Snakelike flow field-based in-situ hydrogen production microbial electroreduction CO2 reactor and reduction method

Abstract

The invention belongs to the technical field of microbial electrosynthesis, and particularly relates to a microbial electroreduction CO2 reactor based on snakelike flow field in-situ hydrogen production and a reduction method.The reactor comprises a first cover plate, a second cover plate, an anode, an anode plate, a proton exchange membrane, cathode carbon cloth, a cathode plate and a graphite collector plate; both the anode plate and the cathode plate are provided with snake-shaped runner reaction cavities and are provided with gas-liquid inlets and outlets; a silica gel waterproof gasket is arranged between any two adjacent silica gel waterproof gaskets; the cathode carbon cloth electrolyzes water to generate in-situ micro-nano hydrogen bubbles, and hydrogen and CO2 are converted into corresponding organic acid by microorganisms in the snake-shaped flow channel of the cathode. According to the method, the retention time of CO2 can be remarkably prolonged, the utilization efficiency of carbon, electrons and hydrogen can be enhanced, mass transfer can be enhanced, and the reaction pressure drop can be effectively reduced, so that the hydrogen yield and the CO2 conversion efficiency are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial electrosynthesis, and in particular to a CO2 reduction reactor and a reduction method based on a serpentine flow field for in-situ hydrogen production by microbial electroreduction. Background Art

[0002] In today's world, the massive consumption of fossil energy has led to a continuous increase in carbon dioxide emissions, which has had a severe impact on global ecosystems and the carbon cycle. Therefore, reducing carbon dioxide emissions and reusing it as a resource have become key challenges that need to be overcome. In recent years, renewable energy sources such as wind, solar, and hydropower have experienced rapid development. However, the inherent intermittent and fluctuating nature of these energy sources has resulted in low energy efficiency and a significant waste of installed capacity. Therefore, how to efficiently store and utilize renewable energy has become a research hotspot. Using renewable electricity to drive novel chemical reactors to capture and convert carbon dioxide is a solution that has attracted much attention. Compared with traditional methods, this technology not only helps reduce carbon emissions but also improves energy efficiency. However, it still faces many challenges in terms of efficiency, stability, and large-scale application.

[0003] Converting carbon dioxide into high-value-added chemicals or fuels can not only alleviate the problem of energy waste, but also provide a new path to reduce carbon emissions. This method can store intermittent renewable electricity and realize the resource utilization of carbon dioxide, and therefore has attracted much attention. In recent years, many studies have focused on the development of efficient electrochemical technologies in order to promote the feasibility and practical application of this process. Although some progress has been made in related fields, such as catalyst development, electrolyte modification and reactor design, carbon dioxide reduction technology still faces multiple challenges. The main problems at present include the need to improve the activity and stability of catalytic materials, and the need to further optimize the selectivity of product types and reaction energy efficiency. These bottlenecks have restricted the progress of technology from the laboratory to industrialization and have become key problems that need to be solved urgently.

[0004] Microbial electrosynthesis (MES) is a technology that uses microorganisms as catalysts to electrochemically convert carbon dioxide into organic compounds (such as methane, acetic acid, or butyric acid). Microorganisms offer unique advantages in MES, such as high product selectivity, good stability (self-regeneration), and the ability to generate long-chain organic compounds. This technology, which combines biocatalysis with electrochemical reactions, provides a sustainable pathway for the resource utilization of carbon dioxide and has important environmental and energy implications. In recent years, rapid progress has been made in the discovery of electroactive microorganisms, the study of electron transfer mechanisms between cathodes and microorganisms, and the optimization of electrode materials. However, MES technology still faces challenges in practical application. Compared with pure electrochemical reduction technology, its product generation rate is relatively low, mainly due to the inefficient electron transfer from the electrode to the microorganism, which directly affects the current density and overall efficiency of the reaction system.

[0005] Although researchers worldwide have conducted extensive research on microbial electrosynthesis (MES) reactors and achieved significant progress in reactor structure optimization, electrode material improvement, and process parameter control, many challenges remain in practical application. For example, they address flow channel design, biofilm growth control, reactor surface area optimization, and increased conversion of organic acid products. Current technologies do not fully meet the requirements for efficient operation. Furthermore, the low efficiency of electron transfer from electrodes to microorganisms makes it difficult to further increase the current density of the reaction system, limiting the overall synthesis rate. To address these challenges, it is necessary to design a new MES reactor with higher mass transfer efficiency, larger surface area, and enhanced biofilm growth capacity. Furthermore, by optimizing the reactor structure and materials, electron transfer efficiency can be further enhanced, improving the selectivity and conversion of target organic acid products, thereby promoting the industrial application of MES technology. Summary of the Invention

[0006] Current challenges in CO2 reduction technology include the need to improve the activity and stability of catalytic materials, as well as further optimization of product selectivity and reaction energy efficiency. These bottlenecks hinder the technology's transition from laboratory to industrial scale, and represent key challenges that urgently need to be addressed. This present invention addresses these challenges by proposing a reactor and method for in-situ hydrogen production using a serpentine flow field.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A microbial electroreduction CO2 reactor for in-situ hydrogen production based on a serpentine flow field, comprising an anode, an anode plate, a proton exchange membrane, a cathode plate, and a current collecting plate, which are sequentially arranged between a first cover plate and a second cover plate;

[0009] The anode plate and the cathode plate are provided with flow channels that penetrate on both sides;

[0010] The side of the anode plate is provided with an oxygen outlet and an anolyte inlet, which are respectively located at the two ends of the flow channel of the anode plate;

[0011] The cathode plate is provided with an exhaust gas outlet and a CO2 inlet on the side thereof, which are respectively located at the two ends of the flow channel of the cathode plate; a cathode is arranged in the flow channel of the cathode plate;

[0012] Lead out wires from the anode and cathode respectively and connect to an external DC power supply;

[0013] The edges of the first cover plate and the second cover plate are pulled and tied to each other, and waterproof gaskets are provided between the second cover plate and the anode, between the anode and the anode plate, between the anode plate and the proton exchange membrane, between the proton exchange membrane and the cathode plate, between the cathode plate and the current collecting plate, and between the current collecting plate and the first cover plate. Under the pulling pressure of the first cover plate and the second cover plate, sealing is achieved at the edges of the waterproof gaskets.

[0014] As a further preferred solution, the flow channel is a serpentine flow channel structure.

[0015] As a further preferred solution, the anode is a ruthenium-iridium-titanium mesh; the cathode is a carbon cloth; and the current collecting plate is made of graphite.

[0016] As a further preferred solution, the flow channel of the anode plate is filled with anolyte, which is water; and the flow channel of the cathode plate is filled with catholyte.

[0017] As a further preferred solution, the exhaust gas outlet and the CO2 inlet are externally connected to a CO2 gas circulation pump; the anode liquid inlet is externally connected to an anode liquid replenishing pump.

[0018] As a further preferred solution, the anode plate and the cathode plate have the same structural dimensions, 40 cm in length, 50 cm in width, and 3 cm in thickness.

[0019] As a further preferred embodiment, the serpentine flow channel structures of the anode plate and the cathode plate have the same size, including seven parallel channels connected end to end, wherein the width of the first channel at the inlet of the serpentine flow channel structure is 2 cm, the width of the second and third channels is 2.2 cm, the width of the fourth and fifth channels is 2.4 cm, and the width of the sixth and seventh channels is 2.6 cm.

[0020] As a further preferred solution, the contact area between the anode plate and the anode accounts for 20%-30% of the anode.

[0021] The above-mentioned reduction method based on the serpentine flow field in-situ hydrogen production microbial electroreduction CO2 reactor comprises the following steps:

[0022] Step 1: Fill the cathode into the serpentine flow channel structure of the cathode plate, inject cathode liquid and add suspended microbial filler into the serpentine flow channel structure, and keep the cathode adsorbing the cathode liquid in a saturated state;

[0023] Step 2: Arrange the anode, anode plate, proton exchange membrane, cathode plate, and current collecting plate in sequence between the first cover plate and the second cover plate, and place waterproof gaskets between each two, and finally tie the first cover plate and the second cover plate together and fix them;

[0024] Step 3: Turn on the DC power supply, start the CO2 gas circulation pump, start the anolyte replenishing pump, the anolyte replenishing pump regularly injects the anolyte into the serpentine flow channel structure of the anode plate, and the CO2 gas circulation pump continuously injects CO2 into the serpentine flow channel structure of the cathode plate for circulation; in this state, the reactor is operated in a sterile state for more than 2 hours to remove the dissolved oxygen in the cathode liquid; the exhaust gas outlet is connected to the CO2 gas circulation pump, and the exhaust gas and the newly introduced carbon dioxide are re-injected into the CO2 inlet by the CO2 gas circulation pump;

[0025] Step 4: The anolyte in the serpentine flow structure of the anode plate is ionized and decomposed into hydrogen and oxygen. The oxygen is discharged from the oxygen outlet, and the hydrogen passes through the proton exchange membrane into the serpentine flow structure of the cathode plate and reacts in the cathode plate.

[0026] Step 5: In the serpentine flow channel structure of the cathode plate, microorganisms convert hydrogen and CO2 into corresponding organic acids (the reactor is inoculated with anaerobic microorganisms that can use hydrogen to reduce CO2). The organic acid dissolves in the cathode liquid to consume CO2 and improve the CO2 conversion efficiency. The reaction process is as follows:

[0027] 4H2+2CO2→CH3COOH(acetic acid)+2H2O;

[0028] Step 6: The cathode liquid in the reactor is replaced in batches during the experiment, and the cathode liquid is replenished regularly using the cathode liquid replenishment pump;

[0029] Step 7: During the operation of the reactor, the microbial concentration, product concentration, outlet gas flow rate, electrode potential of the anode and cathode, and DC power supply output voltage in the reactor are detected.

[0030] Beneficial effects:

[0031] Compared with the existing technology, the in-situ hydrogen production microbial electroreduction CO2 reactor and reduction method based on a serpentine flow field of the present invention has the following advantages:

[0032] 1) The present application utilizes a double-sided multi-serpentine microchannel reaction carrier plate design to increase the specific surface area of ​​the reaction carrier plate, thereby improving the adhesion and adhesion area of ​​the catalyst, thereby significantly increasing the conversion rate of organic matter, helping to achieve higher biocatalytic efficiency within a relatively small reactor volume, thereby increasing the reactor's unit volume production capacity and increasing the hydrogen production rate;

[0033] 2) This application uses serpentine carbon cloth as the cathode, providing more attachment sites for electroactive microorganisms, thereby increasing the adsorption capacity of microorganisms, helping to form a uniform and dense biofilm, shortening the electron transfer path from the cathode to the microorganisms, and significantly improving the transfer efficiency. This improvement not only increases the number of microorganisms but also forms a more stable microbial community;

[0034] 3) The double-sided multi-serpentine channel reaction carrier sheet of the present application has a serpentine channel with rectangular cross-sections of increasing length, which can effectively alleviate the problem of increased gas resistance caused by increased gas volume during the reaction process, thereby significantly reducing the reaction pressure drop and thus reducing the energy required to pump in the reactants;

[0035] 4) The present invention can enhance the convection flow near the biofilm-cathode interface through the design of the serpentine flow channel. The tortuous structure of the serpentine flow channel can avoid the accumulation of gas in the flow channel and can also make the introduced gas stay longer, thereby enhancing the gas utilization efficiency.

[0036] 5) The organic acids produced by this application can be processed into high-value-added chemicals or fuels through other processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the overall three-dimensional structure of the present invention;

[0038] Figure 2 is a top view of the cathode plate of the present invention;

[0039] Among them, 1. second cover plate, 2. anode, 3. anode plate, 4. proton exchange membrane, 5. cathode, 6. cathode plate, 7. current collecting plate, 8. first cover plate, 9. oxygen outlet, 10. anode liquid inlet, 11. exhaust gas outlet, 12. CO2 inlet. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0041] like Figure 1As shown, the reactor includes a first cover plate 8, a second cover plate 1, and an anode 2, an anode plate 3, a proton exchange membrane 4, a cathode 5, a cathode plate 6, and a graphite current collecting plate 7 that are sealed and installed between the left second cover plate in sequence. The edges of the first cover plate 8 and the second cover plate 1 are pulled and fixed to each other.

[0042] Both the anode plate 3 and the cathode plate 6 are provided with a through-type serpentine flow channel reaction chamber. The anode plate 3 and the cathode plate 6 at both ends of the serpentine flow channel are pipeline structures for connecting external equipment, and other areas are structures of flow channels that are through on both sides; specifically, the pipeline structures at both ends of the serpentine flow channel of the anode plate 3 are respectively the oxygen outlet 9 and the anode liquid inlet 10; the pipeline structures at both ends of the serpentine flow channel of the cathode plate 6 are respectively the exhaust gas outlet 11 and the CO2 inlet 12.

[0043] A cathode 5 is arranged in the serpentine flow channel of the cathode plate 6, and the cathode 5 is preferably carbon cloth. During operation, suspended microbial fillers are also added to the serpentine flow channel of the cathode plate 6. The addition of suspended microbial fillers can increase the concentration of microorganisms in the serpentine reaction chamber. At the same time, the serpentine flow channel can change the flow path of electrolytic hydrogen bubbles in the reaction chamber, thereby increasing the retention time of hydrogen bubbles in the reaction chamber, and further improving the utilization efficiency of hydrogen in the reactor.

[0044] In addition, in the present application, it is preferred that the anode 2 is a ruthenium-iridium-titanium mesh; the current collecting plate 7 is made of graphite, which is corrosion-resistant, has good conductivity, and is low in cost. High conductivity can reduce contact resistance and energy loss; the cathode liquid is glucose, and the anode liquid is water.

[0045] In this application, the anode 2 adopts a ruthenium-iridium-titanium mesh, which is connected to a titanium alloy wire (diameter 1.0 mm) by laser welding. The wire passes through a polytetrafluoroethylene sealing sleeve provided on the side wall of the anode plate 3 and is connected to the positive pole of the DC power supply; the cathode 5 is a serpentine carbon cloth, the edge of which is embedded in the groove of the graphite current collecting plate through conductive silver glue, and stainless steel bolts are drilled on the outside of the current collecting plate to install the stainless steel bolts, and the bolts are connected to the negative pole of the power supply through a copper braided belt.

[0046] The method for using the serpentine channel in-situ hydrogen production microbial electrosynthesis reactor of the present application is as follows: (1) adding anolyte and catholyte into the anode and cathode serpentine reaction chambers respectively; (2) connecting the DC power supply, CO2 gas circulation pump, and anolyte replenishing pump, and operating the reactor under sterile conditions for more than 2 hours to remove the dissolved oxygen in the cathode liquid; (3) inoculating the reactor with anaerobic microorganisms that can use hydrogen to reduce CO2; (4) the cathode liquid in the reactor is replaced in batches during the experiment, and the anolyte replenishing pump is used to regularly replenish the anolyte; (5) during the operation of the reactor, the microbial concentration, product concentration, outlet gas flow rate and composition, anode and cathode electrode potential, and DC power supply output voltage are detected.

[0047] The present application is described in detail below with reference to the embodiments:

[0048] A CO2 electroreduction reactor for in-situ hydrogen production based on a serpentine flow field, such as Figure 1 As shown, it includes a first cover plate 8, a second cover plate 1, and an anode 2, an anode plate 3, a proton exchange membrane 4, a cathode carbon cloth 5, a cathode plate 6 and a graphite current collecting plate 7 that are sealed and installed between the left second cover plate in sequence; the anode plate 3 and the cathode plate 6 are both provided with a through-type serpentine flow channel reaction chamber, and are provided with gas and liquid inlets and outlets on the top and side; a silicone waterproof gasket is provided between any adjacent ones; the anode plate 3 is provided with an anode liquid inlet 10 and an oxygen outlet 9, and the cathode plate 6 is provided with a CO2 inlet 12 and an exhaust gas outlet 11, and the exhaust gas discharged from the exhaust gas outlet 11 includes incompletely utilized hydrogen and carbon dioxide.

[0049] Waterproof gaskets are provided between the second cover plate 1 and the anode 2, between the anode 2 and the anode plate 3, between the anode plate 3 and the proton exchange membrane 4, between the proton exchange membrane 4 and the cathode plate 6, between the cathode plate 6 and the current collecting plate 7, and between the current collecting plate 7 and the first cover plate 8. Under the pulling pressure of the first cover plate 8 and the second cover plate 1, sealing is achieved at the edges of the waterproof gaskets. The waterproof gaskets can evenly distribute pressure to avoid local leakage.

[0050] Specifically, in the specific implementation, the first cover plate 8 and the second cover plate 1 are stacked, wherein the anode plate 3 and the cathode plate 6 are 40 cm long, 50 cm wide and 3 cm thick. Figure 2 As shown, the anode plate 3 and cathode plate 6 are equipped with seven parallel serpentine channels. The first channel, used for drainage, has a rectangular cross-section length of 2 cm, the second and third sections are 2.2 cm, the fourth and fifth sections are 2.4 cm, and the sixth and seventh sections are 2.6 cm. The anode and cathode working volumes are 1.55 L.

[0051] The contact area between the anode plate 3 and the anode 2 accounts for 20%-30% of the anode, preferably 25.8%. In this embodiment, the effective area of ​​the anode plate is 516cm 2 The cathode is a carbon cloth filled serpentine flow channel with an effective area of ​​1400cm 2 .

[0052] Specifically, the anolyte is water, and the catholyte formula is: glucose 20g / L; tryptone 3g / L; yeast powder 1g / L; NaCl 3g / L; K2HPO4 2.5g / L; MgCl2 0.1g / L; FeCl2·4H2O 0.157g / L; L-cysteine ​​0.5g / L; trace element stock solution 1mL / L; vitamin stock solution 1mL / L.

[0053] Example 1

[0054] The external current was 1000 mA, the CO2 inlet rate was 2 mL / min, and the pH of the reactor was controlled at 7. The activated strain Sporomus aovata (purchased from Ningbo Mingzhou Biotechnology Co., Ltd.) was cultured to OD 600 When the concentration of acetic acid in the reactor was 0.5-1, 100 mL of a single colony solution was inoculated into the reactor cathode. During the 14-day operation period, the cumulative concentration of acetic acid in the reactor reached 6 g / L, which significantly increased the density of the cathode biofilm (dry cell mass concentration) to 10.4 mmol×cm -3 , the biofilm accounts for more than 99% of the biomass, the average acetic acid production rate reaches 0.43g / L / d, and the average coulombic efficiency reaches 50%.

[0055] Example 2

[0056] When the external current is increased to 2000 mA and the CO2 inlet rate is 4 mL / min, the rest is the same as in Example 1. It is found through testing that the coulombic efficiency of the reactor is maintained at about 65% during the stable period.

[0057] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A CO2 electroreduction reactor for in-situ hydrogen production based on a serpentine flow field, characterized by: It comprises an anode (2), an anode plate (3), a proton exchange membrane (4), a cathode plate (6), and a current collecting plate (7) which are sequentially arranged between a first cover plate (8) and a second cover plate (1); The anode plate (3) and the cathode plate (6) are provided with flow channels that penetrate both sides; The side of the anode plate (3) is provided with an oxygen outlet (9) and an anolyte inlet (10), which are respectively located at the two ends of the flow channel of the anode plate (3); The cathode plate (6) is provided with an exhaust gas outlet (11) and a CO2 inlet (12) on the side thereof, which are respectively located at two ends of the flow channel of the cathode plate (6); a cathode (5) is arranged in the flow channel of the cathode plate (6); Wires are led out from the anode (2) and the cathode (5) to connect to an external DC power supply; The edges of the first cover plate (8) and the second cover plate (1) are mutually pulled and tied, and waterproof gaskets are provided between the second cover plate (1) and the anode (2), between the anode (2) and the anode plate (3), between the anode plate (3) and the proton exchange membrane (4), between the proton exchange membrane (4) and the cathode plate (6), between the cathode plate (6) and the current collecting plate (7), and between the current collecting plate (7) and the first cover plate (8). Under the pulling pressure of the first cover plate (8) and the second cover plate (1), sealing is achieved at the edges of the waterproof gaskets.

2. The in-situ hydrogen production microbial electroreduction CO2 reactor based on a serpentine flow field according to claim 1, characterized in that: The flow channel is a serpentine flow channel structure.

3. The in-situ hydrogen production microbial electroreduction CO2 reactor based on a serpentine flow field according to claim 2, characterized in that: The anode (2) is a ruthenium-iridium-titanium mesh; the cathode (5) is a carbon cloth; and the current collecting plate (7) is made of graphite.

4. The in-situ hydrogen production microbial electroreduction CO2 reactor based on a serpentine flow field according to claim 2, characterized in that: The flow channel of the anode plate (3) is filled with anolyte, which is water; and the flow channel of the cathode plate (6) is filled with catholyte.

5. The in-situ hydrogen production microbial electroreduction CO2 reactor based on a serpentine flow field according to claim 3, characterized in that: The waste gas outlet (11) and the CO2 inlet (12) are externally connected to a CO2 gas circulation pump; the anolyte inlet (10) is externally connected to an anolyte replenishing pump.

6. The in-situ hydrogen production microbial electroreduction CO2 reactor based on a serpentine flow field according to claim 2, characterized in that: The anode plate (3) and the cathode plate (6) have the same structural dimensions, being 40 cm long, 50 cm wide and 3 cm thick.

7. The in-situ hydrogen production microbial electroreduction CO2 reactor based on a serpentine flow field according to claim 2, characterized in that: The serpentine flow channel structures of the anode plate (3) and the cathode plate (6) have the same size and include seven parallel channels connected end to end, wherein the width of the first channel at the inlet of the serpentine flow channel structure is 2 cm, the width of the second and third channels thereafter is 2.2 cm, the width of the fourth and fifth channels is 2.4 cm, and the width of the sixth and seventh channels is 2.6 cm.

8. The in-situ hydrogen production microbial electroreduction CO2 reactor based on a serpentine flow field according to claim 2, characterized in that: The contact area between the anode plate (3) and the anode (2) accounts for 20%-30% of the anode.

9. The reduction method of the serpentine flow field in-situ hydrogen production microbial electroreduction CO2 reactor according to claim 5, characterized in that: The following steps are involved: (1) Filling the cathode (5) into the serpentine flow channel structure of the cathode plate (6), injecting cathode liquid and adding suspended microbial filler into the serpentine flow channel structure, and maintaining the cathode (5) in a saturated state of adsorbing cathode liquid; (2) between the first cover plate (8) and the second cover plate (1), the anode (2), the anode plate (3), the proton exchange membrane (4), the cathode plate (6), and the current collecting plate (7) are arranged in sequence, and waterproof gaskets are arranged between each other, and finally the first cover plate (8) and the second cover plate (1) are tied together and fixed; (3) Turn on the DC power supply, start the CO2 gas circulation pump, start the anolyte replenishing pump, the anolyte replenishing pump regularly injects the anolyte into the serpentine flow channel structure of the anode plate (3), and the CO2 gas circulation pump continuously injects CO2 into the serpentine flow channel structure of the cathode plate (6) for circulation; in this state, the reactor is operated in a sterile state for more than 2 hours to remove the dissolved oxygen in the cathode liquid; (4) The anode liquid in the serpentine flow channel structure of the anode plate (3) is ionized and decomposed into hydrogen and oxygen. The oxygen is discharged from the oxygen outlet (9), and the hydrogen passes through the proton exchange membrane (4) and enters the serpentine flow channel structure of the cathode plate (6), and reacts in the cathode plate (6); (5) In the serpentine flow channel structure of the cathode plate (6), microorganisms use hydrogen to convert CO2 into corresponding organic acids to consume CO2 and improve the conversion efficiency of CO2; (6) The cathode liquid in the reactor was replaced in batches during the experiment, and the cathode liquid was replenished regularly using the cathode liquid replenishment pump; (5) During the operation of the reactor, the concentration of microorganisms, the concentration of products, the outlet gas flow rate, the electrode potentials of the anode (2) and cathode (5), and the output voltage of the DC power supply are detected.

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