A CeO2-loaded nitrogen-doped carbon catalyst, a preparation method and application thereof
By loading CeO2 onto carbon nanotubes, a nitrogen-doped carbon catalyst was developed, which solved the problems of easy poisoning of noble metals and low activity of non-noble metals. This catalyst achieved high activity and high stability in the efficient conversion of glycerol to formic acid, and provided a new method for preparing CeO2-based catalysts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ORDOS INST OF APPLIED TECH
- Filing Date
- 2026-06-23
- Publication Date
- 2026-07-21
AI Technical Summary
Existing precious metal catalysts are expensive and easily poisoned, while non-precious metal catalysts have low catalytic activity and poor stability. Traditional CeO2 catalysts have large particle size and low specific surface area, making it difficult to achieve efficient conversion of glycerol to formic acid.
Using functional carbon nanotubes as a support, phthalocyanine as a nitrogen source and dispersant, and cerium nitrate hexahydrate as a cerium source, a nitrogen-doped carbon catalyst supported on CeO2 was prepared by dispersion coordination and freeze-drying combined with segmented gradient calcination, thereby enhancing the metal-support interface interaction.
This study improved the catalytic activity and stability of the catalyst, enhanced the selectivity of glycerol to formic acid conversion, and provided a new approach for the preparation of CeO2-based catalysts.
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Figure CN122428331A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of CeO2-based catalyst preparation technology, specifically to a nitrogen-doped carbon catalyst supported on CeO2, its preparation method, and its application. Background Technology
[0002] Glycerol is a major byproduct of biodiesel production. Research on efficient and highly selective electrocatalytic oxidation of glycerol to formic acid is an effective way to achieve the resource utilization and high-value use of biomass, while also considering energy conversion and storage. Currently, commonly used glycerol electrooxidation catalysts mainly include noble metals (such as Pt and Au) and their alloys. These catalysts have high catalytic activity, but generally suffer from drawbacks such as high cost, scarce resources, easy oxidation by glycerol to form aldehyde and ketone intermediates, catalytic poisoning due to carbonaceous adsorption species covering active sites, and poor long-term stability. Non-noble metal catalysts, such as nickel and cobalt, are inexpensive and readily available, but generally suffer from low intrinsic catalytic activity, insufficient selectivity for the target product formic acid, susceptibility to over-oxidation, and rapid degradation during cycle service, making them difficult to meet the requirements of industrial applications. Cerium dioxide, as a typical rare earth oxide, has good application potential in the field of electrocatalysis due to its unique Ce(III) / Ce(IV) redox reversible cycle and excellent oxygen storage and release capabilities, as well as lattice oxygen migration ability.
[0003] However, cerium dioxide prepared by traditional processes has problems such as large grain size, low specific surface area, and limited number of surface catalytic active sites. Furthermore, cerium dioxide nanoparticles are prone to agglomeration and sintering on the surface of carbon-based supports such as carbon nanotubes, resulting in weak interfacial interactions between the metal and the support. This makes it impossible to effectively control the adsorption configuration of reaction intermediates, thereby restricting the catalytic activity and selectivity of the electro-oxidation of glycerol to formic acid.
[0004] Therefore, developing a non-precious metal CeO2-based catalyst with high dispersibility, high activity, and high stability to achieve efficient conversion of glycerol to formic acid is a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a nitrogen-doped carbon catalyst supported on CeO2, its preparation method, and its application.
[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a nitrogen-doped carbon catalyst supported on CeO2 includes the following steps: Step (1): Heat the nitric acid solution, add functional carbon nanotubes, ultrasonically disperse and stir, add phthalocyanine, stir, then add cerium nitrate hexahydrate, stir, centrifuge, wash, freeze dry to obtain solid precursor; Step (2): The solid precursor is placed in a protective gas, heated first, held at the temperature, then heated again, held at the temperature, then cooled down, and then cooled with the furnace to obtain a nitrogen-doped carbon catalyst supported on CeO2.
[0007] A method for preparing a nitrogen-doped carbon catalyst supported on CeO2 includes the following specific steps: Step (1): Heat the nitric acid solution to 40-45℃, add functional carbon nanotubes, ultrasonically disperse and stir for 15-20 min, add phthalocyanine, stir for 15-20 min, then add cerium nitrate hexahydrate, stir for 10-20 min, centrifuge, wash, freeze dry to obtain solid precursor; Furthermore, the ratio of nitric acid solution, functional carbon nanotubes, phthalocyanine, and cerium nitrate hexahydrate is 80-90 mL: 1.0 g: 0.25-0.4 g: 0.8-1.2 g; the mass fraction of nitric acid solution is 20-30%.
[0008] Step (2): Place the solid precursor in a protective gas, first heat it to 400-450℃ and hold it for 1-1.5h, then heat it to 700-750℃ and hold it for 2-2.5h, then cool it down to 500-550℃ and then cool it with the furnace to obtain a nitrogen-doped carbon catalyst supported on CeO2.
[0009] Furthermore, in step (ii), the heating rate is 5-7℃ / min and the cooling rate is 1-2℃ / min.
[0010] Furthermore, the preparation method of functional carbon nanotubes includes the following steps: Step (1): Add carbon nanotubes to mixed acid, heat, ultrasonically disperse and stir, centrifuge, wash, and vacuum dry to obtain product 1; Step (2): In a protective gas atmosphere, product 1 is added to thionyl chloride, stirred, DMF is added dropwise, the mixture is heated and stirred under reflux after the addition is complete, cooled, evaporated by rotary evaporation, washed, and dried under vacuum to obtain product 2; Step (3): Add product 2 to a mixed solvent, ultrasonically disperse it, add nitrogen-containing heterocyclic compound and DMAP, introduce protective gas, stir, heat and stir again, centrifuge, wash with DMF and ethanol respectively, and dry under vacuum to obtain functional carbon nanotubes.
[0011] Furthermore, the preparation method of functional carbon nanotubes includes the following specific steps: Step (1): Add carbon nanotubes to mixed acid, heat to 45-55℃, ultrasonically disperse and stir for 1-1.5h, centrifuge, wash with deionized water until the pH of the washing solution is 6-7, wash with ethanol, and dry under vacuum to obtain product 1; Furthermore, the mixed acid is obtained by mixing sulfuric acid and nitric acid in a volume ratio of 3-3.5:1, with the mass fraction of sulfuric acid being 95-98% and the mass fraction of nitric acid being 65-68%.
[0012] Furthermore, the ratio of carbon nanotubes to mixed acid is 0.5-0.7g: 20-25mL.
[0013] In step (1), carbon nanotubes are treated with mixed acid to increase oxygen-containing functional groups such as carboxyl groups on the surface, resulting in product 1.
[0014] Step (2): In a protective gas atmosphere, add product 1 to thionyl chloride, stir for 5-10 min, add DMF dropwise, raise the temperature to 60-70℃ after the addition is complete, reflux and stir for 12-13 h, cool, rotary evaporate, wash, and vacuum dry to obtain product 2. Furthermore, the ratio of product 1 to thionyl chloride is 1g:15-17mL, and the amount of DMF is 3-5% of the amount of thionyl chloride.
[0015] In step (2), the carboxyl groups on the surface of product 1 react with thionyl chloride to generate acyl chloride, resulting in carbon nanotubes with acyl chloride on the surface, i.e., product 2.
[0016] Step (3): Add product 2 to the mixed solvent, ultrasonically disperse for 20-25 min, add nitrogen-containing heterocyclic compound and DMAP, introduce protective gas, stir for 1.5-2 h, heat to 35-40℃, stir for 24-25 h, centrifuge, wash with DMF and ethanol respectively, and vacuum dry to obtain functional carbon nanotubes.
[0017] Furthermore, the mixed solvent is obtained by mixing anhydrous DMF and anhydrous THF in a volume ratio of 3:1-1.5.
[0018] Furthermore, the ratio of product 2, mixed solvent, nitrogen-containing heterocyclic compound, and DMAP is 1g: 16-18mL: 0.5-0.6g: 0.1-0.15g.
[0019] Furthermore, the nitrogen-containing heterocyclic compound is obtained by mixing 2-amino-4-methylpyridine and indole in a mass ratio of 5.5-6.0:6.
[0020] In step (3), the acyl chloride in product 2 reacts with the primary amino group in 2-amino-4-methylpyridine and the secondary amino group in indole in the nitrogen-containing heterocyclic compound, thereby introducing pyridine and indole nitrogen-containing heterocycles into the carbon nanotubes to obtain functional carbon nanotubes.
[0021] The nitrogen-doped carbon catalyst supported on CeO2 was prepared by the above-mentioned method.
[0022] The above-mentioned nitrogen-doped carbon catalyst supported on CeO2 was used in the electrocatalytic oxidation of glycerol to prepare formic acid.
[0023] The beneficial effects of this invention are: This invention provides a nitrogen-doped carbon catalyst supported on CeO2, its preparation method, and its application. The method for preparing the CeO2-supported nitrogen-doped carbon catalyst involves using functional carbon nanotubes as a support, phthalocyanine as a nitrogen source and chelating dispersant, and cerium nitrate hexahydrate as a cerium source. The catalyst is dispersed and coordinated in nitric acid solution, then freeze-dried to obtain a solid precursor. This precursor is then subjected to segmented gradient calcination under a protective gas to achieve in-situ uniform loading of nitrogen doping and cerium dioxide. The functional carbon nanotubes are prepared by first treating them with mixed acid to increase surface carboxyl groups, then reacting them with thionyl chloride to convert them into acyl chlorides, and finally reacting them with the primary amino group in 2-amino-4-methylpyridine and the secondary amino group in indole in a nitrogen-containing heterocyclic compound to introduce pyridine and indole nitrogen-containing heterocycles into the carbon nanotubes.
[0024] In the preparation process of the nitrogen-doped carbon catalyst supported on CeO2 provided by this invention, after preheating the nitric acid solution, functional carbon nanotubes are added and dispersed evenly. Then, phthalocyanine is added. The pyridine and indole nitrogen-containing heterocycles in the functional carbon nanotubes generate strong π-π stacking and hydrogen bonding with the phthalocyanine. The pyridine and indole nitrogen-containing heterocycles synergistically enhance the anchoring and dispersion of phthalocyanine on the carbon nanotube surface. Then, cerium nitrate hexahydrate is added. Pyridine, indole, and phthalocyanine form complexes with cerium ions, thereby enhancing the dispersion of cerium ions on the carbon nanotube surface. This effectively inhibits the migration, growth, and sintering agglomeration of cerium dioxide particles during calcination, enhances the interfacial interaction between the metal and the support, and forms a solid precursor through freeze-drying. Finally, the catalyst is calcined in a protective gas atmosphere with a staged gradient temperature increase. The pyrolysis of pyridine, indole, and phthalocyanine provides a nitrogen source, generating highly dispersed cerium dioxide particles and a nitrogen-doped carbon framework in situ. Ultimately, a nitrogen-doped carbon catalyst supported on CeO2 with strong interfacial bonding, abundant active sites, and uniform component distribution is constructed.
[0025] The nitrogen-doped carbon catalyst supported on CeO2 provided by this invention exhibits high catalytic activity and stability in the electrocatalytic oxidation of glycerol to formic acid, and is less prone to over-oxidation, thus improving the selectivity of glycerol to formic acid conversion. Furthermore, the preparation method of the nitrogen-doped carbon catalyst supported on CeO2 in this invention is simple, providing a new approach for the preparation of CeO2-based catalysts. Attached Figure Description
[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0027] Figure 1 This is a spherical aberration electron microscope image of the nitrogen-doped carbon catalyst supported on CeO2 prepared in Example 6 of the present invention. Detailed Implementation
[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0029] Example 1 Functional carbon nanotubes are prepared by the following steps: Step (1): Add carbon nanotubes (supplier: Beijing Deco Island Gold Technology Co., Ltd., CNT407) to mixed acid, heat to 45℃, ultrasonically disperse at 100W power and stir at 200rpm for 1h, centrifuge at 9000rpm for 10min, wash with deionized water until the pH of the washing solution is 6, wash with ethanol six times, and then vacuum dry at 60℃ for 12h to obtain product 1; the mixed acid is obtained by mixing sulfuric acid and nitric acid in a volume ratio of 3:1, with the mass fraction of sulfuric acid being 95% and the mass fraction of nitric acid being 65%; the volume ratio of carbon nanotubes to mixed acid is 0.5:20mL; the volume fraction of ethanol is 95%.
[0030] Step (2): In a nitrogen atmosphere, product 1 was added to thionyl chloride and stirred at room temperature for 5 min. DMF was added dropwise over 15 min. After the addition was complete, the temperature was raised to 60°C and stirred under reflux for 12 h. The mixture was then cooled to room temperature and rotary evaporated at 50°C. The residual liquid was washed three times with anhydrous toluene and then dried under vacuum at 50°C for 6 h to obtain product 2. The ratio of product 1 to thionyl chloride was 1 g: 15 mL, and the amount of DMF was 3% of the amount of thionyl chloride.
[0031] Step (3): Add product 2 to the mixed solvent, ultrasonically disperse at 150W for 20min, add nitrogen-containing heterocyclic compound and DMAP, purge with nitrogen, stir at room temperature for 1.5h, then heat to 35℃ and stir for 24h, centrifuge at 10000rpm for 5min, wash three times with DMF and ethanol respectively, and vacuum dry at 45℃ for 12h to obtain functional carbon nanotubes; the mixed solvent is anhydrous DMF and anhydrous THF mixed in a volume ratio of 3:1; the ratio of product 2, mixed solvent, nitrogen-containing heterocyclic compound and DMAP is 1g:16mL:0.5g:0.1g; the nitrogen-containing heterocyclic compound is 2-amino-4-methylpyridine and indole mixed in a mass ratio of 5.5:6.
[0032] Example 2 Functional carbon nanotubes are prepared by the following steps: Step (1): Carbon nanotubes (supplier: Beijing Deco Island Gold Technology Co., Ltd., CNT407) were added to the mixed acid, heated to 50°C, ultrasonically dispersed at 100W power and stirred at 200rpm for 1.2h, centrifuged at 9000rpm for 10min, washed with deionized water until the pH of the washing solution was 6.5, washed six times with ethanol, and then vacuum dried at 60°C for 12h to obtain product 1; the mixed acid was obtained by mixing sulfuric acid and nitric acid in a volume ratio of 3.3:1, with the mass fraction of sulfuric acid being 96% and the mass fraction of nitric acid being 66%; the volume ratio of carbon nanotubes to mixed acid was 0.6g:23mL; the volume fraction of ethanol was 95%.
[0033] Step (2): In a nitrogen atmosphere, product 1 was added to thionyl chloride and stirred at room temperature for 8 min. DMF was added dropwise over 15 min. After the addition was complete, the temperature was raised to 65°C and stirred under reflux for 12.5 h. The mixture was then cooled to room temperature and rotary evaporated at 50°C. The residual liquid was washed three times with anhydrous toluene and then dried under vacuum at 50°C for 6 h to obtain product 2. The ratio of product 1 to thionyl chloride was 1 g: 16 mL, and the amount of DMF was 4% of the amount of thionyl chloride.
[0034] Step (3): Add product 2 to the mixed solvent, ultrasonically disperse at 150W for 23min, add nitrogen-containing heterocyclic compound and DMAP, purge with nitrogen, stir at room temperature for 1.7h, then heat to 37℃, stir for 24.5h, centrifuge at 10000rpm for 5min, wash three times with DMF and ethanol respectively, and vacuum dry at 45℃ for 12h to obtain functional carbon nanotubes; the mixed solvent is anhydrous DMF and anhydrous THF mixed in a volume ratio of 3:1.3; the ratio of product 2, mixed solvent, nitrogen-containing heterocyclic compound and DMAP is 1g:17mL:0.55g:0.13g; the nitrogen-containing heterocyclic compound is 2-amino-4-methylpyridine and indole mixed in a mass ratio of 5.8:6.
[0035] Example 3 Functional carbon nanotubes are prepared by the following steps: Step (1): Carbon nanotubes (supplier: Beijing Deco Island Gold Technology Co., Ltd., CNT407) were added to the mixed acid, heated to 55°C, ultrasonically dispersed at 100W power and stirred at 200rpm for 1.5h, centrifuged at 9000rpm for 10min, washed with deionized water until the pH of the washing solution was 7, washed six times with ethanol, and then vacuum dried at 60°C for 12h to obtain product 1; the mixed acid was obtained by mixing sulfuric acid and nitric acid in a volume ratio of 3.5:1, with the mass fraction of sulfuric acid being 98% and the mass fraction of nitric acid being 68%; the volume ratio of carbon nanotubes to mixed acid was 0.7g:25mL; the volume fraction of ethanol was 95%.
[0036] Step (2): In a nitrogen atmosphere, product 1 was added to thionyl chloride and stirred at room temperature for 10 min. DMF was added dropwise over 15 min. After the addition was complete, the temperature was raised to 70 °C and stirred under reflux for 13 h. The mixture was then cooled to room temperature and rotary evaporated at 50 °C. The residual liquid was washed three times with anhydrous toluene and then dried under vacuum at 50 °C for 6 h to obtain product 2. The ratio of product 1 to thionyl chloride was 1 g: 17 mL, and the amount of DMF was 5% of the amount of thionyl chloride.
[0037] Step (3): Add product 2 to the mixed solvent, ultrasonically disperse at 150W for 25min, add nitrogen-containing heterocyclic compound and DMAP, purge with nitrogen, stir at room temperature for 2h, then heat to 40℃ and stir for 25h, centrifuge at 10000rpm for 5min, wash three times with DMF and ethanol respectively, and vacuum dry at 45℃ for 12h to obtain functional carbon nanotubes; the mixed solvent is anhydrous DMF and anhydrous THF mixed in a volume ratio of 3:1.5; the ratio of product 2, mixed solvent, nitrogen-containing heterocyclic compound and DMAP is 1g:18mL:0.6g:0.15g; the nitrogen-containing heterocyclic compound is 2-amino-4-methylpyridine and indole mixed in a mass ratio of 6.0:6.
[0038] Example 4 A method for preparing a nitrogen-doped carbon catalyst supported on CeO2 includes the following steps: Step (1): Heat the nitric acid solution to 40°C, add the functional carbon nanotubes obtained in Example 1, ultrasonically disperse at 100W power and stir at 200rpm for 15min, add phthalocyanine, stir at 40°C for 15min, then add cerium nitrate hexahydrate, stir at 40°C for 10min, centrifuge at 8000rpm for 7min, wash with deionized water until the pH of the washing solution is neutral, freeze-dry at -40°C for 12h to obtain a solid precursor; the ratio of nitric acid solution, functional carbon nanotubes obtained in Example 1, phthalocyanine, and cerium nitrate hexahydrate is 80mL:1.0g:0.25g:0.8g; the mass fraction of nitric acid solution is 20%.
[0039] Step (2): The solid precursor is placed in nitrogen gas and heated to 400°C at a rate of 5°C / min and held for 1 hour. Then, it is heated to 700°C at a rate of 5°C / min and held for 2 hours. Finally, it is cooled to 500°C at a rate of 1°C / min and then cooled to room temperature in the furnace to obtain a nitrogen-doped carbon catalyst supported on CeO2.
[0040] Example 5 A method for preparing a nitrogen-doped carbon catalyst supported on CeO2 includes the following steps: Step (1): Heat the nitric acid solution to 43°C, add the functional carbon nanotubes obtained in Example 2, ultrasonically disperse at 100W power and stir at 200rpm for 18min, add phthalocyanine, stir at 43°C for 18min, then add cerium nitrate hexahydrate, stir at 43°C for 15min, centrifuge at 8000rpm for 7min, wash with deionized water until the pH of the washing solution is neutral, freeze-dry at -40°C for 12h to obtain a solid precursor; the ratio of nitric acid solution, functional carbon nanotubes obtained in Example 2, phthalocyanine, and cerium nitrate hexahydrate is 85mL:1.0g:0.32g:1.0g; the mass fraction of the nitric acid solution is 25%.
[0041] Step (2): The solid precursor is placed in nitrogen gas and heated to 430°C at a rate of 6°C / min and held for 1.3 h. Then, the temperature is increased to 730°C at a rate of 6°C / min and held for 2.3 h. Finally, the temperature is decreased to 530°C at a rate of 1.5°C / min and then cooled to room temperature in the furnace to obtain a nitrogen-doped carbon catalyst supported on CeO2.
[0042] Example 6 A method for preparing a nitrogen-doped carbon catalyst supported on CeO2 includes the following steps: Step (1): Heat the nitric acid solution to 45°C, add the functional carbon nanotubes obtained in Example 3, ultrasonically disperse at 100W power and stir at 200rpm for 20min, add phthalocyanine, stir at 45°C for 20min, then add cerium nitrate hexahydrate, stir at 45°C for 20min, centrifuge at 8000rpm for 7min, wash with deionized water until the pH of the washing solution is neutral, freeze-dry at -40°C for 12h to obtain a solid precursor; the ratio of nitric acid solution, functional carbon nanotubes obtained in Example 3, phthalocyanine, and cerium nitrate hexahydrate is 90mL:1.0g:0.4g:1.2g; the mass fraction of nitric acid solution is 30%.
[0043] Step (2): The solid precursor is placed in nitrogen gas and heated to 450°C at a rate of 7°C / min and held for 1.5 h. Then, the temperature is increased to 750°C at a rate of 7°C / min and held for 2.5 h. Finally, the temperature is decreased to 550°C at a rate of 2°C / min and then cooled to room temperature in the furnace to obtain a nitrogen-doped carbon catalyst supported on CeO2.
[0044] Comparative Example 1 Compared with Example 6, the solid precursor was replaced with solid precursor-1, and everything else was exactly the same as in Example 6, to prepare a nitrogen-doped carbon catalyst supported on CeO2. The preparation of solid precursor-1 is as follows: The nitric acid solution was heated to 45°C, phthalocyanine was added, and the mixture was stirred at 45°C for 20 min. Then, cerium nitrate hexahydrate was added, and the mixture was stirred at 45°C for 20 min. The functional carbon nanotubes obtained in Example 3 were added, and the mixture was ultrasonically dispersed at 100 W and stirred at 200 rpm for 20 min. The mixture was centrifuged at 8000 rpm, washed with deionized water until the pH of the washing solution was neutral, and then freeze-dried at -40°C for 12 h to obtain a solid precursor. The ratio of nitric acid solution, functional carbon nanotubes, phthalocyanine, and cerium nitrate hexahydrate was 90 mL: 1.0 g: 0.4 g: 1.2 g; the mass fraction of the nitric acid solution was 30%.
[0045] Comparative Example 2 Compared with Example 6, the solid precursor was replaced with solid precursor-2, and everything else was exactly the same as in Example 6, to prepare a nitrogen-doped carbon catalyst supported on CeO2. The preparation of solid precursor-2 is as follows: The nitric acid solution was heated to 45°C, and the functional carbon nanotubes obtained in Example 3 were added. The mixture was ultrasonically dispersed at 100W and stirred at 200rpm for 20min. Then, cerium nitrate hexahydrate was added, and the mixture was stirred at 45°C for 40min. The mixture was centrifuged at 8000rpm, washed with deionized water until the pH of the washing solution was neutral, and then freeze-dried at -40°C for 12h to obtain solid precursor-2. The ratio of nitric acid solution, functional carbon nanotubes obtained in Example 3, and cerium nitrate hexahydrate was 90mL:1.0g:1.2g. The mass fraction of the nitric acid solution was 30%.
[0046] Comparative Example 3 Compared with Example 6, the phased gradient heating and holding process in step (II) was replaced by directly heating to 750°C and holding, while the rest was exactly the same as in Example 6, to obtain a nitrogen-doped carbon catalyst supported on CeO2. Specifically: Step (2): The solid precursor is placed in nitrogen and heated to 750°C at a rate of 7°C / min. After holding at this temperature for 4 hours, it is cooled to 550°C at a rate of 2°C / min and then cooled to room temperature in the furnace to obtain a nitrogen-doped carbon catalyst supported on CeO2.
[0047] Comparative Example 4 Compared with Example 6, the nitrogen-containing heterocyclic compound in the preparation process of functional carbon nanotubes was replaced by 2-amino-4-methylpyridine by an equal mass, and the rest was exactly the same as in Example 6, to obtain a nitrogen-doped carbon catalyst supported on CeO2.
[0048] Comparative Example 5 Compared with Example 6, the nitrogen-containing heterocyclic compound in the preparation process of functional carbon nanotubes was replaced with indole by an equal mass, while the rest was exactly the same as in Example 6, to obtain a nitrogen-doped carbon catalyst supported on CeO2.
[0049] The performance of the nitrogen-doped carbon catalysts supported on CeO2 prepared in Examples 4-6 and Comparative Examples 1-5 of this invention was further tested below, and the test results are shown below.
[0050] In an alkaline electrolyte system consisting of 1 mol / L glycerol and 1 mol / L KOH, a nitrogen-doped carbon catalyst supported on CeO2 was prepared and tested under ambient temperature and pressure three-electrode conditions at a potential of 1.57 V (vs. RHE) for 4 h. The catalytic performance of the nitrogen-doped carbon catalyst supported on CeO2 was tested, and the glycerol conversion, formic acid selectivity, and formic acid yield were recorded.
[0051] The above experiment of electro-oxidation of glycerol to formic acid was conducted, with a reaction time of 10 hours. The initial current I0 and the current I at the end of 10 hours were recorded. 10 The current retention rate was calculated and recorded. A higher current retention rate indicates that the nitrogen-doped carbon catalyst supported on CeO2 has better long-term working stability in the electro-oxidation reaction of glycerol.
[0052] The results are recorded in Table 1.
[0053] Table 1: Test results of nitrogen-doped carbon catalysts supported on CeO2 According to the data in Table 1, the nitrogen-doped carbon catalysts supported on CeO2 prepared in Examples 4-6 of this invention have high catalytic activity and excellent stability in the electro-oxidation of glycerol to formic acid.
[0054] Comparing Example 6 with Comparative Example 1, it can be seen that replacing the solid precursor with solid precursor-1 indicates that the present invention first adds functional carbon nanotubes to the nitric acid solution, and after uniform dispersion, adds phthalocyanine and cerium nitrate hexahydrate in sequence. This is more conducive to the formation of complexes between pyridine, indole, and phthalocyanine and cerium ions, thereby enhancing the dispersion of cerium ions on the surface of carbon nanotubes, effectively inhibiting the migration, growth, and sintering agglomeration of cerium dioxide particles during calcination, enhancing the interfacial interaction between the metal and the support, and thus improving the catalytic activity and stability of the nitrogen-doped carbon catalyst in the electro-oxidation of glycerol to formic acid.
[0055] Comparing Example 6 with Comparative Example 2, it can be seen that replacing the solid precursor with solid precursor-2 indicates that the addition of phthalocyanine during the catalyst preparation process in this invention is more conducive to the formation of complexes with cerium ions, thereby enhancing the dispersion of cerium ions on the surface of carbon nanotubes, effectively inhibiting the migration, growth and sintering agglomeration of cerium dioxide particles during calcination, enhancing the interfacial interaction between the metal and the support, and thus improving the catalytic activity and stability of the nitrogen-doped carbon catalyst in the electro-oxidation of glycerol to formic acid.
[0056] Comparing Example 6 with Comparative Example 3, it can be seen that replacing the staged gradient heating and holding process in step (II) with direct heating to 750℃ and holding indicates that the nitrogen-doped carbon catalyst prepared by the staged gradient heating and holding calcination method of the present invention has better dispersion uniformity and high catalytic activity and excellent stability in the electro-oxidation of glycerol to formic acid.
[0057] A comparison of Example 6 and Comparative Example 4 shows that replacing the nitrogen-containing heterocyclic compound in the preparation process of functional carbon nanotubes with 2-amino-4-methylpyridine by an equal mass indicates that the nitrogen-containing heterocyclic compound obtained by mixing 2-amino-4-methylpyridine with indole in this invention helps to form a complex with cerium ions, thereby enhancing the dispersion of cerium ions on the surface of carbon nanotubes, effectively inhibiting the migration, growth and sintering agglomeration of cerium dioxide particles during calcination, enhancing the interfacial interaction between the metal and the support, and thus improving the catalytic activity and stability of the nitrogen-doped carbon catalyst in the electro-oxidation of glycerol to formic acid.
[0058] A comparison of Example 6 and Comparative Example 5 shows that replacing the nitrogen-containing heterocyclic compound in the preparation process of functional carbon nanotubes with indole by an equal mass indicates that the nitrogen-containing heterocyclic compound obtained by mixing 2-amino-4-methylpyridine and indole in this invention helps to form a complex with cerium ions, thereby enhancing the dispersion of cerium ions on the surface of carbon nanotubes, effectively inhibiting the migration, growth and sintering agglomeration of cerium dioxide particles during calcination, enhancing the interfacial interaction between the metal and the support, and thus improving the catalytic activity and stability of the nitrogen-doped carbon catalyst in the electro-oxidation of glycerol to formic acid.
[0059] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.
Claims
1. A method for preparing a nitrogen-doped carbon catalyst supported on CeO2, characterized in that: Includes the following steps: Step (1): Heat the nitric acid solution, add functional carbon nanotubes, ultrasonically disperse and stir, add phthalocyanine, stir, then add cerium nitrate hexahydrate, stir, centrifuge, wash, freeze dry to obtain solid precursor; Step (2): The solid precursor is placed in a protective gas, heated first, held at the temperature, then heated again, held at the temperature, then cooled down, and then cooled with the furnace to obtain a nitrogen-doped carbon catalyst supported on CeO2.
2. The method for preparing a nitrogen-doped carbon catalyst supported on CeO2 according to claim 1, characterized in that: The specific steps include the following: Step (1): Heat the nitric acid solution to 40-45℃, add functional carbon nanotubes, ultrasonically disperse and stir for 15-20 min, add phthalocyanine, stir for 15-20 min, then add cerium nitrate hexahydrate, stir for 10-20 min, centrifuge, wash, freeze dry to obtain solid precursor; Step (2): Place the solid precursor in a protective gas, first heat it to 400-450℃ and hold it for 1-1.5h, then heat it to 700-750℃ and hold it for 2-2.5h, then cool it down to 500-550℃ and then cool it with the furnace to obtain a nitrogen-doped carbon catalyst supported on CeO2.
3. The method for preparing a nitrogen-doped carbon catalyst supported on CeO2 according to claim 2, characterized in that: In step (i), the ratio of the amount of nitric acid solution, functional carbon nanotubes, phthalocyanine, and cerium nitrate hexahydrate used is 80-90 mL: 1.0 g: 0.25-0.4 g: 0.8-1.2 g.
4. The method for preparing a nitrogen-doped carbon catalyst supported on CeO2 according to claim 2, characterized in that: The preparation method of the functional carbon nanotubes includes the following steps: Step (1): Add carbon nanotubes to mixed acid, heat, ultrasonically disperse and stir, centrifuge, wash, and vacuum dry to obtain product 1; Step (2): In a protective gas atmosphere, product 1 is added to thionyl chloride, stirred, DMF is added dropwise, the mixture is heated and stirred under reflux after the addition is complete, cooled, evaporated by rotary evaporation, washed, and dried under vacuum to obtain product 2; Step (3): Add product 2 to a mixed solvent, ultrasonically disperse it, add nitrogen-containing heterocyclic compound and DMAP, introduce protective gas, stir, heat and stir again, centrifuge, wash with DMF and ethanol respectively, and dry under vacuum to obtain functional carbon nanotubes.
5. The method for preparing a nitrogen-doped carbon catalyst supported on CeO2 according to claim 4, characterized in that: In step (1), the ratio of carbon nanotubes to mixed acid is 0.5-0.7g: 20-25mL.
6. The method for preparing a nitrogen-doped carbon catalyst supported on CeO2 according to claim 4, characterized in that: In step (2), the ratio of product 1 to thionyl chloride is 1g:15-17mL, and the amount of DMF is 3-5% of the amount of thionyl chloride.
7. The method for preparing a nitrogen-doped carbon catalyst supported on CeO2 according to claim 4, characterized in that: In step (3), the ratio of product 2, mixed solvent, nitrogen-containing heterocyclic compound, and DMAP is 1g: 16-18mL: 0.5-0.6g: 0.1-0.15g.
8. The method for preparing a nitrogen-doped carbon catalyst supported on CeO2 according to claim 4, characterized in that: In step (3), the nitrogen-containing heterocyclic compound is obtained by mixing 2-amino-4-methylpyridine and indole in a mass ratio of 5.5-6.0:
6.
9. A nitrogen-doped carbon catalyst supported on CeO2 prepared by a method according to any one of claims 1-8.
10. The application of the nitrogen-doped carbon catalyst supported on CeO2 according to claim 9, characterized in that: The nitrogen-doped carbon catalyst supported on CeO2 was used for the electrocatalytic oxidation of glycerol to prepare formic acid.