JP2017117586A - Method of manufacturing electrode composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrode composite that is capable of suppressing deterioration in power generation performance and stably generating electric energy.SOLUTION: A method of producing an electrode composite (10, 10A) comprises a step of coating a film material on one surface of a conductor layer (1) which has oxygen permeability and is made of a first conductive material. Further, the manufacturing method comprises a step of spraying a second conductive material (3) on the film material, and a step of curing the film material to form a film layer (2) having water sealing performance and oxygen permeability.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing an electrode composite. Specifically, the present invention relates to a method for producing an electrode composite capable of purifying waste water and generating electric energy.

  In recent years, microbial fuel cells that generate electricity using biomass have attracted attention as sustainable energy. A microbial fuel cell is an apparatus that converts organic matter into electrical energy by utilizing the metabolic ability of microorganisms, and is an excellent system that can recover energy while processing organic matter. 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, an electrolytic cell, an anode disposed inside the electrolytic cell, and a tank body part of the electrolytic cell, one surface is in contact with the air outside the cell, and the other surface is an electrolytic solution The thing provided with the cathode which contacts is disclosed (for example, refer patent document 1). The electrolytic cell holds an electrolytic solution, a microorganism, and a substrate for oxidative decomposition by the microorganism. The cathode has a water stop layer containing silicone formed on one surface in contact with air.

Japanese Patent Laying-Open No. 2015-46361

  However, since the cathode disclosed in Patent Document 1 has a catalyst layer on the liquid phase side of the water stop layer in contact with air, aerobic microorganisms pass through the catalyst layer and enter the water stop layer. End up. And since oxygen is consumed by the aerobic microorganisms in the vicinity of the water-stopping layer, oxygen is not sufficiently supplied to the catalyst layer, and as a result, the power generation performance is lowered and electric energy cannot be stably obtained. There was a problem.

  The present invention has been made in view of such problems of the prior art. And the objective of this invention is providing the manufacturing method of the electrode composite_body | complex which can suppress the fall of electric power generation performance and can produce electric energy stably.

  In order to solve the above-described problems, a method for manufacturing an electrode assembly according to an aspect of the present invention includes applying a film material to one surface of a conductor layer having oxygen permeability and made of a first conductor material. The process of carrying out. Furthermore, the manufacturing method includes a step of spraying a second conductor material on the film material and a step of forming a film layer having water-stopping property and oxygen permeability by curing the film material.

  According to the present invention, it is possible to easily form a film layer that suppresses entry of microorganisms into the conductor layer. And since the obtained electrode assembly can supply oxygen to an oxygen reduction catalyst efficiently, it becomes possible to suppress the fall of electric power generation performance and to produce electric energy stably.

It is a schematic sectional drawing which shows an example of the electrode composite_body | complex which concerns on embodiment of this invention. It is a schematic sectional drawing which shows the other example of the electrode composite_body | complex which concerns on embodiment of this invention. It is a schematic perspective view which shows an example of the microbial fuel cell which concerns on embodiment of this invention. It is sectional drawing along the AA line in FIG. It is a disassembled perspective view which shows the fuel cell unit in the said microbial fuel cell. It is a graph which shows the relationship between the steady output and elapsed days in the microbial fuel cell using the electrode composite_body | complex of an Example and a comparative example.

  Hereafter, the manufacturing method of the electrode assembly which concerns on this embodiment is demonstrated in detail. In addition, the dimension ratio of drawing is exaggerated on account of description, and may differ from an actual ratio.

[Electrode composite]
As shown in FIG. 1, the electrode assembly 10 of the present embodiment has conductivity and oxygen permeability, and includes a conductor layer 1 made of a first conductor material and one surface 1 a of the conductor layer 1. The film layer 2 is laminated so as to be in contact with the water and has water-stopping property and oxygen permeability. And in the film layer 2, the 2nd conductor material 3 is disperse | distributing.

  In addition, as shown in FIG. 2, the electrode assembly 10 </ b> A of the present embodiment has conductivity and oxygen permeability, and includes one of the conductor layer 1 made of the first conductor material and the conductor layer 1. The film layer 2 is laminated so as to be in contact with the surface 1a and has water-stopping property and oxygen permeability. Furthermore, the electrode assembly 10A is laminated so that the water repellent layer 4 is in contact with the other surface 1b on the side opposite to the one surface 1a of the conductor layer 1. And in the film layer 2, the 2nd conductor material 3 is disperse | distributing.

(Conductor layer)
The electrode assembly 10 of this embodiment includes a conductor layer 1 having conductivity and oxygen permeability. By providing such a conductor layer 1, electrons generated by a local battery reaction described later can be conducted between the second conductor material 3 and the external circuit 90. That is, as will be described later, the second conductive material 3 is dispersed in the film layer 2, and an oxygen reduction catalyst may be supported on the second conductive material 3. Therefore, by providing the conductor layer 1, it is possible to promote the oxygen reduction reaction by oxygen, hydrogen ions, and electrons in the second conductor material 3.

  In the electrode assembly 10, it is preferable that oxygen is efficiently transmitted through the water repellent layer 4 and the conductor layer 1 and supplied to the catalyst particles in order to ensure stable performance. Therefore, the conductor layer 1 is preferably a porous body having many pores through which oxygen can pass. 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.

  The 1st conductor material which comprises the conductor layer 1 will not be specifically limited if high electroconductivity is securable. However, the first conductor 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 first conductor material may be a carbon material. As the carbon material, for example, at least one selected from the group consisting of carbon paper, carbon felt, carbon cloth, and graphite sheet can be used. The first conductor material may be made of one selected from the group consisting of carbon paper, carbon felt, carbon cloth, and graphite sheet, or may be a laminate formed by laminating a plurality of these materials. Carbon paper and carbon felt, which are carbon fiber nonwoven fabrics, carbon cloth, which is carbon fiber woven fabric, and graphite sheets made of graphite have high corrosion resistance and electrical resistance equivalent to that of metal materials. It becomes possible to achieve both durability and conductivity.

  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 thus obtained is used as the conductor layer 1, the graphene layers in the graphite are arranged along the direction Y perpendicular to the stacking direction X. The graphene layers are arranged along a direction Z that is not shown in FIGS. 1 and 2 and is perpendicular to the stacking direction X. Therefore, it is possible to increase the conductivity between the conductor layer 1 and the external circuit 90 and further improve the efficiency of the battery reaction.

(Film layer)
The electrode assembly 10 is provided on one surface 1a of the conductor layer 1 and includes a film layer 2 having water-stopping properties and oxygen permeability. Since the film layer 2 has a function of separating the gas phase 5 containing oxygen and the liquid 70 to be treated which is held in the waste water tank 80 as a liquid phase, the conductor layer 1 and a water repellent layer which will be described later Invasion of microorganisms into 4 can be suppressed. Further, as shown in FIGS. 1 and 2, the film layer 2 holds the particulate second conductive material 3 and further passes oxygen that has passed through the water repellent layer 4 and the conductive layer 1 to the second conductive layer. It has a function of supplying the body material 3.

  The film layer 2 needs to be disposed on at least a part of the one surface 1 a of the conductor layer 1. However, in order to increase the water-stopping property with respect to the liquid 70 to be treated, the film layer 2 is preferably disposed on the entire surface 1a as shown in FIGS.

  The material for the film layer 2 is not particularly limited as long as it can ensure water-stopping and oxygen permeability. As a material of the film layer 2, for example, an elastic material such as silicone rubber or styrene-butadiene rubber, a thermosetting resin material such as an epoxy resin, or a thermoplastic resin material such as an acrylic resin can be used. In addition, the material of the film layer 2 may be used individually by 1 type, and may be used in combination of 2 or more type. Among these, silicone rubber is excellent in oxygen permeability because it has high oxygen solubility and oxygen diffusibility derived from the molecular structure of silicone. Furthermore, since silicone rubber has a small surface free energy, it has excellent water repellency. Therefore, it is particularly preferable that the film layer 2 contains silicone.

The film layer 2 more preferably has an ISO air permeability of 1 × 10 ⁻⁵ μm / Pa · s to 1 × 10 ⁻³ μm / Pa · s. The air permeability is an average flow rate of air that permeates per unit area, unit pressure difference, and unit time, and the higher the numerical value, the easier the air passes. Since the film layer 2 has an air permeability in such a range, sufficient oxygen can be supplied to an oxygen reduction catalyst described later, and the electrode assembly 10 and the microbial fuel cell having stable performance. 100 can be realized.

Specifically, since the ISO air permeability of the film layer 2 is 1 × 10 ⁻⁵ μm / Pa · s or more, a large number of pores are formed, so that oxygen permeability is improved and oxygen and The contact rate with the oxygen reduction catalyst can be increased. In addition, when the ISO air permeability of the film layer 2 is 1 × 10 ⁻³ μm / Pa · s or less, the strength for configuring the sheet-like film layer 2 is ensured while increasing the oxygen permeability. It becomes possible. That is, as the ISO air permeability of the film layer 2 is higher, the oxygen permeability is improved. However, when the ISO air permeability is high, the density of the film layer 2 is lowered and the strength may be insufficient. Therefore, it is preferable that the ISO air permeability of the film layer 2 is 1 × 10 ⁻³ μm / Pa · s or less. In addition, the ISO air permeability of the film layer 2 is peeled off from the electrode assembly 10, and is then subjected to Japanese Industrial Standard JIS P8117: 2009 (Paper and paperboard—Air permeability and air resistance test method (intermediate region) —Gurley method) ) Can be measured.

  Although the film thickness of the film layer 2 will not be specifically limited if water-stopping property and oxygen permeability are securable, For example, it is preferable that they are 1 micrometer-100 micrometers. When the film thickness of the film layer 2 is within this range, high water-stopping property and oxygen permeability can be obtained while ensuring the strength required for the sheet-like film layer 2.

  As will be described later, the conductor layer 1 and the second conductor material 3 are preferably electrically connected. Therefore, the film layer 2 preferably contains conductive particles. Thereby, since the conductor layer 1 and the second conductor material 3 are electrically connected through the conductive particles, the oxygen reduction reaction by oxygen, hydrogen ions and electrons is performed in the second conductor material 3. It becomes possible to promote.

  The conductive particles are not particularly limited as long as they are particles capable of imparting conductivity to the film layer 2, and for example, carbon black can be used. As the carbon black, at least one selected from the group consisting of furnace black, channel black, acetylene black, and thermal black can be used. Therefore, as the film layer 2, for example, a silicone rubber in which carbon black is kneaded can be used. As described above, since the silicone rubber is excellent in oxygen permeability, it is possible to achieve both high oxygen permeability and conductivity by containing carbon black.

(Second conductor material)
In the electrode assembly 10, the second conductor material 3 is dispersed in the film layer 2. Specifically, as shown in FIGS. 1 and 2, the particulate second conductive material 3 is held by the film layer 2, and is further uniformly and densely dispersed throughout the film layer 2. It is preferable. The second conductor material 3 is preferably distributed in the vicinity of the surface 2 a of the film layer 2. Thereby, it is possible to further increase the reaction rate between oxygen transferred by the water repellent layer 4 and the conductor layer 1 and hydrogen ions that have passed through the ion transfer layer 30.

  The second conductor material 3 is preferably in direct contact with the conductor layer 1. Alternatively, it is preferable that the second conductor material 3 is electrically connected to the conductor layer 1 via another second conductor material 3. As will be described later, the second conductor material 3 is preferably an oxygen reduction catalyst. Therefore, when the second conductor material 3 is electrically connected to the conductor layer 1, it is possible to efficiently perform an oxygen reduction reaction by electrons that have moved through the conductor layer 1.

  The second conductor material 3 is not particularly limited as long as it has conductivity. As the second conductor material 3, at least one of a metal and a carbon material can be used. The metal constituting the second conductor material 3 is preferably at least one selected from the group consisting of aluminum, copper, stainless steel, nickel and titanium, for example. Moreover, it is preferable that the carbon material which comprises the 2nd conductor material 3 is at least 1 chosen from the group which consists of carbon black, a graphene, fullerene, and a carbon nanotube, for example. As carbon black, at least one selected from the group consisting of furnace black, channel black, acetylene black and thermal black can be used.

  Although the particle diameter of the 2nd conductor material 3 is not specifically limited, For example, it is preferable that they are 1 micrometer-1 mm. When the particle diameter of the second conductor material 3 is within this range, the dispersibility in the film layer 2 can be increased and the conductivity can be improved. In addition, the particle diameter of the 2nd conductor material 3 can be calculated | required by observing the 2nd conductor material 3 using a scanning electron microscope (SEM).

  The second conductor material 3 is preferably an oxygen reduction catalyst. Since the second conductor material 3 is an oxygen reduction catalyst, the reaction rate between oxygen and hydrogen ions transferred by the water repellent layer 4 and the conductor layer 1 can be further increased.

  The oxygen reduction catalyst is preferably a carbon-based material doped with metal atoms. The metal atom is not particularly limited, but 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 carbon-based material can have 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.

  Here, 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.

(Water repellent layer)
The electrode assembly of this embodiment includes at least the conductor layer 1 and the film layer 2 as described above. However, in order to improve the mechanical strength of the conductor layer 1 and to provide further water-stopping performance, it is preferable that the electrode composite of this embodiment includes the water-repellent layer 4. The water repellent layer 4 is disposed so as to separate the gas phase 5 containing oxygen and the liquid 70 to be treated as a liquid phase held in the waste water tank. In addition, "separation" here means physical interruption | blocking. Thereby, it can suppress that the organic substance and nitrogen-containing compound in the to-be-processed liquid 70 move to the gaseous-phase 5 side mentioned later.

  As shown in FIG. 2, the water repellent layer 4 is disposed so as to contact the other surface 1 b on the side opposite to the one surface 1 a of the conductor layer 1. The water repellent layer 4 is in contact with the gas phase 5, diffuses the gas in the gas phase 5, and supplies the gas substantially uniformly to the surface 1 b of the conductor layer 1. Therefore, the water repellent layer 4 is preferably a porous body so that the gas can be diffused. Moreover, since the water repellent layer 4 has water repellency, it can suppress that the pores of a porous body are obstruct | occluded by dew condensation etc. and gas diffusibility falls.

  The material constituting the water repellent layer 4 is not particularly limited as long as it is a material having oxygen permeability and water repellency through which oxygen in the gas phase 5 is transmitted. As a material of the water repellent layer 4, for example, at least one of silicone rubber and polydimethylsiloxane can be used. Since these materials have high oxygen solubility and oxygen diffusibility derived from the molecular structure of silicone, they are excellent in oxygen permeability. Furthermore, since these materials have small surface free energy, they are excellent in water repellency. Therefore, it is particularly preferable that the water repellent layer 4 contains silicone.

  Moreover, as a material of the water repellent layer 4, at least one selected from the group consisting of ethyl cellulose, poly-4-methylpentene-1, polybutadiene, polytetrafluoroethylene, and butyl rubber can be used. These materials are also preferable because they have high oxygen permeability and water repellency. In addition, these materials can easily form a porous body and have high water repellency, and therefore can suppress gas clogging and improve gas diffusibility. Furthermore, the water repellent layer 4 is also preferably a nonwoven fabric or a film made of the above materials. When the water repellent layer 4 is made of a film of the above material, the water repellent layer 4 includes a plurality of oxygen permeable materials along the stacking direction X of the water repellent layer 4, the conductor layer 1, and the film layer 2. It is preferable to have a through hole.

  In addition, as the water-repellent layer 4, a nonwoven fabric having water repellency and gas permeability and a nonwoven fabric of polyethylene and polypropylene can also be used. Specifically, as the water repellent layer 4, Gore-Tex (registered trademark) formed by combining a film obtained by stretching polytetrafluoroethylene and a polyurethane polymer can be used.

[Microbial fuel cell]
Next, the microbial fuel cell according to this embodiment will be described. As shown in FIGS. 3 and 4, the microbial fuel cell 100 according to the present embodiment is separated from the negative electrode 20 through the negative electrode 20 carrying microorganisms, the ion moving layer 30 that transmits hydrogen ions, and the ion moving layer 30. And the positive electrode 40 made of the electrode assembly 10 described above. In the microbial fuel cell 100, the negative electrode 20 is disposed so as to contact one surface 30a of the ion moving layer 30, and the positive electrode 40 contacts the surface 30b opposite to the surface 30a of the ion moving layer 30. Is arranged.

  The negative electrode 20 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 positive electrode 40, 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.

  As the conductor sheet of the negative electrode 20, a conductor layer used in the electrode composite 10 may be used. In addition, the negative electrode 20 preferably contains graphite, and the graphene layer in the graphite is preferably arranged along a plane in the direction YZ perpendicular to the stacking direction X of the positive electrode 40, the ion moving 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, the electrons generated by the local battery reaction of the negative electrode 20 can be easily conducted to the external circuit, 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 or nitrogen-containing compound in the liquid 70 to be treated. For example, an anaerobic microorganism that does not require oxygen for growth is used. Is preferred. Anaerobic microorganisms do not require air for oxidizing and decomposing organic substances in the liquid 70 to be treated. 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.

  The microbial fuel cell 100 of the present embodiment includes an ion moving layer 30 that transmits hydrogen ions. The ion transfer layer 30 has a function of transmitting hydrogen ions generated in the negative electrode 20 and moving the hydrogen ions to the positive electrode 40 side. As the ion transfer layer 30, 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, as the ion moving layer 30, a porous film having pores that can transmit hydrogen ions may be used. That is, the ion moving layer 30 may be a sheet having a space (void) for moving hydrogen ions between the negative electrode 20 and the positive electrode 40. 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 positive electrode 40.

  The microbial fuel cell 100 of the present embodiment includes a positive electrode 40 made of the above-described electrode composite 10, 10A. That is, the positive electrode 40 includes a conductor layer 1 having conductivity and oxygen permeability, and a film layer 2 laminated so as to be in contact with one surface 1a of the conductor layer 1 and having water blocking properties and oxygen permeability. I have. Alternatively, the positive electrode 40 includes the conductor layer 1, the film layer 2 laminated so as to be in contact with one surface 1a of the conductor layer 1, and the other surface 1b on the opposite side of the surface 1a of the conductor layer 1. And a water repellent layer 4 having oxygen permeability and water repellency. An ion transfer layer 30 is provided on the surface 2 a side of the film layer 2.

  Here, the microbial fuel cell 100 includes a plurality of membrane electrode assemblies 50 including the positive electrode 40, the ion migration layer 30, and the negative electrode 20, as shown in FIGS. 3 and 4. Further, the two membrane electrode assemblies 50 are laminated via the cassette base 51 so that the positive electrodes 40 face each other. As shown in FIG. 5, the cassette base 51 is a U-shaped frame member along the outer periphery of the positive electrode 40, and the upper part is open. That is, the cassette base 51 is a frame member in which the bottom surfaces of the two first columnar members 51a are connected by the second columnar member 51b. The side surface 51 c of the cassette base 51 is joined to the outer peripheral portion of the surface 40 a opposite to the ion moving layer 30 in the positive electrode 40, and the liquid to be processed enters the cassette base 51 from the outer peripheral portion of the positive electrode 40. 70 can be prevented from leaking.

  As shown in FIG. 4, the fuel cell unit 60 formed by laminating the two membrane electrode assemblies 50 and the cassette base material 51 has a waste water tank so that a gas phase 5 communicating with the atmosphere is formed. 80 is arranged inside. A treatment liquid 70 is held inside the wastewater tank 80, and the negative electrode 20, the ion transfer layer 30, and the film layer 2 of the positive electrode 40 are immersed in the treatment liquid 70. That is, the conductor layer 1 or the water repellent layer 4 constituting the positive electrode 40 is disposed so as to be in contact with a gas containing oxygen, and the film layer 2 is disposed so as to be in contact with the liquid 70 to be processed.

  As described above, the film layer 2 and the water repellent layer 4 of the positive electrode 40 have water repellency. Therefore, the to-be-processed liquid 70 held inside the waste water tank 80 is separated from the inside of the cassette base 51, and the internal space formed by the two membrane electrode assemblies 50 and the cassette base 51 is a gas phase. 5 As shown in FIG. 4, the positive electrode 40 and the negative electrode 20 are each electrically connected to the external circuit 90.

  Here, the wastewater tank 80 holds the liquid 70 to be processed therein, but may be configured such that the liquid 70 to be processed flows. For example, as shown in FIGS. 3 and 4, in the wastewater tank 80, a liquid supply port 81 for supplying the liquid 70 to be treated to the wastewater tank 80 and the treated liquid 70 after the treatment are discharged from the wastewater tank 80. And a liquid discharge port 82 may be provided.

  In addition, it is preferable that the inside of the wastewater tank 80 is maintained under 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 to-be-processed liquid 70 in the wastewater tank 80 so that it may hardly contact oxygen.

  Next, the operation of the microbial fuel cell 100 of this embodiment will be described. During operation of the microbial fuel cell 100, the liquid to be treated 70 containing at least one of an organic substance and a nitrogen-containing compound is supplied to the negative electrode 20, and air (or oxygen) is supplied to the positive electrode 40. At this time, the air is continuously supplied through an opening provided in the upper part of the cassette base 51. Note that the liquid 70 to be treated is also preferably supplied continuously through the liquid supply port 81 and the liquid discharge port 82.

  In the positive electrode 40, air is diffused by the water repellent layer 4, oxygen in the air passes through the conductor layer 1, and reaches the film layer 2. In the negative electrode 20, hydrogen ions and electrons are generated from the organic matter and / or the nitrogen-containing compound in the liquid 70 to be treated by the catalytic action of microorganisms. The generated hydrogen ions pass through the ion moving layer 30 and move to the positive electrode 40 side. The generated electrons move to the external circuit 90 through the conductor sheet of the negative electrode 20 and further move from the external circuit 90 to the film layer 2 through the conductor layer 1 of the positive electrode 40. The hydrogen ions and electrons that have moved to the film layer 2 are combined with oxygen by the action of the oxygen reduction catalyst in the second conductor material 3 and consumed as water. At this time, the electric energy flowing in the closed circuit is recovered by the external circuit 90.

  As described above, the positive electrode 40 includes the film layer 2 having water blocking properties and oxygen permeability. Thereby, since it becomes difficult for microorganisms to enter the conductor layer 1 and the water repellent layer 4, excessive consumption of oxygen by the microorganisms is suppressed, and oxygen can be efficiently supplied to the oxygen reduction catalyst. As a result, it is possible to suppress a decrease in power generation performance and stably produce electric energy. Moreover, since it becomes difficult for microorganisms to enter the conductor layer 1 and the water-repellent layer 4, deterioration of the conductor layer 1 and the water-repellent layer 4 due to adhesion of microorganisms is suppressed, and power can be generated efficiently over a long period. Is possible. Moreover, since the positive electrode 40 includes the conductor layer 1, an increase in internal resistance can be suppressed. Further, by attaching a water-repellent water-repellent layer 4 to the conductor layer 1, an electrode in which the gas phase 5 is difficult to be submerged can be produced. Therefore, by supplying oxygen in the atmosphere to the water repellent layer 4, high battery characteristics can be exhibited.

  Here, the negative electrode 20 according to the present embodiment may be modified with, for example, an electron transfer mediator molecule. Or the to-be-processed liquid 70 in the wastewater tank 80 may contain the electron transfer mediator molecule. 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 liquid 70 to be treated, the mediator molecule acts as a final electron acceptor of metabolism, and delivers received electrons to the negative electrode 20. As a result, it is possible to increase the rate of oxidative decomposition of the organic matter in the liquid 70 to be processed. 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 FIGS. 3 and 4 has a configuration in which two membrane electrode assemblies 50 and a cassette base 51 are stacked. However, the present embodiment is not limited to this configuration. For example, the membrane electrode assembly 50 may be bonded to only one side surface 51c of the cassette base 51 and the other side surface may be sealed with a plate member. The cassette base 51 shown in FIGS. 3 and 4 is open at the entire top, but may be partially open if air (oxygen) can be introduced into the inside. It may be closed.

[Method for producing electrode composite]
Next, the manufacturing method of the electrode composites 10 and 10A according to the present embodiment will be described. The manufacturing method of the electrode composites 10 and 10A includes a step of applying a film material to one surface 1a of the conductor layer 1 having oxygen permeability and made of the first conductor material. Furthermore, the manufacturing method includes a step of spraying the second conductor material 3 on the film material and a step of forming the film layer 2 having water-stopping and oxygen permeability by curing the film material.

  In the manufacturing method of this embodiment, first, a film material that is a precursor of the film layer 2 is applied to one surface 1 a of the conductor layer 1. The film material is applied to at least a part of one surface 1 a of the conductor layer 1. However, as described above, since the film layer 2 is preferably disposed on the entire surface 1a in order to increase the water-stopping property to the liquid 70 to be treated, the film material is formed on the one surface of the conductor layer 1. It is preferable to apply to the whole 1a.

  The method for applying the film material is not particularly limited. For example, after the film material is applied to one surface 1a of the conductor layer 1, the film material layer can be formed by stretching the paste flat using a roller or the like. it can. The coating amount of the film material is not particularly limited, but is preferably set so that the thickness of the cured film layer 2 is 1 μm to 100 μm, for example.

  When the material of the film layer 2 is silicone rubber, a silicone adhesive can be used as the film material. As the silicone adhesive, both a room temperature curable type and a heat curable type can be used, and furthermore, both a one-component type and a two-component type can be used. The silicone adhesive may be a condensation reaction type or an addition reaction type. Moreover, when the material of the film layer 2 is a styrene-butadiene rubber, as the film material, for example, an adhesive mainly composed of a styrene-butadiene thermoplastic elastomer can be used. In addition, when the material of the film layer 2 is a thermosetting resin or a thermoplastic resin, the monomer or prepolymer of each resin can be used as a film material.

  Next, after applying a film material to one surface 1a of the conductor layer 1, the second conductor material 3 is sprayed on the film material. The method for spraying the second conductor material 3 is not particularly limited, and a method capable of evenly spraying the film material can be used. In addition, after spraying the 2nd conductor material 3 to a film material, the contact property of the 2nd conductor material 3 and the conductor layer 1 is improved, and also adhesion | attachment of the 2nd conductor material 3 and a film material is carried out. In order to improve the property, the second conductor material 3 may be pressed. Thereby, since the 2nd conductor material 3 is partially embedded in the inside of a film material, the contact property of the 2nd conductor material 3 and the conductor layer 1, and the 2nd conductor material 3 and a film material Adhesiveness can be improved.

  And after sprinkling the 2nd conductor material 3 to film material, the film layer 2 is formed by hardening | curing film material. The method for curing the film material is not particularly limited. That is, when the film material is cured at room temperature, it may be left at room temperature. When it is cured by heating, the film material sprayed with the conductor layer 1 and the second conductor material 3 is integrally heated. do it. In addition, when the film material is a photocurable resin, ultraviolet rays or electron beams are irradiated. Thus, the electrode composite 10 of the present embodiment can be obtained by curing the film material.

  The manufacturing method according to the present embodiment preferably further includes a step of laminating a water repellent layer 4 having oxygen permeability on the other surface 1b of the conductor layer 1 opposite to the one surface 1a. The stage of laminating the water repellent layer 4 is not particularly limited. That is, the water repellent layer 4 may be laminated on the conductor layer 1 before applying the film material to the conductor layer 1, or may be laminated on the conductor layer 1 after applying the film material to the conductor layer 1. Also good. The water repellent layer 4 may be laminated on the conductor layer 1 after forming the film layer 2 on the conductor layer 1.

  The method for bonding the water repellent layer 4 to the conductor layer 1 is not particularly limited, but may be bonded using, for example, an adhesive. In particular, it is preferable to join using an oxygen-permeable adhesive such as a silicone-based adhesive.

  As described above, in the method of manufacturing the electrode composites 10 and 10A of the present embodiment, the film material is applied to the one surface 1a of the conductor layer 1, and the second conductor material 3 is sprayed on the film material. And a step of forming the film layer 2 by curing the film material. Such a process makes it possible to easily obtain the film layer 2 having a uniform film thickness.

  Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples, but the present embodiment is not limited to these examples.

[Example]
First, a graphite sheet and a water-repellent sheet were bonded with a silicone adhesive to prepare a laminated sheet made of graphite sheet / silicone adhesive / water-repellent sheet having a size of 4.5 cm × 6.5 cm. As the graphite sheet as the conductor layer, Carbofit (registered trademark) manufactured by Hitachi Chemical Co., Ltd. was used. As the silicone adhesive, a one-component RTV silicone rubber KE-3475 manufactured by Shin-Etsu Chemical Co., Ltd. was used. As a water repellent sheet which is a water repellent layer, SELPORE (registered trademark) manufactured by Sekisui Chemical Co., Ltd. was used.

  Next, a silicone adhesive was applied on the graphite sheet of the laminated sheet so as to form a thin film having a thickness of 15 μm. Furthermore, after spraying a powdery oxygen reduction catalyst on the silicone adhesive and directly adhering it, the silicone adhesive was dried to obtain an electrode composite of this example having a film layer on a graphite sheet. . In addition, as the silicone adhesive, a one-component RTV silicone rubber KE-3475 manufactured by Shin-Etsu Chemical Co., Ltd. was used. The film layer refers to a silicone layer coated on a graphite sheet and containing an oxygen reduction catalyst.

[Comparative example]
First, a laminated sheet comprising the same graphite sheet / silicone adhesive / water-repellent sheet as in the example was prepared. Next, by preparing a dispersion using the same oxygen reduction catalyst as in the Examples, dropping it on the surface of the graphite sheet of the laminated sheet and drying it, the electrode composite of this example having no film layer on the graphite sheet Got. In addition, the oxygen reduction catalyst of an Example and a comparative example was adjusted so that it might become the same amount.

[Evaluation]
Microbial fuel cells were produced using the positive electrodes made of the electrode composites obtained in the examples and comparative examples, and the output characteristics of the respective fuel cells were examined.

  First, a membrane / electrode assembly was prepared using the positive electrode made of the electrode composite obtained in the example, the negative electrode made of carbon felt holding anaerobic microorganisms, and the ion transfer layer made of polyolefin nonwoven fabric. As the polyolefin nonwoven fabric, polyolefin nonwoven fabric # 210 of Pacific Giken Co., Ltd. was used. Similarly, a membrane electrode assembly was produced using the electrode composite obtained in the comparative example.

  And the microbial fuel cell shown in FIG. 4 was produced using the membrane electrode assembly of an Example and a comparative example. The capacity of the waste water tank was 300 cc. Moreover, the model waste liquid whose total organic carbon (TOC) is 800 mg / L was used for the to-be-processed liquid, and the liquid temperature of the to-be-processed liquid was 30 degreeC. Furthermore, the inflow amount into the wastewater tank was adjusted so that the hydraulic retention time of the liquid to be treated was 24 hours.

Microbial fuel cells using the membrane electrode assemblies of Examples and Comparative Examples were operated for 40 days, and changes in output characteristics of the respective fuel cells were examined. Each evaluation result is shown in FIG. As shown in FIG. 6, in both the example and the comparative example, it took about one week to start up the microbial fuel cell, and the output gradually improved in both cases. However, there was a difference in the subsequent output maintenance. Specifically, the start-up was completed on the 9th day in the microbial fuel cell of the example, and the start-up was completed on the 7th day in the microbial fuel cell of the comparative example. When comparing the output reduction amount per day of at after 28 days from the start-up completion, in the embodiment was 1.25 mW / ^{m 2,} in the comparative example was 6.68mW / ^{m 2} . Thus, it can be seen that by applying the film layer, a decrease in output over time can be suppressed to 1/5, and thus electric energy can be stably produced over a long period of time.

  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 drawing, the electrode composites 10 and 10A including the conductor layer 1, the film layer 2, and the water repellent layer 4, and the negative electrode 20, the ion moving layer 30, and the positive electrode 40 are formed in a rectangular shape. Yes. 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.

DESCRIPTION OF SYMBOLS 1 Conductor layer 2 Film layer 3 Second conductor material 4 Water repellent layer 10, 10A Electrode composite

Claims (5)

A step of applying a film material to one surface of a conductor layer having oxygen permeability and made of a first conductor material;
Sprinkling a second conductor material on the film material;
A step of forming a film layer having water-stopping and oxygen permeability by curing the film material;
The manufacturing method of an electrode composite_body | complex containing.   The method for producing an electrode assembly according to claim 1, wherein the second conductor material is an oxygen reduction catalyst.   The method for producing an electrode assembly according to claim 1, further comprising a step of laminating a water repellent layer having oxygen permeability on the other surface of the conductor layer opposite to the one surface. 4. The electrode composite according to claim 1, wherein an ISO air permeability of the film layer is 1 × 10 ⁻⁵ μm / Pa · s to 1 × 10 ⁻³ μm / Pa · s. Production method.   5. The method for producing an electrode assembly according to claim 1, wherein the film layer has a thickness of 1 μm to 100 μm.

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