A method for preparing a supported copper nitride catalyst

Abstract

The application relates to the technical field of carbon dioxide electro-reduction catalysts, and discloses a preparation method of a supported copper nitride catalyst, which comprises the following steps: mixing copper cyanamide and conductive carbon material and performing ball milling; the rotating speed of the ball milling is 500 r / min-5000 r / min, and the ball milling time is 1h-24h; the mass ratio of the copper cyanamide and the conductive carbon material is 1-10:1-10. The catalyst obtained by the method has better stability, selectivity and activity in a carbon dioxide electro-catalytic reduction reaction, and the addition of the conductive carbon improves the conductivity of the catalyst, so that the overpotential of the catalyst in the carbon dioxide electro-reduction is significantly reduced.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide electroreduction catalyst technology, and more particularly to a method for preparing a supported copper nitride catalyst. Background Technology

[0002] In CO2RR, Cu is the only catalyst capable of producing a considerable number of hydrocarbons and oxygen-containing compounds (such as CH4, C2H4, and C2H5OH) due to its suitable binding energy to intermediates CO and H. However, due to the diversity of products and the complex reaction pathways in CO2RR, it is difficult to obtain high selectivity for a single product when using Cu as a single active site.

[0003] In existing technologies, nitrogen-containing molecules can also be used as promoters to improve the selectivity and stability of Cu single-metal catalysts. Modification of Cu catalysts with nitrogen-containing organic polymers can also achieve higher C content. 2+ Selectivity and reaction rate. For example, N-aromatic pyridine-derived films improve C2H4 selectivity by enhancing the stability of linearly adsorbed CO intermediates. NxC layers deposited on Cu particle surfaces can also enhance CO2 adsorption through specific N-CO2 interactions, thereby improving C2 selectivity and catalytic stability. Nano-Cu3N exhibits good C2H4 selectivity in CO2RR by maintaining the positive valence state of Cu.

[0004] Researchers have developed a method for preparing nitrogen- and carbon-supported Cu3N composite catalysts via the pyrolysis of copper cyanamide (CuNCN), yielding the catalyst product Cu3N / C. x N y The selectivity for C2H4 products can reach 47.6%. This method is simple and easy to implement, but the final product, Cu3N / C, is problematic. x N y Its conductivity and stability are both very poor, so there is still a lot of room for improvement in the product. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a supported copper nitride catalyst. The method is simple and easy to implement, and a carbon dioxide electroreduction catalyst with stable structure and good conductivity can be obtained by decomposing copper cyanamide.

[0006] This invention provides a method for preparing a supported copper nitride catalyst, the method comprising the following steps:

[0007] The mixture of copper cyanamide (CuNCN) and conductive carbon material was ball-milled.

[0008] The ball mill rotation speed is 500 r / min-5000 r / min, and the ball milling time is 1 h-24 h;

[0009] The mass ratio of the copper cyanamide to the conductive carbon material is 1-10:1-10.

[0010] Furthermore, the method of mixing the copper cyanamide (CuNCN) and the conductive carbon material is selected from one of schemes i-ii:

[0011] Option i: Mix copper cyanamide and conductive carbon materials;

[0012] Scheme ii: Prepare a complexing solution by mixing copper cyanamide precursor and ammonia. Add conductive carbon material to the complexing solution and mix with cyanamide solution. Stir to precipitate, filter, wash and dry.

[0013] Those skilled in the art should understand that deionized water is used as the solvent when preparing reagents or mixing solutions.

[0014] In this invention, a small amount of deionized water can be added during ball milling, which is beneficial for thorough ball milling.

[0015] Furthermore, in the ii scheme, the concentration of ammonia is 1 mol / L.

[0016] Furthermore, the complexing solution in the ii scheme also includes deionized water, and the volume ratio of ammonia water to deionized water is 1:10.

[0017] Furthermore, the mass ratio of the balls to the copper cyanamide and conductive carbon material during ball milling is 5-15:1.

[0018] Furthermore, the copper cyanamide precursor in scheme ii includes one or more of CuCl (cuprous chloride), CuCl2 (copper chloride), Cu(NO3)2 (copper nitrate), and CuSO4 (copper sulfate).

[0019] Furthermore, in the ii scheme, the mass ratio of copper cyanamide precursor, monocyanamide, and conductive carbon material is 5:5:2.

[0020] Furthermore, in the ii scheme, the concentration of conductive carbon material in the complexing solution is 1 mg / mL-3 mg / mL.

[0021] Furthermore, in the ii scheme, the stirring time is 4 min-6 min.

[0022] Furthermore, the specific washing method in scheme ii is as follows: the filtered precipitate is washed with deionized water at least twice.

[0023] Furthermore, in the ii scheme, the drying temperature is 70℃-90℃, and the drying time is 1h-10h.

[0024] Furthermore, the conductive carbon material includes one or more of graphene, carbon nanotubes, conductive carbon black, and conductive carbon fibers.

[0025] The present invention also provides a carbon dioxide electroreduction catalyst obtained by the preparation method described above.

[0026] The present invention also provides the application of the catalyst obtained by the preparation method in the electroreduction of carbon dioxide.

[0027] The embodiments of the present invention have the following technical effects:

[0028] The method of this invention is simple and easy to implement, and can be industrially produced. This method yields a catalyst with better stability, selectivity, and activity in the electrocatalytic reduction of carbon dioxide. Furthermore, the addition of conductive carbon improves the catalyst's conductivity, significantly reducing the overpotential during carbon dioxide electroreduction. The ball milling process generates more defect sites on the surface of the conductive carbon material, while copper cyanamide decomposes during ball milling. These decomposed copper cyanamide interacts with the defect sites in the conductive carbon material during ball milling, thereby improving the catalyst's structural stability. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is an HRTEM diagram of an embodiment of the present invention, wherein Figure 1 (a) is the HRTEM image of the catalyst. Figure 1 (b) shows the Cu3N lattice under the microscopic structure of the catalyst. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] In a first aspect, some embodiments of the present invention provide a method for preparing a supported copper nitride catalyst, the method comprising the following steps:

[0033] The copper cyanamide and conductive carbon material were mixed and ball-milled.

[0034] The ball mill rotation speed is 500 r / min-5000 r / min, and the ball milling time is 1 h-24 h;

[0035] The mass ratio of the copper cyanamide to the conductive carbon material is 1-10:1-10.

[0036] In the method of this invention, ball milling of conductive carbon material with copper cyanamide can: first, decompose copper cyanamide to generate Cu3N; second, ball milling promotes the formation of defect sites on the conductive carbon, which is beneficial for the stable loading of Cu3N onto these defect sites; and third, ball milling enables Cu3N to be loaded onto the surface of the conductive carbon material, thereby improving the conductivity of the final catalyst. In summary, the method of this invention can simultaneously improve the conductivity and structural stability of the catalyst, enhancing not only its catalytic activity but also its selectivity for C2H4 products during the electroreduction of carbon dioxide.

[0037] In this invention, the structural stability of the catalyst is fundamental to its catalytic activity. To further enhance structural stability, the invention also incorporates adjustments to the ball milling speed, milling time, and the mass of raw materials added. These adjustments serve to regulate the loading amount. Insufficient loading results in poor catalyst improvement, while excessive loading can hinder dispersion during milling, affecting the loading effect and potentially leading to poor structural stability between the loaded and unloaded substances after milling. Appropriate milling speed and time improve the bond between the loaded and unloaded substances, and the selection of suitable milling speed, time, and raw material mass contributes to enhancing the catalyst's structural stability.

[0038] In some embodiments, the method of mixing copper cyanamide (CuNCN) and conductive carbon material is selected from one of schemes i-ii:

[0039] Option i: Mix copper cyanamide and conductive carbon materials;

[0040] Scheme ii: Prepare a complexing solution by mixing copper cyanamide precursor and ammonia. Add conductive carbon material to the complexing solution and mix with cyanamide solution. Stir to precipitate, filter, wash and dry.

[0041] In some embodiments, the concentration of ammonia in scheme ii is 1 mol / L.

[0042] In some embodiments, the complexing solution in scheme ii further includes deionized water, and the volume ratio of ammonia to deionized water is 1:10.

[0043] In some embodiments, the mass ratio of the balls to the copper cyanamide and conductive carbon material during ball milling is 5-15:1.

[0044] In some embodiments, the copper cyanamide precursor in scheme ii includes one or more of CuCl (cuprous chloride), CuCl2 (copper chloride), Cu(NO3)2 (copper nitrate), and CuSO4 (copper sulfate).

[0045] In some embodiments, the mass ratio of copper cyanamide precursor, monocyanamide, and conductive carbon in scheme ii is 5:5:2.

[0046] In some embodiments, the concentration of conductive carbon material in the complexing solution of scheme ii is 1 mg / mL-3 mg / mL.

[0047] In some embodiments, the stirring time in scheme ii is 4 min-6 min.

[0048] In some embodiments, the specific washing method in scheme ii is as follows: the filtered precipitate is washed with deionized water at least twice.

[0049] In some embodiments, the drying temperature in scheme ii is 70℃-90℃, and the drying time is 1h-10h.

[0050] In some embodiments, the conductive carbon material includes one or more of graphene, carbon nanotubes, conductive carbon black, and conductive carbon fibers.

[0051] Secondly, some embodiments of the present invention provide a carbon dioxide electroreduction catalyst obtained by the preparation method.

[0052] Thirdly, some embodiments of the present invention provide the application of the catalyst obtained by the preparation method in the electroreduction of carbon dioxide.

[0053] The following description, in conjunction with specific embodiments, provides further details.

[0054] Example 1:

[0055] First, 245.7 mg of CuCl was added to a conical flask containing 50 mL of deionized water. Then, 5 mL of concentrated ammonia was added to the flask, and the mixture was stirred for 20 min to form a homogeneous blue complex solution. Next, 480 mg of a 50% (w / w) cyanamide aqueous solution was added to a beaker containing 50 mL of deionized water, and the mixture was stirred to form a homogeneous solution. 50 mL of the diluted cyanamide aqueous solution was added to the Cu complex solution, and the mixture was stirred vigorously for 5 min to form a homogeneous black suspension. The suspension was filtered and washed with deionized water. The resulting black solid was dried in a vacuum drying oven at 80 °C for 1 h to obtain CuNCN.

[0056] 500 mg of CuNCN solid, 500 mg of carbon fiber, and 100 mg of deionized water were added to a ball mill jar. The ball mill jar was then placed in a ball mill and run at 2000 rpm for 12 hours to obtain the carbon fiber supported Cu3N catalyst, denoted as Cu3N-CF-1.

[0057] Test method for carbon dioxide electrocatalytic reduction performance: 3 mg of Cu3N-CF-1 sample was dispersed in 1 mL of isopropanol solution and ultrasonically dispersed for 30 min. 10 μL of 5% Nafion solution was added as a binder, and ultrasonication was continued for another 20 min. 50 μL of Cu3N-CF-1 dispersion was dropped onto the surface of a 6 mm diameter glassy carbon electrode. After drying, the electrode was placed in an H-type electrolytic cell. A platinum wire was used as the counter electrode, and Ag / AgCl was used as the reference electrode. The cathode and anode chambers were separated by a Nafion 117 membrane. 40 mL of KHCO3 solution was added to each of the cathode and anode chambers, and CO2 gas was introduced at a rate of 20 mL / min through the cathode. The carbon dioxide electrocatalytic reduction performance of Cu3N-CF-1 at different potentials was tested. The gaseous products were quantitatively analyzed using online gas chromatography.

[0058] Example 2

[0059] The ball milling conditions in Example 1 were changed to 2000 rpm for 10 hours, while the other conditions remained the same as in Example 1. The resulting catalyst was designated Cu3N-CF-2. The method for testing the electrocatalytic reduction performance of carbon dioxide was the same as in Example 1.

[0060] Example 3:

[0061] The 500 mg of conductive carbon fiber in Example 1 was replaced with 125 mg of conductive carbon fiber, while all other conditions remained the same as in Example 1. The resulting graphene-supported Cu3N catalyst was denoted as Cu3N-CF-3. The method for testing the electrocatalytic reduction performance of carbon dioxide was the same as in Example 1.

[0062] Example 4:

[0063] In Example 1, 500 mg of conductive carbon fiber was replaced with 125 mg of conductive carbon fiber, and the ball milling conditions were changed to 2000 rpm for 20 hours. All other conditions remained the same as in Example 1. The resulting catalyst was designated Cu3N-CF-4. The method for testing the electrocatalytic reduction performance of carbon dioxide was the same as in Example 1.

[0064] Comparative Example 1:

[0065] The preparation method of copper cyanamide (CuNCN) in Comparative Example 1 was consistent with that in Example 1. 100 mg of solid copper cyanamide was placed in a glass or quartz tube sealed at one end, thus sealing the copper cyanamide within the tube. The glass or quartz tube containing the copper cyanamide was then placed in a muffle furnace and heated to 300°C at a heating rate of 1°C / min, held for 1 hour, and allowed to cool naturally. The resulting catalyst was labeled Cu3N-NC. The method for testing the electrocatalytic reduction performance of carbon dioxide was consistent with that in Example 1.

[0066] Results Analysis

[0067] Table 1 Test results of the examples and comparative examples

[0068]

[0069] The catalyst was successfully obtained using the method of this invention. The catalyst was then subjected to a carbon dioxide reduction performance test, and the results are shown in Table 1. As can be seen from Table 1, the catalyst performance of Examples 1-4 of this invention is significantly better than that of Comparative Example 1. The supported Cu3N nanoparticle catalyst prepared by the ball milling method of this invention shows more than 10% higher selectivity for C2H4 than that of Comparative Example 1, and the current density increases by 10 mA / cm². 2 The stability has been improved by more than 5 hours.

[0070] The ball milling method of this invention successfully decomposes CuNCN while simultaneously creating defects in the conductive carbon material, thus facilitating the loading of Cu3N nanoparticles obtained from CuNCN decomposition. Furthermore, ball milling promotes stable bonding between the conductive carbon material and the catalyst, thereby enhancing the catalyst's conductivity. Figure 1 This can also be verified that Cu3N nanoparticles are uniformly dispersed on carbon nanofibers.

[0071] To achieve structural stability of the catalyst, this study further adjusted the ball milling parameters and the mass ratio of CuNCN to conductive carbon, as shown in Examples 1-4 of Table 1. Changes in the mass of CuNCN and conductive carbon, ball milling time, and ball milling speed all affected the catalyst's performance. A comparison of Examples 1 and 3 revealed that increasing the mass ratio of CuNCN to conductive carbon decreased the catalyst's performance and stability. This may be because excessive CuNCN decomposes to produce Cu3N nanoparticles, leading to excessive loading and uneven dispersion, thus affecting catalyst performance. A comparison of Examples 3 and 4 showed that increasing the ball milling speed could disperse the Cu3N nanoparticles, mitigating the impact of an excessively high mass ratio. A comparison of Examples 2 and 4 also revealed that adjusting the ball milling time could further improve catalyst performance. This is likely because extending the ball milling time and speed facilitates sufficient dispersion of nanoparticles, promoting stable connections at defect sites.

[0072] In summary, the method of the present invention successfully yields a catalyst with stable structure and good conductivity.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a supported copper nitride catalyst, characterized in that, The preparation method includes the following steps: The copper cyanamide and conductive carbon material were mixed and ball-milled. The ball mill rotation speed is 500 r / min-5000 r / min, and the ball milling time is 1 h-24 h; The mass ratio of the copper cyanamide and the conductive carbon material is 1-10:1-10; The method for mixing copper cyanamide and conductive carbon material is selected from one of schemes i-ii: Option i: Mechanically mix copper cyanamide and conductive carbon materials; Scheme ii: Prepare a complexing solution by mixing copper cyanamide precursor and ammonia. Add conductive carbon material to the complexing solution and mix with cyanamide solution. Stir to precipitate, filter, wash and dry.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the balls to copper cyanamide and conductive carbon material during ball milling is 5-15:

1.

3. The preparation method according to claim 1, characterized in that, In scheme ii, the concentration of ammonia is 0.2 mol / L; The complexing solution in scheme ii also includes deionized water, and the volume ratio of ammonia to deionized water is 1:

10.

4. The preparation method according to claim 1, characterized in that, In scheme ii, the mass ratio of copper cyanamide precursor, monocyanamide, and conductive carbon material is 5:5:

2.

5. The preparation method according to claim 1, characterized in that, In scheme ii, the concentration of conductive carbon material in the complexing solution is 1 mg / mL-3 mg / mL.

6. The preparation method according to claim 1, characterized in that, In the ii scheme, the stirring time is 4 min-6 min.

7. The preparation method according to claim 1, characterized in that, In the second method, the drying temperature is 70℃-90℃ and the drying time is 1h-10h.

8. The supported copper nitride catalyst obtained by the preparation method according to any one of claims 1-7.

9. The application of the catalyst obtained by the preparation method according to any one of claims 1-7 in the electroreduction of carbon dioxide.

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