JP2010095395A - Porous electrode substrate, method for manufacturing the same, membrane-electrode assembly, and solid polymer fuel cell - Google Patents
Porous electrode substrate, method for manufacturing the same, membrane-electrode assembly, and solid polymer fuel cell Download PDFInfo
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Abstract
Description
本発明は、液体燃料を用いた固体高分子型燃料電池に用いられる多孔質電極基材およびその製造方法、ならびにその多孔質電極基材を用いた膜−電極接合体および固体高分子型燃料電池に関するものである。 The present invention relates to a porous electrode substrate used for a polymer electrolyte fuel cell using a liquid fuel, a method for producing the same, and a membrane-electrode assembly and a polymer electrolyte fuel cell using the porous electrode substrate. It is about.
固体高分子型燃料電池はプロトン伝導性の高分子電解質膜を用いることを特徴としており、水素等の燃料ガスと酸素等の酸化ガスを電気化学的に反応させることにより起電力を得る装置である。固体高分子型燃料電池は、自家発電装置や、自動車等の移動体用の発電装置として利用可能である。 A polymer electrolyte fuel cell is characterized by using a proton-conducting polymer electrolyte membrane, and is an apparatus for obtaining an electromotive force by electrochemically reacting a fuel gas such as hydrogen and an oxidizing gas such as oxygen. . The polymer electrolyte fuel cell can be used as a self-power generation device or a power generation device for a moving body such as an automobile.
このような固体高分子型燃料電池は、水素イオン（プロトン）を選択的に伝導する高分子電解質膜を有する。また、貴金属系触媒を担持したカーボン粉末を主成分とする触媒層とガス拡散電極基材とを有するガス拡散電極が、触媒層側を内側にして、高分子電解質膜の両面に接合された構造となっている。 Such a polymer electrolyte fuel cell has a polymer electrolyte membrane that selectively conducts hydrogen ions (protons). Also, a structure in which a gas diffusion electrode having a catalyst layer mainly composed of carbon powder supporting a noble metal catalyst and a gas diffusion electrode base material is bonded to both surfaces of the polymer electrolyte membrane with the catalyst layer side inside It has become.
このような高分子電解質膜と２枚のガス拡散電極からなる接合体は膜−電極接合体（ＭＥＡ： Ｍｅｍｂｒａｎｅ Ｅｌｅｃｔｒｏｄｅ Ａｓｓｅｍｂｌｙ）と呼ばれている。またＭＥＡの両外側には燃料ガスまたは酸化ガスを供給し、かつ生成ガスおよび過剰ガスを排出することを目的としたガス流路を形成したセパレーターが設置されている。 Such a joined body composed of a polymer electrolyte membrane and two gas diffusion electrodes is called a membrane-electrode assembly (MEA: Membrane Electrode Assembly). In addition, separators are provided on both outer sides of the MEA so as to supply a fuel gas or an oxidizing gas and to form a gas flow path for the purpose of discharging generated gas and excess gas.
多孔質電極基材は電気的な接触抵抗を低減し、かつ、セパレーターより供給される燃料ガスまたは酸化ガスがセル外へ漏出することを抑制することを目的として、セパレーターによって数ＭＰａの荷重で締結されるため、機械的強度が必要となる。 The porous electrode substrate is fastened by a separator with a load of several MPa for the purpose of reducing electrical contact resistance and suppressing leakage of fuel gas or oxidizing gas supplied from the separator to the outside of the cell. Therefore, mechanical strength is required.
さらに、多孔質電極基材は主に次の３つの機能を持つ必要がある。第１に多孔質電極基材の外側に配置されたセパレーターに形成されたガス流路より触媒層中の貴金属系触媒に均一に燃料ガスまたは酸化ガスを供給する機能である。第２に触媒層で反応により生成した水を排出する機能である。第３に触媒層での反応に必要な電子または生成される電子をセパレーターへ導電する機能である。これらの機能を付与するため、多孔質電極基材は一般的に炭素質材料を用いることが有効とされている。 Furthermore, the porous electrode substrate mainly needs to have the following three functions. The first function is to supply the fuel gas or the oxidizing gas uniformly to the noble metal catalyst in the catalyst layer from the gas flow path formed in the separator disposed outside the porous electrode substrate. The second function is to discharge water generated by the reaction in the catalyst layer. The third function is to conduct electrons necessary for the reaction in the catalyst layer or generated electrons to the separator. In order to impart these functions, it is generally effective to use a carbonaceous material for the porous electrode substrate.
したがって、多孔質電極基材には高い反応ガスおよび酸化ガス透過能と水の排出性、電子導電性が必要である。加えて、一般的な固体高分子型燃料電池で用いられる高分子電解質膜は、含水状態でプロトン伝導性を示すことより、多孔質電極基材には生成水の排水のみでなく、高分子電解質膜の保水という相反する機能が求められている。多孔質電極基材のガス透気度を高くし生成水の排水能を高くしたものでは高分子電解質膜が乾燥することによりプロトン伝導抵抗が増大し、発電性能が低下する。逆に多孔質電極基材のガス透気度を低くし高分子電解質膜の保水能を高めたものでは、生成水の排水不良によって反応ガスおよび酸化ガスの拡散が阻害されるフラッディングにより発電性能が低下する。 Therefore, the porous electrode base material needs to have a high reactive gas and oxidizing gas permeability, water discharge property, and electronic conductivity. In addition, the polymer electrolyte membrane used in a general solid polymer fuel cell exhibits proton conductivity in a water-containing state, so that the porous electrode substrate is not only a drainage of generated water, but also a polymer electrolyte. The contradictory function of retaining the membrane is required. In the case where the gas permeability of the porous electrode base material is increased and the drainage capacity of the generated water is increased, the proton conduction resistance is increased and the power generation performance is decreased when the polymer electrolyte membrane is dried. On the contrary, in the case where the gas permeability of the porous electrode base material is lowered and the water retention capacity of the polymer electrolyte membrane is increased, the power generation performance is improved by flooding in which the diffusion of the reaction gas and the oxidizing gas is hindered due to poor drainage of the generated water. descend.
従来は、機械強度を強くするために、炭素短繊維を抄造後有機高分子で結着させ、高温で焼成し有機高分子を炭素化させたペーパー状の炭素／炭素複合体から成る多孔質電極基材を得ていたが、均一性の高い構造であるために、保水性と、生成水の排水性のバランスを保つことが困難であるという問題があった。また、ガス拡散性、排水性の向上を目的として、貫通孔を形成した多孔質電極基材が提案されているが、貫通孔を形成させるため、機械的強度を維持することが困難であることと、保水性を保つことが困難であるという問題があった。 Conventionally, in order to increase the mechanical strength, a porous electrode made of a paper-like carbon / carbon composite in which short carbon fibers are made with paper and then bound with an organic polymer and then fired at a high temperature to carbonize the organic polymer. Although the base material was obtained, there was a problem that it was difficult to maintain a balance between water retention and drainage of generated water because of the highly uniform structure. In addition, for the purpose of improving gas diffusibility and drainage, a porous electrode base material having through-holes has been proposed, but it is difficult to maintain mechanical strength because the through-holes are formed. There was a problem that it was difficult to maintain water retention.
特許文献１には、厚みが０．０５〜０．５ｍｍで嵩密度が０．３〜０．８ｇ／ｃｍであり、かつ、歪み速度１０ｍｍ／ｍｉｎ、支点間距離２ｃｍおよび試験片幅１ｃｍの条件での３点曲げ試験において曲げ強度が１０ＭＰａ以上でかつ曲げの際のたわみが１．５ｍｍ以上であることを特徴とする燃料電池用多孔質炭素電極基材が記載されている。しかし、この多孔質電極基材は、機械的強度、表面平滑性が高く、十分な導電性は有しているもの、均一性の高い構造であるために、保水性と、生成水の排水性のバランスを保つことが困難であるという問題があった。 In Patent Document 1, the thickness is 0.05 to 0.5 mm, the bulk density is 0.3 to 0.8 g / cm, the strain rate is 10 mm / min, the distance between fulcrums is 2 cm, and the specimen width is 1 cm. Describes a porous carbon electrode substrate for a fuel cell, characterized in that the bending strength is 10 MPa or more and the deflection during bending is 1.5 mm or more. However, this porous electrode substrate has high mechanical strength, surface smoothness, sufficient conductivity, and a highly uniform structure, so it has water retention and water drainage. There was a problem that it was difficult to maintain the balance.
特許文献２には、一方の面に触媒層が形成されたカーボンシートからなり、その一方の面から他方の面に亘って複数の貫通孔が形成されていることを特徴とするガス拡散電極が記載されている。この多孔質電極基材は、高いガス拡散性を有しているものの、機械的強度を維持することと、保水性を保つことが困難であるという問題があった。
本発明は、充分なガス透気度、厚みおよび貫通方向抵抗を備え、燃料電池とした時に、加湿条件の変動によっても電池性能の変動が少ない高い水分管理機能を発揮する多孔質電極基材、その製造方法、膜−電極接合体、および固体高分子型燃料電池を提供することを目的とする。 The present invention provides a porous electrode substrate that has a sufficient moisture permeability, thickness, and resistance in the penetration direction, and exhibits a high moisture management function with little variation in cell performance due to variation in humidification conditions when used as a fuel cell. An object of the present invention is to provide a production method thereof, a membrane-electrode assembly, and a polymer electrolyte fuel cell.
本発明は以下の通りである。
（１）以下の（Ａ）〜（Ｄ）工程を順に行う多孔質電極基材の製造方法。
（Ａ）炭素短繊維とバインダー短繊維とを、分散し炭素繊維紙を作製する工程
（Ｂ）前記炭素繊維紙に炭素化後の残炭率が２０％以上の樹脂を溶解した溶液を含浸させた後、炭素化後の残炭率が２０％以上の樹脂に対し貧溶媒となる溶媒に浸漬させ、炭素化後の残炭率が２０％以上の樹脂を凝固させた前駆体シートを作製する工程
（Ｃ）溶媒を除去した前駆体シートを得る工程
（Ｄ）前駆体シート中の炭素化後の残炭率が２０％以上の樹脂を炭素化して多孔質電極基材を得る工程
（２）以下の（ａ）〜（ｄ）工程を順に行う多孔質電極基材の製造方法。
（ａ）炭素短繊維とバインダー短繊維とを、分散し炭素繊維紙を作製する工程
（ｂ）前記炭素繊維紙にポリアクリロニトリルのジメチルアセトアミド溶液を含浸させた後、水に浸漬させポリアクリロニトリルを凝固させた前駆体シートを作製する工程
（ｃ）溶媒を除去した前駆体シートを得る工程
（ｄ）前駆体シート中のポリアクリロニトリルを炭素化して多孔質電極基材を得る工程
（３）（ｂ）と（ｄ）工程を以下の（ｂ’）と（ｄ’）工程に各々替える（２）の多孔質電極基材の製造方法。
（ｂ’） 前記炭素繊維紙にフェノール樹脂組成物のメタノール溶液を含浸させた後、水に浸漬させフェノール樹脂組成物を凝固させた前駆体シートを作製する工程
（ｄ’） 前駆体シート中のフェノール樹脂組成物を炭素化して多孔質電極基材を得る工程
（４）（Ｄ）工程の炭素化の前に加熱加圧する（１）〜（３）のいずれかの多孔質電極基材の製造方法。
（５）加熱加圧後、酸化処理してから炭素化する（４）の多孔質電極基材の製造方法。
（６）（１）〜（５）のいずれかの多孔質電極基材の製造方法で得られる多孔質電極基材。
（７）分散した炭素短繊維同士が、多孔質化した炭素によって接合されている（６）の多孔質電極基材。
（８）分散した炭素短繊維同士が、多孔質化した炭素によって接合されている多孔質電極基材。
（９）（６）〜（８）のいずれかの多孔質電極基材を用いた膜−電極接合体。
（１０）（９）の膜−電極接合体を用いた固体高分子型燃料電池。
The present invention is as follows.
(1) The manufacturing method of the porous electrode base material which performs the following (A)-(D) processes in order.
(A) Step of dispersing carbon short fibers and binder short fibers to produce carbon fiber paper (B) Impregnating the carbon fiber paper with a solution in which a resin having a carbon residue ratio of 20% or more after carbonization is dissolved. After that, a precursor sheet is produced by immersing in a solvent that is a poor solvent for a resin having a carbon residue rate of 20% or more after carbonization, and solidifying a resin having a carbon residue rate of 20% or more after carbonization. Step (C) Obtaining a precursor sheet from which the solvent has been removed (D) Step (2) for obtaining a porous electrode substrate by carbonizing a resin having a carbon residue ratio of 20% or more after carbonization in the precursor sheet The manufacturing method of the porous electrode base material which performs the following (a)-(d) process in order.
(A) Step of dispersing carbon short fibers and binder short fibers to produce carbon fiber paper (b) After impregnating the carbon fiber paper with a dimethylacetamide solution of polyacrylonitrile, it is immersed in water to solidify the polyacrylonitrile. (C) Step for obtaining a precursor sheet from which the solvent has been removed (d) Step for obtaining a porous electrode substrate by carbonizing polyacrylonitrile in the precursor sheet (3) (b) (D) The method for producing a porous electrode substrate according to (2), wherein the step (d) is replaced with the following steps (b ′) and (d ′), respectively.
(B ′) Step of producing a precursor sheet in which the carbon fiber paper is impregnated with a methanol solution of the phenol resin composition and then immersed in water to solidify the phenol resin composition (d ′) in the precursor sheet Step (4) to obtain a porous electrode substrate by carbonizing the phenol resin composition (4) Production of the porous electrode substrate according to any one of (1) to (3) that is heated and pressurized before carbonization in the step (D) Method.
(5) The method for producing a porous electrode base material according to (4), wherein the carbonization is performed after the heating and pressurization, followed by oxidation.
(6) A porous electrode substrate obtained by the method for producing a porous electrode substrate according to any one of (1) to (5).
(7) The porous electrode base material according to (6), in which dispersed short carbon fibers are joined together by porous carbon.
(8) A porous electrode base material in which dispersed carbon short fibers are joined by porous carbon.
(9) A membrane-electrode assembly using the porous electrode substrate according to any one of (6) to (8).
(10) A polymer electrolyte fuel cell using the membrane-electrode assembly according to (9).
本発明によれば、充分なガス透気度、厚みおよび貫通方向抵抗を備え、燃料電池とした時に、加湿条件の変動によっても電池性能の変動が少ない高い水分管理機能を発揮する多孔質電極基材、その製造方法、膜−電極接合体、および固体高分子型燃料電池を得ることができる。 According to the present invention, a porous electrode substrate having sufficient gas permeability, thickness, and penetration direction resistance, and exhibiting a high moisture management function with little variation in cell performance even when the humidification conditions are varied when a fuel cell is obtained. A material, a manufacturing method thereof, a membrane-electrode assembly, and a polymer electrolyte fuel cell can be obtained.
＜炭素短繊維＞
本発明で用いる炭素短繊維の原料である炭素繊維は、ポリアクリロニトリル系炭素繊維、ピッチ系炭素繊維、レーヨン系炭素繊維などいずれであっても良いが、ポリアクリロニトリル系炭素繊維が好ましい。特に、多孔質炭素電極基材の機械的強度が比較的高くすることができることから、用いる炭素繊維がポリアクリロニトリル（ＰＡＮ）系炭素繊維のみからなることが好ましい。
炭素短繊維の直径は、炭素短繊維の生産コスト、分散性の面から、３〜９μｍであることが好ましい。最終的に得られる多孔質電極基材の平滑性の面から、４μｍ以上、８μｍ以下であることがさらに好ましい。
炭素短繊維の繊維長は、分散性の点から、２〜１２ｍｍが好ましい。
<Short carbon fiber>
The carbon fiber that is a raw material of the short carbon fiber used in the present invention may be any of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, etc., but polyacrylonitrile-based carbon fiber is preferable. In particular, since the mechanical strength of the porous carbon electrode substrate can be made relatively high, it is preferable that the carbon fiber to be used is made of only polyacrylonitrile (PAN) based carbon fiber.
The diameter of the short carbon fiber is preferably 3 to 9 μm from the viewpoint of production cost and dispersibility of the short carbon fiber. From the aspect of smoothness of the finally obtained porous electrode substrate, it is more preferably 4 μm or more and 8 μm or less.
The fiber length of the short carbon fiber is preferably 2 to 12 mm from the viewpoint of dispersibility.
＜分散＞
本発明において、「分散」とは、炭素短繊維がおおむね一つの面を形成するように横たわっているという意味である。これにより炭素短繊維による短絡や炭素短繊維の折損を防止することができる。炭素短繊維の配向方向は実質的にランダムであっても、特定方向への配向性が高くなっていても良い。
<Dispersion>
In the present invention, “dispersion” means that the carbon short fibers lie so as to form a single plane. Thereby, the short circuit by carbon short fiber and the breakage of carbon short fiber can be prevented. The orientation direction of the short carbon fibers may be substantially random, or the orientation in a specific direction may be high.
＜製造方法＞
本発明の多孔質電極基材の製造方法は、以下に示す工程を順に行う方法である。多孔質電極基材は、例えば以下の方法により好適に製造することができる。
（Ａ）炭素短繊維とバインダー短繊維とを、分散し炭素繊維紙を作製する工程
（Ｂ）前記炭素繊維紙に炭素化後の残炭率が２０％以上の樹脂を溶解した溶液を含浸させた後、炭素化後の残炭率が２０％以上の樹脂に対し貧溶媒となる溶媒に浸漬させ、炭素化後の残炭率が２０％以上の樹脂を凝固させた前駆体シートを作製する工程
（Ｃ）溶媒を除去した前駆体シートを得る工程
（Ｄ）前駆体シート中の炭素化後の残炭率が２０％以上の樹脂を炭素化して多孔質電極基材を得る工程
<Manufacturing method>
The manufacturing method of the porous electrode base material of this invention is a method of performing the process shown below in order. The porous electrode substrate can be suitably manufactured by the following method, for example.
(A) Step of dispersing carbon short fibers and binder short fibers to produce carbon fiber paper (B) Impregnating the carbon fiber paper with a solution in which a resin having a carbon residue ratio of 20% or more after carbonization is dissolved. After that, a precursor sheet is produced by immersing in a solvent that is a poor solvent for a resin having a carbon residue rate of 20% or more after carbonization, and solidifying a resin having a carbon residue rate of 20% or more after carbonization. Step (C) Obtaining a precursor sheet from which the solvent has been removed Step (D) Step of obtaining a porous electrode substrate by carbonizing a resin having a carbon residue ratio of 20% or more after carbonization in the precursor sheet
＜バインダー短繊維＞
バインダー短繊維は、炭素短繊維を含む炭素短繊維紙中で各成分をつなぎとめるバインダー（糊剤）として使用される。バインダー短繊維としては、ポリビニルアルコール（ＰＶＡ）、ポリ酢酸ビニルなどを用いることができる。特にポリビニルアルコールは炭素短繊維紙作製工程での結着力に優れるため、炭素短繊維の脱落が少なくバインダーとして好ましい。
<Binder staple fiber>
The binder short fiber is used as a binder (glue) that holds the components together in a carbon short fiber paper containing carbon short fibers. As the binder short fiber, polyvinyl alcohol (PVA), polyvinyl acetate or the like can be used. In particular, polyvinyl alcohol is preferable as a binder because it has excellent binding power in the short carbon fiber paper making process, and the short carbon fibers do not fall off.
＜炭素短繊維紙を作製する工程＞
炭素短繊維とバインダー短繊維とを分散させて、炭素短繊維紙を作製する方法としては、液体の媒体中に炭素短繊維とバインダー短繊維を分散させて抄造する湿式法や、空気中に炭素短繊維とバインダー短繊維を分散させて降り積もらせる乾式法が適用できるが、中でも湿式法が好ましい。炭素短繊維が単繊維に分散するのを助け、分散した単繊維が再び収束を防止するのを防ぐことができる。
炭素短繊維とバインダー短繊維を混合する方法としては、炭素短繊維とともに水中で攪拌分散させる方法と、直接混ぜ込む方法があるが、均一に分散させるためには水中で拡散分散させる方法が好ましい。このようにバインダー短繊維を混ぜることにより、炭素繊維紙の強度を保持し、その製造途中で炭素繊維紙から炭素短繊維が剥離したり、炭素短繊維の配向が変化したりするのを防止することができる。
また、炭素短繊維紙の作製は連続で行なう方法やバッチ式で行なう方法があるが、本発明において行なう炭素短繊維紙の作製は、特に目付のコントロールが容易であるという点と生産性及び機械的強度の観点から連続が好ましい。炭素短繊維紙の目付けは、１０〜２００ｇ／ｍ２とすることが好ましい。
<Process for producing short carbon fiber paper>
Carbon short fiber and binder short fiber are dispersed to produce carbon short fiber paper. A wet method in which carbon short fiber and binder short fiber are dispersed in a liquid medium to make paper, or carbon in the air is used. A dry method in which short fibers and binder short fibers are dispersed and piled up can be applied. Among these, a wet method is preferable. The short carbon fibers can be dispersed into the single fibers, and the dispersed single fibers can be prevented from preventing convergence again.
As a method of mixing the short carbon fiber and the short binder fiber, there are a method of stirring and dispersing in water together with the carbon short fiber and a method of mixing directly, but a method of diffusing and dispersing in water is preferable for uniform dispersion. By mixing the binder short fibers in this way, the strength of the carbon fiber paper is maintained, and it is possible to prevent the carbon short fibers from being peeled off from the carbon fiber paper during the production and the orientation of the carbon short fibers from being changed. be able to.
In addition, short carbon fiber paper can be produced continuously or batchwise. The production of carbon short fiber paper in the present invention is particularly easy to control the basis weight, productivity and machine. From the viewpoint of mechanical strength, continuous is preferable. The basis weight of the short carbon fiber paper is preferably 10 to 200 g / m2.
＜炭素化後の残炭率が２０％以上の樹脂＞
本発明で炭素化後の残炭率が２０％以上の樹脂として用いる樹脂は、炭素化後も導電性物質として残存する物質であり、常温において粘着性、あるいは流動性を示すものが好ましい。ポリアクリロニトリル、フェノール樹脂、フラン樹脂、エポキシ樹脂、メラミン樹脂、イミド樹脂、ウレタン樹脂、アラミド樹脂、ピッチ等を単体若しくは混合物として用いることができ、用いる樹脂の種類、後述する樹脂の含浸の際の含浸量、硬化、炭素化温度によって残存する炭素化量が異なる。
フェノール樹脂組成物として、フェノール類とアルデヒド類の反応によって得られるレゾールタイプフェノール樹脂組成物を用いることもできるが、固体の熱融着性を示すノボラックタイプのフェノール樹脂組成物を混合させることもが好ましい。
<Resin with 20% or more carbon residue after carbonization>
The resin used as a resin having a carbon residue ratio of 20% or more after carbonization in the present invention is a substance that remains as a conductive substance even after carbonization, and preferably exhibits adhesiveness or fluidity at room temperature. Polyacrylonitrile, phenol resin, furan resin, epoxy resin, melamine resin, imide resin, urethane resin, aramid resin, pitch, etc. can be used as a single substance or as a mixture, and the type of resin used, impregnation during resin impregnation described later The amount of carbonization remaining varies depending on the amount, curing, and carbonization temperature.
As the phenol resin composition, a resol type phenol resin composition obtained by reaction of phenols and aldehydes can be used, but a novolac type phenol resin composition showing solid heat-fusibility can be mixed. preferable.
＜炭素化後の残炭率が２０％以上の樹脂の含浸方法＞
炭素短繊維紙に炭素化後の残炭率が２０％以上の樹脂を含浸する方法としては、炭素短繊維紙に樹脂を含浸させることができればよく、特に限定されないが、コーターを用いて炭素短繊維紙表面に樹脂を均一にコートする方法、絞り装置を用いるｄｉｐ−ｎｉｐ方法、若しくは炭素短繊維紙と樹脂フィルムを重ねて、樹脂を前駆体シートに転写する方法が、連続的に行なうことができ、生産性及び長尺ものも製造できるという点で好ましい。
<Method of impregnating resin with a residual carbon ratio of 20% or more after carbonization>
The method for impregnating the carbon short fiber paper with a resin having a carbon residue ratio of 20% or more after carbonization is not particularly limited as long as the carbon short fiber paper can be impregnated with the resin. A method of uniformly coating a resin on the surface of fiber paper, a dip-nip method using a squeezing device, or a method of superposing carbon short fiber paper and a resin film and transferring the resin to a precursor sheet can be continuously performed. This is preferable in terms of productivity and production of long products.
＜炭素化後の残炭率が２０％以上の樹脂の含浸量＞
多孔質電極基材に排水性と保湿性、ガス拡散性のバランスを保つことができる水分管理機能を発現させるためには炭素化後の残炭率が２０％以上の樹脂が炭化した多孔質炭素が、炭素短繊維１００質量部に対し２０〜５０質量部であることが好ましいため、炭素短繊維紙に含浸させる炭素化後の残炭率が２０％以上の樹脂量は、炭素短繊維１００質量部に対し、７０〜１２０質量部含浸させることが好ましい。
<Amount of resin impregnated with carbonization rate of 20% or more after carbonization>
Porous carbon obtained by carbonizing a resin with a residual carbon ratio of 20% or more after carbonization in order to develop a moisture management function capable of maintaining a balance between drainage, moisture retention, and gas diffusibility in the porous electrode substrate However, since it is preferable that it is 20-50 mass parts with respect to 100 mass parts of carbon short fibers, the amount of resin whose carbon residue after carbonization to impregnate carbon short fiber paper is 20% or more is 100 mass of carbon short fibers. It is preferable to impregnate 70 to 120 parts by mass with respect to parts.
＜炭素化後の残炭率が２０％以上の樹脂の凝固＞
炭素化後の残炭率が２０％以上の樹脂の凝固は、炭素短繊維とバインダー短繊維から成る炭素短繊維紙に炭素化後の残炭率が２０％以上の樹脂溶液を含浸させた後、炭素化後の残炭率が２０％以上の樹脂に対し、貧溶媒となる凝固浴中に浸漬させ、炭素化後の残炭率が２０％以上の樹脂を凝固させることによって行う。凝固浴に用いる溶媒としては、一般的には水系溶媒を用いることができるが、樹脂に対して貧溶媒となるものであれば特に限定されない。また、単一溶媒であっても、複数の溶媒を混ぜた混合溶媒を用いても良い。
炭素化後の残炭率が２０％以上の樹脂としてポリアクリロニトリルを用いた場合は、水や水／ヂメチルアセトアミドの混合溶媒などを用いることができる。またフェノール樹脂組成物を用いた場合は、水や水／アルコール混合溶媒を用いることができる。
炭素化後の残炭率が２０％以上の樹脂を凝固させることによって空隙を形成させることができ、炭素化後の残炭率が２０％以上の樹脂の多孔質化を促すことができる。
空隙形成は、凝固浴中での凝固速度に依存する。凝固速度が比較的速い方が空隙を形成しやすいため、炭素短繊維紙に炭素化後の残炭率が２０％以上の樹脂を含浸させた際の樹脂溶液濃度、凝固浴組成、凝固浴温度によって精密に制御する。樹脂溶液濃度としては、含浸時の作業性の点で５〜４０質量％とすることが好ましい。
例えば、炭素化後の残炭率が２０％以上の樹脂をポリアクリロニトリルまたはフェノール樹脂組成物とし、貧溶媒となる凝固浴を水とした場合は、好ましい凝固浴温度１０℃〜８０℃である。
多孔質化した炭素は、多孔質電極基材の中で、炭素短繊維間を結着し、かつ自身が多孔質化した樹脂の炭化物であり、多孔質化は、空隙サイズを精密に制御するためには、樹脂含浸後の凝固過程で多孔質化することが好ましい。
<Coagulation of resin with 20% or more carbon residue after carbonization>
The coagulation of the resin having a carbon residue of 20% or more after carbonization is performed after impregnating a carbon short fiber paper composed of carbon short fibers and binder short fibers with a resin solution having a carbon residue of 20% or more after carbonization. The resin having a residual carbon ratio after carbonization of 20% or more is immersed in a coagulation bath as a poor solvent, and the resin having a residual carbon ratio after carbonization of 20% or more is solidified. As the solvent used in the coagulation bath, an aqueous solvent can be generally used, but is not particularly limited as long as it becomes a poor solvent for the resin. Moreover, even if it is a single solvent, you may use the mixed solvent which mixed several solvent.
When polyacrylonitrile is used as a resin having a carbon residue ratio of 20% or more after carbonization, water, a water / dimethylacetamide mixed solvent, or the like can be used. When a phenol resin composition is used, water or a water / alcohol mixed solvent can be used.
A void can be formed by solidifying a resin having a carbon residue ratio of 20% or more after carbonization, and a resin having a carbon residue ratio of 20% or more after carbonization can be promoted to be porous.
Void formation depends on the rate of solidification in the coagulation bath. Since voids are easier to form when the coagulation speed is relatively high, the resin solution concentration, coagulation bath composition, coagulation bath temperature when carbon short fiber paper is impregnated with a resin having a carbon residue ratio of 20% or more after carbonization Precisely controlled by. The resin solution concentration is preferably 5 to 40% by mass in terms of workability during impregnation.
For example, when a resin having a carbon residue rate of 20% or more after carbonization is a polyacrylonitrile or phenol resin composition and a coagulation bath serving as a poor solvent is water, a preferable coagulation bath temperature is 10 ° C to 80 ° C.
Porous carbon is a carbonized resin that binds between short carbon fibers in the porous electrode base material and is itself porous. Porous control precisely controls the void size. In order to achieve this, it is preferable to make it porous in the solidification process after resin impregnation.
＜炭素化＞
炭素化後の残炭率が２０％以上の樹脂を凝固された前駆体シートは、そのまま炭素化することができる。その他、前駆体シートを加熱加圧成型後に炭素化することもでき、さらにその加熱加圧成型後の前駆体シートを酸化処理した後に炭素化することが可能である。
前駆体シートの炭素化は、炭素短繊維を炭素化後の残炭率が２０％以上の樹脂で融着させ、かつ炭素化後の残炭率が２０％以上の樹脂を炭素化することより、多孔質電極基材の機械的強度と導電性を発現させることを目的に行う。
炭素化は、多孔質電極基材の導電性を高めるために、不活性ガス中で行うことが好ましい。炭素化は、１０００℃以上の温度で行う。１０００〜３０００℃の温度範囲で炭素化することが好ましく１０００〜２２００℃の温度範囲がより好ましい。１０００℃未満の温度で炭素化して得られた多孔質電極基材は、導電性が十分ではない。炭素化の前に３００〜８００℃の程度の不活性雰囲気での焼成による前処理を行っても良い。
炭素化の時間は、例えば１０分〜１時間とすることができる。
連続作製による前駆体シートを炭素化する場合は、前駆体シートの全長にわたって連続で炭素化を行うことが、低コスト化という観点で好ましい。多孔質電極基材が長尺であれば、多孔質電極基材の生産性が高くなるだけでなく、その後のＭＥＡ製造も連続で行うことができ、燃料電池のコスト低減に大きく寄与することができる。また、本発明の多孔質電極基材は、連続的に巻き取ることも可能で、多孔質電極基材や燃料電池の生産性、コストの観点から好ましい。
<Carbonization>
The precursor sheet obtained by solidifying a resin having a carbon residue rate of 20% or more after carbonization can be carbonized as it is. In addition, the precursor sheet can be carbonized after the heat and pressure molding, and further, the precursor sheet after the heat and pressure molding can be oxidized and then carbonized.
Carbonization of the precursor sheet is obtained by fusing carbon short fibers with a resin having a carbon residue ratio of 20% or more after carbonization and carbonizing a resin having a carbon residue ratio of 20% or more after carbonization. The purpose is to develop the mechanical strength and conductivity of the porous electrode substrate.
Carbonization is preferably performed in an inert gas in order to increase the conductivity of the porous electrode substrate. Carbonization is performed at a temperature of 1000 ° C. or higher. Carbonization is preferably performed in a temperature range of 1000 to 3000 ° C, and a temperature range of 1000 to 2200 ° C is more preferable. The porous electrode substrate obtained by carbonization at a temperature of less than 1000 ° C. does not have sufficient conductivity. Prior to carbonization, pretreatment by firing in an inert atmosphere of about 300 to 800 ° C. may be performed.
The time for carbonization can be, for example, 10 minutes to 1 hour.
When carbonizing the precursor sheet by continuous production, it is preferable from a viewpoint of cost reduction to perform carbonization continuously over the full length of a precursor sheet. If the porous electrode substrate is long, not only the productivity of the porous electrode substrate is increased, but also the subsequent MEA production can be performed continuously, which can greatly contribute to the cost reduction of the fuel cell. it can. Moreover, the porous electrode base material of the present invention can be continuously wound, and is preferable from the viewpoint of productivity and cost of the porous electrode base material and the fuel cell.
＜加熱加圧＞
炭素化後の残炭率が２０％以上の樹脂を凝固された前駆体シートは、炭素化の前に、２００℃未満の温度で加熱加圧することが、炭素短繊維を炭素化後の残炭率が２０％以上の樹脂で融着させ、かつ、多孔質電極基材の厚みムラを低減できるという点で好ましい。加熱加圧は、前駆体シートを均等に加熱加圧できる技術であれば、いかなる技術も適用できる。その例としては、上下両面から平滑な剛板にて熱プレスする方法や連続ベルトプレス装置を用いて行う方法がある。
連続製造による前駆体シートを加熱加圧する場合は、連続ベルトプレス装置を用いて行う方法が、長尺の多孔質電極基材ができるという点で好ましい。多孔質電極基材が長尺であれば、多孔質電極基材の生産性が高くなるだけでなく、その後のＭＥＡ製造も連続で行うことができ、燃料電池のコスト低減化に大きく寄与することができる。また、本発明の多孔質電極基材は、連続的に巻き取ることも可能で、多孔質電極基材や燃料電池の生産性、コストの観点から好ましい。連続ベルト装置におけるプレス方法としては、ロールプレスによりベルトに線圧で圧力を加える方法と液圧ヘッドプレスにより面圧でプレスする方法があるが、後者の方がより平滑な多孔質電極基材が得られるという点で好ましい。
加熱温度は、効果的に表面を平滑にするために、２００℃未満が好ましく、１２０〜１９０℃がより好ましい。
成型圧力は特に限定されないが、炭素化後の残炭率が２０％以上の樹脂の比率が多い場合は、成型圧が低くても前駆体シートの表面を平滑にすることが容易である。このとき必要以上にプレス圧を高くすることは、加圧時に炭素短繊維を破壊する、多孔質電極基材としたときその組織が緻密になりすぎるなどの問題が生じる場合がある。例えば、２０ｋＰａ〜１０ＭＰａの圧力で加圧することができる。
加熱加圧の時間は、例えば３０秒〜１０分とすることができる。剛板に挟んで、又連続ベルト装置で前駆体シートの加熱加圧を行う時は、剛板やベルトに炭素化後の残炭率が２０％以上の樹脂などが付着しないようにあらかじめ剥離剤を塗っておくか、前駆体シートと剛板やベルトとの間に離型紙を挟んで行うことが好ましい。
<Heating and pressing>
The precursor sheet obtained by solidifying a resin having a carbon residue rate of 20% or more after carbonization is heated and pressed at a temperature of less than 200 ° C. before carbonization, so that the carbon residue is carbonized from the carbon residue. It is preferable in terms of being able to be fused with a resin having a rate of 20% or more and reducing unevenness in the thickness of the porous electrode substrate. Any technique can be applied to the heat and pressure as long as the technique can uniformly heat and press the precursor sheet. As an example, there are a method of performing hot pressing with smooth rigid plates from both upper and lower surfaces, and a method of performing using a continuous belt press apparatus.
In the case where the precursor sheet by continuous production is heated and pressurized, a method using a continuous belt press apparatus is preferable in that a long porous electrode substrate can be formed. If the porous electrode substrate is long, not only the productivity of the porous electrode substrate is increased, but also the subsequent MEA production can be performed continuously, which greatly contributes to the cost reduction of the fuel cell. Can do. Moreover, the porous electrode base material of the present invention can be continuously wound, and is preferable from the viewpoint of productivity and cost of the porous electrode base material and the fuel cell. As a pressing method in the continuous belt device, there are a method of applying pressure to the belt by a roll press by a linear pressure and a method of pressing by a surface pressure by a hydraulic head press, but the latter is a smoother porous electrode substrate. It is preferable in that it is obtained.
In order to effectively smooth the surface, the heating temperature is preferably less than 200 ° C, more preferably 120 to 190 ° C.
The molding pressure is not particularly limited, but when the ratio of the resin having a residual carbon ratio after carbonization of 20% or more is large, it is easy to smooth the surface of the precursor sheet even if the molding pressure is low. If the press pressure is increased more than necessary at this time, there may be problems such as breaking the short carbon fibers during the pressurization or becoming too dense when the porous electrode base material is used. For example, pressurization can be performed at a pressure of 20 kPa to 10 MPa.
The time for heating and pressing can be, for example, 30 seconds to 10 minutes. When a precursor sheet is heated and pressed with a rigid plate or with a continuous belt device, a release agent is used in advance so that a resin with a carbon residue ratio of 20% or more after carbonization does not adhere to the rigid plate or belt. It is preferable to carry out coating or to put a release paper between the precursor sheet and the rigid plate or belt.
＜酸化処理＞
炭素化後の残炭率が２０％以上の樹脂を凝固された前駆体シートは、加熱加圧成型した後、２００℃以上３００℃未満の温度で酸化処理することが、炭素短繊維を炭素化後の残炭率が２０％以上の樹脂でより融着させ、かつ、炭素化後の残炭率が２０％以上の樹脂の炭素化率を向上させるという点で好ましい。
酸化処理は、２００〜３００℃の温度範囲で行うことが好ましく、２４０〜２７０℃で行うことがより好ましい。酸化処理は、大気雰囲気下で行うことが好ましい。
酸化処理の時間は、例えば３０分〜２時間とすることができる。
連続製造による前駆体シートを酸化処理する場合は、前駆体シートの全長にわたって連続で行うことが低コスト化という観点で好ましい。多孔質電極基材が長尺であれば、多孔質電極基材の生産性が高くなるだけでなく、その後のＭＥＡ製造も連続で行うことができ、燃料電池のコスト低減に大きく寄与することができる。また本発明の多孔質電極基材は、連続的に巻き取ることも可能で、多孔質電極基材や燃料電池の生産性、コストの観点から好ましい。
<Oxidation treatment>
The precursor sheet obtained by solidifying a resin having a carbon residue rate of 20% or more after carbonization is heat-press molded and then oxidized at a temperature of 200 ° C. or more and less than 300 ° C. to carbonize short carbon fibers. It is preferable in terms of further fusing with a resin having a residual carbon ratio of 20% or more and improving the carbonization ratio of a resin having a residual carbon ratio of 20% or more after carbonization.
The oxidation treatment is preferably performed at a temperature range of 200 to 300 ° C, more preferably at 240 to 270 ° C. The oxidation treatment is preferably performed in an air atmosphere.
The oxidation treatment time can be, for example, 30 minutes to 2 hours.
When oxidizing the precursor sheet by continuous manufacture, it is preferable from a viewpoint of cost reduction to perform continuously over the full length of a precursor sheet. If the porous electrode substrate is long, not only the productivity of the porous electrode substrate is increased, but also the subsequent MEA production can be performed continuously, which can greatly contribute to the cost reduction of the fuel cell. it can. Further, the porous electrode substrate of the present invention can be continuously wound, and is preferable from the viewpoints of productivity and cost of the porous electrode substrate and the fuel cell.
＜多孔質電極基材＞
本発明の多孔質電極基材の厚みは、５０〜３００μｍであることが好ましい。
<Porous electrode substrate>
The thickness of the porous electrode substrate of the present invention is preferably 50 to 300 μm.
＜膜−電極接合体（ＭＥＡ）、固体高分子型燃料電池＞
以上のような本発明の多孔質電極基材は、膜−電極接合体に好適に用いることができる。そして、本発明の多孔質電極基材を用いた膜−電極接合体は、固体高分子型燃料電池に好適に用いることができる。
<Membrane-electrode assembly (MEA), polymer electrolyte fuel cell>
The porous electrode substrate of the present invention as described above can be suitably used for a membrane-electrode assembly. The membrane-electrode assembly using the porous electrode substrate of the present invention can be suitably used for a polymer electrolyte fuel cell.
以下、本発明を実施例により、さらに具体的に説明する。実施例中の各物性値等は以下の方法で測定した。 Hereinafter, the present invention will be described more specifically with reference to examples. Each physical property value in the examples was measured by the following method.
（１）ガス透気度
ＪＩＳ規格Ｐ−８１１７に準拠し、ガーレーデンソメーターを使用して２００ｍＬの空気が透過するのにかかった時間を測定し、ガス透気度を算出した。
(1) Gas air permeability Based on JIS standard P-8117, the time required for 200 mL of air to permeate was measured using a Gurley densometer, and the gas air permeability was calculated.
（２）厚み
多孔質電極基材の厚みは、厚み測定装置ダイヤルシックネスゲージ７３２１（商品名、ミツトヨ製）を使用して測定した。測定子の大きさは直径１０ｍｍで、測定圧力は１．５ｋＰａとした。
(2) Thickness The thickness of the porous electrode substrate was measured using a thickness measuring device dial thickness gauge 7321 (trade name, manufactured by Mitutoyo Corporation). The size of the probe was 10 mm in diameter, and the measurement pressure was 1.5 kPa.
（３）貫通方向抵抗
多孔質電極基材の厚さ方向の電気抵抗（貫通方向抵抗）は、試料を金メッキした銅板に挟み、金メッキした銅板の上下から１ＭＰａで加圧し、１０ｍＡ／ｃｍ２の電流密度で電流を流したときの抵抗値を測定し、次式より求めた。
(3) Penetration direction resistance The thickness direction electrical resistance (penetration direction resistance) of the porous electrode substrate is obtained by sandwiching a sample between gold-plated copper plates and pressurizing at 1 MPa from above and below the gold-plated copper plate, and a current of 10 mA / cm 2 . The resistance value when a current was passed at a density was measured and obtained from the following equation.
貫通抵抗（ｍΩ・ｃｍ２）＝測定抵抗値（Ω）×試料面積（ｃｍ２） Penetration resistance (mΩ · cm 2 ) = Measured resistance value (Ω) × Sample area (cm 2 )
（実施例１）
炭素短繊維として、平均繊維径が７μｍ、平均繊維長が３ｍｍのポリアクリロニトリル（ＰＡＮ）系炭素繊維を用意した。また、バインダー短繊維として、平均繊維長が３ｍｍのポリビニルアルコール（ＰＶＡ）短繊維（商品名：ＶＢＰ１０５−１、クラレ株式会社製）を用意した。
Example 1
As short carbon fibers, polyacrylonitrile (PAN) carbon fibers having an average fiber diameter of 7 μm and an average fiber length of 3 mm were prepared. Moreover, polyvinyl alcohol (PVA) short fibers (trade name: VBP105-1, manufactured by Kuraray Co., Ltd.) having an average fiber length of 3 mm were prepared as binder short fibers.
炭素短繊維１００質量部を水中に均一に分散して単繊維に解繊し、十分に分散したところに、ＰＶＡ短繊維２５質量部を均一に分散し、標準角型シートマシン（熊谷理機工業（株）製、商品名：Ｎｏ．２５５５ 標準角型シートマシン）を用いてＪＩＳ Ｐ−８２０９法に準拠して手動により炭素短繊維紙の作製を行い、乾燥させて、目付けが２５ｇ／ｍ２の炭素短繊維紙を得た。炭素短繊維の分散状態は良好であった。
この炭素短繊維紙に、ポリアクリロニトリルを１０質量％含むポリアクリロニトリルのジメチルアセトアミド溶液を含浸させた後、室温の水からなる凝固浴中に浸漬させることにより、空隙を有するポリアクリロニトリルを凝固させた。その後、８０℃の乾燥機中で乾燥させることによって、目付けが４６ｇ／ｍ２の前駆体シートを得た。これは、炭素短繊維１００質量部に対し、ポリアクリロニトリルを１０５質量部付着させたことになる。
次に、２枚重ね合わせたこの前駆体シートを２枚のシリコーン系離型剤をコートした紙に挟んだ後、バッチプレス装置にて１８０℃、３０ｋＰａの条件下で３分間加圧加熱した。
加圧加熱した前駆体シートをバッチ炭素化炉にて、窒素ガス雰囲気中、２０００℃の条件下で１時間炭素化することで多孔質電極基材を得た。得られた多孔質電極基材は、ガス透気度、厚み、貫通方向抵抗がそれぞれ良好な結果であった。結果を表１に示した。
なお、得られた多孔質電極基材の表面ＳＥＭ写真を図１に示す。分散した炭素短繊維同士が、炭多孔質化した炭素によって接合されていることが確認できた。また、評価結果を表１に示した。
100 parts by mass of carbon short fibers are uniformly dispersed in water, defibrated into single fibers, and when sufficiently dispersed, 25 parts by mass of PVA short fibers are uniformly dispersed, and a standard square sheet machine (Kumaya Riki Kogyo) Co., Ltd., trade name: Nanba2555 perform fabrication of short carbon fiber paper manually in compliance with JIS P-8209 method using a standard square sheet machine), dried, basis weight of 25 g / m 2 Carbon short fiber paper was obtained. The dispersion state of the short carbon fibers was good.
The carbon short fiber paper was impregnated with a dimethylacetamide solution of polyacrylonitrile containing 10% by mass of polyacrylonitrile, and then immersed in a coagulation bath made of water at room temperature to coagulate the polyacrylonitrile having voids. Then, the precursor sheet | seat of 46 g / m < 2 > of fabric weights was obtained by making it dry in 80 degreeC drying machine. This means that 105 parts by mass of polyacrylonitrile is attached to 100 parts by mass of the short carbon fibers.
Next, two precursor sheets were placed between two sheets of paper coated with a silicone release agent, and then heated under pressure at 180 ° C. and 30 kPa for 3 minutes in a batch press apparatus.
The precursor sheet heated and pressurized was carbonized in a batch carbonization furnace in a nitrogen gas atmosphere at 2000 ° C. for 1 hour to obtain a porous electrode substrate. The obtained porous electrode base material had good gas permeability, thickness, and penetration direction resistance. The results are shown in Table 1.
In addition, the surface SEM photograph of the obtained porous electrode base material is shown in FIG. It was confirmed that the dispersed short carbon fibers were joined together with carbon made into carbon porous. The evaluation results are shown in Table 1.
（実施例２）
凝固浴温度を５７℃としたこと以外は実施例１と同様にして多孔質電極基材を得た。得られた多孔質電極基材は、表面ＳＥＭ観察により分散した炭素短繊維同士が、炭多孔質化した炭素によって接合されており、実施例１と比較して炭化樹脂中の空隙サイズが大きくなっていることが確認できた。また、ガス透気度、厚み、貫通方向抵抗もそれぞれ良好な結果であった。評価結果を表１に示した。
(Example 2)
A porous electrode substrate was obtained in the same manner as in Example 1 except that the coagulation bath temperature was 57 ° C. In the obtained porous electrode base material, short carbon fibers dispersed by surface SEM observation are joined by carbon made into carbon porous, and the void size in the carbonized resin is increased as compared with Example 1. It was confirmed that Moreover, the gas permeability, thickness, and penetration direction resistance were also good results. The evaluation results are shown in Table 1.
（実施例３）
凝固浴を３０質量％のジメチルアセトアミドを含む水／ジメチルアセトアミド混合溶液としたこと以外は実施例１と同様にして多孔質電極基材を得た。得られた多孔質電極基材は、表面ＳＥＭ観察により分散した炭素短繊維同士が、炭多孔質化した炭素によって接合されており、実施例１と比較して炭化樹脂中の空隙サイズが小さくなっていることが確認できた。また、ガス透気度、厚み、貫通方向抵抗もそれぞれ良好な結果であった。評価結果を表１に示した。
(Example 3)
A porous electrode substrate was obtained in the same manner as in Example 1 except that the coagulation bath was a water / dimethylacetamide mixed solution containing 30% by mass of dimethylacetamide. In the obtained porous electrode base material, short carbon fibers dispersed by surface SEM observation are joined together by carbon made into carbon porous, and the void size in the carbonized resin is reduced as compared with Example 1. It was confirmed that Moreover, the gas permeability, thickness, and penetration direction resistance were also good results. The evaluation results are shown in Table 1.
（実施例４）
加圧加熱した前駆体シートをバッチ熱風炉で、空気中、２５０℃の条件下で１時間酸化処理した後、２０００℃の条件下で１時間炭素化したこと以外は実施例１と同様にして多孔質電極基材を得た。得られた多孔質電極基材は、表面ＳＥＭ観察により分散した炭素短繊維同士が、炭多孔質化した炭素によって接合されており、実施例１と比較して炭化樹脂中の空隙サイズが同等であることが確認できた。また、ガス透気度、厚み、貫通方向抵抗もそれぞれ良好な結果であった。評価結果を表１に示した。
Example 4
The precursor sheet heated under pressure was oxidized in a batch hot air oven in air at 250 ° C. for 1 hour, and then carbonized at 2000 ° C. for 1 hour in the same manner as in Example 1. A porous electrode substrate was obtained. In the obtained porous electrode base material, short carbon fibers dispersed by surface SEM observation are joined by carbon made carbon porous, and the void size in the carbonized resin is equivalent to that in Example 1. It was confirmed that there was. Moreover, the gas permeability, thickness, and penetration direction resistance were also good results. The evaluation results are shown in Table 1.
（実施例５）
得られる炭素短繊維紙の目付けが５０ｇ／ｍ２、樹脂凝固乾燥後の前駆体シートの目付けを９２ｇ／ｍ２とし、加圧加熱せずに、２０００℃の条件下で１時間炭素化したこと以外は、実施例１と同様にして多孔質電極基材を得た。得られた多孔質電極基材は、表面ＳＥＭ観察により分散した炭素短繊維同士が、炭多孔質化した炭素によって接合されており、実施例１と比較して炭化樹脂中の空隙サイズが同等であることが確認できた。また、ガス透気度、厚み、貫通方向抵抗もそれぞれ良好な結果であった。評価結果を表１に示した。
(Example 5)
The basis weight of the obtained carbon short fiber paper was 50 g / m 2 , the basis weight of the precursor sheet after resin coagulation drying was 92 g / m 2, and carbonized for 1 hour under the condition of 2000 ° C. without heating under pressure. Except for the above, a porous electrode substrate was obtained in the same manner as in Example 1. In the obtained porous electrode base material, short carbon fibers dispersed by surface SEM observation are joined by carbon made carbon porous, and the void size in the carbonized resin is equivalent to that in Example 1. It was confirmed that there was. Moreover, the gas permeability, thickness, and penetration direction resistance were also good results. The evaluation results are shown in Table 1.
（実施例６）
樹脂溶液をフェノール樹脂組成物を１０質量％含むフェノール樹脂組成物のメタノール溶液とし、凝固乾燥後の前駆体シートの目付けを４６ｇ／ｍ２としたこと以外は、実施例１と同様にして多孔質電極基材を得た。得られた多孔質電極基材は、表面ＳＥＭ観察により分散した炭素短繊維同士が、炭多孔質化した炭素によって接合されており、実施例１と比較して炭化樹脂中の空隙サイズが同等であることが確認できた。また、ガス透気度、厚み、貫通方向抵抗もそれぞれ良好な結果であった。評価結果を表１に示した。
(Example 6)
The resin solution was made into a methanol solution of a phenol resin composition containing 10% by mass of a phenol resin composition, and porous as in Example 1 except that the basis weight of the precursor sheet after coagulation and drying was 46 g / m 2. An electrode substrate was obtained. In the obtained porous electrode base material, short carbon fibers dispersed by surface SEM observation are joined by carbon made carbon porous, and the void size in the carbonized resin is equivalent to that in Example 1. It was confirmed that there was. Moreover, the gas permeability, thickness, and penetration direction resistance were also good results. The evaluation results are shown in Table 1.
（比較例１）
実施例１の樹脂含浸後の前駆体シートを凝固浴中に浸漬させずに１２０℃で1時間乾燥させたこと以外は実施例１と同様にして多孔質電極基材を得た。表面ＳＥＭ観察により分散した炭素短繊維同士が、炭多孔質化していない炭素によって接合されていることが確認できた。また、ガス透気度、厚み、貫通方向抵抗はそれぞれ良好な結果であった。評価結果を表１に示した。
(Comparative Example 1)
A porous electrode substrate was obtained in the same manner as in Example 1 except that the precursor sheet after impregnation with resin in Example 1 was dried at 120 ° C. for 1 hour without being immersed in the coagulation bath. It was confirmed that the short carbon fibers dispersed by surface SEM observation were joined by carbon that was not made porous. The gas permeability, thickness, and penetration direction resistance were good results. The evaluation results are shown in Table 1.
（比較例２）
実施例６の樹脂含浸後の前駆体シートを凝固浴中に浸漬させずに室温で８時間乾燥させたこと以外は実施例６と同様にして多孔質電極基材を得た。表面ＳＥＭ観察により２次元平面内に分散した炭素短繊維同士が、炭多孔質化していない炭素によって接合されていることが確認できた。また、ガス透気度、厚み、貫通方向抵抗はそれぞれ良好な結果であった。評価結果を表１に示した。
(Comparative Example 2)
A porous electrode substrate was obtained in the same manner as in Example 6 except that the precursor sheet after resin impregnation of Example 6 was dried at room temperature for 8 hours without being immersed in the coagulation bath. It was confirmed by surface SEM observation that short carbon fibers dispersed in a two-dimensional plane were joined together by carbon that was not made porous. The gas permeability, thickness, and penetration direction resistance were good results. The evaluation results are shown in Table 1.
（実施例７）
（１）膜−電極接合体（ＭＥＡ）の作製
実施例１で得られた多孔質電極基材をカソード用、アノード用に２組用意した。両面に触媒担持カーボン（触媒：Ｐｔ、触媒担持量：５０質量％）からなる触媒層（触媒層面積：２５ｃｍ２、Ｐｔ付着量：０．３ｍｇ／ｃｍ２）を形成したパーフルオロスルホン酸系の高分子電解質膜（膜厚：３０μｍ）を、カソード用、アノード用の多孔質電極基材で挟持し、これらを接合してＭＥＡを得た。
(Example 7)
(1) Production of membrane-electrode assembly (MEA) Two sets of the porous electrode base material obtained in Example 1 were prepared for the cathode and the anode. Perfluorosulfonic acid based catalyst in which a catalyst layer (catalyst layer area: 25 cm 2 , Pt adhesion amount: 0.3 mg / cm 2 ) composed of catalyst-supported carbon (catalyst: Pt, catalyst support amount: 50% by mass) is formed on both surfaces. A polymer electrolyte membrane (film thickness: 30 μm) was sandwiched between porous electrode substrates for cathode and anode, and these were joined to obtain MEA.
（２）ＭＥＡの燃料電池特性評価
前記（１）で作製したＭＥＡを、蛇腹状のガス流路を有する２枚のカーボンセパレーターによって挟み、固体高分子型燃料電池（単セル）を形成した。
(2) Evaluation of MEA Fuel Cell Characteristics The MEA produced in (1) was sandwiched between two carbon separators having bellows-like gas flow paths to form a polymer electrolyte fuel cell (single cell).
この単セルの電流密度−電圧特性を測定することによって、燃料電池特性評価を行った。燃料ガスとしては水素ガスを用い、酸化ガスとしては空気を用いた。セル温度を８０℃、燃料ガス利用率を６０％、酸化ガス利用率を４０％とした。また、ガス加湿はバブラーにそれぞれ燃料ガスと酸化ガスを通すことによって行った。
加湿器温度８０℃、電流密度が０．８Ａ／ｃｍ２のときの燃料電池セルのセル電圧が０．６４８Ｖであった。
また、加湿器温度６０℃、電流密度が０．８Ａ／ｃｍ２のときの燃料電池セルのセル電圧が０．６０８Ｖと良好な特性を示し、加湿条件の変動によっても電池性能の変動が少ない高い水分管理機能を有していることが確認できた。
The fuel cell characteristics were evaluated by measuring the current density-voltage characteristics of this single cell. Hydrogen gas was used as the fuel gas, and air was used as the oxidizing gas. The cell temperature was 80 ° C., the fuel gas utilization rate was 60%, and the oxidizing gas utilization rate was 40%. Gas humidification was performed by passing fuel gas and oxidizing gas through a bubbler.
The cell voltage of the fuel cell when the humidifier temperature was 80 ° C. and the current density was 0.8 A / cm 2 was 0.648V.
In addition, the cell voltage of the fuel cell when the humidifier temperature is 60 ° C. and the current density is 0.8 A / cm 2 is 0.608 V, which shows good characteristics, and the battery performance fluctuation is small even when the humidification condition changes. It was confirmed that it had a moisture management function.
（比較例３）
比較例１で得られた多孔質電極基材を用いたこと以外は、実施例７と同様にして燃料電池評価を行った。
加湿器温度８０℃、電流密度が０．８Ａ／ｃｍ２のときの燃料電池セルのセル電圧が０．６３７Ｖであった。
また、加湿器温度６０℃、電流密度が０．８Ａ／ｃｍ２のときの燃料電池セルのセル電圧が０．５３２Ｖと燃料電池セル内での保水性の低下による性能低下が顕著に見られた。
(Comparative Example 3)
The fuel cell was evaluated in the same manner as in Example 7 except that the porous electrode substrate obtained in Comparative Example 1 was used.
The cell voltage of the fuel cell when the humidifier temperature was 80 ° C. and the current density was 0.8 A / cm 2 was 0.637V.
In addition, when the humidifier temperature is 60 ° C. and the current density is 0.8 A / cm 2 , the cell voltage of the fuel cell is 0.532 V, and the performance degradation due to the decrease in water retention in the fuel cell is noticeable. .
Claims (10)
（Ａ）炭素短繊維とバインダー短繊維とを、分散し炭素繊維紙を作製する工程
（Ｂ）前記炭素繊維紙に炭素化後の残炭率が２０％以上の樹脂を溶解した溶液を含浸させた後、炭素化後の残炭率が２０％以上の樹脂に対し貧溶媒となる溶媒に浸漬させ、炭素化後の残炭率が２０％以上の樹脂を凝固させた前駆体シートを作製する工程
（Ｃ）溶媒を除去した前駆体シートを得る工程
（Ｄ）前駆体シート中の炭素化後の残炭率が２０％以上の樹脂を炭素化して多孔質電極基材を得る工程 The manufacturing method of the porous electrode base material which performs the following (A)-(D) processes in order.
(A) Step of dispersing carbon short fibers and binder short fibers to produce carbon fiber paper (B) Impregnating the carbon fiber paper with a solution in which a resin having a carbon residue ratio of 20% or more after carbonization is dissolved. After that, a precursor sheet is produced by immersing in a solvent that is a poor solvent for a resin having a carbon residue rate of 20% or more after carbonization, and solidifying a resin having a carbon residue rate of 20% or more after carbonization. Step (C) Obtaining a precursor sheet from which the solvent has been removed Step (D) Step of obtaining a porous electrode substrate by carbonizing a resin having a carbon residue ratio of 20% or more after carbonization in the precursor sheet
（ａ）炭素短繊維とバインダー短繊維とを、分散し炭素繊維紙を作製する工程
（ｂ）前記炭素繊維紙にポリアクリロニトリルのジメチルアセトアミド溶液を含浸させた後、水に浸漬させポリアクリロニトリルを凝固させた前駆体シートを作製する工程
（ｃ）溶媒を除去した前駆体シートを得る工程
（ｄ）前駆体シート中のポリアクリロニトリルを炭素化して多孔質電極基材を得る工程 The manufacturing method of the porous electrode base material which performs the following (a)-(d) process in order.
(A) Step of dispersing carbon short fibers and binder short fibers to produce carbon fiber paper (b) After impregnating the carbon fiber paper with a dimethylacetamide solution of polyacrylonitrile, it is immersed in water to solidify the polyacrylonitrile. (C) Step of obtaining a precursor sheet from which the solvent has been removed (d) Step of obtaining a porous electrode substrate by carbonizing polyacrylonitrile in the precursor sheet
（ｂ’） 前記炭素繊維紙にフェノール樹脂組成物のメタノール溶液を含浸させた後、水に浸漬させフェノール樹脂組成物を凝固させた前駆体シートを作製する工程
（ｄ’） 前駆体シート中のフェノール樹脂組成物を炭素化して多孔質電極基材を得る工程 The method for producing a porous electrode substrate according to claim 2, wherein the steps (b) and (d) are replaced with the following steps (b ') and (d'), respectively.
(B ′) Step of producing a precursor sheet in which the carbon fiber paper is impregnated with a methanol solution of the phenol resin composition and then immersed in water to solidify the phenol resin composition (d ′) in the precursor sheet Process of carbonizing a phenol resin composition to obtain a porous electrode substrate
A polymer electrolyte fuel cell using the membrane-electrode assembly according to claim 9.
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| JPH10167855A (en) * | 1996-12-05 | 1998-06-23 | Toho Rayon Co Ltd | Porous carbon material |
| JP2003286085A (en) * | 2002-03-27 | 2003-10-07 | Toray Ind Inc | Porous carbon plate and manufacturing method thereof |
| JP2006100056A (en) * | 2004-09-29 | 2006-04-13 | Super Technology Innovators Co Ltd | Fuel cell electrode and solid polymer fuel cell |
| JP2007145653A (en) * | 2005-11-29 | 2007-06-14 | Tokai Carbon Co Ltd | Hydrophilic porous carbon material and its producing method |
| JP2007186824A (en) * | 2006-01-16 | 2007-07-26 | Bridgestone Corp | Composite comprising carbonaceous porous support and carbon fiber and method for producing the same |
| JP2008222500A (en) * | 2007-03-13 | 2008-09-25 | Japan Aerospace Exploration Agency | Porous molding, porous filled molding, method for producing porous molding and method for producing porous filled molding |
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|---|---|---|---|---|
| JPS60122711A (en) * | 1983-12-08 | 1985-07-01 | Oji Paper Co Ltd | Manufacture of porous carbon board |
| JPH0544779B2 (en) * | 1987-04-10 | 1993-07-07 | Toray Industries | |
| JPH05251088A (en) * | 1992-03-06 | 1993-09-28 | Oji Paper Co Ltd | Manufacture of porous carbon electrode plate for fuel cell |
| JPH10167855A (en) * | 1996-12-05 | 1998-06-23 | Toho Rayon Co Ltd | Porous carbon material |
| JP2003286085A (en) * | 2002-03-27 | 2003-10-07 | Toray Ind Inc | Porous carbon plate and manufacturing method thereof |
| JP2006100056A (en) * | 2004-09-29 | 2006-04-13 | Super Technology Innovators Co Ltd | Fuel cell electrode and solid polymer fuel cell |
| JP2007145653A (en) * | 2005-11-29 | 2007-06-14 | Tokai Carbon Co Ltd | Hydrophilic porous carbon material and its producing method |
| JP2007186824A (en) * | 2006-01-16 | 2007-07-26 | Bridgestone Corp | Composite comprising carbonaceous porous support and carbon fiber and method for producing the same |
| JP2008222500A (en) * | 2007-03-13 | 2008-09-25 | Japan Aerospace Exploration Agency | Porous molding, porous filled molding, method for producing porous molding and method for producing porous filled molding |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2015063776A (en) * | 2013-09-25 | 2015-04-09 | 日本エクスラン工業株式会社 | Acrylonitrile-based fiber and carbon material constituted by firing the fiber, and electrode containing the material |
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| JP5322212B2 (en) | 2013-10-23 |
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