CN1691386A - Fuel cell power source, method of operating thereof and portable electronic equipment - Google Patents

Abstract

The fuel cell is provided with a means of supplying liquid fuel and water supplied to an anode with one pump in time division manner. Thus, since a concentration control mechanism for detecting the concentration of the liquid fuel and maintaining a specified concentration is used in conventional fuel cells carrying out circulated use of fuel cell, a plurality of pumps, such as the pump to transport high concentration liquid fuel and the pump transporting water were necessary. Furthermore, the problem is solved, wherein the fuel cell power source itself being enlarged, due to the use of a plurality of pumps and having the occupancy space by auxiliary machinery, such as the pumps becoming large as a result.

Description

Fuel cell power supply, method of operating the same, and portable electronic device using the same

Technical Field

The present invention relates to a fuel cell power supply using a liquid such as methanol as a fuel, a method of operating the fuel cell power supply, and a portable electronic device using the fuel cell power supply.

Background

A fuel cell is characterized by high energy efficiency because chemical energy of fuel is directly converted into electric energy by an electrochemical reaction. In addition, since the fuel cell can continuously generate power when only the fuel is replaced or replenished, it is not necessary to temporarily stop the operation of the portable electronic device for charging as observed in the case of the secondary battery. Therefore, in recent years, attention has been paid to the power supply unit for the portable electronic device.

Among them, fuel cells using liquid fuels having a higher volumetric energy density than gases such as hydrogen, for example, methanol, ethanol, propanol, dimethyl ether, and ethylene glycol, have been studied, and development of power supply units for portable electronic devices has been advanced.

In recent years, research and development of a so-called Direct Methanol Fuel Cell (DMFC) which is a fuel cell using methanol as a liquid fuel have been actively carried out.

Among them, a fuel cell power generation device has been proposed which can increase the fuel utilization efficiency and the output of the DMFC by increasing the initial concentration of the aqueous methanol solution in the aqueous methanol solution to a high concentration (see, for example, patent document 1). This patent document 1 is a fuel cell power generation device that evaluates the concentration of the methanol aqueous solution in the methanol aqueous solution container using the total amount of electricity obtained from the cell, and controls the flow rate of the methanol aqueous solution supplied to the cell in accordance with the evaluated concentration of the methanol aqueous solution. Further, patent document 1 includes, as a device which can be driven for a long time, a2 nd aqueous methanol solution container and a2 nd liquid feed pump as methanol replenishing means for replenishing the aqueous methanol solution container with an aqueous methanol solution, and a fuel cell power generation device (fuel cell power supply) for controlling the flow rate of the aqueous methanol solution to be supplied to the cell.

Patent document 1: japanese patent application laid-open No. 2003-22830 (page 2).

Disclosure of Invention

However, in a conventional fuel cell in which liquid fuel is circulated, a concentration control structure is used which detects the concentration of the liquid fuel and maintains a predetermined concentration, and therefore a plurality of pumps such as a pump for supplying high-concentration liquid fuel and a pump for supplying water are necessary. The use of these pumps increases the space occupied by auxiliary equipment such as pumps in the fuel cell power supply, and as a result, there is a problem that the fuel cell power supply itself becomes large in size.

The purpose of the present invention is to miniaturize a fuel cell power source compared with a fuel cell power source requiring a plurality of pumps.

The invention provides a fuel cell having a unit for supplying liquid fuel and water to an anode in a time-division manner by using one pump.

According to the present invention, the number of pumps can be reduced to miniaturize the fuel cell.

Drawings

Fig. 1 is a diagram for explaining the structure of a direct methanol fuel cell.

Fig. 2 is a view for explaining the structure of a fuel cell power supply.

Fig. 3 is a diagram for explaining the flows of liquid fuel and water of the fuel cell power supply.

Fig. 4 is a flowchart of a processing routine I for adjusting the concentration of the liquid fuel used in the fuel cell power supply.

Fig. 5 is a flowchart of a processing routine II for adjusting the concentration of the liquid fuel used in the fuel cell power supply.

Fig. 6 is a diagram for explaining a schematic structure of a liquid feed pump used in a fuel cell power supply.

Fig. 7 is a diagram for explaining a schematic structure of a time-divisible liquid feed pump used in a fuel cell power supply.

Fig. 8 is a graph showing changes with time of the liquid-sending amount and concentration of the time-divisible liquid-sending pump used in the fuel cell power supply of example 5.

Fig. 9 is a graph showing changes with time of the liquid-sending amount and concentration of the time-divisible liquid-sending pump used in the fuel cell power supply of example 6.

Fig. 10 is a graph showing the voltage-current characteristics of the fuel cell power supply of example 1.

Fig. 11 is a graph showing the relationship between time and output voltage when the fuel cell power supply of example 1 continuously generates power.

Fig. 12 is a graph showing the voltage-current characteristics of the fuel cell power supply of comparative example 1.

Fig. 13 is a diagram showing the relationship between time and output voltage when the fuel cell power supply of comparative example 1 continuously generates power.

Fig. 14 is a diagram for explaining a schematic configuration of a notebook personal computer according to the present invention.

Fig. 15 is a photograph showing the appearance of the PDA of the present invention.

Fig. 16 is a diagram for explaining a schematic configuration of the PDA of the present invention.

Fig. 17 is a diagram for explaining the structure of a fuel cell power source used in comparative example 1.

Detailed Description

Embodiments of the fuel cell power supply and the portable electronic device using the fuel cell power supply of the present invention will be described in detail below. However, the present invention is not limited to the following

Provided is an implementation mode.

First, a description will be given of a standard DMFC as an example of a fuel cell using a liquid fuel. Fig. 1 is a diagram showing a schematic structure of a DMFC. DMFC100, comprising: a solid polymer electrolyte membrane 102; an electrolyte membrane/electrode assembly (MEA; membrane electrode assembly) in which an anode catalyst layer 103 and a cathode catalyst layer 104 are integrally joined to both surfaces of the solid polymer electrolyte membrane 102; and an anode diffusion layer 105 and a cathode diffusion layer 106 which are respectively bonded to the outside of the anode catalyst layer 103 and the outside of the cathode catalyst layer 104. Further, a fuel flow plate 107 is disposed outsidethe anode diffusion layer 105. The fuel flow plate 107 is formed with a fuel flow path 110 having a fuel supply port 108 and a fuel discharge port 109.

The methanol aqueous solution is supplied to the fuel supply port 108 via the liquid feed pump. Similarly, an air flow passage plate 111 is also disposed outside the cathode diffusion layer 106. An air flow path 114 having an air supply port 112 and an air discharge port 113 is formed on the air flow path plate 111. An oxidizing agent (here, oxygen) such as air is supplied to the air supply port 112 by a blower, a blower pump, or the like. The methanol aqueous solution sent from the methanol aqueous solution tank by the liquid sending pump and the methanol aqueous solution supplied to the fuel supply port 108 of the fuel flow plate 107 flow through the groove portion (fuel flow path 110) of the fuel flow plate 107. The aqueous methanol solution flowing through the fuel flow path 110 is immersed in the anode diffusion layer 105 in contact with the fuel flow path plate 107, and thus the aqueous methanol solution is uniformly supplied to the anode catalyst layer 103. The anode catalyst layer 103 and the anode diffusion layer 105 are collectively referred to as an anode electrode (negative electrode) or an anode gas diffusion electrode, and are abbreviated as an anode electrode 120 here. Similarly, the cathode catalyst layer 104 and the cathode diffusion layer 106 are collectively referred to as a cathode electrode (negative electrode) or cathode gas diffusion electrode, and are abbreviated herein as cathode electrode 130.

Next, the reaction of the methanol aqueous solution supplied to the anode catalyst layer 103 will be described. The methanol aqueous solution is decomposed into carbon dioxide gas (CO) by the reaction represented by the formula (1) below₂) Hydrogen ion (H)⁺) And electron (e)^-)。

(1)

The generated protons migrate from the anode 120 side to the cathode 130 side in the solid polymer electrolyte membrane 102, and oxygen (O) in the air flows over the cathode catalyst layer 104₂) And electron (e)^-) Reacting according to the formula (2) to produce water (H)₂O)。

(2)

The electrochemical reaction is represented by the general reaction formula (3) according to the general reaction formulas of the electrochemical reactions of the reaction formulas (1) and (2). DMFC generates electromotive force by directly converting chemical energy into electric energy according to the formula (3).

(3)

However, the methanol aqueous solution flowing through the fuel flow plate 107 of the DMFC100 does not completely penetrate into the anode diffusion layer 105. A part of the methanol aqueous solution does not undergo the reaction of the reaction formula (1), and flows out of the fuel outlet 109 of the fuel flow plate 107 as it is. Therefore, there is a problem that the use efficiency (reaction efficiency) of the methanol aqueous solution supplied to the DMFC is lowered. In order to improve the efficiency, attempts have been made to improve the structure of the fuel flow plate 107, but the utilization efficiency has not been improved yet. Therefore, in order to improve the utilization efficiency, the methanol aqueous solution discharged from the fuel discharge port 109 of the fuel flow path plate 107 is once returned to the container of the methanol aqueous solution, and is also tried to be reused.

However, in the anode catalyst layer 103, since the aqueous methanol solution and water are reacted at a 1 to 1 (molar ratio) as shown in the above formula (1), the consumption amount of the aqueous methanol solution (molecular weight: 32) is about 1.8 times as large as that of water. Therefore, when the methanol aqueous solution discharged from the fuel flow path plate 107 is returned to the storage container of the methanol aqueous solution as it is, the concentration of the methanol aqueous solution in the storage container gradually becomes lower. Therefore, when the methanol aqueous solution whose concentration is reduced by recycling is used as it is, the reaction represented by the above reaction formula (1) does not proceed sufficiently because the methanol in the cell is insufficient, and there occurs a problem that the electromotive force (output voltage) decreases rapidly.

In addition, methanol and water in the methanol aqueous solution supplied to the anode catalyst layer 103 in fig. 1 generate protons (H) according to the reaction formula shown in formula (1)⁺) Carbon dioxide gas (CO)₂) And electron (e)^-). The generated carbon dioxide gas is discharged from the anode catalyst layer 103 through the anode diffusion layer 105 along the fuel flow path 110 from the fuel outlet 109. The carbon dioxide gas thus generated may grow from a state of fine bubbles in the methanol aqueous solution to the atmosphere in the anode catalyst layer 103 or the anode diffusion layer 105 in the anodeBubbles, such large bubbles of carbon dioxide gas, in particular, often hinder the flow of the liquid fuel in the anode diffusion layer 105 in some cases. Therefore, the methanol aqueous solution supplied to the anode catalyst layer 103 becomes insufficient, and the power generation capability is lowered (the output voltage is lowered).

Accordingly, it is also necessary to smoothly discharge the generated carbon dioxide gas from the anode catalyst layer 103 or the cathode diffusion layer in the anode without hindering the supply of the methanol aqueous solution to the anode catalyst layer 103.

Fig. 2 shows a structure of a fuel cell power supply of the present invention.

In fig. 2, a fuel cell power supply 1 mainly includes: a fuel cell unit 10, a liquid fuel supply unit 20, a control unit 30, a power storage unit 40, and an oxidizing gas supply unit 50.

The fuel cell section 10 is constituted by a liquid fuel cell similar to the DMFC100 shown in fig. 1. The fuel cell unit 10 is a part that generates electricity by an electrochemical reaction between the liquid fuel (hereinafter, methanol is described as a representative example) supplied from the liquid fuel supply unit 20 and the oxidizing gas (hereinafter, air is described as a representative example) supplied from the oxidizing gas supply unit 50. The liquid fuel supply unit 20 is composed of a container 21 for storing water, a container 22 for storing a high-concentration methanol aqueous solution, and a liquid feed pump 23 for supplying the high-concentration methanol aqueous solution and water to the liquid fuel supply unit 20. A control unit 30 which is composed of a logic circuit centered on a microcomputer and has a signal processing unit 31 for performing signal processing by a CPU; a storage unit 32 for storing data by a memory such as a ROM or a RAM; an input/output board (not shown) for inputting/outputting various signals. A control unit 30 for controlling the entire fuel cell power supply 1, and controlling the supply amounts of the high-concentration methanol aqueous solution and water supplied to the fuel cell unit 10 and the supply liquid feed pump 23 by a microcomputer; control of the power storage unit 40; and control of an air blower supplied from the oxidant gas supply unit 50 to the fuel cell portion 10. The power storage unit 40 is composed of a DC-DC converter (chopper) 41 and a power storage unit 42 (a chargeable/dischargeable lithium ion secondary battery, an ultracapacitor, and the like). The power storage unit 40 is a part that boosts DC power generated by the fuel cell unit 10 by a DC-DC converter (chopper) 41, charges a power storage unit 42 such as a rechargeable lithium ion secondary battery or an ultra capacitor with the boosted DC power, and supplies the power charged in the power storage unit 42 to discharge an external load. The lithium ion secondary battery, the supercapacitor, and the like of the power storage unit 42 can supply the necessary power by discharging at the time of starting the fuel cell power supply 1 or when the power necessary for the external circuit is larger than the discharge power of the fuel cell unit 10. The lithium ion secondary battery and the supercapacitor of the storage unit 42 are applicable to power supplies (not shown) of the control unit 30, the liquid feeding pump 23, the air blower 51, and the like. The oxidizing gas supply unit 50 is a unit for supplying an oxidizing gas such as air to the fuel cell unit 10 by an air blower 51.

An embodiment of the fuel cell power supply 1 of the present invention will be described in more detail below with reference to fig. 3.

First, the flow of the methanol aqueous solution as the liquid fuel will be described. The methanol aqueous solution supplied to the fuel cell unit 10, that is, the DMFC100, is supplied with water and the methanol aqueous solution alternately from the water tank 21 and the methanol aqueous solution tank 22 of the liquid fuel supply unit 20 by the liquid feed pump 23. The alternate supply of water and the methanol aqueous solution is performed by alternately switching the flow path of water and the flow path of the methanol aqueous solution by an electromagnetic valve 24 provided on the inlet side of a liquid feed pump 23 between theflow path of water supplied from a water tank 21 of the liquid fuel supply unit 20 and the flow path of the methanol aqueous solution supplied from a methanol aqueous solution tank 22. Alternatively, water and the methanol aqueous solution may be supplied to each other only by the liquid-feeding pump 23 without using the electromagnetic valve 24. The water and the methanol aqueous solution thus alternately supplied are supplied to the DMFC100 from the fuel supply port 108 of the fuel flow plate 107 and discharged from the fuel discharge port 109 through the fuel flow path 110. Then, the discharged methanol aqueous solution is mixed with water or a methanol aqueous solution alternately supplied from the liquid-feeding pump 23 in the outlet-side pipe of the liquid-feeding pump 23 after the generated carbon dioxide gas is removed in the gas-liquid separation section 25, and is supplied again to the fuel supply port 108 of the fuel flow path plate 107. The methanol aqueous solution flowing through the fuel flow path 110 is immersed in the anode diffusion layer 105 made of a porous material such as carbon paper, and is supplied to the anode catalyst layer 103 through the anode diffusion layer 105. At this time, the methanol aqueous solution enters the cathode diffusion layer in contact with the convex portion (portion not corresponding to the fuel flow path 110) of the fuel flow path plate 107, and is supplied to the anode catalyst layer 103. The methanol aqueous solution supplied to the anode catalyst layer 103 is dissociated into carbon dioxide gas, protons, and electrons according to the reaction formula (1) described above. The generated protons move from the anode side to the cathode side in the solid polymer electrolyte membrane 102. The protons react with oxygen components in the air supplied to the cathode catalyst layer 104 and electrons on the cathode catalyst layer 104 according to the reaction formula (2) described above to generate water. The produced water is separated from the air in the gas-liquid separator 52, and then recovered in the water tank 21 to adjust the concentration of the methanol aqueous solution. The generated electrons are supplied to the power storage unit 40 through the anode catalyst layer 103 and the fuel flow path plate 107. The air supplied to the cathode catalyst layer 104 is supplied to the supply port 112 of the air flow passage plate 111 by the air blower 51 of the oxidizing gas supply unit 50, and is supplied to the cathode catalyst layer 104 through the cathode diffusion layer 106 by the air flow passage 114 provided in the air flow passage plate 111. The supplied air reacts in the cathode catalyst layer 104 to generate water.

The structure of DMFC100 is described in detail below, DMFC100 comprises MEA bonded to both surfaces of solid polymer electrolyte membrane 102, anode diffusion layer 105 bonded to the outside of anode catalyst layer 103 and cathode catalyst layer 104, cathode diffusion layer 106, and fuel flow path plate 107 and air flow path plate 111 bonded to the outside of anode diffusion layer 105 and cathode diffusion layer 106, respectively, fuel flow path plate 110 having fuel supply port 108 and fuel discharge port 109 is formed on fuel flow path plate 107, air flow path 114 having air supply port 112 and air discharge port 113 is formed on air flow path plate 111, solid polymer electrolyte membrane 102 used in the present embodiment is not particularly limited as long as it is a solid polymer electrolyte membrane having proton conductivity, and specifically, for example, Nafion (registered trademark, Dupont company), Aciplex (registered trademark, manufactured by Asahi Kawakawa Kasei corporation), Flemion (registered trademark, tradename of Polyperfluorosulfonic acid-sulfonic acid-type polymer electrolyte membrane, registered trademark, manufactured by Asahi-Suzu corporation, Asahi-Kawakao corporation, Polytetrafluoroethylene-Buzu-A-Buzu-a polymer electrolyte membrane, Polytetrafluoroethylene-Buzu-a polymer electrolyte membrane, a polymer electrolyte membrane prepared by grafting Polytetrafluoroethylene-ethylene-carbonate-ethylene-carbonate-ethylene-carbonate-ethylene-carbonate-ethylene-carbonate-ethylene-carbonate-ethylene-carbonate-ethylene.

Sometimes the mechanical strength of the film is insufficient. As a measure for such a case, it is effective to use a nonwoven fabric or woven fabric of fibers having excellent mechanical strength, durability, and heat resistance as a core material, or to add these fibers as a filler for reinforcement in the production of an electrolyte membrane, in order to improve the electrolyte membrane and further improve the reliability. The method of filling the space with the electrolyte by opening the pores in the membrane is also effective. In addition, in order to reduce the fuel permeability (crossover) of the electrolyte membrane, a membrane doped with sulfuric acid, phosphoric acid, sulfonic acids, and phosphonic acids in polybenzimidazole may also be used.

The sulfonic acid equivalent (dry resin) of the solid polymer electrolyte membrane 102 is preferably 0.5 to 2.0 meq/g, and more preferably 0.7 to 1.6 meq/g. When the sulfonic acid equivalent is less than this range, the ion conductivity of the membrane becomes large (ion conductivity is lowered), while when the sulfonic acid equivalent is more than this range, the membrane is easily dissolved in water, which is not preferable.

The thickness of the solid polymer electrolyte membrane 102 is not particularly limited, but is preferably 10 to 200 μm. Particularly preferably 30 to 100 μm. To obtain a film having a strength which can be practically tolerated, a thickness of more than 10 μm is preferable, and a thickness of less than 200 μm is preferable in order to reduce the film resistance, i.e., to improve the power generation performance. The thickness of the electrolyte membrane can be controlledby the concentration of the electrolyte solution or the thickness of the electrolyte solution applied to the substrate when the solution casting method is used. The thickness of the electrolyte membrane when the membrane is formed from a molten state can be controlled by stretching a membrane having a predetermined thickness obtained by a melt pressing method, a melt-pressure method, or the like at a predetermined magnification. In the production of the solid polymer electrolyte membrane 102 used in the present embodiment, additives such as a plasticizer, a stabilizer, and a releasing agent, which are generally used for polymers, may be used as long as the object of the present embodiment is not impaired.

The catalyst layer of the electrode used in the MEA for use as a fuel cell is composed of a conductive material and fine particles of a catalytic metal supported on a highly conductive material, and may contain a water repellent and a binder as necessary. Further, a layer composed of a catalyst-free conductive material and, if necessary, a water repellent and a binder may be provided outside the catalytic layer. The catalytic metal used in the catalytic layer of the electrode may be any metal that can promote the oxidation reaction of hydrogen and the reduction reaction of oxygen, and examples thereof include platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys thereof. Among such catalysts, platinum is particularly useful as a cathode catalyst, and platinum-ruthenium is useful as an anode catalystGold is often used. The particle diameter of the metal as the catalyst is usually 10 to 300 angstroms. The adhesion of these catalysts to a carrier such as carbon can reduce the amount of the catalyst used, and is advantageous in terms of cost. The amount of the anode catalyst used is 0.5 to 20mg/cm in the electrode-formed state²Preferably 5 to 15mg/cm²The amount of the cathode catalyst used is 0.01-10 mg/cm²Preferably 0.1 to 10mg/cm². It is preferable that the amount of the anode catalyst is larger than that of the cathode catalyst. The anode catalyst layer 103 is preferably thicker than the cathode catalyst layer 104 because the reaction of the reaction formula (1) in which protons and electrons are generated from methanol and water in the anode catalyst is slow. The thickness of the anode catalyst layer 103 is preferably 20 to 300 μm, particularly 50 to 200 μm. The thickness of the cathode catalyst layer 104 is preferably 3 to 150 μm, particularly 5 to 50 μm. The anode catalyst layer 103 and the anode diffusion layer 105 are preferably subjected to hydrophilic treatment in order to be easily wetted with an aqueous fuel solution such as methanol. On the other hand, in order to prevent retention of water generated in the cathode catalyst layer 104 and the cathode diffusion layer 106, it is preferable to perform thinningAnd (6) water treatment.

The method of hydrophilizing the anode catalyst layer 103 and the anode diffusion layer 105 includes, for example, the following methods: first, the carbon (carbon) material used in the anode catalyst layer 103 and the anode diffusion layer 105 is treated with an oxidizing agent selected from hydrogen peroxide, sodium hypochlorite, potassium permanganate, hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, fuming sulfuric acid, fluoric acid, acetic acid, ozone, and the like, and then hydrophilic groups such as hydroxyl groups, sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, sulfate groups, carbonyl groups, amino groups, and the like are introduced into the carbon (carbon) material. In addition, as a method for introducing a hydrophilic group into the carbon (carbon) material, a method of adding a hydrophilic surfactant or the like by activation treatment by electrolytic oxidation (anodic oxidation) or steam oxidation can be used.

Since the hydrophilization treatment of the anode catalyst layer 103 for easily wetting with methanol fuel and the reaction of the above formula (1) dominate the rate of the total reaction, the cathode catalyst layer 104 is made thicker to increase the contact time and to increase the number of reactions; or hydrophilizing the anode diffusion layer 105 and hydrophobizing the cathode diffusion layer 106; carbon dioxide gas generated by the reaction according to the above formula (1) at the anode and water generated by the reaction at the cathode can be smoothly discharged from the battery; and the output voltage of the cell can be made higher, etc., so that it is effective not only for a dilution circulation type fuel cell of a stack type but also for all liquid fuel cells of a so-called passive flat type which rely on natural diffusion supply without using a pump or a blower to feed fuel and air.

The conductive material carrying the catalyst may be any of various metals, electron conductive materials such as carbon (carbon) materials, and the like. Among them, as the carbon material, for example, there are: furnace carbon black, channel carbon black, acetylene black, amorphous carbon, carbon nanotubes, carbon nanohorns, activated carbon, graphite, and the like. These materials may be used alone or in combination. The particle diameter of the carbon (carbon) particles is, for example, 0.01 μm or more and 0.1 μm or less, preferably 0.02 μm or more and 0.06 μm or less. Examples of the hydrophobizing agent for performing the hydrophobic treatment include fluorocarbon and polytetrafluoroethylene. As the binder, a 5 wt% aqueous/ethanol solution of a perfluorocarbon sulfonic acid electrolyte for covering the electrode catalyst of the present embodiment (solvent prepared by mixing water, isopropyl alcohol and n-propyl alcohol at a weight ratio of 20: 40; manufactured by Frukomik (フルカケミカ)) was used as it is,and it is preferable from the viewpoint of adhesiveness, but other various resins may be used. In this case, it is preferable to add a fluorine resin having hydrophobicity, and particularly, it is preferable to use a material having excellent heat resistance and acid resistance, for example, polytetrafluoroethylene, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and a tetrafluoroethylene-hexafluoropropylene copolymer.

The joining method of the electrolyte membrane and the electrode when used as a fuel cell is not particularly limited, and known methods disclosed in Japanese patent application laid-open No. 5-182672 and Japanese patent application laid-open No. 2003-187824 can be applied. As a method for manufacturing the MEA, for example, the following methods are available: the catalyst layer is formed by mixing Pt catalyst powder supported by carbon and polytetrafluoroethylene suspension, coating the mixture on carbon paper, and performing heat treatment. Next, the same electrolyte solution as the electrolyte membrane was applied to the catalyst layer, and the electrolyte membrane and the catalyst layer were integrated by hot pressing. In addition, there is also a method of covering the same electrolyte solution as the electrolyte membrane on the Pt catalytic powder in advance; a method of coating the catalyst slurry on the electrolyte membrane side; a method of disposing an electrode on an electrolyte membrane by electroless plating; and a method of adsorbing platinum group metal complex ions on an electrolyte membrane and then reducing the adsorbed platinum group metal complex ions. The polymer electrolyte fuel cell is configured such that a grooved current collector having a fuel flow path and an oxidant flow path is formed on the outer side of the assembly of the electrolyte membrane and the gas diffusion electrode formed as described above, the current collector is composed of a fuel distribution plate and an oxidant distribution plate arranged in this manner, the resulting product is used as a single cell, and a plurality of such single cells are stacked with a cooling plate or the like interposed therebetween to constitute the polymer electrolyte fuel cell. For connecting the battery cells, a planar connection method may be used in addition to lamination. The method of connecting the battery cells is not particularly limited. The fuel cell is preferable in that, when it is operated at a high temperature, the overvoltage at the electrode is reduced due to the activation of the catalyst at the electrode, but there is no limitation on the operating temperature. The liquid fuel can be vaporized to operate at a high temperature.

Next, the concentration adjustment and supply method of the methanol aqueous solution supplied to the DMFC100 will be described. First, the concentration of the methanol aqueous solution supplied to the DMFC100 will be described. When a fluorine-based solid polymer electrolyte membrane is used, the concentration of the methanol aqueous solution supplied to the DMFC100 is controlled to be 3 to 15 wt%, and preferably 5 to 10 wt%. In this case, when the concentration of the aqueous methanol solution is higher than 15 wt%, the amount of methanol permeating the electrolyte membrane tends to increase, and the efficiency of methanol utilization decreases, which is not preferable. Also, when the concentration of the methanol aqueous solution is less than 3 wt%, it is not preferable because the output voltage of the DMFC100 decreases. In addition, when the aromatic hydrocarbon based solid polymer electrolyte membrane is used, since the amount of methanol passing through the electrolyte membrane is small, the concentration of the methanol aqueous solution in the DMFC100 is preferably in the range of 5 to 64 wt%, more preferably 20 to 60 wt%. Next, a method of adjusting the concentration of the aqueous methanol solution will be described. In the anode catalyst layer 103, since methanol in the aqueousmethanol solution is consumed according to the reaction formula of the above formula (1), the concentration of methanol in the aqueous methanol solution gradually decreases. Therefore, when the methanol aqueous solution discharged from the fuel flow path 110 is returned to the DMFC100 as it is after carbon dioxide gas is removed by the gas-liquid separator 25, there is a problem that methanol is insufficient in the cell and the electromotive force is rapidly reduced.

Then, the concentration of the aqueous methanol solution is detected by a methanol concentration sensor 240 provided in the DMFC100 and the information is transmitted to the control section 30. The control unit 30 outputs a signal from the signal processing unit 31 to control the concentration of methanol in the aqueous methanol solution to a concentration set in advance in the storage unit 32. That is, when the methanol aqueous solution or water is fed by the liquid-feeding pump 23, the control unit 30 outputs a signal from the signal processing unit 31 so that the flow path connecting the outlet of the methanol aqueous solution container 22 and the inlet of the liquid-feeding pump 23 and the flow path connecting the outlet of the water container 21 and the inlet of the liquid-feeding pump 23 are switched in a time-division manner by the electromagnetic valve 24 provided on the inlet side of the liquid-feeding pump 23. Alternatively, water and the methanol aqueous solution may be supplied to each other only by the liquid-feeding pump 23 without using the electromagnetic valve 24.

Fig. 4 and 5 show a method of adjusting the concentration of the aqueous methanol solution supplied to the DMFC100 by the controller 30. Fig. 4 is a flowchart showing a routine I of the concentration adjustment processing of the aqueous methanol solution when the electromagnetic valve 24 is used. Fig. 5 is a flowchart showing a routine II of the concentration adjustment processing ofthe aqueous methanol solution when the electromagnetic valve 24 is not used. In fig. 4, when this processing routine I starts, the control unit 30 performs the following execution steps. That is, the methanol concentration detected by the methanol concentration sensor 240 provided in the DMFC100 is read (step S1). Thereafter, it is judged whether or not the concentration of the methanol aqueous solution of DMFC100 is in an appropriate range based on the detection signal given by methanol concentration sensor 240 (step S2). When it is determined in step S2 that the concentration of the aqueous methanol solution in DMFC100 is not within the appropriate range, the timing (timing stored in the memory in advance) at which the flow path of the aqueous methanol solution and the flow path of the water are switched by solenoid valve 24 is changed (step S3), and this processing routine I is ended. When the concentration of the aqueous methanol solution in the DMFC100 is determined to be within the appropriate range in step S2, the process returns to step S1 to read the methanol concentration again.

In fig. 5, when this processing routine II is started, the control unit 30 performs the following execution steps. That is, the methanol concentration detected by the methanol concentration sensor 240 provided in the DMFC100 is read (step S11).

Thereafter, it is judged whether or not the concentration of the methanol aqueous solution of DMFC100 is in an appropriate range based on the detection signal given by methanol concentration sensor 240 (step S12). When it is determined in step S2 that the concentration of the aqueous methanol solution in the DMFC100 is not within the appropriate range, the timing of time allocation (timing stored in advance in the memory) of the liquid sending pump 23 for supplying the aqueous methanol solution and water is changed (step S13), and this processing routine II is ended. When the concentration of the aqueous methanol solutionin the DMFC100 is determined to be within the appropriate range in step S12, the process returns to step S11 to read the methanol concentration again.

In the concentration control performed in this way, when the aqueous methanol solution or water is fed by the liquid-feeding pump 23, the flow path connecting the outlet of the aqueous methanol solution container 22 and the inlet of the liquid-feeding pump 23 and the flow path connecting the outlet of the water container 21 and the inlet of the liquid-feeding pump 23 are switched in a time-division manner by the electromagnetic valve 24 provided on the inlet side of the liquid-feeding pump 23 so that the concentration is within the appropriate concentration range, in accordance with the timing stored in advance in the memory. The timing of switching the flow path of the methanol aqueous solution and the flow path of the water by the electromagnetic valve 24 is not particularly limited. However, in order to smoothly discharge carbon dioxide gas from the fuel flow path 110 in the DMFC100 by pulsation, it is appropriate that the timing of switching the flow path of the methanol aqueous solution and the flow path of water by the electromagnetic valve 24 is a timing at which the pulsation is easily started 100 times to 0.001 times, preferably 50 times to 0.2 times within 1 second. The concentration of the methanol aqueous solution in the methanol aqueous solution container 22 is not particularly limited, but when the concentration of the methanol aqueous solution is high, the amount of methanol contained is large, and the continuous use time is prolonged when the volume is the same, so that the concentration of the methanol aqueous solution is preferably high. The concentration of the aqueous methanol solution is usually 30 to 100 wt%, and a concentration of 90 wt% or more is particularly preferable. When the liquid-feeding pump 23 is a time-division pump, the ratio of liquid feeding is determined by the volume of the left and right partition walls, and the concentration of the aqueous methanol solution in the aqueous methanol solution container 22 is determined by the volume ratio of the left and right partition walls.

Next, a method of feeding the liquid fuel (methanol aqueous solution) or water separately in a time division manner by one liquid feed pump 23 will be described. The method is not particularly limited as long as it is a method of separately feeding the methanol aqueous solution or the water by one liquid feeding pump 23 in a time division manner. As this specific method, there is the following method.

(1) When the methanol aqueous solution or water is fed by the liquid-feeding pump 23, the methanol aqueous solution or water is fed in a time-division manner at a timing at which a flow path connecting the outlet of the methanol aqueous solution container 22 and the inlet of the liquid-feeding pump 23 and a flow path connecting the outlet of the water container 21 and the inlet of the liquid-feeding pump 23 are switched by the electromagnetic valve 24 provided on the inlet side of the liquid-feeding pump 23.

(2) When a piezoelectric pump, a plunger pump, or the like having two or more volumes is used at the inlet of the pump, the methanol aqueous solution and water supplied to the inlet of the pump having two or more volumes are fed in a time-division manner at each timing.

The liquid feed pump used in the method (1) is not particularly limited, and may be a pump capable of feeding a liquid fuel. As such a pump, there are: (A) a turbo type pump: (A-1) a vortex pump; centrifugal pumps such as diffusion pumps; (A-2) a turbine diagonal flow pump; an oblique flow pump; (A-3) an axial flow pump; (B) a positive displacement pump: (B-1) a piston pump; a piezoelectric pump; a plunger pump; reciprocating pumps such as diaphragm pumps; (B-2) a gear pump; rotary pumps such as screw pumps; (C) a special pump: a vortex gear pump (cascade pump); bubble pumps (air lift pumps); jet pumps, and the like.

In addition, the method (2) is a method using a piezoelectric pump and a plunger pump. Piezoelectric and plunger pumps, which typically expel the same liquid in one pump body during the intake of the liquid in the other, are designed so that the same amount of liquid can always be delivered uniformly. In this method (2), for example, when one of the pump inlets of the piezoelectric pump and the plunger pump is connected to a flow path for supplying liquid fuel such as an aqueous methanol solution and the other pump inlet is connected to a flow path for supplying water, the water is discharged while the aqueous methanol solution is being sucked, and conversely, the aqueous methanol solution is discharged while the water is being sucked. That is, the present invention is a liquid feeding method for time-dividing the timings of feeding the aqueous methanol solution and water to the DMFC 100.

Fig. 6 and 7 show a schematic structure of the piezoelectric liquid-feeding pump. Fig. 6 is a piezoelectric liquid-feeding pump for the method (1), and fig. 7 is a piezoelectric liquid-feeding pump for the method (2). Such a piezoelectric liquid feed pump is employed because it is most suitable for the DMFC100 that needs to feed a small amount of liquid with a high pressure head with low power consumption. First, the operation principle of the conventional piezoelectric liquid-feeding pump shown in fig. 6 will be described. The reverse flow prevention valve 304 is a one-way valve that can be opened only in one direction. In fig. 6, when the bimorph vibrator 301 made of polyvinylidene fluoride is shifted to the right in fig. 6, the backflow prevention valve 304A on the left fluid inlet side is opened, and the backflow prevention valve 304C on the left fluid outlet side is closed. At this time, the fluid is sucked into the leftpartition chamber through the fluid inlet 303. At this time, the backflow prevention valve 304B on the inlet side of the right fluid is closed, the backflow prevention valve 304D on the outlet side of the fluid is opened, and the fluid present in the partition chamber on the right side is sent out. On the other hand, when the bimorph vibrator 301 moves to the left, the fluid present in the right cell is sent out from the cell, and the opposite fluid enters the left cell. Since the bimorph vibrator 301 moves left and right with the amplitude 306 according to the frequency, the amount of liquid delivered in one direction changes according to the frequency by such a repetitive operation, and the amount of liquid delivered is large at high frequencies.

Next, the operation principle of the piezoelectric liquid-feeding pump of the present embodiment shown in fig. 7 will be described. In fig. 7, when the bimorph vibrator 401 made of polyvinylidene fluoride is shifted to the right in fig. 7, the backflow prevention valve 402-B2 of the outlet 408 of the left fluid B is closed, and the fluid portable electronic device is sent into the left partition chamber. On the other hand, the backflow prevention valve 402-a2 at the inlet 405 for the fluid a on the right side is opened, and the fluid a present in the partition chamber on the right side is sent out. Conversely, when the bimorph transducer 401 moves to the left, the fluid B existing on the left side is sent out from the partition chamber, and the fluid a enters the partition chamber on the right side. Since the bimorph vibrator 401 moves left to right according to the frequency at the amplitude 403, the fluid a and the fluid B alternately send liquid by such a repeated operation. The amount of liquid fed varies depending on the frequency, and is large at high frequencies. Fig. 8 shows the relationship between the amount of liquid delivered and the concentration of the liquid delivered by the time-division piezoelectric liquid-delivery pump with time. In the figure, a represents supply of a methanol aqueous solution, and b represents supply of water. Fig. 8 shows that pulsation and concentration gradient exist in the liquid sent to the DMFC100 by the time-division piezoelectric liquid sending pump. Further, by changing the left and right volumes of the partition chamber of the piezoelectric liquid-sending pump, the ratio of the amounts of the liquids to be sent can be changed. Specifically, fig. 9 shows the change with time in the amount of liquid fed and the concentration when the volume of the partition chamber through which water flows is set to be twice the volume of the partition chamber through which the methanol aqueous solution flows. When comparing fig. 9 and 8, the amount of liquid (b in the figure) fed by water is about twice as large as that fed in fig. 8 in fig. 9 compared with fig. 8. Therefore, in the time-division piezoelectric liquid-sending pump, the change of the volume ratio in the partition chamber is also effective.

The features of the present invention will be described below by way of examples and comparative examples, but the present invention is not limited thereto.

(1) Structure of the product

<example 1>

The fuel cell power supply of the present embodiment used in example 1 has the same configuration as that of the fuel cell power supply shown in fig. 2. Here, specifically, it is used in example 1.

Next, the solid polymer electrolyte membrane 102, the anode catalyst layer 103, the cathode catalyst layer 104, the anode diffusion layer 105, the cathode diffusion layer 106, the fuel flow plate 107, and the air flow plate 111 constituting the DMFC100 will be described in detail. As the solid polymer electrolyte membrane 102, a perfluorocarbon sulfonic acid membrane (trade name: Nafion 117; DuPont) was used. The anode catalystlayer 103 was obtained by forming a porous catalyst layer having a width of 10mm × 20mm and a thickness of about 80 μm on a polytetrafluoroethylene membrane by a screen printing method using a slurry of a catalyst powder dispersed and supported at 50 wt% by platinum/ruthenium alloy fine particles prepared by adjusting the atomic ratio of platinum to ruthenium to 1/1 on a carbon support and a 5 wt% aqueous/ethanol mixed solution (solvent obtained by mixing water, isopropyl alcohol, and n-propyl alcohol at a weight ratio of 20: 40, manufactured by frockmick corporation) in which a perfluorocarbon sulfonic acid electrolyte was dissolved, and drying the slurry. At this time, the amount of the catalyst deposited was 6mg/cm². The cathode catalyst layer 104 was prepared by using a catalyst powder comprising platinum fine particles of 30 wt% supported on a carbon support and a 5 wt% aqueous/ethanol mixed solution of a perfluorocarbon sulfonic acid electrolyte dissolved therein (the solvent was water, isopropyl alcohol, or n-propyl alcohol)The alcohol is mixed and used according to the weight ratio of 20: 40: manufactured by frockmick corporation) by screen printingThe method comprises forming a porous catalyst layer having a width of 10mm × 20mm and a thickness of about 50 μm on a polytetrafluoroethylene film, and drying the porous catalyst layer. At this time, the amount of the catalyst deposited was 3mg/cm²。

Next, a method for manufacturing the MEA electrode will be described. An MEA electrode in which an anode catalyst layer 103 is bonded to one surface of a solid polymer electrolyte membrane 102 by (1); (2) the cathode catalyst layer 104 is joined to the surface of the solid polymer electrolyte membrane 102 to which the anode catalyst layer 103 is not joined. The anode catalyst layer 103 and the solid polymer electrolyte membrane 102 were joined by impregnating about 0.5ml of a 5 wt% aqueous/ethanol mixed solution of Nafion117 (solvent obtained by mixing water, isopropyl alcohol, and n-propyl alcohol at a weight ratio of 20: 40, manufactured by frockmike corporation) on the surface of the anode catalyst layer 103, stacking the impregnated solution on the power generation (electrode) portion of the solid polymer electrolyte membrane 102, and heating the membrane at 80 ℃ for 3 hours with a load of about 1 kg. The cathode catalyst layer 104 and the solid polymer electrolyte membrane 102 were joined by impregnating the surface of the cathode catalyst layer 104 with about 0.5ml of a 5 wt% aqueous/ethanol mixed solution of Nafion117 (solvent in which water, isopropyl alcohol, and n-propyl alcohol are mixed at a weight ratio of 20: 40, manufactured by frockmick corporation), stacking the cathode catalyst layer 104 on the power generation (electrode) portion on the side opposite to the side where the solid polymer electrolyte membrane 102 and the anode catalyst layer 103 are joined, and drying the stack at 80 ℃ for 3 hours with a load of about 1 kg.

Next, a method for manufacturing the anode diffusion layer 105 and the cathode diffusion layer 106 will be described. An aqueous dispersion of polytetrafluoroethylene fine particles (fluorine resin dispersion D-1, manufactured by Darkon (ダイキン)) added as a hydrophobizing agent in an amount of 40 wt% based on the weight of the carbon powder after firing was kneaded to form a slurry-like mixture, which was coated on one surface of a carbon cloth support having a thickness of about 350 μm and a porosity of 87% to form a carbon sheet having a thickness of about 20 μm, dried at room temperature, and fired at 270 ℃ for about 3 hours to prepare a carbon sheet. The fabricated carbon sheet was cut into a shape having the same size as the anode electrode of the MEA to form the anode diffusion layer 105. An aqueous dispersion of polytetrafluoroethylene fine particles (fluorine resin dispersion D-1, manufactured by Darkon) added as a hydrophobizing agent in an amount of 40 wt% based on the weight of the carbon powder after firing was mixed to form a slurry-like mixture, and the slurry-like mixture was coated on one surface of a carbon cloth support having a thickness of about 350 μm and a porosity of 87% to form a carbon sheet having a thickness of about 20 μm, dried at room temperature, and fired at 270 ℃ for about 3 hours to prepare a carbon sheet. The obtained carbon sheet was cut into a shape having the same size as the cathode electrode of the MEA to obtain the cathode diffusion layer 106.

The anode catalyst layer 103 is integrally joined to one surface of the solid polymer electrolyte membrane 102, the cathode catalyst layer 104 is integrally joined to the opposite surface of the solid polymer electrolyte membrane, and the anode catalyst layer 103 of the MEA is in close contact with the anode diffusion layer 105, and the cathode catalyst layer 104 on the other side is in close contact with the cathode diffusion layer 106. The air flow passage plate 111 is disposed outside the cathode diffusion layer 106, and is provided with an air flow passage 114 having an air supply port 112 and an air discharge port 113. Air is supplied by the blower 51 of the oxidant gas supply unit 50. On the other hand, the fuel flow plate 107 is disposed outside the anode diffusion layer 105, and is provided with a fuel flow path 110 having a fuel supply port 108 and a fuel discharge port 109. The concentration of the aqueous methanol solution supplied to this fuel flow path plate 107 is controlled to be within an appropriate concentration range by the control unit 30. This control is performed by switching the flow path connecting the outlet of the aqueous methanol solution container 22 and the inlet of the liquid-sending pump 23 and the flow path connecting the outlet of the water container 21 and the inlet of the liquid-sending pump 23 in a time-division manner by the electromagnetic valve 24 provided on the inlet side of the liquid-sending pump 23. In order to smoothly discharge the carbon dioxide gas generated at the anode by the reaction of the formula (1) from the battery, the electromagnetic valve 24 is switched at a timing of 50 times to 0.2 times within 1 second as a timing at which pulsation is easily generated.

In the following description of the fuel cell power sources used in<example 2>to<example 14>and<comparative example 1>, the characteristic portions different from the fuel cell power source used in example 1 will be described, and the description of the common portions will be omitted.

<example 2>

20g of the carbon powder used in example 1 and 200ml of fuming sulfuric acid (concentrated)Degree 60%) was mixed in a 300ml flask and allowed to react under a nitrogen stream at a temperature of 60 ℃ for 2 days. The reacted liquid changed from black to brown. Thereafter, the temperature of the flask was cooled to room temperature, the reaction solution was slowly added to a flask containing 600ml of distilled water while being cooled with ice and stirred, and the reaction solution was filtered after the whole amount was added. Then, the filtered precipitate is sufficiently washed with distilled water, and the precipitate is washed with distilled water until the washing liquid becomes neutral. Then, the resultant is washed with methanol and diethyl ether in this order, and then vacuum-dried at 40 ℃ to obtain carbon powderAnd (3) derivatives. The infrared spectroscopic absorption spectrum of this carbon powder was measured, and it was confirmed that the mass was 1225cm^-1And 1413cm^-1Having a base based on-OSO₃And (4) absorption of H groups. In addition, 1049cm was confirmed^-1There is an absorption based on-OH groups. This indicates that-OSO is introduced into the surface of the carbon powder treated with the fuming sulfuric acid₃H groups and-OH groups. The contact angle of the aqueous methanol solution of the carbon powder treated with fuming sulfuric acid is smaller than that of the aqueous methanol solution of the carbon powder not treated with fuming sulfuric acid, and is hydrophilic. In addition, the carbon powder treated with fuming sulfuric acid is also more conductive than the carbon powder not treated with fuming sulfuric acid. A slurry mixture of carbon powder treated with fuming sulfuric acid and 5 wt% Nafion117 in a water/ethanol mixed solution (solvent obtained by mixing water, isopropyl alcohol and n-propyl alcohol at a weight ratio of 20: 40; manufactured by Frukomik Co., Ltd.) was coated on one side of the carbon cloth support of the anode diffusion layer 105 having a thickness of about 350 μm and a porosity of 87% to a thickness of about 20 μm, and dried at 100 ℃ to prepare a carbon sheet. An experiment was conducted using a fuel cell power supply having the same structure as in example 1, except that the obtained carbon sheet was cut into a shape having the same size as the anode electrode of the MEA as the anode diffusion layer 105.

<example 3>

About 350 μm, porosity to be used in example 1A 87% carbon cloth was immersed in a flask containing fuming sulfuric acid (60% concentration) and treated in the same manner as the fuming sulfuric acid-treated carbon powder of example 2. As a result, the carbon cloth treated with the fuming sulfuric acid had-OSO introduced on the surface thereof₃H group and-OH group are excellent in hydrophilicity and electrical conductivity. An experiment was conducted using a fuel cell power source of exactly the same structure as in example 2, except that this fuming sulfuric acid-treated carbon cloth was used as the anode diffusion layer 105.

<example 4>

The solid polymer electrolyte membrane 102 of example 1 was modified to use a sulfomethylated polyethersulfone hydrocarbon electrolyte membrane instead of the perfluorocarbon sulfonic acid membrane. An experiment was also conducted on a fuel cell power source having the same structure as in example 2, except that 30 wt% of sulfomethylated polyethersulfone hydrocarbon electrolyte was used as the binder for the anode catalyst layer 103. In this case, the anode catalyst layer 103 is produced in the following manner. First, a catalyst powder in which a catalyst of platinum/ruthenium alloy fine particles having an atomic ratio of platinum to ruthenium of 1/1 was dispersed and supported at 50 wt% on carbon powder serving as a support of the anode catalyst layer 103 was adjusted. Then, this catalyst powder and a slurry composed of a 30 wt% water/ethanol mixed solution of a sulfomethylated polyethersulfone hydrocarbon electrolyte (a solvent obtained by mixing water, isopropyl alcohol, and n-propyl alcohol at a weight ratio of 20: 40), a dispersant, and a hydrophobizing agent were adjusted to form a porous catalyst layer having a thickness of about 80 μm on a polytetrafluoroethylene film by a screen printing method, and this porous catalyst layer was used as the anode catalyst layer 103.

<example 5>

An experiment was performed using a fuel cell power supply having the same configuration as that of example 4, except that the concentration of the methanol aqueous solution supplied to the DMFC100 used in example 4 was adjusted, and only the time-division piezoelectric liquid-sending pump shown in fig. 7 was used without using the electromagnetic valve 24.

<example 6>

An experiment was performed using a fuel cell power supply having the same configuration as in example 5, except that the time-division piezoelectric liquid-sending pump was used in which the volumes of the partition chambers of the time-division piezoelectric liquid-sending pump used in example 5 were changed so that the volume of the partition chamber through which water flowed was twice the volume of the partition chamber through which the methanol aqueous solution flowed.

<example 7>

An experiment was performed with a fuel cell power source of the same structure as in example 5, except that the thickness of the anode catalytic layer 103 was increased from 80 μm to 150 μm, and the thickness of the cathode catalytic layer 104 was decreased from 50 μm to 25 μm.

<example 8>

An experiment was conducted using a fuel cell power source having the same structure as in example 7, except that the hydrophilic carbon powder obtained by treating the carbon powder used in example 1 with the same fuming sulfuric acid as in example 2 was used for the anode diffusion layer 105.

<example 9>

An experiment was conducted using a fuel cell power source having the same structure as in example 8, except that a hydrophilic carbon cloth obtained by treating the carbon cloth used in example 3 with fuming sulfuric acid as in example 3 was used for the anode diffusion layer 105.

<example 10>

An experiment was conducted using a fuel cell power source having the same structure as in example 8, except that carbon paper was used instead of the carbon cloth used as the support of the anode diffusion layer 105.

<example 11>

The cathode catalyst layer 104 used in example 7 was produced in the following manner. First, a catalyst powder in which a catalyst of platinum/ruthenium alloy fine particles having an atomic ratio of platinum to ruthenium of 1/1 was dispersed and supported at 50 wt% was adjusted on carbon powder serving as a support of the cathode catalyst layer 104. Then, the catalyst powder was mixed with a slurry comprising a 30 wt% water/ethanol mixed solution of sulfomethylated polyethersulfone and hydrocarbon electrolyte (a solvent obtained by mixing water, isopropyl alcohol, and n-propyl alcohol at a weight ratio of 20: 40), a dispersant, and a water repellent agent, and a porous catalyst layer having a thickness of about 25 μm was formed on the polytetrafluoroethylene film by a screen printing method. This porous catalytic layer was used as the cathode catalytic layer 104. In addition, the cathode diffusion layer 106 uses carbon paper supporting carbon. An experiment was performed using a fuel cell power source having the same structure as that of example 10, except that the cathode catalyst layer 104 and the cathode diffusion layer 106 were changed.

<example 12>

An experiment was performed with a fuel cell power source having exactly the same structure as in example 11, except that the thickness of the anode catalyst layer 103 was changed from 150 μm to 200 μm, and the thickness of the cathode catalyst layer 104 was changed from 25 μm to 15 μm.

<example 13>

An experiment was conducted using a fuel cell power supply of exactly the same structure as in example 12, except that the thickness of the anode catalyst layer 103 was changed from 200 μm to 100 μm, the thickness of the cathode catalyst layer 104 was changed from 15 μm to 10 μm, and hydrophilic carbon powder obtained by treating the carbon powder used in example 1 with the same fuming sulfuric acid as in example 2 was used as the support of the anode catalyst layer 103.

<example 14>

An experiment was performed using a fuel cell power supply having exactly the same structure as in example 13, except that thethickness of the anode catalyst layer 103 was changed from 100 μm to 50 μm, and the thickness of the cathode catalyst layer 104 was changed from 10 μm to 5 μm.

<comparative example 1>

The structure of the fuel cell power source used in comparative example 1 is shown in fig. 17. The fuel cell power supply used in comparative example 1 has the same structure as that of the fuel cell power supply of example 1, except that the liquid fuel supply unit 20 has a different structure. That is, in the configuration of the liquid fuel supply unit 20, the fuel cell power supply used in comparative example 1 is different from that of example 1 only in that the water supply pump 210, the high-concentration methanol aqueous solution supply pump 220, the methanol aqueous solution concentration adjustment tank 230, the methanol concentration sensor 240, and the DMFC supply pump 250 are further used. The pump used in comparative example 1 was a piezoelectric pump shown in fig. 6. The method of adjusting the concentration of the aqueous methanol solution supplied to the fuel flow path plate 107 of the DMFC100 is a method of controlling the supply amount of the aqueous methanol solution concentration adjusting container 230 by the water supply pump 210 and the high-concentration aqueous methanol solution supply pump 220, which are directly connected to the water tank 21 and the aqueous methanol solution container 22, respectively, based on the detected concentration of the methanol concentration sensor 240.

(2) Experimental methods

From<Example 15>Play a role of<Example 28>And<comparative example 2>The fuel cell power source used in (1) was subjected to experiments and evaluations under the following conditions. First, an aqueous methanol solution to be supplied to the anode was supplied at a flow rate of 0.2ml/min to maintain a concentrationof 2M. The air supplied to the cathode was supplied at a flow rate of 500 ml/min. Next, the evaluation of the fuel cell power supply was made based on (i) voltage-current characteristics (the set temperature of the DMFC was 70 ℃); (ii) continuous output characteristic (DMFC set temperature of 70 ℃ C., set current density of 100 mA/cm)²)。

(3) Results

The results of the characteristic evaluation of the above (i) and (ii) are shown below in the order from<example 1>to<example 14>and<comparative example 1>.

(example 1)

The voltage-current characteristic results of the DMFC are shown in fig. 10. As shown in FIG. 10, at 100mA/cm²The output voltage of the DMFC at the current density of (1) is 450 mV. Shown in FIG. 11 at 100mA/cm²The output voltage at the time of continuous power generation varies with time at the current density of (2). According to fig. 11, the output voltage of the DMFC is kept constant even when the DMFC is continuously operated for 5 hours, and the output voltage does not decrease once.

In addition, in the slave<Example 2>Play a role of<Example 14>In the case of DMFC, the voltage-current characteristics were found to be 100mA/cm²Output of current density in continuous power generationThe state of voltage variation with time<Example 1>The states shown in FIGS. 10 and 11 are substantially the same, and thus<Example 2>Play a role of<Example 14>Wherein these drawings are omitted and are respectively shown at 100mA/cm²The sum of the output voltages of the DMFC at a current density of 100mA/cm²The current density of (2) is the time of continuous power generation.

(example 2)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (3) is 470 mV. At 100mA/cm²The time for continuous power generation under the current density of (2) is 8 hours, and during the time, the output voltage is kept constant and is not reduced once.

(example 3)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (3) is 480 mV. At 100mA/cm²The time for continuous power generation under the current density of (2) is 8 hours, and during the time, the output voltage is kept constant and is not reduced once.

(example 4)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (3) is 480 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 16 hours, during which the output voltage is kept constant and is not reduced once.

(example 5)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (3) is 480 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 16 hours, during which the output voltage is kept constant and is not reduced once.

(example 6)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (3) is 480 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 16 hours, during which the output voltage is kept constant and is not reduced once.

(example 7)

Voltage-current characteristics of DMFCAs a result, the concentration of the compound was 100mA/cm²The output voltage of the DMFC at the current density of (1) is 530 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 14.4 hours, during which the output voltage is kept constant and is not reduced once.

(example 8)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (3) is 550 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 14.4 hours, during which the output voltage is kept constant and is not reduced once.

(example 9)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (1) is 570 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 14.4 hours, during which the output voltage is kept constant and is not reduced once.

(example 10)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (1) is 570 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 14.4 hours, during which the output voltage is kept constant and is not reduced once.

(example 11)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (1) is 580 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 14.4 hours, during which the output voltage is kept constant and is not reduced once.

(example 12)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (1) is 620 mV. At 100mA/cm²The time for continuous power generation under the current density of the power generation device is 14.4 hours, during which the output voltage is kept constant and is also kept onceIs not reduced.

(example 13)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (1) is 640 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 14.4 hours, during which the output voltage is kept constant and is not reduced once.

(example 14)

From the result of voltage-current characteristics of DMFC, at 100mA/cm²The output voltage of the DMFC at the current density of (1) is 650 mV. At 100mA/cm²The time for continuous power generation at the current density of (2) is 14.4 hours, during which the output voltage is kept constant and is not reduced once.

Comparative example 1

The voltage-current characteristic results of the DMFC are shown in fig. 12. As shown in the figure, at 100mA/cm²The output voltage of the DMFC at the current density of (1) is 450 mV. The change in output voltage with time when power generation was continued for 5 hours at a current density of 100mA/cm2 is shown in FIG. 13. Referring to fig. 13, the output voltage of the DMFC has a problem that the supply of the methanol aqueous solution of the fuel to the anode becomes unstable due to the carbon dioxide gas generated after 36 minutes and 63 minutes from the start of the operation of the power supply, and the output voltage is temporarily lowered. Further, the supply of methanol fuel was hindered by the generation of large carbon dioxide bubbles after 300 minutes, and the output voltage was greatly reduced. The results obtained from example 1 to example 14 and comparative example 1 are summarized in Table 1 as (i) 100mA/cm²The output voltage of the DMFC at the current density of (d); (ii) at 100mA/cm²Can continuously generate electricity at the current density of (2).

<Table 1>

TABLE 1

	Output voltage (mV)	Whether or not to continuously operate 5 Hours?	Continuous run time (hr)
				Example 15	450	Is that	5
Example 16	470	Is that	8
				Example 17	480	Is that	↑
Example 18	480	Is that	16
				Example 19	480	Is that	↑
Example 20	480	Is that	↑
				Example 21	530	Is that	14.4
Example 22	550	Is that	↑
				Example 23	570	Is that	↑
Example 24	570	Is that	↑
				Example 25	580	Is that	↑
Example 26	620	Is that	↑
				Example 27	640	Is that	↑
Example 28	650	Is that	↑
				Comparative example 2	450	Whether or not	5 or less

Note: the output voltage is at a current density of 100mA/cm²The value of time.

From the results of table 1 and fig. 10 to 13, the following effects shown in the above-described embodiments 1 to 14 can be obtained, respectively.

In example 1, when the results of the voltage-current characteristics of the DMFC of example 1 shown in fig. 10 and the results of the voltage-current characteristics of the DMFC of comparative example 1 shown in fig. 12 are compared, the voltage-current characteristics of the two are substantially the same and are set at 100mA/cm²The output voltage at the current density of (2) is 450 mV.

Next, when the relationship between the time and the output voltage of the continuous power generation of the DMFC of example 1 shown in fig. 11 and the relationship between the time and the output voltage of the continuous power generation of the fuel cell power supply of comparative example 1 shown in fig. 13 are compared, the output voltage of example 1 is stable even in the continuous power generation for 5 hours, and the output voltage does not decrease at one time. On the other hand, in comparative example 1, the output voltage was unstable and decreased during 5 hours of continuous power generation. The reason for this is that, while example 1 provides pulsation when supplying the methanol aqueous solution to the DMFC, the carbon dioxide gas generated at the anode can be smoothly removed from the DMFC, comparative example 1 does not provide pulsation when supplying the methanol aqueous solution to the DMFC, and therefore the carbon dioxide gas generated at the anode cannot be smoothly removed from the DMFC. As described above, as a result of comparing example 1 with comparative example 1, the fuel cell power supply of example 1 can reduce the number of three liquid-sending pumps used in comparative example 1 by one by sending the methanol aqueous solution and water in a time-division manner by using the solenoid valve, so that space and weight can be saved. Further, since the fuel cell power supply of example 1 can smoothly remove the carbon dioxide gas generated at the anode from the DMFC by giving pulsation when supplying the methanol aqueous solution to the DMFC, it is possible to continuously generate power at a stable output voltage (450 mV).

When the result of the voltage-current characteristic of the DMFC of example 2 and the result of the voltage-current characteristic of the DMFC of example 1 are compared, 100mA/cm ofexample 2²The output voltage of the DMFC of current density of (1) was 470mV, which was about 20mV higher than that of example 1. Next, the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of comparative example 2 and the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 1 were comparedIn the voltage relationship, the fuel cell power supply of example 2 can continuously generate electricity at a stable output voltage (470mV) for 8 hours, which is about 3 hours longer than 5 hours in example 1. As described above, the results of comparing example 1 with comparative example 1, example 2, in addition to the effects of example 1 on comparative example 1, were 100mA/cm²The DMFC having the current density of (1) has an output voltage about 20mV higher than that of example 1, and has an effect that the time during which power can be continuously generated at a stable output voltage is about 3 hours longer than that of example 1. This effect should be caused by hydrophilizing the carbon powder of the anode diffusion layer. That is, the anode diffusion layer is easily wetted with the aqueous methanol solution by the hydrophilization treatment, so that a larger amount of the aqueous methanol solution can be smoothly suppliedThe anode catalyst layer 103 is impregnated, so the reaction can further proceed and the output voltage becomes larger. Further, since the carbon dioxide gas bubbles generated on the anode do not grow into large bubbles in the anode diffusion layer 105 by the hydrophilic treatment, and are separated from the anode diffusion layer 105 in a fine state as they are, the methanol aqueous solution can be smoothly supplied to the anode, and power can be continuously generated at a stable voltage for a long time.

When the result of the voltage-current characteristic of the DMFC of example 3 and the result of thevoltage-current characteristic of the DMFC of example 2 are compared, 100mA/cm of example 3²The output voltage of the DMFC of current density of (1) is 480mV, which is about 10mV higher than that of example 2. Next, the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 3 is the same as the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 2. As described above, the results of comparing example 3 with example 2 show that example 3 has 100mA/cm in addition to the effect of example 2 on example 1²The output voltage of the DMFC of current density of (a) is about 10mV higher compared with example 2. This effect should be caused by example 3 further subjecting the carbon cloth of the anode diffusion layer used in example 2 to a hydrophilization treatment. That is, because the anode diffusion layer is changed by such hydrophilization treatmentThe anode catalyst layer 103 can be easily wetted with the methanol aqueous solution, and a larger amount of the methanol aqueous solution can smoothly permeate the anode catalyst layer, so that the reaction can further proceed and the output voltage becomes larger. Further, since the carbon dioxide gas bubbles generated on the anode do not grow into large bubbles in the anode diffusion layer 105 by the hydrophilization treatment, and are separated from the anode diffusion layer 105 in a fine state as they are, the methanol aqueous solution can be smoothly supplied to the anode, and power can be continuously generated at a stable voltage for a long time.

When the result of the voltage-current characteristic of the DMFC of example 4 and the result of the voltage-current characteristic of the DMFC of example 1 are compared, 100mA/cm of example 4²The output voltage of the DMFC of current density of (1) was 480mV, which was about 30mV higher than that of example 1.The difference between example 4 and example 1 is that example 4 uses a hydrocarbon electrolyte as the electrolyte membrane and the adhesive, whereas example 1 uses a fluorine electrolyte as the electrolyte membrane and the adhesive. This is because the ion conductivity of the hydrocarbon-based electrolyte used in example 4 is larger than that of the fluorine-based electrolyte used in example 3, that is, the internal resistance of the DMFC is small. At the time of continuous power generation of DMFC of comparative example 4In the case of the relationship between the time and the output voltage and the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 1, the time during which the fuel cell power supply of example 4 can continuously generate power at a stable output voltage is 16 hours, which is 2 times or more the 5 hours of the time during which the fuel cell power supply of example 1 can continuously generate power.

Next, when comparing the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 4 and the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 1, the time during which the fuel cell power supply of example 4 can continuously generate power at a stable output voltage is 16 hours, which is a time length 2 times or more the time during which continuous power generation is possible of example 1. As described above, as a result of comparison between example 4 and example 1, example 4 can generate power continuously at a stable output voltage for a period of time 2 times or more as long as that of example 1. This effect is caused by changing the adhesive between the solid polymer electrolyte membrane and the anode to a hydrocarbon electrolyte membrane, which has less methanol passing through (cross) than the fluorine electrolyte membrane used in example 1. Since the amount of methanol passing through the solid polymer electrolyte membrane is small, the change in the concentration of methanol in the aqueous methanol solution is small, which contributes to an increase in the stability of the fuel cell and an improvement in the utilization efficiency of fuel.

When the result of the voltage-current characteristic of the DMFC of example 5 and the result of the voltage-current characteristic of the DMFC of example 4 are compared, 100mA/cm of example 5²The output voltage of the DMFC of current density of (1) was 480mV, which was the same as that of example 4. When the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 5 is compared with the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 4, the time during which continuous power generation is possible of the fuel cell power supply of example 5 is the same as that of example 4. As a result of comparison between example 5 and example 4, in example 5, the same effect as in example 4 can be obtained by using only the time-division piezoelectric liquid-sending pump without using the solenoid valve for adjusting the concentration of the methanol aqueous solution supplied to the DMFC.

When the result of the voltage-current characteristic of the DMFC of example 6 and the result of the voltage-current characteristic of the DMFC of example 5 are compared, 100mA/cm of example 6²The output voltage of the DMFC of current density of (1) was 480mV, which was the same as that of example 5.

Next, when the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 6 and the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 5 are compared, the time during which continuous power generation is possible of the fuel cell power supply of example 6 is the same as that of example 5. As a result of comparison between example 6 and example 5, in example 6, the volume of the partition chamber of the time-division piezoelectric liquid-sending pump is changed to the left and right without using the solenoid valve for adjusting the concentration of the methanol aqueous solution supplied to the DMFC, and the liquid can be sent, and the same as in example 5 can be obtained

The same effects as in example 5.

When the result of the voltage-current characteristic of the DMFC of example 7 and the result of the voltage-current characteristic of the DMFC of example 5 are compared, 100mA/cm of example 7²The output voltage of the DMFC of current density of (1) is 530mV, which is about 50mV higher than that of example 5.

Next, when the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 7 and the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 5 were compared, the time during which the fuel cell power supply of example 7 could continuously generate power at a stable output voltage was 14.4 hours, which was slightly shorter than the time during which the continuous power generation could be performed by example 5. As described above, the results of comparing the differences between example 7 and example 5, example 7, in addition to the effects obtained in example 5 on examples 1 to 4, was 100mA/cm²The output voltage of the DMFC of current density of (1) is about 50mV higher than that of example 5, and an effect is obtained that the time during which power can be continuously generated at a stable output voltageis somewhat shorter than that of example 5. This effect increases the thickness of the anode catalytic layer 103 from 80 μm to 150 μm and decreases the thickness of the cathode catalytic layer 104 from 50 μm to 25 μm. Since the area of contact between the aqueous methanol solution and the anode catalyst is increased by increasing the thickness of the anode catalyst layer 103, the reaction between the aqueous methanol solution and water in the anode catalyst layer 103 can be further progressed, which can contribute to the improvement of the fuel utilization efficiency. In addition, the reason why the thickness of the cathode catalyst layer 104 is reduced and air, that is, oxygen is effectively used, DMFC is not made thick is that the total amount of platinum used can be reduced by reducing the amount of the cathode catalyst as much as possible without reducing the output of the fuel cell because the cost of the catalyst such as platinum is high, and the total cost can be reduced. In particular, reducing the thickness of the cathode can effectively use oxygen, which is effective for improving the battery performance.

Results in voltage-current characteristics for DMFC of example 8 and that of example 7When the results of voltage-current characteristics of DMFC are compared, 100mA/cm of example 8²The output voltage of the DMFC of the current density of (1) is 550mVThe output voltage of example 7 was about 20mV higher. Next, when the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 8 and the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 8 are compared, the time during which the fuel cell power supply of example 7 can continuously generate power is the same as that of example 7. As described above, the result of comparison between example 8 and example 7, example 8, is 100mA/cm in addition to the effect obtained in example 7 on example 5²The output voltage of the DMFC of current density of (a) is about 20mV higher compared with example 7. The reason why the output voltage becomes larger is that the carbon powder of the anode diffusion layer is subjected to a hydrophilic treatment, that is, the carbon powder of the anode diffusion layer is subjected to such a hydrophilic treatment, so that the anode diffusion layer is easily wetted with the methanol aqueous solution, and a larger amount of the methanol aqueous solution can smoothly permeate the anode catalyst layer 103. Therefore, the reaction of methanol and water in the anode catalyst layer 103 proceeds further, and the output voltage becomes larger.

When the result of the voltage-current characteristic of the DMFC of example 9 and the result of the voltage-current characteristic of the DMFC of example 8 are compared, 100mA/cm of example 9²The output voltage of the DMFC of current density of (1) is 570mV, which is about 20mV higher than that of example 8. Next, when the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 9 is compared with the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 8, the time during which the fuel cell power supply of example 9 can continuously generate power is the same as that of example 8. As described above, the result of comparison between example 9 and example 8 shows that example 9 is 100mA/cm in addition to the effect obtained in example 8 on example 7²The output voltage of the DMFC of current density of (a) is about 20mV higher compared with example 8. The effect of increasing the output voltage is to make the anode diffusion layer easily wet with the methanol aqueous solution by hydrophilic treatment of the carbon cloth support of the anode diffusion layer 105, so that the anode catalyst layer can be smoothly permeated with a larger amount of the methanol aqueous solution.

Results on the voltage-current characteristics of the DMFC of example 10 and the voltage-current characteristics of the DMFC of example 8Flow characteristics results when compared, 100mA/cm for example 10²The output voltage of the DMFC of current density of (1) is 570mV, which is about 20mV higher than that of example 8.

Next, when the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 10 and the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 8 are compared, the time during which the fuel cell power supply of example 10 can continuously generate power is the same as that of example 8. As described above, as a result of comparing example 10 with example 8, the output voltage can be further increased due to the effect of changing the anode diffusion layer from carbon cloth to carbon paper. This indicates that the carbon paper is more effective than the carbon cloth as the anode diffusion layer.

When the result of the voltage-current characteristic of the DMFC of example 11 and the result of the voltage-current characteristic of the DMFC of example 10 are compared, 100mA/cm of example 10²The output voltage of the DMFC of current density of (1) is 580mV, which is about 10mV higher than that of example 10. Next, when the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 11 and the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 10 are compared, the time during which the fuel cell power supply of example 11 can continuously generate power is the same as that of example 10.

As described above, the result of comparison between example 11 and example 10, example 11, is 100mA/cm in addition to the effect obtained in example 10 on example 9²The output voltage of the DMFC of current density of (a) is about 10mV higher than that of example 10. The effect of making the output voltage higher is that the ion conductivity is further improved, the internal resistance is reduced, and the output voltage is increased by changing the binder of the cathode catalyst layer from the fluorine-based electrolyte to the hydrocarbon-based electrolyte.

When the result of the voltage-current characteristic of the DMFC of example 12 and the result of the voltage-current characteristic of the DMFC of example 11 are compared, 100mA/cm of example 12²The output voltage of the DMFC of current density of (1) was 620mV, which was about 50mV higher than that of example 11. Secondly, the first step is to carry out the first,when the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 12 and the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 11 are compared, the time during which the fuel cell power supply of example 12 can continuously generate power at a stable output voltage is the same as that of example 11. As described above, the result of comparison between example 12 and example 11, example 12, is 100mA/cm in addition to the effect obtained in example 11 for example 10²The output voltage of the DMFC of current density of (a) is about 40mV higher compared with example 11. This effect, by increasing the thickness of the anode catalytic layer 103 from 150 μm to 200 μm, the area of contact between the aqueous methanol solution and the anode catalyst is further increasedIn addition, the reaction between the aqueous methanol solution and water in the anode catalyst layer 103 can proceed further, and thus the output voltage increases. In addition, when the thickness of the cathode catalyst layer 104 is reduced from 25 μm to 15 μm, the efficiency of oxygen utilization increases, which also contributes to an increase in output voltage.

When the result of the voltage-current characteristic of the DMFC of example 13 and the result of the voltage-current characteristic of the DMFC of example 11 are compared, 100mA/cm of example 13²The output voltage of the DMFC of current density of (1) was 640mV, which was about 60mV higher than that of example 11.

Next, when the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 13 and the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 11 are compared, the time during which the fuel cell power supply of example 13 can continuously generate power is the same as that of example 11. As described above, the result of comparison between example 13 and example 11, example 13, is 100mA/cm in addition to the effect of example 11 on example 10²The output voltage of the DMFC of current density of (a) is about 60mV higher compared with example 11. This effect reduces the thickness of the anode catalytic layer 103 from 150 μm to 100 μm, although the area of contact between the methanol aqueous solution and the anode catalyst is reduced because the chance of contact between the methanol aqueous solution and the anode catalyst is increased by hydrophilizing the carbon of the anode diffusion layer 103, and oxygen is diffused until the cathode catalytic layer 104 is reduced from 25 μm to 10 μmThe output voltage can be increased by increasing the efficiency of oxygen utilization.

When the result of the voltage-current characteristic of theDMFC of example 14 and the result of the voltage-current characteristic of the DMFC of example 13 are compared, 100mA/cm of example 14²The output voltage of the DMFC of current density of (1) was 650mV, which was about 10mV higher than that of example 13. Next, when the relationship between the time and the output voltage at the time of continuous power generation of the DMFC of example 14 is compared with the relationship between the time and the output voltage at the time of continuous power generation of the fuel cell power supply of example 13, the time during which the fuel cell power supply of example 14 can continuously generate power is the same as that of example 13. As described above, as a result of comparing example 14 with example 13, example 14 showed a large effect of 100mA/cm, in example 13, on example 12²The output voltage of the DMFC of the current density of (a) can be about 10mV higher than that of example 13. In particular, reducing the thickness of the cathode catalyst layer 104 is effective in improving the efficiency of oxygen utilization and increasing the output voltage.

(3) Application example

<application example 1>

Fig. 14 shows a schematic configuration of a fuel cell power supply and a storage container for a high-concentration methanol aqueous solution of a notebook personal computer using the fuel cell power supply. The fuel cell power supply 501 of this notebook personal computer 500 uses the fuel cell power supply shown in example 12. Further, as a storage container for the high-concentration methanol aqueous solution, a cartridge 502 in the form of a cartridge which can replace a container of the high-concentration methanol aqueous solution which is empty after use with a filled container is used. The notebook personal computer 500 can be continuously used for 8 hours with an average 12W output.

<application example 2>

Fig. 15 and 16 show a PDA (abbreviated as Personal digital assistant, also referred to as a portable information terminal) using a fuel cell power source. Fig. 16 shows an appearance photograph of this PDA (portable information terminal).

Fig. 16 shows a schematic configuration of a fuel cell power supply and a storage container for a high-concentration methanol aqueous solution of the PDA (portable information terminal) 600. The fuel cell power source 601 used was the one shown in example 13. Further, as a storage container for the high-concentration methanol aqueous solution, a cartridge 602 in a cartridge form is used, which can replace a container of the high-concentration methanol aqueous solution that becomes empty after use with a filled container. This PDA (portable information terminal) 600 can be continuously used for 8 hours. In addition, the portable telephone (not shown) using the fuel cell power supply of example 13 was continuously operated for 50 hours. In this case, when the output of the fuel cell decreases, the output of the fuel cell can be increased again by vibrating the portable telephone using the vibration function attached to the method mode of the portable telephone, and the output can be stabilized. This is because the carbon dioxide gas generated at the anode does not grow into large bubbles due to vibration, and can be discharged as fine bubbles without change, so that the fuel in the anode can be uniformly supplied.

The fuel cell using a liquid fuel has the following problems (1) to (5).

(1) In a conventional fuel cell in which a liquid fuel is circulated, a concentration control structure for detecting the concentration of the liquid fuel and maintaining a predetermined concentration is used, and therefore, a plurality of pumps such as a pump for supplying the high-concentration liquid fuel anda pump for supplying water are required. The use of these pumps increases the space occupied by auxiliary equipment such as pumps in the fuel cell power supply, and as a result, the fuel cell power supply itself becomes large.

(2) When the carbon dioxide gas generated at the anode by the reaction of the above chemical formula (1) is not smoothly discharged from the anode, the output of the battery is unstable or decreased because a sufficient amount of liquid fuel such as methanol is not supplied to the anode.

(3) Since the liquid fuel such as methanol supplied to the anode cannot sufficiently infiltrate the cathode diffusion layer, the output and fuel utilization rate are reduced.

(4) Since the liquid fuel such as methanol supplied to the anode does not smoothly react with the anode, the output and the utilization rate of the fuel are reduced.

(5) Since the oxygen supplied to the cathode cannot reach the inside of the cathode catalyst layer, oxidation of protons does not occur, and the output and the utilization rate of fuel are reduced.

The above-described (2) to (5) have a common problem not only with the dilution cycle type laminated fuel cell power supply but also with the plate (planar) type fuel cell power supply which naturally exhales.

The effects of the present embodiment obtained from examples 1 to 14 and application examples 1 to 2 can be summarized as follows:

(1) since it is not necessary to provide a plurality of pumps required for keeping the concentration of a liquid fuel such as methanol at a predetermined concentration, a fuel cell power supply, an operating method thereof, and a portable electronic device using the fuel cell power supply, which can be reduced in size and weight, can be provided.

(2) Further, since the carbon dioxide gas in the anode can be smoothly discharged and the liquid fuel such as methanol can be uniformly supplied to the anode, a fuel cell power supply capable of increasing the output, an operating method thereof, and a portable electronic device using the fuel cell power supply can be provided.

(3) Further, since the liquid fuel such as methanol supplied to the anode can sufficiently infiltrate into the anode diffusion layer, it is possible to provide a fuel cell power supply, an operation method thereof, and a portable electronic device using the fuel cell power supply, which are capable of increasing the output of the fuel cell power supply and the portable electronic device using the fuel cell power supply, and the fuel utilization efficiency.

(4) Further, since the amount of catalyst for performing the reaction of methanol and water is increased by thickening the anode catalyst layer, it is possible to provide a fuel cell power supply and an operation method thereof, and a portable electronic device using the fuel cell power supply, which are capable of promoting the reaction of liquid fuel such as methanol to increase the output and the utilization efficiency of the fuel.

(5) Further, by thinning the cathode catalyst layer, oxygen can be sufficiently diffused up to the cathode catalyst layer and oxygen can be effectively utilized, so that a fuel cell power supply capable of increasing output, an operating method thereof, and a portable electronic device using the fuel cell power supply can be provided.

(6) Further, since carbon dioxide gas generated by the reaction of the fuel cell can be discharged smoothly at all times, a fuel cell power supply capable of being continuously used for a long time, an operating method thereof, and a portable electronic device using the fuel cell power supply can be provided.

(7) Since the fuel cell power supply, the operation method thereof, and the portable electronic device using the fuel cell power supply according to the present embodiment can be used continuously for a long period of time, a charger and a secondary battery attached to a portable telephone, a portable personal computer, a portable audio and video device, or another portable information terminal equipped with a secondary battery do not need to be mounted, and an originally built-in power supply can be used.

The object of the present embodiment is to provide a fuel cell power supply which can be reduced in size and weight without providing a plurality of pumps, an operation method thereof, and a portable electronic device using the fuel cell power supply. Another object of the present embodiment is to provide a fuel cell power supply, an operating method thereof, and a portable electronic device using the fuel cell power supply, which can smoothly discharge carbon dioxide gas generated by a reaction from an anode to improve output.

Further, another object of the present embodiment is to provide a fuel cell power supply, an operation method thereof, and a portable electronic device using the fuel cell power supply, which can increase output and fuel utilization efficiency by allowing a liquid fuel such as methanol supplied to a cell to sufficiently infiltrate into an anode diffusion layer.

It is another object of the present embodiment to provide a fuel cell power supply capable of promoting a reaction of a liquid fuel such as methanol supplied to an anode to increase output and fuel utilization efficiency, a method of operating the same, and a portable electronic device using the fuel cell power supply.

Further, another object of the present embodiment is to provide a fuel cell power supply, an operation method thereof, and a portable electronic device using the fuel cell power supply, which can smoothly discharge carbon dioxide gas generated by a reaction of a fuel cell and can be continuously used with a stable output for a long time. Carbon dioxide gas generated by the reaction of the fuel cell can be smoothly discharged and can be continuously used for a long time with a stable output. In addition, the liquid fuel such as methanol supplied to the cell can sufficiently infiltrate into the anode diffusion layer, and the output and the fuel utilization efficiency can be increased. In addition, the reaction of the liquid fuel such as methanol supplied to the anode can be promoted, and the output and the utilization efficiency of the fuel can be increased.

Claims (13)

1. A fuel cell power plant comprising: a fuel cell unit having an anode, a cathode disposed to face the anode, and a solid polymer electrolyte membrane interposed between the anode and the cathode; and a liquid fuel supply unit that supplies liquid fuel and water to the anode, characterized in that:

the liquid fuel supply unit is a unit configured to supply the liquid fuel and the water to the anode in a time-division manner by one pump.

2. The fuel cell power plant as defined in claim 1, wherein: the liquid fuel supply unit supplies the liquid fuel and water to the anode in a time-division manner by one pump using an electromagnetic valve.

3. The fuel cell power plant as defined in claim 1, wherein: the liquid fuel supply unit is a unit configured to supply the liquid fuel and the water to the anode in a time-division manner by one pump using a piezoelectric pump.

4. The fuel cell powerplant as defined in claim 1, wherein: the liquid fuel supply unit is a unit configured to supply the liquid fuel and the water to the anode in a time-division manner by one pump using a plunger pump.

5. The fuel cell power plant as defined in claim 1, wherein:

an anode having an anode catalyst layer on a surface thereof which is in contact with the solid polymer electrolyte membrane, an anode diffusion layer on a surface thereof which is not in contact with the solid polymer electrolyte membrane, and a liquid fuel flow path plate outside the anode diffusion layer;

a cathode having a cathode catalyst layer on a surface of the cathode catalyst layer which is in contact with the solid polymer electrolyte membrane, a cathode diffusion layer on a surface of the cathode catalyst layer which is not in contact with the solid polymer electrolyte membrane, and an oxidant gas flow field plate outside the cathode diffusion layer;

the anode diffusion layer is subjected to hydrophilization treatment.

6. The fuel cell power plant as defined in claim 1, wherein:

the carbon support used for the anode catalyst layer is subjected to hydrophilization treatment.

7. The fuel cell power plant as defined in claim 1, wherein:

the solid polymer electrolyte membrane is an aromatic hydrocarbon electrolyte membrane into which an alkylene sulfonic acid group is introduced; the binder used for the anode catalyst layer is an aromatic hydrocarbon electrolyte into which an alkylene sulfonate group is introduced.

8. The fuel cell power plant as defined in claim 5, wherein:

the thickness of the anode catalyst layer is larger than that of the cathode catalyst layer.

9. The fuel cell power plant as defined in claim 5, wherein:

the binder used for the cathode catalyst layer is an aromatic hydrocarbon electrolyte into which an alkylene sulfonate group is introduced.

10. A portable electronic device, characterized in that: a fuel cell power plant as claimed in claim 1 is used in a mobile device.

11. The portable electronic device of claim 10, wherein: the portable electronic device is a notebook personal computer.

12. The portable electronic device of claim 10, wherein: the portable electronic device is a portable information terminal.

13. The portable electronic device of claim 10, wherein: the portable electronic device is a portable telephone.

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