JP4357228B2 - Method for producing hydrophilic porous carbon material, separator for polymer electrolyte fuel cell - Google Patents

Description

【００８９】
その後、室温に戻してから、４０％ＮａＯＨ水溶液２５ｍｌを加え、１時間放置して下記式（５）で示される鹸化を行った。
【００９０】
【化２】

【００９１】
更に、メタノールにより繰り返し洗浄し、乾燥させ、表面及び気孔内部にゲル状の親水性物質が形成された多孔質黒鉛板を得た。
得られた親水性の多孔質黒鉛板の形状を加工し、厚さ１ｍｍの平板状のＰＥＦＣ用セパレータの形状にした。
続いて、形状加工後の多孔質黒鉛板の外周部に樹脂を含浸させ、この樹脂を加熱して硬化させて、ＰＥＦＣ用セパレータを作製した。
【００９２】
（２）（１）で作製したＰＥＦＣ用セパレータを用いたこと以外は、実施例１と同様にして２セルからなるＰＥＦＣを作製した。
【００９３】
（実施例４）
反応式（４）で示される重合の時間を３時間としたこと以外は、実施例３と同様にしてＰＥＦＣ用セパレータを作製した。
【００９４】
（実施例５）
（１）平均粒子直径２０μｍの黒鉛粉末を７０重量％、及び、親水性物質のバインダーとしてナイロン６６を３０重量％含有する混合物を２００℃に加熱し、型押し成形し、得られた多孔質黒鉛材の形状を加工して、厚さ１ｍｍの平板状のＰＥＦＣ用セパレータの形状にした。
続いて、形状加工後の多孔質黒鉛板の外周部に樹脂を含浸させ、この樹脂を加熱して硬化させて、ＰＥＦＣ用セパレータを作製した。
【００９５】
（２）（１）で作製したＰＥＦＣ用セパレータを用いたこと以外は、実施例１と同様にして２セルからなるＰＥＦＣを作製した。
【００９６】
（比較例１）
（１）開気孔率１５％の等方性黒鉛（イビデン製、ＥＴ−１０）の形状を加工し、厚さ１ｍｍの平板状のＰＥＦＣ用セパレータの形状をした多孔質黒鉛板を作製した。
続いて、多孔質黒鉛板の外周部に樹脂を含浸させ、この樹脂を加熱して硬化させて、ＰＥＦＣ用セパレータを作製した。
（２）（１）で作製したＰＥＦＣ用セパレータを用いたこと以外は、実施例１と同様にして２セルからなるＰＥＦＣを作製した。
【００９７】
（比較例２）
開気孔率１５％の等方性黒鉛（イビデン製、ＥＴ−１０）からなる厚さ５ｍｍの平板状の多孔質黒鉛板を濃度６１％の硝酸中で酸化処理する際の処理時間を３０分としたこと以外は、実施例１と同様にして２セルからなるＰＥＦＣを作製した。
【００９８】
（比較例３）
反応式（４）で示される重合の時間を１時間としたこと以外は、実施例３と同様にしてＰＥＦＣ用セパレータを作製した。
【００９９】
（水浸透性評価試験）
実施例１、２及び比較例２の評価に用いる板状試験片として、実施例１、２及び比較例２における酸化処理後の厚さ５ｍｍの多孔質黒鉛板を使用し、実施例３、４及び比較例３の評価に用いる板状試験片として、実施例３、４及び比較例３における表面にゲル状の親水性物質が形成された厚さ５ｍｍの多孔質黒鉛板を使用し、実施例５の評価に用いる板状試験片として、実施例５におけるＣＩＰ成形により作製した多孔質黒鉛板を使用し、比較例１の評価に用いる板状試験片として、開気孔率１５％の等方性黒鉛（イビデン製、ＥＴ−１０）からなる厚さ５ｍｍの板状体を使用して水浸透性評価試験を行った。
水浸透性評価試験は、板状試験片を１２０℃で１時間乾燥した後に、上記板状試験片の表面に純水０．０２ｍｌをマイクロシリンジにて滴下し、上記純水０．０２ｍｌがすべて浸透する時間（浸透時間）を測定することにより行った。
結果を表１に示した。
【０１００】
（電池特性試験）
実施例１〜５及び比較例１〜３に係るＰＥＦＣについて、水素導入口圧力：０．０５ＭＰａ、空気導入口圧力：０．０５ＭＰａ、セルの作動温度：８０℃、アノード側の水素ガス加湿器の設定温度：８０℃、カソード側の空気加湿器の設定温度：８０℃、水素利用率：７０％、及び、酸素利用率：４０％の条件で、電子負荷と直流電源を用いて、電流密度１Ａ／ｃｍ^２にて３時間定電流駆動を行った後、開回路電圧を測定し、その後電流密度を１Ａ／ｃｍ^２にして３０分通電した後の１セル当たりの端子間電圧、更に２Ａ／ｃｍ^２にして３０分通電した後の１セル当たりの端子間電圧を測定し、電流電圧特性を確認した。
結果を表１に示した。
【０１０１】
【表１】

【０１０２】
表１に示したように、酸化処理の時間や親水性物質の形成を行う重合の時間を長くすることにより、得られた多孔質炭素材の水浸透性評価試験における浸透時間を短くすることができた。また、ＰＥＦＣ用セパレータを構成する多孔質炭素材の水浸透性評価試験における浸透時間が短いほど、ＰＥＦＣは、電流電圧特性に優れ、高電流密度で通電した後でも、セルの端子間電圧が高かった。
【０１０３】
【発明の効果】
第一の本発明の親水性多孔質炭素材は、本来疎水性である多孔質炭素材を酸化処理することにより親水性にしたものであり、水の浸透性に優れる。
第二の本発明の親水性多孔質炭素材は、本来疎水性である多孔質炭素材の表面及び気孔内部に親水性物質を形成することにより親水性にしたものであり、水の浸透性に優れる。
第三の本発明の親水性多孔質炭素材は、親水性物質からなるバインダーを混合させることにより、本来疎水性である多孔質炭素材の表面及び気孔内部に親水性物質を形成して親水性にしたものであり、水の浸透性に優れる。
【０１０４】
第一、第二及び第三の本発明の親水性多孔質炭素材を用いてなる本発明のＰＥＦＣ用セパレータは、親水性の構成材料からなるので、セパレータ内における水分の移動が容易である。そのため、本発明のＰＥＦＣ用セパレータでは、空気極において生成した水分のうち、排気ガスとともにセル外へ放出される割合を減らし、隣接するセルの燃料極へ供給する割合を増大させることができるので、大出力で運転した際にも、固体高分子電解質膜が乾燥して電気抵抗が増大したりせず、出力低下を抑えることができる。また、セパレータ内の細孔容積を小さくしてもセパレータ内における水分の移動を円滑に行うことが可能となるので、ガスの圧力により破損しない高強度のＰＥＦＣ用セパレータとすることができる。
【図面の簡単な説明】
【図１】ＰＥＦＣを構成する単セルの構造を模式的に示した分解斜視図である。
【図２】（ａ）は、第一の本発明の親水性多孔質炭素材を用いてなるＰＥＦＣ用セパレータの一例を模式的に示した断面図である。（ｂ）は、（ａ）に模式的に示したＰＥＦＣ用セパレータの一例を上からみた平面図である。
【図３】（ａ）は、第一の本発明の親水性多孔質炭素材を用いてなるＰＥＦＣ用セパレータの別の一例を模式的に示した分解斜視図である。（ｂ）は、（ａ）に模式的に示したＰＥＦＣ用セパレータの別の一例を上からみた平面図である。
【符号の説明】
１０ 単セル
１１ 固体高分子電解質膜
１２ 空気極
１３ 燃料極
２０、３０、４０ ＰＥＦＣ用セパレータ
２１、３１、４１、５１ 燃料ガス溝
２２、３２、４２、５２ 空気溝
２３、３３、４３、５３、５４ 燃料ガス孔
２４、３４、４４、５５、５６ 空気孔
４９ 第一の板状部材
５０ 第二の板状部材
５７ 冷却水溝
５８、５９ 冷却水孔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrophilic porous carbon material that can be suitably used for a polymer electrolyte fuel cell separator, a method for producing a hydrophilic porous carbon material, and a polymer electrolyte fuel cell separator using the same. About.
[0002]
[Prior art]
In recent years, development of a polymer electrolyte fuel cell (hereinafter also referred to as PEFC) using a proton conductive solid polymer membrane as an electrolyte has been advanced. PEFC is excellent in that the electrolyte is solid, so that the electrolyte does not scatter, it is resistant to vibration and has low noise, and the differential pressure operation and pressurization operation of the fuel electrode and the air electrode are easy. In addition, since PEFC operates at a temperature as low as about 80 to 100 ° C. among fuel cells, the short start-up time, and the use of inexpensive materials such as resin can prevent the practical use of fuel cells. It is also excellent in that it is easy to solve the problem of cost, and high power density can be obtained despite operating at a low temperature.
[0003]
The basic structure and operating principle of such a PEFC is as follows.
FIG. 1 is an exploded perspective view schematically showing the structure of a single cell constituting a PEFC. As shown in FIG. 1, in the PEFC single cell 10, the air electrode 12 (positive electrode) and the fuel electrode 13 (negative electrode) are bonded to each other via the solid polymer electrolyte membrane 11, PEFC separators 20 and 30 are in contact with the outside of the air electrode 12 and the fuel electrode 13, respectively. The air electrode 12 and the fuel electrode 13 are composed of two layers, a catalyst layer and a porous support layer, in contact with the solid polymer electrolyte membrane 11 on the surface comprising the catalyst layer, and on the surface comprising the porous support layer, the PEFC separator 20, Contact 30.
An external load circuit is connected between the air electrode 12 and the fuel electrode 13 to extract electric power. However, since the potential difference (voltage) obtained from such a single cell 10 of PEFC is small, it is actually used. In this case, a stack is formed by stacking a plurality of single cells 10 of PEFC so that a large potential difference (voltage) can be obtained.
[0004]
In such a PEFC, the PEFC separators 20 and 30 serve as a flow path for supplying hydrogen as a fuel for the PEFC to the fuel electrode 13 and oxygen to the air electrode 12 and to maintain the strength of the cell. have.
Therefore, fuel gas holes 23 and 33 for supplying and discharging fuel gas and air holes 24 and 34 for supplying and discharging air penetrate the PEFC separators 20 and 30 through all cells. The fuel gas grooves 21 and 31 connected to the fuel gas holes 23 and 33 are provided on the surface in contact with the fuel electrode 13, and the air holes 24 and 34 are connected to the surface in contact with the air electrode 12. Air grooves 22 and 32 are provided.
In the PEFC separators 20 and 30, the fuel gas and air (oxygen) made of hydrogen or a substance that easily generates hydrogen pass through the fuel gas holes 23 and 33 and the air holes 24 and 34, and the fuel gas grooves 21, 31 and 31 of each cell. The fuel gas and air after being continuously supplied to the air grooves 22 and 32, and the used fuel gas and air from the fuel gas grooves 21 and 31 and the air grooves 22 and 32 of each cell, are connected to the fuel gas holes 23 and 33 and the air holes 24 and 34, respectively. It is discharged continuously through.
Such PEFC separators 20 and 30 require high airtightness so that the fuel gas and air supplied to the grooves provided on both sides are not mixed. Normally, the PEFC separators 20 and 30 are airtight. It is composed of a highly carbon-based material or metal-based material.
[0005]
In PEFC, when fuel gas is supplied to the fuel electrode 13 and air is supplied to the air electrode 12, the reaction shown in the following reaction formula (1) occurs in the fuel electrode 13, and the following reaction formula ( The reaction shown in 2) occurs.
As a result, the reaction shown in the following reaction formula (3) occurs in the entire PEFC.
[0006]
2H ₂ → 4H ⁺ + 4e ⁻ ... (1)
[0007]
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O ... (2)
[0008]
2H ₂ + O ₂ → 2H ₂ O ... (3)
[0009]
Thus, in the PEFC, electrons (4e) are produced by the reaction represented by the reaction formula (1) at the fuel electrode 13. ⁻ When the electrons move to the air electrode 12 via the external load circuit, work performed in the external load circuit is taken out as electric power.
At the same time, in PEFC, hydrogen ions (4H) are produced in the fuel electrode 13 by the reaction represented by the reaction formula (1). ⁺ The hydrogen ions move to the air electrode 12 via the solid polymer electrolyte membrane 11 and react with oxygen. As a result, in PEFC, as shown in the above reaction formulas (2) and (3), hydrogen and oxygen react with power generation, and water is generated in the air electrode 12.
[0010]
Here, in order to smoothly move the hydrogen ions in the solid polymer electrolyte membrane 11, it is important that the solid polymer electrolyte membrane 11 and the fuel electrode 13 hold sufficient moisture. The fuel gas is moistened to supply moisture to the solid polymer electrolyte membrane 11. However, from the viewpoints of system simplification and energy efficiency, there has been an increasing demand to operate the PEFC without a humidifier. Further, as PEFC increases in power, water removal from the fuel electrode 13 side (electroosmosis phenomenon) accompanying the movement of hydrogen ions occurs, and the solid polymer electrolyte membrane 11 on the fuel electrode 13 side in particular dries. As a result of the increase in electrical resistance, there is a problem that the output density of PEFC is reduced.
[0011]
On the other hand, the moisture generated in the air electrode 12 is considered to be used for humidifying the fuel gas supplied to the adjacent cell without being discharged outside the cell as much as possible through the PEFC separators 20 and 30. Has been.
However, the PEFC separators 20 and 30 need to have high airtightness so that the fuel gas and the air supplied to the grooves provided on both sides are not mixed, as described above, in addition to the function of allowing moisture to permeate. Therefore, contradictory functions were required.
[0012]
Therefore, it has been studied that the PEFC separators 20 and 30 are made of a porous material (for example, see Patent Document 1). In the PEFC separators 20 and 30 formed of the porous material, the water generated in the air electrode 12 fills the porous material, so that the fuel gas supplied to the adjacent cells can be humidified and on both sides. The fuel gas and air supplied to the groove provided are prevented from permeating and mixing.
[0013]
[Patent Document 1]
JP-A-6-231793
[0014]
[Problems to be solved by the invention]
However, the carbon-based material that normally constitutes the PEFC separators 20 and 30 is not sufficiently hydrophilic, so even if it is porous, moisture hardly penetrates, and the moisture can be smoothly transferred from the air electrode to the fuel electrode. There was a problem of not being able to
[0015]
In view of the above problems, the present invention provides a hydrophilic porous carbon material that can be suitably used for the production of a separator for a polymer electrolyte fuel cell, a method for producing a hydrophilic porous carbon material, and a solid using the same An object of the present invention is to provide a polymer fuel cell separator.
[0016]
[Means for Solving the Problems]
The first aspect of the present invention is a hydrophilic porous carbon material obtained by oxidizing a porous carbon material, and 0.02 ml of pure water on the surface of a 5 mm thick plate-shaped test piece dried at 120 ° C. for 1 hour. It is a hydrophilic porous carbon material characterized in that 0.02 ml of the pure water permeates within 5 minutes in a water permeability evaluation test in which water is dropped.
[0017]
The second present invention is a hydrophilic porous carbon material in which a hydrophilic substance is formed on the surface of the porous carbon material and inside the pores, and is a plate-shaped test piece having a thickness of 5 mm dried at 120 ° C. for 1 hour. In a water permeability evaluation test in which 0.02 ml of pure water is dropped on the surface of the water, all the 0.02 ml of pure water permeates within 5 minutes.
[0018]
The third aspect of the present invention is a hydrophilic porous carbon material obtained by uniaxial molding or CIP molding of a mixture containing graphite powder or carbon powder and a hydrophilic substance, and has a thickness of 5 mm dried at 120 ° C. for 1 hour. In a water permeability evaluation test in which 0.02 ml of pure water is dropped on the surface of the plate-shaped test piece, 0.02 ml of the pure water penetrates all within 5 minutes. .
[0019]
DETAILED DESCRIPTION OF THE INVENTION
First, the hydrophilic porous carbon material of the first present invention will be described.
The hydrophilic porous carbon material according to the first aspect of the present invention is a hydrophilic porous carbon material obtained by oxidizing a porous carbon material, and is a plate-shaped test piece having a thickness of 5 mm dried at 120 ° C. for 1 hour. In a water permeability evaluation test in which 0.02 ml of pure water is dropped on the surface, 0.02 ml of the pure water permeates all within 5 minutes.
[0020]
The hydrophilic porous carbon material of the first aspect of the present invention is a water permeability evaluation test in which 0.02 ml of pure water is dropped on the surface of a plate-like test piece having a thickness of 5 mm dried at 120 ° C. for 1 hour. All 0.02 ml penetrates within 5 minutes. In addition, it has been determined that all the pure water has permeated, because the pure water droplet interface cannot be visually confirmed on the surface of the plate-shaped test piece. Further, when 5 minutes have elapsed, the water-absorbing paper piece may be lightly brought into contact with the surface of the test piece and water may not be attached to the paper piece.
[0021]
The hydrophilic porous carbon material of the first aspect of the present invention has water permeability that allows all 0.02 ml of pure water to permeate within 5 minutes in the above water permeability evaluation test, and is therefore used as a separator for PEFC. The fuel gas supplied to the adjacent cells can be sufficiently humidified by the moisture generated at the air electrode, and the moisture flowing in the PEFC separator can be sufficiently retained. It is possible to shield the fuel gas flowing on the other surface from mixing.
[0022]
The plate-shaped test piece used for the water permeability evaluation test has a thickness of 5 mm. It is because the total pore volume of a plate-shaped test piece may be smaller than the volume of 0.02 ml of pure water as it is less than 5 mm. On the other hand, if it exceeds 5 mm, the amount of pores in the plate-shaped test piece increases, which affects the measured value. The shape of the plate-shaped test piece and the area of the surface on which pure water is dropped are not particularly limited as long as the total pore volume of the plate-shaped test piece is larger than the volume of pure water 0.02 ml. .
[0023]
In the water permeability evaluation test, as a pretreatment, the plate test piece is dried at 120 ° C. for 1 hour. The purpose of the pretreatment is to remove moisture from the plate-shaped test piece before dropping pure water in order to improve the reproducibility of the evaluation test.
[0024]
The method for dropping 0.02 ml of pure water onto the surface of the plate-shaped test piece in the water permeability evaluation test is not particularly limited as long as pure water can be dropped in the form of droplets. And the like.
[0025]
The preferable lower limit of the open porosity in the hydrophilic porous carbon material of the first present invention is 10%, and the preferable upper limit is 30%. When it is less than 10%, when used in a PEFC separator, the fuel gas supplied to the adjacent cell may not be sufficiently humidified by the moisture generated in the air electrode. If it exceeds 30%, it will not meet the required strength when used in a PEFC separator, or air flowing on one side of the PEFC separator and fuel gas flowing on the other side will be mixed Sometimes
In the present specification, the open porosity means the ratio of the total volume of pores communicating with the outside of the porous body to the apparent volume of the porous body.
[0026]
The minimum with a preferable average pore radius by the mercury intrusion method in the hydrophilic porous carbon material of 1st this invention is 0.5 micrometer, and a preferable upper limit is 2 micrometers. When it is less than 0.5 μm, when used in a PEFC separator, the fuel gas supplied to the adjacent cell may not be sufficiently humidified by the moisture generated in the air electrode. If it exceeds 2 μm, the air flowing on one surface of the PEFC separator and the fuel gas flowing on the other surface may be mixed.
[0027]
The preferred lower limit of the air permeability in the hydrophilic porous carbon material of the first present invention is 0.2 cm. ² / S, and the preferred upper limit is 3 cm. ² / S. 0.2cm ² When it is less than / s, when used in a PEFC separator, the fuel gas supplied to the adjacent cell may not be sufficiently humidified by the moisture generated in the air electrode. 3cm ² If it exceeds / s, when used in a PEFC separator, the required strength is not satisfied, or air flowing on one side of the PEFC separator and fuel gas flowing on the other side are mixed. Sometimes
The air permeability is the volume of permeated gas (cm ³ Atm) × sample thickness (cm) / (sample area (cm ² ) × permeated gas pressure difference (atm) × time (seconds)).
[0028]
The hydrophilic porous carbon material of the first aspect of the present invention is obtained by oxidizing a porous carbon material.
When the porous carbon material is oxidized, CH in the porous carbon material is obtained. ₃ The terminal part consisting of groups etc. is oxidized, and COOH groups and CH ₂ Since a hydrophilic functional group such as an OH group is formed, the surface of the porous carbon material and the pore surface, which are inherently hydrophobic, become hydrophilic.
[0029]
The porous carbon material is not particularly limited, but is preferably made of graphite, more preferably isotropic graphite.
The method for producing the porous carbon material is not particularly limited. For example, a method in which a mixture in which carbon powder and a binder resin are mixed is molded, and the obtained molded body is fired and graphitized, graphite powder, and binder. The method etc. which shape | mold the mixture which mixed resin etc. are mentioned.
[0030]
The minimum with the preferable average particle diameter of the said carbon powder and graphite powder is 15 micrometers, and a preferable upper limit is 50 micrometers. If it is less than 15 μm, the open porosity in the hydrophilic porous carbon material of the first present invention may become too small, and if it exceeds 50 μm, the open pores in the hydrophilic porous carbon material of the first present invention The rate can be too large.
[0031]
It does not specifically limit as said binder resin, For example, a phenol resin, furfuryl alcohol, polyvinyl alcohol, furan resin etc. are mentioned.
[0032]
The oxidation treatment of the porous carbon material is performed by a method and conditions that can obtain desired water permeability according to the material of the porous carbon material, the degree of graphitization, the pore distribution, and the like.
The oxidation treatment is not particularly limited as long as a hydrophilic functional group can be formed on the porous carbon material. For example, wet oxidation, plasma treatment, electrolytic oxidation, air oxidation and the like are preferable.
[0033]
The wet oxidation is not particularly limited. For example, nitric acid, an alkaline solution in which ozone is dissolved, a dichromate sulfuric acid solution, a dichromate phosphoric acid solution, a potassium iodate phosphoric acid solution, or a potassium permanganate sulfuric acid. A method of immersing the porous carbon material in an oxidant solution such as a solution (Humer reagent) or hydrofluoric acid and heating it is preferably used.
[0034]
Although it does not specifically limit as said plasma processing, For example, oxygen plasma processing, electrolytic plasma processing, fluorine plasma processing etc. are used suitably.
The plasma treatment is performed using, for example, a plasma generator in which two opposing electrode plates connected to a high-frequency generating power source are installed in a reaction vessel whose pressure can be reduced by a vacuum pump. Alternatively, the inside of the reaction vessel is adjusted to a pressure of 1000 Pa or less while flowing a gas such as fluorine, and high-frequency power is applied to generate low-temperature plasma, and the low-temperature plasma is brought into contact with the porous carbon material.
The preferable lower limit of the amount of high frequency power applied when generating the low temperature plasma is 200 W, and the preferable upper limit is 1000 W.
The preferable lower limit of the frequency of the high frequency power applied when generating the low temperature plasma is 10 kHz, and the preferable upper limit is 1000 MHz.
The preferable lower limit of the application time of the high frequency power applied when generating the low temperature plasma is 1 minute, and the preferable upper limit is 20 minutes.
[0035]
The hydrophilic porous carbon material of the first aspect of the present invention is made hydrophilic by oxidizing a porous carbon material that is inherently hydrophobic, and is excellent in water permeability.
Examples of the use of the hydrophilic porous carbon material of the first present invention include constituent materials such as a PEFC separator and a nozzle for discharging water or an aqueous solution. Especially, it can use suitably as a constituent material of the separator for PEFC.
[0036]
Since the separator for PEFC using the hydrophilic porous carbon material of the first aspect of the present invention is made of a hydrophilic constituent material, it is easy to move moisture in the separator. Therefore, in the separator for PEFC using the hydrophilic porous carbon material according to the first aspect of the present invention, the ratio of the moisture generated at the air electrode that is released to the outside of the cell together with the exhaust gas is reduced. Since the ratio supplied to the electrode can be increased, even when the PEFC is operated at a high output, the solid polymer electrolyte membrane does not dry and the electrical resistance does not increase, and the decrease in the output of the PEFC can be suppressed. it can. Further, even if the pore volume in the separator is reduced, it is possible to smoothly move the moisture in the separator, so that a high-strength PEFC separator that is not damaged by gas pressure can be obtained.
A separator for a polymer electrolyte fuel cell using the hydrophilic porous carbon material of the first aspect of the present invention is also one aspect of the present invention.
[0037]
Next, the structure of the separator for PEFC using the hydrophilic porous carbon material of the first present invention will be described with reference to FIGS.
FIG. 2 (a) is a cross-sectional view schematically showing an example of a PEFC separator using the hydrophilic porous carbon material of the first present invention. FIG. 2B is a plan view of an example of the PEFC separator schematically shown in FIG.
[0038]
As shown in FIG. 2, the PEFC separator 40 using the hydrophilic porous carbon material of the first aspect of the present invention has a plate shape, and a fuel gas for supplying and discharging fuel gas to and from the outer periphery. A hole 43 and an air hole 44 for supplying and discharging air are provided, and a fuel gas groove 41 connected to the fuel gas hole 43 is provided in the center of the surface in contact with the fuel electrode. An air groove 42 connected to the air hole 44 is provided in the center portion of the surface in contact with the air hole 44.
[0039]
The outer peripheral portion of the PEFC separator 40 using the hydrophilic porous carbon material of the first aspect of the present invention is made of a highly airtight material, and is provided with fuel gas holes 43 and air holes 44.
The material having high airtightness is not particularly limited, and examples thereof include carbon-based materials and metal-based materials. Of these, the hydrophilic porous carbon material of the first aspect of the present invention or the pores of the porous carbon material are preferably filled with a resin such as a phenol resin or an epoxy resin. Thereby, since the outer peripheral part and center part of the separator 40 for PEFC which uses the hydrophilic porous carbon material of 1st this invention can be produced integrally, these are produced separately and bonded together. This eliminates the need for such work and simplifies the process.
[0040]
The central portion of the separator for PEFC 40 using the hydrophilic porous carbon material of the first invention is composed of the hydrophilic porous carbon material of the first invention, and on the surface in contact with the fuel electrode, A fuel gas groove 41 connected to the fuel gas hole 43 for supplying and discharging the fuel gas is provided, and an air groove 42 connected to the air hole 44 for supplying and discharging air is provided on the surface in contact with the air electrode. It has been.
[0041]
The fuel gas groove 41 is provided in order to secure a cavity serving as a fuel gas flow path when the PEFC separator 40 is brought into contact with the fuel electrode on the surface having the fuel gas groove 41. Thereby, the fuel gas can be supplied to the fuel electrode through the fuel gas groove 41 and the exhaust gas after use can be discharged.
[0042]
The number of fuel gas grooves 41 is not particularly limited, but a plurality of fuel gas grooves 41 are preferably provided. This is because the contact area between the fuel electrode and the fuel gas is sufficiently secured, and the strength of the PEFC separator 40 is not deformed or damaged even in a stack structure in which a plurality of single cells are stacked.
When a plurality of fuel gas grooves 41 are provided, the fuel gas grooves 41 are preferably provided in parallel to each other. This is to ensure the strength required for the PEFC separator 40 while uniformly supplying the fuel gas to the fuel electrode.
[0043]
The cross-sectional shape of the fuel gas groove 41 is not particularly limited, and examples thereof include a concave shape.
The width of the fuel gas groove 41 is not particularly limited, and is determined according to the number of the fuel gas grooves 41, the output density of the PEFC using the hydrophilic porous carbon material of the first present invention, and the like.
The depth of the fuel gas groove 41 is not particularly limited, but is preferably less than half the thickness of the PEFC separator 40 using the hydrophilic porous carbon material of the first aspect of the present invention. This is to ensure the strength required for the PEFC separator 40.
[0044]
The air groove 42 is provided in order to secure a cavity serving as an air flow path when the PEFC separator 40 is brought into contact with the air electrode on the surface having the air groove 42. Thus, air can be supplied to the air electrode through the air groove 42 and exhaust gas after use can be discharged.
[0045]
The number of air grooves 42 is not particularly limited, but a plurality of air grooves 42 are preferably provided. This is to ensure the strength required for the PEFC separator 40 while ensuring a sufficient contact area between the air electrode and air.
Further, when a plurality of air grooves 42 are provided, the air grooves 42 are preferably provided in parallel to each other. This is to ensure the strength required for the PEFC separator 40 while uniformly supplying air to the air electrode. Especially, it is preferable that the air groove 42 and the fuel gas groove 41 are provided in directions orthogonal to each other on the upper and lower surfaces of the PEFC separator 40. It is effective in securing the strength required for the PEFC separator 40, and pipes connected to the fuel gas holes 43 and the air holes 44 are provided when a stack structure in which a plurality of single cells are stacked is provided. It is easy to do.
[0046]
The cross-sectional shape of the air groove 42 is not particularly limited, and examples thereof include a concave shape. The width of the air groove 42 is not particularly limited, and is determined according to the number of the air grooves 42, the output density of the PEFC using the hydrophilic porous carbon material of the first present invention, and the like.
The depth of the air groove 42 is not particularly limited, but is preferably less than half of the thickness of the PEFC separator 40 using the hydrophilic porous carbon material of the first invention. This is to ensure the strength required for the PEFC separator 40.
[0047]
The thickness of the PEFC separator 40 using the hydrophilic porous carbon material of the first invention is not particularly limited, but is required for the PEFC separator 40 to reduce the thickness and weight of a single cell. It is preferable that it is thin as long as it can ensure sufficient strength.
The size of the PEFC separator 40 using the hydrophilic porous carbon material of the first present invention is preferably a size that matches the size of a single cell, and usually includes a fuel electrode and an air electrode. Make them the same size.
The PEFC separator 40 using the hydrophilic porous carbon material according to the first aspect of the present invention usually has a convex portion that partitions the fuel gas groove 41 or the air groove 42 provided in the center portion, and an outer peripheral portion. It is preferable to make the thickness uniform and contact with and adhere to the fuel electrode and air electrode, but when the fuel electrode, air electrode and solid polymer electrolyte membrane are made small, the thickness of the outer peripheral portion is set at the central portion. It may be thicker than the thickness.
[0048]
FIG. 3 (a) is an exploded perspective view schematically showing another example of the PEFC separator using the hydrophilic porous carbon material of the first present invention. FIG. 3B is a plan view of another example of the PEFC separator schematically shown in FIG.
As shown in FIG. 3, the PEFC separator using the hydrophilic porous carbon material of the first aspect of the present invention has the first plate-like shape with the fuel gas groove 51 and the air groove 52 facing outward, respectively. The member 49 and the second plate member 50 may have a structure in which the member 49 and the second plate member 50 are bonded together without any gap.
[0049]
The first plate-like member 49 has a fuel gas hole 53 for supplying and discharging fuel gas, an air hole 55 for supplying and discharging air, and a cooling water supply and discharge to the outer periphery. A cooling water hole 58 is provided, and a fuel gas groove 51 connected to the fuel gas hole 53 is provided at the center of the surface on the side in contact with the fuel electrode.
The second plate-like member 50 is provided with a fuel gas hole 54, an air hole 56, and a cooling water hole 59 in the outer peripheral portion, and the air hole 56 and the central portion of the surface in contact with the air electrode. A connecting air groove 52 is provided.
Further, the first plate-like member 49 and / or the second plate-like member 50 is provided with a cooling water groove 57 for circulating the cooling water connected to the cooling water holes 58 and 59 in the central portion of the bonding surface. It has been. The shape of the cooling water groove 57 is not particularly limited, but it is preferable that the cooling water groove 57 is uniformly formed in the entire center portion of the bonding surface as long as the strength required for the PEFC separator can be secured.
The PEFC separator having the above-mentioned bonded structure has a fuel gas groove on one side and an air on the other side, except that a cooling water groove 57 for circulating cooling water is provided therein. This is the same as the above-mentioned integrated PEFC separator having a groove.
[0050]
In the PEFC using the PEFC separator having such a bonded structure, the cooling water can be circulated in the voids inside the PEFC separator, so that the PEFC separator can absorb moisture reliably and in large quantities, and the fuel gas and Air humidification can be performed effectively, and the heat dissipation capability of PEFC can also be improved.
[0051]
Moreover, the separator for PEFC using the hydrophilic porous carbon material of the first aspect of the present invention has cooling water at the center of the bonding surface of the first plate member 49 and / or the second plate member 50. Instead of providing the groove 57, a cooling member may be interposed between the first plate member 49 and the second plate member 50, and a cooling water groove may be provided in the central portion of the cooling member.
In this case, the cooling member is provided with a fuel gas hole, an air hole, and a cooling water hole in the outer peripheral portion, and a cooling water groove for circulating the cooling water connected to the cooling water hole is provided in the central portion. It is done.
[0052]
Next, the manufacturing method of the separator for PEFC which uses the hydrophilic porous carbon material of 1st this invention is demonstrated.
(1) A porous carbon material having a desired PEFC separator shape or a central shape of the desired PEFC separator is produced by the method for producing a porous carbon material described above. The shape of the porous carbon material can be adjusted by adjusting the shape of the molding die when the porous carbon material is molded, and further performing cutting, drilling, laser processing, etc. as necessary. . Moreover, when producing the separator for PEFC which uses the hydrophilic porous carbon material of 1st this invention which consists of a bonding structure, it bonds together, after producing the several porous carbon material used as a structural member. .
(2) The above-described oxidation treatment is performed on the obtained porous carbon material.
(3) Only the outer peripheral portion of the porous carbon material after the oxidation treatment is impregnated with resin and cured. Alternatively, when only the central portion of the PEFC separator is made of a porous carbon material, the outer peripheral portion is formed by bonding a resin plate or a metal plate with an adhesive or the like.
As described above, the PEFC separator using the hydrophilic porous carbon material of the first invention can be manufactured by the steps (1) to (3).
[0053]
Next, the hydrophilic porous carbon material of the second invention will be described.
The hydrophilic porous carbon material of the second aspect of the present invention is a hydrophilic porous carbon material in which a hydrophilic substance is formed on the surface of the porous carbon material and inside the pores, and is a plate-shaped test piece having a thickness of 5 mm. In the water permeability evaluation test in which 0.02 ml of pure water is dropped on the surface of the plate-shaped test piece after drying at 120 ° C. for 1 hour, all 0.02 ml of the pure water penetrates within 5 minutes. It is characterized by.
[0054]
The hydrophilic porous carbon material of the second aspect of the present invention is a water permeability evaluation test in which 0.02 ml of pure water is dropped on the surface of a plate-like test piece having a thickness of 5 mm dried at 120 ° C. for 1 hour. All 0.02 ml penetrates within 5 minutes. The method for the water permeability evaluation test is the same as the method for the water permeability evaluation test in the hydrophilic porous carbon material of the first aspect of the present invention, and thus the description thereof is omitted.
[0055]
The hydrophilic porous carbon material of the second aspect of the present invention has a water permeability capable of permeating all 0.02 ml of pure water within 5 minutes in the water permeability evaluation test, and is therefore used for a PEFC separator. The fuel gas supplied to the adjacent cells can be sufficiently humidified by the moisture generated at the air electrode, and the moisture flowing in the PEFC separator can be sufficiently retained. It is possible to shield the fuel gas flowing on the other surface from mixing.
[0056]
The preferable lower limit of the open porosity in the hydrophilic porous carbon material of the second invention is 10%, and the preferable upper limit is 30%. When it is less than 10%, when used in a PEFC separator, the fuel gas supplied to the adjacent cell may not be sufficiently humidified by the moisture generated in the air electrode. If it exceeds 30%, it will not meet the required strength when used in a PEFC separator, or air flowing on one side of the PEFC separator and fuel gas flowing on the other side will be mixed Sometimes
[0057]
The preferable lower limit of the average pore radius by the mercury intrusion method in the hydrophilic porous carbon material of the second present invention is 0.5 μm, and the preferable upper limit is 2 μm. When it is less than 0.5 μm, when used in a PEFC separator, the fuel gas supplied to the adjacent cell may not be sufficiently humidified by the moisture generated in the air electrode. If it exceeds 2 μm, the air flowing on one surface of the PEFC separator and the fuel gas flowing on the other surface may be mixed.
[0058]
The preferred lower limit of the air permeability in the hydrophilic porous carbon material of the second invention is 0.2 cm. ² / S, and the preferred upper limit is 3 cm. ² / S. 0.2cm ² When it is less than / s, when used in a PEFC separator, the fuel gas supplied to the adjacent cell may not be sufficiently humidified by the moisture generated in the air electrode. 3cm ² If it exceeds / s, when used in a PEFC separator, the required strength is not satisfied, or air flowing on one side of the PEFC separator and fuel gas flowing on the other side are mixed. Sometimes
[0059]
The hydrophilic porous carbon material of the second aspect of the present invention is obtained by forming a hydrophilic substance on the surface of the porous carbon material and inside the pores.
By forming a hydrophilic substance on the surface of the porous carbon material and inside the pores, the surface of the porous carbon material and the inside of the pores, which are inherently hydrophobic, become hydrophilic.
[0060]
The porous carbon material is not particularly limited, but is preferably made of graphite, more preferably isotropic graphite.
It does not specifically limit as a method to manufacture the said porous carbon material, For example, manufacturing similarly to the porous carbon material used for the hydrophilic porous carbon material of 1st this invention is preferable.
[0061]
The hydrophilic substance formed on the surface of the porous carbon material and inside the pores is not particularly limited, but for example, polyvinyl alcohol, ion exchange resin, gelled solidified water glass, etc. are preferable, and from within the porous carbon material In order to prevent elution, it is preferably a gel.
The polyvinyl alcohol is preferably one having a high degree of saponification in order to prevent dissolution in water and elution from the porous carbon material.
The ion exchange resin is a resin having a three-dimensional network structure in which an ion exchange group is held by a covalent bond. Although it does not specifically limit as said ion exchange group, For example, -SO which is a strongly acidic group ₃ H, strongly basic group —CH ₂ N ⁺ (CH ₃ ) ₂ (C ₂ H ₄ OH) and the like are preferably used.
The gelled solidified product of water glass is water glass (Na ₂ O · nSiO ₂ (N = 2 to 4)) by adding an acid or dissipating moisture from water glass.
[0062]
The hydrophilic substance is formed on the surface of the porous carbon material and inside the pores by a method and conditions that provide desired water permeability.
The method for forming a hydrophilic substance on the surface of the porous carbon material and inside the pores is not particularly limited. For example, a method of removing the solvent after impregnating the porous carbon material with a solution of the hydrophilic substance, hydrophilicity A method of forming a hydrophilic substance inside the porous carbon material after the porous carbon material is impregnated with the monomer of the substance or a solution thereof, an intermediate monomer of the hydrophilic substance or the method thereof A method in which a porous carbon material is impregnated with a solution and then polymerized to form an intermediate of the hydrophilic substance inside the porous carbon material, and further the intermediate of the hydrophilic substance is converted to the hydrophilic substance And a method of solidifying after impregnating a porous carbon material with a liquid hydrophilic substance.
[0063]
First, a method for removing a solvent after impregnating a porous carbon material with a solution of a hydrophilic substance will be described.
The hydrophilic substance solution is not particularly limited as long as it dissolves the hydrophilic substance, but is preferably a low-viscosity liquid so that it can be impregnated to the deep part of the porous carbon material.
The method for impregnating the porous carbon material with the hydrophilic substance solution is not particularly limited, and examples thereof include injection and immersion.
The method for removing the solvent is not particularly limited, and examples thereof include heating.
[0064]
Next, a method of forming the hydrophilic substance inside the porous carbon material after the porous carbon material is impregnated with a monomer of the hydrophilic substance or a solution thereof will be described.
Although it does not specifically limit as the monomer of the said hydrophilic substance, or its solution, It is preferable that it is a low viscosity liquid so that it can be impregnated to the deep part of the said porous carbon material.
The method for impregnating the porous carbon material with the hydrophilic substance monomer or the solution thereof is not particularly limited, and examples thereof include injection and immersion. When the hydrophilic substance is a copolymer obtained by polymerizing two or more monomers, a mixture of two or more monomers or a solution thereof may be impregnated. You may impregnate a solution in order.
It does not specifically limit as a method of performing the said polymerization, For example, a heating etc. are mentioned.
[0065]
Next, the porous carbon material is impregnated with a hydrophilic substance intermediate monomer or solution thereof, and then polymerized to form the hydrophilic substance intermediate inside the porous carbon material, and A method for converting an intermediate of a hydrophilic substance into the hydrophilic substance will be described.
The intermediate monomer of the hydrophilic substance or a solution thereof is not particularly limited. For example, a methanol solution containing vinyl acetate and a compound having a plurality of vinyl groups such as divinylbenzene is preferably used. Moreover, the intermediate monomer of the hydrophilic substance or a solution thereof is preferably a low-viscosity liquid so that it can be impregnated to the deep part of the porous carbon material.
The method for impregnating the porous carbon material with the above-mentioned hydrophilic substance intermediate monomer or solution thereof is not particularly limited, and examples thereof include injection and immersion. When the intermediate of the hydrophilic substance is a copolymer obtained by polymerizing two or more monomers, a mixture of two or more monomers or a solution thereof may be impregnated. The body or its solution may be impregnated in sequence.
It does not specifically limit as a method of performing the said polymerization, For example, a heating etc. are mentioned.
A method for converting the intermediate of the hydrophilic substance into the hydrophilic substance is not particularly limited, and examples thereof include a polar group introduction reaction such as saponification.
[0066]
Next, a method for solidifying after impregnating a porous carbon material with a liquid hydrophilic substance will be described.
Although it does not specifically limit as said liquid hydrophilic substance, Water glass etc. are used suitably.
The method for impregnating the porous carbon material with the liquid hydrophilic substance is not particularly limited, and examples thereof include injection and immersion.
The method for solidifying the liquid hydrophilic substance is not particularly limited. For example, when water glass is used as the liquid hydrophilic substance, a method of adding an acid, a method of dissipating moisture from the water glass, etc. Is mentioned.
[0067]
Among the above-mentioned methods, the step of impregnating the porous carbon material with divinylbenzene and vinyl acetate, the porous carbon material is copolymerized with the divinylbenzene and the vinyl acetate in the impregnated state. The method for producing a hydrophilic porous carbon material having a step of forming a copolymer on the surface of the carbonaceous material and inside the pores and a step of saponifying the copolymer prevents elution from the porous carbon material. The gel-like hydrophilic substance can be suitably used because it can be formed on the surface of the porous carbon material and inside the pores by a simple method.
A method for producing the hydrophilic porous carbon material according to the second aspect of the present invention, in which a gel-like hydrophilic substance is formed on the surface of the porous carbon material and inside the pores, comprising divinylbenzene and vinyl acetate. In the porous carbon material, the divinylbenzene and vinyl acetate are copolymerized in the state of impregnation in the porous carbon material, and the copolymer is formed on the surface of the porous carbon material and inside the pores. A method for producing a hydrophilic porous carbon material having a step of forming saponification and a step of saponifying the copolymer is also one aspect of the present invention.
[0068]
The hydrophilic porous carbon material of the second aspect of the present invention is made hydrophilic by forming a hydrophilic substance on the surface and inside of the porous carbon material that is inherently hydrophobic, and is excellent in water permeability. .
Examples of the use of the hydrophilic porous carbon material of the second invention include constituent materials such as a PEFC separator, a nozzle for discharging water or an aqueous solution, and the like. Especially, it can use suitably as a constituent material of the separator for PEFC.
[0069]
Since the separator for PEFC using the hydrophilic porous carbon material of the second aspect of the present invention is made of a hydrophilic constituent material, it is easy to move moisture in the separator. Therefore, in the separator for PEFC using the hydrophilic porous carbon material of the second aspect of the present invention, the ratio of the moisture generated at the air electrode that is released to the outside of the cell together with the exhaust gas is reduced, and the fuel of the adjacent cell Since the ratio supplied to the electrode can be increased, even when the PEFC is operated at a high output, the solid polymer electrolyte membrane does not dry and the electrical resistance does not increase, and the decrease in the output of the PEFC can be suppressed. it can. Further, even if the pore volume in the separator is reduced, it is possible to smoothly move the moisture in the separator, so that a high-strength PEFC separator that is not damaged by gas pressure can be obtained.
Such a separator for a polymer electrolyte fuel cell using the hydrophilic porous carbon material of the second aspect of the present invention is also one aspect of the present invention.
[0070]
The separator for PEFC using the hydrophilic porous carbon material of the second aspect of the present invention has, as its constituent material, the hydrophilicity of the second aspect of the present invention instead of the hydrophilic porous carbon material of the first aspect of the present invention. Except for using a porous carbon material, it is the same as the separator for PEFC using the hydrophilic porous carbon material of the first aspect of the present invention, has the same structure, and can be manufactured by the same manufacturing method Therefore, the description thereof is omitted.
[0071]
Next, the hydrophilic porous carbon material of the third aspect of the present invention will be described.
The hydrophilic porous carbon material of the third aspect of the present invention is a hydrophilic porous carbon material obtained by uniaxial molding or CIP molding of graphite powder or a mixture containing carbon powder and a hydrophilic substance, and has a thickness of 5 mm. In a water permeability evaluation test in which 0.02 ml of pure water is dropped on the surface of the plate-shaped test piece after drying at 120 ° C. for 1 hour, 0.02 ml of the pure water is within 5 minutes. It is characterized by penetrating into all.
The uniaxial molding includes stamping molding.
[0072]
The hydrophilic porous carbon material of the third aspect of the present invention is a water permeability evaluation test in which 0.02 ml of pure water is dropped on the surface of a plate-like test piece having a thickness of 5 mm dried at 120 ° C. for 1 hour. All 0.02 ml penetrates within 5 minutes. The method for the water permeability evaluation test is the same as the method for the water permeability evaluation test in the hydrophilic porous carbon material of the first aspect of the present invention, and thus the description thereof is omitted.
[0073]
The hydrophilic porous carbon material of the third aspect of the present invention has a water permeability capable of permeating all 0.02 ml of pure water within 5 minutes in the above water permeability evaluation test, and is therefore used as a separator for PEFC. The fuel gas supplied to the adjacent cells can be sufficiently humidified by the moisture generated at the air electrode, and the moisture flowing in the PEFC separator can be sufficiently retained. It is possible to shield the fuel gas flowing on the other surface from mixing.
[0074]
The preferable lower limit of the open porosity in the hydrophilic porous carbon material of the third aspect of the present invention is 10%, and the preferable upper limit is 30%. When it is less than 10%, when used in a PEFC separator, the fuel gas supplied to the adjacent cell may not be sufficiently humidified by the moisture generated in the air electrode. If it exceeds 30%, it will not meet the required strength when used in a PEFC separator, or air flowing on one side of the PEFC separator and fuel gas flowing on the other side will be mixed Sometimes
[0075]
The minimum with a preferable average pore radius by the mercury intrusion method in the hydrophilic porous carbon material of 3rd this invention is 0.5 micrometer, and a preferable upper limit is 2 micrometers. When it is less than 0.5 μm, when used in a PEFC separator, the fuel gas supplied to the adjacent cell may not be sufficiently humidified by the moisture generated in the air electrode. If it exceeds 2 μm, the air flowing on one surface of the PEFC separator and the fuel gas flowing on the other surface may be mixed.
[0076]
The preferred lower limit of the air permeability in the hydrophilic porous carbon material of the third invention is 0.2 cm. ² / S, and the preferred upper limit is 3 cm. ² / S. 0.2cm ² When it is less than / s, when used in a PEFC separator, the fuel gas supplied to the adjacent cell may not be sufficiently humidified by the moisture generated in the air electrode. 3cm ² If it exceeds / s, when used in a PEFC separator, the required strength is not satisfied, or air flowing on one side of the PEFC separator and fuel gas flowing on the other side are mixed. Sometimes
[0077]
The hydrophilic porous carbon material of the third aspect of the present invention is obtained by uniaxial molding or CIP molding of graphite powder or a mixture containing carbon powder and a hydrophilic substance. By producing a porous carbon material by molding a mixture using a hydrophilic substance as a binder and graphite powder or carbon powder as a filler, a porous carbon material having a hydrophilic substance formed on the surface and inside is obtained. The surface of the porous carbon material that is inherently hydrophobic and the inside of the pores can be made hydrophilic.
[0078]
The minimum with a preferable average particle diameter of the said graphite powder and the said carbon powder is 15 micrometers, and a preferable upper limit is 50 micrometers. If it is less than 15 μm, the open porosity in the hydrophilic porous carbon material of the third invention may be too small, and if it exceeds 50 μm, the open pores in the hydrophilic porous carbon material of the third invention will be The rate can be too large.
[0079]
It does not specifically limit as a binder which consists of the said hydrophilic substance, For example, a phenol resin, furfuryl alcohol, polyvinyl alcohol, furan resin etc. are mentioned.
[0080]
The hydrophilic porous carbon material of the third aspect of the present invention is a porous material that is inherently hydrophobic by mixing a binder made of a hydrophilic substance with a filler made of graphite powder or carbon powder and uniaxially molding or CIP molding. A hydrophilic substance is formed on the surface and inside of the carbon material to make it hydrophilic, and has excellent water permeability.
Examples of the use of the hydrophilic porous carbon material of the third aspect of the present invention include constituent materials such as a PEFC separator and a nozzle for discharging water or an aqueous solution. Especially, it can use suitably as a constituent material of the separator for PEFC.
Note that CIP molding can employ either a wet method or a dry method.
[0081]
Since the separator for PEFC using the hydrophilic porous carbon material of the third aspect of the present invention is made of a hydrophilic constituent material, the movement of moisture in the separator is easy. Therefore, in the separator for PEFC using the hydrophilic porous carbon material according to the third aspect of the present invention, the ratio of the moisture generated at the air electrode that is released to the outside of the cell together with the exhaust gas is reduced. Since the ratio supplied to the electrode can be increased, even when the PEFC is operated at a high output, the solid polymer electrolyte membrane does not dry and the electrical resistance does not increase, and the decrease in the output of the PEFC can be suppressed. it can. Further, even if the pore volume in the separator is reduced, it is possible to smoothly move the moisture in the separator, so that a high-strength PEFC separator that is not damaged by gas pressure can be obtained.
A separator for a polymer electrolyte fuel cell using such a hydrophilic porous carbon material of the present invention is also one aspect of the present invention.
[0082]
The separator for PEFC using the hydrophilic porous carbon material of the third aspect of the invention has, as its constituent material, the hydrophilicity of the third aspect of the invention instead of the hydrophilic porous carbon material of the first aspect of the invention. Except for using a porous carbon material, it is the same as the separator for PEFC using the hydrophilic porous carbon material of the first aspect of the present invention, has the same structure, and can be manufactured by the same manufacturing method Therefore, the description thereof is omitted.
[0083]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited only to these examples.
[0084]
(Example 1)
(1) A plate-like porous graphite plate made of isotropic graphite having an open porosity of 15% (product of Ibiden, ET-10) having a length of 35 mm, a width of 35 mm and a thickness of 5 mm in nitric acid having a concentration of 61% for 2 hours After the oxidation treatment, it was washed and dried at a temperature of 120 ° C. for 1 hour.
The shape of the resulting porous graphite plate after the oxidation treatment was processed into a flat PEFC separator having a thickness of 1 mm.
Subsequently, the outer peripheral portion of the porous graphite plate after shape processing was impregnated with resin, and this resin was heated and cured to produce a PEFC separator.
[0085]
(2) Carbon as a porous support layer of the fuel electrode or the air electrode on each side of the membrane / electrode assembly formed by joining the catalyst layer of the fuel electrode, the solid polymer electrolyte membrane, and the catalyst layer of the air electrode Paper and the PEFC separator prepared in (1) were sequentially stacked and sandwiched at a pressure of 0.5 MPa to prepare a PEFC consisting of one cell. Subsequently, two PEFCs composed of one cell were combined so that there was one separator between cells, and a PEFC composed of two cells was produced.
[0086]
(Example 2)
When oxidizing a flat porous graphite plate having a length of 35 mm, a width of 35 mm, and a thickness of 5 mm made of isotropic graphite (ET-10) having an open porosity of 15% in nitric acid with a concentration of 61% A PEFC consisting of 2 cells was produced in the same manner as in Example 1 except that the treatment time was 1 hour.
[0087]
(Example 3)
(1) An isotropic graphite having an open porosity of 15% (product of Ibiden, ET-10) was processed into a flat plate having a length of 35 mm, a width of 35 mm, and a thickness of 5 mm to prepare a porous graphite plate.
After dissolving 150 g of vinyl acetate and 20 g of divinylbenzene in 1000 g of methanol, a solution prepared by dissolving 1 g of azobisisobutyronitrile in 20 g of methanol was further added.
The mixed solution thus prepared was poured into a vacuum vessel in which the porous graphite plate was placed, and then the inside of the vacuum vessel was opened to atmospheric pressure, and the mixed solution was infiltrated into the porous graphite plate.
Next, the porous graphite plate and the mixed solution are transferred to a container attached with a condenser, and the interior of the container is heated to 60 to 63 ° C. while stirring, whereby the polymerization represented by the following reaction formula (4) is performed. Went for hours.
[0088]
[Chemical 1]

[0089]
Then, after returning to room temperature, 25 ml of 40% NaOH aqueous solution was added, and the mixture was allowed to stand for 1 hour for saponification represented by the following formula (5).
[0090]
[Chemical formula 2]

[0091]
Further, it was repeatedly washed with methanol and dried to obtain a porous graphite plate in which a gel-like hydrophilic substance was formed on the surface and inside the pores.
The shape of the obtained hydrophilic porous graphite plate was processed into a flat PEFC separator having a thickness of 1 mm.
Subsequently, the outer peripheral portion of the porous graphite plate after shape processing was impregnated with resin, and this resin was heated and cured to produce a PEFC separator.
[0092]
(2) A PEFC composed of 2 cells was produced in the same manner as in Example 1 except that the PEFC separator produced in (1) was used.
[0093]
(Example 4)
A PEFC separator was produced in the same manner as in Example 3 except that the polymerization time represented by the reaction formula (4) was 3 hours.
[0094]
(Example 5)
(1) A porous graphite obtained by heating a mixture containing 70% by weight of graphite powder having an average particle diameter of 20 μm and 30% by weight of nylon 66 as a binder of a hydrophilic substance to 200 ° C. and embossing the mixture. The shape of the material was processed into a flat PEFC separator with a thickness of 1 mm.
Subsequently, the outer peripheral portion of the porous graphite plate after shape processing was impregnated with resin, and this resin was heated and cured to produce a PEFC separator.
[0095]
(2) A PEFC composed of 2 cells was produced in the same manner as in Example 1 except that the PEFC separator produced in (1) was used.
[0096]
(Comparative Example 1)
(1) The shape of isotropic graphite having an open porosity of 15% (product of Ibiden, ET-10) was processed to prepare a porous graphite plate having the shape of a flat plate-like PEFC separator having a thickness of 1 mm.
Subsequently, the outer peripheral portion of the porous graphite plate was impregnated with resin, and the resin was heated and cured to produce a PEFC separator.
(2) A PEFC composed of 2 cells was produced in the same manner as in Example 1 except that the PEFC separator produced in (1) was used.
[0097]
(Comparative Example 2)
The treatment time when oxidizing a flat porous graphite plate having a thickness of 5 mm made of isotropic graphite (Ibiden, ET-10) having an open porosity of 15% in nitric acid having a concentration of 61% was 30 minutes. Except for this, a PEFC consisting of two cells was produced in the same manner as in Example 1.
[0098]
(Comparative Example 3)
A PEFC separator was produced in the same manner as in Example 3 except that the polymerization time represented by the reaction formula (4) was 1 hour.
[0099]
(Water permeability evaluation test)
As the plate-like test pieces used for the evaluation of Examples 1 and 2 and Comparative Example 2, the porous graphite plate having a thickness of 5 mm after the oxidation treatment in Examples 1 and 2 and Comparative Example 2 was used. And as a plate-shaped test piece used for evaluation of Comparative Example 3, a porous graphite plate having a thickness of 5 mm in which a gel-like hydrophilic substance was formed on the surface in Examples 3, 4 and Comparative Example 3 was used. As a plate-shaped test piece used in the evaluation of 5, a porous graphite plate produced by CIP molding in Example 5 was used, and as a plate-shaped test piece used in the evaluation of Comparative Example 1, an isotropic porosity of 15% was used. A water permeability evaluation test was performed using a 5 mm thick plate-like body made of graphite (Ibiden, ET-10).
In the water permeability evaluation test, after the plate-shaped test piece was dried at 120 ° C. for 1 hour, 0.02 ml of pure water was dropped on the surface of the plate-shaped test piece with a microsyringe. The measurement was carried out by measuring the permeation time (penetration time).
The results are shown in Table 1.
[0100]
(Battery characteristics test)
For PEFCs according to Examples 1 to 5 and Comparative Examples 1 to 3, hydrogen inlet pressure: 0.05 MPa, air inlet pressure: 0.05 MPa, cell operating temperature: 80 ° C., hydrogen gas humidifier on the anode side A current density of 1 A using an electronic load and a DC power source under the conditions of a set temperature: 80 ° C., a cathode side air humidifier set temperature: 80 ° C., a hydrogen utilization rate: 70%, and an oxygen utilization rate: 40%. / Cm ² After 3 hours of constant current driving, the open circuit voltage was measured, and then the current density was 1 A / cm. ² The inter-terminal voltage per cell after 30 minutes of energization, and 2 A / cm ² Then, the voltage between terminals per cell after energization for 30 minutes was measured, and the current-voltage characteristics were confirmed.
The results are shown in Table 1.
[0101]
[Table 1]

[0102]
As shown in Table 1, it is possible to shorten the permeation time in the water permeability evaluation test of the obtained porous carbon material by lengthening the oxidation treatment time and the polymerization time for forming the hydrophilic substance. did it. In addition, the shorter the permeation time in the water permeability evaluation test of the porous carbon material that constitutes the PEFC separator, the better the PEFC has better current-voltage characteristics, and the higher the voltage between the terminals of the cell even after energization at a high current density It was.
[0103]
【The invention's effect】
The hydrophilic porous carbon material of the first aspect of the present invention is made hydrophilic by oxidizing a porous carbon material that is inherently hydrophobic, and is excellent in water permeability.
The hydrophilic porous carbon material according to the second aspect of the present invention is made hydrophilic by forming a hydrophilic substance on the surface and pores of the porous carbon material which is inherently hydrophobic, and is permeable to water. Excellent.
The hydrophilic porous carbon material of the third aspect of the present invention is hydrophilic by forming a hydrophilic material on the surface and pores of the porous carbon material which is inherently hydrophobic by mixing a binder made of a hydrophilic material. The water permeability is excellent.
[0104]
Since the separator for PEFC of the present invention using the hydrophilic porous carbon material of the first, second and third inventions is made of a hydrophilic constituent material, the movement of moisture in the separator is easy. Therefore, in the PEFC separator of the present invention, the moisture generated in the air electrode can be reduced to the outside of the cell together with the exhaust gas, and the proportion supplied to the fuel electrode of the adjacent cell can be increased. Even when operated at a high output, the solid polymer electrolyte membrane does not dry and the electrical resistance does not increase, and a decrease in output can be suppressed. Further, even if the pore volume in the separator is reduced, it is possible to smoothly move the moisture in the separator, so that a high-strength PEFC separator that is not damaged by gas pressure can be obtained.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view schematically showing the structure of a single cell constituting a PEFC.
FIG. 2 (a) is a cross-sectional view schematically showing an example of a PEFC separator using the hydrophilic porous carbon material of the first present invention. (B) is the top view which looked at an example of the separator for PEFC typically shown to (a).
FIG. 3 (a) is an exploded perspective view schematically showing another example of a separator for PEFC using the hydrophilic porous carbon material of the first present invention. (B) is the top view which looked at another example of the separator for PEFC typically shown to (a).
[Explanation of symbols]
10 single cells
11 Solid polymer electrolyte membrane
12 Air electrode
13 Fuel electrode
20, 30, 40 PEFC separator
21, 31, 41, 51 Fuel gas groove
22, 32, 42, 52 Air groove
23, 33, 43, 53, 54 Fuel gas hole
24, 34, 44, 55, 56 Air holes
49 First plate-like member
50 Second plate-shaped member
57 Cooling water groove
58, 59 Cooling water hole

Claims (2)

Water permeation in which 0.02 ml of pure water is dropped on the surface of a 5 mm thick plate-like test piece formed by forming a gel-like hydrophilic substance on the surface of the porous carbon material and inside the pores and drying at 120 ° C. for 1 hour. In a property evaluation test, a method for producing a hydrophilic porous carbon material having a property that 0.02 ml of the pure water completely penetrates within 5 minutes ,
Impregnating the porous carbon material with divinylbenzene and vinyl acetate;
Forming a copolymer on the inside surface and pores of the porous carbon material wherein a porous state of being immersed in a carbon material in said divinylbenzene and the vinyl acetate were copolymerized, and,
A method for producing a hydrophilic porous carbon material, comprising a step of saponifying the copolymer. A separator for a polymer electrolyte fuel cell, comprising the hydrophilic porous carbon material obtained by the method for producing a hydrophilic porous carbon material according to claim 1.

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