Preparation method and application of mixed ionomer-modified cuprous oxide catalyst

Abstract

The present invention relates to the technical field of electrochemical carbon dioxide reduction reaction catalysts and discloses a preparation method and application of a mixed ionomer-modified cuprous oxide catalyst. The method comprises the following steps: surface modification of cuprous oxide powder with a hydrophobic ionomer and a proton exchange ionomer, construction of an effective hydrophobic structure in the form of physical coating on Cu2O active sites, and formation of a stable and controllable hydrophobic gas-liquid-solid three-phase reaction micro-interface. The method solves the problems of low Faradaic efficiency, poor selectivity, severe competitive hydrogen evolution reaction, and carbonate deposition in the existing electrocatalytic carbon dioxide reduction process for preparing carbon dioxide products, thereby achieving the electrocatalytic reduction of carbon dioxide to prepare carbon dioxide products at an industrial current density (>800 milliamperes per square centimeter). The method has the advantages of a simple process flow, low cost, and high product selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical carbon dioxide reduction reaction catalysts, and in particular to a preparation method and application of a mixed ionomer-modified cuprous oxide catalyst. Background Art

[0002] The electrochemical CO2 reduction reaction (CO2RR) using renewable intermittent electricity to produce high value-added chemicals has broad application prospects in CO2 utilization and can achieve sustainable production of value-added fuels and chemicals. Among different types of products, multi-carbon products (C2 + ) is highly favored due to its high energy density. However, this process has the following limitations: (1) Low Faradaic efficiency of C2 product: CO2RR may generate a variety of products (such as CO, formic acid, methane, etc.) under neutral conditions, while C2 product (C2) requires CC coupling step. Since CC coupling process is slow and coupling energy barrier is high, C2 + The selectivity is relatively low; (2) The competitive hydrogen evolution reaction (HER) is serious: under neutral conditions, the overpotential of HER is low, competing with CO2RR, especially in the low overpotential region, the violent hydrogen evolution reaction can significantly reduce The coverage of intermediates reduces the chance of CC coupling, resulting in a decrease in the conversion rate of Faradaic efficiency (FE) to C2+ products; (3) Severe carbonate deposition: CO2 reacts with OH in the electrolyte. - The reaction produces carbonate (CO3 2- ) and with cations (such as K + 、Na + ) combine to form insoluble salts, which leads to blockage of the catalyst active sites, increased mass transfer resistance, and increased local pH, thereby reducing the catalytic efficiency and affecting the catalyst stability.

[0003] Based on the above problems, the field of electrocatalytic carbon dioxide reduction has achieved high selectivity of CO2RR pathway by designing and optimizing catalysts through crystal face and morphology control, alloying and doping, and single-atom catalysts. Crystal face and morphology control can increase active sites and mass transfer efficiency by changing the exposed highly active interface and nanostructure design, thus promoting C2 + For example, patent CN117983310A discloses a carbon dioxide electroreduction catalyst and its preparation method. The catalyst is Ag@CuO@Cu-MOF, where Ag is silver, CuO is copper oxide, and Cu-MOF is a Cu metal framework; the CuO is coated on the Ag surface, and the Cu-MOF is coated on the CuO surface. Alloying and doping optimize the adsorption of intermediates by introducing oxophilic metals or non-metallic doping; single-atom catalysts are stabilized by isolated metal sites. Intermediates promote CC coupling. These measures can improve the Faradaic efficiency of the C2 product in electrocatalytic CO2 reduction at low current densities, but they cannot address the severe competitive hydrogen evolution reaction at industrial current densities. Furthermore, the introduction of expensive precious metal elements increases reaction costs and results in low returns on investment. Therefore, the development of catalysts that achieve high C2 Faradaic efficiencies at industrial-grade current densities is urgently needed. Summary of the Invention

[0004] The present invention aims to overcome the above-mentioned problems existing in the carbon dioxide electroreduction catalysts in the prior art and provides a preparation method and application of a mixed ionomer-modified cuprous oxide catalyst. An effective hydrophobic structure is constructed on the Cu2O active site in the form of a physical coating to form a stable and controllable hydrophobic gas-liquid-solid three-phase reaction microinterface. The present invention solves the problems of low Faraday efficiency of carbon dioxide, poor selectivity, severe competitive hydrogen evolution reaction, and carbonate deposition in the existing electrocatalytic carbon dioxide reduction process to produce carbon dioxide products. The present invention realizes the electrocatalytic reduction of carbon dioxide to produce carbon dioxide products at an industrial current density (>800 mA / cm2). The present invention has the advantages of a simple process flow, low cost, and high product selectivity.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a mixed ionomer-modified cuprous oxide catalyst comprises the following steps:

[0007] (1) Dissolve the organic acid sodium salt, copper salt, alkali, and reducing agent in deionized water to obtain corresponding solutions;

[0008] (2) adding the organic acid sodium salt solution to the copper salt solution, stirring evenly, then adding the alkali solution, continuing to stir evenly, adding the reducing agent solution, stirring to react, separating the precipitate after precipitation, washing, and drying to obtain cuprous oxide powder;

[0009] (3) adding cuprous oxide powder to an organic solvent, and adding a hydrophobic ionomer and a proton exchange ionomer, performing ultrasonic mixing reaction, and drying to obtain the mixed ionomer-modified cuprous oxide catalyst.

[0010] The present invention uses a hydrophobic ionomer and a proton exchange ionomer to modify the surface of cuprous oxide powder, constructs an effective hydrophobic structure in the form of physical coating on the Cu2O active site, and forms a stable and controllable hydrophobic gas-liquid-solid three-phase reaction microinterface. The present invention solves the problems of low Faradaic efficiency, poor selectivity, severe competitive hydrogen evolution reaction, and carbonate deposition in the existing electrocatalytic carbon dioxide reduction process to prepare carbon dioxide products. The present invention realizes the electrocatalytic reduction of carbon dioxide to prepare carbon dioxide products at an industrial current density (>800 milliamperes per square centimeter), and has the advantages of simple process flow, low cost, and high product selectivity.

[0011] Preferably, the hydrophobic ionomer is polytetrafluoroethylene emulsion, and the proton exchange ionomer is Nafion emulsion.

[0012] Preferably, the mass concentration of the polytetrafluoroethylene emulsion is 1-5%, and the mass concentration of the Nafion emulsion is 1-5%; the mass ratio of the volume of the hydrophobic ionomer and the proton exchange ionomer added in step (3) to the cuprous oxide powder is 5-400 μL:10-65 μL:10-50 mg.

[0013] Preferably, the organic acid sodium salt in step (1) is sodium citrate, the copper salt is anhydrous copper sulfate, the base is sodium hydroxide and / or potassium hydroxide; and the reducing agent is ascorbic acid.

[0014] Preferably, in the organic acid sodium salt solution obtained in step (1), the mass volume ratio of the organic acid sodium salt to deionized water is 2-10 g:25-100 mL; in the copper salt solution, the mass volume ratio of the copper salt to deionized water is 5-20 g:25-100 mL; in the alkali solution, the mass volume ratio of the alkali to deionized water is 5-25 g:25-100 mL; and in the reducing agent solution, the mass volume ratio of the reducing agent to deionized water is 5-26 g:25-100 mL.

[0015] Preferably, in step (2), the mass ratio of the organic acid sodium salt, the copper salt, the base and the reducing agent added is 2-10:5-20:5-25:5-26.

[0016] Preferably, both step (2) and step (3) are carried out at room temperature.

[0017] Preferably, the drying conditions in step (2) and step (3) are: drying at 55-90°C under vacuum conditions.

[0018] Preferably, in step (2), the precipitate is separated and then washed repeatedly with deionized water and ethanol.

[0019] The present invention also provides an application of a mixed ionomer-modified cuprous oxide catalyst prepared by the above preparation method in an electrocatalytic carbon dioxide reduction reaction.

[0020] Therefore, the present invention has the following beneficial effects:

[0021] (1) Simple and easy operation: The preparation method provided by the present invention does not involve any high temperature and high pressure synthesis conditions, is simple, convenient and easy to operate, does not require large-scale equipment, the raw materials are easily available, the reaction conditions are mild, and is conducive to large-scale production;

[0022] (2) Good catalytic performance: The catalyst prepared by the present invention has good catalytic performance in the experiment of electrocatalytic reduction of carbon dioxide to produce carbon dioxide (0.1 mol / L KHCO3 solution, current density 800 mA / cm 2 ), achieving a C2 product Faradaic efficiency of over 60% and an ethylene Faradaic efficiency of over 30%, which is of great significance for the industrial promotion of carbon dioxide reduction to produce high value-added C2 products;

[0023] (3) Low price and wide application range: The preparation method provided by the present invention does not use any precious metals, and the required materials are inexpensive and easy to purchase, which can effectively reduce costs; the preparation method can be expanded and applied to the development of other catalysts and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a contact angle test graph of the mixed ionomer-modified cuprous oxide catalyst prepared in Example 3 of the present invention.

[0025] Figure 2 This is a scanning electron microscope image of the mixed ionomer-modified cuprous oxide catalyst prepared in Example 3 of the present invention.

[0026] Figure 3 This is a contact angle test diagram of the cuprous oxide catalyst prepared in Comparative Example 1 of the present invention.

[0027] Figure 4 1 is a scanning electron microscope image of the cuprous oxide catalyst prepared in Comparative Example 1 of the present invention.

[0028] Figure 5 This is a diagram of the ethylene Faraday efficiency of the mixed ionomer-modified cuprous oxide catalyst prepared in Example 1 of the present invention at different current densities.

[0029] Figure 6 This is a diagram of the hydrogen Faraday efficiency of the mixed ionomer-modified cuprous oxide catalyst prepared in Example 1 of the present invention at different current densities.

[0030] Figure 7 This is a graph of the ethylene Faraday efficiency of the mixed ionomer-modified cuprous oxide catalyst prepared in Example 5 of the present invention at different current densities.

[0031] Figure 8 This is a diagram of the hydrogen Faraday efficiency of the mixed ionomer-modified cuprous oxide catalyst prepared in Example 5 of the present invention at different current densities.

[0032] Figure 9 This is a diagram of the ethylene Faraday efficiency of the cuprous oxide catalyst prepared in Comparative Example 1 of the present invention at different current densities.

[0033] Figure 10This is a diagram of the hydrogen Faraday efficiency of the cuprous oxide catalyst prepared in Comparative Example 1 of the present invention at different current densities.

[0034] Figure 11 This is a diagram of the ethylene Faraday efficiency of the hydrophobic ionomer-modified cuprous oxide catalyst prepared in Comparative Example 2 of the present invention at different current densities.

[0035] Figure 12 This is a diagram of hydrogen Faraday efficiency of the hydrophobic ionomer-modified cuprous oxide catalyst prepared in Comparative Example 2 of the present invention at different current densities.

[0036] Figure 13 This is a graph of the ethylene Faraday efficiency of the proton exchange ionomer-modified cuprous oxide catalyst prepared in Comparative Example 3 of the present invention at different current densities.

[0037] Figure 14 This is a diagram of hydrogen Faraday efficiency of the proton exchange ionomer-modified cuprous oxide catalyst prepared in Comparative Example 3 of the present invention at different current densities.

[0038] Figure 15 This is a diagram of the ethylene Faraday efficiency of the mixed ionomer-modified cuprous oxide catalyst prepared in Comparative Example 4 of the present invention at different current densities.

[0039] Figure 16 This is a diagram of the hydrogen Faraday efficiency of the mixed ionomer-modified cuprous oxide catalyst prepared in Comparative Example 4 of the present invention at different current densities. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0041] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0042] Overall embodiment:

[0043] A method for preparing a mixed ionomer-modified cuprous oxide catalyst comprises the following steps:

[0044] (1) Dissolve the organic acid sodium salt, copper salt, alkali, and reducing agent in deionized water to obtain corresponding solutions;

[0045] (2) adding the organic acid sodium salt solution to the copper salt solution, stirring evenly, then adding the alkali solution, continuing to stir evenly, adding the reducing agent solution, stirring to react, separating the precipitate after precipitation, washing, and drying to obtain cuprous oxide powder;

[0046] (3) adding cuprous oxide powder to an organic solvent, and adding a hydrophobic ionomer and a proton exchange ionomer, performing ultrasonic mixing reaction, and drying to obtain the mixed ionomer-modified cuprous oxide catalyst.

[0047] As a specific implementation manner, the hydrophobic ionomer is polytetrafluoroethylene emulsion, and the proton exchange ionomer is Nafion emulsion.

[0048] As a specific embodiment, the mass concentration of the polytetrafluoroethylene emulsion is 1~5%, and the mass concentration of the Nafion emulsion is 1~5%; the mass ratio of the volume of the hydrophobic ionomer and the proton exchange ionomer added in step (3) to the cuprous oxide powder is 5~400 μL:10~65 μL:10~50 mg.

[0049] As a specific embodiment, the organic acid sodium salt in step (1) is sodium citrate, the copper salt is anhydrous copper sulfate, the base is sodium hydroxide and / or potassium hydroxide; and the reducing agent is ascorbic acid.

[0050] As a specific embodiment, in the organic acid sodium salt solution obtained in step (1), the mass volume ratio of the organic acid sodium salt to deionized water is 2-10 g:25-100 mL; in the copper salt solution, the mass volume ratio of the copper salt to deionized water is 5-20 g:25-100 mL; in the alkali solution, the mass volume ratio of the alkali to deionized water is 5-25 g:25-100 mL; in the reducing agent solution, the mass volume ratio of the reducing agent to deionized water is 5-26 g:25-100 mL.

[0051] As a specific embodiment, in step (2), the mass ratio of the organic acid sodium salt, the copper salt, the base and the reducing agent added is 2~10:5~20:5~25:5~26.

[0052] As a specific embodiment, both step (2) and step (3) are reacted at room temperature.

[0053] As a specific implementation, the drying conditions in step (2) and step (3) are: drying at 55-90°C under vacuum conditions.

[0054] As a specific embodiment, in step (2), the precipitate is separated and then repeatedly washed with deionized water and ethanol.

[0055] Example 1:

[0056] A method for preparing a mixed ionomer-modified cuprous oxide catalyst comprises the following steps:

[0057] (1) Dissolve 2.2 g of sodium citrate in 25 mL of deionized water and stir magnetically until the sodium citrate is completely dissolved and a transparent solution is formed to obtain a citric acid solution;

[0058] (2) Dissolve 4.8 g of anhydrous copper sulfate in 25 mL of deionized water and stir magnetically until the anhydrous copper sulfate is completely dissolved and a transparent solution is formed to obtain a copper sulfate solution;

[0059] (3) Dissolve 4.8 g of sodium hydroxide in 25 mL of deionized water and stir magnetically until the sodium hydroxide is completely dissolved and a transparent solution is formed to obtain a sodium hydroxide solution;

[0060] (4) Dissolve 5.3 g of ascorbic acid in 25 mL of deionized water and stir magnetically until the ascorbic acid is completely dissolved and a transparent solution is formed to obtain an ascorbic acid solution;

[0061] (5) Add 25 mL of anhydrous copper sulfate solution to 25 mL of sodium citrate solution, stir with a magnetic stirrer for 5 minutes after mixing, continue to add 25 mL of stirred sodium hydroxide solution to the mixed solution, continue to stir with a magnetic stirrer for 5 minutes after mixing, add 25 mL of ascorbic acid solution to the mixed solution after stirring, and then stir for 30 minutes; collect the obtained precipitate and centrifuge it, then repeatedly wash it with deionized water and ethanol, and dry it in vacuum at 55°C overnight to obtain cuprous oxide powder;

[0062] (6) 10 mg of the obtained cuprous oxide powder was mixed with 12.5 μL of Nafion solution (concentration 5 wt%) and 5 μL of diluted PTFE emulsion (concentration 1 wt%), and then dissolved in 1 mL of methanol. The mixture was ultrasonically mixed and then dried at 90° C. to obtain the mixed ionomer-modified cuprous oxide catalyst.

[0063] Example 2:

[0064] A method for preparing a mixed ionomer-modified cuprous oxide catalyst comprises the following steps:

[0065] (1) Dissolve 2.2 g of sodium citrate in 25 mL of deionized water and stir magnetically until the sodium citrate is completely dissolved and a transparent solution is formed to obtain a citric acid solution;

[0066] (2) Dissolve 4.8 g of anhydrous copper sulfate in 25 mL of deionized water and stir magnetically until the anhydrous copper sulfate is completely dissolved and a transparent solution is formed to obtain a copper sulfate solution;

[0067] (3) Dissolve 4.8 g of sodium hydroxide in 25 mL of deionized water and stir magnetically until the sodium hydroxide is completely dissolved and a transparent solution is formed to obtain a sodium hydroxide solution;

[0068] (4) Dissolve 5.3 g of ascorbic acid in 25 mL of deionized water and stir magnetically until the ascorbic acid is completely dissolved and a transparent solution is formed to obtain an ascorbic acid solution;

[0069] (5) Add 25 mL of anhydrous copper sulfate solution to 25 mL of sodium citrate solution, stir with a magnetic stirrer for 5 minutes after mixing, continue to add 25 mL of stirred sodium hydroxide solution to the mixed solution, continue to stir with a magnetic stirrer for 5 minutes after mixing, add 25 mL of ascorbic acid solution to the mixed solution after stirring, and then stir for 30 minutes; collect the obtained precipitate and centrifuge it, then repeatedly wash it with deionized water and ethanol, and dry it in vacuum at 55°C overnight to obtain cuprous oxide powder;

[0070] (6) 10 mg of the obtained cuprous oxide powder was mixed with 12.5 μL of Nafion solution (concentration 5 wt%) and 10 μL of diluted PTFE emulsion (concentration 1 wt%), and then dissolved in 1 mL of methanol. The mixture was ultrasonically mixed and then dried at 90° C. to obtain the mixed ionomer-modified cuprous oxide catalyst.

[0071] Example 3:

[0072] A method for preparing a mixed ionomer-modified cuprous oxide catalyst comprises the following steps:

[0073] (1) Dissolve 2.2 g of sodium citrate in 25 mL of deionized water and stir magnetically until the sodium citrate is completely dissolved and a transparent solution is formed to obtain a citric acid solution;

[0074] (2) Dissolve 4.8 g of anhydrous copper sulfate in 25 mL of deionized water and stir magnetically until the anhydrous copper sulfate is completely dissolved and a transparent solution is formed to obtain a copper sulfate solution;

[0075] (3) Dissolve 4.8 g of sodium hydroxide in 25 mL of deionized water and stir magnetically until the sodium hydroxide is completely dissolved and a transparent solution is formed to obtain a sodium hydroxide solution;

[0076] (4) Dissolve 5.3 g of ascorbic acid in 25 mL of deionized water and stir magnetically until the ascorbic acid is completely dissolved and a transparent solution is formed to obtain an ascorbic acid solution;

[0077] (5) Add 25 mL of anhydrous copper sulfate solution to 25 mL of sodium citrate solution, stir with a magnetic stirrer for 5 minutes after mixing, continue to add 25 mL of stirred sodium hydroxide solution to the mixed solution, continue to stir with a magnetic stirrer for 5 minutes after mixing, add 25 mL of ascorbic acid solution to the mixed solution after stirring, and then stir for 30 minutes; collect the obtained precipitate and centrifuge it, then repeatedly wash it with deionized water and ethanol, and dry it in vacuum at 55°C overnight to obtain cuprous oxide powder;

[0078] (6) 10 mg of the obtained cuprous oxide powder was mixed with 12.5 μL of Nafion solution (concentration 5 wt%) and 20 μL of diluted PTFE emulsion (concentration 1 wt%) and dissolved in 1 mL of methanol. The mixture was ultrasonically mixed and then dried at 90°C to obtain the mixed ionomer-modified cuprous oxide catalyst. The hydrophilicity of the reaction interface was characterized by contact angle test, as shown in FIG. Figure 1 As shown in , the interface contact angle is 137.3°, showing strong hydrophobicity. In addition, the microstructure of the catalyst layer was characterized by electron scanning electron microscopy, as shown in Figure 2 As shown in , it can be observed that the surface of the catalyst layer is wrapped with a hydrophobic proton exchange ionomer layer.

[0079] Example 4:

[0080] A method for preparing a mixed ionomer-modified cuprous oxide catalyst comprises the following steps:

[0081] (1) Dissolve 2.2 g of sodium citrate in 25 mL of deionized water and stir magnetically until the sodium citrate is completely dissolved and a transparent solution is formed to obtain a citric acid solution;

[0082] (2) Dissolve 4.8 g of anhydrous copper sulfate in 25 mL of deionized water and stir magnetically until the anhydrous copper sulfate is completely dissolved and a transparent solution is formed to obtain a copper sulfate solution;

[0083] (3) Dissolve 4.8 g of sodium hydroxide in 25 mL of deionized water and stir magnetically until the sodium hydroxide is completely dissolved and a transparent solution is formed to obtain a sodium hydroxide solution;

[0084] (4) Dissolve 5.3 g of ascorbic acid in 25 mL of deionized water and stir magnetically until the ascorbic acid is completely dissolved and a transparent solution is formed to obtain an ascorbic acid solution;

[0085] (5) Add 25 mL of anhydrous copper sulfate solution to 25 mL of sodium citrate solution, stir with a magnetic stirrer for 5 minutes after mixing, continue to add 25 mL of stirred sodium hydroxide solution to the mixed solution, continue to stir with a magnetic stirrer for 5 minutes after mixing, add 25 mL of ascorbic acid solution to the mixed solution after stirring, and then stir for 30 minutes; collect the obtained precipitate and centrifuge it, then repeatedly wash it with deionized water and ethanol, and dry it in vacuum at 55°C overnight to obtain cuprous oxide powder;

[0086] (6) 10 mg of the obtained cuprous oxide powder was mixed with 12.5 μL of Nafion solution (concentration 5 wt%) and 40 μL of diluted PTFE emulsion (concentration 1 wt%), and then dissolved in 1 mL of methanol. The mixture was ultrasonically mixed and then dried at 90° C. to obtain the mixed ionomer-modified cuprous oxide catalyst.

[0087] Example 5:

[0088] A method for preparing a mixed ionomer-modified cuprous oxide catalyst comprises the following steps:

[0089] (1) Dissolve 2.2 g of sodium citrate in 25 mL of deionized water and stir magnetically until the sodium citrate is completely dissolved and a transparent solution is formed to obtain a citric acid solution;

[0090] (2) Dissolve 4.8 g of anhydrous copper sulfate in 25 mL of deionized water and stir magnetically until the anhydrous copper sulfate is completely dissolved and a transparent solution is formed to obtain a copper sulfate solution;

[0091] (3) Dissolve 4.8 g of sodium hydroxide in 25 mL of deionized water and stir magnetically until the sodium hydroxide is completely dissolved and a transparent solution is formed to obtain a sodium hydroxide solution;

[0092] (4) Dissolve 5.3 g of ascorbic acid in 25 mL of deionized water and stir magnetically until the ascorbic acid is completely dissolved and a transparent solution is formed to obtain an ascorbic acid solution;

[0093] (5) Add 25 mL of anhydrous copper sulfate solution to 25 mL of sodium citrate solution, stir with a magnetic stirrer for 5 minutes after mixing, continue to add 25 mL of stirred sodium hydroxide solution to the mixed solution, continue to stir with a magnetic stirrer for 5 minutes after mixing, add 25 mL of ascorbic acid solution to the mixed solution after stirring, and then stir for 30 minutes; collect the obtained precipitate and centrifuge it, then repeatedly wash it with deionized water and ethanol, and dry it in vacuum at 55°C overnight to obtain cuprous oxide powder;

[0094] (6) 10 mg of the obtained cuprous oxide powder was mixed with 12.5 μL of Nafion solution (concentration 5 wt%) and 80 μL of diluted PTFE emulsion (concentration 1 wt%), and then dissolved in 1 mL of methanol. The mixture was ultrasonically mixed and then dried at 90° C. to obtain the mixed ionomer-modified cuprous oxide catalyst.

[0095] Comparative Example 1 (without PTFE and Nafion modification):

[0096] A method for preparing a cuprous oxide catalyst without ionomer modification, comprising the following steps:

[0097] (1) Dissolve 2.2 g of sodium citrate in 25 mL of deionized water and stir magnetically until the sodium citrate is completely dissolved and a transparent solution is formed to obtain a citric acid solution;

[0098] (2) Dissolve 4.8 g of anhydrous copper sulfate in 25 mL of deionized water and stir magnetically until the anhydrous copper sulfate is completely dissolved and a transparent solution is formed to obtain a copper sulfate solution;

[0099] (3) Dissolve 4.8 g of sodium hydroxide in 25 mL of deionized water and stir magnetically until the sodium hydroxide is completely dissolved and a transparent solution is formed to obtain a sodium hydroxide solution;

[0100] (4) Dissolve 5.3 g of ascorbic acid in 25 mL of deionized water and stir magnetically until the ascorbic acid is completely dissolved and a transparent solution is formed to obtain an ascorbic acid solution;

[0101] (5) Add 25 mL of anhydrous copper sulfate solution to 25 mL of sodium citrate solution, stir with a magnetic stirrer for 5 minutes after mixing, continue to add 25 mL of stirred sodium hydroxide solution to the mixed solution, continue to stir with a magnetic stirrer for 5 minutes after mixing, add 25 mL of ascorbic acid solution to the mixed solution after stirring, and then stir for 30 minutes; collect the obtained precipitate and centrifuge it, then repeatedly wash it with deionized water and ethanol, and dry it in vacuum at 55°C overnight to obtain cuprous oxide powder;

[0102] (6) Take 10 mg of the obtained cuprous oxide powder and dissolve it in 1 mL of methanol solution. After mixing and ultrasonication, dry it at 90 °C to prepare a cuprous oxide catalyst. Use contact angle test to characterize the hydrophilicity and hydrophobicity of its reaction interface, such as Figure 3 As shown in , the interface contact angle is 23.6°, showing weak hydrophobicity. In addition, the microstructure of the catalyst layer was characterized by electron scanning electron microscopy, as shown in Figure 4 As shown in , the surface of the catalyst layer is not coated with an ionomer layer.

[0103] Comparative Example 2 (modified with PTFE only):

[0104] A method for preparing a hydrophobic ionomer-modified cuprous oxide catalyst comprises the following steps:

[0105] (1) Dissolve 2.2 g of sodium citrate in 25 mL of deionized water and stir magnetically until the sodium citrate is completely dissolved and a transparent solution is formed to obtain a citric acid solution;

[0106] (2) Dissolve 4.8 g of anhydrous copper sulfate in 25 mL of deionized water and stir magnetically until the anhydrous copper sulfate is completely dissolved and a transparent solution is formed to obtain a copper sulfate solution;

[0107] (3) Dissolve 4.8 g of sodium hydroxide in 25 mL of deionized water and stir magnetically until the sodium hydroxide is completely dissolved and a transparent solution is formed to obtain a sodium hydroxide solution;

[0108] (4) Dissolve 5.3 g of ascorbic acid in 25 mL of deionized water and stir magnetically until the ascorbic acid is completely dissolved and a transparent solution is formed to obtain an ascorbic acid solution;

[0109] (5) Add 25 mL of anhydrous copper sulfate solution to 25 mL of sodium citrate solution, stir with a magnetic stirrer for 5 minutes after mixing, continue to add 25 mL of stirred sodium hydroxide solution to the mixed solution, continue to stir with a magnetic stirrer for 5 minutes after mixing, add 25 mL of ascorbic acid solution to the mixed solution after stirring, and then stir for 30 minutes; collect the obtained precipitate and centrifuge it, then repeatedly wash it with deionized water and ethanol, and dry it in vacuum at 55°C overnight to obtain cuprous oxide powder;

[0110] (6) 10 mg of the obtained cuprous oxide powder was mixed with 10 μL of PTFE solution (concentration 1 wt%) and dissolved in 1 mL of methanol. The mixture was ultrasonically mixed and then dried at 90° C. to obtain the hydrophobic ionomer-modified cuprous oxide catalyst.

[0111] Comparative Example 3 (modification with Nafion solution only):

[0112] A method for preparing a proton exchange ionomer-modified cuprous oxide catalyst comprises the following steps:

[0113] (1) Dissolve 2.2 g of sodium citrate in 25 mL of deionized water and stir magnetically until the sodium citrate is completely dissolved and a transparent solution is formed to obtain a citric acid solution;

[0114] (2) Dissolve 4.8 g of anhydrous copper sulfate in 25 mL of deionized water and stir magnetically until the anhydrous copper sulfate is completely dissolved and a transparent solution is formed to obtain a copper sulfate solution;

[0115] (3) Dissolve 4.8 g of sodium hydroxide in 25 mL of deionized water and stir magnetically until the sodium hydroxide is completely dissolved and a transparent solution is formed to obtain a sodium hydroxide solution;

[0116] (4) Dissolve 5.3 g of ascorbic acid in 25 mL of deionized water and stir magnetically until the ascorbic acid is completely dissolved and a transparent solution is formed to obtain an ascorbic acid solution;

[0117] (5) Add 25 mL of anhydrous copper sulfate solution to 25 mL of sodium citrate solution, stir with a magnetic stirrer for 5 minutes after mixing, continue to add 25 mL of stirred sodium hydroxide solution to the mixed solution, continue to stir with a magnetic stirrer for 5 minutes after mixing, add 25 mL of ascorbic acid solution to the mixed solution after stirring, and then stir for 30 minutes; collect the obtained precipitate and centrifuge it, then repeatedly wash it with deionized water and ethanol, and dry it in vacuum at 55°C overnight to obtain cuprous oxide powder;

[0118] (6) 10 mg of the obtained cuprous oxide powder was mixed with 12.5 μL of Nafion solution (concentration 5 wt%) and dissolved in 1 mL of methanol. The mixture was ultrasonically mixed and then dried at 90° C. to obtain the proton exchange ionomer-modified cuprous oxide catalyst.

[0119] Comparative Example 4 (changing the type of hydrophobic ionomer):

[0120] A method for preparing a mixed ionomer-modified cuprous oxide catalyst comprises the following steps:

[0121] (1) Dissolve 2.2 g of sodium citrate in 25 mL of deionized water and stir magnetically until the sodium citrate is completely dissolved and a transparent solution is formed to obtain a citric acid solution;

[0122] (2) Dissolve 4.8 g of anhydrous copper sulfate in 25 mL of deionized water and stir magnetically until the anhydrous copper sulfate is completely dissolved and a transparent solution is formed to obtain a copper sulfate solution;

[0123] (3) Dissolve 4.8 g of sodium hydroxide in 25 mL of deionized water and stir magnetically until the sodium hydroxide is completely dissolved and a transparent solution is formed to obtain a sodium hydroxide solution;

[0124] (4) Dissolve 5.3 g of ascorbic acid in 25 mL of deionized water and stir magnetically until the ascorbic acid is completely dissolved and a transparent solution is formed to obtain an ascorbic acid solution;

[0125] (5) Add 25 mL of anhydrous copper sulfate solution to 25 mL of sodium citrate solution, stir with a magnetic stirrer for 5 minutes after mixing, continue to add 25 mL of stirred sodium hydroxide solution to the mixed solution, continue to stir with a magnetic stirrer for 5 minutes after mixing, add 25 mL of ascorbic acid solution to the mixed solution after stirring, and then stir for 30 minutes; collect the obtained precipitate and centrifuge it, then repeatedly wash it with deionized water and ethanol, and dry it in vacuum at 55°C overnight to obtain cuprous oxide powder;

[0126] (6) 10 mg of the obtained cuprous oxide powder was mixed with 12.5 μL of Nafion solution (concentration 5 wt%) and 10 μL of diluted poly[3,3,4,4-tetra-fluoro-2-methyl-2-(1,1,2,2,3-pentafluoro-3-(trifluoromethoxy)butyl)-5,5-bis(perfluoroethyl)tetrahydrofuran] emulsion (concentration 1 wt%) and dissolved in 1 mL of methanol. After mixing and ultrasonication, the mixture was dried at 90°C to obtain the mixed ionomer-modified cuprous oxide catalyst.

[0127] Application examples:

[0128] 10 mg of each of the mixed ionomer-modified cuprous oxide catalysts prepared in Examples 1 and 5 were dissolved in 1 mL of methanol, mixed, and then ultrasonically sprayed onto carbon paper (1 cm × 1 cm). After drying, a catalyst layer with successful catalyst loading was obtained. The performance of the catalyst was evaluated using a membrane electrode system. Under the conditions of a 0.1 mol / L KHCO3 electrolyte and a continuous flow of 40 sccm of carbon dioxide, different currents were applied to the system, and the Faradaic efficiency (FE) of each product (ethylene and hydrogen) at the corresponding current density was measured. The results are shown in Figure 2. Figures 5 to 8 The results show that the mixed ionomer-modified cuprous oxide catalyst prepared in the present invention has a wide reaction range and maintains excellent performance at high current density, and the competitive hydrogen evolution reaction is significantly reduced at industrial current density.

[0129] Comparative application examples:

[0130] 10 mg of each catalyst prepared in Comparative Examples 1-4 was mixed and dissolved in 1 mL of methanol. After ultrasonic mixing, the mixture was sprayed onto carbon paper (1 cm × 1 cm area). After drying, a catalyst layer with successful catalyst loading was obtained. The performance of the catalyst was evaluated using a membrane electrode system. Under the conditions of 0.1 mol / L KHCO3 electrolyte and a continuous flow of 40 sccm of carbon dioxide, different currents were applied to the system, and the Faradaic efficiency (FE) of each product (ethylene, hydrogen) at the corresponding current density was measured. The results are shown below. Figures 9 to 16 As shown in . The results show that the catalyst surface in Comparative Example 1 is not coated with a mixed ionomer, the competitive hydrogen evolution reaction is severe, the hydrogen evolution reaction is more severe at high current density, and the hydrogen Faraday efficiency is significantly improved at industrial current density. The catalyst surface in Comparative Example 2 is only coated with the hydrophobic ionomer PTFE, and is not coated with a proton exchange ionomer. Due to the lack of an effective proton transmission channel, the proton supply during the reaction is insufficient. When the current density further increases, the side reaction hydrogen evolution reaction (HER) is more serious. The catalyst surface in Comparative Example 3 is only coated with the proton exchange ionomer Nafion emulsion, and is not coated with a hydrophobic ionomer. Due to the slow local carbon dioxide supply, the local carbon dioxide supply at the reaction interface is insufficient, resulting in a decrease in the Faraday efficiency of the carbon two product. The surface of the catalyst in Comparative Example 4 is coated with a proton exchange ionomer Nafion emulsion and a hydrophobic ionomer poly[3,3,4,4-tetra-fluoro-2-methyl-2-(1,1,2,2,3-pentafluoro-3-(trifluoromethoxy)butyl)-5,5-bis(perfluoroethyl)tetrahydrofuran] (PCR). Due to the different hydrophobic ionomers' different ability to regulate local carbon dioxide / water, a comparison found that compared with PTFE, the carbon dioxide diffusion coefficient and porosity of PCR were lower, and the stability of its ability to regulate local carbon dioxide / water was poor, resulting in insufficient stability of the electrocatalytic carbon dioxide reduction to produce carbon dioxide products at high current density, and a relatively low Faradaic efficiency.

[0131] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the scope of protection of the claims of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a mixed ionomer-modified cuprous oxide catalyst, comprising: The steps are as follows: (1) Dissolve the organic acid sodium salt, copper salt, alkali, and reducing agent in deionized water to obtain corresponding solutions; (2) adding the organic acid sodium salt solution to the copper salt solution, stirring evenly, then adding the alkali solution, continuing to stir evenly, adding the reducing agent solution, stirring to react, separating the precipitate after precipitation, washing, and drying to obtain cuprous oxide powder; (3) adding cuprous oxide powder to an organic solvent, and adding a hydrophobic ionomer and a proton exchange ionomer, subjecting the mixture to an ultrasonic mixing reaction, and drying the mixture to obtain the mixed ionomer-modified cuprous oxide catalyst; The hydrophobic ionomer is a polytetrafluoroethylene emulsion with a mass concentration of 1-5%, and the proton exchange ionomer is a Nafion emulsion with a mass concentration of 1-5%. The mass ratio of the added hydrophobic ionomer and proton exchange ionomer to the cuprous oxide powder is 5-400 μL:10-65 μL:10-50 mg.

2. The method for preparing the mixed ionomer-modified cuprous oxide catalyst according to claim 1, wherein: The mass concentration of the polytetrafluoroethylene emulsion is 1%, and the mass concentration of the Nafion emulsion is 5%.

3. The method for preparing the mixed ionomer-modified cuprous oxide catalyst according to claim 1, wherein: The organic acid sodium salt in step (1) is sodium citrate, the copper salt is anhydrous copper sulfate, the base is sodium hydroxide and / or potassium hydroxide; and the reducing agent is ascorbic acid.

4. The method for preparing the mixed ionomer-modified cuprous oxide catalyst according to claim 1 or 3, wherein: In the organic acid sodium salt solution obtained in step (1), the mass volume ratio of the organic acid sodium salt to deionized water is 2-10 g:25-100 mL; in the copper salt solution, the mass volume ratio of the copper salt to deionized water is 5-20 g:25-100 mL; in the alkali solution, the mass volume ratio of the alkali to deionized water is 5-25 g:25-100 mL; in the reducing agent solution, the mass volume ratio of the reducing agent to deionized water is 5-26 g:25-100 mL.

5. The method for preparing the mixed ionomer-modified cuprous oxide catalyst according to claim 1 or 3, wherein: In step (2), the mass ratio of the organic acid sodium salt, copper salt, alkali and reducing agent added is 2~10:5~20:5~25:5~26.

6. The method for preparing the mixed ionomer-modified cuprous oxide catalyst according to claim 1, wherein: Both steps (2) and (3) are carried out at room temperature.

7. The method for preparing the mixed ionomer-modified cuprous oxide catalyst according to claim 1, wherein: The drying conditions in step (2) and step (3) are: drying at 55-90°C under vacuum conditions.

8. The method for preparing the mixed ionomer-modified cuprous oxide catalyst according to claim 1, wherein: In step (2), the precipitate is separated and then washed repeatedly with deionized water and ethanol.

9. An application of a mixed ionomer-modified cuprous oxide catalyst prepared by the preparation method according to any one of claims 1 to 8, characterized in that: Used for electrocatalytic carbon dioxide reduction reaction.

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