JP2009099362A - Catalyst carrying electrode and unit cell of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst carrying electrode having a high gas diffusion property. <P>SOLUTION: Catalyst carrying electrodes 10, 11 each includes: a metal sheet 20 having many holes 22; a porous carrier 15 supported with the metal sheet; and a particulate catalyst 12 carried with the porous carrier. The porous carrier is arranged at least inside a hole 22 of the metal sheet. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a catalyst-carrying electrode for a fuel cell, and more particularly to a catalyst-carrying electrode having an excellent gas diffusion function.

  The present invention also relates to a fuel cell having a catalyst-carrying electrode, and more particularly to a fuel cell having a catalyst-carrying electrode having an excellent gas diffusion function.

  Today, fuel cells that generate electricity and water by reacting hydrogen as fuel with oxygen are attracting attention as power generators that can replace existing power generation systems. 2. Description of the Related Art A fuel cell usually includes a number of fuel cells each having a membrane electrode assembly (MEA) that reacts supplied hydrogen and oxygen and separators disposed on both sides of the membrane electrode assembly. It is out.

  As disclosed in Document 1, there is a gas flow path between the membrane electrode assembly and each separator for flowing hydrogen gas as fuel, oxygen gas that reacts with hydrogen gas, air, or the like. Is formed. The membrane electrode assembly includes an electrolyte membrane, a pair of catalyst layers (electrodes) disposed on both sides of the electrolyte membrane, and a pair of gas diffusion layers respectively disposed between the catalyst layers and the separators. ,have.

For example, as described on page 45 of Document 2, the catalyst layer is a layer supporting an electrode catalyst for reacting the gas supplied from the gas flow path, and generally has a thickness of several tens of μm. It has a thickness. On the other hand, the gas diffusion layer is a layer having a thickness of about 100 μm to 300 μm made of carbon fibers having a diameter of about 5 μm, as described on page 46 of Document 2. This gas diffusion layer is a layer for diffusing gas from the gas flow path and supplying gas to the catalyst layer, and has pores with a pore diameter of about several tens to several hundreds of μm, for example. If the gas from the gas flow path can be sufficiently diffused over the entire surface of the catalyst layer, the fuel cell can be operated with excellent efficiency by effectively using an expensive electrode catalyst.
JP 2007-12325 A “All of illustrated fuel cells” (supervised by Mr. Shinya Honma, published by Kogyo Kenkyukai)

  In literature 1, it is proposed to improve the gas diffusivity while maintaining durability by improving the electrode material, and to effectively use the electrode catalyst. However, today, the demand for operating efficiency of fuel cells is further increased.

  That is, an object of the present invention is to provide a catalyst-carrying electrode (catalyst layer) having excellent gas diffusibility. Another object of the present invention is to provide a fuel cell having a catalyst-carrying electrode (catalyst layer) having excellent gas diffusibility.

  By the way, the fuel cell is configured by stacking several tens to several hundreds of fuel cells, for example, and has a desired electromotive force. In such a fuel cell, it is an important subject today to achieve a reduction in the thickness of the fuel cell and a reduction in the size of the fuel cell. Therefore, it is very convenient if the catalyst-carrying electrode according to the present invention has an excellent gas diffusion function, and thereby the thickness of the fuel cell can be reduced by omitting the conventional gas diffusion layer.

  The catalyst-supporting electrode according to the present invention includes a metal sheet having a large number of pores, a porous carrier supported by the metal sheet, at least a porous carrier disposed in the pores, and the porous carrier. And a particulate electrode catalyst supported on the substrate.

  In the catalyst-carrying electrode according to the present invention, the cross-sectional area of the hole along the sheet surface of the metal sheet may gradually decrease from one surface of the metal sheet to the other surface.

  In the catalyst-carrying electrode according to the present invention, the metal sheet may have an open area ratio of 40% or more, and an average hole diameter of the holes of the metal sheet may be 60 μm or less.

  Furthermore, in the catalyst-carrying electrode according to the present invention, the porous carrier may include a plurality of carrier particles bonded to each other, and the particulate electrode catalyst may be carried on the carrier particles. In such a catalyst-carrying electrode according to the present invention, the carrier particles may include at least one of carbon particles, carbon fibers, carbon nanohorns, and carbon nanotubes.

  Furthermore, in the catalyst-carrying electrode according to the present invention, the porous carrier may be disposed on at least one surface of the metal sheet. In such a catalyst-carrying electrode according to the present invention, the particulate electrode catalyst may be made of platinum or a platinum alloy.

  A fuel cell according to the present invention includes the catalyst-supporting electrode described in any one of the above.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell provided with the catalyst carrying electrode which has the outstanding gas diffusion function, and the catalyst carrying electrode which has the outstanding gas diffusion function is obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 to FIG. 11 are diagrams for explaining an embodiment of a catalyst-carrying electrode and a fuel cell according to the present invention. 1 is a cross-sectional view of a catalyst-carrying electrode, FIG. 2 is an exploded perspective view showing a fuel cell in which the catalyst-carrying electrode is incorporated, and FIG. 3 is a perspective view showing a fuel cell composed of a large number of fuel cells. FIG. The cross section shown in FIG. 1 corresponds to the cross section taken along the line II in FIG.

  As shown in FIG. 2, the fuel cell 50 has a membrane electrode assembly (MEA) 35 and a pair of separators 40 and 41 disposed on both sides of the membrane electrode assembly 35. The membrane electrode assembly 35 includes an electrolyte membrane 30 and a pair of catalyst-carrying electrodes 10 and 11 disposed on both sides of the electrolyte membrane 30. As shown in FIG. 3, the fuel cells 50 are stacked to form a fuel cell 55 (stack 55a) having a desired electromotive force. Hereinafter, each structure of the fuel cell 50 will be described.

  First, the separators 40 and 41 will be described. As shown in FIG. 2, the separators 40 and 41 are formed in a rectangular quadrangular plate shape. In the separators 40 and 41, one through hole 42 is formed in the vicinity of each of the four corners. Further, as shown in FIG. 2, serpentine-shaped grooves 43 are formed on the surfaces of the separators 40 and 41 facing the membrane electrode assembly 35 on the side facing the membrane electrode assembly 35. . Both ends of the groove 43 communicate with one through hole 42. The groove 43 forms a gas flow path provided between the membrane electrode assembly 35 and the separators 40 and 41. A gas supplied to the catalyst-carrying electrodes 10 and 11 of the membrane electrode assembly 35 flows through the gas flow path 43.

  Such separators 40 and 41 may be made of carbon resin, which is a mixture of carbon and resin, or metal such as stainless steel, aluminum or copper. However, when the separators 40 and 41 are formed from metal, it is preferable that the surfaces of the separators 40 and 41 are plated with gold for the purpose of improving the corrosion resistance.

Next, the membrane electrode assembly 35 will be described. As described above, the membrane / electrode assembly 35 includes the electrolyte membrane 30 and the pair of catalyst-supporting electrodes 10 and 11 disposed on both sides of the electrolyte membrane 30. The electrolyte membrane 30 may be composed of a membrane that is permeable to proton H ⁺ , such as a perfluorosulfonic acid ion exchange membrane.

  Next, the catalyst carrying electrodes 10 and 11 will be described in detail. The catalyst-carrying electrode includes a hydrogen electrode (fuel electrode) 10 disposed on one side (right side in FIG. 2) of the electrolyte membrane 30, and an oxygen electrode (air electrode) 11 disposed on the other side of the electrolyte membrane 30. , Including. The two catalyst-carrying electrodes 10 and 11 have substantially the same configuration. The description of the catalyst-carrying electrode in the following description is for both the catalyst-carrying electrodes 10 and 11 unless otherwise specified.

  As shown in FIG. 1, the catalyst-carrying electrodes 10 and 11 include a metal sheet 20 having a large number of holes 22 formed at a predetermined pitch, a porous carrier 15 supported by the metal sheet 20, and a porous carrier 15. And a particulate electrode catalyst 12 supported thereon. First, the metal sheet 20 will be described in detail mainly with reference to FIGS. 4 to 8. 4 is a partial plan view showing the metal sheet 20, and FIG. 5 is a cross-sectional view taken along the line V-V in FIG. In addition, the term “particle” as used herein is a concept including minute pieces having various shapes such as a spherical shape, a polygonal shape, and a fibrous shape.

  The metal sheet 20 is a metal sheet in which a large number of holes 22 are formed. The metal sheet 20 can be formed from, for example, stainless steel, aluminum, copper, or the like. However, like the separators 10 and 11 described above, the surface of the metal sheet is preferably gold-plated for the purpose of improving the corrosion resistance. By the way, when the catalyst-carrying electrodes 10 and 11 are incorporated in the fuel cell 50, it is preferable that the metal sheet 20 is thin as long as strength (durability) during use can be ensured. This is because the fuel cell 50 can be downsized and the electromotive force per unit volume of the fuel cell 50 can be increased. From this, the thickness of the metal sheet 20 can be, for example, 20 μm or more and 100 μm or less, and more preferably 20 μm or more and 50 μm or less.

  As shown in FIG. 4, in the present embodiment, each hole 22 has a substantially circular outline in a plan view of the metal sheet 20 (when viewed from a direction orthogonal to the sheet surface of the metal sheet 20). is doing. The many holes 22 are formed in substantially the same shape (± 5 μm or less).

  As shown in FIG. 4, in the present embodiment, the holes 22 of the metal sheet 20 are arranged such that the arrangement center is separated by an equal distance P from the arrangement center of adjacent holes 22 arranged around the hole. Has been. For this reason, if the diameters of the holes 22 are the same, the spacing between adjacent holes 22 (corresponding to W1 and W2 in FIG. 5) is also the same. Further, as shown in FIG. 5, the hole diameter (inner diameter) of the hole 22 in the plane parallel to the sheet surface is the largest on one surface 20a of the metal sheet 20 and the smallest on the other surface 20b. More strictly, the hole diameter (inner diameter) of the hole 22 in a plane parallel to the sheet surface of the metal sheet 20 gradually decreases from one surface 20a to the other surface 20b. In other words, the cross-sectional area of the hole 22 along the sheet surface of the metal sheet 20 is gradually decreasing from one surface 20a of the metal sheet 20 to the other surface 20b.

  Next, an example of a method for manufacturing such a metal sheet 20 will be described mainly with reference to FIGS. Among these, FIG. 6 is a figure for demonstrating the manufacturing method of a metal sheet.

  The metal sheet manufacturing method illustrated in FIG. 6 includes a metal film (metal sheet) 64 that forms the metal sheet 20 and a resin film (resin sheet) 62 laminated on the metal film 64. A step of supplying a laminated body 60 including: a step of performing etching using a photolithography technique on the metal film 64 of the laminated body 60 to form a large number of holes 22 in the metal film 64; The process of removing the resin-made film 62 from the laminated body 60 later is included.

  In the example illustrated in FIG. 6, a laminated body 59 obtained by winding the laminated body 60 around a supply core 61 is prepared. Then, when the supply core 61 rotates and the wound body 59 is rewound, the laminated body 60 extending in a strip shape is supplied as shown in FIG. Here, the laminated body 60 is supplied so that the metal film 64 is located below and the resin film 62 is located above.

  In addition, the metal film 64 of the laminated body 60 is formed with the holes 22 as described below to form the metal sheet 20. Therefore, as described above, the metal film 64 is made of, for example, stainless steel, aluminum, or copper.

  On the other hand, as the resin film 62, for example, a sheet made of polyethylene terephthalate or polypropylene having a thickness of about 50 μm to 150 μm can be used. In the present embodiment, a resin film 62 is used in which the bonding force to the metal film 64 is reduced when irradiated with UV light. Specifically, the resin film 62 is a base film (base sheet) 62a made of polyethylene terephthalate, and a UV layer 62b that is a layer laminated on the base film 62a and faces the metal film 64. (See FIGS. 6 and 7). The UV release layer 62b is a resin layer that is configured such that the bonding strength to the metal film 64 is reduced when irradiated with UV light.

  The supplied laminated body 60 is subjected to an etching process by an etching apparatus (etching means) 70. Specifically, first, a photosensitive resist material is applied on the surface of the metal film 64 of the laminate 60, and a resist film is formed on the metal film 64. Next, a glass dry plate in which light is transmitted only to a region to be removed of the resist film or light is not transmitted is prepared, and the glass dry plate is disposed on the resist film. Thereafter, the resist film is exposed through a glass dry plate, and the resist film is further developed. As described above, a resist pattern 66 (see FIG. 7) is formed on the metal film 64 of the laminate 60.

  Next, as shown in FIG. 7, the laminate 60 is etched with an etching solution (for example, ferric chloride solution) 68 using the resist pattern 66 formed on the metal film 64 as a mask. In the present embodiment, the etching solution 68 is passed through the resist pattern 66 from the nozzle 71 of the etching apparatus 70 disposed so as to be positioned below the transported laminate 60, and the one surface 64 a of the metal film 64. It is injected toward At this time, as shown by a dotted line in FIG. 7, erosion by the etching solution starts in a region of the metal film 64 that is not covered with the resist pattern 66. Thereafter, erosion proceeds not only in the thickness direction of the metal film 64 but also in the direction along the film surface (sheet surface) of the metal film 64. As described above, erosion by the etching solution proceeds from one surface 64a of the metal film 64 to the other surface 64b, and the hole 22 penetrating the metal film 64 is formed.

  Thereafter, the resist pattern 66 on the stacked body 60 is removed, and the stacked body 60 is further washed with water. The stacked body 60 in which the holes 22 are thus formed by etching is then conveyed into a removing device (removing means) 74.

  As shown in FIG. 8, the removal device 74 in the present embodiment has UV light irradiation means 75 arranged along the transport path of the stacked body 60. The UV light irradiation means 75 is provided along the movement path of the laminate 60, and includes a shade 75a that covers the laminate 60 from the resin film 62 side, and a UV light source 75b disposed in the shade 75a. Yes. And the laminated body 60 conveyed is irradiated with UV light from the resin film 62 side, and the base film 62a and the metal sheet 20 (metal film) are transmitted by the UV light transmitted through the base film 62a of the resin film 62. 64) is strongly weakened. As a result, the resin film 62 and the metal film 64 (metal sheet 20) forming the laminate 60 can be separated, and the resin film 62 is peeled off from the metal film 64 as shown in FIG. It is wound around the take-up core 58.

  In this way, a metal film 64 in which a large number of holes 22 are formed is obtained, and as shown in FIG. 6, by cutting into a predetermined length using a cutting device (cutting means) 79, A sheet-like metal sheet 20 is obtained.

  By the way, unlike the example of such a manufacturing method, if the resin film 62 is not provided, the metal film 64 is penetrated and the hole 22 is formed, and at the same time, the metal film is passed through the hole 22. The etching solution 68 starts to flow from the one surface 64a side of 64 toward the other surface 64b side. In such a method, finally, the fresh etching solution 68 erodes the hole 22 from the inside, the etching solution starts to flow, a large pressure is applied to the hole 22, and the etching solution By staying on the other surface 64b of the metal film 64, the diameter of the hole 22 is rapidly increased in the final stage of the etching process. In particular, on the other surface side, the wall surface forming the hole 22 is displaced, and the hole diameter of the hole 22 is locally increased. For this reason, it becomes very difficult to control the shape and size of the hole 22 to a desired shape and size. Further, the cross-sectional area of the hole 22 is not the smallest on the other surface 64b of the metal film 64, but at a position in the thickness direction between the one surface 64a and the other surface 64b of the metal film 64. The smallest.

  In addition, when the metal film 64 is etched, the metal film 64 is conveyed so as to move intermittently. If the resin film 62 is not provided unlike the above-described example, intermittent tension generated with intermittent conveyance is applied only to the metal film 64. The intermittent tension may cause the metal film 64 to be cut between the holes 22.

  From these facts, according to the conventional metal sheet manufacturing method using etching (a manufacturing method not using the resin film 62), small holes cannot be formed with a high hole area ratio, and the average hole diameter of the holes And the hole area ratio of the metal sheet 20 was reduced. On the other hand, according to the above-described metal sheet manufacturing method (manufacturing method using the resin film 62), the conventional defects can be solved and the fine holes 22 can be formed in the metal film 64 with a high aperture ratio. it can.

  In addition, with the hole area ratio here, each hole 22 which exists in the said arbitrary area | region with respect to the surface area in the case where the hole 22 about the arbitrary area | regions of the metal sheet 20 was not formed is the metal sheet 20's. It means the ratio of the sum of the minimum areas that occupy the surface along the sheet surface. Therefore, in the illustrated example, the ratio of the surface area of the region occupied by the holes 22 in the other surface 20b of the metal sheet 20 to the surface area when no hole is formed in any region of the metal sheet 20 However, the hole area ratio of the metal sheet 20 is obtained. Moreover, the average hole diameter here means the average value of the minimum hole diameters of the holes 22 in the surface along the sheet surface of the metal sheet 20. Therefore, the hole area ratio of the metal sheet 20 shown in FIG. 5 is the other surface 20b of the metal sheet 20 with respect to the surface area when the hole 22 is not formed in an arbitrary region of the illustrated metal sheet 20. The ratio of the area occupied by the holes 22 in FIG. Further, the average hole diameter of the metal sheet 20 shown in FIG. 5 is an average value of the diameters of the holes 22 in the other surface 20 b of the metal sheet 20.

Here, Tables 1 to 3 and FIGS. 9 to 11 show the dimension measurement results of the metal sheet 20 manufactured by the above-described method and the hole area ratio calculated from the measured dimensions. In addition, heat resistant SUS was adopted as the metal film. Table 1 and FIG. 9 show the results when the thickness of the metal film is 20 μm, Tables 2 and 10 show the results when the thickness of the metal film is 25 μm, and Table 3 and FIG. 11 shows the result when the thickness of the metal film was 30 μm. Moreover, in FIG. 9, the range of the metal sheet which can be manufactured with the conventional manufacturing method which does not use the resin film 62 is shown with the oblique line.

  The symbols in Tables 1 to 3 correspond to the symbols in FIGS. 4 and 5. 4 and 5, P is the arrangement pitch of the holes 22, D1 is the average hole diameter of the holes 22 in one surface 20a of the metal sheet 20, and D2 is in the other surface 20b of the metal sheet 20. The average hole diameter of the holes 22, W 1 is the average distance between two adjacent holes 22 on one surface 20 a of the metal sheet 20, and W 2 is the two adjacent holes 22 on the other surface 20 b of the metal sheet 20. The average separation distance.

  From these results, when the thickness of the metal sheet is 20 μm or more and 30 μm or less, at least the average pore diameter is in the range of 50 μm or more and 60 μm or less, and the opening ratio is in the range of 40% or more and 44% or less. It was confirmed that a certain metal sheet 20 can be produced.

  Next, the porous carrier 15 will be described in detail. The porous carrier 15 has conductivity so that the current collecting function can be exhibited together with the metal sheet 20. As shown in FIG. 1, in the present embodiment, the porous carrier 15 is disposed in the hole 22 of the metal sheet 20, on one surface 20 a of the metal sheet 20, and on the other surface 20 b of the metal sheet 20. Has been. The porous carrier 15 is formed by joining a large number of carrier particles (carrier powder) 16 to each other. In addition, the particle | grain here is the concept containing the micro piece which has various shapes, such as spherical shape, polygonal shape, and fibrous shape.

  The carrier particles 16 may include, for example, at least one of carbon particles, carbon fibers, carbon nanohorns, and carbon nanotubes. The particle size of the carrier particles 16 (long diameter if elliptical particles, diameter if fibrous) can increase the specific surface area (surface area per unit weight) and carry the electrode catalyst 12 in a highly dispersed manner. Therefore, the smaller one is preferable, for example, several tens of nm.

  The porous carrier 15 can be formed on the metal sheet 20 by various known methods. For example, the porous carrier 15 held on the metal sheet 20 can be formed on the metal sheet 20 as follows. First, the carrier particles 16 are filled in the holes 22 of the metal sheet 20, and the carrier particles 16 are also arranged on one surface 20 a of the metal sheet 20 and on the other surface 20 b of the metal sheet 20. Next, the carrier particles 16 are sintered by firing, and the carrier particles 16 are fixed to the metal sheet 20. Thereby, a porous carrier 15 composed of a large number of carrier particles 16 is formed on the metal sheet 20.

  As described above, in the present embodiment, the cross-sectional area of the hole 22 of the metal sheet 20 that supports the porous carrier 15 gradually decreases from one surface 20a of the metal sheet 20 to the other surface 20b. It will become. Therefore, the porous carrier 15 can be stably held in the holes 22 of the metal sheet 20. Thereby, the catalyst carrying electrode 10 comes to have excellent durability.

  Next, the particulate (powder) electrode catalyst 12 will be described in detail. The electrode catalyst 12 is made of a material that increases the electromotive force by reducing the activation overvoltage associated with the electrochemical reaction in the catalyst layer, such as platinum or a platinum alloy. However, the present invention is not limited to platinum and platinum alloys, and other materials that can reduce the activation overvoltage and increase the electromotive force, such as other noble metals, can be used as the electrode catalyst.

  The electrode catalyst 12 is generally expensive. In order to effectively use this expensive electrode catalyst 12, the particle size of the particulate electrode catalyst 12 is reduced, and the value of the specific surface area (surface area per unit weight) of the particulate electrode catalyst 12 is increased. It is effective to do. In particular, in the present embodiment, the porous support 15 includes a large number of support particles 16 connected to each other, and the particulate electrode catalyst 12 is supported on the support particles 16. That is, the specific surface area of the porous carrier 15 can be made very large, whereby the porous catalyst 15 can carry the particulate catalyst 12 in a uniformly dispersed state. Therefore, it becomes possible to use the electrode catalyst 12 efficiently by greatly reducing the diameter of the particulate electrode catalyst 12.

  In addition, as a method for supporting the particulate electrode catalyst 12 on the porous carrier 15, various known methods such as an impregnation method can be used.

  As shown in FIG. 3, the fuel cells 50 having the above-described configuration are stacked to form a stack 55a, and are assembled into the fuel cell 55 as the stack 55a. In the stack 55a, for example, the catalyst-carrying electrodes 10 and 11 of adjacent fuel cells 50 are connected in series via conductive separators 40 and 41, for example. As a result, the fuel cell 55 has a high electromotive force. Further, the through holes 42 formed in the separators 40 and 41 of each fuel cell 50 are connected to each other. Thereby, hydrogen and oxygen can be supplied to each fuel cell 50 through the through-holes 42 arranged in a line, and hydrogen and oxygen that have not been used, and generated water can be recovered. it can.

  Next, the operation of the present embodiment having such a configuration will be described.

  First, hydrogen gas is fed into one of the through holes 42 communicating with one end of the gas flow path 43 formed in the separator 40 on the hydrogen electrode (one catalyst carrying electrode) 10 side of each fuel cell 50. The hydrogen gas flows into the gas flow path 43 of each fuel cell 50 through the through hole 42. In the gas flow path 43, a part of the hydrogen gas flows into the hydrogen electrode 10, and the other hydrogen gas is discharged from the fuel cell 50 through the through hole 42 as an unreacted gas.

  The hydrogen gas that has traveled to the hydrogen electrode (one catalyst-supporting electrode) 10 travels through the voids of the porous carrier 15 and moves to the electrolyte membrane 30 side. As described above, the porous carrier 15 is supported by the metal sheet 20, and the hydrogen gas passes through the holes 22 of the metal sheet 20 when moving to the electrolyte membrane 30 side across the hydrogen electrode 10. Therefore, according to the present embodiment, the hydrogen gas supplied from the gas flow path 43 can be sufficiently diffused by passing through the holes 22 of the metal sheet 20. And the variation in the gas supply amount in the surface of the hydrogen electrode 10 resulting from the structure of the gas flow path 43 can be canceled. In particular, as described above, the fine holes 22 are formed in the metal sheet 20 with a high opening ratio. Therefore, the in-plane variation of the gas supply amount can be suppressed and the hydrogen gas can be spread over substantially the entire surface of the hydrogen electrode 10. In order to sufficiently diffuse the gas, the average hole diameter of the holes 22 formed in the metal sheet 20 is preferably 60 μm or less, and the opening ratio of the metal sheet 20 is preferably 40% or more.

In the hydrogen electrode 10, in the electrode catalyst 12 supported on the porous carrier 15, the hydrogen molecule H ₂ releases electrons e ⁻ and becomes protonated (ionized) H ⁺ . Proton H ⁺ passes through the electrolyte membrane 30 and reaches the oxygen electrode 11. On the other hand, in the present embodiment, the electrons e ⁻ are collected by the separator 41 via the conductive porous carrier 15 and the metal sheet 20.

  According to the present embodiment, as described above, hydrogen gas can be diffused over substantially the entire surface of the metal sheet 20 due to the excellent diffusibility of the catalyst-carrying electrodes 10 and 11. Further, according to the present embodiment, the fine electrode catalyst 12 is highly dispersedly supported by the porous carrier 15. Accordingly, hydrogen can be reacted by effectively using the expensive electrode catalyst 12. In particular, according to the present embodiment, as described above, hydrogen passes through the holes 22 of the metal sheet 20. A porous carrier 15 is supported in the holes 22 of the metal sheet 20, and the electrode catalyst 12 is supported by the porous carrier 15. That is, since the expensive electrode catalyst 12 is disposed in the gas passage region, the expensive electrode catalyst 12 can be used very effectively.

  Further, as described above, according to the present embodiment, the porous carrier 15 carrying the particulate catalyst 12 is disposed not only in the hole 22 of the metal sheet 20 but also on both surfaces 20a and 20b. ing. Therefore, hydrogen can be reacted more stably in the catalyst-supporting electrode 10.

  By the way, the movement of hydrogen from the gas flow path 43 toward the electrolyte membrane 30 uses a pressure difference between both sides of the catalyst-carrying electrode 10 as a driving force. The catalyst-carrying electrode 10 is disposed so that one surface 20a of the metal sheet 20 is positioned on the gas flow path 43 (separator 41) side and the other surface 20b of the metal sheet 20 is positioned on the electrolyte membrane 30 side. It is preferable. As described above, the hole 22 of the metal sheet 20 gradually tapers from the one surface 20a side to the other surface 20b side. Therefore, even if the porous carrier 15 supporting the particulate electrode catalyst 12 is pressed by the gas pressure from the separator 41 side to the electrolyte membrane 30 side, the porous carrier 15 falls out of the holes 22 of the metal sheet 20. There is no end. In this way, the catalyst-carrying electrode 10 exhibits excellent durability.

  On the other hand, in parallel with the supply of the hydrogen gas, the oxygen gas is sent into one of the through holes 22 leading to one end of the gas flow path 43 formed in the separator 41 on the oxygen electrode 11 side of each fuel cell 50. . The oxygen gas flows into the gas flow path 43 of each fuel cell 50 through the hole 22. Similar to the hydrogen gas described above, part of the oxygen gas flows into the oxygen electrode 11, and the other oxygen gas is discharged from the fuel cell 50 through the through hole 42 as an unreacted gas.

The oxygen gas that has flowed into the oxygen electrode 11 reaches almost the entire surface of the oxygen electrode 11 due to the excellent diffusibility of the oxygen electrode 11, as in the case of hydrogen gas. Further, in the electrode catalyst 12 supported on the porous carrier 15 in the oxygen electrode 11, oxygen O ₂ takes in electrons e ⁻ and protons H ⁺ that have permeated through the electrolyte membrane 50, and water H ₂ O. Is generated. Along with the generation of such water, electric power is generated by the movement of electrons between the hydrogen electrode 10 and the oxygen electrode 11. Water generated at the oxygen electrode 11 moves to the gas flow path 43 and is discharged from the fuel cell 50 through the through hole 42 together with unreacted oxygen gas. In addition, like the hydrogen electrode 10, the expensive electrode catalyst 12 is also effectively used in the oxygen electrode 11, and the reaction proceeds efficiently and stably.

  In this way, electric power is generated in each fuel cell 50. As described above, in the stack 15a of the fuel cell 15, the plurality of fuel cells 50 are connected to each other in series. As a result, the fuel cell 15 has a desired electromotive force.

The electrons e ⁻ emitted from the hydrogen electrode 10 pass through the adjacent fuel cell 50 via the hydrogen electrode 10, the separator 40 in contact with the hydrogen electrode 10, and the separator 41 in contact with the separator 40 and the oxygen electrode 11. To the oxygen electrode 16. As described above, in the present embodiment, the catalyst-carrying electrodes 10 and 11 include the metal sheet 20 having higher conductivity than the carbon particles. Therefore, the loss of electromotive force due to the electric resistance of the catalyst-carrying electrodes 10 and 11 can be reduced.

  According to the present embodiment as described above, the porous carrier 15 is supported in the holes 22 of the metal sheet 20. Therefore, the gas supplied from the gas flow path 43 can be sufficiently diffused by passing through the holes 22 of the metal sheet 20. Thereby, the variation in the gas supply amount in the surface of the catalyst carrying electrodes 10 and 11 due to the configuration of the gas flow path 43 formed between the catalyst carrying electrodes 10 and 11 and the separators 40 and 41 is largely canceled. Can do.

  A porous carrier 15 carrying the electrode catalyst 12 is disposed in the hole 22 of the metal sheet 20. That is, since the expensive electrode catalyst 12 is disposed in the gas movement path, the expensive electrode catalyst 12 can be effectively used. Further, since the particulate electrode catalyst 12 is supported on the porous carrier 15, the particle diameter of the particulate electrode catalyst 12 can be reduced and the specific surface area of the particulate electrode catalyst 12 can be increased. Further, the expensive electrode catalyst 12 can be used more effectively. That is, when the electrode catalyst 12 having the same volume is used, the surface area of the electrode catalyst 12 can be increased, which is very useful in terms of cost.

  Furthermore, since the catalyst-carrying electrodes 10 and 11 have an excellent diffusion function, it is possible to omit a separate gas diffusion layer that has been conventionally used. Accordingly, it is possible to reduce the size of the fuel cell 55 (stack 55a) configured by omitting the gas diffusion layer from each of the oxygen electrode 10 and the hydrogen electrode 11 and stacking the fuel cells 50. Further, omitting the gas diffusion layer is extremely useful in terms of the cost of the fuel cell 50 (the fuel cell 55, the fuel cell stack 55a).

  Further, the porous carrier 15 carrying the electrode catalyst 12 is supported by the metal sheet 20 having high rigidity and excellent conductivity. Therefore, the catalyst-carrying electrodes 10 and 11 have excellent durability and are hardly damaged.

  Various modifications can be made to the above-described embodiment within the scope of the present invention.

  For example, in the above-described embodiment, the porous carrier 15 supporting the particulate electrode catalyst 12 is not only in the hole 22 of the metal sheet 20, but also on one surface 20 a of the metal sheet 20 and the other of the metal sheet 20. Although the example arrange | positioned also on the surface 20a was shown, it is not restricted to this. For example, the porous carrier 15 that supports the particulate electrode catalyst 12 may be disposed only in the holes 22 of the metal sheet 20. Alternatively, the porous carrier 15 carrying the particulate electrode catalyst 12 is placed in the hole 22 of the metal sheet 20 and on one of the one surface 20a of the metal sheet 20 and the other surface 20b of the metal sheet 20. , May be arranged.

  In the above-described embodiment, the example in which the catalyst-carrying electrodes 10 and 11 are in contact with the separators 40 and 41 has been described, but the present invention is not limited thereto. A gas diffusion layer having a porous structure made of, for example, carbon fiber may be provided between the catalyst-carrying electrodes 10 and 11 and the separators 40 and 41.

FIG. 1 is a cross-sectional view showing an embodiment of the present invention and showing a catalyst-carrying electrode. FIG. 2 is a diagram showing an embodiment according to the present invention, and is an exploded perspective view showing a fuel battery cell in which the catalyst-carrying electrode shown in FIG. 1 is incorporated. FIG. 3 is a view showing an embodiment according to the present invention, and is a perspective view showing a fuel cell (stack) including the fuel cell shown in FIG. FIG. 4 is a partial plan view showing the metal sheet 20 included in the catalyst-carrying electrode of FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is a diagram for explaining an example of a method of manufacturing the metal sheet shown in FIG. FIG. 7 is a view for explaining a method of etching a metal film in the manufacturing method shown in FIG. FIG. 8 is a diagram for explaining a method of removing the resinous film in the manufacturing method shown in FIG. FIG. 9 is a graph showing an average pore diameter and a hole area ratio of a metal sheet having a thickness of 20 μm manufactured by the manufacturing method shown in FIG. FIG. 10 is a graph showing an average pore diameter and a hole area ratio of a metal sheet having a thickness of 25 μm manufactured by the manufacturing method shown in FIG. FIG. 11 is a graph showing an average pore diameter and an opening ratio of a metal sheet having a thickness of 30 μm manufactured by the manufacturing method shown in FIG.

Explanation of symbols

10, 11 Catalyst supported electrode 12 Electrode catalyst (particulate electrode catalyst)
15 Porous carrier 16 Carrier particle 20 Metal sheet 20a One side 20b The other side 22 Hole 50 Fuel cell

Claims (8)

A metal sheet formed with a large number of holes;
A porous carrier supported by the metal sheet, the porous carrier disposed at least in the pores;
A catalyst-supporting electrode comprising: a particulate electrode catalyst supported on the porous carrier. 2. The catalyst-carrying electrode according to claim 1, wherein the cross-sectional area of the holes along the sheet surface of the metal sheet gradually decreases from one surface of the metal sheet to the other surface. The porosity of the metal sheet is 40% or more,
3. The catalyst-carrying electrode according to claim 1, wherein an average hole diameter of the holes of the metal sheet is 60 μm or less. The porous carrier includes a plurality of carrier particles joined together,
The catalyst-carrying electrode according to any one of claims 1 to 3, wherein the particulate electrode catalyst is carried on the carrier particles. The catalyst-supporting electrode according to claim 4, wherein the carrier particles include at least one of carbon particles, carbon fibers, carbon nanohorns, and carbon nanotubes. The catalyst-carrying electrode according to any one of claims 1 to 5, wherein the porous carrier is also disposed on at least one surface of the metal sheet.   The catalyst-carrying electrode according to any one of claims 1 to 6, wherein the particulate electrode catalyst is made of platinum or a platinum alloy. A fuel cell comprising the catalyst-carrying electrode according to any one of claims 1 to 7.

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