JPH05283094A - Fuel cell - Google Patents

Abstract

PURPOSE:To eliminate the complex moisture control, and make a solid highpolymer electrolyte fuel cell compact by collecting the moisture generated in the oxygen pole side and the moisture transferred from the hydrogen pole side to the oxygen pole side inside of a battery cell, and transferring these moisture to the hydrogen pole side through the porous material with the surface tension. CONSTITUTION:A hydrogen electrode 12 for fuel and an oxygen electrode 13 for oxidant are provided in both sides of laminated solid highpolymer electrolyte films 11, and a hydrogen passage 14 and an oxygen passage 15 are provided through a partitioning plate 16 along both the poles. In the hydrogen pole 12, the porous material 17 made of phenol resin is provided as a moisture passage along both the passages to cover a part of the hydrogen pole 12. Water is thereby transferred between the hydrogen pole 12 and the porous material 17 at a part covered with the porous material 17, and the reaction of the hydrogen pole 12 is performed at uncovered parts. During the operation, water is flowed from the hydrogen pole 12 to the oxygen pole 13 through the electrolyte films 11, and the flowed water is stored in a water receiver parts 20, and thereafter, the water is circulated by the capillarity.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to fuel cells.

[0002]

2. Description of the Related Art Conventionally, a fuel cell has been developed as a large power generation system. Therefore, although there is a name of "battery", it is a kind of power plant, and it has a complicated structure consisting of a fuel cell, a fuel supply system, a water supply system, a combustion control system, a cooling / heating control system, and other systems. It is a power generation system.

A solid molecular electrolyte fuel cell can be operated at a low temperature of about 100 ° C. or lower, and an electrolytic solution such as a phosphoric acid fuel cell or an alkaline electrolyte fuel cell which operates at a low temperature corresponding to this and an electrolyte solution Since it does not use a holding matrix, it is attracting attention as a fuel cell that has the potential to simplify the system and reduce its size and weight.

This fuel cell is characterized in that a solid polymer electrolyte composed of a polymer compound having an ion-exchange ability is used as an electrolyte instead of an electrolyte solution, thereby preventing the electrolyte from being washed away and reacting with positive and negative electrodes. A simple system is used to prevent mixing.

However, in order for the solid polymer electrolyte to work normally, it is indispensable to supply water as an ionic solvent by humidifying the electrolyte membrane and electrodes.

For example, in a fuel cell of the type in which hydrogen cations (protons) move in the electrolyte, the fuel electrode (cathode, anode) is likely to dry, and water consumption also occurs particularly in the case of direct power generation using an organic fuel. On the other hand, since water is generated on the oxidant electrode (anode, cathode) side, it is necessary to replenish the fuel electrode with water and remove the water on the surface of the oxidant electrode.

As an example of an oxygen / hydrogen reaction type fuel cell using a proton conductive solid polymer electrolyte, H ₂ → 2H ⁺ + 2e ⁻ (1) on the fuel electrode (hydrogen electrode) side, The reaction of 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O (2) proceeds. On the fuel electrode side, hydrogen gas is always supplied, so the water on the electrode surface evaporates with this gas,
Drying of the surface occurs. Therefore, the electrochemical reaction due to the oxidation catalyst existing on the electrode surface is hindered, and further, the ion dissociation is hindered also in the solid polymer electrolyte near the fuel electrode, and the ion conductivity is lowered. On the oxidant electrode side, since water is generated on the electrode surface, the contact between the catalyst surface and the reactant, that is, oxygen is hindered and the electrochemical reaction is hindered.

In the case of direct power generation using an organic fuel such as methanol, the reaction on the oxidant electrode side is the same as the above example (Equation (2)), but the reaction on the fuel electrode (methanol electrode) side is CH ₃ OH + H ₂ O → 6H ⁺ + 6e ⁻ + CO ₂ ↑ As shown by (3), since water is consumed, the water content on the electrode surface is more likely to be depleted.

[0009] On the other hand, through the electrolyte hydroxide ion (OH ^-)
In an oxygen / hydrogen reaction type fuel cell using an anion conductive solid polymer electrolyte of a type in which hydrogen moves, in the fuel electrode (hydrogen electrode) side, 2H ₂ + 4OH ⁻ → 4H ₂ O + 4e ⁻ (4) Oxidizing agent On the electrode (oxygen electrode) side, the reaction of O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (5) proceeds.

When the above-mentioned solid polymer electrolyte is applied to direct methanol power generation, the reaction of the oxidizer electrode (oxygen electrode) is similar to that of the above formula (4), but the reaction of the fuel electrode (methanol electrode) is The reaction is CH ₃ OH + 60H ⁻ → CO ₂ + 5H ₂ O + 5H ₂ O + 6e ⁻ (6). Contrary to the proton conductive solid electrolyte, the lack of water on the oxidant electrode side and the removal of water generated on the fuel electrode side Is a problem.

However, no matter what type of electrolyte is used, in order to solve the above problems,
Conventional solid polymer electrolyte fuel cells have complicated piping systems, drive systems, and control systems such as a water supply system that uses a pump and a blower, and a system that controls the temperature and flow velocity of gas to diffuse generated water. I was prepared.

[0012]

As described above, in the fuel cell, the control of the water balance between both electrodes is important for normal operation, and particularly in the solid polymer electrolyte fuel cell, the water content of the electrolyte itself is controlled. Therefore, detailed control is required. However, incorporating such a mechanism for control not only hinders the original advantage of the solid polymer electrolyte fuel cell, namely, reduction in size and weight, but also
In the case of the low temperature operation type, there is a problem in that various problems are involved, such as the need to supply energy from the outside to the vaporization of the produced water.

The present invention provides a fuel cell which can be operated without such complicated water content control.

[0014]

The first invention of the present application comprises a fuel electrode, an oxidizer electrode, and a solid polymer electrolyte sandwiched between the fuel electrode and the oxidizer electrode, and comprises a fuel electrode and an oxidizer. In a fuel cell in which one of the agent electrodes is an electrode (moisture generating electrode) that generates water, the fuel electrode and the oxidant electrode are connected by a water passage, and at least the portion of the passage that is in contact with the water generating electrode is water-permeable. A fuel cell comprising a substance having:

In the present application, the water-generating electrode means an electrode which produces water by an electrode reaction on the fuel electrode or the oxidant electrode during the operation of the fuel cell.

That is, when a proton conductive electrolyte is used, the oxygen electrode produces water by an electrode reaction as shown in the formula (2), and the oxidant electrode serves as a water generation electrode.

On the contrary, when an anionic conductive electrolyte is used,
As shown in equation (4), the fuel electrode serves as the water generation electrode.

In the structure of the fuel cell of the present invention, the laminated oxidant electrode side and the fuel electrode side are connected to each other by a water passage outside the battery cell, and the water generated from the electrode in the passage causes water capillarity. Its characteristic is that it moves by the permeation action such as surface tension.

Therefore, the fuel cell of the present invention has two moisture passages connecting the oxidizer electrode and the fuel electrode. That is, a normal passage passing through the solid polymer electrolyte membrane inside the battery cell and a passage outside the battery cell.

Another feature of the structure of the fuel cell of the present invention is that only water permeation is used to move water through the passage outside, and a power unit such as a pump or a blower is not used. ..

Therefore, no pump or any other power unit and its associated piping, drive unit, and control unit are installed in the passage.

The water passage outside the battery cell connecting the oxidizer electrode and the fuel electrode, which is a feature of the fuel cell of the present invention, may be any water passage as long as the water can move without using power. However, it is usually composed of a porous body, a capillary, a narrow groove, a hydrophilic surface, a fiber, a woven fabric, a water-absorbing polymer, a mixture thereof, etc., which allows water to move by an osmotic action such as surface tension. ..

The material forming the above passages may be ceramics, glass, plastics, metals or any other materials. Plastics are preferable because they can be given any shape, and fluorine is used when heat resistance to some extent is desired. A thermosetting resin such as a resin porous material or a phenol resin (for example, a composite of phenol resin particles with a polyester non-woven fabric) is preferable.

The passages made of these materials may be made of the same material from the oxidizer electrode to the fuel electrode, but may be made of partially different materials.

The passage may be continuously connected from the oxidizer electrode to the fuel electrode with these materials, but these materials may be used discontinuously or partially. In short, there is a water passage connecting the oxidant electrode side and the fuel electrode side outside the battery cell (other than the solid polymer electrolyte membrane inside the battery cell),
Any passage may be used as long as water can move freely through it.

The water in the passage may continuously fill the passage or may be present intermittently in the passage. A typical continuous example is a case where a passage is formed by a porous body to connect the oxidant electrode side and the fuel electrode side. Water continuously fills the porous body and connects both electrodes. A typical intermittent example is, for example, when using a proton conductive solid polymer electrolyte, a water receiver is formed below the oxidizer electrode side, and water on the oxidizer electrode side is dropped there to form a water receiver. This is the case where the fuel electrode side is connected with a porous body. At this time, the water becomes discontinuous between the oxidizer electrode and the water receiver. Of course, when an anionic conductive solid polymer electrolyte is used, a water receiver may be installed on the fuel electrode side, and the oxidizer electrode may be connected from the water receiver with a porous body.

It is also possible to combine continuous and intermittent. FIG. 10 is a schematic diagram of a fuel cell in the case where all the stacked oxidant electrode sides and fuel electrode sides are connected by a common water channel.
A fuel electrode 12 and an oxidant electrode 13 are formed on both sides of the solid polymer electrolyte membrane 11 stacked in FIG. Along the two poles, there are respectively a fuel passage 14 and an oxygen passage 15, which are separated by a separator 16. The fuel and the oxidant (air) flow through the passages in the directions of arrows A and B, respectively. Further, a porous body 17 made of phenol resin is formed along the both electrodes 12 and 13 as a passage for water, and the oxidant electrode side and the fuel electrode side are connected. In this case, movable shutters 28 corresponding to the number of solid polymer electrolyte membranes are formed as shown in the figure. This shutter that can be opened and closed is made of an electric insulator, and when it is closed, electricity,
Shut off water. Allow water to pass through when open.

Normally, this shutter is in a closed state, preventing current from flowing on both sides of the shutter.
When the water balance on both sides of the shutter is significantly impaired, the shutter is opened temporarily to flush the water and restore the water balance on both sides of the shutter.

In a fuel cell having a laminated structure in which a plurality of battery cells are laminated, an arbitrary oxidant electrode side and an arbitrary fuel electrode side can be connected. However, in general, when connecting an arbitrary oxidant electrode side and an arbitrary fuel electrode side, it is preferable to make the water discontinuous by the above-mentioned shutter or some other method so as to prevent current leakage flowing through the water.

On the other hand, the passages connecting the oxidant electrode side and the fuel electrode side of the adjacent battery cells do not need to be discontinuous with water because both have the same potential, and can have a simple structure. It is also a particularly preferable structure from the viewpoint of making the water flow path shortest.

In the passage connecting the oxidant electrode side and the fuel electrode side of the same battery cell, the current leakage is small, and there is practically no problem, and the water does not have to be discontinuous. Therefore, this is also a particularly preferable structure because it can have a simple structure and the flow path of water is short.

In the fuel cell of the present invention, the laminated oxidant electrode side and the fuel electrode side are connected to each other by a water passage outside the battery cell, and the water can move freely by the action of the capillary phenomenon. There is.

For example, when a proton conductive electrolyte is used, when the fuel cell is operated, water flows from the fuel electrode side to the oxidant electrode side inside the battery cell through the solid polymer electrolyte membrane, resulting in oxidation. The agent electrode side becomes rich in water, and the fuel electrode side becomes deficient in water.

When the water balance of both electrodes is lost, the water moves through the external passage from the oxidizer electrode side to the fuel electrode side by surface tension, whereby the water on the fuel electrode side is automatically replenished. It On the other hand, when an anionic conductive electrolyte is used, water is replenished from the oxidant side to the fuel electrode side.

As described above, in the fuel cell of the present invention, the water required on the fuel electrode side or the oxidant electrode side is always automatically replenished. Moreover, this replenishment does not require a power (energy consumption) device such as a pump, and does not require a complicated piping system, drive system, or control system associated with the power device.

Further, in the present invention, the water required by the fuel cell can be self-sufficient by the fuel cell itself, and it is not necessary to supply water from the outside. As described above, the fuel cell of the present invention is a very simple cell system and can be miniaturized.

Further, in the present invention, water is always automatically supplied as much as necessary and sufficiently due to the surface tension, so that the battery performance due to excessive supply or insufficient supply, which is observed in the case of supply by a power unit such as a pump, is reduced. There is no trouble such as obstruction.

The second invention of the present application is a fuel cell comprising a fuel electrode, an oxidizer electrode, and an electrolyte sandwiched between the fuel electrode and the oxidizer electrode, wherein the electrolyte is a solid polymer electrolyte and a water-absorbing material. Alternatively, it is a fuel cell containing a water-retaining substance.

That is, the fuel cell of the present invention supplies and holds water in the membrane in addition to the polymer compound (polymer electrolyte) having an ion-exchange ability, which is the main constituent substance of an ordinary solid polymer electrolyte as an electrolyte. Alternatively, a water-absorbing or water-retaining substance that allows water to pass therethrough in accordance with a concentration gradient is used.

The structure and mechanism of the electrolyte used in the fuel cell of the present invention will be described with reference to schematic diagrams. FIG. 1 shows a structural schematic diagram of the electrolyte according to the present invention in the case of proton conductivity. In FIG. 1, a fuel cell electrolyte 1 has a solid polymer electrolyte 2 in which a water-absorbing or water-retaining substance 3 is retained.

FIG. 2 shows a schematic diagram of mass transfer in this electrolyte. As is clear from FIG. 2, the fuel cell electrolyte of the present invention exhibits the ionic (proton) conductivity inherent to the polymer solid electrolyte and, at the same time, exhibits water absorption or water retention by the action of the water absorption or water retention substance, and thus is oxidized. It also rapidly absorbs water generated on the surface of the catalyst on the cathode and keeps the surface of the catalyst in contact with the reactive substance at all times, and at the same time, it also prevents the inside of the membrane and the surface of the anode from drying.

That is, the protons generated on the fuel electrode side are
Due to the proton conductivity of the solid polymer electrolyte, the solid polymer electrolyte is transported to the oxidant electrode side (direction of arrow 4). In addition, the water generated on the side of the oxidizer electrode, by the action of the water-absorbing or water-retaining substance,
As indicated by arrows 5 and 5 ', water is sent to the surface of the fuel electrode and inside the electrolyte to retain water.

In the case of an anionic conductive solid polymer electrolyte, the water produced on the fuel electrode side is completely solid in the above case and is sent to the surface of the oxidizer electrode and the electrolyte to retain water.

As described above, since the electrolyte according to the present invention exhibits water absorption or water retention by itself, it quickly absorbs the water generated on the surface of one of the electrode catalysts and keeps the surface of the catalyst always in contact with the reactive substance. At the same time, the absorbed water diffuses in the electrolyte according to the concentration gradient, and also has a function of preventing the other electrode surface from drying. Further, in this process, the electrolyte itself also exhibits excellent properties that it can always maintain effective ionic dissociation and ionic conduction characteristics without external humidification.

Therefore, in the fuel cell of the present invention,
It is not necessary to provide a separate mechanism for water supply, and the mechanism for removing generated water can be simplified.

Examples of the water-absorbing or water-retaining substance according to the present invention include water-absorbing polymer compounds such as starch / acrylonitrile copolymer, cross-linked acrylate and cross-linked polyethylene oxide; silica hydrogel, denatured protein (gelatin) gel. Compounds and the like can be used.

The solid polymer electrolyte according to the present invention is, as a proton conductive solid polymer electrolyte, a polystyrene-based cation having a perfluorocarbon sulfonic acid polymer (trade name; Nafion (manufactured by Du Pont, USA) sulfonic acid group. Exchange membrane, anion conductive solid polymer electrolyte, anion exchange membrane, trade name: Perma
Plex BHD (I: made by Fiat) can be mentioned.

The simplest method for producing the electrolyte according to the present invention is to impregnate a solid polymer electrolyte with a water-absorbing or water-retaining substance such as an aqueous solution of polyvinyl alcohol.

However, these water-absorbing or water-retaining substances need to be fixed in the solid polymer electrolyte under the use conditions, and therefore, depending on the structure of the fuel cell, the use temperature, the fuel, the oxidant, etc. In some cases, a treatment for solidification is required in advance. For this purpose, a method of impregnating a solid polymer electrolyte with a precursor of a water-absorbing or water-retaining substance or a solution thereof and then treating the precursor to fix the water-absorbing or water-retaining substance to the electrolyte membrane is effective. For example, a method of impregnating a solid polymer electrolyte with a water-soluble polymer and then insolubilizing it by treating with a crosslinking agent, a method of impregnating a solid polymer electrolyte membrane with an alkali silicate membrane, and then gelating by acid treatment, etc. Is available.

As a method of allowing a water-absorbing or water-retaining substance to coexist in the step of producing a solid polymer electrolyte, a solution of the solid polymer electrolyte and a solution of the water-absorbing or water-retaining substance are simultaneously cast, and then the solvent is removed. You can also use the method.

The fuel cell of the present invention can be manufactured by combining the electrolyte membrane thus manufactured with the fuel electrode and the oxidant electrode.

The electrolyte according to the present invention requires almost no humidification and water supply, and its water permeability makes it very easy to control the water balance between the positive and negative electrodes separated by this membrane.

Therefore, the solid polymer electrolyte type fuel cell of the present invention using this electrolyte does not require a mechanism for humidifying the electrolyte through the fuel or the oxidant, and the moisture produced by the recombination reaction is not required. Since a part is moved to the inside of the electrolyte and to the side opposite to the electrolyte for reuse, the mechanism required for drainage / exhaust steam treatment, which is particularly problematic in low-temperature fuel cells, can be reduced or simplified.

Further, when the fuel cell of the present invention is used as a direct power generation type fuel cell using an organic fuel such as methanol, for example, when a proton conductive solid polymer electrolyte is used, water consumed on the fuel electrode side is oxidized. The generated water on the side of the agent electrode can be supplemented, and when an anionic conductive solid polymer electrolyte is used, the water consumed on the side of the oxidant electrode can be replenished with the generated water on the side of the fuel electrode. Therefore, it is possible to reduce the volume of the reaction water supply container or to omit the water circulation system.

As described above, the electrolyte according to the present invention makes it easy to control the water content, and the fuel cell of the present invention using the electrolyte exhibits the practically extremely advantageous characteristics of being easy to control and being small in size.

[0056]

EXAMPLES Examples of the present invention will be described below. (Example 1) A stack type small solid polymer electrolyte type fuel cell was prototyped. The size of the stacked battery cells is 8c vertically
m, width 5 cm, thickness 3 cm.

FIG. 3 is a partial cross-sectional view showing one embodiment of the solid polymer electrolyte fuel cell of the present invention, and FIG. 4 is a partial plan view. This fuel cell has a cooling unit (not shown)
The temperature is adjusted to 60 ° C during operation.

In FIG. 3, a hydrogen (fuel) electrode 12 and oxygen (oxidizer) are provided on both sides of the laminated solid polymer electrolyte membrane 11.
The pole 13 is formed. There are a passage 14 for hydrogen (fuel) and a passage 15 for oxygen (air) along both poles,
These are separated by a separator 16. Hydrogen (fuel) and oxygen (air) flow through the passages in the directions of arrows A and B, respectively. Moreover, each cell is electrically conducted.

Porous bodies 17 and 18 made of phenol resin are formed along the both electrodes 12 and 13 to serve as water passages, respectively. FIG. 4 shows a vertical sectional view. As shown in FIG. 4, the porous bodies 17 and 18 are hydrogen (fuel) electrodes 1
2. It covers a part of the oxygen (oxidizer) electrode 13.

Water is exchanged between the both electrodes and the porous body from the portion covered by the porous body. The reaction between the both electrodes and hydrogen (fuel) or oxygen (air) is carried out from the part not covered by the porous body. The pattern in which the porous body covers both electrodes can be determined to be optimum according to the respective conditions. For example, the hydrogen inlet has a high pattern density because it is easily dried, and the outlet has a low density.

The porous bodies 17 and 18 are the connecting portions 1 of the porous bodies.
9 has an integral structure, and water can move in the porous body by a capillary phenomenon.

During the operation of the fuel cell, water flows from the hydrogen (fuel) electrode 12 to the oxygen (oxidant) electrode 13 through the solid polymer electrolyte membrane 11. The flowing water and the water generated by the reaction at the oxygen (oxidizer) electrode 13 are absorbed by the porous body 18, pass through 19 by the surface tension, and are supplied to 17.
Water from 17 is again absorbed by the hydrogen (fuel) electrode 12 and circulates through the solid polymer electrolyte membrane 11. (Example 2) A stack-type small solid polymer electrolyte fuel cell was prototyped. The size of the stacked battery cells is 6 cm in length,
The width is 7 cm and the thickness is 3 cm.

FIG. 5 is a partial cross-sectional view showing one embodiment of the solid polymer electrolyte fuel cell of the present invention. The present fuel cell is adjusted to have a temperature of 60 ° C. during operation by a cooling unit (not shown).

In FIG. 5, a hydrogen (fuel) electrode 12 and oxygen (oxidizer) are provided on both sides of the laminated solid polymer electrolyte membrane 11.
The pole 13 is formed. There are a passage 14 for hydrogen (fuel) and a passage 15 for oxygen (air) along both poles,
These are separated by a separator 16. Hydrogen (fuel) and oxygen (air) flow through the passages in the directions of arrows A and B, respectively.

A porous body 17 made of phenol resin is formed along the hydrogen (fuel) electrode 12 to serve as a water passage. The porous body 17 has a hydrogen (fuel) electrode 1 as in FIG.
It covers part of 2.

Water is exchanged between the hydrogen (fuel) electrode and the porous body from the portion covered with the porous body. The reaction between the hydrogen (fuel) electrode and hydrogen (fuel) is performed from the portion not covered by the porous body. The pattern in which the porous body covers the hydrogen (fuel) electrode can be determined to be optimal according to each condition. For example, the hydrogen inlet has a high pattern density because it is easily dried, and the outlet has a low density.

The porous body 17 is in contact with the bottom of the water receiving portion 20 and can suck up the water in the water receiving portion 20. In the water receiver 20, the water generated at the oxygen (oxidizer) electrode 13 and the water that has flowed in flow down and are stored.

During operation of the fuel cell, water flows from the hydrogen (fuel) electrode 12 to the oxygen (oxidant) electrode 13 through the solid polymer electrolyte membrane 11. The flowing water and the water produced by the reaction at the oxygen (oxidant) electrode 13 are
It flows down along with and is stored in the water receiving part 20. The stored water is supplied in the direction of arrow C through the porous body 17 by the capillary phenomenon. Water is again absorbed by the hydrogen (fuel) electrode 12 from the porous body 17 and circulates through the solid polymer electrolyte membrane 11. (Examples 3 to 11 and Comparative Examples 1 to 12)
Examples 3 to 8 are solid polymer electrolytes (commercial name: Nafion; USA Du Po), which are commercially available perfluorocarbon sulfonic acid polymers.
(manufactured by nt Co., Ltd.)
Alternatively, the electrolyte of the present invention was prepared by impregnating these precursors or their solutions and, if necessary, performing various treatments for immobilizing a water-absorbing or water-retaining substance on the solid polymer electrolyte. The impregnated materials and treatment method are shown in Table 1.

[0069]

[Table 1] Regarding the obtained fuel cell electrolyte JIS K 720
The water absorption was measured by the method according to 9. That is, the electrolyte membrane as a sample was dried at 50 ° C. for 1 day and then immersed in water at about 23 ° C. for 1 day, and the water absorption rate per unit amount was determined from the weight difference before and after the immersion. The results are also shown in Table 1.

In addition, as a result of applying a solution of Nafion (manufactured by Aldrich) and a solution of a water-absorbing polymer as described in Examples 9 to 11 onto a glass plate, removing the solvent by drying, and forming a film. Is shown in Table 2.

[0071]

[Table 2] In Table 2, the solid specific mixing ratio indicates the mixing ratio of the solid polymer electrolyte and the water-absorbing or water-retaining substance, and is (weight of solid polymer electrolyte / weight of water-absorbing or water-retaining substance).

Further, in Comparative Example 1 and Comparative Example 2, commercially available Nafion membranes were used as they were, and in the case of samples formed by only a starch / sodium polyacrylate copolymer which is one of water-absorbing polymers. The water absorption rate is shown in Table 3.

[0073]

[Table 3] In the last column of each table, these films were obtained from the value of the AC impedance (measured at 1 kHz) of the unit thickness, which was measured by sandwiching the two films after the measurement of the water absorption rate (water absorption state). The conductivity was shown as a percentage as a relative conductivity based on the value of a commercially available Nafion film.

As is clear from Table 1, Table 2 and Table 3, the electrolyte according to the present invention has a higher water retention capacity than a solid polymer electrolyte membrane containing no water-absorbing or water-retaining substance, and It can be seen that the original characteristics of the electrolyte membrane show high ionic conductivity.

Next, a solid polymer electrolyte type simulated fuel cell was produced using some of these membranes. The schematic diagram is shown in FIG. First, a catalyst layer composed of platinum-supporting carbon powder and fluorocarbon was thermocompression-bonded to both sides of the electrolyte, and a nickel mesh was brought into contact with the catalyst layer to form a current collector 6 as a current collector 6 as shown in FIG. 25, and an air chamber 8 and an air inlet 2 for supplying air and fuel to both surfaces of the electrode.
1, an air outlet 22, a fuel chamber 7, a fuel inlet 9, and a fuel outlet 10 were provided to prepare a simulated fuel cell.

Using the simulated fuel cell, the electrolyte membrane for fuel cell of Example 9 and the electrolyte membrane of Comparative Example 1 were used to prepare hot water at 80 ° C. on the fuel electrode side of the solid polymer electrolyte type simulated fuel cell. A potential-current curve in the case of supplying the passed hydrogen gas is shown by a solid line in FIG. It can be seen that the power generation characteristics of Example 2 (91 in the figure) are better than those of the comparative example (93 in the figure). Further, when the supply fuel was changed to dry hydrogen, the curves changed to the curves indicated by the broken lines, respectively, but in the comparative example (94 in the figure), a drastic characteristic deterioration was observed, while in the example (9 in the figure).
In 2), it can be seen that the influence of the decrease in the amount of supplied water is small.

Further, when methanol heated to 60 ° C. was supplied to these cells, the characteristics shown in FIG. 5 were obtained, and it was found that power generation was possible without supplying water together with methanol.

FIG. 9 is a schematic diagram showing mass transfer on the electrolyte when methanol is supplied to the fuel electrode. Figure 9
As shown in (a), if the water required for proton generation from methanol can be replenished from the oxidizer side by the action of the water-absorbing or water-retaining substance in the electrolyte, the electrochemical reaction will proceed even if only methanol is supplied. As shown in FIG. 9 (b), it is considered that no electrochemical reaction occurs unless water is replenished from the oxidant side. (Example 12) A stack-type small solid polymer electrolyte fuel cell was prototyped. The size of the stacked battery cells is 8c vertically
m, width 5 cm, thickness 3 cm.

FIG. 10 is a partial cross-sectional view showing one embodiment of the solid polymer electrolyte fuel cell of the present invention. Example 3 is the same as Example 1 except for the following one point.

The difference is that all the laminated porous bodies 17 and 18 have an integrated structure by a common porous body connecting portion 26, and water can freely flow in the porous body due to surface tension or the like. You can move. However, the common connecting portion 26 is divided for each battery cell by a shutter 28 of an electric insulator. Normally, this shutter is in the closed state, blocking the current flowing through the common connecting portion 26.

During operation of the fuel cell, water flows from the hydrogen (fuel) electrode 12 to the oxygen (oxidant) electrode 13 through the solid polymer electrolyte membrane 11. The flowing water and the water generated by the reaction at the oxygen (oxidizing agent) electrode 13 are absorbed by the porous body 18, pass through 19 due to the surface tension, and are supplied to 17. Water from 17 is again absorbed by the hydrogen (fuel) electrode 12,
It circulates through the solid polymer electrolyte membrane 11.

During operation, the shutter 28 is opened at any time to balance the water in the common connection 26. After the adjustment, the shutter 28 is closed again to maintain the closed state. (Example 13) A stack-type small solid polymer electrolyte fuel cell was prototyped. The size of the stacked battery cells is 8 cm in length,
It is 5 cm wide and 3 cm thick.

FIG. 11 is a partial cross-sectional view showing one embodiment of the solid polymer electrolyte fuel cell of the present invention. Example 4 is the same as Example 1 except for the following two points.

One of the different points is that the hydrogen (fuel) electrode and the oxygen (oxidant) electrode on the outermost sides of the stacked battery cells are connected by the connecting portion 27 of the porous body with the shutter 29, and Water can move freely in the body due to surface tension or the like. However, the connecting portion 27 is closed by a shutter 29 made of an electric insulator, and cuts off a current flowing through the connecting portion 27.

Another difference is that a porous body is not formed on the surface of the hydrogen (fuel) electrode and the oxygen (oxidizing agent) electrode of the battery cell, and a thin groove is formed instead. Is. Due to surface tension, water moves along the narrow groove and moistens the surfaces of both electrodes.

During operation of the fuel cell, water flows from the hydrogen (fuel) electrode 12 to the oxygen (oxidant) electrode 13 through the solid polymer electrolyte membrane 11. The flowing water and the water generated by the reaction at the oxygen (oxidizer) electrode 13 flow along the narrow groove 30 formed on the electrode, pass through the connecting portion 19 of the porous body, and reach the hydrogen (fuel) electrode side. Supplied. From here, water is a thin groove 31 formed on the hydrogen (fuel) pole due to surface tension or the like.
Flow through the water and are absorbed again by the hydrogen (fuel) electrode 12,
It circulates through the solid polymer electrolyte membrane 11.

During operation, the shutter 29 detects the imbalance of water on both sides and opens to adjust the balance of water in the connecting portion 27. After the adjustment, the shutter 29 is closed again,
Keep closed.

[0088]

As described above, according to the present invention, a polymer electrolyte fuel cell can be operated without complicated moisture control, a humidification / water supply system is not required, and a fuel cell is used. Can be made smaller.

Further, according to the electrolyte of the present invention, the fuel cell can be operated without complicated water content control, and in particular, direct power generation by supplying only methanol fuel, which has been required to be supplied with water at the same time. Is also possible, which further contributes to miniaturization of the fuel cell.

[Brief description of drawings]

FIG. 1 is a structural schematic diagram of an electrolyte membrane for a fuel cell of the present invention.

FIG. 2 is a schematic diagram of mass transfer in the electrolyte membrane for a fuel cell of the present invention using a proton conductive solid polymer electrolyte.

FIG. 3 is a partial cross-sectional view showing an embodiment of the present invention.

FIG. 4 is a partial cross-sectional view showing one embodiment of the present invention.

FIG. 5 is a partial cross-sectional view showing one embodiment of the present invention.

FIG. 6 is a configuration diagram of a simulated fuel cell according to an embodiment of the present invention.

FIG. 7 is a potential-current characteristic diagram when hydrogen gas is supplied to the fuel cell according to the embodiment of the present invention.

FIG. 8 is a potential-current characteristic diagram when methanol is supplied to the fuel cell according to the embodiment of the present invention.

FIG. 9 is a schematic diagram of mass transfer in the solid polymer electrolyte membrane of the present invention in the case of direct methanol power generation.

FIG. 10 is a partial cross-sectional view showing one embodiment of the present invention.

FIG. 11 is a partial cross-sectional view showing one embodiment of the present invention.

[Explanation of symbols]

1 ... in the moving direction 5 ... the electrolyte proton of the fuel cell electrolyte 2 ... solid polymer electrolyte 3 ... absorbent or water retention material 4 ... the electrolyte H ₂ O moving direction 5'... of of H ₂ O in the electrolyte Direction of movement 6 ... Power generating element 7 ... Fuel chamber 8 ... Air chamber 9 ... Fuel inlet 10 ... Fuel outlet 11 ... Solid polymer electrolyte membrane 12 ... Hydrogen (fuel) electrode 13 ... Oxygen (air) electrode 14 ... Hydrogen (fuel) Passage 15 ... Oxygen (air) passage 16 ... Separation plates 17, 18, 19 ... Porous body 20 ... Water receiving part 21 ... Air inlet 22 ... Air outlet 23 ... Negative electrode terminal 24 ... Positive electrode terminal 25 ... Simulated cell container 26 ... Common connection part 27 ... Connection parts 28, 29 ... Shutter 30 ... Oxygen (oxidizer) electrode thin groove 31 ... Hydrogen (fuel) electrode thin groove 91 ... Power generation characteristic of this embodiment when supplying wet hydrogen gas 92 ... This example when supplying dry hydrogen gas Power generation characteristics of a comparative example of the power generation characteristics 94 ... dry hydrogen gas supply of a comparative example of the power generation characteristics 93 ... wet hydrogen gas supply

Claims (2)

[Claims] 1. An electrode (moisture) comprising a fuel electrode, an oxidant electrode, and a solid polymer electrolyte sandwiched by the fuel electrode and the oxidant electrode, wherein either the fuel electrode or the oxidant electrode generates moisture. In the fuel cell, which is a generation electrode), the fuel electrode and the oxidizer electrode are connected by a moisture passage, and at least a portion of the passage in contact with the moisture generation electrode is made of a substance having moisture permeability. 2. A fuel cell comprising a fuel electrode, an oxidizer electrode, and an electrolyte sandwiched between the fuel electrode and the oxidizer electrode, wherein the electrolyte contains a solid polymer electrolyte and a water-absorbing or water-retaining substance. A fuel cell characterized by: