Method for eliminating salt precipitation of co2 electroreduction electrodes

Abstract

A method for eliminating salt precipitation of a CO2 electro-reduction electrode, comprising the following steps: detecting parameters of CO2 electro-reduction to determine whether the conditions for eliminating salt precipitation of the CO2 electro-reduction electrode are met; if the conditions for eliminating salt precipitation of the CO2 electro-reduction electrode are met, stopping the introduction of CO2 gas into the cathode chamber, and cleaning the cathode with a cleaning solution; changing the current direction and maintaining the set current for a set time to eliminate salt precipitation of the CO2 electro-reduction electrode; reintroducing CO2 gas into the cathode chamber to purge the cathode, and changing the current direction again to normally perform CO2 electro-reduction. The method can quickly eliminate salt precipitation of the CO2 electro-reduction electrode without disassembling the electrode, and restore the activity of the electrode.

Description

Technical Field

[0001] This invention relates to the field of carbon neutralization technology, and in particular to a method for eliminating salting out of CO2 electroreduction electrodes. Background Technology

[0002] Electrochemically reducing CO2 to high-value-added chemicals such as CO, formic acid, and ethylene using renewable electrical energy is an important pathway to achieving carbon recycling. In the CO2 electroreduction reaction, gas diffusion electrodes are typically used in conjunction with alkaline or near-neutral electrolytes (such as KOH, KH2CO3 solutions) to improve current density and product selectivity. However, during prolonged operation, a localized high pH environment can occur inside and on the surface of the cathode catalyst layer, leading to the reaction of CO2 and OH-. - The reaction produces carbonate or bicarbonate precipitates. These precipitates not only cover the catalytic active sites and block gas mass transfer channels, but also cause an imbalance in the local electrolyte acidification buffering capacity, leading to a significant enhancement of the hydrogen evolution side reaction and a continuous decline in the catalyst's CO2 reduction selectivity and stability.

[0003] In existing technologies, it is generally necessary to disassemble and clean the electrodes and replace the electrolyte. This method requires interrupting the system operation, and the disassembly process is prone to damage to the electrode structure and cannot achieve in-situ, rapid activity recovery. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for eliminating salt precipitation in CO2 electroreduction electrodes. This method can quickly eliminate salt precipitation in CO2 electroreduction electrodes and restore the activity of the electrodes without disassembling them.

[0005] This invention provides a method for eliminating salt precipitation at a CO2 electroreduction electrode, comprising the following steps: The parameters of CO2 electroreduction are detected to determine whether the conditions for eliminating CO2 electroreduction electrode salting out are met. If the CO2 electroreduction electrode salting-out is eliminated, stop the CO2 gas supply to the cathode chamber and clean the cathode with a cleaning solution; Change the direction of the current and maintain the current for a set time to eliminate salting out of the CO2 electroreduction electrode; CO2 gas is reintroduced into the cathode chamber to purge the cathode, and the current direction is reversed to allow for normal CO2 electroreduction.

[0006] Furthermore, the conditions for eliminating CO2 electroreduction electrode salting-out are determined to be met when any of the following conditions are satisfied: The cumulative running time has reached the first preset value; The CO Faraday efficiency of the cathode decreased to a second preset value compared to the initial value; Alternatively, the voltage in the electrolytic cell may increase by more than a third preset value compared to the initial value.

[0007] Furthermore, it includes at least one of the following: The first preset value is 50-100h; The second preset value is 80%; Alternatively, the third preset value is 0.2V.

[0008] Furthermore, the ratio of water to isopropanol by volume is 1:0 to 0:1 (excluding zero).

[0009] Furthermore, when cleaning with the cleaning solution, the flow rate is 5-15 mL / min.

[0010] Furthermore, when cleaning with the cleaning solution, the rinsing time is 3-8 minutes.

[0011] Furthermore, when changing the current direction, the set current is 1-50 mA / cm. 2 .

[0012] Furthermore, the time is set to 60-180 seconds when changing the current direction.

[0013] Furthermore, when purging the cathode with CO2 gas, the purging time is 2-5 minutes.

[0014] In this embodiment, by applying a reverse current to the cathode, the problem of accelerated hydrogen evolution caused by salting out during long-term electrolysis can be effectively suppressed, maintaining high CO selectivity and long-term operational stability. The method of this invention does not require interrupting system operation, disassembling electrodes, or replacing the electrolyte. Only when the elimination conditions are met is the cathode temporarily switched to the anode by power switching, changing the current direction, and utilizing the in-situ oxygen evolution reaction to spontaneously generate H₂. + The process of dissolving carbonate precipitates is completed within a closed electrolytic system. This avoids potential damage to the electrode structure, stripping of the gas diffusion layer, and irreversible performance degradation after reassembly that may occur during disassembly, truly achieving in-situ, rapid, and non-destructive activity recovery.

[0015] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below. Detailed Implementation

[0016] Specific embodiments of the present invention will now be described in detail. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. Based on the description of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0017] In the description of this invention, unless otherwise expressly specified and limited, the terms “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0018] To address the aforementioned problems, this invention provides a method for eliminating salt precipitation in CO2 electroreduction electrodes. This method can quickly eliminate salt precipitation in CO2 electroreduction electrodes and restore the activity of the electrodes without disassembling them.

[0019] The method for eliminating CO2 electroreduction electrode salting-out provided in this embodiment of the invention includes the following steps: S1: Detect the parameters of CO2 electroreduction to determine whether the conditions for eliminating CO2 electroreduction electrode salting-out are met. If the conditions are met, proceed to step S2. More specifically, during the operation of the CO2 electroreduction system, the operating time or cathode performance parameters (such as CO Faradaic efficiency, cell voltage, cathode potential, etc.) of the CO2 electroreduction system can be continuously monitored. The conditions for eliminating CO2 electroreduction electrode salting-out are determined to be met when any of the following conditions are satisfied: the cumulative operating time reaches a first preset value, which can be 50-100 hours; the CO Faradaic efficiency of the cathode decreases from its initial value to a second preset value, which can be 80%; the voltage in the electrolytic cell increases by more than a third preset value, which can be 0.2V.

[0020] In this embodiment, during the electroreduction of carbon dioxide, the data such as running time, carbon monoxide Faraday efficiency, and voltage in the electrolytic cell are all monitored parameters. By processing these parameters, it can be determined whether the conditions for eliminating CO2 electroreduction electrode salting out are met.

[0021] S2: If the CO2 electroreduction electrode salting-out is eliminated, stop the CO2 gas supply to the cathode chamber and clean the cathode with cleaning solution; In this embodiment, the cleaning solution is a mixture of water and isopropanol, with a volume ratio of water to isopropanol of 1:0 to 0:1 (excluding zero). Preferably, the volume ratio is 10:1 to 1:5.

[0022] During cleaning, the electrode can be circulated and rinsed for 3-8 minutes at a flow rate of 5-15 mL / min.

[0023] During this period, the anode maintains normal electrolyte circulation. At this time, the entire electrodeposition cell remains in a state of electrode solution circulation and immersion, and no components are disassembled.

[0024] S3: Change the current direction and maintain the set current for a set time to eliminate CO2 electroreduction electrode salting out; After cleaning the cathode, the current direction can be reversed; that is, the cathode from the electroreduction process can be transformed into the anode. More specifically, the cathode from the electroreduction process can be used as the anode, and the current can be set to 1-50 mA / cm². 2 (The original current was negative, such as -100mA / cm) 2 Preferably, the current is 5-20 mA / cm. 2 The time setting is 10-1000s, preferably 60-180s.

[0025] S4: Re-introduce CO2 gas into the cathode chamber to purge the cathode, and change the current direction to perform CO2 electroreduction normally.

[0026] In this embodiment, CO2 gas can be reintroduced to purge the cathode, thereby blowing out the residual cleaning fluid in the cathode chamber.

[0027] In this embodiment, the purging time can be 2-5 minutes.

[0028] After cleaning, the humidity of the gas discharged from the outlet side of the cathode chamber can be measured. When the humidity no longer changes, it can be determined that the cleaning solution has been blown clean.

[0029] After purging, the original electrolyte flow field conditions and current / voltage parameters can be restored. At this point, the electrode activity has been restored, the CO2 electroreduction reaction can immediately resume normal operation, and the CO Faraday efficiency and cell voltage return to their initial levels.

[0030] In this embodiment, the above steps can be repeated throughout the entire life cycle of the CO2 electroreduction device to achieve in-situ non-destructive regeneration of the electrodes, ensuring long-term high selectivity, high energy efficiency and stable operation of the system.

[0031] In this embodiment, by applying a reverse current to the cathode, the problem of accelerated hydrogen evolution caused by salting out during long-term electrolysis can be effectively suppressed, maintaining high CO selectivity and long-term operational stability. The method of this invention does not require interrupting system operation, disassembling electrodes, or replacing the electrolyte. Only when the elimination conditions are met is the cathode temporarily switched to the anode by power switching, changing the current direction, and utilizing the in-situ oxygen evolution reaction to spontaneously generate H₂. +The process of dissolving carbonate precipitates is completed within a closed electrolytic system. This avoids potential damage to the electrode structure, stripping of the gas diffusion layer, and irreversible performance degradation after reassembly that may occur during disassembly, truly achieving in-situ, rapid, and non-destructive activity recovery.

[0032] The following detailed implementation methods will illustrate this solution: Example 1: S1: The parameters of CO2 electroreduction were detected, and it was determined that the electroreduction had been carried out for 80 hours.

[0033] S2: Stop supplying CO2 gas to the cathode chamber. Use a peristaltic pump to circulate a 9:1 water / isopropanol mixture into the cathode at a flow rate of 10 mL / min, circulating and flushing the electrodes for 5 minutes, while maintaining electrolyte circulation at the anode. At this point, the entire electrolytic cell remains in an electrolyte-wetted state, and no parts need to be disassembled.

[0034] S3: Switch the original applied -100 mA / cm² constant current mode to a 20 mA / cm² constant current mode and perform reverse cleaning for 120 seconds.

[0035] S4: After the predetermined time is reached, reconnect the cathode chamber to CO2 gas and blow air for 3 minutes to remove the residual cleaning liquid in the electrolytic cell.

[0036] After purging, restore the original electrolyte flow field conditions and current / voltage parameters.

[0037] The results showed that the electrode activity was fully restored, and the CO Faraday efficiency and cell voltage were both restored to 98.9% of their initial levels, allowing the CO2 electroreduction reaction to resume normal operation immediately.

[0038] Example 2: (Water / isopropanol volume ratio: 1:0) S1: The parameters of CO2 electroreduction were detected, and it was determined that the electroreduction had been carried out for 100 hours.

[0039] S2: Stop supplying CO2 gas to the cathode chamber. Use a peristaltic pump to circulate a water / isopropanol mixture (preferably at the upper limit of the range) at a flow rate of 10 mL / min to the cathode, circulating and flushing the electrodes for 5 minutes, while maintaining electrolyte circulation at the anode. The entire electrolyzer remains in an electrolyte-circulating, wetted state and does not require disassembly.

[0040] S3: Switch the current from -100 mA / cm² to 20 mA / cm² and perform reverse cleaning for 120 seconds.

[0041] S4: After the predetermined time is reached, reconnect the cathode chamber to CO2 gas and blow air for 3 minutes to remove the residual cleaning liquid in the electrolytic cell.

[0042] After purging, restore the original electrolyte flow field conditions and current / voltage parameters.

[0043] In this embodiment, the cleaning solution is composed of pure water. Due to the hydrophobicity of the electrode, the cleaning solution cannot reach the electrode surface, and the CO Faraday efficiency and cell voltage are not restored.

[0044] Example 3: (Water / isopropanol volume ratio: 0:1) S1: The parameters of CO2 electroreduction are detected, and it is determined that the CO Faraday efficiency has decreased to 70% compared to the initial value.

[0045] S2: Stop supplying CO2 gas to the cathode chamber. Use a peristaltic pump to circulate a water / isopropanol mixture (preferably at the lower limit of the range) at a flow rate of 10 mL / min to the cathode, circulating and flushing the electrodes for 5 minutes, while maintaining electrolyte circulation at the anode. The entire electrolytic cell remains immersed without disassembling any parts.

[0046] S3: Switch the original applied -100 mA / cm² constant current mode to a 20 mA / cm² constant current mode and perform reverse cleaning for 120 seconds.

[0047] S4: After the predetermined time is reached, reconnect the cathode chamber to CO2 gas and blow air for 3 minutes to remove the residual cleaning liquid in the electrolytic cell.

[0048] After purging, restore the original electrolyte flow field conditions and current / voltage parameters.

[0049] In this embodiment, the cleaning solution is composed of pure isopropanol. The reverse electrode cannot remove the salt on the catalyst surface in situ, and the CO Faraday efficiency and cell voltage are not restored.

[0050] Example 4: (Water / isopropanol volume ratio: 1:9) S1: The parameters of CO2 electroreduction are detected, and it is determined that the CO Faraday efficiency has decreased to 75% compared to the initial value.

[0051] S2: Stop supplying CO2 gas to the cathode chamber. Use a peristaltic pump to circulate pure water (water / isopropanol volume ratio 1:9) to the cathode at a flow rate of 10 mL / min, circulating and flushing the electrodes for 5 minutes. Keep the anode in electrolyte circulation. The entire electrolytic cell is in a wetted state, and no parts need to be disassembled.

[0052] S3: Switch the original applied -100 mA / cm² constant current mode to a 20 mA / cm² constant current mode and perform reverse cleaning for 120 seconds.

[0053] S4: After the predetermined time is reached, reconnect the cathode chamber to CO2 gas and blow air for 3 minutes to remove the residual cleaning liquid in the electrolytic cell.

[0054] After purging, restore the original electrolyte flow field and current / voltage parameters.

[0055] In this embodiment, the cleaning solution with low water content has a weaker ability to remove salt precipitation in situ compared to the cleaning solution with high water content. Therefore, the electrode activity is only partially restored, the CO Faraday efficiency is restored to 90.2%, and the cell voltage is slightly higher than the initial value.

[0056] Example 5: (Current density is 5 mA / cm²) S1: The parameters of CO2 electroreduction are detected, and it is determined that the cell voltage in the electrolytic cell has increased by 0.3V compared to the initial value.

[0057] S2: Stop supplying CO2 gas to the cathode chamber. Use a peristaltic pump to circulate a 9:1 water / isopropanol mixture into the cathode at a flow rate of 10 mL / min, circulating the electrodes for 5 minutes. Keep the anode in electrolyte circulation. The entire electrolytic cell is in a wetted state; no parts need to be disassembled.

[0058] S3: Switch the current from -100 mA / cm² to 5 mA / cm² and perform reverse cleaning for 120 seconds.

[0059] S4: After cleaning, reconnect CO2 gas and blow air for 3 minutes to remove the residual cleaning liquid in the electrolytic cell.

[0060] After purging, restore the original electrolyte flow field and current / voltage parameters.

[0061] In this embodiment, due to the low reverse cleaning current density, the driving force for electrochemical removal of precipitates is weakened, and the electrode activity only recovers to 89.3% of the initial level within 120 seconds, with a CO Faradaic efficiency. However, if the cleaning time is appropriately extended to 180 seconds, complete recovery can be achieved, indicating that a longer time is required at low current densities.

[0062] Example 6: (Current density is 50 mA / cm²) S1: Detect the parameters of CO2 electroreduction and determine that the voltage in the electrolytic cell has increased by more than 0.25V compared to the initial value.

[0063] S2: Stop supplying CO2 gas to the cathode chamber. Use a peristaltic pump to circulate a 9:1 water / isopropanol mixture into the cathode at a flow rate of 10 mL / min, circulating the electrodes for 5 minutes. Keep the anode in electrolyte circulation. The entire electrolytic cell remains wetted and does not require disassembly.

[0064] S3: Switch the current to 50 mA / cm² and perform reverse cleaning for 120 seconds.

[0065] S4: After cleaning, reconnect CO2 gas and blow air for 3 minutes to remove the residual cleaning liquid in the electrolytic cell.

[0066] After purging, restore the original electrolyte flow field / electrical parameters.

[0067] In this embodiment, the excessively high reverse current density damaged the iridium oxide catalyst on the counter electrode. The CO Faraday efficiency of the cathode recovered to the initial level of 98.2%, but the cell voltage increased significantly. This increase in cell voltage is attributed to the deactivation of iridium oxide at the reduction potential.

[0068] Example 7: (Cleaning time 60s) S1: The parameters of CO2 electroreduction were detected, and it was determined that the electroreduction had been carried out for 60 hours.

[0069] S2: Stop supplying CO2 gas to the cathode chamber. Use a peristaltic pump to circulate a 9:1 water / isopropanol mixture into the cathode at a flow rate of 10 mL / min, circulating the electrodes for 5 minutes. Keep the anode in electrolyte circulation. The entire electrolytic cell remains wetted and does not require disassembly.

[0070] S3: Switch the current to 20 mA / cm² and perform reverse cleaning for 60 seconds.

[0071] S4: After cleaning, reconnect CO2 gas and blow air for 3 minutes to remove the residual cleaning liquid in the electrolytic cell.

[0072] After purging, restore the original electrolyte flow field and current / voltage parameters.

[0073] In this embodiment, a shorter cleaning time was used, and the Faraday efficiency of CO was restored to 94.1%. The CO Faraday efficiency was slightly lower than that in Example 1, but still within an acceptable range (approximately 98.9%), and the tank voltage was basically restored.

[0074] Example 8: (Cleaning time 180s) S1: The parameters of CO2 electroreduction were detected, and it was determined that the electroreduction had been carried out for 100 hours.

[0075] S2: Stop supplying CO2 gas to the cathode chamber. Use a peristaltic pump to circulate a 9:1 water / isopropanol mixture into the cathode at a flow rate of 10 mL / min, circulating the electrodes for 5 minutes. Keep the anode in electrolyte circulation. The entire electrolytic cell remains wetted and does not require disassembly.

[0076] S3: Switch the current to 20 mA / cm² and perform reverse cleaning for 180 seconds.

[0077] S4: After cleaning, reconnect CO2 gas and blow air for 3 minutes to remove the residual cleaning liquid in the electrolytic cell.

[0078] After purging, restore the original electrolyte flow field and current / voltage parameters.

[0079] In this embodiment, a longer cleaning time is used, and the Faraday efficiency of CO is restored to 98.4%.

[0080] Comparative example: (The electrolytic cell was disassembled and rinsed) Stop the flow of CO2 gas into the cathode chamber. First, disconnect the power supply and piping of the electrolytic cell and remove it from the experimental setup. Carefully open the cathode chamber, remove the gas diffusion electrode, and place it in a clean container. Rinse the electrode surface repeatedly with a pre-prepared cleaning solution (water:isopropanol = 9:1), using 20 mL each time, for a total of 3 rinses, with approximately 1 minute intervals between each rinse, to remove solid precipitates deposited on the electrode surface. After rinsing, dry the surface with nitrogen gas. Then, reinstall the electrode back into the cathode chamber, reassemble the electrolytic cell, and check the airtightness and circuit connections. The entire disassembly, cleaning, and reassembly process takes approximately 30 minutes. Resume the flow of CO2 gas and restart the electrolysis system, applying the original -100 mA / cm² constant current mode. In this embodiment, disassembly and rinsing were used, restoring the Faraday efficiency of CO to 94.3%, indicating that rinsing alone has limited effectiveness in removing precipitates.

[0081] The following is a comparison table of CO Faraday efficiency and electrolytic cell pressure in various embodiments.

[0082] Table 1: Comparison of CO Faraday efficiency and electrolyzer cell voltage in various embodiments

[0083] As shown in Table 1, in the comparison table of CO Faradaic efficiency and electrolytic cell voltage in various embodiments of the method provided by the present invention, both can restore CO Faradaic efficiency and electrolytic cell voltage to a high level, and the time required is relatively short.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for eliminating salt precipitation at a CO2 electroreduction electrode, characterized in that: Includes the following steps: The parameters of CO2 electroreduction are detected to determine whether the conditions for eliminating CO2 electroreduction electrode salting out are met. If the CO2 electroreduction electrode salting-out is eliminated, stop the CO2 gas supply to the cathode chamber and clean the cathode with a cleaning solution; Change the direction of the current and maintain the current for a set time to eliminate salting out of the CO2 electroreduction electrode; CO2 gas is reintroduced into the cathode chamber to purge the cathode, and the current direction is reversed to allow for normal CO2 electroreduction.

2. The method for eliminating CO2 electroreduction electrode salting-out according to claim 1, characterized in that: The conditions for eliminating CO2 electroreduction electrode salting-out are considered met when any of the following conditions are satisfied: The cumulative running time has reached the first preset value; The CO Faraday efficiency of the cathode decreased to a second preset value compared to the initial value; Alternatively, the voltage in the electrolytic cell may increase by more than a third preset value compared to the initial value.

3. The method for eliminating CO2 electroreduction electrode salting-out according to claim 2, characterized in that: Include at least one of the following: The first preset value is 50-100h; The second preset value is 80%; Alternatively, the third preset value is 0.2V.

4. The method for eliminating CO2 electroreduction electrode salting-out according to claim 1, characterized in that: The ratio of water to isopropanol by volume is 1:0 to 0:1 (excluding zero).

5. The method for eliminating CO2 electroreduction electrode salting-out according to claim 1, characterized in that: When cleaning with the cleaning solution, the flow rate is 5-15 mL / min.

6. The method for eliminating CO2 electroreduction electrode salting-out according to claim 1, characterized in that: When cleaning with cleaning solution, the rinsing time is 3-8 minutes.

7. The method for eliminating CO2 electroreduction electrode salting-out according to claim 1, characterized in that: When changing the current direction, the set current is 1-50 mA / cm. 2 .

8. The method for eliminating CO2 electroreduction electrode salting-out according to claim 1, characterized in that: When changing the direction of the current, the set time is 60-180 seconds.

9. The method for eliminating CO2 electroreduction electrode salting-out according to claim 1, characterized in that: When purging the cathode with CO2 gas, the purging time is 2-5 minutes.

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