Co9S8 / MoS2 / CNTs ternary composite catalyst and preparation method and application method thereof

Abstract

The invention discloses a Co9S8 / MoS2 / CNTs ternary composite catalyst and a preparation method and application method thereof, and relates to the technical field of catalysts.The preparation method comprises the following steps that S100, a precursor solution is prepared, specifically, a nitrogen-containing sulfur source compound, a transition metal cobalt compound and a transition metal molybdenum compound are jointly dissolved or dispersed in a first solvent, and a precursor solution is prepared; a uniform metal-sulfur coordination precursor solution is formed; s200, precursor curing: performing cryogenic freezing on the metal-sulfur coordination precursor solution, and then performing freeze drying to obtain a loose solid precursor; and S300, in-situ synthesis and compounding: carrying out one-step high-temperature heat treatment on the solid precursor in a protective gas atmosphere, and then cooling to room temperature to obtain the Co9S8 / MoS2 / CNTs ternary composite catalyst. The catalyst prepared by the preparation method is high in stability, good in catalytic performance, wide in pH application range and capable of being magnetically separated and recycled, and the efficiency of activating peroxymonosulfate to decompose organic pollutants is high.

Description

Technical Field

[0001] This application relates to the field of catalyst technology, and in particular to a Co9S8 / MoS2 / CNTs ternary composite catalyst and its preparation and application methods. Background Technology

[0002] Persulfate (PMS), as a highly efficient oxidant precursor, can generate reactive oxygen species (such as hydroxyl radicals and sulfate radicals) with strong oxidizing properties under ambient temperature and pressure conditions when activated by various heterogeneous catalysts. These strong oxidants can non-selectively attack and mineralize a variety of organic pollutants. Therefore, advanced oxidation processes based on persulfate show broad application prospects in wastewater treatment.

[0003] Nevertheless, the industrial application of this technology is still limited by catalyst performance. Currently, widely studied catalysts generally suffer from the following bottlenecks: first, insufficient catalytic efficiency and stability, resulting in limited PMS utilization and pollutant degradation rates; second, the effective pH window of the catalyst is usually narrow, making it difficult to cope with the fluctuating acidity and alkalinity of actual wastewater; third, solid-liquid separation is difficult, making catalyst recovery and recycling challenging, which not only increases treatment costs but may also cause secondary pollution. Therefore, developing a novel ternary composite catalyst that combines excellent conductivity and catalytic activity with a wide pH range, good stability, and magnetic separation and recovery capabilities has significant application value. Summary of the Invention

[0004] The purpose of this invention is to provide a Co9S8 / MoS2 / CNTs ternary composite catalyst and its preparation and application methods. The catalyst prepared by this method has high stability, good catalytic performance, wide pH range, magnetic separation and recovery, and high efficiency in decomposing organic pollutants by activating persulfate.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In a first aspect, embodiments of the present invention provide a method for preparing a Co9S8 / MoS2 / CNTs ternary composite catalyst, the preparation method comprising the following steps: S100, Precursor solution preparation: Nitrogen-sulfur source compound, transition metal cobalt compound and transition metal molybdenum compound are dissolved or dispersed together in a first solvent to form a homogeneous metal-sulfur coordination precursor solution. S200, Precursor solidification: The metal-sulfur coordination precursor solution is subjected to deep cryo-solidification, followed by freeze-drying to obtain a loose solid precursor; S300, In-situ Synthesis and Composite: The solid precursor is subjected to one-step high-temperature heat treatment in a protective gas atmosphere, and then cooled to room temperature to obtain a Co9S8 / MoS2 / CNTs ternary composite catalyst.

[0006] In some embodiments, after step S300, the following step is further included: S400, Post-processing: The catalyst is washed with a second solvent to remove impurities, and then dried and ground to obtain a powdered Co9S8 / MoS2 / CNTs ternary composite catalyst.

[0007] In some embodiments, during step S100, The nitrogen-containing sulfur source compound is one or more of the following: trithiocyanate, thiocyanate, thiourea, thioacetamide, and L-cysteine. The transition metal cobalt compound is one or more of cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, cobalt oxalate, and their hydrates; The transition metal molybdenum compound is one or more of ammonium molybdate, ammonium tetrathiomolybdate, sodium molybdate, molybdenum trioxide, and molybdenum hexacarbonyl.

[0008] In some embodiments, in step S100, the mass ratio of the transition metal cobalt compound, the transition metal molybdenum compound and the nitrogen-containing sulfur source compound is 1:(1~5):(10~30).

[0009] In some embodiments, in step S300 The high-temperature heat treatment is performed at a temperature of 700℃-900℃; and / or, The heating rate of the high-temperature heat treatment is 1℃ / min-15℃ / min; and / or, The holding time for the high-temperature heat treatment is 1 to 3 hours.

[0010] In some embodiments, prior to step S300, the following steps are further included: S301, the solid precursor mixture is ground to obtain precursor powder.

[0011] Secondly, embodiments of the present invention also provide a Co9S8 / MoS2 / CNTs ternary composite catalyst, which is prepared using the preparation method of the Co9S8 / MoS2 / CNTs ternary composite catalyst described above, wherein the catalyst comprises: Carbon nanotube framework; And Co9S8 nanoparticles and MoS2 nanosheets grown in situ on the carbon nanotube framework; Co9S8 and MoS2 are uniformly distributed on the carbon nanotube framework and form a composite interface with synergistic effect.

[0012] Thirdly, embodiments of the present invention also provide a method for applying the Co9S8 / MoS2 / CNTs ternary composite catalyst as described above, the method comprising: The Co9S8 / MoS2 / CNTs ternary composite catalyst was dispersed in wastewater containing organic pollutants and stirred until the Co9S8 / MoS2 / CNTs ternary composite catalyst and the organic pollutants reached an adsorption-desorption equilibrium state. Then, persulfate was added to degrade the organic pollutants.

[0013] In some embodiments, the pH value of the wastewater is 2-14; and / or, The organic pollutants are one or more of the following: organic dyes, antibiotics, organic pesticides, and food additives.

[0014] In some embodiments, the mass ratio of the Co9S8 / MoS2 / CNTs ternary composite catalyst to the persulfate is 1:1.5 to 1:16; and / or, The molar ratio of the organic pollutant to the persulfate is 1:1 to 20:1.

[0015] The present invention provides a Co9S8 / MoS2 / CNTs ternary composite catalyst, its preparation method, and its application method, which have the following beneficial effects: 1. Efficient and Simple Synthesis Method: This invention employs a one-step high-temperature pyrolysis carbonization synthesis strategy, utilizing nitrogen-containing sulfur source compounds as sulfur, carbon, and metal complexing agents simultaneously. During pyrolysis, in-situ growth of CNTs and in-situ sulfidation and composite formation of Co9S8 / MoS2 nanocrystals are achieved concurrently. This method is simple, with controllable conditions, and effectively suppresses the agglomeration and excessive growth of metal particles by utilizing the confinement effect of sulfur, thus successfully constructing a ternary composite catalyst with uniform structure and tight interfacial coupling.

[0016] 2. Unique Material Structure and Excellent Performance: In the Co9S8 / MoS2 / CNTs ternary composite catalyst prepared in this invention, Co9S8 and MoS2 are bridged by stable Co-Mo-S covalent bonds and uniformly loaded on the CNTs framework. This structure not only establishes a highly efficient electron transport channel, significantly improving catalytic activity, but also, due to the overall weak magnetic properties of the material, allows for convenient separation and recovery of the catalyst after use using an external magnetic field, greatly enhancing its practical application convenience and circular economy.

[0017] 3. Superior Catalytic Degradation Performance: The Co9S8 / MoS2 / CNTs ternary composite catalyst prepared in this invention achieves highly efficient degradation of various pollutants during the degradation of organic pollutants by activated persulfate through a non-radical pathway dominated by high-valence metal oxygen species, supplemented by a sulfate radical pathway. This dual-pathway synergistic mechanism endows the system with a wider pH range and stronger pollutant universality, achieving high removal efficiency at room temperature and exhibiting superior degradation performance and stability compared to traditional nano-metal catalysts and metal oxide catalysts under various water quality conditions. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in some embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual process of the method, etc. involved in the embodiments of this disclosure.

[0019] Figure 1 This is a characterization diagram of the Co9S8 / MoS2 / CNTs ternary composite catalyst in Example 1 of this invention; Figure 2 These are the X-ray diffraction pattern, X-ray photoelectron spectroscopy pattern, nitrogen adsorption-desorption isotherm diagram, and pore size distribution diagram of the Co9S8 / MoS2 / CNTs ternary composite catalyst in Example 1 of this invention. Figure 3 These are the Raman spectra and hysteresis loop diagrams of the Co9S8 / MoS2 / CNTs ternary composite catalyst in Example 1 of this embodiment. Figure 4 This is a performance diagram of the Co9S8 / MoS2 / CNTs ternary composite catalyst for catalytic reuse in Example 1. Figure 5 These are the electrochemical impedance spectra of Example 1 and Comparative Example 1; Figure 6 This is a graph showing the efficiency of catalyst activation of persulfate (eight systems) in the degradation of sulfamethoxazole in Example 1, Comparative Examples 1 to 7. Figure 7 This is a comparison chart of the efficiency of the Co9S8 / MoS2 / CNTs ternary composite catalyst in activating the persulfate system under different conditions (initial concentration of sulfamethoxazole, concentration of persulfate, amount of catalyst added, reaction temperature, inorganic anions in water, background of natural organic matter, and pH value of water) in Example 1 of this invention. Figure 8This is a graph showing the efficiency of the Co9S8 / MoS2 / CNTs / PMS system in this Example 1 in degrading organic pollutants. Detailed Implementation

[0020] The technical solutions in some embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments provided in this disclosure are within the scope of protection of this disclosure.

[0021] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0022] Unless otherwise stated, all raw materials and reagents used in the embodiments of this application were obtained through commercial purchase or synthesized using conventional methods existing in the art. Unless otherwise stated, all experimental methods in the embodiments of this application are conventional methods.

[0023] This invention provides a method for preparing a Co9S8 / MoS2 / CNTs ternary composite catalyst, the preparation method including steps S100~S300.

[0024] S100, Precursor Solution Preparation: Nitrogen-containing sulfur source compound, transition metal cobalt compound and transition metal molybdenum compound are dissolved or dispersed together in a first solvent to form a homogeneous metal-sulfur coordination precursor solution.

[0025] In step S100, the abundant amino / thiol functional groups of nitrogen-containing sulfur source compounds (such as trithiocyanate, thiourea, etc.) are used in conjunction with Co. 2+ Mo 6+ The transition metal ions undergo coordination chelation. The total concentration of transition metal ions should not be too low or too high. If the concentration is too low, the yield will be insufficient and it will not be conducive to the formation of a continuous framework; if the concentration is too high, it will easily lead to excessive crystal growth or precipitation, which will destroy the homogeneous system. In addition, the stirring time is preferably 30 minutes to ensure that the coordination reaction reaches equilibrium and forms a homogeneous metal-sulfur coordination precursor solution.

[0026] S200, Precursor solidification: The metal-sulfur coordination precursor solution is subjected to deep cryo-solidification, followed by freeze-drying to obtain a loose solid precursor.

[0027] In step S200, the precursor solidification employs a "pre-freeze-sublimation" strategy. First, the precursor solution is cryogenically solidified using liquid nitrogen or an ultra-low temperature freezer (-40°C to -80°C). This process effectively "locks" the metal-organic complex molecules in situ within the solvent lattice interstices, suppressing solute migration and segregation during the phase transition. Subsequently, freeze-drying is performed for 36-48 hours under a vacuum of less than 10 Pa. Sublimation drying not only completely preserves the component dispersion in the liquid phase but also endows the solid precursor with a loose and porous microstructure, providing the necessary physical space for gas release during subsequent pyrolysis and the confined growth of nanostructures.

[0028] S300, In-situ Synthesis and Composite: The solid precursor is subjected to one-step high-temperature heat treatment in a protective gas atmosphere, and then cooled to room temperature to obtain a Co9S8 / MoS2 / CNTs ternary composite catalyst.

[0029] In step S300, in-situ synthesis and composite formation are carried out under high-temperature pyrolysis conditions (700℃-900℃, preferably 800℃), which is a key step in constructing the ternary composite structure. Under a protective atmosphere (50-200 sccmAr / N2), multiple in-situ chemical transformations occur within the system: on the one hand, active sulfur species generated from the pyrolysis of nitrogen-containing sulfur sources react with metal ions to generate Co9S8 and MoS2 crystals in situ; on the other hand, carbon-containing organic fragments generated from pyrolysis serve as carbon sources, and under the catalysis of Co / Mo metal species, a high aspect ratio CNT framework is grown in situ following a "tip growth" mechanism, constructing a three-dimensional conductive network. Thanks to the "confinement effect" of carbon nanotube growth and the "pinning effect" of the carbon substrate on the metal particles, Co9S8 and MoS2 avoid high-temperature sintering and agglomeration, but are firmly anchored on the CNT surface at the nanoscale, forming abundant Co9S8 / MoS2 heterojunction interfaces. This close interfacial contact not only induces lattice distortion, but also effectively optimizes the electronic structure of the metal center through electron cloud rearrangement.

[0030] After step S300, step S400 is also included.

[0031] S400, post-processing: The catalyst is washed with a second solvent to remove impurities, and then dried and ground to obtain powdered Co9S8 / MoS2 / CNTs ternary composite catalyst.

[0032] In step S400, the post-treatment process aims to remove unstable impurities by acid etching and further expose deep active sites, thereby obtaining highly active Co9S8 / MoS2 / CNTs ternary composite catalyst powder.

[0033] In step S100, the nitrogen-containing sulfur source compound is one or more of trithiocyanate, thiocyanate, thiourea, thioacetamide, and L-cysteine; the transition metal cobalt compound is one or more of cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, cobalt oxalate, and their hydrates; and the transition metal molybdenum compound is one or more of ammonium molybdate, ammonium tetrathiomolybdate, sodium molybdate, molybdenum trioxide, and molybdenum hexacarbonyl.

[0034] In step S100, the mass ratio of the transition metal cobalt compound, the transition metal molybdenum compound, and the nitrogen-containing sulfur source compound is 1:(1~5):(10~30).

[0035] In step S300, the temperature of the high-temperature heat treatment is 700℃-900℃; and / or, the heating rate of the high-temperature heat treatment is 1℃ / min-15℃ / min; and / or, the holding time of the high-temperature heat treatment is 1 hour to 3 hours.

[0036] Before step S300, the following step is also included: S301, grinding the solid precursor mixture to obtain precursor powder.

[0037] This invention also provides a Co9S8 / MoS2 / CNTs ternary composite catalyst, which is prepared by the Co9S8 / MoS2 / CNTs ternary composite catalyst preparation method described above. The catalyst includes: a carbon nanotube framework, and Co9S8 nanoparticles and MoS2 nanosheets grown in situ on the carbon nanotube framework.

[0038] Co9S8 and MoS2 are uniformly distributed on the carbon nanotube framework and form a composite interface with synergistic effect.

[0039] This invention also provides a method for applying the Co9S8 / MoS2 / CNTs ternary composite catalyst as described above, the method comprising: The Co9S8 / MoS2 / CNTs ternary composite catalyst was dispersed in wastewater containing organic pollutants and stirred until the Co9S8 / MoS2 / CNTs ternary composite catalyst and organic pollutants reached an adsorption-desorption equilibrium state. Then, persulfate was added to degrade the organic pollutants.

[0040] In some embodiments, the pH value of the wastewater is 2 to 14.

[0041] For example, the pH of the wastewater can be 3, 5, 7, 9, 11, or 14. Thanks to the structural stability of the Co9S8 / MoS2 heterojunction and the protective effect of the CNT framework, this catalyst maintains excellent structural integrity and electron transfer efficiency over a wide pH range. This overcomes the limitation of traditional Fenton reactions requiring strict control of the acidic environment (around pH 3.0), ensuring efficient catalysis of persulfate to generate free radicals even in alkaline or complex water bodies, thus achieving full mineralization of organic pollutants.

[0042] In some embodiments, the organic pollutant is one or more of the following: organic dyes, antibiotics, organic pesticides, and food additives.

[0043] For example, organic pollutants include sulfamethoxazole (SMX), phenol (PE), bisphenol A (BPA), p-nitrophenol (4-NP), rhodamine B (RhB), and methylene blue (MB). Therefore, this Co9S8 / MoS2 / CNTs ternary composite catalyst can be used to catalyze the decomposition of organic pollutants by persulfate, and it decomposes a wide variety of organic pollutants, thus having broad application prospects.

[0044] In some embodiments, the mass ratio of the Co9S8 / MoS2 / CNTs ternary composite catalyst to persulfate is 1:1.5 to 1:16; and / or, the molar ratio of organic pollutants to persulfate is 1:1 to 20:1. By optimizing the dosage ratio of catalyst to persulfate, the reaction rate and economic cost can be balanced. If there is too little persulfate, degradation will be incomplete; if there is too much persulfate, a self-quenching effect (self-consumption) will occur. The above ratio range ensures that the catalyst fully activates the persulfate, while maximizing the use of the free radicals generated by the persulfate to decompose pollutant molecules.

[0045] The technical solution of this application will be further described below with reference to the embodiments and accompanying drawings.

[0046] Example 1 Example 1 of this invention discloses a method for preparing a Co9S8 / MoS2 / CNTs ternary composite catalyst, the preparation method including steps S100~S400.

[0047] S100, preparation of precursor solution: Place 4g of trithiocyanate, 0.25g of cobalt nitrate hexahydrate and 0.8g of ammonium molybdate tetrahydrate in a 250mL glass beaker, add 40mL of deionized water, sonicate for 1 minute, and then magnetically stir at 510rpm for 30 minutes until a homogeneous metal-sulfur coordination precursor solution is formed.

[0048] S200, Precursor solidification: The obtained metal-sulfur coordination precursor solution was transferred to a plastic petri dish and placed in a liquid nitrogen environment for deep freezing, causing the suspension to freeze and solidify. The sample was then transferred to a vacuum freeze dryer and freeze-dried for 48 hours to completely remove moisture, obtaining a loose and porous solid precursor.

[0049] S301, Grinding: The above solid precursor is placed in a mortar and ground thoroughly to obtain a fine precursor powder with uniform particles.

[0050] S300, In-situ Synthesis and Composite Process: A suitable amount of precursor powder was weighed and placed in a covered quartz boat, which was then transferred to the isothermal heating zone of a tube furnace. A one-step high-temperature pyrolysis was performed under a protective atmosphere such as argon or nitrogen. The temperature was programmed to rise to 800℃ at a rate of 10℃ / min and held at this temperature for 2 hours for calcination. After the reaction, the furnace was allowed to cool naturally to room temperature to obtain the preliminarily synthesized Co9S8 / MoS2 / CNTs ternary composite catalyst.

[0051] S400, Post-treatment: The pyrolysis products were acid-etched with a 1 mol / L sulfuric acid solution for 6 hours to remove unstable impurities. After etching, the catalyst was washed repeatedly with deionized water 2-3 times until the filtrate was neutral. Finally, the sample was freeze-dried for 24 hours and then lightly ground to obtain the desired powdered Co9S8 / MoS2 / CNTs ternary composite catalyst.

[0052] This embodiment also discloses a method for applying the Co9S8 / MoS2 / CNTs ternary composite catalyst, which is as follows: Add 100 mL of 25 μM sulfamethoxazole (SMX) solution to a 250 mL glass beaker and place the glass beaker on a magnetic stirrer and stir at a speed of 510 rpm. Weigh 4 mg of the above Co9S8 / MoS2 / CNTs ternary composite catalyst using an analytical balance and add it to the above sulfamethoxazole solution. Sonicate for 1 min to disperse the Co9S8 / MoS2 / CNTs ternary composite catalyst evenly. Stir for 30 min to allow the Co9S8 / MoS2 / CNTs ternary composite catalyst and sulfamethoxazole molecules to reach an adsorption-desorption equilibrium state. Add 15.4 mg of persulfate powder to a mixed solution of Co9S8 / MoS2 / CNTs ternary composite catalyst and sulfamethoxazole to initiate the oxidative degradation reaction. At a predetermined time point, take out 1.5 mL of the reaction solution and add 50 μL of dimethyl sulfoxide (DMSO) to terminate the reaction. The solution after the reaction was filtered and the residual concentration of sulfamethoxazole was tested by high performance liquid chromatography to determine the removal effect.

[0053] like Figure 1 As shown, Figure 1 This is a characterization diagram of the Co9S8 / MoS2 / CNTs ternary composite catalyst, in which... Figure 1 Image a is a scanning electron microscope image of the catalyst, which shows that the catalyst is a nanoscale material, a highly porous three-dimensional network structure composed of many multi-walled bamboo-like carbon nanotubes. These carbon nanotubes are interconnected and serve as a carrier for cobalt octasulfide particles and molybdenum disulfide nanosheets, while providing abundant development space and more active sites. Figure 1 b is a transmission electron microscope image of the catalyst, from... Figure 1 b and Figure 1 In step c, we can further understand the composition and microstructure of the catalyst, and see that the cobalt octasulfide nanoparticles, molybdenum disulfide nanosheets and carbon nanotubes are well coupled. Figure 1 d. The sheet structure of molybdenum disulfide nanosheets (sheet side) can be observed. Figure 1 Image e is a high-resolution transmission electron microscope image of the catalyst, showing cobalt octasulfide nanoparticles encapsulated within the carbon nanotube walls. Figure 1 e is a low-resolution high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of the catalyst, which also shows that Co9S8 / MoS2 / CNTs are well combined, indicating the successful synthesis of Co9S8 / MoS2 / CNTs.

[0054] Combination Figure 2 As shown, Figure 2 a is the X-ray diffraction pattern of the Co9S8 / MoS2 / CNTs ternary composite catalyst, derived from... Figure 2 As can be seen from this, the diffraction peaks of Co9S8 / MoS2 / CNTs are sharp, with high intensity and almost no impurity peaks, indicating high crystallinity and a relatively complete crystal structure. They match well with the standard card characteristics of Co9S8 and MoS2, indicating that the Co9S8 / MoS2 / CNTs material was successfully prepared, and the introduction of carbon nanotubes does not change the crystal structure of cobalt octasulfide and molybdenum disulfide. Figure 2 b is the X-ray photoelectron spectrum of the Co9S8 / MoS2 / CNTs ternary composite catalyst, which further confirms that sulfur has entered the interlayer structure of carbon nanotubes and has indeed been doped into the carbon nanotube structure, forming Co-Mo-S covalent bridges inside the Co9S8 / MoS2 / CNTs ternary composite catalyst structure. Figure 2 c and Figure 2 d represents the nitrogen adsorption-desorption isotherm and pore size distribution diagram of the Co9S8 / MoS2 / CNTs ternary composite catalyst, respectively. Figure 2 c and Figure 2As shown in d, the adsorption isotherm of this catalyst exhibits an H3-type hysteresis loop, which is consistent with the characteristics of a type IV adsorption isotherm. It has a porous structure of mesoporous / mesoporous parts, which is conducive to exposing more active sites and promoting the diffusion of active species during the reaction. This proves that the Co9S8 / MoS2 / CNTs ternary composite catalyst is very suitable for catalytic applications.

[0055] Figure 3 a represents the Raman spectrum of the Co9S8 / MoS2 / CNTs ternary composite catalyst, derived from... Figure 3 The observation of typical 2H-MoS2 Raman peaks demonstrates the excellent chemical and physical stability of this catalyst. The strong covalent nature of the Mo-S bond allows MoS2 to act as a stabilizing support, enhancing the strong interaction at the Co-S-Mo interface and inhibiting the aggregation or loss of active components. D / I G A ratio greater than 1 indicates that the catalyst has abundant defect structures. Figure 3 b represents the hysteresis loop of the Co9S8 / MoS2 / CNTs ternary composite catalyst, proving that the catalyst is a soft magnetic material with a saturation magnetization of 0.6 emu / g. The catalyst can be recycled by placing it in an external magnet for a period of time, which can effectively avoid catalyst loss and secondary pollution.

[0056] In summary, the preparation method provided in Example 1 successfully synthesized a Co9S8 / MoS2 / CNTs ternary composite catalyst, and the Co-Mo-S covalent bridge formed inside the structure can serve as a highly efficient electron transport channel, generating a synergistic effect, thereby exhibiting excellent catalytic activity.

[0057] Furthermore, controlling the reaction time to be constant (15 min), the recyclability of the catalyst in the degradation of sulfamethoxazole by activated persulfate was studied. Before reuse, the Co9S8 / MoS2 / CNTs ternary composite catalyst after the above reaction was washed with methanol and deionized water and then added to the next round of reaction. The results are as follows. Figure 4 As shown, the Co9S8 / MoS2 / CNTs ternary composite catalyst still exhibits high catalytic activity after being reused 5 times, and the removal rate of sulfamethoxazole in the reaction system is still greater than 90%, indicating that the Co9S8 / MoS2 / CNTs ternary composite catalyst has good reusability.

[0058] Comparative Example 1 Comparative Example 1 discloses a method for preparing a composite catalyst. The difference between this method and the method for preparing the ternary composite catalyst in Example 1 is that ammonium molybdate tetrahydrate is not added. Specifically, 4g of trithiocyanate and 0.25g of cobalt nitrate hexahydrate are placed in a 250mL glass beaker, followed by the addition of 40mL of deionized water. The mixture is ultrasonically dispersed for 1 minute, then magnetically stirred at 510rpm for 30 minutes until a homogeneous metal-sulfur coordination precursor solution is formed. Subsequent processing is the same as in Example 1, ultimately yielding the target composite catalyst, denoted as Co@CNTs.

[0059] Comparative Example 2 Comparative Example 2 discloses a method for preparing a composite catalyst, which differs from the method for preparing the ternary composite catalyst in Example 1 in that cobalt nitrate hexahydrate is not added. Specifically, 4g of trithiocyanate and 0.8g of ammonium molybdate tetrahydrate are placed in a 250mL glass beaker, followed by the addition of 40mL of deionized water. The mixture is ultrasonically dispersed for 1 minute, then magnetically stirred at 510rpm for 30 minutes until a homogeneous metal-sulfur coordination precursor solution is formed. Subsequent processing is the same as in Example 1, ultimately yielding the target composite catalyst, denoted as MoS2 / CNTs.

[0060] Comparative Example 3 Comparative Example 3 discloses a method for preparing a ternary composite catalyst. The difference between this method and the method in Example 1 is that the mass of ammonium molybdate tetrahydrate is adjusted to 0.4 g. Specifically, 4 g of trithiocyanate, 0.25 g of cobalt nitrate hexahydrate, and 0.4 g of ammonium molybdate tetrahydrate are placed in a 250 mL glass beaker, and 40 mL of deionized water is added. The mixture is ultrasonically dispersed for 1 minute, and then magnetically stirred at 510 rpm for 30 minutes until a homogeneous metal-sulfur coordination precursor solution is formed. Subsequent processing is the same as in Example 1, ultimately yielding the target composite catalyst, denoted as CoMo-400 / CNTs.

[0061] Comparative Example 4 Comparative Example 4 discloses a method for preparing a ternary composite catalyst. The difference between this method and the method in Example 1 is that the mass of ammonium molybdate tetrahydrate is adjusted to 0.6 g. Specifically, 4 g of trithiocyanate, 0.25 g of cobalt nitrate hexahydrate, and 0.6 g of ammonium molybdate tetrahydrate are placed in a 250 mL glass beaker, and 40 mL of deionized water is added. The mixture is ultrasonically dispersed for 1 minute, and then magnetically stirred at 510 rpm for 30 minutes until a homogeneous metal-sulfur coordination precursor solution is formed. Subsequent processing is the same as in Example 1, ultimately yielding the target composite catalyst, denoted as CoMo-600 / CNTs.

[0062] Comparative Example 5 Comparative Example 5 discloses a method for preparing a ternary composite catalyst. The difference between this method and the method in Example 1 is that the mass of ammonium molybdate tetrahydrate is adjusted to 1.0 g. Specifically, 4 g of trithiocyanate, 0.25 g of cobalt nitrate hexahydrate, and 1.0 g of ammonium molybdate tetrahydrate are placed in a 250 mL glass beaker, and 40 mL of deionized water is added. The mixture is ultrasonically dispersed for 1 minute, and then magnetically stirred at 510 rpm for 30 minutes until a homogeneous metal-sulfur coordination precursor solution is formed. Subsequent processing is the same as in Example 1, ultimately yielding the target composite catalyst, denoted as CoMo-1000 / CNTs.

[0063] Comparative Example 6 Comparative Example 6 discloses a method for applying a ternary composite catalyst, which differs from the method for applying the ternary composite catalyst in Example 1 in that: no persulfate is added, that is, the physical adsorption of sulfamethoxazole is used alone by the Co9S8 / MoS2 / CNTs ternary composite catalyst.

[0064] Comparative Example 7 Comparative Example 7 discloses a method for decomposing sulfamethoxazole using persulfate. The difference between this method and the method using the ternary composite catalyst in Example 1 is that the Co9S8 / MoS2 / CNTs ternary composite catalyst is not added; that is, persulfate is used alone to degrade sulfamethoxazole.

[0065] like Figure 5 As shown, Figure 5 The images show the electrochemical impedance spectroscopy (EIS) spectra of the two composite catalysts (Co9S8 / MoS2 / CNTs catalyst and Co@CNTs catalyst) prepared in Example 1 and Comparative Example 1. Figure 5 In the high-frequency region, both the Co9S8 / MoS2 / CNTs and Co@CNTs curves exhibit a semi-circular arc. Compared to Co@CNTs, Co9S8 / MoS2 / CNTs has a smaller semi-circular diameter, demonstrating that the addition of MoS2 enhances the charge transfer capability and ion reaction frequency of the composite material. Co9S8 / MoS2 / CNTs also exhibits lower charge transfer resistance, higher charge kinetics, faster ion diffusion rate, and higher electron mobility, consistent with optimal catalyst performance.

[0066] Figure 6 This is a graph showing the efficiency of activated persulfate (eight systems) in degrading and removing sulfamethoxazole, prepared in Examples 1, 1 to 7. Figure 6It can be seen that, in Comparative Example 6, where Co9S8 / MoS2 / CNTs catalyst is used alone without adding persulfate, the adsorption contribution of Co9S8 / MoS2 / CNTs catalyst to the removal of sulfamethoxazole is negligible. In Comparative Example 7, where sulfamethoxazole is degraded solely by persulfate without adding the Co9S8 / MoS2 / CNTs catalyst, the persulfate does not decompose spontaneously to generate active species leading to the removal of sulfamethoxazole. However, the six composite catalysts used in Example 1 and Comparative Examples 1 to 5 all demonstrated to some extent the performance of activating persulfate to degrade and remove sulfamethoxazole. Among them, the Co9S8 / MoS2 / CNTs catalyst exhibited the best catalytic performance, achieving a 100% removal rate of sulfamethoxazole within 7 minutes, indicating that the Co9S8 / MoS2 / CNTs catalyst has a significant advantage in activating persulfate.

[0067] like Figure 7 As shown, Figure 7 This is a comparison of the efficiency of the Co9S8 / MoS2 / CNTs ternary composite catalyst in activating the persulfate system under different conditions in Example 1 for degrading sulfamethoxazole. Figure 7 It can be seen that the initial concentration of sulfamethoxazole, the concentration of persulfate, the amount of catalyst added, the reaction temperature, the background of inorganic anions in the water, the natural organic matter, and the pH value of the water all have a certain influence on the degradation performance of the system. Figure 7 By adjusting the initial concentration of sulfamethoxazole, it was observed that within a unit time, the concentration ranged from 12.5 to 50 μmol·L⁻¹. -1 The removal rate of sulfamethoxazole reached over 95%, indicating that the surface of the Co9S8 / MoS2 / CNTs ternary composite catalyst has sufficient active sites to adsorb sulfamethoxazole and accelerate the reaction. Figure 7 b indicates that as the concentration of persulfate increases, the Co9S8 / MoS2 / CNTs catalyst and persulfate have more complete contact, which promotes the activation of persulfate and can generate more active species to accelerate the oxidation of sulfamethoxazole. Figure 7 c indicates that the number of available adsorption and active sites increases with the increase of catalyst dosage. Increasing the dosage will result in higher activation efficiency of persulfate and will also accelerate the oxidation rate. Figure 7 d means that the reaction is more favorable as the temperature increases, because high temperature can increase the speed of intermolecular movement. Figure 7 e indicates that substances such as Cl⁻ and HA can quench free radicals or occupy active sites, thereby inhibiting the reaction; while HCO₃ - and H2PO4 - By adjusting the reaction environment and promoting free radical generation, the degradation efficiency of sulfamethoxazole was significantly improved. Figure 7f indicates that it can effectively degrade sulfamethoxazole in a pH range of 3 to 9, especially at pH > 3, the degradation rate is faster, showing excellent wide pH adaptability. This is due to the synergistic effect between the components of the catalyst, which promotes the valence state cycle and regeneration of the active center.

[0068] Figure 8 This is a graph showing the efficiency of the Co9S8 / MoS2 / CNTs / PMS system in Example 1 in degrading organic pollutants. Figure 8 The Co9S8 / MoS2 / CNTs / PMS system demonstrated that it achieved a removal rate of over 95% for various target pollutants (including dyes, phenols, and antibiotics) within 15 minutes, showcasing its excellent broad-spectrum degradation capability and universal applicability.

[0069] The foregoing has provided a detailed description of a Co9S8 / MoS2 / CNTs ternary composite catalyst, its preparation method, and its application method, as disclosed in the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the Co9S8 / MoS2 / CNTs ternary composite catalyst, its preparation method, its application method, and its core ideas. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a Co9S8 / MoS2 / CNTs ternary composite catalyst, characterized in that, The preparation method includes the following steps: S100, Precursor solution preparation: Nitrogen-sulfur source compound, transition metal cobalt compound and transition metal molybdenum compound are dissolved or dispersed together in a first solvent to form a homogeneous metal-sulfur coordination precursor solution. S200, Precursor solidification: The metal-sulfur coordination precursor solution is subjected to deep cryo-solidification, followed by freeze-drying to obtain a loose solid precursor; S300, In-situ Synthesis and Composite: The solid precursor is subjected to one-step high-temperature heat treatment in a protective gas atmosphere, and then cooled to room temperature to obtain a Co9S8 / MoS2 / CNTs ternary composite catalyst.

2. The preparation method according to claim 1, characterized in that, Following step S300, the following steps are also included: S400, Post-processing: The catalyst is washed with a second solvent to remove impurities, and then dried and ground to obtain a powdered Co9S8 / MoS2 / CNTs ternary composite catalyst.

3. The preparation method according to claim 1, characterized in that, In step S100, The nitrogen-containing sulfur source compound is one or more of the following: trithiocyanate, thiocyanate, thiourea, thioacetamide, and L-cysteine. The transition metal cobalt compound is one or more of cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, cobalt oxalate, and their hydrates; The transition metal molybdenum compound is one or more of ammonium molybdate, ammonium tetrathiomolybdate, sodium molybdate, molybdenum trioxide, and molybdenum hexacarbonyl.

4. The preparation method according to claim 1, characterized in that, In step S100, the mass ratio of the transition metal cobalt compound, the transition metal molybdenum compound and the nitrogen-containing sulfur source compound is 1:(1~5):(10~30).

5. The preparation method according to claim 1, characterized in that, In step S300, The high-temperature heat treatment is performed at a temperature of 700℃-900℃; and / or, The heating rate of the high-temperature heat treatment is 1℃ / min-15℃ / min; and / or, The holding time for the high-temperature heat treatment is 1 to 3 hours.

6. The preparation method according to claim 1, characterized in that, Prior to step S300, the following steps are also included: S301, the solid precursor mixture is ground to obtain precursor powder.

7. A Co9S8 / MoS2 / CNTs ternary composite catalyst, prepared by the method for preparing the Co9S8 / MoS2 / CNTs ternary composite catalyst as described in any one of claims 1-6, characterized in that, The catalyst includes: Carbon nanotube framework; And Co9S8 nanoparticles and MoS2 nanosheets grown in situ on the carbon nanotube framework; Co9S8 and MoS2 are uniformly distributed on the carbon nanotube framework and form a composite interface with synergistic effect.

8. A method for applying the Co9S8 / MoS2 / CNTs ternary composite catalyst as described in claim 7, characterized in that, The application method includes: The Co9S8 / MoS2 / CNTs ternary composite catalyst was dispersed in wastewater containing organic pollutants and stirred until the Co9S8 / MoS2 / CNTs ternary composite catalyst and the organic pollutants reached an adsorption-desorption equilibrium state. Then, persulfate was added to degrade the organic pollutants.

9. The application method as described in claim 8, characterized in that, The pH value of the wastewater is 2-14; and / or, The organic pollutants are one or more of the following: organic dyes, antibiotics, organic pesticides, and food additives.

10. The application method as described in claim 8, characterized in that, The mass ratio of the Co9S8 / MoS2 / CNTs ternary composite catalyst to the persulfate is 1:1.5 to 1:16; and / or, The molar ratio of the organic pollutant to the persulfate is 1:1 to 20:1.

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