JP2001102069A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small size fuel cell useful for a power supply of a small size apparatus which can reduce starting time, supplies liquid fuel without being bias to an mounted direction when mounting it and have a structure without leaking out the liquid fuel as well as promote simplification of a feeding system. SOLUTION: In a methanol fuel cell using methanol as fuel constituted by stacking a penetrating plate, a fuel electrode, an electrolyte, an oxide agent electrode and a spreading plate, at least two of consecutive penetrating plates are bonded with absorber consisting of water and methanol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a liquid fuel cell utilizing capillary force for supplying liquid fuel has been disclosed in Japanese Patent Application Laid-Open Nos. −18
It is disclosed in, for example, Japanese Patent Publication No. 8008. Since these liquid fuel cells supply the liquid fuel from the fuel tank to the fuel electrode by capillary force, there is no need for a pump for pumping the liquid fuel required for the liquid supply type fuel cell.

However, the fuel cell having such a configuration has the following problems.

A conventional liquid fuel cell utilizing capillary force is:
Although the configuration is suitable for miniaturization, the fuel is supplied directly to the fuel electrode in a liquid state, so that bubbles in the tank generated during a long unused period or bubbles generated by heat generation during operation of the fuel cell are generated. This has been a cause of hindering the constant supply of fuel to the fuel electrode. In such a case, there has been a problem that it takes a long time to start the engine, or the output fluctuates due to the inability to stably supply the fuel to the fuel electrode during the long-time operation.

[0005]

The conventional fuel cell has a problem that a long start-up time is required or a fluctuation in output during operation because liquid fuel is directly supplied to the fuel electrode.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the above-mentioned conventional fuel cell, and since the liquid fuel is supplied directly to the fuel electrode, the starting characteristics are improved, and the output fluctuation during operation is further improved. An object of the present invention is to provide a fuel cell that is unlikely to cause a problem.

[0007]

According to a first aspect of the present invention, there is provided a fuel cell comprising: an electromotive member formed by sandwiching an electrolyte membrane between a fuel electrode and an oxidant electrode; In a fuel cell in which a plurality of unit cells each having a fuel electrode adjacent to a fuel electrode or via a fuel vaporization layer are stacked, the fuel permeable plate is adjacent to a common absorber at one end of each unit cell. It is characterized by.

According to a second aspect of the present invention, in the fuel cell according to the first aspect, the fuel infiltration plate is formed in parallel with the fuel electrode, and the absorber is formed in a direction perpendicular to the fuel infiltration plate. And

The fuel cell according to claim 3, wherein the fuel cell according to claim 2, further comprising a permselective membrane adjacent to the fuel vaporization layer at the other end of each unit cell. battery.

[0010]

FIG. 1 shows a basic configuration of a fuel cell according to the present invention. FIG. 1A is a sectional view, and FIG. 1B is a plan view. 1 is a fuel tank, 2 is an opening for adjusting the pressure inside the fuel tank, 3 is a fuel supply penetrant, 4 is a fuel supply amount adjusting valve, 5 is a fuel supply path, 6 is a heater, 7 is an absorber, 8 Denotes a fuel cell permeation plate for a unit cell, 9 denotes a unit cell of a fuel cell, 10
Is a carbon dioxide selective permeable membrane, 11 is a fuel cell main body, and 12 is an air blowing means such as a fan.

In the fuel cell of the present invention, the liquid fuel is introduced into the cell by capillary force by the fibrous member in the fuel supply passage 5, so that a driving unit such as a pump for supplying fuel is not required. Further, the liquid fuel introduced into the cell is vaporized in the fuel vaporization layer using the reaction heat of the cell reaction, so that an auxiliary device such as a fuel vaporizer is not required. Also, since the gaseous fuel in the fuel vaporization layer is kept almost saturated, the liquid fuel is vaporized from the fuel permeation plate by the amount of gaseous fuel consumed in the fuel vaporization layer by the cell reaction, and the liquid fuel is further vaporized by the amount of vaporization. It is introduced into the cell by capillary force. As described above, since the fuel supply amount is linked to the fuel consumption amount, there is almost no unreacted fuel discharged out of the cell, and a processing system on the fuel outlet side is required as in the conventional liquid fuel cell. And not.

Thus, the liquid fuel can be smoothly supplied without particularly using auxiliary equipment such as a pump, a blower, a fuel vaporizer, and a condenser, and thus the size can be reduced.

A fuel cell according to the present invention is provided to propose a fuel cell having a structure in which liquid fuel is supplied without depending on how the fuel cell is installed and which does not leak. And a permeable membrane for carbon dioxide gas generated on the anode side. This absorber is a member built in the stack body of the fuel cell of FIG. 1, and has a function of receiving the liquid supplied from the fuel tank by the absorber and supplying it to the permeation plate of each cell. By adopting such a structure, it is possible to make the structure in which the fuel tank and the stack main body are both sealed, and it is possible to supply the fuel without liquid leakage. Further, by providing the stack main body with a methanol-impermeable permselective membrane that permeates carbon dioxide generated on the anode side, it is possible to discharge only carbon dioxide that inhibits the anode reaction and to achieve a structure without fuel leakage. The above-mentioned absorber is effective as a solution to the performance variation caused by the shortening of the start-up time and the uneven fuel supply between cells by selecting a material having high absorption characteristics.

A porous body typified by a flexible filter may be inserted into the connection portion between the receiver and the permeation plate or the like to improve the connection. The receiver may change the water absorption of the polymer and the pore distribution of the porous body so that methanol and water are uniformly supplied to the receiver due to the capillary phenomenon or the like. Also, if a certain pressure or more is applied in the path from the junction to the receiver, the pores and the polymer structure may be destroyed.In this case, when a certain pressure or more is applied, A leak valve that can relieve the pressure may be used.

In the fuel cell of the present invention, it is general that the fuel intake port is in the opposite direction to the exhaust port. However, if it is difficult to discharge in the opposite direction depending on the surrounding environment of the device to be mounted, the fuel intake port is opposite. It may be discharged in a direction other than the direction. Similarly, in the fuel cell of the present invention, it is general that the air intake port is in the opposite direction to the exhaust port, but depending on the surrounding environment of the device to be mounted, if it is difficult to exhaust in the opposite direction, the opposite direction is used. It may be discharged in other than.

Examples of the material of such an absorber include water-absorbing polymers such as cross-linked polyvinyl alcohol, polypyrrolidone film, porous ceramics such as porous silica and porous alumina, fluororesins, polyethylene, polypropylene, polycarbonate, polyimide, polysulfone. , Polysulfide, polybenzimidazole, etc., porous membranes such as carbon molecular sieve, polyimide asymmetric membrane polyimide, asymmetric membrane semi-baked carbon membrane, polycarbonate, polyethylene, polysulfone, polyvinyl alcohol, silica porous body etc. be able to.

FIG. 1 is an overall view of the configuration, and FIG. 2 is a detailed view of the stack section.

[0018]

The invention can be better understood by describing the following illustrative but non-limiting examples.

(Example 1) FIG. 1 shows a configuration diagram of an entire fuel cell, and FIG. 2 shows a stacked cell having a stack structure. Although the manufacturing method is shown below, the structure will be described.

First, a 32 mm × 32 mm fuel electrode 22 having a Pt—Ru catalyst layer coated on a carbon cloth, and a 32 mm × 32 mm oxidizing electrode 23 having a Pt black catalyst layer coated on a carbon cloth
Thus, the electrolyte membrane 21 made of a perfluorosulfonic acid membrane was sandwiched such that the catalyst layer was in contact with the electrolyte membrane. These were joined by hot pressing at 120 ° C. for 5 minutes at a pressure of 100 kg / cm ² . This electromotive part, a carbon porous plate having an average pore diameter of 100 μm as the fuel vaporization layer 24 and a porosity of 70%, and a carbon porous plate having an average pore diameter of 5 μm and a porosity of 40% as the fuel infiltration plate 26 are formed by A diffusion plate 25 having an oxidizing gas supply groove having a width of 2 mm and a width of 1 mm, a fuel electrode side holder 27 and an electromotive unit holder 29 were incorporated. An absorber (t, 10 mm) obtained by partially cross-linking polyvinyl alcohol with formalin from the outside of the electromotive unit holder was brought into contact with the fuel permeation plate, and a polyimide consisting of hexafluoropropyldi (phenyl anhydride) and diaminodiphenyl ether was added. Asymmetric membrane (t: 100μ
m) was placed at position 20 as a carbon dioxide selective permeable membrane to produce a single cell having a reaction area of 10 cm ² .

A 1: 1 (molar ratio) mixture of methanol and water is introduced as a liquid fuel into the thus obtained liquid fuel cell from 28 parts of the absorber by capillary force, and 1 atm as an oxidizing gas.
m of air was flowed through the diffusion plate 25 at 100 ml / min to generate power at 80 ° C. Output 0.5V (load 0.2A / cm2) could be obtained continuously. Further, methanol was not detected in the exhaust gas.

As described above, according to the fuel cell of the present embodiment, the liquid fuel can be smoothly vaporized and supplied with a simple structure without using a pump, a blower, etc. Time can be reduced. Further, a high output can be stably obtained by the uniform branching of the fuel supply. This makes it possible to achieve both high performance and simplification of the system, and to provide a small fuel cell which has been difficult in the past.

Example 2 A liquid fuel cell (unit cell) having the structure shown in FIG. 2 was manufactured in the following manner. First, a 32 mm x 32 mm fuel electrode 22 coated with a Pt-Ru-based catalyst layer on a carbon cloth, and a 32 mm x 32 mm oxidizer electrode 23 coated with a Pt black catalyst layer on a carbon cloth, An electrolyte membrane 1 made of a perfluorosulfonic acid membrane was sandwiched in contact with the membrane. These at 120 ° C
For 5 minutes at a pressure of 100 kg / cm ² and joined. This electromotive section and an average pore diameter of 100 as the fuel vaporization layer 24
μm, 70% porosity carbon porous plate and fuel infiltration plate 26
A carbon porous plate with an average pore diameter of 5 μm and a porosity of 40%, and a diffusion plate with a 2 mm deep and 1 mm wide oxidant gas supply groove
25, fuel electrode side holder 27, and electromotive unit holder 29. Absorber (t, 10m) with polyvinyl alcohol partially cross-linked with formalin from outside the electromotive unit holder
m) is brought into contact with the fuel infiltration plate, and a polyimide asymmetric membrane (t: 100μm) consisting of hexafluoropropyldi (phenyl anhydride) and diaminodiphenylether is placed at position 20 as a carbon dioxide selective permeable membrane. Area 10
A single cell of cm ² was produced. Although not shown, the air outlet may be arranged so that air is discharged in the same direction as the carbon dioxide gas outlet.

A 1: 1 (molar ratio) mixture of methanol and water is introduced into the thus obtained liquid fuel cell as a liquid fuel from the lower part of the absorber 28 by capillary force.
Atm air was flowed through the diffusion plate 25 at 100 ml / min to generate power at 80 ° C. Output 0.5V (load 0.2A / cm2) could be obtained continuously. This value is equivalent to the value obtained in Example 1,
No change in output due to the change in discharge direction was observed.

[0025]

According to the above configuration, according to the above configuration,
It is possible to provide a fuel cell that can stably supply liquid fuel directly to the fuel electrode, improve starting characteristics, and that hardly causes output fluctuation during operation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fuel cell according to Embodiment 1 of the present invention.

FIG. 2 is a cell configuration diagram of a fuel cell according to Embodiment 1 of the present invention.

Claims (3)

[Claims] 1. An electromotive member formed by sandwiching an electrolyte membrane between a fuel electrode and an oxidant electrode, and a fuel infiltration plate adjacent to the fuel electrode of the electromotive member directly or via a fuel vaporization layer. In a fuel cell in which a plurality of unit cells are stacked, the fuel infiltration plate is adjacent to a common absorber at one end of each unit cell. 2. The fuel cell according to claim 1, wherein the fuel permeable plate is formed in parallel with the fuel electrode, and the absorber is formed in a direction perpendicular to the fuel permeable plate. 3. The fuel cell according to claim 2, further comprising a permselective membrane adjacent to the fuel vaporization layer at the other end of each unit cell.