JP2018022570A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell arranged so that the elution amount of a radical inhibitor in a portion where the remaining water amount is large can be reduced while securing the elution amount of the radical inhibitor in a portion where the remaining water amount is small.SOLUTION: In a fuel cell, at least one of a pair of electrodes and a pair of separators includes a first portion including a radical inhibitor, and a second portion including the radical inhibitor and located vertically below the first portion. The amount of the radical inhibitor eluted into water from the second portion per unit volume and per unit time is smaller than that from the first portion when the water is distributed in the first and second portions under the same condition which satisfies at least one of the following requirements: the second portion is lower than the first portion in radical inhibitor concentration; the total superficial area of the radical inhibitor included per unit volume is small; and the radical inhibitor has high crystallinity.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fuel cell.

  In the fuel cell, hydrogen peroxide is generated in the catalyst layer along with the electrochemical reaction, and hydroxy radicals are generated from the hydrogen peroxide. This hydroxy radical makes the electrolyte membrane thinner and lowers strength. For this reason, a fuel cell is known in which a radical inhibitor that suppresses hydroxy radicals is contained in a catalyst layer or the like (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2006-244787

  The radical inhibitor elutes in the residual water remaining in the fuel cell after power generation is stopped, and is accumulated in the electrolyte membrane. For this reason, hydroxy radicals can be suppressed even in the electrolyte membrane. However, the distribution of the remaining water amount in the fuel cell after power generation is stopped is not uniform. For this reason, in the site | part with little residual water amount, the elution amount of a radical inhibitor decreases, and the accumulation amount in the electrolyte membrane in the site | part also decreases. As a result, there is a possibility that the strength of the electrolyte membrane is lowered without being able to suppress hydroxy radicals at a site where the amount of residual water is small. On the other hand, at a site where the amount of residual water is large, the elution amount of the radical inhibitor increases, and the amount of accumulation in the electrolyte membrane at that site also increases. Here, if the accumulated amount of such a radical inhibitor increases more than necessary to suppress hydroxy radicals, the proton transfer resistance in the electrolyte membrane increases, which may reduce the power generation performance of the fuel cell. There is.

  An object of this invention is to provide the fuel cell which can suppress the elution amount of the radical inhibitor in the site | part with much residual water amount, ensuring the elution amount of the radical inhibitor in the site | part with little residual water amount.

  The object is to provide a fuel cell including a cell having a pair of electrodes sandwiching an electrolyte membrane and a pair of separators sandwiching the pair of electrodes, wherein at least one of the pair of electrodes and the pair of separators is radical suppression. A first part containing an agent and a second part containing a radical inhibitor and positioned vertically downward from the first part, wherein the second part is more radical-inhibiting than the first part. Each of the first and second portions is caused by at least one of a low concentration of the agent, a small total surface area of the radical inhibitor contained per unit volume, and a high crystallinity of the radical inhibitor. In the case where water is distributed under the same conditions, the elution amount per unit time of the radical inhibitor into water per unit volume is smaller from the second part than from the first part. It can be achieved by charge the battery.

  The object is to provide a fuel cell in which at least one of a pair of electrodes sandwiching an electrolyte membrane and a pair of separators sandwiching a pair of electrodes includes a plurality of cells containing radical inhibitors, and one of the plurality of cells is stacked. A first cell that is one of the plurality of cells, and a second cell that is positioned vertically downward in the stacking direction of the cells relative to the first cell, and the second cell Is at least one of a lower concentration of radical inhibitor, a smaller total surface area of radical inhibitors contained per unit volume, and a higher crystallinity of the radical inhibitor than the first cell. Thus, when water is distributed in the first and second cells under the same conditions, the elution amount of the radical inhibitor per unit volume of water per unit volume is equal to that from the second cell. Is the first cell Less than can be achieved by the fuel cell.

  In the fuel cell in which at least one of the pair of electrodes sandwiching the electrolyte membrane and the pair of separators sandwiching the pair of electrodes is stacked with a plurality of cells each containing a radical inhibitor, the object passes through the plurality of cells. A supply manifold in which a reaction gas flows in a first direction and a plurality of the cells, the reaction gas flows from the supply manifold through the plurality of cells, and a second direction opposite to the first direction A discharge manifold through which the reaction gas flows, a first cell that is one of the plurality of cells, and one of the plurality of cells, which is located closer to the first direction than the first cell. The second cell has a lower concentration of radical inhibitor than the first cell, a smaller total surface area of radical inhibitors contained per unit volume, and a radio When the water is distributed under the same conditions in the first and second cells by at least one of the high crystallinity of the inhibitor, the unit of the radical inhibitor into water per unit volume The amount of elution per time can also be achieved with a fuel cell, which is less from the second cell than from the first cell.

  In the fuel cell in which at least one of the pair of electrodes sandwiching the electrolyte membrane and the pair of separators sandwiching the pair of electrodes is stacked with a plurality of cells each containing a radical inhibitor, the object passes through the plurality of cells. A supply manifold through which the reaction gas flows in a first direction, and a discharge manifold through which the reaction gas flows from the supply manifold through the plurality of cells and the reaction gas flows in the first direction. One of the plurality of cells, the first cell located closest to the second direction opposite to the first direction, and one of the plurality of cells, A second cell located closer to the first direction than one cell, and a third cell that is one of the plurality of cells and located closest to the first direction, the second cell Are the first and third sections. The concentration of the radical inhibitor is lower than that of each of the above, the total surface area of the radical inhibitor contained per unit volume is small, and the crystallinity of the radical inhibitor is high. When water is distributed in the first, second, and third cells under the same conditions, the elution amount of the radical inhibitor per unit volume of water per unit volume is from the second cell. Can also be achieved with a fuel cell, less than from each of the first and third cells.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell which can suppress the elution amount of the radical inhibitor in a site | part with much residual water amount can be provided, ensuring the elution amount of the radical inhibitor in a site | part with little residual water amount.

FIG. 1A is a cross-sectional view showing a cell constituting the fuel cell, and FIG. 1B is an exploded perspective view showing the cell. FIG. 2 is an exploded view of the fuel cell. FIG. 3A is a graph showing the relationship between the accumulation amount of Ce ^{3+ in} the electrolyte membrane, the decomposition rate of the electrolyte membrane by hydroxy radicals, and the proton transfer resistance of the electrolyte membrane, and FIG. 6 is a graph showing the relationship between the amount of Ce ³⁺ accumulated and the proton transfer resistance of the electrolyte membrane. 4A is a perspective view of a fuel cell, FIG. 4B is a front view showing an insulating member and an anode-side water-repellent layer in a certain cell, and FIG. 4C is a radical suppression in the anode-side water-repellent layer. It is the graph which showed the density | concentration of an agent. FIG. 5A is an external view of the fuel cell of the first modification, FIG. 5B is a graph showing the concentration of the radical inhibitor in each cell in the first modification, and FIG. 5C is the second modification. FIG. 5D is a graph showing the concentration of the radical inhibitor in each cell in the second modified example. 6A is an external view of a fuel cell of a third modification, FIG. 6B is a cross-sectional view showing the inside of the fuel cell of the third modification, and FIG. 6C is each cell in the third modification. It is the graph which showed the density | concentration of the radical inhibitor. FIG. 7A is an external view of a fuel cell 1D according to a fourth modification, FIG. 7B is a cross-sectional view illustrating the inside of the fuel cell according to the fourth modification, and FIG. 7C illustrates each of the fuel cell 1D according to the fourth modification. It is the graph which showed the density | concentration of the radical inhibitor of a cell. 8A to 8D are graphs in the case where the radical inhibitor is changed stepwise. 9A and 9B are explanatory diagrams of the difference in the total surface area of the radical inhibitor per unit volume of the anode-side water-repellent layer of the cell of the fuel cell in the fifth modification, and FIG. 9C shows the fifth modification. It is the graph which showed the total surface area of the radical inhibitor in the anode side water repellent layer in an example. FIG. 10A is a schematic diagram of a crystal structure of CeO ₂ which is a radical inhibitor, and FIG. 10B is a conceptual diagram of a radical inhibitor having high crystallinity. FIG. 10C is a conceptual diagram of a radical inhibitor having low crystallinity, and FIG. 10D is a graph showing the crystallinity of the radical inhibitor in the anode-side water-repellent layer in the sixth modification.

  FIG. 1A is a cross-sectional view showing a cell constituting the fuel cell, and FIG. 1B is an exploded perspective view showing the cell. A fuel cell is a polymer electrolyte fuel cell that generates power by receiving supply of a fuel gas (for example, hydrogen) and an oxidant gas (for example, air) as reaction gases, and is mounted on, for example, a fuel cell vehicle or an electric vehicle. . As shown in FIG. 1A, the cell 10 includes an MEA (Membrane Electrode Assembly) 11 in which an anode catalyst layer 14a is formed on one surface of an electrolyte membrane 12, and a cathode catalyst layer 14c is formed on the other surface.

  The electrolyte membrane 12 is a solid polymer membrane formed of a fluorine resin material or a carbon resin material, and has good proton conductivity in a wet state. The anode catalyst layer 14a and the cathode catalyst layer 14c include carbon particles (for example, carbon black) supporting a catalyst (for example, platinum or a platinum-cobalt alloy) that promotes an electrochemical reaction, and an ionomer having proton conductivity. . The carbon particles of the anode catalyst layer 14a and the cathode catalyst layer 14c have electronic conductivity.

  A pair of water repellent layers (anode side water repellent layer 16a and cathode side water repellent layer 16c) and a pair of gas diffusion layers (anode gas diffusion layer 18a and cathode gas diffusion layer 18c) are disposed on both sides of the MEA 11. Has been. The pair of water repellent layers is provided to keep the moisture contained in the MEA 11 in an appropriate amount. The MEA 11, the pair of water repellent layers, and the pair of gas diffusion layers are collectively referred to as a MEGA (Membrane Electrode Gas diffusion layer Assembly) 30.

  The anode-side water-repellent layer 16a, the cathode-side water-repellent layer 16c, the anode gas diffusion layer 18a, and the cathode gas diffusion layer 18c are formed of members having gas permeability and electron conductivity. For example, carbon cloth or carbon paper is used. It is formed of a porous carbon member such as. The anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c have smaller pores of the porous carbon member than the anode gas diffusion layer 18a and the cathode gas diffusion layer 18c. For example, the pore size of the anode side water repellent layer 16a and the cathode side water repellent layer 16c is about 0.1 μm to 1 μm in diameter, and the pore size of the anode gas diffusion layer 18a and the cathode gas diffusion layer 18c is The diameter is about 10 μm to 100 μm. Thus, since the pores of the anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c are small, the liquid water can be prevented from flowing out from the anode catalyst layer 14a and the cathode catalyst layer 14c, and are included in the MEA 11. Moisture can be kept at an appropriate amount.

  As described above, the anode catalyst layer 14a, the anode-side water-repellent layer 16a, and the anode gas diffusion layer 17a correspond to anode-side electrodes, and the cathode catalyst layer 14c, the cathode-side water-repellent layer 16c, and the cathode gas diffusion layer. 17c corresponds to an electrode on the cathode side, which is an example of a pair of electrodes sandwiching the electrolyte membrane 12.

  A pair of separators (an anode side separator 20a and a cathode side separator 20c) that sandwich the MEGA 30 are disposed on both sides of the MEGA 30. The anode-side separator 20a and the cathode-side separator 20c are formed of members having gas barrier properties and electronic conductivity. For example, a carbon member such as dense carbon which is made impermeable to gas by compressing carbon, or press-molded stainless steel It is formed of a metal member such as steel. The anode-side separator 20a and the cathode-side separator 20c have irregularities for forming a gas flow path through which gas flows on the surface. The anode side separator 20a forms an anode gas flow path 22a between the anode gas diffusion layer 18a. The cathode side separator 20c forms a cathode gas flow path 22c between the cathode gas diffusion layer 18c. During power generation of the fuel cell, the fuel gas flows through the anode gas flow path 22a and the oxidant gas flows through the cathode gas flow path 22c. In addition, although the structure which provides a gas diffusion layer in both an anode and a cathode was shown as an example, it is not limited to this. The structure which does not equip one or both of an anode and a cathode with a gas diffusion layer may be sufficient. In this case, gas is supplied from the anode gas channel or the cathode gas channel directly to the catalyst layer through the water repellent layer. In a configuration that does not include a gas diffusion layer, a sheet member having functions of water repellency, gas permeation, and conductivity may be used as the water repellent layer.

  As shown in FIG. 1B, the MEGA 30 is disposed inside an insulating member 40 made of, for example, a resin (such as an epoxy resin or a phenol resin). In other words, the frame-shaped insulating member 40 is disposed so as to cover the outer periphery of the MEGA 30. The insulating member 40 is sandwiched between the anode side separator 20a and the cathode side separator 20c.

  The anode side separator 20a and the cathode side separator 20c are provided with holes a1 to a3 and holes c1 to c3, respectively. Similarly, the insulating member 40 is provided with holes s1 to s3. The holes a1 to a3, the holes s1 to s3, and the holes c1 to c3 communicate with each other, the holes a1, s1, and c1 are the oxidant gas supply manifold, the holes a2, s2, and c2 are the refrigerant supply manifold, a3, s3, and c3 define a fuel gas discharge manifold.

  The anode side separator 20a and the cathode side separator 20c are provided with holes a4 to a6 and holes c4 to c6, respectively. Similarly, the insulating member 40 is provided with holes s4 to s6. The holes a4 to a6, s4 to s6, and c4 to c6 communicate with each other, the holes a4, s4, and c4 are fuel gas supply manifolds, the holes a5, s5, and c5 are refrigerant discharge manifolds, and the holes a6, s6. , And c6 define an oxidant gas exhaust manifold.

  An anode gas flow path 22a through which the fuel gas flows during power generation is formed on the surface of the anode separator 20a facing the MEGA 30 so that the fuel gas supply manifold and the fuel gas discharge manifold communicate with each other. A cathode gas flow path 22c through which an oxidant gas flows during power generation is formed on the surface of the cathode separator 20c facing the MEGA 30 so that the oxidant gas supply manifold and the oxidant gas discharge manifold communicate with each other. The coolant is supplied to the surface of the anode separator 20a opposite to the surface where the anode gas flow path 22a is formed and to the surface of the cathode separator 20c opposite to the surface where the cathode gas flow path 22c is formed. A refrigerant flow path 24 through which the refrigerant flows is formed through communication between the manifold and the refrigerant discharge manifold.

  FIG. 2 is an exploded view of the fuel cell 1. In FIG. 2, the cell 10 is illustrated in a simplified manner for the sake of clarity. First, the fuel cell will be described. As shown in FIG. 2, the fuel cell 1 includes a plurality of cells 10, a pair of terminal plates 50 and 52, a pair of insulating plates 60 and 62, and a pair of end plates 70 and 72. The fuel cell 1 has a stack structure in which a plurality of cells 10 are sandwiched between a pair of terminal plates 50 and 52, a pair of insulating plates 60 and 62, and a pair of end plates 70 and 72. The terminal plates 50 and 52 are made of metal, and are used for extracting voltage and current from the plurality of cells 10. The end plates 70 and 72 are used for fastening the plurality of cells 10, the terminal plates 50 and 52, and the insulating plates 60 and 62.

  The terminal plate 50, the insulating plate 60, and the end plate 70 are provided with holes t1 to t6, holes i1 to i6, and holes e1 to e6, respectively. Holes t1, i1, and e1 define an oxidant gas supply manifold, holes t2, i2, and e2 define a refrigerant supply manifold, and holes t3, i3, and e3 define a fuel gas discharge manifold. Holes t4, i4, and e4 define a fuel gas supply manifold, holes t5, i5, and e5 define a refrigerant discharge manifold, and holes t6, i6, and e6 define an oxidant gas discharge manifold. On the other hand, the terminal plate 52, the insulating plate 62, and the end plate 72 are not provided with holes. As a result, the fuel gas introduced from the hole e4 flows through the anode gas flow path 22a of each of the plurality of cells 10, and then is discharged from the hole e3. The refrigerant introduced from the hole e2 flows through the refrigerant flow path 24 of each of the plurality of cells 100 and is then discharged from the hole e5. The oxidant gas introduced from the hole e1 flows through the cathode gas flow path 22c of each of the plurality of cells 10, and is then discharged from the hole e6.

  The plurality of cells 10 are stacked in order from the terminal plate 50 side to the terminal plate 52 side. In this specification, each cell is expressed as cells 10-1, 10-2... 10-n-1, 10-n in order from the terminal plate 50 side. Further, in this specification, the cell is a generic term for the cell 10.

Next, the radical inhibitor will be described. The anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c contain a radical inhibitor that suppresses the generation of hydroxy radicals. In this example, the radical inhibitor is a cerium-containing oxide, specifically CeO ₂ . The principle that radical generation is suppressed by CeO ₂ is as follows. During power generation of the fuel cell 1, some oxygen in the oxidant gas supplied to the fuel cell 1 may pass through the electrolyte membrane 12 and reach the anode catalyst layer 14a. When this oxygen is reduced in the anode catalyst layer 14a, hydrogen peroxide is generated, and hydroxy radicals are generated due to the hydrogen peroxide. Hydroxy radicals decompose the electrolyte membrane 12 and reduce its strength. Here, CeO ₂ which is a radical inhibitor contained in the anode-side water-repellent layer 16 a and the cathode-side water-repellent layer 16 c is eluted as Ce ³⁺ in the water in the fuel cell 1, and the following formula (1) Hydroxyl radicals are consumed by this reaction. This suppresses hydroxy radicals.
OH + Ce ³⁺ + H ⁺ → Ce ⁴⁺ + H ₂ O (1)

However, the eluted Ce ³⁺ gradually accumulates in the electrolyte membrane 12 as the fuel cell 1 is used. For this reason, when more than the necessary amount of Ce ³⁺ that suppresses hydroxy radicals is accumulated in the electrolyte membrane 12, Ce ³⁺ increases the proton transfer resistance of the electrolyte membrane 12 as a cation impurity.

FIG. 3A is a graph showing the relationship between the accumulation amount of Ce ^{3+ in} the electrolyte membrane 12, the decomposition rate of the electrolyte membrane 12 by hydroxy radicals, and the proton transfer resistance of the electrolyte membrane 12. If the amount of Ce ³⁺ accumulated in the electrolyte membrane 12 is too small, the decomposition rate of the electrolyte membrane 12 by hydroxy radicals increases, but if the amount of Ce ³⁺ accumulated in the electrolyte membrane 12 is too large, the proton transfer resistance increases. To do. FIG. 3B is a graph showing the relationship between the amount of Ce ³⁺ accumulated in the electrolyte membrane 12 and the proton transfer resistance of the electrolyte membrane 12, and the amount of Ce ³⁺ accumulated when the relative humidity is 30 and 80 percent, respectively. And the proton transfer resistance. When the amount of Ce ³⁺ accumulated is large, the proton transfer resistance increases significantly as the relative humidity decreases. For this reason, when the accumulation amount of Ce ³⁺ is larger than an appropriate amount, the power generation performance of the fuel cell 1 is greatly deteriorated in a low wet state.

Here, in a power generation system in which the fuel cell 1 is employed, generally, after the power generation of the fuel cell 1 is stopped, scavenging control for supplying scavenging gas to the fuel cell 1 and discharging the remaining water in the fuel cell 1 to the outside. Is executed. However, even after the scavenging control is performed, residual water may partially remain in the fuel cell 1, and the distribution of the residual water amount in the fuel cell 1 after power generation is stopped is not uniform. For this reason, in the part where the amount of residual water is small, the amount of Ce ³⁺ eluted into the residual water during power generation stoppage is small, so that the amount of Ce ³⁺ accumulated in the electrolyte membrane 12 cannot be partially secured, and the hydroxyl radical May not be sufficiently suppressed, and the strength of the electrolyte membrane 12 may decrease. On the other hand, in a part where the amount of residual water is large, Ce ³⁺ elutes in the residual water when power generation is stopped, the amount of Ce ³⁺ accumulated in the electrolyte membrane 12 partially increases, and proton transfer resistance partially increases. there's a possibility that. As a result, the power generation performance of the fuel cell 1 may be reduced.

  FIG. 4A is a perspective view of the fuel cell 1. The fuel cell 1 according to this embodiment is used in such a posture that the stacking direction of the cells 10 is substantially parallel to the horizontal direction, and the flow direction of the oxidant gas in each cell 10 is substantially parallel to the horizontal direction. FIG. 4B is a front view showing the insulating member 40 and the anode-side water-repellent layer 16 a in a certain cell 10. The anode side water repellent layer 16a has an upper portion 161a and a lower portion 162a. The lower portion 162a is located on the vertically lower side than the upper portion 161a. For this reason, the remaining water in the fuel cell 1 after the power generation is stopped and after the scavenging control is performed is present more in the vicinity of the lower portion 162a than in the vicinity of the upper portion 161a due to the action of gravity. The anode-side water repellent layer 16a including the upper portion 161a and the lower portion 162a contains a radical inhibitor. Therefore, the upper part 161a is an example of a first part that contains a radical inhibitor, and the lower part 162a is an example of a second part that contains a radical inhibitor and is located vertically below the upper part 161a.

FIG. 4C is a graph showing the concentration of the radical inhibitor in the anode water-repellent layer 16a. The vertical axis indicates the position of the anode water-repellent layer 16a in the vertical direction, and the horizontal axis indicates the concentration of the radical inhibitor. The concentration of the radical inhibitor decreases from the vertically upper side to the vertically lower side of the anode-side water-repellent layer 16a. The concentration of the radical inhibitor in the cathode side water repellent layer 16c is also the same. Accordingly, the concentration of the radical inhibitor is lower in the lower portion 162a than in the upper portion 161a. Thus, since the concentration of the radical inhibitor in the lower portion 162a where there is a large amount of residual water in the vicinity is low, the elution amount per unit time of Ce ³⁺ from the lower portion 162a per unit volume can be suppressed. As a result, an increase in the amount of Ce ³⁺ accumulated in a part of the electrolyte membrane 12 is suppressed, and a decrease in power generation performance of the fuel cell 1 is suppressed.

Further, since the amount of residual water is small around the upper portion 161a, the concentration of the radical inhibitor is higher in the upper portion 161a than in the lower portion 162a. For this reason, the amount of Ce ³⁺ eluted from the upper portion 161a into water per unit volume can be secured, and the amount of Ce ³⁺ accumulated in the electrolyte membrane 12 facing the upper portion 161a through the anode catalyst layer 14a can be secured. Thereby, a hydroxy radical can be suppressed and the fall of the intensity | strength of the electrolyte membrane 12 is suppressed. As described above, a decrease in power generation performance of the fuel cell 1 is also suppressed while suppressing a decrease in the strength of the electrolyte membrane 12.

When water is distributed to the upper part 161a and the lower part 162a under the same conditions, the lower 162a has a lower concentration of radical inhibitor, so that Ce ³⁺ per unit volume is eluted per unit time. The amount is lower from the lower portion 162a than from the upper portion 161a. The case where water is distributed under the same conditions is a case where water is uniformly distributed over the predetermined period with the same density with respect to the upper portion 161a and the lower portion 162a. For example, when sufficient water is supplied into the anode gas flow path 22a with the single cell 10 placed in a horizontal state, or water is put on the anode-side water-repellent layer 16a before being joined to the MEA 11 or the anode gas diffusion layer 18a. Is distributed uniformly, or a single cell 10 or a single anode-side water-repellent layer 16a is submerged in water.

  Although the anode side water repellent layer 16a and the cathode side water repellent layer 16c of other cells contain radical inhibitors in a similar concentration distribution, the present invention is not limited to this. It is sufficient that at least one of the anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c of the fuel cell 1 has a lower concentration in the vertically lower side than in the vertically upper side. The concentration of the radical inhibitor in the other of the anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c and the anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c of other cells 10 is independent of the site. It may be uniform. For example, when a cell that is relatively easily exposed to residual water among the plurality of cells is specified, the radical inhibitor of at least one of the anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c of the cell is specified. The concentration may be lower on the vertically lower side than on the vertically upper side. As a result, the number of cells in which the concentration distribution is biased can be reduced, and the manufacturing cost can be suppressed. Further, in FIG. 4C, the concentration of the radical inhibitor is represented by a straight line, but is not limited thereto, and may be represented by a curve as long as the concentration decreases from the vertical upper side to the lower side. . When the fuel cell 1 of the above embodiment is used in a posture in which the stacking direction of the cells 10 is substantially parallel to the horizontal direction and the holes e1 to e3 are positioned vertically downward or above the holes e4 to e6. It is sufficient that the concentration of the radical inhibitor is lower in the vertically lower portion of the anode-side water-repellent layer 16a in that posture than in the vertically upper portion.

  Next, a plurality of modifications of the fuel cell will be described. In addition, about the some modification demonstrated below, about the same and similar structure as the said Example, the duplicate description is abbreviate | omitted by attaching | subjecting the same and similar code | symbol, respectively. FIG. 5A is an external view of a fuel cell 1A according to a first modification. The fuel cell 1A is used in a posture in which the stacking direction of the plurality of cells 10a is substantially parallel to the vertical direction. Specifically, the terminal plate 50a, the insulating plate 60a, and the end plate 70a are positioned on the vertically lower side, and the terminal plate 52a, the insulating plate 62a, and the end plate 72a are positioned on the vertically upper side. As in the case described above, each anode-side water-repellent layer and cathode-side water-repellent layer of the cell 10a contains a radical inhibitor. However, in the following modifications, for convenience of explanation, the anode side of each cell The average value of the concentration of the radical inhibitor in the water-repellent layer and the concentration of the radical inhibitor in the cathode-side water-repellent layer will be described as the concentration of the radical inhibitor in each cell 10a. The plurality of cells 10a include cells 10a-n and 10a-1 disposed on the uppermost side and the lowermost side in the vertical direction, respectively. The amount of remaining water in the fuel cell 1A after power generation is stopped and the scavenging control is executed is larger in the vicinity of the cell 10a-1 than in the vicinity of the cell 10a-n due to the action of gravity. The cells 10a-n are an example of a first cell that is one of the plurality of cells 10a. The cell 10a-1 is an example of a second cell that is located vertically below the cell 10a in the stacking direction of the cells 10a-n and is one of the plurality of cells 10a.

FIG. 5B is a graph showing the concentration of the radical inhibitor in each cell 10a in the first modification. The vertical axis indicates the position of each cell 10a in the stacking direction, and the horizontal axis indicates the concentration of the radical inhibitor. In the first modification, the concentration of the radical inhibitor in each cell 10 decreases in the stacking direction from the vertically upper side to the lower side. Therefore, the concentration of the radical inhibitor is lower in the cell 10a-1 than in the cell 10a-n. Thus, since the concentration of the radical inhibitor in the cell 10a-1 having a large amount of residual water in the vicinity is low, the elution amount per unit volume of Ce ³⁺ from the cell 10a-1 per unit volume is suppressed. it can. In addition, since the concentration of the radical inhibitor in the cell 10a-n having a small amount of residual water in the periphery is high, it is possible to secure an elution amount per unit time of Ce ³⁺ from the cell 10a-n into water per unit volume. This suppresses a decrease in power generation performance of the fuel cell 1A while suppressing a decrease in the strength of the electrolyte membrane.

When water is distributed in the cells 10a-1 and 10a-n under the same conditions, the concentration of the radical inhibitor is lower in the cell 10a-1, so that Ce ³⁺ of water per unit volume is reduced. The amount of elution per unit time is smaller from the cell 10a-1 than from the cell 10a-n. The case where water is distributed under the same conditions in the first modification is a case where water is distributed uniformly in the cells 10a-1 and 10a-n with the same density and over a certain period in the same posture. . For example, when the single cell 10a-1 and the single cell 10a-n are supplied with sufficient water to at least one of the anode channel and the cathode channel in the same posture, or when the single cell 10a-1 and the single cell 10a-n are supplied, This is the case when 10a-n is submerged in water.

  FIG. 5C is an external view of a fuel cell 1B of the second modification. The fuel cell 1B is used in a posture in which the stacking direction of the plurality of cells 10b is inclined with respect to the vertical direction and the horizontal direction. Also in this case, the terminal plate 50b, the insulating plate 60b, and the end plate 70b are positioned on the vertically lower side, and the terminal plate 52b, the insulating plate 62b, and the end plate 72b are positioned on the vertically upper side. Cells 10b-n and 10b-1 included in the plurality of cells 10b are arranged on the uppermost side and the lowermost side. Even when the fuel cell 1B is disposed obliquely in this way, the amount of remaining water in the fuel cell 1B after power generation is stopped is greater in the vicinity of the cell 10b-1 due to the action of gravity. More than the surroundings. The cell 10b-n is an example of a first cell that is one of the plurality of cells 10b. The cell 10b-1 is an example of a second cell that is located vertically below the cell 10b in the stacking direction of the cell 10b-n and is one of the plurality of cells 10b.

FIG. 5D is a graph showing the concentration of the radical inhibitor in each cell 10b in the second modification. The vertical axis indicates the position of each cell 10b in the stacking direction, and the horizontal axis indicates the concentration of the radical inhibitor. Similar to the first modification, the height decreases from the upper side to the lower side in the stacking direction. For this reason, the elution amount per unit time of the Ce ³⁺ from the cell 10b-1 into water per unit volume can be suppressed, and the elution per unit time of the Ce ³⁺ from the cell 10b-n into water per unit volume. The amount can be secured. This suppresses a decrease in power generation performance of the fuel cell 1B while suppressing a decrease in the strength of the electrolyte membrane.

Also in this case, when water is distributed in the cells 10b-1 and 10b-n under the same conditions, the concentration of the radical inhibitor is lower in the cell 10b-1, so that Ce to water per unit volume is reduced. The elution amount per unit time of ³⁺ is smaller from the cell 10b-1 than from the cell 10b-n. The case where water is distributed under the same conditions in the second modification is the same as in the first modification.

  FIG. 6A is an external view of a fuel cell 1C according to a third modification. 1 C of fuel cells are used with the attitude | position similar to the fuel cell 1 of the Example mentioned above. FIG. 6B is a cross-sectional view showing the inside of the fuel cell 1C of the third modified example. FIG. 6B shows the oxidant gas supply manifold S1 and the oxidant gas discharge manifold S6 described above, and circulates in the oxidant gas supply manifold S1 and the oxidant gas discharge manifold S6 via the cells 10c during the scavenging control. The flow of scavenging gas is indicated by arrows. During power generation, not the scavenging gas but the oxidant gas flows through the oxidant gas supply manifold S1 and the oxidant gas discharge manifold S6 in the same manner as the scavenging gas flow shown in FIG. 6B. Gases flow in opposite directions through the oxidant gas supply manifold S1 and the oxidant gas discharge manifold S6. The oxidant gas supply manifold S1 is an example of a supply manifold that passes through the plurality of cells 10c and in which the oxidant gas flows in the first direction. The oxidant gas discharge manifold S6 passes through the plurality of cells 10c, the oxidant gas flows from the oxidant gas supply manifold S1 through the plurality of cells 10c, and reacts in the second direction opposite to the first direction. It is an example of the exhaust manifold through which gas distribute | circulates.

  The flow rate of the scavenging gas passing through each cell 10c is highest in the cell 10c-1 near the respective inlets and outlets of the oxidant gas supply manifold S1 and the oxidant gas discharge manifold S6, and the oxidant gas supply manifold S1 and the oxidant. Fewer cells 10c-n farthest from the respective inlets and outlets of the gas exhaust manifold S6. This is presumably because the pressure loss of the scavenging gas increases as the distance from the respective inlets and outlets of the oxidizing gas supply manifold S1 and the oxidizing gas discharge manifold S6 increases. For this reason, after power generation is stopped, the amount of residual water is larger in the vicinity of the cell 10c-n than in the vicinity of the cell 10c-1. The cell 10c-1 is an example of a first cell that is one of the plurality of cells 10c. The cell 10c-n is one of the plurality of cells 10c and is an example of a second cell located on the first direction side of the cell 10c-1.

FIG. 6C is a graph showing the concentration of the radical inhibitor in each cell 10c in the third modification. The vertical axis indicates the position of each cell 10c in the stacking direction, and the horizontal axis indicates the concentration of the radical inhibitor. The density | concentration of the radical inhibitor is low in order of the cell 10c-1 to the cell 10c-n. That is, the concentration of the radical inhibitor in the cell 10 on the side away from the inlet of the oxidant gas supply manifold S1 and the outlet of the oxidant gas discharge manifold S6 is low. For this reason, the elution amount per unit time of the Ce ³⁺ from the cell 10c-n into the water per unit volume can be suppressed, and the elution per unit time of the Ce ³⁺ from the cell 10c-1 into the water per unit volume. The amount can be secured. This suppresses a decrease in power generation performance of the fuel cell 1C while suppressing a decrease in the strength of the electrolyte membrane.

Also in this case, when water is distributed in the cells 10c-1 and 10c-n under the same conditions, the concentration of the radical inhibitor is lower in the cell 10c-n, so that Ce to water per unit volume is reduced. The elution amount per unit time of ³⁺ is smaller from the cell 10c-n than from the cell 10c-1. The case where water is distributed under the same conditions in the third modification is the same as in the first modification.

  In the third modification, the portion where the remaining water amount is large when the scavenging gas flows through the oxidant gas supply manifold S1 and the oxidant gas discharge manifold S6 has been described. However, the scavenging gas defines a hole that defines the fuel gas supply manifold. Even in the case where the fuel gas is supplied from e4 and discharged from the hole e3 that defines the fuel gas discharge manifold, the portion where the remaining water amount is large is the same. This is because the flow direction is merely opposite between when the scavenging gas flows through the oxidant gas supply manifold S1 and the oxidant gas discharge manifold S6 and when the scavenging gas flows through the fuel gas supply manifold and the fuel gas discharge manifold. Therefore, in the third modified example, the scavenging gas may flow through the fuel gas supply manifold and the fuel gas discharge manifold. In this case, the fuel gas supply manifold and the fuel gas discharge manifold may be examples of the supply manifold and the discharge manifold, respectively. is there.

  In the third modified example, as in the above-described embodiment, at least one of the anode-side water-repellent layer and the cathode-side water-repellent layer of each cell 10c is more radical-suppressed than the vertically upper side. The concentration of the agent may be low. As described above, in the third modification, when there is a difference in the concentration of the radical inhibitor in the surface direction of each cell 10c, the average value of the concentration of the radical inhibitor in each cell 10c is shown in FIG. 6C. As shown, it is only necessary that the cell 10c-1 to the cell 10c-n become lower in order.

  FIG. 7A is an external view of a fuel cell 1D of the fourth modified example. The fuel cell 1D is used in the same posture as the fuel cells 1 and 1C. However, in the fuel cell 1D, the holes e1 to e3 are provided in the end plate 70d, but the holes e4 to e6 are not provided. Holes corresponding to the holes e4 to e6 are provided in the end plate 72d. That is, the oxidant gas flows from the hole e1 of the end plate 70d and the refrigerant flows from the hole e2 to the insulating plate 60d, the terminal plate 50d, the cell 10d, the terminal plate 52d, the insulating plate 62d, and the end plate 72d in this order. The fuel gas flows in the order of the end plate 72d, the insulating plate 62d, the cell 10d, the terminal plate 50d, and the insulating plate 60d, and is discharged from the hole e1 of the end plate 70d.

  FIG. 7B is a cross-sectional view showing the inside of the fuel cell 1D of the fourth modified example. FIG. 7B shows the oxidant gas supply manifold Sd1 and the oxidant gas discharge manifold Sd6, and the scavenging gas flowing through the oxidant gas supply manifold Sd1 and the oxidant gas discharge manifold Sd6 through the cells 10d during the scavenging control. The flow is shown by arrows. During power generation, not the scavenging gas but the oxidant gas flows through the oxidant gas supply manifold Sd1 and the oxidant gas discharge manifold Sd6 in the same manner as the scavenging gas flow shown in FIG. 7B. Gas flows in the same direction through the oxidant gas supply manifold Sd1 and the oxidant gas discharge manifold Sd6. The oxidant gas supply manifold Sd1 is an example of a supply manifold that passes through the plurality of cells 10d and in which the reaction gas flows in the first direction. The oxidant gas discharge manifold Sd6 is an example of a discharge manifold through which the plurality of cells 10d penetrate, the oxidant gas flows from the oxidant gas supply manifold Sd1 through the plurality of cells 10d, and the reaction gas flows in the first direction. It is.

  The cell 10d-1 is farthest from the outlet of the oxidant gas discharge manifold Sd6, but is closest to the inlet of the oxidant gas supply manifold Sd1. The cell 10d-n is farthest from the inlet of the oxidant gas supply manifold Sd1, but is closest to the outlet of the oxidant gas discharge manifold Sd6. On the other hand, the cell 10d-m arranged at an intermediate position between the cell 10d-1 and the cell 10d-n is supplied from both the inlet of the oxidant gas supply manifold Sd1 and the outlet of the oxidant gas discharge manifold Sd6. is seperated. For this reason, after scavenging is completed, the amount of water around the cell 10d-m is larger than the amount of residual water around each of the cells 10d-1 and 10d-n. The cell 10d-1 is one of the plurality of cells 10d, and is an example of a first cell located on the second direction side opposite to the first direction. The cell 10d-m is one of a plurality of cells 10d and is an example of a second cell located on the first direction side of the cell 10d-1. The cell 10d-n is one cell among the plurality of cells 10d and is an example of a third cell located closest to the first direction.

FIG. 7C is a graph showing the concentration of the radical inhibitor in each cell 10d in the fourth modification. The vertical axis indicates the position of each cell 10d in the stacking direction, and the horizontal axis indicates the concentration of the radical inhibitor. In FIG. 7A, the concentration of the radical inhibitor decreases from the near side in the stacking direction to the middle position in the stacking direction, that is, from the cell 10d-1 to the cell 10d-m in this order. In FIG. 7A, the concentration of the radical inhibitor increases from the middle position in the stacking direction to the back side, that is, in the order of the cells 10d-m to 10d-n. For this reason, the concentration of the radical inhibitor is lower in each of the cells 10d-m than in each of the cells 10d-1 and 10d-n. For this reason, the elution amount per unit time of the Ce ³⁺ from the cell 10d-m into the water per unit volume can be suppressed, and the Ce ³⁺ from each of the cells 10d-1 and 10d-n into the water per unit volume can be suppressed. The amount of elution per unit time can be secured. This suppresses a decrease in power generation performance of the fuel cell 1D while suppressing a decrease in the strength of the electrolyte membrane.

Also in this case, when water is distributed in the cells 10d-1, 10d-m, and 10d-n under the same conditions, the concentration of the radical inhibitor is lower in the cell 10d-m. The amount of Ce ³⁺ dissolved in water per unit time is smaller in the cells 10d-m than in the cells 10d-1 and 10d-n. The case where water is distributed under the same conditions in the third modification is the same as in the first modification.

  In the fourth modification, the cell having the lowest concentration of the radical inhibitor among the plurality of cells 10d is not limited to the cell 10d-m arranged at an intermediate position between the cells 10d-1 to 10d-n. . It is sufficient that the density is the lowest among the cells arranged between the cells 10d-1 to 10d-n.

  In the fourth modification, the portion where the remaining water amount is large when the scavenging gas flows through the oxidant gas supply manifold Sd1 and the oxidant gas discharge manifold Sd6 has been described. However, the scavenging gas is supplied from the hole that defines the fuel gas supply manifold. Even when the fuel gas is discharged from the hole e3 that defines the fuel gas discharge manifold, the portion where the remaining water amount is large is the same. This is because the flow direction is only reversed between when the scavenging gas flows to the oxidant gas supply manifold Sd1 and the oxidant gas discharge manifold Sd6 and when the scavenging gas flows to the fuel gas supply manifold and the fuel gas discharge manifold. Therefore, in the fourth modified example, the scavenging gas may flow through the fuel gas supply manifold and the fuel gas discharge manifold. In this case, the fuel gas supply manifold and the fuel gas discharge manifold may be examples of the above-described supply manifold and discharge manifold, respectively. is there.

  In the said Example and modification, although the case where the density | concentration of the radical inhibitor was changing continuously was demonstrated to the example, it is not limited to this, You may change in steps. 8A to 8D are graphs in the case where the radical inhibitor is changed stepwise. For example, in the above embodiment, the concentration of the radical inhibitor may be decreased stepwise from the upper side to the lower side as shown in FIG. 8A. Thus, when the radical inhibitor concentration changes stepwise, the anode-side water-repellent layer 16a can be easily manufactured, and the manufacturing cost can be suppressed, compared to the case where it continuously changes. In the first modified example, as shown in FIG. 8B, the concentration of the radical inhibitor may be decreased stepwise from cell 10a-n to cell 10a-1. Also in the second modification, the concentration of the radical inhibitor may be decreased stepwise from the cell 10b-n to the cell 10b-1 as in FIG. 8B. Also in the third modification, as shown in FIG. 8C, the concentration of the radical inhibitor may be decreased stepwise from the cell 10c-1 to the cell 10c-n. Also in the fourth modified example, as shown in FIG. 8D, the concentration of the radical inhibitor is decreased stepwise from the cell 10d-1 to the cell 10d-m, and the radical suppression is performed in the order from the cell 10d-m to the cell 10d-n. The concentration of the agent may be increased stepwise. As described above, when the concentration of the radical suppressing member changes stepwise, the fuel cell can be manufactured using a plurality of cells having the same concentration of the radical suppressing agent, so that the manufacturing cost can be suppressed.

  Further, in the third and fourth modified examples, even when the concentration of the radical inhibitor is lower in the vertically lower portion of the anode-side water-repellent layer of the single cell than in the upper portion of the anode-side water-repellent layer on the vertically upper side. In addition, the concentration of the radical inhibitor may be lower in the vertically lower part of the cathode-side water-repellent layer of the single cell than in the upper part of the vertically upper-side cathode-side water-repellent layer.

Next, regarding the fifth modification in which the decrease in the power generation performance of the fuel cell is suppressed while the decrease in the strength of the electrolyte membrane is suppressed based on the difference in the total surface area of the radical inhibitor instead of the concentration of the radical inhibitor. explain. The fuel cell of the fifth modified example is used in the same manner as the embodiment shown in FIG. 4A. 9A and 9B are explanatory diagrams of the difference in the total surface area of the radical inhibitor per unit volume of the anode-side water-repellent layer 16ae of the fuel cell in the fifth modification. In the fifth modification, the mass of the radical inhibitor contained per unit volume in each of the upper part 161ae and the lower part 162ae is the same. For this reason, the concentration of the radical inhibitor is the same in the upper portion 161ae and the lower portion 162ae. However, the particle size of the radical inhibitor particles is larger in the particles P2 at the lower portion 162ae than the particles P1 at the upper portion 161ae, and the number of radical inhibitor particles in the unit volume is higher at the lower portion 162ae. Less than 161ae. For this reason, the particles of the radical inhibitor are finer in the upper part 161ae than in the lower part 162ae, and the total surface area of the radical inhibitor per unit volume of the anode-side water-repellent layer 16ae is lower in the lower part 162ae than in the upper part 161ae. Is also small. Here, the smaller the particle size, the smaller the surface area exposed to water, so that the amount of Ce ³⁺ dissolved in water per unit volume is smaller than that of the larger particle size. Therefore, when water is distributed to the upper part 161ae and the lower part 162ae under the same conditions, the amount of elution of the radical inhibitor per unit volume of water per unit volume is higher from the lower part 162ae to the upper part 161ae. Less than from. The same applies to the cathode-side water-repellent layer 16c. FIG. 9C is a graph showing the total surface area of the radical inhibitor in the anode-side water-repellent layer 16ae in the fifth modified example. The vertical axis indicates the position of the anode water-repellent layer 16ae in the vertical direction, and the horizontal axis indicates the total surface area of the radical inhibitor. Thereby, also in the fifth modified example, a decrease in the power generation performance of the fuel cell is suppressed while suppressing a decrease in the strength of the electrolyte membrane.

  In the fifth modification, the concentration of the radical inhibitor in the upper portion 161ae and the lower portion 162ae is substantially constant, but is not limited to this. That is, the concentration of the radical inhibitor may be lower in the lower portion 162ae than in the upper portion 161ae.

In addition, the lower 162ae may have a higher concentration of radical inhibitor than the upper 161ae, but in this case, the lower 162ae has a smaller total surface area of the radical inhibitor per unit volume than the upper 161ae, and It suffices if the total surface area difference is more dominant than the Ce ³⁺ elution amount than the concentration difference. That is, also in this case, when water is distributed to the upper part 161ae and the lower part 162ae under the same conditions, the amount of Ce ³⁺ dissolved in water per unit volume per unit time is higher from the lower part 162ae. It may be less than from the upper part 161ae. The same applies to the cathode-side water-repellent layer 16c.

  In the first to fourth modified examples, the total surface area of the radical inhibitor may be different from the concentration of the radical inhibitor, similarly to the fifth modified example. For example, in the first modification, instead of the concentration of the radical inhibitor, when the total surface area of the radical inhibitor is different, the total surface area of the radical inhibitor in the single cell 10a is the sum of the cells 10a. The value divided by the volume is defined as the total surface area of the radical inhibitor per unit volume of the cell 10a. The same applies to the second to fourth modified examples.

Next, instead of the concentration of the radical inhibitor, based on the difference in crystallinity of the radical inhibitor, the sixth modified example in which the decrease in the power generation performance of the fuel cell is suppressed while the decrease in the strength of the electrolyte membrane is suppressed. explain. The fuel cell of the sixth modified example is used in the same manner as the embodiment shown in FIG. 4A. Here, high crystallinity is substantially synonymous with high crystallinity. The crystallinity is the weight ratio of the crystal part to the whole in the polymer compound composed of the crystal part and the non-crystal part. FIG. 10A is a schematic diagram of the crystal structure of CeO ₂ which is a radical inhibitor. FIG. 10B is a conceptual diagram of a radical inhibitor with high crystallinity. FIG. 10C is a conceptual diagram of a radical inhibitor having low crystallinity. When the crystallinity is high, the molecules are arranged in a lattice, whereas when the crystallinity is low, the molecules are randomly arranged. For this reason, the amount of Ce ³⁺ dissolved in water per unit volume per unit time is larger when the crystallinity is lower than when the crystallinity is higher.

  FIG. 10D is a graph showing the crystallinity of the radical inhibitor in the anode-side water-repellent layer in the sixth modified example. The vertical axis represents the position of the anode-side water-repellent layer in the vertical direction, and the horizontal axis represents the crystallinity of the radical inhibitor. Note that, in the anode-side water-repellent layer and the cathode-side water-repellent layer of the fuel cell of the sixth modified example, the concentration and the total surface area of the radical inhibitor described above are constant. As described above, in the anode-side water-repellent layer of the cell of the fuel cell of the sixth modified example, the crystallinity of the radical inhibitor is higher in the lower part on the vertically lower side than in the upper part. For this reason, the elution amount of the radical inhibitor from the upper part of the anode side water-repellent layer is ensured while suppressing the elution amount of the radical inhibitor from the lower part of the anode side water-repellent layer. Thereby, also in the sixth modified example, a decrease in the power generation performance of the fuel cell 1A is suppressed while suppressing a decrease in the strength of the electrolyte membrane. The same applies to the crystallinity of the radical inhibitor in the cathode-side water-repellent layer. In addition, when water is distributed to the upper and lower parts of the anode-side water-repellent layer under the same conditions, the elution amount of the radical inhibitor per unit volume of water per unit volume is from the lower part. There is less than from the top.

  In the sixth modification, the concentration of the radical inhibitor is substantially constant regardless of the portion of the anode-side water-repellent layer, and the total surface area of the radical inhibitor per unit volume of the portion is also substantially constant. It is not limited to this. That is, also in the sixth modification, the concentration of the radical inhibitor may be lower in the lower part of at least one of the anode-side water-repellent layers than in the upper part, and the total surface area of the radical inhibitor per unit volume is smaller. May be. The same applies to the cathode-side water-repellent layer.

Further, in the sixth modification, the concentration of the radical inhibitor may be higher in the lower part of the anode-side water-repellent layer than in the upper part, and the total surface area of the radical inhibitor per unit volume of the anode-side water-repellent layer. However, in this case, the lower part has higher crystallinity than the upper part, and the difference in crystallinity is more dominant than the difference in concentration and total surface area with respect to the Ce ³⁺ elution amount. If it is. That is, also in this case, when water is uniformly distributed at the upper and lower portions, the amount of Ce ³⁺ per unit volume of water dissolved per unit volume is higher from the lower portion. Less than. The same applies to the cathode-side water-repellent layer.

  In the first to fourth modifications, the crystallinity of the radical inhibitor may be different instead of the concentration of the radical inhibitor, as in the sixth modification.

  As mentioned above, in the said Example and 1st-6th modification, the elution amount per unit time of the radical inhibitor to the water per unit volume is suppressed in the site | part with much residual water amount, and there is little residual water amount. By securing the elution amount per unit time of the radical inhibitor into water per unit volume at the site, it is possible to suppress a decrease in power generation performance of the fuel cell while suppressing a decrease in the strength of the electrolyte membrane.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

  The fuel cells of the above-described embodiments and modifications are not limited to those in which scavenging control is executed after power generation is stopped. By executing scavenging control, the amount of remaining water in the fuel cell can be reduced, but even when scavenging control is not performed, there are parts where the amount of residual water in the fuel cell is large and parts that are small after stopping power generation. This is because there is no change. For example, in the above embodiment and the first and second modified examples, a portion having a large amount of residual water is generated due to the action of gravity, and in the third and fourth modified examples, the oxidant gas flowing through the same path as the scavenging gas is generated. This is because a part with a large amount of residual water is generated by circulation.

  In the above-described embodiments and modifications, the radical inhibitor is contained in the anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c, but is not limited thereto, and the anode catalyst layer 14a, the cathode catalyst layer 14c, and the anode side. It may be contained in at least one of the water repellent layer 16a, the cathode side water repellent layer 16c, the anode gas diffusion layer 17a, the cathode gas diffusion layer 17c, the anode side separator 20a, and the cathode side separator 20c.

  Here, the case where the anode-side separator 20a contains a radical inhibitor is a case where a layer containing a radical inhibitor is formed on the surface of the anode-side separator 20a on the surface of the substrate facing the MEGA 30. is there. The layer containing the radical inhibitor can be formed, for example, by coating the surface of the substrate of the anode separator 20a facing the MEGA 30 with a paste containing the radical inhibitor. When coating such a paste on the entire surface of the base of the anode separator 20a facing the MEGA 30, conductive particles such as carbon are added to the paste in order to ensure conductivity between the anode separator 20a and the MEGA 30. Furthermore, it is preferable to contain. Moreover, when the conductive particles are not included in the paste, it is preferable to coat the paste only on the bottom of the anode gas flow path 22a of the anode separator 20a that is not in contact with the MEGA 30. The same applies to the cathode-side separator 20c.

  Moreover, a radical inhibitor will not be specifically limited if it is a metal simple substance and / or the metal compound containing the said metal element. Specific examples of the radical inhibitor other than Ce include Mn, Fe, Pt, Pd, Ni, Cr, Cu, Rb, Co, Ir, Ag, Au, Rh, Ti, Zr, Al, Hf, Ta, Nb, A simple substance composed of Os or the like and / or a compound containing the above element.

10, 10a, 10b, 10c, 10d cell 10a-n, 10b-n, 10c-1, 10d-1 cell (first cell)
10a-1, 10b-1, 10c-n, 10dm cell (second cell)
10d-n cell (third cell)
11 MEA
12 Electrolyte membrane 14a Anode catalyst layer 14c Cathode catalyst layer 16a Anode-side water repellent layer 161a Upper part (first part)
162a Lower part (second part)
16c Cathode side water-repellent layer 18a Anode gas diffusion layer 18c Cathode gas diffusion layer 20a Anode side separator 20c Cathode side separator 20 Fuel cell

Claims (4)

In a fuel cell comprising a cell having a pair of electrodes sandwiching an electrolyte membrane and a pair of separators sandwiching a pair of the electrodes,
At least one of the pair of electrodes and the pair of separators includes a first part containing a radical inhibitor, and a second part containing a radical inhibitor and positioned vertically below the first part. Prepared,
The second part has a lower concentration of radical inhibitor than the first part, a small total surface area of radical inhibitors contained per unit volume, and a high crystallinity of the radical inhibitor. According to at least one of the above, when water is distributed to each of the first and second sites under the same conditions, the elution amount of the radical inhibitor per unit volume of water per unit volume is A fuel cell having less from two parts than from the first part. In a fuel cell in which at least one of a pair of electrodes sandwiching an electrolyte membrane and a pair of separators sandwiching a pair of the electrodes is laminated with a plurality of cells containing radical inhibitors,
A first cell that is one of the plurality of cells;
A second cell that is one of the plurality of cells and is positioned vertically lower than the first cell in the stacking direction of the cells,
In the second cell, the concentration of the radical inhibitor is lower than the first cell, the total surface area of the radical inhibitor contained per unit volume is small, and the crystallinity of the radical inhibitor is high. According to at least one of the above, when water is distributed in the first and second cells under the same conditions, the elution amount of the radical inhibitor per unit volume of water per unit volume is the second amount. A fuel cell having fewer cells than the first cell. In a fuel cell in which at least one of a pair of electrodes sandwiching an electrolyte membrane and a pair of separators sandwiching a pair of the electrodes is laminated with a plurality of cells containing radical inhibitors,
A supply manifold that passes through the plurality of cells and in which a reaction gas flows in a first direction;
A discharge manifold through which the reaction gas flows through the plurality of cells, through the plurality of cells from the supply manifold, and in which the reaction gas flows in a second direction opposite to the first direction;
A first cell that is one of the plurality of cells;
A second cell that is one of the plurality of cells and is located closer to the first direction than the first cell,
In the second cell, the concentration of the radical inhibitor is lower than the first cell, the total surface area of the radical inhibitor contained per unit volume is small, and the crystallinity of the radical inhibitor is high. When water is distributed under the same conditions in the first and second cells by at least one of the following, the elution amount of the radical inhibitor per unit volume of water per unit volume is A fuel cell that has fewer cells than two cells than the first cell. In a fuel cell in which at least one of a pair of electrodes sandwiching an electrolyte membrane and a pair of separators sandwiching a pair of the electrodes is laminated with a plurality of cells containing radical inhibitors,
A supply manifold that passes through the plurality of cells and in which a reaction gas flows in a first direction;
A discharge manifold that passes through the plurality of cells, the reaction gas flows from the supply manifold through the plurality of cells, and the reaction gas flows in the first direction;
A first cell that is one of the plurality of cells and is located closest to the second direction opposite to the first direction;
A second cell that is one of the plurality of cells and is located closer to the first direction than the first cell;
A third cell that is one of the plurality of cells and is located closest to the first direction,
The second cell has a lower concentration of radical inhibitor than each of the first and third cells, the total surface area of the radical inhibitor contained per unit volume, and the crystallinity of the radical inhibitor. Per unit time of radical inhibitor into water per unit volume when water is distributed under the same conditions in the first, second and third cells due to at least one of The amount of elution in the fuel cell is smaller from the second cell than from each of the first and third cells.

Images