JP2004030959A - Gas diffusion member, gas diffusion electrode and fuel cell - Google Patents

Abstract

An object of the present invention is to sufficiently supply a reaction gas to a catalyst layer, and to sufficiently supply steam to an electrolyte and discharge generated water.
One side is adjacent to a catalyst layer of a fuel cell, the other side is adjacent to a conductive member having a gas flow path, and has gas permeability and conductivity for supplying a reaction gas from the gas flow path to the catalyst layer. In the gas diffusion member, a hole having a greater gas permeability than the base material of the gas diffusion member is provided from the conductive member side to the catalyst layer side, and the gas diffusion member A gas diffusion electrode comprising a catalyst layer provided on a side opposite to a side adjacent to a conductive member, and a fuel cell using the gas diffusion member.
[Selection diagram] Fig. 1

Description

燃料極２で生成されたプロトンＨ^＋は水分子に伴って、固体高分子電解質膜１中を通って酸化剤極３に向かって移動する。それと同時に、燃料極２で生成された電子ｅ⁻は触媒層２ａ、ガス拡散層２ｂを通して、外部回路を介して燃料極２と酸化剤極３との間に接続された負荷を通って、酸化剤極３に移動する。
【０００７】
一方、酸化剤極３では、加湿された酸素を含む酸化剤ガスが集電体でもあるガス拡散層３ｂを通って、触媒層３ａに到達し、外部回路からガス拡散層３ｂおよび触媒層３ａを通して流れてきた電子を貰って、下記の反応で還元され、燃料極２から固体高分子電解質膜１中を通して移動してきたプロトンＨ^＋と結合して水となる。
【０００８】
【化２】

生成された水の一部は、濃度勾配によって固体高分子電解質膜１中に入り、燃料極２に向かって拡散して移動し、一部は蒸発して、触媒層３ａおよびガス拡散層３ｂを通して酸化剤ガス流路５ａまで拡散して、未反応の酸化剤ガスと一緒に排出される。
【０００９】
セパレータ４とガス拡散層２ｂとの電気的接続のために燃料ガス流路４ａは溝構造をしている。酸化剤ガス流路５ａも同様に溝構造をしている。ガス拡散層２ｂ、３ｂにセパレータ４、５が接触している部分ではガス拡散層２ｂ、３ｂは直接反応ガス（燃料ガスまたは酸化剤ガス）に接触せず、燃料ガス流路４ａ、酸化剤ガス流路５ａの部分からガス拡散層２ｂ、３ｂに入った反応ガスが拡散によって運ばれるしかない。ガス拡散層２ｂ、３ｂは、もともとガス拡散部材と導電性部材が接触している部分に対向する触媒層にも反応ガスを供給する機能を有するものであるが、そのガス透過抵抗のためにガス拡散層２ｂ、３ｂとセパレータ４、５が接触している部分に対向する触媒層２ａ、３ａの部分には、反応ガスが十分に供給されず式（１）、（２）の電極反応が不十分となり発電性能が低くなる問題点があった。また、ガス拡散機能のゆえに逆にガス拡散層２ｂ、３ｂが固体高分子電解質膜１への水蒸気の供給、または酸化剤極３で生成された水の除去の妨げになる問題点があった。
【００１０】
一方、反応ガス中の燃料ガス中の反応活性物質の水素濃度及び酸化剤ガス中の反応活性物質の酸素濃度はそれぞれのガス流路の入口側ほど高く、ガス流路を通過する過程で消費され出口に近いほど低下する。この傾向はガスの利用率が高いほど大きくなる。この反応ガスの濃度分布に従って電極面内の電流密度分布が生じ、発電性能が低くなる問題点があった。
【００１１】
また、反応により水が生成されるので、ガス流路の出口に近いほどガス拡散層内の相対湿度が上昇し、水蒸気の凝縮が発生し反応ガスの拡散阻害が発生しやすい問題点がある。特に酸化剤極３側ではこの現象が顕著に表れる。
【００１２】
従来技術１として、特開平８−２６４１９２号公報には、ガス拡散層を複数に区分し、ガス流路中の反応ガス濃度の高い領域ほどガス透過性を低くしたガス拡散層（電極基材）が開示されている。ガス透過性を低くしたい区画ほど、カーボン繊維からなるピッチの充填率を低くするか、撥水処理剤の付着量を少なくしている。
【００１３】
従来技術２として、特開平１１−１５４５２３号公報には、ガス入口に近い部分がガス出口に近い部分より小さいガス透過度を有する燃料電池単セルが開示されている。ガス透過度を小さくするために、ガス拡散層の気孔率を小さくするか、厚さを大きくしている。
【００１４】
従来技術３として、特開２００１−１３５３２６号公報には、触媒層とガス拡散層の間に、ガス入口側部分の厚さが出口側の厚さより大きくなるようにフッ素樹脂とカーボンブラックからなる混合層を設けた燃料電池が開示されている。
【００１５】
従来技術４として、特開２００１−２３６９７６号公報には、カソード側のガス拡散層の酸化剤ガス導入口付近に対向するアノード側のガス拡散層の領域の水分透過性を、カソード側のガス拡散層の酸化剤ガス排出口付近に対向するアノード側のガス拡散層の領域の水分透過性よりも高くした燃料電池が開示されている。水分透過性を高くするためにガス拡散層中の撥水剤含有量を少なくしている。
【００１６】
【発明が解決しようとする課題】
しかしながら、従来技術１〜４のいずれも、それぞれの区分に応じて異なるガス拡散層を用いたり、区分に応じて量の異なる撥水剤で処理しなければならないため、工程が複雑で、量産性に欠ける問題点がある。またガス拡散層とセパレータが接触している部分に対向する触媒層の部分には、反応ガスが供給されにくいという問題は解決できないため、十分な効果が得られない問題点がある。
【００１７】
本発明は上記課題を解決したもので、ガス拡散層とセパレータが接触している部分に対向する触媒層の部分に反応ガスを十分供給でき、かつ電解質への水蒸気の供給と生成水の排出が十分できるガス拡散部材、ガス拡散電極および燃料電池を提供する。また本発明はガス流路の流れに沿う反応ガスの反応活性物質濃度分布や相対湿度分布を平均化し、発電性能を高くできるガス拡散部材、ガス拡散電極および燃料電池を提供する。
【００１８】
【課題を解決するための手段】
上記技術的課題を解決するために、本発明の請求項１において講じた技術的手段（以下、第１の技術的手段と称する。）は、一方側が燃料電池セルの触媒層に隣接し、他方側がガス流路を有する導電性部材に隣接し、前記ガス流路より前記触媒層に反応ガスを供給するガス透過性と導電性を有するガス拡散部材において、該ガス拡散部材の基材より大きなガス透過性を有する穴部が前記導電性部材側から前記触媒層側に向かって設けられていることを特徴とするガス拡散部材である。
【００１９】
上記第１の技術的手段による効果は、以下のようである。
【００２０】
すなわち、ガス拡散部材の基材より大きなガス透過性を有する穴部がガス拡散部材に設けられているので、ガス流路から供給された反応ガスは穴部を通りガス拡散部材と導電性部材が接触している部分に対向する触媒層に十分供給できる。また、穴部を通って水蒸気が電解質に供給され、逆に生成水が穴部を通って排出されるので、電解質への水蒸気の供給と生成水の排出が十分できる。これらにより、このガス拡散部材を使用した燃料電池の発電性能を向上できる。
【００２１】
上記技術的課題を解決するために、本発明の請求項２において講じた技術的手段（以下、第２の技術的手段と称する。）は、前記穴部は、前記導電性部材側から前記触媒層側に貫通する貫通穴であることを特徴とする請求項１記載のガス拡散部材である。
【００２２】
上記第２の技術的手段による効果は、以下のようである。
【００２３】
すなわち、穴部が貫通穴であるので、より多くの反応ガスをガス拡散部材と導電性部材が接触している部分に対向する触媒層に供給できるとともに水蒸気の供給・排出がしやすい効果を奏する。
【００２４】
上記技術的課題を解決するために、本発明の請求項３において講じた技術的手段（以下、第３の技術的手段と称する。）は、前記穴部は、該穴部の前記導電性部材側からの深さが前記ガス拡散部材の前記導電性部材側から前記触媒層側に向かう厚さより小さいことを特徴とする請求項１記載のガス拡散部材である。
【００２５】
上記第３の技術的手段による効果は、以下のようである。
【００２６】
すなわち、穴部の深さがガス拡散部材の厚さより小さいので、穴部の位置に置いてもガス拡散部材と触媒層の接触部が形成され、触媒層で発生した電気をガス拡散部材を介して出力できるため、このガス拡散部材を使用した燃料電池の発電性能を向上できる。
【００２７】
上記技術的課題を解決するために、本発明の請求項４において講じた技術的手段（以下、第４の技術的手段と称する。）は、前記穴部の断面の径または幅が、互いに隣接する前記ガス流路の間隔より大きいことを特徴とする請求項１〜３のいずれかに記載のガス拡散部材である。
【００２８】
上記第４の技術的手段による効果は、以下のようである。
【００２９】
すなわち、穴部の断面の径または幅が、互いに隣接するガス流路の間隔より大きいので、ガス拡散部材が導電性部材に当接されたとき穴部が必ずガス流路に開口部を有するようにできる。これにより、燃料電池の組立時のコストを低減できる。
【００３０】
上記技術的課題を解決するために、本発明の請求項５において講じた技術的手段（以下、第５の技術的手段と称する。）は、多数の前記穴部が設けられ、前記ガス流路の上流側から下流側に向かって前記穴部の数が増加していることを特徴とする請求項１〜４のいずれかに記載のガス拡散部材である。
【００３１】
上記第５の技術的手段による効果は、以下のようである。
【００３２】
すなわち、ガス流路の上流側から下流側に向かって穴部の数が増加しているので、ガス流路の下流側の方が上流側より、反応ガスが触媒層に供給されやすく、燃料ガス側では触媒層に水蒸気が供給されやすく、酸化剤ガス側では水蒸気が排出されやすいため、ガス流路の流れに沿う反応ガスの反応活性物質濃度分布や相対湿度分布を平均化できる。ガス拡散部材として同質の基材を用いることができるので、量産性に適している。これにより、このガス拡散部材を使用した燃料電池の発電性能を向上でき、低コスト化できる。
【００３３】
上記技術的課題を解決するために、本発明の請求項６において講じた技術的手段（以下、第６の技術的手段と称する。）は、請求項１〜５のいずれかのガス拡散部材の前記導電性部材に隣接する側の反対側に触媒層が設けられていることを特徴とするガス拡散電極である。
【００３４】
上記第６の技術的手段による効果は、以下のようである。
【００３５】
すなわち、ガス拡散部材と導電性部材が接触している部分に対向する触媒層の部分に反応ガスを十分供給できるガス拡散部材を用いているので、供給された反応ガスを触媒層に十分供給できる。ガス流路の流れに沿う反応ガスの反応活性物質濃度分布や相対湿度分布を平均化できるガス拡散部材を用いているので、触媒層に到達する反応活性物質濃度分布を平均化でき、かつ触媒層のフラディング現象を防止できる。
【００３６】
上記技術的課題を解決するために、本発明の請求項７において講じた技術的手段（以下、第７の技術的手段と称する。）は、電解質からなる電解質部材と、該電解質部材の一方面に隣接する酸化剤極触媒層と、前記電解質部材の他方面に隣接する燃料極触媒層と、前記酸化剤極触媒層の前記電解質部材に隣接する側の反対側に隣接する酸化剤極用ガス拡散部材と、該酸化剤極用ガス拡散部材の前記酸化剤極触媒層に隣接する側の反対側に隣接し酸化剤ガス流路を有する導電性部材と、前記燃料極触媒層の前記電解質部材に隣接する側の反対側に隣接する燃料極用ガス拡散部材と、該燃料極用ガス拡散部材の前記燃料極触媒層に隣接する側の反対側に隣接し燃料ガス流路を有する導電性部材とを備え、前記酸化剤極用ガス拡散部材、前記燃料極用ガス拡散部材の少なくとも一方が請求項１〜５のいずれかに記載のガス拡散部材であることを特徴とする燃料電池である。
【００３７】
上記第７の技術的手段による効果は、以下のようである。
【００３８】
すなわち、ガス拡散部材と導電性部材が接触している部分に対向する触媒層の部分に反応ガスを十分供給できるガス拡散部材を用いているので、供給された反応ガスを触媒層に十分供給でき、発電性能に優れた燃料電池ができる。ガス流路の流れに沿う反応ガスの反応活性物質濃度分布や相対湿度分布を平均化できるガス拡散部材を用いているので、触媒層に到達する反応活性物質濃度分布を平均化でき、かつ触媒層のフラディング現象を防止できるため、発電性能に優れた燃料電池ができる。
【００３９】
【発明の実施の形態】
本発明者は鋭意研究し、ガス拡散部材を複雑な構成にすることなく、上記技術的課題を解決した。
【００４０】
以下、本発明の実施形態について、図面に基づいて説明する。図１は本発明の第１実施形態のガス拡散部材の説明図であり、図１（ａ）は平面図、図１（ｂ）はＡＡ断面図である。ガス拡散部材１１の基材は、撥水処理されたカーボンペーパーである。基材は多孔質で所定のガス透過性を有している。ガス拡散部材１１には一方面１１ａから他方面１１ｂに貫通する多数の貫通穴１２が設けられている。
【００４１】
図２は第１実施形態の燃料電池単セルの構造を説明する部分断面図である。図１１と同じ部材は同じ符号を使用し説明は省略する。固体高分子電解質膜（電解質部材）１の一方面に燃料極触媒層１３が設けられ、他方面に酸化剤極１４が設けられている。燃料極触媒層１３、酸化剤極触媒層１４は、カーボン粒子にそれぞれの触媒を担持しペースト化してスクリーン印刷することにより形成されている。
【００４２】
ガス拡散部材１１は、一方面１１ａがセパレータ（導電性部材）４または５に隣接し、他方面１１ｂが燃料極触媒層１３または酸化剤極触媒層１４に隣接している。貫通穴１２は、燃料ガス流路４ａまたは酸化剤ガス流路５ａに連通した状態にある。燃料ガス流路４ａに供給された燃料ガスは紙面垂直方向に流れている。その燃料ガスは燃料ガス流路４ａから貫通穴１２に拡散する。貫通穴１２に拡散した燃料ガスの一部が燃料極触媒層１３に到達し、燃料ガス中の反応活性物質である水素が燃料極触媒層１３の電極反応に消費される。貫通穴１２に拡散した燃料ガスの他の部分は貫通穴１２の側面から拡散し、ガス拡散部材１１とセパレータ４が接触している部分４ｂに対向する燃料極触媒層１３の部分１５に到達する。この部分１５でも、燃料ガス中の水素が燃料極触媒層１３の電極反応に消費される。水素が消費されると貫通穴１２中の水素濃度が低くなるが、燃料ガス流路４ａから水素が拡散し供給される。
【００４３】
ガス拡散部材１１の基材は多孔質でありガス透過性を有するが、貫通穴１２はガス透過を妨げる部材がなく、基材よりガス透過性が大きい。このため、燃料極触媒層１３で水素が消費されても、燃料ガス流路４ａから水素が早く拡散され、貫通穴１２中の水素濃度は燃料ガス流路４ａ中の水素濃度に近いものになっている。燃料極触媒層１３の部分１５にはガス拡散部材１１の基材中を通って供給されるが、部分１５は貫通穴１２から近い位置にあるので、早く水素が拡散でき、部分１５にも十分水素を供給できる。
【００４４】
燃料ガス中には固体高分子電解質膜１を加湿状態にするために水蒸気が含まれているが、水蒸気も貫通穴１２を通って早く拡散するので、固体高分子電解質膜１へ水蒸気を十分供給できる。
【００４５】
一方、酸化剤極触媒層１４側においても、燃料極触媒層１３側と同様に、ガス拡散部材１１とセパレータ５が接触している部分５ｂに対向する酸化剤極触媒層１４の部分１６に酸化剤ガス中の反応活性物質である酸素を十分供給できる。また、酸化剤極触媒層１４で電極反応で生成された生成水は貫通穴１２を通って早く拡散するので、生成水の十分な排出が可能となる。
【００４６】
この結果、燃料極触媒層１３、酸化剤極触媒層１４に反応活性物質を十分供給できるので、燃料電池の発電特性が向上する。また生成水を十分排出できるため、酸化剤極触媒層１４が水浸しになるいわゆるフラッディング現象の発生が抑制されるので、燃料電池の発電特性が向上するとともに信頼性も向上する。
【００４７】
図３は本発明の第２実施形態のガス拡散部材の説明断面図である。平面図は図１（ａ）と同様である。ガス拡散部材２１の基材は、ガス拡散部材１１と同じ撥水処理されたカーボンペーパーである。ガス拡散部材２１には一方面２１ａから他方面２１ｂに向かって穴部２２が設けられている。穴部２２の深さは、ガス拡散部材２１の一方面２１ａから他方面２１ｂに向かう厚さ（ガス拡散部材２１の厚さ）より小さい。すなわち、穴部２２は他方面２１ｂ側には開口していない。
【００４８】
図４は第２実施形態の燃料電池単セルの構造を説明する部分断面図である。図２と同じ部材は同じ符号を使用し説明は省略する。ガス拡散部材２１は、一方面２１ａがセパレータ４または５に隣接し、他方面２１ｂが燃料極触媒層１３または酸化剤極触媒層１４に隣接している。穴部２２は、燃料ガス流路４ａまたは酸化剤ガス流路５ａに連通した状態にある。燃料ガス流路４ａに供給された燃料ガスは紙面垂直方向に流れている。その燃料ガスは燃料ガス流路４ａから穴部２２に拡散する。穴部２２に拡散した燃料ガスの一部は穴部２２の底部に到達し、そこから燃料極触媒層１３側にガス拡散部材２１の基材中を拡散し、燃料極触媒層１３に到達し、燃料ガス中の反応活性物質である水素が燃料極触媒層１３の電極反応に消費される。穴部２２に拡散した燃料ガスの他の部分は穴部２２の側面から拡散し、ガス拡散部材２１とセパレータ４が接触している部分４ｂに対向する燃料極触媒層１３の部分１５に到達する。この部分１５でも、燃料ガス中の水素が燃料極触媒層１３の電極反応に消費される。水素が消費されると穴部２２中の水素濃度が低くなるが、燃料ガス流路４ａから水素が拡散し供給される。
【００４９】
ガス拡散部材２１の基材は多孔質でありガス透過性を有するが、穴部２２はガス透過を妨げる部材がなく、基材よりガス透過性が大きい。このため、燃料極触媒層１３で水素が消費されても、燃料ガス流路４ａから水素が早く拡散され、穴部２２中の水素濃度は燃料ガス流路４ａ中の水素濃度に近いものになっている。燃料極触媒層１３の部分１５にはガス拡散部材２１の基材中を通って供給されるが、部分１５は穴部２２から近い位置にあるので、早く水素が拡散でき、部分１５にも十分水素を供給できる。
【００５０】
第２実施形態では、穴部２２は燃料極触媒層１３に連通されていないが、穴部２２の底部と燃料極触媒層１３の距離はガス拡散部材２１の厚さより小さいので、水素を早く供給できる。第１実施形態では、貫通穴１１に対向する燃料極触媒層１３部分で生成された電子は燃料極触媒層１３中を移動した後、燃料極触媒層１３とガス拡散部材１１とが当接した部分からガス拡散部材１１側に流れるしかない。これに対して、第２実施形態では、穴部２２に対向する燃料極触媒層１３部分もガス拡散部材２１に当接しているので、この部分で生成された電子は直接ガス拡散部材２１に流れることができるため、セル抵抗を小さくし、発電特性を向上できる。
【００５１】
燃料ガス中には固体高分子電解質膜１を加湿状態にするために水蒸気が含まれているが、水蒸気も穴部２２を通って早く拡散するので、固体高分子電解質膜１へ水蒸気を十分供給できる。
【００５２】
一方、酸化剤極触媒層１４側においても、燃料極触媒層１３側と同様に、ガス拡散部材２１とセパレータ５が接触している部分５ｂに対向する酸化剤極触媒層１４の部分１６に酸化剤ガス中の反応活性物質である酸素を十分供給できる。また、燃料極触媒層１３側と同様に、穴部２２に対向する部分でも酸化剤極触媒層１４とガス拡散部材２１が当接しているので、酸化剤極触媒層１４のその部分にもガス拡散部材２１から直接電子が流れ込みことができ、セル抵抗を小さくし、発電特性を向上できる。さらに、穴部２２の底部と酸化剤極触媒層１４の距離はガス拡散部材２１の厚さより小さいため、酸化剤極触媒層１４で電極反応で生成された生成水は早く穴部２２に拡散し、穴部２２を通って早く拡散するので、生成水の十分な排出が可能となる。
【００５３】
この結果、燃料極触媒層１３、酸化剤極触媒層１４に反応活性物質を十分供給できるので、燃料電池の発電特性が向上する。また生成水を十分排出できるため、酸化剤極触媒層１４が水浸しになる、いわゆるフラッディング現象の発生が抑制されるので、燃料電池の発電特性が向上するとともに信頼性も向上する。さらにセル抵抗を小さくでき、発電特性が向上できる。
【００５４】
図５は本発明の第３実施形態のガス拡散電極の説明断面図である。平面図は図１（ａ）と同様である。ガス拡散部材２１は図３に示す第２実施形態と同じものを用いた。ガス拡散部材２１には一方面２１ａから他方面２１ｂに向かって穴部２２が設けられている。他方面２１ｂに触媒層３３が形成されている。燃料極と酸化剤極では触媒層の成分が異なるが、同じ構成をしている。このガス拡散電極を用いた燃料電池単セルは図４で説明した第２実施形態と同様の構造となる。その作用効果も第２実施形態と同様である。
【００５５】
第１実施形態から第３実施形態では貫通穴１２または穴部２２の断面は円であるが、四角形でも、その他の形状でもかまわない。
【００５６】
第１実施形態から第３実施形態では貫通穴１２または穴部２２の径は、ガス流路の幅と一致する形で説明したが、特に限定されない。しかし、穴部の径または幅が、互いに隣接するガス流路の間隔（Ｗ１）より大きくすることによって、ガス拡散部材がセパレータ（導電性部材）当接されたとき、穴部が必ずガス流路に開口部を有するようにできる。すなわち、穴部が必ずガス流路と連通した状態にできる。これにより、ガス拡散部材とセパレータの位置ずれを気にすることなく組み立てても、穴部をガス流路と連通させることができるので、燃料電池の組立時のコストを低減できる。
【００５７】
望ましくは、穴部の径または幅が、互いに隣接するガス流路の間隔（Ｗ１）とガス流路の幅（Ｗ２）の合計より小さい方がよい。穴部の径または幅が、互いに隣接するガス流路の間隔（Ｗ１）とガス流路の幅（Ｗ２）の合計より大きい場合、隣接するガス流路間にショートパスが形成され、発電性能に悪影響を与える恐れがある。なお、互いに隣接するガス流路の間隔（Ｗ１）はガス拡散部材１１とセパレータ５が接触している部分５ｂの幅のことである。
【００５８】
図６は本発明の第４実施形態のガス拡散部材の平面図である。ガス拡散部材３１の基材は、第１実施形態のガス拡散部材１１と同様の撥水処理されたカーボンペーパーである。ガス拡散部材３１には一方面から他方面に貫通する多数の貫通穴３２が設けられている。貫通穴１２がガス拡散部材１１の平面上にほぼ均一に分布している第１実施形態と異なり、第４実施形態では貫通穴３２はガス流路の上流側から下流側に向かって貫通穴３２の数が増加するように分布している。図６において、白抜き矢印はガス流路のガス通流方向を表している。ガス拡散部材３１の中央付近に１つの貫通穴３２が設けられ、これを頂点として図６のように三角形状に貫通穴３２の数がガス流路の下流側に向かって増加している。
【００５９】
第１実施形態で説明したように、貫通穴が存在すると、触媒層に反応ガスが供給されやすく、水蒸気が供給、排出されやすい。供給された原料ガス（燃料ガスまたは酸化剤ガス）はガス流路の上流側から下流側に流れるにつれて原料ガス中の反応活性物質（水素または酸素）が消費され、反応活性物質の濃度が薄くなる。また燃料ガス側ではガス流路の上流側から下流側に流れるにつれて燃料ガス中の水蒸気が少なくなってくる。一方、酸化剤ガス側では酸化剤極で電極反応（２）により水が生成するので、ガス流路の上流側から下流側に流れるにつれて酸化剤ガス中の水蒸気が増加する。
【００６０】
第４実施形態ではガス流路の上流側から下流側に向かって穴部の数が増加しているので、下流側になるにつれて触媒層に反応活性物質が供給されやすく、かつ燃料極側では電解質に水蒸気が供給されやすく、酸化剤極側では生成水が排出されやすい。このため、触媒層の反応活性物質濃度分布や電解質の相対湿度分布を平均化できる。これらの平均化をガス拡散部材の局部的性質の変化によらず、同質のガス拡散部材基材を用いて実現できるので、量産性に適している。これにより、燃料電池の発電性能を向上でき、低コスト化できる。
【００６１】
以下、実施例を用いて説明する。
【００６２】
（実施例１）
１０００ｇの水に、３００ｇのカーボンブラック（平均粒径：４０ｎｍ）を混入し、撹拌機を用いて十分間撹拌してから、ダイキン工業株式会社製のテトラフルオロエチレン（以下、ＰＴＦＥと称する。）の含有濃度が６０％のディスパージョン原液（商品名：ＰＯＬＹＦＬＯＮ、Ｄ１グレード）を２５０ｇ添加して更に十分間撹拌して、カーボンインクを作製した。このカーボンインクにカーボンペーパー（東レ株式会社製、トレカＴＧＰ−０６０、１３７ｍｍ×１６９ｍｍ、厚さ１８０μｍ）を投入して、十分にカーボンインクを含浸させた。次に８０℃の温度に保った乾燥炉で余分な水分を蒸発させた後、焼結温度３９０℃で６０分保持して、ＰＴＦＥを焼結し撥水カーボンペーパーを作製した。
【００６３】
この撥水カーボンペーパーに図６のように貫通穴３２をあけた。貫通穴３２の径は３．８ｍｍである。ガス通流方向に平行方向の貫通穴３２の並びを列、列と直交する方向の貫通穴３２の並びを行と称する。貫通穴３２は９行、１７列に並んでおり、一番ガス上流側の行には１つの貫通穴３２が設けられ、そこから１行ごとに貫通穴３２が２個増加している。貫通穴３２の列ピッチは８ｍｍ、行ピッチは１０ｍｍである。このようにして酸化剤極用ガス拡散部材を作製した。
【００６４】
一方、燃料極用ガス拡散部材は、酸化剤極用ガス拡散部材と同様に作製した撥水カーボンペーパーを使用した。燃料極用ガス拡散部材には穴部が設けられていない。
【００６５】
次に、白金担持濃度が４６ｗｔ％の白金担持カーボン触媒（田中貴金属工業株式会社製：ＴＥＣ１０Ｅ５０Ｅ、以下Ｐｔ／Ｃと称する。）１２ｇと５ｗｔ％濃度のイオン交換樹脂溶液（旭化成工業株式会社製：ＳＳ−１０８０）１８０ｇと水２３ｇ、成形助剤としてのイソプロピルアルコール２３ｇと十分に混合し触媒ペーストを製作した。この触媒ペーストをドクターブレード法により白金担持量が０．６ｍｇ／ｃｍ^２になるようにテトラフロロエチレンシートに触媒層を形成後、乾燥させて、酸化剤極シートとする。酸化剤極シートの大きさは、１３７ｍｍ×１６９ｍｍ、厚さ　０．１０ｍｍ（触媒層厚さは約１０μｍ）である。
【００６６】
同様な方法によってＰｔＣの代わりに白金（担持濃度３０ｗｔ％）−ルテニウム（担持濃度２３ｗｔ％）合金担持カーボン触媒（田中貴金属工業株式会社製：ＴＥＣ６１Ｅ５４、以下Ｐｔ−Ｒｕ／Ｃと称する。）で形成されたものを燃料極シートとする。燃料極シートの大きさは、１３７ｍｍ×１６９ｍｍ、厚さ　０．１０ｍｍ（触媒層厚さは約１０μｍ）である。
【００６７】
厚みが２５μのイオン交換膜（デュポン社製：Ｎａｆｉｏｎ１１１）を固体高分子電解質膜として使用した。イオン交換膜の一方面に酸化剤極シートを、他方面に燃料極シートをそれぞれの触媒層がイオン交換膜に隣接するように当接される。すなわち、それぞれの触媒層がイオン交換膜に隣接するように、イオン交換膜を酸化剤極シートと燃料極シートで挟持した。この状態で、１３０℃、８Ｍｐａの条件で１分間ホットプレスして電解質膜に触媒層を転写し、それぞれのテトラフロロエチレンシートを剥がした。
【００６８】
この酸化剤極触媒層、燃料極触媒層を転写されたものの両側にそれぞれ酸化剤極用ガス拡散部材、燃料極用ガス拡散部材で挟持して、１２０℃、２Ｍｐａの条件で３分間ホットプレスして、ＭＥＡ接合体（膜・電極接合体）を作製した。
【００６９】
図７は、本実施例で使用したセパレータの構造を説明する説明図で、図７（ａ）は平面図、図７（ｂ）は断面図である。セパレータ４１はカーボン製で、その外形寸法は、１９８ｍｍ×２２９ｍｍ、厚さ２ｍｍである。セパレータ４１の一方面には、多数の直線溝形状のガス流路４２が設けられている。ガス流路４２の溝幅は２ｍｍ、深さは０．６ｍｍである。隣接するガス流路４２の間隔は２ｍｍである。白抜き矢印はガス流路４２のガス通流方向を表している。
【００７０】
このセパレータ４１を２つ用いて、上記で作製したＭＥＡ接合体の酸化剤極用ガス拡散部材、燃料極用ガス拡散部材にそれぞれガス流路４２側が隣接するようにＭＥＡ接合体を挟持し燃料電池単セルを作製した。
【００７１】
単セル温度７５℃とし、酸化剤ガスとして空気、燃料ガスとして１０ｐｐｍの一酸化炭素を含む天然ガス改質摸擬ガス（水素：７６％、窒素：４％、二酸化炭素：１９％、メタン：１％）をそれぞれ常圧で供給して水素利用率８５％、電流密度０．１７Ａ／ｃｍ^２に固定し空気利用率を変えてセル電圧を測定して評価した。
【００７２】
（実施例２）
図８は、実施例２で使用した燃料極用ガス拡散部材の平面図である。白抜き矢印はガス流路４２のガス通流方向を表している。実施例１と同様に作製した撥水カーボンペーパーに図８のように貫通穴５２をあけて燃料極用ガス拡散部材５１を作製した。貫通穴５２の断面形状は一辺が３．８ｍｍの正方形である。ガス通流方向に平行方向の貫通穴５２の並びを列、列と直交する方向の貫通穴５２の並びを行と称する。貫通穴５２は１５行、７列に並んでいる。一番ガス上流側の行は燃料極用ガス拡散部材５１のガス上流側端付近の図８左右中央に設けられた１つの貫通穴５２である。一番ガス上流側の行から順に図８に示すように貫通穴５２が増加している。貫通穴５２の列ピッチは１２ｍｍ、行ピッチは１０ｍｍである。
【００７３】
一方、酸化剤極用ガス拡散部材は、実施例１と同様に作製した撥水カーボンペーパーを使用した。酸化剤極用ガス拡散部材には穴部が設けられていない。
【００７４】
この酸化剤極用ガス拡散部材および燃料極用ガス拡散部材５１を用いた以外は、実施例１と同様の部材を使用し、同様にして燃料電池単セルを作製した。
【００７５】
単セル温度７５℃とし、酸化剤ガスとして空気、燃料ガスとして１０ｐｐｍの一酸化炭素を含む天然ガス改質摸擬ガス（水素：７６％、窒素：４％、二酸化炭素：１９％、メタン：１％）をそれぞれ常圧で供給して空気利用率４０％、電流密度０．１７Ａ／ｃｍ^２に固定し水素利用率を変えてセル電圧を測定して評価した。
【００７６】
（比較例）
燃料極用ガス拡散部材、酸化剤極用ガス拡散部材とも実施例１で作製した撥水カーボンペーパーをそのまま使用した。すなわち、ここで使用する燃料極用ガス拡散部材、酸化剤極用ガス拡散部材とも穴部は設けられていない。この燃料極用ガス拡散部材、酸化剤極用ガス拡散部材を用いた以外は、実施例１と同様の部材を使用し、同様にして燃料電池単セルを作製した。
【００７７】
評価は実施例１と比較するために実施例１と同じ方法で、また実施例２と比較するために実施例２と同じ方法で行った。
【００７８】
（評価結果）
図９、１０に評価結果を示す。図９は実施例１と比較例の評価結果を比較したグラフ図、図１０は実施例２と比較例の評価結果を比較したグラフ図である。実施例１、２は比較例に比べてセル出力特性に優れていることが分かった。特に酸化剤極用ガス拡散部材に本発明を使用した実施例１には顕著な効果が現れている。
【００７９】
以上のように、ガス拡散部材に、ガス拡散部材の基材より大きなガス透過性を有する穴部が導電性部材側から触媒層側に向かって設けられていることにより、発電性能が向上できた。また、穴部の配置として、ガス流路の上流側から下流側に向かって穴部の数が増加しているするように設けられていることにより、発電性能が向上できた。その作用効果は上述した通りである。
【００８０】
（付記）
以上説明した内容には以下の技術的思想も含まれる。
【００８１】
・ガス透過性と導電性を有する基材を製造する基材作製工程と、前記基材に、その一方面から他方面に向かう穴部を作製する穴部作製工程が設けられていることを特徴とするガス拡散部材の製造方法。
【００８２】
・ガス透過性と導電性を有する基材を製造する基材作製工程と、前記基材を撥水処理する撥水処理工程と、前記基材に、その一方面から他方面に向かう穴部を作製する穴部作製工程が設けられていることを特徴とするガス拡散部材の製造方法。
【００８３】
・ガス透過性と導電性を有する基材を製造する基材作製工程と、前記基材に、その一方面から他方面に向かう穴部を作製する穴部作製工程と、前記基材の他方面に触媒層を設ける触媒層作製工程が設けられていることを特徴とするガス拡散電極の製造方法。
【００８４】
【発明の効果】
以上のように、本発明は、一方側が燃料電池セルの触媒層に隣接し、他方側がガス流路を有する導電性部材に隣接し、前記ガス流路より前記触媒層に反応ガスを供給するガス透過性と導電性を有するガス拡散部材において、該ガス拡散部材の基材より大きなガス透過性を有する穴部が前記導電性部材側から前記触媒層側に向かって設けられていることを特徴とするガス拡散部材およびこのガス拡散部材の前記導電性部材に隣接する側の反対側に触媒層が設けられていることを特徴とするガス拡散電極およびそのガス拡散部材を用いた燃料電池であるので、ガス拡散層とセパレータが接触している部分に対向する触媒層の部分に反応ガスを十分供給でき、かつ電解質への水蒸気の供給と生成水の排出が十分できる。
【図面の簡単な説明】
【図１】本発明の第１実施形態のガス拡散部材の説明図で、図１（ａ）は平面図、図１（ｂ）はＡＡ断面図である。
【図２】第１実施形態の燃料電池単セルの構造を説明する部分断面図
【図３】本発明の第２実施形態のガス拡散部材の説明断面図
【図４】第２実施形態の燃料電池単セルの構造を説明する部分断面図
【図５】本発明の第３実施形態のガス拡散電極の説明断面図
【図６】本発明の第４実施形態のガス拡散部材の平面図
【図７】本実施例で使用したセパレータの構造を説明する説明図で、図７（ａ）は平面図、図７（ｂ）は断面図である。
【図８】実施例２で使用した酸化剤極用ガス拡散部材の平面図
【図９】実施例１と比較例の評価結果を比較したグラフ図
【図１０】実施例２と比較例の評価結果を比較したグラフ図
【図１１】一般的な固体高分子電解質型燃料電池の単セル構造を説明する部分断面図
【符号の説明】
１…固体高分子電解質膜（電解質部材）
４、５…セパレータ（導電性部材）
４ａ…燃料ガス流路（ガス流路）
５ａ…酸化剤ガス流路（ガス流路）
１１、２１、３１…ガス拡散部材
１２、３２、５２…貫通穴（穴部）
１３…燃料極触媒層（触媒層）
１４…酸化剤極触媒層（触媒層）
２２…穴部
５１…燃料極用ガス拡散部材（ガス拡散部材）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas diffusion member, a gas diffusion electrode, and a fuel cell.
[0002]
[Prior art]
In order to reduce air pollution as much as possible, it is important to reduce exhaust gas from automobiles. As one of the measures, electric vehicles are used, but they have not been widely used due to problems such as charging facilities and mileage. Vehicles using fuel cells are seen as the most promising clean vehicles. Among the fuel cells, solid polymer electrolyte fuel cells are most promising for automobiles because they operate at low temperatures.
[0003]
In general, a fuel cell is formed by stacking a large number of single cells, and the single cell is a separator (conductive member having a gas flow path) formed by sandwiching an electrolyte between two electrodes (a fuel electrode and an oxidant electrode). It has a structure sandwiched by. Fuel gas and oxidant gas are supplied to the fuel electrode and oxidant electrode, respectively, through gas channels provided in the respective separators, and generate electricity by electrochemical reaction, generating clean electricity without any emissions other than water. It is attracting attention as a device. Generally, the electrode has a configuration in which a catalyst layer is provided on a gas diffusion layer. However, in some cases, a single cell is assembled by providing a catalyst layer on the electrolyte, forming the gas diffusion layer with a separate gas diffusion member, and making the gas diffusion member adjacent to the catalyst layer.
[0004]
A solid polymer electrolyte fuel cell uses a solid polymer electrolyte membrane as an electrolyte. FIG. 11 is a partial cross-sectional view illustrating a single cell structure of a general solid polymer electrolyte fuel cell. A solid polymer electrolyte membrane 1 is sandwiched between a fuel electrode 2 and an oxidant electrode 3 and joined to form a membrane / electrode assembly 10. The fuel electrode 2 includes a catalyst layer 2a and a gas diffusion layer 2b, and the oxidizer electrode 3 includes a catalyst layer 3a and a gas diffusion layer 3b. The membrane / electrode assembly 10 is sandwiched between separators 4 and 5 to constitute a single cell of a fuel cell. The separators 4 and 5 are conductive members having a fuel gas passage 4a and an oxidizing gas passage 5a, respectively.
[0005]
The humidified hydrogen or the fuel gas containing hydrogen passes through the gas diffusion layer 2b which is also a current collector, reaches the catalyst layer 2a, and the following electrode reaction occurs.
[0006]
Embedded image

Proton H generated at fuel electrode 2 ⁺ Move toward the oxidant electrode 3 through the solid polymer electrolyte membrane 1 with water molecules. At the same time, the electrons e generated at the fuel electrode 2 ⁻ Moves to the oxidizer electrode 3 through the catalyst layer 2a and the gas diffusion layer 2b, through a load connected between the fuel electrode 2 and the oxidizer electrode 3 via an external circuit.
[0007]
On the other hand, at the oxidant electrode 3, the oxidant gas containing humidified oxygen passes through the gas diffusion layer 3b which is also a current collector, reaches the catalyst layer 3a, and from the external circuit through the gas diffusion layer 3b and the catalyst layer 3a. The protons H which are received by the flowing electrons, are reduced by the following reaction, and move from the fuel electrode 2 through the solid polymer electrolyte membrane 1. ⁺ And combine to form water.
[0008]
Embedded image

Part of the generated water enters the solid polymer electrolyte membrane 1 due to the concentration gradient, diffuses and moves toward the fuel electrode 2, and part of the water evaporates and passes through the catalyst layer 3a and the gas diffusion layer 3b. It diffuses to the oxidizing gas channel 5a and is discharged together with the unreacted oxidizing gas.
[0009]
The fuel gas flow path 4a has a groove structure for electrical connection between the separator 4 and the gas diffusion layer 2b. The oxidizing gas channel 5a also has a groove structure. In the part where the separators 4 and 5 are in contact with the gas diffusion layers 2b and 3b, the gas diffusion layers 2b and 3b do not directly contact the reaction gas (fuel gas or oxidizing gas), and the fuel gas flow path 4a and the oxidizing gas The reaction gas that has entered the gas diffusion layers 2b and 3b from the flow channel 5a must be transported by diffusion. The gas diffusion layers 2b and 3b originally have a function of supplying a reaction gas also to a catalyst layer opposed to a portion where the gas diffusion member and the conductive member are in contact with each other. The reaction gas is not sufficiently supplied to the portions of the catalyst layers 2a and 3a facing the portions where the diffusion layers 2b and 3b are in contact with the separators 4 and 5, and the electrode reactions of Formulas (1) and (2) are not performed. There is a problem that the power generation performance becomes sufficient and the power generation performance becomes low. On the other hand, the gas diffusion layers 2b and 3b have a problem that the gas diffusion layers 2b and 3b hinder the supply of water vapor to the solid polymer electrolyte membrane 1 or the removal of water generated at the oxidant electrode 3.
[0010]
On the other hand, the hydrogen concentration of the reactive substance in the fuel gas in the reaction gas and the oxygen concentration of the reactive substance in the oxidizing gas are higher toward the inlet side of each gas flow path, and are consumed in the process of passing through the gas flow paths. It decreases as you approach the exit. This tendency increases as the gas utilization rate increases. According to the concentration distribution of the reaction gas, a current density distribution in the electrode surface is generated, and there is a problem that power generation performance is reduced.
[0011]
In addition, since water is generated by the reaction, the relative humidity in the gas diffusion layer rises closer to the outlet of the gas flow path, and there is a problem that water vapor is condensed and diffusion of the reaction gas is easily inhibited. This phenomenon is particularly noticeable on the oxidant electrode 3 side.
[0012]
As prior art 1, Japanese Patent Application Laid-Open No. 8-264192 discloses a gas diffusion layer (electrode substrate) in which a gas diffusion layer is divided into a plurality of regions, and the gas permeability becomes lower in a region of the gas flow path where the concentration of the reactive gas is higher. Is disclosed. The lower the gas permeability, the lower the filling rate of the carbon fiber pitch or the smaller the amount of the water-repellent treatment agent attached.
[0013]
As prior art 2, Japanese Patent Application Laid-Open No. H11-154523 discloses a fuel cell unit cell having a portion near a gas inlet having a smaller gas permeability than a portion near a gas outlet. In order to reduce the gas permeability, the porosity or the thickness of the gas diffusion layer is reduced.
[0014]
As prior art 3, Japanese Patent Application Laid-Open No. 2001-135326 discloses a mixture of a fluororesin and carbon black between a catalyst layer and a gas diffusion layer such that the thickness of a gas inlet side portion is larger than the thickness of an outlet side. A fuel cell with a layer is disclosed.
[0015]
As prior art 4, Japanese Patent Application Laid-Open No. 2001-236976 discloses that the moisture permeability of the region of the gas diffusion layer on the anode side facing the vicinity of the oxidizing gas inlet of the gas diffusion layer on the cathode side is determined by the gas diffusion on the cathode side. A fuel cell is disclosed in which the moisture permeability of the region of the gas diffusion layer on the anode side facing the vicinity of the oxidant gas outlet of the layer is higher. The content of the water repellent in the gas diffusion layer is reduced in order to increase the moisture permeability.
[0016]
[Problems to be solved by the invention]
However, all of the prior arts 1 to 4 have to use a different gas diffusion layer according to each section or to treat with a different amount of water repellent according to the section, so that the process is complicated and mass production is difficult. There is a problem that lacks. Further, the problem that the reaction gas is difficult to be supplied cannot be solved in the portion of the catalyst layer opposite to the portion where the gas diffusion layer and the separator are in contact, and thus there is a problem that a sufficient effect cannot be obtained.
[0017]
The present invention has solved the above-mentioned problems, and can sufficiently supply a reaction gas to a portion of a catalyst layer opposite to a portion where a gas diffusion layer and a separator are in contact with each other, and supply of steam to an electrolyte and discharge of generated water. Provided are a gas diffusion member, a gas diffusion electrode, and a fuel cell which can be sufficiently provided. Further, the present invention provides a gas diffusion member, a gas diffusion electrode, and a fuel cell capable of averaging the distribution of the concentration of a reactive substance and the distribution of relative humidity of a reaction gas along the flow of a gas flow path and improving the power generation performance.
[0018]
[Means for Solving the Problems]
In order to solve the above technical problem, the technical means (hereinafter referred to as first technical means) taken in claim 1 of the present invention has one side adjacent to the catalyst layer of the fuel cell and the other side. A gas diffusion member having a gas permeability and conductivity, the side of which is adjacent to a conductive member having a gas flow path and supplies a reaction gas from the gas flow path to the catalyst layer, wherein a gas larger than a base material of the gas diffusion member is provided. A gas diffusion member, wherein a hole having permeability is provided from the conductive member side to the catalyst layer side.
[0019]
The effects of the first technical means are as follows.
[0020]
That is, since the gas diffusion member is provided with a hole having a greater gas permeability than the base material of the gas diffusion member, the reaction gas supplied from the gas flow path passes through the hole and the gas diffusion member and the conductive member are separated from each other. The catalyst layer can be sufficiently supplied to the catalyst layer facing the contacting portion. Further, since the steam is supplied to the electrolyte through the hole and the generated water is discharged through the hole, the supply of the water vapor to the electrolyte and the discharge of the generated water can be sufficiently performed. Thus, the power generation performance of the fuel cell using the gas diffusion member can be improved.
[0021]
In order to solve the above technical problem, a technical means (hereinafter referred to as a second technical means) taken in claim 2 of the present invention is as follows. The gas diffusion member according to claim 1, wherein the gas diffusion member is a through hole penetrating to the layer side.
[0022]
The effects of the second technical means are as follows.
[0023]
That is, since the hole is a through hole, more reactive gas can be supplied to the catalyst layer facing the portion where the gas diffusion member and the conductive member are in contact with each other, and the effect of easily supplying and discharging steam can be obtained. .
[0024]
In order to solve the above technical problem, the technical means (hereinafter, referred to as third technical means) taken in claim 3 of the present invention is that the hole is formed by the conductive member of the hole. The gas diffusion member according to claim 1, wherein a depth from a side is smaller than a thickness of the gas diffusion member from the conductive member side toward the catalyst layer side.
[0025]
The effects of the third technical means are as follows.
[0026]
That is, since the depth of the hole is smaller than the thickness of the gas diffusion member, a contact portion between the gas diffusion member and the catalyst layer is formed even at the position of the hole, and electricity generated in the catalyst layer is passed through the gas diffusion member. Output power, the power generation performance of a fuel cell using this gas diffusion member can be improved.
[0027]
In order to solve the above technical problem, the technical means (hereinafter, referred to as fourth technical means) taken in claim 4 of the present invention is that the diameter or width of the cross section of the hole is adjacent to each other. The gas diffusion member according to any one of claims 1 to 3, wherein the distance is larger than an interval between the gas flow paths.
[0028]
The effects of the fourth technical means are as follows.
[0029]
That is, since the diameter or width of the cross section of the hole is larger than the distance between the gas flow paths adjacent to each other, the hole always has an opening in the gas flow path when the gas diffusion member is brought into contact with the conductive member. Can be. This can reduce the cost of assembling the fuel cell.
[0030]
In order to solve the above technical problem, a technical means (hereinafter referred to as a fifth technical means) taken in claim 5 of the present invention is provided with a large number of the hole portions, 5. The gas diffusion member according to claim 1, wherein the number of the holes increases from an upstream side to a downstream side. 6.
[0031]
The effects of the fifth technical means are as follows.
[0032]
That is, since the number of holes increases from the upstream side to the downstream side of the gas flow path, the reaction gas is more easily supplied to the catalyst layer on the downstream side of the gas flow path than on the upstream side, and the fuel gas On the side, steam is easily supplied to the catalyst layer, and on the oxidizing gas side, steam is easily discharged, so that the distribution of the concentration of the reactive substance and the relative humidity distribution of the reaction gas along the flow of the gas flow path can be averaged. Since a homogeneous substrate can be used as the gas diffusion member, it is suitable for mass production. Thereby, the power generation performance of the fuel cell using the gas diffusion member can be improved, and the cost can be reduced.
[0033]
In order to solve the above technical problem, the technical means (hereinafter referred to as sixth technical means) taken in claim 6 of the present invention is a gas diffusion member according to any one of claims 1 to 5. A gas diffusion electrode, wherein a catalyst layer is provided on a side opposite to a side adjacent to the conductive member.
[0034]
The effects of the sixth technical means are as follows.
[0035]
That is, since the gas diffusion member that can sufficiently supply the reaction gas to the portion of the catalyst layer facing the portion where the gas diffusion member and the conductive member are in contact is used, the supplied reaction gas can be sufficiently supplied to the catalyst layer. . Since the gas diffusion member that can average the distribution of the reactive substance and the relative humidity of the reactive gas along the flow of the gas flow path is used, the concentration distribution of the reactive substance reaching the catalyst layer can be averaged, and the catalyst layer can be averaged. Flooding phenomenon can be prevented.
[0036]
In order to solve the above technical problem, the technical means (hereinafter referred to as seventh technical means) taken in claim 7 of the present invention comprises an electrolyte member made of an electrolyte, and one surface of the electrolyte member. An oxidant electrode catalyst layer adjacent to the first electrode, a fuel electrode catalyst layer adjacent to the other surface of the electrolyte member, and an oxidant electrode gas adjacent to an opposite side of the oxidant electrode catalyst layer adjacent to the electrolyte member. A diffusion member, a conductive member having an oxidant gas flow path adjacent to a side of the oxidant electrode gas diffusion member opposite to a side adjacent to the oxidant electrode catalyst layer, and the electrolyte member of the fuel electrode catalyst layer A fuel gas diffusion member adjacent to the side opposite to the side adjacent to the fuel electrode, and a conductive member having a fuel gas flow path adjacent to the side of the fuel electrode gas diffusion member opposite to the side adjacent to the fuel electrode catalyst layer The gas diffusion member for the oxidant electrode, the fuel electrode At least one of the gas diffusion member is a fuel cell, which is a gas diffusion member according to claim 1.
[0037]
The effects of the seventh technical means are as follows.
[0038]
That is, since the gas diffusion member that can sufficiently supply the reaction gas to the portion of the catalyst layer facing the portion where the gas diffusion member and the conductive member are in contact is used, the supplied reaction gas can be sufficiently supplied to the catalyst layer. Thus, a fuel cell having excellent power generation performance can be obtained. Since the gas diffusion member that can average the distribution of the reactive substance and the relative humidity of the reactive gas along the flow of the gas flow path is used, the concentration distribution of the reactive substance reaching the catalyst layer can be averaged, and the catalyst layer can be averaged. Therefore, a fuel cell having excellent power generation performance can be obtained.
[0039]
BEST MODE FOR CARRYING OUT THE INVENTION
The inventors of the present invention have made intensive studies and have solved the above-mentioned technical problems without making the gas diffusion member a complicated structure.
[0040]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view of a gas diffusion member according to a first embodiment of the present invention. FIG. 1 (a) is a plan view, and FIG. 1 (b) is an AA sectional view. The base material of the gas diffusion member 11 is carbon paper subjected to a water-repellent treatment. The substrate is porous and has a predetermined gas permeability. The gas diffusion member 11 has a large number of through holes 12 penetrating from one surface 11a to the other surface 11b.
[0041]
FIG. 2 is a partial cross-sectional view illustrating the structure of the single fuel cell according to the first embodiment. The same members as those in FIG. 11 are denoted by the same reference numerals, and description thereof will be omitted. The fuel electrode catalyst layer 13 is provided on one surface of the solid polymer electrolyte membrane (electrolyte member) 1, and the oxidant electrode 14 is provided on the other surface. The fuel electrode catalyst layer 13 and the oxidant electrode catalyst layer 14 are formed by carrying each catalyst on carbon particles, forming a paste, and performing screen printing.
[0042]
The gas diffusion member 11 has one surface 11a adjacent to the separator (conductive member) 4 or 5 and the other surface 11b adjacent to the fuel electrode catalyst layer 13 or the oxidant electrode catalyst layer. The through hole 12 is in a state of communicating with the fuel gas passage 4a or the oxidizing gas passage 5a. The fuel gas supplied to the fuel gas passage 4a flows in a direction perpendicular to the plane of the drawing. The fuel gas diffuses from the fuel gas passage 4a to the through hole 12. Part of the fuel gas diffused into the through holes 12 reaches the anode catalyst layer 13, and hydrogen, which is a reactive substance in the fuel gas, is consumed by the electrode reaction of the anode catalyst layer 13. Another portion of the fuel gas diffused into the through hole 12 diffuses from the side surface of the through hole 12 and reaches a portion 15 of the fuel electrode catalyst layer 13 facing the portion 4b where the gas diffusion member 11 and the separator 4 are in contact. . Also in this portion 15, hydrogen in the fuel gas is consumed for the electrode reaction of the fuel electrode catalyst layer 13. When the hydrogen is consumed, the hydrogen concentration in the through hole 12 decreases, but the hydrogen is diffused and supplied from the fuel gas flow path 4a.
[0043]
Although the base material of the gas diffusion member 11 is porous and has gas permeability, the through hole 12 has no member that impedes gas permeation and has higher gas permeability than the base material. Therefore, even if hydrogen is consumed in the fuel electrode catalyst layer 13, hydrogen is rapidly diffused from the fuel gas flow path 4a, and the hydrogen concentration in the through hole 12 becomes close to the hydrogen concentration in the fuel gas flow path 4a. ing. The part 15 of the fuel electrode catalyst layer 13 is supplied through the base material of the gas diffusion member 11, but since the part 15 is located near the through hole 12, hydrogen can be diffused quickly, and Hydrogen can be supplied.
[0044]
Water vapor is contained in the fuel gas to make the solid polymer electrolyte membrane 1 humidified. However, since the water vapor also diffuses quickly through the through-holes 12, the steam is sufficiently supplied to the solid polymer electrolyte membrane 1. it can.
[0045]
On the other hand, also on the oxidant electrode catalyst layer 14 side, similarly to the fuel electrode catalyst layer 13 side, the oxidant electrode catalyst layer 14 is oxidized to the portion 16 of the oxidant electrode catalyst layer 14 facing the portion 5b where the gas diffusion member 11 and the separator 5 are in contact. Oxygen which is a reaction active substance in the agent gas can be sufficiently supplied. Further, generated water generated by the electrode reaction in the oxidant electrode catalyst layer 14 diffuses quickly through the through-holes 12, so that the generated water can be sufficiently discharged.
[0046]
As a result, the reaction active substance can be sufficiently supplied to the fuel electrode catalyst layer 13 and the oxidant electrode catalyst layer 14, so that the power generation characteristics of the fuel cell are improved. Further, since the generated water can be sufficiently discharged, the so-called flooding phenomenon in which the oxidant electrode catalyst layer 14 is flooded is suppressed, so that the power generation characteristics of the fuel cell and the reliability are improved.
[0047]
FIG. 3 is an explanatory sectional view of a gas diffusion member according to a second embodiment of the present invention. The plan view is the same as FIG. The base material of the gas diffusion member 21 is the same water-repellent carbon paper as the gas diffusion member 11. The gas diffusion member 21 is provided with a hole 22 from one surface 21a toward the other surface 21b. The depth of the hole 22 is smaller than the thickness (the thickness of the gas diffusion member 21) from one surface 21 a to the other surface 21 b of the gas diffusion member 21. That is, the hole 22 does not open on the other surface 21b side.
[0048]
FIG. 4 is a partial sectional view illustrating the structure of a single fuel cell according to the second embodiment. The same members as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. The gas diffusion member 21 has one surface 21 a adjacent to the separator 4 or 5, and the other surface 21 b adjacent to the fuel electrode catalyst layer 13 or the oxidant electrode catalyst layer 14. The hole 22 is in a state of communicating with the fuel gas passage 4a or the oxidizing gas passage 5a. The fuel gas supplied to the fuel gas passage 4a flows in a direction perpendicular to the plane of the drawing. The fuel gas diffuses from the fuel gas passage 4a into the hole 22. A part of the fuel gas diffused into the hole 22 reaches the bottom of the hole 22, diffuses through the base material of the gas diffusion member 21 toward the anode catalyst layer 13, and reaches the anode catalyst layer 13. In addition, hydrogen as a reaction active substance in the fuel gas is consumed for the electrode reaction of the fuel electrode catalyst layer 13. Another portion of the fuel gas diffused into the hole 22 diffuses from the side surface of the hole 22 and reaches the portion 15 of the anode catalyst layer 13 facing the portion 4b where the gas diffusion member 21 and the separator 4 are in contact. . Also in this portion 15, hydrogen in the fuel gas is consumed for the electrode reaction of the fuel electrode catalyst layer 13. When the hydrogen is consumed, the hydrogen concentration in the hole 22 becomes low, but the hydrogen is diffused and supplied from the fuel gas flow path 4a.
[0049]
The base material of the gas diffusion member 21 is porous and has gas permeability, but the hole 22 has no member that impedes gas permeation and has higher gas permeability than the base material. Therefore, even if hydrogen is consumed in the fuel electrode catalyst layer 13, hydrogen is rapidly diffused from the fuel gas flow path 4a, and the hydrogen concentration in the hole 22 becomes close to the hydrogen concentration in the fuel gas flow path 4a. ing. The portion 15 of the fuel electrode catalyst layer 13 is supplied through the base material of the gas diffusion member 21, but since the portion 15 is located near the hole 22, hydrogen can be diffused quickly, and Hydrogen can be supplied.
[0050]
In the second embodiment, the hole 22 is not communicated with the anode catalyst layer 13, but the distance between the bottom of the hole 22 and the anode catalyst layer 13 is smaller than the thickness of the gas diffusion member 21, so that hydrogen is supplied quickly. it can. In the first embodiment, the electrons generated in the portion of the fuel electrode catalyst layer 13 facing the through hole 11 move in the fuel electrode catalyst layer 13 and then the fuel electrode catalyst layer 13 and the gas diffusion member 11 come into contact with each other. There is no choice but to flow from the portion to the gas diffusion member 11 side. On the other hand, in the second embodiment, the portion of the fuel electrode catalyst layer 13 facing the hole 22 also contacts the gas diffusion member 21, so that the electrons generated in this portion flow directly to the gas diffusion member 21. Therefore, the cell resistance can be reduced and the power generation characteristics can be improved.
[0051]
Water vapor is contained in the fuel gas in order to make the solid polymer electrolyte membrane 1 humidified. However, since the water vapor also diffuses quickly through the holes 22, the steam is sufficiently supplied to the solid polymer electrolyte membrane 1. it can.
[0052]
On the other hand, also on the oxidant electrode catalyst layer 14 side, similarly to the fuel electrode catalyst layer 13 side, oxidation is performed on the portion 16 of the oxidant electrode catalyst layer 14 facing the portion 5b where the gas diffusion member 21 and the separator 5 are in contact. Oxygen which is a reaction active substance in the agent gas can be sufficiently supplied. Further, as in the case of the fuel electrode catalyst layer 13 side, the oxidant electrode catalyst layer 14 and the gas diffusion member 21 are also in contact with the portion facing the hole 22, so that the gas of the oxidant electrode catalyst layer 14 Electrons can flow directly from the diffusion member 21, thereby reducing cell resistance and improving power generation characteristics. Further, since the distance between the bottom of the hole 22 and the oxidant electrode catalyst layer 14 is smaller than the thickness of the gas diffusion member 21, the water generated by the electrode reaction in the oxidant electrode catalyst layer 14 diffuses into the hole 22 quickly. , And quickly diffuses through the holes 22, so that the generated water can be sufficiently discharged.
[0053]
As a result, the reaction active substance can be sufficiently supplied to the fuel electrode catalyst layer 13 and the oxidant electrode catalyst layer 14, so that the power generation characteristics of the fuel cell are improved. In addition, since the generated water can be sufficiently discharged, the occurrence of the so-called flooding phenomenon in which the oxidant electrode catalyst layer 14 is flooded is suppressed, so that the power generation characteristics of the fuel cell and the reliability are improved. Further, the cell resistance can be reduced, and the power generation characteristics can be improved.
[0054]
FIG. 5 is an explanatory sectional view of a gas diffusion electrode according to a third embodiment of the present invention. The plan view is the same as FIG. The same gas diffusion member 21 as that of the second embodiment shown in FIG. 3 was used. The gas diffusion member 21 is provided with a hole 22 from one surface 21a toward the other surface 21b. The catalyst layer 33 is formed on the other surface 21b. Although the components of the catalyst layer differ between the fuel electrode and the oxidant electrode, they have the same configuration. The single cell of the fuel cell using the gas diffusion electrode has the same structure as the second embodiment described with reference to FIG. The operation and effect are the same as in the second embodiment.
[0055]
In the first to third embodiments, the cross section of the through hole 12 or the hole 22 is a circle, but may be a square or another shape.
[0056]
In the first to third embodiments, the diameter of the through hole 12 or the hole 22 has been described as being equal to the width of the gas flow path, but is not particularly limited. However, when the diameter or width of the hole is made larger than the distance (W1) between the gas flow paths adjacent to each other, the hole is necessarily formed when the gas diffusion member is brought into contact with the separator (conductive member). Can have an opening. That is, it is possible to make the hole always communicate with the gas flow path. Thus, even when the gas diffusion member and the separator are assembled without worrying about the displacement, the hole can be communicated with the gas flow path, so that the cost of assembling the fuel cell can be reduced.
[0057]
Desirably, the diameter or width of the hole is smaller than the sum of the interval (W1) between the gas flow paths adjacent to each other and the width (W2) of the gas flow path. If the diameter or width of the hole is larger than the sum of the interval (W1) between the gas flow paths adjacent to each other and the width (W2) of the gas flow path, a short path is formed between the adjacent gas flow paths, and the power generation performance is reduced. May have adverse effects. The interval (W1) between the gas flow paths adjacent to each other is the width of the portion 5b where the gas diffusion member 11 and the separator 5 are in contact.
[0058]
FIG. 6 is a plan view of a gas diffusion member according to a fourth embodiment of the present invention. The base material of the gas diffusion member 31 is the same water-repellent carbon paper as the gas diffusion member 11 of the first embodiment. The gas diffusion member 31 has a large number of through holes 32 penetrating from one surface to the other surface. Unlike the first embodiment in which the through holes 12 are substantially uniformly distributed on the plane of the gas diffusion member 11, in the fourth embodiment the through holes 32 are formed from the upstream side to the downstream side of the gas flow path. Are distributed so that the number increases. In FIG. 6, the white arrows indicate the gas flow direction of the gas flow path. One through-hole 32 is provided near the center of the gas diffusion member 31, and the number of the through-holes 32 increases in a triangular shape as shown in FIG.
[0059]
As described in the first embodiment, when the through hole exists, the reaction gas is easily supplied to the catalyst layer, and the steam is easily supplied and discharged. As the supplied source gas (fuel gas or oxidant gas) flows from the upstream side to the downstream side of the gas flow path, the reactive material (hydrogen or oxygen) in the raw material gas is consumed, and the concentration of the reactive material decreases. . On the fuel gas side, the amount of water vapor in the fuel gas decreases as it flows from the upstream side to the downstream side of the gas flow path. On the other hand, on the oxidant gas side, water is generated by the electrode reaction (2) at the oxidant electrode, so that the water vapor in the oxidant gas increases as it flows from the upstream side to the downstream side of the gas flow path.
[0060]
In the fourth embodiment, the number of holes increases from the upstream side to the downstream side of the gas flow path, so that the reaction active material is more easily supplied to the catalyst layer toward the downstream side, and the electrolyte is provided at the fuel electrode side. Is easily supplied to the oxidant electrode side, and the generated water is easily discharged on the oxidant electrode side. Therefore, the distribution of the concentration of the reactive substance in the catalyst layer and the distribution of the relative humidity of the electrolyte can be averaged. This averaging can be realized by using a gas diffusion member base material of the same quality regardless of a change in the local properties of the gas diffusion member, so that it is suitable for mass production. Thereby, the power generation performance of the fuel cell can be improved, and the cost can be reduced.
[0061]
Hereinafter, a description will be given using an example.
[0062]
(Example 1)
300 g of carbon black (average particle size: 40 nm) is mixed into 1000 g of water, and the mixture is sufficiently stirred using a stirrer. Then, tetrafluoroethylene (hereinafter, referred to as PTFE) manufactured by Daikin Industries, Ltd. is added. 250 g of a dispersion stock solution (trade name: POLYFLON, D1 grade) having a content of 60% was added, and the mixture was stirred for further sufficient time to prepare a carbon ink. Carbon paper (Toray Industries, Inc., Torayca TGP-060, 137 mm × 169 mm, thickness 180 μm) was charged into the carbon ink to sufficiently impregnate the carbon ink. Next, excess water was evaporated in a drying furnace maintained at a temperature of 80 ° C., and then the PTFE was sintered at a sintering temperature of 390 ° C. for 60 minutes to produce water-repellent carbon paper.
[0063]
A through hole 32 was made in this water-repellent carbon paper as shown in FIG. The diameter of the through hole 32 is 3.8 mm. The arrangement of the through holes 32 in the direction parallel to the gas flow direction is referred to as a column, and the arrangement of the through holes 32 in the direction orthogonal to the column is referred to as a row. The through holes 32 are arranged in nine rows and seventeen columns, and one through hole 32 is provided in the row closest to the gas upstream, and the number of the through holes 32 increases by two from each row. The column pitch of the through holes 32 is 8 mm, and the row pitch is 10 mm. Thus, an oxidant electrode gas diffusion member was produced.
[0064]
On the other hand, as the fuel electrode gas diffusion member, water-repellent carbon paper produced in the same manner as the oxidizer electrode gas diffusion member was used. No hole is provided in the fuel electrode gas diffusion member.
[0065]
Next, 12 g of a platinum-supported carbon catalyst having a platinum support concentration of 46 wt% (manufactured by Tanaka Kikinzoku Kogyo KK: TEC10E50E, hereinafter referred to as Pt / C) and an ion exchange resin solution having a concentration of 5 wt% (manufactured by Asahi Kasei Corporation: SS) -1080) 180 g, water 23 g, and isopropyl alcohol 23 g as a molding aid were sufficiently mixed to prepare a catalyst paste. The amount of platinum carried on the catalyst paste was 0.6 mg / cm by a doctor blade method. ² After a catalyst layer is formed on a tetrafluoroethylene sheet so as to obtain an oxidant electrode sheet, the catalyst layer is dried. The size of the oxidant electrode sheet is 137 mm × 169 mm and the thickness is 0.10 mm (the thickness of the catalyst layer is about 10 μm).
[0066]
In a similar manner, instead of PtC, a platinum (supporting concentration 30 wt%)-ruthenium (supporting concentration 23 wt%) alloy supported carbon catalyst (manufactured by Tanaka Kikinzoku Kogyo KK: TEC61E54, hereinafter referred to as Pt-Ru / C) is used. These are used as fuel electrode sheets. The size of the fuel electrode sheet is 137 mm × 169 mm and the thickness is 0.10 mm (the thickness of the catalyst layer is about 10 μm).
[0067]
An ion exchange membrane having a thickness of 25 μm (manufactured by DuPont: Nafion 111) was used as the solid polymer electrolyte membrane. The oxidant electrode sheet is abutted on one side of the ion exchange membrane and the fuel electrode sheet is abutted on the other side such that the respective catalyst layers are adjacent to the ion exchange membrane. That is, the ion exchange membrane was sandwiched between the oxidant electrode sheet and the fuel electrode sheet such that each catalyst layer was adjacent to the ion exchange membrane. In this state, the catalyst layer was transferred to the electrolyte membrane by hot pressing at 130 ° C. and 8 Mpa for 1 minute, and the respective tetrafluoroethylene sheets were peeled off.
[0068]
The oxidant electrode catalyst layer and the fuel electrode catalyst layer were transcribed on both sides of an oxidant electrode gas diffusion member and a fuel electrode gas diffusion member, respectively, and hot-pressed at 120 ° C. and 2 Mpa for 3 minutes. Thus, an MEA assembly (membrane-electrode assembly) was produced.
[0069]
7A and 7B are explanatory views for explaining the structure of the separator used in the present embodiment. FIG. 7A is a plan view, and FIG. 7B is a sectional view. The separator 41 is made of carbon and has external dimensions of 198 mm × 229 mm and a thickness of 2 mm. On one surface of the separator 41, a number of linear groove-shaped gas flow paths 42 are provided. The groove width of the gas channel 42 is 2 mm, and the depth is 0.6 mm. The distance between adjacent gas channels 42 is 2 mm. The white arrow indicates the gas flow direction of the gas flow channel 42.
[0070]
Using two separators 41, the MEA assembly is sandwiched between the oxidizer electrode gas diffusion member and the fuel electrode gas diffusion member of the MEA assembly manufactured above such that the gas flow path 42 side is adjacent to the fuel cell. A single cell was fabricated.
[0071]
A single cell temperature of 75 ° C., a natural gas reforming simulation gas containing air as an oxidizing gas and 10 ppm of carbon monoxide as a fuel gas (hydrogen: 76%, nitrogen: 4%, carbon dioxide: 19%, methane: 1) %) Are supplied at normal pressure to supply 85% of hydrogen and a current density of 0.17 A / cm. ² The cell voltage was measured and evaluated while changing the air utilization rate.
[0072]
(Example 2)
FIG. 8 is a plan view of the fuel electrode gas diffusion member used in the second embodiment. The white arrow indicates the gas flow direction of the gas flow channel 42. A water-repellent carbon paper produced in the same manner as in Example 1 was provided with a through-hole 52 as shown in FIG. The cross-sectional shape of the through hole 52 is a square having a side of 3.8 mm. An arrangement of the through holes 52 in a direction parallel to the gas flow direction is referred to as a column, and an arrangement of the through holes 52 in a direction perpendicular to the column is referred to as a row. The through holes 52 are arranged in 15 rows and 7 columns. The row closest to the gas upstream is one through hole 52 provided at the center in the left and right direction in FIG. 8 near the gas upstream end of the fuel electrode gas diffusion member 51. As shown in FIG. 8, the through holes 52 increase in order from the row on the upstream side of the gas. The column pitch of the through holes 52 is 12 mm, and the row pitch is 10 mm.
[0073]
On the other hand, as the oxidant electrode gas diffusion member, water-repellent carbon paper produced in the same manner as in Example 1 was used. No holes are provided in the oxidant electrode gas diffusion member.
[0074]
Except for using the oxidant electrode gas diffusion member and the fuel electrode gas diffusion member 51, the same members as in Example 1 were used, and a fuel cell single cell was produced in the same manner.
[0075]
A single cell temperature of 75 ° C., a natural gas reforming simulation gas containing air as an oxidizing gas and 10 ppm of carbon monoxide as a fuel gas (hydrogen: 76%, nitrogen: 4%, carbon dioxide: 19%, methane: 1) %) Are supplied at normal pressure to supply air at a rate of 40% and a current density of 0.17 A / cm. ² And the cell voltage was measured while changing the hydrogen utilization rate to evaluate.
[0076]
(Comparative example)
The water-repellent carbon paper prepared in Example 1 was used as it was for the fuel electrode gas diffusion member and the oxidant electrode gas diffusion member. That is, neither the gas diffusion member for the fuel electrode nor the gas diffusion member for the oxidant electrode used here has a hole. Except for using the fuel electrode gas diffusion member and the oxidant electrode gas diffusion member, the same members as in Example 1 were used, and a single fuel cell was produced in the same manner.
[0077]
The evaluation was performed in the same manner as in Example 1 for comparison with Example 1, and in the same manner as in Example 2 for comparison with Example 2.
[0078]
(Evaluation results)
9 and 10 show the evaluation results. FIG. 9 is a graph comparing the evaluation results of Example 1 and the comparative example, and FIG. 10 is a graph comparing the evaluation results of Example 2 and the comparative example. It was found that Examples 1 and 2 had better cell output characteristics than Comparative Examples. In particular, a remarkable effect appears in Example 1 in which the present invention is used for the gas diffusion member for an oxidant electrode.
[0079]
As described above, since the gas diffusion member is provided with the hole having gas permeability higher than that of the base material of the gas diffusion member from the conductive member side to the catalyst layer side, the power generation performance was improved. . Further, the arrangement of the holes is such that the number of holes increases from the upstream side to the downstream side of the gas flow path, so that the power generation performance can be improved. The operation and effect are as described above.
[0080]
(Note)
The contents described above include the following technical ideas.
[0081]
-Characterized by being provided with a base material manufacturing step of manufacturing a base material having gas permeability and conductivity, and a hole manufacturing step of forming a hole part from one surface to the other surface of the base material. A method for manufacturing a gas diffusion member.
[0082]
A base material producing step of manufacturing a base material having gas permeability and conductivity, a water repellent treatment step of subjecting the base material to a water repellent treatment, and forming a hole in the base material from one surface to the other surface. A method for producing a gas diffusion member, comprising a step of producing a hole to be produced.
[0083]
A base material manufacturing step of manufacturing a base material having gas permeability and conductivity, a hole forming step of forming a hole from one surface to the other surface of the base material, and the other surface of the base material A method for producing a gas diffusion electrode, wherein a catalyst layer preparation step of providing a catalyst layer is provided.
[0084]
【The invention's effect】
As described above, according to the present invention, one side is adjacent to the catalyst layer of the fuel cell, the other side is adjacent to the conductive member having the gas flow path, and the reaction gas is supplied from the gas flow path to the catalyst layer. In the gas diffusion member having permeability and conductivity, a hole having gas permeability larger than a base material of the gas diffusion member is provided from the conductive member side to the catalyst layer side. A gas diffusion member, and a gas diffusion electrode, characterized in that a catalyst layer is provided on a side of the gas diffusion member opposite to a side adjacent to the conductive member. The reaction gas can be sufficiently supplied to the portion of the catalyst layer opposite to the portion where the gas diffusion layer and the separator are in contact, and the supply of water vapor to the electrolyte and the discharge of generated water can be sufficiently performed.
[Brief description of the drawings]
FIGS. 1A and 1B are explanatory views of a gas diffusion member according to a first embodiment of the present invention, wherein FIG. 1A is a plan view and FIG.
FIG. 2 is a partial cross-sectional view illustrating the structure of a single fuel cell according to the first embodiment.
FIG. 3 is an explanatory sectional view of a gas diffusion member according to a second embodiment of the present invention.
FIG. 4 is a partial cross-sectional view illustrating the structure of a single fuel cell according to a second embodiment.
FIG. 5 is an explanatory sectional view of a gas diffusion electrode according to a third embodiment of the present invention.
FIG. 6 is a plan view of a gas diffusion member according to a fourth embodiment of the present invention.
FIGS. 7A and 7B are explanatory views illustrating the structure of a separator used in the present example, where FIG. 7A is a plan view and FIG. 7B is a cross-sectional view.
FIG. 8 is a plan view of a gas diffusion member for an oxidant electrode used in Example 2.
FIG. 9 is a graph comparing the evaluation results of Example 1 and Comparative Example.
FIG. 10 is a graph comparing the evaluation results of Example 2 and Comparative Example.
FIG. 11 is a partial cross-sectional view illustrating a single cell structure of a general solid polymer electrolyte fuel cell.
[Explanation of symbols]
1: Solid polymer electrolyte membrane (electrolyte member)
4, 5 ... separator (conductive member)
4a: Fuel gas flow path (gas flow path)
5a: Oxidant gas flow path (gas flow path)
11, 21, 31 ... gas diffusion member
12, 32, 52 ... through-hole (hole)
13: fuel electrode catalyst layer (catalyst layer)
14: Oxidizer electrode catalyst layer (catalyst layer)
22 ... hole
51 ... Gas diffusion member for fuel electrode (gas diffusion member)

Claims (7)

One side is adjacent to the catalyst layer of the fuel cell, the other side is adjacent to a conductive member having a gas flow path, and a gas diffusion having gas permeability and conductivity for supplying a reaction gas from the gas flow path to the catalyst layer. A gas diffusion member, wherein a hole having greater gas permeability than a substrate of the gas diffusion member is provided from the conductive member side to the catalyst layer side. The gas diffusion member according to claim 1, wherein the hole is a through hole penetrating from the conductive member side to the catalyst layer side. The gas according to claim 1, wherein the hole has a depth from the conductive member side of the hole smaller than a thickness of the gas diffusion member from the conductive member side to the catalyst layer side. Diffusing member. The gas diffusion member according to any one of claims 1 to 3, wherein a diameter or a width of a cross section of the hole is larger than an interval between the gas passages adjacent to each other. The gas diffusion according to any one of claims 1 to 4, wherein a large number of the holes are provided, and the number of the holes increases from an upstream side to a downstream side of the gas flow path. Element. A gas diffusion electrode, wherein a catalyst layer is provided on a side of the gas diffusion member according to any one of claims 1 to 5 opposite to a side adjacent to the conductive member. An electrolyte member made of an electrolyte; an oxidant electrode catalyst layer adjacent to one surface of the electrolyte member; a fuel electrode catalyst layer adjacent to the other surface of the electrolyte member; and an oxidant electrode catalyst layer adjacent to the electrolyte member. A gas diffusion member for the oxidant electrode adjacent to the side opposite to the oxidizing electrode, and a conductive member having an oxidizing gas flow path adjacent to the side of the oxidizing electrode gas diffusion member adjacent to the side adjacent to the oxidant electrode catalyst layer. An anode member, a fuel electrode gas diffusion member adjacent to a side opposite to the side adjacent to the electrolyte member of the anode catalyst layer, and an opposite side of the anode electrode gas diffusion member to a side adjacent to the anode catalyst layer. And a conductive member having a fuel gas flow path adjacent to a side thereof, wherein at least one of the oxidant electrode gas diffusion member and the fuel electrode gas diffusion member is the gas diffusion member according to any one of claims 1 to 5. A fuel cell, which is a member.

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