JP4649705B2 - Polymer electrolyte fuel cell - Google Patents

Description

【００８３】
表１に示した結果から明らかなように、実施例１〜実施例５の本発明の固体高分子型燃料電池は、実用的な作動条件（電池電圧条件）の下で、比較例１〜比較例８の固体高分子型燃料電池に比べて高い起動初期の電池特性を有しており、更には、大きな電池特性の低下を招くことなく１０００時間という長時間にわたり安定して作動することが確認された。
【００８４】
これに対し、比較例１〜比較例６の固体高分子型燃料電池においては、起動初期の電池特性が高い場合には１０００時間後の電池特性が大きく低下してしまうという欠点が、他方、起動初期から１０００時間後の電池特性の低下が抑制される場合には起動初期の電池特性が低く長期にわたり高い電池出力を得ることができないという欠点があることが確認された。特に、特願平１１−２８８７２７の固体高分子型燃料電池に対応する比較例３の固体高分子型燃料電池は、起動初期の電池電圧に対して、１０００時間作動させた後の電池電圧は５０ｍＶも低下してしまうことが確認された。
【００８５】
更に、比較例７の固体高分子型燃料電池は作製することができず、カソードのガス拡散層側の触媒層として触媒層内に含有されるイオン交換樹脂のＡ_Rが非常に小さな値の場合には触媒層を形成できないことが確認された。また、比較例８の固体高分子型燃料電池は、開回路電圧を測定することができたものの、固体高分子型燃料電池を作動させはじめると急激に電池電圧が降下して発電不能状態に陥った。この時、カソードのガス拡散層側の触媒層からイオン交換樹脂が溶出していたことが確認された。このことから、カソードのガス拡散層側の触媒層として触媒層内に含有されるイオン交換樹脂のＡ_Rが非常に大きな値の場合には触媒層内のイオン交換樹脂が固体（結晶）状態を安定して保持できないことが確認された。
【００８６】
【発明の効果】
以上説明したように、本発明の固体高分子型燃料電池によれば、十分に多く確保された反応サイトへの反応ガスの供給を、長期間にわたり保持することのできる良好な排水構造を有する触媒層を構築することが可能となる。そのため、作動中の触媒層内、特に、カソード触媒層内におけるフラッディングの発生を防止して当該触媒層内の反応サイトを有効に利用することが可能となる。従って、本発明によれば、起動初期の電池特性を高くして大電流を流す場合であってもフラッディングの発生が十分に防止され、高い電池特性を起動初期から長期間にわたり安定して得ることのできる固体高分子型燃料電池を提供することができる。
【図面の簡単な説明】
【図１】 本発明による固体高分子型燃料電池の好適な一実施形態を示す模式断面図である。
【符号の説明】
１…高分子電解質膜側の触媒層、２…ガス拡散層側の触媒層、3…カソード触媒層、４…ガス拡散層、５…カソード、６…アノード触媒層、７…ガス拡散層、８…アノード、９…カソード反応ガス流路、１０…アノード反応ガス流路、ＦＣ…燃料電池、ＰＥＭ…高分子電解質膜、ＳＰ１，ＳＰ２…セパレータ、ＵＣ…単位セル。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polymer electrolyte fuel cell.
[0002]
[Prior art]
The fuel cell is attracting attention as a clean power generation system in which the product of the cell reaction is water in principle and has almost no adverse effect on the global environment.
[0003]
In particular, solid polymer fuel cells having a polymer electrolyte membrane include (1) the development of polymer electrolyte membranes having high ionic conductivity, and (2) ion exchange resins of the same type or different types from polymer electrolyte membranes. The use of catalyst-supported carbon fine particles coated with (polymer electrolyte) as the constituent material of the electrode catalyst layer, and the so-called three-dimensional reaction site in the catalyst layer has been achieved, etc. Improved. In addition to obtaining such high battery characteristics, it is easy to reduce the size and weight, so the polymer electrolyte fuel cell is used as a power source for a mobile vehicle such as an electric vehicle or a small cogeneration system. Practical use is expected.
[0004]
The solid polymer fuel cell currently under study has a low operating temperature range of 50 to 120 ° C. due to restrictions on the heat resistance and ion conductivity of the polymer electrolyte membrane, and uses its exhaust heat. High power generation efficiency and high output density can be obtained for practical use, especially under operating conditions where the utilization rate of anode reaction gas such as pure hydrogen and the utilization rate of cathode reaction gas such as air is high. Performance is required.
[0005]
In general, a gas diffusion electrode used for a polymer electrolyte fuel cell includes a catalyst layer containing catalyst-supported carbon fine particles coated with the above-described ion exchange resin, a reaction gas supplied to the catalyst layer, and a catalyst layer. The gas diffusion layer collects the generated charges. Further, in the catalyst layer of the gas diffusion electrode, there is a void portion composed of fine pores formed between the secondary particles of the carbon fine particles as the constituent material, and the void portion is a diffusion flow of the reaction gas. It functions as a road.
[0006]
However, under operating conditions where the reaction rate of the battery reaction is relatively high as described above, water that moves with protons that move in the polymer electrolyte membrane from the anode to the cathode (hereinafter referred to as proton-entrained water). ) And the amount of water produced and condensed by the electrode reaction of the cathode. Therefore, these waters are not quickly discharged from the cathode to the outside, and the phenomenon that the voids in the catalyst layer of the cathode are blocked by these waters, so-called flooding phenomenon, is likely to occur. When such flooding occurs, supply of the cathode reaction gas to the reaction site of the catalyst layer is hindered, and a desired battery output cannot be stably obtained. Therefore, in order to prevent the occurrence of flooding and stably obtain a desired battery output over a long period of time, it is necessary to ensure good drainage of the cathode.
[0007]
Therefore, JP-A-5-36418 discloses polytetrafluoroethylene (hereinafter referred to as PTFE), tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoro (alkyl vinyl ether) as a water repellent. A polymer electrolyte fuel cell in which a fluorine-containing resin such as a copolymer is contained in a cathode catalyst layer has been proposed. However, when a water repellent is contained in the catalyst layer in this way, a water-repellent agent can be used to build a highly water-repellent void, but the electrical resistance of the electrode is increased due to the insulating property of the water repellent, There has been a problem that the battery output may be lowered due to a decrease in gas diffusivity in the catalyst layer due to an increase in the layer thickness of the catalyst layer. In the present specification, “A / B copolymer” refers to a copolymer comprising a polymer unit based on A and a polymer unit based on B.
[0008]
JP-A-11-288727 discloses an ion exchange capacity (hereinafter referred to as A) using two types of catalyst-supported carbon fine particles coated with ion exchange resins having different ion exchange capacities as constituent materials. _R A catalyst layer containing an ion-exchange resin that is 1.10 meq / g dry resin (hereinafter referred to as meq./g); _R 0.97 meq. / G of a catalyst layer containing an ion exchange resin, a solid layer having a cathode catalyst layer having a two-layer structure in which the former is disposed on the polymer electrolyte membrane side and the latter is disposed on the gas diffusion layer side. Molecular fuel cells have been proposed.
[0009]
[Problems to be solved by the invention]
However, the inventors of the present invention, even in the polymer electrolyte fuel cell described in JP-A-11-288727, are relatively The problem is that the battery characteristics deteriorate in a short time and further flooding occurs in the cathode catalyst layer, or if it is attempted to prevent flooding in the cathode catalyst layer, the battery characteristics at the initial start-up are lowered, and therefore the battery characteristics are improved. It has been found that there is a problem that it cannot be obtained over a long period of time and is not yet sufficient.
[0010]
The present invention has been made in view of the above-mentioned problems of the prior art. Flooding is sufficiently prevented even when a large current flows at the initial stage of startup, and high battery characteristics are maintained over a long period from the initial stage of startup. An object of the present invention is to provide a polymer electrolyte fuel cell that can be obtained stably.
[0011]
[Means for Solving the Problems]
As a result of intensive research to achieve the above object, the present inventors have found that the cause of the problem of the polymer electrolyte fuel cell described in JP-A-11-288727 is on the polymer electrolyte membrane side. A of ion exchange resin to be contained in the arranged catalyst layer _R And ion exchange resin A contained in the catalyst layer disposed on the gas diffusion layer side _R Is 0.13 meq. It was found to be small as / g.
[0012]
Therefore, the present invention has an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode, and supplies the anode reaction gas to the anode and the cathode reaction gas to the cathode. A polymer electrolyte fuel cell that generates electric power through an electrochemical reaction,
The cathode includes a gas diffusion layer, and a plurality of catalyst layers disposed between the gas diffusion layer and the polymer electrolyte membrane,
Ion exchange capacity X [milli equivalent / g dry resin] of the ion exchange resin contained in the innermost catalyst layer in contact with the polymer electrolyte membrane, and ions contained in the outermost catalyst layer in contact with the gas diffusion layer The ion exchange capacity Y [milli equivalent / g dry resin] of the exchange resin is the condition of the following formulas (1) to (3): 0.88 ≦ X ≦ 1.50 (1), 0.70 ≦ Y ≦ 1.32 ... (2), 0.18 <= (XY) <= 0.70 ... (3) is satisfy | filled simultaneously, The polymer electrolyte fuel cell characterized by the above-mentioned is provided.
[0013]
Thus, within the range where the values of X and Y satisfy the conditions of (1) and (2), the value of (XY) is set to 0.18 meq. By setting the ratio to / g or more, different functions can be clearly differentiated from each other for the innermost catalyst layer and the outermost catalyst layer. That is, the innermost catalyst layer with a small accumulated amount of reaction product water has a high A _R By distributing the ion exchange resin having the above, it is possible to efficiently bring the innermost catalyst layer into a high water content state and to have a function of mainly performing the electrode reaction by providing a large number of reaction sites. On the other hand, the outermost catalyst layer with a large accumulated amount of reaction product water has a low A _R The outermost catalyst layer is efficiently brought into a low water content state by distributing an ion exchange resin having a high water separation property and excellent drainage so that the reaction product water or proton-entrained water can be externally provided. It can be given the function of mainly draining water.
[0014]
As a result, in the catalyst layer region in the vicinity of the polymer electrolyte membrane, a large number of reaction sites are effectively used, so that the battery can have a higher output density, while the catalyst layer region in the vicinity of the gas diffusion layer. In this case, reaction product water and proton-entrained water can be smoothly drained to the outside, so that flooding can be prevented from occurring. Therefore, by configuring the polymer electrolyte fuel cell in this manner, sufficient supply of the reaction gas and protons to the reaction site is prevented while preventing flooding at the electrode of the polymer electrolyte fuel cell in operation. A catalyst layer having a good drainage structure that can be maintained for a long time can be constructed.
[0015]
Here, the ion exchange resin A contained in the innermost catalyst layer _R The value of X is 0.88 meq. If it is less than / g, the water content of the resin becomes low, and it becomes difficult to secure a sufficient proton conduction path, so that the battery characteristics deteriorate. On the other hand, the value of X is 1.50 meq. When it exceeds / g, the density of ion exchange groups in the resin increases, and the crystallinity is significantly lowered. As described above, the crystallinity is remarkably lowered, and the ion exchange resin is eluted from the catalyst layer during the operation of the polymer electrolyte fuel cell, and it becomes difficult to maintain the structure of the catalyst layer itself. The value of X is 1.00 to 1.35 meq. From the same viewpoint as described above. / G is more preferable.
[0016]
In addition, A of ion exchange resin contained in the outermost catalyst layer _R The value of Y is 0.70 meq. When it is less than / g, proton conductivity is remarkably lowered and resistance is increased, so that the battery output is lowered. Moreover, when preparing a catalyst layer, an ion exchange resin becomes difficult to melt | dissolve in a solution and it becomes difficult to form a catalyst layer. On the other hand, the value of Y is 1.32 meq. If it exceeds / g, the water content of the ion exchange resin increases and the water separation decreases, so that the drainage in the outermost catalyst layer decreases, and flooding is likely to occur. Furthermore, the value of Y is 0.85 to 1.15 meq. / G is more preferable.
[0017]
Furthermore, A of the ion exchange resin contained in the innermost catalyst layer. _R X and A of ion exchange resin contained in the outermost catalyst layer _R The difference from X (XY) is 0.18 meq. If it is less than / g, the former is mainly responsible for the electrode reaction for the innermost catalyst layer and the outermost catalyst layer, and the latter is the drainage of reaction product water or proton-entrained water to the outside. It is difficult to clearly differentiate the functions mainly responsible for.
[0018]
On the other hand, the value of (XY) is 0.70 meq. When exceeding / g, the density of ion exchange groups in the ion exchange resin contained in the innermost catalyst layer increases, and the crystallinity is significantly reduced, and / or contained in the outermost catalyst layer. The proton conductivity of the ion exchange resin is significantly reduced, the resistance is increased and the battery characteristics are deteriorated, and when preparing the catalyst layer, the ion exchange resin is difficult to dissolve in the solution and the catalyst layer is difficult to form. Will occur.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a polymer electrolyte fuel cell of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.
[0020]
FIG. 1 is a cross-sectional view showing a unit cell and a separator according to a preferred embodiment of the polymer electrolyte fuel cell of the present invention. The fuel cell FC shown in the figure is a polymer electrolyte fuel cell suitable for use as a power source for a mobile vehicle or a small cogeneration system. This fuel cell FC generates electric energy by an electrochemical reaction using an anode reaction gas and a cathode reaction gas.
[0021]
The fuel cell FC is composed of a flat unit cell UC and two separators SP1 and SP2 arranged on both sides of the unit cell UC. Furthermore, the unit cell UC includes a cathode 5, an anode 8, and a polymer electrolyte membrane PEM having proton conductivity.
[0022]
As an electrode active material of this fuel cell FC, for example, a hydrogen-containing gas (fuel gas) produced by steam reforming a hydrocarbon-based raw fuel such as methanol or natural gas is used as an anode reaction gas. An oxygen-containing gas is used as the cathode reaction gas. In this case, the anode reaction proceeds in the following equation (4) at the anode 8 and the following equation (5) at the cathode 5, and the whole cell reaction as represented by the equation (6) proceeds as a whole. Electromotive force is generated.
H ₂ → 2H ⁺ + 2e ^- (4)
(1/2) O ₂ + 2H ⁺ + 2e ^- → H ₂ O ... (5)
H ₂ + (1/2) O ₂ → H ₂ O ... (6)
Hereinafter, details of each component of the present embodiment will be described with reference to FIG.
[0023]
The polymer electrolyte membrane PEM is formed of a solid polymer material such as a fluorine-containing polymer, and is an ion exchange membrane that exhibits good ion conductivity in a wet state. Examples of the solid polymer material constituting the polymer electrolyte membrane PEM include perfluorocarbon polymers having sulfonic acid groups (hereinafter referred to as sulfonic acid type perfluorocarbon polymers), polysulfone resins, phosphonic acid groups or carboxylic acid groups. A fluorocarbon polymer or the like can be used. Among them, a sulfonic acid type perfluorocarbon polymer is preferable, and examples of the product include Nafion (manufactured by DuPont) and Flemion (manufactured by Asahi Glass).
[0024]
On the other hand, the cathode 5 and the anode 8 which are gas diffusion electrodes are each composed of gas diffusion layers 4 and 7 and catalyst layers 3 and 6 formed on these gas diffusion layers.
[0025]
The gas diffusion layers 4 and 7 supply the fuel gas or air supplied to the single cell UC smoothly and uniformly to the catalyst layer side, and electrodes shown in the above equations (4) and (5) in the catalyst layers 3 and 8. It plays a role of releasing charges generated by the reaction to the outside of the single cell UC, and a role of releasing reaction product water, unreacted gas and the like to the outside. As a constituent material of the gas diffusion layers 4 and 7, for example, a porous body having electronic conductivity (for example, carbon cloth or carbon paper having a layer formed of a water repellent and carbon powder formed on the surface) is used. Is done.
[0026]
The cathode catalyst layer 3 of the fuel cell FC serves as a reaction field where the electrode reaction shown in the above formula (5) occurs. The cathode catalyst layer 3 is mainly composed of catalyst-supported carbon black fine particles having a large surface area coated with an ion exchange resin.
[0027]
As shown in FIG. 1, the catalyst layer 3 includes a catalyst layer 1 disposed on the polymer electrolyte membrane PEM side and a catalyst layer 2 disposed on the gas diffusion layer 4 side.
[0028]
The catalyst layer 1 and the catalyst layer 2 are an ion exchange resin A contained in the catalyst layer 1 in contact with the polymer electrolyte membrane PEM. _R Xmeq. / G, and A of the ion exchange resin contained in the catalyst layer 2 in contact with the gas diffusion layer _R Ymeq. / G are the conditions of the following formulas (1) to (3): 0.88 ≦ X ≦ 1.50 (1), 0.70 ≦ Y ≦ 1.32 (2), 0.18 ≦ ( XY) ≦ 0.70 (3) is satisfied at the same time.
[0029]
When the conditions of the equations (1) to (3) are satisfied at the same time, among the supply paths to the reaction site of ions, reaction gas, and electrons in the catalyst layer 3, the battery reaction product water and proton-entrained water are affected. The ion conduction path and the gas diffusion path can be secured with good balance during the operation of the fuel cell FC.
[0030]
Under the conditions shown in the above formulas (1) and (2), the ion exchange resin A contained in the catalyst layer 1 as shown in the formula (3) _R X and A of ion exchange resin contained in catalyst layer 2 _R By sufficiently taking the difference (X−Y) from Y, the catalyst layer 1 is mainly responsible for the electrode reaction, and the role of mainly draining the water present in the entire catalyst layer 3 to the outside. It can be clearly distinguished from what the catalyst layer 2 does.
[0031]
That is, the catalyst layer 1 has a high water content of the ion exchange resin contained therein, can secure a route through which protons can sufficiently move, and can provide a wide range of reaction sites. Further, in the catalyst layer 1, the condensate of proton-accompanying water moving through the polymer electrolyte membrane PEM and the interface between the polymer electrolyte membrane PEM and the catalyst layer 1 in the thickness direction of the catalyst layer 1. The reaction product water accumulated while moving is present, but the combined amount of water is small compared to the amount of water in the catalyst layer 2 due to the small amount of reaction product water accumulated, and the water content is low. Even if it is high, the gas diffusivity is not seriously affected. In addition, in the vicinity of the polymer electrolyte membrane PEM, there is also reverse diffusion water whose driving force is a concentration gradient of water from the cathode 3 to the anode 8, so that the burden of drainage is further reduced.
[0032]
On the other hand, the catalyst layer 2 has a low water content of the ion exchange resin and can be easily separated, so that the drainage is good and a path for sufficient gas diffusion can be secured. Also in the catalyst layer 2, as in the catalyst layer 1, there are a condensed amount of proton-entrained water and a cumulative amount of reaction product water. Of these, the amount of accumulated product water becomes very large, which is very large compared to the amount of water in the catalyst layer 1. However, since the catalyst layer 2 has a low water content of the ion exchange resin, a large amount of water can be efficiently discharged to the outside.
[0033]
Thus, a good drainage structure is constructed in the catalyst layer 3 that can maintain a smooth supply of reaction gas to sufficiently secured reaction sites over a long period of time. Therefore, it is possible to prevent the occurrence of flooding in the active catalyst layer 3 and to effectively use the reaction sites in the catalyst layer 3, so that high battery characteristics can be stably obtained over a long period from the initial startup. be able to.
[0034]
Further, A of the ion exchange resin contained in the catalyst layer 1 described above. _R X and A of ion exchange resin contained in catalyst layer 2 _R From the viewpoint of effectively exhibiting the effects produced by taking a sufficiently large difference (X−Y) from Y, the content of the ion exchange resin contained in the catalyst layer 1 and the content of the catalyst layer 2 The difference from the content of the ion exchange resin is 0 to 0.6 mg / cm ^Three It is preferable that
[0035]
In addition, regarding the content of the ion exchange resin contained in the catalyst layer 1 and the catalyst layer 2, in both the catalyst layer 1 and the catalyst layer 2, the range of the ratio (mass ratio) between the catalyst and the ion exchange resin is The mass of the catalyst: the mass of the ion exchange resin = 0.40: 0.60 to 0.95: 0.05, the mass of the catalyst: the mass of the ion exchange resin = 0.60: 0.40-0 .80: 0.20 is more preferable.
[0036]
Here, when the content ratio of the catalyst with respect to the ion exchange resin is lower than the ratio of the mass of the catalyst: the mass of the ion exchange resin = 0.40: 0.60, the amount of the catalyst is insufficient and the reaction sites tend to decrease. . In addition, the thickness of the ion exchange resin coating layer covering the catalyst tends to increase, and the reaction gas diffusion rate in the resin tends to decrease. Furthermore, the pores necessary for reaction gas diffusion may be blocked by the resin, and flooding may easily occur. On the other hand, when the content ratio of the catalyst with respect to the ion exchange resin exceeds the ratio of the mass of the catalyst: the mass of the ion exchange resin = 0.95: 0.05, the amount of the ion exchange resin covering the catalyst with respect to the catalyst Insufficient reaction sites tend to decrease and battery output tends to decrease. The ion exchange resin also functions as a binder for the cathode 5 and an adhesive between the cathode 5 and the polymer electrolyte membrane PEM. However, the function becomes insufficient, and the tendency that the catalyst layer structure cannot be maintained stably increases. In the case of a supported catalyst supported on a carrier such as catalyst-carrying carbon, the catalyst referred to here includes the mass of the carrier.
[0037]
Furthermore, the ion exchange resin contained in the catalyst layer 1 and the catalyst layer 2 is preferably a sulfonic acid type perfluorocarbon polymer. The sulfonic acid type perfluorocarbon polymer is chemically stable for a long time in the catalyst layer 1 and the catalyst layer 2 and enables rapid proton conduction.
[0038]
Such a sulfonic acid type perfluorocarbon polymer includes polymer units based on tetrafluoroethylene and CF. ₂ = CF- (OCF ₂ CFX) _m -O _p -(CF ₂ ) _n -SO _Three Polymerized units based on a fluorovinyl compound represented by H (wherein m is an integer of 0 to 3, n is an integer of 1 to 12, p is 0 or 1, and X is F or CF. _Three Are preferred.
[0039]
Preferable examples of the fluorovinyl compound include the following compounds (i) to (iv). However, in the following formula, q is an integer of 1 to 8, r is an integer of 1 to 8, s is an integer of 1 to 8, and t is an integer of 1 to 3.
CF ₂ = CFO (CF ₂ ) _q SO _Three H (i)
CF ₂ = CFOCF ₂ CF (CF _Three ) O (CF ₂ ) _r SO _Three H (ii)
CF ₂ = CF (CF ₂ ) _s SO _Three H (iii)
CF ₂ = CF (OCF ₂ CF (CF _Three )) _t O (CF ₂ ) ₂ SO _Three H (iv)
The copolymer is based on tetrafluoroethylene if the polymer units based on fluorine-containing olefins such as hexafluoropropylene or perfluoro (alkyl vinyl ether) are 25% by mass or less of the polymer units based on tetrafluoroethylene. It may be substituted for the polymerized unit.
[0040]
Furthermore, the ratio of the pore volume having a pore diameter of 0.1 μm or less to the total pore volume in the catalyst layer 1 of the present invention is 10.0 to 90.0 vol. % Is preferred. In the following description, the ratio of the pore volume with a pore diameter of 0.1 μm or less to the total pore volume is referred to as the “fine pore ratio”, and gas diffusion composed of pores with a pore diameter exceeding 0.1 μm. Voids excellent in water and drainage properties are referred to as “gas diffusion effective voids”. By setting the fine pore ratio in the catalyst layer 1 within the above range, the reaction interface area of the reaction gas in the catalyst layer 1 can be sufficiently ensured.
[0041]
Here, the fine pore ratio in the catalyst layer 1 is 10.0 vol. If it is less than%, the surface area in the pores in the catalyst layer 1 is remarkably reduced, the area that can be contacted by the reaction gas is reduced, and the battery output tends to be reduced. That is, the battery characteristics tend to deteriorate. On the other hand, the fine pore ratio in the catalyst layer 1 is 90.0 vol. If the ratio exceeds 50%, the proportion of gas diffusion paths in the catalyst layer 1 decreases, and flooding tends to occur when the fuel cell FC is operated under conditions where a large amount of water is generated as in a high current density region. Becomes larger. Moreover, the fine pore ratio in the catalyst layer 1 is 15.0 to 70.0 vol. % Is more preferable.
[0042]
And the fine pore ratio in the catalyst layer 2 is 10.0-70.0 vol. % Is preferred. By setting the fine pore ratio in the catalyst layer 2 within the above range, the reaction interface area of the reaction gas in the catalyst layer 2 can be sufficiently ensured. Here, the fine pore ratio in the catalyst layer 2 is 10.0 vol. If it is less than%, the surface area in the pores of the reaction gas in the catalyst layer 2 is remarkably reduced, and the reaction interface area tends to be reduced. On the other hand, the fine pore ratio in the catalyst layer 2 is 70 vol. If it exceeds%, the tendency to make it difficult to secure a gas diffusion path for sufficiently draining the accumulated product water and condensed water to the outside in the catalyst layer 2 increases. In addition, the fine pore ratio in the catalyst layer 2 is 13.0 to 60.0 vol. It is more preferable that
[0043]
In addition, the fine pore ratio of the catalyst layer 1 and the fine pore ratio of the catalyst layer 2 satisfy the conditions indicated by the above numerical ranges, and the fine pore ratio of the catalyst layer 2 is smaller than the fine pore ratio of the catalyst layer 1. The difference between the fine pore ratio of the catalyst layer 2 and the fine pore ratio of the catalyst layer 1 is preferably 5.0 to 45.0 vol. % Is more preferable.
[0044]
Thus, the ion exchange resin A contained in each of the catalyst layer 1 and the catalyst layer 2 _R In addition, the density of reaction sites is increased in the catalyst layer 1 by controlling the pore diameters of the pores formed in the catalyst layer 1 and the catalyst layer 2 respectively. Since drainage can be enhanced, it is possible to more reliably construct a catalyst layer having a good drainage structure that can maintain a smooth supply of reaction gas to the reaction sites in each catalyst layer over a long period of time. It becomes possible.
[0045]
In particular, as described above, the difference between the fine pore ratio in the catalyst layer 1 and the fine pore ratio in the catalyst layer 2 is 5.0 vol. By setting it as% or more, the functions of the catalyst layer 1 and the catalyst layer 2 can be differentiated more clearly. The difference between the fine pore ratio in the catalyst layer 1 and the fine pore ratio in the catalyst layer 2 is 5.0 vol. When it is less than%, it tends to be difficult to clearly differentiate the functions of the catalyst layer 1 and the catalyst layer 2 described above. On the other hand, the difference between the fine pore ratio in the catalyst layer 1 and the fine pore ratio in the catalyst layer 2 is 45.0 vol. If it exceeds%, it tends to become difficult to maintain the structure of the catalyst layer gradually. Further, the tendency for flooding to easily occur in the catalyst layer 1 also increases.
[0046]
Further, most of the pore diameters of the pores in the catalyst layers 1 and 2 are preferably 0.01 to 100 μm, and more preferably 0.01 to 50 μm. The pores having a pore diameter of less than 0.01 μm cannot perform the function of diffusing the reaction gas toward the reaction site. In particular, flooding occurs when a large number of such pores are distributed in the catalyst layer 2. The tendency to occur increases. On the other hand, pores having a pore diameter exceeding 100 μm are difficult to ensure a sufficient reaction area of the reaction gas.
[0047]
Thus, as a method for controlling the pore structure of the voids formed in each catalyst layer, for example, a liquid in which at least an ion exchange resin and a catalyst are dissolved or dispersed in a solvent (hereinafter referred to as catalyst layer forming ink). The kind of the solvent may be changed. For example, a more porous catalyst layer structure can be obtained by using an organic solvent such as ethanol, toluene, or dichloropentafluoropropane than water.
[0048]
Moreover, you may use a pore making material and a foaming agent as another method. As the pore-forming agent, for example, camphor (having sublimation property) or acid-soluble calcium carbonate can be applied. As the foaming agent, those which are efficiently foamed in a small amount are preferable. For example, organic substances represented by azo compounds, nitroso compounds and sulfonyl hydrazide compounds, and also represented by metal carbonates, bicarbonates, nitrites and hydrides. There are inorganic materials. The foaming agent needs to be subjected to a heat treatment that is held at a temperature of 200 to 280 ° C. for 10 seconds to 30 minutes in order to decompose and generate gas. In this heat treatment, the catalyst coating resin may be decomposed, so that the treatment time is preferably short.
[0049]
Moreover, it is preferable that the sum total of each layer thickness of the catalyst layer 1 and the catalyst layer 2 is 1.0-150 micrometers, and it is more preferable that it is 5.0-100 micrometers. If the total thickness of each of the catalyst layer 1 and the catalyst layer 2 is less than 1.0 μm, it is too thin to form a substantially two-layered multi-layer structure and has a sufficient reaction site. Tends to be difficult to form. On the other hand, if the total thickness of each of the catalyst layer 1 and the catalyst layer 2 exceeds 150 μm, the total thickness of the catalyst layer 3 is increased, the gas diffusibility of the catalyst layer 1 and the catalyst layer 2 is significantly reduced, and the catalyst The ohmic resistance (voltage loss) of the entire catalyst layer 3 including the layer 1 and the catalyst layer 2 tends to increase.
[0050]
Furthermore, the layer thickness of the catalyst layer 1 can sufficiently supply the reaction gas to the region where the density of the reaction site is localized in the vicinity of the polymer electrolyte membrane PEM and the region where the density of the reaction site is high. From the viewpoint of securing the reaction gas path and from the viewpoint of efficiently draining water from this region and reliably preventing flooding, the layer thickness is preferably smaller than the thickness of the catalyst layer 2 in contact with the gas diffusion layer 4 side. Specifically, the layer thickness of the catalyst layer 1 is preferably 0.5 to 70 μm, and more preferably 2.0 to 50 μm. If the layer thickness of the catalyst layer 1 is less than 0.5 μm, it is too thin to be substantially difficult to form and it is difficult to form a catalyst layer having sufficient reaction sites. On the other hand, if the layer thickness of the catalyst layer 1 exceeds 70 μm, the gas diffusibility in the catalyst layer 1 decreases, making it difficult to secure a reaction gas path that can sufficiently supply the reaction gas, and efficiently using water from the catalyst layer 1. It tends to be difficult to drain.
[0051]
Further, the catalyst layer 2 has a gas diffusion path capable of supplying a sufficient reaction gas to the catalyst layer 1 and efficiently drains water such as generated water accumulated in the thickness direction of the entire catalyst layer 3 to the outside. Therefore, the layer thickness is preferably as thin as the catalyst layer 1. However, the layer thickness of the catalyst layer 2 may be thicker than that of the catalyst layer 1 as long as the above-described good gas diffusibility can be ensured within a range where the resistance of the catalyst layer 2 does not increase, and the handling property at the time of preparation is improved. You may decide from a viewpoint. Specifically, the layer thickness of the catalyst layer 2 is preferably 0.5 to 80 μm, and more preferably 3.0 to 60 μm. If the layer thickness of the catalyst layer 2 is less than 0.5 μm, it tends to be difficult to form because it is too thin. On the other hand, when the layer thickness of the catalyst layer 2 exceeds 80 μm, the gas diffusibility is lowered and the resistance of the catalyst layer tends to increase.
[0052]
Furthermore, the porosity of each layer of the catalyst layer 3 is preferably 20 to 95%, and more preferably 40 to 80%. When the porosity of each layer of the catalyst layer 3 is less than 20%, the pore volume of pores formed between the constituent materials in the catalyst layer is remarkably reduced, and the pore diameter of the pores constituting the voids is also significantly reduced. In addition, the surface area in the pores is remarkably reduced, the area in contact with the reaction gas is reduced, and the gas diffusibility and drainage are significantly reduced. Further, if the porosity of each layer of the catalyst layer 3 exceeds 95%, it is difficult to maintain the structure of the catalyst layer itself.
[0053]
On the other hand, the catalyst layer 6 of the anode 8 of the fuel cell FC is also composed of catalyst-carrying carbon black fine particles having a large surface area coated with an ion exchange resin. The catalyst layer 6 of the anode 8 plays a role of advancing the electrode reaction shown in the above formula (4).
[0054]
The ion exchange resin contained in the catalyst layer 6 of the anode 8 is preferably a sulfonic acid type perfluorocarbon polymer, like the cathode 5. Further, since the reaction product water is not generated at the anode 8, the drainage performance as the cathode 5 is not required. Therefore, in order to ensure a sufficient reaction site, the ion exchange resin in the anode 8 preferably has a high water content.
[0055]
From the above viewpoint, A of the ion exchange resin contained in the catalyst layer 6 _R Is 0.85 to 1.40 meq. / G is preferable. A of ion exchange resin contained in catalyst layer 6 _R Is 0.85 meq. If it is less than / g, it is difficult to construct a sufficient proton conduction path in the catalyst layer 6 and a sufficient reaction site cannot be secured. On the other hand, the ion exchange resin A contained in the catalyst layer 6 _R 1.40 meq. If it exceeds / g, the drainage property in the catalyst layer 6 decreases, and the tendency for flooding to occur in the catalyst layer 6 due to condensation of humidified water increases. In FIG. 1, the catalyst layer 6 is composed of a single layer, but may be composed of a plurality of layers.
[0056]
Note that the catalyst layer 3 and the catalyst layer 6 may contain a water repellent as necessary. In particular, the inclusion of a water repellent in the catalyst layer 3 is preferable because the drainage in the catalyst layer 3 can be improved and the effect of suppressing flooding is enhanced. However, since the water repellent agent is an insulator, the amount thereof is preferably as small as possible, and the addition amount is preferably 0.01 to 15% by mass. As such a water repellent, PTFE or a fluorine-containing resin soluble in a solvent can be used.
[0057]
The formation method of the cathode 5 and the anode 8 which consist of such a gas diffusion layer and a catalyst layer is not specifically limited, For example, it manufactures according to the following formation methods.
[0058]
First, a catalyst layer forming ink is prepared. Next, this catalyst layer forming ink is sprayed, applied, applied to the surface of a material that becomes a gas diffusion layer such as a polymer electrolyte membrane PEM or a carbon cloth formed with a layer made of a water repellent and carbon. A catalyst layer having a predetermined structure is formed on the surface of the material to be the polymer electrolyte membrane PEM or the gas diffusion layer by filtration and transfer.
[0059]
Next, the polymer electrolyte membrane PEM on which the catalyst layer is formed and the material to be the gas diffusion layer are joined, or the polymer electrolyte membrane PEM and the material to be the gas diffusion layer on which the catalyst layer is formed are joined. The above-described joining may be performed by, for example, hot pressing or roll pressing. At this time, as disclosed in Japanese Patent Application Laid-Open No. 7-220741, etc., both may be joined by non-heating using a special adhesive. Alternatively, a so-called transfer method may be used in which a catalyst layer is formed on a base plate of PTFE, polyethylene terephthalate, or the like prepared in advance, and then transferred to the polymer electrolyte membrane PEM by hot pressing. In this way, the cathode 5, the anode 8, and the unit cell UC are completed.
[0060]
Here, when the catalyst layer 3 having a two-layer structure is formed, for example, the catalyst layer forming ink for forming the cathode may be directly applied twice on the polymer electrolyte membrane PEM. In this case, the first application is a process for forming the catalyst layer 1, and the second application is a process for forming the catalyst layer 2.
[0061]
Further, the viscosity of the above ink for forming a catalyst layer varies depending on the electrode forming method, and a wide viscosity range is used from a dispersion liquid of about several tens of cP to a paste of about 20,000 cP. it can. In order to adjust the viscosity, the catalyst layer forming ink may contain a thickener or a diluting solvent.
[0062]
As shown in FIG. 1, the separators SP1 and SP2 are respectively mounted on the anode 8 side and the cathode 5 side with respect to one unit cell UC. The separators SP1 and SP2 are formed of, for example, a gas-impermeable electron conductive member such as dense carbon that is compressed and impermeable to carbon, and has a rectangular thin plate shape as shown in FIG.
[0063]
Each groove 9 formed on the cathode contact surface of the separator SP1 defines an air flow path 9 with the surface of the cathode 5 of each single cell UC (see FIG. 1). Furthermore, each groove 10 formed on the contact surface of the separator SP2 with the anode 8 defines a fuel gas flow path 10 by the surface of the anode 8 of each single cell UC. As a result, the fuel gas flows into the fuel gas flow path 10 defined by each groove 10 of the separator SP1 and the surface of the anode 8.
[0064]
The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment.
[0065]
For example, in the above embodiment, the polymer electrolyte fuel cell including the cathode having the two-layer catalyst layer structure has been described. However, the polymer electrolyte fuel cell of the present invention is not limited to this. A cathode having a three or more catalyst layer structure may be provided.
[0066]
In this case, the ion exchange resin A contained in each of the plurality of catalyst layers. _R However, it is preferable to decrease from the innermost catalyst layer to the outermost catalyst layer. Thus, the ion exchange resin A in each catalyst layer from the innermost catalyst layer to the outermost catalyst layer _R By providing a negative slope to the innermost layer, the innermost catalyst layer and the outermost catalyst layer can effectively exert the roles of efficient electrode reaction and efficient drainage intended for each. it can.
[0067]
Moreover, it is preferable that the fine pore ratio in each of the plurality of catalyst layers decreases from the innermost catalyst layer to the outermost catalyst layer. Thus, decreasing the fine pore ratio from the innermost catalyst layer to the outermost catalyst layer also increases the gas diffusion effective void portion from the innermost catalyst layer to the outermost catalyst layer. Therefore, by doing so, a catalyst layer having a good drainage structure capable of maintaining a balanced supply of reaction gas and protons to the reaction sites in each catalyst layer for a long period of time can be further ensured. It becomes possible to construct.
[0068]
Further, in the above embodiment, the solid polymer fuel cell having only the unit cell has been described. However, the solid polymer fuel cell of the present invention is not limited to this, and a plurality of unit cells are provided. It may have a so-called stack structure that is laminated.
[0069]
Furthermore, in the above embodiment, a so-called electrode / membrane assembly has been described as a unit cell, but the polymer electrolyte fuel cell of the present invention is not limited to this. For example, the anode and the cathode are not bonded to the polymer electrolyte membrane by heat treatment, but the anode and the cathode are brought into contact with the polymer electrolyte membrane with respect to the polymer electrolyte membrane. The polymer electrolyte membrane may be sandwiched between the anode and the cathode while being mechanically pressurized from the outside so that each contact resistance becomes a minimum value.
[0070]
Furthermore, in the above embodiment, the polymer electrolyte fuel cell in the case of using a gas mainly composed of hydrogen as the anode reaction gas has been described, but the polymer electrolyte fuel cell of the present invention is limited to this. For example, a configuration in which methanol is directly introduced into the anode as an anode reaction gas may be used.
[0071]
【Example】
Hereinafter, the contents of the polymer electrolyte fuel cell of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition, about the polymer electrolyte fuel cell of the Example and comparative example which are shown below, A which shows the characteristic of the structure of the catalyst layer of each cathode _R Table 1 shows the layer thickness and the fine pore ratio.
Example 1
The unit cell of Example 1 was produced according to the procedure described below.
[0072]
A precursor of an ion exchange resin to be contained in the catalyst layer was first prepared by the following procedure. That is, in a stainless steel autoclave, diisopropyl peroxycarbonate as a polymerization initiator and CF ₂ = CF-OCF ₂ CF (CF _Three ) -OCF ₂ CF ₂ SO _Three F was charged. Next, after sufficiently purging the gas in the autoclave with liquid nitrogen, CF ₂ = CF ₂ And the temperature in the autoclave was maintained at 40 ° C. to initiate bulk polymerization. The pressure in the autoclave during the polymerization reaction is CF from outside the system. ₂ = CF ₂ Was kept constant by introducing additional. Next, unreacted CF 10 hours after the start of polymerization. ₂ = CF ₂ To complete the polymerization, and the resulting polymer solution is agglomerated with methanol, washed and dried to form a CF of a precursor of an ion exchange resin. ₂ = CF ₂ / CF ₂ = CF-OCF ₂ CF (CF _Three ) -OCF ₂ CF ₂ SO _Three An F copolymer was obtained.
[0073]
Next, the precursor of the above ion exchange resin is mixed in a mixed aqueous solution containing 30% by mass of dimethyl sulfoxide and 15% by mass of KOH, hydrolyzed, washed with water, and immersed in 1 mol / L hydrochloric acid. A sulfonic acid type perfluorocarbon polymer was obtained. Here, by adjusting the amount of polymerization initiator and the pressure during polymerization, A _R 1.10 meq. / G, 0.90 meq. Two types of ion exchange resins with a / g concentration were synthesized.
[0074]
The catalyst layer forming ink was prepared as follows. That is, as catalyst layer forming ink A, 40% by mass platinum-supporting carbon fine particles and A _R 1.10 meq. / G of an ion exchange resin was prepared in a mass ratio of 2: 1 to prepare a liquid dispersed in a mixed solvent of ethanol / water (1: 1 by mass ratio). Further, as the catalyst layer forming ink B, A _R 0.90 meq. A liquid was prepared in the same manner as in the catalyst layer forming ink A except for using the ion exchange resin at / g. Furthermore, as catalyst layer forming ink C, a solution was prepared in the same manner as catalyst layer forming ink A except that the solvent was ethanol alone.
[0075]
As the gas diffusion layer of the electrode, a material having a thickness of 350 μm in which a water-repellent carbon cloth (fiber woven fabric) is packed with a water-repellent carbon powder layer (a mixture of carbon black and PTFE) is used for both the anode and the cathode.
[0076]
Furthermore, the cathode catalyst layer having a two-layer structure was formed by the following procedure. That is, first, as the catalyst layer on the gas diffusion layer side, the catalyst layer forming ink C for forming the catalyst layer was loaded with a platinum loading amount of 0.3 mg / cm on the water-repellent carbon powder layer side of the gas diffusion layer sheet. ² Then, it was applied once and dried. Next, a platinum carrying amount of catalyst layer forming ink A as a catalyst layer on the polymer electrolyte membrane side is 0.3 mg / cm. ² Then, it was applied once and dried. In this way, a two-layer cathode catalyst layer was formed. Here, the amount of platinum carried on the produced cathode gas diffusion electrode was 0.6 mg / cm. ² The thickness of the catalyst layer was 50 μm (polymer electrolyte membrane side catalyst layer; 20 μm, gas diffusion layer side catalyst layer; 30 μm). The catalyst layer on the cathode membrane side had a fine pore ratio of 62 vol. %, And the catalyst layer on the gas diffusion layer side has a fine pore ratio of 33 vol. %Met.
[0077]
On the other hand, the catalyst layer of the anode is a catalyst layer forming ink A (resin A for resin formation). _R = 1.10 meq. / G) is 0.3 mg / cm of supported platinum per time. ² It was applied and dried so that the same process was repeated twice. Here, the amount of platinum carried on the produced anode gas diffusion electrode was 0.6 mg / cm. ² Met.
[0078]
The produced gas diffusion electrode has an effective electrode area of 25 cm for both the anode and the cathode. ² It cut out so that it might become. Furthermore, as the polymer electrolyte membrane, a sulfonic acid type perfluorocarbon polymer (trade name: Flemion HR, manufactured by Asahi Glass Co., Ltd., A _R = 1.10 meq. / G, dry film thickness 50 μm).
[0079]
The anode, cathode, and polymer electrolyte membrane produced as described above were joined as follows to produce a so-called electrode / membrane assembly. That is, the cathode and the anode were opposed to each other with the surface on which the catalyst layer forming ink was applied facing inward, and the polymer electrolyte membrane was sandwiched between them to perform hot pressing to join them.
(Example 2)
As catalyst layer forming ink D, 40% by mass platinum-supported carbon catalyst and A _R 1.10 meq. / G of ion exchange resin and calcium carbonate as a pore-forming agent are dispersed in a mixed solvent of ethanol / water (mass ratio of 1: 1) in a mass ratio of 2: 1: 0.05. A prepared solution was prepared.
[0080]
The catalyst layer forming ink D was supported on a gas diffusion layer sheet with a platinum loading of 0.3 mg / cm. ² The electrode / membrane assembly was applied in the same manner as in Example 1 except that after the coating was performed, an acid cleaning treatment was performed to remove the pore-forming agent to form a gas diffusion layer side catalyst layer. Got.
(Examples 3-5 and Comparative Examples 1-8)
Table 2 shows the two-layer structure of the cathode catalyst layer. _R The electrode / membrane assembly was prepared in the same manner as in Example 1 except that the layer thickness and the fine pore ratio were changed.
[Battery characteristics test]
A separator is attached to each unit cell (electrode / membrane assembly) of Examples 1 to 5 and Comparative Examples 1 to 8 to form a measurement cell, and a current pulse generator (FK400L and EX750L manufactured by Takasago Seisakusho Co., Ltd.) is used. The battery characteristics were tested by the current interrupter method. Measurement conditions are: hydrogen inlet pressure: 0.15 MPa, air inlet pressure: 0.15 MPa), operating temperature of measurement cell: 80 ° C., current density: 1.0 A / cm ² The change over time of the polarization characteristics of the measurement cell at 1000 hours was measured. The test results for each of these unit cells are shown in Table 1.
[0081]
In Table 1, ΔA _R Is the value of A of the ion exchange resin contained in the catalyst layer on the polymer electrolyte membrane side in the catalyst layer of the cathode having a two-layer structure. _R X and A of the ion exchange resin contained in the catalyst layer on the gas diffusion layer side _R The difference from Y is shown. Further, the value of ΔV indicates the difference between the battery voltage (inter-terminal voltage) of the measurement cell at the beginning of activation (after about 250 minutes from the start of measurement) and the battery voltage of each measurement cell after 1000 hours have elapsed.
Furthermore, the data described as “−” indicates that “measurement is impossible”.
[0082]
[Table 1]

[0083]
As is clear from the results shown in Table 1, the polymer electrolyte fuel cells of the present invention of Examples 1 to 5 were compared with Comparative Examples 1 to 1 under practical operating conditions (battery voltage conditions). Compared to the polymer electrolyte fuel cell of Example 8, it has high battery characteristics at the initial stage of startup, and further, it is confirmed that it operates stably for a long time of 1000 hours without causing a large deterioration in battery characteristics. It was done.
[0084]
On the other hand, in the polymer electrolyte fuel cells of Comparative Examples 1 to 6, when the battery characteristics at the initial start-up are high, the battery characteristics after 1000 hours are greatly deteriorated. It was confirmed that when the deterioration of the battery characteristics after 1000 hours from the initial stage is suppressed, the battery characteristics at the initial start-up are low and a high battery output cannot be obtained over a long period of time. In particular, the polymer electrolyte fuel cell of Comparative Example 3 corresponding to the polymer electrolyte fuel cell of Japanese Patent Application No. 11-288727 has a cell voltage of 50 mV after operating for 1000 hours with respect to the cell voltage at the initial start-up. It was also confirmed that it also decreased.
[0085]
Furthermore, the polymer electrolyte fuel cell of Comparative Example 7 could not be produced, and the ion exchange resin A contained in the catalyst layer as the catalyst layer on the gas diffusion layer side of the cathode. _R It was confirmed that a catalyst layer could not be formed when the value was very small. In addition, although the polymer electrolyte fuel cell of Comparative Example 8 was able to measure the open circuit voltage, when the polymer electrolyte fuel cell was started to operate, the cell voltage suddenly dropped and the power generation was disabled. It was. At this time, it was confirmed that the ion exchange resin was eluted from the catalyst layer on the gas diffusion layer side of the cathode. From this, A of the ion exchange resin contained in the catalyst layer as the catalyst layer on the gas diffusion layer side of the cathode. _R In the case of a very large value, it was confirmed that the ion exchange resin in the catalyst layer could not stably maintain the solid (crystal) state.
[0086]
【The invention's effect】
As described above, according to the polymer electrolyte fuel cell of the present invention, the catalyst having a good drainage structure capable of maintaining the supply of the reaction gas to the sufficiently secured reaction site over a long period of time. It is possible to build a layer. Therefore, it is possible to prevent the occurrence of flooding in the active catalyst layer, particularly in the cathode catalyst layer, and to effectively use the reaction sites in the catalyst layer. Therefore, according to the present invention, even when the battery characteristics at the initial stage of startup are increased and a large current flows, flooding is sufficiently prevented, and high battery characteristics can be stably obtained over a long period from the initial stage of startup. It is possible to provide a solid polymer fuel cell that can be used.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of a polymer electrolyte fuel cell according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Polymer electrolyte membrane side catalyst layer, 2 ... Gas diffusion layer side catalyst layer, 3 ... Cathode catalyst layer, 4 ... Gas diffusion layer, 5 ... Cathode, 6 ... Anode catalyst layer, 7 ... Gas diffusion layer, 8 DESCRIPTION OF SYMBOLS ... Anode, 9 ... Cathode reaction gas flow path, 10 ... Anode reaction gas flow path, FC ... Fuel cell, PEM ... Polymer electrolyte membrane, SP1, SP2 ... Separator, UC ... Unit cell.

Claims (3)

An anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode, supplying an anode reaction gas to the anode and a cathode reaction gas to the cathode; A polymer electrolyte fuel cell that generates electric power through a chemical reaction,
The cathode includes a gas diffusion layer, and a plurality of catalyst layers disposed between the gas diffusion layer and the polymer electrolyte membrane,
The ion exchange capacity X [milli equivalent / g dry resin] of the ion exchange resin contained in the innermost catalyst layer in contact with the polymer electrolyte membrane, and the outermost catalyst layer in contact with the gas diffusion layer A solid polymer fuel cell characterized in that the ion exchange capacity Y [milli equivalent / g dry resin] of the ion exchange resin satisfies the conditions of the following formulas (1) to (3).
0.88 ≦ X ≦ 1.50 (1)
0.70 ≦ Y ≦ 1.32 (2)
0.18 ≦ (X−Y) ≦ 0.70 (3) 2. The polymer electrolyte fuel cell according to claim 1, wherein the ion exchange resin is a perfluorocarbon polymer having a sulfonic acid group. The ratio of the pore volume having a pore diameter of 0.1 μm or less to the total pore volume in the innermost catalyst layer is 10.0 to 90.0 vol. 3. The solid polymer fuel cell according to claim 1, wherein the ratio of the outermost catalyst layer is smaller than the ratio of the innermost catalyst layer. 4.

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