CN1143692A

CN1143692A - Electrolytic functional device and manufacture method of same

Info

Publication number: CN1143692A
Application number: CN96106817A
Authority: CN
Inventors: 光田宪朗; 前田秀雄; 山内四郎; 森口哲雄; 安田胜; 花田武明
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1995-06-30
Filing date: 1996-05-30
Publication date: 1997-02-26
Also published as: DE19621752A1; FR2735991A1; JP3299422B2; JPH0971889A

Abstract

Disclosed are an electrolyte function element and the manufacturing method. Anode and cathode, a catalyst layer and a solid polyelectrolyte membrane are not easy to be peeled off from each other if without clamps. The electrolyte function element comprises a solid polyelectrolyte membrane; and a pair of base courses which have a plurality of through holes and are formed by the metal plate which is buried in the front and rear surface of the solid polyelectrolyte membrane; the membrane is clamped in between as the external electrode of the direct current supply. The catalyst layer is coated on the base course and the outer surface of the exposed part of the polyelectrolyte membrane in the base course through holes, promoting the electrolytic reaction of the external gas and the liquid molecules; moisture permeable and waterproof membrane is coated on the surface of the catalyst close to the exterior.

Description

Electrolytic functional device and method for manufacturing same

The present invention relates to an electrolytic functional device using a solid polymer electrolyte membrane and a method for manufacturing the same.

Fig. 14 is a partial sectional view showing a structure of an electrolytic functional device, for example, one disclosed by Fuji-ta et al, japanese laid-open patent publication nos. 60-114325 and 61-216714, which is applicable to a dehumidifying apparatus and the like, and this prior art is used to show an application of removing water vapor in the environment using the electrolytic functional device.

In fig. 14, reference numeral 1 denotes an anode, 2 denotes a cathode, 3 denotes a solid polymer electrolyte membrane, 4 denotes a junction station, 5 denotes a dehumidifying chamber, and 6 denotes an external dc power supply, and as a practical example, an electrolytic functional device for preventing dew condensation in a semi-sealed electrical unit is discussed in japanese electrochemical society, 59 meeting journal (Yamauchi et al, published 3a31,1992, 3 month, 19). The solid polymer electrolyte membrane 3 is formed of, for example, Nafion-117 material from dupont, with a nominal thickness of about 170 μm. Platinum is plated on the front and rear surfaces of the solid electrolyte membrane 3 by a known method such as electroless plating process (japanese patent laid-open No.57-134486) proposed by Torikaiet al, a membrane-electrode combination is located between collectors 4 formed of, for example, platinum-plated titanium or tantalum mesh, the thus-formed assembly is mounted in a frame made of resin, the edge thereof is fixed to the frame by means of an adhesive or the like, and then the device is formed by hermetic sealing and electrical connection with an external dc power source.

The operation principle of the electrolytic functional device thus constituted will now be discussed.

At the anode 1, water is electrolyzed and reacts according to the following formula (1) by using electric energy supplied from an external direct current power supply 6, thereby reducing the humidity in the dehumidifying chamber 5.

(1)

Hydrogen ion (H) produced by the reaction⁺) Through the solid polymer electrolyte membrane 3 to the cathode2, generation of electrons (e)^-) Through an external circuit to the cathode 2, where the reaction according to the following formula (2) consumes oxygen and produces water.

(2)

Meanwhile, a part of hydrogen ions (H)⁺) The reaction according to the following formula (3) becomes hydrogen gas.

(3)

Furthermore, an average of three water molecules is dissociated from hydrogen (H)⁺) Together with the migration from the cathode 1 to the cathode 2, not only is water generated at the cathode 2 according to the reaction of equation (2), but additional water is also moved from the anode to the cathode 2, thereby reducing the humidity of the dehumidifying chamber 5.

The conventional electrolytic function device of the above-described structure has a problem of increasing the weight and size of the device because it requires planar pressure to be applied to the entire assembly to bring the anode 1 and the cathode 2 into intimate contact with the current collector 4. Here clamps such as clamping plates 7 and bolts 8, nuts 9 are used to apply the plane pressure.

In view of this, a method capable of bringing the anode 1 and the cathode 2 into intimate contact with the current collector 4 without always applying a plane pressure has been invented by the same inventor as this invention, as described in japanese patent laid-open No. 6-63343.

FIG. 15 is a partial sectional view of one embodiment in the specification of Japanese patent laid-open No. 6-63343.

In fig. 15, the anode 1 comprises a loose base layer 1A made of stainless fibers and a platinum-containing catalyst 1B. Similarly, the cathode 2 includes a porous base layer 2A and a platinum-containing catalyst layer 2B catalyst layers 1B and 2B which are thin films three-dimensionally distributed in the base layers 1A and 2A, respectively. In fig. 15, wavy lines indicate catalyst layers 1B and 2B three-dimensionally distributed in base layers 1A and 2A. Reference numeral 3 is a solid polymer electrolyte membrane, which is clamped between the anode 1 and the cathode 2.

A paste consisting of platinum powder and a binder is coated on the base layers 1A and 2A and then dried to form platinum-containing catalyst layers 1B and 2B. Alternatively, the catalyst layers 1B and 2B may be formed by coating a thin film of a kneaded platinum powder and resin mixture on the solid polymer electrolyte membrane 3, or by plating a layer of platinum on the solid polymer electrolyte membrane 3 by a non-electrolytic plating process or the like.

Such an electrolytic functional device is manufactured by a method comprising the steps of: loose base layers 1A, 2A made of stainless fibers on which catalyst layers 1B, 2B are coated and dried) are placed on front and rear surfaces of a solid polymer electrolyte membrane 3 at 190 ℃ and 50kgf/cm²By observing a cross section of a sample of the device under a scanning electron microscope, it was confirmed that the solid polymer electrolyte membrane 3 was embedded in the base layers 1A, 2A, and at the same time, the catalyst layers 1B, 2B were embedded in the solid polymer electrolyte membrane 3 to a depth of about 50 μm, and the catalyst layers 1B, 2B were also formed and three-dimensionally distributed in an irregular pattern.

The electrolyte device of this structure no longer requires the jig indispensable for the device of fig. 14 and succeeds in simplifying the structure, but the long-term life stability test proves that the tendency of peeling of the base layers 1A and 2A gradually increases with time and the performance decreases accordingly. In another finding, the reason why the peeling tendency of the base layers 1A and 2A is enhanced is that the catalyst particles present in the catalyst layers 1B and 2B function to promote loosening, and the moisture accumulated around the catalyst particles of the catalyst layers 1B, 2B accelerates the peeling of the base layers. If the cathode 1 or the cathode 2 is peeled off from the base layers 1A and 1B, there is no current and the electrolytic functional device can no longer operate normally.

The conventional electrolytic function device thus constructed is not satisfactory in practical use, and particularly, the structure of fig. 14 brings about a problem of increasing the weight and size of the device because it requires to apply a plane pressure to the entire assembly, bring the cathode 1 and the cathode 2 into sealing contact with the junction station 4, and apply the plane pressure using the clamping plates 7 and the bolts 8, nuts 9, and the like. In the modified structure of fig. 15, although the catalyst layers 1B, 2B of the anode 1 and the cathode 2 are forcibly embedded in the solid polymer electrolyte membrane 3 together with the base layers 1A and 2A, a disadvantage is also found in that the tendency of the base layers 1A and 2A to peel off is gradually increased with time due to moisture accumulated in the vicinity of the catalyst particles of the catalyst layers 1B, 2B, and the performance is accordingly degraded.

The present invention has been made in view of the above problems, and an object thereof is to provide an electrolytic functional device which can be used for a dehumidifying apparatus or the like without using a jig, and which has a structure in which: the two electrodes, i.e., the anode and the cathode, the catalyst layer, and the solid polymer electrolyte membrane are not easily peeled off from each other.

To achieve this object, an electrolytic functional device according to the present invention comprises a solid polymer electrolyte membrane, a pair of base layers in which a plurality of through holes are formed, formed of metal plates embedded in front and rear surfaces of the solid polymer electrolyte membrane with the electrolyte membrane interposed therebetween and serving as electrodes to which a direct current power supply voltage is applied, and catalyst layers formed to coat outer surfaces of the pair of base layers and surfaces of exposed portions of the solid polymer electrolyte membrane in the through holes formed in the base layers to promote electrolytic reaction of external gas or liquid molecules.

In a preferred mode, the moisture permeation preventing film is covered on the surface of the catalyst layer near the outside.

In another preferable mode, the area of the through-hole formed in at least one of the pair of base layers is different between the outside not contacting the solid polymer electrolyte membrane main body and the inside of the junction-side solid polymer electrolyte membrane main body.

In another preferable mode, the area of the through-holes formed in at least one of the pair of base layers is gradually reduced from the outside not contacting the solid polymer electrolyte membrane main body to the inside contacting the solid polymer electrolyte membrane main body, so that the area of the through-holes on the outside not contacting the solid polymer electrolyte membrane main body is larger than the area of the through-holes on the inside contacting the solid polymer electrolyte membrane main body.

In another preferable mode, the area of the through-holes formed in at least one of the pair of base layers is gradually reduced from the inner side contacting the solid polymer electrolyte membrane main body to the outer side not contacting the solid polymer electrolyte membrane main body, so that the area of the through-holes on the outer side not contacting the solid polymer electrolyte membrane main body is smaller than the area of the through-holes on the inner side contacting the solid polymer electrolyte membrane main body.

In another preferable mode, the aperture of the through-hole formed in at least one of the pair of base layers is gradually decreased from the outside not contacting the solid polymer electrolyte membrane main body to the inside contacting the solid polymer electrolyte membrane main body within a predetermined range, and gradually increased beyond the predetermined range.

In another preferable mode, the area of the through-holes formed in at least one of the pair of base layers is the same between theoutside not contacting the solid polymer electrolyte membrane main body and the inside contacting the solid polymer electrolyte membrane main body.

In another preferable mode, the through-hole formed in at least one of the pair of base layers has a protruding portion on an inner wall thereof.

In another preferred mode, the through-hole formed in at least one of the pair of base layers is most protruded in the middle of the inner wall thereof.

In another preferred mode, the through-hole formed in at least one of the pair of base layers is hexagonal.

In another preferred mode, the through-hole formed in at least one of the pair of base layers is circular.

In another preferred mode, the through-holes formed in at least one of the pair of base layers are rhombic.

In another preferred form, at least one of the pair of base layers is formed of a thin metal foil coated with a thin film formed of at least one member selected from the group consisting of aluminum, gold and palladium.

In another preferable mode, the part of the solid polymer electrolyte membrane exposed in the through-holes of the pair of base layers projects outward from the outer side not contacting the solid polymer electrolyte membrane main body.

In another preferred mode, a portion of the solid polymer electrolyte membrane exposed in the through-hole formed in the pair of base layers is left in the through-hole in a concave shape.

In another preferred mode, each catalyst layer comprises platinum catalyst particles and a solid polymer electrolyte having the same or equivalent composition as the solid polymer electrolyte membrane.

Further, a method for manufacturing an electrolytic functional device according to the present invention includes a burying step of burying a pair of base layers, which are formed of a metal plate on which a plurality of through holes are formed and serve as electrodes externally connected with a direct current power supply voltage, into front and rear surfaces of a solid polymer electrolyte membrane; and a coating step of coating a catalyst on surfaces of exposed portions of the solid polymer electrolyte membrane from the pair of through holes in the base layer and outer surfaces of the pair of base layers, thereby forming a catalyst layer for promoting an electrolytic reaction of external gas or liquid molecules.

In a preferred mode, the burying step is carried out by burying the pair of base layers in the front and rear surfaces of the solid polymer electrolyte membrane by hot pressing at a temperature higher than the softening temperature of the solid polymer electrolyte membrane.

In another preferred mode, the burying step is carried out such that the solid polymer electrolyte membrane absorbs a solvent capable of causing swelling thereof, and then a pair of base layers are buried in the front and rear surfaces of the solid polymer electrolyte membrane by pressurization in a gel state.

In another preferred mode, the solvent is a mixed solvent of an organic solvent and water.

In another preferred form, the burying step is carried out by placing a paper sheet having a rough surface on the outer surfaces of a pair of base layers disposed on the front and rear surfaces of the solid polymer electrolyte membrane, prior to the pressing.

In another preferred form, the method further comprises a step of coating a moisture-permeable waterproof film on the surface of the catalyst layer near the outside.

FIG. 1 is a partial sectional view showing the structure of an electrolytic functional device according to example 1 of the present invention.

FIG. 2 is a partial sectional view showing the structure of an electrolytic functional device according to example 2 of the present invention.

FIG. 3 is a partial sectional view showing the structure of an electrolytic functional device according to example 3 of the present invention.

FIG. 4 is a partial sectional view showing the structure of an electrolytic functional device according to example 4 of the present invention.

FIGS. 5A and 5B are enlarged plan views showing the inner and outer surfaces of the base layer formed of the porous metal plate for use in any one of the electrolytic functional devices according to examples 1 to 4 of the present invention.

Fig. 6 compares in an enlarged manner the electrode structures of electrolytic functional devices according to examples 1 to 4 of the present invention.

FIG. 7 is a characteristic diagram showing the electric field intensity generated from the surface of the catalyst layer between points A and B along the outer surface of the through-hole shown in FIG. 6 for each electrolytic functional device.

FIG. 8 is an exploded partial sectional view of each member relating to example 5 of the present invention, to explain a method of manufacturing an electrolytic functional device.

FIG. 9 is a graph showing the results of evaluation tests of the dehumidifying ability of a conventional electrolytic functional device and an electrolytic functional device of the present invention.

FIG. 10 is a diagram showing a conventional electrolytic functional device and a structure for testing the dehumidifying ability life of the electrolytic functional device of the present invention.

FIG. 11 is a partial sectional view showing the structure of an electrolytic functional device of example 6 of the present invention.

Fig. 12A and 12B are enlarged plan views each showing a surface of a base layer formed of a porous metal plate used in the electrolytic functional device according to example 7 of the present invention.

FIGS. 13A and 13B are sectional views each showing the inner surface of a base layer formed of a porous metal plate used in an electrolytic functional device of example 8 of the present invention.

FIG. 14 is a partial cross-sectional view showing a structure of an electrolytic functional device according to the prior art.

Fig. 15 is a partial sectional view showing a structure of an electrolytic functional device in another prior art.

The structure of the electrolytic functional device of the present invention and the method of manufacturing the same will be described below with reference to the embodiments shown in fig. 1 to 4, 5A, 5B, 6 to 11, 12A, 12B, 13A and 13B, in which the same or equivalent elements as those in the prior art are denoted by the same reference numerals.

First, the structures of the electrolytic functional devices of examples 1 to 4 shown in fig. 1 to 4, 5A, 5B, 6 and 7 will be explained.

Example 1

FIG. 1 is a partial sectional view showing the structure of an electrolytic functional device according to example 1 of the present invention. In fig. 1,1 is an anode, 2 is a cathode, 3 is a solid polymer electrolyte membrane, 5 is a dehumidifying chamber, 6 is an external direct current power supply, 11 and 21 aresubstrates each made of a porous metal plate and serving as a current collector, 12 and 22 are catalyst layers coated not only on the surface of the exposed portion of the solid polymer electrolyte membrane 3 in the through-

holes

31, 32 of the

substrates

11, 21 but also on the outer surfaces of the

substrates

11, 21, 13 and 23 are moisture-permeable waterproof films, i.e., NF paper sheets (trademark of Toknya-ma Soda K.K) respectively covering the surfaces of the catalyst layers 12 and 22, and the moisture-permeable

waterproof films

13 and 23 may or may not be used depending on the specific use.

Conversely, the electrolytic functional device in fig. 1 includes a solid polymer electrolyte membrane 3; a pair of base layers 11, 21 in which a plurality of through

holes

31, 32 are formed, formed of metal plates embedded in the front and rear surfaces of the solid polymer electrolyte membrane 3, sandwiching the membrane 3 therebetween, and serving as electrodes to which a power supply voltage from a direct current power supply 6 is externally connected; a catalyst layer 12 covering the outer surfaces of the pair of base layers 11, 21 and the surface of the exposed portion of the solid polymer electrolyte membrane 3 from the through-

holes

31, 32 of the base layers 11, 21 to promote electrolytic reaction of the outside gas or liquid molecules; and moisture-permeable

waterproof films

13, 23 formed on the surfaces of the catalyst layers 12, 22 close to the outside.

Although shown on an enlarged scale in fig. 1, the actual size of each through-

hole

31, 32 is on the order of several tens of μm. The base layers 11 and 21 made of porous metal plates were each made of an electrolytic nickel thin film patterned to a thickness of 40 μm, manufactured by Futian Metal foil powder industries, and coated with palladium. The solid polymer electrolyte membrane is formed from Nafion-117 sold by dupont. Each of the catalyst layers 12, 22 is coatedas a solid polymer electrolyte from a mixture of Nafion solution (5% by weight, mixed solvent of water and alcohol) sold by Aldrich co and platinum black, or the catalyst layers may be formed by mixing platinum catalyst particles with a solid polymer electrolyte having the same or equivalent composition as the solid polymer electrolyte membrane 3. Furthermore, it has been confirmed that if lead or gold is electroplated on the electrolytic nickel foil of the patterned

base layer

11, 21 instead of on the palladium, the corrosion resistance can be enhanced.

Moreover, in the electrolytic functional device of FIG. 1, the hole area of each of the through

holes

31, 32 is different between the outside thereof not contacting the main body of the solid polymer electrolyte membrane 3 and the inside thereof contacting the main body of the solid polymer electrolyte membrane 3, and the hole size is gradually reduced from the outside not contacting the main body of the solid polymer electrolyte membrane 3 to the inside, so that the hole area of the outside is larger than the hole area of the inside. Next, the exposed portions of the solid polyelectrolyte membrane 3 in the through

holes

31, 32 overflow to project outward.

Fig. 5A and 5B are enlarged plan views showing the surface of each of the base layers 11 to 21 formed of a porous metal plate. Fig. 5A shows the outside not in contact with the main body of the solid polymer electrolyte membrane 3, and fig. 5B shows the inside in contact with the main body of the solid polymer electrolyte membrane 3. In these figures, 41, 43 denotes a metal portion of the

base layer

11 or 21, 42, 44 denotes an end portion of the through hole in the

base layer

11 or 21, and it can be seen that the area of the through hole end portion 44 on the inner side is smaller than that of the through hole end portion 42 on the outer side. Thus, in this example 1, the solid polymer electrolyte membrane 3 is embedded inthe through

holes

31, 32 of the base layers 11, 21, and no catalyst particles are sandwiched between the membrane 3 and the base layers 11, 21. Therefore, the solid polymer electrolyte membrane 3 and the base layers 11, 21 formed of porous metal plates and serving as bus bars are not easily peeled off from each other. Further, the solid polymer electrolyte membrane 3 and the base layers 11, 21 constituting the electrode portions are fixed together with greater mechanical strength, enabling a more stable electrolytic functional device to be obtained.

Further, since the base layers 11, 21 are each formed of a metal foil plate plated with palladium, aluminum, or gold, the corrosion resistance of the base layers 11, 21 is enhanced and the generation of gas from the base layers 11, 21 is suppressed. As a result, the solid polymer electrolyte membrane 3 is less likely to peel. Further, it is possible to increase the electrode surface area and enhance the wetting property due to the overflow and protrusion of the solid polymer electrolyte membrane 3 exposed in the through-

holes

31, 32.

Moreover, since the catalyst layers 12, 22 contain platinum catalyst particles and a solid polymer electrolyte, the surfaces of portions of the solid polymer electrolyte membrane 3 in the through

holes

31, 32 of the

base layer

11, 21 and the platinum catalyst particles in the catalyst layers 12, 22 on the surfaces of the

base layer

11, 21 can be bonded together to maintain the electronic and ionic conductivity.

Further, since the surfaces of the anode 1 and the cathode 2 which are in contact with the external air are coated with the moisture-permeable

waterproof films

13, 23, it is possible to prevent the reaction surfaces of the electrodes from being contaminated and to suppress adverse effects such as corrosion of the local battery due to condensation when no current is applied.

Example 2

FIG. 2 is a partial sectional view showing the structure of an electrolytic functional device according to example 2 of the present invention. In fig. 2, the same reference numerals are used for the same parts as those in fig. 1, and the description thereof will be omitted.

Embodiment 2 in fig. 2 differs from embodiment 1 in fig. 1 in that the hole sizes of the through

holes

31, 32 formed in the base layers 11, 21 are gradually reduced from the inner side contacting the main body of the solid polymer electrolyte membrane 3 to the outer side not contacting the main body of the solid polymer electrolyte membrane 3, so that the hole area on the outer side not contacting the main body of the solid polymer electrolyte membrane 3 is larger than the hole area on the inner side contacting the main body of the solid polymer electrolyte membrane 3.

According to the above structure, the solid polymer electrolyte membrane 3 is fitted into the through

holes

31, 32 from the inner side contacting the main body of the solid polymer electrolyte membrane 3 to the outer side not contacting the main body of the solid polymer electrolyte membrane 3, and is less likely to be peeled off, so that the solid polymer electrolyte membrane 3 and the base layers 11, 21 constituting the electrode portions can be bonded together with higher mechanical strength to increase the strength of the electric field generated on the surface of each catalyst layer, reduce the voltage applied between the electrodes, and improve the voltage characteristics of the device.

Example 3

Next, FIG. 3 is a partial sectional view showing the structure of an electrolytic functional device according to example 3 of the present invention. The same or equivalent portions in fig. 3 as those in example 1 in fig. 1 are denoted by the same reference numerals and will not be described again.

Example 3 of fig. 3 differs from example 1 of fig. 1 in that the through-

holes

31, 32 formed in the base layers 11, 21 have projections on the inner walls thereof, and in particular, the through-

holes

31, 32 are formed such that: that is, the pore size gradually decreases from the outside not contacting the main body of the solid polymer electrolyte membrane 3 to the inside contacting the main body of the solid polymer electrolyte membrane 3 within a predetermined range, and then gradually increases after exceeding the predetermined range.

With the above structure, the solid polymer electrolyte membrane 3 embedded in the through

holes

31, 32 formed in the base layers 11, 21 is less likely to peel off than in example 1 and example 2, and therefore, the solid polymer electrolyte membrane 3 and the base layers 11, 21 constituting the electrode portions can be fixed together with higher mechanical strength.

Example 4

Next, FIG. 4 is a partial sectional view showing the structure of an electrolytic functional device according to example 4 of the present invention. In fig. 4, the same or equivalent parts as in example 1 of fig. 1 are denoted by the same reference numerals and will not be discussed.

Example 4 in fig. 4 differs from example 1 in fig. 1 in that the through-

holes

31, 32 formed in the base layers 11, 21 have the same area between the outside not contacting the main body of the solid polymer electrolyte membrane 3 and the inside contacting the main body of the solid polymer electrolyte membrane 3.

In the case where it is not required that the solid polymer electrolyte membrane 3 and the base layers 11, 21 constituting the electrode portions are fixed together with high mechanical strength, the through

holes

31, 32 can be formed according to this example.

Fig.6 is a graph comparing in an enlarged manner the electrode structures of the above electrolytic functional devices according to examples 1 to 4 of the present invention, and fig. 7 is a characteristic diagram showing the electric field intensity generated between points a and B along the surface of the through-hole of the catalyst layer shown in fig. 6 for each electrolytic functional device, and it is noted that the catalyst layers 12, 22 are drawn flat in fig. 6 for the sake of explanation.

When the through-hole had an outward tapered structure (example 2) as shown in the lower left of FIG. 6, the electric field intensity at the point B was 0.3X 10^-2v/μm, outwardly expanding via structure (example 1) field strength 0.2X 10 at point B^-21.5 times v/μm, as shown in FIG. 7, becauseThe electric field intensity is proportional to the applied voltage, and the above results indicate that the voltage applied between the electrodes in example 2 can be reduced to 1/1.5 of the voltage required in example 1. Thus, the voltage characteristics of the device were improved by adjusting the structure of the via hole in example 2, and the electric field was more concentrated on the outer surface.

As shown in fig. 6, the hole sizes of the through

holes

31, 32 are gradually reduced toward the outside (the catalyst layers 12, 22 side) to increase the electric field strength in the vicinity of the

catalysts

12, 22 in example 2 as compared with example 1, while the opening sizes of the through

holes

31, 32 are first gradually reduced toward the outside and then gradually increased in a local area near the outside before reaching the outside while forming projections on the inner wall of each through hole, so as not only to increase the electric field strength near the catalyst layers 12, 22 but also to fix the base layers 11, 21 constituting the electrode portions and the solid polymer electrolyte membrane 3 with higher mechanical strength. Further, example 4 shows an example in which the through-

holes

31, 32 are formed in parallel, and when the requirement to fix the solid polymer electrolyte membrane 3 and the base layers 11, 21 constituting the electrode portions together with high mechanical strength is not so strong, the through-

holes

31, 32 may be formed similarly to example 4.

With these electrode structures, the magnitude of the electric field intensity was arranged in the order of example 2, example 4, example 3 and example 1, as shown in FIG. 7.

Example 5

A method for producing an electrolytic functional device according to the present invention is described below.

Fig. 8 is a partial sectional view showing various members of the electrolytic functional device 100 before hot pressing in exploded form, and showing through

holes

31, 32 in fig. 1 in enlarged scale.

In fig. 8, 50 is a sandpaper placed on the outer surface of each pair of base layers 11, 21, the base layers 11, 21 being placed on the front and rear surfaces of the solid polymer electrolyte membrane 3, the sandpaper 50 including a cloth portion 51 and a rough portion 52 containing coarse grains.

These members are sequentially placed one by one in a hot press apparatus as shown in the figure, and then heated at a temperature higher than the softening temperature of the solid polymer electrolyte membrane 3, i.e., 190 ℃ and 50kgf/cm²Hot pressing is carried out under the conditions of (1). When cooled to 100 ℃ or below, from hot pressThe hot pressed compact is removed and sandpaper 50 is separated from the compact. Then, a solution prepared by mixing platinum black with Nafion solution (5% by weight, mixed solvent of water and alcohol) sold by Aldrich co. was used as a solid polymer electrolyte, and brushed on the portions of the solid polymer electrolyte membrane 3 penetrating through the through-

holes

31, 32 and the metal portions 41 of the base layers 11, 21. Subsequently, the compact was heat-treated at 150 ℃ for 5 minutes in a nitrogen atmosphere to melt the solid polymer electrolyte membrane 3, firmly bonding the catalyst in place, and form the catalyst layers 12, 22. Thereafter, a moisture-permeable waterproof film 13, 23 (see fig. 1) is formed to cover the surface of the

catalyst layer

12, 22.

Thus, the method of manufacturing an electrolytic functional device according to example 5 includes a burying step of burying a pair of base layers 11, 21, in which a plurality of through

holes

31, 32 are formed, in front and rear surfaces of a solid polymer electrolyte membrane 3; and a coating step of coating a catalyst on the surfaces of the solid polymer electrolyte membrane 3 exposed from the pair of through

holes

31, 32 formed in the base layers 11, 21 and on the outer surfaces of the pair of base layers 11, 21, thereby forming catalyst layers 12, 22 that promote electrolytic reaction of molecules that are gas or liquid outside, so that the solid polymer electrolyte membrane 3 can be forced to be embedded in the through holes of the base layers 11, 21 without interposing non-catalyst particles for separating them between the solid polymer electrolyte membrane 3 and the base layers 11, 21 formed of porous metal plates, and further, the catalyst layers 12, 22 are formed simply, enabling manufacturing costs of electrolytic functional devices to be reduced.

Furthermore, sandpaper 50 having a rough surface is placed on the front and rear surfaces of the solid polymer electrolyte membrane 3 in the burying step, with a pair of base layers 11, 21 sandwiched therebetween (between 50 and 3), and these members are hot-pressed at a temperature higher than the softening temperature of the solid polymer electrolyte membrane 3. This results in a structure in which the solid polymer electrolyte membrane 3 partially overflows to the outside of the through-hole to form a protrusion. Therefore, the solid polymer electrolyte membrane 3 is less likely to peel off, and an electrolytic functional device having more stable performance can be obtained.

Further, the manufacturing method includes a step of coating the moisture-permeable waterproof film 13, 23 (permeable to moisture and waterproof) on the surface of the

catalyst layer

12, 22 near the outside. Thus, since the surfaces of the anode 1 and the cathode 2 which are in contact with the external gas are covered with the moisture-permeable

waterproof films

13, 23, it is possible to prevent the reaction surfaces of the electrodes from being contaminated and to suppress adverse effects such as corrosion of local cells due to condensation when no current is applied.

For the electrolytic functional device fabricated in the above-mentioned manner, the wiring was connected to the terminals for connecting an external direct current power supply, then the device was put into a frame made of resin, the periphery thereof was bonded to the frame, the device was hermetically sealed, the completed electrolytic functional device was put into a box to evaluate its dehumidifying performance, and the whole box was put into a heat and humidity testing box to evaluate its dehumidifying ability.

FIG. 9 is a graph showing the results of the test for evaluating the dehumidifying ability of the electrolytic functional device of the prior art and the present invention.

In FIG. 9, the dotted line 61 indicates the humidity of the external environment in which the cathode is located, the environment being created by a hot-wet assay chamber, maintained at 35 ℃ and 80% relative humidity, the relative humidity and the value of current flowing through the external circuit being monitored while setting the applied voltage in the range of 3V-4V DC. Curves 62, 63 are plotted as humidity changes in the dehumidification chamber representing the dehumidification capability of the electrolytic functional device of the prior art, while curve 64 is plotted as humidity changes in the dehumidification chamber reflecting the dehumidification capability of the electrolytic functional device of the present invention of fig. 1. In fig. 9, the horizontal axis represents time. The curve showing a rapid decrease in humidity indicates a higher dehumidification capability, and thus it was found that the electrolytic functional device according to the present example has a higher dehumidification capability than the conventional electrolytic functional device, and the prior art electrolytic functional device represented by curve 62 was manufactured by sandblasting a Nafion-117 film to roughen both surfaces thereof, depositing platinum on both surfaces thereof by electroless plating, placing the film between two tantalum mesh collectors, and then applying a plane pressure by means of a chucking plate or the like.

Similarly, the prior art electrolytic functional device represented by curve 63 was made by: even with the structure of fig. 15. The difference in the dehumidifying ability between the conventional electrolytic functional device represented by the curve 63 and the electrolytic functional device of the example represented by the curve 64 is small, but the value of the current flowing through the external circuit is much larger in the conventional device of the structure of fig. 15 than in the example of the present invention, and it is confirmed that the device of the example of the present invention has a higher and more excellent current efficiency, probably because the reverse osmosis of water through the solid polymer electrolyte membrane 3 (i.e., the return of water from the cathode to the anode) is less likely to occur because the solid polymer electrolyte membrane 3 is covered withthe base layers 11, 21 formed of porous metal plates in the example of the present invention.

Also, the stability of the dehumidifying ability was tested by operating the existing electrolytic functional device of the structure of fig. 15 and the electrolytic functional device of the embodiment of the present invention.

Fig. 10 shows the results of the long-term dehumidification ability stability test, curve 65 indicates the change in humidity produced by the conventional electrolytic functional device having the structure of fig. 15, curve 66 indicates the change in humidity produced by the electrolytic functional device of the example, and it can be seen from fig. 10 that, for the device of the example, the relative humidity is stable, and the stable dehumidification ability is maintained, whereas, for the prior art device, the relative humidity is gradually increased with time and then sharply increased at approximately 4000 hours, indicating a decrease in dehumidification ability, and after the decomposition and inspection of the two electrolytic functional devices after the test, it is found that, in the prior art device, the solid polymer electrolyte membrane 3 and the confluence collector 4 are separated from each other almost at the center of the device.

Example 6

FIG. 11 is a partial sectional view showing the structure of an electrolytic functional device according to example 6 of the present invention.

Fig. 6 is different from example 1 of fig. 1 in that the solid polymer electrolyte membrane 3 is depressed after passing through the through holes 31, 32 in the base layers 11, 21 formed of a porous metal plate, and the catalyst layers 12, 22 and the moisture-permeable waterproof films 13, 23 are also depressed, and it is found after examining the difference in the dehumidifying ability with respect to the shapeof the solid polymer electrolyte membrane 3 passing through the through holes 31, 32 that the dehumidifying ability is increased in both cases where the membrane 3 is projected in a convex shape as shown in fig. 1 and depressed in a concave shape as shown in fig. 11, probably because the surface areas of the catalyst layers 12, 22 and the waterproof films 13, 23 are increased when the solid polymer electrolyte membrane 3 has a convex or concave shape, providing a larger electrode area, whereby the electrolytic reaction is promoted correspondingly, and, due to the fact that adverse effects such as an increase in electric resistance and a decrease in the dehumidifying ability occur when the catalyst layers 12, 22 on the base layers 11, 21 are removed, the catalyst layers 12, 22 on the base layers 11, 21 are considered to function not only to collect current but also to participate in the dehumidification reaction to some extent, and further, in the experiment in which only platinum black was coated as the catalyst layers 12, 22, the platinum black was peeled off from the solid polymer electrolyte membrane 3.

Example 7

Fig. 12A and 12B show the surface pattern of each of the base layers 11, 21 formed of a porous metal plate used in example 7 of the present invention. The through holes 42, 44 in the base layers 12, 21 do not have to be hexagonal as shown in fig. 5A and 5B, and it has been experimentally confirmed that an electrolytic functional device which is not liable to be peeled off and has high dehumidifying performance can be obtained also in the case of using a porous metal plate having through holes in a pattern shown by 42 in fig. 12A or diamond-shaped through holes shown by 44 in fig. 12B.

The base layers 11, 21 formed of any of such porous metal plates are nickel foils each having a different pattern size between the front and rear surfaces thereof. This is because the porous metal plate on the marketis manufactured by coating a photosensitive solution on only one side of a foil, irradiating light through a negative film having an open pattern to insolubilize the irradiated portion to form an etching-resistant film, and then performing electrolysis in an electrolytic bath to electrodeposit a nickel layer on the remaining portion.

Example 8

FIG. 13A and FIG. 13B are sectional views of a porous metal plate used in example 8 of the present invention. The expanded metal of fig. 13A has a protrusion 33 on the inner wall of each through-hole 31, while the expanded metal of fig. 13B has a raised portion 34 on the inner wall of each through-hole 31, which is most protruded at the center, such protrusion 33 being often formed when the expanded metal is produced by mechanical punching, and such a raised portion 34 being often formed when the expanded metal is produced by chemical etching, in which the center of the inner wall of the hole is less etched, and it has been experimentally confirmed that an electrolytic functional device which is less likely to be peeled off and has high dehumidifying ability can be obtained even when the

base layer

11, 21 formed of any one of these expanded metal is used.

Example 9

A method for producing an electrolytic functional device according to example 9 of the present invention will be described.

First, a Nafion-117 film is impregnated with a mixed solvent of isopropyl alcohol and water (1: 1 by weight), the Nafion-117 film is swollen and gels like a liquid coagulate or pudding, and solid matter can be easily embedded in the film.

Then, the parts were aligned as shown in FIG. 8 at room temperature and 10kgf/cm²Are pressed together under pressure. Portions of the solid polymer electrolyte membrane 3 are thus buried in the through-

holes

31, 32 ofthe base layers 11, 21, and after the pressed compact is dried at 80 ℃, a solution prepared by mixing platinum black and Nafion solution as in example 5 is brushed as a solid polymer electrolyte to the portions of the solid polymer electrolyte membrane 3 passing through the through-

holes

31, 32 and the metal portions 41 of the base layers 11, 21. Thereafter, the compact was heat-treated at 150 ℃ for 5 minutes in nitrogen to soften the solid polymer electrolyte membrane 3 so that the catalyst was firmly bonded in place to form the catalyst layers 12, 22, and it was confirmed that the manufacturing method of this example also enabled an electrolytic functional device with high dehumidifying ability, which was not likely to peel off.

Although the solid polymer electrolyte membrane 3 is gelled into a state in which a solid can be inserted under pressure when an organic solvent such as alcohol or ketones is used alone, when a mixed solvent in which an organic solvent and water are combined is used, the solid polymer electrolyte membrane 3 absorbs a large amount of the solvent and becomes softer during the gelling process, which means that the manufacturing method of the electrolytic functional device according to the present invention is more easily applicable.

Since the porous metal plate constituting the anode of the device is required to have high corrosion resistance, it is necessary to plate the porous metal plate with a material such as nickel or stainless steel. Gold or platinum plating has high corrosion resistance but is expensive. It is therefore desirable to plate inexpensive coatings of palladium, aluminum, lead dioxide or the like on these materials.

The solid polymer electrolyte membrane 3 may be formed of any commercially available thin film as long as it can conduct hydrogen ions. In addition to Nafion-117, Nafion-115, Nafion-112, and Nafion-105 of dupont, commercially available solid polymer electrolyte membranes include Flemion of Asahi glass k.k., Asiprex of Asahi Chemical Industry k.k., XUS-13.204.10 of Dow Chemical co., and the like, and the solid polymer electrolyte membrane may be substituted for the acyl group with a side chain carboxyl group.

As described above, according to the present invention, the base layer formed of the porous metal plate is embedded in the front and rear surfaces of the solid polymer electrolyte membrane, so that the solid polymer electrolyte membrane penetrates through the through-holes formed in the base layer, and the catalyst layers adjacent to the two electrodes are formed on the surfaces of the exposed portions of the solid polymer electrolyte membrane in the through-holes and on the outer surface of the base layer. Therefore, the porous metal plates of the film and the base layer are less likely to peel off from each other, and a high-performance electrolytic functional device stable for a long period of time can be obtained.

By coating the moisture-permeable waterproofing film on the surface of the catalyst layer close to the outside, it is possible to prevent the electrode surface from being contaminated, suppress adverse effects such as local battery corrosion due to condensation during non-energization, and thereby obtain a more reliable electrolytic functional device.

By arranging the through-holes formed on at least a pair of base layers so that the hole areas are different between the outside not contacting the solid polymer electrolyte membrane main body and the inside contacting the solid polymer electrolyte membrane, the electrodes and the solid polymer electrolyte membrane can be fixed together with high mechanical strength, resulting in a more stable electrolytic functional device.

By arranging the through holes formed in at least a pair of base layers such that the hole size is gradually reduced from the outside not contacting the solid polymer electrolyte membrane main body to the inside contacting the solid polymer electrolyte membrane main body, the hole area at the outside not contacting the solid polymer electrolyte membrane main body is larger than the hole area at the inside contacting the solid polymer electrolyte membrane main body, the solid polymer electrolyte membrane and the base layers are less likely to peel off from each other, the electrodes and the solid polymer electrolyte membrane can be fixed together with high mechanical strength, and thereby an electrolytic functional device having more stable performance can be obtained.

By arranging the through holes formed in at least a pair of base layers such that the hole size is gradually reduced from the inner side contacting the solid polymer electrolyte membrane main body to the outer side not contacting the solid polymer electrolyte membrane main body, so that the hole area on the outer side not contacting the solid polymer electrolyte membrane main body is smaller than the hole area on the inner side contacting the solid polymer electrolyte membrane main body, it is possible to increase the electric field intensity generated at each catalyst layer surface to reduce the voltages respectively applied to the two electrodes and improve the voltage characteristics of the device.

By forming through holes in at least a pair of base layers, the hole size gradually decreases from the outside not contacting the solid polymer electrolyte membrane main body to the inside contacting the solid polymer electrolyte membrane main body within a predetermined range and then gradually increases outside the predetermined range, the electrodes and the solid polymer electrolyte membrane can be fixed together with high mechanical strength, the solid polymer electrolyte membrane embedded in the through holes of the base layers is less likely to peel off, and an electrolytic functional device with more stable performance can be obtained.

By arranging the through-holes formed in at least a pair of base layers so that the through-hole area is the same between the outside not contacting the solid polymer electrolyte membrane main body and the inside contacting the solid polymer electrolyte membrane main body, an electrolytic functional device can be obtained whose through-holes are suitable for use in a case where the requirement for fixing the electrodes and the solid polymer electrolyte membrane together with high mechanical strength is not so important.

By providing through holes formed in at least a pair of base layers so that the inner walls thereof have protrusions, the solid polymer electrolyte membrane embedded in the through holes of the base layers is less likely to peel off, and an electrolytic functional device having more stable performance can be obtained.

By arranging the through-holes formed in at least a pair of base layers so that the most projecting portions are located at the central portions of the inner walls thereof, the solid polymer electrolyte membrane embedded in the through-holes of the base layers is less likely to peel off, and an electrolytically functional device having more stable performance can be obtained as in the above example.

By arranging the through holes formed in at least a pair of base layers to be hexagonal, the solid polymer electrolyte membrane embedded in the through holes of the base layers is less likely to peel off, and an electrolytic functional device having more stable performance can be obtained.

By arranging the through holes formed in at least a pair of base layers to be circular, the solid polymer electrolyte membrane embedded in the through holes of the base layers is less likely to peel off, and an electrolytic functional device having more stable performance can be obtained.

By arranging the through holes formed in at least a pair of base layers to be rhombic, the solid polymer electrolyte membrane embedded in the through holes of the base layers is less likely to peel off, and an electrolytic functional device with more stable performance can be obtained.

By forming at least a pair of base layers by using a metal foil and coating a thin film containing at least one component of aluminum, gold and palladium thereon, the corrosion resistance of the porous metal plate constituting the metal portion of the base layer is increased, the generation of gas from the porous metal plate is suppressed, whereby the solid polymer electrolyte membrane is less likely to be peeled off, and an electrolytic functional device having more stable performance can be obtained.

Further, since the portions of the solid polymer electrolyte membrane exposed in the through holes of the pair of base layers overflow and protrude outward from the outer sides not contacting the solid polymer electrolyte membrane main body, it is possible to increase the electrode area and improve the electrolyte reaction characteristics.

Alternatively, since the exposed portions of the solid polymer electrolyte membrane in the through-holes of the pair of base layers are left in the through-holes in a concave manner, it is possible to increase the electrode area and improve the electrolyte reaction characteristics.

Since each catalyst layer contains platinum catalyst particles and a solid polymer electrolyte having the same or equivalent composition to the solid polymer electrolyte membrane, the exposed portions of the solid polymer electrolyte membrane in the through-holes of the base layer can be bonded to the platinum catalyst particles in the catalyst layer on the surface of the metal portion of the base layer, which makes it possible to maintain the electronic and ionic conductivity and the excellent electrolyte reaction characteristics.

According to the electrolytic functional device manufacturing method of the present invention, since the method includes a burying step of burying a pair of base layers formed of metal plates having a plurality of through holes and serving as electrodes externally connected to a direct current power supply voltage into front and rear surfaces of a solid polymer electrolyte membrane, and a coating step of coating a catalyst on surfaces of exposed portions of the solid polymer electrolyte membrane in the through holes of the pair of base layers and on outer surfaces of the pair of base layers, thereby forming a catalyst layer that promotes an electrolytic reaction of an external gas or liquid molecule, the solid polymer electrolyte membrane can be forced to be embedded in the through holes of the base layers without sandwiching non-catalyst particles for separating them from each other between the solid polymer electrolyte membrane and the base layers, and further, the catalyst layer can be simply formed, and the electrolytic functional device can be manufactured at low cost.

Embedding a pair of base layers in the front and rear surfaces of the solid polymer electrolyte membrane by hot pressing at a temperature higher than the softening temperature of the solid polymer electrolyte membrane through the embedding step, the solid polymer electrolyte membrane can be forced to be embedded in the through-holes of the base layers.

Alternatively, since the embedding step is performed such that the solid polymer electrolyte membrane absorbs a solvent capable of swelling the solid polymer electrolyte membrane and then a pair of base layers are embedded in the front and rear surfaces of the solid polymer electrolyte membrane with pressure in a gel state, the solid polymer electrolyte membrane is forced to be embedded in the through-holes of the base layers without heating the solid polymer electrolyte membrane to a high temperature, thereby reducing the production cost.

By using a mixed solvent of an organic solvent and water, the solid polymer electrolyte membrane can be softened to such an extent that it can be inserted into the through-holes of the base layer at a low pressure.

By performing the burying step by placing a paper sheet having a rough surface on the outer surfaces of a pair of base layers located on the front and rear surfaces of the solid polymer electrolyte membrane before applying pressure, a structure in which the solid polymer electrolyte membrane overflows and protrudes from the outside of the through-hole can be realized.

Finally, by further including the step of coating a moisture-permeable waterproof film on the surface of the catalyst layer close to the outside, it is possible to prevent the electrode surface from being contaminated and to suppress adverse effects such as local battery corrosion due to condensation during non-energization.

Claims

1. An electrolytic functional device, comprising:

a solid-state polymer electrolysis functional device, which comprises a solid-state polymer electrolysis functional device,

a pair of base layers having a plurality of through holes, formed of metal plates embedded in front and rear surfaces of the solid polymer electrolyte membrane to sandwich the membrane therebetween, and serving as electrodes externally connected to a direct current power supply voltage; and

and a catalyst layer coated on outer surfaces of the pair of base layers and surfaces of exposed portions of the solid polymer electrolyte membrane in the through-holes of the base layers to promote electrolytic reaction of external gas or liquid molecules.

2. The electrolytic functional device according to claim 1, wherein a moisture-permeable waterproof film is coated on the surface of said catalyst layer near the outside.

3. The electrolytic functional device according to claim 1, wherein hole areas of the through holes formed in at least the pair of base layers are different between an outer side not contacting the solid polymer electrolyte membrane main body and an inner side contacting the solid polymer electrolyte membrane main body.

4. The electrolytic functional device according to claim 3, wherein the hole size of the through-hole formed in the at least one pair of base layers is gradually reduced from the outside not contacting the solid polymer electrolyte membrane main body to the inside contacting the solid polymer electrolyte membrane main body, so that the hole area at the outside not contacting the solid polymer electrolyte membrane main body is larger than the hole area at the inside contacting the solid polymer electrolyte membrane main body.

5. The electrolytic functional device according to claim 3, wherein the pore size of the through-holes formed in the at least one pair of base layers is gradually reduced from an inner side contacting the solid polymer electrolyte body to an outer side not contacting the solid polymer electrolyte body, so that the pore area at the outer side not contacting the solid polymer electrolyte membrane body is smaller than the pore area at the inner side contacting the solid polymer electrolyte membrane body.

6. The electrolytic functional device according to claim 1, wherein the hole size of the through-hole formed in the at least one pair of base layers gradually decreases from the outside not contacting the solid polymer electrolyte membrane main body to the inside contacting the solid polymer electrolyte membrane main body within a predetermined range, and then gradually increases after exceeding the predetermined range.

7. The electrolytic functional device according to claim 1, wherein the through-holes formed in the at least one pair of base layers have the same hole area between an outer side not contacting the solid polymer electrolyte membrane main body and an inner side contacting the solid polymer electrolyte membrane main body.

8. The electrolytic functional device according to claim 7, wherein the through-hole formed in the at least one pair of base layers has a protrusion on an inner wall thereof.

9. The electrolytic functional device according to claim 7, wherein said through-hole formed in said at least one pair of base layers is most bulged at the middle of the inner wall thereof.

10. The electrolytic functional device according to claim 1, wherein the through-hole formed in the at least one pair of base layers is one of hexagonal, circular and rhombic.

11. The electrolytic functional device according to claim 1, wherein the at least one pair of base layers are formed of metal foils coated with a thin film of at least one component of aluminum, gold, and palladium.

12. The electrolytic functional device according to claim 1, wherein the portions of the solid polymer electrolyte membrane exposed in the through holes of the pair of base layers are protruded and protruded outward from the outside without contacting the solid polymer electrolyte membrane main body.

13. The electrolytic functional device according to claim 1, wherein exposed portions of the solid polymer electrolyte membrane in the through-holes of the pair of base layers are left in the through-holes in a concave manner.

14. The electrolytic functional device according to claim 1, wherein each of the catalyst layers contains platinum catalyst particles and a solid polymer electrolyte having the same or equivalent composition as the solid polymer electrolyte membrane.

15. A method of manufacturing an electrolytic functional device, comprising:

a burying step of burying a pair of base layers, which are formed of a metal plate having a plurality of through holes and serve as electrodes externally connected with a DC power supply voltage, into front and rear surfaces of a solid polymer electrolyte membrane; and the number of the first and second groups,

a coating step of coating a catalyst on surfaces of exposed portions of the solid polymer electrolyte membrane within the through-holes of the pair of base layers and on outer surfaces of the pair of base layers, thereby forming a catalyst layer that promotes electrolytic reaction of external gas or liquid molecules.

16. The manufacturing method according to claim 15, wherein the burying step is performed by performing hot pressing at a temperature higher than a softening temperature of the polymer electrolyte membrane to bury the pair of base layers into front and rear surfaces of the solid polymer electrolyte membrane.

17. The production method according to claim 15, wherein the burying step is performed such that the solid polymer electrolyte absorbs a solvent capable of swelling it, and then the pair of base layers are buried into the front and rear surfaces of the solid polymer electrolyte membrane by applying pressure in a gel state.

18. The method of claim 17, wherein the solvent is a mixed solvent of an organic solvent and water.

19. The manufacturing method according to claim 17, wherein the burying step is performed by placing a paper sheet having a rough surface on outer surfaces of the pair of base layers on front and rear surfaces of the solid polymer electrolyte membrane before the pressing.

20. The method of manufacture of claim 15, further comprising applying a moisture-permeable waterproof film to a surface of the catalyst layer adjacent to the exterior.