A ferrous sulfide composite catalyst and a method for preparing the same

Abstract

The application discloses a ferrous sulfide composite catalyst and a preparation method thereof. The ferrous sulfide composite catalyst comprises a nitrogen-doped carbon layer, and ferrous sulfide nanoparticles are loaded on the nitrogen-doped carbon layer. The preparation method comprises the following steps: mixing iron chloride and ethanol, adding thiourea and o-phenanthroline, stirring, obtaining a precursor dispersion, mixing with melamine, stirring, drying, and obtaining a precursor powder; and calcining the precursor powder, acid washing, and obtaining the ferrous sulfide composite catalyst. The ferrous sulfide composite catalyst has the advantages of excellent catalytic activity, strong stability and the like, can effectively activate an oxidant, a system constructed by the ferrous sulfide composite catalyst can quickly generate a large amount of active species, is favorable for quickly and completely degrading refractory organic pollutants in wastewater, and has high use value and good application prospect. The preparation method also has the advantages of simple process, convenient operation, low cost and the like, and can realize large-scale production and be favorable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous catalysis technology and functional materials, and relates to a ferrous sulfide composite catalyst and its preparation method. Background Technology

[0002] As an emerging advanced oxidation process (AOPs), the advanced oxidation system constructed by catalyst-activated oxidants (such as persulfate and hydrogen peroxide) has become a research hotspot due to the advantages of the active species produced, such as strong oxidizing power and good environmental tolerance. Among these, obtaining a low-cost, efficient and stable catalyst is crucial for effectively activating oxidants and promoting the widespread application of AOPs systems in actual water bodies.

[0003] Among various catalysts, heterogeneous metal catalysts have the advantages of simple synthesis methods, high catalytic efficiency, and low metal leaching rate, and can comprehensively meet the above requirements. Among them, iron nanoparticle / supported composite catalysts have been the most studied and used. However, when existing iron nanoparticle / supported composite catalysts are used to activate oxidants such as persulfate (PMS), the low conversion rate between metals of different valence states and the high activation energy barrier of the oxidant (especially the short peroxy bond in PMS) are significant challenges. The relatively high activation energy barrier of iron nanoparticles (FeMS) makes it difficult for existing catalysts to effectively activate oxidants, resulting in low production amounts and rates of various strongly oxidizing active species. Furthermore, existing iron nanoparticle / support composite catalysts suffer from poor structural stability, leading to the easy detachment of active components from the support into the degradation system during use, potentially causing secondary pollution. These shortcomings hinder the widespread application of existing iron nanoparticle / support composite catalysts in advanced oxidation technologies, consequently limiting the application of these technologies in treating recalcitrant organic pollutant wastewater. Therefore, obtaining a ferrous sulfide composite catalyst with strong catalytic activity and good stability is crucial for improving the activation effect of oxidants (such as PMS) and promoting the widespread application of advanced oxidation technologies. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a ferrous sulfide composite catalyst with strong catalytic activity and good stability. It also provides a method for preparing the ferrous sulfide composite catalyst that is simple in process, convenient in operation and low in cost.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A ferrous sulfide composite catalyst, comprising a nitrogen-doped carbon layer on which ferrous sulfide nanoparticles are loaded.

[0007] In a further improvement of the above-mentioned ferrous sulfide composite catalyst, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles in the ferrous sulfide composite catalyst is 5 to 50:1.

[0008] In a further improvement of the aforementioned ferrous sulfide composite catalyst, the mass fraction of nitrogen in the nitrogen-doped carbon layer is 22.85%.

[0009] As a general technical concept, the present invention also provides a method for preparing a ferrous sulfide composite catalyst, comprising the following steps:

[0010] S1. Mix ferric chloride with ethanol, add thiourea and o-phenanthroline, stir to obtain a precursor dispersion;

[0011] S2. Mix the precursor powder with melamine, stir, and dry to obtain the precursor powder.

[0012] S3. The precursor powder is calcined and acid-washed to obtain ferrous sulfide composite catalyst.

[0013] In a further improvement to the above preparation method, in step S1, the mass ratio of ferric chloride to ethanol is 1:80-100; the mass ratio of thiourea to ethanol is 1:100-120; and the mass ratio of o-phenanthroline to ethanol is 1:30-50.

[0014] In a further improvement to the above preparation method, in step S2, the mass-to-volume ratio of melamine to precursor liquid is 50g to 150g: 1L.

[0015] In a further improvement to the above preparation method, the stirring time in step S1 is 5 min to 15 min;

[0016] In a further improvement to the above preparation method, in step S2, the stirring temperature is 20℃~40℃; the stirring time is 2h~4h; the drying is carried out under vacuum conditions; the drying temperature is 60℃~100℃; and the drying time is 10h~15h.

[0017] In a further improvement to the above preparation method, in step S3, the calcination is carried out under a protective atmosphere; the protective atmosphere is an argon atmosphere; the calcination involves first heating the precursor powder to 600℃ and holding it at that temperature for 1 to 3 hours, then heating it to 800℃ and holding it at that temperature for 1 to 3 hours; the heating rate during the calcination process is 2 to 10℃ / min; the acid solution used in the acid washing process is a sulfuric acid solution; the concentration of the acid solution is 80 to 100 g / L; the acid washing time is 10 to 18 hours; after the acid washing is completed, the following step is also included: drying the acid-washed product under vacuum conditions; the drying temperature is 60℃ to 100℃; the drying time is 10 to 15 hours.

[0018] In a further improvement to the above preparation method, the ferrous sulfide composite catalyst includes a nitrogen-doped carbon layer on which ferrous sulfide nanoparticles are loaded.

[0019] In a further improvement to the above preparation method, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles in the ferrous sulfide composite catalyst is 5 to 50:1.

[0020] In a further improvement to the above preparation method, the mass fraction of nitrogen in the nitrogen-doped carbon layer is 22.85%.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] (1) This invention provides a ferrous sulfide composite catalyst, comprising a nitrogen-doped carbon layer on which ferrous sulfide nanoparticles are loaded. On the one hand, the nitrogen-doped carbon layer has a two-dimensional layered structure, which can not only effectively disperse and encapsulate the ferrous sulfide nanoparticles, reducing metal aggregation and leaching, but also provide sufficient surface area for the adsorption of pollutants and oxidants (such as PMS). On the other hand, the surface of the ferrous sulfide crystals exposes a large number of unsaturated metal sites, which can be used to activate oxidants. Based on this, the electron-rich S atoms in the ferrous sulfide nanoparticles can provide electrons during the activation process of the oxidant, thereby changing the valence state of Fe and enhancing the binding ability of Fe sites with oxidants, thus producing excellent catalytic activity. It can be seen that the introduction of S atoms realizes the charge regulation of the metal active center, which can effectively enhance the interaction between the metal and the oxidant (especially PMS), and ultimately improve the catalytic activity. The ferrous sulfide composite catalyst of this invention has the advantages of excellent catalytic activity and strong stability. It is a new type of high-efficiency Fenton-like catalyst that can effectively activate oxidants. The constructed system can rapidly generate a large number of active species, which is conducive to the rapid and thorough degradation of recalcitrant organic pollutants (such as antibiotics) in wastewater. It has high application value and good application prospects.

[0023] (2) In the ferrous sulfide composite catalyst of the present invention, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles is 5 to 50:1. By optimizing the mass ratio of the two, the ferrous sulfide nanoparticles can be moderately dispersed on the nitrogen-doped carbon layer, maximizing the use of the carrier dispersion effect of the nitrogen-doped carbon layer, which is more conducive to improving the catalytic activity of the ferrous sulfide composite catalyst.

[0024] (3) This invention also provides a method for preparing a ferrous sulfide composite catalyst, using ferric chloride as the iron source, thiourea as the sulfur source and complexing agent, o-phenanthroline as the auxiliary complexing agent, and melamine as the carbon source and nitrogen source. The iron source and sulfur source are first mixed with the complexing agent, and then calcined to prepare a ferrous sulfide composite catalyst with excellent catalytic activity and strong stability. Compared with other sulfur sources, in this invention, thiourea is both a sulfur source and a complexing agent. Through a complexation reaction with iron ions, it facilitates the doping of sulfur during the formation of iron particles, thus forming ferrous sulfide nanoparticles instead of zero-valent iron particles. Simultaneously, under the promoting effect of o-phenanthroline, the iron ions can be dispersed by utilizing the complexation between o-phenanthroline and iron ions. Therefore, nano-sized ferrous sulfide anchored on a nitrogen-doped carbon layer can be obtained through a simple one-step pyrolysis and acid washing, exhibiting not only good dispersibility but also firm anchorage on the nitrogen-doped carbon layer. Furthermore, the method for preparing the ferrous sulfide composite catalyst in this invention has advantages such as simple process, convenient operation, and low cost. It also requires minimal equipment, exhibits strong repeatability, and can achieve large-scale production, which is beneficial for industrial application. In contrast, using ferric nitrate as the iron source does not yield catalysts with excellent catalytic performance.

[0025] (4) In the preparation method of the ferrous sulfide composite catalyst of the present invention, the precursor powder is first heated to 600°C and kept at the temperature for 1 to 3 hours. During this process, melamine condenses to form g-C3N4. At this stage, the carbon-nitrogen support will be initially formed and achieve preliminary dispersion and encapsulation of the metal particles. Then, the temperature is raised to 800°C and kept at the temperature for 1 to 3 hours. During this process, ferric iron is reduced to ferrous iron at high temperature and ferrous sulfide particles are formed simultaneously. In addition, the carbon-nitrogen support will also be formally formed at this stage and simultaneously encapsulate and fix the formed nanoparticles. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0027] Figure 1 This is a process flow diagram of the preparation of the ferrous sulfide composite catalyst in Example 1 of the present invention.

[0028] Figure 2This is a scanning electron microscope image of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 of the present invention.

[0029] Figure 3 This is a transmission electron microscope (TEM) image of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 of this invention.

[0030] Figure 4 The X-ray diffraction patterns are those of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 of the present invention and the sulfide composite catalyst (N / CS-1.75) prepared in Comparative Example 1.

[0031] Figure 5 The image shows the X-ray photoelectron spectrum of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 of this invention.

[0032] Figure 6 This is a fine X-ray photoelectron spectrum of the S2p region of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 of this invention.

[0033] Figure 7 This is a comparison chart showing the removal efficiency of ferrous sulfide composite catalysts (Fe@N / CS-1.00, Fe@N / CS-1.25, Fe@N / CS-1.50, Fe@N / CS-1.75, Fe@N / CS-2.00) on sulfamethoxazole in water in Example 6 of this invention.

[0034] Figure 8 This is a diagram showing the mineralization effect of ferrous sulfide composite catalyst (Fe@N / CS-1.75) on sulfamethoxazole in water in Example 6 of the present invention.

[0035] Figure 9 This is a diagram showing the repeated cyclic removal effect of ferrous sulfide composite catalyst (Fe@N / CS-1.75) on sulfamethoxazole in water in Example 7 of the present invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0037] In this embodiment of the invention, all raw materials and instruments used are commercially available. Unless otherwise specified, the process used is a conventional process, the equipment used is conventional equipment, and the data obtained are all average values ​​from three or more repeated experiments.

[0038] Example 1:

[0039] A ferrous sulfide composite catalyst includes a nitrogen-doped carbon layer, wherein ferrous sulfide nanoparticles are loaded on the nitrogen-doped carbon layer.

[0040] In this embodiment, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles in the ferrous sulfide composite catalyst is 100:3.89.

[0041] In this embodiment, the mass fraction of nitrogen in the nitrogen-doped carbon layer is 22.85%.

[0042] A method for preparing the ferrous sulfide composite catalyst in this embodiment is shown in the following process flow diagram. Figure 1 As shown, it includes the following steps:

[0043] (1) Add 0.183g of ferric chloride to 15.824g of anhydrous ethanol and stir for 5min to obtain a ferric chloride dispersion;

[0044] (2) Add 0.133g (1.75mmol) thiourea and 0.396g o-phenanthroline to the ferric chloride dispersion obtained in step (1) and stir for 5min to obtain a complexing agent (thiourea, o-phenanthroline) / ferric ion dispersion, which is the precursor dispersion.

[0045] (3) Weigh 2.0g of melamine and add it to the complexing agent (thiourea, o-phenanthroline) / iron ion dispersion obtained in step (2). Stir at room temperature (20-40℃, for example 25℃) for 3h, and then vacuum dry at 80℃ for 12h to obtain precursor powder.

[0046] (4) Grind the precursor powder obtained in step (3) evenly, and calcine it at 600℃ for 2h at a heating rate of 5℃ / min in an argon atmosphere. Then, calcine it at 800℃ for 2h at the same heating rate to obtain a black powder. The calcined product is acid washed with 1M H2SO4 for 15h, and then washed, filtered, and vacuum dried at 80℃ for 12h to obtain the ferrous sulfide composite catalyst, which is Fe@N / CS-1.75, numbered A4.

[0047] Example 2

[0048] A method for preparing a ferrous sulfide composite catalyst is basically the same as the preparation method in Example 1, except that the amount of thiourea added in Example 2 is 1.0 mmol.

[0049] The ferrous sulfide composite catalyst (Fe@N / CS-1.00) prepared in Example 2 is designated as A1.

[0050] In the ferrous sulfide composite catalyst prepared in Example 2, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles was 100:2.19.

[0051] Example 3

[0052] A method for preparing a ferrous sulfide composite catalyst is basically the same as the preparation method in Example 1, except that the amount of thiourea added in Example 3 is 1.25 mmol.

[0053] The ferrous sulfide composite catalyst (Fe@N / CS-1.25) prepared in Example 3 is designated as A2.

[0054] In the ferrous sulfide composite catalyst prepared in Example 3, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles was 100:2.75.

[0055] Example 4

[0056] A method for preparing a ferrous sulfide composite catalyst is basically the same as the preparation method in Example 1, except that the amount of thiourea added in Example 4 is 1.5 mmol.

[0057] The ferrous sulfide composite catalyst (Fe@N / CS-1.50) prepared in Example 4 is designated as A3.

[0058] In the ferrous sulfide composite catalyst prepared in Example 4, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles was 100:3.32.

[0059] Example 5

[0060] A method for preparing a ferrous sulfide composite catalyst is basically the same as the preparation method in Example 1, except that the amount of thiourea added in Example 5 is 2.00 mmol.

[0061] The ferrous sulfide composite catalyst (Fe@N / CS-2.00) prepared in Example 5 is designated as A5.

[0062] In the ferrous sulfide composite catalyst prepared in Example 5, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles was 100:4.47.

[0063] Comparative Example 1

[0064] The preparation method of an iron-free sulfide composite catalyst is basically the same as that in Example 1, except that ferric chloride is not added in Comparative Example 1.

[0065] The sulfide composite catalyst (N / CS-1.75) prepared in Comparative Example 1 is designated as A6.

[0066] Figure 2 This is a scanning electron microscope image of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 of the present invention. Figure 2 In the diagram, a and b correspond to different magnification factors.

[0067] Figure 3 This is a transmission electron microscope (TEM) image of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 of this invention. Figure 3 In the diagram, a, b, and c correspond to different magnifications. Figure 3 c is a high-resolution transmission electron microscope (TEM) image of Fe@N / CS-1.75. Figure 2 , 3 It can be seen that the ferrous sulfide composite catalyst is composed of many wrinkled layers, and the ferrous sulfide particles are uniformly and firmly dispersed on the nitrogen-doped carbon layer.

[0068] Figure 4 X-ray diffraction patterns of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 and the sulfide composite catalyst (N / CS-1.75) prepared in Comparative Example 1. Figure 4 It can be seen that the diffraction peak at 44.7° corresponds to the 114 crystal plane of ferrous sulfide (JCPDS#37-0477). By comparing the X-ray diffraction pattern of N / CS-1.75, it is further ruled out that the diffraction peak at 44.7° does not belong to the 101 crystal plane of the graphite phase in the nitrogen-doped carbon layer. Thus, it is confirmed that the nanoparticles in the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 belong to ferrous sulfide.

[0069] Figure 5 The image shows the X-ray photoelectron spectrum of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 of this invention. Figure 5 It can be seen that the ferrous sulfide composite catalyst is composed of Fe, N, C, O and S elements.

[0070] Figure 6 This is a fine X-ray photoelectron spectrum (S2p) of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 of this invention. Figure 6 It can be seen that the S element in the ferrous sulfide composite catalyst participates in the formation of Fe-S bonds, further proving the formation of ferrous sulfide in the catalyst.

[0071] The above results indicate that the ferrous sulfide composite catalyst prepared by the method of the present invention exhibits a good crystalline phase, wherein the ferrous sulfide nanoparticles are uniformly dispersed and are very tightly bonded to the nitrogen-doped carbon substrate, making it a catalyst with both good catalytic activity and stability.

[0072] Example 6:

[0073] The removal performance of antibiotics by the system constructed from the ferrous sulfide composite catalyst and persulfate of the present invention was investigated. Specifically, the removal of sulfamethoxazole from water was carried out by activating persulfate with the ferrous sulfide composite catalyst prepared in Examples 1-5, including the following steps:

[0074] Accurately weigh 5 mg of the ferrous sulfide composite catalysts (A1, A2, A3, A4, A5) prepared in Examples 1-5, and add them to 100 mL of 10 ppm sulfamethoxazole solution. Adjust the initial pH of the solution to 7.4 with borate buffer (2.0 mM). Stir magnetically (800 r / min) for 30 min at 25 °C to reach adsorption-desorption equilibrium. Then add 250 μL of persulfate solution (0.2 M) and carry out the catalytic oxidation reaction for 15 min under the same conditions.

[0075] In this embodiment, at different time intervals of oxidation reactions, 1 ml of sample was taken, filtered through a 0.22 μm polytetrafluoroethylene filter membrane, and residual persulfate in the sample was quenched with sodium thiosulfate solution (15 μL, 1.0 M). The content of sulfamethoxazole in the sample was then determined using high-performance liquid chromatography (HPLC), and its removal rate was calculated. The results are as follows: Figure 7 As shown.

[0076] Figure 7 This is a comparative graph showing the removal efficiency of ferrous sulfide composite catalysts (Fe@N / CS-1.00, Fe@N / CS-1.25, Fe@N / CS-1.50, Fe@N / CS-1.75, Fe@N / CS-2.00) on sulfamethoxazole in water in Example 6 of this invention. Figure 7 It is known that all ferrous sulfide composite catalysts can efficiently activate PMS to remove sulfamethoxazole from water. In particular, Fe@N / CS-1.75 exhibits the highest reaction rate and can achieve complete removal of sulfamethoxazole from water within 15 minutes.

[0077] In addition, the total organic carbon (TOC) content at different time intervals during the degradation of sulfamethoxazole by Fe@N / CS-1.75 activated PMS was determined using a total organic carbon (TOC) analyzer. The results are as follows: Figure 8 As shown.

[0078] Figure 8 This image shows the mineralization effect of the ferrous sulfide composite catalyst (Fe@N / CS-1.75) on sulfamethoxazole in water in Example 6 of this invention. Figure 8It can be seen that Fe@N / CS-1.75, which has the best removal performance, achieved a total organic carbon removal rate of 72.31% for sulfamethoxazole within 15 min, indicating that the Fe@N / CS-1.75 / PMS system has a strong mineralization ability.

[0079] Tests showed that the catalyst composed of iron nanoparticles supported on a nitrogen-doped carbon layer had a normalized rate constant of 52 min. -1 M -1 The ferrous sulfide composite catalyst prepared in Example 1 of this invention has a normalized rate constant of 130.36 min. -1 M -1 This indicates that the ferrous sulfide composite catalyst prepared in this invention can activate PMS more efficiently and exhibits superior catalytic performance.

[0080] The above results indicate that the ferrous sulfide composite catalyst prepared in this invention has excellent PMS activation performance and can rapidly and thoroughly degrade sulfamethoxazole in water.

[0081] Example 7

[0082] To investigate the reusability of the ferrous sulfide composite catalyst of the present invention, the ferrous sulfide composite catalyst (Fe@N / CS-1.75) prepared in Example 1 was used to activate persulfate oxidation to remove sulfamethoxazole from water, including the following steps:

[0083] Weigh 5 mg of ferrous sulfide composite catalyst (Fe@N / CS-1.75) and add it to 100 mL of 10 ppm sulfamethoxazole solution. Adjust the initial pH of the solution to 7.4 with borate buffer (2.0 mM). Stir magnetically (800 r / min) for 30 min at 25 °C to reach adsorption-desorption equilibrium. Then add 250 μL of persulfate solution (0.2 M) and carry out catalytic oxidation reaction for 15 min under the same conditions. After the reaction is complete, separate the catalyst from the reaction system and wash it three times with ethanol and deionized water, respectively. Then dry it in a vacuum drying oven at 80 °C for 12 h. Repeat the same reaction steps and conditions for a new round of catalytic reaction three times.

[0084] After three cycles, the catalyst was separated, washed, and dried using the same steps, then placed in a tube furnace and thermally activated at 350°C for 2 hours at a heating rate of 5°C / min. The heat-treated catalyst was then subjected to a fourth round of catalytic reaction under the same reaction steps and conditions, with the results as follows: Figure 9 As shown.

[0085] Figure 9This image shows the effect of repeated cycles in removing sulfamethoxazole from water using the ferrous sulfide composite catalyst (Fe@N / CS-1.75) in Example 7 of this invention. Figure 9 It is evident that the ferrous sulfide catalyst of this invention still achieves a 75% removal rate of sulfamethoxazole within 15 minutes after being reused three times. After three cycles, the catalyst was heat-treated to remove intermediate degradation products from its surface. It was found that the heat-treated catalyst regained its initial catalytic activity, achieving a removal efficiency of over 95% for sulfamethoxazole. This demonstrates that the ferrous sulfide composite catalyst of this invention exhibits excellent reusability and stability.

[0086] In summary, the ferrous sulfide composite catalyst of this invention has the advantages of excellent catalytic activity and strong stability. It is a novel and highly efficient Fenton-like catalyst that can effectively activate oxidants. The constructed system can rapidly generate a large number of active species, which is beneficial for the rapid and thorough degradation of recalcitrant organic pollutants (such as antibiotics) in wastewater. It has high application value and good application prospects.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A ferrous sulfide composite catalyst, characterized in that, The ferrous sulfide composite catalyst comprises a nitrogen-doped carbon layer on which ferrous sulfide nanoparticles are supported; the mass ratio of the nitrogen-doped carbon layer to the ferrous sulfide nanoparticles in the ferrous sulfide composite catalyst is 5–50:1; the preparation method of the ferrous sulfide composite catalyst includes the following steps: (1) Mix ferric chloride with ethanol, add thiourea and o-phenanthroline, stir, and obtain a precursor dispersion; (2) Mix the precursor powder with melamine, stir, and dry to obtain precursor powder; (3) The precursor powder was calcined and acid-washed to obtain ferrous sulfide composite catalyst.

2. The ferrous sulfide composite catalyst according to claim 1, characterized in that, The nitrogen content in the nitrogen-doped carbon layer is 22.85% by mass.

3. A method for preparing a ferrous sulfide composite catalyst, characterized in that, Includes the following steps: S1. Mix ferric chloride with ethanol, add thiourea and o-phenanthroline, stir to obtain a precursor dispersion; S2. Mix the precursor powder with melamine, stir, and dry to obtain the precursor powder. S3. The precursor powder is calcined and acid-washed to obtain ferrous sulfide composite catalyst. The ferrous sulfide composite catalyst includes a nitrogen-doped carbon layer on which ferrous sulfide nanoparticles are loaded; the mass ratio of the nitrogen-doped carbon layer to the ferrous sulfide nanoparticles in the ferrous sulfide composite catalyst is 5 to 50:

1.

4. The preparation method according to claim 3, characterized in that, In step S1, the mass ratio of ferric chloride to ethanol is 1:80-100; the mass ratio of thiourea to ethanol is 1:100-120; and the mass ratio of o-phenanthroline to ethanol is 1:30-50.

5. The preparation method according to claim 4, characterized in that, In step S2, the mass-to-volume ratio of melamine to precursor liquid is 50g to 150g: 1L.

6. The preparation method according to claim 5, characterized in that, In step S1, the stirring time is 5 min to 15 min; In step S2, the stirring temperature is 20℃~40℃; the stirring time is 2h~4h; the drying is carried out under vacuum conditions; the drying temperature is 60℃~100℃; and the drying time is 10h~15h. In step S3, the calcination is carried out under a protective atmosphere, namely argon. The calcination involves first heating the precursor powder to 600°C and holding it at that temperature for 1 to 3 hours, then heating it to 800°C and holding it at that temperature for 1 to 3 hours. The heating rate during the calcination process is 2 to 10°C / min. The acid solution used in the acid washing process is sulfuric acid solution. The concentration of the acid solution is 80 to 100 g / L. The acid washing time is 10 to 18 hours. After the acid washing is completed, the following step is also included: drying the acid-washed product under vacuum conditions. The drying temperature is 60°C to 100°C. The drying time is 10 to 15 hours.

7. The preparation method according to any one of claims 3 to 6, characterized in that, The nitrogen content in the nitrogen-doped carbon layer is 22.85% by mass.

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