A p-block element controllably doped iron single-atom catalyst and its application

Abstract

The present invention discloses a p-zone element controllably doped iron single-atom catalyst and its application. The method first mixes a doping source (boric acid, phosphoric acid, sulfuric acid) with divalent iron ions, and then adds an organic ligand (oxalic acid) to construct an iron complex with different coordination configurations. The components are organized into a supramolecular precursor of a rod-like structure through the supramolecular self-assembly process of melamine and cyanuric acid. Under an argon atmosphere, the precursor is subjected to a high-temperature pyrolysis process to synthesize a series of p-zone element controllably doped iron single-atom catalysts. By constructing an asymmetric Fe-X1N3 configuration (X represents a doping element) and accurately controlling the doping amount and position of the p-zone element, the coordination structure and electronic properties of the Fe single-atom catalyst are effectively regulated, the regulation of the persulfate (PMS) activation path is achieved, the activity and selectivity of the catalyst are improved, and a new approach is provided for the control and treatment of environmental pollutants.

Description

Technical Field

[0001] The present invention belongs to the technical fields of materials engineering and environmental engineering, and particularly relates to an iron single-atom catalyst with controllable doping of p-zone elements and applications thereof. Background Art

[0002] Persulfate (PMS) has a unique asymmetric structure and is easily activated to degrade pollutants. It is a very promising advanced oxidation technology. [1] However, the activation efficiency of PMS is often limited by the structural and electronic properties of the catalyst, which restricts its efficiency in practical applications. Rationally designed catalysts will be able to selectively generate 1 O2, high-valent iron species or catalytic oxidation through electron transfer pathways can not only improve oxidation efficiency but also reduce unnecessary side reactions, providing a greener and more efficient solution for environmental remediation and organic synthesis. However, although traditional Fe-N4 is stable, the symmetry of electron distribution during the catalytic process limits its further improvement in catalytic activity and selectivity. In order to overcome this limitation, p-block elements such as sulfur (S), phosphorus (P) and boron (B) are doped to regulate the electronic structure and coordination environment of the iron metal center of the catalyst.

[0003] The introduction of p-block elements provides a new approach to regulating the activation pathway of PMS. Studies have shown that doping with p-block elements can significantly change the electron density and d-band center position of Fe SACs, thereby affecting their interaction with PMS. For example, sulfur doping can increase the electron density of Fe atoms and improve their adsorption capacity for PMS, thereby promoting the activation of PMS and generating more reactive oxygen species (ROS). Phosphorus doping may optimize the adsorption and activation process of PMS by adjusting the d-band center of Fe atoms, further improving catalytic efficiency. Boron doping, as an effective means of electronic structure regulation, can adjust the electron distribution of Fe-N4 sites through its unique electronic properties, reduce the activation energy barrier of PMS, and thus improve the activity and selectivity of the catalyst.

[0004] They discovered that by constructing an asymmetric Fe-X1N3 configuration (X represents the doping element), breaking the traditional symmetrical coordination structure, and precisely controlling the doping amount and position of the p-block element, they could effectively manipulate the coordination structure and electronic properties of Fe SACs, achieving precise control of the PMS activation pathway. This doping strategy not only improves the utilization efficiency of PMS but also broadens the catalyst's application range in different aqueous environments, opening up new avenues for the control and treatment of environmental pollutants. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and provide an iron single-atom catalyst with controllable doping of p-zone elements and its application.

[0006] The object of the present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides an iron single-atom catalyst with controllable doping of p-zone elements, wherein the iron single-atom catalyst with controllable doping of p-zone elements is prepared by the following method:

[0008] S1: dissolving melamine in deionized water at 70-90° C. to obtain a melamine solution; dissolving cyanuric acid in deionized water at 70-90° C. to obtain a cyanuric acid solution; dissolving ferrous sulfate heptahydrate in deionized water at 20-30° C. to obtain a ferrous sulfate solution; the molar ratio of melamine, cyanuric acid, and ferrous sulfate being 1:0.5-0.9:0.1-0.5;

[0009] S2: adding sulfuric acid and oxalic acid to the ferrous sulfate solution and stirring at 20-30° C. for 5-10 minutes to form solution A; the molar ratio of the sulfuric acid, oxalic acid and ferrous sulfate is 1:0.8 to 1:0.2-0.8;

[0010] S3: adding the solution A to the cyanuric acid solution and stirring at 70-90° C. for 5-10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 2-4 hours; after the reaction is completed, achieving solid-liquid separation by suction filtration and washing the precipitate; then, performing forced air drying at 55-60° C. for 6-8 hours to obtain a supramolecular precursor, and grinding the precursor into a uniform powder;

[0011] S4: Under the protection of an argon atmosphere, the powdered supramolecular precursor is heated to 550-600°C, kept at this temperature for 3-5 hours, and then cooled to room temperature to obtain an iron single-atom catalyst with controllable doping of p-block elements, denoted as FeS / CN.

[0012] In a second aspect, the present invention further provides an iron single-atom catalyst with controllable doping of p-zone elements, wherein the iron single-atom catalyst with controllable doping of p-zone elements is prepared by the following method:

[0013] S1: dissolving melamine in deionized water at 70-90° C. to obtain a melamine solution; dissolving cyanuric acid in deionized water at 70-90° C. to obtain a cyanuric acid solution; dissolving ferrous sulfate heptahydrate in deionized water at 20-30° C. to obtain a ferrous sulfate solution; the molar ratio of melamine, cyanuric acid, and ferrous sulfate being 1:0.5-0.9:0.1-0.5;

[0014] S2: adding oxalic acid and phosphoric acid to the ferrous sulfate solution and stirring at 20-30° C. for 5-10 minutes to form solution A; the molar ratio of the phosphoric acid, oxalic acid and ferrous sulfate is 1:0.8 to 1:0.2-0.8;

[0015] S3: adding the solution A to the cyanuric acid solution and stirring at 70-90° C. for 5-10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 2-4 hours; after the reaction is completed, achieving solid-liquid separation by suction filtration and washing the precipitate; then, performing forced air drying at 55-60° C. for 6-8 hours to obtain a supramolecular precursor, and grinding the precursor into a uniform powder;

[0016] S4: Under the protection of an argon atmosphere, the powdered supramolecular precursor is heated to 550-600°C, kept at this temperature for 3-5 hours, and then cooled to room temperature to obtain an iron single-atom catalyst with controllable doping of p-block elements, denoted as FeP / CN.

[0017] In a third aspect, the present invention further provides an iron single-atom catalyst with controllable doping of p-zone elements, wherein the iron single-atom catalyst with controllable doping of p-zone elements is prepared by the following method:

[0018] S1: dissolving melamine in deionized water at 70-90° C. to obtain a melamine solution; dissolving cyanuric acid in deionized water at 70-90° C. to obtain a cyanuric acid solution; dissolving ferrous sulfate heptahydrate in deionized water at 20-30° C. to obtain a ferrous sulfate solution; the molar ratio of melamine, cyanuric acid, and ferrous sulfate being 1:0.5-0.9:0.1-0.5;

[0019] S2: adding boric acid to the ferrous sulfate solution and stirring at 20-30° C. for 5-10 minutes to form solution A; the molar ratio of the boric acid, oxalic acid, and ferrous sulfate is 1:0.8 to 1:0.2-0.8;

[0020] S3: adding the solution A to the cyanuric acid solution and stirring at 70-90° C. for 5-10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 2-4 hours; after the reaction is completed, achieving solid-liquid separation by suction filtration and washing the precipitate; then, performing forced air drying at 55-60° C. for 6-8 hours to obtain a supramolecular precursor, and grinding the precursor into a uniform powder;

[0021] S4: Under the protection of an argon atmosphere, the powdered supramolecular precursor is heated to 550-600°C, kept at this temperature for 3-5 hours, and then cooled to room temperature to obtain an iron single-atom catalyst with controllable doping of p-block elements, denoted as FeB / CN.

[0022] In a fourth aspect, the present invention also provides an application of an iron single-atom catalyst with controllable doping of p-zone elements for removing phenolic benzene series from surface water, specifically: pouring the iron single-atom catalyst with controllable doping of p-zone elements and peroxymonosulfate into surface water containing phenolic benzene series, the water temperature is 20-30°C, stirring and reacting for 10-15 minutes, and completing the removal of phenolic benzene series from the surface water; the dosage of the iron single-atom catalyst with controllable doping of p-zone elements is 0.2-0.6 g / L; the dosage of the peroxymonosulfate is 100-600 μmol / L; the concentration of the phenolic benzene series in the surface water is 0-200 μmol / L.

[0023] Furthermore, the phenolic benzene series compound is phenol, p-chlorophenol, p-hydroxybenzoic acid or p-nitrophenol.

[0024] The beneficial effects of the present invention are:

[0025] 1) By varying the type of doping element, we achieved the controllable synthesis of iron single atoms doped with different p-block elements, and analyzed the efficiency of catalyst activation of PMS and the types and contents of active species produced;

[0026] 2) Doping with different elements changes the charge density and d-band center position of the Fe metal center, optimizes the interaction between the catalyst and PMS, enhances the activation ability of the catalyst for PMS, and improves the degradation efficiency of phenolic pollutants;

[0027] 3) By precisely controlling the position of the doping elements, an asymmetric Fe-X1N3 configuration is constructed, breaking the symmetry limitations of the traditional Fe-N4 structure and achieving precise control of the PMS activation pathway from singlet oxygen, high-valent iron, to electron transfer pathways;

[0028] 4) It has good adaptability and stability, and can maintain high efficiency in removing chlorophenols in different water quality environments, while also being able to efficiently remove a variety of phenolic benzene series. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11;

[0030] Figure 2 A spherical aberration-corrected high-angle annular dark-field scanning transmission electron micrograph and a Fe and S element distribution spectrum of the sulfur-doped iron single-atom catalyst prepared in Example 4;

[0031] Figure 3 A spherical aberration-corrected high-angle annular dark-field scanning transmission electron micrograph and a Fe and S element distribution spectrum of the phosphorus-doped iron single-atom catalyst prepared in Example 7;

[0032] Figure 4 A spherical aberration-corrected high-angle annular dark-field scanning transmission electron micrograph and a Fe and B element distribution spectrum of the boron-doped iron single-atom catalyst prepared in Example 11;

[0033] Figure 5 is the three-dimensional intensity distribution and line profile analysis diagram, where Figure 5 (a) is a three-dimensional intensity distribution and line cross-section analysis diagram of the catalyst prepared in Example 4. Figure 5 (b) is a three-dimensional intensity distribution and line cross-sectional analysis diagram of the catalyst prepared in Example 7, Figure 5 (c) is a three-dimensional intensity distribution and line profile analysis diagram of the catalyst prepared in Example 11;

[0034] Figure 6 Schematic diagram of the molar ratio of the doping element to iron in the catalysts prepared in Examples 4, 7 and 11;

[0035] Figure 7 The X-ray diffraction patterns of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 are shown;

[0036] Figure 8 Fourier transform Fe K-edge R-space X-ray extended edge absorption fine structure spectra of the catalysts, FePc and iron foil prepared in Comparative Example 1, Example 4, Example 7 and Example 11;

[0037] Figure 9 Graph showing the Fourier transform FeK-edge R-space X-ray extended edge absorption fine structure fitting results of the catalysts prepared in Comparative Example 1, Example 4, Example 7, and Example 11;

[0038] Figure 10 is the wavelet variation EXAFS analysis diagram, where Figure 10 (a) is the wavelet variation EXAFS analysis diagram of the catalyst prepared in Comparative Example 1, Figure 10 (b) is the wavelet variation EXAFS analysis diagram of the catalyst prepared in Example 4. Figure 10 (c) is the wavelet variation EXAFS analysis diagram of the catalyst prepared in Example 7, Figure 10 (d) is the wavelet variation EXAFS analysis graph of the catalyst prepared in Example 11;

[0039] Figure 11 Fe K-edge X-ray absorption near-edge structure spectra of the catalysts, Fe foil, FeO, Fe2O3 and Fe3O4 prepared in Comparative Example 1, Example 4, Example 7 and Example 11;

[0040] Figure 12 4-CP concentration change curve of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 during the process of activating PMS to degrade 4-CP;

[0041] Figure 13 This is a comparison chart of the degradation rates of 4-CP by the catalyst-activated PMS prepared in Comparative Example 1, Example 4, Example 7, and Example 11;

[0042] Figure 14 This is a comparison chart of the quenching experiment of 4-CP degradation by the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11;

[0043] Figure 15 is the EPR spectrum, where Figure 15 (a) is the EPR spectrum of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 using TEMP, Figure 15 (b) is an EPR spectrum of DMPO used for the catalysts prepared in Comparative Example 1, Example 4, Example 7, and Example 11;

[0044] Figure 16 This is a comparison chart of PMS consumption during the degradation of 4-CP by PMS activated by the catalysts prepared in Comparative Example 1, Example 4, Example 7, and Example 11;

[0045] Figure 17 The catalyst activation PMS process produced by Comparative Example 1, Example 4, Example 7 and Example 11 1 O2 and Fe(IV)=O content and PMS utilization graph;

[0046] Figure 18 1 is an EIS curve diagram of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11;

[0047] Figure 19 It curves of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11;

[0048] Figure 20 1 is an LSV curve diagram of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11;

[0049] Figure 21 The degradation rate of 4-CP by the catalyst PMS prepared in Examples 1 to 12, Fe IV =O / 1 Correlation diagram between O2 / electron transfer contribution rate and doping element / iron molar ratio;

[0050] Figure 22 This is a graph showing the degradation rate of 4-CP by activated PMS using the catalysts prepared in Comparative Example 1, Example 4, Example 7, and Example 11 under different water quality conditions;

[0051] Figure 23 The degradation rate of 4-CP by PMS activated by the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 under different pH conditions is shown;

[0052] Figure 24 The degradation rate diagram of 4-CP by activated PMS in the presence of different anions and cations for the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11;

[0053] Figure 25 Graph showing the experimental effects of a continuous flow membrane device in the process of activating PMS and degrading 4-CP under deionized water conditions using the catalysts prepared in Comparative Example 1, Example 4, Example 7, and Example 11;

[0054] Figure 26 Graph showing the experimental effects of a continuous flow membrane device for the process of activating PMS and degrading 4-CP under the first wastewater condition using the catalysts prepared in Comparative Example 1, Example 4, Example 7, and Example 11;

[0055] Figure 27 The experimental results of the continuous flow membrane device and the iron ion dissolution rate of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 in the process of activating PMS and degrading 4-CP under the second wastewater condition;

[0056] Figure 28 This is a comparison chart of the degradation rates of different benzene series and antibiotics by activating PMS using the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present invention, rather than to represent all embodiments. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0058] In the following examples, unless otherwise stated, all experimental methods mentioned are conventional methods; all reagents and materials mentioned, unless otherwise stated, can be obtained through commercial channels.

[0059] The present invention provides a method for preparing an iron single-atom catalyst with controllable doping of p-block elements. By controlling the type of doping source, the synthesis of a series of iron single-atom catalysts doped with different p-block elements is achieved. In addition, by changing the dosage of the doping source, the preparation of iron single-atom catalysts with different dopant concentrations is further achieved, and is described in detail in Examples 1 to 12.

[0060] Example 1 Sulfur-doped iron single-atom catalyst (0.09-FeS / CN) (10 wt%) was synthesized by the following method:

[0061] S1: 1 g of melamine was dissolved in 100 ml of deionized water at 80° C. to obtain a melamine solution; 0.8 g of cyanuric acid was dissolved in 120 ml of deionized water at 80° C. to obtain a cyanuric acid solution; 0.22 g of ferrous sulfate heptahydrate was dissolved in 60 ml of deionized water at 25° C. to obtain a ferrous sulfate solution.

[0062] S2: 0.1 ml of sulfuric acid and 0.14 g of oxalic acid were added to the ferrous sulfate solution, and stirred at 25° C. for 10 minutes to form a uniform solution A.

[0063] S3: After adding the solution A to the cyanuric acid solution, stirring at 80°C for 10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 3 hours; after the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is alternately washed with deionized water and ethanol for 3 times each to remove impurities; then, it is blown dry at 60°C for 8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder.

[0064] S4: Under the protection of a high-purity argon atmosphere with a purity of 99.99%, the powdered supramolecular precursor was heated to 600°C at a heating rate of 5°C / min, kept at this temperature for 4 hours, and then cooled to room temperature to obtain a carbon nitride-supported sulfur-doped iron single-atom catalyst, denoted as 0.09-FeS / CN.

[0065] The sulfur-doped iron single-atom catalyst prepared in Example 1 had a measured sulfur-to-iron molar ratio of 0.09, and was therefore recorded as 0.09-FeS / CN.

[0066] Example 2 Sulfur-doped iron single atom catalyst (0.12-FeS / CN) (10 wt%)

[0067] Compared with Example 1, 0.2 ml of sulfuric acid and 0.3 g of oxalic acid were used in step (2) of this example, and the other steps were the same.

[0068] The sulfur-doped iron single-atom catalyst prepared in Example 2 had a measured sulfur-to-iron molar ratio of 0.12, and was therefore recorded as 0.12-FeS / CN.

[0069] Example 3 Sulfur-doped iron single atom catalyst (0.15-FeS / CN) (10 wt%)

[0070] Compared with Example 1, 0.3 ml of sulfuric acid was used in step (2) of this example, and the other steps were the same.

[0071] The sulfur-doped iron single-atom catalyst prepared in Example 3 had a measured sulfur-to-iron molar ratio of 0.15, and was therefore recorded as 0.15-FeS / CN.

[0072] Example 4 Sulfur-doped iron single atom catalyst (0.21-FeS / CN) (10 wt%)

[0073] Compared with Example 1, 0.4 ml of sulfuric acid was used in step (2) of this example, and the other steps were the same.

[0074] The sulfur-doped iron single-atom catalyst prepared in Example 4 had a measured sulfur-to-iron molar ratio of 0.21, and was therefore recorded as 0.21-FeS / CN.

[0075] Example 5 Phosphorus-doped iron single-atom catalyst (0.09-FeP / CN) (10 wt%) was synthesized by the following method:

[0076] S1: 1 g of melamine was dissolved in 100 ml of deionized water at 80° C. to obtain a melamine solution; 0.8 g of cyanuric acid was dissolved in 120 ml of deionized water at 80° C. to obtain a cyanuric acid solution; 0.22 g of ferrous sulfate heptahydrate was dissolved in 60 ml of deionized water at 25° C. to obtain a ferrous sulfate solution.

[0077] S2: 0.1 ml of phosphoric acid and 0.14 g of oxalic acid were added to the ferrous sulfate solution, and stirred at 25° C. for 10 minutes to form a uniform solution A.

[0078] S3: After adding the solution A to the cyanuric acid solution, stirring at 80°C for 10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 3 hours; after the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is alternately washed with deionized water and ethanol for 3 times each to remove impurities; then, it is blown dry at 60°C for 8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder.

[0079] S4: Under the protection of a high-purity argon atmosphere with a purity of 99.99%, the powdered supramolecular precursor was heated to 600°C at a heating rate of 5°C / min, kept at this temperature for 4 hours, and then cooled to room temperature to obtain a carbon nitride-supported phosphorus-doped iron single-atom catalyst, denoted as 0.09-FeP / CN.

[0080] The phosphorus-to-iron molar ratio of the phosphorus-doped iron single-atom catalyst prepared in Example 5 was measured to be 0.09, and was therefore recorded as 0.09-FeP / CN.

[0081] Example 6 Phosphorus-doped iron single-atom catalyst (0.16-FeP / CN) (10 wt%)

[0082] Compared with Example 5, 0.2 ml of phosphoric acid and 0.3 g of oxalic acid were used in step (2) of this example, and the other steps were the same.

[0083] The phosphorus-doped iron single-atom catalyst prepared in Example 6 had a measured phosphorus-to-iron molar ratio of 0.16, and was therefore recorded as 0.16-FeP / CN.

[0084] Example 7 Phosphorus-doped iron single-atom catalyst (0.23-FeP / CN) (10 wt%)

[0085] Compared with Example 5, 0.3 ml of phosphoric acid and 0.3 g of oxalic acid were used in step (2) of this example, and the other steps were the same.

[0086] The phosphorus-doped iron single-atom catalyst prepared in Example 7 had a measured phosphorus-to-iron molar ratio of 0.23, and was therefore recorded as 0.23-FeP / CN.

[0087] Example 8 Phosphorus-doped iron single-atom catalyst (0.34-FeP / CN) (10 wt%)

[0088] Compared with Example 5, 0.4 ml of phosphoric acid was used in step (2) of this example, and the other steps were the same.

[0089] The phosphorus-to-iron molar ratio of the phosphorus-doped iron single-atom catalyst prepared in Example 8 was measured to be 0.34, and was therefore recorded as 0.34-FeP / CN.

[0090] Example 9 Boron-doped iron single-atom catalyst (0.08-FeB / CN) (10 wt%) was synthesized by the following method:

[0091] S1: 1 g of melamine was dissolved in 100 ml of deionized water at 80° C. to obtain a melamine solution; 0.8 g of cyanuric acid was dissolved in 120 ml of deionized water at 80° C. to obtain a cyanuric acid solution; 0.22 g of ferrous sulfate heptahydrate was dissolved in 60 ml of deionized water at 25° C. to obtain a ferrous sulfate solution.

[0092] S2: 0.1 g of boric acid and 0.3 g of oxalic acid were added to the ferrous sulfate solution, and stirred at 25° C. for 10 min to form a uniform solution A.

[0093] S3: After adding the solution A to the cyanuric acid solution, stirring at 80°C for 10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 3 hours; after the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is alternately washed with deionized water and ethanol for 3 times each to remove impurities; then, it is blown dry at 60°C for 8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder.

[0094] S4: Under the protection of a high-purity argon atmosphere with a purity of 99.99%, the powdered supramolecular precursor was heated to 600°C at a heating rate of 5°C / min, kept at this temperature for 4 hours, and then cooled to room temperature to obtain a carbon nitride-supported boron-doped iron single-atom catalyst, denoted as 0.08-FeB / CN.

[0095] The boron-doped iron single-atom catalyst prepared in Example 9 had a measured boron-to-iron molar ratio of 0.08, and was therefore recorded as 0.08-FeB / CN.

[0096] Example 10 Boron-doped iron single atom catalyst (0.16-FeB / CN) (10 wt%)

[0097] Compared with Example 9, 0.2 g of boric acid was used in step (2) of this example, and the other steps were the same.

[0098] The boron-doped iron single-atom catalyst prepared in Example 10 had a measured boron-to-iron molar ratio of 0.16, and was therefore recorded as 0.16-FeB / CN.

[0099] Example 11 Boron-doped iron single atom catalyst (0.28-FeB / CN) (10 wt%)

[0100] Compared with Example 9, 0.3 g of boric acid was used in step (2) of this example, and the other steps were the same.

[0101] The boron-doped iron single-atom catalyst prepared in Example 11 had a measured boron-to-iron molar ratio of 0.28, and was therefore recorded as 0.28-FeB / CN.

[0102] Example 12 Boron-doped iron single atom catalyst (0.39-FeB / CN) (10 wt%)

[0103] Compared with Example 9, 0.4 g of boric acid was used in step (2) of this example, and the other steps were the same.

[0104] The boron-doped iron single-atom catalyst prepared in Example 12 had a measured boron-to-iron molar ratio of 0.39, and was therefore recorded as 0.39-FeB / CN.

[0105] Comparative Example 1 Iron single atom catalyst (Fe / CN) (10 wt%) was synthesized by the following method:

[0106] S1: 1 g of melamine was dissolved in 100 ml of deionized water at 80° C. to obtain a melamine solution; 0.8 g of cyanuric acid was dissolved in 120 ml of deionized water at 80° C. to obtain a cyanuric acid solution; 0.22 g of ferrous sulfate heptahydrate was dissolved in 60 ml of deionized water at 25° C. to obtain a ferrous sulfate solution.

[0107] S2: 0.6 g of oxalic acid was added to the ferrous sulfate solution, and the mixture was stirred at 25° C. for 10 min to form a uniform solution A.

[0108] S3: After adding the solution A to the cyanuric acid solution, stirring at 80°C for 10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 3 hours; after the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is alternately washed with deionized water and ethanol for 3 times each to remove impurities; then, it is blown dry at 60°C for 8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder.

[0109] S4: Under the protection of a high-purity argon atmosphere with a purity of 99.99%, the powdered supramolecular precursor was heated to 600°C at a heating rate of 5°C / min, kept at this temperature for 4 hours, and then cooled to room temperature to obtain a carbon nitride-supported iron single-atom catalyst, denoted as Fe / CN.

[0110] Comparative Example 2 A graphite phase carbon nitride (CN) was synthesized by the following steps:

[0111] S1: 1 g of melamine was dissolved in 100 ml of deionized water at 80° C. to obtain a melamine solution; 0.8 g of cyanuric acid was dissolved in 120 ml of deionized water at 80° C. to obtain a cyanuric acid solution.

[0112] S2: adding the cyanuric acid solution to the melamine solution, stirring at 80° C. for 10 minutes, and then performing a coprecipitation reaction for 3 hours; after the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is alternately washed with deionized water and ethanol three times each to remove impurities; then, the precipitate is dried with forced air at 60° C. for 8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder.

[0113] S3: Under the protection of a high-purity argon atmosphere with a purity of 99.99%, the powdered supramolecular precursor was heated to 600°C at a heating rate of 5°C / min, kept at this temperature for 4 hours, and then cooled to room temperature to obtain graphite-phase carbon nitride, denoted as CN.

[0114] Comparative Example 3 A sulfur-doped graphite carbon nitride (SCN) was synthesized by the following steps:

[0115] S1: Dissolve 1 g of melamine in 100 ml of deionized water at 80°C to obtain a melamine solution; dissolve 0.8 g of cyanuric acid in 120 ml of deionized water at 80°C to obtain a cyanuric acid solution; and dissolve 0.3 ml of sulfuric acid in 30 ml of deionized water at 25°C to obtain a sulfuric acid solution.

[0116] S2: adding the sulfuric acid solution described in S1 to the cyanuric acid solution, stirring uniformly at 80°C for 10 minutes, then pouring the mixed solution into the melamine solution obtained in step S1, stirring for 3 hours to carry out a co-precipitation reaction; after the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is alternately washed with deionized water and ethanol three times each to remove impurities; then, it is blown dry at 60°C for 8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder.

[0117] S3: Under the protection of a high-purity argon atmosphere with a purity of 99.99%, the powdered supramolecular precursor was heated to 600°C at a heating rate of 5°C / min, kept at this temperature for 4 hours, and then cooled to room temperature to obtain sulfur-doped graphitic carbon nitride, denoted as SCN.

[0118] Comparative Example 4 A phosphorus-doped graphite carbon nitride (PCN) was synthesized by the following steps:

[0119] S1: Dissolve 1 g of melamine in 100 ml of deionized water at 80°C to obtain a melamine solution; dissolve 0.8 g of cyanuric acid in 120 ml of deionized water at 80°C to obtain a cyanuric acid solution; and dissolve 0.3 ml of phosphoric acid in 30 ml of deionized water at 25°C to obtain a phosphoric acid solution.

[0120] S2: adding the phosphoric acid solution described in S1 to the cyanuric acid solution, stirring uniformly at 80°C for 10 minutes, then pouring the mixed solution into the melamine solution obtained in step S1, stirring for 3 hours to carry out a co-precipitation reaction; after the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is alternately washed with deionized water and ethanol three times each to remove impurities; then, the precipitate is dried by forced air at 60°C for 8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder.

[0121] S3: Under the protection of a high-purity argon atmosphere with a purity of 99.99%, the powdered supramolecular precursor was heated to 600°C at a heating rate of 5°C / min, kept at this temperature for 4 hours, and then cooled to room temperature to obtain phosphorus-doped graphitic carbon nitride, denoted as PCN.

[0122] Comparative Example 5 A boron-doped graphite carbon nitride (BCN) was synthesized by the following steps:

[0123] S1: Dissolve 1 g of melamine in 100 ml of deionized water at 80°C to obtain a melamine solution; dissolve 0.8 g of cyanuric acid in 120 ml of deionized water at 80°C to obtain a cyanuric acid solution; and dissolve 0.3 g of boric acid in 120 ml of deionized water at 25°C to obtain a boric acid solution.

[0124] S2: Add the boric acid solution described in S1 to the cyanuric acid solution, stir evenly at 80°C for 10 minutes, then pour the mixed solution into the melamine solution obtained in step S1, and stir for 3 hours to carry out a co-precipitation reaction; after the reaction is completed, separate the solid and liquid by suction filtration, and wash the precipitate alternately with deionized water and ethanol for 3 times each to remove impurities; then dry it with air at 60°C for 8 hours to obtain a supramolecular precursor, and grind it into a uniform powder.

[0125] S3: Under the protection of a high-purity argon atmosphere with a purity of 99.99%, the powdered supramolecular precursor was heated to 600°C at a heating rate of 5°C / min, kept at this temperature for 4 hours, and then cooled to room temperature to obtain boron-doped graphitic carbon nitride, denoted as BCN.

[0126] The structural schematic diagrams of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 are shown in FIG. Figure 1 As shown. Melamine and cyanuric acid are organized into rod-shaped supramolecular precursors through a supramolecular self-assembly process, and sulfuric acid, phosphoric acid or boric acid are added as S source, P source or B source, respectively. This process involves the decomposition and reorganization of the precursor components, and the resulting structure is uniform and stable, which helps to form a catalyst with good catalytic activity and stability. Finally, an iron single-atom catalyst with controllable doping of p-zone elements was successfully synthesized by a high-temperature pyrolysis process under an argon atmosphere, including a sulfur-doped iron single-atom catalyst (for example, 0.21-FeS / CN prepared in Example 4), a phosphorus-doped iron single-atom catalyst (for example, 0.23-FeP / CN prepared in Example 7) and a boron-doped iron single-atom catalyst (for example, 0.28-FeB / CN prepared in Example 11). Among them, the addition of an iron source and a doping element (S, P or B) to the melamine and melamine framework is the key to achieving the expected catalytic performance of the catalyst.

[0127] Figure 2This is a spherical aberration-corrected high-angle annular dark-field scanning transmission electron micrograph of the sulfur-doped iron single-atom catalyst (FeS / CN) prepared in Example 4 and a Fe and S element distribution spectrum. Figure 3 This is a spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy image of the phosphorus-doped iron single-atom catalyst (FeP / CN) prepared in Example 7 and a Fe and P element distribution spectrum. Figure 4 The spherical aberration corrected high-angle annular dark field scanning transmission electron micrograph and Fe and B element distribution spectrum of the boron-doped iron single atom catalyst (FeB / CN) prepared in Example 11. Figure 2 、 Figure 3 and Figure 4 The lamellar structures of FeS / CN, FeP / CN, and FeB / CN were observed. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images corrected for spherical aberration revealed the atomic dispersion of single iron atoms on the support. Energy-dispersive X-ray spectroscopy (EDX) enabled comprehensive visualization of the elemental composition and distribution of the samples. Mapping results showed uniform distribution of iron and doping elements, confirming successful doping with boron, phosphorus, or sulfur.

[0128] Figure 5 is the three-dimensional intensity distribution and line profile analysis diagram, where Figure 5 (a) is the three-dimensional intensity distribution and line profile analysis diagram of the sulfur-doped iron single-atom catalyst (FeS / CN) prepared in Example 4, Figure 5 (b) is the three-dimensional intensity distribution and line profile analysis diagram of the phosphorus-doped iron single-atom catalyst (FeP / CN) prepared in Example 7, Figure 5 (c) is the three-dimensional intensity distribution and line profile analysis diagram of the boron-doped iron single-atom catalyst (FeB / CN) prepared in Example 11. Figure 5 (a) Figure 5 (b) and Figure 5 (c) An in-depth analysis of the microstructure of the iron single-atom catalyst was performed. The 3D intensity distribution image intuitively shows the distribution of iron atoms in the sample. The line profile analysis is from a selected area of ​​the spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy image, highlighting the significant contrast between the iron atoms and the underlying support, confirming the dispersion of the iron atoms without any observable agglomeration. Figure 5 (a) Figure 5 (b) and Figure 5As shown in (c), the distance between iron atoms exceeds the Fe-Fe bond length (0.207nm), further confirming the single-atom nature of the catalyst. At the same time, the atomic distances are measured, where the average minimum distance between adjacent atoms of FeS / CN is 0.41nm, the average minimum distance between adjacent atoms of FeP / CN is 0.40nm, and the average minimum distance between adjacent atoms of FeB / CN is 0.37nm. It is proved that there is structural consistency between Fe SAC samples doped with different elements. The molar ratio of the doping element to iron of the sulfur-doped iron single atom catalyst prepared in Example 4, the phosphorus-doped iron single atom catalyst prepared in Example 7, and the boron-doped iron single atom catalyst prepared in Example 11 is shown in the figure. Figure 6 As shown, the inductively coupled plasma optical emission spectroscopy (ICP-OES) results quantified the mass fractions of iron and doping elements in the catalyst, where the Fe loading was approximately 10 wt%, and the molar ratio of the doping element to iron was calculated (e.g., B / Fe = 0.28, P / Fe = 0.23, S / Fe = 0.21), further indicating that these elements were controllably incorporated into the catalyst.

[0129] The crystal planes of the CN carriers in each catalyst were analyzed using X-ray diffractometer. Figure 7 The X-ray diffraction patterns of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 are shown in FIG. Figure 7 It can be seen that Fe / CN, FeS / CN, FeP / CN and FeB / CN not only maintain the same structure as CN, but also do not show the characteristic diffraction peaks of iron nanoparticles, indicating that the iron in each catalyst exists in the form of small-sized atoms, which is consistent with the test results of spherical aberration electron microscopy.

[0130] Based on the above images and elemental analysis, it is proved that the iron single atom catalyst with controllable doping element distribution is successfully synthesized. The successful doping of elements is important for the influence of the iron single atom microenvironment. In order to further explore the atomic chemical state and coordination structure in Fe SAC, the coordination configuration of the iron single atom catalyst (Fe / CN) prepared in Comparative Example 1, the sulfur-doped iron single atom catalyst (FeS / CN) prepared in Example 4, the phosphorus-doped iron single atom catalyst (FeP / CN) prepared in Example 7 and the boron-doped iron single atom catalyst (FeB / CN) prepared in Example 11 were studied by X-ray absorption fine structure (XAFS) spectrum including X-ray absorption near-edge structure (XANES) and extended edge X-ray absorption fine structure spectrum (EXAFS).

[0131] The Fourier transform Fe K-edge R-space X-ray extended edge absorption fine structure spectra of the catalysts, FePc and iron foil (Fefoil) prepared in Comparative Example 1, Example 4, Example 7 and Example 11 are as follows: Figure 8 As shown, Fe / CN The peaks of Fe-N coordination are shown, while the peak changes of FeS / CN, FeP / CN and FeB / CN may be attributed to the additional features of Fe-S, Fe-P and Fe-B bonds, respectively. There is no Fe-Fe scattering peak near the support, which indicates that the iron atoms are successfully dispersed in the support as single atoms without forming clusters. Figure 8 The R-space X-ray extended edge absorption fine structure spectrum curve of the Riebert transform Fe K-edge shown in the figure is fitted, and the fitting results are shown in Figure 9 It is shown that Fe / CN exhibits a symmetric Fe-N4 coordination environment with a coordination number of 4, while FeP / CN, FeS / CN, and FeB / CN exhibit asymmetric Fe-S1N3, Fe-P1N3, and Fe-B1N3 coordination environments, respectively. Due to the high resolution of wavelet transform (WT) in both K-space and R-space, the EXAFS oscillations of Fe K-edge are further discussed. Figure 10 is the wavelet variation EXAFS analysis diagram, where Figure 10 (a) is the wavelet variation EXAFS analysis diagram of the catalyst prepared in Comparative Example 1, Figure 10 (b) is the wavelet variation EXAFS analysis diagram of the catalyst prepared in Example 4. Figure 10 (c) is the wavelet variation EXAFS analysis diagram of the catalyst prepared in Example 7, Figure 10 (d) is the wavelet variation EXAFS analysis diagram of the catalyst prepared in Example 11; Figure 10 (a) Figure 10 (b) Figure 10 (c) and Figure 10 (d) shows the WT contour map of Fe / CN. There is only one maximum intensity at the Fe-N bond. For FeS / CN and FeP / CN, due to the existence of Fe-S coordination, this will shift to Chuhe Similarly, FeB / CN also has a significant shift. Fe k-edge X-ray absorption near-edge structure (XANES) is shown in Figure 2. Figure 11As shown, the edge positions of Fe / CN, FeS / CN, FeP / CN, and FeB / CN were compared with the oxidation states of iron in standard samples such as Fe foil, Fe2O3, and Fe3O4. The absorption edges and transition energies of Fe in all four materials were between those of ferrous oxide and ferric oxide, indicating that the average valence state of the catalysts was between +2 and +3. It is worth noting that FeP / CN and FeB / CN have lower oxidation states, which may be related to the higher contribution of high-valent iron active species shown in subsequent experimental results.

[0132] Application Example 1

[0133] The effects of four different catalysts (Fe / CN, FeS / CN, FeP / CN and FeB / CN) on the degradation efficiency of parachlorophenol (4-CP) were investigated. A saturated aqueous solution of 4-CP was added to 50 ml of deionized water, and the initial concentration of the 4-CP solution was accurately adjusted to 0.1 mmol / L. 25 mg of four different catalysts were weighed separately: the catalysts prepared by Comparative Example 1, Example 4, Example 7 and Example 11. The above catalysts were added to containers containing 0.1 mmol / L 4-CP solution. Ultrasonic dispersion was used to ensure that the catalyst was uniformly dispersed in the solution, and the containers were then placed on a magnetic stirrer to maintain a continuous stirring state until the equilibrium of the adsorption reaction was reached between the solid and the liquid. A saturated solution of PMS was added, and the initial concentration of PMS was controlled to be 0.5 mmol / L. From the moment the saturated PMS solution was added, the timing was started, and samples were taken at specific time points (0, 0.3, 0.6, 1, 2, 3, 5 and 10 min) using a clean syringe. The sample was filtered through a 0.22-micron filter for solid-liquid separation. The separated solution was then transferred to an ampoule containing 10% methanol by volume to stabilize the sample. Finally, the concentrations of 4-CP and PMS in the solution were accurately measured using high-performance liquid chromatography (HPLC) and ultraviolet spectrophotometry.

[0134] Figure 12 The curves showing the change of 4-CP concentration in the process of activating PMS and degrading 4-CP by the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 are shown. The degradation curves all show the characteristics of first-order kinetics, such as Figure 13 As shown in Figure 2, it can be calculated that the degradation rate of Fe / CN is 0.417 min -1 The degradation rate of FeS / CN catalyst is 0.423min -1 The degradation rate of FeP / CN catalyst is 0.915min -1 The degradation rate of FeB / CN catalyst is 1.871min -1 .from Figure 13It can be seen that Fe / CN, as the control group, has the lowest degradation efficiency, which confirms the importance of doping elements in improving the degradation performance of materials. It shows that the doping of p-block elements can increase the degradation rate of 4-CP in solution by the catalyst to varying degrees, among which B doping has the most significant improvement on the degradation effect. This may be attributed to the unique structure of FeB / CN material. These characteristics may enhance its adsorption capacity and catalytic activity.

[0135] Application Example 2

[0136] A saturated aqueous solution of 4-CP was added to an 80ml beaker containing 50ml of deionized water to ensure that the initial concentration of 4-CP was 0.1mmol / L. Various quenching experiments were added, wherein the concentrations of methanol and tert-butanol were 500mmol / L, the concentration of nitroblue tetrazolium was 5mmol / L, the concentration of methylphenyl sulfoxide was 5mmol / L, and the concentration of sodium azide was 5mmol / L. Subsequently, 25mg of the catalysts prepared in Comparative Example 1, Example 4, Example 7, and Example 11 were weighed and added to a 0.1mmol / L 4-CP solution containing a corresponding concentration of quencher. Ultrasonic dispersion and magnetic stirring were used to ensure that the adsorption reaction equilibrium was reached between the solid and liquid. After adding a saturated PMS solution and starting the timing, samples were taken at different time points (0, 0.3, 0.6, 1, 2, 3, 5, and 10min) using a syringe, and after solid-liquid separation with a 0.22 micron filter membrane, placed in an ampoule containing a 10% methanol solution by volume. The concentration of 4-CP in the solution was determined by high performance liquid chromatography.

[0137] The comparison of the quenching experiments of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 for degradation of 4-CP is shown in the figure below. Figure 14 As shown, it was observed that when methanol (MeOH), tert-butanol (TBA), nitro blue tetrazolium (NBT), sodium azide (NaN3) and methyl phenyl sulfoxide (DMSO) were added to the Fe / CN / PMS / 4-CP system, the degradation of 4-CP was basically uninhibited. However, when sodium azide (NaN3) was added, the degradation of 4-CP was significantly inhibited. Under the same experimental conditions, sodium azide and methyl phenyl sulfoxide significantly inhibited the degradation of 4-CP in both FeS / CN / PMS / 4-CP and FeP / CN / PMS / 4-CP systems. In contrast, methanol, tert-butanol and nitro blue tetrazolium had no effect on the degradation of 4-CP in the FeB / CN / PMS / 4-CP system, while sodium azide and methyl phenyl sulfoxide partially inhibited the degradation of 4-CP in the system, but not completely. Combined with further experiments, the electron transfer pathway will also have an impact on the degradation. Further analysis showed that Fe / CN activated PMS mainly produced 1 O2. In contrast, FeS / CN activated PMS mainly produced FeIV =O and 1 O2, the contribution rate was 41% and 59% respectively; FeP / CN activated PMS was also the main source of Fe IV =O and 1 O2, the contribution rates were 76% and 24% respectively; while FeB / CN activated PMS in addition to producing Fe IV =O and 1 O2, the contribution of the electron transfer pathway is 35%.

[0138] In order to further explore the reasons for the differences in the degradation effects of different catalysts on organic pollutants under the reaction conditions, the main active substances produced during the activation of persulfate (PMS) were analyzed by electron paramagnetic resonance (EPR) test. The EPR spectra of the iron single atom catalyst prepared in Comparative Example 1, the sulfur-doped iron single atom catalyst prepared in Example 4, the phosphorus-doped iron single atom catalyst prepared in Example 7, and the boron-doped iron single atom catalyst prepared in Example 11 during the activation of PMS are shown in FIG. Figure 15 As shown (TEMP and DMPO were present as capture agents, respectively). Figure 15 is the EPR spectrum, where Figure 15 (a) is the EPR spectrum of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 using TEMP, Figure 15 (b) is the EPR spectra of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 using DMPO; Figure 15 (a) shows EPR analysis using 2,2,6,6-tetramethylpiperidine (TEMP) as a spin trapping agent, revealing that the TEMP- 1 The triple O2-related signal indicates the generation of singlet oxygen in this system. In particular, the combinations of TEMP+PMS+FeS / CN and TEMP+PMS+Fe / CN show strong signals, indicating that the FeS / CN and Fe / CN catalysts are very effective in generating singlet oxygen. Figure 15 The electron paramagnetic resonance (EPR) spectrum shown in (b) shows that when 5,5-dimethyl-1-pyrrolidine N-oxide (DMPO) is used as a capture agent, the electron paramagnetic resonance spectrum (EPR) detects a DMPOX signal. This peak is produced by the oxidation of DMPO by a strong oxidizing substance. According to literature reports and the analysis of the quenching experiment results in the previous article, this substance is very likely a high-valent iron species. The peak intensity comparison shows that the P-doped catalyst (FeP / CN) may be more inclined to generate high-valent iron, which is consistent with the results of the quenching experiment in the previous article.

[0139] In addition, the change of PMS concentration in each reaction system over time was further monitored. The comparison of PMS consumption during the degradation of 4-CP by PMS activation of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 is shown in FIG. Figure 16 As shown in the figure, the consumption of FeB / CN is greatly affected by the pollutants. After adding pollutants, the consumption of PMS can be increased by 40%. At the same time, it shows the best performance. This result suggests that there may be an electron transfer pathway in the system. In the process of activating persulfate (PMS), 1 O2 and Fe IV =O are two important active substances. Using DPBF as a probe in the quantitative reaction system 1 The content of O2 can be measured in Fe / CN / PMS, FeS / CN / PMS, FeP / CN / PMS and FeB / CN / PMS systems. 1 The contents of O2 were 0.13mmol, 0.11mmol, 0.083mmol and 0.060mmol respectively. Using PMSO conversion rate as an indicator of high-valent iron, the quantitative results are as follows Figure 17 shown. Figure 17 The catalyst activation PMS process produced by Comparative Example 1, Example 4, Example 7 and Example 11 1 The quantitative results of O2 and Fe(IV)=O content and PMS utilization rate show that Fe in Fe / CN / PMS, FeS / CN / PMS, FeP / CN / PMS and FeB / CN / PMS systems IV =O content is 0.004mmol, 0.036mmol, 0.10mmol and 0.015mmol respectively. 1 O2 and Fe IV =O yield was the lowest, contradicting its optimal performance. However, the quenching results previously reported further suggest that other pathways for pollutant degradation, such as electron transfer, are likely to exist within this system. Compositional analysis, combined with the content of the various active species generated, revealed that, without the addition of a catalyst, the PMS utilization rates for the Fe / CN / PMS, FeS / CN / PMS, FeP / CN / PMS, and FeB / CN / PMS systems were 43.9%, 46.8%, 45.5%, and 31.3%, respectively.

[0140] The electrochemical test results provide strong evidence for the existence of electron transfer pathways during FeB / CN activation of PMS. Figure 18 : is the EIS curve diagram of the catalyst prepared in Comparative Example 1, Example 4, Example 7 and Example 11, Figure 19It curve diagram of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11, Figure 20 : is the LSV curve of the catalyst prepared in Comparative Example 1, Example 4, Example 7 and Example 11; Figure 18 、 Figure 19 and Figure 20 As shown, the potential versus time plot shows that FeB / CN has a significant current response after the introduction of PMS and pollutants. This change in current density is attributed to the formation of reactive surface complexes that promote the transfer of electrons from adsorbed organic pollutants to activated PMS. The negative current signal in the presence of PMS and organic substrates indicates that electrons are transferred from the organic substrate (as an electron donor) to the activated PMS (as an electron acceptor). As observed in the LSV and EIS curves, FeB / CN has the best conductivity and the lowest resistance, indicating that the catalyst has the potential to promote the transfer of electrons from the solution to PMS. This observation is consistent with the electron transfer mechanism, where the catalyst acts as a conductive bridge to mediate electron transfer between organic pollutants and persulfate ions.

[0141] The effects of different dopant concentrations on the non-radical pathway of persulfate activation were further investigated. The degradation rates of 4-CP, Fe IV =O / 1 The correlation diagram between O2 / electron transfer contribution rate and doping element (S, P, B) / iron molar ratio, such as Figure 21 Initially, in the absence of dopants, the system relies entirely on the intrinsic properties of the iron catalyst for persulfate activation. However, the introduction of dopants triggers a shift to a non-radical mechanism, and this shift becomes increasingly prominent with increasing molar ratios of S / Fe, P / Fe, and B / Fe. Specifically, with increasing S doping levels, 1 The contribution rate of O2 increases, the increase of P doping leads to an increase in the contribution rate of high-valent iron, and B doping increases the contribution of the electron transfer pathway. This series of quenching experimental results show that the doping of different elements (S, P, B) is indeed an important reason for the transformation of the non-radical pathway during the peroxymonosulfate activation process.

[0142] Application Example 3

[0143] A saturated aqueous solution of 4-CP was added to several 80 mL beakers containing 50 mL of deionized water (DI water), tap water, groundwater, and wastewater, respectively, to achieve an initial 4-CP concentration of 0.1 mmol / L. 25 mg of the catalysts prepared in Comparative Example 1, Example 4, Example 7, and Example 11 were weighed and added to the 0.1 mmol / L 4-CP solution. After ultrasonic dispersion, the mixture was placed on a magnetic stirrer and stirred continuously. After the adsorption reaction reached equilibrium between the solid and liquid, a saturated solution of PMS was added to achieve an initial PMS concentration of 0.5 mmol / L. Furthermore, when the saturated PMS solution was added, a timer was started, and samples were taken at 0, 0.3, 0.6, 1, 2, 3, 5, and 10 minutes using a clean syringe. After solid-liquid separation using a 0.22 μm filter, the samples were placed in an ampoule containing a 10% (v / v) methanol solution. Figure 22 The degradation rate of 4-CP by PMS activated by the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 under different water quality conditions is shown in FIG. Figure 22 It can be clearly seen that the FeB / CN catalyst showed high removal efficiency in all tested water bodies. Figure 23 The degradation rate of 4-CP by PMS activated by the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 under different pH conditions is shown in FIG. Figure 23 It can be seen that the removal efficiency remains relatively stable in the pH range of 4.95 to 10.98. This shows that the FeB / CN catalyst has good pH adaptability and stability, and can maintain high efficiency in removing chlorophenols under different water quality conditions, showing its application potential in the field of water treatment, especially in situations where it is necessary to adapt to variable water quality conditions. In the water treatment process, various ions (such as Cl - ,HCO3 - , SO4 2- , NO3 - , H2PO4 2- The ions may be present in the solution and may interact with the catalyst surface, thereby affecting the activity and selectivity of the catalyst. The degradation rate of 4-CP by activated PMS under different anion and cation conditions for the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 is shown in the figure. Figure 24 As shown, even in the presence of various inorganic anions or cations, the degradation efficiency of the catalyst for 4-chlorophenol was not significantly affected. This indicates that the four catalysts have good selectivity and stability and can effectively catalyze the degradation of pollutants in complex water environments.

[0144] In order to verify the stability of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11, a continuous flow membrane device experiment was carried out. The experimental results of the continuous flow membrane device of the catalysts prepared in Comparative Example 1, Example 4, Example 7 and Example 11 in the process of activating PMS and degrading 4-CP under deionized water (DI water) are shown in the figure. Figure 25 Comparative Example 1, Example 4, Example 7 and Example 11 prepared catalysts activated under the first wastewater (Wastewater 1) conditions PMS degradation 4-CP process of continuous flow membrane device experimental results shown as follows Figure 26 As shown; Comparative Example 1, Example 4, Example 7 and Example 11 prepared by the catalyst activation PMS degradation 4-CP process under the second wastewater (Wastewater 2) conditions of the continuous flow membrane device experimental results and iron ion dissolution rate diagram as shown Figure 27 As shown. Figure 25 、 Figure 26 and Figure 27 As shown, the device experiments achieved highly efficient para-chlorophenol removal, demonstrating successful scalability from small to large-scale. In the FeB / CN system, the chlorophenol concentration decreased rapidly, demonstrating the effectiveness of the FeB / CN catalyst in the degradation process. The iron ion dissolution rate was less than 5% of the iron loading on the catalyst. Therefore, this catalyst exhibits excellent reusability in chlorophenol wastewater treatment, effectively reducing operating costs.

[0145] Application Example 4

[0146] Degradation experiments were carried out on a series of different pollutants, including CP (chlorophenol), AN (aniline), PNP (p-nitrophenol), HBA (p-hydroxybenzoic acid), PhOH (phenol), 2,4-DCP (2,4-di-4-CP), NB (nitrobenzene), BA (benzoic acid), LEV (levofloxacin), CIP (ciprofloxacin) and NOX (norfloxacin). These pollutants represent different chemical properties, such as phenols, amines, nitro compounds, antibiotics and halogenated aromatic compounds. First, saturated aqueous solutions of these phenolic compounds were added to 80 ml beakers containing 50 ml of deionized water to ensure that the initial concentration was uniformly 0.1 mmol / L. 25 mg of catalyst was weighed, respectively from the preparation processes of Comparative Example 1, Example 4, Example 7 and Example 11. After the catalyst was added to the solution containing the corresponding pollutants, ultrasonic dispersion was used to ensure that the catalyst was fully mixed with the solution, and it was placed on a magnetic stirrer and kept stirring to promote the adsorption reaction between the solid and liquid to reach equilibrium. A saturated solution of PMS was added, and the initial concentration of PMS was 0.5 mmol / L. The timer started from the moment PMS was added, and samples were taken at specific time points of 0, 0.3, 0.6, 1, 2, 3, 5, and 10 min using a clean syringe. Each sample was separated by solid-liquid separation using a 0.22 μm filter membrane and then transferred to an ampoule containing 10% methanol solution to prevent the degradation of phenolic substances during the analysis. Finally, a high performance liquid chromatography (HPLC) was used to accurately determine the concentration of pollutants. Figure 28 It can be seen that FeB / CN maintains the best degradation effect on different pollutants. In addition, the PMS utilization rate is significantly affected by the pollutant and is consistent with the degradation effect of the pollutant, further demonstrating that the electron transfer pathway is a key factor in pollutant degradation.

[0147] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An iron single-atom catalyst with controllable doping of p-block elements, characterized in that: The iron single-atom catalyst with controllable doping of p-zone elements is prepared by the following method: S1: dissolving melamine in deionized water at 70-90° C. to obtain a melamine solution; dissolving cyanuric acid in deionized water at 70-90° C. to obtain a cyanuric acid solution; dissolving ferrous sulfate heptahydrate in deionized water at 20-30° C. to obtain a ferrous sulfate solution; the molar ratio of melamine, cyanuric acid, and ferrous sulfate being 1:0.5-0.9:0.1-0.5; S2: adding sulfuric acid and oxalic acid to the ferrous sulfate solution and stirring at 20-30° C. for 5-10 minutes to form solution A; the molar ratio of sulfuric acid, oxalic acid and ferrous sulfate is 1:0.8-1:0.2-0.8; S3: adding the solution A to the cyanuric acid solution, stirring at 70-90° C. for 5-10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 2-4 hours; After the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is washed; Then, the product is dried under forced air at 55-60°C for 6-8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder. S4: Under the protection of an argon atmosphere, the powdered supramolecular precursor is heated to 550-600°C, kept at this temperature for 3-5 hours, and then cooled to room temperature to obtain an iron single-atom catalyst with controllable doping of p-block elements, denoted as FeS / CN.

2. An iron single-atom catalyst with controllable doping of p-block elements, characterized in that: The iron single-atom catalyst with controllable doping of p-zone elements is prepared by the following method: S1: dissolving melamine in deionized water at 70-90° C. to obtain a melamine solution; dissolving cyanuric acid in deionized water at 70-90° C. to obtain a cyanuric acid solution; dissolving ferrous sulfate heptahydrate in deionized water at 20-30° C. to obtain a ferrous sulfate solution; the molar ratio of melamine, cyanuric acid, and ferrous sulfate being 1:0.5-0.9:0.1-0.5; S2: adding oxalic acid and phosphoric acid to the ferrous sulfate solution and stirring at 20-30° C. for 5-10 minutes to form solution A; the molar ratio of the phosphoric acid, oxalic acid, and ferrous sulfate is 1:0.8-1:0.2-0.8; S3: adding the solution A to the cyanuric acid solution, stirring at 70-90° C. for 5-10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 2-4 hours; After the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is washed; Then, the product is dried under forced air at 55-60°C for 6-8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder. S4: Under the protection of an argon atmosphere, the powdered supramolecular precursor is heated to 550-600°C, kept at this temperature for 3-5 hours, and then cooled to room temperature to obtain an iron single-atom catalyst with controllable doping of p-block elements, denoted as FeP / CN.

3. An iron single-atom catalyst with controllable doping of p-block elements, characterized in that: The iron single-atom catalyst with controllable doping of p-zone elements is prepared by the following method: S1: dissolving melamine in deionized water at 70-90° C. to obtain a melamine solution; dissolving cyanuric acid in deionized water at 70-90° C. to obtain a cyanuric acid solution; dissolving ferrous sulfate heptahydrate in deionized water at 20-30° C. to obtain a ferrous sulfate solution; the molar ratio of melamine, cyanuric acid, and ferrous sulfate being 1:0.5-0.9:0.1-0.5; S2: adding boric acid and oxalic acid to the ferrous sulfate solution and stirring at 20-30° C. for 5-10 minutes to form solution A; the molar ratio of the boric acid, oxalic acid, and ferrous sulfate is 1:0.8-1:0.2-0.8; S3: adding the solution A to the cyanuric acid solution, stirring at 70-90° C. for 5-10 minutes to obtain a mixed solution B; then adding the mixed solution B to the melamine solution to carry out a coprecipitation reaction for 2-4 hours; After the reaction is completed, solid-liquid separation is achieved by suction filtration, and the precipitate is washed; Then, the product is dried under forced air at 55-60°C for 6-8 hours to obtain a supramolecular precursor, which is then ground into a uniform powder. S4: Under the protection of an argon atmosphere, the powdered supramolecular precursor is heated to 550-600°C, kept at this temperature for 3-5 hours, and then cooled to room temperature to obtain an iron single-atom catalyst with controllable doping of p-block elements, denoted as FeB / CN.

4. Use of a p-block element controllably doped iron single atom catalyst according to claim 1, 2 or 3 for removing phenolic benzene series in surface water, characterized in that: Specifically, the iron single-atom catalyst with controllable doping of p-block elements and peroxymonosulfate are poured into surface water containing phenolic benzene series, the water temperature is 20-30°C, and the reaction is stirred for 10-15 minutes to complete the removal of phenolic benzene series in the surface water; the addition amount of the iron single-atom catalyst with controllable doping of p-block elements is 0.2-0.6 g / L; the addition amount of the peroxymonosulfate is 100-600 μmol / L; and the concentration of the phenolic benzene series in the surface water is 0-200 μmol / L.

5. The use according to claim 4, characterized in that The phenolic benzene series compound is phenol, p-chlorophenol or p-nitrophenol.

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