JP6305132B2 - Polymer electrolyte fuel cell - Google Patents

Description

  The present invention comprises a membrane electrode assembly comprising a solid polymer electrolyte membrane sandwiched between a fuel electrode and an air electrode, and a plurality of cells that generate power using a reaction gas supplied to the membrane electrode assembly. The present invention relates to a polymer electrolyte fuel cell including a cell stack formed in the above manner.

  In the polymer electrolyte fuel cell, proton conductivity is increased by wetting the polymer electrolyte membrane and the fuel electrode and the air electrode sandwiching it from both sides, thereby enabling power generation. Therefore, the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the air electrode are operated with humidification such as mixing water vapor. In stationary applications where long-term durability is required, operation under saturated humidification conditions in which the cell temperature and the dew points of the fuel gas and the oxidant gas are substantially the same are generally used from the viewpoint of suppressing deterioration. Under these conditions, the battery temperature is lowered during condensation and water is likely to be generated during low-load operation, so the water blockage of the gas flow path required for the reaction causes deterioration in battery performance and instability. It will be. For this reason, measures have been taken to discharge excess moisture such as ensuring the gas flow rate in the gas flow path (see, for example, Patent Document 1).

On the other hand, cost can be reduced by simplifying or eliminating the humidification function for the fuel gas and the oxidant gas. For this reason, development that suppresses cell deterioration even under non-saturated humidification conditions has been advanced (see, for example, Non-Patent Document 1).
In such a low humidification condition, how efficiently the water generated by power generation can be used to wet the cell, that is, the low humidification adaptation that represents the adaptive performance of the membrane electrode assembly used in the low humidification condition. High performance (for example, water retention performance, proton conductivity performance under low humidification conditions, anti-degradation performance under low humidification conditions, etc.) is important for extracting power generation performance, and optimization of cell components is promoted (See, for example, Non-Patent Document 2).

JP 2004-247289 A

Eiji Endoh, ECS Transactions, 16 (2), 1229, (2008) Nishikawa, Nakamura, Matsuyama, Kaoru, Proc. Of 15th Fuel Cell Symposium, 123, (2008)

  However, a cell component having high low humidification adaptability adapted to low humidification conditions, particularly a solid polymer electrolyte membrane, is expensive with respect to general saturated humidification condition specifications, and is not suitable for cost reduction for popularization.

  In addition, the membrane electrode assembly in the vicinity of the inflow portion of the reaction gas to the cell (that is, the upstream side) is easily dried by the inflowing reaction gas, although water is generated by the power generation reaction there. On the other hand, the membrane electrode assembly in the vicinity of the outflow part of the reaction gas from the cell (that is, the downstream side) generates water generated by the power generation reaction and is carried by the flow of the reaction gas. There will be a lot of water. Therefore, when the membrane / electrode assembly is configured to have high low humidification adaptive performance (for example, high water retention capability of easily retaining water) in accordance with the upstream conditions that are easy to dry as described above, On the side, wetting becomes excessive, and the water that remains can cause blockage of the gas flow path required for the reaction. Conversely, the membrane electrode assembly is configured to have low water retention performance (that is, performance that water is easily discharged) in accordance with downstream conditions where a large amount of water is present as described above. As a result, there is a problem in that wetting is insufficient on the upstream side, and the proton conductivity of the membrane electrode assembly cannot be sufficiently secured.

  The present invention has been made in view of the above problems, and its object is to provide a polymer electrolyte fuel cell capable of sufficiently exhibiting the performance required for a membrane electrode assembly while suppressing an increase in cost. Is to provide

In order to achieve the above object, the solid polymer fuel cell according to the present invention has a membrane electrode assembly configured by sandwiching a solid polymer electrolyte membrane between a fuel electrode and an air electrode, and the membrane electrode A polymer electrolyte fuel cell comprising a cell stack formed by stacking a plurality of cells that generate power using a reaction gas supplied to a joined body,
The cell includes an inflow portion into which the reaction gas flows, an outflow portion from which the reaction gas flows out after being used in power generation, and the reaction gas between the inflow portion and the outflow portion in the cell. A flowing gas flow path,
The low humidification adaptive performance of the membrane electrode assembly facing the gas flow path in the cell is configured so that the vicinity of the inflow portion is higher than the vicinity of the outflow portion ,
The membrane electrode assembly is formed by combining a plurality of membrane electrode assembly members having different low humidification adaptability . This low-humidification adaptive performance is a characteristic that represents the adaptive performance of the membrane electrode assembly when used under low humidification conditions. For example, the water retention performance, proton conductivity performance under low humidification conditions, and under low humidification conditions. Is at least one of the deterioration resistance performance of

According to the above characteristic configuration, the low humidification adaptive performance of the membrane electrode assembly facing the gas flow path in the cell is configured to be higher in the vicinity of the inflow portion than in the vicinity of the outflow portion. In other words, the membrane electrode assembly in the vicinity of the inflow portion of the reaction gas has a relatively high low humidification adaptability (that is, high water retention performance (performance that can easily retain water) in accordance with low humidification conditions in which relatively little water is present. ), At least one of high proton conductivity performance under low humidification conditions and high deterioration resistance performance under low humidification conditions). On the other hand, the membrane electrode assembly in the vicinity of the outflow part of the reaction gas is in a condition where a relatively large amount of water is present, and therefore the low humidification adaptive performance is not high (that is, the water retention performance is low). Even so, it can be expected that the proton conductivity can be sufficiently secured. Moreover, if the water retention performance is low, the problem that the flow path of the reaction gas is blocked by water is less likely to occur. As a result, the required performance can be sufficiently exerted over the entire membrane electrode assembly.
Further, in this feature configuration, the entire membrane electrode assembly is not configured to have a high low humidification adaptive performance that matches the low humidification condition, so that the membrane electrode assembly does not become very expensive.
Therefore, it is possible to provide a polymer electrolyte fuel cell that can sufficiently exhibit the performance required for the membrane electrode assembly while suppressing an increase in cost.

In addition , by combining a plurality of membrane electrode assembly members with different low humidification adaptability, the low humidification adaptability of the membrane electrode assembly facing the gas flow path in the cell can be improved in the vicinity of the inflow portion of the reaction gas. It is possible to obtain a configuration in which the height is higher than that in the vicinity of the outflow portion of the reaction gas.

Another characteristic configuration of the polymer electrolyte fuel cell according to the present invention is that the reaction gas is configured to flow into the inflow portion in a state where a dew point is lower than an operating temperature of the cell.

If the polymer electrolyte fuel cell is operated under saturated humidification conditions where the dew point of the reaction gas is equal to or higher than the cell operating temperature, that is, if the reaction gas contains a large amount of water, for example, the reaction gas or water A lot of energy is needed, such as the need to raise the temperature.
However, according to this characteristic configuration, the polymer electrolyte fuel cell is operated under a low humidification condition in which the reaction gas is allowed to flow into the inflow portion in a state where the dew point is lower than the operating temperature of the cell. That is, the energy required for humidifying the reaction gas can be made relatively small.
Further, since the amount of water present in the cell can be relatively reduced, it is possible to suppress the occurrence of a problem that the flow path of the reaction gas is blocked with water.

  Yet another characteristic configuration of the polymer electrolyte fuel cell according to the present invention is that the reaction gas is an oxidant gas supplied to the air electrode.

Since water is generated by the power generation reaction at the air electrode to which the oxidant gas is supplied, there is a relatively large amount of water present compared to the fuel electrode side. Therefore, the problem that the membrane electrode assembly in the vicinity of the inflow portion of the reaction gas to the cell is easily dried by the inflowing reaction gas is common to the fuel electrode side and the air electrode side. The phenomenon that a lot of water is present in the vicinity of the outflow portion is more remarkable on the air electrode side than on the fuel electrode side.
In this feature configuration, the low humidification adaptive performance of the membrane electrode assembly facing the gas flow path of the oxidant gas supplied to the air electrode is configured so that the vicinity of the inflow portion is higher than the vicinity of the outflow portion. Therefore, it is possible to better cope with a phenomenon in which a large amount of water is present in the vicinity of the outflow portion of the reaction gas from the cell, which becomes prominent on the air electrode side.

It is a figure which shows the structure of a fuel cell system. It is a schematic diagram explaining the structure of a cell stack. It is a disassembled perspective view of a cell. It is a figure which shows the cross-section of a membrane electrode assembly. It is a disassembled perspective view of a cell.

<First Embodiment>
The configuration of the polymer electrolyte fuel cell according to the first embodiment will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a fuel cell system, FIG. 2 is a schematic diagram illustrating a configuration of a cell stack CS, and FIG. 3 is an exploded perspective view of a cell. As shown in the figure, the fuel cell system includes a power generation unit U1 and a hot water storage unit U2. In the drawings shown in the present application, in order to facilitate understanding of the present invention, there are places where the positional relationship and size of each member are drawn differently from the original positional relationship and size.

  The power generation unit U1 has a polymer electrolyte fuel cell as a combined heat and power generation device that generates heat and electricity together. The polymer electrolyte fuel cell includes a membrane electrode assembly 40 configured by sandwiching a polymer electrolyte membrane 10 between a fuel electrode 11 and an air electrode 12, and a fuel electrode 11 side of the membrane electrode assembly 40. A fuel electrode separator 13 that introduces fuel gas into the fuel electrode 11 through the gas flow path 13a, and the air electrode 12 side of the membrane electrode assembly 40 are provided, and the oxidant gas is supplied to the air electrode 12 through the oxidant gas flow path 14a. And a cell stack CS formed by laminating a plurality of cells C each having an air electrode separator 14 for introducing air. The fuel cell system also includes operation control means 36 for controlling its own operation.

In the present embodiment, hydrogen as a fuel gas and air (oxygen) as an oxidant gas are supplied to the polymer electrolyte fuel cell.
Hydrogen as the fuel gas is generated when the reformer 8 provided in the power generation unit U1 reforms raw fuel containing hydrocarbons. In the example shown in FIG. 1, raw fuel gas (city gas or the like) mainly composed of methane (CH ₄ ) is supplied to the reformer 8 through the raw fuel gas supply path 6 and reformed. The resulting fuel gas mainly composed of hydrogen is supplied to the cell C through the fuel gas supply path 7. In addition, air as an oxidant gas is also supplied to the cell C through the oxidant gas supply path 1.

  A fuel electrode side humidifier 4 is provided in the middle of the fuel gas supply path 7 to humidify the fuel gas supplied to the cell C. An air electrode side humidifier 2 is provided in the middle of the oxidant gas supply path 1 to humidify the oxidant gas supplied to the cell C. Various existing humidifiers can be used for the fuel electrode side humidifier 4 and the air electrode side humidifier 2. The operation control means 36 controls the operations of the fuel electrode side humidifier 4 and the air electrode side humidifier 2. Specifically, the operation control means 36 adjusts the dew points of the fuel gas and the oxidant gas by controlling the temperatures at the humidified portions of the fuel electrode side humidifier 4 and the air electrode side humidifier 2. For example, when the operation control means 36 increases the temperature at the humidifying portion of the fuel electrode side humidifier 4, the amount of water contained in the fuel gas can be increased (that is, the dew point of the fuel gas is increased). . In the present embodiment, the operation control means 36 includes inflow portions 13a1 and 14a1 which will be described later with fuel gas and oxidant gas as reaction gases in a state where their dew points are lower than the operating temperature of the cell C (for example, 70 ° C.). The operation of the humidifiers 2 and 4 is controlled so as to flow into.

  In addition, the fuel gas after being used for the power generation reaction in the cell C (hereinafter also referred to as “exhaust fuel gas”) is supplied to the combustor 9 via the exhaust fuel gas passage 5. In addition, air (oxygen) is supplied through the oxidant gas supply path 1a. Then, the exhaust fuel gas is combusted in the combustor 9 and the combustion heat is transmitted to the reformer 8, whereby the reforming reaction in the reformer 8 is promoted. Then, the exhaust gas discharged from the combustor 9 and the air after being used for the power generation reaction in the cell C are discharged to the outside of the power generation unit U1 through the exhaust gas path 3. FIG. 1 shows a state in which exhaust fuel gas and air are mixed in advance and then supplied to the combustor 9 (a state in which the exhaust fuel gas passage 5 is connected to the oxidant gas supply passage 1a). However, the exhaust fuel gas and air may be separately supplied to the combustor 9.

  In the cell C, the fuel electrode separator 13 is provided on the fuel electrode 11 side of the membrane electrode assembly 40, and the air electrode separator 14 is provided on the air electrode 12 side of the membrane electrode assembly 40. Then, the fuel gas is introduced into the fuel electrode 11 through the fuel gas channel 13 a formed in the fuel electrode separator 13, and the oxidant gas is introduced into the air electrode 12 through the oxidant gas channel 14 a formed in the air electrode separator 14. Is done. In the example shown in FIG. 1, one cell C includes a fuel electrode separator 13 in which a fuel gas groove 13a serving as a fuel gas passage 13a through which fuel gas flows is formed on one surface, and an oxidant on one surface. An air electrode separator 14 in which an oxidant gas groove serving as an oxidant gas flow path 14a through which gas flows is formed and a cooling water groove through which cooling water flows is formed on the other surface; a membrane electrode assembly 40; It is configured using. Then, in one cell C, the fuel gas is introduced into the fuel electrode 11 by making one surface of the fuel electrode separator 13 in which the fuel gas groove is formed relative to the fuel electrode 11 of the membrane electrode assembly 40, The oxidant gas is introduced into the air electrode 12 by making one surface of the air electrode separator 14 in which the groove for the oxidant gas is formed facing the air electrode 12 of the membrane electrode assembly 40. . In the cell stack CS, the other surface of the air electrode separator 14 in which the cooling water groove of one cell C is formed is connected to the other surface of the fuel electrode separator 13 in which the groove for fuel gas of the other cell C is not formed. A plurality of cells C are sequentially stacked so as to face the surface.

  The cell C is sequentially stacked in the Y-axis direction shown in FIG. The cell stack CS extends from the upstream side to the downstream side along the stacking direction of the cells C (that is, extends along the Y-axis direction), and the fuel gas supply through which the fuel gas supplied to the cell stack CS flows. Manifold part 15, oxidant gas supply manifold part 17 through which oxidant gas supplied to cell stack CS flows, fuel gas discharge manifold part 16 through which fuel gas discharged from cell stack CS flows, and exhaust from cell stack CS And an oxidant gas discharge manifold portion 18 through which the oxidant gas flows. A fuel gas supply path 7 is connected to the fuel gas supply manifold section 15, whereby fuel gas is supplied to the cell stack CS. The oxidant gas supply passage 1 is connected to the oxidant gas supply manifold section 17 so that the oxidant gas is supplied to the cell stack CS. The exhaust gas passage 5 is connected to the fuel gas discharge manifold section 16, whereby the fuel gas (exhaust fuel gas) after being used for the power generation reaction in the cell C is discharged from the cell stack CS. The exhaust gas passage 3 is connected to the oxidant gas discharge manifold portion 18 so that the oxidant gas after being used for the power generation reaction in the cell C is discharged from the cell stack CS.

  Inside each cell C, the fuel gas flow path 13a connects between the fuel gas supply manifold section 15 and the fuel gas discharge manifold section 16, and the oxidant gas flow path 14a is connected to the oxidant gas supply manifold section 17. The oxidant gas discharge manifold portion 18 is connected. In the fuel gas supply manifold section 15, the fuel gas flows into the fuel gas flow path 13 a while flowing from the upstream side to the downstream side, and in the oxidant gas supply manifold section 17, the oxidant gas flows from the upstream side. It flows into the oxidant gas flow path 14a while flowing toward the downstream side. In the example shown in FIG. 2, in order to simplify the drawing, in the cell C, the fuel gas flow path 13a is formed in a straight line shape along the X-axis direction, and the oxidant gas flow path 14a is straight along the Z-axis direction. Although a schematic diagram is illustrated as being formed in a shape, the shape of the fuel gas flow path 13a and the shape of the oxidant gas flow path 14a inside the cell C can be freely designed. For example, in one cell C, the fuel gas flow path 13a can be formed so that the fuel gas flows in the positive direction of the X axis as a whole while meandering in the XZ plane. Further, in one cell C, the oxidant gas flow path 14a can be formed so that the oxidant gas flows in the positive direction of the Z axis as a whole while meandering in the XZ plane. . Further, in the example shown in FIG. 2, description of the cooling water is omitted.

  The cooling water described above plays a role of cooling the cell C and also plays a role of recovering exhaust heat from the cell C. In the present embodiment, the cooling water flows through the cooling water circulation path 19. In the middle of the cooling water circulation path 19, the cooling water flow path 20 in the cell stack CS, the cooling water heat exchanger 21, and the cooling water pump 22 are provided. The energized cooling water is circulated while flowing through the cell stack CS (cooling water flow path 20) and the cooling water heat exchanger 21 in order. Moreover, the hot water stored in the hot water storage tank 25 provided in the hot water storage unit U <b> 2 flows into the cooling water heat exchanger 21 through the exhaust heat recovery path 23. As a result, in the cooling water heat exchanger 21, heat exchange is performed between the cooling water flowing through the cooling water circulation path 19 and the hot water flowing through the exhaust heat recovery path 23. The flow rate of hot water in the exhaust heat recovery path 23 is adjusted by controlling the output of the exhaust heat recovery pump 24 provided in the middle of the exhaust heat recovery path 23. The operation of the cooling water pump 22 and the exhaust heat recovery pump 24 is controlled by the operation control means 36.

  In the hot water storage tank 25 provided in the hot water storage unit U2, hot water at a relatively high temperature is stored in the upper part, and hot water at a relatively low temperature is stored in the lower part. Specifically, the exhaust heat recovery path 23 is provided so as to connect the lower part of the hot water storage tank 25 and the upper part of the hot water storage tank 25, and the cooling water heat exchanger 21 is provided therebetween. As a result, the relatively low temperature hot water stored in the lower part of the hot water storage tank 25 is heated up to the cooling water heat exchanger 21 through the exhaust heat recovery path 23, and the heated temperature is relatively increased. Hot hot water returns to the upper part of the hot water storage tank 25 and flows in.

  A hot water supply passage 27 is connected to the upper part of the hot water storage tank 25 to supply hot water for hot water supply such as a kitchen or a bath. In addition, a water supply path 26 is connected to the lower part of the hot water storage tank 25 so that hot water is replenished to the hot water storage tank 25.

Next, the cell structure will be described.
FIG. 3 is an exploded perspective view of one cell C. FIG. As shown in the figure, the cell C has a structure in which the membrane electrode assembly 40 is sandwiched between the fuel electrode separator 13 and the air electrode separator 14 from both sides. A gasket (an example of a sealing member) 41 is provided around the membrane electrode assembly 40, and the membrane electrode assembly 40 and the gasket 41 are combined into one member to form the fuel electrode separator 13 and the air electrode separator. 14 between the two sides. The gasket 41 is formed in an annular shape having an opening at the center, and the membrane electrode assembly 40 is fitted into the opening. In addition, in FIG. 3, description about the flow path of a cooling water is abbreviate | omitted.

  As shown in FIG. 3, the fuel gas supply manifold portion 15, the fuel gas discharge manifold portion 16, the oxidant gas supply manifold portion 17, and the oxidant gas discharge manifold portion 18 are formed in the cell C. Among these, the fuel gas supply manifold portion 15 and the fuel gas discharge manifold portion 16 are connected to the fuel gas flow path 13a formed in the fuel electrode separator 13, and the oxidant gas supply manifold portion 17, the oxidant gas discharge manifold portion 18 and the like. Is connected to an oxidant gas flow path 14 a formed in the air electrode separator 14. The fuel gas flowing through the fuel gas channel 13a is in direct contact with the surface on one side (fuel electrode 11 side) of the membrane electrode assembly 40, and the oxidant gas flowing through the oxidant gas channel 14a is contacted with the membrane electrode assembly 40. Directly from the surface on the other side (air electrode 12 side). As described above, the cell C includes the inflow portions 13a1 and 14a1 into which the reaction gas (fuel gas and oxidant gas) flows, and the outflow portion from which the reaction gas (fuel gas and oxidant gas) used in power generation flows out. 13a2 and 14a2 and gas flow paths 13a and 14a through which reaction gases (fuel gas and oxidant gas) flow from the inflow portions 13a1 and 14a1 in the cell C to the outflow portions 13a2 and 14a2.

Next, the structure of the membrane electrode assembly 40 will be described. As shown in FIG. 1, the membrane electrode assembly 40 is configured by sandwiching a solid polymer electrolyte membrane 10 between a fuel electrode 11 and an air electrode 12.
FIG. 4 is a view showing a cross-sectional structure of the membrane electrode assembly 40. As shown in FIG. 4, the fuel electrode 11 includes a fuel electrode side catalyst layer 11 b provided on the solid polymer electrolyte membrane 10 side and a fuel electrode side gas diffusion layer 11 a provided on the fuel electrode separator 13 side. Is done. Similarly, the air electrode 12 includes an air electrode side catalyst layer 12b provided on the solid polymer electrolyte membrane 10 side and an air electrode side gas diffusion layer 12a provided on the air electrode separator 14 side.

  In the present embodiment, the membrane electrode assembly 40 is arranged in order from the reaction gas (fuel gas and oxidant gas) inflow portions 13a1 and 14a1 to the outflow portions 13a2 and 14a2 as shown in FIG. It has the 1st field 40a and the 2nd field 40b. The low humidification adaptive performance of the membrane electrode assembly 40 facing the gas flow paths 13a and 14a in the cell C is that the first region 40a near the inflow portions 13a1 and 14a1 is closer to the outflow portions 13a2 and 14a2. It is comprised so that it may become higher than a certain 2nd area | region 40b. That is, the low humidification adaptive performance of the first region 40a of the membrane electrode assembly 40 is higher than the low humidification adaptive performance of the second region 40b of the membrane electrode assembly 40. This low-humidification adaptive performance is a characteristic that represents the adaptive performance of the membrane electrode assembly 40 when used under low humidification conditions. Water retention performance, proton conductivity performance under low humidification conditions, and under low humidification conditions. Is at least one of the deterioration resistance performance of

  The difference in the low humidification adaptability of the membrane electrode assembly 40 is that at least any of the solid polymer electrolyte membrane 10, the catalyst layers 11b and 12b, and the gas diffusion layers 11a and 12a constituting the membrane electrode assembly 40. It can be created by the difference of one characteristic. In order to enhance the low humidification adaptive performance of the fuel electrode side catalyst layer 11b and the air electrode side catalyst layer 12b, a configuration in which a water management layer or the like in which moisture does not easily flow out is applied to increase the water retention performance can be employed. . In order to improve the low humidification adaptability of the fuel electrode side gas diffusion layer 11a and the air electrode side gas diffusion layer 12a, for example, the pore size of the porous carbon material used as the material of the gas diffusion layer is reduced or the water repellent treatment ( It is possible to adopt a configuration in which the water retention performance is increased by reducing the degree of coating (such as coating with Teflon (registered trademark)) (lowering the water repellency). In order to enhance the low humidification adaptability of the solid polymer electrolyte membrane 10, a configuration is adopted in which the proton conductivity performance under low humidification conditions is increased by using a raw material having high proton conductivity at low humidity. In addition, it is possible to adopt a configuration in which the deterioration resistance performance under the low humidification condition is increased by adding an additive that suppresses the deterioration phenomenon that easily occurs under the low humidification condition.

  For example, a portion of the solid polymer electrolyte membrane 10 corresponding to the first region 40a and a portion of the solid polymer electrolyte membrane 10 corresponding to the second region 40b are made of materials having different low humidification adaptability as described above. Form. On the other hand, each of the catalyst layers 11b and 12b and the gas diffusion layers 11a and 12a is formed of a material having no difference in low humidification performance over the entire membrane electrode assembly 40. By comprising in this way, a difference can be provided in low humidification adaptive performance by the part corresponding to the 1st area | region 40a, and the part corresponding to the 2nd area | region 40b.

  Alternatively, portions of the catalyst layers 11b and 12b corresponding to the first region 40a and portions of the catalyst layers 11b and 12b corresponding to the second region 40b are formed of materials having different low humidification adaptability as described above. . On the other hand, each of the solid polymer electrolyte membrane 10 and the gas diffusion layers 11a and 12a is formed of a material that does not have a difference in low humidification adaptability throughout the membrane electrode assembly 40. By comprising in this way, a difference can be provided in low humidification adaptive performance by the part corresponding to the 1st area | region 40a, and the part corresponding to the 2nd area | region 40b.

  Alternatively, the portions of the gas diffusion layers 11a and 12a corresponding to the first region 40a and the portions of the gas diffusion layers 11a and 12a corresponding to the second region 40b have different low humidification adaptability as described above. Form with. On the other hand, each of the solid polymer electrolyte membrane 10 and the catalyst layers 11b and 12b is formed of a material that has no difference in low humidification adaptability throughout the membrane electrode assembly 40. By comprising in this way, a difference can be provided in low humidification adaptive performance by the part corresponding to the 1st area | region 40a, and the part corresponding to the 2nd area | region 40b.

As described above, the low humidification adaptive performance of the membrane electrode assembly 40 facing the fuel gas channel 13a and the oxidant gas channel 14a in the cell C is the solid polymer electrolyte membrane constituting the membrane electrode assembly 40. 10. By making at least one of the characteristics of the catalyst layers 11b and 12b and the gas diffusion layers 11a and 12a different, the vicinity of the inflow portions 13a1 and 14a1 becomes higher than the vicinity of the outflow portions 13a2 and 14a2. Configured as follows. That is, the membrane electrode assembly 40 in the vicinity of the reaction gas inflow portions 13a1 and 14a1 has a relatively high low humidification adaptive performance (that is, high water retention performance (water At least one of high proton conductivity performance under low humidification conditions and high deterioration resistance performance under low humidification conditions). On the other hand, since the membrane electrode assembly 40 in the vicinity of the outflow portions 13a2 and 14a2 of the reaction gas is in a condition where the amount of water present is relatively large, even if the low humidification adaptive performance is not high (that is, Even if the water retention performance is low), it can be expected that the proton conductivity can be sufficiently secured. Moreover, if the water retention performance is low, the problem that the flow path of the reaction gas is blocked by water is less likely to occur.
As a result, the required performance can be sufficiently exhibited throughout the membrane electrode assembly 40. In addition, since the entire membrane electrode assembly 40 is not configured to have a high low humidification adaptive performance that matches the low humidification conditions, the membrane electrode assembly 40 does not become very expensive.

  Further, when the polymer electrolyte fuel cell is operated under saturated humidification conditions in which the dew point of the reaction gas (fuel gas and oxidant gas) is equal to or higher than the operating temperature of the cell C, that is, the fuel electrode side humidifier 4 and the air If a large amount of water is included in the fuel gas and the oxidant gas using the pole-side humidifier 2, a large amount of energy is required, for example, the temperature of the reaction gas or water needs to be raised. However, in the present embodiment, the operation control means 36 flows into the inflow portions 13a1 and 14a1 in a state where the dew point of the fuel gas and oxidant gas as the reaction gas is lower than the operating temperature of the cell C (for example, 70 ° C.). The operation of the humidifiers 2 and 4 is controlled. As a result, the energy required for humidifying the reaction gas can be made relatively small. In addition, since the amount of water present inside the cell C can be relatively reduced, it is possible to suppress the occurrence of a problem that the flow path of the reaction gas inside the membrane electrode assembly 40 is blocked with water.

Second Embodiment
The polymer electrolyte fuel cell according to the second embodiment is different from the above embodiment in that the membrane electrode assembly 40 is divided into a plurality of parts. Although the structure of the polymer electrolyte fuel cell of 2nd Embodiment is demonstrated below, description is abbreviate | omitted about the structure similar to the said embodiment.

  FIG. 5 is an exploded perspective view of the cell. As shown in the figure, the cell C has a structure in which the membrane electrode assembly 40 is sandwiched between the fuel electrode separator 13 and the air electrode separator 14 from both sides. Specifically, a gasket (an example of a sealing member) 41 is provided around the membrane electrode assembly 40, and the membrane electrode assembly 40 and the gasket 41 serve as a single member so that the fuel electrode separator 13 and the air electrode The separator 14 is sandwiched from both sides. The gasket 41 is formed in the shape of “8” having two openings at the center, and the membrane electrode assembly 40 (first membrane electrode assembly member 40A, second membrane electrode assembly member) is formed in each opening portion. 40B) is fitted. In FIG. 5, description of the cooling water flow path is omitted.

  In the present embodiment, the first membrane electrode assembly member 40A and the second membrane electrode assembly member are directed from the inflow portions 13a1, 14a1 side of the reaction gas (fuel gas and oxidant gas) toward the outflow portions 13a2, 14a2. 40B are arranged in order. That is, the first membrane electrode assembly member 40A is closer to the reaction gas (fuel gas and oxidant gas) inflow portions 13a1 and 14a1, and the second membrane electrode assembly member 40B is more reactive gas (fuel). Gas and oxidant gas) near the outflow portions 13a2 and 14a2. The low humidification adaptive performance of the membrane electrode assembly 40 facing the gas flow paths 13a and 14a in the cell C is that the first membrane electrode assembly member 40A in the vicinity of the inflow portions 13a1 and 14a1 is the outflow portion. It is comprised so that it may become higher than the 2nd membrane electrode assembly member 40B in the vicinity of 13a2 and 14a2. That is, the low humidification adaptive performance of the first membrane electrode assembly member 40A of the membrane electrode assembly 40 is higher than the low humidification adaptive performance of the second membrane electrode assembly member 40B.

  The difference in such low-humidification adaptive performance is similar to the first embodiment in that the solid polymer electrolyte membrane 10 and the catalyst constituting each of the first membrane electrode assembly member 40A and the second membrane electrode assembly member 40B are provided. It can be produced by a difference in characteristics of at least one of the layers 11b and 12b and the gas diffusion layers 11a and 12a. In other words, the membrane electrode assembly 40 is formed by combining a plurality of membrane electrode assembly members 40A and 40B having different low humidification adaptability, whereby the membrane electrode facing the gas flow paths 13a and 14a in the cell C. The low humidification adaptive performance of the joined body 40 can be obtained such that the vicinity of the reaction gas inflow portions 13a1 and 14a1 is higher than the vicinity of the reaction gas outflow portions 13a2 and 14a2.

<Another embodiment>
<1>
In the above embodiment, the configuration of the fuel cell system can be changed as appropriate.
For example, a transformer, a carbon monoxide remover, or the like may be additionally provided in the power generation unit U1 shown in FIG. That is, in the example shown in FIG. 1, the example in which the reformed gas (gas containing hydrogen as a main component) generated by the reformer 8 is supplied to the cell C of the polymer electrolyte fuel cell is shown. The carbon monoxide contained in the reformed gas is transformed into carbon dioxide using a transformer, and the monoxide remaining in the reformed gas after the transformation treatment is performed using a carbon monoxide remover. You may change so that it may supply to the cell C, after removing carbon.
In addition, the configuration of each gas channel, the configuration of the cooling water channel, the configuration of the hot water channel, and the like shown in FIG.

<2>
In the above embodiment, only the low humidification adaptive performance of the membrane electrode assembly 40 on the side where the oxidant gas flows, not the both surface sides of the membrane electrode assembly 40, and the vicinity of the inflow portion 14a1 is the outflow portion as described above. It may be different so as to be higher than the vicinity of 14a2. Since water is generated by the power generation reaction at the air electrode 12 to which the oxidant gas is supplied, there is a relatively large amount of water present compared to the fuel electrode 11 side. Therefore, the problem that the membrane electrode assembly 40 in the vicinity of the reaction gas inflow portions 13a1 and 14a1 to the cell C is easily dried by the inflowing reaction gas is common to the fuel electrode 11 side and the air electrode 12 side. The phenomenon that a large amount of water is present in the vicinity of the outflow portions 13a2 and 14a2 of the reaction gas from the cell becomes more remarkable on the air electrode 12 side than on the fuel electrode 11 side. In such a case, the low humidification adaptive performance of the membrane electrode assembly 40 facing the gas flow path 14a of the oxidant gas supplied to the air electrode 12 is shown in the vicinity of the inflow portion 14a1 than in the vicinity of the outflow portion 14a2. If it is configured to be higher, it is possible to better cope with a phenomenon in which a large amount of water exists in the vicinity of the oxidant gas outflow portion 14a2 from the cell C, which becomes conspicuous on the air electrode 12 side.

Alternatively, only the low humidification adaptive performance of the membrane electrode assembly 40 on the side where the fuel gas flows may be changed so that the vicinity of the inflow portion 13a1 is higher than the vicinity of the outflow portion 13a2 as described above. In this case, the membrane electrode assembly 40 on the side where the fuel gas flows located in the vicinity of the inflow portion 13a1 exhibits a relatively high low humidification adaptive performance even if there is relatively little water, The required performance can be fully exhibited.
For example, when the low humidification adaptive performance is water retention performance, the water retention performance of the membrane electrode assembly 40 in the vicinity of the outflow portion 13a2 on the fuel gas flow side is the membrane in the vicinity of the inflow portion 13a1 on the fuel gas flow side. It becomes lower than the water retention performance of the electrode assembly 40 (that is, water is easily discharged). In addition, in the comparison between the vicinity of the fuel gas inflow portion 13a1 and the vicinity of the oxidant gas inflow portion 14a1 at the positions facing each other with the membrane electrode assembly 40 interposed therebetween, the inflow portion on the side where the fuel gas flows is compared. The water retention performance of the membrane electrode assembly 40 in the vicinity of 13a1 is higher than the water retention performance of the membrane electrode assembly 40 in the vicinity of the inflow portion 14a1 on the side through which the oxidant gas flows (that is, it becomes difficult for water to be discharged). As a result, the amount of water generated on the air electrode 12 side diffusing to the fuel electrode 11 side via the solid polymer electrolyte membrane 10 is suppressed, and the water stays on the air electrode 12 side. Therefore, drying of the membrane electrode assembly 40 in the vicinity of the oxidant gas inflow portion 14a1 on the air electrode 12 side where the amount of gas supplied is relatively large compared to the fuel electrode 11 side can be suppressed.

<3>
The area of the first region 40a of the membrane electrode assembly 40 described in the first embodiment (that is, “the area facing the fuel electrode separator 13 and the air electrode separator 14”, the same applies hereinafter) and the area of the second region 40b. May not be the same as each other, and the area of the first membrane electrode assembly member 40A and the area of the second membrane electrode assembly member 40B described in the second embodiment may not be the same.
Further, the low humidification adaptive performance of the membrane electrode assembly 40 is divided into two, such as the first region 40a and the second region 40b, or the first membrane electrode assembly member 40A and the second membrane electrode assembly member 40B. Instead of making them different, they may be divided into three or more and made different from each other. Furthermore, as described above, the low humidification adaptive performance of the membrane electrode assembly 40 is varied in stages so that the vicinity of the inflow portions 13a1 and 14a1 is higher than the vicinity of the outflow portions 13a2 and 14a2. Instead, it may be changed continuously.

<4>
In the cell C illustrated in FIGS. 3 and 5, the flow direction of the fuel gas and the flow direction of the oxidant gas with respect to the membrane electrode assembly 40 are the same direction (parallel flow). The flow direction of the fuel gas and the flow direction of the oxidant gas with respect to 40 may be changed to the opposite direction (opposite flow) or may be changed so as to intersect (for example, intersect at an angle of 90 degrees). May be. When such a modification is made, the low humidification adaptive performance of the membrane electrode assembly 40 facing the oxidant gas flow path 14a as the gas flow path in the cell C is shown, and the outflow part 14a2 is closer to the inflow part 14a1. It is preferable to be configured to be higher than the vicinity.

  INDUSTRIAL APPLICABILITY The present invention can be used for a polymer electrolyte fuel cell that can sufficiently exhibit the performance required for a membrane electrode assembly while suppressing an increase in cost.

DESCRIPTION OF SYMBOLS 10 Solid polymer electrolyte membrane 11 Fuel electrode 12 Air electrode 13a Fuel gas flow path 13a1 Inflow part 13a2 Outflow part 14a Oxidant gas flow path 14a1 Inflow part 14a2 Outflow part 40 Membrane electrode assembly 40A, 40B Membrane electrode assembly member 41 Gasket C cell CS cell stack

Claims (3)

A membrane electrode assembly having a solid polymer electrolyte membrane sandwiched between a fuel electrode and an air electrode, and a plurality of cells that generate power using a reaction gas supplied to the membrane electrode assembly are stacked. A polymer electrolyte fuel cell comprising a cell stack,
The cell includes an inflow portion into which the reaction gas flows, an outflow portion from which the reaction gas flows out after being used in power generation, and the reaction gas between the inflow portion and the outflow portion in the cell. A flowing gas flow path,
The low humidification adaptive performance of the membrane electrode assembly facing the gas flow path in the cell is configured so that the vicinity of the inflow portion is higher than the vicinity of the outflow portion ,
The membrane electrode assembly is a polymer electrolyte fuel cell formed by combining a plurality of membrane electrode assembly members having different low humidification adaptability . 2. The polymer electrolyte fuel cell according to claim 1, wherein the reaction gas is configured to flow into the inflow portion in a state where a dew point is lower than an operating temperature of the cell. The polymer electrolyte fuel cell according to claim 1 or 2, wherein the reaction gas is an oxidant gas supplied to the air electrode.

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