A photocatalyst with surface Cu and S dual defect sites, a preparation method thereof, and an application thereof

Abstract

The present invention belongs to the technical field of photocatalysts, and discloses a Cu 1.95 S 1‑x photocatalyst with surface Cu and S dual defect sites, its preparation method and application. By adding cetyltrimethylammonium bromide and hexamethylenetetramine to an ethylene glycol solution containing copper element, adding a certain amount of thioacetamide, stirring for a certain time at a certain temperature and then pouring it into a reaction kettle, and carrying out hydrothermal reaction at a certain temperature for a certain time, after washing and drying, a Cu 1.95 S 1‑x photocatalyst with surface Cu and S dual defect sites is obtained. The specific surface area of the photocatalyst prepared by the present invention is larger, and it has higher photocatalytic activity. In particular, the photocatalytic reduction activity of CO2 is enhanced, and the preparation method of the catalyst reduces the production cost and simplifies the production process. The prepared Cu 1.95 S 1‑x photocatalyst with surface Cu and S dual defect sites can photocatalytically reduce CO2 to CH4.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysts, and particularly relates to a CuS photocatalyst with surface Cu and S dual defect sites, a preparation method thereof, and an application thereof in the field of photocatalytic reduction of CO 1.95 S 1-x and its application in the field of photocatalytic reduction of CO 2 . Background Technique

[0002] At present, photocatalytic reduction of CO 2 technology provides an effective strategy for solving the energy crisis under the background of "dual carbon". The core of photocatalytic technology is photocatalysts. In recent years, CuS, as a traditional photocatalyst, has shown its unique advantages in the field of photocatalysis. In order to further improve the catalytic performance of CuS photocatalysts, scientific researchers have begun to design a series of modification strategies. Currently, the activity of CuS photocatalysts can be improved by methods such as doping other elements, noble metal deposition, and constructing heterojunction structures. For example, Bi / CuS metal deposition photocatalysts, CuS / Cu 9 S 5 heterojunction photocatalysts, Ni-CuS element-doped photocatalysts, etc. However, the number of surface-exposed reactive sites of the above modified CuS photocatalysts is relatively small, which is not conducive to significantly improving the photocatalytic activity of CuS. With the in-depth research, defect engineering is considered an effective strategy to provide more active sites for photocatalytic reactions by constructing defect sites on the surface of photocatalysts. For CuS catalysts, currently, non-stoichiometric CuS-based photocatalysts containing surface Cu defects can be prepared by controlling reaction parameters to adjust the ratio of Cu elements and S elements, such as Cu 1.96 S, Cu 9 S 5 , etc. Or reducing reagents can be used to construct CuS-based photocatalysts containing surface S defects, such as CuS 1-x , etc. Although both of these strategies can construct single-type cationic defects or anionic defects on the surface of CuS photocatalysts, single-type defects as exposed active sites still have certain limitations. Therefore, finding simple and effective modification methods to make copper sulfide-based photocatalysts have high photocatalytic activity is an important research topic in the field of photocatalysis.

[0003] Through the above analysis, the problems and defects existing in the prior art are as follows:

[0004] (1) Among the existing strategies for improving the activity of CuS photocatalysts, the cost of metal deposition is relatively high, which will limit its large-scale industrial application. The CuS photocatalysts after ion doping are not conducive to carrier separation and have poor stability; the synthesis methods of heterojunction photocatalysts are cumbersome and do not have the prospect of industrial application.

[0005] (2) The CuS photocatalyst modified by defect engineering still has the problem of a small number of reactive sites even though a single type of cationic or anionic defect is exposed on its surface, which limits the improvement of its photocatalytic activity. SUMMARY OF THE INVENTION

[0006] In view of the problems existing in the prior art, the present invention provides a Cu 1.95 S 1-x photocatalyst with surface Cu and S dual defect sites, a preparation method thereof, and an application thereof in the field of photocatalytic reduction of CO 2 The prepared Cu 1.95 S 1-x photocatalyst has both surface Cu defects and S defects, and can provide more active sites for photocatalytic reduction of CO 2

[0007] To achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] A preparation method of a photocatalyst with surface Cu and S dual defect sites, comprising the following steps:

[0009] (1) Under stirring conditions, a compound containing a certain amount of copper element is dissolved in a certain amount of ethylene glycol to obtain an ethylene glycol solution;

[0010] (2) A certain amount of cetyltrimethylammonium bromide and hexamethylenetetramine are added to the ethylene glycol solution obtained in step (1) to obtain a mixture a;

[0011] (3) A certain amount of thioacetamide is added to the mixture a obtained in step (2), and stirred for a period of time to obtain a mixture b;

[0012] (4) The mixture b obtained in step (3) is poured into a reaction kettle, hydrothermally reacted at a certain temperature for a period of time, and then the reaction product is taken out and washed;

[0013] (5) The washed reaction product is dried to obtain a Cu 1.95 S 1-x photocatalyst with surface Cu and S dual defect sites.

[0014] Further, the compound containing a certain amount of copper element in step (1) is selected from copper dichloride dihydrate, and the addition amount of the copper dichloride dihydrate is 1 mmol; the addition amount of ethylene glycol for dissolving 1 mmol of copper dichloride dihydrate is 20 - 40 mL, including 20 mL, 30 mL or 40 mL, preferably 40 mL.

[0015] ​Further, the addition amount of cetyltrimethylammonium bromide described in step (2) is 100-400 mg, including 100 mg, 200 mg, 300 mg or 400 mg, and preferably 300 mg.

[0016] Further, the addition amount of hexamethylenetetramine described in step (2) is 100-400 mg, including 100 mg, 200 mg, 300 mg or 400 mg, and preferably 300 mg.

[0017] Further, the addition amount of thioacetamide described in step (3) is 1-2 mmol, including 1 mmol, 1.5 mmol or 2 mmol, and preferably 1.5 mmol.

[0018] Further, the stirring time in step (3) is 1-3 h, including 1 h, 2 h or 3 h, and preferably 2 h.

[0019] Further, the temperature in step (4) is 160-200 °C, including 160 °C, 180 °C, or 200 °C, and preferably 180 °C; the hydrothermal reaction time is 12-48 h, including 12 h, 24 h or 48 h, and preferably 24 h.

[0020] Further, the reaction product in step (5) is dried in an oven, the drying time is 7-15 h, preferably 12 h; the drying temperature is 60-80 °C, including 60 °C, 70 °C or 80 °C, and preferably 70 °C.

[0021] The purpose of the present invention is to provide a photocatalyst with surface Cu and S double defect sites. The photocatalyst is a modified structure copper sulfide-based photocatalyst, and the specific surface area is 100-120 m 2 g -1 .

[0022] Another purpose of the present invention is to provide an application of a photocatalyst with surface Cu and S double defect sites. The photocatalyst with surface Cu and S double defect sites is used for photocatalytic reduction of CO 2 .

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The Cu 1.95 S 1-x photocatalyst with surface Cu and S double defect sites prepared by the hydrothermal method in the present invention has better catalytic activity than the CuS photocatalyst. The Cu 1.95 S 1-x photocatalyst with surface double defect sites provided by the present invention has a specific surface area of 100-120 m 2 g-1 , the increase in specific surface area exposes more Cu and S dual active sites, improving the catalytic activity of the catalyst. The photocatalyst prepared in the present invention can generate more photoexcited electrons under light illumination. The presence of Cu and S dual active sites greatly reduces the electron-hole recombination rate, and the photocatalytic activity is significantly improved, especially for photocatalytic reduction of CO 2 has high activity, and the preparation method is simple and the conditions are mild, achieving the purpose of reducing costs and simplifying the production process, and can be applied to photocatalytic reduction of CO 2 .

[0025] (2) The present invention optimizes the preparation process of this type of photocatalyst, achieving the purpose of reducing costs and simplifying the production process.

[0026] (3) The photocatalyst described in the present invention has surface Cu and S dual active sites, improving the photocatalytic activity.

[0027] (4) Using the photocatalyst described in the present invention to reduce CO 2 , under the light irradiation of simulated sunlight, it can obtain 149.04 μmol g 2 in the 12-hour photocatalytic reduction of CO -1 reaction of CH 4 , greatly improving the photocatalytic performance.

[0028] (5) The present invention uses non-toxic components, reducing the harm to human health and the ecological environment.

[0029] (6) The photocatalyst prepared in the present invention does not require the addition of other chemical reagents and other post-preparation treatments, and the method is simple.

[0030] (7) The Cu 1.95 S 1-x photocatalyst with surface double defect sites prepared in the present invention has a larger specific surface area, higher photocatalytic activity, and the photocatalyst preparation method is simple and the conditions are mild, and can be applied to photocatalytic energy conversion.

[0031] (8) The Cu 1.95 S 1-x photocatalyst with surface Cu and S double defect sites provided by the present invention has better photocatalytic performance compared with the existing CuS photocatalyst. The preparation method of this catalyst reduces the production cost and simplifies the production process. The prepared Cu 1.95 S 1-x photocatalyst with surface Cu and S double defect sites can photocatalytically reduce CO 2 to CH 4 . BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required in the embodiments of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other accompanying drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 is the CuS photocatalyst with surface Cu and S dual defect sites provided by the embodiments of the present invention 1.95 S 1-x Flow chart of the preparation method of the photocatalyst.

[0034] Figure 2 is the CuS photocatalyst with surface Cu and S dual defect sites provided by the embodiments of the present invention 1.95 S 1-x and the XRD spectrum of the CuS photocatalyst.

[0035] Figure 3 is the CuS photocatalyst with surface Cu and S dual defect sites provided by the embodiments of the present invention 1.95 S 1-x and the EPR spectrum of the CuS photocatalyst.

[0036] Figure 4 is the CuS photocatalyst with surface Cu and S dual defect sites provided by the embodiments of the present invention 1.95 S 1-x Transmission electron micrograph of the photocatalyst.

[0037] Figure 5 is the CuS photocatalyst with surface Cu and S dual defect sites provided by the embodiments of the present invention 1.95 S 1-x and the methane production graph of the CuS photocatalyst. Detailed implementation manners

[0038] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] As Figure 1 shown, the preparation method of the CuS photocatalyst with surface Cu and S dual defect sites provided by the embodiments of the present invention 1.95 S 1-x includes the following steps:

[0040] S101, under stirring conditions, dissolve a compound containing a certain amount of copper element in a certain amount of ethylene glycol;

[0041] S102, Add a certain amount of cetyltrimethylammonium bromide and hexamethylenetetramine to the ethylene glycol solution obtained in step S101;

[0042] S103, Add a certain amount of thioacetamide to the solution obtained in step S102, and stir for a period of time;

[0043] S104, Pour the solution obtained in step S103 into a 50 mL reaction kettle, carry out hydrothermal reaction at a certain temperature for a period of time, and then take out the reaction product for cleaning;

[0044] S105, Dry the cleaned reaction product to obtain a Cu 1.95 S 1-x photocatalyst with surface double defect sites.

[0045] In the embodiment of the present invention, by adding compounds such as thioacetamide to ethylene glycol containing copper element, after stirring at a certain temperature for a certain time, a Cu 1.95 S 1-x photocatalyst with surface double defect sites is obtained.

[0046] The inorganic compound containing copper element provided in the embodiment of the present invention is selected from copper dichloride dihydrate.

[0047] In the embodiment of the present invention, the addition amount of copper dichloride dihydrate is 1 mmol; the addition amount of ethylene glycol for dissolving 1 mmol of copper dichloride dihydrate is 20 - 40 mL, including 20 mL, 30 mL or 40 mL, and preferably 40 mL.

[0048] In the embodiment of the present invention, for the addition amounts of cetyltrimethylammonium bromide and hexamethylenetetramine, for cetyltrimethylammonium bromide, the addition amount is 100 - 400 mg, including 100 mg, 200 mg, 300 mg or 400 mg, and preferably 300 mg. For hexamethylenetetramine, the addition amount is 100 - 400 mg, including 100 mg, 200 mg, 300 mg or 400 mg, and preferably 300 mg.

[0049] In the embodiment of the present invention, the addition amount of thioacetamide is 1 - 2 mmol, including 1 mmol, 1.5 mmol or 2 mmol, and preferably 1.5 mmol.

[0050] In the embodiment of the present invention, the stirring time is 1 - 3 h, including 1 h, 2 h or 3 h, and preferably 2 h.

[0051] In the embodiment of the present invention, the reaction temperature is 160 - 200 °C, including 160 °C, 180 °C or 200 °C, and preferably 180 °C.

[0052] In the embodiment of the present invention, the hydrothermal reaction time is 12 to 48 hours, including 12 hours, 24 hours or 48 hours, preferably 24 hours.

[0053] In the embodiment of the present invention, the reaction product is dried in an oven, and the drying time is 7 to 15 hours, preferably 12 hours.

[0054] In the embodiment of the present invention, the drying temperature is 60 to 80 °C, including 60 °C, 70 °C or 80 °C, preferably 70 °C.

[0055] The technical solution of the present invention will be further described below through more specific embodiments.

[0056] Example 1

[0057] A preparation method of a Cu 1.95 S 1-x photocatalyst with surface Cu and S double defect sites, comprising the following steps:

[0058] Dissolve 300 mg of cetyltrimethylammonium bromide and 300 mg of hexamine in 40 ml of ethylene glycol, add 1 mmol of copper dichloride dihydrate to the solution and stir until completely dissolved. Subsequently, add 1.5 mmol of thioacetamide and stir vigorously for 2 h, then transfer the solution to a 50 mL autoclave and heat at 180 °C for 24 h. After the reaction, wash and centrifuge repeatedly with ethanol and deionized water, then pour the precipitate into a glass petri dish and dry at 70 °C for 12 h to obtain a Cu 1.95 S 1-x photocatalyst with surface double defect sites.

[0059] The Cu 1.95 S 1-x photocatalyst with surface Cu and S double defect sites prepared in the embodiment of the present invention and the XRD patterns of the CuS photocatalyst are as Figure 2 shown. The Cu 1.95 S 1-x photocatalyst with surface double Cu and S defect sites and the electron paramagnetic resonance spectrum (EPR) of the CuS photocatalyst prepared in the embodiment of the present invention are as Figure 3 shown. The transmission electron microscope image of the Cu 1.95 S 1-x photocatalyst with surface double Cu and S defect sites prepared in the embodiment of the present invention is as Figure 4 shown.

[0060] Comparative Example 1

[0061] Dissolve 1 mmol of copper chloride dihydrate in 40 ml of ethylene glycol. Subsequently, add 1 mmol of thioacetamide and stir vigorously for 2 h. Then transfer the solution to a 50 mL autoclave and heat it at 180 °C for 24 h. After the reaction, wash the precipitate repeatedly with ethanol and deionized water by centrifugation, and then pour the precipitate into a glass petri dish and dry it at 70 °C for 12 h to obtain the catalyst.

[0062] Example 2

[0063] Cu with surface Cu and S dual defect sites 1.95 S 1-x Photocatalyst CO 2 Evaluation of reduction performance

[0064] The experimental conditions are as follows: CO 2 The photoreduction experiment was carried out in a gas-solid phase reactor of the Labsolar 6A closed-loop system (Beijing Perfectlight Co., Ltd.). First, disperse 10 mg of the sample in 10 ml of distilled water and dry it on the surface of a microporous membrane with a diameter of 2.0 cm. Subsequently, evacuate the reaction system and purge it with pure CO 2 under a constant pressure of about 1 atm. The light source is a 300 w xenon lamp with an AM1.5G filter (PLS-SXE 300UV, Beijing Perfectlight Co., Ltd.). The reaction temperature is maintained at 298 K using a circulating cooling system (DC-0506, Shanghai Shunyu Hengping Scientific Instrument Co., Ltd.). CO 2 The photoreduction products were analyzed using a GC2002 gas chromatograph (Shanghai Kechuang Chromatographic Instrument Co., Ltd.). Automatic injection was performed every hour, and the products were used as the evaluation index of photocatalytic activity with μmol g -1

[0065] The Cu 1.95 S 1-x photocatalyst with surface dual defect sites obtained in Example 1 of the present invention and the test performance values of the unmodified CuS photocatalyst obtained in Comparative Example 1 are as Figure 5 shown in Table 1. It can be seen from the table that the specific surface area of the catalyst prepared in Example 1 of the present invention is 110.05 m 2 g -1 . Compared with the photocatalytic reduction CO 2 performance of the unmodified CuS photocatalyst, the Cu 1.95 S 1-x photocatalyst with surface dual defect sites can obtain 149.04 μmol g 2 of CH -1 in the 12 h photocatalytic reduction CO 4 reaction, and the yield will further increase with the extension of time.

[0066] Table 1 Performance values of the photocatalysts obtained in Example 1 and Comparative Example 1

[0067]

[0068]

[0069] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention by those skilled in the art within the technical scope disclosed by the present invention shall be covered by the protection scope of the present invention.

Claims

1. A preparation method of a photocatalyst with surface Cu and S dual defect sites, characterized in that, it includes the following steps: (1) Under stirring conditions, dissolve a compound containing a certain amount of copper element in a certain amount of ethylene glycol to obtain an ethylene glycol solution; (2) Add a certain amount of cetyltrimethylammonium bromide and hexamethylenetetramine to the ethylene glycol solution obtained in step (1) to obtain mixture a; (3) Add a certain amount of thioacetamide to mixture a obtained in step (2), stir for a period of time to obtain mixture b; (4) Pour mixture b obtained in step (3) into a reaction kettle, carry out hydrothermal reaction at a certain temperature for a period of time, and then take out and wash the reaction product; (5) Dry the washed reaction product to obtain a Cu 1.95 S 1-x photocatalyst with surface Cu and S dual defect sites.

2. The preparation method of the photocatalyst with surface Cu and S dual defect sites according to claim 1, characterized in that, in step (1), the compound containing a certain amount of copper element is selected from copper dichloride dihydrate, and the addition amount of the copper dichloride dihydrate is 1 mmol; the addition amount of ethylene glycol for dissolving 1 mmol of copper dichloride dihydrate is 20 - 40 mL.

3. The preparation method of the photocatalyst with surface Cu and S dual defect sites according to claim 1, characterized in that, the addition amount of the cetyltrimethylammonium bromide in step (2) is 100 - 400 mg.

4. The preparation method of the photocatalyst with surface Cu and S dual defect sites according to claim 1, characterized in that, the addition amount of the hexamethylenetetramine in step (2) is 100 - 400 mg.

5. The preparation method of the photocatalyst with surface Cu and S dual defect sites according to claim 1, characterized in that, the addition amount of the thioacetamide in step (3) is 1 - 2 mmol.

6. The preparation method of the photocatalyst with surface Cu and S dual defect sites according to claim 1, characterized in that, the stirring time in step (3) is 1 - 3 h.

7. The preparation method of the photocatalyst with surface Cu and S dual defect sites according to claim 1, characterized in that, the temperature in step (4) is 160 - 200 °C; the hydrothermal reaction time is 12 - 48 h.

8. The preparation method of the photocatalyst with surface Cu and S dual defect sites according to claim 1, characterized in that, in step (5), the reaction product is dried in an oven, the drying time is 7 - 15 h; the drying temperature is 60 - 80 °C.

9. A photocatalyst with surface Cu and S dual defect sites prepared by the method according to any one of claims 1 - 8, characterized in that, The photocatalyst described is a modified-structured copper sulfide-based photocatalyst with a specific surface area of 100 to 120 m 2 g -1 .

10. An application of the photocatalyst with surface Cu and S dual defect sites according to claim 9, characterized in that, The photocatalyst with surface Cu and S dual defect sites is used for photocatalytic reduction of CO 2 .

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