JP2011204420A - Biofuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biofuel cell system, capable of obtaining desired battery performance by preventing of failures or output deterioration of a battery due to supply of inappropriate liquid, by automatic determining the degree of adaptation of liquid supplied by a user as a fuel solution.SOLUTION: The biofuel cell system is provided with an inlet 5 for leading-in a liquid from the outside; a cell electrode 4 as a reacting field of redox reaction of fuel by using oxidoreductase as catalyst; and a control means (a controller 3, a switching valve 6 and a sensor electrode 7) for automatically determining the degree of adaptation of liquid as fuel solution and controlling supplying of the liquid to the cell electrode.

Description

  The present invention relates to a biofuel cell system. More specifically, the present invention relates to a biofuel cell system including a mechanism for automatically determining the suitability of a liquid supplied from the outside as a fuel solution and controlling the supply to an electrode.

  In recent years, biofuel cells in which an oxidoreductase is immobilized as a catalyst on at least one of an anode and a cathode have been developed. In a biofuel cell, a high capacity can be obtained by efficiently extracting electrons from a fuel that is difficult to react with normal industrial catalysts such as glucose and ethanol. For this reason, in the biofuel cell, it is also possible to use a liquid such as a beverage containing glucose or ethanol as the fuel solution. For example, Patent Literature 1 discloses a power supply device including a fuel cell unit that uses beverage as fuel.

JP 2009-048858 A

  If a liquid such as a commercially available beverage containing glucose or ethanol can be used as a fuel solution for a biofuel cell, it is expected that the problem of fuel procurement, which is a problem of the fuel cell, can be solved. However, liquids that may contain glucose, ethanol, and the like include many types of beverages and liquids other than beverages, and naturally these include those that are suitable as fuel solutions for biofuel cells and those that are not suitable.

  Therefore, if a biofuel cell user uses an inappropriate liquid as a fuel solution, the redox enzyme immobilized on the electrode is deactivated and the cell does not function, or the fuel redox It is conceivable that the expected battery performance may not be obtained due to low reaction efficiency.

  Therefore, the present invention can automatically determine the suitability of a user-supplied liquid as a fuel solution to prevent battery failure and output reduction due to improper liquid supply and obtain desired battery performance. The main purpose is to provide a biofuel cell system.

In order to solve the above problems, the present invention provides an inlet for introducing a liquid from the outside, a battery electrode serving as a reaction field for a redox reaction of a fuel using an oxidoreductase as a catalyst, and a suitability as a liquid fuel solution A biofuel cell system and a biofuel cell, comprising: a control unit that automatically determines whether the liquid is supplied to the battery electrode.
In this biofuel cell system or the like, the control means can contact the liquid between the switching valve disposed in the liquid supply path from the inlet to the battery electrode and between the inlet and the switching valve. And a sensor electrode on which the oxidoreductase is immobilized, and based on the current value measured at the sensor electrode in contact with the liquid, the suitability of the liquid as a fuel solution is automatically determined, When it is determined that the fuel solution is appropriate, the switching valve is opened to supply the liquid to the battery electrode, and when it is determined to be inappropriate, the switching valve is closed to stop supplying the liquid to the battery electrode. can do.
By automatically determining the suitability of the liquid supplied from the outside as a fuel solution and controlling the supply of the liquid to the battery electrode, it is possible to prevent a failure or a decrease in output due to an inappropriate supply of liquid.
In this biofuel cell system or the like, it is preferable that the oxidoreductase on the battery electrode and the sensor electrode are the same enzyme.
Further, the sensor electrode comprises a sensor electrode positive electrode having the same enzyme as the oxidoreductase on the battery electrode positive electrode constituting the battery electrode, and an enzyme identical to the oxidoreductase on the battery electrode negative electrode constituting the battery electrode. Preferably, the counter electrode is composed of a sensor electrode negative electrode.
Battery performance when the externally supplied liquid is used as a fuel solution by making the oxidoreductase on the sensor electrode the same as the enzyme on the battery electrode and / or by using the sensor electrode as the counter electrode. Can be accurately determined to control the supply of the liquid to the battery electrode.

  According to the present invention, it is possible to automatically determine the suitability of a liquid supplied by a user as a fuel solution as a fuel, prevent a battery failure or a decrease in output due to an inappropriate liquid supply, and obtain a desired battery performance. A biofuel cell system is provided.

It is a figure explaining the internal structure of the biofuel cell system which concerns on this invention. It is a figure explaining the functional structure of the biofuel cell system which concerns on this invention.

Hereinafter, preferred embodiments for carrying out the present invention will be described. In addition, embodiment described below shows an example of typical embodiment of this invention, and, thereby, the range of this invention is not interpreted narrowly. The description will be given in the following order.

1. 1. Internal configuration of biofuel cell system (1) Overall configuration (2) Battery unit (3) Controller Functional configuration of biofuel cell system (1) Output detection unit (2) Control unit (3) Display unit (4) Specific examples of suitability as a fuel solution

1. Internal Configuration of Biofuel Cell System (1) Overall Configuration FIG. 1 is a diagram illustrating an internal configuration of a biofuel cell system according to the present invention. In the figure, the biofuel cell system denoted by reference numeral 1 is generally composed of a battery unit 2 and a controller 3. In the following, the configuration of the biofuel cell system will be described, but the biofuel cell according to the present invention has the same configuration.

(2) Battery Unit The battery unit 2 has a battery electrode 4 that serves as a reaction field for the oxidation-reduction reaction of fuel using an oxidoreductase as a catalyst, and an inlet 5 through which a liquid (fuel solution) is introduced from the outside. is doing. A liquid supplied as a fuel solution from the outside to the biofuel cell system 1 is injected into the introduction port 5, flows through a supply path indicated by a block arrow in the figure, and is supplied to the battery electrode 4, and redox on the battery electrode 4. It is subjected to an oxidation-reduction reaction using an enzyme as a catalyst.

[Fuel solution]
The fuel solution introduced into the introduction port 5 is preferably a liquid that can be used as a fuel for a biofuel cell and contains one or more substances that can serve as a substrate for the oxidoreductase on the battery electrode 4. Examples of substances that can be used as fuel include sugars, alcohols, aldehydes, lipids, and proteins. Specific examples include sugars such as glucose, fructose, and sorbose, alcohols such as methanol, ethanol, propanol, glycerin, and polyvinyl alcohol, aldehydes such as formaldehyde and acetaldehyde, and organic acids such as acetic acid, formic acid, and pyruvic acid. It is done. In addition, fats and proteins, organic acids that are intermediate products of these sugar metabolisms, and the like can be mentioned.

[Battery electrode]
The battery electrode 4 includes a fuel electrode (negative electrode) that extracts electrons by an oxidation reaction of the above-described substances and an air electrode (positive electrode) that performs a reduction reaction of oxygen supplied from the outside. The material of the negative electrode (anode) and the positive electrode (cathode) is not particularly limited as long as it is a material that can be electrically connected to the outside. For example, Pt, Ag, Au, Ru, Rh, Os, Nb, Mo, In, Ir, Zn, Mn, Fe, Co, Ti, V, Cr, Pd, Re, Ta, W, Zr, Ge, Hf and other metals, alumel, brass, duralumin, bronze, nickel, platinum rhodium, hyperco, permalloy, permendur, German silver, an alloy such as phosphor bronze, conductive polymers such as polyacetylenes, graphite, carbon materials such as carbon black, HfB _2, NbB, borides such as _{CrB 2, B 4 C, TiN} , such as ZrN _{nitrides, VSi 2, NbSi 2, MoSi} 2, silicides such as TaSi _2, and these can be used mixed material, or the like.

[Current collector]
The anode and the cathode are formed of the same material as the electrode, and are connected to an anode current collector and a cathode current collector for sending electrons emitted from the anode to the cathode via an external circuit.

[Proton conductor]
The anode and the cathode are disposed via a proton conductor (not shown). The material used for the proton conductor is not particularly limited as long as the electrolyte has no electronic conductivity and can transport H ⁺ , and any known material can be selected and used.

For the proton conductor, for example, an electrolyte containing a buffer substance can be used. Examples of buffer substances include sodium dihydrogen phosphate (NaH ₂ PO ₄ ), potassium dihydrogen phosphate (KH ₂ PO ₄ ), and the like, and dihydrogen phosphate ions (H ₂ PO ₄ —), 2-amino-2. -Hydroxymethyl-1,3-propanediol (abbreviation Tris), 2- (N-morpholino) ethanesulfonic acid (MES), cacodylic acid, carbonic acid (H ₂ CO ₃ ), hydrogen citrate ion, 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-hydroxyethyl Perazine-N′-3-propanesulfonic acid (HEPPS), N- [tris (hydroxymethyl) methyl] glycine (abbreviation tricine), glycylglycine, N, N-bis (2-hydroxyethyl) glycine (abbreviation bicine) Imidazole, triazole, pyridine derivative, bipyridine derivative, imidazole derivative (histidine, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, imidazole-2-carboxylate, 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-mercaptobenzimidazole, benzimidazole, 1-benzylimidazole And compounds containing an imidazole ring such as 1-butylimidazole). Moreover, Nafion etc. which are solid electrolytes can also be used.

[Anode enzymes]
The oxidase on the anode of the battery electrode 4 is an enzyme that catalyzes the oxidation reaction of the above-described substances and extracts electrons.
Examples of such enzymes include glucose dehydrogenase, gluconate 5 dehydrogenase, gluconate 2 dehydrogenase, alcohol dehydrogenase, aldehyde reductase, aldehyde dehydrogenase, lactate dehydrogenase, hydroxy parvate reductase, glycerate dehydrogenase, formate dehydrogenase, fructose dehydrogenase, galactose dehydrogenase, malic acid Dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, sucrose dehydrogenase, fructose dehydrogenase, sorbose dehydrogenase, pyruvate dehydrogenase, isosylate dehydrogenase, 2-oxoglutarate dehydrogenase, succinate dehydrogenase Examples include hydrogenase, malate dehydrogenase, acyl-CoA dehydrogenase, L-3-hydroxyacyl-CoA dehydrogenase, 3-hydroxypropionate dehydrogenase, and 3-hydroxybutyrate dehydrogenase.

  In addition to the above oxidase, an oxidized coenzyme and a coenzyme oxidase may be fixed to the anode. Examples of the oxidized coenzyme include nicotinamide adenine dinucleotide (nicotinamide adenine dinucleotide, hereinafter referred to as “NAD +”), nicotinamide adenine dinucleotide phosphate (hereinafter referred to as “NADP +”), and flavin adenine dinucleotide. And nucleotides (flavin adenine dinucleotide, hereinafter referred to as “FAD +”), pyrrolo-quinoline quinone (hereinafter referred to as “PQQ2 +”), and the like. Examples of the coenzyme oxidase include diaphorase.

  Furthermore, in addition to the above oxidase and oxidized coenzyme, an electron transfer mediator may be fixed to the anode. This is for smooth delivery of the generated electrons to the electrodes. Although various materials can be used as the electron transfer mediator, it is preferable to use a compound having a quinone skeleton or a compound having a ferrocene skeleton, and the compound having a quinone skeleton particularly has a naphthoquinone skeleton or an anthraquinone skeleton. Compounds are preferred. Furthermore, if necessary, together with a compound having a quinone skeleton or a compound having a ferrocene skeleton, one or more other compounds acting as an electron transfer mediator may be used in combination.

Specific examples of the compound having a naphthoquinone skeleton include, for example, 2-amino-1,4-naphthoquinone (ANQ), 2-amino-3-methyl-1,4-naphthoquinone (AMNQ), 2-amino- 3-carboxy-1,4-naphthoquinone (ACNQ), 2,3-diamino-1,4-naphthoquinone, 4-amino-1,2-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, 2-methyl-3 - hydroxy-1,4-naphthoquinone, vitamin _{K 1 (2-methyl-3} -phyty1,4-naphthoquinone), vitamin _{K 2 (2-farnesyl-3} -methyl-1,4-naphtoquinone), vitamin _{K 3} (2 -methy 1,4-naphthoquinone), etc. can be used. Further, as the compound having a quinone skeleton, for example, a compound having an anthraquinone skeleton such as anthraquinone-1-sulfonate, anthraquinone-2-sulfonate, or a derivative thereof can be used. Examples of the compound having a ferrocene skeleton include vinyl ferrocene, dimethylaminomethyl ferrocene, 1,1′-bis (diphenylphosphino) ferrocene, dimethyl ferrocene, and ferrocene monocarboxylic acid. Furthermore, as other compounds, for example, ruthenium (Ru), cobalt (Co), manganese (Mn), molybdenum (Mo), chromium (Cr), osmium (Os), iron (Fe), cobalt (Co), etc. Metal complexes, viologen compounds such as benzyl viologen, compounds having a nicotinamide structure, compounds having a riboflavin structure, compounds having a nucleotide-phosphate structure, and the like can be used. More specific examples include, for example, cis- [Ru (NH ₃ ) _{4 Cl 2} ] ^{1 + / 0} , trans- [Ru (NH ₃ ) _{4 Cl 2} ] ^{1 + / 0} , [Co (dien) ₂ ] ^{3 + / 2 +} , [Mn (CN) ₆ ] ^3-4- , [Mn (CN) ₆ ] ^{4- / 5-} , [Mo ₂ O ₃ S (edta)] ^{2- / 3-} , [ Mo ₂ O ₂ S ₂ (edta)] ^{2- / 3-} , [Mo ₂ O ₄ (edta)] ^{2- / 3-} , [Cr (edta) (H ₂ O)] ^{1- / 2-} , [Cr (CN) ₆ ] 3- / 4-, methylene blue, pycocyanine, indigo-tetrasulfonate, luciferin, gallocyanine, pyocyanine, methyl apri blue, resorufin, indigo-trisulfonate, 6,8,9-trimethyl-isoalloxazine, chloraphine, indigo disulfonate , Nile blue, indigocarmine, 9-phenyl-isoalloxazine, thioglycolic acid, 2-amino-N-methyl phenazinemethosulfate, azure A, indigo-monosulfonate, anthraquinone-1,5-disulfonate, alloxazine, brilliant alizarin blue, crystal violet, patent blue , 9-methyl-isoalloxazine, cibachron blue, phenol red, anthraquinone-2,6-disulfonate, neutral blue, bromphenol blue, anthraquinone-2,7-disulfonate, quinoline yellow, riboflavin, Flavin mononucleotide (FMN), fl avin adenine dinucleotide (FAD), phenosafranin, lipoamide, safranine T, lipoic acid, indulin scarlet, 4-aminoacridine, acridine, nicotinamide adenine dinucleotide (NAD), nicotinamide adenine dinucleotide phosphate (NADP), neutral red, cysteine, benzyl viologen (2 + / 1+), 3-aminoacridine, 1-aminoacridine, methyl viologen (2 + / 1 +), 2-aminoacridine, 2,8-diaminoacridine, 5-aminoacridine and the like can be used. In the chemical formula, dien represents diethylenetriamine and edta represents ethylenediaminetetraacetate tetraanione.

[Cathode enzymes]
The enzyme on the cathode of the battery electrode 4 is an enzyme that catalyzes the reduction reaction of oxygen supplied from the outside.
Examples of such enzymes include enzymes having oxidase activity using oxygen as a reaction substrate, and examples thereof include laccase, bilirubin oxidase, ascorbate oxidase, CueO, and CotA.

  In addition to the above enzyme, an electron transfer mediator may be fixed to the cathode. This is for smooth reception of electrons sent from the anode. The electron transfer mediator that can be fixed to the cathode only needs to have a higher oxidation-reduction potential than the electron transfer mediator used for the anode, and can be freely selected as necessary.

Specific examples include ABTS (2,2′-azinobis (3-ethylbenzoline-6-sulfonate)), K ₃ [Fe (CN) ₆ ], RuO ₄ ^{0 / 1-} , [Os (trpy) ₃ ] ^{3 + / 2 +} , [Rh (CN) ₆ ] ^{3- / 4-} , [Os (trpy) (dpy) (py)] ^{3 + / 2 +} , IrCl ₆ ^{2- / 3-} , [Ru (CN) ₆ ] ^{3- / 4-} , OsCl ₆ ^{2- / 3-} , [Os (py) ₂ (dpy) ₂ ] ^{3 + / 2 +} , [Os (dpy) ₃ ] ^{3 + / 2 +} , Cu ^{III / II} ( H ₂ A ₃ ) ^{0 / 1-} , [Os (dpy) (py) ₄ ] ^{3 + / 2 +} , IrBr ₆ ^{2- / 3-} , [Os (trpy) (py) ₃ ] ^{3 + / 2 +} , [Mo (CN) ₈ ] ^{3- / 4-} , [Fe (dpy)] ^{3 + / 2 +} , [Mo (CN) ₈ ] ^{3- / 4-} , Cu ^{III / II} (H ₂ G ₃ a) ^{0 / 1-} , [Os (4,4'-Me2-dpy) ₃ ] ^{3 + / 2 +} , [Os (CN) ₆ ] ^{3- / 4-} , RuO ₄ ^{1- / 2-} , [Co (ox) ₃ ] ^{3- / 4-} , [Os (trpy) (dpy) Cl] ^{2 + / 1 +} , I _3- / I-, [W (CN) ₈ ] ^{3- / 4-} , [Os (2-Me -Im) ₂ (dpy) ₂ ] ^{3 + / 2 +} , ferrocene carboxylic acid, [Os (Im) ₂ (dpy) ₂ ] ^{3 + / 2 +} , [Os (4-Me-Im) ₂ (dpy) ₂ ] ^{3 + / 2 +} , OsBr ₆ ^{2- / 3-} , [Fe (CN) ₆ ] ^{3- / 4-} , ferrocene ethanol, [Os (Im) ₂ (4,4'-Me ₂ -dpy) ₂ ] ^{3 + / 2 +} , [Co (edta)] ^{1- / 2-} , [Co (pdta)] ^{1- / 2-} , [Co (cydta)] ^{1- / 2-} , [Co (phen) ₃ ] ^{3 + / 2 +} , [OsCl (1-Me-Im) (dpy) ₂ ] ^{3 + / 2 +} , [OsCl (Im) (dpy) ₂ ] ^{3 + / 2 +} , [C o (5-Me-phen) ₃ ] ^{3 + / 2 +} , [Co (trdta)] ^{1- / 2-} , [Ru (NH ₃ ) ₅ (py)] ^{3 + / 2 +} , [Co (dpy) ₃ ] ^{2 + / 3 +} , [Ru (NH ₃ ) ₅ (4-thmpy)] ^{3 + / 2 +} , Fe ^{3 + / 2 +} , malonate, Fe ^{3 + / 2 +} , salycylate, [Ru (NH ₃ ) ₅ (4-Me-py)] ^{3 + / 2 +} , [Co (trpy) ₂ ] ^{3 + / 2 +} , [Co (4-Me-phen) ₃ ] ^{3 + / 2 +} , [Co (5 -NH ₂ -phen) ₃ ] ^{3 + / 2 +} , [Co (4,7- (bhm) ₂ phen) ^{3 + / 2 +} , [Co (5,6-Me4-phen) ₃ ] ^{3 + / 2 +} , Trans (N)-[Co (gly) ₃ ] ^{0 / 1-} , [OsCl (1-Me-Im) (4,4'-Me2-dpy) ₂ ] ^{3 + / 2 +} , [OsCl (Im ) (4,4'-Me ₂ -dpy) ₂ ] ^{3 + / 2 +} , [Fe (edta)] ^{1- / 2-} , [Co (4,7-Me ₂ -phen) ₃ ] ^{3 + / 2 +} , [Co (4,7-Me ₂ -phen) ₃ ] ^{3 + / 2 +} , [Co (3,4,7,8-Me4-phen) ₃ ] ^{3 + / 2 +} , [Co (NH3) ₆ ] ^{3 + / 2 +} , [Ru (NH ₃ ) ₆ ] ^{3 + / 2 +} , [Fe (ox) ₃ ] ^{3- / 4-} , promazine (n = 1) [ammonium form], chloramine-T, TMPDA (N, N, N ', N'-tetramethylphenylenediamine), porphyrexide, syringaldazine, o-tolidine, bacteriochlorophyll a, dopamine, 2,5-dihydroxy-1,4-benzoquinone, p-amino-dimethylaniline, o-quinone / 1,2-hydroxybenzene (catechol), p-aminophenoltetrahydroxy-p-benzoquinone, 2,5-dichloro-p-benzoquinone , 1,4-benzoquinone, diaminodurene, 2,5-dihydroxyphenylacetic acid, 2,6,2'-trichloroindophenol, indophenol, o-toluidine blue, DCPIP (2,6-dichlorophenolindophenol), 2,6-dibromo-indophenol, phenol blue, 3-amino-thiazine, 1,2-napthoquinone-4-sulfonate, 2,6-dimethyl-p-benzoquinone, 2,6-dibromo-2'-methoxy-indophenol, 2,3-dimethoxy-5-methyl -1,4-benzoquinone, 2,5-dimethyl-p-benzoquinone, 1,4-dihydoxy-naphthoic acid, 2,6-dimethyl-indophenol, 5-isopropyl-2-methyl-p-benzoquinone, 1,2- naphthoquinone, 1-naphthol-2-sulfonate indophenol, toluylene blue, TTQ (tryptophan tryptophylquinone) model (3-methyl-4- (3'-methylindol-2'-yl) indol-6,7-dione), ubiquinone (coenzyme Q), PMS (N-methylphenazinium methosulfate), TPQ (topa quinone or 6-hydroxydopa quinone), PQQ (pyrroloquinolinequinone), thionine, thionine-tetrasulfonate, ascorbic acid, PES (phenazineethosulphate), cresyl blue, 1,4-naphthoquinone, toluidine blue, thiazine blue, gallocyanine, thioindigo disulfonate, met hylene blue, vitamin K3 (2-methyl-1,4-naphthoquinone), etc. can be used. In the chemical formula, dpy is 2,2'-dipyridine, phen is 1,10-phenanthroline, Tris is tris (hydroxymethyl) aminomethane, trpy is 2,2 ': 6', 2 ''-terpyridine , Im is imidazole, py is pyridine, thmpy is 4- (tris (hydroxymethyl) methyl) pyridine, bhm is bis (bis (hydroxymethyl) methyl, G3a is triglycineamide, A3 is trialanine, ox is oxalate dianione, edta represents ethylenediaminetetraacetate tetraanione, gly represents glycinate anion, pdta represents propylenediaminetetraacetate tetraanione, trdta represents trimethylenediaminetetraacetate tetraanione, and cydta represents 1,2-cyclohexanediaminetetraacetate tetraanione.

  Immobilization of the enzyme, coenzyme, and electron transfer mediator to the battery electrode 4 can be performed by a conventionally known method, for example, using an immobilization carrier using glutaraldehyde and poly-L-lysine as a cross-linking agent. And a method using a polymer having proton conductivity such as acrylamide can be employed.

[Switching valve / sensor electrode]
A switching valve 6 for stopping or starting the supply of the liquid injected from the introduction port 5 to the battery electrode 4 is disposed in the supply path of the battery unit 2. Further, a sensor electrode 7 that is in contact with the liquid injected from the inlet 5 and flowing through the supply path is disposed between the inlet 5 of the supply path and the switching valve 6.

  The switching valve 6 receives a signal output from the controller 3, opens and closes the valve according to this signal, and stops or starts the supply of the liquid injected from the introduction port 5 to the battery electrode 4.

  An oxidoreductase is immobilized on the sensor electrode 7. When the sensor electrode 7 comes into contact with the liquid flowing through the supply path, electrons are taken out by the oxidation-reduction reaction of the substance contained in the liquid, and an electric current is generated in the sensor electrode 7. The current generated in the sensor electrode 7 is output to the controller 3. The oxidoreductase on the sensor electrode 7 can be arbitrarily selected from the enzymes described for the battery electrode 4, but is preferably the same as the enzyme on the battery electrode 4.

(3) Controller The controller 3 is provided with a CPU (Central Processing Unit) 3A and a memory 3B in which a program for the CPU 3A to control each unit is stored. The CPU 3A includes a communication unit that communicates data via a network typified by the Internet as necessary, a storage unit such as a semiconductor memory that stores various data such as programs, and data for a recording medium such as a removable memory. Is connected (not shown). A program for controlling the biofuel cell system 1 is supplied to the biofuel cell system 1 in a state stored in a removable memory, read by the drive, and installed in a hard disk drive built in the storage unit. The program installed in the storage unit is loaded from the storage unit to the memory 3B and executed by a command from the CPU 3A.

  The controller 3 receives the output of the current from the sensor electrode 7 and outputs a signal to the switching valve 6 to control its opening and closing. The controller 3, the switching valve 6 and the sensor electrode 7 function as control means for automatically determining the suitability of the liquid supplied from the outside to the inlet 5 as a fuel solution and controlling the supply to the battery electrode 4. .

2. Functional Configuration of Biofuel Cell System With reference to FIG. 2, the control mode of the system by the controller 3, the switching valve 6 and the sensor electrode 7 will be specifically described. FIG. 2 is a diagram illustrating a functional configuration of the biofuel cell system 1. The controller 3 includes an output detection unit 31 and a control unit 32.

(1) Output detection part The output detection part 31 receives the output of the electric power from the sensor electrode 7 which contacted the liquid inject | poured from the inlet 5 and flowing through a supply path. Then, the current value of the input current is measured, and the measured current value is output to the control unit 32.

(2) Control unit The control unit 32 automatically determines the suitability of the liquid supplied from the inlet 5 as a fuel solution based on the current value output from the output detection unit 31, and switches according to the determination result. A signal is output to the valve 6 to control the opening and closing of the valve. Specifically, the control unit 32 opens the switching valve 6 and supplies the liquid to the battery electrode 4 when it is determined that the liquid is appropriate as the fuel solution. On the other hand, if it is determined as inappropriate, the control unit 32 closes the switching valve 6 and stops the supply of the liquid to the battery electrode 4. More specifically, when the current value output from the output detection unit 31 is equal to or greater than a predetermined threshold, the control unit 32 determines that the liquid is appropriate as the fuel solution, and opens the switching valve 6 so that the liquid is discharged from the battery. Supply to the electrode 4. On the other hand, when the current value output from the output detection unit 31 is less than the predetermined threshold value, the control unit 32 determines that the current value is inappropriate and closes the switching valve 6 to supply liquid to the battery electrode 4. Stop.

  As described above, the fuel solution introduced into the introduction port 5 is a substance that can be used as a fuel such as sugar or alcohol, and is a liquid that contains one or more substances that can serve as a substrate for the oxidoreductase on the battery electrode 4. Preferably there is. However, there are cases where the user does not always use an appropriate liquid as the fuel solution. If an inappropriate liquid is used, not only the expected battery performance is obtained but also a battery failure is caused.

The suitability of a liquid as a fuel solution depends on the “substrate suitability” of the substance contained in the liquid and the “activity inhibition degree” of the substance contained in the liquid and the liquid.
Here, “substrate suitability” means that a substance contained in a liquid can serve as a substrate of an oxidoreductase on the battery electrode 4 or a redox reaction of the enzyme using the substance as a substrate. It can be defined by how much the reaction efficiency is. When the substrate compatibility is high, the oxidation-reduction reaction of the substance on the battery electrode 4 proceeds with high efficiency, and a high battery output is obtained.
In addition, “activity inhibition degree” means that the liquid or a substance contained in the liquid inhibits the activity of the oxidoreductase on the battery electrode 4 or the enzyme in the presence of the liquid or the substance. It can be defined by how much the reaction efficiency of the oxidation-reduction reaction is. When the degree of activity inhibition is high, the activity of the enzyme on the battery electrode 4 is inhibited, the efficiency of the oxidation-reduction reaction is lowered, the battery output is reduced, or the enzyme is deactivated, and the battery is disabled.

In the biofuel cell system 1, the suitability of a certain liquid as a fuel solution can be uniquely determined based on the current value of the current output from the sensor electrode 7 in contact with the liquid.
That is, when a liquid having a high degree of compatibility as a fuel solution is supplied from the introduction port 5, the oxidation-reduction reaction proceeds with high efficiency on the sensor electrode 7 in contact therewith, and a large current value is output. On the other hand, when the compatibility of the liquid supplied as the fuel solution is low, the enzyme activity is inhibited or deactivated on the sensor electrode 7 in contact therewith, and only a small current value is output.

  When the current value output from the sensor electrode 7 and measured by the output detection unit 31 is equal to or greater than a predetermined threshold, the control unit 32 has a high degree of suitability as the liquid fuel solution supplied from the inlet 5. Is determined. Then, the switching valve 6 is opened to supply liquid to the battery electrode 4. On the other hand, when the current value output from the output detection unit 31 is less than the predetermined threshold, the control unit 32 determines that the suitability of the liquid supplied from the inlet 5 as a fuel solution is low, and the switching valve 6 Is closed to stop the supply of liquid to the battery electrode 4.

  As a result, the biofuel cell system 1 automatically determines the suitability of the liquid supplied from the outside as the fuel solution, and supplies only the liquid determined to be suitable as the fuel solution to the battery electrode 4 to provide the desired battery. Performance can be obtained. Further, it is possible to prevent a failure or a decrease in output due to an inappropriate liquid being supplied to the battery electrode 4.

  Further, by making the oxidoreductase on the sensor electrode 7 the same as the enzyme on the battery electrode 4, the battery performance when the liquid supplied from the outside is used as a fuel solution can be accurately determined. The supply of liquid to can be controlled.

  Further, the sensor electrode 7 includes a sensor electrode 7 positive electrode having the same enzyme as the oxidoreductase on the battery electrode 4 positive electrode, and a sensor electrode 7 negative electrode to which the same enzyme as the oxidoreductase on the battery electrode 4 negative electrode is fixed. It is good also as a counter electrode which consists of. The sensor electrode 7 is configured as such a counter electrode, and a current collector and a circuit are connected to the counter electrode, whereby a small biofuel cell having the same configuration as the battery electrode 4 is obtained. Then, the current generated at the counter electrode is output to the controller 3 for use in determining the suitability of the fuel solution. Thereby, the battery performance when the liquid supplied from the outside is used as the fuel solution can be determined more accurately, and the supply of the liquid to the battery electrode can be controlled. In this case, the electric power obtained by the counter electrode can be supplied to the switching valve 6 and used as a power source for opening and closing the switching valve 6.

(3) Display unit When the oxidoreductase on the sensor electrode 7 is the same as the oxidoreductase on the battery electrode 4 and / or when the sensor electrode 7 is a counter electrode, the supplied liquid is the fuel solution. Can be predicted based on the current value of the current output from the sensor electrode 7. In this case, the biofuel cell system 1 may be provided with a display unit (see reference numeral 8 in FIGS. 1 and 2) to present the predicted battery performance to the user.

  Specifically, the current output from the sensor electrode 7 in contact with the liquid injected from the inlet 5 and flowing through the supply path is input to the output detection unit 31 of the controller 3. Then, the output detection unit 31 measures the current value of the input current and outputs it to the control unit 32. Based on the current value output from the output detection unit 31, the control unit 32 displays the predicted battery performance (current value, voltage value, output duration, etc.) when the supplied liquid is a fuel solution. 8 to present to the user. As a result, the user can select an appropriate liquid and use it as a fuel solution to obtain a desired cell performance, thereby preventing a failure or a decrease in output due to the use of an inappropriate fuel solution.

(4) Specific examples of suitability as a fuel solution Hereinafter, the suitability as a fuel solution will be described with a specific example.

  A biofuel cell can use, as a fuel, a substance that is highly safe for the human body, such as glucose and ethanol. Theoretically, a biofuel cell can generate electricity using a food or drink that contains sugar, alcohol, aldehyde, lipid, protein, or the like, or waste such as garbage. However, in reality, food and drink, waste, etc. cannot be taken out by redox reaction as they are, or substances that cause inhibition of enzyme activity, solution pH and salt concentration may be changed. In some cases.

  For example, in a biofuel cell in which a glucose-degrading enzyme is solid-phased on a battery electrode, both the output and the battery life are improved if a saccharide, particularly a beverage having a high sugar concentration composition is used as the fuel solution. For this reason, these drinks are liquids with high suitability as fuel solutions. In addition, sake and wine also contain sugar in the composition and therefore have a certain degree of suitability. On the other hand, a beverage composed solely of a sweetener other than sugar and a saccharide such as fructose other than glucose is regarded as a liquid having a low suitability as a fuel solution.

  In addition, in a biofuel cell in which fructose-degrading enzyme is solid-phased on an electrode, a fruit juice beverage having a composition with a high fructose concentration has high output and long life. For this reason, these drinks are liquids with high suitability as fuel solutions. Moreover, since wine also contains fructose in its composition, it has a certain degree of fitness. On the other hand, alcoholic beverages made from rice, such as sake, have a high sugar content and a low fructose content.

Further, for example, a liquid containing the following substances is a liquid having a high activity inhibition degree and a low suitability as a fuel solution. Iodoacetic acid, malonic acid, various surfactants, various oxidizing agents, heavy metals (silver, mercury), parachloromercuribenzoic acid, mercury chloride, orthophenanthroline, acetyl-CoA.
Furthermore, for example, acidic solutions containing high concentrations of acetic acid, citric acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc., or strongly basic solutions such as high concentration sodium hydroxide, sodium hypochlorite aqueous solution Or when using a liquid containing a high concentration of salts containing inorganic ions such as sodium, potassium, calcium, magnesium, iron, zinc, copper, and polyvalent anions such as phosphate ions and sulfate ions, There is a possibility that the pH and salt concentration of the fuel solution will change, leading to a decrease in enzyme activity. The reason for this is that the enzyme activity depends on the pH, and when it goes out of the optimum pH, the activity drops rapidly. In a solution containing a large amount of salts, the solubility of the protein decreases and precipitation occurs (salting out). Is mentioned.

  Currently, biofuel cells using enzymes that decompose sugars such as glucose and alcohols such as ethanol are in the practical stage. In addition, biofuel cells that use fat-degrading enzymes, such as olive oil as fuel, and biofuel cells that use amino acid beverages or protein beverages as fuels using proteolytic enzymes or amino acid-degrading enzymes Is also being developed.

  According to the biofuel cell system and the like according to the present invention, it is possible to automatically determine the suitability of an externally supplied liquid as a fuel solution and supply only an appropriate liquid to the battery electrode. For this reason, the present invention is applied to various biofuel cells using saccharides, alcohols, fats, proteins, and the like as fuels to prevent failure and output reduction due to improper liquid supply. Can be used to obtain battery performance.

Claims (5)

An inlet through which liquid is introduced from the outside;
A battery electrode serving as a reaction field for the oxidation-reduction reaction of the fuel catalyzed by oxidoreductase,
A biofuel cell system comprising: control means for automatically determining the suitability of the liquid as a fuel solution and controlling the supply of the liquid to the cell electrode. The control means is disposed between a switching valve disposed in the liquid supply path from the inlet to the battery electrode, and between the inlet and the switching valve so as to be in contact with the liquid, and the oxidoreductase is fixed. A sensor electrode,
Based on the current value measured by the sensor electrode in contact with the liquid, the suitability of the liquid as a fuel solution is automatically determined, and when it is determined that the liquid is suitable as the fuel solution, the switching valve is opened to remove the liquid from the battery. 2. The biofuel cell system according to claim 1, wherein the biofuel cell system is supplied to the electrode, and the supply of the liquid to the battery electrode is stopped by closing the switching valve when it is determined to be inappropriate.   The biofuel cell system according to claim 2, wherein the oxidoreductase on the battery electrode and the sensor electrode are the same enzyme.   The sensor electrode has a sensor electrode positive electrode having the same enzyme as the redox enzyme on the battery electrode positive electrode constituting the battery electrode, and a sensor having the same enzyme as the redox enzyme on the battery electrode negative electrode constituting the battery electrode The biofuel cell system according to claim 3, which is a counter electrode comprising an electrode negative electrode. An inlet through which liquid is introduced from the outside;
A battery electrode serving as a reaction field for the oxidation-reduction reaction of the fuel catalyzed by oxidoreductase,
A biofuel cell comprising: control means for automatically determining the suitability of the liquid as a fuel solution and controlling the supply of the liquid to the cell electrode.

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