JP2007214055A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell for efficiently supplying liquid fuel to a power generation cell in a passive fuel cell. <P>SOLUTION: The fuel cell A is provided with a fuel storage body 20 for storing the liquid fuel, the power generation cell 30 applying the liquid fuel for power generation, and a fuel supplying member 40 having a continuous flow path 41 extending from the fuel storing body 20 to the power generation cell 30. The flow path 41 of the fuel supplying member 40 being a flow path having a cross section with a bottom has a capillary force for inducing the liquid fuel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell that uses liquid fuel, and more particularly to a fuel cell that can efficiently supply liquid fuel in a so-called passive fuel cell to a power generation cell.

  In general, a fuel cell includes a fuel cell in which an air electrode layer, an electrolyte layer, and a fuel electrode layer are stacked, a fuel supply unit for supplying fuel as a reducing agent to the fuel electrode layer, and an oxidant for the air electrode layer. As an air supply unit for supplying air as a battery, an electrochemical reaction is generated in the fuel cell by the fuel and oxygen in the air, and electric power is obtained outside. Has been developed.

In recent years, due to increasing awareness of environmental issues and energy conservation, the use of fuel cells as clean energy sources for various applications has been studied. In particular, power can be generated simply by supplying liquid fuel containing methanol and water directly. Fuel cells have attracted attention (see, for example, Patent Documents 1 to 3).
Among these, each liquid fuel cell etc. which utilized capillary force for supply of liquid fuel are known (for example, refer to patent documents 4 and 5).
The liquid fuel cell described in each of these patent documents, so-called passive fuel cell, is a method of supplying fuel to the power generation cell by capillary force, so there is no need to provide a pump or valve for fuel supply, This is a fuel supply system that can be expected to reduce the size of the generator.
The applicant of the present application relates to a liquid fuel transportation method for a fuel cell and the like that utilizes the capillary force of a porous body and / or a fiber bundle (wicking material) for transportation of liquid fuel and exhaust fuel that has passed through a power generation cell. Specific examples are given (see, for example, Patent Documents 6 to 11).

  Generally, a wicking material made of a porous material such as a cloth, a nonwoven fabric, a particle sintered body, a fiber bundle, or a foamed sponge is used as a member for supplying the fuel of such a passive fuel cell. These materials can change the capillary force by adjusting the porosity and the pore diameter, but the flow path is narrow and complicated, so it becomes resistance to liquid feeding, causing pressure loss, fuel loss There is a problem in that the transportation speed of is low.

  Further, when the power generation output of the fuel cell is increased, the amount of fuel consumed is increased, so that a material having a higher fuel transportation speed is required. By increasing the thickness of the wicking material, the amount of fuel transport can be increased and the fuel transport speed can be increased. For example, when there is no fuel in the wicking material, for example, during the first use, more fuel is wicked. There is a problem in that fuel cannot be supplied to the entire power generation cell unless it is supplied to the material.

Furthermore, in the fuel cell using the wicking material as described above, a process of arranging the wicking material is necessary in manufacturing, and a material cost relating to the wicking material itself is required.
As described above, the fuel cell using the wicking material is also expected to have a disadvantageous manufacturing cost.
JP-A-5-258760 (Claims, Examples, etc.) JP-A-5-307970 (Claims, Examples, etc.) JP 2001-313047 A (Claims, Examples, etc.) JP-A-6-188008 (Claims, Examples, etc.) JP 2001-93551 A (Claims, Examples, etc.) JP-A-2004-63200 (Claims, Examples, etc.) JP-A-2005-216817 (Claims, Examples, etc.) Japanese Patent Laying-Open No. 2005-216818 (Claims, Examples, etc.) Japanese Patent Laying-Open No. 2005-216819 (Claims, Examples, etc.) Japanese Patent Laying-Open No. 2005-216820 (Claims, Examples, etc.) JP-A-2005-216821 (Claims, Examples, etc.)

  The present invention has been made in order to solve the problems and the present situation of the liquid fuel supply system in the conventional passive fuel cell, and can supply the liquid fuel regardless of the orientation of the cartridge. In a liquid fuel supply system in a passive fuel cell, an efficient supply of liquid fuel and efficient recovery of liquid fuel and exhausted fuel used for power generation can be achieved by capillary force without using a wicking material. It is an object of the present invention to provide a passive fuel cell using a fuel supply body having a flow path that can be formed.

  As a result of earnest studies on the above-described conventional problems and the like, the present inventors have continued from the fuel storage body that stores liquid fuel, the power generation cell that supplies the liquid fuel for power generation, and the fuel storage body to the power generation cell. In the fuel cell comprising a fuel supply body having a flow path, a passive fuel cell having a specific structure for supplying the liquid fuel of the fuel cell by the fuel supply body is provided. It succeeded in being obtained and came to complete this invention.

That is, this invention exists in following (1)-(11).
(1) A fuel cell comprising a fuel reservoir that stores liquid fuel, a power generation cell that uses the liquid fuel for power generation, and a fuel supply body that has a continuous flow path from the fuel reservoir to the power generation cell. The fuel supply channel is a flow channel having a bottomed cross-sectional shape and having a capillary force capable of guiding the liquid fuel.
(2) In the flow path of the fuel supply body, the cross-sectional line length of the flow path having the bottomed cross-sectional shape is L1, the cross-sectional area of the flow path portion of the bottomed cross-sectional shape is s1, the specific gravity of the liquid fuel is ρ1, and the liquid When the fuel surface tension is γ1, the contact angle between the liquid fuel and the flow path surface is θ1, and the gravitational acceleration is g, the flow path length h1 of the fuel supply body is represented by the following formula (I). The fuel cell according to (1), comprising the flow path.
h1 ≦ (L1 × γ1 × cos θ1) / (s1 × ρ1 × g) (I)
(3) A fuel cell further comprising a waste fuel discharger having a continuous flow path from the power generation cell to the outside of the fuel cell or to a waste fuel reservoir for storing waste fuel after being used for power generation. The fuel cell according to (1), wherein the flow path of the waste fuel discharger is a flow path having a bottomed cross-sectional shape and having a capillary force capable of guiding the exhaust fuel. .
(4) The cross-sectional line length of the bottomed cross-sectional channel is L2, the cross-sectional area of the bottomed cross-sectional channel is s2, the specific gravity of the waste fuel is ρ2, and the surface tension of the waste fuel is When γ2, the contact angle between the waste fuel and the flow path surface is θ2, and the gravitational acceleration is g, the flow path length h2 of the waste fuel discharger is in the range represented by the following formula (II). The fuel cell according to (1) above, comprising a path.
h2 ≦ (L2 × γ2 × cos θ2) / (s2 × ρ2 × g) (II)
(5) The fuel cell according to any one of (1) to (4), wherein the cross-sectional shape of the flow channel is a flow channel having a bottomed cross-sectional shape that lacks one side of a rectangle.
(6) The length of one side of the rectangle is a, the length of the missing side is b, the specific gravity of the fuel is ρ1, the surface tension of the fuel is γ1, and the contact angle between the fuel and the flow path surface is The fuel cell according to (5), wherein the flow path length h1 includes a flow path in a range represented by the following formula (III), where θ1 and gravitational acceleration are g.
h1 ≦ [(2a + b) × γ1 × cos θ1] / (a × b × ρ1 × g) (III)
(7) The fuel cell according to any one of (1) to (6), wherein a part of the channel is tubular.
(8) The fuel cell according to any one of (1) to (7), wherein the flow path surface is subjected to a hydrophilic treatment.
(9) The fuel cell according to (8), wherein the hydrophilization treatment is selected from any one of plasma treatment, ozone treatment, flame treatment, and laser treatment.
(10) The fuel cell according to any one of (1) to (9), wherein a portion of the fuel supply body other than the flow path surface is subjected to water repellent treatment.
(11) The fuel cell according to any one of (1) to (10), wherein the fuel supply body is made of a material selected from an organic polymer resin and a carbon material.

  According to the present invention, the liquid fuel can be circulated regardless of the direction of the fuel cell, and the liquid fuel can be efficiently used more quickly than a flow path made of a wicking material such as a porous body or a fiber bundle. There is provided a passive type fuel cell that can be distributed well and that can omit the arrangement of a wicking material and that is inexpensive and has a fast start-up time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 show a fuel cell A as an example of an embodiment of the present invention. FIG. 1 (a) is a perspective view showing the inside of the fuel cell in a transparent manner, and FIG. 1 (b) is a fuel cell. FIG. 2A is a plan view of a basic form of a fuel supply body in the fuel cell of the present invention, and FIG. 2B is a cross-sectional view taken along line bb in FIG.
As shown in FIGS. 1A and 1B, the fuel cell A of the present embodiment includes a cartridge-type fuel storage body 20 that stores liquid fuel in a case member 10, and power generation that uses the liquid fuel for power generation. A cell 30 and a fuel supply body 40 having a continuous flow path from the fuel reservoir 20 to the power generation cell 30 are provided.

  The case member 10 includes a case main body 11 having an upper surface opening, and an lid 12 having an insertion port 12 for inserting the fuel reservoir 20 and a mesh portion 13 serving as an air intake port. The case main body 11 and the lid portion 14 are freely connectable by connecting members 15 attached to the four corners of the lid portion 14. The case member 10 is provided with current extraction lead portions 16 and 16 for extracting current generated by the power generation cell 30.

  The fuel reservoir 20 is of a fuel cartridge type and can be attached to the case member 10 via the insertion port 12 of the case member 10. The fuel storage body 20 is used to generate power by supplying the liquid fuel in the cartridge to the flat power generation cell 30 via the flat fuel supply body 40. For example, the fuel storage body 20 stores liquid fuel. It has a liquid fuel storage section 21 in which a fiber bundle to which a capillary force is applied is covered with a sheet body, and a flow path of the fuel supply body 40 via a fuel guide section 22 provided on one end face of the liquid fuel storage section 21 41 is configured to supply liquid fuel.

The fiber bundle of the liquid fuel storage unit 21 is provided with capillary force by converging the fibers, and occludes liquid fuel. Examples of fibers that can be used include natural fibers, animal hair fibers, polyacetal resins, acrylic resins, polyester resins, polyamide resins, polyurethane resins, polyolefin resins, polyvinyl resins, polycarbonate resins, and polyresins. Examples thereof include fibers made of one type or a combination of two or more types such as ether resins and polyphenylene resins.
The sheet-like porous body is configured to hold the fiber bundle in a bundled state to form the liquid fuel storage unit 21 and to discharge the liquid fuel from the end face of the liquid fuel storage unit 21.
In addition, as a sheet body to be used, the fiber bundle is held in a bundle state with a resin film or a molten resin coat, and the liquid fuel does not leak from other than the fuel guide portion 22 on the end face of the liquid fuel storage portion 21. If it is.
Further, the fuel guiding part 22 is composed of a fiber bundle or the like similar to the liquid fuel storage part 21, and the liquid fuel stored in the liquid fuel storage part 21 is supplied to the flow path 41 of the fuel supply body 40. It has a function of supplying efficiently.

The liquid fuel storage unit 21 is configured by covering (including) a fiber bundle with a capillary force that occludes the above-described liquid fuel with a sheet body, and the liquid fuel can be discharged from one end face thereof. is there.
The occlusion amount of the liquid fuel in the liquid fuel storage unit 21 varies depending on the type of the fiber bundle, the structure of the fuel cell, the structure of the fuel electrode, the power generation time, etc., but can be 0.5 to 70 ml, for example.

Examples of the liquid fuel to be stored in the liquid fuel storage unit 21 of the fuel storage body 20 include an aqueous methanol solution composed of methanol and water. The liquid fuel can be efficiently used from a compound supplied as fuel in the fuel electrode body of the power generation cell described later. As long as hydrogen ions (H ⁺ ) and electrons (e ⁻ ) can be obtained, the liquid fuel is not particularly limited and depends on the structure of the fuel electrode body, but in addition to the methanol aqueous solution, for example, dimethyl ether (DME) ), Liquid fuel such as ethanol aqueous solution, formic acid, hydrazine, ammonia solution, ethylene glycol, sodium borohydride aqueous solution and the like can also be used.
Moreover, the liquid fuel of various density | concentrations can be used for the density | concentration of these liquid fuels by the structure of a fuel cell, a characteristic, etc. For example, the liquid fuel of 1-100% density | concentration can be used.

  The power generation cell 30 to be used is disposed on a fuel supply body 40 which will be described later, and a fuel electrode, an electrolyte membrane, and an air electrode are sequentially stacked from the lower surface side. The fuel electrode (fuel electrode body) is a flat plate-like fuel electrode to which capillary force is applied, and may have a porous structure that sucks up the liquid fuel of the flat plate fuel supply body 40. For example, a three-dimensional mesh A carbon composite molded body composed of amorphous carbon and carbon powder, an isotropic high-density carbon molded body, a carbon fiber papermaking molded body, an activated carbon molded body, or the like can be used. In addition, a platinum-ruthenium (Pt-Ru) catalyst, an iridium-ruthenium (Ir-Ru) catalyst, a platinum-tin (Pt-Sn) catalyst, etc. are present on the outer surface portion of the fuel electrode. It is formed by a method of impregnating or dipping a solution containing the metal fine particle precursor and a reduction treatment after the immersion treatment, an electrodeposition method of metal fine particles, or the like.

Examples of the electrolyte membrane include ion exchange membranes having proton conductivity or hydroxide ion conductivity, such as fluorine ion exchange membranes such as Nafion (manufactured by Du Pont), heat resistance, methanol Good crossover suppression, for example, a composite membrane using an inorganic compound as a proton conducting material and a polymer as a membrane material, specifically, using a zeolite as the inorganic compound and a styrene-butadiene rubber as the polymer And composite membranes made of these, hydrocarbon-based graft membranes, and the like.
Further, as the air electrode, a porous carbon body having a porous structure in which platinum (Pt), palladium (Pd), rhodium (Rh) or the like is supported by a method using a solution containing the above-mentioned metal fine particle precursor or the like. Is mentioned.

The fuel supply body 40 of the present embodiment has a flow path 41 continuous from the fuel reservoir 20 to each power generation cell 30, and the flow path 41 is a flow made of a slit groove having a bottomed cross-sectional shape. The flow path 41 has a structure having a capillary force capable of guiding the liquid fuel. Specifically, as shown in FIGS. 2 (a) and 2 (b), the fuel supply body 40 has eight flow paths 41, and the starting flow path 41a and the spiral flow in a rectangular spiral shape, respectively. A waste fuel discharge passage 42 having a waste fuel discharge passage 41c and an end point passage 41d, and a straight line having corners other than the spiral passage 41b. It is a flow path. The fuel supply body 40 includes a starting flow path 41a that becomes a flow path 41 continuous from the fuel storage body 20 to each power generation cell 30, and a spiral flow path 41b having a rectangular spiral shape. The waste fuel discharge body 42 which has the waste fuel discharge flow path 41c and the end point flow path 41d which are the continuous flow paths which discharge | emit the waste fuel after having been provided to has become the structure continuous.
Each of the flow paths 41 is started from a starting flow path 41a, and the starting flow path 41a of the fuel supply body 40 is not cut off at the end thereof. Further, each end flow path 41d is also a dead end and is not cut out. The power generation cells 30 are respectively disposed on the spiral spiral flow paths 41b of the flow paths 41 of the present embodiment, and liquid fuel is supplied from the flow paths 41 to the fuel electrode side of the power generation cells 30. It has a configuration that can. The rectangular spiral flow passage 41b has a rectangular spiral shape in accordance with the rectangular power generation cell 30, but preferably has the same shape as the power generation cell 30 and is appropriately set according to the shape of the power generation cell 30. It is desirable.

In order to move the liquid fuel from the spiral flow path 41b of the flow path 41 to the fuel electrode, it is preferable to install a porous body having a capillary force between the power generation cell 30 and the spiral flow path 41b. Fuel can be supplied more efficiently to the entire surface of the power generation cell 30. As an example of the porous body, a material such as carbon paper can be provided, but a slit groove continuous to the surface of the fuel electrode may be provided.
The substrate material constituting the fuel supply body 40 is not particularly limited as long as it is a material that is not eroded by the liquid fuel to be circulated and does not penetrate the liquid fuel, and various materials can be used. Examples include organic polymer resins (thermoplastic resins, thermosetting resins, etc.), various carbon materials, metals, glass, wood, rocks, cement, clay, and fired products thereof. From the standpoint of ease, organic polymer resins (such as thermoplastic resins and thermosetting resins), various carbon materials, and metals are preferable.
Examples of the material of the carbon material include glassy carbon, isotropic carbon material, graphite powder [including highly oriented pyrolytic graphite (HOPG), quiche graphite, natural graphite, artificial graphite, fullerene], carbon fiber [ Vapor-grown carbon fibers, PAN-based carbon fibers, and graphite fibers], carbon nanotubes, expanded graphite sheets, and the like. Moreover, you may comprise combining these materials suitably.

  The capillary force of each flow path 41 is set so as to increase as it goes from the start flow path 41a to the end flow path 41d, so that the liquid fuel flows from the start flow path 41a to the end flow path 41d. Can be. In the case of the present embodiment, the capillary force is increased from the start-point flow path 41a portion to the end-point flow path 41d portion by forming the cross-sectional line length L of the flow path so as to be gradually reduced to 41a> 41b> 41c> 41d. It is formed as follows. In the present invention, the “cross-sectional line length L of the flow path 41” is a cross-sectional view of the fuel supply body 40 perpendicular to the flow path 41. For example, in the case of FIG. And the length of the line of intersection with the cross section.

  As a cross-sectional shape of the flow path 41, “U-shape”, “V-shape”, trapezoidal shape as well as “U-shape” lacking one side of the rectangle as shown in FIG. There is no limitation as long as it is a “bottomed shape” having a capillary force, such as a shape lacking one side.

In this embodiment, the capillary force of the flow path 41 is controlled by the cross-sectional line length L of the flow path, but the capillary force is appropriately set by setting wettability (contact angle: θ) to the liquid fuel on the flow path wall surface. It can also be controlled. In designing the actual flow path, the capillary force can be controlled while appropriately combining these control methods.
For example, a water repellent process is performed on the “upstream” flow path (that is, in the vicinity of the start-point flow path 41a) of the liquid fuel flow, and a hydrophilization process is performed on the “downstream” flow path (that is, in the vicinity of the end-point flow path 41d). Thus, the flow of the liquid fuel can be appropriately controlled.
The inside of the flow path 41 and the surface of the fuel supply body 40 can be subjected to a hydrophilic treatment and a water repellent treatment depending on the reason described above. By applying the hydrophilization treatment to the inside of the channel 41, the capillary force of the channel 41 can be increased and the fuel transport speed can be further increased.

Examples of hydrophilic treatment methods include plasma treatment, ozone treatment, flame treatment, laser treatment, electron beam treatment, ion implantation method, ion beam treatment, ion irradiation treatment, and the like. It can employ | adopt suitably according to the desired degree of hydrophilicity.
In particular, laser processing, electron beam processing, ion implantation processing, ion beam processing, and ion irradiation processing are performed by irradiating the flow path 41 with a laser beam or an electron beam whose output is adjusted. However, the treatment is not particularly limited.

As a preferred hydrophilic treatment method, laser treatment is desirable from the viewpoint of work efficiency and reliable hydrophilic treatment. As the laser irradiation treatment to be used, a predetermined surface portion of the flow path 41, for example, the laser treatment portion is at least partly or entirely of the flow path surface, and the irregularity that increases the formation of hydrophilic functional groups and the surface roughness Ra is less than 50 μm. Part, preferably an uneven portion having an average surface roughness Ra of less than 30 μm, more preferably, laser irradiation capable of forming an uneven portion having an average surface roughness Ra of 0.3 to 7 μm. For example, a YAG laser, a carbon dioxide laser, an excimer laser, an argon laser, a ruby laser, a glass laser and the like can be mentioned. A YAG laser is preferable from the viewpoint of oscillation wavelength and versatility.
The laser irradiation treatment is performed on a predetermined surface portion of the flow channel 41, for example, at least a part or the whole of the flow channel surface, with at least one hydrophilic functional group such as —OH group, —COOH group,> C═O group. From the viewpoint of increasing the formation efficiency efficiently and economically, it is preferably carried out at room temperature (25 ° C.) in an air atmosphere or in a gas atmosphere containing at least oxygen. Further, it may be performed in a humidified state at room temperature or higher.

The laser irradiation condition is that a predetermined surface portion of the flow path 41 is formed with, for example, at least part or all of the flow path surface so as to form an uneven portion with an increased formation of hydrophilic functional groups and an average surface roughness Ra of less than 50 μm. It is not particularly limited as long as it can be irradiated, and it varies depending on the raw material type, size, shape, etc. of the fuel supply body, but when using a YAG laser or the like, it is between 3 and 15 W. Arbitrary conditions such as output adjustment, laser scan speed adjustment, laser pulse width adjustment, laser spot diameter or energy density adjustment by focal length (approximately 10 ³ to 10 ⁶ W / cm ² ), and laser irradiation pattern adjustment By performing the adjustment, it is possible to form an uneven portion where the target hydrophilic functional group is increased and the average roughness Ra of the surface is less than 50 μm.
The output adjustment between 3 to 15 W varies depending on the laser specifications, irradiation conditions, etc., and cannot be generally stated. However, if the output is less than 3 W, it is difficult to increase the formation of hydrophilic functional groups. In some cases, the time required for the treatment increases, or the hydrophilic functional group fixing function cannot be exhibited over time. On the other hand, if the output is more than 15 W, the irradiation amount becomes large and the irradiated part is deeply cut, so that it is not possible to form the target hydrophilic functional group and increase the uneven part, The dimensional accuracy of the flow path surface or flow path surface becomes a problem, and the performance of the fuel cell becomes unstable.

  In addition to the hydrophilization treatment, the surface of the fuel supply body 40 other than the flow path 41 is subjected to water repellency treatment such as polyvinylidene fluoride, polytetrafluoroethylene-co-hexafluoropropylene (FEP), The method of coating with fluorine resin, such as tetrafluoroethylene, is mentioned. By performing such processing, leakage of the fuel from the flow path 41 can be prevented.

  Further, as shown in FIG. 2 (b), the flow path 41 of the present embodiment is constituted by a slit groove having a bottomed cross-sectional shape. In the liquid fuel supply body 40 of the present embodiment, the power generation cell 30 can be disposed only on the surface where the flow path 41 is open, and liquid fuel can be supplied. For this reason, there is no leakage of liquid fuel or evaporation of evaporation from the closed side, and the fuel flow is easy to manage. In the present embodiment, the flow path 41 does not reach the end of the liquid fuel supply body 40 and is suitable for fuel supply and exhaust fuel discharge from the side (one side) where the power generation cell 30 is disposed.

In this embodiment, in FIGS. 2A and 2B, the width a of the flow channel and the depth b of the flow channel (represented by the cross-sectional line length L of the flow channel together) stand the fuel supply body 40 upright. It is possible to control so that a capillary force capable of supplying fuel can be applied even when the fuel is supplied.
That is, in the flow path 41 of the fuel supply body 40, the cross-sectional line length of the flow path having the bottomed cross-sectional shape is L1, the cross-sectional area of the flow path portion having the bottomed cross-sectional shape (slipping cross-sectional area) is s1, When the specific gravity of the liquid fuel is ρ1, the surface tension of the liquid fuel is γ1, the contact angle between the liquid fuel and the flow path surface is θ1, and the gravitational acceleration is g, the length of the flow path (distance between the slit entrance and the power generation cell) ) It is preferable that h has a flow path in a range represented by the following formula (I).
h ≦ (L1 × γ1 × cos θ1) / (s1 × ρ1 × g) (I)

For example, when an aqueous methanol solution is used as the liquid fuel of the present embodiment, the surface tension and specific gravity for each methanol concentration and the calculated width of the channel 41 are shown in Table 1 below.
Here, the height difference from the electronic device using the fuel cell is 10 cm, and the liquid fuel storage part is placed on the floor (ie, h = 0.1 m). In addition, when the contact angle was measured using a contact angle meter CA-X manufactured by Kyowa Interface Science Co., Ltd. and subjected to hydrophilic treatment, all measured values were 20 ° or less. Therefore, cos θ≈1 was set. Furthermore, assuming that the as shown in FIG. 2 (b) the cross-sectional shape of the slit "width" = "depth" of the "U-shaped", approximate in L1 = 3a, s1 = a ² Calculated.
From h ≧ 0.1m
From h = (3a × γ1 × cos θ1) / (a ² × ρ1 × g),
a = 3γ1 / 0.98ρ1
The reason for describing the methanol concentration of 0% (that is, water) is that it is sometimes necessary to make a slit groove for water, such as when it is necessary to previously wet the fuel electrode of the fuel cell with water during power generation.

Conversely, the height H (H ≧ h) that the slit can suck up by capillary force is:
From H × a × b × ρ1 × g = [2 (a + b)] × γ1 × cos θ1, H = [2 (a + b) × γ1 × cos θ1] / (a × b × ρ1 × g)
From the numerical values such as the width and depth of the slit, the height that can be sucked can be calculated. Here, the trial calculation is omitted. In addition, when a fuel other than methanol aqueous solution, for example, dimethyl ether (DME), ethanol aqueous solution, formic acid, hydrazine, ammonia solution, ethylene glycol, sodium borohydride aqueous solution or the like is used as the liquid fuel, If the surface tension and specific gravity are calculated, similarly, the optimum width of the channel 41 can be shown in the same manner as the methanol aqueous solution in Table 1 above.

More practically, it is considered that the liquid fuel reservoir 20 is often placed in the vicinity of the electronic device (fuel cell main body), and there is almost no difference in height between the reservoir 20 and the power generation cell 30. Since it is considered, it is possible to make a slit larger than that described in Table 1 above. For example, considering the case where pure methanol is used as fuel with h = 5 mm, the slit groove width can be calculated as 1.74 × 10 ⁻³ m.

  In consideration of the actual slit groove width in consideration of various factors in addition to the above calculated values, 0.01 to 2.00 mm is preferable, and an optimum value can be designed according to the size of the power generation unit. If the width of the slit groove is less than 0.01 mm, the absolute amount of fuel that can be transported decreases, and if it is greater than 2.00 mm, the necessary capillary force may not be applied.

  In addition, regarding the depth of the slit groove, an optimum value can be designed and studied in consideration of various factors such as the size of the power generation cell 30 serving as a power generation unit. The actual slit groove depth is preferably 0.01 to 5.00 mm. If the depth of the slit groove is less than 0.01 mm, the absolute amount of fuel that can be transported decreases, and if it exceeds 5.00 mm, the thickness of the fuel supply member must be increased, and the fuel cell becomes smaller. It is not suitable for.

  Furthermore, when the cross-sectional line length L of the slit groove is examined, it is presumed that 0.03 to 6.00 mm, which is about three times the preferable “width”, is preferable. Actually, if it is less than 0.03 mm, the absolute amount of fuel that can be transported decreases, and if it exceeds 6.00 mm, the fuel supply member itself must be enlarged, which is not suitable for miniaturization of the fuel cell. .

  In the present invention, in FIG. 1A, the number of power generation cells 30 is eight, but the number of slit grooves serving as flow paths is one or more, depending on the number of power generation cells 30, respectively. An independent slit groove may be provided. An independent slit groove is a layout for preventing fuel that has passed through one power generation cell 30 from being supplied to another power generation cell 30, and prevents spent fuel from being supplied to another power generation cell 30. Is the purpose. The number of slit grooves that supply fuel to a single power generation cell 30 may be one or more.

  Further, in the fuel cell of the present embodiment, the fuel supply body 40 has a slit groove that becomes the flow path 41, as shown in FIGS. 1 and 2, a slit groove “upstream” from the power generation cell 30 for transporting fuel. The discharge slit groove “downstream” from the power generation cell 30 for discharging the air that is connected to the starting flow path 41a and the spiral flow path 41b having a rectangular spiral shape and is required to be discharged by fuel transportation. The waste fuel discharge channel 41c and the end point channel 41d are configured as follows. The discharge slit groove is for discharging air that was present when there was no fuel in the slit groove. In addition to that, carbon dioxide gas generated by power generation or used fuel is discharged from the power generation cell 30. This is a slit groove for connecting to the outside or a waste fuel recovery member.

The sectional line length L2 of the discharge slit groove is arbitrarily designed according to the needs of air discharge, carbon dioxide gas discharge and waste fuel discharge, both larger and smaller than the slit grooves 41a and 41b for fuel supply. The From the viewpoint of air discharge accompanying fuel supply, since air has a higher transport speed, it is sufficient that the discharge slit groove is narrow.
In particular, from the viewpoint of carbon dioxide gas and waste fuel discharge, if carbon dioxide does not dissolve or does not completely dissolve in the exhaust fuel or fuel, bubbles of carbon dioxide gas are generated, and the inside of the slit groove including the discharge slit groove A carbon dioxide gas-waste fuel or a gas-liquid interface of fuel is generated. Then, a meniscus of carbon dioxide gas / waste fuel / slit wall surface is generated in the waste fuel discharge flow path 41c and the end flow path 41d, which are discharge slit grooves, in which a capillary force opposite to the direction in which the discharge is desired is generated. Since the fuel supply may be hindered, it may be necessary to design a thicker than the fuel supply slit and reduce the capillary force.

For this reason, it may be necessary to reduce the capillary force of the waste fuel discharge flow path 41c and the end flow path 41d that become the discharge slit grooves. As a method for reducing the capillary force, in addition to widening the slit groove width, it is possible to increase the discharge efficiency of air, carbon dioxide gas, and waste fuel by performing a water repellent treatment.
Thus, when the capillary force of the discharge slit is lowered, a waste fuel recovery body having a capillary force stronger than any of the slit grooves of the fuel supply body 40 may be provided on the outlet side of the discharge slit groove. Is.

In this embodiment, in FIGS. 2A and 2B, the width a of the flow path and the depth b of the flow path (represented by the cross-sectional line length L of the flow path together) Control can be performed so that a capillary force capable of discharging the waste fuel can be applied even when the fuel supply body 40 is upright.
That is, in the waste fuel discharge flow channel 41c and the end flow channel 41d, the cross-sectional line length of the flow channel having the bottomed cross-sectional shape is L2, and the cross-sectional area of the flow channel portion having the bottomed cross-sectional shape (slipping cross-sectional area) S2, the specific gravity of the waste fuel is ρ2, the surface tension of the waste fuel is γ2, the contact angle between the waste fuel and the flow path surface is θ2, and the gravitational acceleration is g, the length of the flow path (from the power generation cell to the end point flow) It is desirable that the distance (h2) to the road cell is provided with a flow path in a range represented by the following formula (II).
h2 ≦ (L2 × γ2 × cos θ2) / (s2 × ρ2 × g) (II)

As described above, in the fuel cell A of the present embodiment, the member for transporting the liquid fuel to the power generation cell 30 of the passive fuel cell is not a capillary body having a finely curved channel like a porous body, but has a cross-sectional line length. The fuel supply body comprised from the slit groove | channel used as the flow path 41 which controlled etc. is used. A slit groove serving as a flow path is connected to a fuel reservoir 20 that stores fuel so that fuel is supplied. The optimum capillary force required by controlling the width of the slit groove, etc. can be applied, and furthermore, since the flow path is thick and there is no shield, there is little flow resistance and the fuel transportation speed can be increased. it can.
Therefore, the liquid fuel can be circulated regardless of the direction of the fuel cell, and the liquid fuel can be circulated very quickly and efficiently compared to a flow path made of a wicking material such as a porous body or a fiber bundle. In addition, it is possible to obtain a passive type fuel cell that can omit the disposition of the wicking material and that is inexpensive and has a fast start-up time of the fuel cell.
In addition, since the slit groove serving as the flow path can be cut to have a suitable capillary force according to the structure of the fuel cell, the fuel type and its concentration, etc., fuel can be efficiently supplied, distributed, and recovered. A fuel cell will be obtained.

FIG. 3 shows another basic form (second embodiment) of the fuel supply body 40 in the fuel cell of the present invention. The present embodiment (FIG. 3) is different from the fuel cell A of the above embodiment only in the configuration of the fuel supply body 40, and is used in the same manner as the fuel cell shown in FIG. Further, the same configurations as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted (the same applies to the following embodiments in FIGS. 4 to 6).
In the present embodiment, as shown in FIG. 3, each of the plurality of bottomed slit grooves reaches the end of the fuel supply body 40 at each end of the start flow path 41 a and the end flow path 41 d of the fuel supply body 40. It is different in point.
In this embodiment, the configuration is convenient when it is intended to provide a fuel storage body and a waste fuel recovery body at the end of the fuel supply body.

FIG. 4 shows another basic form (third embodiment) of the fuel supply body 40 in the fuel cell of the present invention.
In the present embodiment, the capillary force generated by the cross-sectional line length is increased from 14a by forming the bottomed slits so that the cross-sectional line length is 14a <14d, which is opposite to that of the first embodiment (FIG. 2). It is molded so as to be reduced to 14d.
As described above, when carbon dioxide does not dissolve or does not completely dissolve in the waste fuel or fuel, bubbles of carbon dioxide gas are generated, and the slit including the exhaust slit grooves of the waste fuel discharge channel 41c and the end point channel 41d A carbon dioxide gas-waste fuel or fuel gas-liquid interface is generated in the groove. In this case, carbon dioxide gas / waste fuel / slit wall meniscus is formed in the discharge slit groove, where a capillary force opposite to the direction in which discharge is desired is generated, which may hinder fuel supply. This is because it may be necessary to reduce the capillary force by designing the cross-sectional line length to be larger than that of the starting flow path 41a which is a slit groove and the spiral flow path 41b having a rectangular spiral shape.

  Also in this embodiment, the capillary force of the slit groove serving as the flow path is controlled by the cross-sectional line length of the slit. However, as in other embodiments, the capillary force is controlled by the wettability (contact angle) of the slit groove wall surface with liquid fuel. ) Etc. can be appropriately set and controlled. In the actual flow path design, these control methods are combined as appropriate, and the flow path from the fuel storage pair 20 to the power generation cell 30 causes the waste power from the power generation cell 30 so that the capillary force is 14a <14b. Up to the discharge section, the capillary force can be controlled so that 14c> 14d.

FIG. 5 shows another basic form (fourth embodiment) of the liquid fuel supply body 40 in the fuel cell of the present invention.
This embodiment is different from the third embodiment (FIG. 4) only in that each of the plurality of bottomed slit grooves reaches the end of the fuel supply body.

FIG. 6 shows another basic form (fifth embodiment) of the liquid fuel supply body 40 in the fuel cell of the present invention.
In FIG. 6, the slit grooves serving as the starting flow paths 41 a or the waste fuel discharge flow paths 41 c may have a layout that merges or a layout that branches, respectively. Can be designed according to fuel removal. As shown in FIG. 6, the spent fuel discharge channel 41c and the end point channel 41d, which are slit grooves for transporting the spent fuel, have a layout that merges, thereby transporting the spent fuel to a single waste fuel recovery material or the like. can do. Further, the above-mentioned thick slit groove for discharging carbon dioxide gas and waste fuel and the thin slit groove for discharging air can be branched. On the other hand, the starting channel 41a serving as a slit groove for supplying fuel has a layout branched from one, so that the contact portion with the fuel storage body 20 can be simplified. In the present embodiment, the end of the fuel supply body 40 is configured to reach the starting flow path 41a and the end flow path 41d. However, as illustrated in FIG.

7A and 7B show a fuel cell B which is another example of the embodiment of the present invention. FIG. 7A is a perspective view showing the inside of the fuel cell in a transparent manner. FIG. FIG. 2 is a perspective view showing an appearance of a fuel cell.
This embodiment is different from the fuel cell A of FIG. 1 and the like only in that a waste fuel recovery body 50 is further attached. The same configurations as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted.
As shown in FIGS. 7A and 7B, the fuel cell B of the present embodiment includes a cartridge-type fuel storage body 20 that stores liquid fuel in the case member 10, and power generation that uses the liquid fuel for power generation. A cell 30, a fuel supply body 40 having a continuous flow path from the fuel reservoir 20 to the power generation cell 30, and a cartridge-type military fuel recovery 60 for recovering waste fuel are provided.

The case member 10 includes a case main body 11 having an upper surface opening, an insertion port 12 for inserting a fuel storage body 20, a lid portion 14 having a mesh portion 13 serving as an air intake port, and a waste fuel recovery body 60. And the insertion port 17.
The waste fuel recovery body 60 is a cartridge type and can be attached to the case member 10 via the insertion port 17 of the case member 10. The waste fuel recovery body 60 is used for recovering carbon dioxide gas generated by power generation, spent fuel, a mixture thereof, or the like. For example, a fiber bundle having a capillary force for storing waste fuel. The waste fuel storage section 61 is covered with a sheet body, and the waste fuel is recovered from the end point flow path 41d of the fuel supply body 40 via the waste fuel guide section 62 provided on one end face of the waste fuel storage section 61. It is the composition to do.
The fiber bundle of the waste fuel storage unit 61 is provided with capillary force by converging the fibers in the same manner as the fuel storage unit 21 described above, and occludes the waste fuel. The waste fuel guiding part 62 is composed of the same fiber bundle as the waste fuel storage part 61.
In the fuel cell B of this embodiment, compared to the fuel cell A of FIG. 1, the liquid fuel can be efficiently supplied, distributed, and efficiently recovered such as waste fuel. In addition, as the fuel supply body 40, the fuel supply body 40 of each form of FIGS. 3-6 other than the form of FIG. 2 may be used.

  The fuel cell of the present invention is configured as described above, but is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, in each of the above embodiments, the slit 41 (bottomed slit groove) closed on one side has been described as the flow path 41. However, the present invention is not limited to these “slit grooves”, and the power generation cell 30 and the like. In the flow paths 412, 41 c and 41 d other than the contacting part 41 b, a tubular flow path can also be adopted in a part where it is desired to prevent fuel evaporation or waste fuel leakage. In this case, in order to meet the above-described conditions for the flow channel, the overall alignment can be achieved by controlling the flow channel cross-sectional area of the tubular flow channel and the contact angle of the tubular flow channel wall surface.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in full detail, this invention is not limited to the following Example.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by the following Example.

[Example 1 and Comparative Example 1]
After obtaining the fuel supply for the fuel cell by the following adjustment method and processing method, the fuel cell is assembled using the fuel supply, and the speed at which the liquid fuel moves from the fuel reservoir to the waste fuel reservoir is measured. Also observed.

Example 1
To a mixed resin of 10 parts by weight of a furan resin [Hitafuran VF-303 manufactured by Hitachi Chemical Co., Ltd.] and 40 parts by weight of a polyvinyl chloride-polyvinyl acetate copolymer (ZEST-C150S manufactured by Shin-Daiichi PVC Co., Ltd.) 50 parts by weight of natural scale graphite (manufactured by Nippon Graphite Industries Co., Ltd., average particle size 5 μm), and further mixed with 20 parts by weight of diallyl phthalate as a plasticizer are mixed and dispersed with a Henschel mixer, using a two-roll mixing roll The kneading was sufficiently repeated to prepare a fuel cell separator composition, which was further pulverized and sieved to obtain a powder.
The obtained powder was press-molded with a molding die having a predetermined groove pattern conforming to FIG. 3, and then dried and solidified at a temperature of 300 ° C. in an aerobic gas atmosphere, and 1500 ° C. in an inert gas atmosphere. Heat treatment was performed to obtain a carbon fuel supply body.
The dimensions of the obtained fuel supply body were 60 mm × 100 mm × 1.2 mm (flow path surface width 0.05 mm, depth 0.2 mm).
Further, the flow path surface of the obtained fuel supply body was subjected to laser treatment by the following method to form a hydrophilic functional group, and after adjusting the capillary force against the liquid fuel, a fuel supply body was obtained.
Laser treatment is performed on the flow path surface of the obtained carbon fuel supply body using a YAG laser device in a room temperature air atmosphere under conditions of an output of 12 W and a pulse width of 50 μs to perform hydrophilic treatment. A base and an uneven part were formed.

(Comparative Example 1)
What was obtained by further sintering the resin particles made of polypropylene to the flow path surface of the fuel supply body not subjected to laser treatment obtained in Example 1 and cutting it in accordance with the shape of the flow path surface. The fuel was supplied to the flow path surface.

When the hydrophilic functional group on the flow path surface of the fuel supply body in Example 1 was measured with an X-ray photoelectron spectrometer (ESCA-3400) manufactured by Shimadzu Corporation, the binding energy peaks of C—O and C═O were measured. It was found that there was growth, a new bond of a carboxyl group (COOH group) was generated, and there was further growth of the binding energy peak of oxygen. Further, when the average roughness Ra was measured at a driving speed of 0.3 mm / min using an average roughness shape measuring device Surfcom manufactured by Tokyo Seimitsu Co., Ltd., it was found that the average roughness Ra was 1.1 μm.
For the fuel supply bodies of Example 1 and Comparative Example 1 above, the contact angle of the flow path surface was measured by using a contact angle meter CA-X manufactured by Kyowa Interface Chemical Co., Ltd. In Example 1, it was found to be 20 ° or less and excellent in the degree of hydrophilicity, but in Comparative Example 1, it was 110 °.
In addition, when a reservoir made of a fiber bundle porous body with a porosity of 90% impregnated with a 50 wt% aqueous methanol solution was connected to the fuel flow path by capillary connection, in Example 1, all the fuel flowed within 10 seconds. Although it was supplied, in Comparative Example 1, it took 5 minutes to supply the fuel to all the fuel flow paths.

  As is clear from the above results, the fuel supply body of Example 1 that does not depend on the porous body that falls within the scope of the present invention is a fuel supply body that uses the porous body of Comparative Example 1 that falls outside the scope of the present invention. By comparison, it was found that the fuel has an excellent fuel transportation speed and a stable fuel transportation capacity.

  In a fuel cell of a solid polymer type or the like, a fuel cell including a fuel supply body that can efficiently supply liquid fuel to a power generation cell can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS An example of embodiment of the fuel cell of this invention is shown, (a) is a perspective view which shows the inside of a fuel cell with a transparent aspect, (b) is a perspective view which shows the external appearance of a fuel cell. The top view which shows the basic form of the fuel supply body in the fuel cell of this invention, (b) is a cross-sectional view in the bb line of (a). It is a top view which shows other embodiment of the fuel supply body in the fuel cell of this invention. It is a top view which shows other embodiment of the fuel supply body in the fuel cell of this invention. It is a top view which shows other embodiment of the fuel supply body in the fuel cell of this invention. It is a top view which shows other embodiment of the fuel supply body in the fuel cell of this invention. FIG. 2 shows another example of a fuel cell according to an embodiment of the present invention, in which (a) is a perspective view showing the inside of the fuel cell in a transparent manner, and (b) is a perspective view showing the appearance of the fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Case member 20 Fuel storage body 30 Power generation cell 40 Fuel supply body

Claims (11)

  A fuel cell comprising: a fuel storage body that stores liquid fuel; a power generation cell that uses the liquid fuel for power generation; and a fuel supply body that has a flow path that is continuous from the fuel storage body to the power generation cell. The fuel cell according to claim 1, wherein the flow path of the supply body is a flow path having a bottomed cross-sectional shape and having a capillary force capable of guiding the liquid fuel. In the flow path of the fuel supply body, the cross-sectional line length of the flow path having the bottomed cross-sectional shape is L1, the cross-sectional area of the flow path portion having the bottomed cross-sectional shape is s1, the specific gravity of the liquid fuel is ρ1, and the surface of the liquid fuel When the tension is γ1, the contact angle between the liquid fuel and the channel surface is θ1, and the gravitational acceleration is g, the channel length h1 of the fuel supply body is in the range represented by the following formula (I). The fuel cell according to claim 1, comprising:
h1 ≦ (L1 × γ1 × cos θ1) / (s1 × ρ1 × g) (I)   A fuel cell further comprising a waste fuel discharger having a continuous flow path from the power generation cell to the outside of the fuel cell, or a waste fuel reservoir for storing waste fuel after being subjected to power generation, The fuel cell according to claim 1, wherein the flow path of the waste fuel discharger is a flow path having a bottomed cross-sectional shape and having a capillary force capable of guiding the exhaust fuel. The cross-sectional line length of the bottomed cross-sectional flow path is L2, the cross-sectional area of the bottomed cross-sectional flow path portion is s2, the specific gravity of the waste fuel is ρ2, the surface tension of the waste fuel is γ2, When the contact angle between the waste fuel and the flow path surface is θ2 and the gravitational acceleration is g, the length h2 of the flow path of the waste fuel discharger is provided in a range represented by the following formula (II). The fuel cell according to claim 1.
h2 ≦ (L2 × γ2 × cos θ2) / (s2 × ρ2 × g) (II)   The fuel cell according to any one of claims 1 to 4, wherein a cross-sectional shape of the flow path is a flow path having a bottomed cross-sectional shape in which one side of a rectangle is missing. The length of one side of the rectangle is a, the length of the missing side is b, the specific gravity of the fuel is ρ1, the surface tension of the fuel is γ1, the contact angle between the fuel and the flow path surface is θ1, and gravity 6. The fuel cell according to claim 5, wherein when the acceleration is g, the flow path has a flow path having a length h <b> 1 in a range represented by the following formula (III).
h1 ≦ [(2a + b) × γ1 × cos θ1] / (a × b × ρ1 × g) (III)   The fuel cell according to any one of claims 1 to 6, wherein a part of the flow path is tubular.   The fuel cell according to any one of claims 1 to 7, wherein the flow path surface is hydrophilized.   The fuel cell according to claim 8, wherein the hydrophilization treatment is selected from any one of plasma treatment, ozone treatment, flame treatment, and laser treatment.   The fuel cell according to any one of claims 1 to 9, wherein a portion of the fuel supply body other than the surface of the flow path is subjected to water repellent treatment.   The fuel cell according to any one of claims 1 to 10, wherein the fuel supply body is made of a material selected from an organic polymer resin and a carbon material.

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