A preparation method of a photo-thermal catalyst capable of realizing carbon dioxide reduction

Abstract

The application belongs to the technical field of material preparation, and discloses a preparation method of a light-thermal catalyst capable of realizing carbon dioxide reduction. The method is solvent-thermal, and uses multilayer Ti3C2 MXene as a substrate, thiourea as a sulfur source, ethanol as a solvent, and ethylene glycol as a binder. The method combines the principles of sulfuration and in-situ intercalation, generates TiS2 in-situ between the multilayer Ti3C2 layers, thereby increasing the reaction active sites of the catalyst for CO2 reduction, improving the absorption capacity of the catalyst for near-infrared light, and fully exerting the light-thermal conversion characteristics of the material.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation technology, and relates to a photothermal catalyst for achieving efficient carbon dioxide reduction: the preparation method of sulfide Ti3C2 (referred to as S-Ti3C2) and its application. Background Technology

[0002] The continuous rise in atmospheric carbon dioxide levels has led to global environmental problems, making the development of sustainable CO2 emission reduction solutions urgent. To date, researchers have developed various technologies to convert CO2 into hydrocarbons or high-value-added chemicals, primarily including thermocatalysis, biocatalysis, photoelectrocatalysis, electrocatalysis, and photocatalytic reduction. Traditional thermocatalytic CO2 reduction reactions require high temperatures (at least 500°C) and high pressures (10 bar). Photocatalytic CO2 reduction mimics natural photosynthesis, utilizing solar energy and photocatalysts to catalytically convert CO2 and H2O (also known as artificial photosynthesis). This allows for the production of solar fuels and high-value-added chemicals such as CO, CH4, and C2H4 under ambient temperature and pressure conditions. Therefore, photocatalytic CO2 reduction technology is considered one of the most promising solutions to global energy and environmental problems.

[0003] In recent years, research on photocatalytic CO2 reduction has been increasing. The photocatalytic CO2 reduction reaction is a complex, multi-step process. Generally, this reaction mainly involves the following three steps:

[0004] ① Semiconductor photocatalysts are excited by light with energy greater than their band gap (Eg);

[0005] ② Separation of photogenerated electrons and photogenerated holes;

[0006] ③ Photogenerated electrons migrate to the surface of the photocatalyst and react with CO2 and H2. + A reaction occurs, forming reduction products. Photogenerated holes react with H2O to produce O2.

[0007] However, due to the C=O dissociation energy (~750 kJ mol) -1 The high-energy barrier imposed by photon excitation makes the development of efficient and inexpensive photocatalysts for converting low-frequency visible and near-infrared (NIR) solar energy into CO2 photoreduction a major challenge.

[0008] Photo-to-thermal (PTT) conversion is an emerging research hotspot that can effectively improve the performance of photocatalytic CO2 reduction systems. When incident light irradiates a photocatalyst, a portion of the absorbed energy is converted into heat through non-radiative relaxation. This increases the temperature of the catalyst and the surrounding reaction environment, promoting CO2 activation and increasing the reaction rate. Materials with broad absorption spectra, especially black materials, can effectively capture the energy of low-frequency visible to near-infrared photons, generating a large amount of heat through PTT conversion, thereby improving catalytic activity and the selectivity of multi-carbon products.

[0009] MXenes are a unique class of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides, which have broad application prospects in photocatalysis due to their excellent electrical conductivity, large surface area, and strong light absorption properties. Ti3C2, in particular, with its flexible surface tunability and activation ability, is an excellent candidate material for CO2 reduction catalysts. Although researchers have focused more on the application of Ti3C2 in composite catalysts, its inherent active Ti sites and affinity for CO2 molecules suggest that its potential as a standalone catalyst material deserves further exploration. Furthermore, Ti3C2 exhibits excellent photothermal conversion capabilities due to its broad visible to NIR absorption, but its performance needs further improvement. Summary of the Invention

[0010] This invention is based on a CO2 conversion system and combines photothermal catalysis technology to prepare a photothermal catalyst that can achieve efficient carbon dioxide reduction.

[0011] The technical solution of this invention refers to using multilayer Ti3C2 as the base material, and sulfiding it with thiourea to generate TiS2 in situ between its layers, thereby increasing the reactive sites for CO2 reduction inside the catalyst and improving the catalyst's absorption capacity for near-infrared light, thus fully utilizing the photothermal conversion characteristics of the material. The catalytic material is named: S-Ti3C2.

[0012] A method for preparing a photothermal catalyst capable of carbon dioxide reduction, comprising the following specific steps:

[0013] (1) Synthesis of multilayer Ti3C2

[0014] First, a certain amount of Ti3AlC2 is slowly added to the HF solution to avoid overheating, and the mixture is stirred continuously in a room temperature water bath for 24 to 48 hours. After the reaction is completed, the mixture is washed several times with deionized water, centrifuged, and finally the solid residue is collected, vacuum dried, and multilayer Ti3C2 is obtained.

[0015] In step (1), the ratio of Ti3AlC2 to HF solution is 1g:20mL, and the concentration of HF solution is 40wt%.

[0016] (2) Synthesis of S-Ti3C2

[0017] First, a certain amount of thiourea CH4N2S was added to a certain amount of ethanol and stirred at room temperature until the solid was completely dissolved. The resulting solution was labeled as solution A.

[0018] Subsequently, a certain amount of multilayer Ti3C2 was added to a mixed solvent of ethanol and ethylene glycol, and stirred at room temperature for 0.5 to 1 hour. The resulting dispersion system was labeled as solution B.

[0019] Then, solutions A and B are mixed and stirred continuously at room temperature for at least 2 hours. Finally, the mixture is transferred to a high-temperature and high-pressure reactor and subjected to a solvothermal reaction in an oven. After the reaction is completed and cooled to room temperature, the mixture is washed several times with deionized CH4N2S water and ethanol. Finally, the washed precipitate is dried in a vacuum drying oven to obtain S-Ti3C2.

[0020] In step (2), the ratio of thiourea CH4N2S to multilayer Ti3C2 is calculated according to the molar ratio of Ti:S from 1:2 to 1:16.

[0021] In a mixed solvent of ethanol and ethylene glycol, the volume ratio of ethanol to ethylene glycol is 9:1.

[0022] In step (2), the temperature of the solvothermal reaction is 120-180℃ and the time is 12h.

[0023] The S-Ti3C2 prepared according to this invention is used for the photocatalytic reduction of carbon dioxide to produce CO, CH4, and C2H4. The specific operation is as follows:

[0024] The synthesized catalyst S-Ti3C2 was tested for photocatalytic carbon dioxide reduction. The photocatalytic CO2 reduction reaction was carried out in a sealed quartz reactor using a xenon lamp as the light source. First, a certain amount of catalyst was dispersed in an appropriate amount of deionized water and ultrasonically dispersed for 20 minutes to ensure complete dispersion of the powdered catalyst in the water. Subsequently, high-purity CO2 gas (99.999%) was introduced into the reactor and maintained for a sufficient time to completely remove air from the system. The gaseous products obtained after photocatalysis were detected and analyzed by gas chromatography equipped with a flame ionization detector (FID).

[0025] Furthermore, the products of S-Ti3C2 in photocatalytic carbon dioxide reduction were analyzed and tested:

[0026] (i) Selectivity analysis of carbon dioxide reduction products

[0027] The gaseous products were analyzed by gas chromatography every 60 minutes, using high-purity nitrogen (99.999%) as the carrier gas. The concentrations of CO, CH4, C2H4, and other possible hydrocarbon gases were quantified using a flame ionization detector (FID). The yield of the gaseous products was calculated using the following formula:

[0028]

[0029] Yield i This refers to the yield of gaseous product i, V i M refers to the volume of the gaseous products. photocatalyst Irradiation time and Irradiation time are the mass of catalyst added during the reaction and the reaction time, respectively.

[0030] The selectivity of gaseous product i can be calculated from the above results, using the following formula:

[0031]

[0032] Where, n i This represents the number of electrons that need to be transferred to produce gaseous product i during the reaction process.

[0033] (ii) Analysis of the solar energy conversion efficiency of carbon dioxide reduction products

[0034] The energy conversion efficiency from simulated sunlight (xenon lamp, AM 1.5G) to light-to-carbon-fuels (LTF) is calculated using the following formula:

[0035]

[0036] Among them, Rate i This refers to the gas production rate, determined by Yield. i Obtained through transformation This refers to the change in Gibbs free energy of gaseous product i during the reaction process. Light intensity and surface refer to the light intensity and illuminated area of ​​the xenon lamp, respectively. In this experiment, Light intensity = 100 mW cm⁻¹ -2 Surface = 2cm 2 .

[0037] The beneficial effects of this invention are as follows:

[0038] (1) The present invention uses a hydrothermal method to prepare a photothermal catalyst for achieving efficient carbon dioxide reduction: the operation is simple, the raw materials used are cheap and readily available, and the invention process is economical.

[0039] (2) The obtained sulfided multilayer Ti3C2 (referred to as S-Ti3C2) was obtained by non-metallic doping and in-situ intercalation. After sulfidation, the stability of the catalyst was greatly improved and the photothermal conversion efficiency was significantly improved.

[0040] (3) When S-Ti3C2 was applied to photocatalytic CO2 reduction, the experimental results showed that the catalyst had high selectivity for CH4, and under direct sunlight, it showed excellent selectivity for C2+ products and good stability. Attached Figure Description

[0041] Figure 1 The experimental flowchart for preparing S-Ti3C2.

[0042] Figure 2 The images are scanning electron microscope (SEM) images of the original multilayer Ti3C2 (a, b) and S-Ti3C2 (c, d), respectively.

[0043] Figure 3 This is a diagram of the reaction apparatus for a photo-thermal catalytic CO2 reduction experiment. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific implementation examples.

[0045] Example 1

[0046] (1) Synthesis of multilayer Ti3C2

[0047] First, 2g of Ti3AlC2 was slowly added to 40mL of HF (40wt%) to avoid overheating (due to vigorous reaction), and the mixture was stirred continuously in a water bath at room temperature for 24 hours. After the reaction was complete, the mixture was washed several times with deionized water and centrifuged until the pH of the supernatant was equal to 6. The supernatant was discarded, and the solid residue was collected. The obtained solid was dried in a vacuum drying oven at 60℃ to obtain multilayer Ti3C2. All substrate materials (Ti3C2) used below were synthesized using this method.

[0048] (2) Synthesis of S-Ti3C2 (based on a Ti:S molar ratio of 1:2 for calculating the raw material feed ratio)

[0049] First, 0.7612 g of thiourea (CH4N2S) was added to 20 mL of ethanol and stirred at room temperature until the solid was completely dissolved. The resulting solution was labeled as solution A.

[0050] Subsequently, 0.279 g of multilayer Ti3C2 MXene was added to 10 mL of a mixed solution of ethanol and ethylene glycol (volume ratio: ethanol: ethylene glycol = 9:1), and stirred at room temperature for 0.5 hours. The resulting dispersion system was labeled as solution B.

[0051] Then, solutions A and B were mixed and stirred continuously at room temperature for 2 hours. Finally, the mixture was transferred to a 50 mL high-temperature and high-pressure reactor and reacted in an oven at 150 °C for 12 hours. After the reaction was completed and cooled to room temperature, the mixture was washed three times with deionized water and ethanol, respectively. Finally, the washed precipitate was dried in a vacuum drying oven at 60 °C for 12 hours to obtain S-Ti3C2 solid powder (based on a Ti:S molar ratio of 1:2).

[0052] Figure 2 Figures a and b are scanning electron microscope (SEM) images of multilayer Ti3C2, and figures c and d are SEM images of S-Ti3C2, indicating that TiS2 was successfully synthesized in situ between the layers of multilayer Ti3C2 after the sulfidation reaction.

[0053] (3) Photocatalytic carbon dioxide reduction test and result analysis of S-Ti3C2 (based on a Ti:S molar ratio of 1:2).

[0054] The photocatalytic CO2 reduction reaction was carried out in a sealed 200mL quartz reactor using a 300W xenon lamp as the light source, with a light intensity of 500mW cm⁻¹. -2 In this experiment, 4 hours is defined as a complete photocatalytic CO2 reduction reaction.

[0055] First, 10 mg of S-Ti3C2 (based on a Ti:S molar ratio of 1:2) was dispersed in 10 mL of deionized water and ultrasonically dispersed for 20 minutes to ensure complete dispersion of the powdered catalyst. Then, high-purity CO2 gas (99.999%) was introduced into the reactor and maintained for 20 minutes to completely remove air from the system. Gas was extracted from the reactor every 60 minutes until the reaction was completed after 4 hours. The gaseous products obtained after photocatalysis were detected and analyzed by gas chromatography equipped with a flame ionization detector (FID). Similarly, a photocatalytic CO2 reduction reaction experiment was conducted on unsulfurized multilayer Ti3C2 under the same conditions for comparison.

[0056] The experimental results show that, under the same xenon lamp (illuminance of 500 mW / cm²), -2 Under irradiation, the gas yield of S-Ti3C2 (with a Ti:S molar ratio of 1:2) was slightly increased compared to unsulfurized multilayer Ti3C2. The CH4 yield increased from 8.01 μmol g / L. -1 h-1 Increased to 28.62 μmol g -1 h -1 This represents a 3.6-fold increase. Notably, CH4 is the main product, with product selectivity improved to 85.51%.

[0057] Example 2

[0058] (1) The synthesis of multilayer Ti3C2 is the same as step (1) in Example 1;

[0059] (2) Synthesis of S-Ti3C2 (based on a Ti:S molar ratio of 1:4 for calculating the raw material feed ratio)

[0060] First, 0.7612 g of thiourea (CH4N2S) was added to 20 mL of ethanol and stirred at room temperature until the solid was completely dissolved. The resulting solution was labeled as solution A. Then, 0.1395 g of multilayer Ti3C2 was added to a mixed solution of 10 mL of ethanol and ethylene glycol (volume ratio: ethanol:ethylene glycol = 9:1), and stirred at room temperature for 0.5 hours. The resulting dispersion was labeled as solution B. Next, solutions A and B were mixed and stirred continuously at room temperature for 2 hours. Finally, the mixture was transferred to a 50 mL high-temperature and high-pressure reactor and reacted at 150 °C for 12 hours in an oven. After the reaction was complete and cooled to room temperature, the mixture was washed three times with deionized water and ethanol, respectively. Finally, the washed precipitate was dried in a vacuum drying oven at 60 °C for 12 hours to obtain S-Ti3C2 solid powder (raw material feed ratio calculated according to a Ti:S molar ratio of 1:4).

[0061] (3) Photocatalytic carbon dioxide reduction test and result analysis of S-Ti3C2 (based on a Ti:S molar ratio of 1:4).

[0062] The photocatalytic CO2 reduction reaction was carried out in a sealed 200mL quartz reactor using a 300W xenon lamp as the light source, with a light intensity of 500mW cm⁻¹. -2 In this experiment, 4 hours is defined as a complete photocatalytic CO2 reduction reaction.

[0063] First, 10 mg of S-Ti3C2 (based on a Ti:S molar ratio of 1:4) was dispersed in 10 mL of deionized water and ultrasonically dispersed for 20 minutes to ensure complete dispersion of the powdered catalyst. Then, high-purity CO2 gas (99.999%) was introduced into the reactor and maintained for 20 minutes to completely remove air from the system. Gas was extracted from the reactor every 60 minutes until the reaction was completed after 4 hours. The gaseous products obtained after photocatalysis were detected and analyzed by gas chromatography equipped with a flame ionization detector (FID). Similarly, a photocatalytic CO2 reduction reaction experiment was conducted on unsulfurized multilayer Ti3C2 under the same conditions for comparison.

[0064] Experimental results show that, under the same xenon lamp (illuminance 500mW cm⁻¹), -2 Under irradiation, the gas yield of S-Ti3C2 (with a Ti:S molar ratio of 1:4) was further improved compared to unsulfurized multilayer Ti3C2. The CH4 yield increased from 8.01 μmol g / L. -1 h -1 Increased to 35.01 μmol g -1 h -1 This represents a 4.4-fold increase. Notably, CH4 is the main product, with selectivity improved to 83.88%. Furthermore, as the proportion of thiourea in the feed ratio increases, the yield of C2+ product C2H4 generated during the S-Ti3C2 reaction (based on a Ti:S molar ratio of 1:4) increases (4.08 μmol g). -1 h -1 The selectivity (14.66%) also improved.

[0065] Example 3

[0066] (1) The synthesis of multilayer Ti3C2 is the same as step (1) in Example 1;

[0067] (2) Synthesis of S-Ti3C2 (based on a Ti:S molar ratio of 1:8, calculated as the raw material feed ratio) (Optimal performance material)

[0068] First, 0.7612 g of thiourea (CH4N2S) was added to 20 mL of ethanol and stirred at room temperature until the solid was completely dissolved. The resulting solution was labeled as solution A. Then, 0.070 g of multilayer Ti3C2 was added to a mixed solution of 10 mL of ethanol and ethylene glycol (volume ratio: ethanol:ethylene glycol = 9:1), and stirred at room temperature for 0.5 hours. The resulting dispersion was labeled as solution B. Next, solutions A and B were mixed and stirred continuously at room temperature for 2 hours. Finally, the mixture was transferred to a 50 mL high-temperature and high-pressure reactor and reacted at 150 °C for 12 hours in an oven. After the reaction was complete and cooled to room temperature, the mixture was washed three times with deionized water and ethanol, respectively. Finally, the washed precipitate was dried in a vacuum drying oven at 60 °C for 12 hours to obtain S-Ti3C2 solid powder (raw material feed ratio calculated according to a Ti:S molar ratio of 1:8).

[0069] (3) Photocatalytic carbon dioxide reduction test and result analysis of S-Ti3C2 (based on a Ti:S molar ratio of 1:8).

[0070] The photocatalytic CO2 reduction reaction was carried out in a sealed 200mL quartz reactor using a 300W xenon lamp as the light source, with a light intensity of 500mW cm⁻¹. -2 In this experiment, 4 hours is defined as a complete photocatalytic CO2 reduction reaction.

[0071] First, 10 mg of S-Ti3C2 (based on a Ti:S molar ratio of 1:8) was dispersed in 10 mL of deionized water and ultrasonically dispersed for 20 minutes to ensure complete dispersion of the powdered catalyst. Then, high-purity CO2 gas (99.999%) was introduced into the reactor and maintained for 20 minutes to completely remove air from the system. Gas was extracted from the reactor every 60 minutes until the reaction was completed after 4 hours. The gaseous products obtained after photocatalysis were detected and analyzed by gas chromatography equipped with a flame ionization detector (FID). Similarly, a photocatalytic CO2 reduction reaction experiment was conducted on unsulfurized multilayer Ti3C2 under the same conditions for comparison.

[0072] Experimental results show that, under the same xenon lamp (illuminance 500mW cm⁻¹), -2 Under irradiation, the gas yield of S-Ti3C2 (with a Ti:S molar ratio of 1:8) was significantly improved compared to unsulfurized multilayer Ti3C2. The CH4 yield increased from 8.01 μmol g / L. -1 h -1 Increased to 65.17 μmol g -1 h -1This represents an 8.1-fold increase. Notably, CH4 is the main product, with selectivity improved to 88.36%. Furthermore, as the proportion of thiourea in the feed ratio increases, the yield of C2+ product C2H4 generated during the S-Ti3C2 reaction (based on a Ti:S molar ratio of 1:8) is found to be 5.28 μmol g. -1 h -1 Both the selectivity (10.74%) and the non-sulfurized multilayer Ti3C2 showed significant improvements and differences.

[0073] Comparative example:

[0074] Experiments on the reduction of carbon dioxide by S-Ti3C2 (with a Ti:S molar ratio of 1:8 calculated) under simulated and real sunlight:

[0075] (1) Carbon dioxide reduction test and results analysis of S-Ti3C2 (raw material feed ratio calculated according to Ti:S molar ratio of 1:8) under simulated sunlight.

[0076] The photocatalytic CO2 reduction reaction was carried out in a sealed 200 mL quartz reactor using an A.M1.5G xenon lamp as the light source, with a light intensity of 100 mW cm⁻¹. -2 In this experiment, a complete photocatalytic CO2 reduction reaction was defined as lasting 4 hours. First, 10 mg of S-Ti3C2 (based on a Ti:S molar ratio of 1:8) was dispersed in 10 mL of deionized water and ultrasonically dispersed for 20 minutes to ensure complete dispersion of the powdered catalyst. Then, high-purity CO2 gas (99.999%) was introduced into the reactor and maintained for 20 minutes to completely remove air from the system. The gas in the reactor was extracted every 60 minutes until the 4-hour reaction was completed. The gaseous products obtained after photocatalysis were detected and analyzed by gas chromatography equipped with a flame ionization detector (FID).

[0077] Experimental results show that at A.M1.5G (xenon lamp, 100mW cm⁻¹), -2 Under irradiation, the CH4 yield of S-Ti3C2 (based on a Ti:S molar ratio of 1:8) was 18.25 μmol g. -1 h -1 The selectivity was 83.60%, and the yield of the C2+ product C2H4 produced during the reaction was 2.25 μmol g. -1 h -1 The selectivity was 15.48%. Under simulated sunlight, the light-to-carbon-fuels (LTF) conversion efficiency of this invention reached 0.025%.

[0078] (2) Carbon dioxide reduction test and results analysis of S-Ti3C2 (raw material feed ratio calculated according to Ti:S molar ratio of 1:8) under natural sunlight

[0079] The photocatalytic CO2 reduction reaction was carried out in a sealed 100 mL quartz reactor, using natural sunlight focused by a solar cooker as the light source, with a light intensity of 4500 mW / cm². - 2 to 6000mW cm - 2. The values ​​are calculated based on the intensity of natural sunlight, and the light intensity parameter was measured using a light intensity meter. First, 10 mg of S-Ti3C2 (the raw material feed ratio was calculated according to a Ti:S molar ratio of 1:8) was dispersed in 2 mL of deionized water and ultrasonically dispersed for 5 minutes to disperse the powdered catalyst in the water. Then, high-purity CO2 gas (99.999%) was introduced into the reactor and maintained for 20 minutes to completely remove air from the system. Subsequently, a 100 mL reactor was placed on the central tray of the solar cooker, the focus of the sunlight was adjusted to be aimed at the bottom of the reactor, the timer was pressed, and the reaction was stopped after 1 minute of illumination. 4 mL of the gaseous product obtained after illumination was extracted and detected and analyzed by gas chromatography equipped with a flame ionization detector (FID).

[0080] Experimental results show that under the irradiation of focused natural sunlight by a solar cooker, the CH4 yield of S-Ti3C2 (based on a Ti:S molar ratio of 1:8) is 12.03 mmol g. -1 h -1 The yield of CO was 2.11 mmol g. -1 h -1 Furthermore, the yield of the C2+ product C2H4 generated during the reaction was increased to 3.55 mmol g. -1 h -1 Furthermore, the selectivity is improved to 29.76%. Under natural sunlight, the solar-to-carbon-fuels (STF) efficiency of this invention reaches the highest value of 0.057% in this research field to date.

Claims

1. The use of a photo-thermal catalyst for the photocatalytic reduction of carbon dioxide to produce CO, CH4, and C2H4, characterized in that, The photo-thermal catalyst is prepared by the following steps: (1) Synthesis of multilayer Ti3C2 First, a certain amount of Ti3AlC2 was slowly added to the HF solution to avoid overheating, and the mixture was stirred continuously in a room temperature water bath. After the reaction was completed, the mixture was washed several times with deionized water, centrifuged, and finally the solid residue was collected and dried under vacuum to obtain multilayer Ti3C2. (2) Synthesis of S-Ti3C2 First, a certain amount of thiourea CH4N2S was added to a certain amount of ethanol and stirred at room temperature until the solid was completely dissolved. The resulting solution was labeled as solution A. Subsequently, a certain amount of multilayer Ti3C2 was added to a mixed solvent of ethanol and ethylene glycol, and stirred at room temperature. The resulting dispersion system was labeled as solution B. Then, solutions A and B were mixed and stirred continuously at room temperature. Finally, the mixture was transferred to a high-temperature and high-pressure reactor and subjected to a solvothermal reaction in an oven. After the reaction was completed and cooled to room temperature, the mixture was washed several times with deionized CH4N2S water and ethanol. Finally, the washed precipitate was dried in a vacuum drying oven to obtain S-Ti3C2.

2. The use as described in claim 1, characterized in that, In step (1), the ratio of Ti3AlC2 to HF solution is 1g:20mL, and the concentration of HF solution is 40wt%.

3. The use as described in claim 1, characterized in that, In step (1), the stirring time is 24 to 48 hours.

4. The use as described in claim 1, characterized in that, In step (2), the ratio of thiourea CH4N2S to multilayer Ti3C2 is calculated according to the molar ratio of Ti:S from 1:2 to 1:

16.

5. The use as described in claim 1, characterized in that, In step (2), the volume ratio of ethanol to ethylene glycol in the mixed solvent of ethanol and ethylene glycol is 9:

1.

6. The use as described in claim 1, characterized in that, In step (2), the temperature of the solvothermal reaction is 120-180℃ and the time is 12h.

7. The use as described in claim 1, characterized in that, In step (2), when preparing solution B, the stirring time is 0.5 to 1 hour; when mixing solutions A and B, the stirring time is at least 2 hours.

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