JP5168639B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell. More specifically, the present invention relates to an improvement in the structure of a fuel cell constituting a fuel cell.

  In general, a fuel cell is composed of a joined body (for example, MEGA) composed of an electrolyte membrane and a pair of electrodes disposed on both sides thereof, and a pair of separators sandwiching the joined body, and a fuel gas (for example, hydrogen gas) and An oxidizing gas is supplied to each electrode.

  For example, in the case of a polymer electrolyte fuel cell, an anode (hydrogen electrode) and a cathode (oxygen electrode) are formed on both surfaces of an electrolyte membrane having proton conductivity. Further, a catalyst layer for promoting an electrochemical reaction and a gas diffusion layer for supplying a reaction gas while diffusing the catalyst gas are formed on both electrodes. In the catalyst layer on the cathode side, water is generated during power generation. The generated water passes through the gas diffusion layer and is discharged out of the fuel cell together with the fuel off gas.

One problem with such fuel cells is that they can be damaged under low temperature conditions, such as below freezing. That is, for example, when starting under a low temperature condition, the produced water may freeze before being discharged to the outside, and destruction (cohesive failure) due to the phase change (water → ice) at this time ) May occur (see, for example, Patent Document 1). In general, such freezing of generated water often occurs at the interface between the catalyst layer on the cathode side and the gas diffusion layer. As one of the countermeasures, the catalyst layer and the gas diffusion layer are formed on the power generation surface of the fuel cell. Increasing the adhesion strength can be mentioned.
JP 2007-328935 A

  However, in the prior art, a specific method for increasing the adhesion strength is unknown.

  SUMMARY OF THE INVENTION The present invention provides a fuel cell in which a technique for increasing the adhesion strength between a catalyst layer and a gas diffusion layer is clarified and damage to the catalyst layer and the like due to freezing of water can be suppressed. .

  In order to solve this problem, the present inventor has made various studies. As described above, in order to suppress damage to the catalyst layer and the like due to water freezing, one of the countermeasures is to increase the adhesion strength between the catalyst layer and the gas diffusion layer. In this case, it is desirable to increase the adhesion strength between the catalyst layer and the gas diffusion layer on the entire power generation surface of the fuel cell, but if this is done, the performance as a fuel cell will be improved. May decrease. In addition, there is a phenomenon that water inside the fuel cell tends to remain particularly in the turn portion of the reaction gas from the disassembly investigation of the fuel cell after power generation. The present inventor, who has repeatedly studied focusing on these phenomena in fuel cells, has obtained new knowledge that leads to the solution of such problems.

  The present invention is based on such knowledge, and comprises an electrolyte membrane, a catalyst layer formed on both surfaces of the electrolyte, and a reaction gas supplied to the electrolyte membrane that is a layer formed further outside the catalyst layer. In a fuel cell in which a fuel cell having a gas diffusion layer to be diffused and a separator that supplies a reaction gas to the gas diffusion layer is laminated, at least part of the space between the catalyst layer and the gas diffusion layer An adhesion part is provided for bringing the catalyst layer and the gas diffusion layer into close contact with each other, and the adhesion part is a ratio of Nafion (registered trademark) to carbon on the end side of the fuel cell. It is formed by blending with a high value of N / C.

  In this fuel cell, the value of N / C is partially increased, and the increased portion is caused to function as an adhesive portion so that the adhesion strength between the catalyst layer and the gas diffusion layer is increased. That is, if the value of N / C is partially high, the I / C (ratio of ions to carbon) of the part increases, and it functions as an adhesive part having a relatively high adhesion strength compared to other parts. Yes. According to this, it becomes possible to suppress damage to the catalyst layer and the like due to freezing of water.

  Moreover, in the present invention, the adhesive portion is provided on the end side (near the periphery) of the fuel battery cell. The end portion of the fuel cell has a small contribution to the total power generation amount and is a portion corresponding to a portion where water is likely to remain. Therefore, by taking measures to increase the adhesion strength by focusing on this portion, the fuel cell It is possible to suppress breakage of the catalyst layer and the like while suppressing the performance degradation.

  In the above fuel cell, the end portion side of the fuel cell is a non-power generation site in the fuel cell. Since the non-power generation part is an equal part with no contribution to the total power generation amount, even if the adhesion strength between the catalyst layer and the gas diffusion layer is increased in the non-power generation part, it is possible to suppress a decrease in the performance of the fuel cell. is there. In such a case, damage to the catalyst layer or the like can be suppressed while suppressing deterioration of the fuel cell.

In the above fuel cell, for example, the catalyst layer is a cathode side catalyst layer, and the gas diffusion layer is a cathode side gas diffusion layer. For example, in a proton transfer type fuel cell (that is, an ion conductive species is H ⁺ ), generated water is generated on the cathode side. ADVANTAGE OF THE INVENTION According to this invention, damage to the catalyst layer etc. which can occur when produced water freezes on the cathode side can be suppressed.

  According to the present invention, a technique for increasing the adhesion strength between the catalyst layer and the gas diffusion layer is clarified, and damage to the catalyst layer and the like due to freezing of water can be suppressed.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  FIG. 1 shows a schematic configuration of a fuel cell (fuel cell) 2 in the present embodiment. There are a plurality of types of fuel cells configured by stacking the cells 2 such as a phosphoric acid type. The fuel cell according to the present embodiment is a solid polymer electrolyte type suitable for in-vehicle use or stationary use. The fuel cell can be used as, for example, an on-vehicle power generation system of a fuel cell vehicle (FCHV), but is not limited thereto, and various mobile objects (for example, ships and airplanes), robots, and the like It can also be used in a power generation system mounted on a self-propelled device such as a stationary power generation system.

  The cell 2 includes a joined body 30 and a pair of separators (indicated by reference numerals 20a and 20b in FIG. 1) that sandwich the joined body 30 (see FIG. 1). The joined body 30 and the separators 20a and 20b are formed in a substantially rectangular plate shape. Moreover, the joined body 30 and each separator 20a, 20b are molded by molding resin with the 1st seal member 13a and the 2nd seal member 13b in the peripheral part between them.

  As the assembly 30, a membrane / electrode assembly (MEA: Membrane Electrode Assembly) in which electrode catalyst layers 321 and 331 such as platinum are arranged on both surfaces of an electrolyte (solid polymer membrane) made of an ion exchange membrane, or a catalyst layer Membrane Electrode & Gas Diffusion Layer Assembly (MEGA) in which gas diffusion layers 322 and 332 are further provided on 321 and 331 can be used. For example, in this embodiment, a joined body 30 made of a membrane-electrode-diffusion layer assembly (MEGA) is used (see FIG. 3).

  The joined body 30 includes a polymer electrolyte membrane (hereinafter also simply referred to as an electrolyte membrane) 31 made of an ion exchange membrane of a polymer material, and a pair of electrodes (an anode side diffusion electrode 32 and a cathode side) sandwiching the electrolyte membrane 31 from both sides. And a diffusion electrode 33) (see FIG. 3). Each of the diffusion electrodes 32 and 33 is made of, for example, a porous carbon material carrying a catalyst such as platinum attached to the surface thereof. The anode side diffusion electrode 32 is supplied with hydrogen gas as a fuel gas (reaction gas), and the cathode side diffusion electrode 33 is supplied with an oxidizing gas (reaction gas) such as air or an oxidant. An electrochemical reaction occurs in the cell 30 so that the electromotive force of the cell 2 can be obtained. In FIG. 3, the catalyst layer and the gas diffusion layer constituting the anode side diffusion electrode 32 are denoted by reference numerals 321 and 322, respectively, and the catalyst layer and the gas diffusion layer constituting the cathode side diffusion electrode 33 are denoted by reference numerals 331 and 332, respectively. Is shown.

  Separator 20a, 20b is comprised with the gas-impermeable electroconductive material. Examples of the conductive material include carbon and a hard resin having conductivity, and metals such as aluminum and stainless steel. The base material of the separators 20a and 20b of this embodiment is formed of a plate-like metal (metal separator), and a film (for example, gold plating) having excellent corrosion resistance is provided on the surface of the base material on the electrodes 32a and 32b side. Is formed).

  Further, on both surfaces of the separators 20a and 20b, a groove-like flow path constituted by a plurality of concave portions is formed in a serpentine shape, for example. These flow paths can be formed by press molding in the case of the separators 20a and 20b of the present embodiment in which the base material is formed of, for example, a plate-like metal. The groove-shaped flow path formed in this way constitutes a gas flow path 34 for oxidizing gas, a gas flow path 35 for hydrogen gas, or a cooling water flow path 36.

  Near one end of the separators 20a and 20b in the longitudinal direction, an oxidizing gas inlet side manifold 15a, a hydrogen gas outlet side manifold 16b, and a cooling water outlet side manifold 17b are formed. For example, in the case of this embodiment, these manifolds 15a, 16b, and 17b are formed by substantially rectangular or trapezoidal through holes provided in the separators 20a and 20b (see FIG. 1). Further, an oxidant gas outlet side manifold 15b, a hydrogen gas inlet side manifold 16a, and a cooling water inlet side manifold 17a are formed at opposite ends of the separators 20a and 20b (see FIG. 5). 1).

  Of the manifolds as described above, the inlet side manifold 16a and the outlet side manifold 16b for the hydrogen gas in the separator 20a have an inlet side communication passage 61 and an outlet side communication passage 62 formed in the separator 20a in a groove shape. Each communicates with a gas flow path 35 of hydrogen gas. Similarly, the inlet side manifold 15a and the outlet side manifold 15b for the oxidizing gas in the separator 20b are oxidized via the inlet side communication passage 63 and the outlet side communication passage 64 formed in the separator 20b in a groove shape. The gas communicates with the gas flow path 34 (see FIG. 1). Further, the inlet side manifold 17a and the outlet side manifold 17b of the cooling water in each separator 20a, 20b are connected to each separator 20a, 20b through an inlet side communication passage 65 and an outlet side communication passage 66 formed in a groove shape. Each communicates with the cooling water passage 36.

  The first seal member 13a and the second seal member 13b are both frame-shaped members that are formed in substantially the same shape (see FIG. 1). Among these, the first seal member 13a is provided between the joined body 30 and the separator 20a. More specifically, the peripheral portion of the electrolyte membrane 31 and the portion around the gas flow path 35 in the separator 20a. Between the two. Further, the second seal member 13b is provided between the joined body 30 and the separator 20b, and more specifically, the peripheral portion of the electrolyte membrane 31 and the portion around the gas flow path 34 in the separator 20b. Between the two. Further, a frame-shaped third seal member 13c is provided between the separators 20b and 20a of the adjacent cells 2 and 2 (see FIG. 1).

  Moreover, the frame-shaped member shown by the code | symbol 40 is a member (resin frame) which consists of resin between the separators 20a and 20b with the joined body 30, for example.

  Next, a structure unique to the fuel cell in the present embodiment will be described (see FIGS. 2 and 3).

  In the fuel cell of the present embodiment, an adhesive portion is provided at least partially between the cathode side catalyst layer 331 and the cathode side gas diffusion layer 332. On the other hand, the part where the adhesive part is not provided is a part where the cathode side catalyst layer 331 and the cathode side gas diffusion layer 332 are not in close contact (hereinafter referred to as a non-adhesive part).

  The adhesion part is a part that functions to increase the adhesion strength between the cathode side catalyst layer 331 and the cathode side gas diffusion layer 332. For example, in this embodiment, the value of N / C is mixed partially high, and the increased portion is functioned as an adhesive portion. N / C is a value representing the ratio of Nafion (registered trademark) to carbon. The registered trademark Nafion is a name of one product of DuPont. Nafion (registered trademark), which is an ionic polymer, is a kind of ionomer and constitutes a fluorine resin ion exchange membrane having proton conductivity. When the value of N / C is mixed partially high, the I / C (ratio of ions to carbon) of the portion increases. Thus, the part which functions as an adhesion part has relatively high adhesion strength compared with other parts (non-adhesion part).

  It is preferable that such an adhesive portion is provided corresponding to a position where water is likely to remain, particularly after power generation. Under low-temperature conditions such as below freezing, destruction (cohesive failure) may occur due to the phase change of water (water ← → ice). In order to cope with this, it is desirable to increase the adhesion strength between the cathode-side catalyst layer 331 and the cathode-side gas diffusion layer 332 over the entire power generation surface of the fuel battery cell 2, but this makes it difficult for gas to flow and flooding occurs. There is a possibility that the performance as a fuel cell is deteriorated, such as being easily generated. In this regard, in the present embodiment, the adhesive portion is provided on the end side (near the periphery) of the fuel battery cell 2. Since the end portion of the fuel cell 2 has a small contribution to the total amount of power generation and is a portion corresponding to a portion where water tends to remain, it is effective to squeeze the portion to increase the adhesion strength. is there.

  In this case, the end of the fuel cell 2 is preferably a non-power generation site in the fuel cell. Since the non-power generation part is an equal part with no contribution to the total power generation amount, even if the adhesion strength between the cathode-side catalyst layer 331 and the cathode-side gas diffusion layer 332 is increased in the non-power generation part, the performance of the fuel cell is reduced. It is possible to suppress it.

  Further, for example, in the case of a fuel cell having a serpentine type flow path (oxidizing gas flow path 34 or hydrogen gas flow path 35) as in this embodiment, it corresponds to the turn portion 19 of the flow path. In the portion, the adhesion strength between the cathode side catalyst layer 331 and the cathode side gas diffusion layer 332 may be increased. Since the turn part 19 of the serpentine channel is located closer to the end in the power generation site, the degree of adhesion between the cathode side catalyst layer 331 and the cathode side gas diffusion layer 332 is increased at the part corresponding to the turn part 19. Even if this is the case, it is possible to suppress the performance degradation of the fuel cell (see FIG. 2). In particular, considering the result of the decomposition investigation that moisture tends to remain in the turn part 19, the adhesion strength between the cathode side catalyst layer 331 and the cathode side gas diffusion layer 332 is increased in the part corresponding to the turn part 19 in this way. Is preferable in that deterioration of the contact layer or the like of the portion can be suppressed. In addition, the dimple 23 is formed in the turn part 19 of the oxidizing gas flow path 34 illustrated in FIG. 2 (see FIG. 2).

  As described above, in the present embodiment, the location of the countermeasure in the fuel cell is specified by using the adhesion portion where the cathode side catalyst layer 331 and the cathode side gas diffusion layer 332 are in close contact and the non-contact portion where the cathode side gas diffusion layer 332 is not in close contact. However, it is provided. According to this, it is possible to increase the adhesion strength between the catalyst layer and the gas diffusion layer at a predetermined portion while suppressing the deterioration of the performance of the fuel cell, and to suppress the damage of the catalyst layer due to freezing.

  Moreover, in the present embodiment, a technique for increasing the adhesion strength is clarified, such as forming the above-mentioned adhesive portion by blending a high N / C value on the end portion side of the fuel cell 2. It has become. Therefore, it is possible to suppress damage to the catalyst layer and the like due to water freezing as appropriate in response to differences in the shape and structure of the fuel cell 2.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, an example in which an adhesive portion is provided at least at a part between the cathode side catalyst layer 331 and the cathode side gas diffusion layer 332 has been shown. Of course, on the contrary, the anode side catalyst layer 321 and the anode are provided. It is also possible to provide an adhesive portion between the side gas diffusion layer 322. In short, if the fuel cell is a so-called proton transfer type such as a solid polymer type, it is preferable to increase the adhesion strength between the catalyst layer and the gas diffusion layer on the cathode side because generated water is generated on the cathode side. Therefore, for different types of fuel cells, it is possible to prevent damage to the catalyst layer and the like by appropriately increasing the adhesion strength between the catalyst layer and the gas diffusion layer on the anode side.

  Moreover, although embodiment mentioned above illustrated and demonstrated the case where separator 20 (20a, 20b) was what is called a metal separator, the application object of this invention is not restricted to this. The present invention can also be applied when the separator is other than this (for example, when it is a carbon separator).

It is a disassembled perspective view of the fuel battery cell in one Embodiment of this invention. It is a top view which shows the structural example of a separator. It is sectional drawing which shows the structural example of a fuel cell.

Explanation of symbols

2 ... cell (fuel cell), 31 ... polymer electrolyte membrane (electrolyte membrane), 20 (20a, 20b) ... separator, 321 ... anode side catalyst layer (catalyst layer), 322 ... anode side gas diffusion layer (gas diffusion) Layer), 331 ... cathode side catalyst layer (catalyst layer), 332 ... cathode side gas diffusion layer (gas diffusion layer)

Claims (3)

An electrolyte membrane, a catalyst layer formed on both surfaces of the electrolyte, a gas diffusion layer formed on the outer side of the catalyst layer and diffusing a reaction gas supplied to the electrolyte membrane, and the gas diffusion In a fuel cell in which a fuel cell having a separator for supplying the reaction gas to a layer is laminated,
At least a part between the catalyst layer and the gas diffusion layer is provided with an adhesion part that makes the catalyst layer and the gas diffusion layer more closely contact with each other than the other parts
Adhesive portion is formulated Nafion value of N / C is the ratio of (R) partially higher against mosquito Bon, the adhesion strength of the high formulated portion and the catalyst layer and the gas diffusion layer It is formed with parts that function to raise ,
In addition, the adhesive portion is formed in a non-power generation portion that is a portion near the periphery of the fuel battery cell and that has no or no contribution to the total power generation amount of the fuel battery cell. A fuel cell. 2. The fuel cell according to claim 1, wherein the fuel cell is a fuel cell having a serpentine-type channel, and the adhesive portion is formed at a portion corresponding to a turn portion of the serpentine-type channel .   The fuel cell according to claim 1, wherein the catalyst layer is a cathode side catalyst layer, and the gas diffusion layer is a cathode side gas diffusion layer.

Images