JP2017091639A - Catalyst powder for solid polymer fuel cell, manufacturing method thereof, and solid polymer fuel cell arranged by use of catalyst powder - Google Patents

Catalyst powder for solid polymer fuel cell, manufacturing method thereof, and solid polymer fuel cell arranged by use of catalyst powder Download PDF

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JP2017091639A
JP2017091639A JP2015216403A JP2015216403A JP2017091639A JP 2017091639 A JP2017091639 A JP 2017091639A JP 2015216403 A JP2015216403 A JP 2015216403A JP 2015216403 A JP2015216403 A JP 2015216403A JP 2017091639 A JP2017091639 A JP 2017091639A
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catalyst
activated carbon
fuel cell
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carbon
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正孝 日吉
Masataka Hiyoshi
正孝 日吉
健一郎 田所
Kenichiro Tadokoro
健一郎 田所
孝 飯島
Takashi Iijima
孝 飯島
工 西本
Takumi Nishimoto
工 西本
晋也 古川
Shinya Furukawa
晋也 古川
広幸 林田
Hiroyuki Hayashida
広幸 林田
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Nippon Steel Corp
Nippon Steel Chemical and Materials Co Ltd
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Nippon Steel and Sumikin Chemical Co Ltd
Nippon Steel and Sumitomo Metal 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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    • 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

PROBLEM TO BE SOLVED: To provide catalyst powder for a solid polymer fuel cell, which is high in the rate of utilization of a catalyst metal, and which enables the development of a stable power generation performance particularly under a high-humidification condition and a low-humidification condition when a catalyst layer is formed therefrom, and incorporated in a solid polymer fuel cell; a method for manufacturing such catalyst powder; and a solid polymer fuel cell.SOLUTION: Provided are catalyst powder for a solid polymer fuel cell, a manufacturing method thereof, and a solid polymer fuel cell. The catalyst powder comprises: active carbon; catalyst metal particles supported by the active carbon; and a catalyst-covering portion covering the active carbon and the catalyst metal particles and made of an electrolyte resin. The active carbon is 1000 m/g or more in BET specific surface area, and it is 10% or less in the rate of an external surface area determined from Nadsorption T-plot analysis to the BET specific surface area. The mass ratio (I/C: g-ionomer/g-carbon) of the electrolyte resin (I) forming the catalyst-covering portion to the active carbon (C) is within a range of 0.05-0.1.SELECTED DRAWING: None

Description

この発明は、固体高分子形燃料電池用の触媒粉末及びその製造方法、並びにこの触媒粉末を用いて調製された固体高分子形燃料電池に関するものであり、特に燃料電池の使用環境下において触媒粉末に含まれる白金粒子の利用率を高め、白金の使用量を低減することができると共に、高加湿条件下及び低加湿条件下の何れの場合においても安定した電池性能を発揮し得る固体高分子形燃料電池用の触媒粉末及びその製造方法、並びにこの触媒粉末を用いて調製された固体高分子形燃料電池に関する。   The present invention relates to a catalyst powder for a polymer electrolyte fuel cell, a method for producing the same, and a polymer electrolyte fuel cell prepared using the catalyst powder. Solid polymer form that can increase the utilization of platinum particles contained in the catalyst, reduce the amount of platinum used, and can exhibit stable battery performance under both high and low humidification conditions The present invention relates to a catalyst powder for a fuel cell, a method for producing the same, and a polymer electrolyte fuel cell prepared using the catalyst powder.

一般的な固体高分子形燃料電池は、プロトン伝導性電解質膜を挟んでアノードとなる触媒層とカソードとなる触媒層とが配置され、更にこれらを挟んで触媒層の外側にガス拡散層が配置され、更にこれらを挟んでガス拡散層の外側にセパレーターが配置された基本構造を有し、通常は、必要な出力を達成するために、上記の基本構造を単位セルとし、必要な数の単位セルをスタックして電池を構成している。   In a general polymer electrolyte fuel cell, a catalyst layer serving as an anode and a catalyst layer serving as a cathode are disposed with a proton conductive electrolyte membrane interposed therebetween, and a gas diffusion layer is disposed on the outside of the catalyst layer sandwiching these layers. And having a basic structure in which a separator is disposed outside the gas diffusion layer with these interposed therebetween, and in order to achieve a required output, the above basic structure is usually used as a unit cell, and a necessary number of units are provided. Cells are stacked to form a battery.

このような基本構造の固体高分子形燃料電池から電流を取り出すためには、アノードとカソードの両極に配されたセパレーターのガス流路からガス拡散層を介して、カソード側には酸素あるいは空気等の酸化性ガスを、また、アノード側には水素等の還元性ガスをそれぞれ触媒層まで供給し、各触媒層で起こる還元性ガス及び酸化性ガスの化学反応を利用して電流を取り出す。例えば、還元性ガスが水素ガスであって酸化性ガスが酸素ガスである場合には、アノード側触媒層の触媒上で起こる下記の化学反応（１）と、カソード側触媒層の触媒上で起こる下記の化学反応（２）との間のエネルギー差（電位差）を利用し、電流を取り出している。
Ｈ２ → ２Ｈ＋＋２ｅ−（Ｅ０＝０Ｖ）……（１）
Ｏ２＋４Ｈ＋＋４ｅ− → ２Ｈ２Ｏ（Ｅ０＝１．２３Ｖ）……（２） In order to take out the current from the solid polymer fuel cell having such a basic structure, oxygen or air or the like is provided on the cathode side through the gas diffusion layer from the gas flow path of the separator disposed on both electrodes of the anode and the cathode. Further, a reducing gas such as hydrogen is supplied to the catalyst layer on the anode side, and an electric current is taken out using a chemical reaction of the reducing gas and the oxidizing gas that occurs in each catalyst layer. For example, when the reducing gas is hydrogen gas and the oxidizing gas is oxygen gas, the following chemical reaction (1) that occurs on the catalyst of the anode side catalyst layer and the catalyst on the cathode side catalyst layer occur. The current is taken out by utilizing the energy difference (potential difference) between the following chemical reaction (2).
H 2 → 2H + + 2e − (E 0 = 0V) (1)
O 2 + 4H + + 4e − → 2H 2 O (E 0 = 1.23 V) (2)

そして、上記の化学反応（１）及び（２）に利用されるアノード側及び／又はカソード側の触媒層には、これら必要な化学反応（１）及び（２）を促進する機能を有する触媒金属、具体的には白金、パラジウム、金、タングステン、コバルト、ニッケル、タンタル、ジルコニウム、モリブデン等の純金属や、炭化物、窒化物等の金属化合物が使用可能ではあるが、純金属としてはＰtが最も高い反応活性を有することから、一般的には白金(Pt)若しくはＰtを主成分とするＰt合金が使用されている。ここで、Ｐtと共に使用される金属元素としては、触媒金属としての活性向上を目的としてＣo、Ｎi、Ｆe、Ｐd、Ａu、Ｒu、Ｒh、Ｉr等があるが、これら金属元素の添加量は、このＰt以外の金属元素の添加量が５０at%を超えると、触媒金属の粒子表面におけるＰt以外の金属元素の存在割合が多くなり、燃料電池の作動下で溶解して発電性能が低下する場合があることから、通常、Ｐtに対する原子組成百分率として５０at%以下である。   The anode-side and / or cathode-side catalyst layer used in the chemical reactions (1) and (2) has a catalytic metal having a function of promoting these necessary chemical reactions (1) and (2). Specifically, pure metals such as platinum, palladium, gold, tungsten, cobalt, nickel, tantalum, zirconium and molybdenum and metal compounds such as carbides and nitrides can be used, but Pt is the most pure metal. In general, platinum (Pt) or a Pt alloy containing Pt as a main component is used because of its high reaction activity. Here, as the metal element used together with Pt, there are Co, Ni, Fe, Pd, Au, Ru, Rh, Ir and the like for the purpose of improving the activity as a catalyst metal. If the amount of the metal element other than Pt exceeds 50 at%, the ratio of the metal element other than Pt on the catalyst metal particle surface increases, and it dissolves under the operation of the fuel cell and the power generation performance may decrease. Therefore, the atomic composition percentage with respect to Pt is usually 50 at% or less.

また、白金(Pt)については、その資源埋蔵量に制約があり、高価であることから、国の産業上の方針として白金触媒の使用量を削減することが挙げられている（独立行政法人新エネルギー・産業技術総合開発機構 燃料電池・水素技術開発ロードマップ2010）。従って、固体高分子形燃料電池の低コスト化を達成して普及を図るためには、白金原子の使用量を可及的に低減することができる触媒の開発が必要不可欠になっている。   As for platinum (Pt), its resource reserves are limited and expensive, so the national industrial policy is to reduce the amount of platinum catalyst used (independent administrative agency Energy and Industrial Technology Development Organization Fuel Cell / Hydrogen Technology Development Roadmap 2010). Therefore, in order to achieve a reduction in cost of the polymer electrolyte fuel cell and to promote its use, it is indispensable to develop a catalyst capable of reducing the amount of platinum atoms used as much as possible.

そこで、従来においても、固体高分子形燃料電池において、白金使用量を低減するために、様々な観点で様々な試みがなされている。
例えば、特許文献１及び２においては、触媒金属成分、電解質材料(電解質樹脂)、及び炭素材料を含む触媒層に関して、前記炭素材料については触媒金属成分を担持した触媒金属担体炭素材料と触媒金属成分を担持していないガス拡散炭素材料とで構成し、また、これら触媒金属担体炭素材料とガス拡散炭素材料の保水性を最適化して、触媒層内で電子伝導経路が分断されることなく低加湿時及び高加湿時のあらゆる運転環境下において十分な発電特性を発揮する固体高分子型燃料電池が提案されている。 Therefore, conventionally, various attempts have been made from various viewpoints in order to reduce the amount of platinum used in the polymer electrolyte fuel cell.
For example, in Patent Documents 1 and 2, regarding a catalyst layer containing a catalyst metal component, an electrolyte material (electrolyte resin), and a carbon material, a catalyst metal carrier carbon material carrying a catalyst metal component and a catalyst metal component for the carbon material It is composed of a gas diffusion carbon material that does not support the catalyst, and the water retention of the catalytic metal carrier carbon material and the gas diffusion carbon material is optimized to reduce the humidification without breaking the electron conduction path in the catalyst layer. A polymer electrolyte fuel cell has been proposed that exhibits sufficient power generation characteristics under various operating environments at times and during high humidification.

また、特許文献３においては、触媒層において、第１電解質樹脂で被覆されたＰt担持カーボン粒子と、第２電解質樹脂で被膜されたＰt未担持カーボン粒子とを混在させ、また、第２電解質樹脂として、イオン交換基当量が第１電解質樹脂のイオン交換基当量よりも小さくてより高い保水性を備えた電解質樹脂を用い、発電能力の低下抑制において実効性の高い触媒層及びこれを用いた燃料電池が提案されている。   In Patent Document 3, in the catalyst layer, Pt-supported carbon particles coated with the first electrolyte resin and Pt non-supported carbon particles coated with the second electrolyte resin are mixed, and the second electrolyte resin is mixed. As an example, an electrolyte resin having an ion exchange group equivalent that is smaller than the ion exchange group equivalent of the first electrolyte resin and having higher water retention, and a catalyst layer that is highly effective in suppressing a decrease in power generation capacity and a fuel using the same Batteries have been proposed.

更に、特許文献４においては、触媒と、この触媒が担持された電子伝導体(カーボン粒子)と、電子伝導体を覆う炭化水素系のプロトン伝導性樹脂(電解質樹脂)とを有する燃料電池の触媒電極層(触媒層)において、前記プロトン伝導性樹脂として分子量が異なる少なくとも２種類以上のプロトン伝導性樹脂を用い、電子伝導体側により小さな分子量のプロトン伝導性樹脂を用い、また、その外側により大きな分子量のプロトン伝導性樹脂を用い、これによってカーボンブラック等の電子伝導体の細孔内部にプロトン伝導性樹脂を侵入させ、電子伝導体の細孔内部に存在する触媒金属の有効利用率を改善し、電池出力を改善した燃料電池が提案されている。   Further, in Patent Document 4, a fuel cell catalyst comprising a catalyst, an electron conductor (carbon particles) carrying the catalyst, and a hydrocarbon-based proton conductive resin (electrolyte resin) covering the electron conductor. In the electrode layer (catalyst layer), at least two kinds of proton conductive resins having different molecular weights are used as the proton conductive resin, a proton conductive resin having a smaller molecular weight is used on the electronic conductor side, and a larger molecular weight is provided on the outside thereof. The proton conductive resin is used, thereby allowing the proton conductive resin to penetrate into the pores of the electron conductor such as carbon black, thereby improving the effective utilization rate of the catalytic metal existing inside the pores of the electron conductor, Fuel cells with improved battery output have been proposed.

また、特許文献５においては、水と有機溶媒とを含有する分散媒に、触媒を担持した触媒担体と、プロトン伝導性アイオノマーとを分散させた燃料電池の電極形成用触媒インクであって、この触媒インクによって形成される電極触媒層における三相界面（すなわち、電極触媒層内を通過するガスの流路と、電極触媒層を形成するアイオノマーと、電極触媒層を形成する触媒担体に担持された触媒とが接する界面）での触媒へのガス接触機会を増やすための手法として、触媒への表面積当たりのアイオノマーの吸着量（ＢＩ値）と、触媒の周囲に１０nm以上の細孔が分布している細孔分布における表面積（ＣＡｓ）とに着目し、これに基づいて水と有機溶媒との重量比を調整して最適化することにより、高い発電能力を備えた燃料電池を製造できるとされた電極形成用触媒インクの発明が提案されている。   Patent Document 5 discloses a catalyst ink for forming a fuel cell electrode in which a catalyst carrier carrying a catalyst and a proton conductive ionomer are dispersed in a dispersion medium containing water and an organic solvent. Three-phase interface in the electrode catalyst layer formed by the catalyst ink (that is, a gas flow path that passes through the electrode catalyst layer, an ionomer that forms the electrode catalyst layer, and a catalyst carrier that forms the electrode catalyst layer) As a method for increasing the chance of gas contact with the catalyst at the interface with the catalyst), the adsorption amount (BI value) of ionomer per surface area to the catalyst and pores of 10 nm or more are distributed around the catalyst. By focusing on the surface area (CAs) in the pore distribution and adjusting the weight ratio of water and organic solvent based on this, a fuel cell with high power generation capacity can be manufactured. Invention of the catalyst ink Lutosa electrodes formed has been proposed.

更にまた、特許文献６においては、触媒と、この触媒の表面に接する高酸素透過アイオノマー又は高酸素透過ポリマーからなる第１層と、この第１層の表面に接する第２アイオノマーからなる第２層とを備え、前記第１層を形成する高酸素透過アイオノマー又は前記高酸素透過ポリマーが、前記第２層を形成する第２アイオノマーよりも、触媒との界面における酸素移動抵抗が小さいことに特徴を有し、酸素透過性が高く、低コストであって出力性能を低下させることがなく、触媒使用量を低減することが可能な燃料電池用の触媒層が提案されている。   Furthermore, in Patent Document 6, a catalyst, a first layer made of a high oxygen permeable ionomer or a high oxygen permeable polymer in contact with the surface of the catalyst, and a second layer made of a second ionomer in contact with the surface of the first layer. The high oxygen permeable ionomer or the high oxygen permeable polymer that forms the first layer has a smaller oxygen transfer resistance at the interface with the catalyst than the second ionomer that forms the second layer. A catalyst layer for a fuel cell has been proposed that has a high oxygen permeability, is low in cost, does not degrade output performance, and can reduce the amount of catalyst used.

しかしながら、炭素材料、触媒金属、及び電解質樹脂を含む触媒層において電解質樹脂に着目してみると、この電解質樹脂には、触媒金属を被覆し３相界面を形成して触媒金属の利用率を高める役割と、触媒を形成する触媒粒子の粒子間を接着して形成される触媒層においてプロトン伝導経路となる役割と、この触媒層を多孔性に形成して触媒層に還元性ガスや酸化性ガスのガス拡散経路となる役割とがあり、触媒金属の利用率を高めるという観点から精査してみると、触媒層を構成する炭素材料の種類が異なる場合に、作製された固体高分子形燃料電池においてその電池性能が低下することがあり、上述した特許文献１〜６においても、特に高加湿条件下及び低加湿条件下での電池性能の安定化という点で必ずしも十分であるとは言えないことが判明した。   However, when attention is paid to the electrolyte resin in the catalyst layer containing the carbon material, the catalyst metal, and the electrolyte resin, the catalyst resin is coated with the catalyst metal to form a three-phase interface to increase the utilization rate of the catalyst metal. The role of the proton conduction path in the catalyst layer formed by adhering the particles of the catalyst particles that form the catalyst, and the catalyst layer is formed into a porous layer by forming a reducing gas or an oxidizing gas in the catalyst layer. From the viewpoint of increasing the utilization rate of the catalyst metal, the polymer electrolyte fuel cell produced was produced when the types of carbon materials constituting the catalyst layer were different. In the above-mentioned Patent Documents 1 to 6, it is not necessarily sufficient in terms of stabilization of battery performance especially under high and low humidification conditions. Theft was found.

特開2003-109,643号公報Japanese Patent Laid-Open No. 2003-109,643 特開2013-225,433号公報JP 2013-225,433 A 特開2012-123,927号公報JP 2012-123,927 特開2009-187,848号公報JP 2009-187,848 JP 特開2014-060,097号公報JP 2014-060,097 特開2014-216,157号公報JP-A-2014-216,157

そこで、本発明者らは、触媒層を構成する炭素材料の種類に応じて触媒金属の利用率が低下し、電池性能が低下することの原因について鋭意検討した結果、意外なことには、炭素材料、触媒金属、及び電解質樹脂で触媒粉末を形成し、この触媒粉末を用いて触媒層を形成するに際し、触媒粉末を形成する際に使用される炭素材料の種類に応じて、この炭素材料における全体のBET比表面積に対する外表面積の割合、及び触媒粉末を形成する際の電解質樹脂と炭素材料との質量比率に大きな違いがあり、それぞれ適切な範囲が存在することを突き止めた。   Therefore, as a result of earnestly examining the cause of the decrease in the utilization rate of the catalytic metal and the battery performance depending on the type of the carbon material constituting the catalyst layer, the present inventors surprisingly When forming a catalyst powder with a material, a catalyst metal, and an electrolyte resin, and forming a catalyst layer using this catalyst powder, depending on the type of carbon material used in forming the catalyst powder, The ratio of the outer surface area to the entire BET specific surface area and the mass ratio between the electrolyte resin and the carbon material when forming the catalyst powder were greatly different, and it was found that there was an appropriate range for each.

そして、更にこの問題を解決すべく鋭意検討を進めた結果、炭素材料としてBET比表面積１０００m2/g以上の活性炭を用いた場合には、このBET比表面積に対してＮ2吸着のT-plot解析で得られる外表面積の割合が１０%以下であり、また、電解質樹脂(I)と活性炭(C)との質量比率(I/C: g-ionomer/g-carbon)が０．０５〜０．１の範囲内である場合に触媒金属の利用率が高くなり、高加湿条件下及び低加湿条件下での発電性能を安定化できることを見出し、本発明を完成した。 Further, as a result of diligent investigation to solve this problem, when activated carbon having a BET specific surface area of 1000 m 2 / g or more is used as the carbon material, N 2 adsorption T-plot with respect to this BET specific surface area is used. The ratio of the outer surface area obtained by the analysis is 10% or less, and the mass ratio (I / C: g-ionomer / g-carbon) between the electrolyte resin (I) and the activated carbon (C) is 0.05 to 0. The present inventors have found that the utilization rate of the catalyst metal is high when the ratio is within the range of .1 and the power generation performance under high and low humidification conditions can be stabilized, and the present invention has been completed.

従って、本発明の目的は、触媒金属の利用率が高く、触媒層を形成して固体高分子形燃料電池に組み込んだ際に特に高加湿条件下及び低加湿条件下で安定した発電性能を発現することができる固体高分子形燃料電池用の触媒粉末を提供することにある。
また、本発明の他の目的は、このような固体高分子形燃料電池用の触媒粉末の製造方法を提供することにある。
更に、本発明の他の目的は、このような固体高分子形燃料電池用の触媒粉末を用いて製造された固体高分子形燃料電池を提供することにある。 Therefore, the object of the present invention is that the utilization rate of the catalyst metal is high, and when the catalyst layer is formed and incorporated in the polymer electrolyte fuel cell, a stable power generation performance is exhibited particularly under high and low humidification conditions. It is an object of the present invention to provide a catalyst powder for a polymer electrolyte fuel cell.
Another object of the present invention is to provide a method for producing a catalyst powder for such a polymer electrolyte fuel cell.
Furthermore, another object of the present invention is to provide a polymer electrolyte fuel cell manufactured using such a catalyst powder for polymer electrolyte fuel cells.

すなわち、本発明の要旨は以下の通りである。
(1) 炭素材料である活性炭と、前記活性炭に担持された触媒金属からなる触媒金属粒子と、電解質樹脂からなり、前記活性炭及び触媒金属粒子を被覆する触媒被覆部とからなる固体高分子形燃料電池用の触媒粉末であり、前記活性炭は、BET比表面積が１０００m2/g以上であって、このBET比表面積に対してＮ2吸着のT-plot解析で得られる外表面積の割合が１０%以下であり、かつ、前記触媒被覆部を形成する電解質樹脂(I)と前記活性炭(C)との質量比率(I/C: g-ionomer/g-carbon)が０．０５〜０．１の範囲内であることを特徴とする固体高分子形燃料電池用の触媒粉末。
(2) 炭素材料である活性炭に触媒金属からなる触媒金属粒子を担持させ、得られた触媒金属担持活性炭の表面を電解質樹脂からなる触媒被覆部で被覆して触媒粉末を製造する方法であって、
前記活性炭は、BET比表面積が１０００m2/g以上であって、このBET比表面積に対してＮ2吸着のT-plot解析で得られる外表面積の割合が１０%以下である活性炭を用い、
この活性炭に前記触媒金属粒子を担持させて得られた触媒金属担持活性炭と前記電解質樹脂とを分散媒中に、前記電解質樹脂(I)と前記活性炭(C)との質量比率(I/C: g-ionomer/g-carbon)が０．０５〜０．１の範囲内になるように分散させ、温度５０〜１００℃及び１０〜２０時間の条件で撹拌下に接触させ、前記触媒金属担持活性炭の表面を前記電解質樹脂からなる触媒被覆部で被覆することを特徴とする固体高分子形燃料電池用の触媒粉末の製造方法。
(3) プロトン伝導性電解質膜を挟んだ一対のアノード触媒層及びカソード触媒層を有する固体高分子形燃料電池であり、少なくとも前記カソード触媒層を形成する触媒粉末が、炭素材料である活性炭と、触媒金属からなると共に前記活性炭に担持された触媒金属粒子と、電解質樹脂からなると共に前記活性炭及び触媒金属粒子を被覆する触媒被覆部とを有し、前記触媒粉末を形成する活性炭が、BET比表面積が１０００m2/g以上であって、このBET比表面積に対してＮ2吸着のT-plot解析で得られる外表面積の割合が１０%以下であり、かつ、前記触媒粉末を形成する触媒被覆部の電解質樹脂(I)と活性炭(C)との質量比率(I/C: g-ionomer/g-carbon)が０．０５〜０．１の範囲内であることを特徴とする固体高分子形燃料電池。
(4) 前記一対のアノード触媒層及びカソード触媒層のうちの少なくともカソード触媒層が、前記触媒粉末(CP)に対してカーボンブラック(CB)を質量比(CB/CP)０．０５〜０．３の割合で含むことを特徴とする前記(3)に記載の固体高分子形燃料電池。
(5) 触媒層を形成するカーボンブラック(CB)は、その平均粒子直径(CBd)と前記触媒粉末(CP)の平均粒子直径(CPd)との直径比率(CBd／CPd)が０．１〜０．７の範囲内であることを特徴とする前記(3)又は(4)に記載の固体高分子形燃料電池。 That is, the gist of the present invention is as follows.
(1) Solid polymer fuel comprising activated carbon as a carbon material, catalyst metal particles made of catalyst metal supported on the activated carbon, and a catalyst coating portion made of an electrolyte resin and covering the activated carbon and the catalyst metal particles. The activated carbon has a BET specific surface area of 1000 m 2 / g or more, and the ratio of the external surface area obtained by T-plot analysis of N 2 adsorption to this BET specific surface area is 10%. And the mass ratio (I / C: g-ionomer / g-carbon) of the electrolyte resin (I) and the activated carbon (C) forming the catalyst coating portion is 0.05 to 0.1. A catalyst powder for a polymer electrolyte fuel cell, characterized by being in the range.
(2) A method for producing catalyst powder by supporting catalyst metal particles made of catalyst metal on activated carbon, which is a carbon material, and coating the surface of the obtained catalyst metal-supported activated carbon with a catalyst coating portion made of an electrolyte resin. ,
The activated carbon used is an activated carbon having a BET specific surface area of 1000 m 2 / g or more and a ratio of an outer surface area obtained by T-plot analysis of N 2 adsorption to the BET specific surface area of 10% or less.
In the dispersion medium, the catalyst metal-supported activated carbon obtained by supporting the catalyst metal particles on the activated carbon and the electrolyte resin, the mass ratio of the electrolyte resin (I) and the activated carbon (C) (I / C: g-ionomer / g-carbon) is dispersed in a range of 0.05 to 0.1, and contacted with stirring at a temperature of 50 to 100 ° C. for 10 to 20 hours. A method for producing a catalyst powder for a polymer electrolyte fuel cell, wherein the surface is coated with a catalyst coating portion made of the electrolyte resin.
(3) A solid polymer fuel cell having a pair of an anode catalyst layer and a cathode catalyst layer sandwiching a proton conductive electrolyte membrane, and at least the catalyst powder forming the cathode catalyst layer is activated carbon as a carbon material; The catalyst metal particles made of catalyst metal and supported on the activated carbon, and the catalyst coating portion made of an electrolyte resin and covering the activated carbon and the catalyst metal particles, and the activated carbon forming the catalyst powder is a BET specific surface area a is but 1000 m 2 / g or more, the ratio of external surface area obtained by T-plot analysis of N 2 adsorption with respect to the BET specific surface area of not more than 10%, and the catalyst coating unit for forming the catalyst powder Solid polymer form characterized in that the mass ratio (I / C: g-ionomer / g-carbon) of the electrolyte resin (I) and the activated carbon (C) is in the range of 0.05 to 0.1 Fuel cell.
(4) At least the cathode catalyst layer of the pair of anode catalyst layer and cathode catalyst layer has a carbon black (CB) mass ratio (CB / CP) of 0.05-0. The solid polymer fuel cell as described in (3) above, which is contained in a ratio of 3.
(5) The carbon black (CB) forming the catalyst layer has a diameter ratio (CBd / CPd) between the average particle diameter (CBd) and the average particle diameter (CPd) of the catalyst powder (CP) of 0.1 to 0.1. The polymer electrolyte fuel cell as described in (3) or (4) above, which is within the range of 0.7.

本発明の固体高分子形燃料電池用の触媒粉末によれば、触媒金属の利用率が高く、触媒層を形成して固体高分子形燃料電池に組み込んだ際に安定した発電性能を発現することができ、また、これによって固体高分子形燃料電池において白金原子の使用量を可及的に低減することができる。
また、本発明によれば、上記の如き固体高分子形燃料電池用の触媒粉末の製造方法を提供することができ、また、このような固体高分子形燃料電池用の触媒粉末を用いて製造され、白金原子の使用量を可及的に低減した固体高分子形燃料電池を提供することができる。 According to the catalyst powder for a polymer electrolyte fuel cell of the present invention, the utilization rate of the catalyst metal is high, and when the catalyst layer is formed and incorporated in the polymer electrolyte fuel cell, stable power generation performance is exhibited. In addition, the amount of platinum atoms used in the polymer electrolyte fuel cell can be reduced as much as possible.
In addition, according to the present invention, a method for producing a catalyst powder for a polymer electrolyte fuel cell as described above can be provided, and the catalyst powder for such a polymer electrolyte fuel cell can be produced. Thus, a polymer electrolyte fuel cell in which the amount of platinum atoms used is reduced as much as possible can be provided.

図１は、本発明の固体高分子形燃料電池用の触媒粉末を構成する活性炭、触媒金属、及び電解質樹脂の関係を説明するための模式図である。FIG. 1 is a schematic diagram for explaining the relationship among activated carbon, catalyst metal, and electrolyte resin that constitute the catalyst powder for a polymer electrolyte fuel cell of the present invention. 図２は、図１の触媒粉末において形成される三相界面の概念を説明するための模式図である。FIG. 2 is a schematic diagram for explaining the concept of a three-phase interface formed in the catalyst powder of FIG.

以下、本発明の固体高分子形燃料電池用の触媒粉末及びその製造方法、並びにこの触媒粉末を用いた固体高分子形燃料電池について詳細に説明する。
本発明の固体高分子形燃料電池用の触媒粉末は、図１及び図２に示すように、炭素材料である活性炭１と、前記活性炭１に担持された触媒金属からなる触媒金属粒子２と、電解樹脂であって前記活性炭１及び触媒金属粒子２を被覆する触媒被覆部３とからなり、これら活性炭１と触媒金属粒子２と触媒被覆部３との間には、前記触媒金属粒子２が前記活性炭１及び触媒被覆部３の電解質樹脂に接触する界面（三相界面）４が形成され、この三相界面における触媒金属粒子の表面が燃料電池における反応場として機能する。 Hereinafter, the catalyst powder for the polymer electrolyte fuel cell of the present invention, the production method thereof, and the polymer electrolyte fuel cell using the catalyst powder will be described in detail.
As shown in FIGS. 1 and 2, the catalyst powder for a polymer electrolyte fuel cell of the present invention includes activated carbon 1 that is a carbon material, and catalytic metal particles 2 made of a catalytic metal supported on the activated carbon 1, It consists of a catalyst coating 3 which is an electrolytic resin and coats the activated carbon 1 and the catalyst metal particles 2. Between the activated carbon 1, the catalyst metal particles 2 and the catalyst coating 3, the catalyst metal particles 2 are An interface (three-phase interface) 4 that contacts the activated carbon 1 and the electrolyte resin of the catalyst coating 3 is formed, and the surface of the catalyst metal particles at the three-phase interface functions as a reaction field in the fuel cell.

本発明の固体高分子形燃料電池用の触媒粉末は、炭素材料としての活性炭と、白金(Pt)若しくはこのＰtを主成分としてＣo、Ｎi、Ｆe、Ｐd、Ａu、Ｒu、Ｒh、Ｉr等の金属元素が活性向上等を目的として原子組成百分率５０at%以下の割合で添加された白金合金(Ｐt合金)からなる触媒金属であって前記活性炭に担持された触媒金属粒子と、電解質樹脂であって前記活性炭及び触媒金属粒子を被覆する触媒被覆部とを備えているものである。   The catalyst powder for the polymer electrolyte fuel cell of the present invention comprises activated carbon as a carbon material and platinum (Pt) or Pt as a main component such as Co, Ni, Fe, Pd, Au, Ru, Rh, Ir, etc. A catalytic metal composed of a platinum alloy (Pt alloy) to which a metal element is added in an atomic composition percentage of 50 at% or less for the purpose of improving activity, etc., and catalytic metal particles supported on the activated carbon, and an electrolyte resin. And a catalyst coating portion for coating the activated carbon and the catalyst metal particles.

そして、本発明において、炭素材料としての活性炭については、その全体のBET比表面積が通常１０００m2/g以上、好ましくは１０００m2/g以上２０００m2/g以下、より好ましくは１０００m2/g以上１８００m2/g以下であり、また、このBET比表面積に対してＮ2吸着のT-plot解析で得られる外表面積の割合（以下、単に「外表面積割合」ということがある。）が１０%以下、好ましくは８%以上１０%以下の範囲内である。ここで、全体のBET比表面積が１０００m2/gより小さいと、触媒金属粒子が担持されるサイトが小さくなって触媒金属粒子が密集して担持され、燃料電池運転条件下（例えば、燃料電池自動車のアクセルのON/OFFの際に０．６〜１．０Vの範囲で電位変動が発生する。）において触媒金属粒子が凝集し粗大化して電池性能が低下する虞がある。また、前記外表面積がBET比表面積に対して１０%より大きくなると、ミクロ孔容積が減少し、低加湿条件下の運転時に触媒層中の保水性能が低下し、触媒層中が乾燥し易い環境になって触媒金属の利用率が低下し、結果として電池性能が低下する虞がある。また、該表面積割合が８%以上１０%以下であると、後述する触媒被覆部を形成する電解質樹脂(I)とカーボンブラック(C)との質量比率(I/C)を適切な値の範囲内に調整することにより、触媒被覆部を介したプロトン(H+)伝導経路の確保が確かになり、所望の数の三相界面が形成され易くなって触媒金属の利用率がより改善する。 Then, in the present invention, for the activated carbon as the carbon material, BET specific surface area of the entire normal 1000 m 2 / g or more, preferably 1000 m 2 / g or more 2000 m 2 / g or less, more preferably 1000 m 2 / g or more 1800m 2 / g or less, and the ratio of the external surface area obtained by T-plot analysis of N 2 adsorption to the BET specific surface area (hereinafter sometimes simply referred to as “external surface area ratio”) is 10% or less. Preferably, it is in the range of 8% or more and 10% or less. Here, if the overall BET specific surface area is smaller than 1000 m 2 / g, the site where the catalyst metal particles are supported becomes smaller and the catalyst metal particles are densely supported, and the fuel cell operating conditions (for example, fuel cell vehicle) When the accelerator is turned ON / OFF, the potential fluctuation occurs in the range of 0.6 to 1.0 V.), the catalyst metal particles aggregate and become coarse, and the battery performance may be deteriorated. In addition, when the outer surface area is larger than 10% with respect to the BET specific surface area, the micropore volume is decreased, the water retention performance in the catalyst layer is lowered during operation under low humidification conditions, and the catalyst layer is easily dried. As a result, the utilization factor of the catalyst metal is lowered, and as a result, the battery performance may be lowered. In addition, when the surface area ratio is 8% or more and 10% or less, the mass ratio (I / C) of the electrolyte resin (I) and carbon black (C) forming the catalyst coating portion to be described later is within a suitable range. By adjusting inward, it is ensured that a proton (H + ) conduction path through the catalyst coating portion is ensured, and a desired number of three-phase interfaces are easily formed, and the utilization rate of the catalyst metal is further improved.

ここで、炭素材料として用いる活性炭の「Ｎ2吸着のT-plot解析で得られる外表面積」とは、一般的な窒素(N2)吸着法により全体のBET比表面積を測定し、得られたBET比表面積からミクロ孔(直径2nm未満の細孔)由来の比表面積を差し引いて得られたメソ孔(直径2〜50nmの細孔)以上の細孔を含む比表面積のことであり、窒素(N2)吸着法により得られた相対圧(p/p0)と吸着量(v)との関係を示す吸着等温線を、Lippensとde-Boreの式を用いて相対圧(p/p0)を吸着膜の平均厚さ(t)に変換してT-plot解析を実施し、得られた結果から全体のBET比表面積をミクロ孔由来の表面積と外表面積とに区別して得られる値である〔近藤精一、石川達雄、安部郁夫著、丸善(株)平成13年2月25日発行「吸着の科学」48〜50参照〕。このような窒素吸着法の測定や、BET比表面積及び外表面積は、例えば自動比表面積測定装置（日本ベル社製BELSORP36）等の吸着測定装置を用いて実施することができる。そして、このBET比表面積及び外表面積については、例えば活性炭の平均粒子径の調整や、各種の賦活方法等により調節することができる。 Here, the “outer surface area obtained by T-plot analysis of N 2 adsorption” of activated carbon used as a carbon material was obtained by measuring the entire BET specific surface area by a general nitrogen (N 2 ) adsorption method. BET specific surface area is a specific surface area including pores more than mesopores (pores with a diameter of 2 to 50 nm) obtained by subtracting the specific surface area derived from micropores (pores with a diameter of less than 2 nm), nitrogen ( N 2 ) The adsorption isotherm showing the relationship between the relative pressure (p / p 0 ) obtained by the adsorption method and the amount of adsorption (v) is expressed using the Lippens and de-Bore equations as the relative pressure (p / p 0 ) Is converted to the average thickness (t) of the adsorbed film, and T-plot analysis is performed.From the obtained results, the overall BET specific surface area is obtained by distinguishing between the micropore-derived surface area and the external surface area. Yes [see Seiichi Kondo, Tatsuo Ishikawa, Ikuo Abe, Maruzen Co., Ltd., February 25, 2001 "Science of adsorption" 48-50]. Such measurement of the nitrogen adsorption method, the BET specific surface area, and the outer surface area can be carried out using an adsorption measuring device such as an automatic specific surface area measuring device (BELSORP36 manufactured by Nippon Bell Co., Ltd.). The BET specific surface area and the external surface area can be adjusted, for example, by adjusting the average particle diameter of activated carbon, various activation methods, and the like.

また、本発明の触媒粉末において前記活性炭及び触媒金属粒子を被覆する触媒被覆部を形成するための電解質樹脂としては、プロトン伝導性を有する電解質樹脂であれば特に制限されるものではなく、従来から固体高分子形燃料電池の分野で用いられてきた各種のプロトン伝導性電解質樹脂を用いることができ、例えば、パーフルオロアルキレン基を主鎖骨格とし、一部にパーフルオロビニルエーテルの側鎖の末端にスルホン基を有するパーフルオロスルホン酸系プロトン伝導性電解質樹脂や，スチレンジビニルベンゼンスルホン酸等のイオン交換樹脂や、ポリイミド系スルホン酸、ポリエーテル系スルホン酸等の樹脂等を用いることができる。   In addition, the electrolyte resin for forming the catalyst coating portion for coating the activated carbon and the catalyst metal particles in the catalyst powder of the present invention is not particularly limited as long as it is an electrolyte resin having proton conductivity, and has been conventionally used. Various proton conductive electrolyte resins that have been used in the field of polymer electrolyte fuel cells can be used. For example, a perfluoroalkylene group is a main chain skeleton, and a part of the side chain of perfluorovinyl ether is at the end. A perfluorosulfonic acid proton conductive electrolyte resin having a sulfone group, an ion exchange resin such as styrenedivinylbenzenesulfonic acid, a resin such as polyimide sulfonic acid or polyether sulfonic acid, or the like can be used.

更に、本発明においては、触媒粉末において触媒被覆部を形成する電解質樹脂(I)と活性炭(C)との質量比率(I/C: g-ionomer/g-carbon)が０．０５以上０．１以下、好ましくは０．０５以上０．０８以下の範囲内であることが必要であり、この電解質樹脂(I)と活性炭(C)との質量比率(I/C)が０．０５より低いと、燃料電池において反応場となる三相界面（活性炭及び電解質樹脂と接触する触媒金属粒子の表面）において電解質樹脂量を介したH＋伝導経路が貧弱になり、三相界面の数が少なくなり、触媒金属粒子の利用率が低下する虞があり、反対に、０．１よりも大きくなると、触媒粉末において電解質樹脂からなる触媒被覆部の被覆厚みが厚くなり過ぎ、活性炭上の触媒金属粒子への酸素の拡散性が悪くなって触媒金属粒子の利用率が低くなる虞がある。電解質樹脂(I)と活性炭(C)との質量比率(I/C)を０．０５〜０．１の範囲内とすることにより、電解質樹脂を介したH＋伝導と触媒金属粒子への空気拡散がバランスし、三相界面に存在する触媒金属粒子の量が最大となり、最も触媒金属粒子の利用効率が高くなる。
なお、従来においては、事前に炭素材料である活性炭に電解質樹脂を被覆することが無いため、本発明の電解質樹脂量と比べ使用量が少ない状態で触媒層を構成することとなる。具体的には、従来技術では触媒層を構成している全体の電解質樹脂(Ｉca)と活性炭(Ｃca)とのＩca／Ｃca質量比が０．５〜１．２程度である。これに対して、本発明においては、触媒粉末での電解質樹脂(I)と活性炭(C)との質量比(I/C)が０．０５〜０．１であり、その後に、触媒層形成時に添加される電解質樹脂を加えた触媒層を構成している全体の電解質樹脂(Ｉca)と活性炭(Ｃca)とのＩca／Ｃca質量比は２．０〜２．５程度となり、従来の触媒層に比べて電解質樹脂量が多くなる。 Furthermore, in the present invention, the mass ratio (I / C: g-ionomer / g-carbon) of the electrolyte resin (I) and the activated carbon (C) forming the catalyst coating portion in the catalyst powder is 0.05 or more and 0.0. 1 or less, preferably 0.05 or more and 0.08 or less, and the mass ratio (I / C) between the electrolyte resin (I) and the activated carbon (C) is lower than 0.05. In addition, the H + conduction path through the amount of electrolyte resin is poor at the three-phase interface (the surface of the catalytic metal particles that are in contact with the activated carbon and the electrolyte resin), which becomes a reaction field in the fuel cell, and the number of three-phase interfaces is reduced. There is a possibility that the utilization rate of the catalyst metal particles may be reduced. On the other hand, when the catalyst metal particles are larger than 0.1, the coating thickness of the catalyst coating portion made of the electrolyte resin in the catalyst powder becomes too thick, and the catalyst metal particles on the activated carbon are converted into the catalyst metal particles. Oxygen diffusibility of the catalyst may deteriorate and the utilization rate of the catalyst metal particles may be reduced By adjusting the mass ratio (I / C) between the electrolyte resin (I) and the activated carbon (C) within the range of 0.05 to 0.1, H + conduction through the electrolyte resin and air to the catalyst metal particles Diffusion is balanced, the amount of catalytic metal particles present at the three-phase interface is maximized, and the utilization efficiency of the catalytic metal particles is highest.
In the prior art, since the activated carbon, which is a carbon material, is not coated with an electrolyte resin in advance, the catalyst layer is configured in a state where the amount used is smaller than the amount of the electrolyte resin of the present invention. Specifically, in the prior art, the I ca / C ca mass ratio of the entire electrolyte resin (I ca ) and activated carbon (C ca ) constituting the catalyst layer is about 0.5 to 1.2. On the other hand, in the present invention, the mass ratio (I / C) of the electrolyte resin (I) and the activated carbon (C) in the catalyst powder is 0.05 to 0.1, and then the catalyst layer formation The I ca / C ca mass ratio of the entire electrolyte resin (I ca ) and activated carbon (C ca ) constituting the catalyst layer to which the electrolyte resin added sometimes is about 2.0 to 2.5, The amount of the electrolyte resin is larger than that of the conventional catalyst layer.

本発明の固体高分子形燃料電池用の触媒粉末を製造する方法については、以下の通りである。
すなわち、先ず、本発明で用いる活性炭として、BET比表面積が１０００m2/g以上であって外表面積割合が１０%以下の活性炭を用意する。
このような活性炭については、その調製方法等については特に限定されるものではなく、例えば具体的な例として、石油系や石炭系のピッチ及びピッチコークス、人造黒鉛、石油又は石炭由来の樹脂等を原料として調製される種々の炭素材料、天然植物を原料として調製される炭素材料、チャー、いわゆる炭素繊維等を粗原料として用い、これらの粗原料を賦活処理し多孔質化して得られた活性炭や、また、ヤシガラ、竹、木材等の特定の天然植物から製造される活性炭等を用いることができる。 The method for producing the catalyst powder for the polymer electrolyte fuel cell of the present invention is as follows.
That is, first, as the activated carbon used in the present invention, activated carbon having a BET specific surface area of 1000 m 2 / g or more and an outer surface area ratio of 10% or less is prepared.
For such activated carbon, the preparation method thereof is not particularly limited. For example, as a specific example, petroleum-based or coal-based pitch and pitch coke, artificial graphite, resin derived from petroleum or coal, etc. Various carbon materials prepared as raw materials, carbon materials prepared using natural plants as raw materials, char, so-called carbon fibers, etc. are used as raw materials, activated carbon obtained by activating these raw materials and making them porous, In addition, activated carbon produced from a specific natural plant such as coconut shell, bamboo, and wood can be used.

そして、上記の賦活処理の方法としては、例えば、空気、酸素等の酸化性雰囲気中で酸化処理を行う方法、水酸化カリウム(KOH)、水酸化ナトリウム(NaOH)等を用いて５００〜８００℃の温度で反応させるアルカリ賦活の方法、水蒸気を用いて７５０〜１１００℃の温度で反応させる水蒸気賦活の方法、炭酸ガスを用いて７５０〜１１００℃の温度で反応させる炭酸ガス賦活の方法、塩化亜鉛を用いて４００〜１０００℃の温度で処理し反応させる塩化亜鉛賦活の方法等を挙げることができる。更に、このような賦活処理の後に、不活性ガス、還元性ガス、アンモニアガス、酸化性ガス等のガスを各々単独で、あるいは、複数のガスの混合ガスとして用い、ガス雰囲気中常圧又は加圧下に熱処理を行い、活性炭の表面における官能基の種類やその量を選択的に付与しまた制御し、水蒸気吸着特性や窒素ガス吸着特性を制御してもよい。   And as a method of said activation treatment, for example, a method of performing an oxidation treatment in an oxidizing atmosphere such as air, oxygen, 500 to 800 ° C. using potassium hydroxide (KOH), sodium hydroxide (NaOH) or the like. Alkaline activation method in which the reaction is carried out at a temperature of 750 to 1100 ° C using water vapor, a carbon dioxide activation method in which the reaction is carried out at a temperature of 750 to 1100 ° C using carbon dioxide, zinc chloride A method of activating zinc chloride in which a reaction is carried out at a temperature of 400 to 1000 ° C. using a nitrile can be used. Furthermore, after such activation treatment, gases such as inert gas, reducing gas, ammonia gas, oxidizing gas, etc. are used alone or as a mixed gas of a plurality of gases, respectively, under normal pressure or pressure in a gas atmosphere. Heat treatment may be performed to selectively impart and control the type and amount of functional groups on the surface of the activated carbon, thereby controlling water vapor adsorption characteristics and nitrogen gas adsorption characteristics.

また、より具体的には、例えば市販の活性炭として、クラレカミカル社製の活性炭ＹＰ５０Ｆ（BET比表面積1700m2/g）や活性炭ＹＰ８０Ｆ（BET比表面積2000m2/g）、関西熱化学社製の活性炭ＭＳＰ２０（BET比表面積1970m2/g）、クラレカミカル社製の活性炭ＲＰ２０（BET比表面積1700m2/gのものと2000m2/gのもの）等を粉砕して及び／又は賦活処理して用いることができる。 More specifically, for example, commercially available activated carbon such as activated carbon YP50F (BET specific surface area 1700 m 2 / g) or activated carbon YP80F (BET specific surface area 2000 m 2 / g) manufactured by Kuraray Chemical Co., Ltd., activated carbon manufactured by Kansai Thermochemical Co., Ltd. MSP20 (BET specific surface area 1970 m 2 / g), activated carbon RP20 (BET specific surface area 1700 m 2 / g and 2000 m 2 / g) manufactured by Kuraray Chemical, etc. are used after being crushed and / or activated. Can do.

次に、以上のように炭素材料として用意した活性炭に触媒金属粒子を担持させ、触媒金属担持活性炭を調製するが、この際の方法については、特に制限はなく、炭素材料に触媒金属を担持させる従来の方法をそのまま採用することができる。   Next, catalytic metal particles are supported on activated carbon prepared as a carbon material as described above to prepare catalytic metal-supported activated carbon, but there is no particular limitation on the method at this time, and the catalytic metal is supported on the carbon material. Conventional methods can be employed as they are.

更に、このようにして作製した触媒金属担持活性炭を用いて本発明の触媒粒子を調製するには、触媒金属担持活性炭をエタノール、1-プロパノ―ル、2-プロパノ―ル等の適当な分散媒中に均一に分散させ、得られた分散溶液中に所定の電解質樹脂を、この電解質樹脂(I)と活性炭(C)との質量比率(I/C)が０．０５〜０．１の範囲内になるように添加し、撹拌下に混合し、その後、温度５０℃以上及び１０時間以上の条件で、好ましくは温度５０℃以上１００℃以下及び１０時間以上２０時間以下、より好ましくは温度５０℃以上７０℃以下及び１０時間以上１５時間以下の条件で撹拌下に保持して接触させ、その後、分散媒を蒸発させて乾固物を得る。この得られ乾固物を所定の温度及び減圧下に乾燥させ、表面が電解質樹脂で被覆された本発明の固体高分子形燃料電池用の触媒粉末を調製する。前記触媒粉末調製時の条件については、温度が５０℃より低いと電解質樹脂のネットワークが十分に広がりを持たない状態で触媒金属担持活性炭を被覆してしまうため、電解質樹脂中に含まれる親水性基（例えば、スルホン基）が均一に分散しない虞があり、反対に、１００℃を超えても性能的には問題ないが、７０℃を超えて高くしても性能が更に改善されるというものではなく、高温に加熱できる加熱装置が必要になってコスト高になり、また、時間が１０時間より短いと電解質樹脂のネットワークが十分に広がりを持たない状態で触媒金属担持活性炭を被覆してしまうため、電解質樹脂中に含まれる親水性基（例えば、スルホン基）が均一に分散しない虞があり、反対に、２０時間を超えても性能的には問題ないが、１５時間を超えても性能が更に改善されるというものではなく、生産性が低下する。   Furthermore, in order to prepare the catalyst particles of the present invention using the catalyst metal-supported activated carbon thus produced, the catalyst metal-supported activated carbon is used as an appropriate dispersion medium such as ethanol, 1-propanol, 2-propanol and the like. A predetermined electrolyte resin is uniformly dispersed in the obtained dispersion solution, and the mass ratio (I / C) between the electrolyte resin (I) and the activated carbon (C) is in the range of 0.05 to 0.1. Then, the mixture is mixed under stirring, and then, at a temperature of 50 ° C. or more and 10 hours or more, preferably at a temperature of 50 ° C. or more and 100 ° C. or less and 10 to 20 hours or less, more preferably a temperature of 50 The mixture is kept in contact with stirring under the conditions of not lower than 70 ° C. and not higher than 70 ° C. and not shorter than 10 hours and not longer than 15 hours, and then the dispersion medium is evaporated to obtain a dry solid. The dried product thus obtained is dried under a predetermined temperature and reduced pressure to prepare a catalyst powder for a polymer electrolyte fuel cell of the present invention whose surface is coated with an electrolyte resin. Regarding the conditions at the time of preparing the catalyst powder, when the temperature is lower than 50 ° C., the catalyst resin-supported activated carbon is coated in a state where the network of the electrolyte resin does not sufficiently spread, so that the hydrophilic group contained in the electrolyte resin is covered. (For example, a sulfone group) may not be uniformly dispersed. Conversely, if the temperature exceeds 100 ° C., there is no problem in performance, but if the temperature exceeds 70 ° C., the performance is further improved. In addition, a heating device that can be heated to a high temperature is required, resulting in high costs, and if the time is shorter than 10 hours, the catalyst resin-supported activated carbon is coated in a state where the network of the electrolyte resin does not sufficiently spread. There is a possibility that the hydrophilic group (for example, sulfone group) contained in the electrolyte resin is not uniformly dispersed. On the contrary, if it exceeds 20 hours, there is no problem in performance, but it exceeds 15 hours. And not that the performance is further improved, the productivity is lowered.

このようにして調製された触媒粉末を用いて固体高分子形燃料電池用の触媒層を調製する方法についても、特に制限されるものではなく、従来から知られている方法と同様の方法で、固体高分子形燃料電池用の触媒層を形成し、また、この触媒層を用いて固体高分子形燃料電池を製造することができる。そして、この触媒層の調製に際して用いる電解質樹脂については、特に制限されるものではなく、従来から固体高分子形燃料電池の分野で用いられてきた各種のプロトン伝導性電解質樹脂を用いることができる。なお、この触媒層の調製に際して用いる電解質樹脂については、触媒粉末の触媒被覆部を形成する電解質樹脂との関係で、例えば電解質樹脂の単位質量当りに含まれるスルホン酸基当量(EW)を勘案し、この触媒粉末の触媒被覆部を形成する電解質樹脂と同じ又は異なるＥＷを有する電解質樹脂を用いてもよく、必要により、例えば、触媒粉末の触媒被覆部を形成する電解質樹脂のＥＷを低くし（保水性を高くし）、また、触媒層を形成する際に用いる電解質樹脂のＥＷを高くし（保水性を低くし）、これによって、水の少ない低電流密度領域では触媒金属粒子近傍に必要最小限の水を保持できるようにし、また、水の多い大電流密度領域では触媒層内の保水性を下げて排水性を向上させるようにしてもよい。   The method for preparing a catalyst layer for a polymer electrolyte fuel cell using the catalyst powder thus prepared is not particularly limited, and may be a method similar to a conventionally known method, A catalyst layer for a polymer electrolyte fuel cell is formed, and a polymer electrolyte fuel cell can be produced using this catalyst layer. The electrolyte resin used in preparing the catalyst layer is not particularly limited, and various proton conductive electrolyte resins that have been used in the field of solid polymer fuel cells can be used. Note that the electrolyte resin used in the preparation of the catalyst layer is in consideration of, for example, the sulfonic acid group equivalent (EW) contained per unit mass of the electrolyte resin in relation to the electrolyte resin that forms the catalyst coating portion of the catalyst powder. An electrolyte resin having the same or different EW as the electrolyte resin forming the catalyst coating portion of the catalyst powder may be used. If necessary, for example, the EW of the electrolyte resin forming the catalyst coating portion of the catalyst powder is lowered ( Increase water retention), and increase the EW of the electrolyte resin used to form the catalyst layer (decrease the water retention), which makes it necessary to be near the catalyst metal particles in the low current density region where water is low. Limiting water can be retained, and in a large current density region with a large amount of water, the water retention in the catalyst layer may be lowered to improve drainage.

また、この触媒層を調製する際には、好ましくは前記触媒粉末(CP)に対してカーボンブラック(CB)を質量比(CB/CP)０．０５以上０．３以下、好ましくは０．０５以上０．２５以下の割合で配合するのがよい。この際の質量比(CB/CP)が０．０５未満であると触媒層中の単位体積当りの活性炭に対するカーボンブラックの接触面積が少なくなり、電子の導電バスが少なくなって導電抵抗が高くなり、結果として燃料電池の発電性能が低下する虞があり、反対に、質量比(CB/CP)が０．３を超えると触媒層を構成するために用いる電解質樹脂の必要量が多くなり、この電解質樹脂として親水性のスルホン基を有する樹脂が用いられると、触媒層中における単位体積当りのスルホン基の数が多くなり過ぎ、大電流放電時にフラッディング現象が発生し易くなり、この場合にも燃料電池の発電性能が低下する虞が生じる。このように触媒粉末(CP)に対してカーボンブラック(CB)を質量比(CB/CP)０．０５〜０．３の範囲内で用いることにより、触媒層のプロトン伝導抵抗の上昇を抑えつつ、フラッディング現象の発生を抑制し、高い電池性能を発現させることができる。   Further, when preparing this catalyst layer, preferably the mass ratio (CB / CP) of 0.05 to 0.3, preferably 0.05, of carbon black (CB) to the catalyst powder (CP). It is good to mix | blend in the ratio of 0.25 or less. If the mass ratio (CB / CP) at this time is less than 0.05, the contact area of carbon black with activated carbon per unit volume in the catalyst layer is reduced, and the conductive bus of electrons is reduced, resulting in an increased conductive resistance. As a result, there is a risk that the power generation performance of the fuel cell may be reduced, and conversely, when the mass ratio (CB / CP) exceeds 0.3, the required amount of electrolyte resin used to constitute the catalyst layer increases. If a resin having a hydrophilic sulfone group is used as the electrolyte resin, the number of sulfone groups per unit volume in the catalyst layer becomes too large, and a flooding phenomenon is likely to occur during a large current discharge. The power generation performance of the battery may be reduced. In this way, by using carbon black (CB) with respect to catalyst powder (CP) within a mass ratio (CB / CP) in the range of 0.05 to 0.3, an increase in proton conduction resistance of the catalyst layer is suppressed. The occurrence of flooding phenomenon can be suppressed and high battery performance can be exhibited.

また、この触媒層を形成する際に用いられるカーボンブラック(CB)については、その平均粒子直径(CBd)と前記触媒粉末(CP)の平均粒子直径(CPd)との直径比率(CBd／CPd)が０．１以上０．７以下、好ましくは０．２以上０．６以下の範囲内であるのがよく、この際の直径比率(CBd／CPd)が０．１未満であるとカーボンブラック(CB)と触媒粉末(CP)とが密に充填されてしまい、生成水が溜り易くてガスの拡散性が悪い触媒層構造となり、結果として電池性能が低下する虞があり、反対に、直径比率(CBd／CPd)が０．７を超えると触媒層中の単位体積当りの活性炭との接触面積が少なくなり、電子の導電バスが少なくなって導電抵抗が高くなり、発電性能が低下する虞が生じる。このようにカーボンブラック(CB)として触媒粉末(CP)の平均粒子直径(CPd)に対する直径比率(CBd／CPd)が０．１〜０．７のものを用いることにより、多孔性を維持して排水性とガス拡散性とが共に優れた触媒層が得られる。   In addition, for carbon black (CB) used in forming this catalyst layer, the diameter ratio (CBd / CPd) between the average particle diameter (CBd) and the average particle diameter (CPd) of the catalyst powder (CP) Is 0.1 or more and 0.7 or less, preferably 0.2 or more and 0.6 or less. When the diameter ratio (CBd / CPd) is less than 0.1, carbon black ( CB) and catalyst powder (CP) are packed closely, resulting in a catalyst layer structure in which the produced water tends to accumulate and gas diffusibility is poor, and as a result, the battery performance may be lowered, and conversely, the diameter ratio If (CBd / CPd) exceeds 0.7, the contact area with the activated carbon per unit volume in the catalyst layer will be reduced, there will be a risk that the electric conduction bus will be reduced and the conductive resistance will be increased, leading to a decrease in power generation performance. Arise. Thus, by using carbon black (CB) having a catalyst powder (CP) diameter ratio (CBd / CPd) to average particle diameter (CPd) of 0.1 to 0.7, the porosity is maintained. A catalyst layer excellent in both drainage and gas diffusibility can be obtained.

以下、実験例（実施例及び比較例）に基づいて、本発明の固体高分子形燃料電池用の触媒粉末及びその製造方法、並びに固体高分子形燃料電池について、より具体的に説明する。   Hereinafter, based on experimental examples (Examples and Comparative Examples), the catalyst powder for the polymer electrolyte fuel cell of the present invention, the production method thereof, and the polymer electrolyte fuel cell will be described more specifically.

(1) 諸物性値の測定方法
〔BET比表面積とＮ2吸着のT-plot解析で得られる外表面積〕
BET比表面積(m2/g)の測定は、試料約５０mgを測り採り、これを９０℃で真空乾燥し、得られた乾燥後の試料について、自動比表面積測定装置（日本ベル製、BELSORP36）を使用し、窒素ガスを用いたガス吸着法にて測定し、ＢＥＴ法に基づく１点法にて比表面積を決定した。
また、Ｎ2吸着のT-plot解析で得られる外表面積については、BET比表面積の測定で得られた吸着等温線を用い、T-plot解析を実施して求めた。 (1) Measurement method of various physical properties [BET specific surface area and outer surface area obtained by T-plot analysis of N 2 adsorption]
The BET specific surface area (m 2 / g) is measured by measuring about 50 mg of sample, vacuum-drying it at 90 ° C, and using the resulting dried sample, an automatic specific surface area measuring device (BELSORP36, manufactured by Nippon Bell) The specific surface area was determined by a one-point method based on the BET method.
Further, the outer surface area obtained by T-plot analysis of N 2 adsorption was obtained by performing T-plot analysis using the adsorption isotherm obtained by measurement of the BET specific surface area.

〔触媒粉末(CP)とカーボンブラック(CB)の間の質量比率(CB／CP)及び直径比率(CBd／CPd)〕
触媒粉末(CP)とカーボンブラック(CB)の間の質量比率(CB／CP)及び直径比率(CBd／CPd)については、触媒層インクの調製に先駆けて、それぞれ触媒粉末(CP) 及びカーボンブラック(CB)の質量を測定すると共に、電子顕微鏡観察によりカーボンブラック(CB)の平均粒子直径(CBd)及び触媒粉末(CP)の平均粒子直径(CPd)を測定し、これら測定された質量及び平均粒子直径(CBd, CPd)からそれぞれ比をとって質量比率(CB／CP)及び直径比率(CBd／CPd)とした。 [Mass ratio (CB / CP) and diameter ratio (CBd / CPd) between catalyst powder (CP) and carbon black (CB)]
Regarding the mass ratio (CB / CP) and diameter ratio (CBd / CPd) between catalyst powder (CP) and carbon black (CB), prior to preparation of catalyst layer ink, catalyst powder (CP) and carbon black, respectively. While measuring the mass of (CB), by measuring the average particle diameter (CBd) of carbon black (CB) and the average particle diameter (CPd) of the catalyst powder (CP) by electron microscope observation, these measured mass and average The ratio was calculated from the particle diameter (CBd, CPd) to obtain the mass ratio (CB / CP) and diameter ratio (CBd / CPd).

(2) 活性炭の準備及び調製
以下に示す各実験例では、活性炭としてクラレカミカル社製の活性炭ＹＰ５０Ｆ（試料Ａ：BET比表面積1700m2/g）、活性炭ＹＰ８０Ｆ（試料Ｂ：BET比表面積2000m2/g）、及び活性炭ＲＰ２０（試料Ｃ：BET比表面積1800m2/g）、及び関西熱化学社製の活性炭ＭＳＰ２０（試料Ｄ：BET比表面積1970m2/g）を用い、ボールミルを用いて平均粒子径が１μm以下になるまで粉砕し、活性炭として用いた。
活性炭として用意され、あるいは、調製された活性炭の試料名と、BET比表面積、外表面積割合についての測定結果を下記の表１に示す。 (2) In each of the experimental examples below the preparation and the preparation of activated carbon, Kuraray Kamikaru Ltd. as active carbon activated carbon YP50F (Sample A: BET specific surface area 1700 m 2 / g), activated charcoal YP80F (Sample B: BET specific surface area of 2000 m 2 / g), and activated carbon RP20 (sample C: BET specific surface area of 1800 m 2 / g), and Kansai thermochemical Co. activated carbon MSP20 (sample D: BET specific surface area of 1970m 2 / g) with an average particle size in a ball mill Was pulverized until it became 1 μm or less and used as activated carbon.
Table 1 below shows a sample name of the activated carbon prepared as the activated carbon or the measurement results of the BET specific surface area and the external surface area ratio.

Figure 2017091639
Figure 2017091639

(3) 白金粒子担持活性炭の調製
以上のようにして調製された各実験例の活性炭を蒸留水中に分散させ、この分散液にホルムアルデヒドを加え、４０℃に設定したウォーターバスにセットし、分散液の温度がバスと同じ４０℃になってから、撹拌下にこの分散液中にジニトロジアミンPt錯体硝酸水溶液をゆっくりと注ぎ入れた。その後、約２時間撹拌を続けた後、濾過し、得られた固形物の洗浄を行った。このようにして得られた固形物を９０℃で真空乾燥した後、乳鉢で粉砕し、触媒金属粒子として白金粒子を担持した各実験例の白金粒子担持活性炭（Pt担持活性炭）を作製した。
なお、各実験例のPt担持活性炭の白金担持量については、活性炭と白金粒子の合計質量に対して白金粒子の質量が４０質量%となるように調整し、誘導結合プラズマ発光分光分析(ICP-AES: Inductively Coupled Plasma-Atomic Emission Spectrometry)により測定して確認した。 (3) Preparation of platinum particle-supported activated carbon The activated carbon of each experimental example prepared as described above was dispersed in distilled water, formaldehyde was added to this dispersion, and set in a water bath set at 40 ° C. After the temperature reached 40 ° C., which was the same as that in the bath, an aqueous dinitrodiamine Pt complex nitric acid solution was slowly poured into the dispersion with stirring. Thereafter, stirring was continued for about 2 hours, followed by filtration, and washing of the obtained solid was performed. The solid material thus obtained was vacuum-dried at 90 ° C. and then pulverized in a mortar to prepare platinum particle-supported activated carbon (Pt-supported activated carbon) of each experimental example supporting platinum particles as catalyst metal particles.
The platinum loading of the Pt-supported activated carbon in each experimental example was adjusted so that the mass of the platinum particles was 40% by mass with respect to the total mass of the activated carbon and the platinum particles, and inductively coupled plasma emission spectroscopy (ICP- The measurement was confirmed by AES: Inductively Coupled Plasma-Atomic Emission Spectrometry.

(4) 各実験例の触媒粉末(CP)の調製
このようにして作製された上記各実験例のPt担持活性炭をエタノール（分散媒）中に分散させ、超音波ホモジナイザー（株式会社エスエムテ―社製UH-50）を用いて分散液中に超音波を５分間照射（パワーコントローラーのボリュームを10とし、振動子の先端から最も気泡が出ている状態で）し、その後、直径１mmの硝子ビーズと撹拌子とを分散溶液中に入れ、また、表２〜表５に示す触媒粉末形成時の電解質樹脂（触媒被覆部の樹脂）としてDupont社製ナフィオン〔登録商標：Nafion；パースルホン酸系イオン交換樹脂DE2020CS（試料イ）〕又は旭硝子社製フレミオン（試料ロ）を、この電解質樹脂(I)とPt担持活性炭中の活性炭(C)との質量比率が表２〜表５に示す割合になるように前記分散溶液中に加え、表２〜表５に示す温度及び時間の条件で撹拌下に保持した。その後、エバポレータ―を用いて８０℃に保持しながら分散媒のエタノールを蒸発させ、乾固物を得た。その後、得られ乾固物を９０℃に保持して真空(減圧)下に乾燥させ、表面が電解質樹脂で被覆されて触媒被覆部を有する各実験例の固体高分子形燃料電池用の触媒粉末(CP)を得た。 (4) Preparation of catalyst powder (CP) of each experimental example The Pt-supported activated carbon of each of the above experimental examples thus prepared was dispersed in ethanol (dispersion medium), and an ultrasonic homogenizer (manufactured by SMT Co., Ltd.) UH-50) is used to irradiate the dispersion with ultrasonic waves for 5 minutes (with the power controller volume set to 10 and with the most bubbles coming out from the tip of the vibrator), and then with glass beads with a diameter of 1 mm. A stirrer is placed in the dispersion, and Nafion (registered trademark: Nafion; persulfonic acid ion exchange) manufactured by DuPont as an electrolyte resin (resin for the catalyst coating portion) when forming the catalyst powder shown in Tables 2 to 5 is used. Resin DE2020CS (Sample A)] or Flemion (Sample B) manufactured by Asahi Glass Co., Ltd., so that the mass ratio of the electrolyte resin (I) and the activated carbon (C) in the Pt-supported activated carbon is as shown in Tables 2 to 5. In Table 2 to Table 5 Kept under stirring at conditions to temperature and time. Thereafter, while maintaining the temperature at 80 ° C. using an evaporator, ethanol of the dispersion medium was evaporated to obtain a dried product. Thereafter, the dried product thus obtained is maintained at 90 ° C. and dried under vacuum (reduced pressure), and the catalyst powder for the polymer electrolyte fuel cell of each experimental example having a catalyst coating portion whose surface is coated with an electrolyte resin (CP) was obtained.

(5) 触媒層インクの調製
以上のようにして調製された各実験例の触媒粉末を用い、また、カーボンブラック(CB)として親水性のカーボンブラックであるライオン社製ケッチェンブラックEC600JD（試料ａ）又はライオン社製ケッチェンブラックEC300（試料ｂ）を用い、更に、触媒層形成時の電解質樹脂としてDupont社製ナフィオン〔登録商標：Nafion；パースルホン酸系イオン交換樹脂DE2020CS（試料イ）〕又は旭硝子社製フレミオン（試料ロ）を用い、Ａr雰囲気下でこれら各触媒粉末、カーボンブラック(CB)、及び電解質樹脂を表２〜表５に示す割合で配合し、軽く撹拌した後、得られた固形分を超音波で解砕し、更にエタノールを加えて各実験例の触媒粉末と新たに添加された電解質樹脂とを合わせた合計の固形分濃度が１．１質量%となるように調整し、各実験例の触媒粉末と新たに添加された電解層形成時の電解質樹脂とが混合した触媒層インクＡを調製した。 (5) Preparation of catalyst layer ink The catalyst powder of each experimental example prepared as described above was used, and Ketjen Black EC600JD manufactured by Lion Corporation, which is hydrophilic carbon black as carbon black (CB) (sample a) ) Or Lion Ketjen Black EC300 (sample b), and Nafion [registered trademark: Nafion; persulfonic acid ion exchange resin DE2020CS (sample a)] as an electrolyte resin for forming the catalyst layer or Using Flemion (sample B) manufactured by Asahi Glass Co., Ltd., each of these catalyst powders, carbon black (CB), and electrolyte resin were blended in the proportions shown in Tables 2 to 5 under an Ar atmosphere, and obtained after lightly stirring. The solid content is crushed with ultrasonic waves, and ethanol is further added to adjust the total solid content concentration of the catalyst powder of each experimental example and the newly added electrolyte resin to 1.1% by mass. And the catalyst layer ink A of the electrolyte and the resin are mixed at the time of catalyst powder and the newly added electrolytic layer formed of each of the experimental examples were prepared.

また、カーボンブラック(CB)として疎水性カーボンブラックであるアセチレンブラック〔電気化学工業製商品名：デンカブラック粒状品（試料ｃ）〕をエタノール中に分散させ固形分濃度が３質量％である触媒層インクＢを調製した。
更に、上記の触媒層インクＡと触媒層インクＢとを表２〜表５に示す質量混合比(AB混合比)で混合し、表２〜表５に示すカーボンブラック(CB)と触媒粉末(CP)との質量比(CB/CP)を有するように調整し、エタノールを加えて白金濃度が０．５質量%のスプレー塗布用の触媒層インクABを作製した。 In addition, acetylene black (trade name: Denka Black granular product (sample c) manufactured by Denki Kagaku Kogyo Co., Ltd.), which is a hydrophobic carbon black, is dispersed as a carbon black (CB) in ethanol, and the catalyst layer has a solid content concentration of 3% by mass. Ink B was prepared.
Further, the catalyst layer ink A and the catalyst layer ink B described above were mixed at a mass mixing ratio (AB mixing ratio) shown in Tables 2 to 5, and carbon black (CB) and catalyst powder ( The catalyst layer ink AB for spray coating having a platinum concentration of 0.5 mass% was prepared by adding ethanol and adjusting the mass ratio (CB / CP) to CP).

(6) 触媒層の調製
このようにして調製された各実験例の触媒層インクを用い、白金の触媒層単位面積当りの質量（以下、「白金目付量という。）が０．２mg/cm2となるようにスプレー条件を調節し、上記スプレー塗布用触媒層インクをテフロン(登録商標)シート上にスプレーした後、アルゴン中１２０℃で６０分間の乾燥処理を行い、各実験例の触媒層を作製した。 (6) Preparation of catalyst layer Using the catalyst layer ink of each experimental example thus prepared, the mass per unit area of the platinum catalyst layer (hereinafter referred to as “platinum areal weight”) was 0.2 mg / cm 2. The spray conditions were adjusted so that the catalyst layer ink for spray application was sprayed onto a Teflon (registered trademark) sheet and then dried at 120 ° C. for 60 minutes in argon. Produced.

(7) 膜電極複合体(MEA)の調製
以上のようにして作製した上記各実験例の触媒層を用い、以下の方法でＭＥＡ（膜電極複合体）を作製した。
ナフィオン膜（Dupont社製NR211）から一辺６cmの正方形状の電解質膜を切り出した。また、テフロン(登録商標)シート上に塗布されたアノード及びカソードの各触媒層については、それぞれカッターナイフで一辺２．５cmの正方形状に切り出した。 (7) Preparation of membrane electrode assembly (MEA) MEA (membrane electrode assembly) was prepared by the following method using the catalyst layer of each experimental example prepared as described above.
A square electrolyte membrane having a side of 6 cm was cut out from a Nafion membrane (NR211 manufactured by Dupont). Further, each of the anode and cathode catalyst layers coated on the Teflon (registered trademark) sheet was cut into a square shape having a side of 2.5 cm with a cutter knife.

このようにして切り出されたアノード及びカソードの各触媒層の間に、各触媒層が電解質膜の中心部を挟んでそれぞれ接すると共に互いにずれが無いように、この電解質膜を挟み込み、１２０℃、１００kg/cm2で１０分間プレスし、次いで室温まで冷却した後、アノード及びカソード共にテフロン(登録商標)シートのみを注意深く剥ぎ取り、アノード及びカソードの各触媒層が電解質膜に定着した触媒層−電解質膜接合体を調製した。 Between each of the anode and cathode catalyst layers cut out in this way, each catalyst layer is in contact with each other with the center portion of the electrolyte membrane interposed therebetween, and the electrolyte membrane is sandwiched so that there is no deviation from each other. After pressing at 10 cm / cm 2 for 10 minutes and then cooling to room temperature, only the Teflon sheet was carefully peeled off for both the anode and cathode, and the catalyst layer in which the anode and cathode catalyst layers were fixed to the electrolyte membrane-electrolyte membrane A zygote was prepared.

次に、ガス拡散層として、カーボンペーパー（SGLカーボン社製35BC）から一辺２．５cmの大きさで一対の正方形状カーボンペーパーを切り出し、これらのカーボンペーパーの間に、アノード及びカソードの各触媒層が一致してずれが無いように、上記触媒層−電解質膜接合体を挟み、１２０℃、５０kg/cm2で１０分間プレスしてＭＥＡを作製した。 Next, as a gas diffusion layer, a pair of square carbon paper having a side of 2.5 cm is cut out from carbon paper (35BC manufactured by SGL Carbon Co.), and the catalyst layers of the anode and the cathode are sandwiched between these carbon papers. So that there is no deviation and the catalyst layer-electrolyte membrane assembly was sandwiched and pressed at 120 ° C. and 50 kg / cm 2 for 10 minutes to prepare an MEA.

(8) 燃料電池の性能の評価試験
作製した各実験例のＭＥＡについては、それぞれセルに組み込み、燃料電池測定装置にセットして、次の手順で燃料電池の性能評価を行った。
ガスについては、カソードに空気を、また、アノードに純水素を、それぞれ利用率が３５%と７０%となるように、０．２メガパスカルに加圧して供給した。また、セル温度は８０℃に設定した。供給するガスについては、高加湿条件での評価ではカソード、アノードの相対湿度が１００％に、また、低加湿条件での評価ではカソード、アノードの相対湿度が５０％になるように、蒸留水を用いた加湿器中でバブリングし、改質水素相当の水蒸気を含ませてセルに供給した。 (8) Performance Test of Fuel Cell Performance The MEAs of each experimental example produced were assembled in a cell and set in a fuel cell measurement device, and the performance evaluation of the fuel cell was performed according to the following procedure.
As for the gas, air was supplied to the cathode and pure hydrogen was supplied to the anode, pressurized to 0.2 megapascals so that the utilization rates were 35% and 70%, respectively. The cell temperature was set to 80 ° C. For the gas to be supplied, distilled water is used so that the relative humidity of the cathode and anode is 100% in the evaluation under high humidification conditions, and the relative humidity of the cathode and anode is 50% in the evaluation under low humidification conditions. Bubbling was performed in the used humidifier, and steam corresponding to the reformed hydrogen was included and supplied to the cell.

このような設定の下にセルにガスを供給した条件下で、負荷を徐々に増やし、電流密度が２００mA/cm2及び５００mA/cm2におけるセル端子間電圧を出力電圧として燃料電池の性能評価を実施した。
得られた燃料電池の性能評価については、高加湿条件下及び低加湿条件下での測定結果について、それぞれ“２００mA/cm2での出力電圧０．８０V以上”及び“５００mA/cm2での出力電圧０．７５V以上”を満たす場合を「◎」とし、また、“２００mA/cm2での出力電圧０．７５V以上０．８０V未満”及び“５００mA/cm2での出力電圧０．７０V以上０．７５V未満”を満たす場合を「〇」とし、更に、上記以外の場合を不合格の「×」として評価した。
そして、これら高加湿条件下及び低加湿条件下での４つの評価結果を基に、総合評価として、◎が３個以上である場合を「◎」とし、○が２個以上であって×がない場合を「○」とし、×が１つでもある場合を不合格の「×」とした。 Under the conditions where gas is supplied to the cell under such settings, the load is gradually increased, and the performance evaluation of the fuel cell is performed using the voltage between the cell terminals when the current density is 200 mA / cm 2 and 500 mA / cm 2 as the output voltage. Carried out.
For the performance evaluation of the obtained fuel cell, the measurement result in the high humidification conditions and low humidification conditions, "the output voltage 0.80V or more at 200 mA / cm 2", respectively, and "output at 500mA / cm 2 The case where “Voltage of 0.75 V or more” is satisfied is indicated by “◎”, and “Output voltage at 200 mA / cm 2 is 0.75 V or more and less than 0.80 V” and “Output voltage at 500 mA / cm 2 is 0.70 V or more and 0 The case where “less than .75 V” was satisfied was evaluated as “◯”, and the cases other than the above were evaluated as rejected “x”.
And based on these four evaluation results under high and low humidification conditions, as a comprehensive evaluation, a case where ◎ is 3 or more is designated as “◎”, ○ is 2 or more and x is The case where there was no symbol was “◯”, and the case where there was at least one “x” was regarded as an unacceptable “x”.

活性炭としてとして試料Ａ〜Ｃを用いた場合の結果をそれぞれ表２、表３、及び表４に示す。
また、活性炭として試料Ｄ、試料Ｅ、及び試料Ｆを用いた場合の結果を表５に示す。
なお、上記の各表中に記載されている下記の各記号は、以下に示す通りである。
Ｍ比：カーボンブラック(CB)と触媒粉末(CP)との質量比(CB/CP)
Ｄ比：カーボンブラック(CB)の平均粒子直径(CBd)と触媒粉末(CP)の平均粒子直径(CPd)との直径比率(CBd／CPd)
E2OP：電流密度２００mA/cm2時の出力電圧
E5OP：電流密度５００mA/cm2時の出力電圧
AB組成比(A/B)：触媒層インクAB作製時の触媒層インクＡの炭素材料と触媒層インクＢの炭素材料とのA/B組成比
Ex.：実施例(Example)
CEx.：比較例(Comparative Example) The results when samples A to C are used as the activated carbon are shown in Table 2, Table 3, and Table 4, respectively.
Table 5 shows the results when Sample D, Sample E, and Sample F were used as the activated carbon.
In addition, each following symbol described in each said table is as showing below.
M ratio: Mass ratio of carbon black (CB) to catalyst powder (CP) (CB / CP)
D ratio: Diameter ratio of carbon black (CB) average particle diameter (CBd) to catalyst powder (CP) average particle diameter (CPd) (CBd / CPd)
E2OP: Output voltage at a current density of 200 mA / cm 2
E5OP: Output voltage at a current density of 500 mA / cm 2
AB composition ratio (A / B): A / B composition ratio between the carbon material of catalyst layer ink A and the carbon material of catalyst layer ink B at the time of preparation of catalyst layer ink AB
Ex .: Example
CEx .: Comparative Example

Figure 2017091639
Figure 2017091639

Figure 2017091639
Figure 2017091639

Figure 2017091639
Figure 2017091639

Figure 2017091639
Figure 2017091639

表２〜表５に示す結果から明らかなように、本発明の各実施例においては、各比較例の場合に比べて、カソード、アノードの相対湿度が１００%の高加湿条件及び５０%の低加湿条件において、いずれも電流密度が２００mA/cm2時のセル電圧及び５００mA/cm2時のセル電圧が共にバランス良く高いことから、触媒金属粒子として用いた白金粒子の利用率が高く、しかも、高加湿条件下及び低加湿条件下で安定した発電性能を発揮していることが判明した。 As is clear from the results shown in Tables 2 to 5, in each example of the present invention, the relative humidity of the cathode and the anode is 100% higher humidification condition and 50% lower than in each comparative example. In humidification conditions, since the cell voltage at 200 mA / cm 2 and the cell voltage at 500 mA / cm 2 are both high in balance, the utilization rate of the platinum particles used as the catalyst metal particles is high, It was found that stable power generation performance was exhibited under high and low humidification conditions.

１…活性炭、２…触媒金属粒子、３…触媒被覆部、４…三相界面（活性炭１及び触媒被覆部３の電解質樹脂に接触する界面）。   DESCRIPTION OF SYMBOLS 1 ... Activated carbon, 2 ... Catalyst metal particle, 3 ... Catalyst coating | coated part, 4 ... Three-phase interface (interface which contacts the electrolyte resin of activated carbon 1 and the catalyst coating | coated part 3).

Claims (5)

炭素材料である活性炭と、前記活性炭に担持された触媒金属からなる触媒金属粒子と、電解質樹脂からなり、前記活性炭及び触媒金属粒子を被覆する触媒被覆部とからなる固体高分子形燃料電池用の触媒粉末であり、
前記活性炭は、BET比表面積が１０００m2/g以上であって、このBET比表面積に対してＮ2吸着のT-plot解析で得られる外表面積の割合が１０%以下であり、かつ、
前記触媒被覆部を形成する電解質樹脂(I)と前記活性炭(C)との質量比率(I/C: g-ionomer/g-carbon)が０．０５〜０．１の範囲内であることを特徴とする固体高分子形燃料電池用の触媒粉末。 For a polymer electrolyte fuel cell comprising activated carbon as a carbon material, catalyst metal particles made of catalyst metal supported on the activated carbon, and a catalyst coating portion made of an electrolyte resin and covering the activated carbon and the catalyst metal particles. Catalyst powder,
The activated carbon has a BET specific surface area of 1000 m 2 / g or more, and the ratio of the external surface area obtained by T-plot analysis of N 2 adsorption to the BET specific surface area is 10% or less, and
The mass ratio (I / C: g-ionomer / g-carbon) of the electrolyte resin (I) and the activated carbon (C) forming the catalyst coating portion is in the range of 0.05 to 0.1. A catalyst powder for a polymer electrolyte fuel cell. 炭素材料である活性炭に触媒金属からなる触媒金属粒子を担持させ、得られた触媒金属担持活性炭の表面を電解質樹脂からなる触媒被覆部で被覆して触媒粉末を製造する方法であって、
前記活性炭は、BET比表面積が１０００m2/g以上であって、このBET比表面積に対してＮ2吸着のT-plot解析で得られる外表面積の割合が１０%以下であり、
この活性炭に前記触媒金属粒子を担持させて得られた触媒金属担持活性炭と前記電解質樹脂とを分散媒中に、前記電解質樹脂(I)と前記活性炭(C)との質量比率(I/C: g-ionomer/g-carbon)が０．０５〜０．１の範囲内になるように分散させ、温度５０〜１００℃及び１０〜２０時間の条件で撹拌下に接触させ、前記触媒金属担持活性炭の表面を前記電解質樹脂からなる触媒被覆部で被覆することを特徴とする固体高分子形燃料電池用の触媒粉末の製造方法。 A method for producing catalyst powder by supporting catalyst metal particles made of catalyst metal on activated carbon which is a carbon material, and coating the surface of the obtained catalyst metal-supported activated carbon with a catalyst coating portion made of an electrolyte resin,
The activated carbon has a BET specific surface area of 1000 m 2 / g or more, and the ratio of the external surface area obtained by T-plot analysis of N 2 adsorption to the BET specific surface area is 10% or less,
In the dispersion medium, the catalyst metal-supported activated carbon obtained by supporting the catalyst metal particles on the activated carbon and the electrolyte resin, the mass ratio of the electrolyte resin (I) and the activated carbon (C) (I / C: g-ionomer / g-carbon) is dispersed in a range of 0.05 to 0.1, and contacted with stirring at a temperature of 50 to 100 ° C. for 10 to 20 hours. A method for producing a catalyst powder for a polymer electrolyte fuel cell, wherein the surface is coated with a catalyst coating portion made of the electrolyte resin. プロトン伝導性電解質膜を挟んだ一対のアノード触媒層及びカソード触媒層を有する固体高分子形燃料電池であり、
少なくとも前記カソード触媒層を形成する触媒粉末が、炭素材料である活性炭と、触媒金属からなると共に前記活性炭に担持された触媒金属粒子と、電解質樹脂からなると共に前記活性炭及び触媒金属粒子を被覆する触媒被覆部とを有し、
前記触媒粉末を形成する活性炭が、BET比表面積が１０００m2/g以上であって、このBET比表面積に対してＮ2吸着のT-plot解析で得られる外表面積の割合が１０%以下であり、また、
前記触媒粉末を形成する触媒被覆部の電解質樹脂(I)と活性炭(C)との質量比率(I/C: g-ionomer/g-carbon)が０．０５〜０．１の範囲内であることを特徴とする固体高分子形燃料電池。 A polymer electrolyte fuel cell having a pair of an anode catalyst layer and a cathode catalyst layer sandwiching a proton conductive electrolyte membrane;
A catalyst in which at least the catalyst powder forming the cathode catalyst layer is made of activated carbon that is a carbon material, catalyst metal particles that are supported on the activated carbon while being made of a catalyst metal, and an electrolyte resin that covers the activated carbon and the catalyst metal particles. And having a covering portion,
The activated carbon forming the catalyst powder has a BET specific surface area of 1000 m 2 / g or more, and the ratio of the external surface area obtained by T-plot analysis of N 2 adsorption to this BET specific surface area is 10% or less. ,Also,
The mass ratio (I / C: g-ionomer / g-carbon) of the electrolyte resin (I) and the activated carbon (C) in the catalyst coating portion forming the catalyst powder is in the range of 0.05 to 0.1. A polymer electrolyte fuel cell characterized by the above. 前記一対のアノード触媒層及びカソード触媒層のうちの少なくともカソード触媒層が、前記触媒粉末(CP)に対してカーボンブラック(CB)を質量比(CB/CP)０．０５〜０．３の割合で含むことを特徴とする請求項３に記載の固体高分子形燃料電池。   At least the cathode catalyst layer of the pair of anode catalyst layer and cathode catalyst layer is a ratio of carbon black (CB) to the catalyst powder (CP) in a mass ratio (CB / CP) of 0.05 to 0.3. The polymer electrolyte fuel cell according to claim 3, comprising: 触媒層を形成するカーボンブラック(CB)は、その平均粒子直径(CBd)と前記触媒粉末(CP)の平均粒子直径(CPd)との直径比率(CBd／CPd)が０．１〜０．７の範囲内であることを特徴とする請求項３又は４に記載の固体高分子形燃料電池。   Carbon black (CB) forming the catalyst layer has a ratio of diameter (CBd / CPd) of 0.1 to 0.7 of the average particle diameter (CBd) and the average particle diameter (CPd) of the catalyst powder (CP). 5. The solid polymer fuel cell according to claim 3, wherein the solid polymer fuel cell is within the range of
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