Microbial fuel cell using an electron acceptor having a high reduction potential and method for producing electric energy using the same

Abstract

The present invention relates to a microbial fuel cell using an electron acceptor having a high reduction potential and a method for producing electric energy using the microbial fuel cell. More specifically, the present invention relates to a microbial fuel cell and a method for producing electric energy using the microbial fuel cell. In the microbial fuel cell, an electron acceptor solution having a high reduction potential is used as a reducing electrolyte, an organic solution serving as an electron donor is used as an oxidizing electrolyte, the reduced reducing electrolyte is regenerated by electrolysis in an electrolytic cell and supplied again as a reducing electrolyte, and the cell includes a diaphragm provided with one or more O-rings to prevent leakage. Hydrogen generated during electrolysis can be supplied to the fuel cell to produce additional electric energy, thereby enabling high power generation at an effective cost. Energy generated from an existing power generation system, such as solar power, or electric energy generated from the microbial fuel cell can be used for electrolysis, thereby significantly improving energy utilization and increasing the life of the fuel cell.

Description

Technical Field

[0001] The present invention relates to a microbial fuel cell using an electron acceptor having a high reduction potential and a method for producing electric energy using the microbial fuel cell. More specifically, the present invention relates to a microbial fuel cell and a method for producing electric energy using the microbial fuel cell. In the microbial fuel cell, an electron acceptor solution having a high reduction potential is used as a reducing electrolyte, an organic solution serving as an electron donor is used as an oxidizing electrolyte, the reduced reducing electrolyte is regenerated by electrolysis in an electrolytic cell and supplied again as a reducing electrolyte, and the cell includes a diaphragm provided with one or more O-rings to prevent leakage. Hydrogen generated during electrolysis can be supplied to the fuel cell to produce additional electric energy, thereby enabling high power generation at an effective cost. Energy generated from an existing power generation system, such as solar power, or electric energy generated from the microbial fuel cell can be used for electrolysis, thereby improving energy utilization and extending the life of the fuel cell. Background Art

[0002] Over the past few decades, microbial fuel cells (MFCs) have been studied as sustainable alternative energy production and as a useful resource for water treatment and pollution removal. MFCs convert chemical energy stored in biodegradable substances into useful electrical energy.

[0003] In addition, the electric current can be used for many other functions, including operating microbial electrolysis cells or purifying water in microbial purification cells (Wang, H.; Ren, Z. A comprehensive review of microbial electrochemical systems as a platform technology. Biotechnol. Adv. 2013, 31(8), 1796-1807; Harnisch, F.; Schroder, U. From MFC to MEC: Chemical and biological cathodes and their potential for microbial bioelectrochemical systems. Chem. Soc. Rev. 2010, 39(11), 4433-4448.).

[0004] Ioannis Ieropoulos also reported applications related to energy acquisition or utilization (IA Eropoulos, C. Melhuish, J. Greenman. Artificial metabolism towards true energetic autonomy in artificial life. European conference in artificial life. Lect. Notes Artif. Intell., 2801 (2003), pp. 792-799).

[0005] They are reportedly the first robots to be powered directly by a glucose-infused MFC, rather than utilizing other forms of existing power sources.

[0006] Despite these promising results, MFCs have struggled to make progress due to several limitations.

[0007] The electricity production of MFC depends on various factors such as lipid form, electrogenic microorganisms, circuit resistance, electrode material, reactor form and electron acceptor (Deniz Ucar, Yifeng Zhang, and Irini Angelidaki. An Overview of Electron Acceptors in Microbial Fuel Cells. Front Microbiol. 2017; 8: 643; Pant D, Van Bogaert G, Diels L, Vanbroekhoven KA review of the substrates used in microbial fuel cells (MFCs) for sustainable energy production. Bioresour Technol. 2010 Mar; 101(6): 1533-43.).

[0008] Oxygen is an ideal electron acceptor for MFCs due to its high reduction potential and low cost.

[0009] However, oxygen reduction occurs very slowly at the surface of the carbon electrode, resulting in a high overvoltage, which is one of the limiting factors in high current density MFCs (Gil, GC; Chang, IS; Kim, BH; Kim, M.; Jang, JK; Park, HS; Kim, HJ. Persistent parameters affecting the performance of a mediator-less microbial fuel cell. Biosens. Bioelectron. 2003, 18, 327-334.).

[0010] To overcome this problem, various metal ions with high reduction potentials have been used as electron acceptors in reducing electrolytes.

[0011] Recently, Deniz Ucar, Chuan-Shu He, et al. analyzed the performance and applicability of various electron acceptors for MFC (Deniz Ucar, Yifeng Zhang, and Irini Angelidaki. An Overview of Electron Acceptors in Microbial Fuel Cells. Front Microbiol. 2017; 8: 643; Chuan-Shu He, Zhe-Xuan Mu, Hou-Yun Yang, Ya-Zhou Wang, Yang Mu, Han-Qing Yu. Electron acceptors for energy generation in microbial fuel cells fed with wastewaters: A mini-review. Chemosphere (2015).).

[0012] Different electron acceptors have different reduction potentials, which affect the efficiency of power generation.

[0013] Therefore, the use of novel electron acceptors in MFCs has an important effect on power generation (JG Ibanez, CS Choi, RS Becker, Electrochemical Applications of Aqueous Redox Transition Metal Complexes as a Function of pH. J Electrochem. Soc. 134, 12 (1987), 3084-3087).

[0014] The present inventor has applied for patent application No. 10-2015-0128739, which relates to a method for manufacturing a novel renewable energy storage and utilization device using a microbial fuel cell.

[0015] Compared with existing microbial fuel cells, the patent improves current efficiency, voltage efficiency, and energy efficiency, but there is still a need for a microbial fuel cell with excellent power production performance. Summary of the Invention

[0016] Technical problems to be solved

[0017] The object of the present invention is to solve the problems of the above-mentioned prior art, and the technical problem is to provide a microbial fuel cell and a method for producing electrical energy using the microbial fuel cell, in which an electron acceptor solution with a high reduction potential is used as a reducing electrolyte, and an organic solution as an electron donor is used as an oxidizing electrolyte. The reduced reducing electrolyte is regenerated by electrolysis in an electrolytic cell and supplied again as a reducing electrolyte, and includes a diaphragm provided with one or more O-rings to prevent leakage. Hydrogen generated in electrolysis can be supplied to the fuel cell to produce additional electrical energy, thereby producing high electricity at an effective cost, and energy generated from an existing power generation system such as solar power or electricity generated from a microbial fuel cell is used for electrolysis, thereby improving energy utilization and increasing the life of the fuel cell.

[0018] Technical Solution

[0019] In order to achieve the above technical problems, the present invention provides a microbial fuel cell, which includes an anode chamber, a cathode chamber, a diaphragm located between the anode chamber and the cathode chamber, and an electrolytic cell. The anode chamber includes an anode with a microbial film formed on the surface and an organic solution as an electron donor as an oxidizing electrolyte, and the organic solution is continuously supplied to the anode chamber. The cathode chamber includes a cathode as a conductor electrode with no microbial film formed on the surface and an electron acceptor solution as a reducing electrolyte. The electrolytic cell includes a cathode and an anode to which electricity is applied, and a reduced reducing electrolyte transported from the cathode chamber. The reduced reducing electrolyte transported from the cathode chamber is regenerated by electrolysis using external electricity, and the regenerated reducing electrolyte is resupplied to the cathode chamber. Hydrogen generated by electrolysis in the electrolytic cell is discharged to the outside of the electrolytic cell. The diaphragm is provided with one or more O-rings to prevent leakage.

[0020] According to another aspect of the present invention, a method for generating electrical energy using the microbial fuel cell is provided.

[0021] Beneficial effects

[0022] The microbial fuel cell of the present invention utilizes an electron acceptor having a high reduction potential in the cathode and a high solubility in an aqueous solution and a low overvoltage in a graphite electrode, for example, Fe(III)(4,4-dimethyl-2,2'-bipyridyl)3, Fe(III)(2,2'-bipyridyl)3, Fe(III)(2,2'-bipyridyl)3, Fe(III)(2,2'-bipyridine-4,4'-disulfonate)3, Fe(III)(2,2'-bipyridine-5-sulfonate)3, and Fe(III)(2,2'-bipyridine-5-sulfonate). Fe(III)(2,2'-bipyridine-5-sulfonate)3), Fe(III)(4,4'-bis(triethylammoniummethyl)-2,2'-bipyridine3), Fe(III)(triethylammonium-2,2'-bipyridine3), Fe(III)(2,2'-bipyridine-5,5'-dicarboxylic acid3 acid)3), Fe(III)(1,10-phenanthroline)3, Ru(III)(2,2'-bipyridine)3, Ru(III)(4,4'-bis(triethylammoniummethyl)-2,2'-bipyridine)3, 4-trimethylammonium-2,2,6,6-tetramethylpiperidine-1-oxyl-iodide, 2,2,6,6-tetramethylpiperidine-1-oxylsulfonate, sodium salt salt), TEMPO-4-sulfate potassium, 4-[3-(trimethylammonium)propoxy]-2,2,6,6-Tetramethylpiperidine-1-oxyl chloride (4-[3-(trimethylammonium)propoxy]-2,2,6,6-tetramethylpiperidine-1-oxyl chloride), (2,2,6,6-tetramethylpiperidine-1-yl)-oxyl copolymer copolymer), poly(TEMPO), 4-hydroxy 2,2,6,6-tetramethylpiperidine-1-oxyl, 4-amino 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethylpiperidine-1-oxyl, 4-carboxy 2,2,6,6-tetramethylpiperidinyloxy, 3-ureido 2,2,5,5-tetramethyl-3-ureido-3-pyrroline-1-oxyl, phthalimide N-oxyl, N,N,N-2,2,6,6-heptamethylpiperidine-oxy-4-ammoniumdichloride, poly(TEMPO-CO-PEGMA), 4,5-dihydroxy-1,3-benzenedisulfonate disodium disodium), 3,6-dihydroxy-2,4-dimethylbenzenesulfonate sodium, N-hydroxyimide derivatives, (ferrocenylmethyl)trimethylammonium chloride, bis[(trimethylammonium)propyl]ferrocene, bis(3-trimethylaminopropyl)-ferrocene dichloride, ferrocenylamine chloride, ferrocenediazole dibromide, Br2, I3, - 、Mn 3+ Electron acceptors such as α-Hydroxy ...

[0023] Since the reduced electrolyte produced by fuel cell discharge can be regenerated and reused through electrolysis using external power such as solar cells or wind power cells, the utilization rate of energy generated by existing power generation systems, such as solar power, can be increased by more than two times. Hydrogen produced as a byproduct of electrolysis can be supplied to fuel cells to generate electricity, or the hydrogen can be used directly as fuel.

[0024] In addition, the microbial fuel cell of the present invention can use organic matter solutions such as food wastewater, domestic wastewater, anaerobic sludge from wastewater treatment plants, algae plants, etc. as oxidizing electrolytes, thereby utilizing fuel cell fuel at no or low cost while also taking advantage of the purification effect.

[0025] Furthermore, the microbial fuel cell of the present invention uses a diaphragm provided with more than one O-ring, thereby preventing leakage and increasing the life of the cell, thereby making it possible to manufacture an almost permanent fuel cell.

[0026] The microbial fuel cell system of the present invention can generate electricity at low cost. Furthermore, by combining individual microbial fuel cell cells connected in parallel and series, current multiplication and voltage boosting can be achieved. Furthermore, due to the low reduction potential of these cells, most difficult-to-recover heavy metals, such as rare earth elements, can be removed or recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a schematic diagram showing an electrolytic cell (using electricity from a solar cell to regenerate a reduced electrolyte serving as an electron acceptor and produce hydrogen) and a method of generating electricity by connecting the microbial fuel cells in parallel, and also showing a method of generating electricity using hydrogen produced in the electrolytic cell and a hydrogen-oxygen fuel cell.

[0028] Figure 2 The present invention is a schematic diagram illustrating a microbial fuel cell (wherein the purpose of using the microbial fuel cell is to produce low-cost hydrogen) and a power generation method connecting the microbial fuel cell and a hydrogen-oxygen fuel cell utilizing hydrogen. In the present invention, the microbial fuel cell does not utilize electricity from a solar cell, but instead directly connects the electricity from the microbial fuel cell to an electrolytic cell, thereby regenerating a reduced electrolyte serving as an electron acceptor and returning the reduced electrolyte to the cathode chamber.

[0029] Figure 3 This is a photo of a battery consisting of three MFC cells operating in parallel.

[0030] Figure 4Graphs of voltage versus current density and graphs of power versus current density for various connections of (a) single MFC cell, (b) series MFC cells, and (c) parallel MFC cells as MFCs with cathodes using Cr(VI) concentrations of 100 ppm, 1000 ppm, and 5000 ppm.

[0031] Figure 5 The figures show (A) the discharge curve of a battery with three MFC units connected in series and (B) the discharge curve of a battery with three MFC units connected in parallel (wherein a graphite electrode plate (2.5 cm*6 cm) is used as the cathode, 170 mL of 5000 ppm Cr(VI) is used as the reducing electrolyte, a carbon brush (D 4 cm, H 7 cm) is used as the anode, and 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS are used as the oxidizing electrolyte).

[0032] Figure 6 Graphs showing polarization curves and power versus current density for (a) a single cell, (b) a cell with three unit MFCs connected in series, and (c) a cell with three unit MFCs connected in parallel, using various electron acceptors in the cathode chamber.

[0033] Figure 7 Figure 3 shows the discharge curves of a three-unit MFC battery connected in series, containing (a) Fe(III), (b) Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3, and (c) Fe(III)(1,10-phenanthroline)3 as various electron acceptors, at various discharge currents (where a carbon brush (D 4 cm, H 7 cm) was used as the anode, and 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS were used as the oxidizing electrolyte).

[0034] Figure 8 The figure shows the discharge curves of a battery with three MFC units connected in parallel, containing (a) Fe(III), (b) Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 and (c) Fe(III)(1,10-phenanthroline)3 as various electron acceptors, at various discharge currents (where a carbon brush (D 4 cm, H 7 cm) was used as the anode, and 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS were used as the oxidizing electrolyte).

[0035] Figure 9Figure 3 shows the voltage versus current density graphs and the power density versus current density graphs of (a) and (b) parallel MFCs and (c) and (d) series MFCs with other types of anode materials (carbon brushes and carbon felt) (wherein the reducing electrolyte uses 5000 ppm of Fe(III)(4,4'-dimethyl-2,2'-bipyridine) as an electron acceptor, and the oxidizing electrolyte uses 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS).

[0036] Figure 10 The figure shows the discharge performance of cells using carbon felt anodes in (a) parallel cells and (b) series cells at various discharge currents, and the inset shows the discharge curve of an MFC cell using a carbon brush as an anode (wherein the reducing electrolyte uses a 5000 ppm solution of Fe(III)(4,4'-dimethyl-2,2'-bipyridine) as an electron acceptor, the anode uses a carbon brush (D 4 cm, H 7 cm), and the oxidizing electrolyte uses 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS).

[0037] Figure 11 It is a graph showing the residual Cr(III) concentration and the conversion efficiency of Cr(III) to Cr(VI) as a function of time when Cr(III) is converted into Cr(VI) in the anode chamber by applying power at a constant current of 0.2 mA (wherein, the regeneration rate of Cr(VI); a solution (180 mL) of 5000 ppm of Cr(III) and 0.1 M Na2SO4, NaHSO4 (pH 2), the reducing electrolyte being 180 mL of 0.1 M Na2SO4, NaHSO4).

[0038] Figure 12 Graphs showing the Fe(II) / Fe(III) ratio over time when Fe(II) is converted to Fe(III) in the anode chamber by applying power at a constant current of (A) 0.05 mA and (B) 0.01 mA (wherein, the regeneration rate of Fe(III); a solution (180 mL) of 5000 ppm of Fe(III) and 0.1 M Na2SO4, NaHSO4 (pH 2), with the reducing electrolyte being 180 mL of 0.1 M Na2SO4, NaHSO4).

[0039] Figure 13Graph showing the ratio of Fe(III)(2,2'-bipyridine)2 / Fe(II)(2,2'-bipyridine)3 over time when Fe(III)(2,2'-bipyridine)2(Fe(III)(2,2'-bipy)2) is converted into Fe(II)(2,2'-bipyridine)3(Fe(II)(2,2'-bipy)3) in the anode chamber by applying electric power at a constant current of (A) 0.05 mA and (B) 0.01 mA (wherein, regeneration rate of Fe(III)(2,2'-bipyridine)3; solution (180 mL) of 5000 ppm of Fe(III)(2,2'-bipyridine)3 and 0.1 M Na2SO4, NaHSO4 (pH 2), reducing electrolyte being 180 mL of 0.1 M Na2SO4, NaHSO4).

[0040] Figure 14 Graph showing the ratio of Fe(III)(o-phenanthroline)2 / Fe(III)(o-phenanthroline)3 over time when Fe(III)(o-phenanthroline)2(Fe(III)(PHEN)2) is converted into Fe(III)(o-phenanthroline)3(Fe(III)(PHEN)3) in the anode chamber by applying electric power at a constant current of (A) 0.05 mA and (B) 0.01 mA (wherein, regeneration rate of Fe(III)(o-phenanthroline)3; solution (180 mL) of 5000 ppm of Fe(III)(o-phenanthroline)3 and 0.1 M Na2SO4, NaHSO4 (pH 2), reducing electrolyte being 180 mL of 0.1 M Na2SO4, NaHSO4). DETAILED DESCRIPTION

[0041] Hereinafter, the present invention will be described in more detail.

[0042] The microbial fuel cell of the present invention includes an anode chamber, a cathode chamber, a diaphragm located between the anode chamber and the cathode chamber, and an electrolytic cell. The anode chamber includes an anode having a microbial film formed on its surface and an organic solution serving as an electron donor as an oxidizing electrolyte, and the organic solution is continuously supplied to the anode chamber. The cathode chamber includes a cathode serving as a conductor electrode having no microbial film formed on its surface and an electron acceptor solution serving as a reducing electrolyte. The electrolytic cell includes a cathode and an anode to which power is applied, and a reduced reducing electrolyte transported from the cathode chamber. The reduced reducing electrolyte transported from the cathode chamber is regenerated by electrolysis using external power, and the regenerated reducing electrolyte is resupplied to the cathode chamber. Hydrogen generated by electrolysis in the electrolytic cell is discharged to the outside of the electrolytic cell. The diaphragm is provided with one or more O-rings to prevent leakage.

[0043] An object of the present invention is to provide a microbial fuel cell that can produce high electricity at an effective cost and use energy generated from existing power generation systems such as solar power or electricity generated from microbial fuel cells for electrolysis, thereby improving energy utilization and extending the life of the fuel cell. To achieve the above-mentioned objects, heavy metal ions and their complexes or other inorganic or organic substances with excellent solubility and high reduction potential can be used.

[0044] When a microbial fuel cell discharges electricity, there is the problem of regenerating and reusing the discharged reduced electrolyte. To achieve this, an external power source is required. To this end, the power applied to the electrolytic cell can be selected from the electricity generated in the microbial fuel cell, solar power, wind power, midnight power, and combinations thereof.

[0045] In one embodiment, the reduced electrolyte discharged from the microbial battery is added to the anode chamber of the electrolytic cell (or electrolyzer), the electrolyte is added to the counter electrode chamber to reduce water, and solar power can be applied between the two electrodes. In the electrolyzer, while the regenerated reduced electrolyte required for the microbial fuel cell is returned, hydrogen is produced in the cathode chamber of the electrolyzer. Figure 1 As can be seen in the paper, this hydrogen can also generate electricity when supplied to a hydrogen-oxygen fuel cell. Solar power is used to supply the materials required for both the microbial fuel cell and the hydrogen-oxygen fuel cell, thus generating two types of electricity using solar power as a single energy source. Furthermore, these materials can be stored and used to generate electricity when needed.

[0046] In addition, from Figure 2 As shown in the paper, instead of using solar power, a microbial fuel cell can be used to generate electricity for a regenerative electrolyzer to produce hydrogen. The regenerated reduced electrolyte is also returned to the cathode chamber of the microbial fuel cell. In this case, continuous hydrogen production can be achieved.

[0047] It is important to study the suitability of electron acceptors because this has an important effect on power generation (JG Ibanez, C S Choi, R S Becker, Electrochemical Applications of Aqueous Redox Transition Metal Complexes as a Function of pH. J Electrochem. Soc. 134, 12 (1987), 3084-3087). Electron acceptors having a high reduction potential, a low overvoltage in a graphite electrode, and a very fast electron transfer reaction can be used, for example, Fe(III)(4,4-dimethyl-2,2'-bipyridine)3, Fe(III)(2,2'-bipyridine)3, Fe(III)(2,2'-bipyridine-4,4'-disulfonate)3, Fe(III)(2,2'-bipyridine-5-sulfonate)3, Fe(III)(4,4'-bis(triethylammoniummethyl)-2,2'-bipyridine)3, Fe(III) I)(triethylammonium-2,2'-bipyridine)3, Fe(III)(2,2'-bipyridine-5,5'-dicarboxylic acid)3, Fe(III)(1,10-phenanthroline)3, Ru(III)(2,2'-bipyridine)3, Ru(III)(4,4'-bis(triethylammoniummethyl)-2,2'-bipyridine)3, 4-trimethylammonium-2,2,6,6-tetramethylpiperidin-1-oxyl iodide, 2,2,6,6-tetramethylpiperidin-1-oxyl sulfonate, sodium salt, TEMPO-4-sulfate potassium, 4-[3-(Trimethylammonium)propoxy]-2,2,6,6-tetramethylpiperidin-1-yloxy chloride, (2,2,6,6-tetramethylpiperidin-1-yl)-oxy copolymer, poly(TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-yloxy, 4-amino-2,2,6,6-tetramethylpiperidin-1-yloxy, 2,2,6,6-tetramethylpiperidin-1-yloxy, 4-carboxy-2,2,6,6-tetramethylpiperidinyloxy, 3-ureido-2,2,5,5-tetramethyl-3-ureido-3-pyrroline-1 -oxy, phthalimide N-oxyl, N,N,N-2,2,6,6-heptamethylpiperidinium-oxy-4-diammonium chloride, poly (TEMPO-CO-PEGMA), disodium 4,5-dihydroxy-1,3-benzenedisulfonate, sodium 3,6-dihydroxy-2,4-dimethylbenzenesulfonate, N-hydroxyimide derivatives, (ferrocenylmethyl)trimethylammonium chloride, bis[(trimethylammonium)propyl]ferrocene, bis(3-trimethylaminopropyl)-ferrocene dichloride, ferrocenium ammonium chloride, ferrocenium dinitrogen dibromide, Br2, I3 - 、Mn 3+Furthermore, the electron transfer rate increased by using these metal ions, metal complexes, and organic substances can produce a high current, thereby making it possible to manufacture an MFC exhibiting high power production performance.

[0048] The present inventors have studied the use of metal ions, metal complexes and organic matter as electron acceptors at the cathode to manufacture efficient MFC cells for energy production. These MFC cells are used to study the effects of various electron acceptors on the performance of MFC cells.

[0049] Furthermore, the combined cells of three MFC cells in series and parallel were studied to compare the performance of the MFC cells in terms of open circuit voltage, current density and power density.

[0050] In a specific embodiment, the anode may be selected from the group consisting of carbon brushes, carbon felt, carbon plates, carbon plates coated with porous carbon, and combinations thereof.

[0051] In addition, in a specific embodiment, the cathode can be a cathode of a metal or precious metal material with low overvoltage for generating hydrogen, such as a carbon brush, a carbon felt, a carbon plate, a carbon plate coated with porous carbon, a carbon plate coated with carbon nanotubes, a platinum plate, a titanium plate, a stainless steel plate, and a combination thereof.

[0052] To investigate the impact on power generation, the inventors used carbon brushes as anodes. They also investigated power generation in MFC cells comparing carbon felt with carbon brushes. Finally, they investigated the sustainability of power generation in MFC cells using real wastewater as the lipid.

[0053] like Figure 3 As shown, in order to evaluate the performance of the MFC battery, polarization experiments and discharge experiments were carried out. Research such as this experiment has not been reported before. In the present invention, a stable voltage can be obtained when connected in parallel, and the current is expressed as the sum of each single cell, so the batteries are connected in parallel and the parallel bundles are connected in series again, so that a high voltage can be achieved. In addition, in order to increase the area of the electrode in the battery chamber, the electrode material is added to the maximum extent, so that a high current can be achieved. In particular, when a carbon brush is used for manufacturing to achieve a smooth supply of electrode area and solution, the current is greatly increased compared to carbon felt.

[0054] The reduced electrolyte, which is the result of the reduction of the discharge material, can be regenerated by various external power sources such as solar cells and returned to the MFC. In this case, an electrolytic cell is used, separated by a diaphragm between two electrode chambers. Hydrogen is generated in the electrode chamber opposite the regeneration chamber, and this hydrogen can also be supplied to the fuel cell to generate electricity.

[0055] The anode chamber of the microbial fuel cell of the present invention includes an anode having a microbial film formed on its surface. The microorganisms may be anaerobic microorganisms from an anaerobic digester in a wastewater treatment plant. The microbial film can be formed by adding a phosphate buffer solution mixed with organic matter as a carbon source and anaerobic sludge obtained from the anaerobic digester to the anode chamber containing the anode. The phosphate buffer solution, which is identical to that used in the anode chamber except for the organic matter, is added to a cathode chamber separated from the anode chamber by an ion exchange membrane such as Membrane International, Celegard, or Selemion DSV. Aeration is then performed to allow oxygen to serve as an electron acceptor, thereby forming a microbial film on the anode in the anode chamber. An external resistor of approximately 1000 ohms is connected to the circuit between the anode and cathode to form a closed circuit.

[0056] The anode chamber contains an organic solution as an electron donor as an oxidizing electrolyte. Figure 1 and Figure 2 As can be seen in the figure, the organic solution is continuously supplied to the anode chamber. Although not particularly limited, the organic solution may comprise a substance selected from acetate, glucose, protein, food hydrolysate, domestic wastewater, anaerobic sludge, algae, and combinations thereof.

[0057] In one embodiment, the anode chamber and cathode chamber of the microbial fuel cell of the present invention are separated into two areas within a single-piece container made of insulating material. The diaphragm is in the form of a window frame, inserted between the anode chamber and the cathode chamber by compression, and is provided with one or more O-rings, for example, one to three O-rings. Leakage is more frequent when the diaphragm is separated by compression using bolts and nuts than when separated by a single O-ring.

[0058] To extend the life of the battery, leakage should be prevented. To this end, a method is used in which a diaphragm (ion exchange membrane) that moves the electrolyte is sandwiched between a frame plate made of a material such as plastic to form an integral structure. One or more O-rings are used on the frame to prevent leakage. The diaphragm can be in the form of a cation exchange membrane, an anion exchange membrane, a cation-anion composite membrane, or a microporous membrane that allows ions to pass through.

[0059] In the microbial fuel cell of the present invention, the anode and cathode are carbon brushes, and the amount of the carbon brushes contained in the cathode chamber may be greater than the amount of the carbon brushes contained in the anode chamber.

[0060] The electrolytic cell included in the microbial fuel cell of the present invention includes a cathode and an anode to which power is applied, and a reduced reducing electrolyte supplied from a cathode chamber. The reduced reducing electrolyte supplied from the cathode chamber is regenerated by electrolysis using external power, and the regenerated reducing electrolyte is resupplied to the cathode chamber of the microbial fuel cell. Hydrogen generated by electrolysis performed in the electrolytic cell can be discharged to the outside of the electrolytic cell.

[0061] The electrodes of the electrolytic cell may include: an anode with a high oxygen overvoltage, such as a lead dioxide electrode or an electrode coated with lead dioxide on a metal plate such as titanium; and a cathode made of a metal or precious metal material with a low overvoltage for generating hydrogen, such as a carbon brush, carbon felt, carbon plate, carbon plate coated with porous carbon, carbon plate coated with carbon nanotubes, platinum plate, titanium plate, stainless steel plate, etc., for example, the cathode may include a cathode selected from platinum plate, titanium plate, stainless steel plate and a combination thereof.

[0062] The microbial fuel cell of the present invention may further include: a reduced electrolyte storage unit that stores reduced electrolyte regenerated in the electrolytic cell and supplies the stored reduced electrolyte to the cathode chamber; and a hydrogen storage unit that stores hydrogen generated in the electrolytic cell. The reduced electrolyte regenerated in the electrolytic cell can be supplied directly to the cathode chamber, or it can be stored in the reduced electrolyte storage unit and then supplied to the cathode chamber as needed. Furthermore, the hydrogen generated in the electrolytic cell can be directly discharged to the outside, or it can be stored in the hydrogen storage unit and then supplied to the hydrogen-oxygen fuel cell to further generate electricity.

[0063] According to another aspect of the present invention, a method for generating electrical energy using the microbial fuel cell is provided.

[0064] Although not particularly limited, multiple microbial fuel cells can be connected in parallel or in series to produce electrical energy. In a specific embodiment, the microbial fuel cells are connected in parallel and the parallel bundles are again connected in series to achieve high voltage.

[0065] Furthermore, in the method for producing electric energy of the present invention, the hydrogen produced in the electrolytic cell can be supplied to a hydrogen-oxygen fuel cell to further produce electric energy.

[0066] Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited thereto.

[0067] [Example]

[0068] Preparation of MFC for polarization and discharge experiments ( Figure 3 )

[0069] To investigate the effect of electron acceptors in MFC performance, a two-compartment microbial fuel cell design with an anode chamber having a working volume of 500 mL and a cathode chamber having a volume of 600 mL was used.

[0070] To test the electrodes, a carbon brush (D 4 cm*L 7 cm) or carbon felt (W 4 cm*H 7 cm) was used as the anode material. The carbon brush used had a diameter of 4 cm and a length of 7 cm and provided an area of 28 cm 2 In addition, a graphite plate (2.5 cm*6 cm) or a carbon brush was used as a cathode.

[0071] An external circuit resistor of 1000Ω was connected between the anode and cathode except during polarization experiments.Anode and cathode were separated by a pretreated ion exchange membrane (AEM, AMI-7001 or CEM, CEM-7001, Membrane International, USA).

[0072] The anaerobic inoculum was collected from anaerobic sludge previously published by Choi and Cui (Recovery of silver from wastewater coupled with power generation using a microbial fuel cell. J. Bioresource Technol 107 (2012), 522-525.). Inoculation was performed by filling the three chambers of the cell with a mixture of 400 mL of sludge and 100 mL of artificial wastewater (pH 7) as the oxidizing electrolyte. The composition of each liter of artificial wastewater was as follows: 2.0 g of CH3COONa, 1.05 g of NH4Cl, 1.5 g of KH2PO4, 2.2 g of K2HPO4 and 0.2 g of yeast extract. The oxidizing electrolyte was continuously circulated and the buffer solution was poured into the cathode chamber. At the same time, aeration was performed with air in order to utilize dissolved oxygen as an electron acceptor during microbial growth. The anode chamber was covered with an aluminum film to prevent the oxidizing bacteria from being exposed to light.

[0073] Prior to the run, nitrogen was bubbled through the oxidizing electrolyte solution for approximately 15 minutes to create an anaerobic environment. This process was repeated, with the electrolyte medium replaced when the voltage dropped below 50 mV. After achieving stable voltage generation with the wastewater, the oxidizing electrolyte was replaced with the growth medium. An initial run was performed after achieving stable MFC performance, indicating adequate microbial film formation.

[0074] In the preparation of the reducing electrolyte, K2Cr2O7, FeCl3 6H2O, NaHSO4 and Na2SO4 were purchased from Daejeong Chemical in South Korea, and 4,4'-dimethyl-2,2'-bipyridine (4,4'-dimethyl-2,2'-bipyridine, 4,4'-dimethyl-2,2'-BIPY), 2,2'-bipyridine (2,2'-bipyridine, 2,2'-BIPY) and 1,10-phenanthroline (1,10-PHEN) were purchased from Aldrich Chemical Company in the United States. A 5000 ppm Cr(VI) and 5000 ppm Fe(III) reducing electrolyte solution (pH 2) containing a supporting electrolyte (0.1 M Na2SO4) was prepared using appropriate reagents. Fe(III)(bipyridine)3 (JG Ibanez, C.-S. Choi, R.S. Becker, Electrochemical Applications of Aqueous Redox Transition Metal Complexes as a Function of pH. J Electrochem. Soc. 134, 12 (1987), 3084-3087) was prepared as follows. The metal to ligand ratio was 1:4. The complex and supporting electrolyte were 5000 ppm and 0.1 M, respectively, based on Fe(III). 3 M NaOH was used to adjust the pH to 2. Fe(III)(1,10-phenanthroline)3 was prepared using the same conditions. The preparation of the metal complex is usually carried out at room temperature.

[0075] Polarization experiment and discharge experiment

[0076] Polarization experiment - Polarization experiment is carried out to evaluate the performance of MFC battery by obtaining maximum power density and internal resistance. The data of battery potential is measured once every minute using LabView system (National Instruments model (Models), NI-cDAQ 9219, USA). Various external resistances from 150kΩ to 0.010kΩ are applied to obtain polarization curves for determining maximum power production. Current density is calculated by the following formula:

[0077] I d =V / RA, (1)

[0078] Where V(V) is the voltage across the resistors, R(Ω) is the external resistance, and A(cm 2 ) is the surface area of the cathode. Power density (Pd ) is calculated by the following formula:

[0079] P d =V 2 / RA (2)

[0080] Discharge experiment - In order to evaluate the discharge characteristics of the MFC battery, the voltage change under constant current is used. Each cathode chamber contains 180mL of reducing electrolyte, and the anode chamber also contains the same volume of oxidizing electrolyte solution. After the first discharge of the MFC battery, the solution in the anode chamber is replaced with a new solution. The discharge experiment is carried out under constant current using a constant voltage device IVIUM made in the Netherlands, which can perform discharge experiments under constant current conditions using a two-electrode system. The discharge current is selected to ensure that a considerable battery voltage and power production are obtained. The discharge current is selected based on the power curve. In order to obtain the power density curve of MFC batteries with different reducing electrolytes with different maximum power points, different discharge currents are used to evaluate whether effective discharge can be achieved. Due to the high energy output, the current at the maximum power point is the ideal operating point. The discharge experiments are compared and carried out at various current levels.

[0081] Effect of electron acceptor concentration on the performance of three-cell MFC cells with various connection configurations

[0082] The effect of initial electrolyte concentration on Cr(VI) reduction was investigated. Three MFC cells were connected in series or parallel to increase voltage and current, respectively. The effect on microbial power generation was tested. Polarization and power curves were presented, and electrochemical parameters were reported and discussed. Discharge performance was also presented and discussed.

[0083] Figure 4 Graphs of voltage versus current density and graphs of power versus current density for various connections of (a) single MFC cell, (b) series MFC cells, and (c) parallel MFC cells as MFCs with cathodes using Cr(VI) concentrations of 100 ppm, 1000 ppm, and 5000 ppm.

[0084] The following are embodiments showing examples of power production by MFCs for high power production, but the scope of the present invention is not limited thereto.

[0085] (1) Polarization behavior of MFC with Cr(VI) as electron acceptor

[0086] To determine the maximum power density achievable with various concentrations of Cr(VI), polarization curve experiments were performed by varying the external resistance from 150 kΩ to 10 Ω to obtain a stable voltage and then measuring the voltage. Figure 4 , curves of voltage versus current density and curves of power density versus current density with variations in the initial concentration of Cr(VI) are shown.

[0087] [Table 1]

[0088]

[0089] *C Cr(VI) : Cr(VI) concentration, V ocv : open circuit voltage, J 最大 : Maximum current density, J 峰 : Peak current density, P 最大 : Maximum power density (maximum power density).

[0090] The electrochemical parameters are summarized in Table 1. When the Cr(VI) concentration increased from 100 ppm to 5000 ppm, the maximum power output of the unit MFC increased. The power production increased from 377.7 mWm -2 P 最大 (for a Cr(VI) concentration of 100 ppm) increased to 571.9 mWm -2 P 最大 (For a Cr(VI) concentration of 5000 ppm). The voltage of the MFC cells connected in series increased as expected. During the series connection, for a Cr(VI) concentration of 100 ppm, the open circuit voltage was shown to be 2.697 V, P 最大 Displayed as 850.1mWm -2 , compared with the case where the open circuit voltage is 3.059 V for a Cr(VI) concentration of 5000 ppm, P 最大 Displayed as 1323.2mWm -2 , the maximum power showed a 1.55-fold higher value at a concentration of 5000 ppm compared to that at 100 ppm.

[0091] In parallel, for a Cr(VI) concentration of 100 ppm, at 714.7 mWm -2 P 最大 Under this condition, the maximum current density is 2730.8mAm -2 , for a Cr(VI) concentration of 5000ppm, at 1432.3mWm -2 P 最大 Under the condition of -2 The power density was doubled when the concentration was 5000 ppm compared to when the concentration was 100 ppm.

[0092] This study demonstrated that high concentrations of Cr(VI) as an electron acceptor have excellent potential for MFC performance. However, as described below, this resulted in lower power generation compared to when Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 was used as the electron acceptor.

[0093] (2) Discharge performance of 5000ppm Cr(VI)-MFC composed of three single cells

[0094] Figure 5 The figures show (A) the discharge curve of a battery with three MFC units connected in series and (B) the discharge curve of a battery with three MFC units connected in parallel (wherein a graphite electrode plate (2.5 cm*6 cm) is used as the cathode, 170 mL of 5000 ppm Cr(VI) is used as the reducing electrolyte, a carbon brush (D 4 cm, H 7 cm) is used as the anode, and 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS are used as the oxidizing electrolyte).

[0095] Figure 5 The results of the comparison of the discharge behavior of series-connected and parallel-connected cells with 5000 ppm of Cr(VI) at various constant currents are presented. It can be seen that the discharge characteristics of MFCs are highly dependent on the selected current. In the series connection, as the discharge current increases from 0.5 mA to 1.5 mA, the voltage remains almost flat at the beginning, but then rapidly decreases at the end ( Figure 5 In parallel connection, when the discharge current changes from 1.5 mA to 4.5 mA, the voltage also shows a shape that initially shows a flat portion but then rapidly decreases.

[0096] Although not shown in the graph, another study conducted in this laboratory showed that, for the same discharge current, the voltage decreased more rapidly at a Cr(VI) concentration of 1000 ppm than at a Cr(VI) concentration of 5000 ppm. This means that MFCs with a Cr(VI) concentration of 5000 ppm exhibited superior discharge performance compared to those with a Cr(VI) concentration of 1000 ppm.

[0097] Until all the electron acceptors in 170 mL of reducing electrolyte were consumed, it lasted for about 70 hours at 0.5 mA in series and for a similar duration of 68 hours at 1.5 mA in parallel. This means that the current density in series is similar to that in parallel, and it can be assumed that the reduction reaction rate at the cathode is almost the same in the two connections.

[0098] The higher discharge voltage at high Cr(VI) concentrations can be attributed to the increased reaction rate and reduced internal resistance of the cathode. The voltage in series connections is significantly lower than the expected 3V, believed to be due to increased resistance in the wire connections and increased battery leakage. By increasing the surface area of the electrodes placed in the electrode compartment, the current can be increased.

[0099] (3) Polarization characteristics of MFCs with various electron acceptors

[0100] To determine the maximum power density achievable using various reduced electron acceptors, polarization experiments were performed by varying the external resistor from 150 kΩ to 0.010 kΩ to obtain a stable voltage output and then measuring the voltage. The MFC demonstrated excellent performance using Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 as the electron acceptor. Figure 6 Graphs of voltage and current density and power and current density using various electron acceptors are shown in FIG.

[0101] Figure 6 Graphs showing polarization curves and power versus current density for (a) a single cell, (b) a cell with three unit MFCs connected in series, and (c) a cell with three unit MFCs connected in parallel, using various electron acceptors in the cathode chamber.

[0102] [Table 2]

[0103]

[0104] *C Cr(VI) : Cr(VI) concentration, V ocv : open circuit voltage, J 最大 : Maximum current density, J 峰 : Peak current density, P 最大 : Maximum power density.

[0105] In a single MFC cell, when Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 was used as the electron acceptor, the maximum electrochemical parameters were obtained, with an OCV of 1.250 V, an OCV of 2628 mA·m -2 The maximum current density (J 最大 ) and 1212mW·m -2 The maximum power density is 2.3 times that of the case when Cr(VI) is used, and the maximum current density is 2.8 times that of the case when Cr(VI) is used (see Table 2).

[0106] It is known that the role of electron acceptors is very important for the production of electrical energy. In the series connection, when Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 was used as the electron acceptor, the maximum electrochemical parameters were also displayed, with a voltage (OCV) of 3.323V and a current of 3179mA·m -2 The maximum current density (J 最大 ) and 2951mW·m -2 The maximum power density is 2.7 times that of the case when Cr(VI) is used, and the maximum current density is 2.6 times that of the case when Cr(VI) is used (see Table 2).

[0107] In parallel, when Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 was used as the electron acceptor, the maximum electrochemical parameters were also obtained, with a voltage (OCV) of 1.210 V, a current of 8179 mA·m -2 The maximum current density (J 最大 ) and 3937mW·m -2 The maximum power density is 3.13 times that of the case when Cr(VI) is used, and the maximum current density is 3.19 times that of the case when Cr(VI) is used (see Table 2).

[0108] Compared to a single battery in parallel, the OCV of three cells in series is approximately 2.7 times higher, and the current in parallel is approximately 3.1 times higher than when a single battery is connected or connected in series. Furthermore, the power density in parallel is only approximately 1.3 times higher than when connected in series, but approximately 3.2 times higher than when connected in series. This indicates that, like ordinary batteries, power increases proportionally with the number of cells when cells are connected in series or in parallel.

[0109] (4) Discharge performance of MFC batteries with various electron acceptors

[0110] Figure 7 The figure shows the discharge curves of a battery consisting of three MFC units connected in series, containing (a) Fe(III), (b) Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 and (c) Fe(III)(1,10-phenanthroline)3 as various electron acceptors, at various discharge currents (wherein a carbon brush (D 4 cm, H 7 cm) was used as the anode, and 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS were used as the oxidizing electrolyte).

[0111] Figure 8The figure shows the discharge curves of a battery with three MFC units connected in parallel, containing (a) Fe(III), (b) Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 and (c) Fe(III)(1,10-phenanthroline)3 as various electron acceptors, at various discharge currents (wherein a carbon brush (D 4 cm, H 7 cm) was used as the anode, and 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS were used as the oxidizing electrolyte).

[0112] The performance of the battery was evaluated using the discharge characteristics of an MFC in which three single cells were connected at a constant current. Figure 7 The results of the discharge behavior of MFCs with a series connection of MFC single cells having a concentration of 5000 ppm of Fe(III), Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 and Fe(III)(1,10-phenanthroline)3 as electron acceptors at various constant currents are shown in FIG.

[0113] In the Fe(III)-MFC system with an open circuit voltage of about 2.9 V, the discharge voltage slowly decreases from 2.5 V to 1.0 V at a discharge current of 1.5 mA, and the discharge lasts for 25 hours. Figure 7 As shown, as the discharge current increases above 1.5 mA, the voltage also decreases significantly. Stable discharge characteristics are shown at currents below 1.5 mA. In Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3-MFC, the discharge voltage slowly decreases from 2.5 V to 1 V at a discharge current of 1.5 mA, and the discharge time lasts for 25 hours. The open circuit voltage at this time is around 3.4 V. The situation at a discharge current of 2 mA is similar to that at a discharge current of 1.5 mA, but the discharge time is shown to be around 19 hours.

[0114] At discharge currents above 2 mA, the discharge voltage decreases rapidly and continuously. Therefore, at currents below 2 mA, the battery exhibits stable discharge characteristics. In the case of Fe(III)(1,10-phenanthroline)3 as an electron acceptor, a continuous decrease in discharge voltage was observed at all discharge currents, suggesting the presence of battery leakage.

[0115] like Figure 8As shown, in a parallel connection using Fe(III) as an electron acceptor in the cathode chamber, discharge currents were stable at currents below 1.5 mA. However, with Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 as the reducing electrolyte, discharge was also stable at currents of 3 mA or 4.5 mA. In a parallel connection, discharge characteristics were stable at currents below 4.5 mA. In the Fe(III)-MFC system, discharge was achieved at an average discharge voltage of 0.925 V for 21 hours at a discharge current of 1.5 mA, resulting in an open circuit voltage of 1.056 V.

[0116] like Figure 8 As shown in the figure, as the discharge current increases above 1.5 mA, the voltage also decreases significantly. In Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3-MFC, it was confirmed that the average discharge voltage was 0.927 V and the open circuit voltage was 1.209 V at a discharge current of 3.0 mA, and this lasted for more than 20 hours. On the other hand, at a discharge current of 4.5 mA, the open circuit voltage was 1.279 V and the average discharge voltage was 0.83004 V, and this lasted for more than 20 hours. Figure 8 As shown in Figure b, the voltage decreases significantly as the discharge current increases to 6 mA. Fe(III)(1,10-phenanthroline)3-MFC exhibits unstable discharge characteristics at all discharge currents. This is likely due to battery leakage.

[0117] (5) Effect of anode material on polarization performance

[0118] In MFC cells, the anode material shows an important effect on the current density and maximum power density of MFC.

[0119] Figure 9 Figure 3 shows the voltage versus current density curves and the power density versus current density curves of (a) and (b) parallel MFCs and (c) and (d) series MFCs with other types of anode materials (carbon brush and carbon felt) (wherein the reducing electrolyte uses 5000 ppm of Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 as an electron acceptor, and the oxidizing electrolyte uses 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS).

[0120] Figure 9 A battery with three cells connected in parallel using 5000 ppm of Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 as an electron acceptor in the cathode and carbon brushes and carbon felt as anodes is shown in FIG. Figure 9 a) and the same MFC cells in series ( Figure 9Polarization curves in b). In the series connection case, the carbon brush electrode MFC performs slightly better, with the maximum power curve for the carbon brush electrode being approximately 1.2 times higher than that for the carbon felt electrode (Table 3). The maximum current density for the carbon brush electrode is approximately 1.6 times that of the carbon felt electrode.

[0121] In parallel, the carbon brush electrodes show significantly better polarization characteristics of MFC ( Figure 9 The maximum power using the carbon brush is approximately 2.7 times higher (Table 3). The open-circuit voltages of the two electrodes are similar, but the maximum current of the carbon brush electrode is approximately 2.6 times that of the carbon felt electrode, indicating that using the carbon brush electrode as the anode is beneficial in terms of battery efficiency (Table 3).

[0122] The difference in performance as described above can be explained by the fact that fewer microorganisms adhere to the carbon felt anode compared to the carbon brush anode, and the microorganisms cannot be smoothly supplied to the oxidizing electrolyte.

[0123] [Table 3]

[0124]

[0125] *V ocv : open circuit voltage, J 最大 : Maximum current density, J 峰 : Peak current density, P 最大 : Maximum power density. The reducing electrolyte contained 5000 ppm of Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 as an electron acceptor, and the oxidizing electrolyte was a solution of 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS.

[0126] (6) Discharge performance of MFCs with other anode materials

[0127] Figure 10 The figure shows the discharge performance of an MFC with three cells connected in parallel and series, using 5000 ppm of Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 as the electron acceptor at various discharge currents. Carbon felt was used in the anode compartment and compared with a previously studied carbon brush electrode (inset).

[0128] In the parallel connection with carbon felt as the anode, the discharge voltage slowly decreases with the increase of discharge time. At a discharge current of 3.0 mA, the open circuit voltage is 1.29 V, the average discharge voltage is 0.79 V, and the discharge time lasts for 25.6 hours.

[0129] On the other hand, at a discharge current of 3.0 mA, in the case of a parallel connection using a carbon brush electrode as an anode, the average discharge voltage was 0.93 V, 15% higher than the case of using carbon felt (0.79 V), and the discharge time lasted for more than 20 hours. The open circuit voltage at this time was 1.21 V. When the discharge current was 4.5 mA, the discharge lasted for 10.6 hours in the carbon felt anode, but lasted for more than 20 hours in the carbon brush electrode (refer to Figure 10 ).

[0130] In a series connection of MFCs using carbon felt anodes, the discharge voltage decreased as the discharge current increased from 1.5 mA to 2.0 mA or higher. Stable discharge characteristics were confirmed at discharge currents below 1.5 mA. At a discharge current of 2.0 mA, the discharge voltage decreased more rapidly when using carbon felt as the anode than when using a carbon brush electrode. When using carbon felt, the average discharge voltage was 0.51 V and the open circuit voltage was 3.50 V, which lasted for 1.58 hours.

[0131] When the carbon brush electrode was used as the anode, the open circuit voltage reached 2.78V, the average discharge voltage was 0.42V, and the discharge voltage lasted for 17 hours. These results indicate that in MFC cells connected to single cells, the carbon brush electrode, when used as the anode, effectively formed a microbial biofilm, demonstrating exceptional performance. This is because the carbon brush electrode provides a higher specific surface area and porosity, and it is believed that more anaerobic microorganisms grow on the carbon brush than on carbon felt. A greater number of bacteria means faster reactions.

[0132] (7) Cr(VI) regeneration test using solar cells as external power

[0133] Figure 11 The figure shows the residual Cr(III) concentration and the conversion efficiency of Cr(III) to Cr(VI) according to time when Cr(III) is converted to Cr(VI) by applying a constant current of 0.2 mA. The electrode area of 20 cm2 of the Ti metal plate coated with PbO2 is shown in FIG. 2 The electrode was used as the anode, and a stainless steel plate of the same width was used as the counter electrode. The initial concentration of the solution was 5000 ppm, and the solution volume was 180 mL.

[0134] The final conversion efficiency after 25 hours of reaction was 53%. The generation of hydrogen can be calculated by Faraday's law, which is 1.09×10 -7 The hydrogen gas is produced at a ratio of 1 mol / g of Cr(VI). This hydrogen can be used as fuel for fuel cells, thereby generating electricity. At an initial concentration of 1000 ppm of Cr(III) and 100 ppm of Cr(III), the ratios reached 62% and 83% after 10 and 7.5 hours of reaction time, respectively.

[0135] Generally, the conversion time is longer than that of Fe(III) or its complexes that appear later because the oxidation of Cr(III) requires 3 electrons, while the oxidation of Fe(II) requires 1 electron.

[0136] (8) Fe(III) regeneration test using solar cells as external power

[0137] Fe(III) is not easily measured in the presence of Fe(II), so the regeneration rate of Fe(III) can be expressed as the ratio of Fe(III) / Fe(II) using the following Nernst equation:

[0138] E rev =E 0 '-RT / F ln [Fe(II)] / [Fe(III)] (3)

[0139] [Fe(II)] / [Fe(III)]=e (E0'-Erev) / RT (4)

[0140] The ratio of [Fe(II)] / [Fe(III)] in the oxidizing electrolyte can be determined by measuring the voltage of the oxidizing electrolyte relative to a reference electrode such as Ag / AgCl. The degree of regeneration can be determined by the same method for other Fe(III) complexes.

[0141] Figure 12 The ratio of Fe(II) / Fe(III) over time when a constant current of 0.05 mA is applied to convert Fe(II) into Fe(III) is shown in a. The electrode area of the Ti metal plate coated with PbO2 is 20 cm 2 The electrode was used as the anode, and a stainless steel plate of the same width was used as the counter electrode.

[0142] The initial Fe(II) concentration in the oxidizing electrolyte solution at this point was 5000 ppm, and the solution volume was 180 mL. As the reaction time passed, the Fe(II) / Fe(III) ratio continued to decrease, indicating that regeneration was proceeding well.

[0143] At a current of 0.05 mA, the regeneration was almost complete within 15 hours under the experimental conditions. At a constant current of 0.01 mA, the complete conversion took more than 24 hours (refer to Figure 12 b). Faraday's law can be used to calculate the amount of hydrogen produced when the reaction is carried out at a current of 0.05 mA for 24 hours, which is 1.38×10 -7 The ratio of mol / g of Fe(II) yields hydrogen gas, which can be used as fuel for fuel cells and thus for power generation.

[0144] (9) Regeneration test of Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 using solar cells as external power

[0145] Figure 13 The electrode area of the Ti metal plate coated with PbO2 is 20 cm 2 The electrode was used as the anode, and a stainless steel plate of the same width was used as the counter electrode. The oxidizing electrolyte solution at this time was Fe(II) with an initial concentration of 5000 ppm and a solution volume of 180 mL.

[0146] As the reaction time passed, the ratio of Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 / Fe(II)(4,4'-dimethyl-2,2'-bipyridine)3 continued to decrease. By applying a constant current of 0.05 mA, regeneration was almost completed within a reaction time of less than 7 hours (refer to Figure 13 a).

[0147] At a constant current of 0.01 mA, the reaction rate was slow and the reaction was not completed after 24 hours. According to Faraday's law, the amount of hydrogen produced when the current was 0.05 mA for 24 hours was 1.38×10 -7 The hydrogen gas is obtained at a ratio of 1 mol / g. This hydrogen gas can be used as fuel for fuel cells to generate electricity.

[0148] (10) Regeneration test of Fe(III)(o-phenanthroline)3 using solar cells as external power

[0149] exist Figure 14 In Figure 13 Under the same conditions, similar to the Fe(III)(2,2'-bipyridine)3 / Fe(II)(2,2'-bipyridine)3, the ratio of Fe(III)(o-phenanthroline)3 / Fe(II)(o-phenanthroline)3 continued to decrease with the passage of reaction time, and regeneration was completed within a reaction time of less than 10 hours at a constant current of 0.05 mA and 0.01 mA. Hydrogen production was also similar to the Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3 / Fe(II)(4,4'-dimethyl-2,2'-bipyridine)3 experiment.

Claims

1. A microbial fuel cell comprising an anode chamber, a cathode chamber, a diaphragm located between the anode chamber and the cathode chamber, and an electrolytic cell. The anode chamber comprises an anode having a microbial film formed on the surface thereof and an organic solution as an oxidizing electrolyte and an electron donor, wherein the organic solution is continuously supplied to the anode chamber. The cathode chamber includes a cathode as a conductor electrode with no microbial film formed on the surface and an electron acceptor solution as a reducing electrolyte. The electrolytic cell includes a cathode and an anode to which power is applied and a reduced electrolyte delivered from the cathode chamber, The reduced reducing electrolyte transported from the cathode chamber is regenerated by electrolysis using external power, and the regenerated reducing electrolyte is supplied to the cathode chamber again. hydrogen gas generated in the cathode chamber due to electrolysis performed in the electrolytic cell is discharged to the outside of the electrolytic cell, The diaphragm is provided with one or more O-rings to prevent leakage. The electron acceptor is Fe(III)(4,4'-dimethyl-2,2'-bipyridine)3, and the anode is a carbon brush electrode.

2. The microbial fuel cell according to claim 1, wherein The anode chamber and the cathode chamber are two separated areas in an integrated container of insulating material. The diaphragm is in the form of a window frame. The diaphragm is inserted between the anode chamber and the cathode chamber by extrusion and is provided with 1-3 O-rings.

3. The microbial fuel cell according to claim 1, wherein The cathode is selected from the group consisting of carbon brushes, carbon felt, carbon plates, carbon plates coated with porous carbon, carbon plates coated with carbon nanotubes, platinum plates, titanium plates, stainless steel plates, and combinations thereof.

4. The microbial fuel cell according to claim 1, wherein The anode and the cathode are carbon brushes, and the amount of the carbon brushes contained in the cathode chamber is greater than the amount of the carbon brushes contained in the anode chamber.

5. The microbial fuel cell according to claim 1, wherein The diaphragm is a cation exchange membrane, anion exchange membrane, a cation-anion composite membrane or a microporous membrane.

6. The microbial fuel cell according to claim 1, wherein The organic solution in the anode chamber comprises a substance selected from the group consisting of acetate, glucose, protein, food hydrolysate, domestic wastewater, anaerobic sludge, algae, and combinations thereof.

7. The microbial fuel cell according to claim 1, wherein The power applied to the electrolytic cell is selected from the group consisting of power generated in the microbial fuel cell, solar power, wind power, midnight power, and combinations thereof.

8. The microbial fuel cell according to claim 1, wherein The electrodes of the electrolytic cell include: an anode, which is a lead dioxide electrode or a metal coated with lead dioxide; and The cathode is selected from the group consisting of carbon brushes, carbon felt, carbon plates, carbon plates coated with porous carbon, carbon plates coated with carbon nanotubes, platinum plates, titanium plates, stainless steel plates, and combinations thereof.

9. The microbial fuel cell according to claim 1, wherein Further including: a reduced electrolyte storage portion that accumulates the reduced electrolyte regenerated in the electrolytic cell and supplies the accumulated reduced electrolyte to the cathode chamber; as well as A hydrogen storage unit stores the hydrogen generated in the electrolytic cell.

10. A method for producing electrical energy using the microbial fuel cell according to any one of claims 1 to 9.

11. The method for producing electric energy according to claim 10, wherein: Multiple microbial fuel cells are connected in parallel or in series.

12. The method for producing electric energy according to claim 10, wherein: The hydrogen produced in the electrolysis cell is supplied to a hydrogen-oxygen fuel cell for further production of electrical energy.

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