JP4240285B2 - Method for producing gas diffusion layer of polymer electrolyte fuel cell - Google Patents

Method for producing gas diffusion layer of polymer electrolyte fuel cell Download PDF

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JP4240285B2
JP4240285B2 JP2003045684A JP2003045684A JP4240285B2 JP 4240285 B2 JP4240285 B2 JP 4240285B2 JP 2003045684 A JP2003045684 A JP 2003045684A JP 2003045684 A JP2003045684 A JP 2003045684A JP 4240285 B2 JP4240285 B2 JP 4240285B2
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gas diffusion
diffusion layer
fuel cell
carbon
layer
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JP2004259463A (en
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崇徳 和田
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Fuji Electric Co Ltd
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Fuji Electric Holdings Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Description

【０００１】
【発明の属する技術分野】
この発明は、固体高分子型燃料電池におけるガス拡散層の製造方法に関する。
【０００２】
【従来の技術】
燃料電池は水素と酸素を利用し、電解質を介在して発電する装置である。固体高分子型燃料電池は、電解質として、高分子膜が含水することでイオン導電性を示す樹脂膜を用いたもので、その燃料電池セルの構成の斜視図を図４に示し、その一部拡大断面図を図３に示す。
【０００３】
図３および図４において、固体高分子電解質膜１の両面には、触媒層２と、多孔質のガス拡散層３とを備え、さらに、一方のガス拡散層に反応ガスとしての水素を含む燃料ガスを供給・排出するための燃料ガス流路を有し，他方の拡散層に反応ガスとしての酸化剤ガスを供給・排出するための酸化剤ガス流路を有してなるセパレータ５を備える。なお、図４においてセパレータは、一つのセパレータの両側に反応ガス流路を有するものを示したが、製造上の理由から、図３に示すように片側に流路を有するものを背中合わせに積層する場合もある。上記セルを多数積層したものをスタックという。
【０００４】
固体高分子電解質膜１としては、例えばパーフルオロスルホン酸ポリマー膜（米国，デュポン社，商品名Nafion膜）が用いられる。この膜は、飽和に含水させることで、常温で20Ω・cm以下の比抵抗を示し、プロトン伝導性電解質として機能する。膜の飽和含水量は温度によって可逆的に変化する。
【０００５】
固体高分子電解質膜１の両側に接合しているガス拡散層３の片方より水素、もう一方より酸素あるいは空気を供給することにより、固体高分子電解質膜１と触媒層２の界面における水素の酸化反応、酸素の還元反応によってプロトン，電子の移動が起こり、電気を得ることができる。
【０００６】
触媒層２は、粒子状の白金黒あるいは白金担持カーボンと撥水性を有するフッ素樹脂とから形成される。触媒層２としては、触媒の反応面積を拡大するため、触媒層の中に固体高分子電解質樹脂を混合した構成の電解質樹脂付触媒がよく用いられる。
【０００７】
ガス拡散層３としては、導電性のカーボンペーパーあるいはカーボンクロスを用いる。通常、固体高分子電解質膜１と触媒層２の接合体を作製したのち、ガス拡散層３をホットプレスにて接合するが、ガス拡散層３上に触媒層２を塗布して接合した後、固体高分子電解質膜１との接合体を作成する場合もある。
【０００８】
前記ガス拡散層３に関して、さらに詳述する。高い発電効率を得るためには、前記反応ガス流路から触媒層２へ反応ガス（H2、O2）が拡散により移動して、触媒層中の白金表面で反応させる際に、触媒層面内へ均等に反応ガスを供給する必要がある。そのために、前述のように、反応ガス流路と触媒層２との間にガス拡散層３を設けている。このガス拡散層３は、導電性多孔質材料からなり、一般に、数μmのカーボン繊維からなる厚さ数百μmのクロスやペーパーから形成される。
【０００９】
図２にガス拡散層の模式的構成図を示す。ガス拡散層としては、カーボンペーパーやカーボンクロス等の導電性多孔質基材のみで形成する場合（図２（ａ））と、基材の上に、カーボン撥水剤層を形成する場合（図２（ｂ））とがある。
【００１０】
図２（ａ）の場合、多数のカーボン繊維１３が絡み合って導電性多孔質の基材１１を構成し、この基材を所定寸法に形成してガス拡散層とする。図２（ｂ）のガス拡散層は、触媒層とガス拡散層との接触抵抗を下げるために、カーボン粒子と撥水剤とからなる、例えば厚さ数十μmのカーボン撥水剤層１２を、触媒層側の基材１１表面に形成してなる。
【００１１】
ところで、前述のように、ガス拡散層に、数μmのカーボン繊維からなる厚さ数百μmのクロスやペーパーを用いたような場合、その基材表面から、カーボン繊維が突出する場合がある。燃料電池スタックにおいては、ガス拡散層を含む電極部材間の接触抵抗増加による出力の損失を防ぐために、スタックの各積層部材は、その積層方向に加圧して締付けられる。
【００１２】
電池スタックを締付けた際に、基材１１の表面から突出したカーボン繊維１３により、触媒層２や固体高分子電解質膜１が損傷し、ピンホールができる場合がある。この場合には、燃料極と空気極の反応ガスのクロスリークが生じ、安定した運転ができなくなる可能性がある。また、触媒層側にカーボン撥水剤層１２が形成された場合においても、カーボン繊維１３がカーボン撥水剤層１２の表面から突出した場合には、同様の問題が生ずる。
【００１３】
上記の問題を解消するために、特許文献１は、下記の製造方法を開示している。即ち、「カーボンクロスの表面に撥水性カーボン層を形成した後、ホットプレスを施し表面を平坦化したものをガス拡散層とし、次いで撥水性カーボン層に隣接して触媒層を配置することにより電極を構成する製造方法」である（詳細は、特許文献１参照）。
【００１４】
【特許文献１】
特開２００１−８５０１９号公報（第２−３頁）
【００１５】
【発明が解決しようとする課題】
ところで、前述の特許文献１に記載された電極、主として、ガス拡散層の製造方法によれば、ホットプレスにより、ある程度の基材表面の平坦化を図ることができるものの、基材表面から突出したカーボン繊維は、反り返りがあるので、所期の平坦化もしくは平滑化がなされず、前記触媒層や固体高分子電解質膜の損傷が発生する可能性が残る。
【００１６】
また、特許文献１の方法のように、ホットプレスにより平坦化を図る場合、ホットプレスによりガス拡散層の少なくとも一部は塑性変形が生ずるので、寸法精度を安定して得るために相応の管理が必要となる。
【００１７】
この発明は、上記の点に鑑みてなされたもので、この発明の課題は、触媒層と隣接する側のガス拡散層表面の充分なる平滑化を安定的に図ることを可能とし、もって、燃料電池の安定した長時間連続運転を可能とする固体高分子型燃料電池のガス拡散層の製造方法を提供することにある。
【００１８】
【課題を解決するための手段】
前述の課題を解決するために、この発明は、固体高分子電解質膜を挟んで両主面に配設した触媒層と、この触媒層の両外側に配設した多孔質のガス拡散層とを備えた固体高分子型燃料電池の前記ガス拡散層の製造方法において、前記ガス拡散層は、カーボンペーパーやカーボンクロス等の導電性多孔質基材からなるものとし、この導電性多孔質基材を所定寸法に形成した後、前記触媒層と隣接する側の前記基材表面を、放電のアーク熱により平滑化処理し、前記平滑化処理は、前記導電性多孔質基材を一方の電極とし、かつグラファイト電極を他方の電極として、電気絶縁性の加工液中で前記両電極間にパルス電圧を印加し、これにより放電のアーク熱を発生させ、このアーク熱により、導電性多孔質基材の前記基材表面から突出したカーボン繊維を溶融させて平滑化する処理とする（請求項１の発明）。
【００１９】
上記によれば、触媒層側のガス拡散層表面から突出したカーボン繊維を、放電のアーク熱加工により焼失させることができ、これにより前記ガス拡散層表面が平滑化する。その結果、スタックを締付けた際に、ガス拡散層が原因となって触媒層や固体高分子膜が損傷することが防止され、空気極と燃料極の反応ガスクロスリークが起こりにくくなり、長時間安定した連続運転が可能となる。
【００２０】
上記請求項１の発明のように、グラファイト電極を用いることなしに、金属電極を用いた場合には、電極材料の溶融物が導電性多孔質基材に付着して、ガス拡散層の性能に悪影響を及ぼす問題が発生する恐れがあるが、導電性多孔質基材と同系統の電極材料を用いることにより前記悪影響は抑制される。なお、前記電気絶縁性の加工液としては、例えば、一般的な放電加工において使用される灯油が使用できる。
【００２１】
上記請求項１の発明の実施態様としては、下記請求項２ないし４の発明が好ましい。
【００２２】
即ち、前記請求項１に記載の製造方法において、前記パルス電圧を印加する両電極面の間隙は、１０〜５００μｍとする（請求項２の発明）。
【００２３】
さらに、カーボン撥水剤層を備える場合には、下記請求項３または４とする。即ち、前記請求項１または２に記載の製造方法において、前記平滑化処理後に、カーボン撥水剤層を前記基材表面に形成する（請求項３の発明）。または、前記請求項１または２に記載の製造方法において、予めカーボン撥水剤層を前記基材表面に形成した後に、前記平滑化処理を行なう（請求項４の発明）。
【００２４】
【発明の実施の形態】
図面に基づき、この発明の実施例について以下にのべる。
【００２５】
図１は、この発明の実施例に関わるガス拡散層の表面処理方法の模式的説明図を示し、ガス拡散層としては図２（ａ）に示したものに適用した例を示す。図１において、１１は基材、１４は放電加工反応槽、１５はグラファイト電極、１６は加工液、１７はアーク発生装置を示す。
【００２６】
放電加工反応槽１４の中には、電気絶縁性の加工液６（例えば、灯油）が満たされ、基材１１とグラファイト電極１５とが対面して配置される。基材１１を例えば陽極、グラファイト電極１５を陰極として、パルス電源を備えるアーク発生装置１７により、基材１１とグラファイト電極１５との間に、放電によりアークを発生させる。発生したアークにより、基材１１の表面から突出したカーボン繊維が焼失する。
【００２７】
基材１１とグラファイト電極１５との間の表面間距離は、基材表面から突出したカーボン繊維の状態により調整するが、電極表面にグラファイト電極５が接触すると、基材１１の表面が焼失する可能性があり、距離が長すぎると基材表面から突出したカーボン繊維が焼失する効果が得られない可能性がある。上記観点から、好ましい両電極の間隙の範囲は、10〜500μmとする。
【００２８】
なお、本実施例では、基材１１のみでガス拡散層が形成される場合の表面処理について説明したが、図２（ｂ）に示したカーボン撥水剤層を有するガス拡散層に関しても、その表面処理方法は同様である。また、前述のように、カーボン撥水剤層を上記図１の表面処理後に形成することもできる。
【００２９】
【発明の効果】
上記のとおり、この発明によれば、固体高分子電解質膜を挟んで両主面に配設した触媒層と、この触媒層の両外側に配設した多孔質のガス拡散層とを備えた固体高分子型燃料電池の前記ガス拡散層の製造方法において、前記ガス拡散層は、カーボンペーパーやカーボンクロス等の導電性多孔質基材からなるものとし、この導電性多孔質基材を所定寸法に形成した後、前記触媒層と隣接する側の前記基材表面を、放電のアーク熱により平滑化処理し、前記平滑化処理は、前記導電性多孔質基材を一方の電極とし、かつグラファイト電極を他方の電極として、電気絶縁性の加工液中で前記両電極間にパルス電圧を印加し、これにより放電のアーク熱を発生させ、このアーク熱により、導電性多孔質基材の前記基材表面から突出したカーボン繊維を溶融させて平滑化する処理とし、
前記ガス拡散層が、カーボン撥水剤層を備えるものとする場合には、前記平滑化処理後にカーボン撥水剤層を形成する、もしくは予めカーボン撥水剤層を形成した後に前記平滑化処理を行なうこととしたので、
触媒層と隣接する側のガス拡散層表面の充分なる平滑化を安定的に図ることを可能とし、もって、燃料電池の安定した長時間連続運転を可能とすることができる。
【図面の簡単な説明】
【図１】 この発明の実施例に関わるガス拡散層の表面処理方法の模式的説明図
【図２】 この発明に関わるガス拡散層の模式的構成図
【図３】 固体高分子型燃料電池セルの一部拡大断面図
【図４】 固体高分子型燃料電池セルの構成の斜視図
【符号の説明】
１：固体高分子電解質膜、２：触媒層、３：ガス拡散層、５：セパレータ、１１：基材、１２：カーボン撥水剤層、１３：カーボン繊維、１４：放電加工反応槽、１５：グラファイト電極、１６：加工液、１７：アーク発生装置。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a gas diffusion layer in a polymer electrolyte fuel cell.
[0002]
[Prior art]
A fuel cell uses hydrogen and oxygen to generate electricity via an electrolyte. The polymer electrolyte fuel cell uses a resin membrane that exhibits ionic conductivity by containing a polymer membrane as an electrolyte. FIG. 4 shows a perspective view of the configuration of the fuel cell, and a part thereof. An enlarged sectional view is shown in FIG.
[0003]
3 and 4, a catalyst layer 2 and a porous gas diffusion layer 3 are provided on both surfaces of the solid polymer electrolyte membrane 1, and further, one gas diffusion layer contains hydrogen as a reaction gas. A separator 5 having a fuel gas flow path for supplying and discharging gas and an oxidant gas flow path for supplying and discharging oxidant gas as a reaction gas to the other diffusion layer is provided. In FIG. 4, the separator has a reaction gas channel on both sides of one separator, but for manufacturing reasons, a separator having a channel on one side is laminated back to back as shown in FIG. In some cases. A stack of many of the above cells is called a stack.
[0004]
As the solid polymer electrolyte membrane 1, for example, a perfluorosulfonic acid polymer membrane (US, DuPont, trade name Nafion membrane) is used. This membrane exhibits a specific resistance of 20 Ω · cm or less at room temperature when saturated with water, and functions as a proton conductive electrolyte. The saturated water content of the membrane changes reversibly with temperature.
[0005]
Oxidation of hydrogen at the interface between the solid polymer electrolyte membrane 1 and the catalyst layer 2 by supplying hydrogen from one side of the gas diffusion layer 3 bonded to both sides of the solid polymer electrolyte membrane 1 and oxygen or air from the other side. Proton and electron transfer occur by reaction and oxygen reduction reaction, and electricity can be obtained.
[0006]
The catalyst layer 2 is formed from particulate platinum black or platinum-supporting carbon and a fluororesin having water repellency. As the catalyst layer 2, a catalyst with an electrolyte resin having a structure in which a solid polymer electrolyte resin is mixed in the catalyst layer is often used in order to expand the reaction area of the catalyst.
[0007]
As the gas diffusion layer 3, conductive carbon paper or carbon cloth is used. Usually, after producing a joined body of the solid polymer electrolyte membrane 1 and the catalyst layer 2, the gas diffusion layer 3 is joined by hot pressing. After the catalyst layer 2 is applied on the gas diffusion layer 3 and joined, In some cases, a joined body with the solid polymer electrolyte membrane 1 is prepared.
[0008]
The gas diffusion layer 3 will be further described in detail. In order to obtain high power generation efficiency, the reaction gas (H 2 , O 2 ) moves from the reaction gas flow path to the catalyst layer 2 by diffusion and reacts on the platinum surface in the catalyst layer. It is necessary to supply the reaction gas evenly. Therefore, as described above, the gas diffusion layer 3 is provided between the reaction gas flow path and the catalyst layer 2. The gas diffusion layer 3 is made of a conductive porous material, and is generally formed of cloth or paper having a thickness of several hundreds μm made of carbon fibers of several μm.
[0009]
FIG. 2 shows a schematic configuration diagram of the gas diffusion layer. As a gas diffusion layer, when forming only with conductive porous base materials, such as carbon paper and carbon cloth (Drawing 2 (a)), when forming a carbon water repellent layer on a base material (Drawing) 2 (b)).
[0010]
In the case of FIG. 2A, a large number of carbon fibers 13 are intertwined to form a conductive porous base material 11, and this base material is formed to a predetermined size to form a gas diffusion layer. The gas diffusion layer shown in FIG. 2B has a carbon water repellent layer 12 made of carbon particles and a water repellent, for example, having a thickness of several tens of μm, in order to reduce the contact resistance between the catalyst layer and the gas diffusion layer. And formed on the surface of the substrate 11 on the catalyst layer side.
[0011]
By the way, as described above, when a cloth or paper having a thickness of several hundreds of μm made of carbon fiber of several μm is used for the gas diffusion layer, the carbon fiber may protrude from the surface of the substrate. In a fuel cell stack, in order to prevent output loss due to an increase in contact resistance between electrode members including a gas diffusion layer, each stack member of the stack is pressed and tightened in the stacking direction.
[0012]
When the battery stack is tightened, the carbon fiber 13 protruding from the surface of the base material 11 may damage the catalyst layer 2 or the solid polymer electrolyte membrane 1 to form a pinhole. In this case, a cross leak of the reaction gas between the fuel electrode and the air electrode may occur, and stable operation may not be possible. Even when the carbon water repellent layer 12 is formed on the catalyst layer side, the same problem occurs when the carbon fibers 13 protrude from the surface of the carbon water repellent layer 12.
[0013]
In order to solve the above problem, Patent Document 1 discloses the following manufacturing method. That is, the electrode is formed by forming a water-repellent carbon layer on the surface of the carbon cloth and then applying a hot press to flatten the surface as a gas diffusion layer, and then placing a catalyst layer adjacent to the water-repellent carbon layer. Manufacturing method ”(for details, refer to Patent Document 1).
[0014]
[Patent Document 1]
JP 2001-85019 A (page 2-3)
[0015]
[Problems to be solved by the invention]
By the way, according to the manufacturing method of the electrode described mainly in the above-mentioned Patent Document 1, mainly the gas diffusion layer, the substrate surface can be flattened to some extent by hot pressing, but protruded from the substrate surface. Since the carbon fiber is warped, the intended flattening or smoothing is not performed, and there is a possibility that the catalyst layer or the solid polymer electrolyte membrane may be damaged.
[0016]
In addition, when flattening by hot pressing as in the method of Patent Document 1, since at least a part of the gas diffusion layer is plastically deformed by hot pressing, appropriate management is required to stably obtain dimensional accuracy. Necessary.
[0017]
The present invention has been made in view of the above points, and an object of the present invention is to enable stable smoothing of the surface of the gas diffusion layer on the side adjacent to the catalyst layer. It is an object of the present invention to provide a method for producing a gas diffusion layer of a polymer electrolyte fuel cell that enables stable continuous operation of the battery for a long time.
[0018]
[Means for Solving the Problems]
In order to solve the aforementioned problems, the present invention comprises a catalyst layer disposed on both main surfaces with a solid polymer electrolyte membrane interposed therebetween, and a porous gas diffusion layer disposed on both outer sides of the catalyst layer. In the method for producing the gas diffusion layer of the solid polymer fuel cell provided, the gas diffusion layer is made of a conductive porous substrate such as carbon paper or carbon cloth, and the conductive porous substrate is After forming to a predetermined dimension, the base material surface adjacent to the catalyst layer is smoothed by arc heat of discharge, and the smoothing treatment uses the conductive porous base material as one electrode, And, using the graphite electrode as the other electrode, a pulse voltage is applied between the two electrodes in the electrically insulating working fluid, thereby generating arc heat of discharge, and this arc heat causes the conductive porous substrate to Carbo protruding from the substrate surface And processing for smoothing by melting fibers (the invention of claim 1).
[0019]
According to the above, the carbon fibers protruding from the gas diffusion layer surface on the catalyst layer side can be burned away by arc heat processing of the discharge, thereby smoothing the surface of the gas diffusion layer. As a result, the gas diffusion layer prevents the catalyst layer and the solid polymer membrane from being damaged when the stack is tightened, and the reaction gas cross-leak between the air electrode and the fuel electrode is less likely to occur and is stable for a long time. Continuous operation is possible.
[0020]
When the metal electrode is used without using the graphite electrode as in the first aspect of the invention, the melt of the electrode material adheres to the conductive porous substrate, and the performance of the gas diffusion layer is improved. Although there is a possibility that a problem that has an adverse effect may occur, the adverse effect is suppressed by using an electrode material of the same system as the conductive porous substrate. In addition, as the electrically insulating working fluid, for example, kerosene used in general electric discharge machining can be used.
[0021]
As an embodiment of the invention of claim 1, the inventions of claims 2 to 4 below are preferable.
[0022]
That is , in the manufacturing method according to claim 1 , a gap between both electrode surfaces to which the pulse voltage is applied is set to 10 to 500 μm (invention of claim 2 ) .
[0023]
Furthermore, when a carbon water repellent layer is provided, it is set as the following claim 3 or 4 . That is, in the manufacturing method according to claim 1 or 2 , a carbon water repellent layer is formed on the substrate surface after the smoothing treatment (invention of claim 3 ). Alternatively, in the manufacturing method according to claim 1 or 2 , the smoothing treatment is performed after a carbon water repellent layer is previously formed on the surface of the base material (invention of claim 4 ).
[0024]
DETAILED DESCRIPTION OF THE INVENTION
With reference to the drawings, embodiments of the present invention will be described below.
[0025]
FIG. 1 is a schematic explanatory view of a surface treatment method for a gas diffusion layer according to an embodiment of the present invention, and shows an example in which the gas diffusion layer is applied to the one shown in FIG. In FIG. 1, 11 is a base material, 14 is an electric discharge machining reaction tank, 15 is a graphite electrode, 16 is a machining fluid, and 17 is an arc generator.
[0026]
The electric discharge machining reaction tank 14 is filled with an electrically insulating working fluid 6 (for example, kerosene), and the base material 11 and the graphite electrode 15 are arranged facing each other. For example, an arc is generated between the base material 11 and the graphite electrode 15 by an electric discharge by an arc generator 17 having a pulse power source using the base material 11 as an anode and the graphite electrode 15 as a cathode. Due to the generated arc, the carbon fibers protruding from the surface of the base material 11 are burned off.
[0027]
The surface-to-surface distance between the base material 11 and the graphite electrode 15 is adjusted by the state of the carbon fiber protruding from the base material surface, but if the graphite electrode 5 comes into contact with the electrode surface, the surface of the base material 11 may be burned out. If the distance is too long, there is a possibility that the carbon fiber protruding from the substrate surface will not be burned off. From the above viewpoint, the preferable range of the gap between both electrodes is 10 to 500 μm.
[0028]
In addition, although the present Example demonstrated surface treatment in case a gas diffusion layer is formed only by the base material 11, also about the gas diffusion layer which has a carbon water repellent layer shown in FIG.2 (b), The surface treatment method is the same. Further, as described above, the carbon water repellent layer can also be formed after the surface treatment of FIG.
[0029]
【The invention's effect】
As described above, according to the present invention, a solid comprising a catalyst layer disposed on both main surfaces with a solid polymer electrolyte membrane interposed therebetween, and a porous gas diffusion layer disposed on both outer sides of the catalyst layer. In the method for producing the gas diffusion layer of the polymer fuel cell, the gas diffusion layer is made of a conductive porous substrate such as carbon paper or carbon cloth, and the conductive porous substrate is made to have a predetermined size. After the formation, the surface of the base material adjacent to the catalyst layer is smoothed by the arc heat of discharge, and the smoothing treatment uses the conductive porous base material as one electrode and a graphite electrode. As the other electrode, a pulse voltage is applied between the electrodes in an electrically insulating working fluid, thereby generating arc heat of discharge, and the arc heat causes the base material of the conductive porous base material to Carbon fiber protruding from the surface And the process of smoothing by melting,
When the gas diffusion layer includes a carbon water repellent layer, the carbon water repellent layer is formed after the smoothing treatment, or the carbon smoothing treatment is performed after the carbon water repellent layer is formed in advance. I decided to do so
It is possible to stably achieve sufficient smoothing of the surface of the gas diffusion layer adjacent to the catalyst layer, thereby enabling stable and continuous operation of the fuel cell.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view of a surface treatment method of a gas diffusion layer according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a gas diffusion layer according to the present invention. [Fig. 4] Perspective view of the configuration of the polymer electrolyte fuel cell [Explanation of symbols]
1: solid polymer electrolyte membrane, 2: catalyst layer, 3: gas diffusion layer, 5: separator, 11: substrate, 12: carbon water repellent layer, 13: carbon fiber, 14: electric discharge machining reactor, 15: Graphite electrode, 16: machining fluid, 17: arc generator.

Claims (4)

固体高分子電解質膜を挟んで両主面に配設した触媒層と、この触媒層の両外側に配設した多孔質のガス拡散層とを備えた固体高分子型燃料電池の前記ガス拡散層の製造方法において、
前記ガス拡散層は、カーボンペーパーやカーボンクロス等の導電性多孔質基材からなるものとし、この導電性多孔質基材を所定寸法に形成した後、前記触媒層と隣接する側の前記基材表面を、放電のアーク熱により平滑化処理し、
前記平滑化処理は、前記導電性多孔質基材を一方の電極とし、かつグラファイト電極を他方の電極として、電気絶縁性の加工液中で前記両電極間にパルス電圧を印加し、これにより放電のアーク熱を発生させ、このアーク熱により、導電性多孔質基材の前記基材表面から突出したカーボン繊維を溶融させて平滑化する処理とすることを特徴とする固体高分子型燃料電池のガス拡散層の製造方法。The gas diffusion layer of a solid polymer fuel cell comprising a catalyst layer disposed on both main surfaces with a solid polymer electrolyte membrane interposed therebetween, and a porous gas diffusion layer disposed on both outer sides of the catalyst layer In the manufacturing method of
The gas diffusion layer is made of a conductive porous substrate such as carbon paper or carbon cloth, and after forming the conductive porous substrate to a predetermined size, the substrate on the side adjacent to the catalyst layer. The surface is smoothed by the arc heat of the discharge ,
In the smoothing treatment, the conductive porous substrate is used as one electrode and the graphite electrode is used as the other electrode, and a pulse voltage is applied between the electrodes in an electrically insulating working fluid, thereby discharging The solid polymer fuel cell is characterized in that the arc heat is generated and the carbon fiber protruding from the base material surface of the conductive porous base material is melted and smoothed by the arc heat . A method for producing a gas diffusion layer. 請求項１に記載の製造方法において、前記パルス電圧を印加する両電極面の間隙は、１０〜５００μｍとすることを特徴とする固体高分子型燃料電池のガス拡散層の製造方法。2. The method for producing a gas diffusion layer of a polymer electrolyte fuel cell according to claim 1 , wherein a gap between both electrode surfaces to which the pulse voltage is applied is 10 to 500 [mu] m. 請求項１または２に記載の製造方法において、前記平滑化処理後に、カーボン撥水剤層を前記基材表面に形成することを特徴とする固体高分子型燃料電池のガス拡散層の製造方法。The method of manufacture according to claim 1 or 2, wherein after the smoothing treatment, a manufacturing method of the gas diffusion layer of a polymer electrolyte fuel cell and forming a carbon water-repellent layer on the substrate surface. 請求項１または２に記載の製造方法において、予めカーボン撥水剤層を前記基材表面に形成した後に、前記平滑化処理を行なうことを特徴とする固体高分子型燃料電池のガス拡散層の製造方法。 3. The manufacturing method according to claim 1, wherein the smoothing treatment is performed after a carbon water repellent layer is previously formed on the surface of the base material. Production method.
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