JP2004079266A - Electrolyte membrane for direct methanol type fuel cell and its process of manufacture - Google Patents
Electrolyte membrane for direct methanol type fuel cell and its process of manufacture Download PDFInfo
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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
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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
- 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
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、携帯電話機等の電源として、耐メタノール透過性に優れた直接メタノール型燃料電池用電解質膜とその製造方法に関する。
【０００２】
【従来の技術】
直接メタノール型燃料電池は、燃料の利便性、安全性、改質器が不要であるなどの特徴があることから、小型、携帯用電源としての研究、開発が進められている。これまで、直接メタノール発電用の電解質膜には、専らパーフルオロ（アルキル）スルホン酸膜（商品名：Ｎａｆｉｏｎ）が用いられていたが、発電の際、燃料であるメタノールが電解質膜を透過し（クロスオーバー）、電池性能を低下させてしまうという欠点を有していた（自動車技術会学術講演会前刷集、直接メタノール型燃料電池のメタノールクロスオーバー量に及ぼす運転条件とＭＥＡ性状の影響、ｐｐ．１−６，２０００）。この原因は、メタノールと上記電解質膜との親和性が極めてよく、メタノール水溶液に対し電解質膜が膨潤し、メタノールが容易に電解質膜中に入り込めるためである。この欠点を克服するため、メタノール水溶液に対する膨潤を抑え、サイズの小さい水素イオンは透過するがサイズの大きいメタノールは透過しない新たな電解質膜の設計が必要とされている。例えば、これまでメタノールに対して化学的に安定な延伸多孔質高分子膜中に電解質成分を充填することにより、メタノールの透過を抑え、水素イオンのみを透過させる電解質膜の製造方法が検討されてきたが、充分な性能を得るには至らなかった。一般に、延伸多孔質高分子膜は、高分子フィルムを延伸して、各微小部分を引き裂くことにより無数の微細孔を形成して作製される。このような方法で作製された高分子フィルムは、細孔自体が不均一で孔径がある分布幅を持つことから、電解質成分を充填しても、孔径の大きな部分に充填された電解質部がメタノール水溶液に対して膨潤し、そこがメタノール伝導路となってしまい、メタノール透過量を低減できないという課題を有していた。
【０００３】
【発明が解決しようとする課題】
上述したように、従来の直接メタノール型燃料電池用の電解質膜では、水素イオン伝導性、耐メタノール透過性の両方の特性を同時に満足できないという課題を有していた。これらの特性を満足させるには、均一な空孔径を有する微細空孔を作製し、この微細孔中に電解質成分を充填する方法が望まれていた。
【０００４】
本発明の目的は、上記従来技術における問題点を解消するものであって、携帯電話機等の電源として、耐メタノール透過性に優れた直接メタノール型燃料電池用電解質膜とその製造方法を提供することにある。
【０００５】
【課題を解決するための手段】
上記目的を達成するために、本発明は特許請求の範囲に記載のような構成とするものである。すなわち、
請求項１に記載のように、メタノールを燃料とし、上記メタノールの供給を受け電気化学反応により発電する直接メタノール型燃料電池であって、陽イオン導電性を有する電解質膜を有し、上記電解質膜の片面に燃料極、異なる片面に空気極を設けた直接メタノール型用燃料電池の電解質膜において、上記電解質膜が高分子薄膜で構成され、上記高分子薄膜中に複数の均一な微細空孔を設け、その微細空孔中に電解質材料を充填した構造の直接メタノール型燃料電池用電解質膜とするものである。
【０００６】
また、請求項２に記載のように、請求項１に記載の直接メタノール型燃料電池用電解質膜において、上記微細空孔は直径が２０ｎｍ〜２０μｍ、好ましくは２０〜８００ｎｍである直接メタノール型燃料電池用電解質膜とするものである。また、請求項３に記載のように、請求項１または請求項２に記載の直接メタノール型燃料電池用電解質膜において、上記高分子薄膜が、ポリテトラフルオロエチレンまたはポリシロキサンであり、上記ポリシロキサン中の有機基が、メチル基、フェニル基、水素基または水酸基のうちから選択される少なくとも１種の基よりなる直接メタノール型燃料電池用電解質膜とするものである。
【０００７】
また、請求項４に記載のように、請求項１ないし請求項３のいずれか１項に記載の直接メタノール型燃料電池用電解質膜において、上記高分子薄膜中の複数の微細空孔内に、イオン伝導性の電解質（例えば高分子あるいは無機系の電解質）が充填されている構造の直接メタノール型燃料電池用電解質膜とするものである。
【０００８】
また、請求項５に記載のように、請求項１ないし請求項４のいずれか１項に記載の直接メタノール型燃料電池用電解質膜の製造方法であって、上記高分子薄膜中の複数の微細空孔がレーザー照射により形成される工程を有する直接メタノール型燃料電池用電解質膜の製造方法とするものである。
【０００９】
本発明は、直接メタノール型燃料電池用の電解質膜において水素イオン伝導性と耐メタノール透過性の両方の特性を同時に満足させる機能を有する直接メタノール型燃料電池に関するものであって、陽イオン導電性を有する電解質膜を有し、上記電解質膜の片面に燃料極、異なる片面に空気極を設けた直接メタノール型燃料電池用電解質膜において、上記直接メタノール型燃料電池用電解質膜が高分子薄膜で構成され、上記高分子薄膜中に複数の均一な微細空孔を設け、その微細空孔中に電解質材料が充填されている直接メタノール型燃料電池用電解質膜およびその製造方法とするものである。
【００１０】
また、本発明は上記高分子薄膜の主成分が、ポリテトラフルオロエチレンまたはポリシロキサンであり、上記ポリシロキサン中の有機基が、メチル基、フェニル基、水素基または水酸基のうちより選ばれる少なくとも１種の基よりなる直接メタノール型燃料電池用電解質膜である。
また、本発明は微細な空孔内にイオン伝導性の高分子あるいは無機系電解質が充填されている直接メタノール型燃料電池とするものである。
また、上記高分子薄膜中の複数の均一な微細空孔が、レーザー照射により設けられる工程を有する直接メタノール型燃料電池用電解質膜の製造方法とするものである。
【００１１】
以下に、本発明の直接メタノール型燃料電池用電解質膜の構成ならびにその製造方法について詳細に説明する。
直接メタノール型燃料電池用電解質膜を作製するに際し、高分子薄膜材料には、メタノール、水等に対して、膨潤、吸収等が発生せず、化学的に安定であること、また電解質膜の製造工程中の加熱や、高温使用環境等を考慮し、耐熱性に優れた特性が要求される。
【００１２】
本発明に用いられる高分子薄膜材料としては、上記の特性に優れたポリテトラフルオロエチレン、ポリシロキサン化合物を用いる。両化合物とも、撥水性に優れメタノールにも比較的安定な化合物である。ポリテトラフルオロエチレン薄膜は、市販されているデュポン社製テフロン（登録商標）フィルムを用いることができる。また、ポリシロキサン薄膜は、低粘性の液状シロキサンオリゴマーを、所定の割合で硬化剤と混合して型枠等に流し込むことにより、溶剤で溶解することなく得ることができる。硬化に要する時間は、室温で約２時間、温度を上げることによりさらに短くすることができる。
【００１３】
本発明で用いるポリシロキサンとしては、ポリシロキサン中の有機基が、メチル基、フェニル基、水素基または水酸基であり、ポリジメチルシロキサンが好適に用いられる。また、上記のポリシロキサン薄膜の膜としての強度を確保するため、上記の製造工程中にシリカ等の充填材を添加しても良い。ポリテトラフルオロエチレン、ポリシロキサン化合物ともに電解質部の厚さは、５〜２００μｍ、好ましくは５〜５０μｍであり、５μｍ以下であると機械的強度が低下し、後述する電極作製工程で膜が破れ易くなり、また空気中の酸素が空気極から燃料極へ透過し電池性能を低下させる。また、２００μｍより厚くなるとイオン伝導性が低下し、電池の性能を低下させる。
【００１４】
次に、上記電解質部に均一な微細空孔を設ける。均一な微細空孔は、高分子薄膜にレーザー照射することにより得られる。照射時間は、できるだけ短い方が高分子薄膜が熱による損傷を受けにくく、鋭利な形の空孔を作製できることから、パルス幅がナノ（１０−９）秒からフェムト（１０−１５）秒で、強度の大きいレーザー加工機を用いるのが好ましい。一度に多数の空孔を明けるには、マイクロレンズアレー法または干渉法により、複数のレーザー光を同時に電解質膜に照射することにより、得られる。
【００１５】
なお、図１（ａ）に本発明の高分子薄膜中に微細空孔を作製するレーザー照射による孔開け工程を示す。空孔の大きさは２０ｎｍ〜２０μｍ、好ましくは２０〜８００ｎｍであり、２０ｎｍより小さい空孔径では、空孔自体の作製が困難となり、また２０μｍを超える空孔径では、メタノールの電解質部からの透過量が大きくなり、メタノールの透過を抑制できなくなる。空孔率は２０〜９０％であり、５０〜８０％が好ましく、９０％以上の空孔率では膜の強度が著しく低下し、また２０％以下ではイオン伝導性が低くなり、著しく電池性能を低下させる。
【００１６】
次に、微細な空孔を複数設けたポリテトラフルオロエチレンまたはポリシロキサン薄膜中に、イオン伝導基を有するモノマーおよび重合開始剤で空孔内を充填し、硬化させることにより薄膜中にイオン導電部を形成する。硬化反応は、加熱によって促進し、また適宜、架橋剤を用いることにより架橋結合を導入してもよい。イオン導電基を有するモノマーには、構造中にスルホン酸等の強酸基を有する化合物、例えばビニルスルホン酸、ビニルホスホン酸、アリルスルホン酸、アリルホスホン酸、スチレンスルホン酸、スチレンホスホン酸が好ましいが、本発明ではこれらに限定されるものではない。
【００１７】
あるいは、イオン伝導性高分子の溶液あるいは反応性オリゴマー等の高分子前駆体を溶解した溶液を調整し、その中に微細な空孔を複数設けたポリテトラフルオロエチレン、またはポリシロキサン薄膜を浸漬した後、この膜を乾燥して、溶媒を除去する。高分子前駆体を用いた場合には、その後、加熱等による高分子化または架橋反応による高分子化を行い空孔内への充填を完了する。この高分子溶液または高分子前駆体溶液として、ポリサルホン、ポリベンズイミダゾール、あるいはポリエーテルエーテルケトンなどのスルホン化ポリマー、パーフルオロアルキルスルホン酸の溶液を用いることができるが、本発明ではこれらに限定されるものではない。
【００１８】
無機材料の充填方法としては、導伝性ガラスとなり得るゾルを作製し、その中に微細な空孔を複数設けたポリテトラフルオロエチレン、またはポリシロキサン基板を浸漬した後、この膜を乾燥して、溶媒を除去する方法、あるいは上記ポリシロキサン基板中に、上記ゾルを塗布、乾燥、加熱することにより得られる。この方法では、テトラメトキシシラン、テトラメトキシリン酸をアルコールに溶解したゾルが好適に用いられるが、本発明ではこれらに限定されるものではない。
【００１９】
また、本発明においては、上記の高分子薄膜中の空孔内に電解質を充填する工程の前に、電解質が空孔内に速やかに浸入させると共に、電解質と高分子薄膜との結着性を向上させるため、シランカップリング剤等による空孔内の親水化処理、グリシジルメタクリレート等のエポキシ基を持つモノマーを空孔内へ放射線グラフ重合させた後、エポキシ基をスルホン基置換する等の親水化処理を行ってもよい。なお、図１（ｂ）に電解質溶液充填工程を模式的に示す。
【００２０】
以上の方法で作製した電解質部の両面に、触媒層、ガス拡散層を兼ねた集電板を配置し、ホットプレス法等により接合して、燃料極および空気極を作製する。燃料極用の触媒層は、Ｐｔ（白金）−Ｒｕ（ルテニウム）を主成分としたメタノール酸化触媒が、空気極用触媒層は、Ｐｔを主成分とした酸素還元触媒が専ら用いられ、Ｄｅｃａｌ法やスプレー法等で作製することにより得られるが、本発明ではこれらの作製法に限定されるものではない。
【００２１】
【発明の実施の形態】
〈実施の形態１〉
厚さ１２．５μｍのデュポン社製ポリテトラフルオロエチレン膜中央部に、レーザー加工機を用いて、波長３００ｎｍ、強度０．３Ｊ／ｃｍ２、パルス幅１００フェムト秒のレーザーを照射しエッチングすることにより、孔径５００ｎｍ、空孔率５０％の多孔質部を作製した。その空孔内にビニルスルホン酸系高分子電解質を充填することにより電解質部を形成し、その電解質部の一方の面に、カーボン担持されたＰｔ−Ｒｕ触媒層、集電板をホットプレスし圧着することにより燃料極を形成し、もう一方の面に、カーボン担持されたＰｔ触媒層を形成したプラスチック基板を作製した。得られた電解質膜について、プロトンイオン伝導性をインピーダンス測定装置により測定した。その結果、プロトン伝導率は、室温２５℃において、０．１５Ｓ／ｃｍとＮａｆｉｏｎ膜（０．０８Ｓ／ｃｍ）に比べ高いプロトン伝導率を示すことが分かった。また、膜電極複合体のＩ−Ｖ特性を測定した結果、温度約４０℃、大気圧中で、最大出力は５０ｍＷ／ｃｍ２であり、Ｎａｆｉｏｎ膜を電解質膜に用いたときの最大出力２０ｍＷ／ｃｍ２に比べ、高い出力が得られた。また、メタノールの透過性試験を行い、Ｎａｆｉｏｎ膜の１／１０以下の透過量であった。
【００２２】
〈実施の形態２〉
ポリジメチルシロキサンの高分子前駆体の主剤および硬化剤（Ｓｙｌｇａｒｄ １８４：Ｄｏｗ Ｃｏｒｎｉｎｇ Ｃｏ．）を１０：１の割合で混合し、充分に撹拌した後に１５分間真空脱法して、プレポリマー混合液を作製する。このプレポリマー混合液をマスター上に注ぎ、６５℃で１時間、９５℃で１５分間キュアリングを行った。こうして得られた厚さ５０μｍポリジメチルシロキサン膜中央部に、レーザー加工機を用いて、波長３００ｎｍ、強度０．２Ｊ／ｃｍ２、パルス幅１００フェムト秒のレーザーを照射しエッチングすることにより、孔径５００ｎｍ、空孔率５０％の多孔質部を作製した。その空孔内にビニルスルホン酸系高分子電解質を充填することにより電解質部を形成し、その電解質部の一方の面にカーボン担持されたＰｔ−Ｒｕ触媒層、集電板をホットプレスし圧着することにより燃料極を形成し、もう一方の面にカーボン担持されたＰｔ触媒層を形成しプラスチック基板を作製した。その結果、プロトン伝導率は、室温２５℃において、０．１５Ｓ／ｃｍと高いプロトン伝導率を示すことが分かった。また、膜電極複合体のＩ−Ｖ特性を測定した結果、温度約４０℃、大気圧中で、最大出力は５０ｍＷ／ｃｍ２であり、高い出力が得られた。また、メタノールの透過性試験を行い、Ｎａｆｉｏｎ膜の１／１０以下の透過量であった。
【００２３】
【発明の効果】
本発明により、メタノールの透過（クロスオーバー）を抑制し、イオン伝導性に優れた新規な直接メタノール型燃料電池用電解質膜を提供することができる。
【図面の簡単な説明】
【図１】本発明の直接メタノール型燃料電池用電解質膜の作製工程を示す模式図。
【符号の説明】
１…高分子薄膜
２…マイクロレンズアレー
３…レーザー光
４…レーザー加工機
５…微細空孔
６…イオン伝導性電解質溶液
７…電解質部
８…電解質部の一方の面（例えば燃料極とする）
９…電解質部のもう一方の面（例えば空気極とする）
１０…空孔の拡大模式図
１１…電解質[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrolyte membrane for a direct methanol fuel cell having excellent resistance to methanol permeation as a power source for a mobile phone or the like, and a method for producing the same.
[0002]
[Prior art]
Direct methanol fuel cells are being researched and developed as small, portable power sources because of their features such as fuel convenience, safety, and the need for a reformer. Until now, a perfluoro (alkyl) sulfonic acid membrane (trade name: Nafion) has been used exclusively as an electrolyte membrane for direct methanol power generation. However, during power generation, methanol as a fuel permeates the electrolyte membrane ( Crossover), which had the drawback of degrading the cell performance (Preprints of the Academic Lecture Meeting of the Society of Automotive Engineers of Japan, the influence of operating conditions and MEA properties on the amount of methanol crossover in direct methanol fuel cells, pp. .1-6, 2000). This is because the affinity between methanol and the electrolyte membrane is extremely good, and the electrolyte membrane swells in an aqueous methanol solution, so that methanol can easily enter the electrolyte membrane. To overcome this drawback, there is a need to design a new electrolyte membrane that suppresses swelling in methanol aqueous solution and allows small-sized hydrogen ions to permeate but not large-sized methanol. For example, a method for manufacturing an electrolyte membrane that suppresses methanol permeation and allows only hydrogen ions to permeate by filling an electrolyte component in a stretched porous polymer membrane that is chemically stable to methanol has been studied. However, it did not lead to sufficient performance. In general, a stretched porous polymer membrane is produced by stretching a polymer film and tearing each minute portion to form an infinite number of micropores. Since the polymer film produced by such a method has a nonuniform pore itself and a distribution width having a pore diameter, even if the electrolyte component is filled, the electrolyte part filled in the large pore part is methanol. It swells with respect to the aqueous solution and becomes a methanol conduction path, so that there is a problem that the amount of permeated methanol cannot be reduced.
[0003]
[Problems to be solved by the invention]
As described above, the conventional electrolyte membrane for a direct methanol fuel cell has a problem that it cannot simultaneously satisfy both the properties of hydrogen ion conductivity and methanol permeation resistance. In order to satisfy these characteristics, there has been a demand for a method of producing fine pores having a uniform pore diameter and filling the fine pores with an electrolyte component.
[0004]
An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide an electrolyte membrane for a direct methanol fuel cell having excellent resistance to methanol permeation and a method for producing the same as a power source for a mobile phone or the like. It is in.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as described in the claims. That is,
2. A direct methanol fuel cell according to claim 1, wherein the fuel is methanol, and the supply of the methanol is supplied to generate electricity by an electrochemical reaction. The fuel cell has an electrolyte membrane having cation conductivity, and the electrolyte membrane is a fuel cell. In the electrolyte membrane of a direct methanol fuel cell having a fuel electrode on one side and an air electrode on a different side, the electrolyte membrane is composed of a polymer thin film, and a plurality of uniform fine pores are formed in the polymer thin film. And an electrolyte membrane for a direct methanol fuel cell having a structure in which the pores are filled with an electrolyte material.
[0006]
Further, as described in claim 2, in the electrolyte membrane for a direct methanol fuel cell according to claim 1, the fine pores have a diameter of 20 nm to 20 µm, preferably 20 to 800 nm. Electrolyte membrane for use. According to a third aspect of the present invention, in the electrolyte membrane for a direct methanol fuel cell according to the first or second aspect, the polymer thin film is polytetrafluoroethylene or polysiloxane; The organic membrane therein is a direct methanol fuel cell electrolyte membrane comprising at least one group selected from a methyl group, a phenyl group, a hydrogen group and a hydroxyl group.
[0007]
Further, as described in claim 4, in the electrolyte membrane for a direct methanol fuel cell according to any one of claims 1 to 3, in the plurality of micropores in the polymer thin film, This is an electrolyte membrane for a direct methanol fuel cell having a structure filled with an ion-conductive electrolyte (for example, a polymer or inorganic electrolyte).
[0008]
According to a fifth aspect of the present invention, there is provided the method for producing an electrolyte membrane for a direct methanol fuel cell according to any one of the first to fourth aspects, wherein a plurality of fine particles in the polymer thin film are provided. The present invention provides a method for producing an electrolyte membrane for a direct methanol fuel cell, which comprises a step of forming holes by laser irradiation.
[0009]
The present invention relates to a direct methanol fuel cell having a function of simultaneously satisfying both properties of hydrogen ion conductivity and methanol permeation resistance in an electrolyte membrane for a direct methanol fuel cell. An electrolyte membrane for a direct methanol fuel cell having an electrolyte membrane having a fuel electrode on one side of the electrolyte membrane and an air electrode on a different side, wherein the electrolyte membrane for a direct methanol fuel cell is formed of a polymer thin film. The present invention also provides an electrolyte membrane for a direct methanol fuel cell, wherein a plurality of uniform fine holes are provided in the polymer thin film, and the minute holes are filled with an electrolyte material.
[0010]
In the present invention, the main component of the polymer thin film is polytetrafluoroethylene or polysiloxane, and the organic group in the polysiloxane is at least one selected from a methyl group, a phenyl group, a hydrogen group, and a hydroxyl group. It is an electrolyte membrane for a direct methanol fuel cell composed of various kinds of groups.
Further, the present invention is directed to a direct methanol fuel cell in which fine pores are filled with an ion-conductive polymer or an inorganic electrolyte.
Further, the present invention provides a method for producing an electrolyte membrane for a direct methanol fuel cell, comprising the step of providing a plurality of uniform fine holes in the polymer thin film by laser irradiation.
[0011]
Hereinafter, the configuration of the electrolyte membrane for a direct methanol fuel cell of the present invention and the method for producing the same will be described in detail.
When fabricating an electrolyte membrane for a direct methanol fuel cell, the polymer thin film material is chemically stable without swelling or absorption with respect to methanol, water, etc. In consideration of heating during the process, high-temperature use environment, and the like, excellent heat resistance is required.
[0012]
As the polymer thin film material used in the present invention, a polytetrafluoroethylene or polysiloxane compound excellent in the above properties is used. Both compounds are excellent in water repellency and relatively stable in methanol. As the polytetrafluoroethylene thin film, a commercially available Teflon (registered trademark) film manufactured by DuPont can be used. Further, the polysiloxane thin film can be obtained without mixing with a solvent by dissolving a low-viscosity liquid siloxane oligomer at a predetermined ratio with a curing agent and pouring the mixture into a mold or the like. The time required for curing can be further reduced by increasing the temperature for about 2 hours at room temperature.
[0013]
As the polysiloxane used in the present invention, the organic group in the polysiloxane is a methyl group, a phenyl group, a hydrogen group or a hydroxyl group, and polydimethylsiloxane is preferably used. In order to secure the strength of the polysiloxane thin film, a filler such as silica may be added during the manufacturing process. Both the polytetrafluoroethylene and the polysiloxane compound have a thickness of the electrolyte portion of 5 to 200 μm, preferably 5 to 50 μm. When the thickness is 5 μm or less, the mechanical strength is reduced, and the film is easily broken in an electrode manufacturing step described later. In addition, oxygen in the air permeates from the air electrode to the fuel electrode to lower the cell performance. On the other hand, when the thickness is more than 200 μm, the ionic conductivity is reduced, and the performance of the battery is reduced.
[0014]
Next, uniform fine pores are provided in the electrolyte part. Uniform fine pores can be obtained by irradiating the polymer thin film with laser. When the irradiation time is as short as possible, the polymer thin film is less susceptible to thermal damage and a sharp hole can be formed. Therefore, the pulse width is from nano (10 −9 ) seconds to femto (10 −15 ) seconds. It is preferable to use a laser processing machine having high strength. A plurality of holes can be formed at once by irradiating the electrolyte membrane with a plurality of laser beams simultaneously by a microlens array method or an interference method.
[0015]
FIG. 1A shows a hole forming step by laser irradiation for forming fine holes in the polymer thin film of the present invention. The size of the pores is 20 nm to 20 μm, preferably 20 to 800 nm. If the pore size is smaller than 20 nm, it becomes difficult to form the pores. If the pore size exceeds 20 μm, the permeation amount of methanol from the electrolyte part is reduced. Becomes large, and the permeation of methanol cannot be suppressed. The porosity is from 20 to 90%, preferably from 50 to 80%. If the porosity is more than 90%, the strength of the membrane is remarkably reduced. Lower.
[0016]
Next, a polytetrafluoroethylene or polysiloxane thin film having a plurality of fine pores is filled with a monomer having an ion-conducting group and a polymerization initiator, and cured to form an ion conductive portion in the thin film. To form The curing reaction is accelerated by heating, and a crosslinking bond may be introduced by using a crosslinking agent as appropriate. The monomer having an ion conductive group, a compound having a strong acid group such as sulfonic acid in the structure, for example, vinyl sulfonic acid, vinyl phosphonic acid, allyl sulfonic acid, allyl phosphonic acid, styrene sulfonic acid, styrene phosphonic acid is preferred, The present invention is not limited to these.
[0017]
Alternatively, a solution of an ion conductive polymer or a solution in which a polymer precursor such as a reactive oligomer was dissolved was prepared, and a polytetrafluoroethylene or polysiloxane thin film having a plurality of fine pores was immersed therein. Thereafter, the film is dried to remove the solvent. In the case where the polymer precursor is used, thereafter, the polymerization by heating or the like or the polymerization by a cross-linking reaction is performed to complete the filling of the pores. As the polymer solution or the polymer precursor solution, a sulfonated polymer such as polysulfone, polybenzimidazole, or polyetheretherketone, or a solution of perfluoroalkylsulfonic acid can be used, but the present invention is not limited thereto. Not something.
[0018]
As a method for filling the inorganic material, a sol that can be a conductive glass is prepared, and a polytetrafluoroethylene or polysiloxane substrate having a plurality of fine holes is immersed therein, and then the film is dried. Or by removing the solvent, or by applying, drying and heating the sol on the polysiloxane substrate. In this method, a sol obtained by dissolving tetramethoxysilane or tetramethoxyphosphoric acid in an alcohol is preferably used, but the present invention is not limited to these.
[0019]
Further, in the present invention, before the step of filling the pores in the polymer thin film with the electrolyte, the electrolyte is quickly penetrated into the pores, and the binding property between the electrolyte and the polymer thin film is improved. In order to improve the hydrophilicity, the silane coupling agent or the like is used to hydrophilize the pores, and after a monomer having an epoxy group such as glycidyl methacrylate is polymerized into the pores by radiation graph polymerization, the epoxy group is replaced with a sulfone group. Processing may be performed. FIG. 1B schematically shows the electrolyte solution filling step.
[0020]
A current collector plate serving also as a catalyst layer and a gas diffusion layer is arranged on both sides of the electrolyte part produced by the above method, and joined by a hot press method or the like to produce a fuel electrode and an air electrode. The catalyst layer for the fuel electrode is a methanol oxidation catalyst containing Pt (platinum) -Ru (ruthenium) as a main component, and the catalyst layer for the air electrode is exclusively used an oxygen reduction catalyst containing Pt as a main component. It can be obtained by a method such as spraying or spraying, but the present invention is not limited to these methods.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
<Embodiment 1>
The center of the polytetrafluoroethylene film manufactured by DuPont with a thickness of 12.5 μm is irradiated with a laser beam having a wavelength of 300 nm, an intensity of 0.3 J / cm 2 , and a pulse width of 100 femtoseconds by using a laser beam machine to perform etching. A porous portion having a pore size of 500 nm and a porosity of 50% was produced. The pores are filled with a vinyl sulfonic acid-based polymer electrolyte to form an electrolyte part, and a carbon-supported Pt-Ru catalyst layer and a current collector are hot-pressed and pressed onto one surface of the electrolyte part. By doing so, a fuel electrode was formed, and a plastic substrate having a carbon-supported Pt catalyst layer formed on the other surface was produced. Proton ion conductivity of the obtained electrolyte membrane was measured by an impedance measuring device. As a result, the proton conductivity was found to be 0.15 S / cm at room temperature and 25 ° C., which is higher than that of the Nafion film (0.08 S / cm). In addition, as a result of measuring the IV characteristics of the membrane electrode assembly, the maximum output was 50 mW / cm 2 at a temperature of about 40 ° C. and the atmospheric pressure, and the maximum output was 20 mW / cm 2 when the Nafion membrane was used as the electrolyte membrane. Higher output was obtained compared to cm 2 . Further, a methanol permeability test was performed, and the permeation amount was 1/10 or less of the Nafion membrane.
[0022]
<Embodiment 2>
A main component of a polymer precursor of polydimethylsiloxane and a curing agent (Sylgard 184: Dow Corning Co.) are mixed at a ratio of 10: 1, sufficiently stirred, and then subjected to vacuum removal for 15 minutes to prepare a prepolymer mixed solution. I do. The prepolymer mixture was poured onto a master and subjected to curing at 65 ° C. for 1 hour and at 95 ° C. for 15 minutes. The 50 μm-thick polydimethylsiloxane film thus obtained was irradiated with a laser having a wavelength of 300 nm, an intensity of 0.2 J / cm 2 , and a pulse width of 100 femtoseconds by using a laser beam machine, and was etched to obtain a hole diameter of 500 nm. A porous portion having a porosity of 50% was produced. The pores are filled with a vinyl sulfonic acid-based polymer electrolyte to form an electrolyte part, and a carbon-supported Pt-Ru catalyst layer and a current collector plate on one surface of the electrolyte part are hot pressed and pressed. Thus, a fuel electrode was formed, and a Pt catalyst layer carrying carbon was formed on the other surface to produce a plastic substrate. As a result, it was found that the proton conductivity showed a high proton conductivity of 0.15 S / cm at room temperature of 25 ° C. Further, as a result of measuring the IV characteristics of the membrane electrode assembly, the maximum output was 50 mW / cm 2 at a temperature of about 40 ° C. and atmospheric pressure, and a high output was obtained. Further, a methanol permeability test was performed, and the permeation amount was 1/10 or less of the Nafion membrane.
[0023]
【The invention's effect】
According to the present invention, it is possible to provide a novel electrolyte membrane for a direct methanol fuel cell that suppresses permeation (crossover) of methanol and has excellent ion conductivity.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a process for producing an electrolyte membrane for a direct methanol fuel cell according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Polymer thin film 2 ... Microlens array 3 ... Laser beam 4 ...
9: The other surface of the electrolyte part (for example, an air electrode)
10: Enlarged schematic diagram of pores 11: Electrolyte
Claims (5)
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| JP2002235621A JP2004079266A (en) | 2002-08-13 | 2002-08-13 | Electrolyte membrane for direct methanol type fuel cell and its process of manufacture |
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| JP2002235621A JP2004079266A (en) | 2002-08-13 | 2002-08-13 | Electrolyte membrane for direct methanol type fuel cell and its process of manufacture |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007011054A1 (en) * | 2005-07-19 | 2007-01-25 | Toyota Jidosha Kabushiki Kaisha | Composite porous membrane, method for production thereof, solid polymer electrolyte membrane, and fuel cell |
| JP2007115609A (en) * | 2005-10-24 | 2007-05-10 | Asahi Kasei Chemicals Corp | Electrolyte film and fuel cell |
| WO2007076595A1 (en) * | 2005-12-30 | 2007-07-12 | Tekion, Inc. | Composite polymer electrolyte membranes and electrode assemblies for reducing fuel crossover in direct liquid feed fuel cells |
| WO2008079529A2 (en) * | 2006-11-07 | 2008-07-03 | Polyfuel, Inc. | Passive recovery of liquid water produced by fuel cells |
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2002
- 2002-08-13 JP JP2002235621A patent/JP2004079266A/en active Pending
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007011054A1 (en) * | 2005-07-19 | 2007-01-25 | Toyota Jidosha Kabushiki Kaisha | Composite porous membrane, method for production thereof, solid polymer electrolyte membrane, and fuel cell |
| JP2007026917A (en) * | 2005-07-19 | 2007-02-01 | Toyota Motor Corp | Compound porous membrane, manufacturing method of compound porous membrane, solid polyelectrolyte membrane, and fuel cell |
| JP2007115609A (en) * | 2005-10-24 | 2007-05-10 | Asahi Kasei Chemicals Corp | Electrolyte film and fuel cell |
| WO2007076595A1 (en) * | 2005-12-30 | 2007-07-12 | Tekion, Inc. | Composite polymer electrolyte membranes and electrode assemblies for reducing fuel crossover in direct liquid feed fuel cells |
| US7368200B2 (en) | 2005-12-30 | 2008-05-06 | Tekion, Inc. | Composite polymer electrolyte membranes and electrode assemblies for reducing fuel crossover in direct liquid feed fuel cells |
| WO2008079529A2 (en) * | 2006-11-07 | 2008-07-03 | Polyfuel, Inc. | Passive recovery of liquid water produced by fuel cells |
| WO2008079529A3 (en) * | 2006-11-07 | 2008-11-13 | Polyfuel Inc | Passive recovery of liquid water produced by fuel cells |
| US8298719B2 (en) | 2006-11-07 | 2012-10-30 | University Of North Florida Board Of Trustees | Passive recovery of liquid water produced by fuel cells |
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