JP2010073608A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell with a stable and high output (power generation performance) and capable of size reduction. <P>SOLUTION: The fuel cell 1 is provided with an MEA 10 having an anode (a fuel electrode) 13, a cathode (an air electrode) 16 and an electrolyte membrane 17 pinched between them, and a fuel supply mechanism 30 arranged on an anode side of the MEA 10. Moreover, at least either the anode side or the cathode side includes a layer containing a latent heat storage material having a phase transition temperature which is higher than 35°C and lower than an operation temperature of a fuel cell 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell using liquid fuel.

  In recent years, advances in electronic technology have led to downsizing, higher performance, and portability of electronic devices. In portable electronic devices, there is an increasing demand for higher energy density of batteries used. Therefore, a secondary battery having a high capacity while being lightweight and small is required.

  Under such circumstances, small fuel cells are attracting attention in place of lithium ion secondary batteries. In particular, a direct methanol fuel cell (DMFC) uses methanol with high energy density as a fuel, and can directly extract an electric current from methanol on an electrode catalyst. Therefore, compared to a fuel cell using hydrogen gas, there is no difficulty in handling hydrogen gas, and a reformer for producing hydrogen by reforming organic fuel is unnecessary and can be downsized. Because of its high output density, it is promising as a power source for portable devices.

  The main power generation part of the DMFC is called a membrane electrode assembly (MEA), which includes a fuel electrode (anode) and an air electrode (cathode) each having a gas diffusion layer and a catalyst layer, and an anode catalyst layer. A proton conductive polymer electrolyte membrane is sandwiched between the cathode catalyst layer. The cell reaction proceeds in the catalyst layer. Specifically, the oxidative decomposition reaction of the fuel proceeds with the supply of water in the anode catalyst layer, and protons (hydrogen ions) and electrons are generated. The protons reach the cathode catalyst layer through the polymer electrolyte membrane, while the electrons pass through the external circuit and reach the cathode catalyst layer. In the cathode catalyst layer, oxygen in the supplied air reacts with the protons and electrons, and oxygen is reduced to produce water. In addition, power is supplied by electrons passing through the external circuit (see, for example, Patent Document 1).

  In the DMFC configured as described above, in order to supply water necessary for the reaction at the anode, a moisture retention layer is provided on the cathode to suppress water evaporation, and a part of the water generated in the cathode catalyst layer is provided. Is diffused to the anode side. In order to increase the output, it is considered to reduce the amount of water transpiration by increasing the thickness of the moisturizing layer and increase the amount of water diffusion from the cathode to the anode.

In addition, in order to suppress heat generation during power generation and maintain battery performance, a fuel cell has been proposed in which a member including a latent heat storage agent that reversibly absorbs heat (stores heat) is disposed on a container surface or the like (for example, , See Patent Document 2).
International Publication No. 2005/112172 Pamphlet JP 2004-186097 A

  However, the method of suppressing the transpiration of water by increasing the thickness of the moisturizing layer goes against the demand for miniaturization and portability of fuel cells, and is difficult to mount on portable electronic devices. Therefore, there is a need for a method for improving the output by generating and retaining sufficient water with MEA without increasing the thickness of the moisturizing layer. In addition, even the method described in Patent Document 2 cannot obtain a small and stable high output fuel cell.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel cell that has a stable and high output (power generation performance) and can be miniaturized.

  In order to achieve the above object, a fuel cell according to a first aspect of the present invention includes a fuel electrode (anode), an air electrode (cathode), and a proton-conducting electrolyte membrane sandwiched between the anode and the cathode. And a fuel supply mechanism for supplying fuel to the anode, the anode and the anode side outside the anode and / or the cathode and outside the cathode. It is characterized by having a layer containing a latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than an operating temperature on the cathode side.

  The fuel cell according to the second aspect of the present invention includes a fuel electrode (anode) having a fuel electrode (anode) catalyst layer, an air electrode (cathode) having an air electrode (cathode) catalyst layer, the anode catalyst layer, and the A membrane electrode assembly having a proton conductive electrolyte membrane sandwiched between the cathode catalyst layer, a fuel supply mechanism disposed outside the anode and supplying fuel to the anode catalyst layer, and outside the cathode A fuel cell comprising: a surface layer having an air inlet disposed; and a moisturizing layer disposed between the surface layer and the cathode and suppressing transpiration of water generated in the cathode catalyst layer, At least one of the cathode catalyst layer, the moisturizing layer, and the surface layer contains a latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than an operating temperature, or the latent It characterized by having a layer containing a heat storage material.

  A fuel cell according to a third aspect of the present invention includes a fuel electrode (anode) having a fuel electrode (anode) catalyst layer, an air electrode (cathode) having an air electrode (cathode) catalyst layer, the anode catalyst layer, and the A membrane electrode assembly having a proton conductive electrolyte membrane sandwiched between the cathode catalyst layer, a fuel supply mechanism disposed outside the anode and supplying fuel to the anode catalyst layer, and outside the cathode A fuel cell comprising: a surface layer having an air inlet disposed; and a moisturizing layer disposed between the surface layer and the cathode and suppressing transpiration of water generated in the cathode catalyst layer, At least one of the anode catalyst layer and the member constituting the fuel supply mechanism contains a latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than an operating temperature, or It characterized by having a layer containing a heat storage material.

  A fuel cell according to a fourth aspect of the present invention includes a fuel electrode (anode) having a fuel electrode (anode) catalyst layer, an air electrode (cathode) having an air electrode (cathode) catalyst layer, the anode catalyst layer, and the A membrane electrode assembly having a proton conductive electrolyte membrane sandwiched between the cathode catalyst layer, a fuel supply mechanism disposed outside the anode and supplying fuel to the anode catalyst layer, and outside the cathode A fuel cell comprising: a surface layer having an air inlet disposed; and a moisturizing layer disposed between the surface layer and the cathode and suppressing transpiration of water generated in the cathode catalyst layer, At least one of the cathode catalyst layer, the moisturizing layer, and the surface layer contains a latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than an operating temperature, or the latent heat storage material. A layer containing a material and at least one of the anode catalyst layer and the member constituting the fuel supply mechanism contains a latent heat storage material having the phase transition temperature, or contains the latent heat storage material It has a layer.

  According to the fuel cell of the present invention, the electrical resistance (impedance) can be lowered, and a stable high output can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of an embodiment of a fuel cell 1 according to the present invention.

  As shown in FIG. 1, the fuel cell 1 of the embodiment includes an anode 13 having an anode catalyst layer 11 and an anode gas diffusion layer 12, a cathode 16 having a cathode catalyst layer 14 and a cathode gas diffusion layer 15, and an anode. A membrane electrode assembly (MEA) 10 including a proton-conducting electrolyte membrane 17 sandwiched between the catalyst layer 11 and the cathode catalyst layer 14 is provided. In addition, an anode conductive layer 18 and a fuel supply mechanism 30 for supplying the liquid fuel F to the anode 13 (anode catalyst layer 11) are provided outside the anode 13 of the MEA 10. Furthermore, a cathode cover layer 21 having a plurality of air inlets 21 a stacked on the cathode conductive layer 19, the moisture retention layer 20, and the moisture retention layer 20 is provided outside the cathode 16 of the MEA 10. The fuel supply mechanism 30 includes a fuel distribution layer 31 having a plurality of openings 31 a provided to face the anode conductive layer 18, and a fuel supply unit main body 32 that supplies the liquid fuel F to the fuel distribution layer 31. Have.

  And at least one of the anode side and the cathode side of such a fuel cell 1 has a latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than the operating temperature of the fuel cell 1 (hereinafter referred to as a low-temperature type latent heat storage material and It has a layer containing. The anode side of the fuel cell 1 means the anode 13 and a portion outside the anode 13 (opposite to the electrolyte membrane 17), and the cathode side is outside the cathode 16 and cathode 16 (opposite the electrolyte membrane 17). Side).

  The latent heat storage material stores generated heat as latent heat, and repeats phase change of solidification and melting at a predetermined temperature (phase change temperature). In the embodiment, a low-temperature latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than the operating temperature of the fuel cell 1 (usually 40 to 55 ° C.) is used as the latent heat storage material.

  Examples of the low-temperature latent heat storage material include normal paraffins such as pentadecane, hexadecane, heptadecane, and octadecane, emulsions thereof, and materials obtained by encapsulating normal paraffins. These normal paraffin microencapsulated materials can be arbitrarily and accurately set the phase transition temperature in the temperature range above 35 ° C. and below the operating temperature of the fuel cell 1 by adjusting the molecular weight of the normal paraffin. Can do. Further, this microencapsulated latent heat storage material can be handled as an aqueous slurry having high dispersion stability or a powder from which the dispersion medium has been removed, and can be easily contained in the members constituting the fuel cell 1. There is.

  On the anode side of the fuel cell 1 of the embodiment, at least one of members constituting the anode catalyst layer 11 and the fuel supply mechanism 30 (for example, the fuel distribution layer 31 and the fuel supply unit main body 32) is a low-temperature type latent heat. It contains a heat storage material or has a layer containing a low-temperature latent heat storage material. More specifically, the anode catalyst layer 11 and the fuel distribution layer 31 contain the low-temperature latent heat storage material (for example, a material obtained by encapsulating normal paraffin) in the layers themselves. In addition, a mode in which a layer containing a low-temperature latent heat storage material (for example, a sheet formed by mixing normal paraffin microcapsules with resin) is installed on the outer peripheral surface of the fuel supply unit main body 32. . Further, a mode in which a layer of the low-temperature type latent heat storage material or a resin sheet containing the low-temperature type latent heat storage material can be arranged between the members constituting the fuel supply mechanism 30 is also possible.

  On the cathode side, at least one of the cathode catalyst layer 14, the moisture retention layer 20, and the surface cover layer 21 contains a low-temperature type latent heat storage material or has a layer containing a low-temperature type latent heat storage material. Yes. More specifically, the cathode catalyst layer 14 and the moisturizing layer 20 are configured such that these layers themselves contain a low-temperature latent heat storage material (for example, a material in which normal paraffin is microencapsulated). Moreover, the aspect which arrange | positions the layer of the said low-temperature-type latent heat storage material or the resin sheet containing a low-temperature-type latent heat storage material between the moisture retention layer 20 and the surface cover layer 21 can also be taken.

  Note that it is not necessary to provide a layer containing a low-temperature latent heat storage material on both the anode side and the cathode side of the fuel cell 1, and a layer containing a low-temperature latent heat storage material is provided on at least one side. If configured, the effect of reducing the resistance and improving the output can be obtained. In particular, it is desirable to dispose a layer containing a low-temperature latent heat storage material on the cathode 16 side.

  By providing a layer containing a low-temperature latent heat storage material on at least one of the anode side and the cathode side of the fuel cell 1, the cell resistance can be lowered and the output can be improved for the following reason.

  That is, in the fuel cell 1 provided with a layer containing a low-temperature latent heat storage material having a melting point that is a phase transition temperature lower than the operating temperature (usually 40 to 55 ° C.), at the start of operation (power generation), the MEA 10 When the temperature exceeds the phase transition temperature (melting point), the latent heat storage material absorbs heat generated from the MEA 10 and causes a phase transition (melting) from a solid to a liquid. And until this phase transition (melting) is completed, the rise in temperature of the MEA 10 is suppressed, so that the transpiration of water through the moisturizing layer 20 and the like is suppressed, and the amount of water remaining in the cathode 16 and The amount of water diffusing from the cathode 16 to the anode 13 increases. And by the increase in the amount of water in such MEA10, the cell resistance (impedance) of a fuel cell falls and an output improves.

  When the phase transition temperature (melting point) of the latent heat storage material is lower than 35 ° C., the latent heat storage material melts even when not in use when the temperature is high, such as in summer, and the latent heat storage material is The endothermic action (latent heat storage action) may not be used. Therefore, a latent heat storage material having a phase transition temperature higher than 35 ° C. is used. Moreover, since the low-temperature type latent heat storage material used in the embodiment has a phase transition temperature lower than the operating temperature of the fuel cell 1, the usable latent heat storage material varies depending on the operating temperature. That is, the latent heat storage material having a predetermined phase transition temperature (for example, 50 ° C.), when used in the fuel cell 1 whose operating temperature exceeds the phase transition temperature (50 ° C.), lowers the cell resistance and improves the output. However, the effect cannot be increased at an operating temperature not higher than the phase transition temperature (50 ° C.). Therefore, it cannot be used as a low-temperature latent heat storage material for the fuel cell 1 operated at a temperature of 50 ° C. or less.

  Examples of the catalyst contained in the anode catalyst layer 11 and the cathode catalyst layer 14 constituting the MEA 10 include a simple substance of a platinum group element such as Pt, Ru, Rh, Ir, Os, and Pd, an alloy containing the platinum group element, and the like. Is mentioned. As the anode catalyst, it is preferable to use, for example, Pt—Ru, Pt—Mo or the like having strong resistance to methanol, carbon monoxide, and the like. As the cathode catalyst, for example, Pt, Pt—Ni, Pt—Co or the like is preferably used. However, the catalyst is not limited to these, and various substances having catalytic activity can be used. The catalyst may be either a supported catalyst using a conductive support such as a carbon material or an unsupported catalyst. Such anode catalyst layer 11 and / or cathode catalyst layer 14 can contain the low-temperature latent heat storage material (for example, a material in which normal paraffin is microencapsulated).

  Examples of the proton conductive material constituting the electrolyte membrane 17 include organic materials such as fluorine resins such as perfluorosulfonic acid polymers having sulfonic acid groups, hydrocarbon resins having sulfonic acid groups, or the like. Examples thereof include inorganic materials such as tungstic acid and phosphotungstic acid. Specifically, the electrolyte membrane 17 includes Nafion (trade name, manufactured by DuPont), Flemion (trade name, manufactured by Asahi Glass Co., Ltd.), Aciplex (trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.), and the like. The proton-conducting electrolyte membrane 17 is not limited to these. For example, a copolymer membrane of a trifluorostyrene derivative, a polybenzimidazole membrane impregnated with phosphoric acid, an aromatic polyether ketone sulfonic acid membrane, Alternatively, an electrolyte membrane capable of transporting protons such as an aliphatic hydrocarbon resin membrane can be used.

  The anode gas diffusion layer 12 laminated on the anode catalyst layer 11 has a function of uniformly supplying a hydrogen-containing gas that is a fuel gas to the anode catalyst layer 11 and also has a function as a current collector of the anode catalyst layer 11. ing. The cathode gas diffusion layer 15 laminated on the cathode catalyst layer 14 has a function of uniformly supplying an oxygen-containing gas as an oxidant to the cathode catalyst layer 14 and also has a function as a current collector of the cathode catalyst layer 14. ing. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 are each made of a conductive material. A known material can be used as the conductive material, but in order to efficiently transport the raw material gas to the catalyst, it is preferable to use a porous carbon woven fabric or carbon paper. Specific forms of the anode gas diffusion layer 3 and the cathode gas diffusion layer 6 include carbon paper, carbon cloth, carbon non-woven fabric, carbon woven fabric, paper-like paper body, felt and the like.

  An anode conductive layer 18 is stacked on the anode gas diffusion layer 12 of the MEA 10 configured as described above, and a cathode conductive layer 19 is stacked on the cathode gas diffusion layer 15.

  The anode conductive layer 18 and the cathode conductive layer 19 are, for example, a porous film (for example, a mesh) or a foil body made of a conductive metal material having excellent electrical characteristics and chemical stability such as gold (Au) and nickel (Ni). Or a composite material or the like in which a conductive metal material such as stainless steel (SUS) is coated with a good conductive metal such as gold. Especially, it is preferable to be comprised with the thin film which has several opening part, and the fuel sent from the opening part 31a of the fuel distribution layer 31 is guide | induced to MEA10 through this opening part. The anode conductive layer 18 and the cathode conductive layer 19 are configured so that fuel and oxidant do not leak from their peripheral edges. Further, rubber O-rings 22 are interposed between the electrolyte membrane 17 and the anode conductive layer 18 and between the electrolyte membrane 17 and the cathode conductive layer 19, respectively, and thereby fuel leakage and oxidation from the MEA 10. Agent leakage is prevented. Here, the fuel cell 1 including the anode conductive layer 18 and the cathode conductive layer 19 is shown, but the anode gas diffusion layer 12 and the cathode gas diffusion layer are not provided without the anode conductive layer 18 and the cathode conductive layer 19. 15 may function as a conductive layer.

  A moisturizing layer 20 is laminated on the cathode conductive layer 19. The moisturizing layer 20 has a function of suppressing the transpiration of water generated in the cathode catalyst layer 14 and diffusing part of the generated water to the anode 13. The cathode gas diffusion layer 15 also functions as an auxiliary diffusion layer that uniformly introduces air as an oxidant and promotes uniform diffusion of the oxidant into the cathode catalyst layer 14. As the moisture retaining layer 20, for example, a porous polyethylene film or the like can be used. The moisturizing layer 20 can contain the low-temperature latent heat storage material (for example, a material in which normal paraffin is microencapsulated).

  On the moisturizing layer 20, a surface cover layer 21 having a plurality of air inlets 21a for taking in air as an oxidant is disposed. The surface cover layer 21 also plays a role of increasing the adhesion by pressurizing the MEA 10 and the moisturizing layer 20, and is made of a metal such as SUS304. Between the moisturizing layer 20 and the surface cover layer 21, a layer of the low-temperature type latent heat storage material (such as a coating layer) or a resin layer (sheet) containing the low-temperature type latent heat storage material can be disposed.

  A fuel supply mechanism 30 is disposed on the anode side of the MEA 10. The fuel supply mechanism 30 includes a fuel distribution layer 31 having a plurality of openings 31 a provided to face the anode conductive layer 18, and a fuel distribution layer 31 disposed on a side different from the MEA 10 side of the fuel distribution layer 31. A fuel supply main body 32 that supplies the liquid fuel F, a fuel storage portion 33, a flow path 34, and a pump 35 interposed in the flow path 34 are provided.

  The fuel storage unit 33 stores liquid fuel F corresponding to the MEA 10. Examples of the liquid fuel F include methanol fuels such as methanol aqueous solutions having various concentrations and pure methanol. The liquid fuel F is not necessarily limited to methanol fuel. For example, an organic aqueous solution containing hydrogen such as an ethanol aqueous solution, pure ethanol, propanol aqueous solution, formic acid aqueous solution, sodium formate aqueous solution, acetic acid aqueous solution, ethylene glycol aqueous solution, dimethyl ether or the like. Alternatively, a sodium borohydride aqueous solution, a potassium borohydride aqueous solution, a lithium hydride aqueous solution, or the like may be used. Among these liquid fuels F, the aqueous methanol solution is carbon dioxide generated at the time of reaction with 1 carbon, and can generate electricity at a low temperature, and is relatively easily produced from industrial waste. be able to. Therefore, it is preferable to use a methanol aqueous solution as the liquid fuel F.

  The liquid fuel F can be used in various concentrations with a fuel component concentration ranging from 100 wt% to several wt%. Particularly in the case of an aqueous methanol solution, the fuel methanol concentration is 60 wt% or more. It is desirable to use The reason is that power can be generated with a smaller volume of fuel.

  The fuel supply unit main body 32 includes a fuel supply unit 36 formed of a recess in order to uniformly supply the supplied liquid fuel F to the fuel distribution layer 31. The fuel supply unit 36 is connected to the fuel storage unit 33 via a flow path 34 formed of piping or the like. Liquid fuel F is introduced into the fuel supply unit 36 from the fuel storage unit 33 via the flow path 34, and the introduced liquid fuel F and / or the vaporized component of the liquid fuel F vaporized are the fuel distribution layer 31 and It is supplied to the MEA 10 through the anode conductive layer 18. A resin layer (sheet) containing the low-temperature latent heat storage material can be disposed on the outer periphery of the fuel supply unit main body 32.

  The flow path 34 is not limited to piping independent of the fuel supply unit 36 and the fuel storage unit 33. For example, when the fuel supply unit 36 and the fuel storage unit 33 are stacked and integrated, a flow path of the liquid fuel F that connects them may be used. In other words, the fuel supply unit 36 only needs to communicate with the fuel storage unit 33 via the flow path 34 or the like.

  A pump 35 is inserted in a part of the flow path 34, and the liquid fuel F stored in the fuel storage unit 33 is forcibly sent to the fuel supply unit 36. Instead of interposing the pump 35 in the flow path 34, the liquid fuel F stored in the fuel storage unit 33 may be dropped to the fuel supply unit 36 using gravity and fed. Alternatively, the flow path 34 may be filled with a porous body or the like, and the liquid fuel F stored in the fuel storage unit 33 may be fed to the fuel supply unit 36 by capillary action.

  The pump 35 functions as a supply pump that simply sends the liquid fuel F from the fuel storage unit 33 to the fuel supply unit 36, and functions as a circulation pump that circulates excess liquid fuel F supplied to the MEA 10. It does not have. Since the fuel cell 1 including such a pump 35 does not circulate the fuel, the configuration is different from that of the conventional active method. Also, the configuration is different from a pure passive method such as a conventional internal vaporization type, which corresponds to a so-called semi-passive type. The type of the pump 35 that functions as the fuel supply means is not particularly limited, but from the viewpoint that a small amount of liquid fuel F can be fed with good controllability, and that further reduction in size and weight is possible. It is preferable to use a vane pump, an electroosmotic flow pump, a diaphragm pump, a squeezing pump, or the like. The rotary vane pump feeds liquid by rotating wings with a motor. The electroosmotic flow pump uses a sintered porous body such as silica that causes an electroosmotic flow phenomenon. A diaphragm pump drives a diaphragm with an electromagnet or piezoelectric ceramics to send liquid. The squeezing pump presses a part of a flexible fuel flow path and squeezes the fuel. Among these, it is more preferable to use an electroosmotic pump or a diaphragm pump having piezoelectric ceramics from the viewpoint of driving power, size, and the like. The pump 35 is electrically connected to control means (not shown), and the supply amount of the liquid fuel F supplied to the fuel supply unit 36 is controlled by the control means.

  Here, since the main target object of the fuel cell 1 is a small electronic device, it is preferable that the liquid feeding amount of the pump 35 be in the range of 10 μL / min to 1 mL / min. When the amount of liquid delivery exceeds 1 mL / min, the amount of liquid fuel F that is fed at a time becomes too large, and the stop time of the pump 35 that occupies the entire operation period becomes long. Therefore, the fluctuation in the amount of fuel supplied to the MEA 10 increases, and as a result, the fluctuation in output increases. A reservoir for preventing this may be provided on the downstream side of the pump 35. However, even if such a configuration is applied, fluctuations in the fuel supply amount cannot be sufficiently suppressed, and further the size of the apparatus is increased. Etc. will be invited.

  On the other hand, if the amount of liquid fed by the pump 35 is less than 10 μL / min, there may be a shortage of supply capacity when the amount of fuel consumption increases as at the start of operation. As a result, the starting characteristics of the fuel cell 1 are deteriorated. From such a point, it is preferable to use the pump 35 having a liquid feeding capacity in the range of 10 μL / min to 1 mL / min. It is more preferable that the liquid feeding amount of the pump 35 be in the range of 10 μL / min to 200 μL / min. In order to stably realize such a liquid feeding amount, it is preferable to apply an electroosmotic flow pump or a diaphragm pump to the pump 35.

  The fuel distribution layer 31 is made of a material that does not allow the liquid fuel F or its vaporized component to permeate, and is made of a flat plate having a plurality of openings 31a. Specifically, the fuel distribution layer 31 is made of polyethylene terephthalate (PET) resin, polyethylene naphthalate (PEN) resin, polyimide resin, or the like, and is sandwiched between the anode conductive layer 18 and the fuel supply unit main body 32. . The fuel distribution layer 31 can contain the low-temperature latent heat storage material (for example, a material in which normal paraffin is microencapsulated).

  Further, the fuel distribution layer 31 may be constituted by, for example, a gas-liquid separation membrane that separates the vaporized component of the liquid fuel F and the liquid fuel F and permeates the vaporized component to the MEA 10. Gas-liquid separation membranes include, for example, silicone rubber thin film, low density polyethylene (LDPE) thin film, polyvinyl chloride (PVC) thin film, polyethylene terephthalate (PET) thin film, fluororesin (for example, polytetrafluoroethylene (PTFE), tetra A microporous film of fluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) or the like is used. The liquid fuel F introduced into the fuel supply unit 32 a is supplied to the entire surface of the anode 13 from the plurality of openings 31 a of the fuel distribution layer 31. As described above, the fuel distribution layer 31 makes it possible to equalize the amount of fuel supplied to the anode 13.

  Next, in the embodiment configured as described above, a method for manufacturing the fuel cell 1 having a configuration in which the anode catalyst layer 11 and the cathode catalyst layer 14 contain a low-temperature latent heat storage material will be described below. First, an anode catalyst is produced, for example, as shown below.

  That is, a conductive carrier such as carbon is brought into contact with an aqueous solution or slurry containing a metal compound constituting a simple substance of a platinum group element or a platinum group element alloy, and the metal compound or ions thereof are adsorbed on the conductive support. . While stirring the slurry at a high speed, a suitable fixing agent such as sodium hydroxide, ammonia, hydrazine, formic acid, citric acid, formalin, methanol, ethanol, and propanol is slowly added dropwise to form a metal salt. Or as a partially reduced metal fine particle on a conductive support. Next, the anode catalyst is manufactured by drying and performing a heat treatment in a reducing gas or inert gas atmosphere.

  Next, the obtained anode catalyst and a low-temperature latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than the operating temperature of the fuel cell 1 (for example, 40 ° C.) are mixed with a solution of a proton conductive electrolyte, The viscosity is adjusted by adding an alcohol such as methanol, ethanol or propanol and a dispersion medium such as glycerin or ethylene glycol to obtain an anode catalyst layer forming slurry (hereinafter referred to as anode catalyst slurry).

  The anode catalyst slurry thus obtained is applied to a conductive porous substrate such as carbon paper or carbon cloth serving as the anode gas diffusion layer 12 using a suction filtration method, a spray method, a roll coater method, a bar coater method, or the like. The anode catalyst layer 11 is formed by applying and drying. The anode 13 is formed by forming the anode catalyst layer 11 on the anode gas diffusion layer 12 in this way.

  Similarly, the cathode 16 is formed. That is, a cathode catalyst is produced in the same manner as the anode catalyst, and the obtained cathode catalyst and a low-temperature latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than the operating temperature of the fuel cell 1 (for example, 40 ° C.) Is mixed with a proton conductive electrolyte solution, and the viscosity is adjusted by adding an alcohol such as methanol, ethanol or propanol, and a dispersion medium such as glycerin or ethylene glycol, to form a cathode catalyst layer slurry (hereinafter referred to as a cathode catalyst slurry). .)

  Next, the obtained cathode catalyst slurry is subjected to suction filtration, spraying, roll coater, bar coater, etc. on a conductive porous substrate such as carbon paper or carbon cloth to be the cathode gas diffusion layer 15. The cathode catalyst layer 14 is formed by coating and drying. Thus, the cathode 16 is formed by forming the cathode catalyst layer 14 on the cathode gas diffusion layer 15.

  Next, a proton conductive electrolyte membrane 17 is sandwiched between the anode 13 (anode catalyst layer 11) and the cathode 16 (cathode catalyst layer 14) thus obtained, and these are thermocompression bonded by a roll or a press. MEA10 is obtained. Further, the anode conductive layer 18 and the cathode conductive layer 19 are laminated on the MEA 10. The fuel cell 1 can be manufactured by disposing the fuel supply mechanism 30 on the anode side of the MEA 10 and integrating the moisturizing layer 20 and the surface cover layer 21 in order on the cathode side.

  Next, the operation of the fuel cell 1 shown in the embodiment will be described.

The liquid fuel F supplied from the fuel storage unit 33 through the flow path 34 to the fuel supply unit 36 remains as a liquid fuel, or in a state where liquid fuel and vaporized fuel vaporized from the liquid fuel are mixed. And supplied to the anode gas diffusion layer 12 of the MEA 10 via the anode conductive layer 18. The fuel supplied to the anode gas diffusion layer 12 is diffused in the anode gas diffusion layer 12 and supplied to the anode catalyst layer 11. When methanol fuel is used as the liquid fuel F, an internal reforming reaction of methanol shown in the following formula (1) occurs in the anode catalyst layer 11.
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ Formula (1)

  When pure methanol is used as the methanol fuel, is methanol reformed by water generated in the cathode catalyst layer 14 or water in the electrolyte membrane 17 and the internal reforming reaction of the above formula (1)? Or other reaction mechanisms that do not require water. Part of the heat generated by the reaction shown in the equation (1) is absorbed (heat storage) by the low-temperature latent heat storage material contained in the anode catalyst layer 11, the fuel distribution layer 31, and the like. And the rise in the temperature of the anode 13 is suppressed until the phase transition of the latent heat storage material is completed. Moreover, since this heat absorption (heat storage) suppresses the transpiration of water necessary for the reaction of the formula (1), the internal reforming reaction of methanol is promoted.

Electrons (e ⁻ ) generated by this reaction are guided to the outside via a current collector, and are guided to the cathode 16 after operating a portable electronic device or the like as so-called electricity. In addition, protons (H ⁺ ) generated by the internal reforming reaction of the formula (1) are guided to the cathode 16 through the electrolyte membrane 17. Air is supplied to the cathode 16 as an oxidant. The electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode 16 cause a reaction shown in the following equation (2) with oxygen in the air in the cathode catalyst layer 14, and water is generated along with this power generation reaction. .
(3/2) O ₂ + 6e ⁻ + 6H ⁺ → 3H ₂ O (2)

  Part of the heat generated by the reaction shown in the formula (2) is absorbed (stored) by the low-temperature latent heat storage material contained in the cathode catalyst layer 14, the moisturizing layer 20, and the like. Until the phase transition of the latent heat storage material is completed, the temperature rise of the cathode 16 is suppressed, so that the transpiration of water through the moisturizing layer 20 is suppressed, and the amount of water staying at the cathode 16 is reduced. Increase. Then, due to the increase in the amount of water staying at the cathode 16, the diffusion amount of water to the anode 13 increases and the amount of water contained in the anode 13 also increases.

  With such an increase in the water content in the cathode 16 and the anode 13, the cell resistance (impedance) is lowered and the output is improved in the fuel cell 1 of the embodiment. In the embodiment, in the aspect in which the anode catalyst layer 11, the cathode catalyst layer 14, the moisturizing layer 20 and the like constituting the fuel cell 1 contain the low-temperature latent heat storage material, the member containing the latent heat storage material is used. Compared to a configuration in which (resin sheet or the like) is separately provided, there is an advantage that no additional process is required during manufacturing and the thickness and volume of the entire fuel cell are not increased.

  The fuel cell of the above-described embodiment is effective when various liquid fuels are used, and the type and concentration of the liquid fuel are not limited. Further, the above-described embodiment has been described by taking a semi-passive type using a pump for supplying fuel as an example of the configuration of the fuel cell main body, but for a purely passive type fuel cell such as an internal vaporization type However, the present invention can be applied.

  Next, it will be described based on Examples 1 to 5 and Comparative Examples 1 and 2 that the fuel cell according to the present invention has excellent output characteristics.

Example 1
A carbon carrier, Ketjen ECP (trade name, manufactured by Lion Corporation) is loaded with a Pt—Ru alloy (Ru60 at.%), Which is an anode catalyst metal, and subjected to liquid phase reduction using sodium borohydride. A solid solution treatment was performed in an inert atmosphere at 1 ° C. for 1 hour to produce an anode catalyst.

  Next, this anode catalyst, Nafion solution DE2020 (trade name, manufactured by DuPont) and solvent (1-propanol, 2-propanol and glycerin) were added to the anode catalyst content (weight percentage) and Nafion content (weight percentage). ) To prepare an anode catalyst slurry. The obtained anode catalyst slurry was applied to one surface of carbon paper (trade name TGP-H-120, manufactured by Toray Industries, Inc., 40 mm × 30 mm rectangle) serving as an anode gas diffusion layer using a bar coater and then dried. Thus, an anode catalyst layer (thickness: 200 μm) was formed. Thus, an anode was produced.

  In addition, a cathode catalyst was manufactured in the same manner as the anode catalyst by supporting the cathode catalyst metal Pt on the carbon support Ketjen ECP. Next, this cathode catalyst and normal paraffin (trade name HS Capsule-P, manufactured by Mitsubishi Paper Industries Co., Ltd.) enclosed in microcapsules which are low-temperature latent heat storage materials (phase transition temperature 40 ° C., endothermic amount (heat storage amount)) 170 joules / g), Nafion solution DE2020 (trade name, manufactured by DuPont), and solvent (1-propanol, 2-propanol and glycerin), cathode catalyst content (weight percentage) and Nafion content (weight) The cathode catalyst slurry was prepared by mixing so that the ratio to the ratio was 74:26. The blending amount of the low-temperature latent heat storage material was adjusted so that the heat absorption amount (heat storage amount) of the latent heat storage material contained in the finally formed cathode catalyst layer was 150 joules. This cathode catalyst slurry was applied to one surface of carbon paper (trade name TGP-H-090, manufactured by Toray Industries, Inc., 40 mm × 30 mm rectangle) serving as a cathode gas diffusion layer using a bar coater and dried. A catalyst layer (thickness 80 μm) was formed. In this way, a cathode was produced.

Next, Nafion NRE-212CS (trade name, manufactured by DuPont) is used as the proton conductive electrolyte membrane, and the electrolyte membrane, the anode (electrode area 12 cm ² ), and the cathode (electrode area 12 cm ² ) are used as an anode catalyst. After laminating the layer and the cathode catalyst layer so as to be on the side of the electrolyte membrane, pressing was performed under the conditions of a heating temperature of 150 ° C., a pressure of 30 kgf / cm ² , and a pressurization time of 5 minutes to prepare an MEA. And the fuel cell shown in FIG. 1 was produced using MEA produced in this way. Note that a porous polyethylene film having a thickness of 1.0 mm was used as the moisturizing layer.

Example 2
In the preparation of the cathode catalyst slurry, the blending amount of the low-temperature type latent heat storage material was adjusted so that the endothermic amount (heat storage amount) of the latent heat storage material contained in the finally formed cathode catalyst layer was 500 joules. . Other than that was carried out similarly to Example 1, and produced the cathode. Further, an anode was produced in the same manner as in Example 1.

  Next, using the anode and the cathode thus obtained, a fuel cell shown in FIG. 1 was produced in the same manner as in Example 1.

Example 3
An anode catalyst manufactured in the same manner as in Example 1, and normal paraffin (trade name HS capsule-P) enclosed in microcapsules which are low-temperature latent heat storage materials (phase transition temperature 40 ° C., endothermic amount (heat storage amount)) 170 joules / g), Nafion solution DE2020, and solvent (1-propanol, 2-propanol and glycerin) were mixed so that the ratio of the content ratio (weight ratio) of the anode catalyst to Nafion was 37:63, An anode catalyst slurry was prepared. The blending amount of the low-temperature latent heat storage material was adjusted so that the endothermic amount (heat storage amount) of the latent heat storage material contained in the finally formed anode catalyst layer was 150 joules. The obtained anode catalyst slurry was applied to one side of a carbon paper (trade name TGP-H-120, 40 mm × 30 mm rectangle) serving as an anode gas diffusion layer using a bar coater, and then dried, and the anode catalyst layer ( A thickness of 200 μm) was formed. Thus, an anode was produced.

  Further, the cathode catalyst manufactured in the same manner as in Example 1, the Nafion solution DE2020 and the solvent (1-propanol, 2-propanol and glycerin), and the ratio of the cathode catalyst and the content of Nafion (weight ratio) is 74: 26 to prepare a cathode catalyst slurry. This cathode catalyst slurry was applied to one surface of carbon paper (trade name TGP-H-090, 40 mm × 30 mm rectangle) serving as a cathode gas diffusion layer using a bar coater and dried, and then the cathode catalyst layer (thickness 80 μm). ) Was formed. In this way, a cathode was produced.

  Next, using the anode and the cathode thus obtained, a fuel cell shown in FIG. 1 was produced in the same manner as in Example 1.

Example 4
In the preparation of the anode catalyst slurry, the blending amount of the low-temperature type latent heat storage material was adjusted so that the heat absorption amount (heat storage amount) of the latent heat storage material contained in the finally formed anode catalyst layer was 500 joules. . Other than that was carried out similarly to Example 3, and produced the anode. Further, a cathode was produced in the same manner as in Example 3.

  Next, using the anode and the cathode thus obtained, a fuel cell shown in FIG. 1 was produced in the same manner as in Example 1.

Example 5
An anode catalyst produced in the same manner as in Example 1, and normal paraffin (trade name HS capsule-P) enclosed in microcapsules which are low-temperature latent heat storage materials (phase transition temperature 40 ° C., endothermic amount (heat storage amount)) 170 joules / g), Nafion solution DE2020 and solvent (1-propanol, 2-propanol and glycerin) were mixed so that the ratio of the anode catalyst to Nafion content (weight ratio) was 37:63, and the anode A catalyst slurry was prepared. The blending amount of the low-temperature latent heat storage material was adjusted so that the heat absorption amount (heat storage amount) of the latent heat storage material contained in the finally formed anode catalyst layer was 150 joules. The obtained anode catalyst slurry was applied to one side of a carbon paper (trade name TGP-H-120, 40 mm × 30 mm rectangle) serving as an anode gas diffusion layer using a bar coater, and then dried, and the anode catalyst layer ( A thickness of 200 μm) was formed. Thus, an anode was produced.

  In addition, the cathode catalyst produced in the same manner as in Example 1 and normal paraffin (trade name HS capsule-P) enclosed in microcapsules which are low-temperature latent heat storage materials (phase transition temperature 40 ° C., endothermic amount (heat storage) Amount) 170 joules / g), Nafion solution DE2020 and solvent (1-propanol, 2-propanol and glycerin) were mixed so that the ratio of the cathode catalyst to the content ratio (weight ratio) of Nafion was 74:26. A cathode catalyst slurry was prepared. The blending amount of the low-temperature latent heat storage material was adjusted so that the heat absorption amount (heat storage amount) of the latent heat storage material contained in the finally formed cathode catalyst layer was 150 joules. This cathode catalyst slurry was applied to one surface of carbon paper (trade name TGP-H-090, 40 mm × 30 mm rectangle) serving as a cathode gas diffusion layer using a bar coater and dried, and then the cathode catalyst layer (thickness 80 μm). ) Was formed. In this way, a cathode was produced.

  Next, using the anode and the cathode thus obtained, a fuel cell shown in FIG. 1 was produced in the same manner as in Example 1.

Comparative Example 1
In preparation of the cathode catalyst slurry, the low-temperature latent heat storage material was not blended, and the cathode catalyst, the Nafion solution DE2020, and the solvent (1-propanol, 2-propanol and glycerin) were mixed. Otherwise, a cathode catalyst slurry was prepared in the same manner as in Example 1, and a cathode catalyst layer was formed using this cathode catalyst slurry to produce a cathode. Further, in the same manner as in Example 1, an anode catalyst layer was formed on the anode gas diffusion layer to produce an anode.

  Next, using the anode and the cathode thus obtained, a fuel cell shown in FIG. 1 was produced in the same manner as in Example 1.

Comparative Example 2
In the preparation of the cathode catalyst slurry, instead of the low-temperature type latent heat storage material, a latent heat storage material having a phase transition temperature equal to or higher than the operating temperature of the fuel cell (trade name HS capsule-P) (phase transition temperature 60 ° C., endothermic amount (heat storage) Amount) 170 joules / g) was blended so that the heat absorption amount (heat accumulation amount) of the latent heat storage material contained in the finally formed cathode catalyst layer was 500 joules. Otherwise, a cathode catalyst slurry was prepared in the same manner as in Example 1, and a cathode catalyst layer was formed using this cathode catalyst slurry to produce a cathode. Further, in the same manner as in Example 1, an anode catalyst layer was formed on the anode gas diffusion layer to produce an anode.

  Using the anode and cathode thus obtained, a fuel cell shown in FIG. 1 was produced in the same manner as in Example 1.

Next, methanol having a purity of 99.99% was supplied to the fuel storage portions of the fuel cells obtained in Examples 1 to 5 and Comparative Examples 1 and 2. And it was made to drive | operate by the operating temperature 55 degreeC-0.35V constant potential, and the output density after a 2-hour driving | operation was measured. Here, the output density (mW / cm ² ) of the fuel cell is obtained by multiplying the current density by the output voltage. Moreover, the AC impedance of 1 kHz was measured after the operation was stopped, and the sheet resistivity (Ω · cm ² ) was obtained. The results are shown in Table 1.

  From the results in Table 1, the following was found. That is, Example 1 in which the anode catalyst layer and / or the cathode catalyst layer includes a low-temperature latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than a fuel cell operating temperature (55 ° C.). In the fuel cells of -5, the area resistivity was reduced and the output density was improved as compared with the fuel cell of Comparative Example 1 in which none of the catalyst layers contained a low-temperature latent heat storage material. Further, the fuel cells of Examples 1 and 2 in which the cathode catalyst layer contains the low-temperature latent heat storage material are the fuel cells of Examples 3 and 4 in which the low-temperature latent heat storage material is contained only in the anode catalyst layer. Compared with the area resistivity, the output density was higher. Further, in the fuel cell of Example 5 in which both the anode catalyst layer and the cathode catalyst layer contain the low-temperature latent heat storage material, the effect of improving the output density is higher than the content of the latent heat storage material, It was found that the output can be improved efficiently with a small content by including a low-temperature latent heat storage material on both sides of the anode and the cathode.

  Furthermore, in the fuel cell of Comparative Example 2 configured so that the cathode catalyst layer includes a latent heat storage material (phase transition temperature 60 ° C.) having a phase transition temperature higher than the operating temperature (55 ° C.) of the fuel cell, the latent heat storage Compared to the fuel cell of Comparative Example 1 containing no material, the resistance (area resistivity) is hardly reduced, and the cathode catalyst layer contains a material that becomes a foreign substance other than the catalyst. Compared with the fuel cell of Example 1, the power density was lowered.

  In the fuel cells of Examples 1 to 5, the effects of lowering the electrical resistance (area resistivity) and improving the output (output density) continued for 100 hours or more, but thereafter the resistance gradually increased and the output also decreased. However, when the fuel cell was started and operated again, the same effect was obtained, and the sheet resistivity was lowered and the output density was improved.

  The present invention can be applied to various fuel cells using liquid fuel. Further, the specific configuration of the fuel cell, the supply state of the fuel, etc. are not particularly limited. All of the fuel supplied to the fuel cell is liquid fuel vapor, all is liquid fuel, or part is liquid. The present invention can be applied to various forms such as liquid fuel vapor supplied in a state. In the implementation stage, the constituent elements can be modified and embodied without departing from the technical idea of the present invention. Furthermore, various modifications are possible, such as appropriately combining a plurality of components shown in the above embodiment, or deleting some components from all the components shown in the embodiment. Embodiments of the present invention can be expanded or modified within the scope of the technical idea of the present invention, and these expanded and modified embodiments are also included in the technical scope of the present invention.

It is sectional drawing which shows the structure of one Embodiment of the fuel cell which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 10 ... MEA, 11 ... Anode catalyst layer, 12 ... Anode gas diffusion layer, 13 ... Anode (fuel electrode), 14 ... Cathode catalyst layer, 15 ... Cathode gas diffusion layer, 16 ... Cathode (air electrode) , 17 ... Electrolyte membrane, 18 ... Anode conductive layer, 19 ... Cathode conductive layer, 20 ... Moisturizing layer, 21 ... Surface cover layer, 22 ... O-ring, 30 ... Fuel supply mechanism, 31 ... Fuel distribution layer, 32 ... Fuel supply Part main body, 33 ... fuel storage part, 34 ... flow path, 35 ... pump, 36 ... fuel supply part.

Claims (5)

A membrane electrode assembly having a fuel electrode (anode), an air electrode (cathode), a proton conductive electrolyte membrane sandwiched between the anode and the cathode, and a fuel supply mechanism for supplying fuel to the anode A fuel cell with
A layer containing a latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than an operating temperature on the anode and the anode side outside the anode and / or the cathode and the cathode side outside the cathode. A fuel cell comprising: Proton conduction sandwiched between a fuel electrode (anode) having a fuel electrode (anode) catalyst layer, an air electrode (cathode) having an air electrode (cathode) catalyst layer, and the anode catalyst layer and the cathode catalyst layer A membrane electrode assembly having a conductive electrolyte membrane, a fuel supply mechanism that is disposed outside the anode and supplies fuel to the anode catalyst layer, and a surface layer having an air inlet disposed outside the cathode, A fuel cell comprising a moisturizing layer that is disposed between the surface layer and the cathode and suppresses the transpiration of water generated in the cathode catalyst layer;
At least one of the cathode catalyst layer, the moisturizing layer, and the surface layer contains a latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than an operating temperature, or contains the latent heat storage material. A fuel cell comprising a layer. Proton conduction sandwiched between a fuel electrode (anode) having a fuel electrode (anode) catalyst layer, an air electrode (cathode) having an air electrode (cathode) catalyst layer, and the anode catalyst layer and the cathode catalyst layer A membrane electrode assembly having a conductive electrolyte membrane, a fuel supply mechanism that is disposed outside the anode and supplies fuel to the anode catalyst layer, and a surface layer having an air inlet disposed outside the cathode, A fuel cell comprising a moisturizing layer that is disposed between the surface layer and the cathode and suppresses the transpiration of water generated in the cathode catalyst layer;
At least one of the anode catalyst layer and the member constituting the fuel supply mechanism contains a latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than an operating temperature, or a layer containing the latent heat storage material A fuel cell comprising: Proton conduction sandwiched between a fuel electrode (anode) having a fuel electrode (anode) catalyst layer, an air electrode (cathode) having an air electrode (cathode) catalyst layer, and the anode catalyst layer and the cathode catalyst layer A membrane electrode assembly having a conductive electrolyte membrane, a fuel supply mechanism that is disposed outside the anode and supplies fuel to the anode catalyst layer, and a surface layer having an air inlet disposed outside the cathode, A fuel cell comprising a moisturizing layer that is disposed between the surface layer and the cathode and suppresses the transpiration of water generated in the cathode catalyst layer;
At least one of the cathode catalyst layer, the moisturizing layer and the surface layer contains a latent heat storage material having a phase transition temperature higher than 35 ° C. and lower than an operating temperature, or a layer containing the latent heat storage material And at least one of the members constituting the anode catalyst layer and the fuel supply mechanism contains a latent heat storage material having the phase transition temperature, or has a layer containing the latent heat storage material. A fuel cell.   The fuel cell according to any one of claims 1 to 4, wherein a concentration of a fuel component in the fuel is 60 wt% or more.

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