Electrochemical catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the field of electrochemical catalysts, and discloses an electrochemical catalyst and a preparation method and application thereof.Pretreated foamy copper serves as a carrier, a six-nuclear copper substituted phosphotungstate material grows on the surface of the carrier in situ, a highly-ordered copper-oxygen-tungsten atom interface exists in the structure, and the surface of the copper-oxygen-tungsten atom interface is modified; therefore, the orderly spaced copper atom layer loaded foamy copper catalyst is obtained. Therefore, the invention provides an integrated technical scheme of controllable synthesis of a microstructure, enhancement of heterogeneous interface performance and improvement of overall electron conduction, and comprehensive improvement of catalytic activity, selectivity and stability is realized in a reaction process of generating dimethyl carbonate through electrochemical reduction of carbon dioxide.

Description

Technical Field

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

[0002] Dimethyl carbonate is an environmentally friendly organic compound with a variety of unique chemical properties. It is often used as an electrolyte for lithium-ion batteries or to replace toxic reagents in carbonylation and methylation reactions. However, the methods commonly used in industry to produce dimethyl carbonate at present are methanol photochemical method, methanol oxidative carbonylation method, transesterification method, urea alcoholysis method, etc. These traditional processes have disadvantages such as serious pollution and high process risks, posing a huge challenge to the green synthesis of dimethyl carbonate.

[0003] Utilizing greenhouse gas carbon dioxide and methanol, a downstream product of biochemistry, as reactants is an effective way to achieve carbon cycle utilization and green synthesis of dimethyl carbonate. However, the carbon dioxide molecule has a symmetric carbon-oxygen double bond structure, and the C=O chemical bond has extremely high stability, making the reaction of carbon dioxide with methanol to form dimethyl carbonate thermodynamically difficult to proceed. Secondly, the electrocatalytic reduction process of carbon dioxide involves multi-electron transfer, and the reaction products are complex and diverse, resulting in difficult regulation of product selectivity. Moreover, the carbon dioxide reduction has a reaction potential similar to that of the hydrogen evolution reaction, and the hydrogen evolution reaction rate is often much higher than the carbon dioxide reduction rate, which seriously affects the conversion efficiency of carbon dioxide to dimethyl carbonate.

[0004] Regulating the structure and components of the catalyst can effectively improve the catalytic selectivity and efficiency of the electrocatalyst. At present, CeO2 materials rich in a large number of oxygen defects are considered to be electrocatalysts with excellent performance in promoting the conversion of carbon dioxide to dimethyl carbonate. Because a large number of oxygen defects in the material can serve as effective active sites to adsorb CH3O – and generate the *OCH3 reaction intermediate, promoting the smooth formation of dimethyl carbonate. However, the CeO2 materials rich in defects often have poor activation ability for CO2, making it necessary to further improve the efficiency of generating dimethyl carbonate.

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

[0006] The present invention aims to solve at least one of the technical problems in the related art to some extent. The present invention provides an electrochemical catalyst, a preparation method thereof, and an application thereof. For the process of electrochemically reducing carbon dioxide to dimethyl carbonate, the electrochemical catalyst has good catalytic activity, selectivity, and stability.

[0007] In one aspect of the present invention, a method for preparing an electrocatalyst is proposed. According to an embodiment of the present invention, the method includes: (1) Mix {PW9}, ethylenediamine, copper salt, acetic acid and water to obtain a reaction solution; (2) Heat and react the copper foam and the reaction solution to obtain an electrocatalyst.

[0008] In some embodiments, 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.

[0009] In some embodiments, in step (2), the copper foam is pretreated, and the pretreatment includes: putting the copper foam into ethanol, acetone, hydrochloric acid solution for ultrasonic cleaning, and then drying. Through the above pretreatment, the oxide layer and impurities on the surface of the copper foam can be removed. As a preferred embodiment, first put the copper foam into a 1:1 mixture of ethanol and acetone and ultrasonically clean for 30 - 60 min. After the ultrasonic cleaning, wash it with water, then put it into a 2 M hydrochloric acid solution and ultrasonically clean for 15 - 30 min. After the ultrasonic cleaning, wash it with water and ethanol until neutral, and finally dry it in vacuum at 60 °C for 6 h.

[0010] In some embodiments, in step (2), the temperature of the heat reaction is 75 - 85 °C, and the heat reaction is carried out for 3 - 5 days.

[0011] In some embodiments, the thickness of the copper foam is 1.5 - 2.0 cm; the size of the copper foam is 1×2 cm 2 .

[0012] In some embodiments, the copper salt includes one or more of copper chloride, copper sulfate, copper nitrate, copper dichloride dihydrate.

[0013] In a second aspect of the present invention, an electrocatalyst is provided, and the electrocatalyst is prepared by the above method.

[0014] In a third aspect of the present invention, an application of the above electrocatalyst in the preparation of dimethyl carbonate from carbon dioxide is proposed.

[0015] The present invention has the following beneficial effects: (1) The preparation method of the present invention can be firmly combined with the metal current collector without any chemical binder, and maintain the overall stability of its own micro-ring structure during the electrocatalytic process, thereby ensuring good stability in the whole process of electrocatalytic reduction of CO2 to produce dimethyl carbonate; (2) The electrocatalyst of the present invention can promote the adsorption of CO2 on the coordinatively unsaturated copper catalytic active sites formed by the loss of ethylenediamine ligands. The tungsten atoms with Lewis acidity can provide 5d orbitals to form a feedback π bond with the O 2p orbitals in CO2, enabling tungsten to refill its own electrons back into the antibonding orbitals of CO2 and promoting the efficient conversion of CO2 to the *CO intermediate. The μ3-OH in the copper-oxygen nanocluster can effectively convert CH3OH to *OCH3 and H2O, achieving the partitioned adsorption and activation of CO2 and CH3OH. (3) The electrocatalyst of the present invention utilizes the fixed metal-metal spacing to promote the coupling of the *CO and *OCH3 intermediates, thereby enhancing the selectivity of the catalytic material for the conversion of CO2 to dimethyl carbonate. (4) The electrocatalyst of the present invention utilizes multiple heterogeneous interfaces to enhance the synergistic effect between components, promoting the rapid charge transfer of the material, and thereby increasing the conductivity and catalytic activity of the catalyst during the electrocatalytic process. In summary, the present invention uses pretreated copper foam as a carrier, and in-situ grows a hexanuclear copper-substituted phosphotungstate material on its surface. There is a highly ordered copper-oxygen-tungsten atomic interface in this structure, that is, a copper foam catalyst supported by an orderly spaced copper atom layer is obtained. Thus, the present invention provides an integrated technical solution for controllable synthesis of microstructure, enhanced performance of heterogeneous interfaces, and improved overall electron conduction, achieving a comprehensive improvement in the catalytic activity, selectivity, and stability of electrochemically reducing carbon dioxide to dimethyl carbonate.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a topological stacking diagram of Material A along the c-axis direction; Figure 2 It is a structural characterization diagram of Material A, where (a) is the scanning electron microscope image of Material A; (b) is the transmission electron microscope image of Material A; (c) is the high-resolution transmission electron microscope image of Material A; (d) is the atomic force microscope image of Material A; Figure 3 It is a structural characterization diagram of Material B, where (a) is the schematic molecular structure diagram of Material B; (b) is the scanning electron microscope image of Material B at low magnification; (c) is the scanning electron microscope image of Material B at high magnification; Figure 4 It is the test result of Material A under the experimental conditions of Application Example 1, where (a) is the bar chart of the Faraday efficiency of Material A at different voltages at room temperature; (b) is the bar chart of the production of Material A at different voltages at room temperature.

[0018] Figure 5 The test results of Material B under the experimental conditions of Application Example 1, where (a) is the bar chart of the Faraday efficiency of Material B at different voltages at room temperature; (b) is the bar chart of the production of Material B at different voltages at room temperature.

[0019] Figure 6 The test results of Material C under the experimental conditions of Application Example 1, where (a) is the bar chart of the Faraday efficiency of Material C at different voltages at room temperature; (b) is the bar chart of the production of Material C at different voltages at room temperature.

[0020] Figure 7 The test results of Material D under the experimental conditions of Application Example 1, where (a) is the bar chart of the Faraday efficiency of Material D at different voltages at room temperature; (b) is the bar chart of the production of Material D at different voltages at room temperature.

[0021] Figure 8 The test results of Material E under the experimental conditions of Application Example 1, where (a) is the bar chart of the Faraday efficiency of Material E at different voltages at room temperature; (b) is the bar chart of the production of Material E at different voltages at room temperature.

[0022] Figure 9 The test results of Material A under the experimental conditions of Application Example 2, where (a) is the bar chart of the Faraday efficiency of Material A at different voltages at - 15 o °C; (b) is the bar chart of the production of Material A at different voltages at - 15 o °C; Figure 10 The X - ray photoelectron spectroscopy diagrams of copper, tungsten, carbon, and nitrogen elements in Material A before and after the electrochemical reaction, where (a) is the X - ray photoelectron spectroscopy diagram of copper element in Material A before and after the electrocatalytic reaction; (b) is the X - ray photoelectron spectroscopy diagram of tungsten element in Material A before and after the electrocatalytic reaction; (c) is the X - ray photoelectron spectroscopy diagram of carbon element in Material A before and after the electrocatalytic reaction; (d) is the X - ray photoelectron spectroscopy diagram of nitrogen element in Material A before and after the electrocatalytic reaction; Figure 11 The in - situ characterization diagrams of Material A, where (a) is the in - situ X - ray diffraction diagram of Material A; (b) is the in - situ infrared diagram of Material A; Figure 12 The schematic diagram of the reaction path participated by Material A. Detailed implementation manners

[0023] The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way. In the following embodiments and comparative examples, unless otherwise specified, the raw materials used are ordinary commercially available products that can be directly purchased in the art or prepared by conventional methods existing in the art.

[0024] The size of the copper foam is 1 cm × 2 cm, and the thickness is 1.5 mm. It is purchased from Suzhou Shenghe Metal Materials Co., Ltd.

[0025] Copper oxide and cuprous oxide are both purchased from Aladdin Reagent Co., Ltd.

[0026] {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 Ziming et al., Preparation of a novel photocatalytic catalyst PW9@ZnO / Ag and photocatalytic degradation of butyl xanthate under visible light, Environmental Research, 2022, Volume 214, Page 113776.) Obtained.

[0027] Example 1 (1) Weigh 246 mg of {PW9}, add 30 μL of 99 wt.% ethylenediamine, 170 mg of copper chloride dihydrate, 100 μL of acetic acid, and 5 mL of water, mix and stir for 30 min to obtain a reaction solution, and then transfer the reaction solution to a 10 mL high-pressure sterile reaction kettle; (2) Immerse the copper foam in a mixed solution of ethanol and acetone with a volume ratio of 1:1 and ultrasonicate for 30 min, then wash it 3 times with secondary water; then put it into concentrated hydrochloric acid and ultrasonicate for 20 min, then wash it with water and ethanol until neutral, and finally vacuum dry at 60 o °C for 6 h to obtain the pretreated copper foam; (3) Immerse the pretreated copper foam in the solution in the reaction kettle, and react continuously at a temperature of 80 o °C for 3 days, then naturally cool to room temperature and take it out, and dry the residual reaction solution on the surface with filter paper to obtain Material A. The material loading is 10 mg.

[0028] Comparative Example 1 Comparative Example 1 is the copper foam after pretreatment in Step (2) of Example 1, i.e., Material B is obtained.

[0029] Comparative Example 2 Take 10.0 mg of {PW9} powder, disperse it in 5.0 mL of ethanol solution, add 25 μL of Nafion solution, and ultrasonicate for 30 min until homogeneous. Then, drop the prepared solution onto a 1×2 cm copper foam, and dry it to obtain Material C.

[0030] Comparative Example 3 Take 10.0 mg of commercial CuO powder, disperse it in 5.0 mL of ethanol solution, add 25 μL of Nafion solution, and ultrasonicate for 30 min until homogeneous. Then, drop the prepared solution onto a 1×2 cm copper foam, and dry it to obtain Material D.

[0031] Comparative Example 4 Take 10.0 mg of commercial Cu2O powder, disperse it in 5.0 mL of ethanol solution, add 25 μL of Nafion solution, and ultrasonicate for 30 min until homogeneous. Then, drop the prepared solution onto a 1×2 cm copper foam, and dry it to obtain Material E.

[0032] The materials of Example 1 and Comparative Example 1 were subjected to detailed structural determination and characterization.

[0033] Figure 1 is the topological stacking diagram of Material A along the c-axis direction. This structural unit can be regarded as a {PW9} connecting 1 six-core copper-oxygen nanocluster through a vacancy site. The 6 copper atoms in this copper-oxygen nanocluster are arranged in an equilateral triangle, and each copper atom has an octahedral configuration with six coordination. Looking from the c-axis direction, this structure can be regarded as an ordered alternating copper atom layer structure formed by layered {PW9} and copper-oxygen nanoclusters.

[0034] Figure 2 is the structural characterization diagram of Material A. Among them, Figure 2 (a) in is the scanning electron microscope image of Material A. It can be seen that the alternating copper nanolayers are attached to the copper foam in a layered structure, providing a high specific surface area and more catalytic active sites for the electrocatalytic reaction. Figure 2 (b) in is the transmission electron microscope image of Material A, Figure 2 (c) in is the high-resolution transmission electron microscope image of Material A. It can be seen that this nanolayered material has high crystallinity, indicating that the alternating copper nanolayers are highly ordered. Figure 2Figure (d) is the atomic force microscope image of Material A. It can be seen that the flake thickness of this ordered-interval copper atom layer material is about 10 - 15 nm, which is equivalent to the stacking of 10 - 15 layers of hexanuclear copper-substituted phosphotungstate materials.

[0035] Such as Figure 3 is the structural characterization diagram of Material B. Among them, Figure 3 Figure (a) is the schematic molecular structure diagram of Material B, Figure 3 Figure (b) is the scanning electron microscope image of Material B at low magnification, Figure 3 Figure (c) is the scanning electron microscope image of Material B at high magnification. It can be seen that Material B does not have a similar ordered-interval copper atom layer, and its surface is smooth without the existence of flake structures. The commercially purchased copper oxide and cuprous oxide also do not have a similar ordered-interval copper atom layer.

[0036] Application Example 1 The electrocatalytic performances of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 were respectively tested in a super-dry methanol solution saturated with CO2.

[0037] At room temperature (25 ± 5 o °C), it was carried out in an H-type electrolytic cell using a three-electrode system (a saturated Ag / AgCl electrode as the reference electrode, a platinum sheet as the counter electrode, and the catalytic material fixed by a titanium sheet electrode clip as the working electrode). Among them, the catalytic materials were Material A, Material B, Material C, Material D, and Material E prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4. The anodic electrolyte was a super-dry methanol solution of 0.01 M NaOH, the cathodic electrolyte was a super-dry methanol solution containing 0.03 M KOH, and the cathode and anode were separated by a Nafion 211 proton exchange membrane.

[0038] The catalytic performance of the materials was monitored for gas products using a Shimadzu online gas chromatograph, and the flow rate of CO2 introduced into the cathode was 20 sccm. The liquid products were analyzed using nuclear magnetic resonance hydrogen spectroscopy.

[0039] Application Example 2 The operating temperature of the three-electrode system was -15 o °C, and the others were the same as in Application Example 1.

[0040] Figure 4 and Figure 5 and Figure 6 and Figure 7 and Figure 8 are respectively the test results of Material A, Material B, Material C, Material D, and Material E under the experimental conditions of Application Example 1: Figure 4In (a), it is a bar chart of the Faraday efficiency of Material A at different voltages under room temperature conditions. It can be seen that the Faraday efficiencies of dimethyl carbonate prepared by running Material A of Example 1 for 60 min at potentials of -0.8 V, -1.0 V, -1.2 V, -1.4 V, and -1.6 V (vs. Ag / AgCl) are 82%, 83%, 83%, 85%, and 81% respectively; Figure 4 In (b), it is a bar chart of the production of Material A at different voltages under room temperature conditions. It can be seen that the concentrations (production) are 0.61 mol·L –1 , 0.99mol·L –1 , 1.26 mol·L –1 , 2.37 mol·L –1 , 2.40 mol·L –1 .

[0041] Figure 5 In (a), it is a bar chart of the Faraday efficiency of Material B at different voltages under room temperature conditions. It can be seen that the Faraday efficiencies of dimethyl carbonate prepared by running Material B of Comparative Example 1 for 60 min at potentials of -0.8 V, -1.0 V, -1.2 V, -1.4 V, and -1.6 V (vs. Ag / AgCl) are 73%, 76%, 81%, 84%, and 70% respectively; Figure 5 In (b), it is a bar chart of the production of Material B at different voltages under room temperature conditions. It can be seen that the concentrations (production) 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 .

[0042] Figure 6 In (a), it is a bar chart of the Faraday efficiency of Material C at different voltages under room temperature conditions. It can be seen that the Faraday efficiencies of dimethyl carbonate prepared by running Material C of Comparative Example 2 for 60 min at potentials of -0.8 V, -1.0 V, -1.2 V, -1.4 V, and -1.6 V (vs. Ag / AgCl) are 41%, 46%, 43%, 35%, and 33% respectively; Figure 6 In (b), it is a bar chart of the production of Material C at different voltages under room temperature conditions. It can be seen that the concentrations (production) are 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 。

[0043] Figure 7 In (a), it is a bar chart of the Faraday efficiency of Material D at different voltages under room temperature conditions. It can be seen that the Faraday efficiencies of dimethyl carbonate prepared from 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) potentials for 60 min are 25%, 30%, 37%, 40%, and 13% respectively; Figure 7 In (b), it is a bar chart of the production of Material D at different voltages under room temperature conditions. It can be seen that the concentrations (production) are 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 。

[0044] Figure 8 In (a), it is a bar chart of the Faraday efficiency of Material E at different voltages under room temperature conditions. It can be seen that the Faraday efficiencies of dimethyl carbonate prepared from 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) potentials for 60 min are 35%, 37%, 25%, 21%, and 17% respectively; Figure 8 In (b), it is a bar chart of the production of Material E at different voltages under room temperature conditions. It can be seen that the concentrations (production) are 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 。

[0045] It can be seen from this that compared with Materials B, C, D, and E, Material A has significantly improved catalytic activity and selectivity.

[0046] Figure 9 It is the test result of Material A under the experimental conditions of Application Example 2.

[0047] Figure 9 In (a), it is -15 oAt 0 °C, the bar chart of the Faraday efficiency of Material A at different voltages shows that when Material A of Example 1 was operated at -0.8 V, -1.0 V, -1.2 V, -1.4 V, and -1.6 V (vs. Ag / AgCl) for 60 min, the Faraday efficiencies of dimethyl carbonate prepared were 66%, 68%, 70%, 72%, and 66% respectively; Figure 9 In (b) is -15 o At 0 °C, the bar chart of the yield of Material A at different voltages shows that the concentrations (yields) were 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 the catalytic effects of other comparative examples were poor under low-temperature conditions. It can be seen that Material A of Example 1 also has high catalytic activity and selectivity at low temperatures.

[0048] From the above data, it can be seen that Material A of Example 1 (i.e., copper foam loaded with an ordered copper atom layer at intervals) has stable catalytic activity and selectivity for the conversion of CO2 to dimethyl carbonate whether at room temperature or low temperature, and its catalytic performance is hardly affected by temperature changes, making it a potential electrocatalyst for industrial production of dimethyl carbonate.

[0049] To further explore the structure-activity relationship between the structure and properties of copper foam loaded with an ordered copper atom layer at intervals, a series of structural characterizations were carried out. Figure 10 It is the X-ray photoelectron spectroscopy diagram of copper, tungsten, carbon, and nitrogen elements in Material A before and after the electrochemical reaction.

[0050] Figure 10 In (a) is the X-ray photoelectron spectroscopy diagram of copper element in Material A before and after the electrocatalytic reaction. It can be seen that the valence states of copper atoms in Example 1 are +1 and +2. The +1 valence is due to the growth of the ordered copper atom layer on the copper foam; the +2 valence is the valence state of copper atoms in the copper-oxygen nanoclusters in the structure. As the electrocatalytic reaction proceeds, the content of Cu 2+ in Example 1 gradually decreases, while the content of Cu + gradually increases, indicating that during the electrocatalytic process of Material A, Cu 2+ is gradually reduced to form Cu + .

[0051] Figure 10 In (b) is the X-ray photoelectron spectroscopy diagram of tungsten element in Material A before and after the electrocatalytic reaction. It can be seen that during the electrochemical reaction, tungsten element is reduced from +6 to +4. At the same time,Figure 10 In (c), it is the X-ray photoelectron spectroscopy of carbon element in Material A before and after the electrocatalytic reaction. Figure 10 In (d), it is the X-ray photoelectron spectroscopy of nitrogen element in Material A before and after the electrocatalytic reaction. It can be seen that the contents of carbon element and nitrogen element decrease significantly after the electrocatalytic reaction. Since the carbon element and nitrogen element only come from the ethylenediamine organic ligand, it indicates that ethylenediamine gradually dissolves during the electrocatalytic process, forming coordinatively unsaturated copper sites. These copper sites can adsorb CO2 during the reduction process, thereby promoting the electrochemical reduction of CO2 to the *CO intermediate. The reduction of CO2 can also reduce the degree of Cu 2+ being reduced, resulting in an increase in the content of Cu + without the generation of Cu 0 .

[0052] To explore the change law of Material A during the electrocatalytic process, we carried out in-situ X-ray diffraction (XRD) tests and in-situ infrared tests, as Figure 11 shown in the in-situ characterization diagram of Material A.

[0053] Figure 11 In (a), it is the in-situ X-ray diffraction diagram of Material A. It can be seen that the crystal phase of the copper foam catalyst loaded with the ordered interlayer of copper atoms hardly changes during the electrocatalytic process, proving that only the valence states of copper and tungsten elements change during the electrochemical catalysis while the structure remains unchanged, still maintaining the original highly ordered interlayer of copper, which provides a good structural basis for the coupling of *CO and *OCH3 intermediates. On this basis, we carried out in-situ infrared tests. Figure 11 In (b), it is the in-situ infrared diagram of Material A. It can be seen that 1604 cm –1 , 1663 cm –1 are respectively the vibration peaks of *OOCH – , *CO intermediates. It shows that CO2 is first adsorbed on the catalyst surface and further generates the *OOCH – intermediate through a hydrogenation reduction reaction, and then is further reduced to generate *CO. And 1307 cm –1 is the vibration peak position of C-OCH3, indicating that coupling occurs between *CO and *OCH3, thus forming the dimethyl carbonate compound.

[0054] Analyzing the above experimental results, it can be concluded that: as Figure 12 shown in the reaction path schematic diagram participated by Material A, the copper foam catalyst loaded with a highly ordered interlayer of copper atoms follows the reaction path of first reducing CO2 and then coupling *CO and *OCH3 intermediates to generate dimethyl carbonate. And in the copper-oxygen nanocluster μ3-OH is the main catalytic active site for promoting the conversion of CH3OH to the intermediate product *OCH3. It can be seen from this that the copper foam catalyst supported by the ordered spaced copper atom layer has the ability to simultaneously adsorb and activate the two reactants, CO2 and CH3OH, and can further promote the coupling of the intermediate products *CO and *OCH3 based on the structural advantages of its own ordered spaced copper atom layer, thereby improving the selectivity of CO2 conversion to dimethyl carbonate.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an electrocatalyst, characterized in that, The method includes: (1) Mix {PW9}, ethylenediamine, copper salt, acetic acid and water to obtain a reaction solution; (2) Heat and react the copper foam and the reaction solution to obtain an electrocatalyst.

2. The method according to claim 1, characterized in that, 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.

3. The method according to claim 1, wherein In step (2), pre-treat the copper foam, and the pre-treatment includes: putting the copper foam into one or more of ethanol, acetone and hydrochloric acid solution for ultrasonic cleaning, and then drying.

4. The method according to claim 1, characterized in that In step (2), the temperature of the heat reaction is 75 - 85 °C, and the time is 3 - 5 days.

5. 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 .

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

7. An electrocatalyst, characterized in that, The electrocatalyst is prepared by the method according to any one of claims 1 - 6.

8. Use of an electrocatalyst according to claim 7 in the preparation of dimethyl carbonate from carbon dioxide.

9. The application according to claim 8, characterized in that, Using an Ag / AgCl electrode as the reference electrode, platinum as the counter electrode, the electrocatalyst as the working electrode, the anolyte is a methanol solution of 0.01 - 0.02 M NaOH, the catholyte is a methanol solution containing 0.03 - 0.04 M KOH, and the flow rate of CO2 introduced into the cathode is 20 - 25 sccm.

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