Preparation method of visible light responsive CO2 photocatalyst

Abstract

The present invention is a visible light responsive CO 2 The invention discloses a method for preparing a photocatalyst, which belongs to the field of photocatalytic reduction technology. The method comprises: step 1) preparing SnO from a tin chloride solution and a sodium hydroxide solution; 2 ‑NPs; Step 2) SnO 2 ‑NPs, 2‑methylimidazole solution, Zn(NO 3 ) 2 6H 2 T‑ZIF‑8@SnO was prepared from O solution. 2 The method of the present invention generates an interface effect between different components through a heterogeneous structure, thereby generating different catalytic reaction adsorption sites, thereby affecting the activity, selectivity and stability of the catalyst. 2 The powder size is uniform, the light response wavelength can reach 760nm, and it is sensitive to CH 4 The selectivity can reach 77%.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalytic reduction, and in particular to a method for preparing a visible light responsive CO2 photocatalyst. Background Art

[0002] In recent years, excessive CO2 emissions have caused serious environmental pollution and greenhouse effects. Among the various solutions to these problems, photocatalytic CO2 reduction is an ideal strategy to meet the growing global energy demand and environmental pressure. Photocatalytic CO2 reduction can not only reduce the content of CO2 in the atmosphere, inhibit the greenhouse effect, and alleviate environmental pressure, but also produce renewable resources, converting solar energy that is difficult to store into chemical energy that is easy to store and use. It is considered to be one of the most promising strategies to reduce environmental pressure while alleviating current energy needs.

[0003] So far, researchers have explored a variety of materials as effective photocatalysts, such as metal organic frameworks (MOFs), metal sulfides, carbon nitrides, and metal oxides. Among these semiconductor materials, zeolite imidazolate framework-8 (ZIF-8), as a MOF material, has the characteristics of high specific surface area, adjustable pore size, and strong chemical stability that MOF materials usually have. In addition, it has a strong adsorption capacity for CO2, and has different adsorption capacities for different gases, which is selective. It has received great attention in the field of photocatalytic carbon dioxide reduction. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a visible light responsive CO2 photocatalyst in view of the background technology.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing a visible light responsive CO2 photocatalyst comprises the following steps:

[0007] 1) Preparation of SnO2-NPs by hydrothermal method

[0008] SnCl4·5H2O is dissolved in water to obtain a tin chloride solution, and NaOH is dissolved in a mixture of water and ethanol to obtain a sodium hydroxide solution;

[0009] Adding the sodium hydroxide solution dropwise into the tin chloride solution until the pH reaches 12 to obtain a mixed solution;

[0010] The obtained mixed solution is transferred into an autoclave for hydrothermal treatment;

[0011] After cooling, the precipitate is separated and washed at least three times with a mixture of deionized water and ethanol to remove impurities;

[0012] The washed precipitate was dried in a desiccator overnight to obtain white powdery SnO2-NPs.

[0013] 2) Preparation of T-ZIF-8@SnO2

[0014] 2-Methylimidazole (C4H6N2) was dissolved in ethanol to obtain solution A; Zn(NO3)2·6H2O was dissolved in ethanol to obtain solution B;

[0015] SnO2-NPs were added to solution A and ultrasonically treated to obtain a uniformly dispersed suspension;

[0016] Pour solution B into the suspension, combine and stir at room temperature to obtain a mixture;

[0017] The mixture was washed by centrifugation at least three times, and the precipitate was dried in a drying oven overnight to obtain a white solid;

[0018] The white solid was placed in a box furnace for heat treatment to obtain a yellow powdery T-ZIF-8@SnO2 composite, which is the visible light responsive CO2 photocatalyst.

[0019] Furthermore, in step 1), the concentration of the tin chloride solution is 0.12-0.18 mol / mL, and the concentration of the sodium hydroxide solution is 0.4-0.5 mol / mL.

[0020] Furthermore, in step 1), the water and ethanol mixture is prepared by mixing water and ethanol in a volume ratio of 1:1.

[0021] Furthermore, in step 1), the temperature of the hydrothermal treatment is 200°C and the time is 24 h.

[0022] Furthermore, in step 2), when preparing solution A, 0.35-0.45 g of 2-methylimidazole is dissolved in every 10 ml of ethanol; when preparing solution B, 0.1-0.15 g of Zn(NO3)2·6H2O is dissolved in every 10 ml of ethanol.

[0023] Furthermore, in step 2), when preparing the suspension, 15 mg SnO2-NPs is added to every 10 ml of solution A, and the ultrasonic treatment time is at least 20 min.

[0024] Furthermore, in step 2), the volume ratio of solution B to the suspension is 1:1, and the stirring time is at least 15 minutes.

[0025] Furthermore, in step 2), the white solid is first ground into flakes of 1-5 mm and then placed in a box furnace.

[0026] Furthermore, in step 2), the heat treatment is carried out in an O2 atmosphere at a temperature of 250°C for 4 hours.

[0027] The method of the present invention includes two steps: the preparation of SnO2-NPs and the preparation of T-ZIF-8@ SnO2. The heterogeneous structure generates an interface effect between different components, resulting in different catalytic reaction adsorption sites, thereby affecting the activity, selectivity and stability of the catalyst. The T-ZIF-8@SnO2 powder prepared by the method of the present invention has a uniform size, a light response wavelength of up to 760nm, and a selectivity for CH4 of up to 77%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is the ultraviolet-visible reflectance spectrum of T-ZIF-8@SnO2 prepared by the method of Example 1 of the present invention.

[0030] Figure 2 This is a comparison chart of the infrared spectra of T-ZIF-8@SnO2 prepared by the method of Example 1 of the present invention.

[0031] Figure 3 This is the XRD spectrum of T-ZIF-8@SnO2 prepared by the method of Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention. Example 1

[0033] A method for preparing a visible light responsive CO2 photocatalyst comprises the following steps:

[0034] 1) Preparation of SnO2-NPs by hydrothermal method

[0035] Dissolve 0.787 g of SnCl4·5H2O in 15 mL of water to obtain a tin chloride solution, and dissolve 0.7 g of NaOH in a mixture of 20 mL of water and 20 mL of ethanol to obtain a sodium hydroxide solution;

[0036] Adding the sodium hydroxide solution dropwise into the tin chloride solution until the pH reaches 12 to obtain a mixed solution;

[0037] The obtained mixed solution was transferred to an autoclave for hydrothermal treatment at a temperature of 200°C and a time of 24 h.

[0038] After cooling, the precipitate is separated and washed at least three times with a mixture of deionized water and ethanol to remove impurities;

[0039] The washed precipitate was dried in a desiccator overnight to obtain white powdery SnO2-NPs.

[0040] 2) Preparation of T-ZIF-8@SnO2

[0041] 0.809 g of 2-methylimidazole was dissolved in 20 mL of ethanol to obtain solution A; 0.293 g of Zn(NO3)2·6H2O was dissolved in 20 mL of ethanol to obtain solution B;

[0042] 30 mg of SnO2-NPs were added to solution A and ultrasonicated for at least 20 min to obtain a uniformly dispersed suspension;

[0043] Pour solution B into the suspension, combine and stir at room temperature for at least 15 min to obtain a mixture;

[0044] The mixture was washed by centrifugation at least three times, and the precipitate was dried in a drying oven overnight to obtain a white solid;

[0045] The white solid was ground into 3 mm flakes and placed in a box furnace, and heat treated at 250° C. for 4 h in an O 2 atmosphere to obtain a yellow powdery T-ZIF-8@SnO 2 composite, which is the visible light responsive CO 2 photocatalyst.

[0046] The composition, structure, light response range and photocatalytic performance of T-ZIF-8@SnO2 prepared by the method of Example 1 above were detected, analyzed and characterized:

[0047] 1) Spectral analysis of T-ZIF-8@SnO2 using near-infrared spectrophotometer

[0048] like Figure 1As shown, near-infrared diffuse reflectance spectroscopy shows that compared with SnO2 and T-ZIF-8, the UV-visible absorption spectrum of the T-ZIF-8@SnO2 composite material extends to around 760 nm, and the assembly of T-ZIF-8 leads to a significant red shift in the absorption edge, which greatly improves the light absorption capacity, and T-ZIF-8@SnO2 has a smaller impedance radius, indicating more effective charge transfer performance, which further proves the improvement of the separation and transfer efficiency of photogenerated carriers in the composite material. Fluorescence photoluminescence spectroscopy tests the recombination ability of photoinduced electron-hole pairs of SnO2, T-ZIF-8 and T-ZIF-8@SnO2. The PL peak intensity of pure SnO2 is high and the recombination efficiency is high. In contrast, the PL peak intensity of T-ZIF-8@SnO2 is smaller than that of SnO2 and T-ZIF-8. The results show that the formation of a heterostructure with multi-channel charge transfer pathways in T-ZIF-8@SnO2 can significantly promote charge separation.

[0049] 2) Analyze the structure of T-ZIF-8@SnO2 using Fourier transform infrared spectroscopy

[0050] like Figure 2 As shown in the FT-IR spectrum, it can be obtained that at 421 cm -1 The absorption peak at , corresponding to 2-methylimidazole and Zn 2+ The stretching vibration peak of the Zn-N bond generated after coordination indicates that the transformation from ZIF-8 to T-ZIF-8 does not cause Zn-N to break. -1 A weak absorption peak is generated at 1380 cm -1 The absorption peaks at 664 and 564 cm correspond to the symmetrical angle peaks of -CH3 in 2-methylimidazole. -1 They belong to the asymmetric stretching vibration of O-Sn-O and the symmetric stretching vibration of Sn-O, respectively. T-ZIF-8@SnO2 shows similar spectra to those of T-ZIF-8 and SnO2, confirming the successful synthesis of the T-ZIF-8@SnO2 composite.

[0051] 3) Crystallinity analysis of T-ZIF-8@SnO2 using XRD diffractometer

[0052] like Figure 3As shown in the figure, the diffraction peaks of SnO2 at 26.5°, 33.9°, 37.7°, 51.8°, and 65.4° are consistent with the (110), (101), (200), (211), and (301) crystal planes of the standard card (JCPDS 41-1445), indicating the successful synthesis of SnO2. T-ZIF-8 has diffraction peaks at 7.39°, 10.43°, 12.74°, 14.74°, 16.47°, and 18.08°, corresponding to the (011), (002), (112), (022), (013), and (222) crystal plane diffraction of T-ZIF-8, which are consistent with the reported ZIF-8 spectrum, indicating that the thermal oxygen sensitization treatment will not destroy the crystal structure of ZIF-8. It can be verified that T-ZIF-8@SnO2 was successfully constructed in the composite photocatalyst. Example 2

[0053] A method for preparing a visible light responsive CO2 photocatalyst comprises the following steps:

[0054] 1) Preparation of SnO2-NPs by hydrothermal method

[0055] SnCl4·5H2O was dissolved in water to obtain a 0.18 mol / L tin chloride solution, and NaOH was dissolved in a mixture of water and ethanol to obtain a 0.5 mol / L sodium hydroxide solution;

[0056] Adding the sodium hydroxide solution dropwise into the tin chloride solution until the pH reaches 12 to obtain a mixed solution;

[0057] The obtained mixed solution was transferred to an autoclave for hydrothermal treatment at a temperature of 200°C and a time of 24 h.

[0058] After cooling, the precipitate is separated and washed at least three times with a mixture of deionized water and ethanol to remove impurities;

[0059] The washed precipitate was dried in a desiccator overnight to obtain white powdery SnO2-NPs.

[0060] 2) Preparation of T-ZIF-8@SnO2

[0061] Dissolve 0.9 g of 2-methylimidazole (C4H6N2) in 20 mL of ethanol to obtain solution A; dissolve 0.3 g of Zn(NO3)2·6H2O in 20 mL of ethanol to obtain solution B;

[0062] 30 mg of SnO2-NPs were added to solution A and ultrasonicated for at least 20 min to obtain a uniformly dispersed suspension;

[0063] Pour solution B into the suspension, combine and stir at room temperature for at least 15 min to obtain a mixture;

[0064] The mixture was washed by centrifugation at least three times, and the precipitate was dried in a drying oven overnight to obtain a white solid;

[0065] The white solid was ground into 5 mm flakes and placed in a box furnace, and heat treated at 250° C. for 4 h in an O 2 atmosphere to obtain a yellow powdery T-ZIF-8@SnO 2 composite, which is the visible light responsive CO 2 photocatalyst. Example 3

[0066] A method for preparing a visible light responsive CO2 photocatalyst comprises the following steps:

[0067] 1) Preparation of SnO2-NPs by hydrothermal method

[0068] SnCl4·5H2O was dissolved in water to obtain a 0.12 mol / L tin chloride solution, and NaOH was dissolved in a mixture of water and ethanol to obtain a 0.4 mol / L sodium hydroxide solution;

[0069] Adding the sodium hydroxide solution dropwise into the tin chloride solution until the pH reaches 12 to obtain a mixed solution;

[0070] The obtained mixed solution was transferred to an autoclave for hydrothermal treatment at a temperature of 200°C and a time of 24 h.

[0071] After cooling, the precipitate is separated and washed at least three times with a mixture of deionized water and ethanol to remove impurities;

[0072] The washed precipitate was dried in a desiccator overnight to obtain white powdery SnO2-NPs.

[0073] 2) Preparation of T-ZIF-8@SnO2

[0074] Dissolve 0.7 g of 2-methylimidazole (C4H6N2) in 20 mL of ethanol to obtain solution A; dissolve 0.2 g of Zn(NO3)2·6H2O in 20 mL of ethanol to obtain solution B;

[0075] 30 mg of SnO2-NPs were added to solution A and ultrasonicated for at least 20 min to obtain a uniformly dispersed suspension;

[0076] Pour solution B into the suspension, combine and stir at room temperature for at least 15 min to obtain a mixture;

[0077] The mixture was washed by centrifugation at least three times, and the precipitate was dried in a drying oven overnight to obtain a white solid;

[0078] The white solid was ground into 1 mm flakes and placed in a box furnace, and heat treated at 250° C. for 4 h in an O 2 atmosphere to obtain a yellow powdery T-ZIF-8@SnO 2 composite, which is the visible light responsive CO 2 photocatalyst.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Application of a visible light responsive CO2 photocatalyst in photocatalytic CO2 reduction, characterized in that: The preparation of the visible light responsive CO2 photocatalyst comprises the following steps: 1) Preparation of SnO2-NPs by hydrothermal method SnCl4·5H2O is dissolved in water to obtain a tin chloride solution, and NaOH is dissolved in a mixture of water and ethanol to obtain a sodium hydroxide solution; Adding the sodium hydroxide solution dropwise into the tin chloride solution until the pH reaches 12 to obtain a mixed solution; The obtained mixed solution is transferred into an autoclave for hydrothermal treatment; After cooling, the precipitate is separated and washed at least three times with a mixture of deionized water and ethanol to remove impurities; The washed precipitate was dried in a desiccator overnight to obtain white powdery SnO2-NPs; 2) Preparation of T-ZIF-8@SnO2 Dissolve 2-methylimidazole in ethanol to prepare solution A; dissolve Zn(NO3)2·6H2O in ethanol to prepare solution B; when preparing solution A, dissolve 0.35-0.45g 2-methylimidazole in every 10ml ethanol; when preparing solution B, dissolve 0.1-0.15g Zn(NO3)2·6H2O in every 10ml ethanol; SnO2-NPs were added to solution A and ultrasonically treated to obtain a uniformly dispersed suspension. When the suspension was prepared, 15 mg SnO2-NPs was added to every 10 ml of solution A, and the ultrasonic treatment time was at least 20 min. Pour solution B into the suspension, combine and stir at room temperature to obtain a mixture; The mixture was washed by centrifugation at least three times, and the precipitate was dried in a drying oven overnight to obtain a white solid; The white solid was placed in a box furnace for heat treatment in an O2 atmosphere at a temperature of 250°C for 4 hours to obtain a yellow powdery T-ZIF-8@SnO2 composite, which is the visible light responsive CO2 photocatalyst.

2. The use of the visible light responsive CO2 photocatalyst according to claim 1 in photocatalytic CO2 reduction, characterized in that: In step 1), the concentration of the tin chloride solution is 0.12-0.18 mol / L, and the concentration of the sodium hydroxide solution is 0.4-0.5 mol / L.

3. The use of the visible light responsive CO2 photocatalyst according to claim 1 in photocatalytic CO2 reduction, characterized in that: In step 1), the water and ethanol mixture is prepared by mixing water and ethanol in a volume ratio of 1:

1.

4. The use of the visible light responsive CO2 photocatalyst according to claim 1 in photocatalytic CO2 reduction, characterized in that: In step 1), the temperature of the hydrothermal treatment is 200°C and the time is 24 h.

5. The use of the visible light responsive CO2 photocatalyst according to claim 1 in photocatalytic CO2 reduction, characterized in that: In step 2), the volume ratio of solution B to suspension is 1:1, and the stirring time is at least 15 minutes.

6. The use of the visible light responsive CO2 photocatalyst according to claim 1 in photocatalytic CO2 reduction, characterized in that: In step 2), the white solid is first ground into 1-5 mm flakes and then placed in a box furnace.

Images