A Bi2Sn2O7 / NiFe-LDH composite photocatalyst, its preparation method and application

Abstract

The application belongs to the technical field of catalyst preparation, and particularly relates to a preparation method and application of a Bi2Sn2O7 / NiFe-LDH composite photocatalyst. The preparation method comprises the following steps: S1, dissolving Bi(NO3)3.5H2O and SnCl4.5H2O in deionized water, and performing a hydrothermal reaction after sufficient stirring, and obtaining Bi2Sn2O7 through centrifugation, washing and drying; S2, mixing Bi2Sn2O7 with deionized water to obtain a suspension, adding a nickel source and an iron source into the suspension, again stirring sufficiently, performing a hydrothermal reaction, and obtaining the Bi2Sn2O7 / NiFe-LDH composite photocatalyst through centrifugation, washing and drying. The preparation process of the application is simple, easy to control and low in production cost, and the prepared Bi2Sn2O7 / NiFe-LDH composite photocatalyst has the characteristics of high activity, good selectivity and excellent cycle stability.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic reduction of CO2, and in particular to a Bi2Sn2O7 / NiFe-LDH composite photocatalyst, its preparation method, and its application. Background Technology

[0002] With rapid industrialization, the large-scale consumption of fossil fuels has led to a continuous increase in atmospheric CO2 concentration, triggering global environmental problems such as the greenhouse effect and climate change. How to efficiently reduce CO2 emissions and realize its resource utilization has become an important topic in scientific research and technological development. Traditional CO2 treatment methods suffer from drawbacks such as high energy consumption, secondary pollution, or insufficient economic viability. In contrast, photocatalytic CO2 reduction technology utilizes solar energy to drive semiconductor materials to generate photogenerated electron-hole pairs, converting CO2 into hydrocarbon fuels or organic compounds under mild conditions. This technology, combining environmental friendliness and energy conversion advantages, has become the mainstream approach.

[0003] Among numerous photocatalytic materials, bismuth-based oxides have attracted widespread attention due to their suitable bandgap structure, good chemical stability, and unique photoelectric properties. Among them, Bi₂Sn₂O₇ with a pyrochlore structure exhibits certain visible light response capabilities. Its open framework, composed of [SnO₆] octahedra and corner-sharing Bi₂O tetrahedra, facilitates charge transport, and Bi₂O₇... 3+ The lone pairs of electrons can form electron-rich active sites, which is beneficial for the adsorption and activation of CO2. However, Bi2Sn2O7 still faces problems such as fast photogenerated carrier recombination rate and limited visible light absorption range, resulting in a large gap between its photoelectric quantum efficiency and the requirements of practical applications.

[0004] Layered bimetallic hydroxides (LDHs) are a class of two-dimensional materials composed of positively charged host layers and interlayer anions. Among them, NiFe-LDH shows promising applications in photocatalysis due to its abundant surface hydroxyl groups, tunable layer composition, and excellent CO2 adsorption and activation capabilities. Its layer hydroxyl groups readily react with CO2 to form carbonate species, increasing the CO2 concentration on the catalyst surface; simultaneously, its two-dimensional layered structure can serve as a channel for electron transport. However, single NiFe-LDH typically suffers from inherent drawbacks such as low photogenerated charge separation efficiency and a narrow photoresponse range.

[0005] To overcome the limitations of single materials, constructing heterojunction composite materials is an effective strategy for improving photocatalytic performance. By combining two semiconductor materials with matched band structures, it is expected to achieve effective spatial separation of photogenerated electrons and holes, broaden the light absorption range, and synergistically optimize the surface reaction process. However, how to rationally design and construct a composite photocatalyst that can fully utilize the structural advantages of Bi2Sn2O7 and NiFe-LDH to achieve efficient charge separation and CO2 activation remains a technical problem to be solved in this field. There are currently no systematic reports on using Bi2Sn2O7 and NiFe-LDH composites for efficient and highly selective photocatalytic reduction of CO2 to CO through precise control of interface engineering.

[0006] Therefore, developing a novel, efficient, and stable composite photocatalyst to address the problems of rapid carrier recombination, low light utilization efficiency, insufficient CO2 activation capacity, and poor stability in the photocatalytic reduction of CO2 by the aforementioned materials is of significant research importance and application value. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing Bi2Sn2O7 / NiFe-LDH composite photocatalysts and their applications. In this invention, Bi2Sn2O7 is first prepared hydrothermally, and then a heterojunction of Bi2Sn2O7 and NiFe-LDH is constructed using a hydrothermal method to prepare the Bi2Sn2O7 / NiFe-LDH composite photocatalyst.

[0008] This invention provides a method for preparing a Bi2Sn2O7 / NiFe-LDH composite photocatalyst, comprising the following steps:

[0009] S1: Bi(NO3)3·5H2O and SnCl4·5H2O are dispersed separately in deionized water and dispersed evenly to obtain SnCl4 solution and Bi(NO3)3 solution; the SnCl4 solution is slowly added dropwise to the Bi(NO3)3 solution. After mixing evenly, the pH of the solution is adjusted to 12 with 2M NaOH solution. The evenly mixed solution is transferred to a reaction vessel for hydrothermal reaction. After natural cooling, it is washed until neutral and dried in an oven at 60℃ to obtain Bi2Sn2O7.

[0010] Furthermore, the mass ratio of Bi(NO3)3·5H2O to SnCl4·5H2O is 4.85:3.51.

[0011] Furthermore, the hydrothermal reaction temperature in step S1 is 160-180℃, and the time is 24-48h.

[0012] Furthermore, the drying temperature in step S1 is 60-80℃, and the drying time is 24-48h.

[0013] S2: Bi2Sn2O7 was dispersed in deionized water to prepare a Bi2Sn2O7 suspension. Ni(NO3)2·6H2O was added to the Bi2Sn2O7 suspension and stirred thoroughly. Fe(NO3)3·9H2 and urea were then added and stirred until dissolved. The mixture was then placed in a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction. After the reaction was completed, the mixture was cooled, centrifuged, washed, and dried to obtain the Bi2Sn2O7 / NiFe-LDH composite photocatalyst.

[0014] Furthermore, in step S2, the mass ratio of Bi2Sn2O7, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea is 0.2~0.4:0.291:0.404:0.9.

[0015] Furthermore, in step S2, the hydrothermal reaction temperature is 120℃ and the reaction time is 6-12h.

[0016] Furthermore, in step S2, the centrifugal washing speed is 8000 rpm.

[0017] Furthermore, in step S2, the drying temperature is 60-80℃.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] This invention provides a Bi₂Sn₂O₇ / NiFe-LDH composite photocatalyst, successfully prepared via a hydrothermal method, achieving highly efficient and selective CO₂ reduction to CO under visible light. This composite material combines the structural advantages of both components: Bi₂Sn₂O₇ possesses an open pyrochlore framework structure, and Bi₂Sn₂O₇ has an electron-rich structure. 3+ The active sites facilitate electron transport and CO2 activation; while the layered structure of NiFe-LDH is rich in hydroxyl groups, which enhances CO2 adsorption, and its two-dimensional plates can also serve as electron transport channels. The combination of the two forms a stable heterojunction interface, which not only broadens the light absorption range, but also significantly promotes the separation and migration of photogenerated carriers and inhibits electron-hole recombination, thereby greatly improving the light energy conversion efficiency.

[0020] Furthermore, NiFe-LDH, acting as a support, ensures the uniform dispersion and stable anchoring of Bi₂Sn₂O₇ nanoparticles, enabling the composite material to maintain excellent structural stability and cycling performance during long-term reactions. Experiments show that this composite photocatalyst effectively solves the problems of high carrier recombination rate and insufficient reduction capacity in single-component catalysts, significantly improves CO₂ activation efficiency, optimizes the reaction pathway, and suppresses side reactions such as hydrogen evolution. It represents a highly promising and efficient photocatalytic CO₂ reduction material. Attached Figure Description

[0021] Figure 1 XRD patterns of Bi2Sn2O7, NiFe-LDH, and the Bi2Sn2O7 / NiFe-LDH composite photocatalyst of Example 1;

[0022] Figure 2 Bar charts showing the yield of CO2 to CO reduction by Bi2Sn2O7 (BSO), NiFe-LDH (LDH), and Bi2Sn2O7 / NiFe-LDH composite photocatalysts prepared in Examples 1-3;

[0023] Figure 3 Yield curves of CO2 reduction to CO by Bi2Sn2O7, Bi2Sn2O7 / NiAl-LDH, and Bi2Sn2O7 / NiFe-LDH composite photocatalysts prepared in Example 2;

[0024] Figure 4 SEM images of Bi2Sn2O7, NiFe-LDH, and Bi2Sn2O7 / NiFe-LDH composite photocatalysts. Detailed Implementation

[0025] Example 1

[0026] The preparation method of Bi2Sn2O7-20% / NiFe-LDH composite photocatalyst (20-BSO / LDH) is as follows:

[0027] 1) Dissolve 4.85 g of Bi(NO3)3·5H2O in 20 mL of deionized water and stir magnetically until transparent. Dissolve 3.51 g of SnCl4·5H2O in 30 mL of deionized water and stir until completely dissolved to obtain SnCl4 solution and Bi(NO3)3 solution. Gradually add SnCl4 solution to Bi(NO3)3 solution while stirring continuously. Simultaneously, add 2 mol / L NaOH solution to adjust the pH to 12. A latex-like precipitate appears. Transfer the mixture to a 100 mL polytetrafluoroethylene high-pressure reactor for hydrothermal reaction (180℃, 24 h). After the reaction, a white precipitate is obtained. Wash the sample until neutral and dry at 60℃ for 6 h to obtain Bi2Sn2O7.

[0028] 2) Disperse Bi2Sn2O7 (0.2g) in 40mL of deionized water and sonicate for 30 minutes. Then add Ni(NO3)2·6H2O (0.291g) and Fe(NO3)3·9H2O (0.404g) and stir until completely dissolved. Add 0.9g of urea, stir until dissolved, and then place in a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction (120℃, 6h). After the reaction, wash the sample and dry it at 60℃ for 6h to obtain Bi2Sn2O7 / NiFe-LDH composite photocatalyst.

[0029] Example 2

[0030] The preparation method of Bi2Sn2O7-30% / NiFe-LDH composite photocatalyst (30-BSO / LDH) is as follows:

[0031] 1) Same as Example 1;

[0032] 2) Disperse Bi2Sn2O7 (0.3g) in 40mL of deionized water and sonicate for 30 minutes. Then add Ni(NO3)2·6H2O (0.291g) and Fe(NO3)3·9H2O (0.404g) and stir until completely dissolved. Add 0.9g of urea, stir until dissolved, and then place in a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction (120℃, 6h). After the reaction, wash the sample and dry it at 60℃ for 6h to obtain Bi2Sn2O7 / NiFe-LDH composite photocatalyst.

[0033] Example 3

[0034] The preparation method of Bi2Sn2O7-40% / NiFe-LDH composite photocatalyst (40-BSO / LDH) is as follows:

[0035] 1) Same as Example 1;

[0036] 2) Disperse Bi2Sn2O7 (0.4g) in 40mL of deionized water and sonicate for 30 minutes. Then add Ni(NO3)2·6H2O (0.291g) and Fe(NO3)3·9H2O (0.404g) and stir until completely dissolved. Add 0.9g of urea, stir until dissolved, and then place in a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction (120℃, 6h). After the reaction, wash the sample and dry it at 60℃ for 6h to obtain Bi2Sn2O7 / NiFe-LDH composite photocatalyst.

[0037] Example 4

[0038] The preparation method of Bi2Sn2O7 / NiAl-LDH composite photocatalyst is as follows:

[0039] 1) Dissolve 4.85 g of Bi(NO3)3·5H2O in 20 mL of deionized water and stir magnetically until transparent. Dissolve 3.51 g of SnCl4·5H2O in 30 mL of deionized water and stir until completely dissolved. Gradually add the SnCl4 solution to the Bi(NO3)3 solution while stirring continuously. Simultaneously add 2 mol / L NaOH solution until pH=12, resulting in a latex-like precipitate. Transfer the mixture to a 100 mL polytetrafluoroethylene high-pressure reactor for hydrothermal reaction (180℃, 24 h). After the reaction, a white precipitate is obtained. Wash the sample and dry it at 60℃ for 6 h to obtain Bi2Sn2O7.

[0040] 2) Dissolve 1.5 mmol of Bi₂Sn₂O₇ in 50 mL of deionized water to prepare a suspension. The molar ratio of Bi₂Sn₂O₇ to Ni(NO₃)₂·6H₂O and Al(NO₃)₃·9H₂O is 1:1:2. Adjust the pH to 10 using sodium hydroxide, continue stirring for 1 h, and then react at 180 °C for 12 h. After centrifugation and washing, the Bi₂Sn₂O₇ / NiAl-LDH composite photocatalyst is obtained.

[0041] Figure 1 The image shows the XRD pattern of the Bi2Sn2O7 / NiFe-LDH composite photocatalyst prepared in Example 1. The results show that the prepared catalyst is free of impurities and is relatively pure.

[0042] Figure 2 The bar charts show the CO reduction yields of the Bi₂Sn₂O₇ / NiFe-LDH composite photocatalysts prepared in Examples 1-3. The Bi₂Sn₂O₇-30% / NiFe-LDH (30-BSO / LDH) composite prepared in this invention exhibits the best photocatalytic activity, with a CO generation rate of 42.87 µmol·h⁻¹. -1 .

[0043] Figure 3 The figure compares the application of Bi2Sn2O7 / NiFe-LDH and Bi2Sn2O7 / NiAl-LDH composite photocatalysts in the photocatalytic reduction of carbon dioxide. As can be seen from the figure, Bi2Sn2O7 / NiFe-LDH and Bi2Sn2O7 / NiAl-LDH have higher carbon monoxide generation rates, indicating that Bi2Sn2O7 / NiFe-LDH has a better photocatalytic effect than Bi2Sn2O7 / NiAl-LDH.

[0044] Figure 4This is a SEM image of the Bi₂Sn₂O₇ / NiFe-LDH composite photocatalyst. It clearly shows that Bi₂Sn₂O₇ / NiFe-LDH particles are uniformly distributed on the surface and between layers of the NiFe-LDH nanosheets, with close contact between the two phases. This effectively reduces the aggregation degree of Bi₂Sn₂O₇ / NiFe-LDH while preserving the rich porous structure of LDH. This unique morphology and interface structure facilitates light absorption, reactant adsorption, and the separation and migration of photogenerated carriers, thereby improving photocatalytic performance.

[0045] 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 Bi₂Sn₂O₇ / NiFe-LDH composite photocatalyst, characterized in that, Heterojunction made of Bi2Sn2O7 and NiFe-LDH composite.

2. The preparation method of the Bi2Sn2O7 / NiFe-LDH composite photocatalyst as described in claim 1, characterized in that, Includes the following steps: S1: Disperse Bi(NO3)3·5H2O and SnCl4·5H2O separately in deionized water and disperse them evenly. Slowly add SnCl4 solution to Bi(NO3)3 solution. After mixing evenly, adjust the pH of the solution to 12 with 2M NaOH solution. Transfer the evenly mixed solution to a reaction vessel for hydrothermal reaction. After natural cooling, wash until neutral and dry in an oven at 60℃ to obtain Bi2Sn2O7. S2: Bi2Sn2O7 was added to a certain amount of deionized water and mixed to prepare a Bi2Sn2O7 suspension. Ni(NO3)2·6H2O was added to the suspension and stirred thoroughly. Fe(NO3)3·9H2O was then added, followed by urea. After stirring thoroughly again, the mixture was placed in a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction. After the reaction was completed, the mixture was cooled, centrifuged, washed, and dried to obtain the Bi2Sn2O7 / NiFe-LDH composite photocatalyst.

3. The preparation method of the Bi2Sn2O7 / NiFe-LDH composite photocatalyst as described in claim 2, characterized in that, The mass ratio of Bi(NO3)3·5H2O to SnCl4·5H2O is 4.85:3.

51.

4. In the preparation method of Bi2Sn2O7 / NiFe-LDH composite photocatalyst as described in claim 2, in step S1, the hydrothermal reaction temperature is 160-180℃ and the time is 24-48h.

5. The preparation method of the Bi2Sn2O7 / NiFe-LDH composite photocatalyst as described in claim 2, characterized in that, The mass ratio of Bi2Sn2O7, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea is 0.2~0.4:0.291:0.404:0.

9.

6. The preparation method of the Bi2Sn2O7 / NiFe-LDH composite photocatalyst as described in claim 2, characterized in that, In step S2, the hydrothermal reaction temperature is 120℃ and the reaction time is 6-12h.

7. The application of the Bi2Sn2O7 / NiFe-LDH composite photocatalyst as described in claim 1 in the photocatalytic reduction of CO2.

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