JP4367983B2 - Electrode electrolyte assembly for polymer electrolyte fuel cell, polymer electrolyte fuel cell and production method thereof - Google Patents
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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
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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
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Description
【０００１】
【発明の属する技術分野】
本発明は、ポータブル電源、分散型電源、コージェネシステム等に使用される燃料電池に関する。
【０００２】
【従来の技術】
燃料電池は、水素などの燃料と空気などの酸化剤ガスをガス拡散電極によって電気化学的に反応させ、電気と熱を同時に供給するものである。水素イオンを選択的に輸送する電解質には、リン酸型燃料電池においては、ＳｉＣマトリックスに含浸したリン酸が用いられる。電解質の両面には、白金系の金属触媒を担持したカーボン粉末を主成分とする電極反応層が密着して形成される。さらに、電極反応層の外面には、ガス通気性と導電性を兼ね備えた一対の電極基材が密着して形成され、電極反応層と合わせて電極とされる。電極の外側には、これらの電極および電解質の接合体を機械的に固定するとともに、隣接する接合体を互いに電気的に直列に接続するための導電性のセパレータ板が配置される。
通常、電極基材にはカーボン繊維が用いられ、セパレータ板にはカーボン板が用いられる。セパレータ板の電極と接触する部分には、電極面に反応ガスを供給し、生成ガスや余剰ガスを運び去るためのガス流路が形成される。
【０００３】
水素が供給される電極では、ガス流路から電極基材を経て電極反応層へ供給された水素は酸化され、水素イオンとなってリン酸水溶液中へ入る。空気が供給されるもう一方の電極では、電極反応層において酸素がリン酸水溶液中の水素イオンと反応して水が生成する。その結果、電子が外部回路を通って水素側電極から空気側電極へ流れることによって発電する。それぞれの電極反応層へは水素や空気などの反応ガスを供給し、水蒸気などのドレインガスを効率よく除去するための気道の確保が必要である。このため、従来はポリテトラフルオロエチレン（以下ＰＴＦＥで表す）などのフッ素系ポリマーからなる撥水剤を電極反応層や電極基材、セパレータ板上のガス流路の表面に配するための撥水処理が施されていた。この撥水剤は、ＳｉＣマトリックスに含浸したリン酸水溶液の電池外への漏出を抑制する働きがあるとも考えられている。
【０００４】
フッ素系ポリマーの撥水剤は、従来次のようにして所定の部位に配置されていた。たとえばカーボン繊維紙やセパレータのガス流路に、フッ素系ポリマーのコロイド分散液を含浸・塗布し、溶媒を乾燥により除去した後、３５０℃〜４５０℃で熱処理してカーボン繊維やセパレータのガス流路にフッ素系ポリマーを固着させていた。また、電極反応層には、白金を担持するカーボン粉末とは別のカーボン粉末に予めフッ素系ポリマーの撥水剤を固着させ、これを白金を担持したカーボン粉末と混合して用いていた。フッ素系ポリマーとしては、ＰＴＦＥの他にもパーフルオロメチル基など種々の置換基を修飾して、ガラス転移点などの物性を変えたものも用いられる。
また、リン酸型燃料電池の他に、水溶液系の燃料電池として固体高分子型燃料電池がある。この固体高分子型燃料電池の電極反応層や電極基材にも同様に撥水剤が用いられる。
【０００５】
【発明が解決しようとする課題】
ＰＴＦＥなどのフッ素系ポリマーは、水との接触角が〜１１０度である。より高性能の電池を得ようとすれば、この水との接触角がより大きく、撥水性の高い撥水剤を用いることが望ましい。また、撥水剤を被処理面に固着するためには、撥水剤のコロイド分散液を塗布・乾燥後、３５０℃以上の高温で熱処理する必要がある。しかし、この方法によると、被処理剤が耐熱性材料に限定される。
一方、耐熱性の低い材料の撥水処理には、撥水剤のコロイド分散液を塗布・乾燥した状態で用いなければならない。しかし、被処理面に撥水剤が固着されていないので、長期間電池を運転すると、撥水剤が脱落し撥水性が低下する可能性がある。さらに、このような方法では、撥水処理を施したい部分、例えば電極基材の片側の表面、に限定して撥水処理を施すことが困難である。
【０００６】
【課題を解決するための手段】
以上の課題を解決するため本発明の固体高分子型燃料電池用電極電解質接合体は、電極反応層及び電極基材を含む一対の電極と、前記一対の電極で挟持された固体高分子電解質膜と、を具備し、前記電極基材の前記電極反応層側の面に、フッ化ピッチを配したことを特徴とする。
前記フッ化ピッチの平均分子量は、５００以上かつ１００００以下であることが有用である。
前記フッ化ピッチに含まれるフッ素とカーボンの比（Ｆ／Ｃ）は、１．２５以上かつ１．６５以下であることが有用である。
前記フッ化ピッチに含まれるフッ素と水素の比（Ｆ／Ｈ）は、９以上であることが有用である。
前記フッ化ピッチの水に対する接触角は、１３０度以上であることが有用である。
前記フッ化ピッチの炭素骨格が６員環を有し、積層した平面構造であることが望ましい。
前記フッ化ピッチは、石炭系ピッチまたは石油系ピッチのフッ素化により合成したものが有用である。
また、本発明は、前記電極電解質接合体と、前記電極の一方に少なくとも水素を含む燃料を供給分配し、前記電極の他方に少なくとも酸素を含む酸化剤ガスを供給分配するガス流路と、を具備する固体高分子型燃料電池に関する。
【０００７】
本発明の固体高分子型燃料電池用電極電解質接合体の製造法は、溶媒に溶かしたフッ化ピッチの溶液を、電極基材の電極反応層側の面に塗布し、溶媒を乾燥、除去することによりフッ化ピッチを固着する工程を有することを特徴とする。
また、別の好ましい実施形態において、本発明の固体高分子型燃料電池用電極電解質接合体の製造法は、フッ化ピッチを気相からの析出により、電極基材の電極反応層側の面に固着する工程を含むことを特徴とする。
【０００８】
【発明の実施の形態】
本発明は、燃料電池の電極反応層、電極基材、ガス流路溝の表面などへの撥水処理剤として、従来のフッ素系ポリマーに代わり、より接触角の高いフッ化黒鉛やフッ化ピッチなどの非ポリマー材料を撥水剤として用いることによって性能を改善するものである。なかでもフッ化ピッチは、パーフルオロベンゼンなどのフッ素系溶媒に良く溶け、被処理材に塗布・乾燥するだけで被処理材の表面に良く固着し、ガスフローによって脱落しにくいという特徴がある。さらにフッ化ピッチは、分子量が数千とポリマーに比べて大幅に小さく、形状もポリマーのように糸状でなく塊になっているので、温度を上げるとガス化することができる。その結果、蒸着によって、撥水処理を施したい部分、たとえば電極基材の片側の表面のみに撥水処理を施すことができ、電池の性能を改善することができる。
【０００９】
このフッ化ピッチは、石炭系ピッチまたは石油系ピッチのフッ素化により得られたもので、平均分子量が５００〜１００００のフッ化ピッチでは溶媒への溶解性、蒸着性において秀でていた。材料組成としては、含まれるフッ素とカーボンの比（Ｆ／Ｃ）が１．２５〜１．６５であるフッ化ピッチ、もしくは含まれるフッ素と水素の比（Ｆ／Ｈ）が９以上であるフッ化ピッチが好ましい。フッ化ピッチの水に対する接触角は１３０度以上であることが望ましい。また、化学構造としては６員環の炭素骨格を主体とし、積層した平面構造を有している。
本発明は、特に固体高分子型燃料電池など電解質や反応生成物に水を含む燃料電池について有効である。
【００１０】
【実施例】
以下、本発明の実施例を説明する。
《参考例１》
粒径が数ミクロン以下のカーボン粉末を塩化白金酸水溶液に浸漬し、還元処理によりカーボン粉末表面に白金触媒を担持した。カーボンと担持した白金の重量比は、ほぼ１：１とした。
電極反応層１の撥水剤として、フッ化黒鉛を用いた。フッ化黒鉛は、フッ素と炭素がほぼ１：１で化合しているもので、水との接触角は約１４３度であった。このフッ化黒鉛を白金担持カーボン粉末と５重量％の割合で混合し、エチルアルコールを主体とした溶媒を加えて混練しインクとした。
一方、電極基材２となる厚さ５００ミクロンのカーボンペーパーを、前記と同じフッ化黒鉛を超音波分散させた有機溶媒中に含浸し、乾燥して撥水性を付与した。前記の白金担持カーボンおよびフッ化黒鉛を含むインクを、撥水処理した電極基材の片面に金属マスクを用いて、均一に塗布し乾燥させて電極反応層を形成した。
多孔質ＳｉＣ板でできたマトリックス材３に１０５％のポリリン酸を含浸し、これに、前記電極反応層を形成した一対の電極基材を、両面から接合した。さらに、これらの電極反応層に反応ガスを供給したり、生成ガスを排出するためのガス流路溝を設けたリブ付きカーボン板からなる一対のセパレータ板４によって、前記電極基材を挟持して単電池を構成した。この単電池の概略構成を図１に示す。
【００１１】
つぎに、電池温度を２００℃程度にコントロールするためのヒータや断熱材、反応ガスの供給装置などを接続した。供給するガス圧を大気圧にして測定を行い、撥水剤としてポリテトラフルオロエチレン（ＰＴＦＥ）を用いた従来の電池の性能と比較した。
図３に示したように初期性能としては、従来電池が６００ｍＶ−２００ｍＡ／ｃｍ2に対して、本参考例の電池では６５０ｍＶ−２００ｍＡ／ｃｍ2と性能が大幅に向上した。これはＰＴＦＥの水との接触角が約１１０度であるのに対して、本参考例で用いたフッ化黒鉛のそれが１４３度と大きく、電極反応部位である三相帯がリン酸電解液や生成水で濡れすぎることもなく、良好に保たれたためと考えられる。
【００１２】
《参考例２》
フッ化黒鉛に代わって、水との接触角が大きく、被処理面への固着が容易な撥水剤を検討した。溶剤に可溶なフッ素系有機物としてポリフッ化ビニリデンなどと並んでフッ化ピッチを選定した。実験結果ではポリフッ化ビニリデンの接触角が１００度程度なのに対して、フッ化ピッチは最大で１４５度あった。また、その溶液もポリフッ化ビニリデンでは粘度が高く、扱いが難しいのに対して、フッ化ピッチでは溶媒として例えばパーフルオロベンゼンなどを選ぶと比較的粘度が低く、取り扱いも容易であった。これは分子がポリマーではなくその形も塊状であるためと考えられる。また、撥水性が高いのはフッ化ピッチの端部に−ＣＦ3基が多く存在するためと考えられる。
【００１３】
本参考例および以下の実施例に用いた代表的なフッ化ピッチは白色の粉末で、石炭系ピッチの直接フッ素化によって得た。反応温度を６０〜１２０℃前後とし、反応時間は４〜１２時間であった。
前記のフッ化ピッチを溶媒パーフルオロベンゼンに溶解し、白金触媒を担持したカーボン粉末に加えて混合後、乾燥することにより、白金触媒を担持したカーボン粉末に撥水性を付与した。同様にフッ化ピッチのパーフルオロベンゼン溶液を電極基材に含浸し、乾燥することによって電極基材にも撥水性を付与した。フッ化ピッチの固着した状態を顕微鏡で観察すると、被処理面にしっかりと融着していることが確認された。
【００１４】
異なる条件下で合成したフッ化ピッチを用いて、電極反応層には５重量％、電極基材には１０重量％となるようにそれぞれ撥水処理を施したリン酸型燃料電池を構成した。図４に、その中の代表的なフッ化ピッチとして、石炭系ピッチを原料とし、平均分子量が約２０００で、フッ素とカーボンの比（Ｆ／Ｃ）が約１．４、フッ素と水素の比（Ｆ／Ｈ）が約１２のものを用いた電池性能を、従来のＰＴＦＥを用いたものと比較して表した。
初期性能として従来電池が６００ｍＶ−２００ｍＡ／ｃｍ2に対して、本参考例の電池では６７０ｍＶ−２００ｍＡ／ｃｍ2と性能が大幅に向上した。また、１００時間連続運転後も性能の低下は認められなかった。
【００１５】
つぎに、フッ化ピッチの最適化を図るために、原料や分子量、構成元素比の異なるフッ化ピッチを用いて実験を行い、次の結果を得た。すなわち、原料としては石炭系ピッチの他には石油系ピッチも良好で、平均分子量としては５００〜１００００が従来のＰＴＦＥを用いた電池より性能が高かった。Ｆ／Ｃ比としては１．２５〜１．６５、Ｆ／Ｈ比としては９以上がそれぞれ好ましかった。また、接触角としては１３０度以上であれば性能改善が著しいことが分かった。さらに、Ｘ線回折やＮＭＲ法などの公知の解析手法により分子構造を調べると、撥水剤として用いて性能の改善が大きいものは、炭素骨格が６員環を主体とし、積層した平面構造を有しているものであることがわかった。
【００１６】
《実施例１》
電極における撥水性制御が重要である電池として、これまでの参考例で説明したリン酸型燃料電池の他に、固体高分子型燃料電池についても評価を行った。固体高分子型は、フッ素系の電解質膜に水分を含み、その水分量によって性能が大きく左右されるので、撥水性制御がより重要であると考えられる。
【００１７】
電極反応層の撥水剤として、新たにフッ化ピッチを表面に塗着した白金担持カーボン粉末を、電解質膜のアルコール溶液中に混練し、スラリーとした。また、同じフッ化ピッチによって電極基材となるカーボンペーパーに撥水処理を施した。このカーボンペーパーの片面に、前記のカーボン粉末を含むスラリーを均一に塗布して電極反応層を形成した。こうして電極基材を形成した２枚のカーボンペーパーを、電極反応層を内側に向け、固体高分子電解質膜を挟んで重ね合わせた後、乾燥して電極電解質接合体（以下ＭＥＡで表す）とした。２枚のカーボンペーパからなる電極基材は、長さおよび幅をともに１０ｃｍとし、一回り大きい長さおよび幅ともに１２ｃｍの高分子電解質膜の中央に配置した。このＭＥＡを、その両面から気密性を有するカーボン製のセパレータ板で挟み込んで単電池を構成とした。
電池試験の結果は、図５に示すように、従来のＰＴＦＥを用いた電池が６００ｍＶ−７００ｍＡ／ｃｍ2に対して、本発明の電池では６５０ｍＶ−７００ｍＡ／ｃｍ2と性能を飛躍的に改善することができた。
【００１８】
これまで参考例および実施例として用いたリン酸型燃料電池、固体高分子型燃料電池とも新しい撥水剤を用いた撥水処理は、電極反応層と電極基材の両方に施したが、どちらか一方でもある程度の効果を有することは言うまでもない。また、ガス流路となるセパレータの溝やマニホルド孔に同様に撥水処理を施すことも有効であると考えられる。
【００１９】
《実施例２》
参考例１、２および実施例１では、アルコールに分散させたり、パーフルオロベンゼンに溶解させた撥水剤を含む液を被撥水処理材に含浸し、乾燥するという手法を取った。一方、電極反応部における三相帯の働きを考慮すると、より局所的な撥水処理が望ましいと考えられる。
また、フッ化ピッチは、有機物ではあるがポリマーではないので昇華する。そこで、固体高分子型燃料電池の種々の構成面に熱蒸着によってフッ化ピッチを蒸着した電池を試作した。フッ化ピッチの蒸着によって撥水処理した部分は、電極基材のガス流路側の面、電極基材の電極反応層側の面、電極反応層を塗布・乾燥後の高分子電解質膜と接合する面である。電池試験の結果は、電極基材の電極反応層側の面に撥水処理を施したものが最も効果的であった。
【００２０】
【発明の効果】
以上のように本発明で用いる撥水剤は、水との接触角が従来のポリテトラフルオロエチレンより大きく、三相帯が良好に保たれるので、電池性能を改善することができる。また、フッ化ピッチは、溶媒に溶け、昇華性を有するので、撥水処理が容易にでき、限られた部分への撥水処理も可能となる。
【図面の簡単な説明】
【図１】 本発明の参考例におけるリン酸型燃料電池の要部の構成を示す縦断面略図である。
【図２】 同電池の電極反応層の構成を示す模式図である。
【図３】 同電池の初期性能を従来例と比較した図である。
【図４】 本発明の別の参考例におけるリン酸型燃料電池の性能を従来例と比較した図である。
【図５】 本発明の実施例における固体高分子型燃料電池の性能を従来例と比較した図である。
【符号の説明】
１ 電極反応層
２ 電極基材
３ マトリックス材
４ セパレータ
５ カーボン粉末
６ 白金触媒
７ フッ化黒鉛[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell used for a portable power source, a distributed power source, a cogeneration system, and the like.
[0002]
[Prior art]
In a fuel cell, a gas such as hydrogen and an oxidant gas such as air are electrochemically reacted by a gas diffusion electrode to supply electricity and heat simultaneously. In the phosphoric acid fuel cell, phosphoric acid impregnated in a SiC matrix is used as an electrolyte that selectively transports hydrogen ions. An electrode reaction layer mainly composed of carbon powder carrying a platinum-based metal catalyst is formed on both surfaces of the electrolyte in close contact. Furthermore, a pair of electrode base materials having both gas permeability and conductivity are formed in close contact with the outer surface of the electrode reaction layer, and the electrode reaction layer is used as an electrode. Outside the electrodes, a conductive separator plate is disposed to mechanically fix the joined body of these electrodes and electrolyte, and to electrically connect adjacent joined bodies to each other in series.
Usually, a carbon fiber is used for the electrode substrate, and a carbon plate is used for the separator plate. In the portion of the separator plate that comes into contact with the electrode, a gas flow path is formed for supplying the reaction gas to the electrode surface and carrying away the generated gas and surplus gas.
[0003]
In the electrode to which hydrogen is supplied, the hydrogen supplied from the gas flow path to the electrode reaction layer through the electrode base material is oxidized and enters into the phosphoric acid aqueous solution as hydrogen ions. In the other electrode to which air is supplied, oxygen reacts with hydrogen ions in the phosphoric acid aqueous solution in the electrode reaction layer to generate water. As a result, power is generated by electrons flowing through the external circuit from the hydrogen side electrode to the air side electrode. Reactive gas such as hydrogen or air is supplied to each electrode reaction layer, and it is necessary to secure an airway for efficiently removing drain gas such as water vapor. Therefore, conventionally, a water repellent for disposing a water repellent made of a fluorine-based polymer such as polytetrafluoroethylene (hereinafter referred to as PTFE) on the surface of a gas flow path on an electrode reaction layer, an electrode base material, or a separator plate. Processing has been applied. This water repellent is also considered to have a function of suppressing leakage of the phosphoric acid aqueous solution impregnated in the SiC matrix to the outside of the battery.
[0004]
Conventionally, the fluorine-based polymer water repellent has been disposed at a predetermined site as follows. For example, a carbon fiber paper or separator gas channel is impregnated and coated with a colloidal dispersion of a fluoropolymer, and the solvent is removed by drying, followed by heat treatment at 350 ° C. to 450 ° C. to form a carbon fiber or separator gas channel. A fluorine-based polymer was fixed to the surface. In the electrode reaction layer, a fluoropolymer water repellent was previously fixed to a carbon powder different from the carbon powder carrying platinum, and this was mixed with the carbon powder carrying platinum. As the fluorine-based polymer, in addition to PTFE, those in which various substituents such as a perfluoromethyl group are modified to change physical properties such as a glass transition point are also used.
In addition to the phosphoric acid fuel cell, there is a solid polymer fuel cell as an aqueous fuel cell. Similarly, a water repellent is used for the electrode reaction layer and the electrode substrate of the polymer electrolyte fuel cell.
[0005]
[Problems to be solved by the invention]
A fluorine-based polymer such as PTFE has a contact angle with water of ˜110 degrees. In order to obtain a battery with higher performance, it is desirable to use a water repellent having a larger contact angle with water and high water repellency. In order to fix the water repellent to the surface to be treated, it is necessary to heat-treat at a high temperature of 350 ° C. or higher after applying and drying the colloidal dispersion of the water repellent. However, according to this method, the agent to be treated is limited to a heat resistant material.
On the other hand, for a water repellent treatment of a material having low heat resistance, a colloidal dispersion of a water repellent must be applied and dried. However, since the water repellent is not fixed to the surface to be treated, when the battery is operated for a long time, the water repellent may fall off and the water repellency may decrease. Furthermore, in such a method, it is difficult to perform the water repellent treatment only on a portion where the water repellent treatment is desired, for example, the surface on one side of the electrode substrate.
[0006]
[Means for Solving the Problems]
Or more solid polymer fuel cell electrode electrolyte assembly of the present invention for solving the problem, a pair of electrodes comprising an electrode reaction layer and the electrode substrate, a solid polymer electrolyte membrane sandwiched by the pair of electrodes And fluorinated pitch is arranged on the surface of the electrode base material on the side of the electrode reaction layer .
It is useful that the average molecular weight of the fluorinated pitch is 500 or more and 10,000 or less.
It is useful that the ratio of fluorine to carbon (F / C) contained in the fluorinated pitch is 1.25 or more and 1.65 or less.
It is useful that the ratio of fluorine to hydrogen (F / H) contained in the fluorinated pitch is 9 or more.
It is useful that the contact angle of the fluorinated pitch with water is 130 degrees or more.
It is desirable that the fluorinated pitch carbon skeleton has a six-membered ring and has a laminated planar structure.
The pitch fluoride, Ru is useful der those synthesized by fluorination of a coal type pitch or petroleum pitch.
Further, the present invention provides the electrode electrolyte assembly, and a gas flow path for supplying and distributing a fuel containing at least hydrogen to one of the electrodes and supplying and distributing an oxidant gas containing at least oxygen to the other of the electrodes. The present invention relates to a solid polymer fuel cell.
[0007]
In the method for producing an electrode electrolyte assembly for a polymer electrolyte fuel cell according to the present invention, a solution of a fluorinated pitch dissolved in a solvent is applied to the electrode reaction layer side surface of the electrode substrate, and the solvent is dried and removed. And a step of fixing the fluorinated pitch.
In another preferred embodiment, the method for producing an electrode electrolyte assembly for a polymer electrolyte fuel cell according to the present invention is a method in which a fluoride pitch is deposited on a surface of an electrode substrate on an electrode reaction layer side by precipitation from a gas phase. It includes a step of fixing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a water repellent treatment agent for the electrode reaction layer, electrode base material, gas flow channel groove surface, etc. of a fuel cell. The performance is improved by using a non-polymer material such as a water repellent. Among them, the fluorinated pitch is well-dissolved in a fluorine-based solvent such as perfluorobenzene, and has a feature that it adheres well to the surface of the material to be treated simply by being applied to the material to be treated and dried, and is not easily removed by gas flow. Furthermore, the fluorinated pitch has a molecular weight of several thousand, which is significantly smaller than that of a polymer, and the shape is not a string but a lump like a polymer, so that it can be gasified when the temperature is raised. As a result, it is possible to perform the water repellent treatment only on a portion where water repellent treatment is desired, for example, the surface on one side of the electrode base material by vapor deposition, thereby improving the performance of the battery.
[0009]
This fluorinated pitch was obtained by fluorination of coal-based pitch or petroleum-based pitch, and the fluorinated pitch having an average molecular weight of 500 to 10,000 was excellent in solubility in a solvent and vapor deposition. The material composition includes a fluoride pitch with a fluorine to carbon ratio (F / C) of 1.25 to 1.65, or a fluorine with a ratio of fluorine to hydrogen (F / H) of 9 or more. A pitch is preferred. The contact angle of the fluorinated pitch with water is desirably 130 degrees or more. The chemical structure is mainly composed of a six-membered ring carbon skeleton and has a laminated planar structure.
The present invention is effective for a fuel cell including the water in the electrolyte and reaction products such as solid high polymer electrolyte fuel cell in Japanese.
[0010]
【Example】
Examples of the present invention will be described below.
<< Reference Example 1 >>
Carbon powder having a particle size of several microns or less was immersed in a chloroplatinic acid aqueous solution, and a platinum catalyst was supported on the surface of the carbon powder by reduction treatment. The weight ratio of carbon to platinum supported was approximately 1: 1.
As the water repellent for the electrode reaction layer 1, graphite fluoride was used. Fluorinated graphite is a combination of fluorine and carbon in a ratio of about 1: 1, and the contact angle with water was about 143 degrees. This fluorinated graphite was mixed with platinum-supporting carbon powder at a ratio of 5% by weight, and a solvent mainly composed of ethyl alcohol was added and kneaded to prepare an ink.
On the other hand, carbon paper having a thickness of 500 microns serving as the
A
[0011]
Next, a heater, a heat insulating material, a reaction gas supply device, and the like for controlling the battery temperature to about 200 ° C. were connected. The measurement was carried out with the supplied gas pressure set to atmospheric pressure, and compared with the performance of a conventional battery using polytetrafluoroethylene (PTFE) as a water repellent.
The initial performance as shown in FIG. 3, the conventional battery with respect to 600mV-200mA / cm 2, the battery of the present embodiment 650mV-200mA / cm 2 and performance has been greatly improved. This is because the contact angle of PTFE with water is about 110 degrees, while that of the fluorinated graphite used in this reference example is as large as 143 degrees, and the three-phase zone that is the electrode reaction site is a phosphate electrolyte. It is thought that it was maintained well without being too wet with water or product water.
[0012]
<< Reference Example 2 >>
In place of fluorinated graphite, a water repellent agent having a large contact angle with water and easy to adhere to the surface to be treated was examined. A fluorinated pitch was selected along with polyvinylidene fluoride as a fluorine-based organic material soluble in a solvent. In the experimental results, the contact angle of polyvinylidene fluoride was about 100 degrees, while the fluoride pitch was 145 degrees at the maximum. In addition, the polyvinylidene fluoride solution has a high viscosity and is difficult to handle, whereas the fluoride pitch has a relatively low viscosity when, for example, perfluorobenzene is selected as a solvent and is easy to handle. This is presumably because the molecule is not a polymer and its shape is also agglomerated. Also, the high water repellency is considered to be due to the presence of many —CF 3 groups at the ends of the fluorinated pitch.
[0013]
The typical fluorinated pitch used in this reference example and the following examples was a white powder and was obtained by direct fluorination of a coal-based pitch. The reaction temperature was around 60 to 120 ° C., and the reaction time was 4 to 12 hours.
The fluorinated pitch was dissolved in the solvent perfluorobenzene, added to the carbon powder carrying the platinum catalyst, mixed and then dried to impart water repellency to the carbon powder carrying the platinum catalyst. Similarly, the electrode substrate was impregnated with a perfluorobenzene solution of fluorinated pitch and dried to impart water repellency to the electrode substrate. When the state in which the fluoride pitch was fixed was observed with a microscope, it was confirmed that the fluoride pitch was firmly adhered to the surface to be processed.
[0014]
A phosphoric acid fuel cell was formed by using water-repellent treatment so that the electrode reaction layer might be 5 wt% and the electrode base material would be 10 wt% using fluorinated pitch synthesized under different conditions. In FIG. 4, as a typical fluorinated pitch, coal-based pitch is used as a raw material, the average molecular weight is about 2000, the ratio of fluorine to carbon (F / C) is about 1.4, and the ratio of fluorine to hydrogen. The battery performance using about 12 (F / H) is shown in comparison with that using conventional PTFE.
In contrast to the conventional battery of 600 mV-200 mA / cm 2 as the initial performance, the performance of the battery of this reference example was greatly improved to 670 mV-200 mA / cm 2 . In addition, no deterioration in performance was observed after 100 hours of continuous operation.
[0015]
Next, in order to optimize the fluoride pitch, experiments were performed using fluoride pitches having different raw materials, molecular weights, and constituent element ratios, and the following results were obtained. That is, as a raw material, a petroleum-based pitch was also good in addition to a coal-based pitch, and an average molecular weight of 500 to 10,000 was higher than that of a battery using conventional PTFE. The F / C ratio was preferably 1.25 to 1.65, and the F / H ratio was preferably 9 or more. Further, it was found that the performance improvement was remarkable when the contact angle was 130 degrees or more. Further, when the molecular structure is examined by a known analysis method such as X-ray diffraction or NMR method, the carbon skeleton is mainly composed of a 6-membered ring and the laminated planar structure is used as a water repellent. It turns out that it has.
[0016]
Example 1
As a battery in which water repellency control in the electrode is important, a solid polymer fuel cell was evaluated in addition to the phosphoric acid fuel cell described in the above reference examples. In the solid polymer type, water is contained in the fluorine-based electrolyte membrane, and the performance is greatly influenced by the amount of the water, so it is considered that water repellency control is more important.
[0017]
As a water repellent for the electrode reaction layer, platinum-supported carbon powder newly coated with a fluorinated pitch on the surface was kneaded into an alcohol solution of an electrolyte membrane to obtain a slurry. Moreover, the water repellent process was performed to the carbon paper used as an electrode base material with the same fluoride pitch. The slurry containing the carbon powder was uniformly applied to one side of the carbon paper to form an electrode reaction layer. The two carbon papers on which the electrode base material was formed in this manner were stacked with the electrode reaction layer facing inward and the solid polymer electrolyte membrane sandwiched between them, and then dried to obtain an electrode electrolyte assembly (hereinafter referred to as MEA). . The electrode substrate made of two carbon papers was 10 cm in length and width, and was placed in the center of a polymer electrolyte membrane having a length and width of 12 cm. The MEA was sandwiched between carbon separator plates having airtightness from both sides to form a unit cell.
Results of the battery test, as shown in FIG. 5, the battery is 600mV-700mA / cm 2 using the conventional PTFE, the battery of the present invention dramatically improves the 650mV-700mA / cm 2 and Performance I was able to.
[0018]
The phosphoric acid fuel cells and solid polymer fuel cells used as reference examples and examples so far have been subjected to water repellent treatment using a new water repellent on both the electrode reaction layer and the electrode substrate. Needless to say, it has some effect. It is also considered effective to perform a water repellent treatment on the grooves and manifold holes of the separator that form the gas flow path.
[0019]
Example 2
In Reference Examples 1 and 2 and Example 1 , a water repellent treatment material was impregnated with a liquid containing a water repellent dispersed in alcohol or dissolved in perfluorobenzene and dried. On the other hand, considering the action of the three-phase zone in the electrode reaction part, more local water repellent treatment is considered desirable.
Further, the fluorinated pitch is sublimated because it is an organic substance but not a polymer. In view of this, a battery in which fluorinated pitch was vapor-deposited by thermal vapor deposition on various constituent surfaces of the polymer electrolyte fuel cell was experimentally manufactured. The water-repellent-treated portion by vapor deposition of fluoride pitch is joined to the surface of the electrode substrate on the gas flow path side, the surface of the electrode substrate on the side of the electrode reaction layer, and the polymer electrolyte membrane after applying and drying the electrode reaction layer Surface. The result of the battery test was most effective when the surface of the electrode base material on the side of the electrode reaction layer was subjected to water repellent treatment.
[0020]
【The invention's effect】
As described above, the water repellent used in the present invention has a larger contact angle with water than that of conventional polytetrafluoroethylene and can maintain a good three-phase band, so that battery performance can be improved. Further, since the fluorinated pitch is dissolved in a solvent and has sublimation properties, the water repellent treatment can be easily performed, and the water repellent treatment to a limited portion is also possible.
[Brief description of the drawings]
FIG. 1 is a schematic vertical cross-sectional view showing a configuration of a main part of a phosphoric acid fuel cell according to a reference example of the present invention.
FIG. 2 is a schematic view showing a configuration of an electrode reaction layer of the battery.
FIG. 3 is a diagram comparing the initial performance of the battery with a conventional example.
FIG. 4 is a diagram comparing the performance of a phosphoric acid fuel cell in another reference example of the present invention with a conventional example.
5 is a diagram of a polymer electrolyte fuel cell performance in real施例was compared with a conventional example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1
Claims (10)
前記電極基材の前記電極反応層側の面に、フッ化ピッチを配したことを特徴とする固体高分子型燃料電池用電極電解質接合体。 A pair of electrodes including an electrode reaction layer and an electrode substrate , and a solid polymer electrolyte membrane sandwiched between the pair of electrodes,
Wherein the surface of the electrode reaction layer side, a solid polymer fuel cell electrode electrolyte assembly, characterized in that arranged fluoride pitch of the electrode substrate.
溶媒に溶かしたフッ化ピッチの溶液を、前記電極基材の前記電極反応層側の面に塗布し、溶媒を乾燥、除去することによりフッ化ピッチを固着する工程を有することを特徴とする固体高分子型燃料電池用電極電解質接合体の製造法。 A method for producing an electrode electrolyte assembly for a polymer electrolyte fuel cell, comprising: a pair of electrodes including an electrode reaction layer and an electrode base material; and a solid polymer electrolyte membrane sandwiched between the pair of electrodes,
A solid having a step of fixing a fluoride pitch by applying a solution of a fluoride pitch dissolved in a solvent to the surface of the electrode substrate on the electrode reaction layer side , and drying and removing the solvent. A method for producing an electrode electrolyte assembly for a polymer fuel cell.
フッ化ピッチを気相からの析出により、前記電極基材の前記電極反応層側の面にフッ化ピッチを固着する工程を含むことを特徴とする固体高分子型燃料電池用電極電解質接合体の製造法。 A method for producing an electrode electrolyte assembly for a polymer electrolyte fuel cell, comprising: a pair of electrodes including an electrode reaction layer and an electrode base material; and a solid polymer electrolyte membrane sandwiched between the pair of electrodes,
An electrode electrolyte assembly for a polymer electrolyte fuel cell comprising a step of fixing a fluoride pitch to a surface of the electrode base material on the electrode reaction layer side by depositing the fluoride pitch from a gas phase Manufacturing method.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23437498A JP4367983B2 (en) | 1998-08-20 | 1998-08-20 | Electrode electrolyte assembly for polymer electrolyte fuel cell, polymer electrolyte fuel cell and production method thereof |
| CNB998098582A CN1190859C (en) | 1998-08-20 | 1999-08-09 | Fuel cell and manufacture thereof |
| PCT/JP1999/004312 WO2000011741A1 (en) | 1998-08-20 | 1999-08-09 | Fuel cell and method of menufacture thereof |
| US09/763,263 US6660424B1 (en) | 1998-08-20 | 1999-08-09 | Fuel cell and method of manufacture thereof |
| KR10-2001-7001719A KR100421708B1 (en) | 1998-08-20 | 1999-08-09 | Fuel cell and method of menufacture thereof |
| EP99937001A EP1117142A4 (en) | 1998-08-20 | 1999-08-09 | Fuel cell and method of manufacture thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23437498A JP4367983B2 (en) | 1998-08-20 | 1998-08-20 | Electrode electrolyte assembly for polymer electrolyte fuel cell, polymer electrolyte fuel cell and production method thereof |
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| JP2000067874A JP2000067874A (en) | 2000-03-03 |
| JP2000067874A5 JP2000067874A5 (en) | 2005-11-04 |
| JP4367983B2 true JP4367983B2 (en) | 2009-11-18 |
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| WO2000044060A1 (en) * | 1999-01-25 | 2000-07-27 | Asahi Glass Company, Limited | Solid polymer type fuel cell and production method thereof |
| JP3382213B2 (en) * | 2000-08-08 | 2003-03-04 | 松下電器産業株式会社 | Method for producing gas diffusion electrode for polymer electrolyte fuel cell |
| GB0200253D0 (en) * | 2002-01-08 | 2002-02-20 | Johnson Matthey Plc | Improved material for electrode manufacture |
| JP4892912B2 (en) * | 2004-12-02 | 2012-03-07 | 大日本印刷株式会社 | Water-repellent separator for polymer electrolyte fuel cells |
| JP4882225B2 (en) * | 2004-12-02 | 2012-02-22 | 大日本印刷株式会社 | Water-repellent electrode catalyst layer, catalyst layer transfer sheet and catalyst layer-electrolyte assembly for polymer electrolyte fuel cell |
| JP2006164574A (en) * | 2004-12-02 | 2006-06-22 | Dainippon Printing Co Ltd | Water-repellent electrode catalyst layer for solid polymer fuel cell |
| JP4978578B2 (en) * | 2008-07-29 | 2012-07-18 | 大日本印刷株式会社 | Paste composition for imparting water repellency and method for producing gas diffusion layer |
| JP5608972B2 (en) * | 2008-11-28 | 2014-10-22 | 大日本印刷株式会社 | Water repellent layer forming paste composition and gas diffusion layer manufacturing method |
| JP5051203B2 (en) * | 2009-03-24 | 2012-10-17 | 大日本印刷株式会社 | Membrane-electrode assembly of fuel cell, transfer sheet for electrode production, and production method thereof |
| JP4691189B1 (en) | 2009-11-25 | 2011-06-01 | 株式会社東芝 | Direct methanol fuel cell |
| JP7229110B2 (en) * | 2019-06-25 | 2023-02-27 | 株式会社Ｓｃｒｅｅｎホールディングス | Cell potential measuring device |
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| JPH06349498A (en) * | 1993-06-11 | 1994-12-22 | Asahi Chem Ind Co Ltd | Gas diffusion electrode, connecting body, fuel cell, and manufacture thereof |
| JPH07211324A (en) * | 1994-01-19 | 1995-08-11 | Osaka Gas Co Ltd | Electrode catalyst composition, electrode material, and manufacture thereof |
| JP3591123B2 (en) * | 1996-03-08 | 2004-11-17 | トヨタ自動車株式会社 | Fuel cell and fuel cell electrode |
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