fiber length of 3 mm was prepared. Further, as the carbon fiber precursor short fibers (b), acrylic short fibers (Mitsubishi Rayon Co., Ltd., trade name: D122) having an average fiber diameter of 4 μm and an average fiber length of 3 mm, fibrillated carbon precursor fibers (b) ′), An easily split fiber acrylic sea-island type composite short fiber (made by Mitsubishi Rayon Co., Ltd., trade name: Bonnell MVP) consisting of an acrylic polymer fibrillated by beating and diacetate (cellulose acetate). . -C651, average fiber length: 3 mm).

  By following the operations (1) to (6), a precursor sheet having a sinusoidal channel on the surface and a precursor sheet obtained by laminating and integrating two or more precursor sheets having a three-dimensional entangled structure are continuously formed. Manufactured.

(1) Disaggregation of carbon short fibers (A) The carbon short fibers (A) are dispersed in water so that the fiber concentration is 1% (10 g / L), disaggregated through a mixer, and disaggregated slurry fibers (SA) ).

(2) Disaggregation of carbon fiber precursor short fibers (b) The carbon fiber precursor short fibers (b) are dispersed in water so that the fiber concentration is 1% (10 g / L), and disaggregated through a mixer. A disaggregated slurry fiber (Sb) was obtained.

(3) Disaggregation of fibrillar carbon precursor fibers (b ′) The above split fiber acrylic sea-island composite short fibers are dispersed in water so that the fiber concentration is 1% (10 g / L) and beaten through a mixer. -It disaggregated and it was set as the disaggregation slurry fiber (Sb ').

(4) Production of precursor sheet Carbon short fiber (A), carbon fiber precursor short fiber (b), and fibrillar carbon precursor fiber (b ') are in a mass ratio of 60:20:20 and in slurry. The disaggregation slurry fiber (SA), disaggregation slurry fiber (Sb), disaggregation slurry fiber (Sb ′), and dilution water are weighed so that the concentration of the fiber becomes 2.88 g / L, and a standard square sheet machine (Kumaya) Using a product manufactured by Riki Kogyo Co., Ltd., trade name: No. 2555), it is manually dispersed in a two-dimensional plane (250 mm long, 250 mm wide) in accordance with JIS P-8209 method and dried. A precursor sheet having a basis weight of 60 g / m ² was obtained. In addition, the dispersion state of the carbon short fiber (A), the carbon fiber precursor short fiber (b), and the fibrillar carbon fiber precursor short fiber (b ′) in the precursor sheet was good.

(5) Manufacture of a precursor sheet having a three-dimensional entangled structure having a flow path A sheet made of a net that is continuously rotated by connecting a net drive unit and a plain woven mesh made of plastic net having a width of 60 cm and a length of 585 cm in a belt shape. The processing apparatus which consists of a shaped article conveyance apparatus, the slurry supply apparatus whose slurry supply part width is 48 cm, and the reduced pressure dehydration apparatus arrange | positioned under the net was used. A pressurized water jet treatment apparatus provided with the following three water jet nozzles was disposed downstream of the treatment apparatus.

Nozzle 1: hole diameter φ0.15 mm × 501 holes, width direction hole pitch 1 mm (1001 holes / width 1 m), single row arrangement, nozzle effective width 500 mm
Nozzle 2: hole diameter φ0.15 mm × 501 holes, pitch in the width direction hole 1 mm (1001 holes / width 1 m), one line arrangement, nozzle effective width 500 mm
Nozzle 3: hole diameter φ0.15 mm × 1002 holes, width direction hole pitch 1.5 mm, three rows, row pitch 5 mm, nozzle effective width 500 mm
The precursor sheet obtained in the above (4) was placed on a sheet-like conveying device. A three-dimensional entangled structure with a pressurized water jetting pressure of 1 MPa nozzle 1, a pressure of 2 MPa (nozzle 2), and a pressure of 1 MPa (nozzle 3), passing the precursor sheet in the order of nozzle 1, nozzle 2, nozzle 3 and adding an entanglement process A laminated integrated precursor sheet was obtained. This precursor sheet was formed with sinusoidal grooves (flow channels) having an amplitude of 2 mm and a period of 2 mm at a pitch of 1 mm, and the groove depth was 10 μm and the width was 0.5 mm.

(6) Drying treatment The precursor sheet integrated and laminated with the three-dimensional entangled structure was dried at 150 ° C. for 3 minutes by a pin tenter tester (PT-2A-400 manufactured by Sakurai Dyeing Machine Co., Ltd.). The dispersion state of the carbon short fibers (A), the carbon fiber precursor short fibers (b), and the fibrillar carbon precursor fibers (b ′) in the precursor sheet having the grooves and the three-dimensional entangled structure is good. Further, the entanglement of the fibers was good, no peeling occurred, and the handling property was good.

(7) Pressure heating molding Next, both sides of this precursor sheet are sandwiched between papers coated with a silicone release agent, and then heated under pressure at 180 ° C. and 3 MPa for 3 minutes in a batch press apparatus. Molded.

(8) Carbonization treatment Thereafter, this precursor sheet was carbonized in a batch carbonization furnace in a nitrogen gas atmosphere at 2000 ° C. for 1 hour to obtain a gas diffusion electrode. The obtained gas diffusion electrode is shown in FIG. On this gas diffusion electrode, sinusoidal grooves (flow channels) having an amplitude of 2 mm and a period of 2 mm were formed with a groove interval of 1 mm pitch, the groove depth was 10 μm, and the groove width was 0.5 mm.

(9) Fabrication of fuel cell A catalyst layer (catalyst layer area: 25 cm ² , Pt adhesion amount: 0.3 mg / cm ² ) made of catalyst-supported carbon (catalyst: Pt, catalyst support amount: 50% by mass) is formed on both sides. Perfused perfluorosulfonic acid polymer electrolyte membrane (film thickness: 30 μm) with two sets of gas diffusion so that the surface of the gas diffusion electrode that does not have a groove (flow path) is in contact with the polymer electrolyte membrane The membrane-electrode assembly (MEA) obtained by sandwiching the electrodes and joining them was sandwiched between two carbon separators having bellows-like gas flow paths to form a polymer electrolyte fuel cell (single cell). . At this time, the gas diffusion electrodes on the fuel electrode side and the oxidant electrode side are arranged so that the groove flow path faces the separator, and the amplitude of the sine wave is orthogonal to the horizontal direction for each of the fuel electrode and the oxidant electrode. (See FIG. 3).

(10) Evaluation of battery performance Hydrogen gas and air were supplied to the single cell at a temperature of 80 ° C. through a bubbler so that the relative humidity inside the cell would be 40%, thereby generating electric power. An electromotive force-current density curve was recorded, and the electromotive force taken out during power generation was evaluated at a current density of 0.8 A / cm ² . Similarly, hydrogen gas and air were supplied to the single cell at a temperature of 60 ° C. through a bubbler so that the relative humidity inside the cell was 100% to generate electric power. An electromotive force-current density curve was recorded, and the electromotive force taken out during power generation was evaluated at a current density of 0.8 A / cm ² . Regardless of the humidity conditions inside the battery, it showed good power generation performance. The results are shown in Table 1.

<Example 2>
Example 1 except that the groove (flow path) shape of the gas diffusion electrode on the oxidant electrode side is arranged so that the sine wave is rotated by 90 ° C. compared to Example 1 when the fuel cell is manufactured. It is the same. As a result of evaluating the battery performance, it showed good power generation performance regardless of humidification conditions. The results are shown in Table 1.

<Example 3>
Similar to Example 1 except that the groove (flow path) shape of the gas diffusion electrode on the fuel electrode side is arranged so that the sine wave is rotated by 90 ° C. compared to Example 1 when the fuel cell is manufactured. It is. As a result of evaluating the battery performance, it showed good power generation performance regardless of humidification conditions. The results are shown in Table 1.

<Example 4>
Similar to Example 2 except that the groove (flow path) shape of the gas diffusion electrode on the fuel electrode side is arranged so that the sine wave is rotated by 90 ° C. compared to Example 1 when the fuel cell is manufactured. It is. As a result of evaluating the battery performance, it showed good power generation performance regardless of humidification conditions. The results are shown in Table 1.

<Example 5>
When manufacturing a precursor sheet having three-dimensional entanglement, the water jet nozzle was not vibrated, and a linear groove (flow channel) shape was formed, and when a fuel cell was formed, a linear groove (flow Road) The same as in Example 1 except that the shape is arranged so as to extend in the vertical direction of the fuel cell. In addition, the groove | channel on the gas diffusion electrode after a precursor sheet | seat and a carbonization process was formed with the space | interval of 1 mm, the groove depth was 10 micrometers, and the groove width was 0.5 mm.
As a result of evaluating the battery performance, it showed good power generation performance regardless of humidification conditions. The results are shown in Table 1.

<Comparative Example 1>
The three-dimensional entanglement process was not performed when manufacturing the precursor sheet. That is, a gas diffusion electrode was obtained in the same manner as in Example 1 except that the groove (flow path) was not formed. A fuel cell was produced using the obtained gas diffusion electrode (gas diffusion electrode having no groove (channel)), and the power generation performance was evaluated. In the fuel cell using the obtained gas diffusion electrode, a decrease in electromotive force was observed under both low and high humidification conditions. The results are shown in Table 1.

<Comparative example 2>
The fuel cell is obtained by arranging the gas diffusion electrodes on the fuel electrode side and the oxidant electrode side so that the groove (flow path) surface of the gas diffusion electrode obtained in the same manner as in Example 1 faces the polymer electrolyte side. The power generation performance was evaluated. In the fuel cell using the obtained gas diffusion electrode, a decrease in electromotive force was observed under both low and high humidification conditions. The results are shown in Table 1.

Claims (6)

  A gas diffusion electrode for a polymer electrolyte fuel cell using a carbonaceous porous body, wherein a groove is provided on a contact surface with a separator.   The gas diffusion electrode according to claim 1, wherein grooves having a width of 0.1 to 2.0 mm and a depth of 5 to 100 µm are provided on a contact surface with the separator at a pitch of 0.5 to 2.0 mm.   The gas diffusion electrode according to claim 1 or 2, wherein the groove is formed by applying a water jet punching method to the paper body.   The gas diffusion electrode according to any one of claims 1 to 3, wherein the groove has a sinusoidal shape.   A polymer electrolyte fuel cell using the gas diffusion electrode according to claim 1.   5. A polymer electrolyte fuel cell in which the gas diffusion electrode according to claim 1 is disposed so that a surface having a groove faces a separator.