Ti3C2T for photocatalytic carbon dioxide methanation x MXene / CuInSnS4 composite photocatalyst

Abstract

The application relates to the technical field of photocatalytic carbon dioxide reduction, in particular to a Ti3C2Tx MXene / CuInSnS4 composite photocatalyst for photocatalytic carbon dioxide methanation. x The reaction yield of photocatalytic carbon dioxide reduction to methane by a single CuInSnS4 catalyst is poor. x The Ti3C2Tx MXene / CuInSnS4 composite photocatalyst is obtained by compounding Ti3C2Tx MXene and CuInSnS4. x The addition of the Ti3C2Tx MXene enhances the conductivity of the composite material, inhibits the recombination of photo-generated electrons and holes to a certain extent, and is more favorable to the photocatalytic carbon dioxide reduction methanation reaction.

Description

Technical Field

[0001] This invention relates to the field of catalysts for photocatalytic carbon dioxide methanation, specifically to a Ti3C2T catalyst for photocatalytic carbon dioxide methanation. x MXene / CuInSnS4 composite photocatalyst. Background Technology

[0002] With the acceleration of industrialization, environmental pollution and energy consumption have become challenges facing all of humanity. Since Fujishima and Honda first demonstrated photoelectrocatalytic water splitting on a photoactive semiconductor catalyst in 1972, researchers have been dedicated to developing highly efficient photocatalysts capable of harvesting solar energy and converting it into chemical energy. Polymetallic chalcogenides, mainly composed of abundant and non-toxic elements found on Earth, show promise for photocatalytic carbon dioxide reduction due to their flexible composition, diverse structures, and tunable characteristics.

[0003] Copper indium tin sulfide (CuInSnS4) exhibits excellent performance in the photocatalytic reduction of carbon dioxide due to its unique crystal structure and optical properties. However, CuInSnS4 crystals are prone to aggregation during preparation, and photogenerated electrons and holes easily recombine, resulting in limited photocatalytic activity for carbon dioxide methanation.

[0004] MXene materials were first discovered in 2011 by Professors Yury Gogotsi and Michel Barsoum at Drexel University in the United States. Due to the presence of hydroxyl groups or terminal oxygen atoms on their surface, MXene materials exhibit the metallic conductivity of transition metal carbides. MXenes possess broad application potential in electrochemical energy storage, sensors, and catalysis due to their high conductivity, tunable work function, good light transmittance, and ease of composite with other materials. Summary of the Invention

[0005] A problem with existing technologies is that the photocatalytic reduction of carbon dioxide to methane using a single CuInSnS4 catalyst yields poor results. To address this issue, this invention provides a Ti3C2T catalyst for the photocatalytic methanation of carbon dioxide. x The preparation method of the MXene / CuInSnS4 composite photocatalyst includes the following steps:

[0006] (1) Lithium fluoride was fully dissolved in concentrated hydrochloric acid. Then, Ti3AlC2 powder was added to the concentrated hydrochloric acid, and the mixture was stirred until the aluminum layer in the Ti3AlC2 layered structure was completely etched away. After the reaction was completed, the obtained solid product was washed with deionized water until the filtrate was neutral. The obtained solid product was dispersed in deionized water and ultrasonically dispersed uniformly under an inert atmosphere. The obtained dispersion was subjected to solid-liquid separation to obtain the solid product, which was then freeze-dried to obtain Ti3C2Tx MXene powder;

[0007] (2) Cuprous chloride, tin tetrachloride pentahydrate and indium trichloride tetrahydrate were added to deionized water and stirred to disperse evenly. Then, thioacetamide was added to the above dispersion as a sulfur source. After being dispersed and stirred evenly, the mixture was placed in a reaction vessel for high-temperature hydrothermal reaction. After the reaction was completed, the obtained product was washed with deionized water and dried to obtain CuInSnS4 powder.

[0008] (3) Ti3C2T x MXene powder and CuInSnS4 powder were uniformly dispersed in deionized water to obtain Ti3C2T with the same mass concentration. x MXene powder solution and CuInSnS4 powder solution, while sonicating, Ti3C2T x MXene powder solution was added dropwise to CuInSnS4 powder solution to obtain a mixed solution. After the addition was complete, the mixture was ultrasonically dispersed and then stirred for at least 8 hours. The resulting reaction solution was collected by solid-liquid separation to obtain a solid product. After drying, Ti3C2T was obtained. x MXene / CuInSnS4 composite photocatalyst;

[0009] The mixed solution contains Ti3C2T x The mass ratio of MXene powder to CuInSnS4 powder is 1:2.

[0010] Preferably, in step (2), the mass ratio of cuprous chloride to tin tetrachloride pentahydrate, indium trichloride tetrahydrate, and thioacetamide is (0.095-0.01):(0.345-0.355):(0.29-0.30):(0.37-0.38).

[0011] Preferably, the temperature of the high-temperature hydrothermal reaction in step (2) is 170-190℃, and the hydrothermal reaction time is 22-26h.

[0012] Preferably, the concentration of concentrated hydrochloric acid in step (1) is 8-10 M.

[0013] The present invention has the following beneficial effects:

[0014] (1) The preparation method of this invention is simple and easy to implement, and the preparation conditions are easy to control. Ti3C2T x The addition of MXene enhances the conductivity of the composite material and inhibits the recombination of photogenerated electrons and holes to a certain extent, which is more conducive to the photocatalytic carbon dioxide reduction methanation reaction.

[0015] (2) Through experiments, the present invention found that the Ti3C2Tx MXene powder and CuInSnS4 powder were combined in a mass ratio of 1:2, and the resulting Ti3C2Tx MXene / CuInSnS4 composite photocatalyst had the best photocatalytic effect, with a methane yield of up to 48.51 μmol / g / h. Attached Figure Description

[0016] Figure 1 The Ti3C2T prepared in Example 2 x MXene, CuInSnS4, Ti3C2T x XRD diffraction comparison of MXene / CuInSnS4 composite photocatalyst.

[0017] Figure 2 SEM image of the 2-MXene / CuInSnS4 composite photocatalyst.

[0018] Figure 3 Example 2: MXene, CuInSnS4 and 2-Ti3C2T x Comparison of the effects of MXene / CuInSnS4, 1-MXene / CuInSnS4, and 3-MXene / CuInSnS4 on photocatalytic carbon dioxide methanation reaction.

[0019] Figure 4 Comparison of test results of photocatalytic carbon dioxide reduction cycle experiments of MXene, CuInSnS4 and 2-MXene / CuInSnS4 obtained in Example 2. Detailed Implementation

[0020] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0021] Example 1

[0022] (1)Ti3C2T x Preparation of MXene powder

[0023] 2.0 g of lithium fluoride was dissolved in 25.7 mL of hydrochloric acid (9 M) and stirred in an oil bath at 40 °C for 15 min. Then, 1.5 g of Ti3AlC2 powder was added, and the mixture was stirred for 48 h. The reaction solution was then washed with deionized water until the supernatant was neutral. The obtained solid product was dispersed in deionized water and ultrasonically dispersed under argon atmosphere for 3 h. The solid product was then collected by centrifugation and freeze-dried to obtain Ti3C2T. x MXene powder;

[0024] (2) Preparation of CuInSnS4

[0025] 0.099 g cuprous chloride, 0.35 g tin tetrachloride pentahydrate and 0.293 g indium trichloride tetrahydrate were added to 40 mL of deionized water and stirred until homogeneous. Then, 0.375 g thioacetamide was added and stirred until homogeneous. Subsequently, the solution was transferred to a reaction vessel and sealed. The reaction was carried out hydrothermally at 180 °C for 24 h. After natural cooling, the product was centrifuged. The obtained solid product was washed with deionized water and vacuum dried overnight at 60 °C to obtain CuInSnS4 powder.

[0026] (3)Ti3C2T x Preparation of MXene / CuInSnS4 composite photocatalyst

[0027] 0.02g Ti3C2T x MXene powder and 0.02 g CuInSnS4 powder were each dissolved in 40 mL of deionized water and ultrasonically dispersed for 30 min. After uniform dispersion, the MXene aqueous solution was added dropwise to the CuInSnS4 solution while ultrasonicating. The mixture was ultrasonically dispersed for another 1 h, and then stirred for another 8 h. The solid product was collected by centrifugation and dried under vacuum at 60 °C to obtain Ti3C2T. x MXene / CuInSnS4 composite photocatalyst (denoted as 1-MXene / CuInSnS4).

[0028] Example 2 is the same as Example 1, except that the amount of CuInSnS4 powder added in step (3) of Example 2 is 0.04 g. The composite photocatalyst obtained in Example 2 is designated as 2-MXene / CuInSnS4.

[0029] Example 3 is the same as Example 1, except that the amount of CuInSnS4 powder added in step (3) of Example 3 is 0.06 g. The composite photocatalyst obtained in Example 3 is designated as 3-MXene / CuInSnS4.

[0030] The Ti3C2T prepared in Example 2 x MXene, CuInSnS4, Ti3C2T x The crystal structure of the MXene / CuInSnS4 composite photocatalyst was analyzed using a Rigaku D / max2500PC rotating X-ray diffractometer (Japan), where the X-rays were from a Cu target Kα. Voltage 40kV, current 100mA, step size 0.02°, scanning range 5–80°. X-ray diffraction pattern as shown in the instruction manual. Figure 1 As shown, Ti3C2T xBoth MXene and CuInSnS4 exhibit strong diffraction peaks, and CuInSnS4 shows good matching with its standard card (PDF#29-0548), proving that Ti3C2T x MXene and CuInSnS4 were successfully synthesized. Meanwhile, Ti3C2T... x The MXene / CuInSnS4 composite photocatalyst (corresponding to MCISS in the figure) clearly belongs to Ti3C2T. x The (002) crystal plane characteristic peak is present, and all the characteristic peaks of CuInSnS4 are also present, indicating that Ti3C2T x The MXene / CuInSnS4 composite material was successfully synthesized.

[0031] The Ti3C2T obtained in Example 2 was observed using a Japanese JSM-6360A scanning electron microscope. x Scanning electron microscopy (SEM) images of 2-MXene / CuInSnS4 with a MXene powder to CuInSnS4 powder mass ratio of 1:2 are shown in the attached instruction manual. Figure 2 As shown in the figure, CuInSnS4 nanocrystals are loaded onto sheet-like Ti3C2T x MXene surface.

[0032] The MXene, CuInSnS4 and 2-Ti3C2T prepared in Example 2 were used. x MXene / CuInSnS4 (corresponding to MCISS(1:2) in the figure), 1-MXene / CuInSnS4 (corresponding to MCISS(1:1) in the figure), and 3-MXene / CuInSnS4 (corresponding to MCISS(1:3) in the figure) composite materials were used as photocatalysts for the carbon dioxide reduction methanation reaction. The performance of different photocatalysts in the carbon dioxide methanation reaction was tested. The specific test steps are as follows:

[0033] Dissolve 6 mg of photocatalyst in 2 mL of deionized water, mix thoroughly by ultrasonication, and then use a dropper to add the catalyst solution to the upper surface of a clean glass slide. Dry the slide at 70°C. Place a glass slide containing the dispersed catalyst at the opening of a small beaker. Take a transparent glass reactor with only one inlet and two outlets at the top (the reactor is sealed when both inlets and outlets are closed, and the reactor volume is 370 mL). The bottom of the reactor contains 20 mL of aqueous solution. Place a small beaker with a capacity of 25 mL inside the reactor and place the glass slide sample horizontally at the opening at the top of the small beaker, with the side of the glass slide sample bearing the photocatalyst facing upwards. Close one outlet of the reactor and open the other outlet. Continuously introduce high-purity CO2 gas through the inlet and expel the air from the reactor through the open outlet. This process is maintained for 15 minutes. Then, stop the gas flow and stop both the inlet and outlet. Then turn on the xenon lamp above the reaction. The light shines through the transparent container lid at the top of the reactor and irradiates the small beaker inside the reactor with an irradiation power of 300 W. After 4 hours of illumination, gas was extracted from one of the reactor outlets using a syringe and injected into a gas chromatograph for analysis of gas composition and content. The yields of CH4 and CO were calculated from the peak areas obtained by the chromatograph analysis (yield calculation formula: V=[(S / 40.663)×(0.001127232 / m)×350×2] / t. Where S: peak area of ​​CH4 or CO obtained by chromatograph analysis, m: mass of photocatalyst, t: illumination time).

[0034] The experimental results are as shown in the attached instruction manual. Figure 3 As shown, the CO production rates of pure MXene and CuInSnS4 were 4.29 and 2.24 μmol / g / h, respectively, while the CH4 production rates were 7.85 and 11.16 μmol / g / h, respectively. The CO production rate of the 2-MXene / CuInSnS4 composite photocatalyst was 18.92 μmol / g / h, approximately 4.4 and 8.4 times that of pure MXene and CuInSnS4, respectively. The CH4 production rate of the 2-MXene / CuInSnS4 composite photocatalyst was 48.51 μmol / g / h, approximately 6.4 and 4.3 times that of pure bismuth oxybromide and zinc oxide, respectively. This demonstrates that the combination of MXene and CuInSnS4 can effectively improve the photocatalytic carbon dioxide reduction activity of the photocatalyst. The prepared Ti3C2T x The MXene / CuInSnS4 composite photocatalyst exhibits higher photocatalytic activity.

[0035] To verify the Ti3C2T prepared in this invention xThe stability of the MXene / CuInSnS4 composite photocatalyst was assessed by conducting cyclic experiments on the photocatalytic reduction of carbon dioxide to methane of the MXene, CuInSnS4, and 2-MXene / CuInSnS4 (corresponding to MCISS in the figure) prepared in Example 2. The specific test steps are as follows:

[0036] Dissolve 6 mg of photocatalyst in 2 mL of deionized water, mix thoroughly by ultrasonication, and then drop the catalyst solution onto the upper surface of a clean glass slide using a dropper. Dry the slide at 70°C to obtain the glass slide sample. Take a transparent glass reactor with a volume of 370 mL, which has only one inlet and two outlets at the top. Fill the bottom of the reactor with 20 mL of aqueous solution. Place a small beaker with a capacity of 25 mL inside the reactor, and place the glass slide sample horizontally at the top opening of the beaker, with the photocatalyst-loaded side of the glass slide sample facing upwards. Close one outlet of the reactor and open the other outlet. Continuously introduce high-purity CO2 gas through the inlet and expel the air from the reactor through the open outlet. Maintain this process for 15 minutes. Then, stop the gas flow and stop both the inlet and outlet. Turn on the xenon lamp above the reactor, and let the light shine through the transparent container lid on top of the reactor to irradiate the small beaker inside the reactor. The irradiation power is 300 W. After 4 hours of illumination, gas was extracted from one of the reactor outlets using a syringe and injected into a gas chromatograph for composition and content determination. The yields of CH4 and CO were calculated from the peak areas of CH4 and CO obtained from the chromatograph analysis (test results are attached to the instruction manual). Figure 4 (4th in the middle).

[0037] After the test, the photocatalyst was scraped off the glass slide sample and redispersed in 2 mL of deionized water to obtain a catalyst solution. After ultrasonic mixing, the catalyst solution was added dropwise to the upper surface of a clean glass slide using a dropper. The sample was then dried at 70°C to obtain a new glass slide sample. Following the above photocatalytic steps, the yields of CH4 and CO were tested after a second 4 hours of illumination (test results correspond to the attached instruction manual). Figure 4 (8th in the middle).

[0038] After the test, the photocatalyst was scraped off the glass slide sample again and redispersed in 2 mL of deionized water to obtain a catalyst solution. After ultrasonic mixing, the catalyst solution was added dropwise to the upper surface of a clean glass slide using a dropper. The sample was then dried at 70°C to obtain a new glass slide sample. The yields of CH4 and CO after 4 hours of light irradiation were tested following the above photocatalytic steps (test results correspond to the attached instruction manual). Figure 4 (12th in the text).

[0039] After the test, the photocatalyst was scraped off the glass slide sample and redispersed in 2 mL of deionized water to obtain a catalyst solution. After ultrasonic mixing, the catalyst solution was added dropwise to the upper surface of a clean glass slide using a dropper. The sample was then dried at 70°C to obtain a new glass slide sample. Following the above photocatalytic steps, the yields of CH4 and CO were tested after a second 4 hours of illumination (test results correspond to the attached instruction manual). Figure 4 (16th).

[0040] The experimental results are as shown in the attached instruction manual. Figure 4 As shown, after four photocatalytic cycles, Ti3C2T x The CH4 yield of the MXene / CuInSnS4 composite photocatalyst was 43.66 μmol / g / h, a decrease of only 10% compared to the initial CH4 yield. This indicates that the prepared Ti3C2T x The MXene / CuInSnS4 composite photocatalyst exhibits good stability.

[0041] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A Ti3C2T photocatalytic carbon dioxide methanation method x MXene / CuInSnS4 composite photocatalyst, characterized in that, The preparation method includes the following steps: (1) Lithium fluoride was fully dissolved in concentrated hydrochloric acid. Then, Ti3AlC2 powder was added to the concentrated hydrochloric acid and stirred until the aluminum layer in the Ti3AlC2 layered structure was completely etched away. After the reaction was completed, the obtained solid product was washed with deionized water until the filtrate was neutral. The obtained solid product was dispersed in deionized water and ultrasonically dispersed uniformly under an inert atmosphere. The obtained dispersion was separated into solid and liquid to obtain the solid product. After freeze-drying, Ti3C2T was obtained. x MXene powder; (2) Add cuprous chloride, tin tetrachloride pentahydrate and indium trichloride tetrahydrate to deionized water, stir and disperse evenly, then add thioacetamide as a sulfur source to the above dispersion, disperse and stir evenly, place the mixture in a reaction vessel for high-temperature hydrothermal reaction, after the reaction is completed, the obtained product is washed with deionized water and dried to obtain CuInSnS4 powder. (3) Ti3C2T x MXene powder and CuInSnS4 powder were uniformly dispersed in deionized water to obtain Ti3C2T with the same mass concentration. x MXene powder solution and CuInSnS4 powder solution, while sonicating, Ti3C2T x MXene powder solution was added dropwise to CuInSnS4 powder solution to obtain a mixed solution. After the addition was complete, the mixture was ultrasonically dispersed and then stirred for at least 8 hours. The resulting reaction solution was collected by solid-liquid separation to obtain a solid product. After drying, Ti3C2T was obtained. x MXene / CuInSnS4 composite photocatalyst; The mixed solution contains Ti3C2T x The mass ratio of MXene powder to CuInSnS4 powder is 1:

2.

2. The Ti3C2Tx MXene / CuInSnS4 composite photocatalyst for photocatalytic carbon dioxide methanation according to claim 1, characterized in that, In step (2), the mass ratio of cuprous chloride to tin tetrachloride pentahydrate, indium trichloride tetrahydrate, and thioacetamide is (0.095-0.01):(0.345-0.355):(0.29-0.30):(0.37-0.38).

3. The Ti3C2Tx MXene / CuInSnS4 composite photocatalyst for photocatalytic carbon dioxide methanation according to claim 1, characterized in that, In step (2), the temperature of the high-temperature hydrothermal reaction is 170-190℃, and the hydrothermal reaction time is 22-26h.

4. The Ti3C2Tx MXene / CuInSnS4 composite photocatalyst for photocatalytic carbon dioxide methanation according to claim 1, characterized in that, The concentration of concentrated hydrochloric acid in step (1) is 8-10M.

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