JP5228339B2 - Electrode catalyst layer for fuel cell, MEA (electrolyte membrane electrode assembly) and polymer electrolyte fuel cell comprising the same - Google Patents
Electrode catalyst layer for fuel cell, MEA (electrolyte membrane electrode assembly) and polymer electrolyte fuel cell comprising the same Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description
本発明は、燃料電池に用いる電極触媒層に関し、更に詳しくは、スルホン酸基が導入された無定形炭素を含有させることにより水管理性を付与した燃料電池用電極触媒層に関するものである。 The present invention relates to an electrode catalyst layer for use in a fuel cell, and more particularly, to an electrode catalyst layer for a fuel cell to which water management is imparted by incorporating amorphous carbon into which a sulfonic acid group has been introduced.
燃料電池は、水素などの燃料と空気などの酸化剤を電気化学的に反応させることにより、化学エネルギーを電気エネルギーに変換して成る発電方式を採用しており、発電効率が高く、静粛性に優れ、大気汚染の原因となるＮＯｘ、ＳＯｘ、また、地球温暖化の原因となるＣＯ２の排出量が少ないなどの長所を持つため、開発が盛んに行われている。 Fuel cells employ a power generation system that converts chemical energy into electrical energy by electrochemically reacting a fuel such as hydrogen with an oxidant such as air, resulting in high power generation efficiency and quietness. Development is actively conducted because it has advantages such as excellent emission of NOx and SOx that cause air pollution and low CO 2 emission that causes global warming.
燃料電池の種類は使用する電解質によって、固体高分子型、リン酸型、溶融炭酸塩型、固体酸化物型、アルカリ型等に分類され、それぞれ運転温度が大きく異なり、それに伴い発電規模や利用分野も異なる。 The types of fuel cells are classified into solid polymer type, phosphoric acid type, molten carbonate type, solid oxide type, alkaline type, etc., depending on the electrolyte used. Is also different.
燃料電池の中でも、固体高分子型燃料電池は、低温領域での運転が可能であり、８０〜１００℃の運転温度で使用されるのが一般的であり、車載用電源や家庭据置用電源などへの展開が期待されている。 Among the fuel cells, the polymer electrolyte fuel cell can be operated in a low temperature region and is generally used at an operating temperature of 80 to 100 ° C., such as an in-vehicle power source or a home stationary power source. Expansion to is expected.
固体高分子型燃料電池は、電解質膜の一方の面にアノード（燃料極）、他方の面にカソード（空気極）を設けた電解質膜電極接合体（以下ＭＥＡと記述する）の両側に、セパレータを配した単電池セルを単数あるいは複数積層した構造を有している。 The polymer electrolyte fuel cell has separators on both sides of an electrolyte membrane electrode assembly (hereinafter referred to as MEA) in which an anode (fuel electrode) is provided on one surface of the electrolyte membrane and a cathode (air electrode) on the other surface. Has a structure in which a single battery cell or a plurality of stacked single battery cells is stacked.
アノード（燃料極）およびカソード（空気極）は、白金系貴金属などの触媒物質を担持したカーボン粒子と高分子電解質からなる電極触媒層と、ガス通気性と電導性を兼ね備えたガス拡散層からなる。 The anode (fuel electrode) and cathode (air electrode) are composed of an electrode catalyst layer made of carbon particles supporting a catalytic substance such as a platinum-based noble metal and a polymer electrolyte, and a gas diffusion layer having both gas permeability and conductivity. .
固体高分子型燃料電池は、電解質膜の導電性を確保するために、ＭＥＡを加湿する必要があるが、燃料電池システム全体のエネルギー効率の点から低加湿での運転が望ましく、その為にはＭＥＡの水管理性が重要となる。 In the polymer electrolyte fuel cell, it is necessary to humidify the MEA in order to ensure the conductivity of the electrolyte membrane, but it is desirable to operate with low humidification from the viewpoint of the energy efficiency of the entire fuel cell system. MEA water management is important.
優れたＭＥＡ水管理性を有する低加湿運転可能な燃料電池として、触媒粒子、高分子電解質、および、スメクタイト族鉱物又は合成雲母粒子などの層状珪酸塩粒子からなる電極触媒層を有する燃料電池が提案されている。（特許文献１） A fuel cell having an electrode catalyst layer made of layered silicate particles such as catalyst particles, polymer electrolyte, and smectite group minerals or synthetic mica particles is proposed as a fuel cell having excellent MEA water management and capable of low humidification operation. Has been. (Patent Document 1)
しかしながら、前記層状珪酸塩粒子のイオン交換容量は０．５ｍｅｑ／ｇ程度と低く、該層状珪酸塩粒子を多量に含有させることにより、電極触媒層のプロトン伝導性を低下させるという問題が生じる。 However, the ion exchange capacity of the layered silicate particles is as low as about 0.5 meq / g, and there is a problem that the proton conductivity of the electrode catalyst layer is lowered by containing a large amount of the layered silicate particles.
本発明の課題は、低加湿運転が可能な固体高分子型燃料電池、並びに、それに用いるＭＥＡ、並びに、それに用いる電極触媒層を提供することである。 An object of the present invention is to provide a polymer electrolyte fuel cell capable of low humidification operation, an MEA used therefor, and an electrode catalyst layer used therefor.
請求項１に記載の発明は、触媒粒子を担持したカーボンとプロトン伝導性高分子とスルホン酸基が導入された無定形炭素とを含有し、前記スルホン酸基が導入された無定形炭素が、１３Ｃ核磁気共鳴スペクトルにて、縮合芳香族炭素６員環及びスルホン酸基が結合した縮合芳香族炭素６員環の化学シフトが検出され、且つ、粉末Ｘ線回折にて、半値幅（２θ）が５〜３０°である炭素（００２）面の回折ピークが検出されるものであり、前記スルホン酸基が導入された無定形炭素が、電極触媒層の面内方向または膜厚方向に濃度傾斜していることを特徴とする燃料電池用電極触媒層である。 Invention of Claim 1 contains the carbon which carry | supported the catalyst particle, the proton conductive polymer, and the amorphous carbon in which the sulfonic acid group was introduce | transduced, The amorphous carbon in which the said sulfonic acid group was introduce | transduced, In the 13C nuclear magnetic resonance spectrum, a chemical shift of the condensed aromatic carbon 6-membered ring and the condensed aromatic carbon 6-membered ring to which the sulfonic acid group is bonded was detected, and a half width (2θ) was detected by powder X-ray diffraction. The diffraction peak of the carbon (002) plane having an angle of 5 to 30 ° is detected, and the amorphous carbon introduced with the sulfonic acid group has a concentration gradient in the in-plane direction or the film thickness direction of the electrode catalyst layer It is the electrode catalyst layer for fuel cells characterized by having carried out .
請求項２に記載の発明は、プロトン伝導性高分子電解質膜の少なくとも一つの面に、請求項１に記載の電極触媒層を配置させ、更に両面にガス拡散層を配置して成るＭＥＡ（電解質膜電極接合体）である。 According to a second aspect of the present invention, there is provided an MEA (electrolyte ) in which the electrode catalyst layer according to the first aspect is disposed on at least one surface of a proton conductive polymer electrolyte membrane, and gas diffusion layers are disposed on both surfaces. Membrane electrode assembly).
請求項３に記載の発明は、前記プロトン伝導性高分子電解質膜と前記電極触媒層の間に、プロトン伝導性高分子からなる中間層を有することを特徴とする請求項２に記載のＭＥＡ（電解質膜電極接合体）である。 According to a third aspect of the present invention, there is provided an MEA according to the second aspect, wherein an intermediate layer made of a proton conductive polymer is provided between the proton conductive polymer electrolyte membrane and the electrode catalyst layer. Electrolyte membrane electrode assembly).
請求項４に記載の発明は、請求項２または請求項３に記載のＭＥＡの両面に一対のセパレータを配置して成る固体高分子型燃料電池である。 The invention described in claim 4 is a polymer electrolyte fuel cell comprising a pair of separators disposed on both sides of the MEA described in claim 2 or claim 3 .
固体高分子型燃料電池の電極触媒層に、イオン交換容量が高く、優れたプロトン伝導性を有するスルホン酸基が導入された無定形炭素（以下、スルホン酸基導入無定形炭素と記載する）を含有させることにより、ＭＥＡ水管理性を備えた、低加湿運転が可能な固体高分子型燃料電池を得ることができる。 Amorphous carbon (hereinafter referred to as sulfonic acid group-introduced amorphous carbon) in which a sulfonic acid group having a high ion exchange capacity and excellent proton conductivity is introduced into an electrode catalyst layer of a polymer electrolyte fuel cell By containing, a polymer electrolyte fuel cell capable of low humidification operation with MEA water manageability can be obtained.
図１は、本発明の燃料電池の最小の単位である単セルの構造の一例を説明するための図である。 FIG. 1 is a diagram for explaining an example of the structure of a single cell which is the minimum unit of the fuel cell of the present invention.
本発明の燃料電池単セルは、一対の電極触媒層２ａ、２ｂで挟まれたプロトン伝導性高分子電解質膜１と、一対のガス拡散層３ａ、３ｂからなるものである。 The single fuel cell of the present invention comprises a proton conductive polymer electrolyte membrane 1 sandwiched between a pair of electrode catalyst layers 2a and 2b and a pair of gas diffusion layers 3a and 3b.
電極触媒層２ａ、２ｂの少なくとも一方の電極触媒層にスルホン酸基が導入された無定形炭素を含有させることにより、水管理性を有する電極触媒層を得ることができる。 By containing amorphous carbon having sulfonic acid groups introduced into at least one of the electrode catalyst layers 2a and 2b, an electrode catalyst layer having water manageability can be obtained.
スルホン酸基が導入された無定形炭素は、スルホン酸基を持ち、無定形炭素としての性質を示す物質であればどのようなものでも良い。 The amorphous carbon into which the sulfonic acid group has been introduced may be any substance that has a sulfonic acid group and exhibits the properties of amorphous carbon.
ここで「無定形炭素」とは、炭素からなる物質であって、ダイヤモンドや黒鉛のような明確な結晶構造を持たない物質であり、より具体的には、粉末Ｘ線回折において、明確なピークが検出されないか、あるいは幅の広いピークが検出される物質を意味する。 Here, “amorphous carbon” is a substance composed of carbon and does not have a clear crystal structure such as diamond or graphite, and more specifically, a clear peak in powder X-ray diffraction. Means a substance in which no or a broad peak is detected.
また、スルホン酸基が導入された無定形炭素の表面を化学処理した物質も本発明に好適に用いることができる。 In addition, a substance obtained by chemically treating the surface of amorphous carbon into which a sulfonic acid group has been introduced can also be suitably used in the present invention.
スルホン酸基導入無定形炭素のプロトン伝導度は特に限定されないが、０．０１Ｓ／ｃｍ以上、特に、０．０４Ｓ／ｃｍ以上が好ましい。 The proton conductivity of the sulfonic acid group-introduced amorphous carbon is not particularly limited, but is preferably 0.01 S / cm or more, and particularly preferably 0.04 S / cm or more.
無定形炭素のプロトン伝導度が、０．０４Ｓ／ｃｍ以上であれば、プロトンを効率良く伝導できる。（該プロトン伝導度は、温度８０℃、相対湿度１００％条件下、交流インピーダンス法によって測定される値である。） If the proton conductivity of amorphous carbon is 0.04 S / cm or more, protons can be efficiently conducted. (The proton conductivity is a value measured by the AC impedance method under conditions of a temperature of 80 ° C. and a relative humidity of 100%.)
本発明に用いられる電解質膜は、プロトン伝導性に優れ、且つ電子を流さない材料からなる物であれば特に限定されず、例えば、プロトン伝導性又は水酸化物イオン伝導性を有するイオン交換膜、例えば、パーフルオロカーボンスルホン酸（Ｄｕ ｐｏｎｔ社製、商品名Ｎａｆｉｏｎ２１２またはＮａｆｉｏｎ１１７等）などのフッ素系イオン交換膜などを用いることができ、中でも、プロトン伝導性が良いという観点から、スルホン化されたプロトン伝導性高分子電解質であるパーフルオロカーボンスルホン酸（Ｄｕ ｐｏｎｔ社製、商品名Ｎａｆｉｏｎ２１２またはＮａｆｉｏｎ１１７等）が好ましい。 The electrolyte membrane used in the present invention is not particularly limited as long as it is made of a material that is excellent in proton conductivity and does not flow electrons. For example, an ion exchange membrane having proton conductivity or hydroxide ion conductivity, For example, a fluorine-based ion exchange membrane such as perfluorocarbon sulfonic acid (trade name Nafion 212 or Nafion 117) manufactured by Du Pont, etc. can be used. Among them, sulfonated proton conduction from the viewpoint of good proton conductivity. Perfluorocarbon sulfonic acid (trade name Nafion 212 or Nafion 117, manufactured by Du Pont), which is a conductive polymer electrolyte, is preferable.
また、電解質膜としては、無機化合物をプロトン伝導材料としポリマーを膜材料とした耐熱性、メタノールクロスオーバー防止性に優れたコンポジット（複合）膜、例えば、無機化合物としてゼオライトを用い、ポリマーとしてスチレン−ブタジエン系ラバーからなる複合膜、または、プロトン伝導基を有するポリイミド等の炭化水素系樹脂、あるいは、炭化水素系グラフト膜を用いても良い。 In addition, as the electrolyte membrane, a composite membrane excellent in heat resistance and methanol crossover prevention property using an inorganic compound as a proton conducting material and a polymer as a membrane material, for example, using zeolite as an inorganic compound and styrene as a polymer. A composite film made of butadiene rubber, a hydrocarbon resin such as polyimide having a proton conductive group, or a hydrocarbon graft film may be used.
本発明で用いる触媒粒子としては、白金やパラジウム、ルテニウム、イリジウム、ロジウム、オスミウムの白金族元素の他、鉄、鉛、銅、クロム、コバルト、ニッケル、マンガン、バナジウム、モリブデン、ガリウム、アルミニウムなどの金属又はこれらの合金、または酸化物、複酸化物等が使用できる。また、これらの触媒の粒径は、大きすぎると触媒の活性が低下し、小さすぎると触媒の安定性が低下するため、０．５〜２０ｎｍが好ましい。更に好ましくは、１〜５ｎｍが良い。 Catalyst particles used in the present invention include platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and the like. A metal or an alloy thereof, or an oxide or a double oxide can be used. Moreover, since the activity of a catalyst will fall when the particle size of these catalysts is too large, and stability of a catalyst will fall when too small, 0.5-20 nm is preferable. More preferably, 1-5 nm is good.
触媒の粒径は０．５〜２０ｎｍの範囲から選択することができる。
粒径が０．５ｎｍ未満であると触媒安定性が低下し、また、２０ｎｍを超えると、触媒活性が低下してしまう。
The particle size of the catalyst can be selected from the range of 0.5 to 20 nm.
When the particle size is less than 0.5 nm, the catalyst stability is lowered, and when it exceeds 20 nm, the catalyst activity is lowered.
触媒インク中に含まれるプロトン伝導性高分子としては、用いる電解質膜と同じ成分とするのが好ましく、パーフルオロカーボンスルホン酸（Ｄｕ ｐｏｎｔ社製、商品名Ｎａｆｉｏｎ２１２またはＮａｆｉｏｎ１１７等）などのフッ素系イオン交換膜などを用いることができ、中でも、プロトン伝導性が良いという観点から、スルホン化されたプロトン伝導性高分子電解質であるパーフルオロカーボンスルホン酸（Ｄｕ ｐｏｎｔ社製、商品名Ｎａｆｉｏｎ）が好ましい。 The proton conductive polymer contained in the catalyst ink is preferably the same component as the electrolyte membrane to be used, and a fluorine-based ion exchange membrane such as perfluorocarbon sulfonic acid (manufactured by Du Pont, trade name Nafion212 or Nafion117). Among them, perfluorocarbon sulfonic acid (trade name Nafion, manufactured by Du Pont), which is a sulfonated proton conductive polymer electrolyte, is preferable from the viewpoint of good proton conductivity.
触媒インクの分散媒として使用される溶媒は、触媒粒子や水素イオン伝導性樹脂を浸食することがなく、流動性の高い状態でプロトン伝導性高分子を溶解または微細ゲルとして分散できるものであれば特に制限はないが、例えば、メタノール、エタノール、１−プロパノ―ル、２−プロパノ―ル、１−ブタノ−ル、２−ブタノ−ル、イソブチルアルコール、ｔｅｒｔ−ブチルアルコール、ペンタノ−ル、２−ヘプタノ−ル、ベンジルアルコール等のアルコール類、アセトン、メチルエチルケトン、メチルプロピルケトン、メチルブチルケトン、メチルイゾブチルケトン、メチルアミルケトン、ペンタノン、へプタノン、シクロヘキサノン、メチルシクロヘキサノン、アセトニルアセトン、ジエチルケトン、ジプロピルケトン、ジイソブチルケトンなどのケトン類、テトラヒドロフラン、テトラヒドロピラン、ジオキサン、ジエチレングリコールジメチルエーテル、アニソール、メトキシトルエン、ジエチルエーテル、ジプロピルエーテル、ジブチルエーテル等のエーテル類、イソプロピルアミン、ブチルアミン、イソブチルアミン、シクロヘキシルアミン、ジエチルアミン、アニリンなどのアミン類、蟻酸プロピル、蟻酸イソブチル、蟻酸アミル、酢酸メチル、酢酸エチル、酢酸プロピル、酢酸ブチル、酢酸イソブチル、酢酸ペンチル、酢酸イソペンチル、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸ブチルなどのエステル類、その他酢酸、プロピオン酸、ジメチルホルムアミド、ジメチルアセトアミド、Ｎ−メチルピロリドン、エチレングリコール、ジエチレングリコール、プロピレングリコール、エチレングリコールモノメチルエーテル、エチレングリコールジメチルエーテル、エチレングリコールジエチルエーテル、ジアセトンアルコール、１−メトキシ−２−プロパノール等の極性溶媒などを用いることができる。 The solvent used as the dispersion medium of the catalyst ink is not particularly eroded by catalyst particles and hydrogen ion conductive resin, and can dissolve the proton conductive polymer in a highly fluid state or can be dispersed as a fine gel. Although there is no particular limitation, for example, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, pentaanol, 2- Alcohols such as heptanol, benzyl alcohol, acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, pentanone, heptanone, cyclohexanone, methyl cyclohexanone, acetonyl acetone, diethyl ketone, di- Propyl ketone, diisobutylke Ketones such as ethylene, tetrahydrofuran, tetrahydropyran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, diethyl ether, dipropyl ether, dibutyl ether and other ethers, isopropylamine, butylamine, isobutylamine, cyclohexylamine, diethylamine, aniline, etc. Amines such as propyl formate, isobutyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, butyl propionate, Other acetic acid, propionic acid, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol Lumpur, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diacetone alcohol, and the like can be used polar solvents such as 1-methoxy-2-propanol.
また、上記溶媒は単独で用いても、また、二種以上を混合させて用いても良い。 Moreover, the said solvent may be used independently or may be used in mixture of 2 or more types.
上記溶媒の中でも、誘電率が異なる二種類の溶媒を用いることにより、触媒インク分散液中のプロトン伝導性高分子の分散状態を制御することができる。 By using two types of solvents having different dielectric constants among the above solvents, the dispersion state of the proton conductive polymer in the catalyst ink dispersion can be controlled.
上記溶媒のうち低級アルコールを用いたものは発火の危険性が高く、このような溶媒を用いる際は水との混合溶媒にするのが好ましい。 Among the above solvents, those using lower alcohols have a high risk of ignition, and when using such solvents, it is preferable to use a mixed solvent with water.
また、溶媒中に、プロトン伝導性高分子と馴染みの良い水が含まれていても良い。
水の添加量は、プロトン伝導性高分子が分離して白濁を生じたり、ゲル化しない程度であれば特に制限はない。
The solvent may contain water that is familiar to the proton-conducting polymer.
The amount of water added is not particularly limited as long as the proton conductive polymer is separated to cause white turbidity or does not gel.
また、溶媒中に、電極触媒層の空孔率を制御するために、造孔剤として、グリセリンや界面活性剤を添加しても良い。 Moreover, in order to control the porosity of an electrode catalyst layer in a solvent, you may add glycerol and surfactant as a pore making agent.
電極触媒層の形成方法としては、ドクターブレード法、ディッピング法、スクリーン印刷法、ロールコーティング法、スプレー法などを用いることができる。 As a method for forming the electrode catalyst layer, a doctor blade method, a dipping method, a screen printing method, a roll coating method, a spray method, or the like can be used.
触媒インクの粘度は、塗布方法によって最適値が異なるが、例えば、スクリーン印刷法やドクターブレード法による塗布の場合、インキの粘度は５０〜５００ｃＰであることが好ましい。 The optimum viscosity of the catalyst ink varies depending on the coating method. For example, in the case of coating by a screen printing method or a doctor blade method, the viscosity of the ink is preferably 50 to 500 cP.
触媒インクの粘度が５０ｃｐ未満であると、触媒インクの流動性が大き過ぎ、触媒インクを導電性ガス拡散材上に塗工する際に、導電性ガス拡散材の気孔への触媒インクの含浸量が多くなり過ぎ、導電性ガス拡散材の気孔が塞がってしまう。 When the viscosity of the catalyst ink is less than 50 cp, the fluidity of the catalyst ink is too high, and the amount of impregnation of the catalyst ink into the pores of the conductive gas diffusion material when the catalyst ink is applied on the conductive gas diffusion material Too much and the pores of the conductive gas diffusion material are blocked.
また、触媒インクの粘度が５００ｃｐを超えると触媒インクの流動性が小さ過ぎ、触媒インクを導電性ガス拡散材上に塗工する際に、導電性ガス拡散材の気孔への触媒インクの含浸量が少なくなり過ぎ、触媒インクと導電性ガス拡散材との密着強度が低くなってしまう。 Further, when the viscosity of the catalyst ink exceeds 500 cp, the fluidity of the catalyst ink is too small, and when the catalyst ink is applied onto the conductive gas diffusion material, the amount of impregnation of the catalyst ink into the pores of the conductive gas diffusion material However, the adhesion strength between the catalyst ink and the conductive gas diffusion material is lowered.
また、触媒インクをスプレー法により導電性ガス拡散材上に噴霧する場合は、インキの粘度が０．１〜１００ｃＰであることが好ましい。 Moreover, when spraying catalyst ink on a conductive gas diffusion material by a spray method, it is preferable that the viscosity of ink is 0.1-100 cP.
触媒インクの粘度が０．１ｃｐ未満であると、成膜レートが非常に遅く、生産性が低下してしまう。 When the viscosity of the catalyst ink is less than 0.1 cp, the film formation rate is very slow, and the productivity is lowered.
また、触媒インクの粘度が１００ｃｐを超えると触媒インクの流動性が小さ過ぎ、スプレーノズルが詰まり易くなり、生産性が低下してしまう。 On the other hand, when the viscosity of the catalyst ink exceeds 100 cp, the fluidity of the catalyst ink is too small, the spray nozzle is easily clogged, and the productivity is lowered.
触媒インクの粘度は、用いる溶媒の種類、および／または固形分濃度を変化させることで最適化できる。
また、触媒インクに分散剤を添加することにより、粘度の制御をしても良い。
The viscosity of the catalyst ink can be optimized by changing the type of solvent used and / or the solid content concentration.
Further, the viscosity may be controlled by adding a dispersant to the catalyst ink.
電極触媒層の形成方法としては、前記スクリーン印刷法、ドクターブレード法、スプレー法を用いることができるが、発電で生成した水による発電セル流路上流から下流における燃料ガスの局所的な相対湿度変化を少なくすることを目的とし、前期電極触媒層の面内方向または膜厚方向に、スルホン酸基が導入された無定形炭素を最適に濃度分布できるという観点から、導電性ガス拡散材上に触媒インクをスプレーし、その後、該触媒インクを乾燥させる方法（スプレー法）を用いることができる。 As a method for forming the electrode catalyst layer, the screen printing method, the doctor blade method, and the spray method can be used, but the local relative humidity change of the fuel gas from the upstream to the downstream of the power generation cell channel due to the water generated by the power generation From the viewpoint that the concentration of amorphous carbon introduced with sulfonic acid groups can be optimally distributed in the in-plane direction or the film thickness direction of the previous electrode catalyst layer, the catalyst is formed on the conductive gas diffusion material. A method of spraying ink and then drying the catalyst ink (spray method) can be used.
スプレー法を用いると、微粒子化された触媒インク中の溶剤の大部分が、導電性ガス拡散材やプロトン伝導性高分子電解質膜の表面に付着する前に、蒸発する。
該蒸発の速度を速める事により、塗着後の触媒インク液滴の流動による粒子凝集が少なくなり、均質な電極触媒層を作製する事ができる。
When the spray method is used, most of the solvent in the finely divided catalyst ink evaporates before adhering to the surface of the conductive gas diffusion material or the proton conductive polymer electrolyte membrane.
By increasing the evaporation speed, particle aggregation due to the flow of the catalyst ink droplets after coating is reduced, and a homogeneous electrode catalyst layer can be produced.
ＭＥＡの形成方法としては、プロトン伝導性高分子膜と前記電極触媒層を、熱圧着法を用いて接合する手法や、プロトン伝導性高分子膜の両面に触媒インクを噴霧した後、ガス拡散層で挟持する手法や、離型性の基材上に触媒インクを噴霧した後、触媒インク層をプロトン伝導性高分子膜の両面に転写し、その後、ガス拡散層で挟持する手法を用いることができる。 As a method for forming MEA, a method in which a proton conductive polymer membrane and the electrode catalyst layer are joined using a thermocompression bonding method, or after spraying catalyst ink on both sides of the proton conductive polymer membrane, a gas diffusion layer is used. Or a method in which the catalyst ink layer is sprayed on both sides of the proton conductive polymer film after the catalyst ink is sprayed on the releasable substrate and then sandwiched between the gas diffusion layers. it can.
導電性ガス拡散材としては、ガスの供給・拡散・排出機能を有し、かつ、集電機能を有する物であれば、特に限定されず、例えば、カーボンクロス、カーボンペーパー、カーボンネットおよびメッシュ状カーボン等や、導電性高分子繊維集合体、カーボンの焼結体、焼結金属、発泡金属などの電導性多孔質材を用いることができる The conductive gas diffusion material is not particularly limited as long as it has a gas supply / diffusion / discharge function and a current collecting function, for example, carbon cloth, carbon paper, carbon net and mesh shape. Conductive porous materials such as carbon, conductive polymer fiber aggregate, carbon sintered body, sintered metal, foam metal, etc. can be used
導電性ガス拡散材の厚さとしては、所望する電池特性が得られるように適宜決定すればよく、特に限定されない。 The thickness of the conductive gas diffusion material may be appropriately determined so as to obtain desired battery characteristics, and is not particularly limited.
触媒電極を、プレス機等を用いて、パーフルオロカーボンスルホン酸（Ｄｕ ｐｏｎｔ社製、商品名Ｎａｆｉｏｎ）やスルホン化されたエンジニアリングプラスチックから成る電解質膜に熱圧着することにより、膜・電極接合体（ＭＥＡ）を得ることができる。 The catalyst electrode is thermocompression-bonded to an electrolyte membrane made of perfluorocarbon sulfonic acid (manufactured by Du Pont, trade name Nafion) or a sulfonated engineering plastic by using a press or the like, so that a membrane / electrode assembly (MEA) is obtained. ) Can be obtained.
電極触媒層と電解質膜を熱圧着する際に、該電極触媒層と電解質膜の密着性を高める為に、プロトン伝導性高分子を含む溶液を結着剤として用いても良い。
該プロトン伝導性高分子と、電解質膜および電極触媒層に含有されるプロトン伝導性高分子を、同一とすることが好ましい。
In thermocompression bonding of the electrode catalyst layer and the electrolyte membrane, a solution containing a proton conductive polymer may be used as a binder in order to improve the adhesion between the electrode catalyst layer and the electrolyte membrane.
The proton conductive polymer and the proton conductive polymer contained in the electrolyte membrane and the electrode catalyst layer are preferably the same.
膜・電極接合体（ＭＥＡ）にセパレータや補助的な装置（ガス供給装置、冷却装置など）を組み合わせることにより燃料電池を作製することが出来る。 A fuel cell can be produced by combining a membrane / electrode assembly (MEA) with a separator or an auxiliary device (such as a gas supply device or a cooling device).
セパレータは、ガス遮断性、および、導電性を有していればよく、焼成カーボン切削材や、ステンレス鋼およびステンレス鋼表面に金めっきを施した金属材や、熱硬化性樹脂または熱可塑性樹脂で炭素粉末を支持した炭素複合材などを用いることができる。 The separator is only required to have gas barrier properties and conductivity, and is made of a fired carbon cutting material, a stainless steel and a metal material with a gold plating on the stainless steel surface, a thermosetting resin or a thermoplastic resin. A carbon composite material supporting carbon powder can be used.
また、セパレータは、直線状の流路溝を複数備えたストレート型や、複数の凸部を設け該凸部間の隙間により流路を構成した分割リブ型を用いることができるが、中でも、ガスの拡散性と生成水（燃料電池発電に際して生成する水）の排水性に優れているという観点から、分割リブ型が好ましい。
（分割リブ型のセパレータは、流路が複数方向に分散するため、フラッディング（燃料電池発電に際して生成する水の凝縮）により一つの流路が閉塞されても、ガスや生成水は他の流路に回り込むことが可能である。）
The separator may be a straight type having a plurality of linear flow channel grooves or a split rib type having a plurality of convex portions and having a flow path formed by a gap between the convex portions. The split rib type is preferable from the viewpoint of excellent diffusibility of water and drainage of generated water (water generated during fuel cell power generation).
(Since the split rib type separator has flow paths dispersed in a plurality of directions, even if one flow path is blocked by flooding (condensation of water generated during fuel cell power generation), gas and generated water are not It is possible to wrap around.)
上記燃料電池システムは、外部加湿装置が存在しない燃料電池に限定されない。
外部加湿装置によって高分子電解質膜が加湿される場合であっても、補機を用いて供給する加湿量が減少し、燃料電池システム全体の発電効率が向上する。
The fuel cell system is not limited to a fuel cell without an external humidifier.
Even when the polymer electrolyte membrane is humidified by the external humidifier, the amount of humidification supplied using the auxiliary machine is reduced, and the power generation efficiency of the entire fuel cell system is improved.
（触媒インクの調整）
白金触媒を担持したカーボン、パーフルオロカーボンスルホン酸（Ｄｕ ｐｏｎｔ社製、商品名Ｎａｆｉｏｎ溶液）、および、スルホン酸基が導入された無定形炭素を溶媒（水、１−プロパノ−ル、２−プロパノ−ル＝１：１：１（体積比））中で混合し、遊星型ボールミル（ＦＲＩＴＳＣＨ社製 Ｐｕｌｖｅｒｉｓｅｔｔｅ７）（ボールミルのポット、ボールはジルコニア製）を用いて分散処理を行った。
触媒インク中の固形分含有量は１０重量％であった。
(Catalyst ink adjustment)
Carbon supported on a platinum catalyst, perfluorocarbon sulfonic acid (manufactured by Du Pont, trade name Nafion solution), and amorphous carbon into which a sulfonic acid group has been introduced are used as a solvent (water, 1-propanol, 2-propanol). And mixed with a planetary ball mill (Pulverisette 7 manufactured by FRITSCH) (ball mill pot, balls are manufactured by zirconia).
The solid content in the catalyst ink was 10% by weight.
（電極触媒層の作製方法）
触媒インクを、アプリケータを用いてカーボンクロス上に塗布することにより、電極触媒層を作製した。
電極触媒層の厚さは、電極触媒層における触媒担持量が０．５ｍｇ／ｃｍ２になるように調節した。
(Method for producing electrode catalyst layer)
An electrode catalyst layer was prepared by applying the catalyst ink on the carbon cloth using an applicator.
The thickness of the electrode catalyst layer was adjusted so that the amount of catalyst supported on the electrode catalyst layer was 0.5 mg / cm 2 .
＜比較例＞
（触媒層形成用塗工液の調整）
スルホン酸基が導入された無定形炭素を使用しなかったこと以外は実施例１と同様に触媒層形成用塗工液を調整した。
<Comparative example>
(Adjustment of catalyst layer forming coating solution)
A catalyst layer forming coating solution was prepared in the same manner as in Example 1 except that amorphous carbon into which a sulfonic acid group was introduced was not used.
（膜・電極接合体の作製）
プロトン伝導性高分子膜（Ｄｕ ｐｏｎｔ社製、商品名Ｎａｆｉｏｎ２１２）を実施例および比較例の触媒電極にて挟持した後、温度１２０℃、圧力５．９ＭＰａの条件にてホットプレスを行い、膜・電極接合体（ＭＥＡ）を得た。
(Production of membrane / electrode assembly)
After sandwiching a proton conductive polymer membrane (manufactured by Du Pont, trade name Nafion 212) between the catalyst electrodes of Examples and Comparative Examples, hot pressing was performed under the conditions of a temperature of 120 ° C. and a pressure of 5.9 MPa. An electrode assembly (MEA) was obtained.
（固体高分子型燃料電池の作製）
前記膜・電極接合体（ＭＥＡ）を一対の焼成カーボン製のセパレータで挟持することにより、固体高分子型燃料電池を作製した。
(Production of polymer electrolyte fuel cell)
The membrane / electrode assembly (MEA) was sandwiched between a pair of calcined carbon separators to produce a polymer electrolyte fuel cell.
（発電特性評価）
燃料電池測定装置（東陽テクニカ社製ＧＦＴ−ＳＧ１）を用いて、燃料ガスとして水素を毎分２００ｍｌ、酸化剤ガスとして酸素を毎分１００ｍｌ一定に流し、燃料電池セル温度８０℃、アノード１００％ＲＨ、カソード２６％ＲＨの条件下において、固体高分子型燃料電池を運転し、最大出力（ｍＷ／ｃｍ２）およびセル抵抗（ｍΩ・ｃｍ２）を計測した。
各電流密度におけるセル抵抗の値を表１に示した。
(Evaluation of power generation characteristics)
Using a fuel cell measuring apparatus (GFT-SG1 manufactured by Toyo Technica Co., Ltd.), hydrogen as a fuel gas was constantly flowed at 200 ml / min and oxygen as an oxidant gas at a constant flow of 100 ml / min. The polymer electrolyte fuel cell was operated under the condition of cathode 26% RH, and the maximum output (mW / cm 2 ) and cell resistance (mΩ · cm 2 ) were measured.
Table 1 shows the cell resistance values at each current density.
表１に示す様に、イオン交換容量が高く、優れたプロトン伝導性を有するスルホン酸基が導入された無定形炭素を含有した電極触媒層を用いた燃料電池は、相対湿度（％ＲＨ）が低い環境下において、セル抵抗を下げる働きがあることを確認した。 As shown in Table 1, the relative humidity (% RH) of the fuel cell using the electrode catalyst layer containing amorphous carbon having a high ion exchange capacity and a sulfonic acid group having excellent proton conductivity is introduced. It was confirmed that there is a function to lower the cell resistance in a low environment.
１・・・・・・・固体高分子電解質膜
２ａ、２ｂ・・・電極触媒層
３ａ、３ｂ・・・導電性ガス拡散材
４・・・・・・・アノード
５・・・・・・・カソード
1 ... Solid polymer electrolyte membranes 2a, 2b ... Electrocatalyst layers 3a, 3b ... Conductive gas diffusion material 4 ... Anode 5 ... Cathode
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