Electrochemical device and method for manufacturing the same

Abstract

According to the present invention, an electrochemical device which utilizes microorganisms and is able to output sufficient electric power in a short period of time after starting is able to be achieved by means of: an electrochemical device which comprises a first electrode that is provided with a surface part having at least one pore that has an opening, wherein the pore has a conductive site at least on the inner surface thereof, the first electrode has a conduction path that electrically connects the conductive sites of the pores to each other, and each one of the pores holds electron-donating microorganisms of different classification classes, different electron-donating microorganisms in a same classification class, or electron-donating microorganisms that have significantly different average particle diameters; and a method for producing this electrochemical device.

Description

Technical Field

[0001] The present invention relates to an electrochemical device using microorganisms typified by a microbial fuel cell, and a method for manufacturing the same.

Background Art

[0002] In conventional power generation systems using fossil fuels such as thermal power generation, against the backdrop of serious environmental problems such as global warming due to greenhouse gas emissions and depletion of fossil fuels, electrochemical devices using microorganisms such as microbial fuel cells have attracted attention as alternative environmentally friendly systems. A microbial fuel cell is a system that can generate electricity using only sunlight and water by utilizing microorganisms included in a phylum also called photosynthetic bacteria or cyanobacteria. Since it has no emissions and has a long lifespan, it has the advantage of being clean and sustainable.

[0003] However, in electrochemical devices using microorganisms, generally, the output current density (the value obtained by dividing the current value by the electrode area) is low, and improvement of the output power (hereinafter simply referred to as output) is necessary for practical use. In addition, in conventional electrochemical devices using microorganisms, planar electrodes such as ITO are used as the working electrode, the initial number of bacteria captured on the electrode is small, and the increase in the number of bacteria depends only on bacterial growth, and it has taken dozens of hours or more to obtain sufficient output from startup.

[0004] In addition, International Publication No. 2012 / 66806 pamphlet (Patent Document 1) discloses a microbial fuel cell in which a carbon nanowire structure is formed on the surface of a graphite felt or a graphite plate to increase the electrode surface area for improving the output current density. However, although a certain improvement can be expected in the output by an electrochemical device using microorganisms by increasing the electrode surface area, further improvement is desired from the viewpoint of obtaining sufficient output in a short time from startup.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 Pamphlet of International Publication No. 2012 / 66806 Patent Document 2 Japanese Patent No. 6375578 Summary of the Invention Problems to be Solved by the Invention

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide an electrochemical device using microorganisms capable of outputting sufficient power in a short time from startup. Means for Solving the Problems

[0007] The present invention relates to an electrochemical device (hereinafter, the present invention is referred to as "first electrochemical device") including a first electrode having a surface layer portion having at least one pore having an opening, wherein the pore has a conductive site on at least its inner surface, the first electrode has a conductive path for electrically connecting the conductive sites of the pores to each other, and different classes or different electron-donating microorganisms within the same class are held in the pores.

[0008] The present invention also relates to an electrochemical device (hereinafter, the present invention is referred to as "second electrochemical device") including a first electrode having a surface layer portion having at least one pore having an opening, wherein the pore has a conductive site on at least its inner surface, the first electrode has a conductive path for electrically connecting the conductive sites of the pores to each other, and electron-donating microorganisms having significantly different average particle sizes are held in the pores.

[0009] In any of the first and second electrochemical devices, the electron-donating microorganisms are preferably cyanobacteria, and more preferably a combination of Synechocystis and Synechococcus included in the order Chlorococcales of the class Oxyphotobacteria.

[0010] In the second electrochemical device, the electron-donating microorganisms having significantly different average particle sizes may be the same electron-donating microorganisms within the same taxonomic rank.

[0011] In either the first or the second electrochemical device, it is preferable that the surface layer portion has a plurality of pores arranged in a honeycomb shape.

[0012] In either the first or the second electrochemical device, it is preferable that light having a wavelength capable of causing photosynthesis is irradiated.

[0013] In either the first or the second electrochemical device, the electron-donating microorganisms may be negatively charged, and the electron-donating microorganisms may be bound via positively charged magnetic nanoparticles to form a complex.

[0014] In either the first or the second electrochemical device, it is preferable to include the first electrode as an anode and a second electrode different from the first electrode as a cathode.

[0015] The present invention also relates to a method for manufacturing an electrochemical device, including the steps of preparing an electrode including a surface layer portion having at least one pore having an opening, wherein the pore has a conductive site at least on its inner surface and includes a conductive path for electrically connecting the conductive sites of the pores, and retaining electron-donating microorganisms in the pores, wherein the electron-donating microorganisms retained in the pores are different taxonomic ranks or different electron-donating microorganisms within the same taxonomic rank (hereinafter, the present invention is referred to as the "first manufacturing method").

[0016] The present invention also provides a method for manufacturing an electrochemical device, including: preparing an electrode having a surface layer portion with at least one pore having an opening, wherein the pore has a conductive site on at least its inner surface and includes a conductive path for electrically connecting the conductive sites of the pores; and retaining electron-donating microorganisms in the pores. Here, the electron-donating microorganisms retained in the pores are electron-donating microorganisms having significantly different average particle sizes (hereinafter, this invention is referred to as the "second manufacturing method").

[0017] In either the first or second manufacturing method, it is preferable to collect electron-donating microorganisms in the pores by generating convection in the liquid by irradiating a laser beam on the surface layer portion of the electrode while the electrode is in contact with a liquid containing electron-donating microorganisms.

[0018] Also, in either the first or second manufacturing method, it is preferable that the electron-donating microorganisms are negatively charged and form a complex via positively charged magnetic nanoparticles, and the complex is collected in the pores using magnetic force.

Advantages of the Invention

[0019] According to the present invention, it is possible to provide an electrochemical device using microorganisms that can output sufficient power in a short time from startup. For example, it is possible to provide a highly efficient microbial solar cell.

Brief Description of the Drawings

[0020]

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DETAILED DESCRIPTION OF THE INVENTION

[0021] [1] Electrochemical device The electrochemical device of the present invention includes an electrode (the "first electrode") having a surface layer portion having at least one pore having an opening. The pores each have a conductive site on at least their inner surfaces. The first electrode includes a conductive path that electrically connects the conductive sites of the pores (when referring to both the above-mentioned "first electrochemical device" and "second electrochemical device", it is collectively referred to as the "electrochemical device of the present invention"). In the electrochemical device of the present invention, electron-donating microorganisms are held in the pores. An "electron-donating microorganism" is a microorganism that generates electrons by metabolic action. This enables efficient transfer of electrons generated by the microorganisms within the pores. When photosynthetic bacteria are used as the electron-donating microorganisms, electrons can be donated efficiently by irradiating light having a wavelength capable of causing photosynthesis (white light, for example, sunlight, simulated sunlight by a solar simulator, light from a fluorescent lamp, an LED, etc.), and can be used for power generation or photosensing. As the wavelength capable of causing photosynthesis, wavelengths of 200 to 3500 nm, preferably wavelengths in the near ultraviolet-visible-near infrared region of 400 to 800 nm can be used.

[0022] Since the electron-donating microorganisms captured in the pores on the surface layer of the first electrode frequently or constantly come into contact with the conductive sites on the inner surface of the pores, electrons are efficiently transferred between the conductive sites and the electron-donating microorganisms. The electrons that have migrated to the conductive sites flow through the electrode via a conductive path that electrically connects the conductive sites to each other and are collected. That is, the distance between the microorganisms and the conductive path is extremely short, the electron transfer efficiency is excellent, and there are few resistance elements. Such an electrochemical device is excellent in power output performance and sensitivity and can easily achieve a high current density in a short time.

[0023] The first electrochemical device is characterized in that the electron-donating microorganisms retained in the pores are electron-donating microorganisms that are in different taxonomic ranks or are different even within the same taxonomic rank. Here, the taxonomic rank of microorganisms refers to kingdom, phylum, class, order, family, genus, and species. Here, "different taxonomic ranks" refers to electron-donating microorganisms that are different in "kingdom", "phylum", "class", "order", "family", "genus", and "species", and "different even within the same taxonomic rank" refers to different electron-donating microorganisms included in the same "kingdom", "phylum", "class", "order", "family", "genus", and "species". The first electrochemical device only needs to contain electron-donating microorganisms that are in different taxonomic ranks or are different even within the same taxonomic rank in the pores, and the electron-donating microorganisms are not limited to two types and may of course include three or more types.

[0024] Examples of electron-donating microorganisms include cyanobacteria such as Synechocystis sp., Synechococcus sp., Arthrospira platensis (Spirulina), Anabaena sp. PCC 7120, Pseudanabaena (Limnothrix) sp. ABRG5-3, and Halomicronema hongdechloris; microorganisms of the genus Shewanella such as Shewanella loihica, Shewanella oneidensis, Shewanella putrefaciens, and Shewanella algae; microorganisms of the genus Geobacter such as Geobacter sulfurreducens and Geobacter metallireducens; microorganisms of the genus Pseudomonas such as Pseudomonas aeruginosa; and microorganisms of the genus Rhodopseudomonas such as Rhodopseudomonas ferrireducens, but are not limited thereto. Preferably, in the first electrochemical device, at least two types selected from the above-exemplified electron-donating microorganisms are used.

[0025] In the first electrochemical device, if different electron-donating microorganisms are used within different taxonomic ranks or even within the same taxonomic rank, their average particle sizes (the definition will be described later) do not necessarily have to be significantly different from each other (the definition will be described later).

[0026] For the second electrochemical device, the plurality of electron-donating microorganisms retained in the pores may have significantly different average particle sizes. Here, the "average particle size" of the electron-donating microorganisms refers to the average value ± standard deviation of the diameter in the case of cocci such as Synechocystis and Synechococcus, and refers to the average value ± standard deviation of the length of the major axis in the case of bacilli such as Shewanella loihica. Also, "significantly different average particle sizes" means that the calculated average values are different by 1.1 times or more, preferably 2 times or more. Specifically, the average particle size of the electron-donating microorganisms is calculated by measuring the particle size of the sample from the microscopic image and taking the average.

[0027] Here, the average particle size of the electron-donating microorganisms used in the second electrochemical device is not particularly limited as long as they can be accommodated in the pores. The average particle size of the electron-donating microorganisms with a large average particle size is preferably in the range of 1 to 10 μm, more preferably in the range of 2 to 5 μm. Also, from the viewpoint of being able to fill the pores with electron-donating microorganisms with significantly different average particle sizes at a high density, when the average particle size of the electron-donating microorganisms with a small average particle size is set to 1, the average particle size of the electron-donating microorganisms with a large average particle size is preferably in the ratio range of 1.2 to 10 times, more preferably in the ratio range of 1.5 to 5 times.

[0028] As the electron-donating microorganisms used in the second electrochemical device, those with significantly different average particle sizes can be preferably used from among those exemplified as the electron-donating microorganisms preferably used in the first electrochemical device, but of course, it is not limited thereto.

[0029] In the second electrochemical device, if the average particle sizes of the electron-donating microorganisms used are significantly different, they may be the same electron-donating microorganisms within the same taxonomic class. Specifically, even among the same electron-donating microorganisms within the same taxonomic class, there are variations in particle size among individuals. In the present invention, the same electron-donating microorganisms within the same taxonomic class are divided into groups with significantly different average particle sizes according to the size, and a mixture thereof may be used (this is distinguished from the case of a plurality of the same electron-donating microorganisms within the same taxonomic class with particle size variations without undergoing the operation of dividing into groups).

[0030] In the electrochemical device of the present invention, the electron-donating microorganisms retained in the pores are (1) different electron-donating microorganisms within different taxonomic classes or within the same taxonomic class (the first electrochemical device), and / or (2) those with significantly different average particle sizes (the second electrochemical device). Of course, it may be the case that both the above (1) and (2) are simultaneously satisfied, such as the combination of Synechocystis and Synechococcus described later. According to the electrochemical device of the present invention having the above (1) and / or (2), compared with conventional electrochemical devices, it becomes possible to retain electron-donating microorganisms in the pores at a higher density, and an electrochemical device using microorganisms that can output sufficient power in a short time from startup can be provided. For example, a highly efficient microbial solar cell can be provided.

[0031] During normal use, in the electrochemical device of the present invention, a medium is retained in the pores, and electron-donating microorganisms are encapsulated in the medium. This medium is also called an electrolyte and may be any of a gas, a liquid, and a solid, or a medium in an intermediate state between these. Among them, a liquid containing ions is preferable, and as this liquid containing ions, a liquid mainly composed of water is suitable, but it is not particularly limited as long as it can form an environment in which microorganisms can survive.

[0032] The conductive part only needs to be provided on at least a part of the inner surface of the pores that can come into contact with the electron-donating microorganisms, but it is preferably provided in as many regions as possible of the inner surface of the pores (for example, the entire inner surface of the pores or 90% or more of the entire surface). Further, it is preferable that the conductive paths can conduct through as many regions as possible (for example, 90% or more of all the pores) of the surface layer part. The entire surface layer part or the entire first electrode may be the conductive part.

[0033] The shape of the first electrode is not particularly limited, and it only needs to include a surface layer part having at least one pore with an opening. Also, the pore shape and the opening shape are not particularly limited and may be any shape. Examples of the pore shape include cylindrical, prismatic, spherical, ellipsoidal, or shapes similar thereto.

[0034] When the first electrode is formed of a non-conductive material and a conductive material, at least the conductive paths that connect the conductive parts to each other are formed of the conductive material. The conductive material may be a metal material, carbon, a semiconductor, or an organic substance.

[0035] At least a part of the liquid containing ions that encapsulate the electron-donating microorganisms is carried in the pores by the interfacial tension at the interface between the inner surface of the pores and the liquid. That is, the size of the pores of the first electrode only needs to be a size capable of holding the liquid containing ions that encapsulate the electron-donating microorganisms by the interfacial tension. In such pores, the electron-donating microorganisms are likely to come into contact with the conductive parts on the inner surface of the pores more frequently, enabling more efficient power generation.

[0036] The surface layer portion having pores preferably contains a light-absorbing material. By using a light-absorbing material, it becomes possible to efficiently collect microorganisms in the pores as described later. Examples of the light-absorbing material include nano-sized and micro-sized particles of metals, semiconductors, organic substances, etc. Here, "light-absorbing" means the property that the intensity of light absorbed by a substance is greater than zero. The wavelength region of light may be any one of the ultraviolet region, visible region, and near-infrared region, or a region spanning two of these three regions, or a region spanning all three regions. The light-absorbing property can be defined, for example, by the range of the light absorption rate. The lower limit of the range of the absorption rate only needs to be greater than zero and is not particularly limited. Note that the upper limit of the range of the absorption rate is 100%.

[0037] The surface layer portion has a plurality of pores, and it is preferable that these plurality of pores are arranged in the surface layer portion with a certain degree or more of regularity. By supporting microorganisms in the regularly arranged plurality of pores, the microorganisms can be uniformly present on the surface layer portion of the electrode. Therefore, advantages such as (i) an increase in the amount of microorganisms supported per unit area, (ii) a uniform distribution of microorganisms, and (iii) a uniform supply of fuel to the microorganisms can be obtained. Among them, in terms of being able to efficiently increase the pore density in the surface layer portion, the pores are preferably arranged in a honeycomb shape in the surface layer portion. Here, "honeycomb shape" refers to a shape in which a plurality of regular hexagons are arranged in a hexagonal lattice (honeycomb-like) in a two-dimensional direction, as also described in Patent No. 6375578 (Patent Document 2) by the inventors of the present application. Pores are formed in each of the plurality of regular hexagons, and each pore is a hole having an opening in the range from the order of nanometers to the order of micrometers, and may be a through-hole or a non-through-hole. Also, the shape of the pore is not particularly limited and may include any shape such as a cylindrical shape, a prismatic shape, a spherical shape excluding a true spherical shape (for example, a hemispherical shape or a semi-elliptical spherical shape). Among the honeycomb shapes, a hexagonal closest packing lattice is particularly preferable.

[0038] The electrochemical devices of the present invention include microbial fuel cells, microbial fuel cells, microbial electrolysis cells, biosensors, and the like. These electrochemical devices include a first electrode as an anode and a second electrode different from the first electrode as a cathode. The first electrode has a medium containing ions held in pores and electron-donating microorganisms encapsulated in the medium containing ions. Further, if necessary, an electrolytic cell for accommodating a medium containing ions as an electrolyte is provided. However, the electrochemical device according to the embodiment of the present invention is not particularly limited, and includes, for example, components of these electrochemical devices. Examples of the components include a probe, a sensor unit, and the like.

[0039] Hereinafter, as a preferred example of the electrochemical device of the present invention, the configuration of a microbial fuel cell will be described. FIG. 1 is a conceptual diagram of a microbial fuel cell 1 according to an embodiment of the present invention. The microbial fuel cell 1 includes an electrolytic cell 2, an anode 3, and a cathode 4. The anode 3 and the cathode 4 are immersed in an electrolyte 5 accommodated in the electrolytic cell 2, and oxygen (air) is supplied to the cathode 4 by aeration or the like. The anode 3 and the cathode 4 are electrically connected to an external circuit 6. As the anode 3 in such a configuration, the above-described first electrode is used, and electron-donating microorganisms 7 are held in at least one pore included in the surface layer portion of the anode 3. It is preferable that a part of the electrolytic cell 2 or each electrode transmits light (sunlight in FIG. 1) having a wavelength capable of causing photosynthesis and can reach the anode 3.

[0040] In the microbial fuel cell 1 having the configuration shown in FIG. 1, when receiving sunlight 8, on the anode 3 side, electrons (e - ) 9 and protons (H + ) are supplied, and these electrons 9 move to the cathode side 4 via the external circuit 6. On the cathode 4 side, protons are oxidized by oxygen, and as a result, water (H2O) is generated.

[0041] In the microbial fuel cell 1 as shown in Fig. 1, as the cathode 4, for example, conductors such as carbon and metal are used, and a catalyst such as platinum is supported on the surface of the cathode 4. The electrolyte 5 is not particularly limited, but water can be preferably used.

[0042] Although not shown in Fig. 1, a diaphragm may be provided between the anode 3 and the cathode 4 to form a two-chamber microbial fuel cell. In this case, as the diaphragm, a proton exchange membrane (PEM) that can selectively permeate hydrogen ions is preferably used. As such a proton exchange membrane, for example, a perfluorocarbon sulfonic acid-based polymer electrolyte can be used, and a specific example is Nafion (registered trademark: DuPont). Alternatively, a membrane of an organic / inorganic composite compound in which a hydrocarbon polymer such as polyvinyl alcohol and an inorganic compound such as tungstic acid are compounded may be used.

[0043] Furthermore, an electron-conductive mediator substance M can be added as necessary. The electron-conductive mediator substance refers to an electron carrier that can transport electrons from microorganisms to the electrode, such as a redox mediator compound, an electron mediator, or conductive fine particles.

[0044] The redox mediator compound mainly refers to an electron shuttle compound that is produced in electron-donating microorganisms and then released extracellularly. The electron shuttle compound transports the electrons generated by the metabolism of microorganisms to the electrode through its own oxidation-reduction while reciprocating between the microorganisms / electrode. For example, phenazine-1-carboxamide, pyocyanin, 2-amino-3-carboxy-1,4-naphthoquinone (ACNQ) can be mentioned.

[0045] The electron mediator refers to an artificially synthesized redox compound having the same function as the redox mediator compound. For example, neutral red, safranine, phenazine ethosulfate, thionin, methylene blue, toluidine blue, phenothiazinone, resorufin, galocyanine, 2-hydroxy-1,4-naphthoquinone (HNQ), porphyrin can be mentioned.

[0046] The conductive microparticles are microparticles made of metal or semiconductor that can bind to electron-donating microorganisms, extract electrons from the microorganisms, and then transfer the electrons to an electrode. Examples thereof include iron oxide, iron sulfide, and manganese oxide.

[0047] Here, FIG. 2(a) is a plan view of an example of the first electrode in the electrochemical device of the present invention used for the anode 3 in FIG. 1, and FIG. 2(b) is an enlarged cross-sectional view thereof. In the electrochemical device of the present invention, it is preferable that the surface layer portion of the first electrode has a plurality of pores arranged in a honeycomb shape as shown in FIG. 2(a), but the array pattern in the case of having a plurality of pores is of course not limited to this. Further, in FIG. 2(b), the inner surface of the pore is spherical, but it is not limited thereto. Adjacent pores may be connected inside the surface layer portion of the electrode, or each pore may be surrounded by an inner wall and be independent.

[0048] When the inner surface of the pore is spherical as shown in FIG. 2(b), once the electron-donating microorganisms trapped in the pore are restricted from moving in the direction along the spherical inner surface, it is considered that they are not easily released outside the pore. It has been clarified that the electron-donating microorganisms captured in the pore continue to stay in the pore for a long time even when they are then brought into contact with the electrolyte and used as an electrochemical device.

[0049] Each pore has an opening through which electron-donating microorganisms can enter. The size of the pore may be such that the liquid containing the electron-donating microorganisms can be held by the interfacial tension at the interface between the inner surface of the pore and the liquid. The shape of the electron-donating microorganisms held in the pore may be spherical (coccus) or rod-shaped (bacillus).

[0050] As described above, in the electrochemical device of the present invention, the electron-donating microorganisms retained in the pores are (1) different electron-donating microorganisms within different taxonomic ranks or even within the same taxonomic rank (the first electrochemical device), and / or (2) those with significantly different average particle sizes (the second electrochemical device). Figure 3 shows SEM images (20,000 times magnification) (Figure 3(a)) and stereomicroscope images (400 times magnification) (Figure 3(b)) of Synechocystis sp., which is a cyanobacterium. Figure 4 shows SEM images (20,000 times magnification) (Figure 4(a)) and stereomicroscope images (400 times magnification) (Figure 4(b)) of Synechococcus sp., which is also a cyanobacterium. Synechocystis and Synechococcus differ in family or species. Also, when the average particle sizes of 100 samples were measured with a stereomicroscope, the average particle size of Synechococcus was 1.32 ± 0.13 μm, and the average particle size of Synechocystis was 2.74 ± 0.24 μm, indicating a particle size difference of 10% or more. Thus, the combination of Synechocystis and Synechococcus is different electron-donating microorganisms (different in family or species) within the same taxonomic rank (see Komarek, J., Kastovsky, J., Mares, J. & Johansen, J.R. (2014). “Taxonomic classification of cyanoprokaryotes (cyanobacterial genera) 2014, using a polyphasic approach”. Preslia 86: 295-335) and has significantly different average particle sizes, corresponding to the case where both (1) and (2) above are simultaneously satisfied.

[0051] FIG. 5 is a diagram schematically showing a composite 21 of electron-donating microorganisms 22, 23 and magnetic nanoparticles 24 that can be suitably used in the electrochemical device of the present invention. FIG. 6 is a SEM image of the composite actually produced in an experimental example described later. In the electrochemical device of the present invention, the electron-donating microorganisms are negatively charged, and the electron-donating microorganisms 22, 23 may be combined via positively charged magnetic nanoparticles to form a composite 21. In the example shown in FIG. 5, both of the electron-donating microorganisms 22, 23 are negatively charged (when the electron-donating microorganism 22 with a large average particle size is Synechocystis, the zeta potential is -11 mV; when the electron-donating microorganism 23 with a small average particle size is Synechococcus, the zeta potential is -21 mV), and a plurality of positively charged magnetic nanoparticles are electrostatically bonded to the surface of the electron-donating microorganism 22 with a large average particle size. A plurality of electron-donating microorganisms 23 with a small average particle size are electrostatically bonded to the plurality of magnetic nanoparticles 24 electrostatically bonded to the surface of the electron-donating microorganism 22, thereby forming a composite 21 in which a plurality of electron-donating microorganisms 23 are bonded to one electron-donating microorganism 22 via magnetic nanoparticles 24.

[0052] As materials for the magnetic nanoparticles, magnetite, hematite, cobalt, and iron platinum etc. are used, but magnetite is preferred because the raw materials are inexpensive and it is possible to synthesize them in large quantities. Here, FIG. 7 is a diagram schematically showing the surface of the positively charged magnetic nanoparticles 24. FIG. 7 shows the case where a positive charge (NH3 + ) is added to the surface of magnetite (magnetic nanoparticles) using silane coupling. The zeta potential of magnetite is about +15 mV, but after the silane coupling treatment, the zeta potential becomes about +24 to 54 mV.

[0053] FIG. 8 is a diagram schematically showing the collection into pores when the composite 21 shown in FIG. 5 is used. When the composite 21 as shown in FIG. 5 is used, since it contains magnetic nanoparticles 24, as described later, it becomes possible to collect the composite 21 into the pores 31 using the magnetic force with a magnet 32. As the magnet 32, for example, a neodymium magnet or an electromagnet can be suitably used, but of course it is not limited thereto.

[0054] [2] Method for manufacturing an electrochemical device The method for manufacturing an electrochemical device of the present invention includes a step of preparing an electrode having a surface layer portion having at least one pore having an opening, wherein the pore has a conductive site on at least its inner surface, and a conductive path for electrically connecting the conductive sites of the pores, and a step of holding electron-donating microorganisms in the pores (collectively referred to as "the method for manufacturing an electrochemical device of the present invention" when referring to both the "first manufacturing method" and the "second manufacturing method" described above).

[0055] The first manufacturing method is characterized in that the electron-donating microorganisms to be held in the pores are different taxonomic classes or different electron-donating microorganisms even within the same taxonomic class. Such a first manufacturing method is a method for manufacturing the first electrochemical device described above, and the definitions of terms such as "different taxonomic classes" and "different even within the same taxonomic class" are as described above for the first electrochemical device.

[0056] The second manufacturing method is characterized in that the electron-donating microorganisms to be held in the pores are a plurality of electron-donating microorganisms having significantly different average particle sizes. Such a second manufacturing method is a method for manufacturing the second electrochemical device described above, and the definitions of terms such as "average particle size" and "significantly different average particle sizes" are as described above for the second electrochemical device.

[0057] In the method for manufacturing an electrochemical device of the present invention, the step of preparing the electrode can be performed, for example, as follows.

[0058] First, a liquid composition in which a thin film forming material is dissolved in a hydrophobic organic solvent is prepared, and a liquid film of the liquid composition is formed. The liquid film of the liquid composition may be formed on a support. Examples of the support include glass, metal, carbon materials, silicon materials, and polymer materials. As the polymer materials, depending on the application, highly flexible polyethylene naphthalate, polyethylene terephthalate, polypropylene, etc. can be used.

[0059] Next, droplets of an aqueous solvent are formed on the liquid film. Water is preferred as the aqueous solvent. For example, high-humidity air may be blown onto the liquid film. The high-humidity air preferably has a relative humidity of 50 to 95%. When the organic solvent evaporates from the liquid film of the liquid composition, the latent heat at the surface of the liquid film is taken away. Therefore, the temperature of the liquid film surface drops, and the water vapor in the high-humidity air condenses into minute water droplets and adheres to the liquid film surface. At this time, since the surface tensions of the organic solvent and water act to minimize their interface, the water droplets aggregate and grow together.

[0060] It is preferable to add an amphiphilic compound or a surfactant having an affinity for both the organic solvent and the aqueous solvent to the liquid composition. Due to the action of the amphiphilic compound or surfactant in the liquid composition, the state in which the organic solvent (liquid composition) exists around the water droplets becomes stable. Therefore, the water droplets are incorporated into the liquid film and become spherical within the liquid film to minimize their surface area. Furthermore, due to the action of the transverse capillary force, the water droplets are filled as densely as possible along the liquid film surface and grow while forming a honeycomb-like arrangement. When the evaporation of the organic solvent proceeds from this state and the thin-film forming material in the liquid composition reaches a certain concentration or more, the thin-film components are precipitated and the arrangement of the water droplets is fixed.

[0061] Thereafter, when the water droplets evaporate, pores arranged in a honeycomb shape and a skeletal portion of the thin-film components surrounding the pores remain, and an electrode precursor having a surface layer portion in which the pores having openings are arranged in a honeycomb shape can be obtained. Since the honeycomb-like arrangement proceeds spontaneously due to surface tension and natural convection, it is called self-organization and is known to have an extremely uniform and regular structure.

[0062] As the thin film forming material, a polymer material or its raw material is preferably used. Specifically, aliphatic polyesters such as polylactic acid, polyhydroxybutyric acid, polycaprolactone, polyethylene adipate, and polybutylene adipate; polyacrylic acid esters such as polymethyl methacrylate and polytetrahydrofurfuryl methacrylate; aliphatic polycarbonates such as polybutylene carbonate and polyethylene carbonate; polyimides such as polyimide, polyamideimide, polyetherimide, and polyesterimide; polystyrene, etc. can be mentioned. Further, two or more kinds may be used as a polymer blend.

[0063] As the thin film forming material, a monomer material may be used and polymerized after forming a liquid film. In this case, the monomer compounds used for the polymerization of the above-mentioned polymer materials can be appropriately selected and used. Further, a polymer material may be combined with a monomer material and / or an oligomer material, polyion, etc. Also, a crosslinking agent, a catalyst, etc. may be used.

[0064] The hydrophobic organic solvent may be any one that is insoluble in an aqueous solvent. Specifically, halogen-based organic solvents such as chloroform and methylene chloride; aromatic hydrocarbons such as benzene, toluene, and xylene; esters such as ethyl acetate and butyl acetate; water-insoluble ketones such as methyl isobutyl ketone; ethers such as diethyl ether, etc. can be mentioned. Also, solvents such as carbon disulfide can also be used.

[0065] The amphiphilic compound is not particularly limited, and examples thereof include an amphiphilic polymer having a polyacrylamide as a main chain skeleton, a dodecyl group as a hydrophobic side chain, and a carboxyl group as a hydrophilic side chain, polyethylene glycol, a polypropylene glycol block copolymer, etc.

[0066] The hydrophobic side chain is a non-polar linear group such as a methylene group or a phenylene group, and preferably has a structure in which hydrophilic groups such as polar groups and ionic dissociation groups do not branch to the end except for linking groups such as ester groups and amide groups. For example, when using a methylene group, it is preferably composed of 5 or more units. The hydrophilic side chain preferably has a structure having a polar group, an ionic dissociation group, or a hydrophilic moiety such as an oxyethylene group at the end through a linking moiety such as a methylene group. Among them, it is preferable to use a compound having dimethyldistearylammonium bromide as the hydrophilic group component and sodium polystyrene sulfonate as the hydrophobic group component in the form of a polyion complex.

[0067] As the surfactant, commonly known anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, etc. can be used. Among them, hexadecyltrimethylammonium bromide (CTAB) is preferable.

[0068] In addition, the height of the inner wall of the pore is preferably larger than the minor axis (diameter in the case of cocci) of the electron-donating microorganism. However, it is not particularly limited as long as at least one electron-donating microorganism can be captured. Specifically, the height of the inner wall of the pore is, for example, 0.5 μm to 500 μm, preferably 2 μm to 100 μm, more preferably 2 μm to 50 μm, and even more preferably 2 μm to 10 μm. Also, the diameter of the pore (horizontal diameter) is not particularly limited, but is preferably 0.5 μm to 500 μm, more preferably 2 μm to 50 μm, and even more preferably 2 μm to 10 μm. In addition, the pores in the surface layer portion of the first electrode are preferably in a state where 2 or more (that is, at least including electron-donating microorganisms that are different in classification level or different even within the same classification level, or have significantly different average particle sizes) electron-donating microorganisms are captured per pore, preferably 10 or more.

[0069] Next, a conductive site is formed on the inner surface of each of the plurality of pores of the electrode precursor, and a conductive path for electrically connecting the conductive sites to each other is formed to form the first electrode. As a specific means for forming the conductive site and the conductive path, for example, a conductive film may be formed entirely on the outermost surface of the surface layer portion of the electrode precursor including the inner surface of the pores. Alternatively, the surface layer portion of the electrode precursor may be doped with conductive fine particles. Or, conductivity may be imparted to the entire electrode precursor by mixing conductive fine particles in the thin film forming material in advance.

[0070] As a method for forming the conductive film, known methods such as sputtering, vapor deposition, electroplating, electroless plating, spraying, and spin coating can be used. Among them, sputtering is preferable in that a thin and uniform conductive film can be formed. As a material for forming the conductive film, metal oxides such as gold, platinum, silver, copper, titanium, nickel, zinc, carbon, and ITO are preferable, and gold is particularly preferable.

[0071] Next, a method for collecting microorganisms in the pores of the surface layer portion of the first electrode will be described. When using the composite 21 formed by the binding of negatively charged electron-donating microorganisms via positively charged magnetic nanoparticles as shown in FIG. 5, as shown in FIG. 8, a magnet 32 is arranged on the side of the electrode opposite to the surface layer portion having pores, and the magnetic nanoparticles can be attracted together with the composite by magnetic force and collected in the pores. When collecting using such a method, compared with the case of using one-point laser light irradiation in the method of collecting using convection described later, there is an advantage that electron-donating microorganisms can be collected in a relatively short time.

[0072] Also, when not using the complex as shown in Fig. 5, as is conventionally known, convection may be generated in the liquid to move the electron-donating microorganisms and collect them in the pores. The method of causing convection in the liquid is not particularly limited, and examples include a method of circulating the liquid with a pump, a method of sucking and discharging the liquid using a nozzle or the like (pipetting), and a method of shaking the liquid. A method using electrophoresis or dielectrophoresis may also be used. For example, by utilizing the arrangement of electron-donating microorganisms parallel to the electric field and controlling the direction of the electron-donating microorganisms by the electric field, the electron-donating microorganisms can be moved to a stable region of the electromagnetic potential.

[0073] It is also possible to generate electromagnetic forces or convection in the liquid by using light or heat. By using an optical tweezer that utilizes the property of light as an electromagnetic wave to capture a micro-object with an electromagnetic force, the electron-donating microorganisms can be captured at an arbitrary location. Further, when the surface layer portion contains a light-absorbing material, by irradiating the surface layer portion of the first electrode with a laser beam, a temperature gradient can be generated in the liquid by utilizing the photothermal conversion effect, and convection can be effectively generated. Generally, the vicinity of the laser beam irradiation point becomes high temperature. On the other hand, when heating the upper part of the partition wall of the honeycomb-shaped electrode having a light-absorbing film formed on the surface layer portion, the high-temperature portion is suppressed to only a local narrow region. Therefore, convection can be effectively caused, and the influence of heat on the electron-donating microorganisms can be suppressed in most regions on the electrode, and the microorganisms can be captured while maintaining the function of the electron-donating microorganisms.

[0074] When irradiating the surface layer portion of the first electrode with laser light, it is preferable to limit the light irradiation area to a minute range. Specifically, avoiding the pore area carrying the electron-donating microorganisms, the focus (laser spot) may be irradiated onto the wall portion between adjacent pores. The laser light irradiated onto the wall portion between the pores is converted into heat at this portion, forming minute bubbles and causing a local temperature rise. Thereby, a temperature difference occurs in the liquid, and convection that transports electron-donating microorganisms from the outside of the surrounding pores into the pores occurs centering around the laser spot. Such convection also has the effect of continuously capturing the electron-donating microorganisms once captured inside the pores. The electron-donating microorganisms captured inside the pores can only proceed in one direction due to their chemotaxis, and thus continue to be captured even after the laser light irradiation is stopped.

[0075] Also, by irradiating a plurality of multiply branched laser lights onto the surface layer portion of the electrode, convection can be generated at a plurality of locations in the liquid. Specifically, the laser light may be multiply branched by a microlens array and the laser light may be irradiated onto a number of wall portions simultaneously in one irradiation. Fig. 9(a) shows a state where the laser light branched by the microlens array is irradiated onto a plurality of wall portions, and a plurality of minute bubbles are formed. Thereby, convection occurs in the liquid at a plurality of locations in the surface layer portion. Fig. 9(b) shows a state where the electron-donating microorganisms move due to the convection and the electron-donating microorganisms are simultaneously captured in a plurality of pores. By using the microlens array, the efficiency of the operation of collecting the electron-donating microorganisms in the pores is greatly improved.

[0076] As the laser light, light with a wavelength of 200 nm to 2000 nm (in air or water, the same applies hereinafter) can be used. Among them, by selecting the constituent material of the surface layer portion of the first electrode, the pore shape, the wavelength of the laser light, etc. so that the localized surface plasmon resonance conditions are satisfied, a remarkable photothermal conversion effect can be obtained. For example, when laser light with a wavelength of 400 nm to 800 nm is irradiated onto metal particles on the nano-order, localized surface plasmon resonance occurs. The conductive film of gold thin film formed by sputtering is an integrated structure of fine nano metal particles of several tens of nanometers and is likely to exhibit a photothermal conversion effect. Materials close to a black body with a high light absorption rate (such as carbon nanotube black body, metal nanoparticle-immobilized beads, etc.) are also preferable.

[0077] As described later in the experimental example, when comparing the density of electron-donating microorganisms collected in the pores between the case of multi-point laser light irradiation and the case of using the magnetic force with the above-mentioned composite 21, it was found that the density was higher in the case of multi-point laser light irradiation and the electron-donating microorganisms could be collected in the pores.

[0078] Hereinafter, the present invention will be described more specifically based on experimental examples. However, the following experimental examples do not limit the present invention. In the experimental examples, an electrode in which pores having a spherical inner surface are arranged in a honeycomb shape is also referred to as a "honeycomb thin film".

[0079] <Experimental Example> (Preparation of Raw Material Solution) A solution obtained by dissolving 64.5 mg of sodium polystyrene sulfonate in 50 mL of ultrapure water was stirred until it became transparent. Also, a solution obtained by dissolving 200 mg of dimethyldistearylammonium bromide in 100 mL of ultrapure water was stirred while heating to 70 to 80 °C until it became translucent.

[0080] Subsequently, while stirring the solution of dimethyldistearylammonium bromide, a solution of sodium polystyrenesulfonate was added to the solution of dimethyldistearylammonium bromide while maintaining the temperature, and the mixture was further stirred for 20 minutes. The colloidal polyion complex (PIC) precipitate thus formed was subjected to suction filtration. The suction-filtered PIC was dried in a vacuum desiccator. Thereafter, 12.5 mg of polystyrene and 2.5 mg of PIC were mixed in 10 mL of chloroform, and the mixed solution was vigorously mixed for 5 minutes to prepare a raw material solution.

[0081] (Fabrication of honeycomb thin film) 450 μL of the raw material solution was dropped onto a glass support of 24 mm × 60 mm × 0.15 mm. After spraying air with a relative humidity of 50 - 70% at a rate of 90 mL / min with an air pump, the honeycomb thin film was fabricated by natural drying.

[0082] Figure 2(a) is a plan view image of the obtained honeycomb thin film, and Figure 2(b) is an enlarged cross-sectional image thereof. The diameter of the pore opening is 5.0 μm, the depth is 3.0 μm, the standard deviation of the diameter of the opening is 0.1 μm or less, and a honeycomb thin film having highly uniform pores was obtained. The film thickness of the honeycomb thin film was 3 μm. From the enlarged cross-sectional image of the honeycomb thin film (Figure 2(b)), it was confirmed that the pores had a spherical inner surface. Adjacent pores were connected by through-holes near the middle in the thickness direction of the honeycomb thin film.

[0083] (Formation of conductive film) Using a sputtering apparatus (Ion Sputter MC1000) manufactured by Hitachi High-Technologies Corporation and an Au target (03E - 4233), gold sputtering treatment was performed on the honeycomb thin film to fabricate the first electrode.

[0084] Elemental analysis was performed on the honeycomb thin film (first electrode) subjected to gold sputtering using an X-ray elemental analyzer (SwiftED3000 attached to TM3000) manufactured by Hitachi High-Technologies Corporation, and it was confirmed that peaks derived from gold atoms were observed. The above peaks were observed across the upper surface of the honeycomb thin film, the bottom surface and the wall surface inside a plurality of pores, confirming that conductive sites were formed in the plurality of pores and that a conductive path was formed to electrically connect the conductive sites to each other. The film thickness of the gold film was 45 nm.

[0085] (Preparation of positively charged magnetic nanoparticles) 4.32 g of FeCl3·6H2O and 1.59 g of FeCl2·4H2O (molar ratio 2:1) were weighed out, dissolved in 80 mL of pure water, heated to 80 °C with stirring, 10 mL of 28% aqueous ammonia was added, and reacted as follows to obtain magnetite (Fe3O4) as magnetic nanoparticles. When the zeta potential of the obtained magnetite was measured using a zeta potential measuring device (ELSZ-DN2) manufactured by Otsuka Electronics Co., Ltd., it was +15.04 mV.

[0086] Fe 2+ + 2OH - → Fe(OH)2↓ Fe 3+ + 3OH - → Fe(OH)3↓ → FeOOH↓ + H2O Fe(OH)2↓ + 2FeOOH↓ → Fe3O4↓ + 2H2O Thereafter, 1 to 3 mL of 3-aminopropyltriethoxysilane was added, and heating and stirring were carried out for 90 minutes to perform a silane coupling treatment (all heating was at 80 °C). After drying, it was dispersed in pure water to a concentration of 10 mg / mL, and positively charged magnetic nanoparticles as schematically shown in Fig. 7 were obtained. The average particle size of these positively charged magnetic nanoparticles was 12.4 nm, and the zeta potential was +24 to 54 mV.

[0087] (Preparation of electron-donating microorganisms) Synechocystis sp. (obtained from the Microbial Strain Preservation Facility of the National Institute for Environmental Studies) and Synechococcus sp. (obtained from the Microbial Strain Preservation Facility of the National Institute for Environmental Studies) were concentrated. For Synechocystis sp., a dispersion with an OD of 8 and a dispersion with an OD of 10 were prepared. For Synechococcus sp., a dispersion with an OD of 2 and a dispersion with an OD of 10 were prepared. A phosphate buffer was used as the dispersion medium. When the zeta potential of the electron-donating microorganisms was measured, it was -11 mV for Synechocystis sp. and -21 mV for Synechococcus sp.

[0088] (Preparation of the complex) A 100 mM p-benzoquinone solution and a dispersion of positively charged magnetic nanoparticles (dispersion medium: ultrapure water) at 10 mg / mL were prepared. Into two microtubes each, 1 mL of a dispersion of Synechocystis sp. with an OD of 10, a dispersion of Synechocystis sp. with an OD of 8, and a dispersion of Synechococcus sp. with an OD of 10 were respectively placed. To the dispersion of Synechocystis sp. with an OD of 8, 5 μL of the dispersion of positively charged magnetic nanoparticles was added and stirred, and centrifuged for 5 minutes using a Chibitan-R (manufactured by Tokyo Glass Kikai Co., Ltd.). The supernatant was replaced with the same amount of the dispersion of Synechococcus sp. with an OD of 2, 10 μL of the p-benzoquinone solution was added, and stirred well to prepare a bacterial mixed solution. To the tubes of the dispersion of Synechocystis sp. with an OD of 10 and the dispersion of Synechococcus sp. with an OD of 10, 5 μL of the dispersion of positively charged magnetic nanoparticles and 10 μL of the p-benzoquinone solution were respectively added and stirred well. In this way, a complex as shown in Fig. 5 was prepared, in which the electron-donating microorganisms were negatively charged and Synechocystis sp. and Synechococcus sp. were bound via positively charged magnetic nanoparticles. Fig. 6 is an SEM image (400 times) of the obtained complex.

[0089] [Comparative Experiment 1] The following samples were respectively prepared.

[0090] · Sample 1: Synechococcus sp. alone · Sample 2: A mixture of Synechococcus sp. and positively charged magnetic nanoparticles · Sample 3: Synechocystis alone · Sample 4: Mixture of Synechocystis and positively charged magnetic nanoparticles · Sample 5: Complex (Synechocystis - positively charged magnetic nanoparticles - Synechococcus) · Sample 6: Mixture of Synechocystis and Synechococcus For each of these samples, as shown in Fig. 8, a neodymium magnet was used to collect them into the pores of the honeycomb thin film by utilizing magnetic force. Fig. 10 is a diagram showing the results of this Comparative Experiment 1. Fig. 10(a) shows the results for Synechococcus (left: Sample 1, right: Sample 2), Fig. 10(b) shows the results for Synechocystis (left: Sample 3, right: Sample 4), and Fig. 10(c) shows the fluorescence microscope images (100 times magnification) of the results for Synechococcus and Synechocystis (left: Sample 5, right: Sample 6). From Fig. 10, by using the complex (Synechocystis - positively charged magnetic nanoparticles - Synechococcus), Synechocystis and Synechococcus could be collected at a high density into the pores of the honeycomb thin film by utilizing magnetic force.

[0091] [Comparative Experiment 2] (Assembly of the cell for anode electrode evaluation) Fig. 11 shows the cell for anode electrode evaluation used in Comparative Experiment 2. Fig. 11(a) is a conceptual diagram and Fig. 11(b) is a photograph. The first electrode was sandwiched between an upper cell member and a lower cell member made of polytetrafluoroethylene together with a glass support to assemble the cell for anode electrode evaluation. The upper cell member was provided with a cylindrical through-hole having a diameter of 2.0 mm, and the surface layer portion of the first electrode (anode) was exposed on the bottom surface of the through-hole. The space formed by the through-hole and the surface layer portion of the first electrode (anode) is the electrolytic cell. The electrolytic cell has a bottom area of 3.14 cm 2, with a depth of 7.0 mm and a volume of 2.0 mL. A counter electrode made of platinum (Pt) wire and an Ag / AgCl (saturated KCl solution) reference electrode were inserted into the electrolytic cell. Also, the three electrodes consisting of the first electrode (anode) at the bottom of the electrolytic cell, the counter electrode, and the reference electrode were connected to a potentiostat (ALS-830C, manufactured by BAS Corporation). 2 mL of the dispersion of the composite (Synechocystis - positively charged magnetic nanoparticles - Synechococcus) was injected into the first electrode, a voltage of 0.6 V was applied, and simulated sunlight of 1000 W / m 2 was irradiated at 30-second intervals to measure the current. For comparison, the same was done for the cases of Synechococcus alone and Synechocystis alone. Also, the light irradiation intensity (light intensity) was switched to 50, 100, 500, 1000 W / m 2 to evaluate the light intensity dependence of the current density.

[0092] Figure 12 is a graph showing the results regarding the simulated sunlight responsiveness of the current density in Comparative Experiment 2. Figure 12(a) shows the results for Synechococcus alone, Figure 12(b) shows the results for Synechocystis alone, and Figure 12(c) shows the results for the composite. In all cases, the vertical axis is the current density (A / m 2 ), and the horizontal axis is the time (s). As shown in Figures 12(a), (b), and (c), in all cases, a sharp increase and decrease in the current density were confirmed with the on / off of the irradiation light, and the light responsiveness of the current density was confirmed.

[0093] Also, Figure 13 is a graph showing the results regarding the simulated sunlight intensity dependence of the increase in current density ΔI due to simulated sunlight irradiation in Comparative Experiment 2. The vertical axis is ΔI (A / m 2 ), and the horizontal axis is the light intensity (W / m 2 ). As shown in Figure 13, in all cases, it was confirmed that the current density increased with the increase in the light intensity. Here, when the light intensity was 1000 W / m 2When compared in the case of, the current density in the case of Synechocystis alone (judging from the relationship between the average particle size and the size of one pore of the first electrode, it is considered that one cell of Synechocystis is retained per pore) was about 42 times that of the case of Synechococcus alone (judging from the relationship between the average particle size and the size of one pore of the first electrode, it is considered that 19 cells of Synechococcus are retained per pore). In contrast, the current density in the case of the complex (Synechocystis - positively charged magnetic nanoparticles - Synechococcus) (judging from the relationship between the average particle size and the size of one pore of the first electrode, it is considered that one cell of Synechocystis and 12 cells of Synechococcus are retained per pore) was about 76 times that of the case of Synechococcus alone. Thus, by retaining different electron-donating microorganisms at different taxonomic levels or different electron-donating microorganisms with significantly different average particle sizes within the pores, in the case of Synechocystis alone, a synergistic high current density higher than simply adding the current densities of one cell of Synechocystis alone and 12 cells of Synechococcus alone can be achieved compared to the case of Synechocystis alone.

[0094] [Comparative Experiment 3] Figure 14(a) schematically shows the electrical circuit diagram for power evaluation used in Comparative Experiment 3, and Figure 14(b) schematically shows the microbial fuel cell 41 for power evaluation used in Comparative Experiment 3. The microbial fuel cell 41 includes a first electrode with the complex (Synechocystis - positively charged magnetic nanoparticles - Synechococcus) retained in the pores prepared as described above, with the anode 42. On the anode side, a complex of 3×10 8 cells / mL, 10 mM phosphate buffer, and 1 mM para-benzoquinone (an electron transfer substance) were added. As the cathode 43, a platinum wire was used, and a Nafion membrane (registered trademark) was interposed as the diaphragm 44 between the anode 42 and the cathode 43. Also, 10 mM potassium ferricyanide was added to the cathode side.

[0095] In Comparative Experiment 3, first, the resistance R in the electric circuit shown in Fig. 14(a) was varied within the range of 500 Ω to 10 MΩ, and the voltage V was measured. The current I and power P were calculated from the measured values. From the I-V relationship (in the graph with the voltage V on the vertical axis and the current I on the horizontal axis, the intercept is the open-circuit voltage V oc , and the slope is the internal resistance R int ), and the I-P relationship (in the graph with the power density P on the vertical axis and the current I on the horizontal axis, the peak is the maximum power P max ), the battery characteristics V oc , R int , and P max were calculated. Fig. 15(a) is a graph showing the I-V relationship obtained in Comparative Experiment 3, where the vertical axis is the voltage V (mV) and the horizontal axis is the current I (mA). Fig. 15(b) is a graph showing the I-P relationship obtained in Comparative Experiment 3, where the vertical axis is the power density (mW / m 2 ), and the horizontal axis is the current I (mA). As a result, the open-circuit voltage V oc was 417.52 mV, the internal resistance R int was 798.79 Ω, and the maximum power P max was 139.411 mW / m 2 .

[0096] [Comparative Experiment 4] As a method for collecting electron-donating microorganisms in the pores of the first electrode, a comparison was made between the case of using magnetic force with the above-described composite (Synechocystis - positively charged magnetic nanoparticles - Synechococcus) and the case of using convection by laser light. When using magnetic force, 50 μL of the bacterial solution containing the composite was used. When using convection by laser light, 50 μL of the bacterial solution containing the same amount of Synechocystis and Synechococcus as those constituting the composite was used. The collection using magnetic force was performed using a neodymium magnet in the same manner as in Comparative Experiment 1. When using convection by laser light, laser irradiation was performed at 100 points with a laser wavelength of 1064 nm, an output of 0.021 W (the output was 0.04 W) after passing through the cover glass, a 100-fold oil lens, an irradiation time of 20 seconds per point, and an irradiation interval of 50 μm. Fig. 16 is a diagram showing the results of this Comparative Experiment 4. Fig. 16(a) is a fluorescence microscope image (100-fold) when using magnetic force, and Fig. 16(b) is a fluorescence microscope image (100-fold) when using convection by laser light.

[0097] Also, when using magnetic force and when using convection by laser light, the first electrodes on which the respective electron-donating microorganisms were collected were incorporated into the anode electrode evaluation cell described above in Comparative Experiment 2, and while applying a voltage of 0.6 V, 2 simulated sunlight of 1000 W / m was applied for current measurement. Fig. 17 is a graph showing a comparison of the increase in current density ΔI when simulated sunlight was irradiated in the case of collecting electron-donating microorganisms using magnetic force in Comparative Experiment 4 and in the case of collecting electron-donating microorganisms using convection by laser light. The vertical axis is ΔI (A / m 2 ). As shown in Fig. 17, when using convection by laser light, a ΔI approximately 2.5 times higher than that when using magnetic force was obtained. It is considered highly likely that electron-donating microorganisms can be accumulated at a higher density in the pores when using convection by laser light.

Industrial Applicability

[0098] The electrochemical device according to the present invention is suitable for supporting and growing microorganisms and has excellent electrochemical properties, so it can be widely applied to microbial fuel cells, microbial electrolysis cells, biosensors, microbial solar cells, optical sensors, etc.

Explanation of Symbols

[0099] 1 Microbial solar cell, 2 Electrolytic cell, 3 Anode, 4 Cathode, 5 Electrolyte, 6 External circuit, 7 Electron-donating microorganism, 8 Sunlight, 9 Electron, 21 Composite, 22 Electron-donating microorganism, 23 Electron-donating microorganism, 24 Magnetic nanoparticle, 31 Pore, 32 Magnet, 41 Microbial solar cell, 42 Anode, 43 Cathode, 44 Diaphragm.

Claims

1. including a first electrode having a surface layer portion with at least one pore having an opening, wherein the pore has at least a conductive site on its inner surface, the first electrode has a conductive path for electrically connecting the conductive sites of the pores to each other, an electrochemical device in which a plurality of electron-donating microorganisms having significantly different average particle sizes are held in the pores.

2. The electrochemical device according to claim 1, wherein the electron-donating microorganism is cyanobacteria.

3. The electrochemical device according to claim 2, wherein the electron-donating microorganism is a combination of Synechocystis and Synechococcus.

4. The electrochemical device according to claim 1, wherein the electron-donating microorganisms having significantly different average particle sizes are the same electron-donating microorganisms within the same taxonomic rank.

5. The electrochemical device according to claim 1, wherein the surface layer portion has a plurality of pores arranged in a honeycomb shape.

6. The electrochemical device according to claim 1, which is irradiated with light having a wavelength capable of causing photosynthesis.

7. The electrochemical device according to claim 1, wherein the electron-donating microorganism is negatively charged and forms a complex by binding the electron-donating microorganism via positively charged magnetic nanoparticles.

8. The electrochemical device according to claim 1, comprising the first electrode as an anode and a second electrode different from the first electrode as a cathode.

9. preparing an electrode having a surface layer portion with at least one pore having an opening, wherein the pore has at least a conductive site on its inner surface and includes a conductive path for electrically connecting the conductive sites of the pores to each other; and a step of holding electron-donating microorganisms in the pores, wherein the electron-donating microorganisms to be held in the pores are a plurality of electron-donating microorganisms having significantly different average particle sizes, a method for manufacturing an electrochemical device.

10. The method for manufacturing an electrochemical device according to claim 9, wherein by irradiating a laser beam on the surface layer portion of the electrode while the electrode is in contact with a liquid containing electron-donating microorganisms, convection is generated in the liquid, thereby collecting the electron-donating microorganisms in the pores.

11. The method for manufacturing an electrochemical device according to claim 9, wherein the electron-donating microorganism is negatively charged, forms a complex via positively charged magnetic nanoparticles, and the complex is collected in the pores using a magnetic force.

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