JP4892873B2 - Conductive porous body and fuel cell used in fuel cell - Google Patents

Description

  The present invention relates to a conductive porous body used in a fuel cell and a fuel cell.

As this type of fuel cell, for example, a polymer electrolyte fuel cell, a direct methanol fuel cell (DMFC), etc. are known, and in general, a conductive material through which fuel or air passes from the front side to the back side. A porous body is provided. As this conductive porous body, for example, a configuration having a three-dimensional network structure as shown in Patent Document 1 below is known.
Japanese Patent Laid-Open No. 2005-29806

However, in this fuel cell, further improvement in output has been demanded in recent years.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a conductive porous body and a fuel cell used for a fuel cell capable of further improving output.

In order to solve such problems and achieve the above object, the conductive porous body used in the fuel cell of the present invention is used in a fuel cell, and fuel or air flows from the front side to the back side. It is a conductive porous body made of a sintered metal foam sheet in which metal powders are sintered , and the same foam holes open on the front and back surfaces, and the adjacent foam holes communicate with each other in the surface direction. The thickness of the conductive porous body is set to be equal to or smaller than the virtual foaming diameter of the foaming hole .
Further, when the conductive porous body is provided in a so-called direct methanol fuel cell (DMFC), carbon dioxide generated as a by-product at the anode electrode is allowed to pass through the conductive porous body satisfactorily. It becomes possible to prevent the carbon dioxide from adhering to the conductive porous body and closing the foamed holes. Therefore, in the process of using the DFMC, it is possible to suppress a decrease in the supply efficiency of the aqueous methanol solution (fuel) to the reaction field due to the adhesion of the carbon dioxide.
As mentioned above, it can suppress that the output of a fuel cell falls gradually in the process of use.

In the present invention, since the same foamed holes are opened on the front and back surfaces of the conductive porous body, the conductive porous body is provided in the fuel cell, and the fuel or air is supplied to the conductive porous body in the thickness thereof. When passing in the vertical direction, it is possible to minimize the decrease in the flow velocity of the fuel after the passage, that is, the pressure loss. Therefore, in this fuel cell, for example, a pump is provided, and in the configuration in which the fuel or the like is supplied to the conductive porous body by the pump, the power consumption of the pump can be minimized, and the pump In a so-called passive type fuel cell, the flow rate of the fuel and the like passing through the conductive porous body can be increased in place of the configuration using.
As described above, the output of the fuel cell can be improved.

Further, when the conductive porous body is provided in a so-called direct methanol fuel cell (DMFC), carbon dioxide generated as a by-product at the anode electrode is allowed to pass through the conductive porous body satisfactorily. It becomes possible to prevent the carbon dioxide from adhering to the conductive porous body and closing the foamed holes. Therefore, in the process of using the DFMC, it is possible to suppress a decrease in the supply efficiency of the aqueous methanol solution (fuel) to the reaction field due to the adhesion of the carbon dioxide.
As mentioned above, it can suppress that the output of a fuel cell falls gradually in the process of use.

  Further, since the adjacent foam holes in the surface direction of the conductive porous body communicate with each other, when the fuel or the like passes through the conductive porous body in the thickness direction, the fuel or the like is electrically conductive. It is possible to pass through the inside of the porous porous body while diffusing in the surface direction. Therefore, the flow velocity of the fuel or the like passing through the conductive porous body varies in the direction along the surface of the conductive porous body, that is, the pressure difference of the fuel or the like occurs in the direction along the surface. And the output of the fuel cell can be improved.

A fuel cell according to the present invention is characterized in that the conductive porous body used in the fuel cell according to claim 1 is provided as an electrode member .

  In the conductive porous body and the fuel cell used in the fuel cell according to the present invention, the output can be further improved.

  The conductive porous body 11 used in the fuel cell according to one embodiment of the present invention is formed into a sheet shape, and as shown in FIG. 1, innumerable foam holes 11a are formed inside the porous body 11. The front and back surfaces 11b and 11b and the side surfaces are opened. That is, the same foaming hole 11a opens to the front and back surfaces 11b and 11b of the conductive porous body 11, and the foaming holes 11a and 11a adjacent in the surface direction communicate with each other. Further, the thickness of the conductive porous body 10 is set to be equal to or smaller than the virtual foam diameter A of the foam holes 11a. In addition, the virtual foaming diameter A is the maximum foaming of the foaming agent described later as indicated by the two-dot chain line in FIG. 1 when the thickness of the conductive porous body 11 (slurry S described later) is sufficiently large. It refers to the inner diameter of the foamed hole 11a.

  The bone portion 12 positioned between the foam holes 11a and 11a adjacent in the surface direction gradually increases from the front and back surfaces 11b and 11b of the conductive porous body 11 toward the central portion in the thickness direction. The porous porous body 11 has a tapered shape in which the size in the direction along the front and back surfaces 11b and 11b is reduced, and the adjacent foam holes 11a and 11a in the surface direction are the thickness of the conductive porous body 11. It communicates at the center of the direction. In addition, this electroconductive porous body 11 is formed from the foam metal sintering sheet | seat which can adjust a porosity and thickness suitably and can use the raw material metal variously.

  Here, the manufacturing method of the foam metal sintered sheet suitable for the electroconductive porous body 11 is demonstrated. This foamed metal sintered sheet is produced, for example, by firing a green sheet G obtained by thinly forming and drying a slurry S containing metal powder.

  The slurry S is a conductive metal powder, a foaming agent (for example, a water-insoluble hydrocarbon-based organic solvent having 5 to 8 carbon atoms (for example, neopentane, hexane, heptane)), an organic binder (for example, methylcellulose or hydroxypropylmethylcellulose), A solvent (water) or the like is mixed. A green sheet manufacturing apparatus 50 for thinly forming the slurry S by the doctor blade method is shown in FIG.

  In the green sheet manufacturing apparatus 50, first, the slurry S is supplied onto the carrier sheet 52 from the hopper 51 in which the slurry S is stored. The carrier sheet 52 is conveyed by a roller 53, and the slurry S on the carrier sheet 52 is extended between the moving carrier sheet 52 and the doctor blade 54 and formed to a required thickness.

  The formed slurry S is further conveyed by the carrier sheet 52 and sequentially passes through a foaming tank 55 and a heating furnace 56 that perform heat treatment. Since the heat treatment is performed in the high-humidity atmosphere in the foaming tank 55, the foaming agent can be foamed without forming cracks in the slurry S to form foaming holes. At this time, the same foaming hole reaches the front and back surfaces of the slurry S and opens on the front and back surfaces, and the foaming holes adjacent in the surface direction are communicated with each other at the center in the thickness direction of the slurry S. And when this slurry S is dried with the heating furnace 56, the green sheet G of the state by which the metal powder was joined by the organic binder will be formed.

  The green sheet G is removed from the carrier sheet 52, and then degreased and fired in a vacuum furnace (not shown), whereby the organic binder is removed and a foam metal sintered sheet in which metal powders are sintered is obtained. And the conductive porous body 11 is obtained by cut | disconnecting this foam metal sintered sheet to arbitrary magnitude | sizes.

Next, a first embodiment in which the conductive porous body 11 is used in a fuel cell will be described with reference to FIG.
The fuel cell 20 has a so-called planar arrangement structure, and is sandwiched between a pair of electrode members 10 and 10 each having a conductive porous body 11 and electrode surfaces 10a and 10a of these electrode members 10 and 10. The schematic configuration includes an electrolyte layer 30 and a fuel supply unit 40 that supplies fuel to one electrode member 10 as the fuel electrode A. The electrolyte layer 30 is formed of, for example, a fluororesin-based polymer electrolyte membrane, and has the property of not allowing electrons to pass while hydrogen ions can move in the membrane. The other of the pair of electrode members 10 and 10 is an air electrode B.

Here, as shown in FIG. 3, the electrode member 10 fills the space between the conductive porous bodies 11 with a plurality of conductive porous bodies 11 arranged at intervals in the plane direction. A resin portion 13 is provided so as to surround the entire outer periphery. A thin metal plate tab 92 extending to the outer periphery of the resin portion 13 is connected to one end of each conductive porous body 11.
The electrode member 10 is formed by molding the resin portion 13 by injection molding using, for example, a metal porous plate 11 welded to the conductive porous body 11 as an insert part. Thereby, the electrode member 10 in which the conductive porous body 11, the metal thin plate 92, and the resin portion 13 are integrated is obtained.

  In the fuel electrode A, one surface 11b of the conductive porous body 11 constituting the electrode surface 10a is connected to the electrolyte layer 30 through the catalyst layer C, and the back surface 11b opposite to the surface 11b receives fuel. The fuel supply unit 40 is connected to the holding and supplying unit. The catalyst layer C is similarly formed on the conductive porous body 11 of the air electrode B, and a polymer containing carbon particles carrying platinum catalyst fine particles on the one surface 11 b of each conductive porous body 11. It is formed by applying an electrolyte solution.

  Each of the four conductive porous bodies 11 connected to the fuel electrode A and the air electrode B in series is connected in series in the connection direction of the conductive porous bodies 11 through the metal thin plates 92 provided separately for each of these 11. As shown in FIG. 3, the conductive porous body 11 is connected to the thin metal plate 92 of the conductive porous body 11 located next to the connecting direction through the electrolyte layer 30 via the wiring 16. The thin metal plates 92 located at both ends in the connecting direction function as the anode 21 and the cathode 22 of the fuel cell 20.

  The fuel supply unit 40 holds a fuel (here, methanol aqueous solution) and a porous part 41 made of felt or the like that supplies the fuel to the conductive porous body 11 of the fuel electrode A is covered with a resin frame 42. It has been configured. Then, the porous portion 41 of the fuel supply unit 40 is disposed in contact with the conductive porous body 11 of the fuel electrode A, so that the fuel held in the porous portion 41 is converted into the conductive porous body by osmotic pressure. 11 can be supplied. The resin frame 42 of the fuel supply unit 40 and the resin part 13 of the electrode member 10 are ultrasonically bonded, for example.

As described above, the conductive porous body 11 of the fuel electrode A and the air electrode B is provided with air permeability and conductivity in the fuel cell 20 so as to serve as both a so-called gas diffusion layer and a current collector plate. .
In the present embodiment, the catalyst layer C is formed on the surface 11b of the electrode surface 10a of each conductive porous body 11 in the fuel electrode A and the air electrode B. 11 may be provided on the interface between the electrolyte layer 30 and the electrolyte layer 30.

In the fuel cell 20 configured as described above, hydrogen in the fuel supplied from the fuel supply unit 40 to the conductive porous body 11 of the fuel electrode A is ionized by an electrode reaction on the catalyst layer C, and the electrolyte layer. 30 moves toward the air electrode B. The hydrogen ions that have reached the air electrode B are in the air electrode B at the interface between the electrolyte layer 30 and the catalyst layer C and on the opposite side of the surface 11b that constitutes the electrode surface 10a of the conductive porous body 11. The water reacts with the oxygen in the air supplied from the back surface 11b of the water to generate water.
On the other hand, the electrons generated at the fuel electrode A due to the ionization of hydrogen move from the fuel electrode A to the air electrode B through the metal thin plate 92, and electric energy is generated by the movement.

  Next, a second embodiment in which the conductive porous body 11 is used for a fuel cell will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the site | part same as the form shown in FIGS. 1-3, and the description is abbreviate | omitted.

  The fuel cell 60 has a so-called stack type structure, each of which includes a pair of electrode members 61 and 61 each having a conductive porous body 11, and an electrolyte sandwiched between electrode surfaces 61a and 61a of these electrode members 61 and 61. A laminated structure 60 a including the layer 30 has a schematic configuration in which the separators 62 are stacked via the separator 62. In each laminated structure 60 a, one electrode member 61 is a fuel electrode A, and the other electrode member 61 is an air electrode B. In the illustrated example, the fuel electrode A of one laminated structure 60 a is disposed so as to face the air electrode B of another laminated structure 60 a with the separator 62 interposed therebetween. The separator 62 is formed of a conductive material that does not pass air or fuel gas or liquid, such as a carbon plate or a corrosion-resistant metal (stainless steel) plate.

The electrode member 61 of the present embodiment surrounds the outer peripheral edge of the conductive porous body 11 over the entire region, and the resin portion 13 extending in the surface direction of the porous body 11 is formed outside the conductive porous body 11. It is set as the schematic structure joined to the peripheral part.
The fuel cell 60 is formed with a plurality of through holes 60b penetrating in the stacked direction at positions where the conductive porous body 11 is avoided.

  In the laminated structure 60a, the electrode surfaces 61a and 61a, that is, the surfaces of the conductive porous bodies 11 constituting the pair of electrode members 61 and 61, respectively, facing each other, are the same as in the first embodiment. A catalyst layer C is formed, and each conductive porous body 11 is connected to the electrolyte layer 30 through the catalyst layer C.

  In the above configuration, the fuel supplied to one through-hole 61b passes hydrogen through the conductive porous body 11 of each fuel electrode A in the thickness direction, and supplies hydrogen to the interface between the electrolyte layer 30 and the catalyst layer C. By supplying, the hydrogen is ionized as in the first embodiment. The hydrogen ions are supplied to the fuel cell 60 at the interface between the electrolyte layer 30 and the catalyst layer C in the air electrode B when the hydrogen ions reach the air electrode B positioned opposite to the electrolyte layer 30. It reacts with the oxygen in the air and generates water. On the other hand, the electrons generated by the ionization of hydrogen move from the fuel electrode A to the air electrode B together with the hydrogen ions, and electric energy is generated by the movement. In the present embodiment, since the separator 62 is provided, the one stacked structure 60a and the other stacked structure 60a are separated from each other in an airtight manner, and electrons are transmitted between the stacked structures 60a through the separator 62. An exchange will take place.

  As described above, according to the conductive porous body 11 according to the present embodiment, since the same foamed hole 11a is opened in the front and back surfaces 11b and 11b of the conductive porous body 11, this conductive porous body 11 is used. When the body 11 is provided in the electrode members 10 and 61 of the fuel cells 20 and 60, and the fuel or air is passed through the conductive porous body 11 in the thickness direction, the flow velocity of the fuel or the like after the passage Reduction, that is, pressure loss can be minimized.

Therefore, in this fuel cell, for example, a pump is provided, and in the configuration in which fuel or air is supplied to the conductive porous body 11 by the pump, the power consumption of the pump can be suppressed to a minimum. In a so-called passive type fuel cell instead of a configuration using a pump, it is possible to increase a flow rate at which the fuel or the like passes through the conductive porous body 11.
As described above, the output of the fuel cell can be improved.

Further, when the conductive porous body 11 is provided in a so-called direct methanol fuel cell (DMFC), carbon dioxide generated as a by-product at the anode electrode passes through the conductive porous body 11 well. It is possible to prevent the carbon dioxide from adhering to the bone portion 12 of the conductive porous body 11 and closing the foam holes 11a. Therefore, in the process of using the DFMC, it is possible to suppress a decrease in the supply efficiency of the aqueous methanol solution (fuel) to the reaction field due to the adhesion of the carbon dioxide.
It becomes possible to suppress this.
As mentioned above, it can suppress that the output of a fuel cell falls gradually in the process of use.

  Further, since the adjacent foam holes 11a communicate with each other in the surface direction of the conductive porous body 11, when the fuel or the like passes through the conductive porous body 11 in the thickness direction, the fuel or the like is removed. It is possible to pass through the inside of the conductive porous body 11 while diffusing it in the surface direction. Therefore, the flow velocity of the fuel or the like passing through the conductive porous body 11 varies in the direction along the surface of the conductive porous body 11, that is, the fuel or the like in the direction along the surfaces 11b and 11b. It becomes possible to suppress the occurrence of a pressure difference, and the output of the fuel cell can be improved.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  The output of the fuel cell can be further improved.

It is the electroconductive porous body shown as one Embodiment of this invention, Comprising: (a) The enlarged plan view, (b) A-A 'sectional view taken on the line (a). It is sectional drawing which shows 1st Embodiment of the fuel cell using the electroconductive porous body shown in FIG. It is a schematic perspective view of the electrode member shown in FIG. It is sectional drawing which shows 2nd Embodiment of the fuel cell using the electroconductive porous body shown in FIG. It is a schematic diagram which shows an example of the method of manufacturing an electroconductive porous body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 61 Electrode member 11 Conductive porous body 11a Foamed hole 11b Front or back surface of conductive porous body 20, 60 Fuel cell

Claims (2)

A conductive porous body made of a foamed metal sintered sheet used in a fuel cell, in which fuel or air is passed from the front side to the back side, in which metal powders are sintered ,
While the same foaming hole opens on the front and back, the foaming holes adjacent in the surface direction communicate with each other ,
A conductive porous body used in a fuel cell, wherein the thickness of the conductive porous body is equal to or less than a virtual foam diameter of the foamed pores . A fuel cell comprising the conductive porous body used in the fuel cell according to claim 1 as an electrode member .

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