JP6351448B2 - Microbial fuel cell - Google Patents

Description

  The present invention relates to a cell structure of a microbial fuel cell.

A fuel cell in which hydrogen (H ₂ ) and oxygen (O ₂ ) are combined to produce water (H ₂ O) and take out electrons (e ⁻ ) is produced only by water and is clean. In recent years, it has attracted attention as an energy source. However, hydrogen fuel cells, which are hydrogen fuel cells, are expensive because noble metals such as platinum are used for the electrode catalyst, and hydrogen as a fuel is not around us and requires separate purification and reforming. is there.

In contrast, by using the microorganisms to the electrode catalyst, personal hydrocarbons, as a generator capable fuel cell from organic substances such as amino acids, microorganisms (bio) fuel cells are attracting attention as clean energy at low cost ing. In general, a microbial fuel cell has a configuration in which oxygen is reduced at a cathode electrode, and organic fuel such as hydrocarbons and amino acids is oxidized at an anode electrode. In the microbial fuel cell, in the reduction of oxygen at the cathode electrode, in addition to the noble metal catalyst such as platinum, the reaction can be performed with an electrode material having oxygen reducing ability such as carbon. In the microbial fuel cell, the oxidation of fuel at the anode electrode is performed by the electrode receiving electrons transmitted in the process of metabolism (oxidation) of the fuel by the microorganisms supported on the anode electrode.

  For example, in Japanese Patent Application Laid-Open No. 2007-32405 (Patent Document 1), an anode tank (culture tank) and a cathode tank (oxidation-reduction reaction tank) are separated by an insulating ion exchange membrane, and a microorganism serving as an anode catalyst in the anode tank and Disclosed is a microbial fuel cell having a structure in which a solvent mixed with organic molecules serving as the fuel is sealed, and a solvent different from that in the anode tank is sealed in which the cathode tank is mixed with oxygen and molecules responsible for electron mediation between the electrodes. ing.

  In order to construct a microbial fuel cell at a simpler and lower cost, it is possible to construct a microbial fuel cell by embedding an electrode serving as an anode in the soil and disposing a cathode electrode on the soil surface (Keego Tech). See the publicly known document (Non-Patent Document 1) listed in the item “Education” (http://www.keegotech.com/Community/Education) in the item “Community” on the company's website. to MFCs "Dirt = Power: An Intro to Microbial Fuel Cells"). Such a battery structure eliminates the need for microbial extraction, adjustment of the anolyte and catholyte solutions, and expensive ion exchange membranes with high molecular permeation selectivity. Is possible.

  However, the microorganisms used in the anode of such microbial fuel cells are usually anaerobic in many cases. Here, anaerobic includes obligate anaerobic and facultative anaerobic. When power is generated by placing electrodes in soil or mud, obligate anaerobic microorganisms cannot live on oxygen-rich soil and mud surface parts, and facultative anaerobic microorganisms do not have oxygen-rich soil. In addition, since the fuel cannot be metabolized (oxidized) at the surface of the mud, the anode must be disposed at a deep location away from the surface. Further, the presence of oxygen in the vicinity of the anode causes a decrease in battery performance due to an oxygen reduction reaction at the anode. For this reason, the distance between the anode and the cathode must be increased, making it difficult to reduce the thickness and size of the battery.

JP 2007-32005 A

Keego Tech homepage (http://www.keegotech.com/Community/Education)

  The present invention has been made in view of the present situation, and an object of the present invention is to provide a microbial fuel cell that has high power generation performance and can be reduced in thickness and size by direct power generation from soil or mud at low cost.

  In order to solve the above-mentioned problems, the present inventors paid attention to disposing an “oxygen permeation limiting layer” between the anode electrode and the cathode electrode. That is, the present invention is as follows.

  The microbial fuel cell according to the present invention includes an anode electrode that oxidizes an organic fuel supplied from soil or mud, and oxygen supplied from air and water, using a current generating bacterium supplied from soil or mud as a catalyst. A microbial fuel cell comprising a cathode electrode for performing reduction of oxygen, wherein an oxygen permeation limiting layer is provided between the anode electrode and the cathode electrode facing each other.

  In the microbial fuel cell of the present invention, the oxygen permeation limiting layer is preferably a layer formed of a hydrogel, and more preferably the hydrogel is formed of a polymer sugar chain.

  In the microbial fuel cell of the present invention, it is preferable that a moisture retention layer is provided on the cathode electrode.

  The microbial fuel cell of the present invention preferably further comprises a housing having one or more holes in which at least one of microorganisms and nutrients thereof can be exchanged on the anode electrode side of the oxygen permeation limiting layer.

  ADVANTAGE OF THE INVENTION According to this invention, the microbial fuel cell which can maintain a thin and high electric power generation performance rather than the direct electric power generation from soil or mud can be provided at low cost.

It is a figure which shows typically the microbial fuel cell 1 of Embodiment 1 of this invention. It is a figure which shows typically the microbial fuel cell 11 of Embodiment 2 of this invention. It is a figure which shows typically the microbial fuel cell 21 of Embodiment 3 of this invention. It is a figure which shows typically the microbial fuel cell 31 of Embodiment 4 of this invention. It is a figure which shows typically the microbial fuel cell 41 of Embodiment 5 of this invention. It is a figure which shows typically the microbial fuel cell 51 of Embodiment 6 of this invention. It is a figure which shows typically the microbial fuel cell 61 of Embodiment 7 of this invention. It is a figure which shows typically the microbial fuel cell 71 of Embodiment 8 of this invention. It is a figure which shows typically the microbial fuel cell 81 of Embodiment 9 of this invention. 6 is a graph showing a change in the distance between electrodes of output power of the microbial fuel cell of Example 1 and Comparative Example 1. In the microbial fuel cell of Example 1, it is the graph which plotted the output electric power when changing the thickness of an oxygen permeation restriction layer.

<Embodiment 1>
FIG. 1 is a diagram schematically showing a microbial fuel cell 1 according to Embodiment 1 of the present invention. The microbial fuel cell 1 of the example shown in FIG. 1 includes an anode electrode 2, a cathode electrode 3, an oxygen permeation limiting layer 4, soil or mud 5 (5 a, 5 b, 5 c), and a housing 6. In the example shown in FIG. 1, the housing 6 has an opening on one side and is arranged so that the opening is on the upper side, and soil or mud 5 (5a, 5b, 5c) is put therein. In the example shown in FIG. 1, the anode electrode 2 is disposed on the bottom side (lower side) of the housing 6, and the cathode electrode 3 is disposed on the opening side (upper side) of the housing 6.

  In the microbial fuel cell 1 of the present invention, as long as the oxygen permeation limiting layer 4 is sandwiched between the anode electrode 2 and the cathode electrode 3, the anode electrode 2, the cathode electrode 3, and the oxygen permeation limiting layer 4 Although there is no particular limitation on the arrangement, as in the example shown in FIG. 1, the opening side of the housing having an opening on one side is the upper side, and the cathode electrode 3, the oxygen permeation limiting layer 4, and the anode electrode are sequentially arranged from top to bottom. 2 is preferably arranged. The anode electrode 2, the oxygen permeation limiting layer 4, and the cathode electrode 3 may be disposed in this order from top to bottom, but the cathode electrode 3, the oxygen permeation limiting layer 4, the anode electrode 2, soil, Since the mud 5 (5a, 5b, 5c) and the water contained in them are difficult to fall, they are arranged with the cathode electrode 3, the oxygen permeation limiting layer 4 and the anode electrode 2 in order from the top to the bottom as shown in FIG. It is preferable that

(Anode electrode)
In the microbial fuel cell 1 of the present invention, the anode electrode 2 uses an anaerobic current generating bacterium 7 supplied from soil or mud as a catalyst, and oxidizes organic fuel supplied from the soil or mud. . As such an anode electrode 2, a material that requires electrical conductivity and excellent in corrosiveness is used. As such a material, preferably, a material such as stainless steel, platinum, gold, or carbon, or a conductive material such as a metal is used. Examples of the material include stainless steel, platinum, gold, and carbon coated.

  Furthermore, if the anode electrode 2 having a structure / shape such as a fine structure, mesh shape, etc. that can increase the electrode area than the projected area can be used, the adsorption area of microorganisms can be increased and a large generated current can be obtained.

  When carbon felt, carbon paper, or the like is used for the anode electrode 2, the electrical resistance is low, the amount of microorganisms adsorbed can be increased, and the cost can be kept lower than that of precious metal materials. I can't.

  In addition, by using an electron mediator (electron mediator) such as a quinone molecule or iron oxide for the anode electrode 2, electrons can be exchanged with microorganisms smoothly and the current can be improved. A substance (electron mediator) may be placed around the electrode or fixed to the electrode, but this is not always necessary.

  In the present invention, examples of current generating bacteria used for the anode electrode 2 include conventionally known appropriate anaerobic current generating bacteria such as Shewanella bacteria, Geobacter genus bacteria, Rhodoferax ferrireducens, and Desulfobulus propionicus. Shewanella bacteria are preferred because they are abundant and easy to exchange electrons with the anode electrode. Moreover, as an organic compound oxidized with the anode electrode 2, hydrocarbons, such as glucose, acetic acid, and lactic acid, an amino acid, etc. are preferable, for example.

(Cathode electrode)
In the microbial fuel cell 1 of the present invention, the cathode electrode 3 performs reduction of oxygen supplied from the air and water. As such a cathode electrode 3, a material that requires electrical conductivity and excellent in corrosiveness and electrochemically has an oxygen reducing ability is used. As such a material, stainless steel, platinum, Examples thereof include materials such as gold and carbon, and conductive materials such as metals coated with stainless steel, platinum, gold and carbon. In addition, a conductive material coated with an enzyme or a microorganism having oxygen reducing ability can be used for the electrode.

  Furthermore, since the reaction area with oxygen can be increased by using the cathode electrode 3 having a structure / shape such as a fine structure, mesh shape, etc. that can obtain an electrode area larger than the projected area, a large generated current is obtained in that case. be able to.

  When carbon felt, carbon paper, or the like is used for the cathode electrode 3, the electrical resistance is low, the electrode area capable of oxygen reduction can be increased, and the cost can be kept lower than the precious metal material. Not limited to materials.

  In addition, since an electron mediator (electron mediator) such as ferrocyan ion is used for the cathode electrode 3, the exchange of electrons between the electrode and oxygen can be performed smoothly and the current can be improved. (Electron mediator) may be arranged around the electrode or fixed to the electrode, but this is not always necessary.

(Oxygen permeation limiting layer)
The microbial fuel cell 1 of the present invention is characterized by having an oxygen permeation limiting layer 4 between the anode electrode 2 and the cathode electrode 3 as described above. Here, the “oxygen permeation limiting layer” limits the diffusion of oxygen in the anode electrode 2 from the cathode electrode 3 side exposed to air, and enables the movement of ions from the anode electrode 2 to the cathode electrode 3. Refers to a layer having a function of The “layer” in the “oxygen permeation limiting layer” refers to a layer including a plane perpendicular to the vertical direction of the casing 6 of the microbial fuel cell 1 and extending over the entire area of the opening of the casing. The oxygen permeation limiting layer 4 used for this purpose may be formed as long as it can inhibit the diffusion and permeation of oxygen from the cathode side in contact with the air to the anode. Considering the fact that it can respond to the shape of the housing 6 and can block oxygen tightly, and that it is easy to adjust the physical properties of the material by adjusting the salinity and density, a hydrogel-like one is preferred, especially agar Is more preferable.

  The hydrogel formed by containing a large amount of water using a polymer material as a base material is disposed between the cathode electrode 3 and the anode electrode 2, so that oxygen that enters and diffuses from the cathode side reaches the anode. Therefore, the battery can be constructed without impairing the internal resistance of the microbial fuel cell 1. In addition, it is possible to adjust the oxygen permeability, ionic conductivity, and flexibility by adjusting the polymer structure, polymer material, water content, ionic strength, etc. of the hydrogel. This is an advantage of improving the degree of freedom. Further, it can be manufactured at a very low cost compared to the case where the oxygen permeation limiting layer is formed using Nafion (registered trademark) manufactured by DuPont.

  In addition, hydrogel has high fluidity, so it can fill between soil gravel and between soil and housing, and can be easily sealed without using a gasket, has a high oxygen permeation limiting effect, and is a microbial fuel cell. Since the number of parts can be reduced, there is an advantage that it can be manufactured at a lower cost.

  Various polymer materials can be used for the hydrogel. For example, by using agar, effective production can be achieved at low cost. Agar can be inserted after it has been cured, but a more reliable oxygen permeation limiting effect can be obtained by curing in the housing.

  The oxygen permeation limiting layer 4 can be configured by using a material that consumes oxygen in addition to a material that physically limits (and prevents) the permeation of oxygen. For example, if a material such as an enzyme that reduces oxygen is used, oxygen can be consumed before reaching the anode electrode 2.

  In the microbial fuel cell of the present invention, FIG. 1 shows the case where the oxygen permeation limiting layer 4 is formed separately from the anode electrode 2 and the cathode electrode 3 separately. Of course, the anode electrode 2 and the cathode electrode 3 may be integrated.

(Microbial fuel cell)
In the microbial fuel cell 1 of the present invention having the above-described configuration, the oxygen permeation limiting layer 4 is provided between the anode electrode 2 and the cathode electrode 3 so that oxygen that reacts with the cathode electrode as in the conventional case is applied to the anode electrode. When it reaches, the problem that the performance of the anode electrode is reduced does not occur, the oxygen concentration in the vicinity of the anode electrode 2 is reduced, and a microbial fuel cell with improved performance can be provided. Further, by disposing the oxygen permeation limiting layer 4, an expensive ion exchange (cation selective permeation) membrane that has been necessary in the past can be made unnecessary, and further, the distance between the anode electrode 2 and the cathode electrode 3 can be reduced. It is also possible to provide a microbial fuel cell with improved performance and reduced thickness without causing a current loss due to a large distance between the anode electrode and the cathode electrode. There is also.

  In the microbial fuel cell of the present invention, the soil or mud 5 (5a, 5b, 5c) can be used without limitation, and includes the current generating bacteria 7 that can be used as a catalyst in the anode electrode 2 and its nutrients. However, it is preferable to use humus. Further, in the microbial fuel cell of the present invention, the housing 6 is not particularly limited, but it is preferable to use one formed to have insulating properties such as plastic.

  Further, FIG. 1 shows an example in which the lead wires 8 and 9 are electrically connected to the anode electrode 2 and the cathode electrode 3, respectively, so that the electricity generated by the microbial power generation can be taken out to the outside. Has been. The lead wires 8 and 9 may be electrically connected to, for example, a control circuit (not shown), a load (not shown), or the like.

Hereinafter, the operation of the microbial fuel cell 1 shown in FIG. 1 will be described.
Anaerobic current-generating bacteria (for example, the above-mentioned Shewanella bacteria) 7 contained in the soil or mud are adsorbed to the anode electrode 2, and hydrocarbons (for example, glucose and acetic acid, etc.) and amino acids contained in the soil or mud When the organic fuel is metabolized (oxidized), electrons (e ⁻ ) are released from the electron transfer system to the anode electrode (the oxidized organic fuel becomes an oxidant). The electrons (e ⁻ ) reach the cathode electrode 3 through an external circuit to generate power.

Protons (H ⁺ ) generated simultaneously with the electrons (e ⁻ ) pass through the soil or mud 5 and the oxygen permeation limiting layer 4 and reach the cathode electrode 3. Electrons (e ⁻ ), protons (H ⁺ ), oxygen (O ₂ ) in the air and water react on the cathode electrode 3 to generate water.

  The oxygen that has not been consumed by the cathode electrode passes through the soil or mud 5 or diffuses in the moisture of the soil or mud 5 and moves toward the anode electrode 2 side. The oxygen permeation limiting layer 4 prevents the oxygen electrode from reaching the anode electrode 2 due to the diffusion and permeation of oxygen. Therefore, as described above, in the vicinity of the anode electrode 2, the oxygen concentration can be kept low, the growth of the anaerobic current-generating bacteria 7 used as an electrode catalyst can be promoted, and Since the electrode reaction of oxygen can be prevented, the battery performance can be improved, the distance between the anode electrode 2 and the cathode electrode 3 can be reduced, and the microbial fuel cell 1 can be thinned.

<Embodiment 2>
FIG. 2 is a diagram schematically showing a microbial fuel cell 11 according to Embodiment 2 of the present invention. 2, parts having the same configuration as the example shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. The microbial fuel cell 11 of the example shown in FIG. 2 is the microbial fuel cell 1 of the example shown in FIG. 1 except that the anode electrode 12 and the oxygen permeation limiting layer 13 are integrally disposed adjacent to each other. It is the same. With this configuration, as in the microbial fuel cell 1 of the example shown in FIG. 1, an oxygen permeation restricting effect to the anode electrode 12 can be obtained, and the anode electrode 12 and the oxygen permeation restricting layer 13 are simultaneously replaced. It becomes possible. There is also an advantage that the distance between the anode electrode 12 and the cathode electrode 3 can be shortened.

<Embodiment 3>
FIG. 3 is a diagram schematically showing a microbial fuel cell 21 according to Embodiment 3 of the present invention. 3, parts having the same configurations as those in the example shown in FIGS. The microbial fuel cell 21 of the example shown in FIG. 3 is the microbial fuel cell 1 of the example shown in FIG. 1 except that the cathode electrode 22 and the oxygen permeation limiting layer 23 are integrally disposed adjacent to each other. It is the same. With this configuration, the oxygen permeation limiting effect to the canode electrode 22 can be obtained and the canode electrode 22 and the oxygen permeation limiting layer 23 can be exchanged at the same time, as in the microbial fuel cell 1 of the example shown in FIG. It becomes possible. There is also an advantage that the distance between the anode electrode 2 and the cathode electrode 22 can be shortened.

<Embodiment 4>
FIG. 4 is a diagram schematically showing a microbial fuel cell 31 according to Embodiment 4 of the present invention. 4, parts having the same configuration as the example shown in FIGS. 1, 2, and 3 are denoted by the same reference numerals and description thereof is omitted. The microbial fuel cell 31 of the example shown in FIG. 4 is shown in FIG. 1 except that the anode electrode 32 and the cathode electrode 33 are integrally arranged adjacent to each other with the oxygen permeation limiting layer 34 interposed therebetween. This is the same as the microbial fuel cell 1 of the example. With this configuration, the oxygen permeation restricting effect to the canode electrode 33 is obtained as in the microbial fuel cell 1 of the example shown in FIG. 1, and the anode electrode 32, the canode electrode 33 and the oxygen permeation restricting layer 34 are obtained. Can be exchanged at the same time. There is also an advantage that the distance between the anode electrode 32 and the cathode electrode 33 can be further shortened.

<Embodiment 5>
FIG. 5 is a diagram schematically showing a microbial fuel cell 41 according to Embodiment 5 of the present invention. In FIG. 5, parts having the same configurations as those in the examples shown in FIGS. In the microbial fuel cell of the present invention, the upper side of the cathode electrode 3 may be released as in the example shown in FIG. 1, but the microbial fuel cell is placed on the upper side of the cathode electrode 3 as in the example shown in FIG. A moisturizing layer 42 that protects 41 from drying may be provided. Since the moisturizing layer 42 is provided, the cathode electrode 3 and the soil or mud 5 can be moisturized, so that the long-term stability of the microbial fuel cell 41 can be ensured.

  The moisturizing layer 42 only needs to be able to store the moisture of the microbial fuel. For example, a plastic or polymer may be covered as a moisturizing layer 42 on the cathode electrode. In that case, it may be blocked from the outside air, but by using an oxygen-permeable film or the like as the moisture retaining layer 42, the cathode electrode 3 and the soil or mud 5 are protected from drying, and are consumed by the cathode electrode 3 during power generation. There is an advantage that oxygen can be supplied. Further, the moisture retention layer 42 may be formed of a material that releases moisture and oxygen, preferably a material that can retain moisture and supply oxygen consumed by the cathode, and plants and the like are preferably used as such a material. be able to. When using a plant, it is possible to grow the plant by utilizing nutrients contained in soil and mud in the microbial fuel cell.

<Embodiment 6>
FIG. 6 is a diagram schematically showing a microbial fuel cell 51 according to Embodiment 6 of the present invention. In FIG. 6, parts having the same configurations as those shown in FIGS. 1, 2, 3, 4, and 5 are designated by the same reference numerals and description thereof is omitted. The microbial fuel cell 51 of the example shown in FIG. 6 has a hole (through hole) 53 in which the case 52 can exchange the microorganisms, nutrients, and the like of the microbial fuel cell 51 from the outside. As described above, the microbial fuel cell of the present invention may further include a housing having one or more holes in the lower part where at least one of microorganisms and nutrients thereof can be exchanged. By using the casing having such a hole, even when the current generating bacteria 7 and the nutrients in the soil or mud 5 contained in the housing 52 are reduced, the microbial fuel cell can be supplied from the outside. The long-term stability of 51 can be ensured. In addition, for example, it is possible to generate power in the long term by embedding it in the soil of a farm, and to effectively use the land.

<Embodiment 7>
FIG. 7 is a diagram schematically showing a microbial fuel cell 61 according to Embodiment 7 of the present invention. 7, parts having the same configuration as the example shown in FIGS. 1, 2, 3, 4, 5, and 6 are given the same reference numerals and description thereof is omitted. The microbial fuel cell 61 of the example shown in FIG. 7 is the microbial fuel cell 1 shown in FIG. 1 except that each of the anode electrode 62, the cathode electrode 63, and the oxygen permeation limiting layer 64 is separable and replaceable. It is the same. Thus, each part of the microbial fuel cell of the present invention may be designed to be replaceable at each part. In this case, for example, when only the cathode electrode 63 is deteriorated, only the cathode electrode 63 may be replaced. By exchanging only a part of the parts, the function of the microbial fuel cell can be recovered and improved, and a microbial fuel cell excellent in maintainability can be provided.

<Eighth embodiment>
FIG. 8 is a diagram schematically showing a microbial fuel cell 71 according to Embodiment 8 of the present invention. 8, parts having the same configurations as those shown in FIGS. 1, 2, 3, 4, 5, 6, and 7 are denoted by the same reference numerals and description thereof is omitted. The microbial fuel cell 71 of the example shown in FIG. 8 has the microbial fuel cell 1 of the example shown in FIG. 1 except that an oxygen consumption layer 72 is provided between the anode electrode 2 and the cathode electrode 3 as an oxygen permeation limiting layer. It is the same. By consuming oxygen in the oxygen consuming layer 72, it also functions as an oxygen permeation limiting layer and can prevent oxygen entering from the cathode electrode 3 side from reaching the anode electrode 2 . The oxygen consumption layer 72 such as this, for example, a catalyst for performing the reduction of oxygen (e.g., glucose oxidase, etc.) may be included, the material being the absorption of oxygen (e.g. iron compound) be included, such as Good.

<Embodiment 9>
FIG. 9 is a diagram schematically showing a microbial fuel cell 81 according to Embodiment 9 of the present invention. 9, parts having the same configurations as those in the examples shown in FIGS. 1, 2, 3, 4, 5, 6, 7, and 8 are denoted by the same reference numerals and description thereof is omitted. The microbial fuel cell 81 in the example shown in FIG. 9 is provided with an oxygen permeation limiting layer 4 ′, soil or mud 5 d, a cathode electrode 3 ′ in order in the direction of the bottom surface of the soil or mud 5 a, and at least one of the bottom surfaces of the housing 6. Except that the holes 53 are provided more than the above, it is the same as the microbial fuel cell 1 of the example shown in FIG. By setting it as such a form, since the area of a cathode electrode can be increased, the microbial fuel cell excellent in power generation capability can be provided.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.

<Example 1>
A circular carbon felt (5 mm thickness) (made by Alfa Aesar) having a diameter of 90 mm is used as the anode electrode 2 and the cathode electrode 3, a stainless steel wire is used as the lead wires 8 and 9, and a carbon felt used as the anode electrode 2 and the cathode electrode 3 We were electrically connected by weaving into. The casing 6 was a cylindrical plastic container having a diameter of 92 mm. Agar with a diameter of 90 mm (for example, manufactured by Pioneer Planning Co., Ltd.) was used as the oxygen permeation limiting layer 13 and was arranged between the anode electrode 2 and the cathode electrode 3 in the vertical direction of the housing. As soil or mud 5, commercially available humus was used. Thus, a microbial fuel cell having the configuration shown in FIG. 1 was produced.

<Comparative Example 1>
A microbial fuel cell of Comparative Example 1 was produced in the same manner as in Example 1 except that the oxygen permeation limiting layer was not used.

  Using the microbial fuel cells prepared in Example 1 and Comparative Example 1, respectively, variable resistance was inserted between the terminals of the anode electrode 2 and the cathode electrode 3 under room temperature (25 ° C.) conditions, and the output power was compared. FIG. 10 is a graph showing a change in the distance between electrodes of output power of a microbial fuel cell (Example 1) provided with an oxygen permeation preventive layer and a microbial fuel cell (Comparative Example 1) not provided with an oxygen permeation limiting layer. The vertical axis represents electromotive force (mW), and the horizontal axis represents the distance between electrodes (mm). As shown in FIG. 10, for each microbial fuel cell of Example 1 and Comparative Example 1, the distance between the electrodes was changed by adjusting the thickness of soil or mud (5b, 5c). In the microbial fuel cell 1 including 4, high performance was obtained even at the same interelectrode distance. FIG. 11 is a graph plotting output power when the thickness of the oxygen permeation restricting layer 4 is changed in the microbial fuel cell of Example 1. The vertical axis represents electromotive force (mW), and the horizontal axis represents oxygen permeation. This is the thickness (mm) of the limiting layer. From the above results, it can be seen that by using the oxygen permeation limiting layer, it is possible to realize a microbial fuel cell with improved performance and reduced thickness.

  1 microbial fuel cell, 2 anode electrode, 3, 3 ′ cathode electrode, 4, 4 ′ oxygen permeation limiting layer, 5, 5a, 5b, 5c, 5d soil or mud, 6 housing, 7 anaerobic current-generating bacteria, 8,9 Lead wire, 11 Microbial fuel cell, 12 Anode electrode, 13 Oxygen permeation limiting layer, 21 Microbial fuel cell, 22 Cathode electrode, 23 Oxygen permeation limiting layer, 31 Microbial fuel cell, 32 Anode electrode, 33 Oxygen permeation limiting layer 34 Cathode electrode, 41 Microbial fuel cell, 42 Moisturizing layer, 51 Microbial fuel cell, 52 Housing, 53 holes, 61 Microbial fuel cell, 62 Anode electrode, 63 Cathode electrode, 64 Oxygen permeation limiting layer, 71 Microbial fuel cell, 72 oxygen consumption layer, 81 microbial fuel cell.

Claims (4)

An anode electrode that oxidizes organic fuel supplied from soil or mud, and a cathode electrode that reduces oxygen supplied from air or water, using a current-generating fungus supplied from soil or mud as a catalyst. A microbial fuel cell comprising:
Between the anode electrode and the cathode electrode facing each other, only the oxygen permeation limiting layer, or only the oxygen permeation limiting layer and soil or mud are arranged,
The microbial fuel cell, wherein the oxygen permeation restricting layer is formed of hydrogel, has a function of restricting diffusion of oxygen from the cathode electrode side to the anode electrode side, and enabling movement of ions from the anode electrode to the cathode electrode . The microbial fuel cell according to claim 1 , wherein the hydrogel is formed of a polymer sugar chain. The moisturizing layer on the cathode electrode is provided, microbial fuel cell according to claim 1 or 2. The microbial fuel cell according to any one of claims 1 to 3 , further comprising a housing having one or more holes in which at least one of microorganisms and nutrients thereof can be exchanged on an anode electrode side of the oxygen permeation restriction layer. .

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