JP2009146864A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of achieving increase of an output, and capable of producing water necessary for reaction at an anode (a fuel electrode) from fuel, and stably supplying water and the fuel to the anode (the fuel electrode). <P>SOLUTION: The fuel cell 1 is provided with the anode (the fuel electrode) 13 equipped with an anode catalyst layer 11 and an anode gas diffusion layer 12, a cathode (an air electrode) 16 equipped with a cathode catalyst layer 14 and a cathode gas diffusion layer 15, an electrolyte membrane 17 pinched by the anode (fuel electrode) 13 and the cathode (air electrode) 16, a fuel housing part 41 which is arranged at an anode (fuel electrode) side and houses the fuel consisting of a first fuel generating hydrogen ions and electrons and a second fuel containing peroxide, and a catalyst layer 80 for the second fuel which is arranged between the anode catalyst layer 11 and the fuel housing part 41 and mainly functions as a catalyst for the second fuel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  A fuel cell is a system that can generate electricity simply by supplying fuel and an oxidant. In particular, direct methanol fuel cells (DMFCs) use methanol with a high energy density as fuel, and since direct current can be taken out from methanol on the electrocatalyst, a reformer is not required, so it is for small equipment. Promising as a power source.

  As a fuel supply method in the DMFC, a gas supply type DMFC in which the liquid fuel is vaporized and then fed into the fuel cell with a blower or the like, and a liquid supply type in which a liquid fuel having a concentration of 50 mol% or less is directly fed into the fuel cell with a pump or the like DMFCs and internal vaporization type DMFCs that vaporize liquid fuel having a concentration of 50 mol% or more inside the fuel cell are known.

  The internal vaporization type DMFC includes a fuel permeation layer that retains liquid fuel, and a gas-liquid separation membrane for diffusing a vaporized component of the liquid fuel retained in the fuel permeation layer. It is supplied from the gas-liquid separation membrane to the anode (fuel electrode).

In the anode (fuel electrode), as shown in Formula (1), vaporized methanol and water react with each other in the anode catalyst layer to generate carbon dioxide and hydrogen ions.
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ Formula (1)

In the cathode (air electrode), methanol diffused from the anode (fuel electrode) side to the cathode (air electrode) side is directly oxidized in the cathode catalyst layer as shown in formula (2) to generate water. To do. This water is supplied to the anode (fuel electrode) side by self-diffusion, and is used as water necessary for the reaction of the above formula (1) at the anode (fuel electrode).
CH ₃ OH + (3/2) O ₂ → CO ₂ + 2H ₂ O Formula (2)

Further, as another method for supplying water to the anode (fuel electrode), a method is disclosed in which methanol fuel containing water is used and water and fuel are supplied directly to the anode catalyst layer (for example, patents). Reference 1).
JP 2007-149687 A

  However, when water generated on the cathode (air electrode) side is supplied to the anode (fuel electrode) side by self-diffusion as in a conventional fuel cell, methanol is supplied to the cathode (air electrode) side by methanol crossover. However, this methanol crossover causes a decrease in fuel cell performance.

  In addition, when using methanol fuel diluted with water, the energy density per unit volume of liquid fuel decreases, so the problem of having to increase the flow rate of fuel containing water to be supplied and the power generation efficiency decrease. Had the problem of doing.

  Moreover, it is necessary to supply methanol in a gaseous state to the anode catalyst layer. For this reason, when liquid methanol is converted to gaseous methanol, the amount of heat is used as the heat of vaporization, so the temperature of the anode (fuel electrode) decreases, causing problems in operation at low temperatures, or to the anode (fuel electrode). There was a problem that sufficient methanol fuel could not be supplied.

  Accordingly, the present invention has been made to solve the above-described problems, and can improve the output and generate water necessary for the reaction in the anode (fuel electrode) from the fuel, and stabilize it in the anode (fuel electrode). An object of the present invention is to provide a fuel cell capable of supplying water and fuel.

  According to one aspect of the present invention, a fuel electrode including an anode catalyst layer and an anode gas diffusion layer, an air electrode including a cathode catalyst layer and a cathode gas diffusion layer, and an electrolyte sandwiched between the fuel electrode and the air electrode A membrane, a fuel accommodating portion that is disposed on the fuel electrode side and that accommodates a fuel composed of a first fuel that generates hydrogen ions and electrons, and a second fuel that contains peroxide, the anode catalyst layer, and the fuel accommodation And a second fuel catalyst layer functioning mainly as a catalyst for the second fuel. The fuel cell is provided.

  Further, according to one aspect of the present invention, the fuel electrode including the anode catalyst layer and the anode gas diffusion layer, the air electrode including the cathode catalyst layer and the cathode gas diffusion layer, and the fuel electrode and the air electrode are sandwiched. An electrolyte membrane, a fuel supply unit disposed on the fuel electrode side for supplying fuel to the fuel electrode, a first fuel for generating hydrogen ions and electrons supplied to the fuel supply unit, and a peroxide And a second fuel catalyst layer that is disposed between the anode catalyst layer and the fuel supply portion and mainly functions as a catalyst for the second fuel. A fuel cell is provided.

  According to the fuel cell of the present invention, output can be improved, water necessary for reaction at the anode (fuel electrode) is generated from the fuel, and water and fuel are stably supplied to the anode (fuel electrode). Can do.

  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 a fuel cell 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the fuel cell 1 when the pump 90 is provided in the fuel cell according to the embodiment of the present invention.

  As shown in FIG. 1, the fuel cell 1 includes a fuel cell 10 constituting an electromotive unit, and anode conductivity provided on the anode (fuel electrode) side and the cathode (air electrode) side of the fuel cell 10. A layer 18, a cathode conductive layer 19, a gas-liquid separation film 70 provided by being laminated on the anode conductive layer 18, a second fuel catalyst layer 80 provided by being laminated on the gas-liquid separation film 70, A fuel distribution layer 30 having a plurality of openings 31 provided to face the second fuel catalyst layer 80, and a fuel distribution layer disposed on a side different from the fuel cell 10 side of the fuel distribution layer 30. 30, a fuel supply mechanism 40 that supplies liquid fuel F to 30, a moisturizing layer 50 laminated on the cathode conductive layer 19, and a surface cover 60 having a plurality of air inlets 61 laminated on the moisturizing layer 50. .

  The fuel cell 10 is a so-called membrane electrode assembly (MEA), and includes an anode (fuel electrode) 13 having an anode catalyst layer 11 and an anode gas diffusion layer 12, a cathode catalyst layer 14, and a cathode gas diffusion. A cathode (air electrode) 16 having a layer 15 and an electrolyte membrane 17 having proton (hydrogen ion) conductivity sandwiched between the anode catalyst layer 11 and the cathode catalyst layer 14.

  Examples of the catalyst contained in the anode catalyst layer 11 and the cathode catalyst layer 14 include a simple substance of a platinum group element such as Pt, Ru, Rh, Ir, Os, and Pd, and an alloy containing the platinum group element. As the anode catalyst layer 11, for example, Pt—Ru, Pt—Mo, or the like having strong resistance to methanol, carbon monoxide, or the like is preferably used. As the cathode catalyst layer 14, 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.

  Examples of proton conductive materials 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 tungstic acid. And inorganic materials such as 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, it can be composed of an electrolyte membrane capable of transporting protons such as aliphatic hydrocarbon resin soot.

  The anode gas diffusion layer 12 laminated on the anode catalyst layer 11 serves to uniformly supply fuel to the anode catalyst layer 11 and also functions as a current collector for the anode catalyst layer 11. The cathode gas diffusion layer 15 laminated on the cathode catalyst layer 14 serves to uniformly supply the oxidant to the cathode catalyst layer 14 and also functions as a current collector for the cathode catalyst layer 14. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 are porous bodies or meshes made of a porous carbonaceous material such as carbon paper, carbon cloth, or carbon silk, or a metal material such as titanium, titanium alloy, stainless steel, or gold. Etc.

  The anode conductive layer 18 laminated on the surface of the anode gas diffusion layer 12 and the cathode conductive layer 19 laminated on the surface of the cathode gas diffusion layer 15 have electrical characteristics and chemical stability such as Au and Ni. It is composed of a porous layer (for example, mesh) or a foil body made of an excellent conductive metal material, or a composite material in which a conductive metal material such as stainless steel (SUS) is coated with a good conductive metal such as gold. Among these, the anode conductive layer 18 and the cathode conductive layer 19 are preferably formed of a thin film having a plurality of openings that correspond to the fuel cells 10, and the fuel is supplied through these openings. Lead to the fuel cell side. 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. Also, rubber O-rings 20 are interposed between the electrolyte membrane 17 and the anode conductive layer 18 and the cathode conductive layer 19, respectively, thereby preventing fuel leakage and oxidant leakage from the fuel cell 10. is doing. Here, the fuel cell 2 including the anode conductive layer 18 and the cathode conductive layer 19 is shown, but the anode gas diffusion layer 12 and the anode conductive layer 18 and the cathode conductive layer 19 are not provided as described above. The cathode gas diffusion layer 15 may function as a diffusion layer and may function as a conductive layer.

  The moisturizing layer 50 is impregnated with a part of the water generated in the cathode catalyst layer 14 to suppress the transpiration of water and promote uniform diffusion of air to the cathode catalyst layer 14. The moisturizing layer 50 is composed of a flat plate made of, for example, a polyethylene porous film.

  The front cover 60 adjusts the amount of air taken in, and the adjustment is performed by changing the number and size of the air inlets 61. For example, the front cover 60 can be made of a metal such as SUS304, but is not limited thereto.

  The gas-liquid separation film 70 disposed on the fuel supply mechanism 40 side of the anode conductive layer 18 separates the vaporized component of the liquid fuel F and the liquid fuel F and passes the vaporized component to the anode (fuel electrode) side. It is. The gas-liquid separation membrane 70 is formed into a sheet shape with an inert material that does not dissolve in the liquid fuel F, and specifically, silicone rubber, low-density polyethylene (LDPE) thin film, polyvinyl chloride (PVC) thin film. , Polyethylene terephthalate (PET) thin film, fluororesin (for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), etc.), etc. The gas-liquid separation membrane 70 is configured so that fuel and the like do not leak from the periphery.

  A resin frame (not shown) may be provided between the gas-liquid separation membrane 70 and the anode conductive layer 18. The space surrounded by the frame functions as a vaporized fuel storage chamber (so-called vapor pool) that temporarily stores the vaporized fuel that has diffused through the gas-liquid separation membrane 70, and closely contacts the fuel cell 10 and the anode conductive layer 18. It also functions as a reinforcing plate. Due to the effect of suppressing the permeated methanol amount of the vaporized fuel storage chamber and the gas-liquid separation membrane 70, it is possible to avoid supplying a large amount of vaporized fuel to the anode catalyst layer at a time. The frame is a short frame, and is made of, for example, engineering plastic having high chemical resistance such as polyether ether ketone (PEEK).

  The second fuel catalyst layer 80 arranged on the fuel supply mechanism 40 side of the gas-liquid separation membrane 70 mainly functions as a catalyst for the second fuel among the fuel supplied by the fuel supply mechanism 40. . The second fuel catalyst layer 80 is preferably composed of at least one element or more of a noble metal or an alloy containing the noble metal. Examples of the noble metal used include metals of platinum group elements (Pt, Ir, Os, Pd, etc.). The second fuel catalyst layer 80 is preferably supported on a carbon-based carrier or a carrier containing an inorganic metal.

  The fuel supply mechanism 40 mainly includes a fuel storage part 41, a fuel supply part main body 42, and a flow path 44.

  The fuel storage unit 41 stores liquid fuel F corresponding to the fuel battery cell 10. The liquid fuel F is a fuel composed of a first fuel that generates hydrogen ions and electrons and a second fuel that contains peroxide.

  The first fuel is preferably an aqueous solution or a non-aqueous solution of one or more substances selected from the group consisting of alcohols containing hydrocarbons, carboxylic acids, and aldehydes. The first fuel is preferably an aqueous solution or non-aqueous solution of one or more substances selected from the group consisting of methanol, ethanol, formic acid, acetic acid, formaldehyde and acetaldehyde, for example. Among these liquid fuels, an aqueous methanol solution has carbon atoms of 1 and is generated by carbon dioxide during the reaction, 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 first fuel. Moreover, it is preferable that content of a 1st fuel is 0.1-24.5M. The content in this range is preferable because, when the content of the first fuel is smaller than 0.1M, the generation amount of hydrogen ions and electrons is small, and the power generation performance of the fuel cell is lowered. This is because the efficiency of the second fuel is reduced when it is greater than 24.5M. In addition, M means volume molar concentration (mol / L).

Further, the second fuel generates water and generates heat in the second fuel catalyst layer 80, and is made of a peroxide having at least one of carbon atoms, hydrogen atoms, and metal atoms. It is preferably composed of a solution of one or more substances selected from the group. The peroxide content in the second fuel is 0.1 to 20 mol% when the peroxide is represented by the following chemical formula 1 and R is a hydrogen atom, that is, hydrogen peroxide. It is preferable that when R is a compound composed of hydrocarbon, it is preferably 0.1 to 33.3 mol%. Examples of the hydrocarbon compound include cyclic hydrocarbon compounds having an alkyl group, a cyclo ring, a benzene ring, and the like. Examples of the alkyl group include methyl and ethyl. Examples of the cyclic hydrocarbon compound include cyclohexane, benzene and the like.
R—O—O—R (Chemical Formula 1)

  Here, when R is a hydrogen atom, it is preferable that the peroxide content in the case where R is a hydrocarbon compound is within the above ranges, the internal reforming reaction of methanol (the above formula ( This is because the generation of water and heat generation for promoting 1) or formula (5)) can be maintained.

  Further, the peroxide in the second fuel may be an inorganic metal peroxide. In this case, the peroxide content in the second fuel is preferably 0.1 to 50 mol%. Examples of the inorganic metal peroxide include sodium peroxide and calcium peroxide. Here, it is preferable that the content of the inorganic metal peroxide is in the above range. The generation of water for promoting the internal reforming reaction of methanol (see the above formula (1) or (5)) and This is because heat generation can be maintained.

  The second fuel may be composed of a solution of one or more substances selected from the group consisting of percarboxylic acids and peroxo acids having at least one of carbon atoms and hydrogen atoms. In this case, the content of percarboxylic acid and peroxo acid in the second fuel is preferably 0.1 to 50 mol%. Examples of the percarboxylic acid having a carbon atom or a hydrogen atom include peracetic acid and benzoic acid, and examples of the peroxo acid having a carbon atom or a hydrogen atom include diperoxysuccinic acid. Here, it is preferable that the content of the percarboxylic acid and the peroxo acid is within the above range. The generation of water for promoting the internal reforming reaction of methanol (see formula (1) or formula (5)) and This is because heat generation can be maintained.

  The fuel supply unit main body 42 includes a fuel supply unit 43 including recesses for uniformly dispersing the liquid fuel F in order to uniformly supply the supplied liquid fuel F to the fuel distribution layer 30. The fuel supply unit 43 is connected to the fuel storage unit 41 via a flow path 44 of the liquid fuel F configured by piping or the like. Liquid fuel F is introduced into the fuel supply unit 43 from the fuel storage unit 41 via the flow path 44. The flow path 44 is not limited to piping independent of the fuel supply unit 43 and the fuel storage unit 41. For example, when the fuel supply unit 43 and the fuel storage unit 41 are stacked and integrated, a flow path of the liquid fuel F that connects them may be used. That is, the fuel supply part 43 should just be connected with the fuel accommodating part 41 via the flow path.

  The liquid fuel F stored in the fuel storage part 41 can be dropped and sent to the fuel supply part 43 via the flow path 44 using gravity. Alternatively, the flow path 44 may be filled with a porous body or the like, and the liquid fuel F stored in the fuel storage unit 41 may be fed to the fuel supply unit 43 by capillary action. Further, as shown in FIG. 2, the liquid fuel F stored in the fuel storage unit 41 may be forcibly sent to the fuel supply unit 43 by interposing a pump 90 in a part of the flow path 44. .

  The pump 90 functions as a supply pump that simply supplies the liquid fuel F from the fuel storage unit 41 to the fuel supply unit 43, and is a circulation pump that circulates excess liquid fuel F supplied to the fuel cells 10. It does not have the function as. The fuel cell 1 provided with the pump 90 is called a so-called semi-passive type, which does not circulate fuel, and therefore has a different configuration from the conventional active method and a different configuration from a pure passive method such as a conventional internal vaporization type. Applicable to the method. The type of the pump 90 is not particularly limited, but a rotary vane pump and an electroosmotic flow pump can be used from the viewpoint that a small amount of liquid fuel F can be fed with good controllability and can be reduced in size and weight. It is preferable to use 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 the 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. When the pump 90 is provided as described above, the pump 90 is electrically connected to control means (not shown), and the supply amount of the liquid fuel F supplied to the fuel supply unit 43 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 supply amount of the pump 90 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 90 that occupies the entire operation period becomes long. For this reason, the fluctuation of the amount of fuel supplied to the fuel battery cell 10 becomes large, and as a result, the fluctuation of the output becomes large. A reservoir for preventing this may be provided on the downstream side of the pump 90. However, even if such a configuration is applied, fluctuations in the fuel supply amount cannot be sufficiently suppressed, and the size of the apparatus is further increased. Etc. will be invited.

  On the other hand, if the amount of liquid delivered by the pump 90 is less than 10 μL / min, there is a risk of insufficient supply capacity when the amount of fuel consumption increases when the apparatus is started up. As a result, the starting characteristics of the fuel cell 1 are deteriorated. From such a point, it is preferable to use a pump 90 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 90 be in the range of 10 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 90.

  The fuel distribution layer 30 is formed of, for example, a flat plate in which a plurality of openings 31 are formed, and is sandwiched between the second fuel catalyst layer 80 and the fuel supply unit 43. The fuel distribution layer 30 is made of a material that does not allow the vaporized component of the liquid fuel F or the liquid fuel F to permeate. Specifically, for example, a polyethylene terephthalate (PET) resin, a polyethylene naphthalate (PEN) resin, or a polyimide resin. Etc. Here, in the fuel cell 1, the liquid fuel introduced into the fuel supply unit 43 is guided to the second fuel catalyst layer 80 from the plurality of openings 31 of the fuel distribution layer 30, via the gas-liquid separation membrane 70. The vaporized component of the liquid fuel F is supplied to the entire surface of the anode (fuel electrode) 13. In this way, the fuel distribution layer 30 can make the amount of fuel supplied to the anode (fuel electrode) 13 uniform.

  Next, the operation of the fuel cell 1 described above will be described.

  The liquid fuel F supplied from the fuel storage unit 41 to the fuel supply unit 43 via the flow path 44 is uniformly distributed in the fuel distribution layer 30 and guided to the second fuel catalyst layer 80. Here, the case where methanol is used as the first fuel and hydrogen peroxide is used as the second fuel will be described.

The liquid fuel F guided to the second fuel catalyst layer 80 undergoes reactions of the following formulas (3) and (4).
2H ₂ O ₂ → 2H ₂ O + O ₂ Formula (3)
CH ₃ OH + 3 / 2O ₂ → 2H ₂ O + CO ₂ Formula (4)

  In the presence of the second fuel catalyst layer 80, the hydrogen peroxide easily generates the reaction of the above-described formula (3), generates water and oxygen, and further generates heat along with this reaction. The generated heat is used as the heat of vaporization of water generated in the reaction of methanol of the liquid fuel F and the formula (3), and promotes spontaneous vaporization. Incidentally, oxygen as a by-product is supplied to the fuel cell 10 through the gas-liquid separation membrane 70 together with the vaporized component of the liquid fuel F, or by the reaction of the above formula (4) with methanol as the first fuel. It generates water and heat, but if it is a small amount, it does not significantly affect performance. Moreover, when oxygen affects the output of the fuel cell 1, etc., for example, an oxygen removing film for removing oxygen may be provided.

For example, when permethanol is used as the peroxide, the reaction formula corresponding to the above formula (3) is “CH ₃ OOH → CO + H ₂ O + H ₂ ”. For example, when magnesium peroxide is used as the peroxide, the reaction formula corresponding to the above formula (3) is “MgO ₂ → Mg + O ₂ ”. For example, when formic acid is used as the peroxide, the reaction formula corresponding to the above formula (3) is “HC (═O) OOH → CO ₂ + H ₂ O”. Even when any of the above-described peroxides is used, water is generated and heat is generated with each reaction.

Methanol and water vaporized in the second fuel catalyst layer 80 pass through the gas-liquid separation membrane 70, diffuse through the anode gas diffusion layer 12 and are supplied to the anode catalyst layer 11, and methanol represented by the following formula (5) Internal reforming reaction occurs.
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ Formula (5)

Electrons (e ⁻ ) generated by this reaction are guided to the outside through a current collector, and are operated to a cathode (air electrode) 16 after operating a portable electronic device or the like as so-called electricity. The proton (H ⁺ ) generated by the internal reforming reaction of the formula (5) is guided to the cathode (air electrode) 16 through the electrolyte membrane 17. Air is supplied to the cathode (air electrode) 16 as an oxidant. The electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode (air electrode) 16 cause a reaction shown in the following formula (6) with oxygen in the air in the cathode catalyst layer 14, and accompanying this power generation reaction Water is produced.
(3/2) O ₂ + 6e ⁻ + 6H ⁺ → 3H ₂ O Formula (6)

  Thus, in the fuel cell 1, the internal reforming reaction described above is performed smoothly, and a high output and a stable output can be obtained.

  According to the fuel cell 1 of the embodiment of the present invention described above, the liquid fuel F is constituted by a fuel composed of a first fuel that generates hydrogen ions and electrons and a second fuel that contains peroxide, By providing the second fuel catalyst layer 80 that mainly functions as a catalyst for the second fuel, water is obtained by the reaction of the peroxide in the second fuel catalyst layer 80, and heat is accordingly obtained. This water can be used for the internal reforming reaction of methanol in the anode catalyst layer 11, and the generated heat is used as the heat of vaporization of the water generated in the reaction of methanol and peroxide of the liquid fuel F. Can do. Further, the generated heat can promote the vaporization of the water generated in the reaction of methanol and peroxide of the liquid fuel F. Thereby, the output of the fuel cell 1 can be improved, and in particular, the output can be improved and the output can be stabilized at the initial stage of power generation.

For example, in a conventional internal vaporization fuel cell using pure methanol as fuel, water generated by the combustion reaction of methanol crossing over, represented by the following formula (7), is moved to the anode (fuel electrode), It was used for the internal reforming reaction of methanol.
CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O (7)

  However, when the reaction in the equation (7) is promoted, the output in the fuel cell is reduced. Further, since the reaction in the equation (7) is an exothermic reaction, measures to improve the heat dissipation in the fuel cell must be taken. I had to.

  On the other hand, according to the fuel cell 1 of one embodiment of the present invention, the water required for the internal reforming reaction of methanol in the anode catalyst layer 11 is obtained by containing the second fuel in the liquid fuel F. It is done. As a result, water can be supplied to the anode (fuel electrode) by a method different from that of the above-described conventional fuel cell, so that the output of the fuel cell 1 can be improved without causing problems in the above-described conventional fuel cell. .

  The configuration of the fuel cell 1 according to the embodiment of the present invention is not particularly limited to the above-described configuration. For example, the fuel cell 1 is configured without the gas-liquid separation film 70 in the fuel cell 1. May be. In the fuel cell 1 described above, the arrangement position of the second fuel catalyst layer 80 is not limited to this, and may be arranged, for example, between the anode conductive layer 18 and the gas-liquid separation film 70. . The second fuel catalyst layer 80 may be disposed facing the fuel supply mechanism side of the anode catalyst layer 11, that is, between the anode catalyst layer 11 and the anode gas diffusion layer 12. Even when the second fuel catalyst layer 80 is disposed between the anode catalyst layer 11 and the anode gas diffusion layer 12, the gas-liquid separation membrane 70 is not provided between the fuel distribution layer 30 and the anode conductive layer 18. Alternatively, the fuel cell 1 may be configured. In addition, also in the structure of these fuel cells, the same effect as the effect in the fuel cell 1 of one embodiment mentioned above is acquired.

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

(Example 1 to Example 3)
The fuel cells used in Examples 1 to 3 have the same configuration as the fuel cell 1 shown in FIG. 2 and will be described with reference to FIG.

  First, a method for producing the fuel battery cell 10 will be described.

  To the carbon black supporting the anode catalyst particles (Pt: Ru = 1: 1), a perfluorocarbon sulfonic acid solution as a proton conductive resin and water and methoxypropanol as a dispersion medium were added to support the anode catalyst particles. A paste was prepared by dispersing carbon black. The obtained paste was applied to porous carbon paper (30 mm × 40 mm rectangle) as the anode gas diffusion layer 12 to obtain an anode catalyst layer 11 having a thickness of 100 μm.

  To the carbon black carrying the cathode catalyst particles (Pt), a perfluorocarbon sulfonic acid solution as a proton conductive resin and water and methoxypropanol as a dispersion medium are added to disperse the carbon black carrying the cathode catalyst particles. A paste was prepared. The obtained paste was applied to porous carbon paper as the cathode gas diffusion layer 15 to obtain a cathode catalyst layer 14 having a thickness of 100 μm. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 have the same shape and size, and the anode catalyst layer 11 and the cathode catalyst layer 14 applied to these gas diffusion layers have the same shape and size.

  Further, water and methoxypropanol were added as a dispersion medium to carbon black carrying the second fuel catalyst particles (Pt), and the carbon black carrying the second fuel catalyst particles was dispersed to prepare a paste. The obtained paste was applied to porous carbon paper to obtain a second fuel catalyst layer 80 having a thickness of 100 μm. The second fuel catalyst layer 80 has the same shape and size as the anode catalyst layer 11.

A perfluorocarbon sulfonic acid membrane (trade name: nafion membrane) having a thickness of 30 μm and a water content of 10 to 20% by weight as the electrolyte membrane 17 between the anode catalyst layer 11 and the cathode catalyst layer 14 produced as described above. The fuel cell 10 was obtained by performing hot pressing in a state where the anode catalyst layer 11 and the cathode catalyst layer 14 face each other. The electrode area was 12 cm ² for both the anode (fuel electrode) 13 and the cathode (air electrode) 16.

  Subsequently, the fuel battery cell 10 was sandwiched between gold foils having a plurality of openings to form an anode conductive layer 18 and a cathode conductive layer 19. A rubber O-ring 20 was sandwiched between the electrolyte membrane 17 and the anode conductive layer 18 and between the electrolyte membrane 17 and the cathode conductive layer 19 for sealing. Further, a frame made of polyetheretherketone (PEEK) from the anode conductive layer 18 side, the gas-liquid separation membrane 70, and the second fuel-use space between the anode conductive layer 18 and the fuel supply unit body 42 as the fuel supply mechanism 40. A stack of catalyst layers 80 in this order was sandwiched.

Further, as the moisture retaining layer 50, the thickness is 500 μm, the air permeability is 2 seconds / 100 cm ³ (according to the measurement method specified in JIS P-8117), and the moisture permeability is 4000 g / (m ² · 24 h) (JIS L -1099 A-1 polyethylene porous film (by the measurement method specified in A-1) was used.

  A stainless steel plate (SUS304) having a thickness of 2 mm on which an air introduction port 61 (diameter 3 mm, number of ports 60) for taking in air was formed on the moisture retaining layer 50 was used as the surface cover 60.

  Further, an ironing pump is used as the pump 90, a part of the flow path 44 is squeezed in a certain direction to generate pressure, and the liquid fuel F stored in the fuel storage unit 41 is sent to the fuel supply unit 43. . Here, a control circuit for controlling the rotational speed of the ironing pump by the current flowing through the fuel cell 1 is configured, and the fuel supply amount necessary for causing an electrochemical reaction in the fuel cell 1 (per 1 A of current per minute) The fuel was controlled so as to be always supplied at 1.2 times the methanol supply amount (3.3 mg).

  Further, as liquid fuel F, hydrogen peroxide was added to pure methanol, and three types of fuels having a hydrogen peroxide molar concentration of 1 mol%, 10 mol%, and 20 mol% were prepared, and each liquid fuel F was described above. It was accommodated in the fuel accommodating part 41 of the fuel cell, and the output characteristics were measured. In addition, the case where the molar concentration of hydrogen peroxide is 1 mol% is Example 1, the case where it is 10 mol% is Example 2, and the case where it is 20 mol% is Example 3.

  In measuring the output characteristics, the output was measured 10 minutes and 50 hours after the start of power generation in an environment where the temperature was 25 ° C. and the relative humidity was 50%. The measurement results are shown in Table 1. In Table 1, the output after 10 minutes and 50 hours after the start of power generation in Comparative Example 1 described later is 100, and each measurement result is shown as a ratio of output to 100, that is, an output rate.

  Moreover, in Example 1, the change of the output with respect to the power generation time was measured. In FIG. 3, the change of the output with respect to the electric power generation time in Example 1 is shown.

(Example 4 to Example 6)
The fuel cells used in Examples 4 to 6 are the same as those in Examples 1 to 3, except that the positions of the fuel cells used in Examples 1 to 3 and the second fuel catalyst layer 80 are different. The configuration of the fuel cell used was the same. In the fuel cells used in Examples 4 to 6, the second fuel catalyst layer 80 was disposed between the anode conductive layer 18 and the gas-liquid separation membrane 70.

  The configuration and set values other than those described above were the same as those of the fuel cell used in Example 1. Further, as the liquid fuel F, hydrogen peroxide is added to pure methanol, and three types of fuel having a hydrogen peroxide molar concentration of 1 mol%, 10 mol%, and 20 mol% are prepared, and each liquid fuel F is used as a fuel cell. And was measured in the output characteristics. In addition, the case where the molar concentration of hydrogen peroxide is 1 mol% is Example 4, the case of 10 mol% is Example 5, and the case of 20 mol% is Example 6. The output characteristic measurement method and measurement conditions were the same as those in Example 1. The measurement results are shown in Table 1.

(Example 7 to Example 9)
The fuel cells used in Examples 7 to 9 are the same as those in Examples 1 to 3, except that the positions of the fuel cells used in Examples 1 to 3 and the second fuel catalyst layer 80 are different. The configuration of the fuel cell used was the same. In the fuel cells used in Examples 7 to 9, the second fuel catalyst layer 80 was disposed between the anode catalyst layer 11 and the anode gas diffusion layer 12.

  The configuration and set values other than those described above were the same as those of the fuel cell used in Example 1. Further, as the liquid fuel F, hydrogen peroxide is added to pure methanol, and three types of fuel having a hydrogen peroxide molar concentration of 1 mol%, 10 mol%, and 20 mol% are prepared, and each liquid fuel F is used as a fuel cell. And was measured in the output characteristics. In addition, the case where the molar concentration of hydrogen peroxide is 1 mol% is Example 7, the case where it is 10 mol% is Example 8, and the case where it is 20 mol% is Example 9. The output characteristic measurement method and measurement conditions were the same as those in Example 1. The measurement results are shown in Table 1.

(Comparative Example 1)
The fuel cell used in Comparative Example 1 is the fuel used in Examples 1 to 3 except that the fuel cell used in Examples 1 to 3 is not provided with the second fuel catalyst layer 80. The battery configuration was the same. That is, the fuel cell used in Comparative Example 1 is configured not to include the second fuel catalyst layer 80.

  The configuration and set values other than those described above were the same as those of the fuel cell used in Example 1. Further, pure methanol was used as the liquid fuel F. The output characteristic measurement method and measurement conditions were the same as those in Example 1. The measurement results are shown in Table 1. As described above, in Table 1, the outputs after 10 minutes and 50 hours from the start of power generation in Comparative Example 1 are shown as 100, respectively.

  Moreover, in the comparative example 1, the change of the output with respect to power generation time was measured. In FIG. 3, the change of the output with respect to the electric power generation time in the comparative example 1 is shown.

(Comparative Example 2 to Comparative Example 4)
The fuel cells used in Comparative Examples 2 to 4 have the same configuration as the fuel cell used in Comparative Example 1. Further, as the liquid fuel F, hydrogen peroxide is added to pure methanol, and three types of fuel having a hydrogen peroxide molar concentration of 1 mol%, 10 mol%, and 20 mol% are prepared, and each liquid fuel F is used as a fuel cell. And was measured in the output characteristics. In addition, the case where the molar concentration of hydrogen peroxide is 1 mol% is Comparative Example 2, the case of 10 mol% is Comparative Example 3, and the case of 20 mol% is Comparative Example 4. The output characteristic measurement method and measurement conditions were the same as those in Example 1. The measurement results are shown in Table 1.

(Comparative Example 5)
The fuel cell used in Comparative Example 5 had the same configuration as the fuel cell used in Example 1. Further, pure methanol was used as the liquid fuel F. The output characteristic measurement method and measurement conditions were the same as those in Example 1. The measurement results are shown in Table 1.

(Summary of Examples 1 to 9 and Comparative Examples 1 to 5)
Comparing the outputs 10 minutes and 50 hours after the start of power generation of the fuel cells in Examples 1 to 3 and Comparative Example 1 shown in Table 1, both the outputs of Examples 1 to 3 are higher. It was. In addition, the fuel cells in Examples 1 to 3 were found to have an output that was improved 10 minutes after the start of power generation, as compared with the fuel cell in Comparative Example 1. This is also apparent from the measurement results shown in FIG. 1. The fuel cell in Example 1 has a faster output rise after the start of power generation and a higher value than the fuel cell in Comparative Example 1. I understood it.

  The reason why the rise in output after the start of power generation is improved is that the fuel cells of Examples 1 to 3 include the second fuel catalyst layer 80, the fuel contains hydrogen peroxide, and the above-described formula (3 ) By generating water and generating heat, the vaporization of the liquid fuel F is promoted, and the water necessary for the internal reforming reaction of methanol shown in Formula (5) is supplied. Conceivable.

  Also, in the fuel cells in Examples 4 to 6, it was found that both the outputs after 10 minutes and 50 hours from the start of power generation were higher than those of the fuel cell in Comparative Example 1.

  Next, when the outputs after 10 minutes and 50 hours from the start of power generation of the fuel cells in Examples 1 to 3 and Comparative Examples 2 to 3 are compared, the outputs of Examples 1 to 3 are both outputs. Both were high. In the fuel cells in Comparative Examples 2 to 3, it is considered that although the fuel contains hydrogen peroxide, the second fuel catalyst layer 80 is not provided, so that the output cannot be improved.

  Next, when the outputs after 10 minutes and 50 hours from the start of power generation of the fuel cell in Example 1 and Comparative Example 5 were compared, Example 1 was higher in both outputs. Although the fuel cell in Comparative Example 5 includes the second fuel catalyst layer 80, it is considered that the output cannot be improved because the fuel does not contain hydrogen peroxide.

  In the above-described embodiment, an example in which hydrogen peroxide is added to pure methanol as the liquid fuel F has been described. However, even when the above-described other liquid fuel F including the first fuel and the second fuel is used, In the fuel cell provided with the second fuel catalyst layer 80, the output is improved as compared with the fuel cell not including the second fuel catalyst layer 80, and the liquid fuel F does not contain the second fuel. The output has 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, and the like are not particularly limited. 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.

Sectional drawing which shows the structure of the fuel cell of one Embodiment which concerns on this invention. 1 is a cross-sectional view illustrating a configuration of a fuel cell 1 when a pump is provided in a fuel cell according to an embodiment of the present invention. The figure which shows the change of the output with respect to the power generation time in Example 1 and Comparative Example 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 10 ... Fuel cell, 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 ... O-ring, 30 ... fuel distribution layer, 31 ... opening, 40 ... fuel supply mechanism, 41 ... fuel storage, 42 ... Fuel supply unit main body, 43 ... Fuel supply unit, 44 ... Channel, 50 ... Moisturizing layer, 60 ... Surface cover, 61 ... Air inlet, 70 ... Gas-liquid separation membrane, 80 ... Catalyst layer for second fuel, F ... Liquid fuel.

Claims (13)

A fuel electrode comprising an anode catalyst layer and an anode gas diffusion layer;
An air electrode comprising a cathode catalyst layer and a cathode gas diffusion layer;
An electrolyte membrane sandwiched between the fuel electrode and the air electrode;
A fuel storage unit that is disposed on the fuel electrode side and stores a fuel composed of a first fuel that generates hydrogen ions and electrons and a second fuel that contains peroxide;
A fuel cell comprising: a second fuel catalyst layer which is disposed between the anode catalyst layer and the fuel storage portion and mainly functions as a catalyst for the second fuel. A fuel electrode comprising an anode catalyst layer and an anode gas diffusion layer;
An air electrode comprising a cathode catalyst layer and a cathode gas diffusion layer;
An electrolyte membrane sandwiched between the fuel electrode and the air electrode;
A fuel supply unit disposed on the fuel electrode side and supplying fuel to the fuel electrode;
A fuel storage section for storing fuel comprising a first fuel for generating hydrogen ions and electrons and a second fuel containing peroxide, which are supplied to the fuel supply section;
A fuel cell comprising: a second fuel catalyst layer which is disposed between the anode catalyst layer and the fuel supply unit and functions mainly as a catalyst for the second fuel.   3. The fuel cell according to claim 1, wherein a gas-liquid separation membrane that allows a vaporized component of the fuel to pass to the fuel electrode side is disposed on the fuel electrode side of the second fuel catalyst layer.   The said 2nd fuel is a solution of the 1 or more substance selected from the group which consists of a peroxide which has at least 1 sort (s) of a carbon atom, a hydrogen atom, and a metal atom. 4. The fuel cell according to any one of 3 above. The peroxide content in the second fuel is 0.1 to 20 mol% when the peroxide is represented by the following chemical formula 1 and R is a hydrogen atom, and R is composed of a hydrocarbon. The fuel cell according to any one of claims 1 to 4, wherein in the case of a compound, the content is 0.1 to 33.3 mol%.
R—O—O—R (Chemical Formula 1)   The content of the peroxide in the second fuel is 0.1 to 50 mol% when the peroxide is an inorganic metal peroxide. The fuel cell according to item.   2. The second fuel is a solution of one or more substances selected from the group consisting of a percarboxylic acid and a peroxo acid having at least one of a carbon atom and a hydrogen atom. 4. The fuel cell according to any one of 3 above.   The fuel cell according to claim 7, wherein the content of percarboxylic acid and peroxo acid in the second fuel is 0.1 to 50 mol%.   9. The first fuel according to claim 1, wherein the first fuel is an aqueous solution or a non-aqueous solution of one or more substances selected from the group consisting of hydrocarbon-containing alcohols, carboxylic acids, and aldehydes. The fuel cell as described.   10. The fuel cell according to claim 9, wherein the first fuel is an aqueous solution or a non-aqueous solution of one or more substances selected from the group consisting of methanol, ethanol, formic acid, acetic acid, formaldehyde, and acetaldehyde.   The fuel cell according to any one of claims 1 to 10, wherein the content of the first fuel is 0.1 to 24.5M.   12. The fuel cell according to claim 1, wherein the catalyst in the second fuel catalyst layer is a noble metal of at least one element or an alloy of the noble metal.   The fuel cell according to any one of claims 1 to 12, wherein the catalyst in the second fuel catalyst layer is supported on a carbon-based support or a support containing an inorganic metal.

Images