Preparation method of nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid through carbon dioxide electrocatalysis
阅读说明：本技术 一种用于二氧化碳电催化产甲酸的氮掺杂石墨烯负载核壳状铜-碳复合催化剂的制备方法 (Preparation method of nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid through carbon dioxide electrocatalysis ) 是由 冯玉杰 李达 田妍 吴晶 于 2020-05-28 设计创作，主要内容包括：一种用于二氧化碳电催化产甲酸的氮掺杂石墨烯负载核壳状铜-碳复合催化剂的制备方法,本发明涉及氮掺杂石墨烯负载核壳状铜-碳复合催化剂的制备方法。本发明要解决现有多孔碳负载金属催化剂存在着产物选择性差且稳定性低的问题。方法：一、配置前驱溶液；二、水热反应；三、清洗烘干；四、产物碳化。本发明用于二氧化碳电催化产甲酸的氮掺杂石墨烯负载核壳状铜-碳复合催化剂的制备。(The invention discloses a preparation method of a nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid by carbon dioxide electrocatalysis, and relates to a preparation method of a nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst. The invention aims to solve the problems of poor product selectivity and low stability of the existing porous carbon supported metal catalyst. The method comprises the following steps: firstly, preparing a precursor solution; secondly, carrying out hydrothermal reaction; thirdly, cleaning and drying; fourthly, carbonizing the product. The method is used for preparing the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid by carbon dioxide electrocatalysis.)
1. A preparation method of a nitrogen-doped graphene loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid by carbon dioxide electrocatalysis is characterized by comprising the following steps:
firstly, preparing a precursor solution:
adding nitrogen-doped reduced graphene oxide into a mixed solution of N, N-dimethylformamide and ethanol for full dispersion, and then adding Cu (NO)3)2·3H2Continuously stirring the O until the O is completely dissolved to obtain a mixed solution; dissolving benzimidazole in a mixed solution of N, N-dimethylformamide and ethanol, and stirring until the benzimidazole is dissolved to obtain a benzimidazole solution; dissolving trimesic acid in a mixed solution of N, N-dimethylformamide and ethanol, and stirring until the solution is dissolved to obtain a trimesic acid solution;
cu (NO) in the mixed solution3)2·3H2The concentration of O is 2.5 mg/mL-3.0 mg/mL; cu (NO) in the mixed solution3)2·3H2The mass ratio of the O to the nitrogen-doped reduced graphene oxide is 1 (0.1-0.3); the concentration of benzimidazole in the benzimidazole solution is 10 mg/mL-15 mg/mL; the concentration of trimesic acid in the trimesic acid solution is 1.0 mg/mL-1.5 mg/mL;
secondly, hydrothermal reaction:
mixing the mixed solution with a benzimidazole solution, stirring until the mixed solution is bright blue, adding a trimesic acid solution into the benzimidazole solution, continuously mixing and stirring to obtain a precursor solution, transferring the precursor solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and carrying out hydrothermal reaction for 5-8 h under the constant temperature condition of 80-100 ℃ to obtain a nitrogen-doped graphene-loaded Cu _ MOF precursor;
cu (NO) in the precursor solution3)2·3H2The mass ratio of O to benzimidazole is 1 (3-5); cu (NO) in the precursor solution3)2·3H2The mass ratio of O to trimesic acid is 1 (0.7-1.0);
thirdly, cleaning and drying:
centrifuging a nitrogen-doped graphene-loaded Cu _ MOF precursor, cleaning the precursor for several times by using absolute ethyl alcohol, and then placing the precursor in a vacuum drying oven for drying to obtain a dried product;
fourthly, carbonizing a product:
placing the dried product in a tubular furnace, introducing high-purity Ar gas, heating to 700-1000 ℃ at the heating rate of 1-5 ℃/min, and calcining for 3-8 h at the temperature of 700-1000 ℃ to obtain the nitrogen-doped graphene-loaded core-shell structure Cu2O/Cu @ C composite catalyst.
2. The preparation method of the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid through carbon dioxide electrocatalysis according to claim 1, characterized in that the nitrogen-doped reduced graphene oxide in the step one is prepared by the following steps: adding graphene oxide powder into deionized water, then adding urea, transferring the mixture into a reaction kettle, and reacting for 3-8 hours at the temperature of 150-200 ℃ to obtain nitrogen-doped reduced graphene oxide; the volume ratio of the mass of the graphene oxide powder to the deionized water is 1mg (1-5) mL; the mass ratio of the graphene oxide powder to the urea is 1 (20-40).
3. The preparation method of the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid by electrocatalysis of carbon dioxide according to claim 1, wherein the purity of the high-purity Ar gas in the fourth step is 99.99%.
4. The preparation method of the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid through electrocatalysis of carbon dioxide according to claim 1, which is characterized in that the volume ratio of N, N-dimethylformamide to ethanol in the mixed solution of N, N-dimethylformamide and ethanol in the step one is 1 (0.5-2.0).
5. The preparation method of the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid through electrocatalysis of carbon dioxide according to claim 1, which is characterized in that the step three is carried out by placing the catalyst in a vacuum drying oven for drying, specifically, placing the catalyst in a vacuum drying oven for drying at the temperature of 60 ℃.
6. The preparation method of the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid through carbon dioxide electrocatalysis according to claim 1, characterized in that Cu (NO) in the mixed solution in the step one3)2·3H2The concentration of O is 2.7 mg/mL-3.0 mg/mL; cu (NO) in the mixed solution in the step one3)2·3H2The mass ratio of the O to the nitrogen-doped reduced graphene oxide is 1 (0.2-0.3); the concentration of benzimidazole in the benzimidazole solution in the step one is 11.2 mg/mL-15 mg/mL; the concentration of the trimesic acid in the trimesic acid solution in the step one is 1.2 mg/mL-1.5 mg/mL.
7. The preparation method of the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid through electrocatalysis of carbon dioxide according to claim 1, which is characterized in that in the second step, the mixed solution and the benzimidazole solution are mixed and stirred until the mixture is bright blue, the trimesic acid solution is added into the mixture and continuously mixed and stirred to obtain a precursor solution, the precursor solution is transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and hydrothermal reaction is carried out for 6-8 h under the constant temperature condition of 90-100 ℃ to obtain the nitrogen-doped graphene-loaded Cu _ MOF precursor.
8. The preparation method of the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid through electrocatalysis of carbon dioxide according to claim 1, which is characterized in that Cu (NO) in the precursor solution in the step two3)2·3H2The mass ratio of O to benzimidazole is 1 (4.2-5); cu (NO) in the precursor solution in the second step3)2·3H2The mass ratio of O to trimesic acid is 1 (0.88-1.0).
9. The preparation method of the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid by electrocatalysis of carbon dioxide according to claim 1, which is characterized in that in the fourth step, the temperature is increased to 800-1000 ℃ under the condition that the temperature increase rate is 2-5 ℃/min.
10. The preparation method of the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid through carbon dioxide electrocatalysis according to claim 1, which is characterized in that in the fourth step, the nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst is calcined for 5 to 8 hours at the temperature of 800 to 1000 ℃.
Technical Field
The invention relates to a preparation method of a nitrogen-doped graphene loaded nuclear shell-shaped copper-carbon composite catalyst.
Background
The increasing of the human industrialization and urbanization process has increased the demand for various fuels, and the CO discharged by the fuel combustion2The global "greenhouse effect" is getting worse, and thus the dual problems of energy crisis and environmental pollution are getting worse. CO as a carbon-containing resource with abundant reserves2Not only can relieve CO in the atmospheric environment2Concentration, thereby alleviating the greenhouse effect thereof, and also alleviating the crisis of resource shortage which is increasingly in shortage. Due to CO2The molecules are stable and require high energy to activate, resulting in atmospheric CO2Less than 5.5% of the total amount of the organic compounds is effectively utilized. Therefore, the global attention is raised by searching for efficient transformation approaches and constructing reasonable transformation methods. Compared with biological method and photocatalytic method, the electrochemical catalytic reduction of CO2Can be realized at normal temperature and normal pressure. The method is simple and convenient to operate and easy to control, and the selection of products can be effectively controlled by changing the electrolysis conditions. Thus, the catalyst designed to synthesize high efficiency, stability and high selectivity is the electro-reduction of CO2The key point of the reaction is the research focus and difficulty in the field at present. The copper-based metal organic framework material (Cu _ MOF) becomes a good precursor template due to the advantages of large specific surface area, high porosity, adjustable pore size, adjustable structure and the like, and the prepared porous carbon supported metal catalyst is used for CO2Catalytic studies of (2). However, such catalysts have poor selectivity to formic acid, often accompanied by the production of small molecular alcohols in the product, and have the significant disadvantage of low stability (usually less than 10 h).
Disclosure of Invention
The invention provides a preparation method of a nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid by carbon dioxide electrocatalysis, aiming at solving the problems of poor product selectivity and low stability of the existing porous carbon-loaded metal catalyst.
A preparation method of a nitrogen-doped graphene-loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid by carbon dioxide electrocatalysis is carried out according to the following steps:
firstly, preparing a precursor solution:
adding nitrogen-doped reduced graphene oxide into a mixed solution of N, N-dimethylformamide and ethanol for full dispersion, and then adding Cu (NO)3)2·3H2Continuously stirring the O until the O is completely dissolved to obtain a mixed solution; dissolving benzimidazole in a mixed solution of N, N-dimethylformamide and ethanol, and stirring until the benzimidazole is dissolved to obtain a benzimidazole solution; dissolving trimesic acid in a mixed solution of N, N-dimethylformamide and ethanol, and stirring until the solution is dissolved to obtain a trimesic acid solution;
cu (NO) in the mixed solution3)2·3H2The concentration of O is 2.5 mg/mL-3.0 mg/mL; cu (NO) in the mixed solution3)2·3H2The mass ratio of the O to the nitrogen-doped reduced graphene oxide is 1 (0.1-0.3); the concentration of benzimidazole in the benzimidazole solution is 10 mg/mL-15 mg/mL; the concentration of trimesic acid in the trimesic acid solution is 1.0 mg/mL-1.5 mg/mL;
secondly, hydrothermal reaction:
mixing the mixed solution with a benzimidazole solution, stirring until the mixed solution is bright blue, adding a trimesic acid solution into the benzimidazole solution, continuously mixing and stirring to obtain a precursor solution, transferring the precursor solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and carrying out hydrothermal reaction for 5-8 h under the constant temperature condition of 80-100 ℃ to obtain a nitrogen-doped graphene-loaded Cu _ MOF precursor;
cu (NO) in the precursor solution3)2·3H2The mass ratio of O to benzimidazole is 1 (3-5); cu (NO) in the precursor solution3)2·3H2The mass ratio of O to trimesic acid is 1 (0.7-1.0);
thirdly, cleaning and drying:
centrifuging a nitrogen-doped graphene-loaded Cu _ MOF precursor, cleaning the precursor for several times by using absolute ethyl alcohol, and then placing the precursor in a vacuum drying oven for drying to obtain a dried product;
fourthly, carbonizing a product:
drying the productPlacing the product in a tubular furnace, introducing high-purity Ar gas, heating to 700-1000 ℃ at the heating rate of 1-5 ℃/min, calcining for 3-8 h at the temperature of 700-1000 ℃ to obtain the nitrogen-doped graphene-loaded core-shell structure Cu2O/Cu @ C composite catalyst.
The invention has the beneficial effects that:
1. the method adopts a simple hydrothermal synthesis method to prepare the nitrogen-doped graphene-loaded Cu _ MOF precursor, and prepares the nitrogen-doped graphene-loaded core-shell structure Cu through a high-temperature carbonization method2The O/Cu @ C composite catalyst effectively improves the electrochemical activity of the catalyst.
2. The invention introduces nitrogen-doped graphene and Cu2Compared with an O/Cu @ C catalyst, the introduction of the nitrogen-doped graphene can disperse effective metal sites, so that the electrochemical active surface area of the catalyst is increased by 4.3 times and reaches 47.2mF/cm2And the internal resistance of charge transfer is reduced to 3.91 omega, which is reduced by 48.8 percent; in addition the catalyst is on CO2The adsorption capacity is improved by 2.3 times and reaches 0.95mmol/g, thereby obviously improving the electrocatalytic reduction of CO by the Cu catalyst2And (4) activity. Nitrogen-doped graphene-loaded core-shell structure Cu2The Faraday efficiency of the O/Cu @ C composite catalyst on the reduction of carbon dioxide to produce formic acid is up to 82.9 percent, and the synthesis rate of the formic acid is up to 430.2mg/L/h/m2。
3. Nitrogen-doped graphene-loaded core-shell structure Cu prepared by adopting method2The O/Cu @ C composite catalyst has good stability, and the Faraday current efficiency of formic acid is still maintained to be over 73 percent after continuous electrolysis for 30 hours.
The invention provides a preparation method of a nitrogen-doped graphene loaded nuclear shell-shaped copper-carbon composite catalyst for producing formic acid by carbon dioxide electrocatalysis.
Drawings
FIG. 1 shows nitrogen-doped graphene-loaded core-shell structure Cu prepared in first embodiment2Scanning electron microscope picture of O/Cu @ C composite catalyst, wherein A is octahedral Cu2O/Cu @ C, wherein B is Cu particles, and C is nitrogen-doped graphene;
FIG. 2 is a schematic view of an embodimentExample I prepared Nitrogen-doped graphene loaded core-shell structure Cu2An LSV graph obtained by testing the O/Cu @ C composite catalyst under the conditions of nitrogen and carbon dioxide, wherein A is an LSV curve obtained under the condition of nitrogen, and B is an LSV curve obtained under the condition of carbon dioxide;
FIG. 3 shows comparative experimental preparation of core-shell structure Cu2An LSV graph obtained by testing an O/Cu @ C catalyst under the conditions of nitrogen and carbon dioxide, wherein A is an LSV curve obtained under the condition of nitrogen, and B is an LSV curve obtained under the condition of carbon dioxide;
FIG. 4 shows the catalyst in CO2Faradaic efficiency diagram of methanogenic acid electrolyzed in saturated 0.1mol/L potassium bicarbonate solution for 1 hour, a is Cu of nitrogen-doped graphene load core-shell structure prepared in the first embodiment2O/Cu @ C composite catalyst, b is core-shell structure Cu prepared by contrast experiment2An O/Cu @ C catalyst;
FIG. 5 shows the catalyst in CO2A methanogenic rate of 1 hour electrolysis in a saturated 0.1mol/L potassium bicarbonate solution, a is the nitrogen-doped graphene-loaded core-shell structure Cu prepared in example one2O/Cu @ C composite catalyst, b is core-shell structure Cu prepared by contrast experiment2An O/Cu @ C catalyst;
FIG. 6 shows the catalyst in CO2A linear fit plot of current in a saturated 0.1mol/L potassium bicarbonate solution with sweep rate; a is nitrogen-doped graphene-loaded core-shell structure Cu prepared in embodiment one2O/Cu @ C composite catalyst, b is core-shell structure Cu prepared by contrast experiment2An O/Cu @ C catalyst;
FIG. 7 shows the catalyst in CO2Nyquist diagram in saturated 0.1mol/L potassium bicarbonate solution; a is nitrogen-doped graphene-loaded core-shell structure Cu prepared in embodiment one2O/Cu @ C composite catalyst, b is core-shell structure Cu prepared by contrast experiment2An O/Cu @ C catalyst;
FIG. 8 shows catalyst vs. CO2The adsorption curve of (c); a is nitrogen-doped graphene-loaded core-shell structure Cu prepared in embodiment one2O/Cu @ C composite catalyst, b is core-shell structure Cu prepared by contrast experiment2An O/Cu @ C catalyst;
FIG. 9 is a graph of a sample prepared in accordance with example oneNitrogen-doped graphene loaded core-shell structure Cu2The stability test curve of the O/Cu @ C composite catalyst is that 1 is current density and 2 is Faraday efficiency.
Detailed Description
The technical solution of the present invention is not limited to the specific embodiments listed below, and includes any combination of the specific embodiments.