Microbial electrosynthesis device and method using conductive gas permeable membrane composite cathode

Abstract

This invention discloses a microbial electrosynthesis carbon fixation device and method employing a conductive and breathable membrane composite cathode, belonging to the field of carbon dioxide resource utilization. The device uses a stacked reactor, with its cathode chamber containing an integrated functional composite cathode composed of three layers: a conductive and breathable layer using a conductive and breathable hollow fiber membrane to achieve gaseous carbon dioxide supply and electron transfer; a diffusion-enhancing layer consisting of a three-dimensional porous carbon-based material coating the outer surface to optimize mass transfer and current distribution; and a bio-attachment layer consisting of a micro / nanofiber network grown on the surface of the conductive and breathable membrane, extending into the pores of the diffusion-enhancing layer. Carbon dioxide diffuses through the hollow fiber membrane in the gas phase, while electrons are transferred via the membrane-carbon-based-fiber network, synergistically driving microorganisms to reduce it into high-value chemicals. This invention overcomes the bottlenecks in gas-phase mass transfer and bio-electron interface transfer, featuring a compact structure, high modularity, and ease of scalability, providing an innovative solution for efficient microbial electrosynthesis carbon fixation.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide resource utilization technology, and relates to a microbial electrosynthesis carbon fixation device and method using a conductive and breathable membrane composite cathode. Background Technology

[0002] With the acceleration of global industrialization, greenhouse gas emissions have increased dramatically, especially the excessive emission of carbon dioxide (CO2), which has become a major driver of global warming. In response, the international community has set carbon neutrality targets, and carbon capture and utilization (CCU) technology has become a key pathway to address climate change. Converting captured CO2 into high-value-added chemicals and fuels not only reduces carbon emissions but also creates economic value, forming a virtuous cycle. Traditional chemical catalytic conversion methods often require harsh conditions of high temperature and pressure, resulting in high energy consumption, expensive catalysts, and low product selectivity. Therefore, developing a CO2 conversion technology that can operate at ambient temperature and pressure, is environmentally friendly and pollution-free, and can directionally synthesize specific products is of great significance for developing a low-carbon economy.

[0003] Microbial electrosynthesis (MES) technology ingeniously combines electrochemistry with biocatalysis, utilizing electroactive microorganisms as living catalysts to accept electrons on the cathode surface and reduce CO2 to synthesize a series of organic compounds such as methane, acetic acid, and ethanol. MES processes are typically carried out at ambient temperature and pressure, with mild reaction conditions. Relying on the exceptional specific catalytic capabilities of microorganisms, it can achieve highly efficient synthesis of single or specific target products, avoiding the problems of product complexity and separation difficulties encountered in traditional chemical catalysis.

[0004] Patent application CN201710461719.9 discloses a MES method for producing volatile fatty acids by reducing carbon dioxide using mixed anaerobic microorganisms. This method employs a typical two-chamber reactor configuration, relying on conventional carbon electrode materials and the dissolution of carbon dioxide in the catholyte for mass transfer. While this design represents progress in microbial community regulation, its reactor configuration inherently suffers from long mass transfer paths, gas-liquid-solid interface separation, limited space utilization, and difficulty in modular scaling. The stacked reactor configuration of this invention, through its compact layered design, significantly improves the integration and space utilization efficiency of the reaction units. It not only effectively shortens the mass transfer and electron transport distances but also facilitates modular expansion and large-scale scaling of the system.

[0005] Patent application CN202210968224.6 discloses an electrolytic gas-lift MES reactor, consisting of a tubular electrolyzer at the bottom, a gas-lift bubbling tower at the top, and an outdoor circulating gas path for the cathode. Its core principle is the in-situ generation of micro / nano hydrogen bubbles through the tubular electrolyzer at the bottom, and the use of the gas-lift bubbling tower to achieve thorough mixing and mass transfer between the gas phase (carbon dioxide and H2) and suspended microorganisms. Although this design enhances mixing efficiency through gas circulation and a flow guide, its mass transfer process essentially still relies on the dissolution and diffusion of bubbles in the liquid phase, failing to overcome the fundamental mass transfer limitation of low carbon dioxide solubility in water. This invention, by employing a direct gas-phase mass transfer interface constructed with a conductive and permeable hollow fiber membrane, completely avoids the liquid-phase dissolution step of carbon dioxide, fundamentally solving the mass transfer bottleneck problem.

[0006] Patent application CN202110803191.5 discloses a MES reactor that uses a hollow fiber membrane to supply CO2, employing a combination of stainless steel sheets and a biological carrier. The electrodes, combining stainless steel sheets and the biological carrier, enhance electron transfer; the hollow fiber membrane provides sufficient carbon source to the microorganisms in the biological carrier through bubble-free aeration. While this patented solution addresses the problem limiting anaerobic biofilm activity, its system is essentially a physical functional superposition. Electrons originate from the stainless steel cathode, resulting in a long and inefficient transmission path. Furthermore, the attachment space provided by the biological carrier does not completely overlap with the optimal CO2 supply area, leading to insufficient space utilization efficiency within the reactor. This invention spatially integrates gas supply, electron conduction, and microbial attachment, creating a highly coupled "carbon source-electron-microorganism" reaction interface, significantly improving interface efficiency and space utilization.

[0007] Patent application CN202310533804.7 discloses a method for enhancing bioelectrosynthesis to achieve CO2 resource recovery. This method utilizes electrodes obtained by modifying or altering ordinary carbon electrode materials with redox substances or porous functional materials with good conductivity as biocathodes, effectively improving the electron transfer rate between the electrode and microorganisms, thereby promoting the efficiency of processes such as CO2 reduction to methanogenesis. However, this method involves complex modification processes, and the long-term stability of the electrode and the risk of media loss remain potential challenges. To construct an efficient, stable, and integrated MES system, further improvements to the gas mass transfer and electron transfer mechanisms are needed. This invention employs a structurally integrated functional layered composite membrane cathode, achieving stable and direct electron conduction through the material's inherent properties, avoiding the risks of adding and losing exogenous media, while also possessing highly efficient gas-phase mass transfer capabilities. This provides a more promising solution for achieving a stable, efficient, and integrated MES system. Summary of the Invention

[0008] The purpose of this invention is to provide a microbial electrosynthesis carbon fixation device and method that uses a functional layered composite membrane as the cathode and can simultaneously achieve efficient mass transfer of gas-phase CO2, hierarchical electron conduction, and stable attachment of microorganisms.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A microbial electrosynthesis carbon fixation device employing a conductive and breathable membrane composite cathode is characterized by comprising a stacked reactor, wherein the stacked reactor comprises an anode chamber, an ion exchange membrane, and a cathode chamber stacked sequentially from left to right; The cathode chamber is equipped with a composite biological cathode, and the anode chamber is equipped with an anode; It also includes a gas supply system for providing carbon dioxide to the cathode chamber, a liquid inlet system and a liquid outlet system for providing liquid inlet and outlet to the stacked reactor, and an external circuit system connecting the anode and the composite biocathode. The composite biocathode comprises a conductive and breathable hollow fiber membrane and a diffusion-enhancing material; the conductive and breathable hollow fiber membrane is used to realize direct mass transfer of carbon dioxide in the gas phase and electron transfer; the diffusion-enhancing material is a porous conductive material, which is sandwiched around the conductive and breathable hollow fiber membrane and composited by hot pressing or conductive adhesive.

[0010] Preferably, the gas supply system includes a carbon dioxide gas source, a gas flow controller, and a gas distribution pipe; the gas distribution pipe is located at the bottom or side of the cathode chamber, the inlet of the gas distribution pipe is connected to a carbon dioxide gas cylinder through the gas flow controller, and the outlet of the gas distribution pipe is sealed to the inlet of the cavity of the conductive and breathable hollow fiber membrane, for supplying carbon dioxide gas into the cavity of the conductive and breathable hollow fiber membrane.

[0011] Preferably, the liquid inlet and outlet system includes an anolyte inlet located at the lower part of the anode chamber and an anolyte outlet located at the upper part; a catholyte inlet located at the lower part of the cathode chamber and a catholyte outlet located at the upper part; the catholyte inlet and the catholyte outlet are connected to an external catholyte circulation tank and circulation pump to form a catholyte circulation loop.

[0012] Preferably, the external circuit system includes a DC power supply, wires, and an adjustable resistor; the positive terminal of the DC power supply is connected to the anode via a wire, and the negative terminal of the DC power supply is connected to the composite biological cathode via a wire; the adjustable resistor is connected in series between the DC power supply and the composite biological cathode to adjust the current intensity or cathode potential.

[0013] Preferably, the conductive and breathable hollow fiber membrane is prepared by any of the following methods: (1) The spinning solution containing conductive filler and hydrophobic polymer is extruded into shape using a dry-wet electrospinning process; (2) First, a hollow fiber membrane is made from a spinnable polymer, and then it is subjected to high-temperature carbonization treatment; (3) Construct a conductive coating on the surface of a hollow fiber membrane substrate by chemical vapor deposition, in-situ polymerization or impregnation coating method; The conductive and breathable hollow fiber membrane has a micro-nano pore structure in its membrane wall, which allows carbon dioxide gas to pass through while blocking liquid water, and the membrane body or surface layer has conductive pathways.

[0014] Preferably, the diffusion-enhancing material is a porous conductive material with a three-dimensional interconnected pore structure, including carbon fiber felt, carbon foam, or metal foam.

[0015] Preferably, the composite biocathode further includes a micro / nanofiber layer attached to the outer surface of the conductive and breathable hollow fiber membrane and the diffusion-reinforcing material; the micro / nanofiber layer comprises a conductive polymer and a biocompatible material, which are composited by an electrospinning process to enhance the attachment of microorganisms to the composite cathode and the electron transfer at the cathode interface.

[0016] Preferably, the top of the cathode chamber is provided with a gas collection port for collecting gaseous products generated during the reaction; the top of the anode chamber is provided with an exhaust port.

[0017] Preferably, the anode is a carbon felt, carbon cloth, or metal mesh electrode; the ion exchange membrane is a cation exchange membrane.

[0018] In addition, the present invention also provides a method for microbial electrosynthetic carbon fixation based on a microbial electrosynthetic carbon fixation device employing a conductive and breathable membrane composite cathode, comprising the following steps: Step S1: Assemble the microbial electrosynthesis carbon fixation device, and inject the corresponding liquids into the cathode chamber and anode chamber respectively, while simultaneously inoculating microorganisms; Step S2: Connect the carbon dioxide gas source to the conductive and breathable hollow fiber membrane cavity of the composite biocathode through the gas supply system. Step S3: The external circuit system is connected and the DC power supply is turned on to control the cathode potential; Step S4: While maintaining the circulation of cathodic liquid, continuously introduce carbon dioxide gas into the membrane cavity so that microorganisms can use carbon dioxide and electrons to synthesize products. Step S5: Collect the liquid products flowing out with the cathode liquid, and at the same time, export the gaseous products from the gas collection port of the cathode chamber.

[0019] Preferably, the cathode potential is controlled at -0.6 V to -1.0 V relative to a standard hydrogen electrode; the carbon dioxide gas pressure is maintained at a level slightly higher than the hydrostatic pressure of the liquid column in cathode chamber 2.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention uses an integrated composite cathode that integrates gas phase carbon dioxide supply, electron transfer and microbial attachment functions to form a highly efficient coupled reaction interface.

[0021] 2) This invention enables direct diffusion of carbon dioxide in the gas phase through a conductive and breathable hollow fiber membrane, overcoming the limitations of liquid-phase mass transfer and improving mass transfer efficiency.

[0022] 3) This invention achieves graded electron transfer and high-density microbial attachment through a three-layer composite structure (conductive and breathable layer, diffusion enhancement layer, and bio-attachment layer).

[0023] 4) The cathode of this invention conducts electricity through its own material, without the need for an external medium, thus avoiding loss and deactivation and making the operation more stable.

[0024] 5) The device of the present invention has a rectangular double-chamber structure, which is easy to modularize and scale up, and is equipped with an integrated control system, which facilitates continuous operation.

[0025] 6) The method of the present invention operates at normal temperature and pressure, and can efficiently convert carbon dioxide into high-value chemicals such as methane and acetic acid by adjusting the conditions, thus achieving both emission reduction and resource utilization benefits. Attached Figure Description

[0026] Figure 1 A schematic diagram of a microbial electrosynthesis carbon fixation device employing a conductive and breathable membrane composite cathode is provided for an embodiment of the present invention. Figure 2 A vertically enlarged structural schematic diagram of the composite biocathode in a microbial electrosynthesis carbon fixation device employing a conductive and breathable membrane composite cathode, provided for an embodiment of the present invention; Figure 3 This is a magnified lateral view of the composite biocathode in a microbial electrosynthesis carbon fixation device employing a conductive and breathable membrane composite cathode, provided as an embodiment of the present invention.

[0027] The serial numbers in the diagram are as follows: 1. Anode chamber, 2. Cathode chamber, 3. Ion exchange membrane, 4. Composite biocathode, 5. Conductive and breathable hollow fiber membrane, 6. Diffusion-enhancing material, 7. Micro / nanofiber layer, 8. Anode, 9. External circuit system, 10. Carbon dioxide gas source, 11. Gas flow controller, 12. Gas distribution pipe, 13. Anode liquid inlet, 14. Anode liquid outlet, 15. Cathode liquid inlet, 16. Cathode liquid outlet, 17. Cathode liquid circulation tank, 18. Circulation pump, 19. DC power supply, 20. Adjustable resistor, 21. Gas collection port, 22. Exhaust port. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] Example 1

[0030] like Figure 1 As shown, a microbial electrosynthesis carbon fixation device employing a conductive and breathable membrane composite cathode is a stacked reactor. It includes an anode chamber 1, a cation exchange membrane 3, and a cathode chamber 2 stacked sequentially from left to right. A composite biocathode 4 is disposed within the cathode chamber 2. An anode 8 is disposed within the anode chamber 1. The device also includes a gas supply system for providing carbon dioxide to the cathode chamber 2, a liquid inlet system and a liquid outlet system for providing liquid inlet and outlet to the stacked reactor, and an external circuit system 9 connecting the anode 8 and the composite biocathode 4.

[0031] In this embodiment, the composite biocathode 4 includes a conductive and permeable layer and a diffusion-enhancing material 6. The conductive and permeable layer of the composite biocathode 4 is a conductive and permeable hollow fiber membrane 5 prepared by high-temperature carbonization of polyacrylonitrile hollow fiber membrane, used to realize direct mass transfer of carbon dioxide gas phase and electron transfer.

[0032] The diffusion-strengthening material 6 is made of carbon foam material, which is used to wrap the hollow fiber membrane 5 bundles in a sandwich manner and then composited by hot pressing.

[0033] like Figure 2 and Figure 3 As shown, in this embodiment, the composite biocathode 4 further includes a bio-attachment layer attached to the outer surface of the conductive and breathable hollow fiber membrane 5 and the diffusion-reinforcing material 6. The bio-attachment layer is a micro / nanofiber layer 7 formed on the surface of the composite structure. The micro / nanofiber layer 7 includes a conductive polymer and a biocompatible material. The conductive polymer and the biocompatible material are formed on the surface of the composite structure by electrospinning a poly(3,4-ethylenedioxythiophene) and gelatin composite micro / nanofiber network, which is used to enhance the attachment of microorganisms on the composite cathode and the electron transfer at the cathode interface.

[0034] Furthermore, in this embodiment, the anode 8 is a carbon cloth electrode; the ion exchange membrane 3 is a cation exchange membrane.

[0035] The gas supply system includes a carbon dioxide gas source 10, a gas flow controller 11, and a gas distribution pipe 12. The gas distribution pipe 12 is located at the bottom or side of the cathode chamber 2. The inlet of the gas distribution pipe 12 is connected to a carbon dioxide gas cylinder through the gas flow controller 11, and its outlet is sealed to the inlet of the cavity of the conductive and breathable hollow fiber membrane 5, for supplying carbon dioxide gas into the cavity of the conductive and breathable hollow fiber membrane 5.

[0036] The liquid inlet and outlet system includes an anolyte inlet 13 located at the lower part of the anode chamber 1 and an anolyte outlet 14 located at the upper part; a catholyte inlet 15 located at the lower part of the cathode chamber 2 and a catholyte outlet 16 located at the upper part; the catholyte inlet 15 and the catholyte outlet 16 are connected to an external catholyte circulation tank 17 and a circulation pump 18 to form a catholyte circulation loop.

[0037] The external circuit system 9 includes a DC power supply 19, wires, and an adjustable resistor 20; the positive terminal of the DC power supply 19 is connected to the anode 8 through a wire, and the negative terminal of the DC power supply 19 is connected to the composite biocathode 4 through a wire; the adjustable resistor 20 is connected in series between the DC power supply 19 and the composite biocathode 4 to adjust the current intensity or cathode potential.

[0038] Furthermore, in this embodiment, the conductive and breathable hollow fiber membrane 5 is prepared by any of the following methods: A dry-wet electrospinning process is used to extrude a spinning solution containing conductive fillers and hydrophobic polymers. First, a hollow fiber membrane is made from a spinnable polymer, and then it undergoes high-temperature carbonization treatment. A conductive coating is constructed on the surface of a hollow fiber membrane substrate by chemical vapor deposition, in-situ polymerization, or impregnation coating. The membrane wall of the conductive and breathable hollow fiber membrane 5 has a micro-nano pore structure to allow carbon dioxide gas to pass through and block liquid water, and the membrane or its surface has conductive pathways.

[0039] Furthermore, in this embodiment, the top of the cathode chamber 2 is provided with a gas collection port 21 for collecting gaseous products generated during the reaction process; the top of the anode chamber 1 is provided with an exhaust port 22.

[0040] In this embodiment, the anolyte is a 50 mM phosphate buffer solution, and the catholyte is a basal culture medium containing minerals, vitamins, and trace elements. The cathode chamber is inoculated with a mixed methanogenic bacterial community enriched and cultured from anaerobic sludge.

[0041] In addition, the following steps are included when performing microbial electrosynthesis carbon fixation using the above-mentioned device: Step S1: Assemble the microbial electrosynthesis carbon fixation device, and inject the corresponding liquids into the cathode chamber 2 and anode chamber 1 respectively, while simultaneously inoculating microorganisms; Step S2: Connect the carbon dioxide gas source 10 to the conductive and breathable hollow fiber membrane 5 cavity of the composite biocathode 4 through the gas supply system. Step S3: The external circuit system 9 is connected and the DC power supply 19 is turned on to control the cathode potential; Step S4: While maintaining the circulation of cathodic liquid, continuously introduce carbon dioxide gas into the membrane cavity so that microorganisms can use carbon dioxide and electrons to synthesize products. Step S5: Collect the liquid products flowing out with the cathode liquid, and at the same time, discharge the gaseous products from the gas collection port 21 of the cathode chamber 2.

[0042] The operating conditions are: temperature 35±1℃, cathode potential controlled at -0.8 V (relative to the standard hydrogen electrode), carbon dioxide supply pressure 1.5 kPa higher than the static pressure of the cathode liquid column, and cathode liquid circulation flow rate of 5 mL / min.

[0043] In practical applications, the device in this embodiment operated continuously for 20 days, with a stable methane yield of 120 mL / L per day, an average coulombic efficiency of 82%, and a carbon dioxide conversion rate exceeding 90%. The system operated stably, the composite biocathode 4 structure remained intact, and the biofilm adhered well.

[0044] Example 2:

[0045] like Figure 1 As shown, a microbial electrosynthesis carbon fixation device using a conductive and breathable membrane composite cathode is constructed with a structure essentially the same as that in Example 1. It includes a stacked reactor comprising an anode chamber 1, an ion exchange membrane 3, and a cathode chamber 2 stacked sequentially from left to right; a composite biocathode 4 is disposed within the cathode chamber 2, and an anode 8 is disposed within the anode chamber 1.

[0046] In this embodiment, the conductive and breathable layer of the composite biocathode 4 is a conductive and breathable hollow fiber membrane 5 prepared by constructing a graphene conductive coating on the surface of a polytetrafluoroethylene hollow fiber membrane using chemical vapor deposition; the diffusion strengthening material 6 is a stainless steel metal foam material; the bio-attachment layer is a micro / nanofiber layer 7 formed on the outer surface of the composite structure, which is composed of a polyaniline and chitosan composite micro / nanofiber network. The anode is an anode 8, which is a titanium-based ruthenium dioxide coated electrode.

[0047] The composite biocathode 4 includes a conductive and breathable hollow fiber membrane 5 and a diffusion-enhancing material 6. The diffusion-enhancing material 6 wraps the conductive and breathable hollow fiber membrane 5 in a sandwich manner to form a composite conductive structure. The outer surface of the composite biocathode 4 is further formed with a micro-nano fiber layer 7 to enhance microbial attachment and interfacial electron transfer.

[0048] In this embodiment, cathode chamber 2 is inoculated with acetic acid-producing bacteria enriched and cultured from sludge from the anaerobic digester of a wastewater treatment plant.

[0049] The operating conditions are: temperature 30±1℃, cathode potential controlled at -0.6 V (relative to the standard hydrogen electrode), carbon dioxide supply pressure 1.0 kPa higher than the static pressure of the liquid column in cathode chamber 2, and cathode liquid circulation flow rate of 10 mL / min.

[0050] In practical applications, the device in this embodiment operated continuously for 15 days, with a stable acetic acid yield of 200 mg / L per day, a selectivity of over 85%, and a coulombic efficiency of 78%. During system operation, the composite biocathode 4 exhibited stable conductivity and no significant biofilm shedding was observed, achieving efficient and directional conversion of carbon dioxide to acetic acid.

[0051] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A microbial electrosynthesis carbon fixation device employing a conductive and breathable membrane composite cathode, characterized in that, The reactor includes a stacked reactor comprising an anode chamber (1), an ion exchange membrane (3), and a cathode chamber (2) stacked from left to right. The cathode chamber (2) is provided with a composite biological cathode (4), and the anode chamber (1) is provided with an anode (8). It also includes a gas supply system for providing carbon dioxide to the cathode chamber (2), a liquid inlet system and a liquid outlet system for providing liquid inlet and outlet to the stacked reactor, and an external circuit system (9) connecting the anode (8) and the composite biocathode (4). The composite biocathode (4) includes a conductive and breathable hollow fiber membrane (5) and a diffusion-enhancing material (6); the conductive and breathable hollow fiber membrane (5) is used to realize direct mass transfer of carbon dioxide gas phase and electron transfer; the diffusion-enhancing material (6) is a porous conductive material, which is wrapped around the conductive and breathable hollow fiber membrane (5) by a core-sandwich method and composited by hot pressing or conductive adhesive.

2. The microbial electrosynthesis carbon fixation device using a conductive and breathable membrane composite cathode according to claim 1, characterized in that, The gas supply system includes a carbon dioxide gas source (10), a gas flow controller (11), and a gas distribution pipe (12). The gas distribution pipe (12) is located at the bottom or side of the cathode chamber (2). The inlet of the gas distribution pipe (12) is connected to a carbon dioxide gas cylinder through the gas flow controller (11). The outlet of the gas distribution pipe (12) is sealed to the inlet of the cavity of the conductive and breathable hollow fiber membrane (5) for supplying carbon dioxide gas into the cavity of the conductive and breathable hollow fiber membrane (5).

3. The microbial electrosynthesis carbon fixation device using a conductive and breathable membrane composite cathode according to claim 1, characterized in that, The liquid inlet and outlet system includes an anolyte inlet (13) located at the bottom of the anode chamber (1) and an anolyte outlet (14) located at the top; a cathode inlet (15) located at the bottom of the cathode chamber (2) and a cathode outlet (16) located at the top; the cathode inlet (15) and the cathode outlet (16) are connected to an external cathode circulation tank (17) and circulation pump (18) to form a cathode circulation loop.

4. The microbial electrosynthesis carbon fixation device using a conductive and breathable membrane composite cathode according to claim 1, characterized in that, The external circuit system (9) includes a DC power supply (19), wires and an adjustable resistor (20); the positive terminal of the DC power supply (19) is connected to the anode (8) through a wire, and the negative terminal of the DC power supply (19) is connected to the composite biocathode (4) through a wire; the adjustable resistor (20) is connected in series between the DC power supply (19) and the composite biocathode (4) to adjust the current intensity or cathode potential.

5. The microbial electrosynthesis carbon fixation device using a conductive and breathable membrane composite cathode according to claim 1, characterized in that, The conductive and breathable hollow fiber membrane (5) is prepared by any of the following methods: A dry-wet electrospinning process is used to extrude a spinning solution containing conductive fillers and hydrophobic polymers. First, a hollow fiber membrane is made from a spinnable polymer, and then it undergoes high-temperature carbonization treatment. A conductive coating is constructed on the surface of a hollow fiber membrane substrate by chemical vapor deposition, in-situ polymerization, or impregnation coating. The conductive and breathable hollow fiber membrane (5) has a micro-nano pore structure in its membrane wall, which allows carbon dioxide gas to pass through and blocks liquid water, and the membrane or its surface layer has a conductive path.

6. The microbial electrosynthesis carbon fixation device using a conductive and breathable membrane composite cathode according to claim 1, characterized in that, The diffusion-strengthening material (6) is a porous conductive material with a three-dimensional interconnected pore structure, including carbon fiber felt, carbon foam or metal foam material.

7. The microbial electrosynthesis carbon fixation device using a conductive and breathable membrane composite cathode according to claim 1, characterized in that, The composite biocathode (4) also includes a micro / nanofiber layer (7) attached to the outer surface of the conductive and breathable hollow fiber membrane (5) and the diffusion-enhancing material (6); the micro / nanofiber layer (7) includes a conductive polymer and a biocompatible material, which are combined by electrospinning process to enhance the attachment of microorganisms on the composite cathode and the electron transfer at the cathode interface.

8. The microbial electrosynthesis carbon fixation device using a conductive and breathable membrane composite cathode according to claim 1, characterized in that, The top of the cathode chamber (2) is provided with a gas collection port (21) for collecting gaseous products generated during the reaction; the top of the anode chamber (1) is provided with an exhaust port (22).

9. A microbial electrosynthesis carbon fixation device employing a conductive and breathable membrane composite cathode according to claim 1, characterized in that, The anode (8) is a carbon felt, carbon cloth or metal mesh electrode; the ion exchange membrane (3) is a cation exchange membrane.

10. A method for microbial electrosynthetic carbon fixation based on the microbial electrosynthetic carbon fixation device using a conductive and breathable membrane composite cathode as described in claim 1, characterized in that, Includes the following steps: Step S1: Assemble the microbial electrosynthesis carbon fixation device and inject the corresponding liquids into the cathode chamber (2) and anode chamber (1) respectively, while inoculating microorganisms; Step S2: Connect the carbon dioxide gas source (10) to the conductive and breathable hollow fiber membrane (5) cavity of the composite biocathode (4) through the gas supply system; Step S3: The external circuit system (9) is connected and the DC power supply (19) is turned on. The cathode potential is controlled between -0.6 V and -1.0 V (relative to the standard hydrogen electrode). Step S4: Under the condition of maintaining the circulation of cathodic liquid, carbon dioxide gas is continuously introduced into the membrane cavity so that microorganisms can use carbon dioxide and electrons to synthesize products. The carbon dioxide gas pressure is maintained at a level slightly higher than the static pressure of the liquid column in the cathode chamber (2). Step S5: Collect the liquid products flowing out with the cathode liquid, and at the same time, export the gaseous products from the gas collection port (21) of the cathode chamber (2).

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