JP5273645B2 - Biofuel cell - Google Patents

Description

  The present invention relates to a biofuel cell, and more particularly to a biofuel cell that uses protein as a catalyst.

  To build a sustainable society by solving global warming issues represented by the Kyoto Protocol, food waste (food waste) treatment issues represented by the Food Recycling Law, and next-generation energy issues Hydrogen energy related technology has been developed. In particular, biofuel cells, which are fuel cells that use biochemical reactions, are expected to generate renewable energy and contribute to the improvement of global warming problems. As an ultimate clean energy conversion system with features such as being usable as

  In other words, biofuel cells can be expected to contribute to the 3R (Reduce, Reuse, Recycle) field in the energy field, and to have a ripple effect in various fields such as agriculture, industry, and medicine. It is superior to other energy-related technologies. In addition, biofuel cells are considered to be the only power generation method that is expected to be put into practical use from small to ultra-small devices carried by individuals, such as mobile phones, personal computers, and pacemaker power supplies.

In the biofuel cell according to the prior art, an enzyme is mainly used as a biocatalyst that catalyzes a fuel cell reaction, and a noble metal such as gold or platinum, or carbon is used as an electrode base material ( Patent Document 1 and Non-Patent Documents 1 to 3).
JP 2005-79001 A (published March 24, 2005) RA Bullen, TC Arnot, JB Lakeman, FC Walsh, “Biofuel cells and their development”, Biosensors and Bioelectronics, 21 (2006) pp. 2015-2045. H. Park, J.-S. Park, Y.-B. Shin, “Electrochemical and in situ UV-visible spectroscopic behavior of cytochrome c at a cardiolipin-modified electrode”, J. Electroanal. Chem., 514 (2001) 67-74. E. Katz, I. Willner, AB Kotlyar, “A non-compartmentalized glucose | O2 biofuel cell by bioengineered electrode surfaces”, Journal of Electroanalytical Chemistry, 479 (1999) pp. 64-68. Y. Ayato, T. Itahashi, N. Matsuda, “Direct Electron Transfer of Hemoglobin Molecules on Bare ITO Electrodes”, Chemistry Letters, 36 (2007) pp. 406-407. Y. Ayato, A. Takaktsu, K. Kato, and N. Matsuda, “Direct Electrochemistry of Hemoglobin Molecules Adsorbed on Bare Indium Tin Oxide Electrode Surfaces”, Japanese Journal of Applied Physics, 47, (2008) pp. 1333-1336

  However, in the biofuel cell according to the prior art, a complicated mechanism such as surface treatment of the electrode or addition of a mediator, a promoter, or the like is required for electron transfer between the electrode and an enzyme that catalyzes the fuel cell reaction. is necessary. Therefore, there is a strong demand for a biofuel cell that can generate power with a simple mechanism.

  This invention is made | formed in view of the said subject, and makes it a main objective to provide the biofuel cell which can generate electric power with a simple mechanism.

  The present inventors have reported that hemoglobin adsorbed directly on an indium tin oxide electrode exhibits electron transfer activity (see Non-Patent Documents 4 and 5). However, there is no report that the electrode is used for a biofuel cell. That is, it is not clear whether the hemoglobin can catalyze a redox reaction on the electrode and the biofuel cell can operate. The present inventors have repeatedly studied the use of an indium tin oxide electrode for a biofuel cell based on original knowledge, and completed the present invention.

  That is, the fuel cell according to the present invention is a fuel cell including a cathode electrode and an anode electrode, and at least one of the cathode electrode and the anode electrode adsorbs a protein catalyst that catalyzes a redox reaction. It is characterized by being an indium tin oxide electrode.

  According to the above configuration, at least one of the cathode electrode and the anode electrode, which are the indium tin oxide electrodes, is adsorbed to the one electrode without the need for a mediator, a promoter, and a special surface treatment. Electrons can be transferred to and from the protein catalyst. Therefore, it is easy to move electrons obtained by the oxidation reaction catalyzed by the protein catalyst to the anode electrode, or to catalyze the reduction reaction using the electrons from the cathode electrode. . As a result, it is possible to generate an electron flow from the anode electrode to the cathode electrode, and to generate power by a mediator, a promoter, and a simple mechanism that does not require special surface treatment.

  The protein catalyst can also be used as a mediator. That is, since the indium tin oxide electrode easily transfers electrons to and from the protein catalyst, even when the protein catalyst is used as a mediator, the surface treatment of the electrode, and between the protein catalyst and the electrode It is possible to generate electric power with a simple mechanism that does not require additional mediators.

  In the fuel cell according to the present invention, the cathode electrode may be the indium tin oxide electrode.

  According to the above configuration, since the cathode electrode is an indium tin oxide electrode on which a protein catalyst that catalyzes a redox reaction is adsorbed, the oxidant supply is performed by electrons transferred from the cathode electrode to the protein catalyst. The oxidant supplied by the means can be reduced. Thereby, electric power generation can be performed suitably.

  In the above configuration, an oxidant supply unit may be further provided, and the oxidant may be hydrogen peroxide.

  When the protein catalyst reduces the oxidizing agent, if the oxidizing agent is hydrogen peroxide, the reduction reaction of the oxidizing agent by the protein catalyst can be suitably performed.

  In the fuel cell according to the present invention, the protein catalyst is preferably a metal protein containing iron ions or copper ions as a prosthetic group.

  According to said structure, since the said protein catalyst is a metal protein which contains a transition metal like iron ion or copper ion as a prosthetic group, it can catalyze a redox reaction suitably.

  In the fuel cell according to the present invention, the protein catalyst is preferably a heme protein.

  According to said structure, since the said protein catalyst is heme protein, it can catalyze a redox reaction suitably.

  In the fuel cell according to the present invention, the protein catalyst is selected from the group consisting of hemoglobin, cytochrome c, cytochrome P-450, myoglobin, catalase, laccase, peroxidase, cytochrome c oxidase, cytochrome c reductase, bilirubin oxidase, and glucose oxidase. One or more proteins are preferred.

  According to the above configuration, the protein catalyst is selected from the group consisting of hemoglobin, cytochrome c, cytochrome P-450, myoglobin, catalase, laccase, peroxidase, cytochrome c oxidase, cytochrome c reductase, bilirubin oxidase, and glucose oxidase. Since it is one or more proteins, the redox reaction can be suitably catalyzed.

  In the fuel cell according to the present invention, the protein catalyst may be dissolved in an electrolyte solution.

  If the protein catalyst is dissolved in the electrolyte solution, the protein catalyst can be stably adsorbed to the at least one electrode.

  Furthermore, in the above configuration, it is preferable that an ion exchange membrane is further provided in the liquid electrolyte at a position where the anode electrode and the cathode electrode are separated, and the pore diameter of the ion exchange membrane is 1 nm or more. More preferably, it is in the range of 20 nm or less.

  According to the above configuration, since the ion exchange membrane is further provided at a position where the anode electrode and the cathode electrode are separated, the protein catalyst dissolved in the liquid electrolyte is the at least one of the above. It can be made to adsorb only to the electrodes.

  Moreover, if the pore diameter of the ion exchange membrane is in the range of 1 nm or more and 20 nm or less, the protein catalyst can be preferably adsorbed only on the one electrode.

  In the above configuration, the protein catalyst may be cytochrome c. In this case, the protein concentration is preferably in the range of 1 μM to 50 μM.

  When the protein catalyst is cytochrome c, the oxidation-reduction reaction can be suitably catalyzed by setting the concentration in the range of 1 μM to 50 μM.

Supplying a fuel to an anode electrode provided in contact with the electrolyte, and supplying an oxidant to a cathode electrode provided in contact with the electrolyte;
A power generation method, wherein at least one of the cathode electrode and the anode electrode is an indium tin oxide electrode to which a protein catalyst that catalyzes a redox reaction is adsorbed.

  According to said structure, there can exist an effect similar to the fuel cell which concerns on this invention.

  According to the fuel cell of the present invention, the protein catalyst that catalyzes the oxidation-reduction reaction is adsorbed on the indium tin oxide electrode, so that the electron transfer between the protein catalyst and the electrode is controlled by the mediator. Can be generated without the need for a promoter and special surface treatment, so that power can be generated by a simple mechanism.

  FIG. 1 is a schematic diagram showing a schematic configuration of a fuel cell 100 according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the detailed structure of the fuel cell 100. As shown in FIGS. 1 and 2, the fuel cell 100 includes a cathode electrode 101, an anode electrode 102, an electrolyte 103, a fuel supply port 110, and an oxidant supply port (oxidant supply means) 112.

The fuel supply port 110 supplies the fuel 120 to the anode electrode 101. The fuel 120 may be any substance that can serve as a substrate for the proton generation reaction. For example, hydrogen (H ₂ ), methanol, ascorbic acid, hydrazine, glucose, reduced nicotinamide adenine dinucleotide (NADH), or the like can be used. .

  In the anode electrode 101, for example, when hydrogen is used as the fuel 120, a reaction represented by the following formula (1) or (2) occurs.

H ₂ → 2H ⁺ + 2e ⁻ (1)
H ₂ + 2OH → 2H ₂ O + 2e ⁻ (2)
As a result, electrons (e ⁻ ) are generated and move from the anode electrode 101 to the cathode electrode 102 via the conducting wire 107.

  Even when a substance other than hydrogen is used as the fuel 120, electrons and protons 121 are generated by the respective proton generation reactions.

  Electrons generated by the proton generation reaction and substances other than the proton 121 are discharged from the discharge port 111.

  For the supply of hydrogen, for example, a water electrolysis cell 500 as shown in FIG. 3 can be used. The water electrolysis cell 500 is filled with a concentrated sulfuric acid aqueous solution 503 in a glass bottle 506, and energizes a hydrogen generation electrode 501 and an oxygen generation electrode 502 made of platinum, respectively. Gas can be transported.

The oxidant supply unit 112 supplies the oxidant 122 to the cathode electrode 102. The oxidant 122 may be any substance that can receive electrons and be reduced. For example, oxygen (O ₂ ) or hydrogen peroxide (H ₂ O ₂ ) can be used, and unlike a general fuel cell, In particular, hydrogen peroxide can be preferably used.

  In the cathode electrode 102, for example, when oxygen is used as the oxidant 122, a reaction represented by any of the following formulas (5) to (8) occurs.

O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (5)
O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (6)
O ₂ + 2H ⁺ 2e ⁻ → H ₂ O ₂ (7)
O ₂ + H ₂ O + 2e ⁻ → O ₂ H ⁻ + OH ⁻ (8)
For example, when hydrogen peroxide is used as the oxidant 122, a reaction represented by any of the following formulas (9) to (11) occurs.

H ₂ O ₂ + 2H ⁺ + 2e ⁻ → 2H ₂ O (9)
2O ₂ H ⁻ → 2OH ⁻ + O ₂ (10)
H ₂ O ₂ + 2e ⁻ → 2OH ⁻ (11)
Thus, in the cathode electrode 102, the oxidant 122 becomes the oxidant 123 that has been reduced by receiving electrons.

  At this time, the anode electrode 101 and the cathode electrode 102 are connected via an electrolyte 103 and a conducting wire 107 as shown in FIG. Since electrons cannot pass through the electrolyte 103, they move from the anode electrode 101 to the cathode electrode 102 through the conducting wire 107 provided with the load 105. Thereby, electric power generation can be performed.

  Here, in the present invention, at least one of the anode electrode 101 and the cathode electrode 102 is composed of an indium tin oxide electrode on which the protein catalyst 104 that catalyzes the oxidation-reduction reaction as described above is adsorbed. Electron transfer between the indium tin oxide electrode and the protein catalyst is possible without the need for mediators, promoters, and special surface treatment of the electrode. Therefore, there is an effect that the fuel cell can be configured with a simple configuration. In the present embodiment, hereinafter, the case where the indium tin oxide electrode is used as the cathode electrode 102 will be described. However, the effect described above is easy to transfer electrons between the protein catalyst and the indium tin oxide electrode. This is based on whether the electrode is the anode electrode 101 or the cathode electrode 102.

  In the present embodiment, the cathode electrode 102 may be formed by coating indium tin oxide on a substrate such as glass or quartz by an evaporation method, a spray method, or the like as an electrode base material. The surface of the cathode electrode 102 is preferably washed with acetone, ethanol, pure water or the like.

  In this embodiment, the anode electrode 101 uses a platinum electrode. For example, platinum foil or platinum foil with platinum black can be used. The surface of the anode electrode 101 is preferably polished, washed, or the like.

  The protein catalyst 104 is not particularly limited as long as it is a protein that catalyzes the redox reaction as described above, but is preferably a metal protein containing a transition metal such as an iron ion or a copper ion as a prosthetic group. More preferably one or more proteins selected from the group consisting of hemoglobin, cytochrome c, cytochrome P-450, myoglobin, catalase, laccase, peroxidase, cytochrome c oxidase, cytochrome c reductase, bilirubin oxidase, and glucose oxidase. More preferably. Such a protein can suitably catalyze the oxidation-reduction reaction. These proteins can also act as mediators responsible for the transfer of electrons between microorganisms or enzymes and electrodes. When the protein catalyst 104 is used as a mediator, the fuel cell 100 further includes microorganisms such as E. coli and Proteus bulgaris, or cytochrome c oxidase, microperoxidase-11, and laccase that catalyze the redox reaction. It is preferable to provide such an enzyme. At this time, the protein catalyst 104 mediates the exchange of electrons produced or consumed in the oxidation-reduction reaction catalyzed by the microorganism or enzyme with the electrode.

  In this embodiment, the electrolyte 103 is a liquid, and the pH and type are not limited. However, in consideration of denaturation of the protein catalyst 104, it is preferable to use phosphate buffered saline (PBS, pH 7.4). The electrolyte 103 according to the present invention is not necessarily a liquid, and a solid electrolyte can be used as long as conditions described later are satisfied.

  In the present embodiment, the protein catalyst 104 is dissolved in the electrolyte 103. Thereby, a state in which the protein catalyst 104 is naturally adsorbed to the cathode electrode 102 can be formed. When cytochrome c is used as the protein catalyst 104, the protein concentration in the electrolyte 103 is preferably in the range of 1 μM to 50 μM.

  At this time, in order to suppress the protein catalyst 104 from adsorbing to the anode electrode 101, the electrolyte 103 is ion-exchanged into an electrolyte 103a in which the anode electrode 101 is disposed and an electrolyte 103b in which the cathode electrode is disposed. Preferably, they are separated by a membrane 108 (see FIG. 2).

  The ion exchange membrane 108 allows protons to pass but does not allow the protein catalyst 104 to pass. As such an ion exchange membrane 108, a membrane having a pore diameter in the range of 1 nm to 20 nm can be suitably used. The ion exchange membrane 108 is preferably an anion exchange membrane in an alkaline atmosphere, and is preferably a cation exchange membrane in an acidic atmosphere. For example, “Nafion (registered trademark) 117” is preferably used. Can do.

  Note that the fuel cell according to the present invention may be configured not to use the ion exchange membrane 108. That is, an electrolyte solution containing the protein catalyst 104 is dropped on the surface of the indium tin oxide electrode to adsorb the protein catalyst 104, and the surface of the indium tin oxide adsorbed to the protein catalyst 104 is washed with phosphate buffered saline or the like. The cathode electrode 101 to which the protein catalyst 104 is adsorbed is produced by the above operation. In this case, a solid electrolyte 103 may be used. Further, since the protein catalyst 104 is not adsorbed on the anode electrode 101, the ion exchange membrane 108 is not necessary.

  Further, as shown in FIG. 2, the fuel cell according to the present embodiment includes a battery tank 106 including blocks 106 a, 106 b, 106 c, and 106 d, thereby holding each part including the electrolyte 103. doing. The battery cell 106 can be formed of, for example, polytetrafluoroethylene. Further, a protective film such as a fluoro rubber sheet may be provided between the cathode electrode and the battery cell 106d.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  Moreover, all the academic literatures and patent literatures described in this specification are incorporated herein by reference.

  EXAMPLES Hereinafter, although an Example and a reference example demonstrate this invention more concretely, this invention is not limited at all by these Examples.

[Reference Example 1: Measurement of H ₂ O ₂ reduction reaction by hemoglobin adsorbed on indium tin oxide]
A 20 mm × 20 mm quartz substrate coated with indium tin oxide (ITO) to a thickness of about 20 nm by an evaporation method was used as an electrode. The surface of the electrode was washed with acetone, ethanol, and pure water (Milli-Q, resistance> 18 MΩcm) in this order.

PBS solution, 3.6 mM H ₂ O ₂ solution, and 100 μM hemoglobin (Hb) prepared with PBS solution and 3.6 mM H ₂ O ₂ solution are mixed in the same amount to obtain 1.8 mM H ₂ O ₂ /0.01 M PBS. solution and _{1.8mM H 2 O 2 / 50μM Hb} / 0.01M PBS solution was prepared.

  The measurement was performed according to the following procedure.

(A) A silicon cell (inner diameter: 12 mmΦ) was placed on the electrode surface, and 1 mL of 0.01 M PBS solution was filled in the cell. The electrode was wired as a working electrode, a platinum (Pt) wire immersed in the solution, and an Ag / AgCl saturated KCl electrode as a counter electrode and a reference electrode on a potentiostat. Cyclic voltammetry (CV) measurement was performed in a sweep range of +0.6 to −0.4 V at a scanning speed of 0.8 Vs ⁻¹ , and only non-Faraday current was measured.

(B) The solution in the cell was replaced with about 1 ml of a 1.8 mM H ₂ O ₂ /0.01M PBS solution, and CV measurement was performed under the same conditions. Replace the solution in the cell to _{18mM H 2 O 2 / 50μM Hb} / 0.01M PBS solution about 1 ml, were carried out at a scan rate 0.8Vs ^-1 CV measurement + sweep range of 0.2 to-0.45 V .

FIG. 4 shows a CV curve measured by the method as described above. When the case of using a solution containing hemoglobin (Hb) and a solution containing no hemoglobin (Hb) was compared, the reduction current value of H ₂ O ₂ was greatly different. Therefore, it was found that H ₂ O ₂ was reduced by hemoglobin. From the potential at the beginning of the flow of the reduction current, the reduction potential of hydrogen peroxide under this condition is about -0.1 V vs. It was found to be near Ag / AgCl.

[Reference Example 2: Measurement of H ₂ O ₂ reduction reaction by cytochrome c adsorbed on indium tin oxide]
A 20 mm × 20 mm quartz substrate coated with indium tin oxide (ITO) to a thickness of about 20 nm by an evaporation method was used as an electrode. The surface of the electrode was washed with acetone, ethanol, and pure water (Milli-Q, resistance> 18 MΩcm) in this order.

PBS solution and 3.6 mM H ₂ O ₂ solution and PBS solution was prepared by 20μM cytochrome c and (Cyt c) a 3.6 mM H ₂ O ₂ solution mixed equal _{amounts, 1.8mM H 2 O 2/0} . 01M PBS solution and _{1.8mM H 2 O 2 / 10μM Cyt} c / 0.01M PBS solution was prepared.

The measurement was performed according to the same procedure as in Reference Example 1 except that the CV measurement conditions were a sweep range of +0.3 to -0.45 V and a scanning speed of 0.1 Vs- ¹ .

FIG. 5 shows a CV curve measured by the method as described above. When the case of using a solution containing cytochrome c and a solution containing no cytochrome c were compared, the reduction current value of H ₂ O ₂ was different. Therefore, it was found that H ₂ O ₂ was also reduced using cytochrome c. Further, from the potential at which the reduction current begins to flow, the reduction potential of hydrogen peroxide under this condition is about 0.0 V vs. It was found to be near Ag / AgCl.

Furthermore, CV measurement was performed by changing the concentration of cytochrome c from 5 to 100 μM for the purpose of examining the concentration dependency of the electron transfer activity of cytochrome c adsorbed on the indium tin oxide electrode. The CV measurement conditions at this time are a sweep range of +0.3 to -0.23 V and a scanning speed of 0.1 Vs- ¹ .

  FIG. 6 shows cyclic voltammograms of indium tin oxide electrodes measured using PBS and a 5 μM Cyt c solution prepared with PBS. From this graph, an oxidation-reduction current derived from heme iron of cytochrome c was measured at about 0.1 and 0.05 V, and it was confirmed that cytochrome c maintained the electron transfer activity on the surface of the indium tin oxide electrode. It could be confirmed.

  FIG. 7 shows CV measured by changing the concentration of cytochrome c from 5 to 100 μM. At a concentration of 5 to 50 μM, the CV peak current value increased with increasing concentration (see FIG. 7A). On the other hand, when the concentration was further increased to 100 μM, the CV result shown in FIG. 7B was obtained, suggesting the possibility that the electron transfer activity of cytochrome c was lost at such a concentration. Therefore, it was found that protein concentration is very important for use as a biofuel cell.

[Reference Example 3: CV measurement in a PBS (pH 7.4) solution using a platinum electrode]
The surface of the platinum (Pt) disk electrode was polished using a polishing cloth and 0.05 μm alumina, and ultrasonically cleaned in the order of water, acetone, and ethanol.

The measurement was performed as follows. A 0.01M PBS (pH 7.4) solution was used as an electrolyte solution, and the Pt disk electrode was wired to a potentiostat with a working electrode, a platinum (Pt) wire, and an Ag / AgCl saturated KCl electrode as a counter electrode and a reference electrode. After performing constant potential cleaning of the Pt disk electrode, the solution was replaced with a new one. CV measurement was performed at a scanning speed of 0.1 Vs ⁻¹ in a sweep range of +1.2 to −0.9 V.

  FIG. 8 shows a CV curve measured by the method as described above. A hydrogen generation current was confirmed at about -0.8V.

From the results of Reference Examples 1 to 3, an OCV of at least about 0.7 V to 0.8 V is obtained by assembling a single cell with Hb / ITO or cytochrome c / ITO as the oxygen electrode and H ₂ / Pt as the hydrogen electrode. I found that I can expect to be.

_Further, reaction with H 2 / Pt system is sufficiently _fast, since the reaction with H ₂ O ₂ / Hb / ITO system is considered the rate-determining, from the experimental results of Example 1, at least ¹⁰ -5 ^{Wcm -2} of about It turns out that power generation can be expected.

[Example 1]
In order to prove that the biofuel cell of the present invention actually generates power, a single cell power generation experiment was conducted.

A fuel cell single cell was produced using a polytetrafluoroethylene block or the like (see FIG. 2). The constituent material of the single cell was washed with ethanol, immersed and washed with a mixed acid of 50/50 H ₂ SO ₄ / HNO ₃ , and washed with water. The Pt electrode was washed in the same manner using platinum foil. The ITO electrode was cleaned in the same manner as in Reference Example 1. The ion exchange membrane (“Nafion (registered trademark) 117”) was boiled and washed in about 3% aqueous H ₂ O ₂ solution and then stored in dilute sulfuric acid.

The single cell was assembled by the following procedure. A single cell was assembled with the configuration shown in FIG. As the electrolyte and the electrode catalyst of the cathode electrode side, satisfied the _{1.8mM H 2 O 2 / 50μM Hb} / 0.01M PBS solution, together with adsorption of Hb in ITO _surface, allowed to coexist H 2 _{O 2.} As an electrolyte on the anode side, 0.01M PBS was filled.

For the purpose of supplying H ₂ gas to the anode, a water electrolysis cell as shown in FIG. 3 was assembled. The water electrolysis reaction was performed at about 0.1 A in the water electrolysis cell, and the generated H ₂ gas was supplied to the anode side of the single fuel cell.

The measurement of the single cell power generation experiment was performed according to the following procedure. Open circuit voltage (OCV) measurement was performed until the battery electromotive force became constant. After the OCV measurement, current sweep measurement was performed at a scanning speed from 0 A to 2 × 10 ⁻⁹ As ⁻¹ to obtain a current-potential curve.

  FIG. 9 shows a current-potential curve of single-cell power generation measured by the method as described above. An open circuit voltage (OCV, electromotive force) of approximately 0.3 V was obtained from the intercept of the Y axis.

FIG. 10 shows the output density characteristics. The maximum power density was about 5.5 × 10 ⁻⁸ W / cm ² .

  As described above, it was demonstrated that the biofuel cell according to the present invention generates power.

  The present invention can be used in the field of manufacturing a power generation device, or the field of manufacturing a device in which a power generation device is incorporated, such as an automobile, a portable device, and a biological implantable device.

It is a mimetic diagram showing a schematic structure of a fuel cell concerning one embodiment of the present invention. It is a schematic diagram which shows the detailed structure of the fuel cell which concerns on one Embodiment of this invention. It is a schematic diagram which shows schematic structure of the water electrolysis cell for hydrogen gas supply. It is a graph showing a cyclic voltammogram of H ₂ O ₂ reduction reaction with adsorbed hemoglobin indium tin oxide. It is a graph which shows the cyclic voltammogram of H2O2 reduction | restoration reaction by the cytochrome c adsorb | sucked to indium tin oxide. It is a graph which shows the cyclic voltammogram of indium tin oxide measured using 10 micro | micron | muCyt c solution prepared by PBS and PBS. It is a graph which shows the cyclic voltammogram of indium tin oxide measured using the (A) 5, 20, 50, (B) 100microMCyt c solution prepared by PBS. It is a graph which shows the cyclic voltammogram of a platinum electrode. It is a graph which shows the current-potential curve of the fuel cell which concerns on one Embodiment of this invention. It is a graph which shows the output density characteristic of the fuel cell which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Fuel cell 101 Anode electrode 102 Cathode electrode 103 Electrolyte 104 Protein catalyst 105 Load 106 Battery tank 107 Conductor 108 Ion exchange membrane 109 Screw fastening hole 110 Fuel supply port 111 Discharge port 112 Oxidant supply port (Oxidant supply means)
113 Discharge port 114 Protective membrane 120 Fuel 121 Proton 122 Oxidant 123 Reduced oxidant 500 Water electrolysis cell 501 Hydrogen generation electrode 502 Oxygen generation electrode 503 Concentrated sulfuric acid aqueous solution 504 Hydrogen transport pipe 505 Oxygen transport pipe 506 Glass bottle

Claims (11)

A fuel cell comprising a cathode electrode and an anode electrode,
A fuel cell, wherein at least one of the cathode electrode and the anode electrode is an indium tin oxide electrode to which only a protein catalyst that catalyzes a redox reaction is adsorbed.   The fuel cell according to claim 1, wherein the cathode electrode is the indium tin oxide electrode.   The fuel cell according to claim 2, further comprising an oxidant supply means, wherein the oxidant is hydrogen peroxide.   The fuel protein according to any one of claims 1 to 3, wherein the protein catalyst is a metal protein containing iron ions or copper ions as a prosthetic group.   The fuel cell according to any one of claims 1 to 3, wherein the protein catalyst is a heme protein.   The protein catalyst is one or more proteins selected from the group consisting of hemoglobin, cytochrome c, cytochrome P-450, myoglobin, catalase, laccase, peroxidase, cytochrome c oxidase, cytochrome c reductase, bilirubin oxidase, and glucose oxidase. The fuel cell according to any one of claims 1 to 3, wherein:   The fuel cell according to claim 1, wherein the protein catalyst is dissolved in an electrolyte solution.   8. The fuel cell according to claim 7, wherein an ion exchange membrane is further provided at a position in the electrolyte solution that separates the anode electrode and the cathode electrode.   9. The fuel cell according to claim 8, wherein the pore size of the ion exchange membrane is in the range of 1 nm to 20 nm.   The fuel cell according to any one of claims 7 to 9, wherein the protein catalyst is cytochrome c, and the protein concentration is in the range of 1 µM to 50 µM. Supplying a fuel to an anode electrode provided in contact with the electrolyte, and supplying an oxidant to a cathode electrode provided in contact with the electrolyte;
A power generation method, wherein at least one of the cathode electrode and the anode electrode is an indium tin oxide electrode to which only a protein catalyst that catalyzes a redox reaction is adsorbed.

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