JP3613654B2

JP3613654B2 - Electrode for fuel cell and method for producing power generation layer

Info

Publication number: JP3613654B2
Application number: JP35538396A
Authority: JP
Inventors: 竜也川原
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 1996-12-20
Filing date: 1996-12-20
Publication date: 2005-01-26
Anticipated expiration: 2016-12-20
Also published as: JPH10189012A

Description

【０００１】
【発明の属する技術分野】
本発明は、燃料電池用の電極および発電層の製造方法に関し、詳しくは、燃料電池に用いられる電極および燃料電池に用いられ電解質膜とこれを挟持する２つの電極とを備える発電層の製造方法に関する。
【０００２】
【従来の技術】
燃料電池、例えば、固体高分子型燃料電池では、電解質膜を挟んで対峙する２つの電極（酸素極と燃料極）に、水素を含有する燃料ガスと酸素を含有する酸化ガスとをそれぞれ供給することにより、次式（１）および式（２）に示す反応が行なわれ、物質の持つ化学エネルギを直接電気エネルギに変換する。
【０００３】
カソード反応（酸素極）：２Ｈ^＋＋２ｅ⁻＋（１／２）Ｏ_２→Ｈ_２Ｏ …（１）
アノード反応（燃料極）：Ｈ_２→２Ｈ^＋＋２ｅ⁻ …（２）
【０００４】
この反応を連続的にかつ円滑に行なうためには、酸素極では生成する水を速やかに排除すると共に酸化ガスを連続的に供給する必要があり、燃料極では生成した水素イオンを水和により電解質膜中にスムーズに拡散するための水と燃料ガスとを連続的に供給する必要がある。このほか、接触抵抗を小さくし効率の良い燃料電池とするために、電解質膜と両電極とを密着する必要もある。
【０００５】
従来、こうした要求に応える燃料電池用の電極の製造方法としては、亜鉛，アルミニウム，クロム等の金属あるいはこれらの金属塩などの無機塩の粉末を造孔剤として用いて触媒を担持したカーボンを混在するシート状の電極部材を形成し、この形成した電極部材を溶液に浸漬して内部の造孔剤を溶出させて除去することにより内部に複数の細孔を有する電極を製造する方法が提案されている（例えば、特開平６−３６７７１号公報や特開平６−２０３８５２号公報など）。
【０００６】
また、燃料電池用の発電層の製造方法としては、上述の従来例の燃料電池用の電極の製造方法における電極部材を溶液に浸漬して電極部材内の造孔剤を溶出させる工程の前に、電極部材と高分子電解質膜とを接合して一体化させる方法が提案されている（例えば、特開平６−２０３８５２号公報など）。このように高分子電解質膜と接合した後に造孔剤を溶出することにより、接合の際に電極の細孔がつぶれるのを防止している。
【０００７】
【発明が解決しようとする課題】
しかしながら、上記製造方法では、電極に十分なガスの透過性を確保しようとすると、電極内に必要以上の空間を形成されて、燃料電池の性能を低下させたり、電極を脆弱なものにしてしまうといった問題があった。粒状の金属あるいは金属塩を造孔剤として用いると、形成される細孔は、造孔剤の形状である略球状の空孔を連通した形状となる。このため、細孔の径は、その長さ方向に大きく変化し、一定とならない。電極におけるガスの透過性は、電極に形成される細孔の径に依存するから、細孔の径が大きく変化する電極では、十分なガスの透過性を得ようとすると、その内部に必要以上の空間を形成することになる。こうした必要以上の空間は、電極の導電面積を減少させてその導電性を低下させると共に、電極を脆弱なものにする。
【０００８】
本発明の燃料電池用の電極の製造方法は、こうした問題を解決し、十分なガス透過性と導電性とを有する電極の製造方法を提供することを目的の一つとする。また、本発明の燃料電池用の発電層の製造方法は、電解質膜の性能を高く維持した状態で十分なガス透過性と導電性とを有する電極を備える発電層の製造方法を提供することを目的の一つとする。
【０００９】
なお、出願人は、上述の目的の一部を達成するために、本発明とは異なる発明として、水溶性の短繊維を造孔剤として用いて電極部材を形成し、電極部材を水に浸漬して内部の造孔剤を溶出させて除去することにより十分なガス透過性と導電性とを有する電極を製造する方法や、電極部材を水に浸漬して内部の造孔剤を溶出させる前に、電極部材を電解質膜と接合して一体化することにより十分なガス透過性と導電性とを有する２つの電極を有する発電層を製造する方法を提案している（特開平８−１８０８７９号公報）。
【００１０】
【課題を解決するための手段およびその作用・効果】
本発明の燃料電池用の電極や発電層の製造方法は、上述の目的の少なくとも一部を達成するために以下の構成を採った。
【００１６】
本発明の燃料電池用の電極の製造方法は、
所定の場を作用させたとき長手方向が該所定の場に基づいて所定方向に配向する性質を有し所定の溶液に溶解可能な材料により長手形状の造孔剤を形成する造孔剤形成工程と、
該形成された造孔剤と触媒を担持したカーボン粒子とを所定の溶媒に分散させてインクを調整するインク調整工程と、
該調整されたインクによりシート状の電極形成部材を形成する電極形成部材形成工程と、
該形成された電極形成部材に対して所定の角度をもって前記所定の場を作用させる場作用工程と、
該所定の場を作用させた電極形成部材に含まれる溶媒を乾燥させる乾燥工程と、
該乾燥させた電極形成部材を前記所定の溶液に浸漬して前記造孔剤を溶出させる溶出工程と
を備えることを要旨とする。
【００１７】
この本発明の電極の製造方法によれば、長手方向に所定の配向性をもった複数の細孔を有する電極を製造することができる。こうして製造された電極によれば、長手方向に所定の配向性をもった細孔により所定の方向へのガスの透過性をよくすることができ、この電極を用いることにより、燃料電池における電気化学反応を連続してスムーズに行わせることができる。なお、「所定の場」とは、所定方向の何らかの力を作用させることができる場であり、所定方向の磁界を形成する磁場や所定方向の電界を形成する電場あるいは所定方向の重力場などが含まれる。造孔剤を形成する材料は、こうした「所定の場」が所定方向の磁界を形成する磁場のときには強磁性を示す材料であり、「所定の場」が所定方向の電界を形成する電場のときには強誘電性を示す材料である。
【００１８】
本発明の電極の製造方法において、前記場作用工程と前記乾燥工程は、前記形成された電極形成部材に所定の角度をもって前記所定の場を作用させた状態で該電極形成部材に含まれる溶媒を乾燥させることにより同時に行う工程であるものとすることもできる。
【００１９】
また、本発明の電極の製造方法において、前記造孔剤形成工程は、前記材料により長手方向を有する３次元構造の造孔剤を形成する工程であるものとすることもできる。こうすれば、長手方向のガスの透過性に優れているだけでなく、長手方向とは異なる方向への拡散性にも優れた電極を製造することができる。
【００２０】
さらに、本発明の電極の製造方法において、前記所定の溶液に溶解可能な材料により第２の造孔剤を形成する第２造孔剤形成工程を備え、前記インク調整工程は、前記造孔剤と前記第２の造孔剤と触媒を担持したカーボン粒子とを所定の溶媒に分散させてインクを調整する工程であるものとすることもできる。こうすれば、長手方向のガスの透過性に優れているだけでなく、長手方向とは異なる方向への拡散性にも優れた電極を製造することができる。
【００２６】
本発明の燃料電池用の発電層の製造方法は、
所定の場を作用させたとき長手方向が該所定の場に基づいて所定方向に配向する性質を有し所定の溶液に溶解可能な材料により長手形状の造孔剤を形成する造孔剤形成工程と、
該形成された造孔剤と触媒を担持したカーボン粒子とを所定の溶媒に分散させてインクを調整するインク調整工程と、
該調整されたインクによりシート状の電極形成部材を形成する電極形成部材形成工程と、
該形成された電極形成部材に対して所定の角度をもって前記所定の場を作用させる場作用工程と、
該所定の場を作用させた電極形成部材に含まれる溶媒を乾燥させる乾燥工程と、
該乾燥させた電極形成部材を電解質膜の両面に接合して発電層形成部材を形成する発電層形成部材形成工程と、
該形成された発電層形成部材を前記所定の溶液に浸漬して該発電層形成部材の前記電極形成部材から前記造孔剤を溶出させる溶出工程と
を備えることを要旨とする。
【００２７】
この本発明の発電層の製造方法によれば、長手方向に所定の配向性をもった複数の細孔を有する電極を備える発電層を製造することができる。こうして製造された発電層によれば、長手方向に所定の配向性をもった細孔を有する電極により燃料ガスや酸化ガスがスムーズに供給されるから、電気化学反応を連続してスムーズに行なうことができる。なお、「所定の場」とは、所定方向の何らかの力を作用させることができる場であり、所定方向の磁界を形成する磁場や所定方向の電界を形成する電場あるいは所定方向の重力場などが含まれる。造孔剤を形成する材料は、こうした「所定の場」が所定方向の磁界を形成する磁場のときには強磁性を示す材料であり、「所定の場」が所定方向の電界を形成する電場のときには強誘電性を示す材料である。
【００２８】
こうした本発明の発電層の製造方法において、前記場作用工程と前記乾燥工程は、前記形成された電極形成部材に所定の角度をもって前記所定の場を作用させた状態で該電極形成部材に含まれる溶媒を乾燥させることにより同時に行う工程であるものとすることもできる。
【００２９】
また、本発明の発電層の製造方法において、前記造孔剤形成工程は、前記材料により長手方向を有する３次元構造の造孔剤を形成する工程であるものとすることもできる。こうすれば、長手方向への燃料ガスや酸化ガスの透過性に優れているだけでなく、長手方向とは異なる方向への燃料ガスや酸化ガスの拡散性にも優れた電極を備える発電層を製造することができる。
【００３０】
あるいは、本発明の発電層の製造方法において、前記所定の溶液に溶解可能な材料により第２の造孔剤を形成する第２造孔剤形成工程を備え、前記インク調整工程は、前記造孔剤と前記第２の造孔剤と触媒を担持したカーボン粒子とを所定の溶媒に分散させてインクを調整する工程であるものとすることもできる。こうすれば、長手方向への燃料ガスや酸化ガスの透過性に優れているだけでなく、長手方向とは異なる方向への燃料ガスや酸化ガスの拡散性にも優れた電極を備える発電層を製造することができる。
【００３１】
【発明の実施の形態】
次に、本発明の実施の形態を実施例に基づき説明する。図１は本発明の好適な一実施例である電解質膜１２と触媒電極１４との接合体である発電層１５の製造の様子を例示する工程図であり、図２は図１の工程により製造される発電層１５の構造の概略を例示する模式図である。まず、図１の工程図に基づき発電層１５の製造の様子について説明する。
【００３２】
実施例の発電層１５の製造は、まず、鉄により半径０．１μｍ，長さ１μｍの針状の造孔剤Ｆを形成し（工程Ｓ１００）、形成した造孔剤Ｆを、造孔剤Ｆ１ｇに対して、触媒Ｐとしての白金あるいは白金と他の金属との合金の微粒子（平均粒径約１ｎｍ）を２０ｗｔ％担持した触媒担持カーボンＣを１ｇ、５ｗｔ％パーフルオロカーボンスルホン酸溶液（例えば、アルドリッチケミカル社製のナフィオンソリューション）を１０ｍｌ、シクロヘキサノールの１０ｍｌの割合で混合し、超音波を照射して造孔剤Ｆおよび触媒担持カーボンＣを均一に分散させてペースト状のインクを調整する（工程Ｓ１１０）。なお、超音波の照射による分散は、実施例では市販されている超音波洗浄機を用いて周波数３０ｋＨｚないし５０ｋＨｚの超音波を照射することによって行なった。
【００３３】
続いて、このペースト状のインクをドクターブレード式の印刷装置を用いてテフロンシート上に厚さ３０μｍないし５００μｍ好ましくは８０μｍないし３００μｍに調整して印刷することによりシート状の電極形成部材１７を形成し（工程Ｓ１２０）、形成した電極形成部材１７をそのシート面に略垂直な方向の磁界を作用させた状態で４０℃ないし１００℃好ましくは６０℃ないし８０℃の温度で真空乾燥することにより、その厚さが１μｍないし１００μｍ好ましくは３μｍないし１０μｍになるまで電極形成部材１７中の溶媒を乾燥させる（工程Ｓ１３０）。このように磁界を電極形成部材１７に作用させると、電極形成部材１７中の造孔剤Ｆが強磁性の鉄により形成されていることから、その長手方向が磁界の方向となるように配向する。この様子を図３に示す。図３（ａ）は磁場を作用させる前の電極形成部材１７内の造孔剤Ｆの状態を模式的に示す説明図、図３（ｂ）は磁場を作用させているときの電極形成部材１７内の造孔剤Ｆの状態を模式的に示す説明図、図３（ｃ）は磁場を作用させた状態で溶媒を乾燥させた後の電極形成部材１７内の造孔剤Ｆの状態を模式的に示す説明図である。造孔剤Ｆは、磁界を作用させる前は、図３（ａ）に示すように配向性を示さないが、磁界を作用させると、図３（ｂ）に示すようにその磁化作用により長手方向が磁力線の方向を向くようになる。したがって、シート面に略垂直な方向の磁界を作用させた状態で電極形成部材１７を乾燥させれば、図３（ｃ）に示すように造孔剤Ｆの長手方向がシート面に略垂直な方向の配向性をもった乾燥した電極形成部材１７とすることができる。なお、実施例では、作用させる磁場としては、単位面積当たりの磁界の強さが１００［Ａ／ｍ］ないし１０００［Ａ／ｍ］の磁界を作用させた。なお、磁界の強さは、造孔剤Ｆと触媒担持カーボンＣとにより調整されたインクの粘度や造孔剤Ｆの材質によって定まるものであり、上述の範囲に限られるものでないことはいうまでもない。
【００３４】
次に、予め希硫酸，過酸化水素水およびイオン交換水で順次煮沸洗浄を行って得られた厚さ１０μｍないし２００μｍ好ましくは３０μｍないし１００μｍの電解質膜１２（例えば、デュポン社製商品名「ナフィオン」として販売されているパーフルオロカーボンスルホン酸高分子膜など）を乾燥させた電極形成部材１７により印刷面を内側として挟み、サンドイッチ構造とした状態で１００℃ないし１６０℃好ましくは１１０℃ないし１３０℃の温度で１ＭＰａないし２０ＭＰａ好ましくは５ＭＰａないし１５ＭＰａの圧力を作用させて接合するホットプレス法によって電解質膜１２と電極形成部材１７とを接合する（工程Ｓ１４０）。
【００３５】
こうして得られた電解質膜１２と電極形成部材１７との接合体からテフロンシートを剥がして造孔剤Ｆを溶解可能な酸に浸漬して電極形成部材１７から造孔剤Ｆを溶出させ（工程Ｓ１５０）、洗浄，乾燥して、図２に示すような面に対して略垂直な配向性をもった複数の細孔Ｓを有する２つの触媒電極１４と電解質膜１２との接合体である発電層１５を完成する。なお、実施例では、造孔剤Ｆを溶解可能な酸としては１規定の希硫酸を用い、この希硫酸による煮沸洗浄とイオン交換水による煮沸洗浄を２回ないし５回程度繰り返すことにより電極形成部材１７から造孔剤Ｆを完全に溶出させた。
【００３６】
次に、こうして製造された発電層１５を用いた燃料電池１０について説明する。図４は実施例の発電層１５を備える燃料電池１０の構成を例示する模式図である。図示するように、燃料電池１０は、前述の製造方法により製造された電解質膜１２と２つの触媒電極１４との接合体である発電層１５と、この発電層１５を挟持する２つのガス拡散電極１６と、発電層１５と共にガス拡散電極１６をも挟持する集電極２０とからなる。
【００３７】
２つのガス拡散電極１６は、表面をポリ四フッ化エチレンでコーティングした炭素繊維と何等処理されていない炭素繊維とを１対１の割合とした糸で織成したカーボンクロスにより形成されている。このガス拡散電極１６は、炭素繊維にコーティングされたポリ四フッ化エチレンが撥水性を呈することから、ガス拡散電極１６の表面全体が水で覆われてることがなく、良好なガス透過性を有する。
【００３８】
集電極２０は、カーボンを圧縮して緻密化しガス不透過とした緻密質カーボンにより形成されており、集電極２０のガス拡散電極１６と接触する面には、平行に配置された複数のリブ２２が形成されている。このリブ２２は、ガス拡散電極１６とで酸素を含有する酸化ガス（例えば、空気等）または水素を含有する燃料ガス（例えば、メタノール改質ガス等）の流路２４を形成する。
【００３９】
こうして構成された燃料電池１０の発電層１５と２つのガス拡散電極１６とを挟んで対峙する集電極２０とガス拡散電極１６とにより形成される流路２４に、水素を含有する燃料ガスおよび酸素を含有する酸化ガスを供給すれば、電解質膜１２を挟んで対峙する２つの触媒電極１４に燃料ガスおよび酸化ガスが供給されて、前述の反応式（１）および式（２）に示す電気化学反応が行なわれ、化学エネルギが直接電気エネルギに変換される。
【００４０】
次に、こうして構成された燃料電池１０の性能について従来例の燃料電池と比較して説明する。図５は、実施例の燃料電池１０と従来例の燃料電池とにおける電流密度と電圧との関係を例示したグラフであり、図６は従来例の燃料電池の触媒電極の構造を例示する模式図である。図５のグラフ中、曲線Ａは実施例の発電層１５を備える燃料電池１０における電流密度と電圧との関係を示し、曲線Ｃは金属塩の粒状の造孔剤Ｚを用いて細孔ＳＣを形成した触媒電極１４Ｃと電解質膜１２Ｃとを接合してなる発電層１５Ｃ（図６の模式図を参照）を備える燃料電池（従来例の燃料電池）における電流密度と電圧との関係を示す。なお、図中曲線Ｂについては後述する。
【００４１】
従来例の燃料電池が備える発電層１５Ｃの触媒電極１４Ｃは、１ｇの触媒担持カーボンＣに対して５００ｍｇの平均粒径１μｍの炭酸カルシウムの粉末を混合して電極形成部材を形成し、この電極形成部材と実施例の電解質膜１２と同一の電解質膜１２Ｃとを実施例の接合条件と同一の条件で接合し、その後、電極形成部材中の炭酸カルシウムを強酸性水溶液により溶出して形成したものである。触媒電極１４Ｃは、粒状の炭酸カルシウムを造孔剤として用いるから、形成される細孔ＳＣは、図６に示すように、平均径１μｍの略球形の空孔を小さな径の連通孔で連通したものとなる。触媒電極におけるガスの透過性は細孔の径に依存するから、従来例の触媒電極１４Ｃでは、空孔を連絡する連通孔の径に依存することになり、十分なガス透過性を確保しようとすると、その内部に必要以上の空間が形成されてしまう。この結果、触媒電極１４Ｃは、導電面積が小さくなって導電率が低下すると共に脆弱なものとなる。
【００４２】
一方、実施例の燃料電池１０が備える触媒電極１４の細孔Ｓは、磁界を作用させることにより表面に対して略垂直に配向された半径０．１μｍ，長さ１μｍの針状の造孔剤Ｆによるものであるから、半径が約０．１μｍ，長さが１μｍで表面に対して略垂直なものとなり、ガスの透過に対し必要以上の空間が形成されるものではない。このことは、細孔Ｓが触媒電極１４におけるガスの透過に対してその機能を十分果たすことを意味する。これらのことから、実施例の燃料電池１０の性能を従来例の燃料電池と比較すると、図５に示すように、実施例の燃料電池１０は、ガス透過性の影響が大きくなる高電流密度領域で従来例の燃料電池に比して著しい性能の向上が認められる。
【００４３】
なお、実施例の燃料電池１０が従来例の燃料電池に比して良好な性能を示すのは、燃料電池１０が備える発電層１５の性能の差、即ち触媒電極１４の性能の差に基づくのは言うまでもない。
【００４４】
以上説明した実施例の発電層１５の製造方法によれば、表面に対して略垂直な配向性をもった複数の細孔を有する触媒電極１４と電解質膜１２との接合体である発電層１５を製造することができる。
【００４５】
こうして製造された発電層１５によれば、触媒電極１４が表面に対して略垂直な配向性をもった複数の細孔を有することにより、より良好なガス透過性と導電性とを示すから、発電層１５の性能をより高くすることができる。また、こうして製造された発電層１５を燃料電池に用いることにより、より性能のよい燃料電池とすることができる。
【００４６】
実施例の発電層１５の製造方法では、鉄により半径０．１μｍ，長さ１μｍの針状に形成された造孔剤Ｆを用いたが、長手方向を有する３次元的な構造の造孔剤を用いるものとしてもよい。例えば、平均粒径０．１μｍの鉄粉末を焼成，粉砕して鉄粉末粒子が５個ないし２００個程度、大きさでは０．５μｍないし５μｍ程度に３次元構造に形成された造孔剤を用いるものとしてもよい。こうした３次元構造の造孔剤を用いて電極形成部材を形成し、これをシート面と略垂直な方向の磁界を作用させることにより、造孔剤はその長手方向がシート面と略垂直な方向に揃う。したがって、この３次元構造の造孔剤を用いて実施例の発電層１５と同様に発電層を製造すれば、長手方向が表面に略垂直な配向性をもつ３次元構造の複数の細孔を有する触媒電極と電解質膜との接合体である発電層を得ることができる。こうして得られる変形例の発電層の模式図を図７に示す。図示するように、この変形例の発電層は、長手方向が表面に略垂直な配向性をもった細孔ＳＢを有する触媒電極１４Ｂを備えることにより、実施例の発電層１５と同様の効果を奏することができ、更に、触媒電極１４Ｂの細孔ＳＢが３次元的に連通していることから、長手方向とは異なる方向へのガスの拡散性をも有するものとすることができる。この変形例の発電層を用いた燃料電池の電流密度と電圧との関係を図５の曲線Ｂとして示す。図示するように、変形例の発電層を用いた燃料電池は、ガス透過性の影響が大きくなる高電流密度領域で、従来例の燃料電池との比較においてはもとより、実施例の燃料電池１０に比しても性能の向上が認められる。
【００４７】
このように、長手方向が触媒電極の表面に略垂直な配向性をもち、かつ長手方向とは異なる方向にも連通する細孔を有する触媒電極を得るためには、変形例の３次元構造の造孔剤ＦＢを用いる手法の他、実施例の針状の造孔剤Ｆと常磁性で造孔剤Ｆと同一の溶液に溶解可能な材料により球状，針状，３次元構造，その他の形状に形成された造孔剤とを混ぜて用いるものとしてもよい。実施例の針状の造孔剤Ｆと鉄により球状に形成された造孔剤Ｆ２とを混ぜて用いることによって、表面に対して略垂直な配向性をもつと共にこの方向とは異なる方向にも連通する複数の細孔ＳＤを有する触媒電極１４Ｄと電解質膜１２Ｄとの接合体である変形例の発電層の構成の概略を示す模式図を図８に示す。
【００４８】
また、実施例の発電層１５や変形例の発電層の製造方法では、ペースト状に調整したインクをドクターブレード式の印刷装置を用いてテフロンシート上に印刷することによりシート状の電極形成部材１７を形成したが、電解質膜１２へスクリーン印刷などにより直接印刷して形成するものとしたり、テフロンシート上にあるいは電解質膜１２上にスプレーにより吹き付けて形成するものなど、種々の方法で形成してもよい。
【００４９】
実施例の発電層１５や変形例の発電層が備える触媒電極では、長手方向が表面に対して略垂直な配向性をもった細孔を有するが、この角度に限られるものではなく、例えば、ガスを透過させたい方向が表面から所定の角度をもっているときには、長手方向が表面に対して所定の角度となる配向性をもった細孔を有するものとしてもよい。こうした触媒電極を備える発電層を製造するには、図１の製造工程の工程Ｓ１３０に代えて、シート面に対して所定の角度の方向の磁界を作用させた状態で電極形成部材１７を乾燥させればよい。
【００５０】
実施例の発電層１５や変形例の発電層の製造方法では、電極形成部材１７を磁界を作用させた状態で乾燥させたが、電極形成部材１７に磁界を作用させて造孔剤Ｆの長手方向に配向性をもたせ、その後に磁界を作用させずに電極形成部材１７を乾燥させる２段階の工程としてもよい。
【００５１】
実施例の発電層１５や変形例の発電層の製造方法では、造孔剤を形成する材料として鉄を用いたが、電解質膜１２に影響を与えることがない溶液により溶解可能な強磁性材料であれば如何なるものでもよいから、例えば、鉄と他の金属との合金，コバルトやニッケルあるいはこれらと他の金属との合金などを用いてもよい。
【００５２】
また、実施例の発電層１５や変形例の発電層の製造方法では、強磁性材料により長手形状の造孔剤Ｆを形成し、電界を作用させることにより電極形成部材１７中の造孔剤Ｆの長手方向に配向性をもたせたが、所定の場を作用させたとき長手方向が所定の場に基づいて所定方向に配向する性質を有し所定の溶液に溶解可能な材料により長手形状の造孔剤を形成し、所定の場に電極形成部材をおくことにより電極形成部材中の造孔剤の長手方向に配向性をもたせるものとしてもよい。例えば、強誘電性材料により長手形状の造孔剤を形成し、電界を作用させることにより電極形成部材中の造孔剤の長手方向に配向性をもたせるものとしてもよい。また、長手方向に密度分布を有するよう造孔剤を形成し、電極形成部材を所定の重力場（例えば遠心回転機などにより与えられる重力場）に置くことにより電極形成部材中の造孔剤の長手方向に配向性をもたせるものとしてもよい。
【００５３】
以上、長手方向が表面に対して略垂直な配向性をもった複数の細孔を有する触媒電極１４と電解質膜１２との接合体である発電層１５やその変形例の発電層を製造する方法について説明したが、この発電層１５や変形例の発電層の製造工程のうち電解質膜１２と電極形成部材１７との接合の工程（図１の工程Ｓ１４０）を除くことにより、長手方向が表面に対して略垂直な配向性をもった複数の細孔を有する触媒電極１４を製造する方法や、変形例の発電層が備える触媒電極を製造する方法とすることができる。こうした触媒電極１４の製造方法や変形例の発電層が備える触媒電極の製造方法についてのこれ以上の説明は重複するから省略する。こうした触媒電極１４の製造方法や変形例の発電層が備える触媒電極の製造方法によれば、長手方向が表面に対して略垂直な配向性をもった複数の細孔や、更に長手方向とは異なる方向に連通する細孔を有することにより、その長手方向に対する十分なガス透過性を有すると共に導電性とを備える触媒電極１４や更にその長手方向とは異なる方向へのガスの拡散性を有する触媒電極を得ることができる。したがって、この触媒電極１４や変形例の触媒電極を用いることにより、より性能のよい発電層を形成することができると共に、より性能のよい燃料電池を構成することができる。
【００５４】
以上、本発明の実施の形態について説明したが、本発明はこうした実施の形態に何等限定されるものではなく、本発明の要旨を逸脱しない範囲内において、種々なる形態で実施し得ることは勿論である。
【図面の簡単な説明】
【図１】本発明の好適な一実施例である電解質膜１２と触媒電極１４との接合体である発電層１５の製造の様子を例示する工程図である。
【図２】図１の工程により製造された発電層１５の構造の概略を例示する模式図である。
【図３】電極形成部材１７中の造孔剤Ｆが配向される様子を説明する説明図である。
【図４】実施例の発電層１５を備える燃料電池１０の構成を例示する模式図である。
【図５】実施例の発電層１５を備える燃料電池１０と変形例の発電層を備える燃料電池と従来例の燃料電池とにおける電流密度と電圧との関係を例示したグラフである。
【図６】従来例の燃料電池の発電層１５Ｃの構造の概略を拡大して示す模式図である。
【図７】変形例の発電層の構造の概略を例示する模式図である。
【図８】変形例の発電層の構造の概略を例示する模式図である。
【符号の説明】
１０…燃料電池
１２…電解質膜
１４…触媒電極
１５…発電層
１６…ガス拡散電極
１７…電極形成部材
２０…集電極
２２…リブ
２４…流路
Ｃ…触媒担持カーボン
Ｆ…造孔剤
Ｐ…触媒
Ｓ…細孔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode and power generation for a fuel cell. Layered More specifically, the power generation method includes an electrode used for a fuel cell and an electrolyte membrane used for the fuel cell and two electrodes sandwiching the electrode. Layered It relates to a manufacturing method.
[0002]
[Prior art]
In a fuel cell, for example, a polymer electrolyte fuel cell, a fuel gas containing hydrogen and an oxidizing gas containing oxygen are supplied to two electrodes (an oxygen electrode and a fuel electrode) facing each other with an electrolyte membrane interposed therebetween. Thus, the reactions shown in the following formulas (1) and (2) are performed, and the chemical energy of the substance is directly converted into electric energy.
[0003]
Cathode reaction (oxygen electrode): 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O ... (1)
Anode reaction (fuel electrode): H ₂ → 2H ⁺ + 2e ⁻ ... (2)
[0004]
In order to carry out this reaction continuously and smoothly, it is necessary to quickly remove the generated water at the oxygen electrode and continuously supply the oxidizing gas. At the fuel electrode, the generated hydrogen ions are hydrated into the electrolyte by hydration. It is necessary to continuously supply water and fuel gas for smoothly diffusing into the membrane. In addition, in order to reduce the contact resistance and to make an efficient fuel cell, it is also necessary to closely contact the electrolyte membrane and both electrodes.
[0005]
Conventionally, as a method of manufacturing an electrode for a fuel cell that meets these requirements, a catalyst-supported carbon is mixed using powders of metals such as zinc, aluminum, chromium, or inorganic salts such as these metal salts as pore-forming agents. A method of manufacturing an electrode having a plurality of pores inside is proposed by forming a sheet-like electrode member to be formed and immersing the formed electrode member in a solution to elute and remove the internal pore-forming agent. (For example, JP-A-6-36771 and JP-A-6-203852).
[0006]
In addition, as a method for producing a power generation layer for a fuel cell, before the step of immersing the electrode member in a solution and eluting the pore-forming agent in the electrode member in the above-described conventional method for producing an electrode for a fuel cell. A method for joining and integrating the electrode member and the polymer electrolyte membrane has been proposed (for example, JP-A-6-203852). Thus, the pore forming agent is eluted after being joined to the polymer electrolyte membrane, thereby preventing the pores of the electrode from being crushed during joining.
[0007]
[Problems to be solved by the invention]
However, in the manufacturing method described above, if an attempt is made to ensure sufficient gas permeability in the electrode, an excessive space is formed in the electrode, which deteriorates the performance of the fuel cell or makes the electrode fragile. There was a problem. When a granular metal or metal salt is used as a pore-forming agent, the formed pores have a shape in which substantially spherical pores that are the shape of the pore-forming agent are communicated. For this reason, the diameter of the pores varies greatly in the length direction and is not constant. Since the gas permeability in the electrode depends on the diameter of the pores formed in the electrode, in an electrode with a large change in the diameter of the pores, if an attempt is made to obtain sufficient gas permeability, the inside of the electrode is more than necessary. Will form a space. Such extra space reduces the conductive area of the electrode, lowers its conductivity, and makes the electrode fragile.
[0008]
Electricity for the fuel cell of the present invention Extreme The manufacturing method solves these problems and has sufficient gas permeability and conductivity. Extreme An object is to provide a manufacturing method. Further, the power generation for the fuel cell of the present invention Layered The manufacturing method includes generating an electrode having sufficient gas permeability and conductivity while maintaining high performance of the electrolyte membrane. Layered An object is to provide a manufacturing method.
[0009]
In order to achieve a part of the above object, the applicant forms an electrode member using water-soluble short fibers as a pore-forming agent as an invention different from the present invention, and immerses the electrode member in water. And then eluting and removing the internal pore former to produce an electrode having sufficient gas permeability and conductivity, or before immersing the electrode member in water and eluting the internal pore former In addition, a method for producing a power generation layer having two electrodes having sufficient gas permeability and conductivity by joining and integrating an electrode member with an electrolyte membrane is proposed (Japanese Patent Laid-Open No. 8-180879). Publication).
[0010]
[Means for solving the problems and their functions and effects]
Electrode and power generation for fuel cell of the present invention Layered In order to achieve at least a part of the above-mentioned object, the manufacturing method is as follows. Constitution Was taken.
[0016]
The method for producing an electrode for a fuel cell of the present invention comprises:
A pore-forming agent forming step of forming a longitudinal pore-forming agent from a material that has a property that the longitudinal direction is oriented in a predetermined direction based on the predetermined field when a predetermined field is applied, and is soluble in a predetermined solution When,
An ink adjusting step of adjusting the ink by dispersing the formed pore forming agent and carbon particles supporting the catalyst in a predetermined solvent;
An electrode forming member forming step of forming a sheet-like electrode forming member with the adjusted ink;
A field action step of causing the predetermined field to act on the formed electrode forming member at a predetermined angle;
A drying step of drying the solvent contained in the electrode forming member that has acted on the predetermined field;
An elution step of immersing the dried electrode forming member in the predetermined solution to elute the pore-forming agent;
It is a summary to provide.
[0017]
According to the electrode manufacturing method of the present invention, an electrode having a plurality of pores having a predetermined orientation in the longitudinal direction can be manufactured. According to the electrode manufactured in this manner, the gas permeability in a predetermined direction can be improved by the pores having a predetermined orientation in the longitudinal direction. The reaction can be performed continuously and smoothly. The “predetermined field” is a field where a certain force in a predetermined direction can be applied, such as a magnetic field that forms a magnetic field in a predetermined direction, an electric field that forms an electric field in a predetermined direction, or a gravitational field in a predetermined direction. included. The material forming the pore-forming agent is a material exhibiting ferromagnetism when such a “predetermined field” is a magnetic field that forms a magnetic field in a predetermined direction, and when the “predetermined field” is an electric field that forms an electric field in a predetermined direction. It is a material exhibiting ferroelectricity.
[0018]
In the method for producing an electrode of the present invention, the field action step and the drying step are performed by applying a solvent contained in the electrode forming member in a state where the predetermined field is applied to the formed electrode forming member at a predetermined angle. It can also be a process performed simultaneously by drying.
[0019]
Moreover, in the manufacturing method of the electrode of this invention, the said pore forming agent formation process shall be a process of forming the pore forming agent of the three-dimensional structure which has a longitudinal direction with the said material. By doing so, it is possible to manufacture an electrode that is not only excellent in gas permeability in the longitudinal direction but also excellent in diffusivity in a direction different from the longitudinal direction.
[0020]
Furthermore, the electrode manufacturing method of the present invention further includes a second pore forming agent forming step of forming a second pore forming agent from a material that can be dissolved in the predetermined solution, wherein the ink adjusting step includes the pore forming agent. And the second pore former and the carbon particles supporting the catalyst may be dispersed in a predetermined solvent to adjust the ink. By doing so, it is possible to manufacture an electrode that is not only excellent in gas permeability in the longitudinal direction but also excellent in diffusivity in a direction different from the longitudinal direction.
[0026]
A method for producing a power generation layer for a fuel cell according to the present invention includes:
A pore-forming agent forming step of forming a longitudinal pore-forming agent from a material that has a property that the longitudinal direction is oriented in a predetermined direction based on the predetermined field when a predetermined field is applied, and is soluble in a predetermined solution When,
An ink adjusting step of adjusting the ink by dispersing the formed pore forming agent and carbon particles supporting the catalyst in a predetermined solvent;
An electrode forming member forming step of forming a sheet-like electrode forming member with the adjusted ink;
A field action step of causing the predetermined field to act on the formed electrode forming member at a predetermined angle;
A drying step of drying the solvent contained in the electrode forming member that has acted on the predetermined field;
A power generation layer forming member forming step of forming the power generation layer forming member by bonding the dried electrode forming member to both surfaces of the electrolyte membrane;
An elution step of immersing the formed power generation layer forming member in the predetermined solution to elute the pore-forming agent from the electrode forming member of the power generation layer forming member;
It is a summary to provide.
[0027]
According to this power generation layer manufacturing method of the present invention, a power generation layer including an electrode having a plurality of pores having a predetermined orientation in the longitudinal direction can be manufactured. According to the power generation layer thus manufactured, the fuel gas and the oxidizing gas are smoothly supplied by the electrode having pores having a predetermined orientation in the longitudinal direction, so that the electrochemical reaction can be performed continuously and smoothly. Can do. The “predetermined field” is a field where a certain force in a predetermined direction can be applied, such as a magnetic field that forms a magnetic field in a predetermined direction, an electric field that forms an electric field in a predetermined direction, or a gravitational field in a predetermined direction. included. The material forming the pore-forming agent is a material exhibiting ferromagnetism when such a “predetermined field” is a magnetic field that forms a magnetic field in a predetermined direction, and when the “predetermined field” is an electric field that forms an electric field in a predetermined direction. It is a material exhibiting ferroelectricity.
[0028]
In such a power generation layer manufacturing method of the present invention, the field action step and the drying step are included in the electrode forming member in a state where the predetermined field is applied to the formed electrode forming member at a predetermined angle. It can also be a process performed simultaneously by drying the solvent.
[0029]
In the method for producing a power generation layer of the present invention, the pore forming agent forming step may be a step of forming a pore forming agent having a three-dimensional structure having a longitudinal direction with the material. In this way, a power generation layer including an electrode that is not only excellent in permeability of fuel gas and oxidizing gas in the longitudinal direction but also excellent in diffusibility of fuel gas and oxidizing gas in a direction different from the longitudinal direction. Can be manufactured.
[0030]
Alternatively, in the method for producing a power generation layer according to the present invention, the method includes a second pore forming agent forming step of forming a second pore forming agent with a material that can be dissolved in the predetermined solution, and the ink adjustment step includes It is also possible to adjust the ink by dispersing the agent, the second pore-forming agent, and the carbon particles carrying the catalyst in a predetermined solvent. In this way, a power generation layer including an electrode that is not only excellent in permeability of fuel gas and oxidizing gas in the longitudinal direction but also excellent in diffusibility of fuel gas and oxidizing gas in a direction different from the longitudinal direction. Can be manufactured.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described based on examples. FIG. 1 is a process diagram illustrating the production of a power generation layer 15 which is a joined body of an electrolyte membrane 12 and a catalyst electrode 14 according to a preferred embodiment of the present invention, and FIG. 2 is produced by the process of FIG. It is a schematic diagram which illustrates the outline of the structure of the electric power generation layer 15 to be performed. First, a state of manufacturing the power generation layer 15 will be described based on the process diagram of FIG.
[0032]
In the production of the power generation layer 15 of the example, first, a needle-like pore forming agent F having a radius of 0.1 μm and a length of 1 μm is formed from iron (step S100), and the formed pore forming agent F is used as the pore forming agent F1g. On the other hand, 1 g of a catalyst-supporting carbon C carrying 20 wt% of fine particles (average particle diameter of about 1 nm) of platinum or an alloy of platinum and other metals as the catalyst P, 5 wt% perfluorocarbon sulfonic acid solution (for example, Aldrich (Chemical Nafion Solution) is mixed at a ratio of 10 ml and cyclohexanol at a ratio of 10 ml, and ultrasonic waves are applied to uniformly disperse the pore-forming agent F and the catalyst-carrying carbon C to prepare paste-like ink (process) S110). In addition, the dispersion | distribution by irradiation of an ultrasonic wave was performed by irradiating an ultrasonic wave with a frequency of 30 kHz to 50 kHz using the commercially available ultrasonic cleaning machine.
[0033]
Subsequently, the paste-like ink is printed on a Teflon sheet by using a doctor blade type printing apparatus with a thickness of 30 μm to 500 μm, preferably 80 μm to 300 μm, thereby forming a sheet-like electrode forming member 17. (Step S120), by vacuum drying the formed electrode forming member 17 at a temperature of 40 ° C. to 100 ° C., preferably 60 ° C. to 80 ° C. in a state where a magnetic field in a direction substantially perpendicular to the sheet surface is applied. The solvent in the electrode forming member 17 is dried until the thickness becomes 1 μm to 100 μm, preferably 3 μm to 10 μm (step S130). When the magnetic field is applied to the electrode forming member 17 in this way, the pore forming agent F in the electrode forming member 17 is formed of ferromagnetic iron, so that the longitudinal direction thereof becomes the magnetic field direction. . This is shown in FIG. 3A is an explanatory view schematically showing the state of the pore-forming agent F in the electrode forming member 17 before the magnetic field is applied, and FIG. 3B is an electrode forming member 17 when the magnetic field is applied. FIG. 3C schematically shows the state of the pore-forming agent F in the electrode forming member 17 after the solvent is dried in a state where a magnetic field is applied. FIG. Before the magnetic field is applied, the pore-forming agent F does not exhibit orientation as shown in FIG. 3 (a). However, when the magnetic field is applied, the pore-forming agent F has a longitudinal direction due to its magnetization as shown in FIG. 3 (b). Turns to the direction of the magnetic field lines. Therefore, if the electrode forming member 17 is dried in a state where a magnetic field in a direction substantially perpendicular to the sheet surface is applied, the longitudinal direction of the pore former F is substantially perpendicular to the sheet surface as shown in FIG. It can be set as the dry electrode formation member 17 with the orientation of direction. In the examples, as the magnetic field to be applied, a magnetic field having a magnetic field intensity per unit area of 100 [A / m] to 1000 [A / m] was applied. The strength of the magnetic field is determined by the viscosity of the ink adjusted by the pore-forming agent F and the catalyst-carrying carbon C and the material of the pore-forming agent F, and is not limited to the above range. Nor.
[0034]
Next, an electrolyte membrane 12 having a thickness of 10 μm to 200 μm, preferably 30 μm to 100 μm, obtained by sequentially performing boiling cleaning with dilute sulfuric acid, hydrogen peroxide water and ion exchange water in advance (for example, trade name “Nafion” manufactured by DuPont). The printed surface is sandwiched between the electrode-forming member 17 dried with a perfluorocarbon sulfonic acid polymer membrane, etc., sold as an inner surface, and in a sandwich structure, a temperature of 100 ° C. to 160 ° C., preferably 110 ° C. to 130 ° C. In step S140, the electrolyte membrane 12 and the electrode forming member 17 are joined by a hot press method in which a pressure of 1 MPa to 20 MPa, preferably 5 MPa to 15 MPa is applied.
[0035]
The Teflon sheet is peeled from the joined body of the electrolyte membrane 12 and the electrode forming member 17 thus obtained, and the pore forming agent F is immersed in an acid capable of being dissolved to elute the pore forming agent F from the electrode forming member 17 (step S150). ), Washed and dried, and a power generation layer which is a joined body of two catalyst electrodes 14 having a plurality of pores S having an orientation substantially perpendicular to the surface as shown in FIG. Complete 15 In the examples, 1N dilute sulfuric acid is used as the acid capable of dissolving the pore-forming agent F, and the electrode is formed by repeating boiling washing with dilute sulfuric acid and boiling washing with ion-exchanged water about 2 to 5 times. The pore former F was completely eluted from the member 17.
[0036]
Next, the fuel cell 10 using the power generation layer 15 thus manufactured will be described. FIG. 4 is a schematic view illustrating the configuration of the fuel cell 10 including the power generation layer 15 of the embodiment. As shown in the figure, the fuel cell 10 includes a power generation layer 15 that is a joined body of the electrolyte membrane 12 manufactured by the above-described manufacturing method and two catalyst electrodes 14, and two gas diffusion electrodes that sandwich the power generation layer 15. 16 and a collecting electrode 20 that sandwiches the gas diffusion electrode 16 together with the power generation layer 15.
[0037]
The two gas diffusion electrodes 16 are formed of carbon cloth woven with yarns in which carbon fibers whose surfaces are coated with polytetrafluoroethylene and carbon fibers which are not treated at all are in a ratio of 1: 1. The gas diffusion electrode 16 has good gas permeability because the entire surface of the gas diffusion electrode 16 is not covered with water because the polytetrafluoroethylene coated on the carbon fiber exhibits water repellency. .
[0038]
The collector electrode 20 is formed of dense carbon that is compressed and densified by compressing carbon, and a plurality of ribs 22 arranged in parallel are arranged on the surface of the collector electrode 20 in contact with the gas diffusion electrode 16. Is formed. The rib 22 forms a flow path 24 of an oxidizing gas (for example, air) containing oxygen or a fuel gas (for example, methanol reformed gas) containing hydrogen with the gas diffusion electrode 16.
[0039]
Fuel gas containing hydrogen and oxygen are provided in the flow path 24 formed by the collector electrode 20 and the gas diffusion electrode 16 facing each other with the power generation layer 15 of the fuel cell 10 and the two gas diffusion electrodes 16 sandwiched therebetween. When the oxidizing gas containing is supplied, the fuel gas and the oxidizing gas are supplied to the two catalyst electrodes 14 facing each other with the electrolyte membrane 12 interposed therebetween, and the electrochemical shown in the above reaction formulas (1) and (2) A reaction takes place and chemical energy is converted directly into electrical energy.
[0040]
Next, the performance of the fuel cell 10 thus configured will be described in comparison with a conventional fuel cell. FIG. 5 is a graph illustrating the relationship between the current density and the voltage in the fuel cell 10 of the example and the fuel cell of the conventional example, and FIG. 6 is a schematic diagram illustrating the structure of the catalyst electrode of the fuel cell of the conventional example. It is. In the graph of FIG. 5, the curve A shows the relationship between the current density and the voltage in the fuel cell 10 including the power generation layer 15 of the example, and the curve C shows the pore SC using the granular pore forming agent Z of the metal salt. The relationship between the current density and voltage in a fuel cell (conventional fuel cell) including a power generation layer 15C (see the schematic diagram of FIG. 6) formed by joining the formed catalyst electrode 14C and the electrolyte membrane 12C is shown. The curve B in the figure will be described later.
[0041]
The catalyst electrode 14C of the power generation layer 15C provided in the conventional fuel cell is formed by mixing 500 g of calcium carbonate powder having an average particle diameter of 1 μm with 1 g of the catalyst-supporting carbon C to form an electrode forming member. The member and the electrolyte membrane 12C identical to the electrolyte membrane 12 of the example were joined under the same conditions as those of the example, and then the calcium carbonate in the electrode forming member was eluted with a strong acidic aqueous solution. is there. Since the catalyst electrode 14C uses granular calcium carbonate as a pore-forming agent, the formed pores SC are formed by communicating substantially spherical holes having an average diameter of 1 μm with small-diameter communication holes as shown in FIG. It will be a thing. Since the gas permeability in the catalyst electrode depends on the diameter of the pores, the catalyst electrode 14C of the conventional example depends on the diameter of the communicating holes communicating with the pores, and attempts to ensure sufficient gas permeability. Then, an unnecessarily large space is formed in the interior. As a result, the catalyst electrode 14C becomes fragile as the conductive area decreases, the conductivity decreases.
[0042]
On the other hand, the pores S of the catalyst electrode 14 provided in the fuel cell 10 of the embodiment are needle-shaped pore-forming agents having a radius of 0.1 μm and a length of 1 μm that are oriented substantially perpendicular to the surface by applying a magnetic field. Since it is based on F, the radius is about 0.1 μm, the length is 1 μm, and the surface is substantially perpendicular to the surface, so that an unnecessary space for gas permeation is not formed. This means that the pores S sufficiently perform their functions for the permeation of gas through the catalyst electrode 14. From these facts, when the performance of the fuel cell 10 of the embodiment is compared with the fuel cell of the conventional example, as shown in FIG. 5, the fuel cell 10 of the embodiment has a high current density region where the influence of gas permeability is large. Thus, a marked improvement in performance is recognized as compared with the conventional fuel cell.
[0043]
The reason why the fuel cell 10 of the example shows better performance than the fuel cell of the conventional example is based on the difference in the performance of the power generation layer 15 included in the fuel cell 10, that is, the difference in the performance of the catalyst electrode 14. Needless to say.
[0044]
According to the method of manufacturing the power generation layer 15 of the embodiment described above, the power generation layer 15 which is a joined body of the catalyst electrode 14 having a plurality of pores having an orientation substantially perpendicular to the surface and the electrolyte membrane 12. Can be manufactured.
[0045]
According to the power generation layer 15 thus manufactured, since the catalyst electrode 14 has a plurality of pores having an orientation substantially perpendicular to the surface, it exhibits better gas permeability and conductivity. The performance of the power generation layer 15 can be further increased. Further, by using the power generation layer 15 thus manufactured for a fuel cell, a fuel cell with higher performance can be obtained.
[0046]
In the manufacturing method of the power generation layer 15 of the embodiment, the pore forming agent F formed in a needle shape with a radius of 0.1 μm and a length of 1 μm is used with iron, but the pore forming agent having a three-dimensional structure having a longitudinal direction. May be used. For example, an iron powder having an average particle diameter of 0.1 μm is fired and pulverized to use a pore-forming agent formed in a three-dimensional structure so that the number of iron powder particles is about 5 to 200, and the size is about 0.5 to 5 μm. It may be a thing. The electrode forming member is formed using such a three-dimensional pore forming agent, and this is subjected to a magnetic field in a direction substantially perpendicular to the sheet surface, whereby the pore forming agent has a longitudinal direction substantially perpendicular to the sheet surface. It is aligned. Therefore, if a power generation layer is manufactured in the same manner as the power generation layer 15 of the embodiment using this three-dimensional pore forming agent, a plurality of pores having a three-dimensional structure having an orientation in which the longitudinal direction is substantially perpendicular to the surface. A power generation layer that is a joined body of the catalyst electrode and the electrolyte membrane can be obtained. A schematic diagram of the power generation layer of the modification obtained in this way is shown in FIG. As shown in the figure, the power generation layer of this modified example has the same effect as the power generation layer 15 of the embodiment by including the catalyst electrode 14B having the pores SB having the orientation in which the longitudinal direction is substantially perpendicular to the surface. Furthermore, since the pores SB of the catalyst electrode 14B are three-dimensionally communicated, it can also have gas diffusivity in a direction different from the longitudinal direction. The relationship between the current density and the voltage of the fuel cell using the power generation layer of this modification is shown as curve B in FIG. As shown in the figure, the fuel cell using the power generation layer of the modified example is in a high current density region where the influence of gas permeability becomes large, and in comparison with the fuel cell of the conventional example, the fuel cell 10 of the example is used. In comparison, an improvement in performance is recognized.
[0047]
Thus, in order to obtain a catalyst electrode having an orientation in which the longitudinal direction is substantially perpendicular to the surface of the catalyst electrode and also communicating with a direction different from the longitudinal direction, the three-dimensional structure of the modified example is used. In addition to the method using the pore-forming agent FB, the needle-like pore-forming agent F of the embodiment and the material that is paramagnetic and soluble in the same solution as the pore-forming agent F are spherical, needle-shaped, three-dimensional structure, and other shapes It is good also as what mixes with the pore-forming agent formed in this. By mixing the needle-shaped pore-forming agent F of the example and the pore-forming agent F2 formed into a spherical shape with iron, the orientation is substantially perpendicular to the surface and the direction is different from this direction. FIG. 8 is a schematic diagram showing an outline of the configuration of the power generation layer of a modified example that is a joined body of the catalyst electrode 14D having a plurality of communicating pores SD and the electrolyte membrane 12D.
[0048]
In the method for producing the power generation layer 15 of the embodiment or the power generation layer of the modification, the sheet-shaped electrode forming member 17 is printed on the Teflon sheet by using the doctor blade type printing device. However, it may be formed by various methods such as direct printing on the electrolyte membrane 12 by screen printing or by spraying on the Teflon sheet or the electrolyte membrane 12. Good.
[0049]
In the catalyst electrode provided in the power generation layer 15 of the example or the power generation layer of the modified example, the longitudinal direction has pores having an orientation substantially perpendicular to the surface, but is not limited to this angle, for example, When the gas permeation direction has a predetermined angle from the surface, it may have pores having an orientation in which the longitudinal direction is a predetermined angle with respect to the surface. In order to manufacture a power generation layer including such a catalyst electrode, instead of step S130 of the manufacturing process of FIG. 1, the electrode forming member 17 is dried in a state where a magnetic field in a direction of a predetermined angle is applied to the sheet surface. Just do it.
[0050]
In the manufacturing method of the power generation layer 15 of the embodiment or the power generation layer of the modification, the electrode forming member 17 is dried in a state where a magnetic field is applied, but the length of the pore former F is increased by applying a magnetic field to the electrode forming member 17. It may be a two-stage process in which the orientation is given to the direction, and then the electrode forming member 17 is dried without applying a magnetic field.
[0051]
In the manufacturing method of the power generation layer 15 of the embodiment and the power generation layer of the modification, iron is used as a material for forming the pore forming agent, but it is a ferromagnetic material that can be dissolved in a solution that does not affect the electrolyte membrane 12. Any material may be used, and for example, an alloy of iron and another metal, cobalt or nickel, or an alloy of these and another metal may be used.
[0052]
Moreover, in the manufacturing method of the power generation layer 15 of the embodiment or the power generation layer of the modification, the pore forming agent F in the electrode forming member 17 is formed by forming a longitudinal pore forming agent F from a ferromagnetic material and applying an electric field. However, when a predetermined field is applied, the longitudinal direction is oriented in a predetermined direction based on the predetermined field, and the longitudinal shape is made of a material that can be dissolved in a predetermined solution. It is good also as what has orientation in the longitudinal direction of the pore making material in an electrode formation member by forming a pore agent and putting an electrode formation member in a predetermined field. For example, a longitudinal pore forming agent may be formed of a ferroelectric material, and an electric field may be applied to provide orientation in the longitudinal direction of the pore forming agent in the electrode forming member. Further, a pore-forming agent is formed so as to have a density distribution in the longitudinal direction, and the electrode-forming member is placed in a predetermined gravitational field (for example, a gravitational field given by a centrifugal rotating machine or the like), thereby It is good also as what has orientation in a longitudinal direction.
[0053]
As described above, the method of manufacturing the power generation layer 15 which is a joined body of the catalyst electrode 14 having the plurality of pores having the orientation in which the longitudinal direction is substantially perpendicular to the surface and the electrolyte membrane 12 and the power generation layer of the modified example. However, the step of joining the electrolyte membrane 12 and the electrode forming member 17 (step S140 in FIG. 1) is excluded from the manufacturing steps of the power generation layer 15 and the power generation layer of the modification. On the other hand, a method of manufacturing a catalyst electrode 14 having a plurality of pores having a substantially perpendicular orientation, or a method of manufacturing a catalyst electrode included in a power generation layer of a modification can be used. Since the further description about the manufacturing method of such a catalyst electrode 14 and the manufacturing method of the catalyst electrode with which the power generation layer of a modification is provided overlaps, it abbreviate | omits. According to the method of manufacturing the catalyst electrode 14 and the method of manufacturing the catalyst electrode included in the power generation layer of the modification, a plurality of pores having an orientation in which the longitudinal direction is substantially perpendicular to the surface, and the longitudinal direction By having pores communicating in different directions, the catalyst electrode 14 has sufficient gas permeability in the longitudinal direction and has conductivity, and further has a gas diffusivity in a direction different from the longitudinal direction. An electrode can be obtained. Therefore, by using this catalyst electrode 14 or a modified catalyst electrode, it is possible to form a power generation layer with better performance and to construct a fuel cell with better performance.
[0054]
As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement with a various form. It is.
[Brief description of the drawings]
FIG. 1 is a process diagram illustrating the production of a power generation layer 15 which is a joined body of an electrolyte membrane 12 and a catalyst electrode 14 according to a preferred embodiment of the present invention.
2 is a schematic view illustrating the outline of the structure of a power generation layer 15 manufactured by the process of FIG. 1;
FIG. 3 is an explanatory view for explaining a state in which a pore forming agent F in an electrode forming member 17 is oriented.
FIG. 4 is a schematic view illustrating the configuration of a fuel cell 10 including a power generation layer 15 according to an embodiment.
FIG. 5 is a graph illustrating the relationship between current density and voltage in a fuel cell 10 including a power generation layer 15 of an example, a fuel cell including a power generation layer of a modified example, and a fuel cell of a conventional example.
FIG. 6 is an enlarged schematic view showing an outline of the structure of a power generation layer 15C of a conventional fuel cell.
FIG. 7 is a schematic view illustrating the outline of the structure of a power generation layer according to a modification.
FIG. 8 is a schematic view illustrating the outline of the structure of a power generation layer according to a modification.
[Explanation of symbols]
10. Fuel cell
12 ... electrolyte membrane
14 ... Catalyst electrode
15 ... Power generation layer
16 ... Gas diffusion electrode
17 ... Electrode forming member
20 ... collector electrode
22 ... Ribs
24 ... Flow path
C ... Catalyst supported carbon
F ... Pore forming agent
P ... Catalyst
S ... pore

Claims

A method for producing an electrode for a fuel cell, comprising:
A pore-forming agent forming step of forming a longitudinal pore-forming agent from a material that has a property that the longitudinal direction is oriented in a predetermined direction based on the predetermined field when a predetermined field is applied, and is soluble in a predetermined solution When,
An ink adjusting step of adjusting the ink by dispersing the formed pore forming agent and carbon particles supporting the catalyst in a predetermined solvent;
An electrode forming member forming step of forming a sheet-like electrode forming member with the adjusted ink;
A field action step of causing the predetermined field to act on the formed electrode forming member at a predetermined angle;
A drying step of drying the solvent contained in the electrode forming member that has acted on the predetermined field;
An elution process comprising immersing the dried electrode forming member in the predetermined solution to elute the pore-forming agent.

The field action step and the drying step are performed simultaneously by drying the solvent contained in the electrode forming member in a state where the predetermined field is applied to the formed electrode forming member at a predetermined angle. The manufacturing method of the electrode of Claim 1 .

A method of manufacturing an electrode according to claim 1 or claim 2 ,
The predetermined field is a magnetic field forming a magnetic field in a predetermined direction;
A method for producing an electrode, wherein the property is ferromagnetic.

A method of manufacturing an electrode according to claim 1 or claim 2 ,
The predetermined field is an electric field forming an electric field in a predetermined direction;
A method of manufacturing an electrode, wherein the property is ferroelectric.

The method for producing an electrode according to claim 1 , wherein the pore forming agent forming step is a step of forming a three-dimensional pore forming agent having a longitudinal direction with the material.

A method for producing an electrode according to any one of claims 1 to 4 ,
A second pore forming agent forming step of forming a second pore forming agent from a material that is soluble in the predetermined solution;
The ink adjustment step is an electrode manufacturing method in which the pore forming agent, the second pore forming agent, and carbon particles carrying a catalyst are dispersed in a predetermined solvent to adjust ink.

A method for producing a power generation layer for a fuel cell, comprising:
A pore-forming agent forming step of forming a longitudinal pore-forming agent from a material that has a property that the longitudinal direction is oriented in a predetermined direction based on the predetermined field when a predetermined field is applied, and is soluble in a predetermined solution When,
An ink adjusting step of adjusting the ink by dispersing the formed pore forming agent and carbon particles supporting the catalyst in a predetermined solvent;
An electrode forming member forming step of forming a sheet-like electrode forming member with the adjusted ink;
A field action step of causing the predetermined field to act on the formed electrode forming member at a predetermined angle;
A drying step of drying the solvent contained in the electrode forming member that has acted on the predetermined field;
A power generation layer forming member forming step of forming the power generation layer forming member by bonding the dried electrode forming member to both surfaces of the electrolyte membrane;
An elution step of immersing the formed power generation layer forming member in the predetermined solution to elute the pore-forming agent from the electrode forming member of the power generation layer forming member.

The field action step and the drying step are simultaneously performed by drying the solvent contained in the electrode forming member in a state where the predetermined field is applied to the formed electrode forming member at a predetermined angle. The manufacturing method of the electric power generation layer of Claim 7 .

A method for producing a power generation layer according to claim 7 or claim 8 ,
The predetermined field is a magnetic field forming a magnetic field in a predetermined direction;
A method for producing a power generation layer, wherein the property is ferromagnetic.

A method for producing a power generation layer according to claim 7 or claim 8 ,
The predetermined field is an electric field forming an electric field in a predetermined direction;
A method for producing a power generation layer, wherein the property is ferroelectric.

The method for producing a power generation layer according to any one of claims 7 to 10 , wherein the pore forming agent forming step is a step of forming a three-dimensional structure pore forming agent having a longitudinal direction with the material.

A method of manufacturing an electrode according to any one of claims 7 to 10 ,
A second pore forming agent forming step of forming a second pore forming agent from a material that is soluble in the predetermined solution;
The ink adjustment step is a method for producing a power generation layer, which is a step of adjusting ink by dispersing the pore-forming agent, the second pore-forming agent, and carbon particles carrying a catalyst in a predetermined solvent.