SiC / BiOCl composite photocatalytic material for carbon dioxide reduction and preparation method and application thereof

Abstract

The application belongs to the technical field of catalytic material preparation and application, and particularly relates to a SiC / BiOCl composite photocatalytic material for carbon dioxide reduction and a preparation method and application thereof. The photocatalytic material is composed of SiC and BiOCl, and the preparation method comprises the following steps: etching SiC in a mixed solution of hydrofluoric acid and nitric acid, dispersing in a Bi(NO3)3 ethylene glycol solution to form a suspension, and then adding a KCl solution into the suspension to perform an in-situ precipitation reaction at room temperature to obtain the SiC / BiOCl composite photocatalytic material. The photocatalytic material has a greatly reduced interface defect, higher electron transmission efficiency and electron-hole separation efficiency, and higher catalytic activity, selectivity and stability. The preparation method does not require special equipment and harsh conditions, and has simple process, strong controllability, easy realization of large-scale production and good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalytic material preparation and application, and particularly relates to a SiC / BiOCl composite photocatalytic material for carbon dioxide reduction and a preparation method and application thereof. BACKGROUND

[0002] In recent years, the extensive use of fossil fuels (coal, oil, natural gas) is accompanied by a large amount of carbon dioxide being discharged into the atmosphere, which seriously affects the carbon cycle of the earth. Through photocatalysis, the catalytic conversion of carbon dioxide can be driven by clean energy solar energy, which is an effective way to realize the green cycle of carbon dioxide at present. However, how to construct a catalytic material with high catalytic efficiency and scalable production is one of the core problems to be solved at present.

[0003] BiOCl photocatalytic material has the advantages of simple synthesis and easy to obtain raw materials, and is one of the most common materials used in the photocatalytic reduction of carbon dioxide at present. Its two-dimensional structure can provide a large number of reaction sites for reactants, and it is easy to assemble in situ with different materials, and has strong controllability. However, the high recombination rate of photo-generated electron-hole pairs in BiOCl photocatalytic material and the small light absorption range caused by wide band gap seriously inhibit its catalytic efficiency. In addition, the general preparation method of BiOCl is mainly hydrothermal method, which has large energy consumption. For example, the preparation method of a BiOCl nano photocatalyst, the prepared photocatalyst and application disclosed in patent CN107159273, the preparation method of a bismuth oxychloride photocatalyst and application disclosed in patent CN114790008A and the preparation method of a modified bismuth oxychloride photocatalyst and its preparation method disclosed in patent CN116870935A are all hydrothermal methods. Compared with the above methods, SiC material has excellent electron mobility (1000 μ e ) and saturation electron velocity (2.7 x 10 7cm / s) and light absorption ability of the full wave band of ultraviolet-visible light, after being compounded with different materials, not only can effectively improve the electron transport efficiency and reduce the recombination of photo-generated electron-hole pairs, but also can further enhance the light absorption range of the base material. For example, after being compounded with C3N4(Wang et al. Applied Surface Science 391 (2017) 449-456), BiVO4(Wang et al., Chemical Engineering Journal 281 (2015) 102-108) and BiOBr(Hou et al. Applied Surface Science 534 (2021) 148779), the light absorption ability and electron-hole separation efficiency of SiC can be effectively improved, thereby significantly enhancing the photocatalytic performance of each material. In addition, when Liu et al. prepared SiC / BiOCl composite material, they also used the water hydrothermal method with high energy consumption, which is not easy to realize large-scale application (Liu et al., Catalysts 10 (2020) 946). Therefore, it is urgent to develop a preparation method of SiC / BiOCl composite photocatalytic material which is easy to scale production. SUMMARY

[0004] In view of the deficiencies of the prior art, in order to further improve the efficiency of bismuth-based photocatalytic materials for solar carbon dioxide reduction, the present application provides a SiC / BiOCl composite photocatalytic material for carbon dioxide reduction and a preparation method and application thereof. The present application prepares a SiC / BiOCl composite photocatalytic material with high electron-hole separation efficiency, high carbon dioxide catalytic reduction activity and I-type heterojunction by a simple in-situ precipitation method at room temperature. When used for photocatalytic reduction of carbon dioxide, the present application can increase the carbon monoxide yield by 4 to 7 times, solving the problems of low separation efficiency of photo-generated electrons and holes, weak light absorption ability and poor catalytic performance of BiOCl materials.

[0005] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0006] A SiC / BiOCl composite photocatalytic material for carbon dioxide reduction is a material with I-type heterojunction composed of SiC and BiOCl in a mass ratio of 1:1 to 100.

[0007] A preparation method of the SiC / BiOCl composite photocatalytic material as described above, comprising the following steps:

[0008] Step 1: etching SiC powder in a mixed solution of hydrofluoric acid / nitric acid to obtain etched SiC;

[0009] Step 2: etching SiC is added into the Bi(NO3)3·5H2O ethylene glycol solution to form a suspension;

[0010] Step 3: KCl solution is added into the suspension to perform in-situ precipitation reaction to obtain SiC / BiOCl composite photocatalytic material.

[0011] Preferably, the volume ratio of hydrofluoric acid to nitric acid in the mixed solution of hydrofluoric acid / nitric acid in step 1 is 3:1; and the solid-liquid ratio of SiC powder to the mixed solution of hydrofluoric acid / nitric acid is 1:30-50.

[0012] Preferably, the etching time in step 1 is 3-12h.

[0013] Preferably, the molar ratio of Bi(NO3)3·5H2O to KCl in step 3 is 1:7.5.

[0014] Preferably, the in-situ precipitation reaction time in step 3 is 1-3h.

[0015] An application of the SiC / BiOCl composite photocatalytic material as described above is used for photocatalytic reduction of carbon dioxide.

[0016] Preferably, the SiC / BiOCl composite photocatalytic material is dispersed in water, and after ultrasonic dispersion to form a suspension, the suspension is added into a photochemical reactor, carbon dioxide gas is introduced after sealing and vacuumizing, and carbon dioxide reduction reaction is performed under Xe lamp irradiation.

[0017] Preferably, the mass ratio of SiC / BiOCl composite photocatalytic material to water is 1:2000.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] 1. The SiC in the SiC / BiOCl composite photocatalyst prepared by the present application is modified by surface etching, which not only increases the specific surface area of the material (from 11.3m 2 / g to 46.8m 2 / g), but also effectively removes the surface inert oxide layer (such as silicon dioxide) and residual organic matter, and accelerates the surface electron transport rate.

[0020] 2. The SiC / BiOCl catalyst prepared by the present application is an I-type heterostructure, the electrons on the conduction band of BiOCl migrate to the conduction band of SiC, and the holes on the valence band of BiOCl migrate to the valence band of SiC, which significantly promotes the photoelectron transport efficiency and the separation efficiency of photoelectrons-holes of SiC.

[0021] 3、The SiC / BiOCl composite photocatalyst prepared by the method has a nanosheet / nanosphere close contact structure, which is beneficial to the migration of photo-generated charges at the interface.

[0022] 4、The SiC / BiOCl composite photocatalyst prepared by the method can efficiently reduce CO2 into CO without any sacrificial agent and photosensitizer, and the CO yield can reach 56.57 μmol·g -1 ·h -1 , which is 7.72 times that of pure BiOCl and 11.9 times that of etched SiC, and has high selectivity and good cycle stability.

[0023] 5、The preparation method is one-step in-situ precipitation at room temperature, and has the advantages of simple operation, mild reaction conditions, easy industrial production and wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 XRD spectra of the SiC / BiOCl composite photocatalytic materials obtained in Examples 1-4, the BiOCl material obtained in Comparative Example 1, and the etched SiC obtained in Comparative Example 2;

[0025] Figure 2 SEM spectra of the SiC / BiOCl composite photocatalytic materials obtained in Examples 1-4, the BiOCl material obtained in Comparative Example 1, and the etched SiC obtained in Comparative Example 2;

[0026] Figure 3 Photocatalytic reduction CO2 performance graph of the SiC / BiOCl composite photocatalytic materials obtained in Examples 1-4, the BiOCl material obtained in Comparative Example 1, and the etched SiC obtained in Comparative Example 2. DETAILED DESCRIPTION

[0027] The application will be further described and illustrated below in combination with the drawings and specific examples. The examples are implemented on the premise of the technical scheme of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the examples described below.

[0028] Example 1

[0029] A preparation method of a SiC / BiOCl composite photocatalytic material for carbon dioxide reduction, comprising the following steps:

[0030] Step 1: 0.5g of commercially available nanoscale SiC powder is added to 20mL of a mixed solution of hydrofluoric acid / nitric acid with a volume ratio of 3:1, stirred at room temperature for 6h, then centrifuged and washed with distilled water and anhydrous ethanol until neutral, and dried in an oven at 60℃ for 8h to obtain etched SiC;

[0031] Step 2: 1.117 g (0.002 mol) of Bi(NO)3·5H2O was dissolved in ethylene glycol, and a clear and transparent solution was obtained by stirring at room temperature. Then, 0.075 g of the etched SiC obtained in step 1 was added to the solution, and a uniformly dispersed gray suspension was obtained by ultrasonic treatment;

[0032] Step 3: 0.1717 g (0.015 mol) of KCl was added to distilled water, and a KCl solution was obtained by stirring and dissolving;

[0033] Step 4: The KCl solution obtained in step 3 was slowly added to the suspension obtained in step 2 under continuous stirring, and a gray-white precipitate was generated. After stirring at room temperature for 3 h, centrifugal separation was performed, and the obtained solid product was washed with distilled water and anhydrous ethanol until neutral. Then, the product was dried in an oven at 60°C for 8 h to obtain a SiC / BiOCl composite photocatalytic material with a theoretical mass ratio of 1:1.

[0034] Example 2

[0035] A method for preparing a SiC / BiOCl composite photocatalytic material for carbon dioxide reduction, comprising the following steps:

[0036] Step 1: 0.5 g of commercially available nanospherical SiC powder was added to a 20 mL mixed solution of hydrofluoric acid and nitric acid with a volume ratio of 3:1. After stirring at room temperature for 6 h, centrifugal separation was performed, and the product was washed with distilled water and anhydrous ethanol until neutral. Then, the product was dried in an oven at 60°C for 8 h to obtain etched SiC.

[0037] Step 2: 1.117 g (0.002 mol) of Bi(NO)3·5H2O was dissolved in ethylene glycol, and a clear and transparent solution was obtained by stirring at room temperature. Then, 0.075 g of the etched SiC obtained in step 1 was added to the solution, and a uniformly dispersed gray suspension was obtained by ultrasonic treatment;

[0038] Step 3: 0.1717 g (0.015 mol) of KCl was added to distilled water, and a KCl solution was obtained by stirring and dissolving;

[0039] Step 4: The KCl solution obtained in step 3 was slowly added to the suspension obtained in step 2 under continuous stirring, and a gray-white precipitate was generated. After stirring at room temperature for 3 h, centrifugal separation was performed, and the obtained solid product was washed with distilled water and anhydrous ethanol until neutral. Then, the product was dried in an oven at 60°C for 8 h to obtain a SiC / BiOCl composite photocatalytic material with a theoretical mass ratio of 1:8.

[0040] Example 3

[0041] A method for preparing a SiC / BiOCl composite photocatalytic material for carbon dioxide reduction, comprising the following steps:

[0042] Step 1: 0.5 g of commercially available nanometer spherical SiC powder is added to a 20 mL mixed solution of hydrofluoric acid / nitric acid with a volume ratio of 3:1, and after stirring and etching at room temperature for 6 h, centrifugal separation is performed, and washing with distilled water and anhydrous ethanol is performed until neutral, and drying at 60°C in an oven for 8 h to obtain etched SiC;

[0043] Step 2: 1.117 g (0.002 mol) of Bi(NO)3·5H2O is weighed and dissolved in ethylene glycol, a clear and transparent solution is obtained by stirring and dissolving at room temperature, and 0.015 g of etched SiC obtained from step 1 is added to the solution, and a uniformly dispersed gray suspension is obtained by ultrasonic treatment;

[0044] Step 3: 0.1717 g (0.015 mol) of KCl is added to distilled water, and a KCl solution is obtained by stirring and dissolving;

[0045] Step 4: The KCl solution obtained in step 3 is slowly added to the suspension obtained in step 2 under continuous stirring, a gray-white precipitate is generated, centrifugal separation is performed after continuing to stir at room temperature for 3 h, the obtained solid product is washed with distilled water and anhydrous ethanol until neutral, and drying at 60°C in an oven for 8 h to obtain a SiC / BiOCl composite photocatalytic material with a theoretical mass ratio of 1:40.

[0046] Example 4

[0047] A method for preparing a SiC / BiOCl composite photocatalytic material for carbon dioxide reduction, comprising the following steps:

[0048] Step 1: 0.5 g of commercially available nanometer spherical SiC powder is added to a 20 mL mixed solution of hydrofluoric acid / nitric acid with a volume ratio of 3:1, and after stirring and etching at room temperature for 6 h, centrifugal separation is performed, and washing with distilled water and anhydrous ethanol is performed until neutral, and drying at 60°C in an oven for 8 h to obtain etched SiC;

[0049] Step 2: 1.117 g (0.002 mol) of Bi(NO)3·5H2O is weighed and dissolved in ethylene glycol, a clear and transparent solution is obtained by stirring and dissolving at room temperature, and 0.006 g of etched SiC obtained from step 1 is added to the solution, and a uniformly dispersed gray suspension is obtained by ultrasonic treatment;

[0050] Step 3: 0.1717 g (0.015 mol) of KCl is added to distilled water, and a KCl solution is obtained by stirring and dissolving;

[0051] Step 4: The KCl solution obtained in Step 3 was slowly added to the suspension obtained in Step 2 under continuous stirring, resulting in a grayish white precipitate. After continuous stirring at room temperature for 3 h, the obtained solid product was centrifuged, washed with distilled water and anhydrous ethanol until neutral, and dried in an oven at 60°C for 8 h to obtain the SiC / BiOCl composite photocatalytic material with a theoretical mass ratio of 1:100.

[0052] Comparative Example 1

[0053] Step 1: 1.117 g (0.002 mol) of Bi(NO)3·5H2O was added to ethylene glycol and stirred to dissolve at room temperature to obtain a clear transparent solution;

[0054] Step 2: 0.1717 g (0.015 mol) of KCl was added to distilled water and stirred to dissolve to obtain a KCl solution;

[0055] Step 3: The KCl solution obtained in Step 2 was slowly added to the Bi(NO)3·5H2O ethylene glycol solution obtained in Step 1 under continuous stirring, resulting in a white precipitate. After continuous stirring at room temperature for 3 h, the obtained solid product was centrifuged, washed with distilled water and anhydrous ethanol until neutral, and dried in an oven at 60°C for 8 h to obtain the BiOCl material.

[0056] Comparative Example 2

[0057] 0.5 g of commercially available nanospherical SiC powder was added to a 20 mL volume ratio of 3:1 hydrofluoric acid / nitric acid mixed solution, and after stirring and etching at room temperature for 6 h, the obtained product was centrifuged, washed with distilled water and anhydrous ethanol until neutral, and dried in an oven at 60°C for 8 h to obtain the etched SiC.

[0058] Structural Characterization

[0059] See the attached Figure 1 , Figure 1 The XRD spectra of the SiC / BiOCl composite photocatalytic materials obtained in Examples 1-4, the BiOCl material obtained in Comparative Example 1, and the etched SiC obtained in Comparative Example 2 are shown in the attached Figure 1 It can be seen that when the mass ratio of BiOCl to etched SiC is 1:1 (Example 1), a very weak β-SiC (111) crystal face characteristic peak can be observed, while in Examples 2-4 only the characteristic peaks of BiOCl can be observed, which may be due to the small amount of SiC and the fact that the SiC is wrapped by BiOCl crystals. In addition, the diffraction peak intensity of BiOCl gradually increases with the decrease of the content of etched SiC, indicating that the etched SiC nanoparticles act as nucleation sites to promote the growth of BiOCl sheet crystals.

[0060] See the attached Figure 2 ,Figure 2 SEM images of the SiC / BiOCl composite photocatalytic materials obtained in Examples 1-4, the BiOCl material obtained in Comparative Example 1 and the etched SiC obtained in Comparative Example 2 were taken. From the SEM images, it can be seen that the morphology of the BiOCl in Comparative Example 1 was agglomerated flake, and the morphology of the etched SiC in Comparative Example 2 was uniformly dispersed spherical particles. The SiC / BiOCl composite photocatalytic materials in Examples 1-4 exhibited better dispersibility and larger size, which can be due to the fact that the growth of BiOCl was more likely to occur at the defect sites on the surface of the etched SiC, promoting the crystal growth, thus gradually increasing the size of the composite material. Figure 2

[0061] Photocatalytic reduction of CO2 experiment

[0062] The SiC / BiOCl composite photocatalytic materials obtained in Examples 1-4, the BiOCl material obtained in Comparative Example 1 and the etched SiC obtained in Comparative Example 2 were subjected to a photocatalytic reduction of carbon dioxide performance test experiment. The photocatalytic reduction of carbon dioxide performance test experiment was evaluated in a system composed of a Labsolar-6A micro gas analysis device of Beijing Portifex Technology Co., Ltd. and a gas chromatograph GC9790PLUS of Zhejiang Fulai Analytical Instrument Co., Ltd. The specific process was as follows: 50 mg of photocatalyst was added to 100 mL of ultrapure water without adding any sacrificial agent and photosensitizer, ultrasonic dispersion for 10 min until the catalyst was uniformly dispersed in the aqueous phase, then transferred to a 250 mL photochemical reactor, tightly connected with the Labsolar-6A device and the entire system was evacuated to vacuum, then pure carbon dioxide gas with a purity of 99.995% was introduced into the system until the vacuum reading was 80.0 kPa, then the system was evacuated to remove the gas, and this was repeated three times. After the third time, the carbon dioxide gas was introduced to 80 kPa, and after 30 min, the Xe lamp light source (PLS-SXE300+ / UV) was turned on for the experiment, and the products were analyzed by gas chromatograph GC9790PLUS. Among them, the gas chromatograph carrier gas was Ar, the detector was hydrogen ion flame (FID), the injection port temperature was set to 200°C, the column oven temperature was set to 60°C, and the detector temperature was set to 200°C.

[0063] Referring to the attached Figure 3 , Figure 3 ​The photocatalytic reduction of CO2 performance chart of the SiC / BiOCl composite photocatalytic materials obtained in Examples 1-4, the BiOCl material obtained in Comparative Example 1 and the etched SiC obtained in Comparative Example 2. Under the experimental conditions, no other gas phase products and liquid phase products were detected except CO, indicating that the synthesized catalysts can convert CO2 into CO with high selectivity. As can be seen from the chart, the photocatalytic activity of the single etched SiC is the lowest, with a CO yield of only 4.22 μmol / g / h; the CO yield of pure BiOCl is 7.32 μmol / g / h; after the BiOCl is compounded with the etched SiC, the photocatalytic activity of the SiC / BiOCl composite material is significantly improved, and increases first and then decreases with the increase of the content of the etched SiC; when the mass ratio of BiOCl to etched SiC is 8:1, the photocatalytic activity is the highest, with a CO yield of 56.57 μmol / g / h, which is about 7.72 times of that of pure BiOCl and 11.9 times of that of etched SiC.

[0064] The above examples are only used to illustrate the technical solutions of the present application, but not limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent ones; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A SiC / BiOCl composite photocatalytic material for carbon dioxide reduction, characterized in that, It is a material with a type I heterostructure composed of SiC and BiOCl in a mass ratio of 1:1 to 100; The SiC / BiOCl composite photocatalytic material is prepared through the following steps: Step 1: Add SiC powder to a mixed solution of hydrofluoric acid / nitric acid for etching to obtain etched SiC; Step 2: Add the etched SiC to an ethylene glycol solution of Bi(NO3)3·5H2O and mix to form a suspension; Step 3: Add KCl solution to the suspension to carry out in-situ precipitation reaction to obtain SiC / BiOCl composite photocatalytic material.

2. A method for preparing the SiC / BiOCl composite photocatalytic material according to claim 1, characterized in that, Includes the following steps: Step 1: Add SiC powder to a mixed solution of hydrofluoric acid / nitric acid for etching to obtain etched SiC; Step 2: Add the etched SiC to an ethylene glycol solution of Bi(NO3)3·5H2O and mix to form a suspension; Step 3: Add KCl solution to the suspension to carry out in-situ precipitation reaction to obtain SiC / BiOCl composite photocatalytic material; In step 1, the volume ratio of hydrofluoric acid to nitric acid in the hydrofluoric acid / nitric acid mixed solution is 3:1; the solid-liquid ratio of SiC powder and the hydrofluoric acid / nitric acid mixed solution is 1g:30~50mL.

3. The method for preparing the SiC / BiOCl composite photocatalytic material according to claim 2, characterized in that, The etching time in step 1 is 3~12 h.

4. The method for preparing the SiC / BiOCl composite photocatalytic material according to claim 2, characterized in that, In step 3, the molar ratio of Bi(NO3)3·5H2O to KCl is 1:7.

5.

5. The method for preparing the SiC / BiOCl composite photocatalyst material according to any one of claims 2 or 4, characterized in that, The in-situ precipitation reaction time in step 3 is 1~3 h.

6. An application of the SiC / BiOCl composite photocatalyst material according to claim 1, characterized in that, Used for photocatalytic reduction of carbon dioxide.

7. The application of the SiC / BiOCl composite photocatalyst material according to claim 6, characterized in that, The SiC / BiOCl composite photocatalyst material was dispersed in water, ultrasonically dispersed to form a suspension, and then added to a photochemical reactor. After sealing and evacuation, carbon dioxide gas was introduced, and the carbon dioxide reduction reaction was carried out under Xe lamp illumination.

8. The application of the SiC / BiOCl composite photocatalyst material according to claim 7, characterized in that, The mass ratio of SiC / BiOCl composite photocatalyst material to water is 1:2000.

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