JP3807038B2 - POLYMER ELECTROLYTE MEMBRANE-GAS DIFFUSION ELECTRODE AND METHOD FOR PRODUCING THE SAME - Google Patents
POLYMER ELECTROLYTE MEMBRANE-GAS DIFFUSION ELECTRODE AND METHOD FOR PRODUCING THE SAME Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0082—Organic polymers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Description
【０００１】
【発明の属する技術分野】
本発明は、固体高分子電解質型燃料電池に属するものである。
【０００２】
【従来の技術】
固体高分子電解質型燃料電池は、イオン交換膜（固体高分子電解質）の両面にガス拡散電極が配された構造をしており、反応ガスである酸素と水素とを電気化学的に反応させて、電力を得る装置である。ガス拡散電極は、ガス拡散部と反応部とからなり、アノードおよびカソードのそれぞれの反応部には白金系の金属粒子あるいはこれらの粒子を担持したカーボン粒子などが触媒として付与されている。
【０００３】
アノードでは、
２Ｈ２→４Ｈ＋＋４ｅ−
カソードでは、
Ｏ２＋４Ｈ＋＋４ｅ−→２Ｈ２Ｏ
の電気化学反応が進行する。
ガス拡散部は多孔体であり、反応部への反応ガス供給と集電との機能を有している。カソード側での反応によって生成する水は、ガス拡散部を介して排出される。このとき、生成水によりガス拡散部の孔が閉塞されると、反応ガスの透過性が低下し、電池特性が低下する。このため、ガス拡散部はガス透過性と導電性に加えて撥水性が要求される。ガス拡散部として、市販のカーボンペーパーをポリテトラフロロエチレンなどの撥水性樹脂を用いて、撥水性を付与したものなどが用いられる。カーボンペーパーは、直径１０μｍ程度の炭素の短繊維をバインダーで固めたものを焼成したものである。
【０００４】
【発明が解決しようとする課題】
ガス拡散部の抵抗を低減するために薄いカーボンペーパーの使用が好ましいが、薄いカーボンペーパーは機械的な強度が不充分であり、高分子電解質膜−ガス拡散電極体の作製工程において破壊等の問題が生じ、その取り扱いが容易でない。また、高分子電解質膜−ガス拡散電極体を作製するためには、高分子電解質膜に反応部を形成してこれにガス拡散部である撥水性のカーボンペーパーを圧接する方法、あるいはカーボンペーパーに反応部を形成してこれを高分子電解質膜に圧接する方法などがある。しかし、この圧接するとき、とくにカーボンペーパーのエッジ部分において炭素の短繊維が高分子電解質膜に必要以上に食い込むことがある。このために高分子電解質膜の機械的強度が低下したり、ときには貫通しピンホール生成の原因となる。
【０００５】
また、高分子電解質膜に１０μｍ程度の薄い反応部を形成し、これに撥水性のカーボンペーパーを圧接する場合、反応部とカーボンペーパーとの接触を十分にするために接合圧を高くする必要がある。接合圧を高くする場合、カーボンペーパーは圧迫に対して非弾性体的な性質を有しているために、上記のピンホール生成の問題に加えて、カーボンペーパーの潰れが発生し厚みが減少する。このガス拡散部の厚みが減少は不可逆的であり、集電体あるいはセパレータとの接触不良の原因となる。つまり、このカーボンペーパーの潰れのために接触抵抗が増大し、電池特性の低下を引き起こす。
【０００６】
固体高分子電解質型燃料電池の単セルを構成する部材において、圧迫に対して弾性体的な性質を示すものは高分子電解質膜だけである。しかし、高分子電解質膜は薄いために過度の圧迫を加えると前述のようなピンホール生成等の問題が生じる。したがって、圧迫に対して寸法変化が少なく非弾性体的な性質を有する集電体あるいはセパレータと高分子電解質膜−ガス拡散電極体との接触を十分に保つためには、各構成部材の高度な寸法精度が要求される。特に、複数のセルをスタックした場合、各構成部材の接触を十分に保つために要求される寸法精度はますます厳しくなる。しかし、各構成部材、特に高分子電解質膜−ガス拡散電極体の作製方法において、高分子電解質膜に反応部を圧接する工程や次のガス拡散部を圧接する工程を経るために、その寸法精度を十分に確保することは容易でない。したがって、各構成部材の接触を十分に保ち接触抵抗を低減するためには、高分子電解質膜以外に弾性体的な性質を有する構成部材が含まれることが望ましい。
【０００７】
請求項１の発明は、反応層とガス拡散層とを有するガス拡散電極を高分子電解質膜の少なくとも一方に備えた高分子電解質膜−ガス拡散電極体であって、前記ガス拡散層は、炭素粉末あるいは炭素繊維またはその両者の混合物と、ポリテトラフルオロエチレンの粉末と、ポリフッ化ビニリデンとを含有し、前記ポリテトラフルオロエチレンの粉末が、ポリフッ化ビニリデンによって、前記炭素粉末あるいは炭素繊維またはその両者の混合物に結着されてなることを特徴とする。
【０００８】
請求項２の発明は、高分子電解質膜−ガス拡散電極体の製造方法において、Ｎ−メチル−２−ピロリドンにポリフッ化ビニリデンを溶解した溶液に、炭素材とポリテトラフルオロエチレン粉末とを添加し、ガス拡散層形成用分散物を調製する工程と、この分散物を基体に塗布した後、水中に浸漬し、前記分散物に含有されるＮ−メチル−２−ピロリドンを抽出することにより、ポリフッ化ビニリデンを固化しガス拡散層を形成する工程と、触媒と高分子電解質樹脂を有する触媒分散物を前記ガス拡散層に塗布し、ガス拡散層上に反応層を形成する工程と、この反応層が高分子電解質膜に対向するよう、ガス拡散電極を形成した基体と高分子電解質膜とを圧接し、基体を除去して高分子電解質膜−ガス拡散電極接合体を形成する工程とを、備えてなることを特徴とする。
【０００９】
請求項３の発明は、請求項２の発明において、基体が剥離性を有するシートであることを特徴とする。
【００１０】
【発明の実施の形態】
次に、本発明にかかる高分子電解質膜−ガス拡散電極体およびその製造方法の一実施の形態を好適な図面を用いて説明する。
【００１１】
図１は、本発明である高分子電解質膜−ガス拡散電極体の概略図である。
【００１２】
図１によれば、高分子電解質膜１の両側に反応層２とガス拡散層３が配されている。４はガス拡散電極である。反応層２は触媒と高分子電解質樹脂とを有しており、ガス拡散層は導電材としての炭素材たとえば炭素粉末、撥水材としてのポリテトラフロロエチレン粉末および結着材としてのポリフッ化ビニリデンとを有している。
【００１３】
図２は、本発明である高分子電解質膜−ガス拡散電極体のガス拡散層の構造を示す概略図である。
【００１４】
図２によれば、炭素粉末とポリテトラフロロエチレン粉末がポリフッ化ビニリデンにより結着されクラスターを形成し、このクラスターとクラスターとの間にはランダムに空孔が形成されている。図２において、５はカーボン粒子、６はポリテトラフロロエチレン粒子、７はポリフッ化ビニリデン被膜である。
【００１５】
図３は、本発明である高分子電解質膜−ガス拡散電極体の製造方法のフロー図である。
【００１６】
まず、結着材としてのポリフッ化ビニリデン（ＰＶｄＦ、商品名：呉羽化学工業（株）、ＫＦ１１００）とＮ−メチル−２−ピロリドン（ＮＭＰ）とをそれぞれ適宜規定量秤量し、ＮＭＰにＰＶｄＦを加え、溶解してＰＶｄＦのＮＭＰ溶液を調製する。この溶液に導電材と撥水材としてのポリテトラフルオロエチレン粉末（ＰＴＦＥ粉末、商品名：ダイキン工業（株）、ルブロン）とを添加し、十分混合してガス拡散層形成用分散物を調製する。導電材としてはカーボン粉末（商品名：ＣＡＢＯＴ社、ＶＡＬＣＡＮ ＸＣ）を用いことができる。
【００１７】
このガス拡散層形成用分散物をこの分散物と親和性の低い基体、たとえば剥離性を有するシートに塗布する。剥離性を有するシートとしてはテトラフロロエチレン−ヘキサフロロプロピレン共重合体のシート（商品名：ダイキン工業（株）、ネオフロン）を用いることができ、このシートの上にガス拡散層形成用分散物を塗布する。塗布方法としては、ドクターブレード法などの方法を用いることができる。
【００１８】
ガス拡散層形成用分散物が乾燥するまでに、この分散物が塗布された基体を精製水に浸漬して、分散物に含まれるＮＭＰを抽出する。ＮＭＰが抽出されるとＰＶｄＦが固化し、この結着作用により導電材とＰＴＦＥ粉末とのクラスターが形成される。このとき、ＮＭＰと水の置換にともなう固化はＰＶｄＦの急激な体積収縮をともないクラスター部と水が占める部分がランダムに混在する状態が形成される。この水分を乾燥し除去すると水が占めた部分が空孔となり、孔を有するガス拡散層が形成される。このガス拡散層は、炭素材により電子伝導性を示し、適度に形成された孔が反応ガスの供給経路となり、混在する撥水材としてのＰＴＦＥ粉末により付与された撥水性が生成水による孔の閉塞を防止することで、優れたガス透過性を示す。
【００１９】
次に、この基体のガス拡散層に、触媒と高分子電解質樹脂とを有する触媒分散物を塗布して、反応層を形成してガス拡散電極を得る。触媒としてはカーボン粉末に白金粒子を担持したのものを用いることができ、高分子電解質樹脂としてはパーフロロスルホン酸樹脂の溶液（商品名：アルドリッチ社、Ｎａｆｉｏｎ溶液）を用いることができ、これらを規定量混合し、粘度を調整して触媒分散物を調製する。塗布方法としては、スクリーン印刷法を用いることができる。
【００２０】
次に、この基体に形成したガス拡散電極の反応層が高分子電解質膜と接触するように、高分子電解質膜の両面もしくは片側に積層して、圧接する。するとガス拡散電極が高分子電解質膜に接合され、基体を除去すると、高分子電解質膜−ガス拡散電極体が形成される。
【００２１】
本発明によれば、ＮＭＰに溶解するＰＶｄＦと、炭素粉末あるいは短繊維などの導電材と、撥水材としてのＰＴＦＥ粉末とからなる分散物を基体に塗布し、水に浸漬して分散物に含有されるＮＭＰを抽出することにより、非水溶性であるＰＶｄＦが固化してガス拡散層を形成する。このとき水が占める部分およびＰＶｄＦにより結着された炭素材（炭素粉末あるいは炭素繊維またはその混合物）とＰＴＦＥ粉末が占める部分が分離し、これらの２つの部分が細かくランダムに混在する状態が形成される。つぎに、この水分を乾燥除去するとその部分が空孔となって残留する。つまり、多孔状のガス拡散部が形成される。したがって、このガス拡散層はＰＶｄＦを結着材とした多孔質体でありかつＰＴＦＥ粉末により適度に撥水性が付与されているために電池反応にともなう生成水による閉塞が起こらない。よって、このガス拡散層は反応ガスの透過性が良く、炭素材により良好な電子伝導性を示す。また、このガス拡散層は弾性体的な性質を有しており、電池を構成するときに加わる圧迫により適度に変形し電池構成部材間の接触が十分となり接触抵抗が低減される。また高分子電解質膜との接合のときのピンホールの形成等の心配もない。
【００２２】
このように、本発明のガス拡散層は反応ガスの供給性と導電性に優れ、弾性体的な性質を有するので電池構成材間の接触抵抗を低減することができ、優れた発電能力を有する固体高分子電解質型燃料電池を提供できる。
【００２３】
【実施例】
親水性の有機溶媒、Ｎ−メチル−２−ピロリドン：１３０ｇにポリフッ化ビニリデン（呉羽化学工業（株）、ＫＦ１１００）４ｇを添加し溶解して、濃度が約３ｗｔ％結着材の溶液を調製した。この結着材の溶液に導電材としてカーボン粉末（ＣＡＢＯＴ社、ＶＡＬＣＡＮ ＸＣ）:１４ｇを攪拌しながら徐々に加えて、結着材の溶液中に導電材を分散させる。ついで、撥水材としてポリテトラフロロエチレン粉末（商品名：ダイキン工業（株）製、ルブロン）２ｇを加えて、十分攪拌して、ガス拡散部形成用分散物を調製した。
【００２４】
また、カーボン粉末（ＣＡＢＯＴ社、ＶＡＬＣＡＮ ＸＣ）の担体に白金を約３０ｗｔ％付与した白金担持カーボン触媒と市販の高分子電解質樹脂の溶液（アルドリッチケミカル社、Ｎａｆｉｏｎ溶液、５ｗｔ％）を用いて触媒分散物を調製した。すなわち、Ｎａｆｉｏｎ溶液：１５ｇに白金担持カーボン触媒：２ｇを加えて分散し、攪拌しながら７０℃に加熱し分散媒の一部を除去して触媒分散物の粘度を調整して、粘度が約１２０００ｃＰである触媒分散物を得た。
【００２５】
ドクターブレード法により、前述のガス拡散層形成用分散物を基体としてポリテトラフロロエチレン−ポリヘキサフロロプロピレン共重合体のシート（商品名：ダイキン工業（株）、ネオフロン）に塗布し、厚さ約０．１ｍｍのガス拡散層形成用分散物の塗布物を作製した。この塗布物が乾燥しない間に、この塗布物を精製水に約２０分間浸漬した後、室温にて自然乾燥して基体上にガス拡散層を形成した。
【００２６】
スクリーン印刷により、前述のガス拡散層に前述の触媒分散物を塗布、乾燥し、厚さ約１０μｍの反応層を形成し、基体上にガス拡散層と反応層とを有するガス拡散電極を作製した。
【００２７】
このガス拡散電極を５ｃｍ×５ｃｍの電極サイズに裁断し、高分子電解質膜の両側に反応層面が対向するように配し、８０℃、１５０ｋｇ／ｃｍ２、２分間の条件で圧接してガス拡散電極を接合した。ついで、基体を取り除き高分子電解質膜−ガス拡散電極体を得た。このとき、高分子電解質膜としてＮａｆｉｏｎ１１５（デュポン社）を用いた。以下、これを本発明にかかる高分子電解質膜−ガス拡散電極体Ａとする。
【００２８】
［比較例］
スクリーン印刷により、実施例で調製した触媒と高分子電解質の溶液（Ｎａｆｉｏｎ溶液）からなる触媒分散物を剥離シート（ポリテトラフロロエチレン−ポリヘキサフロロプロピレン共重合体シート）に塗布、乾燥して、このシート上に厚み約１０μｍの反応層を形成した。この反応層５ｃｍ×５ｃｍの電極サイズに裁断し、高分子電解質膜：Ｎａｆｉｏｎ１１５の両側に反応層面が対向するように配し、８０℃、１５０ｋｇ／ｃｍ２、２分間の条件で圧接して反応層を接合した。剥離シートを取り除き高分子電解質膜−反応層接合体を得た。
【００２９】
高分子電解質膜−反応層接合体の両側にＰＴＦＥで撥水性を付与したカーボンペーパーを積層し、１２０℃、１５０ｋｇ／ｃｍ２、２分間の条件で圧接して高分子電解質膜−ガス拡散電極体を得た。以下、これを比較用高分子電解質膜−ガス拡散電極体Ｂとする。
【００３０】
［実験］
上記作製した本発明にかかる高分子電解質膜−ガス拡散電極体Ａを用いて燃料電池を構成した。この電池を本発明にかかる固体高分子型電解質燃料電池Ａとする。また、上記比較例で作製した高分子電解質膜−ガス拡散電極体Ｂを用いて燃料電池を構成した。この電池を比較燃料電池Ｂとする。
【００３１】
そして、燃料ガスとして水素ガス、酸化剤ガスとして酸素ガスを大気圧で供給し、本発明燃料電池Ａと比較燃料電池Ｂとの電池電圧と電流密度の関係を調べた。
【００３２】
下記に作動条件を示す。
【００３３】
作動温度６５℃、酸素加湿温度６０℃、水素加湿温度６０℃、酸素利用率５０％、水素利用率７０％
その結果を図４に示す。図４から明らかなように、本発明燃料電池Ａは比較燃料電池Ｂよりも高い電流密度での電圧の降下が小さい。比較燃料電池Ｂより本発明燃料電池Ａは、抵抗過電圧と濃度過電圧の影響が小さいものと思われる。すなわち、本発明燃料電池Ａのガス拡散層は、薄く抵抗が小さいこと及び弾性体的な性質を有しており圧迫によりガス拡散層が適度に変形して集電体あるいはセパレータ等の各構成材との接触が十分になる。すなわち、接触抵抗が低減したために、本発明燃料電池Ａの抵抗過電圧が減少した。また、このガス拡散層は多孔性でありかつ適度に撥水性を有しているので生成水がこれらの孔を閉塞することがなく、反応ガスの透過が妨げられない。このために、このガス拡散層はガスの透過性が優れており、反応ガス供給が円滑であるため濃度過電圧の影響が減少したものと思われる。
【００３４】
【発明の効果】
以上説明したように、本発明の高分子電解質膜−ガス拡散電極体のガス拡散層は弾性体的な性質を有し燃料電池を構成するときに加わる圧迫により適度に変形することで接触抵抗が低減し抵抗過電圧が小さくなり、多孔性でガス透過性に優れており反応ガスが速やかに供給されるので濃度過電圧が小さくなる。したがって、高い電流密度でも電圧降下が少なく優れた電流−電圧特性を有する燃料電池を提供できる。また、ガス拡散層が弾性体的な性質を有するために、これが高分子電解質膜に必要以上にくい込みピンホール形成等の問題が発生することなく信頼性の高い高分子電解質膜−ガス拡散電極体を提供することができる。
【図面の簡単な説明】
【図１】本発明高分子電解質膜−ガス拡散電極体の断面の模式図
【図２】本発明高分子電解質膜−ガス拡散電極体のガス拡散層の模式図
【図３】本発明高分子電解質膜−ガス拡散電極体の作製のフロー図
【図４】本発明燃料電池Ａと比較燃料電池Ｂの電池電圧−電流密度特性の比較図
【符号の説明】
１ 高分子電解質膜
２ 反応層
３ ガス拡散層
４ ガス拡散電極
５ カーボン粒子
６ ポリテトラフロロエチレン粒子
７ ポリフッ化ビニリデン被膜[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to a solid polymer electrolyte fuel cell.
[0002]
[Prior art]
A solid polymer electrolyte fuel cell has a structure in which gas diffusion electrodes are arranged on both sides of an ion exchange membrane (solid polymer electrolyte), and the reaction gas oxygen and hydrogen are reacted electrochemically. A device that obtains power. The gas diffusion electrode is composed of a gas diffusion part and a reaction part, and platinum metal particles or carbon particles carrying these particles are applied as a catalyst to each reaction part of the anode and the cathode.
[0003]
In the anode,
2H 2 → 4H + + 4e −
At the cathode,
O 2 + 4H + + 4e − → 2H 2 O
The electrochemical reaction proceeds.
The gas diffusion part is a porous body and has functions of supplying a reaction gas to the reaction part and collecting current. Water generated by the reaction on the cathode side is discharged through the gas diffusion part. At this time, if the pores of the gas diffusion portion are blocked by the generated water, the permeability of the reaction gas is lowered and the battery characteristics are lowered. For this reason, the gas diffusion part is required to have water repellency in addition to gas permeability and conductivity. As the gas diffusion part, a commercially available carbon paper provided with water repellency using a water repellent resin such as polytetrafluoroethylene is used. Carbon paper is obtained by firing carbon short fibers having a diameter of about 10 μm, which are hardened with a binder.
[0004]
[Problems to be solved by the invention]
In order to reduce the resistance of the gas diffusion part, it is preferable to use a thin carbon paper. However, the thin carbon paper has insufficient mechanical strength, and there is a problem such as destruction in the production process of the polymer electrolyte membrane-gas diffusion electrode body. This is difficult to handle. Further, in order to produce a polymer electrolyte membrane-gas diffusion electrode body, a reaction part is formed on the polymer electrolyte membrane and a water-repellent carbon paper as a gas diffusion part is pressure-contacted thereto, or a carbon paper is used. There is a method of forming a reaction part and press-contacting it with a polymer electrolyte membrane. However, when this pressure welding is performed, carbon short fibers may bite into the polymer electrolyte membrane more than necessary, particularly at the edge of the carbon paper. For this reason, the mechanical strength of the polymer electrolyte membrane is reduced, or sometimes penetrates and causes pinholes.
[0005]
In addition, when a thin reaction part of about 10 μm is formed on the polymer electrolyte membrane and water-repellent carbon paper is pressed against this, it is necessary to increase the bonding pressure in order to ensure sufficient contact between the reaction part and the carbon paper. is there. When the bonding pressure is increased, the carbon paper has an inelastic property to the compression, so in addition to the above-mentioned problem of pinhole generation, the carbon paper is crushed and the thickness is reduced. . The reduction of the thickness of the gas diffusion portion is irreversible, and causes a contact failure with the current collector or the separator. That is, the contact resistance increases due to the crushing of the carbon paper, and the battery characteristics are deteriorated.
[0006]
Of the members constituting a single cell of a solid polymer electrolyte fuel cell, only a polymer electrolyte membrane exhibits elastic properties against compression. However, since the polymer electrolyte membrane is thin, if excessive pressure is applied, problems such as pinhole generation as described above occur. Therefore, in order to sufficiently maintain the contact between the current collector or separator having a non-elastic property and a non-elastic property with respect to compression and the polymer electrolyte membrane-gas diffusion electrode body, a high level of each component is required. Dimensional accuracy is required. In particular, when a plurality of cells are stacked, the dimensional accuracy required for maintaining sufficient contact between the constituent members becomes increasingly severe. However, in the manufacturing method of each constituent member, in particular, the polymer electrolyte membrane-gas diffusion electrode body, the dimensional accuracy is required to go through the process of pressing the reaction part to the polymer electrolyte membrane and the process of pressing the next gas diffusion part. It is not easy to secure enough. Therefore, in order to sufficiently maintain the contact between the constituent members and reduce the contact resistance, it is desirable to include constituent members having elastic properties in addition to the polymer electrolyte membrane.
[0007]
The invention of claim 1 is a polymer electrolyte membrane-gas diffusion electrode body comprising a gas diffusion electrode having a reaction layer and a gas diffusion layer on at least one of the polymer electrolyte membranes , wherein the gas diffusion layer comprises carbon Powder or carbon fiber or a mixture of both, polytetrafluoroethylene powder , and polyvinylidene fluoride, and the polytetrafluoroethylene powder is made of polyvinylidene fluoride, the carbon powder or carbon fiber, or both It is characterized by being bound to a mixture of
[0008]
According to a second aspect of the present invention, in the method for producing a polymer electrolyte membrane-gas diffusion electrode body , a carbon material and polytetrafluoroethylene powder are added to a solution obtained by dissolving polyvinylidene fluoride in N-methyl-2-pyrrolidone. A step of preparing a dispersion for forming a gas diffusion layer, and applying the dispersion to a substrate, immersing it in water, and extracting N-methyl-2-pyrrolidone contained in the dispersion , A step of solidifying vinylidene fluoride to form a gas diffusion layer, a step of applying a catalyst dispersion having a catalyst and a polymer electrolyte resin to the gas diffusion layer, and forming a reaction layer on the gas diffusion layer; and the reaction layer Pressing the substrate on which the gas diffusion electrode is formed and the polymer electrolyte membrane so that the polymer electrolyte membrane faces the polymer electrolyte membrane, and removing the substrate to form a polymer electrolyte membrane-gas diffusion electrode assembly. It is characterized by.
[0009]
The invention of
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a polymer electrolyte membrane-gas diffusion electrode body and a manufacturing method thereof according to the present invention will be described with reference to suitable drawings.
[0011]
FIG. 1 is a schematic view of a polymer electrolyte membrane-gas diffusion electrode body according to the present invention.
[0012]
According to FIG. 1 , a
[0013]
FIG. 2 is a schematic view showing the structure of the gas diffusion layer of the polymer electrolyte membrane-gas diffusion electrode body according to the present invention.
[0014]
According to FIG. 2 , carbon powder and polytetrafluoroethylene powder are bound by polyvinylidene fluoride to form clusters, and pores are randomly formed between the clusters. In FIG. 2 , 5 is a carbon particle, 6 is a polytetrafluoroethylene particle, and 7 is a polyvinylidene fluoride coating.
[0015]
FIG. 3 is a flowchart of the method for producing a polymer electrolyte membrane-gas diffusion electrode body according to the present invention.
[0016]
First, polyvinylidene fluoride (PVdF, trade name: Kureha Chemical Industry Co., Ltd., KF1100) and N-methyl-2-pyrrolidone (NMP) are weighed appropriately as a binder, and PVdF is added to NMP. Dissolve to prepare an NMP solution of PVdF . A conductive material and polytetrafluoroethylene powder (PTFE powder, trade name: Daikin Industries, Ltd., Lubron) as a water repellent material are added to this solution and mixed well to prepare a dispersion for forming a gas diffusion layer. . The conductive material of carbon powder (trade name: CABOT Co., Valcan XC) Ru can used.
[0017]
The dispersion for forming a gas diffusion layer is applied to a substrate having a low affinity with the dispersion, for example, a sheet having releasability. As the sheet having releasability, a sheet of tetrafluoroethylene-hexafluoropropylene copolymer (trade name: Daikin Industries, Ltd., NEOFLON) can be used, and a dispersion for forming a gas diffusion layer is formed on this sheet. Apply. As a coating method, a doctor blade method or the like can be used.
[0018]
Until the dispersion for forming the gas diffusion layer is dried, the substrate coated with this dispersion is immersed in purified water to extract NMP contained in the dispersion. When NMP is extracted, PVdF is solidified , and a cluster of conductive material and PTFE powder is formed by this binding action. At this time, the solidification accompanying the substitution of NMP and water forms a state in which the cluster portion and the portion occupied by water are randomly mixed together with the rapid volume shrinkage of PVdF . When this moisture is dried and removed, the portion occupied by water becomes pores, and a gas diffusion layer having pores is formed. This gas diffusion layer exhibits electronic conductivity by the carbon material, and the appropriately formed pores serve as a supply path for the reaction gas, and the water repellency imparted by the PTFE powder as a mixed water repellent material is the pore of the generated water. By preventing clogging, excellent gas permeability is exhibited.
[0019]
Next, a catalyst dispersion having a catalyst and a polymer electrolyte resin is applied to the gas diffusion layer of the substrate to form a reaction layer to obtain a gas diffusion electrode. As the catalyst, carbon powder carrying platinum particles can be used, and as the polymer electrolyte resin, a solution of perfluorosulfonic acid resin (trade name: Aldrich, Nafion solution) can be used. Mix the specified amount and adjust the viscosity to prepare a catalyst dispersion. As a coating method, a screen printing method can be used.
[0020]
Next, the reaction layer of the gas diffusion electrode formed on the substrate is laminated on both sides or one side of the polymer electrolyte membrane so as to come into contact with the polymer electrolyte membrane, and pressed. Then, the gas diffusion electrode is joined to the polymer electrolyte membrane, and when the substrate is removed, a polymer electrolyte membrane-gas diffusion electrode body is formed.
[0021]
According to the present invention, a dispersion composed of PVdF dissolved in NMP , a conductive material such as carbon powder or short fiber, and PTFE powder as a water repellent material is applied to a substrate and immersed in water to form a dispersion. By extracting the contained NMP , PVdF , which is water-insoluble, is solidified to form a gas diffusion layer. In this case a more binding carbon material portion and PVdF occupied by water (carbon powder or carbon fibers or mixtures thereof) with part separated occupied PTFE powder, the state in which these two parts are mixed in finely randomly formed Is done. Next, when this moisture is removed by drying, the portion remains as a void. That is, a porous gas diffusion part is formed. Therefore, this gas diffusion layer is a porous body using PVdF as a binder and is appropriately given water repellency by the PTFE powder. Therefore, the gas diffusion layer is not clogged with generated water due to the battery reaction. Therefore, this gas diffusion layer has a good permeability of the reaction gas and shows a good electron conductivity by the carbon material. In addition, the gas diffusion layer has an elastic property, and is appropriately deformed by the pressure applied when the battery is configured, so that the contact between the battery constituent members becomes sufficient and the contact resistance is reduced. Further, there is no concern about the formation of pinholes when joining with the polymer electrolyte membrane.
[0022]
As described above, the gas diffusion layer of the present invention is excellent in the supply property and conductivity of the reaction gas, and has elastic properties, so that the contact resistance between the battery components can be reduced, and the power generation capability is excellent. A solid polymer electrolyte fuel cell can be provided.
[0023]
【Example】
Hydrophilic organic solvent, N-methyl-2-pyrrolidone: 130 g of polyvinylidene fluoride (Kureha Chemical Industry Co. , Ltd. , KF1100) 4 g was added and dissolved to prepare a binder solution having a concentration of about 3 wt%. . Carbon powder (CABOT , VALCAN XC): 14 g as a conductive material is gradually added to the binder solution while stirring to disperse the conductive material in the binder solution. Subsequently, 2 g of polytetrafluoroethylene powder (trade name: manufactured by Daikin Industries, Ltd. , Lubron) was added as a water repellent material, and the mixture was sufficiently stirred to prepare a dispersion for forming a gas diffusion part.
[0024]
In addition, catalyst dispersion using a platinum-supported carbon catalyst obtained by adding about 30 wt% platinum to a support of carbon powder (CABOT , VALCAN XC) and a commercially available polymer electrolyte resin solution (Aldrich Chemical, Nafion solution, 5 wt%) A product was prepared. That is, 2 g of platinum supported carbon catalyst: 2 g was added to 15 g of Nafion solution, dispersed, heated to 70 ° C. with stirring to remove part of the dispersion medium, and the viscosity of the catalyst dispersion was adjusted, so that the viscosity was about 12000 cP. A catalyst dispersion was obtained.
[0025]
Using the doctor blade method, the above-mentioned dispersion for forming a gas diffusion layer is applied to a sheet of polytetrafluoroethylene-polyhexafluoropropylene copolymer (trade name: Daikin Industries, Ltd. , Neoflon), and the thickness is about A 0.1 mm- thick dispersion for forming a gas diffusion layer was prepared. While the coating was not dried, the coating was immersed in purified water for about 20 minutes, and then naturally dried at room temperature to form a gas diffusion layer on the substrate.
[0026]
The above-mentioned catalyst dispersion was applied to the gas diffusion layer by screen printing and dried to form a reaction layer having a thickness of about 10 μm, and a gas diffusion electrode having a gas diffusion layer and a reaction layer on the substrate was produced. .
[0027]
This gas diffusion electrode is cut into an electrode size of 5 cm × 5 cm, arranged so that the reaction layer surface faces the both sides of the polymer electrolyte membrane, and pressure-welded under conditions of 80 ° C. and 150 kg / cm 2 for 2 minutes to form a gas A diffusion electrode was joined. Subsequently, the substrate was removed to obtain a polymer electrolyte membrane-gas diffusion electrode body. At this time, Nafion 115 (DuPont) was used as the polymer electrolyte membrane. Hereinafter, this is referred to as a polymer electrolyte membrane-gas diffusion electrode body A according to the present invention.
[0028]
[Comparative example]
A screen dispersion is applied to a release sheet (polytetrafluoroethylene-polyhexafluoropropylene copolymer sheet) with a catalyst dispersion comprising a catalyst and a polymer electrolyte solution (Nafion solution) prepared in the examples, and dried. A reaction layer having a thickness of about 10 μm was formed on this sheet. This reaction layer is cut into an electrode size of 5 cm × 5 cm, placed so that the reaction layer surface faces both sides of the polymer electrolyte membrane: Nafion 115, and reacted by pressure contact at 80 ° C. and 150 kg / cm 2 for 2 minutes. The layers were joined. The release sheet was removed to obtain a polymer electrolyte membrane-reaction layer assembly.
[0029]
Carbon paper to which water repellency is imparted with PTFE is laminated on both sides of the polymer electrolyte membrane-reaction layer assembly, and pressure-welded under conditions of 120 ° C., 150 kg / cm 2 for 2 minutes, polymer electrolyte membrane-gas diffusion electrode body Got. Hereinafter, this is referred to as a comparative polymer electrolyte membrane-gas diffusion electrode body B.
[0030]
[Experiment]
A fuel cell was constructed using the polymer electrolyte membrane-gas diffusion electrode body A according to the present invention produced above. This battery is a solid polymer electrolyte fuel cell A according to the present invention. A fuel cell was constructed using the polymer electrolyte membrane-gas diffusion electrode body B produced in the above comparative example. This battery is referred to as a comparative fuel cell B.
[0031]
Then, hydrogen gas as the fuel gas and oxygen gas as the oxidant gas were supplied at atmospheric pressure, and the relationship between the cell voltage and current density of the fuel cell A of the present invention and the comparative fuel cell B was examined.
[0032]
The operating conditions are shown below.
[0033]
Operating temperature 65 ° C , oxygen humidification temperature 60 ° C, hydrogen humidification temperature 60 ° C , oxygen utilization rate 50%, hydrogen utilization rate 70%
The result is shown in FIG. As is clear from FIG. 4, the fuel cell A of the present invention has a smaller voltage drop than the comparative fuel cell B at a higher current density. The fuel cell A of the present invention is considered to be less affected by the resistance overvoltage and the concentration overvoltage than the comparative fuel cell B. That is, the gas diffusion layer of the fuel cell A of the present invention is thin and has low resistance and elastic properties, and the gas diffusion layer is appropriately deformed by the compression, so that each constituent material such as a current collector or a separator Contact with is sufficient. That is, since the contact resistance was reduced, the resistance overvoltage of the fuel cell A of the present invention was reduced. Further, since this gas diffusion layer is porous and has an appropriate water repellency, the generated water does not block these pores, and the permeation of the reaction gas is not hindered. For this reason, this gas diffusion layer is excellent in gas permeability, and since the reaction gas supply is smooth, it seems that the influence of the concentration overvoltage is reduced.
[0034]
【The invention's effect】
As described above, the gas diffusion layer of the polymer electrolyte membrane-gas diffusion electrode body of the present invention has elastic properties and has a contact resistance that is appropriately deformed by the pressure applied when constituting a fuel cell. The resistance overvoltage is reduced, the porosity is excellent in gas permeability, and the reaction gas is rapidly supplied, so the concentration overvoltage is reduced. Therefore, it is possible to provide a fuel cell having excellent current-voltage characteristics with little voltage drop even at a high current density. In addition, since the gas diffusion layer has elastic properties, the polymer electrolyte membrane-gas diffusion electrode body is highly reliable without causing problems such as formation of pinholes that are difficult to form in the polymer electrolyte membrane. Can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a cross-section of the polymer electrolyte membrane-gas diffusion electrode body of the present invention. FIG. 2 is a schematic diagram of a gas diffusion layer of the polymer electrolyte membrane-gas diffusion electrode body of the present invention. Flow chart of production of electrolyte membrane-gas diffusion electrode body [FIG. 4] Comparison diagram of cell voltage-current density characteristics of fuel cell A of the present invention and comparative fuel cell B [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20076097A JP3807038B2 (en) | 1997-07-10 | 1997-07-10 | POLYMER ELECTROLYTE MEMBRANE-GAS DIFFUSION ELECTRODE AND METHOD FOR PRODUCING THE SAME |
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|---|---|---|---|
| JP20076097A JP3807038B2 (en) | 1997-07-10 | 1997-07-10 | POLYMER ELECTROLYTE MEMBRANE-GAS DIFFUSION ELECTRODE AND METHOD FOR PRODUCING THE SAME |
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| JPH1131515A JPH1131515A (en) | 1999-02-02 |
| JP3807038B2 true JP3807038B2 (en) | 2006-08-09 |
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| KR100442819B1 (en) * | 2000-10-25 | 2004-08-02 | 삼성전자주식회사 | Membrane electrode assembly for fuel cell operable in non-humidified fuel condition |
| JPWO2002050338A1 (en) * | 2000-12-20 | 2004-04-22 | ソニー株式会社 | Hydrogen production apparatus, electrochemical device, hydrogen production method and electrochemical energy generation method |
| JP2005293910A (en) * | 2004-03-31 | 2005-10-20 | Yamanashi Tlo:Kk | Fuel cell and its aggregate |
| JP2006019174A (en) * | 2004-07-02 | 2006-01-19 | Tomoegawa Paper Co Ltd | Gas diffusion electrode, membrane-electrode assembly, its manufacturing method, and solid polymer fuel cell |
| JP4736385B2 (en) * | 2004-09-27 | 2011-07-27 | 大日本印刷株式会社 | Transfer sheet for producing catalyst layer-electrolyte membrane laminate and method for producing the same |
| JP4530892B2 (en) * | 2005-03-28 | 2010-08-25 | 三洋電機株式会社 | Polymer electrolyte fuel cell |
| JP4530893B2 (en) * | 2005-03-28 | 2010-08-25 | 三洋電機株式会社 | Polymer electrolyte fuel cell |
| JP2007012424A (en) * | 2005-06-30 | 2007-01-18 | Tomoegawa Paper Co Ltd | Gas diffusion electrode, membrane-electrode joined body and its manufacturing method, and solid polymer fuel cell |
| JP5401751B2 (en) * | 2005-08-12 | 2014-01-29 | 大日本印刷株式会社 | Transfer sheet, catalyst layer-electrolyte membrane laminate, electrode-electrolyte membrane assembly, and methods for producing them |
| JP5343298B2 (en) * | 2005-08-30 | 2013-11-13 | 大日本印刷株式会社 | Transfer sheet, catalyst layer-electrolyte membrane laminate, electrode-electrolyte membrane assembly, and methods for producing them |
| FR2892861B1 (en) * | 2005-11-02 | 2013-07-05 | Commissariat Energie Atomique | CONTINUOUS CCB TYPE "ELECTRODE-MEMBRANE-ELECTRODE" ASSEMBLY PROCESS |
| CN101617424B (en) | 2007-02-02 | 2012-11-28 | 旭硝子株式会社 | Process for producing membrane electrode assembly for solid polymer electrolyte fuel cell, and process for producing solid polymer electrolyte fuel cell |
| JP5126292B2 (en) * | 2010-06-09 | 2013-01-23 | 大日本印刷株式会社 | Transfer sheet for producing catalyst layer-electrolyte membrane laminate and method for producing the same |
| JP5530954B2 (en) * | 2011-02-21 | 2014-06-25 | 株式会社日本自動車部品総合研究所 | Fuel cell |
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