Carbon-supported silver catalysts, methods for their preparation and use

Abstract

The application discloses a carbon-loaded silver catalyst and a preparation method and application thereof. Silver nitrate and carbon are impregnated at room temperature, and then the obtained precursor is ground into powder at room temperature, and the carbon-loaded silver catalyst is obtained after calcination. The carbon-loaded silver catalyst can be applied to electrocatalytic reduction of carbon dioxide to carbon monoxide. The application mainly adjusts the calcination temperature in the preparation process to adjust the interaction between silver and carbon. The formation of the carbon-loaded silver with a carbon semi-coating structure not only strengthens the electron transfer in the reaction process, but also strengthens the adsorption and stability of an intermediate COO ‑ . In addition, the enhancement of the interaction between silver and carbon limits the reconstruction of silver in the reaction process, and realizes stability at a high current. The application in the reduction of carbon dioxide to carbon monoxide shows excellent performance in the reduction of carbon dioxide to carbon monoxide.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrocatalytic carbon dioxide reduction electrode, and particularly relates to a preparation method of carbon-loaded transition metal catalyst and application thereof in promoting generation of carbon monoxide product. BACKGROUND

[0002] In recent years, with the excessive use of fossil fuels, the emission amount of carbon dioxide (CO2) increases year by year, and the greenhouse effect caused thereby is also increasingly serious. A promising method for realizing carbon neutralization is to convert CO2 into valuable carbon-based products by using renewable electricity. Among numerous reduction products, carbon monoxide (CO) as a most basic chemical raw material has attracted widespread attention. In thermodynamics, it is feasible to reduce CO2 to CO by using an electrochemical method, but in the reaction process, the first step of CO2 adsorption of electrons is difficult, the HER competitive reaction is limited, and the catalyst is reconstructed in the reaction process, which still faces great challenges in further developing a CO catalyst with high activity and high stability.

[0003] To date, researchers have explored a series of homogeneous and heterogeneous electrocatalysts for CO2 reduction to CO. Among these catalysts, silver (Ag)-based catalysts have shown excellent catalytic performance for CO and have received extensive attention. However, their activity and stability need to be further improved. Currently, various methods have been attempted to further improve the CO2RR performance of Ag electrocatalysts, such as particle size control (Salehi-Khojin A, Jhong H R M, Rosen B A, et al. Nanoparticle silver catalysts that show enhanced activity for carbon dioxide electrolysis [J]. The Journal of Physical Chemistry C, 2013, 117(4): 1627-1632), surface modification (Li P, Bi J, Liu J, et al. In situ dual doping for constructing efficient CO2-to-methanol electrocatalysts [J]. Nature Communications, 2022, 13(1): 1-9), heteroatom doping, etc. (Zhang Z, Wen G, Luo D, et al. “Two ships in a bottle” design for Zn-Ag-O catalyst enabling selective and long-lasting CO2 electroreduction [J]. Journal of the American Chemical Society, 2021, 143(18): 6855-6864). Liu et al. improved the adsorption of COOH by establishing a strong atomic local electric field through Sn heteroatom doping of Ag. The obtained Ag / Sn catalyst maintained almost constant CO faradaic efficiency (CO FE of about 100%) for more than 20 hours and achieved a current density of 200 mA / cm 2high current density (Cai C, Liu B, Liu K, et al. Heteroatoms induce localization of the electric field and promote a wide potential-window selectivity towards CO in the CO2 electroreduction [J]. Angewandte Chemie International Edition, 2022, 61(44): e202212640). Zhao et al. introduced a Cr2O3 support and found that the formation of Ag-Cr2O3 interface sites effectively stabilized CO2 ·- / *COOH intermediate product, which achieved excellent activity and stability in the process of electrocatalytic reduction of CO2 to CO (Fu H Q, Liu J, Bedford N M, et al. Synergistic Cr2O3@Ag heterostructure enhanced electrocatalytic CO2 reduction to CO [J]. Advanced Materials, 2022: 2202854).

[0004] It can be found that although the corresponding research has made certain progress, in most of the research, the current density is still ≤300mA / cm -2 , and in the process of electrocatalysis, the reconstruction of Ag often leads to the gradual loss of activity and stability. Therefore, it is still a challenge to develop Ag-based catalysts that can simultaneously achieve high current density, high selectivity and high stability to generate CO. SUMMARY

[0005] The present application aims to solve the technical problem of low reaction activity and stability of Ag-based catalysts, and provides a carbon-loaded silver catalyst and its preparation method and application. Through impregnation and further calcination, the characteristics of Ag and carbon (C) interaction are adjusted by high-temperature calcination to realize the adjustment of Ag and C interaction, promote the electron transfer in the reaction process and strengthen the adsorption and stability of the intermediate *COOH - ; and limit the reconstruction of silver in the reaction process, so that it exhibits excellent reaction activity and stability in the reduction of CO2 to CO, and can be applied in the electrocatalytic reduction of CO2 to CO.

[0006] In order to solve the above technical problems, the present application is realized by the following technical scheme:

[0007] Carbon supported silver catalyst and its preparation method, Ag particles with a particle size of 4-75 nm, preferably 4-22 nm, are uniformly supported on the surface of carbon according to the following steps:

[0008] Step 1, carbon powder is added to an aqueous solution of silver nitrate and dispersed, and then the product is collected by centrifugation and dried, and the amount of carbon powder added is 50-100% of the mass of silver nitrate;

[0009] Step 2, under the protection of an inert atmosphere, the product obtained in step 1 is heated from room temperature 20-25 degrees Celsius to 400-800 degrees Celsius at a rate of 5-10 degrees Celsius per minute and kept for 1-2 hours, and then naturally cooled to room temperature to obtain a carbon supported silver catalyst.

[0010] In the technical solution of the present application, the carbon powder (i.e. C carbon) is Cabot VXC 72 or Super P.

[0011] In the technical solution of the present application, the inert protective gas is nitrogen, helium or argon.

[0012] In the technical solution of the present application, the amount of carbon powder added is 60-100% of the mass of silver nitrate.

[0013] In the technical solution of the present application, carbon powder is added to an aqueous solution of silver nitrate and dispersed to allow carbon and silver to be fully impregnated, and ultrasonic or stirring treatment is selected, and the time is 10-15 hours, preferably 10-12 hours.

[0014] Application of the carbon supported silver catalyst of the present application in electrocatalytic reduction of CO2 to CO.

[0015] In the application, the carbon supported silver catalyst is sprayed onto a gas diffusion electrode (such as carbon paper) as a working electrode, and IrO2 is used as a counter electrode, which is assembled into an electrochemical cell, CO2 is introduced into the electrolyte, and the electrolyte is a 0.05-0.005 mol / L aqueous solution of Cs2CO3, and the electrocatalytic reaction is carried out by applying electricity.

[0016] In the application, 0.5-2 mg of carbon supported silver catalyst is sprayed per square centimeter of gas diffusion electrode.

[0017] The silver carbon catalyst of the present application, by adjusting the calcination temperature, obtains a more stable silver carbon, the introduction of C carrier improves the dispersion of Ag particles, so that Ag particles with a particle size of 4-75 nm are uniformly supported on the C carrier. At the same time, the enhancement of the interaction between Ag and C effectively avoids the agglomeration of Ag particles, and forms an interface site rich in electrons, which promotes the formation and stability of COO - , thereby improving the activity and stability of the CO2 reduction reaction.

[0018] The preparation method of the silver-carbon catalyst of the application, using commonly used conductive carbon black (Cabot VXC 72 or Super P) as the C source and silver nitrate as the silver source, obtains the silver-carbon catalyst through the method of impregnation and further calcination. The raw materials required in the preparation process are simple, the preparation method is simple and easy to implement, batch preparation can be realized, and it has certain industrialization prospect.

[0019] The silver-carbon catalyst of the application is used for electrocatalytic CO2 reduction to prepare CO, the enhancement of the interaction between Ag and C strengthens the electron transfer in the reaction process, on the other hand, the high localized electron density at the silver-carbon interface site promotes the formation and stability of COOH - , and improves the reaction activity; at the same time, the semi-coated Ag / C catalyst enhances the interaction force between Ag and C, limits the reconstruction of Ag in the reaction process, and the faradic efficiency of CO is more than 90% in the current density range of 100-1100 mA / cm 2 , and realizes long-time stability of up to 600 h at the current density of 500 mA / cm 2 , and has superior performance in electrocatalytic CO2 reduction to prepare CO. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The transmission electron microscope photos and particle size statistical graphs of Ag-C VXC 72 , Ag / C VXC 72 and Ag@C VXC 72 obtained in Examples 1, 3 and 4.

[0021] Figure 2 The transmission electron microscope photos of Ag-C VXC 72 , Ag / C VXC 72 and Ag@C VXC 72 obtained in Examples 1, 3 and 4.

[0022] Figure 3 The XRD diffraction spectra of Ag-C VXC 72 , Ag / C VXC 72 and Ag@C VXC 72 obtained in Examples 1, 3 and 4.

[0023] Figure 4 The transmission electron microscope photo of the Ag-C VXC 72 catalyst obtained in Example 2.

[0024] Figure 5 The transmission electron microscope photo and particle size statistical graph of the Ag / C Super P catalyst prepared in Example 5.

[0025] Figure 6 The transmission electron microscope photos of Ag-C VXC 72 , Ag / CVXC 72 and Ag@C VXC 72 CO2 reduction performance test chart under the condition of the embodiment.

[0026] Figure 7 Ag-C VXC 72 , Ag / C VXC 72 and Ag@C VXC 72 Cell voltage chart and energy efficiency chart of CO2 reduction performance test under the condition of the embodiment.

[0027] Figure 8 Ag-C VXC 72 , Ag / C VXC 72 and Ag@C VXC 72 CO2 reduction stability test chart under the condition of the embodiment.

[0028] Figure 9 Ag-C VXC 72 , Ag / C VXC 72 and Ag@C VXC 72 Transmission electron microscope photos and particle size statistics chart after CO2 reduction stability test under the condition of the embodiment.

[0029] Figure 10 In-situ infrared test chart of Ag-C VXC 72 , Ag / C VXC 72 and Ag@C VXC 72 corresponding to the embodiment 1, 3, 4 obtained by the embodiment. DETAILED DESCRIPTION

[0030] The present application will be further described in detail by specific embodiments, which can make the professional technical personnel more comprehensive understanding of the present application, but not in any way limit the present application.

[0031] Example 1 - Preparation of Ag-C VXC 72 (i.e. silver-carbon catalyst with silver particles simply dispersed on the surface of carbon)

[0032] (1) Accurately weigh 0.5g AgNO3 into 50mL deionized water, stir to dissolve to obtain AgNO3 aqueous solution, then add 0.3g C powder (Cabot VXC 72) and ultrasonic treatment for 1h to obtain Ag-C + suspension; stir the obtained suspension (300 revolutions per minute) for 12 hours, then centrifugal collect the product and dry at 60℃. VXC 72

[0033] ​(2) The obtained powder was heated in a tube furnace, after the oxygen was removed by nitrogen, and the N2 flow rate was maintained at 80 standard cubic centimeters per minute (sccm) to maintain an inert protective gas atmosphere, from room temperature 20-25 degrees Celsius to 400 degrees Celsius at a rate of 10 degrees Celsius per minute and maintained for 2 hours, and after natural cooling to room temperature, Ag-C VXC 72 .

[0034] From Figure 1 a of the Ag-C VXC 72 of Example 1, it can be seen that the transmission electron micrograph of the Ag-C VXC 72 , the Ag particles are uniformly loaded on the surface of C. From Figure 1 b of the Ag-C VXC 72 of Example 1, it can be seen that the particle size distribution graph of the Ag-C VXC 72 , the particle size distribution of Ag is 4-18 nm. From Figure 2 a of the Ag-C VXC 72 of Example 1, it can be seen that the transmission electron micrograph of the Ag-C VXC 72 , the Ag is dispersed on the surface of C. From Figure 3 , it can be seen that the Ag-C VXC 72 of Example 1, in addition to the diffraction peak of C at about 20° (2 theta), the remaining diffraction peaks are completely matched with the standard card of Ag (PDF #04-0738), indicating that the obtained Ag has good crystallinity.

[0035] Example 2 - Preparation of Ag-C VXC 72

[0036] The difference from Example 1 is only that the obtained powder is heated to 400 degrees Celsius in a tube furnace with an N2 flow rate of 80 sccm and maintained for 1 hour, and after cooling to room temperature, Ag-C VXC 72 .

[0037] Figure 4 is the transmission electron micrograph of the Ag / C VXC 72 prepared in Example 2; from Figure 4 , it can be seen that the Ag particles are uniformly loaded on the surface of C.

[0038] Example 3 - Preparation of Ag / C VXC 72 (semi-coated silver carbon catalyst in which silver particles are partially coated by carbon)

[0039] The difference from Example 1 is only that the obtained powder is heated to 600 degrees Celsius in a tube furnace with an N2 flow rate of 80 sccm and maintained for 2 hours, and after cooling to room temperature, Ag / C VXC 72 .

[0040] From​Figure 1 As can be seen from c, the Ag / C prepared in Example 3 VXC 72 Transmission electron microscopy images of the Ag / C prepared in Example 3. VXC 72 In the middle, Ag particles are uniformly loaded on the C surface. From Figure 1 In d, the Ag / C prepared in Example 3 is acceptable. VXC 72 The particle size distribution diagram of Ag / C prepared in Example 3. VXC 72 The particle size distribution of Ag was observed to be 4-22 nm. From... Figure 2 As can be seen from b, the Ag / C prepared in Example 3 VXC 72 Transmission electron microscopy images of the Ag / C prepared in Example 3. VXC 72 In this structure, Ag is partially coated with carbon, forming a semi-coated silver-carbon structure. From Figure 3 As can be seen from the results, the Ag-C prepared in Example 3... VXC 72 Except for the diffraction peak around 20° (2Theta) belonging to C, the remaining diffraction peaks completely match the standard card of Ag (PDF#04-0738), indicating that Ag with good crystallinity was obtained.

[0041] Example 4—Ag@C VXC 72 Preparation of (i.e., a fully coated silver-carbon catalyst in which silver particles are completely coated with carbon).

[0042] The only difference from Example 1 is that the obtained powder was heated to 800°C in a tube furnace with an N2 gas flow of 80 sccm and held for 2 hours. After cooling to room temperature, Ag@C was obtained. VXC 72 .

[0043] from Figure 1 As can be seen from e, the Ag@C prepared in Example 4 VXC 72 Transmission electron microscopy images of Ag@C prepared in Example 4. VXC 72 In the middle, Ag particles are uniformly loaded on the C surface. From Figure 1 As can be seen in f, the Ag / C prepared in Example 4 VXC 72 The particle size distribution diagram of Ag@C prepared in Example 4. VXC 72 In this study, the particle size distribution of Ag ranged from 35 to 75 nm. From... Figure 2 As can be seen from c, the Ag@C prepared in Example 4 VXC 72 Transmission electron microscopy images of Ag@C prepared in Example 4. VXC 72 In this structure, Ag is completely coated with carbon, forming a fully coated silver-carbon structure. From Figure 3 As can be seen from the results, the Ag@C prepared in Example 4... VXC 72Except for the diffraction peak around 20° (2Theta) belonging to C, the remaining diffraction peaks completely match the standard card of Ag (PDF#04-0738), indicating that Ag with good crystallinity was obtained.

[0044] Example 5—Ag / C Super P Preparation

[0045] The only difference from Example 3 is that Super P is used instead of Cabot VXC 72.

[0046] Figure 5 The Ag / C prepared in Example 5 Super P Transmission electron microscope images; from Figure 5 As can be seen, Ag particles are uniformly loaded on the C surface, and the Ag particle size distribution is 8-22 nm.

[0047] Example 6—Ag / C VXC 72 Preparation

[0048] The difference from Example 1 is that the amount of AgNO3 added in step (1) is 0.3g, and the calcination temperature in step (2) is 600℃ and the time is 1h.

[0049] Example 7—Electrocatalytic CO2

[0050] The catalysts prepared in Examples 1-6 were tested for their electrocatalytic CO2 reduction performance.

[0051] The catalyst prepared in the above embodiments was drop-coated onto a glassy carbon electrode as the working electrode (0.5-2 mg of silver-carbon catalyst per square centimeter of glassy carbon electrode, i.e., the catalyst prepared in the embodiments of this invention). IrO2 supported on a Ti mesh served as the counter electrode. The system was assembled into an electrochemical cell to form a dual-electrode system. CO2 was continuously introduced into the electrochemical cell to test the electrocatalytic CO2 reduction performance and electrode stability. The electrolyte was a 0.05 mol / L Cs2CO3 aqueous solution, and the working electrode area was 4 cm². 2 Gas-phase products were detected by gas chromatography, and liquid-phase products were detected quantitatively using a combination of liquid chromatography and nuclear magnetic resonance. The 0.5 mg catalyst prepared in Examples 1-6 was analyzed at an applied current density of 500 mA / cm². 2 The selectivity of CO products is shown in the table below.

[0052] CO FE (%) Example 1 97 Example 2 97 Example 3 99 Example 4 92 Example 5 89 Example 6 98

[0053] Catalytic activity tests were conducted using 2 mg of catalysts prepared in Examples 1, 3, and 4 at different current densities, and the product distribution is shown below. Figure 6 As shown. From Figure 6 It can be seen from Ag / C VXC 72Its performance is far superior to Ag-C over a wider range of current densities. VXC 72 and Ag@C VXC 72 : Figure 6 In the text, 'a' represents Ag-C prepared in Example 1. VXC 72 The CO2 reduction performance of the Ag-C prepared in Example 1 was demonstrated by experimental results. VXC 72 Catalyst, at 100-700 mA / cm 2 At current densities, the selectivity of CO remained above 90%. Figure 6 b is the Ag / C prepared in Example 3. VXC 72 The CO2 reduction performance of the Ag-C prepared in Example 3 was demonstrated by experimental results. VXC 72 Catalyst, at 100-1100 mA / cm 2 At current densities, the selectivity of CO remained above 90%. Figure 6 c represents Ag@C obtained in Example 4. VXC 72 The CO2 reduction performance of the Ag@C prepared in Example 4 was demonstrated by experimental results. VXC 72 Catalyst, at 100-500 mA / cm 2 At current densities, the selectivity of CO remained above 90%.

[0054] Figure 7 The Ag-C obtained in Examples 1, 3, and 4 VXC 72 Ag / C VXC 72 and Ag@C VXC 72 Cell voltage and energy efficiency graphs for CO2 reduction performance testing under the conditions of the examples. 'a' represents Ag-C prepared in Examples 1, 3, and 4. VXC 72 Ag / C VXC 72 and Ag@C VXC 72 In the range of 100-1500 mA / cm 2 Slot voltage at current density, from Figure 7 As can be seen from a in Figure 3, throughout the entire test period, the Ag / C obtained in Example 3... VXC 72 The slot voltages of the samples were all superior to those of the Ag-C obtained in Example 1. VXC 72 And the Ag@C obtained in Example 4 VXC 72 b represents Ag-C prepared in Examples 1, 3, and 4. VXC 72 Ag / C VXC 72 and Ag@C VXC 72 In the range of 100-1500 mA / cm 2 Energy efficiency at current density, from Figure 7 As can be seen from b, throughout the entire test period, the Ag / C obtained in Example 3 VXC 72 The energy efficiency of both is higher than that of Ag-C obtained in Example 1. VXC 72And the Ag@C obtained in Example 4 VXC 72 .

[0055] Figure 8 Ag-C obtained in Examples 1, 3, and 4 VXC 72 Ag / C VXC 72 and Ag@C VXC 72 At 500 mA / cm 2 CO2 reduction stability diagram under current density. From Figure 8 As can be seen from a and b in the figure, in the 100h stability test, Ag-C VXC 72 and Ag@C VXC 72 The cell voltage changed significantly over time, and the FE of CO decreased significantly. Meanwhile, the Ag / C... VXC 72 Throughout the test, the cell voltage and the FE of CO remained essentially constant, which was far superior to the Ag-C obtained in Example 1. VXC 72 And the Ag@C obtained in Example 3 VXC 72 When the electrolyte concentration was further reduced to 0.005 mol / L, the Ag / C ratio obtained in Example 3... VXC 72 A stability test was conducted on the catalyst for up to 600 hours, during which the cell voltage remained essentially constant, and the FE of CO remained above 95%. Figure 8 As shown in c.

[0056] Figure 9 Ag-C obtained in Examples 1, 3, and 4 VXC 72 Ag / C VXC 72 and Ag@C VXC 72 At 500 mA / cm 2 Transmission electron microscopy (TEM) images and particle size distributions after stability testing at current density. Figure 9 From 'a', we can see Ag-C VXC 72 The Ag particles in the catalyst exhibited significant agglomeration, with a marked increase in particle size compared to before the reaction. See details... Figure 1 b and Figure 9 b in Ag / C VXC 72 and Ag@C VXC 72 After stability testing, the particle size remained essentially unchanged; see details. Figure 1 cf and Figure 9 The cf in the text indicates Ag / C VXC 72 and Ag@C VXC 72 It has good stability.

[0057] Ag / C of the present invention VXC 72 The formation of the semi-encapsulated structure effectively improves the activity and stability of CO2 reduction, such as... Figure 6 As shown in Figure 7. Figure 10As shown, Ag-C was prepared in Examples 1, 3, and 4. VXC 72 Ag / C VXC 72 and Ag@C VXC 72 The in-situ infrared spectroscopy results showed that the Ag-C obtained in Example 1... VXC 72 And the Ag@C obtained in Example 4 VXC 72 No *COO was detected on the surface. - / *For the absorption peak of COOH, see [link / ] Figure 10 a and c in the figure indicate that the CO2RR intermediate is in Ag-C VXC 72 and Ag@C VXC 72 The binding on Ag / C is not strong. VXC 72 Two distinct peaks can be observed above; see details. Figure 10 b, located at 1378cm -1 The peak belongs to *COO - Symmetrical extension, located at 1284cm -1 Another absorption peak is attributed to the C-OH extension of *COOH. The Ag / C ratio changes as the applied potential varies from -0.3 to -1.1 V vs. RHE. VXC 72 *COOH and *COO on the surface - A broadened peak indicates that *COO - / *High COOH coverage. Ag / C VXC 72 Surface COO - / *The formation and stabilization of COOH intermediates play a decisive role in the reduction of CO2 to CO. Appropriate interactions between Ag and C favor *COO* - / *The adsorption of COOH on the catalyst surface gives the catalyst a higher CO2 reduction performance. * /

[0058] As demonstrated by the above embodiments, the carbon-supported silver catalyst of the present invention exhibits good activity and stability for the electrocatalytic reduction of CO2 to CO. This is achieved at a current density of 100-1100 mA / cm². 2 Under these conditions, the FE of CO remains above 90%. At 500 mA / cm² 2 Under these conditions, long-term durability exceeding 600 hours was achieved, with the cell voltage remaining almost constant throughout the reaction, and the FE of CO maintained above 95%. In-situ ATR-SEIRAS and electrochemical experiments indicate that the strong interaction between Ag and C not only promotes electron transfer but also stabilizes *COO. - This improves the activity and effectively inhibits the reconstruction of Ag during the electrocatalytic process, thus exhibiting high stability.

[0059] According to the adjustment of the preparation process according to the content of the present application, the preparation of the catalyst of the present application can be realized, and the test shows that the performance is basically consistent with the present application. The above describes the present application by way of example, and it should be noted that any simple modification, modification or other equivalent replacement which can not cost the creative labor of the person skilled in the art without departing from the core of the present application falls within the protection scope of the present application.

Claims

1. A carbon-supported silver catalyst characterized in that, The carbon surface is uniformly loaded with Ag particles with a particle size of 4-75 nm, and the following steps are performed: Step 1: carbon powder is added to an aqueous silver nitrate solution and dispersed, and then the product is collected by centrifugation and dried, and the amount of carbon powder added is 50-100% of the mass of silver nitrate; Step 2: under the protection of an inert atmosphere, the product obtained in step 1 is heated from room temperature 20-25 degrees Celsius to 600 degrees Celsius at a rate of 5-10 degrees Celsius per minute and maintained for 1-2 hours, and then naturally cooled to room temperature to obtain a carbon-supported silver catalyst.

2. The carbon-supported silver catalyst according to claim 1, characterized in that, The particle size of the Ag particles is 4-22 nm.

3. The carbon-supported silver catalyst according to claim 1 or 2, characterized in that, The amount of carbon powder added is 60-100% of the mass of silver nitrate.

4. The method of preparing a carbon-supported silver catalyst according to claim 1, wherein The following steps are performed: Step 1: carbon powder is added to an aqueous silver nitrate solution and dispersed, and then the product is collected by centrifugation and dried, and the amount of carbon powder added is 50-100% of the mass of silver nitrate; Step 2: under the protection of an inert atmosphere, the product obtained in step 1 is heated from room temperature 20-25 degrees Celsius to 600 degrees Celsius at a rate of 5-10 degrees Celsius per minute and maintained for 1-2 hours, and then naturally cooled to room temperature to obtain a carbon-supported silver catalyst.

5. The method of preparing a carbon-supported silver catalyst according to claim 4, characterized in that, The amount of carbon powder added is 60-100% of the mass of silver nitrate.

6. The method of preparing a carbon-supported silver catalyst according to claim 4, characterized by, The carbon powder is Cabot VXC 72 or Super P.

7. The method of preparing a carbon-supported silver catalyst according to claim 4, characterized by, The inert protective gas is nitrogen, helium or argon.

8. The method of preparing a carbon-supported silver catalyst according to claim 4, characterized by, Carbon powder is added to an aqueous silver nitrate solution and dispersed to allow carbon and silver to be fully impregnated, and ultrasonic or stirring treatment is selected, and the time is 10-15 hours.

9. The method of preparing a carbon-supported silver catalyst according to claim 8, characterized in that, Ultrasonic or stirring treatment is selected, and the time is 10-12 hours.

10. Use of the carbon-supported silver catalyst of any one of claims 1-3 in the electrocatalytic reduction of CO2 to produce CO.

11. Use of the carbon-supported silver catalyst according to claim 10 for the electrocatalytic reduction of CO2 to CO, characterized in that, In use, the carbon-supported silver catalyst is sprayed onto a gas diffusion electrode as a working electrode, and IrO2 is used as a counter electrode, and the electrochemical cell is assembled, CO2 is introduced into the electrolyte, and the electrocatalytic reaction is carried out by applying electricity, and 0.5-2 mg of carbon-supported silver catalyst is sprayed per square centimeter of gas diffusion electrode.

12. Use of the carbon-supported silver catalyst according to claim 11 for the electrocatalytic reduction of CO2 to CO, characterized in that, The gas diffusion electrode is carbon paper.

13. Use of the carbon supported silver catalyst according to claim 11 for the electrocatalytic reduction of CO2 to CO, characterized in that, The electrolyte is an aqueous solution of 0.05-0.005 mol / L Cs2CO3. The electrolyte is an aqueous solution of 0.05-0.005 mol / L Cs2CO3.

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