Preparation method of silver-copper aerogel catalyst modified by dicarboxyl chelating agent and used for electrocatalysis of CO2 reduction

Abstract

The invention relates to a preparation method of a silver-copper aerogel catalyst modified by a dicarboxyl chelating agent and used for electrocatalytic CO2 reduction. The silver-copper aerogel is prepared by a wet chemical reduction method which comprises the following steps: dissolving and mixing copper salt and silver salt, then adding an EDTA (Ethylene Diamine Tetraacetic Acid) sodium salt solution to fully chelate, then adding a reducing agent to reduce and precipitate, and filtering and washing to obtain the aerogel. Finally, the catalyst is used for electrocatalytic CO2 reduction. The problem that a copper-based catalyst in eCO2RR (electro-catalytic carbon dioxide) is low in ethylene selectivity is solved, and the conversion performance of carbon dioxide is improved.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical catalyst material preparation, and in particular relates to a method for preparing a silver-copper aerogel catalyst modified by a dicarboxyl chelating agent for electrocatalytic CO2 reduction. Background Art

[0002] In recent years, the research on electrochemical carbon dioxide reduction driven by renewable energy has attracted extensive attention from researchers. Compared with other traditional catalytic methods (such as thermal catalysis), it has milder reaction conditions, lower energy consumption and more diverse reduction products. These reduction products mainly include CO, HCOO - , CH4, C2H4, C2H5OH, CH3COO - , isopropanol, etc. Among them, multi-carbon products, such as ethylene, have higher economic benefits in the fields of chemical industry, medicine and food. Copper-based catalysts are the only efficient catalyst type for the electrochemical reduction of carbon dioxide into multi-carbon products. The reason for the special nature of metallic copper for eCO2RR is mainly because it has negative adsorption energy for *CO (the key intermediate of eCO2RR, whose subsequent reaction determines the final reduction product of CO2), and positive adsorption energy for H* (the reaction intermediate of HER, the competitive reaction of eCO2RR). In addition, a high energy barrier needs to be overcome in the reaction process of coupling between *CO to form ethylene.

[0003] During the catalytic process, the influence of the local coordination environment around the active site on the catalytic performance of electrochemical eCO2RR has received significant attention. However, the complex interaction between various factors in the catalytic system hinders the establishment of structure-activity relationships and limits the rational design of efficient catalysts. The method of utilizing coordination effects has been proven to be one of the effective strategies to regulate and coordinate metal-centered catalytic active sites, which highlights the key bridge between catalyst activity and structural characteristics during eCO2RR. However, the limited availability of various organic ligands has hindered the development of new high-performance electrocatalysts. In contrast, small organic molecules are widely used as metal coordination agents due to their simple structure, low cost and easy access. Liu et al. prepared a new type of bifunctional heterogeneous molecular catalyst using functionalized small organic molecules such as aminobenzoic acid. This organic functionalized Bi-based catalyst exhibits excellent electrocatalytic activity at a potential of -0.95 V relative to the reversible hydrogen electrode ( vs. Under the conditions of RHE), a high formic acid Faradaic efficiency of 89.8% and a high formic acid efficiency of 40.0 mA·cm -2 These molecular catalysts enhance the conversion of CO2 to formate in the eCO2RR. Summary of the Invention

[0004] This invention utilizes EDTA disodium salt as a dicarboxyl chelating agent to modify a silver-copper (Ag-Cu) aerogel catalyst for electrocatalytic CO2 reduction, enhancing metal dispersion and stability. EDTA disodium salt, acting as a metal chelator, coordinates with metal ions (Ag⁺ and Cu²⁺) to achieve uniform dispersion of metal nanoparticles during aerogel formation and prevent agglomeration. This structure enhances catalyst stability, ensuring sustained operation. Furthermore, this structure optimizes the electronic structure and reaction pathway. The synergistic effect of Ag and Cu, combined with the electronic regulation of EDTA, modulates the local electronic environment of active sites, promoting CO2 adsorption and the formation of intermediates (such as *COOH). The aerogel's three-dimensional porous structure provides high specific surface area and mass transfer efficiency, while also providing abundant reactive sites. EDTA modification further enhances porosity, accelerating mass transfer between CO2 and the electrolyte. Furthermore, EDTA modification modulates the charge distribution on the catalyst surface, suppressing the HER (Heat Reduction) reaction (HER), and improving the Faradaic efficiency of multi-carbon products in the eCO2RR process.

[0005] This silver-copper aerogel catalyst is prepared using a wet chemical reduction method. The specific steps are: first, dissolving and mixing a copper salt and a silver salt; then adding a disodium EDTA solution for complete chelation; and finally, adding a sodium borohydride solution dropwise for reduction precipitation, followed by filtration and washing. The silver-copper aerogel catalyst prepared in this invention overcomes the low selectivity of the catalyst for ethylene in eCO2RR, improving carbon dioxide conversion performance.

[0006] Therefore, in order to solve the problem of low selectivity of eCO2RR to ethylene, this patent uses a wet chemical reduction method to prepare a silver-copper aerogel electrode modified with EDTA sodium salt as a catalyst for ECO2RR, thereby improving the selectivity of carbon dioxide to ethylene conversion.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: A method for preparing a silver-copper aerogel catalyst modified with a dicarboxyl chelating agent for electrocatalytic CO2 reduction, characterized in that the catalyst comprises the following steps: Step 1: Prepare the metal salt solution as follows: S1. Prepare 50 ml of each of the following: 0.05-0.2 mol / L copper salt solution, 0.02-0.2 mol / L AgNO3 solution, 0.01-0.2 mol / L dicarboxyl chelating agent aqueous solution, and 0.1-1 mol / L strong reducing agent solution; S2, adding the AgNO3 solution to the above-mentioned copper salt solution, and then adding the dicarboxyl chelating agent solution and stirring thoroughly to achieve chelation; S3. Add 50 mL of strong reducing agent solution into the above system at a rate of 0.2 mL / min and maintain stirring at a rate of 400 r / min; S4. After continuing to stir the obtained dispersion system for 15 minutes, the mixed solution was centrifuged and then washed three times with deionized water and ethanol respectively, and then transferred to a 60°C oven for drying to obtain aerogel powder.

[0008] Step 2: Coordinate the metal salt solution, dicarboxyl chelating agent and reducing agent solution to prepare a catalyst ink dispersion, as follows; Weigh 5 mg of catalyst metal powder, add 750 μl of isopropanol, 250 μl of deionized water, and add 50 μl of Nafion ® The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion; Step 3: Disperse the material evenly on the hydrophobic carbon paper by spraying. The steps for preparing the cathode electrode loaded with cathode catalyst are as follows: take 150 μl of the obtained catalyst ink dispersion and spray the dispersion evenly on a 1.5×1.5 cm 2 The silver-copper aerogel catalyst modified with a dicarboxyl chelating agent was obtained, and then a cathode electrode loaded with a cathode catalyst was prepared.

[0009] The metal copper salts described include CuSO4, Cu(NO3)2, CuCl2, and CH3COOCu.

[0010] The dicarboxyl chelating agent is EDTA-2Na, ethylenediaminediacetic acid, iminooxalic acid, malonic acid, aspartic acid, glutamic acid and tartaric acid.

[0011] The reducing agent solution (NaBH4, boron ammonia complex, hydrazine hydrate, glucose and other common metal reducing agents.

[0012] Furthermore, using a Pt sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared silver-copper aerogel catalyst as the working electrode, a 0.5 mol / L KHCO3 solution was used as the electrolyte in an H-type electrolytic cell. After CO2 gas was introduced for 15 minutes, an external bias voltage was applied to carry out the electrocatalytic reaction, and the reaction products were quantitatively analyzed by gas chromatography (GC).

[0013] The beneficial effects of the present invention are: In the catalytic conversion of CO₂ to ethylene, the three-dimensional porous network structure of silver-copper aerogels is a crucial physical foundation for their efficient catalysis. The aerogel's high surface area (typically reaching hundreds of m² / g) provides abundant adsorption sites for CO₂ molecules, while its interconnected pore structure (mostly with a pore size distribution ranging from nanometers to micrometers) significantly accelerates the mass transfer of reactants (CO₂, H₂O) and products (C₂H₄, H₂, etc.). This structural feature allows catalytically active sites (such as copper step sites and silver defect sites) to be fully exposed to the electrolyte interface, thereby enhancing surface reaction kinetics. For example, studies have shown that unmodified silver-copper aerogels can achieve a current density of approximately 20 mA / cm² at a potential of -1.2 V (vs. RHE). Modification with sodium EDTA increases this current density to over 35 mA / cm², directly reflecting the improved mass transfer efficiency. Sodium EDTA, a strong chelating agent, forms a stable hexadentate coordination structure with silver and copper ions through its four carboxylic acid groups and two amino groups. This coordination effect plays a dual role during catalyst synthesis: first, it inhibits the excessive growth of metal nanoparticles during the reduction process, keeping their size within the 5-10 nm range (transmission electron microscopy characterization shows that the particle size of the unmodified sample is 20-50 nm), thereby increasing the density of active sites; second, it prevents nanoparticle aggregation during electrochemical cycling through steric hindrance. For example, after 100 cyclic voltammetry tests, the specific surface area of ​​the unmodified catalyst decreased by approximately 40%, while that of the EDTA-modified sample decreased by only 12%. This stability is directly related to the long-term performance of the catalyst. The chelation effect of EDTA significantly improves the durability of the catalyst. During 50 hours of continuous operation, the ethylene Faradaic efficiency of the modified catalyst decreased only from 54% to 49%, with a current density fluctuation of less than 8%. In contrast, the efficiency of the unmodified system decayed to 60% of its initial value within 20 hours. This stability is due to two factors: first, the strong coordination of EDTA with copper prevents Cu²⁻¹ from oxidizing and degrading. 0 Dissolution (ICP-MS detection shows that Cu² 0 The concentration of the catalyst was reduced by 90%; secondly, the mechanical strength of the aerogel (the compression modulus increased from 10 MPa to 25 MPa after modification) resisted structural collapse during electrochemical cycling. Furthermore, the catalyst maintained a 45% Faradaic efficiency for ethylene in a membrane electrode assembly (MEA) system, demonstrating potential for practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a transmission electron microscope photograph of the EDTA-2Na modified copper-silver aerogel catalyst obtained in Example 1 of the present invention.

[0015] Figure 2This is a high-resolution transmission electron microscopy photograph of the EDTA-2Na modified copper-silver aerogel catalyst obtained in Example 1 of the present invention.

[0016] Figure 3 This is a scanning electron microscope photograph of the EDTA-2Na modified copper-silver aerogel catalyst obtained in Example 1 of the present invention.

[0017] Figure 4 This is the X-ray diffraction pattern of the EDTA-2Na modified copper-silver aerogel catalyst obtained in Example 1 of the present invention.

[0018] Figure 5 This is the eCO2RR reduction performance of the EDTA-2Na modified copper-silver aerogel catalyst obtained in Example 1 of the present invention under certain conditions.

[0019] Figure 6 This is a transmission electron microscope photograph of the EDTA-4Na modified copper-silver aerogel catalyst obtained in Example 2 of the present invention.

[0020] Figure 7 This is a high-resolution transmission electron microscopy photograph of the EDTA-4Na modified copper-silver aerogel catalyst obtained in Example 2 of the present invention.

[0021] Figure 8 This is a scanning electron microscope photograph of the EDTA-4Na modified copper-silver aerogel catalyst obtained in Example 2 of the present invention.

[0022] Figure 9 This is the X-ray diffraction pattern of the EDTA-4Na modified copper-silver aerogel catalyst obtained in Example 2 of the present invention.

[0023] Figure 10 This is the ECO2RR reduction performance of the EDTA-4Na modified copper-silver aerogel catalyst obtained in Example 2 of the present invention under certain conditions.

[0024] Figure 11 This is a transmission electron microscope photograph of the copper-silver aerogel catalyst obtained in Example 3 of the present invention.

[0025] Figure 12 This is a high-resolution transmission electron microscope photograph of the copper-silver aerogel catalyst obtained in Example 3 of the present invention.

[0026] Figure 13 This is a scanning electron microscope photograph of the copper-silver aerogel catalyst obtained in Example 3 of the present invention.

[0027] Figure 14 This is the X-ray diffraction pattern of the copper-silver aerogel catalyst obtained in Example 3 of the present invention.

[0028] Figure 15 This is the eCO2RR reduction performance of the copper-silver aerogel catalyst obtained in Example 3 of the present invention under certain conditions. DETAILED DESCRIPTION

[0029] The present invention is further described below with reference to the embodiments and accompanying drawings.

[0030] like Figure 1 、 2 , 3, 4, and 5 show a method for preparing a silver-copper aerogel catalyst modified with a dicarboxyl chelating agent for electrocatalytic CO2 reduction, and the performance is shown in the figure: Example

[0031] (1) Take 0.399 g CuSO4, 0.170 g AgNO3, 1 g EDTA-2Na, and 0.94 g NaBH4 and dissolve them in 50 mL of water respectively (the EDTA-2Na solution is refrigerated for later use, the AgNO3 solution and CuSO4 solution are metal ion solutions, and the NaBH4 solution is prepared and used immediately); (2) Mix a certain amount of AgNO3 solution and CuSO4 solution, then add a certain amount of the above EDTA-2Na solution and stir thoroughly to achieve chelation; (3) Add 50 mL of NaBH4 solution into the above system at a rate of 0.2 mL / min and maintain stirring at a rate of 400 r / min; (4) The obtained dispersion system was stirred for 15 min, and then the dispersion was centrifuged and washed with deionized water and ethanol three times respectively, and then transferred to an oven at 60 °C and dried overnight to obtain an EDTA-modified copper-silver aerogel catalyst; (5) Weigh 5 mg of EDTA-modified copper-silver aerogel catalyst and add 750 μl of isopropanol, 250 μl of deionized water and 50 μl of Nafion ® The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion; (6) Take 150 μl of the obtained catalyst ink dispersion and evenly apply the dispersion on a 1.5×1.5 cm carbon paper using a disposable dropper. Then transfer it to an oven and dry it at 60 °C for 1 h to obtain an EDTA-2Na modified silver-copper aerogel catalyst electrode. (7) Using a Pt sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared silver-copper aerogel catalyst as the working electrode, a 0.5 mol / L KHCO3 solution was used as the electrolyte in an H-type electrolytic cell. After CO2 gas was introduced for 15 minutes, an external bias voltage was applied to carry out the electrocatalytic reaction. The reaction products were quantitatively analyzed by gas chromatography (GC).

[0032] like Figure 6 、 7 , 8, 9, and 10, a method for preparing a silver-copper aerogel catalyst modified with a dicarboxyl chelating agent for electrocatalytic CO2 reduction, the performance of which is shown in the figure: Example

[0033] (1) Take 0.399 g CuSO4, 0.170 g AgNO3, 0.96 g EDTA-4Na, and 0.94 g NaBH4 and dissolve them in 50 mL of water respectively (the EDTA-2Na solution is refrigerated for later use, the AgNO3 solution and CuSO4 solution are metal ion solutions, and the NaBH4 solution is prepared and used immediately); (2) Mix a certain amount of AgNO3 solution and CuSO4 solution, then add a certain amount of the above EDTA-2Na solution and stir thoroughly to achieve chelation; (3) Add 50 mL of NaBH4 solution into the above system at a rate of 0.2 mL / min and maintain stirring at a rate of 400 r / min; (4) The obtained dispersion system was stirred for 15 min, and then the dispersion was centrifuged and washed with deionized water and ethanol three times respectively, and then transferred to an oven at 60 °C and dried overnight to obtain an EDTA-modified copper-silver aerogel catalyst; (5) Weigh 5 mg of EDTA-modified copper-silver aerogel catalyst and add 750 μl of isopropanol, 250 μl of deionized water and 50 μl of Nafion ® The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion; (6) Take 150 μl of the obtained catalyst ink dispersion and evenly apply the dispersion on a 1.5×1.5 cm carbon paper using a disposable dropper. Then transfer it to an oven and dry it at 60 °C for 1 h to obtain an EDTA-2Na modified silver-copper aerogel catalyst electrode. (7) Using a Pt sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared silver-copper aerogel catalyst as the working electrode, a 0.5 mol / L KHCO3 solution was used as the electrolyte in an H-type electrolytic cell. After CO2 gas was introduced for 15 minutes, an external bias voltage was applied to carry out the electrocatalytic reaction. The reaction products were quantitatively analyzed by gas chromatography (GC).

[0034] like Figure 11 、 12 , 13, 14, and 15 show a method for preparing a silver-copper aerogel catalyst modified with a dicarboxyl chelating agent for electrocatalytic CO2 reduction, and the performance is shown in the figure: Example

[0035] (1) Take 0.399 g CuSO4, 0.170 g AgNO3, and 0.94 g NaBH4 and dissolve them in 50 mL water respectively (the EDTA-2Na solution is refrigerated for later use, the AgNO3 solution and CuSO4 solution are metal ion solutions, and the NaBH4 solution is prepared and used immediately); (2) Mix a certain amount of AgNO3 solution and CuSO4 solution, then add a certain amount of the above EDTA-2Na solution and stir thoroughly to achieve chelation; (3) Add 50 mL of NaBH4 solution into the above system at a rate of 0.2 mL / min and maintain stirring at a rate of 400 r / min; (4) The obtained dispersion system was stirred for 15 min, and then the dispersion was centrifuged and washed with deionized water and ethanol three times respectively, and then transferred to an oven at 60 °C and dried overnight to obtain an EDTA-modified copper-silver aerogel catalyst; (5) Weigh 5 mg of EDTA-modified copper-silver aerogel catalyst and add 750 μl of isopropanol, 250 μl of deionized water and 50 μl of Nafion ® The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion; (6) Take 150 μl of the obtained catalyst ink dispersion and evenly apply the dispersion on a 1.5×1.5 cm carbon paper using a disposable dropper. Then transfer it to an oven and dry it at 60 °C for 1 h to obtain an EDTA-2Na modified silver-copper aerogel catalyst electrode. (7) Using a Pt sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared silver-copper aerogel catalyst as the working electrode, a 0.5 mol / L KHCO3 solution was used as the electrolyte in an H-type electrolytic cell. After CO2 gas was introduced for 15 minutes, an external bias voltage was applied to carry out the electrocatalytic reaction. The reaction products were quantitatively analyzed by gas chromatography (GC).

Claims

1. A method for preparing a silver-copper aerogel catalyst modified with a dicarboxyl chelating agent for electrocatalytic CO2 reduction, characterized in that: The catalyst is composed of the following steps: Step 1: Prepare the metal salt solution as follows: S1. Prepare 50 ml of each of the following: 0.05-0.2 mol / L copper salt solution, 0.02-0.2 mol / L AgNO3 solution, 0.01-0.2 mol / L dicarboxyl chelating agent aqueous solution, and 0.1-1 mol / L strong reducing agent solution; S2, adding the AgNO3 solution to the above-mentioned copper salt solution, and then adding the dicarboxyl chelating agent solution and stirring thoroughly to allow chelation; S3. Add 50 mL of strong reducing agent solution into the above system at a rate of 0.2 mL / min and maintain stirring at a rate of 400 r / min; S4, after continuing to stir the obtained dispersion system for 15 minutes, the mixed solution was centrifuged and then washed with deionized water and ethanol three times respectively, and then transferred to a 60°C oven for drying to obtain aerogel powder; Step 2: Coordinate the metal salt solution, dicarboxyl chelating agent and reducing agent solution to prepare a catalyst ink dispersion, as follows; Weigh 5 mg of catalyst metal powder, add 750 μl of isopropanol, 250 μl of deionized water, and add 50 μl of Nafion ® The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion; Step 3: Disperse the material evenly on the hydrophobic carbon paper by spraying. The steps for preparing the cathode electrode loaded with cathode catalyst are as follows: take 150 μl of the obtained catalyst ink dispersion and spray the dispersion evenly on a 1.5×1.5 cm 2 The silver-copper aerogel catalyst modified with a dicarboxyl chelating agent was obtained, and then a cathode electrode loaded with a cathode catalyst was prepared.

2. The method for preparing a silver-copper aerogel catalyst modified with a dicarboxyl chelating agent for electrocatalytic CO2 reduction according to claim 1, characterized in that: The metal copper salts described include CuSO4, Cu(NO3)2, CuCl2, and CH3COOCu.

3. The method for preparing a silver-copper aerogel catalyst modified with a dicarboxyl chelating agent for electrocatalytic CO2 reduction according to claim 1, characterized in that: The dicarboxyl chelating agent is EDTA-2Na, ethylenediaminediacetic acid, iminooxalic acid, malonic acid, aspartic acid, glutamic acid and tartaric acid.

4. The method for preparing a silver-copper aerogel catalyst modified with a dicarboxyl chelating agent for electrocatalytic CO2 reduction according to claim 1, characterized in that: The reducing agent solution (NaBH4, boron ammonia complex, hydrazine hydrate, glucose and other common metal reducing agents.

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