A B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst and its preparation and application
Through B, N co-doped carbon nanotube-supported copper-iron bimetal oxide catalyst, the low selectivity problem of electrochemical reduction nitrate is solved, and efficient nitrate reduction and ammonia production performance is achieved.
Patent Information
- Application Number
- CN202510695147.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-28
- Publication Date
- 2025-08-12
- Estimated Expiration
- 2045-05-28
AI Technical Summary
The prior art has complex 8-electron transfer process and low selectivity in the preparation of ammonia by electrochemical reduction of nitrates, resulting in frequent side reactions and it is difficult to achieve efficient nitrate reduction and Faraday efficiency.
B and N co-doped carbon nanotubes were prepared by calcining method, and copper-iron bimetallic ions were loaded through immersion and adsorption method, and copper-iron bimetallic oxide clusters were constructed to regulate the size and density of metal active sites.
High nitrate reduction performance was achieved, the ammonia production rate reached 95.2 mgh-1 mgcat-1 and the Faraday efficiency reached 91.3%, which improved the selectivity and efficiency of nitrate reduction.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of electrocatalytic reduction of nitrates to prepare ammonia, and specifically relates to a B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst and its preparation and application. Background Art
[0002] Traditional ammonia synthesis processes require high temperatures and pressures, and they emit significant amounts of carbon dioxide. However, electrochemical nitrate reduction has attracted considerable attention as a mild, green ammonia synthesis technology. Its main advantages lie in the fact that the N=O bond energy of the nitrate ion (204 kJ / mol) is much lower than the N≡N bond energy of the N₂ molecule (941 kJ / mol). Furthermore, it has extremely high solubility in water, which reduces the thermodynamic energy barrier for the reaction. Furthermore, nitrate is currently the primary nitrogen pollutant in water. Converting it into a usable energy source is an excellent waste-to-energy strategy and can serve as a promising hydrogen storage strategy, providing high-quality energy for production and daily life. However, this reaction involves a complex eight-electron transfer process and multiple intermediates, which can lead to side reactions and low selectivity. Therefore, designing and constructing an efficient catalytic system to improve the selectivity and Faradaic efficiency of nitrate reduction is crucial. Summary of the Invention
[0003] The purpose of the present invention is to provide a B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst and its preparation and application, so as to solve the problems existing in the prior art.
[0004] The present invention uses simple technical means to uniformly mix perylene tetracarboxylic dianhydride, boric acid, and urea and calcine them to construct carbon nanotubes co-doped with B and N. The doping amount is adjusted, and metal atoms are loaded on the surface of the carbon nanotubes through a coordination adsorption strategy. A catalyst with high nitrate reduction efficiency to produce ammonia and high Faradaic efficiency is obtained through thermal decomposition.
[0005] A method for preparing a B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst comprises the following steps:
[0006] (1) uniformly mixing an aromatic compound, boric acid, and urea in an organic solvent, and then removing the organic solvent;
[0007] (2) Then, the carbon nanotubes were calcined in a tube furnace at 400-800 °C under an argon atmosphere to obtain B and N co-doped carbon nanotubes;
[0008] (3) washing, filtering and drying the B, N co-doped carbon nanotubes obtained in step (2), immersing the carbon nanotubes in a solution containing copper and iron metal ions, and then washing and drying the carbon nanotubes;
[0009] (4) The catalyst is then placed in a tube furnace and pyrolyzed at 300-480°C in an inert gas atmosphere for 1-4 hours to obtain a B, N co-doped carbon nanotube-loaded copper-iron bimetallic oxide catalyst.
[0010] If the calcination temperature in step (2) is higher than 800°C, the carbon material will be excessively decomposed, and carbon nanotubes with smooth surfaces cannot be obtained, or even all of them will be decomposed. If the calcination temperature is lower than 400°C, the precursor red powder cannot be completely carbonized, and carbon nanotubes cannot be obtained, but flakes.
[0011] Furthermore, the aromatic compound in step (1) is one or more of perylenetetracarboxylic dianhydride, anthracene, quinone and phenanthrene.
[0012] Furthermore, when the aromatic compound is perylene tetracarboxylic dianhydride, the mass ratio of perylene tetracarboxylic dianhydride, boric acid, and urea is 10:0.1-10:80-89.8. If too much boric acid is added, the resulting material is not a carbon nanotube, but a material such as boron carbide.
[0013] Furthermore, the organic solvent in step (1) is ethanol. Ethanol is a solvent with good solubility and is easy to remove. During the exploration process, it was found that the use of other solvents could not achieve the effect of ethanol as a solvent.
[0014] Furthermore, the solution containing copper and iron metal ions in step (3) is a mixed solution of copper chloride and ferric chloride.
[0015] Furthermore, the mass ratio of copper chloride to ferric chloride is 1-10:1-10. The best effect is achieved when the mass ratio of copper chloride to ferric chloride is 5:5.
[0016] Furthermore, in step (3), the amount of B, N co-doped carbon nanotubes added is 100-300 mg, and the amount of the mixed solution of copper chloride and ferric chloride added is 1-4 mmol.
[0017] The present invention, after doping B and N on the surface of carbon nanotubes, allows metal ions to be adsorbed on the carbon material surface and forms copper-iron bimetallic oxide clusters through high-temperature pyrolysis. Most existing processes utilize pre-prepared MOF material pyrolysis to prepare bimetallic catalysts, while the present invention uses high-temperature pyrolysis to construct a new structure. In addition, the present invention mixes B with perylene tetracarboxylic dianhydride and carbonizes them together. During the carbonization process, B is located in the carbon tubes, not doped by grafting. The carbon tubes obtained by the present invention are more uniformly doped with B, and it is easier to incorporate B into the carbon tubes, making the experimental operation and principle simpler.
[0018] The B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst prepared by the above preparation method comprises a carbon nanotube material having a B, N co-doping mechanism and metal oxide nanoparticles supported on the surface of the carbon nanotube. The B and N co-doping mechanisms in the B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst of the present invention are synergistic. The N atoms coordinate and anchor the metal atoms and simultaneously regulate their electronic structure, thereby promoting the nitrate reduction process. The B atoms form electron-deficient centers on the carbon nanotube surface, thereby adsorbing nitrate ions and increasing the nitrate concentration near the electrode, thereby promoting nitrate reduction.
[0019] The present invention enhances the nitrate adsorption capacity by B doping and fixes the metal atoms on the surface of carbon nanotubes by N anchoring, thereby forming an electrocatalytic nitrate reduction material with a high nitrate reduction to ammonia production rate and high Faradaic efficiency. This provides a simple and universal method for electrocatalytic nitrate reduction and offers a useful reference for the research and development of high-performance nitrate reduction materials.
[0020] Nitrogen atoms doped into carbon nanotubes have excellent adsorption properties for metal ions. By doping the carbon nanotube surface with nitrogen and then adsorbing metal ions, the adsorption of metal ions can be regulated, thereby achieving controlled dispersion of metal ions on the carbon-based material surface. This allows for precise control of the size of metal oxide nanoparticles formed during high-temperature processes, thereby increasing the number of active sites. Boron is used to control the adsorption of nitrate ions, thereby accelerating the transfer process on electrode or catalyst surfaces. The doping of boron atoms creates electron-deficient centers on the carbon nanotube surface, which facilitates nitrate ion adsorption and further accelerates the nitrate reduction rate. Carbon nanotubes are used for electron conduction.
[0021] Copper and iron ions are active centers for nitrate reduction. By regulating the metal ion loading, ratio, and pyrolysis temperature, the amount of metal oxide loaded on the carbon nanotube surface can be controlled. This allows for the formation of oxide clusters of varying sizes and densities on the carbon material surface, thereby creating active centers for nitrate reduction.
[0022] The above electrocatalytic materials are used for nitrate reduction to produce ammonia, nitrate degradation, etc.
[0023] Compared with the prior art, the present invention prepares B and N co-doped carbon nanotubes by a calcination method, and adsorbs metal ions on the surface of the carbon material by an immersion adsorption method, and then places the carbon material in a tube furnace and performs high-temperature pyrolysis in an argon atmosphere. The size and density of the metal active sites on the surface of the carbon material can be controlled by regulating the concentration, ratio, and temperature of the metal ions, thereby constructing a bimetallic oxide cluster structure. The carbon nanotube material obtained by the present invention not only retains the complete structure of the carbon material itself, but also loads a large number of copper-iron bimetallic oxide clusters on the surface. The role of the N atom is to coordinate and anchor the metal atoms and simultaneously regulate their electronic structure to promote the nitrate reduction process; the role of the B atom is to form an electron-deficient center on the surface of the carbon tube, thereby adsorbing nitrate ions, increasing the nitrate concentration near the electrode, and thus promoting nitrate reduction. The catalyst obtained by the present invention can effectively promote the electrocatalytic reduction of nitrate to produce ammonia, effectively increase the nitrate reduction performance, and significantly improve the yield. At -0.8V RHE It can reach 95.2 mgh at a potential of -1 mg cat -1 The ammonia production rate and Faradaic efficiency of 91.3% were achieved. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 is a surface morphology of B, N co-doped carbon nanotubes in Example 1;
[0025] Figure 2 This is a surface morphology of the B, N co-doped carbon nanotubes loaded with copper-iron bimetallic oxide in Example 1;
[0026] Figure 3 1 is an elemental analysis diagram of the B, N co-doped carbon nanotubes loaded with copper-iron bimetallic oxide in Example 1;
[0027] Figure 4 is the XRD pattern of B, N co-doped carbon nanotubes before and after loading with metal oxide in Example 1;
[0028] Figure 5 This is a high-resolution image of the B, N co-doped carbon nanotubes loaded with copper-iron bimetallic oxide in Example 1;
[0029] Figure 6 1 is a graph showing the nitrate reduction performance of the B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide material of Example 1 at different potentials;
[0030] Figure 7 1 is a performance comparison chart of the B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide of Example 1 and the N-doped carbon nanotube-supported copper-iron bimetallic oxide of Comparative Example 2 under different nitrate concentrations;
[0031] Figure 8 This is the morphology of the B, N co-doped carbon nanotube-loaded copper-iron bimetallic oxide material prepared in Example 13 after pyrolysis at 500°C for 4 hours;
[0032] Figure 9 1 is a performance comparison chart of the catalysts of Example 5 and Example 1;
[0033] Figure 10 1 is a performance comparison chart of the catalysts of Examples 6 and 7 and Example 1;
[0034] Figure 11 1 is a performance comparison chart of the catalysts of Example 8 and Example 1;
[0035] Figure 12 This is a morphology picture of the catalyst of Example 9. DETAILED DESCRIPTION
[0036] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be described in further detail below with reference to the accompanying drawings.
[0037] Example 1
[0038] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed in 40 mL of ethanol as solvent. The solvent was then removed by rotary evaporation and then dried in vacuum to obtain a red mixture. The mixture was then placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes, which were recorded as N,B-CNTs. The carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, and the mixture was heated to 80°C and stirred for 30 minutes. The mixture was then filtered and dried. 300 mg of the mixture was weighed and transferred to a beaker, 40 mL of water was added, and 3 mmol of copper chloride and ferric chloride were added in a 5:5 ratio. The mixture was stirred at room temperature for 10 hours, filtered, washed, and dried. The mixture was then placed in a tube furnace and pyrolyzed at 400°C under an inert gas atmosphere for 3 hours to obtain B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst, which was recorded as CuFeOx / BNCNTs.
[0039] Example 2
[0040] 810 mg of perylene tetracarboxylic dianhydride, 81 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed with 40 mL of ethanol as solvent, and the solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture; the mixture was then placed in a tube furnace and calcined at 800 °C under an argon atmosphere to obtain B, N co-doped carbon nanotubes; the carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, heated to 80 °C and stirred for 30 minutes; then filtered and dried, and 300 mg was weighed from it and transferred to a beaker, 40 mL of water was added, and then 3 mmol of copper chloride and ferric chloride were added in a ratio of 5:5, stirred at room temperature for 10 hours, filtered, washed, and dried, and then placed in a tube furnace and pyrolyzed at 400 °C in an inert gas atmosphere for 3 hours to obtain B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst.
[0041] Example 3
[0042] 810 mg of perylene tetracarboxylic dianhydride, 814 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed with 40 mL of ethanol as solvent, and the solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture; the mixture was then placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes; the carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, heated to 80°C and stirred for 30 minutes; then filtered and dried, and 300 mg was weighed from the mixture and transferred to a beaker, 40 mL of water was added, and 3 mmol of copper chloride and ferric chloride were added in a ratio of 5:5. The mixture was stirred at room temperature for 10 hours, filtered, washed, and dried. The mixture was then placed in a tube furnace and pyrolyzed at 400°C in an inert gas atmosphere for 3 hours to obtain B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst.
[0043] Example 4
[0044] The difference from Example 1 is that the red mixture is placed in a tube furnace and calcined at 400° C. under an argon atmosphere to obtain B, N co-doped carbon nanotubes; the other steps are the same as Example 1.
[0045] Example 5
[0046] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed with 40 mL of ethanol as solvent, and the solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture; the mixture was then placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes; the carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, heated to 80°C and stirred for 30 minutes; then filtered and dried, and 300 mg was weighed from it and transferred to a beaker, 40 mL of water was added, and 3 mmol of copper chloride was added, stirred at room temperature for 10 hours, filtered, washed, and dried, and then placed in a tube furnace and pyrolyzed at 400°C in an inert gas atmosphere for 3 hours to obtain B, N co-doped carbon nanotube-supported copper metal oxide catalyst, recorded as CuOx / BNCNTs.
[0047] Example 6
[0048] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed in 40 mL of ethanol as solvent. The solvent was then removed by rotary evaporation and then vacuum dried to obtain a red mixture. The mixture was then placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes. The carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, and the mixture was heated to 80°C and stirred for 30 minutes. The mixture was then filtered and dried. 300 mg of the mixture was weighed and transferred to a beaker, 40 mL of water was added, and 3 mmol of copper chloride and ferric chloride were added in a ratio of 3:7. The mixture was stirred at room temperature for 10 hours, filtered, washed, and dried. The mixture was then placed in a tube furnace and pyrolyzed at 400°C in an inert gas atmosphere for 3 hours to obtain B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst, denoted as Cu3Fe7Ox / BNCNTs.
[0049] Example 7
[0050] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed in 40 mL of ethanol as solvent. The solvent was then removed by rotary evaporation and then dried in vacuum to obtain a red mixture. The mixture was then placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes. The carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, and the mixture was heated to 80°C and stirred for 30 minutes. The mixture was then filtered and dried. 300 mg of the mixture was weighed and transferred to a beaker, 40 mL of water was added, and 3 mmol of copper chloride and ferric chloride were added in a ratio of 7:3. The mixture was stirred at room temperature for 10 hours, filtered, washed, and dried. The mixture was then placed in a tube furnace and pyrolyzed at 400°C in an inert gas atmosphere for 3 hours to obtain B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst, denoted as Cu7Fe3Ox / BNCNTs.
[0051] Example 8
[0052] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were mixed uniformly in 40 mL of ethanol as solvent. The solvent was then removed by rotary evaporation and dried under vacuum to obtain a red mixture. The mixture was then calcined at 800°C in a tube furnace under an argon atmosphere to produce B- and N-codoped carbon nanotubes. The carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, and the mixture was heated to 80°C and stirred for 30 minutes. The mixture was then filtered and dried. Another 300 mg portion was transferred to a beaker, added to 40 mL of water, and then 3 mmol of ferric chloride was added. The mixture was stirred at room temperature for 10 hours, filtered, washed, and dried. The mixture was then pyrolyzed at 400°C in an inert gas atmosphere for 3 hours in a tube furnace to obtain the B- and N-codoped carbon nanotube-supported iron metal oxide catalyst, designated as FeOx / BNCNTs.
[0053] Example 9
[0054] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed with 40 mL of ethanol as solvent, and the solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture; then the mixture was placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes; the carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, heated to 80°C and stirred for 30 minutes; then filtered and dried, and 300 mg was weighed from it and transferred to a beaker, 40 mL of water was added, and then 1 mmol of copper chloride and ferric chloride were added in a ratio of 5:5, stirred at room temperature for 10 hours, filtered, washed, and dried, and then placed in a tube furnace and pyrolyzed at 400°C in an inert gas atmosphere for 3 hours.
[0055] Example 10
[0056] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed with 40 mL of ethanol as solvent, and the solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture; then the mixture was placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes; the carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, heated to 80°C and stirred for 30 minutes; then filtered and dried, and 300 mg was weighed from it and transferred to a beaker, 40 mL of water was added, and then 2 mmol of copper chloride and ferric chloride were added in a ratio of 5:5, stirred at room temperature for 10 hours, filtered, washed, and dried, and then placed in a tube furnace and pyrolyzed at 400°C in an inert gas atmosphere for 3 hours.
[0057] Example 11
[0058] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed with 40 mL of ethanol as solvent, and the solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture; then the mixture was placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes; the carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, heated to 80°C and stirred for 30 minutes; then filtered and dried, and 300 mg was weighed from it and transferred to a beaker, 40 mL of water was added, and then 4 mmol of copper chloride and ferric chloride were added in a ratio of 5:5, stirred at room temperature for 10 hours, filtered, washed, and dried, and then placed in a tube furnace and pyrolyzed at 400°C in an inert gas atmosphere for 3 hours.
[0059] Example 12
[0060] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed with 40 mL of ethanol as solvent, and the solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture; then the mixture was placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes; the carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, heated to 80°C and stirred for 30 minutes; then filtered and dried, and 300 mg was weighed from it and transferred to a beaker, 40 mL of water was added, and then 3 mmol of copper chloride and ferric chloride were added in a ratio of 5:5, stirred at room temperature for 10 hours, filtered, washed, and dried, and then placed in a tube furnace and pyrolyzed at 300°C in an inert gas atmosphere for 3 hours.
[0061] Example 13
[0062] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and uniformly mixed with 40 mL of ethanol as solvent, and the solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture; then the mixture was placed in a tube furnace and calcined at 800°C under an argon atmosphere to obtain B, N co-doped carbon nanotubes; the carbon nanotubes were transferred to a beaker, an appropriate amount of water was added, heated to 80°C and stirred for 30 minutes; then filtered and dried, and 300 mg was weighed from it and transferred to a beaker, 40 mL of water was added, and then 3 mmol of copper chloride and ferric chloride were added in a ratio of 5:5, stirred at room temperature for 10 hours, filtered, washed, and dried, and then placed in a tube furnace and pyrolyzed at 500°C in an inert gas atmosphere for 3 hours.
[0063] Comparative Example 1
[0064] Preparation of boron-doped carbon nanotubes: 810 mg of perylene tetracarboxylic dianhydride and 570 mg of boric acid were mixed uniformly in 40 mL of ethanol. The solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture. The mixture was then calcined in a tube furnace at 800°C under an argon atmosphere to obtain boron-doped carbon nanotubes.
[0065] Copper chloride and ferric chloride were then loaded using the method of Example 1. It was found that without nitrogen doping, copper and iron metals were difficult to anchor on carbon nanotubes and could only be physically adsorbed. Consequently, the loading was very small, and the corresponding performance was also very low, to the point that almost no nitrate was reduced to ammonia.
[0066] Comparative Example 2
[0067] Preparation of N-doped carbon nanotubes: 810 mg of perylene tetracarboxylic dianhydride and 6.62 g of urea were mixed uniformly in 40 mL of ethanol as solvent. The solvent was removed by rotary evaporation and then vacuum dried to obtain a red mixture. The mixture was then calcined in a tube furnace at 800°C under an argon atmosphere to obtain N-doped carbon nanotubes.
[0068] Then, the method of Example 1 was used to load copper chloride and ferric chloride, and the corresponding performance comparison was as follows: Figure 7 shown.
[0069] Comparative Example 3
[0070] The carbon nanotubes are mixed evenly with a boron-containing organic compound (such as boric acid) and a nitrogen-containing organic compound (such as urea), and then calcined at 800°C in a tube furnace under an argon atmosphere to obtain B, N co-doped carbon nanotubes;
[0071] Then, copper chloride and ferric chloride were loaded using the method of Example 1. It was found that the carbon nanotube material obtained by B and N doping by grafting had a weaker anchoring effect on the metal than direct doping, and the corresponding agglomeration phenomenon was more serious, resulting in a decrease in performance.
[0072] Comparative Example 4
[0073] Weigh 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea and mix them evenly with 40 mL of ethanol as solvent. Then, remove the solvent by rotary evaporation and vacuum dry to obtain a red mixture. Then, place it in a tube furnace and calcine it at 850°C or 900°C under an argon atmosphere. The carbon material will decompose excessively, and carbon nanotubes with smooth surfaces will not be obtained, or even all of it will be decomposed.
[0074] Comparative Example 5
[0075] 810 mg of perylene tetracarboxylic dianhydride, 570 mg of boric acid, and 6.62 g of urea were weighed and evenly mixed with 40 mL of ethanol as solvent. The solvent was then removed by rotary evaporation and vacuum dried to obtain a red mixture. The mixture was then placed in a tubular furnace and calcined at 350°C under an argon atmosphere. The precursor red powder could not be completely carbonized, and carbon nanotubes were not obtained, but were in the form of flakes.
[0076] Performance testing
[0077] from Figure 1 It can be seen that the B, N co-doped carbon nanotubes of the present invention are uniform in size and widely distributed.
[0078] from Figure 2 It can be seen that the copper-iron bimetallic oxide is evenly and densely distributed on the surface of the carbon nanotubes. The B in the carbon tubes directly formed by calcination exists in the carbon tubes. No other conditions such as grafting were observed through SEM characterization.
[0079] from Figure 3 It can be seen that the metal is successfully adsorbed on the surface of carbon nanotubes.
[0080] from Figure 4 It can be seen that after the metal oxide is loaded, its XRD does not show obvious absorption peaks, which confirms that the metal oxide is evenly distributed on the carbon nanotubes and no agglomeration occurs (the CuFeOx / NBCNTs and NBCNTs shown are both materials of Example 1).
[0081] The morphology of the specific bimetallic oxide clusters is as follows: Figure 5 As shown by Figure 5 It can be seen that there are multiple crystal phases within the range shown in the figure, confirming the formation of bimetallic oxide clusters.
[0082] The performance advantages of the material are mainly reflected in high ammonia production performance and excellent Faradaic efficiency. At present, different copper-iron ratios have been tried, and all have certain nitrate reduction performance, but under the same conditions, the copper-iron ratio of 5:5 is the best. Figure 6 It can be seen that the B, N co-doped carbon nanotube-loaded copper-iron bimetallic oxide material of the present invention has a high RHE It can reach 95.2 mgh at a potential of -1 mg cat -1 Ammonia production rate and 91.3% Faradaic efficiency; Figure 7 It can be seen that the performance of the material is significantly improved when doped with B. Figure 8 It can be seen that when the pyrolysis temperature is 500 ℃, the metal oxides on the surface of carbon nanotubes agglomerate, the particles become significantly larger, and the density becomes smaller; Figure 9It can be seen that the performance of the material loaded with only single metal copper is far inferior to that of the bimetallic material; Figure 10 It can be seen that among materials with different copper-iron ratios, the best performance is achieved when the ratio of Cu to Fe is 5:5; Figure 11 It can be seen that the performance of the material loaded with only single metal iron is far inferior to that of the bimetallic material; Figure 12 It can be seen from the figure that when only 1 mmol of metal is added, its loading on the carbon nanotubes is significantly reduced.
[0083] It can be concluded that the appropriate copper-iron ratio, reasonable metal loading and suitable pyrolysis temperature effectively increase the nitrate reduction performance of the material.
[0084] The present invention includes but is not limited to the above embodiments. Any equivalent replacement or partial improvement made under the spirit and principle of the present invention shall be deemed to be within the protection scope of the present invention.
Claims
1. A method for preparing a B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst, characterized in that: The following steps are involved: (1) uniformly mixing an aromatic compound, boric acid, and urea in an organic solvent, and then removing the organic solvent; (2) Then, the carbon nanotubes were calcined in a tube furnace at 400-800 °C under an argon atmosphere to obtain B and N co-doped carbon nanotubes; (3) washing, filtering and drying the B, N co-doped carbon nanotubes obtained in step (2), immersing the carbon nanotubes in a solution containing copper and iron metal ions, and then washing and drying the carbon nanotubes; (4) placing the carbon nanotubes in a tube furnace and pyrolyzing them at 300-480°C for 1-4 hours in an inert gas atmosphere to obtain a B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst; In step (1), the aromatic compound is perylene tetracarboxylic dianhydride, and the mass ratio of perylene tetracarboxylic dianhydride, boric acid, and urea added is 10:0.1-10:80-89.8; The solution containing copper and iron metal ions in step (3) is a mixed solution of copper chloride and ferric chloride.
2. The preparation method according to claim 1, characterized in that The organic solvent in step (1) is ethanol.
3. The preparation method according to claim 1, characterized in that: The mass ratio of copper chloride to ferric chloride is 1-10:1-10.
4. The preparation method according to claim 3, characterized in that In step (3), the amount of B, N co-doped carbon nanotubes added is 100-300 mg, and the amount of the mixed solution of copper chloride and ferric chloride added is 1-4 mmol.
5. The B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst prepared according to the preparation method according to any one of claims 1 to 4.
6. The use of the B, N co-doped carbon nanotube-supported copper-iron bimetallic oxide catalyst according to claim 5, characterized in that: Used for nitrate reduction to produce ammonia and nitrate degradation.
Citation Information
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Carbon nanotube composite material as well as preparation method and application thereof
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