JP2011228195A - Fuel cell, method for manufacturing the same, and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell and method for manufacturing the same, which stably obtains high current values when a positive electrode or a negative electrode is composed of an enzyme immobilized electrode.SOLUTION: In a biofuel cell having a structure in which a positive electrode 2 and a negative electrode 1 are opposed through an electrolyte layer 3, at least one of the positive electrode 1 or the negative electrode 2 is composed of an enzyme immobilized electrode, in which a contact angle to a buffer solution is equal to or more than 80 degrees and equal to or less than 120 degrees, or an enzyme immobilized electrode which is made of a material having regular fabric structure. For example, carbon is used as a material for the electrode. When carbon, which has regular fabric structure, is used as the material of the electrode, the porosity is equal to or more than 70% and equal to or less than 96%.

Description

  The present invention relates to a fuel cell, a method for manufacturing a fuel cell, and an electronic device, and particularly suitable for application to a biofuel cell using an enzyme, a method for manufacturing the same, and various electronic devices using the biofuel cell as a power source. Is.

In recent years, a fuel cell (biofuel cell) using an enzyme has attracted attention (for example, see Patent Documents 1 to 13). In this biofuel cell, fuel is decomposed by enzymes and separated into protons (H ⁺ ) and electrons. Alcohols such as methanol and ethanol, monosaccharides such as glucose, and polysaccharides such as starch are used as fuel. What has been developed.

JP 2000-133297 A JP 2003-282124 A JP 2004-71559 A JP 2005-13210 A JP 2005-310613 A JP 2006-24555 A JP 2006-49215 A JP 2006-93090 A JP 2006-127957 A JP 2006-156354 A JP 2007-12281 A JP 2007-35437 A JP 2007-87627 A

Generally, a material having a void such as carbon felt or carbon paper is used for the positive electrode of the above-described biofuel cell in order to supply oxygen.
However, the current value obtained by such a biofuel cell is not necessarily sufficiently high, and further improvement of the current value has been desired.

Therefore, the problem to be solved by the present invention is to provide a fuel cell that can stably obtain a high current value when the positive electrode is made of an electrode on which an enzyme is immobilized, and a method for manufacturing the same. is there.
Another problem to be solved by the present invention is to provide an electronic device using the excellent fuel cell as described above.
The above and other problems will become apparent from the description of this specification.

  The present inventors have intensively studied to solve the above problems. As a result, when a material having voids such as carbon felt or carbon paper is used as the material of the positive electrode, the penetration of the buffer solution into the electrode is poor, and even if the surface area of the electrode increases due to the voids It was found that the surface area of the electrode could not be used effectively. Further, as a result of intensive studies to improve the ease of penetration of the buffer solution into the electrode, the contact angle of the positive electrode with respect to the buffer solution is set to 80 ° or more and 120 ° or less, thereby buffering the electrode. It has been found that the ease of penetration of the liquid can be greatly improved. It has also been found that the ease of penetration of the buffer solution into the electrode can be greatly improved by using a material having a regular fiber structure as the material for the positive electrode. As a result of further investigation, even when the negative electrode is composed of an electrode on which an enzyme is immobilized, the contact angle of the electrode with respect to the buffer solution is 80 ° or more and 120 ° or less, or a regular fiber as a material of the electrode. It was concluded that it is effective to use a material having a structure.

That is, in order to solve the above problems, the present invention provides:
Having a structure in which the positive electrode and the negative electrode are opposed to each other via a proton conductor;
At least one of the positive electrode and the negative electrode is a fuel cell comprising an electrode on which an enzyme is immobilized and a contact angle with respect to a buffer solution is 80 ° or more and 120 ° or less.
In addition, this invention
When manufacturing a fuel cell having a structure in which a positive electrode and a negative electrode are opposed to each other via a proton conductor and at least one of the positive electrode and the negative electrode is an electrode on which an enzyme is immobilized, a buffer is used as the electrode. This is a method of manufacturing a fuel cell using an electrode having a contact angle with respect to a liquid of 80 ° or more and 120 ° or less.
In addition, this invention
Using one or more fuel cells,
At least one of the fuel cells is
Having a structure in which the positive electrode and the negative electrode are opposed to each other via a proton conductor;
At least one of the positive electrode and the negative electrode is an electronic device that is a fuel cell including an electrode on which an enzyme is immobilized and a contact angle with respect to a buffer solution is 80 ° or more and 120 ° or less.

In addition, this invention
Having a structure in which the positive electrode and the negative electrode are opposed to each other via a proton conductor;
At least one of the positive electrode and the negative electrode is a fuel cell comprising an electrode made of a material having a regular fiber structure, to which an enzyme is immobilized.
In addition, this invention
When manufacturing a fuel cell having a structure in which a positive electrode and a negative electrode are opposed to each other via a proton conductor, and at least one of the positive electrode and the negative electrode is an electrode on which an enzyme is immobilized, the rule is used as the electrode. This is a method of manufacturing a fuel cell using an electrode made of a material having a typical fiber structure.

In addition, this invention
Using one or more fuel cells,
At least one of the fuel cells is
Having a structure in which the positive electrode and the negative electrode are opposed to each other via a proton conductor;
At least one of the positive electrode and the negative electrode is an electronic device that is a fuel cell including an electrode made of a material having a regular fiber structure to which an enzyme is immobilized.

  In the present invention, carbon is preferably used as the material for the positive electrode or the negative electrode, but other materials may be used. When a material having a regular fiber structure is used as a material for a positive electrode or a negative electrode, the material having a regular fiber structure has a shape woven or knitted using a fibrous material (such as fibrous carbon). Have. The thickness of the fibrous material is selected as necessary, and is, for example, 100 μm or more and 300 μm or less, typically 150 μm or more and 250 μm or less. The porosity of the material having a regular fiber structure is, for example, 70% to 96%, preferably 80% to 95%, and more preferably 80% to 90%.

  In the present invention, from the viewpoint of improving the ease of penetration of the buffer solution into the electrode, it is desirable that the surface of the positive electrode or the negative electrode be water repellent. For this purpose, for example, a water repellent containing a water repellent material is formed on the surface of the electrode. Specifically, for example, the water repellent is applied or soaked on the surface of the electrode, or the electrode is dipped (immersed) in the water repellent. Various water repellents can be used and are selected as necessary. For example, a water repellent material, particularly a fine water repellent material dispersed in an organic solvent can be used. . The ratio of the water repellent material in the water repellent may be extremely small. The water repellent is preferably an organic solvent that separates at least the water repellent material and water, or at least a sufficiently low solubility of the water repellent material and the enzyme, for example, a solubility of 10 mg / ml or less, preferably 1 mg. / Ml or less organic solvent is used.

  As the organic solvent as described above, methyl isobutyl ketone, heptane, hexane, toluene, isooctane, diethyl ether and the like are preferably used, but more generally aliphatic, alicyclic or aromatic type are used. Various organic solvents such as hydrocarbon solvents, ether solvents, and halides thereof can be used. More specifically, examples of the organic solvent include butanes, pentanes, hexanes, heptanes, octanes, nonanes, decanes, dodecanes, cyclohexane, cyclopentane, benzene, xylenes, butanol, pens. Benzene solvent substituted with one or more of tanol, methyl ether, ethyl ether, isopropyl ether, methylene chloride, methyl chloroform, carbon tetrachloride, dichlorodifluoromethane, perchloroethylene, chlorine atom, bromine atom and / or iodine atom However, it is not limited to these, Moreover, these may be used independently and may use 2 or more types together.

  Organic solvents include methylene chloride, 1,2-dichloroethane, chloroform, monochlorobenzene, 1,2-dichlorobenzene, 2-chlorotoluene, 3-chlorotoluene, 4-chlorotoluene, 2-chloro-m-xylene, 2 -Chloro-p-xylene, 4-chloro-o-xylene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, 3,4-dichlorotoluene, Examples thereof include halogenated hydrocarbon solvents such as monofluorobenzene, and hydrocarbon solvents such as nitrobenzene and benzene. Examples of the organic solvent include cyclohexane, normal hexane, cyclohexanone, 1-methoxyisopropanol acetate, ethyl acetate, butyl acetate, petroleum ether, silicon oil, and the like.

  Furthermore, an ionic liquid can also be used as the organic solvent. Examples of the ionic liquid include those containing at least one anion selected from the group consisting of a fluoroalkyl sulfate anion, a fluorocycloalkyl sulfate anion, and a fluorobenzyl sulfate anion as anions.

  If necessary, the water repellent contains a binder in addition to the water repellent material and the organic solvent. Various binders can be used as the binder, but it is more preferable to use a binder having high water repellency such as polyvinyl butyral. The ratio of the binder in the water repellent is, for example, 0.01 to 10%, but is not limited thereto. In the case where the binder has water repellency such as polyvinylidene fluoride (PVDF), the binder itself can be used as the water repellent material.

  As the water repellent material, various materials can be used. For example, a carbon-based material, preferably carbon powder can be used. As the carbon powder, for example, graphite such as natural graphite, activated carbon, carbon nanofiber (gas phase carbon fiber) used for an additive of a lithium ion battery, ketjen black and the like can be used. A water-repellent polymer can also be used as the water-repellent material. As such a water-repellent polymer, for example, various fluorine-based polymers can be used in addition to polyvinyl butyral. Specific examples of the fluoropolymer include tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyfluoride. Vinyl, perfluoroalkoxy resin, tetrafluoroethylene-ethylene copolymer, polychlorotrifluoroethylene, polyether sulfone and the like are not limited thereto.

  The enzyme immobilized on the positive electrode and the negative electrode may be various, and is selected as necessary. In addition, when an enzyme is immobilized on the positive electrode and the negative electrode, an electron mediator is preferably immobilized in addition to the enzyme.

The enzyme immobilized on the positive electrode typically includes an oxygen reductase. As this oxygen reductase, for example, bilirubin oxidase, laccase, ascorbate oxidase and the like can be used. In this case, an electron mediator is preferably immobilized on the positive electrode in addition to the enzyme. As the electron mediator, for example, potassium hexacyanoferrate, potassium ferricyanide, potassium octacyanotungstate and the like are used. The electron mediator is preferably immobilized at a sufficiently high concentration, for example, 0.64 × 10 ⁻⁶ mol / mm ² or more on average.

For example, when a monosaccharide such as glucose is used as the fuel, the enzyme immobilized on the negative electrode includes an oxidase that promotes and decomposes the monosaccharide and is usually reduced by the oxidase. A coenzyme oxidase that returns the coenzyme to an oxidant. By the action of the coenzyme oxidase, electrons are generated when the coenzyme returns to the oxidized form, and the electrons are transferred from the coenzyme oxidase to the electrode via the electron mediator. For example, NAD ⁺ -dependent glucose dehydrogenase (GDH) is used as the oxidase, nicotinamide adenine dinucleotide (NAD ⁺ ) is used as the coenzyme, and diaphorase is used as the coenzyme oxidase.

  When using polysaccharides (a broadly defined polysaccharide, which refers to all carbohydrates that produce two or more monosaccharides by hydrolysis, including oligosaccharides such as disaccharides, trisaccharides, and tetrasaccharides) as fuel, Preferably, in addition to the above-mentioned oxidase, coenzyme oxidase, coenzyme and electron mediator, a degradation enzyme that promotes degradation such as hydrolysis of polysaccharides and produces monosaccharides such as glucose is also immobilized. . Specific examples of the polysaccharide include starch, amylose, amylopectin, glycogen, cellulose, maltose, sucrose, and lactose. These are a combination of two or more monosaccharides, and any polysaccharide contains glucose as a monosaccharide of the binding unit. Note that amylose and amylopectin are components contained in starch, and starch is a mixture of amylose and amylopectin. When glucoamylase is used as a polysaccharide-degrading enzyme and glucose dehydrogenase is used as an oxidase that degrades monosaccharides, polysaccharides that can be degraded to glucose by glucoamylase, such as starch, amylose, amylopectin, glycogen As long as it contains any one of maltose, it is possible to generate electricity using this as fuel. Glucoamylase is a degrading enzyme that hydrolyzes α-glucan such as starch to produce glucose, and glucose dehydrogenase is an oxidase that oxidizes β-D-glucose to D-glucono-δ-lactone. Preferably, the degradation enzyme that decomposes the polysaccharide is also immobilized on the negative electrode, and the polysaccharide that will eventually become the fuel is also immobilized on the negative electrode.

  Further, when starch is used as fuel, it is possible to use a gelatinized fuel obtained by gelatinizing starch. In this case, it is preferable to use a method in which gelatinized starch is brought into contact with a negative electrode on which an enzyme or the like is immobilized, or is immobilized on the negative electrode together with the enzyme or the like. When such an electrode is used, the starch concentration on the negative electrode surface can be maintained at a higher level than when starch dissolved in the solution is used, the enzymatic degradation reaction becomes faster, and the output is improved. The fuel handling is easier than in the case of a solution, the fuel supply system can be simplified, and the fuel cell does not need to be used upside down, which is very advantageous when used for mobile devices, for example. .

  Basically, any electron mediator may be used, but a compound having a quinone skeleton, particularly, a compound having a naphthoquinone skeleton is preferably used. As the compound having a naphthoquinone skeleton, various naphthoquinone derivatives can be used. Specifically, for example, 2-amino-1,4-naphthoquinone (ANQ), 2-amino-3-methyl-1 2, 4-naphthoquinone (AMNQ), 2-methyl-1,4-naphthoquinone (VK3), 2-amino-3-carboxy-1,4-naphthoquinone (ACNQ), and the like are used. As a compound having a quinone skeleton, for example, anthraquinone or a derivative thereof can be used in addition to a compound having a naphthoquinone skeleton. In addition to the compound having a quinone skeleton, the electron mediator may contain one or two or more other compounds that function as an electron mediator, if necessary. As a solvent used when a compound having a quinone skeleton, particularly a compound having a naphthoquinone skeleton, is immobilized on the negative electrode, acetone is preferably used. Thus, by using acetone as a solvent, the solubility of the compound having a quinone skeleton can be increased, and the compound having a quinone skeleton can be efficiently immobilized on the negative electrode. If necessary, the solvent may contain one or two or more other solvents other than acetone.

  Various materials can be used as an immobilizing material for immobilizing an enzyme, a coenzyme, an electron mediator, etc. on the negative electrode and the positive electrode, preferably poly-L-lysine (PLL). A polyion complex formed using a polycation or a salt thereof and a polyanion or a salt thereof such as polyacrylic acid (for example, sodium polyacrylate (PAAcNa)) can be used, and an enzyme is contained inside the polyion complex. , Coenzymes, electron mediators, and the like can be included.

  Various proton conductors can be used and are selected as necessary. Specifically, for example, cellophane, non-woven fabric, perfluorocarbon sulfonic acid (PFS) resin film, trifluorostyrene derivative Copolymer film, polybenzimidazole film impregnated with phosphoric acid, aromatic polyether ketone sulfonic acid film, PSSA-PVA (polystyrene sulfonate polyvinyl alcohol copolymer), PSSA-EVOH (polystyrene sulfonate ethylene vinyl alcohol) Copolymer), an ion exchange resin having a fluorine-containing carbon sulfonic acid group (Nafion (trade name, DuPont, USA), etc.) and the like.

When an electrolyte containing a buffer substance (buffer solution) is used as the proton conductor, even when the increase or decrease in protons occurs in the electrode or in the immobilized membrane of the enzyme due to an enzyme reaction via protons during high output operation, In order to be able to obtain a sufficient buffering action, to suppress the deviation of pH from the optimum pH to a sufficiently small value, and to fully demonstrate the ability of the enzyme, the electrolyte It is effective that the concentration of the buffer substance contained is 0.2 M or more and 2.5 M or less, preferably 0.2 M or more and 2 M or less, more preferably 0.4 M or more and 2 M or less, and further preferably 0. 8M or more and 1.2M or less. Buffer substances, in general, as long as _a pK _a of 5 to 9, may it be used What Specific examples and, dihydrogen phosphate ion (H ₂ PO ₄ ^- ), 2-amino-2-hydroxymethyl-1,3-propanediol (abbreviated to Tris), 2- (N-morpholino) ethanesulfonic acid (MES), cacodylic acid, carbonic acid (H ₂ CO ₃ ), hydrogen citrate Ions, N- (2-acetamido) iminodiacetic acid (ADA), piperazine-N, N′-bis (2-ethanesulfonic acid) (PIPES), N- (2-acetamido) -2-aminoethanesulfonic acid ( ACES), 3- (N-morpholino) propanesulfonic acid (MOPS), N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES), N-2-hydroxyethylpiperazine- '-3-propanesulfonic acid (HEPPS), N- [tris (hydroxymethyl) methyl] glycine (abbreviation tricine), glycylglycine, N, N-bis (2-hydroxyethyl) glycine (abbreviation bicine), etc. . Examples of the substance that generates dihydrogen phosphate ions (H ₂ PO ₄ ⁻ ) include sodium dihydrogen phosphate (NaH ₂ PO ₄ ) and potassium dihydrogen phosphate (KH ₂ PO ₄ ). As the buffer substance, a compound containing an imidazole ring is also preferable. Specifically, the compound containing an imidazole ring includes imidazole, triazole, pyridine derivative, bipyridine derivative, imidazole derivative (histidine, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, imidazole- 2-carboxylate ethyl, imidazole-2-carboxaldehyde, imidazole-4-carboxylic acid, imidazole-4,5-dicarboxylic acid, imidazol-1-yl-acetic acid, 2-acetylbenzimidazole, 1-acetylimidazole, N- Acetylimidazole, 2-aminobenzimidazole, N- (3-aminopropyl) imidazole, 5-amino-2- (trifluoromethyl) benzimidazole, 4-azabenzimidazole, 4-aza-2-merca Ptobenzimidazole, benzimidazole, 1-benzylimidazole, 1-butylimidazole) and the like. Buffer materials include 2-aminoethanol, triethanolamine, TES (N-Tris (hydroxymethyl) methyl-2-aminoethanesulfonic acid), BES (N, N-Bis (2-hydroxyethyl) -2-aminoethanesulfonic
acid) or the like. The pH of the electrolyte containing the buffer substance is preferably around 7, but may generally be any of 1-14. If necessary, these buffer substances may also be immobilized on the immobilized membrane of the enzyme or electron mediator.

This fuel cell can be used for almost anything that requires electric power, and can be of any size. For example, electronic devices, mobile objects (automobiles, motorcycles, aircraft, rockets, spacecrafts, etc.), power devices, construction machinery It can be used for machine tools, power generation systems, cogeneration systems, etc. The output, size, shape, type of fuel, etc. are determined depending on the application.
Electronic devices may be basically any type, including both portable and stationary types, but specific examples include mobile phones, mobile devices, robots, personal computers. , Game equipment, in-vehicle equipment, home appliances, industrial products, etc.

  In the present invention configured as described above, the contact angle of the electrode with respect to the buffer solution is 80 ° or more and 120 ° or less, or the electrode material is made of a material having a regular fiber structure. It is possible to greatly improve the ease of penetration of the buffer solution into the interior.

  According to the present invention, a fuel cell capable of stably obtaining a high current value can be realized by greatly improving the ease of penetration of the buffer solution into the electrode. By using this excellent fuel cell, a high-performance electronic device can be realized.

1 is a schematic diagram showing a biofuel cell according to a first embodiment of the present invention. FIG. 2 is a schematic diagram schematically showing a configuration of a negative electrode of the biofuel cell according to the first embodiment of the present invention, an example of an enzyme group immobilized on the negative electrode, and an electron transfer reaction by the enzyme group. . It is a basic diagram which shows an example of the whole structure of the biofuel cell by 1st Embodiment of this invention. It is a basic diagram which shows the other example of the whole structure of the biofuel cell by 1st Embodiment of this invention. It is a drawing substitute photograph which shows the scanning electron microscope image of carbon silk (trademark). It is a drawing substitute photograph which shows the scanning electron microscope image of carbon felt. It is a drawing substitute photograph which shows the scanning electron microscope image of carbon paper. It is a basic diagram which shows the measurement system used for the measurement of the chronoamperometry performed for evaluation of the biofuel cell by 1st Embodiment of this invention. It is a basic diagram which shows the result of the chronoamperometry performed using the positive electrode which consists of an enzyme / electron mediator fixed electrode using the carbon silk (trademark) or carbon felt made water-repellent by the water repellent. Concentration of water repellent, current density, and buffer solution when chronoamperometry was performed using a positive electrode composed of an enzyme / electron mediator immobilized electrode using carbon silk (registered trademark) made water repellent with a water repellent. It is a basic diagram which shows the relationship with a contact angle. Relationship between buffer contact angle and current density when chronoamperometry is performed using a positive electrode composed of an enzyme / electron mediator-immobilized electrode using carbon silk (registered trademark) made water repellent with a water repellent. FIG. Concentration of water repellent, current density, and buffer contact angle when chronoamperometry was performed using a positive electrode composed of an enzyme / electron mediator-immobilized electrode using carbon felt made water repellent with water repellent. It is a basic diagram which shows a relationship. Outline line showing the relationship between the contact angle of the buffer solution and the current density when chronoamperometry is performed using a positive electrode composed of an enzyme / electron mediator-immobilized electrode using carbon felt made water-repellent with a water repellent. FIG. Concentration of water repellent, current density, and buffer contact angle when chronoamperometry was performed using a positive electrode composed of an enzyme / electron mediator-immobilized electrode made of carbon paper made water repellent with a water repellent. It is a basic diagram which shows a relationship. Outline line showing the relationship between the contact angle of the buffer solution and the current density when chronoamperometry was performed using a positive electrode composed of an enzyme / electron mediator-immobilized electrode using carbon paper made water-repellent with a water repellent. FIG. Current when chronoamperometry is performed using a positive electrode composed of an enzyme / electron mediator-immobilized electrode using carbon silk (registered trademark) with a porosity of carbon silk (registered trademark) and water repellency with a water repellent. It is a basic diagram which shows the relationship with a value. Current value when chronoamperometry was performed using a positive electrode consisting of an enzyme / electron mediator-immobilized electrode using seven types of carbon silk (registered trademark) with different porosity, which were made water repellent with a water repellent. FIG. It is a drawing substitute photograph which shows the scanning electron microscope image of four types of carbon silk (trademark) from which the porosity differs. The concentration and current value of the electron mediator in the positive electrode when chronoamperometry was performed using a positive electrode composed of an enzyme / electron mediator fixed electrode using carbon silk (registered trademark) made water repellent with a water repellent. It is a basic diagram which shows the relationship of these. It is a drawing substitute photograph which shows the scanning electron microscope image of the other example of carbon which has a regular fiber structure.

Hereinafter, modes for carrying out the invention (hereinafter referred to as “embodiments”) will be described. The description will be given in the following order.
1. First embodiment (biofuel cell)
2. Second embodiment (biofuel cell)

<1. First Embodiment>
[Bio fuel cell]
FIG. 1 schematically shows a biofuel cell according to a first embodiment. In this biofuel cell, glucose is used as a fuel. FIG. 2 schematically shows details of the configuration of the negative electrode of the biofuel cell, an example of an enzyme group immobilized on the negative electrode, and an electron transfer reaction by the enzyme group.

As shown in FIG. 1, this biofuel cell has a structure in which a negative electrode 1 and a positive electrode 2 face each other with an electrolyte layer 3 conducting only protons. The negative electrode 1 decomposes glucose supplied as fuel with an enzyme to extract electrons and generate protons (H ⁺ ). The positive electrode 2 generates water by protons transported from the negative electrode 1 through the electrolyte layer 3, electrons transmitted from the negative electrode 1 through an external circuit, and oxygen in the air, for example.

The negative electrode 1 is composed of, for example, an electrode 11 (see FIG. 2) made of porous carbon or the like, an enzyme involved in glucose decomposition, and a coenzyme in which a reductant is generated in an oxidation reaction in the glucose decomposition process (for example, , NAD ⁺ , NADP ^{+ and the} like), a coenzyme oxidase (eg, diaphorase) that oxidizes a reduced form of the coenzyme (eg, NADH, NADPH, etc.), and coenzyme oxidase is produced along with the oxidation of the coenzyme. An electron mediator that receives electrons and passes them to the electrode 11 is configured to be fixed by a fixing material made of, for example, a polymer.

  As an enzyme involved in the degradation of glucose, for example, glucose dehydrogenase (GDH) can be used. In the presence of this oxidase, for example, β-D-glucose can be oxidized to D-glucono-δ-lactone.

  Furthermore, this D-glucono-δ-lactone can be decomposed into 2-keto-6-phospho-D-gluconate by the presence of two enzymes, gluconokinase and phosphogluconate dehydrogenase (PhGDH). Can do. That is, D-glucono-δ-lactone is converted to D-gluconate by hydrolysis, and D-gluconate is converted to adenosine triphosphate (ATP) and adenosine diphosphate (ADP) in the presence of gluconokinase. And then phosphorylated to 6-phospho-D-gluconate. This 6-phospho-D-gluconate is oxidized to 2-keto-6-phospho-D-gluconate by the action of the oxidase PhGDH.

In addition to the above decomposition process, glucose can also be decomposed to CO ₂ by utilizing sugar metabolism. The decomposition process utilizing sugar metabolism is roughly divided into glucose decomposition and pyruvic acid generation by a glycolysis system and a TCA cycle, which are widely known reaction systems.

The oxidation reaction in the monosaccharide decomposition process is accompanied by a coenzyme reduction reaction. This coenzyme is almost determined by the acting enzyme. In the case of GDH, NAD ⁺ is used as the coenzyme. That is, when β-D-glucose is oxidized to D-glucono-δ-lactone by the action of GDH, NAD ⁺ is reduced to NADH to generate H ⁺ .

The produced NADH is immediately oxidized to NAD ⁺ in the presence of diaphorase (DI), generating two electrons and H ⁺ . Therefore, two electrons and two H ⁺ are generated by one-step oxidation reaction per glucose molecule. In the two-stage oxidation reaction, a total of four electrons and four H ⁺ are generated.

The electrons generated in the above process are transferred from diaphorase to the electrode 11 through the electron mediator, and H ⁺ is transported to the positive electrode 2 through the electrolyte layer 3.

  The electron mediator transfers electrons to and from the electrode 11, and the output voltage of the fuel cell depends on the redox potential of the electron mediator. That is, in order to obtain a higher output voltage, it is preferable to select an electron mediator having a more negative potential on the negative electrode 1 side. However, the reaction affinity of the electron mediator to the enzyme, the rate of electron exchange with the electrode 11, an inhibitor (light, Structural stability against oxygen) must also be considered. From such a viewpoint, 2-amino-3-carboxy-1,4-naphthoquinone (ACNQ), vitamin K3, and the like are preferable as the electron mediator acting on the negative electrode 1. In addition, for example, compounds having a quinone skeleton, metal complexes such as osmium (Os), ruthenium (Ru), iron (Fe), cobalt (Co), viologen compounds such as benzyl viologen, compounds having a nicotinamide structure, riboflavin structure A compound having a nucleotide, a compound having a nucleotide-phosphate structure, or the like can also be used as an electron mediator.

The electrolyte layer 3 is a proton conductor that transports H ⁺ generated in the negative electrode 1 to the positive electrode 2, and is made of a material that does not have electronic conductivity and can transport H ⁺ . As the electrolyte layer 3, for example, one appropriately selected from those already mentioned can be used. In this case, the electrolyte layer 3 preferably includes a buffer solution containing a compound having an imidazole ring as a buffer solution. The compound having an imidazole ring can be appropriately selected from those already mentioned, such as imidazole. The concentration of the compound having an imidazole ring as the buffer substance is selected as necessary, but it is preferably included at a concentration of 0.2 M or more and 3 M or less. By doing so, a high buffering capacity can be obtained, and the original ability of the enzyme can be fully exhibited even during high power operation of the fuel cell. Further, the ionic strength (IS) is too large or too small to adversely affect the enzyme activity, but considering the electrochemical response, it should be an appropriate ionic strength, for example, about 0.3. Is preferred. However, pH and ionic strength have optimum values for each enzyme used, and are not limited to the values described above. The buffer solution soaks not only in the electrolyte layer 3 but also in the negative electrode 1 and the positive electrode 2.

  The enzyme, coenzyme, and electron mediator are preferably immobilized on the electrode 11 using an immobilizing material in order to efficiently capture an enzyme reaction phenomenon occurring in the vicinity of the electrode as an electric signal. Furthermore, the enzyme reaction system of the negative electrode 1 can be stabilized by immobilizing the enzyme and the coenzyme for decomposing the fuel on the electrode 11. As such an immobilizing material, for example, a combination of glutaraldehyde (GA) and poly-L-lysine (PLL) or a combination of sodium polyacrylate (PAAcNa) and poly-L-lysine (PLL). These may be used, these may be used alone, or other polymers may be used. By using an immobilization material combining glutaraldehyde and poly-L-lysine, it becomes possible to greatly improve the enzyme immobilization ability of each, and to obtain an excellent enzyme immobilization ability as a whole immobilization material. Can do. In this case, the optimum composition ratio between glutaraldehyde and poly-L-lysine varies depending on the enzyme to be immobilized and the substrate of the enzyme, but generally an arbitrary composition ratio may be used. As a specific example, a glutaraldehyde aqueous solution (0.125%) and a poly-L-lysine aqueous solution (1%) are used, and the ratio thereof is 1: 1, 1: 2, 2: 1, or the like.

In FIG. 2, for example, glucose dehydrogenase (GDH) is an enzyme involved in the degradation of glucose, NAD ⁺ is a coenzyme that produces a reductant in the oxidation reaction in the glucose degradation process, and a reductant of coenzyme. The case where the coenzyme oxidase that oxidizes a certain NADH is diaphorase (DI), and the electron mediator that receives electrons from the coenzyme oxidase accompanying the oxidation of the coenzyme and passes it to the electrode 11 is ACNQ is shown.

The positive electrode 2 is composed of, for example, an electrode made of carbon or the like having a contact angle with respect to a buffer solution of 80 ° to 120 °, or an electrode made of a material such as carbon having a regular fiber structure. An electron mediator that transfers electrons between the two is fixed. Various carbons can be used as the carbon having a regular fiber structure, and are selected as necessary. As the oxygen reductase, for example, bilirubin oxidase (BOD), laccase, ascorbate oxidase and the like can be used. As the electron mediator, for example, hexacyanoferrate ions generated by ionization of potassium hexacyanoferrate can be used. This electron mediator is preferably immobilized at a sufficiently high concentration, for example, 0.64 × 10 ⁻⁶ mol / mm ² or more on average.

In the positive electrode 2, in the presence of oxygen reductase, oxygen in the air is reduced by H ⁺ from the electrolyte layer 3 and electrons from the negative electrode 1 to generate water.

When glucose is supplied to the negative electrode 1 side during operation (in use) of the fuel cell configured as described above, the glucose is decomposed by a decomposing enzyme including an oxidase. Since oxidase is involved in the monosaccharide decomposition process, electrons and H ⁺ can be generated on the negative electrode 1 side, and a current can be generated between the negative electrode 1 and the positive electrode 2.

  In this biofuel cell, at least a part, preferably most of the surface of the electrode used for the positive electrode 2 is water-repellent. Here, the surface of the electrode includes the entire outer surface of the electrode and the inner surface of the void inside the electrode. Specifically, for example, a water repellent material is formed by forming a water repellent material on at least a part of the surface of the electrode. In order to form this water-repellent material on the inner surface of the gap inside the electrode, the water-repellent material is in the form of fine particles (powder) sufficiently smaller than the size of the gap, and most of the space inside the gap is the water-repellent material. It is necessary not to be occupied by the material. Various materials can be used as the water-repellent material, and the water-repellent material is selected as necessary. For example, carbon particles such as graphite powder are preferably used. Thus, in order to form a water-repellent material on at least a part of the surface of the electrode, for example, a water-repellent agent in which the water-repellent material is dispersed in an organic solvent is applied to the surface of the electrode. After impregnating the electrode through the gap, the organic solvent is removed. When using such a water repellent, it is important not to inactivate the enzyme immobilized on the positive electrode 2, but the use of those already mentioned as the organic solvent prevents inactivation of the enzyme. be able to. In addition, it is desirable that the water-repellent electrode has a high hydrophilicity for an immobilizing substance such as an enzyme or an electron mediator for the electrode.

Two examples of the overall configuration of this biofuel cell are shown in FIGS.
The biofuel cell shown in FIG. 3 has a structure in which the negative electrode 1 and the positive electrode 2 face each other with the electrolyte layer 3 interposed therebetween, and air passes through the surface of the positive electrode 2 on the side opposite to the electrolyte layer 3. The solution 12 is affixed with a sheet 13 made of a material that does not permeate, the entire outer surface (upper surface and side surface) of the negative electrode 1, the side surface of the negative electrode 1, the positive electrode 2, and the portion of the electrolyte layer 3 protruding outside the positive electrode 2. The fuel solution 12 (the container for containing the fuel solution 12 is not shown) is in contact with the fuel solution 12. For example, a nonwoven fabric is used as the electrolyte layer 3, but is not limited thereto. Moreover, as the sheet | seat 13, although a PTFE (polytetrafluoroethylene) membrane is used, for example, it is not limited to this. In this biofuel cell, since the side surface of the positive electrode 2 and the fuel solution 12 are in contact with each other, water generated in the positive electrode 2 as the cell reaction proceeds passes through the side surface of the positive electrode 2 and the fuel solution. Therefore, the concentration of the fuel solution 12 can be kept almost constant.

  The biofuel cell shown in FIG. 4 has a structure in which the negative electrode 1 and the positive electrode 2 face each other with the electrolyte layer 3 interposed between the entire outer surface (upper surface and side surface) of the negative electrode 1 and the outside of the negative electrode 1 and the positive electrode 2. The fuel solution 12 (illustration of the container for the fuel solution 12 is omitted) is in contact with the protruding portion of the electrolyte layer 3. For example, cellophane is used as the electrolyte layer 3, but is not limited thereto.

The results of evaluating the positive electrode 2 by changing the electrode material will be described.
As the positive electrode 2, an enzyme / electron mediator fixed electrode prepared as follows was used. First, as a material having a regular fiber structure, carbon silk (registered trademark) manufactured by Shinano Kenshi Co., Ltd. was prepared, and the carbon silk was cut into 1 cm square. A scanning electron microscope image (magnification is 100 times) of this carbon silk is shown in FIG. Next, 80 μl of hexacyanoferrate ion (100 mM), 80 μl of poly-L-lysine (1 wt%), 80 μl of BOD solution (50 mg / ml) are sequentially infiltrated into the carbon silk and dried. Next, the carbon silk was dipped in a water repellent, and the water repellent was applied to the surface of the carbon silk. This water repellent contains 13 to 18% natural graphite as a water repellent material, 3 to 8% polyvinyl butyral as a binder, 8.4% carbon black, and 69.48% methyl isobutyl ketone as an organic solvent. It is. Thereafter, drying is performed to remove the organic solvent contained in the water repellent. Thus, graphite powder was formed as a water repellent material on the surface of the carbon silk to make it water repellent. The enzyme / electron mediator-immobilized electrode thus obtained has a thickness of 2 mm. Separately from this, a positive electrode 2 similar to that described above was produced except that carbon felt or carbon paper was used instead of carbon silk as the electrode material. FIG. 6 shows a scanning electron microscope image (magnification 100 times) of carbon felt, and FIG. 7 shows a scanning electron microscope image (magnification 100 times) of carbon paper (manufactured by Toray: model number TGP-H-090).

  In order to examine the influence of the above-mentioned water repellent on the enzyme immobilized on the positive electrode 2, ie, BOD, methyl isobutyl ketone, which is an organic solvent contained in this water repellent, and BOD solution (5 mg / ml 50 mM phosphate buffer solution) ) And the ABTS solution were confirmed to phase separate into methyl isobutyl ketone and water. In this case, it was confirmed that the activity of BOD was maintained. This is because BOD is not easily deactivated because it exists in the aqueous phase. Here, the solubility of methyl isobutyl ketone in water is 1.91 g / 100 mL.

  Further, when heptane, hexane, toluene, isooctane and diethyl ether were used as organic solvents, and these organic solvents, BOD solution and ABTS solution were mixed, it was confirmed that the phases were separated into these organic solvents and water. . Also in these cases, it was confirmed that the activity of BOD was maintained. Here, heptane, toluene and isooctane are insoluble in water, the solubility of hexane in water is 13 mg / L, and the solubility of diethyl ether in water is 6.9 g / 100 mL.

  On the other hand, when tetrahydrofuran (THF), acetone, ethanol, N, N-dimethylformamide (DMF) is used as the organic solvent and these organic solvent, BOD solution, and ABTS solution are mixed, these mixed solutions become cloudy. Was confirmed. This shows that BOD has denatured. That is, when these organic solvents are used, BOD is deactivated. Here, these tetrahydrofuran, acetone, ethanol and N, N-dimethylformamide are all miscible with water.

  The results of measuring the electrochemical characteristics of the positive electrode 2 composed of the enzyme / electron mediator immobilized electrode prepared as described above will be described. The measurement system used is shown in FIG. As shown in FIG. 8, the positive electrode 2 was used as a working electrode, this was placed on a gas-permeable PTFE membrane 14 and pressed, and the measurement was performed with the buffer solution 15 in contact with the positive electrode 2. The counter electrode 16 and the reference electrode 17 were immersed in the buffer solution 15, and an electrochemical measurement device (not shown) was connected to the positive electrode 2, the counter electrode 16, and the reference electrode 17 as working electrodes. Pt wire was used as the counter electrode 16 and Ag | AgCl was used as the reference electrode 17. The measurement was performed at atmospheric pressure, and the measurement temperature was 25 ° C. As the buffer solution 15, an imidazole / hydrochloric acid buffer solution (pH 7, 2.0M) was used. Chronoamperometry was performed for 300 seconds using the measurement system shown in FIG. As the positive electrode 2, an enzyme / electron mediator immobilized electrode using carbon silk having a thickness of 2 mm made water-repellent with a water repellent and an enzyme / electronic using a carbon felt having a thickness of 2 mm made water-repellent with a water repellent. A mediator immobilized electrode was used. The amount of the enzyme (BOD) immobilized on the carbon silk of the former enzyme / electron mediator immobilization electrode is 2 / of the amount of the BOD immobilized on the carbon felt of the latter enzyme / electron mediator immobilization electrode. 3. The measurement results are shown in FIG. From FIG. 9, when the positive electrode 2 composed of an enzyme / electron mediator-immobilized electrode using carbon silk made water-repellent with a water repellent is used, an enzyme / electron mediator using carbon felt having a water-repellent surface. It can be seen that the initial current density is greatly improved as compared with the case where the positive electrode 2 made of the fixed electrode is used. This proves the effectiveness of using carbon silk having a regular fiber structure as the electrode material of the positive electrode 2 and making the surface water-repellent.

  FIG. 10 shows the contact angle and current density of the buffer solution for the positive electrode 2 composed of an enzyme / electron mediator-immobilized electrode using carbon silk made water-repellent with a water-repellent agent while changing the concentration of the water-repellent agent. Results are shown. The concentration of the water repellent is 18% natural graphite as a water repellent material, 4.12% polyvinyl butyral as a binder, 8.4% carbon black, and 69.48% methyl isobutyl ketone as an organic solvent. This is the standard value when the concentration of graphite is 1. FIG. 11 is a plot of current density versus contact angle based on the results of FIG. FIG. 10 shows that a high current density can be obtained when the concentration of the water repellent is from 0.05 to 0.3. Further, from FIG. 11, a high current density is obtained when the contact angle is 80 ° or more and 120 ° or less, a higher current density is obtained when the contact angle is 90 ° or more and 120 ° or less, and a particularly high current density is obtained when the contact angle is 100 ° or more and 110 ° or less. You can see that

  FIG. 12 shows the contact angle and current density of the buffer solution for the positive electrode 2 composed of an enzyme / electron mediator-immobilized electrode using carbon felt made water-repellent with a water-repellent agent while changing the concentration of the water-repellent agent. Results are shown. The concentration of the water repellent is 18% natural graphite as a water repellent material, 4.12% polyvinyl butyral as a binder, 8.4% carbon black, and 69.48% methyl isobutyl ketone as an organic solvent. This is the standard value when the concentration of graphite is 1. FIG. 13 is a plot of current density versus contact angle based on the results of FIG. From FIG. 12, it can be seen that a high current density is obtained when the concentration of the water repellent is 0.16 or more and 1 or less. Further, FIG. 13 shows that a high current density is obtained when the contact angle is 80 ° or more and 120 ° or less, and a higher current density is obtained when the contact angle is 90 ° or more and 110 ° or less.

  FIG. 14 shows the contact angle and current density of the buffer solution for the positive electrode 2 composed of an enzyme / electron mediator-immobilized electrode using carbon paper made water-repellent with a water-repellent agent while changing the concentration of the water-repellent agent. Results are shown. The concentration of the water repellent is 18% natural graphite as a water repellent material, 4.12% polyvinyl butyral as a binder, 8.4% carbon black, and 69.48% methyl isobutyl ketone as an organic solvent. This is the standard value when the concentration of graphite is 1. FIG. 15 is a plot of current density versus contact angle based on the results of FIG. FIG. 14 shows that a high current density can be obtained when the concentration of the water repellent is 0.15 or more and 1 or less. From FIG. 15, a high current density is obtained when the contact angle is 80 ° or more and 120 ° or less, a higher current density is obtained when the contact angle is 90 ° or more and 120 ° or less, and a particularly high current density is obtained when the contact angle is 90 ° or more and 100 ° or less. It can be seen that

  FIG. 16 shows chronoamperometry measurements similar to those described above using seven types of carbon silk having different porosity, and the current values (relative values) after 300 seconds and 600 seconds are plotted against the porosity. Is. Carbon silk is manufactured by Shinano Kenshi Co., Ltd. Model No. WF-24-0007, WF-24-0008, WF-24-0009, WF-24-0010, WF-24-0011, WF-24-0017, WF-24- 0018. FIG. 17 is a bar graph showing the current value (relative value) after 300 seconds of FIG. FIG. 18 shows scanning electron micrographs (magnification 100 times) of WF-24-0007, WF-24-0008, WF-24-0009, and WF-24-0010. FIG. 18 shows the thickness of carbon silk fibers.

  From FIG. 17, a high current value is obtained when the porosity is 88% or more and 94% or less, a higher current value is obtained when the porosity is 89% or more and 93% or less, and a higher current value is obtained when the porosity is 90% or more and 92% or less. I understand that.

  Next, the chronoamperometry measurement similar to the above was performed by changing the concentration of the electron mediator in the positive electrode 2 composed of the enzyme / electron mediator fixed electrode using carbon silk (registered trademark) made water repellent with a water repellent. went. FIG. 19 is a plot of current values (relative values) after 300 seconds, 600 seconds and 3600 seconds against the concentration of the electron mediator in the positive electrode 2.

  FIG. 19 shows that the current value does not improve even when the concentration of the electron mediator in the positive electrode 2 is increased. In consideration of elution of the electron mediator from the positive electrode 2 and the like, the amount of the electron mediator is preferably as small as possible. Therefore, the concentration of the electron mediator is optimally 0.15 mol / l or more and 0.2 mol / l or less. It is believed that there is.

  As described above, according to the first embodiment, the contact angle of the electrode of the positive electrode 2 with respect to the buffer solution is 80 ° or more and 120 ° or less, or a regular fiber structure is used as the material of the electrode of the positive electrode 2. For example, carbon is used, and the surface of the electrode of the positive electrode 2 is made water repellent. For this reason, it is possible to greatly improve the ease of penetration of the buffer solution into the positive electrode 2, and thereby a high current value can be stably obtained. In addition, since the amount of enzyme immobilized on the electrode of the positive electrode 2 can be reduced, the cost of the biofuel cell can be reduced. In addition, when the electrolyte layer 3 contains an electrolytic solution containing a compound containing an imidazole ring as a buffer substance, a sufficient buffer capacity can be obtained. For this reason, at the time of high output operation of the biofuel cell, even if the increase or decrease of protons occurs in the proton electrode or in the enzyme immobilization membrane due to the proton-mediated enzyme reaction, sufficient buffer capacity can be obtained, Deviation from the optimum pH of the electrolyte surrounding the enzyme can be suppressed sufficiently small. For this reason, the ability inherent to the enzyme can be sufficiently exerted, and the electrode reaction by the enzyme, coenzyme, electron mediator and the like can be performed efficiently and constantly. As a result, a high-performance biofuel cell capable of high output operation can be realized. This biofuel cell is suitable for application to power sources of various electronic devices, mobile objects, power generation systems, and the like.

<2. Second Embodiment>
[Bio fuel cell]
In this biofuel cell, starch, which is a polysaccharide, is used as a fuel. In addition, with the use of starch as fuel, glucoamylase, which is a degrading enzyme that decomposes starch into glucose, is also immobilized on the negative electrode 11.

In this biofuel cell, when starch is supplied as fuel to the negative electrode 1 side, this starch is hydrolyzed into glucose by glucoamylase, and this glucose is further decomposed by glucose dehydrogenase, accompanied by an oxidation reaction in this decomposition process. NAD ⁺ is reduced to produce NADH, which is oxidized by diaphorase and separated into two electrons, NAD ⁺ and H ⁺ . Therefore, two electrons and two H ⁺ are generated by one-step oxidation reaction per molecule of glucose. In the two-stage oxidation reaction, a total of 4 electrons and 4 H ⁺ are generated. The electrons thus generated are transferred to the electrode 11 of the negative electrode 1, and H ⁺ moves to the positive electrode 2 through the electrolyte layer 3. In the positive electrode 2, this H ⁺ reacts with oxygen supplied from the outside and electrons sent from the negative electrode 1 through an external circuit to generate H ₂ O.
Other than the above, the biofuel cell according to the first embodiment is the same.

  According to the second embodiment, the same advantages as those of the first embodiment can be obtained, and since the starch is used as the fuel, the amount of power generation can be reduced as compared with the case where glucose is used as the fuel. The advantage that it can be increased can be obtained.

  Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

  For example, the numerical values, structures, configurations, shapes, materials, and the like given in the above-described embodiments are merely examples, and different numerical values, structures, configurations, shapes, materials, and the like may be used as necessary.

  Specifically, for example, as carbon having a regular fiber structure, regular carbon fiber (manufactured by Toho Tenax Co., Ltd.) as shown in FIG. 20 can also be used.

  DESCRIPTION OF SYMBOLS 1 ... Negative electrode, 2 ... Positive electrode, 3 ... Electrolyte layer, 11 ... Electrode

Claims (18)

Having a structure in which the positive electrode and the negative electrode are opposed to each other via a proton conductor;
A fuel cell comprising at least one of the positive electrode and the negative electrode comprising an electrode on which an enzyme is immobilized and a contact angle with respect to a buffer solution is 80 ° or more and 120 ° or less.   The fuel cell according to claim 1, wherein the electrode is made of carbon.   The fuel cell according to claim 2, wherein the electrode on which the enzyme is immobilized is a positive electrode.   The fuel cell according to claim 3, wherein the enzyme comprises an oxygen reductase.   The fuel cell according to claim 4, wherein water repellency is achieved by forming a water repellent on the surface of the electrode.   The fuel cell according to claim 5, wherein the water repellent contains at least a water repellent material and an organic solvent capable of phase separation with water.   When manufacturing a fuel cell having a structure in which a positive electrode and a negative electrode are opposed to each other via a proton conductor and at least one of the positive electrode and the negative electrode is an electrode on which an enzyme is immobilized, a buffer is used as the electrode. A fuel cell manufacturing method using an electrode having a contact angle with respect to a liquid of 80 ° or more and 120 ° or less. Using one or more fuel cells,
At least one of the fuel cells is
Having a structure in which the positive electrode and the negative electrode are opposed to each other via a proton conductor;
At least one of the positive electrode and the negative electrode is an electronic device that is a fuel cell including an electrode on which an enzyme is immobilized and a contact angle with respect to a buffer solution is 80 ° or more and 120 ° or less. Having a structure in which the positive electrode and the negative electrode are opposed to each other via a proton conductor;
A fuel cell in which at least one of the positive electrode and the negative electrode is composed of an electrode made of a material having a regular fiber structure to which an enzyme is immobilized.   The fuel cell according to claim 9, wherein the electrode is made of carbon.   The fuel cell according to claim 10, wherein the porosity of the carbon is 70% or more and 96% or less.   The fuel cell according to claim 11, wherein the electrode made of a material having a regular fiber structure to which the enzyme is immobilized is a positive electrode.   The fuel cell according to claim 12, wherein the enzyme comprises an oxygen reductase.   14. The fuel cell according to claim 13, wherein a water repellent is formed on the surface of the electrode to make it water repellent.   The fuel cell according to claim 14, wherein the water repellent contains at least a water repellent material and an organic solvent that is phase-separated from water.   When manufacturing a fuel cell having a structure in which a positive electrode and a negative electrode are opposed to each other via a proton conductor, and at least one of the positive electrode and the negative electrode is an electrode on which an enzyme is immobilized, the rule is used as the electrode. Of manufacturing a fuel cell using an electrode made of a material having a typical fiber structure.   The method for producing a fuel cell according to claim 16, wherein the electrode is made of carbon. Using one or more fuel cells,
At least one of the fuel cells is
Having a structure in which the positive electrode and the negative electrode are opposed to each other via a proton conductor;
At least one of the positive electrode and the negative electrode is an electronic device that is a fuel cell including an electrode made of a material having a regular fiber structure to which an enzyme is immobilized.

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