A first main group metal gradient-doped Cs2NaBiCl6 perovskite material, a preparation method and application thereof

Abstract

The application discloses a first main group metal gradient doped Cs2NaBiCl6 perovskite material and a preparation method and application thereof, and belongs to the technical field of photocatalytic material for preventing and treating air pollution. The preparation method comprises the following steps: dissolving cesium chloride, sodium chloride, lithium chloride and bismuth chloride in hydrochloric acid and stirring uniformly; placing the mixture into a reaction kettle to perform hydrothermal reaction; after the reaction is completed, centrifuging, washing and drying are performed to obtain Cs2Na 1‑ x Li x BiCl6, wherein x is 0.1-0.5. The lithium-doped cesium-sodium-bismuth-chlorine double perovskite photocatalyst has stronger photocatalytic reduction capacity, and can greatly improve the activity of the lithium-doped cesium-sodium-bismuth-chlorine double perovskite in photocatalytic reduction of carbon dioxide, and the generation rate of carbon monoxide can reach 10.25 mu mol per hour ‑1 ·g ‑1 .

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials for the prevention and control of air pollution, specifically relating to a first group metal gradient-doped Cs2NaBiCl6 perovskite material, 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 (CCO2 reduction) utilizes inexhaustible solar energy to directly convert carbon dioxide gas into hydrocarbon solar fuels, representing a feasible method to simultaneously address the energy crisis and environmental pollution. Recently, some relatively stable lead-free perovskite materials have shown promising prospects in photocatalytic CO2 reduction, such as Cs3Sb2I9, Cs3Sb2Br9, Cs3Bi2I9, Cs3Bi2Br9, Cs2AgBiBr6, Cs2AgInCl6, Cs2NaBiCl6, CsAgCl2, and Cs2PdBr6. However, due to insufficient photogenerated charge separation and a lack of active sites in their original state, the photocatalytic CO2 reduction activity of these semiconductor materials is typically very low. Furthermore, since the size of sodium ions (1.02 Å) is similar to that of bismuth ions (1.03 Å), and both are relatively large, doping with another ion, along with chloride ions, can form a six-coordinate octahedral structure with high symmetry and small porosity. This makes the Cs2NaBiCl6 double perovskite structure more conducive to H2O insertion, thus exhibiting better environmental and water stability than other lead-free perovskites. Consequently, the photocatalytic performance of Cs2NaBiCl6 can be significantly improved, making it a promising photocatalytic material among halide perovskite materials. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a group 1 metal gradient-doped Cs₂NaBiCl₆ perovskite material, its preparation method, and its applications. This invention utilizes a hydrothermal method to construct a lithium-doped cesium sodium bismuth chloride double perovskite, which can improve carrier separation efficiency, thereby enhancing the photocatalytic reduction activity of carbon dioxide.

[0004] The technical solution adopted in this invention is: a method for preparing Cs₂NaBiCl₆ perovskite material with gradient doping of Group 1 metals, characterized by the following steps: dissolving cesium chloride, sodium chloride, lithium chloride and bismuth chloride in hydrochloric acid and stirring until homogeneous; placing the mixture in a reaction vessel for hydrothermal reaction; centrifuging, washing and drying after the reaction to obtain Cs₂NaBiCl₆. 1-x Li x BiCl6, where x is 0.1-0.5.

[0005] Furthermore, in molar ratio, cesium chloride:sodium chloride:bismuth chloride:lithium chloride = 2:0.5-1:1:0.1-0.5.

[0006] Furthermore, the hydrothermal reaction time is 12h-36h, and the hydrothermal reaction temperature is 120℃-200℃.

[0007] Furthermore, the ratio of bismuth chloride to hydrochloric acid is 1 mmol / L: 3 mL - 15 mL.

[0008] A first-group metal gradient-doped Cs2NaBiCl6 perovskite material prepared according to the above preparation method.

[0009] Application of the above-mentioned Group 1 metal gradient-doped Cs2NaBiCl6 perovskite material in photocatalytic reduction of carbon dioxide.

[0010] Furthermore, the application of the aforementioned Group 1 metal gradient-doped Cs2NaBiCl6 perovskite material in photocatalytic reduction of carbon dioxide is as follows: Under visible light irradiation, the Group 1 metal gradient-doped Cs2NaBiCl6 perovskite material is placed in a sealed space filled with carbon dioxide gas, and the carbon dioxide gas is reduced to carbon monoxide gas.

[0011] The beneficial effects of this invention are as follows.

[0012] 1. This invention utilizes a hydrothermal method to prepare a group I metal gradient-doped Cs2NaBiCl6 perovskite material, namely a lithium-doped cesium sodium bismuth chloride double perovskite photocatalyst. The radius of the Li ion is significantly smaller than that of the substituted Na ion. Both are monovalent cations, which can achieve isovalent substitution doping. There is no lattice charge imbalance, and the lattice size and tolerance factor can be precisely controlled, which enhances the stability of the cubic phase structure and inhibits photocorrosion.

[0013] 2. This invention utilizes a hydrothermal method to prepare a lithium-doped cesium sodium bismuth chloride double perovskite photocatalyst. Li doping can modulate the energy band and broaden the visible light response. The lattice dipole difference forms an internal electric field that suppresses electron-hole recombination and prolongs carrier lifetime, thereby achieving the purpose of improving the photocatalytic reduction activity of carbon dioxide.

[0014] 3. The lithium-doped cesium sodium bismuth chloride double perovskite 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

[0015] Figure 1 Cs2NaBiCl6, Cs2Na 0.9 Li 0.1 BiCl6, Cs2Na0.8 Li 0.2 BiCl6, Cs2Na 0.7 Li 0.3 BiCl6 and Cs2Na 0.5 Li 0.5 XRD pattern of BiCl6.

[0016] Figure 2 Cs2NaBiCl6, Cs2Na 0.9 Li 0.1 BiCl6, Cs2Na 0.8 Li 0.2 BiCl6, Cs2Na 0.7 Li 0.3 BiCl6 and Cs2Na 0.5 Li 0.5 PL diagram of BiCl6.

[0017] Figure 3 For (a) Cs2NaBiCl6 and (b) Cs2Na 0.7 Li 0.3 SEM images of BiCl6 and (c)Cs2Na 0.7 Li 0.3 Energy spectrum of BiCl6.

[0018] Figure 4 Cs2NaBiCl6, Cs2Na 0.9 Li 0.1 BiCl6, Cs2Na 0.8 Li 0.2 BiCl6, Cs2Na 0.7 Li 0.3 BiCl6 and Cs2Na 0.5 Li 0.5 Comparison chart of BiCl6 photocatalytic reduction performance of carbon dioxide to carbon monoxide.

[0019] Figure 5 Cs2NaBiCl6, Cs2Na 0.9 Li 0.1 BiCl6, Cs2Na 0.8 Li 0.2 BiCl6, Cs2Na 0.7 Li 0.3 BiCl6 and Cs2Na 0.5 Li 0.5 Comparison chart of the photocatalytic reduction rate of carbon dioxide to carbon monoxide by BiCl6. Detailed Implementation

[0020] Comparative Example 1: A cesium sodium bismuth chloride perovskite photocatalyst (Cs2NaBiCl6).

[0021] Dissolve 2.0 mmol CsCl2, 1.0 mmol NaCl and 1.0 mmol BiCl in 10 mL of hydrochloric acid and stir at a constant stirring rate until homogeneous.

[0022] The above solution was added to a 25 mL stainless steel autoclave. The autoclave was then sealed and placed in an oven to be heated to 180°C and maintained at this temperature for 12 hours. Subsequently, it was naturally cooled to room temperature, and the resulting precipitate was centrifuged with isopropanol, washed until hydrochloric acid was completely removed, and then vacuum dried to obtain Cs₂NaBiCl₆.

[0023] Example 1: A Group 1 metal gradient-doped Cs2NaBiCl6 perovskite material (Cs2Na 0.9 Li 0.1 BiCl6).

[0024] (a) Preparation method.

[0025] Dissolve 2.0 mmol CsCl2, 0.9 mmol NaCl, 0.1 mmol LiCl and 1.0 mmol BiCl in 10 mL of 36% hydrochloric acid and stir at a constant speed until homogeneous.

[0026] The above solution was added to a 25 mL stainless steel autoclave. The autoclave was then sealed and placed in an oven to heat to 180°C, where it was maintained for 12 hours. Afterward, it was allowed to cool naturally to room temperature. The resulting precipitate was centrifuged with isopropanol, washed until hydrochloric acid was completely removed, and then vacuum dried to obtain Cs₂Na. 0.9 Li 0.1 BiCl6.

[0027] (ii) Characterization.

[0028] The Cs₂NaBiCl₆ prepared in Comparative Example 1 and the Cs₂Na prepared in this example were compared. 0.9 Li 0.1 BiCl6 was subjected to XRD testing, and the results are as follows: Figure 1 .from Figure 1 As can be seen from Cs2Na 0.9 Li 0.1 The characteristic peak intensity of BiCl6 is lower than that of Cs2NaBiCl6, indicating that Cs2Na was successfully prepared. 0.9 Li 0.1 BiCl6.

[0029] The Cs₂NaBiCl₆ prepared in Comparative Example 1 and the Cs₂Na prepared in this example were compared.0.9 Li 0.1 BiCl6 line PL test, results are as follows Figure 2 .from Figure 2 As can be seen from Cs2Na 0.9 Li 0.1 The PL emission peak of BiCl6 is lower than that of Cs2NaBiCl6, indicating that the introduction of Li ions can effectively improve the separation efficiency of photogenerated carriers, thereby improving photocatalytic performance.

[0030] Example 2: A Group 1 metal gradient-doped Cs2NaBiCl6 perovskite material (Cs2Na 0.8 Li 0.2 BiCl6).

[0031] (a) Preparation method.

[0032] Dissolve 2.0 mmol CsCl2, 0.8 mmol NaCl, 0.2 mmol LiCl and 1.0 mmol BiCl in 10 mL of 36% hydrochloric acid and stir at a constant speed until homogeneous.

[0033] The above solution was added to a 25 mL stainless steel autoclave. The autoclave was then sealed and placed in an oven to heat to 180°C, where it was maintained for 12 hours. Afterward, it was allowed to cool naturally to room temperature. The resulting precipitate was centrifuged with isopropanol, washed until hydrochloric acid was completely removed, and then vacuum dried to obtain Cs₂Na. 0.8 Li 0.2 BiCl6.

[0034] (ii) Characterization.

[0035] The Cs₂NaBiCl₆ prepared in Comparative Example 1 and the Cs₂Na prepared in this example were compared. 0.8 Li 0.2 BiCl6 was subjected to XRD testing, and the results are as follows: Figure 1 .from Figure 1 As can be seen from Cs2Na 0.8 Li 0.2 The characteristic peak intensity of BiCl6 is lower than that of Cs2NaBiCl6, indicating that Cs2Na was successfully prepared. 0.8 Li 0.2 BiCl6.

[0036] The Cs₂NaBiCl₆ prepared in Comparative Example 1 and the Cs₂Na prepared in this example were compared. 0.8 Li 0.2 BiCl6 line PL test, results are as follows Figure 2 .from Figure 2 As can be seen from Cs2Na 0.8Li 0.2 The PL emission peak of BiCl6 is lower than that of Cs2NaBiCl6, indicating that the introduction of Li ions can effectively improve the separation efficiency of photogenerated carriers, thereby improving photocatalytic performance.

[0037] Example 3: A Group 1 metal gradient-doped Cs2NaBiCl6 perovskite material (Cs2Na 0.7 Li 0.3 BiCl6).

[0038] (a) Preparation method.

[0039] Dissolve 2.0 mmol CsCl2, 0.7 mmol NaCl, 0.3 mmol LiCl and 1.0 mmol BiCl in 10 mL of 36% hydrochloric acid and stir at a constant speed until homogeneous.

[0040] The above solution was added to a 25 mL stainless steel autoclave. The autoclave was then sealed and placed in an oven to heat to 180°C, where it was maintained for 12 hours. Afterward, it was allowed to cool naturally to room temperature. The resulting precipitate was centrifuged with isopropanol, washed until hydrochloric acid was completely removed, and then vacuum dried to obtain Cs₂Na. 0.7 Li 0.3 BiCl6.

[0041] (ii) Characterization.

[0042] The Cs₂NaBiCl₆ prepared in Comparative Example 1 and the Cs₂Na prepared in this example were compared. 0.7 Li 0.3 BiCl6 was subjected to XRD testing, and the results are as follows: Figure 1 .from Figure 1 As can be seen from Cs2Na 0.7 Li 0.3 The characteristic peak intensity of BiCl6 is lower than that of Cs2NaBiCl6, indicating that Cs2Na was successfully prepared. 0.7 Li 0.3 BiCl6.

[0043] The Cs₂NaBiCl₆ prepared in Comparative Example 1 and the Cs₂Na prepared in this example were compared. 0.7 Li 0.3 BiCl6 line PL test, results are as follows Figure 2 .from Figure 2 As can be seen from Cs2Na 0.7 Li 0.3 The PL emission peak of BiCl6 is lower than that of Cs2NaBiCl6, indicating that the introduction of Li ions can effectively improve the separation efficiency of photogenerated carriers, thereby improving photocatalytic performance.

[0044] The Cs₂NaBiCl₆ prepared in Comparative Example 1 and the Cs₂Na prepared in this example were compared. 0.8 Li 0.2 BiCl6 was tested using SEM, and the results are as follows: Figure 3 .from Figure 3 As can be seen from (a) and (b), Cs2Na 0.8 Li 0.2 The BiCl6 composite sample is larger in size than the Cs2NaBiCl6 sample, and Figure 3 The presence of Li can be clearly observed in the EDS energy spectrum image in (c), indicating that Cs2Na 0.8 Li 0.2 Successful synthesis of BiCl6.

[0045] Example 4: A Group 1 metal gradient-doped Cs2NaBiCl6 perovskite material (Cs2Na 0.5 Li 0.5 BiCl6).

[0046] (a) Preparation method.

[0047] Dissolve 2.0 mmol CsCl2, 0.5 mmol NaCl, 0.5 mmol LiCl and 1.0 mmol BiCl in 10 mL of 36% hydrochloric acid and stir at a constant speed until homogeneous.

[0048] The above solution was added to a 25 mL stainless steel autoclave. The autoclave was then sealed and placed in an oven to heat to 180°C, where it was maintained for 12 hours. Afterward, it was allowed to cool naturally to room temperature. The resulting precipitate was centrifuged with isopropanol, washed until hydrochloric acid was completely removed, and then vacuum dried to obtain Cs₂Na. 0.5 Li 0.5 BiCl6.

[0049] (ii) Characterization.

[0050] The Cs₂NaBiCl₆ prepared in Comparative Example 1 and the Cs₂Na prepared in this example were compared. 0.5 Li 0.5 BiCl6 was subjected to XRD testing, and the results are as follows: Figure 1 .from Figure 1 As can be seen from Cs2Na 0.5 Li 0.5 The characteristic peak intensity of BiCl6 is lower than that of Cs2NaBiCl6, indicating that Cs2Na was successfully prepared. 0.5 Li 0.5 BiCl6.

[0051] The Cs₂NaBiCl₆ prepared in Comparative Example 1 and the Cs₂Na prepared in this example were compared. 0.5 Li 0.5 BiCl6 line PL test, results are as follows Figure 2 .from Figure 2 As can be seen from Cs2Na 0.5 Li 0.5 The PL emission peak of BiCl6 is lower than that of Cs2NaBiCl6, indicating that the introduction of Li ions can effectively improve the separation efficiency of photogenerated carriers, thereby improving photocatalytic performance.

[0052] Example 5: Application of a Group 1 metal gradient-doped Cs2NaBiCl6 perovskite material in photocatalytic reduction of carbon dioxide.

[0053] I. Methods.

[0054] Using a 300W xenon lamp as the light source, 0.03g of Cs₂NaBiCl₆ and Cs₂Na were respectively... 0.9 Li 0.1 BiCl6, Cs2Na 0.8 Li 0.2 BiCl6, Cs2Na 0.7 Li 0.3 BiCl6 or Cs2Na 0.5 Li 0.5 BiCl6 and 1 mL of deionized water were placed in a sealed reaction vessel. The sealed vessel was evacuated using a vacuum pump, and carbon dioxide gas was passed through it. This process was repeated three times, and then the carbon dioxide was reduced under visible light irradiation.

[0055] Depend on Figure 4 It can be seen that the lithium-doped cesium sodium bismuth chloride double perovskite photocatalyst prepared in this invention exhibits good photocatalytic activity and stability. After 2 hours of irradiation, the Cs₂Na₂O₃ prepared in Example 1 showed good photocatalytic activity and stability. 0.9 Li 0.1 The yield of carbon monoxide from BiCl6 reached 12.54 μmol·g. -1 Cs2Na prepared in Example 2 0.8 Li 0.2 The yield of carbon monoxide from BiCl6 reached 15.87 μmol·g. -1 Cs2Na prepared in Example 3 0.7 Li 0.3 The yield of carbon monoxide from BiCl6 reached 20.5 μmol·g. -1 Cs2Na prepared in Example 4 0.5 Li 0.5 The yield of carbon monoxide from BiCl6 reached 15.41 μmol·g. -1In contrast, the yield of carbon monoxide prepared from Cs₂NaBiCl₆ in Comparative Example 1 was only 10.62 μmol·g⁻¹. -1 .

[0056] Depend on Figure 5 It can be seen that the Cs2Na prepared in Example 1 0.9 Li 0.1 The carbon monoxide formation rate of BiCl6 reached 6.27 μmol·h⁻¹. -1 ·g -1 Cs2Na prepared in Example 2 0.8 Li 0.2 The carbon monoxide formation rate of BiCl6 reached 7.94 μmol·h⁻¹. -1 ·g -1 Cs2Na prepared in Example 3 0.7 Li 0.3 The carbon monoxide formation rate of BiCl6 reached 10.25 μmol·h⁻¹. -1 ·g -1 Cs2Na prepared in Example 3 0.5 Li 0.5 The carbon monoxide formation rate of BiCl6 reached 7.71 μmol·h⁻¹. -1 ·g -1 In contrast, the carbon monoxide formation rate of Cs₂NaBiCl₆ prepared in Comparative Example 1 was only 5.31 μmol·h⁻¹. -1 ·g -1 .

Claims

1. A method for preparing a Group 1 metal gradient-doped Cs₂NaBiCl₆ perovskite material, characterized in that, The process includes the following steps: Cesium chloride, sodium chloride, lithium chloride, and bismuth chloride are dissolved in hydrochloric acid and stirred until homogeneous; the mixture is then placed in a reaction vessel for a hydrothermal reaction; after the reaction is complete, the mixture is centrifuged, washed, and dried to obtain Cs₂Na. 1-x Li x BiCl6, where x is 0.1-0.

5.

2. The method for preparing a first-group metal gradient-doped Cs₂NaBiCl₆ perovskite material according to claim 1, characterized in that, The molar ratio is cesium chloride:sodium chloride:bismuth chloride:lithium chloride = 2:0.5-1:1:0.1-0.

5.

3. The method for preparing a first-group metal gradient-doped Cs₂NaBiCl₆ perovskite material according to claim 1, characterized in that, The hydrothermal reaction time is 12h-36h, and the hydrothermal reaction temperature is 120℃-200℃.

4. The method for preparing a first-group metal gradient-doped Cs₂NaBiCl₆ perovskite material according to claim 1, characterized in that, Bismuth chloride: hydrochloric acid = 1 mmol / L: 3 mL - 15 mL.

5. A first group metal gradient-doped Cs2NaBiCl6 perovskite material prepared according to the preparation method of any one of claims 1-4.

6. The application of the first group metal gradient-doped Cs2NaBiCl6 perovskite material as described in claim 5 in the photocatalytic reduction of carbon dioxide.

7. The application of the first main group metal gradient-doped Cs₂NaBiCl₆ perovskite material according to claim 6 in the photocatalytic reduction of carbon dioxide, characterized in that, The method is as follows: Under visible light irradiation, Cs2NaBiCl6 perovskite material with gradient doping of Group 1 metals is placed in a closed space filled with carbon dioxide gas, and the carbon dioxide gas is reduced to carbon monoxide gas.

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