JP5130691B2 - Fuel cell module structure - Google Patents

Description

  The present invention relates to a fuel cell that includes an anode, an electrolyte membrane, a cathode, and a diffusion layer, in which fuel is oxidized at the anode and oxygen is reduced at the cathode. The present invention also relates to a power generation device including such a fuel cell, a small portable power source, and an electric device or electronic device using such a power source.

  Advances in electronic technology have led to a rapid spread of electronic devices such as telephones, book-type personal computers, audio / visual devices, or mobile information terminal devices, electronic devices, and miniaturized portable electronic devices. Yes.

  Conventionally, such portable electronic devices have been driven by primary batteries or secondary batteries. In secondary batteries, new secondary batteries have been developed from sealed lead batteries to Ni / Cd batteries, Ni / hydrogen batteries, and further to Li-ion batteries, and have been developed by miniaturization / lightening and high energy density technologies. However, secondary batteries must be charged after using a certain amount of power, and charging equipment and charging time are required, so many problems remain in long-term continuous driving of portable electronic devices. Yes. In the future, portable electronic devices are moving toward a direction that requires a power source with a higher energy density, that is, a power source with a long continuous use time, corresponding to the increasing amount of information and its speed, and a small size that does not require charging. The need for generators (micro generators) is increasing.

  A fuel cell power supply has been proposed as a response to such a demand. A fuel cell converts chemical energy of fuel directly into electric energy electrochemically. It does not require a power unit using an internal combustion engine such as a normal engine generator, and has the potential as a small power generation device. In addition, since fuel cells can continue to generate electricity just by refueling, it is not necessary to stop the driving of portable electronic devices that are in use for charging as seen in conventional secondary batteries. And can.

Among such fuel cells, a polymer electrolyte fuel cell that generates power by oxidizing hydrogen gas at the anode and reducing oxygen at the cathode using a perfluorocarbon sulfonic acid electrolyte membrane
(PEFC: Polymer Electrolyte Fuel Cell) is known as a battery having a high output density.

  In order to further reduce the size of this fuel cell, for example, as shown in Patent Document 1, a cylindrical battery assembly in which an anode and a cathode electrode are attached to the inner surface and outer surface of a hollow fiber electrolyte is provided inside and outside the cylinder. A small PEFC power generator that supplies hydrogen gas and air has been proposed.

  However, when applied to a power source of a portable electronic device, since the fuel is hydrogen gas, the volumetric energy density is low and the volume of the fuel tank needs to be increased.

  In addition, this system requires auxiliary equipment such as a device that sends fuel gas and oxidant gas (such as air) to the power generation device, and a device that humidifies the electrolyte membrane to maintain battery performance, making the power generation system complex. The configuration is not sufficient to reduce the size of the power supply.

  In order to increase the volumetric energy density of the fuel, it is effective to use a liquid fuel and to have a simple configuration that eliminates an auxiliary device that supplies fuel, an oxidant, and the like to the battery, and several proposals have been made. As a recent example, a direct methanol fuel cell (DMFC) using methanol and water as fuels as shown in Patent Documents 2 and 3 has been proposed.

JP-A-9-223507 JP 2000-268835 A JP 2000-268836 A

In general, a polymer electrolyte fuel cell mainly has a structure in which a supported carbon layer (hereinafter simply referred to as an electrode catalyst layer) supporting a catalytic metal serving as an anode and a cathode is disposed on both sides of a solid polymer electrolyte membrane. The electrode / solid polymer electrolyte membrane assembly (MEA:
Membrane Electrode Assembly). Here, a diffusion layer is disposed on the surface of the anode and cathode opposite to the solid polymer electrolyte membrane in order to smoothly diffuse hydrogen, methanol, air, and oxygen as fuel.

  Further, a current collecting plate for collecting current and a fastening plate for fastening the MEA, the diffusion layer, and the current collecting plate are arranged on the outer side. Here, the clamping plate on the anode side functions as a methanol tank that holds methanol and supplies methanol to the anode.

  For example, in a fuel cell using a methanol aqueous solution as a fuel, power is generated in such a manner that the chemical energy possessed by methanol is directly converted into electrical energy by the following electrochemical reaction. On the anode electrode side, the supplied aqueous methanol solution reacts according to the equation (1) and dissociates into carbon dioxide, hydrogen ions, and electrons.

CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
The generated hydrogen ions move in the electrolyte membrane from the anode to the cathode side, and react with oxygen gas diffused from the air on the cathode electrode and electrons on the electrode according to the formula (2) to generate water.

6H ⁺ + 3 / 2O ₂ + 6e ⁻ → 3H ₂ O (2)
Therefore, as shown in the formula (3), the total chemical reaction associated with the power generation is that methanol is oxidized by oxygen to generate carbon dioxide gas and water, and the chemical reaction formula is the same as that of the flame combustion of methanol.

CH ₃ OH + 3 / 2O ₂ → CO ₂ + 3H ₂ O (3)
Therefore, in DMFC, it is necessary to smoothly diffuse and permeate methanol and oxygen into the anode and cathode. However, the water generated at the cathode by the power generation reaction stays in the cathode diffusion layer, on the surface, and in the slits of the current collector plate and clamping plate, thereby preventing oxygen diffusion and permeation. As a result, there is a problem that the cell voltage and output density of the DMFC are lowered and the cell life is shortened. Therefore, it is necessary to efficiently discharge the water generated at the cathode.

  An object of the present invention is to provide a high-performance and long-life fuel cell that prevents stagnation of water produced at the cathode by a power generation reaction.

  The PEFC and the DMFC having a relatively large output perform the supply of oxygen on the cathode side by sending air with a fan or a blower. At this time, by supplying an excessive amount of air to the cathode, the generated water discharged from the diffusion layer of the cathode can be conveyed or evaporated to be carried out.

  However, in a DMFC with an output of about several watts, the power generation efficiency of the battery system as a whole is drastically reduced if power for operating auxiliary machines such as fans and blowers is supplied from the output of the battery. For this reason, a DMFC with a small output employs a system that eliminates fans, blowers, and the like for supplying air to the cathode and generates power only by natural diffusion.

  In such a system, the generated water cannot be treated by supplying an excessive amount of air to the cathode as described above.

  Therefore, in the present invention, the surfaces of the current collector plate and the clamping plate on the cathode side are subjected to a hydrophilic treatment, and the generated water from the cathode is transferred from the cathode side diffusion layer to the outer surface of the fuel cell through the current collector plate and the clamping plate. Remove.

  In addition, the outer surface of the fuel cell is also subjected to a hydrophilization treatment, and the amount of water generated is increased by moving the water generated from the cathode to the fuel cell outer surface to increase the water evaporation area.

  Furthermore, the fuel cell power generation system casing connected from the outer surface of the fuel cell is also subjected to a hydrophilic treatment, and the water generated from the cathode is moved and deployed on the surface of the fuel cell power generation system casing to increase the water evaporation area. As a result, the evaporation amount of the generated water is increased.

  At this time, it is desirable that the contact angle with the water of the part which performed the hydrophilic treatment is 50 degrees or less.

  Moreover, in order to facilitate the movement of water from the outer surface of the fuel cell to the fuel cell power generation system casing, it is desirable to install a water-retaining substrate at these connecting portions.

  The amount of water produced at the cathode is increased by applying hydrophilic treatment to the outer surface of the fuel cell and the fuel cell power generation system casing power generation, and increasing the amount of water produced by increasing the evaporation area of water produced at the cathode. This prevents the water from staying in the cathode, improves the cell voltage and output density, and increases the cell life.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an example of the fuel cell of this embodiment. In FIG. 1, 1 is a clamping plate, 2 is a current collecting plate, and 3 is a gasket. FIG. 2 shows an example of a cross section of the fuel cell of this embodiment. In FIG. 2, 4 is a solid polymer electrolyte membrane, 5 is an anode, 6 is a cathode, 7a is an anode diffusion layer, and 7c is a cathode diffusion layer.

  The anode 5 and the cathode 6 formed (joined) on the solid polymer electrolyte membrane 4 and integrated are referred to as an electrode / solid polymer electrolyte membrane assembly (MEA).

  The clamping plate 1 is smooth so that the surface pressure is uniformly applied when the fuel cell is assembled, and the current collector plate 2 and the outside are insulated so as not to be short-circuited with each other. There is no particular limitation. High-density vinyl chloride, high-density polyethylene, high-density polypropylene, epoxy resin, polyether ether ketones, polyether sulfones, polycarbonate, or a fiber reinforced with glass fibers may be used. In addition, carbon plate, steel, nickel, other lightweight alloy materials such as aluminum and magnesium, or intermetallic compounds such as copper-aluminum and various stainless steels, and methods to make the surface nonconductive A method of applying insulation to insulate can be used. Also, the cathode side clamping plate needs to be perforated so that sufficient oxygen is supplied to the air electrode. The opening ratio of this hole is usually 50%, but it is sufficient that the opening efficiency is 20% or more so that oxygen is sufficiently supplied to the air electrode. Moreover, since the intensity | strength of a power generation panel will become weak when it becomes 80% or more, 80% or less is desirable.

  The current collector plate 2 is made of a gold-plated titanium plate, but may be any material that has conductivity and is not easily corroded by an aqueous methanol solution. Alternatively, a composite material such as a clad of carbon metal, stainless steel, copper, nickel, or the like can be used with these metal-based materials. In addition, in metal-based current collector plates, the current-carrying contact portions of the processed current collector plates can be plated with corrosion-resistant noble metals such as gold, or conductive carbon paint can be applied to reduce the contact resistance during mounting. Is effective in improving battery power density and ensuring long-term performance stability. Further, when a resin material is used for the fastening plate 1, it is also possible to perform integral molding with the current collector plate 2 in order to improve the strength of the fastening plate. Also, the cathode side clamping plate needs to be perforated so that sufficient oxygen is supplied to the air electrode. The opening ratio of this hole is usually 50%, but it is sufficient that the opening efficiency is 20% or more so that oxygen is sufficiently supplied to the air electrode. Moreover, since the intensity | strength of a power generation panel will become weak when it becomes 80% or more, 80% or less is desirable.

  The gasket 3 may be any material that has insulating properties, has little permeation of hydrogen and methanol, and can maintain confidentiality. Examples thereof include butyl rubber, viton rubber, and ethylene propylene diene terpolymer (EPDM) rubber.

  When a hydrogen ion conductive material is used for the solid polymer electrolyte membrane 4, a stable fuel cell can be realized without being affected by carbon dioxide in the atmosphere. As such materials, carbonization of sulfonated fluoropolymers such as polyperfluorostyrene sulfonic acid and perfluorocarbon sulfonic acid, polystyrene sulfonic acid, sulfonated polyether sulfones, sulfonated polyether ether ketones, etc. A material obtained by sulfonating a hydrogen-based polymer or a material obtained by alkylating a hydrocarbon-based polymer can be used. If these materials are used as the electrolyte membrane, the fuel cell can generally be operated at a temperature of 80 ° C. or lower. In addition, by using a composite electrolyte membrane or the like in which hydrogen ion conductive inorganic substances such as tungsten oxide hydrate, zirconium oxide hydrate, tin oxide hydrate and the like are micro-dispersed in a heat resistant resin or a sulfonated resin, A fuel cell that operates to a higher temperature range may also be used. In particular, sulfonated polyether sulphones, polyether ether sulphones, or composite electrolytes using hydrogen ion conductive inorganic substances are preferable as electrolyte membranes having lower methanol permeability of fuel than polyperfluorocarbon sulphonic acids. In any case, if an electrolyte membrane with high hydrogen ion conductivity and low methanol permeability is used, the power generation utilization rate of the fuel increases, so that the high performance and long-time power generation, which are the effects of this embodiment, are achieved at a higher level. be able to.

  For the diffusion layer 7, a material that can achieve both diffusion of gas and liquid and electronic conductivity, such as water-repellent carbon paper, carbon cloth, or metal porous body is used.

  The hydrophilization treatment layer 8 needs to hydrophilize only a part of each member of the fuel cell. That is, if the terminals of the current collector plate are made hydrophilic, there is a possibility of short-circuiting. Therefore, it is better not to make these parts hydrophilic.

The formation of the member hydrophilic layer is composed of the following three steps. (1) Mask formation. (2) Hydrophilization treatment. (3) Mask removal.
(1) Mask molding Mask the part that does not need to be hydrophilized. In simple terms, masking is performed with masking tape or a seal. Further, the printing method is suitable when a large amount of material is processed or when fine position control is required. As a printing method, there are a method of printing a mask agent and a method of stencil printing a mask agent by putting a member of a fuel cell in a printing machine or an ink jet printer instead of paper. Since it is necessary to remove the masking agent after the hydrophilic treatment, those that are easily soluble in water or an organic solvent and can be easily removed are suitable. Moreover, it is more suitable if the waste liquid generated when the mask agent is removed has a low environmental impact. For example, masking agents that dissolve in organic solvents include offset printing inks or laser printer toners. However, the mask method is preferably an office or home inkjet printer using water-soluble ink. This is because the ink for the printer is easily soluble in water, has a high positional accuracy of discharge, and is easy to dispose of waste liquid.
(2) Hydrophilization treatment Metal, plastic, glass, etc. are used for each member of the fuel cell. These hydrophilic treatment methods will be described.
1) Method applied when the substrate is a metal When the substrate is a metal, the contact angle with water is often 70 ° or more. In the case of aluminum, the contact angle with water is about 90 to 95 °. Stainless steel has a contact angle with water of about 70 to 95 ° although it depends on the type. When these are made hydrophilic, the contact angle can be lowered by immersing them in hydrochloric acid, nitric acid, sulfuric acid or the like. In the case of aluminum, the contact angle decreases to about 10 to 20 ° when immersed in a mixed solution of 30% by weight nitric acid and 5% by weight hydrochloric acid for about 5 to 10 minutes. Also in the case of stainless steel, SUS304, 316, etc., when immersed in 30% by weight nitric acid for about 5 to 10 minutes, the contact angle decreases to about 10 to 20 °. In addition, when Fe-42Ni is immersed in 15% by weight of nitric acid for about 1 to 2 minutes, the contact angle decreases to 10 ° or less.

Other methods include a method of treating with oxygen plasma. With an oxygen partial pressure of 1 Torr, a high frequency power output of 300 W, and a treatment time of 3 minutes, the contact angle of aluminum and stainless steel with water was 20 ° or less.
2) Method applied when the substrate is glass or quartz When the substrate is glass or quartz, hydrophilicity can be improved by methods such as treatment with oxygen plasma or immersion in a basic solution. is there. In the case of oxygen plasma, the oxygen partial pressure was 1 Torr, the output of the high-frequency power source was 300 W, and the contact angle with water was 10 ° or less after a treatment time of 3 minutes. When a 1% by weight aqueous solution of sodium hydroxide was used as the basic solution, the contact angle with water became 20 ° or less after immersion for 5 minutes.
3) Method applied when the substrate is a resin When the substrate is a resin, the hydrophilicity can be improved by a method such as treatment with oxygen plasma or immersion in an acid / basic solution.

  When oxygen plasma is used, for example, polystyrene, acrylic resin, styrene / acrylic resin, polyester resin, acetal resin, polycarbonate, polyethersulfone, polysulfone, polyethersulfone, etc., oxygen partial pressure 1 Torr, high-frequency power output 100 W, processing The contact angle with water became 20 ° or less under conditions of 1 minute.

The immersion in a basic solution is particularly effective in the case of a material having an ester bond in the molecule such as an acrylic resin, a styrene / acrylic resin, a polyester resin, an acetal resin, or a polycarbonate. This is because the hydrophilicity of the surface is generally enhanced by the formation of a highly hydrophilic carboxylate residue and / or hydroxyl group by cleaving the ester bond in the surface and its vicinity. In addition, in the case of a resin that is polymerized by condensation of amino groups and carboxyl groups such as polyimide and polyamide, the amino group that does not react during polymerization by dipping in an acid such as hydrochloric acid has a highly hydrophilic ammonium salt structure, By immersing in an aqueous sodium hydroxide solution, the remaining carboxyl groups that remain unreacted during polymerization are converted into highly hydrophilic carboxylates, so that the hydrophilicity of the surface can be enhanced as a whole. In soaking in an acid / basic solution, as the temperature of the solution increases, hydrophilicity with a higher concentration tends to proceed more rapidly. However, care should be taken because high temperatures and high concentrations tend to damage the substrate.
4) Method applied to various base materials Examples of the hydrophilization method that can be processed even if the base material is a metal, glass, or resin include a method of applying a paint that exhibits hydrophilicity. These materials generally include those shown in a) to d), but other than these, there is no particular limitation. A general method other than paint is shown in e).
a) Solution of water-soluble polymer material Examples of the water-soluble polymer include polyethylene glycol, polyvinyl alcohol, polyacrylic acid, polyacrylate, polyallylamine, polyallylamine hydrochloride, starch and the like. Those having a hydrophilic residue such as a hydroxyl group, an amino group, a carboxyl group, or a salt structure residue in the molecule. These aqueous solutions or organic solvent solutions are prepared as coatings. This is applied to the base material of the cell and dried to form a hydrophilic coating film. Among these water-soluble polymers, there is a strong tendency to reduce the contact angle of the surface coated with polyethylene glycol. The higher the molecular weight, the higher the molecular weight, so that a smooth hydrophilic film with less light scattering can be formed. Further, when the surface to be treated has high water repellency, the paint is repelled, and as a result, a flat film cannot be formed. This is because when the solvent is water, the surface tension of the polymer solution used increases. Therefore, if an oxygen plasma treatment is performed in advance before applying these paints, a flat coating film is easily formed. By the way, polyethylene glycol is dissolved in an organic solvent such as tetrahydrofuran. For this reason, the surface tension of this solution is smaller than that of the same aqueous solution of polyethylene glycol, and it can be easily applied to the surface of aluminum or the like having high water repellency.
b) Paint containing hydrophilic particles A mixture of a dispersion containing hydrophilic alumina particles or hydrophilic silica particles and an alkoxysilane solution is used as a paint. When this paint is used, film formation is completed by heating after application to the cell substrate. It is hydrophilic alumina particles and hydrophilic silica particles that mainly exhibit hydrophilicity in this paint, and alkoxysilane mainly functions as a support for these particles. Therefore, increasing hydrophilicity can be dealt with by increasing the proportion of hydrophilic alumina particles or hydrophilic silica particles. In addition, increasing the proportion of alkoxysilane improves the physical strength of the film. It is preferable that the alkoxysilane is crosslinked to some extent between molecules because the rate of volatilization by heating after coating decreases. In addition, hydrochloric acid or the like may be added to the alkoxysilane to promote intermolecular polymerization, but in the case of hydrophilic silica, the dispersion may be basic in order to improve the dispersion. Therefore, when both are mixed, the hydrophilic silica may agglomerate. Therefore, attention should be paid to the liquid state and the dispersion of the hydrophilic silica when mixed. In this respect, in the case of alumina, the dispersion is mainly acidic, so there are few troubles during mixing. Examples of the alkoxysilane include methyltrimethoxysilane, ethyltrimethoxysilane, butyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, tetramethoxysilane, and tetraethoxysilane. Note that alkoxy titanium may be used instead of alkoxy silane as long as the liquidity and the solvent match. Examples of the alkoxytitanium include tetra-i-propyl titanate, tetra-n-butyl titanate, tetrastearyl titanate, triethanolamine titanate, titanium acetylacetonate, titanium ethyl acetoacetate, titanium lactate, and tetraoctylene glycol titanate. Further, those obtained by polymerizing several compounds of these compounds can also be used.
c) A paint containing a water-soluble polymer and a crosslinking agent thereof A paint which forms a hydrophilic surface by mixing the water-soluble polymer mentioned in a) with the alkoxysilane or alkoxytitanium listed in b) as a crosslinking agent It is also possible to do. In this case, the solvent may be water, but if the substrate has high water repellency, the paint will be repelled, and therefore alcohol solvents such as methanol and ethanol are preferred.
d) Combined use of alkoxysilane solution and alkali solution After applying the alkoxysilane solution mentioned in b) to the substrate and heating at about 120 to 180 ° C. for several minutes, a silicon oxide film is formed on the surface of the substrate. Subsequent immersion in an alkaline solution increases the hydrophilicity of the surface. Finally, the hydrophilic treatment is completed by washing the alkaline solution with water. As the alkaline solution, an aqueous solution of hydroxide such as sodium hydroxide or potassium hydroxide, an alcohol solution, or a hydrous alcohol solution is used. The higher the concentration, the shorter the immersion time, but it depends on the type of hydroxide used. When sodium hydroxide is used, the immersion time is preferably 1 to 5 minutes at a solution concentration of 1% by weight and about 10 to 30 seconds at 5% by weight. As a solvent used in the alkoxysilane solution, a ketone solvent (acetone, methyl ethyl ketone, etc.) is preferably an alcohol solvent, an ester solvent, or an ether solvent because the alkoxysilane is easily changed to silicon dioxide. In particular, the alcohol type is particularly suitable when the base material is a resin because it is difficult to dissolve the resin.
e) Supplement: Methods other than paint The surface of a substrate such as metal, glass / quartz or resin, which can be considered as a substrate material, can be made hydrophilic by irradiating it with ultraviolet light or leaving it in an ozone atmosphere.

The amount of UV irradiation, ozone treatment time and concentration vary depending on the substrate material.
(3) Mask removal The mask is removed after the hydrophilic treatment. The mask is removed by a method such as washing the substrate with a solvent in which the mask dissolves, dissolving and sucking the mask by heating, and peeling off the mask.

  Thus, the fuel cell structure of the present embodiment can be realized by applying hydrophilic treatment to each member of the fuel cell.

  The present embodiment will be described in detail below, but the scope of the present embodiment is not limited to the embodiment disclosed herein.

Example 1
The fastening plate 1 was masked with a masking tape so that the hydrophilization solution did not come into contact with the portion in contact with the current collector plate 2 and the portion where the methanol solution stayed. Here, the portion where methanol stays is inside the methanol tank 11. The current collector plate 2 was masked with a masking tape so that only the cathode-side current collector plate 2 would not be in contact with the hydrophilic treatment solution at the portion other than the opening that leads to the diffusion layer 7. The gasket 3 was masked with a masking tape so that the hydrophilization solution did not contact the portion in contact with the current collector plate 2 and the portion in contact with the MEA and the diffusion layer 7.

  Glycidyl group-terminated silane coupling agent (S-510 manufactured by Chisso) (1 part by weight), 20% by weight dispersion of hydrophilic alumina (Nissan Chemical No. 520) (20 parts by weight), and ethanol (250 (Part by weight) is prepared. This solution was applied to the portions of the fastening plate 1, the cathode side current collector plate 2, and the gasket 3 that did not form the mask, constituting the fuel cell. After the application, it was heated at 100 ° C. for 3 hours. Thus, a film holding hydrophilic alumina is formed on the surface of each member. The contact angle of this membrane with water was 10 ° or less.

  The mask was removed by peeling off the masking tape.

The anode 5 uses an electrode catalyst in which platinum and ruthenium are supported on carbon black at a 1: 1 atomic ratio and a platinum loading amount of 50 wt%, and the cathode 6 uses an electrode catalyst in which platinum is supported on carbon black at 50 wt%. NaPoion (registered trademark) of DuPont was dissolved in the electrode catalyst
A Nafion solution (concentration 5 wt%, manufactured by Aldrich) was combined at a ratio of 1: 9 by weight of the electrode catalyst and Nafion solution, and mixed while volatilizing the solvent to prepare a viscous electrode catalyst slurry. .

This electrode catalyst slurry was applied to a tetrafluoroethylene sheet by screen printing, and the solvent of the electrode catalyst slurry was dried to form a catalyst layer. The amount of platinum in the catalyst layer was 5 mg / cm ² per unit area for the anode 5 and 2 mg / cm ² per unit area for the cathode 6.

  The catalyst layer described above was used as a solid polymer electrolyte membrane 4 from a DuPont Nafion membrane (Nafion 112 (registered trademark), thickness 50 μm), and both sides thereof were pressure-bonded by hot pressing to produce an MEA.

  The cathode diffusion layer 7c is composed of a water-repellent porous carbon substrate for enhancing water repellency, increasing the water vapor pressure in the vicinity of the cathode, and preventing diffusion exhaust of generated water vapor and aggregation of water. A conductive and porous material is used for the porous carbon substrate of the cathode diffusion layer 7c. In general, carbon fiber woven fabric or non-woven fabric, for example, carbon fiber woven fabric (carbon fiber (Torayca cloth: Toray) or carbon paper (Toray: TGP-H-060)) is used for water repellency. Water repellent fine particles, water repellent fibrils or water repellent fibers such as polytetrafluoroethylene are used.

  The water repellency of the porous carbon substrate will be described in more detail. A carbon paper (manufactured by Toray: TGP-H-060) is cut into a predetermined size, the water absorption amount is obtained in advance, and then the carbon paper is baked. It is immersed in a polytetrafluorocarbon / water dispersion diluted to a weight ratio of 20 to 60 wt% (D-1: manufactured by Daikin Industries, Ltd.), dried at 120 ° C. for about 1 hour, and further 270 to 270 in air. A baking operation is performed at a temperature of 360 ° C. for 0.5 to 1 hour.

  The air permeability and moisture permeability of the cathode diffusion layer 7c, that is, the diffusibility of supplied oxygen and generated water largely depends on the amount of polytetrafluoroethylene added, dispersibility, and baking temperature, so the design performance and operating environment of the fuel cell Appropriate conditions are selected in consideration of such factors.

  The anode diffusion layer 7a is a carbon fiber woven or non-woven fabric that satisfies the requirements of electrical conductivity and porosity. For example, as the carbon fiber woven fabric, carbon cloth (Toray Cross: manufactured by Toray) or carbon paper (Toray: TGP-H- Materials such as 060) are suitable. The function of the anode diffusion layer 70a is to promote the supply of the aqueous fuel and the rapid dissipation of the generated carbon dioxide, so that the surface of the carbon porous substrate is hydrophilized by gradual oxidation or ultraviolet irradiation. The method, the method of dispersing a hydrophilic resin on a carbon porous substrate, and the method of dispersing and supporting a highly hydrophilic substance typified by titanium oxide, etc., cause bubble growth in the carbon porous substrate generated at the anode. This is an effective method for suppressing the above and increasing the output density of the fuel cell. The anode diffusion layer 7a is not limited to the above-described materials, but is substantially made of an electrochemically inactive metal material (for example, stainless steel fiber nonwoven fabric, porous body, porous titanium, tantalum, etc.). A porous material can also be used.

  As shown above, the fastening plate 1, the current collector plate 2, the gasket 3, the MEA as the power generation material, and the diffusion layers 7a and 7c are assembled as shown in FIG. .

  When a 30 wt% aqueous methanol solution was injected into the fuel chamber of the fuel cell thus prepared and a power generation test was performed at room temperature, the water generated by the power generation flowed out from the surface of the cathode side diffusion layer 7c as time passed, It was confirmed that it spreads on the outer surface of the fuel cell through the hydrophilic portion of the wall surface of the opening of the electric plate 2 and the fastening plate 1.

  It is preferable that at least the opening of the current collector on the cathode side, the opening of the clamping plate on the cathode side, and the outer surface thereof are hydrophilized. Here, the opening refers to the edge of the hole or its wall surface. Oxygen is supplied to the cathode through a hole formed in the cathode side current collector plate and the cathode side clamping plate. On the other hand, the generated water is generated at the cathode and stays in the pores, so that oxygen does not reach the cathode. Since the opening of the cathode current collector plate and the opening of the cathode clamping plate are hydrophilized, the generated water does not stay in the hole and travels along the wall surface (opening) of the hole. Move to the outer surface. And since the outer surface of the clamping plate is also made hydrophilic, the generated water moves to the outer surface of the clamping plate, the surface area increases, and it is easy to evaporate when exposed to the outside air.

  According to this embodiment, the generated water from the cathode easily flows out from the cathode side diffusion layer to the outside of the fuel cell through the current collector plate and the clamping plate, and the retention of water at the cathode can be made difficult to occur. .

(Example 2)
In addition to the fuel cell hydrophilized in Example 1, a mask is formed on the inner side of the housing 9 surrounding the fuel cell in the same manner as in Example 1, and the hydrophilization solution is adjusted to make the mask hydrophilic, and the mask is removed. did.

  FIG. 4 shows the fuel cell system including the housing 9. When a fuel cell is installed in the housing 9, a 30 wt% aqueous methanol solution is injected into the fuel chamber of the fuel cell, and a power generation test is performed at room temperature, water generated by power generation flows out from the surface of the cathode side diffusion layer 7c with time. And spreads to the outer surface of the fuel cell through the hydrophilic portion of the wall surface of the opening of the cathode side current collector plate 2 and the clamping plate 1 and further spreads to the hydrophilic portion of the inside of the housing 9 in contact with the fuel cell. It was confirmed.

(Example 3)
A microfactory was produced in the same manner as in Example 1 except that the liquid used in the hydrophilic treatment of Example 1 had the following two compositions. The composition of the two types of liquid is as follows.

  1): A silane coupling agent having a glycidyl group at the end (S-510 manufactured by Chisso) (1 part by weight), a 20% by weight dispersion of hydrophilic alumina (No. 520 manufactured by Nissan Chemical Industries) (2 parts by weight), and A liquid mixed with ethanol (50 parts by weight).

  2): A silane coupling agent having a glycidyl group at the end (S-510 manufactured by Chisso Corporation) (1 part by weight), a 20% by weight dispersion of hydrophilic alumina (No. 520 manufactured by Nissan Chemical Industries) (5 parts by weight), and A liquid mixed with ethanol (50 parts by weight).

  Moreover, the kind of base material used is polycarbonate, glass, and SUS304. As a result, the contact angle between these substrates after hydrophilic treatment with the liquid of 1) was 32 to 34 °. When water was gradually dropped onto the surface of the substrate subjected to these hydrophilic treatments, the water spread to about 90% of the material surface. Subsequently, the contact angle of each of the base materials after the hydrophilic treatment with water using the liquid 2) was 28 to 30 °. When water was gradually dropped onto the surface of the substrate subjected to the hydrophilic treatment, the material surface was completely covered with water. This indicates that the contact angle between the hydrophilic portion and water needs to be 30 ° or less.

Example 4
When the fuel cell and the fuel cell power generation system casing 9 are subjected to hydrophilic treatment as in the second embodiment so that the cathode generation water spreads from the fuel cell to the fuel cell system casing, the fuel cell and the fuel cell power generation system casing It was confirmed that when a gap is formed between the bodies 9, the cathode generated water does not move smoothly from the fuel cell to the fuel cell system housing.

  Therefore, as shown in FIG. 5, the moisture transport base material 10 was installed so as to be in contact with the fuel cell and the fuel cell power generation system housing 9.

  The moisture transport substrate is not particularly limited as long as it exhibits a capillary action. For example, polypropylene, polyethylene, polyvinyl chloride, acrylic, aromatic polyamide, aromatic polyaramid, polysulfone, polyethersulfone, polyetherketone, polyphenylene sulfide, polyamideimide, polyurethane, polystyrene, polyester, epoxy There are organic open-cell porous bodies such as phenol and silicone, open-cell porous ceramics, metal open-cell porous bodies manufactured by a sintering method, a plating method, a foaming method, and a pressure casting method.

  In this case, it was confirmed that the cathode generated water on the outer surface of the fuel cell spreads smoothly through the moisture transport base material to the hydrophilized portion inside the fuel cell power generation system housing 9.

It is a figure which shows one Example of the fuel cell of this invention. It is sectional drawing which shows one Example of the fuel cell of this invention. It is a figure which shows one Example of the fuel cell of this invention. It is a figure which shows one Example of the fuel cell of this invention. It is a figure which shows one Example of the fuel cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fastening plate 2 Current collector plate 3 Gasket 4 Solid polymer electrolyte membrane 5 Anode 6 Cathode 7 Diffusion layer 8 Hydrophilization treatment layer 9 Case 10 Moisture transport substrate 11 Methanol tank

Claims (4)

In a fuel cell having an anode for oxidizing fuel, a cathode for reducing oxygen, and a solid polymer electrolyte sandwiched between the anode and the cathode,
The cathode with side clamping plate covering the cathode-side current collecting plate及beauty before Symbol cathode-side current collecting plate to collect the electricity from the cathode, an opening for supplying oxygen to the cathode,
A fuel cell in which openings of the cathode side current collector plate and the cathode side clamping plate and an outer surface of the cathode side clamping plate are hydrophilized. 2. The fuel cell according to claim 1 , wherein a contact angle between water and the hydrophilized surfaces of the cathode-side current collecting plate and the cathode-side clamping plate is 0 ° or more and 30 ° or less. Fuel cell power generation system in which a part or the whole of the inner wall surface of the housing is hydrophilic surrounding the fuel cell according to claim 1. 4. The fuel cell power generation system according to claim 3 , wherein the hydrophilic surface of the cathode side current collector plate and the cathode side clamping plate and the hydrophilic surface of the casing surrounding the fuel cell are connected. A fuel cell power generation system having a substrate.

Images