A nitrogen-doped carbon-modified high-entropy alloy catalyst, its preparation method and application

Abstract

This application relates to the field of catalytic degradation technology for organic pollutants. A nitrogen-doped carbon-modified high-entropy alloy catalyst is disclosed. The high-entropy alloy comprises five or more multi-element high-entropy alloys selected from Fe, Co, Ni, Cu, Mn, Al, and Zn, with Zn being at least one component. The carbon component includes amorphous carbon and nanocrystalline graphitic carbon. The catalyst exhibits high catalytic activity, good stability, and rapid degradation. It has a wide applicable pH range, showing good degradation effects between pH 3 and 13. It is versatile and widely applicable, capable of degrading various organic pollutants. The catalyst is magnetic, facilitating recovery and allowing for reuse without any substantial alteration to its microstructure and performance. This application also discloses a preparation method.

Description

Technical Field

[0001] This application relates to the field of catalytic degradation technology of organic pollutants, such as a nitrogen-doped carbon-modified high-entropy alloy catalyst, its preparation method, and its application. Background Technology

[0002] The continuous accumulation of antibiotic residues in the environment, especially in freshwater ecosystems, poses a significant threat to human health. In recent years, advanced oxidation technologies (AOPs) have been widely used to remove organic pollutants from water. Among them, molecular oxygen activation technology utilizes oxygen from the air as an oxidant to generate •OH and •O2. - Oxygen is a green, clean, and widely available oxidant compared to other advanced oxidation technologies, enabling the degradation of organic pollutants by reactive oxygen species (ROS). This avoids the secondary pollution caused by the addition of additional oxidants. Catalysts used to activate molecular oxygen mainly fall into two categories: noble metal catalysts and transition metal catalysts. Currently, single-metal catalysts are widely studied due to their strong reducing properties, safety, ease of operation, and low energy consumption. However, their development and application are limited by drawbacks such as a narrow pH range and low activity. Studies have shown that introducing other metal components to form multi-metal catalysts can improve these shortcomings.

[0003] Emerging high-entropy alloys (HEAs) are alloys composed of five or more metallic elements in equal or near-equal proportions. They possess tunable electronic structures and optimizable d-band centers, providing the necessary conditions for them to become excellent catalysts. Currently, no research reports have been found on the catalytic degradation of organic pollutants in water using high-entropy alloys. Summary of the Invention

[0004] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or describe the scope of protection of these embodiments, but rather as a prelude to the detailed description that follows.

[0005] This disclosure provides a nitrogen-doped carbon-modified high-entropy alloy catalyst and its preparation method. Using a high-entropy alloy as the matrix, nitrogen-doped carbon modification is carried out to achieve effective catalytic degradation of organic matter in water, and the catalyst has a wide applicable pH range.

[0006] In some embodiments, the nitrogen-doped carbon-modified high-entropy alloy catalyst comprises five or more multi-element high-entropy alloys selected from Fe, Co, Ni, Cu, Mn, Al, and Zn, and the high-entropy alloy includes at least Zn; the carbon component includes amorphous carbon and nanocrystalline graphite carbon.

[0007] In some embodiments, the preparation method of the nitrogen-doped carbon-modified high-entropy alloy catalyst includes: dissolving multiple metal salts selected from five or more metal elements (Fe, Co, Ni, Cu, Mn, Al, and Zn) in water at an equimolar ratio of metal atoms, stirring to dissolve, and obtaining solution A; wherein solution A includes at least zinc salt; dissolving trimesic acid and an organic nitrogen source in an organic solvent to obtain solution B; the organic nitrogen source includes melamine or polyvinylpyrrolidone; mixing solution A and solution B, stirring to mix, and obtaining a reaction solution; placing the reaction solution in a hydrothermal reactor, reacting at 120–180°C for a first preset time, and obtaining a reaction solution; centrifuging the reaction solution to obtain a precipitate, washing the precipitate and vacuum drying it to obtain a multi-metal precursor; holding the multi-metal precursor at 600–900°C in an inert gas atmosphere for a second preset time, and then cooling it to room temperature to obtain the nitrogen-doped carbon-modified high-entropy alloy catalyst.

[0008] The nitrogen-doped carbon-modified high-entropy alloy catalyst and its preparation method provided in this disclosure can achieve the following technical effects:

[0009] The nitrogen-doped carbon-modified high-entropy alloy catalyst of this disclosure exhibits high catalytic activity, good stability, and rapid degradation rate. It has a wide applicable pH range, showing good degradation effects across pH values ​​from 3 to 13. It also demonstrates good versatility and wide applicability, capable of degrading a variety of organic pollutants. The catalyst is magnetic, allowing for convenient recovery of consumed catalyst from the degradation reaction system by applying an external magnetic field, enabling reuse without any substantial alteration to its microstructure and performance.

[0010] The preparation method of this embodiment uses a hydrothermal method to synthesize high-entropy alloy catalysts, which can form a uniform precursor solution and achieve effective mixing of elements at a lower temperature, reducing energy consumption and synthesis difficulty. Moreover, the hydrothermal method conforms to the principles of green chemistry, reducing environmental harm by using environmentally friendly solvents (such as water and ethanol) and controllable reaction conditions, making it more environmentally friendly.

[0011] The above general description and the description below are exemplary and illustrative only and are not intended to limit this application. Attached Figure Description

[0012] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein:

[0013] Figure 1 This is a flowchart illustrating a method for preparing a nitrogen-doped carbon-modified high-entropy alloy catalyst according to an embodiment of this disclosure.

[0014] Figures 2(a) and 2(b) are SEM images of a catalyst sample prepared in Example 1 according to the present disclosure.

[0015] Figure 3 These are X-ray diffraction patterns of various catalyst samples obtained in Example 1 of this disclosure;

[0016] Figure 4 This is an EDS spectrum of a catalyst sample prepared in Example 1 of this disclosure;

[0017] Figure 5 This is a graph showing the removal efficiency of norfloxacin at different pH values ​​of a catalyst sample obtained in Example 1 of this disclosure.

[0018] Figure 6 This is a graph showing the removal efficiency of various catalyst samples obtained in Example 1 of this disclosure for norfloxacin at pH 7.

[0019] Figure 7 This is a graph showing the removal effect of a catalyst sample obtained in Example 1 of this disclosure on different organic pollutants.

[0020] Figure 8 These are Raman spectra of catalyst samples from Examples 1 to 3 of this disclosure at different hydrothermal reaction temperatures;

[0021] Figure 9 This is a graph showing the removal effect of various catalyst samples obtained in Examples 1 to 3 of this disclosure on norfloxacin at a pH value of 3;

[0022] Figure 10 This is a graph showing the removal effect of various catalyst samples obtained at different pyrolysis temperatures in Examples 4, 5 and Comparative Example 1 of the present disclosure on norfloxacin at pH 7.

[0023] Figures 11(a) and 11(b) are SEM images of a catalyst sample prepared in Example 6 according to the embodiments of this disclosure;

[0024] Figure 12 These are X-ray diffraction patterns of various catalyst samples obtained in Example 6 of this disclosure;

[0025] Figure 13 This is a graph showing the removal effect of various catalyst samples obtained in Example 6 of this disclosure on norfloxacin at a pH value of 3;

[0026] Figure 14This is a graph showing the removal effect of various catalyst samples obtained in Example 6 of this disclosure on norfloxacin at a pH value of 9;

[0027] Figure 15 This is a graph showing the removal effect of various catalyst samples obtained in Example 6 of this disclosure on norfloxacin at a pH value of 11.

[0028] Figure 16 These are X-ray diffraction patterns of various catalyst samples obtained in Example 7 and Comparative Example 2 of this disclosure;

[0029] Figure 17 This is Example 7 of the present disclosure, showing the removal effect curves of norfloxacin on a catalyst sample at different pH values;

[0030] Figure 18 This is a figure showing the nitrogen adsorption-desorption experimental characterization results of two catalyst samples obtained in Example 1 and Comparative Example 1 of this disclosure;

[0031] Figure 19 This is a graph showing the rate of change of pore size versus pore volume for two catalyst samples obtained in Example 1 and Comparative Example 1 of this disclosure. Detailed Implementation

[0032] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0033] Unless otherwise stated, the term "multiple" means two or more.

[0034] In this embodiment of the disclosure, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0035] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in the present disclosure can be combined with each other.

[0037] This disclosure provides a nitrogen-doped carbon-modified high-entropy alloy catalyst, which includes nanoparticles. The high-entropy alloy is a multi-element high-entropy alloy containing five or more of Fe, Co, Ni, Cu, Mn, Al and Zn, and the high-entropy alloy includes at least Zn. The carbon component includes amorphous carbon and nanocrystalline graphitic carbon.

[0038] In the nitrogen-doped carbon-modified high-entropy alloy catalyst of this disclosure, the high-entropy alloy is a pentagonal or higher-order high-entropy alloy including Zn. The electrode potential (E) of zero-valent iron is... 0 (Fe 2+ / Fe 0 Cobalt has a low v=-0.44, strong reducing properties, and is an effective electron donor. Cobalt can catalyze reactions not only through the traditional hydroxyl radical pathway but also through non-radical pathways to directly degrade organic matter, providing multiple degradation pathways. Nickel exhibits highly efficient catalytic performance in degrading organic pollutants; for example, the fine grain structure of nickel-aluminum alloys provides numerous active sites, facilitating catalytic reactions. During catalysis, copper promotes the generation of reactive oxygen species, which are crucial for the degradation of organic pollutants. Manganese possesses good chemical and thermal stability, maintaining stable catalytic activity over a wide temperature and pH range. The addition of zinc effectively increases the specific surface area of ​​the material. By controlling the pyrolysis temperature to not exceed the boiling point of zinc during high-temperature pyrolysis, some zinc volatilizes, leaving voids and increasing the contact area between the catalyst and organic pollutants. Simultaneously, carbon components are coated / loaded onto the surface of nitrogen-modified high-entropy alloy nanoparticles. The confinement effect of carbon coating / loading reduces the leaching of metal ions, providing stability to the high-entropy alloy catalyst. Nitrogen doping improves the electronic structure of carbon materials, further enhancing electron transport rates and thus enhancing catalytic activity. The synergistic effect between the metal components of the high-entropy alloy, as well as between the metals and the carbon components, accelerates electron transport, resulting in high catalytic activity and fast degradation rate of the high-entropy alloy catalyst. Moreover, the high-entropy alloy catalyst has a wide applicable pH range, showing good degradation effect in pH values ​​between 3 and 13, thus optimizing the problem of narrow pH response range of traditional catalysts.

[0039] The nitrogen-doped carbon-modified high-entropy alloy catalyst of this disclosure is magnetic. By applying an external magnetic field, the consumed catalyst can be easily recovered from the degradation reaction system, allowing for reuse without any substantial change to its microstructure and performance.

[0040] Optionally, the high-entropy alloy is a pentagonal high-entropy alloy comprising Fe, Co, Ni, Cu and Zn.

[0041] Optionally, the high-entropy alloy is a hexa-element high-entropy alloy comprising Fe, Co, Ni, Cu, Mn and Zn.

[0042] The nitrogen-doped carbon-modified high-entropy alloy catalyst of this embodiment is a black powder.

[0043] The nitrogen-doped carbon-modified high-entropy alloy catalyst of this disclosure includes nanospheres, and the particle size of the nanospheres is less than or equal to 500 nm.

[0044] Optionally, the particle size of the nanospheres is less than or equal to 400 nm.

[0045] Optionally, the particle size of the nanospheres is less than or equal to 300 nm.

[0046] Optionally, the particle size of the nanospheres is less than or equal to 200 nm.

[0047] Combination Figure 1 As shown in the embodiments of this disclosure, a method for preparing a carbon framework-modified nitrogen-doped high-entropy alloy catalyst is provided, comprising the following steps:

[0048] S10. Dissolve multiple metal salts selected from five or more metallic elements from Fe, Co, Ni, Cu, Mn, Al and Zn in water in equal molar ratios of metal atoms, stir to dissolve, and obtain solution A; wherein solution A includes at least zinc salt.

[0049] S20. Dissolve pyromellitic acid and an organic nitrogen source in an organic solvent to obtain solution B; the organic nitrogen source includes melamine or polyvinylpyrrolidone.

[0050] S30. Mix solution A and solution B, stir and mix well to obtain the reaction solution.

[0051] S40. Place the reaction solution in a hydrothermal reactor and react at 120-180°C for a first preset time to obtain the reaction solution; centrifuge the reaction solution to obtain the precipitate, wash the precipitate and vacuum dry it to obtain the multi-metal precursor.

[0052] S50. The multi-metal precursor is kept at a temperature of 600-900°C for a second preset time in an inert gas atmosphere, and then cooled to room temperature to obtain a nitrogen-doped carbon-modified high-entropy alloy catalyst.

[0053] The method for preparing nitrogen-doped carbon-modified high-entropy alloy catalysts in this embodiment uses pyromellitic acid (H3BTC) as an organic carbon source ligand and melamine (Mel) or polyvinylpyrrolidone (PVP) as a nitrogen source. A multi-metal precursor is prepared by hydrothermal reaction, and then the multi-metal precursor is pyrolyzed at high temperature to obtain a nitrogen-doped carbon-modified high-entropy alloy catalyst.

[0054] The preparation method of this disclosure utilizes a hydrothermal method to synthesize high-entropy alloys, which can form a homogeneous precursor solution and achieve effective mixing of elements at a relatively low temperature, reducing energy consumption and synthesis difficulty. The hydrothermal method conforms to the principles of green chemistry, reducing environmental harm by using environmentally friendly solvents (such as water and ethanol) and controllable reaction conditions; moreover, it is carried out in a closed system, reducing the emission of harmful gases and making it more environmentally friendly. Furthermore, the hydrothermal reaction can obtain high-entropy alloys in the form of nanospherical particles, and the size of these nanospherical particles is controllable, with the particle size of the obtained high-entropy alloy catalyst nanoparticles controlled to be less than or equal to 500 nm.

[0055] In the preparation method of this disclosure, melamine is added as a nitrogen source during hydrothermal synthesis. After introducing nitrogen species into the carbon layer, the difference in electronegativity allows nitrogen atoms to significantly influence the charge distribution of the carbon material, creating vacancies or defect sites in the carbon structure, accelerating electron transfer, and improving its catalytic degradation performance. Melamine or polyvinylpyrrolidone not only serves as a nitrogen source but also provides a reducing atmosphere as a carbon source during high-temperature pyrolysis, allowing for more complete metal reduction in the MOF. Tristyrene, as a polycarboxylic acid, has high chemical stability. Its abundant carboxyl groups can form stable complexes with metal ions, providing a basis for synthesizing metal-organic frameworks (MOFs) with high chemical stability. Simultaneously, during high-temperature carbonization, tristyrene-based MOFs maintain structural stability, forming a carbon framework structure. MOFs prepared from tristyrene can have a high specific surface area after carbonization. This high specific surface area is beneficial for increasing the number of active sites in the catalyst, thereby enhancing catalytic efficiency.

[0056] In the preparation method of this embodiment, Zn is added to the high-entropy alloy material. Zn has a low boiling point of around 900°C. During the high-temperature pyrolysis process, by controlling the pyrolysis temperature within the range of 600–900°C, some of the Zn volatilizes, leaving pores, thereby giving the material a porous structure and forming nanoparticles with a high specific surface area. This increases the number of active sites on the catalyst surface, increases the contact area with organic pollutants, and improves the degradation rate and activity.

[0057] In step S10 of the preparation method of this embodiment, the metal salts of the seven metals are soluble salts, capable of dissolving in water to form solution A. The specific metal salts are not limited and are determined according to actual conditions.

[0058] Alternatively, the metal salts of Fe include Fe(NO3)3•9H2O, Fe(CH3COO)3•4H2O, or FeCl3•6H2O.

[0059] Alternatively, the metal salts of Co include Co(NO3)2·6H2O, Co(CH3COO)2·4H2O, or CoCl2·6H2O.

[0060] Alternatively, the metal salts of Ni include Ni(NO3)2·6H2O, Ni(CH3COO)2·4H2O, or NiCl2·6H2O.

[0061] Alternatively, the metal salts of Cu include Cu(NO3)2·3H2O, Cu(CH3COO)2·H2O, or CuCl2·2H2O.

[0062] Alternatively, the metal salts of Zn include Zn(NO3)2·6H2O, Zn(CH3COO)2·2H2O or ZnCl2·6H2O.

[0063] Alternatively, the metal salts of Mn include Mn(NO3)2·6H2O, Mn(CH3COO)2·4H2O or MnCl2·4H2O.

[0064] Alternatively, metal salts of Al include Al(NO3)3·9H2O, Al(CH3COO)3·2H2O, or AlCl3·6H2O.

[0065] In some embodiments, in step S10, the ratio of the amount of one type of metal atom to water is controlled to be 1–2 mmol: 15–30 mL. In this embodiment, each metal atom is added in an equimolar ratio, that is, the ratio of the amount of each metal atom to water is the same and is within 1–2 mmol: 15–30 mL. That is, in solution A, the molar concentration of each metal salt is approximately 0.03–0.13 mol / L.

[0066] Optionally, in step S10, the ratio of the amount of one of the metal atoms to water is controlled to be 1.5 mmol: 20 mL. That is, in solution A, the molar concentration of each metal salt is approximately 0.075 mol / L.

[0067] In step S10, the stirring and dissolving time is not limited, as long as the metal salts are dissolved and mixed evenly. For example, stirring for 20 to 50 minutes.

[0068] In some embodiments, in step S20, the ratio of trimesic acid to organic solvent is 4–8 mmol: 15–30 mL.

[0069] Optionally, in step S20, the ratio of pyromellitic acid to organic solvent is 5–6 mmol: 20 mL.

[0070] Optionally, in step S20, the ratio of pyromellitic acid to organic solvent is 5.5 mmol: 20 mL.

[0071] In some embodiments, in step S20, the ratio of organic nitrogen source to organic solvent is 0.2–1 g: 15–30 mL.

[0072] Optionally, in step S20, the ratio of organic nitrogen source to organic solvent is 0.3–0.9 g: 15–25 mL.

[0073] Optionally, in step S20, the ratio of organic nitrogen source to organic solvent is 0.5–0.8 g: 18–23 mL.

[0074] Optionally, in step S20, the ratio of organic nitrogen source to organic solvent is 0.6 g: 20 mL.

[0075] In step S20 of this embodiment, the organic solvent includes anhydrous ethanol, dimethylformamide (DMF), or ethylene glycol.

[0076] In step S20, stirring can be performed while dissolving the trimellitic acid and organic nitrogen source in the organic solvent to accelerate the dissolution. The stirring time is not limited, as long as the trimellitic acid and organic nitrogen source are completely dissolved. For example, stirring for 20–50 minutes.

[0077] In some embodiments, step S30, mixing solution A with solution B, includes adding solution A to solution B at a rate of 5 to 15 mL / s.

[0078] Optionally, in step S30, the rate at which solution A is added to solution B is 6–14 mL / s.

[0079] Optionally, in step S30, the rate at which solution A is added to solution B is 7–13 mL / s.

[0080] Optionally, in step S30, the rate at which solution A is added to solution B is 8–12 mL / s.

[0081] Optionally, in step S30, the rate at which solution A is added to solution B is 9–11 mL / s.

[0082] Optionally, in step S30, the rate at which solution A is added to solution B is 10 mL / s.

[0083] In step S40, the reaction solution is placed in a hydrothermal reactor for hydrothermal reaction. The hydrothermal reaction temperature is controlled within the range of 120–180°C. The low hydrothermal reaction temperature results in low energy consumption. Specifically, the hydrothermal reaction temperature can be any temperature within the range of 120–180°C, such as 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, and 180°C, etc.

[0084] Optionally, the reaction solution is placed in a hydrothermal reactor and reacted at 130–160°C for a first preset time to obtain the reaction solution.

[0085] Optionally, the reaction solution is placed in a hydrothermal reactor and reacted at 150°C for a first preset time to obtain the reaction solution.

[0086] In some embodiments, in step S40, the first preset duration is 20 to 30 hours.

[0087] Optionally, in step S40, the first preset duration is 22 to 28 hours.

[0088] Optionally, in step S40, the first preset duration is 24 hours.

[0089] In step S40, during the vacuum drying process after washing the precipitate, the specific washing method is not limited, as long as it can remove soluble impurities from the reaction solution. Optionally, washing includes washing the precipitate N times with deionized water and the organic solvent from step S20, respectively. The value of N is not limited and is determined according to the actual situation. For example, N is any positive integer greater than 1, specifically, N is 2, 3, 4, 5, or 6.

[0090] In step S40, during the vacuum drying process after washing the precipitate, the vacuum drying includes drying in a vacuum environment at 50–100°C. The drying time is not limited and is determined according to the actual situation.

[0091] Optionally, in step S40, the vacuum drying time is 6 to 10 hours.

[0092] Optionally, in step S40, the vacuum drying time is 8 hours.

[0093] Optionally, in step S40, vacuum drying includes drying in a vacuum environment at 50–80°C for 6–10 hours.

[0094] Optionally, in step S40, vacuum drying includes drying in a vacuum environment at 60°C for 8 hours.

[0095] Optionally, in step S40, the vacuum drying process is carried out using a vacuum drying oven. That is, the washed precipitate is placed in a vacuum drying oven for vacuum drying.

[0096] Step S50 of this embodiment involves obtaining a nitrogen-doped carbon-modified high-entropy alloy catalyst by high-temperature pyrolysis of a multi-metal precursor. The high-temperature pyrolysis temperature is controlled within the range of 600–900°C. This pyrolysis temperature allows some Zn to volatilize, thereby forming catalyst nanoparticles with a high specific surface area. Optionally, the high-temperature pyrolysis temperature is 800°C.

[0097] Optionally, the hydrothermal reaction product is kept at 800°C for a second preset time in an inert gas atmosphere.

[0098] In some embodiments, step S50, holding the multi-metal precursor at a temperature of 600–900°C in an inert gas atmosphere for a second preset time, includes: placing the multi-metal precursor in an inert gas atmosphere, heating it to 600–900°C at a rate of 3–8°C / min, and holding it at that temperature for the second preset time. In this embodiment, by controlling the heating rate, it is possible to better ensure that all parts of the sample can uniformly reach the required temperature.

[0099] Optionally, the temperature is raised to 600-900°C at a rate of 4-6°C / min and held for a second preset time.

[0100] Optionally, the temperature is raised to 600–900°C at a rate of 5°C / min and held for a second preset time.

[0101] In some embodiments, the inert gas in step S50 includes nitrogen or argon.

[0102] In some embodiments, in step S50, the second preset duration is 1 to 3 hours.

[0103] Optionally, in step S50, the second preset duration is 2 hours.

[0104] In some embodiments, step S50, cooling to room temperature includes: cooling down to room temperature at a rate of 3 to 8 °C / min.

[0105] Optionally, in step S50, cooling to room temperature includes cooling down to room temperature at a rate of 4 to 6 °C / min.

[0106] Optionally, in step S50, cooling to room temperature includes: cooling down to room temperature at a rate of 5°C / min.

[0107] This disclosure also provides the application of the aforementioned nitrogen-doped carbon-modified high-entropy alloy catalyst or the nitrogen-doped carbon-modified high-entropy alloy catalyst prepared by the aforementioned preparation method in the degradation of organic pollutants in water.

[0108] In the applications of this disclosure, the nitrogen-doped carbon-modified high-entropy alloy catalyst exhibits good versatility and a wide range of applications, capable of degrading various organic pollutants in water. It is suitable for degrading organic pollutants in water with a pH between 3 and 13, achieving a degradation rate of over 80% within 40 minutes. At pH 7, it degrades organic compounds such as norfloxacin, rhodamine B, methyl orange, methylene blue, and tetracycline hydrochloride with a degradation rate exceeding 95% within 40 minutes.

[0109] The following specific embodiments illustrate, in more detail, the nitrogen-doped carbon-modified high-entropy alloy catalysts of this disclosure, their preparation methods, and their applications.

[0110] Example 1: FeCoNiCuZn-based high-entropy alloy catalyst

[0111] A method for preparing a nitrogen-doped carbon-modified high-entropy alloy catalyst includes the following steps:

[0112] S101. Dissolve Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cu(NO3)2·3H2O, and Zn(NO3)2·6H2O in deionized water in equimolar ratios, and stir for 30 min to obtain solution A. The ratio of the amount of each metal salt to deionized water is 1.5 mmol: 20 mL.

[0113] S201. Dissolve pyromellitic acid and an organic nitrogen source in anhydrous ethanol and stir for 30 min to obtain solution B; the organic nitrogen source includes melamine (Mel). The ratio of pyromellitic acid to anhydrous ethanol is 5.5 mmol: 20 mL; the ratio of melamine (Mel) to anhydrous ethanol is 0.2–1 g: 20 mL.

[0114] S301. Add solution A to solution B at a rate of 10 mL / s, stir for 30 min, mix well, and obtain the reaction solution. The volume ratio of solution A to solution B is 1:1.

[0115] S401. Place the reaction solution in a hydrothermal reactor and react at 150°C for 24 hours to obtain the reaction solution; centrifuge the reaction solution to obtain the precipitate, wash the precipitate and vacuum dry it at 60°C for 8 hours to obtain the pentagonal metal precursor.

[0116] S501. The multi-metal precursor is placed in a ceramic boat and placed in a tube furnace. It is heated to 800℃ at a rate of 5℃ / min in an argon inert gas atmosphere and held for 2h. Then it is cooled to room temperature to obtain a nitrogen-doped carbon-modified FeCoNiCuZn-based high-entropy alloy catalyst.

[0117] The nitrogen-doped carbon-modified FeCoNiCuZn-based high-entropy alloy catalyst prepared in Example 1 is a black powder containing nanoparticles. The nanoparticles are basically spherical, with a particle size in the range of 100 nm to 200 nm. The high-entropy alloy is a pentagonal high-entropy alloy containing Fe, Co, Ni, Cu and Zn. The carbon component includes amorphous carbon and nanocrystalline graphitic carbon.

[0118] In this Example 1, different catalyst samples were obtained by adjusting the amount of melamine in step S201. Specifically, the amounts of melamine were 0.3g, 0.6g and 0.9g, and the corresponding catalyst samples were denoted as HEAs@CN3-800, HEAs@CN6-800 and HEAs@CN9-800, respectively.

[0119] Meanwhile, in this Example 1, a comparative experiment 1 was conducted. No melamine was added in step S201, that is, the amount of melamine used was 0g. The other steps and parameters remained unchanged, and a corresponding catalyst comparison sample was obtained, denoted as HEAs@C-800.

[0120] As shown in Figure 2(a) and Figure 2(b), the scanning electron microscope (SEM) images of HEAs@CN6-800 show that spherical particles are formed in the powdered catalyst, and the particles are uniform in size with a particle size of about 100 nm to 200 nm.

[0121] like Figure 3 The X-ray diffraction patterns of HEAs@CN3-800, HEAs@CN6-800, HEAs@CN9-800, and HEAs@C-800 shown are derived from... Figure 3 It can be observed that all four samples exhibited characteristic peaks at 43.3°, 50.4°, and 74.1°, corresponding to the (111), (200), and (220) crystal planes, respectively (PDF#04-0836 is the XRD curve of the FCC-structured high-entropy alloy obtained from the standard card database in the XRD data analysis software (jade6)). This indicates that the obtained samples all have a face-centered cubic (FCC) structure, consistent with the literature reports. This also shows that the pentagonal metal precursor was successfully transformed into a high-purity high-entropy alloy phase. It can be seen that the intensity of the diffraction peaks increases with the addition of Mel. This may be because Mel not only acts as a nitrogen source during pyrolysis but also provides a reducing atmosphere, making the reduction of the metal more complete. The diffraction peaks are strongest when the Mel doping amount is 0.6g. As the doping amount continues to increase, the intensity of the diffraction peaks weakens. This may be because the addition of excessive Mel will form more amorphous carbon on the sample surface.

[0122] Figure 4 The EDS spectrum of HEAs@CN6-800 shows that iron, cobalt, nickel, copper, and zinc are relatively evenly distributed, and the presence of nitrogen and carbon indicates successful nitrogen doping. Meanwhile, the zinc content is lower than other metals, indicating that some zinc volatilized during pyrolysis.

[0123] In Example 1, an application experiment 1-1 on the degradation of organic pollutants in water was conducted. The experiment was as follows: A norfloxacin (NOR) solution with an initial concentration of 20 ppm C0 was used as the degradation solution. The pH of the degradation solution was adjusted with 0.1 mol / L NaOH and 0.1 mol / L H2SO4 to obtain six degradation solutions with pH values ​​of 3, 5, 7, 9, 11, and 13. The HEAs@CN6-800 catalyst sample from Example 1 was added to each of these six degradation solutions, and the mixture was stirred, with timing starting at the moment of addition. The dosage of the HEAs@CN6-800 catalyst sample was 1 g / L. During the degradation process, 3 mL of the degradation solution was taken at regular intervals, filtered through a 0.22 μm filter membrane to remove the catalyst, and placed in a 1 cm quartz cuvette. The absorbance was measured using a UV-Vis spectrophotometer to determine the concentration C of norfloxacin. t To obtain such Figure 5 The graph shows the removal efficiency curves of norfloxacin at different pH values.

[0124] pass Figure 5 It can be seen that the degradation effect is excellent within a pH range of 3–11, with norfloxacin removal rates exceeding 95% within 40 minutes. Under acidic conditions, the degradation rate is 96.22% at pH 3 and 98.30% at pH 5; under alkaline conditions, the degradation rate is 97.15% at pH 9, 98.12% at pH 11, and 74.04% at pH 13; at pH 7, all norfloxacin can be removed. At pH 13, due to the strong alkalinity, hydroxylation may occur on the catalyst surface, leading to the occupation of surface active sites, thereby reducing the contact between the catalyst and the active sites and slowing down the degradation rate.

[0125] Similarly, degradation application experiments were conducted on HEAs@CN3-800, HEAs@CN9-800, and HEAs@C-800 (comparative experiment 1) according to the degradation application experiment 1-1 described above. A pH value of 7 was selected, and the following results were obtained: Figure 6 The graph shows the removal efficiency of different catalysts for norfloxacin at pH 7. Figure 6 As can be seen, when the Mel doping amount is 0%, the catalyst removes 86.10% of norfloxacin. After adding an appropriate amount of Mel, a significant improvement in the degradation performance of norfloxacin can be observed. When the Mel addition amount is 0.3g, the removal rate of norfloxacin reaches 95.5%, indicating that Mel doping can effectively enhance the catalytic activity of the catalyst. The degradation effect is best when the Mel addition amount is 0.6g, and all NOR can be removed within 40 minutes. When the Mel doping amount is further increased to 0.9g, the removal rate is 97.6%.

[0126] In this Example 1, application experiments 1-2 on the degradation of organic pollutants in water were also conducted. These included: various common organic pollutants found in the environment, such as the organic dyes Rhodamine B (RhB), methyl orange (MO), and methylene blue (MB), and the antibiotics metronidazole (MNZ), norfloxacin (NOR), and tetracycline hydrochloride (TCH). Degradation solutions for the six different organic pollutants were prepared with an initial concentration (C0) of 20 ppm. The pH of each solution was adjusted to 7 using 1 mol / L NaOH and 1 mol / L H2SO4. Then, the HEAs@CN6-800 catalyst sample from Example 1 was added to each solution, stirred, and timing was started upon addition. The dosage of the HEAs@CN6-800 catalyst sample was 1 g / L. During the degradation process, 3 mL of the degradation solution was taken at regular intervals, filtered through a 0.22 μm filter membrane to remove the catalyst, and placed in a 1 cm quartz cuvette. The absorbance was measured using a UV-Vis spectrophotometer to determine the concentration C of the organic pollutants contained in each solution. t To obtain such Figure 7 The graphs show the removal efficiency curves for different organic pollutants.

[0127] pass Figure 7 It can be seen that for dye pollutants, methylene blue (MB) and methyl orange (MO) have relatively fast degradation rates, and can be completely removed within 20 minutes of catalyst addition. Rhodamine B (RhB) can also be degraded by 97.11% within 40 minutes. For antibiotic pollutants, tetracycline hydrochloride (TCH) and norfloxacin (NOR) can both be completely removed within 40 minutes. Metronidazole (MNZ) has relatively poor degradation performance, with only 65.04% removed within 40 minutes. This may be attributed to the high stability given by the nitro group and imidazole ring in the metronidazole molecule. It can be observed that the catalyst has good versatility, almost completely removing the vast majority of organic pollutants in a short time, demonstrating excellent degradation performance. This strongly proves that the HEAs@CN6-800 catalyst is suitable for wastewater environments containing various organic pollutants and can adapt to the complex components in various industrial wastewaters in practical applications, providing an efficient solution for wastewater treatment.

[0128] Example 2

[0129] Unlike Example 1, in step S201, the ratio of melamine (Mel) to anhydrous ethanol is 0.6 g: 20 mL; in step S401, the reaction solution is placed in a hydrothermal reactor and reacted at 120°C for 24 h to obtain the reaction solution. The remaining steps and parameters are the same as in Example 1.

[0130] The nitrogen-doped carbon-modified FeCoNiCuZn-based high-entropy alloy catalyst prepared in Example 2 is designated HEAs@CN6-800'.

[0131] Example 3

[0132] Unlike Example 1, in step S201, the ratio of melamine (Mel) to anhydrous ethanol is 0.6 g: 20 mL; in step S401, the reaction solution is placed in a hydrothermal reactor and reacted at 180°C for 24 h to obtain the reaction solution. The remaining steps and parameters are the same as in Example 1.

[0133] The nitrogen-doped carbon-modified FeCoNiCuZn-based high-entropy alloy catalyst prepared in Example 3 is designated HEAs@CN6-800".

[0134] Examples 1 to 3 yielded catalyst samples (HEAs@CN6-800, HEAs@CN6-800', and HEAs@CN6-800") with hydrothermal reaction temperatures of 120℃, 150℃, and 180℃, respectively. Raman spectroscopy analysis was performed on these three catalyst samples, yielding the following results: Figure 8 The Raman spectra of the catalyst at different hydrothermal reaction temperatures are shown. Figure 8 As shown, all three catalyst samples were at 1350 cm⁻¹. -1 and 1850cm -1 Two peaks appeared nearby, corresponding to the D peak and the G peak, respectively. The D peak represents the degree of lattice defects and disorder in carbon materials, and is usually associated with sp... 3 Related to hybridized carbon atoms; the G peak represents sp in the material 2 In-plane stretching vibrations of hybridized carbon atoms. Typically, the ratio of the D peak intensity to the G peak intensity (I...) D / I G I is an important indicator for measuring the degree of graphitization of carbon components, and is generally considered to be... D / I G The smaller the Ig, the higher the degree of graphitization. However, unlike crystalline carbon materials, amorphous carbon exhibits higher Ig. D / I G The ratio indicates the presence of numerous amorphous structures and defects in the sample. This is because the formation of nanocrystalline graphite enhances the intensity of the D peak by reducing bond torsion and bond angles of disordered carbon atoms and tightening the corresponding vibrational density. Therefore, I D / I G The larger the value, the higher the degree of graphitization. Combined with XRD analysis, it can be seen that the carbon component in HEAs@CN-800 is amorphous carbon. When the hydrothermal temperature increases from 120℃ to 180℃, I... D / I GThe ratio increased from 0.96 to 1.02, indicating that increasing the hydrothermal temperature promotes the formation of nanocrystalline graphite and increases the degree of graphitization in the catalyst. Figure 9 As shown in the degradation effect curve and Table 1, the degree of graphitization of the catalyst in the embodiments of this disclosure is closely related to the electron transport rate of the catalyst. The higher the degree of graphitization, the higher the electron mobility, thereby improving the catalytic performance of the catalyst.

[0135] Degradation application experiments 1-3 were conducted on the catalyst samples HEAs@CN6-800, HEAs@CN6-800', and HEAs@CN6-800" obtained in Examples 1 to 3, as well as the control catalyst sample HEAs@C-800. The degradation solution was a norfloxacin (NOR) solution with an initial concentration of 20 ppm and a pH of 3 (the pH adjustment method can be referred to the aforementioned degradation application experiment 1-1, and will not be repeated here). Four parallel portions of this degradation solution were prepared, with HEAs@CN6-800, HEAs@CN6-800', HEAs@CN6-800", and HEAs@C-800 added respectively, at a dosage of 1 g / L for each catalyst sample. During the degradation process, 3 mL of the degradation solution was transferred at regular intervals, filtered through a 0.22 μm filter membrane to remove the catalyst, placed in a 1 cm quartz cuvette, and the absorbance was measured using a UV-Vis spectrophotometer to determine the concentration C of norfloxacin. The resulting solution was as follows: Figure 9 The graph shows the removal efficiency of the catalysts obtained at different hydrothermal reaction temperatures at pH 3 for norfloxacin removal. Figure 9 It is evident that, under acidic conditions with a water pH of 3, after 40 minutes, the degradation rate of the catalyst obtained at 120℃ (HEAs@CN6-800') was 87.42%; the degradation rate of the catalyst obtained at 150℃ (HEAs@CN6-800) was 96.22%; and the degradation rate of the catalyst obtained at 180℃ (HEAs@CN6-800") was 84.45%, all exhibiting excellent degradation rates. In contrast, the degradation rate of undoped HEAs@C-800 was 81.87%.

[0136] Similarly, HEAs@CN6-800, HEAs@CN6-800', HEAs@CN6-800" and HEAs@C-800 were subjected to degradation experiments using the methods described in Degradation Application Experiments 1-3 above, with pH values ​​of 7, 9 and 11 respectively, and the degradation rates at 40 min were obtained (as shown in Table 1). The degradation trends of each catalyst sample were consistent at different pH values.

[0137] Table 1

[0138]

[0139] Example 4

[0140] Unlike Example 1, in step S201, the ratio of melamine (Mel) to anhydrous ethanol is 0.6 g: 20 mL; in step S501, the temperature is raised to 600 °C (i.e., the pyrolysis temperature is 600 °C); the remaining steps and parameters are the same as in Example 1.

[0141] The nitrogen-doped carbon-modified FeCoNiCuZn-based high-entropy alloy catalyst prepared in Example 4 is designated HEAs@CN6-600.

[0142] Example 5

[0143] Unlike Example 1, in step S201, the ratio of melamine (Mel) to anhydrous ethanol is 0.6 g: 20 mL; in step S501, the temperature is raised to 900 °C (i.e., the pyrolysis temperature is 900 °C); the remaining steps and parameters are the same as in Example 1.

[0144] The nitrogen-doped carbon-modified FeCoNiCuZn-based high-entropy alloy catalyst prepared in Example 5 is designated HEAs@CN6-900.

[0145] Comparative Example 1: FeCoNiCu-based high-entropy alloy catalyst

[0146] The difference between Comparative Example 1 and Example 1 is that in step S101, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and Cu(NO3)2·3H2O are dissolved in deionized water in an equimolar ratio and stirred for 30 min to obtain solution A. The ratio of the amount of each metal salt to deionized water is 1.5 mmol: 20 mL. In step S201, the ratio of melamine (Mel) to anhydrous ethanol is 0.6 g: 20 mL; therefore, a quaternary metal precursor is obtained in step S401. All other steps and parameters are the same as in Example 1.

[0147] The catalyst obtained in Comparative Example 1 is a carbon-nitrogen modified and doped FeCoNiCu-based high-entropy alloy catalyst without Zn element, denoted as FeCoNiCu@CN6-800.

[0148] Degradation application experiments 1-4 were conducted on four catalyst samples obtained in Examples 1, 4, and 5, as well as Comparative Example 1. The degradation solution was a norfloxacin (NOR) solution with an initial concentration of 20 ppm and a pH of 7 (the pH adjustment method can be referred to the aforementioned degradation application experiment 1-1, and will not be repeated here). Four parallel portions of this degradation solution were prepared, with HEAs@CN6-600, HEAs@CN6-800, HEAs@CN6-900, and FeCoNiCu@CN6-800 added respectively, at a dosage of 1 g / L for each catalyst sample. The remaining operations are as described in the aforementioned degradation application experiments 1-3. The obtained catalysts were as follows: Figure 10 The graph shows the removal efficiency of norfloxacin by catalysts obtained at different pyrolysis temperatures at pH 7. Figure 10 As shown, after 40 minutes of degradation, the catalyst obtained at a pyrolysis temperature of 600℃ had a degradation rate of 82.5%, the catalyst obtained at 800℃ had a degradation rate of 100%, and the catalyst obtained at 900℃ had a degradation rate of 89.7%. In contrast, the degradation rate of the control catalyst obtained without Zn and at a pyrolysis temperature of 800℃ was 78.3%. This demonstrates that the introduction of Zn and control of the pyrolysis temperature within the range of 600℃ to 800℃ can significantly improve the degradation rate.

[0149] In Examples 1 to 5 above, "HEAs" represents "FeCoNiCuZn".

[0150] Example 6

[0151] A method for preparing a nitrogen-doped carbon-modified high-entropy alloy catalyst includes the following steps:

[0152] S102. Dissolve Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cu(NO3)2·3H2O, and Zn(NO3)2·6H2O in deionized water in equimolar ratios, and stir for 30 min to obtain solution A. The ratio of the amount of each metal salt to deionized water is 1.5 mmol: 20 mL.

[0153] S202. Dissolve pyromellitic acid and an organic nitrogen source in anhydrous ethanol and stir for 30 min to obtain solution B; the organic nitrogen source includes polyvinylpyrrolidone (PVP). The ratio of pyromellitic acid to anhydrous ethanol is 5.5 mmol: 20 mL; the ratio of polyvinylpyrrolidone (PVP) to anhydrous ethanol is 0.2–1 g: 20 mL.

[0154] S302. Add solution A to solution B at a rate of 10 mL / s, stir for 30 min, mix well, and obtain the reaction solution. The volume ratio of solution A to solution B is 1:1.

[0155] S402. Place the reaction solution in a hydrothermal reactor and react at 120℃~180℃ for 24h to obtain the reaction solution; centrifuge the reaction solution to obtain the precipitate, wash the precipitate and dry it under vacuum at 60℃ for 8h to obtain the pentagonal metal precursor.

[0156] S502. The multi-metal precursor is placed in a ceramic boat and placed in a tube furnace. It is heated to 800℃ at a rate of 5℃ / min in an argon inert gas atmosphere and held for 2 hours. Then it is cooled to room temperature to obtain a nitrogen-doped carbon-modified FeCoNiCuZn-based high-entropy alloy catalyst.

[0157] In Example 6, a nitrogen-doped carbon-modified FeCoNiCuZn-based high-entropy alloy catalyst was prepared using polyvinylpyrrolidone (PVP) as a nitrogen source. The catalyst was a black powder containing nanoparticles, which were basically spherical with a particle size in the range of 100 nm to 200 nm. The high-entropy alloy was a pentagonal high-entropy alloy containing Fe, Co, Ni, Cu and Zn. The carbon component included amorphous carbon and nanocrystalline graphite.

[0158] In this Example 6, different catalyst samples were obtained by adjusting the hydrothermal reaction temperature in step S402. Specifically, with the ratio of PVP to anhydrous ethanol in step S202 being 0.6g:20mL, catalyst samples were obtained at hydrothermal reaction temperatures of 120℃, 150℃, and 180℃, respectively, and were denoted as catalyst sample I, catalyst sample II, and catalyst sample III.

[0159] In this Example 6, a comparative experiment 2 was conducted. In step S202, no polyvinylpyrrolidone (PVP) was added, that is, the amount of polyvinylpyrrolidone used was 0g. In step S402, the hydrothermal reaction temperature was 150℃, and the corresponding catalyst sample comparison II was obtained.

[0160] As shown in Figures 11(a) and 11(b), the scanning electron microscope (SEM) images of catalyst sample II show that the catalyst contains a large number of spherical particles with a particle size of less than 400 nm, and most of the particles are distributed between 100 nm and 200 nm. Moreover, the morphology is consistent with that of the catalyst obtained by using melamine as a nitrogen source.

[0161] like Figure 12 The X-ray diffraction patterns of catalyst sample I, catalyst sample II, and catalyst sample III shown are derived from... Figure 12It can be seen that characteristic peaks appeared at 43.3°, 50.4°, and 74.1° for all three catalyst samples, corresponding to the (111), (200), and (220) crystal planes, respectively, indicating that the obtained catalyst samples all have a face-centered cubic (FCC) structure. This also shows that the pentagonal metal precursor was successfully transformed into a high-purity high-entropy alloy phase. Furthermore, it was found that the diffraction peaks of the samples were strongest at 150°C, indicating that the crystallinity was best at this temperature, and that a suitable temperature is beneficial for crystal growth.

[0162] In Example 6, an application experiment 2-1 on the degradation of organic pollutants in water was conducted. The solution to be degraded was a norfloxacin (NOR) solution with an initial concentration of 20 ppm and a pH value of 3 (the pH adjustment method can be referred to the aforementioned degradation application experiment 1-1, and will not be repeated here). Four parallel portions of this solution to be degraded were prepared, with catalyst sample I, catalyst sample II, catalyst sample III, and catalyst sample control II added respectively, and the dosage of each catalyst sample was 1 g / L. The remaining operations are the same as those in the aforementioned degradation application experiment 1-3. The following was obtained: Figure 13 The graph shows the removal efficiency of the catalyst for norfloxacin at different hydrothermal reaction temperatures at pH 3. Figure 13 As can be seen, under acidic conditions with a pH of 3 in the water, after 30 minutes, the degradation rate of catalyst sample I obtained at 120℃ was 87.38%; the degradation rate of catalyst sample II obtained at 150℃ was 95.11%; and the degradation rate of catalyst sample III obtained at 180℃ was 98.12%, all exhibiting excellent degradation rates. Compared with the degradation rate of sample II (77.70%), nitrogen doping can significantly improve the degradation performance of the catalyst.

[0163] Similarly, degradation experiments were conducted on catalyst samples I, II, III, and Comparative II using the degradation application experiment 2-1 above with degradation solutions (initial concentration of norfloxacin solution of 20 ppm) at pH 9 and 11, respectively, and the corresponding results were obtained. Figure 14 and Figure 15 , Figure 14 The graph shows the removal efficiency of the catalysts obtained at different hydrothermal reaction temperatures with a pH of 9 for norfloxacin. Figure 15 The graph shows the removal efficiency of the catalysts obtained at different hydrothermal reaction temperatures with a pH of 11 for norfloxacin. The corresponding degradation rate data are shown in Table 2.

[0164] Table 2

[0165]

[0166] As can be seen, the nitrogen-doped carbon-modified FeCoNiCuZn-based high-entropy alloy catalyst obtained in Example 6 has a good degradation rate for organic pollutants in water.

[0167] Example 7

[0168] A method for preparing a carbon framework-modified nitrogen-doped high-entropy alloy catalyst includes the following steps:

[0169] S103. Dissolve Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cu(NO3)2·3H2O, Mn(NO3)2·6H2O, and Zn(NO3)2·6H2O in deionized water in equimolar ratios. Stir for 30 min to obtain solution A. The ratio of the amount of each metal salt to deionized water is 1.5 mmol: 20 mL.

[0170] S203. Dissolve pyromellitic acid and an organic nitrogen source in anhydrous ethanol and stir for 30 min to obtain solution B; the organic nitrogen source includes melamine (Mel). The ratio of pyromellitic acid to anhydrous ethanol is 5.5 mmol: 20 mL; the ratio of melamine (Mel) to anhydrous ethanol is 0.2–1 g: 20 mL.

[0171] S303. Add solution A to solution B at a rate of 10 mL / s, stir for 30 min, mix well, and obtain the reaction solution. The volume ratio of solution A to solution B is 1:1.

[0172] S403. Place the reaction solution in a hydrothermal reactor and react at 120℃~180℃ for 24h to obtain the reaction solution; centrifuge the reaction solution to obtain the precipitate, wash the precipitate and dry it under vacuum at 60℃ for 8h to obtain the hexametal precursor.

[0173] S503. The multi-metal precursor is placed in a ceramic boat and placed in a tube furnace. It is heated to 800℃ at a rate of 5℃ / min in an argon inert gas atmosphere and held for 2h. Then it is cooled to room temperature to obtain a nitrogen-doped carbon-modified FeCoNiCuMnZn-based high-entropy alloy catalyst.

[0174] In Example 7, a nitrogen-doped carbon-modified FeCoNiCuMnZn-based high-entropy alloy catalyst was prepared using melamine (Mel) as a nitrogen source. The catalyst was a black powder containing nanoparticles, which were basically spherical with a particle size mainly distributed in the range of 100 nm to 200 nm. The high-entropy alloy was a hexa-element high-entropy alloy containing Fe, Co, Ni, Cu, Mn and Zn. The carbon component included amorphous carbon and nanocrystalline graphite carbon.

[0175] In this Example 7, specifically, in step S203, the ratio of Mel to anhydrous ethanol is 0.6 g: 20 mL, and in step S403, the hydrothermal reaction temperature is 150 °C, to prepare catalyst sample V (FeCoNiCuMnZn@CN6-800).

[0176] Meanwhile, in this Example 7, a comparative experiment 3 was conducted. No melamine was added in step S203, that is, the amount of melamine used was 0g. The other steps and parameters remained unchanged, and the corresponding catalyst comparative sample V (FeCoNiCuMnZn@C-800) was obtained.

[0177] Comparative example: 2FeCoNiCuMn-based high-entropy alloy catalyst

[0178] The difference between Comparative Example 2 and Example 7 is that in step S103, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cu(NO3)2·3H2O, and Mn(NO3)2·6H2O are dissolved in deionized water in an equimolar ratio and stirred for 30 min to obtain solution A. The ratio of the amount of each metal salt to deionized water is 1.5 mmol: 20 mL. Therefore, the pentagonal metal precursor obtained in step S401 is the same as in Example 7. All other steps and parameters are the same.

[0179] Comparative Example 2 yielded a carbon-nitrogen modified and doped FeCoNiCuMn-based high-entropy alloy catalyst (denoted as FeCoNiCuMn@CN6-800), which did not contain Zn.

[0180] like Figure 16 The X-ray diffraction patterns of catalyst sample V, catalyst control sample V, and FeCoNiCuMn@CN6-800 in Comparative Example 2 are shown below. Figure 16 It can be observed that all three formed the high-entropy alloy phase of FCC. After adding the nitrogen source (Mel), the diffraction peaks of FeCoNiCuMnZn@CN6-800 were stronger, indicating better crystallinity. This is because the nitrogen source provides a reducing atmosphere during pyrolysis, which makes the reduction of the metal more complete.

[0181] In Example 7, an application experiment 3-1 on the degradation of organic pollutants in water was conducted. A norfloxacin (NOR) solution with an initial concentration of 20 ppm C0 was prepared as the degradation solution. The pH value was adjusted using the method described in Application Experiment 1-1, resulting in four degradation solutions with pH values ​​of 3, 7, 9, and 11. Catalyst sample V from Example 7 was added to each of these four degradation solutions at a dosage of 1 g / L. During the degradation process, 3 mL of the degradation solution was taken periodically, filtered through a 0.22 μm filter membrane to remove the catalyst, and placed in a 1 cm quartz cuvette. The absorbance was measured using a UV-Vis spectrophotometer to determine the concentration C of norfloxacin. t To obtain such Figure 17 The graphs show the removal efficiency of catalyst sample V for norfloxacin at different pH values.

[0182] Depend on Figure 17 As shown, catalyst sample V was almost completely degraded within 40 minutes, with a degradation rate of 98.9% at pH 3, 99.1% at pH 7, 97% at pH 9, and 95.82% at pH 11. It exhibits good degradation performance over a wide pH range.

[0183] Similarly, for FeCoNiCuMn@CN6-800 in Comparative Example 2, degradation experiments were conducted using the method described in Application Experiment 3-1. Degradation solutions with pH values ​​of 3, 9, and 11 were selected, and the degradation rates at 40 min were obtained, as shown in Table 3. Its degradation trend is consistent with that of catalyst sample V.

[0184] Table 3

[0185]

[0186] It is evident that the degradation rate of FeCoNiCuMn@CN6-800 without the introduction of Zn element is significantly reduced at all pH values.

[0187] In this embodiment, the HEAs@CN6-800 catalyst (abbreviated as FeCoNiCuZn@CN) from Example 1 and the FeCoNiCu-based high-entropy alloy catalyst (abbreviated as FeCoNiCu@CN) from Comparative Example 1 were subjected to nitrogen adsorption-desorption experiments. The pore characteristics and specific surface area of ​​the catalysts with and without added Zn were characterized by the nitrogen adsorption-desorption experiments, and the effect of Zn addition on the specific surface area and pore size of the catalysts was investigated. The results are as follows: Figure 18As shown, the N2 adsorption-desorption isotherm of FeCoNiCuZn@CN6-800 exhibits a significant H3-type hysteresis loop within the relative pressure range of 0.45~1.0, exhibiting typical type IV adsorption isotherms, indicating the presence of mesopores in the FeCoNiCuZn@CN6-800 catalyst. Conversely, the FeCoNiCu@CN6-800 catalyst shows a similar hysteresis loop shape, but its adsorption-desorption isotherm is significantly lower than that of the FeCoNiCuZn@CN6-800 catalyst, indicating that some metallic Zn acts as a sacrificial template during pyrolysis, evaporating and leaving voids, thus improving the catalyst's pore structure. Furthermore, combined with the average pore size distribution diagram (…),… Figure 19 According to the results calculated by the Brunauer-Emmet-Teller formula in Table 4, the addition of metallic Zn significantly increased the specific surface area and pore volume of the catalyst, while the pore size decreased. This indicates that some Zn acts as a sacrificial template, which is of great significance in improving the performance of the catalyst.

[0188] Table 4

[0189]

[0190] This application is not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

[0191] In this application, each embodiment may focus on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other.

Claims

1. A nitrogen-doped carbon-modified high-entropy alloy catalyst, characterized in that, The high-entropy alloy is a multi-element high-entropy alloy containing five or more of the following: Fe, Co, Ni, Cu, Mn, Al, and Zn, and the high-entropy alloy must contain at least Zn; the carbon component includes amorphous carbon and nanocrystalline graphitic carbon. The nitrogen-doped carbon-modified high-entropy alloy catalyst is suitable for the degradation of organic pollutants in water bodies with a pH between 3 and 13. The method for preparing the nitrogen-doped carbon-modified high-entropy alloy catalyst includes: Multiple metal salts selected from five or more metallic elements, namely Fe, Co, Ni, Cu, Mn, Al and Zn, are dissolved in water in equal molar ratios of metal atoms and stirred to obtain solution A; wherein solution A contains at least zinc salt. Pyromellitic acid and an organic nitrogen source are dissolved in an organic solvent to obtain solution B; the organic nitrogen source includes melamine or polyvinylpyrrolidone. Mix solution A and solution B, stir until well mixed, and obtain the reaction solution; The reaction solution is placed in a hydrothermal reactor and reacted at 120–180°C for a first preset time to obtain the reaction solution; the reaction solution is centrifuged to obtain the precipitate, and the precipitate is washed and vacuum dried to obtain the multi-metal precursor; The multi-metal precursor was kept at 800°C for a second preset time in an inert gas atmosphere and then cooled to room temperature to obtain a nitrogen-doped carbon-modified high-entropy alloy catalyst.

2. The nitrogen-doped carbon-modified high-entropy alloy catalyst according to claim 1, characterized in that, This includes nanospheres, with a particle size of less than or equal to 500 nm.

3. The nitrogen-doped carbon-modified high-entropy alloy catalyst according to claim 1, characterized in that, High-entropy alloys are pentagonal high-entropy alloys comprising Fe, Co, Ni, Cu, and Zn; or, High-entropy alloys are hexa-element high-entropy alloys including Fe, Co, Ni, Cu, Mn and Zn.

4. The method for preparing the nitrogen-doped carbon-modified high-entropy alloy catalyst according to any one of claims 1 to 3, characterized in that, include: Multiple metal salts selected from five or more metallic elements, namely Fe, Co, Ni, Cu, Mn, Al and Zn, are dissolved in water in equal molar ratios of metal atoms and stirred to obtain solution A; wherein solution A contains at least zinc salt. Pyromellitic acid and an organic nitrogen source are dissolved in an organic solvent to obtain solution B; the organic nitrogen source includes melamine or polyvinylpyrrolidone. Mix solution A and solution B, stir until well mixed, and obtain the reaction solution; The reaction solution is placed in a hydrothermal reactor and reacted at 120–180°C for a first preset time to obtain the reaction solution; the reaction solution is centrifuged to obtain the precipitate, and the precipitate is washed and vacuum dried to obtain the multi-metal precursor; The multi-metal precursor was kept at 800°C for a second preset time in an inert gas atmosphere and then cooled to room temperature to obtain a nitrogen-doped carbon-modified high-entropy alloy catalyst.

5. The method for preparing the nitrogen-doped carbon-modified high-entropy alloy catalyst according to claim 4, characterized in that, The ratio of the amount of one metal atom in the metal element to water is controlled to be 1-2 mmol: 15-30 mL. Metal salts of five or more metal elements selected from Fe, Co, Ni, Cu, Mn, Al and Zn are dissolved in water in equal molar ratios of metal atoms.

6. The method for preparing the nitrogen-doped carbon-modified high-entropy alloy catalyst according to claim 4, characterized in that, In the step of dissolving pyromellitic acid and an organic nitrogen source in an organic solvent, the ratio of pyromellitic acid to organic solvent is 4–8 mmol: 15–30 mL; and / or, the ratio of organic nitrogen source to organic solvent is 0.3–0.9 g: 15–25 mL.

7. The method for preparing a nitrogen-doped carbon-modified high-entropy alloy catalyst according to claim 4, characterized in that, Mixing solution A with solution B includes: adding solution A to solution B at a rate of 5–15 mL / s; and / or, Mixing solution A with solution B includes adding solution A to solution B at a volume ratio of 0.8 to 1.2:

1.

8. The method for preparing the nitrogen-doped carbon-modified high-entropy alloy catalyst according to claim 4, characterized in that, The hydrothermal reaction products are kept at 800°C in an inert gas atmosphere for a second preset time, including: The multi-metal precursor is placed in an inert gas atmosphere and heated to 800°C at a rate of 3–8°C / min and held at that temperature for a second preset time.

9. The method for preparing a nitrogen-doped carbon-modified high-entropy alloy catalyst according to claim 4, characterized in that, In the step of vacuum drying after washing the precipitate, vacuum drying includes drying in a vacuum environment at 50–100°C.

10. The application of the nitrogen-doped carbon-modified high-entropy alloy catalyst prepared by the method of any one of claims 1 to 3 or the method of any one of claims 4 to 9 in the degradation of organic pollutants in water.

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