JP2011003277A - Manufacturing method of catalyst electrode for fuel cell - Google Patents

Manufacturing method of catalyst electrode for fuel cell Download PDF

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JP2011003277A
JP2011003277A JP2009142883A JP2009142883A JP2011003277A JP 2011003277 A JP2011003277 A JP 2011003277A JP 2009142883 A JP2009142883 A JP 2009142883A JP 2009142883 A JP2009142883 A JP 2009142883A JP 2011003277 A JP2011003277 A JP 2011003277A
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catalyst
support layer
electrode
water repellent
fuel cell
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Nobuyasu Suzuki
信靖 鈴木
Akira Taomoto
昭 田尾本
Junichi Kondo
淳一 近藤
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Panasonic 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a catalyst electrode for a fuel cell having an inclined structure.SOLUTION: The manufacturing method of the catalyst electrode for the fuel cell includes a step 1 forming a catalyst carrying layer by binding conductive powder with a conductive thin film on a porous substrate, a step 2 evaporating a solvent of a catalyst precursor solution applied on the catalyst carrying layer in a state in which the catalyst carrying layer is mounted on a water repellent material, a step 3 fixing the catalyst precursor on the catalyst carrying layer by drying the catalyst carrying layer formed in the step 2, a step 4 making deposited catalyst nano-particles on the catalyst carrying layer by raising temperature with heating the catalyst precursor on the catalyst carrying layer formed in the step 3, a step 5 evaporating a solvent of a proton-conductive polymer dispersed solution applied to the catalyst nano-particles on the catalyst carrying layer with the catalyst carrying layer in a state mounted on the water repellent material formed in the step 4, and a step 6 drying the catalyst carrying layer formed in the step 5.

Description

本発明は、白金触媒の有効利用率が高い燃料電池用触媒電極の作製方法に関するものである。   The present invention relates to a method for producing a catalyst electrode for a fuel cell having a high effective utilization rate of a platinum catalyst.

水素と酸素を使用する燃料電池は、その反応生成物が原理的に水のみであり環境への悪影響がほとんどない発電システムとして注目されている。近年、燃料電池の中でも、プロトン伝導性を有する高分子膜を電解質として使用する固体高分子型燃料電池は、作動温度が低く、出力密度が高く、かつ、小型化が容易に可能である。そのため、車載用電源や家庭据置用電源などへの使用が有望視されている。   A fuel cell using hydrogen and oxygen is attracting attention as a power generation system that has almost no adverse environmental impact because its reaction product is essentially only water. In recent years, a solid polymer fuel cell using a polymer membrane having proton conductivity as an electrolyte among fuel cells has a low operating temperature, a high output density, and can be easily downsized. For this reason, it is considered promising for use in in-vehicle power sources, household stationary power sources, and the like.

燃料電池の発電性能は、触媒電極に含まれる触媒の表面積の大小に強く依存する。触媒の表面積が増大すれば、発電の電流密度が増加し、それに伴い出力電圧も上昇する。触媒の単位質量当りの表面積を向上させるためには、触媒を数ナノメートルの粒子にするのが有効である。一般的に直径が5nm前後の白金又は白金合金の触媒ナノ粒子が触媒として広く用いられており、直径50nm前後のカーボン粒子に触媒ナノ粒子を担持させて粒子状とする。そして、この粒子状としたものをプロトン伝導性高分子で電極基材に固定して触媒層が構成されている。   The power generation performance of the fuel cell strongly depends on the surface area of the catalyst contained in the catalyst electrode. If the surface area of the catalyst increases, the current density of power generation increases, and the output voltage increases accordingly. In order to improve the surface area per unit mass of the catalyst, it is effective to make the catalyst particles of several nanometers. Generally, platinum or platinum alloy catalyst nanoparticles having a diameter of about 5 nm are widely used as the catalyst, and the catalyst nanoparticles are supported on carbon particles having a diameter of about 50 nm to form particles. The particulate material is fixed to the electrode substrate with a proton conductive polymer to form a catalyst layer.

一方、固体高分子型燃料電池が普及する上で、上述した白金触媒の使用量の低減が重要な課題として挙げられる。その理由として、地球全体における白金の埋蔵量が限られているためである。   On the other hand, as the polymer electrolyte fuel cell becomes widespread, reduction of the amount of platinum catalyst used is an important issue. The reason is that the amount of platinum reserves in the entire earth is limited.

たとえば、現在の自動車台数がガソリン車から燃料電池車に置き換わっていった場合に、現在の単位面積あたりの白金使用量では地球の埋蔵量をオーバーしてしまう恐れがある。   For example, if the current number of automobiles is replaced by a fuel cell vehicle from a gasoline vehicle, the current amount of platinum used per unit area may exceed the reserves of the earth.

白金触媒の使用量の低減を図るためには、白金触媒の有効利用率を高めることが重要である。しかしながら、ダイコーターやスクリーン印刷などの一般的な湿式法による塗工方法で上記のような触媒層を形成した場合には、溶媒を徐々に乾燥するため、この乾燥工程中で白金触媒担持カーボンの凝集が進行する。このため、触媒層における空孔度が低下してガスの経路が遮断されやすくなり、触媒層における触媒とプロトン伝導性高分子から形成される三相界面を十分に形成させることが困難となってしまう。結果として、白金触媒の有効利用率を高めることが困難となり、単位白金量あたりで得られる電池性能が低下してしまうという欠点があった。   In order to reduce the amount of platinum catalyst used, it is important to increase the effective utilization rate of the platinum catalyst. However, when the above catalyst layer is formed by a general wet coating method such as die coater or screen printing, the solvent is gradually dried. Aggregation proceeds. For this reason, the porosity in the catalyst layer is lowered and the gas path is likely to be blocked, making it difficult to sufficiently form a three-phase interface formed by the catalyst and the proton conductive polymer in the catalyst layer. End up. As a result, it is difficult to increase the effective utilization rate of the platinum catalyst, and there is a drawback that the battery performance obtained per unit platinum amount is lowered.

また、電池性能を向上させるために、従来から種々の傾斜構造を有する触媒電極が提案されている。例えば、ガス拡散電極側は比較的ガス濃度が高く、プロトン伝導性高分子電解質膜側はプロトンおよび電子の濃度が比較的高いという点に着目し、触媒電極層の厚み方向の組成を変化させる。これにより、プロトン伝導性電解質膜側の触媒担持量を多くして反応サイトを増加させる技術がある（特許文献１）。また、反応ガスの拡散制御を目的として厚み方向のプロトン伝導性高分子量を変化させる技術（特許文献２）がある。また厚み方向にプロトン伝導性や電子伝導性を変化させる技術（特許文献３）等が挙げられる。   In addition, in order to improve battery performance, catalyst electrodes having various inclined structures have been conventionally proposed. For example, paying attention to the fact that the gas concentration is relatively high on the gas diffusion electrode side and the proton and electron concentration is relatively high on the proton conductive polymer electrolyte membrane side, the composition in the thickness direction of the catalyst electrode layer is changed. As a result, there is a technique for increasing the number of reaction sites by increasing the amount of catalyst supported on the proton conductive electrolyte membrane side (Patent Document 1). Moreover, there exists a technique (patent document 2) which changes the proton conductive high molecular weight of the thickness direction for the purpose of diffusion control of the reaction gas. Moreover, the technique (patent document 3) etc. which change proton conductivity and electronic conductivity to the thickness direction are mentioned.

特開平9-180730号公報Japanese Unexamined Patent Publication No. 9-80730 特開2001-319663号公報JP 2001-319663 特開2005-259525号公報JP 2005-259525 A

しかしながら、上記従来技術はいずれも、ダイコーターやスクリーン印刷などの一般的な湿式法による塗工方法や、高圧スプレーを用いて、傾斜構造を有する触媒層を作製する方法である。ダイコーターやスクリーン印刷などによって傾斜構造に連続的な傾斜勾配を与えた触媒層を作成する事は極めて困難である。   However, any of the above conventional techniques is a coating method by a general wet method such as a die coater or screen printing, or a method for producing a catalyst layer having an inclined structure using a high-pressure spray. It is extremely difficult to produce a catalyst layer in which a gradient structure is given a continuous gradient by a die coater or screen printing.

また、高圧スプレーを用いた場合でも、オーバースプレーおよび二次飛散によって膜厚のムラが起こりやすいため、傾斜構造の傾斜を制御することは難しい。これは、塗工する溶液の分散質ないしは溶質の濃度を変化させて傾斜勾配を与えようとするためである。そのため、上記従来技術では、触媒層は、図２(ａ)に模式的に示したように連続的でない傾斜配置となる。図２（a）の左図は触媒層の構造模式図を示し、右図は白金（Pt）原子並びにフッ素（F）原子（プロトン伝導性高分子に含まれる）濃度の模式的な分布を示している。   Even when high-pressure spray is used, it is difficult to control the inclination of the inclined structure because film thickness unevenness is likely to occur due to overspray and secondary scattering. This is because the gradient of the solution to be applied is changed by changing the concentration of the dispersoid or solute. Therefore, in the above prior art, the catalyst layer has a non-continuous inclined arrangement as schematically shown in FIG. The left figure in Fig. 2 (a) shows a schematic diagram of the structure of the catalyst layer, and the right figure shows a schematic distribution of platinum (Pt) atoms and fluorine (F) atoms (contained in the proton conducting polymer). ing.

そこで、本発明は、触媒ナノ粒子の凝集を生じさせることなく、多孔性基材の厚さ方向に触媒ナノ粒子濃度、ならびにプロトン伝導性高分子濃度が傾斜している燃料電池用触媒電極の作製方法を提供する。   Accordingly, the present invention provides a catalyst electrode for a fuel cell in which the concentration of catalyst nanoparticles and the proton conductive polymer concentration are inclined in the thickness direction of the porous substrate without causing aggregation of the catalyst nanoparticles. Provide a method.

前記従来の課題を解決するために、本発明は多孔性基材上に導電性粉末を導電性薄膜で結着させ触媒担持層を形成する第1の工程と、前記触媒担持層を撥水材料上に配置した状態で、前記触媒担持層上に塗布された触媒前駆体溶液の溶媒を蒸発させる第2の工程と、前記第2の工程による前記触媒担持層を乾燥し、触媒前駆体を前記触媒担持層上に固定化する第3の工程と、前記第３の工程による触媒担持層上の前記触媒前駆体を加熱昇温して触媒ナノ粒子を前記触媒担持層上に析出させる第4の工程と、前記第４の工程による前記触媒担持層を撥水材料上に配置した状態で、前記触媒担持層上の前記触媒ナノ粒子に塗布されたプロトン伝導性高分子分散溶液の溶媒を蒸発させる第5の工程と、前記第5の工程による触媒担持層を乾燥する第6の工程と、を有する、燃料電池用触媒電極の作製方法を提供する。   In order to solve the above-mentioned conventional problems, the present invention provides a first step of forming a catalyst supporting layer by binding a conductive powder on a porous substrate with a conductive thin film, and the catalyst supporting layer as a water repellent material. A second step of evaporating the solvent of the catalyst precursor solution applied onto the catalyst support layer in a state of being placed on the top, drying the catalyst support layer according to the second step, and A third step of immobilizing on the catalyst supporting layer, and a fourth step of heating and heating the catalyst precursor on the catalyst supporting layer according to the third step to deposit catalyst nanoparticles on the catalyst supporting layer. And evaporating the solvent of the proton conductive polymer dispersion applied to the catalyst nanoparticles on the catalyst support layer in a state where the catalyst support layer in the step and the fourth step is disposed on the water repellent material. A fifth step and a sixth step of drying the catalyst-supporting layer in the fifth step; The a, provides a method of making the catalyst electrode for a fuel cell.

本発明の燃料電池用触媒電極の作製方法を用いることにより、多孔性基材の厚さ方向に触媒ナノ粒子濃度、並びにプロトン伝導性高分子濃度が連続的に傾斜している燃料電池用触媒電極を作製することが可能になる。   By using the method for producing a fuel cell catalyst electrode of the present invention, the catalyst nanoparticle concentration and the proton conductive polymer concentration are continuously inclined in the thickness direction of the porous substrate. Can be produced.

本発明の燃料電池用触媒電極の作製方法の工程フロー図。The process flow figure of the preparation methods of the catalyst electrode for fuel cells of the present invention. 触媒ナノ粒子濃度ならびにプロトン伝導性高分子濃度が傾斜している触媒層の模式図。The schematic diagram of the catalyst layer in which the catalyst nanoparticle density | concentration and the proton conductive polymer density | concentration are inclined. 実施の形態1における、多孔性基材の厚さ方向に触媒ナノ粒子濃度ならびにプロトン伝導性高分子濃度が傾斜している燃料電池用触媒電極の断面を観察した走査電子顕微鏡反射電子像と、波長分散型X線マイクロアナライザで得られた白金原子ならびにフッ素原子の分布図。Scanning electron microscope reflected electron image obtained by observing a cross section of the catalyst electrode for a fuel cell in which the concentration of the catalyst nanoparticles and the proton conductive polymer concentration are inclined in the thickness direction of the porous substrate in the first embodiment, and the wavelength Distribution diagram of platinum atoms and fluorine atoms obtained with a dispersive X-ray microanalyzer. 比較例１における、燃料電池用触媒電極の断面を観察した走査電子顕微鏡反射電子像と、波長分散型X線マイクロアナライザで得られた白金原子ならびにフッ素原子の分布図。The scanning electron microscope backscattered electron image which observed the cross section of the catalyst electrode for fuel cells in the comparative example 1, and the distribution map of the platinum atom and fluorine atom which were obtained with the wavelength dispersion type | mold X-ray microanalyzer. 実施例ならびに比較例で作製した触媒電極を用いた燃料電池の出力特性図。The output characteristic figure of the fuel cell using the catalyst electrode produced in the Example and the comparative example.

以下本発明の実施の形態について説明する。   Embodiments of the present invention will be described below.

（実施の形態１）
図１に、本発明の触媒電極を作成する工程フローを示す。図１に示すように、本発明の工程フローは四つの工程に分かれる。第一工程は、導電性を有する多孔性基材上に導電性粉末を導電性薄膜で結着させ触媒担持層を形成する行程である。第二工程は、触媒担持層上に触媒前駆体溶液を塗布、乾燥し、触媒前駆体を固定化する行程である。第三工程は、触媒前駆体を加熱昇温して触媒ナノ粒子を触媒担持層上に析出させる行程である。そして、第四の工程は、触媒ナノ粒子にプロトン伝導性高分子分散溶液を塗布、乾燥する工程である。また、前述の第二、第四工程では、多孔性基材を撥水性材料上に配置している。 (Embodiment 1)
FIG. 1 shows a process flow for producing the catalyst electrode of the present invention. As shown in FIG. 1, the process flow of the present invention is divided into four steps. The first step is a step of forming a catalyst support layer by binding conductive powder with a conductive thin film on a porous substrate having conductivity. The second step is a step of immobilizing the catalyst precursor by applying and drying the catalyst precursor solution on the catalyst support layer. In the third step, the catalyst precursor is heated and heated to deposit catalyst nanoparticles on the catalyst support layer. And a 4th process is a process of apply | coating a proton conductive polymer dispersion solution to a catalyst nanoparticle, and drying. In the second and fourth steps described above, the porous base material is disposed on the water repellent material.

このように、撥水材料上に配置した多孔性基材に触媒前駆体溶液ないしはプロトン伝導性高分子分散溶液を塗布、乾燥することで、多孔性基材の上部で溶媒蒸発が促進される。溶媒蒸発が促進されると、溶解、分散している触媒前駆体、プロトン伝導性高分子が蒸発に伴って上部に凝集する。その結果、触媒ナノ粒子、ならびにプロトン伝導性高分子が上部に偏った分布を生じることになる。   Thus, by evaporating the catalyst precursor solution or the proton conductive polymer dispersion solution on the porous substrate disposed on the water-repellent material and drying, the solvent evaporation is promoted on the porous substrate. When the evaporation of the solvent is promoted, the dissolved and dispersed catalyst precursor and the proton conductive polymer are aggregated on the upper part as the evaporation proceeds. As a result, the catalyst nanoparticles and the proton conductive polymer are distributed in a biased upward direction.

本発明で用いる導電性を有する多孔性基材としては、カーボンペーパ、カーボン不織布、カーボンフェルト等を用いることができる。導電性薄膜としては、ポリアクリロニトリルやポリアクリル酸等のカーボンを含む高分子を熱処理したカーボン薄膜を用いることができる。導電性粉末としては高い比表面積を有するアセチレンブラック等のカーボンブラックを用いることができる。触媒前駆体は貴金属塩と有機高分子と有機溶媒で構成されることが望ましい。プロトン伝導性高分子は、ナフィオン（デュポン社製；登録商標）等のフッ素系陽イオン交換樹脂を用いることができる。   As the conductive porous substrate used in the present invention, carbon paper, carbon non-woven fabric, carbon felt and the like can be used. As the conductive thin film, a carbon thin film obtained by heat-treating a polymer containing carbon such as polyacrylonitrile or polyacrylic acid can be used. As the conductive powder, carbon black such as acetylene black having a high specific surface area can be used. The catalyst precursor is preferably composed of a noble metal salt, an organic polymer, and an organic solvent. As the proton conductive polymer, a fluorine-based cation exchange resin such as Nafion (manufactured by DuPont; registered trademark) can be used.

前述したように、本発明における作製方法で作製した燃料電池用触媒電極は傾斜構造を有する。   As described above, the fuel cell catalyst electrode produced by the production method of the present invention has an inclined structure.

ここで、傾斜構造とは、触媒電極における白金触媒粒子とプロトン伝導性高分子の含有量が、前記触媒電極の厚さ方向に変化する構造である。例えば、図２に示したようにプロトン伝導性高分子膜（図中上方向）からガスを供給するセパレータ（図中下方向）に向かって、白金触媒ナノ粒子の含有量（白金原子の分布を反映）と、プロトン伝導性高分子電解質の含有量（フッ素原子の分布を反映）がともに減少するような傾斜構造である。触媒層にこのような傾斜構造を与えることにより、均一な単一層である場合と比較して、ガス拡散層側から供給される酸化性ガスが反応サイトに運ばれやすく白金触媒ナノ粒子が反応しやくなる。さらに、反応して生じた水分子を円滑にセパレータ側に流れやすくすることができる。そのため、結果的に、燃料電池の内部抵抗が減少し、発電性能を向上させることができる。   Here, the inclined structure is a structure in which the content of platinum catalyst particles and proton conductive polymer in the catalyst electrode changes in the thickness direction of the catalyst electrode. For example, as shown in FIG. 2, the platinum catalyst nanoparticle content (platinum atom distribution) is directed from the proton conductive polymer membrane (upward in the figure) toward the separator (downward in the figure) that supplies gas. (Reflected) and the proton conductive polymer electrolyte content (reflecting the distribution of fluorine atoms). By giving such a tilted structure to the catalyst layer, the platinum catalyst nanoparticles react more easily when the oxidizing gas supplied from the gas diffusion layer side is transported to the reaction site compared to the case of a uniform single layer. I'll do it. Furthermore, water molecules generated by the reaction can be made to flow smoothly to the separator side. As a result, the internal resistance of the fuel cell is reduced, and the power generation performance can be improved.

(実施例１)触媒電極の作製
触媒電極層の作成に際して、導電性基材であるカーボンペーパ上に導電性粉末であるアセチレンブラックを用いた。また、導電性薄膜としてポリアクリロニトリルを熱処理したカーボン薄膜を用いて結着して触媒担持相を形成した。カーボンペーパを撥水性材料上に配置し、触媒担持層表面上に、塩化白金酸とポリアミド酸をジメチルアセトアミド溶媒に溶解した触媒前駆体溶液を塗布、乾燥して触媒前駆体を固定化した。さらに触媒前駆体を加熱昇温して白金ナノ粒子を析出させた後、再び撥水性材料上にカーボンペーパを配置し、ナフィオン分散溶液を塗布乾燥させて触媒電極を作製した。具体的には、以下の第一から第四工程で作製を行った。 (Example 1) Production of catalyst electrode In producing the catalyst electrode layer, acetylene black as a conductive powder was used on carbon paper as a conductive substrate. Further, a carbon thin film obtained by heat-treating polyacrylonitrile as a conductive thin film was used to form a catalyst-supporting phase. Carbon paper was placed on the water repellent material, and a catalyst precursor solution in which chloroplatinic acid and polyamic acid were dissolved in a dimethylacetamide solvent was applied to the surface of the catalyst support layer and dried to immobilize the catalyst precursor. Furthermore, after heating and heating the catalyst precursor to deposit platinum nanoparticles, carbon paper was again placed on the water repellent material, and a Nafion dispersion solution was applied and dried to produce a catalyst electrode. Specifically, the fabrication was performed in the following first to fourth steps.

（第一工程）
まず、直径約50nmのアセチレンブラック1.2g（デンカ工業）、ポリアクリルニトリル1.2g（シグマアルドリッチ）及びジメチルアセトアミド（和光純薬）22.8gを混合し、ボールミルを用いて20時間攪拌した。この混合液を面積22.6cm2のカーボンペーパ（東レ）上に2.38g滴下し、低真空の容器中で溶媒を蒸発させた。次に低真空の乾燥機を用いて、前記カーボンペーパを加熱した。室温から120℃まで40分で昇温し、同温度を2時間保持した。最後にこのカーボンペーパをアルゴン雰囲気下の赤外線イメージ炉内に移し、昇温速度毎秒20℃、到達温度800℃で加熱を30分間行った。以上により、アセチレンブラックをカーボン薄膜で結着した触媒担持層を形成したカーボンペーパを得た。 (First step)
First, 1.2 g of acetylene black having a diameter of about 50 nm (Denka Kogyo), 1.2 g of polyacrylonitrile (Sigma Aldrich) and 22.8 g of dimethylacetamide (Wako Pure Chemical Industries) were mixed and stirred for 20 hours using a ball mill. 2.38 g of this mixed solution was dropped on carbon paper (Toray) having an area of 22.6 cm 2, and the solvent was evaporated in a low vacuum container. Next, the carbon paper was heated using a low vacuum dryer. The temperature was raised from room temperature to 120 ° C. in 40 minutes, and the same temperature was maintained for 2 hours. Finally, the carbon paper was transferred into an infrared image furnace under an argon atmosphere, and heated at a rate of temperature increase of 20 ° C. per second and an ultimate temperature of 800 ° C. for 30 minutes. As described above, a carbon paper having a catalyst support layer in which acetylene black was bound with a carbon thin film was obtained.

（第二工程）
塩化白金酸(IV)・6水和物（和光純薬）1.44g、ポリアミド酸溶液11.31g、ジメチルアセトアミド（和光純薬特級）101.17gを混合し、白金を含む触媒前駆体溶液を作成した。ポリアミド酸は、4,4'ジアミノジフェニルエーテル（東京化成）とピロメリット酸無水物（東京化成）から合成したものである。合成は、4,4'ジアミノジフェニルエーテル5.00gとジメチルアセトアミド120gを混合して溶解し、そこにピロメリット酸無水物5.45gを加え約３時間撹拌することにより行った。 (Second step)
A catalyst precursor solution containing platinum was prepared by mixing 1.44 g of chloroplatinic acid (IV) hexahydrate (Wako Pure Chemical), 11.31 g of polyamic acid solution and 101.17 g of dimethylacetamide (special grade of Wako Pure Chemical). The polyamic acid is synthesized from 4,4 ′ diaminodiphenyl ether (Tokyo Kasei) and pyromellitic anhydride (Tokyo Kasei). The synthesis was carried out by mixing 5.00 g of 4,4 ′ diaminodiphenyl ether and 120 g of dimethylacetamide, adding 5.45 g of pyromellitic anhydride thereto, and stirring for about 3 hours.

さらに、前述の触媒前駆体溶液を、第一工程で得られたカーボンペーパ上に1.42g滴下し、低真空の容器中で溶媒を蒸発させた。このとき、カーボンペーパは、撥水性材料であるポリフロンフィルタ上に配置されている。圧力133Paの環境下で約1時間、乾燥を行うことで液相の溶媒を蒸発させた。この時間は、液相の溶媒がほとんど蒸発する時間であり、経験的な知見に基づくものである。なお、圧力などの条件が変わると、蒸発に要する時間も変わる。前記工程で得られた触媒担持層を形成した後、低真空の乾燥機を用いて、カーボンペーパを加熱した。室温から200℃まで40分で昇温し、同温度を2時間保持した。撥水性材料であるポリフロンフィルタは、液相の溶媒を蒸発させた後(圧力133Paの環境下で約1時間、乾燥した後)、取り除いた。なお、触媒担持層を乾燥時の温度に耐えうる撥水材料を用いれば、カーボンペーパが乾燥機に入れられる際に取り除かなくても良い。   Further, 1.42 g of the catalyst precursor solution described above was dropped on the carbon paper obtained in the first step, and the solvent was evaporated in a low vacuum container. At this time, the carbon paper is disposed on a polyflon filter which is a water repellent material. The liquid phase solvent was evaporated by drying for about 1 hour in an environment of 133 Pa pressure. This time is the time for most of the liquid phase solvent to evaporate and is based on empirical knowledge. When conditions such as pressure change, the time required for evaporation also changes. After forming the catalyst support layer obtained in the above step, the carbon paper was heated using a low vacuum dryer. The temperature was raised from room temperature to 200 ° C. in 40 minutes, and the same temperature was maintained for 2 hours. The polyflon filter, which is a water repellent material, was removed after the liquid phase solvent was evaporated (after drying in an environment of pressure 133 Pa for about 1 hour). If a water repellent material that can withstand the temperature at the time of drying is used for the catalyst support layer, it is not necessary to remove the carbon paper when it is put into the dryer.

（第三工程）
アルゴン雰囲気下の赤外線イメージ炉内で、昇温速度毎秒10℃、到達温度800℃で加熱を30分間行った。 (Third process)
In an infrared image furnace in an argon atmosphere, heating was performed for 30 minutes at a temperature rising rate of 10 ° C. per second and an ultimate temperature of 800 ° C.

（第四工程）
固形分濃度7.5wt%のナフィオン分散溶液（ナフィオン3.84g、エタノール8.66g、ジメチルアセトアミド64.25gを混合）を、第三工程で処理されたカーボンペーパ上に2.58g滴下し、低真空の容器中で溶媒を蒸発させた。このとき、カーボンペーパは撥水性材料であるポリフロンフィルタ上に配置されている。圧力133Paの環境下で約1時間、乾燥を行うことで液相の溶媒を蒸発させた。この時間は、液相の溶媒がほとんど蒸発する時間であり、経験的な知見に基づくものである。なお、圧力などの条件が変わると、蒸発に要する時間も変わる。この後、低真空の乾燥機中で室温から80℃まで40分で昇温し、同温度を2時間保持した。撥水性材料であるポリフロンフィルタは、液相の溶媒を蒸発させた後(圧力133Paの環境下で約1時間、乾燥した後)、取り除いた。なお、触媒担持層を乾燥時の温度に耐えうる撥水材料を用いれば、カーボンペーパが乾燥機に入れられる際に取り除かなくても良い。 (Fourth process)
2.58 g of Nafion dispersion solution (solid Nafion 3.84 g, ethanol 8.66 g, and dimethylacetamide 64.25 g) was dropped on the carbon paper treated in the third step in a low vacuum container. The solvent was evaporated. At this time, the carbon paper is disposed on a polyflon filter which is a water repellent material. The liquid phase solvent was evaporated by drying for about 1 hour in an environment of 133 Pa pressure. This time is the time for most of the liquid phase solvent to evaporate and is based on empirical knowledge. When conditions such as pressure change, the time required for evaporation also changes. Thereafter, the temperature was raised from room temperature to 80 ° C. in 40 minutes in a low vacuum dryer, and the same temperature was maintained for 2 hours. The polyflon filter, which is a water repellent material, was removed after the liquid phase solvent was evaporated (after drying in an environment of pressure 133 Pa for about 1 hour). If a water repellent material that can withstand the temperature at the time of drying is used for the catalyst support layer, it is not necessary to remove the carbon paper when it is put into the dryer.

［比較例１］比較電極の作製
比較例として、本発明の第二工程、第四工程において、撥水性材料上ではなくガラス上に配置して触媒電極を作成した例を示す。この比較例において、カーボンペーパをガラス上に配置した以外は実施例１と同一の方法により触媒電極を作成した。白金ナノ粒子の担持量は0.3mg/cm2であり、実施例１とほぼ同じである。 [Comparative Example 1] Production of Comparative Electrode As a comparative example, an example in which a catalyst electrode was produced by arranging on a glass instead of a water repellent material in the second and fourth steps of the present invention is shown. In this comparative example, a catalyst electrode was prepared by the same method as in Example 1 except that carbon paper was placed on glass. The supported amount of platinum nanoparticles is 0.3 mg / cm 2, which is almost the same as in Example 1.

（触媒ナノ粒子ならびにプロトン伝導性高分子濃度の評価）
図３は本発明の実施の形態における実施例１で作製した多孔性基材を観察した図である。図３中の左図は、実施例１で作成した多孔性基材の厚さ方向の断面図である。図３の真ん中の図は、多孔性基材の厚さ方向の断面において触媒ナノ粒子濃度ならびにプロトン伝導性高分子濃度が傾斜している様子を観察した走査電子顕微鏡反射電子像である。 (Evaluation of catalyst nanoparticles and proton conducting polymer concentration)
FIG. 3 is a view of the porous substrate produced in Example 1 according to the embodiment of the present invention. The left figure in FIG. 3 is a cross-sectional view in the thickness direction of the porous substrate prepared in Example 1. The middle figure in FIG. 3 is a scanning electron microscope reflected electron image in which the catalyst nanoparticle concentration and the proton conductive polymer concentration are observed to be inclined in the cross section in the thickness direction of the porous substrate.

また図３の右図は、多孔性基材の厚さ方向の断面において波長分散型X線マイクロアナライザで得られた白金原子ならびにフッ素原子の分布図である。本図において、上側は固体高分子膜に接する方向、下側はガスを供給するセパレータに接する方向である。図中のラインプロファイル（白線部分の濃度分布）を見ると白金原子、フッ素原子とも上側の濃度が特に固体高分子膜に接する部分で高くなっており、電極断面全体ではラインプロファイルを積分平均化した分布となっている。   3 is a distribution diagram of platinum atoms and fluorine atoms obtained by a wavelength dispersion type X-ray microanalyzer in a cross section in the thickness direction of the porous substrate. In this figure, the upper side is the direction in contact with the solid polymer film, and the lower side is the direction in contact with the separator supplying the gas. Looking at the line profile (concentration distribution in the white line) in the figure, the upper concentration of both platinum and fluorine atoms is high especially at the part in contact with the solid polymer film, and the line profile is integrated and averaged over the entire electrode cross section. Distribution.

そのため、多孔性基材の厚さ方向に触媒ナノ粒子濃度ならびにプロトン伝導性高分子濃度が連続的に傾斜していることが分かる。   Therefore, it can be seen that the catalyst nanoparticle concentration and the proton conductive polymer concentration are continuously inclined in the thickness direction of the porous substrate.

図４は、比較例１で作製した多孔性基材の厚さ方向の断面図の結果である。左から、多孔性基材の厚さ方向の断面図、走査電子顕微鏡反射電子像、白金原子ならびにフッ素原子の分布図である。ラインプロファイルを見ても分布に明確な偏りは見られず、多孔性基材の厚さ方向に触媒ナノ粒子濃度、プロトン伝導性高分子濃度とも傾斜していないことが分かる。   4 is a result of a cross-sectional view in the thickness direction of the porous substrate produced in Comparative Example 1. FIG. It is sectional drawing of the thickness direction of a porous base material from the left, a scanning electron microscope reflected electron image, the distribution map of a platinum atom and a fluorine atom. Even when the line profile is seen, no clear bias is seen in the distribution, and it can be seen that neither the catalyst nanoparticle concentration nor the proton conductive polymer concentration is inclined in the thickness direction of the porous substrate.

（触媒電極の出力特性比較）
図５に実施例１で作成した触媒電極を組み込んだ燃料電池の出力特性と、比較例1で作製した触媒電極を組み込んだ燃料電池の出力特性とを示す。アノードに水素ガスを流通させ、カソードには酸素ガスを流通させ、電池温度90℃、加湿器温度64℃として電流密度に対する出力電圧を評価した。 (Comparison of output characteristics of catalyst electrode)
FIG. 5 shows the output characteristics of the fuel cell incorporating the catalyst electrode prepared in Example 1 and the output characteristics of the fuel cell incorporating the catalyst electrode prepared in Comparative Example 1. Hydrogen gas was passed through the anode and oxygen gas was passed through the cathode, and the output voltage against the current density was evaluated at a battery temperature of 90 ° C. and a humidifier temperature of 64 ° C.

図５からも明らかなように、実施例1の出力特性が比較例１の出力特性と比べて明らかに向上していることが分かる。つまり、多孔性基材の厚さ方向に触媒ナノ粒子濃度ならびにプロトン伝導性高分子濃度が連続的に傾斜すると、プロトンが供給されるプロトン伝導性高分子膜側（図2上方向）で白金並びにプロトン伝導性高分子濃度が高いため、酸素還元反応が集中的に生じる。結果として反応過電圧が低下し、電流0の開回路電位が上昇し、低電流密度における出力電位が大きくなる。   As is apparent from FIG. 5, it can be seen that the output characteristics of Example 1 are clearly improved as compared with the output characteristics of Comparative Example 1. In other words, when the catalyst nanoparticle concentration and the proton conductive polymer concentration continuously incline in the thickness direction of the porous substrate, platinum and the proton conductive polymer membrane side to which protons are supplied (upward in FIG. 2) Since the proton conductive polymer concentration is high, the oxygen reduction reaction occurs intensively. As a result, the reaction overvoltage decreases, the open circuit potential of current 0 increases, and the output potential at low current density increases.

加えて、ガス供給、生成水排出が行われるセパレータ側（図2下方向）では濃度が低いため、ガス拡散性が相対的に高くなる。結果としてガス供給、生成水排出が効率的に生じるため高電流密度側の電位降下が抑制される。ここで述べた過電圧とは、言い換えれば触媒電極中の反応ロスの尺度である。電流は、電気化学的に、触媒電極中の反応速度を表すパラメータであり、電流値に対して反応ロスが少ないのは電池として性能が良い事を表す。通常、電池の端子間電圧である開回路電位は、理論的には1.23Vであるが、実際には、反応ロス（過電圧）が起因して理論値よりも下がるからである。   In addition, since the concentration is low on the separator side (downward in FIG. 2) where gas supply and product water discharge are performed, gas diffusivity is relatively high. As a result, gas supply and product water discharge are efficiently generated, so that a potential drop on the high current density side is suppressed. The overvoltage described here is, in other words, a measure of reaction loss in the catalyst electrode. The current is a parameter that electrochemically represents the reaction rate in the catalyst electrode, and a small reaction loss with respect to the current value indicates that the battery has good performance. Usually, the open circuit potential, which is the voltage between the terminals of the battery, is theoretically 1.23 V, but actually, it is lower than the theoretical value due to reaction loss (overvoltage).

本発明の燃料電池用触媒電極の作製方法は、多孔性基材の厚さ方向に触媒ナノ粒子濃度ならびにプロトン伝導性高分子濃度が傾斜している燃料電池用触媒電極の作製方法として有用である。また、触媒ナノ粒子を用いるデバイス全般の作製にも応用できる。   The method for producing a fuel cell catalyst electrode of the present invention is useful as a method for producing a fuel cell catalyst electrode in which the catalyst nanoparticle concentration and the proton conductive polymer concentration are inclined in the thickness direction of the porous substrate. . It can also be applied to the production of devices using catalyst nanoparticles.

Claims (4)

多孔性基材上に導電性粉末を導電性薄膜で結着させ触媒担持層を形成する第1の工程と、
前記触媒担持層を撥水材料上に配置した状態で、前記触媒担持層上に塗布された触媒前駆体溶液の溶媒を蒸発させる第2の工程と、
前記第2の工程による前記触媒担持層を乾燥し、触媒前駆体を前記触媒担持層上に固定化する第3の工程と、
前記第３の工程による触媒担持層上の前記触媒前駆体を加熱昇温して触媒ナノ粒子を前記触媒担持層上に析出させる第4の工程と、
前記第４の工程による前記触媒担持層を撥水材料上に配置した状態で、前記触媒担持層上の前記触媒ナノ粒子に塗布されたプロトン伝導性高分子分散溶液の溶媒を蒸発させる第5の工程と、
前記第5の工程による触媒担持層を乾燥する第6の工程と、
を有する、燃料電池用触媒電極の作製方法。 A first step of binding a conductive powder on a porous substrate with a conductive thin film to form a catalyst support layer;
A second step of evaporating the solvent of the catalyst precursor solution applied on the catalyst supporting layer in a state where the catalyst supporting layer is disposed on the water repellent material;
A third step of drying the catalyst support layer in the second step and immobilizing a catalyst precursor on the catalyst support layer;
A fourth step of heating and heating the catalyst precursor on the catalyst support layer in the third step to deposit catalyst nanoparticles on the catalyst support layer;
In a state where the catalyst support layer according to the fourth step is disposed on a water repellent material, a solvent of the proton conductive polymer dispersion solution applied to the catalyst nanoparticles on the catalyst support layer is evaporated. Process,
A sixth step of drying the catalyst-supporting layer in the fifth step;
The manufacturing method of the catalyst electrode for fuel cells which has these. 前記第２工程における撥水性材料は前記第2工程が終了したあと、取り除かれ、前記第5工程における撥水性材料は前記第5工程が終了したあと、取り除かれる、請求項１記載の燃料電池用触媒電極の作製方法。 The water repellent material in the second step is removed after the second step is finished, and the water repellent material in the fifth step is removed after the fifth step is finished. A method for producing a catalyst electrode. 多孔性基材上に導電性粉末を導電性薄膜で結着させ触媒担持層を形成する第1の工程と、
前記触媒担持層を撥水材料上に配置した状態で、前記触媒担持層上に塗布された触媒前駆体溶液の溶媒を蒸発させる第2の工程と、
前記第2の工程による前記触媒担持層を乾燥し、触媒前駆体を前記触媒担持層上に固定化する第3の工程と、
前記第３の工程による触媒担持層上の前記触媒前駆体を加熱昇温して触媒ナノ粒子を前記触媒担持層上に析出させる第4の工程と、
前記第４の工程による前記触媒担持層を撥水材料上に配置した状態で、前記触媒担持層上の前記触媒ナノ粒子に塗布されたプロトン伝導性高分子分散溶液の溶媒を蒸発させる第5の工程と、
前記第5の工程による触媒担持層を乾燥する第6の工程と、
により製造される触媒電極。 A first step of binding a conductive powder on a porous substrate with a conductive thin film to form a catalyst support layer;
A second step of evaporating the solvent of the catalyst precursor solution applied on the catalyst supporting layer in a state where the catalyst supporting layer is disposed on the water repellent material;
A third step of drying the catalyst support layer in the second step and immobilizing a catalyst precursor on the catalyst support layer;
A fourth step of heating and heating the catalyst precursor on the catalyst support layer in the third step to deposit catalyst nanoparticles on the catalyst support layer;
In a state where the catalyst support layer according to the fourth step is disposed on a water repellent material, a solvent of the proton conductive polymer dispersion solution applied to the catalyst nanoparticles on the catalyst support layer is evaporated. Process,
A sixth step of drying the catalyst-supporting layer in the fifth step;
Catalytic electrode manufactured by 燃料電池に用いられる触媒電極であって、
燃料電池におけるセパレータに接する側から、燃料電池における固体分子膜に接する側に向かって、触媒電極内に含まれる触媒ナノ粒子濃度とプロトン伝導性高分子濃度とが高くなる、触媒電極。 A catalyst electrode used in a fuel cell,
A catalyst electrode in which the concentration of catalyst nanoparticles and the concentration of proton-conducting polymer contained in the catalyst electrode increase from the side in contact with the separator in the fuel cell toward the side in contact with the solid molecular film in the fuel cell.
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