Microbial fuel cell
Patent Information
- Application Number
- JP2022076291
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-05-02
- Publication Date
- 2025-04-28
- Estimated Expiration
- 2042-05-02
AI Technical Summary
Microbial fuel cells with open negative electrodes are slow to activate in environments with high dissolved oxygen, requiring a prolonged time to generate expected power.
Incorporating an anaerobic condition generation/maintenance layer with a DO2/DO1 ratio of 80% or less over the negative electrode surface, utilizing materials like aerobic microorganisms, oxygen scavengers, and oxygen permeation suppression filters to reduce dissolved oxygen, ensuring rapid activation of current-producing microorganisms.
The solution enables microbial fuel cells to quickly generate expected power even in oxygen-rich environments by reducing dissolved oxygen levels, thereby shortening the activation time of current-producing microorganisms.
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Abstract
Description
[Technical Field]
[0001] The present disclosure relates to microbial fuel cells. [Background technology]
[0002] Microbial fuel cells that use anaerobic current-producing microorganisms are known. In a microbial fuel cell, current-producing microorganisms living near the negative electrode take in organic matter (electron donors) such as sugars and organic acids and water during their metabolic process, generating carbon dioxide, protons, and electrons, and donating the electrons to the negative electrode (Reaction Formula 1). The electrons are transferred from the negative electrode to the positive electrode via an external circuit. At the positive electrode, oxygen (electron acceptor) and protons accept the electrons, producing water (Reaction Formula 2). Microbial fuel cells generate electricity through this series of reactions. Negative electrode: Organic matter +2H2O→CO2+4H + +4e - (Reaction Scheme 1) Positive electrode: O2+4H + +4e - →2H2O (Reaction 2)
[0003] For example, Patent Document 1 discloses a microbial fuel cell in which a negative electrode and a positive electrode are placed on the lower and upper parts of the inner wall surface of a cylindrical holder. The negative electrode of this microbial fuel cell is placed in a mud layer (sludge layer) containing organic matter and anaerobic microorganisms, and the positive electrode is placed in a water layer above the mud layer. Patent Document 2 also discloses a microbial fuel cell that has a cylindrical holder with an opening, a negative electrode placed on the outer surface of the cylindrical holder, and a positive electrode placed inside the cylindrical holder, with the negative electrode and positive electrode connected to the opening via an ion conductor. This microbial fuel cell can be easily installed by simply sticking it into soil or mud containing anaerobic current-producing bacteria (electric current-producing microorganisms), and can generate electricity semi-permanently from natural ecosystems. [Prior art documents] [Patent documents]
[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-84541 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-54053 Summary of the Invention [Problem to be solved by the invention]
[0005] In both the microbial fuel cells of Patent Documents 1 and 2, the generation of electricity by Reaction Scheme 1 requires the supply of organic matter to the current-producing microorganisms near the negative electrode, and therefore the negative electrode is open to the outside world.
[0006] When a microbial fuel cell is placed in an environment with a high dissolved oxygen content, the current-producing microorganisms are anaerobic and do not activate easily, so it may take some time before the expected amount of electricity is produced.
[0007] The present disclosure has been made in consideration of the above-mentioned circumstances, and the purpose of the present disclosure is to provide a microbial fuel cell that can quickly generate the expected amount of power even when installed in an environment with a high amount of dissolved oxygen. [Means for solving the problem]
[0008] One aspect of the present disclosure is The battery comprises a negative electrode, a positive electrode, an ion conductor, and an anaerobic condition generating and maintaining layer, the negative electrode and the positive electrode are connected via the ion conductor, the anaerobic condition generating / maintaining layer covers at least a part of a surface of the negative electrode to which an organic substance is supplied, The anaerobic condition generating and maintaining layer is permeable to the organic matter, and the microbial fuel cell is characterized in that, when the following experiment is carried out, DO2 / DO1 is 80% or less. experiment: The connecting pipe (inner diameter: 3.3 cm) between the first cell and the second cell is separated by the anaerobic condition generating and maintaining layer, the first cell includes a first top opening and the second cell includes a second top opening; the first upper opening is always open, and the first cell is always exposed to the atmosphere; the second cell is filled with pure water with all openings other than the second upper opening closed, the second upper opening is opened to expose the pure water to the atmosphere, and the dissolved oxygen amount (DO1) of the pure water in which a saturated amount of oxygen has been dissolved is measured; The pure water is bubbled with nitrogen gas to remove dissolved oxygen, the second upper opening is closed, and after 25 hours, the amount of dissolved oxygen (DO2) in the pure water is measured.
[0009] By covering at least a portion of the surface of the negative electrode where organic matter is supplied with an anaerobic condition generation and maintenance layer, where DO2 / DO1 is 80% or less in the above experiment, the amount of dissolved oxygen in that area is reduced in a relatively short period of time, and the current-producing microorganisms can be activated, thereby providing a microbial fuel cell that can quickly generate the expected amount of power even when installed in an environment with a high amount of dissolved oxygen.
[0010] In one aspect of the present disclosure, The anaerobic condition generating and maintaining layer preferably contains aerobic microorganisms, an oxygen absorber, an oxygen permeation suppressing filter, a water-absorbent polymer, or soil.
[0011] Dissolved oxygen is consumed by aerobic microorganisms and oxygen absorbers, and oxygen permeation is inhibited by oxygen permeation inhibiting filters, water-absorbent polymers, or soil, so the amount of dissolved oxygen in those areas is reduced in a shorter time, the current-producing microorganisms are activated, and the time until the expected electricity is obtained is further shortened.
[0012] In one aspect of the present disclosure, The anaerobic condition generating and maintaining layer preferably covers the entire surface of the negative electrode on the side to which the organic substance is supplied.
[0013] As the area covered with the anaerobic condition generation and maintenance layer increases, the amount of dissolved oxygen is reduced in a shorter time, the current-producing microorganisms are activated, and the time until the expected electricity is obtained is further shortened.
[0014] In one aspect of the present disclosure, Further provided with a cylindrical holder, It is preferable that the anaerobic condition generating and maintaining layer, the negative electrode, the ion conductor, and the positive electrode are arranged in this order from one end to the other end inside the cylindrical holder.
[0015] When the cylindrical holder is buried in soil or other materials, organic matter is supplied to the negative electrode from one end of the holder through the anaerobic condition generating and maintaining layer, and oxygen is supplied to the positive electrode from the other end of the holder, generating electricity. Because the microbial fuel cell can be handled as a unit housed in the cylindrical holder, installation and wiring are simple. Therefore, it is easy to connect multiple microbial fuel cells in series or parallel to increase the electromotive force. [Brief explanation of the drawings]
[0016] [Figure 1] 1 illustrates an embodiment of a microbial fuel cell. [Figure 2] The experimental setup is shown. [Figure 3] The experimental setup is shown. [Figure 4] The experimental setup is shown. DETAILED DESCRIPTION OF THE INVENTION
[0017] Preferred embodiments of the present invention will be described in detail below. Note that the embodiments described below do not unduly limit the content of the present disclosure described in the claims, and not all of the configurations described in the embodiments are necessarily essential as means for solving the problems of the present disclosure.
[0018] FIG. 1 shows one embodiment of a microbial fuel cell 10 of the present disclosure. The microbial fuel cell 10 includes an anode 11, a cathode 12, an ion conductor 13, an anaerobic condition generating and maintaining layer 14, and a cylindrical support 15. The anaerobic condition generating and maintaining layer 14, the anode 11, the ion conductor 13, and the cathode 12 are arranged in this order from one end to the other inside the cylindrical support 15. The anode 11 and the cathode 12 are connected via the ion conductor 13, and the anaerobic condition generating and maintaining layer 14 covers the entire surface of the anode 11 on the side to which organic matter is supplied. Note that the anaerobic condition generating and maintaining layer 14 only needs to cover at least a portion of the surface of the anode 11 on the side to which organic matter is supplied. The anaerobic condition generating and maintaining layer 14 is permeable to organic matter, and in the following experiment, the DO2 / DO1 ratio was 80% or less.
[0019] When one end of the microbial fuel cell 10 is placed in soil or mud, organic matter in the soil or mud flows through one end of the tubular support 15 and passes through the anaerobic condition generating and maintaining layer 14 along with the water flow, and is supplied to the negative electrode 11. Current-producing microorganisms living near the negative electrode 11 generate carbon dioxide, protons, and electrons according to reaction formula 1, and donate the electrons to the negative electrode 11. The electrons are transmitted from the negative electrode 11 to an external circuit via the negative electrode lead wire 16, and then from the external circuit to the positive electrode 12 via the positive electrode lead wire 17. The protons generated by the current-producing microorganisms are transmitted to the positive electrode 12 via the ion conductor 13. The other end of the tubular support 15 is open to the atmosphere, and oxygen is supplied from the other end to the positive electrode 12. At the positive electrode 12, oxygen (electron acceptor) and protons accept electrons, and water is produced according to reaction formula 2.
[0020] The negative electrode 11 preferably has a surface structure that is conducive to the habitation of current-producing microorganisms and is electrically conductive. Examples of materials that can be used include carbon, stainless steel, iron, titanium, platinum, gold, silver, copper, nickel, cobalt, ruthenium, and alloys thereof, as well as biocathodes using enzymes or microorganisms as electrode catalysts and composites of these with carbon. Examples of forms that can be used include flat shapes such as sheets, brushes, and meshes; cotton-like shapes such as felt and nonwoven fabrics; and rod-like shapes such as rods. Current-producing microorganisms may be enriched and cultured on the surface of the negative electrode 11 in advance.
[0021] The positive electrode 12 preferably has a large contact area with the atmosphere and is electrically conductive. Examples of materials that can be used include carbon, stainless steel, iron, titanium, platinum, gold, silver, copper, nickel, cobalt, ruthenium, and alloys thereof, as well as non-platinum catalysts such as iron phthalocyanine-based organometallic complexes, biocathodes using enzymes or microorganisms as electrode catalysts, and composites of these with carbon. The positive electrode 12 can be in a flat form such as a sheet, brush, or mesh; a cotton-like form such as a felt or nonwoven fabric; or a rod-like form such as a rod.
[0022] The ion conductor 13 transfers the protons generated by the current-producing microorganisms to the positive electrode 12. Examples of materials that can be used include porous membranes, ion-exchange polymer membranes such as DuPont's Nafion, aramid nonwoven paper, cellulose fibers, fibers such as Japanese paper and glass fibers, electrolyte solutions containing ionic salts such as sodium chloride and potassium chloride, gels (agar, etc.), soil, and water.
[0023] The anaerobic condition generating / maintaining layer 14 is permeable to organic matter, and the following experiment shows that the DO2 / DO1 ratio is 80% or less, preferably 75% or less, more preferably 65% or less, even more preferably 55% or less, and particularly preferably 51% or less. The smaller the DO2 / DO1 ratio, the more rapidly the amount of dissolved oxygen is reduced on the surface of the anode 11 covered by the anaerobic condition generating / maintaining layer 14, which activates the current-producing microorganisms. Therefore, even if the microbial fuel cell 10 is installed in an environment with a high dissolved oxygen content, the time required to obtain the expected power can be shortened. The anaerobic condition generating / maintaining layer 14 is permeable to organic matter, and the following experiment shows that the DO2 / DO1 ratio is small. Methods for reducing the DO2 / DO1 ratio include oxygen consumption and oxygen permeation inhibition. The former anaerobic condition generating / maintaining layer 14 may contain, for example, aerobic microorganisms or oxygen scavengers. The latter anaerobic condition generating / maintaining layer 14 may contain, for example, soil deaerated by blowing nitrogen gas or carbon dioxide gas, an oxygen permeation suppression filter, a water-absorbent polymer, or soil (humic substances or humic substances). The aerobic microorganisms and oxygen absorbers may be contained in the anaerobic condition generating / maintaining layer 14 alone, or may be added to soil, a solution, a gel, or the like and then contained in the anaerobic condition generating / maintaining layer 14. Examples of oxygen absorbers that can be used include reducing agents such as divalent iron ions (FeO), ascorbic acid, and oxalic acid. Examples of oxygen permeation suppression filters that can be used include dialysis tubing.
[0024] The experiment will be described with reference to Figures 2 to 4. The experimental apparatus 20 includes a first cell 21, a second cell 22, a connecting pipe 23 with an inner diameter of 3.3 cm, and an anaerobic condition generating and maintaining layer 14. The first cell 21, the second cell 22, and the connecting pipe 23 form a so-called H-shaped cell, and the connecting pipe 23 between the first cell 21 and the second cell 22 is separated by the anaerobic condition generating and maintaining layer 14. The first cell 21 includes a first upper opening 24, and the second cell 22 includes a second upper opening 25. The first upper opening 24 is always open, and the first cell 21 is always exposed to the atmosphere. The second cell 22 has all openings closed except for the second upper opening 25, and is filled with pure water 26. The second upper opening 25 is opened, exposing the pure water 26 to the atmosphere (Figure 2), and the amount of dissolved oxygen (DO1) in the pure water 26, which has reached a saturated oxygen concentration, is measured using a dissolved oxygen meter. Nitrogen gas is then bubbled through the pure water 26 to remove the dissolved oxygen (Figure 3), and the second upper opening 25 is closed with a lid 27 (Figure 4). Because the atmosphere comes into contact with the anaerobic condition generating and maintaining layer 14 through the first upper opening 24, the first cell 21, and the connecting pipe 23, oxygen passes through the anaerobic condition generating and maintaining layer 14 and gradually dissolves into the pure water 26 in the second cell 22. After 25 hours, the amount of dissolved oxygen (DO2) in the pure water 26 is measured using a dissolved oxygen meter.
[0025] As examples of the above experiment, the results of a case where an unloaded dialysis tube was used as the anaerobic condition generating / maintaining layer 14 (Example 1) and a case where a dialysis tube loaded with soil containing aerobic microorganisms was used as the anaerobic condition generating / maintaining layer 14 (Example 2) are shown in Table 1. As a comparative example, Table 1 shows the results of a case where the connecting tube 23 was covered with an impermeable lid and the second upper opening 25 of the second cell 22 was always open, i.e., not closed with the lid 27 (Comparative Example). [Table 1]
[0026] In the comparative example, oxygen permeated through the second upper opening 25 and dissolved in the pure water 26 in the second cell 22, resulting in an increase in the amount of dissolved oxygen to 96% of the saturated amount after 25 hours. In contrast, in Example 1, the amount of dissolved oxygen after 25 hours was reduced to approximately 74% of the saturated amount. This is believed to be because oxygen permeated through the dialysis tubing and gradually diffused into the pure water 26 in the second cell 22. In Example 2, the amount of dissolved oxygen after 25 hours was reduced to approximately 50% of the saturated amount. This is believed to be because the aerobic microorganisms contained in the anaerobic condition generating / maintaining layer 14 consumed oxygen. Because the anaerobic condition generating / maintaining layer 14 uses dialysis tubing, it is able to permeate organic matter supplied to the current-producing microorganisms and retain aerobic microorganisms. Therefore, by using a microbial fuel cell 10 in which at least a portion of the surface of the negative electrode 11 on which organic matter is supplied is covered with this anaerobic condition generating / maintaining layer 14, the amount of dissolved oxygen in that area is reduced in a relatively short period of time, activating the current-producing microorganisms and shortening the time required to obtain the expected amount of electricity even when the fuel cell is installed in an environment with a high amount of dissolved oxygen.
[0027] Although the present embodiment has been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel features and advantages of the present disclosure. Therefore, all such modifications are included within the scope of the present disclosure. For example, a term described at least once in the specification or drawings together with a different term having a broader or similar meaning may be replaced with that different term anywhere in the specification or drawings. Furthermore, the configuration of the present embodiment is not limited to that described in the present embodiment, and various modifications are possible. [Explanation of symbols]
[0028] 10 microbial fuel cell, 11 anode, 12 cathode, 13 ion conductor, 14 anaerobic condition generating and maintaining layer, 15 cylindrical holder, 16 anode lead wire, 17 cathode lead wire, 20 experimental apparatus, 21 first cell, 22 second cell, 23 connecting pipe, 24 first upper opening, 25 second upper opening, 26 pure water, 27 lid
Claims
1. The battery includes a negative electrode, a positive electrode, an ion conductor, and an anaerobic condition generating and maintaining layer, the negative electrode and the positive electrode are connected via the ion conductor, the anaerobic condition generating and maintaining layer covers at least a part of a surface of the negative electrode to which an organic substance is supplied, A microbial fuel cell characterized in that the anaerobic condition generating and maintaining layer is permeable to the organic matter, and when the following experiment is performed, DO2 / DO1 is 80% or less. experiment: The connecting pipe (inner diameter: 3.3 cm) between the first cell and the second cell is separated by the anaerobic condition generating and maintaining layer, the first cell includes a first top opening, and the second cell includes a second top opening; the first upper opening is always open, and the first cell is always exposed to the atmosphere; the second cell is filled with pure water with all openings other than the second upper opening closed, the second upper opening is opened to expose the pure water to the atmosphere, and the dissolved oxygen amount (DO1) of the pure water in which a saturated amount of oxygen has been dissolved is measured; The pure water is bubbled with nitrogen gas to remove dissolved oxygen, the second upper opening is closed, and after 25 hours, the amount of dissolved oxygen (DO2) in the pure water is measured.
2. The microbial fuel cell according to claim 1, A microbial fuel cell, wherein the anaerobic condition generating and maintaining layer comprises aerobic microorganisms, an oxygen absorber, an oxygen permeation suppressing filter, a water-absorbent polymer, or soil.
3. The microbial fuel cell according to claim 1, A microbial fuel cell characterized in that the anaerobic condition generating and maintaining layer covers the entire surface of the negative electrode on the side to which the organic matter is supplied.
4. The microbial fuel cell according to claim 1, Further provided with a cylindrical holder, A microbial fuel cell characterized in that the anaerobic condition generating and maintaining layer, the negative electrode, the ion conductor, and the positive electrode are arranged in order from one end to the other inside the cylindrical holder.