A membrane composite electrochemical carbon capture system and method

Abstract

The application discloses a membrane composite electrochemical carbon capture system and method, and belongs to the field of electrochemistry, and comprises the following steps: driving solution pH change based on electrochemical proton coupling electron transfer (PCET) reaction, and utilizing MOF membrane to avoid the influence of oxygen on a novel electrochemical CO2 capture and purification.The application can realize a low-energy-consumption, continuous and stable CO2 capture and purification process.

Description

Technical Field

[0001] This invention relates to the field of electrochemistry, and more specifically, to a membrane composite electrochemical carbon capture system and method. Background Technology

[0002] CO2 capture involves absorbing and separating low-concentration CO2 to high purity for subsequent storage or utilization. Current CO2 capture technologies face bottlenecks due to high energy consumption and high cost. Especially in existing CCUS (Continuous Coal-to-Unit) technology systems, most CO2 capture technologies used in coal-fired power plants employ amine chemical absorption. This method utilizes amines to absorb CO2 and then uses thermal desorption, resulting in high desorption energy consumption (~2-4.5 GJ / ton CO2). Existing electrochemical CO2 capture technologies utilize the PCET (Polyhydrol-Organic Emission Reduction) reaction to alter the pH environment of the solution, disrupting the CO2 absorption-desorption equilibrium in the solution, thereby achieving CO2 capture and purification at low energy consumption (<2 GJ / ton CO2). Currently, this method typically uses organic PCET reactants as carriers for the electrochemical redox reaction. A major challenge in using organic PCET reactants is that the oxidation of these reactants by O2 reduces their concentration. Flue gas from coal-fired power plants typically contains 3–6% O2, while the atmosphere contains approximately 21% O2. The presence of O2 causes a rapid decay of electrochemical proton-coupled electron transfer (PCET) reactants, making it difficult for the system to operate stably under real CO2 capture conditions (including an O2 environment). From a thermodynamic perspective, oxygen-resistant organic PCET reactants usually have high electrode potentials, inevitably leading to increased system energy consumption. Therefore, achieving low-energy-consumption and stable operation of the system under real CO2 capture conditions (including an O2 environment) is a critical technical challenge that electrochemical CO2 capture technology urgently needs to overcome. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a membrane composite electrochemical carbon capture system and method. It provides a novel electrochemical CO2 capture and purification system and method based on electrochemical proton-coupled electron transfer (PCET) reaction to drive solution pH change and using MOF membrane to avoid the influence of oxygen. It can realize a low-energy-consumption, continuous and stable CO2 capture and purification process.

[0004] The objective of this invention is achieved through the following solution:

[0005] A membrane-composite electrochemical carbon capture system includes an electrolytic cell comprising an absorption chamber, a MOF membrane, a Q chamber, a cation exchange membrane, and a potassium ferricyanide chamber. The absorption chamber and the Q chamber are separated by the MOF membrane, and the Q chamber and the potassium ferricyanide chamber are separated by the cation exchange membrane. The Q chamber and the potassium ferricyanide chamber are connected to an external power source. A K2CO3 solution is added to the absorption chamber, a water-soluble organic PCET reduced substance Q and a KCl solution are added to the Q chamber, a potassium ferricyanide solution is added to the potassium ferricyanide chamber, and flue gas is introduced into the absorption chamber. Purified CO2 is collected in the Q chamber.

[0006] In addition, it includes a flue gas source, a CO2 collection bottle and an exhaust gas outlet. The absorption chamber is connected to the flue gas source. CO2 is introduced into the absorption chamber from the flue gas source and unabsorbed gas is released from the exhaust gas outlet. The Q chamber is connected to the CO2 collection bottle. After the system exchanges electrodes, the Q chamber releases purified CO2 into the CO2 collection bottle.

[0007] A method for operating a membrane composite electrochemical carbon capture system, based on the membrane composite electrochemical carbon capture system described above, includes the following steps: Oxygen-containing flue gas is introduced into the absorption chamber from the flue gas source; a K₂CO₃ solution in the absorption chamber absorbs CO₂ from the flue gas to generate KHCO₃; and an external power supply is turned on, causing a reduction reaction at the cathode of chamber Q to generate OH⁻. - OH - The CO2 passes through the MOF membrane to the absorption chamber, increasing the alkalinity of the absorption chamber and promoting CO2 absorption. The HCO3 produced by absorbing CO2 in the absorption chamber... - It passes through the MOF membrane to reach the Q chamber, ensuring charge conservation in each chamber; during electrolysis, the potassium ferricyanide chamber undergoes an oxidation reaction at the anode to produce K. + The gas passes through the cation exchange membrane into chamber Q; the remaining gas exits the absorption chamber and is then vented; the reaction equation is as follows:

[0008] Cathode of chamber Q: Q + H₂O → QH₂ + OH⁻ -

[0009]

[0010] After a period of time, the electrodes are switched, and an oxidation reaction occurs at the anode of chamber Q to produce H. + HCO3 in chamber Q - The reaction desorbs CO2, and K is released during electrolysis. + The CO2 desorbed from chamber Q passes through the cation exchange membrane to the potassium ferricyanide chamber, where a reduction reaction occurs at the cathode. The CO2 desorbed from chamber Q and the absorption chamber is collected in a CO2 collection bottle. The reaction equation is as follows:

[0011]

[0012] Finally, the conversion of QH2 to Q is achieved by exchanging the electrodes again, thereby realizing the cyclic operation of the membrane composite electrochemical carbon capture system.

[0013] Furthermore, organic PCET reactants include phenazines, fluoromethines, quinones, and their derivatives.

[0014] Furthermore, carbon-based materials are used as electrode materials in the electrolytic cell, and the carbon-based material matrix includes graphite felt, carbon paper, carbon cloth, carbon rods, and carbon sheets.

[0015] Furthermore, the carbon-based material electrode in the electrolytic cell can be modified or altered by using a substrate or doping material. The doping material includes any one of carbon nanotubes and graphene; the substrate includes any one of nickel foam, platinum sheet, and nickel-plated platinum mesh.

[0016] A membrane composite electrochemical carbon capture system is disclosed, based on the membrane composite electrochemical carbon capture system described above; wherein potassium carbonate is used as the CO2 absorbent, providing an alkaline environment to the solution, and after CO2 absorption, HCO3- is released. - The CO2 absorbent is introduced into the Q chamber through the MOF membrane; in addition to potassium carbonate, the CO2 absorbent also includes: ammonia, monoethanolamine, ethylenediamine, triethanolamine and piperazine; potassium chloride is used as the supporting electrolyte, which can provide high ionic conductivity for the battery system. In addition to potassium chloride, the supporting electrolyte also includes salt supporting electrolyte or ionic liquid.

[0017] Furthermore, the entire membrane composite electrochemical carbon capture system is designed as an integrated device according to requirements, or as a large-scale integrated device through series and parallel connection of the system, and is suitable for CO2 capture including flue gas from coal-fired power plants, factory exhaust gas, transportation exhaust gas and atmospheric environment.

[0018] A membrane composite electrochemical carbon capture system is provided, based on the membrane composite electrochemical carbon capture system described above; wherein the MOF membrane can be replaced with a membrane that isolates oxygen and allows ion passage, specifically including a hybrid matrix membrane.

[0019] The beneficial effects of this invention include:

[0020] This invention enables the electrochemical capture and purification of CO2 in an oxygen-containing flue gas environment. In practical applications, the system is powered by an external power source and utilizes a proton-coupled electron transfer (PCET) reaction to drive pH changes in the solution. An oxygen-barrier, ion-passing MOF membrane is added between Q / QH2 and the absorbent solution, preventing oxygen from contacting Q / QH2 and allowing Q / QH2 to effectively participate in the electrochemical reaction. Through electrode exchange, the system absorbs and desorbs CO2, achieving the conversion between Q and QH2, thus realizing a low-energy-consumption, continuous, and stable CO2 capture and purification process.

[0021] In this embodiment of the invention, the system causes pH fluctuations in the solution through a redox reaction of the organic PCET reactant (organic proton carrier Q). An oxygen-barrier, ion-passing MOF membrane is added between the Q chamber and the absorption chamber. The reduction reaction of Q generates QH2, increasing the alkalinity of the Q chamber. Hydroxide ions from the Q chamber permeate through the MOF membrane into the absorption chamber, thereby promoting the absorption of low-concentration CO2 in the absorption chamber, producing HCO3-. - The potassium ferricyanide (KF) permeates through the MOF membrane to the Q chamber, where it undergoes oxidation at the anode to form potassium ferricyanide. After a period of time, the electrodes are switched, and QH₂ undergoes oxidation to form H₂. + With HCO3 in solution - The reaction desorbs CO2, and potassium ferricyanide undergoes a reduction reaction in the potassium ferricyanide chamber to produce potassium ferrocyanide. In the CO2 absorption and desorption process, the MOF membrane acts as an interlayer to isolate large molecules (such as O2 and Q / QH2 macromolecules) from the passage of ions (OH-). - HCO3 - The MOF membrane separates the oxygen in the flue gas from Q / QH2, preventing QH2 from being oxidized by the oxygen in the flue gas, which would affect the electrochemical reaction and thus the system's ability to absorb and desorb CO2.

[0022] In this embodiment of the invention, a reduction reaction occurs at the cathode, where Q reacts with water under electrolysis conditions to produce OH-. - and QH2, OH - The CO2 reaches the CO2 absorption chamber through the MOF membrane, increasing the alkalinity of the absorbent solution, which can be used to absorb low concentrations of CO2. The system uses an oxygen-barrier and ion-passing MOF membrane to separate the Q chamber and the absorption chamber, completely avoiding the interference of O2 in the flue gas on Q, and can achieve direct capture of real oxygen-containing CO2 (flue gas or atmosphere).

[0023] The system in this embodiment of the invention uses a water-soluble organic proton carrier. After exchanging the electrode, H is released through electrochemical oxidation. + and HCO3 passing through the absorption chamber - The reaction produces high-purity CO2 and water, achieving CO2 purification and regeneration. Because the Q chamber only involves a solid-liquid two-phase electrochemical reaction, the use of a gas diffusion electrode is avoided, completely eliminating the electrochemical "gas-liquid-solid" three-phase reaction interface and significantly improving the stability of the system during long-term operation.

[0024] In this embodiment of the invention, an organic proton carrier Q is used as the reactant on one electrode. To avoid high electrolysis energy consumption, a pyrrolizine / isopyrrolizine derivative (e.g., FMN) or phenazine derivative (e.g., DHPS, DHPC, BHPC) with suitable potential is used as Q. The pH value fluctuates through the redox reaction of Q, achieving the process of CO2 capture and separation. Furthermore, through an exchange electrode, regeneration between Q and QH2 can be achieved, realizing the continuous and stable cycling of the organic PCET reactant. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the CO2 absorption system in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the CO2 desorption (exchange electrode) system in an embodiment of the present invention;

[0028] Figure 3 This is a system structure diagram in an embodiment of the present invention;

[0029] Figure 4 Energy consumption curve for capturing oxygen-containing flue gas by the membrane composite electrochemical carbon capture system (DSPZ);

[0030] Figure 5 Energy consumption curve for capturing oxygen-containing flue gas using a membrane-based electrochemical carbon capture system (FMN).

[0031] Figure 6 The CO2 absorption concentration curve of the membrane composite electrochemical carbon capture system;

[0032] Figure 7 The CO2 desorption concentration curve of the membrane composite electrochemical carbon capture system;

[0033] Figure 8 Energy consumption curve for capturing oxygen-containing flue gas using a membrane-free electrochemical carbon capture system (DSPZ);

[0034] In the diagram, 1-external power supply, 2-electrolytic cell, 3-absorption chamber, 4-MOF membrane, 5-Q chamber, 6-cation exchange membrane, 7-potassium ferricyanide chamber, 8-flue gas source, 9-CO2 collection bottle, 10-exhaust gas. Detailed Implementation

[0035] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0036] Example 1

[0037] This invention provides a novel electrochemical CO2 capture and purification system that uses an MOF membrane to avoid the influence of oxygen by driving changes in solution pH based on an electrochemical proton-coupled electron transfer (PCET) reaction.

[0038] In this embodiment of the invention, the inventive concept is as follows: a membrane composite electrochemical carbon capture system, through the redox reaction of organic PCET reactants (Q), causes fluctuations in the solution pH, achieving alkalinization absorption and acidification desorption of low-concentration CO2. Simultaneously, an oxygen-barrier and ion-passing MOF membrane is added between the Q chamber (a solution containing Q and KCl) and the absorption chamber (a solution containing K2CO3) to prevent direct contact between the organic PCET reactants and oxygen in the flue gas, thus avoiding side reactions and capacity loss. First, Q is reduced to QH2 through electrolysis, causing an increase in the alkalinity of the Q chamber. Hydroxide ions in the Q chamber, due to charge conservation, permeate through the MOF membrane to the absorption chamber, where potassium ferricyanide undergoes an oxidation reaction to generate potassium ferricyanide. Subsequently, the flue gas is passed into the absorbent solution, while oxygen in the flue gas cannot pass through the MOF membrane, avoiding contact with Q / QH2. This allows all Q / QH2 to effectively participate in the electrochemical reaction, and the absorbent solution absorbs CO2 to produce HCO3. - It then reaches the Q chamber through the MOF membrane. After a period of time, the electrodes are switched, and QH2 undergoes an oxidation reaction to generate H. + With HCO3 in solution - The reaction desorbs CO2, and a potassium ferricyanide reduction reaction occurs in the potassium ferricyanide chamber to generate potassium ferrocyanide, thus enabling the electrochemical CO2 capture system to operate continuously and stably. This embodiment of the invention utilizes an oxygen-barrier, ion-permeable MOF membrane to completely avoid the influence of O2 and dissolved oxygen in CO2 on organic PCET reactants, thereby achieving direct electrochemical capture of oxygen-containing flue gas.

[0039] In a specific embodiment, the present invention provides a membrane-composite electrochemical carbon capture system, such as... Figure 1 and Figure 2As shown. The system includes an electrolytic cell 2 (comprising an external power supply 1, an absorption chamber 3, an MOF membrane 4, a Q chamber 5, a cation exchange membrane 6, and a potassium ferricyanide chamber 7). The absorption chamber 3 and the Q chamber 5 are separated by the MOF membrane 4, and the Q chamber 5 and the potassium ferricyanide chamber 7 are separated by the cation exchange membrane 6. The Q chamber 5 and the potassium ferricyanide chamber 7 are connected to the external power supply 1. A K2CO3 solution is added to the absorption chamber 3, a water-soluble organic PCET reduced substance Q and a KCl solution are added to the Q chamber 5, and a potassium ferricyanide solution is added to the potassium ferricyanide chamber 7. Flue gas is introduced into the absorption chamber 3, and purified CO2 is collected in the Q chamber. In addition, the system also includes a flue gas source 8, a CO2 collection bottle 9, an exhaust gas 10, an absorption chamber 3 connected to the flue gas source 8, CO2 is introduced into the absorption chamber 3 from the flue gas source 8, and unabsorbed gases (such as N2) are released from the exhaust gas 10. A Q chamber 5 is connected to the CO2 collection bottle 9. After the system exchanges electrodes, the Q chamber releases purified CO2 into the CO2 collection bottle 9.

[0040] An external power supply 1 is connected to the anode and cathode of the electrolysis reactor, providing electrical energy to the electrolyzer. The two electrodes of the electrolyzer are separated by a cation exchange membrane 6. Oxygen-containing flue gas is introduced into the absorption chamber 3 from the flue gas source 8. The K2CO3 solution in the absorption chamber absorbs CO2 from the flue gas to generate KHCO3, and the external power supply 1 is turned on. A reduction reaction occurs in chamber Q 5 (cathode) to produce OH-. - OH - The CO2 is absorbed through the MOF membrane 4 into absorption chamber 3, increasing the alkalinity of absorption chamber 3 and promoting CO2 absorption. Simultaneously, to ensure charge conservation in each chamber, the HCO3 produced by absorbing CO2 in absorption chamber 3... - It will pass through MOF membrane 4 to reach chamber Q 5. During electrolysis, potassium ferricyanide in chamber 7 (anode) undergoes an oxidation reaction to produce K. + The gas passes through cation exchange membrane 6 and reaches chamber Q 5. The remaining gas (e.g., N2) exits from absorption chamber 3 and is then vented. The reaction equation is as follows:

[0041] Cathode (Q chamber): Q + H₂O → QH₂ + OH⁻ -

[0042]

[0043] After a period of time, the electrodes are switched, and oxidation occurs in chamber Q5 (anode) to produce H. + HCO3 in chamber Q5 - The reaction desorbs CO2, and K is released during electrolysis. + CO2 desorbed from chamber Q5 passes through cation exchange membrane 6 to potassium ferricyanide chamber 7 (cathode), where a reduction reaction occurs. The CO2 desorbed from chamber Q5 and absorption chamber 3 is collected in CO2 collection bottle 9. The reaction equation is as follows:

[0044]

[0045] Finally, by exchanging the electrodes again, the conversion between QH2 and Q is achieved, thereby realizing the cyclic operation of the membrane composite electrochemical carbon capture system.

[0046] The specific operating steps are as follows: In this embodiment, the effective area inside the electrolytic cell is 4 cm². 2 The electrolytic cell used was equipped with a self-synthesized MOF membrane. 50 mL of 0.5 mol / L K₂CO₃ solution was added to the absorption chamber. In chamber Q, 50 mL of 1 mol / L KCl and 0.05 mol / L of sodium DSPZ (a phenazine derivative in its oxidized state) solution were added as the cathode solution. In the potassium ferrocyanide chamber, 50 mL of 0.1 mol / L potassium ferrocyanide (K₄Fe(CN)₆) solution was added as the anolyte. An external power supply was turned on, and constant current electrolysis was performed at 40 mA DC. In chamber Q, a reduction reaction occurred to produce QH₂ (a phenazine derivative in its reduced state, 3,3'-(phenazine-2,3-dimethyldioxy)bis(alkyl-1-sulfonic acid) sodium DSPZH₂) and OH⁻. - OH - The gas passes through the MOF membrane to the absorption chamber. Flue gas is introduced into the absorption chamber, where CO2 is absorbed, forming a KHCO3 solution, while HCO3- in the absorption chamber... - Through the MOF membrane to the Q chamber. After a period of time, at the exchange electrode, QH2 in the Q chamber undergoes an oxidation reaction to produce Q and H. + Increased acidity in chamber Q, H + HCO3 in chamber Q - The reaction desorbs purified CO2. Power source 1 is connected to the anode and cathode of the battery system to supply electrical energy. The relationship between capture stability and voltage is shown in the graph. Figure 4 .like Figure 4 As shown, the initial capture voltage was 0.1V, which slowly increased to 0.2V after 3 hours. Due to the decrease in substance concentration, the voltage rapidly increased to 1.2V. Subsequently, the electrodes were switched to discharge, and the voltage dropped from 1.2V to 0V. The stability was good after multiple cycles, and the capture capacity hardly decreased.

[0047] Example 2

[0048] The operation process in this embodiment is basically the same as in Embodiment 1, except that in this embodiment, 50 mL of 1 mol / L KCl and 0.05 mol / L Q (oxidized state ② riboflavin monophosphate sodium salt FMN-Na) solution are added to chamber Q as the cathode liquid. After the electrode exchange, when chamber Q acts as the anode, Q is converted into QH2 (reduced state ② riboflavin monophosphate sodium salt FMN-NaH2). Power supply 1 is connected to the anode and cathode of the battery system to supply electrical energy.

[0049] The relationship between capture stability and voltage is shown in the graph. Figure 5 .

[0050] like Figure 4 As shown, the initial capture voltage was 0.15V, which slowly increased to 0.3V after 3 hours. Due to the decrease in substance concentration, the voltage rapidly increased to 1.8V. Subsequently, the electrodes were switched to discharge, and the voltage dropped from 1.8V to 0V. The stability was good after multiple cycles, and the capture capacity hardly decreased.

[0051] Example 3

[0052] In this example, 50 mL of 0.5 mol / L K₂CO₃ solution was added to the absorption chamber. In chamber Q, 50 mL of 1 mol / L KCl and 0.05 mol / L sodium Q (oxidized state of phenazine derivative 3,3'-(phenazine-2,3-dimethyldioxy)bis(alkyl-1-sulfonic acid) DSPZ) solution were added as the catholyte. In the potassium ferrocyanide chamber, 50 mL of 0.1 mol / L potassium ferrocyanide (K₄Fe(CN)₆) solution was added as the anolyte. Constant current electrolysis was performed using a DC current of 40 mA. Figure 6 When the capture side is operating stably, the CO2 concentration first decreases steadily, then increases slightly, and finally stabilizes. The CO2 absorption rate is 99.9%, demonstrating high absorption efficiency.

[0053] Example 4

[0054] In this example, 50 mL of 0.5 mol / L K₂CO₃ solution was added to the absorption chamber. In chamber Q, 50 mL of 1 mol / L KCl and 0.05 mol / L sodium Q (oxidized state of phenazine derivative 3,3'-(phenazine-2,3-dimethyldioxy)bis(alkyl-1-sulfonic acid) DSPZ) solution were added as the catholyte. In the potassium ferrocyanide chamber, 50 mL of 0.1 mol / L potassium ferrocyanide (K₄Fe(CN)₆) solution was added as the anolyte. Constant current electrolysis was performed using a DC current of 40 mA. Figure 7 After electrode exchange, the CO2 concentration initially increased steadily, then stabilized, and began to decrease after 25 hours of stable operation. The CO2 desorption rate was 99.9%, demonstrating high desorption efficiency.

[0055] The system of this invention has the following advantages:

[0056] 1) This system incorporates a MOF membrane between the absorption chamber and the Q chamber, which prevents the passage of O2 from the flue gas while allowing the passage of ions. This membrane divides the organic PCET reaction side of the system into the absorption chamber and the Q chamber, preventing the oxidation of organic PCET reactants by O2. The potassium ferricyanide chamber utilizes the redox reaction of potassium ferricyanide as the anode and cathode before and after the exchange electrode. Available organic PCET reactants include, but are not limited to, phenazines, fluoroquinones, quinones, and their derivatives. When absorbing low-concentration CO2 (oxygenated CO2), the low-concentration CO2 (oxygenated CO2) is absorbed in the absorption chamber to generate HCO3. - The O2 contained therein cannot permeate through the MOF membrane into the Q chamber to oxidize organic PCET reactants. During the desorption of high-concentration CO2 at the exchange electrode, HCO3- permeates from the absorption chamber through the MOF membrane into the Q chamber. - H+ generated by the oxidation of ions with QH2 + The reaction produces high-purity CO2.

[0057] 2) The system uses carbon-based materials as electrodes, including graphite felt, carbon paper, and carbon cloth. Electrode materials can also be modified or altered using metal electrode substrates or metal catalysts. Common metal electrode substrates include, but are not limited to: nickel foam, platinum sheets, and nickel-plated platinum mesh. Common catalyst supports include, but are not limited to: Pt / C and Pd / C.

[0058] 3) The CO2 absorbent (potassium carbonate) used in the system provides an alkaline environment for the solution, and after absorbing CO2, HCO3- - It can pass through the MOF membrane into the Q chamber. Commonly used CO2 absorbents include, but are not limited to: ammonia, monoethanolamine, ethylenediamine, triethanolamine, piperazine, etc. Potassium chloride as the supporting electrolyte can provide high ionic conductivity for the battery system; other conventional salt supporting electrolytes or ionic liquids can also be used.

[0059] 4) This system employs unipolar absorption and desorption; the potassium ferricyanide chamber does not participate in the absorption and desorption of CO2. Low-concentration CO2 (oxygen-containing CO2) is first absorbed in the alkaline absorption chamber, and after acidification by the exchange electrode, high-concentration CO2 is desorbed in the Q chamber.

[0060] 5) The entire system can be designed as a simple integrated device according to requirements, or it can be designed into a large-scale integrated device through series and parallel connections. It can be applied to CO2 capture in environments including flue gas from coal-fired power plants, factory exhaust gas, transportation exhaust gas, and even the atmosphere.

[0061] Comparative Example 1

[0062] The operation process of this comparative example is basically the same as that of Example 1, except that the MOF membrane is removed in this comparative example, allowing O2 to reach chamber Q from the absorption chamber. During carbon dioxide absorption, O2 from the flue gas or air enters the absorption chamber and then chamber Q to oxidize QH2 (reduced form of phenazine derivative 3,3'-(phenazine-2,3-dimethyldioxy)bis(alkyl-1-sulfonic acid)sodium DSPZH2). Cyclic studies of this system showed a sharp decrease in capacity during cycling (e.g., ...). Figure 8 This indicates a sharp decrease in the amount of QH2 (reduced state ① sodium 3,3'-(phenazine-2,3-dimethyldioxy)bis(alkyl-1-sulfonic acid) DSPZH2) generated during the discharge process, as QH2 is rapidly oxidized by oxygen. This suggests that if O2 is not prevented from entering the Q chamber, the CO2 capture capacity will decrease, ultimately leading to the inability to capture CO2.

[0063] Comparative Example 2

[0064] The operation process of this comparative example is basically the same as that of Example 1, except that in this comparative example, 50 mL of 0.5 mol / L K2CO3 solution is added to the absorption chamber, 50 mL of 0.5 mol / L KCl and 0.01 mol / L QH2 (reduced form of phenazine derivative 3,3'-(phenazine-2,3-dimethyldioxy)bis(alkyl-1-sulfonic acid) sodium DSPZ) solution is added to the Q chamber as the anolyte, and 50 mL of 0.5 mol / L potassium ferrocyanide (K4Fe(CN)6) solution is added to the potassium ferricyanide chamber as the catholyte. Flue gas is introduced into the absorption chamber and the external power supply is turned on. The system has no input current and cannot react. This illustrates the importance of correctly selecting organic PCET reactants and matching them with the electrolysis system.

[0065] In summary, this invention describes a membrane-based electrochemical carbon capture system that utilizes a proton-coupled electron transfer (PCET) reaction to drive pH changes in the solution. An oxygen-barrier, ion-passing MOF membrane is added between Q / QH2 and the absorption solution, preventing oxygen from contacting Q / QH2 and allowing Q / QH2 to effectively participate in the electrochemical reaction. Through an exchange electrode, the system absorbs and desorbs CO2, achieving the conversion between Q and QH2, thus realizing a low-energy-consumption, continuous, and stable process for capturing and purifying CO2 from oxygen-containing flue gas.

[0066] First, flue gas is introduced into the absorption chamber, and the external power supply is turned on. After absorbing CO2, the absorption chamber generates KHCO3 solution. In chamber Q, a reduction reaction occurs to produce QH2 and OH-. - OH- ions pass through the MOF membrane into the absorption chamber, while HCO3- in the absorption chamber... - CO2 is continuously absorbed through the MOF membrane into the Q chamber, while unabsorbed exhaust gases (such as N2) are discharged into the atmosphere. After a period of time, the electrodes are switched, and the QH2 in the Q chamber undergoes an oxidation reaction to produce Q and H.+ Q chamber acidity increases, H + HCO3 in chamber Q - The reaction desorbs purified CO2, which is then passed into a CO2 collection bottle. This enables the continuous and stable operation of the membrane-based electrochemical carbon capture system.

[0067] In addition to the examples above, other embodiments may be obtained by those skilled in the art based on the above disclosure or by making modifications using knowledge or technology in related fields. The features of each embodiment may be interchanged or replaced. Modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A membrane composite electrochemical carbon capture system, characterized in that, The electrolytic cell (2) includes an absorption chamber (3), an oxygen-isolating MOF membrane (4), a Q chamber (5), a cation exchange membrane (6), and a potassium ferricyanide chamber (7). The absorption chamber (3) and the Q chamber (5) are separated by the MOF membrane (4), and the Q chamber (5) and the potassium ferricyanide chamber (7) are separated by the cation exchange membrane (6). The Q chamber (5) and the potassium ferricyanide chamber (7) are connected to an external power supply (1). K2CO3 solution is added to the absorption chamber (3), water-soluble organic PCET oxidized substance Q and KCl solution are added to the Q chamber (5), potassium ferricyanide solution is added to the potassium ferricyanide chamber (7), and flue gas is introduced into the absorption chamber (3). Purified CO2 is collected in the Q chamber (5). In addition, it also includes a flue gas source (8), a CO2 collection bottle (9) and an exhaust tail gas (10). The absorption chamber (3) is connected to the flue gas source (8). CO2 is introduced into the absorption chamber (3) from the flue gas source (8) and unabsorbed gas is released from the exhaust tail gas (10). The Q chamber (5) is connected to the CO2 collection bottle (9). After the system exchanges electrodes, the Q chamber releases purified CO2 into the CO2 collection bottle (9).

2. The membrane composite electrochemical carbon capture system according to claim 1, characterized in that, Organic PCET reactants include phenazines, pyrazines, quinones and their derivatives.

3. The membrane composite electrochemical carbon capture system according to claim 1, characterized in that, In the electrolytic cell (2), carbon-based materials are used as electrode materials. The carbon-based material matrix includes graphite felt, carbon paper, carbon cloth, carbon rod and carbon sheet.

4. The membrane composite electrochemical carbon capture system according to claim 1, characterized in that, The carbon-based material electrode in the electrolytic cell (2) can be modified with a substrate or doping material. The doping material includes any one of carbon nanotubes and graphene. The substrate includes any one of nickel foam, platinum sheet, and nickel-plated platinum mesh.

5. The membrane composite electrochemical carbon capture system according to claim 1, characterized in that, Using potassium carbonate as a CO2 absorbent provides an alkaline environment to the solution, and after absorbing CO2, HCO3- - Through the MOF membrane, it enters the Q chamber; In addition to potassium carbonate, CO2 absorbents also include: ammonia, monoethanolamine, ethylenediamine, triethanolamine, and piperazine; Using potassium chloride as a supporting electrolyte can provide high ionic conductivity for battery systems. In addition to potassium chloride, supporting electrolytes also include other salt supporting electrolytes or ionic liquids.

6. The membrane composite electrochemical carbon capture system according to claim 1, characterized in that, The entire membrane composite electrochemical carbon capture system is designed as an integrated device according to requirements, or as a large-scale integrated device through series and parallel connection of the system, and is suitable for flue gas from coal-fired power plants, factory exhaust gas and transportation exhaust gas.

7. The membrane composite electrochemical carbon capture system according to claim 1, characterized in that, MOF membrane (4) can be replaced by a membrane that has the function of isolating oxygen and allowing ions to pass through, specifically including a hybrid matrix membrane.

8. A method for operating a membrane composite electrochemical carbon capture system, characterized in that, The membrane composite electrochemical carbon capture system according to claim 1 includes the following working steps: the flue gas source (8) introduces oxygen-containing flue gas into the absorption chamber (3), the K2CO3 solution in the absorption chamber absorbs CO2 in the flue gas to generate KHCO3, and the external power supply (1) is turned on, and the cathode of the Q chamber (5) undergoes a reduction reaction to generate OH. - OH - The CO2 passes through the MOF membrane (4) to the absorption chamber (3), increasing the alkalinity of the absorption chamber (3) and promoting CO2 absorption. The HCO3 produced by absorbing CO2 in the absorption chamber (3) is then absorbed. - It will reach the Q chamber (5) through the MOF membrane (4) to ensure the charge conservation of each chamber; During electrolysis, an oxidation reaction occurs at the anode of the potassium ferricyanide chamber (7) to produce K. + The gas passes through the cation exchange membrane (6) and reaches chamber Q (5); the remaining gas exits from the absorption chamber (3) and is then vented; the reaction equation is as follows: After a period of time, the electrodes are switched, and an oxidation reaction occurs at the anode of chamber Q (5) to produce H. + HCO3 in chamber Q (5) - The reaction desorbs CO2, and K is released during electrolysis. + CO2 desorbed from chamber Q (5) passes through cation exchange membrane (6) to potassium ferricyanide chamber (7), where a reduction reaction occurs at the cathode of potassium ferricyanide chamber (7). The CO2 desorbed from chamber Q (5) and absorption chamber (3) is collected in CO2 collection bottle (9). The reaction equation is as follows: Finally, the conversion of QH2 to Q is achieved by exchanging the electrodes again, thereby realizing the cyclic operation of the membrane composite electrochemical carbon capture system.

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