Preparation method and application of nitrogen-doped carbon layer coated bimetallic material
The bimetallic material wrapped by nitrogen-doped carbon layer solves the stability and cost problems of zero-valent metal-based materials in Fenton-like catalysts, and achieves efficient organic pollutant degradation and stable catalytic performance.
Patent Information
- Application Number
- CN202411206313.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2024-12-10
AI Technical Summary
As Fenton-like catalysts, existing zero-valent metal-based materials have problems such as metal ion leaching, poor stability, complex preparation process and high cost, which affect their application in water treatment.
The preparation method of bimetallic materials wrapped with nitrogen-doped carbon layer is used to form bimetallic materials wrapped with carbon layer through hydrothermal reaction and high-temperature nitriding, which promotes electron transfer and regeneration of active sites, improves catalytic efficiency, and is in strong acids or strong Provides protection in an alkaline environment.
It significantly improves the catalytic activity and stability of the catalyst, reduces metal ion leaching, simplifies the preparation process and reduces costs, and improves the degradation efficiency of organic pollutants.
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Figure CN119098171A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of water treatment, and specifically relates to a preparation method and application of a bimetallic material wrapped in a nitrogen-doped carbon layer. Background Art
[0002] As a kind of advanced oxidation process, Fenton process 2+ It reacts with H2O2 to generate ·OH, which has extremely strong oxidizing properties and can effectively degrade organic pollutants. The traditional Fenton reaction process has obvious advantages, but it still has many defects, such as narrow pH response range, large iron sludge production, low H2O2 utilization rate, poor stability, etc., which limit the application of Fenton technology.
[0003] In order to make up for the shortcomings of the traditional homogeneous Fenton reaction, researchers have made many improvements on the traditional Fenton reaction and developed a Fenton-like oxidation technology. In recent years, the research on Fenton-like oxidation technology has mainly focused on the development of high-efficiency catalysts. Common catalytic materials include transition metals such as Fe, Cu, Co, Ni and their oxides, as well as supported catalytic materials based on the above active species. Among them, zero-valent metal-based materials as Fenton-like catalysts have great advantages in improving the utilization efficiency of oxidation media and sewage treatment. Zero-valent metal materials have a low overall valence state and a strong electron supply capacity. In theory, they can activate H2O2 or persulfate to produce more strong oxidizing free radicals. However, at present, zero-valent metal-based materials as Fenton-like catalysts often have problems such as high catalyst preparation cost, complex process, poor stability and low catalytic efficiency. In addition, there is a risk of metal ions precipitating. Direct application in water bodies is prone to heavy metal pollution and poses a potential hazard to human health, which affects its use as a Fenton-like catalyst. Therefore, the development of an efficient and stable zero-valent metal-based material is a problem that remains to be solved. Summary of the invention
[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for preparing a bimetallic material wrapped in a nitrogen-doped carbon layer in view of the shortcomings of the prior art, so as to solve the problems faced by existing zero-valent metal-based materials as Fenton-like catalysts, such as metal ion leaching, poor stability, complex preparation process and high cost.
[0005] Bimetallic synergy has the advantages of promoting electron transfer, enhancing active site regeneration, and improving catalytic efficiency, so bimetallic zero-valent metal-based materials can be constructed. In addition, carbon layer wrapping is conducive to the rapid transfer of electrons at the electrocatalytic reaction interface, and can effectively prevent the internal metal-based materials from being corroded in strong acid or strong alkaline environments. Therefore, adding a carbon layer wrapping to the outer layer of the metal-based catalyst can significantly improve the catalytic activity and stability of the catalyst. Nitrogen doping can further increase the active site density of bimetallic materials and improve the activity of the catalyst. Therefore, doping nitrogen into bimetallic materials is expected to further enhance the catalytic performance of the material.
[0006] In order to solve the above technical problems, the present invention discloses a method for preparing a bimetallic material wrapped by a nitrogen-doped carbon layer, comprising the following steps:
[0007] S1: dissolving two metal salts and urea in pure water and stirring to obtain a mixed solution, wherein one salt is a Co salt and the other salt is any one of a Cu salt, a Fe salt, or a Ni salt;
[0008] S2: transferring the obtained solution to a reactor for hydrothermal reaction to obtain a bimetallic precursor. Preferably, the reactor is a stainless steel high-pressure reactor lined with polytetrafluoroethylene;
[0009] S3: After centrifugal washing and vacuum drying, the bimetallic precursor is placed in a porcelain boat A in a reactor and evenly spread. The porcelain boat A is then placed in a tube furnace, and a porcelain boat B with sufficient urea is placed in front. In a high temperature and N2 atmosphere, urea is decomposed into NH3, and the bimetallic precursor is subjected to high temperature nitridation and reduction under the action of NH3;
[0010] S4: The powder obtained after the treatment in S3 is immersed in an aqueous solution with a pH of 3-5 to remove surface impurities, and then stirred on a shaker and centrifuged and dried to obtain a bimetallic material wrapped in a nitrogen-doped carbon layer.
[0011] In one embodiment, in step S1, the Co salt is Co(NO3)2·6H2O, and the other salt is any one of Cu(NO3)2·3H2O, FeSO4·7H2O or NiSO4·7H2O.
[0012] In one embodiment, in step S1, the molar ratio of the Co salt to the other salt is 1:3; and the amount of urea is 5-10 mmol.
[0013] Preferably, in step S1, the stirring time is 4-6 min; in step S2, the hydrothermal reaction temperature is 110-130° C., and the hydrothermal reaction time is 5-7 h.
[0014] In step S3, the metal precursor is first centrifuged and then washed with ultrapure water. The centrifugal speed is 3000-4000r / min and the centrifugal time is 0.5-1.5min. The centrifugal washing process is repeated several times, preferably three times. The vacuum drying temperature is 55-65°C and the vacuum drying time is 10-14h. In step S3, the high-temperature nitriding time is 2.5-3.5h and the temperature of high-temperature nitriding is 400-800°C.
[0015] In step S4, the pH is adjusted using dilute NaOH and HCl solutions; the shaking time is 0.5-1.5 hours, and the shaking speed is 200-300 r / min; the number of centrifugation is 3 times, the centrifugal speed is 3000-4000 r / min, and the centrifugal time is 0.5-1.5 min; the last centrifugation is completed and dried, the drying temperature is 55-65° C., and the drying time is 10-14 hours.
[0016] The bimetallic material wrapped in a nitrogen-doped carbon layer prepared by the above-mentioned preparation method is also within the protection scope of the present application.
[0017] The present application further proposes the use of the above-mentioned bimetallic material wrapped in a nitrogen-doped carbon layer as a catalyst in a Fenton-like system for degrading wastewater containing organic pollutants.
[0018] In a specific embodiment, the organic pollutant is tetracycline hydrochloride.
[0019] Beneficial effects: The present invention proposes a method for preparing a bimetallic material wrapped in a nitrogen-doped carbon layer, wherein the two metals used can produce a synergistic effect, which can effectively promote electron transfer and active site regeneration. Nitrogen doping can further increase the active sites of the bimetallic material and improve the catalytic efficiency. The large specific surface area and high porosity of the carbon skeleton formed by the carbon layer wrapping are conducive to the adsorption of reaction media and pollutants, shortening the diffusion distance of reactants, facilitating the rapid transfer of electrons at the electrocatalytic reaction interface, and can effectively prevent the internal metal-based materials from being corroded in a strong acid or strong base environment and the leaching of metal ions, significantly improving the catalytic activity and stability of the catalyst. The preparation method of the present invention is simple and low in cost. In the hydrothermal method, urea is used as a carbon source and inducer for the carbon layer to promote the formation of the precursor; high-temperature nitridation and reduction adopt a one-step method, and urea is decomposed at high temperature to produce NH3, thereby reducing and nitrogen-doping the bimetallic material and forming a carbon layer wrapping, which protects the elemental metal. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1In the figure, (a) is the XRD graph of CuCo@NC prepared in Example 1, Example 2, and Example 3 at different temperatures; (b) is the XRD graph of CuCo@NC, FeCo@NC, and NiCo@NC prepared in Example 1, Example 4, and Example 5;
[0021] Figure 2 In the figure, (a) is the TEM image of CuCo@NC prepared in Example 1; (b) is the TEM image of FeCo@NC prepared in Example 4;
[0022] Figure 3 X-ray photoelectron spectroscopy (XPS) of CuCo@NC prepared in Example 1;
[0023] Figure 4 This is a graph showing the degradation rate of tetracycline hydrochloride degraded by bimetallic materials wrapped in carbon layers doped with different nitrogen elements and single metal Co as catalysts of PMS in the catalytic experiments of Example 6 and Example 7;
[0024] Figure 5 This is a stability experiment of Example 8, and a graph of metal element leaching concentration measured by ICP-MS mass spectrometer for bimetallic materials wrapped with carbon layers doped with different nitrogen elements. DETAILED DESCRIPTION
[0025] The technical scheme of the present invention is further described in detail below through embodiments, but the content of the present invention is not limited thereto, and the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, without departing from the essence of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0026] The methods in this example are all conventional methods unless otherwise specified, and the materials, reagents, etc. used are all obtained from commercial channels or prepared according to conventional methods unless otherwise specified.
[0027] Example 1: A method for preparing a bimetallic material wrapped with a nitrogen-doped carbon layer is completed by the following steps:
[0028] S1: Solution mixing
[0029] 0.5 mmol of Cu(NO3)2·3H2O, 1.5 mmol of Co(NO3)2·6H2O and 8 mmol of urea were dissolved in 40 ml of pure water and stirred for 5 min to obtain a mixed solution.
[0030] S2: Hydrothermal reaction
[0031] The obtained solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and maintained at 120°C for 6 h to obtain a bimetallic precursor.
[0032] S3: High temperature nitriding
[0033] The bimetallic precursor was centrifuged at a speed of 3500r / min for 1min and then washed with ultrapure water. The centrifugal washing process was repeated 3 times. After centrifugal washing, it was vacuum dried at 60°C for 12h. Then, the bimetallic precursor was evenly spread and loaded into a porcelain boat A. The porcelain boat A was placed in a tube furnace, and a porcelain boat B with sufficient urea was placed in front. At 550°C and in a N2 atmosphere, urea was decomposed into NH3, and the bimetallic precursor was subjected to high-temperature nitridation and reduction under the action of NH3.
[0034] S4: Pickling
[0035] The calcined powder was immersed in an aqueous solution adjusted with a pH of 5 by a dilute solution of NaOH and HCl to remove surface impurities. The powder was stirred on a shaker at 250 r / min for 1 h, and then centrifuged at 3500 r / min for 1 min. This was repeated 3 times, and then dried at 60°C for 12 h to obtain CuCo@NC-550 coated with a carbon layer.
[0036] Example 2: The preparation method of this example is basically the same as that of Example 1, the only difference being that in step S3, the high-temperature nitridation temperature is 800°C, and the obtained catalyst is CuCo@NC-800.
[0037] Example 3: The preparation method of this example is basically the same as that of Example 1, the only difference being that in step S3, the high-temperature nitridation temperature is 300°C, and the obtained catalyst is CuCo@NC-300.
[0038] The CuCo@NC prepared at three different temperatures in Example 1, Example 2 and Example 3 were characterized by XRD. Figure 1 As shown in (a), it can be seen from the figure that all diffraction peaks of the product CuCo@NC-550 of Example 1 and the product CuCo@NC-800 of Example 2 are completely consistent with the typical Co card and Cu card, which shows that CuCo@NC is successfully synthesized. However, the product peaks prepared in Example 3 are many and mixed. This is because at 300°C, urea is not completely decomposed into NH3. The lack of NH3 causes the bimetallic precursor to be oxidized during the high-temperature nitridation process, resulting in no single substance being formed. The material prepared at 300°C cannot form a catalyst with a specific structure.
[0039] The morphology of the prepared CuCo@NC was analyzed by TEM. Figure 2As shown in (a), it can be seen from the figure that it is a spherical structure with a smooth surface. The CuCo metal particles are tightly wrapped by the spherical carbon skeleton, and due to the confinement of the carbon skeleton, the CuCo particles are uniformly embedded in the carbon shell.
[0040] The present invention simultaneously prepares two catalysts, FeCo@NC and NiCo@NC, as supplements to CuCo@NC.
[0041] Example 4: The preparation method of this example is basically the same as that of Example 1, the only difference being that in step S1, Cu(NO3)2·3H2O is replaced by FeSO4·7H2O, the amount of the substance remains unchanged, and the final catalyst obtained is FeCo@NC.
[0042] Example 5: The preparation method of this example is basically the same as that of Example 1, the only difference being that in step S1, Cu(NO3)2·3H2O is replaced by NiSO4·7H2O, the amount of the substance remains unchanged, and the final catalyst obtained is NiCo@NC.
[0043] The FeCo@NC prepared in Example 3 and the NiCo@NC prepared in Example 4 were characterized by XRD. Figure 1 (b) as shown.
[0044] It can be seen from the figure that all diffraction peaks of the product FeCo@NC in Example 3 are completely consistent with the typical Co cal and Fe cal; all diffraction peaks of the product NiCo@NC in Example 4 are completely consistent with the typical Co cal and Ni cal, which indicates that FeCo@NC and NiCo@NC were successfully synthesized.
[0045] The morphology of the prepared FeCo@NC was analyzed by TEM. Figure 2 As shown in (b), it can be seen from the figure that there is a carbon layer on the surface, and the FeCo bimetal is wrapped in it.
[0046] The surface chemical composition of the CuCo@NC prepared in Example 1 was studied by X-ray photoelectron spectroscopy (XPS). Figure 3 As shown, the XPS full spectrum shows that Cu, Co, C, N, and O elements exist in the sample after calcination, proving that a bimetallic material wrapped by a nitrogen-doped carbon layer has been successfully prepared.
[0047] Catalytic experiment:
[0048] Example 6: Experimental test on degradation of tetracycline hydrochloride by the prepared material: 100 mL of a 20 ppm tetracycline hydrochloride deionized water solution was prepared. 5 mg of the prepared catalyst was added to the solution, mechanically stirred and dispersed, and then PMS (permonosulfate) solution was added to make the PMS concentration in the system 0.64 mmol / L. PMS acts as a strong oxidant to provide free radicals to degrade organic pollutants. The temperature was set at 25°C, and the change in tetracycline hydrochloride concentration over time after the addition of PMS was measured.
[0049] Example 7: The experimental process of this example is basically the same as that of Example 6, the only difference being that single metal Co is used as a catalyst for degrading tetracycline hydrochloride.
[0050] The application of bimetallic materials wrapped in carbon layers doped with different nitrogen elements and single metal Co as catalysts for the degradation of tetracycline hydrochloride was shown in the following results. Figure 4 As shown in the figure, the three different materials all have good catalytic performance for the degradation of tetracycline hydrochloride, among which CuCo@NC has the best catalytic performance, and can achieve complete degradation of tetracycline hydrochloride within 180s. Within 120s, the degradation rates of tetracycline hydrochloride when CuCo@NC, NiCo@NC, and FeCo@NC are 99.32%, 95.11%, and 94.19%, respectively. The effect of single metal Co as a catalyst in the degradation of tetracycline hydrochloride is worse than that of bimetallic materials, indicating that the two metals can produce a synergistic effect to improve the catalytic activity.
[0051] Stability test:
[0052] Example 8: Experimental test of metal element leaching of the three prepared materials CuCo@NC, FeCo@NC and NiCo@NC under different pH conditions: 100 ml of aqueous solutions with pH = 3, pH = 7, and pH = 11 were prepared with dilute NaOH and HCl solutions, and then 5 mg of each of the three catalysts were added respectively. After stirring for 24 hours, 20 ml of the sample was taken and passed through a 0.45 um PES membrane, and the leaching concentration of each metal element was determined using an ICP-MS mass spectrometer.
[0053] The stability test results of bimetallic materials wrapped with three different nitrogen-doped carbon layers are as follows: Figure 5As shown in the figure, with the increase of pH, the leaching amount of metal elements gradually decreases, and the leaching concentration of each metal element is the highest at pH = 3. At pH = 3, the Co leaching amount in CuCo@NC is 177.749ug / L, and the Cu leaching amount is 16.371ug / L. According to the relevant provisions of the "Surface Water Environmental Quality Standard" (GB3838-2002), the concentration of Co is less than the specific project labeling limit of centralized drinking water surface water sources (1.0mg / L), and the concentration of Cu reaches the Class II water standard (1.0mg / L); the Co leaching amount in FeCo@NC is 205.170ug / L, and the Fe leaching amount is 29.751ug / L. The concentration of Co is 205.170ug / L, and the Fe leaching amount is 29.751ug / L. The concentration of NiCo@NC is less than the labeled limit of the specific project of the centralized drinking water surface water source (1.0 mg / L), and the concentration of Fe is less than the labeled limit of the supplementary project of the centralized drinking water surface water source (0.3 mg / L); the Co leaching amount in NiCo@NC is 255.526 ug / L, and the Ni leaching amount is 16.778 ug / L. The concentration of Co is less than the labeled limit of the specific project of the centralized drinking water surface water source (1.0 mg / L), and the concentration of Ni is less than the labeled limit of the specific project of the centralized drinking water surface water source (0.02 mg / L). By measuring the leaching concentration of different metal elements in the three materials, it is shown that the bimetallic material wrapped by the nitrogen-doped carbon layer prepared by the present invention is stable under different pH conditions.
[0054] The bimetallic material wrapped in a nitrogen-doped carbon layer prepared by the present invention has a simple preparation method, low cost, and the characteristics of high catalytic activity and high stability, and thus has the potential to become a Fenton-like catalyst.
[0055] The present invention provides a preparation idea and method of a bimetallic material wrapped by a nitrogen-doped carbon layer. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.
Claims
1. A method for preparing a bimetallic material wrapped with a nitrogen-doped carbon layer, characterized in that: The following steps are involved: S1: dissolving two metal salts and urea in pure water and stirring to obtain a mixed solution, wherein one salt is a Co salt and the other salt is any one of a Cu salt, a Fe salt, or a Ni salt; S2: transferring the obtained solution to a reactor for hydrothermal reaction to obtain a bimetallic precursor; S3: After centrifugal washing and vacuum drying, the bimetallic precursor is placed in a porcelain boat A in a reactor and evenly spread. The porcelain boat A is then placed in a tube furnace, and a porcelain boat B with sufficient urea is placed in front. In a high temperature and N2 atmosphere, urea is decomposed into NH3, and the bimetallic precursor is subjected to high temperature nitridation and reduction under the action of NH3; S4: The powder obtained after the treatment in S3 is immersed in an aqueous solution with a pH of 3-5 to remove surface impurities, and then stirred on a shaker and centrifuged and dried to obtain a bimetallic material wrapped in a nitrogen-doped carbon layer.
2. The preparation method according to claim 1, characterized in that: In step S1, the Co salt is Co(NO3)2·6H2O, and the other salt is any one of Cu(NO3)2·3H2O, FeSO4·7H2O or NiSO4·7H2O.
3. The preparation method according to claim 1, characterized in that: In step S1, the molar ratio of the Co salt to the other salt is 1:1-3; the amount of urea is 5-10 mmol.
4. The preparation method according to claim 1, characterized in that: In step S1, the stirring time is 4-6 min; in step S2, the hydrothermal reaction temperature is 110-130° C., and the hydrothermal reaction time is 5-7 h.
5. The preparation method according to claim 1, characterized in that: In step S3, the metal precursor is first centrifuged and then washed with ultrapure water at a centrifugal speed of 3000-4000 r / min and a centrifugal time of 0.5-1.5 min. The centrifugal washing process is repeated several times. The vacuum drying temperature is 55-65 o C, the vacuum drying time is 10-14 h; in step S3, the high temperature nitriding time is 2.5-3.5 h, and the high temperature nitriding temperature is 400-800°C.
6. The preparation method according to claim 1, characterized in that: In step S4, the pH is adjusted using dilute NaOH and HCl solutions; the shaking time is 0.5-1.5 h, and the shaking speed is 200-300 r / min; the number of centrifugation is 3 times, the centrifugal speed is 3000-4000 r / min, and the centrifugal time is 0.5-1.5 min; the last centrifugation is completed and dried, the drying temperature is 55-65° C., and the drying time is 10-14 h.
7. A bimetallic material wrapped with a nitrogen-doped carbon layer prepared according to the preparation method according to any one of claims 1 to 7.
8. Use of the bimetallic material wrapped with a nitrogen-doped carbon layer as claimed in claim 8 as a catalyst in a Fenton-like system for degrading wastewater containing organic pollutants.
9. The use according to claim 9, characterized in that: The organic pollutant is tetracycline hydrochloride.