Electrode catalyst for preparing ethylene through electrolytic reduction of carbon dioxide as well as preparation method and application of electrode catalyst

Abstract

The invention provides an electrode catalyst for preparing ethylene through electrolytic reduction of carbon dioxide and a preparation method and application thereof.The electrode catalyst for preparing ethylene through electrolytic reduction of carbon dioxide comprises a conductive carrier and copper-based nanoparticles, and the copper-based nanoparticles are loaded on the conductive carrier; the total weight of the conductive carrier is 100%, and the loading capacity of the copper-based nanoparticles is 0.3 wt%-65 wt%. The electrode catalyst for preparing ethylene through electrolytic reduction of carbon dioxide provided by the invention has more excellent activity of electrochemical reduction of carbon dioxide.

Description

Technical Field

[0001] The invention relates to an electrode catalyst for electrolytic reduction of carbon dioxide to prepare ethylene and a preparation method and application thereof, belonging to the technical field of electrochemical reduction of carbon dioxide. Background Art

[0002] Carbon dioxide (CO 2 ) has become a new method to utilize renewable energy to utilize CO 2 When using copper (Cu)-based catalysts, CO 2 Electroreduction platforms can produce multi-carbon (C2+) fuels and chemicals with nearly net-zero emissions, helping to close the anthropogenic carbon cycle. Nevertheless, the rational design and development of copper-based catalysts is essential for achieving highly selective and efficient CO 2 Electroreduction is crucial. However, since metallic copper is the only element that can achieve carbon-carbon coupling, most of the existing electrode catalysts for electrocatalytic reduction of carbon dioxide are directly based on metallic copper and its oxides, with a high metal content, resulting in high electrode costs. At the same time, since copper nanoparticles are difficult to disperse during electrode formation, stacked metal particles will increase the resistance at the electrode-electrolyte interface, thereby increasing the overpotential in electrode testing. In addition, some metal sites may not be in sufficient contact with the reactants during the electrolysis reaction, or may be dissolved in the electrolyte, resulting in deterioration of the electrolyte and affecting the electrolysis efficiency.

[0003] Therefore, providing a new type of electrode catalyst for electrolytic reduction of carbon dioxide to ethylene and its preparation method and application has become a technical problem that urgently needs to be solved in this field. Summary of the invention

[0004] In order to solve the above-mentioned shortcomings and deficiencies, an object of the present invention is to provide an electrode catalyst for electrolytic reduction of carbon dioxide to produce ethylene.

[0005] Another object of the present invention is to provide a method for preparing the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene.

[0006] Another object of the present invention is to provide the use of the above-mentioned electrode catalyst for electrolytic reduction of carbon dioxide to produce ethylene in the electrochemical reduction of carbon dioxide to produce ethylene.

[0007] To achieve the above object, on the one hand, the present invention provides an electrode catalyst for electrolytic reduction of carbon dioxide to ethylene. Among them, the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene includes a conductive carrier and copper-based nanoparticles, and the copper-based nanoparticles are loaded on the conductive carrier; based on the total weight of the conductive carrier being 100%, the loading amount of the copper-based nanoparticles is 0.3 wt% - 65 wt%, preferably 5 wt% - 45 wt%, and more preferably 15 wt% - 45 wt%.

[0008] As a specific embodiment of the above-mentioned electrode catalyst of the present invention, among them, the copper-based nanoparticles include copper nanoparticles or copper alloy nanoparticles.

[0009] As a specific embodiment of the above-mentioned electrode catalyst of the present invention, among them, the metal elements other than copper in the copper alloy nanoparticles include one or a combination of several of Zn, Fe, Co, etc. The present invention does not make specific requirements on the content ratio between the various metal elements in the copper alloy nanoparticles, and can be reasonably adjusted according to the actual on-site operation needs.

[0010] As a specific embodiment of the above-mentioned electrode catalyst of the present invention, among them, the copper-based nanoparticles include copper-based nanoparticles after surface modification with non-metallic elements, that is, copper-based nanoparticles doped with non-metallic elements. Using copper-based nanoparticles after surface modification with non-metallic elements can improve the adsorption effect of carbon dioxide, thereby improving the activity of the catalyst and the ethylene yield.

[0011] As a specific embodiment of the above-mentioned electrode catalyst of the present invention, among them, the non-metallic elements include one or a combination of several of nitrogen, phosphorus, sulfur, etc. Among them, the surface modification with non-metallic elements can be realized by existing conventional methods. The present invention does not make specific requirements on the corresponding non-metallic element source of the non-metallic elements and the doping amount of the non-metallic elements, and can also be reasonably adjusted according to the actual on-site operation needs. For example, in some embodiments of the present invention, the surface modification with non-metallic elements can be realized by an electrochemical method, and the corresponding sulfur source can be Na 2 S, etc.

[0012] As a specific embodiment of the above-mentioned electrode catalyst of the present invention, among them, the particle size of the copper-based nanoparticles is 0.3 - 850 nm.

[0013] As a specific embodiment of the above-mentioned electrode catalyst of the present invention, among them, the conductive carrier includes any one of conductive carbon materials and C 3 N 4 and so on.

[0014] As a specific embodiment of the electrode catalyst described above in the present invention, when the conductive carrier is a conductive carbon material, the loading amount of the copper-based nanoparticles is 15 wt% - 45 wt%.

[0015] As a specific embodiment of the electrode catalyst described above in the present invention, the conductive carbon material includes carbon black and / or graphene, etc. Using carbon black and / or graphene, etc. as the conductive carrier in the present invention can not only provide a large specific surface area, but also increase the conductivity of the electrode.

[0016] The electrode catalyst for electrolytic reduction of carbon dioxide to ethylene provided by the present invention can be prepared by a variety of different preparation methods. To further illustrate the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene of the present invention, on the other hand, the present invention also provides a preparation method of the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene described above. The preparation method includes the following steps:

[0017] Step 1, uniformly mix a conductive carrier dispersion liquid, a precursor solution containing at least a copper salt, and a dispersion aid to obtain a mixed solution;

[0018] Step 2, add a reducing agent to the mixed solution, and stir while heating in a water bath to obtain the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene.

[0019] As a specific embodiment of the above-mentioned preparation method of the present invention, step 1 further includes: uniformly mixing a conductive carrier dispersion liquid, a precursor solution containing at least a copper salt, a templating agent, and a dispersion aid to obtain a mixed solution. When preparing the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene, adding a templating agent can induce changes in the morphology of the copper-based nanoparticles, thereby exposing more high-activity crystal planes.

[0020] The present invention does not make specific requirements on the mixing order of the conductive carrier dispersion liquid, the precursor solution containing at least a copper salt, the templating agent, and the dispersion aid in step 1 of the above-mentioned preparation method, and can be reasonably adjusted according to the actual on-site operation needs, as long as the four are mixed before adding the reducing agent. In some relatively preferred embodiments of the present invention, first uniformly mix the precursor solution containing at least a copper salt and the dispersion aid, then uniformly mix the conductive carrier dispersion liquid and the templating agent, and finally uniformly mix the mixed liquids obtained in the two steps.

[0021] As a specific embodiment of the above-described preparation method of the present invention, in step 1, the ratio of the volume of the template agent to the total volume of the conductive carrier dispersion liquid and the precursor solution containing at least a copper salt is 5:1 - 20:1. By using the template agent, the present invention can induce a change in the morphology of the copper-based nanoparticles, exposing more highly active crystal planes. Thus, when using the prepared catalyst to catalyze the electrochemical reduction of carbon dioxide to produce ethylene, more C2 products can be generated, and correspondingly, the yield of ethylene will also increase.

[0022] As a specific embodiment of the above-described preparation method of the present invention, in step 1, the template agent is an aldehyde-based template agent.

[0023] As a specific embodiment of the above-described preparation method of the present invention, in step 1, the aldehyde-based template agent includes one or a combination of several of formaldehyde, acetaldehyde, propionaldehyde, etc.

[0024] As a specific embodiment of the above-described preparation method of the present invention, in step 1, the concentration of the conductive carrier in the conductive carrier dispersion liquid is less than or equal to 5 mg / mL;

[0025] The concentration of Cu in the precursor solution containing at least a copper salt 2+ is 50 mg / mL - 150 mg / mL.

[0026] When the copper-based nanoparticles are copper alloy nanoparticles, in step 1 of the above-described preparation method, appropriate metal salts can be selected according to the actual situation of the metal elements contained in the copper alloy and dissolved in the precursor solution.

[0027] As a specific embodiment of the above-described preparation method of the present invention, in step 1, the molar ratio of the dispersion aid to the metal elements contained in the mixed solution is 1:2 - 1:1. When the copper-based nanoparticles are copper alloy nanoparticles, the metal elements at this time are all the metal elements contained in the mixed solution.

[0028] As a specific embodiment of the above-described preparation method of the present invention, the dispersion aid includes one or a combination of several surfactants such as trisodium citrate, sodium dodecyl sulfate, sodium hexadecyl sulfate, triethanolamine, glycerol fatty acid ester, quaternary ammonium compound, and polyvinylpyrrolidone.

[0029] As a specific embodiment of the above-described preparation method of the present invention, in step 1, the copper salt is copper nitrate and / or copper chloride.

[0030] As a specific embodiment of the above-described preparation method of the present invention, in step 2, the reducing agent includes any one of hydrazine hydrate or hydroxylamine.

[0031] The present invention does not make specific requirements on the dosage and concentration of the reducing agent, etc., and can be reasonably adjusted according to the actual on-site operation needs. For example, in some relatively preferred embodiments of the present invention, the mass concentration of the reducing agent is 60%-85%; and the addition amount of the reducing agent is based on dropping until no more bubbles are generated in the system. In some embodiments of the present invention, the reducing agent can be, for example, an aqueous hydrazine solution with a mass concentration of 85%, that is, the mass concentration of hydrazine in the aqueous hydrazine solution is 85%.

[0032] As a specific embodiment of the above-mentioned preparation method of the present invention, in step 2, the temperature of the water bath heating is 45°C - 80°C.

[0033] As a specific embodiment of the above-mentioned preparation method of the present invention, in step 2, the reducing agent is added dropwise to the mixed solution.

[0034] The present invention does not make specific requirements on the mixing order of the conductive carrier dispersion liquid, the precursor solution containing at least copper salt, and the dispersion aid in step 1 of the above-mentioned preparation method, and can be reasonably adjusted according to the actual on-site operation needs, as long as it is ensured that the three are mixed before adding the reducing agent. In some relatively preferred embodiments of the present invention, the precursor solution containing at least copper salt and the dispersion aid are first mixed evenly, and then the obtained mixed solution is mixed evenly with the conductive carrier dispersion liquid.

[0035] As a specific embodiment of the above-mentioned preparation method of the present invention, step 1 includes the following specific steps:

[0036] Step 11, ultrasonically disperse the conductive carrier in the dispersant to form a carrier dispersion liquid.

[0037] As a specific embodiment of the above-mentioned preparation method of the present invention, in step 11, the dispersant is any one or a combination of isopropanol, ethanol, and acetone.

[0038] The above-mentioned preparation method of the present invention can prepare a catalyst with copper-based nanoparticles loaded on a conductive carrier. Through the support expansion of the conductive material, the problem of large internal resistance caused by the stacking of copper-based nanoparticles is reduced.

[0039] The catalyst prepared by the above-mentioned preparation method of the present invention is a highly dispersed supported copper-based catalyst. During the preparation process, adding a dispersion aid can inhibit the excessive growth of active phase crystal grains during the loading process, making the metal particles highly dispersed on the carrier. Compared with the catalyst obtained by physically mixing copper particles and carbon black, the catalyst provided by the present invention has a lower cell voltage and internal resistance. By changing the total amount of the precursor solution containing at least copper salt, the particle size of the copper-based nanoparticles loaded on the conductive carrier can be adjusted.

[0040] On the other hand, the present invention also provides an application of the above-mentioned electrode catalyst for electrolytic reduction of carbon dioxide to ethylene in the electrochemical reduction of carbon dioxide to prepare ethylene.

[0041] As a specific embodiment of the above-mentioned application of the present invention, the application includes:

[0042] Step a: Uniformly disperse the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene in a solvent to obtain a slurry;

[0043] Step b: Coat the slurry on an electrode and then dry it to obtain an electrode loaded with the catalyst;

[0044] Step c: Install the electrode loaded with the catalyst in a gas diffusion electrolytic cell to electrochemically reduce carbon dioxide to prepare ethylene, that is, electrolytically reduce carbon dioxide to generate ethylene.

[0045] As a specific embodiment of the above-mentioned application of the present invention, the electrode is a hydrophobic carbon paper electrode.

[0046] The present invention does not make specific requirements for the solvent used in step a of the above-mentioned application, and the specific substance of the solvent can be reasonably selected according to the actual situation such as the electrode used in step b. For example, in some embodiments of the present invention, when the electrode is a hydrophobic carbon paper electrode, the solvent is a mixed solvent of isopropyl alcohol and deionized water.

[0047] Compared with the prior art, the beneficial technical effects that can be achieved by the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene provided by the present invention include:

[0048] 1) The electrode catalyst for electrolytic reduction of carbon dioxide to ethylene provided by the present invention includes a conductive carrier and copper-based nanoparticles, and the copper-based nanoparticles are loaded on the conductive carrier; through the support and expansion of the conductive carrier material, the problem of large internal resistance caused by the stacking of copper-based nanoparticles is reduced; at the same time, the use of a conductive carrier with a large specific surface area (such as a conductive carbon material) increases the loading rate of metal active sites, so that more metal active sites can be exposed on the electrode surface, thereby making the catalyst have more excellent electrochemical reduction activity of carbon dioxide.

[0049] 2) When spraying a fixed weight of the electrode catalyst on a fixed electrode area, compared with the existing electrode catalysts for electrocatalytic reduction of carbon dioxide, the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene prepared by loading copper-based nanoparticles on a conductive carrier in the present invention reduces the metal usage by 50%, thereby achieving the purpose of reducing the total amount of copper metal in the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0051] Figure 1 5% Cu@C prepared in Example 2 of the present invention 3 N 4 High-magnification transmission electron microscopy image.

[0052] Figure 2 High-magnification transmission electron microscopy image of the electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene prepared in Example 4 of the present invention. Detailed implementation manners

[0053] It should be noted that the term "including" and any of its variations in the description, claims and accompanying drawings of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0054] The "range" disclosed in the present invention is given in the form of a lower limit and an upper limit. There can be one or more lower limits, and one or more upper limits. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundary of a particular range. All ranges defined in this way are combinable, that is, any lower limit can be combined with any upper limit to form a range. For example, for a specific parameter, ranges of 60-120 and 80-110 are listed, and it is understood that ranges of 60-110 and 80-120 are also expected. In addition, if the minimum range values listed are 1 and 2, and the maximum range values listed are 3, 4 and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0055] In the present invention, unless otherwise stated, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been fully listed in the present invention, and "0-5" is only an abbreviated representation of these numerical combinations.

[0056] In the present invention, if there is no special instruction, all the implementation manners and preferred implementation manners mentioned in the present invention can be combined with each other to form a new technical solution.

[0057] In the present invention, unless otherwise specified, all the technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0058] In the present invention, unless otherwise specified, all the steps mentioned herein can be carried out in sequence or randomly, but preferably in sequence. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out in sequence, or may also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0059] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the attached tables, drawings and embodiments. The following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0060] Comparative Example 1

[0061] This comparative example provides a series of electrode catalysts for the electrolytic reduction of carbon dioxide to ethylene, which are prepared by a preparation method including the following specific steps:

[0062] (1) Preparation of the conductive carrier dispersion: Take 200 mg of dry conductive carrier (MOF, specifically MIL-101) and add it to 90 mL of deionized water. Ultrasonically disperse it until it is in a uniform state to obtain a mixed solution. Transfer the mixed solution to a 100 mL volumetric flask and make up the volume to 100 mL with deionized water to obtain a carrier dispersion solution with a concentration of 2 mg / mL. Shake well and set aside.

[0063] (2) Preparation of the copper precursor solution: Weigh 3.802 g of copper nitrate trihydrate and add it to 9.15 g of deionized water. After fully dissolving, a dark blue copper nitrate solution is obtained (the total volume of the solution is 10 mL, and the Cu 2+ concentration is 100 mg / mL).

[0064] (3) Prepare a series of xCu@MOF (x = 5 - 45%) electrocatalysts by the in-situ impregnation reduction method. The specific operation is as follows:

[0065] Take four clean 100 mL beakers, and add 50 mL of the carrier dispersion solution into each of the four beakers; under continuous stirring conditions, use a pipette to separately pipette different volumes of the copper precursor solution and add them into the four beakers respectively. The volumes of the copper precursor solution are 50 μL, 100 μL, 200 μL, and 300 μL respectively; then add 20 mg, 40 mg, 80 mg, and 120 mg of trisodium citrate into the four beakers respectively; then heat the obtained mixed solution in a water bath to 60 °C and stir for 8 h, and then add 0.5 mL of hydrazine hydrate (85 wt%) dropwise into the reaction solution, and continue to stir at 60 °C for 2 h until no more bubbles emerge from the solution.

[0066] (4) Catalyst washing: After cooling the temperature of the suspension obtained in step (3) to room temperature, carry out centrifugal separation and dispersion, discard the supernatant, and wash the precipitate with ultrapure water and ethanol three times or more in sequence, and finally dry the washed wet precipitate in a vacuum drying oven at 60 - 85 °C overnight to obtain the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene.

[0067] The electrode catalyst for electrolytic reduction of carbon dioxide to ethylene obtained in this comparative example includes a MOF conductive carrier and copper nanoparticles, and the copper nanoparticles are loaded on the MOF conductive carrier;

[0068] Based on the total weight of the MOF conductive carrier being 100%, the loading amounts of the copper nanoparticles are 5 wt%, 10 wt%, 20 wt%, and 30 wt% respectively, and are denoted as 5%Cu@MOF, 10%Cu@MOF, 20%Cu@MOF, and 30%Cu@MOF respectively.

[0069] Comparative Example 2

[0070] This comparative example provides a series of electrode catalysts for electrolytic reduction of carbon dioxide to ethylene, which are prepared by a preparation method including the following specific steps:

[0071] (1) Preparation of the conductive carrier dispersion solution: Take 200 mg of dry conductive carrier (graphene) and add it to 90 mL of deionized water, and ultrasonically disperse it to a uniform state to obtain a mixed solution. Transfer the mixed solution to a 100 mL volumetric flask, and make up the volume to 100 mL with deionized water to obtain a carrier dispersion solution with a concentration of 2 mg / mL, and shake well for later use.

[0072] (2) Preparation of the copper precursor solution: Weigh 3.802 g of copper nitrate trihydrate, add it to 9.15 g of deionized water, and fully dissolve it to obtain a dark blue copper nitrate solution (the total volume of the solution is 10 mL, and the Cu 2+ concentration is 100 mg / mL).

[0073] (3) A series of xCu@ graphene (x = 5% and 10%) electrocatalysts were prepared by in-situ impregnation reduction method, and the specific operation is as follows:

[0074] Take two clean 100 mL beakers, and add 50 mL of the carrier dispersion solution into the two beakers respectively; Under continuous stirring conditions, use a pipette to respectively pipette different volumes of the copper precursor solution and add them into the two beakers, and the volumes of the copper precursor solution are 50 μL and 100 μL respectively; Then add 20 mg and 40 mg of trisodium citrate into the two beakers respectively; Then heat the obtained mixed solution in a water bath to 60 °C and stir for 8 h, and then gradually add 0.5 mL of hydrazine hydrate (85 wt%) dropwise into the reaction solution, and continue to stir at 60 °C for 2 h until no more bubbles emerge from the solution.

[0075] (4) Catalyst washing: After cooling the temperature of the suspension obtained in step (3) to room temperature, carry out centrifugal separation and dispersion, discard the supernatant, and wash the precipitate with ultrapure water and ethanol three times or more in sequence. Finally, dry the washed wet precipitate in a vacuum drying oven at 60 - 85 °C overnight to obtain the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene.

[0076] The electrode catalyst for electrolytic reduction of carbon dioxide to ethylene obtained in this comparative example includes a graphene conductive carrier and copper nanoparticles, and the copper nanoparticles are loaded on the graphene conductive carrier;

[0077] Based on the total weight of the graphene conductive carrier being 100%, the loading amounts of the copper nanoparticles are 5 wt% and 10 wt% respectively, which are denoted as 5% Cu@ graphene and 10% Cu@ graphene respectively.

[0078] Example 1

[0079] This example provides a series of electrode catalysts for electrolytic reduction of carbon dioxide to ethylene, which are prepared by a preparation method including the following specific steps:

[0080] (1) Preparation of the conductive carrier dispersion solution: Take 200 mg of dry conductive carrier (graphene) and add it to 90 mL of deionized water, ultrasonically disperse it to a uniform state to obtain a mixed solution, transfer the mixed solution to a 100 mL volumetric flask, and make up the volume to 100 mL with deionized water to obtain a carrier dispersion solution with a concentration of 2 mg / mL, and shake well for use.

[0081] (2) Preparation of the copper precursor solution: Weigh 3.802 g of copper nitrate trihydrate, add it to 9.15 g of deionized water, and fully dissolve it to obtain a dark blue copper nitrate solution (the total volume of the solution is 10 mL, and the Cu 2+ concentration is 100 mg / mL).

[0082] (3) A series of xCu@ graphene (x = 20% and 30%) electrocatalysts were prepared by in-situ impregnation reduction method, and the specific operation is as follows:

[0083] Take two clean 100 mL beakers, and add 50 mL of the carrier dispersion solution into the two beakers respectively; under continuous stirring conditions, use a pipette to respectively pipette different volumes of the copper precursor solution and add them into the two beakers, and the volumes of the copper precursor solution are 200 μL and 300 μL respectively; then add 80 mg and 120 mg of trisodium citrate into the two beakers respectively; then heat the obtained mixed solution in a water bath to 60 °C and stir for 8 h, and then gradually add 0.5 mL of hydrazine hydrate (85 wt%) dropwise into the reaction solution, and continue to stir at 60 °C for 2 h until no bubbles emerge from the solution.

[0084] (4) Catalyst washing: After cooling the temperature of the suspension obtained in step (3) to room temperature, perform centrifugal separation and dispersion, discard the supernatant, and wash the precipitate with ultrapure water and ethanol three times or more in sequence. Finally, dry the washed wet precipitate in a vacuum drying oven at 60 - 85 °C overnight to obtain the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene.

[0085] The electrode catalyst for electrolytic reduction of carbon dioxide to ethylene obtained in this example includes a graphene conductive carrier and copper nanoparticles, and the copper nanoparticles are loaded on the graphene conductive carrier;

[0086] Based on the total weight of the graphene conductive carrier being 100%, the loading amounts of the copper nanoparticles are 20 wt% and 30 wt% respectively, which are denoted as 20% Cu@ graphene and 30% Cu@ graphene respectively.

[0087] Example 2

[0088] This example provides a series of electrode catalysts for electrolytic reduction of carbon dioxide to ethylene, which are prepared by a preparation method including the following specific steps:

[0089] (1) Preparation of the conductive carrier dispersion: Take 200 mg of dry conductive carrier (C 3 N 4 ) and add it to 90 mL of deionized water, ultrasonically disperse it to a uniform state to obtain a mixed solution, transfer the mixed solution to a 100 mL volumetric flask, and make up the volume to 100 mL with deionized water to obtain a carrier dispersion solution with a concentration of 2 mg / mL, shake well and set aside.

[0090] (2) Preparation of the copper precursor solution: Weigh 3.802 g of copper nitrate trihydrate, add it to 9.15 g of deionized water, and fully dissolve it to obtain a dark blue copper nitrate solution (the total volume of the solution is 10 mL, Cu 2+(with a concentration of 100 mg / mL).

[0091] (3) A series of xCu@C 3 N 4 (x = 5 - 45%) electrocatalysts were prepared by the in-situ impregnation reduction method. The specific operations are as follows:

[0092] Take four clean 100 mL beakers, and add 50 mL of the carrier dispersion solution to each of the four beakers. Under continuous stirring, use a pipette to separately transfer different volumes of the copper precursor solution and add them to the four beakers. The volumes of the copper precursor solution are 50 μL, 100 μL, 200 μL, and 300 μL respectively. Then add 20 mg, 40 mg, 80 mg, and 120 mg of trisodium citrate to the four beakers respectively. Then heat the resulting mixture in a water bath to 60 °C and stir for 8 h. Then gradually add 0.5 mL of hydrazine hydrate (85 wt%) dropwise to the reaction solution, and continue to stir at 60 °C for 2 h until no more bubbles emerge from the solution.

[0093] (4) Catalyst washing: After cooling the suspension obtained in step (3) to room temperature, perform centrifugal separation and dispersion, discard the supernatant, and wash the precipitate with ultrapure water and ethanol three times or more in sequence. Finally, dry the washed wet precipitate in a vacuum drying oven at 60 - 85 °C overnight to obtain the electrode catalyst for electroreduction of carbon dioxide to ethylene.

[0094] The electrode catalyst for electroreduction of carbon dioxide to ethylene obtained in this example includes C 3 N 4 a conductive carrier and copper nanoparticles, and the copper nanoparticles are loaded on the C 3 N 4 conductive carrier;

[0095] Taking the total weight of the C 3 N 4 conductive carrier as 100%, the loading amounts of the copper nanoparticles are 5 wt%, 10 wt%, 20 wt%, and 30% respectively, and are denoted as 5%Cu@C 3 N 4 , 10%Cu@C 3 N 4 , 20%Cu@C 3 N 4 and 30%Cu@C 3 N 4 .

[0096] Example 3

[0097] This example provides an electrode catalyst for electroreduction of carbon dioxide to ethylene, which is prepared by a preparation method including the following specific steps:

[0098] (1) Preparation of the conductive carrier dispersion: Take 200 mg of dry conductive carrier (C 3 N 4 ) and add it to 90 mL of deionized water. Ultrasonically disperse it until it is in a homogeneous state to obtain a mixed solution. Transfer the mixed solution to a 100 mL volumetric flask and make up the volume to 100 mL with deionized water to obtain a carrier dispersion solution with a concentration of 2 mg / mL. Shake well for later use.

[0099] (2) Preparation of the metal mixed salt precursor solution: Take 100 mL of deionized water, weigh 24.156 g of copper nitrate trihydrate, 14.8745 g of zinc nitrate hexahydrate, 2.9103 g of cobalt nitrate trihydrate and 2.4186 g of iron nitrate, and add them to the deionized water. After dissolution, prepare a metal mixed salt precursor solution, where the molar ratio of the contents of each metal is Cu:Zn:Fe:Co = 10:5:1:1, and the concentration of Cu 2+ is 64 mg / mL, and the total metal concentration is 104.5 mg / mL.

[0100] (3) Preparation of the electrocatalyst by the in-situ impregnation reduction method. The specific operation is as follows:

[0101] Take a clean 100 mL beaker and add 50 mL of the carrier dispersion solution to the beaker; under continuous stirring conditions, add 100 μL of the metal mixed salt precursor solution to the beaker and mix the two evenly; then add 30 mg of trisodium citrate to the beaker and mix it evenly; then heat the obtained mixed solution in a water bath to 60 °C and stir for 8 h. Then, dropwise add 0.5 mL of hydrazine hydrate (85 wt%) to the reaction solution, and continue to stir at 60 °C for 2 h until no more bubbles emerge from the solution.

[0102] (4) Catalyst washing: After cooling the temperature of the suspension obtained in step (3) to room temperature, perform centrifugal separation and dispersion, discard the supernatant, and wash the precipitate with ultrapure water and ethanol three times or more in sequence. Finally, dry the washed wet precipitate in a vacuum drying oven at 60 - 85 °C overnight to obtain an electrode catalyst for electrolytic reduction of carbon dioxide to ethylene, denoted as Cu 10 Zn 5 FeCo@C 3 N 4 .

[0103] The electrode catalyst for electrolytic reduction of carbon dioxide to ethylene obtained in this example includes C 3 N 4 conductive carrier and Cu 10 Zn 5 FeCo nanoparticles, and the Cu 10 Zn 5FeCo nanoparticles are loaded on the C 3 N 4 conductive carrier;

[0104] Taking the total weight of the C 3 N 4 conductive carrier as 100%, the loading amounts of the Cu 10 Zn 5 FeCo nanoparticles are 10.5 wt% respectively.

[0105] Example 4

[0106] This example provides an electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene, which is prepared by a preparation method including the following specific steps:

[0107] (1) Preparation of the conductive carrier dispersion: Take 200 mg of dry conductive carrier (C 3 N 4 ) and add it to 90 mL of deionized water. Ultrasonically disperse it until it is in a uniform state to obtain a mixed solution. Transfer the mixed solution to a 100 mL volumetric flask and make up the volume to 100 mL with deionized water to obtain a carrier dispersion solution with a concentration of 2 mg / mL. Shake it well for later use.

[0108] (2) Preparation of the copper precursor solution: Weigh 3.802 g of copper nitrate trihydrate and add it to 9.15 g of deionized water. After fully dissolving, a dark blue copper nitrate solution is obtained (the total volume of the solution is 10 mL, and the Cu 2+ concentration is 100 mg / mL).

[0109] (3) Prepare the electrocatalyst by the in-situ impregnation reduction method. The specific operation is as follows:

[0110] Take a clean 100 mL beaker, add 50 mL of the carrier dispersion solution to the beaker, add 5 mL of acetaldehyde to the beaker as a templating agent and mix it evenly to induce more exposure of the (100) crystal plane of the loaded copper active phase; under continuous stirring conditions, use a pipette to transfer 50 μL of the copper precursor solution and add it to the beaker; then add 40 mg of trisodium citrate to the beaker and mix it evenly; then heat the obtained mixed solution in a water bath to 60 °C and stir for 8 h, and then gradually add 0.5 mL of hydrazine hydrate (85 wt%) to the reaction solution, and continue to stir at 60 °C for 2 h until no more bubbles emerge from the solution.

[0111] (4) Catalyst washing: After reducing the temperature of the suspension obtained in step (3) to room temperature, perform centrifugal separation and dispersion, discard the supernatant, and wash the precipitate with ultrapure water and ethanol successively more than three times. Finally, dry the washed wet precipitate in a vacuum drying oven at 60 - 85 °C overnight to obtain an electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene.

[0112] The electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene obtained in this example includes C 3 N 4 a conductive carrier and copper nanoparticles, and the copper nanoparticles are loaded on the C 3 N 4 conductive carrier;

[0113] Taking the total weight of the C 3 N 4 conductive carrier as 100%, the loading amount of the copper nanoparticles is 5 wt%.

[0114] Example 5

[0115] This example provides an electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene, which is prepared by a preparation method including the following specific steps:

[0116] Disperse 10 mg of the electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene provided in Example 4 uniformly in a mixed solvent of 10 mL of isopropanol and deionized water to obtain a slurry, and then coat (spin-coat) the slurry on a hydrophobic carbon paper electrode and dry it to obtain an electrode loaded with the catalyst;

[0117] Using the electrode loaded with the catalyst as the working electrode, using a carbon rod and a saturated calomel electrode as the counter electrode and the reference electrode respectively, in the working electrode chamber, add 0.1 mol / L of Na 2 S solution, in the counter electrode chamber, add 0.1 mol / L of NaOH solution, and use cyclic voltammetry to scan 1 - 3 cycles in the voltage range of 0.5 - 1.5 V to obtain an electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene.

[0118] The electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene obtained in this example includes C 3 N 4 a conductive carrier and copper nanoparticles, and the copper nanoparticles are loaded on the C 3 N 4 conductive carrier;

[0119] Taking the total weight of the C 3 N 4 conductive carrier as 100%, the loading amount of the copper nanoparticles is 5 wt%, and the copper-based nanoparticles are copper-based nanoparticles after surface modification with S element.

[0120] Characterization Test Example 1

[0121] This characterization test example respectively performs transmission electron microscopy analysis on the 5% Cu@C 3 N 4 prepared in Example 2 of the present invention and the electrode catalyst for electrolytic reduction of carbon dioxide to ethylene prepared in Example 4. The obtained high-magnification transmission electron microscopy images are respectively as shown in Figure 1 and Figure 2 shown. It can be seen from Figure 1 that copper nanoparticles are uniformly loaded on the C 3 N 4 conductive carrier, indicating that the present invention can make the active phase, that is, the copper nanoparticles, have good dispersion on the conductive carrier by using a dispersion aid. It can be seen from Figure 2 that the copper nanoparticles loaded on the C 3 N 4 conductive carrier expose more target crystal planes, which indicates that the present invention can induce the morphology change of copper-based nanoparticles by using a templating agent, thereby exposing more high-activity crystal planes.

[0122] Performance Test Example 1

[0123] This performance test example respectively performs electrochemical tests on the electrode catalysts for electrolytic reduction of carbon dioxide to ethylene provided in Examples 1-4 of the present invention and Comparative Examples 1-2. All electrochemical tests are completed on an electrochemical workstation (PARSTST 4000+). First, 10 mg of the electrode catalysts for electrolytic reduction of carbon dioxide to ethylene provided in Examples 1-4 and Comparative Examples 1-2 are respectively uniformly dispersed in a mixed solvent of 10 mL of isopropanol and deionized water to obtain a slurry, and then the slurry is coated (spin-coated) on a hydrophobic carbon paper electrode and dried to obtain an electrode loaded with the catalyst.

[0124] Before the CO 2 RR test, N 2 gas is first introduced into the electrolyte for 1 h, and then CO 2 gas is introduced into the electrolyte for 30 min to reach CO 2 saturation. In this test example, an H-type electrolytic cell is used as the test device, and the cathode and the anode are separated by a cation exchange membrane (Nafion N117, DuPont), and electrochemical performance tests are carried out in a three-electrode system, where a graphite rod electrode is used as the counter electrode, silver / silver chloride (Ag / AgCl) is used as the reference electrode, and the hydrophobic carbon paper loaded with the above catalyst is used as the working electrode, and the concentration is 0.1 M KHCO 3The aqueous solution serves as the electrolyte. Under the condition of a scanning rate of 5 mV / s, linear sweep voltammetry (LSV) curves are collected, and the overpotential is evaluated by taking the potential value at a current density of 10 mA / cm 2 The potentiostatic electrolysis is carried out for 60 min of CO 2 RR measurement at different potentials. During this period, CO 2 gas is introduced into the cathode chamber at a constant rate of 20 sccm. The gas-phase products are obtained by gas chromatography, and the liquid-phase products are obtained by nuclear magnetic resonance using DMSO as the internal standard. The yield of the products is based on the average yield collected within 1 h. The Faraday efficiency (FE%) of the reduction products can be calculated based on the following formula:

[0125] FE == e × F × n / Q;

[0126] Among them, e is the number of electron transfers of the obtained product (for C 2 H 6 ,C 2 H 4 ,CH 4 ,CO and H 2 are 14, 12, 8, 2, and 2 respectively), n is the total amount (moles) of each product, F is the Faraday constant (96485 C / mol), and Q is the total charge amount.

[0127] Among them, the electrochemical test results of 10% Cu@MOF, 20% Cu@MOF, and 30% Cu@MOF provided in Comparative Example 1 are shown in Tables 1 - 3 below respectively.

[0128] Table 1 Electrochemical test results of 10% Cu@MOF

[0129]

[0130] Table 2 Electrochemical test results of 20% Cu@MOF

[0131]

[0132] Table 3 Electrochemical test results of 30% Cu@MOF

[0133]

[0134] In Comparative Example 1, MOF is used as the conductive carrier substrate of the catalyst, and catalysts are prepared by adjusting different Cu contents. It can be seen from Tables 1 - 3 that: when electrolyzing in an H-type electrolytic cell, the highest current density of the catalyst can reach 50 mA·cm -2, the overall current density is large. In addition, the starting potential of the catalyst is low, among which the starting potential of 20% Cu@MOF is the lowest, indicating that the catalyst has good conductivity. As the copper content in the catalyst increases, the current density increases and the conductivity increases. However, it can be seen from Tables 1 to 3 that the FE (C 2 H 4 ) is 0, indicating that ethylene cannot be produced when catalyzing the electrochemical reduction of carbon dioxide, which may be related to the use of MOF as a conductive carrier.

[0135] Among them, the electrochemical test results of 10% Cu@graphene, 20% Cu@graphene and 30% Cu@graphene provided by Comparative Example 2 and Example 1 are shown in Tables 4 to 6 below, respectively.

[0136] Table 4 Electrochemical test results of 10% Cu@graphene

[0137]

[0138] Table 5 Electrochemical test results of 20%Cu@graphene

[0139]

[0140] Table 6 Electrochemical test results of 30%Cu@graphene

[0141]

[0142] In both Example 1 and Comparative Example 2 of the present invention, graphene was used as the conductive carrier substrate of the catalyst, and the catalyst was prepared by adjusting the different Cu contents. It can be seen from Tables 4 to 6 that in the electrolysis in the H-type electrolytic cell, as the content of copper nanoparticles in the catalyst increases, the starting potential of the catalyst decreases, the current density increases, and the conductivity increases. However, compared with the catalyst provided in Example 1 of the present invention, the FE (C 2 H 4 ) is 0, indicating that ethylene cannot be produced when catalyzing the electrochemical reduction of carbon dioxide, which may be related to the low content of copper nanoparticles.

[0143] Among them, the 5% Cu@C provided in Example 2 3 N 4 、10%Cu@C 3 N 4 、20%Cu@C 3 N 4 and 30%Cu@C 3 N 4 The electrochemical test results are shown in Tables 7 to 10 below.

[0144] Table 7 5%Cu@C3 N 4 Electrochemical test results of

[0145]

[0146] Table 8 10% Cu@C 3 N 4 Electrochemical test results of

[0147]

[0148] Table 9 20% Cu@C 3 N 4 Electrochemical test results of

[0149]

[0150] Table 10 30% Cu@C 3 N 4 Electrochemical test results of

[0151]

[0152] In Example 2 of the present invention, C 3 N 4 is used as the conductive carrier substrate of the catalyst, and the catalyst is prepared by adjusting different Cu contents. It can be seen from Tables 7 - 10 that: when electrolyzing in an H-type electrolytic cell and with the same Cu content, the initial potential of the catalyst with C 3 N 4 as the conductive carrier is lower than that of the catalyst with graphene as the conductive carrier. Additionally, the conductive performance of these catalysts is good. Catalysts with different Cu contents all have obvious ethylene products, but with the change of the applied voltage, there is no significant change rule for the ethylene production.

[0153] Additionally, by comparing the experimental data in Tables 1 - 3 and Tables 4 - 10, it can be known that when using MOF as the conductive carrier substrate of the catalyst, the FE(C 2 H 4 ) of this catalyst is 0, indicating that ethylene cannot be produced when it catalyzes the electrochemical reduction of carbon dioxide; while when using graphene and C 3 N 4 as the conductive carrier substrates of the catalyst and controlling the appropriate content of copper-based nanoparticles, ethylene can be produced when the catalyst catalyzes the electrochemical reduction of carbon dioxide, which indicates that the performance of the electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene is also closely related to the substrate.

[0154] Among them, the electrochemical test results of the catalyst provided in Example 3 are shown in Table 11 below.

[0155] Table 11 Electrochemical test results of the catalyst provided in Example 3

[0156]

[0157] The electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene obtained in Example 3 includes C 3 N 4 a conductive carrier, and Cu 10 Zn 5 FeCo nanoparticles, and the Cu 10 Zn 5 FeCo nanoparticles are supported on the C 3 N 4 conductive carrier. It can be seen from Table 11 that the use of this catalyst increases the yield of ethylene to a certain extent, indicating that alloying the metal active phase can improve the activity of the catalyst.

[0158] Among them, the electrochemical test results of the catalyst provided in Example 4 are shown in Table 12 below.

[0159] Table 12 Electrochemical test results of the catalyst provided in Example 4

[0160]

[0161] Compared with 5% Cu@C 3 N 4 , in Example 4 of the present invention, a template agent is used in the preparation of the catalyst. As Figure 2 shown, more target crystal planes of the copper nanoparticles supported on the C 3 N 4 conductive carrier in the catalyst are exposed. This indicates that by using a template agent, the present invention can induce changes in the morphology of copper-based nanoparticles, thereby exposing more high-activity crystal planes. Correspondingly, comparing Table 7 and Table 12, it can be seen that the catalyst prepared in Example 4 of the present invention by using a template agent can obtain a higher ethylene yield at a lower voltage, up to nearly 18%. While for the 5% Cu@C 3 N 4 prepared in Example 2 without using a template agent, the ethylene yield can only reach 15.6% under relatively higher voltage conditions. In addition, under the same voltage (-1.09112V) condition, the ethylene yield of the catalyst prepared in Example 4 of the present invention by using a template agent is also significantly higher than that of 5% Cu@C 3 N 4 . The above results show that more (100) crystal planes exposed by the copper-based nanoparticles in the catalyst can generate more C2 products, and correspondingly, the ethylene yield will also increase.

[0162] The above are only specific embodiments of the present invention and cannot limit the scope of the invention. Therefore, the replacement of equivalent components or equivalent changes and modifications made according to the scope of protection of the present invention should still fall within the scope covered by this patent. In addition, the technical features in the present invention can be freely combined with each other, between technical features and technical inventions, and between technical inventions.

Claims

1. An electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene, characterized in that, the electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene comprises a conductive carrier and copper-based nanoparticles, and the copper-based nanoparticles are loaded on the conductive carrier; based on the total weight of the conductive carrier being 100%, the loading amount of the copper-based nanoparticles is 0.3 wt% - 65 wt%.

2. The electrode catalyst according to claim 1, characterized in that, the copper-based nanoparticles include copper nanoparticles or copper alloy nanoparticles.

3. The electrode catalyst according to claim 2, characterized in that, the metal elements other than copper in the copper alloy nanoparticles include one or a combination of several of Zn, Fe, and Co.

4. The electrode catalyst according to any one of claims 1-3, characterized in that, the copper-based nanoparticles include copper-based nanoparticles after surface modification with non-metallic elements.

5. The electrode catalyst according to claim 4, characterized in that, the non-metallic elements include one or a combination of several of nitrogen, phosphorus, and sulfur.

6. The electrode catalyst according to any one of claims 1-3, characterized in that, the particle size of the copper-based nanoparticles is 0.3 nm - 850 nm.

7. The electrode catalyst according to any one of claims 1-3, characterized in that, The conductive carrier includes a conductive carbon material and any one of C 3 N 4 ; preferably, when the conductive carrier is a conductive carbon material, the loading amount of the copper-based nanoparticles is 15 wt% - 45 wt%.

8. The electrode catalyst according to claim 7, characterized in that, the conductive carbon material includes carbon black and / or graphene.

9. A preparation method of the electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene according to any one of claims 1-8, characterized in that, the preparation method includes: Step 1, uniformly mixing a conductive carrier dispersion, a precursor solution containing at least a copper salt, and a dispersion aid to obtain a mixed solution; Step 2, adding a reducing agent to the mixed solution, and stirring while heating in a water bath to obtain the electrode catalyst for the electrolytic reduction of carbon dioxide to ethylene.

10. The preparation method according to claim 9, characterized in that, Step 1 further includes: uniformly mixing a conductive carrier dispersion, a precursor solution containing at least a copper salt, a template agent, and a dispersion aid to obtain a mixed solution; preferably, the ratio of the volume of the template agent to the total volume of the conductive carrier dispersion and the precursor solution containing at least a copper salt is 5:1 - 20:1; more preferably, the template agent is an aldehyde template agent; further preferably, the aldehyde template agent includes one or a combination of several of formaldehyde, acetaldehyde, and propionaldehyde.

11. The preparation method according to claim 9 or 10, characterized in that, in Step 1, the concentration of the conductive carrier in the conductive carrier dispersion is less than or equal to 5 mg / mL; Cu in the precursor solution containing at least a copper salt 2+ has a concentration of 50 mg / mL - 150 mg / mL.

12. The preparation method according to claim 9, characterized in that, in Step 1, the molar ratio of the dispersion aid to the metal elements contained in the mixed solution is 1:2 - 1:

1.

13. The preparation method according to claim 9 or 12, characterized in that, The dispersion aids include one or a combination of several of sodium citrate, sodium dodecylsulfonate, sodium cetylsulfonate, triethanolamine, glycerol fatty acid ester, quaternary ammonium compound, and polyvinylpyrrolidone.

14. According to the preparation method described in claim 9, characterized in that, in step 2, the reducing agent includes any one of hydrazine hydrate or hydroxylamine; Preferably, in step 2, the temperature of the water bath heating is 45°C - 80°C.

15. Application of the electrode catalyst for electrochemically reducing carbon dioxide to ethylene described in any one of claims 1 - 8 in the preparation of ethylene by electrochemically reducing carbon dioxide.

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