A multi-active site synergistic Bi / OVs-Bi2WO6-Cl catalyst and a preparation method and application thereof

Abstract

The application discloses a kind of Bi / OVs-Bi2WO6-Cl catalysts with multiple active sites synergy and a preparation method and application thereof, and belongs to the field of photocatalysis technology, the application uses hydrothermal method to dope Cl into Bi2WO6, then in-situ reduction is generated by using chemical reduction method Bi element and oxygen vacancy, the introduction of multiple active sites, on the one hand, promote the effective separation of photoinduced electron-hole pairs, fully play the catalytic performance of semiconductor, on the other hand, can provide more CO2 activation site, finally make Bi / OVs-Bi2WO6-Cl photocatalyst have better CO2 reduction performance;The material has high photocatalytic selectivity, and the production cost is low, and the production process is simple.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis technology, specifically to a Bi / OVs-Bi2WO6-Cl catalyst with synergistic multi-active-site activity, and also to the preparation method and application of the photocatalyst. Background Technology

[0002] With the rapid consumption of fossil fuels and the massive emission of carbon dioxide into the atmosphere, the concentration of carbon dioxide in the atmosphere is constantly increasing, and the global energy crisis and environmental problems are becoming increasingly serious. Photocatalytic carbon dioxide reduction is an environmentally friendly and sustainable method that uses sunlight as an energy source to convert carbon dioxide into usable fuels or chemical feedstocks, and it has broad application prospects. Unfortunately, due to the high C=O dissociation energy of carbon dioxide molecules (approximately 750 kJ·mol⁻¹), the process is limited. -1 The high concentration of carbon dioxide leads to low conversion efficiency and poor selectivity of the products. Therefore, exploring and designing photocatalysts that can effectively adsorb and activate carbon dioxide and promote photoinduced charge separation and transfer is a critical scientific problem that urgently needs to be solved.

[0003] In recent years, Bi-based semiconductor photocatalysts such as BiOBr, BiOCl, Bi2O2CO3, Bi4MoO9, BiPO4, and Bi2WO6 have attracted widespread attention. Among them, Bi2WO6 is a promising photocatalyst with a suitable band gap (2.6-2.8 eV) and is composed of perovskite-like WO3. 6- Plate and (Bi2O2) 2+ It boasts advantages such as layer composition, structural stability, non-toxicity, and low cost. Despite these attractive properties, Bi2WO6 exhibits poor photoreduction activity for carbon dioxide due to severe charge recombination and weak light absorption. Summary of the Invention

[0004] In view of this, one objective of the present invention is to provide a method for preparing a Bi / OVs-Bi2WO6-Cl catalyst with synergistic effects of multiple active sites; a second objective of the present invention is to provide the Bi / OVs-Bi2WO6-Cl catalyst with synergistic effects of multiple active sites; and a third objective of the present invention is to provide the application of the Bi / OVs-Bi2WO6-Cl catalyst with synergistic effects of multiple active sites in the photocatalytic reduction of carbon dioxide.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] 1. A method for preparing a multi-active-site synergistic Bi / OVs-Bi2WO6-Cl catalyst, comprising the following preparation steps:

[0007] 1) Add Bi(NO3)3·5H2O and Na2WO4·2H2O to deionized water;

[0008] 2) Add sodium chloride, sonicate for a certain time, and then stir to obtain an opaque white dispersion;

[0009] 3) Adjust the pH to 9-11 with 1M sodium hydroxide solution and stir for a period of time;

[0010] 4) The solution obtained in step 3 is transferred to a stainless steel autoclave for reaction, washed and dried to obtain Cl-doped Bi2WO6;

[0011] 5) Weigh the Cl-doped Bi2WO6 obtained in step 4 and add it to deionized water, then stir ultrasonically.

[0012] 6) Add NaBH4 solution dropwise to the solution obtained in step 5, stir and react for a period of time, then centrifuge and vacuum dry; under the action of NaBH4, Bi in Bi2WO6... 3+ It is reduced to elemental Bi, while generating oxygen vacancies, to obtain the Bi / OVs-Bi2WO6-Cl catalyst.

[0013] Preferably, in step 1 of this invention, the molar mass ratio of Bi(NO3)3·5H2O and Na2WO4·2H2O is 2:1.

[0014] Preferably, the amount of sodium chloride added is the same as the molar amount of Na2WO4·2H2O in step 1.

[0015] Preferably, in step 2 of this invention, the ultrasound duration is 5 to 15 minutes.

[0016] Preferably, in step 4 of this invention, the reaction is carried out at 150–180°C for 15–25 hours.

[0017] 10. Preferably, in step 6 of the present invention, the concentration of the NaBH4 solution added per 0.5g Cl-doped Bi2WO6 is 30-50mmol / L, and the amount added is 15ml.

[0018] In a preferred embodiment of the present invention, the reaction time in step 6 is 1 to 2 hours.

[0019] 2. The multi-active-site synergistic Bi / OVs-Bi2WO6-Cl catalyst prepared by the method.

[0020] 3. Application of the multi-active-site synergistic Bi / OVs-Bi2WO6-Cl catalyst in photocatalytic reduction of carbon dioxide.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) In this invention, Cl is doped into Bi2WO6 using a hydrothermal method, followed by in-situ reduction of elemental Bi and oxygen vacancies using a chemical reduction method. The introduction of multiple active sites promotes the effective separation of photogenerated electron-hole pairs, fully leveraging the catalytic performance of the semiconductor, and provides more CO2 activation sites, ultimately giving the Bi / OVs-Bi2WO6-Cl photocatalyst better CO2 reduction performance.

[0023] (2) The material has high photocatalytic selectivity, low production cost and simple production process. Attached Figure Description

[0024] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0025] Figure 1 XRD patterns of the prepared BWO, BWO-Cl and Bi / OVs-BWO-Cl-30 catalysts;

[0026] Figure 2 SEM and TEM images of the prepared Bi / OVs-BWO-Cl-30 catalyst;

[0027] Figure 3 EDX image of the prepared Bi / OVs-BWO-Cl-30 catalyst;

[0028] Figure 4 Electron paramagnetic resonance (EPR) spectra of the prepared BWO, BWO-Cl and Bi / OVs-BWO-Cl-30 catalysts;

[0029] Figure 5 The UV-vis absorption spectra of the prepared BWO, BWO-Cl and Bi / OVs-BWO-Cl-30 catalysts are shown.

[0030] Figure 6 To assess the CO yield of BWO, BWO-Cl, and Bi / OVs-BWO-Cl-X catalysts prepared under simulated sunlight irradiation for CO2 reduction. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0032] Example 1

[0033] The preparation method of Bi2WO6 catalyst is as follows:

[0034] (1) Weigh 2 mmol Bi(NO3)3·5H2O and 1 mmol Na2WO4·2H2O and add them to 75 ml of deionized water;

[0035] (2) Then, after sonication for a certain time, the mixture was stirred to obtain an opaque white dispersion.

[0036] (3) Then adjust the pH to 9-11 with 1M sodium hydroxide solution and stir for 30 min;

[0037] (4) The solution obtained in step 3) was transferred to a stainless steel autoclave and reacted at 160°C for 20 h. After washing and drying, Bi2WO6 was obtained and the product was named BWO.

[0038] Example 2

[0039] The preparation method of Cl-doped Bi₂WO₆ catalyst is as follows:

[0040] (1) Weigh 2 mmol Bi(NO3)3·5H2O and 1 mmol Na2WO4·2H2O and add them to 75 ml of deionized water;

[0041] (2) Then add 0.058g of sodium chloride, sonicate for a certain time and stir to obtain an opaque white dispersion;

[0042] (3) Then adjust the pH to 9-11 with 1M sodium hydroxide solution and stir for 30 min;

[0043] (4) The solution obtained in step 3) is transferred to a stainless steel autoclave and reacted at 160°C for 20 h. After washing and drying, Cl-doped Bi2WO6 is obtained and the product is named BWO-Cl.

[0044] Example 3

[0045] The preparation method of Bi / OV-Bi2WO6-Cl catalyst is as follows:

[0046] (1) Weigh 0.5g of Cl-doped Bi2WO6 prepared in Example 2 and add it to 35ml of deionized water, and stir ultrasonically;

[0047] (2) Prepare different concentrations of NaBH4 at mmol / L, add 15 ml dropwise to the solution in step 1), stir for 1–2 h, then centrifuge and vacuum dry. Under the action of NaBH4, Bi in Bi2WO6... 3+ The substance is reduced to elemental Bi, generating oxygen vacancies to obtain Bi / OV-Bi2WO6-Cl. Based on the addition of X mmol / L NaBH4, the product is named Bi / OVs-BWO-Cl-X.

[0048] Figure 1 The figures show the XRD patterns of the materials prepared in Examples 1, 2, and 3 of this invention. It is clear from the figures that the XRD diffraction peaks of BWO prepared in Example 1 are consistent with the standard card JCPDS No. 73-2020, indicating that the prepared sample is pure Bi₂WO₆ material. The XRD diffraction peaks of BWO-Cl prepared in Example 2 are consistent with the standard card JCPDS No. 73-2020, indicating that Cl doping did not change the crystal structure of Bi₂WO₆. In the XRD pattern of the Bi / OVs-BWO-Cl-30 catalyst prepared in Example 3, diffraction peaks of Bi₂WO₆ and elemental Bi (JCPDS No. 44-1246) are observed simultaneously. This proves that under the action of NaBH₄, Bi₂WO₆ in Bi₂WO₆... 3+ It is reduced to elemental Bi.

[0049] Figure 2 SEM and TEM images of Bi / OVs-BWO-Cl-30. From Figure 2 As can be seen from a, the prepared Bi / OVs-BWO-Cl-30 material has a nanosheet structure. Figure 2 The TEM image of b shows both the (111) crystal plane of Bi2WO6 and the (110) crystal plane of elemental Bi, which confirms the formation of elemental Bi.

[0050] Figure 3 It is EDX of Bi / OVs-BWO-Cl-30 ( Figure 3 EDX analysis showed that Cl was uniformly distributed in Bi / OVs-BWO-Cl-30, confirming the presence of Cl. Therefore, the above results indicate that Cl atoms were successfully doped into the material.

[0051] Figure 4 This is the EPR spectrum of the prepared Bi / OVs-BWO-Cl-30 material. The EPR signal at g = 2.001 confirms the presence of oxygen vacancies on the sample surface. The signal intensity of BWO material is the weakest, followed by BWO-Cl. A stronger signal than BWO and BWO-Cl was detected in Bi / OVs-BWO-Cl-30, indicating that sodium borohydride treatment can effectively increase the OVs concentration.

[0052] Figure 5 The photocatalysts prepared in Examples 1, 2, and 3 of this invention were subjected to ultraviolet-visible light absorption (UV-vis) tests and analyses. As can be seen from the figures, the light absorption capacity of Bi / OVs-BWO-Cl-30 was significantly improved, especially in terms of visible light utilization.

[0053] Example 4

[0054] Study on the photocatalytic reduction performance of Bi / OV-BWO-Cl-30 obtained in this invention:

[0055] This invention employs a Labsolar-6A instrument (Beijing Perfectlight, China) to conduct photocatalytic carbon dioxide reduction experiments under simulated sunlight irradiation to evaluate the photocatalytic performance of the materials. The experiments were carried out in a 250 mL glass reactor using a 300 W Xe lamp (PLS-300, Beijing Perfectlight, China) with a light intensity of approximately 100 mW·cm². -2 A 1.0 mL deionized water solution containing 10 mg of sample was evenly dropped onto a glass fiber filter membrane and dried at 60 °C. The reactor was connected to circulating water to maintain the temperature at 20 ± 0.03 °C. Before turning on the lights, the reactor was sealed and purged three times with high-purity carbon dioxide (≥99.999%) to remove any foreign gases. Then, carbon dioxide was introduced into the reactor to reach a pressure of 91 kPa, followed by the injection of a small amount of water (100 μL). During the reaction, analysis was performed every hour using gas chromatography (GC2002, CeChuang) and a flame ionization detector (FID) and thermal conductivity detector (TCD).

[0056] Figure 6 The figure shows the CO yield of the prepared material after 5 hours of xenon lamp irradiation. The image reveals that Bi / OVs-BWO-Cl-30 exhibits the best photocatalytic CO2 reduction performance under simulated sunlight irradiation. The CO yield of Bi / OVs-BWO-Cl-30 after 5 hours of illumination is approximately 6.72 μmol·g⁻¹. -1 .

[0057] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. The application of a multi-active-site synergistic Bi / OVs-Bi2WO6-Cl catalyst in the photocatalytic reduction of CO2 to CO, characterized in that, The method for preparing the catalyst includes the following steps: 1) Add Bi(NO3)3·5H2O and Na2WO4·2H2O to deionized water; the molar ratio of Bi(NO3)3·5H2O and Na2WO4·2H2O is 2:1; 2) Add sodium chloride, sonicate for 5-15 minutes and stir to obtain an opaque white dispersion; the amount of sodium chloride added is the same as the molar amount of Na2WO4·2H2O in step 1). 3) Adjust the pH to 9-11 with 1M sodium hydroxide solution and stir for a period of time; 4) Transfer the solution obtained in step 3) to a stainless steel autoclave and react at 150~180℃ for 15~25h. Wash and dry to obtain Cl-doped Bi2WO6. 5) Weigh the Cl-doped Bi2WO6 obtained in step 4) and add it to deionized water, then stir ultrasonically. 6) Add NaBH4 solution dropwise to the solution obtained in step 5), stir and react for 1-2 hours, then centrifuge and vacuum dry. Under the action of NaBH4, Bi in Bi2WO6... 3+ The catalyst is reduced to elemental Bi, generating oxygen vacancies, to obtain Bi / OVs-Bi2WO6-Cl catalyst. The concentration of NaBH4 solution added is 30-50 mmol / L for every 0.5 g of Cl-doped Bi2WO6, and the dropwise addition is 15 mL.

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