Preparation method and application method of copper-based catalyst for electrochemical CO2 reduction

Abstract

The invention relates to a preparation method and application method of a copper-based catalyst for electrochemical CO2 reduction, and the preparation method of the copper-based catalyst for electrochemical CO2 reduction comprises the following steps: S100: obtaining copper powder, dissolving the copper powder in a solvent, and ultrasonically mixing uniformly to obtain a copper-based mixed solution; and S200, the copper-based mixed solution is transferred into a high-pressure kettle to be heated, after the temperature rises to the preset temperature, CO2 gas is introduced into the high-pressure kettle till the high-pressure kettle is in a supercritical state, constant-temperature reaction is conducted for 3-24 h, the high-pressure kettle is cooled to the room temperature, then centrifugation is conducted, solid at the bottom is taken, washing and drying are conducted, and the copper-based catalyst for electrochemical CO2 reduction is obtained.

Description

Technical Field

[0001] This invention relates to the fields of new energy materials and catalysis technology, and in particular to methods for preparing and applying copper-based catalysts for electrochemical CO2 reduction. Background Technology

[0002] Copper-based catalysts, with their abundant reserves, low cost, and excellent catalytic performance, have been widely used in the field of catalysis, including but not limited to methanol synthesis, hydrocarbon reforming, carbon monoxide oxidation, water-gas shift reaction, and electrochemical carbon dioxide reduction (CO2RR). Driven by electricity generated from renewable energy sources such as solar and wind power, utilizing copper-based catalysts to reduce CO2 into high-value-added chemicals is an important pathway to achieving renewable energy storage and carbon cycling. In copper-based catalyst systems, cuprous oxide is the key phase for optimizing CO2RR catalytic performance. Its exposed crystal facets can significantly affect catalytic performance by controlling key factors such as the atomic arrangement, coordination unsaturation, and electronic structure of the catalyst surface. In other words, different crystal facets result in different atomic arrangements, coordination states, and electronic structures on the catalyst surface, leading to varying abilities to activate CO2 and adsorb and convert intermediates, thus affecting catalytic performance.

[0003] Currently, the control of cuprous oxide crystal planes mainly relies on methods such as surfactant modification, pH adjustment, element doping, and electrochemical deposition. However, these techniques generally suffer from problems such as difficulty in removing surfactant residues, limited precision in crystal plane control, complex synthesis processes, and high equipment requirements. Summary of the Invention

[0004] In view of the above analysis, the embodiments of the present invention aim to provide a method for preparing and applying a copper-based catalyst for electrochemical CO2 reduction, so as to at least solve one of the above problems.

[0005] On one hand, the present invention provides a method for preparing a copper-based catalyst for electrochemical CO2 reduction, comprising the following steps: S100: Obtain copper powder, dissolve the copper powder in a solvent and ultrasonically mix to obtain a copper-based mixed solution; S200: Transfer the copper-based mixed solution to a high-pressure reactor and heat it. When the temperature reaches the preset temperature, introduce CO2 gas to the supercritical state and react at a constant temperature for 3-24 hours. Cool it to room temperature, then centrifuge to collect the bottom solid, wash and dry it to obtain the copper-based catalyst for electrochemical CO2 reduction.

[0006] Furthermore, in step S100, the copper powder is nano-copper powder.

[0007] Further, in step S100, the weight-to-volume ratio of copper powder to solvent is 5 mg / 10 mL to 20 mg / 10 mL.

[0008] Furthermore, in step S100, the solvent is a mixed solvent or a single solvent; The single solvent is deionized water or an alcohol solvent; The mixed solvent is a mixture of deionized water and alcohol.

[0009] Further, in step S100, the volume ratio of deionized water to alcohol solvent in the mixed solvent is 1:0 to 1:4.

[0010] Furthermore, the crystal facets of the copper-based catalyst can be controlled by adjusting the volume ratio of the deionized water to the alcohol.

[0011] Furthermore, in step S200, the preset temperature is 40~100℃.

[0012] Furthermore, in step S200, the supercritical state pressure of the carbon dioxide is 8~20 MPa.

[0013] On the other hand, the present invention provides a method for using a copper-based catalyst for electrochemical CO2 reduction, wherein the copper-based catalyst for electrochemical CO2 reduction is prepared by the above-described preparation method.

[0014] Furthermore, the application method includes the following steps: A100: Disperse the copper-based catalyst in an alcohol solution, add 5 wt.% perfluorosulfonic acid ion exchange resin solution and carbon powder, and ultrasonically disperse to obtain a uniform slurry. Take the slurry and coat it on the surface of the pretreated carbon paper electrode. A200: A three-electrode testing system is used, with carbon paper coated with catalyst slurry as the working electrode, Ag / AgCl as the reference electrode, and Pt electrode as the counter electrode. CO2 is passed into the electrolyte to obtain a CO2-saturated electrolyte. A300: Uses an electrochemical workstation to apply voltage and reduce CO2.

[0015] Compared with the prior art, the present invention can achieve at least the following beneficial effects: (1) This invention applies a supercritical CO2 system to the oxidation process of copper nanoparticles. By controlling the critical solubility characteristics of CO2 and the synergistic effect of solvent polarity, it achieves a breakthrough in the directional generation and precise control of Cu2O (110) and (111) crystal planes. Experimental results show that when the water-alcohol ratio in the solvent is adjusted from 1:0 to 2:1, the proportion of (110) crystal plane increases from 0 to 33.3%, and the proportion of (111) crystal plane decreases from 100% to 66.7%, achieving precise control of the proportions of the two crystal planes. The preparation method of this invention is an integrated oxidation-crystal plane control method, which provides a new technical path and design idea for the structural design and green preparation of new heterogeneous catalyst materials. It effectively fills the application gap of existing crystal plane control technology under mild conditions and is of great significance for promoting technological innovation in the field of heterogeneous catalysis. (2) By leveraging the synergistic effect of the specific crystal plane Cu2O catalyst prepared in this invention and the electrochemical CO2 reduction process, the syngas (CO / H2) ratio can be precisely adjusted over a wide range (e.g., it can be precisely controlled within the range of 0.2 to 1.0). This technology can flexibly adjust the product ratio according to the personalized needs of different industrial scenarios (such as Fischer-Tropsch synthesis, methanol synthesis, etc.) for the composition of syngas, solving the pain point that the syngas ratio is difficult to accurately match industrial needs in traditional technologies. The application scenarios are highly expandable and have significant industrial application value and market prospects.

[0016] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0017] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0018] Figure 1 The image shows a TEM image of the copper-based catalyst prepared in Example 1 of the specific implementation method. Figure 2 This is a TEM image of the copper-based catalyst prepared in Example 2 of the specific implementation method. Detailed Implementation

[0020] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0021] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the term "connected" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or an electrical connection; it can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0022] Throughout the text, the terms “top,” “bottom,” “above,” “below,” and “on top” refer to the relative positions of components of the device, such as the relative positions of the top and bottom substrates within the device. It is understood that the device is multifunctional and independent of its spatial orientation.

[0023] The working surface of this invention can typically be a plane or a curved surface, and can be inclined or horizontal. For ease of explanation, the embodiments of this invention are placed on a horizontal surface and used on a horizontal surface, thereby defining "height" and "vertical".

[0024] A specific embodiment of the present invention discloses a method for preparing a copper-based catalyst for electrochemical CO2 reduction, comprising the following steps: S100: Obtain copper powder, dissolve the copper powder in a solvent and ultrasonically mix to obtain a copper-based mixed solution; S200: The copper-based mixed solution is transferred to an autoclave and heated. When the temperature reaches the preset temperature, CO2 gas is introduced to the supercritical state. The reaction is carried out at a constant temperature for 3 to 24 hours. After cooling to room temperature, the solid at the bottom of the autoclave is removed, washed, and dried to obtain the copper-based catalyst for electrochemical CO2 reduction.

[0025] In step S100, The copper powder is nano-copper powder with a particle size of less than or equal to 500 nm and a purity of 99.9%. Due to its small particle size, nano-copper powder is beneficial for subsequent oxidation.

[0026] The solvent can be a mixed solvent or a single solvent. The mixed solvent is a mixture of deionized water and an alcohol, and the single solvent is either deionized water or an alcohol solvent. For example, the alcohol solvent in the mixed solvent and the single solvent is a monohydric alcohol, such as ethanol.

[0027] The volume ratio of deionized water to alcohol solvent in the mixed solvent is 1:0 to 1:4.

[0028] The weight-to-volume ratio of the copper powder to the solvent is 5 mg / 10 mL to 20 mg / 10 mL.

[0029] The ultrasonic frequency is 20~40KHz, and the duration is 30~40min.

[0030] In step S200 The preset temperature is 40~100℃, preferably 60℃. Furthermore, the autoclave is heated at a uniform rate. The supercritical state refers to a carbon dioxide pressure of 8~20MPa.

[0031] The conditions for carbon dioxide to reach supercriticality are 31.1°C and 7.38 MPa. The preset temperature and carbon dioxide pressure of this invention can ensure that the reaction system is always in a supercritical state.

[0032] The chemical reactions that occur inside the autoclave are CO2→CO + *O; 2Cu + *O → Cu2O.

[0033] The reaction is carried out at a constant temperature for 3 to 24 hours, preferably 3 to 12 hours.

[0034] For example, the centrifugation conditions are 10,000 rpm / 10 min.

[0035] The drying conditions are vacuum drying at a temperature of 40~80℃ for 8~12 hours.

[0036] When washing the solids at the bottom, first wash with an alcohol solvent (such as monohydric alcohol) and then wash with deionized water, repeating three times.

[0037] The purpose of this invention is to provide a method for preparing cuprous oxide nanoparticles based on supercritical CO2 at low temperature. This method can adjust the crystal facets of cuprous oxide, and can precisely target the preparation of two products with different crystal facets: Cu2O(111) and Cu2O(110). Cuprous oxide materials with different crystal facets can effectively regulate the catalytic performance of the electrochemical CO2 reduction reaction and inhibit the occurrence of hydrogen evolution reaction.

[0038] In a supercritical environment, hydrogen bonding of water molecules promotes the dissociation of CO2 molecules, generating active oxygen species (*O) that are stably adsorbed on the surface of copper nanoparticles. These active species then oxidize the copper nanoparticles, oriented to form Cu2O(111) crystal faces. Alcohol molecules tend to preferentially adsorb onto Cu2O(110) crystal faces. Therefore, introducing alcohols into the solvent system can selectively induce the growth of Cu2O(110) crystal faces through selective adsorption.

[0039] This invention proposes a surfactant-free, simple, and green preparation method that can precisely control the cuprous oxide crystal facets. This method utilizes the unique physicochemical properties of supercritical CO2, such as low viscosity and excellent diffusion performance, to achieve the oxidation of nanoparticles under low-temperature conditions. Simultaneously, it precisely controls the selective formation of Cu2O(110) and Cu2O(111) crystal facets. Compared to the Cu2O(111) crystal facet, the (110) crystal facet exhibits superior CO2 reduction performance. Cuprous oxide materials with different crystal facets can effectively control the CO2RR catalytic performance and the inhibition of hydrogen evolution side reactions, thereby achieving precise control of the syngas (CO / H2) ratio.

[0040] This invention also discloses a method for applying the copper-based catalyst for electrochemical CO2 reduction, comprising the following steps: A100: Disperse the copper-based catalyst in an alcohol solution, add 5 wt.% perfluorosulfonic acid ion exchange resin solution and carbon powder, and ultrasonically disperse to obtain a uniform slurry. Take the slurry and coat it on the surface of the pretreated carbon paper electrode. A200: A three-electrode testing system is used (the CHI 660E from Shanghai Chenhua Instrument Co., Ltd. can be used). Carbon paper coated with catalyst slurry is used as the working electrode, Ag / AgCl is used as the reference electrode, and Pt electrode is used as the counter electrode. CO2 is passed into the electrolyte to obtain a CO2-saturated electrolyte. A300: Uses an electrochemical workstation to apply voltage and reduce CO2.

[0041] In step A100, The ratio of the copper-based catalyst to the alcohol solution is: .

[0042] The mass ratio of the copper-based catalyst to the carbon powder is 10:3.

[0043] Pick The paste is coated onto the surface of the carbon paper electrode, with a coating area of ​​1 cm². 2 .

[0044] The pretreatment refers to cleaning the surface of the carbon paper electrode. For example, the pretreatment refers to cleaning the surface of the carbon paper electrode with HCl, propanol and H2O in sequence.

[0045] The alcohol solution is an ethanol or propanol solution, and the perfluorosulfonic acid ion exchange resin solution is a Nafion solution from DuPont.

[0046] The volume ratio of the alcohol solution to the perfluorosulfonic acid ion exchange resin solution is 250:6.

[0047] The alcohol solution, Nafion solution, and toner mentioned above are used as dispersant, binder, and conductive agent, respectively.

[0048] In step A200 The electrolyte is a 0.1~1.0M bicarbonate electrolyte, which has good conductivity and stability.

[0049] In step A300 An electrochemical workstation (such as the CHI 660E from Shanghai Chenhua Instrument Co., Ltd.) was used, and the electrochemical reduction parameters were: potential -0.3 to -1.2 V (vs. RHE relative to the reversible hydrogen electrode).

[0050] [Example 1] A method for preparing a copper-based catalyst for electrochemical CO2 reduction is provided, comprising the following steps: S100: Weigh 20mg of nano copper powder with a particle size ≤100nm, add it to 10mL of a mixed solution of deionized water and ethanol with a volume ratio of 2:1, and then sonicate for 30min to fully disperse to obtain a copper-based mixed solution. S200: The copper-based mixed solution obtained in S100 was transferred to a 50 mL stainless steel autoclave and heated uniformly to 60 °C. CO2 gas was introduced into the autoclave at 60 °C to 16 MPa to reach the supercritical state, and the reaction was kept at a constant temperature for 6 h. After the reaction was completed, the autoclave was removed and cooled to room temperature. Then, the solid was separated by centrifugation at 10000 rpm / 10 min, washed three times with ethanol and deionized water, and dried under vacuum at 60 °C for 12 h to obtain the copper-based catalyst of Example 1.

[0051] like Figure 1 The image shown is a TEM image of the copper-based catalyst in Example 1. Figure 1 It can be seen that the catalyst exposes both Cu2O(110) and Cu2O(111) crystal planes.

[0052] [Example 2] A method for preparing a copper-based catalyst for electrochemical CO2 reduction is provided, comprising the following steps: S100: Weigh 20 mg of nano copper powder with a particle size ≤100 nm, add it to 10 mL of deionized water, and then sonicate for 30 min to fully disperse it to obtain a copper-based mixed solution; S200: The copper-based mixed solution obtained in S100 was transferred to a 50 mL stainless steel autoclave and heated uniformly to 60 °C. CO2 gas was introduced into the autoclave at 60 °C to 16 MPa to reach the supercritical state, and the reaction was kept at a constant temperature for 6 h. After the reaction was completed, the autoclave was removed and cooled to room temperature. Then, the solid was separated by centrifugation at 10000 rpm / 10 min, washed three times with ethanol and deionized water, and dried under vacuum at 60 °C for 12 h to obtain the copper-based catalyst of Example 2.

[0053] like Figure 2The image shown is a TEM image of the copper-based catalyst in Example 2. Figure 2 It can be seen that the catalyst only exposes the Cu2O (111) crystal plane.

[0054] [Example 3] A method for preparing a copper-based catalyst for electrochemical CO2 reduction is provided, comprising the following steps: S100: Weigh 20 mg of nano copper powder with a particle size ≤100 nm, add it to 10 mL of pure ethanol solution, and then sonicate for 30 min to fully disperse it to obtain a copper-based mixed solution; S200: The copper-based mixed solution obtained in S100 was transferred to a 50 mL stainless steel autoclave and heated uniformly to 60 °C. CO2 gas was introduced into the autoclave at 60 °C to 16 MPa to reach the supercritical state, and the reaction was kept at a constant temperature for 6 h. After the reaction was completed, the autoclave was removed and cooled to room temperature. Then, the solid was separated by centrifugation at 10000 rpm / 10 min, washed three times with ethanol and deionized water, and dried under vacuum at 60 °C for 12 h to obtain the copper-based catalyst of Example 3.

[0055] In Example 3, the nano-copper particles were basically not oxidized during the preparation process.

[0056]

Comparative Example 1

[0057]

Comparative Example 2

[0058] The catalysts prepared in Examples 1 through 3, as well as the copper powder from Comparative Examples 1 and 2, were used in the electrochemical reduction of CO2. The specific steps included: A100: Disperse 2 mg of catalyst or copper powder in 250 μL of ethanol solution, add 0.6 mg of carbon powder and 6 μL of 5 wt.% Nafion solution, and ultrasonically disperse to obtain a uniform slurry. Coat the slurry onto the pretreated clean carbon paper electrode surface. A200: A three-electrode testing system is used, with a carbon paper electrode coated with slurry as the working electrode, Ag / AgCl as the reference electrode, Pt electrode as the counter electrode, and 0.1M KHCO3 as the electrolyte. CO2 is continuously introduced into the electrolyte for 15 minutes to obtain a CO2-saturated 0.1M KHCO3 electrolyte. A300: Uses an electrochemical workstation to apply voltage to reduce CO2. The electrochemical reduction parameters are: potential −0.1 V (vs. RHE).

[0059] The catalysts prepared in Examples 1 to 3, as well as the copper powder in Comparative Examples 1 and 2, were used in the electrochemical reduction of CO2, and the results are shown in the table below.

[0060] <![CDATA[Reduction current density value / mA cm -2 > Syngas Faraday efficiency <![CDATA[CO / H2 ratio]]> Example 1 −18.7 75% 1.0 Example 2 −17.7 64% 0.7 Example 3 −21.4 64% 0.8 Compare with Example 1 −16.9 62% 0.5 Compare with Example 2 −17.1 64% 0.5

[0061] As can be seen from the table, the absolute values ​​of the reduction current density in all examples are higher than those in the control examples (Example 3 > Example 1 > Example 2 > Control Example 2 > Control Example 1). This indicates that the catalysts in the examples can more effectively promote electron transfer in the CO2 reduction reaction, exhibiting superior catalytic activity. The CO / H2 ratios in the examples are all higher than those in the control examples (Example 1 > Example 3 > Example 2 > Control Example 2 > Control Example 1). This indicates that the examples can obtain syngas with a higher CO content by controlling the reaction conditions or catalyst structure, better meeting the industrial demand for syngas with a high CO ratio, and exhibiting better product selectivity. In particular, Example 1 shows higher syngas Faraday efficiency and more efficient conversion of electrical energy into the target product. These data verify that the examples (catalysts containing Cu2O (110) and (111) crystal planes) have higher activity, efficiency, and product control capabilities in the electrocatalytic CO2 syngas production system compared to the control strategy, providing a better solution for the practical application of electrocatalytic CO2 reduction.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-based catalyst for electrochemical CO2 reduction, characterized in that, Includes the following steps: S100: Obtain copper powder, dissolve the copper powder in a solvent and ultrasonically mix to obtain a copper-based mixed solution; S200: Transfer the copper-based mixed solution to a high-pressure reactor and heat it. When the temperature reaches the preset temperature, introduce CO2 gas to the supercritical state and react at a constant temperature for 3-24 hours. Cool it to room temperature, then centrifuge to collect the bottom solid, wash and dry it to obtain the copper-based catalyst for electrochemical CO2 reduction.

2. The method for preparing the copper-based catalyst for electrochemical CO2 reduction according to claim 1, characterized in that, In step S100, the copper powder is nano copper powder.

3. The method for preparing the copper-based catalyst for electrochemical CO2 reduction according to claim 1, characterized in that, In step S100, the weight-to-volume ratio of copper powder to solvent is 5 mg / 10 mL to 20 mg / 10 mL.

4. The method for preparing the copper-based catalyst for electrochemical CO2 reduction according to claim 1, characterized in that, In step S100, the solvent is a mixed solvent or a single solvent; The single solvent is deionized water or an alcohol solvent; The mixed solvent is a mixture of deionized water and alcohol.

5. The method for preparing the copper-based catalyst for electrochemical CO2 reduction according to claim 1, characterized in that, In step S100, the volume ratio of deionized water to alcohol solvent in the mixed solvent is 1:0 to 1:

4.

6. The method for preparing the copper-based catalyst for electrochemical CO2 reduction according to claim 5, characterized in that, The crystal facets of the copper-based catalyst can be controlled by adjusting the volume ratio of the deionized water to the alcohol.

7. The method for preparing the copper-based catalyst for electrochemical CO2 reduction according to claim 1, characterized in that, In step S200, the preset temperature is 40~100℃.

8. The method for preparing the copper-based catalyst for electrochemical CO2 reduction according to claim 1, characterized in that, In step S200, the supercritical pressure of the carbon dioxide is 8~20 MPa.

9. A method for applying a copper-based catalyst for electrochemical CO2 reduction, characterized in that, The copper-based catalyst for electrochemical CO2 reduction is prepared by the preparation method described in any one of claims 1 to 8.

10. The method of applying the copper-based catalyst for electrochemical CO2 reduction according to claim 8, characterized in that, Includes the following steps: A100: Disperse the copper-based catalyst in an alcohol solution, add 5 wt.% perfluorosulfonic acid ion exchange resin solution and carbon powder, and ultrasonically disperse to obtain a uniform slurry. Take the slurry and coat it on the surface of the pretreated carbon paper electrode. A200: A three-electrode testing system is used, with carbon paper coated with catalyst slurry as the working electrode, Ag / AgCl as the reference electrode, and Pt electrode as the counter electrode. CO2 is passed into the electrolyte to obtain a CO2-saturated electrolyte. A300: Uses an electrochemical workstation to apply voltage and reduce CO2.

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