A manganese ferrite / silver bismuth hexabromate heterojunction photocatalyst, a preparation method and application thereof

Abstract

This invention belongs to the field of photocatalytic materials technology, specifically relating to a manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, its preparation method, and its application. The mass ratio of manganese ferrite to cesium hexabromobismuthate dicesium heterojunction photocatalyst is 1:3 to 1:7. The preparation method includes: dissolving manganese chloride and ferric chloride hydrate in deionized water, then adding sodium hydroxide, and obtaining manganese ferrite using a hydrothermal method; dissolving silver bromide and bismuth bromide in hydrobromic acid, heating in an oil bath, then adding cesium bromide, and obtaining cesium hexabromobismuthate dicesium using an acid precipitation method; and dissolving manganese ferrite and cesium hexabromobismuthate dicesium in an ethanol solution, and obtaining the manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst using a mechanical stirring method. The formation of the heterojunction can significantly improve the photocatalytic reduction activity of carbon dioxide by manganese ferrite / silver hexabromobismuthate dicesium.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, its preparation method, and its application. Background Technology

[0002] In recent years, massive carbon dioxide emissions have exacerbated the global greenhouse effect, leading to a series of environmental and social problems. Photocatalytic carbon dioxide reduction, utilizing inexhaustible solar energy, can directly convert carbon dioxide gas into hydrocarbon solar fuels, representing a feasible method to simultaneously address the energy crisis and environmental pollution. Cesium hexabromosiliconate dibismuthate (Cs₂AgBiBr₆) is a typical lead-free double perovskite halide semiconductor material, attracting widespread attention in the scientific research field as a novel and highly efficient visible-light photocatalytic material. It possesses a regular double perovskite crystal structure, with Ag₂ inside the crystal... + Bi 3+ With Br - With its ordered coordination and unique halide crystal framework, the band structure and optical absorption properties can be precisely tuned. This special crystal structure possesses excellent photogenerated carrier transport performance, effectively shortening charge migration paths and suppressing electron-hole recombination. Furthermore, the material itself exhibits low toxicity, strong structural tunability, and good photochemical stability and environmental adaptability. However, pure-phase dicesium hexabromosilyl bismuthate still has certain limitations in its applications. Its photogenerated carrier separation efficiency is limited, its carbon dioxide molecule adsorption and activation ability is weak, and the interfacial charge transfer resistance during the photocatalytic reaction is relatively large, which greatly restricts its large-scale practical application in the field of visible light-catalyzed carbon dioxide reduction.

[0003] Therefore, manganese ferrite, due to its narrow bandgap, excellent photochemical stability, and environmental friendliness, has broad prospects for photocatalytic applications and can be composited with Cs₂AgBiBr₆ to construct highly efficient heterostructures. As a typical narrow bandgap transition metal oxide, manganese ferrite can not only broaden the spectral response range of composite materials and improve light energy utilization, but also introduce abundant surface-active metal sites, significantly enhancing the adsorption and activation capacity of dicesium hexabromosiliconate (CBIS) materials for carbon dioxide gas. Constructing a manganese ferrite / CBIS heterojunction can form a well-matched bandgap system, effectively driving the rapid transfer and separation of photogenerated charges at the interface, thereby efficiently improving the photocatalytic reduction activity and cycle stability of CBIS-based composite materials. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, its preparation method, and its application. This method is simple, convenient, low-cost, and operates under mild conditions, which is conducive to large-scale production. The obtained manganese ferrite / silver hexabromobismuthate dicesium photocatalyst exhibits excellent photocatalytic reduction activity of carbon dioxide.

[0005] The specific solution of the present invention is: a manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, wherein the mass ratio of manganese ferrite to silver hexabromobismuthate dicesium heterojunction photocatalyst is 1:3 to 1:7.

[0006] A method for preparing the above-mentioned manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst includes the following steps.

[0007] 1) Manganese chloride tetrahydrate and ferric chloride hexahydrate hydrates were dissolved in deionized water, and then sodium hydroxide solution was added to obtain manganese ferrate by hydrothermal method; silver bromide and bismuth bromide were dissolved in hydrobromic acid, stirred and heated, and then cesium bromide was added to obtain dicesium hexabromosilyl bismuthate by acid precipitation method.

[0008] 2) Dissolve manganese ferrite and dicesium hexabromosiliconate in ethanol, stir, centrifuge, and dry to obtain manganese ferrite / dicesium hexabromosiliconate heterojunction photocatalyst.

[0009] In the preparation method of the above-mentioned manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, in step 1), the ratio of ferric chloride hexahydrate: manganese chloride tetrahydrate: sodium hydroxide solution = 2.0~2.5g: 1~1.5g: 8~12ml, and the concentration of sodium hydroxide solution is 7~9mol / L.

[0010] In the preparation method of the above-mentioned manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, in step 1), the hydrothermal reaction temperature is 200℃ and the hydrothermal reaction time is 12h.

[0011] In the above-mentioned preparation method of manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, in step 1), the molar ratio of silver bromide:bismuth bromide:cesium bromide is 1:1:3.5-4.5.

[0012] In the above-mentioned preparation method of manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, in step 1), the heating temperature is 110°C, and the acid precipitation method involves stirring, heating, cooling, precipitating the precipitate, and vacuum drying to obtain dicesium hexabromobismuthate dicesium, wherein the vacuum drying temperature is 60°C.

[0013] In the preparation method of the above-mentioned manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, in step 2), the stirring time is 2 hours and the ultrasonication time is 1 hour.

[0014] Application of the above-mentioned manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst in photocatalytic reduction of carbon dioxide.

[0015] The above-mentioned manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst is used in the photocatalytic reduction of carbon dioxide. The method is as follows: under visible light irradiation, the manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst is placed in a closed space filled with carbon dioxide gas to reduce carbon dioxide gas to carbon monoxide gas.

[0016] The beneficial effects of the present invention.

[0017] 1. This invention utilizes a mechanical stirring method to prepare a manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst. The heterojunction structure of this material can improve the carrier separation efficiency, thereby achieving the purpose of improving photocatalytic activity.

[0018] 2. The present invention utilizes a mechanical stirring method to construct a manganese ferrite / dicesium hexabromosiliconate heterojunction photocatalyst. Manganese ferrite has a large specific surface area, which can provide more reactive sites in the photocatalytic reaction; the introduction of dicesium hexabromosiliconate can form a heterostructure with manganese ferrite, which is beneficial to further improve the carrier separation efficiency.

[0019] 3. The manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst prepared by this invention has stronger photocatalytic reduction ability, participates in catalytic reactions, and has good photocatalytic reduction performance of carbon dioxide. Moreover, the method is simple, convenient, low-cost, mild, and conducive to large-scale production. Attached Figure Description

[0020] Figure 1 XRD patterns for MFO, CABB, MFO / CABB-1, MFO / CABB-2, and MFO / CABB-3.

[0021] Figure 2 This is a SEM image of MFO.

[0022] Figure 3 This is a SEM image of CABB.

[0023] Figure 4 SEM image of MFO / CABB-2.

[0024] Figure 5 Comparison of photocatalytic reduction of carbon dioxide reactions for MFO, CABB, MFO / CABB-1, MFO / CABB-2, and MFO / CABB-3.

[0025] Figure 6A comparison of the photocatalytic reduction activities of carbon dioxide by MFO, CABB, MFO / CABB-1, MFO / CABB-2, and MFO / CABB-3.

[0026] Figure 7 are the PL diagrams of MFO, CABB, MFO / CABB-1, MFO / CABB-2 and MFO / CABB-3. Detailed Implementation

[0027] Example 1: Manganese ferrite photocatalyst.

[0028] 1.2 g of manganese chloride tetrahydrate and 2.3 g of ferric chloride hexahydrate were completely dissolved in 20 mL of deionized water and stirred for 30 minutes. Then, 10 mL of 8 mol / L sodium hydroxide solution was added and diluted with deionized water to 60 mL. The solution was hydrothermally heated at 200 °C for 12 h. After cooling, filtration, washing, and drying, manganese ferrite (denoted as MFO) was obtained.

[0029] Example 2: Dicesium hexabromosilyl bismuthate photocatalyst.

[0030] 0.02 mol bismuth bromide and 0.02 mol silver bromide were dissolved in 20 ml hydrobromic acid and stirred for 1 hour. The mixture was heated in an oil bath at 110 °C, and 0.04 mol cesium bromide was added. The mixture was heated to 110 °C and kept at that temperature for 2 hours. After cooling to room temperature, an orange precipitate was formed. The precipitate was dried under vacuum at 60 °C to obtain the dicesium hexabromosilbismuthate photocatalyst (denoted as CABB).

[0031] Example 3: A manganese ferrite / silver hexabromobismuthate dicesium photocatalyst (the mass ratio of manganese ferrite to silver hexabromobismuthate dicesium photocatalyst is 1:3).

[0032] 0.02 g of manganese ferrite prepared in Example 1 and 0.06 g of dicesium hexabromosiliconate prepared in Example 2 were mixed and dispersed in an ethanol solution, stirred for 60 min, sonicated for 30 min, centrifuged, washed, dried and ground to obtain the manganese ferrite / dicesium hexabromosiliconate composite material (denoted as MFO / CABB-1).

[0033] The MFO, CABB, and MFO / CABB-1 prepared in Examples 1, 2, and 3 were subjected to XRD and PL tests. The test results are as follows: Figure 1 As shown in the figure, typical characteristic peaks of MFO and CABB were detected in MFO / CABB-1, indicating the successful preparation of MFO / CABB-1.

[0034] Example 4: Photocatalytic reduction of carbon dioxide using MFO / CABB-1 photocatalyst.

[0035] The MFO, CABB, and MFO / CABB-1 photocatalysts prepared in Examples 1-3 were used to conduct photocatalytic reduction experiments on carbon dioxide. The test procedure was as follows: using a 300W xenon lamp as the light source, 0.05g of the prepared MFO, CABB, and MFO / CABB-1 were placed in a sealed reaction vessel along with 1mL of deionized water. The sealed vessel was evacuated using a vacuum pump, and carbon dioxide gas was introduced through the gas cycle three times. Then, carbon dioxide was reduced under visible light irradiation. The results are as follows: Figure 5 , 6 As shown, the manganese ferrite / silver hexabromobismuthate dicesium photocatalyst MFO / CABB-1 prepared in Example 3 exhibits excellent photocatalytic activity and stability, with a carbon monoxide generation rate of 46.57 μmol·g⁻¹. -1 ·h -1 The carbon monoxide formation rate of MFO is only 28.94 μmol·g. -1 ·h -1 .

[0036] Example 5: A manganese ferrite / silver hexabromobismuthate dicesium photocatalyst (the mass ratio of manganese ferrite to silver hexabromobismuthate dicesium photocatalyst is 1:5).

[0037] 0.02 g of manganese ferrite prepared in Example 1 and 0.10 g of dicesium hexabromosiliconate prepared in Example 2 were mixed and dispersed in an ethanol solution, stirred for 60 min, sonicated for 30 min, centrifuged, washed, dried and ground to obtain the manganese ferrite / dicesium hexabromosiliconate composite material (denoted as MFO / CABB-2).

[0038] The MFO, CABB, and MFO / CABB-2 prepared in Examples 1, 2, and 4 were subjected to XRD and PL tests. The test results are as follows: Figure 1 and Figure 7 As shown in the figure, typical characteristic peaks of MFO and CABB were detected in MFO / CABB-2, indicating the successful preparation of MFO / CABB-2.

[0039] The prepared MFO, CABB, and MFO / CABB-2 were subjected to SEM testing, such as... Figure 2 , Figure 3 and Figure 4 As shown, MFO has an irregular prismatic structure, while CABB has a blocky structure. MFO grows on the surface of CABB, indicating the successful synthesis of MFO / CABB-2.

[0040] Example 6: Photocatalytic reduction of carbon dioxide using MFO / CABB-2 photocatalyst.

[0041] The MFO / CABB-2 photocatalyst prepared in Example 5 was used to conduct a photocatalytic reduction experiment of carbon dioxide. The test procedure was as follows: using a 300W xenon lamp as the light source, 0.05g of the prepared MFO, CABB, and MFO / CABB-2 were placed in 1mL of deionized water into a self-made sealed reaction vessel. A vacuum pump was used to evacuate the sealed vessel, and carbon dioxide gas was passed through three times. Then, carbon dioxide was reduced under visible light irradiation. Figure 5 , 6 As shown, the manganese ferrite / silver hexabromobismuthate dicesium photocatalyst prepared in Example 3 exhibits excellent photocatalytic activity and stability, with the carbon monoxide generation rate of MFO / CABB-2 reaching 37.07 μmol·g. -1 ·h -1 The carbon monoxide formation rate of MFO is only 28.94 μmol·g. -1 ·h -1 .

[0042] Example 7: A manganese ferrite / silver hexabromobismuthate dicesium photocatalyst (the mass ratio of manganese ferrite to silver hexabromobismuthate dicesium photocatalyst is 1:7).

[0043] 3) 0.02g of manganese ferrite prepared in Example 1 and 0.14g of dicesium hexabromosilicon bismuthate prepared in Example 2 were mixed and dispersed in an ethanol solution, stirred for 60 min, sonicated for 30 min, centrifuged, washed, dried and ground to obtain the manganese ferrite / dicesium hexabromosilicon bismuthate composite material (denoted as MFO / CABB-3).

[0044] The MFO, CABB, and MFO / CABB-3 prepared in Examples 1, 2, and 6 were subjected to XRD and PL tests. The test results are as follows: Figure 1 As shown in the figure, typical characteristic peaks of MFO and CABB were detected in MFO / CABB-3, indicating the successful preparation of MFO / CABB-3.

[0045] Example 8: Photocatalytic reduction of carbon dioxide using MFO / CABB-3 photocatalyst.

[0046] The MFO / CABB-3 photocatalyst prepared in Example 7 was used to conduct a photocatalytic reduction experiment of carbon dioxide. The test procedure was as follows: using a 300W xenon lamp as the light source, 0.05g of the prepared MFO, CABB, and MFO / CABB-3 were placed in 1mL of deionized water into a self-made sealed reaction vessel. A vacuum pump was used to evacuate the sealed vessel, and carbon dioxide gas was passed through three times. Then, carbon dioxide was reduced under visible light irradiation. The results are as follows: Figure 5 , 6As shown, the manganese ferrite / silver hexabromobismuthate dicesium photocatalyst prepared in Example 5 exhibits excellent photocatalytic activity and stability, with the carbon monoxide formation rate of MFO / CABB-3 reaching 30.61 μmol·g⁻¹. -1 ·h -1 The carbon monoxide formation rate of MFO is only 28.94 μmol·g. -1 ·h -1 .

Claims

1. A manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst, characterized in that, The mass ratio of manganese ferrite to dicesium hexabromosilicon bismuthate heterojunction photocatalyst is 1:3 to 1:7; The preparation method of the aforementioned manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst includes the following steps: 1) Manganese chloride tetrahydrate and ferric chloride hexahydrate hydrates are dissolved in deionized water, and then sodium hydroxide solution is added. Manganese ferrate is obtained by hydrothermal reaction. Silver bromide and bismuth bromide are dissolved in hydrobromic acid, stirred, heated, and then cesium bromide is added. Dicesium hexabromosilyl bismuthate is obtained by acid precipitation. 2) Dissolve manganese ferrite and dicesium hexabromosiliconate in ethanol, stir, centrifuge, and dry to obtain manganese ferrite / dicesium hexabromosiliconate heterojunction photocatalyst.

2. The manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst according to claim 1, characterized in that, In step 1), the ratio of ferric chloride hexahydrate: manganese chloride tetrahydrate: sodium hydroxide solution is 2.0~2.5g: 1~1.5g: 8~12mL, and the concentration of sodium hydroxide solution is 7~9mol / L.

3. The manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst according to claim 1, characterized in that, In step 1), the hydrothermal reaction temperature is 200℃ and the hydrothermal reaction time is 12h.

4. The manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst according to claim 1, characterized in that, In step 1), the molar ratio is silver bromide:bismuth bromide:cesium bromide = 1:1:3.5-4.

5.

5. The manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst according to claim 1, characterized in that, In step 1), the heating temperature is 110°C, and the acid precipitation method involves stirring, heating, cooling, precipitating the precipitate, and vacuum drying to obtain dicesium hexabromosilicon bismuthate. The vacuum drying temperature is 60°C.

6. The manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst according to claim 1, characterized in that, In step 2), the stirring time is 2 hours and the sonication time is 1 hour.

7. The application of the manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst according to any one of claims 1-6 in the photocatalytic reduction of carbon dioxide.

8. The application of the manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst according to claim 7 in the photocatalytic reduction of carbon dioxide, characterized in that, The method is as follows: Under visible light irradiation, the manganese ferrite / silver hexabromobismuthate dicesium heterojunction photocatalyst is placed in a sealed space filled with carbon dioxide gas, and the carbon dioxide gas is reduced to carbon monoxide gas.

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