JP5093640B2 - Solid oxide fuel cell and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solid polymer fuel cell using a solid polymer electrolyte membrane as an electrolyte membrane and a method for producing the same.

  Since a polymer electrolyte fuel cell using a liquid fuel can be easily reduced in size and weight, research and development as a power source for various electronic devices such as portable devices are being actively promoted today.

The polymer electrolyte fuel cell includes an electrode-electrolyte membrane assembly (MEA) having a structure in which a solid polymer electrolyte membrane is sandwiched between an anode and a cathode. A fuel cell of a type that supplies liquid fuel directly to the anode is called a direct fuel cell, and decomposes the supplied liquid fuel on a catalyst supported on the anode to generate cations, electrons, and intermediate products. . Further, in this type of fuel cell, the generated cations permeate the solid polymer electrolyte membrane and move to the cathode side, and the generated electrons move to the cathode side through an external load, and these are oxygen in the air at the cathode. To generate electricity. For example, in a direct methanol fuel cell (hereinafter referred to as DMFC) using a methanol aqueous solution as a liquid fuel as it is, the reaction represented by the following formula 1 occurs at the anode, and the reaction represented by the following formula 2 occurs at the cathode. .
(Scheme 1); CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻
(Scheme 2); 6H ⁺ + 6e ⁻ + 3/2 O ₂ → 3H ₂ O

(Theoretical concentration of aqueous methanol solution)
As apparent from these formulas 1 and 2, in DMFC, 1 mol of methanol and 1 mol of water react theoretically at the anode to produce 1 mol of reaction product (carbon dioxide). At this time, since hydrogen ions and electrons are also generated, the theoretical concentration of methanol in the methanol aqueous solution as the fuel is about 70 vol% in volume%.

(About crossover)
However, conventionally, when the concentration of methanol supplied to the anode increases, a “crossover” occurs in which methanol permeates the solid polymer electrolyte membrane without contributing to the reaction represented by the above formula 1, and the power generation capacity and It is known that the generated power decreases. When the crossover increases, (a) the output (voltage) decreases, (b) the fuel utilization efficiency deteriorates, (c) the heat generation amount increases and the temperature of the MEA increases, so the fuel temperature increases. The temperature rises more than necessary, and the crossover is further accelerated, thereby causing a problem such as causing a further temperature rise.

  In relation to the above, Patent Document 1 discloses a technique for improving the output density of DMFC. Patent Document 4 is a power generation element for a liquid fuel cell including a positive electrode that reduces oxygen, a negative electrode that oxidizes fuel, and a solid electrolyte disposed between the positive electrode and the negative electrode. Each of the negative electrodes includes a catalyst layer having a thickness of 20 μm or more, and at least one of the catalyst layers has pores having a pore diameter of 0.3 μm to 2.0 μm, and the pore volume of the pores is A power generation element for a liquid fuel cell, which is 4% or more based on all pores, is disclosed.

  In order to increase the output of the MEA, it is necessary to increase the proton conduction of the electrolyte membrane, which leads to an increase in the permeation rate of methanol. For this reason, in order to secure the necessary output, even if a methanol aqueous solution of about 20 vol% is used, it is currently affected by crossover. Conversely, it is easy to reduce crossover by using a low-concentration aqueous methanol solution, but when such a low-concentration aqueous methanol solution is used as a liquid fuel, the amount of power generation per unit mass of the liquid fuel is reduced. Therefore, there arises a problem that the energy density of the solid polymer fuel cell cannot be increased. Therefore, in order to obtain a polymer electrolyte fuel cell having a high energy density, only a necessary fuel is consumed and a crossover is suppressed by using a liquid fuel as close as possible to the theoretically optimal methanol concentration (70 vol%). A mechanism is required.

  As a prior art for optimizing the fuel supply to such an MEA, for example, the one described in Patent Document 2 can be cited. Patent Document 1 discloses an oxidant electrode, an electrolyte plate formed on the oxidant electrode, a fuel electrode formed on the electrolyte plate, and a separation membrane for separating a liquid and a gas provided on the fuel electrode. And a liquid fuel holding part connected to the separation membrane.

  Further, as a related technique, Patent Document 3 is a fuel cell in which a positive electrode and a negative electrode are provided on both sides of an electrolyte layer, and a liquid fuel impregnated layer that impregnates and holds liquid fuel on the negative electrode side, A fuel cell is disclosed that is made of a conductive porous material and includes a fuel distribution layer that distributes liquid fuel and gaseous fuel to the negative electrode between the negative electrode and the liquid fuel-impregnated layer.

  As for the material of the liquid absorption holding member, Patent Document 4 discloses a porous liquid absorption holding member characterized by comprising a porous sintered body having a skeleton obtained by sintering metal powder around the pores. is doing.

In addition, as a technique for reducing the size and increasing the output of a fuel cell system, Patent Document 5 uses a carbonaceous porous body having electrical conductivity as a base material, and an electrode / electrolyte / electrode is formed on the surface of the base material. Provided with a unit cell in which each layer is formed or a connected body in which two or more of the unit cells are connected to each other, allows the liquid fuel to penetrate into the base material, and exposes the electrode surface formed on the outer surface of the base material to air. A fuel cell is disclosed.
JP 2005-183368 A JP 2001-15130 A JP 2003-68325 A Japanese Patent Laid-Open No. 2004-183055 JP-A-2005-251715

  However, in the fuel cell having a structure in which only the gas component is selectively permeated from the liquid fuel through the gas-liquid separation membrane, the present inventors have conducted further studies. Then, we found that stable power generation cannot be performed.

  When a porous body made of fluororesin is used as the gas-liquid separation membrane for vaporizing and supplying the anode electrode, the insulating porous membrane including the porous membrane made of fluororesin is not touched by liquid fuel In the dry state, large static electricity is generated on the surface. In a fuel cell, it is assumed that more or less fine impurities such as deterioration of internal members and external dust are mixed during operation. Such impurities are liable to adhere to a gas-liquid separation membrane having a large static electricity in a dry state, and hinder the supply of liquid fuel to the gas-liquid separation membrane. That is, when the gas-liquid separation membrane is started from a dry state, fuel supply to the gas-liquid separation membrane is hindered, so that stable fuel vaporization and supply to the anode electrode cannot be performed sufficiently. In addition to physical fuel inhibition, the permeation characteristics of the separation membrane may be changed by altering the surface state of the gas-liquid separation membrane. In addition, even when a member is peeled off on the anode electrode side, if the porous membrane to be vaporized is dried, the probability of impurities adhering to the opposite gas-liquid separation membrane is also expected to be extremely high. This also leads to fuel supply hindrance and membrane surface alteration.

  For the above reasons, in a state where the gas-liquid separation membrane is dry, it becomes difficult to stably supply fuel due to physical fuel inhibition due to adhesion of impurities and alteration of the membrane surface, and power generation characteristics are likely to deteriorate.

  In addition, even if a metal material is brought into close contact with the gas-liquid separation membrane to prevent the gas-liquid separation membrane from being charged, it is corroded by by-products (such as formic acid) generated in the fuel cell, and the surface is oxidized. Since it is covered and stabilized by the film, the conductivity is more or less lowered. In general, a metal material is hard and has large irregularities. If the gas-liquid separation membrane used for vaporization supply is thin, the membrane may be damaged.

  The present invention has been made to solve the above-mentioned problems, and its object is to provide a solid state capable of reducing the adhesion of impurities to a gas-liquid separation membrane in a fuel cell that vaporizes and supplies using the gas-liquid separation membrane. The object is to provide a polymer fuel cell.

  [Means for Solving the Problems] will be described below using the numbers and symbols used in [Best Mode for Carrying Out the Invention]. These numbers and symbols are added in parentheses in order to clarify the correspondence between the description of [Claims] and [Best Mode for Carrying Out the Invention]. However, these numbers and symbols should not be used for the interpretation of the technical scope of the invention described in [Claims].

A polymer electrolyte fuel cell (10) according to the present invention includes a solid polymer electrolyte membrane (5), and a cathode (7) disposed in contact with one surface of the solid polymer electrolyte membrane (5). The anode (6) disposed in contact with the other surface of the solid polymer electrolyte membrane (5) and the liquid fuel holding for temporarily holding the fuel supplied to the anode (6) in a liquid state Gas-liquid separation membrane (20) disposed between the section (16), the liquid fuel holding section (16), and the anode (6), and selectively passing only the gaseous component of the fuel and supplying the fuel to the anode (6) And). The gas-liquid separation membrane (20) and the liquid fuel holding part (16) are in contact with each other. The liquid fuel holding part (16) has conductivity.
Since the fuel holding portion (16) has conductivity, static electricity on the surface of the gas-liquid separation membrane (20) is removed even in a dry state. Since static electricity is removed, the adhesion of impurities to the surface of the gas-liquid separation membrane (20) can be remarkably suppressed. Since it is not affected by impurities, even when power is generated from a situation where the liquid fuel is depleted and the gas-liquid separation membrane (20) is dried, the liquid fuel necessary for the gas-liquid separation membrane (20) is supplied, In addition, vaporization and supply from the gas-liquid separation membrane to the anode (6) can be performed stably. Further, from the long-term viewpoint, alteration of the surface of the gas-liquid separation membrane (20) due to adhesion of impurities can be prevented. That is, with the above-described configuration, it is possible to realize extremely stable power generation characteristics in a situation where power generation is performed from a state where the gas-liquid separation membrane (20) is dry, such as when the fuel is depleted.

In the polymer electrolyte fuel cell (10), the surface resistance value of the liquid fuel holder (16) is preferably larger than 0 (Ω) and not larger than 10 ¹² (Ω).
If the surface resistance value of the liquid fuel holding part (16) is larger than 10 ¹² (Ω), the effect of adhering impurities tends to be insufficient.

In the polymer electrolyte fuel cell (10), the liquid fuel holding part (16) is preferably a polymer foam.
There are a wide variety of chemically stable polymeric materials having acid resistance, and it is possible to select those that are stable against by-products of the power generation reaction.

In the polymer electrolyte fuel cell (10), the liquid fuel holding part (16) preferably has a porosity of 50% or more and 95% or less.
When the porosity is less than 50%, the liquid fuel is not sufficiently infiltrated, and it becomes difficult to supply the fuel to the gas-liquid separation membrane side. On the other hand, if it is greater than 95%, the fuel holding function is significantly impaired.

  In the polymer electrolyte fuel cell (10), the liquid fuel holding part (16) preferably has a continuous three-dimensional pore structure.

  In the polymer electrolyte fuel cell (10), the liquid fuel holding part (16) is preferably in close contact with the gas-liquid separation membrane (20) over the entire surface.

In the polymer electrolyte fuel cell (10), the liquid fuel holding part (16) is preferably grounded.
Since the liquid fuel holding part (16) is grounded, static electricity removed by the liquid fuel holding part (16) can be removed to the outside.

In the polymer electrolyte fuel cell (10), the liquid fuel holding part (16) is preferably an elastic body.
By being an elastic body, even if it makes contact with the gas-liquid separation membrane (20), the gas-liquid separation membrane (20) is not damaged.

  According to the present invention, there is provided a polymer electrolyte fuel cell that can reduce adhesion of impurities to the gas-liquid separation membrane in a fuel cell that is vaporized and supplied using the gas-liquid separation membrane.

  Hereinafter, the polymer electrolyte fuel cell of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a cell structure of a polymer electrolyte fuel cell of the present invention. The present invention is not limited to these drawings and the embodiments described below.

  As shown in FIG. 1, a solid polymer fuel cell 10 of the present invention includes a solid polymer electrolyte membrane 5 and a cathode 7 disposed on one surface of the solid polymer electrolyte membrane 5 in contact with the surface. An anode 6 disposed on the other surface in contact with the surface; a cathode current collector 2 and an anode current collector 1 disposed on and in contact with the cathode 7 and the anode 6; and a cathode current collector. Moisturizing material 9 disposed on electric body 2, gas-liquid separation membrane 20 for vaporizing and supplying liquid fuel before being supplied to anode 6, and fuel for sending liquid fuel to gas-liquid separation membrane 20 A liquid fuel holding unit 16 that temporarily holds the liquid fuel.

  The solid polymer electrolyte membrane 5 is sandwiched between the cathode 7 and the anode 6. The solid polymer electrolyte membrane 5, the cathode 7, and the anode 6 constitute an MEA 3 (electrode-electrolyte membrane assembly; Membrane and Electrode Assembly).

  A cathode current collector 2 and an anode current collector 1 are provided on the upper and lower surfaces of the MEA 3. The anode current collector 1 and the cathode current collector 2 are provided for taking out the electromotive force generated by the MEA 3. In the cross-sectional view of FIG. 1, the anode current collector 1 and the cathode current collector 2 are drawn so as to cover the entire surfaces of the anode 6 and the cathode 7. There is no contact with the current collector. In a portion not in contact with the current collector, fuel is supplied to the anode 6, and oxidant gas is supplied to the cathode 7. In addition, an insulating and sealing material 11 for filling the gap and insulating the outside from the sides of the anode 6 and the cathode 7 is disposed.

  A moisturizing material 21 is disposed on the cathode current collector 2. The cathode 7 is humidified by the moisturizing material 21. When the cathode 7 is dried, the ionic conductivity may be lost and the power generation efficiency may be reduced, but the ionic conductivity is not lost by the moisturizing material 21.

  The liquid fuel holding part 16 is inserted into a fuel tank 15 formed as a concave part of a frame or a casing. The gas-liquid separation membrane 20 is disposed so as to cover the opening of the fuel tank 15. The MEA 3 described above is disposed above the opening of the fuel tank 15 with the gas-liquid separation membrane 20 interposed therebetween. The MEA 3 is arranged with the anode 6 on the fuel tank 15 side (gas-liquid separation membrane 20 side).

  The material of the solid polymer electrolyte membrane 5 is not particularly limited, but commercially available materials used in the examples described later can also be used.

  Each of the cathode 7 and the anode 6 is manufactured by applying a catalyst paste containing carbon particles carrying a catalyst onto, for example, a carbon paper that is a porous substrate. The produced cathode 7 and anode 6 are arranged and pressure-bonded so that the catalyst paste layer side is on the solid polymer electrolyte membrane 5 side, whereby the MEA 3 is produced.

  The gas-liquid separation membrane 20 is provided to vaporize and supply liquid fuel to the anode 6. The gas-liquid separation membrane 20 is insulative. The gas-liquid separation membrane 20 is a polymer porous body. Specifically, a fluororesin such as polytetrafluoroethylene (PTFE) is used. As the gas-liquid separation membrane 20, other materials can be used as long as they are insulative and can supply a necessary amount of fuel. For example, a partially insulating film such as a pore filling film in which an ion conductor is injected into a polymer porous body can also be used.

  The thickness of the gas-liquid separation membrane 20 can be 1 mm or less, for example. In such a range, gas-liquid separation can be reliably performed, and the charge removal effect of the liquid fuel holding unit 16 described later can be exerted on the constituent members on the anode 6 side of the gas-liquid separation film 20. Since the charging of the constituent member on the anode 6 side is removed, adhesion of dust and impurities to the anode 6 is suppressed.

  The liquid fuel holding unit 16 is in contact with the gas-liquid separation membrane 20. The fuel holding unit 16 temporarily holds liquid fuel (methanol) and supplies it to the gas-liquid separation membrane 20. Here, the fuel supply to the gas-liquid separation membrane 20 may utilize the capillary phenomenon of the holding material, or the liquid fuel may be continuously circulated inside the fuel tank 15 by an external auxiliary device such as a pump.

The liquid fuel holding part 16 has conductivity. Since the gas-liquid separation membrane 20 has an insulating property, it is strongly charged in the dry state, so that dust and impurities generated inside the fuel cell are likely to adhere to the membrane surface. The adhesion of dust and impurities to the gas-liquid separation membrane 20 may lead to deterioration of the membrane surface over the long term as well as physical fuel supply obstruction. Since the liquid fuel holding unit 16 that is in contact with the gas-liquid separation membrane 20 has conductivity, the charge of the gas-liquid separation membrane 20 in a dry state is removed, and the adhesion of impurities to the membrane surface is significantly reduced. be able to. Further, if the gas-liquid separation membrane 20 is thin, it is possible to prevent charging on the anode electrode side. The surface resistance value of the liquid fuel holding unit 16 is preferably 10 ¹² (Ω) or less. If the surface resistance value exceeds 10 ¹² (Ω), the gas-liquid separation membrane 20 may not be sufficiently charged and dust or impurities may adhere.

  The liquid fuel holding part 16 is a foam. The liquid fuel holding part 16 does not necessarily have a uniform porosity as a whole. In some cases, the supply of liquid fuel is controlled by giving a difference in the porosity between the surface and the inside depending on the concentration or application of the liquid fuel to be used. However, from the viewpoint of fuel holding, the porosity of the liquid fuel holding unit 16 as a whole is desirably 50% or more and 95% or less. When the porosity is less than 50%, it is difficult for the fuel to permeate and it may be difficult to supply the liquid fuel to the anode side. On the other hand, if it is greater than 95%, the fuel holding function is significantly impaired.

  Further, the liquid fuel holding portion 16 has a foam structure in which the pores are three-dimensionally continuous. The continuous three-dimensional pore structure has a strong fuel holding power and is preferable for temporarily holding the liquid fuel.

  Further, the pore diameter of the foam structure of the liquid fuel holding portion 16 is desirably 30 μm to 100 μm. When the hole diameter is smaller than 30 μm, it becomes difficult for the liquid fuel to penetrate the liquid fuel holding portion 16 and it becomes difficult to supply the liquid fuel to the anode side. On the other hand, if it is larger than 100 μm, the fuel retention of liquid fuel may not be sufficiently obtained.

  The liquid fuel holding part 16 is preferably a polymer body. Moreover, it is preferable that the liquid fuel holding | maintenance part 16 is a material which has an elastic force. Further, those having acid resistance are preferred in that they have resistance to formic acid generated as a by-product during the power generation reaction of the fuel cell.

  As a material for the liquid fuel holding part 16 having the above-described function, specifically, a polymer material made of polyurethane having a methanol resistance property or a crosslinked polyvinyl alcohol polymer is made of fine particles such as carbon, graphite, and metal. Examples include foamed conductive fillers and foamed conductive polymers such as polyolefins.

  The surface roughness of the liquid fuel holding portion 16 is preferably as small as possible. Since the surface contact with the surface of the gas-liquid separation membrane 20 is increased due to the small surface roughness, the gas-liquid separation membrane 20 can be more efficiently charged and removed.

  The liquid fuel holding unit 16 is grounded. Specifically, the liquid fuel holding unit 16 is connected to the ground 23 via the grounding material 22. The liquid fuel holding unit 16 can be grounded by connecting to a metal used for a housing or a component or by connecting to a short-circuit portion of an electronic device incorporating a fuel cell.

An operation during power generation of the polymer electrolyte fuel cell having the above-described configuration will be described. The liquid fuel (methanol) is supplied to the anode 6 side as follows. First, liquid fuel is supplied into the fuel tank unit 15. The liquid fuel supplied into the fuel tank unit 15 is held by the liquid fuel holding unit 16. The liquid fuel held by the liquid fuel holding unit 16 is supplied to the gas-liquid separation membrane 20. In the gas-liquid separation membrane 20, the liquid fuel is vaporized, and only the vaporized component permeates. The gas component that has passed through the gas-liquid separation membrane 20 is supplied to the anode 6. When the fuel is supplied, the reaction shown by the following reaction formula 3 occurs at the anode 6.
(Scheme 3); CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻

On the other hand, oxidant gas (air) is supplied to the cathode 7 side through the moisturizing material 21. Upon receiving the supply of the oxidant gas, the reaction shown by the following reaction formula 4 occurs at the cathode 7.
(Scheme 4); 6H ⁺ + 6e ⁻ + 3/2 O ₂ → 3H ₂ O

  The electric power generated by the power generation reaction shown in the reaction formulas 3 and 4 is taken out by the anode current collector 1 and the cathode 2 current collector.

  As described above, according to the polymer electrolyte fuel cell according to the present invention, the gas-liquid separation membrane 20 in the dry state is obtained by using the polymer foam having conductivity as the liquid fuel holding portion 16. Can be removed. Since the charge of the gas-liquid separation membrane 20 is removed, impurities and dust do not adhere to the gas-liquid separation membrane 20. Therefore, the supply of fuel through the gas-liquid separation membrane 20 is not hindered by impurities and dust. That is, even when the gas-liquid separation membrane 20 is dried and the fuel is supplied to cause the power generation reaction, the power generation reaction can be caused smoothly. Further, alteration of the gas-liquid separation membrane 20 due to the reaction of impurities and dust with the gas-liquid separation membrane 20 is also prevented.

Example 1
Hereinafter, the polymer electrolyte fuel cell of the present invention will be specifically described by showing the results of experiments conducted by the present inventors.

A single cell fuel cell having the structure shown in FIG. 1 was produced by the following procedure. First, catalyst-supported carbon fine particles prepared by supporting 55% by weight of platinum fine particles having a particle diameter in the range of 3 to 5 nm on carbon particles (Ketjen Black EC600JD manufactured by Lion Corporation) were prepared. An appropriate amount of a 5 wt% Nafion solution (trade name; DE521, “Nafion” is a registered trademark of DuPont) manufactured by DuPont was added to 1 g and stirred to obtain a catalyst paste for forming the cathode 7. This catalyst paste was applied in an amount of 1 to 8 mg / cm ² on carbon paper (TGP-H-120 manufactured by Toray Industries, Inc.) as a base material, and then dried to produce a 4 cm × 4 cm cathode 7. On the other hand, the catalyst paste for forming the cathode 7 except that platinum (Pt) -ruthenium (Ru) alloy fine particles (Ru ratio is 60 at%) having a particle diameter in the range of 3 to 5 nm are used instead of the platinum fine particles. A catalyst paste for forming the anode 6 was obtained under the same conditions as for obtaining the above. An anode electrode 6 was produced under the same conditions as the cathode 7 except that this catalyst paste was used.

  Next, an 8 cm × 8 cm × 180 μm thick membrane made of Nafion 117 manufactured by DuPont was used as the solid polymer electrolyte membrane 5, and the cathode 5 was placed on one side in the thickness direction of the membrane with the carbon paper outside. The anode 6 was placed on the other surface in the orientation in which the carbon paper was on the outside, and hot-pressed from the outside of each carbon paper. As a result, the cathode 7 and the anode 6 were joined to the solid polymer electrolyte membrane 5 to obtain MEA 3 (electrode-electrolyte membrane assembly).

Next, on the cathode 7 and the anode 6, a collector electrode (anode current collector 1, cathode) made of a stainless steel (SUS316) made of a rectangular frame having an outer dimension of 6 cm ² , a thickness of 1 mm, and a width of 11 mm. A current collector 2) was arranged. Further, between the solid polymer electrolyte membrane 5 and the current collecting electrode (the anode current collector 1 and the cathode current collector 2), the insulating and sealing material 11 is made of silicon rubber (outside dimension 6 cm ² , thickness 0.2 mm). A rectangular frame with a width of 10 mm). Here, the silicon rubber on the anode current collector 1 side was provided with a total of eight incisions having a width of 2 mm, two on each side of the frame, as vents for discharging carbon dioxide (CO ₂ gas outlet 14).

Next, as a fluorine-based porous membrane to be the gas-liquid separation membrane 20, a PTFE (polytetrafluoroethylene) porous membrane having a thickness of 25 μm, a pore diameter of 1 μm, and a porosity of 85% and made of PP (polypropylene), an outer dimension of 6 cm ² , A fuel tank 15 provided on a frame having a height of 8 mm, an inner dimension of 44 mm ² and a depth of 3 mm was also prepared.

Next, as a conductive polymer foam used for the liquid fuel holding unit 16, a conductive polyurethane continuous foam (surface resistance 106Ω, porosity 85%, pore diameter 50um) made of polyurethane and carbon filler is 4cm ² and thickness 3mm. Prepared by molding. This was assembled in the fuel tank 15. Finally, the PTFE membrane, the conductive urethane continuous foam, and the fuel tank 15 were arranged in this order on the anode current collector 1 side.

  The fuel tank 15 is provided with a fuel inlet / outlet (not shown), and an external fuel container (not shown) in which 300 ml of 15 vol% methanol aqueous solution is placed and a diagram pump (not shown) are connected to a silicon tube (not shown). ).

  Further, in order to short-circuit the liquid fuel holding part 16 with the outside, a hole of Φ5 mm is provided on the side surface of the fuel tank 15, and a stainless steel screw (not shown) is disposed so as to contact the fuel holding part 15. . The screw hole is sealed with an O-ring so that liquid fuel does not leak. The screw was arranged to be grounded.

On the other hand, a moisturizing material 11 made of a fiber mat was provided above the cathode 7. This moisturizing material 21 functions as a moisturizing layer, and a cellulose fiber sheet processed into a 35 mm square is placed on the cathode 7, and further, as a heat retaining material, the outer dimensions are 6 cm ² , the thickness is 0.5 mm, and the hole diameter is 3 mm. A perforated plate having an aperture ratio of 20% was placed on the cathode current collector 2.

  Among these members, the whole except the moisturizing material 21 was screwed and integrated. A screw (not shown) used at this time was a resin screw to prevent electrical leakage. Thus, the polymer electrolyte fuel cell in which the MEA 3, the cathode current collector 2, the anode current collector 1, the sealing material 11, the gas-liquid separation membrane 20, and the liquid fuel holding unit 16 are integrated and has the cross-sectional structure shown in FIG. 10 was obtained.

The polymer electrolyte fuel cell 10 was subjected to power generation for 100 hours under a load of 60 mA / cm ² , then the liquid fuel was removed, and the polymer electrolyte fuel cell 10 was dried in an oven at 40 ° C. for 24 hours. Next, liquid fuel was supplied from the dry-up state in which the gas-liquid separation membrane 20 was dried and circulated for 10 minutes, and then the power generation characteristics of the fuel cells were confirmed again with a load of 60 mA / cm ² . FIG. 2 is a graph showing the time variation of power generation at that time, which is indicated by reference numeral 32.

  As shown in FIG. 2, it can be seen that the fuel is supplied, the MEA 3 is moistened, the output is increased, and thereafter a high voltage is stably obtained. Further, the amount of consumption estimated from the amount of decrease per unit time of fuel was 0.5 g / h, and the liquid fuel fuel was ideally vaporized and supplied to the anode 6. Thus, when the conductive polyurethane foam was used for the fuel holding portion, stable fuel supply and power generation characteristics were obtained. Furthermore, when the fuel cell was disassembled after power generation, the gas-liquid separation membrane 20 had little adhesion of impurities and the like, and the membrane surface was almost 100% usable.

(Comparative Example 1)
Next, as Comparative Example 1, the fuel holding portion of Example 1 has a resistance of 10 ¹⁵ (Ω) and a normal polyurethane continuous foam having no conductivity is used to generate power in the same procedure as in Example 1. The characteristics were confirmed. The result is shown in FIG. 2 with reference numeral 31 superimposed on Example 1. As can be seen from FIG. 2, in Comparative Example 1, the voltage was low from the beginning, and the voltage decreased with time. After decomposition, more precipitates were confirmed on the gas-liquid separation membrane surface than in Example 1, and only 70% of the membrane surface was available. Here, a large amount of precipitates are mainly found on the surface of the film facing the anode electrode side, and carbon is the main component from fluorescent X-ray analysis. Conceivable.

  Thus, when the results of Comparative Example 1 are combined, in this example, the use of a polymer foam having conductivity for the liquid fuel holding portion 16 can prevent adhesion of impurities, and as a result, stable power generation can be realized. It was confirmed.

It is a schematic cross section which shows an example of the cell structure of the polymer electrolyte fuel cell of this invention. 4 is a graph showing time-voltage characteristics of fuel cells shown in Example 1 and Comparative Example 1.

Explanation of symbols

1 Anode current collector 2 Cathode current collector 3 MEA
5 the solid polymer electrolyte membrane 6 anode 7 cathode 10 solid polymer electrolyte fuel cell 11 insulating and sealing material 14 CO ₂ gas exhaust port 15 the fuel tank 16 the liquid fuel holding portion 20 gas-liquid separation membrane 21 moisturizing material 22 grounding distribution member 23 Earth 31 Comparative Example 1
32 Example 1

Claims (7)

A solid polymer electrolyte membrane;
A cathode disposed in contact with one surface of the solid polymer electrolyte membrane;
An anode disposed in contact with the other surface of the solid polymer electrolyte membrane;
A liquid fuel holding unit that temporarily holds the fuel supplied to the anode in a liquid state;
A gas-liquid separation membrane that is disposed between the liquid fuel holding unit and the anode, and selectively supplies only the gaseous component of the fuel to the anode;
Comprising
The gas-liquid separation membrane and the liquid fuel holding unit are in contact with each other,
The liquid fuel holding unit has conductivity and is grounded . The polymer electrolyte fuel cell according to claim 1,
A solid polymer fuel cell in which the liquid fuel holding portion has a surface resistance value greater than 0 (Ω) and 10 ¹² (Ω) or less. A polymer electrolyte fuel cell according to claim 1 or 2,
The liquid fuel holding part is a polymer electrolyte fuel cell which is a polymer foam. The polymer electrolyte fuel cell according to claim 3,
The liquid fuel holding part is a polymer electrolyte fuel cell having a porosity of 50% or more and 95% or less. The polymer electrolyte fuel cell according to claim 3 or 4, wherein
The liquid fuel holding part is a polymer electrolyte fuel cell having a continuous three-dimensional pore structure. A polymer electrolyte fuel cell according to any one of claims 1 to 5,
The liquid fuel holding unit is a solid polymer fuel cell in which the entire surface is in close contact with the gas-liquid separation membrane. A polymer electrolyte fuel cell according to any one of claims 1 to 6 ,
The liquid fuel holding part is a polymer electrolyte fuel cell that is an elastic body.

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