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

Abstract

A preparation method of a silver-copper aerogel catalyst modified by a diamino chelating agent and used for electrocatalytic reduction of CO2 is characterized in that a silver-copper aerogel electrode is prepared by adopting a wet chemical reduction method and comprises the following steps: dissolving and mixing copper salt and silver salt, then adding an ethylenediamine solution to fully chelate the copper salt and the silver salt, then adding a reducing agent to reduce and precipitate the copper salt and the silver salt, and finally drying to obtain the silver-copper aerogel catalyst modified by the diamino chelating agent. And filtering and washing to obtain the aerogel. Finally, the catalyst is used in the carbon dioxide electro-catalysis process. 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 diamine-based chelating agent for electrocatalytic CO2 reduction. Background Art

[0002] Amidst growing global energy and environmental challenges, electrocatalytic carbon dioxide reduction (eCO2RR) is an effective method for converting carbon dioxide (CO2) into valuable fuels, such as CH4, C2H4, CH3OH, and isopropanol. Multi-carbon products, such as ethylene, have high economic value in the chemical, pharmaceutical, and food industries. Therefore, this method demonstrates considerable potential for achieving carbon neutrality, addressing global pollution, and addressing energy shortages.

[0003] The core of eCO2RR lies in the development of efficient and stable catalysts. Traditional silver (Ag) and copper (Cu) catalysts show good activity in CO2 reduction, but have problems such as low selectivity and poor stability. In recent years, bimetallic catalysts (such as Ag-Cu) have received widespread attention due to their synergistic effect and controllable electronic structure. However, how to further improve the active site exposure and product selectivity of the catalyst remains a technical difficulty. To this end, the present invention proposes the use of ethylenediamine-modified silver-copper aerogel catalyst. The three-dimensional porous aerogel structure prepared by wet chemical reduction not only greatly increases the specific surface area of ​​the catalyst, but also provides abundant mass transfer channels. The introduction of ethylenediamine further optimizes the electronic structure and surface chemical environment of the catalyst, significantly improving its catalytic performance.

[0004] The amine group (-NH2) in ethylenediamine (NH2CH2CH2NH2) plays a key role in improving catalyst performance through nitrogen doping. Ning et al. revealed the principle behind this improved reaction performance: the nitrogen atom in the amine group acts as an electron donor, forming a stable coordination bond (MN bond) with the Ag / Cu metal surface, regulating the metal's electron cloud density and optimizing its adsorption strength for reaction intermediates. For example, Yang et al. experimentally demonstrated that nitrogen doping weakened the strong adsorption of CO on the Cu surface, avoiding catalyst deactivation due to catalyst reconstruction, while also promoting the conversion of CO2 to high-value-added products such as formic acid. Fiorio et al. proposed a theory that nitrogen doping forms a nitrogen-rich chemical microenvironment on the catalyst surface, which can stabilize key intermediates (such as *OCHO-) and improve the selectivity of the target product. In addition, ethylenediamine acts as a structure-directing agent during aerogel formation, guiding the self-assembly of metal precursors to form a highly ordered three-dimensional network structure, significantly increasing the exposure and accessibility of active sites.

[0005] Therefore, to address the issues of catalyst selectivity and stability still requiring further improvement, high cost, and short lifespan in eCO2RR, this patent uses a wet chemical reduction method to prepare an ethylenediamine-modified silver-copper aerogel electrode as an ECO2RR catalyst. The ethylenediamine-modified silver-copper aerogel electrode exhibits high activity, high selectivity, and long-term stability in CO2 electrocatalytic reduction, laying the foundation for industrial application. Furthermore, the preparation method is simple and easy, with low raw material costs, and has good economic and scalability. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a method for preparing a silver-copper aerogel catalyst modified with a diamine-based chelating agent for electrocatalytic CO2 reduction. The silver-copper aerogel electrode 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 an ethylenediamine solution to achieve thorough chelation; and finally, dropwise adding a sodium borohydride solution to induce 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, thereby improving the performance of carbon dioxide to ethylene conversion.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing a silver-copper aerogel catalyst modified with a diamine-based chelating agent for electrocatalytic CO2 reduction, characterized by comprising the following steps:

[0009] Step 1: preparing a metal salt solution, comprising the following steps:

[0010] S1. Prepare 50 ml of each of the following substances: 0.05-0.2 mol / L copper salt solution, 0.02-0.2 mol / L AgNO3 solution, 0.01-0.2 mol / L diamine chelating agent aqueous solution, and 0.1-1 mol / L strong reducing agent solution;

[0011] S2, adding AgNO3 solution to the copper salt solution, and then adding the diamine chelating agent solution and stirring thoroughly to react;

[0012] 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;

[0013] 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;

[0014] Step 2: Coordinate the metal salt solution, the diamine chelating agent and the reducing agent solution to prepare a catalyst ink dispersion, as follows;

[0015] Weigh 5 mg of catalyst metal powder, add 750 μl of isopropanol, 250 μl of deionized water and 50 μl of The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion;

[0016] Step 3: Disperse the material evenly on the hydrophobic carbon paper by spraying. Take 150 μl of the prepared catalyst ink dispersion and spray the dispersion evenly on a 1.5×1.5 cm 2 The carbon paper was then transferred to an oven and dried at 60°C for 1 hour to obtain a silver-copper aerogel catalyst modified with a diamine chelating agent, thereby preparing a cathode electrode loaded with a cathode catalyst.

[0017] The metal copper salt solution is a solution of one of CuSO4, Cu(NO3)2, CuCl2 and CH3COOCu.

[0018] The diamine-based chelating agent is one of ethylenediamine, EDDA, ​​EDDS, and DETA.

[0019] The reducing agent solution is a metal reducing agent, including one of NaBH4, boron ammonia complex, hydrazine hydrate, and glucose.

[0020] Furthermore, using a Pt sheet as a counter electrode, an Ag / AgCl electrode as a reference electrode, and the prepared silver-copper aerogel catalyst as a 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).

[0021] The beneficial effects of the present invention are:

[0022] The present invention first dissolves and mixes copper salt and silver salt, then adds ethylenediamine solution to fully chelate them, then adds a reducing agent to reduce and precipitate them, and obtains aerogel by filtering and washing. Finally, the catalyst is used in the electrocatalytic carbon dioxide process. Compared with the prior art, the ethylenediamine modification in the present invention has significant advantages. In the electrocatalytic carbon dioxide reduction (eCO2RR) system, the amine group (-NH2) in the ethylenediamine molecular structure acts as a strong electron donor. Based on the lone pair of electrons on its nitrogen atom, it can form a stable coordination bond (MN bond) with the empty orbital on the silver-copper metal surface. This coordination effect promotes the redistribution of the electron cloud density of the metal and optimizes the electronic structure of the metal atoms from the quantum chemical level. From the adsorption theory analysis, this change in electronic structure accurately regulates the adsorption energy of the electrode surface to the reaction intermediate. Specifically, the chemical adsorption intensity of CO on the copper surface is weakened. According to the adsorption isotherm model, the coverage of CO on the copper active site is reduced, effectively avoiding the catalyst poisoning and deactivation phenomenon caused by strong CO adsorption. At the same time, the optimized electronic structure enhances the adsorption stability of carbon dioxide into intermediate products such as formic acid. According to the transition state theory, it reduces the activation energy of the reaction and promotes the conversion of carbon dioxide into high-value-added products.

[0023] At the same time, nitrogen doping creates a nitrogen-rich chemical microenvironment on the catalyst surface, altering the surface electronic state density. Density functional theory calculations indicate that this microenvironment stabilizes key reaction intermediates, such as *OCHO-, lowering their reaction energy barrier and improving selectivity for the target product, ethylene. This addresses the low ethylene selectivity of conventional copper-based catalysts in eCO2RR. Furthermore, by adjusting the ethylenediamine dosage and reaction conditions, the degree of coordination with silver and copper salts can be flexibly altered. From a coordination chemistry perspective, this shift influences the electron cloud distribution and steric hindrance around the metal ions, thereby modulating the adsorption energy of carbon dioxide on the electrode surface and the reaction energy barrier of the carbon-carbon coupling step, enabling precise control of eCO2RR product selectivity. Ethylenediamine modification significantly enhances the electrode's electrochemical stability. Furthermore, the resulting silver-copper aerogel electrode exhibits high electrocatalytic stability and an extremely high electrochemically active surface area. Based on electrochemical double-layer capacitance theory, this demonstrates enhanced intrinsic electrochemical activity, providing strong technical support for the industrial application of eCO2RR. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the eCO2RR reduction performance of the ethylenediamine-modified copper-silver aerogel material obtained in Example 1 of the present invention under certain conditions.

[0025] Figure 2 This is the X-ray diffraction pattern of the ethylenediamine-modified copper-silver aerogel material obtained in Example 1 of the present invention.

[0026] Figure 3 This is the eCO2RR reduction performance of the acetylacetone-modified copper-silver aerogel material obtained in Example 2 of the present invention under certain conditions.

[0027] Figure 4 This is the X-ray diffraction pattern of the acetylacetone-modified copper-silver aerogel material obtained in Example 2 of the present invention.

[0028] Figure 5 This is the eCO2RR reduction performance of the triethanolamine-modified copper-silver aerogel material obtained in Example 3 of the present invention under certain conditions.

[0029] Figure 6 This is the X-ray diffraction pattern of the triethanolamine-modified copper-silver aerogel material obtained in Example 3 of the present invention.

[0030] Figure 7 This is the eCO2RR reduction performance of the sodium oxalate-modified copper-silver aerogel material obtained in Example 4 of the present invention under certain conditions.

[0031] Figure 8 This is the X-ray diffraction pattern of the sodium oxalate-modified copper-silver aerogel material obtained in Example 4 of the present invention.

[0032] Figure 9 This is the eCO2RR reduction performance of the sodium thiosulfate-modified copper-silver aerogel material obtained in Example 5 of the present invention under certain conditions.

[0033] Figure 10 This is the X-ray diffraction pattern of the sodium thiosulfate-modified copper-silver aerogel material obtained in Example 5 of the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and several preferred embodiments of the present invention.

[0035] Example 1;

[0036] like Figure 1 、 2 The preparation of a silver-copper aerogel catalyst modified with a diamine-based chelating agent for electrocatalytic CO2 reduction is shown in the figure. The performance is shown in the figure: (1) 0.399g CuSO4, 0.170g AgNO3, 0.25g ethylenediamine, and 0.94g NaBH4 are taken and dissolved in 50mL water respectively (the ethylenediamine solution is refrigerated for later use, the AgNO3 solution and the CuSO4 solution are metal ion solutions, and the NaBH4 solution is prepared and used immediately);

[0037] (2) Mixing a certain amount of AgNO3 solution and CuSO4 solution, and then adding a certain amount of the above-mentioned ethylenediamine solution and stirring thoroughly to achieve chelation;

[0038] (3) 50 mL of NaBH4 solution was added dropwise into the above system at a rate of 0.2 mL / min and stirred at a rate of 400 r / min;

[0039] (4) The obtained dispersion system was stirred for 15 minutes, and then the dispersion was centrifuged, washed with deionized water and ethanol three times respectively, and transferred to a 60°C oven for drying overnight to obtain an ethylenediamine-modified silver-copper aerogel catalyst;

[0040] (5) Weigh 5 mg of catalyst metal powder and add 750 μl of isopropanol, 250 μl of deionized water and 50 μl of The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion;

[0041] (6) Take 150 μl of the prepared 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 ethylenediamine-modified silver-copper aerogel catalyst electrode.

[0042] (7) Using a Pt sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared silver-copper aerogel electrode 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).

[0043] Example 2: Figure 3 、 4 The preparation of a silver-copper aerogel catalyst modified with a diamine chelating agent for electrocatalytic CO2 reduction is shown in the figure. The performance is shown in the figure:

[0044] (1) Take 0.399g CuSO4, 0.170g AgNO3, 0.25g acetylacetone, and 0.94g NaBH4 and dissolve them in 50mL water respectively (the acetylacetone 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);

[0045] (2) Mixing a certain amount of AgNO3 solution and CuSO4 solution, and then adding a certain amount of the above-mentioned acetylacetone solution and stirring thoroughly to achieve chelation;

[0046] (3) 50 mL of NaBH4 solution was added dropwise into the above system at a rate of 0.2 mL / min and stirred at a rate of 400 r / min;

[0047] (4) The obtained dispersion system was stirred for 15 minutes, and then the dispersion was centrifuged, washed with deionized water and ethanol three times respectively, and transferred to a 60°C oven for drying to obtain a silver-copper aerogel catalyst modified with acetylacetone;

[0048] (5) Weigh 5 mg of catalyst metal powder and add 750 μl of isopropanol, 250 μl of deionized water and 50 μl of The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion;

[0049] (6) 150 μl of the prepared catalyst ink dispersion was evenly applied on a 1.5 × 1.5 cm carbon paper using a disposable dropper, and then transferred to an oven and dried at 60° for 1 h to obtain an acetylacetone-modified silver-copper aerogel catalyst electrode;

[0050] (7) Using a Pt sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared silver-copper aerogel electrode 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).

[0051] Example 3: Figure 5 、 6 The preparation of a silver-copper aerogel catalyst modified with a diamine chelating agent for electrocatalytic CO2 reduction is shown in the figure. The performance is shown in the figure:

[0052] (1) Take 0.399g CuSO4, 0.170g AgNO3, 0.37g triethanolamine, and 0.94g NaBH4, and dissolve them in 50mL water respectively (the triethanolamine solution is refrigerated for later use, the AgNO3 solution and the CuSO4 solution are metal ion solutions, and the NaBH4 solution is prepared and used immediately);

[0053] (2) Mixing a certain amount of AgNO3 solution and CuSO4 solution, and then adding a certain amount of the above triethanolamine solution and stirring thoroughly to achieve chelation;

[0054] (3) 50 mL of NaBH4 solution was added dropwise into the above system at a rate of 0.2 mL / min and stirred at a rate of 400 r / min;

[0055] (4) After the obtained dispersion system was stirred for 15 minutes, the dispersion was centrifuged, washed with deionized water and ethanol three times respectively, and then transferred to a 60°C oven and dried overnight to obtain a triethanolamine-modified silver-copper aerogel catalyst;

[0056] (5) Weigh 5 mg of catalyst metal powder and add 750 μl of isopropanol, 250 μl of deionized water and 50 μl of The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion;

[0057] (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 a triethanolamine-modified silver-copper aerogel catalyst electrode.

[0058] (7) Using a Pt sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared silver-copper aerogel electrode 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).

[0059] Example 4: Figure 7 、 7 The preparation of a silver-copper aerogel catalyst modified with a diamine chelating agent for electrocatalytic CO2 reduction is shown in the figure. The performance is shown in the figure:

[0060] (1) Take 0.399g CuSO4, 0.170g AgNO3, 0.335g Na2C2O4, and 0.94g NaBH4 and dissolve them in 50mL water respectively (the Na2C2O4 solution is refrigerated for later use, the AgNO3 solution and the CuSO4 solution are metal ion solutions, and the NaBH4 solution is prepared and used immediately);

[0061] (2) Mix a certain amount of AgNO3 solution and CuSO4 solution, then add a certain amount of the above-mentioned Na2C2O4 and stir thoroughly to achieve chelation;

[0062] (3) 50 mL of NaBH4 solution was added dropwise into the above system at a rate of 0.2 mL / min and stirred at a rate of 400 r / min;

[0063] (4) The obtained dispersion system was stirred for 15 minutes, and then the dispersion was centrifuged, washed with deionized water and ethanol three times respectively, and transferred to a 60°C oven for drying overnight to obtain a Na2C2O4-modified silver-copper aerogel catalyst;

[0064] (5) Weigh 5 mg of catalyst metal powder and add 750 μl of isopropanol, 250 μl of deionized water and 50 μl of The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion;

[0065] (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 a Na2C2O4-modified silver-copper aerogel catalyst electrode;

[0066] (7) Using a Pt sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared silver-copper aerogel electrode 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).

[0067] Example 5: Figure 9 、 10 The preparation of a silver-copper aerogel catalyst modified with a diamine chelating agent for electrocatalytic CO2 reduction is shown in the figure. The performance is shown in the figure:

[0068] (1) Take 0.399g CuSO4, 0.170g AgNO3, 0.395g Na2S2O3, and 0.94g NaBH4 and dissolve them in 50ml water respectively (the Na2S2O3 solution is refrigerated for later use, the AgNO3 solution and the CuSO4 solution are metal ion solutions, and the NaBH4 solution is prepared and used immediately);

[0069] (2) Mix a certain amount of AgNO3 solution and CuSO4 solution, then add Na2S2O3 solution and stir thoroughly to achieve chelation;

[0070] (3) 50 mL of NaBH4 solution was added dropwise into the above system at a rate of 0.2 mL / min and stirred at a rate of 400 r / min;

[0071] (4) The obtained dispersion system was stirred for 15 minutes, and then the dispersion was centrifuged, washed with deionized water and ethanol three times respectively, and transferred to a 60°C oven for drying overnight to obtain a Na2S2O3-modified silver-copper aerogel catalyst;

[0072] (5) Weigh 5 mg of catalyst metal powder and add 750 μl of isopropanol, 250 μl of deionized water and 50 μl of The membrane solution was ultrasonically treated for 1 h to obtain a catalyst ink dispersion modified with Na2S2O3;

[0073] (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 a Na2S2O3-modified silver-copper aerogel catalyst electrode;

[0074] (7) Using a Pt sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared silver-copper aerogel electrode 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).

Claims

1. A method for preparing a silver-copper aerogel catalyst modified with a diamine chelating agent for electrocatalytic CO2 reduction, characterized in that: The following steps are involved: Step 1: preparing a metal salt solution, comprising the following steps: 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 diamine chelating agent aqueous solution, and 0.1-1 mol / L strong reducing agent solution; S2, adding AgNO3 solution to the copper salt solution, and then adding the diamine chelating agent solution and stirring thoroughly to react; S3. Add 50 mL of strong reducing agent solution dropwise 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, the diamine chelating agent and the 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 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. Take 150 μl of the prepared catalyst ink dispersion and spray the dispersion evenly on a 1.5×1.5 cm 2 The carbon paper was then transferred to an oven and dried at 60°C for 1 hour to obtain a silver-copper aerogel catalyst modified with a diamine chelating agent, thereby preparing a cathode electrode loaded with a cathode catalyst.

2. The method for preparing a silver-copper aerogel catalyst modified with a diamine-based chelating agent for electrocatalytic CO2 reduction according to claim 1, characterized in that: The metal copper salt solution is a solution of one of CuSO4, Cu(NO3)2, CuCl2 and CH3COOCu.

3. The method for preparing a silver-copper aerogel catalyst modified with a diamine chelating agent for electrocatalytic CO2 reduction according to claim 1, characterized in that: The diamine chelating agent is one of ethylenediamine, EDDA, ​​EDDS and DETA.

4. The method for preparing a silver-copper aerogel catalyst modified with a diamine chelating agent for electrocatalytic CO2 reduction according to claim 1, characterized in that: The reducing agent solution is a metal reducing agent, including one of NaBH4, boron ammonia complex, hydrazine hydrate, and glucose.

Images