Mxene-based composite material, preparation method and application thereof, and method for catalytically converting nitrate into ammonia

Abstract

The present application belongs to the technical field of ammonia synthesis, and particularly relates to an Mxene-based composite material and a preparation method and application thereof, and a method for catalytically converting nitrate into ammonia. The present application provides an Mxene-based composite material, which comprises an MXene carrier and SnS2 loaded on the MXene carrier. The composite material obtained by the present application is stable in structure, and as a catalyst for catalytically converting nitrate into ammonia, can further improve the catalytic efficiency and increase the synthesis amount of ammonia.

Description

Technical Field

[0001] This invention belongs to the field of ammonia synthesis technology, specifically relating to an Mxene-based composite material and its preparation method and application, and a method for catalytically converting nitrate into ammonia. Background Technology

[0002] With the continuous advancement of industrialization, the proportion of nitrogen oxides in air pollutants has gradually increased, becoming the main culprit of acid rain. As it is deposited in soil and water bodies by rainfall, it has a serious impact on basic farmland, forest land, and aquatic environment.

[0003] Ammonia is an indispensable raw material for the synthesis of nitrogen fertilizers and a promising hydrogen-rich fuel. Furthermore, due to its high energy density, it is considered an ideal alternative energy source for achieving carbon neutrality. Currently, the energy-intensive Haber-Bosch (HB) process, invented in 1905, still dominates the industrial-scale production of NH3. In this process, NH3 is produced by the catalytic reaction of hydrogen and nitrogen under harsh conditions (400–500 °C, 150–300 atm) using a heterogeneous catalyst, with typical yields below 200 mmol·g⁻¹. cat -1 ·h -1 However, the HB process, with its high energy consumption (accounting for over 2% of global energy supply) and severe environmental pollution, no longer meets the requirements of sustainable development. The piezoelectric catalytic value-added conversion of nitrate to NH3 synthesis is an attractive and sustainable option.

[0004] In existing research on piezoelectric catalytic methods for the conversion of nitrates to NH3, Ru-based catalysts are commonly used. The preparation method first involves preparing amorphous ruthenium oxychloride using a modified sol-gel method, then titrating it onto a carbon paper substrate, followed by electrochemical reduction of the ruthenium oxychloride, and finally heat treatment in an H2 atmosphere for 6 hours. It can be seen that this method suffers from cumbersome preparation procedures; furthermore, due to the dropwise addition method, the catalyst-carbon paper bonding is poor, leading to insufficient stability during long-term operation and consequently reducing catalytic efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide an Mxene-based composite material, its preparation method and application, and a method for catalyzing the conversion of nitrate to ammonia. The Mxene-based composite material provided by this invention has good stability and can further improve catalytic efficiency as a piezoelectric catalytic catalyst for the value-added conversion of nitrate to NH3.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The present invention provides an Mxene-based composite material, comprising an MXene carrier and SnS2 loaded on the MXene carrier.

[0008] Preferably, the Mxene support includes one or more of titanium nitride MXene support, molybdenum carbide MXene support, and titanium carbide MXene support;

[0009] The SnS2 loading percentage is 10% to 60%.

[0010] This invention also provides a method for preparing the Mxene-based composite material described above, comprising the following steps:

[0011] The Mxene support, soluble tin source, soluble sulfur source, surfactant and solvent are mixed and subjected to a liquid-phase reaction to obtain the Mxene-based composite material.

[0012] Preferably, the soluble tin source includes tin tetrachloride pentahydrate;

[0013] The soluble sulfur source includes thioacetamide and / or thiourea;

[0014] The surfactant includes polyvinylpyrrolidone and / or hexadecyltrimethylammonium bromide;

[0015] The solvent includes anhydrous ethanol or water.

[0016] Preferably, the ratio of the Mxene carrier to the soluble tin source is 30 mg: 1-5 mmol;

[0017] The molar ratio of the soluble tin source to the soluble sulfur source is 0.1 to 1:1.6;

[0018] The mass ratio of the Mxene carrier to the surfactant is 5 to 30:1.

[0019] Preferably, the temperature of the liquid phase reaction is 160–180°C, and the holding time is 18–24 h.

[0020] The present invention also provides the application of the Mxene-based composite material described in the above technical solution or the Mxene-based composite material prepared by the preparation method described in the above technical solution as a catalyst in the catalytic conversion of nitrate to ammonia.

[0021] The present invention also provides a method for catalytically converting nitrate to ammonia, comprising the following steps:

[0022] The nitrate solution and the catalyst were mixed to carry out a piezoelectric catalytic reaction;

[0023] The catalyst is the Mxene-based composite material described in the above technical solution or the Mxene-based composite material prepared by the preparation method described in the above technical solution.

[0024] Preferably, the concentration of the nitrate solution is 0.1–1.0 mol / L;

[0025] The catalyst concentration in the nitrate solution is 10–200 mg / L.

[0026] Preferably, the piezoelectric catalytic reaction is carried out under stirring or ultrasonic conditions; the ultrasonic power is 37-80 kHz; and the stirring speed is 400-1000 rpm.

[0027] This invention provides an MXene-based composite material comprising an MXene support and SnS2 supported on the MXene support. The composite material obtained by this invention has a stable structure and, as a catalyst for the conversion of nitrate to ammonia, can further improve catalytic efficiency and increase the amount of ammonia synthesized.

[0028] This invention also provides a method for preparing the Mxene-based composite material described in the above technical solution, comprising the following steps: mixing an Mxene support, a soluble tin source, a soluble sulfur source, a surfactant, and a solvent, and carrying out a liquid-phase reaction to obtain the Mxene-based composite material. The catalyst grown in situ through liquid-phase reaction of this invention has a nanoflower-like structure, and is uniformly distributed without agglomeration; simultaneously, a heterojunction is formed between MXene and the supported SnS2, and the built-in electric field facilitates electron transfer; due to its special structure and size effect, as well as the possible interactions between the support and the grown material (in-situ growth is not only the interaction between the support and the grown material, but also involves synergistic effects between different piezoelectric materials), the catalyst provided by this invention exhibits superior activity and stability compared to general supported catalysts.

[0029] This invention also provides a method for catalytically converting nitrate to ammonia, comprising the following steps: mixing a nitrate solution and a catalyst to carry out a piezoelectric catalytic reaction. The method provided by this invention has low energy consumption, requires a small amount of piezoelectric catalyst, has a high utilization rate of reactants to products, produces no gaseous pollutants, exhibits stable operation and significant effects, and has a lower cost than existing ammonia synthesis processes. Attached Figure Description

[0030] Figure 1 The image shows a scanning electron microscope (SEM) image of the SnS2 / Mxene composite material obtained in Example 3.

[0031] Figure 2 A standard curve for ammonia concentration measurement;

[0032] Figure 3 This is the ultraviolet absorption spectrum of ammonia;

[0033] Figure 4 The results are the ammonia production test results from Examples 1-4 and Comparative Example 1. Detailed Implementation

[0034] The present invention provides an Mxene-based composite material, comprising an MXene carrier and SnS2 loaded on the MXene carrier.

[0035] In this invention, the Mxene support preferably includes one or more of titanium nitride MXene support, molybdenum carbide MXene support, and titanium carbide MXene support; the SnS2 loading percentage is preferably 10% to 60%, more preferably 20% to 50%, and even more preferably 30% to 40%.

[0036] In this invention, the Mxene-based composite material preferably has a nanoflower-like structure, and the nanosheets on the nanoflower-like structure preferably have a diameter of 200-250 nm.

[0037] This invention also provides a method for preparing the Mxene-based composite material described above, comprising the following steps:

[0038] The Mxene support, soluble tin source, soluble sulfur source, surfactant and solvent are mixed and subjected to a liquid-phase reaction to obtain the Mxene-based composite material.

[0039] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0040] In this invention, the soluble tin source preferably comprises tin tetrachloride pentahydrate; the soluble sulfur source preferably comprises thioacetamide (TAA) and / or thiourea; the surfactant preferably comprises polyvinylpyrrolidone (PVP) and / or hexadecyltrimethylammonium bromide; the solvent preferably comprises anhydrous ethanol or water, wherein the water is preferably ultrapure water. In this invention, the addition of a surfactant can promote better growth of SnS2 on the Mxene support.

[0041] In this invention, the preferred ratio of the Mxene carrier to the soluble tin source is 30 mg: 1 to 5 mmol; the preferred molar ratio of the soluble tin source to the soluble sulfur source is 0.1 to 1: 1.6; and the preferred mass ratio of the Mxene carrier to the surfactant is 5 to 30: 1.

[0042] In this invention, the mixing process preferably includes: subjecting the Mxene carrier and solvent to a first ultrasonic treatment, followed by adding a soluble tin source, a soluble sulfur source, and a surfactant for a second ultrasonic treatment. In this invention, the conditions for the first ultrasonic treatment preferably include: an ultrasonic frequency of 37–80 kHz, a discontinuous ultrasonic process, switching off after every 3 hours, changing the water, and continuing ultrasonic treatment; the total ultrasonic time is 48 hours. In this invention, the conditions for the second ultrasonic treatment include: an ultrasonic frequency of 37–80 kHz, a discontinuous ultrasonic process, switching off after every 30 minutes, changing the water, and continuing ultrasonic treatment; the total ultrasonic time is 60 minutes.

[0043] In this invention, the temperature of the liquid-phase reaction is preferably 160–180°C, and the holding time is preferably 18–24 h, more preferably 20–22 h. In this invention, the liquid-phase reaction is preferably carried out in a lined stainless steel reactor.

[0044] After the liquid-phase reaction, the present invention preferably further includes: cooling the obtained reaction system to room temperature and then filtering it, and washing and drying the obtained solid; the washing preferably includes washing with deionized water and washing with anhydrous ethanol in sequence, and the number of times the deionized water washing and the anhydrous ethanol washing are independent is preferably 2 times.

[0045] The present invention also provides the application of the Mxene-based composite material described in the above technical solution or the Mxene-based composite material prepared by the preparation method described in the above technical solution as a catalyst in the catalytic conversion of nitrate to ammonia.

[0046] The present invention also provides a method for catalytically converting nitrate to ammonia, comprising the following steps:

[0047] The nitrate solution and the catalyst were mixed to carry out a piezoelectric catalytic reaction;

[0048] The catalyst is the Mxene-based composite material described in the above technical solution or the Mxene-based composite material prepared by the preparation method described in the above technical solution.

[0049] In this invention, the nitrate solution is preferably a freshly prepared nitrate solution or wastewater containing nitrate.

[0050] In this invention, the concentration of the nitrate solution is preferably 0.1 to 1.0 mol / L; the content of the catalyst in the nitrate solution is 10 to 200 mg / L.

[0051] In this invention, the piezoelectric catalytic reaction is preferably carried out under stirring or ultrasonic conditions; the ultrasonic power is preferably 37-80 kHz; and the stirring speed is preferably 400-1000 rpm.

[0052] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, describes an Mxene-based composite material, its preparation method and application, and a method for catalytically converting nitrate to ammonia, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] Weigh 0.3g of titanium carbide MXene support and place it in a beaker. Add anhydrous ethanol solution as a solvent.

[0055] The solution was placed in an ultrasonic device at a frequency of 37kHz. The ultrasonic process was discontinuous, and the device was turned off every 3 hours with water changed. The total ultrasonic time was 48 hours to obtain a dispersion.

[0056] Weigh out 10 mmol of SnCl4·5H2O, 20 mmol of TAA and 10 mg of PVP respectively and add them to the above dispersion. Continue to sonicate at a frequency of 37 kHz. The sonication process is discontinuous. Turn off the sonication every 30 minutes and change the water. The total sonication time is 60 minutes to obtain a mixture.

[0057] The obtained mixture was placed in the lining of a stainless steel reactor, tightened, and then placed in an oven at 160°C for liquid-phase reaction and kept at that temperature for 20 hours.

[0058] After the solution cooled, it was removed and filtered. The obtained solid was washed twice with deionized water and twice with anhydrous ethanol, and then dried to obtain the SnS2 / Mxene composite material.

[0059] Using the obtained SnS2 / Mxene composite material as a catalyst, ammonia was synthesized via a piezoelectric catalytic reaction. The steps were as follows:

[0060] Weigh 300 mL of nitrate-containing wastewater with a concentration of 0.1 mol / L, add 50 mg of catalyst, and disperse it fully in the wastewater under ultrasonic conditions; then place it in an ultrasonic piezoelectric reactor (ultrasonic frequency of 37 kHz) for piezoelectric catalytic ammonia synthesis. The total reaction time is 5 h. Samples are taken at 1 h, 2 h, 3 h, 4 h and 5 h to test the yield of synthesized ammonia.

[0061] Example 2

[0062] Weigh 0.3g of titanium carbide MXene support and place it in a beaker. Add anhydrous ethanol solution as a solvent.

[0063] The solution was placed in an ultrasonic device at a frequency of 37kHz. The ultrasonic process was discontinuous, and the device was turned off every 3 hours with water changed. The total ultrasonic time was 48 hours to obtain a dispersion.

[0064] Weigh out 20 mmol of SnCl4·5H2O, 40 mmol of TAA and 10 mg of PVP respectively and add them to the above dispersion. Continue to sonicate at a frequency of 37 kHz. The sonication process is discontinuous. Turn off the sonication every 30 minutes and change the water. The total sonication time is 60 minutes to obtain a mixture.

[0065] The obtained mixture was placed in the lining of a stainless steel reactor, tightened, and then placed in an oven at 160°C for liquid-phase reaction and kept at that temperature for 20 hours.

[0066] After the solution cooled, it was removed and filtered. The obtained solid was washed twice with deionized water and twice with anhydrous ethanol, and then dried to obtain the SnS2 / Mxene composite material.

[0067] Using the obtained SnS2 / Mxene composite material as a catalyst, ammonia was synthesized via a piezoelectric catalytic reaction. The steps were as follows:

[0068] Weigh 300 mL of nitrate-containing wastewater with a concentration of 0.1 mol / L, add 50 mg of catalyst, and disperse it fully in the wastewater under ultrasonic conditions; then place it in an ultrasonic piezoelectric reactor (ultrasonic frequency of 37 kHz) for piezoelectric catalytic ammonia synthesis. The total reaction time is 5 h. Samples are taken at 1 h, 2 h, 3 h, 4 h and 5 h to test the yield of synthesized ammonia.

[0069] Example 3

[0070] Weigh 0.3g of titanium carbide MXene support and place it in a beaker. Add anhydrous ethanol solution as a solvent.

[0071] The solution was placed in an ultrasonic device at a frequency of 37kHz. The ultrasonic process was discontinuous, and the device was turned off every 3 hours with water changed. The total ultrasonic time was 48 hours to obtain a dispersion.

[0072] Weigh out 30 mmol of SnCl4·5H2O, 60 mmol of TAA and 10 mg of PVP respectively and add them to the above dispersion. Continue to sonicate at a frequency of 37 kHz. The sonication process is discontinuous. Turn off the sonication every 30 minutes and change the water. The total sonication time is 60 minutes to obtain a mixture.

[0073] The obtained mixture was placed in the lining of a stainless steel reactor, tightened, and then placed in an oven at 160°C for liquid-phase reaction and kept at that temperature for 20 hours.

[0074] After the solution cooled, it was removed and filtered. The obtained solid was washed twice with deionized water and twice with anhydrous ethanol, and then dried to obtain the SnS2 / Mxene composite material.

[0075] Figure 1SEM images of the obtained SnS2 / Mxene composite material were obtained from... Figure 1 It can be seen that the SnS2 / Mxene composite material obtained by this invention exhibits a nanoflower morphology formed by nanosheets.

[0076] Using the obtained SnS2 / Mxene composite material as a catalyst, ammonia was synthesized via a piezoelectric catalytic reaction. The steps were as follows:

[0077] Weigh 300 mL of nitrate-containing wastewater with a concentration of 0.1 mol / L, add 50 mg of catalyst, and disperse it fully in the wastewater under ultrasonic conditions; then place it in an ultrasonic piezoelectric reactor (ultrasonic frequency of 37 kHz) for piezoelectric catalytic ammonia synthesis. The total reaction time is 5 h. Samples are taken at 1 h, 2 h, 3 h, 4 h and 5 h to test the yield of synthesized ammonia.

[0078] Example 4

[0079] Weigh 0.3g of titanium carbide MXene support and place it in a beaker. Add anhydrous ethanol solution as a solvent.

[0080] The solution was placed in an ultrasonic device at a frequency of 37kHz. The ultrasonic process was discontinuous, and the device was turned off every 3 hours with water changed. The total ultrasonic time was 48 hours to obtain a dispersion.

[0081] Weigh out 40 mmol of SnCl4·5H2O, 80 mmol of TAA and 10 mg of PVP respectively and add them to the above dispersion. Continue to sonicate at a frequency of 37 kHz. The sonication process is discontinuous. Turn off the sonication every 30 minutes and change the water. The total sonication time is 60 minutes to obtain a mixture.

[0082] The obtained mixture was placed in the lining of a stainless steel reactor, tightened, and then placed in an oven at 160°C for liquid-phase reaction and kept at that temperature for 20 hours.

[0083] After the solution cooled, it was removed and filtered. The obtained solid was washed twice with deionized water and twice with anhydrous ethanol, and then dried to obtain the SnS2 / Mxene composite material.

[0084] Using the obtained SnS2 / Mxene composite material as a catalyst, ammonia was synthesized via a piezoelectric catalytic reaction. The steps were as follows:

[0085] Weigh 300 mL of nitrate-containing wastewater with a concentration of 0.1 mol / L, add 50 mg of catalyst, and disperse it fully in the wastewater under ultrasonic conditions; then place it in an ultrasonic piezoelectric reactor (ultrasonic frequency of 37 kHz) for piezoelectric catalytic ammonia synthesis. The total reaction time is 5 h. Samples are taken at 1 h, 2 h, 3 h, 4 h and 5 h to test the yield of synthesized ammonia.

[0086] Comparative Example 1

[0087] Weigh 0.3g of titanium carbide MXene support and place it in a beaker. Add anhydrous ethanol solution as a solvent.

[0088] The solution was placed in an ultrasonic device at a frequency of 37kHz. The ultrasonic process was discontinuous, and the device was turned off every 3 hours with water changed. The total ultrasonic time was 48 hours to obtain a dispersion.

[0089] The obtained dispersion was filtered, and the obtained solid was washed twice each with deionized water and anhydrous ethanol, and then dried to obtain Mxene material.

[0090] Using the obtained Mxene material as a catalyst, ammonia was synthesized via a piezoelectric catalytic reaction. The steps were as follows:

[0091] Weigh 300 mL of nitrate-containing wastewater with a concentration of 0.1 mol / L, add 50 mg of catalyst, and disperse it fully in the wastewater under ultrasonic conditions; then place it in an ultrasonic piezoelectric reactor (ultrasonic frequency of 37 kHz) for piezoelectric catalytic ammonia synthesis. The total reaction time is 5 h. Samples are taken at 1 h, 2 h, 3 h, 4 h and 5 h to test the yield of synthesized ammonia.

[0092] Performance testing

[0093] Test methods for ammonia synthesis yield in the examples and comparative examples:

[0094] (1) First, 4.97g of salicylic acid and 4.39g of sodium citrate were dissolved in 100mL of 0.625M potassium hydroxide aqueous solution to prepare a coloring reagent;

[0095] (2) Dilute the sample obtained from sampling to 2 mL to ensure that the concentration is within the detection range;

[0096] (3) Add 1.25 mL of coloring reagent, 150 μL of 10 mg / mL C5FeN6Na2O (sodium nitroferricyanide) aqueous solution and 75 μL of sodium hypochlorite (sodium hypochlorite, available chlorine 4.0%), and let stand at room temperature for 2 h.

[0097] (4) Place the solution in a 5cm cuvette and measure its 658nm absorption spectrum using a UV-spectrum spectrophotometer. Determine its concentration by comparing the ammonia UV absorption spectrum with the ammonia concentration measurement standard curve (NH4Cl). The ammonia concentration measurement standard curve is shown below. Figure 2 As shown, the ultraviolet absorption spectrum of ammonia is as follows: Figure 3 As shown;

[0098] The test results obtained from Examples 1-4 and Comparative Example 1 are shown in Table 1 and 2. Figure 4 As shown;

[0099] Table 1. Results of ammonia synthesis yield tests in Examples 1-4 and Comparative Example 1

[0100]

[0101]

[0102] According to Table 1 and Figure 4 It can be seen that the activity of piezoelectric catalytic reduction of nitrate mainly comes from SnS2, and the tin source is proportional to the activity of ammonia synthesis within a certain range.

[0103] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for catalytically converting nitrate to ammonia, characterized in that, Includes the following steps: The nitrate solution and the catalyst were mixed to carry out a piezoelectric catalytic reaction; The catalyst is an Mxene-based composite material, which includes an MXene support and SnS2 supported on the MXene support. The Mxene support is a titanium carbide MXene support; The preparation method of the Mxene-based composite material includes the following steps: mixing Mxene support, soluble tin source, soluble sulfur source, surfactant and solvent, and carrying out a liquid phase reaction to obtain the Mxene-based composite material; The catalyst has a nanoflower-like structure.

2. The method according to claim 1, characterized in that, The SnS2 loading percentage is 10% to 60%.

3. The method according to claim 1, characterized in that, The soluble tin source includes tin tetrachloride pentahydrate; The soluble sulfur source includes thioacetamide and / or thiourea; The surfactant includes polyvinylpyrrolidone and / or hexadecyltrimethylammonium bromide; The solvent includes anhydrous ethanol or water.

4. The method according to claim 1, characterized in that, The ratio of the Mxene carrier to the soluble tin source is 30 mg: 1–5 mmol; The molar ratio of the soluble tin source to the soluble sulfur source is 0.1 to 1:1.6; The mass ratio of the Mxene carrier to the surfactant is 5 to 30:

1.

5. The method according to claim 1, characterized in that, The temperature of the liquid phase reaction is 160–180°C, and the holding time is 18–24 h.

6. The method according to claim 1, characterized in that, The concentration of the nitrate solution is 0.1–1.0 mol / L; The catalyst concentration in the nitrate solution is 10–200 mg / L.

7. The method according to claim 1, characterized in that, The piezoelectric catalytic reaction is carried out under stirring or ultrasonic conditions; the ultrasonic power is 37-80 kHz; the stirring speed is 400-1000 rpm.

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