JP5354956B2 - Polymer electrolyte membrane fuel cell - Google Patents

Polymer electrolyte membrane fuel cell Download PDF

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JP5354956B2
JP5354956B2 JP2008135798A JP2008135798A JP5354956B2 JP 5354956 B2 JP5354956 B2 JP 5354956B2 JP 2008135798 A JP2008135798 A JP 2008135798A JP 2008135798 A JP2008135798 A JP 2008135798A JP 5354956 B2 JP5354956 B2 JP 5354956B2
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electrolyte membrane
polymer electrolyte
fuel cell
electrode
water
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JP2009283364A (en
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将一 干鯛
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Toshiba Corp
Toshiba Energy Systems and Solutions Corp
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Toshiba Fuel Cell Power Systems Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • 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
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    • Y02E60/50—Fuel cells

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a fuel cell of a long lifetime, in which drying at a gas entrance is prevented for a desired time to obtain its effect in the internal humidification method, and which can be used while maintaining the voltage at a normal level at the time of continuous operation. <P>SOLUTION: The polymer electrolyte membrane type fuel cell 30 includes: a pair of electrodes (fuel electrode/oxidant electrode) arranged on both sides of a polymer electrolyte membrane 14; and a reactant gas transmission prevention layer 18 installed jointed to at least one surface of the polymer electrolyte membrane 14. The ion exchange capacity of the electrolyte component contained in the reactant gas transmission prevention layer 18 is made smaller than the ion exchange capacity of the polymer electrolyte membrane 14. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

本発明は、燃料電池の単電池に係り、連続運転時における電圧の低下要因を改善して、燃料電池の寿命を向上させる高分子電解質膜型燃料電池に関する。   The present invention relates to a unit cell of a fuel cell, and more particularly to a polymer electrolyte membrane fuel cell that improves the voltage drop factor during continuous operation and improves the life of the fuel cell.

高分子電解質膜型燃料電池は、高分子電解質膜の両側に触媒層を塗布した電極を配置して構成される。一般的に燃料極側に水素を含む燃料ガスを、酸化剤極側に酸素を含む酸化剤ガスを導入する。燃料ガスとしては、純水素あるいは、都市ガスあるいはＬＰＧを改質して得られる改質ガスを適用している。   A polymer electrolyte membrane fuel cell is configured by arranging electrodes coated with a catalyst layer on both sides of a polymer electrolyte membrane. In general, a fuel gas containing hydrogen is introduced on the fuel electrode side, and an oxidant gas containing oxygen is introduced on the oxidant electrode side. As the fuel gas, pure hydrogen, a reformed gas obtained by reforming city gas or LPG is applied.

酸化剤ガスとしてはブロアあるいはコンプレッサによって空気を導入するのが一般的である。   As the oxidant gas, air is generally introduced by a blower or a compressor.

そして、燃料極においては、（１）式のように水素が乖離してプロトンを生成する。プロトンは高分子電解質膜を通って酸化剤極において（２）式の反応によって、水と熱を生成する。   At the fuel electrode, hydrogen is separated as shown in the equation (1) to generate protons. Protons generate water and heat through the polymer electrolyte membrane at the oxidizer electrode by the reaction of formula (2).

Ｈ2 → ２Ｈ＋＋２ｅ- （１）
Ｏ2 ＋４Ｈ＋＋４ｅ- →２Ｈ2Ｏ （２）
高分子電解質膜はプロトン伝導体として機能すると同時に、両極の反応ガスをシールする機能も有している。高分子電解質膜の劣化が進行し反応ガスがクロスリークすると、水素と酸素が直接燃焼反応し発電効率が下がるとともに、燃焼反応熱で高分子電解質膜の劣化を加速する。最終的には高分子電解質膜が破損し、燃料電池として運転不能に至る原因となっている。 H 2 → 2H + + 2e- (1)
O 2 + 4H + + 4e− → 2H 2 O (2)
The polymer electrolyte membrane functions as a proton conductor and at the same time has a function of sealing the reaction gas of both electrodes. When the deterioration of the polymer electrolyte membrane proceeds and the reaction gas cross-leaks, hydrogen and oxygen directly react with each other to reduce power generation efficiency, and the deterioration of the polymer electrolyte membrane is accelerated by the heat of combustion reaction. Eventually, the polymer electrolyte membrane is damaged, causing the fuel cell to become inoperable.

酸化剤極における通常の燃料電池反応においては、（２）式のようにプロトンと酸素が反応し水を生成する反応が生じている。この反応には４つの電子が寄与するため４電子反応と呼ばれる。（２）式の反応の素過程として、（３）式のような反応によって、Ｈ2Ｏ2が生成する。この反応には２つの電子が寄与するため２電子反応と呼ばれる。 In a normal fuel cell reaction at the oxidizer electrode, a reaction occurs in which protons and oxygen react to generate water as shown in equation (2). This reaction is called a four-electron reaction because four electrons contribute. As an elementary process of the reaction of the formula (2), H 2 O 2 is generated by the reaction of the formula (3). This reaction is called a two-electron reaction because two electrons contribute.

２Ｈ+＋Ｏ2＋２ｅ- → Ｈ2Ｏ2 （３）
２電子反応で生成したＨ2Ｏ2は、高分子電解質膜の劣化を引起す原因物質であるＯＨラジカルを生成すると言われている。 2H + + O 2 + 2e− → H 2 O 2 (3)
It is said that H 2 O 2 generated by the two-electron reaction generates OH radicals that are causative substances that cause deterioration of the polymer electrolyte membrane.

すなわち、高分子電解質膜の劣化を防止するためには、Ｈ2Ｏ2の生成を抑制することが有効である。クロスリークした酸素と水素によるＨ2Ｏ2の生成を防止する技術として、反応ガス透過防止層を付けるという技術がある。 That is, in order to prevent deterioration of the polymer electrolyte membrane, it is effective to suppress the generation of H 2 O 2 . As a technique for preventing generation of H 2 O 2 by cross leaked oxygen and hydrogen, there is a technique of attaching a reaction gas permeation preventive layer.

この技術を採用することにより、高分子電解質膜を介した対極への反応ガスの透過を抑制し、高分子電解質膜の劣化を抑制できる燃料電池が実現している（例えば、［特許文献１］参照）。   By adopting this technology, a fuel cell that can suppress the permeation of the reaction gas to the counter electrode through the polymer electrolyte membrane and suppress the deterioration of the polymer electrolyte membrane has been realized (for example, [Patent Document 1]). reference).

反応ガス透過防止層を適用した従来の燃料電池について、図５を参照して説明する。   A conventional fuel cell to which a reactive gas permeation preventive layer is applied will be described with reference to FIG.

図５は、燃料電池を構成する単電池の概要を示す要部断面図である。図５に示す燃料電池（単電池）１０は、高分子電解質膜１４と反応ガス透過防止層１８を備えた高分子電解質膜１９と、この高分子電解質膜１９の外側に設けられ、燃料極触媒層１２と燃料極ガス拡散層１１を備えた燃料極１３と、上述の高分子電解質膜１９の反応ガス透過防止層１８の外側に設けられ、酸化剤極触媒層１７と酸化剤極ガス拡散層１６を備えた酸化剤極１５と、上述の燃料極１３の燃料極ガス拡散層１１の外側に設けられた燃料ガス供給用セパレータ２０と、上述の酸化剤極１５の酸化剤極ガス拡散層１６の外側に設けられた酸化剤ガス供給用セパレータ２１とで構成されている。   FIG. 5 is a cross-sectional view of an essential part showing an outline of the unit cell constituting the fuel cell. A fuel cell (single cell) 10 shown in FIG. 5 is provided with a polymer electrolyte membrane 19 having a polymer electrolyte membrane 14 and a reaction gas permeation preventing layer 18, and an outer side of the polymer electrolyte membrane 19. A fuel electrode 13 having a layer 12 and a fuel electrode gas diffusion layer 11, and an outer side of the reaction gas permeation preventive layer 18 of the polymer electrolyte membrane 19, and an oxidant electrode catalyst layer 17 and an oxidant electrode gas diffusion layer. 16, the fuel gas supply separator 20 provided outside the fuel electrode gas diffusion layer 11 of the fuel electrode 13, and the oxidant electrode gas diffusion layer 16 of the oxidant electrode 15. And an oxidant gas supply separator 21 provided outside.

高分子電解質膜１４は、一般にパーフルオロスルホン酸膜あるいは炭化水素系スルホン酸膜が用いられる。   The polymer electrolyte membrane 14 is generally a perfluorosulfonic acid membrane or a hydrocarbon sulfonic acid membrane.

反応ガス透過防止層１８は、高分子電解質中に炭素粒子上に白金を担持した触媒を含有させている。   The reactive gas permeation preventive layer 18 contains a catalyst in which platinum is supported on carbon particles in a polymer electrolyte.

上記のように構成されている従来の燃料電池１０は、燃料極１３、高分子電解質膜１４、反応ガス透過防止層１８、酸化剤極１５を順次重ね合わせ、例えば熱圧着してＭＥＡ（Membran Elerode Assembly；膜／電極接合体）を形成する。   In the conventional fuel cell 10 configured as described above, the fuel electrode 13, the polymer electrolyte membrane 14, the reaction gas permeation prevention layer 18, and the oxidizer electrode 15 are sequentially stacked and, for example, thermocompression bonded to form a MEA (Membran Elerode Assembly (membrane / electrode assembly) is formed.

このような従来の燃料電池１０によれば、反応ガス透過防止層１８中における触媒において、クロスリークした酸素を消費することによって、酸素のクロスリークを防止することができる。酸素のクロスリークがなければH2O2の生成が抑制されるため、高分子電解質膜の劣化が抑制される。また、反応ガス透過防止層１８を特に燃料極１３側につけることによって、一層効果的であることも見出されている。 According to such a conventional fuel cell 10, oxygen cross-leakage can be prevented by consuming cross-leaked oxygen in the catalyst in the reaction gas permeation preventive layer 18. If there is no cross leak of oxygen, generation of H 2 O 2 is suppressed, so that deterioration of the polymer electrolyte membrane is suppressed. It has also been found that the reactive gas permeation preventive layer 18 is particularly effective by attaching it to the fuel electrode 13 side.

高分子電解質膜１４のプロトン導電性は含水率に依存する。すなわち、含水率が高い方がプロトン導電性が高くなる。従って、外部から水分を供給して高分子電解質膜１９を加湿する必要がある。   The proton conductivity of the polymer electrolyte membrane 14 depends on the water content. That is, the higher the water content, the higher the proton conductivity. Therefore, it is necessary to humidify the polymer electrolyte membrane 19 by supplying moisture from the outside.

加湿方式は、大別して外部加湿方式と内部加湿方式がある。外部加湿方式では、燃料電池スタックに供給される反応ガス中に蒸気を混入するため、燃料電池スタックに加湿器が必要である。一方、内部加湿方式では、液体の水を燃料電池スタックに導入し燃料電池を加湿する。内部加湿方式では反応ガスを予め加湿する必要がないため、加湿器が必要ないという利点がある。反面、加湿されていない乾燥ガスを燃料電池に導入するためにガス入口付近の高分子電解質膜が乾燥し、連続運転時には乾燥領域が広がっていくために反応面積が低下し、セル電圧が低下するという欠点があった。
特開２００５−１４９８５９号公報 The humidification method is roughly classified into an external humidification method and an internal humidification method. In the external humidification system, a vapor is mixed in the reaction gas supplied to the fuel cell stack, and thus a humidifier is necessary for the fuel cell stack. On the other hand, in the internal humidification method, liquid water is introduced into the fuel cell stack to humidify the fuel cell. The internal humidification method has an advantage that a humidifier is not necessary because the reaction gas does not need to be humidified in advance. On the other hand, the polymer electrolyte membrane near the gas inlet dries in order to introduce dry gas that has not been humidified into the fuel cell. During continuous operation, the drying area increases and the reaction area decreases and the cell voltage decreases. There was a drawback.
JP 2005-149859 A

高分子電解質膜型燃料電池において、所望の時間に亘ってガス入口における乾燥を所望の時間に亘って防止する効果が得られ、連続運転時には電圧を通常レベルに維持しつつ使用に耐える、長寿命の燃料電池を提供することを目的とする。   In polymer electrolyte membrane fuel cells, the effect of preventing drying at the gas inlet for a desired time is obtained for a desired time, and it is durable to use while maintaining the voltage at a normal level during continuous operation An object of the present invention is to provide a fuel cell.

上記目的を達成するために、本発明は、高分子電解質膜の両側に配置された燃料極および酸化剤極と、前記高分子電解質膜の少なくとも１つの面に接合して設けた反応ガス透過防止層と、を備え、前記反応ガス透過防止層は少なくとも反応ガスを消費させるための触媒成分と電解質成分を含有し、前記反応ガス透過防止層に含まれる電解質成分のイオン交換容量が、前記高分子電解質膜のイオン交換容量よりも低くしたことを特徴とする。 In order to achieve the above object, the present invention provides a fuel gas and an oxidant electrode disposed on both sides of a polymer electrolyte membrane, and a reaction gas permeation prevention device provided to be joined to at least one surface of the polymer electrolyte membrane. The reaction gas permeation prevention layer contains at least a catalyst component for consuming the reaction gas and an electrolyte component, and the ion exchange capacity of the electrolyte component contained in the reaction gas permeation prevention layer is the polymer. It is characterized by being lower than the ion exchange capacity of the electrolyte membrane .

連続運転時には電圧を低下させない、長寿命の高分子電解質膜型燃料電池を得ることができる。   A long-life polymer electrolyte membrane fuel cell that does not lower the voltage during continuous operation can be obtained.

本発明に係る高分子電解質膜型燃料電池の単電池の実施形態について、図５と同一部分に同一符号を附して説明する。   An embodiment of a unit cell of a polymer electrolyte membrane fuel cell according to the present invention will be described by attaching the same reference numerals to the same portions as FIG.

図１は、本発明の高分子電解質膜型燃料電池の一実施形態の模式図である。図１に示す高分子電解質膜型燃料電池３０は、燃料極側ガス拡散層１１と燃料極触媒層１２を備えた燃料極１３と、酸化剤極触媒層１７と酸化剤側ガス拡散層１６を備えた酸化剤極１５と、燃料極１３の燃料極触媒層１２と面接合して設けられる高分子電解質膜１４と、この電解質膜１４の燃料極１３側と反対側に面接合して設けた酸化剤極１５とから構成される。   FIG. 1 is a schematic view of one embodiment of a polymer electrolyte membrane fuel cell of the present invention. A polymer electrolyte membrane fuel cell 30 shown in FIG. 1 includes a fuel electrode 13 including a fuel electrode side gas diffusion layer 11 and a fuel electrode catalyst layer 12, an oxidant electrode catalyst layer 17, and an oxidant side gas diffusion layer 16. The oxidizer electrode 15 provided, the polymer electrolyte membrane 14 provided in surface contact with the fuel electrode catalyst layer 12 of the fuel electrode 13, and surface-attached on the opposite side of the electrolyte membrane 14 from the fuel electrode 13 side. And an oxidizer electrode 15.

反応ガス透過防止層１８は、高分子電解質膜１４と密接に面接合して設けられる。   The reactive gas permeation preventive layer 18 is provided in close surface contact with the polymer electrolyte membrane 14.

また、燃料極１３および酸化剤極１５の外側には、図示しないが、燃料ガス供給用セパレータおよび酸化剤ガス供給用セパレータが設けられる。   Although not shown, a fuel gas supply separator and an oxidant gas supply separator are provided outside the fuel electrode 13 and the oxidant electrode 15.

高分子電解質膜１４は、例えば膜厚が２５〜５０ミクロンのナフィオン膜（デュポン社製）が用いられる。   As the polymer electrolyte membrane 14, for example, a Nafion membrane (made by DuPont) having a thickness of 25 to 50 microns is used.

また、反応ガス透過防止層１８は、原材料であるナフィオン（デュポン社商品名）の溶液中にカーボンに担持された白金触媒を添加したインクを層状に形成して用いられる。ナフィオンのＥＷ（Equivalent Weight；モル当量）として、ＥＷ１１００の溶液が用いられる。ＥＷは、イオン交換容量の逆数であり、１モル規定当たりの重量を表し、単位はｇ／ｍｏｌｌである。   The reactive gas permeation preventive layer 18 is used by forming a layer of ink in which a platinum catalyst supported on carbon is added to a solution of Nafion (trade name of DuPont) as a raw material. As Nafion's EW (Equivalent Weight; molar equivalent), a solution of EW1100 is used. EW is the reciprocal of the ion exchange capacity, and represents the weight per 1 mole regulation, and the unit is g / mol.

このインクを脱法混合器で攪拌した後に、ＰＥＴフィルム上にバーコーターあるいはカーテンコーターなどで塗布する。塗布後には８０℃の恒温槽中で３０分間乾燥させて製作する。インクの層の厚さは乾燥後の値を管理値とし、例えば２０ミクロン程度の厚さで層を形成する。   After the ink is stirred with a desiccant mixer, it is applied onto a PET film with a bar coater or a curtain coater. After coating, it is dried in a constant temperature bath at 80 ° C. for 30 minutes. The thickness of the ink layer is set to a control value after drying, and the layer is formed with a thickness of about 20 microns, for example.

ＰＥＴフィルム上に形成された反応ガス透過防止層１８は、高分子電解質膜上に熱圧着される。熱圧着は高分子電解質膜のガラス転移温度以上の温度、例えば１６０℃、面圧が、例えば３０Ｋｇ／ｃｍ２で１分間ホットプレスし、ＰＥＴフィルムは熱圧着後に剥がして除去される。 The reactive gas permeation preventive layer 18 formed on the PET film is thermocompression bonded onto the polymer electrolyte membrane. In the thermocompression bonding, hot pressing is performed at a temperature equal to or higher than the glass transition temperature of the polymer electrolyte membrane, for example, 160 ° C. and a surface pressure of, for example, 30 kg / cm 2 for 1 minute, and the PET film is peeled off and removed after thermocompression bonding.

また、高分子電解質膜としては、例えばＥＷ９００、膜厚５０ミクロンのナフィオン膜ＮＲＥ（デュポン社商品名）が用いられる。酸化剤極は、例えばＰｔ触媒が、燃料極は、例えばＰｔＲｕ合金触媒を適用する。電極は、例えばホットプレスで高分子電解質膜と一体化し、例えば図１に示すように製作したＭＥＡを用いる。そして、このＭＥＡを積層したスタック（導電性セパレータで連結されて構成される）（図示せず）を作成する。   As the polymer electrolyte membrane, for example, EW900 and a Nafion membrane NRE (trade name of DuPont) having a thickness of 50 microns are used. For example, a Pt catalyst is used as the oxidant electrode, and a PtRu alloy catalyst is used as the fuel electrode, for example. For example, the electrode is integrated with the polymer electrolyte membrane by hot pressing, and for example, MEA manufactured as shown in FIG. 1 is used. Then, a stack (configured by connecting with a conductive separator) (not shown) in which the MEAs are stacked is created.

次に、本発明の高分子電解質膜型燃料電池３０の作用について図２〜図４を参照して説明する。   Next, the operation of the polymer electrolyte membrane fuel cell 30 of the present invention will be described with reference to FIGS.

図２は、高分子電解質膜型燃料電池３０内における水移動量の差の状態を例示すグラフである。図３は、高分子電解質膜型燃料電池３０に用いられる電解質膜の水移動量を例示するグラフである。図４は、高分子電解質膜型燃料電池３０の特性を例示するグラフである。   FIG. 2 is a graph illustrating an example of a difference in the amount of water movement in the polymer electrolyte membrane fuel cell 30. FIG. 3 is a graph illustrating the amount of water movement of the electrolyte membrane used in the polymer electrolyte membrane fuel cell 30. FIG. 4 is a graph illustrating characteristics of the polymer electrolyte membrane fuel cell 30.

図２には、２種類の異なるＥＷの高分子電解質膜を透過する水移動量を測定結果に基づいた相対比を示す。ＥＷ９００の場合の方がＥＷ１０００の場合よりも水移動量の割合が大きいことを示している。   FIG. 2 shows a relative ratio of the amount of water movement permeating through two different types of EW polymer electrolyte membranes based on the measurement results. It shows that the ratio of the amount of water movement is larger in the case of EW900 than in the case of EW1000.

この実験の基本原理として採用した以下の式について具体的に説明する。   The following formula adopted as the basic principle of this experiment will be specifically described.

高分子電解質膜を透過する水の移動量φは（４）式で表される。   The amount of movement φ of the water that permeates the polymer electrolyte membrane is expressed by equation (4).

φ＝｛Ｄ・ρ／（ＥＷ・ｔ）｝（λ酸化剤極−λ燃料極） （４）
ここで、Ｄは拡散係数、ρは密度、ｔは膜厚、λ燃料極は燃料極側表面における含水量、λ酸化剤極はカソード側表面における含水量を示している。（４）式から、φは高分子電解質膜のＥＷに反比例することがわかる。 φ = {D · ρ / (EW · t)} (λ oxidant electrode− λ fuel electrode ) (4)
Here, D is the diffusion coefficient, ρ is the density, t is the film thickness, λ fuel electrode is the water content on the fuel electrode side surface, and λ oxidant electrode is the water content on the cathode side surface. From the equation ( 4 ), it can be seen that φ is inversely proportional to the EW of the polymer electrolyte membrane.

この測定には、高分子電解質膜を一対の流路板で挟み、一方の流路には水を、他方の流路には乾燥窒素を導入した。窒素排ガス中に含まれる水分の重量を計測し、高分子電解質膜を透過する水の量を算出した。図２に示す結果から水移動量はＥＷに反比例していることが確認された。   For this measurement, the polymer electrolyte membrane was sandwiched between a pair of flow path plates, water was introduced into one flow path, and dry nitrogen was introduced into the other flow path. The weight of water contained in the nitrogen exhaust gas was measured, and the amount of water that permeated the polymer electrolyte membrane was calculated. From the results shown in FIG. 2, it was confirmed that the amount of water movement was inversely proportional to EW.

反応ガス透過防止層１８を透過する水移動量も同様に電解質のＥＷに反比例する。   Similarly, the amount of water movement through the reactive gas permeation prevention layer 18 is inversely proportional to the EW of the electrolyte.

高分子電解質膜型燃料電池３０においては、反応ガス透過防止層１８のＥＷが高いために、水移動量が低下する。一方、高分子電解質膜１４の含水量は、官能基であるスルホン酸基の数に比例する。すなわち、ＥＷに反比例する。反応ガス透過防止層１８を付けることによって水移動量は減少するものの、高分子電解質膜１４のＥＷが変わらなければ、反応ガス透過防止層１８に関わらず高分子電解質膜１４の含水量は、高い状態に保つことができる。一方、プロトン抵抗は、電解質の含水量に依存するため、高分子電解質膜１４の含水量を高く保つことによって、高分子電解質膜１４の抵抗を低く維持することができる。   In the polymer electrolyte membrane fuel cell 30, since the EW of the reaction gas permeation prevention layer 18 is high, the amount of water movement decreases. On the other hand, the water content of the polymer electrolyte membrane 14 is proportional to the number of sulfonic acid groups that are functional groups. That is, it is inversely proportional to EW. Although the water transfer amount is reduced by attaching the reactive gas permeation preventive layer 18, the water content of the polymer electrolyte membrane 14 is high regardless of the reactive gas permeation preventive layer 18 as long as the EW of the polymer electrolyte membrane 14 does not change. Can be kept in a state. On the other hand, since the proton resistance depends on the water content of the electrolyte, the resistance of the polymer electrolyte membrane 14 can be kept low by keeping the water content of the polymer electrolyte membrane 14 high.

上述のように、高分子電解質膜型燃料電池３０によれば、高分子電解質膜１４の両側に配置された一対の電極（燃料極／酸化剤極）と、高分子電解質膜１４の少なくとも１つの面に接合して設けた反応ガス透過防止層１８とを備え、この反応ガス透過防止層１８による電解質成分のイオン交換容量が、高分子電解質膜１４によるイオン交換容量よりも低くしたために、セル抵抗を低く維持することによってセル特性を高く維持し、電池特性の低下を所望の時間に亘って防止する効果が得られる。   As described above, according to the polymer electrolyte membrane fuel cell 30, at least one of the pair of electrodes (fuel electrode / oxidant electrode) disposed on both sides of the polymer electrolyte membrane 14 and the polymer electrolyte membrane 14. A reaction gas permeation preventive layer 18 bonded to the surface, and the ion exchange capacity of the electrolyte component by the reaction gas permeation preventive layer 18 is lower than the ion exchange capacity by the polymer electrolyte membrane 14, so that the cell resistance By maintaining a low value, cell characteristics can be maintained high, and an effect of preventing deterioration of battery characteristics over a desired time can be obtained.

したがって、高分子電解質膜型燃料電池３０によれば、連続運転時には電圧を通常レベルに維持しつつ使用に耐えることができ、長寿命の燃料電池を提供することができる。   Therefore, the polymer electrolyte membrane fuel cell 30 can withstand use while maintaining the voltage at a normal level during continuous operation, and can provide a long-life fuel cell.

内部加湿方式においては、ガス入口の乾燥が課題となっている。特に、酸化剤極の方が燃料極よりも反応ガスの体積流量が大きいために、乾燥も顕著である。電池内の水移動量は、燃料極からプロトンと一緒に水分子が酸化剤極側に移動するドラッグ水と、酸化剤極から燃料極へと湿度勾配によって拡散する逆拡散水がある。ドラッグ水の量はプロトンの数によって決まるが、逆拡散水の量は高分子電解質膜１４の拡散係数に影響される。反応ガス透過防止層１８を付けることによって、トータルの拡散係数は低下し、逆拡散水が減少する。すなわち、酸化剤極側に水を保持する傾向にある。特に、ガス入口が乾燥している状態では、酸化剤極で水を保持することによって乾燥を防止することができる。   In the internal humidification method, drying of the gas inlet is a problem. In particular, the oxidizer electrode has a larger volume flow rate of the reaction gas than the fuel electrode, so that drying is also remarkable. The amount of water movement in the battery includes drag water in which water molecules move from the fuel electrode together with protons to the oxidant electrode side, and reverse diffusion water that diffuses from the oxidant electrode to the fuel electrode by a humidity gradient. The amount of drag water is determined by the number of protons, but the amount of reverse diffusion water is affected by the diffusion coefficient of the polymer electrolyte membrane 14. By attaching the reactive gas permeation preventive layer 18, the total diffusion coefficient is lowered and the back diffusion water is reduced. That is, water tends to be retained on the oxidizer electrode side. In particular, when the gas inlet is dry, drying can be prevented by holding water at the oxidant electrode.

酸化剤極入口で乾燥が生じると、湿潤部分でより反応が進行するために、面内で電流密度の偏りが生じる。入口の乾燥部分では電流密度が低くなる傾向にあるため、生成水量が減少し、更に乾燥が進行するという悪循環になる。結果として、電池の反応面を有効に活用できないために、セル電圧がどんどん低下していく。   When drying occurs at the oxidant electrode inlet, the reaction proceeds more in the wet part, and thus the current density is biased in the plane. Since the current density tends to be low in the dry portion at the inlet, the amount of generated water decreases, and a vicious cycle occurs in which drying proceeds. As a result, since the battery reaction surface cannot be used effectively, the cell voltage is steadily reduced.

一方、高分子電解質膜型燃料電池３０によれば、ガス入口における乾燥を抑制するため、電池の反応面を全体に有効に活用することができる。すなわち、セル電圧の低下を抑制し安定に運転することができる。   On the other hand, according to the polymer electrolyte membrane fuel cell 30, since the drying at the gas inlet is suppressed, the reaction surface of the cell can be effectively used as a whole. That is, it is possible to stably operate while suppressing a decrease in the cell voltage.

したがって、高分子電解質膜型燃料電池３０によれば、内部加湿方式におけるガス入口における乾燥を防止する効果が得られるため、連続運転時には電圧を通常レベルに維持しつつ使用に耐えることができ、長寿命の燃料電池を提供することができる。   Therefore, according to the polymer electrolyte membrane fuel cell 30, the effect of preventing drying at the gas inlet in the internal humidification method can be obtained, so that it can withstand use while maintaining the voltage at a normal level during continuous operation. A long-life fuel cell can be provided.

次に、反応ガス透過防止層１８の効果を検証するために、ＥＷ１１００の反応ガス透過防止層１８をＥＷ９００の高分子電解質膜１４に一体化し、図１のＰ（点線矢視）からＱ（点線矢視）方向への水移動量を測定した。   Next, in order to verify the effect of the reaction gas permeation prevention layer 18, the reaction gas permeation prevention layer 18 of the EW 1100 is integrated with the polymer electrolyte membrane 14 of the EW 900, and from P (dotted line arrow) to Q (dotted line) in FIG. The amount of water movement in the direction indicated by the arrow was measured.

測定した結果、反応ガス透過防止層１８は高分子電解質膜１４の片面に熱圧着されているが、その面に水を導入した場合と、ガスを導入した場合について図３に比較した。図３は、高分子電解質膜型燃料電池３０に用いられる高分子電解質膜１４、反応ガス透過防止層１８のガス側および水側における水移動量を示している。この図３から明らかな通り、反応ガス透過防止層１８を付けた側にガスを導入した場合に、水の移動量が抑制される傾向にある。更に、この場合には水側にＥＷの低い高分子電解質膜１４が位置するため、含水量が高くなり、膜抵抗が抑制される。   As a result of the measurement, the reaction gas permeation preventive layer 18 is thermocompression bonded to one surface of the polymer electrolyte membrane 14, and the case where water is introduced to that surface and the case where gas is introduced are compared with FIG. FIG. 3 shows the amount of water movement on the gas side and the water side of the polymer electrolyte membrane 14 and the reaction gas permeation preventive layer 18 used in the polymer electrolyte membrane fuel cell 30. As apparent from FIG. 3, when gas is introduced to the side where the reactive gas permeation preventive layer 18 is attached, the amount of water movement tends to be suppressed. Further, in this case, since the polymer electrolyte membrane 14 having a low EW is located on the water side, the water content is increased and the membrane resistance is suppressed.

酸化剤極入口における乾燥を防止することを考えた場合、燃料極の湿度が高く、酸化剤極において水が蒸発することが望ましい。このことから、水移動量測定における、水を導入した面が燃料極、ガスを導入した面が酸化剤極になるように設けられる。水移動を抑制し、なおかつ含水量を高く維持するためには、酸化剤極面に反応ガス透過防止層１８を付けた方が効果的である。   In consideration of preventing drying at the oxidant electrode inlet, it is desirable that the humidity of the fuel electrode is high and water evaporates at the oxidant electrode. For this reason, in measuring the amount of water movement, the surface into which water is introduced is provided as a fuel electrode, and the surface into which gas is introduced is provided as an oxidizer electrode. In order to suppress water movement and maintain a high water content, it is more effective to attach the reactive gas permeation preventive layer 18 to the oxidant electrode surface.

次に、高分子電解質膜型燃料電池３０の効果を検証するために連続発電運転試験を行った結果を図４に示す。連続発電試験を行うにあたって、燃料極には改質ガス組成を模擬した混合ガスを、酸化剤極には空気を導入する。加湿方式としては、内部加湿方式を適用しており、両極の反応ガスはいずれも湿度０％で電池スタックに導入している。本試験は、加速試験として電流密度を定格電流の２倍の値として運転した。図４に示すように、高分子電解質膜型燃料電池３０の特性を示すデータＸによれば、平均セル電圧（Ｖ）で、０．６〜０．７Ｖに維持しつつ３，０００Ｈ（時間）の連続運転に耐えることを示している。   Next, FIG. 4 shows the result of a continuous power generation operation test for verifying the effect of the polymer electrolyte membrane fuel cell 30. In conducting the continuous power generation test, a mixed gas simulating the reformed gas composition is introduced into the fuel electrode, and air is introduced into the oxidizer electrode. As the humidification method, an internal humidification method is applied, and both reactive gases are introduced into the battery stack at a humidity of 0%. In this test, the current density was operated as an acceleration test at a value twice the rated current. As shown in FIG. 4, according to the data X indicating the characteristics of the polymer electrolyte membrane fuel cell 30, the average cell voltage (V) is maintained at 0.6 to 0.7 V and 3,000 H (hours). It can withstand continuous operation.

このデータＸの得られる電池スタックには、反応ガス透過防止層１８以外は通常仕様の電池材料を適用し、試験条件も同じ条件で運転した。このデータＸの特性を示した高分子電解質膜型燃料電池３０の電池電圧は低下せずに安定に推移していることがわかる。   For the battery stack from which this data X was obtained, battery materials of normal specifications were applied except for the reactive gas permeation prevention layer 18, and the test conditions were also operated under the same conditions. It can be seen that the cell voltage of the polymer electrolyte membrane fuel cell 30 exhibiting the characteristics of the data X is stable without decreasing.

他方、比較用に一般的な燃料電池の特性を示すデータＹ（反応ガス透過防止層１８を適用しない電池の場合）の電池スタックによれば、発電試験開始時から連続的に電圧が低下し続けている。   On the other hand, according to the battery stack of data Y (in the case of a battery to which the reaction gas permeation preventive layer 18 is not applied) indicating the characteristics of a general fuel cell for comparison, the voltage continuously decreases from the start of the power generation test. ing.

したがって、高分子電解質膜型燃料電池３０による電圧低下速度が小さく抑えられることが確認された。   Therefore, it was confirmed that the voltage drop rate by the polymer electrolyte membrane fuel cell 30 can be kept small.

本発明の高分子電解質膜型燃料電池の一実施形態の模式図。The schematic diagram of one Embodiment of the polymer electrolyte membrane type fuel cell of this invention. 本発明の高分子電解質膜型燃料電池内における水移動量の差の状態の例を示すグラフ。The graph which shows the example of the state of the difference of the amount of water movement in the polymer electrolyte membrane type fuel cell of this invention. 本発明の高分子電解質膜型燃料電池に用いられる電解質膜の水移動量の例を示すグラフ。The graph which shows the example of the amount of water movement of the electrolyte membrane used for the polymer electrolyte membrane type fuel cell of this invention. 本発明の高分子電解質膜型燃料電池の特性の例を示すグラフ。The graph which shows the example of the characteristic of the polymer electrolyte membrane type fuel cell of this invention. 従来の高分子電解質膜型燃料電池の模式図。The schematic diagram of the conventional polymer electrolyte membrane type fuel cell.

符号の説明Explanation of symbols

３０ 高分子電解質膜型燃料電池
１１ 燃料極ガス拡散層
１２ 燃料極触媒層
１３ 燃料極
１４ 高分子電解質膜
１５ 酸化剤極
１６ 酸化剤極ガス拡散層
１７ 酸化剤極触媒層
１８ 反応ガス透過防止層
１９ 高分子電解質膜 30 Polymer Electrolyte Membrane Fuel Cell 11 Fuel Electrode Gas Diffusion Layer 12 Fuel Electrode Catalyst Layer 13 Fuel Electrode 14 Polymer Electrolyte Membrane 15 Oxidant Electrode 16 Oxidant Electrode Gas Diffusion Layer 17 Oxidant Electrode Catalyst Layer 18 Reactive Gas Permeation Prevention Layer 19 Polymer electrolyte membrane

Claims (2)

高分子電解質膜の両側に配置された燃料極および酸化剤極と、前記高分子電解質膜の少なくとも１つの面に接合して設けた反応ガス透過防止層と、を備え、前記反応ガス透過防止層は少なくとも反応ガスを消費させるための触媒成分と電解質成分を含有し、
前記反応ガス透過防止層に含まれる電解質成分のイオン交換容量が、前記高分子電解質膜のイオン交換容量よりも低くしたことを特徴とする高分子電解質膜型燃料電池。 A fuel electrode and an oxidant electrode disposed on both sides of the polymer electrolyte membrane; and a reaction gas permeation prevention layer provided in contact with at least one surface of the polymer electrolyte membrane, the reaction gas permeation prevention layer Contains at least a catalyst component and an electrolyte component for consuming the reaction gas,
A polymer electrolyte membrane fuel cell, wherein an ion exchange capacity of an electrolyte component contained in the reaction gas permeation prevention layer is lower than an ion exchange capacity of the polymer electrolyte membrane. 前記反応ガス透過防止層は、高分子電解質膜の酸化剤極側にのみ設けられたことを特徴とする請求項１に記載の高分子電解質膜型燃料電池。   2. The polymer electrolyte membrane fuel cell according to claim 1, wherein the reactive gas permeation prevention layer is provided only on the oxidant electrode side of the polymer electrolyte membrane.
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