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

Abstract

A microbial fuel cell that can improve energy utilization rate and extend the life of the fuel cell, and a method for producing electric energy using the same are provided. [Solution] An electron absorber solution with a high reduction potential is used as the posolite, and an organic solution that is an electron donor is used as the negolite. The reduced posolite is regenerated by electrolysis with electrolytic electricity and supplied to the posolite again. A separator membrane equipped with one or more O-rings is included to prevent leakage, and hydrogen gas generated by electrolysis is supplied to the fuel cell.

Description

[Technical field]

[0001] The present invention relates to a microbial fuel cell using an electron absorber having a high reduction potential and a method for producing electric energy using the same. More specifically, the present invention relates to a microbial fuel cell using an electron absorber solution having a high reduction potential as a posolite and an organic solution as an electron donor as a negolite, the reduced posolite is regenerated by electrolysis in an electrolytic cell and supplied to the posolite again, a separator having one or more O-rings to prevent leakage is included, hydrogen gas generated by electrolysis is supplied to a fuel cell to produce additional electric energy, high power can be produced at an efficient cost, energy from an existing power generation system such as solar electric energy or power generated from a microbial fuel cell is used for electrolysis, energy utilization rate is improved, and the life of the fuel cell can be improved. The present invention relates to a microbial fuel cell and a method for producing electric energy using the same. [Background technology]

[0002] Microbial fuel cells (MFCs) have been investigated over the past decades as a sustainable alternative energy production and as an effective resource for water treatment and decontamination. MFCs convert chemical energy stored in biodegradable materials into useful electrical energy.

[0003] In addition, electrical current has been used for many other functions, such as operating microbial electrolysis cells and decontaminating water in water decontamination cells (Non-Patent Documents 1, 2).

[0004] Applications related to energy capture and utilization have been reported by Ioannis Ieropoulos et al. (Non-Patent Document 3)

[0005] They were reported as the first robot to be powered directly by glucose-infused MFCs, without the use of any other form of conventional power source.

[0006] Despite these promising results, progress in MFC has been hindered by several limitations.

[0007] The power generation of MFCs depends on several factors, such as the lipid morphology, electron-emitting microorganisms, circuit resistance, electrode materials, reactor type, and electron absorbers (Non-Patent Documents 4, 5).

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

[0009] However, oxygen reduction occurs at a very slow rate on the surface of the carbon electrode, resulting in high overpotentials, which is one of the limiting factors in high current density MFCs (Non-Patent Document 6).

[0010] To overcome this problem, various high reduction potential metal ions were used as electron absorbers in posolites.

[0011] Recently, Deniz Ucar, Chuan-Shu He and colleagues have investigated the performance and applicability of various electron absorbers used in MFCs (Non-Patent Documents 4, 7).

[0012] Different electron absorbers have different reduction potentials, which affects the efficiency of power generation. Therefore, the use of new electron absorbers in MFCs will have a significant effect on power generation (Non-Patent Document 8).

[0013] The present inventors have filed a patent application (Patent Application No. 10-2015-0128739) for a method for manufacturing an apparatus for storing and using new renewable energy using a microbial fuel cell.

[0014] Although the technique disclosed in Patent Document 1 has improved current efficiency, voltage efficiency, and energy efficiency compared to conventional microbial fuel cells, there remains a need for microbial fuel cells with excellent power generation performance. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Korea Patent Application No. 10-2015-0128739

Non-licensed documents

[0016]

Non-patent document 1

Non-patent document 2

Non-patent document 3

Non-patent document 4

Non-patent document 5

[0017] The object of the present invention is to provide a microbial fuel cell and a method for producing electric energy using the same, which uses an electron absorber solution having a high reduction potential as a posolite and an organic solution as an electron donor as a negolite, in which the reduced posolite is regenerated by electrolysis in an electrolytic cell and supplied to the posolite again, includes a separation membrane equipped with one or more O-rings to prevent leakage, supplies hydrogen gas generated by electrolysis to a fuel cell to produce additional electric energy, and can produce high electric power at an efficient cost; and uses energy from an existing power generation system such as solar electric energy or electric power generated from a microbial fuel cell for electrolysis, thereby improving energy utilization rate and extending the life of the fuel cell. [Means for solving the problem]

[0018] In order to achieve the above-mentioned technical objectives, the present invention provides a microbial fuel cell including an anode chamber, a cathode chamber, a separation membrane disposed between the anode chamber and the cathode chamber, and an electrolysis cell, the anode chamber including an anode having a microbial membrane formed on its surface and an organic solution serving as an electron donor as negolite, the organic solution being continuously supplied to the anode chamber, the cathode chamber including a cathode serving as a conductor electrode having no microbial membrane formed on its surface and an electron absorber solution serving as posolite, the electrolysis cell including a cathode and an anode to which electric power is applied, and reduced posolite transported from the cathode chamber, the reduced posolite transported from the cathode chamber being regenerated by electrolysis using external electric power, the regenerated posolite being supplied again to the cathode chamber, hydrogen gas generated in the cathode chamber by electrolysis performed in the electrolysis cell being discharged to the outside of the electrolysis cell, and the separation membrane including one or more O-rings capable of preventing liquid leakage.

[0019] According to another aspect of the present invention, there is provided a method for producing electrical energy using the microbial fuel cell. Effect of the Invention

[0020] The microbial fuel cell according to the present invention uses an electron acceptor (electron absorber) having a high reduction potential at the cathode, high solubility in aqueous solution, and low overvoltage at the electrode, such as Fe(III)(4,4-dimethyl-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, Fe(III)(4,4'-bis(triethylammoniummethyl)-2,2' -bipyridine)3, Fe(III)(triethylammonium-2,2'-bipyridine)3, Fe(III)(2,2'-bipyridine-5,5'-dicarboxylic acid)3, Fe(III)(1,10-phen)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 Lysine-1-oxylsulfonate, sodium salt, TEMPO-4-sulfate, potassium salt, 4-[3-(trimethylammonium)propoxy]-2,2,6,6-tetramethylpiperidine-1-oxyl chloride, (2,2,6,6-tetramethylpiperidin-1-yl)-oxyl 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-tetramethylpiperidine-1-oxyl, 3-carbamido-2,2,5,5-tetramethyl-3-carbamido-3-pyrroline-1-oxyl, phthalimido-N-oxyl, N,N,N-2,2,6,6-heptamethylpiperidine-oxy-4-ammonium chloride, poly(TEMPO-co-PEGMA), 4,5-dihydroxy-1,3-benzenedisulfonate, disodium salt, 3,6-dihydroxy-2,4-Dimethylbenzenesulfonate, sodium salt, N-hydroxyimide derivatives, (ferrocenylmethyl)trimethylammonium chloride, bis[(trimethylammonium)propyl]ferrocene, bis(3-trimethylaminopropyl)-ferrocene dichloride, ferroceneamine chloride, ferrocene dinitrogen dibromide, Br2, I, 3- , Mn 3+ Electron acceptors such as phosphates can be used as posolites to generate high power output at an efficient cost. The electron acceptors can be regenerated and used continuously using redox couples with various charges, such as heavy metals, other complexes, and organic substances. [Any electron acceptor that has high reduction potential, solubility, stability, and produces a neutral aqueous solution can be used.]

[0021] The reduced electrolyte produced by the discharge of the fuel cell can be regenerated and reused through electrolysis using external electricity from solar cells or wind power, making it possible to more than double the energy utilization of existing power generation systems such as solar cells. Hydrogen gas, a by-product of electrolysis, can be supplied to the fuel cell to produce electrical energy, or it can be used directly as fuel.

[0022] In addition, the microbial fuel cell of the present invention can use organic solutions such as food wastewater, domestic wastewater, and anaerobic sludge from wastewater treatment plants and algae factories as oxidizing electrolytes, so it can simultaneously provide the benefit of purification at no cost or at low cost.

[0023] Furthermore, the microbial fuel cell of the present invention uses a separator membrane equipped with one or more O-rings to prevent leakage, extend the life of the cell, and make the fuel cell nearly permanent.

[0024] By using such a microbial fuel cell of the present invention, electric energy can be produced at low cost. Furthermore, a combination cell of microbial fuel cell unit cells connected in series or parallel can double the current and increase the voltage. By utilizing this, it is possible to remove and recover almost all heavy metals such as rare earth elements, which have low reduction potential and are difficult to recover. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram showing a power generation mode in which the electrolysis cell of the present invention, which uses solar cell power to regenerate the electron absorber posolite and produce hydrogen gas, and the microbial fuel cell are connected in parallel, and also shows power generation in a hydrogen-oxygen fuel cell using the hydrogen gas produced in the electrolysis cell. [Diagram 2] This is a schematic diagram showing the power generation aspect of the microbial fuel cell of the present invention (here, the microbial fuel cell is used for the purpose of producing inexpensive hydrogen gas) in which the power of the microbial fuel cell is directly connected to an electrolysis cell without using power from a solar cell, and the electron absorber posolite is regenerated and returned to the cathode chamber, and the microbial fuel cell is connected to a hydrogen-oxygen fuel cell that uses hydrogen gas. [Diagram 3] The photo shows a battery consisting of three unit cells of MFC connected in parallel. [Figure 4] 1 shows potential vs. current density curves and power vs. current density curves for (a) a single cell, (b) series connected MFCs, and (c) parallel connected MFCs with Cr(VI) cathodes with various Cr(VI) concentrations of 100 ppm, 1000 ppm, and 5000 ppm. [Diagram 5] Graph showing (A) the discharge curve of a battery containing three unit MFCs connected in series and (B) the discharge curve of a battery containing three unit MFCs connected in parallel (wherein the cathode was a graphite electrode plate (2.5 cm x 6 cm), the posolite was 170 mL of 5000 ppm Cr(VI), the anode was a carbon brush (D 4 cm, H 7 cm), and the negolite was 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS). [Figure 6] FIG. 1 shows polarization curves and power vs. current density curves of (a) a single cell, (b) a three-unit MFC connected in series, and (c) a three-unit MFC connected in parallel with various electron absorbers in the cathode chamber. [Figure 7]Graph showing discharge curves of a series-connected 3-unit MFC cell containing various electron absorbers (a) Fe(III), (b) Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3, and (c) Fe(III)(1,10-phen)3, discharged at various discharge currents (wherein the anode was a carbon brush (D 4 cm, H 7 cm) and the negolite was 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS). [Figure 8] Graph showing discharge curves of a three-unit MFC cell connected in parallel containing various electron absorbers (a) Fe(III), (b) Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3, and (c) Fe(III)(1,10-phen)3, discharged at various discharge currents (where the anode was a carbon brush (D 4 cm, H 7 cm) and the negolite was 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS). [Figure 9] Graphs showing voltage vs. current density curves and power density vs. current density curves of (a) and (b) parallel connected and (c) and (d) series connected MFCs with other types of anode materials (carbon brush and carbon felt) (where Posolite was used as electron absorber 5000 ppm Fe(III) (4,4'-dimethyl-2,2'-bipyridyl), Negolite; 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS). [Figure 10] Graphs showing the discharge performance of cells using carbon felt anodes in (a) parallel and (b) series connected cells at various discharge currents, and inset graphs showing the discharge curves of MFC cells using carbon brushes as anodes (where, posolite was a solution of 5000 ppm Fe(III) (4,4'-dimethyl-2,2'-bipyridyl) as electron absorber, the anode was a carbon brush (D 4 cm, H 7 cm), and negolite was 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS). [Figure 11]Graph showing the residual Cr(III) concentration and the conversion efficiency of Cr(III) to Cr(VI) over time when power is applied at a constant current of 0.2 mA and Cr(III) is converted to Cr(VI) in the anode chamber (where Cr(VI) regeneration rate: 5000 ppm Cr(III) and a solution (180 mL) of 0.1 M Na2SO4, NaHSO4 (pH 2); posolite is 180 mL of 0.1 M Na2SO4, NaHSO4). [Figure 12] Graph showing the Fe(II) / Fe(III) ratio over time during conversion of Fe(II) to Fe(III) in the anode chamber when powered at a constant current of (A) 0.05 mA and (B) 0.01 mA (where Fe(III) regeneration rate; 5000 ppm Fe(III) in a solution (180 mL) of 0.1 M Na2SO4, NaHSO4 (pH 2); posolite is 180 mL of 0.1 M Na2SO4, NaHSO4). [Figure 13] Graph showing the Fe(III)(2,2'-bipy)2 / Fe(II)(2,2'-bipy)3 ratio over time during the conversion of Fe(III)(2,2'-bipy)2 to Fe(II)(2,2'-bipy)3 in the anode chamber when powered with a constant current of (A) 0.05 mA and (B) 0.01 mA (where Fe(III)(2,2'-bipy)3 regeneration rate; 5000 ppm Fe(III)(2,2'-bipy)3 in a solution (180 mL) of 0.1 M Na2SO4, NaHSO4 (pH 2.0); the posolite is 180 mL of 0.1 M Na2SO4, NaHSO4). [Figure 14] Graph showing the Fe(III)(PHEN)2 / Fe(III)(PHEN)3 ratio over time during conversion of Fe(III)(PHEN)2 to Fe(III)(PHEN)3 in the anode chamber when powered at a constant current of (A) 0.05 mA and (B) 0.01 mA (where Fe(III)(PHEN)3 regeneration rate; 5000 ppm Fe(III)(PHEN)3 in 180 mL of 0.1 M Na2SO4, NaHSO4 solution (pH 2; posolite is 180 mL of 0.1 M Na2SO4, NaHSO4). BEST MODE FOR CARRYING OUT THEINVENTION

[0026] The present invention will now be described in more detail. The microbial fuel cell of the present invention is a microbial fuel cell including an anode chamber, a cathode chamber, a separation membrane and an electrolysis cell arranged between the anode chamber and the cathode chamber, the anode chamber includes an anode having a microbial membrane formed on its surface and an organic solution that is an electron donor as negolite, the organic solution being continuously supplied to the anode chamber, the cathode chamber includes a cathode that is a conductor electrode having no microbial membrane formed on its surface and an electron absorber solution as posolite, the electrolysis cell includes a cathode and an anode to which power is applied, and reduced posolite transferred from the cathode chamber, the reduced posolite transferred from the cathode chamber is regenerated by electrolysis using external power, and the regenerated posolite is supplied again to the cathode chamber, hydrogen gas generated in the cathode chamber by electrolysis performed in the electrolysis cell is discharged to the outside of the electrolysis cell, and the separation membrane is provided with one or more O-rings that can prevent liquid leakage.

[0027] The object of the present invention is to provide a microbial fuel cell that can produce high power at an efficient cost, and can use energy from existing power generation systems such as solar electric energy or power generated by the microbial fuel cell for electrolysis, improving the energy utilization rate and improving the life of the fuel cell. To achieve this object, heavy metal ions and their complexes, or other inorganic or organic substances with good solubility and high reduction potential can be used.

[0028] When discharging a microbial fuel cell, the problem arises of regenerating and reusing the discharged porphyrite, which requires the use of an external power source.

[0029] To this end, the power applied to the electrolysis cell may be selected from the group consisting of electricity generated from the microbial fuel cell, solar electricity, wind electricity, midnight electricity and combinations thereof.

[0030] In one embodiment, the electrolyte discharged from the microbial cell is placed in the anode chamber of an electrolysis cell (or electrolyzer), and an electrolyte is added to the counter electrode chamber to reduce water, and solar power can be applied between the two electrodes. In this electrolysis cell, hydrogen gas is produced in the cathode chamber of the electrolysis cell, along with the return of the regenerated porphyrite required for the microbial fuel cell. As shown in FIG. 1, this can be supplied to a hydrogen-oxygen fuel cell to produce electrical energy. With the help of solar power, the necessary materials for the microbial fuel cell and the hydrogen-oxygen fuel cell can be supplied, producing two forms of electricity from a single solar power source, and these necessary materials can be stored and generated as needed.

[0031] On the other hand, as shown in Figure 2, hydrogen gas production can be achieved by using a microbial fuel cell to power a regenerative electrolyzer without using solar power, where the regenerated posolite is returned to the cathode chamber of the microbial fuel cell. In this case, sustainable hydrogen production can be achieved.

[0032] Since electron absorbers have a large effect on power generation, it is important to investigate their applicability (G. 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). Electron absorbers with high reduction potentials and low overpotentials at graphite electrodes and very fast electron transfer reactions, such as Fe(III)(4,4-dimethyl-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)(4,4'-bis(triethylammoniummethyl)-2 ,2'-bipyridine)3, Fe(III)(triethylammonium-2,2'-bipyridine)3, Fe(III)(2,2'-bipyridine-5,5'-dicarboxylic acid)3, Fe(III)(1,10-phen)3, Ru(III)(2,2'-bipyridine)3, Ru(III)(4,4'-bis(triethylammoniummethyl)-2,2'-bipyridine)3, 4-trimethylammonium-2,2,6,6-tetramethyl 2,2,6,6-Tetramethylpiperidine-1-oxyl iodide, 2,2,6,6-tetramethylpiperidine-1-oxyl sulfonate, sodium salt, TEMPO-4-sulfate, potassium salt, 4-[3-(trimethylammonium)propoxy]-2,2,6,6-tetramethylpiperidine-1-oxyl chloride, (2,2,6,6-tetramethylpiperidin-1-yl)-oxyl 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-tetramethylpiperidine-1-oxyl, 3-carbamido-2,2,5,5-tetramethyl-3-carbamido-3-pyrroline-1-oxyl, phthalimido-N-oxyl, N,N,N-2,2,6,6-Heptamethylpiperidine-oxy-4-ammonium chloride, Poly(TEMPO-co-PEGMA), 4,5-Dihydroxy-1,3-benzenedisulfonate, disodium salt, 3,6-Dihydroxy-2,4-dimethylbenzenesulfonate, sodium salt, N-Hydroxyimide derivatives, (ferrocenylmethyl)trimethylammonium chloride, Bis[(trimethylammonium)propyl]ferrocene, Bis(3-trimethylaminopropyl)-ferrocene dichloride, Ferroceneamine chloride, Ferrocene dinitrogen dibromide, Br2, I, 3- , Mn 3+ and combinations thereof. Furthermore, the improved electron transfer rate by these metal ions, metal complexes, and organics can produce a high current and produce MFCs with high electrical energy production performance. Throughout our research, we have fabricated highly efficient MFC batteries for energy production using metal ions and their metal complexes and organics as electron absorbers in the cathode, and used them to investigate the effect of various electron acceptors on the performance of the MFC cells.

[0033] Furthermore, a combined battery of three MFC unit cells connected in series and in parallel was used to compare the performance of the MFC battery in terms of open circuit voltage, current density and power density.

[0034] In one embodiment, the anode may be selected from the group consisting of a carbon brush, a carbon felt, a carbon plate, a carbon plate coated with porous carbon, and combinations thereof.

[0035] In one embodiment, the cathode may be selected from the group consisting of a carbon brush, a carbon felt, a carbon plate, a carbon plate coated with porous carbon, a carbon plate coated with carbon nanotubes, a cathode made of a metal or a precious metal material having a low hydrogen generation overvoltage, such as a platinum plate, a titanium plate, a stainless steel plate, and a combination thereof.

[0036] We used carbon brushes as anodes to investigate their impact on power generation. Carbon felts were also investigated to compare the power generation of MFC cells with carbon brushes. Finally, we also investigated the sustainability of the power generation of MFC cells using real wastewater as lipid.

[0037] As shown in Figure 3, a polarization test and a discharge experiment were conducted to evaluate the performance of the MFC battery. Research like this has not been reported so far. In the present invention, the voltage can be stably obtained by parallel connection, and the current is expressed as the sum of each unit cell, so the cells are connected in parallel, and the parallel bundles are connected in series again to achieve a high voltage. In addition, the electrode material was maximized to increase the electrode area in the battery chamber, resulting in a large current. In particular, when a carbon brush was used to smoothly supply the electrode area and solution, the current was significantly increased compared to the current of carbon felt.

[0038] The reduced posolite, which is the discharge material, can be regenerated by various external power sources such as solar cells and returned to the MFC. This is done using an electrolysis cell separated by a separation membrane between the two electrode chambers. Hydrogen gas is generated in the electrode chamber opposite the regeneration electrode chamber, and this can be supplied to the fuel cell to obtain electrical energy.

[0039] The anode contained in the anode chamber of the microbial fuel cell of the present invention is an anode with a microbial membrane formed on its surface, and the microorganisms can be anaerobic microorganisms in an anaerobic digester in a wastewater treatment plant. The microbial membrane can be prepared by a method including placing an organic matter-mixed phosphate buffer as a carbon source and anaerobic sludge obtained from an anaerobic digester in an anode chamber containing an anode. The microbial membrane can be prepared by a method including placing a microbial membrane on the anode of the anode chamber by adding the same phosphate buffer as the anode chamber except for the organic matter to a cathode chamber separated from the anode chamber by using an ion exchange membrane such as Membrane International, Celegard, or Selemion DSV as a separation membrane, and providing air to the cathode chamber to use oxygen as an electron absorber. A closed circuit is formed by connecting an external resistor of about 1000 ohms to the circuit between the anode and the cathode.

[0040] The anode chamber contains an organic solution that is an electron donor as negolite, and the organic solution can be continuously supplied to the anode chamber as can be seen from Figures 1 and 2. The organic solution can include, but is not limited to, acetate, glucose, protein, food hydrolyzate, domestic wastewater, anaerobic sludge, algae, and combinations thereof.

[0041] In one embodiment, the anode and cathode chambers of the microbial fuel cell of the present invention are two separate regions in an integrated container of insulating material, and the separation membrane is in the form of a window frame that is pressed and inserted between the anode and cathode chambers, and may include one or more O-rings, for example, 1 to 3 O-rings. In the case of the separation membrane, leakage occurred more frequently when it was compressed and separated using a bolt and knot than when it was separated with a single O-ring.

[0042] In order to extend the life of the battery, it is necessary to prevent leakage. For this purpose, a method is used that includes preparing a separation membrane (ion exchange membrane) that moves the electrolyte by sandwiching it between frame plates of a material such as plastic, and using one or more O-rings in the frame. The separation membrane may be in the form of a cation exchange membrane, an anion exchange membrane, a cation-anion complex membrane, or a microporous membrane that allows ions to pass through.

[0043] In the microbial fuel cell of the present invention, the anode and cathode are carbon brushes, and the amount of carbon brushes contained in the cathode chamber may be in excess of the amount of carbon brushes contained in the anode chamber.

[0044] The electrolysis cell included in the microbial fuel cell of the present invention includes a cathode and an anode to which electric power is applied, and reduced posolite transferred from the cathode chamber. The reduced posolite transferred from the cathode chamber is regenerated by electrolysis using external electric power, and the regenerated posolite is returned to the cathode chamber of the microbial fuel cell. Hydrogen gas generated in the cathode chamber by electrolysis performed in the electrolysis cell can be discharged to the outside of the electrolysis cell.

[0045] The electrodes of the electrolytic cell include anodes with high oxygen overvoltage, such as a lead dioxide electrode or an electrode in which lead dioxide is coated on a metal plate such as titanium; and cathodes made of metal or precious metal materials with low hydrogen generation overvoltage, 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., and can include, for example, a cathode selected from the group consisting of platinum, titanium plate, stainless steel plate, and combinations thereof.

[0046] The microbial fuel cell of the present invention may further include a posolite storage unit for storing the posolite regenerated in the electrolysis cell and supplying the stored posolite to the cathode chamber; and a hydrogen gas storage unit for storing hydrogen gas generated in the electrolysis cell. The posolite regenerated in the electrolysis cell may be immediately supplied to the cathode chamber, or may be stored in the posolite storage unit and then supplied to the cathode chamber as necessary. The hydrogen gas generated in the electrolysis cell may be immediately discharged to the outside, or may be stored in the hydrogen gas storage unit and then supplied to the hydrogen-oxygen fuel cell to produce additional electrical energy.

[0047] In another aspect of the invention, a method for producing electrical energy using the microbial fuel cell is provided.

[0048] Without limitation, multiple microbial fuel cells can be connected in parallel or in series to produce electrical energy. In one embodiment, high voltages can be achieved by first connecting microbial fuel cells in parallel and then connecting the parallel connected bundles back in series.

[0049] In addition, the method for producing electrical energy of the present invention can additionally produce electrical energy by supplying the hydrogen gas generated in the electrolysis cell to a hydrogen-oxygen fuel cell.

[0050] The present invention will be described in more detail through the following examples and comparative examples. However, the scope of the present invention is not limited thereby in any way.

[0051] Working Example Preparation of the MFC for polarization tests and discharge experiments (Figure 3) To investigate the effect of the electron absorber on the MFC performance, a two-chamber microbial fuel cell design with an anode chamber with a working volume of 500 mL and a cathode chamber with a volume of 600 mL was used.

[0052] To experiment with the electrodes, carbon brushes (D 4 cm × L 7 cm) or carbon felt (W 4 cm × H 7 cm) were used as anode materials. The carbon brushes used had a diameter of 4 cm and a length of 7 cm, with an area of ​​28 cm. 2 A graphite plate (2.5 cm x 6 cm) or a carbon brush was used as the cathode.

[0053] Except during polarization tests, an external circuit resistance of 1000 Ω was connected between the anode and the cathode, which were separated by a pretreated ion exchange membrane (AEM, AMI-7001 or CEM, CEM-7001; Membrane International, Inc.).

[0054] The anaerobic inoculum was collected from an anaerobic sludge previously published by Choi and Cui (Recovery of silver from wastewater coupled with power generation using a microbial fuel cell. J. Bioresour Technol 107(2012), 522-525). Three tanks of the cell were inoculated by filling a mixture of 400 mL of sludge and 100 mL of artificial wastewater (pH 7) as negolite. The composition per liter of artificial wastewater was as follows: 2.0 g CH3COONa, 1.05 g NH4Cl, 1.5 g KH2PO4, 2.2 g K2HPO4, and 0.2 g yeast extract. The negolite was circulated continuously and the buffer was poured into the cathode chamber. At the same time, air was supplied to the cathode chamber to use dissolved oxygen as an electron absorber in growing the microorganisms. The anode chamber was covered with a thin film of aluminum to prevent the oxidizing bacteria from being exposed to light.

[0055] Prior to operation, nitrogen gas was bubbled through the negolite solution for approximately 15 minutes to create an anaerobic environment. This process was repeated and the electrolyte medium was replaced when the voltage dropped below 50 mV. After obtaining a stable voltage production with wastewater, the negolite was replaced with growth medium. Initial operation was performed after obtaining stable MFC performance indicating proper microbial film formation.

[0056] For the preparation of posolite, K2Cr2O7, FeCl3.6H2O, NaHSO4 and Na2SO4 were purchased from Daejeong Chemical Co., Ltd. (Korea), 4,4'-dimethyl-2,2'-bipyridine (4,4'-dimethyl-2,2'-BIPY), 2,2'-bipyridine (2,2'-BIPY) and 1,10-phenanthroline (1,10-PHEN) were purchased from Aldrich Chemical Company, Inc. (USA). Using the appropriate reagents, a posolite solution (pH 2) containing 5000 ppm Cr(VI) and 5000 ppm Fe(III) in supporting electrolyte (0.1 M Na2SO4) was prepared. Fe(III)(BIPY)3 was prepared as follows (JG Ibanez, C.-S. Choi, RS Becker, Electrochemical Applications of Aqueous Redox Transition Metal Complexes as a Function of pH. J Electrochem. Soc. 134, 12(1987), 3084-3087). 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). The pH was adjusted to 2 using 3 M NaOH. Fe(III)(1,10-PHEN)3 was made using the same conditions. The preparation of the metal complexes was carried out at room temperature.

[0057] Polarization and discharge experiments Polarization Experiments - Polarization experiments were performed to evaluate the performance of the MFC cell by obtaining the maximum power density and internal resistance. The cell potential data was measured every minute using a LabView System (National Instruments Models, NI-cDAQ9219, USA). Various external resistances ranging from 150 kΩ to 0.010 kΩ were applied to obtain polarization curves to determine the maximum power generation. The current density was calculated by the following equation (1): I d =V / RA (1) (Where, V (V) is the voltage across the resistor, R (Ω) is the external resistance, and A (cm2 ) is the surface area of ​​the cathode. Power density (P d ) was calculated using the following formula (2): P d =V 2 / RA (2) Discharge Experiments - Voltage changes at constant current were used to evaluate the discharge characteristics of the MFC cells. Each cathode compartment contained 180 mL of posolite and the anode compartment contained the same volume of negolite solution. After the first discharge of the MFC cells, the solution in the anode compartment was replaced with fresh solution. Discharge experiments were performed under constant current conditions using a Dutch constant voltage device IVIUM. This device allows discharge experiments at constant current using a two-electrode system. The discharge current was chosen to ensure that a reasonable cell voltage and power generation were obtained. The discharge current was selected based on the power curves. For the power density curves of MFC cells with posolite with different maximum power points, different discharge currents were used to evaluate whether efficient discharge could be achieved. The current at the maximum power point is the ideal operating point due to its high energy output. Discharge experiments were comparatively run at various current levels.

[0058] Effect of electron absorber concentration on the performance of variously connected three-unit MFC cells The effect of the initial reduction electrolyte concentration of Cr(VI) was investigated. Connecting three MFC unit cells in series or parallel increases the 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.

[0059] FIG. 4 shows voltage vs. current density curves and power vs. current density curves for (a) a single cell, (b) series-connected MFCs, and (c) parallel-connected MFCs with different connections of MFCs having cathodes used with different Cr(VI) concentrations of 100 ppm, 1000 ppm, and 5000 ppm.

[0060] The following is an example showing an example of power generation by a high-output MFC, but the scope of the present invention is not limited thereto.

[0061] (1) Polarization behavior of MFC using Cr(VI) as an electron absorber To determine the maximum power density achievable using various concentrations of Cr(VI), polarization curve tests were performed by changing the external resistance from 150 kΩ to 10 Ω to obtain a stable voltage and measuring the voltage. Figure 4 shows the voltage vs. current density curves and power density vs. current density curves for varying initial concentrations of Cr(VI).

[0062] [Table 1] *C Cr(VI) ; Cr(VI) concentration, V ocv ;open circuit voltage, J max ;maximum current density, J peak ; peak current density, P max ;maximum power density

[0063] The electrochemical parameters are summarized in Table 1. The maximum power output of the unit MFC increased with increasing Cr(VI) concentration from 100 ppm to 5000 ppm. max 377.7mWm -2 (For 100 ppm Cr(VI) concentration) to P max 571.9mWm -2 (5000 ppm Cr(VI) concentration). The series-connected MFC cells were able to increase the voltage as expected. In the series connection, the open circuit voltage was 2.697 V for 100 ppm Cr(VI) concentration, and P max 850.1mWm -2 For the 5000 ppm Cr(VI) concentration, the open circuit voltage was 3.059 V and P max 1323.2mWm -2 The maximum power was 1.55 times higher at the 5000 ppm concentration than at the 100 ppm concentration.

[0064] In parallel connection, for 100 ppm Cr(VI) concentration, P max 714.7mWm -2 Maximum current density 2730.8mAm -2However, for a 5000 ppm Cr(VI) concentration, max 1432.3mWm -2 Maximum current density 3833.3mAm -2 The power density showed a two-fold improvement at the 5000 ppm concentration compared to the 100 ppm concentration.

[0065] This study demonstrated that high concentration Cr(VI) as an electron absorber had superior capability for MFC performance, although it produced less electricity than using Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 as the electron acceptor, as discussed below.

[0066] (2) Discharge performance of Cr(VI)-MFC consisting of three unit cells at 5000 ppm Figure 5 shows graphs showing (A) the discharge curves of a battery containing three unit MFCs connected in series, and (B) the discharge curves of a battery containing three unit MFCs connected in parallel (wherein the cathode was a graphite electrode plate (2.5 cm × 6 cm), the posolite was 170 mL of 5000 ppm Cr(VI), the anode was a carbon brush (D 4 cm, H 7 cm), and the negolite was 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS).

[0067] In Figure 5, we compare the results of the discharge operation of series-connected and parallel-connected cells of 5000 ppm Cr(VI) at various constant currents. It can be seen that the discharge characteristics of the MFC are highly dependent on the selected current. In the series-connected discharge voltage, as the discharge voltage increased from 0.5 mA to 1.5 mA, the voltage initially maintained a nearly flat portion and then dropped sharply at the end (Figure 5A). In the parallel connection, when changed from 1.5 mA to 4.5 mA, the discharge voltage also showed a flat portion at the beginning and then a sharp drop at the end.

[0068] Although not shown as a graph, another study conducted in this laboratory showed that the voltage dropped more rapidly with 1000 ppm Cr(VI) than with 5000 ppm Cr(VI) at the same discharge current, meaning that the MFC with 5000 ppm Cr(VI) showed superior discharge performance compared to 1000 ppm.

[0069] It lasted for about 70 hours at 0.5 mA in series connection and a similar duration of 68 hours at 1.5 mA in parallel connection until the electron absorber was consumed in 170 mL of reduction electrolyte. This means that the current density in series connection is similar to that in parallel connection, and it can be said that the reduction reaction rate of the cathode in the electrode reaction of both connections is almost the same.

[0070] The higher discharge voltage for higher Cr(VI) concentrations may be due to the increased reaction rate at the cathode and the decreased internal resistance of the cathode. The reason why the voltage of the series connection is significantly lower than the expected 3V level may be due to the resistance of the wire connections and the deepening of the cell leakage. The magnitude of the current can be improved by expanding the surface of the electrodes placed in the current chamber.

[0071] (3) Polarization characteristics of MFCs equipped with various electron absorbers To determine the maximum power density achievable with various reduced electron acceptors, polarization tests were performed by measuring the voltage after obtaining a stable voltage output while varying the external resistance from 150 kΩ to 0.010 kΩ. The MFC showed superior performance by using Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 as the electron absorber. Figure 6 shows the voltage vs. current density and power vs. current density curves using various electron absorbers.

[0072] Figure 6 shows the polarization curves and power density curves for (a) a single cell, (b) a three-unit MFC connected in series, and (c) a three-unit MFC connected in parallel, using various electron absorbers in the cathode compartment.

[0073] [Table 2] *C Cr(VI) ; Cr(VI) concentration, V ocv ;open circuit voltage, J max ;maximum current density, J peak ; peak current density, P max ;maximum power density

[0074] The single MFC cell showed the highest electrochemical factors when using Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 as the electron absorber, which had an overcurrent voltage (OCV) of 1.250 V and a maximum current density (J max )2628mA·m -2 and maximum power density of 1212 mW m -2 The maximum current density was 2.3 times that of Cr(VI), and the maximum power density was 2.8 times (see Table 2). It can be seen that the action of the electron absorber is very important for the production of electrical energy. In the series connection, the use of Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 as the electron absorber also showed the highest electrochemical factors, which were the OCV of 3.323 V and the maximum current density (J max )3179mA·m -2 and maximum power density of 2951 mW m -2 The maximum current density was 2.7 times that of Cr(VI), and the maximum power density was 2.6 times (see Table 2).

[0075] In the parallel connection, the highest electrochemical factors were also shown when using Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)O3 as the electron absorber, which had an OCV of 1.210 V and a maximum current density of 1.210 J max )8179mA·m -2 and maximum power density of 3937mW m -2 The maximum current density was 3.13 times that of Cr(VI), and the maximum power density was 3.19 times (see Table 2).

[0076] Compared to the parallel connection of single cells, the OCV of the three unit cells connected in series was 2.7 times higher, and the current of the parallel connection was about 3.1 times higher than that of the single cell or series connection. Meanwhile, the power density of the parallel connection was 1.3 times that of the series connection, but 3.2 times that of the single cell connection. This shows that when single cells are connected in series or parallel, the power increases in proportion to the number of cells, as in general batteries.

[0077] (4) Discharge performance of MFC batteries equipped with various electron absorbers Figure 7 shows the discharge curves of a series-connected 3-unit MFC cell containing (a) Fe(III), (b) Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3, and (c) Fe(III)(1,10-phen)3 as various electron absorbers discharged at various discharge currents (wherein the anode was a carbon brush (D 4 cm, H 7 cm) and the negolite was 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS).

[0078] Figure 8 shows the discharge curves of a three-unit MFC cell connected in parallel containing various electron absorbers, (a) Fe(III), (b) Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3, and (c) Fe(III)(1,10-phen), discharged at various discharge currents (where the anode was a carbon brush (D 4 cm, H 7 cm) and the negolite was 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS).

[0079] The discharge characteristics of the MFC connected to three unit cells at constant current were used to evaluate the performance of the battery. Figure 7 shows the results of the discharge behavior of the MFC connected in series with MFC unit cells containing 5000 ppm concentration of Fe(III), Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 and Fe(III)(1,10-phen)3 as electron absorbers at various constant currents.

[0080] In the Fe(III)-MFC system, the open circuit voltage was about 2.9 V, and the discharge voltage gradually decreased from 2.5 V to 1.0 V at a discharge current of 1.5 mA, and the discharge time was 25 hours. As shown in Figure 7, the voltage decreased obviously when the discharge current increased above 1.5 mA. At a current of 1.5 mA or less, the system showed stable discharge characteristics. In the Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3-MFC system, the discharge voltage gradually decreased from 2.5 V to 1 V at a discharge current of 1.5 mA, and the discharge time lasted for 25 hours. The open circuit voltage at this time was about 3.4 V. The pattern at a discharge current of 2 mA was similar to that at a discharge current of 1.5 mA, but the discharge time was about 19 hours.

[0081] When the discharge current was 2 mA or more, the discharge voltage dropped rapidly and continuously. Therefore, stable discharge characteristics were observed at currents of 2 mA or less. When the electron absorber Fe(III)(1,10-phen)3 was used, the discharge voltage dropped continuously at all discharge currents, suggesting that the battery was leaking.

[0082] As shown in Figure 8, the parallel connection using Fe(III) as the electron absorber in the cathode chamber discharged stably at a discharge current of 1.5 mA or less, while the cell using Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 as the posolite discharged stably at a discharge current of 3 mA or 4.5 mA. The parallel connection showed stable discharge characteristics at 4.5 mA or less. In the Fe(III)-MFC system, the cell discharged stably for 21 hours at a discharge current of 1.5 mA and an average discharge voltage of 0.925 V, with an open circuit voltage of 1.056 V.

[0083] As shown in Figure 8, the voltage also decreased obviously when the discharge current increased above 1.5 mA. For Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3-MFC, 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 it lasted for more than 20 h. Meanwhile, for 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 it lasted for more than 20 h. As shown in Figure 8b, the voltage decreased obviously when the discharge current was increased to 6 mA. For Fe(III)(1,10-phen)3-MFC, the discharge characteristics were unstable at all discharge currents. This is probably due to the fact that the discharge current was unstable at all discharge currents. This could be the result of battery leakage.

[0084] (5) Effect of anode material on polarization performance In the MFC cell, the anode material had a significant effect on the current density and maximum power density of the MFC.

[0085] FIG. 9 shows the voltage vs. current density curves and power density vs. current density curves of (a) and (b) parallel connected and (c) and (d) series connected MFCs with different types of anode materials (carbon brush and carbon felt) (wherein Posolite was used as the electron absorber 5000 ppm Fe(III)(4,4′-dimethyl-2,2′-bipyridyl)3, Negolite; 2 g / L acetate and 0.2 g / L yeast extract dissolved in PBS).

[0086] Figure 9 shows the polarization curves of a parallel-connected three-unit cell battery (Figure 9a) using 5000 ppm Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 as the electron absorber in the cathode and carbon brush and carbon felt as the anodes, and an MFC battery like that in series connection (Figure 9b). For the series connection, the performance of the MFC with carbon brush electrodes was slightly better, and the power-efficiency curve of the carbon brush electrodes was about 1.2 times the maximum power of the power curve of the carbon felt electrodes (Table 3). The maximum current density of the carbon brush electrodes was about 1.6 times the maximum current density of the carbon felt electrodes.

[0087] In parallel connection, the carbon brush electrodes showed superior polarization characteristics of the MFC (Figure 9a). The maximum power was 2.7 times higher when using the carbon brush (Table 3). The open circuit voltage was similar for the two electrodes, but the maximum current was about 2.6 times higher for the carbon brush electrode than for the carbon felt electrode, indicating that employing the carbon brush electrode as the anode is advantageous in terms of cell efficiency (Table 3).

[0088] The difference in performance can be explained by the fact that fewer microorganisms adhere to the carbon felt anode compared to the carbon brush anode, and therefore the microorganisms are not smoothly supplied to the negolite.

[0089] [Table 3] *V ocv ;open circuit voltage, J max ;maximum current density, J peak ; peak current density, P max ;maximum power density

[0090] Posolite contained 5000 ppm Fe(III)(4,4′-dimethyl-2,2′-bipyridyl)3 as an electron absorber, and negolite was a solution obtained by dissolving 2 g / L acetate and 0.2 g / L yeast extract in PBS.

[0091] (6) Discharge performance of MFCs using different anode materials Figure 10 shows the discharge performance of three unit cell MFCs connected in parallel and in series using Fe(III)(4,4'-dimethyl-2,2'-bipyridyl)3 as the electron absorber with 5000 ppm as Fe(III) at various discharge currents. Carbon felt was used in the anode chamber and compared with the carbon brush electrode (inset) previously investigated.

[0092] When the cells with carbon felt anodes were connected in parallel, the discharge voltage slowly decreased with increasing discharge time. The average discharge voltage had an open circuit voltage of 1.29 V at a discharge current of 3.0 mA and was sustained for a discharge time of 25.6 h with an average discharge voltage of 0.79 V.

[0093] On the other hand, in the parallel connection using the carbon brush electrode as the anode, the average discharge voltage of the batteries was 0.93 V at a discharge current of 3.0 mA, 15% higher than when the carbon felt was used (0.79 V), and the discharge time lasted for more than 20 hours. The open circuit voltage at this time was 1.21 V. At a discharge current of 4.5 mA, the battery with the carbon felt anode lasted for 10.6 hours, while the battery with the carbon brush electrode lasted for more than 20 hours (see Figure 10).

[0094] In the 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 more. The cells were found to show stable discharge characteristics at discharge currents of 1.5 mA or less. At a discharge current of 2.0 mA, the discharge voltage decreased faster when carbon felt was used as the anode than when carbon brush electrodes were used. When carbon felt was used, the average discharge voltage was 0.51 V and the open circuit voltage was 3.50 V, lasting for 1.58 h.

[0095] When the carbon brush electrode was used as the anode, the open circuit voltage was 2.78 V and the average discharge voltage was 0.42 V, lasting for 17 hours. These results show that in MFC cells connected to a unit cell, the use of the carbon brush electrode as the anode ensures good formation of microbial film and the battery performs very well. The reason is that the carbon brush electrode ensures a higher specific surface area and porosity, which is thought to lead to more anaerobic microorganisms growing on the carbon brush than on the carbon felt. The higher the number of bacteria, the faster the reaction.

[0096] (7) Regeneration test of Cr(VI) using solar cells as external power source Figure 11 shows the residual Cr(III) concentration over time and the conversion efficiency from Cr(III) to Cr(VI) when a constant current of 0.2 mA is applied to convert Cr(III) to Cr(VI) in the anode chamber. Alternatively, a Ti metal plate with a PbO2 coating and an electrode area of ​​20 cm2 was used as the electrode. 2The 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.

[0097] After 25 hours of reaction, the final conversion efficiency was 53%. The hydrogen gas evolution rate was calculated using Faraday's law as 1.09×10 -7 The ratio of mol / g Cr(VI) was obtained, which can be used as fuel for fuel cells and power generation. At initial concentrations of 1000 ppm and 100 ppm of Cr(III), 62% of Cr(III) was converted to Cr(VI) in 10 h and 83% of Cr(III) was converted to Cr(VI) in 7.5 h, respectively.

[0098] In general, the conversion takes longer than with Fe(III) or its complexes, likely because the oxidation of Cr(III) involves three electrons, whereas the oxidation of Fe(II) requires one electron.

[0099] (8) Regeneration test of Fe(III) using solar cells as external power source Since it is not possible to measure Fe(III) in the presence of Fe(II), the regeneration rate of Fe(III) can be expressed as the ratio Fe(III) / Fe(II) using the Nernst equation: E rev =E O' -RT / Fln[Fe(II)] / [Fe(III)] (3) [Fe(II)] / [Fe(III)]=e (EO'-Erev) / RT (4) The ratio of [Fe(II)] / [Fe(III)] in negolite can be determined by measuring the voltage of negolite against a reference electrode such as Ag / AgCl. The regeneration degree can be similarly determined for other Fe(III) complexes.

[0100] Figure 12a shows the Fe(II) / Fe(III) ratio versus time for converting Fe(II) to Fe(III) by applying power at a constant current of 0.05 mA. A Ti metal plate coated with PbO2 with an electrode area of ​​20 cm2 was used as the anode, and a stainless steel plate of the same width was used as the counter electrode.

[0101] The initial concentration of the negolite solution was 5000 ppm Fe(II) and the solution volume was 180 mL. The Fe(II) / Fe(III) ratio continued to decrease with reaction time, indicating that the regeneration was successful.

[0102] At a current of 0.05 mA, Fe(III) was almost completely regenerated within 15 h under these experimental conditions. At a constant current of 0.01 mA, complete conversion took more than 24 h (see Figure 12b). The evolution of hydrogen gas during the reaction at a current of 0.05 mA for 24 h can be calculated by Faraday's law as 1.38 × 10 -7 The ratio was calculated as mol / g Fe(II), which can be used as a fuel for fuel cells and power generation.

[0103] (9) Regeneration test of Fe(III)(4,4'-dimethyl-2,2'-bipy)3 using solar cells as external power source Figure 13 shows an electrode area of ​​20 cm 2 A Ti metal plate coated with PbO2 was used as the anode, and a stainless steel plate of the same width was used as the counter electrode. The negolite solution was Fe(II), with an initial concentration of 5000 ppm and a solution volume of 180 mL.

[0104] The ratio of Fe(III)(dimethyl-2,2'-bipy)3 / Fe(II)(4,4'-dimethyl-2,2'-bipy)3 continuously decreased with reaction time. By applying a constant current of 0.05 mA, the regeneration was almost complete within 7 h of reaction time (see Figure 13a).

[0105] At a constant current of 0.01 mA, the reaction rate was slow and the reaction was not completed even after 24 hours. The hydrogen gas generated by the reaction at a current of 0.05 mA for 24 hours can be calculated by Faraday's law as 1.38 × 10 -7 The ratio of 1,2-dichloro-1,2,3-trifluoroethylene (1,2,3,4-tetrafluoroethylene) to 1,2-dichloro-1,2,3-tetrafluoroethylene (1,2,3,4-tetrafluoroethylene) was obtained in the ratio of mol / g. This can be used as a fuel for fuel cells and power generation.

[0106] (10) Regeneration test of Fe(III)(PHEN)3 using solar cells as external power source In Figure 14, under the same conditions as in Figure 13, Fe(III)(2,2'-bipy)3 / Fe(II)(2,2'-bipy)3, Fe(III)(PHEN)3 / Fe(III)(PHEN)3 decreased continuously with reaction time, and regeneration was nearly complete within 10 hours of reaction time at both 0.05 mA and 0.01 mA constant currents. Hydrogen gas production was similar to the Fe(III)(4,4'-dimethyl-2,2'-bipy)3 / Fe(II)(4,4'-dimethyl-2,2'-bipy)3 experiments.

Claims

1. A microbial fuel cell comprising: a microbial fuel cell unit cell having an anode chamber, a cathode chamber, and a separation membrane disposed between the anode chamber and the cathode chamber; and an electrolysis cell, The anode chamber includes an anode having a microbial film formed on its surface and an organic solution as an electron donor, the organic solution being continuously supplied to the anode chamber; The cathode chamber contains a cathode, which is a conductor electrode having no microbial film formed on its surface, and an electron absorber solution as a posolite; The electrolysis cell includes a cathode and an anode to which electric power is applied, and reduced posolite transferred from the cathode chamber, the reduced posolite transferred from the cathode chamber is regenerated by electrolysis using external electric power, the regenerated posolite is supplied to the cathode chamber again, and hydrogen gas generated at the cathode by electrolysis performed in the electrolysis cell is discharged to the outside of the electrolysis cell, The separation membrane is provided with one or more O-rings to prevent leakage of liquid; the electron absorber is Fe(III)(4,4-dimethyl-2,2'-bipyridyl) 3 ; The anode in the anode chamber is a carbon brush. Microbial fuel cell.

2. The anode chamber and the cathode chamber are two separate regions in an integral container made of an insulating material; The microbial fuel cell of claim 1, wherein the separation membrane is pressed and inserted between the anode chamber and the cathode chamber, and is provided with 1 to 3 O-rings.

3. The microbial fuel cell of claim 1, wherein the cathode of the cathode chamber is selected from the group consisting of 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 combinations thereof.

4. the anode of the anode chamber and the cathode of the cathode chamber are carbon brushes; 2. The microbial fuel cell of claim 1, wherein the amount of carbon brushes contained in the cathode chamber is in excess of the amount of carbon brushes contained in the anode chamber.

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

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

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

8. The electrodes of the electrolytic cell are anodes which are lead dioxide electrodes or metals coated with lead dioxide; and 2. The microbial fuel cell of claim 1, comprising a cathode selected from the group consisting of 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 combinations thereof.

9. A posolite storage section for accumulating the posolite regenerated in the electrolytic cell and supplying the accumulated posolite to the cathode chamber; and a hydrogen gas storage unit for storing hydrogen gas generated by the electrolysis cell; The microbial fuel cell of claim 1 further comprising:

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

11. 11. The method for producing electrical energy according to claim 10, wherein the method is carried out by connecting a plurality of microbial fuel cells connected in parallel or in series.

12. 11. The method for producing electrical energy as claimed in claim 10, wherein the hydrogen gas generated in the electrolysis cell is supplied to a hydrogen-oxygen gas fuel cell to further produce electrical energy.

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