Preparation method of NiCe bimetallic catalyst for promoting conversion of CO2 into CO

Abstract

The invention discloses a preparation method of a NiCe bimetallic catalyst for promoting conversion of CO2 into CO, the prepared NiCe-NC-C catalyst has the characteristics of low cost, high specific surface area and high activity by introducing Ni and Ce bimetallic, and shows higher Faraday efficiency (gt; and the carbon layer formed by coating with dopamine can significantly improve the catalytic stability of CO production through CO2 conversion, provides an efficient, low-cost and environment-friendly solution for CO2 electrocatalytic reduction, and meets the dual-carbon target.

Description

Technical Field

[0001] This invention patent belongs to the technical field of the preparation of functional catalytic materials, and specifically relates to a preparation method of a catalyst for promoting the conversion of CO2 into CO. Background Art

[0002] With the acceleration of the global industrialization process, the extensive use of fossil fuels has led to a sharp rise in the concentration of carbon dioxide (CO2) in the atmosphere, triggering serious environmental problems such as global warming and climate change. To achieve sustainable development, reducing CO2 emissions and realizing its resource utilization have become the focus of global attention and are important ways to achieve the "dual carbon" goal. The electrocatalytic reduction of CO2 technology (CO2RR) is a potential solution that can convert CO2 into high-value chemicals (such as carbon monoxide, formic acid, methane, ethylene, etc.) while realizing carbon recycling.

[0003] Currently, the development of efficient, stable and low-cost catalysts is one of the main research focuses in CO2RR. Although noble metal catalysts (such as Pd, Au, etc.) exhibit high catalytic activity and selectivity, their high cost limits their large-scale application. In recent years, non-noble metal catalysts (such as Ni, Fe, Co, etc.) have received extensive attention due to their low cost and high activity. However, non-noble metal catalysts still face challenges such as insufficient catalytic activity, poor stability and low selectivity during the CO2RR process.

[0004] To solve the above problems, there have been many attempts in the synthesis of catalysts, and the performance of catalysts can be optimized through various strategies. For example, the introduction of bimetallic synergistic effects can improve the activity and stability of catalysts; using metal-organic framework (MOFs) materials as precursors to derive porous carbon materials with a high specific surface area to enhance the adsorption and conversion efficiency of CO2; in addition, through coating or surface modification technologies, the durability and corrosion resistance of catalysts can be further improved.

[0005] Although some research has made progress, the existing catalyst preparation processes are complex, costly, and it is still difficult to balance high activity, high selectivity and long-term stability in practical applications. Therefore, the development of a low-cost, efficient and stable CO2 electrocatalytic reduction catalyst has important scientific significance and application value.

[0006] The present invention provides a preparation method of a catalyst for promoting the conversion of CO2 into CO, and proposes a preparation method of a NiCe-NC@C catalyst based on a ZIF-8 precursor. By introducing the synergistic effect of Ni and Ce bimetals and combining with dopamine polymerization technology for coating, the active sites of the catalyst are protected during the reaction process. In addition, using ZIF-8 as a precursor, its porous structure and high specific surface area are utilized to further enhance the adsorption and conversion efficiency of CO2. The present invention provides an efficient, low-cost and environmentally friendly solution for the electrocatalytic reduction of CO2, meeting the requirements of the "dual carbon" goal. Summary of the Invention

[0007] The object of the present invention is to provide a preparation method of a NiCe-NC@C catalyst based on a ZIF-8 precursor. By controlling the loading ratio of Ni and Ce, it is ensured that the bimetals are deposited on the surface of the porous carbon support in the form of highly dispersed active sites. The loading amounts of Ni and Ce can be adjusted within the ranges of 0.1 - 3 mmol and 0.05 - 1 mmol respectively, so as to prepare composite catalysts with different catalytic performances. This method significantly improves the activity, selectivity and stability of the catalyst by introducing the synergistic effect of Ni and Ce bimetals and combining with dopamine polymerization coating technology. In particular, for the first time, the technical contribution of dopamine polymerization coating of NiCe-NC to the stability of the electrochemical reduction of CO2 to CO is discovered. In addition, the present invention uses ZIF-8 as a precursor, and utilizes its porous structure and high specific surface area to further enhance the adsorption and conversion efficiency of CO2. The NiCe-NC@C catalyst prepared by the present invention exhibits a high Faraday efficiency (>95%) for the production of CO from CO2 conversion within a wide potential range (-0.9~1.2 V vs. RHE), and has significant application prospects.

[0008] The technical solution of the present invention discloses a preparation method of a NiCe bimetal catalyst for promoting the conversion of CO2 into CO, which includes the following steps: (1) Dissolve zinc nitrate (Zn(NO3)2·6H2O) and 2-methylimidazole (2-mim) with a molar ratio of 10:85 in methanol solutions respectively to obtain solution A and solution B; (2) Ultrasonically treat the two solutions for more than 10 minutes to ensure complete dissolution. Slowly add solution B to solution A without stirring. After a few seconds, the mixture turns milky white, indicating the formation of ZIF-8 particles; (3) Incubate the mixture in an oven at 60 o °C for 24 hours, naturally cool to room temperature, centrifuge to remove the liquid and wash three times with ethanol; dry the solid in a vacuum oven at 50 o °C for 12 hours to obtain ZIF-8 powder; (4) Disperse the ZIF-8 powder in 50 mL of ethanol; (5) Pour a 15 mL ethanol solution containing 0.05 - 5 mmol cerium nitrate hexahydrate (Ce(NO3)3·6H2O) or cerium chloride heptahydrate (CeCl3·7H2O) and 0.1 - 3 mmol nickel nitrate hexahydrate (Ni(NO3)2·6H2O) into the above dispersion, and stir for 30 minutes; (6) Dissolve 5 - 20 mmol of benzimidazole in 15 mL of ethanol. After stirring evenly, add it to the mixture and continue stirring for 1 - 8 hours; Collect the precipitate by centrifugation to obtain the NiCe - NC precursor; (7) Disperse half of the NiCe - NC precursor in 30 mL of deionized water and 80 mL of ethanol; (8) Add a 40 mL aqueous solution containing 10 - 200 mmol of tris(hydroxymethyl)aminomethane, and stir for 30 minutes; Dropwise add a 30 mL aqueous solution containing 0.05 - 0.50 mmol of dopamine hydrochloride (DA·HCl), and continue stirring for 0.5 - 24 hours; (9) Collect the product by centrifugation, mix water and ethanol in a ratio of 1:1, 30 mL each time, and wash 8 times; Dry overnight at 60 o °C to obtain the NiCe - NC@PDA precursor; (10) Place the dried black NiCe - NC@PDA solid in a tubular furnace, and under gas protection, heat it to 900 o °C at a heating rate of 2 o °C / min and hold for 2 hours.

[0009] The beneficial effects of the present invention are as follows: 1. Bimetallic synergistic effect: By introducing Ni and Ce bimetals and controlling the metal loading from 0.05 - 20%, the catalytic activity is adjusted.

[0010] 2. Carbon layer protection enhances durability and stability: The carbon layer formed by dopamine coating plays a protective role for the catalyst, further improving its durability and stability.

[0011] 3. Low - cost preparation: Using ZIF - 8 as the precursor provides a large specific surface area. Combining with the use of non - precious metals reduces the preparation cost of the catalyst and is suitable for large - scale production.

[0012] 4. Simple and controllable process: The preparation method of the present invention has simple steps, clear parameter ranges, and a controllable process, and is suitable for large - scale applications. Brief Description of the Drawings

[0013] Attached Figure 1 is a schematic diagram of the test results of the electrocatalytic reduction of CO2 performance in Example 1 of the present invention; AttachedFigure 2 Schematic diagram of the test results of the electrocatalytic reduction of CO2 performance in Example 2 of the present invention; Appendix Figure 3 Schematic diagram of the test results of the electrocatalytic reduction of CO2 performance in Example 3 of the present invention; Appendix Figure 4 Schematic diagram of the test results of the electrocatalytic reduction of CO2 performance in Comparative Example 1 of the present invention; Appendix Figure 5 Schematic diagram of the stability test results of Example 3 and Comparative Example 1 of the present invention; Appendix Figure 6 Schematic diagram of the TEM-Mapping test results of Example 3 of the present invention; Appendix Figure 7 Schematic diagram of the SEM test results of the present invention. Detailed implementation mode

[0014] The present invention will be further described in detail below through examples.

[0015] Example 1 A preparation method of a catalyst for promoting the conversion of CO2 to CO, comprising the following steps: (1) Dissolve Zn(NO3)2·6H2O and 2-mim with a molar ratio of 10:85 in methanol solution respectively to obtain solution A and solution B; (2) Ultrasonically treat the two solutions for more than 10 minutes to ensure complete dissolution. Slowly add solution B to solution A without stirring. After a few seconds, the mixture turns milky white, indicating the formation of ZIF-8 particles; (3) Incubate the mixture in an oven at 60 o °C for 24 hours, naturally cool to room temperature, centrifuge to remove the liquid and wash three times with ethanol; dry the solid in a vacuum oven at 50 o °C for 12 hours to obtain ZIF-8 powder; (4) Disperse the ZIF-8 powder in 50 mL of ethanol; (5) Pour a 15 mL ethanol solution containing 0.05 mmol Ce(NO3)3·6H2O and 0.1 mmol Ni(NO3)2·6H2O into the above dispersion and stir for 30 minutes; (6) Dissolve 5 mmol of benzimidazole in 15 mL of ethanol, stir evenly and add it to the mixture, and continue to stir for 3 hours; collect the precipitate by centrifugation to obtain the NiCe-NC precursor; (7) Disperse half of the NiCe-NC precursor in 30 mL of deionized water and 80 mL of ethanol; (8) Add 40 mL of an aqueous solution containing 100 mmol of tris(hydroxymethyl)aminomethane and stir for 30 minutes; add dropwise 30 mL of an aqueous solution containing 0.32 mmol of DA·HCl and continue stirring for 1 hour; (9) Collect the product by centrifugation, wash it 8 times with a 1:1 mixture of water and ethanol, 30 mL each time; dry it overnight at 60 o °C to obtain the NiCe-NC@PDA precursor; (10) Place the dried black NiCe-NC@PDA solid in a tubular furnace and heat it to 900 o °C at a heating rate of 2 o °C / min and hold for 1 hour to obtain the NiCe-NC@C catalyst.

[0016] Example 2 A method for preparing a catalyst for promoting the conversion of CO2 to CO, comprising the following steps: (1) Dissolve Zn(NO3)2·6H2O and 2-mim with a molar ratio of 10:85 in methanol solutions respectively to obtain solution A and solution B; (2) Ultrasonically treat the two solutions for more than 10 minutes to ensure complete dissolution. Slowly add solution B to solution A without stirring. After a few seconds, the mixture turns milky white, indicating the formation of ZIF-8 particles; (3) Incubate the mixture in an oven at 60 o °C for 24 hours, cool it to room temperature naturally, centrifuge to remove the liquid and wash it three times with ethanol; dry the solid in a vacuum oven at 5 o °C for 12 hours to obtain ZIF-8 powder; (4) Disperse the ZIF-8 powder in 50 mL of ethanol; (5) Pour 15 mL of an ethanol solution containing 0.05 mmol of Ce(NO3)3·6H2O and 0.3 mmol of Ni(NO3)2·6H2O into the above dispersion and stir for 30 minutes; (6) Dissolve 5 mmol of benzimidazole in 15 mL of ethanol, add it to the mixture after stirring evenly and continue stirring for 3 hours; collect the precipitate by centrifugation to obtain the NiCe-NC precursor; (7) Disperse half of the NiCe-NC precursor in 30 mL of deionized water and 80 mL of ethanol; (8) Add 40 mL of an aqueous solution containing 100 mmol of tris(hydroxymethyl)aminomethane and stir for 30 minutes; add dropwise 30 mL of an aqueous solution containing 0.32 mmol of DA·HCl and continue stirring for 1 hour; (9) Collect the product by centrifugation, wash it 8 times with 30 mL each time using a 1:1 mixture of water and ethanol; dry it overnight at 60 o °C to obtain the NiCe-NC@PDA precursor; (10) Place the dried black NiCe-NC@PDA solid in a tube furnace, and under gas protection, heat it to 900 o °C at a heating rate of 2 o °C / min and hold for 2 hours to obtain the NiCe-NC@C catalyst.

[0017] Example 3 A preparation method of a catalyst for promoting the conversion of CO2 to CO, which comprises the following steps: (1) Dissolve Zn(NO3)2·6H2O and 2-mim with a molar ratio of 10:85 in methanol solutions respectively to obtain solution A and solution B; (2) Ultrasonically treat the two solutions for more than 10 minutes to ensure complete dissolution. Slowly add solution B to solution A without stirring. After a few seconds, the mixture turns milky white, indicating the formation of ZIF-8 particles; (3) Incubate the mixture in an oven at 60 o °C for 24 hours, naturally cool to room temperature, centrifuge to remove the liquid and wash it three times with ethanol; dry the solid in a vacuum oven at 5 o °C for 12 hours to obtain ZIF-8 powder; (4) Disperse the ZIF-8 powder in 50 mL of ethanol; (5) Pour a 15 mL ethanol solution containing 0.05 mmol Ce(NO3)3·6H2O and 0.1 mmol Ni(NO3)2·6H2O into the above dispersion and stir for 30 minutes; (6) Dissolve 5 mmol of benzimidazole in 15 mL of ethanol, add it to the mixture after stirring evenly, and continue to stir for 3 hours; collect the precipitate by centrifugation to obtain the NiCe-NC precursor; (7) Disperse half of the NiCe-NC precursor in 30 mL of deionized water and 80 mL of ethanol; (8) Add a 40 mL aqueous solution containing 100 mmol of tris(hydroxymethyl)aminomethane and stir for 30 minutes; add dropwise a 30 mL aqueous solution containing 0.32 mmol of DA·HCl and continue to stir for 1 hour; (9) Collect the product by centrifugation, wash it 8 times with 30 mL each time using a 1:1 mixture of water and ethanol; dry it overnight at 60 o °C to obtain the NiCe-NC@PDA precursor; (10) Place the dried black NiCe-NC@PDA solid in a tube furnace and heat it to 900 o °C at a heating rate of 2 o °C / min and hold for 2 hours to obtain the NiCe-NC@C catalyst.

[0018] Comparative Example 1 A method for preparing a catalyst for promoting the conversion of CO2 to CO, which comprises the following steps: (1) Dissolve Zn(NO3)2·6H2O and 2-mim with a molar ratio of 10:85 in methanol solutions respectively to obtain Solution A and Solution B; (2) Ultrasonically treat the two solutions for more than 10 minutes to ensure complete dissolution. Slowly add Solution B to Solution A without stirring. After a few seconds, the mixture turns milky white, indicating the formation of ZIF-8 particles; (3) Incubate the mixture in an oven at 60 o °C for 24 hours, naturally cool to room temperature, centrifuge to remove the liquid and wash three times with ethanol; dry the solid in a vacuum oven at 5 o °C for 12 hours to obtain ZIF-8 powder; (4) Disperse the ZIF-8 powder in 50 mL of ethanol; (5) Pour a 15 mL ethanol solution of 0.1 mmol Ni(NO3)2·6H2O into the above dispersion and stir for 30 minutes; (6) Dissolve 5 mmol of benzimidazole in 15 mL of ethanol, stir evenly and add it to the mixture, and continue to stir for 3 hours; collect the precipitate by centrifugation to obtain the NiCe-NC precursor; (7) Collect the product by centrifugation, wash it 8 times with a 1:1 mixture of water and ethanol, 30 mL each time; dry it overnight at 60 o °C to obtain the NiCe-NC precursor; (8) Place the dried sample in a tube furnace and heat it to 900 o °C at a heating rate of 2 o °C / min and hold for 2 hours to obtain the NiCe-NC@C catalyst.

[0019] The catalysts prepared in Examples 1-3 and Comparative Example 1 were respectively used for the performance test of electrocatalytic reduction of CO2: (1) Weigh 5 mg of the catalyst, add it to 0.9 mL of absolute ethanol, and then add 0.1 mL of 5 wt.% nafion solution, and ultrasonically treat for 20 min to form a uniformly dispersed solution; (2) Take a 1.0 cm 2The carbon paper was placed in a diluted sulfuric acid solution overnight to remove impurity oxides, and then ultrasonically cleaned with deionized water and absolute ethanol. 200 μL of the solution obtained in step (1) was taken and coated on the surface of the carbon paper, and dried at room temperature for standby; (3) The reaction gas was 99.999% CO2. CO, CO2, and H2 were separated by gas chromatography, and the carrier gas was high-purity nitrogen with a flow rate of 20 mL·min -1 . The electrochemical workstation was CHI660e, and the chromatograph was Shimadzu GC-2014C.

[0020] As Figure 1-4 shown, the test results are as follows: Example 1: When -0.7~1.1 V vs. RHE, FE CO >70%.

[0021] Example 2: When -0.9~1.2 V vs. RHE, FE CO >90%.

[0022] Example 3: When -0.8~1.2 V vs. RHE, FE CO >90%.

[0023] Comparative Example 1: When -0.8~1.0 V vs. RHE, FE CO >70%.

[0024] From the above tests, it can be seen that the dual-atom NiCe catalysts in Examples 1, 2, and 3 all have excellent Faraday efficiency for CO2 conversion to CO. Compared with the catalyst without Ce in Comparative Example 1, the Faraday efficiency of the catalysts prepared by the methods of Examples 1, 2, and 3 of the present invention is significantly higher; and the Faraday efficiency of CO2 conversion to CO in Example 3 is better than that of Examples 1 and 2. Refer to the appendix Figure 7 It can be seen that the NiCe bimetallic catalyst of the present invention is polygonal nanoparticles with a cluster size of 100-150 nm, and the particle surface is coated with a cracked carbon shell, which is convenient for active mass transfer and improves the catalytic effect.

[0025] It should be noted that refer to the appendix Figure 1 , appendix Figure 2 and appendix Figure 3 , and compared with appendix Figure 4 , it can be obtained that the Faraday efficiency of the catalysts in Examples 1-3 is not only much higher than that in Comparative Example 1, but also its stability is better than that in Comparative Example 1. The stability test was carried out at a constant voltage of -0.9V for the optimal Example 3. Refer to the appendix Figure 5 , in Example 3 at -0.9V vs. RHE, FE COThe fluctuation range is between 97.27% and 97.54%, with extremely high stability. In contrast, for Comparative Example 1, at -0.9V vs. RHE, FE CO The fluctuation range is between 73.5% and 77.5%, and the stable fluctuation effect is more than 20 times that of Example 3. For details, please refer to the attached Figure 5 , from which it can be seen that the carbon layer formed by dopamine coating plays a stabilizing role in the catalytic effect of the catalyst. For the coating effect, please refer to the attached Figure 6 SEM-Mapping test, which can significantly improve the stability of the catalyst itself. Although the technical contribution of Ce to stability cannot be excluded, the present invention believes that the technical contribution of Ce lies in the overall catalytic effect of the catalyst. For example, the optimal FE of Comparative Example 1 CO (-0.9V vs. RHE) can achieve ） ≈77%, while the carbon layer formed by dopamine coating is more concentrated on the technical contribution in terms of stability.

[0026] The above are the preferred embodiments of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a NiCe bimetallic catalyst for promoting the conversion of CO2 to CO, characterized in that, It includes the following steps: (1) Preparation of ZIF-8: Zinc nitrate (Zn(NO3)2·6H2O) and 2-methylimidazole (2-mim) with a molar ratio of 10:85 are respectively dissolved in methanol solution to obtain solution A and solution B; the two solutions are ultrasonically treated for more than 10 minutes to ensure complete dissolution; Then, solution B was slowly added to solution A without stirring. After a few seconds, the mixture turned milky white, indicating the formation of ZIF-8 particles. The mixture was incubated in an oven at 60 o °C for 24 hours to complete the self-assembly process. The colloidal solution containing ZIF-8 crystals was taken out, naturally cooled to room temperature, centrifuged to remove the liquid, and washed three times with ethanol. Finally, the solid was dried in a vacuum oven at 50 o °C for 12 hours to obtain ZIF-8 powder. (2) Preparation of NiCe-NC precursor: The ZIF-8 powder obtained in step (1) is dispersed in 50 mL of ethanol, and then a 15 mL ethanol solution containing 0.05 - 5 mmol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) or cerium chloride heptahydrate (CeCl3·7H2O) and 0.1 - 3 mmol of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) is poured into the above dispersion and stirred for 30 minutes; then 5 - 20 mmol of benzimidazole is dissolved in 15 mL of ethanol, stirred evenly and added to the mixture, and stirring is continued for 1 - 8 hours; the precipitate is collected by centrifugation to obtain the NiCe-NC precursor; (3) Preparation of carbon-coated NiCe-NC precursor: Disperse half of the NiCe-NC precursor obtained in step (2) in 30 mL of deionized water and 80 mL of ethanol, then add 40 mL of aqueous solution containing 10 - 200 mmol of tris(hydroxymethyl)aminomethane, and stir for 30 minutes; subsequently, dropwise add 30 mL of aqueous solution containing 0.05 - 0.50 mmol of dopamine hydrochloride (DA·HCl), and continue stirring for 0.5 - 24 hours; collect the product by centrifugation, wash it 8 times with a 1:1 mixture of water and ethanol, 30 mL each time, and finally dry it overnight at 60 o °C. (4) Calcination: Place the dried black solid in step (3) into a tubular furnace and heat it to 900 o °C at a heating rate of 2 o °C / min and hold for 2 hours to obtain the NiCe-NC@C catalyst.

2. The preparation method of a NiCe bimetallic catalyst for promoting the conversion of CO2 to CO according to claim 1, characterized in that, In step (2), the dosage of Ce(NO3)3·6H2O or CeCl3·7H2O is 0.05 - 5 mmol, the dosage of Ni(NO3)2·6H2O is 0.1 - 3 mmol, and the dosage of benzimidazole is 5 - 20 mmol.

3. The preparation method of a NiCe bimetallic catalyst for promoting the conversion of CO2 to CO according to claim 1, characterized in that, In step (3), the dosage of tris(hydroxymethyl)aminomethane is 10 - 200 mmol, and the dosage of DA·HCl is 0.05 - 0.50 mmol.

4. The preparation method of a NiCe bimetallic catalyst for promoting the conversion of CO2 to CO according to claim 1, characterized in that, In step (3), the polymerization time of DA·HCl is 0.5 - 24 h.

5. The preparation method of a NiCe bimetallic catalyst for promoting the conversion of CO2 to CO according to claim 1, characterized in that, In step (3), the washing solvent is a mixed solution of water and ethanol with a mixing volume ratio of 1:

1.

6. The preparation method of a NiCe bimetallic catalyst for promoting the conversion of CO2 to CO according to claims 1-5, characterized in that, In step (4), the protective gas is one or several of oxygen, nitrogen, argon or argon-hydrogen mixture.

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