L-cysteine modified nanosilver electrocatalyst and its application

Abstract

The present invention relates to a carbon dioxide electrocatalytic reduction catalyst, and in particular to an L-cysteine modified nano-silver electrocatalyst and its application, belonging to the field of carbon dioxide emission reduction resource utilization and electrocatalytic material synthesis technology. An L-cysteine modified nano-silver electrocatalyst is prepared by the following method: S1, dissolving silver nitrate in water to obtain a 0.05-100mM silver nitrate solution, adding it to ethylene glycol and stirring evenly; the volume ratio of the silver nitrate solution to the ethylene glycol is 1: (2-20); S2, adding L-cysteine to the mixed solution, stirring evenly and then microwave heating, the obtained solid is centrifuged and washed at least three times with ethanol and ultrapure water respectively, and dried in a vacuum drying oven to obtain nano-silver particles; the molar ratio of silver element to L-cysteine is 1: (0.01-10). The present invention achieves high selectivity and high stability for the product CO in a CO2 in-situ conversion system by improving the adsorption capacity of the electrocatalyst for active substances.

Description

Technical Field

[0001] The present invention relates to a carbon dioxide electrocatalytic reduction catalyst, in particular to an L-cysteine-modified nanosilver electrocatalyst and applications thereof, belonging to the technical field of carbon dioxide emission reduction resource utilization and electrocatalytic material synthesis. Background Art

[0002] The rapid development of modern industrial society and economic development has led to a massive consumption of fossil energy (coal, oil, natural gas, etc.). This combustion of fossil fuels releases large amounts of carbon dioxide (CO2) into the atmosphere each year. To address climate change caused by CO2 emissions, the capture and utilization of CO2 already released into the environment has been a key research focus in recent years. CCUS (CO2 capture, utilization, and storage) technology is a comprehensive suite of technologies for CO2 capture, utilization, and storage. Combining electrochemical reduction with carbon capture technology, directly using carbon capture media as a carbon source for in-situ conversion of CO2 to green fuels, not only effectively avoids the low CO2 utilization rate caused by large amounts of unreacted CO2, but also bypasses the energy-intensive steps of CO2 regeneration and purification and pressurization, reducing overall process energy consumption. This is key to developing efficient and energy-efficient CO2 capture and value-added utilization technologies.

[0003] Different from the traditional CO2 electrochemical reduction which uses direct input of CO2 as reactant, CO3 2- / HCO3 - During in-situ electroreduction, the primary reactant is CO2 generated in situ on the surface of the ion exchange membrane due to proton transport. For electrolyzers equipped with a cation exchange membrane (CEM), protons are provided by the anode reaction, while for electrolyzers based on a bipolar membrane (BPM), protons come from water dissociation in the membrane's intermediate layer. The in-situ generated CO2 can be further converted on the catalyst surface into common CO2 electroreduction products such as CO, formic acid, methane, and ethylene. However, current catalysts for in-situ CO2 electrocatalytic reduction mostly use commercial nanoparticles and porous metal electrodes, and research and development of specific catalysts is lacking. Summary of the Invention

[0004] According to the existing technology, the lack of development of specific electrocatalysts in the CO2 in situ conversion system leads to low selectivity of the target product and low utilization of carbon-containing components. The purpose of the present invention is to develop an L-cysteine-modified nanosilver electrocatalyst with simple synthesis and controllable conditions. By improving the adsorption capacity of the electrocatalyst for active substances, high selectivity and high stability of the product CO in the CO2 in situ conversion system can be achieved.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] An L-cysteine-modified nanosilver electrocatalyst is prepared by the following method:

[0007] S1. Dissolve silver nitrate in water to obtain a 0.05-100 mM silver nitrate solution, add it to ethylene glycol and stir evenly; the volume ratio of the silver nitrate solution to ethylene glycol is 1:(2-20);

[0008] S2. L-cysteine was added to the mixture, stirred evenly, and then microwaved. The resulting solid was washed at least three times with ethanol and ultrapure water, respectively, by centrifugation, and dried in a vacuum drying oven to obtain silver nanoparticles.

[0009] The molar ratio of silver element to L-cysteine is 1:(0.01~10).

[0010] Preferably, the stirring in S1 is 700-1500 rpm, and the stirring is carried out at a temperature of 20-40° C. for 30-60 min;

[0011] The microwave heating time in S2 is 30-60 minutes, the microwave power is 100-300W, and the heating temperature is 120-160°C; the drying in S2 is oven drying, the oven drying temperature is 80-100°C, and the oven drying time is 1-24 hours. More preferably, in S2, the microwave power is 150W, and the heating is performed at 120°C for 60 minutes.

[0012] Preferably, the molar ratio of silver element to L-cysteine in S2 is 1:(0.5~1).

[0013] Preferably, 10 mL of 0.1 M silver nitrate aqueous solution is added to 90 mL of ethylene glycol and stirred at 800 rpm for 30 min until uniformly mixed; 0.12 g of L-cysteine is added to the mixture.

[0014] A nanosilver catalytic electrode is prepared by the following method: dispersing the L-cysteine-modified nanosilver electrocatalyst particles of the present invention in an appropriate amount of isopropanol, preparing a catalyst ink with Nafion ionomer, wherein the amount of Nafion ionomer used is 10%±2% of the catalyst mass, ultrasonically dispersing the obtained catalyst ink, and spraying the catalyst ink on an electrode substrate until the catalyst loading reaches 0.5-4 mg / cm 2 , to obtain a nano silver catalytic electrode. The preferred catalyst loading is 1~2.5mg / cm 2 .

[0015] Preferably, the electrode substrate is a carbon-containing electrode substrate such as carbon paper, carbon cloth, or carbon felt.

[0016] The invention discloses an application of the L-cysteine-modified nano-silver electrocatalyst in the in-situ electroconversion of CO2 to efficiently produce CO. The application comprises using the L-cysteine-modified nano-silver electrocatalyst as a catalyst for the in-situ conversion of carbon dioxide to directly reduce carbonate or bicarbonate to carbon monoxide.

[0017] An application of the nano-silver catalytic electrode of the present invention in the efficient production of CO by in-situ electrochemical conversion of CO2, wherein the nano-silver catalytic electrode modified with L-cysteine is used as a working electrode in an in-situ electrochemical conversion system of CO2.

[0018] As a preferred embodiment, the electrolyte used in the cathode chamber of the electrolytic cell in the CO2 in-situ electroconversion system is a 0.5-3M potassium carbonate or potassium bicarbonate solution; the working electrode in the cathode chamber of the CO2 in-situ electroconversion system converts HCO3 in the cathode electrolyte into - and CO3 2- The carbon-containing components are directly converted into CO. During the reaction, no exogenous carbon-containing gases such as CO2 and CO are introduced into the cathode chamber. The current density of the CO2 in-situ electroconversion system is 10~1000mA / cm 2 .

[0019] Preferably, the electrolytic cell device of the CO2 in-situ electroconversion system includes an anode flow plate, an anode porous electrode, a diaphragm, a cathode porous electrode and a cathode flow plate that are tightly fitted in sequence, an annular sealing gasket is provided between the anode flow plate and the cathode flow plate, and the anode flow plate and the cathode flow plate are connected by a double-headed threaded screw and a nut to form a sealed electrolysis chamber, the anode flow plate and the diaphragm are between the anode chamber, and the cathode flow plate and the diaphragm are between the cathode chamber; the anode flow plate is provided with an anode liquid inlet and an anode liquid outlet, and the anode flow plate is provided with an anode liquid groove flow channel on the side close to the anode porous electrode, and the anode liquid groove The two ends of the flow channel are respectively connected to the anode liquid inlet and the anode liquid outlet; the cathode flow plate is provided with a cathode liquid inlet and a cathode liquid outlet, and a cathode liquid groove flow channel is provided on the side of the cathode flow plate close to the cathode porous electrode, and the two ends of the cathode liquid groove flow channel are respectively connected to the cathode liquid inlet and the cathode liquid outlet; the anode flow plate and the cathode flow plate are respectively provided with an anode pole ear and a cathode pole ear for connecting the two ends of direct current; the cathode working electrode is the L-cysteine modified nanosilver catalytic electrode described in the present invention, the substrate of the anode porous electrode is a porous nickel foam material, and the diaphragm is an ion exchange membrane.

[0020] The beneficial effects of the present invention are:

[0021] The present invention utilizes L-cysteine in a silver nitrate-ethylene glycol system, utilizing amino functional groups to locally capture active substances and improve selectivity for the target product. Furthermore, the present invention utilizes a microwave heating process, where microwave energy directly acts on molecules within the substance, generating intense thermal motion within the material, accelerating chemical reactions and producing highly uniform nanosilver particles to increase specific surface area while preventing agglomeration. In an in-situ CO2 electroconversion system, the electrocatalyst provided by the present invention achieves high selectivity and stability for the target product, CO, due to its uniform dispersion, large specific surface area, and numerous active sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Surface morphologies of the catalytic electrodes prepared in Comparative Example 1, Comparative Example 2, and Example 1;

[0023] Figure 2 The PVP / conventional heating, L-cysteine / conventional heating and L-cysteine / microwave heating at 20 mA / cm in Example 1 were used. 2 Comparison of selectivity for CO at different current densities;

[0024] Figure 3 The PVP / conventional heating, L-cysteine / conventional heating and L-cysteine / microwave heating at 20 mA / cm in Example 1 were used. 2 Comparison of CO2 utilization under different current densities

[0025] Figure 4 The three electrodes with silver:L-cysteine molar ratios of 2:1, 1:1, and 1:3 in Example 2 were tested at 120 mA / cm 2 Comparison of selectivity for CO at different current densities;

[0026] Figure 5 The three electrodes with different microwave heating powers at 170 mA / cm in Example 3 2 Comparison of CO selectivity at different current densities. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described in detail below through specific examples. It should be understood that the implementation of the present invention is not limited to the following examples, and any form of modification and / or change made to the present invention will fall within the scope of protection of the present invention.

[0028] In the present invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. The methods in the following examples are all conventional methods in the art unless otherwise specified.

[0029] Unless otherwise specified, the reagents used in the following examples can be purchased from conventional biochemical reagent stores.

[0030] The CO2 in-situ electric conversion system described in the present invention has a specific structure, which can be found in the carbon pollution absorption liquid electrically driven conversion unit P1 of CN 119075604 A patent entitled "A carbon pollution absorption liquid electrothermal catalytic green fuel preparation device and method". The electrolyzer device of the CO2 in-situ electric conversion system includes an anode flow plate, an anode porous electrode, a diaphragm, a cathode porous electrode and a cathode flow plate that are tightly fitted in sequence. An annular sealing gasket is provided between the anode flow plate and the cathode flow plate, and the anode flow plate and the cathode flow plate are connected by a double-headed threaded screw and a nut to form a sealed electrolysis chamber. The anode chamber is between the anode flow plate and the diaphragm, and the cathode chamber is between the cathode flow plate and the diaphragm. The anode liquid inlet and the anode liquid outlet are provided on the anode flow plate, and the anode flow plate is close to the anode porous electrode. An anode liquid groove flow channel is provided on one side of the electrode, and the two ends of the anode liquid groove flow channel are respectively connected to the anode liquid inlet and the anode liquid outlet; a cathode liquid inlet and a cathode liquid outlet are provided on the cathode flow plate, and a cathode liquid groove flow channel is provided on the side of the cathode flow plate close to the cathode porous electrode, and the two ends of the cathode liquid groove flow channel are respectively connected to the cathode liquid inlet and the cathode liquid outlet; an anode electrode ear and a cathode electrode ear for connecting the two ends of direct current are respectively provided on the anode flow plate and the cathode flow plate; the cathode working electrode is the L-cysteine modified nanosilver catalytic electrode described in the present invention, the substrate of the anode porous electrode is a porous nickel foam material, and the diaphragm is an ion exchange membrane.

[0031] Carbon paper substrate, Freudenberg H23 carbon paper, commercially available.

[0032] Nafion ionomer, aqueous solution is Nafion TM The polymer dispersant is Nafion 117 solution (McLean N831951 Nafion 117 perfluorinated resin solution, ~5% in a mixture of lower aliphatic alcohols and water), Cas number: 31175-20-9, commercially available.

[0033] Example: Preparation of L-cysteine-modified nanosilver catalytic electrode and in-situ CO2 conversion

[0034] Example 1: Preparation of L-cysteine-modified nanosilver catalytic electrode (L-cysteine / microwave heating): 10 mL of 0.1 M silver nitrate aqueous solution was added to 90 mL of ethylene glycol and stirred at 800 rpm for 30 min until uniformly mixed; 0.12 g of L-cysteine was added to the mixture and stirred until the L-cysteine was completely dissolved. The microwave power was set to 150 W and heated at 120° C. for 60 min. The obtained solid was centrifuged and washed three times with anhydrous ethanol and ultrapure water, respectively, and dried in a vacuum drying oven at 100° C. for 12 h to obtain L-cysteine-modified nanosilver particles; 105 mg of L-cysteine-modified nanosilver particles were taken and dispersed in 20 mL of isopropanol. Catalyst ink was prepared with Nafion ionomer, and the amount of Nafion ionomer was 10% of the catalyst mass. The obtained catalyst ink was ultrasonically dispersed for 60 min and then the catalyst ink was sprayed on a 2x0.5 cm 2 Carbon paper substrate, solid catalyst loading weight 1.0 mg / cm 2 , and obtain L-cysteine modified nanosilver catalytic electrode.

[0035] Comparative Example 1 Preparation of PVP-modified nanosilver catalytic electrode (PVP / conventional heating): 10 mL of 0.1 M silver nitrate aqueous solution was added to 90 mL of ethylene glycol and stirred at 800 rpm for 30 min until uniformly mixed; 0.11 g of polyvinyl pyrrolidone (PVP) was added to the mixture and stirred until the PVP was completely dissolved. The mixture was placed in an oil bath and heated at 120 ° C for 60 min. The obtained solid was centrifuged and washed three times with anhydrous ethanol and ultrapure water, respectively, and dried in a vacuum drying oven at 100 ° C for 12 h to obtain PVP-modified nanosilver particles. 105 mg of PVP-modified nanosilver particles were taken and dispersed in 20 mL of isopropanol. Catalyst ink was prepared with Nafion ionomer. The amount of Nafion ionomer was 10% of the mass of the catalyst. The obtained catalyst ink was ultrasonically dispersed for 60 min and then the catalyst ink was sprayed on a 2x0.5 cm 2 Carbon paper substrate, solid catalyst loading weight 1.0 mg / cm 2 , and obtain the PVP-modified nanosilver catalytic electrode.

[0036] Comparative Example 2: Preparation of L-cysteine-modified nanosilver catalytic electrode (L-cysteine / conventional heating): The specific method is the same as Example 1, except that the heating method is the same as that in Comparative Example 1, which is heating in an oil bath at 120° C. for 60 min.

[0037] The surface morphology of the catalytic electrodes obtained in Comparative Example 1, Comparative Example 2 and Example 1 is shown in FIG. Figure 1 , Figure 1 (a) is PVP / normal heating, Figure 1 (b) is L-cysteine / normal heating, Figure 1 (c) in the figure is L-cysteine / microwave heating. The average particle size of the silver nanoparticles produced by PVP / conventional heating is 400nm, the average particle size of the silver nanoparticles produced by L-cysteine / conventional heating is 50nm, but they easily aggregate into nanoclusters with a particle size of 600-800nm, and the average particle size of the silver nanoparticles produced by L-cysteine / microwave heating is 10nm, and they are evenly distributed without obvious clustering. Figure 1 It can be seen that the catalytic electrode prepared by microwave heating has the advantages of uniform dispersion and large specific surface area.

[0038] The L-cysteine modified nanosilver catalytic electrode was tested in a flow-type electrolytic cell: the catalytic electrodes prepared in Example 1, Comparative Example 1, and Comparative Example 2 were used as working electrodes, and Ni mesh was used as the counter electrode. Electrochemical tests were performed in a flow-type electrolytic cell. The cathode electrolyte was 2M KHCO3, the anolyte was 1M KOH, and the cathode and anode compartments were separated by a bipolar membrane. The flow rate was 20 mA / cm 2 The constant current test was carried out under the current density. After 30 minutes of electrolysis, the gas products were detected by gas chromatography. The results are shown in Figure 2 The CO Faradaic efficiencies of the electrodes prepared by PVP / conventional heating, L-cysteine / conventional heating, and L-cysteine / microwave heating were 29.0%, 41.0%, and 58.9%, respectively. The CO2 utilization rate can be calculated based on the ratio of CO and CO2 concentrations in the gas at the system outlet. The results are shown in Figure 3 The CO Faradaic efficiencies of the electrodes prepared by PVP / conventional heating, L-cysteine / conventional heating, and L-cysteine / microwave heating were 25.3%, 40.4%, and 55.0%, respectively.

[0039] Combine Figure 1 、 Figure 2 The results show that compared to the L-cysteine-modified nanosilver catalytic electrode prepared by conventional oil bath heating, microwave heating achieves uniform heating of the entire material sample, rapidly decomposes the metal precursor, and obtains nanosilver particles with highly uniform particle size to increase the specific surface area while avoiding agglomeration. Compared with the test results of the catalytic electrode obtained by preparing nanosilver particles in the silver nitrate-ethylene glycol system plus polyvinylpyrrolidone (PVP) in the prior art, the selectivity for the product CO is higher. In addition, due to the local capture of active substances by the surface amino functional groups of the L-cysteine-modified nanosilver catalytic electrode, a higher CO2 utilization rate is achieved in the in situ conversion of CO2.

[0040] Example 2: Preparation of Nanosilver Catalytic Electrodes Modified with Different L-Cysteine Ratios and In-Situ CO2 Conversion

[0041] 1) Preparation of L-cysteine modified nanosilver catalytic electrode:

[0042] 10 mL of 0.1 M silver nitrate aqueous solution was added to 90 mL of ethylene glycol and stirred at 800 rpm for 30 min until uniformly mixed; 0.06 g, 0.12 g, and 0.36 g of L-cysteine were added to the mixture (the molar ratio of silver: L-cysteine was 2:1, 1:1, and 1:3, respectively), and stirred until L-cysteine was completely dissolved. The microwave power was set to 150 W and heated at 120 ° C for 60 min. The obtained solid was centrifuged and washed three times with anhydrous ethanol and ultrapure water, respectively, and dried in a vacuum drying oven at 100 ° C for 12 h to obtain L-cysteine-modified silver nanoparticles; 105 mg of L-cysteine-modified silver nanoparticles were taken and dispersed in 20 mL of isopropanol. Catalyst ink was prepared with Nafion ionomer. The amount of Nafion ionomer was 10% of the catalyst mass. The obtained catalyst ink was ultrasonically dispersed for 60 min and then the catalyst ink was sprayed on a 2x2 cm 2 Carbon paper substrate, solid catalyst loading weight 1.0 mg / cm 2 , and obtain L-cysteine modified nanosilver catalytic electrode.

[0043] 2) Testing of L-cysteine-modified nanosilver catalytic electrodes in a CO2 in situ conversion system

[0044] The three catalytic electrodes prepared in step 1) were used as working electrodes and IrO2 mesh as counter electrode. Electrochemical tests were carried out in a CO2 in situ conversion system. The cathode electrolyte was 1.5M KHCO3, the anolyte was 0.01M H2SO4, and the cathode and anode compartments were separated by a Nafion proton exchange membrane. The current was 120 mA / cm 2 A constant current test was performed at a current density of 100 nm. After 30 min of electrolysis, the gas products were detected by gas chromatography.

[0045] Silver: L-cysteine = 2:1, 1:1, 1:3 molar ratio three electrodes at 120mA / cm 2 The selectivity comparison results for CO at different current densities are shown in Figure 4 During the test, the CO Faradaic efficiencies of the three electrodes with silver: L-cysteine = 2:1, 1:1, and 1:3 molar ratios were 66.5%, 75.6%, and 54.6%, respectively; Figure 4 The results show that the selectivity of the target product CO and the utilization rate of the carbon-containing components of the L-cysteine-modified nanosilver catalytic electrode first increase and then decrease with the change of the molar ratio of L-cysteine and silver source added during the reduction process, and the best performance is shown under the condition of a silver:L-cysteine molar ratio of 1:1.

[0046] Example 3: Preparation of L-cysteine-modified nanosilver catalytic electrodes prepared at different microwave heating powers and in-situ conversion of CO2

[0047] 1) Preparation of L-cysteine modified nanosilver catalytic electrode:

[0048] 10 mL of 0.1 M silver nitrate aqueous solution was added to 90 mL of ethylene glycol and stirred at 800 rpm for 30 min until uniformly mixed; 0.12 g of L-cysteine was added to the mixture and stirred until L-cysteine was completely dissolved. The microwave power was set to 100, 150, and 200 W, respectively, and heated at 120 ° C for 60 min. The obtained solid was centrifuged and washed three times with anhydrous ethanol and ultrapure water, respectively, and dried in a vacuum drying oven at 100 ° C for 12 h to obtain L-cysteine-modified silver nanoparticles; 105 mg of L-cysteine-modified silver nanoparticles were taken and dispersed in 20 mL of isopropanol. Catalyst ink was prepared with Nafion ionomer. The amount of Nafion ionomer was 10% of the catalyst mass. The obtained catalyst ink was ultrasonically dispersed for 60 min and then sprayed on a 2x2 cm 2 Carbon paper substrate, solid catalyst loading weight 1.0 mg / cm 2 , and obtain L-cysteine modified nanosilver catalytic electrode.

[0049] 2) Testing of L-cysteine-modified nanosilver catalytic electrodes in a CO2 in situ conversion system

[0050] The three catalytic electrodes prepared in step 1) were used as working electrodes and Ni mesh as counter electrode. Electrochemical tests were carried out in a CO2 in situ conversion system. The cathode electrolyte was 1.5M KHCO3, the anolyte was 1.5M KOH, and the cathode and anode compartments were separated by a bipolar membrane. The electrochemical current was 170mA / cm 2 A constant current test was performed at a current density of 100 nm. After 30 min of electrolysis, the gas products were detected by gas chromatography.

[0051] Three electrodes with different microwave heating powers at 170 mA / cm 2 The selectivity comparison results for CO at different current densities are shown in Figure 5 During the test, the CO Faraday efficiencies of the three electrodes with microwave heating at 100W, 150W and 200W were 61.5%, 73.5% and 58.4% respectively. Figure 5 It can be seen that changes in microwave power during the reduction process will lead to changes in the performance of the catalytic electrode tested in the CO2 in situ conversion system, among which a microwave power of 150W shows the best CO selectivity.

[0052] In summary, the present invention adds L-cysteine to the silver nitrate-ethylene glycol system and utilizes the modification of the amino functional group to achieve local capture of the active substance, thereby improving the selectivity of the target product. Utilizing the microwave heating process, the microwave energy directly acts on the molecules inside the substance, causing intense thermal motion inside the material, accelerating the chemical reaction, and obtaining nanosilver particles with high particle size uniformity to increase the specific surface area while avoiding agglomeration. In the CO2 in-situ electroconversion system, due to the advantages of uniform dispersion, large specific surface area, and multiple active sites, the electrocatalyst provided by the present invention achieves high selectivity and high stability for the target product CO, and can directly electrolyze and convert carbonate or bicarbonate solutions into efficient synthesis of CO, thereby realizing a short-process and efficient treatment process for carbon reduction and emission reduction.

[0053] The L-cysteine-modified nanosilver catalytic electrode prepared by microwave heating can improve the selectivity of the target product CO and enhance the utilization rate of carbon-containing components in the CO2 in situ conversion system.

[0054] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. Reference can be made to the descriptions of the identical or similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and the relevant parts can be referred to the descriptions of the methods.

[0055] The above describes in detail the L-cysteine-modified nanosilver electrocatalyst and its application provided by the present invention. Specific examples are used herein to illustrate the principles and embodiments of the present invention. The description of the above embodiments is intended only to facilitate understanding of the method and core concept of the present invention. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A nano silver catalytic electrode for in-situ conversion of CO2 to efficiently produce CO, characterized by The nano silver catalytic electrode is prepared by the following method: S1. Dissolve silver nitrate in water to obtain a 0.05-100 mM silver nitrate solution, add it to ethylene glycol and stir evenly; the volume ratio of the silver nitrate solution to ethylene glycol is 1:(2-20); S2. L-cysteine was added to the mixture, stirred evenly, and then microwaved. The resulting solid was washed at least three times with ethanol and ultrapure water, respectively, by centrifugation, and dried in a vacuum drying oven to obtain L-cysteine-modified nanosilver electrocatalyst particles. The microwave heating time is 30-60 min, the microwave power is 100-300 W, and the heating temperature is 120-160° C. The molar ratio of silver element to L-cysteine is 1:(0.5~1); S3. Disperse the L-cysteine-modified nanosilver electrocatalyst particles in an appropriate amount of isopropanol, prepare a catalyst ink with Nafion ionomer, and use the Nafion ionomer in an amount of 10% ± 2% of the catalyst mass. After ultrasonic dispersion of the obtained catalyst ink, spray the catalyst ink on the electrode substrate until the catalyst loading reaches 0.5-4 mg / cm 2 , obtaining a nanosilver catalytic electrode; This nanosilver catalytic electrode is used in the CO2 in-situ conversion reaction system. Without introducing exogenous gaseous CO2, carbonate or bicarbonate is directly reduced to CO. Due to the local capture of active substances by amino functional groups on the catalyst surface, a higher CO2 utilization rate can be achieved in the CO2 in-situ conversion.

2. The nanosilver catalytic electrode according to claim 1, characterized in that: The stirring in S1 is 700-1500 rpm, and the stirring is carried out at a temperature of 20-40° C. for 30-60 min; The drying in S2 is oven drying at a temperature of 80-100° C. for 1-24 hours.

3. The nanosilver catalytic electrode according to claim 1, characterized in that: In S2, the microwave power was 150 W and the temperature was heated at 120°C for 60 min.

4. The nanosilver catalytic electrode according to claim 1, characterized in that: S1 is to add 10 mL of 0.1 M silver nitrate aqueous solution to 90 mL of ethylene glycol and stir at 800 rpm for 30 minutes until uniformly mixed; and add 0.12 g of L-cysteine to the mixture.

5. The nanosilver catalytic electrode according to claim 1, characterized in that: The electrode substrate is a carbon-containing electrode substrate such as carbon paper, carbon cloth, carbon felt, etc.

6. Use of the nanosilver catalytic electrode for efficient in-situ conversion of CO to CO according to claim 1 in efficient in-situ electrochemical conversion of CO to CO, characterized in that: L-cysteine-modified nanosilver electrocatalyst was used as a catalyst for the in situ conversion of carbon dioxide to directly reduce carbonate or bicarbonate to carbon monoxide.

7. Use of the nanosilver catalytic electrode for efficient in-situ conversion of CO2 to CO according to claim 6 in efficient in-situ electrochemical conversion of CO2 to CO, characterized in that: L-cysteine-modified nanosilver catalytic electrode was used as the working electrode and applied to the CO2 in situ electroconversion system.

8. The use according to claim 7, characterized in that: The electrolyte used in the cathode chamber of the electrolyzer in the CO2 in-situ electroconversion system is 0.5~3M potassium carbonate or potassium bicarbonate solution; the working electrode in the cathode chamber of the CO2 in-situ electroconversion system converts HCO3 in the cathode electrolyte into - and CO3 2- The carbon-containing components are directly converted into CO, and no exogenous carbon-containing gas is introduced into the cathode chamber during the reaction. The current density of the CO2 in-situ electroconversion system is 10~1000mA / cm 2 .

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