Microbial electrolysis cell driven by duty-cycle method and hydrogen production method using the same

Abstract

A microbial electrolysis cell including an intermittent voltage supply device according to a preferred embodiment of the present invention and a method for generating hydrogen using the same can reduce the amount of energy consumed and, at the same time, reduce the dead zone locally generated at the reduction electrode, thereby efficiently utilizing the surface area of ​​the reduction electrode and improving hydrogen production.

Description

Technology Field

[0001] The present invention relates to a microbial electrolysis cell and a method for producing hydrogen using the same, and more specifically, to a microbial electrolysis cell operated through a duty-cycle method and a method for producing hydrogen using the same. Background Technology

[0002] Green energy, including hydrogen energy, is attracting attention as a clean and highly efficient energy source to replace fossil fuels, and it holds great potential as a future energy source as it can reduce the impact of climate change.

[0003] Among the technologies for high energy efficiency in hydrogen production, Microbial Electrolysis Cell (MEC) technology has been developed to convert biodegradable organic matter into hydrogen gas using electrochemically active microorganisms (exoelectrogens). The operating mechanism of a microbial electrolysis cell consists of a process in which organic matter is anaerobically oxidized, causing electrons to move to the anode; then, by applying a potential to the circuit, the electrons move to the cathode, where they reduce protons to generate hydrogen gas.

[0004] Since electrons transferred to the oxidation electrode (anode) after the oxidation of organic matter cannot flow to the reduction electrode (cathode) without applying an external voltage, the application of voltage (electrical energy) is an essential factor for making the microbial electrolysis cell (MEC) highly efficient. However, there is a problem in that the hydrogen generation efficiency decreases because some hydrogen generated at the reduction electrode (cathode) reduces the active surface area of ​​the electrode, causing localized dead zones to form. Prior art literature

[0005] Korean Patent Publication No. 10-2343270 (December 21, 2021) The problem to be solved

[0006] The present invention was conceived to solve the aforementioned problem, and can resolve the issue of reduced hydrogen generation efficiency caused by localized dead zones resulting from hydrogen generated at the cathode covering the active surface area, thereby saving the amount of electrical energy consumed.

[0007] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0008] A method for generating bioelectrochemical hydrogen through intermittent voltage supply according to an embodiment of the present invention for achieving the above technical problem comprises: a step (S01) of arranging an air cathode coated with a diffusion layer and an anode facing each other within a chamber where a microbial electrolysis reaction is performed; a step (S02) of forming a biofilm by culturing electroactive microorganisms on the anode; a step (S03) of replacing the air cathode with a cathode after the formation of the biofilm is completed; a step (S04) of applying an intermittent voltage (duty-cycle) from an intermittent voltage supply device connected to the cathode; and a step (S05) of collecting hydrogen gas generated by applying the intermittent voltage (duty-cycle).

[0009] The intermittent voltage (Duty-cycle) supplied by the above intermittent voltage supply device may have an application / non-application (ON / OFF) ratio of 3:1 to 5:1.

[0010] The intermittent voltage (Duty-cycle) supplied by the above intermittent voltage supply device may have a non-application (OFF) time of voltage of 5 to 60 seconds.

[0011] The amount of hydrogen generated by the intermittent voltage (duty-cycle) supplied by the above intermittent voltage supply device may be greater compared to the amount of hydrogen generated by supplying a continuous voltage.

[0012] The electrical energy efficiency (η) of a microbial electrolysis cell due to the intermittent voltage (Duty-cycle) supplied by the above intermittent voltage supply device E ) is the electrical energy efficiency (η) of a microbial electrolysis cell due to continuous voltage application. E It can be improved by 20 to 30 percent compared to ).

[0013] The above diffusion layer may include PTFE (Polytetrafluoroethylene) as a polymer coating layer.

[0014] A microbial electrolysis cell including an intermittent voltage supply device according to an embodiment of the present invention for achieving the above technical problem may include: a chamber in which a microbial electrolysis reaction is performed; an oxidation electrode (anode) and a reduction electrode (cathode) disposed opposite each other within the chamber; an intermittent voltage (duty-cycle) supply device connected to the reduction electrode (cathode); and a gas collection device connected to the upper part of the chamber to collect hydrogen generated therefrom.

[0015] The intermittent voltage (Duty-cycle) supplied by the above intermittent voltage supply device may have an application / non-application (ON / OFF) ratio of 3:1 to 5:1.

[0016] The intermittent voltage (Duty-cycle) supplied by the above intermittent voltage supply device may have a non-application (OFF) time of voltage of 5 to 60 seconds.

[0017] The amount of hydrogen generated by the intermittent voltage (duty-cycle) supplied by the above intermittent voltage supply device may be greater compared to the amount of hydrogen generated by supplying a continuous voltage.

[0018] The electrical energy efficiency (η) of a microbial electrolysis cell due to the intermittent voltage (Duty-cycle) supplied by the above intermittent voltage supply device E ) is the electrical energy efficiency (η) of a microbial electrolysis cell due to continuous voltage application. E It can be improved by 20 to 30 percent compared to ).

[0019] The above reduction electrode (cathode) comprises carbon black, carbon cloth, and a platinum catalyst layer, wherein an air reduction electrode (air cathode) coated with a diffusion layer is used before seeding of electroactive microorganisms, and after seeding of electroactive microorganisms, the reduction electrode is changed to one from which the diffusion layer has been removed.

[0020] The above diffusion layer may include PTFE (Polytetrafluoroethylene) as a polymer coating layer. Effects of the invention

[0021] According to the present invention as described above, a microbial electrolysis cell including an intermittent voltage supply device according to a preferred embodiment of the present invention and a method for generating hydrogen using the same can reduce the amount of energy consumed and, at the same time, reduce the dead zone locally generated at the reduction electrode, thereby efficiently utilizing the surface area of ​​the reduction electrode and improving hydrogen production.

[0022] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below. Brief explanation of the drawing

[0023] FIG. 1 is a schematic diagram showing a reactor of a microbial electrolysis cell according to one embodiment of the present invention. FIG. 2 is a schematic diagram of (a) a photograph of a microbial electrolysis cell, (b) an air cathode, and (c) a cathode according to Examples 1 to 4 of the present invention. FIG. 3 is a schematic diagram showing the hydrogen generation mechanism through a microbial electrolysis cell according to (a) a continuous voltage supply and (b) an intermittent voltage supply method according to one embodiment of the present invention. FIG. 4 is a graph showing the amount of hydrogen generated by operating a microbial electrolysis cell according to the voltage application method and duty cycle according to Examples 1 to 4 and Comparative Example of the present invention. FIG. 5 shows the energy efficiency (η) for microbial electrolysis cells operated according to the voltage application method and duty cycle according to Examples 1 to 4 and Comparative Example of the present invention. E ), energy efficiency through substrate (η S ) and total energy efficiency (η E+S This is a graph showing the calculation results. Specific details for implementing the invention

[0024] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Accordingly, in some embodiments, well-known process steps, well-known device structures, and well-known techniques are not specifically described to avoid the present invention being interpreted ambiguously. Throughout the specification, like reference numerals refer to like components.

[0025] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements.

[0026] In each step, identification codes are used for convenience of explanation and do not describe the order of the steps; unless the context clearly indicates a specific order, the steps may be performed differently from the specified order. That is, the steps may be performed in the same order as specified, substantially simultaneously, or in the reverse order.

[0027] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0029] Microbial electrolysis cell including an intermittent voltage supply device and a method for producing hydrogen using the same

[0030] FIG. 1 is a schematic diagram showing a microbial electrolysis cell according to one embodiment of the present invention.

[0031] Referring to FIG. 1, the microbial electrolysis cell (100) includes a chamber (10) in which a microbial electrolysis reaction is performed, an oxidation electrode (anode, 20) and a reduction electrode (cathode, 30) arranged facing each other within the chamber (10). An intermittent voltage (Duty-cycle) supply device (50) is connected to the reduction electrode (cathode, 30) and includes a gas collection device (40) connected to the upper part of the chamber (10) to collect hydrogen generated.

[0032] Microbial electrolytic cells (MEC, 100) can be applied to wastewater treatment processes and can produce green hydrogen while simultaneously performing wastewater treatment.

[0033] In particular, an intermittent voltage (duty cycle) process can be applied to the operation of a Microbial Electrolysis Cell (MEC). A duty cycle is a numerical value representing the ratio of the time a signal is turned on (ON) during one cycle of a signal, expressed as a percentage. Here, a cycle refers to the time taken from when a signal is turned on and off until it is turned on again. By applying an intermittent voltage (duty cycle) process to the operation of a Microbial Electrolysis Cell (MEC), the amount of electrical energy consumed can be reduced, and at the same time, the localized dead zones occurring at the reduction electrode are reduced, thereby efficiently utilizing the surface area of ​​the reduction electrode and increasing hydrogen production.

[0034] The intermittent voltage (duty-cycle) supplied by the above intermittent voltage supply device may have an ON / OFF ratio of 3:1 to 5:1, specifically 4:1, but is not limited thereto. When intermittent voltage is supplied, the supply of electrical energy is cut off during the OFF time, so the amount of electrical energy consumed can be saved compared to the method of supplying continuous voltage.

[0035] The intermittent voltage (Duty-cycle) supplied by the above intermittent voltage supply device may have a non-application (OFF) time of voltage of 5 to 60 seconds, specifically 5 to 30 seconds, and more specifically 5 to 15 seconds. The shorter the non-application (OFF) time, the more effectively the decrease in activity of electroactive bacteria (EAB) can be prevented, thereby increasing the amount of hydrogen generated.

[0036] In particular, when the above ON / OFF ratio is the same, the amount of hydrogen generated increases as the voltage OFF time decreases, and the electrical energy efficiency (η E ), energy efficiency through substrate (η S ) and total energy efficiency (η E+S ) can increase.

[0037] In one embodiment, the off-time of the voltage may be 5 seconds, but is not limited thereto.

[0038] The amount of hydrogen generated by the intermittent voltage (duty-cycle) supplied by the above intermittent voltage supply device may be greater compared to the amount of hydrogen generated by supplying a continuous voltage.

[0039] The electrical energy efficiency (η) of a microbial electrolysis cell due to the intermittent voltage (Duty-cycle) supplied by the above intermittent voltage supply device E ) is the electrical energy efficiency (η) of a microbial electrolysis cell due to continuous voltage application. E It can be increased by 20 to 30 percent compared to ).

[0040] The above reduction electrode (cathode) comprises carbon black, carbon cloth, and a platinum catalyst layer, and an air reduction electrode coated with a diffusion layer may be used before the seeding of electroactive microorganisms, that is, before the microbial culture is completed and a biofilm is formed, and after the seeding of electroactive microorganisms, that is, after the biofilm is formed, the reduction electrode may be changed to one from which the diffusion layer has been removed.

[0042] FIG. 3 is a schematic diagram showing the hydrogen generation mechanism through a microbial electrolysis cell according to (a) a continuous voltage supply and (b) an intermittent voltage supply method according to one embodiment of the present invention.

[0043] Referring to Figure 3, it can be seen that when a constant voltage input is used, some hydrogen generated at the cathode reduces the active surface area of ​​the electrode, causing a localized dead zone and a decrease in hydrogen generation efficiency. On the other hand, when an intermittent voltage input method (ON / OFF duty-cycle voltage input) is used, the localized dead zone at the cathode is reduced, allowing for efficient utilization of the cathode's surface area and improved hydrogen production.

[0044] A method for generating bioelectrochemical hydrogen through intermittent voltage supply according to an example of the present invention may first perform a step (S01) of arranging an air cathode and an oxidation anode coated with a diffusion layer facing each other within a chamber where a microbial electrolysis reaction is performed.

[0045] The air cathode may be equipped with a diffusion layer coated with PTFE (Polytetrafluoroethylene) as an inert polymer coating layer so that electroactive microorganisms are well cultured on the anode and a stable biofilm is formed. Specifically, the air cathode may be a cathode comprising carbon black, a carbon cloth, and a platinum catalyst layer, wherein a PTFE layer is coated on the surface of the carbon black.

[0046] The above oxidation electrode (anode) can use a graphite fiber brush.

[0047] Next, a step (S02) of forming a biofilm by culturing electroactive microorganisms on the oxidation electrode (anode) may be performed.

[0048] The process of forming the above biofilm involves performing the seeding process of the above electroactive microorganism, during which an external resistance, such as 1 kΩ, may be applied for several tens of days, for example, 45 days.

[0049] Afterward, a step (S03) of replacing the air cathode with a cathode can be performed after the formation of the biofilm is completed.

[0050] Finally, a step (S04) of applying an intermittent voltage (Duty-cycle) from an intermittent voltage supply device connected to the cathode and a step (S05) of capturing hydrogen gas generated by the application of the intermittent voltage (Duty-cycle) may be performed.

[0051] The above-mentioned applied intermittent voltage (Duty-cycle) can be used in the same way as described above, and is omitted for the sake of brevity in the specification.

[0052] The present invention will be explained in more detail below using embodiments and comparative examples. However, the following embodiments and comparative examples are for illustrating the present invention and the scope of the present invention is not limited thereto.

[0054] Preparation Example 1: Preparation of a microbial electrolysis cell reactor

[0055] Referring again to FIG. 1, a chamber (10) having an effective volume of 20 ml (total volume 28 mL) was used as a microbial electrolysis cell reactor (100) for batch experiments. The oxidation electrode (anode, 20) was a graphite fiber brush (25 mm * 25 mm) used after heat-treating it in an electric furnace at 450 ℃ for 30 minutes, and the reduction electrode (cathode, 30) was a carbon cloth (7 cm 2 carbon black powder and 0.5 mg / cm² in ) 2 A platinum catalyst was coated and used. A plastic tube (40) with a volume of 16 mL was installed at the top of the chamber to collect hydrogen produced at the reduction electrode (30) of the reactor. A butyl rubber stopper (41) was attached to the top of the tube to prevent air from leaking out, and a 30 mL syringe (not shown) coated with grease was connected to the inside of the butyl rubber stopper to be used as a gas collection device. A power supply was used to apply a duty cycle (intermittent voltage), and an external resistor (10 Ω) was connected to the reduction electrode (cathode, 30).

[0057] Examples 1 to 4: Seeding and operation of microbial electrolytic cells according to the application of a duty cycle

[0058] FIG. 2 is a schematic diagram of (a) a photograph of a microbial electrolysis cell, (b) an air cathode, and (c) a cathode according to Examples 1 to 4 of the present invention.

[0059] Referring to FIG. 2, the operating mechanism of a microbial electrolysis cell according to one embodiment of the present invention can be observed. A microbial electrolysis cell prepared in Preparation Example 1 was used. The inoculum source for the anode was the supernatant of digested sludge that had finished operating in another microbial electrolysis cell reactor (applied voltage 0.3 V, effective volume 2.5 L). The digested sludge supernatant and synthetic wastewater (containing 50 mM phosphate buffer solution (PBS), 5.36 g / L K2HPO4, 2.5 g / L KH2PO4, 0.31 g / L NH4Cl, 16.8 g / L NaHCO3, and trace amounts of minerals and vitamins) with 1 g / L sodium acetate as a carbon source were mixed in a 1:1 volume ratio and injected in a batch manner, and operated in an incubator at a temperature of 30 ℃. To ensure that electroactive microorganisms were properly cultured on the anode and a stable biofilm was formed, the system was operated as a microbial fuel cell (MFC) for 45 days by connecting an air cathode (Fig. 2b) with an external resistance of 1 kΩ and a diffusion layer coated with PTFE (Polytetrafluoroethylene). After seeding was completed, the system was operated by replacing the air cathode (Fig. 2b) with a cathode (Fig. 2c) without PTFE. To apply the duty cycle (intermittent voltage application), a voltage of 0.9 V was applied using a power supply, and an external resistance of 10 Ω was connected. The duty cycle (intermittent voltage application) was operated based on a ratio of ON / OFF = 4:1 for all experimental groups except the control reactor, and the cycle refers to the time required for a signal to complete one ON / OFF cycle.The ON / OFF cycle conditions were 240 seconds / 60 seconds (Example 1), 120 seconds / 30 seconds (Example 2), 60 seconds / 15 seconds (Example 3), and 20 seconds / 5 seconds (Example 4), respectively. The total operating time was 24 hours, after which 50 mM PBS containing 1 g / L sodium acetate was replaced with the new solution for each cycle. Before the start of each cycle, the reactor was purged with N2 gas to maintain an anaerobic state. The generated hydrogen gas was collected using a collection syringe.

[0061] Comparative Example 1: Seeding and operation of a microbial electrolytic cell without applying a duty cycle

[0062] Hydrogen was generated by operating a microbial electrolysis cell in the same manner as in Examples 1 to 4, except that instead of applying a duty cycle (intermittent voltage application) using the power supply of Examples 1 to 4, a DC power supply was used to continuously apply voltage.

[0064] Analysis Example 1: Measurement of Hydrogen Generation Using Gas Chromatography

[0065] The voltage of the reactor was measured every 10 seconds using a data acquisition device connected to a computer. The influent and effluent injected into the reactor were filtered using a 0.45 μm syringe filter, and the SOCD (amount of dissolved organic matter) was measured using the CODCr method (chromium method) to determine the COD (chemical oxygen demand) removal rate. The composition of the reactor headspace and the biogas collected in the syringe was analyzed using gas chromatography (GC) equipped with a thermal conductivity detector (TCD).

[0067] FIG. 4 is a graph showing the amount of hydrogen generated by operating a microbial electrolysis cell according to the voltage application method and duty cycle according to Examples 1 to 4 and Comparative Example of the present invention.

[0068] Referring to Fig. 4, the amount of hydrogen generated by operating the microbial electrolysis cell according to the duty cycle was measured as 25.6 mL under ON / OFF cycle conditions of 240 seconds / 60 seconds (Example 1), 25.7 mL under 120 seconds / 30 seconds (Example 2), 25.9 mL under 60 seconds / 15 seconds (Example 3), and 27.0 mL under 20 seconds / 5 seconds (Example 4). It can be confirmed that the amount of hydrogen generated is higher when voltage is supplied at short intervals at the same ON / OFF ratio of 4:1. While voltage is applied intermittently according to the duty cycle, electroactive bacteria (EABs) at the oxidation electrode (anode) decompose organic matter, causing protons to move to the reduction electrode (cathode) through the internal fluid and electrons to move to the reduction electrode (cathode) through the external circuit, thereby generating hydrogen. The hydrogen bubbles generated at this time remain attached to the surface of the cathode, reducing the surface area of ​​the active electrode to which the catalyst is attached. This decreases the amount of protons transferred to the surface, resulting in a tendency for the amount of hydrogen generated to gradually decrease.

[0069] When the voltage is turned ON again after being turned OFF, the generated hydrogen bubbles detach from the surface of the cathode and move to a collection syringe, thereby restoring the active surface area of ​​the cathode. As the ON / OFF time becomes shorter (240 / 60 → 120 / 30 → 60 / 15 → 20 / 5), the OFF time during which the voltage supply is stopped also becomes shorter, and the decrease in the activity of electroactive bacteria (EAB) when OFF is prevented, thereby increasing the amount of hydrogen generated. On the other hand, as the ON / OFF time becomes longer (20 / 5 → 60 / 15 → 120 / 30 → 240 / 60), the OFF time during which the voltage supply is stopped also becomes relatively longer, and the activity of electroactive bacteria (EAB) is reduced. Even if the active surface area of ​​the cathode is restored, the number of transferred protons decreases, a dead zone where hydrogen is not generated occurs, and the amount of hydrogen generated is small.

[0070] On the other hand, when voltage was continuously applied using a DC power supply (Comparative Example 1, labeled Control), 24.1 mL of hydrogen was generated, and it can be confirmed that the amount of hydrogen generated is significantly lower compared to when voltage was intermittently applied according to a duty cycle with an ON / OFF ratio (Examples 1 to 4).

[0072] Analysis Example 2: Electrical energy efficiency (η) of a microbial electrolysis cell E ), energy efficiency through substrate (η S ) and total energy efficiency (η E+S ) calculate

[0073] FIG. 5 shows the energy efficiency (η) for microbial electrolysis cells operated according to the voltage application method and duty cycle according to Examples 1 to 4 and Comparative Example of the present invention. E ), energy efficiency through substrate (η S ) and total energy efficiency (η E+S) is a graph showing the calculation results, and Table 1 shows the hydrogen generation amount (mL) and energy efficiency (η) for microbial electrolysis cells operated according to the voltage application method and duty cycle according to Examples 1 to 4 and Comparative Examples of the present invention. E ), energy efficiency through substrate (η S ) and total energy efficiency (η E+S This is a table summarizing the calculation results.

[0074] Comparative Example 1 Example 1 (240 seconds / 60 seconds) Example 2 (120 seconds / 30 seconds) Example 3 (60 seconds / 15 seconds) Example 4 (20 seconds / 5 seconds) H2 generation amount (mL) 24.1 25.6 25.7 25.9 27.0 or S (%) 69.0 72.4 69.1 70.0 79.0 or E (%) 97.5 128.4 128.8 129.8 135.4 or E+S (%) 40.4 46.3 45.0 45.5 50.0

[0075] Referring to Fig. 5 and Table 1, the energy efficiency (η) of the microbial electrolysis cell E ), energy efficiency through substrate (η S ) and total energy efficiency (η E+S You can compare the calculation results.

[0076] The hydrogen yield (Y) was calculated using the following Equation 1.

[0077] [Equation 1]

[0078]

[0079] In Equation 1 above, H2 Volume is the amount of hydrogen generated (L), and ΔCOD is the amount of chemical oxygen demand (COD) removed (kg COD).

[0080] Energy efficiency (η) E ) was calculated using the following Equation 2.

[0081] [Equation 2]

[0082]

[0083] In the above Equation 2, n H2 ΔH is the number of moles recovered during one batch. H2 is the combustion enthalpy of hydrogen, which is 285.83 KJ / mol, and W E is electrical energy supplied by passing through an external resistance via a voltage supply device.

[0084] Energy efficiency through the substrate (ηS ) was calculated using the following Equation 3.

[0085] [Equation 3]

[0086]

[0087] In Equation 3 above, W H2 = n H2 ΔH2 and n H2 ΔH is the number of moles recovered during one batch. H2 is the combustion enthalpy of hydrogen, which is 285.83 KJ / mol, and W S is energy supplied through the substrate.

[0088] Total energy efficiency (η) E+S ) was calculated using the following Equation 4.

[0089] [Equation 4]

[0090]

[0091] Energy efficiency through the substrate (η S The efficiency (indicated by the square mark) was highest at 79.0% in Example 4 (ON / OFF = 20 seconds / 5 seconds), which had the shortest ON / OFF time, while no significant numerical difference was observed in Examples 1 to 3 and Comparative Example 1, which had long ON / OFF times. The efficiency with respect to electrical energy (η E When a duty cycle injecting electrical energy through intermittent voltage supply was applied, all ) exhibited high efficiency compared to 97.5% of Comparative Example 1, in which voltage was continuously applied; furthermore, as the ON / OFF time decreased (240 / 60 (Example 1) → 120 / 30 (Example 2) → 60 / 15 (Example 3) → 20 / 5 (Example 4)), the efficiency for electrical energy (η) increased in the order of 128.4%, 128.8%, 129.8%, and 135.4%. E ) showed an increasing trend.

[0092] This is the electrical energy efficiency (η) of a microbial electrolysis cell due to the intermittent voltage (Duty-cycle) supplied by an intermittent voltage supply device. E ) is a result that increased by 20 to 30% compared to the case of continuous voltage application. Therefore, intermittent voltage supply not only saves the amount of electrical energy injection compared to continuous voltage application, but also increases the amount of hydrogen generated because when the voltage is turned ON after being OFF, the generated hydrogen bubbles detach from the cathode surface and move to a capture syringe, thereby restoring the active surface area of ​​the cathode. Therefore, the total energy efficiency (η) E+S The total energy efficiency (η) was 40.4% in Comparative Example 1, whereas it increased to 46.3%, 45.0%, 45.5%, and 49.9% in the order of 240 / 60 (Example 1), 120 / 30 (Example 2), 60 / 15 (Example 3), and 20 / 5 (Example 4). E+S You can confirm that it displays a numerical value.

[0094] The embodiments of the present invention described above are merely exemplary, and the scope of protection of the present invention may include various modifications and equivalents therefrom by those skilled in the art. Explanation of the symbols

[0096] 100: Microbial electrolytic cell 10: Chamber 20: Anode 30: Reduction electrode (cathode) 40: Gas capture device 41: Butyl rubber stopper 50: Voltage supply device applying intermittent voltage

Claims

Claim 1 A method for generating bioelectrochemical hydrogen through intermittent voltage supply, comprising: a step (S01) of arranging an air cathode coated with a diffusion layer and an oxidation electrode (anode) facing each other within a chamber where a microbial electrolysis reaction is performed; a step (S02) of forming a biofilm by culturing electroactive microorganisms on the oxidation electrode (anode); a step (S03) of replacing the air cathode with a reduction electrode (cathode) after the formation of the biofilm is completed; a step (S04) of applying an intermittent voltage (duty-cycle) from an intermittent voltage supply device connected to the reduction electrode (cathode); and a step (S05) of capturing hydrogen gas generated by the application of the intermittent voltage (duty-cycle), wherein the intermittent voltage (duty-cycle) supplied by the intermittent voltage supply device has an ON / OFF voltage application / non-application ratio of 3:1 to 5:

1. Claim 2 delete Claim 3 A method for bioelectrochemical hydrogen generation through intermittent voltage supply, wherein the intermittent voltage (Duty-cycle) supplied by the intermittent voltage supply device has a voltage non-application (OFF) time of 5 to 60 seconds. Claim 4 A method for generating bioelectrochemical hydrogen through intermittent voltage supply according to claim 1, wherein the amount of hydrogen generated by the intermittent voltage (Duty-cycle) supplied by the intermittent voltage supply device is greater compared to the amount of hydrogen generated by supplying a continuous voltage. Claim 5 In claim 1, the electrical energy efficiency (η) of the microbial electrolysis cell by the intermittent voltage (Duty-cycle) supplied by the intermittent voltage supply device E ) is the electrical energy efficiency (η) of a microbial electrolysis cell due to continuous voltage application. E A bioelectrochemical hydrogen generation method through intermittent voltage supply, improved by 20 to 30 percent compared to ). Claim 6 A method for generating bioelectrochemical hydrogen through intermittent voltage supply, wherein the diffusion layer comprises PTFE (Polytetrafluoroethylene) as a polymer coating layer in accordance with claim 1. Claim 7 A microbial electrolysis cell comprising: a chamber in which a microbial electrolysis reaction is performed; an oxidation electrode (anode) and a reduction electrode (cathode) disposed facing each other within the chamber; a duty-cycle supply device connected to the reduction electrode (cathode); and a gas collection device connected to the upper part of the chamber to collect generated hydrogen; wherein the duty-cycle supplied by the duty-cycle supply device is characterized by having an ON / OFF voltage application / non-application ratio of 3:1 to 5:

1. Claim 8 delete Claim 9 A microbial electrolysis cell according to claim 7, characterized in that the intermittent voltage (Duty-cycle) supplied by the intermittent voltage supply device has a voltage non-application (OFF) time of 5 to 60 seconds. Claim 10 A microbial electrolysis cell according to claim 7, characterized in that the amount of hydrogen generated by the intermittent voltage (Duty-cycle) supplied by the intermittent voltage supply device is greater compared to the amount of hydrogen generated by supplying a continuous voltage. Claim 11 In claim 7, the electrical energy efficiency (η) of the microbial electrolysis cell by the intermittent voltage (Duty-cycle) supplied by the intermittent voltage supply device. E ) is the electrical energy efficiency (η) of a microbial electrolysis cell due to continuous voltage application. E A microbial electrolysis cell characterized by being 20 to 30% better than ). Claim 12 A microbial electrolysis cell according to claim 7, wherein the reduction electrode (cathode) comprises carbon black, carbon cloth, and a platinum catalyst layer, and wherein an air reduction electrode (air cathode) coated with a diffusion layer is used before seeding of electroactive microorganisms, and after seeding of electroactive microorganisms, the reduction electrode is changed to one from which the diffusion layer has been removed. Claim 13 A microbial electrolysis cell according to claim 12, characterized in that the above-mentioned diffusion layer comprises PTFE (Polytetrafluoroethylene) as a polymer coating layer.

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