JP2010257929A - Method of manufacturing electrode catalyst slurry for fuel cell, electrode for polymer electrolyte fuel cell, and membrane electrode assembly - Google Patents

Method of manufacturing electrode catalyst slurry for fuel cell, electrode for polymer electrolyte fuel cell, and membrane electrode assembly Download PDF

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JP2010257929A
JP2010257929A JP2009180752A JP2009180752A JP2010257929A JP 2010257929 A JP2010257929 A JP 2010257929A JP 2009180752 A JP2009180752 A JP 2009180752A JP 2009180752 A JP2009180752 A JP 2009180752A JP 2010257929 A JP2010257929 A JP 2010257929A
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ionomer
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JP5374273B2 (en
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Koji Matsuoka
孝司 松岡
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Eneos Celltech Co Ltd
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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
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    • Y02E60/50—Fuel cells
    • 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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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of manufacturing an electrode catalyst slurry for a fuel cell good in mixing uniformity with electrode catalyst and ionomer and an electrode and a membrane electrode assembly for PEFC capable of a good catalyst utilization rate. <P>SOLUTION: The method of manufacturing an electrode catalyst slurry for a fuel cell used to form PEFC electrodes includes: (a) to mix water and low-class alcohol (≤4C) in an electrode catalyst and disperse electrode catalyst particles to have a dispersion liquid; (b) to mix the ionomer in solvent to have an ionomer solution whose relative dielectric constant at 20°C is 30 or more; (c) to mix the dispersion liquid obtained in the process (a) with the ionomer solution obtanined in the process (b) to have a dispersion liquid; and (d) to enhance the viscosity of the dispersion liquid by mixing a low relative dielectric constant dispersion medium being a dispersion medium whose relative dielectric constant at 20°C is 20 or less into the dispersion liquid obtained in the process (c). The electrode for a polymer electrolyte fuel cell obtained from the electrode catalyst slurry manufactured by this method and the membrane electrode assembly having this electrode are also provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は固体高分子型燃料電池の電極を形成するために用いる電極触媒スラリーの製造方法に関する。また本発明は、固体高分子型燃料電池用の電極および膜・電極接合体に関する。   The present invention relates to a method for producing an electrocatalyst slurry used for forming an electrode of a polymer electrolyte fuel cell. The present invention also relates to an electrode for a polymer electrolyte fuel cell and a membrane / electrode assembly.

固体高分子型燃料電池の電極を形成するために、電極触媒を分散媒に分散させた分散体である電極触媒スラリーが用いられる。電極触媒スラリーを電解質膜に塗布して乾燥させて、膜・電極接合体（ＭＥＡ）を作成し、ＭＥＡをセパレータで挟むことにより、固体高分子型燃料電池を形成することができる。   In order to form an electrode of a polymer electrolyte fuel cell, an electrode catalyst slurry which is a dispersion in which an electrode catalyst is dispersed in a dispersion medium is used. A polymer electrolyte fuel cell can be formed by applying an electrode catalyst slurry to an electrolyte membrane and drying it to form a membrane-electrode assembly (MEA) and sandwiching the MEA with a separator.

特許文献１に、水より沸点が高く水溶液としたときに所定の温度以下で共沸する共沸溶剤の水溶液に触媒を担持する触媒担持カーボン粉末を分散してなる分散溶液から調製されてなる電極触媒溶液が記載される。   Patent Document 1 discloses an electrode prepared from a dispersion solution in which a catalyst-supporting carbon powder supporting a catalyst is dispersed in an aqueous solution of an azeotropic solvent that has an azeotropic boiling below a predetermined temperature when the aqueous solution has a higher boiling point than water. A catalyst solution is described.

特開２００１−２６６９０１号公報JP 2001-266901 A

電極触媒スラリーには、電極触媒の他に、アイオノマーが加えられる。電極触媒とアイオノマーが均一に混合したスラリーを得ることは容易とはいえなかった。触媒とアイオノマーの混合均一性が良好でないと、触媒の利用率が低くなることがあった。   In addition to the electrode catalyst, an ionomer is added to the electrode catalyst slurry. It was not easy to obtain a slurry in which the electrode catalyst and ionomer were uniformly mixed. If the mixing uniformity of the catalyst and ionomer is not good, the utilization rate of the catalyst may be lowered.

本発明の目的は、電極触媒とアイオノマーの混合均一性が良好な電極触媒スラリーを製造可能な燃料電池用電極触媒スラリーの製造方法を提供することである。   The objective of this invention is providing the manufacturing method of the electrode catalyst slurry for fuel cells which can manufacture the electrode catalyst slurry with favorable mixing uniformity of an electrode catalyst and an ionomer.

本発明の別の目的は、触媒の利用率が良好になり得る固体高分子型燃料電池用の電極および膜・電極接合体を提供することである。   Another object of the present invention is to provide an electrode and a membrane / electrode assembly for a polymer electrolyte fuel cell that can improve the utilization rate of the catalyst.

本発明によれば、
固体高分子型燃料電池の電極形成に用いられる電極触媒スラリーの製造方法であって、
ａ）電極触媒に水と低級アルコールを混合し、電極触媒粒子を分散させて、分散液を得る工程、ただし低級アルコールは炭素数が４以下のアルコールであり、
ｂ）アイオノマーを、溶媒に混合し、２０℃における比誘電率が３０以上のアイオノマー溶液を得る工程、
ｃ）工程ａで得られた分散液と工程ｂで得られたアイオノマー溶液とを混合して、分散液を得る工程、および
ｄ）工程ｃで得られた分散液に、２０℃における比誘電率が２０以下の分散媒である低比誘電率分散媒を混合することにより、分散液の粘度を高める工程
を有する、燃料電池用電極触媒スラリーの製造方法が提供される。 According to the present invention,
A method for producing an electrocatalyst slurry used for forming an electrode of a polymer electrolyte fuel cell,
a) Step of mixing water and lower alcohol in an electrode catalyst and dispersing electrode catalyst particles to obtain a dispersion, wherein the lower alcohol is an alcohol having 4 or less carbon atoms,
b) mixing an ionomer with a solvent to obtain an ionomer solution having a relative dielectric constant at 20 ° C. of 30 or more;
c) mixing the dispersion obtained in step a with the ionomer solution obtained in step b to obtain a dispersion; and d) adding the dielectric constant at 20 ° C. to the dispersion obtained in step c. There is provided a method for producing a fuel cell electrode catalyst slurry, which comprises a step of increasing the viscosity of a dispersion by mixing a low relative dielectric constant dispersion medium having a dispersion medium of 20 or less.

工程ｃにおいて、工程ｂで得られたアイオノマー溶液を、１分間あたり工程ａで用いた分散媒の合計体積の１／５以下の速さで、工程ａで得られた分散液に加えることが好ましい。   In step c, it is preferable to add the ionomer solution obtained in step b to the dispersion obtained in step a at a rate of 1/5 or less of the total volume of the dispersion medium used in step a per minute. .

工程ｄにおいて、比誘電率２０以下の低比誘電率分散媒を、１分間あたり工程ｃで用いた分散媒の合計体積の１／５以下の速さで、工程ｃで得られた分散液に加えることが好ましい。   In step d, the low relative dielectric constant dispersion medium having a relative dielectric constant of 20 or less is applied to the dispersion liquid obtained in step c at a speed of 1/5 or less of the total volume of the dispersion medium used in step c per minute. It is preferable to add.

前記工程ａで加えた低級アルコールの蒸気圧が２７ｋＰａ以上になる温度で、工程ｃを行うことが好ましい。   It is preferable to perform step c at a temperature at which the vapor pressure of the lower alcohol added in step a is 27 kPa or higher.

前記低比誘電率分散媒の蒸気圧が２００ｋＰａ以下になる温度で、工程ｄを行うことが好ましい。   It is preferable to perform the step d at a temperature at which the vapor pressure of the low dielectric constant dispersion medium is 200 kPa or less.

本発明によれば、
上記の方法によって製造された燃料電池用電極触媒スラリーから得られる固体高分子型燃料電池用の電極が提供される。 According to the present invention,
An electrode for a polymer electrolyte fuel cell obtained from the electrode catalyst slurry for a fuel cell produced by the above method is provided.

本発明によれば、
上記の電極を有する固体高分子型燃料電池用の膜・電極接合体が提供される。 According to the present invention,
A membrane / electrode assembly for a polymer electrolyte fuel cell having the above electrode is provided.

本発明によれば、電極触媒とアイオノマーの混合均一性が良好な電極触媒スラリーを製造可能な燃料電池用電極触媒スラリーの製造方法が提供される。   ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrode catalyst slurry for fuel cells which can manufacture the electrode catalyst slurry with favorable mixing uniformity of an electrode catalyst and an ionomer is provided.

本発明によれば、触媒の利用率が良好になり得る固体高分子型燃料電池用の電極および膜・電極接合体が提供される。   ADVANTAGE OF THE INVENTION According to this invention, the electrode for polymer electrolyte fuel cells and a membrane electrode assembly which can make the utilization factor of a catalyst favorable are provided.

比誘電率と触媒有効表面積（比較例１の触媒有効表面積を１００とした相対値）の関係を示すグラフである。It is a graph which shows the relationship between a dielectric constant and a catalyst effective surface area (relative value which made the catalyst effective surface area of the comparative example 1 100). 比誘電率と触媒有効表面積（比誘電率４の時の触媒有効表面積を１００とした相対値）の関係を示すグラフである。It is a graph which shows the relationship between a dielectric constant and a catalyst effective surface area (relative value which set the catalyst effective surface area at the time of the dielectric constant 4 to 100). 工程ｃにおいて、工程ｂで得られたアイオノマー溶液を工程ａで得られた分散液に加える速さを変化させた試験の結果を示すグラフである。It is a graph which shows the result of the test which changed the speed | rate which adds the ionomer solution obtained at the process b to the dispersion liquid obtained at the process a in the process c. 工程ｄにおいて、低比誘電率分散媒を工程ｃで得られた分散液に加える速さを変化させた試験の結果を示すグラフである。It is a graph which shows the result of the test which changed the speed | rate which adds the low dielectric constant dispersion medium to the dispersion liquid obtained at the process c in the process d.

本発明は、固体高分子型燃料電池の電極形成に用いられる電極触媒スラリーの製造方法であり、工程ａ〜ｄを有する。   The present invention is a method for producing an electrode catalyst slurry used for forming an electrode of a polymer electrolyte fuel cell, and includes steps a to d.

なお、特に断りの無い限り、比誘電率は２０℃における値である。   The relative dielectric constant is a value at 20 ° C. unless otherwise specified.

〔工程ａ〕
電極触媒に水と低級アルコールを混合し、電極触媒粒子を分散させて、分散液を得る。 [Step a]
Water and lower alcohol are mixed in the electrode catalyst, and the electrode catalyst particles are dispersed to obtain a dispersion.

ただし低級アルコールは、炭素数が４以下のアルコールである。低級アルコールとして、メタノール、エタノール、１−プロパノール、２−プロパノール、１−ブタノール、２−ブタノール、２−メチル−１−プロパノール、２−メチル−２−プロパノールから選ばれる少なくとも一種を用いることで高い分散性を得ることができ、電極触媒スラリーを用いて製造した触媒の有効表面積を増加させることができる。   However, the lower alcohol is an alcohol having 4 or less carbon atoms. High dispersion by using at least one selected from methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol and 2-methyl-2-propanol as the lower alcohol And the effective surface area of the catalyst produced using the electrode catalyst slurry can be increased.

工程ａにおいて、水（例えば純水）を先に触媒と混合し、その後に低級アルコールを加えることが、触媒からの発火を容易に抑制することができる点で、好ましい。また、低級アルコールを０℃以上５℃以下の温度に冷却して混合することが、蒸気圧を低下させ触媒からの発火を容易に抑制することができる点で、好ましい。   In the step a, it is preferable that water (for example, pure water) is first mixed with the catalyst, and then a lower alcohol is added, since ignition from the catalyst can be easily suppressed. Moreover, it is preferable that the lower alcohol is cooled to a temperature of 0 ° C. or higher and 5 ° C. or lower in that the vapor pressure is lowered and ignition from the catalyst can be easily suppressed.

〔工程ｂ〕
アイオノマーを、溶媒に混合し、２０℃における比誘電率が３０以上のアイオノマー溶液を得る。 [Step b]
The ionomer is mixed with a solvent to obtain an ionomer solution having a relative dielectric constant of 30 or more at 20 ° C.

本明細書において、アイオノマーとは、プロトン伝導性を持つ固体高分子を意味する。   In this specification, an ionomer means a solid polymer having proton conductivity.

アイオノマーの溶解性は、溶媒の比誘電率に大きく影響され、結果として得られる溶液の比誘電率が３０以上になる溶媒を使用することで、アイオノマーの凝集やゲル化を抑制し、アイオノマーが溶液中に均一に混ざっている状態を保ち、その結果触媒の利用率を向上させることができる。   The solubility of the ionomer is greatly affected by the relative dielectric constant of the solvent, and by using a solvent with a relative dielectric constant of 30 or more as a result, the ionomer is prevented from agglomerating and gelling. It is possible to maintain a uniformly mixed state in the inside, and as a result, the utilization rate of the catalyst can be improved.

溶液中の混合均一性の観点、また工程ｃにおける凝集体生成防止の観点から、工程ｂで調製する溶液におけるアイオノマー濃度は、０．１質量％以上１５質量％以下が好ましく、１質量％以上１０質量％以下がより好ましく、５質量％以下がさらに好ましい。５質量％よりも小さくした場合、電極触媒スラリーを用いて製造した触媒の触媒有効表面積にほとんど変化はないので、混合する溶液量の増加を抑える観点から、特に５質量％が最適な濃度といえる。   From the viewpoint of mixing uniformity in the solution and from the viewpoint of preventing the formation of aggregates in step c, the ionomer concentration in the solution prepared in step b is preferably 0.1% by mass to 15% by mass, and preferably 1% by mass to 10%. More preferably, it is more preferably 5% by mass or less. When the amount is less than 5% by mass, there is almost no change in the catalytic effective surface area of the catalyst produced using the electrode catalyst slurry. From the viewpoint of suppressing an increase in the amount of the solution to be mixed, 5% by mass is particularly an optimum concentration. .

アイオノマーとしては、固体高分子型燃料電池用の電極触媒スラリーに用いられる公知のアイオノマーから適宜選んで用いることができる。   As an ionomer, it can select from the well-known ionomer used suitably for the electrode catalyst slurry for polymer electrolyte fuel cells, and can use it.

アイオノマーとして、溶液の形態で市販されているアイオノマー溶液（溶媒として水やアルコールが用いられる）を用い、アイオノマー溶液を追加の溶媒に混合し、２０℃における比誘電率が３０以上のアイオノマー溶液を得ることができる。アイオノマー溶液として、例えば、Ｄｕ Ｐｏｎｔ社製のＮａｆｉｏｎ（登録商標）ＤＥ２０２０、同ＤＥ２０２１、同ＤＥ５２０、同ＤＥ５２１、同ＤＥ１０２０、同ＤＥ１０２１が使用できる。また、旭化成ケミカルズ（株）製のＡｃｉｐｌｅｘ（登録商標）ＳＳ７００Ｃ／２０、同ＳＳ９００／１０、同ＳＳ１１００／５を用いることもできる。   As an ionomer, an ionomer solution commercially available in the form of a solution (water or alcohol is used as a solvent) is mixed with an additional solvent to obtain an ionomer solution having a relative dielectric constant of 30 or more at 20 ° C. be able to. As the ionomer solution, for example, Nafion (registered trademark) DE2020, DE2021, DE520, DE521, DE521, DE1020 and DE1021 manufactured by Du Pont can be used. Also, Aciplex (registered trademark) SS700C / 20, SS900 / 10, and SS1100 / 5 manufactured by Asahi Kasei Chemicals Corporation can be used.

工程ｂでアイオノマーに混合する溶媒としては、アルコールや水を用いることができるが、工程ｂで得られる溶液の比誘電率が３０になれば、アルコールや水以外の溶媒を用いることもできる。   As the solvent mixed with the ionomer in step b, alcohol or water can be used. However, if the relative dielectric constant of the solution obtained in step b is 30, a solvent other than alcohol or water can be used.

〔工程ｃ〕
工程ａで得られた分散液と工程ｂで得られたアイオノマー溶液とを混合して、分散液を得る。 [Step c]
The dispersion obtained in step a and the ionomer solution obtained in step b are mixed to obtain a dispersion.

アイオノマーと触媒の凝集体が発生することを防止する観点から、本工程では、工程ｂで得られた溶液を、１分間あたり工程ａで用いた分散媒の合計体積の１／５以下の速さで、工程ａで得られた分散液に加えることが望ましい。   From the viewpoint of preventing the formation of ionomer and catalyst aggregates, in this step, the solution obtained in step b is 1/5 or less of the total volume of the dispersion medium used in step a per minute. Therefore, it is desirable to add to the dispersion obtained in step a.

なお、「工程ａで用いた分散媒の合計体積」は、工程ａで用いた水と低級アルコールとを混合した場合の混合液の体積を意味する。   The “total volume of the dispersion medium used in step a” means the volume of the mixed solution when water and lower alcohol used in step a are mixed.

また、工程ｃを行う際の、工程ａで得られた分散液の温度は、工程ａで加えた低級アルコールの蒸気圧が２７ｋＰａ以上になる温度以上を選択することが望ましい。すなわち、工程ｃにおける混合を上記温度で行うことが好ましい。こうすることで、大部分の低級アルコールの除去を行うことができ、工程ｃで得られる分散液の比誘電率を増加させることができ、アイオノマーの溶解性を高めることができる。   Moreover, it is desirable to select the temperature of the dispersion liquid obtained in step a when performing step c so that the vapor pressure of the lower alcohol added in step a is 27 kPa or higher. That is, the mixing in step c is preferably performed at the above temperature. By doing so, most of the lower alcohol can be removed, the relative dielectric constant of the dispersion obtained in step c can be increased, and the solubility of the ionomer can be increased.

〔工程ｄ〕
工程ｃで得られた分散液に、２０℃における比誘電率が２０以下の分散媒（低比誘電率分散媒）を混合することにより、分散液の粘度を高める。 [Step d]
The viscosity of the dispersion is increased by mixing the dispersion obtained in step c with a dispersion medium having a relative dielectric constant of 20 or less (low relative dielectric constant dispersion medium) at 20 ° C.

比誘電率２０以下の低比誘電率分散媒を加えることにより、工程ｃで得られた分散液中のアイオノマーの溶解性が低下し、触媒粒子にアイオノマーがコーティングし、プロトン伝導パスを形成する。アイオノマーの溶解性が低下することでスラリーの粘度は増加する。これによって、粘度調節をすることが可能となる。   By adding a low relative dielectric constant dispersion medium having a relative dielectric constant of 20 or less, the solubility of the ionomer in the dispersion obtained in step c is lowered, and the ionomer is coated on the catalyst particles to form a proton conduction path. The viscosity of the slurry increases as the solubility of the ionomer decreases. This makes it possible to adjust the viscosity.

低比誘電率分散媒には、メタノール、エタノール、１−プロパノール、２−プロパノール、１−ブタノール、２−ブタノール、２−メチル−１−プロパノール、２−メチル−２−プロパノール、１−ヘキサノール、ペンタノール、ジメチルエーテル、ジエチルエーテル、アセトンやこれらの混合液を用いることができ、また、これらの分散媒と水を混合した水溶液が利用できる。なかでも、比誘電率が１８程度になる１−プロパノールと１−ブタノールの１：１（質量比）混合液は、触媒が最も高い分散性を示し、蒸気圧も低いため塗布性に優れたスラリーとなる。   Low relative dielectric constant dispersion media include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-hexanol, pen Tanol, dimethyl ether, diethyl ether, acetone or a mixture thereof can be used, and an aqueous solution obtained by mixing these dispersion medium and water can be used. Among these, a 1: 1 (mass ratio) mixture of 1-propanol and 1-butanol having a relative dielectric constant of about 18 is a slurry having the highest dispersibility of the catalyst and having a low vapor pressure and excellent coating properties. It becomes.

低比誘電率分散媒を、工程ｃで得られた分散液中に加える速さは、１分間あたり工程ｃで用いた分散媒の合計体積の１／５以下の速度であることが望ましい。こうすることにより、アイオノマーの分散度低下が早くることを抑制し、アイオノマーのみの凝集体が生成することを抑制し、触媒の利用率が低下することを抑制することができる。   The speed at which the low dielectric constant dispersion medium is added to the dispersion obtained in step c is desirably 1/5 or less of the total volume of the dispersion medium used in step c per minute. By doing so, it is possible to suppress a rapid decrease in the dispersion of the ionomer, to suppress the formation of an aggregate of only the ionomer, and to suppress the decrease in the utilization rate of the catalyst.

なお、「工程ｃで用いた分散媒の合計体積」は、工程ａで用いた水および低級アルコールと、工程ｂで用いた溶媒と、を混合した場合の混合液の体積を意味する。   The “total volume of the dispersion medium used in step c” means the volume of the mixed solution when the water and lower alcohol used in step a and the solvent used in step b are mixed.

なお、工程ｂにおいて、アイオノマーとしてＮａｆｉｏｎ溶液ＤＥ２０２０等のアイオノマー溶液を用いた場合、「工程ｂで用いた溶媒」は、工程ｂで用いたアイオノマー溶液に含まれる溶媒と、工程ｂで用いた溶媒（追加の溶媒）と、を混合した場合の混合液の体積を意味する。   When an ionomer solution such as Nafion solution DE2020 is used as the ionomer in step b, the “solvent used in step b” includes the solvent contained in the ionomer solution used in step b and the solvent used in step b ( Additional solvent) means the volume of the mixed solution.

電極触媒スラリーの粘度は、加える低比誘電率分散媒の量のほかに、超音波時間や強度によっても制御することができる。つまり、工程ｄにおいて超音波を用いてアイオノマーの溶解性を調節することができ、低比誘電率分散媒を含む分散液に超音波をかける時間を長くしたり、超音波の強度を強くしたりすることで、スラリー中のアイオノマーの溶解性を低下させ、粘度を増加させることができる。   The viscosity of the electrode catalyst slurry can be controlled not only by the amount of the low relative dielectric constant dispersion medium added but also by the ultrasonic time and strength. That is, the solubility of the ionomer can be adjusted using ultrasonic waves in step d, and the time for applying ultrasonic waves to the dispersion liquid containing the low relative dielectric constant dispersion medium can be increased, or the intensity of the ultrasonic waves can be increased. By doing so, the solubility of the ionomer in the slurry can be lowered and the viscosity can be increased.

本発明によれば、分散度を高めた触媒分散液の中に、アイオノマー溶解性を高めたアイオノマー溶液を投入し、その後にアイオノマーの溶解性を低下させることで、触媒の周りにアイオノマーをコートすることができる。   According to the present invention, an ionomer solution with improved ionomer solubility is introduced into a catalyst dispersion with increased dispersibility, and then the ionomer is coated around the catalyst by lowering the solubility of the ionomer. be able to.

電極触媒スラリーの適正粘度は、触媒層の形成法によってことなるが、例えば、スクリーン印刷法では０．０１〜０．５Ｐａ・ｓ、スプレー塗布法では０．００１〜０．１Ｐａ・ｓ程度、ダイコーター法では０．０８〜２０Ｐａ・ｓになる。   The appropriate viscosity of the electrode catalyst slurry depends on the method of forming the catalyst layer. For example, the screen printing method is 0.01 to 0.5 Pa · s, the spray coating method is about 0.001 to 0.1 Pa · s, In the ter method, it becomes 0.08 to 20 Pa · s.

工程ｄは、アイオノマーの溶解性低下の速度を上げるために温度を上げることが望ましいが、工程ｄで加えた低比誘電率分散媒が揮発しないようにするために、低比誘電率分散媒の蒸気圧が２００ｋＰａ以下になる温度を選択することが望ましい。   In step d, it is desirable to increase the temperature in order to increase the rate of decrease in the solubility of the ionomer. However, in order to prevent the low relative dielectric constant dispersion medium added in step d from volatilizing, the low relative dielectric constant dispersion medium It is desirable to select a temperature at which the vapor pressure is 200 kPa or less.

本発明の方法によれば、まずは電極触媒の分散（工程ａ）と、アイオノマーの溶解（工程ｂ）とを行うことができ、さらに超音波を用いれば、超音波分散時の熱によって低級アルコールの除去を行うことができる。そして、粘度増加、表面張力の低下による塗布性の向上や良好なアイオノマーのプロトン伝導パスを構築することができる。   According to the method of the present invention, first, the electrode catalyst can be dispersed (step a) and the ionomer can be dissolved (step b). Further, if ultrasonic waves are used, the lower alcohol is heated by the heat during ultrasonic dispersion. Removal can be performed. Further, it is possible to improve the coating property by increasing the viscosity and decreasing the surface tension and to construct a good proton conduction path of ionomer.

工程ｂにおいては、超音波を用いた混合ではなく、例えば攪拌翼等を用いた攪拌によって混合を行うことが好ましい。   In the step b, it is preferable to perform the mixing not by using ultrasonic waves but by stirring using, for example, a stirring blade.

また工程ａにおいて超音波分散を行うこともできる。ただし、その場合、低級アルコールが除去されることを防止するために、電極触媒粒子を分散させる際に、分散液を収容する容器等に、パラフィルム（ＰＡＲＡＦＩＬＭ（登録商標））などを用いて蓋をすることが好ましい。また、工程ａにおいて、攪拌翼等の攪拌によって分散を行うこともできる。   Moreover, ultrasonic dispersion | distribution can also be performed in the process a. However, in that case, in order to prevent the lower alcohol from being removed, when the electrode catalyst particles are dispersed, the container containing the dispersion liquid is covered with parafilm (PARAFILM (registered trademark)) or the like. It is preferable to Further, in step a, dispersion can be performed by stirring with a stirring blade or the like.

電極触媒とアイオノマーをそれぞれ分散もしくは溶解しやすい液体で別々に分散もしくは混合し（工程ａおよびｂ）、その後混合（工程ｃ）および増粘（工程ｄ）を行うことができ、その結果、高分散でプロトン伝導性、塗布性に優れたスラリーを得ることができる。   Electrocatalyst and ionomer can be dispersed or mixed separately in a liquid that is easily dispersed or dissolved (steps a and b), and then mixed (step c) and thickened (step d), resulting in high dispersion. Thus, a slurry excellent in proton conductivity and coatability can be obtained.

このようにして得られる電極スラリーを用いて電極を形成すると、さらには、この電極を有する膜・電極接合体を用いると、電極触媒の利用率を向上させることができる。   When an electrode is formed using the electrode slurry thus obtained, the utilization ratio of the electrode catalyst can be improved by using a membrane / electrode assembly having this electrode.

以下の例において、比誘電率は、比誘電率計（商品名：ＨＰ４１９４Ａ・ＨＰ４２８４Ａ、アジレントテクノロジ（株）製）によって測定し、測定温度は２０℃とした。   In the following examples, the relative dielectric constant was measured with a relative dielectric constant meter (trade name: HP4194A / HP4284A, manufactured by Agilent Technologies), and the measurement temperature was 20 ° C.

〔実施例１〕
＜カソード側＞
・工程ａ
２００ｍｌのビーカーに電極触媒Ｐｔ−Ｃｏ／Ｃ（商品名：ＴＥＣ３６Ｆ５２，Ｐｔ：Ｃｏ＝３：１（モル比），田中貴金属製）５ｇを入れ、そこに純水（沸点１００℃）１５ｇとエタノール（低級アルコール、沸点６５℃、９９．８質量％，和光純薬）１０ｇをこの順に加え、超音波分散器（商品名：ＵＳＳ１、日本精機製作所製）を用いて１時間電極触媒粒子を分散させ、分散液Ａ１を得た。この時にエタノールの蒸発を防ぐため、パラフィルムでビーカーにふたをした。分散液Ａ１の比誘電率は、５０であった。 [Example 1]
<Cathode side>
・ Process a
In a 200 ml beaker, 5 g of an electrocatalyst Pt—Co / C (trade name: TEC36F52, Pt: Co = 3: 1 (molar ratio), Tanaka Kikinzoku), 15 g of pure water (boiling point 100 ° C.) and ethanol ( Lower alcohol, boiling point 65 ° C., 99.8 mass%, Wako Pure Chemical Industries, Ltd.) 10 g was added in this order, and the electrode catalyst particles were dispersed for 1 hour using an ultrasonic dispersing device (trade name: USS1, manufactured by Nippon Seiki Seisakusho) Dispersion A1 was obtained. At this time, in order to prevent ethanol evaporation, the beaker was covered with parafilm. The relative permittivity of the dispersion A1 was 50.

工程ａは室温（約２５℃）にて行った。   Step a was performed at room temperature (about 25 ° C.).

・工程ｂ
アイオノマーとしてＮａｆｉｏｎ（登録商標）溶液ＤＥ２０２０（固形分２０質量％、Ｄｕ Ｐｏｎｔ製、溶媒：１−プロパノールおよび水）を用いた。追加の溶媒として、水（比誘電率：８０）と１−プロパノール（比誘電率：２０）混合して作製した７０質量％のプロパノール水溶液（比誘電率：３７）を用いた。 ・ Process b
Nafion (registered trademark) solution DE2020 (solid content 20% by mass, manufactured by Du Pont, solvent: 1-propanol and water) was used as an ionomer. As an additional solvent, a 70 mass% propanol aqueous solution (relative permittivity: 37) prepared by mixing water (relative permittivity: 80) and 1-propanol (relative permittivity: 20) was used.

アイオノマー濃度が５質量％になるように、上記Ｎａｆｉｏｎ溶液に上記プロパノール水溶液（比誘電率：３７）を加え、撹拌し、溶液Ｂ１を得た。この時のアイオノマー溶液Ｂ１の比誘電率は３６であった。   The propanol aqueous solution (dielectric constant: 37) was added to the Nafion solution so that the ionomer concentration was 5% by mass and stirred to obtain a solution B1. At this time, the relative permittivity of the ionomer solution B1 was 36.

工程ｂは室温（約２５℃）にて行った。   Step b was performed at room temperature (about 25 ° C.).

なお、Ａｃｉｐｌｅｘ（登録商標）分散液ＳＳ７００／２０（固形分２０質量％、旭化成ケミカルズ製、溶媒：水）についても、同様の希釈をすることが可能であった。この場合は、初期の溶媒が水のみであり、アイオノマー溶液の比誘電率が高いことから、追加する溶媒として低級アルコールのみの添加で比誘電率が３０以上かつ５質量％のアイオノマー溶液の作製が可能であった。   In addition, it was possible to perform the same dilution for the Aciplex (registered trademark) dispersion SS700 / 20 (solid content: 20% by mass, manufactured by Asahi Kasei Chemicals, solvent: water). In this case, since the initial solvent is only water and the relative permittivity of the ionomer solution is high, an ionomer solution having a relative permittivity of 30 or more and 5% by mass can be prepared by adding only a lower alcohol as a solvent to be added. It was possible.

・工程ｃ
温度６０℃において、分散液Ａ１を超音波分散器で超音波分散しながら、分散液Ａ１にアイオノマー溶液Ｂ１を３０分かけて滴下し、続いて３０分間超音波分散させ、分散液Ｃ１を得た。６０℃におけるエタノールの蒸気圧は４７ｋＰａである。この時に、エタノールの蒸気圧が２７ｋＰａ以上（温度４８℃以上）にすることでエタノールを十分に除去することができ、塗布性に優れたスラリーになる。分散液Ｃ１の粘度は、０．００５Ｐａ・ｓ（５ｍＰａ・ｓ）であった。 ・ Process c
At a temperature of 60 ° C., while dispersing the dispersion A1 with an ultrasonic disperser, the ionomer solution B1 was dropped into the dispersion A1 over 30 minutes, followed by ultrasonic dispersion for 30 minutes to obtain a dispersion C1. . The vapor pressure of ethanol at 60 ° C. is 47 kPa. At this time, when the vapor pressure of ethanol is set to 27 kPa or more (temperature of 48 ° C. or more), ethanol can be sufficiently removed, and a slurry excellent in coatability is obtained. The viscosity of the dispersion C1 was 0.005 Pa · s (5 mPa · s).

・工程ｄ
低比誘電率分散媒として、１−プロパノールと１−ブタノールの１：１（質量比）混合液（比誘電率：１８）を用いた。この混合液の６０℃における蒸気圧は１０３ｋＰａである。 ・ Process d
As a low relative dielectric constant dispersion medium, a 1: 1 (mass ratio) liquid mixture (relative dielectric constant: 18) of 1-propanol and 1-butanol was used. The vapor pressure of this mixed solution at 60 ° C. is 103 kPa.

温度６０℃において、分散液Ｃ１を超音波分散器で超音波分散しながら、分散液Ｃ１に上記の低比誘電率分散媒を、３０分かけて滴下し、続いて３０分間分散させ、分散液Ｃ１より粘度が高い分散液Ｄ１を得た（比誘電率：４０）。分散液Ｄ１は、電極触媒スラリーとして好適に使用できるものである。分散液Ｄ１の粘度は０．０５Ｐａ・ｓであった。   At a temperature of 60 ° C., the dispersion C1 is ultrasonically dispersed with an ultrasonic disperser, and the above-mentioned low relative dielectric constant dispersion medium is dropped into the dispersion C1 over 30 minutes, followed by dispersion for 30 minutes. A dispersion D1 having a viscosity higher than that of C1 was obtained (relative dielectric constant: 40). The dispersion D1 can be suitably used as an electrode catalyst slurry. The viscosity of the dispersion D1 was 0.05 Pa · s.

作製した電極触媒スラリー（分散液Ｄ１）をカソード触媒スラリーとして用いた。このスラリーをスクリーン印刷法（スクリーン版：１５０メッシュ）によって、バルカン（登録商標）ＸＣ７２（Ｃａｂｏｔ製）によってマイクロポーラスレーヤーを形成したカーボンペーパーＴＧＰ−Ｈ−０６０（（株）東レ製）上に塗布し、８０℃、３ｈｒｓの乾燥および１８０℃、４５ｍｉｎの熱処理を行った。こうして、カソード電極を作製した。   The produced electrode catalyst slurry (dispersion D1) was used as the cathode catalyst slurry. This slurry was applied by screen printing (screen plate: 150 mesh) onto carbon paper TGP-H-060 (manufactured by Toray Industries, Inc.) on which a microporous layer was formed by Vulcan (registered trademark) XC72 (manufactured by Cabot). , 80 ° C., 3 hrs drying and 180 ° C., 45 min heat treatment. In this way, a cathode electrode was produced.

＜アノード側＞
アノード触媒スラリー作製は、次の点を除いて、上記カソード触媒スラリーの作製方法と同様に行った。
・工程ａにおいて、電極触媒には、Ｐｔ−Ｒｕ／Ｃ（商品名：ＴＥＣ６１Ｅ５４、田中貴金属製）を使用し、アイオノマーとして市販のアイオノマー溶液Ａｃｉｐｌｅｘ（登録商標）ＳＳ１１００／５を使用した。
・工程ｂにおいて、溶媒として１−プロパノールのみを用いてアイオノマー濃度が５質量％のアイオノマー溶液（比誘電率は４０）を得た。
・工程ｃの操作はカソード側と同じだが、得られた分散液の粘度は、０．００６Ｐａ・ｓであった。
・工程ｄの操作はカソード側と同じだが、得られた分散液すなわち電極触媒スラリー（アノード触媒スラリー）の粘度は０．２５Ｐａ・ｓであった。 <Anode side>
The anode catalyst slurry was produced in the same manner as the cathode catalyst slurry except for the following points.
In Step a, Pt-Ru / C (trade name: TEC61E54, manufactured by Tanaka Kikinzoku) was used as the electrode catalyst, and a commercially available ionomer solution Aciplex (registered trademark) SS1100 / 5 was used as the ionomer.
In Step b, an ionomer solution (relative permittivity is 40) having an ionomer concentration of 5 mass% was obtained using only 1-propanol as a solvent.
The operation of step c was the same as that on the cathode side, but the viscosity of the obtained dispersion was 0.006 Pa · s.
The operation of step d is the same as that on the cathode side, but the viscosity of the obtained dispersion, that is, the electrode catalyst slurry (anode catalyst slurry) was 0.25 Pa · s.

上記アノード触媒スラリーをスクリーン印刷法（１５０メッシュ）によって、バルカン（登録商標）ＸＣ７２（Ｃａｂｏｔ製）によってマイクロポーラスレーヤーを形成したカーボンペーパーＴＧＰ−Ｈ−０６０（（株）東レ製）上に塗布し、８０℃、３時間の乾燥および１３０℃、４５ｍｉｎの熱処理を行った。こうして、アノード電極を作製した。   The anode catalyst slurry was applied by screen printing (150 mesh) onto carbon paper TGP-H-060 (manufactured by Toray Industries, Inc.) on which a microporous layer was formed by Vulcan (registered trademark) XC72 (manufactured by Cabot). Drying at 80 ° C. for 3 hours and heat treatment at 130 ° C. for 45 minutes were performed. Thus, an anode electrode was produced.

＜単セルの製造および触媒有効表面積の測定＞
電解質膜Ａｃｉｐｌｅｘ（登録商標）ＳＦ７２０２（旭化成ケミカルズ製、ガラス転移温度（Ｔｇ）約１６０℃）を、上記のように作製したアノード電極（面積２５ｃｍ2、５ｃｍ×５ｃｍ）とカソード電極（面積２５ｃｍ2、５ｃｍ×５ｃｍ）で挟み１９０℃、７８秒のホットプレスをすることで膜・電極接合体（ＭＥＡ）を作製した。ホットプレスの温度は、電解質膜が軟化するガラス転移温度よりも高く、電解質膜が分解する温度よりも低い温度で行うことが望ましい。したがって、ホットプレス温度は、ガラス転移温度に対して、１０℃〜４０℃高い温度であることが好ましく、２０℃〜３０℃高い温度であることがより望ましい。 <Manufacture of single cell and measurement of catalyst effective surface area>
Electrolyte membrane Aciplex (registered trademark) SF7202 (manufactured by Asahi Kasei Chemicals, glass transition temperature (Tg) of about 160 ° C.), and an anode electrode formed as described above (area 25cm 2, 5cm × 5cm) and the cathode electrode (area 25 cm 2, A membrane / electrode assembly (MEA) was manufactured by hot pressing at 190 ° C. for 78 seconds with 5 cm × 5 cm). The hot pressing temperature is preferably higher than the glass transition temperature at which the electrolyte membrane softens and lower than the temperature at which the electrolyte membrane decomposes. Therefore, the hot press temperature is preferably a temperature that is 10 to 40 ° C. higher than the glass transition temperature, and more preferably a temperature that is 20 to 30 ° C. higher.

作製したＭＥＡを単セルに組み付け、アノードに水素（３００Ｎｍｌ／ｍｉｎ）、カソードに空気（１０００Ｎｍｌ／ｍｉｎ）を流し、アノード加湿温度８０℃、カソード加湿温度７０℃、セル温度８０℃で、１Ａ／ｃｍ2の電流密度で６時間発電させることで、セルのコンディショニングを行った。その後、アノード加湿温度２５℃、カソード加湿温度２５℃、セル温度２５℃に自然冷却し、アノードに水素（１００Ｎｍｌ／ｍｉｎ）、カソードに空気（１００Ｎｍｌ／ｍｉｎ）を流すことで、セル電圧を０．１Ｖ以下になるまで放置した。セル電圧が０．１Ｖ以下になった後に、電気化学測定システム（ＨＺ５０００、北斗電工（株）製）を用いて、カソードを作用極、アノードを対極兼参照極にし、５ｍＶ／ｓの走査速度、０．０８Ｖ〜０．８Ｖの走査範囲でサイクリックボルタメトリーを行い、サイクリックボルタモグラムの０．０８〜０．４Ｖに現れる水素の吸着および脱離にともなう電気量から触媒の有効表面積を求めた。 The prepared MEA was assembled in a single cell, hydrogen (300 Nml / min) was passed through the anode and air (1000 Nml / min) was passed through the cathode, and the anode humidification temperature was 80 ° C., the cathode humidification temperature was 70 ° C., and the cell temperature was 80 ° C., 1 A / cm The cell was conditioned by generating power for 6 hours at a current density of 2 . Thereafter, the anode is naturally cooled to an anode humidification temperature of 25 ° C., a cathode humidification temperature of 25 ° C., and a cell temperature of 25 ° C., and hydrogen (100 Nml / min) is supplied to the anode and air (100 Nml / min) is supplied to the cathode. It was left until it became 1V or less. After the cell voltage becomes 0.1 V or less, using an electrochemical measurement system (HZ5000, manufactured by Hokuto Denko Co., Ltd.), the cathode is the working electrode, the anode is the counter electrode and the reference electrode, a scanning speed of 5 mV / s, Cyclic voltammetry was performed in the scanning range of 0.08 V to 0.8 V, and the effective surface area of the catalyst was determined from the amount of electricity associated with the adsorption and desorption of hydrogen appearing at 0.08 to 0.4 V in the cyclic voltammogram.

なお「ＮｍＬ」は、０℃、１ａｔｍ（０．１０１ＭＰａ）基準の体積を表す単位である。   “NmL” is a unit representing a volume based on 0 ° C. and 1 atm (0.101 MPa).

表１に、このようにして求めた触媒有効表面積（ただし比較例１の触媒有効表面積を１００として相対比で示す）と、得られた電圧（０．３Ａｃｍ-2で発電を行った時の測定値）を示す。サイクリックボルタモグラムは、膜電極接合体に水素／窒素を供給し得られるボルタモグラムの水素脱離波から算出した。電圧は、膜電極接合体に水素／空気を供給し、０．３Ａｃｍ-2の電流密度で測定を行った。 Table 1 shows the effective catalyst surface area obtained in this way (however, the catalyst effective surface area of Comparative Example 1 is shown as a relative ratio with the catalyst effective surface area being 100) and the voltage obtained (measured when power is generated at 0.3 Acm -2 ). Value). The cyclic voltammogram was calculated from the hydrogen desorption wave of the voltammogram obtained by supplying hydrogen / nitrogen to the membrane electrode assembly. The voltage was measured at a current density of 0.3 Acm −2 by supplying hydrogen / air to the membrane electrode assembly.

〔実施例２〜８、比較例１〜４〕
カソード側の電極触媒スラリー製造において、工程ａで用いたエタノールを、表１の「加えたアルコール」の欄に示したアルコールに替えた以外は実施例１と同様にして、固体高分子型燃料電池の単セルを製造し、触媒の有効表面積を求め、電圧を測定した。ただし、比較例１ではカソード電極製造の工程ａにおいてアルコールは使用しなかった（水のみ用いた）。結果を表１に示す。 [Examples 2-8, Comparative Examples 1-4]
In the production of the electrocatalyst slurry on the cathode side, a solid polymer fuel cell was obtained in the same manner as in Example 1, except that the ethanol used in step a was replaced with the alcohol shown in the column of “added alcohol” in Table 1. A single cell was manufactured, the effective surface area of the catalyst was determined, and the voltage was measured. However, in Comparative Example 1, alcohol was not used in the step a of manufacturing the cathode electrode (only water was used). The results are shown in Table 1.

〔工程ｂで得られる分散液の比誘電率を変化させた試験〕
カソード側の電極触媒スラリー製造において、工程ｂで得られるアイオノマー溶液の比誘電率を種々変化させた試験を行った。 [Test in which the dielectric constant of the dispersion obtained in step b is changed]
In the production of the cathode-side electrocatalyst slurry, tests were performed in which the relative permittivity of the ionomer solution obtained in step b was variously changed.

具体的には、カソード側電極触媒スラリー製造の工程ｂにおいて、Ｎａｆｉｏｎ ＤＥ２０２０に加えた追加の溶媒中の水と１−プロパノールの混合比を種々変えた。これ以外は実施例１と同様にして単セルを製造し、各ケースについて触媒有効表面積を求めた。結果を図１に示す。横軸は各ケースにおいて工程ｂで得られたアイオノマー溶液の比誘電率、縦軸は各ケースの触媒有効表面積を、工程ｂで得られたアイオノマー溶液の比誘電率が３０のケースにおける触媒有効表面積を１００とした相対値で示したものである。   Specifically, in the step b of producing the cathode-side electrode catalyst slurry, the mixing ratio of water and 1-propanol in the additional solvent added to Nafion DE2020 was variously changed. Except for this, a single cell was produced in the same manner as in Example 1, and the effective catalyst surface area was determined for each case. The results are shown in FIG. The abscissa represents the relative dielectric constant of the ionomer solution obtained in step b in each case, the ordinate represents the catalytic effective surface area of each case, and the effective catalytic surface area of the ionomer solution obtained in step b is 30. Is expressed as a relative value where 100 is 100.

工程ｂで得られたアイオノマー溶液の比誘電率が３０以上の場合に、良好な触媒有効表面積が得られ、上記比誘電率３０を境に触媒有効表面積が大きく変化することがわかる。   It can be seen that when the relative dielectric constant of the ionomer solution obtained in step b is 30 or more, a good catalytic effective surface area is obtained, and the effective catalytic surface area changes greatly with the relative dielectric constant 30 as a boundary.

〔工程ｄで加える低比誘電率分散媒の比誘電率を変化させた試験〕
カソード側の電極触媒スラリー製造において、工程ｄで加える低比誘電率分散媒の比誘電率を種々変化させた試験を行った。 [Test in which the relative dielectric constant of the low relative dielectric constant dispersion medium added in step d is changed]
In the production of the electrocatalyst slurry on the cathode side, tests were conducted in which the relative dielectric constant of the low relative dielectric constant dispersion medium added in step d was variously changed.

具体的には、カソード側電極触媒スラリー製造の工程ｄで用いる低比誘電率分散媒として、１−プロパノールと１−ブタノールの１：１（質量比）混合液に、さらに場合によって水を加え、これらの混合比を種々変えた。これ以外は実施例１と同様にして単セルを製造し、各ケースについて触媒有効表面積を求めた。結果を図２に示す。横軸は各ケースで用いた低比誘電率分散媒の比誘電率、縦軸は各ケースの触媒有効表面積を、低比誘電率分散媒の比誘電率が４のケースにおける触媒有効表面積を１００とした相対値で示したものである。   Specifically, as a low relative dielectric constant dispersion medium used in step d of cathode electrode catalyst slurry production, water is optionally added to a 1: 1 (mass ratio) mixture of 1-propanol and 1-butanol. These mixing ratios were variously changed. Except for this, a single cell was produced in the same manner as in Example 1, and the effective catalyst surface area was determined for each case. The results are shown in FIG. The horizontal axis represents the relative dielectric constant of the low dielectric constant dispersion medium used in each case, the vertical axis represents the catalyst effective surface area of each case, and the catalyst effective surface area in the case where the relative dielectric constant of the low dielectric constant dispersion medium is 4 is 100. It is shown as a relative value.

低比誘電率分散媒の比誘電率が２０以下の場合に、良好な触媒有効表面積が得られ、上記比誘電率が２０を境に触媒有効表面積が大きく変化することがわかる。   It can be seen that when the relative dielectric constant of the low relative dielectric constant dispersion medium is 20 or less, a good catalytic effective surface area is obtained, and the effective catalytic surface area changes greatly with the relative dielectric constant of 20 as a boundary.

〔工程ｃにおいて、工程ｂで得られた分散液を工程ａで得られた分散液に加える速さを変化させた試験〕
工程ｃにおいて、工程ｂで得られたアイオノマー溶液を工程ａで得られた分散液に加える速さを種々変化させた試験を行った。 [A test in which the speed of adding the dispersion obtained in step b to the dispersion obtained in step a was changed in step c]
In step c, a test was performed in which the speed at which the ionomer solution obtained in step b was added to the dispersion obtained in step a was variously changed.

具体的には、カソード側電極触媒スラリー製造の工程ｃにおいて、分散液Ａ１にアイオノマー溶液Ｂ１を滴下する時間を種々変化させた。これ以外は実施例１と同様にして単セルを製造し、各ケースについて触媒有効表面積を求めた。   Specifically, in the step c of producing the cathode side electrode catalyst slurry, the time for dropping the ionomer solution B1 into the dispersion A1 was variously changed. Except for this, a single cell was produced in the same manner as in Example 1, and the effective catalyst surface area was determined for each case.

結果を図３に示す。横軸は「工程ａで用いた分散媒の合計体積」に対する「工程ｃにおいて１分間あたりに工程ａで得られる分散液に加える、工程ｂで得られたアイオノマー溶液の体積」の比であり、縦軸は各ケースの触媒有効表面積を、この比が０．０２ｍｉｎ-1のケース（実施例１）を１００とした相対値で示したものである。 The results are shown in FIG. The horizontal axis is the ratio of “the volume of the ionomer solution obtained in step b added to the dispersion obtained in step a per minute in step c” to “the total volume of the dispersion medium used in step a”; the vertical axis of the catalytically active surface area of each case, in which this ratio is expressed as a relative value taken as 100 cases (example 1) of 0.02min -1.

工程ｂで得られたアイオノマー溶液を、１分間あたり工程ａで用いた分散媒の合計体積の１／５（０．２）以下の速さで加えることで触媒有効表面積を増やすことができ、好ましい。速さを遅くした場合には、触媒有効表面積に変化はないが、工程時間が長くなるため、上記比は１／１００以上１／５以下がより望ましい。   The effective surface area of the catalyst can be increased by adding the ionomer solution obtained in step b at a rate of 1/5 (0.2) or less of the total volume of the dispersion medium used in step a per minute. . When the speed is decreased, there is no change in the effective catalyst surface area, but the process time becomes longer. Therefore, the ratio is more preferably 1/100 or more and 1/5 or less.

〔工程ｄにおいて、低比誘電率分散媒を工程ｃで得られた分散液に加える速さを変化させた試験〕
工程ｄにおいて、低比誘電率分散媒を工程ｃで得られた分散液に加える速さを種々変化させた試験を行った。 [Test in which the rate of adding the low relative dielectric constant dispersion medium to the dispersion obtained in step c was changed in step d]
In step d, a test was performed in which the speed of adding the low relative dielectric constant dispersion medium to the dispersion obtained in step c was variously changed.

具体的には、カソード側電極触媒スラリー製造の工程ｄにおいて、低比誘電率分散媒を分散液Ｃ１に滴下する時間を種々変化させた。これ以外は実施例１と同様にして単セルを製造し、各ケースについて触媒有効表面積を求めた。結果を図４に示す。横軸は「工程ｃで用いた分散媒の合計体積」に対する「工程ｄにおいて１分間あたりに工程ｃで得られた分散液に加える、低比誘電率分散媒の体積」の比であり、縦軸は各ケースの触媒有効表面積を、この比が０．０１６ｍｉｎ-1のケース（実施例１）を１００とした相対値で示したものである。 Specifically, in the step d of producing the cathode-side electrode catalyst slurry, the time for dropping the low relative dielectric constant dispersion medium into the dispersion C1 was variously changed. Other than this, a single cell was produced in the same manner as in Example 1, and the effective catalyst surface area was determined for each case. The results are shown in FIG. The horizontal axis is the ratio of “volume of low relative dielectric constant dispersion medium added to dispersion obtained in step c per minute in step d” to “total volume of dispersion medium used in step c”. The axis shows the effective catalytic surface area of each case as a relative value with the case (Example 1) having this ratio of 0.016 min −1 as 100.

低比誘電率分散媒を、１分間あたり工程ｃで用いた分散媒の合計体積の１／５（０．２）以下の速さで加えることで触媒有効表面積を増やすことができ、好ましい。速さを遅くした場合には、触媒有効表面積に変化はないが、工程時間が長くなるため、上記比は１／１００以上１／５以下がより望ましい。   The effective surface area of the catalyst can be increased by adding a low relative dielectric constant dispersion medium at a rate of 1/5 (0.2) or less of the total volume of the dispersion medium used in step c per minute. When the speed is decreased, there is no change in the effective catalyst surface area, but the process time becomes longer. Therefore, the ratio is more preferably 1/100 or more and 1/5 or less.

Claims (7)

固体高分子型燃料電池の電極形成に用いられる電極触媒スラリーの製造方法であって、
ａ）電極触媒に水と低級アルコールを混合し、電極触媒粒子を分散させて、分散液を得る工程、ただし低級アルコールは炭素数が４以下のアルコールであり、
ｂ）アイオノマーを、溶媒に混合し、２０℃における比誘電率が３０以上のアイオノマー溶液を得る工程、
ｃ）工程ａで得られた分散液と工程ｂで得られたアイオノマー溶液とを混合して、分散液を得る工程、および
ｄ）工程ｃで得られた分散液に、２０℃における比誘電率が２０以下の分散媒である低比誘電率分散媒を混合することにより、分散液の粘度を高める工程
を有する、燃料電池用電極触媒スラリーの製造方法。 A method for producing an electrocatalyst slurry used for forming an electrode of a polymer electrolyte fuel cell,
a) Step of mixing water and lower alcohol in an electrode catalyst and dispersing electrode catalyst particles to obtain a dispersion, wherein the lower alcohol is an alcohol having 4 or less carbon atoms,
b) mixing an ionomer with a solvent to obtain an ionomer solution having a relative dielectric constant at 20 ° C. of 30 or more;
c) mixing the dispersion obtained in step a with the ionomer solution obtained in step b to obtain a dispersion; and d) adding the dielectric constant at 20 ° C. to the dispersion obtained in step c. The manufacturing method of the electrode catalyst slurry for fuel cells which has the process of raising the viscosity of a dispersion liquid by mixing the low relative dielectric constant dispersion medium which is a dispersion medium of 20 or less. 工程ｃにおいて、工程ｂで得られたアイオノマー溶液を、１分間あたり工程ａで用いた分散媒の合計体積の１／５以下の速さで、工程ａで得られた分散液に加える、請求項１記載の方法。   In step c, the ionomer solution obtained in step b is added to the dispersion obtained in step a at a rate of 1/5 or less of the total volume of the dispersion medium used in step a per minute. The method according to 1. 工程ｄにおいて、比誘電率２０以下の低比誘電率分散媒を、１分間あたり工程ｃで用いた分散媒の合計体積の１／５以下の速さで、工程ｃで得られた分散液に加える、請求項１または２記載の方法。   In step d, the low relative dielectric constant dispersion medium having a relative dielectric constant of 20 or less is applied to the dispersion liquid obtained in step c at a speed of 1/5 or less of the total volume of the dispersion medium used in step c per minute. The method according to claim 1 or 2, which is added. 前記工程ａで加えた低級アルコールの蒸気圧が２７ｋＰａ以上になる温度で、工程ｃを行う、請求項１〜３のいずれか一項記載の方法。   The method according to any one of claims 1 to 3, wherein step c is performed at a temperature at which the vapor pressure of the lower alcohol added in step a is 27 kPa or higher. 前記低比誘電率分散媒の蒸気圧が２００ｋＰａ以下になる温度で、工程ｄを行う、請求項１〜４のいずれか一項記載の方法。   The method according to any one of claims 1 to 4, wherein step d is performed at a temperature at which a vapor pressure of the low dielectric constant dispersion medium becomes 200 kPa or less. 請求項１〜５のいずれか一項記載の方法によって製造された燃料電池用電極触媒スラリーから得られる固体高分子型燃料電池用の電極。   The electrode for solid polymer fuel cells obtained from the electrode catalyst slurry for fuel cells manufactured by the method as described in any one of Claims 1-5. 請求項６記載の電極を有する固体高分子型燃料電池用の膜・電極接合体。   A membrane / electrode assembly for a polymer electrolyte fuel cell comprising the electrode according to claim 6.
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