JP3689322B2 - Electrolyte membrane-electrode assembly of polymer electrolyte fuel cell - Google Patents

Description

【００３６】
図２は，実施例（１）〜（６）ならびに比較例（１），（２）及び参考例に関し，表１に基づいて，イオン交換容量Ｉｃと電流密度１Ａ／cm² 時のセル電位との関係をグラフ化したものである。図２から明らかなように，実施例（１）〜（６）のようにイオン交換容量Ｉｃを０．９ｍｅｑ／ｇ≦Ｉｃ≦５ｍｅｑ／ｇに設定すると，電流密度１Ａ／cm² 時のセル電位を，実用レベルである０．４Ｖ以上に高く維持することができる。比較例（１），（２）はセル電位が低い。
【００３７】
図３は，実施例（１）〜（６）ならびに比較例（１）及び参考例に関し，表１に基づいて，動的粘弾性係数Ｄｖと，厚さ減少量および電流密度１Ａ／cm² 時のセル電位との関係をグラフ化したものである。図３から明らかなように，実施例（１）〜（７）のごとく動的粘弾性係数Ｄｖを５×１０⁸ Ｐａ≦Ｄｖ≦１×１０¹⁰Ｐａに設定すると，厚さ減少量を１０μｍ以下にし得ると共に電流密度１Ａ／cm² 時のセル電位を０．４０Ｖ以上に高く維持することができる。この場合，比較例（２）は動的粘弾性係数ＤｖがＤｖ＝４×１０⁸ Ｐａであって，Ｄｖ＜５×１０⁸ Ｐａであることから厚さ減少量が大となる。
【００３８】
図４は，実施例（１）〜（６）及び参考例に関し，表１に基づいて，高分子イオン交換成分の重量Ｘと触媒粒子の重量Ｗとの比Ｘ／Ｗと，電流密度１Ａ／cm² 時のセル電位との関係をグラフ化したものである。図４から明らかなように，実施例（１）〜（６）のごとく，イオン交換容量Ｉｃが０．９ｍｅｑ／ｇ≦Ｉｃ≦５ｍｅｑ／ｇであり，また動的粘弾性係数Ｄｖが５×１０⁸ Ｐａ≦Ｄｖ≦１×１０¹⁰Ｐａである，ということを前提として比Ｘ／Ｗを０．０５≦Ｘ／Ｗ≦０．８０に設定すると，電流密度１Ａ／cm² 時のセル電圧を０．４７Ｖ以上に高く維持することができる。
【００３９】
【発明の効果】
本発明によれば，前記のように構成することによって，８５℃以上の運転温度下において発電性能を十分に高く維持し得る固体高分子型燃料電池の電解質膜−電極集成体を提供することができる。
【図面の簡単な説明】
【図１】 固体高分子型燃料電池（セル）の概略側面図である。
【図２】 イオン交換容量Ｉｃと電流密度１Ａ／cm² 時のセル電位との関係を示すグラフである。
【図３】 動的粘弾性係数Ｄｖと，厚さ減少量および電流密度１Ａ／cm² 時のセル電位との関係を示すグラフである。
【図４】 高分子イオン交換成分の重量Ｘと触媒粒子の重量Ｗとの比Ｘ／Ｗと，電流密度１Ａ／cm² 時のセル電位との関係を示すグラフである。
【符号の説明】
１…………固体高分子型燃料電池
２…………電解質膜
３…………空気極
４…………燃料極
９…………電解質膜−電極集成体[0001]
BACKGROUND OF THE INVENTION
The present invention includes an electrolyte membrane-electrode assembly of a solid polymer fuel cell, in particular, an electrolyte membrane, an air electrode and a fuel electrode sandwiching the electrolyte membrane, and each of the electrolyte membrane, the air electrode and the fuel electrode is a polymer. The present invention relates to an electrolyte membrane-electrode assembly having an ion exchange component.
[0002]
[Prior art]
In the polymer electrolyte fuel cell, if water generated during power generation stays in the assembly, the power generation performance deteriorates. Therefore, an attempt has been made to increase the vapor pressure of the produced water by setting the operating temperature to 85 ° C. or higher, thereby discharging the produced water out of the assembly.
[0003]
[Problems to be solved by the invention]
However, the moisture in the assembly tends to be excessively discharged under the high operating temperature as described above, and the conventional assembly does not have a low electrical resistance that can cope with the excessive discharge of moisture. There was a problem that the power generation performance was reduced.
[0004]
In the cell stack, the cells are clamped to reduce the contact resistance due to the lamination of a plurality of cells, but the conventional assembly is thinned by creep due to the clamping at an operating temperature of 85 ° C. As a result, problems such as the occurrence of gas leaks and the accompanying decrease in power generation performance also occurred.
[0005]
[Means for Solving the Problems]
An object of the present invention is to provide the assembly capable of maintaining high power generation performance at an operating temperature of 85 ° C. or higher.
[0006]
In order to achieve the above object, according to the present invention, an electrolyte membrane, an air electrode and a fuel electrode sandwiching the electrolyte membrane, and each of the electrolyte membrane, the air electrode, and the fuel electrode have a polymer ion exchange component are provided. In the electrolyte membrane-electrode assembly of the polymer fuel cell, the polymer ion exchange component is a sulfonated aromatic hydrocarbon polymer, and the ion exchange capacity Ic is 0.9 meq / g ≦ Ic ≦ 5 meq / g. The dynamic viscoelastic coefficient Dv at 85 ° C. is 5 × 10 ⁸ Pa ≦ Dv ≦ 1 × 10 ¹⁰ Pa, the weight of the catalyst particles contained in the air electrode and the fuel electrode is W, and the air Electrolyte membrane-electrode assembly in which the ratio X / W of W and X is 0.05 ≦ X / W ≦ 0.80, where X is the weight of the polymer ion exchange component contained in the electrode and the fuel electrode Body is It is subjected.
[0007]
When the ion exchange capacity Ic of the assembly is set as described above, even when the moisture in the assembly is excessively discharged at an operating temperature of 85 ° C. or higher, the assembly has a low electrical resistance. It is possible to maintain high power generation performance. However, when the ion exchange capacity Ic is Ic <0.9 meq / g, the electrical resistance of the assembly cannot be kept low. On the other hand, when Ic> 5 meq / g, the power generation performance under a high current density is lowered. This is considered to be because water tends to stay in the air electrode and the fuel electrode when Ic> 5 meq / g.
[0008]
Further, when the dynamic viscoelastic coefficient Dv at 85 ° C. of the assembly is set as described above, the assembly has excellent creep resistance against the clamping pressure on the stack configuration at an operating temperature of 85 ° C. or higher. It can be used to avoid thinning the film, thereby maintaining high power generation performance. However, when the dynamic viscoelastic coefficient Dv is Dv <5 × 10 ⁸ Pa, the creep resistance of the assembly is low at the operating temperature, whereas when Dv> 1 × 10 ¹⁰ Pa, the electrolyte membrane, the air electrode, and the fuel Since the hardness of the poles increases, when they are joined to produce the assembly, their bondability deteriorates.
[0009]
Furthermore, setting the ratio X / W of the weights of the catalyst particles and the polymer ion exchange component in the air electrode and the fuel electrode as described above is effective in maintaining high power generation performance. However, if the ratio X / W of both weights deviates from the above range, this effect cannot be obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, a polymer electrolyte fuel cell (cell) 1 includes an electrolyte membrane 2, an air electrode 3 and a fuel electrode 4 that are in close contact with both sides thereof, and two diffusion layers 5 that are in close contact with both electrodes 3 and 4, respectively. , 6 and a pair of separators 7 and 8 that are in close contact with both diffusion layers 5 and 6. These electrolyte membrane 2, air electrode 3 and fuel electrode 4 constitute an electrolyte membrane-electrode assembly 9.
[0011]
The electrolyte membrane 2 is composed of a polymer ion exchange component. Each of the air electrode 3 and the fuel electrode 4 includes a plurality of catalyst particles in which a plurality of Pt particles are supported on the surface of carbon black particles, and a polymer ion exchange component that is the same as or different from the above.
[0012]
Each of the diffusion layers 5 and 6 is made of porous carbon paper, carbon plate or the like, and each of the separators 7 and 8 is made of graphitized carbon so as to have the same form. Air is supplied to the plurality of existing grooves 10, and hydrogen is supplied to the plurality of grooves 11 in the separator 8 on the fuel electrode 4 side and intersecting the grooves 10.
[0013]
The polymer electrolyte fuel cell is operated at a high temperature of 85 ° C. or higher. From the viewpoint of maintaining a high power generation performance during the high temperature operation, the ion exchange capacity Ic of the electrolyte membrane-electrode assembly 9 is 0. 9 meq / g ≦ Ic ≦ 5 meq / g, and the dynamic viscoelastic coefficient Dv at 85 ° C. is set to 5 × 10 ⁸ Pa ≦ Dv ≦ 1 × 10 ¹⁰ Pa.
[0014]
Polymer ion exchange components include polyetheretherketone (PEEK), polyethersulfone (PES), polysulfone (PSF), polyetherimide (PEI), polyphenylenesulfide (PPS), and polyphenyleneoxide (PPO). A sulfonated product of an aromatic hydrocarbon polymer is applicable.
[0015]
When the weight of the catalyst particles contained in the air electrode 3 and the fuel electrode 4 is W, respectively, and the weight of the polymer ion exchange component contained in the air electrode 3 and the fuel electrode 4 is X, respectively, those X in one electrode , W ratio X / W is set to 0.05 ≦ X / W ≦ 0.80.
[0016]
Specific examples will be described below.
[0017]
I. Production of Electrolyte Membrane-Electrode Assembly Carbon black particles (furnace black) were supported with Pt particles having an average particle size of 3 nm, and catalyst particles having a Pt particle content of 50 wt% were prepared. The average particle size of the Pt particles is measured by the X-ray diffraction method, and this is the same hereinafter.
[0018]
[Example-I]
In order to produce the PEEK sulfonated product which is a polymer ion exchange component, PEEK (manufactured by Aldrich) was placed in fuming sulfuric acid and sulfonated until the ion exchange capacity Ic was Ic = 2.4 meq / g. .
[0019]
An electrolyte membrane 2 having a thickness of 50 μm was formed using this PEEK sulfonated product. The PEEK sulfonated product was reflux-dissolved in NMP (N-methylpyrrolidone, manufactured by Aldrich) to prepare a solution having a PEEK sulfonated content of 12 wt%.
[0020]
The catalyst particles are mixed with the PEEK sulfonated solution so that the weight of PEEK sulfonated product is X: the weight of catalyst particles W = 1.25: 2 (X / W≈0.63), and then the catalyst is mixed using a ball mill. The particles were dispersed to prepare a slurry for the air electrode 3 and the fuel electrode 4.
[0021]
Also, a slurry is prepared by mixing and dispersing carbon black particles and PTFE particles in ethylene glycol. The slurry is applied to one surface of carbon paper and dried to form a base layer, whereby a diffusion consisting of carbon paper and base layer is formed. Layers 5 and 6 were made.
[0022]
The slurry for the air electrode 3 and the fuel electrode 4 is applied on the base layers of the diffusion layers 5 and 6 so that the Pt amount is 0.5 mg / cm ² , dried at 60 ° C. for 10 minutes, and at 120 ° C. The air electrode 3 and the fuel electrode 4 were formed by drying under reduced pressure.
[0023]
The air electrode 3 and the fuel electrode 4 integral with both diffusion layers 5 and 6 are applied to both surfaces of the electrolyte membrane 2, respectively, and primary hot pressing is performed at 80 ° C., 5 MPa for 2 minutes, and then 160 ° C., 4 MPa. Then, secondary hot pressing was performed under the conditions of 1 minute to obtain an electrolyte membrane-electrode assembly 9 having a pair of diffusion layers 5 and 6. This is referred to as Example (1).
[0024]
[Example- II ]
As a polymer ion exchange component, a PEEK sulfonated product having an ion exchange capacity Ic = 2.4 meq / g as in Example-I, and an electrolyte membrane 2 having a thickness of 50 μm formed using the PEEK sulfonated product. That is, the same thing as Example-I was prepared, respectively. Thereafter, in the process of forming the air electrode 3 and the fuel electrode 4, with the NMP remaining after drying at 60 ° C. for 10 minutes, the air electrode 3 and the fuel electrode 4 are applied to both surfaces of the electrolyte membrane 2, respectively. The same electrolyte membrane-electrode assembly 9 was obtained by carrying out the same method as in Example-I except that hot pressing was performed under the conditions of 4 MPa, 1 minute. This is designated as Example ( 2 ).
[0025]
[Example- III ]
As a polymer ion exchange component, a PEEK sulfonated product having an ion exchange capacity Ic = 2.4 meq / g as in Example-I, and an electrolyte membrane 2 having a thickness of 50 μm formed using the PEEK sulfonated product. That is, the same thing as Example-I was prepared, respectively. Thereafter, in preparing the slurry for the air electrode 3 and the fuel electrode 4, the weight of PEEK sulfonated product X: the weight of the catalyst particles W = 0.1: 2 (X / W = 0.05), and the air electrode 3 and the fuel electrode 4, with the NMP remaining after drying at 60 ° C. for 10 minutes, the air electrode 3 and the fuel electrode 4 are applied to both surfaces of the electrolyte membrane 2, respectively, at 160 ° C., 4 MPa, 1 The same electrolyte membrane-electrode assembly 9 as described above was obtained by carrying out the same method as in Example-I except that the hot pressing was performed under the condition of minutes. This is designated as Example ( 3 ).
[0026]
[Example- IV ]
As a polymer ion exchange component, a PEEK sulfonated product having an ion exchange capacity Ic = 2.4 meq / g as in Example-I, and an electrolyte membrane 2 having a thickness of 50 μm formed using the PEEK sulfonated product. That is, the same thing as Example-I was prepared, respectively. Thereafter, in the preparation of the slurry for the air electrode 3 and the fuel electrode 4, the weight of PEEK sulfonated product X: the weight of catalyst particles W = 1.6: 2 (X / W = 0.80) was set. 3 and the fuel electrode 4, with the NMP remaining after drying at 60 ° C. for 10 minutes, the air electrode 3 and the fuel electrode 4 are applied to both surfaces of the electrolyte membrane 2, respectively, at 160 ° C., 4 MPa, 1 The same electrolyte membrane-electrode assembly 9 as described above was obtained by carrying out the same method as in Example-I except that the hot pressing was performed under the condition of minutes. This is designated as Example ( 4 ).
[0027]
[Example- V ]
As a polymer ion exchange component, a PEEK sulfonated product having an ion exchange capacity Ic = 2.4 meq / g was prepared as in Example-I. Also, a mixture of PEEK (manufactured by Aldrich) and PEI (manufactured by Aldrich) is put into fuming sulfuric acid and subjected to sulfonation until the ion exchange capacity Ic≈0.95 meq / g, and the PEEK-PEI sulfonated product is used. An electrolyte membrane 2 having a thickness of about 80 μm was prepared. Thereafter, the same method as in Example-I was carried out to obtain the same electrolyte membrane-electrode assembly 9 as described above. This is designated as Example ( 5 ).
[0028]
[Example- VI ]
As a polymer ion exchange component, a PEEK sulfonated product having an ion exchange capacity Ic = 2.4 meq / g was prepared as in Example-I. Also, a mixture of PEEK (manufactured by Aldrich) and PEI (manufactured by Aldrich) is put into fuming sulfuric acid and subjected to sulfonation until the ion exchange capacity Ic≈5.1 meq / g, and the PEEK-PEI sulfonated product is used. An electrolyte membrane 2 having a thickness of about 80 μm was prepared. Thereafter, the same method as in Example-I was carried out to obtain the same electrolyte membrane-electrode assembly 9 as described above. This is designated as Example ( 6 ).
[0029]
[Example- VII ]
As a polymer ion exchange component, a PEEK sulfonated product having an ion exchange capacity Ic = 2.4 meq / g was prepared as in Example-I. Also, a mixture of PEEK (manufactured by Aldrich) and PEI (manufactured by Aldrich) is put into fuming sulfuric acid and subjected to sulfonation until the ion exchange capacity Ic≈0.90 meq / g, and the PEEK-PEI sulfonated product is used. An electrolyte membrane 2 having a thickness of about 80 μm was prepared. Thereafter, the same method as in Example-I was carried out to obtain the same electrolyte membrane-electrode assembly 9 as described above. This is referred to as Comparative Example (1).
[0030]
[Example- VIII ]
As a polymer ion exchange component, a PEEK sulfonated product having an ion exchange capacity Ic = 2.4 meq / g was prepared as in Example-I. Also, a mixture of PEEK (manufactured by Aldrich) and PEI (manufactured by Aldrich) is put into fuming sulfuric acid and subjected to sulfonation until the ion exchange capacity Ic≈5.5 meq / g, and the PEEK-PEI sulfonated product is used. An electrolyte membrane 2 having a thickness of about 80 μm was prepared. Thereafter, the same method as in Example-I was carried out to obtain the same electrolyte membrane-electrode assembly 9 as described above. This is designated as Comparative Example (2).
[0031]
[Example- IX ]
As polymer ion exchange component, the PTFE sul Hong product of ion-exchange capacity Ic = 0.9 meq / g, and as the electrolyte membrane 2, Example -I Similarly, PEEK sulfonated ion exchange capacity Ic = 2.4 meq / g Each having a thickness of 50 μm was prepared. Thereafter, the same method as in Example-I was carried out to obtain the same electrolyte membrane-electrode assembly 9 as described above. This is a reference example.
II. Membrane - electrode ion exchange capacity Ic of the assembly, the dynamic viscoelastic coefficient Dv, current density 1A / cm measured examples of cell potential and thickness reduction of ^2:00 (1) to (6) and Comparative Example (1 ), (2) and the reference example , the ion exchange capacity Ic is measured under the application of the titration method, and the dynamic viscoelastic coefficient Dv is measured under the tensile mode when the frequency is set to 10 Hz at 85 ° C. did.
[0032]
The cell stack was assembled using the embodiment (1), the temperature of the embodiment (1): 85 ° C .; the gas in the air electrode 3: air, the pressure 100 kPa, the utilization factor 50%; the gas in the fuel electrode 4: pure hydrogen, the pressure Power generation was performed under the conditions of 100 kPa, utilization factor 50%; dew point of each gas: 80 ° C., and the cell potential at a current density of 1 A / cm ² was measured. Moreover, the same measurement as described above was performed for the cell stacks using Examples (2) to ( 6 ) and Comparative Examples (1), (2) and Reference Example .
[0033]
For the cell stack using Example (1), power generation was performed under the conditions of a cell clamping pressure of 0.5 MPa, a temperature of 90 ° C. of Example (1), and an operation time of 200 hours, and the thickness reduction of Example (1) The amount was measured. Moreover, the same measurement as described above was performed for the cell stacks using Examples (2) to ( 6 ) and Comparative Examples (1), (2) and Reference Example .
[0034]
Table 1 shows the measurement results. The cell potential in the table is a value related to the cell stack using Example (1) and the like. Table 1 also shows the ratio X / W between the weight X of the polymer ion exchange component and the weight W of the catalyst particles for convenience.
[0035]
[Table 1]

[0036]
FIG. 2 relates to Examples (1) to ( 6 ) and Comparative Examples (1), (2) and Reference Example , based on Table 1, the ion exchange capacity Ic and the cell potential at a current density of 1 A / cm ^2. Is a graph of the relationship. As can be seen from FIG. 2, when the ion exchange capacity Ic is set to 0.9 meq / g ≦ Ic ≦ 5 meq / g as in Examples (1) to ( 6 ), the cell potential at a current density of 1 A / cm ^{2 is obtained.} Can be maintained at a high practical level of 0.4 V or higher. In Comparative Examples (1) and (2), the cell potential is low.
[0037]
FIG. 3 shows dynamic viscoelasticity coefficient Dv, thickness reduction amount, and current density of 1 A / cm ² based on Table 1 with respect to Examples (1) to ( 6 ) and Comparative Example (1) and Reference Example. This is a graph of the relationship with the cell potential. As is clear from FIG. 3, when the dynamic viscoelastic coefficient Dv is set to 5 × 10 ⁸ Pa ≦ Dv ≦ 1 × 10 ¹⁰ Pa as in Examples (1) to (7), the thickness reduction amount is 10 μm or less. And the cell potential at a current density of 1 A / cm ² can be maintained at 0.40 V or higher. In this case, in the comparative example (2), the dynamic viscoelastic coefficient Dv is Dv = 4 × 10 ⁸ Pa and Dv <5 × 10 ⁸ Pa. Therefore, the thickness reduction amount is large.
[0038]
FIG. 4 relates to Examples (1) to (6) and the reference example , based on Table 1, the ratio X / W of the weight X of the polymer ion exchange component and the weight W of the catalyst particles, and the current density 1 A / The graph shows the relationship with the cell potential at cm ² . As is clear from FIG. 4, as in Examples (1) to (6) , the ion exchange capacity Ic is 0.9 meq / g ≦ Ic ≦ 5 meq / g, and the dynamic viscoelastic coefficient Dv is 5 × 10 5. ^{If the} ratio X / W is set to 0.05 ≦ X / W ≦ 0.80 on the premise that ⁸ Pa ≦ Dv ≦ 1 × 10 ¹⁰ Pa, the cell voltage at a current density of 1 A / cm ² is reduced to 0. It can be kept higher than 47V.
[0039]
【The invention's effect】
According to the present invention, it is possible to provide an electrolyte membrane-electrode assembly of a polymer electrolyte fuel cell that can maintain power generation performance sufficiently high at an operating temperature of 85 ° C. or higher by being configured as described above. it can.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a polymer electrolyte fuel cell (cell).
FIG. 2 is a graph showing the relationship between ion exchange capacity Ic and cell potential at a current density of 1 A / cm ² .
FIG. 3 is a graph showing a relationship between a dynamic viscoelastic coefficient Dv, a thickness reduction amount, and a cell potential at a current density of 1 A / cm ² .
FIG. 4 is a graph showing the relationship between the ratio X / W between the weight X of the polymer ion exchange component and the weight W of the catalyst particles and the cell potential at a current density of 1 A / cm ² .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ………… Solid polymer fuel cell 2 ………… Electrolyte membrane 3 ………… Air electrode 4 ………… Fuel electrode 9 ………… Electrolyte membrane-electrode assembly

Claims (2)

An electrolyte membrane (2), an air electrode (3) and a fuel electrode (4) sandwiching the electrolyte membrane (2) are provided, and the electrolyte membrane (2), air electrode (3) and fuel electrode (4) are respectively In an electrolyte membrane-electrode assembly of a polymer electrolyte fuel cell having a polymer ion exchange component,
The polymer ion exchange component is a sulfonated aromatic hydrocarbon polymer, the ion exchange capacity Ic is 0.9 meq / g ≦ Ic ≦ 5 meq / g, and the dynamic viscoelastic coefficient Dv at 85 ° C. is 5 × 10 ⁸ Pa ≦ Dv ≦ 1 × 10 ¹⁰ Pa, the weight of the catalyst particles contained in the air electrode (3) and the fuel electrode (4) is W, and the air electrode (3) and the fuel electrode ( 4) When the weight of the polymer ion exchange component contained in 4) is X, the ratio X / W of W and X is 0.05 ≦ X / W ≦ 0.80. An electrolyte membrane-electrode assembly of a molecular fuel cell.   2. The electrolyte membrane of a polymer electrolyte fuel cell according to claim 1, wherein the aromatic hydrocarbon polymer includes polyether ether ketone, polyether sulfone, polysulfone, polyether imide, polyphenylene sulfide, and polyphenylene oxide. An electrode assembly.

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