JP2017228411A - Electrode composite and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an electrode composite which enables an effective oxygen reductive reaction by reducing the oxygen consumption by aerobic microorganisms; and a fuel cell arranged by use of the electrode composite.SOLUTION: An electrode composite (10) comprises: a sheet-like porous base material (11) having a first surface (11a) and a second surface (11b) on a side opposite to the first surface; and a first conductor layer (1) provided in part of the porous base material and extending from the first surface toward the second surface in a thickness direction (X) of the porous base material. A microbial fuel cell (100) comprises: a first electrode (1A) arranged by use of the electrode composite (10); and a second electrode (20).SELECTED DRAWING: Figure 9

Description

  The present invention relates to an electrode assembly and a fuel cell. More specifically, the present invention relates to an electrode composite capable of purifying waste water and generating electric energy, and a fuel cell using the same.

  In recent years, microbial fuel cells that generate electricity using biomass have attracted attention as sustainable energy. A microbial fuel cell is a wastewater treatment apparatus that converts the chemical energy of an organic substance contained in domestic wastewater or factory wastewater into electrical energy and oxidizes and decomposes the organic substance. The microbial fuel cell is characterized by little generation of sludge and low energy consumption. However, since the power generated by microorganisms is very small and the output current density is low, further improvement is necessary.

  As such a microbial fuel cell, the thing of the following patent documents 1 is indicated. The microbial fuel cell is disposed in an electrolytic cell holding an electrolytic solution, an anode disposed inside the electrolytic cell, a tank body of the electrolytic cell, one surface is in contact with air outside the cell, and the other surface is A cathode in contact with the electrolyte. In addition to the electrolytic solution, the electrolytic cell holds microorganisms and a substrate for oxidative degradation by the microorganisms. As the microorganism, anaerobic microorganisms such as Geobacter genus and Shewanella genus are disclosed. The cathode includes an electrode substrate having electron conductivity and gas permeability, and a water-stopping layer containing silicone is formed on one surface of the electrode substrate that comes into contact with air. A catalyst layer supporting a cathode catalyst is formed on the surface. In the microbial fuel cell of Patent Document 1, after microorganisms oxidize and decompose a substrate to generate electrons and protons, electrons supplied from the anode through an external circuit, protons in the electrolytic solution, and the outside of the electrolytic cell The supplied oxygen reacts with the catalyst layer of the cathode.

  Here, in addition to the above-mentioned anaerobic microorganisms, the microbial fuel cell electrolyte often contains aerobic microorganisms that require oxygen for growth. And since an aerobic microorganism makes oxygen essential, it exists in the interface vicinity of the water stop layer and electrode base material with high oxygen concentration.

Japanese Patent Laying-Open No. 2015-46361

  As described above, in the microbial fuel cell of Patent Document 1, since aerobic microorganisms exist near the interface between the water blocking layer and the electrode base material, oxygen is consumed by the aerobic microorganisms near the interface. End up. As a result, oxygen does not sufficiently reach the catalyst layer disposed inside the electrolytic cell rather than the electrode base material, so that the oxygen reduction reaction is not performed and electric energy cannot be stably obtained.

  The present invention has been made in view of such problems of the prior art. An object of the present invention is to provide an electrode complex that can suppress oxygen consumption by aerobic microorganisms and can effectively perform an oxygen reduction reaction, and a fuel cell using the electrode complex. .

  In order to solve the above problems, an electrode composite according to a first aspect of the present invention comprises a sheet-like porous group comprising a first surface and a second surface opposite to the first surface. Has material. Furthermore, the electrode composite body has a first conductor layer provided on a part of the porous substrate from the first surface toward the second surface in the thickness direction of the porous substrate.

  The fuel cell according to the second aspect of the present invention has a first electrode using the electrode assembly according to the first aspect, and a second electrode.

  The fuel cell according to the third aspect of the present invention has an electrode assembly. The electrode composite includes a sheet-like porous substrate having a first surface and a second surface opposite to the first surface, and the first surface in the thickness direction of the porous substrate. And a first conductor layer provided on a part of the porous substrate toward the second surface. Furthermore, the electrode composite body has a second conductor layer provided on a part of the porous substrate from the second surface toward the first surface in the thickness direction of the porous substrate. And let the 1st conductor layer in an electrode composite be a 1st electrode, and let a 2nd conductor layer be a 2nd electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the oxygen consumption by an aerobic microorganism can be suppressed, and the electrode complex and microbial fuel cell which can perform an oxygen reductive reaction effectively can be obtained.

It is sectional drawing which shows the electrode composite_body | complex which concerns on 1st embodiment of this invention. It is sectional drawing which shows the state which provided the water-repellent layer in the electrode composite_body | complex which concerns on 1st embodiment. It is a perspective view which shows the state which coat | covered the electrode complex which concerns on 1st embodiment with the sealing material. It is sectional drawing for demonstrating the effect | action of the electrode complex which concerns on 1st embodiment. It is sectional drawing for demonstrating the effect | action of the electrode complex which concerns on 1st embodiment. It is sectional drawing which shows the electrode composite_body | complex which concerns on 2nd embodiment of this invention. It is sectional drawing which shows the state which provided the water repellent layer in the electrode composite_body | complex which concerns on 2nd embodiment. It is a perspective view which shows an example of the microbial fuel cell which concerns on 3rd embodiment of this invention, and used the electrode complex of 1st embodiment. It is sectional drawing along the AA line in FIG. It is a disassembled perspective view which shows the fuel cell unit in the microbial fuel cell of FIG. It is sectional drawing which shows the other example of the microbial fuel cell using the electrode composite_body | complex of 1st embodiment. It is sectional drawing which concerns on 4th embodiment of this invention, and shows the other example of the microbial fuel cell using the electrode complex of 1st embodiment. It is sectional drawing which concerns on 5th embodiment of this invention, and shows an example of the microbial fuel cell using the electrode complex of 2nd embodiment.

  Hereinafter, the electrode assembly according to the present embodiment and the fuel cell will be described in detail. In addition, the dimension ratio of drawing is exaggerated on account of description, and may differ from an actual ratio. The electrode assembly according to the present embodiment is applicable, for example, as an electrode assembly for a fuel cell, and is particularly applied as an electrode assembly for a microbial fuel cell. Therefore, the case where the electrode composite according to the present embodiment is used as an electrode composite for a microbial fuel cell will be described.

[First embodiment]
As shown in FIG. 1, the electrode assembly according to the present embodiment includes a conductor layer 1 and a porous body layer 2 provided on one surface 1 a of the conductor layer 1.

(Conductor layer)
The conductor layer 1 in the electrode assembly 10 has conductivity, oxygen permeability, and proton permeability. By providing such a conductor layer 1 in the electrode composite 10, when the conductor layer 1 is used as a positive electrode, electrons generated by a local battery reaction described later are conducted between the catalyst and the external circuit 110. It becomes possible. That is, as will be described later, when the conductor layer 1 is used as a positive electrode of a microbial fuel cell, a catalyst is supported on the conductor layer 1. Then, electrons move from the external circuit 110 to the catalyst through the conductor layer 1, and the oxygen reduction reaction by oxygen, hydrogen ions and electrons can be advanced by the catalyst. Further, when the conductor layer 1 is used as the negative electrode of the microbial fuel cell, electrons generated by the catalytic action of anaerobic microorganisms can be conducted between the conductor layer 1 and the external circuit 110.

  In the electrode assembly 10, it is preferable that oxygen and hydrogen ions efficiently pass through the conductor layer 1 and be supplied to the catalyst in order to ensure stable performance. Therefore, the conductor layer 1 is preferably a porous body having a large number of pores through which oxygen and hydrogen ions pass from the surface 1b to the opposite surface 1a. The shape of the conductor layer 1 is particularly preferably a three-dimensional mesh. With such a mesh shape, high oxygen permeability and conductivity can be imparted to the conductor layer 1.

  In this embodiment, the conductor layer 1 has a first surface relative to a sheet-like porous substrate 11 having a first surface 11a and a second surface 11b opposite to the first surface 11a. It is formed by providing a conductive material from 11a toward the second surface 11b. That is, the conductor layer 1 and the porous body layer 2 are produced separately, and they are not laminated, but the conductor layer 1 and the porous body layer 2 are composed of a single-layer porous substrate 11. Has been. Thus, by forming the conductor layer 1 and the porous body layer 2 on the basis of the porous substrate 11, peeling between the conductor layer 1 and the porous body layer 2 is prevented, and the mechanical strength is increased. Can be increased.

  The conductive material constituting the conductor layer 1 is not particularly limited as long as high conductivity can be secured. However, the conductive material is preferably made of at least one conductive metal selected from the group consisting of aluminum, copper, stainless steel, nickel and titanium. Since these conductive metals have high corrosion resistance and conductivity, they can be suitably used as a material constituting the conductor layer 1.

  The conductive material may be a carbon material. Examples of the carbon material include carbon powders such as graphite, activated carbon, carbon black, Vulcan (registered trademark) XC-72R, acetylene black, furnace black, and Denka black. Examples of the carbon material include fine structure substances such as carbon nanotubes, carbon nanohorns, and carbon nanoclusters. Since such a carbon material also has high corrosion resistance and conductivity, it can be suitably used as a material constituting the conductor layer 1. In addition, the said conductive metal and carbon material may be used individually by 1 type, and may be used in combination of 2 or more type.

  The porous substrate 11 is a sheet having a large number of pores that allow oxygen, hydrogen ions, and the electrolytic solution 70 to pass therethrough. The porous substrate 11 preferably has continuous pores from the first surface 11a to the second surface 11b. Thereby, oxygen and hydrogen ions easily reach the catalyst in the positive electrode, and the oxygen reduction reaction can be promoted. The pore diameter of the porous substrate 11 is not particularly limited as long as oxygen, hydrogen ions, and the electrolyte solution 70 can permeate, but is preferably 0.5 μm or more, for example. When the pore diameter of the porous substrate 11 is 0.5 μm or more, it is possible to sufficiently transmit oxygen, hydrogen ions, and the electrolytic solution 70 to increase power generation efficiency. Although the upper limit of the pore diameter of the pores in the porous substrate 11 is not particularly limited, it can be set to, for example, 1.0 mm. The pore diameter of the porous substrate 11 can be measured, for example, by a mercury intrusion method.

  The thickness t1 of the porous substrate 11 is preferably 1.0 mm to 50 mm. Since the thickness t <b> 1 of the porous substrate 11 is 1.0 mm to 50 mm, the thickness of the porous body layer 2 formed on the electrode assembly 10 can be increased. Aerobic microorganisms can be prevented from entering the porous body layer 2.

  The porous substrate 11 may be a conductor or an electrical insulator. However, the porous substrate 11 is preferably an electrical insulator. Since the porous base material 11 is an electrical insulator, as will be described later, when the electrode assembly 10 is used in a microbial fuel cell, the ion migration layer 30 is not required, and thus the microbial fuel cell is made thinner and the battery It is possible to simplify the structure.

  Examples of the material constituting the porous substrate 11 include resin materials such as polyethylene and polypropylene, conductive metals such as aluminum, copper, stainless steel, nickel and titanium, and carbon materials such as carbon paper and carbon felt. At least one selected from the group can be used. The porous substrate 11 is preferably formed of a synthetic resin. By comprising a synthetic resin, it is possible to easily ensure electrical insulation.

  As the porous substrate 11, at least one selected from the group consisting of a sheet having a woven fabric structure, a sheet having a nonwoven fabric structure, and a sheet having a continuous foam structure can be used. The porous substrate 11 may be a laminated body in which a plurality of sheets are laminated. However, the porous substrate 11 is preferably made of a nonwoven fabric. By using a sheet having such a plurality of pores as the porous substrate 11, oxygen and hydrogen ions can easily move and the rate of the oxygen reduction reaction can be increased.

  As described above, the conductor layer 1 is formed by providing a conductive material from the first surface 11 a to the second surface 11 b in the porous substrate 11. Although the formation method of the conductor layer 1 is not specifically limited, For example, the method of apply | coating the slurry containing an electroconductive material, the method of printing the said slurry, the method of vapor-depositing an electroconductive material, etc. are applicable. The conductor layer 1 may be formed by combining two or more of these methods.

  The conductive material may be held on the surface of the porous substrate 11 and inside the pores using a binder. Thereby, it can suppress that electroconductive material detach | desorbs from the surface of the porous base material 11, and the inside of a pore, and electroconductivity falls. Such a binder is not particularly limited as long as particles can be bound to each other. As the binder, for example, at least one selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM) and Nafion is preferably used.

(Porous body layer)
As shown in FIG. 1, the electrode assembly 10 according to this embodiment includes a porous body layer 2 provided on one surface 1 a of the conductor layer 1. As described above, the conductor layer 1 is formed by providing a conductive material from the first surface 11 a to the second surface 11 b in the porous substrate 11. Therefore, a portion of the porous substrate 11 other than the conductor layer 1 provided constitutes the porous body layer 2.

  In the electrode assembly 10, the thickness t2 of the porous body layer 2 is at least smaller than the thickness t1 of the porous substrate 11. Therefore, the thickness t2 of the porous body layer 2 is preferably 0.5 mm to 40 mm. When the thickness t2 of the porous body layer 2 is 0.5 mm to 40 mm, it is possible to prevent the aerobic microorganisms contained in the electrolytic solution 70 from entering the inside of the porous body layer 2. The thickness t2 of the porous body layer 2 is more preferably 1.0 mm to 40 mm, and further preferably 1.5 mm to 10 mm. When the thickness t2 of the porous body layer 2 is within this range, the aerobic microorganisms are prevented from entering the inside of the porous body layer 2, and the hydrogen ion permeability is increased and the hydrogen ions are reduced. It is possible to efficiently reach the catalyst.

  As described above, the porous body layer 2 is composed of a part of the porous substrate 11. Therefore, the porous body layer 2 preferably has continuous pores from the surface 2a to the opposite surface 2b. Thereby, it becomes easy for hydrogen ions to reach the catalyst in the positive electrode, and the oxygen reduction reaction can be promoted. The pore diameter of the porous substrate 11 is not particularly limited as long as hydrogen ions and the electrolyte solution 70 can permeate, but is preferably 0.5 μm or more, for example.

(Water repellent layer)
As shown in FIG. 2, the electrode assembly 10 may be provided with a water repellent layer 3 on the surface 1 b of the conductor layer 1. Since the water repellent layer 3 has water repellency, when the conductor layer 1 is used as the positive electrode of the microbial fuel cell, the electrolytic solution 70 and the gas phase 90 as the liquid phase retained in the waste water tank 80 are used. And are separated. And by providing the water repellent layer 3, it can suppress that the electrolyte solution 70 moves to the gaseous-phase 90 side. In addition, "separation" here means physical interruption | blocking.

  The water repellent layer 3 is in contact with the gas phase 90 containing oxygen, and diffuses oxygen in the gas phase 90. The water repellent layer 3 supplies oxygen substantially uniformly to the surface 1 b of the conductor layer 1. Therefore, the water repellent layer 3 is preferably a porous body so that the oxygen can be diffused. In addition, since the water repellent layer 3 has water repellency, it can suppress that the pore of a porous body obstruct | occludes by dew condensation etc., and the diffusibility of oxygen falls. In addition, since the electrolytic solution 70 hardly penetrates into the water repellent layer 3, oxygen can be efficiently circulated from the surface 3 b in contact with the gas phase 90 in the water repellent layer 3 to the surface 3 a facing the conductor layer 1. Is possible.

  The water repellent layer 3 is preferably formed in a sheet shape from a woven fabric or a non-woven fabric. The material constituting the water repellent layer 3 is not particularly limited as long as it has water repellency and can diffuse oxygen in the gas phase 90. Examples of the material constituting the water repellent layer 3 include polyethylene, polypropylene, polybutadiene, nylon, polytetrafluoroethylene (PTFE), ethyl cellulose, poly-4-methylpentene-1, butyl rubber, and polydimethylsiloxane (PDMS). At least one selected from the group can be used. Since these materials are easy to form a porous body and also have high water repellency, they can suppress clogging of pores and improve gas diffusibility. The water repellent layer 3 preferably has a plurality of through holes in the stacking direction X of the water repellent layer 3 and the conductor layer 1.

  The water repellent layer 3 may be subjected to a water repellent treatment using a water repellent as necessary in order to increase water repellency. Specifically, a water repellent such as polytetrafluoroethylene may be attached to the porous body constituting the water repellent layer 3 to improve water repellency.

  In the electrode assembly 10 shown in FIG. 2, in order to efficiently supply oxygen to the surface 1b of the conductor layer 1, the water repellent layer 3 is bonded to the conductor layer 1 through an adhesive. preferable. That is, it is preferable that the surface 3a of the water repellent layer 3 is bonded to the surface 1b of the opposing conductor layer 1 via an adhesive. Thereby, the diffused oxygen is directly supplied to the surface 1b of the conductor layer 1, and the oxygen reduction reaction can be performed efficiently. The adhesive is preferably provided on at least a part between the water repellent layer 3 and the conductor layer 1 from the viewpoint of securing the adhesiveness between the water repellent layer 3 and the conductor layer 1. However, from the viewpoint of improving the adhesiveness between the water repellent layer 3 and the conductor layer 1 and supplying oxygen to the conductor layer 1 stably over a long period of time, the adhesive is made of the water repellent layer 3 and the conductor layer. It is more preferable that it is provided on the entire surface between the two.

  The adhesive preferably has oxygen permeability, and includes at least one selected from the group consisting of polymethyl methacrylate, methacrylic acid-styrene copolymer, styrene-butadiene rubber, butyl rubber, nitrile rubber, chloroprene rubber, and silicone. Resin can be used.

(catalyst)
When the conductor layer 1 is used as a positive electrode, the conductor layer 1 preferably supports a catalyst. The catalyst is preferably an oxygen reduction catalyst. Since the catalyst is an oxygen reduction catalyst, the reaction rate between oxygen and hydrogen ions supplied to the conductor layer 1 can be further increased, and the reduction reaction efficiency of oxygen can be improved. It can be realized.

  The catalyst is preferably supported on the surface of the conductor layer 1. That is, the catalyst may be supported on the surface 1b of the conductive layer 1 on the water repellent layer 3 side, and may be further supported on the inside of the conductive layer 1. And from the viewpoint of promoting the oxygen reduction reaction by oxygen, hydrogen ions and electrons, the conductor layer 1 and the catalyst are preferably electrically connected, and the conductor layer 1 and the catalyst are in contact with each other. Is preferred.

  The catalyst may be supported on the surface of the conductor layer 1 and inside the pores using a binder. Thereby, it can suppress that a catalyst detach | desorbs from the surface of the conductor layer 1, and the inside of a pore, and an oxygen reduction characteristic falls. Such a binder is not particularly limited as long as particles can be bound to each other. As the binder, for example, at least one selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, an ethylene-propylene-diene copolymer, and Nafion is preferably used.

  The oxygen reduction catalyst is preferably a carbon-based material doped with metal atoms. Although it does not specifically limit as a metal atom, Titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, hafnium, tantalum, tungsten, rhenium, osmium, iridium It is preferably an atom of at least one metal selected from the group consisting of platinum, and gold. In this case, the carbon-based material exhibits excellent performance as a catalyst for promoting the oxygen reduction reaction. What is necessary is just to set suitably the quantity of the metal atom which carbonaceous material contains so that carbonaceous material may have the outstanding catalyst performance.

  The carbon-based material is preferably further doped with one or more nonmetallic atoms selected from nitrogen, boron, sulfur and phosphorus. What is necessary is just to set suitably the quantity of the nonmetallic atom doped by the carbonaceous material so that carbonaceous material may have the outstanding catalyst performance.

  The carbon-based material is based on a carbon source material such as graphite and amorphous carbon, for example, and the carbon source material is doped with a metal atom and one or more non-metal atoms selected from nitrogen, boron, sulfur and phosphorus. Can be obtained.

  A combination of a metal atom and a nonmetal atom doped in the carbon-based material is appropriately selected. In particular, it is preferable that the nonmetallic atom contains nitrogen and the metallic atom contains iron. In this case, the carbonaceous material can have a particularly excellent catalytic activity. The nonmetallic atom may be only nitrogen. Further, the metal atom may be only iron.

  The nonmetallic atom may contain nitrogen, and the metallic atom may contain at least one of cobalt and manganese. Also in this case, the carbon-based material can have a particularly excellent catalytic activity. The nonmetallic atom may be only nitrogen. Further, the metal atom may be only cobalt, only manganese, or only cobalt and manganese.

  A carbon-based material configured as an oxygen reduction catalyst can be prepared as follows. First, for example, a mixture containing a nonmetallic compound containing at least one nonmetal selected from the group consisting of nitrogen, boron, sulfur, and phosphorus, a metal compound, and a carbon source material is prepared. And this mixture is heated at the temperature of 800 degreeC or more and 1000 degrees C or less for 45 second or more and less than 600 second. Thereby, the carbonaceous material comprised as an oxygen reduction catalyst can be obtained.

  As the carbon source material, for example, graphite or amorphous carbon can be used as described above. Further, the metal compound is not particularly limited as long as it is a compound containing a metal atom capable of coordinating with a nonmetal atom doped in the carbon source material. Metal compounds include, for example, metal chlorides, nitrates, sulfates, bromides, iodides, fluorides, etc .; inorganic metal salts such as acetates; inorganic metal salt hydrates; and organic metal salts At least one selected from the group consisting of hydrates can be used. For example, when graphite is doped with iron, the metal compound preferably contains iron (III) chloride. Moreover, when graphite is doped with cobalt, the metal compound preferably contains cobalt chloride. When the carbon source material is doped with manganese, the metal compound preferably contains manganese acetate. The amount of the metal compound used is preferably set so that, for example, the ratio of the metal atom in the metal compound to the carbon source material is in the range of 5 to 30% by mass, and the ratio is in the range of 5 to 20% by mass. It is more preferable to set so as to be within.

  As described above, the nonmetallic compound is preferably at least one nonmetallic compound selected from the group consisting of nitrogen, boron, sulfur and phosphorus. Non-metallic compounds include, for example, pentaethylenehexamine, ethylenediamine, tetraethylenepentamine, triethylenetetramine, ethylenediamine, octylboronic acid, 1,2-bis (diethylphosphinoethane), triphenyl phosphite, benzyldisal At least one compound selected from the group consisting of fido can be used. The amount of the nonmetallic compound used is appropriately set according to the amount of the nonmetallic atom doped into the carbon source material. The amount of the nonmetallic compound used is preferably set so that the molar ratio of the metal atom in the metal compound to the nonmetallic atom in the nonmetallic compound is within the range of 1: 1 to 1: 2. : It is more preferable to set it within the range of 1.5 to 1: 1.8.

  A mixture containing a nonmetallic compound, a metal compound, and a carbon source raw material when preparing a carbon-based material configured as an oxygen reduction catalyst is obtained, for example, as follows. First, a carbon source material, a metal compound, and a nonmetal compound are mixed, and if necessary, a solvent such as ethanol is added to adjust the total amount. These are further dispersed by an ultrasonic dispersion method. Subsequently, after heating them at an appropriate temperature (for example, 60 ° C.), the mixture is dried to remove the solvent. Thereby, the mixture containing a nonmetallic compound, a metal compound, and a carbon source raw material is obtained.

  Next, the obtained mixture is heated, for example, under a reducing atmosphere or an inert gas atmosphere. Thereby, a non-metallic atom is doped to a carbon source raw material, and also a metallic atom is doped by the coordinate bond of a non-metallic atom and a metallic atom. The heating temperature is preferably in the range of 800 ° C. to 1000 ° C., and the heating time is preferably in the range of 45 seconds to less than 600 seconds. Since the heating time is short, the carbon-based material is efficiently produced, and the catalytic activity of the carbon-based material is further increased. In the heat treatment, the temperature rising rate of the mixture at the start of heating is preferably 50 ° C./s or more. Such rapid heating further improves the catalytic activity of the carbon-based material.

  Further, the carbon-based material may be further subjected to acid cleaning. For example, the carbon-based material may be dispersed in pure water with a homogenizer for 30 minutes, and then the carbon-based material may be placed in 2M sulfuric acid and stirred at 80 ° C. for 3 hours. In this case, elution of the metal component from the carbon-based material can be suppressed.

  By such a production method, a carbon-based material having a significantly low content of inert metal compounds and metal crystals and high conductivity can be obtained.

(Sealing material)
The side surface 1 e of the conductor layer 1 and the side surface 2 e of the porous body layer 2 in the electrode assembly 10 are preferably sealed with a sealing material 4. Specifically, it is preferable that the upper surface 1 d, the side surface 1 e, and the bottom surface 1 f of the conductor layer 1 are sealed with the sealing material 4 as in the electrode assembly 10 </ b> B illustrated in FIG. 3. Furthermore, it is preferable that the outer peripheral portion 2 c, the upper surface 2 d, the side surface 2 e, and the bottom surface 2 f of the surface 2 a in the porous body layer 2 are also sealed with the sealing material 4. As described above, the upper surface, the side surface, and the bottom surface of the conductor layer 1 and the porous body layer 2 are sealed with the sealing material 4, so that the aerobic microorganisms enter the inside from the upper surface, the side surface, and the bottom surface. Can be suppressed. As a result, it becomes possible to prevent aerobic microorganisms from growing inside the electrode assembly 10B. In FIG. 3, the upper surface 1 d, the side surface 1 e and the bottom surface 1 f of the conductor layer 1 and the outer peripheral portion 2 c, the upper surface 2 d, the side surface 2 e and the bottom surface 2 f of the porous body layer 2 are sealed with the sealing material 4. ing. However, in order to suppress the invasion of aerobic microorganisms, at least the side surface 1e of the conductor layer 1 and the side surface 2e of the porous body layer 2 may be sealed with the sealing material 4.

  The sealing material 4 is preferably made of a material that does not allow at least aerobic microorganisms to pass through. For example, epoxy resin, polymethyl methacrylate, methacrylic acid-styrene copolymer, styrene-butadiene rubber, butyl rubber, nitrile rubber, chloroprene rubber, and A resin containing at least one selected from the group consisting of silicones can be used.

  The effect | action of the porous body layer 2 in the electrode composites 10 and 10A of this embodiment is demonstrated. As shown in FIG. 4, when the conductor layer 1 of the electrode composite 10A is used as the positive electrode of the microbial fuel cell, the conductor layer 1 and the porous body layer 2 of the electrode composite 10 are immersed in the electrolytic solution 70, At least a part of the surface 3 b of the water repellent layer 3 is exposed to the gas phase 90. Since oxygen reaches the conductor layer 1 through the water-repellent layer 3 exposed in the gas phase 90, the aerobic microorganism in the electrolytic solution 70 is a conductor when the porous body layer 2 is not present. It passes through the layer 1 and grows in the vicinity of the interface between the conductor layer 1 and the water repellent layer 3. As a result, oxygen is consumed by aerobic microorganisms in the vicinity of the interface between the conductor layer 1 and the water repellent layer 3, so that oxygen is not sufficiently supplied to the catalyst supported on the conductor layer 1, and the oxygen reduction reaction It becomes difficult to occur.

  On the other hand, when the porous body layer 2 is provided on the conductor layer 1, the electrolyte 70 contains an organic substance serving as a bait for aerobic microorganisms. Therefore, as shown in FIG. A microbial membrane 12 is formed on the surface 2a exposed in the electrolytic solution 70 in FIG. That is, aerobic microorganisms consume organic matter and propagate, and a microbial membrane 12 formed by aerobic microorganisms gathering on the surface 2 a of the porous body layer 2 is formed. The aerobic microorganisms proceed to the gas phase 90 side to which oxygen is supplied. However, the organic substances are consumed by the aerobic microorganisms in the microorganism film 12, and the organic substances entering the porous body layer 2 are reduced. . Furthermore, by increasing the thickness of the porous body layer 2, it becomes difficult for organic substances to move to the conductor layer 1 side, which is preferable on the conductor layer 1 side than the interface between the conductor layer 1 and the porous body layer 2. Aerobic microorganisms cannot grow. As a result, since aerobic microorganisms are not grown near the interface between the conductor layer 1 and the water repellent layer 3, oxygen consumption by the aerobic microorganisms is suppressed, and oxygen is sufficiently supplied to the catalyst supported on the conductor layer 1. Since it is supplied, it is possible to effectively perform an oxygen reduction reaction.

  When the conductor layer 1 of the electrode assembly 10 is used as the negative electrode of the microbial fuel cell, the conductor layer 1 and the porous body layer 2 of the electrode assembly 10 are immersed in the electrolytic solution 70. Further, the positive electrode is laminated on the surface 2 a of the porous body layer 2, and at least a part of the surface of the positive electrode opposite to the surface on the electrode composite 10 side is exposed to the gas phase 90. And since oxygen reaches | attains the positive electrode from the gaseous phase 90, when the porous body layer 2 does not exist, the aerobic microorganisms in the electrolyte solution 70 will pass through the conductor layer 1, and will proliferate on a positive electrode. . As a result, oxygen is consumed by the aerobic microorganisms at the positive electrode, so that oxygen is not sufficiently supplied to the catalyst supported on the positive electrode, and the oxygen reduction reaction hardly occurs.

  On the other hand, when the porous body layer 2 is provided on the conductor layer 1, the microbial membrane 12 is formed on the surface 1b of the conductor layer 1 exposed in the electrolytic solution 70 as shown in FIG. . The aerobic microorganisms proceed to the positive electrode side to which oxygen is supplied, but organic substances are consumed by the aerobic microorganisms in the microbial film 12, and the organic substances entering the conductor layer 1 and the porous body layer 2 are reduced. Resulting in. Furthermore, by increasing the thickness of the porous body layer 2, it becomes difficult for organic substances to move to the positive electrode side, and aerobic microorganisms cannot grow on the positive electrode. As a result, oxygen consumption by aerobic microorganisms is suppressed, and oxygen is sufficiently supplied to the catalyst supported on the positive electrode, so that an oxygen reduction reaction can be effectively performed.

  As described above, the electrode assembly 10 according to this embodiment includes the sheet-like porous substrate 11 including the first surface 11a and the second surface 11b opposite to the first surface 11a. . Furthermore, the electrode assembly 10 includes a first conductive material provided in a part of the porous substrate 11 from the first surface 11a toward the second surface 11b in the thickness direction X of the porous substrate 11. It has a body layer (conductor layer 1). With such a configuration, since aerobic microorganisms are not grown inside the electrode assembly 10, oxygen consumption by the aerobic microorganisms is suppressed. For this reason, the microbial fuel cell using the electrode assembly 10 is prevented from being deteriorated in power generation performance, and can stably produce electric energy.

[Second Embodiment]
Next, the electrode assembly according to the second embodiment will be described in detail based on the drawings. In addition, the same code | symbol is attached | subjected to the same structure as the electrode composite_body | complex of 1st embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 6, the electrode assembly 10 </ b> C of the present embodiment includes a first surface 11 a and a sheet-like porous substrate 11 including a second surface 11 b opposite to the first surface 11 a. Have In addition, the electrode assembly 10 </ b> C is a first conductive material provided in a part of the porous substrate 11 from the first surface 11 a toward the second surface 11 b in the thickness direction X of the porous substrate 11. It has a body layer 1. Furthermore, the electrode assembly 10C is a second conductor provided on a part of the porous substrate 11 from the second surface 11b toward the first surface 11a in the thickness direction X of the porous substrate 11. Layer 5 is included.

  In the electrode assembly 10C of the present embodiment, the first conductor layer 1 is provided on the first surface 11a side, and the second conductor layer 5 is provided on the second surface 11b side. A porous body layer 2 is interposed between the first conductor layer 1 and the second conductor layer 5. Therefore, when the porous body layer 2 is made of an electrical insulator, a short circuit between the first conductor layer 1 and the second conductor layer 5 can be prevented, so that the first conductor layer Either one of the first and second conductor layers 5 can be a positive electrode, and the other can be a negative electrode.

  Similar to the first embodiment, the first conductor layer 1 is formed by providing a conductive material on the porous substrate 11 from the first surface 11a toward the second surface 11b. The second conductor layer 5 is formed by providing a conductive material from the second surface 11b toward the first surface 11a. That is, the first conductor layer 1, the second conductor layer 5, and the porous body layer 2 are produced separately and are not laminated, but the first conductor layer 1, the second conductor layer 2 The conductor layer 5 and the porous body layer 2 are composed of a single layer porous substrate 11. In this way, the first conductor layer 1, the second conductor layer 5, and the porous body layer 2 are formed on the basis of the porous base material 11, thereby preventing separation between the layers, and mechanically. The strength can be increased.

  In electrode assembly 10C, porous substrate 11 is preferably an electrical insulator. Thereby, since the porous body layer 2 also becomes an electrical insulator, a short circuit between the first conductor layer 1 and the second conductor layer 5 can be prevented.

  The same conductive material as that of the first embodiment can be used for the first conductive layer 1 and the second conductive layer 5, and the first conductive layer 1 and the second conductive layer can be used. The forming method 5 can be the same as that in the first embodiment.

  When the 1st conductor layer 1 is a positive electrode and the 2nd conductor layer 5 is a negative electrode, it is preferable that the 1st conductor layer 1 contains a catalyst similarly to 1st embodiment. Further, when the first conductor layer 1 is a positive electrode and the second conductor layer 5 is a negative electrode as in the electrode assembly 10D shown in FIG. 7, a water repellent layer is formed on the first surface 11a. 3 may be provided.

  The side surfaces of the first conductor layer 1, the second conductor layer 5, and the porous body layer 2 in the electrode assembly 10 </ b> C are preferably sealed with a sealing material 4. In addition to the side surfaces of the first conductor layer 1, the second conductor layer 5, and the porous body layer 2 in the electrode assembly 10 </ b> C, the top surface and the bottom surface are sealed with the sealing material 4. Is preferred. Since the side surfaces of the first conductor layer 1, the second conductor layer 5, and the porous body layer 2 are sealed with the sealing material 4, aerobic microorganisms enter the electrode assembly 10B. This can be suppressed. As a result, it becomes possible to prevent aerobic microorganisms from growing inside the electrode assembly 10C.

  The operation of the porous body layer 2 in the electrode assemblies 10C and 10D of the present embodiment will be described. As shown in FIG. 7, when the first conductor layer 1 of the electrode assembly 10D is used as the positive electrode of the microbial fuel cell and the second conductor layer 5 is used as the negative electrode, the first conductor layer 1, The second conductor layer 5 and the porous body layer 2 are immersed in the electrolytic solution 70. At least a part of the surface 3 b of the water repellent layer 3 is exposed to the gas phase 90. In this case, oxygen passes through the water-repellent layer 3 exposed to the gas phase 90 and reaches the first conductor layer 1, and therefore, when the porous body layer 2 is not present, the aerobic property in the electrolytic solution 70. The microorganisms pass through the first conductor layer 1 and the second conductor layer 5. Then, it grows near the interface between the first conductor layer 1 and the water repellent layer 3. As a result, oxygen is consumed by aerobic microorganisms in the vicinity of the interface between the first conductor layer 1 and the water repellent layer 3, so that oxygen is sufficiently supplied to the catalyst supported on the first conductor layer 1. The oxygen reduction reaction is not likely to occur.

  On the other hand, when the porous body layer 2 is provided between the first conductor layer 1 and the second conductor layer 5, the electrolyte 70 contains organic matter serving as a food for aerobic microorganisms. Therefore, a microbial film is formed on the second surface 11 b exposed in the electrolytic solution 70. That is, aerobic microorganisms consume organic matter and propagate, and a microbial film is formed by aerobic microorganisms gathering on the second surface 11b. Aerobic microorganisms proceed to the first conductor layer 1 side to which oxygen is supplied, but organic substances are consumed by aerobic microorganisms in the microorganism film, and organic substances that enter the porous body layer 2 are reduced. Resulting in. Furthermore, by increasing the thickness of the porous body layer 2, it becomes difficult for organic substances to move to the first conductor layer 1 side, and aerobic microorganisms cannot grow on the first conductor layer 1. As a result, oxygen consumption by aerobic microorganisms is suppressed, and oxygen can be sufficiently supplied to the catalyst supported on the first conductor layer 1 to effectively perform an oxygen reduction reaction.

[Third embodiment]
Next, the microbial fuel cell according to the third embodiment will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure as the electrode assembly of 1st embodiment and 2nd embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIGS. 8 and 9, the microbial fuel cell 100 according to the present embodiment includes a negative electrode 20 that holds microorganisms, and a positive electrode 1 </ b> A that includes the conductor layer 1 in the electrode complex 10 </ b> A described above. The microbial fuel cell 100 further includes an ion moving layer 30 provided between the electrode assembly 10A and the negative electrode 20 and having hydrogen ion permeability.

(Negative electrode)
The negative electrode 20 in the present embodiment carries a microbe described later and further has a function of generating hydrogen ions and electrons from at least one of an organic substance and a nitrogen-containing compound in the electrolytic solution 70 by the catalytic action of the microbe. For this reason, the negative electrode 20 of the present embodiment is not particularly limited as long as it has such a function.

  The negative electrode 20 of the present embodiment has a structure in which microorganisms are supported on a conductive sheet having conductivity. As the conductor sheet, it is possible to use at least one selected from the group consisting of a porous conductor sheet, a woven conductor sheet, and a nonwoven conductor sheet. The conductor sheet may be a laminate in which a plurality of sheets are laminated. By using such a sheet having a plurality of pores as the conductor sheet of the negative electrode 20, hydrogen ions generated in the local battery reaction described later easily move toward the ion moving layer 30, and the oxygen reduction reaction The speed can be increased. Further, from the viewpoint of improving ion permeability, the conductor sheet of the negative electrode 20 has a space (void) continuous in the stacking direction X of the electrode composite 10A, the ion moving layer 30 and the negative electrode 20, that is, in the thickness direction. It is preferable.

  The conductor sheet may be a metal plate having a plurality of through holes in the thickness direction. Therefore, as a material constituting the conductor sheet of the negative electrode 20, for example, at least one selected from the group consisting of conductive metals such as aluminum, copper, stainless steel, nickel and titanium, carbon paper, and carbon felt is used. be able to.

  A graphite sheet may be used as the conductor sheet of the negative electrode 20. Moreover, the negative electrode 20 preferably contains graphite, and the graphene layer in the graphite is preferably arranged along a plane in a direction YZ perpendicular to the stacking direction X of the electrode composite 10A, the ion transfer layer 30, and the negative electrode 20. . By arranging the graphene layers in this way, the conductivity in the direction YZ perpendicular to the stacking direction X is improved as compared with the conductivity in the stacking direction X. Therefore, it becomes easy to conduct the electrons generated by the local battery reaction of the negative electrode 20 to the external circuit 110, and the efficiency of the battery reaction can be further improved.

  The above graphite sheet can be obtained as follows. First, natural graphite is chemically treated with an acid to form an insert between the graphite graphene layers. Next, this is rapidly heated at a high temperature to obtain expanded graphite in which the graphene interlayer is pushed and expanded by the gas pressure due to the thermal decomposition of the intercalated insert. Then, the expanded graphite is pressurized and roll-rolled to obtain a graphite sheet. When the graphite sheet obtained in this way is used as the conductor sheet of the negative electrode 20, the graphene layers in the graphite are arranged along the direction YZ perpendicular to the stacking direction X. Therefore, the conductivity between the negative electrode 20 and the external circuit 110 can be increased, and the efficiency of the battery reaction can be further improved.

  The microorganism supported on the negative electrode 20 is not particularly limited as long as it is a microorganism that decomposes an organic substance in the electrolyte solution 70 or a compound containing nitrogen. For example, an anaerobic microorganism that does not require oxygen for growth is used. preferable. Anaerobic microorganisms do not require air for oxidizing and decomposing organic substances in the electrolyte solution 70. Therefore, the electric power required for sending air can be significantly reduced. Moreover, since the free energy which microbes acquire is small, it becomes possible to reduce the amount of sludge generation.

  The anaerobic microorganism held in the negative electrode 20 is preferably an electricity producing bacterium having an extracellular electron transfer mechanism, for example. Specifically, examples of the anaerobic microorganism include Geobacter genus bacteria, Shewanella genus bacteria, Aeromonas genus bacteria, Geothrix genus bacteria, and Saccharomyces genus bacteria.

  Anaerobic microorganisms may be held on the negative electrode 20 by stacking and fixing a biofilm containing anaerobic microorganisms on the negative electrode 20. The biofilm generally refers to a three-dimensional structure including a microbial population and an extracellular polymeric substance (EPS) produced by the microbial population. However, the anaerobic microorganisms may be held on the negative electrode 20 without depending on the biofilm. Moreover, the anaerobic microorganisms may be held not only on the surface of the negative electrode 20 but also inside.

(Positive electrode)
The microbial fuel cell 100 of the present embodiment includes a positive electrode 1A composed of the conductor layer 1 in the electrode complex 10A shown in FIG.

(Ion moving layer)
The microbial fuel cell 100 of the present embodiment further includes an ion transfer layer 30 provided between the porous body layer 2 of the electrode assembly 10A and the negative electrode 20 and having proton permeability. That is, the ion migration layer 30 is provided on the surface 2a side of the porous body layer 2 in the electrode assembly 10A. As shown in FIGS. 8 and 9, the negative electrode 20 is separated from the electrode assembly 10 </ b> A through the ion moving layer 30. The ion moving layer 30 has a function of transmitting hydrogen ions generated in the negative electrode 20 and moving the hydrogen ions to the electrode assembly 10A side.

  As the ion migration layer 30, for example, an ion exchange membrane using an ion exchange resin can be used. As the ion exchange resin, for example, NAFION (registered trademark) manufactured by DuPont, and Flemion (registered trademark) and Selemion (registered trademark) manufactured by Asahi Glass Co., Ltd. can be used.

  Further, a porous membrane having pores through which hydrogen ions can permeate may be used as the ion moving layer 30. That is, the ion moving layer 30 may be a sheet having a space (void) for moving hydrogen ions from the negative electrode 20 to the electrode assembly 10A. Therefore, the ion migration layer 30 preferably includes at least one selected from the group consisting of a porous sheet, a woven sheet, and a nonwoven sheet. Moreover, the ion migration layer 30 can use at least one chosen from the group which consists of a glass fiber membrane, a synthetic fiber membrane, and a plastic nonwoven fabric, and the laminated body formed by laminating | stacking these two or more may be used. Since such a porous sheet has a large number of pores inside, hydrogen ions can easily move. The pore diameter of the ion moving layer 30 is not particularly limited as long as hydrogen ions can move from the negative electrode 20 to the electrode composite 10A.

  As described above, the ion moving layer 30 has a function of transmitting the hydrogen ions generated in the negative electrode 20 and moving the hydrogen ions to the electrode assembly 10A side. Therefore, for example, if the negative electrode 20 and the electrode assembly 10A are close to each other without being in contact with each other, hydrogen ions can move from the negative electrode 20 to the positive electrode 1A. Therefore, in the microbial fuel cell 100 of this embodiment, the ion moving layer 30 is not an essential component. However, since the provision of the ion moving layer 30 enables efficient movement of hydrogen ions from the negative electrode 20 to the positive electrode 1A, it is preferable to provide the ion moving layer 30 from the viewpoint of improving the output.

  As shown in FIGS. 8 and 9, the microbial fuel cell 100 according to the present embodiment includes a plurality of electrode assemblies 40 including an electrode assembly 10 </ b> A, a negative electrode 20, and an ion transfer layer 30. In the microbial fuel cell 100, as shown in FIG. 9, the negative electrode 20 is disposed so as to contact one surface 30 a of the ion moving layer 30, and an electrode is disposed on the surface 30 b opposite to the surface 30 a of the ion moving layer 30. It arrange | positions so that 10 A of composites may contact.

  As shown in FIG. 10, the two electrode assemblies 40 are laminated via the cassette base material 50 so that the water-repellent layers 3 of the electrode assembly 10A face each other. The cassette base material 50 is a U-shaped frame member along the outer peripheral portion of the surface 3b of the water repellent layer 3 of the electrode assembly 10A, and the upper portion is open. That is, the cassette base material 50 is a frame member in which the bottom surfaces of the two first columnar members 51 are connected by the second columnar member 52. The side surface 53 of the cassette base material 50 is joined to the outer peripheral portion of the surface 3 b of the water repellent layer 3, and the electrolyte solution 70 leaks into the cassette base material 50 from the outer peripheral portion of the surface 3 b of the water repellent layer 3. Can be suppressed.

  As shown in FIG. 9, the fuel cell unit 60 formed by laminating the two electrode assemblies 40 and the cassette base material 50 has a wastewater tank 80 so that a gas phase 90 communicating with the atmosphere is formed. Placed inside. The wastewater tank 80 holds an electrolytic solution 70 as a liquid to be treated, and the positive electrode 1A, the porous body layer 2, the negative electrode 20, and the ion transfer layer 30 of the electrode composite 10A are immersed in the electrolytic solution 70. Yes.

  As described above, the water repellent layer 3 of the electrode composite 10A has water repellency. Therefore, the electrolytic solution 70 held in the waste water tank 80 is separated from the inside of the cassette base material 50, and the internal space formed by the two electrode assemblies 40 and the cassette base material 50 is the gas phase 90. It has become. As shown in FIG. 9, the positive electrode 1A and the negative electrode 20 are electrically connected to the external circuit 110, respectively.

  Next, the operation of the microbial fuel cell 100 of this embodiment will be described. When the electrode assembly 40 composed of the electrode assembly 10A, the negative electrode 20, and the ion moving layer 30 is immersed in the electrolytic solution 70, the positive electrode 1A, the porous body layer 2, and the negative electrode 20 of the electrode composite 10A are the electrolytic solution 70. So that at least a part of the water-repellent layer 3 is exposed to the gas phase 90.

  During the operation of the microbial fuel cell 100, an electrolyte solution 70 containing at least one of an organic substance and a nitrogen-containing compound is supplied to the negative electrode 20, and air is supplied to the electrode assembly 10A. At this time, the air is continuously supplied through an opening provided in the upper part of the cassette base material 50.

  In the electrode assembly 10A, oxygen diffuses through the water-repellent layer 3 to the positive electrode 1A. In the negative electrode 20, hydrogen ions and electrons are generated from at least one of the organic substance and the nitrogen-containing compound in the electrolytic solution 70 by the catalytic action of anaerobic microorganisms. The generated hydrogen ions pass through the ion moving layer 30 and move to the electrode assembly 10A side. Further, the hydrogen ions pass through the porous body layer 2 in the electrode assembly 10A and reach the positive electrode 1A. Further, the generated electrons move to the external circuit 110 through the conductor sheet of the negative electrode 20, and further move from the external circuit 110 to the positive electrode 1A. And hydrogen ion and an electron couple | bond with oxygen by the effect | action of the catalyst in 1 A of positive electrodes, and are consumed as water. At this time, the electric energy flowing in the closed circuit is recovered by the external circuit 110.

  Here, in addition to the anaerobic microorganisms described above, the electrolytic solution 70 also includes aerobic microorganisms that require oxygen for growth. Since the electrode assembly 10A is provided with the porous body layer 2 on the positive electrode 1A, the microbial membrane 12 is formed on the surface 2a of the porous body layer 2 as shown in FIG. The aerobic microorganisms proceed to the gas phase 90 side to which oxygen is supplied. However, the organic substances are consumed by the aerobic microorganisms in the microorganism film 12, and the organic substances entering the porous body layer 2 are reduced. . Furthermore, since the porous body layer 2 has a predetermined thickness, it becomes difficult for organic substances to move to the positive electrode 1A side, and aerobic microorganisms are present on the positive electrode 1A side from the boundary between the positive electrode 1A and the porous body layer 2. Can no longer grow. As a result, since the aerobic microorganisms are not grown near the interface between the positive electrode 1A and the water repellent layer 3, oxygen consumption by the aerobic microorganisms is suppressed, and the oxygen reduction reaction can be performed efficiently.

  Thus, the microbial fuel cell 100 of the present embodiment includes the first electrode (positive electrode 1A) using the electrode assembly 10 and the second electrode (negative electrode 20). In this case, the first conductor layer (conductor layer 1) in the electrode assembly 10 becomes the first electrode (positive electrode 1A). The microbial fuel cell 100 further includes an ion transfer layer 30 provided between the second surface 11b of the electrode assembly 10 and the second electrode and having proton permeability. Such a configuration makes it difficult for the positive electrode 1A to inhibit oxygen consumption due to aerobic microorganisms, so that the oxygen reduction characteristics of the positive electrode 1A can be improved and electric energy can be stably produced.

  In the electrode assembly 10, when the porous body layer 2 is electrically insulating, the microbial fuel cell 100 </ b> A does not need to provide the ion transfer layer 30 as shown in FIG. 11. Specifically, the microbial fuel cell 100 </ b> A includes a plurality of electrode assemblies 40 </ b> A composed of the electrode assembly 10 and the negative electrode 20. In the microbial fuel cell 100 </ b> A, one surface 20 a of the negative electrode 20 is disposed so as to be in contact with the surface 2 a of the porous body layer 2 in the electrode assembly 10. And two electrode assembly 40A is laminated | stacked through the cassette base material 50 so that the water-repellent layers 3 of electrode assembly 10A may face each other. The side surface 53 of the cassette base material 50 is joined to the outer peripheral portion of the surface 3 b in the water repellent layer 3. Further, the fuel cell unit 60A formed by laminating the two electrode assemblies 40A and the cassette base material 50 is arranged inside the waste water tank 80 so that the gas phase 90 is formed, and the electrode assembly 10A The positive electrode 1A, the porous body layer 2, and the negative electrode 20 are immersed in the electrolytic solution 70.

  When the porous body layer 2 of the electrode composite body 10A is electrically insulating, the positive electrode 1A and the negative electrode 20 of the electrode composite body 10A are insulated by the porous body layer 2, so that the ion migration layer 30 is not interposed. However, a short circuit between the conductor layer 1 and the negative electrode 20 can be prevented. In addition, as described above, the porous body layer 2 can transmit hydrogen ions and can reach the conductor layer 1. Thus, since the porous body layer 2 can perform the same function as the ion moving layer 30, the ion moving layer 30 may not be provided. In FIG. 11, the one surface 20 a of the negative electrode 20 is disposed so as to be in contact with the surface 2 a of the porous body layer 2 in the electrode assembly 10 </ b> A, but the surface 20 a of the negative electrode 20 and the porous body layer 2 are arranged. There may be a gap between the surface 2a.

  For example, the negative electrode 20 according to the present embodiment may be modified with an electron transfer mediator molecule. Alternatively, the electrolytic solution 70 in the waste water tank 80 may contain electron transfer mediator molecules. Thereby, the electron transfer from an anaerobic microorganism to the negative electrode 20 is accelerated | stimulated, and more efficient liquid processing is realizable.

  Specifically, in the metabolic mechanism by anaerobic microorganisms, electrons are transferred between cells or with the final electron acceptor. When a mediator molecule is introduced into the electrolytic solution 70, the mediator molecule acts as a final electron acceptor of metabolism, and delivers received electrons to the negative electrode 20. As a result, it becomes possible to increase the rate of oxidative decomposition of the organic matter in the electrolytic solution 70. Such an electron transfer mediator molecule is not particularly limited. As the electron transfer mediator molecule, for example, at least one selected from the group consisting of neutral red, anthraquinone-2,6-disulfonic acid (AQDS), thionine, potassium ferricyanide, and methylviologen can be used.

  The fuel cell unit 60 shown in FIG. 10 has a configuration in which two electrode assemblies 40 and a cassette base material 50 are stacked. However, the present embodiment is not limited to this configuration. For example, the electrode assembly 40 may be bonded to only one side surface 53 of the cassette base material 50 and the other side surface may be sealed with a plate member. 8 to 10, the entire upper portion of the cassette base 50 is open, but may be partially open if air (oxygen) can be introduced into the inside. It may be closed.

  The waste water tank 80 holds the electrolytic solution 70 therein, but may have a configuration in which the electrolytic solution 70 circulates. For example, as shown in FIGS. 8 and 9, in the wastewater tank 80, a wastewater supply port 81 for supplying the electrolytic solution 70 to the wastewater tank 80 and a discharged electrolytic solution 70 after the treatment are discharged from the wastewater tank 80. The waste water discharge port 82 may be provided. The electrolytic solution 70 is preferably continuously supplied through the waste water supply port 81 and the waste water discharge port 82.

  It is preferable that the inside of the waste water tank 80 is maintained in anaerobic conditions in which, for example, molecular oxygen does not exist or even if molecular oxygen is present, the concentration thereof is extremely small. Thereby, it becomes possible to hold | maintain the electrolyte solution 70 so that it may hardly contact oxygen in the wastewater tank 80. FIG.

[Fourth embodiment]
Next, a microbial fuel cell according to a fourth embodiment will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the structure same as the microbial fuel cell which concerns on the electrode assembly of 1st embodiment and 2nd embodiment, and 3rd embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 12, the microbial fuel cell 100 </ b> B of the present embodiment includes a positive electrode 1 </ b> B and a negative electrode 20 </ b> A composed of the conductor layer 1 in the electrode assembly 10 described above.

(Positive electrode)
The positive electrode 1B according to the present embodiment has a function of causing an oxygen reduction reaction between hydrogen ions and electrons generated in the negative electrode 20A and oxygen in the gas phase 90. For this reason, the positive electrode 1B of the present embodiment is not particularly limited as long as it has such a function. As the positive electrode 1B, for example, a gas diffusion electrode including a water repellent layer and a gas diffusion layer stacked so as to be in contact with the water repellent layer can be used. By using such a thin plate-like gas diffusion electrode, oxygen in the gas phase 90 can be easily supplied to the catalyst in the positive electrode 1B.

  The water repellent layer in the positive electrode 1B is a layer having both water repellency and oxygen permeability. The water repellent layer is configured to allow oxygen to move from the gas phase to the liquid phase while favorably separating the gas phase and the liquid phase in the electrochemical system of the microbial fuel cell 100B. That is, the water-repellent layer can suppress the movement of the electrolytic solution 70 toward the gas phase 90 while allowing oxygen in the gas phase 90 to permeate and move to the gas diffusion layer. As such a water-repellent layer, the same layer as the water-repellent layer 3 of the first embodiment can be used.

  The gas diffusion layer in the positive electrode 1B preferably includes a porous conductive material and a catalyst supported on the conductive material. The gas diffusion layer may be composed of a porous and conductive catalyst. By providing such a gas diffusion layer in the positive electrode 1 </ b> B, it is possible to conduct electrons generated in the negative electrode between the catalyst and the external circuit 110. In addition, the said catalyst can use the same catalyst as what was demonstrated in 1st embodiment.

  In the positive electrode 1B, in order to ensure stable performance, it is preferable that oxygen is efficiently transmitted through the water-repellent layer and the gas diffusion layer and supplied to the catalyst. Therefore, the gas diffusion layer is preferably a porous body having a large number of pores through which oxygen passes from the surface facing the water repellent layer to the surface on the opposite side. The shape of the gas diffusion layer is particularly preferably a three-dimensional mesh. With such a mesh shape, it is possible to impart high oxygen permeability and conductivity to the gas diffusion layer.

  In the positive electrode 1B, in order to efficiently supply oxygen to the gas diffusion layer, the water repellent layer is preferably bonded to the gas diffusion layer through an adhesive. Thereby, the diffused oxygen is directly supplied to the gas diffusion layer, and the oxygen reduction reaction can be performed efficiently. As the adhesive, the same adhesive as described in the first embodiment can be used.

  Here, the gas diffusion layer of the positive electrode 1B in the present embodiment will be described in more detail. As described above, the gas diffusion layer can be configured to include a porous conductive material and a catalyst supported on the conductive material.

  The conductive material in the gas diffusion layer can be composed of, for example, one or more materials selected from the group consisting of carbon-based substances, conductive polymers, semiconductors, and metals. Here, the carbon-based material means a material containing carbon as a constituent component. Examples of carbon-based materials include, for example, carbon powder such as graphite, activated carbon, carbon black, Vulcan (registered trademark) XC-72R, acetylene black, furnace black, Denka black, graphite felt, carbon wool, carbon woven cloth, etc. Carbon fiber, carbon plate, carbon paper, carbon disk, carbon cloth, carbon foil, and carbon-based material obtained by compression molding carbon particles are included. Examples of the carbon-based material also include fine-structured materials such as carbon nanotubes, carbon nanohorns, and carbon nanoclusters. Furthermore, as a conductive material in the gas diffusion layer, a metal material such as a mesh and a foam can also be used.

  The conductive polymer is a general term for polymer compounds having conductivity. Examples of the conductive polymer include aniline, aminophenol, diaminophenol, pyrrole, thiophene, paraphenylene, fluorene, furan, acetylene, or a polymer of two or more monomers having a structural unit as a constituent unit. Can be mentioned. Specifically, examples of the conductive polymer include polyaniline, polyaminophenol, polydiaminophenol, polypyrrole, polythiophene, polyparaphenylene, polyfluorene, polyfuran, and polyacetylene. An example of the metal conductive material is a stainless mesh. In consideration of availability, cost, corrosion resistance, durability, and the like, the conductive material is preferably a carbon-based substance.

  The shape of the conductive material is preferably a powder shape or a fiber shape. Further, the conductive material may be supported by a support. The support means a member that itself has rigidity and can give a certain shape to the gas diffusion electrode. The support may be an insulator or a conductor. When the support is an insulator, examples of the support include glass, plastic, synthetic rubber, ceramics, water-resistant or water-repellent treated paper, plant pieces such as wood pieces, bone pieces, animal pieces such as shells, and the like. . Examples of the porous structure support include porous ceramics, porous plastics, and sponges. When the support is a conductor, examples of the support include carbon materials such as carbon paper, carbon fiber, and carbon rod, metals, conductive polymers, and the like. When the support is a conductor, the support can also function as a current collector by disposing a conductive material carrying a carbon-based material on the surface of the support.

  In the gas diffusion layer, the catalyst may be bound to the conductive material using a binder. That is, the catalyst may be supported on the surface of the conductive material and inside the pores using a binder. As the binder, the same binder as described in the first embodiment can be used.

(Negative electrode)
The microbial fuel cell 100 of this embodiment includes a negative electrode 20A made of the conductor layer 1 in the electrode assembly 10 shown in FIG.

  As shown in FIG. 12, the microbial fuel cell 100 </ b> B according to the present embodiment includes a plurality of electrode assemblies 40 </ b> B including the positive electrode 1 </ b> B and the electrode assembly 10. In the microbial fuel cell 100 </ b> B, the gas diffusion layer of the positive electrode 1 </ b> B is disposed in contact with the second surface 11 b of the electrode assembly 10.

  Similar to the fuel cell unit 60 shown in FIG. 10, the two electrode assemblies 40 </ b> B are stacked via the cassette base material 50 so that the water-repellent layers of the positive electrode 1 </ b> B are opposed to each other. The cassette base material 50 is a U-shaped frame member along the outer periphery of the water-repellent layer of the positive electrode 1B, and the upper part is open. And the side surface 53 of the cassette base material 50 is joined with the outer peripheral part of the water repellent layer, and it can suppress that the electrolyte solution 70 leaks into the inside of the cassette base material 50 from the said outer peripheral part.

  Then, as shown in FIG. 12, the fuel cell unit 60B formed by laminating the two electrode assemblies 40B and the cassette base material 50 has a waste water tank 80 so that a gas phase 90 communicating with the atmosphere is formed. Placed inside. The wastewater tank 80 holds an electrolytic solution 70 as a liquid to be treated, and the gas diffusion layer of the positive electrode 1B and the negative electrode 20A and the porous body layer 2 of the electrode composite 10 are immersed in the electrolytic solution 70. Yes.

  As described above, the water repellent layer of the positive electrode 1B has water repellency. Therefore, the electrolytic solution 70 held in the waste water tank 80 is separated from the inside of the cassette base material 50, and the internal space formed by the two electrode assemblies 40 </ b> B and the cassette base material 50 is the gas phase 90. It has become. As shown in FIG. 12, the positive electrode 1B and the negative electrode 20A are electrically connected to the external circuit 110, respectively.

  Next, the operation of the microbial fuel cell 100B of this embodiment will be described. When the electrode assembly 40B composed of the positive electrode 1B and the electrode assembly 10 described above is immersed in the electrolytic solution 70, the negative electrode 20A and the porous body layer 2 of the electrode composite 10, and the gas diffusion layer of the positive electrode 1B become the electrolytic solution 70. So that at least a part of the water-repellent layer of the positive electrode 1 </ b> B is exposed to the gas phase 90.

  During operation of the microbial fuel cell 100B, an electrolyte solution 70 containing at least one of an organic substance and a nitrogen-containing compound is supplied to the negative electrode 20A, and air is supplied to the positive electrode 1B. In the positive electrode 1B, oxygen diffuses into the gas diffusion layer through the water repellent layer. In the negative electrode 20A, hydrogen ions and electrons are generated from at least one of the organic matter and the nitrogen-containing compound in the electrolytic solution 70 by the catalytic action of anaerobic microorganisms. The generated hydrogen ions pass through the porous body layer 2 in the electrode assembly 10 and reach the positive electrode 1B. The generated electrons move to the external circuit 110 through the negative electrode 20A, and further move from the external circuit 110 to the gas diffusion layer of the positive electrode 1B. And hydrogen ion and an electron couple | bond with oxygen by the effect | action of the catalyst in the gas diffusion layer in the positive electrode 1B, and are consumed as water. At this time, the electric energy flowing in the closed circuit is recovered by the external circuit 110.

  As described above, the electrode assembly 10 according to the present embodiment can suppress the growth of aerobic microorganisms in the positive electrode 1B in order to prevent the entry of aerobic microorganisms. Therefore, oxygen consumption by aerobic microorganisms is suppressed, and oxygen reduction reaction can be performed efficiently.

  In the microbial fuel cell 100B of the present embodiment, since the porous body layer 2 of the electrode assembly 10 is electrically insulating, the positive electrode 1B is disposed in contact with the second surface 11b of the electrode assembly 10. Even so, a short circuit between the positive electrode 1B and the negative electrode 20A can be prevented. However, when the porous body layer 2 of the electrode assembly 10 is conductive, it is between the gas diffusion layer of the positive electrode 1B and the second surface 11b of the electrode assembly 10 as in the third embodiment. It is preferable to provide an ion transfer layer.

[Fifth embodiment]
Next, a microbial fuel cell according to a fifth embodiment will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure as the microbial fuel cell which concerns on the electrode assembly of 1st embodiment and 2nd embodiment, and 3rd embodiment and 4th embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 13, the microbial fuel cell 100 </ b> C of this embodiment uses the electrode assembly 10 </ b> D of the second embodiment. The two electrode composites 10D are laminated via the cassette base material 50 so that the water-repellent layers 3 provided on the first conductor layer 1 side face each other. The cassette base material 50 is a U-shaped frame member along the outer periphery of the water repellent layer 3, and the upper part is open. Similarly to the fuel cell unit 60 shown in FIG. 10, the side surface 53 of the cassette base material 50 is joined to the outer peripheral portion of the water-repellent layer 3, and the electrolytic solution 70 enters the cassette base material 50 from the outer peripheral portion. Can be prevented from leaking.

  As shown in FIG. 13, the fuel cell unit 60C formed by stacking the two electrode composites 10D and the cassette base material 50 has a wastewater tank 80 so that a gas phase 90 communicating with the atmosphere is formed. Placed inside. An electrolytic solution 70 that is a liquid to be treated is held inside the waste water tank 80, and the electrode assembly 10 </ b> D is immersed in the electrolytic solution 70.

  As described above, the water repellent layer 3 has water repellency. Therefore, the electrolytic solution 70 held in the waste water tank 80 is separated from the inside of the cassette base material 50, and the internal space formed by the two electrode composites 10 </ b> D and the cassette base material 50 is a gas phase 90. It has become. As shown in FIG. 13, the first conductor layer 1 and the second conductor layer 5 are each electrically connected to the external circuit 110.

  In the microbial fuel cell 100C, the first conductor layer 1 in the electrode assembly 10D is the positive electrode 1C, and the second conductor layer 5 is the negative electrode 20B. And since the porous body layer 2 is an electrical insulator, the short circuit between the positive electrode 1C and the negative electrode 20B can be prevented. A catalyst is supported on the first conductor layer 1 which is the positive electrode 1C.

  Next, the operation of the microbial fuel cell 100C of this embodiment will be described. When the electrode composite 10D is immersed in the electrolytic solution 70, the first conductive layer 1, the second conductive layer 5, and the porous body layer 2 are immersed in the electrolytic solution 70, and at least one of the water repellent layer 3 is immersed. The part is exposed to the gas phase 90.

  During the operation of the microbial fuel cell 100C, the electrolytic solution 70 containing at least one of an organic substance and a nitrogen-containing compound is supplied to the negative electrode 20B, and air is supplied to the water repellent layer 3. Then, oxygen diffuses into the positive electrode 1C through the water repellent layer 3. In the negative electrode 20B, hydrogen ions and electrons are generated from at least one of the organic matter and the nitrogen-containing compound in the electrolytic solution 70 by the catalytic action of anaerobic microorganisms. The generated hydrogen ions pass through the porous body layer 2 in the electrode assembly 10D and reach the positive electrode 1C. Further, the generated electrons move to the external circuit 110 through the negative electrode 20B, and further move from the external circuit 110 to the positive electrode 1C. The hydrogen ions and electrons are combined with oxygen by the action of the catalyst in the positive electrode 1C and consumed as water. At this time, the electric energy flowing in the closed circuit is recovered by the external circuit 110.

  Thus, the microbial fuel cell 100C according to the present embodiment has the electrode assembly 10D. The electrode assembly 10D includes a sheet-like porous substrate 11 including a first surface 11a and a second surface 11b opposite to the first surface 11a. In addition, the electrode assembly 10D includes a first conductive member provided in a part of the porous substrate 11 from the first surface 11a toward the second surface 11b in the thickness direction X of the porous substrate 11. It has a body layer 1. Furthermore, the electrode assembly 10D is a second conductor provided in a part of the porous substrate 11 from the second surface 11b toward the first surface 11a in the thickness direction X of the porous substrate 11. Layer 5 is included. Furthermore, the porous substrate 11 is an electrical insulator. In the microbial fuel cell 100C, the first conductor layer 1 in the electrode assembly 10D is the first electrode (positive electrode 1C), and the second conductor layer 5 is the second electrode (negative electrode 20B). As described above, the electrode assembly 10D can suppress the growth of aerobic microorganisms in the vicinity of the interface between the positive electrode 1C and the water-repellent layer in order to prevent the entry of aerobic microorganisms. Therefore, oxygen consumption by aerobic microorganisms is suppressed, and oxygen reduction reaction can be performed efficiently.

  Hereinafter, the present embodiment will be described in more detail by way of examples, but the present embodiment is not limited to these examples.

[Example 1]
In Example 1, the electrode assembly shown in FIG. 1 was produced. First, as a porous substrate, a nonwoven fabric having a thickness of 1 mm (“NLAT150” manufactured by Nippon Nonwoven Fabric Co., Ltd.) was prepared. Furthermore, JELCON CH-8 (high performance low resistance carbon paste) manufactured by Jujo Chemical Co., Ltd. was prepared as a conductive carbon material for forming the conductor layer.

  And after apply | coating a conductive carbon material to the surface of a nonwoven fabric, the electrode composite of this example was produced by leaving still for 15 minutes in 120 degreeC oven.

[Example 2]
In Example 2, the microbial fuel cell shown in FIG. 12 was produced using the electrode assembly obtained in Example 1.

(Preparation of positive electrode)
First, a polytetrafluoroethylene (PTFE) dispersion was applied to one surface of carbon paper (fuel cell electrode base material TGP-H-120, manufactured by Toray Industries, Inc.), and heated at 380 ° C. for 20 minutes. Thus, an air cathode obtained by sintering a polytetrafluoroethylene layer on carbon paper was obtained. As the polytetrafluoroethylene dispersion, 60 wt% dispersion in H ₂ O manufactured by Sigma-Aldrich was used.

Next, the catalyst ink was applied to the other surface of the carbon paper. The catalyst ink was prepared by mixing a Pt / C catalyst, Nafion and ion exchange water. And after apply | coating the said catalyst ink so that a platinum catalyst may become a 4 mg / cm < ² > basis weight, the positive electrode of this example was produced by drying at 380 degreeC for 20 minutes. Note that “TEC10E70TPM” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. was used as the Pt / C catalyst in the catalyst ink. Moreover, Nafion used "Nafion perfluorinated resin solution" by Sigma-Aldrich Japan.

(Production of microbial fuel cell)
An electrode assembly was prepared by laminating the surface coated with the catalyst ink in the positive electrode on the surface opposite to the surface carrying the conductive carbon material in the electrode composite obtained in Example 1. Furthermore, the fuel cell unit shown in FIG. 12 was obtained by laminating two electrode assemblies and a U-shaped cassette base material.

As shown in FIG. 12, the obtained fuel cell unit was installed in a 300 cc water tank, and artificial waste water as a liquid to be treated was allowed to flow into the water tank. In the operation of the microbial fuel cell, artificial wastewater containing an organic polymer such as starch was continuously flowed over 30 days so as to be in contact with the negative electrode. At this time, the BOD concentration of the artificial wastewater was set to 800 mg / L. The flow rate of the artificial waste water was set so that the BOD area load, which is the BOD load amount per outer area of the negative electrode, was 16 g / m ² / day. In addition, soil microorganisms were planted in the artificial wastewater as anaerobic microorganisms responsible for power generation. Thus, the microbial fuel cell of this example was obtained.

  In general, since the output of a microbial fuel cell decreases as the distance between the positive electrode and the negative electrode increases, conventionally, it has been important to reduce the distance between the positive electrode and the negative electrode. However, contrary to conventional technical common sense, it is understood that if the distance between the positive electrode and the negative electrode is increased to some extent using the porous body layer, the output does not decrease in the long term, and a high output can be maintained. The invention of this embodiment has been completed.

  Although the present embodiment has been described above, the present embodiment is not limited to these, and various modifications can be made within the scope of the gist of the present embodiment. Specifically, in the drawings, the electrode composites 10, 10A, 10C, 10D, the positive electrode 1B, the negative electrode 20, and the ion transfer layer 30 are formed in a rectangular shape. However, these shapes are not particularly limited, and can be arbitrarily changed depending on the size of the fuel cell and the desired power generation performance. Further, the area of each layer can be arbitrarily changed as long as a desired function can be exhibited.

1 First conductor layer (conductor layer)
DESCRIPTION OF SYMBOLS 1A 1st electrode 2 Porous body layer 3 Water repellent layer 4 Sealing material 5 2nd conductor layer 10, 10A, 10B, 10C, 10D Electrode complex 11 Porous base material 11a First surface 11b Second Surface 20 Second electrode 30 Ion transfer layer 100, 100A, 100B, 100C Microbial fuel cell

Claims (7)

A sheet-like porous substrate comprising a first surface and a second surface opposite to the first surface;
In the thickness direction of the porous substrate, a first conductor layer provided on a part of the porous substrate from the first surface toward the second surface;
An electrode assembly.   The electrode assembly according to claim 1, wherein the porous substrate has a thickness of 1.0 mm to 50 mm.   The electrode composite according to claim 1, wherein the porous substrate is an electrical insulator.   4. The apparatus further comprises a second conductor layer provided on a part of the porous substrate from the second surface toward the first surface in the thickness direction of the porous substrate. The electrode composite according to 1. A first electrode using the electrode composite according to any one of claims 1 to 3,
A second electrode;
A fuel cell.   The fuel cell according to claim 5, further comprising an ion transfer layer provided between the second surface of the electrode complex and the second electrode and having proton permeability. The electrode composite according to claim 4,
A fuel cell in which the first conductor layer in the electrode assembly is a first electrode, and the second conductor layer is a second electrode.

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