JP2010153222A - Flexible type gas diffusion electrode substrate and membrane-electrode assembly - Google Patents

Flexible type gas diffusion electrode substrate and membrane-electrode assembly Download PDF

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JP2010153222A
JP2010153222A JP2008330626A JP2008330626A JP2010153222A JP 2010153222 A JP2010153222 A JP 2010153222A JP 2008330626 A JP2008330626 A JP 2008330626A JP 2008330626 A JP2008330626 A JP 2008330626A JP 2010153222 A JP2010153222 A JP 2010153222A
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diffusion electrode
resin
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Hiroshi Yoshikawa
大士 吉川
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Noritake Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas diffusion electrode with both high conductivity and gas permeability as well as excellent flexibility, and an MEA equipped with the same. <P>SOLUTION: The gas diffusion electrodes 18, 20 have both high conductivity and gas permeability as well as excellent flexibility because a glass cloth 22 as a substrate thereof and the like have high flexibility, and carbon fibers 24 and carbon fine particles 26 are covered with resin in a state in which they fully got inside the substrates by slurry impregnation, so a construction is provided in an overall thickness direction in which a plurality of the carbon fibers 24 are mutually bonded by the resin through a plurality of the carbon fine particles 26 therebetween. Also it is excellent in mass production and capable of suppressing manufacturing cost, because the manufacturing by impregnation treatment is possible and making it into a roll is possible due to excellent flexibility. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、固体高分子形燃料電池を構成するためのガス拡散電極およびこれを備えた膜−電極接合体に関する。   The present invention relates to a gas diffusion electrode for constituting a polymer electrolyte fuel cell and a membrane-electrode assembly provided with the gas diffusion electrode.

燃料電池は、燃料として水素、メタノール、化石燃料からの改質水素等の還元剤を用い、空気や酸素を酸化剤として、電池内で燃料を電気化学的に酸化することにより、燃料の化学エネルギーを直接電気エネルギーに変換して取り出すものである。そのため、内燃機関に比較して効率が高く、静粛性に優れると共に、大気汚染の原因となるNOx、SOx、粒子状物質(PM)等の排出量が少ないことから、近年、クリーンな電気エネルギー供給源として注目されている。例えば、自動車用エンジンの代替、住宅用等の分散型電源や熱電供給システムとしての利用が期待されている。 A fuel cell uses a reducing agent such as hydrogen, methanol, or reformed hydrogen from fossil fuels as a fuel, and electrochemically oxidizes the fuel in the cell using air or oxygen as an oxidant, thereby chemical energy of the fuel. Is directly converted into electrical energy and extracted. As a result, it has higher efficiency and quietness compared to internal combustion engines, and has low emissions of NO x , SO x , particulate matter (PM), etc. that cause air pollution. It is attracting attention as an energy supply source. For example, it is expected to be used as a distributed power source or a thermoelectric supply system for automobile engines, residential use, etc.

このような燃料電池は、用いる電解質の種類によって、アルカリ形、リン酸形、溶融炭酸塩形、固体酸化物形、固体高分子形等に分類される。これらのうちプロトン伝導性の電解質を用いるリン酸形および固体高分子形は、熱力学におけるカルノーサイクルの制限を受けることなく高い効率で運転できるものであり、その理論効率は、25(℃)において83(％)にも達する。特に、固体高分子形燃料電池は、近年電解質膜や触媒技術の発展により性能の向上が著しくなり、低公害自動車用電源や高効率発電方法として注目を集めている。   Such fuel cells are classified into alkali type, phosphoric acid type, molten carbonate type, solid oxide type, solid polymer type, and the like depending on the type of electrolyte used. Among these, the phosphoric acid form and the solid polymer form using a proton-conducting electrolyte can be operated with high efficiency without being restricted by the Carnot cycle in thermodynamics, and the theoretical efficiency is 25 (° C). It reaches 83 (%). In particular, solid polymer fuel cells have been remarkably improved in performance in recent years due to the development of electrolyte membranes and catalyst technology, and are attracting attention as a low-pollution automobile power source and high-efficiency power generation method.

ところで、固体高分子形燃料電池は、例えば薄板状の高分子電解質層の両面に一対の触媒層を介してガス拡散電極を設けた構造を備えるものであり、通常は、このような膜−電極接合体(Membrane Electrode Assembly：以下、ＭＥＡ)をセパレータを介して積層したスタック構造で用いられる。上記高分子電解質層は水素イオン(プロトン)を選択的に透過させるもので、上記触媒層は白金等から成る貴金属系触媒を担持した炭素微粒子を主成分とするものである。上記ガス拡散電極には、これら触媒層および電解質層表面に燃料ガスや空気を導き且つ生成ガスおよび過剰ガスを排出すると共に、発生した電流を取り出すために、高いガス拡散性能と高い導電性とが共に要求される。   By the way, a solid polymer fuel cell has a structure in which a gas diffusion electrode is provided on both sides of a thin polymer electrolyte layer, for example, via a pair of catalyst layers. Usually, such a membrane-electrode is used. It is used in a stack structure in which a bonded body (Membrane Electrode Assembly: hereinafter referred to as MEA) is laminated via a separator. The polymer electrolyte layer selectively permeates hydrogen ions (protons), and the catalyst layer is mainly composed of carbon fine particles carrying a noble metal catalyst made of platinum or the like. The gas diffusion electrode has high gas diffusion performance and high conductivity in order to guide the fuel gas and air to the catalyst layer and the electrolyte layer surface, discharge the generated gas and excess gas, and take out the generated current. Both are required.

従来、このようなガス拡散電極としては、炭素繊維等を樹脂炭化物で結着した炭素繊維紙(すなわちカーボンペーパー)と称されるものが一般的に用いられている(例えば特許文献１，２を参照。)。また、膨張黒鉛等の導電性粉末、炭素繊維、有機繊維、および樹脂を含むスラリーを抄紙し、乾燥処理を施すことにより、例えば300(℃)以下の比較的低温で製膜するものも知られている(例えば特許文献３を参照。)。また、金属メッシュに貴金属コートを施した電極基材が提案されている(例えば特許文献４を参照。)。また、ガラス繊維不織布にアクリル樹脂や酢酸ビニル樹脂を付着させ、これに炭素粒子とPVDF(ポリ弗化ビニリデン)やPTFE(ポリテトラフルオロエチレン)とを溶媒に分散させた導電性ペーストを被着して乾燥するガス拡散電極の製造方法が提案されている(例えば特許文献６を参照。)。
特開２００７−０８０７４２号公報 特開２００８−２０４８２４号公報 特開２００４−０７９４０６号公報 特開２００８−１０３１４２号公報 特開２００８−１７６９７１号公報 特開２００８−２０４９４５号公報 Conventionally, as such a gas diffusion electrode, what is called carbon fiber paper (that is, carbon paper) in which carbon fiber or the like is bound with resin carbide is generally used (for example, Patent Documents 1 and 2). reference.). Also known is a paper that is made at a relatively low temperature of, for example, 300 (° C.) or less by making a paper containing a slurry containing conductive powder such as expanded graphite, carbon fiber, organic fiber, and resin, and performing a drying treatment. (For example, refer to Patent Document 3). An electrode base material in which a noble metal coat is applied to a metal mesh has been proposed (see, for example, Patent Document 4). In addition, an acrylic resin or vinyl acetate resin is attached to a glass fiber nonwoven fabric, and a conductive paste in which carbon particles and PVDF (polyvinylidene fluoride) or PTFE (polytetrafluoroethylene) are dispersed in a solvent is applied thereto. A method of manufacturing a gas diffusion electrode to be dried is proposed (see, for example, Patent Document 6).
JP 2007-080742 A JP 2008-204824 A JP 2004-079406 A JP 2008-103142 A JP 2008-176971 A JP 2008-204945 A

ところで、燃料電池の量産性を考慮すると、ガス拡散電極基材には、前述したガス拡散性や導電性に加えて、生産時にロール化できる程度の柔軟性を有して連続製膜可能であることが望まれる。また、量産するためには安価に製造できることも必要である。しかしながら、前記特許文献１，２に記載されているような炭素繊維紙は、炭素繊維や炭素質粉末を樹脂炭化物で結着していることから、1700(℃)以上の高温で不活性或いは還元雰囲気で焼成する必要があるため、製造コストが高くなると共に、高温焼結させるので硬く且つ脆くなる問題があった。また、前記特許文献３に記載されているガス拡散電極基材は、300(℃)以下の低温で安価に製造できると共に高い柔軟性を有する利点があるが、炭素繊維相互間の導電性を付与するために混合される導電性粉末が比較的粗大であるため、ガス透過性が阻害されると共に、導電性も低い問題がある。しかも、混合されている有機繊維は柔軟性に寄与する反面で導電性を阻害するので、導電性の確保が一層困難になる。   By the way, in consideration of the mass productivity of the fuel cell, the gas diffusion electrode base material can be continuously formed in addition to the above-described gas diffusibility and conductivity, and has flexibility that can be rolled during production. It is desirable. In addition, it is necessary to be able to manufacture at low cost for mass production. However, the carbon fiber papers described in Patent Documents 1 and 2 are inactive or reduced at a high temperature of 1700 (° C.) or higher because carbon fibers and carbonaceous powder are bound with resin carbide. Since it is necessary to perform firing in an atmosphere, there are problems that the manufacturing cost is increased, and that sintering is performed at a high temperature, which makes it hard and brittle. Further, the gas diffusion electrode substrate described in Patent Document 3 can be manufactured at a low temperature of 300 (° C.) or less at low cost and has an advantage of high flexibility, but imparts conductivity between carbon fibers. Therefore, since the conductive powder to be mixed is relatively coarse, the gas permeability is hindered and the conductivity is low. In addition, the mixed organic fiber contributes to flexibility, but inhibits conductivity, so that it is more difficult to ensure conductivity.

また、前記特許文献４に記載されているガス拡散電極用基材も十分な柔軟性を有するものであるが、金属メッシュの反応活性を低下させ或いは耐酸性を高めるための貴金属コートは高価であることから、燃料電池の量産時には適用が困難である。なお、耐酸コートのない金属メッシュでは、腐食すると共に溶出した金属イオンで電解質が劣化させられるため、金属メッシュを用いる場合には何らかの耐酸処理が必須である。また、前記特許文献６に記載されているガス拡散電極用基材は、導電成分としてカーボンブラックを用いるものであるが、カーボンブラックの体積固有抵抗は100(mΩ・cm)程度であって、炭素繊維紙等の主成分であるピッチ系炭素繊維の体積固有抵抗0.15(mΩ・cm)程度に比較すると桁違いに大きいので、導電性が不十分である。   The gas diffusion electrode substrate described in Patent Document 4 is also sufficiently flexible, but a noble metal coat for reducing the reaction activity of the metal mesh or increasing the acid resistance is expensive. Therefore, it is difficult to apply at the time of mass production of fuel cells. In addition, in the metal mesh without an acid-resistant coat, the electrolyte is deteriorated by the metal ions that corrode and are eluted. Therefore, when the metal mesh is used, some kind of acid-resistant treatment is essential. The gas diffusion electrode substrate described in Patent Document 6 uses carbon black as a conductive component, and the volume resistivity of carbon black is about 100 (mΩ · cm), and carbon Compared with the volume resistivity of 0.15 (mΩ · cm) of pitch-based carbon fiber, which is the main component of fiber paper, etc., the conductivity is insufficient.

本発明は、以上の事情を背景として為されたものであって、その目的は、導電性およびガス透過性が共に高く、しかも柔軟性に優れたガス拡散電極、およびこれを備えたＭＥＡを提供することにある。   The present invention has been made against the background of the above circumstances, and its object is to provide a gas diffusion electrode having both high conductivity and gas permeability and excellent flexibility, and an MEA equipped with the gas diffusion electrode. There is to do.

斯かる目的を達成するため、第１発明の要旨とするところは、固体高分子形燃料電池を構成するために固体高分子電解質上に気体を導き得る状態で設けられる多孔質のガス拡散電極であって、(ａ)直径3(cm)の円筒に巻き付け得る柔軟性を有する多孔性薄膜にスラリーを含浸して炭素繊維、炭素微粒子、および樹脂を被着させて成ることにある。   In order to achieve such an object, the gist of the first invention is a porous gas diffusion electrode provided in a state in which a gas can be guided onto a solid polymer electrolyte in order to constitute a solid polymer fuel cell. (A) A porous thin film having flexibility that can be wound around a cylinder having a diameter of 3 (cm) is impregnated with a slurry, and carbon fibers, carbon fine particles, and a resin are deposited thereon.

また、前記目的を達成するための第２発明の要旨とするところは、固体高分子形燃料電池を構成するために固体高分子電解質上に気体を導き得る状態で設けられる多孔質のガス拡散電極であって、(ａ)有機繊維或いは無機繊維から成る織布或いは不織布、金属メッシュ、または孔空き金属薄板から成る柔軟性を有する多孔性薄膜にスラリーを含浸して炭素繊維、炭素微粒子、および樹脂を被着させて成ることにある。   The gist of the second invention for achieving the above object is to provide a porous gas diffusion electrode provided in a state in which gas can be guided onto the solid polymer electrolyte in order to constitute a solid polymer fuel cell. And (a) a carbon fiber, a carbon fine particle, and a resin obtained by impregnating a slurry into a flexible porous thin film made of a woven or non-woven fabric made of organic fibers or inorganic fibers, a metal mesh, or a perforated metal thin plate It is to be made to adhere.

また、前記目的を達成するための第３発明の要旨とするところは、固体高分子電解質層と、その一面および他面にそれぞれ設けられた触媒層と、それら触媒層の各々の表面に設けられた第１発明または第２発明の柔軟型ガス拡散電極とを、含むことにある。   The gist of the third invention for achieving the above object is that the solid polymer electrolyte layer, the catalyst layer provided on one side and the other side thereof, and provided on each surface of the catalyst layer, respectively. And the flexible gas diffusion electrode of the first invention or the second invention.

前記第１発明によれば、ガス拡散電極は、その基材である多孔性薄膜が直径3(cm)の円筒に巻き付け得る程度に高い柔軟性を有すると共に、これに炭素繊維および炭素微粒子がスラリーの含浸により内部まで十分に入った状態で樹脂で被着させられていることから、多数の炭素繊維がその相互間に多数の炭素微粒子が介在した状態で相互に樹脂で接合された構造を厚み方向の全体に亘って備えるので、導電性およびガス透過性が共に高く、しかも柔軟性に優れたガス拡散電極が得られる。すなわち、炭素繊維相互が相互に絡み合った構造を備えるので、それらの接触部に炭素微粒子が存在しても繊維相互間に十分に大きな隙間が生ずるため、ガス透過性を確保しつつ高い導電性が得られる。そして、この構造が柔軟性の高い基材で支持されることになるので、柔軟性、ガス透過性、および導電性を併せ持つガス拡散電極が得られるのである。なお、「直径3(cm)の円筒に巻き付け得る」とは、巻き付けた場合に破損やひび割れ等が生じないことを意味する。基材がこのような柔軟性を有していれば、これに炭素繊維等を被着したガス拡散電極を直径4(cm)程度の軸棒に巻き取って連続製膜可能となるため、量産性が高められる。   According to the first aspect of the invention, the gas diffusion electrode has such a high flexibility that the porous thin film as the base material can be wound around a cylinder having a diameter of 3 (cm), and the carbon fiber and the carbon fine particles are slurried therein. Since it is coated with resin in a state where it has entered the interior sufficiently due to impregnation, a structure in which a large number of carbon fibers are bonded to each other with a large number of carbon fine particles interposed therebetween Since it is provided over the entire direction, it is possible to obtain a gas diffusion electrode having both high conductivity and gas permeability and excellent flexibility. That is, since the carbon fibers have a structure in which the carbon fibers are entangled with each other, a sufficiently large gap is generated between the fibers even if carbon fine particles are present at the contact portions, so that high conductivity is ensured while ensuring gas permeability. can get. Since this structure is supported by a highly flexible base material, a gas diffusion electrode having both flexibility, gas permeability, and conductivity can be obtained. Note that “can be wound around a cylinder having a diameter of 3 (cm)” means that no damage or cracking occurs when wound. If the base material has such flexibility, a gas diffusion electrode coated with carbon fiber or the like can be wound around a shaft rod with a diameter of about 4 (cm) to enable continuous film formation. Sexuality is enhanced.

しかも、上記構造によれば、導電性を得る目的で樹脂を炭化させる必要が無いことから、不活性或いは還元雰囲気中における高温の焼成処理が無用であるため、高温の焼成処理を施していた炭素繊維紙に比較して、製造コストが低くなる利点もある。   In addition, according to the above structure, since there is no need to carbonize the resin for the purpose of obtaining conductivity, there is no need for a high-temperature baking treatment in an inert or reducing atmosphere. There is also an advantage that the manufacturing cost is lower than that of fiber paper.

また、上記のように樹脂を炭化させる必要がないため、高い機械的強度が得られることから、ガス拡散電極の薄膜化が容易になり、延いてはＭＥＡの薄膜化が容易になるので、使用材料を削減できて一層の低コスト化が可能である。なお、上記第１発明の構造によれば、含浸するスラリー量を調節することで膜厚を容易に制御できるので、要求特性や必要な強度等に応じた膜厚のガス拡散電極が得られる。   Moreover, since it is not necessary to carbonize the resin as described above, it is possible to obtain a high mechanical strength. Therefore, it is easy to reduce the thickness of the gas diffusion electrode, and it is easy to reduce the thickness of the MEA. The material can be reduced and the cost can be further reduced. In addition, according to the structure of the said 1st invention, since a film thickness can be easily controlled by adjusting the slurry quantity to impregnate, the gas diffusion electrode of the film thickness according to a required characteristic, required intensity | strength, etc. is obtained.

また、前記第２発明によれば、ガス拡散電極は、その基材である多孔性薄膜が有機繊維或いは無機繊維から成る織布或いは不織布、金属メッシュ、または孔空き金属薄板から成ることから高い柔軟性を有すると共に、これに炭素繊維および炭素微粒子がスラリーの含浸により内部まで十分に入った状態で樹脂で被着させられていることから、前記第１発明と同様に、導電性およびガス透過性が共に高く、しかも柔軟性に優れたガス拡散電極が低コストで得られる。   According to the second invention, the gas diffusion electrode is highly flexible because the porous thin film which is the base material thereof is made of a woven or non-woven fabric made of organic fibers or inorganic fibers, a metal mesh, or a perforated metal thin plate. In addition to the above, the carbon fiber and the carbon microparticles are coated with the resin in a state where the carbon fiber and the carbon fine particles sufficiently enter the interior by impregnation with the slurry. Therefore, it is possible to obtain a gas diffusion electrode that is both high and flexible, at low cost.

因みに、前述したように、ガス拡散電極に金属を用いる場合には何らかの耐酸処理が必須であり、前記特許文献４には貴金属コートを施すことがが示されているが、第１発明および第２発明によれば、スラリー中の樹脂成分が耐酸コートとして機能するので、高価な貴金属コートは無用である。また、前記特許文献５には、燃料電池の発電時の生成水を排出する目的で導入されるメッシュシートではあるが、柔軟性の高い多孔性薄膜が示されている。しかしながら、このメッシュシートはその目的上導電性が全く考慮されていないもので、これを電極用基材として用いると、導電面積が不足すると共に、材料自体の導電性不足に起因してガス拡散電極全体の導電性が不十分になる問題がある。   Incidentally, as described above, when a metal is used for the gas diffusion electrode, some kind of acid resistance treatment is indispensable, and Patent Document 4 shows that a noble metal coat is applied. According to the invention, since the resin component in the slurry functions as an acid-resistant coat, an expensive noble metal coat is unnecessary. Moreover, although the said patent document 5 is a mesh sheet | seat introduced in order to discharge | emit the generated water at the time of the electric power generation of a fuel cell, the highly flexible porous thin film is shown. However, this mesh sheet does not consider conductivity at all for its purpose. When this mesh sheet is used as an electrode substrate, the conductive area is insufficient and the gas diffusion electrode is caused by insufficient conductivity of the material itself. There is a problem that the overall conductivity becomes insufficient.

なお、第１発明および第２発明において、「電解質上に」とは、固体高分子電解質の上にガス拡散電極が直接設けられている場合の他、触媒層等の他の層を介してガス拡散電極が設けられている場合が含まれる。   In the first and second inventions, “on the electrolyte” means that the gas diffusion electrode is directly provided on the solid polymer electrolyte, and the gas is passed through another layer such as a catalyst layer. The case where the diffusion electrode is provided is included.

また、前記第３発明によれば、固体高分子電解質層の一面および他面に触媒層を介して前記第１発明または第２発明のガス拡散電極が設けられることによってＭＥＡが構成されることから、柔軟性の高いガス拡散電極は取扱性に優れるため、高い導電性および高いガス透過性を有するガス拡散電極を備えたＭＥＡを低コストで容易に製造できる。   According to the third invention, the MEA is configured by providing the gas diffusion electrode of the first invention or the second invention via a catalyst layer on one surface and the other surface of the solid polymer electrolyte layer. Since a highly flexible gas diffusion electrode is excellent in handleability, an MEA including a gas diffusion electrode having high conductivity and high gas permeability can be easily manufactured at low cost.

ここで、好適には、前記第２発明において、前記多孔性薄膜は直径3(cm)の円筒に巻き付け得るものである。多孔性薄膜としては、この程度の柔軟性を有するものが好ましい。   Here, preferably, in the second invention, the porous thin film can be wound around a cylinder having a diameter of 3 (cm). As the porous thin film, those having such a degree of flexibility are preferable.

また、好適には、前記樹脂は分解温度が200(℃)以上の熱可塑性樹脂または硬化温度が40乃至200(℃)の範囲内の熱硬化性樹脂である。このようにすれば、何れの樹脂を用いる場合にも、200(℃)以下の温度で加熱処理を施すことで柔軟性や機械的強度の高いガス拡散電極を得ることができ、しかも、200(℃)以下の使用温度に耐え得るので、固体高分子形燃料電池のガス拡散電極として特に好ましい。因みに、固体高分子形燃料電池の運転時の最高温度は200(℃)までであるため、200(℃)程度の温度で使用可能であることが望まれる一方、安価に製造するためには、積層タイプのＭＥＡに構成可能なように200(℃)以下でガス拡散電極を形成できることが望ましい。そのため、上記のような温度特性を有する熱可塑性樹脂および熱硬化性樹脂が好ましいのである。   Preferably, the resin is a thermoplastic resin having a decomposition temperature of 200 (° C.) or higher or a thermosetting resin having a curing temperature in the range of 40 to 200 (° C.). In this way, regardless of which resin is used, a gas diffusion electrode with high flexibility and mechanical strength can be obtained by performing a heat treatment at a temperature of 200 (° C.) or less, and 200 ( C.), it is particularly preferable as a gas diffusion electrode of a polymer electrolyte fuel cell. Incidentally, since the maximum temperature during the operation of the polymer electrolyte fuel cell is up to 200 (° C.), it is desirable that it can be used at a temperature of about 200 (° C.). It is desirable that the gas diffusion electrode can be formed at 200 (° C.) or less so that it can be configured as a stacked type MEA. Therefore, a thermoplastic resin and a thermosetting resin having the above temperature characteristics are preferable.

また、好適には、前記炭素繊維は繊維長が500(μm)以下である。このようにすれば、導電性の一層高いガス拡散電極が得られる。炭素繊維の繊維長は特に限定されるものでは無いが、長くなるほどガス拡散電極の断面加圧抵抗が増大する傾向があり、500(μm)を超えると増大傾向が著しくなるので500(μm)以下が好ましい。炭素繊維の繊維長は、10(μm)以上であることが一層好ましく、50(μm)以上であることが更に好ましい。   Preferably, the carbon fiber has a fiber length of 500 (μm) or less. In this way, a gas diffusion electrode with higher conductivity can be obtained. The fiber length of the carbon fiber is not particularly limited, but as the length increases, the cross-sectional pressurization resistance of the gas diffusion electrode tends to increase, and if it exceeds 500 (μm), the increasing tendency becomes remarkable, so 500 (μm) or less Is preferred. The fiber length of the carbon fiber is more preferably 10 (μm) or more, and further preferably 50 (μm) or more.

また、好適には、前記スラリーは、前記炭素繊維に対する割合で、前記炭素微粒子を10乃至20(wt％)の範囲内、および前記樹脂を3.3乃至16.7(wt％)の範囲内で含むものである。このようにすれば、ガス透過性が一層高く且つ断面加圧抵抗が一層低いガス拡散電極が得られる。   Preferably, the slurry contains the carbon fine particles in a range of 10 to 20 (wt%) and the resin in a range of 3.3 to 16.7 (wt%) in a ratio to the carbon fiber. In this way, a gas diffusion electrode having higher gas permeability and lower cross-sectional pressure resistance can be obtained.

また、前記炭素繊維は特に限定されず、ポリアクリロニトリル系炭素繊維、ピッチ系炭素繊維、レーヨン系炭素繊維等の適宜のものを用い得る。ポリアクリロニトリル系炭素繊維を用いた場合には、炭素繊維の強度が高いため機械的強度の特に高いガス拡散電極が得られる。また、ピッチ系炭素繊維を用いた場合には、電気伝導性の特に高いガス拡散電極が得られる。   Further, the carbon fiber is not particularly limited, and appropriate ones such as polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and rayon-based carbon fiber can be used. When polyacrylonitrile-based carbon fiber is used, a gas diffusion electrode with particularly high mechanical strength can be obtained because the strength of the carbon fiber is high. In addition, when pitch-based carbon fibers are used, a gas diffusion electrode having particularly high electrical conductivity can be obtained.

また、前記熱硬化性樹脂は特に限定されず、フェノール系樹脂、アクリル樹脂、エポキシ系樹脂、メラミン系樹脂、シリコーン系樹脂、ポリエステル系樹脂等の適宜のものを用い得る。これらの樹脂は、何れも十分な耐酸性および耐熱性を有し且つ安価であるため好ましく、所望する特性等を考慮して用途に応じて選択されるが、例えば、機械的強度および耐熱性の点では特にフェノール樹脂、中でもレゾール系フェノール樹脂が好ましい。   In addition, the thermosetting resin is not particularly limited, and an appropriate resin such as a phenol resin, an acrylic resin, an epoxy resin, a melamine resin, a silicone resin, or a polyester resin can be used. These resins are preferable because they have sufficient acid resistance and heat resistance and are inexpensive, and are selected according to the application in consideration of desired characteristics and the like. For example, mechanical strength and heat resistance In particular, a phenol resin, particularly a resol phenol resin is preferable.

また、前記熱可塑性樹脂は特に限定されず、ポリエステル樹脂やポリアミド樹脂等の適宜のものを用い得る。   The thermoplastic resin is not particularly limited, and an appropriate one such as a polyester resin or a polyamide resin can be used.

また、固体高分子形燃料電池には、燃料極側および空気極側のそれぞれにガス拡散電極が備えられるが、本発明は、それら燃料極側および空気極側の何れの電極にも適用され得る。但し、両極で同一構成の電極が設けられることが必須ではなく、所望する特性や製造上の都合等に応じて、適宜の電極構成を採用することができ、本発明を適用されるのが両極のうちの一方のみであってもよい。   Further, the polymer electrolyte fuel cell is provided with gas diffusion electrodes on the fuel electrode side and the air electrode side, respectively, but the present invention can be applied to any electrode on the fuel electrode side and the air electrode side. . However, it is not essential that electrodes having the same configuration are provided in both electrodes, and an appropriate electrode configuration can be adopted according to desired characteristics and manufacturing convenience, and the present invention is applied to both electrodes. Only one of them may be used.

また、本発明は、種々の固体高分子電解質が用いられた固体高分子形燃料電池に適用され、固体高分子電解質の材質は特に限定されない。例えば、イオン交換基(-SO3H基等)を有するモノマーの単独重合体または共重合体、イオン交換基を有するモノマーとそのモノマーと共重合可能な他のモノマーとの共重合体、加水分解等の後処理によりイオン交換基に転換し得る官能基(すなわちイオン交換基の前駆的官能基)を有するモノマーの単独重合体、または共重合体(プロトン伝導性高分子前駆体)に同様な後処理を施したもの等が挙げられる。 Further, the present invention is applied to a solid polymer fuel cell using various solid polymer electrolytes, and the material of the solid polymer electrolyte is not particularly limited. For example, a homopolymer or copolymer of a monomer having an ion exchange group (such as —SO 3 H group), a copolymer of a monomer having an ion exchange group and another monomer copolymerizable with the monomer, hydrolysis Similar to the homopolymer or copolymer (proton conductive polymer precursor) of a monomer having a functional group (that is, a precursor functional group of an ion exchange group) that can be converted into an ion exchange group by a post-treatment such as The thing etc. which processed are mentioned.

上記高分子電解質の具体例としては、例えば、パーフルオロカーボンスルホン酸樹脂等のパーフルオロ型のプロトン伝導性高分子、パーフルオロカーボンカルボン酸樹脂膜、スルホン酸型ポリスチレン−グラフト−エチレンテトラフルオロエチレン(ＥＴＦＥ)共重合体膜、スルホン酸型ポリ(トリフルオロスチレン)−グラフト−ＥＴＦＥ共重合体膜、ポリエーテルエーテルケトン(ＰＥＥＫ)スルホン酸膜、２−アクリルアミド−２−メチルプロパンスルホン酸(ＡＴＢＳ)膜、炭化水素系膜等が例示される。   Specific examples of the polymer electrolyte include, for example, perfluoro proton conductive polymer such as perfluorocarbon sulfonic acid resin, perfluorocarbon carboxylic acid resin film, sulfonic acid type polystyrene-graft-ethylenetetrafluoroethylene (ETFE). Copolymer membrane, sulfonic acid type poly (trifluorostyrene) -graft-ETFE copolymer membrane, polyetheretherketone (PEEK) sulfonic acid membrane, 2-acrylamido-2-methylpropanesulfonic acid (ATBS) membrane, carbonized Examples include hydrogen-based films.

以下、本発明の一実施例を図面を参照して詳細に説明する。なお、以下の実施例において図は適宜簡略化或いは変形されており、各部の寸法比および形状等は必ずしも正確に描かれていない。   Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

図１は、本発明の一実施例である平板型のＭＥＡ１０の断面構造を示す図である。図１において、ＭＥＡ１０は、薄い平板層状の電解質膜１２と、その両面に備えられた触媒層１４，１６と、触媒層１４，１６の各々の表面に設けられたガス拡散電極１８，２０とから構成されている。   FIG. 1 is a diagram showing a cross-sectional structure of a flat plate MEA 10 according to an embodiment of the present invention. In FIG. 1, an MEA 10 includes a thin flat layer electrolyte membrane 12, catalyst layers 14 and 16 provided on both surfaces thereof, and gas diffusion electrodes 18 and 20 provided on the surfaces of the catalyst layers 14 and 16, respectively. It is configured.

上記の電解質膜１２は、例えばNafion(デュポン社の登録商標) DE520等のプロトン導電性電解質から成るもので、例えば200(μm)程度の厚さ寸法を備えている。   The electrolyte membrane 12 is made of a proton conductive electrolyte such as Nafion (registered trademark of DuPont) DE520, and has a thickness dimension of about 200 (μm), for example.

また、上記の触媒層１４，１６は、例えば球状の炭素粉末に白金等の触媒を担持させたPt担持カーボンブラックから成るものである。これは、例えば田中貴金属工業(株)から市販されているもの(例えばTEC10E70TPM等)を用い得る。触媒層１４，１６の厚さ寸法は、例えば50(μm)程度である。   The catalyst layers 14 and 16 are made of, for example, Pt-supported carbon black in which a catalyst such as platinum is supported on spherical carbon powder. For example, those commercially available from Tanaka Kikinzoku Kogyo Co., Ltd. (for example, TEC10E70TPM) can be used. The thickness dimension of the catalyst layers 14 and 16 is, for example, about 50 (μm).

また、上記のガス拡散電極１８，２０は、例えばそれぞれ200(μm)程度の厚さ寸法を備え、その表面と裏面(すなわち触媒層１４，１６側の一面)との間で容易に気体が流通し得るように構成された多孔質層である。   Further, each of the gas diffusion electrodes 18 and 20 has a thickness dimension of about 200 (μm), for example, and gas easily flows between the front surface and the back surface (that is, one surface on the catalyst layers 14 and 16 side). It is a porous layer comprised so that it can do.

上記のガス拡散電極１８，２０は、例えば、図２に断面構造を模式的に示すように、ガラスクロス２２と、これに付着させられた炭素繊維２４および炭素微粒子２６等から成るものである。ガラスクロス２２は、例えばＥガラス繊維を縦横共70本/25mm程度の密度で平織りしたもので、21(μm)程度の厚さ寸法を備えている。本実施例においては、このガラスクロス２２が多孔質薄膜に相当する。また、上記炭素繊維２４は、例えば、ピッチ系ファイバーと称されるもので、繊維径が10(μm)程度、繊維長が50(μm)程度のものである。また、上記炭素微粒子２６は、例えば、平均粒径が19(nm)程度のケッチェンブラックである。   The gas diffusion electrodes 18 and 20 are made of, for example, a glass cloth 22, carbon fibers 24 and carbon fine particles 26 attached thereto, as schematically shown in a sectional structure in FIG. 2. The glass cloth 22 is, for example, plain weave of E glass fibers at a density of about 70/25 mm in both length and width, and has a thickness dimension of about 21 (μm). In this embodiment, the glass cloth 22 corresponds to a porous thin film. The carbon fiber 24 is called, for example, a pitch fiber, and has a fiber diameter of about 10 (μm) and a fiber length of about 50 (μm). The carbon fine particles 26 are, for example, ketjen black having an average particle size of about 19 (nm).

図３に、上記ガス拡散電極１８，２０における炭素繊維２４と炭素微粒子２６との結合状態の一例を模式的に示す。多数の炭素繊維２４は、各繊維が相互に絡み合い、それらの接触点或いはその近傍などに多数の炭素微粒子２６が相互間に介在した状態で樹脂２８によって互いに結合させられている。樹脂２８は、例えばレゾール系フェノール樹脂で、炭素繊維２４相互或いは炭素繊維２４と炭素微粒子２６との結合剤として機能すると共に、これらを前記ガラスクロス２２に付けるための接合剤としても機能するものである。ガス拡散電極１８，２０は、ガラスクロス２２に上記のような炭素繊維２４および炭素微粒子２６が樹脂２８で被着させられることによって構成されているため、高い導電性と、高いガス拡散性と、高い柔軟性および機械的強度と備えている。   FIG. 3 schematically shows an example of the bonding state between the carbon fibers 24 and the carbon fine particles 26 in the gas diffusion electrodes 18 and 20. A large number of carbon fibers 24 are entangled with each other, and are bonded to each other by a resin 28 in a state where a large number of carbon fine particles 26 are interposed therebetween at the contact point or in the vicinity thereof. The resin 28 is, for example, a resol-based phenol resin, which functions as a binder between the carbon fibers 24 or between the carbon fibers 24 and the carbon fine particles 26 and also functions as a bonding agent for attaching them to the glass cloth 22. is there. Since the gas diffusion electrodes 18 and 20 are configured by adhering the carbon fiber 24 and the carbon fine particles 26 as described above to the glass cloth 22 with the resin 28, the high conductivity, the high gas diffusibility, With high flexibility and mechanical strength.

上記平板型のガス拡散電極１８，２０は、例えば以下のようにして製造される。以下、図４を参照して製造方法を説明する。まず、炭素繊維と、炭素微粒子と、樹脂と、溶剤とを用意する。溶剤は例えば２-プロパノールである。これらの調合割合は適宜定められるが、一例を挙げると、例えば、炭素繊維を3(ｇ)、樹脂(固形分20wt％)を1.5(ｇ)、炭素微粒子を0.5(g)、溶剤を20(ｇ)である。この調合例では、炭素繊維に対して、炭素微粒子が16.7(wt％)、樹脂が固形分で10(wt％)含まれることになる。   The flat gas diffusion electrodes 18 and 20 are manufactured, for example, as follows. Hereinafter, the manufacturing method will be described with reference to FIG. First, carbon fibers, carbon fine particles, a resin, and a solvent are prepared. The solvent is for example 2-propanol. These blending ratios are determined as appropriate. For example, for example, carbon fiber 3 (g), resin (solid content 20 wt%) 1.5 (g), carbon fine particles 0.5 (g), solvent 20 ( g). In this blending example, the carbon fiber contains 16.7 (wt%) of carbon fine particles and 10 (wt%) of resin in solid content.

次いで、上記の材料を全て混合容器に投入し、混合工程１において、例えばスターラーによって300(rpm)程度の回転数で１日程度の混合を行う。次いで、含浸工程２において、別途用意した前記ガラスクロスすなわち基材を上記混合工程１で得られたスラリーに浸し、これを含浸させる。   Next, all of the above materials are put into a mixing container, and in the mixing step 1, mixing is performed for about one day at a rotational speed of about 300 (rpm) using, for example, a stirrer. Next, in the impregnation step 2, the separately prepared glass cloth, that is, the base material is immersed in the slurry obtained in the mixing step 1 and impregnated therewith.

次いで、乾燥工程３において、スラリーを含浸させたガラスクロスに例えば室温で６時間程度の乾燥処理を施し、更に、熱処理工程４において、これを乾燥機に入れて例えば150(℃)で３時間程度の熱処理を施す。これにより、スラリーから溶剤が除去され、ガラスクロスの表面や隙間などにおいて、炭素繊維が相互に絡み合い且つ炭素微粒子を介して樹脂で結着させられたシート状物が得られる。すなわち、前記ＭＥＡ１０のガス拡散電極１８，２０を構成するためのガス拡散電極用基材が得られる。   Next, in the drying step 3, the glass cloth impregnated with the slurry is subjected to a drying treatment, for example, at room temperature for about 6 hours. Heat treatment. As a result, the solvent is removed from the slurry, and a sheet-like material is obtained in which carbon fibers are entangled with each other and bound with a resin via carbon fine particles on the surface of a glass cloth or a gap. That is, the base material for gas diffusion electrodes for constituting the gas diffusion electrodes 18 and 20 of the MEA 10 is obtained.

このようにして製造したガス拡散電極１８，２０の特性を評価した結果を図５、図６に示す。図５は断面加圧抵抗の測定結果で、図６はガス拡散性能の測定結果である。これら図５、図６において、横軸には評価したガス拡散電極の基材材料を示している。金属メッシュは、165メッシュ、膜厚67(μm)の304Nステンレスメッシュで、不織布は膜厚140(μm)のBEMCOT S-2(旭化成せんい(株)の登録商標、製品番号)で、炭素繊維紙は市販品(東レ(株)製TGP-H-060)である。金属メッシュおよび不織布は実施例のガラスクロスと同様にスラリーを含浸してガス拡散電極基材を製造し、炭素繊維紙は上記の市販品をそのまま用いた。   The results of evaluating the characteristics of the gas diffusion electrodes 18 and 20 thus manufactured are shown in FIGS. FIG. 5 shows the measurement result of the cross-sectional pressure resistance, and FIG. 6 shows the measurement result of the gas diffusion performance. 5 and 6, the horizontal axis represents the evaluated base material of the gas diffusion electrode. The metal mesh is 304N stainless mesh with 165 mesh and a film thickness of 67 (μm), and the nonwoven fabric is BEMCOT S-2 (registered trademark, product number of Asahi Kasei Fibers Co., Ltd.) with a film thickness of 140 (μm). Is a commercial product (TGP-H-060 manufactured by Toray Industries, Inc.). The metal mesh and non-woven fabric were impregnated with slurry in the same manner as the glass cloth of the example to produce a gas diffusion electrode substrate, and the above-mentioned commercially available carbon fiber paper was used as it was.

また、上記評価結果において、断面加圧抵抗は、電極面積を25(mm)×35(mm)とし、小型熱プレス機(アズワン製AH-2003)を用いて25(℃)にて2(MPa)で加圧した状態で50(mA)の電流を印加し、そのときの電圧値から抵抗値を計算した。また、ガス透過性は、25(mm)×25(mm)のサンプルを切り出し、パームポロメータ(PMI社製Capillary Flow Porometer 1200AEL)でサンプル厚を入力してガス透過測定を行った。   In the above evaluation results, the cross-sectional pressure resistance is 2 (MPa) at 25 (° C.) using a small heat press machine (AH-2003 manufactured by ASONE) with an electrode area of 25 (mm) × 35 (mm). ) Was applied with a current of 50 (mA), and the resistance value was calculated from the voltage value at that time. Further, for gas permeability, a sample of 25 (mm) × 25 (mm) was cut out, and gas permeation measurement was performed by inputting the sample thickness with a palm porometer (Capillary Flow Porometer 1200AEL manufactured by PMI).

断面加圧抵抗の測定結果を表す図５において、サンプルの膜厚が著しく異なるものがあることから、膜厚を考慮しないサンプル自体の抵抗値(mΩ・cm2)で比較した。抵抗値は一般に使用されている炭素繊維紙と同程度か、それよりも十分に低い値であることが確かめられた。 In FIG. 5 showing the measurement result of the cross-sectional pressurization resistance, since the film thickness of the sample is remarkably different, the resistance value (mΩ · cm 2 ) of the sample itself without considering the film thickness was compared. It was confirmed that the resistance value was comparable to or sufficiently lower than that of commonly used carbon fiber paper.

また、ガス透過性の測定結果を表す図６においても、全てのサンプルにおいて、炭素繊維紙よりも僅かに或いは十分に高い値であることが確かめられた。なお、ガス透過性は、装置の測定可能な上限近傍で測定しているため、この測定結果から何れのサンプルも炭素繊維紙よりも良い結果が得られていることは明らかであるが、値自体の信頼性は低く、何れのサンプルも更に良い特性を有している可能性がある。   Also, in FIG. 6 showing the gas permeability measurement results, it was confirmed that all samples had values slightly or sufficiently higher than the carbon fiber paper. In addition, since gas permeability is measured in the vicinity of the measurable upper limit of the apparatus, it is clear from this measurement result that any sample has a better result than carbon fiber paper, but the value itself Is less reliable and any sample may have better properties.

なお、これらの測定結果において、ガラスクロスを基材とするものは、評価には膜厚が21(μm)のものを用いているが、機械的強度や柔軟性が十分に高いことから、実機では膜厚を更に薄くすることが可能である。したがって、ガラスクロスを用いた場合の断面加圧抵抗およびガス透過性は、上記測定結果よりも更に良い特性を期待できる。   In these measurement results, glass cloth as a base material has a film thickness of 21 (μm) for evaluation, but the mechanical strength and flexibility are sufficiently high. Then, the film thickness can be further reduced. Therefore, the cross-sectional pressure resistance and gas permeability when using a glass cloth can be expected to be better than the above measurement results.

また、上記測定と併せて、ガス拡散電極基材の柔軟性の評価を行った。柔軟性の評価は、φ4(cm)のガラス製円筒に巻き付け、破損やひび割れ等の有無を確認することで行った。ガラスクロス、金属メッシュ、不織布を基材として用いたものは、何れも破損やひび割れが認められなかった。これに対して、市販の炭素繊維紙は、破損やひび割れが生じ、柔軟性が不足することが確かめられた。なお、前記スラリーをガラスクロス等の基材に含浸することなく硬化させたサンプルも同様に評価したが、炭素繊維紙と同様に破損やひび割れが生ずる結果となった。   In addition to the above measurements, the flexibility of the gas diffusion electrode substrate was evaluated. Flexibility was evaluated by wrapping around a φ4 (cm) glass cylinder and checking for breakage, cracks, and the like. No damage or cracks were observed in any glass cloth, metal mesh, or nonwoven fabric used as a base material. On the other hand, it was confirmed that the commercially available carbon fiber paper was damaged and cracked and lacked flexibility. In addition, although the sample which hardened | cured the said slurry without impregnating base materials, such as a glass cloth, was evaluated similarly, it resulted in that a breakage and a crack produced like carbon fiber paper.

上述した評価結果によれば、ガラスクロス、金属メッシュ、或いは不織布等の柔軟な多孔性薄膜から成る基材に、炭素繊維、炭素微粒子、樹脂を含むスラリーを含浸して複合化することにより、従来から用いられている炭素繊維紙と同等以上の特性を有し、且つロール化できる程度に高い柔軟性を有するガス拡散電極基材が得られる。   According to the above-described evaluation results, a substrate made of a flexible porous thin film such as glass cloth, metal mesh, or non-woven fabric is impregnated with a slurry containing carbon fiber, carbon fine particles, and resin to form a composite. Thus, a gas diffusion electrode base material having characteristics equivalent to or better than the carbon fiber paper used from the above and having a high flexibility enough to be rolled can be obtained.

すなわち、本実施例によれば、ガス拡散電極１８，２０は、その基材であるガラスクロス２２等が高い柔軟性を有すると共に、これに炭素繊維２４および炭素微粒子２６がスラリーの含浸により内部まで十分に入った状態で樹脂２８で被着させられていることから、多数の炭素繊維２４がその相互間に多数の炭素微粒子２６が介在した状態で相互に樹脂２８で接合された構造を厚み方向の全体に亘って備えるので、導電性およびガス透過性が共に高く、しかも柔軟性に優れたガス拡散電極１８，２０が得られる。また、含浸処理によって製造することができ、且つ柔軟性に優れていることからロール化が可能であるので、量産性に優れ製造コストも抑えることが可能である。   That is, according to the present embodiment, the gas diffusion electrodes 18 and 20 have high flexibility in the glass cloth 22 or the like that is the base material, and the carbon fibers 24 and the carbon fine particles 26 are impregnated therein by slurry impregnation. Since the resin 28 is deposited in a fully contained state, a structure in which a large number of carbon fibers 24 are joined to each other with the resin 28 in a state where a large number of carbon fine particles 26 are interposed therebetween is provided in the thickness direction. Therefore, the gas diffusion electrodes 18 and 20 having both high conductivity and gas permeability and excellent flexibility can be obtained. In addition, since it can be manufactured by impregnation treatment and is excellent in flexibility, it can be rolled, so that it is excellent in mass productivity and manufacturing cost can be suppressed.

しかも、本実施例によれば、導電性を得る目的で樹脂を炭化させる必要が無いことから、不活性或いは還元雰囲気中における高温の焼成処理が無用で、前述したように例えば150(℃)程度の乾燥処理を施せば足りる。そのため、高温の焼成処理を施していた炭素繊維紙に比較して、製造コストが低くなる利点もある。   Moreover, according to this embodiment, since there is no need to carbonize the resin for the purpose of obtaining conductivity, there is no need for a high-temperature baking treatment in an inert or reducing atmosphere, and as described above, for example, about 150 (° C.). It is sufficient to apply the drying process. Therefore, there is also an advantage that the manufacturing cost is lower than that of carbon fiber paper that has been subjected to a high-temperature firing treatment.

また、ガラスクロス２２の他にも、前記評価結果にて説明したように、多孔性薄膜を基材とすれば、ガラスクロス２２を用いた場合と同様に柔軟性の高いガス拡散電極基材が得られる。したがって、柔軟で、200(℃)程度までの耐熱性を有し、耐酸性を有する多孔質材料であれば、種々の材料を基材として用いて、同様な或いは同等以上の特性のガス拡散電極を得ることができる。   In addition to the glass cloth 22, as explained in the evaluation results, if a porous thin film is used as a base material, a highly flexible gas diffusion electrode base material can be obtained as in the case of using the glass cloth 22. can get. Therefore, if it is a porous material that is flexible, heat resistant up to about 200 (° C.), and has acid resistance, various materials can be used as a base material, and gas diffusion electrodes having similar or equivalent characteristics can be used. Can be obtained.

次に、基材および樹脂材料を種々変更すると共に、炭素繊維に対するそれらの添加割合を種々変更してガス拡散電極基材を製造し、特性を評価した結果を説明する。   Next, various changes are made to the base material and the resin material, and the addition ratio to the carbon fiber is changed to produce a gas diffusion electrode base material.

下記の表１は、前記実施例と同一の基材、樹脂を用いて、炭素微粒子および樹脂の添加量を変更した実験結果を示したものである。これらの添加量の他は、前述した調合仕様でスラリーを調製し、基材に含浸処理を行った。表において、「×」はスラリー成分と多孔質薄膜との結合が弱く、剥離、破損が著しく、測定不能であったサンプルである。これは樹脂量が不十分であったものと考えられる。また、空欄はサンプル作製或いは測定を実施していない。   Table 1 below shows experimental results obtained by changing the addition amount of the carbon fine particles and the resin using the same base material and resin as those in the above-described example. In addition to these addition amounts, a slurry was prepared according to the above-mentioned preparation specifications, and the substrate was impregnated. In the table, “x” indicates a sample in which the bond between the slurry component and the porous thin film was weak, peeling and breakage were remarkable, and measurement was impossible. This is considered that the resin amount was insufficient. In the blank, sample preparation or measurement is not performed.

Figure 2010153222
Figure 2010153222

ガス透過性は、3000(ml・mm/cm2/min)以上であることが好ましく、10000(ml・mm/cm2/min)以上が一層好ましい。また、加圧抵抗は、10(mΩ・cm2)未満であることが好ましく、7(mΩ・cm2)未満が一層好ましい。ガス透過性が3000(ml・mm/cm2/min)以上且つ加圧抵抗が10(mΩ・cm2)未満の範囲を一点鎖線で、ガス透過性が10000(ml・mm/cm2/min)以上且つ加圧抵抗が7(mΩ・cm2)未満の範囲を破線で、それぞれ表１に示した。測定データが欠けている部分は、隣接データから適否を推定した。上記表１に示す評価結果によれば、一点鎖線で囲まれた範囲、特に炭素繊維に対する割合で炭素微粒子が10〜20(wt％)、樹脂が3.3〜16.7(wt％)の範囲で、ガス透過性、加圧抵抗共に好ましい値が得られ、破線で囲まれた範囲、特に炭素繊維に対する割合で炭素微粒子13.3〜16.7(wt％)、樹脂3.3〜10(wt％)(好ましくは6.7〜10(wt％))の範囲で、ガス透過性、加圧抵抗共に一層好ましい値が得られる。 The gas permeability is preferably 3000 (ml · mm / cm 2 / min) or more, and more preferably 10000 (ml · mm / cm 2 / min) or more. The pressure resistance is preferably less than 10 (mΩ · cm 2 ), and more preferably less than 7 (mΩ · cm 2 ). The gas permeability is 10000 (ml ・ mm / cm 2 / min) with a one-dot chain line in the range where the gas permeability is 3000 (ml ・ mm / cm 2 / min) or more and the pressure resistance is less than 10 (mΩ ・ cm 2 ). ) And the range where the pressure resistance is less than 7 (mΩ · cm 2 ) are shown in Table 1 with broken lines. In the case of missing measurement data, suitability was estimated from adjacent data. According to the evaluation results shown in Table 1 above, in the range surrounded by the alternate long and short dash line, particularly in the range of 10 to 20 (wt%) carbon fine particles and 3.3 to 16.7 (wt%) resin in proportion to the carbon fiber, Preferred values are obtained for both permeability and pressure resistance, and in the range surrounded by the broken line, particularly carbon fine particles 13.3 to 16.7 (wt%), resin 3.3 to 10 (wt%) (preferably 6.7 to 10) in the ratio to the carbon fiber. In the range of (wt%), more preferable values of gas permeability and pressure resistance can be obtained.

下記の表２は、基材として前記の金属メッシュを用いた場合について、同様に実験した結果をまとめたものである。この実験は、前記表１に示した実験結果に基づいて好ましいと判断した添加量の上下限のみについて行った。表２に示される通り、ガラスクロスを用いた場合に比較して、金属メッシュを用いた場合には、ガス透過性が若干高く、加圧抵抗が若干高い傾向が認められたが、何れの特性も好ましい範囲内にある。   Table 2 below summarizes the results of similar experiments for the case where the metal mesh was used as a base material. This experiment was conducted only for the upper and lower limits of the addition amount that was determined to be preferable based on the experimental results shown in Table 1. As shown in Table 2, gas permeability was slightly higher and pressure resistance tended to be slightly higher when a metal mesh was used than when glass cloth was used. Is also within the preferred range.

Figure 2010153222
Figure 2010153222

下記の表３は、基材として前記不織布を用いた場合について、同様に実験結果をまとめたものである。この実験も、前記表１に示した実験結果に基づいて好ましいと判断した添加量の上下限のみについて行った。表３に示される通り、ガラスクロスを用いた場合に比較して、不織布を用いた場合には、ガス透過性は同程度で、加圧抵抗が若干高い傾向が認められたが、何れの特性も好ましい範囲内にある。   Table 3 below summarizes the experimental results in the same manner for the case where the nonwoven fabric was used as the base material. This experiment was also performed only for the upper and lower limits of the addition amount that was determined to be preferable based on the experimental results shown in Table 1. As shown in Table 3, compared to the case of using a glass cloth, when the nonwoven fabric was used, the gas permeability was similar and the pressure resistance tended to be slightly higher. Is also within the preferred range.

Figure 2010153222
Figure 2010153222

また、同様にして、基材としてガラスクロスを用い、樹脂として熱可塑性を有するポリエステル樹脂を用いて、炭素微粒子の添加量を16.7(wt％)、樹脂の添加量を10.0(wt％)として、その他は前記調合仕様に従ってガス拡散電極用基材を製造して特性を評価した。ガス透過性が5000(ml・mm/cm2/min)、加圧抵抗が9.6(mΩ・cm2)であり、何れも実用的な値を得ることができた。 Similarly, using glass cloth as a base material, using a polyester resin having thermoplasticity as a resin, the amount of carbon fine particles added is 16.7 (wt%), the amount of resin added is 10.0 (wt%), Others manufactured the gas diffusion electrode substrate according to the above-mentioned preparation specifications and evaluated the characteristics. The gas permeability was 5000 (ml · mm / cm 2 / min) and the pressurization resistance was 9.6 (mΩ · cm 2 ).

また、添加する樹脂をポリエステル樹脂に代えて熱可塑性を有するポリアミド樹脂とした他は、上記実験と同様にしてガス拡散電極用基材を製造し、特性を評価した。ガス透過性が5800(ml・mm/cm2/min)、加圧抵抗が17.2(mΩ・cm2)であった。ガス透過性は満足できる値であるが、加圧抵抗が高い結果となった。樹脂の溶媒への溶解性が高く、樹脂によって導電経路が小さくなっている可能性が考えられる。しかしながら、ポリアミド樹脂を用いたものは柔軟性が高いので、燃料電池を構成する際にＭＥＡを加圧締め付けして接触面積を増すことができる。そのため、使用時の加圧抵抗を上記測定値よりも十分に低くできるので、これもガス拡散電極として好適に用い得る。 Moreover, the base material for gas diffusion electrodes was manufactured in the same manner as in the above experiment except that the resin to be added was replaced with a polyester resin instead of a polyester resin, and the characteristics were evaluated. Gas permeability is 5800 (ml · mm / cm 2 / min), pressure resistance was 17.2 (mΩ · cm 2). The gas permeability was a satisfactory value, but the result was high pressure resistance. There is a possibility that the resin has a high solubility in a solvent, and the conductive path is reduced by the resin. However, since the thing using a polyamide resin is highly flexible, when comprising a fuel cell, MEA can be pressure clamped and a contact area can be increased. Therefore, the pressurization resistance at the time of use can be made sufficiently lower than the above measured value, and this can also be suitably used as a gas diffusion electrode.

また、下記の表４は、ガス拡散電極の特性の炭素繊維の繊維長依存性について評価した結果である。この実験では、炭素繊維として繊維長が10〜6000(μm)の範囲内のものを用い、その他は前述した実施例の調合仕様に従ってガス拡散電極基材を製造して評価した。下記の評価結果に示す通り、繊維長が10〜500(μm)の範囲のものを用いると、断面加圧抵抗が十分に小さく且つガス透過性も十分に大きい特性が得られる。また、繊維長が50(μm)以上のものを用いれば、10000(ml・mm/cm2/min)以上の高いガス透過性が得られ、加圧抵抗も一層小さくなるので一層好ましい。 Table 4 below shows the results of evaluating the dependence of the characteristics of the gas diffusion electrode on the fiber length of the carbon fiber. In this experiment, carbon fibers having a fiber length in the range of 10 to 6000 (μm) were used, and the others were manufactured and evaluated according to the preparation specifications of the above-described examples. As shown in the following evaluation results, when a fiber having a fiber length in the range of 10 to 500 (μm) is used, characteristics with sufficiently small cross-sectional pressure resistance and sufficiently large gas permeability can be obtained. Further, it is more preferable to use a fiber having a fiber length of 50 (μm) or more because a high gas permeability of 10,000 (ml · mm / cm 2 / min) or more can be obtained and the pressure resistance is further reduced.

Figure 2010153222
Figure 2010153222

以上、本発明を図面を参照して詳細に説明したが、本発明は更に別の態様でも実施でき、その主旨を逸脱しない範囲で種々変更を加え得るものである。   As mentioned above, although this invention was demonstrated in detail with reference to drawings, this invention can be implemented also in another aspect, A various change can be added in the range which does not deviate from the main point.

本発明の一実施例である平板型のＭＥＡの断面を模式的に示す図である。It is a figure which shows typically the cross section of the flat type MEA which is one Example of this invention. 図１のＭＥＡを構成するガス拡散電極の断面を模式的に示す図である。It is a figure which shows typically the cross section of the gas diffusion electrode which comprises MEA of FIG. 図２のガス拡散電極を構成する炭素繊維の接合部を拡大して示す模式図である。It is a schematic diagram which expands and shows the junction part of the carbon fiber which comprises the gas diffusion electrode of FIG. 図２のガス拡散電極の製造方法を説明するための工程図である。It is process drawing for demonstrating the manufacturing method of the gas diffusion electrode of FIG. ガス拡散電極の基材種類と断面加圧抵抗との関係を示す図である。It is a figure which shows the relationship between the base material kind of gas diffusion electrode, and cross-sectional pressurization resistance. ガス拡散電極の基材種類とガス透過性との関係を示す図である。It is a figure which shows the relationship between the base material kind of gas diffusion electrode, and gas permeability.

符号の説明Explanation of symbols

１０：ＭＥＡ、１２：電解質膜、１４，１６：触媒層、１８，２０：ガス拡散電極、２２：ガラスクロス、２４：炭素繊維、２６：炭素微粒子、２８：樹脂 10: MEA, 12: electrolyte membrane, 14, 16: catalyst layer, 18, 20: gas diffusion electrode, 22: glass cloth, 24: carbon fiber, 26: carbon fine particle, 28: resin

Claims (7)

固体高分子形燃料電池を構成するために固体高分子電解質上に気体を導き得る状態で設けられる多孔質のガス拡散電極であって、
直径3(cm)の円筒に巻き付け得る柔軟性を有する多孔性薄膜にスラリーを含浸して炭素繊維、炭素微粒子、および樹脂を被着させて成ることを特徴とする柔軟型ガス拡散電極。 A porous gas diffusion electrode provided in a state in which a gas can be guided on a solid polymer electrolyte in order to constitute a solid polymer fuel cell,
A flexible gas diffusion electrode, comprising a porous thin film having flexibility that can be wound around a cylinder having a diameter of 3 (cm) and impregnated with a slurry to deposit carbon fibers, carbon fine particles, and a resin. 固体高分子形燃料電池を構成するために固体高分子電解質上に気体を導き得る状態で設けられる多孔質のガス拡散電極であって、
有機繊維或いは無機繊維から成る織布或いは不織布、金属メッシュ、または孔空き金属薄板から成る柔軟性を有する多孔性薄膜にスラリーを含浸して炭素繊維、炭素微粒子、および樹脂を被着させて成ることを特徴とする柔軟型ガス拡散電極。 A porous gas diffusion electrode provided in a state in which a gas can be guided on a solid polymer electrolyte in order to constitute a solid polymer fuel cell,
It is made by impregnating carbon fiber, carbon fine particles, and resin by impregnating slurry into a flexible porous thin film made of woven or non-woven fabric made of organic fiber or inorganic fiber, metal mesh, or perforated metal sheet. A flexible gas diffusion electrode. 前記多孔性薄膜は直径3(cm)の円筒に巻き付け得るものである請求項２の柔軟型ガス拡散電極。   3. The flexible gas diffusion electrode according to claim 2, wherein the porous thin film can be wound around a cylinder having a diameter of 3 cm. 前記樹脂は分解温度が200(℃)以上の熱可塑性樹脂または硬化温度が40乃至200(℃)の範囲内の熱硬化性樹脂である請求項１乃至請求項３の何れか１項に記載の柔軟型ガス拡散電極。   4. The resin according to claim 1, wherein the resin is a thermoplastic resin having a decomposition temperature of 200 (° C.) or higher, or a thermosetting resin having a curing temperature in a range of 40 to 200 (° C.). 5. Flexible gas diffusion electrode. 前記炭素繊維は繊維長が500(μm)以下である請求項１乃至請求項４の何れか１項に記載の柔軟型ガス拡散電極。   The flexible gas diffusion electrode according to any one of claims 1 to 4, wherein the carbon fiber has a fiber length of 500 (µm) or less. 前記スラリーは、前記炭素微粒子を10乃至20(wt％)の範囲内、および前記樹脂を3.3乃至16.7(wt％)の範囲内で含むものである請求項１乃至請求項５の何れか１項に記載の柔軟型ガス拡散電極。   6. The slurry according to claim 1, wherein the slurry contains the carbon fine particles in a range of 10 to 20 (wt%) and the resin in a range of 3.3 to 16.7 (wt%). Flexible gas diffusion electrode. 固体高分子電解質層と、その一面および他面にそれぞれ設けられた触媒層と、それら触媒層の各々の表面に設けられた請求項１乃至請求項６の何れか１項に記載の柔軟型ガス拡散電極とを、含むことを特徴とする膜−電極接合体。   The flexible gas according to any one of claims 1 to 6, wherein the solid polymer electrolyte layer, a catalyst layer provided on one surface and the other surface thereof, and a surface of each of the catalyst layers are provided. A membrane-electrode assembly comprising a diffusion electrode.
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WO2012026498A1 (en) 2010-08-27 2012-03-01 東邦テナックス株式会社 Conductive sheet and production method for same
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