Method for electrolysis of carbon dioxide and electrolysis device

Abstract

An electrolysis method and apparatus for carbon dioxide, comprising: an electrolysis container for holding a molten salt electrolyte; an anode for the electrolysis reaction, inserted into the molten salt electrolyte during the electrolysis reaction; a cathode for the electrolysis reaction, which is a liquid metal during the electrolysis reaction, with the molten salt electrolyte covering the cathode; a composite component including a cathode container and a vent pipe, the cathode container holding the cathode and the vent pipe connected to the cathode container; and a power supply component, the positive terminal of which is electrically connected to the anode and the negative terminal of which is electrically connected to the cathode. The liquid metal cathode is placed inside the cathode container, and the size of the reaction interface can be flexibly changed by adjusting the volume of the container. Combining the cathode container and the vent pipe into a composite component allows carbon dioxide to enter the liquid metal from the bottom up, achieving direct gas introduction rather than just introducing the molten salt electrolyte, ensuring more complete contact between carbon dioxide and the cathode reaction area, and effectively improving cathode passivation.

Description

Technical Field

[0001] This invention relates to the field of electrolysis technology, and in particular to a method and apparatus for electrolyzing carbon dioxide. Background Technology

[0002] The resource utilization of CO2 is crucial for achieving the goal of net-zero CO2 emissions. Converting CO2 into value-added carbon materials or important fuels such as methane and ethylene through electrolysis is an important means of realizing CO2 resource utilization. High-temperature molten salt electrolysis technology, due to its advantages such as high CO2 solubility, wide electrochemical window, good electrical and thermal conductivity, and no reliance on precious metal catalysts, has become an important pathway for CO2 electrolytic conversion, demonstrating enormous potential for large-scale application.

[0003] In high-temperature molten salt electrolysis of CO2, common cathodes include solid electrodes such as nickel and stainless steel, where carbonate to carbon conversion occurs. An inherent problem is that the carbon products from electrolysis deposit on the surface of the solid cathode, accumulating and covering the effective reaction area, hindering the continuous reaction. Besides product accumulation, Li2O metal oxide is generated during electrolysis, which has very low solubility in molten salt. Although Li2O participates in the CO2 capture process, combining with CO2 to form Li2CO3 for electrolyte regeneration, when the electrochemical reaction rate exceeds the capture rate, the generated Li2O becomes excessive and also covers the cathode-electrolyte interface, affecting the reaction. This is known as "cathode passivation" in molten salt electrolysis. One solution is to use liquid metal electrodes instead of solid electrodes, utilizing the fluidization properties of liquid metal electrodes to achieve self-cleaning of the reaction interface. The carbon obtained from electrolysis also floats to the melt surface due to density differences, which not only avoids the impact of carbon deposition on the reaction continuity but also facilitates the subsequent separation and collection of carbon products. However, for the removal of Li₂O metal oxides, using liquid metal electrodes can only improve the transport and migration rate of Li₂O, allowing it to move away from the cathode reaction interface as quickly as possible after its formation. This physical approach is far from sufficient to improve the "cathode passivation" phenomenon caused by Li₂O. Considering that in addition to accelerating mass migration, Li₂O removal can also be achieved through chemical means such as enhancing the capture reaction between Li₂O and CO₂ to reduce the accumulation of Li₂O at the cathode reaction interface.

[0004] However, there are still many problems in the existing technology for molten salt electrolysis of CO2 using liquid metal electrodes. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a method and apparatus for the electrolysis of carbon dioxide to improve the phenomenon of cathode passivation.

[0006] To address the aforementioned problems, the present invention provides a carbon dioxide electrolysis device, comprising: an electrolysis container, the electrolysis container being sealed at the bottom and open at the top for holding a molten salt electrolyte; an anode for the electrolysis reaction, inserted into the molten salt electrolyte during the electrolysis reaction; a cathode for the electrolysis reaction, which is a liquid metal during the electrolysis reaction, with the molten salt electrolyte covering the cathode; a composite assembly, the composite assembly including a cathode container and a vent pipe, the cathode container being sealed at the bottom and open at the top for holding the cathode, the vent pipe being connected to the cathode container; and a power supply assembly, the positive terminal of the power supply assembly being adapted to be electrically connected to the anode, and the negative terminal of the power supply assembly being adapted to be electrically connected to the cathode.

[0007] Optionally, it may also include: an outer container, the bottom of which is sealed and the top of which is open, and the electrolytic container is adapted to be placed inside the cavity of the outer container.

[0008] Optionally, it may also include a sealing cap adapted to seal the opening of the outer container.

[0009] Optionally, one end of the anode is adapted to penetrate the sealing cap and extend into the cavity of the electrolytic container; the cathode container is adapted to be placed in the cavity of the electrolytic container; and the vent pipe is adapted to penetrate the sealing cap and extend to the outside.

[0010] Optionally, it may also include: a gas guide tube adapted to penetrate the sealing cap and extend into the cavity of the outer container for discharging gas generated during the electrolysis reaction.

[0011] Optionally, the composite component is made of a conductive material, and the negative terminal of the power supply component is adapted to be in direct contact with the composite component.

[0012] Accordingly, the present invention also provides a method for electrolyzing carbon dioxide, using the carbon dioxide electrolysis device described in any of the above technical solutions. The electrolysis method includes: placing the prepared molten salt electrolyte in the electrolysis container; inserting the cathode container, which holds the cathode, below the liquid surface of the molten salt electrolyte, such that the molten salt electrolyte covers the cathode; inserting the anode into the molten salt electrolyte, and electrically connecting the cathode and the anode to the power supply component respectively; and starting the electrolysis after the power supply component is electrically connected.

[0013] Optionally, starting electrolysis includes: cycling between an electrolysis stage and a settling stage; wherein, the electrolysis stage includes: continuously introducing carbon dioxide into the melt through the vent pipe and turning on the power supply component to carry out the electrolysis reaction, with the electrolysis time maintained for a first time period; after the first time period is reached, the settling stage is carried out, wherein the settling stage includes: turning off the power supply component and continuing to continuously introduce carbon dioxide, with the settling time maintained for a second time period.

[0014] Optionally, the molten salt electrolyte includes one or more of Li2CO3, Na2CO3, K2CO3, MgCO3, and Al2(CO3)3.

[0015] Optionally, the molten salt electrolyte is composed of Li2CO3, Na2CO3 and K2CO3 mixed in a molar ratio of 3:5:2 to 5:2:3.

[0016] Optionally, before starting electrolysis, the process further includes: heating the electrolyte to 280°C~300°C and holding it at that temperature for 22h~26h to remove moisture from the molten salt electrolyte; then raising the temperature to reach a reaction temperature of 550°C~800°C.

[0017] Optionally, during the electrolysis stage, the power supply component outputs a DC electrolysis voltage of 2.5V to 5V.

[0018] Optionally, the first time period can be in the range of 30 min to 60 min.

[0019] Optionally, the range of the second time period is 30s to 60s.

[0020] Optionally, the flow rate of carbon dioxide gas introduced during the settling stage is greater than the flow rate of carbon dioxide gas introduced during the electrolysis stage.

[0021] Compared with the prior art, the technical solution of the present invention has the following advantages: In the carbon dioxide electrolysis apparatus of this invention, the liquid metal cathode is placed inside a dedicated cathode container. The size of the cathode's reaction interface can be flexibly changed by adjusting the volume of the cathode container to adapt to different electrolysis requirements. The composite component is formed by functionally combining the cathode container (for supporting the cathode) with a vent pipe (for introducing carbon dioxide). The vent pipe is connected to the cathode container, allowing the introduced carbon dioxide to enter the interior of the liquid metal cathode from bottom to top. This composite component enables the direct introduction of carbon dioxide into the liquid metal, rather than simply into the molten salt electrolyte, thereby ensuring that the carbon dioxide gas can more fully and directly contact the cathode reaction area, thus improving cathode passivation.

[0022] Furthermore, it also includes an outer container, which is sealed at the bottom and open at the top, and the electrolytic container is adapted to be placed inside the cavity of the outer container. The outer container is made of high-temperature resistant stainless steel, which can effectively support the electrolytic container and place it in a high-temperature furnace for heating. It not only provides stable support and protection for the electrolytic container, but also effectively prevents safety hazards caused by leakage of the high-temperature molten salt electrolyte. At the same time, it facilitates the handling and temperature control of the entire device, significantly improving the safety and ease of operation of the electrolytic device in high-temperature working environments.

[0023] Furthermore, it also includes a sealing cap, which is adapted to seal the opening of the outer container. Since the carbon dioxide electrolysis reaction requires a specific gaseous environment, the sealing cap can prevent impurities such as oxygen and moisture from the outside air from entering and disrupting the reaction gaseous environment, avoiding side reactions, and ensuring the stability and reliability of the electrolysis process.

[0024] Furthermore, it also includes a gas guide pipe, which is adapted to penetrate the sealing cap and extend into the cavity of the external container for discharging gases generated during the electrolysis reaction. During electrolysis, the reaction at the anode produces oxygen, the reaction at the cathode produces carbon monoxide, and unreacted carbon dioxide also needs to be discharged. The gas guide pipe forms an independent gas outlet channel, effectively collecting and discharging these gaseous products, preventing gas accumulation inside the device that could cause pressure increases or affect the reaction balance, facilitating subsequent separation, collection, and reuse of the gaseous products, and improving the safety and resource utilization efficiency of the device.

[0025] Furthermore, the composite component is made of a conductive material, and the negative terminal of the power supply component is adapted to directly contact the composite component. The conductive composite component serves both as a container for the cathode and as a current collector for the cathode, eliminating the need for additional independent conductive parts. This structural design simplifies the device structure, reduces contact resistance to improve electron conduction efficiency, and ensures that the power supply component can efficiently conduct electrons to the liquid metal cathode, driving the electrolysis reaction to occur smoothly at the electrode-electrolyte interface.

[0026] In the carbon dioxide electrolysis method of this invention, the liquid metal cathode in the electrolysis device is placed inside a dedicated cathode container. The size of the cathode's reaction interface can be flexibly changed by adjusting the volume of the cathode container to adapt to different electrolysis requirements. The composite component is formed by functionally combining the cathode container (for supporting the cathode) with a vent pipe (for introducing carbon dioxide). The vent pipe is connected to the cathode container, allowing the introduced carbon dioxide to enter the interior of the liquid metal cathode from bottom to top. This composite component enables the direct introduction of carbon dioxide into the liquid metal, rather than simply into the molten salt electrolyte, thereby ensuring that the carbon dioxide gas can more fully and directly contact the cathode reaction area, thus improving cathode passivation.

[0027] Furthermore, the electrolysis initiation process includes a cycle of an electrolysis phase and a settling phase. The electrolysis phase includes continuously introducing carbon dioxide into the melt through the vent pipe and turning on the power supply to initiate the electrolysis reaction, maintaining the electrolysis time for a first time period. After the first time period, the settling phase begins, which includes turning off the power supply while continuing to continuously introduce carbon dioxide, maintaining the settling time for a second time period. Through a step-by-step electrolysis control method, the power is turned off after the electrolysis phase to enter the settling phase. During the settling phase, the continuously introduced carbon dioxide bubbles, migrating upwards, not only transport metal oxides and electrolysis products but also fully react with the metal oxides to trap them, consuming more solid metal oxides, further improving cathode passivation, and ensuring continuous and stable operation of the reaction.

[0028] Furthermore, before starting electrolysis, the process includes: a heating treatment, first raising the temperature to 280℃~300℃ and holding it for 22h~26h to remove moisture from the molten salt electrolyte; then raising the temperature to reach a reaction temperature of 550℃~800℃. This low-temperature pre-baking stage effectively removes crystal water and adsorbed moisture from the molten salt electrolyte, preventing water from hydrolyzing with the molten salt electrolyte during the high-temperature reaction stage to form hydroxides or acidic substances, thereby preventing changes in the composition of the molten salt electrolyte and corrosion of the equipment. The subsequent heating to the reaction temperature ensures that the molten salt electrolyte is fully melted and reaches its optimal ionic conductivity state, providing a stable and uniform liquid phase environment for the electrolysis reaction, significantly improving electrolysis efficiency and the stability of the equipment operation.

[0029] Furthermore, the flow rate of carbon dioxide gas introduced during the settling stage is greater than that introduced during the electrolysis stage. Increasing the carbon dioxide flow rate during the settling stage accelerates the upward migration rate of bubbles, enhances the physical transport of metal oxides and electrolysis products, and simultaneously increases the contact frequency and reaction rate between carbon dioxide and residual metal oxides in the cathode region. This ensures that the capture reaction is fully completed within a shorter settling time, completely consuming the solid metal oxides. This differentiated flow control avoids interference from excessively high gas flow rates during the electrolysis stage on the electrochemical reaction, while simultaneously achieving rapid removal of metal oxides during the settling stage, optimizing the reaction rhythm and energy utilization efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the carbon dioxide electrolysis device according to an embodiment of the present invention; Figure 2 This is a side view of the composite component in the carbon dioxide electrolysis device according to an embodiment of the present invention; Figure 3 This is a flowchart of the steps of the carbon dioxide electrolysis method according to an embodiment of the present invention; Figure 4 This is a flowchart of the steps for starting electrolysis in the carbon dioxide electrolysis method of this invention. Detailed Implementation

[0031] As described in the background section, there are still many problems in the existing technology for molten salt electrolysis of CO2 using liquid metal electrodes. These will be explained in detail below.

[0032] Current CO2 electrolysis methods use a liquid metal cathode, with a CO2 introducer inserted into a molten salt electrolyte above the liquid metal. However, this apparatus limits the amount of molten salt electrolyte used and cannot flexibly adjust the size of the cathode reaction interface. Furthermore, the introduced CO2 exists as bubbles; under high current density electrolysis, CO2 may not diffuse to the cathode-electrolyte reaction interface in time, reacting with Li2O to form soluble Li2CO3. This results in the reaction interface being covered by solid metal oxides, thus affecting the continuous operation of the reaction.

[0033] Based on this, the present invention provides a method and apparatus for the electrolysis of carbon dioxide. The cathode of the liquid metal is placed in a dedicated cathode container. By adjusting the volume of the cathode container, the size of the reaction interface of the cathode can be flexibly changed to adapt to different electrolysis requirements. The composite component is formed by functionally combining the cathode container for supporting the cathode with a vent pipe for introducing carbon dioxide. The vent pipe is connected to the cathode container, allowing the introduced carbon dioxide to enter the interior of the liquid metal cathode from bottom to top. The composite component enables the direct introduction of carbon dioxide into the liquid metal, rather than simply into the molten salt electrolyte, thereby ensuring that the carbon dioxide gas can more fully and directly contact the cathode reaction area, thus improving the passivation phenomenon of the cathode.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] Figure 1 This is a schematic diagram of the structure of the carbon dioxide electrolysis device according to an embodiment of the present invention; Figure 2 This is a side view of the composite component in the carbon dioxide electrolysis device according to an embodiment of the present invention.

[0036] Please refer to Figure 1 and Figure 2 An electrolysis device for carbon dioxide includes: an electrolysis container 100, which is sealed at the bottom and open at the top for holding a molten salt electrolyte 109; an anode 101 for the electrolysis reaction, inserted into the molten salt electrolyte 109 during the electrolysis reaction; a cathode 102 for the electrolysis reaction, which is a liquid metal during the electrolysis reaction, with the molten salt electrolyte 109 covering the cathode 102; a composite component 103, which includes a cathode container 1031 and a vent pipe 1032, wherein the cathode container 1031 is sealed at the bottom and open at the top for holding the cathode 102, and the vent pipe 1032 is connected to the cathode container 1031; and a power supply component 104, wherein the positive terminal of the power supply component 104 is adapted to be electrically connected to the anode 101, and the negative terminal of the power supply component 104 is adapted to be electrically connected to the cathode 102.

[0037] The liquid metal cathode 102 is placed within a dedicated cathode container 1031. The size of the reaction interface of the cathode 102 can be flexibly changed by adjusting the volume of the cathode container 1031 to adapt to different electrolysis requirements. The composite component 103 is formed by functionally combining the cathode container 1031 for supporting the cathode 102 with the vent pipe 1032 for introducing carbon dioxide. The vent pipe 1032 is connected to the cathode container 1031, allowing the introduced carbon dioxide to enter the interior of the liquid metal cathode 102 from bottom to top. The composite component 103 enables the direct introduction of carbon dioxide into the liquid metal, rather than simply into the molten salt electrolyte 109, thereby ensuring that the carbon dioxide gas can more fully and directly contact the reaction area of ​​the cathode 102, thus improving the passivation phenomenon of the cathode 102.

[0038] In this embodiment, the electrolysis container 100 can be a crucible container made of ceramic crucible sintered at high temperature, which is resistant to high temperature and corrosion by the molten salt electrolyte 109. The size of the crucible can be customized according to the scale of electrolysis and the amount of electrolyte used.

[0039] In this embodiment, the molten salt electrolyte 109 is composed of Li2CO3, Na2CO3 and K2CO3 mixed in a molar ratio of 3:5:2 to 5:2:3.

[0040] In other embodiments, the molten salt electrolyte includes one or more of Li2CO3, Na2CO3, K2CO3, MgCO3, and Al2(CO3)3.

[0041] In this embodiment, the anode 101 is an oxygen electrode that extends into the molten salt electrolyte 109. As the anode 101 in the electrolytic reaction, the oxygen electrode undergoes an oxidation reaction of oxygen ions to generate oxygen, which is the product of the anode 101. The electrode material of the anode 101 is preferably nickel-containing stainless steel.

[0042] In this embodiment, the cathode 102 is solid at room temperature, such as small particles or powder. During electrolysis, the temperature reached during the reaction melts the cathode 102 into liquid metal. The liquid metal cathode 102 is placed in a dedicated cathode container 1031, which extends into the molten salt electrolyte 109, allowing the molten salt electrolyte 109 to cover the surface of the liquid metal cathode 102. The cathode container 1031 can be made of conductive stainless steel, and therefore can also serve as a current collector for the liquid metal cathode 102, conducting electrons. At the reaction interface of the cathode 102, a reduction reaction of carbonate ions occurs, generating carbon or carbon monoxide, and oxygen ions. Some oxygen ions migrate to the anode 101 and undergo oxidation to generate oxygen, while other oxygen ions combine with metal cations in the molten salt electrolyte 109 to generate metal oxides. Ultimately, different types of metal oxides spontaneously undergo displacement reactions to generate Li2O. The metal oxide Li₂O reacts with carbon dioxide to form Li₂CO₃, thereby regenerating the electrolyte and consuming the solid metal oxide Li₂O. The cathode 102 is preferably made of metals such as antimony, bismuth, or tin.

[0043] In this embodiment, the composite component 103 serves two purposes: firstly, it can hold the liquid metal cathode 102 and act as a current collector for the cathode 102; secondly, it also functions as a conductor for carbon dioxide gas. The cathode container 1031 has a through-hole 1033 on its side, which connects to the vent pipe 1032, forming a pathway for carbon dioxide. To enhance stability, the cathode container 1031 and the vent pipe 1032 can be connected using welding. Both the cathode container 1031 and the vent pipe 1032 are made of the same material, such as stainless steel, which is resistant to high temperatures, electrolyte corrosion, and has good electrical conductivity.

[0044] Since the composite component 103 is made of a conductive material, the negative terminal of the power supply component 104 is adapted to directly contact the composite component 103, specifically, the negative terminal of the power supply component 104 is adapted to directly contact the vent pipe 1032. The conductive composite component 103 serves both as a container for the cathode 102 and as a current collector for the cathode 102, eliminating the need for additional independent conductive components. This structural design simplifies the device structure, reduces contact resistance to improve electron conduction efficiency, and ensures that the power supply component 104 can efficiently conduct electrons to the liquid metal cathode 102, driving the electrolysis reaction to occur smoothly at the electrode-electrolyte interface.

[0045] In this embodiment, the device further includes an outer container 105, which is sealed at the bottom and open at the top. The electrolytic container is adapted to be placed within the cavity of the outer container 105. The outer container 105 is made of high-temperature resistant stainless steel, which can effectively support the electrolytic container and place it in a high-temperature furnace for heating. It not only provides stable support and protection for the electrolytic container, but also effectively prevents safety hazards caused by leakage of the high-temperature molten salt electrolyte 109. At the same time, it facilitates the handling and temperature control of the entire device, significantly improving the safety and ease of operation of the electrolytic device in high-temperature working environments.

[0046] In this embodiment, a sealing cap 106 is also included, which is adapted to seal the opening of the outer container 105. The outer container 105 is made of high-temperature resistant stainless steel, which can effectively support the electrolysis container 100 and place it in a high-temperature furnace for heating. It not only provides stable support and protection for the electrolysis container 100, but also effectively prevents safety hazards caused by leakage of the high-temperature molten salt electrolyte 109. At the same time, it facilitates the removal and placement of the entire device and temperature control, significantly improving the safety and operational convenience of the electrolysis device in high-temperature working environments. The sealing cap 106 is preferably made of high-temperature resistant silicone or high-temperature resistant stainless steel.

[0047] In this embodiment, one end of the anode 101 is adapted to penetrate the sealing cap 106 and extend into the cavity of the electrolytic container 100; the cathode container 1031 is adapted to be placed in the cavity of the electrolytic container 100; and the vent pipe 1032 is adapted to penetrate the sealing cap 106 and extend to the outside.

[0048] In this embodiment, a gas guide tube 107 is also included. The gas guide tube 107 is adapted to penetrate the sealing cap 106 and extend into the cavity of the external container 105 for discharging the gas generated during the electrolysis reaction. Since the carbon dioxide electrolysis reaction needs to be carried out in a specific gaseous environment, the sealing cap 106 can prevent impurities such as oxygen and moisture in the external air from entering and disrupting the reaction gas environment, avoiding side reactions, and ensuring the stability and reliability of the electrolysis process. The gas guide tube 107 is preferably made of high-temperature resistant ceramic material.

[0049] In this embodiment, the power supply component 104 uses a DC power supply. During the electrolysis reaction, electrons are generated by the power supply component 104 and conducted through the cathode container 1031 (i.e., the current collector of the cathode 102) to the liquid metal cathode 102, driving the electrolysis reaction at the electrode-electrolyte reaction interface.

[0050] Figure 3 This is a flowchart of the steps of the carbon dioxide electrolysis method according to an embodiment of the present invention; Figure 4This is a flowchart of the steps for starting electrolysis in the carbon dioxide electrolysis method of this invention.

[0051] Accordingly, this invention also provides a method for the electrolysis of carbon dioxide, please refer to... Figure 3 And continue to combine with references Figure 1 and Figure 2 The carbon dioxide electrolysis apparatus described in any of the above embodiments is used to perform carbon dioxide electrolysis. The electrolysis method includes: placing the prepared molten salt electrolyte 109 in the electrolysis container 100; inserting the cathode container 1031, which holds the cathode 102, below the liquid surface of the molten salt electrolyte 109, so that the molten salt electrolyte 109 covers the cathode 102; inserting the anode 101 into the molten salt electrolyte 109, and electrically connecting the cathode 102 and the anode 101 to the power supply assembly 104 respectively; and starting the electrolysis after the power supply assembly 104 is electrically connected.

[0052] In the electrolysis apparatus, the liquid metal cathode 102 is placed within a dedicated cathode container 1031. The size of the reaction interface of the cathode 102 can be flexibly altered by adjusting the volume of the cathode container 1031 to adapt to different electrolysis requirements. The composite component 103 is formed by functionally combining the cathode container 1031 (for supporting the cathode 102) with the vent pipe 1032 (for introducing carbon dioxide). The vent pipe 1032 is connected to the cathode container 1031, allowing the introduced carbon dioxide to enter the interior of the liquid metal cathode 102 from bottom to top. The composite component 103 enables the direct introduction of carbon dioxide into the liquid metal, rather than simply into the molten salt electrolyte 109, thereby ensuring that the carbon dioxide gas can more fully and directly contact the reaction area of ​​the cathode 102, thus improving the passivation phenomenon of the cathode 102.

[0053] In this embodiment, before starting electrolysis, the process includes: a heating treatment, first raising the temperature to 280℃~300℃ and holding it at that temperature for 22h~26h to remove moisture from the molten salt electrolyte 109; then raising the temperature to reach a reaction temperature of 550℃~800℃. The low-temperature pre-baking stage effectively removes the water of crystallization and adsorbed moisture from the molten salt electrolyte 109, preventing moisture from hydrolyzing with the molten salt electrolyte 109 during the high-temperature reaction stage to generate hydroxides or acidic substances, thereby preventing changes in the composition of the molten salt electrolyte 109 and corrosion of the equipment. The subsequent heating to the reaction temperature ensures that the molten salt electrolyte 109 is fully melted and reaches its optimal ionic conductivity state, providing a stable and uniform liquid phase environment for the electrolysis reaction, significantly improving electrolysis efficiency and device operational stability.

[0054] In this embodiment, the reaction temperature melts the cathode 102 inserted into the molten salt electrolyte 109 from its initial solid state into a liquid state, thereby forming a liquid metal electrode.

[0055] Please refer to Figure 4 In this embodiment, starting electrolysis includes: cycling between an electrolysis stage and a settling stage; wherein, the electrolysis stage includes: continuously introducing carbon dioxide into the melt through the vent pipe 1032 and turning on the power supply component 104 to carry out the electrolysis reaction, with the electrolysis time maintained for a first time period; after the first time period is reached, the settling stage is carried out, which includes: turning off the power supply component 104 and continuing to continuously introduce carbon dioxide, with the settling time maintained for a second time period.

[0056] By using a step-by-step electrolysis control method, the power is turned off after the electrolysis stage and the system enters the settling stage. During the settling stage, the carbon dioxide bubbles that are continuously introduced not only carry the transport of metal oxides and electrolysis products as they migrate from bottom to top, but also fully react with the metal oxides to capture them, thus consuming more solid metal oxides and further improving the passivation phenomenon of cathode 102, ensuring the continuous and stable operation of the reaction.

[0057] In this embodiment, during the electrolysis stage, with a continuous gas supply, the power supply component 104 is turned on, outputting a DC electrolysis voltage of 2.5V~5V to perform the electrolysis reaction of carbonate ions in the molten salt electrolyte 109 and the capture reaction of carbon dioxide with metal oxides. The carbonate generated by the capture reaction is used as supplementary molten salt electrolyte 109. The first time period of the electrolysis stage ranges from 30min to 60min.

[0058] In this embodiment, during the settling phase, the DC power supply is turned off and carbon dioxide gas is continuously introduced. Only the trapping reaction occurs during this phase. The migration of carbon dioxide bubbles not only facilitates the transport of metal oxides and electrolysis products but also allows for a thorough trapping reaction with the metal oxide Li₂O during the settling phase, completely consuming the solid metal oxide Li₂O and thus improving the passivation phenomenon of the cathode 102. The second time period of the settling phase ranges from 30s to 60s, after which the DC power supply is turned back on, returning to the electrolysis phase, and this cycle is repeated.

[0059] In this embodiment, the flow rate of carbon dioxide gas introduced during the settling stage is greater than that introduced during the electrolysis stage. Increasing the carbon dioxide flow rate during the settling stage accelerates the upward migration rate of bubbles, enhances the physical transport effect on metal oxides and electrolysis products, and simultaneously increases the contact frequency and reaction rate between carbon dioxide and the residual metal oxides in the cathode 102 region. This ensures that the capture reaction is fully completed within a shorter settling time, completely consuming the solid metal oxides. This differentiated flow control avoids interference from excessively high gas flow rates during the electrolysis stage on the electrochemical reaction, while also achieving rapid removal of metal oxides during the settling stage, optimizing the reaction rhythm and energy utilization efficiency.

[0060] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A carbon dioxide electrolysis device, characterized in that, include: An electrolytic container, the electrolytic container being sealed at the bottom and open at the top, is used to hold molten salt electrolyte; The anode used in the electrolysis reaction is inserted into the molten salt electrolyte during the electrolysis reaction; The cathode used in the electrolysis reaction is a liquid metal during the electrolysis reaction, and the molten salt electrolyte covers the cathode. A composite component, comprising a cathode container and a vent pipe, wherein the cathode container is sealed at the bottom and open at the top for holding the cathode, and the vent pipe is connected to the cathode container; A power supply assembly, wherein the positive terminal of the power supply assembly is adapted to be electrically connected to the anode, and the negative terminal of the power supply assembly is adapted to be electrically connected to the cathode.

2. The carbon dioxide electrolysis apparatus as described in claim 1, characterized in that, Also includes: An outer container, the bottom of which is sealed and the top of which is open, wherein the electrolytic container is adapted to be placed within the cavity of the outer container.

3. The carbon dioxide electrolysis apparatus as described in claim 2, characterized in that, Also includes: A sealing cap, the sealing cap being adapted to seal the opening of the outer container.

4. The carbon dioxide electrolysis apparatus as described in claim 3, characterized in that, One end of the anode is adapted to penetrate the sealing cap and extend into the cavity of the electrolytic container; the cathode container is adapted to be placed in the cavity of the electrolytic container; the vent pipe is adapted to penetrate the sealing cap and extend to the outside.

5. The carbon dioxide electrolysis apparatus as described in claim 3, characterized in that, Also includes: A gas duct, adapted to penetrate the sealing cap and extend into the cavity of the outer container, for discharging gases generated during the electrolysis reaction.

6. The carbon dioxide electrolysis apparatus as described in claim 1, characterized in that, The composite component is made of a conductive material, and the negative terminal of the power supply component is adapted to be in direct contact with the composite component.

7. A method for electrolyzing carbon dioxide, comprising using the carbon dioxide electrolysis apparatus according to any one of claims 1 to 6, characterized in that, Electrolysis methods include: The prepared molten salt electrolyte is placed inside the electrolysis container; The cathode container holding the cathode is inserted below the surface of the molten salt electrolyte, such that the molten salt electrolyte covers the cathode. The anode is inserted into the molten salt electrolyte, and the cathode and the anode are electrically connected to the power supply assembly, respectively. Electrolysis is initiated after the power supply components are electrically connected.

8. The method for electrolyzing carbon dioxide as described in claim 7, characterized in that, The electrolysis process includes a cycle of an electrolysis phase and a settling phase. The electrolysis phase includes continuously introducing carbon dioxide into the melt through the vent pipe and turning on the power supply to initiate the electrolysis reaction, with the electrolysis time maintained for a first time period. After the first time period is reached, the settling phase is initiated, which includes turning off the power supply and continuing to continuously introduce carbon dioxide, with the settling time maintained for a second time period.

9. The method for electrolyzing carbon dioxide as described in claim 7, characterized in that, The molten salt electrolyte includes one or more of the following: Li2CO3, Na2CO3, K2CO3, MgCO3, and Al2(CO3)3.

10. The method for electrolyzing carbon dioxide as described in claim 7, characterized in that, The molten salt electrolyte is composed of Li2CO3, Na2CO3 and K2CO3 mixed in a molar ratio of 3:5:2 to 5:2:

3.

11. The method for electrolyzing carbon dioxide as described in claim 7, characterized in that, Before starting electrolysis, the process also includes: heating treatment, first raising the temperature to 280℃~300℃ and holding it for 22h~26h to remove moisture from the molten salt electrolyte; then raising the temperature to reach a reaction temperature of 550℃~800℃.

12. The method for electrolyzing carbon dioxide as described in claim 8, characterized in that, During the electrolysis stage, the power supply component outputs a DC electrolysis voltage of 2.5V to 5V.

13. The method for electrolyzing carbon dioxide as described in claim 8, characterized in that, The first time period is in the range of 30 min to 60 min.

14. The method for electrolyzing carbon dioxide as described in claim 8, characterized in that, The second time period is 30s to 60s.

15. The method for electrolyzing carbon dioxide as described in claim 8, characterized in that, The flow rate of carbon dioxide gas introduced during the settling stage is greater than the flow rate of carbon dioxide gas introduced during the electrolysis stage.

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