JP2002042832A - Electrochemical device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical device with lightened weight, simplified and miniaturized as a whole body by using fullerene derivative as a proton conductor to a fuel cell using gaseous hydrogen as a fuel and to provide its manufacturing method. SOLUTION: This electrochemical device is so constituted that the proton conductor part 1 composed of the fullerene derivative is disposed by sandwiched between a first electrode 2 which has a structure substantially not transmitting the hydrogen in its gaseous state, and a second electrode, in a frame comprising a housing outer frame 5a and a housing inner frame 5b, and the first electrode 2 is closely contacted with a partitioning plate 6. The gaseous hydrogen 12 introduced to the first electrode 2 side is thus fed from a feed port 7 to the first electrode 2 without being in contact with the proton transmission part, the hydrogen becomes a proton in the first electrode 2, moves to the second electrode 3, and is reacted with the air 13 introduced to the second electrode 3 side so as to generate power. This constitution can eliminate any necessity of applying gas non-permeability to a proton transmission part 1, and dispense with a humidifier, so as to thin the proton transmission part and to lighten, simplify, and miniaturize the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical device suitable for obtaining electric energy from hydrogen and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, hydrogen has been a chemical energy source capable of obtaining thermal energy by direct combustion or obtaining electrical energy by an electrochemical method. The latter method is particularly realized by a so-called fuel cell system. Is done.

[0003] A fuel cell has two electrodes, an electrode for separating hydrogen gas into protons and electrons, and an electrode for generating water from oxygen, protons, and electrons, and has a structure in which they are connected by a certain ionic conductor. are doing. There are various types of ionic conductors, according to which fuel cells are divided into several types.

That is, an SOF operating at a high temperature of about 800 ° C. to 1000 ° C. and using a ceramic oxygen ion conductor
C (solid electrolyte fuel cell), MCFC (molten carbonate fuel cell) using molten carbonate as electrolyte, PAFC (phosphoric acid fuel cell) using phosphoric acid, AFC (alkali fuel cell) using alkaline aqueous solution, And a polymer electrolyte fuel cell (PEFC) using a polymer solid electrolyte. Particularly, the last PEFC has been actively researched and developed to be put to practical use in electric power sources for electric vehicles and home power sources because its operating temperature is 80 ° C., which is relatively lower than that of others.

[0005]

Although the concept of a fuel cell has been known for a long time, very few fuel cells have been put to practical use at the present time. It is limited to research and development systems or special applications such as space exploration and military use.

This is because the various ionic conductors described above have many problems. SOFC and M
The problems with CFCs include that the operating temperature is high, so that it is limited to use as a large-sized device, and that a material that is resistant to heat, corrosion, and the like must be used, resulting in a very high cost.

[0007] In addition, since the conductor of MCFC, PAFC, AFC, etc. is a liquid (liquid), a technique for preventing leakage is required, and it is compatible with the use of an electrode permeable to hydrogen or oxygen gas. Is a big problem.

[0008] Among these, PEFC is very excellent, and since the operating temperature is low and a solid ionic electrolyte is used, there is virtually no fear of liquid leakage or the like. However, Dupont, a typical material used for PEFC,
There is a problem that the material cost is very high, including Nafion (R) of Company t.

Further, although it is a solid electrolyte, it has a property of not exhibiting sufficient ionic conductivity unless it is in a humidified state with sufficient water vapor contained therein. Since the control section is required, and the film thickness is further increased to prevent gas permeation, the entire system is large and costly.

[0010] Although operation at room temperature is not impossible, sufficient performance cannot be obtained, and it is necessary to heat to about 80 ° C. This is also for sufficient humidification. As a result, startups often take several hours.

[0011]

Under such circumstances, the present inventors have solved a problem of such a solid polymer electrolyte, and have developed a new proton conductor which can make a fuel cell more practical. And Japanese Patent Application No. 11-20438 for a fuel cell using the same.
Filed on March 19, and Japanese Patent Application No. 2000-058116, which has been proposed by filing on March 3, 2000 (hereinafter, referred to as a prior application).

The proton conductor of the prior application introduces a plurality of proton dissociable substituents into a carbon material having a cage-like structure called fullerene, and the protons move alone in the carbon material by aggregating them. That is, it is a material to which protons can move without performing a treatment such as humidification.

[0013] However, although the proton conductor itself is a very excellent invention as described above, since a device using the proton conductor uses a conventional fuel cell, the essential problems of the fuel cell are considered. There are many parts that have not yet been resolved, such as the following 1-3.

That is, 1. Since the fuel cell uses a gas such as hydrogen gas as a reactant, it is necessary to use a relatively thick gas electrode having a high porosity and a gas, an electron conductor (that is, a current collector) and an ion A three-phase interface must be created in which the three phases of the (proton) conductor are integrated, which complicates the manufacturing method of the fuel cell. 2. Since hydrogen gas has the property of permeating even a very small gap, a solid electrolyte between the hydrogen-side electrode and the oxygen-side electrode is required to have high gas non-permeability. 3. Since the gas or moisture for humidification enters the electrolyte directly from the outside, if the gas or moisture is contaminated with other gases, dust, ions, etc., they are also transferred to the electrolyte together. This may cause penetration, which may cause rapid deterioration of the performance of the electrolyte.

In view of the above circumstances, it is an object of the present invention to provide a further improved electrochemical device using a fullerene derivative while maintaining the features of the prior application, and a method of manufacturing the same.

[0016]

That is, the present invention has a first electrode in which hydrogen dissociates into electrons and protons, and a second electrode in which reducing species receive electrons and protons and change to oxidizing species. Wherein a proton conductor is present between the first electrode and the second electrode, and the first electrode has a structure that does not substantially transmit at least hydrogen in a gaseous state. The present invention relates to a chemical device (hereinafter, referred to as a first electrochemical device of the present invention).

According to the first electrochemical device of the present invention, since the first electrode has a structure that does not substantially transmit at least hydrogen in a gaseous state, hydrogen directly contacts the solid electrolyte which is a proton conductor. Never do. Therefore,
Since it is not necessary to impart gas impermeability to the proton conductor, physical restrictions on the film quality of the proton conductor are relaxed, the film thickness can be reduced, and power generation with a higher load can be performed. In addition, by using the same proton conductor as in the prior application, there is no need for a humidifier because of the proton conductivity without humidification. Can be simplified and further miniaturized.

Further, the present invention has a first electrode in which hydrogen dissociates into electrons and protons, and a second electrode in which reducing species receives electrons and protons and changes to oxidizing species, and the first electrode has A proton conductor is present between the second electrode and the surface opposite to the first electrode, or at least between the first electrode and the second electrode. The present invention relates to an electrochemical device (hereinafter, referred to as a second electrochemical device of the present invention), which is provided with a barrier layer having a structure that does not transmit light. The barrier layer of the second electrochemical device of the present invention can be added to the above-mentioned first electrochemical device of the present invention.

According to the second electrochemical device of the present invention, at least hydrogen does not substantially permeate in a gaseous state on the surface opposite to the first electrode or between the first electrode and the second electrode. Since the blocking layer having the structure is provided, hydrogen does not come into direct contact with the solid electrolyte which is a proton conductor, so that it has almost the same performance and effect as the first electrochemical device described above, The electrode can be made thinner, and the thickness can be reduced accordingly.

Further, the present invention has a first electrode in which hydrogen dissociates into electrons and protons, and a second electrode in which the reducing species receives electrons and protons and changes to oxidizing species, and the first electrode and the second electrode When manufacturing an electrochemical device in which a proton conductor exists between two electrodes, the hydrogen gas supply port side of a housing member having a hydrogen gas supply port, or the first electrode.
Forming between the electrode and the second electrode the first electrode or a blocking layer having a structure that does not substantially transmit at least hydrogen in a gaseous state; and forming the proton conductor on the first electrode, Or forming on the first electrode provided on the blocking layer, and forming the second electrode on the proton conductor layer.
And a method of manufacturing an electrochemical device (hereinafter, referred to as a manufacturing method of the present invention).

According to the manufacturing method of the present invention, since the method includes the steps of forming the above-described first and second electrochemical device structures of the present invention, reproducibility can be achieved without impairing the function of each part. Can be provided.

Here, the electromotive force of the electrochemical device having the above configuration is closely related to the gas permeability. As will be described later, when the gas permeability becomes 10% or more, the electromotive voltage becomes 0.8 V or less when the terminals are open. Since this is inconvenient for device performance, the hydrogen partial pressure on the second electrode is set to 1
It is desirable that the electromotive voltage be 0.8 V or higher while being suppressed to within 0%. From this, the above “structure that does not substantially transmit hydrogen in a gaseous state” is a concept that, even if hydrogen is transmitted from the first electrode to the second electrode, the gas permeability is set to 10% or less. is there.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below.
In the following description, if there is no description of the first or second electrochemical device, the matters common to both the inventions and the manufacturing method described above are shown.

In the first electrochemical device, it is preferable that the first electrode is made of a substance that does not substantially transmit hydrogen and water vapor in a gaseous state to the proton conductor side.

In the second electrochemical device, at least hydrogen is supplied in a gaseous state between a surface of the first electrode opposite to the proton conductor or between the first electrode and the second electrode. It is desirable to provide a barrier layer having a structure that is substantially impermeable. In addition, this barrier layer can be provided in the above-mentioned first electrochemical device.

In this case, it is desirable that the first electrode and the blocking layer have a hydrogen gas permeation preventing ability such that the hydrogen partial pressure on the second electrode side is 10% or less.

That is, the electromotive force of this energy device is greatly affected by the hydrogen partial pressure near the second electrode. When hydrogen enters the second electrode, the hydrogen
The reaction with oxygen on the electrode lowers the apparent oxygen partial pressure, or the reaction of hydrogen on the second electrode causes the second electrode to exhibit a so-called hybrid potential, and the electromotive force of the device is reduced by that much. Will decrease.

Although the electromotive force of a device is expressed by the Nernst equation, it is not always easy to formulate the effects such as the generation of the above-mentioned mixed potential. However, we can estimate the approximate voltage by utilizing Nernst's theorem and the like.

That is, if the electromotive voltage in the open state of this device is lower than 0.8 V, it becomes practically difficult to use it for many purposes. Therefore, when the hydrogen partial pressure on the second electrode when the electromotive force (pressure) becomes 0.8 V is calculated, it is about 10%. Therefore, the gas transmittance must be within 10%.

However, the voltage is preferably 3% or less at which the voltage becomes 1 V or more, and more preferably 1% or less.

It is desirable that the first electrode and the blocking layer are made of a substance capable of absorbing hydrogen as atoms or protons.

Further, it is preferable that the first electrode and the blocking layer are made of a hydrogen storage metal, a hydrogen storage alloy, or a substance containing the same.

In the present invention, the proton conductor desirably contains, as a main component, a fullerene derivative obtained by introducing a proton-dissociable group into a carbon atom constituting a fullerene molecule.

Here, the term "proton dissociable group" is a concept meaning a group from which a proton can be eliminated by ionization.

Further, it is desirable that the first electrode side is covered with a housing member, and the housing member is provided with a hydrogen gas supply port for supplying hydrogen gas to the first electrode side.

Thus, the fuel cell can be configured as a fuel cell and can be configured as an air cell.

Hereinafter, embodiments of the present invention will be described more specifically.

In the present embodiment, the parent fullerene molecule into which the proton-dissociative group is introduced is not particularly limited as long as it is a spherical cluster molecule.
36, C60 (see FIG. 6 (A)), C70 (see FIG. 6 (B)), C76, C78, C80, C82, C84, etc., or a mixture of two or more of these fullerene molecules is preferable. Used.

These fullerene molecules were discovered in 1985 in the mass spectrometry spectrum of a cluster beam by laser ablation of carbon (Kroto, HW; Hea
th, JR; O'Brien, SC; Curl, RF; Smalley, R.
E. Nature 1985.318,162.). It is only five years later that the manufacturing method is actually established. In 1990, a manufacturing method of a carbon electrode by an arc discharge method was discovered, and since then fullerene has been attracting attention as a carbon-based semiconductor material. Was.

The present inventor has conducted various studies on the proton conductivity of this fullerene molecule derivative. As a result, the polyhydroxylated fullerene obtained by introducing a hydroxyl group into a carbon atom constituting the fullerene molecule can be used at room temperature even in a dry state. It was found that the polymer exhibits high proton conductivity in a wide temperature range, that is, in the freezing point of water and in a temperature range exceeding the boiling point (at least 160 ° C. to −40 ° C.). Then, it was found that this proton conductivity becomes more remarkable when a hydrogen sulfate ester group is introduced into a carbon atom constituting fullerene instead of a hydroxyl group.

More specifically, as shown in FIG. 4, polyhydroxylated fullerene is a general term for a substance having a structure in which a plurality of hydroxyl groups are added to fullerene, and is generally called "fullerenol". Naturally,
Some variations are possible for the number of hydroxyl groups and the arrangement in the molecule. Fullerenol was Chia in 1992
ng et al. first reported a synthetic example (Chiang, L.
Y.; Swirczewski, Jw; Hsu, CS; Chowdhury, SK; Ca
meron, S .; Creegan, KJ Chem. Soc, Chem. Commun. 1
992,1791). Since then, fullerenol, in which a certain amount or more of hydroxyl groups have been introduced, has been particularly noted for its water-soluble properties, and has been studied mainly in the field of biotechnology.

The present inventor has shown such fullerenol in FIG.
As shown schematically in (A), an aggregate is formed, and an interaction is caused between hydroxyl groups of adjacent fullerenol molecules (in the figure, は indicates a fullerene molecule). It has been found for the first time that the aggregate exhibits high proton conductivity (in other words, dissociation of H + from the phenolic hydroxyl group of the fullerenol molecule).

The object of the present invention can also be achieved by using, for example, a fullerene aggregate having a plurality of —OSO ₃ H groups as a proton conductor in addition to fullerenol.
Polyhydroxy fullerenes as shown in FIG. 5 (B), in which the OH groups have been replaced by OSO ₃ H groups, ie, hydrogen sulfated esterified fullerenol, are also disclosed by Chiang et al. In 1994.
(Chiang. LY; Wang, LY; Swi
rczewski, JW; Soled, S .; Cameron, SJ Org. Che
m. 1994,59,3960). Some hydrogen sulfate-esterified fullerenes contain only an OSO ₃ H group in one molecule, or a plurality of this group and a plurality of hydroxyl groups can be provided.

When a large number of the fullerene derivatives described above are aggregated, the proton conductivity of the aggregates as a bulk is determined by the fact that a large amount of protons originally contained in the molecule and originating from the OSO ₃ H group are directly involved in the transfer. There is no need to take in hydrogen and protons originating from water vapor molecules and the like, and there is no need to replenish moisture from the outside, in particular, to absorb moisture from outside air, and there is no restriction on the atmosphere. In addition, fullerene, which is a substrate of these derivative molecules, has an electrophilic property, which is a significant factor in promoting ionization of hydrogen ions not only in highly acidic OSO ₃ H groups but also in hydroxyl groups and the like. It is considered to have contributed. This is one of the reasons why the proton conductor used in the present invention exhibits excellent proton conductivity.

Furthermore, since a large number of hydroxyl groups and OSO ₃ H groups can be introduced into one fullerene molecule, the number density of protons involved in conduction per conductor volume becomes very large. This is another reason why the proton conductor exhibits an effective conductivity.

Since most of the proton conductor is composed of carbon atoms of fullerene, it is light in weight, hardly deteriorates, and contains no contaminants. The production cost of fullerenes is also rapidly decreasing. In addition, fullerene is considered to be a near ideal carbon-based material over all other materials in terms of resources, environment and economy.

Further, according to the study of the present inventors, the proton dissociable group does not need to be limited to the above-mentioned hydroxyl group or OSO ₃ H group.

That is, this dissociable group is represented by the formula -XH, and X may be any atom or atomic group having a divalent bond. Furthermore, this group has the formula -OH or -YO
It is represented by H, and Y may be any atom or atomic group having a divalent bond.

[0049] Specifically, examples of the proton dissociative group, the -OH, -COOH besides -OSO ₃ H, -
Either SO ₃ H or —OPO (OH) ₂ is preferable.

Further, in the present embodiment, an electron-withdrawing group such as a nitro group, a carbonyl group,
Carboxyl group, nitrile group, alkyl halide group,
It is preferable that a halogen atom (such as fluorine and chlorine) is introduced.

In the present embodiment, the number of the proton-dissociable groups introduced into the fullerene molecule may be any number within the range of the number of carbon atoms constituting the fullerene molecule, but is preferably 5 or more. Is good. The number of the above groups is preferably not more than half the number of carbon atoms constituting fullerene in order to maintain the π-electron property of fullerene and to exhibit an effective electron-withdrawing property.

In order to synthesize the fullerene derivative used in the proton conductor of the present embodiment, as will be apparent from the specific examples described below, the fullerene molecule powder is prepared by a known method such as acid treatment or hydrolysis. By appropriately combining the treatments, a desired proton-dissociable group may be introduced into the constituent carbon atoms of the fullerene molecule.

In the present embodiment, the powder of the fullerene derivative thus obtained can be formed into a desired shape, for example, into a pellet. At this time, a binder is not necessary, which is effective in increasing proton conductivity and achieving reduction in weight of the proton conductor.

The first proton conductor can be suitably used for various electrochemical devices. That is, in the basic structure including the first electrode, the second electrode, and the proton conductor sandwiched between these two electrodes, the proton conductor described above can be preferably applied to the proton conductor.

More specifically, an electrochemical device in which the first and / or second electrode is a gas electrode, an electrochemical device in which an active material electrode is used as the first and / or second electrode, etc. On the other hand, the proton conductor described above can be preferably applied.

Hereinafter, an example in which the above-described proton conductor of the present embodiment is applied to a fuel cell will be described.

The proton conduction of the fuel cell is as shown in the schematic diagram of FIG. 3, and the proton conducting portion 1 is sandwiched between a first electrode (for example, hydrogen electrode) 2 and a second electrode (for example, oxygen electrode) 3. The dissociated protons move from the first pole 2 side to the second pole 3 side in the direction of the arrow shown in the figure.

FIG. 1 shows a fuel cell 15 which is a first electrochemical device using the proton conductor of the present embodiment.

The fuel cell 15 is made of, for example, platinum having a proton dissociating property (charge separating ability) and having a thickness of 1 μm.
A 0.5 μm-thick, for example, 0.5 μm-thick proton conducting portion 1 made of a fullerene derivative such as fullerenol is sandwiched between the electrode 2 and a 50 μm-thick second electrode 3 made of carbon carrying a platinum catalyst. Electrode 2 is housing outer frame 5
It is in close contact with the partition plate 6 in a.

A flow path 10a is formed between the housing outer frame 5a and the partition plate 6, and hydrogen gas 12 introduced into the flow path 10a from the introduction pipe 8 provided in the housing outer frame 5a is
It is supplied to the first electrode 2 from a supply port 7 provided in the partition plate 6 and discharged from a discharge port (not shown). A flow path 10b is also formed between the second electrode 3 and the housing inner frame 5b, and an air inlet 9a and an air outlet 9b for the air 13 are provided.

Therefore, the second electrode (positive electrode) 3 is in direct contact with the atmosphere, is capable of taking in oxygen in the atmosphere, and has the first surface covering one surface of the proton conducting portion 1.
The electrode (negative electrode) 2 is connected to a flow path 10 by a hydrogen gas introduction pipe 8.
directly touches hydrogen 12 introduced into a. Although not shown, a lead wire is connected to each of the first electrode 2 and the second electrode 3 so that electricity generated thereby can be taken out.

When the fuel cell 15 is used, hydrogen is supplied from the inlet 8 on the negative electrode 2 side, and the fuel (H ₂ ) 12 is supplied from the supply port 7 of the partition plate 6 to the first electrode while passing through the flow path 10a. 2. Then, the supplied fuel (H ₂ ) is dissociated by the first electrode 2, and protons are generated at the first electrode 2 by the dissociation, and the protons move toward the positive electrode 3 together with the protons generated at the proton conductor 1. Then, it reacts with oxygen (air) 13 supplied from the introduction port 9a to the flow path 10b toward the exhaust port 9b, thereby extracting a desired electromotive force.

The fuel cell having such a structure is characterized in that protons supplied from the negative electrode 2 move to the positive electrode 3 while the protons are dissociated in the proton conducting portion 1, so that the proton conductivity is high. Therefore, since a humidifying device or the like is not required, the system can be simplified and reduced in weight. Therefore, the entire fuel cell can be reduced from several tens to several hundreds μm to 1 μm or less.

As described above, the most significant feature of this embodiment is that the solid electrolyte, which is a proton conductor, and the hydrogen gas, which is a reaction active material, are supplied in such a manner that they are not in direct contact with each other. is there. In this respect, the energy device is an energy device completely different from the conventional fuel cell, and can be realized by the structure in which the first electrode 2 in which hydrogen dissociates into electrons and protons does not transmit hydrogen and water vapor in a gaseous state.

The electrode of this type is made of a substance capable of absorbing hydrogen as atoms or protons. For example, a thin film of a hydrogen storage metal, a hydrogen storage alloy, and platinum can be used. Of course, the material is not limited to metals and alloys as long as the material is capable of absorbing hydrogen as atoms or protons and has a function of dissociating hydrogen into electrons and protons. In addition, since these substances are present between the hydrogen gas and the electrolyte, a state in which the hydrogen gas does not directly contact the electrolyte can be realized.

In the conventional solid polymer electrolyte, it is necessary to perform humidification during use. Therefore, a method of supplying a sufficient amount of water vapor to the electrolyte using hydrogen gas as a carrier gas is usually employed. Therefore, when a conventional solid polymer electrolyte is used, it is not appropriate to adopt a structure as in this embodiment because humidification is prevented. However, such a structure is made possible by using the proton conductive electrolyte according to the present embodiment.

Further, as shown in FIG. 2, the surface of the first electrode 2 opposite to the proton conducting portion 1 or between the first electrode 2 and the second electrode 3 as shown in FIGS. In addition, it can also be realized by newly forming a blocking layer 4 having a structure that does not allow hydrogen gas and water vapor to pass through in a gaseous state.

That is, FIG. 2 shows a fuel cell 16 which is a second electrochemical device using the proton conductor of the present embodiment.
It shows. As shown in the figure, the fuel cell 16 includes a partition plate 6 of a housing outer frame 5a and a thinly formed first electrode 2A having a thickness of, for example, 1 μm (which may be formed of fine powder of platinum having charge separation ability, Quality.)
Is provided with a 1 μm-thick hydrogen gas blocking layer 4 made of, for example, an alloy of lanthanum and nickel. This blocking layer 4 is similar to the fuel cell 15 shown in FIG. 1 except that it absorbs hydrogen but does not allow it to permeate to the proton conductor side, and is arranged in close contact with the partition plate 6. Is formed.

Therefore, when the fuel cell 16 is used,
On the blocking layer 4 side, hydrogen is supplied from the inlet 8 and the fuel (H
₂ ) While 12 passes through the flow path 10a, it is supplied from the supply port 7 of the partition plate 6 to the blocking layer 4. Therefore, the barrier layer 4 which is a hydrogen storage alloy absorbs hydrogen, and the absorbed hydrogen is dissociated by the first electrode 2A adjacent to the barrier layer 4, and protons are generated at the first electrode 2A by the dissociation. The protons move to the positive electrode 3 side together with the protons generated in the conduction part 1, and react with oxygen (air) 13 supplied from the inlet 9 a to the flow path 10 b toward the outlet 9 b, thereby extracting a desired electromotive force. .

As described above, this fuel cell 16 is different from the fuel cell 15 shown in FIG. 1 in that the first electrode 2A for ionizing hydrogen and the blocking layer 4 for blocking the hydrogen gas 12 are made of different materials. In other words, the blocking layer 4 does not have a role as an electrode, but is made of a substance capable of absorbing hydrogen as atoms or protons. Therefore, for example, a hydrogen storage metal or a hydrogen storage alloy is preferably used, but is not limited to a metal or an alloy as long as it is a substance capable of absorbing hydrogen as atoms or as protons.

The portion of the substance capable of absorbing hydrogen as an atom or as a proton may be formed in a very thin layer. In this case, hydrogen as an active material is replaced with hydrogen gas as described above. It is good to supply from outside.

Alternatively, the blocking layer 4 may have a certain volume and be used as a storage location for the hydrogen active material. In this case, the portion determines the energy capacity of the device. However, the device can be a device in which the power generation portion and the storage portion are integrated, and the size of the entire device can be reduced.

The second electrochemical device is constructed as shown in FIGS. 13 to 15 using the same materials as described above, and can function in the same manner as described above.

That is, FIG. 13 shows a structure in which the first electrode 2A, the blocking layer 4, the proton conducting portion 1, and the second electrode 3 are formed in this order from the first electrode side, and FIG. 2
A, proton conducting portion 1A, blocking layer 4, proton conducting portion 1
A 'and the second electrode 3 are formed in this order.
Has a structure in which a first electrode 2A, a proton conducting portion 1, a blocking layer 4, and a second electrode 3 are similarly formed in this order.

As described above, the proton conductor made of the fullerene derivative of the present embodiment forms a proton conductor without using a binder, but a binder can be used in combination. Thereby, almost the same effect (high proton conductivity) as that of the proton conductor of the present embodiment can be exhibited, and unlike the case of using the fullerene derivative alone, the film can be formed into a high-strength thin film because it has good film-forming properties.

For example, the hydrogen-air battery shown in FIG.
A hydrogen electrode 21 made of a hydrogen storage material such as a hydrogen storage alloy and an air electrode 22 are opposed to each other with a thin-film proton conductor 20 using a binder interposed therebetween. Plate 24a and a Teflon plate 24b provided with a large number of holes 25, and the whole is bolt 2
6a, 26b and nuts 27a, 27b, and a hydrogen electrode lead 28a and an air electrode lead 28b are taken out of each electrode.

As described above, since the present invention uses the fullerene derivative as the proton conductor, the electrolyte can be made much thinner than when Nafion is used as the proton conductor.

At present, Nafion is most often used with a thickness of about 180 μm, but it has been reported that there is a minimum thickness of about 30-20 μm in those studied experimentally. However, further thinning seems to be practically difficult. This is because Nafion has to prevent gas permeation by itself.

However, in the energy device of the present embodiment, since the first electrode 2 or the blocking layer 4 blocks gas, it is not always necessary for the electrolyte layer to block gas.

As a limit of thinning, the first electrode 2 and the second electrode 2
Since it may be as thin as the electrode 3 does not contact, it may be as low as 0.1 μm or 0.01 μm, depending on the type of film and the manufacturing method.

That is, since the fullerenol-based electrolyte used in the present embodiment is an aggregate of molecules, it can be made as thin as one molecule as a theoretical limit. In that case, about 0.001 μm, about 1 nm
Levels are possible.

As described above, since the electrolyte can be made thinner, the electrochemical device of the present embodiment has a very small resistance due to the electrolyte, can achieve an increase in voltage and an improvement in output, and can have a reduced thickness of the whole element. The size of the device can be reduced.

Hereinafter, a fullerenol-based solid electrolyte as a proton conductor used in the present embodiment will be specifically described.

<Synthesis of Polyhydroxylated Fullerene> This synthesis is described in the literature (Chieng, LY; Wang, LY; Swirczewski. JW; S
oled, S .; Cameron, SJOrg. Chem. 1994, 59, 3960). The powder 2g charged into oleum 30ml of a C ₇₀ C ₆₀ / C ₇₀ fullerene mixture containing about 15%
The mixture was stirred in a nitrogen atmosphere at 60 ° C. for 3 days. The obtained reaction product is dropped little by little into anhydrous diethyl ether cooled in an ice bath, and the precipitate is separated by centrifugation, further three times with diethyl ether, and a 2: 1 mixture of diethyl ether and acetonitrile. After washing twice with the liquid, it was dried at 40 ° C. under reduced pressure. Further, the dried product was placed in 60 ml of ion-exchanged water and stirred at 85 ° C. for 10 hours while bubbling with nitrogen. A precipitate was separated from the reaction product by centrifugation, and the precipitate was further washed with pure water several times, and after repeating centrifugation, dried under reduced pressure at 40 ° C. FT-IR measurement of the brown powder obtained in this manner showed an almost identical IR spectrum of C ₆₀ (OH) ₁₂ shown in the above-mentioned literature, and this powder was found to be the target substance polywater. Identified as fullerene oxide.

<Production of Aggregated Pellets of Poly (hydroxylated fullerene)> Next, 90 mg of the powder of the poly (hydroxylated fullerene) was pressed in one direction so as to form a circular pellet having a diameter of 15 mm. The pressing pressure at this time was about 5 tons / cm ² . As a result, the polyhydroxylated fullerene powder was excellent in moldability despite not containing any binder resin and the like, and could be easily pelletized. The pellet has a thickness of about 300 microns and is referred to as the pellet of Example 1.

<Synthesis 1 of Polyhydroxylated Fullerene Hydrogen Sulfate (Total Esterification)> This was also performed with reference to the above-mentioned literature. 1 g of polyhydroxylated fullerene powder was dropped into 60 ml of fuming sulfuric acid and stirred at room temperature under a nitrogen atmosphere for 3 days. The obtained reaction product is dropped little by little into anhydrous diethyl ether cooled in an ice bath, and the precipitate is separated by centrifugation, further three times with diethyl ether, and a 2: 1 mixture of diethyl ether and acetonitrile. After washing twice with the liquid, it was dried at 40 ° C. under reduced pressure. The powder thus obtained was subjected to TF-IR measurement. The IR spectrum of all the hydroxyl groups converted to hydrogen sulfate was almost the same as that shown in the above-mentioned literature, indicating that the powder was the target substance. Was confirmed.

<Production 1 of Aggregated Pellets of Hydrogen Sulfuric Acid Polyester Fullerene Hydroxide> 70 mg of the powder of hydrogenated polysulfuric acid fullerene was pressed in one direction so as to form a circular pellet having a diameter of 15 mm. The pressing pressure at this time was about 5 tons / cm ² . As a result, although this powder did not contain any binder resin or the like, it was excellent in moldability and could be easily pelletized. This pellet has a thickness of about 300 microns and is referred to as the pellet of Example 2.

<Synthesis 2 of Polyhydroxylated Fullerene Hydrogen Sulfate (Partial Esterification)> C ₆₀ containing about 15% of C ₇₀
/ C ₇₀ fullerene mixture powder 2g and fuming sulfuric acid 30ml
While maintaining the temperature at 60 ° C in a nitrogen atmosphere.
Stirred for days. The resulting reaction was dropped little by little into diethyl ether cooled in an ice bath. However, in this case, diethyl ether which had not been subjected to dehydration treatment was used. The obtained precipitate was separated by centrifugation, further washed three times with diethyl ether and twice with a 2: 1 mixture of diethyl ether and acetonitrile, and dried at 40 ° C. under reduced pressure. FT-IR measurement of the thus obtained powder showed that the IR spectrum of the fullerene derivative partially containing a hydroxyl group and an OSO ₃ H group almost coincided with the IR spectrum shown in the above-mentioned literature. It was confirmed that it was the target substance.

<Production 2 of Aggregated Pellets of Poly (hydroxylated fullerene hydrogen sulfate)> 80 mg of partially hydrosulfated poly (fullerene hydroxide) powder was taken, and
Pressing was performed in one direction so as to form a circular pellet having a diameter of 15 mm. Press pressure at this time is about 5 tons / cm
^{Was 2} . As a result, although this powder did not contain any binder resin or the like, it was excellent in moldability and could be easily pelletized. This pellet has a thickness of about 300 microns and is referred to as the pellet of Example 3.

<Production of Fullerene Aggregated Pellets> For comparison, fullerene powder 90 used as a raw material for synthesis in the above example was used.
mg, and pressed in one direction to form a circular pellet having a diameter of 16 mm. The pressing pressure at this time was about 5 tons / cm ² . As a result, although this powder did not contain any binder resin or the like, it was relatively excellent in moldability and could be easily pelletized. This pellet has a thickness of about 300 microns and is used as a comparative pellet.

<Measurement of Proton Conductivity of Pellets Obtained in Each Example> In order to measure the conductivities of the pellets of Examples 1 to 3 and the comparative pellets, first, the diameter of the pellet was 15 m, which was equal to the diameter of the pellet.
An AC voltage (amplitude: 0.1 V) from 7 MHz to 0.01 Hz was applied to both sides of each pellet with an aluminum plate having a length of m, and the complex impedance at each frequency was measured. The measurement was performed under a dry atmosphere.

Regarding the impedance measurement, the proton conducting portion 1 of the proton conductor made of the pellet electrically forms an equivalent circuit as shown in FIG. Capacitors 6 and 6 'are formed between the first pole 2 and the second pole 3 including the proton conducting portion 1 represented by a circuit. The capacitance 5 represents a delay effect when the proton moves (phase lag at a high frequency), and the resistance 4 represents a parameter of the ease of movement of the proton.

Here, the measured impedance Z is Z = R
The frequency dependence of the proton conducting portion represented by e (Z) + i · Im (Z) and represented by the above equivalent circuit was examined.

FIG. 7B is an equivalent circuit when a normal fullerene molecule having no proton dissociation property is used (comparative example).

FIG. 8 shows the results of impedance measurement of the pellet of Example 1 and the comparative pellet.

According to this, in the comparative pellet,
The frequency characteristic of the complex impedance was almost the same as the behavior of the capacitor alone, and no conduction behavior of charged particles (electrons, ions, etc.) was observed in the aggregate of fullerene itself. On the other hand, in the case of Example 1, it is possible to see a single semicircular arc that is flat in the high-frequency portion but very clear. This indicates that some charged particle conduction behavior exists inside the pellet. Furthermore, in the low frequency region, a sharp rise in the imaginary part of the impedance is observed. This indicates that the charged particles are blocking between the aluminum electrode as the voltage gradually approaches the DC voltage, and naturally the charged particles on the aluminum electrode side are electrons. It is understood that the charged particles are not electrons or holes but other charged particles, that is, ions. Due to the configuration of the fullerenol used, this charged particle cannot be considered other than protons.

The conductivity of the charged particles can be determined from the X-axis intercept of the arc seen on the high frequency side, and is calculated to be approximately 5 × 10 ⁻⁶ S / cm in the pellet of Example 1. Furthermore, when the same measurement was performed for the pellets of Examples 2 and 3, the frequency characteristics of the impedance were similar to those of Example 1 for the overall shape.
However, the conductivity obtained from the X-intercept of the arc is shown in Table 1.
As shown in FIG.

[0098]

Table 1 Conductivity of proton conductor pellets in each example (25 ° C)

As described above, when the hydroxyl group is replaced by the OSO ₃ H group, the conductivity in the pellet tends to increase. This is because hydrogenation of an OSO ₃ H group is more likely to occur than a hydroxyl group. Further, the present inventors have found that this type of fullerene derivative aggregate can conduct protons at room temperature in a dry atmosphere, in both cases of a hydroxyl group and an OSO ₃ H group, or in a case where both are mixed. Was completed.

Next, using the pellet of Example 1, the above-described complex impedance measurement was performed in a temperature range from 160 ° C. to −40 ° C., and the temperature dependence of the conductivity obtained from the high-frequency arc at that time was examined. . FIG. 9 shows the results as an Arrhenius type plot. Thus, it can be seen that the conductivity changes sharply and linearly from 160 ° C. to −40 ° C. That is, the figure shows that a single ion conduction mechanism can proceed in this temperature range. That is, the proton conductor of the present invention can conduct electricity in a wide temperature range including room temperature, particularly in a high temperature of 160 ° C. and a low temperature of −40 ° C.

[0101]

EXAMPLES Based on the above embodiment, the fuel cell of the present invention was manufactured by the following manufacturing method.

FIG. 1 is a sectional view showing a fuel cell 15 according to the first embodiment. That is, the introduction pipe 8 is attached to the housing outer frame 5a.
After the combination of the partition plate 6 and the partition plate 6, platinum is sputtered on the surface including the supply port 7 of the partition plate 6 to form the first electrode 2 having a thickness of 1 μm, and the fullerenol derivative-based solid electrolyte 1 is formed thereon. 0.5 μm, and further provided thereon a platinum-catalyzed gas electrode having a thickness of 50 μm as a second electrode 3,
The housing inner frame 5b was connected to this. The thickness of the first electrode 2 is determined so as to exert its hydrogen gas permeation preventing ability.

When hydrogen gas 12 was supplied to the fuel cell 15 through the hydrogen gas introducing pipe 8, the open-circuit voltage was approximately 1%.
V generation was confirmed. In addition, the load characteristics of power generation when the load was changed were measured.

FIG. 11 shows the result. That is, even if the current increased, the voltage did not decrease much, and good power generation could be performed.

FIG. 2 shows another fuel cell 16 according to the second embodiment.
FIG. That is, after combining the introduction pipe 8 and the partition plate 6 with the housing outer frame 5a, the 1 μm thick gas barrier layer 4 is formed on the surface of the partition plate 6 including the supply port 7 by binary metal sputtering of a lanthanum-nickel alloy. And an ultra-thin platinum thin film having a thickness of 1 μm is formed thereon.
A, a fullerenol derivative-based solid electrolyte 1 is applied thereon, and a 50 μm thick second electrode 3 is further applied thereon.
Was provided with a gas electrode provided with a platinum catalyst, and the housing inner frame 5b was connected to the gas electrode. In this embodiment, since the blocking layer 4 is provided, the thickness of the first electrode 2A can be smaller than that of the first embodiment.

When hydrogen gas 12 was supplied to the fuel cell 16 through the hydrogen gas introduction pipe 8, the open-circuit voltage was approximately 1%.
V generation was confirmed. In addition, the load characteristics of power generation when the load was changed were measured.

FIG. 12 shows the result. That is, also in this case, even if the current increased, the voltage did not decrease much, and good power generation could be performed almost in the same manner as the fuel cell 15 of FIG.

According to the present embodiment, each of the fuel cells 15 and 16 has a simple structure and is easy to manufacture as compared with a fuel cell or the like having a gas electrode. Since it can be used, the first electrode 2 or the blocking layer 4 can be formed without impairing the function of the supply port 7 including the area of the supply port 7 of the partition plate 6, and even if the area is large, it can be easily formed. Can be made.

Further, a device unique in thickness is not required, and a very thin device can be manufactured. Furthermore, since it is not necessary to impart gas impermeability to the solid electrolyte, physical restrictions on the solid electrolyte membrane are relaxed, and a thinner film that has not been possible when using Nafion or the like as a proton conductor has been achieved. It is possible to generate electric power at a higher load than ever before by making the film thinner. Therefore, in the present example, it was demonstrated that the proton conductor of the prior application works very effectively, and this makes it difficult to manufacture a fuel cell, which is a problem of the related art, and impermeability to a solid electrolyte. Requirements and electrolyte contamination can be eliminated.

The above embodiments and examples can be variously modified based on the technical idea of the present invention.

For example, as long as the proton conductor has proton conductivity, other materials can be used in addition to the fullerene derivative. Further, the size of the holes of the first electrode made of a porous material can be made smaller than usual, so that the gas can be made more difficult to permeate.

Further, the structure, shape, material, and the like of the fuel cells of the above-described embodiments and examples can be appropriately formed without being limited to the above-described embodiments and examples.

[0113]

As is apparent from the above, the first electrochemical device of the present invention has a structure in which the first electrode does not substantially transmit at least hydrogen in a gaseous state.
The rate of direct hydrogen contact with the proton conductor is very small or zero. Therefore, since it is not necessary to impart gas impermeability to the proton conductor, physical restrictions on the film quality of the proton conductor are relaxed, the film thickness can be reduced, and power generation with a higher load can be performed. In addition, by using the same proton conductor as in the prior application, there is no need for a humidifier because of the proton conductivity without humidification. Can be simplified and further miniaturized.

Further, in the second electrochemical device of the present invention, at least hydrogen is substantially converted into a gaseous state on the surface of the first electrode opposite to the proton conductor or between the first electrode and the second electrode. Since the blocking layer having a structure that does not allow the proton conductor to pass through is provided, the direct contact of hydrogen with the proton conductor is significantly suppressed, so that the same performance and effects as those of the first electrochemical device described above are exhibited. In addition to being able to
Even if the first electrode is made thinner, the function of preventing hydrogen gas permeation is exerted by the blocking layer, so that the electrode can be made thinner.

Since the manufacturing method of the present invention includes the steps of forming the above-described first and second electrochemical device structures of the present invention, reproducibility can be achieved without impairing the function of each part. Can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first fuel cell according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a second fuel cell.

FIG. 3 is a schematic diagram showing an example of a proton conductor used in the example.

FIG. 4 is a structural diagram of polyhydroxylated fullerene which is an example of a fullerene derivative used in Examples.

FIG. 5 is a schematic diagram showing an example of a fullerene derivative used in Examples.

FIG. 6 is a structural diagram of a fullerene molecule.

FIG. 7 is a diagram showing an equivalent circuit of the same.

FIG. 8 is a view showing a measurement result of a complex impedance of a fullerene derivative or a fullerene pellet.

FIG. 9 is a diagram showing the temperature dependence of the proton conductivity of the fullerene derivative pellet.

FIG. 10 is a structural diagram of a hydrogen-air battery showing one embodiment of the present invention.

FIG. 11 is a diagram showing power generation characteristics of the first fuel cell according to the example.

FIG. 12 is a diagram showing the power generation characteristics of a second fuel cell according to the example.

FIG. 13 is a sectional view showing a modified example of the second fuel cell.

FIG. 14 is a sectional view showing another modified example of the second fuel cell.

FIG. 15 is a sectional view showing still another modified example of the second fuel cell.

[Explanation of symbols]

1, 1A, 1A ', 20 ... proton conducting part, 2, 2A ...
First electrode (negative electrode), 3 second electrode (positive electrode), 4 blocking layer, 5a outer housing frame, 5b inner housing frame, 6
... Partition plate, 7 ... Supply port, 8 ... Introduction pipe, 9a ... Introduction port,
9b: exhaust port, 10a, 10b: flow path, 12, H ₂ : hydrogen (fuel), 13, O: air (oxygen), 15, 16: fuel cell, 21: hydrogen electrode, 22: air electrode, 24a, 24b
... Teflon plate, 25 ... air hole, 26a, 26b ... bolt, 27a, 27b ... nut, 28a ... air electrode lead,
28b: hydrogen electrode lead

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 8/10 H01M 8/10

Claims (34)

[Claims] A first electrode configured to dissociate hydrogen into electrons and protons; and a second electrode configured to receive reduced electrons from the electrons and protons and convert them into oxidized species. The first electrode and the second electrode Wherein the first electrode has a structure in which at least hydrogen does not substantially permeate in a gaseous state. 2. The electrochemical device according to claim 1, wherein the first electrode is made of a substance that does not substantially transmit hydrogen and water vapor in a gaseous state toward the proton conductor. 3. The electrochemical device according to claim 1, wherein the first electrode has a hydrogen gas permeation preventing ability such that a hydrogen partial pressure on the second electrode side is 10% or less. 4. The electrochemical device according to claim 1, wherein the first electrode is made of a substance capable of absorbing hydrogen as atoms or protons. 5. The electrochemical device according to claim 1, wherein the first electrode is made of a hydrogen storage metal, a hydrogen storage alloy, or a substance containing the same. 6. A structure that does not substantially transmit at least hydrogen in a gaseous state at a surface of the first electrode opposite to the proton conductor or between the first electrode and the second electrode. The electrochemical device according to claim 1, wherein a barrier layer is provided. 7. The barrier layer according to claim 6, wherein the barrier layer is made of a substance capable of absorbing hydrogen as atoms or protons.
The electrochemical device described in 1 above. 8. The electrochemical device according to claim 6, wherein the barrier layer is made of a hydrogen storage metal, a hydrogen storage alloy, or a substance containing the same. 9. The electrochemical device according to claim 1, wherein the proton conductor contains, as a main component, a fullerene derivative obtained by introducing a proton-dissociable group into a carbon atom constituting a fullerene molecule. 10. The method according to claim 10, wherein the proton-dissociable group is —OH,
_{-OSO 3 H, -COOH, -SO 3} H, -OPO (O
The electrochemical device according to claim 9, which is a group selected from any of H) ₃ . 11. The fullerene molecule is a spherical carbon cluster molecule Cm (m = 36, 60, 70, 78, 82,
84 etc.). 12. The electrochemical device according to claim 1, wherein the first electrode side is covered with a housing member, and the housing member is provided with a hydrogen gas supply port for supplying hydrogen gas to the first electrode side. device. 13. The electrochemical device according to claim 1, configured as a fuel cell. 14. The first hydrogen dissociation into electrons and protons.
An electrode, and a second electrode in which the reduced species receives electrons and protons and changes to an oxidized species, wherein a proton conductor is present between the first electrode and the second electrode; That the surface opposite to the proton conductor or between the first electrode and the second electrode is provided with a blocking layer having a structure that does not substantially transmit at least hydrogen in a gaseous state. An electrochemical device, characterized by: 15. The electrochemical device according to claim 14, wherein the barrier layer is made of a substance that does not substantially transmit hydrogen and water vapor in a gaseous state to the proton conductor side. 16. The electrochemical device according to claim 14, wherein the blocking layer has a hydrogen gas permeation preventing ability such that a hydrogen partial pressure on the second electrode side is 10% or less. 17. The electrochemical device according to claim 14, wherein the blocking layer is made of a substance capable of absorbing hydrogen as atoms or protons. 18. The electrochemical device according to claim 14, wherein the barrier layer is made of a hydrogen storage metal, a hydrogen storage alloy, or a substance containing the same. 19. The proton conductor according to claim 14, wherein the proton conductor contains, as a main component, a fullerene derivative obtained by introducing a proton-dissociable group into a carbon atom constituting a fullerene molecule.
The electrochemical device described in 1 above. 20. The proton-dissociable group is -OH,
_{-OSO 3 H, -COOH, -SO 3} H, -OPO (O
20. The electrochemical device according to claim 19, which is a group selected from any of H) ₃ . 21. The fullerene molecule is a spherical carbon cluster molecule Cm (m = 36, 60, 70, 78, 82,
84 etc.). 22. The barrier layer side is covered with a housing member, and the housing member is provided with a hydrogen gas supply port for supplying hydrogen gas to the barrier layer side.
The electrochemical device described in 1 above. 23. The electrochemical device according to claim 14, configured as a fuel cell. 24. The electrochemical device according to claim 14, configured as an air cell. 25. The first wherein hydrogen dissociates into electrons and protons.
Manufacturing an electrochemical device having an electrode and a second electrode in which a reducing species receives an electron and a proton to change to an oxidizing species, wherein a proton conductor exists between the first electrode and the second electrode. In doing so, at least the hydrogen gas supply port side of the housing member having a hydrogen gas supply port or between the first electrode and the second electrode has a structure that does not substantially transmit at least hydrogen in a gaseous state. Forming one electrode or a blocking layer; forming the proton conductor on the first electrode or on the first electrode provided on the blocking layer; and forming the proton conductor on the proton conductor layer. Forming a second electrode. 26. The method for manufacturing an electrochemical device according to claim 25, wherein the first electrode or the blocking layer is made of a substance that does not substantially transmit hydrogen and water vapor in a gaseous state to the proton conductor side. 27. The electrochemical device according to claim 25, wherein the first electrode or the blocking layer has an ability to prevent hydrogen gas permeation such that the hydrogen partial pressure on the second electrode side is 10% or less. Production method. 28. The first electrode or the blocking layer is composed of a substance capable of absorbing hydrogen as atoms or protons.
A method for manufacturing the electrochemical device according to claim 25. 29. The method according to claim 25, wherein the first electrode or the blocking layer is made of a hydrogen storage metal, a hydrogen storage alloy, or a substance containing the same. 30. A fullerene derivative obtained by introducing a proton-dissociable group into a carbon atom constituting a fullerene molecule as a main component in the proton conductor.
5. The method for producing an electrochemical device according to 5. 31. The proton-dissociable group includes —OH,
_{-OSO 3 H, -COOH, -SO 3} H, -OPO (O
H) A group selected from any one of ₃ ) is used.
3. The method for producing an electrochemical device described in 1. above. 32. A spherical carbon cluster molecule Cm (m = 36, 60, 70, 78, 82,
84). The method for producing an electrochemical device according to claim 30, wherein the method comprises the steps of: 33. A fuel cell comprising a fuel cell.
3. The method for producing an electrochemical device described in 1. above. 34. An air battery configured as an air battery.
3. The method for producing an electrochemical device described in 1. above.