JP4375480B2 - Polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a polymer electrolyte fuel cell having a polymer electrolyte membrane having ion conductivity, and more particularly to a polymer electrolyte fuel cell in which a gas flow path forming member for an oxidizer electrode is made porous.

  The polymer electrolyte fuel cell is advantageous in terms of energy and environment, and has been developed in recent years. A polymer electrolyte fuel cell includes a polymer electrolyte membrane having ion conductivity, a fuel electrode provided on one side of the polymer electrolyte membrane and supplied with fuel, and an oxidation provided on the other side of the polymer electrolyte membrane. It has a drug electrode. If the polymer electrolyte membrane is excessively dried, the ionic conductivity is lowered, so that sufficient power generation performance cannot be obtained.

  Therefore, conventionally, a method has been adopted in which moisture is supplied to the oxidant-containing gas and fuel-containing gas before being supplied to the fuel cell, and the oxidant-containing gas and fuel-containing gas containing moisture are supplied to the fuel cell.

As another method, conventionally, a gas flow path forming member also called a separator provided outside at least one of the fuel electrode and the oxidant electrode is made porous, and the porous gas flow path forming member is made fine. A method of supplying water and water vapor to the polymer electrolyte membrane through the holes is employed (Patent Documents 1 to 3). According to this method, the porous gas flow path forming member has a large number of pores, and the pores communicate with each other in the thickness direction of the gas flow path forming member so that water and water vapor can pass therethrough. It is a communication hole.
JP-A-6-338338 Patent Publication No. 2922132 JP-A-1-309263

  By the way, according to the polymer electrolyte fuel cell adopting the latter method described above, as described above, the porous gas flow path forming member also called a separator has a large number of pores. The pores are communication holes that communicate in the thickness direction of the gas flow path forming member so that water and water vapor can permeate. Here, the diameter and porosity of the pores are basically uniform in each part of the gas flow path forming member. That is, the water permeability between the water passage and the oxidant electrode is basically uniform in each part of the gas flow path forming member. In the industry, there is a demand for further improvement in the power generation performance of the above-described polymer electrolyte fuel cell.

  The present invention has been made in view of the above-described circumstances, and it is possible to effectively draw excess water in the downstream region of the oxidizer electrode to the water channel side, and hence the downstream side of the oxidizer electrode. It is possible to suppress the retention of surplus water in the region, and therefore it is possible to suppress the flooding phenomenon in which the gas flow path of the oxidizer electrode is closed with water, which is advantageous for further improving the power generation performance. It is an object to provide a molecular fuel cell.

A polymer electrolyte fuel cell according to the present invention includes a polymer electrolyte membrane having ion conductivity, a fuel electrode provided on one side of the polymer electrolyte membrane and supplied with fuel, and on the other side of the polymer electrolyte membrane. An oxidant electrode provided with an oxidant-containing gas, a gas flow path forming member for the fuel electrode provided outside the fuel electrode, and an oxide having pores provided outside the oxidant electrode and capable of forming communication holes A porous gas flow path forming member for the agent electrode, a water flow path forming member for forming a water flow path through which water flows outside the gas flow path forming member for the oxidant electrode, and a water flow through the water flow path. A polymer electrolyte fuel cell comprising a water flow portion for flowing water through a water channel,
In the porous gas flow path forming member for the oxidant electrode,
When the downstream where the oxidant gas flows is defined as the downstream region and the upstream where the oxidant gas flows is defined as the upstream region,
Moisture permeability through which at least one of liquid phase water and water vapor passes between the oxidant electrode and the water passage is set larger in the downstream region than in the upstream region. It is.

  According to the polymer electrolyte fuel cell of the present invention, in the porous gas flow path forming member for the oxidant electrode, the moisture permeability between the water passage and the oxidant electrode is upstream in the downstream region. It is set larger than the side area. For this reason, excess water in the downstream region of the oxidizer electrode can be effectively sucked to the side of the water passage. Therefore, the stagnation of excess water in the downstream region of the oxidizer electrode can be suppressed. Therefore, the flooding phenomenon that the gas flow path of the oxidant electrode is closed with water can be suppressed.

  According to the polymer electrolyte fuel cell according to the present invention, in the porous gas flow path forming member for the oxidant electrode, the moisture permeability between the water channel and the oxidant electrode is upstream in the downstream region. It is set larger than the area. For this reason, excess water in the downstream region of the oxidizer electrode can be effectively sucked to the water channel side. Therefore, the stagnation of excess water in the downstream region of the oxidizer electrode can be suppressed. Therefore, the flooding phenomenon in which the gas flow path of the oxidizer electrode is closed with water can be suppressed, which is advantageous in improving the power generation performance.

  According to the preferred embodiment of the polymer electrolyte fuel cell according to the present invention, in the porous gas flow path forming member for the oxidant electrode, at least one of the average pore diameter and the porosity is more than the upstream region. In the downstream region, it is possible to adopt a large set form. Thereby, the water permeability between the water channel and the oxidant electrode is set relatively large in the downstream region and relatively small in the upstream region. In this case, excess water staying in the downstream region of the oxidant electrode can be effectively sucked from the oxidant electrode toward the water passage. Therefore, the flooding phenomenon in the downstream region of the oxidizer electrode can be suppressed.

  Preferably, in the porous gas flow path forming member for the oxidizer electrode, at least one of the average pore diameter and the porosity is set to be relatively small in the upstream region, and relatively in the downstream region. It is possible to exemplify a form that is set so as to gradually increase from the upstream region to the downstream region.

  According to the polymer electrolyte fuel cell according to the present invention, the moisture permeability means permeability of at least one of liquid phase water and water vapor. The relatively large average pore diameter means that the pore diameter is relatively large among all the pores in the porous gas flow path forming member, and the average pore diameter is in the range of 10 to 1000 μm. it can. The relatively small average pore diameter means that the pore diameter is relatively small among all the pores in the porous gas flow path forming member, and the average pore diameter is in the range of less than 0.1 to 10 μm. The inside can be illustrated. Most of the pores are communication holes, and give water permeability to the gas flow path forming member.

  The relatively high porosity means that the porosity is relatively high in the porous gas flow path forming member, and can be exemplified within the range of 40 to 95% porosity. The phrase “porosity is relatively small” means that the porosity of the porous gas flow path forming member is relatively small, and examples include a range of porosity of less than 0.1 to 40%. However, the average pore diameter and the porosity are not limited to the above ranges.

  According to the polymer electrolyte fuel cell according to the present invention, in the porous gas flow path forming member for the oxidant electrode, the ratio of the water repellent per unit volume is larger in the upstream region than in the downstream region. The set form can be adopted. When the ratio of the water repellent is large, it is not easy to put water in and out. In said form, the ratio of a water repellent is set relatively large in an upstream area | region, and is set relatively small in a downstream area | region. For this reason, it becomes advantageous to attract the surplus water in the downstream area of the MEA to the water channel, and can further contribute to suppressing the retention of the surplus water in the downstream area. The water repellent agent can be provided on the surface and / or in the pores of the porous gas flow path forming member.

  First, the first reference example will be described prior to the description of the embodiment.

  The concept of this reference example of the present invention will be described below with reference to FIGS. FIG. 1 schematically shows the concept of a polymer electrolyte fuel cell according to this reference example. The polymer electrolyte fuel cell according to this reference example employs a system in which water is pumped through the first water passage 41. MEA 1 (membrane / electrode assembly) includes a polymer electrolyte membrane 11 formed of a polymer electrolyte material having proton conductivity, and a fuel electrode provided on one side of the polymer electrolyte membrane 11 in the thickness direction and supplied with fuel. 12 and an oxidant electrode 15 which is provided on the other side in the thickness direction of the polymer electrolyte membrane 11 and is supplied with an oxidant-containing gas (generally air) and has gas permeability.

  The oxidant electrode 15 is porous and has a first gas diffusion layer 16 formed of a carbon material such as carbon fiber so as to have gas permeability and conductivity, and a first gas diffusion layer 16 formed on the polymer electrolyte membrane 11 side. The catalyst layer 17 is formed. The fuel electrode 12 is porous and has a second gas diffusion layer 13 made of a carbon material such as carbon fiber so as to have gas permeability and conductivity, and a second catalyst formed on the polymer electrolyte membrane 11 side. And the layer 14. The first catalyst layer 17 and the second catalyst layer 14 are formed using, as main components, an aggregate of carbon fine particles supporting a catalyst metal such as platinum and an electrolyte polymer having proton conductivity.

  As shown in FIG. 1, the gas flow path forming member 2 for the fuel electrode is provided outside the fuel electrode 12 in the thickness direction. The gas flow path forming member 2 for the fuel electrode is also called a separator, and is formed of a dense body. The gas flow path forming member 2 for the fuel electrode is made of a material having corrosion resistance and conductivity (generally a carbon material), and the fuel gas supplied to the second gas diffusion layer 13 of the fuel electrode 12 is A flowing groove-like gas flow path 21 is provided.

  On the outer side of the oxidant electrode 15 in the thickness direction, a porous gas flow path forming member 3 for the oxidant electrode having a large number of pores that can be communication holes is provided. In the gas flow path forming member 3 shown in FIG. 1, the pores are schematically shown as ◯. In the gas flow path forming member 3, the pores communicate with each other and have moisture permeability in the thickness direction of the gas flow path forming member 3. The gas flow path forming member 3 for the oxidant electrode is also referred to as a separator, and is formed of a material having corrosion resistance and conductivity (generally a carbon material). It has a groove-like gas flow path 31 through which an oxidant-containing gas (generally air) supplied to the layer 16 flows. As shown in FIG. 1, the fuel electrode 12 and the oxidant electrode 15 are electrically connected via a conductive path 60 and a load 61.

  In the gas flow path forming member 3 for the oxidant electrode, an upstream side in which the oxidant-containing gas flows is defined as an upstream region 91, and a downstream side in which the oxidant-containing gas flows is defined as a downstream region 93. On the outer side in the thickness direction of the gas flow path forming member 3 for the oxidizer electrode, a partition plate-shaped first passage that forms a first water passage 41 through which water for cooling and humidification supplied from the water supply source 40 flows. A water channel forming member 51 is provided. The first water passage 41 has a water supply port 43 and a water discharge port 44.

Furthermore, a water flow part 49 is provided for allowing water from the water supply source 40 to be pumped to the first water flow path 41 and passed therethrough. The water flow part 49 can be formed with a pump, for example. The water flow portion 49 is provided on the upstream side of the water supply port 43 of the first water flow channel 41, causes water to be pumped to the first water flow channel 41, and flows from the water supply port 43 of the first water flow channel 41 toward the water discharge port 44. Let water through. The water pressure Pm in the first water passage 41 exceeds 1 atm in absolute pressure, and is set to be higher than the pressure P ₁ in the groove-like gas flow path 31 through which the oxidant-containing gas (generally air) flows. (Pm> P ₁ ). The differential pressure is basically the Pm and P _1, it can be replenished toward the direction of arrow M1 water first water passage 41 on the side of the oxidizer electrode 15 of the MEA 1.

  Now, according to the present reference example, the average pore diameter and the porosity of the porous gas flow path forming member 3 for the oxidant electrode change along the direction in which the oxidant-containing gas (generally air) flows. It is set to be. That is, in the porous gas flow path forming member 3 for the oxidizer electrode, both the average pore diameter and the porosity are set to be larger in the upstream region 91 than in the downstream region 93.

  Specifically, in the porous gas flow path forming member 3 for the oxidizer electrode, both the average pore diameter and the porosity are set relatively large in the upstream region 91, and in the downstream region 93. It is set relatively small. That is, in FIG. 2, the characteristic line A1 indicates the pore diameter, and the characteristic line A2 indicates the porosity. As shown by the characteristic lines A1 and A2 in FIG. 2, it is set so as to gradually and gradually decrease from the upstream region 91 to the downstream region 93. As a result, the moisture permeability between the first water passage 41 and the oxidant electrode 15 is relatively large in the upstream region 91 and relatively small in the downstream region 93.

  In addition, that the average pore diameter is relatively large can be exemplified by an average pore diameter in the range of 10 to 1000 μm. The relatively small average pore diameter can be exemplified by the average pore diameter in the range of 0.1 to 10 μm. A relatively large porosity can be exemplified by a porosity in the range of 40 to 95%. That the porosity is relatively small can be exemplified by a range of porosity of 0.1 to less than 40%. However, the pore diameter and porosity are not limited to the above values.

When the fuel cell is operated, an oxidant-containing gas (generally air) is supplied from the carrier source 68 to the groove-shaped gas flow path 31 of the gas flow path forming member 3 for the oxidant electrode. This oxidant-containing gas flows into the first gas diffusion layer 16 and the first catalyst layer 17 of the oxidant electrode 15 from the groove-like gas flow path 31. Further, the fuel gas (hydrogen-containing gas) is supplied from the carrier source 69 to the groove-like gas flow path 21 of the fuel electrode gas flow path forming member 2. The fuel gas flows from the gas flow path 21 into the second gas diffusion layer 13 and the second catalyst layer 14 of the fuel electrode 12. Then, protons (hydrogen ions) and electrons (e ⁻ ) are generated from the hydrogen of the fuel gas by the catalytic action of the second catalyst layer 14. The generated protons permeate the polymer electrolyte membrane 11 in the thickness direction and reach the oxidant electrode 15. The electrons flow through the conductive path 60, perform electrical work with the load 61 of the conductive path 60, and then reach the oxidizer electrode 15. In the oxidant electrode 15, the oxidant-containing gas (generally air) supplied to the oxidant electrode 15 reacts with protons and electrons by the catalytic action of the first catalyst layer 17 of the oxidant electrode 15, and water Is generated. Although heat is generated by such a power generation reaction, since the water from the water supply source 40 is passed through the first water passage 41 by the water passage portion 49, the fuel cell is cooled.

  In the MEA 1 in which the power generation reaction is expressed, the generated water tends to be relatively more in the downstream region 93 than in the upstream region 91 of the oxidant-containing gas. Therefore, in such MEA 1, the relative humidity is generally relatively low in the upstream region 91 and relatively high in the downstream region 93. In the above-described MEA 1, drying may occur in the upstream region 91, and surplus water may stay in the downstream region 93.

  In this regard, according to this reference example, the moisture permeability between the first water passage 41 and the oxidant electrode 15 is set to be relatively large in the upstream region 91 and relatively in the downstream region 93. Is set to a small value. That is, both the average pore diameter and the porosity in the porous gas flow path forming member 3 for the oxidant electrode are set to be relatively large in the upstream region 91 and relatively in the downstream region 93. It is set small. For this reason, when water is pumped and passed through the first water passage 41, the water in the first water passage 41 is larger in the MEA 1 than in the downstream region 93 in the upstream region 91 having a larger average pore diameter and porosity. It becomes easy to permeate in the direction of the arrow M1 relatively to the oxidant electrode 15 side. As a result, in the upstream region 91 that tends to dry, the amount of humidification with respect to the oxidizer electrode 15 can be relatively increased, and consequently, excessive drying in the upstream region 91 that tends to dry can be suppressed.

  In contrast, in the downstream region 93 where water tends to be excessive based on the above-described power generation reaction, the humidification amount of the MEA 1 with respect to the polymer electrolyte membrane 11 can be made relatively smaller than that of the upstream region 91. . As a result, the flooding phenomenon in the downstream region 93 where moisture tends to be excessive can be suppressed. As a result, it can contribute to improving the power generation performance of the polymer electrolyte fuel cell. The flooding phenomenon means that the gas passage through which the gas passes is closed with excess water, and the passage area of the gas passage is reduced. When the flooding phenomenon occurs, it is disadvantageous to obtain sufficient power generation performance.

(Second reference example)
The second reference example has basically the same configuration as the first reference example, and basically exhibits the same operational effects. Hereinafter, a description will be given centering on portions different from the first reference example. According to this reference example, as shown by characteristic lines A1 and A2 in FIG. 3, in the porous gas flow path forming member 3 for the oxidant electrode, both the average pore diameter and the porosity are in the upstream region 91. Is set relatively large and the downstream region 93 is set relatively small. Here, as shown by characteristic lines A1 and A2 in FIG. 3, both the average pore diameter and the porosity change discontinuously from the upstream region 91 to the downstream region 93.

(Third reference example)
FIG. 4 schematically shows the concept of the third reference example. The third reference example has basically the same configuration as the first reference example, and basically exhibits the same operational effects. Hereinafter, a description will be given centering on portions different from the first reference example. According to this reference example, as shown in FIG. 4, in the porous gas flow path forming member 3B for the oxidizer electrode, the average pore diameter of each pore is basically substantially the same. 5-10 micrometers can be illustrated.

  The porosity of the gas channel forming member 3B for the oxidant electrode is set so as to change along the direction in which the oxidant-containing gas flows. That is, the porosity of the porous gas flow path forming member 3 </ b> B for the oxidant electrode is set to be larger in the upstream region 91 than in the downstream region 93.

  As a result, in the porous gas flow path forming member 3B for the oxidant electrode, the moisture permeability between the first water passage 41 and the oxidant electrode 15 is set relatively large in the upstream region 91. And is set relatively small in the downstream region 93.

  According to this reference example, the gas flow path forming member 2B for the fuel electrode is not a dense body but is formed of a porous body having a large number of pores. In the gas flow path forming member 2B for the fuel electrode, an upstream side in which the fuel gas flows is defined as an upstream region 91X, and a downstream side in which the fuel gas flows is defined as a downstream region 93X.

  In the gas flow path forming member 3B and the gas flow path forming member 2B shown in FIG. 4, the pores are modeled as ◯. The pores communicate with each other in the gas flow path forming member 3B and the gas flow path forming member 2B, and each of the gas flow path forming member 3B and the gas flow path forming member 2B has moisture permeability in the thickness direction.

  As shown in FIG. 4, the 2nd water flow path formation member 52 which forms the 2nd water flow path 42 is provided in the outer side of the gas flow path formation member 2B for fuel electrodes. The second water passage 42 has a water supply port 43 and a water discharge port 44. Similarly to the first water passage 41, the water from the water supply source 40 flows through the second water passage 42 by being pumped by the operation of the water passage portion 49.

  The porosity of the gas flow path forming member 2B for the fuel electrode is set so as to change along the direction in which the fuel gas flows. That is, the porosity of the gas flow path forming member 2B for the porous fuel electrode is set larger in the upstream region 91X than in the downstream region 93X. Specifically, the porosity in the gas flow path forming member 2B for the porous fuel electrode is set to be relatively large in the upstream region 91X, and is set to be relatively small in the downstream region 93X. . Accordingly, the moisture permeability between the second water passage 42 and the fuel electrode 12 is set to be relatively large in the upstream region 91X and relatively small in the downstream region 93X.

  As described above, according to this reference example, the porosity of the porous gas flow path forming member 3B for the oxidant electrode is set to be relatively large in the upstream region 91, and the downstream side. The area 93 is set relatively small. Similarly, for the gas flow path forming member 2B for the fuel electrode, the porosity is set relatively large in the upstream region 91X and relatively small in the downstream region 93X.

  For this reason, when water is pumped and passed through the first water passage 41 and the second water passage 42, the water in the first water passage 41 and the second water passage 42 has upstream areas 91 and 91X having a large porosity. Then, it becomes relatively easier to transmit in the direction of the arrow M1 toward the MEA1 side than the downstream regions 93 and 93X. As a result, the humidification amount for MEA 1 can be relatively increased in the upstream regions 91 and 91X that tend to dry. Furthermore, in the downstream regions 93 and 93X where water tends to be excessive, the humidification amount for the MEA 1 can be made relatively small.

(4th reference example)
FIG. 5 schematically shows the concept of the fourth reference example. The fourth reference example has basically the same configuration as the third reference example shown in FIG. 4, and basically has the same function and effect. Hereinafter, a description will be given centering on portions different from the third reference example shown in FIG. In the gas flow path forming member 3 </ b> B and the gas flow path forming member 2 </ b> B shown in FIG. 5, the pores are modeled as ◯. The pores communicate with each other in the gas flow path forming member 3B and the gas flow path forming member 2B, and the gas flow path forming member 3B and the gas flow path forming member 2B are each permeable in the thickness direction.

  According to this reference example, the water repellent 8 is attached to the surface of the gas flow path forming member 3B for the oxidant electrode and the surface of the pores. FIG. 5 schematically shows the strength of the water repellent 8 and does not indicate the thickness of the water repellent 8. Examples of the water repellent 8 include perfluorocarbon and fluorocarbon. In the gas flow path forming member 3B for the oxidant electrode, when the ratio of the water repellent 8 per unit volume is large, water is repelled, so that it becomes difficult to take in and out the MEA1. Further, if the ratio of the water repellent 8 is small or the water repellent 8 is not present, the water can be easily taken in and out of the MEA 1 as compared with the case where the ratio of the water repellent 8 is large.

  According to this reference example, the ratio of the water repellent 8 in the porous gas flow path forming member 3B for the oxidant electrode is set so as to change along the direction in which the oxidant gas flows. That is, the ratio of the water repellent 8 in the porous gas flow path forming member 3 </ b> B for the oxidant electrode is set in the upstream region 91 or less than the downstream region 93. Specifically, the ratio of the water repellent 8 in the gas flow path forming member 3B for the oxidant electrode is set to be relatively small in the upstream region 91 (including no water repellent), and The downstream area 93 is set relatively large. For this reason, the moisture permeability between the first water passage 41 and the oxidant electrode 15 is set relatively large in the upstream region 91 in the gas flow path forming member 3B for the oxidant electrode, and The downstream region 93 is set to be relatively small.

  Further, as shown in FIG. 5, a water repellent 8 is attached to the surface of the gas flow path forming member 2B for the fuel electrode. The ratio of the water repellent 8 in the gas flow path forming member 2B for the porous fuel electrode is set so as to change along the direction in which the fuel gas flows. That is, the ratio of the water repellent 8 in the porous gas flow path forming member 2B for the fuel electrode is set to be none or less in the upstream region 91X than in the downstream region 93X. Specifically, the ratio of the water repellent 8 in the gas flow path forming member 2B for the oxidant electrode is set to be relatively small in the upstream region 91X and relatively large in the downstream region 93X. Is set. For this reason, the water permeability between the second water passage 42 and the fuel electrode 12 is set to be relatively large in the upstream region 91X in the gas flow path forming member 2B for the fuel electrode, and downstream. The side region 93X is set to be relatively small.

  According to such a reference example, when water is pumped and passed through the first water passage 41 and the second water passage 42 by the operation of the water passage portion 49, the first water passage 41 and the second water passage. In the upstream areas 91 and 91X where the ratio of water repellent 8 is absent or relatively small, 42 water is directed toward MEA 1 rather than the downstream areas 93 and 93X where the ratio of water repellent 8 is relatively large. It becomes relatively easy to transmit in the direction of the arrow M1. As a result, the humidification amount in the upstream regions 91 and 91X can be increased, and excessive drying in the upstream regions 91 and 91X can be suppressed.

  As described above, in changing the ratio of the water repellent 8 along the direction in which the oxidant-containing gas and the fuel gas flow, for example, the water repellent 8 is used as the gas flow path forming member 3B for the oxidant electrode and the fuel electrode. When the gas flow path forming member 2B is attached to the surface of the gas flow path forming member 2B, the gas flow path forming member 3B and the gas flow path forming member 2B are covered with a masking member, and the masking member is moved relative to each other, thereby making the masking time variable. Can be performed.

  In some cases, in the embodiment shown in FIG. 5, either the water repellent 8 attached to the gas flow path forming member 3B or the water repellent 8 attached to the gas flow path forming member 2B may be eliminated. it can.

(First embodiment)
The concept of the first embodiment of the present invention will be described below with reference to FIG. The polymer electrolyte fuel cell according to the present embodiment is a system in which water is caused to flow through the first water passage 41 by sucking the water through the first water passage 41. The MEA 1 according to this embodiment includes a polymer electrolyte membrane 11 formed of a polymer material having proton conductivity, a fuel electrode 12 provided on one side in the thickness direction of the polymer electrolyte membrane 11, and supplied with fuel. It is provided on the other side in the thickness direction of the polymer electrolyte membrane 11 and has a porous oxidant electrode 15 that is supplied with an oxidant-containing gas (generally air) and has gas permeability.

  The oxidant electrode 15 is formed of a first gas diffusion layer 16 made of a carbon material so as to be porous and gas permeable, and a first catalyst layer 17 formed on the polymer electrolyte membrane 11 side. ing. The fuel electrode 12 is formed of a second gas diffusion layer 13 made of a carbon material so as to be porous and gas permeable, and a second catalyst layer 14 formed on the polymer electrolyte membrane 11 side. Yes.

  As in the first reference example, the fuel electrode gas flow path forming member 2 is provided outside the fuel electrode 12 in the thickness direction. The gas flow path forming member 2 for the fuel electrode is also called a separator, and is formed not by a porous body but by a dense body. The gas flow path forming member 2 for the fuel electrode is made of a material having corrosion resistance and conductivity (generally a carbon material), and the fuel gas supplied to the second gas diffusion layer 13 of the fuel electrode 12 is A flowing groove-like gas flow path 21 is provided.

  As shown in FIG. 6, a porous gas flow path forming member 3E for the oxidant electrode having a large number of pores is provided outside the oxidant electrode 15 in the thickness direction. In the gas flow path forming member 3E shown in FIG. 6, the pores are schematically shown as ◯. In the gas flow path forming member 3E, the pores communicate with each other, and the gas flow path forming member 3E has permeability in the thickness direction.

  The gas flow path forming member 3E for the oxidant electrode is also called a separator, is formed of a material having corrosion resistance and conductivity (generally a carbon material), and the first gas diffusion of the oxidant electrode 15 It has a groove-like gas flow path 31 through which an oxidant-containing gas (generally air) supplied to the layer 16 flows. The oxidant electrode 15 and the fuel electrode 12 are electrically connected through a conductive path 60 and a load 61.

  As shown in FIG. 6, a partition plate-like first passage that forms a first water passage 41 through which water for cooling and humidification flows is provided on the outer side in the thickness direction of the gas flow path forming member 3E for the oxidant electrode. A water channel forming member 51 is provided.

Further, a water passage portion 49 </ b> E that allows water to flow through the first water passage 41 is provided. The water flow portion 49E is provided on the downstream side of the first water flow channel 41, and by sucking the water in the first water flow channel 41 in the direction of the arrow W2, the water supply port 43 of the first water flow channel 41 is connected to the water discharge port 44. Allow water to pass. The water flow part 49E can be formed with a suction pump. The water pressure Pm in the first water passage 41 is less than 1 atm in absolute pressure, and is set to be smaller than the pressure P ₁ in the groove-like gas flow path 31 through which the oxidant-containing gas (generally air) flows. (Pm <P ₁ ). The differential pressure is basically the Pm and P _1, can be sucked in the arrow M2 direction excess water remaining in the oxidant electrode 15 of the MEA1 to the first water passage 41.

  Now, according to the present embodiment, the average pore diameter and porosity in the porous gas flow path forming member 3E for the oxidant electrode are set so as to change along the direction in which the oxidant-containing gas flows. . That is, both the average pore diameter and the porosity of the porous gas flow path forming member 3E for the oxidant electrode are set to be larger in the downstream region 93 than in the upstream region 91. Specifically, both the average pore diameter and the porosity in the porous gas flow path forming member 3E for the oxidant electrode are set to be relatively large in the downstream region 93, and relatively in the upstream region 91. 7 and is set so as to gradually and gradually increase from the upstream region 91 to the downstream region 93 as indicated by characteristic lines E1 and E2 in FIG. In FIG. 7, a characteristic line E1 indicates the pore diameter, and a characteristic line E2 indicates the porosity.

  As a result, the moisture permeability between the first water passage 41 and the oxidant electrode 15 is set relatively large in the downstream region 93 and relatively small in the upstream region 91.

When the fuel cell is operated, as in the first embodiment, fuel gas (hydrogen-containing gas) is supplied to the groove-like gas flow path 21 by the transport source 69 and oxidant-containing gas (generally, Is supplied to the groove-like gas flow path 31 by the conveyance source 68. The fuel gas reaches the second gas diffusion layer 13 of the fuel electrode 12 from the groove-shaped gas flow path 21 and is further contained in the fuel gas by the catalytic action of the second catalyst layer 14 contained in the fuel electrode 12. Protons (hydrogen ions) and electrons (e ⁻ ) are generated from hydrogen. Protons permeate the polymer electrolyte membrane 11 in the thickness direction and reach the oxidizer electrode 15. The electrons flow through the conductive path 60. The electrons reach the oxidant electrode 15 after performing electrical work with the load 61 of the conductive path 60. In the oxidant electrode 15, the oxidant-containing gas (generally air) supplied to the oxidant electrode 15 reacts with protons and electrons by the catalytic action of the first catalyst layer 17 of the oxidant electrode 15, and water Is generated. In MEA1 in which such a power generation reaction is expressed, the generated water is relatively more in the downstream region 93 than in the upstream region 91 of the oxidant-containing gas. Therefore, in such MEA 1, the relative humidity is relatively low in the upstream region 91 and relatively high in the downstream region 93.

  In this regard, according to the present embodiment, as described above, in the porous gas flow path forming member 3E for the oxidizer electrode, both the average pore diameter and the porosity are relatively small in the upstream region 91. In addition to being set, the downstream area 93 is set to be relatively large. That is, in the porous gas flow path forming member 3E for the oxidizer electrode, both the average pore diameter and the porosity are set relatively large in the downstream region 93 and relatively small in the upstream region 91. As shown by characteristic lines E1 and E2 in FIG. 7, it is set so as to gradually and gradually increase from the upstream region 91 to the downstream region 93.

  Therefore, according to this embodiment, as can be understood from FIG. 6, when the water supplied from the water supply source 40 is sucked in the direction of the arrow W <b> 2 in the first water passage 41, the downstream region 93 of the oxidant electrode 15. The excess water accumulated in the water is more easily sucked in the direction of the arrow M2 toward the first water passage 41 than the upstream region 91. As a result, excess water in the downstream region 93 where moisture tends to be excessive is removed by suction, and as a result, the flooding phenomenon in the downstream region 93 can be suppressed. As a result, it can contribute to improving the power generation performance of the polymer electrolyte fuel cell.

(Second embodiment)
FIG. 8 schematically shows the concept of the second embodiment. This embodiment has basically the same configuration as that of the first embodiment shown in FIG. 6, and basically has the same functions and effects. In the following, description will be made centering on differences from the embodiment shown in FIG. According to the present embodiment, in the porous gas flow path forming member 3E for the oxidant electrode, the porosity is set relatively large in the downstream region 93 and relatively small in the upstream region 91. Has been. And as shown by the characteristic line E1 of FIG. 8, the pore diameter is set so as to increase discontinuously from the upstream region 91 to the downstream region 93. Further, as shown by the characteristic line E2 in FIG. 8, the porosity is set to increase discontinuously from the upstream region 91 to the downstream region 93.

(Third embodiment)
FIG. 9 schematically shows the concept of the third embodiment. This embodiment has basically the same configuration as the embodiment shown in FIG. 6, and basically has the same function and effect. Hereinafter, a description will be given focusing on the differences from the embodiment shown in FIG. In the gas flow path forming members 3F and 2F shown in FIG. 9, the pores are schematically shown as ◯. In the gas flow path forming members 3F and 2F, the pores communicate with each other, and the gas flow path forming members 3F and 2F have moisture permeability in the thickness direction. According to this embodiment, as shown in FIG. 9, the average pore diameter is basically uniform in the porous gas flow path forming member 3F for the oxidant electrode. However, the moisture permeability between the first water passage 41 and the oxidant electrode 15 in the porous gas flow path forming member 3F for the oxidant electrode, specifically, the porosity is relative in the downstream region 93. The upstream area 91 is set relatively small.

  According to the present embodiment, as is apparent from FIG. 9, the gas flow path forming member 2F for the fuel electrode is not a dense body but is formed of a porous body having a large number of pores. The water permeability between the first water passage 41 and the fuel electrode 12 in the gas flow path forming member 2F for the fuel electrode, that is, the porosity in the gas flow path forming member 2F for the porous fuel electrode, is downstream. The side area 93X is set larger than the upstream area 91X.

  Specifically, in the gas flow path forming member 2F for the porous fuel electrode, the porosity is set relatively small in the upstream region 91X and relatively large in the downstream region 93X. . That is, the porosity of the fuel electrode gas flow path forming member 2F is set so as to gradually and gradually increase from the upstream region 91X to the downstream region 93X.

  A second water passage forming member 52 that forms a second water passage 42 is provided outside the gas flow passage forming member 2F for the fuel electrode. The second water passage 42 has a water supply port 43 and a water discharge port 44. By the suction operation of the water flow portion 49F, the cooling water from the water supply source 40 is sucked and flows into the second water flow path 42 in the same manner as the first water flow path 41.

  According to the present embodiment, as shown in FIG. 9, the porosity of the porous gas flow path forming member 3F for the oxidant electrode is set to be relatively small in the upstream region 91, The downstream region 93 is set to be relatively large. Similarly, the porosity of the gas flow path forming member 2F for the fuel electrode is set to be relatively small in the upstream region 91X and relatively large in the downstream region 93X.

  For this reason, when the water from the water supply source 40 is sucked into the first water passage 41 and the second water passage 42 by the suction operation of the second water passage portion 49F, the excess water remaining on the MEA 1 side is The downstream regions 93 and 93X having a large average pore diameter and porosity are more easily sucked in the direction of the arrow M2 toward the first water passage 41 and the second water passage 42 than the upstream regions 91 and 91X. As a result, the amount of excess water sucked and removed can be relatively increased in the downstream regions 93 and 93X where the excess water tends to stay, which can contribute to suppressing flooding in the downstream regions 93 and 93X. .

(Fourth embodiment)
FIG. 10 schematically shows the concept of the fourth embodiment. This embodiment has basically the same configuration as that of the embodiment shown in FIG. 9, and basically has the same function and effect. In the following, the description will focus on parts that are different from the embodiment shown in FIG. In the gas flow path forming members 3F and 2F shown in FIG. 10, the pores are schematically shown as ◯. In the gas flow path forming members 3F and 2F, the pores communicate with each other, and the gas flow path forming members 3F and 2F have moisture permeability in the thickness direction.

  According to the present embodiment, as shown in FIG. 10, the water repellent 8 is attached to the surface of the gas flow path forming member 3F for the oxidant electrode and the inner wall surface of the pore. The water repellent 8 is also attached to the surface of the gas flow path forming member 2F for the fuel electrode and the inner wall surface of the pore. FIG. 10 schematically illustrates the strength of the water repellent 8 and does not indicate the thickness of the water repellent 8. When the ratio of the water repellent 8 is large per unit volume of the gas flow path forming member 3F for the oxidant electrode and the gas flow path forming member 2F for the fuel electrode, water is repelled, so that water can be taken in and out of the MEA 1. It becomes difficult to do. In addition, if the ratio of the water repellent 8 is small or there is no water repellent, water can be taken in and out of the MEA 1 more easily than when the ratio of the water repellent 8 is large.

  According to the present embodiment, the ratio of the water repellent 8 in the porous gas flow path forming member 3F for the oxidant electrode is set so as to change along the direction in which the oxidant-containing gas flows. Similarly, the ratio of the water repellent 8 in the gas flow path forming member 2F for the porous fuel electrode is set so as to change along the direction in which the fuel gas flows.

  That is, the ratio of the water repellent 8 in the porous gas flow path forming member 3 </ b> F for the oxidant electrode is set so as not to be present in the downstream region 93 or relatively smaller than that in the upstream region 91. In addition, the ratio of the water repellent 8 in the gas flow path forming member 2F for the porous fuel electrode is set so as not to be present in the downstream region 93X or relatively smaller than that in the upstream region 91X.

  For this reason, when the water from the water supply source 40 is sucked into the first water passage 41 and the second water passage 42 by the suction operation of the water passage portion 49F, the excess water stayed on the MEA 1 side. Is likely to be sucked out in the direction of the arrow M2 toward the first water passage 41 and the second water passage 42 in the downstream regions 93 and 93X in which the ratio of the water repellent 8 is relatively small. Therefore, the retention of excess water in the downstream regions 93 and 93X can be suppressed. Thereby, the flooding phenomenon in the downstream region 93.93X where excess water tends to stay can be suppressed. As a result, it can contribute to improving the power generation performance of the polymer electrolyte fuel cell.

(Production Example 1)
FIG.11 and FIG.12 shows typically the cross section of the porous body 200 which concerns on the manufacture example 1 which can become the porous gas flow path formation member 3 for oxidant electrodes. According to Production Example 1, in the first step, as shown in FIG. 11, a porous body 200 in which one end 201 side is thick and the other end 203 side is thin is produced. The porous body 200 has a large number of pores. The pores can be formed by using an appropriately sized disappearance substance such as a vaporizable sublimation substance or a disappearable burnout substance, and burying the disappearance substance and then disappearing the disappearance substance by sublimation, burnout, or the like. In the multi-body 200 that has undergone the first step, the average pore diameter and porosity are basically the same from one end 201 side to the other end 203 side.

  Next, in the second step, the porous body 200 is compressed in the thickness direction based on the press pressure by the press die 100. As shown in FIG. 12, according to the porous body 200 after being compressed by the press die 100, the thickness is basically the same from the one end 201 side to the other end 203 side.

  According to the porous body 200 after compression, the compression rate is set high on the one end 201 side, and the compression rate is set low on the other end 203 side. As a result, according to the compressed porous body 200, the density on the one end 201 side is high, and the density on the other end 203 side is low. Therefore, the average pore diameter and the porosity on the one end 201 side are set to be relatively small, and the average pore diameter and the porosity on the other end 203 side are set to be relatively large.

  When the porous body 200 according to Production Example 1 is applied to the gas flow path forming member 3 for the oxidant electrode according to the example illustrated in FIG. 1, the average pore diameter and the porosity of the compressed porous body 200. Is set to be small, the one end 201 side having a relatively high density can be set in the downstream region 93 of the gas flow path forming member 3 for the oxidant electrode. Further, since the average pore diameter and the porosity are set large, the other end 203 side having a relatively low density can be set as the upstream region 91 of the gas flow path forming member 3 for the oxidant electrode.

  Moreover, when applying the porous body 200 which concerns on the manufacture example 1 to the gas flow path formation member 3 for oxidant electrodes which concerns on the Example shown in FIG. Since the porosity is set to be relatively small, the one end 201 side having a relatively high density can be set to the upstream region 91 of the gas flow path forming member 3 for the oxidant electrode. Further, since the average pore diameter and the porosity are set relatively large, the other end 203 side having a relatively low density is set as the downstream region 93 of the gas flow path forming member 3 for the oxidant electrode. Can do. The same applies to the gas flow path forming member 2 for the porous fuel electrode.

(Production Example 2)
13 and 14 schematically show a cross section of a porous body 300 according to Production Example 2 that can be a porous gas flow path forming member 3 for an oxidant electrode. According to Production Example 2, in the first step, as shown in FIG. 13, a porous body 300 having basically the same thickness is produced from one end 301 side to the other end 303 side. The porous body 300 has a large number of pores. In this porous body 300, the average pore diameter and the porosity are set small on the one end 301 side and set large on the other end 303 side.

  Next, in the second step, as shown in FIG. 14, the porous body 300 is compressed in the thickness direction based on the press pressure by the press die 100. According to the porous body 300 after compression, the average pore diameter and porosity on the one end 301 side are set small, and the average pore diameter and porosity on the other end 303 side are set large.

  In the case where the porous body 300 according to Production Example 2 is applied to the gas flow path forming member 3 for the oxidant electrode according to the reference example shown in FIG. 1, the average pore diameter and pores in the compressed porous body 300 The one end 301 side where the rate is set small can be set in the downstream region 93 of the gas flow path forming member 3 for the oxidant electrode. Moreover, the other end 303 side where the average pore diameter and the porosity are set large can be set in the upstream region 91 of the gas flow path forming member 3 for the oxidant electrode.

  Moreover, when applying the porous body 300 which concerns on the manufacture example 2 to the gas flow path formation member 3B for oxidant electrodes which concerns on the Example shown in FIG. 6, among the porous body 300 after compression, average pore diameter and The one end 301 side where the porosity is set to be relatively small can be set in the downstream region 93 of the gas flow path forming member 3B for the oxidant electrode. Further, the other end 303 side where the average pore diameter and the porosity are set relatively large can be set in the upstream region 91 of the gas flow path forming member 3B for the oxidant electrode. The same applies to the gas flow path forming member 2 for the porous fuel electrode.

(Production Example 3)
The porous body that can be the porous gas flow path forming member 3 for the oxidant electrode can be formed as follows. A matrix forming process for forming a matrix in which a disappearance substance is embedded using a disappearance substance of an appropriate size such as a vaporizable sublimation substance and a lossable burnout substance; The porous body forming step for forming the material can be performed in order. The disappearance trace of the disappearing substance becomes pores in the matrix. In the matrix forming step, by changing at least one of the size and the amount of the disappearing substance embedded in the matrix from one end to the other end of the matrix, at least one of the pore diameter and the porosity in the porous body. One can be changed.

  (Others) The first catalyst layer 17 and the second catalyst layer 14 may be laminated on the front and back of the polymer electrolyte membrane 11. In addition, the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications within a range not departing from the gist.

The following technical idea can also be grasped from the above description.
(Additional Item 1) A polymer electrolyte membrane having ion conductivity, a fuel electrode provided on one side of the polymer electrolyte membrane and supplied with fuel, and an oxidant-containing gas provided on the other side of the polymer electrolyte membrane A supplied oxidant electrode, a gas flow path forming member for the fuel electrode provided outside the fuel electrode, and a porous gas flow path forming member for the oxidant electrode provided outside the oxidant electrode; A solid passage comprising a water passage forming member that forms a water passage through which water flows outside the gas flow passage forming member for the oxidant electrode, and a water passage portion that pumps water through the water passage and flows water through the water passage. A polymer fuel cell,
In the porous gas flow path forming member for the oxidant electrode, when the downstream where the oxidant gas flows is defined as a downstream region and the upstream where the oxidant gas flows is defined as an upstream region, a water repellent Is set to be smaller in the upstream region than in the downstream region.

When the ratio of the water repellent is large, it is not easy to put water in and out. The ratio of the water repellent is set to be relatively large in the downstream region and relatively small in the upstream region. For this reason, it becomes advantageous to permeate | transmit the water of a water channel to the MEA side, and it can contribute to suppression of the excessive drying in the upstream area | region of MEA.
(Additional Item 2) A polymer electrolyte membrane having ion conductivity, a fuel electrode provided on one side of the polymer electrolyte membrane and supplied with fuel, and an oxidant-containing gas provided on the other side of the polymer electrolyte membrane A supplied oxidant electrode, a gas flow path forming member for the fuel electrode provided outside the fuel electrode, and a porous gas flow path forming member for the oxidant electrode provided outside the oxidant electrode; A water flow path forming member that forms a water flow path through which water flows outside the gas flow path forming member for the oxidizer electrode; and a water flow section that sucks water from the water flow path and flows water through the water flow path. A polymer electrolyte fuel cell,
In the porous gas flow path forming member for the oxidant electrode, when the downstream where the oxidant gas flows is defined as a downstream region and the upstream where the oxidant gas flows is defined as an upstream region, The ratio is set larger in the upstream region than in the downstream region. When the ratio of the water repellent is large, it is not easy to put water in and out. The ratio of the water repellent is set to be relatively large in the upstream region and relatively small in the downstream region. For this reason, it becomes advantageous to attract the surplus water in the downstream area of the MEA to the water channel, and can contribute to suppressing the retention of surplus water in the downstream area.

It is sectional drawing which shows typically the concept of the fuel cell which concerns on a 1st reference example. It is a graph which shows typically a change of a pore diameter and a porosity concerning the 1st reference example. It is a graph which shows typically the change of the pore diameter concerning the 2nd reference example, and the porosity. It is sectional drawing which shows typically the concept of the fuel cell which concerns on a 3rd reference example. It is sectional drawing which shows typically the concept of the fuel cell which concerns on a 4th reference example. It is sectional drawing which shows typically the concept of the fuel cell which concerns on 1st Example. It is a graph which shows typically a change of a pore diameter and a porosity concerning a 1st example. It is a graph which shows typically the change of the pore diameter concerning the 2nd example, and the porosity. It is sectional drawing which shows typically the concept of the fuel cell which concerns on 3rd Example. It is sectional drawing which shows typically the concept of the fuel cell which concerns on 4th Example. It is sectional drawing which concerns on the manufacture example 1 of a gas flow path formation member, and shows the concept of the gas flow path formation member in the state before finally compressing. It is sectional drawing which concerns on the manufacture example 1 of a gas flow path formation member, and shows the concept of the gas flow path formation member in the state after finally compressing. It is sectional drawing which concerns on the manufacture example 2 of a gas flow path formation member, and shows typically the concept of the gas flow path formation member in the state before finally compressing. It is sectional drawing which concerns on the manufacture example 2 of a gas flow path formation member, and shows typically the concept of the gas flow path formation member in the state after finally compressing.

Explanation of symbols

  In the figure, 1 is an MEA, 11 is a polymer electrolyte membrane, 12 is a fuel electrode, 15 is an oxidant electrode, 2 is a gas flow path forming member for the fuel electrode, 3 is a gas flow path forming member for the oxidant electrode, Reference numeral 41 denotes a first water passage, 42 denotes a second water passage, 49 denotes a water passage, 51 denotes a water passage forming member, 91 denotes an upstream region, 93 denotes a downstream region, and 8 denotes a water repellent.

Claims (4)

A polymer electrolyte membrane having ion conductivity, a fuel electrode provided on one side of the polymer electrolyte membrane and supplied with fuel, and an oxidant-containing gas provided on the other side of the polymer electrolyte membrane Porous gas flow for the oxidant electrode, the gas flow path forming member for the fuel electrode provided outside the fuel electrode, and the pores provided outside the oxidant electrode and having pores that can be communication holes A channel forming member, a water channel forming member that forms a water channel through which water flows outside the gas channel forming member for the oxidant electrode, and water in the water channel is sucked to flow into the water channel A polymer electrolyte fuel cell comprising a water flow portion,
In the porous gas flow path forming member for the oxidant electrode,
When the downstream where the oxidant gas flows is defined as a downstream region, and the upstream where the oxidant gas flows is defined as an upstream region,
Moisture permeability through which at least one of liquid phase water and water vapor passes between the oxidant electrode and the water passage is set larger in the downstream region than in the upstream region. A polymer electrolyte fuel cell. The porous gas channel forming member for the oxidant electrode according to claim 1, wherein at least one of the average pore diameter and the porosity is:
The polymer electrolyte fuel cell is characterized in that it is set larger in the downstream region than in the upstream region. In Claim 1 or Claim 2, in the gas channel forming member for the porous oxidant electrode, at least one of the average pore diameter and the porosity is:
It is set to be relatively large in the downstream region, is set to be relatively small in the upstream region, and is set to gradually increase from the upstream region to the downstream region. Solid polymer fuel cell.   4. The porous gas flow path forming member for the oxidant electrode according to claim 1, wherein a ratio of the water repellent per unit volume is larger in the upstream region than in the downstream region. A polymer electrolyte fuel cell characterized by being set.

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