JP2009140781A - Fuel cell, its manufacturing method, enzyme-immobilized electrode, and its manufacturing method, as well as electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell and its manufacturing method wherein output is improved by optimization of a negative electrode structure. <P>SOLUTION: In the fuel cell having a structure in which a positive electrode 2 and a negative electrode 1 are opposed to each other via a proton conductor 3, and of which at least the negative electrode 1 is consisting of an enzyme-immobilized electrode 11, a porous electrode having at least one through-hole 12 or non-through-hole is used as the electrode 11. Enzyme, coenzyme, and an electronic mediator are immobilized on the electrode 11. The diameter of the through-hole 12 or the non-through-hole is set to 1 mm or less, and the spacing of the through-holes or the non-through-holes is set to 2 mm or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell, a method for producing the same, an enzyme-immobilized electrode, a method for producing the same, and an electronic device, and more particularly, to a biofuel cell using an enzyme and various electronic devices using the biofuel cell as a power source. Is preferred.

The fuel cell has a structure in which a positive electrode (oxidant electrode) and a negative electrode (fuel electrode) face each other with an electrolyte (proton conductor) interposed therebetween. In the conventional fuel cell, the fuel (hydrogen) supplied to the negative electrode is oxidized and separated into electrons and protons (H ⁺ ), the electrons are transferred to the negative electrode, and H ⁺ moves through the electrolyte to the positive electrode. In the positive electrode, this H ⁺ reacts with oxygen supplied from the outside and electrons sent from the negative electrode through the external circuit to generate H ₂ O.

  In this way, fuel cells are highly efficient power generators that directly convert the chemical energy of fuel into electrical energy, and the chemical energy of fossil energy such as natural gas, oil, and coal can be used regardless of where and when it is used. Moreover, it can be extracted as electric energy with high conversion efficiency. For this reason, research and development of fuel cells for large-scale power generation has been actively conducted. For example, a fuel cell is mounted on the space shuttle, and it has proven that it can supply water for crew members at the same time as electric power, and that it is a clean power generator.

Furthermore, in recent years, fuel cells having a relatively low operating temperature range from room temperature to about 90 ° C., such as solid polymer fuel cells, have been developed and attracting attention. For this reason, not only large-scale power generation applications but also applications to small systems such as automobile power supplies and portable power supplies such as personal computers and mobile devices are being sought.
Thus, the fuel cell can be used in a wide range of applications from large-scale power generation to small-scale power generation, and has attracted much attention as a highly efficient power generation device. However, in fuel cells, natural gas, petroleum, coal, etc. are usually used as fuel by converting them into hydrogen gas using a reformer, which consumes limited resources and needs to be heated to a high temperature. There are various problems such as the need for expensive noble metal catalysts such as (Pt). Even when hydrogen gas or methanol is used directly as a fuel, care must be taken when handling it.

Accordingly, attention has been paid to the fact that biological metabolism performed in living organisms is a highly efficient energy conversion mechanism, and proposals have been made to apply this to fuel cells. The biological metabolism here includes respiration, photosynthesis and the like performed in microbial somatic cells. Biological metabolism has the characteristics that the power generation efficiency is extremely high and the reaction proceeds under mild conditions of about room temperature.
For example, respiration takes nutrients such as sugars, fats, and proteins into microorganisms or cells, and these chemical energies are converted into carbon dioxide (glycolytic and citrate (TCA) circuits through multiple enzymatic reaction steps and carbon dioxide (TCA) circuit. In the process of generating CO ₂ ), nicotinamide adenine dinucleotide (NAD ⁺ ) is reduced to reduced nicotinamide adenine dinucleotide (NADH) to convert it into redox energy, that is, electric energy, and further, an electron transfer system In this mechanism, the electric energy of NADH is directly converted into electric energy of proton gradient, and oxygen is reduced to generate water. The electrical energy obtained here produces ATP from adenosine diphosphate (ADP) via adenosine triphosphate (ATP) synthase, and this ATP is used for reactions necessary for the growth of microorganisms and cells. Used. Such energy conversion occurs in the cytosol and mitochondria.

In addition, photosynthesis captures light energy and reduces nicotinamide adenine dinucleotide phosphate (NADP ⁺ ) via an electron transfer system to reduce nicotinamide adenine dinucleotide phosphate (NADPH), thereby converting it into electrical energy. In the process of conversion, it is a mechanism that oxidizes water to produce oxygen. This electric energy takes in CO ₂ and is used for carbon fixation reaction, and is used for carbohydrate synthesis.
As a technique for utilizing the above-described biometabolism for a fuel cell, a microbial cell that obtains an electric current by taking out the electric energy generated in the microorganism through the electron mediator and passing the electrons to the electrode has been reported. (For example, refer to Patent Document 1).

However, since microorganisms and cells have many unnecessary reactions in addition to the intended reaction such as conversion from chemical energy to electrical energy, the above method consumes chemical energy for unwanted reactions, resulting in sufficient energy conversion efficiency. Is not demonstrated.
Then, the fuel cell (biofuel cell) which performs only a desired reaction using an enzyme is proposed (for example, refer patent documents 2-11). In this biofuel cell, fuel is decomposed by an enzyme and separated into protons and electrons. As fuel, alcohols such as methanol and ethanol, monosaccharides such as glucose, or polysaccharides such as starch are used. Things are being developed.
In this biofuel cell, a porous carbon electrode is generally used as a negative electrode to which fuel is supplied.

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

In the above-described biofuel cell, efforts have been made to improve the output. However, at present, the output is not always sufficient, and it is desired to further improve the output.
Accordingly, the problem to be solved by the present invention is a fuel cell capable of improving output by optimizing the structure of the negative electrode, a method for producing the same, an enzyme-immobilized electrode suitable for use in the negative electrode of the fuel cell, and A manufacturing method and an electronic device using the fuel cell are provided.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have made through-holes or non-through holes in porous electrodes such as porous carbon electrodes as electrodes for immobilizing enzymes in the negative electrode of a biofuel cell. As a result of finding that it is extremely effective to use a hole provided, and confirming its effectiveness through experiments, and conducting various studies based on this knowledge, the present invention has been devised. is there.

That is, in order to solve the above problem, the first invention
A fuel cell having a structure in which a positive electrode and a negative electrode are opposed to each other via a proton conductor, wherein at least the negative electrode is an electrode on which an enzyme is immobilized;
The electrode is a porous electrode having at least one through hole or non-through hole.

The second invention is
A method for producing a fuel cell having a structure in which a positive electrode and a negative electrode face each other via a proton conductor, wherein at least the negative electrode is an electrode on which an enzyme is immobilized,
It has the process of forming the said electrode which consists of a porous electrode which has an at least 1 through-hole or a non-through-hole.

  In the first and second inventions, the through hole is a hole penetrating from one surface of the porous electrode to the other surface, and the non-through hole is formed on one surface of the porous electrode, It is a hole that does not penetrate through the surface. The non-through hole may be formed on one surface of the porous electrode, may be formed on the other surface, or may be formed on both surfaces. The planar shape and cross-sectional shape of the through-hole or non-through-hole are not particularly limited and are appropriately selected. Examples of the planar shape include a circle, an ellipse, a polygon (triangle, quadrangle (square, rectangle), pentagon, six A square, a rectangle, a trapezoid, etc., a shape obtained by deforming all or a part thereof, or a combination of these shapes. Different shapes can be used. The porous electrode typically has a plurality of through holes or non-through holes separated from each other, and these through holes and non-through holes may be mixed. The plurality of through holes or non-through holes are typically provided in a two-dimensional array (for example, a square lattice, a rectangular lattice, a hexagonal lattice, etc.), but are not limited thereto. Generally, it can arrange | position regularly or irregularly in the arbitrary parts of a porous electrode. The diameter of the through hole or non-through hole (when the planar shape of the through hole or non-through hole is a circle, the diameter of the through hole or other shape means the maximum dimension of the planar shape) and the interval (pitch) are appropriately selected The diameter and / or spacing may vary depending on the location of the porous electrode, but is generally on the order of millimeters or submillimeters, and preferably the diameter is 1 mm or less, for example 0.4 mm or more and 1 mm or less, The interval is 2 mm or less. A porous carbon electrode is typically used as the porous electrode, but is not limited thereto. The thickness of the porous electrode is appropriately selected. Regardless of the method of forming this porous electrode, a through hole or a non-through hole may be formed in a plate-like porous electrode by a conventionally known method, or a porous material having a through hole or a non-through hole by an injection molding method. A quality electrode may be formed directly.

  Similarly to the negative electrode, the positive electrode may be formed of an electrode on which an enzyme is immobilized, and a porous electrode having at least one through hole or non-through hole may be used as this electrode. Various materials can be used as the electrode material of the positive electrode. For example, carbon-based materials such as porous carbon, carbon pellets, carbon felt, and carbon paper are used. Preferably, an electron mediator is also immobilized on the positive electrode and / or the negative electrode in addition to the enzyme, and further, a coenzyme is also immobilized on the positive electrode and / or the negative electrode, if necessary, in addition to the enzyme and the electron mediator.

  As an immobilizing material for immobilizing an enzyme or the like on the positive electrode and / or the negative electrode, basically any material may be used, and a conventionally known material such as a polyion complex may be used. As the polyion complex, conventionally known ones can be used, and are selected as necessary. For example, polycations such as poly-L-lysine (PLL) or salts thereof and polyacrylic acid (for example, poly A polyion complex formed using a polyanion such as sodium acrylate (PAAcNa)) or a salt thereof can be used.

Various fuels can be used, and are selected as necessary. Typical examples include methanol, ethanol, monosaccharides, polysaccharides, fats, and the like. When monosaccharides, polysaccharides and the like are used as fuel, they are typically used in the form of a fuel solution in which these are dissolved in a conventionally known buffer solution such as a phosphate buffer or a Tris buffer.
For example, when a monosaccharide such as glucose is used as the fuel, preferably, in the enzyme-immobilized electrode used as the negative electrode, as the enzyme, an oxidase that promotes and decomposes the oxidation of the monosaccharide and a reduction by the oxidase And the coenzyme oxidase that returns the coenzyme to the oxidized form is immobilized. 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 an oxidase, nicotinamide adenine dinucleotide (NAD ⁺ ) or nicotinamide adenine dinucleotide phosphate (NADP ⁺ ) is used as a coenzyme, and coenzyme oxidase is used as a coenzyme oxidase. For example, diaphorase (DI) is used.

  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 , 4-naphthoquinone (AMNQ), 2-methyl-1,4-naphthoquinone (VK3), 2-amino-3-carboxy-1,4-naphthoquinone (ACNQ), vitamin K1, 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.

  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 degrading monosaccharides, polysaccharides that can be decomposed 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.

  In a fuel cell using cellulase as a degrading enzyme and glucose dehydrogenase as an oxidase, cellulose that can be decomposed into glucose by cellulase can be used as a fuel. More specifically, the cellulase may be any of cellulase (EC 3.2.1.4), exocellobiohydrase (EC 3.2.1.91), β-glucosidase (EC 3.2.1.21) and the like. Or at least one kind. In addition, glucoamylase and cellulase may be mixed and used as the degrading enzyme. In this case, most of the polysaccharides produced in nature can be decomposed, so those containing a large amount of these, for example, garbage Etc. can be used as fuel.

In a fuel cell using α-glucosidase as a degrading enzyme and glucose dehydrogenase as an oxidase, maltose that is decomposed into glucose by α-glucosidase can be used as a fuel.
In a fuel cell using sucrose as a decomposing enzyme and glucose dehydrogenase as an oxidase, sucrose that is decomposed into glucose and fructose by sucrose can be used as a fuel. More specifically, sucrase is α-glucosidase (EC 3.2.1.20), sucrose-α-glucosidase (EC 3.2.1.48), β-fructofuranosidase (EC 3.2.1. 26) or the like.
In a fuel cell using β-galactosidase as a degrading enzyme and glucose dehydrogenase as an oxidase, lactose that is decomposed into glucose and galactose by β-galactosidase can be used as a fuel.
If necessary, these polysaccharides serving as fuel may also be immobilized on the negative electrode.

  In particular, in a fuel cell using starch as a fuel, a gelatinized solid fuel obtained by gelatinizing starch can also be used. In this case, the gelatinized starch can be brought into contact with a negative electrode on which an enzyme or the like is immobilized, or can be 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 in a mobile device.

In one example, the negative electrode is 2-methyl-1,4-naphthoquinone (VK3) as an electron mediator, reduced nicotinamide adenine dinucleotide (NADH) as a coenzyme, glucose dehydrogenase and coenzyme oxidase as oxidases The diaphorase as is immobilized, and preferably 1.0 (mol): 0.33-1.0 (mol): (1.8-3.6) × 10 ⁶ (U): (0. It is fixed at a ratio of 85 to 1.7) × 10 ⁷ (U). However, U (unit) is an index indicating enzyme activity, and indicates the degree to which 1 μmol of substrate reacts per minute at a certain temperature and pH.

On the other hand, when an enzyme is immobilized on the positive electrode, this enzyme typically contains 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 or potassium octacyanotungstate is 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.

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

When an electrolyte containing a buffer substance (buffer solution) is used as the proton conductor, sufficient buffer capacity can be obtained during high output operation, and the ability inherent to the enzyme can be fully demonstrated. Therefore, it is effective that the concentration of the buffer substance contained in the electrolyte 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, More preferably, it is 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. The pH of the electrolyte containing the buffer substance is preferably around 7, but may generally be any of 1-14.

  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 units, 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.

The third invention is
An enzyme-immobilized electrode comprising an enzyme-immobilized electrode,
The electrode is a porous electrode having at least one through hole or non-through hole.
The fourth invention is:
A method for producing an enzyme-immobilized electrode comprising an electrode on which an enzyme is immobilized,
It has the process of forming the said electrode which consists of a porous electrode which has an at least 1 through-hole or a non-through-hole.
In the third and fourth inventions, what has been described in relation to the first and second inventions holds true for matters other than those described above.

The fifth invention is:
In an electronic device using one or more fuel cells,
At least one of the fuel cells is
A fuel cell having a structure in which a positive electrode and a negative electrode are opposed to each other via a proton conductor, wherein at least the negative electrode is an electrode on which an enzyme is immobilized;
The electrode is made of a porous electrode having at least one through hole or non-through hole.

Electronic devices may be basically any type, and include both portable and stationary devices. Specific examples include cell phones, mobile devices (portable information terminals). (PDA, etc.), robots, personal computers (including both desktop and notebook computers), game machines, camera-integrated VTRs (video tape recorders), in-vehicle devices, home appliances, industrial products, and the like.
In the fifth invention, what has been described in relation to the first and second inventions holds true for matters other than those described above.

  In the present invention configured as described above, by using a porous electrode having at least one through hole or non-through hole as a negative electrode, fuel supplied to the negative electrode is added to the outer surface of the porous electrode. Since the inner surface of the through hole or the non-through hole is also contacted, the contact area of the fuel with respect to the porous electrode can be increased as compared with the case where the through hole or the non-through hole is not provided. For this reason, the fuel in contact with the porous electrode is efficiently transported to the inside through the void inside the porous electrode, so that the fuel easily spreads over the entire porous electrode. That is, when the porous electrode has through holes or non-through holes, diffusion of fuel supplied to the negative electrode into the porous electrode is promoted. As a result, the fuel is efficiently supplied to the vicinity of the enzyme immobilized on the entire surface of the porous electrode including the surface of the void inside the porous electrode, and the fuel is decomposed by the catalytic reaction by the enzyme. Is promoted. In particular, when the material supply (fuel supply) to the negative electrode is ruled in the battery reaction, in other words, when the enzyme-catalyzed reaction at the negative electrode is dominant, a porous electrode having a through hole or a non-through hole is used for the negative electrode. Is valid. In general, when the concentration of the fuel increases, the viscosity increases and the fuel does not easily permeate into the porous electrode. Therefore, the substance supply rule tends to be stronger, but the porous electrode having a through hole or a non-through hole. By using for the negative electrode, the influence of the viscosity of the fuel can be avoided.

  According to this invention, the output of the fuel cell can be improved by optimizing the structure of the negative electrode. By using such a high-output fuel cell, a high-performance electronic device or the like can be realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the embodiments, the same or corresponding parts are denoted by the same reference numerals.
FIG. 1 schematically shows a biofuel cell according to a first embodiment of the present invention. In this biofuel cell, glucose is used as the 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 a proton conductor 3 interposed therebetween. 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 from protons transported from the negative electrode 1 through the proton conductor 3, electrons sent from the negative electrode 1 through an external circuit, and oxygen in the air, for example.

The negative electrode 1 is an electrode 11 (see FIG. 2) made of, for example, plate-like porous carbon, and an enzyme that participates in glucose decomposition and a supplement that generates a reductant in the oxidation reaction in the glucose decomposition process. Receiving an enzyme (for example, NAD ⁺ ), a coenzyme oxidase (for example, diaphorase) that oxidizes a reduced form of the coenzyme (for example, NADH), and an electron generated from the coenzyme oxidase with the oxidation of the coenzyme An electron mediator (for example, ACNQ) to be passed to the electrode 11 is fixed. A conventionally known fixing material can be used for this fixing.

3A and B show the detailed structure of the electrode 11. Here, FIG. 3A is a perspective view, and FIG. 3B is a cross-sectional view taken along line BB in FIG. 3A. As shown in FIGS. 3A and 3B, the electrode 11 has through holes 12 arranged at equal intervals in a two-dimensional array in two directions orthogonal to each other. The planar shape of the electrode 11 is appropriately selected, but FIG. 3 shows a case of a square as an example. Moreover, although the planar shape of the through hole 12 is selected as appropriate, FIG. 3 shows a circular case as an example. Furthermore, although the cross-sectional shape of the through hole 12 is appropriately selected, FIG. 3 shows a rectangular case as an example. The diameter of the through hole 12 is preferably 1 mm or less (for example, 0.4 to 1.0 mm) and the interval is 2 mm or less, but is not limited thereto. Here, when the diameter of the through-hole 12 is small, if the interval is large, the total area of the through-hole 12 decreases, and it becomes difficult to sufficiently increase the fuel transportation efficiency. It is desirable to reduce the interval within a range in which the above can be maintained.
4A, B, C, and D show specific examples of the through holes 12 of the electrode 11. The diameter and interval of the through holes 12 of each electrode 11 are 0.4 mm in diameter and 0.8 mm in the electrode 11 shown in FIG. 4A, 0.7 mm in diameter and 1.4 mm in the electrode 11 shown in FIG. The electrode 11 shown has a diameter of 1.0 mm and a spacing of 2.0 mm, and the electrode 11 shown in FIG. 4D has a diameter of 1.3 mm and a spacing of 2.0 mm. The electrode 11 has a 1 cm × 1 cm square shape.

As an enzyme involved in the degradation of glucose, for example, glucose dehydrogenase (GDH), preferably NAD-dependent glucose dehydrogenase 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 from adenosine triphosphate (ATP) to adenosine diphosphate (ADP) and phosphate 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.
Electrons generated in the above process are transferred from diaphorase to the electrode 11 via the electron mediator, and H ⁺ is transported to the positive electrode 2 through the proton conductor 3.

The above enzyme, coenzyme, and electron mediator use an electrolyte layer containing a buffer solution such as a phosphate buffer solution or a Tris buffer solution as the proton conductor 3 in order to perform the electrode reaction efficiently and constantly. The buffer solution is preferably maintained at an optimum pH for the enzyme, for example, around pH 7. As the phosphate buffer, for example, NaH ₂ PO ₄ or KH ₂ PO ₄ is used. Furthermore, the ionic strength (I.S.) is too large or too small to adversely affect the enzyme activity. However, considering the electrochemical responsiveness, it is preferably an appropriate ionic strength. However, pH and ionic strength have optimum values for each enzyme used, and are not limited to the values described above.

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 obtained by immobilizing an oxygen reductase that decomposes oxygen, such as bilirubin oxidase, laccase, and ascorbate oxidase, on a porous carbon electrode. The outer part of the positive electrode 2 (the part opposite to the proton conductor 3) is usually formed by a gas diffusion layer made of porous carbon. Preferably, in addition to the above oxygen reductase, an electron mediator that transfers electrons to and from the positive electrode 2 is also immobilized on the positive electrode 2.
In the positive electrode 2, in the presence of the oxygen reductase, oxygen in the air is reduced by H ⁺ from the proton conductor 3 and electrons from the negative electrode 1 to generate water.

The proton conductor 3 is for transporting H ⁺ generated in the negative electrode 1 to the positive electrode 2 and is made of a material that does not have electron conductivity and can transport H ⁺ . As the proton conductor 3, for example, those already mentioned can be used.
In the biofuel cell configured as described above, when glucose is supplied to the negative electrode 1, the glucose is decomposed by a degrading enzyme containing 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.

Next, a specific structural example of the biofuel cell will be described.
As shown in FIGS. 5A and 5B, this biofuel cell has a configuration in which a negative electrode 1 and a positive electrode 2 face each other with a proton conductor 3 interposed therebetween. In this case, Ti current collectors 21 and 22 are placed under the positive electrode 2 and the negative electrode 1, respectively, so that current collection can be performed easily. Reference numerals 23 and 24 denote fixed plates. The fixing plates 23 and 24 are fastened to each other by screws 25, and the positive electrode 2, the negative electrode 1, the proton conductor 3 (cellophane or the like), and the Ti current collectors 21 and 22 are sandwiched therebetween. . One surface (outer surface) of the fixing plate 23 is provided with a circular recess 23a for taking in air, and a plurality of holes 23b penetrating to the other surface are provided on the bottom surface of the recess 23a. These holes 23 b serve as air supply paths to the positive electrode 2. On the other hand, a circular recess 24a for fuel loading is provided on one surface (outer surface) of the fixing plate 24, and a number of holes 24b penetrating to the other surface are provided on the bottom surface of the recess 24a. These holes 24 b serve as fuel supply paths to the negative electrode 1. A spacer 26 is provided in the periphery of the other surface of the fixing plate 24, and when the fixing plates 23 and 24 are fastened to each other with screws 25, the interval between them is set to a predetermined interval. .
As shown in FIG. 5B, a load 27 is connected between the Ti current collectors 21 and 22, and electricity is generated by putting, for example, a glucose solution in which glucose is dissolved in a phosphate buffer into the concave portion 24 a of the fixing plate 24. .

As shown in FIG. 4B, an enzyme-immobilized electrode was prepared using an electrode 11 having a size of 1 cm × 1 cm in which through holes 12 having a diameter of 0.7 mm were arranged in a two-dimensional array at intervals of 1.4 mm. On this electrode 11, GDH and DI as enzymes, NADH as a coenzyme, and ANQ as an electron mediator were immobilized. Apart from this enzyme-immobilized electrode, enzyme-immobilized electrodes differing only in that the electrode 11 does not have the through hole 12 were produced.
The enzyme, coenzyme and electron mediator were immobilized on these enzyme-immobilized electrodes as follows.
First, various solutions were prepared as follows. As a buffer solution for preparing the solution, a 100 mM sodium dihydrogen phosphate (NaH ₂ PO ₄ ) buffer solution (IS = 0.3, pH = 7.0) was used.

GDH / DI enzyme buffer solution ((1))
10 to 100 mg of DI (EC 1.6.99, manufactured by Amano Enzyme) was weighed and dissolved in 0.2 mL of the above buffer solution (solution (1) ′). The buffer solution for dissolving the enzyme is preferably refrigerated at 8 ° C. or lower until immediately before, and the enzyme buffer solution is preferably refrigerated at 8 ° C. or lower as much as possible. 5-30 mg of GDH (NAD-dependent, EC 1.1.1.17, Amano Enzyme) was weighed and dissolved in 0.3 mL of the above buffer solution. 20 μL of the solution (1) ′ was added to this solution and mixed well to obtain a GDH / DI enzyme buffer solution ((1)).

-NADH buffer solution ((2))
50-100 mg of NADH (manufactured by Sigma Aldrich, N-8129) was weighed and dissolved in 0.1 mL of buffer solution to obtain NADH buffer solution ((2)).
・ ANQ acetone solution ((3))
50-100 mg of 2-amino-1,4-naphthoquinone (ANQ) (synthetic product) was weighed and dissolved in 1 mL of an acetone solution to obtain an ANQ acetone solution ((3)).
・ PLL aqueous solution ((4))
An appropriate amount of poly-L-lysine hydrobromide (PLL) (manufactured by Wako, 164-16961) was weighed and dissolved in ion-exchanged water so as to be 2 wt% to obtain a PLL aqueous solution ((4)).
-PAAcNa aqueous solution ((5))
Sodium polyacrylate (PAAcNa) (manufactured by Aldrich, 041-00595) was weighed in an appropriate amount and dissolved in ion-exchanged water so as to be 0.022 wt% to obtain a PAAcNa aqueous solution ((5)).

The solutions (1) to (3) prepared as described above were mixed at a ratio of GDH / DI enzyme buffer solution (1): NADH buffer solution (2): ANQ acetone solution (3) = 4: 1: 10. Then, the volume of the mixed solution is changed to five levels of 25 μL, 50 μL, 75 μL, 100 μL, and 125 μL, and these mixed solutions are applied onto the above-described electrode 11 using a microsyringe, followed by drying as appropriate, and enzyme / complements. An enzyme / electron mediator-coated electrode was prepared.
After applying the following amounts of PLL aqueous solution (4) and PAAcNa aqueous solution (5) on the above enzyme / coenzyme / electron mediator-coated electrode, drying was performed as appropriate to prepare an enzyme / coenzyme / electron mediator immobilized electrode. .
PLL aqueous solution (4): 10 μL (total mass of PLL is 0.2 mg and mass per unit area is 7.1 × 10 ⁻³ mg / mm ² )
PAAcNa aqueous solution (5): 12 μL (total mass of PAAcNa is 0.003 mg and mass per unit area is 1.1 × 10 ⁻⁴ mg / mm ² )

Electrochemical measurement was performed in a glucose solution using these enzyme-immobilized electrodes. The glucose concentration was 400 mM. The measurement result of the current after 1 hour (3600 seconds) is shown in FIG. As shown in FIG. 6, the enzyme-immobilized electrode using the electrode 11 having the through hole 12 has a larger current density than the enzyme-immobilized electrode using the electrode 11 not having the through hole 12.
In addition, using these enzyme-immobilized electrodes, chronoamperometry was performed by setting the reference electrode Ag | AgCl to 0.1 V, which is sufficiently higher than the redox potential of the electron mediator. As the measurement solution, a solution in which glucose of fuel was dissolved in 2M imidazole buffer (pH 7.0) so as to have concentrations of 200 mM, 400 mM, 600 mM, and 800 mM was used. Table 1 shows the results of measuring the current density after 600 seconds and 3600 seconds of chronoamperometry. However, Table 1 shows the current density as a ratio.

  As can be seen from Table 1, the current density maintenance rate after 1 hour is high even when the fuel with any glucose concentration is used, especially when the glucose concentration is as high as 400 mM, 600 mM, and 800 mM. It is extremely high as 80% or more. In this way, when the glucose concentration is high, the viscosity of the measurement solution becomes considerably high, but a high current density maintenance rate can be obtained because the electrode 11 has the through hole 12. This is probably because the measurement solution is efficiently transported into the electrode 11 through the inner surface of 12.

  The method of forming the electrode 11 having the through hole 12 is not limited. For example, various well-known hole forming methods (mechanical processing, electric discharge processing, etching method, laser processing method, etc.) for the electrode 11 having no through hole 12 are available. Or by direct injection molding. 7A and 7B show a method of forming the electrode 11 having the through hole 12 by an injection molding method. In this method, as shown in FIG. 7A, first, a pair of molds 31 and 32 for forming the electrode 11 are prepared. The mold 31 is provided with a protrusion 31 a having the same shape as the through hole 12 at a portion corresponding to the through hole 12 of the electrode 11. Next, a material for forming the electrode 11 is introduced into a hopper (material input port) of a molding machine (not shown), and the material is melted by passing through a cylinder (heating cylinder) heated by a heater. Next, as shown in FIG. 7B, the melted material 33 is injected into the space between the molds 31 and 32 through the injection hole 32a of the mold 32 from the nozzle at the tip of the cylinder. Next, the injected material 33 is cooled while being placed in the space between the molds 31 and 32. After the material 33 is hardened in this way, the molds 31 and 32 are separated from each other. Thereafter, the molded product is removed from the mold 31. Thus, the electrode 11 having the through hole 12 is formed.

  As described above, according to the first embodiment, the negative electrode 1 is made of a porous material such as porous carbon, and the enzyme, coenzyme, and electron mediator are immobilized on the electrode 11 having the through hole 12. Since the glucose solution supplied as fuel to the negative electrode 1 is in contact with the inner surface of the through hole 12 in addition to the outer surface of the electrode 11, the electrode solution is compared with a case where the through hole 12 is not provided. The contact area of the glucose solution with respect to 11 can be increased. For this reason, the glucose solution in contact with the electrode 11 is efficiently transported into the inside of the electrode 11 through the void inside the electrode 11, so that the glucose solution is easily spread over the entire electrode 11. That is, since the electrode 11 has the through hole 12, the diffusion of the glucose solution supplied to the negative electrode 1 into the electrode 11 is promoted. As a result, glucose is efficiently supplied in the vicinity of the enzyme immobilized on the entire surface of the electrode 11 including the surface of the void inside the electrode 11, and the decomposition of glucose is promoted by the catalytic reaction of the enzyme. Is done. Further, when the concentration of the glucose solution is increased, the viscosity is increased and the glucose solution is less likely to penetrate into the electrode 11, so that the substance supply rule tends to be stronger. By using for the negative electrode 1, the influence of the viscosity of a glucose solution can be avoided and a high concentration glucose solution can be used for a fuel. As described above, it is possible to increase the output of the biofuel cell.

Next explained is a biofuel cell according to the second embodiment of the invention.
In this biofuel cell, starch, which is a polysaccharide, is used as a fuel. In addition, with the use of starch as a fuel, glucoamylase, which is a degrading enzyme that decomposes starch into glucose, is also immobilized on the negative electrode 1.
In this biofuel cell, when starch is supplied to the negative electrode 1 as fuel, this starch is hydrolyzed into glucose by glucoamylase, and this glucose is further decomposed by glucose dehydrogenase, which accompanies the 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 the amount of power generation can be increased by using starch as the fuel, compared with the case where glucose is used as the fuel. The advantage that it can be obtained.

Next explained is a biofuel cell according to the third embodiment of the invention.
In this biofuel cell, the enzyme-immobilized electrode shown in FIG. As shown in FIG. 8, in this enzyme-immobilized electrode, a phospholipid bilayer membrane 41 is physically provided on an electrode 11 having a through hole 12 (not shown in FIG. 8) similar to that in the first embodiment. Immobilized by adsorption. Two types of enzymes 42 and 43 are immobilized on the phospholipid bilayer membrane 41 via anchors 44. Here, a case where two types of enzymes 42 and 43 are immobilized will be described, but the same applies when three or more types of enzymes are immobilized. For example, a polyethylene glycol chain can be used as the anchor 44, but the anchor 44 is not limited thereto. In addition to these enzymes 42 and 43, an electron mediator 45 is also immobilized on the phospholipid bilayer membrane 41.
This enzyme-immobilized electrode can be prepared, for example, by dropping or applying a mixture of phospholipid, enzymes 42 and 43 and electron mediator 45 on electrode 11 and then drying it.
The biofuel cell other than the above is the same as the biofuel cell according to the first embodiment.

<Example 1>
Proteins are generally classified into three types: membrane proteins distributed in cell membranes, water-soluble proteins distributed in extracellular and intracellular solutions, and membrane-bound proteins existing in contact with cell membranes. The Of these, membrane proteins and membrane-bound proteins can be easily introduced into liposomes. On the other hand, some of the proteins used for biofuel are often distributed in intracellular and extracellular solutions, and have relatively few fat-soluble sites.

  On the other hand, spherical liposomes in the form of phospholipid bilayers are well known as phospholipid aggregates. Membranes constituting a living body are mostly made of liposomes, which are aggregates of these phospholipids, and are very good reaction fields for stably maintaining enzymes and proteins, particularly membrane proteins, with high activity. Therefore, in Example 1, first, a fat-soluble site is introduced into the two types of enzymes 42 and 43, and this is introduced into a liposome which is a thermodynamically stable phospholipid assembly. Specifically, diaphorase and glucose dehydrogenase, which are generally water-soluble, are used as the enzymes 42 and 43, and fat-soluble sites are chemically introduced into these to distribute the liposomes in any amount and in any proportion. I made it. The compound used to chemically introduce a fat-soluble site into diaphorase and glucose dehydrogenase (manufactured by NOF Corporation, trade name SUNBRIGHT OE-040CS) is a phospholipid membrane and a site for covalently binding these diaphorase and glucose dehydrogenase. It consists of an oleoyl group, which is a site to be introduced into the chain, and a polyethylene glycol chain connecting these two. This compound was prepared with reference to literature.

Liposomes can have different sizes and shapes depending on the production method. Here, liposomes were produced by an ultrasonic treatment method. As the type of phospholipid, Egg yolk-derived phospholipid was used.
Proteoliposomes in which diaphorase and glucose dehydrogenase are arranged in liposomes are prepared by mixing the liposomes prepared as described above with diaphorase and glucose dehydrogenase into which a lipophilic site is chemically introduced and the electron mediator 45 at the same time. It went by leaving it for a while. In order to observe introduction of these diaphorases and glucose dehydrogenases into liposomes, fluorescent substances are labeled on these diaphorases and glucose dehydrogenases, and water-soluble diaphorases and glucose dehydrogenases having chemically lipophilic sites are attached to the liposomes. As a result of examining whether it was introduced, it was confirmed that both were introduced. A schematic diagram of this proteoliposome is shown in FIG. Reference numeral 46 indicates a liposome.

  By dropping the proteoliposome prepared as described above onto the substrate 11, the liposome can be immobilized. Although it depends on the form of the liposome, it is known that a phospholipid monomolecular film is formed on a water-repellent substrate and a phospholipid bimolecular film is formed on a hydrophilic substrate. In Example 1, a porous carbon electrode that was previously hydrophilized by ozone treatment was used as the substrate 11.

  According to the third embodiment, the phospholipid bilayer membrane 41 is immobilized on the electrode 11 having the through hole 12, and two kinds of enzymes 42 and 43 and an electron mediator 45 are attached to the phospholipid bilayer membrane 41. Since the immobilized enzyme-immobilized electrode is used as the negative electrode 1, in addition to the same advantages as those of the first embodiment, these two types of enzymes 42 and 43 are stably fixed at an optimum ratio at an optimum position. Therefore, a biofuel cell with higher efficiency and higher output can be obtained.

Next explained is a biofuel cell according to the fourth embodiment of the invention.
In this biofuel cell, the enzyme-immobilized electrode shown in FIG. As shown in FIG. 10, in this enzyme-immobilized electrode, an intermediate layer 47 made of protein or the like is formed on the electrode 11 having the same through-hole 12 (not shown in FIG. 10) as in the first embodiment. The phospholipid bilayer film 41 is immobilized on the intermediate layer 47 by physical adsorption or the like. Two types of enzymes 42 and 43 are immobilized on the phospholipid bilayer membrane 41. In addition to these enzymes 42 and 43, an electron mediator 45 is also immobilized on the phospholipid bilayer membrane 41.
In this enzyme-immobilized electrode, for example, the intermediate layer 47 is formed by immersing the electrode 11 in a solution containing protein or the like, and a mixture of the phospholipid, the enzymes 42 and 43, and the electron mediator 45 is formed thereon. It can be prepared by dripping or applying and then drying.
The biofuel cell other than the above is the same as the biofuel cell according to the first embodiment.

<Example 2>
A porous carbon electrode is used as the electrode 11, and this porous carbon electrode is activated by an ultraviolet (UV) ozone treatment apparatus to make the surface hydrophilic, and then the enzyme is phosphate buffer solution of about 500 μg / mL to 5 mg / mL. And soaked overnight. Then, the porous carbon electrode which has an enzyme as the intermediate | middle layer 47 was obtained by wash | cleaning with a phosphate buffer and drying.

Next, liposomes containing ANQ as the electron mediator 45, diaphorase and glucose dehydrogenase as the enzymes 42 and 43, and NADH as the coenzyme are added dropwise to the porous carbon electrode having the enzyme as the intermediate layer 47, and then dried to fix the enzyme. An electrode was prepared.
According to the fourth embodiment, the same advantages as those of the third embodiment can be obtained.

Next explained is a biofuel cell according to the fifth embodiment of the invention.
In this biofuel cell, the enzyme-immobilized electrode shown in FIG. As shown in FIG. 11, in this enzyme-immobilized electrode, an intermediate layer 47 made of protein or the like is fixed on the electrode 11 made of porous carbon or the like by physical adsorption or the like. The complex 48 is fixed. Two types of enzymes 42 and 43 are immobilized on the polyion complex 48. In addition to these enzymes 42 and 43, an electron mediator 45 is also immobilized on the polyion complex 48.
In this enzyme-immobilized electrode, for example, the electrode 11 is immersed in a solution containing protein or the like to form the intermediate layer 47, and the polycation and polyanion, the enzymes 42 and 43, and the electron mediator 45 are mixed thereon. It can be prepared by dripping or applying a thing and then drying it.
The biofuel cell other than the above is the same as the biofuel cell according to the first embodiment.

<Example 3>
A porous carbon electrode is used as the electrode 11, and this porous carbon electrode is activated by an ultraviolet (UV) ozone treatment apparatus to make the surface hydrophilic, and then the enzyme is phosphate buffer solution of about 500 μg / mL to 5 mg / mL. And soaked overnight. Then, the porous carbon electrode which has an enzyme as the intermediate | middle layer 47 was obtained by wash | cleaning with a phosphate buffer and drying.

Next, on the porous carbon electrode having an enzyme as the intermediate layer 47, ANQ as the electron mediator 45, diaphorase and glucose dehydrogenase as the enzymes 42 and 43, NADH as the coenzyme, PLL as the polycation, PLL as the polyanion, as the polycation A solution containing PAAcNa was added dropwise and dried to prepare an enzyme-immobilized electrode.
According to the fifth embodiment, advantages similar to those of the first embodiment can be obtained.

Next explained is a biofuel cell according to the sixth embodiment of the invention.
In this biofuel cell, the enzyme-immobilized electrode shown in FIG. As shown in FIG. 12, in this enzyme-immobilized electrode, an intermediate layer 47 made of albumin is fixed on the electrode 11 made of porous carbon or the like by physical adsorption or the like. A molecule 49 having a soluble functional group is covalently bonded, and a polyion complex 48 in which two kinds of enzymes 42 and 43 are immobilized is immobilized using the molecule 49 as an anchor. In addition to these enzymes 42 and 43, an electron mediator 45 is also immobilized on the polyion complex 48.
In this enzyme-immobilized electrode, for example, the intermediate layer 47 is formed by immersing the electrode 11 in a solution containing albumin, the molecule 49 is covalently bonded to the intermediate layer 47, and a polycation, polyanion and enzyme are formed thereon. It can be prepared by dripping or applying a mixture of 42 and 43 and the electron mediator 45 and then drying.
The biofuel cell other than the above is the same as the biofuel cell according to the first embodiment.

<Example 4>
After activating the porous carbon electrode with a UV ozone treatment apparatus to make the surface hydrophilic, the albumin solution (derived from bovine) (phosphate buffer) adjusted to a concentration of about 1% was left overnight at room temperature. Thereafter, the porous carbon electrode was washed with a phosphate buffer and dried to prepare an electrode 11 having albumin as the intermediate layer 47. Further, a molecule 49 having a fatty group and capable of covalently binding to a compound having an amino group such as a protein was allowed to act on the electrode 11 having the intermediate layer 47. Actually, the product name SUNBRIGHT OE-040CS manufactured by NOF Corporation was used as the molecule 49 and dissolved in a dimethyl sulfoxide (DMSO) solution, and then 100 μL of this was deposited on the electrode 11 having albumin as the intermediate layer 47. Dropped and left for 1 hour. Thereafter, this was washed with a phosphate buffer and used as an immobilizing electrode.

  Next, a polyion complex method, which is a method for producing a conventional electrode film, was applied to the porous carbon electrode whose surface was hydrophilized by a UV ozone treatment apparatus and the above-described immobilizing electrode. According to the sixth embodiment, the same advantages as those of the first embodiment can be obtained.

As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, The various deformation | transformation based on the technical idea of this invention is 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.

1 is a schematic diagram showing a biofuel cell according to a first embodiment of the present invention. It is a basic diagram which shows typically the detail of a structure of the negative electrode of the biofuel cell by 1st Embodiment of this invention, an example of the enzyme group fix | immobilized by this negative electrode, and the electron transfer reaction by this enzyme group. It is the perspective view and sectional drawing which show the electrode which has a through-hole used for the negative electrode in the biofuel cell by 1st Embodiment of this invention. It is a top view which shows the specific example of the electrode which has a through-hole used for a negative electrode in the biofuel cell by 1st Embodiment of this invention. It is a basic diagram which shows the specific structural example of the biofuel cell by 1st Embodiment of this invention. It is a basic diagram which shows the result of the electrochemical measurement by the monopolar performed for evaluation of the biofuel cell by 1st Embodiment of this invention. It is sectional drawing which shows an example of the formation method of the electrode which has a through-hole used for the negative electrode of the biofuel cell by 1st Embodiment of this invention. It is a basic diagram which shows the enzyme fixed electrode used as a negative electrode in the biofuel cell by the 3rd Embodiment of this invention. It is a basic diagram which shows the liposome used in Example 1 of this invention. It is a basic diagram which shows the enzyme fixed electrode used as a negative electrode in the biofuel cell by the 4th Embodiment of this invention. It is a basic diagram which shows the enzyme fixed electrode used as a negative electrode in the biofuel cell by the 5th Embodiment of this invention. It is a basic diagram which shows the enzyme fixed electrode used as a negative electrode in the biofuel cell by the 6th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Negative electrode, 2 ... Positive electrode, 3 ... Proton conductor, 11 ... Electrode, 21, 22 ... Ti current collector, 23, 24 ... Fixing plate, 27 ... Load, 41 ... Phospholipid bilayer, 42, 43 ... Enzyme, 44 ... anchor, 45 ... electron mediator, 46 ... liposome, 47 ... intermediate layer, 48 ... polyion complex, 49 ... molecule

Claims (11)

A fuel cell having a structure in which a positive electrode and a negative electrode are opposed to each other via a proton conductor, wherein at least the negative electrode is an electrode on which an enzyme is immobilized;
The fuel cell, wherein the electrode comprises a porous electrode having at least one through hole or non-through hole.   2. The fuel cell according to claim 1, wherein the porous electrode has a plurality of the through holes or the non-through holes separated from each other.   The fuel cell according to claim 2, wherein the diameter of the through hole or the non-through hole is 1 mm or less.   4. The fuel cell according to claim 3, wherein the interval between the through holes or the non-through holes is 2 mm or less.   The fuel cell according to claim 4, wherein the plurality of through holes or the non-through holes are provided in a two-dimensional array.   6. The fuel cell according to claim 5, wherein the porous electrode is a porous carbon electrode. A method for producing a fuel cell having a structure in which a positive electrode and a negative electrode face each other via a proton conductor, wherein at least the negative electrode is an electrode on which an enzyme is immobilized,
A method for producing a fuel cell, comprising the step of forming the electrode comprising a porous electrode having at least one through hole or non-through hole.   8. The method of manufacturing a fuel cell according to claim 7, wherein the porous electrode is formed by an injection molding method. An enzyme-immobilized electrode comprising an enzyme-immobilized electrode,
The enzyme-immobilized electrode, wherein the electrode comprises a porous electrode having at least one through hole or non-through hole. A method for producing an enzyme-immobilized electrode comprising an electrode on which an enzyme is immobilized,
A method for producing an enzyme-immobilized electrode, comprising the step of forming the electrode comprising a porous electrode having at least one through hole or non-through hole. In an electronic device using one or more fuel cells,
At least one of the fuel cells is
A fuel cell having a structure in which a positive electrode and a negative electrode are opposed to each other via a proton conductor, wherein at least the negative electrode is an electrode on which an enzyme is immobilized;
An electronic apparatus, wherein the electrode is a porous electrode having at least one through hole or non-through hole.

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