Photovoltaically driven direct air carbon capture and electrocatalytic conversion coupled system and method

Abstract

A photovoltaic-driven direct air carbon capture and electrocatalytic conversion coupling system and method are disclosed. This system constructs a fully liquid-phase direct-connection process without intermediate desorption steps through the synergistic coupling of a photovoltaic power generation unit, a direct air capture reaction tower, an electrochemical pH adjustment unit, and an electrocatalytic conversion unit. This achieves efficient capture, enrichment, and highly selective conversion of low-concentration carbon dioxide in the air. The photovoltaic-driven mode is versatile and can be adapted to various scenarios with abundant light resources, solving the problems of high regeneration energy consumption and carbon dioxide electroreduction dependence on high-purity feedstock and limited mass transfer in traditional direct air carbon capture.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, and specifically relates to a photovoltaic-driven direct air carbon capture and electrocatalytic conversion coupling system and method. Background Technology

[0002] Direct air capture (DAC) technology is considered to have significant application prospects due to its ability to directly remove CO2 from the atmosphere and its flexibility in distributed deployment. Current DAC technologies mainly employ chemical absorption, utilizing strongly alkaline solutions to capture CO2 from the air. While this method demonstrates excellent capture efficiency, its regeneration process suffers from severe energy efficiency bottlenecks. Sanz-Perez ES et al., in their paper "Direct Capture of CO2 from Ambient Air" published in Chemical Reviews, pointed out that traditional industrial processes typically require high-temperature calcination to decompose carbonate intermediates and release pure CO2 gas, with energy demands as high as 12–17 GJ / tCO2. Furthermore, the regeneration process is often accompanied by significant sensible heat losses (Chem. Rev., 2016, 116, 11840-11876). On the other hand, while electrocatalytic carbon dioxide reduction (CO2RR) technology can convert CO2 into high-value-added chemicals, existing electroreduction devices face the problem of extremely low gas solubility in the electrolyte, approximately 33 mM at 25°C, leading to limited mass transfer. This separation of capture and conversion creates a serious technological gap: the capture end consumes a large amount of energy to obtain high-purity gas, while the conversion end increases system complexity to handle gas mass transfer.

[0003] To address this contradiction, integrated carbon capture and utilization (ICC) concepts are gradually emerging as a cutting-edge approach. The core of this approach lies in the direct electrocatalytic conversion of the captured carbon-containing absorbent, thereby completely eliminating the energy-intensive intermediate desorption step. However, existing integrated systems still face challenges when processing ultra-low concentrations of carbon dioxide at the air level, including slow capture kinetics, intense competition for hydrogen evolution during electroreduction, and difficulties in achieving closed-loop material circulation. For example, patent CN119951268B discloses a solar-driven direct air carbon capture system, but it only couples direct air carbon capture with solar energy, lacking a pH adjustment unit and an electrocatalytic CO2 reduction unit, thus failing to achieve integrated capture-conversion and exhibiting defects such as discontinuous process and difficulty in achieving closed-loop material circulation. Furthermore, how to reduce the overall system operating cost while ensuring high Faraday efficiency remains a key constraint on the large-scale application of this technology. Summary of the Invention

[0004] To overcome the shortcomings of the existing technologies, this invention aims to provide a photovoltaic-driven direct air carbon capture and electrocatalytic conversion coupling system and method that combines direct air carbon capture, electrochemical pH adjustment, and carbon dioxide electrocatalytic conversion. This system achieves efficient capture, enrichment, and highly selective conversion of low-concentration carbon dioxide in the air through the synergistic coupling of a photovoltaic power generation unit, a DAC reaction tower, an electrochemical pH adjustment unit, and an electrocatalytic conversion unit. The photovoltaic-driven mode is versatile and can be adapted to various scenarios with abundant light resources, solving the problems of high regeneration energy consumption and carbon dioxide electroreduction dependence on high-purity feedstock and limited mass transfer in traditional direct air carbon capture.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A photovoltaic-driven direct air carbon capture and electrocatalytic conversion device includes a DAC reaction tower, an electrochemical pH adjustment unit, an electrocatalytic conversion unit, and a photovoltaic power generation unit; the photovoltaic power generation unit supplies power to each unit. The DAC reaction tower uses a collection liquid to capture CO2 from ambient air, obtaining a CO3-rich solution. 2- Collection fluid; The electrochemical pH adjustment unit is connected to the DAC reaction tower and receives the CO3-rich solution. 2- The collecting solution utilizes an electrochemical reaction to obtain H at the anode. + For the CO3-rich 2- The collection solution is acidified; The electrocatalytic conversion unit is connected to the electrochemical pH adjustment unit, and receives the acidified collection solution. It then utilizes the H2O obtained at the anode via an electrocatalytic oxidation reaction. + A secondary acidification treatment is performed, followed by an electrocatalytic reduction reaction at the cathode to obtain CO and a liquid with increased alkalinity. The liquid with increased alkalinity is returned to the cathode of the electrochemical pH adjustment unit for a secondary increase in alkalinity, and then returned to be mixed with the capture liquid of the DAC reaction tower to participate in the next round of carbon capture.

[0006] The DAC reaction tower includes a tower body 11. The bottom of the tower body 11 is divided into an upper liquid storage chamber 2 and a lower liquid storage chamber 1, which are connected by a throttling valve A 3 for gravity flow and circulation of the liquid. An atomizing nozzle 4 is installed above the upper liquid storage chamber 2 within the tower body 11. The atomizing nozzle 4 is connected to the lower liquid storage chamber 1 via a pipeline with a throttling valve B 10 and a circulating water pump 7, forming a fluid circulation loop. An induced draft fan 6 and a demister 5 are installed above the atomizing nozzle 4 within the tower body 11. The induced draft fan 6 is located above the demister 5. The lower liquid storage chamber 1 receives the collected liquid with increased alkalinity after secondary treatment, while the upper liquid storage chamber 2 provides the CO3-rich liquid to the electrochemical pH adjustment unit. 2-The upper liquid storage chamber 2 is connected to an air inlet 9.

[0007] The induced draft fan 6 is set to a wind speed of 3~10 m / s, the circulating water pump 7 has a flow rate of 10~20 L / min, and the atomizing nozzle 4 is set to an atomization angle of 60°~90°.

[0008] The electrochemical pH adjustment unit includes a flow electrochemical reactor 15, which includes an A cathode liquid chamber 19 and an A anolyte liquid chamber 21 separated by a cation exchange membrane 20; the A cathode liquid chamber 19 contains an A cathode 18, and the A anolyte liquid chamber 21 contains an A anode 22. The Anode liquid chamber 21 receives the CO3-rich solution. 2- The collecting solution, using an electrochemical reaction at anode 22 of A, yields H... + For the CO3-rich 2- The collection solution is acidified; The cathode liquid chamber 19 receives the liquid with increased alkalinity and provides OH- through a reduction reaction. - The alkalinity increases secondary.

[0009] The feed rate of the flow electrochemical reactor 15 is controlled at 10~50 mL / min.

[0010] The electrocatalytic conversion unit includes a flow electrochemical reaction cell 26, which includes a B cathode liquid chamber 32 and a B anolyte chamber 30 separated by an anion exchange membrane 31. The B anode liquid chamber 30 receives the acidified collection solution, and H is obtained from the B anode 29 through an electrocatalytic oxidation reaction. + A second acidification treatment is performed; In the cathode liquid chamber 32 of the B chamber, CO and an increasingly alkaline liquid are obtained by electrocatalytic reduction reaction, which are then separated by a gas-liquid separation device and the CO is discharged.

[0011] The liquid inlet rate of the flow electrochemical reactor 26 is controlled at 10~50 mL / min.

[0012] A conversion method for a photovoltaic-driven direct air carbon capture and electrocatalytic conversion device includes the following operating steps: Step 1: The ambient air to be treated is fed into the DAC reaction tower for CO2 capture. After the capture liquid absorbs CO2 and reaches a steady state, it yields a CO3-rich solution. 2- Collection fluid; Step two, the CO3-rich 2- The collected solution is fed into the electrochemical pH adjustment unit, and an electrochemical reaction is initiated by applying electricity, utilizing the H+ obtained at the anode. + For the CO3-rich2- The collection solution is acidified; Step 3: After acidification, the acidified collection solution is fed into the electrocatalytic conversion unit, and the electrocatalytic oxidation and electrocatalytic reduction reactions are initiated by energizing the unit. H₂ is obtained through the electrocatalytic oxidation reaction. + The collection liquid is subjected to secondary acidification treatment, and the collection liquid obtained by the secondary acidification treatment is converted into CO and a liquid with increased alkalinity through the electrocatalytic reduction reaction. Step four: The liquid with increased alkalinity is returned to the cathode of the electrochemical pH adjustment unit for a secondary increase in alkalinity; Step 5: The liquid with increased alkalinity is returned to the DAC reaction tower to participate in the next round of carbon capture.

[0013] The collecting solution in step one is an aqueous solution of KOH with a concentration of 0.25~1.0 mol / L.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. Unlike the high-energy-consuming high-temperature desorption and purification steps in traditional processes, this invention constructs a fully liquid-phase direct-connection process flow, which directly uses the captured absorbent for subsequent electrochemical conversion. The system actively utilizes the cathode hydrogen evolution reaction to construct an internal gas circulation mechanism, realizing low-carbon closed-loop operation of carbon capture and conversion at room temperature and pressure.

[0015] 2. To ensure the long-term stable operation of the system, this invention proposes a dynamic matching strategy for the reaction rates of the front and back ends. By synergistically optimizing the spray absorption parameters of the front-end capture tower and the working current density of the back-end flow electrochemical reactor, the material flow balance between carbon capture mass flux and electrocatalytic reduction rate is achieved. This mechanism not only maintains the stable evolution of CO2 concentration in the circulating liquid, but also ensures the high selectivity of CO generation in the electrocatalytic process. 3. This invention resolves the process conflict between high pH, ​​which favors carbon capture, and low pH, which favors electrocatalytic CO2 reduction, through stepwise pH control. The system oxidizes and releases acid from the internally circulating H2 at the anode of the pH adjustment unit, lowering the pH of the strongly alkaline rich solution and converting it into a weakly alkaline substrate suitable for subsequent electroreduction. In the regeneration stage of step five, K... + Transmembrane migration and cathodic electrolysis of water produce alkali, the solution pH rises and is directly returned to the front-end collection tower. The results of secondary acidification in step four and secondary alkalization in step five achieve long-term self-sustaining of high-concentration strong alkali absorbent.

[0016] In summary, this invention effectively overcomes the technical bottlenecks of high energy consumption and limited mass transfer in traditional carbon capture and utilization technologies. By proposing a photovoltaic-driven, non-desorption liquid-phase direct-connection architecture and an H2 internal circulation pH control mechanism, this system effectively coordinates the physicochemical contradiction between high pH, ​​which is conducive to air capture, and low pH, which is conducive to electrochemical reduction, and achieves precise dynamic matching of material flow and electron flow under complex operating conditions. This coupled system significantly reduces the carbon footprint and overall operating energy consumption throughout its life cycle, while providing a highly efficient, stable, and self-sustaining low-carbon closed-loop solution for areas with abundant solar resources and grid deficiencies, such as offshore areas and plateau regions. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the operating principle of the present invention.

[0018] Figure 2 This is a schematic diagram of the reaction principle.

[0019] Figure 3 This is a schematic diagram of the device structure of the present invention.

[0020] Figure 4 This is a schematic diagram of the DAC reaction tower of the present invention.

[0021] Figure 5 This is a schematic diagram of the electrochemical pH adjustment unit and the photovoltaic power generation unit of the present invention.

[0022] Figure 6 This is a schematic diagram of the flow-type electrochemical reactor in the electrochemical pH adjustment unit of the present invention.

[0023] Figure 7 This is a schematic diagram showing the connection relationship of the electrocatalytic conversion unit of the present invention.

[0024] Figure 8 This is a schematic diagram of the flow-type electrochemical reaction cell in the electrocatalytic conversion unit of the present invention.

[0025] Figure 9 The time evolution of CO2 concentration under different KOH concentration conditions is shown.

[0026] Figure 10 The selectivity of CO2 electroreduction products under different current densities.

[0027] Figure 4 In the middle, 1-lower liquid storage chamber, 2-upper liquid storage chamber, 3-A throttling valve, 4-atomizing nozzle, 5-demister, 6-expelled fan, 7-circulating water pump, 8-lower liquid storage chamber injection opening, 9-air inlet, 10-B throttling valve, 11-tower body.

[0028] Figure 5Among them, 12-A is the inlet peristaltic pump, 13-battery bracket, 14-photovoltaic power generation panel, 15-flow electrochemical reactor, and 16-A is the outlet peristaltic pump.

[0029] Figure 6 Among them, 17-A is the cathode cover plate, 18-A is the cathode, 19-A is the cathode liquid chamber, 20- is the cation exchange membrane, 21-A is the anolyte chamber, 22-A is the anode, and 23-A is the anode cover plate.

[0030] Figure 7 In the middle, 24-reaction tank support, 25-B inlet peristaltic pump, 26-flow electrochemical reaction tank, 27-B outlet peristaltic pump.

[0031] Figure 8 Among them, 28-B anode cover plate, 29-B anode, 30-B anolyte chamber, 31-anion exchange membrane, 32-B catholyte chamber, 33-B cathode, and 34-B cathode cover plate. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] Example 1 Reference Figure 1 , Figure 3 A photovoltaic-driven direct air carbon capture and electrocatalytic conversion device includes a DAC reaction tower, the liquid output end of which is connected to the liquid input end of an electrochemical pH adjustment unit to receive CO3-rich water. 2- The collecting solution utilizes an electrochemical reaction to obtain H at the anode. + For the CO3-rich 2- The collected solution is acidified; the liquid output of the electrochemical pH adjustment unit is connected to the liquid input of the electrocatalytic conversion unit to receive the acidified collected solution, and the H2O obtained at the anode is generated by the electrocatalytic oxidation reaction. + The solution undergoes a secondary acidification treatment, followed by an electrocatalytic reduction reaction at the cathode to obtain CO and a liquid with increased alkalinity. The solution after the electrocatalytic conversion unit reaction flows back to the electrochemical pH adjustment unit via peristaltic pump B 27 to further increase alkalinity, undergoing a secondary alkalinity increase. Then, it flows back to the DAC reaction tower via peristaltic pump A 16, and is subsequently mixed with the capture liquid of the DAC reaction tower to participate in the next round of carbon capture. The DAC reaction tower, electrochemical pH adjustment unit, and electrocatalytic conversion unit are electrically connected to the photovoltaic power generation unit, which provides the operating power for the entire system.

[0034] Reference Figure 4The DAC reaction tower includes a tower body 11, which is divided into upper, middle, and lower sections and sealed together by flanges. The bottom of the tower body 11 is divided into an upper liquid storage chamber 2 and a lower liquid storage chamber 1. The upper liquid storage chamber 2 and the lower liquid storage chamber 1 are connected by a throttling valve A 3 on their sides for gravity flow and circulation of the liquid. An induced draft fan 6 and a demister 5 are sequentially arranged in the upper chamber of the tower body 11. An atomizing nozzle 4 is arranged in the middle chamber of the tower body 11. The atomizing nozzle 4 is connected to the lower liquid storage chamber 1 via a throttling valve B 10, a circulating water pump 7, and the lower liquid storage chamber 1 to form a fluid circulation loop. The lower liquid storage chamber 1 receives the secondary alkalinity-increasing collection liquid, and the upper liquid storage chamber 2 provides the CO3-rich liquid to the electrochemical pH adjustment unit. 2- The collecting liquid has a lower liquid storage chamber 1 with a liquid injection opening 8 and an air inlet 9 on the upper side of the upper liquid storage chamber 2.

[0035] Reference Figure 5 The electrochemical pH adjustment unit includes an A inlet peristaltic pump 12 connected to the DAC reaction tower, an A inlet peristaltic pump 12 connected to a flow electrochemical reactor 15, an A outlet peristaltic pump 16 connected to the outlet of the flow electrochemical reactor 15, and an A outlet peristaltic pump 16 connected to the DAC reaction tower.

[0036] Reference Figure 6 The flow-type electrochemical reactor 15 includes an A cathode liquid chamber 19 and an A anolyte chamber 21 separated by a cation exchange membrane 20. The A cathode liquid chamber 19 contains an A cathode 18, and the A anolyte chamber 21 contains an A anode 22. Specifically, an A cathode cover plate 17 is provided at its left end, with the inner side of the A cathode cover plate 17 tightly fitted to the A cathode 18, and the side of the A cathode 18 away from the A cathode cover plate 17 fitted to the A cathode liquid chamber 19. The other side of the A cathode liquid chamber 19 is sealed and separated by the cation exchange membrane 20, with the other side of the cation exchange membrane 20 fitted to the A anolyte chamber 21. The side of the A anolyte chamber 21 away from the cation exchange membrane 20 is fitted to the A anode 22, and the outer side of the A anode 22 is tightly fitted to the A anode cover plate 23, thus forming an integrally sealed assembly structure. The reactor also has communication ports for liquid and gas inlet and outlet. The A anolyte chamber 21 receives the CO3-rich liquid. 2- The collecting solution, using an electrochemical reaction at anode 22 of A, yields H... + For the CO3-rich 2- The collecting solution is acidified; the A cathode liquid chamber 19 receives the liquid with increased alkalinity and undergoes a secondary alkalinity increase through a reduction reaction.

[0037] Reference Figure 7The electrocatalytic conversion unit includes a flow-type electrochemical reaction cell 26 mounted on a reaction cell support 24. The inlet and outlet of the flow-type electrochemical reaction cell 26 are respectively equipped with a B inlet peristaltic pump 25 and a B outlet peristaltic pump 27. The B anode liquid chamber 30 receives the acidified collected liquid, and H2O is obtained at the B anode 29 through an electrocatalytic oxidation reaction. + A secondary acidification treatment is performed; in the cathode liquid chamber 32 of B, CO and an increasingly alkaline liquid are obtained by electrocatalytic reduction reaction, which are then separated by a gas-liquid separation device and the CO is discharged.

[0038] Reference Figure 8 The flow-type electrochemical reaction cell 26, wherein the B anolyte chamber 30 receives the acidified collection solution, and the H2O obtained at the B anode 29 is obtained through an electrocatalytic oxidation reaction. + A secondary acidification treatment is performed; the collected liquid from the secondary acidification treatment is directly introduced into the B cathode liquid chamber 32 through an external channel; in the B cathode liquid chamber 32, CO and an increasingly alkaline liquid are obtained by electrocatalytic reduction reaction, which are then separated by a gas-liquid separation device and the CO is discharged.

[0039] The flow-type electrochemical reaction cell 26 is specifically arranged as follows: a B anode cover plate 28 is provided at its left end, the inner side of the B anode cover plate 28 is tightly attached to the B anode 29, and the side of the B anode 29 away from the B anode cover plate 28 is attached to the B anode liquid chamber 30; the other side of the B anode liquid chamber 30 is sealed and separated by anion exchange membrane 31, and the other side of the anion exchange membrane 31 is attached to the B cathode liquid chamber 32; the side of the B cathode liquid chamber 32 away from the anion exchange membrane 31 is attached to the B cathode 33, and the outer side of the B cathode 33 is tightly attached to the B cathode cover plate 34, thus forming an integral sealed assembly structure; the reaction cell is also provided with a communication port for liquid and gas inlet and outlet.

[0040] Reference Figure 5 , Figure 7 The photovoltaic power generation unit includes a battery bracket 13 and a photovoltaic power generation panel 14 mounted on the battery bracket 13.

[0041] Reference Figure 2 A method for using a photovoltaic-driven direct air carbon capture and electrocatalytic conversion device includes the following operating steps: Step 1: 16 L of a collecting solution (0.5 mol / L KOH aqueous solution) is added to the lower storage chamber through opening 8. Ambient air to be treated is then introduced into the DAC reaction tower through inlet 9 for CO2 capture. After the collecting solution absorbs CO2 and reaches a steady state, a CO3-rich solution is obtained. 2- Collection fluid; After adding the collecting liquid, the induced draft fan 6, circulating water pump 7, and throttle valve 10 are turned on. The collecting liquid, drawn by the circulating water pump 7, is atomized and sprayed downwards at a certain atomization angle through the atomizing nozzle 4, making countercurrent contact with the air drawn in and flowing upwards by the induced draft fan 6, thus absorbing CO2 from the air. The liquid, having absorbed CO2, falls into the upper storage chamber 2 and flows back to the lower storage chamber 1 controlled by throttle valve A 3. This collecting cycle lasts for 10 hours. Preferably, during this stage, the induced draft fan is set to a wind speed of 9 m / s, the circulating water pump flow rate is 10 L / min, and the atomization angle of the atomizing nozzle is set to 60°.

[0042] Step 2, pH adjustment stage: After the collected solution absorbs CO2 and reaches a steady state, start the inlet peristaltic pump 12 and the flow electrochemical reactor 15 to process the CO3-rich solution. 2- The collected liquid is introduced into the A anolyte chamber 21 of the electrochemical reaction cell 15 of the electrochemical pH adjustment unit via the A inlet peristaltic pump 12. Driven by photovoltaic power, the electrochemical reaction is initiated. A reduction reaction occurs at the A cathode to produce H2. The H2 is then introduced to the A anode through the gas outlet, where it is oxidized to produce H2. + Utilizing H obtained at the anode + For the CO3-rich 2- The collection solution is acidified to react with CO3. 2- Combine to generate HCO3 - This acidifies the collected liquid. Preferably, the flow rate of the inlet peristaltic pump 16 is controlled at 10 mL / min. The current density of the flow electrochemical reactor 15 during operation is set to 15 mA / cm². 2 .

[0043] Step 3: After acidification, the acidified collection solution is fed into the electrocatalytic conversion unit, and the electrocatalytic oxidation and electrocatalytic reduction reactions are initiated by energizing the unit. H₂ is obtained through the electrocatalytic oxidation reaction. + The collection solution is subjected to secondary acidification treatment. Specifically, the collected solution, acidified by the electrochemical pH adjustment unit, enters the B anolyte chamber 30 of the flow-type electrochemical reaction tank 26 via the inlet peristaltic pump 25. Under the drive of photovoltaic power, the B anolyte chamber undergoes an electrocatalytic oxidation reaction to produce O2, which in turn generates H2. + The collected solution is further acidified, and the secondary acidified collected solution is introduced into cathode chamber 32 (B), where an electrocatalytic reduction reaction occurs under the drive of photovoltaic power. Preferably, the flow rate of peristaltic pump 25 (B inlet) is controlled at 10 mL / min. The current density of the flow-type electrochemical reaction cell 26 is set to 15 mA / cm² during operation. 2 .

[0044] Step four: Product separation and regeneration cycle. The gaseous product CO from the reaction is discharged through the gas outlet of the B cathode liquid chamber 32 of the flow electrochemical reactor 26 for subsequent post-processing. The liquid, whose alkalinity increases after electrocatalytic reduction, is transported back to the A cathode liquid chamber 19 of the electrochemical pH adjustment unit via the B outlet peristaltic pump 27, where it provides OH- through a reduction reaction. - Further increasing alkalinity is equivalent to performing a secondary increase in alkalinity. Step 5: The liquid with increased alkalinity is transported back to the lower storage chamber 1 of the DAC reaction tower via the A outlet peristaltic pump 16 to continue circulating and participate in the next round of carbon capture.

[0045] This invention utilizes the oxidation of H2 circulating in the internal circulation system at the anode of the pH adjustment unit to release acid, thereby reducing the pH of the strongly alkaline rich solution from 12.4 to 9.0, converting it into a weakly alkaline substrate suitable for subsequent electroreduction. In the regeneration stage, K... + Transmembrane migration and cathodic electrolysis of water produce alkali, causing the solution pH to rise back to 13.8 and be directly returned to the front-end collection tower.

[0046] Example 2 This embodiment is the same as Embodiment 1, except that the induced draft fan is set to a wind speed of 9 m / s, the circulating water pump flow rate is 10 L / min, and the atomization angle of the atomizing nozzle is set to 60°.

[0047] Example 3 This embodiment is the same as Embodiment 1, except that the induced draft fan is set to a wind speed of 9 m / s, the circulating water pump flow rate is 10 L / min, and the atomization angle of the atomizing nozzle is set to 80°.

[0048] Example 4 This embodiment is the same as Embodiment 1, except that the induced draft fan is set to a wind speed of 9 m / s, the circulating water pump flow rate is 10 L / min, and the atomization angle of the atomizing nozzle is set to 90°.

[0049] The atomizing nozzle can achieve its function with an atomization angle set between 60° and 90°, with 90° being the optimal design.

[0050] Example 5 This embodiment is the same as Embodiment 1, except that the current density during operation is set to 10 mA / cm². 2 .

[0051] Example 6 This embodiment is the same as Embodiment 1, except that the current density during operation is set to 20 mA / cm². 2 .

[0052] Example 7 This embodiment is the same as Embodiment 1, except that the current density during operation is set to 50 mA / cm². 2 .

[0053] Example 8 This embodiment is the same as Embodiment 1, except that the current density during operation is set to 100 mA / cm². 2 .

[0054] Figure 9 This paper demonstrates the relationship between CO2 concentration and operating time in the direct air carbon capture coupling system of this invention under the action of different concentrations of KOH absorbent. The evolution characteristics of CO2 concentration over time were investigated under two KOH concentrations: 0.75 mol / L and 1.00 mol / L. Experimental results show that the concentration of the alkali solution has a significant regulatory effect on the CO2 capture performance of the system: as the KOH concentration increases, the average CO2 absorption efficiency of the system first increases and then decreases, reaching a peak of 19.0% at a concentration of 0.75 mol / L; the selectivity for electroreduction to CO reaches 97.1%. This route eliminates the intermediate desorption process, significantly reducing overall operating energy consumption and providing a new pathway for the efficient enrichment and conversion of CO2.

[0055] Figure 10 This demonstrates the selectivity of the three products, CO, H2, and HCOOH, during the electrocatalytic reduction of CO2 (CO2RR) as a function of current density (20–200 mA / cm²). 2 The variation pattern of CO was observed. Combined with Examples 5-8, the results show that CO is the dominant reduction product in this system: in the low current density range (20~60 mA / cm²), CO exhibits the following characteristics. 2 The selectivity for CO remained at an ultra-high level of 95%–98%, and the hydrogen evolution reaction (HER) and formic acid formation side reaction were significantly suppressed; as the current density increased to the medium-high range (80–200 mA / cm²), the CO selectivity remained at an ultra-high level. 2 The selectivity for CO showed a slow decreasing trend, but at 200 mA / cm², it remained relatively high. 2 Even under high current conditions, the catalyst maintains a high selectivity of approximately 66%, while the proportions of H2 and HCOOH gradually increase in tandem, remaining minor byproducts throughout the entire current density range. Overall, this catalyst exhibits excellent CO2RR-to-CO selectivity across a wide current density range, demonstrating promising potential for practical applications.

[0056] In summary, the key to achieving deep coupling in this invention lies in the dynamic matching of material and electron flows between multi-stage reaction units. The system ensures a balance in the flux of material conversion between the front and back ends by regulating the transmembrane ion migration rate and the dual-cathode alkali production rate, thus guaranteeing the efficient and self-sustaining operation of the closed-loop process. The introduced electrochemical pH adjustment unit can acidify the captured carbon-rich liquid, converting it into a solution rich in HCO3-. 2- The electrolyte significantly improves CO2 availability and the conversion efficiency of subsequent electrochemical reduction reactions. Simultaneously, the alkaline absorbent is cyclically generated at room temperature and pressure on the cathode side of this regulation process, providing a new pathway to bypass traditional high-energy-consuming steps such as intermediate desorption, high-purity gas purification, and pressurization. Based on this, the entire system relies on photovoltaic power to drive the process, drastically reducing the carbon footprint of carbon capture and conversion throughout its entire lifecycle. Furthermore, it can flexibly adapt to different application scenarios without modifying core equipment or the overall closed-loop process, making it extremely suitable for offshore or plateau areas with abundant solar resources to meet the low-carbon conversion needs of areas without grid access or with insufficient grid coverage.

Claims

1. A photovoltaic-driven direct air carbon capture and electrocatalytic conversion device, characterized in that, It includes a DAC reaction tower, an electrochemical pH adjustment unit, an electrocatalytic conversion unit, and a photovoltaic power generation unit; the photovoltaic power generation unit supplies power to each unit. The DAC reaction tower uses a collection liquid to capture CO2 from ambient air, obtaining a CO3-rich solution. 2- Collection fluid; The electrochemical pH adjustment unit is connected to the DAC reaction tower and receives the CO3-rich solution. 2- The collecting solution utilizes an electrochemical reaction to obtain H at the anode. + For the CO3-rich 2- The collection solution is acidified; The electrocatalytic conversion unit is connected to the electrochemical pH adjustment unit, and receives the acidified collection solution. It then utilizes the H2O obtained at the anode via an electrocatalytic oxidation reaction. + A secondary acidification treatment is performed, followed by an electrocatalytic reduction reaction at the cathode to obtain CO and a liquid with increased alkalinity. The liquid with increased alkalinity is returned to the cathode of the electrochemical pH adjustment unit for a secondary increase in alkalinity, and then returned to be mixed with the capture liquid of the DAC reaction tower to participate in the next round of carbon capture.

2. The photovoltaic-driven direct air carbon capture and electrocatalytic conversion device according to claim 1, characterized in that, The DAC reaction tower includes a tower body (11). The bottom of the tower body (11) is divided into an upper liquid storage chamber (2) and a lower liquid storage chamber (1). The upper liquid storage chamber (2) and the lower liquid storage chamber (1) are connected by a throttle valve (3) for gravity flow and circulation of the liquid. An atomizing nozzle (4) is installed above the upper liquid storage chamber (2) in the tower body (11). The atomizing nozzle (4) is connected to the lower liquid storage chamber (1) through a pipeline with a throttle valve (10) and a circulating water pump (7) to form a fluid circulation loop. An induced draft fan (6) and a demister (5) are installed above the atomizing nozzle (4) in the tower body (11). The induced draft fan (6) is located above the demister (5). The lower liquid storage chamber (1) receives the secondary alkalinity-increasing collection liquid, and the upper liquid storage chamber (2) provides the CO3-rich liquid to the electrochemical pH adjustment unit. 2- The upper liquid storage chamber (2) is connected to an air inlet (9).

3. The photovoltaic-driven direct air carbon capture and electrocatalytic conversion device according to claim 1, characterized in that, The electrochemical pH adjustment unit includes a flow-type electrochemical reactor (15), which includes an A cathode liquid chamber (19) and an A anolyte liquid chamber (21) separated by a cation exchange membrane (20); the A cathode liquid chamber (19) contains an A cathode (18), and the A anolyte liquid chamber (21) contains an A anode (22). The Anode chamber (21) receives the CO3-rich solution. 2- The collecting solution, using an electrochemical reaction at anode A (22) yields H + For the CO3-rich 2- The collection solution is acidified; The A cathode liquid chamber (19) receives the liquid with increased alkalinity and undergoes a secondary alkalinity increase through a reduction reaction.

4. The photovoltaic-driven direct air carbon capture and electrocatalytic conversion device according to claim 3, characterized in that, The feed rate of the flow electrochemical reactor (15) is controlled at 10~50 mL / min.

5. The photovoltaic-driven direct air carbon capture and electrocatalytic conversion device according to claim 1, characterized in that, The electrocatalytic conversion unit includes a flow-type electrochemical reaction cell (26), which includes a B cathode liquid chamber (32) and a B anolyte chamber (30) separated by an anion exchange membrane (31). The B anolyte chamber (30) receives the acidified collection solution, and H is obtained at the B anode (29) through an electrocatalytic oxidation reaction. + A secondary acidification treatment is performed; the collection solution of the secondary acidification treatment is introduced into the B cathode liquid chamber (32) through an external channel. In the cathode liquid chamber (32) of the B, CO and an increased alkalinity liquid are obtained by electrocatalytic reduction reaction, and then separated by a gas-liquid separation device and the CO is discharged.

6. The photovoltaic-driven direct air carbon capture and electrocatalytic conversion device according to claim 1, characterized in that, The liquid inlet of the flow electrochemical reactor (26) is controlled at 10~50 mL / min.

7. The conversion method of a photovoltaic-driven direct air carbon capture and electrocatalytic conversion device according to claim 1, characterized in that, The following steps are included: Step 1: The ambient air to be treated is fed into the DAC reaction tower for CO2 capture. After the capture liquid absorbs CO2 and reaches a steady state, it yields a CO3-rich solution. 2- Collection fluid; Step two, the CO3-rich 2- The collected solution is fed into the electrochemical pH adjustment unit, and an electrochemical reaction is initiated by applying electricity, utilizing the H+ obtained at the anode. + For the CO3-rich 2- The collection solution is acidified; Step 3: After acidification, the acidified collection solution is fed into the electrocatalytic conversion unit, and the electrocatalytic oxidation and electrocatalytic reduction reactions are initiated by energizing the unit. H₂ is obtained through the electrocatalytic oxidation reaction. + The collection liquid is subjected to secondary acidification treatment, and the collection liquid obtained by the secondary acidification treatment is converted into CO and a liquid with increased alkalinity through the electrocatalytic reduction reaction. Step four: The liquid with increased alkalinity is returned to the cathode of the electrochemical pH adjustment unit for a secondary increase in alkalinity; Step 5: The liquid with increased alkalinity is returned to the DAC reaction tower to participate in the next round of carbon capture.

8. The conversion method of a photovoltaic-driven direct air carbon capture and electrocatalytic conversion device according to claim 7, characterized in that, The collecting solution in step one is an aqueous solution of KOH with a concentration of 0.25~1.0 mol / L.

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