An electrochemical catalyst and its preparation method and application

Abstract

The application belongs to the field of electrochemical catalysts, and discloses an electrochemical catalyst and a preparation method and application thereof; a pretreated foamed copper is used as a carrier, and a hexanuclear copper-substituted phosphotungstate material is in-situ grown on the surface of the carrier; a highly ordered copper-oxygen-tungsten atomic interface exists in the structure, so that a foamed copper catalyst with ordered and spaced copper atomic layers is obtained. Thus, the application provides an integrated technical solution of controllable microstructure synthesis, performance strengthening of a heterogeneous interface, and improvement of overall electron conduction, and the comprehensive improvement of catalytic activity, selectivity and stability is realized for a reaction process of electrochemical reduction of carbon dioxide to generate dimethyl carbonate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrocatalysis, and particularly relates to an electrochemical catalyst and a preparation method and application thereof. BACKGROUND

[0002] Dimethyl carbonate is an environmentally friendly organic compound with many unique chemical properties, and is often used as a lithium ion battery electrolyte or to replace toxic reagents for carbonylation and methylation reactions. However, the current industrial method for producing dimethyl carbonate is the methanol photochemical method, the methanol oxidative carbonylation method, the ester exchange method, the urea alcoholysis method and the like, and these traditional processes have the disadvantages of serious pollution and high process risk, which makes the green synthesis of dimethyl carbonate face great challenges.

[0003] Using greenhouse gas carbon dioxide and bio-chemical downstream product methanol as reactants is an effective way to realize carbon recycling and green synthesis of dimethyl carbonate. However, the carbon-oxygen double bond structure of carbon dioxide molecule is symmetrical, and the C=O chemical bond has very high stability, which makes the reaction of carbon dioxide and methanol to generate dimethyl carbonate difficult to proceed thermodynamically; secondly, the process of electrocatalytic reduction of carbon dioxide involves multi-electron transfer, and the reaction products are complex and diverse, which makes it difficult to control the selectivity of the products; and thirdly, the reaction potential of carbon dioxide reduction is similar to that of hydrogen evolution reaction, while the rate of hydrogen evolution reaction is often much higher than that of carbon dioxide reduction, which seriously affects the conversion efficiency of carbon dioxide to generate dimethyl carbonate.

[0004] Adjusting the structure and components of the catalyst can effectively improve the catalytic selectivity and efficiency of the electrocatalyst. At present, CeO2 material rich in a large number of oxygen defects is considered to be an excellent electrocatalyst for promoting the conversion of carbon dioxide to dimethyl carbonate. Because a large number of oxygen defects in the material can act as effective active sites to adsorb CH3O – and generate OCH3 reaction intermediates, which promotes the smooth generation of dimethyl carbonate. However, the activation ability of the defect-rich CeO2 material for CO2 is often poor, and the efficiency of generating dimethyl carbonate needs to be further improved.

[0005] Therefore, designing and synthesizing a carbon dioxide reduction electrochemical catalyst with high selectivity and high catalytic efficiency plays a crucial role in improving the yield and selectivity of dimethyl carbonate. SUMMARY

[0006] The present application aims to at least solve one of the technical problems in the related art. The present application proposes an electrochemical catalyst and a preparation method and application thereof, which has good catalytic activity, selectivity and stability for the process of electrochemical reduction of carbon dioxide to generate dimethyl carbonate.

[0007] In one aspect of the present application, a method for preparing an electrochemical catalyst is provided. According to an embodiment of the present application, the method comprises:

[0008] (1) mixing {PW9}, ethylenediamine, a copper salt, acetic acid and water to obtain a reaction solution;

[0009] (2) heating the reaction solution and foamed copper to obtain an electrochemical catalyst.

[0010] In some embodiments, in step (1), the molar ratio of {PW9}, ethylenediamine, a copper salt, acetic acid and water is 0.1: (0.4 ~ 0.7): 1: 1.8: 278.

[0011] In some embodiments, in step (2), the foamed copper is pretreated, and the pretreatment comprises: placing the foamed copper in ethanol, acetone and hydrochloric acid solution for ultrasonic cleaning, and then drying. The above pretreatment can remove the surface oxide layer and impurities of the foamed copper. As a preferred embodiment, the foamed copper is first placed in 1:1 ethanol and acetone for ultrasonic cleaning for 30-60 min, then washed with water after ultrasonic cleaning, then placed in a 2 M hydrochloric acid solution for ultrasonic cleaning for 15-30 min, then washed with water and ethanol until neutral, and finally dried at 60°C under vacuum for 6 h.

[0012] In some embodiments, in step (2), the heating reaction is carried out at a temperature of 75-85°C for 3-5 days.

[0013] In some embodiments, the thickness of the foamed copper is 1.5-2.0 cm; and the size of the foamed copper is 1x2 cm 2 .

[0014] In some embodiments, the copper salt comprises one or more of copper chloride, copper sulfate, copper nitrate, and copper chloride dihydrate.

[0015] In a second aspect of the present application, an electrochemical catalyst is provided, which is prepared by the above method.

[0016] In a third aspect of the present application, the above electrochemical catalyst is used in the preparation of carbon dioxide into dimethyl carbonate.

[0017] The present application has the following advantages:

[0018] (1) The preparation method of the present application can be firmly combined with a metal current collector without any chemical binder, and can maintain the overall stability of its own micro-ring structure during the electrocatalytic process, thereby ensuring the stability of the entire process of CO2 electrocatalytic reduction to generate dimethyl carbonate.

[0019] (2) The electrochemical catalyst of the present application can promote CO2 to be first adsorbed on the coordination unsaturated copper catalytic active site formed by losing ethylenediamine ligand, and the tungsten atom with Lewis acidity can provide 5d orbit to form feedback π bond with O 2p orbit in CO2, so that the tungsten element fills the electron back to the antibonding orbital of CO2, promotes the efficient conversion of CO2 to CO intermediate product, and the μ3-OH in the copper oxygen nanocluster can effectively convert CH3OH into OCH3 and H2O, realizing the partition adsorption and activation of CO2 and CH3OH;

[0020] (3) The electrochemical catalyst of the present application utilizes the fixed metal-metal spacing to promote the coupling of *CO and *OCH3 intermediate products, thereby improving the selectivity of the catalytic material in converting CO2 into dimethyl carbonate;

[0021] (4) The electrochemical catalyst of the present application utilizes multiple heterojunctions to enhance the synergistic effect between components, promotes the rapid charge transfer of the material, and thereby increases the conductivity and catalytic activity of the catalyst in the electrocatalytic process;

[0022] In summary, the present application uses pretreated foamed copper as a carrier, and in-situ grows hexanuclear copper-substituted tungstophosphate material on the surface thereof. The structure has a highly ordered copper-oxygen-tungsten atomic interface, i.e. a foamed copper catalyst with ordered and spaced copper atomic layers is obtained. Thus, the present application provides an integrated technical solution of controllable microstructure synthesis, performance enhancement of heterojunction, and improvement of overall electron conduction, and realizes the comprehensive improvement of catalytic activity, selectivity and stability of carbon dioxide electrochemical reduction to generate dimethyl carbonate.

[0023] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter in the description. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a topological packing diagram of material A along the c-axis direction;

[0025] Figure 2 is a structure characterization diagram of material A, wherein (a) is a scanning electron microscope diagram of material A; (b) is a transmission electron microscope diagram of material A; (c) is a high-resolution transmission electron microscope diagram of material A; (d) is an atomic force microscope diagram of material A;

[0026] Figure 3 is a structure characterization diagram of material B, wherein (a) is a molecular structure schematic diagram of material B; (b) is a low-magnification scanning electron microscope diagram of material B; (c) is a high-magnification scanning electron microscope diagram of material B;

[0027] Figure 4 are the test results of material A under the experimental conditions of application example 1, wherein (a) is the faradic efficiency column chart of material A under different voltages at room temperature; (b) is the yield column chart of material A under different voltages at room temperature.

[0028] Figure 5 are the test results of material B under the experimental conditions of application example 1, wherein (a) is the faradic efficiency column chart of material B under different voltages at room temperature; (b) is the yield column chart of material B under different voltages at room temperature.

[0029] Figure 6 are the test results of material C under the experimental conditions of application example 1, wherein (a) is the faradic efficiency column chart of material C under different voltages at room temperature; (b) is the yield column chart of material C under different voltages at room temperature.

[0030] Figure 7 are the test results of material D under the experimental conditions of application example 1, wherein (a) is the faradic efficiency column chart of material D under different voltages at room temperature; (b) is the yield column chart of material D under different voltages at room temperature.

[0031] Figure 8 are the test results of material E under the experimental conditions of application example 1, wherein (a) is the faradic efficiency column chart of material E under different voltages at room temperature; (b) is the yield column chart of material E under different voltages at room temperature.

[0032] Figure 9 are the test results of material A under the experimental conditions of application example 2, wherein (a) is the faradic efficiency column chart of material A under different voltages at -15 o C; (b) is the yield column chart of material A under different voltages at -15 o C.

[0033] Figure 10 are the X-ray photoelectron spectrograms of copper, tungsten, carbon and nitrogen elements in material A before and after electrochemical reaction, wherein (a) is the X-ray photoelectron spectrogram of copper element in material A before and after electrocatalytic reaction; (b) is the X-ray photoelectron spectrogram of tungsten element in material A before and after electrocatalytic reaction; (c) is the X-ray photoelectron spectrogram of carbon element in material A before and after electrocatalytic reaction; (d) is the X-ray photoelectron spectrogram of nitrogen element in material A before and after electrocatalytic reaction.

[0034] Figure 11 are the in-situ characterization diagrams of material A, wherein (a) is the in-situ X-ray diffraction diagram of material A; (b) is the in-situ infrared diagram of material A.

[0035] Figure 12 Schematic diagram of the reaction path in which material A participates. DETAILED DESCRIPTION

[0036] The present application will be described with reference to specific examples, it should be noted that these examples are merely illustrative and do not limit the present application in any way. In the following examples and comparative examples, the raw materials used are ordinary commercially available products or are prepared according to the conventional methods in the art, unless otherwise specified.

[0037] The size of the foamed copper is 1 cm x 2 cm, and the thickness is 1.5 mm, which is purchased from Suzhou Shenghe Metal Material Co., Ltd.

[0038] Copper oxide and cuprous oxide are purchased from Aladdin Reagent Co., Ltd.

[0039] {PW9}Reference Z. Xin, S. Wang, Q. He, X. Han, Z. Fu, X. Xu, X. Zhao, Preparation of a novel photocatalytic catalyst PW9@ZnO / Ag and the photocatalytic degradation of butyl xanthate under visible light, Environmental Research, 2022, 214, 113776. (Xin Z., Wang S., He Q., Han X., Fu Z., Xu X., Zhao X., Preparation of a novel photocatalytic catalyst PW9@ZnO / Ag and the photocatalytic degradation of butyl xanthate under visible light, Environmental Research, 2022, 214, 113776.) Obtained.

[0040] Example 1

[0041] (1) 246 mg of {PW9} was weighed, 30 μL of 99 wt.% ethylenediamine, 170 mg of copper chloride dihydrate, 100 μL of acetic acid and 5 mL of water were added, and mixed and stirred for 30 min to obtain a reaction solution, and then the reaction solution was transferred to a 10 mL high-pressure sterile reaction kettle;

[0042] (2) The foamed copper was placed in a mixed solution of ethanol and acetone in a volume ratio of 1:1 and ultrasonicated for 30 min, then washed with double-distilled water for 3 times; then placed in concentrated hydrochloric acid and ultrasonicated for 20 min, then washed with water and ethanol until neutral, and finally vacuum dried at 60 o C for 6 h to obtain pretreated foamed copper;

[0043] (3) The pretreated foamed copper was immersed in the solution in the reaction kettle at 80 oThe reaction was continued at C for 3 days, then the material A was taken out after natural cooling to room temperature, and the surface residual reaction solution was absorbed with filter paper, to obtain the material A. The loading capacity of the material was 10 mg.

[0044] Comparative Example 1

[0045] Comparative Example 1 was the foam copper pretreated by step (2) in Example 1, to obtain material B.

[0046] Comparative Example 2

[0047] 10.0 mg of {PW9} powder was taken, dispersed in 5.0 mL of ethanol solution, and 25 μL of Nafion solution was added, and ultrasonic was performed for 30 min until uniform, and the prepared solution was dropped onto the 1×2 cm foam copper, and dried to obtain material C.

[0048] Comparative Example 3

[0049] 10.0 mg of commercial CuO powder was taken, dispersed in 5.0 mL of ethanol solution, and 25 μL of Nafion solution was added, and ultrasonic was performed for 30 min until uniform, and the prepared solution was dropped onto the 1×2 cm foam copper, and dried to obtain material D.

[0050] Comparative Example 4

[0051] 10.0 mg of commercial Cu2O powder was taken, dispersed in 5.0 mL of ethanol solution, and 25 μL of Nafion solution was added, and ultrasonic was performed for 30 min until uniform, and the prepared solution was dropped onto the 1×2 cm foam copper, and dried to obtain material E.

[0052] Detailed structural determination and characterization were performed on the materials of Example 1 and Comparative Example 1.

[0053] Figure 1 is the topological packing diagram of material A along the c-axis direction. The structural unit can be regarded as a {PW9} connected with a six-nuclear copper oxide nanocluster through a vacancy site. The six copper atoms in the copper oxide nanocluster are arranged in an equilateral triangle, and each copper atom is hexa-coordinated in an octahedral configuration. From the c-axis direction, the structure can be regarded as an ordered and spaced copper atom layer structure formed by layered {PW9} and copper oxide nanoclusters.

[0054] Figure 2 is the structural characterization diagram of material A. Among them, Figure 2 (a) in the middle is a scanning electron microscope diagram of material A, which can be seen that the spaced copper nanolayer is attached on the foam copper in a layered structure, which provides a higher specific surface area and more catalytic active sites for the electrocatalytic reaction. Figure 2Figure 2 is a transmission electron microscope image of material A, Figure 2 Figure 3 is a high-resolution transmission electron microscope image of material A, which shows that the nanolayered material has a high degree of crystallinity, indicating that the interlayer copper nanolayer is highly ordered. Figure 2 Figure 4 is an atomic force microscope image of material A, which shows that the sheet thickness of the ordered interlayer copper atom layer material is about 10-15 nm, which is equivalent to 10-15 layers of six-nucleus copper-substituted tungstophosphate material stacked together.

[0055] As shown in Figure 5, Figure 3 Figure 6 is a structural characterization image of material B. Among them, Figure 3 Figure 7 is a schematic diagram of the molecular structure of material B, Figure 3 Figure 8 is a low-magnification scanning electron microscope image of material B, Figure 3 Figure 9 is a high-magnification scanning electron microscope image of material B. As can be seen, material B does not have a similar ordered interlayer copper atom layer, and the surface is smooth, without sheet structure. The commercially available copper oxide and cuprous oxide also do not have a similar ordered interlayer copper atom layer.

[0056] Application Example 1

[0057] The electrocatalytic performance of Example 1 and Comparative Examples 1, 2, 3, 4 was tested in CO2-saturated super-dry methanol solution, respectively.

[0058] In a three-electrode system (saturated Ag / AgCl electrode as reference electrode, platinum sheet as counter electrode, and catalytic material fixed by titanium sheet electrode as working electrode) at room temperature (25 ± 5 o C), in an H-type electrolytic cell. Among them, the catalytic material is material A, material B, material C, material D, and material E prepared by Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4. The anode electrolyte is a super-dry methanol solution containing 0.01 M NaOH, and the cathode electrolyte is a super-dry methanol solution containing 0.03 M KOH, and the cathode and anode are separated by Nafion 211 proton exchange membrane.

[0059] The catalytic performance of the material was monitored by Shimadzu online gas chromatograph for gaseous products, and the CO2 flow rate into the cathode was 20 sccm. Liquid products were analyzed by nuclear magnetic resonance hydrogen spectrum.

[0060] Application Example 2

[0061] The working temperature of the three-electrode system is -15 o C, and the others are the same as in Application Example 1.

[0062] Figure 4 , Figure 5 ,Figure 6 , Figure 7 and Figure 8 are the test results of material A, material B, material C, material D, material E under the experimental conditions of application example 1, respectively:

[0063] Figure 4 In (a) of the figure, it is the Faraday efficiency column chart of material A at different voltages under room temperature conditions. It can be seen that the Faraday efficiency of dimethyl carbonate prepared by running material A of example 1 for 60 min at –0.8 V, –1.0 V, –1.2 V, –1.4 V and –1.6 V (vs. Ag / AgCl) potentials are 82%, 83%, 83%, 85%, 81%, respectively; Figure 4 In (b) of the figure, it is the yield column chart of material A at different voltages under room temperature conditions. It can be seen that the concentration (yield) are 0.61 mol·L –1 , 0.99 mol·L –1 , 1.26 mol·L –1 , 2.37 mol·L –1 , 2.40 mol·L –1 , respectively.

[0064] Figure 5 In (a) of the figure, it is the Faraday efficiency column chart of material B at different voltages under room temperature conditions. It can be seen that the Faraday efficiency of dimethyl carbonate prepared by running material B of comparative example 1 for 60 min at –0.8 V, –1.0 V, –1.2 V, –1.4 V and –1.6 V (vs. Ag / AgCl) potentials are 73%, 76%, 81%, 84%, 70%, respectively; Figure 5 In (b) of the figure, it is the yield column chart of material B at different voltages under room temperature conditions. It can be seen that the concentration (yield) are 0.38 mol·L –1 , 0.42 mol·L –1 , 0.53 mol·L –1 , 0.52 mol·L –1 , 0.59 mol·L –1 , respectively.

[0065] Figure 6 In (a) of the figure, it is the Faraday efficiency column chart of material C at different voltages under room temperature conditions. It can be seen that the Faraday efficiency of dimethyl carbonate prepared by running material C of comparative example 2 for 60 min at –0.8 V, –1.0 V, –1.2 V, –1.4 V and –1.6 V (vs. Ag / AgCl) potentials are 41%, 46%, 43%, 35%, 33%, respectively; Figure 6(b) is the yield column chart of material C at different voltages under room temperature conditions, it can be seen that the concentration (yield) is 0.29 mol·L –1 , 0.36 mol·L –1 , 0.47 mol·L –1 , 0.42 mol·L –1 , 0.38 mol·L –1 .

[0066] Figure 7 (a) is the faradic efficiency column chart of material D at different voltages under room temperature conditions, it can be seen that the faradic efficiency of dimethyl carbonate prepared by material D of comparative example 3 at –0.8 V, –1.0 V, –1.2 V, –1.4 V and –1.6 V (vs. Ag / AgCl) potential for 60 min is 25%, 30%, 37%, 40%, 13% respectively; Figure 7 (b) is the yield column chart of material D at different voltages under room temperature conditions, it can be seen that the concentration (yield) is 0.73 mol·L –1 , 0.76 mol·L –1 , 0.72 mol·L –1 , 0.62 mol·L –1 , 0.61 mol·L –1 .

[0067] Figure 8 (a) is the faradic efficiency column chart of material E at different voltages under room temperature conditions, it can be seen that the faradic efficiency of dimethyl carbonate prepared by material E of comparative example 4 at –0.8 V, –1.0 V, –1.2 V, –1.4 V and –1.6 V (vs. Ag / AgCl) potential for 60 min is 35%, 37%, 25%, 21%, 17% respectively; Figure 8 (b) is the yield column chart of material E at different voltages under room temperature conditions, it can be seen that the concentration (yield) is 0.17 mol·L –1 , 0.24 mol·L –1 , 0.20 mol·L –1 , 0.16 mol·L –1 , 0.12 mol·L –1 .

[0068] Therefore, compared with material B, material C, material D and material E, material A has obvious improvement in catalytic activity and selectivity.

[0069] Figure 9The test results of material A under the experimental conditions of application example 2.

[0070] Figure 9 The middle (a) is -15 o The faradaic efficiency column chart of material A under different voltages under condition C can be seen that the dimethyl carbonate faradaic efficiency prepared by material A of example 1 running for 60 min under -0.8 V, -1.0 V, -1.2 V, -1.4 V and -1.6 V (vs. Ag / AgCl) potential is 66%, 68%, 70%, 72%, 66% respectively; Figure 9 The middle (b) is -15 o The yield column chart of material A under different voltages under condition C can be seen that the concentration (yield) is 0.32 mol·L –1 , 0.70 mol·L –1 , 1.10 mol·L –1 , 1.24 mol·L –1 , 1.31 mol·L –1 respectively, while other comparative examples have poor catalytic effect under low temperature condition. It can be known that material A of example 1 has high catalytic activity and selectivity under low temperature.

[0071] From the above data, it can be known that material A of example 1 (i.e. foam copper with ordered interval copper atomic layer loading) has stable catalytic activity and selectivity for CO2 conversion to dimethyl carbonate under normal temperature or low temperature condition, and its catalytic performance is hardly changed by temperature change, which is a potential industrialized production of dimethyl carbonate electrocatalyst.

[0072] In order to further explore the structure-performance relationship of foam copper with ordered interval copper atomic layer loading, a series of structure characterization are carried out. Figure 10 The X-ray photoelectron spectrograms of copper, tungsten, carbon and nitrogen elements in material A before and after electrochemical reaction.

[0073] Figure 10 The middle (a) is the X-ray photoelectron spectrograms of copper element in material A before and after electrocatalytic reaction, it can be seen that the valence state of copper atom in example 1 is +1 and +2. +1 valence is due to the formation of ordered interval copper atomic layer on foam copper; +2 valence is the valence state of copper atom in copper oxygen nanocluster in the structure. With the electrocatalytic reaction, the content of Cu 2+ in example 1 gradually decreases, while the content of Cu + gradually increases, indicating that Cu 2+ is gradually reduced to Cu + in the process of electrocatalysis.

[0074] Figure 10 (b) is the X-ray photoelectron spectrum of tungsten in material A before and after the electrocatalytic reaction. It can be seen that during the electrochemical reaction, tungsten is reduced from +6 to +4. At the same time, Figure 10 (c) is the X-ray photoelectron spectrum of carbon element in material A before and after electrocatalytic reaction. Figure 10 (d) is the X-ray photoelectron spectrum of nitrogen in material A before and after the electrocatalytic reaction. It can be seen that the content of carbon and nitrogen elements is significantly reduced after the electrocatalytic reaction. However, carbon and nitrogen elements are only derived from the organic ligand of ethylenediamine, indicating that ethylenediamine gradually dissolves during the electrocatalytic process, forming unsaturated copper sites. These copper sites can adsorb CO2 during the reduction process, thereby promoting the electrochemical reduction of CO2 to *CO intermediates. The reduction of CO2 can also reduce Cu 2+ The degree of reduction leads to Cu + The increase in content, without Cu 0 Generation.

[0075] In order to explore the changing rules of material A during the electrocatalytic process, we conducted in situ X-ray diffraction (XRD) tests and in situ infrared tests, such as Figure 11 This is the in-situ characterization image of material A.

[0076] Figure 11 (a) shows the in situ X-ray diffraction pattern of Material A. It shows that the crystalline phase of the copper foam catalyst, supported by the ordered intercalated copper atomic layer, barely changes during the electrocatalytic process. This demonstrates that during the electrochemical catalytic process, only the valence of the copper and tungsten elements changes, while the structure remains unchanged, maintaining the original highly ordered intercalated copper layer. This provides a good structural foundation for the coupling of *CO and *OCH3 intermediates. Building on this foundation, we also conducted in situ infrared measurements. Figure 11 (b) is the in-situ infrared image of material A. It can be seen that 1604 cm –1 、1663 cm –1 *OOCH – , *CO intermediate product vibration peaks. This indicates that CO2 is first adsorbed on the catalyst surface and further reduced to *OOCH by hydrogenation reaction. – intermediate, which is then further reduced to generate *CO. –1 is the vibration peak position of C-OCH3, indicating that coupling occurs between *CO and *OCH3 to form dimethyl carbonate compound.

[0077] Analyzing the above experimental results, we can conclude that: Figure 12For the reaction path of material A, the foam copper catalyst with highly ordered and spaced copper atomic layers follows the reaction path of reducing CO2 first and then coupling *CO and *OCH3 intermediate product to generate dimethyl carbonate. While the copper oxygen nanoclusters in the foam copper catalyst follow the reaction path of coupling *CO and *OCH3 intermediate product first and then reducing CO2 to generate dimethyl carbonate. μ 3-OH is the main catalytic active site for promoting the conversion of CH3OH to generate *OCH3 intermediate product. It can be seen that the foam copper catalyst with ordered and spaced copper atomic layers has the ability to simultaneously adsorb and activate CO2 and CH3OH, two reactants, and can further promote the coupling of *CO and *OCH3 intermediate product according to the structural advantages of the ordered and spaced copper atomic layers, thereby improving the selectivity of CO2 conversion to generate dimethyl carbonate.

[0078] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that it is still possible to modify the technical solutions recorded in the foregoing examples, or to make equivalent substitutions for part of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing an electrochemical catalyst, characterized in that: The method comprises: (1) mixing {PW9}, ethylenediamine, copper salt, acetic acid and water to obtain a reaction solution; (2) heating the copper foam and the reaction solution to react and obtain an electrochemical catalyst; In step (1), the molar ratio of {PW9}, ethylenediamine, copper salt, acetic acid and water is 0.1: (0.4 ~ 0.7): 1: 1.8: 278; In step (2), the heating reaction temperature is 75-85°C and the time is 3-5 days.

2. The method according to claim 1, characterized in that In step (2), the copper foam is pretreated, and the pretreatment includes: placing the copper foam in one or more of ethanol, acetone and hydrochloric acid solutions for ultrasonic cleaning, and then drying.

3. The method according to claim 1, characterized in that The thickness of the copper foam is 1.5 to 2.0 cm; the size of the copper foam is 1×2 cm 2 .

4. The method according to claim 1, wherein The copper salt includes one or more of copper chloride, copper sulfate, copper nitrate, and copper chloride dihydrate.

5. An electrochemical catalyst, characterized in that The electrochemical catalyst is prepared by the method according to any one of claims 1 to 4.

6. Use of the electrochemical catalyst according to claim 5 in preparing dimethyl carbonate from carbon dioxide.

7. The use according to claim 6, characterized in that An Ag / AgCl electrode was used as a reference electrode, platinum was used as a counter electrode, the electrochemical catalyst was used as a working electrode, the anolyte was a methanol solution containing 0.01-0.02 M NaOH, the catholyte was a methanol solution containing 0.03-0.04 M KOH, and the CO2 flow rate introduced into the cathode was 20-25 sccm.

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