JP2008097984A - Direct methanol type fuel battery system and portable electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct methanol type fuel battery system supplying methanol as gas, with the use of solid methanol extremely safe in a fuel cartridge state, and solving such problems as liquid leak, crossover, degradation of outputs in the case of use of liquid fuel as a system. <P>SOLUTION: The direct methanol type fuel battery system is provided with a fuel container part 3 containing solid methanol solidifying methanol, a fuel battery cell 5, and a fuel gas supply means supplying the fuel battery cell with fuel gas containing methanol vaporized from the solid methanol by circulation of carrier gas. The fuel gas supply means is provided with air guide-in means 10A, 10B which can be controlled. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a direct methanol fuel cell system using solid methanol as a fuel, and more particularly to a direct methanol fuel cell system suitable for small portable electronic devices.

  A solid polymer electrolyte fuel cell has a solid electrolyte membrane such as a perfluorosulfonic acid membrane as an electrolyte, and a fuel electrode (anode) and an oxidant electrode (cathode) are joined to both sides of the membrane, and hydrogen is connected to the anode. It is a device that generates electricity through an electrochemical reaction by supplying oxygen to methanol and cathode. Among these, a solid polymer electrolyte fuel cell using methanol as a fuel is called a “direct methanol fuel cell (DMFC)”, and power is generated by the following reaction formula.

Anode: CH ₃ OH + H ₂ O → 6H ⁺ + CO ₂ + 6e ⁻ ... [1]
Cathode: 3/2 O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O [2]
In order to cause this reaction, both electrodes are composed of a mixture of carbon fine particles carrying a catalyst material and a solid polymer electrolyte.

  In such a direct methanol fuel cell, the methanol supplied to the anode passes through the pores in the electrode and reaches the catalyst. The methanol is decomposed by this catalyst, and the electrons in the reaction of the above reaction formula [1]. And hydrogen ions are produced. The hydrogen ions reach the cathode through the electrolyte in the anode and the solid electrolyte membrane between the two electrodes, react with oxygen supplied to the cathode and electrons flowing from the external circuit, and water as shown in the above reaction formula [2]. Produce. On the other hand, electrons released from methanol are led to the external circuit through the catalyst carrier in the anode, and flow into the cathode from the external circuit. As a result, in the external circuit, electrons flow from the anode to the cathode, and electric power is taken out.

  The direct methanol fuel cell using methanol as a fuel is useful as a small power source for portable electronic devices because it has a low operating temperature and does not require a large auxiliary machine. Development has been activated as a next-generation power source.

  On the other hand, since methanol used for fuel is liquid, it easily leaks, and there are concerns about the flammability and toxicity of methanol itself, and measures for safe use have become issues. In addition, as a disadvantage of using liquid fuel, the performance of the fuel cell is deteriorated when impurities dissolved in the liquid fuel are supplied to the fuel cell, and methanol, which is a liquid fuel component, permeates the electrolyte membrane of the fuel cell. And a crossover phenomenon that reaches the air electrode.

Therefore, in order to solve such problems such as the safety of methanol, the present applicant has variously reported about "solid methanol fuel" which solidifies methanol by forming a molecular compound, makes it difficult to leak and greatly reduces flammability. Proposed (see Patent Documents 1 to 3). This solid methanol releases methanol in the solid to the water side when it comes into contact with water. The aqueous methanol solution thus produced can be used directly as a fuel for a methanol fuel cell.
JP 2006-040629 A JP 2005-325254 A International Publication No. 2005/0624210 Pamphlet

  However, the method of use proposed in Patent Documents 1 to 3 is that methanol is extracted by bringing solid methanol into contact with water to produce an aqueous methanol solution, and the aqueous methanol solution is supplied to the fuel cell. It is. Therefore, the fuel cell system has problems such as leakage of methanol aqueous solution and crossover as in liquid fuel. In addition, this water supply system requires water supply means such as a water tank and a pump, but it is preferable that the apparatus has a simple device structure that does not require them in order to be applied to a portable electronic device or the like.

  Therefore, there is a demand for a direct methanol fuel cell system in which methanol is extracted from solid methanol as a gas and supplied. However, this method tends to lack sufficient water equivalent to methanol at the anode. There has been a demand for a direct methanol fuel cell capable of continuing the above.

  The present invention has been made in view of the above problems, and uses liquid methanol that is very safe in the state of the fuel cartridge, and also uses liquid fuel as a system, such as liquid leakage, crossover, output reduction, etc. An object of the present invention is to provide a direct methanol fuel cell system in which methanol is supplied as a gas, which solves the above problem. Another object of the present invention is to provide a portable electronic device using the direct methanol fuel cell system.

  In order to solve the above-described problems, the present invention provides a fuel containing portion containing solid methanol obtained by solidifying methanol, a fuel cell, and a fuel containing methanol vaporized from the solid methanol by circulation of a carrier gas. A fuel cell system comprising fuel gas supply means for supplying gas to a fuel cell, wherein the fuel gas supply means is provided with controllable air introduction means (claim) Item 1).

  According to the above invention (invention 1), when gas is supplied to the solid methanol in the fuel storage section by the fuel gas supply means, in the solid methanol, the methanol is loosened by an intermolecular force such as an inclusion phenomenon inside the material. The fuel gas containing the gas is gradually vaporized and supplied to the fuel electrode of the fuel cell, and the vaporized methanol is decomposed on the fuel electrode catalyst. Power is generated.

  At this time, in the fuel cell, it is necessary to supply methanol and an equimolar amount of water to the fuel electrode in order to generate power, but the reaction proceeds by utilizing the water originally held by the electrolyte membrane at the start of power generation. However, as the reaction proceeds, water generated at the air electrode reversely osmosis through the electrolyte membrane and is supplied to the fuel electrode. Therefore, power generation occurs without supplying water. And by continuing supply of this carrier gas, methanol is replenished to a fuel electrode, and electric power generation is continued.

  However, as a result of studies by the present inventors, an equimolar amount of methanol and water react at the fuel electrode of the fuel cell, but when the amount of water consumption is large, that is, when the output of the fuel cell is increased, It has been found that if the operation is continued in such a state, the water is insufficient with only the moisture supplied to the fuel electrode by reverse osmosis from the air electrode and the humidity in the air, and the output may decrease over time. . This is considered to be caused by the fact that when the water in the fuel electrode is insufficient, not only the water necessary for the reaction cannot be supplied, but also the electrical conductivity of the electrolyte membrane decreases.

  Therefore, in the present invention (Claim 1), by providing a controllable air introduction means in the fuel gas supply means, air is introduced from the air introduction means continuously or intermittently, or moisture is insufficient. Then, by introducing air, methanol is oxidized to oxygen in the air to produce water, and this water is supplied to the anode along the flow of fuel gas, so that water as a liquid is put into the system. Even if it is not present, it is possible to supply moisture necessary for the wetting of the electrolyte and the reaction at the fuel electrode, and stable power generation can be performed.

  In the above invention (invention 1), the fuel gas supply means includes a carrier gas supply means, a carrier gas supply path communicating with the carrier gas supply means provided in the fuel storage portion, and a fuel cell unit. A fuel gas flow passage communicating with the fuel electrode side, and the fuel cell is provided with an exhaust gas flow path communicating with the fuel electrode side, and the controllable air introduction means is connected to the carrier gas. When the carrier gas is provided in the supply path or the fuel gas flow path and the carrier gas is supplied to the fuel storage portion, the fuel gas containing methanol vaporized from the solid methanol is supplied to the fuel electrode of the fuel cell, It can be set as the structure discharged | emitted from an exhaust gas flow path (Claim 2).

  According to the above invention (invention 2), when the carrier gas is supplied to the fuel storage portion by a blower such as a gas cylinder, a pump, or a blower, the methanol in the solid methanol is intermolecular such as an inclusion phenomenon inside the material. Since it is gently restrained by force, it does not vaporize at once, but it is gradually vaporized, and the fuel gas containing this is supplied to the fuel electrode of the fuel cell, and this vaporized methanol is fed onto the catalyst of the fuel electrode. Electric power is generated by disassembling in step (b).

  And by continuing supply of this carrier gas, while a fuel electrode is replenished with methanol and electric power generation is continued, excess methanol is discharged | emitted from an exhaust gas flow path. Thus, since excess methanol is not supplied to a fuel electrode, it can be set as the direct methanol fuel cell system by which problems, such as crossover and a liquid leak, were solved.

  Furthermore, a controllable air introduction means is provided in the carrier gas supply path or the fuel gas flow path, and air is introduced from the air introduction means continuously or intermittently, or when moisture is insufficient, air is introduced. In addition, air is mixed in the carrier gas or fuel gas, and methanol is oxidized by oxygen in the air to produce water, and this water is supplied to the fuel electrode, so there is water as a liquid in the system. Even if it does not make it, the water | moisture content required for the wetting of an electrolyte and reaction at a fuel electrode can be supplied.

  In the above invention (invention 1), the fuel gas supply means includes a carrier gas circulation means, a carrier gas supply path communicating with the carrier gas supply means provided in the fuel accommodating portion, and the fuel cell. A fuel gas flow passage communicating with the fuel electrode side of the cell, and a circulation flow path connecting the fuel electrode side of the fuel cell and the carrier gas circulation means, the controllable air introduction means being supplied with carrier gas A fuel gas containing methanol vaporized from the solid methanol when the carrier gas is provided from the carrier gas circulation means through the carrier gas supply path to the fuel accommodating portion. However, after being supplied to the fuel electrode of the fuel battery cell, the fuel gas can be recirculated from the circulation channel to the carrier gas circulation means. Section 3).

  According to the above invention (invention 3), when the carrier gas is supplied to the fuel storage portion by the carrier gas circulation means such as a pump, the methanol in the solid methanol is intermolecularly forced by the intermolecular force such as the inclusion phenomenon inside the material. Since it is gently restrained, it does not vaporize at once, it is gradually vaporized, and the fuel gas containing this is supplied to the fuel electrode of the fuel cell, and this vaporized methanol is decomposed on the catalyst of the fuel electrode. As a result, power generation is performed.

  And by continuing supply of this carrier gas, methanol is replenished to a fuel electrode and electric power generation is continued, On the other hand, surplus methanol recirculates from a circulation flow path to a carrier gas circulation means, and is reused. Thus, since excess methanol is not supplied to a fuel electrode, it can be set as the direct methanol fuel cell system by which problems, such as crossover and a liquid leak, were solved. In addition, since the carrier gas is circulated and used, it is not necessary to separately provide a gas cylinder or the like, and the methanol contained in the solid methanol can be effectively used.

  Furthermore, if a controllable air introduction means is provided in the carrier gas supply path, the fuel gas flow path or the circulation flow path, air is introduced from the air introduction means continuously or intermittently, or if moisture is insufficient By introducing air, air is mixed into the carrier gas or fuel gas, and methanol is oxidized by the oxygen in the air to produce water, and this water is supplied to the fuel electrode. Even without the presence of water as a liquid, it is possible to supply water necessary for the wetting of the electrolyte and the reaction at the fuel electrode.

  In the said invention (Invention 1-3), it is preferable that the said fuel accommodating part is a detachable cartridge (Invention 4). According to this invention (invention 4), when the amount of methanol contained in the solid methanol decreases, the methanol concentration in the fuel gas decreases, and the output of the fuel cell decreases, the cartridge is replaced. Thus, it can be used again in a good state.

  Moreover, this invention provides the portable electronic device characterized by including the direct methanol fuel cell system of the said invention (Invention 1-4) (Invention 5). According to this invention (Claim 5), problems such as crossover and liquid leakage are improved, stable power generation is possible stably for a long period of time, and stable by using a compact direct methanol fuel cell system. And can be a compact portable electronic device.

  ADVANTAGE OF THE INVENTION According to this invention, problems, such as crossover and a liquid leak, are improved, problems, such as a power fall, can be solved, and the direct methanol type fuel cell system which can generate electric power efficiently can be provided. In addition, since it is not necessary to provide a device such as a water supply means, the direct methanol fuel cell system can be made compact.

Hereinafter, a direct methanol fuel cell system according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flow diagram showing a direct methanol fuel cell system according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a solid methanol container in FIG.

As shown in FIGS. 1 and 2, the direct methanol fuel cell system of the present embodiment includes a carrier having a compressed gas cylinder of nitrogen gas (N ₂ ) serving as carrier gas supply means so that oxygen is not supplied to the fuel electrode. A gas source 1, a solid methanol fuel cartridge 3 containing solid methanol, and a fuel cell 5 are provided. The carrier gas source 1 and the solid methanol fuel cartridge 3 communicate with each other through a carrier gas supply path 2. In addition, the solid methanol fuel cartridge 3 and the fuel battery cell 5 communicate with each other through the fuel gas flow passage 4.

  The fuel cell 5 includes a fuel electrode 6, a solid polymer electrolyte membrane 7, and an air electrode 8. The fuel electrode 6 is disposed in a cover 5A in which the fuel gas flow path 4 and the exhaust gas flow path 9 communicate with each other. Sealed. The air electrode 8 is open to the atmosphere.

  In the present embodiment, the carrier gas supply means, which is the carrier gas supply means 1, the carrier gas supply path 2, and the fuel gas flow path 4, constitute a fuel gas supply means.

  Then, an air pump 10A or an air pump 10B as air introduction means is connected to the carrier gas supply path 2 (1) or the fuel gas flow path 4 (2). The air pumps 10A and 10B are connected to a control means (not shown) having an output sensor of the fuel cell 5 and are normally stopped, but the output of the fuel cell 5 is below a predetermined value. When it becomes, it is controlled to supply a predetermined amount of air.

  In such a direct methanol fuel cell system, the solid methanol fuel cartridge 3 is provided with a partition wall 3B so as to form a bent channel in the box-shaped casing 3A as shown in FIG. Filled with solid methanol S. Then, one side (the upper side in the figure) partitioned by the partition wall 3B is connected to the carrier gas supply path 2, and the other side (the lower side in the figure) is connected to the fuel gas flow path 4, so that the carrier gas is The solid methanol S passes while making sufficient contact.

In the direct methanol fuel cell system according to the first embodiment as described above, nitrogen gas (N ₂ ) is used as the carrier gas. However, the present invention is not limited to this, for example, an inert gas such as Ar. Alternatively, CO ₂ or the like may be supplied.

  Further, as the solid methanol S, a methanol molecular compound including a clathrate compound of methanol, methanol solidified with a polymer or gelled with dibenzylidene-D-sorbitol, magnesium aluminate metasilicate, etc. Substances that contain methanol and show a solid state, such as those made solid by holding methanol by adsorption or the like on inorganic materials, and those in which the vaporization temperature of methanol is adjusted by coating them. Anything can be used.

  A molecular compound is a compound in which two or more kinds of compounds that can exist stably alone are bonded by a relatively weak interaction other than a covalent bond, such as a hydrogen bond or van der Waals force. Hydrates, solvates, addition compounds, inclusion compounds and the like.

  Such a molecular compound can be formed by a contact reaction between a compound that forms the molecular compound and methanol, can convert methanol into a solid compound, and can store methanol in a relatively lightweight and stable manner. Can do. In particular, an inclusion compound in which methanol is included by a reaction between a host compound and methanol is preferable.

  As solid methanol, the thing of various forms, such as a sheet form, block shape (block shape), and a granular form, can be used. Among these, the particulate form is preferable. By using particulate methanol as the solid methanol and reducing the particle size, the vaporization rate of methanol can be increased and the generated methanol vapor can be easily transferred.

  The particle size of the solid methanol is preferably in the range of 1 μm to 10 mm, particularly 100 μm to 5 mm in consideration of handling properties, filling properties, gas mobility and the like.

  Such solid methanol is preferably obtained by incorporating 1 to 3 parts by mass of methanol with respect to 1 part by mass of the base material.

  Such solid methanol does not have to be 100% pure methanol, but water added to methanol to obtain a methanol aqueous solution with a desired concentration. Also good.

  If the water shortage is significant, the fuel cartridge 3 may contain a water-containing solid material together with the solid methanol S. The water-containing solid material may be any material that can be constrained to the extent that water does not leak out as a liquid, such as inorganic porous materials such as magnesium aluminate metasilicate, organic porous materials, fibrous materials, and water-absorbing polymer materials. Etc. can be applied. Specific examples include silica-based and titania-based inorganic porous materials, activated carbon, porous glass materials, glass fibers, fiber materials such as general cloth and paper, cellulose fibers, and polyamide water-absorbing resins. However, it is not limited to these. Moreover, you may use what adjusted the vaporization temperature of water by coating a water-containing solid material.

  Such a water-containing solid material is preferably obtained by incorporating 1 to 3 parts by mass of water with respect to 1 part by mass of the base material.

The operation of the direct methanol fuel cell system of the first embodiment having such a configuration will be described.
1, when the carrier gas source 1 to supply N ₂ gas, the N ₂ gas flows through the carrier gas supply channel 2 to the solid methanol fuel cartridge 3.

The solid methanol S in the fuel cartridge 3 does not vaporize at a stroke because the methanol is gently restrained by the intermolecular force including the inclusion phenomenon inside the material, but gradually vaporizes. Then, the methanol molecules gradually vaporized from the surface of the solid methanol S are mixed with N ₂ gas and supplied as fuel gas from the fuel gas flow passage 4 to the fuel electrode 6 of the fuel cell 5.

As a result, power generation is performed according to the following reaction formula.
Anode: CH ₃ OH + H ₂ O → 6H ⁺ + CO ₂ + 6e ⁻ ... [1]
Cathode: 3/2 O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O [2]

  At this time, the methanol concentration in the vicinity of the fuel electrode 6 is considerably dilute compared with the method of directly supplying liquid methanol (aqueous solution), but not all of the methanol in the fuel electrode 6 reacts even in the liquid supply method. Only partly decomposed due to the limit of activity. Moreover, the more methanol is, the more methanol is crossed over to the air electrode 8 side.

Therefore, the high concentration of methanol in the fuel electrode 6 is not necessarily a merit, and even with methanol having a concentration obtained by vaporizing N ₂ gas from solid methanol as a carrier gas, an output almost equivalent to that of the liquid supply method is obtained. Is obtained.

Then, while the methanol is reduced is decomposed in the fuel electrode 6, by continuous supply of N ₂ gas from the carrier gas source 1, the methanol gas from the solid methanol is also supplied, the power generation reaction Will continue.

  At this time, in the above reaction formula [1], equimolar water with methanol is required, the moisture in the carrier gas is low, and only the water generated by the cathode reaction can supply the water necessary for the reaction at the anode. In addition, since the electrical conductivity of the solid polymer electrolyte membrane 7 is lowered, the output of the fuel cell 5 may be lowered.

  Therefore, when the output of the fuel cell 5 falls below a predetermined value, the air pump 10A or the air pump 10B is activated by a control device (not shown) to supply a predetermined amount of air.

  Methanol is oxidized by oxygen in the air to generate water, and this water is supplied to the fuel electrode 6 together with the fuel gas. Therefore, the MEA is moistened and the fuel electrode can be obtained without the presence of water as a liquid in the system. Since the water necessary for the reaction in 6 can be supplied, the output of DMFC does not decrease due to the lack of water.

  In order to reliably perform initial power generation, the fuel electrode 6 may contain water in advance. The reaction between methanol and water produces carbon dioxide gas that is equimolar with methanol, and this carbon dioxide gas is released from the exhaust gas passage 9 to the external environment.

  Then, since solid methanol is supplied to the fuel cell with methanol contained in the power generation, the methanol content is reduced, so when power is generated for a predetermined time or when the output voltage falls below a predetermined level. The power generation can be continued by exchanging the fuel cartridge 3 together.

Next, a second embodiment of the present invention will be described in detail based on FIG.
FIG. 3 is a flowchart showing a direct methanol fuel cell system according to the second embodiment of the present invention.

  As shown in FIG. 3, the direct methanol fuel cell system of the present embodiment includes a pump 11 that is a carrier gas circulation means that takes in normal air (air) as a carrier gas, and a solid state that is a solid methanol fuel storage unit. A methanol fuel cartridge 13 and a fuel cell 15 are provided. The exhaust side of the pump 11 and the solid methanol fuel cartridge 13 are communicated with each other by a carrier gas supply path 12, and the solid methanol fuel cartridge 13 and the fuel cell are connected. The cell 15 communicates with the fuel gas flow passage 14.

  The fuel cell 15 includes a fuel electrode 16, a solid polymer electrolyte membrane 17, and an air electrode 18, and the fuel electrode 16 is connected to the fuel gas flow passage 14 and the circulation channel 19 connected to the intake side of the pump 11. The air electrode 18 is open to the atmosphere. The circulation channel 19 is provided with a pressure regulating valve (not shown).

  In the present embodiment, the fuel gas supply means is constituted by the pump 11 serving as the carrier gas circulation means, the carrier gas supply path 12, the fuel gas flow path 14, and the circulation flow path 19.

  Then, an air pump 20A, an air pump 20B, or an air pump 20C, which is an air introduction unit, is connected to any one of the carrier gas supply path 12 (1), the fuel gas flow path 14 (2), and the circulation flow path 19 (3). The air pump 20A, 20B or 20C is connected to a control means (not shown) having an output sensor of the fuel cell 5 and is always stopped, but the output of the fuel cell 15 is a predetermined value. When it becomes below, it is controlled to supply a predetermined amount of air.

  The air pumps 20A, 20B, and 20C may be provided at any one location, but are preferably provided in the carrier gas supply passage 12 and the fuel gas flow passage 14, that is, the air pumps 20A and 20B. This is because when the air pump 20C is provided in the circulation channel 19, the methanol concentration in the fuel gas may be lowered.

In such a direct methanol fuel cell system, normal air (air) is used as a carrier gas in the present embodiment, but not limited thereto, an inert gas such as nitrogen gas (N ₂ ) or Ar is used. You may supply. Note that when air is used as a carrier gas, oxygen is contained, so that oxidation of methanol produces harmful substances such as formaldehyde, formic acid, and methyl formate in addition to water. However, in this embodiment, since the carrier gas is recycled, oxygen is consumed immediately, and this oxidation reaction does not occur only in the initial stage. Therefore, the harmful substance has substantially no problem, and moisture generated in the initial state is supplied to the fuel electrode.

  Further, as the solid methanol fuel cartridge 13, the same one as in the first embodiment described above can be used. Moreover, the same thing as 1st Embodiment mentioned above can also be used as solid methanol.

The operation of the direct methanol fuel cell system of the second embodiment having such a configuration will be described.
In FIG. 3, when air is introduced into the circulation flow path and is circulated by the pump 11, the air flows into the solid methanol fuel cartridge 13 through the carrier gas supply path 12.

  The solid methanol S in the fuel cartridge 13 does not vaporize at a stroke because the methanol is gently restrained by the intermolecular force including the inclusion phenomenon inside the material, but gradually vaporizes. Then, the methanol molecules gradually vaporized from the surface of the solid methanol S are mixed with air and supplied as fuel gas from the fuel gas flow passage 14 to the fuel electrode 16 of the fuel cell 15.

As a result, power generation is performed according to the following reaction formula.
Anode: CH ₃ OH + H ₂ O → 6H ⁺ + CO ₂ + 6e ⁻ ... [1]
Cathode: 3/2 O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O [2]

  At this time, the methanol concentration in the vicinity of the fuel electrode 16 is considerably dilute compared with the method of supplying liquid methanol (aqueous solution) directly, but even in the liquid supply method, not all of the methanol in the fuel electrode 16 reacts, and the catalyst Only partly decomposed due to the limit of activity. Moreover, the more methanol is, the more methanol is crossed over to the air electrode 18 side.

Therefore, a high concentration of methanol in the fuel electrode 16 is not necessarily a merit, and even with methanol having a concentration obtained by vaporizing N ₂ gas from a solid methanol as a carrier gas, an output almost equivalent to that of the liquid supply method is obtained. Is obtained.

  And while methanol is decomposed | disassembled and reduced by the fuel electrode 16, since the methanol gas from solid methanol is also supplied by continuing supply of carrier gas by the pump 11, the said electric power generation reaction will continue. Become.

  At this time, in the above reaction formula [1], equimolar water with methanol is required, but in this embodiment, air is circulated as a carrier gas, and water is generated by an oxidation reaction of methanol in the initial state. Therefore, the reaction is started by the moisture resulting from the oxidation of methanol and the moisture originally held by the solid polymer electrolyte membrane 17. However, since oxygen in the carrier gas is quickly consumed as it circulates, the water necessary for the reaction at the anode cannot be continuously supplied only by the water generated by the cathode reaction. Since the electrical conductivity of the membrane 17 is reduced, the output of the fuel cell 15 may be reduced.

  Therefore, when the output of the fuel cell 15 falls below a predetermined value, the air pump 20A, 20B or 20C is activated by a control device (not shown) to supply a predetermined amount of air.

  Methanol is oxidized by oxygen in the air to generate water, and this water is supplied to the fuel electrode 16 together with the fuel gas. Therefore, the solid polymer electrolyte membrane can be obtained without having water as a liquid in the system. Moisture required for 17 wetting and reaction at the anode 16 can be supplied. Therefore, the output of the direct methanol fuel cell system does not decrease due to the lack of moisture.

  In order to reliably perform initial power generation, the fuel electrode 16 may contain water in advance.

  The reaction between methanol and water produces carbon dioxide gas in an equimolar amount with methanol, but this carbon dioxide gas is not released to the external environment but is circulated back to the pump 11 from the circulation channel 19. Further, methanol (gas) remaining without reacting at the fuel electrode 16 is also circulated from the circulation flow path 19 to the pump 11. Thereby, since the methanol contained in the solid methanol S does not diffuse to the external environment, the methanol can be effectively used and the life of the fuel cartridge 13 can be extended. Furthermore, it is not necessary to prepare a carrier gas cylinder or the like separately.

  When the pressure in the circulation path exceeds a predetermined pressure due to carbon dioxide gas generated by the anode reaction or air supplied from the air pumps 20A, 20B, or 20C, a pressure adjusting valve ( An appropriate amount of carrier gas may be released from (not shown).

  And, since the methanol content in the solid methanol is reduced by supplying methanol to the fuel cell along with the power generation, if the power is generated for a predetermined time or falls below a predetermined level of output voltage, Power generation can be continued by exchanging the entire fuel cartridge 13.

  As mentioned above, although this invention has been demonstrated based on embodiment, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible.

  For example, the air pump 10A or 10B or the air pump 20A, 20B, or 20C is controlled by the control device based on the output value of the output sensor in each of the above embodiments. A predetermined amount of air may be intermittently supplied every time, or a small amount of air may be continuously or intermittently supplied.

  Further, when solid methanol and a water-containing solid material are used in combination, it is not necessary to mix the solid methanol and the water-containing solid material into the fuel cartridge 3 (13) as in the above embodiment. Separately from the fuel cartridge 3 (13), a water-containing solid material cartridge (refill container) is placed between the fuel cartridge 3 (13) and the fuel cell 5 (15), that is, in the fuel gas flow path 4 (14). It may be provided.

  The direct methanol fuel cell system of the present invention as described above does not have a liquid inside the system, can be made compact, and as long as the solid methanol has a predetermined amount of methanol, there is no decrease in output, etc. It is particularly suitable as a required power source for portable electronic devices.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[Example 1]
[Fuel battery cell]
The following fuel cell was used for the test.
MEA: MEA for DMFC manufactured by Chemix
・ Electrolyte membrane: Nafion117 (DuPont, film thickness 50μm)
・ Anode (fuel electrode) catalyst; Pt-Ru / C
・ Cathode (air electrode) catalyst; Pt / C
-Effective membrane area: 40 x 40 mm
Current collecting material: SUS mesh (Au plating)
Fuel electrode: sealed structure Air electrode: open structure

[Preparation of film-forming solid methanol]
After blending hydroxypropyl cellulose (2 g) and methanol (300 g) with magnesium aluminate metasilicate powder (100 g), the mixture was granulated into spherical particles having a diameter of about 3 mm using a granulator to obtain solid methanol particles. .

  After introducing the solid methanol particles into the coating apparatus, a 0.5% methanol aqueous solution of ethyl cellulose, which is a film forming material, is sprayed at a flow rate of 10 mL / min for 5 minutes and dried to form a film of ethyl cellulose having a thickness of about 30 μm on the surface. The film-forming solid methanol particles were formed. The methanol content of the film-forming solid methanol particles was about 65%.

[Direct methanol fuel cell system]
2 g of the film-forming solid methanol particles were filled in the cartridge 3 shown in FIG. 2 having a size of 40 × 40 × 10 (mm) and mounted on the system shown in FIG. 1 to prepare a system. At this time, as the fuel electrode 6 of the fuel cell 5, pure water was previously stretched and wetted, pure water was removed before the test, and water droplets were removed with a nitrogen gas flow. The flow rate of N ₂ gas as the carrier gas was 80 mL / min, and 20 mL of air was supplied from the fuel gas flow passage 4 by an air pump every 4 minutes.

[Comparative Example 1]
A direct methanol fuel cell system (Comparative Example 1) was produced in the same manner as in Example 1 except that a 3% aqueous methanol solution was supplied to the fuel electrode 6 of the fuel cell 5 without using a carrier gas.

[Reference example]
A direct methanol fuel cell system (reference example) was produced in the same manner as in Example 1 except that no pump was provided and no air was mixed.

[Power generation test]
With respect to the direct methanol fuel cell systems of Example 1, Comparative Example 1 and Reference Example, a current was passed by an electronic load device and the characteristics of the fuel cell were measured. In the direct methanol fuel cell system of Example 1, The cell voltage during measurement was stable, and the maximum output was about 16 mW / cm ² . Furthermore, there was almost no decrease in output even when operating for 2 hours in that state.

In contrast, in the direct methanol fuel cell system of Comparative Example 1 to which an aqueous methanol solution was supplied, the cell voltage during measurement was stable, but the maximum output was as low as about 14 mW / cm ^2, and the operation was continued for 1 hour in that state. When this was done, a decrease in output was observed. This is considered to be due to a decrease in reactivity at the fuel electrode 6 due to carbon dioxide gas.

In the direct methanol fuel cell system of the reference example in which air was not supplied regularly, the cell voltage during measurement was stable and the maximum output was as high as about 16 mW / cm ^2. A decrease in output was observed when operated for hours. This is thought to be due to the lack of moisture.

[Example 2]
2 g of the film-forming solid methanol produced in Example 1 was filled in the cartridge 3 shown in FIG. 2 having a size of 40 × 40 × 10 (mm) and mounted on the system shown in FIG. At this time, as the fuel electrode 6 of the fuel cell 5, pure water was previously stretched and wetted, pure water was removed before the test, and water droplets were removed with a nitrogen gas flow. The carrier gas, air, was circulated at 80 mL / min, and 20 mL of air was supplied from the fuel gas flow passage 14 by an air pump every 4 minutes.

  The direct methanol fuel cell system of Example 2 was subjected to a power generation test similar to that of Example 1, and the characteristics of the fuel cell were measured. As a result, results equivalent to those of Example 1 were obtained.

1 is a flowchart showing a direct methanol fuel cell system according to a first embodiment of the present invention. 1 is a cross-sectional view showing a fuel cartridge in a direct methanol fuel cell system according to a first embodiment of the present invention. It is a flowchart which shows the direct methanol fuel cell system which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

1 ... Carrier gas source (carrier gas supply means)
2, 12 ... Carrier gas supply path 3 ... Solid methanol fuel cartridge (fuel storage part)
4, 14 ... Fuel gas flow passages 5, 15 ... Fuel cell 6, 16 ... Fuel electrode 7, 17 ... Solid polymer electrolyte membrane 8, 18 ... Air electrode 9 ... Exhaust gas flow path 10A, 20A ... Air pump (air introduction) means)
10B, 20B ... Air pump (air introduction means)
11 ... Pump (carrier gas circulation means)
13. Solid methanol fuel cartridge (fuel storage part)
19 ... circulation flow path 20C ... air pump (air introduction means)
S: Solid methanol

Claims (5)

A fuel storage section for storing solid methanol obtained by solidifying methanol;
A fuel cell;
A fuel cell system comprising fuel gas supply means for supplying a fuel cell containing fuel gas containing methanol vaporized from the solid methanol by circulation of carrier gas,
A fuel cell system comprising a controllable air introduction means in the fuel gas supply means. The fuel gas supply means includes a carrier gas supply means, a carrier gas supply path that communicates with the carrier gas supply means provided in the fuel accommodating portion, and a fuel gas flow path that communicates with the fuel electrode side of the fuel cell. And consist of
The fuel battery cell is provided with an exhaust gas passage in communication with the fuel electrode side,
The controllable air introduction means is provided in the carrier gas supply path or the fuel gas flow path,
When a carrier gas is supplied to the fuel storage unit, a fuel gas containing methanol vaporized from the solid methanol is supplied to the fuel electrode of the fuel cell and then discharged from the exhaust gas flow path. The fuel cell system according to claim 1. The fuel gas supply means includes a carrier gas circulation means, a carrier gas supply path that communicates with the carrier gas supply means provided in the fuel storage portion, and a fuel gas flow path that communicates with the fuel electrode side of the fuel cell. And a circulation channel connecting the fuel electrode side of the fuel cell and the carrier gas circulation means,
The controllable air introduction means is provided in the carrier gas supply path, the fuel gas flow path or the circulation flow path,
When the carrier gas is supplied from the carrier gas circulation means to the fuel storage portion via the carrier gas supply path, after the fuel gas containing methanol vaporized from the solid methanol is supplied to the fuel electrode of the fuel cell, The fuel cell system according to claim 1, wherein the fuel gas is returned from the circulation flow path to the carrier gas circulation means.   The direct methanol fuel cell system according to claim 1, wherein the fuel storage unit is a detachable cartridge.   A portable electronic device comprising the direct methanol fuel cell system according to claim 1.

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