WO2004032270A1

WO2004032270A1 - Fuel cell and method for driving fuel cell

Info

Publication number: WO2004032270A1
Application number: PCT/JP2003/012435
Authority: WO
Inventors: Tsutomu Yoshitake; Hidekazu Kimura; Takashi Manako; Yoshimi Kubo
Original assignee: Nec Corporation
Priority date: 2002-10-01
Filing date: 2003-09-29
Publication date: 2004-04-15
Also published as: TW200406079A; JP2004127672A

Abstract

In a fuel cell (100), a fuel electrode (102) is provided with a fuel channel. One end of the fuel channel is connected to one end of a fuel supply line (435), and the other end is connected to one end of a fuel return line (437). The other ends of the fuel supply line (435) and fuel return line (437) are connected to a fuel container (425). Meanwhile, a fuel (124) is hermetically sealed in a route from the fuel channel to the fuel container (425) through the fuel return line (437).

Description

Description Fuel cell and fuel cell driving method

The present invention relates to a fuel cell and a driving method of the fuel cell. Background art

A solid oxide fuel cell is composed of a solid electrolyte membrane such as a perfluorosulfonate membrane as an electrolyte, and a fuel electrode and an oxidizer electrode joined to both sides of the membrane. This is a device that supplies oxygen to the drug electrode and generates power by an electrochemical reaction. The electrochemical reaction that occurs at each electrode is as follows:

_{_{CH 3 OH + H 2 0 →}} 6H + + C0 2 + 6 e- [1]

And at the oxidant electrode,

3/20 ₂ + 6H ⁺ +6 e- → 3H ₂ 0 [2]

It is. In order to cause this reaction, both electrodes are composed of a mixture of carbon fine particles carrying a catalyst substance and a solid polymer electrolyte.

When methanol is used as the fuel in this configuration, the methanol supplied to the fuel electrode passes through the pores in the electrode and reaches the catalyst, where the methanol is decomposed and the reaction represented by the reaction formula [1] is performed. Generates electrons and hydrogen ions. The hydrogen ions reach the oxidizer electrode through the electrolyte in the electrode and the solid electrolyte membrane between the electrodes, and react with oxygen supplied to the oxidizer electrode and electrons flowing from an external circuit, as shown in the above reaction equation [2]. Generates water. On the other hand, the electrons emitted from methanol are led to the external circuit through the catalyst carrier in the electrode and the electrode substrate, and flow from the external circuit to the oxidant electrode. As a result, in the external circuit, electrons flow from the fuel electrode to the oxidizer electrode, and power is extracted.

As described above, in a direct fuel cell, hydrogen ions can be obtained from an aqueous methanol solution, so that a reformer or the like is not required, and the size and weight can be reduced. The benefits of applying are great. In addition, liquid methanol aqueous solution As a fuel, the energy density is very high.

However, in a conventional direct methanol fuel cell, carbon dioxide generated by the above reaction formula [1] or carbon monoxide, which is an intermediate product of the reaction formula [1], accumulates in pores in the fuel electrode and the fuel As a result, the power generation efficiency is reduced and the effective catalyst surface is reduced, resulting in a decrease in output. Therefore, it is necessary to take measures to discharge the gas adsorbed in the form of bubbles on the electrode surface.

As a method of discharging the gas adsorbed in a bubble shape on the electrode surface, a flow channel for supplying liquid fuel is formed at the interface between the catalyst layer of the fuel electrode and the solid polymer electrolyte membrane, and flows through this groove. A method has been proposed in which a gas is diffused in a liquid fuel and discharged outside the cell (Patent Document 1).

However, in the method described in Patent Document 1, since bubbles generated in the fuel electrode are removed from the electrode by supplying the fuel by the liquid feed pump, it is difficult to apply the method to a portable electronic device. Had issues. This is because, when applied to portable electronic devices, such as power supplies for mobile phones, the capacity of the power supply is small and the available power is limited. This is because it is difficult to feed the fuel by setting it up at the same time.

On the other hand, as a method for supplying liquid fuel without using a pump or the like, a method has been proposed in which liquid fuel is introduced from a fuel storage container into a cell by capillary force, and is vaporized and supplied to a fuel electrode ( Patent Document 2).

However, in the method described in Patent Document 2, although a gas introduction thin tube for guiding gas generated in the fuel cell body into the fuel container can be provided, the gas is discharged from the fuel electrode by external pressure or the like. Therefore, the gas removal effect was not sufficient. Furthermore, since the gas introduced into the fuel container is for preventing the fuel container from becoming a negative pressure, the fuel supply from the fuel container to the fuel cell body is insufficient, and a high output is stabilized. It was difficult to make it manifest.

Patent Document 1 Japanese Patent Application Laid-Open No. 2000-5626-856

Patent Document 2 Japanese Patent Application Laid-Open No. 2000-1930531 Disclosure of the invention

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a fuel cell that is thin, small, lightweight, and stably exhibits a high output. Another object of the present invention is to provide a driving method of a fuel cell that stabilizes the output of the fuel cell easily.

According to the present invention, there is provided a fuel cell main body having a fuel electrode, and a fuel container for storing liquid fuel, and a part of the liquid fuel supplied from the fuel container to the fuel electrode is a fuel electrode. A fuel cell is provided which is configured to be collected in the fuel container together with the generated gas.

According to the fuel cell of the present invention, a gas such as carbon dioxide generated by an electrochemical reaction at a fuel electrode can be discharged to a fuel container together with a part of liquid fuel such as unused liquid fuel. . This makes it possible to efficiently remove bubbles adhering to the fuel electrode, thereby improving the utilization efficiency of the catalyst at the fuel electrode. Therefore, the output of the fuel cell can be improved.

According to the present invention, there is provided a fuel cell main body having a fuel electrode, a fuel container for storing liquid fuel, and a fuel supply channel and a fuel recovery channel connecting the fuel electrode and the fuel container, A fuel cell is provided, wherein a part of the liquid fuel supplied from the fuel container to the fuel electrode is collected in the fuel container together with a gas generated at the fuel electrode. You.

In the fuel cell according to the present invention, the gas such as carbon dioxide generated by the electrochemical reaction at the fuel electrode is discharged into the fuel recovery channel together with a part of the liquid fuel such as unused liquid fuel, and the fuel container Will be collected. By doing so, it is possible to efficiently remove bubbles attached to the fuel electrode, so that the efficiency of use of the catalyst at the fuel electrode can be improved. Therefore, the output of the fuel cell can be improved.

The fuel cell according to the present invention may be configured such that a path from the fuel electrode to the fuel container via the fuel recovery flow path is sealed. In this case, the air bubbles adhering to the fuel electrode can be more efficiently discharged to the fuel container together with a part of the liquid fuel, so that the utilization efficiency of the catalyst at the fuel electrode can be improved. Yo Thus, the output of the fuel cell can be improved.

In the fuel cell according to the aspect of the invention, a path from the fuel container to the fuel container via the fuel supply flow path, the fuel recovery flow path, and the fuel electrode may be a closed system circulation path. it can.

The fuel cell according to the present invention has a circulating configuration in which unused fuel, which is supplied from the fuel container to the fuel electrode, is again introduced into the fuel electrode, and the fuel is sealed in the circulation path. ing. Therefore, gas such as carbon dioxide generated by the electrochemical reaction at the fuel electrode can be discharged to the fuel container together with the unused fuel. This makes it possible to efficiently remove bubbles attached to the fuel electrode, thereby improving the efficiency of using the catalyst at the fuel electrode. Therefore, the output of the fuel cell can be improved. Furthermore, since the passage of the liquid fuel is closed, the internal pressure of the fuel container increases due to the gas collected from the fuel electrode to the fuel container. By this internal pressure, the fuel in the fuel container can be pumped out to the fuel electrode. This eliminates the need for a driving means such as a pump. Therefore, the fuel cell can be made smaller and lighter. Further, power required for use in the driving means is not required, so that power can be saved.

In the fuel cell according to the aspect of the invention, the fuel cell may further include a fuel flow path provided in the fuel electrode and communicating with the fuel supply flow path and the fuel recovery flow path. By doing so, when the fuel supplied from the fuel supply flow path to the fuel electrode flows through the fuel electrode and is discharged to the fuel recovery flow path, the gas generated at the fuel electrode is more efficiently discharged. be able to. Therefore, the catalyst utilization efficiency of the fuel electrode can be further improved. Note that there is no particular limitation on the position and shape of the fuel flow path provided in the fuel electrode as long as the liquid fuel flows through the fuel electrode and gas can be removed along with the flow. For example, a configuration may be adopted in which a current collector is provided on the fuel electrode, and the fuel flow path is formed in the current collector. In this way, fuel can be efficiently supplied to the entire fuel electrode, and the airtightness of the fuel flow path can be ensured, so that gas can be discharged efficiently.

In the fuel cell according to the present invention, the fuel container may be provided with a pressure release member. Can be.

By doing so, it is possible to avoid a risk that the internal pressure of the fuel container excessively increases and damages the fuel container and the fuel cell. Therefore, the internal pressure of the fuel container can be adjusted to an internal pressure that is sufficient for extruding the fuel and that is highly safe.

According to the present invention, there is provided a method of driving a fuel cell including a fuel cell main body having an anode and a fuel container storing a liquid fuel, wherein a gas generated at the anode is supplied to the anode. A fuel cell driving method is provided, wherein the fuel is collected in a fuel container together with a part of the fuel, and the liquid fuel is supplied to the fuel electrode by the pressure of the gas collected in the fuel container.

According to the driving method of the fuel cell according to the present invention, gas such as carbon dioxide generated by the electrochemical reaction at the fuel electrode is discharged to the fuel container together with some liquid fuel such as unused liquid fuel. In this way, the bubbles attached to the fuel electrode can be efficiently removed, so that the utilization efficiency of the catalyst at the fuel electrode can be improved. Therefore, the output of the fuel cell can be improved and stabilized. Furthermore, since the passage of the liquid fuel is sealed, the internal pressure of the fuel container increases due to the gas collected from the fuel electrode to the fuel container. By this internal pressure, the fuel in the fuel container can be pumped out to the fuel electrode. By doing so, the fuel cell can be operated without using a driving means such as a pump. Therefore, the size and weight of the fuel cell can be further reduced. In addition, since power required for use in the driving means is not required, power can be saved.

According to the present invention, a fuel cell including a fuel cell main body including a fuel electrode, a fuel container storing liquid fuel, and a fuel supply flow path and a fuel recovery flow path connecting the fuel electrode and the fuel container is provided. Wherein the gas generated at the fuel electrode is recovered in the fuel container via the fuel recovery flow path together with a part of the liquid fuel supplied to the fuel electrode, and is recovered in the fuel container. A method for driving a fuel cell is provided, wherein the liquid fuel is supplied to the fuel electrode via the fuel supply channel by the pressure of the gas.

According to the driving method of the fuel cell according to the present invention, the electrochemical reaction at the fuel electrode The generated gas such as carbon dioxide is discharged to the fuel recovery channel together with some liquid fuel such as unused liquid fuel, and is recovered in the fuel container. This makes it possible to efficiently remove bubbles attached to the fuel electrode, thereby improving the efficiency of use of the catalyst at the fuel electrode. Therefore, the output of the fuel cell can be improved and stabilized. Furthermore, since the passage of the liquid fuel is closed, the internal pressure of the fuel container rises due to the gas collected from the fuel electrode to the fuel container. With this internal pressure, the fuel in the fuel container can be pumped out to the fuel electrode via the fuel supply channel. By doing so, the fuel cell can be operated without using driving means such as a pump. Therefore, the fuel cell can be made smaller and lighter. In addition, since power required for use in the driving means is not required, power can be saved.

In the driving method for a fuel cell according to the present invention, the internal pressure of the fuel container may be controlled by a pressure release member provided in the fuel container.

With this configuration, it is possible to avoid a danger that the internal pressure of the fuel container excessively increases due to an increase in the gas generated from the fuel electrode, thereby causing damage to the fuel container and the fuel cell body. Therefore, the internal pressure of the fuel container can be controlled to an internal pressure that is high enough to express the fuel and high in safety, so that the fuel cell can operate safely and exhibit a high output.

As described above, according to the present invention, a part of the liquid fuel supplied from the fuel container to the fuel electrode is collected in the fuel container together with the gas generated at the fuel electrode, thereby achieving a thin, small, and lightweight structure. Thus, a fuel cell in which a powerful output is stably exhibited is realized. Further, according to the present invention, the gas generated at the fuel electrode is recovered in the fuel container together with a part of the liquid fuel supplied to the fuel electrode, and the liquid fuel is supplied to the fuel electrode by the pressure of the gas recovered in the fuel container. By supplying the fuel cell, a driving method of the fuel cell that stabilizes the output of the fuel cell easily is realized. BRIEF DESCRIPTION OF THE FIGURES

The above and other objects, features and advantages will become more apparent from the preferred embodiments described below and the accompanying drawings. FIG. 1 is a diagram showing an example of a configuration of a fuel cell according to the present invention.

FIG. 2 is a diagram showing an example of the configuration of the fuel electrode side current collector of the fuel cell according to the present invention. FIG. 3 is a diagram showing an example of the configuration of the fuel cell according to the present invention.

FIG. 4 is a cross-sectional view of the fuel electrode shown in FIG. 3 in the AA ′ direction.

FIG. 5 is a diagram showing an example of the configuration of the fuel cell according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a specific configuration of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view schematically showing the structure of a fuel cell 100 according to the present embodiment. FIG. 2 is a cross-sectional view of the fuel electrode 102 in FIG. 1 in the AA ′ direction. The catalyst electrode-solid electrolyte membrane assembly 101 is composed of a fuel electrode 102, an oxidizer electrode 108, and a solid electrolyte membrane 114. The fuel electrode and the oxidant electrode are collectively called a catalyst electrode. The fuel electrode 102 includes a substrate 104 and a catalyst layer 106. The oxidant electrode 108 is composed of a base 110 and a catalyst layer 112. One or more catalyst electrode-solid electrolyte membrane assemblies 101 are electrically connected via a fuel electrode side current collector 120 and an oxidant electrode side current collector 122.

When a fuel cell is applied to portable equipment, in addition to the basic performance of high output and stability, it is necessary for the fuel cell to be small, thin and lightweight. Therefore, the following configuration is employed in the fuel cell of FIG. That is, a fuel supply line 435 and a fuel return line 437 are provided between the fuel container 425 and the fuel electrode side current collector 120. A fuel flow path 4 33 is formed in the fuel electrode side current collector 120, and one end of the fuel flow path 4 33 is connected to one end of the fuel supply line 4 35, and the fuel flow path 4 The other end is connected to one end of the fuel return line 437.

As the fuel electrode side current collector 120, for example, carbon or metal can be used. There is no particular limitation on the method of forming the fuel flow path 4 33 to the anode-side current collector 120, but, for example, a method of forming the anode-side current collector 120 at the same time as forming the plate into a plate shape And a method of forming a plate-shaped material by machining.

In the fuel cell 100 configured as described above, each catalyst electrode was connected to the solid electrolyte membrane. Fuel 124 is supplied to the fuel electrode 102 of the combined unit 101 via the fuel electrode-side current collector 120. Further, the oxidant electrode 126 of the catalyst electrode-solid electrolyte membrane assembly 101 is supplied with the oxidant 126 via the oxidant electrode side current collector 122. As the fuel 124, organic liquid fuel such as methanol, ethanol, dimethyl ether, other alcohols, or liquid hydrocarbon such as cycloparaffin can be used. The organic liquid fuel can be an aqueous solution. As the oxidizing agent 126, air can be usually used, but oxygen gas or the like may be supplied.

When the fuel 124 is supplied from the fuel container 425 to the anode-side current collector 120 through the fuel supply line 435, when the fuel 124 is methanol, the fuel is represented by the above reaction formula [1]. Since the reaction mainly occurs, a gas mainly including carbon dioxide is generated. The generated gas, together with the unconsumed fuel 1 24, is guided from the fuel flow path 4 3 3 through the fuel return line 4 3 7 to the fuel container 4 25. Then, the internal pressure of the fuel container 4 25 rises due to the gas led from the fuel electrode 102. Due to this increase in the internal pressure, the fuel 124 is pumped out of the fuel container 425 to the fuel supply line 435.

As described above, in the fuel cell 100, the fuel flow path 4 33 is formed in the fuel electrode side current collector 120, and the collection path of the fuel 124 is excellent in sealing property. Is recirculated from the fuel container 4 25 again, so that the fuel 124 can be efficiently supplied to the fuel electrode 102 without using a fuel delivery member such as a pump. The gas generated at the fuel electrode 102 can be quickly removed. Therefore, it is small and has high output stability.

For example, the battery of FIG. 1 can be suitably used for a direct methanol fuel cell. When applied to a direct methanol fuel cell, gas mainly composed of carbon dioxide generated at the fuel electrode 102 is efficiently collected in the fuel container 425. When the internal pressure of the fuel container 425 rises due to the collected gas, the internal pressure of the fuel container 425 becomes a driving force, and the aqueous methanol solution in the fuel container 425 is pressed out to the fuel electrode 102.

FIG. 3 is a diagram showing an example of another configuration of the fuel cell 100. As shown in FIG. FIG. 4 is a cross-sectional view of the fuel electrode 102 in FIG. 3 in the AA ′ direction. In FIG. 3, the base body 104 and the base body 110 are respectively joined to the fuel electrode side current collector plate 421, and the oxidizer electrode side current collector plate 423. Configuration. Further, the outer periphery of the fuel electrode 102 is covered with a fuel leakage prevention member 445 to ensure hermeticity. A fuel supply line 4 35 and a fuel return line 4 37 are connected to the fuel electrode side current collector plate 4 21, and fuel 124 is supplied from the fuel container 4 25. As the fuel leakage prevention member 445, for example, a metal thin film film or a laminate film composed of a metal thin film and a heat-fusible resin film can be used. Further, as the fuel electrode side current collector plate 421 and the oxidant electrode side current collector plate 423, for example, a porous plate-mesh of a conductive metal or an alloy thereof can be used. In the fuel electrode 102, electric power can be extracted from the fuel electrode side terminal 447 connected to the fuel electrode side current collector plate 421. Similarly, the oxidizer electrode 108 can be provided with an oxidizer electrode side terminal 449 as appropriate. With the fuel cell 100 having such a configuration, it is possible to further reduce the thickness, size, and weight.

In the fuel cell 100 shown in FIG. 1 or FIG. 3, a line opening / closing member such as a valve linked to the power supply of a device on which the fuel cell is mounted is provided in the fuel supply line 435 or the fuel return line 437. Can be installed. In this way, for example, the supply of fuel 124 is cut off when the equipment is turned off, and the supply of fuel 124 is restarted when the equipment is turned on again. it can.

In the fuel cell 100, a material having corrosion resistance to organic liquid fuel can be used for the fuel container 4 25, the fuel supply line 4 35, and the fuel return line 4 37. Further, it is preferable that the weight is as light as possible. Further, it is preferable to provide a pressure release member 439 on the outer wall of the fuel container 425. By doing so, when the internal pressure of the fuel container 4 25 reaches a certain value, for example, 2 atm, the gas inside the fuel container 4 25 can be automatically released, so that the fuel container 4 25 The internal pressure can be kept constant. As the pressure release member 439, a pressure release valve or a permeable membrane of gas generated at the fuel electrode 102 can be used. For example, when methanol is used as the fuel 124, a carbon dioxide permeable membrane can be provided. In order to further improve the sealing property of the fuel 124, the side surface of the fuel electrode 102 and the periphery of the circulation path of the fuel 124 may be appropriately sealed with a sealing material.

In addition, the supply of the fuel 124 to the fuel container 425 may be performed, for example, by injection. it can. In addition, it is also possible to use a cartridge containing fuel and replace it.

In addition, as a method of starting the fuel cell 100 in the initial stage, for example, a method of using a spare power supply can be used. In other words, a small liquid supply pump can be driven by a spare power supply mounted on the device to supply fuel 124 to fuel electrode 102. As the small liquid pump, for example, a small piezoelectric pump such as a bimorph type piezoelectric pump can be used.

Also, as shown in FIG. 5, the fuel container 4 25 has a two-chamber structure, and the fuel electrode 102 is provided with a fuel absorbing material 45 1 for absorbing the fuel 124 so that the fuel 124 is It can also be supplied after being absorbed by the pole 102. In FIG. 5, the fuel absorber 4 51 is provided in contact with the fuel electrode side current collector 4 21. By doing so, the fuel 124 can be efficiently supplied to the entire surface of the fuel electrode side current collector plate 421. There is no particular limitation on the material of the fuel absorber 451, but for example, urethane or the like can be used.

In the fuel cell 100, the solid electrolyte membrane 114 has a role of separating the fuel electrode 102 and the oxidant electrode 108 and of transferring hydrogen ions between the two. For this reason, the solid electrolyte membrane 114 is preferably a membrane having high conductivity of hydrogen ions. Further, it is preferable that it is chemically stable and has high mechanical strength. As a material constituting the solid electrolyte membrane 114, an organic polymer having a polar group such as a strong acid group such as a sulfone group or a phosphate group or a weak acid group such as a carboxyl group is preferably used. Examples of such organic polymers include aromatic condensed polymers such as sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) and alkylsulfonated polybenzoimidazole; Perfluorocarbon containing (Nafion (DuPont) (registered trademark), Aspirex (Asahi Kasei Corporation)); perfluorocarbon containing carboxyl group (Flemion S membrane (Asahi Glass Co., Ltd.) (registered trademark)); Etc. are exemplified.

The fuel electrode 102 and the oxidant electrode 108 are respectively formed of a catalyst layer 106 and a catalyst layer 112 each containing carbon particles carrying a catalyst and fine particles of a solid electrolyte, as a substrate 104 and a substrate, respectively. A structure formed on 110 can be adopted. The surfaces of the substrate 104 and the substrate 110 may be subjected to a water-repellent treatment. Platinum, gold, silver, ruthenium, orifice, palladium, osmium, iridium, cobalt, nickel, rhenium, lithium, lanthanum, strontium, yttrium, or these Alloys etc. are shown. As the catalyst for the catalyst layer 112 on the oxidizer electrode 108 side, the same catalyst as that for the catalyst layer 106 on the fuel electrode 102 side can be used, and the above-mentioned exemplified substances can be used. You. The catalysts of the catalyst layer 106 and the catalyst layer 112 may be the same or different.

Examples of the carbon particles supporting the catalyst include acetylene black (Denka Black (manufactured by Denki Kagaku) (registered trademark), XC72 (manufactured by Vulcan), etc.), Ketjen Black, carbon nanotubes, carbon nanohorn, etc. Is done.

The fine particles of the solid electrolyte in the catalyst layer 106 and the catalyst layer 112 may be the same or different. Here, as the solid electrolyte fine particles, the same material as the solid electrolyte membrane 114 can be used, but a material different from the solid electrolyte membrane 114 or a plurality of materials can also be used.

For both the fuel electrode 102 and the oxidizer electrode 108, the base material 104 and the base material 110 are made of carbon paper, molded carbon, sintered carbon, sintered metal, foamed metal, etc. Substrates can be used. Further, a water repellent such as polytetrafluoroethylene can be used for the water repellent treatment of the substrate 104 and the substrate 110.

Next, a method for manufacturing the fuel cell 100 will be described. The method of manufacturing the fuel cell 100 is not particularly limited, but can be manufactured, for example, as follows.

The fuel electrode 102 and the oxidant electrode 108 can be obtained, for example, by the following method. First, a catalyst is supported on carbon particles by a generally used impregnation method. Next, the carbon particles carrying the catalyst and the fine particles of the solid electrolyte are dispersed in a solvent to form a paste, which is then applied to the substrate 104 or the substrate 110 that has been subjected to the water-repellent treatment. The method for applying the paste to the substrate 104 or 110 is not particularly limited, and for example, methods such as brush coating, spray coating, and screen printing can be used. After the paste is applied, for example, the fuel electrode 102 and the oxidizer electrode 108 are obtained by drying at a heating temperature of 100 ° C. to 25 O and a heating time of 30 seconds to 30 minutes. It is.

For example, when the solid electrolyte membrane 114 is composed of an organic polymer material, the solid electrolyte membrane 114 may be formed of a liquid obtained by dissolving or dispersing the organic polymer material in a solvent by using a peelable sheet such as polytetrafluoroethylene. It can be obtained by casting and drying on the like.

Next, the solid electrolyte membrane 114 is sandwiched between the fuel electrode 102 and the oxidant electrode 108 and hot-pressed to obtain a catalyst electrode-solid electrolyte membrane assembly 101. At this time, the catalyst layer 106 and the catalyst layer 112 are in contact with the solid electrolyte membrane 114. For example, when the fine particles of the solid electrolyte in the solid electrolyte membrane 114, the catalyst layer 106, and the catalyst layer 112 are composed of organic polymers, the hot pressing conditions are the softening temperature of these organic polymers. Or a temperature exceeding the glass transition temperature. Specifically, for example, temperature 100 T: ~ 25 O: pressure 1 kg Z cm ² ~ l 0 kg Z cm ² , time 10 seconds ~

Set to 300 seconds.

The catalyst electrode-solid electrolyte membrane assembly 101 formed as described above has a single cell structure, and is stacked via the fuel electrode side current collector 120 and the oxidant electrode side current collector 122 Thus, a fuel cell stack in which a plurality of single cell structures are connected in series can be provided.

In the fuel cell 100 obtained as described above, bubbles such as carbon dioxide and carbon monoxide generated on the surface of the catalyst layer 106 in the fuel electrode 102 are promptly removed, and the fuel electrode 100 While maintaining an effective surface area, it is removed from the anode 102 and the fuel container

Since the fuel 124 is supplied to the fuel electrode 102 by the pressure of the gas collected in the fuel tank 4, high output is stably exhibited, and the fuel cell is small and lightweight.

Although the use of the fuel cell according to the present embodiment is not particularly limited, for example, a portable type such as a mobile phone, a notebook computer, a PDA (Personal Digital Assistant), various cameras, a navigation system, a portable music player, etc. Suitable for small electrical equipment.

(Example)

In this example, a fuel cell 100 having the configuration shown in FIG. 1 was manufactured and evaluated. (Example 1)

A direct methanol fuel cell for a mobile phone having the configuration shown in FIG. 1 was manufactured. First, 0.19 mm thick carbon paper (manufactured by Toray Industries, Inc.) was used as a carbon-based material for the catalyst electrode, that is, for the fuel electrode 102 and the oxidizer electrode 108. A catalyst layer was formed on the carbon paper surface as follows. First, as a solid polymer electrolyte select 5 wt% naphthoquinone ion alcohol solution of Arudoritsuchi Chemical Co., and n- butyl acetate as a solid polymer electrolyte mass is 0. 1~0. 4mgZcm ³ mixture By stirring, a colloidal dispersion of the solid polymer electrolyte was prepared. The catalyst used for the fuel electrode is carbon fine particles (denka black; manufactured by Denki Kagaku Co., Ltd.) using 50% by weight of a platinum-ruthenium alloy catalyst with a particle diameter of 3 to 5 nm supported by catalyst. As the catalyst of the agent electrode, catalyst-supported carbon fine particles in which 50% by weight of a platinum catalyst having a particle diameter of 3 to 5 nm was supported on carbon fine particles (Denka Black; manufactured by Denki Kagaku) in a weight ratio of 50% were used. The catalyst-supporting carbon fine particles were added to a colloidal dispersion of a solid polymer electrolyte, and the mixture was made into a paste using an ultrasonic disperser. At this time, the mixing was performed so that the weight ratio of the solid polymer electrolyte and the catalyst was 1: 1. This paste was applied on carbon paper by ² mgZcm ² by screen printing, and then heated and dried to produce a fuel cell electrode. This electrode was hot-pressed on both sides of a solid electrolyte membrane Naphion 112 manufactured by DuPont at a temperature of 130 and a pressure of 10 kgZcm ² to produce a catalyst electrode-solid electrolyte membrane assembly 101.

Next, the obtained catalyst electrode-solid electrolyte membrane assembly 101 was sandwiched between a fuel electrode side current collector 120 and an oxidant electrode side current collector 122, and fastened with a port and a nut. Here, carbon was used for the fuel electrode side current collector 120 and the oxidant electrode side current collector 122. Further, the fuel electrode side current collector 120 was provided with a fuel flow channel 433 shown in FIG. 2 by machining on a carbon plate having a thickness of 1 mm. Thus, a fuel cell body was obtained.

One end of a fuel supply line 435 and one end of a fuel return line 437 were connected to the obtained fuel cell body, and the other end of these lines was connected to a fuel container 425 made of aluminum. In addition, a pressure relief valve designed to release pressure at 2.0265 × 10 ⁵ Pa was installed as a pressure relief member 439 on the upper part of the aluminum fuel container 425. The fuel supply line 435 and the fuel return line 437 have a 1 mm inner diameter Teflon (registered (Trademark) tube was used.

A 5 v / v% methanol aqueous solution was injected as fuel 124 into the fuel container 425 of the fuel cell 100 thus obtained. Then, the time change of the voltage of the fuel cell 100 was measured under a load condition of a current of 500 mA.

As a result, in a 24-hour continuous load test, the voltage fluctuation with respect to the output voltage of 3.5 V was 0.2 V or less. Therefore, in this example, it was confirmed that the fuel cell 100 exhibited a stable output. Further, the internal pressure of the fuel container 4 2 5 at this time, it was also confirmed to be stable at around 2 xl 0 ⁵ P a.

(Example 2)

In this example, a fuel cell 100 was manufactured and evaluated in the same manner as in Example 1. However, in this example, the fuel electrode side current collector 120 was used as the substrate 104. That is, a fuel flow channel 433 having the shape shown in FIG. 2 was formed in the carbon current collector, and the catalyst layer 106 was formed directly on the surface where the fuel flow channel 433 was provided.

The obtained fuel cell 100 was subjected to a continuous load test for 24 hours under the same conditions as in Example 1. As a result, the maximum voltage variation with respect to the output voltage of 3.5 V was 0.25 V. Therefore, also in this example, it was confirmed that the fuel cell 100 exhibited a stable output. Further, the internal pressure of the fuel container 4 2 5 at this time, it was also confirmed to be stable at around 2 xl 0 ⁵ P a.

(Comparative Example 1)

In this comparative example, the fuel container 4 25 was directly connected to the fuel electrode 102 without providing the fuel flow path 4 33, the fuel supply line 4 35 5 and the fuel recovery line 4 37 in the fuel electrode 102. A fuel cell for supplying fuel was manufactured by contact. The fabrication of the fuel cell was performed in the same manner as in Example 1.

The obtained fuel cell was subjected to a continuous load test for 24 hours under the same conditions as in Example 1. As a result, the maximum voltage fluctuation with respect to the output voltage of 3.5 V was 2.5 V. In the fuel cell according to this comparative example, since the fuel flow path 433, the fuel supply line 435, and the fuel recovery line 433 are not provided, carbon dioxide generated at the fuel electrode 102, etc. Gas could not be removed, leading to a decrease in output. (Comparative Example 2)

In this comparative example, a fuel cell was manufactured in the same manner as in Example 1, except that the fuel return line 437 was not provided between the fuel electrode 102 and the fuel container 425.

The obtained fuel cell was subjected to a continuous load test for 24 hours under the same conditions as in Example 1. As a result, also in this comparative example, a voltage fluctuation of a maximum of 2.5 V was observed with respect to the output voltage of 3.5 V. In the fuel cell according to this comparative example, the fuel electrode 102 and the fuel container 4

Since the fuel return line 4 3 7 is not provided between the fuel tank 4 and the fuel tank 4 2 5, it is not possible to supply the fuel 1 2 4 from the fuel container 4 2 5 to the fuel electrode 10 2 in a stable manner. Probably caused.

(Comparative Example 3)

In this comparative example, the fuel return line 4 is provided between the fuel electrode 102 and the fuel container 4 25.

As in Example 1, a fuel cell having a configuration in which a fuel pump with power consumption of 1 W is provided between the fuel container 4 25 and the catalyst electrode-solid electrolyte membrane assembly 101 without the provision of 3 7 was provided. It was made.

The obtained fuel cell was subjected to a continuous load test for 24 hours under the same conditions as in Example 1. As a result, the voltage fluctuation with respect to the output voltage of 3.5 V was 0.2 V or less.

From the above examples and comparative examples, in the fuel cell according to the present example, the fuel supply line 435 and the fuel return line 433 are provided between the fuel electrode 102 and the fuel container 425. As a result, the inside of the fuel container 4 25 was naturally pressurized by gas such as carbon dioxide generated at the fuel electrode 102, and the same level of output stability as when a liquid feed pump was used was secured. .

Claims

The scope of the claims

1. A fuel cell body having an anode, and a fuel container for storing liquid fuel, wherein a part of the liquid fuel supplied from the fuel container to the anode is a gas generated at the anode. And a fuel cell configured to be collected in the fuel container.

2. A fuel cell main body having a fuel electrode, a fuel container for storing liquid fuel, a fuel supply flow path and a fuel recovery flow path connecting the fuel electrode and the fuel container, and A fuel cell, wherein a part of the liquid fuel supplied to the fuel electrode is collected in the fuel container together with a gas generated at the fuel electrode.

3. The fuel cell according to claim 2, wherein a path from the fuel electrode to the fuel container via the fuel recovery flow path is sealed.

4. The fuel cell according to claim 2 or 3, wherein a path returning from the fuel container to the fuel container via the fuel supply flow path, the fuel recovery flow path, and the fuel electrode is a closed system. A fuel cell, which is a circulation path.

5. The fuel cell according to any one of claims 1 to 4, further comprising a fuel flow path provided in the fuel electrode and communicating with the fuel supply flow path and the fuel recovery flow path. Fuel cell.

6. The fuel cell according to any one of claims 1 to 5, wherein a current collector is provided on the fuel electrode, and the fuel flow path is formed in the current collector.

7. The fuel cell according to claim 1, wherein a pressure release member is provided in the fuel container.

8. A driving method of a fuel cell including a fuel cell main body having an anode and a fuel container for storing liquid fuel, wherein a part of the liquid fuel supplied to the anode with gas generated at the anode. And a method for driving the fuel cell, wherein the liquid fuel is supplied to the fuel electrode by the pressure of the gas collected in the fuel container.

9. A fuel cell body having a fuel electrode, a fuel container for storing a liquid fuel, and the fuel A method for driving a fuel cell having a fuel supply flow path and a fuel recovery flow path connecting an electrode and the fuel container, wherein a part of the liquid fuel supplied to the fuel electrode And collecting the liquid fuel into the fuel container via the fuel supply flow path by using the pressure of the gas recovered in the fuel container through the fuel recovery flow path. Method for driving a fuel cell.

10. The method for driving a fuel cell according to claim 8 or 9, wherein the internal pressure of the fuel container is controlled by a pressure release member provided in the fuel container. Method.