Method and structure for generating microbubbles through in-situ shearing and electrochemical CO2 reduction device

Abstract

The invention relates to the technical field of electrochemical carbon dioxide reduction, and mainly discloses a method and structure for generating microbubbles through in-situ shearing and an electrochemical CO2 reduction device.The method comprises the steps that bubbles in gas-liquid two-phase flow are subjected to in-situ shearing through a framework of an electrode, so that the bubbles are broken into microbubbles with the same size as electrode pores, and the microbubbles are obtained; the gas molecules are uniformly dispersed in a liquid phase, so that the solubility of local gas in the liquid phase can be remarkably improved, and the gas-liquid mass transfer efficiency and the reaction rate between the gas molecules and the electrode are improved; by changing the size of the electrode pores and the flow velocity of the gas-liquid two-phase flow, the size and rate of the microbubbles can be controlled. Besides, the generation and dispersion of the microbubbles adopting the device are cut in situ by the fiber electrode, an additional microbubble generation device is not needed, the energy consumption can be reduced, and the system stability can be improved. The method and the device can be applied to various gas-liquid two-phase electrochemical reaction processes, and particularly can show excellent performance in electrochemical carbon dioxide reduction application.

Description

Technical Field

[0001] This invention relates to the technical field of electrochemical carbon dioxide reduction, and in particular to a method, structure, and electrochemical CO2 reduction device for generating microbubbles through in-situ shearing. Background Technology

[0002] Since the Industrial Revolution, human use of fossil fuels has led to massive carbon dioxide emissions, which in turn cause global climate change through the greenhouse effect, threatening human survival and development. To address this, numerous carbon dioxide capture, storage, and conversion technologies have been developed to reduce emissions and mitigate climate change caused by the greenhouse effect. Electrochemical carbon dioxide reduction technology is one promising example. It utilizes electricity generated from clean energy sources such as wind and solar power—energy that is difficult to store and transmit—to drive the reduction reaction of carbon dioxide, converting it into high-value chemicals. Compared to other carbon dioxide conversion technologies, electrochemical carbon dioxide reduction technology offers advantages such as mild operating conditions (room temperature and pressure), high conversion rates, easy clean energy storage, and easy coupling with existing carbon dioxide sources.

[0003] Currently, commonly used electrochemical carbon dioxide conversion devices mainly include H-cells and flow cells and membrane electrode assemblies based on gas diffusion electrodes. H-cells are limited by the low solubility and diffusion rate of carbon dioxide in the electrolyte, failing to meet industrial requirements. In recent years, electrolytic cells based on gas diffusion electrodes have emerged in the field of carbon dioxide reduction. Gas diffusion electrodes not only shorten the carbon dioxide transport path but also reduce the thickness of the carbon dioxide diffusion boundary layer at the solid-liquid interface, overcoming the gas mass transfer limitations of H-cells.

[0004] However, gas diffusion electrodes struggle to maintain pressure balance for gas diffusion under potential conditions, exhibiting poor stability and prone to "flooding" and "salting out," leading to mass transfer failure at the three-phase interface. This problem has become a major obstacle to the industrialization of electrochemical carbon dioxide reduction technology.

[0005] To address the issues in H-cells and gas diffusion electrodes, existing micro- and nano-bubble-assisted electrochemical devices can enhance the desorption and transport of reaction products, thereby improving performance. However, these devices require additional micro- and nano-bubble generation components, increasing energy consumption and making the system more complex and prone to instability. As demand increases, it is necessary to further improve this technology so that the advantages of microbubbles can be better utilized in the field of electrochemistry. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is that the microbubbles generated by existing devices require additional micro-nano bubble generation components, which increases energy consumption and makes the system more complex and prone to instability.

[0007] The above-mentioned technical problems are solved by the following technical solution: The present invention proposes a method for generating microbubbles by in-situ shearing, which includes the following steps: mixing gas phase and liquid phase to form a stable bubbly flow; the bubbly flow passing through a first flow channel with built-in electrodes at a preset speed; wherein the electrodes are not parallel to the flow direction of the bubbly flow; the bubbles in the bubbly flow impact the electrodes and break to form microbubbles, and the microbubbles are uniformly dispersed in the liquid phase.

[0008] In a preferred embodiment of the method for generating microbubbles by in-situ shearing according to the present invention: the electrode is at least one of a fiber electrode and a porous electrode, and the surface of the electrode is loaded with a catalyst material; the size and generation rate of the microbubbles are controlled by adjusting the gap size of the electrode and the flow rate of the gas-liquid two-phase flow.

[0009] To solve the above-mentioned technical problems, the present invention also proposes the following technical solution: a structure for generating microbubbles by in-situ shearing, which is applied to a method for generating microbubbles by in-situ shearing, comprising a first flow channel formed on a first plate; the first flow channel includes a mixing section, a shearing section and a collecting section, wherein the two ends of the shearing section are respectively connected to the mixing section and the collecting section, and an electrode is fixed in the shearing section; wherein, the end of the mixing section is provided with a liquid phase inlet, and a gas phase inlet is provided in the mixing section following the liquid phase inlet.

[0010] In a preferred embodiment of the structure for in-situ shearing to generate microbubbles according to the present invention: the straight line to which the extension direction of the mixing section belongs is a first direction line, the straight line to which the extension direction of the shearing section belongs is a second direction line, the straight line to which the extension direction of the collecting section belongs is a third direction line, and the second direction line is respectively set to coincide with the first direction line and the third direction line.

[0011] In a preferred embodiment of the structure for in-situ shearing to generate microbubbles according to the present invention: the first direction line is parallel to the third direction line, and the second direction line is set at an angle to both the first direction line and the third direction line.

[0012] In a preferred embodiment of the structure for in-situ shearing to generate microbubbles according to the present invention: at least one liquid phase inlet is provided at the end of the mixing section away from the shearing section; at least one gas phase inlet is provided in the mixing section between the liquid phase inlet and the shearing section; and at least one reflux port is provided at the end of the collection section away from the shearing section.

[0013] To solve the above-mentioned technical problems, the present invention also proposes the following technical solution: an electrochemical carbon dioxide reduction device, which includes a structure for in-situ shearing to generate microbubbles, and further includes a cathode assembly and an anode assembly symmetrically arranged. The cathode assembly includes a cathode end plate and a first plate fixed thereto. The anode assembly includes an anode end plate and a second plate fixed thereto. The second plate is provided with a second flow channel. An exchange assembly is fixed between the first plate and the second plate. An exchange membrane is provided in the exchange assembly in the corresponding area of ​​the first flow channel and the second flow channel.

[0014] In a preferred embodiment of the electrochemical carbon dioxide reduction device of the present invention: the cathode assembly further includes a first fixing plate and a first sealing plate, the first fixing plate being fixed to the side of the cathode end plate away from the first plate, and the first sealing plate being fixed between the cathode end plate and the first plate; a liquid phase channel, a gas phase channel, and a reflux channel are provided inside the cathode end plate, the inlets of the liquid phase channel, the gas phase channel, and the reflux channel are opened on the outer wall of the cathode end plate, and the outlets are opened on the side of the cathode end plate near the first sealing plate; the first sealing plate is provided with liquid phase connection holes, gas phase connection holes, and reflux connection holes corresponding to the outlet positions of the liquid phase channel, the gas phase channel, and the reflux channel, and the liquid phase connection holes, the gas phase connection holes, and the reflux connection holes are respectively connected to the liquid phase inlet, the gas phase inlet, and the reflux outlet.

[0015] In a preferred embodiment of the electrochemical carbon dioxide reduction device of the present invention: the anode assembly further includes a second fixing plate and a second sealing plate, the first fixing plate is fixed to the side of the anode end plate away from the second plate, and the second sealing plate is fixed between the anode end plate and the second plate; the anode end plate is provided with an inlet channel and an outlet channel, the inlets of the inlet channel and the outlet channel are opened on the outer wall of the anode end plate, and the outlets are opened on the side of the anode end plate close to the second sealing plate; the second sealing plate is provided with an inlet connection hole and an outlet connection hole at positions corresponding to the outlets of the inlet channel and the outlet channel.

[0016] In a preferred embodiment of the electrochemical carbon dioxide reduction device of the present invention: the exchange component includes symmetrically arranged gaskets, each gasket having a through groove, and the exchange membrane is fixed between the gaskets and covers the through grooves on both sides; wherein, the through grooves also cover the corresponding area of ​​the shear section; the second flow channel includes a reaction section and an inlet section and an outlet section connected at both ends thereof, the inlet section and the outlet section being sealed and connected to the inlet connection hole and the outlet connection hole respectively; wherein, the exchange membrane is fixedly fitted within the reaction section.

[0017] The beneficial effects of this invention are as follows: The method of this invention innovatively forms microbubbles by shearing with built-in fiber electrodes, avoiding the use of additional microbubble generation equipment. It has the characteristics of simple structure, reduced energy consumption, and dynamic stability, and has good application prospects in the fields of energy conversion and electrochemistry.

[0018] In addition, the present invention introduces gas into the electrode in the form of microbubbles generated by in-situ shearing. On the one hand, it introduces a local gas source into the electrolyte, shortening the gas transfer path to the electrode; on the other hand, the surface tension of the microbubbles increases the gas concentration inside and around the bubbles, enhancing the mass transfer process of gas molecules in the solution, thereby increasing the reaction rate and improving the partial current density of the product. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention. Wherein: Figure 1 A step diagram illustrating the method for generating microbubbles through in-situ shearing is shown.

[0020] Figure 2 A schematic diagram of bubble micro-dispersion behavior is shown.

[0021] Figure 3 A schematic diagram of bubble distribution is shown.

[0022] Figure 4 A diagram of the internal microstructure of the electrode is shown.

[0023] Figure 5 The resulting diagram shows the structure used for in-situ shearing to generate microbubbles.

[0024] Figure 6 The diagram shows the locations of the liquid phase inlet and the gas phase inlet.

[0025] Figure 7 A schematic diagram showing the overlapping of the mixing section, shearing section, and collection section is shown.

[0026] Figure 8 Another schematic diagram of the opening of the mixing segment, the cutting segment, and the collecting segment is shown.

[0027] Figure 9 The diagram shows the gas phase inlet opened at different angles.

[0028] Figure 10 A schematic diagram of the main structure of the electrochemical carbon dioxide reduction device is shown.

[0029] Figure 11 A schematic diagram of the overall structure of the electrochemical carbon dioxide reduction device is shown.

[0030] Figure 12 The diagram shows the layout of the liquid phase channel, gas phase channel, and reflux channel.

[0031] Figure 13 The diagram shows the layout of the inlet and outlet channels.

[0032] Figure 14 The second flow channel structure diagram is shown.

[0033] Figure 15 The graph shows the relationship between bubble size and CO2 solubility.

[0034] Figure 16 An optical microscope image of microbubble formation is shown.

[0035] Figure 17 The measured confocal Raman spectrum is shown.

[0036] Figure 18 The graph shows the formic acid selectivity and partial current density as a function of cathode potential. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0038] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0039] Example 1

[0040] Reference Figures 1 to 18 The first embodiment of the present invention provides a method for generating microbubbles through in-situ shearing, which includes the following steps: The gas phase and liquid phase are mixed through cross-contact mixing to form a stable bubble flow A. Specifically, the gas phase conveying direction and the liquid phase conveying direction are non-parallel and intersect, with the intersection angle preferably being 30°~90°. The lateral impact force of the liquid phase on the gas phase is used to achieve shearing, ensuring that the initial size of the bubble A1 is on the order of millimeters and is uniformly dispersed in the liquid phase.

[0041] Bubble flow A passes through the first flow channel 100, which contains electrode B, at a preset speed. Electrode B is not parallel to the flow direction of bubble flow A, that is, the axial extension direction of electrode B is not parallel to the flow direction of bubble flow A. This ensures that bubble flow A can fully impact the porous structure of electrode B and avoids the airflow from sliding along the electrode surface, which could lead to shear failure.

[0042] Bubbles A1 in the bubbly flow A impact electrode B and are broken into microbubbles A2 by the shearing action of the through-pores inside electrode B. The size of microbubbles A2 is consistent with the pore size of electrode B and they are uniformly dispersed in the liquid phase.

[0043] Electrode B is at least one of fiber electrode and porous electrode. Porous electrode can be selected from foam metal electrode, porous carbon-based electrode, etc. In this embodiment, electrode B is preferably a fiber electrode, and the surface of electrode B is loaded with catalyst material.

[0044] By adjusting the gap size of electrode B and the flow rate of the gas-liquid two-phase flow, the size and generation rate of microbubbles A2 can be precisely controlled. The smaller the pore size of electrode B and the faster the flow rate, the smaller the microbubble size. The faster the flow rate of the two-phase flow, the higher the generation rate of microbubbles A2.

[0045] Example 2

[0046] Reference Figures 1 to 18 This is the second embodiment of the present invention. The difference between this embodiment and the first embodiment is that it provides a structure Q for generating microbubbles by in-situ shearing, which is applied to the method of generating microbubbles by in-situ shearing. It includes a first flow channel 100, which is formed on a first plate 200. The first plate 200 is preferably a rigid plate material resistant to electrolyte corrosion, such as a polytetrafluoroethylene plate or a stainless steel plate.

[0047] The first flow channel 100 includes a mixing section 101, a shearing section 102, and a collecting section 103. The two ends of the shearing section 102 are connected to the mixing section 101 and the collecting section 103, respectively. The electrode B is fixed in the shearing section 102 by embedding it into a pre-set groove in the middle of the shearing section 102. This allows for slip-free operation under bubbly flow impact without additional reinforcement.

[0048] The mixing section 101 is provided with a liquid inlet 101a at its end, and a gas inlet 101b is provided in the mixing section 101 following the liquid inlet 101a. The size of the liquid inlet 101a is preferably 1 mm, and the size of the gas inlet 101b is preferably 0.1 mm, to ensure that a stable bubbly flow is formed after the gas and liquid are mixed.

[0049] Reference Figure 7 and Figure 8The straight line extending in the direction of the mixing segment 101 is the first direction line X1, the straight line extending in the direction of the shearing segment 102 is the second direction line X2, and the straight line extending in the direction of the collecting segment 103 is the third direction line X3. The second direction line X2 is set to coincide with the first direction line X1 and the third direction line X3 respectively.

[0050] Alternatively, the first direction line X1 is parallel to the third direction line X3, and the second direction line X2 is set at an angle to both the first direction line X1 and the third direction line X3. That is, the shearing section 102 forms a zigzag structure with the mixing section 101 and the collecting section 103, which prolongs the contact time between the bubbly flow A and the electrode B and improves the shearing uniformity.

[0051] In this embodiment, when the second direction line X2 coincides with the first direction line X1 and the third direction line X3 respectively, the first flow channel 100 is opened in a "I" shape. The "I" shaped flow channel adopts a straight through design, which has prominent advantages: no complicated turning process is required during processing, the manufacturing difficulty of the plate and mold is low and the cost is controllable, and the straight shape has no dead corners, so bubbles or impurities are not easy to be trapped, and subsequent cleaning and maintenance operations are more convenient; at the same time, the energy loss of the gas-liquid two-phase flow along the straight line is small, and a stable bubbly flow can be maintained without additional increase in flow rate, which can effectively reduce the power consumption of the system, and the flow state is more uniform, and it is not easy for bubbles to aggregate and grow due to flow rate fluctuations.

[0052] However, its limitations are also quite obvious: due to the lack of turbulence effect caused by the lack of flow channel turning, the contact time between the bubble and the electrode of shear section 102 is short, the shear uniformity of microbubble A2 is insufficient, and it is difficult to ensure the microbubble size consistency required for subsequent reactions.

[0053] When the first direction line X1 is parallel to the third direction line X3, and the second direction line X2 is set at an angle to both the first direction line X1 and the third direction line X3, the first flow channel 100 is opened in a zigzag structure. In this structure, the electrode B can be stably engaged and installed in the shearing section 102 and will not be washed away by the two-phase flow.

[0054] Specifically, the vertical zigzag flow channel (90° turn) is a design that balances effectiveness and practicality. It uses the 90° vertical turn to create local vortices, which not only prolongs the contact time between the bubbly flow A and the shear section 102 electrode, allowing the bubbles to be fully sheared and making the generated microbubbles A2 more uniform in size, but also enhances gas-liquid mixing and reduces bubble aggregation. At the same time, the compact vertical turn layout can extend the total length of the flow channel within the limited plate space, adapting to the design requirements of miniaturized devices. Moreover, this turn retains sufficient turbulence effect to improve shearing efficiency without excessively increasing flow resistance. Although the resistance is slightly higher than that of a straight flow channel, the increase is within the range that the system can bear and will not significantly increase the dynamic load.

[0055] Furthermore, the advantage of the obtuse-angled zigzag flow channel (with a turn greater than 90°) is that the flow resistance is gentler and the energy loss of gas-liquid flow is lower than that of the vertical type, which can further reduce the system energy consumption. At the same time, the weak turbulence state can maintain the basic shearing and mixing effect. In addition, the impact intensity of bubbles on the shear section 102 electrode is gentler, which can reduce the risk of catalyst falling off the electrode surface and extend the service life of the electrode to a certain extent.

[0056] However, its shearing effect is relatively weak, making it difficult to precisely control the size of microbubbles A2, and the degree of gas-liquid mixing is also limited, so its effect on improving subsequent mass transfer efficiency is not obvious.

[0057] Furthermore, the core advantage of the acute-angled zigzag flow channel (with a turn of less than 90°) is its high shear efficiency. The strong turbulence formed by the acute-angle turn can provide concentrated shear force, quickly shearing millimeter-sized bubbles into target micron-sized microbubbles A2. At the same time, the strong turbulence can also promote molecular-level mixing of gas and liquid, initially improving the solubility of the gas phase in the liquid phase.

[0058] However, its shortcomings are also quite prominent: the strong turbulence brings greater flow resistance, which will significantly increase the system's power consumption, and strong impacts can easily cause flow channel wear, and may even cause bubble accumulation and blockage due to excessively strong local eddies, which is detrimental to the long-term stability of the device.

[0059] In summary, while the straight-line flow channel is easy to process and maintain, its shearing effect is insufficient; the obtuse-angled flow channel has low energy consumption but struggles to guarantee microbubble quality; and the acute-angled flow channel has high shearing efficiency but poor stability and energy consumption. The vertical zigzag flow channel, however, achieves uniform microbubble shearing and good gas-liquid mixing, while also balancing space utilization and energy efficiency. Its slight increase in resistance does not impose an additional burden on the system, making it the preferred structure for this design.

[0060] Furthermore, at least one liquid inlet 101a is provided at the end of the mixing section 101 away from the shearing section 102, and the number can be increased according to the gas-liquid ratio requirements to ensure a stable supply of liquid phase.

[0061] At least one gas phase inlet 101b is provided in the mixing section 101 between the liquid phase inlet 101a and the shear section 102. The inlet 101b is located close to the shear section 102 to shorten the conveying distance of bubble A1 in the mixing section and prevent the bubble from agglomerating and growing larger.

[0062] At least one reflux port 103a is provided at the end of the collection section 103 away from the shearing section 102 for recovering the gas-liquid mixture after shearing to generate microbubbles A2, which can be directly introduced into the subsequent electrochemical reaction zone or recycled.

[0063] Example 3

[0064] Reference Figures 1 to 18 This is the third embodiment of the present invention, which differs from the second embodiment in that: an electrochemical carbon dioxide reduction device Z includes a structure Q for in-situ shearing to generate microbubbles, and further includes: a cathode assembly 300 and an anode assembly 400 symmetrically arranged. The cathode assembly 300 includes a cathode end plate 301 and a first plate 200 fixed thereto. The anode assembly 400 includes an anode end plate 401 and a second plate 402 fixed thereto. The second plate 402 is provided with a second flow channel 402a, which is used for the reaction and flow of the anolyte.

[0065] An exchange component 500 is fixed between the first plate 200 and the second plate 402. An exchange membrane 501, preferably an ion exchange membrane, is provided in the exchange component 500 in the corresponding area of ​​the first flow channel 100 and the second flow channel 402a. A proton exchange membrane or an anion exchange membrane can be selected according to the reaction requirements to achieve ion transfer and isolate the anode and cathode materials.

[0066] The cathode assembly 300 also includes a first fixing plate 302 and a first sealing plate 303. The first fixing plate 302 is fixed to the side of the cathode end plate 301 away from the first plate 200 to enhance the structural strength of the cathode assembly 300 and prevent pressure deformation. The first sealing plate 303 is fixed between the cathode end plate 301 and the first plate 200 and uses a corrosion-resistant sealing material, such as a fluororubber gasket, to ensure that the gas and liquid on the cathode side are sealed and leak-proof.

[0067] The cathode end plate 301 is provided with a liquid phase channel 301a, a gas phase channel 301b, and a reflux channel 301c. The inlets of the liquid phase channel 301a, the gas phase channel 301b, and the reflux channel 301c are located on the outer wall of the cathode end plate 301 and are respectively connected to the electrolyte storage tank, the gas cylinder, and the product recovery device. The outlet is located on the side of the cathode end plate 301 near the first sealing plate 303 to ensure accurate material delivery.

[0068] The first sealing plate 303 has liquid phase connection holes 303a, gas phase connection holes 303b and reflux connection holes 303c respectively at the outlet positions of liquid phase channel 301a, gas phase channel 301b and reflux channel 301c. The liquid phase connection holes 303a, gas phase connection holes 303b and reflux connection holes 303c are respectively sealed and connected to the liquid phase inlet 101a, gas phase inlet 101b and reflux port 103a to avoid material leakage and pressure imbalance.

[0069] The anode assembly 400 also includes a second fixing plate 403 and a second sealing plate 404. The second fixing plate 403 is fixed to the side of the anode end plate 401 away from the second plate 402 to enhance the structural strength of the anode assembly 400. The second sealing plate 404 is fixed between the anode end plate 401 and the second plate 402 and is made of the same material as the first sealing plate 403 to ensure that the anode side is sealed and leak-proof.

[0070] The anode plate 401 has an inlet channel 401a and an outlet channel 401b. The inlets of the inlet channel 401a and the outlet channel 401b are located on the outer wall of the anode plate 401 and are connected to the anode electrolyte circulation device. The outlets are located on the side of the anode plate 401 near the second sealing plate 404, so as to realize the continuous circulation supply of the anode electrolyte.

[0071] The second sealing plate 404 has an inlet connection hole 404a and an outlet connection hole 404b at positions corresponding to the outlets of the inlet channel 401a and the outlet channel 401b, to ensure that the anolyte is accurately introduced into the second flow channel 402a.

[0072] The exchange assembly 500 includes symmetrically arranged gaskets 502, which are corrosion-resistant elastic gaskets. A through groove 502a is opened in the gasket 502. The exchange membrane 501 is fixed between the gaskets 502 and covers the through grooves 502a on both sides. The exchange membrane 501 is sealed and fixed by the elastic compression of the gaskets 502, thus avoiding cross-contamination of electrolyte.

[0073] Among them, the through groove 502a also covers the area corresponding to the shear section 102, ensuring that the microbubbles A2 generated by shearing can participate in the reaction in the area close to the exchange membrane 501, thus shortening the ion transfer path.

[0074] The second flow channel 402a includes a reaction section 402a-1 and an inlet section 402a-2 and an outlet section 402a-3 connected at both ends thereto. The inlet section 402a-2 and the outlet section 402a-3 are respectively sealed and connected to the inlet connection hole 404a and the outlet connection hole 404b to ensure smooth flow of the anolyte.

[0075] The exchange membrane 501 is fixed in the reaction section 402a-1, so that the ions generated by the oxidation reaction on the anode side can be quickly transferred to the cathode side through the exchange membrane 501, maintaining the charge balance of the system and ensuring the continuous and stable progress of the electrochemical carbon dioxide reduction reaction.

[0076] Example 4

[0077] Reference Figures 1 to 18 This is the fourth embodiment of the present invention, in which electrode B is preferably a fiber electrode. Figure 2 and Figure 3This is a schematic diagram of the microbubble dispersion behavior of A2 bubbles generated by in-situ shearing. When the bubbles contact the fiber electrode filled with electrolyte in the first flow channel 100 and flow through the throat of the fiber medium, there are two main bubble shearing and dispersion behavior mechanisms: snap-off and Lamella division.

[0078] Among them, snap-off is considered to be the most important behavioral mechanism of bubble micro-dispersion. This behavior occurs because when a bubble flows through a narrow pore throat, the surrounding liquid medium is pulled back towards the pore throat by the capillary pressure difference, which brings a shearing effect to the bubble and forces its front part to break into independent microbubbles.

[0079] Based on the above analysis of the shear-microdispersion behavior characteristics of bubbles flowing through the fiber medium, when the gas-liquid two-phase flow in this invention flows to the fiber electrode, after the bubbles come into contact with the fiber bundle electrode, they can be sheared through the snap-off or Lamelladivision mechanism, resulting in microdispersion behavior. Small-radius microbubbles A2 are introduced in situ into the channels between the fibers, and a gas phase is introduced at the original solid-liquid two-phase interface, creating a favorable gas-liquid-solid three-phase interface for the reaction. The gas phase is carbon dioxide gas, the liquid phase is electrolyte, and the solid phase is fiber electrode.

[0080] Furthermore, according to the Laplace-Young equation, the partial pressure of gas inside a bubble is inversely proportional to the radius of curvature of the bubble. Therefore, the small size of the microbubble results in a higher internal gas pressure than the surrounding environment. Also, according to Henry's law, at a constant temperature, the concentration of dissolved CO2(aq) in a dilute solution is directly proportional to the partial pressure of CO2 in the gas phase. Therefore, the microbubble A2 with high internal CO2 partial pressure obtained above can effectively enhance the local dissolution of CO2, providing a bulk boundary CO2(aq) concentration that is proportional to the internal partial pressure of the microbubble A2 for electrochemical CO2 reduction.

[0081] Furthermore, in order to verify whether the method of the present invention can generate microbubbles in situ and improve the solubility of CO2 in the electrolyte, the interior of the fiber electrode was observed using scanning electron microscopy and optical microscopy, and in situ testing was performed using confocal Raman spectroscopy.

[0082] Figure 4 This is the electrode before the gas phase is introduced. You can see the fibers and their internal pores clearly, with pore sizes between 5 and 11 μm. Figure 16 This is a fiber electrode that is generating microbubbles A2. You can see that the microbubbles generated and uniformly dispersed inside the fiber electrode have a radius of less than 5 μm.

[0083] This verifies that the proposed method can effectively generate microbubbles of the desired size. Simultaneously, from... Figure 15The relationship between the size of microbubbles (A2) and CO2 solubility shows that when the radius of CO2 bubble size is 1 μm, its solubility increases by nearly 100%, which is beneficial to solving the problem of limited CO2 solubility in electrochemical CO2 reduction.

[0084] The solubility curves demonstrate that the method of the present invention can greatly increase the local CO2(aq) concentration.

[0085] To further demonstrate the beneficial effects of the method of this invention from an experimental perspective, confocal Raman spectroscopy was used to detect and compare the CO2(aq) concentration around the CO2 bubble at the entrance of the fiber electrode and the CO2(aq) concentration around the CO2 microbubbles in the pores inside the fiber electrode. The signal acquisition position was fixed at approximately 1 μm from the CO2 bubble.

[0086] The Raman spectra at the different locations are as follows: Figure 17 As shown, the location is at 1280cm. -1 With 1391cm -1 The characteristic peak at [value] is attributed to the Fermi resonance doublet of the symmetric stretching and bending vibrations of dissolved CO2 (aq). Simultaneously, characteristic peaks belonging to different vibrational modes of the H2O molecule can also be clearly identified, including the peak at 1641 cm⁻¹. -1 H-O-H bending vibration at 3000cm and -1～ 3700cm -1 O-H stretching vibration within the interval.

[0087] In addition, located at 2450cm -1～ 3000cm -1 The characteristic peaks belonging to -CHx within the interval originate from the plexiglass between the probe lens and the confocal detection focal point; these peaks belong to the background signal.

[0088] Furthermore, the spectrum shows that the unnormalized Raman signal exhibits good homogeneity in the H2O characteristic peak and background peak, while the CO2(aq) concentration varies significantly in different regions.

[0089] To compare the CO2 (aq) concentration at different locations, a reference peak is selected to normalize and quantize the CO2 peak area before obtaining the peak area of ​​the CO2 characteristic peak.

[0090] Considering that the H-O-H bending vibration in H2O molecules has a similar vibrational energy to that of CO2(aq) molecules compared to the O-H stretching vibration, it is more sensitive to fluctuations in the intensity of CO2 characteristic peaks and is a very suitable probe for quantifying CO2(aq) concentration.

[0091] Therefore, with 1641cm -1The H-O-H bending vibration peak in H2O is used as the reference peak. The area of ​​the CO2(aq) Raman peak near the bubble at different locations is 1391 cm². -1 The concentration of CO2 (aq) was normalized and quantified using the bimodal area as a standard for the local CO2 concentration.

[0092] Table 1 shows a comparison of the peak area of ​​CO2(aq) Fermi doublet and H-O-H bending vibration in different regions and the results of normalized quantization.

[0093] Table 1: Comparison of Fermi bimodal and H-O-H bending vibration peak areas and normalized quantization results for CO2 (aq) in different regions

[0094] As can be seen from Table 1, the CO2(aq) concentration near the microbubbles in the pores inside the fiber electrode is 1.38 times that near the bubble at the fiber electrode inlet. This concentration comparison confirms that the method of the present invention can form uniformly dispersed microbubbles through in-situ shearing of the fiber electrode. It also provides data support for the beneficial effects of the method and device of the present invention in improving the local CO2 concentration and electrochemical CO2 reduction.

[0095] Example 5

[0096] Reference Figures 1 to 18 This is the fifth embodiment of the present invention, which is intended to verify the application prospects of the electrochemical carbon dioxide reduction device Z in the field of electrochemical CO2 reduction.

[0097] First, add excess electrolyte to two sealed feed bottles. The cathode electrolyte can be a 0.5 M potassium bicarbonate solution, and the anode electrolyte is generally a potassium hydroxide solution of the same concentration.

[0098] Next, turn on the power to preheat the flow controller, electrochemical workstation, peristaltic pump and other equipment, and at the same time, bubble CO2 into the cathode electrolyte for more than 30 minutes to ensure that the electrolyte is saturated with CO2.

[0099] A mass flow controller is used to control the stable supply of CO2 gas, a peristaltic pump is used to circulate the electrolyte, and an electrochemical workstation is used to provide the power required for electrolysis.

[0100] Finally, according to Figure 11 After assembling the device in sequence, CO2 gas and circulating electrolyte were introduced normally for a sealing test.

[0101] Furthermore, place a white cleanroom cloth under the device, run it for ten minutes without power, and observe the cleanroom cloth. If there are no traces of liquid, it proves that there is no liquid leakage and the seal is good, then it can be started.

[0102] Furthermore, a constant potential experiment was set up to test the selectivity and reactivity of the present invention for specific products.

[0103] In this embodiment, a three-electrode configuration was used, with an electrolyte flow rate of 40 mL / min. -1 The gas flow rate was 20 standard milliliters per minute (SCCM), and the cathode electrolyte was a 0.5 M potassium bicarbonate solution.

[0104] Figure 18 This is a graph showing the formic acid selectivity and partial current density as a function of cathode potential, where the horizontal axis represents Potential (Vvs. RHE) and the vertical axis represents FE. formate For the formic acid Faraday efficiency, J formate The figure shows the formic acid current density. As can be seen from the figure, within a wide potential window of -0.8V to -1.5V, the formic acid selectivity is always greater than 90%, and the partial current density does not show a limiting trend.

[0105] At a potential of -1.6V, the selectivity of formic acid decreases slightly, but remains above 85%, while the partial current density of formic acid can reach 600 mA / cm². 2 .

[0106] This is because the microbubbles generated by in-situ shearing of the fiber electrode can not only shorten the CO2 mass transfer path, but also increase the local pressure of CO2 near the electrode.

[0107] Furthermore, based on the experimental conditions set above: the target size of microbubble A2 is consistent with the pore size of electrode B, ranging from 5 to 15 μm; the actual generated microbubble radius is < 5 μm; the flow channel is a zigzag structure with a width of 1 mm; a 0.5 M potassium bicarbonate aqueous electrolyte is used, with a surface tension γ of approximately 0.072 N / m; and the gas-liquid operation parameters are an electrolyte flow rate of 40 mL / min. -1 The CO2 gas flow rate is 20 SCCM, and the device employs a thirteen-layer stacked sealing structure to ensure pressure stability. Combining the core physical law of microbubble pressure, namely the Laplace equation, and the actual flow characteristics of the flow channel, the specific calculation and derivation yields that the absolute pressure range inside microbubble A2 is 0.1 MPa to 0.2 MPa. The specific process is as follows: The absolute pressure inside microbubble A2 consists of two parts: "ambient pressure" and "additional pressure generated by surface tension". The core follows the Laplace equation: P_internal (absolute pressure) = P_annual (ambient pressure) + ΔP (additional pressure). The formula for calculating the additional pressure ΔP is: ΔP = 2γ / r, where γ is the surface tension of the electrolyte and r is the radius of the microbubble.

[0108] Furthermore, the basic parameters were set as follows: the ambient pressure P was taken as standard atmospheric pressure, approximately 0.1 MPa; the surface tension γ of the electrolyte was measured to be 0.072 N / m; and the radius r of the microbubble A2 was set according to the designed range of 5 μm to 15 μm and the experimental observation of "actual radius < 5 μm", with 15 μm, 5 μm, and 3 μm selected as key calculation nodes.

[0109] Case 1: When the microbubble radius r = 15 μm: Additional pressure ΔP1 = 2 × 0.072 N / m ÷ (15 × 10) -6 m)≈9600Pa=0.0096MPa The internal absolute pressure P1 = 0.1 MPa + 0.0096 MPa ≈ 0.11 MPa Case 2: When the microbubble radius r = 5 μm Additional pressure ΔP2 = 2 × 0.072 N / m ÷ (5 × 10) -6 m)≈28800Pa=0.0288MPa The internal absolute pressure P2 = 0.1 MPa + 0.0288 MPa ≈ 0.13 MPa Case 3: When the microbubble radius r = 3 μm Additional pressure ΔP3 = 2 × 0.072 N / m ÷ (3 × 10) -6 m)≈48000Pa=0.048MPa The internal absolute pressure P3 = 0.1MPa + 0.048MPa ≈ 0.15MPa.

[0110] Furthermore, the 1mm wide zigzag flow channel in this design will generate local eddies in the gas-liquid flow. These eddies bring a slight pressure gain, measured to be approximately 0.02~0.05MPa. After superimposing the above calculation results, the absolute pressure inside the microbubble can reach up to 0.15MPa + 0.05MPa = 0.2MPa. Moreover, the thirteen-layer stacked sealing structure of the device can stably maintain this pressure without any pressure loss.

[0111] Based on the above calculations, the basic range of absolute pressure inside the microbubble is 0.11~0.15MPa. After superimposing the pressure gain of the flow channel vortex, it finally stabilizes at 0.1~0.2MPa.

[0112] The core advantage of this range of absolute pressures within the microbubble A2 is its ability to precisely adapt to the microbubble A2 size, flow channel structure, and operating parameters of the solution. It effectively alleviates mass transfer limitations by increasing the solubility of CO2 in the electrolyte, while ensuring the stability of the microbubble morphology and the sealing safety of the device, avoiding excessive energy consumption or structural damage. At the same time, it directly optimizes the reaction performance of electrochemical CO2 reduction without requiring additional high-voltage equipment, thus balancing practicality and economy and possessing good adaptability for industrial applications.

[0113] The above process further demonstrates the advantages of this device and method, and its application prospects in the field of electrochemical CO2 reduction, which can lay a technical foundation for the industrialization of electrochemical CO2 reduction.

[0114] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A method for generating microbubbles through in-situ shearing, characterized in that: Includes the following steps, To mix the gas phase and the liquid phase to form a stable bubbly flow (A); The bubble flow (A) passes through the first flow channel (100) with built-in electrode (B) at a preset speed. The electrode (B) is not parallel to the flow direction of the bubble flow (A); The bubbles (A1) in the bubbly flow (A) impact the electrode (B) and break into microbubbles (A2), which are uniformly dispersed in the liquid phase.

2. The method for generating microbubbles through in-situ shearing according to claim 1, characterized in that: The electrode (B) is at least one of a fiber electrode and a porous electrode, and the surface of the electrode (B) is loaded with a catalyst material; The size and generation rate of microbubbles (A2) can be controlled by adjusting the gap size of the electrode (B) and the flow rate of the gas-liquid two-phase flow.

3. A structure (Q) for in-situ shearing to generate microbubbles, characterized in that: Methods for generating microbubbles through in-situ shearing include, The first flow channel (100) is located on the first plate (200); The first flow channel (100) includes a mixing section (101), a shearing section (102) and a collecting section (103). The two ends of the shearing section (102) are connected to the mixing section (101) and the collecting section (103) respectively, and the electrode (B) is fixed inside the shearing section (102). The mixing section (101) is provided with a liquid phase inlet (101a) at its end, and a gas phase inlet (101b) is provided in the mixing section (101) following the liquid phase inlet (101a).

4. The structure for in-situ shearing to generate microbubbles according to claim 3, characterized in that: The straight line extending in the direction of the mixing segment (101) is the first direction line (X1), the straight line extending in the direction of the shearing segment (102) is the second direction line (X2), and the straight line extending in the direction of the collecting segment (103) is the third direction line (X3). The second direction line (X2) is set to coincide with the first direction line (X1) and the third direction line (X3) respectively.

5. The structure for in-situ shearing to generate microbubbles according to claim 3, characterized in that: The first direction line (X1) is parallel to the third direction line (X3), and the second direction line (X2) is set at an angle to both the first direction line (X1) and the third direction line (X3).

6. The structure for in-situ shearing to generate microbubbles according to any one of claims 3 to 5, characterized in that: The liquid inlet (101a) is provided at least once at one end of the mixing section (101) away from the shear section (102); The gas phase inlet (101b) is provided at least once in the mixing section (101) between the liquid phase inlet (101a) and the shear section (102); The collection section (103) has at least one reflux port (103a) at the end away from the shear section (102).

7. An electrochemical carbon dioxide reduction device (Z), characterized in that: This includes structures (Q) for in-situ shearing to generate microbubbles, and also includes... A symmetrically arranged cathode assembly (300) and anode assembly (400), wherein the cathode assembly (300) includes a cathode end plate (301) and a first plate (200) fixed thereto, and the anode assembly (400) includes an anode end plate (401) and a second plate (402) fixed thereto, wherein a second flow channel (402a) is provided in the second plate (402). An exchange component (500) is fixed between the first plate (200) and the second plate (402), and an exchange membrane (501) is provided in the exchange component (500) in the corresponding area of ​​the first flow channel (100) and the second flow channel (402a).

8. The electrochemical carbon dioxide reduction apparatus according to claim 7, characterized in that: The cathode assembly (300) further includes a first fixing plate (302) and a first sealing plate (303). The first fixing plate (302) is fixed to the side of the cathode end plate (301) away from the first plate (200), and the first sealing plate (303) is fixed between the cathode end plate (301) and the first plate (200). The cathode end plate (301) is provided with a liquid phase channel (301a), a gas phase channel (301b) and a reflux channel (301c). The inlets of the liquid phase channel (301a), the gas phase channel (301b) and the reflux channel (301c) are opened on the outer wall of the cathode end plate (301), and the outlets are opened on the side of the cathode end plate (301) near the first sealing plate (303). The first sealing plate (303) has liquid phase connection hole (303a), gas phase connection hole (303b) and reflux connection hole (303c) respectively at the outlet positions of liquid phase channel (301a), gas phase channel (301b) and reflux channel (301c). The liquid phase connection hole (303a), gas phase connection hole (303b) and reflux connection hole (303c) are respectively connected to liquid phase inlet (101a), gas phase inlet (101b) and reflux port (103a).

9. The electrochemical carbon dioxide reduction device according to claim 8, characterized in that: The anode assembly (400) further includes a second fixing plate (403) and a second sealing plate (404), wherein the first fixing plate (302) is fixed to the side of the anode end plate (401) away from the second plate (402), and the second sealing plate (404) is fixed between the anode end plate (401) and the second plate (402); The anode plate (401) is provided with an inlet channel (401a) and an outlet channel (401b). The inlets of the inlet channel (401a) and the outlet channel (401b) are located on the outer wall of the anode plate (401), and the outlets are located on the side of the anode plate (401) near the second sealing plate (404). The second sealing plate (404) has an inlet connection hole (404a) and an outlet connection hole (404b) at positions corresponding to the outlets of the inlet channel (401a) and the outlet channel (401b).

10. The electrochemical carbon dioxide reduction device according to claim 9, characterized in that: The exchange assembly (500) includes symmetrically arranged gaskets (502), each gasket (502) having a through groove (502a) inside it, and the exchange membrane (501) being fixed between the gaskets (502) and covering the through grooves (502a) on both sides. The through groove (502a) also covers the area corresponding to the shear section (102); The second flow channel (402a) includes a reaction section (402a-1) and an inlet section (402a-2) and an outlet section (402a-3) connected at both ends thereto. The inlet section (402a-2) and the outlet section (402a-3) are respectively sealed and connected to the inlet connection hole (404a) and the outlet connection hole (404b). The exchange membrane (501) is fixed within the reaction section (402a-1).

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