Feocl / mos2 heterojunction catalyst and preparation method and application thereof

Abstract

This invention discloses a FeOCl / MoS2 heterojunction catalyst, its preparation method, and its application, belonging to the field of water treatment materials technology. The FeOCl / MoS2 heterojunction catalyst comprises a two-dimensional layered 2H phase MoS2 substrate and FeOCl nanosheets grown in situ on the surface of the MoS2 substrate. A tightly contacted heterojunction interface is formed between FeOCl and MoS2, and an internal electric field exists at the interface pointing from MoS2 to FeOCl. The potential difference generated by the band structure difference at the FeOCl and MoS2 interface leads to interfacial polarization, driving electrons to transfer directionally from the low work function MoS2 to the high work function FeOCl at the interface. This regulates the electron density and structure of Fe sites, thereby significantly enhancing catalytic activity and achieving efficient degradation of pollutants in water.

Description

Technical Field

[0001] This invention relates to the field of water treatment materials technology, specifically to a FeOCl / MoS2 heterojunction catalyst, its preparation method, and its application. Background Technology

[0002] In recent years, driven by the needs of the pharmaceutical and livestock industries, the production and use of persistent emerging organic pollutants (ECs) such as antibiotics and phenols have increased dramatically. Therefore, developing a highly efficient technology for EC removal is of significant practical importance.

[0003] Built-in electric fields, as a core strategy in catalyst design, profoundly influence the catalytic process by modulating carrier dynamics and reaction energy barriers, holding a crucial position in the field of catalysts. Among them, heterojunction catalysts, through band engineering to construct built-in electric fields at the interface, fundamentally regulate the electronic properties, charge behavior, and surface reactions of the catalyst, breaking through the intrinsic activity limitations of single catalysts and playing a significant role in photocatalysis, electrocatalysis, and other fields.

[0004] Over the past few decades, various iron-containing catalysts have been applied in heterogeneous Fenton catalysis. Among them, FeOCl is a novel heterogeneous catalyst with a layered structure. Its unique atomic configuration and reducible electronic properties endow it with excellent Fenton catalytic performance. Since Fe sites act as active centers in Fenton-like reactions, the catalytic activity and stability of FeOCl are closely related to the electronic structure of iron atoms. However, FeOCl also suffers from drawbacks such as insufficient structural stability, easy aggregation of active sites, the need to improve redox cycle rates, and difficulty in achieving the directed generation of active species, which urgently need to be improved. Furthermore, in-depth research on the correlation between catalyst interface coupling, electronic structure, and reaction pathways is lacking. Summary of the Invention

[0005] In view of this, the present invention provides a FeOCl / MoS2 heterojunction catalyst, its preparation method and application. The difference in energy bands at the interface contact of FeOCl and MoS2 causes interfacial polarization and generates a potential difference, which drives the directional transfer of electrons from the low work function MoS2 to the high work function FeOCl at the interface. This regulates the electron density and structure of Fe sites, thereby achieving a significant improvement in catalytic activity and achieving the goal of efficiently degrading pollutants in water.

[0006] Unlike existing technologies that primarily rely on Fe-O-Mo electron-mediated acceleration of Fe 3 + / Fe 2+The degradation is achieved through hydroxyl radicals (·OH) in the cycle. The key to this invention lies in utilizing the band difference at the FeOCl and MoS2 interface to form a directional built-in electric field, driving electron transfer and regulating the spin state of Fe sites. This transforms the reaction pathway from a traditional radical-dominated approach to a non-radical pathway synergistic with high-valence ferrous oxide species (Fe(IV)=O) and electron transfer (ETP). This mechanistic shift is the essential innovation of this application in achieving highly efficient catalysis.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention discloses a FeOCl / MoS2 heterojunction catalyst, the catalyst comprising:

[0009] A two-dimensional layered 2H phase MoS2 substrate, and FeOCl nanosheets grown in situ on the surface of the MoS2 substrate; wherein, a heterojunction interface is formed between FeOCl and MoS2 in close contact, and an internal electric field pointing from MoS2 to FeOCl exists at the heterojunction interface.

[0010] The work function of the catalyst is 4.9~5.3 eV.

[0011] The effective magnetic moment of Fe at the center in the catalyst is 4.5-5.2 μm. B .

[0012] As a further aspect of the present invention: the Fermi levels of the FeOCl and MoS2 catalyst are aligned after forming a heterojunction.

[0013] As a further aspect of the present invention, the average number of unpaired electrons at the Fe sites in the catalyst is 3.61-4.30.

[0014] As a further aspect of the present invention: the catalyst has a nanoflower-like morphology and a heterojunction structure in which (002) lattice stripes of MoS2 and (021) lattice stripes of FeOCl coexist.

[0015] Secondly, this invention discloses a method for preparing the FeOCl / MoS2 heterojunction catalyst as described above, comprising the following steps:

[0016] (1) The iron-containing chlorine source and 2H phase MoS2 powder are self-assembled in an organic solvent to load the iron-containing chlorine source on the surface of MoS2 to obtain the precursor;

[0017] (2) The precursor obtained in step (1) is heat-treated in an inert atmosphere to convert the iron source into FeOCl and form a heterojunction with MoS2 to obtain a composite.

[0018] (3) The complex is purified to remove unreacted iron-containing chlorine sources and surface impurities to obtain FeOCl / MoS2 heterojunction catalyst.

[0019] As a further aspect of the present invention: the iron-containing chlorine source is ferric chloride hexahydrate; the mass ratio of the iron-containing chlorine source to MoS2 is 1:3 to 3:1.

[0020] As a further aspect of the present invention, the preparation method of the 2H phase MoS2 powder is as follows:

[0021] Ammonium molybdate tetrahydrate and thiourea were dissolved in water at a mass ratio of 1:(1.6~2) and subjected to hydrothermal reaction at 180~220℃ for 20~28h. After centrifugation, washing and drying, 2H phase MoS2 powder was obtained.

[0022] As a further aspect of the present invention: the self-assembly composite is specifically performed by placing the organic solvent containing an iron-containing chlorine source and 2H phase MoS2 powder under a power of 100W~200W for 5~15 minutes and then letting it stand for 0.5~2 hours, and repeating the treatment 2~4 times.

[0023] As a further aspect of the present invention: in step (2), the heat treatment specifically involves: first, holding the temperature at 40~60℃ for 10~30 min under an inert atmosphere, and then raising the temperature to 240~260℃ at a rate of 2~5℃ / min and holding for 2~3 h.

[0024] As a further aspect of the present invention: in step (3), the purification process includes: thoroughly washing the complex, drying it, and then performing plasma treatment; wherein the plasma treatment time is 3-5 min and the power is 50-100 W.

[0025] Thirdly, the present invention discloses the application of the FeOCl / MoS2 heterojunction catalyst as described above in the degradation of organic pollutants in wastewater.

[0026] Fourthly, this invention discloses a method for removing organic pollutants from wastewater, comprising the following steps:

[0027] The FeOCl / MoS2 heterojunction catalyst described above is added to the wastewater, and a catalytic degradation reaction is carried out in the presence of persulfate to remove organic pollutants from the wastewater.

[0028] Based on the volume of wastewater, the amount of FeOCl / MoS2 heterojunction catalyst added is 50~500 mg / L, and the amount of persulfate added is 20~300 mg / L;

[0029] The reaction solution for the catalytic degradation reaction has a pH value of 3-11, a reaction temperature of 20-50℃, and a reaction time of 10-60 min;

[0030] The persulfate is at least one of potassium peroxymonosulfate, sodium peroxymonosulfate, potassium peroxydisulfate, and sodium peroxydisulfate.

[0031] The organic pollutants include at least one of tetracycline, sulfadiazine, sulfamethoxazole, sulfisoxazole, bisphenol A, and phenol.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] (1) This invention utilizes the strong interfacial coupling between FeOCl and MoS2 to generate a directional built-in electric field, thereby optimizing its electronic structure and reaction pathway. Specifically:

[0034] Electron density modulation: After interfacial coupling between FeOCl and MoS2, the band difference induces interfacial polarization, generating a potential difference and forming a directional built-in electric field. Utilizing the difference in work function between the two materials, electrons are driven to transfer directionally from the low work function MoS2 to the high work function FeOCl at the interface until the Fermi levels on both sides are aligned. This significantly accelerates the transfer of Fe to the active metal sites in the catalyst. 3+ To Fe 2+ The cycle / regeneration promotes the activation of PMS (potassium peroxymonosulfate).

[0035] Interface-induced spin modulation: Most of the iron ions in FeOCl are Fe 3+ , in the state of O² - and Cl - In a twisted octahedral coordination field composed of ligands. In O 2- and Cl - Under weak field conditions, electrons tend to occupy as many orbitals as possible and maintain spin parallelism, adopting a high-spin state. After introducing MoS2 to form a heterojunction, a significant charge redistribution occurs at the FeOCl / MoS2 heterojunction interface. Electrons transfer from MoS2 to FeOCl, leading to Fe... 3+ Partially reduced to Fe 2+ The local electric field and chemical environment at the interface can create a coordination field different from that in the bulk phase, prompting some iron ions to undergo a spin transition to a lower spin level.

[0036] (2) This invention utilizes the built-in electric field at the interface between FeOCl and MoS2 to modulate the spin state of Fe sites, thereby achieving the transformation from the generation of active species to the non-radical electron transfer pathway (ETP). Specifically:

[0037] Built-in electric field and electron transfer: The built-in electric field between FeOCl and MoS2 directionally attracts and enriches negatively charged pollutant molecules onto the catalyst surface, forming stable persulfate surface complex intermediates, which promotes electron transfer from pollutants to persulfate surface complexes. The built-in electric field effectively modulates the electronic structure of the Fe active center, significantly enhancing its electron accepting and donating capabilities, thereby greatly improving the kinetic rate of interfacial charge transfer and providing a key driver for efficient catalytic degradation.

[0038] Pathway switching mechanism: The introduction of MoS2 reduces the valence state of Fe in FeOCl, weakens the oxidation capacity of Fe, inhibits the traditional free radical reaction pathway, enhances the generation rate of high-valence iron-oxygen species (Fe(IV)=O), and opens up a pathway for direct oxidation of pollutants through the ETP mechanism, thereby improving the degradation effect of organic pollutants in water.

[0039] (3) This invention utilizes the built-in electric field at the FeOCl / MoS2 heterojunction interface to regulate the electronic structure of Fe sites, thereby achieving a synergistic enhancement of catalytic activity and stability, and ultimately degrading and removing organic pollutants from water. Specifically:

[0040] Gradient ratio activity trend: Changes in the electronic structure of Fe sites caused by strong coupling at the FeOCl / MoS2 heterojunction interface and Fe 3+ To Fe 2+ The synergistic regulation of the conversion rate led to an increase in the catalytic activity of catalysts with different ratios. Among them, the catalytic activity of the FeOCl:MoS2=2:1 ratio reached the peak, finding a balance between electron transfer efficiency and Fe site content. It was superior to traditional iron-based Fenton catalysts. The k value of the heterojunction catalyst for the degradation of sulfadiazine was nearly ten times that of FeOCl.

[0041] Anti-interference and universality: Unlike the traditional OH radical pathway, which heavily relies on acidic conditions, the (Fe(IV)=O)-mediated oxidation reaction maintains high activity in near-neutral and even alkaline pH ranges, and (Fe(IV)=O) possesses strong oxidizing power due to its high redox potential. In contrast, the non-radical ETP mechanism involves the direct transfer of pollutants to peroxides via catalysts, subject to humic acid (HA) and most ions (Cl-). - HCO3 - SO4 2- The inhibition interference from other substances is minimal. Furthermore, unlike the traditional Fenton system which is dependent on acidic environments, the FeOCl / MoS2 heterojunction catalyst maintains high catalytic activity across a pH range of 3–11.

[0042] Extremely low metal leaching rate and cycling stability: Due to the built-in electric field, electrons flow directionally from the MoS2 side to the FeOCl side. This continuous electron supply can leach Fe from the FeOCl surface. 3+ Instantaneous reduction to Fe 2+ This avoids Fe 3+ The long-term accumulation of active species through Fenton-like reaction pathways leads to the oxidative dissolution of the catalyst itself. Meanwhile, MoS2, as an electron donor, exhibits extremely stable structure, resulting in a metal leaching rate far lower than that of traditional Fenton-like systems. Similarly, FeOCl and MoS2 are structurally stable in non-strong oxidizing acids, and their strong coupling after forming a heterojunction further enhances the catalyst's stability, enabling it to maintain high catalytic activity even after five cycles.

[0043] (4) This invention utilizes the built-in electric field at the FeOCl / MoS2 heterojunction interface to modulate the electronic structure of Fe sites, achieving scientific value and technological innovation, specifically as follows:

[0044] Built-in electric field strength-quantitative activity model: A three-dimensional correlation model of FeOCl / MoS2 ratio gradient, electronic structure and reaction path is established to provide a theoretical framework for the rational design of heterojunction catalysts driven by built-in electric field.

[0045] Dynamic Mechanism Analysis: This study reveals the dynamic process of reaction pathway transformation at the FeOCl / MoS2 heterojunction interface, elucidates the synergistic mechanism of "adsorption-electron transfer-desorption" and "cyclic generation of high-valence ferrous oxide species," and promotes in-depth research on the mechanism of advanced oxidation technologies.

[0046] (5) This invention achieves the gradient ratio of FeOCl and MoS2 and the regulation of the spin state through secondary gradient heating calcination. High temperature promotes the hydrolysis of ferric chloride hexahydrate to generate FeOCl, while simultaneously enabling FeOCl and MoS2 to form a strong interfacial coupling, preventing the active sites from sintering or being lost.

[0047] (6) The present invention ensures initial nanoscale dispersion and breaks agglomeration through multi-level ultrasonic self-assembly. Under the action of intermolecular forces (such as electrostatic attraction and van der Waals forces), orderly self-assembly is carried out, avoiding the formation of uneven agglomeration of heterojunctions.

[0048] (7) The FeOCl / MoS2 heterojunction prepared by the present invention needs to be washed with a large amount of acetone and ethanol to remove the residual ferric chloride hexahydrate, and then the amorphous carbon and organic impurities on the catalyst surface are further cleaned with low-power Ar plasma to expose the active sites, thereby improving the purity, uniformity of active sites and stability of the final product.

[0049] Therefore, this invention uses an internal electric field to regulate the electronic structure and reaction pathway of the catalyst, breaking through the traditional catalyst activity-stability trade-off and achieving efficient and green water treatment via a non-radical pathway. Attached Figure Description

[0050] Figure 1 SEM images of FeOCl prepared in Comparative Example 1, MoS2 prepared in Comparative Example 2, and the FeOCl / MoS2 catalyst prepared in Example 1 are shown, where a is the SEM image of FeOCl in Comparative Example 1, b is the SEM image of MoS2 in Comparative Example 2, and c is the SEM image of FeOCl / MoS2 in Example 1.

[0051] Figure 2 TEM images of FeOCl prepared in Comparative Example 1, MoS2 prepared in Comparative Example 2, and the FeOCl / MoS2 catalyst prepared in Example 1, where a is the TEM image of FeOCl in Comparative Example 1, b is the TEM image of MoS2 in Comparative Example 2, and c is the TEM image of FeOCl / MoS2 in Example 1.

[0052] Figure 3 XPS images of FeOCl and MoS2 prepared in Comparative Examples 1 and 2 and the catalyst FeOCl / MoS2 prepared in Example 1, where a is a comparison of Fe 2p between FeOCl and FeOCl / MoS2, and b is a comparison of Mo 3d between MoS2 and FeOCl / MoS2.

[0053] Figure 4 The ultraviolet photoelectron spectroscopy (UV PES) spectra of FeOCl and MoS2 prepared in Comparative Examples 1 and 2, and the FeOCl / MoS2 catalyst prepared in Example 1.

[0054] Figure 5 The magnetic susceptibility curves of the catalysts FeOCl and FeOCl / MoS2 prepared in Comparative Example 1 and Example 1 are shown.

[0055] Figure 6 The graph shows the effect of FeOCl and MoS2 prepared in Comparative Examples 1 and 2, and the catalyst FeOCl / MoS2 prepared in Example 1 on the activation of potassium persulfate for the degradation of sulfadiazine.

[0056] Figure 7 The graph shows the contribution rate of active species in the degradation of sulfadiazine by activated potassium persulfate using FeOCl prepared in Comparative Example 1 and the FeOCl / MoS2 catalyst prepared in Example 1. Detailed Implementation

[0057] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0059] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail; unless otherwise specified, the parts in the following embodiments refer to parts by weight.

[0060] Example 1

[0061] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0062] (2) Dissolve 2g of ferric chloride hexahydrate in 20mL of acetone, add 1g of MoS2 powder obtained in step (1), sonicate at 150W power for 10min, let stand for 1h, repeat the sonication-standing process three times, and then stir until dry.

[0063] (3) The dried powder was calcined under argon protection by gradient heating: first, the temperature was raised to 50°C at a rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 250°C at a rate of 3°C / min and held for 2.5 h to obtain the calcined product.

[0064] (4) The calcined product is repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant is colorless and transparent, and then vacuum dried for 16 hours to obtain a dry powder.

[0065] (5) The dried powder was subjected to Ar plasma treatment at 50W for 3 minutes to obtain the FeOCl / MoS2 heterojunction catalyst, denoted as FeOCl / MoS2.

[0066] Example 2

[0067] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0068] (2) Dissolve 1g of ferric chloride hexahydrate in 20mL of acetone, add 1g of MoS2 powder obtained in step (1), sonicate at 150W power for 10min, let stand for 1h, repeat the sonication-standing process three times, and then stir until dry.

[0069] (3) The dried powder was calcined under argon protection by gradient heating: first, the temperature was raised to 50°C at a rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 250°C at a rate of 3°C / min and held for 2.5 h to obtain the calcined product.

[0070] (4) The calcined product was repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant was colorless and transparent, and then vacuum dried for 16 hours to obtain a dry powder.

[0071] (5) The dried powder was subjected to Ar plasma treatment at 50W for 3 minutes to obtain the FeOCl / MoS2 heterojunction catalyst, which is denoted as 1-FeOCl / MoS2.

[0072] Example 3

[0073] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0074] (2) Dissolve 2g of ferric chloride hexahydrate in 20mL of acetone, add 1g of MoS2 powder obtained in step (1), sonicate at 150W power for 10min, let stand for 1h, repeat the sonication-standing process three times, and then stir until dry.

[0075] (3) The dried powder was calcined under argon protection by gradient heating: first, the temperature was raised to 50°C at a rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 250°C at a rate of 5°C / min and held for 2.5 h to obtain the calcined product.

[0076] (4) The calcined product was repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant was colorless and transparent, and then vacuum dried for 16 hours to obtain a dry powder.

[0077] (5) The dried powder was subjected to Ar plasma treatment at 50W for 3 minutes to obtain the FeOCl / MoS2 heterojunction catalyst, which is denoted as 2-FeOCl / MoS2.

[0078] Example 4

[0079] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0080] (2) Dissolve 3g of ferric chloride hexahydrate in 20mL of acetone, add 1g of MoS2 powder obtained in step (1), sonicate at 100W power for 10min, let stand for 1h, repeat the sonication-standing process three times, and then stir until dry.

[0081] (3) The dried powder was calcined under argon protection by gradient heating: first, the temperature was raised to 50°C at a rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 250°C at a rate of 3°C / min and held for 2.5 h to obtain the calcined product.

[0082] (4) The calcined product is repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant is colorless and transparent, and then vacuum dried for 16 hours to obtain a dry powder.

[0083] (5) The dried powder was subjected to Ar plasma treatment at 75W for 3min to obtain the FeOCl / MoS2 heterojunction catalyst, which is denoted as 3-FeOCl / MoS2.

[0084] Example 5

[0085] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0086] (2) Dissolve 1g of ferric chloride hexahydrate in 20mL of acetone, add 3g of MoS2 powder obtained in step (1), sonicate at 200W power for 10min, let stand for 1h, repeat the sonication-standing process three times, and then stir until dry.

[0087] (3) The dried powder was calcined under argon protection by gradient heating: first, the temperature was raised to 50°C at a rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 250°C at a rate of 3°C / min and held for 2.5 h to obtain the calcined product.

[0088] (4) The calcined product is repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant is colorless and transparent, and then vacuum dried for 16 hours to obtain a dry powder.

[0089] (5) The dried powder was subjected to Ar plasma treatment at 10W for 3 minutes to obtain the FeOCl / MoS2 heterojunction catalyst, which is denoted as 4-FeOCl / MoS2.

[0090] Comparative Example 1

[0091] (1) The pure ferric chloride hexahydrate was calcined under inert gas protection by gradient heating. The temperature was increased to 50°C at a rate of 5°C / min and held for 20 min (to remove residual acetone). Then the temperature was increased to 250°C at a rate of 3°C / min and held for 2.5 h.

[0092] (2) After calcination, the product was centrifuged and washed with a large amount of acetone and ethanol until the supernatant was colorless and transparent; the product was vacuum dried for 16 h and then treated with low-power Ar plasma for 3 min. The catalyst obtained was named FeOCl.

[0093] Comparative Example 2

[0094] 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then vacuum dried for 16 h. The resulting catalyst was denoted as MoS2.

[0095] Test Example 1

[0096] The catalysts FeOCl, MoS2, and FeOCl / MoS2 prepared in Comparative Examples 1 and 2 and Example 1 were tested for relevant parameters, and the test results are as follows:

[0097] (1) Figure 1Image a shows the SEM image of FeOCl, image b shows the SEM image of MoS2, and image c shows the SEM image of FeOCl / MoS2. The results indicate that the FeOCl / MoS2 catalyst prepared in this invention possesses a nanoflower-like structure similar to that of MoS2. The mixing of ferric chloride hexahydrate and MoS2, along with the increase in temperature, causes ferric chloride hexahydrate to hydrolyze on the MoS2 surface to generate FeOCl. Therefore, the catalyst grows along the MoS2 direction. This structural change transforms the original multilayered lamellar morphology of the catalyst on FeOCl into a nanoflower structure, significantly improving the exposure rate of active sites and the mass transfer efficiency.

[0098] (2) Figure 2 In the image, a is a TEM image of FeOCl, b is a TEM image of MoS2, and c is a TEM image of FeOCl / MoS2. The results show that the FeOCl / MoS2 catalyst prepared in this invention has the same (002) lattice fringes as MoS2 and the same (021) lattice fringes as FeOCl. Both of these characteristics demonstrate that the FeOCl / MoS2 catalyst successfully formed a heterojunction structure.

[0099] (3) Figure 3 XPS test results for catalysts FeOCl / MoS2, FeOCl, and MoS2. From... Figure 3 As can be seen from a, compared to before calcination, Fe 2+ The content of FeOCl increased significantly, and the peak position shifted towards lower binding energies, indicating that FeOCl has a tendency to gain electrons from MoS2. Meanwhile, Figure 3 As can be seen in b, the XPS spectrum of Mo 3d shows a characteristic of Mo after calcination. 6+ A new peak was observed. The results indicate that with the interfacial coupling between FeOCl and MoS2, electrons tend to transfer from MoS2 to FeOCl, increasing the electron density at Fe sites and correspondingly altering the electronic structure.

[0100] (4) Figure 4 The UPS diagrams show the catalysts FeOCl, MoS2, and FeOCl / MoS2 prepared in Comparative Examples 1, 2, and Example 1. The results show that the work functions of FeOCl / MoS2, FeOCl, and MoS2 are 5.14 eV, 5.44 eV, and 4.07 eV, respectively. This indicates that after high-temperature calcination, with the generation of the built-in electric field, FeOCl and MoS2 undergo Fermi level alignment through interfacial coupling, with the work function of FeOCl / MoS2 positioned between the two.

[0101] (5) Figure 5 The graphs show the magnetic susceptibility curves of the catalysts FeOCl and FeOCl / MoS2 prepared in Comparative Example 1 and Example 1. The results show that the effective central magnetic moments of FeOCl and FeOCl / MoS2 are 5.79 μm and 5.79 μm, respectively.B and 4.95μ B It can be seen that after the formation of the heterojunction, FeOCl acquired electrons from MoS2, and the average number of unpaired electrons at the Fe site decreased from 4.9 to 4.05.

[0102] Test Example 2

[0103] Test for activating peroxysulfate degradation of sulfadiazine in wastewater:

[0104] Weigh 10 mg each of the catalysts FeOCl, MoS2, and FeOCl / MoS2 prepared in Comparative Examples 1, 2, and Example 1, and add them to water samples containing 100 mL of sulfadiazine at a concentration of 10 mg / L (denoted as C0). Then add 30 mg of potassium peroxymonosulfate to each sample, adjust the pH to 7, and react at 25°C. After thorough stirring at 300 rpm / min, take samples at predetermined time intervals (e.g., at 0, 2, 5, 10, 20, and 30 minutes), filter, and use high-performance liquid chromatography (HPLC) to detect the sulfadiazine content (denoted as C) in the water samples. The results are as follows: Figure 6 As shown in the figure, after 30 minutes of reaction, the removal rates of sulfadiazine by FeOCl, MoS2, and FeOCl / MoS2 activated PMS were 47.5%, 33.1%, and 99%, respectively. The reaction rate values ​​(kobs) followed the order of FeOCl / MoS2 (0.1396 min). -1 ) > FeOCl (0.0142min -1 > MoS2 (0.0103 min) -1 The order of ).

[0105] Test Example 3

[0106] Benzoic acid, nitrobenzene, p-chlorobenzoic acid, furfuryl alcohol, and methyl phenyl sulfoxide were used as probe substances to quantitatively detect hydroxyl radicals (·OH) and sulfate radicals (SO4). ·- ), superoxide radicals (O2) ·- Singlet oxygen ( 1 The steady-state concentrations of O2 and high-valent iron oxides (Fe(Ⅳ)=O) were determined. The contribution rate of each active species in the catalytic degradation system was calculated using a competitive kinetic method.

[0107] The experiment was conducted under the same conditions as in Test Example 2 (catalyst dosage 10 mg, initial sulfadiazine concentration 10 mg / L, potassium peroxymonosulfate dosage 30 mg, pH=7, reaction temperature 25℃). The contribution rate of each active species in the FeOCl / PMS system and the FeOCl / MoS2 / PMS system to the degradation of sulfadiazine was determined.

[0108] The results are as follows Figure 7 As shown, in the FeOCl / PMS system, high-valent ferrooxide species (Fe(Ⅳ)=O) contribute 85.2%, making them the dominant active species for the degradation of sulfadiazine. In the FeOCl / MoS2 / PMS system, high-valent ferrooxide species (Fe(Ⅳ)=O) contribute 41.1%, while the electron transfer pathway (ETP) contributes 47.4%, becoming the main degradation pathway. Simultaneously, the high-valent ferrooxide pathway still maintains a high contribution rate.

[0109] The above results indicate that the introduction of MoS2 not only enhances the generation efficiency of the original high-valence ferrite species, but more importantly, it opens up a new non-radical degradation pathway through electron transfer, realizing a shift in the reaction pathway from a single high-valence ferrite pathway to a dual-pathway mode of "electron transfer-dominated, high-valence ferrite-assisted pathway". This pathway shift is closely related to the formation of the built-in electric field at the FeOCl / MoS2 heterojunction interface. The built-in electric field directionally drives electron transfer from MoS2 to FeOCl, regulating the electronic structure of Fe sites, thereby realizing the transformation of the reaction pathway from a single high-valence ferrite pathway to a dual-pathway mode of high-valence ferrite and electron transfer synergy.

[0110] Comparative Example 3

[0111] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0112] (2) 2g of ferric chloride hexahydrate was calcined under an inert gas protection by gradient heating: first, the temperature was raised to 50℃ at a heating rate of 5℃ / min and held for 20min to remove residual acetone; then the temperature was raised to 250℃ at a heating rate of 3℃ / min and held for 2.5h to obtain the calcined product.

[0113] (3) The calcined product was repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant was colorless and transparent. It was then vacuum dried for 16 hours. The dried powder was then physically ground and mixed with 1g of MoS2. The mixture was then subjected to Ar plasma treatment at 50W for 3 minutes. The resulting catalyst was named p-FeOCl / MoS2.

[0114] Comparative Example 4

[0115] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0116] (2) Dissolve 4g of ferric chloride hexahydrate in 20mL of acetone, add 1g of MoS2 powder obtained in step (1), sonicate at 150W power for 10min, let stand for 1h, repeat the sonication-standing process three times, and then stir until dry.

[0117] (3) The dried powder was calcined under an inert gas protection by gradient heating: first, the temperature was raised to 50°C at a heating rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 250°C at a heating rate of 3°C / min and held for 2.5 h to obtain the calcined product.

[0118] (4) The calcined product is repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant is colorless and transparent, and then vacuum dried for 16 hours to obtain a dry powder.

[0119] (5) The dry powder was subjected to Ar plasma treatment at 50W for 3 min, and the resulting catalyst was denoted as FeOCl / MoS2-1.

[0120] Comparative Example 5

[0121] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0122] (2) Dissolve 2g of ferric chloride hexahydrate in 20mL of acetone, add 1g of MoS2 powder obtained in step (1), and stir until dry.

[0123] (3) The dried powder was calcined under an inert gas protection by gradient heating: first, the temperature was raised to 50°C at a heating rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 250°C at a heating rate of 3°C / min and held for 2.5 h to obtain the calcined product.

[0124] (4) The calcined product is repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant is colorless and transparent, and then vacuum dried for 16 hours to obtain a dry powder.

[0125] (5) The dry powder was subjected to Ar plasma treatment at 50W for 3 minutes, and the resulting catalyst was denoted as FeOCl / MoS2-2.

[0126] Comparative Example 6

[0127] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0128] (2) Dissolve 2g of ferric chloride hexahydrate in 20mL of acetone, add 1g of MoS2 powder obtained in step (1), sonicate at 150W power for 10min, let stand for 1h, repeat the sonication-standing process three times, and then stir until dry.

[0129] (3) The dried powder was calcined under an inert gas protection by gradient heating: first, the temperature was raised to 50°C at a heating rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 230°C at a heating rate of 3°C / min and held for 2.5 h to obtain the calcined product.

[0130] (4) The calcined product is repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant is colorless and transparent, and then vacuum dried for 16 hours to obtain a dry powder.

[0131] (5) The dry powder was subjected to Ar plasma treatment at 50W for 3 minutes, and the resulting catalyst was denoted as FeOCl / MoS2-3.

[0132] Comparative Example 7

[0133] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0134] (2) Dissolve 2g of ferric chloride hexahydrate in 20mL of acetone, add 1g of MoS2 powder obtained in step (1), sonicate at 150W power for 10min, let stand for 1h, repeat the sonication-standing process three times, and then stir until dry.

[0135] (3) The dried powder was calcined under an inert gas protection by gradient heating: first, the temperature was raised to 50°C at a heating rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 270°C at a heating rate of 3°C / min and held for 2.5 h to obtain the calcined product.

[0136] (4) The calcined product is repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant is colorless and transparent, and then vacuum dried for 16 hours to obtain a dry powder.

[0137] (5) The dry powder was subjected to Ar plasma treatment at 50W for 3 min, and the resulting catalyst was denoted as FeOCl / MoS2-4.

[0138] Comparative Example 8

[0139] (1) 0.742 g of ammonium molybdate tetrahydrate and 1.37 g of thiourea were added to 70 mL of deionized water, stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, the precipitate was washed by centrifugation with deionized water and ethanol, and then dried under vacuum for 16 h to obtain 2H phase MoS2 powder.

[0140] (2) Dissolve 2g of ferric chloride hexahydrate in 20mL of acetone, add 1g of MoS2 powder obtained in step (1), sonicate at 150W power for 10min, let stand for 1h, repeat the sonication-standing process three times, and then stir until dry.

[0141] (3) The dried powder was calcined under an inert gas protection by gradient heating: first, the temperature was raised to 50°C at a heating rate of 5°C / min and held for 20 min to remove residual acetone; then the temperature was raised to 250°C at a heating rate of 3°C / min and held for 2.5 h to obtain the calcined product.

[0142] (4) The calcined product is repeatedly centrifuged and washed with a large amount of acetone and ethanol until the supernatant is colorless and transparent. It is then vacuum dried for 16 hours to obtain a dry powder, which is the catalyst, denoted as FeOCl / MoS2-5.

[0143] Test Example 4

[0144] The catalysts prepared in Examples 1-3 and Comparative Examples 1-8 were subjected to bisphenol A degradation tests to investigate the catalytic activity and differences in reaction pathways of each catalyst.

[0145] Experimental conditions: 5 mg of each catalyst was weighed and added to 100 mL of bisphenol A aqueous solution (initial concentration 15 mg / L). Then, 2 mg of sodium peroxymonosulfate was added, and the pH of the reaction solution was adjusted to 3. The mixture was shaken thoroughly at 200 rpm in a shaker at 50℃ for 60 min. After the reaction, samples were taken, filtered, and the concentration of remaining bisphenol A in the water samples was determined by high-performance liquid chromatography (HPLC), and the degradation rate was calculated. Simultaneously, the contribution rate of key active species in each catalyst system was determined using a probe competition kinetic method.

[0146] The results are shown in Table 1.

[0147] Table 1

[0148]

[0149] As can be seen from Table 1:

[0150] (1) The FeOCl / MoS2 heterojunction catalysts prepared in Examples 1-3 all achieved a degradation rate of more than 86.4% for bisphenol A. Among them, the degradation rate of Example 1 (FeOCl:MoS2=2:1) ​​reached 100%, which was significantly better than Comparative Example 1 (47.5%) and Comparative Example 2 (33.7%). This indicates that the catalytic activity was greatly improved after FeOCl and MoS2 were combined to form a heterojunction.

[0151] (2) The catalyst prepared in Comparative Example 3 was only physically mixed, and its degradation rate was only 41.6%, which was much lower than that in Example 1. This proves that FeOCl and MoS2 must form a strong interface coupling through in-situ composite in order to generate a directional built-in electric field and achieve efficient catalysis.

[0152] (3) The degradation rate of the catalyst FeOCl / MoS2-1 prepared in Comparative Example 4 was 85.1%, which was lower than that in Example 1. This indicates that when the FeOCl ratio is too high, it cannot form an effective interface coupling with MoS2, the built-in electric field strength is weakened, and the catalytic activity decreases.

[0153] (4) The catalyst FeOCl / MoS2-2 prepared in Comparative Example 5 had an uneven distribution of FeOCl and incomplete interfacial coupling with MoS2 due to the lack of multi-stage ultrasonic self-assembly. The built-in electric field effect was weak, and the degradation rate of the catalyst was 66.3%, which was significantly lower than that in Example 1. This proves that the multi-stage ultrasonic static self-assembly process is the key step to achieve uniform loading of FeOCl precursor on the surface of MoS2 and the formation of strong interfacial coupling.

[0154] (5) The second calcination temperature of the catalyst FeOCl / MoS2-3 prepared in Comparative Example 6 was too low (230℃). Since the formation of FeOCl is relatively sensitive to temperature, FeOCl at 230℃ has a dense structure and cannot form loose nanosheets, resulting in a reduced contact area between FeOCl and MoS2, making it difficult to form a strong and effective built-in electric field through interfacial coupling. Therefore, the degradation rate of the prepared catalyst decreased compared to Example 1, reaching only 90.9%.

[0155] (6) The second calcination temperature of the catalyst FeOCl / MoS2-4 prepared in Comparative Example 7 was too high (270℃). FeOCl showed partial agglomeration at 270℃, and the active sites were shielded, resulting in a decrease in the specific surface area of ​​the catalyst and a decrease in the overall catalytic ability. The degradation rate was 87.8%. Examples 1, Comparative Example 6 and Comparative Example 7 together show that only at around 250℃ can a loose nanosheet structure be formed and strong interfacial coupling be maintained.

[0156] (7) The catalyst FeOCl / MoS2-5 prepared in Comparative Example 8 was not treated with Ar plasma, and its degradation rate was 87.5%. This is because low-power Ar plasma treatment can effectively remove amorphous carbon and organic impurities on the catalyst surface, expose active sites, and further enhance catalytic activity.

[0157] (8) From the perspective of reaction pathways, in the Comparative Example 1 (pure FeOCl) system, the high-valence ferrite species (Fe(Ⅳ)=O) is the dominant non-radical pathway, with a contribution rate as high as 85%. In the Example 1 (FeOCl / MoS2 heterojunction) system, the electron transfer pathway (ETP) contributes 47.4%, while the high-valence ferrite pathway contributes 41.1%, forming a dual-pathway synergistic mode. This indicates that the introduction of MoS2 not only enhances the contribution of the high-valence ferrite pathway, but more importantly, opens up a new reaction pathway of electron transfer.

[0158] In summary, the FeOCl / MoS2 heterojunction catalyst prepared in this invention forms a heterojunction structure with strong interfacial coupling and a directional built-in electric field through the synergistic effect of multi-stage ultrasonic self-assembly, gradient temperature calcination, and Ar plasma treatment. The introduction of MoS2 induces strong coupling between FeOCl and MoS2, generating a directional built-in electric field. This enhances the original high-valence ferrite species cycling pathway while regulating the spin state transition of Fe, opening up a new reaction pathway, ETP. FeOCl exhibits a clear tendency to acquire electrons from MoS2, significantly increasing the electron density at Fe sites, and aligning the Fermi levels of both. Furthermore, the generation of the directional built-in electric field promotes the adsorption of pollutants, optimizes the PMS adsorption and activation balance, and exhibits a catalytic activity (kobs) approximately nine times higher than that of ordinary FeOCl, achieving a removal rate of over 99% for sulfadiazine. This invention achieves directional optimization of the "chemical environment-electronic structure-reaction pathway" through a three-dimensional design involving built-in electric field, electron transfer, and spin state regulation.

[0159] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0160] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A FeOCl / MoS2 heterojunction catalyst, characterized in that, The catalyst includes: A two-dimensional layered 2H phase MoS2 substrate, and FeOCl nanosheets grown in situ on the surface of the MoS2 substrate; wherein, a heterojunction interface is formed between FeOCl and MoS2 in close contact, and an internal electric field pointing from MoS2 to FeOCl exists at the heterojunction interface. The work function of the catalyst is 4.9~5.3 eV; The effective magnetic moment of Fe at the center in the catalyst is 4.5-5.2 μm. B .

2. The FeOCl / MoS2 heterojunction catalyst according to claim 1, characterized in that, The Fermi levels in the catalyst are aligned after FeOCl and MoS2 form a heterojunction.

3. The FeOCl / MoS2 heterojunction catalyst according to claim 1, characterized in that, The catalyst has an average number of unpaired electrons at Fe sites of 3.61-4.

30.

4. The FeOCl / MoS2 heterojunction catalyst according to claim 1, characterized in that, The catalyst exhibits a nanoflower-like morphology and has a heterojunction structure in which (002) lattice stripes of MoS2 and (021) lattice stripes of FeOCl coexist.

5. A method for preparing the FeOCl / MoS2 heterojunction catalyst according to any one of claims 1-4, characterized in that, Includes the following steps: (1) The iron-containing chlorine source and 2H phase MoS2 powder were self-assembled in an organic solvent to load the iron-containing chlorine source on the surface of MoS2 and obtain the precursor. (2) The precursor obtained in step (1) is heat-treated in an inert atmosphere to convert the iron source into FeOCl and form a heterojunction with MoS2 to obtain a composite material. (3) The complex is purified to remove unreacted iron-containing chlorine sources and surface impurities to obtain FeOCl / MoS2 heterojunction catalyst.

6. The preparation method according to claim 5, characterized in that, The iron-containing chlorine source is ferric chloride hexahydrate; the mass ratio of the iron-containing chlorine source to MoS2 is 1:3 to 3:

1.

7. The preparation method according to claim 5, characterized in that, The preparation method of the 2H phase MoS2 powder is as follows: Ammonium molybdate tetrahydrate and thiourea were dissolved in water at a mass ratio of 1:(1.6~2) and subjected to hydrothermal reaction at 180~220℃ for 20~28h. After centrifugation, washing and drying, 2H phase MoS2 powder was obtained.

8. The preparation method according to claim 5, characterized in that, The self-assembly composite is specifically performed by placing the organic solvent containing an iron-containing chlorine source and 2H phase MoS2 powder under ultrasonication at 100W~200W power for 5~15 minutes, then letting it stand for 0.5~2 hours, and repeating the treatment 2~4 times.

9. The preparation method according to claim 5, characterized in that, In step (2), the heat treatment specifically involves: first, holding the temperature at 40~60℃ for 10~30 min under an inert atmosphere, and then raising the temperature to 240~260℃ at a rate of 2~5℃ / min and holding for 2~3 h.

10. The preparation method according to claim 5, characterized in that, In step (3), the purification process includes: thoroughly washing the complex, drying it, and then subjecting it to plasma treatment; wherein the plasma treatment time is 3-5 min and the power is 50-100 W.

11. The application of the FeOCl / MoS2 heterojunction catalyst as described in any one of claims 1-4 in the degradation of organic pollutants in wastewater.

12. A method for removing organic pollutants from wastewater, characterized in that, Includes the following steps: The FeOCl / MoS2 heterojunction catalyst as described in any one of claims 1-4 is added to wastewater, and a catalytic degradation reaction is carried out in the presence of persulfate to remove organic pollutants from the wastewater. Based on the volume of wastewater, the amount of FeOCl / MoS2 heterojunction catalyst added is 50~500 mg / L, and the amount of persulfate added is 20~300 mg / L; The reaction solution for the catalytic degradation reaction has a pH value of 3-11, a reaction temperature of 20-50℃, and a reaction time of 10-60 min; The persulfate is at least one of potassium peroxymonosulfate, sodium peroxymonosulfate, potassium peroxydisulfate, and sodium peroxydisulfate. The organic pollutants include at least one of tetracycline, sulfadiazine, sulfamethoxazole, sulfisoxazole, bisphenol A, and phenol.

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