A charge confinement monatomic catalyst, a preparation method thereof and application of the catalyst in synchronous activation of periodate and electron transfer

Abstract

The application discloses a charge-limited single-atom catalyst, a preparation method thereof and application of the catalyst in synchronous activation of periodate and electron transfer, and the catalyst comprises a carrier and iron single-atom active sites supported on the carrier; the carrier is sulfur-doped graphite phase carbon nitride; the iron single-atom active sites are combined on the carrier in N and S co-coordination, and the active sites exhibit the characteristics of charge limitation; the sulfur doping in the carrier not only reduces the local electron density of the iron single atom, but also exhibits characteristic adsorption of the periodate, so that the iron single-atom catalyst of the application realizes the "sub-site, same adsorption" of the pollutant and the periodate when degrading the electron-rich type of refractory organic pollutants, and induces the degradation of the organic pollutants in the electron transfer pathway; meanwhile, the special heptazine ring structure in the carrier has a local limiting effect on the transferred charge in the reaction process, so that the single electron received by the periodate is activated and further generates active oxygen species for degrading the pollutants.

Description

Technical Field

[0001] This invention relates to the field of single-atom catalytic degradation of recalcitrant organic pollutants, and particularly to the application of a charge-confined single-atom catalyst, its preparation method, and simultaneous activation of periodate via electron transfer. Background Technology

[0002] In recent years, due to the continuous advancement of industrialization, a large amount of persistent organic pollutants (POPs) have been discharged into environmental water bodies, posing a threat to human health. Among the various treatment methods for POPs, advanced oxidation technologies (AOs) have received widespread attention due to their advantages of high efficiency and ease of operation. However, the free radical reactive species commonly used in AOs, due to their strong oxidizing power, are easily consumed by anions, cations, and natural organic matter in natural water bodies, leading to a decrease in the degradation efficiency of target organic pollutants. Non-radical AO processes (such as singlet oxygen, electron transfer, and high-valence metal species) have gained widespread attention due to their mild oxidizing power and strong resistance to interference. Among these, the electron transfer pathway has advantages such as high selectivity for target pollutants and high oxidant utilization. However, in the electron transfer pathway, pollutants that lose electrons and become positively charged easily combine to form oligomers, hindering the deep treatment of POPs. Furthermore, when using catalyst materials with excellent conductivity as "electron bridges," the oxidant easily accepts two electrons and is directly converted into inorganic anions (OH-). - SO4 2- In some cases, electrons transferred from pollutants are not further utilized, resulting in low oxidation efficiency. Therefore, by designing a suitable catalyst material, the number of electrons gained by the oxidant in the electron transfer pathway can be limited, allowing the oxidant to receive single electrons and be reduced to reactive oxygen species, thereby achieving further in-depth treatment of organic pollutants. Summary of the Invention

[0003] The purpose of this invention is to provide a charge-confined single-atom catalyst and its preparation method, along with its application in the simultaneous activation of periodate via electron transfer. The single-atom catalyst of this invention, through the charge confinement of its active sites, allows periodate (PI) to receive only a single electron conducted from pollutants and be further activated into superoxide radicals and singlet oxygen, thereby achieving deeper treatment and mineralization of organic pollutants.

[0004] To achieve the above objectives, the present invention provides a charge-confined single-atom catalyst, comprising a support and iron single-atom active sites supported on the support. The support is sulfur-doped graphitic carbon nitride. The support has a special heptaazine ring structure, which has a local confinement effect on the charge transferred during the reaction. In the iron single-atom active sites, iron atoms are bound to the support in an N / S co-coordinated manner, and the active sites exhibit charge-confined characteristics. The mass content of iron single atoms in the iron single-atom catalyst is 5-15%.

[0005] A method for preparing the charge-confined single-atom catalyst described above, the method comprising the following steps:

[0006] S1: Melamine and cyanuric acid are dissolved separately under water bath stirring to obtain melamine solution and cyanuric acid solution;

[0007] S2: Dissolve soluble iron salt and organic ligand together in water to fully complex iron ions and organic ligands to obtain an iron-organic complex solution;

[0008] S3: Mix the iron-organic complex solution, melamine solution and cyanuric acid solution to fully carry out the hydrogen bond self-assembly reaction. After solid-liquid separation by suction filtration, dry and grind to obtain precursor powder.

[0009] S4: The precursor powder is uniformly mixed with the sulfur source and then pyrolyzed to obtain an iron single-atom catalyst.

[0010] Preferably, in step S2, the soluble iron salt includes one or more of ferrous chloride, ferric nitrate, and ferric sulfate; the organic ligand includes anhydrous oxalic acid and / or o-phenanthroline.

[0011] Preferably, in steps S2 and S3, the molar ratio of the organic ligand, soluble iron salt, cyanuric acid and melamine is (0.1-0.4):(0.05-0.2):(0.6-0.9):1.

[0012] Preferably, in step S4, the sulfur source includes one or more of thiourea, elemental sulfur, and trithiocyanate, and the mass ratio of the precursor to the sulfur source is (1-5):(0.5-2).

[0013] Preferably, in step S4, the pyrolysis temperature is 500–800°C and the time is 2–6 hours.

[0014] Preferably, the pyrolysis is carried out under a protective atmosphere, which is nitrogen and / or argon.

[0015] The charge-confined single-atom catalyst prepared according to the above-described charge-confined single-atom catalyst or the above-described charge-confined single-atom catalyst preparation method achieves simultaneous activation of periodate degradation of organic pollutants through electron transfer via charge confinement of active sites.

[0016] Preferably, according to the above-described application, the iron single-atom catalyst achieves "fractional site co-adsorption" of organic pollutants and periodate, inducing the degradation of organic pollutants via an electron transfer pathway.

[0017] Preferably, according to the above-described application, the iron single-atom catalyst uses the special heptaazine ring structure in the support to confine and transfer charges during the reaction process, so that periodate accepts single electrons and is further activated into reactive oxygen species; the reactive oxygen species can deeply degrade organic pollutants and avoid the generation of oligomers in the traditional electron transfer pathway.

[0018] Beneficial effects of this invention:

[0019] This invention provides an iron single-atom catalyst that enables simultaneous electron activation of periodate to generate reactive oxygen species during electron transfer through charge confinement, along with its preparation method and application. This invention belongs to the field of single-atom catalytic advanced oxidation degradation of persistent organic pollutants.

[0020] The single-atom catalyst of the present invention includes a support and iron single-atom active sites supported on the support; the support is sulfur-doped graphitic carbon nitride; the iron single-atom active sites are N and S co-coordinated on the support, and the active sites exhibit charge confinement characteristics.

[0021] In the carrier described in this invention, sulfur doping not only reduces the local electron density of iron single atoms but also exhibits characteristic adsorption of periodate. This further enables the iron single-atom catalyst of this invention to achieve "fractional site co-adsorption" of pollutants and periodate when degrading electron-rich recalcitrant organic pollutants, inducing the degradation of organic pollutants via an electron transfer pathway. Simultaneously, the special heptaazine ring structure in the carrier has a localized confinement effect on the transferred charge during the reaction, allowing periodate to receive single electrons, become activated, and further generate reactive oxygen species for pollutant degradation. This avoids the pollutant dimerization phenomenon in traditional electron transfer pathways, achieving deep treatment of persistent organic pollutants.

[0022] In summary, the preparation method provided by this invention can successfully prepare iron single-atom catalysts with charge confinement characteristics. Moreover, the preparation method is simple to operate, has a wide range of raw material sources, low production cost, and controllable iron single-atom loading. Attached Figure Description

[0023] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0024] Figure 1 The images show the XRD patterns of Fe / SCN obtained in Example 1, Fe / CN obtained in Comparative Example 1, CN obtained in Comparative Example 2, and SCN obtained in Comparative Example 3.

[0025] Figure 2The FT-IR plots are of Fe / SCN obtained in Example 1, Fe / CN obtained in Comparative Example 1, CN obtained in Comparative Example 2, and SCN obtained in Comparative Example 3.

[0026] Figure 3 The image shows a TEM image of Fe / SCN obtained in Example 1.

[0027] Figure 4 The elemental distribution diagram of Fe / SCN obtained in Example 1 is shown below.

[0028] Figure 5 The image shows the AC-HAADF-STEM image of Fe / SCN obtained in Example 1.

[0029] Figure 6 The graph shows the degradation efficiency of 4-CP by PI activated by Fe / SCN obtained in Example 1, Fe / CN obtained in Comparative Example 1, CN obtained in Comparative Example 2, and SCN obtained in Comparative Example 3.

[0030] Figure 7 The figure shows the experimental results of Fe / SCN activated PI degradation and quenching of 4-CP free radicals obtained in Example 1;

[0031] Figure 8 The graph shows the test results of Fe / SCN obtained in Example 1, Fe / CN obtained in Comparative Example 1, CN obtained in Comparative Example 2, and SCN obtained in Comparative Example 3.

[0032] Figure 9 The graph shows the test results of PI consumption during the degradation of 4-CP by Fe / SCN activated PI obtained in Example 1.

[0033] Figure 10 The figure shows the TOC test results of Fe / SCN activated PI after 4-CP degradation, obtained in Example 1.

[0034] Figure 11 The graph shows the effect of different pH values ​​on the degradation of 4-CP by Fe / SCN activated PI obtained in Example 1.

[0035] Figure 12 This is a periodic experimental diagram of the degradation of 4-CP by Fe / SCN activated PI obtained in Example 1. Detailed Implementation

[0036] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0037] This invention provides a charge-confined single-atom catalyst, comprising a support and iron single-atom active sites supported on the support; the support is sulfur-doped graphitic carbon nitride; the iron single-atom active sites are bound to the support in an N, S co-coordinated manner, and the active sites exhibit charge-confined characteristics; the mass content of iron single atoms in the iron single-atom catalyst is 5-15%.

[0038] This invention does not have specific requirements regarding the amount of sulfur doping in sulfur-doped graphitic carbon nitride. In this invention, sulfur doping is introduced to enhance the adsorption of periodate by the catalyst material.

[0039] In this invention, the iron single-atom catalyst contains 5-15% iron single atoms by mass, more preferably 6-12%. In an embodiment of this invention, it is specifically 6.20%. In this invention, the iron single atoms are distributed inside and on the surface of the support.

[0040] This invention provides a method for preparing the iron single-atom catalyst described above, comprising the following steps:

[0041] S1: Melamine and cyanuric acid are dissolved separately under water bath stirring to obtain melamine solution and cyanuric acid solution;

[0042] S2: Dissolve soluble iron salt and organic ligand together in water to fully complex iron ions and organic ligands to obtain an iron-organic complex solution;

[0043] S3: The iron-organic complex solution, melamine solution and cyanuric acid solution are mixed to carry out hydrogen bond self-assembly reaction. After solid-liquid separation by suction filtration, the mixture is dried and ground to obtain precursor powder.

[0044] S4: The precursor powder is uniformly mixed with a sulfur source and then pyrolyzed to obtain the iron single-atom catalyst.

[0045] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0046] This invention involves dissolving an organic ligand and a soluble iron salt in water, allowing the iron ions and the organic ligand to fully complex, resulting in an iron-organic complex solution. In this invention, the organic ligand includes anhydrous oxalic acid and / or o-phenanthroline, more preferably anhydrous oxalic acid.

[0047] In this invention, the soluble iron salt preferably includes one or more of ferrous chloride, ferric nitrate and ferric sulfate; when the iron salt includes multiple of the above substances, this invention does not have special requirements on the ratio of each iron salt.

[0048] This invention does not have special requirements on the amount of water used, as long as it is sufficient to dissolve the organic ligands and soluble iron salts.

[0049] In this invention, the water is preferably deionized water. In this invention, the sulfur source preferably includes one or more of thiourea, elemental sulfur, and trithiocyanate.

[0050] After obtaining the iron-organic complex solution, the present invention mixes the iron-organic complex solution, cyanuric acid solution and melamine solution to fully carry out hydrogen bond self-assembly reaction, and after solid-liquid separation by suction filtration, the precursor powder is dried and ground.

[0051] In this invention, the amounts of the iron-organic complex solution, cyanuric acid solution, and melamine solution are preferably such that the molar ratio of the organic ligand, soluble iron salt, cyanuric acid, and melamine is (0.1-0.4):(0.05-0.2):(0.6-0.9):1, and more preferably (0.2-0.3):(0.1-0.15):(0.7-0.8):1.

[0052] This invention controls the loading of iron single atoms in the final material by controlling the amount of soluble iron salt used.

[0053] In the hydrogen-bonded self-assembly reaction process of this invention, iron-organic complexes and cyanuric acid self-assemble with melamine through hydrogen bonds to form supramolecular structures, thereby fixing iron ions and allowing for more uniform loading of iron atoms onto the support during subsequent pyrolysis. After the hydrogen-bonded self-assembly reaction is completed, the present invention performs solid-liquid separation by suction filtration, washes the obtained solid with water, and then dries and grinds it to obtain precursor powder. This invention does not have special requirements for drying conditions; drying conditions well-known in the art can be used. In the embodiments of this invention, drying is preferably carried out overnight at 60°C.

[0054] After obtaining the precursor powder, the present invention mixes the precursor powder with a sulfur source uniformly and then pyrolyzes it to obtain an iron single-atom catalyst.

[0055] In this invention, the mass ratio of the precursor to the sulfur source is (1-5):(0.5-2), more preferably (2-2.5):(0.4-0.5).

[0056] In this invention, the pyrolysis temperature is preferably 500-800℃, more preferably 550-600℃; the pyrolysis time is preferably 2-6h, more preferably 3-4h.

[0057] In this invention, the pyrolysis is preferably carried out under a protective atmosphere, which preferably includes argon and / or nitrogen. In this invention, the heating rate to the pyrolysis temperature is preferably 4–5 °C / min.

[0058] In the pyrolysis process of this invention, iron ions are converted into single-atom states and loaded onto sulfur-doped graphitic carbon nitride formed by the precursor and sulfur source.

[0059] This invention provides the application of the iron single-atom catalyst described in the above scheme or the iron single-atom catalyst prepared by the preparation method described in the above scheme to achieve electron transfer through charge confinement of active sites and simultaneously activate periodate to degrade organic pollutants.

[0060] In this invention, the application preferably includes the following steps:

[0061] The iron single-atom catalyst can achieve "fractional site co-adsorption" of organic pollutants and periodate, inducing the degradation of organic pollutants through an electron transfer pathway. The special heptaazine ring structure in the support performs confined charge transfer during the reaction process, allowing periodate to receive single electrons and be further activated into reactive oxygen species. The reactive oxygen species generated during the reaction can deeply degrade organic pollutants, avoiding the formation of oligomers in traditional electron transfer pathways.

[0062] In this invention, the persistent organic pollutant to be treated is preferably one or more of p-chlorophenol, phenol, 2,4,6-trichlorophenol and p-aminophenol.

[0063] In this invention, the preferred mass ratio of the iron single-atom catalyst to periodate is (3-10):(2-10), more preferably (4-6):(5-6). In this invention, the preferred mass ratio of the iron single-atom catalyst to the organic pollutant to be treated is (40-60):(1-3).

[0064] In this invention, the degradation temperature is preferably room temperature, and the degradation time is preferably 20 to 40 minutes.

[0065] The preparation method provided by this invention can successfully prepare iron single-atom catalysts. The preparation method is simple to operate, has a wide range of raw material sources, low production cost, and controllable iron single-atom loading.

[0066] The following detailed description of the iron single-atom catalyst, its preparation method, and its application provided by the present invention, with reference to specific examples, should not be construed as limiting the scope of protection of the present invention.

[0067] Example 1

[0068] (1) Weigh 0.65g of anhydrous oxalic acid and add it to 150mL of deionized water to dissolve it and obtain anhydrous oxalic acid solution;

[0069] (2) Weigh 1.45g of ferric nitrate and add it to anhydrous oxalic acid solution. Stir for 5 minutes to obtain an iron-oxalic acid complex solution.

[0070] (3) Weigh 2.17g of cyanuric acid and 3.03g of melamine respectively, add 300mL of deionized water, stir in a water bath at 80℃ for 15min to obtain cyanuric acid solution and melamine solution.

[0071] (4) Mix the iron-oxalic acid complex solution and the cyanuric acid solution, then add the melamine solution and mix. After stirring for 4 hours, filter the mixture, wash the precipitate with water, and dry it overnight at 60°C to obtain the precursor.

[0072] (5) After grinding the precursor into powder, weigh 2.50g of the precursor powder, mix and grind it evenly with 0.50g of thiourea, place it in a tube furnace, heat it to 600℃ at 5℃ / min under argon atmosphere protection and keep it at 4h. The resulting iron single-atom catalyst is denoted as Fe / SCN. The mass content of Fe in the catalyst obtained by ICP-AES test is 6.20%.

[0073] Comparative Example 1

[0074] (1) Weigh 0.65g of anhydrous oxalic acid and add it to 150mL of deionized water to dissolve it and obtain anhydrous oxalic acid solution;

[0075] (2) Weigh 1.45g of ferric nitrate and add it to anhydrous oxalic acid solution. Stir for 5 minutes to obtain an iron-oxalic acid complex solution.

[0076] (3) Weigh 2.17g of cyanuric acid and 3.03g of melamine respectively, add 300mL of deionized water, stir in a water bath at 80℃ for 15min to obtain cyanuric acid solution and melamine solution.

[0077] (4) Mix the iron-oxalic acid complex solution and the cyanuric acid solution, then add the melamine solution and mix. After stirring for 4 hours, filter the mixture, wash the precipitate with water, and dry it overnight at 60°C to obtain the precursor.

[0078] (5) The precursor was ground into powder and placed in a tube furnace. Under the protection of argon atmosphere, the temperature was increased to 600℃ at 5℃ / min and held for 4h. The resulting iron single-atom catalyst was denoted as Fe / CN. The mass content of Fe in the catalyst was 10.26% as determined by ICP-AES.

[0079] Comparative Example 2

[0080] (1) Weigh 0.65g of anhydrous oxalic acid and add it to 150mL of deionized water to dissolve it and obtain anhydrous oxalic acid solution;

[0081] (2) Weigh 2.17g of cyanuric acid and 3.03g of melamine respectively, add 300mL of deionized water, stir in a water bath at 80℃ for 15min to obtain cyanuric acid solution and melamine solution.

[0082] (3) Mix anhydrous oxalic acid solution and cyanuric acid solution, then add melamine solution and mix. After stirring for 4 hours, filter, wash the precipitate with water, and dry at 60°C overnight to obtain the precursor.

[0083] (4) The precursor is ground into powder and placed in a tube furnace. Under the protection of argon atmosphere, the temperature is increased to 600°C at 5°C / min and held for 4 hours. The resulting graphitic carbon nitride is denoted as CN.

[0084] Comparative Example 3

[0085] (1) Weigh 0.65g of anhydrous oxalic acid and add it to 150mL of deionized water to dissolve it and obtain anhydrous oxalic acid solution;

[0086] (2) Weigh 2.17g of cyanuric acid and 3.03g of melamine respectively, add 300mL of deionized water, stir in a water bath at 80℃ for 15min to obtain cyanuric acid solution and melamine solution.

[0087] (3) Mix anhydrous oxalic acid solution and cyanuric acid solution, then add melamine solution and mix. After stirring for 4 hours, filter, wash the precipitate with water, and dry at 60°C overnight to obtain the precursor.

[0088] (4) After grinding the precursor into powder, weigh 2.50g of the precursor powder, mix it with 0.50g of thiourea and grind it evenly. Then place it in a tube furnace and heat it to 600℃ at 5℃ / min under argon atmosphere protection and keep it at the temperature for 4h. The sulfur-doped graphitic carbon nitride obtained is denoted as SCN.

[0089] Figure 1 The images show the XRD patterns of Fe / SCN obtained in Example 1, Fe / CN obtained in Comparative Example 1, CN obtained in Comparative Example 2, and SCN obtained in Comparative Example 3. Figure 2 The images show the FT-IR spectra of Fe / SCN obtained in Example 1, Fe / CN obtained in Comparative Example 1, CN obtained in Comparative Example 2, and SCN obtained in Comparative Example 3. Figure 1 and Figure 2 It can be seen that the catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 3 exhibit characteristic diffraction peaks of the (100) and (002) crystal planes of graphitic carbon nitride (CN) at 13.1° and 27.8°; FT-IR at 1638 cm⁻¹... -1 1570cm -1 1247cm -1 and 1410cm -1Characteristic absorption peaks corresponding to CN heterocyclic stretching vibration and aromatic stretching vibration modes appeared at the specified location. The results indicate that neither sulfur doping nor iron atom loading altered the crystal structure of graphitic carbon nitride, and no iron nanoparticles or their oxides were present in the Fe / SCN sample obtained in Example 1.

[0090] Figure 3 The image shows a TEM image of Fe / SCN obtained in Example 1. Figure 4 The elemental distribution diagram of Fe / SCN obtained in Example 1 is shown below. Figure 3 and 4 It can be seen that no Fe nanoparticles or clusters were observed in the transmission electron microscope, and the elemental distribution map shows that Fe is uniformly distributed on the SCN support. Figure 5 The image shown is the AC-HAADF-STEM image of Fe / SCN obtained in Example 1. Figure 5 It can be seen that Fe is dispersed on the support in the form of single atoms.

[0091] Figure 6 The graph shows the degradation efficiency of 4-CP by activated PI using Fe / SCN obtained in Example 1, Fe / CN obtained in Comparative Example 1, CN obtained in Comparative Example 2, and SCN obtained in Comparative Example 3. Figure 6 As shown, Fe / SCN activation of PI resulted in the best degradation effect on 4-CP. To investigate the active species in the Fe / SCN-activated PI reaction system, a free radical quenching experiment was conducted, and the results are as follows: Figure 7 As shown, the addition of tert-butanol (TBA) did not affect the degradation rate of 4-CP, while the addition of p-benzoquinone (p-BQ), furfuryl alcohol (FFA), and potassium dichromate (K2Cr2O7) all inhibited the degradation rate, demonstrating the presence of O2 in the reaction system. - , 1 O2 and e - Possible effects of transfer.

[0092] To verify the role of electron transfer in the reaction system, the it test results of Fe / SCN obtained in Example 1, Fe / CN obtained in Comparative Example 1, CN obtained in Comparative Example 2, and SCN obtained in Comparative Example 3 were compared. Figure 8 It can be seen that Fe / SCN material has the strongest electron transport capability. The opposite current flow changes generated when 4-CP and PI are added respectively prove that there is an electron transfer pathway in the reaction system that conducts electrons from 4-CP to PI. Figure 9 This is a graph showing the test results of PI consumption during the degradation of 4-CP by Fe / SCN activated PI obtained in Example 1. Figure 9As shown, when Fe / SCN reacts with PI alone, no PI consumption can be detected in the reaction system, indicating that Fe / SCN alone cannot activate PI; only after the addition of 4-CP is PI consumed, and the amount of PI consumed is proportional to the amount of 4-CP added. This result further proves that PI in the reaction system is activated by electrons conducted from 4-CP.

[0093] Figure 10 The image shows the TOC test results of PI after degradation of 4-CP by Fe / SCN activated in Example 1. The test results show that the reaction system can progressively degrade 4-CP into smaller molecule products and even mineralize it, with an overall mineralization rate of approximately 60%. This demonstrates the ability of Fe / SCN to achieve electron transfer and simultaneous activation of PI for deep processing of 4-CP through charge confinement of active sites.

[0094] Figure 11 The graph shows the effect of different pH values ​​on the degradation of 4-CP by Fe / SCN activated PI obtained in Example 1. Figure 12 This is a periodic experimental diagram of the Fe / SCN activated PI degradation of 4-CP obtained in Example 1. Within a relatively wide pH range (2.5–10.5), the removal rate of 4-CP by Fe / SCN remained around 100%. Figure 11 This indicates that the reaction system has excellent pH adaptability. Cyclic experiments ( Figure 12 This indicates that Fe / SCN exhibits better stability.

[0095] The Fe / SCN prepared in this invention achieves simultaneous electron transfer through charge confinement of active sites, activating PI to degrade organic pollutants. Qualitative analysis of the active substances revealed that Fe / SCN can simultaneously activate PI to generate O2 during electron transfer through charge confinement of active sites. - and 1 O2 is used to prevent the polymerization of organic pollutants during the degradation of aromatic organic pollutants, and it has the advantages of high efficiency, wide pH tolerance range and good stability.

[0096] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0097] The above description is only a preferred embodiment of the present invention. Any technical solution that achieves the purpose of the present invention by essentially the same means is within the protection scope of the present invention.

Claims

1. A single-atom catalyst for the simultaneous activation of periodate degradation of organic pollutants through charge confinement of active sites to achieve electron transfer, characterized in that: The catalyst comprises a support and iron single-atom active sites supported on the support. The support is sulfur-doped graphitic carbon nitride. The support has a special heptaazine ring structure, which has a localized confinement effect on the charge transferred during the reaction. In the iron single-atom active sites, iron atoms are bound to the support in an N / S co-coordinated manner, and the active sites exhibit charge confinement characteristics. The mass content of iron single atoms in the iron single-atom catalyst is 5-15%. The preparation method of this catalyst includes the following steps: S1: Melamine and cyanuric acid are dissolved separately under water bath stirring to obtain melamine solution and cyanuric acid solution; S2: Dissolve soluble iron salt and organic ligand together in water to fully complex iron ions and organic ligands to obtain an iron-organic complex solution; S3: Mix the iron-organic complex solution, melamine solution and cyanuric acid solution to fully carry out the hydrogen bond self-assembly reaction. After solid-liquid separation by suction filtration, dry and grind to obtain precursor powder. S4: The precursor powder is uniformly mixed with the sulfur source and then pyrolyzed to obtain an iron single-atom catalyst. In step S4, the sulfur source includes one or more of thiourea and trithiocyanate; the mass ratio of the precursor to the sulfur source is (1~5):(0.5~2). In step S4, the pyrolysis temperature is 500~800℃ and the time is 2~6 h.

2. The single-atom catalyst according to claim 1, characterized in that: In step S2, the soluble iron salt includes one or more of ferrous chloride, ferric nitrate, and ferric sulfate; the organic ligand includes anhydrous oxalic acid and / or o-phenanthroline.

3. The single-atom catalyst according to claim 1, characterized in that: In steps S2 and S3, the molar ratio of organic ligand, soluble iron salt, cyanuric acid and melamine is (0.1~0.4):(0.05~0.2):(0.6~0.9):

1.

4. The single-atom catalyst according to claim 1, characterized in that: The pyrolysis is carried out under a protective atmosphere, namely nitrogen and / or argon.

5. The single-atom catalyst according to claim 1, characterized in that: Iron single-atom catalysts achieve "fractional site co-adsorption" of organic pollutants and periodate, inducing the degradation of organic pollutants through an electron transfer pathway.

6. The single-atom catalyst according to claim 1, characterized in that: Iron single-atom catalysts utilize the unique heptaazine ring structure in the support to confine and transfer charges during the reaction process, enabling periodate to accept single electrons and be further activated into reactive oxygen species. These reactive oxygen species can deeply degrade organic pollutants, avoiding the formation of oligomers in traditional electron transfer pathways.

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