JP2005302596A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve efficiency of a fuel cell by raising utilization efficiency of gas which is supplied to an electrode. <P>SOLUTION: The fuel cell 10 is equipped with an electrolyte membrane 12, the electrode having a catalyst layer 14 on its surface contacting with the membrane 12, a separator 18 which is disposed adjacently to the electrode, a first gas conduit 22 disposed in the separator 18 and communicated with only an anode gas supply conduit 20, which supplies the gas to the catalyst layer 14, and a differential pressure generation portion 26 disposed between the first gas conduit 22 and the electrode, which generates differential pressure in such a way that pressure in the first gas conduit 22 becomes higher than that near the electrode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell, and is suitable for application to a fuel cell having a flow path for supplying gas to an electrolyte membrane.

  Since the fuel cell generates electric power by reacting hydrogen supplied to the anode side and oxygen supplied to the cathode side, hydrogen and oxygen flow paths are provided on the anode side and the cathode side, respectively. For example, in Japanese Patent Application Laid-Open No. 11-16591, a gas supply channel and a gas discharge channel disposed discontinuously with the gas supply channel are disposed in a separator, A configuration is disclosed in which a gas supplied to a passage passes through an electrode and is discharged to a gas discharge passage.

JP-A-11-16591 JP 2003-10031 A JP 2002-313367 A JP-A-6-168728

  However, in the technique described in Japanese Patent Application Laid-Open No. 11-16591, the gas supplied to the gas supply channel passes through the electrode while diffusing in all directions. Therefore, the gas whose diffusion direction is not the direction of the catalyst layer is It diffuses in the other direction before the catalyst layer and does not reach the catalyst layer. For this reason, there is a possibility that the utilization efficiency of the gas is lowered and the efficiency of the fuel cell is lowered.

  The present invention has been made in order to solve the above-described problems, and an object thereof is to improve the utilization efficiency of gas supplied to an electrode and improve the efficiency of a fuel cell.

  In order to achieve the above object, a first invention is a fuel cell comprising an electrolyte, an electrode having a catalyst on a contact surface with the electrolyte, and a separator disposed adjacent to the electrode. Disposed in the separator, communicated only with the gas supply channel, and communicated between the first gas channel for supplying gas to the electrode, and between the first gas channel and the electrode. And a differential pressure generating means for generating a differential pressure so that the pressure in the first gas flow path is higher than that in the vicinity of the electrode.

  In a second aspect based on the first aspect, the first gas flow path extends along a surface facing the electrode, and the differential pressure generating means is provided in the first gas flow path. It is characterized by being continuously provided in the gas flow direction.

  According to a third invention, in the first or second invention, the differential pressure generating means is made of a porous material through which gas can permeate.

  The fourth invention is characterized in that, in the third invention, the porous body located on the downstream side in the gas flow direction in the first gas flow path has a higher gas permeability.

  According to a fifth invention, in any one of the first to fourth inventions, the second gas flow path is disposed in the separator, communicates only with the gas discharge flow path, and discharges the gas supplied to the electrode. It is provided with.

  A sixth invention is characterized in that, in any one of the first to fifth inventions, an operation mode for stopping a flow of gas discharged from the gas discharge flow path is provided.

  According to the first invention, since the differential pressure is generated so that the pressure in the first gas flow path is higher than that in the vicinity of the electrode, it is possible to prevent the gas from diffusing before the electrode. It is possible to reliably reach the electrode. Accordingly, it becomes possible to supply more gas to the electrode, and it is possible to suppress a decrease in gas utilization efficiency.

  According to the second invention, since the differential pressure generating means is continuously provided in the gas flow direction, the planar space of the differential pressure generating means can be widened, and more gas can reach the electrodes. it can.

  According to the third invention, since the differential pressure generating means is composed of a porous body through which gas can permeate, the differential pressure can be generated so that the pressure in the first gas flow path is higher than that in the vicinity of the electrode. It becomes possible.

  According to the fourth invention, in the gas flow direction in the first gas flow path, the porous body located on the downstream side has higher gas permeability, so the influence of the pressure loss in the first gas flow path. The pressure can be made uniform on the upstream side and the downstream side of the first gas flow path. Thereby, it becomes possible to supply gas uniformly with respect to an electrode.

  According to the fifth aspect, since the second gas flow path for discharging the gas supplied to the electrode is provided, the gas supplied to the electrode can be discharged from the second gas flow path. In addition, since the second gas flow communicates only with the gas discharge flow channel and does not communicate with the gas supply flow channel, the gas flowing through the gas supply flow channel reaches the electrode and then passes through the second gas flow channel. Will be discharged. Accordingly, the gas supplied to the gas supply channel can be reliably supplied to the electrode.

  According to the sixth aspect of the invention, since the operation mode for stopping the flow of the gas discharged from the gas discharge passage is provided, the gas supplied to the fuel cell can be kept inside the fuel cell, and the reaction in the fuel cell can be performed. Can be promoted.

  An embodiment of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

  FIG. 1 is a schematic diagram showing a configuration of a fuel cell 10 according to a first embodiment of the present invention and its periphery. The fuel cell 10 is, for example, a fuel cell (PEMFC) provided with a solid polymer separation membrane, and is configured by stacking a plurality of unit cells. Each unit cell includes an electrolyte membrane (separation membrane), an anode electrode, a cathode electrode, and a separator.

An anode gas containing hydrogen is sent to the anode electrode of the fuel cell 10, and an oxidizing gas containing oxygen is sent to the cathode electrode. In the anode electrode, when the anode gas is sent, hydrogen ions are generated from hydrogen in the anode gas (H ₂ → 2H ⁺ + 2e ⁻ ), and when the cathode gas is sent in, the cathode electrode is oxygen in the cathode gas. Oxygen ions are generated from the fuel and electric power is generated in the fuel cell 10. At the same time, water is generated from the hydrogen ions and oxygen ions at the cathode electrode ((1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O). Most of this water absorbs the heat generated in the fuel cell 10 and is generated as water vapor.

  As shown in FIG. 1, a control valve 11 is provided in the flow path of the anode off gas discharged from the anode side. The fuel cell 10 of the present embodiment performs an operation (dead end operation) in which the flow of the anode off gas is appropriately stopped by the control valve 11 in order to increase the utilization efficiency of hydrogen in the anode gas. As a result, the amount of hydrogen in the anode gas discharged outside the fuel cell 10 can be reduced, and the proportion of hydrogen in the anode gas used for the reaction can be further increased.

  FIG. 2 is a schematic diagram showing a state in which the unit cell is viewed from the anode side in the stacking direction, and shows the configuration of the separator 18 arranged mainly on the anode side. FIG. 3 is a schematic diagram showing a cross section taken along the alternate long and short dash line I-I ′ of FIG. 2, and mainly shows a cross section on the anode side of the electrolyte membrane 12. As shown in FIG. 3, the anode electrode of the fuel cell 10 has a catalyst layer 14 and a diffusion layer 16 laminated on the electrolyte membrane 12, and a separator 18 is laminated on the diffusion layer 16. The electrolyte membrane 12 is a proton conductive ion exchange membrane formed of a solid polymer material such as a fluorine-based resin. The catalyst layer 14 is configured by, for example, applying a carbon paste carrying platinum (Pt) to the surface of the electrolyte membrane 12. The diffusion layer 16 is made of carbon cloth or the like woven from carbon fibers. The separator 18 is formed of a gas-impermeable conductive member such as dense carbon which is compressed by carbon and impermeable to gas.

  As shown in FIG. 2, an anode gas supply channel 20 for supplying an anode gas is provided at the end of the planar region of the unit cell. A plurality of flow paths 22 are connected to the anode gas supply flow path 20, and the anode gas supplied to the anode gas supply flow path 20 is sent through the flow path 22 to almost the entire planar area of the unit cell. .

  As shown in FIG. 3, the flow path 22 is provided at a position away from the diffusion layer 16 in the stacking direction of the unit cells. A flow path 24 is provided between the adjacent flow paths 22 on the surface of the separator 18 facing the diffusion layer 16.

  As shown in FIG. 2, the flow path 24 is connected to the anode gas discharge flow path 25. The anode gas supplied from the flow path 22 is sent to the diffusion layer 16 and the catalyst layer 14, and then sent to the anode gas discharge flow path 25 via the flow path 24 and discharged.

  As shown in FIG. 2, the end of the flow path 22 and the anode gas discharge flow path 25 are not connected, and the end of the flow path 24 and the anode gas supply flow path 20 are not connected. Accordingly, the anode gas sent to the flow path 22 is always sent to the diffusion layer 16 and the catalyst layer 14 on the anode side, and then discharged from the anode gas discharge flow path 25 via the flow path 24. Therefore, the anode gas can be prevented from being discharged without being supplied to the electrode, and the reaction can be promoted.

  As shown in FIG. 3, a groove-shaped differential pressure generator 26 is provided between the flow path 22 and the diffusion layer 16. As shown in FIG. 2, the differential pressure generating section 26 is provided along the flow path 22 with a narrower width than the flow path 22. The anode gas supplied to the flow path 22 is sent to the diffusion layer 16 and the catalyst layer 14 through the differential pressure generator 26.

  Since the differential pressure generating section 26 is formed to be narrower than the flow path 22, a differential pressure is generated between the gas flowing through the flow path 22 and the gas flowing through the differential pressure generating section 26, and the gas on the flow path 22 side. Is higher than that on the diffusion layer 16 side.

  Accordingly, the gas flowing through the flow path 22 flows toward the catalyst layer 14 of the anode electrode due to the pressure difference, and the gas flow toward the anode electrode can be forcibly generated. Thereby, the anode gas can flow in a direction perpendicular to the surfaces of the diffusion layer 16 and the catalyst layer 14, and the anode gas can be prevented from diffusing in the other direction in the diffusion layer 16. . Therefore, the anode gas can surely reach the catalyst layer 14, and the activation of the reaction can be enhanced by the gas stirring effect in the catalyst layer 14. Thereby, the utilization efficiency of anode gas can be improved and the efficiency of the fuel cell 10 can be significantly improved.

  In particular, in the fuel cell 10 in which the dead end operation is performed on the anode side, it is necessary to appropriately open the control valve 11 to generate a flow of anode gas in the fuel cell 10. Since the flow of the anode gas toward the catalyst layer 14 can be reliably generated by the generator 26, the time for opening the control valve 11 can be further shortened. Therefore, discharge of unreacted hydrogen from the fuel cell 10 can be suppressed, and most of the anode gas supplied from the anode gas supply channel 20 can be used for the reaction in the fuel cell 10.

  In addition, on the cathode side of the fuel cell 10, moisture is generated by the reaction as described above. A part of this moisture permeates to the anode side together with nitrogen contained in the cathode gas and is absorbed by the catalyst layer 14 on the anode side. May be. In particular, when dead-end operation is performed on the anode side, the flow of anode gas is small, so that the catalyst layer 14 is likely to contain moisture and nitrogen. If the catalyst layer 14 contains moisture and nitrogen, the power generation reaction is hindered. There is a case. However, according to the present embodiment, since the flow of the anode gas from the flow path 22 toward the catalyst layer 14 can be forcibly created, the moisture contained in the catalyst layer 14 by the anode gas flowing into the catalyst layer 14, Nitrogen can be pushed out and eliminated.

  Therefore, moisture and nitrogen are not contained in the catalyst layer 14 and the reaction is not suppressed, and the efficiency of the fuel cell 10 can be increased. The moisture and nitrogen removed from the catalyst layer 14 flow from the flow path 24 to the anode gas discharge flow path 25, but a large amount of impurities such as moisture and nitrogen accumulated in the flow path 24 or the anode gas discharge flow path 25. In such a case, the control valve 11 is opened to discharge these impurities to the outside.

  Further, in the fuel cell 10 of the present embodiment, as shown in FIG. 3, the flow path 22 and the diffusion layer 16 are separated from each other in the stacking direction of the unit cells. Therefore, the flow path 22 and the flow path 24 can be brought closer to each other as compared with the case where the flow path 22 and the flow path 24 are provided at the same layer position. Therefore, the planar space in which the flow path 22 and the flow path 24 are arranged can be reduced, and the fuel cell 10 can be downsized.

  FIG. 4 is a schematic diagram showing another example of the present embodiment, and shows a state in which the unit cell is viewed from the stacking direction as in FIG. In the example of FIG. 4, the differential pressure generating unit 26 is divided and provided in the flow path 22. As described above, the differential pressure generating unit 26 may be provided only in a partial region in the flow path 22. Various shapes can be adopted as the shape of the differential pressure generating portion 26 as long as the pressure of the gas flowing through the flow path 22 can be increased by generating a differential pressure.

  FIG. 5 shows an example in which a differential pressure generator is provided also on the cathode gas supply side. In FIG. 5, the cathode gas is supplied from the flow path 28 to the diffusion layer 16 and the catalyst layer 14 on the cathode side through the differential pressure generating unit 30. The cathode gas supplied to the diffusion layer 16 and the catalyst layer 14 is discharged from the flow path 32. As described above, by providing the differential pressure generating section 30 also on the cathode side, the cathode gas can surely reach the catalyst layer 14 similarly to the anode side, and the utilization efficiency of the cathode gas can be improved. Become.

  As described above, according to the first embodiment, the flow path 22 for supplying the anode gas and the anode electrode (diffusion layer 16, catalyst layer 14) are separated from each other, and a differential pressure generating section is provided between the flow path 22 and the anode electrode. 26 is provided, the anode gas can be reliably sent from the flow path 22 toward the diffusion layer 16 and the catalyst layer 14. As a result, the anode gas can be prevented from diffusing in the other direction in the diffusion layer 16, and the anode gas can surely reach the catalyst layer 14. Accordingly, the utilization efficiency of the anode gas can be increased, and the efficiency of the fuel cell 10 can be improved.

  In addition, since the anode gas can be reliably sent to the catalyst layer 14, moisture and nitrogen that permeate from the cathode side to the anode side and are contained in the catalyst layer 14 on the anode side can be removed by the anode gas. Become. Accordingly, it is possible to eliminate the power generation inhibiting factor due to the moisture and nitrogen contained in the catalyst layer 14, promote the reaction in the fuel cell 10, and increase the efficiency of the fuel cell 10.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. 6 and 7 are schematic diagrams showing the configuration of the second embodiment. FIG. 6 is a schematic diagram showing a planar configuration of a unit cell of the fuel cell 10 according to Embodiment 2, and shows a state in which the unit cell is viewed from the anode side in the stacking direction. FIG. 7 is a cross-sectional view showing a cross section taken along the alternate long and short dash line II ′ of FIG. 6, and mainly shows a cross section on the anode side of the electrolyte membrane 12.

  In the second embodiment, the porous portion 34 is disposed between the flow path 22 and the diffusion layer 16. The porous portion 34 is configured by, for example, embedding a porous material (porous material) in the differential pressure generating portion 26 of FIG. 2, and has a narrower width than the flow channel 22 along the flow channel 22 as shown in FIG. Is provided. The anode gas supplied to the flow path 22 is sent to the diffusion layer 16 and the catalyst layer 14 through fine holes in the porous portion 34.

  Thus, by forming the porous portion 34 made of a porous material, a differential pressure is generated between the gas flowing in the flow path 22 and the gas flowing in the porous portion 34, and the pressure of the gas on the flow path 22 side. Becomes higher than the diffusion layer 16 side.

  Accordingly, the gas flowing through the flow path 22 flows toward the catalyst layer 14 of the anode electrode due to the pressure difference, and the gas flow toward the anode electrode can be forcibly generated. Thereby, the anode gas can flow in a direction perpendicular to the surfaces of the diffusion layer 16 and the catalyst layer 14, and the anode gas can be prevented from diffusing in the other direction in the diffusion layer 16. . Therefore, the anode gas can surely reach the catalyst layer 14 and the utilization efficiency of the anode gas can be improved.

  Further, by providing the porous portion 34, the strength of the separator 18 can be increased even when the differential pressure generating portion 26 is formed in a groove shape as shown in FIG.

  When the separator 18 is made of carbon, the porous portion 34 is also preferably made of porous carbon. In this case, the porous portion 34 can be disposed by embedding porous carbon in the differential pressure generating portion 26 of FIG. Even when the separator 18 is made of metal, the porous portion 34 can be disposed by combining a porous material with the metal separator.

  As described above, according to the second embodiment, since the porous portion 34 is provided between the flow path 22 and the anode electrode, the anode gas is reliably supplied from the flow path 22 toward the diffusion layer 16 and the catalyst layer 14. It becomes possible to send. As a result, the anode gas can be prevented from diffusing in the other direction in the diffusion layer 16, and the anode gas can surely reach the catalyst layer 14. Accordingly, the utilization efficiency of the anode gas can be increased, and the efficiency of the fuel cell 10 can be improved.

  In addition, since the anode gas can be reliably sent to the catalyst layer 14, moisture and nitrogen that permeate from the cathode side to the anode side and are contained in the catalyst layer 14 on the anode side can be removed by the anode gas. Become. Accordingly, it is possible to eliminate the power generation inhibiting factor due to the moisture and nitrogen contained in the catalyst layer 14, promote the reaction in the fuel cell 10, and increase the efficiency of the fuel cell 10.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described. FIG. 8 is a schematic diagram showing the configuration of the third embodiment. In the third embodiment, as in the second embodiment, the differential pressure is generated by providing the porous portion 34 between the flow path 22 and the diffusion layer 16. FIG. 8 shows a state in which the unit cell is viewed from the anode side in the stacking direction as in FIG. 6, and only the anode gas supply channel 20, the channel 22, and the porous portion 34 are shown for convenience of explanation. Yes.

  As described in the first embodiment, the anode gas is supplied to the diffusion layer 16 and the catalyst layer 14 through the flow path 22. At this time, since a pressure loss occurs while passing through the flow path 22, the pressure of the anode gas in the flow path 22 decreases as the distance from the anode gas supply flow path 20 increases. Therefore, the pressure of the anode gas sent to the diffusion layer 16 and the catalyst layer 14 becomes lower as the position is farther from the anode gas supply channel 20.

  In Embodiment 3, the distribution (density) of micropores in the porous portion 34 is varied in the longitudinal direction of the flow path 22, and the gas permeability in the porous section 34 increases as the distance from the anode gas supply flow path 20 increases. doing. As a result, the porous portion 34 located on the downstream side of the flow path 22 is more likely to escape the gas, and the anode gas is reliably supplied to the diffusion layer 16 and the catalyst layer 14 even at a position away from the anode gas supply flow path 20. It becomes possible to do. Therefore, the anode gas can be uniformly supplied to the diffusion layer 16 and the catalyst layer 14 in the entire region in the extending direction of the flow path 22.

  In addition, in order to vary the gas permeability of the porous portion 34 in the longitudinal direction of the flow path 22, the diameter distribution of the micropores of the porous portion 34, the degree of bending of the micropores, etc. may be varied. Further, the width of the porous portion 34 may be varied along the longitudinal direction of the flow path 22.

  As described above, according to the third embodiment, the gas permeability in the porous portion 34 is increased as the distance from the anode gas supply flow path 20 increases, so that the influence of the pressure loss in the flow path 22 can be eliminated. Therefore, the anode gas can be uniformly supplied to the anode electrode in the entire longitudinal direction of the flow path 22. Thereby, the reaction at the anode electrode can be performed uniformly, and the efficiency of the fuel cell 10 can be increased.

It is a schematic diagram which shows the structure of the fuel cell concerning Embodiment 1 of this invention, and its periphery. It is a schematic diagram which shows the structure of the fuel cell concerning Embodiment 1 of this invention. FIG. 3 is a schematic diagram illustrating a cross section taken along the alternate long and short dash line I-I ′ of FIG. 2. FIG. 6 is a schematic diagram showing another example of the first embodiment. It is a schematic diagram which shows the example which provided the differential pressure generation part also in the cathode side. It is a schematic diagram which shows the structure of the fuel cell concerning Embodiment 2 of this invention. It is a schematic diagram which shows the cross section along the dashed-dotted line I-I 'of FIG. It is a schematic diagram which shows the structure of Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 12 Electrolyte membrane 14 Catalyst layer 16 Diffusion layer 18 Separator 20 Anode gas supply flow path 22 Flow path 24 Flow path 25 Anode gas discharge flow path 26 Differential pressure generation part 34 Porous part

Claims (6)

A fuel cell comprising an electrolyte, an electrode having a catalyst on a contact surface with the electrolyte, and a separator disposed adjacent to the electrode,
A first gas channel disposed in the separator, communicating only with a gas supply channel, and supplying gas to the electrode;
A differential pressure generating means that is disposed in communication between the first gas flow path and the electrode and generates a differential pressure so that the pressure of the first gas flow path is higher than the vicinity of the electrode. When,
A fuel cell comprising:   The first gas flow path extends along a surface facing the electrode, and the differential pressure generating means is continuously provided in the gas flow direction in the first gas flow path. The fuel cell according to claim 1.   3. The fuel cell according to claim 1, wherein the differential pressure generating means is made of a porous material that allows gas to pass therethrough.   4. The fuel cell according to claim 3, wherein in the gas flow direction in the first gas flow path, the gas permeability is higher in the porous body located downstream. 5.   The second gas flow path disposed in the separator, communicating only with the gas discharge flow path and discharging the gas supplied to the electrode, is provided. Fuel cell.   6. The fuel cell according to claim 1, further comprising an operation mode for stopping a flow of gas discharged from the gas discharge passage.

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