A high-temperature gas-phase sulfidation method for preparing two-dimensional bismuth sulfide catalysts

Abstract

This invention discloses a high-temperature gas-phase sulfidation method for preparing a two-dimensional bismuth sulfide catalyst, comprising: (1) dissolving bismuth salt in solvent A to prepare a homogeneous bismuth salt solution; (2) mixing uniformly sized substance A powder with the bismuth salt solution to obtain a mixed liquid; then drying to remove solvent A to obtain a mixed powder; (3) annealing the mixed powder to decompose the bismuth salt into bismuth oxide, obtaining a mixed powder of bismuth oxide and substance A; (4) placing the mixed powder of bismuth oxide and substance A in an inert gas environment, and carrying sulfur vapor to the mixed powder of bismuth oxide and substance A through continuous inert gas flow for a high-temperature sulfidation reaction; after the reaction, completely removing substance A to obtain bismuth sulfide nanosheets. This invention is based on a high-temperature gas-phase sulfidation-growth strategy, directly performing high-temperature sulfidation on bulk bismuth oxide obtained from bismuth salt pyrolysis to achieve the direct growth of two-dimensional bismuth sulfide.

Description

Technical Field

[0001] This invention belongs to the field of low-dimensional bismuth-based nanomaterial preparation, specifically a high-temperature gas-phase sulfidation method for preparing two-dimensional bismuth sulfide catalysts. Background Technology

[0002] The concentration of CO2 in the atmosphere has been increasing year by year, causing a series of environmental problems. While reducing CO2 emissions, it is also necessary to vigorously develop the CO2 conversion and utilization industry. Electrocatalytic CO2 reduction (CO2RR), driven by renewable energy sources (such as wind, hydro, and solar power), converts CO2 into high-value-added chemicals and energy fuels. This is of great significance for achieving the recycling of global carbon resources and building a low-carbon society, and is a recognized efficient and environmentally friendly method. Formate (or formic acid) is an important chemical raw material intermediate and energy fuel, and high-performance electrocatalysts are key to achieving the efficient conversion of CO2 into formate.

[0003] Bismuth-based catalysts exhibit high formic acid selectivity, and their weak metal-hydrogen bonding provides a high hydrogen evolution barrier, effectively suppressing the competing reaction of CO2 electroreduction (i.e., the hydrogen evolution reaction). Compared to pure metallic bismuth, bismuth-based chalcogenides possess superior CO2RR performance due to their unique surface structure and local electronic configuration. Furthermore, the interlayer bonding is primarily van der Waals forces, enabling the effective construction of thin-layer two-dimensional structures. Their high specific surface area and excellent electrochemical activity make them highly efficient energy conversion electrocatalysts. However, current methods for synthesizing bismuth-based chalcogenides mainly utilize soluble metallic bismuth salts at low temperatures via hydrothermal or solvothermal processes. The addition of surfactants in these methods inevitably reduces catalytic activity, and the presence of ions in the solution is difficult to control regarding the catalyst's crystal structure and morphology. Low yields and unstable performance still fail to meet current requirements. Therefore, developing an efficient and controllable synthesis method with high activity, high selectivity, and high stability remains a significant challenge. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to provide a high-temperature gas-phase sulfidation method for preparing two-dimensional bismuth sulfide catalysts.

[0005] The technical solution of this invention to solve the aforementioned technical problem is to provide a high-temperature gas-phase sulfidation method for preparing a two-dimensional bismuth sulfide catalyst, characterized in that the method includes the following steps:

[0006] (1) Powdering of substance A to obtain uniformly sized powder of substance A; dissolving bismuth salt in solvent A to prepare a homogeneous bismuth salt solution;

[0007] Substance A is a substance with a melting point higher than the decomposition temperature of bismuth salt, which does not react with bismuth salt and is insoluble in solvent A; the bismuth salt is a bismuth salt that can decompose at high temperatures; solvent A is a solvent that can dissolve bismuth salt but does not dissolve substance A.

[0008] (2) Mix the powder of substance A with the bismuth salt solution and stir until homogeneous to obtain a mixture; then dry the mixture to remove solvent A and obtain a mixed powder.

[0009] (3) The mixed powder is annealed to decompose the bismuth salt into bismuth oxide, resulting in a uniformly mixed powder of bismuth oxide and substance A.

[0010] (4) Place the mixed powder of bismuth oxide and substance A in an inert gas environment, and carry sulfur vapor to the mixed powder of bismuth oxide and substance A through continuous inert gas to carry out a high-temperature sulfidation reaction; after the reaction is completed, substance A is completely removed to obtain bismuth sulfide nanosheets.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] (1) Based on the high-temperature gas phase sulfidation-growth strategy, the present invention directly sulfidates the bulk bismuth oxide obtained by pyrolysis of bismuth salt to achieve the direct growth of two-dimensional bismuth sulfide and efficiently and controllably prepare two-dimensional bismuth sulfide nanosheets.

[0013] (2) This invention can efficiently prepare large quantities of two-dimensional bismuth sulfide nanosheets, solving the problem of low yield of low-dimensional bismuth-based catalysts.

[0014] (3) The present invention can quickly realize the sulfidation process at high temperature. The chalcogen vapor atmosphere is the reaction environment. The high local chalcogen vapor pressure is conducive to the replacement of oxygen atoms by chalcogen atoms to form new chemical components. At high temperature, the reaction gas is continuously released, which prevents the formation of van der Waals layers, thus forming a layered material.

[0015] (4) The two-dimensional bismuth sulfide nanosheets of the present invention have high activity, high selectivity and high stability, and have excellent CO2 electroreduction performance, achieving a high formic acid generation rate. Attached Figure Description

[0016] Figure 1 This is a SEM image of the bismuth sulfide nanosheets prepared in Example 1 of the present invention;

[0017] Figure 2 The image shows the XRD pattern of the bismuth sulfide nanosheets prepared in Example 1 of this invention.

[0018] Figure 3 This is a low-magnification TEM image of the bismuth sulfide nanosheets prepared in Example 1 of this invention;

[0019] Figure 4This is a high-magnification TEM image of the bismuth sulfide nanosheets prepared in Example 1 of this invention;

[0020] Figure 5 This is a TEM image of a cross-section of the bismuth sulfide nanosheets prepared in Example 1 of this invention;

[0021] Figure 6 AFM image of bismuth sulfide nanosheets prepared in Example 1 of this invention;

[0022] Figure 7 The 1H NMR spectrum of the formate, the electrocatalytic CO2 reduction product of bismuth sulfide nanosheets prepared in Example 1 of this invention;

[0023] Figure 8 This is a Faraday efficiency diagram of the formate product of CO2 reduction by electrocatalysis of bismuth sulfide nanosheets prepared in Example 1 of this invention;

[0024] Figure 9 This is a current density diagram of the long-term electrocatalytic CO2 reduction process of bismuth sulfide nanosheets prepared in Example 1 of the present invention. Detailed Implementation

[0025] Specific embodiments of the present invention are given below. These specific embodiments are only used to further illustrate the present invention and do not limit the scope of protection of the claims of this application.

[0026] This invention provides a high-temperature gas-phase sulfidation method for preparing two-dimensional bismuth sulfide catalysts (hereinafter referred to as the method), characterized in that the method includes the following steps:

[0027] (1) Powdering of substance A to obtain uniformly sized powder of substance A; dissolving bismuth salt in solvent A to prepare a homogeneous bismuth salt solution;

[0028] Substance A is a substance with a melting point higher than the decomposition temperature of bismuth salt, which does not react with bismuth salt and is insoluble in solvent A; the bismuth salt is a bismuth salt that can decompose at high temperatures; solvent A is a solvent that can dissolve bismuth salt but does not dissolve substance A.

[0029] Preferably, in step (1), substance A mainly acts as a dispersant to disperse bismuth oxide evenly so that it can be fully sulfidated. Inorganic salts (preferably alkali metal salts and alkaline earth metal salts) are used, specifically sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, magnesium chloride or magnesium sulfate; the bismuth salt is bismuth nitrate, bismuth oxycarbonate, bismuth acetate or bismuth oxynitrate; the solvent A is ethylene glycol, ethanol or isopropanol.

[0030] Preferably, in step (1), the pulverization process is performed by ball milling for 2 to 10 hours.

[0031] Preferably, in step (1), the size of the substance A powder is 5 to 30 μm (preferably 20 μm).

[0032] Preferably, in step (1), the substance A, bismuth salt and solvent A used are all commercial products.

[0033] (2) Mix the powder of substance A with the bismuth salt solution and stir until homogeneous to obtain a mixture; then dry the mixture to remove solvent A and obtain a mixed powder.

[0034] Preferably, in step (2), the mixing and stirring time is 0.5 to 3 hours; the drying process is: vacuum drying at 60 to 90°C for 5 to 12 hours. Vacuum drying can also prevent bismuth salt from absorbing moisture and hydrolyzing.

[0035] Preferably, in step (2), the mass ratio of the solute bismuth salt to substance A in the bismuth salt solution is 1 to 3:10 (preferably 2:10).

[0036] (3) The mixed powder is annealed to decompose the bismuth salt into bismuth oxide, resulting in a uniformly mixed powder of bismuth oxide and substance A.

[0037] Preferably, step (3) specifically involves: annealing the mixed powder to decompose the bismuth salt into bismuth oxide; and then cooling it to room temperature to obtain a uniformly mixed powder of bismuth oxide and substance A.

[0038] Preferably, in step (3), the annealing temperature is 500-600°C and the annealing time is at least 30 min (preferably 30-60 min).

[0039] (4) Place the mixed powder of bismuth oxide and substance A in an inert gas environment, and carry sulfur vapor to the mixed powder of bismuth oxide and substance A through continuous inert gas to carry out a high-temperature sulfidation reaction; after the reaction is completed, completely wash away substance A to obtain bismuth sulfide nanosheets.

[0040] Preferably, in step (4), the inert gas is argon or nitrogen, with argon being preferred.

[0041] Preferably, in step (4), the temperature of the high-temperature vulcanization reaction is 600-700°C and the time is at least 30 min (preferably 30-60 min); the flow rate of the inert gas is 200-600 sccm.

[0042] Preferably, step (4) specifically involves: placing the mixed powder of bismuth oxide and substance A into a high-temperature resistant container (preferably a ceramic boat) that does not react with it, and then placing it into the lower temperature zone of a closed heating environment (preferably a tubular furnace heating center) under vacuum to atmospheric pressure (i.e., 0-760 Torr); placing sulfur powder into the upper temperature zone of the heating environment; raising the lower temperature zone to 600-700°C and the upper temperature zone to 100-150°C respectively under a constant inert gas flow of 200-600 sccm; then carrying the sulfur vapor obtained in the upper temperature zone to the lower temperature zone through the continuously introduced inert gas, and carrying out a high-temperature sulfidation reaction in the lower temperature zone for at least 30 minutes; after the reaction is completed, naturally cooling to room temperature, stopping the gas supply, and then completely washing away substance A to obtain bismuth sulfide nanosheet powder.

[0043] Example 1

[0044] (1) 20g of sodium chloride was ball-milled for 2h to obtain sodium chloride powder with uniform particles; 4g of bismuth nitrate was dissolved in 20mL of ethylene glycol to prepare a homogeneous bismuth nitrate solution;

[0045] (2) Mix 20g of sodium chloride powder with 20mL of bismuth nitrate solution and stir for 1h until homogeneous to obtain a mixture; then vacuum dry the mixture at 80℃ for 6h to obtain a mixed powder.

[0046] (3) The mixed powder was annealed at 500°C for 30 min and then naturally cooled to room temperature to obtain a uniformly mixed powder of bismuth oxide and sodium chloride.

[0047] (4) Place the mixed powder of bismuth oxide and sodium chloride into a ceramic boat, and then place it into the lower temperature zone of the heat center of a sealed tubular furnace; place the sulfur powder into the upper temperature zone of the heat center of the tubular furnace; under a constant flow of argon gas at a flow rate of 500 sccm, raise the temperature of the lower temperature zone of the tubular furnace to 650°C and the temperature of the upper temperature zone to 120°C respectively; then carry the sulfur vapor obtained in the upper temperature zone to the lower temperature zone through the flowing argon gas, and carry out a high-temperature sulfidation reaction in the lower temperature zone for 40 min; after the reaction is completed, cool naturally to room temperature, and completely wash away substance A to obtain bismuth sulfide nanosheet powder.

[0048] Depend on Figure 1 As can be seen, the obtained product has a two-dimensional thin-layer structure.

[0049] Depend on Figure 2 It can be seen that the main diffraction peaks of the obtained product correspond well with the PDF (17-0320) card of standard Bi2S3.

[0050] Depend on Figure 3 It can be seen that Bi₂S₃ has a two-dimensional thin-layer structure. (From...) Figure 4It can be seen that the interplanar spacing of Bi2S3 is 0.358 nm, corresponding to the Bi2S3(130) crystal plane.

[0051] Depend on Figure 5 It can be seen that Bi₂S₃ has a few-layer structure. (From...) Figure 6 It can be seen that the thickness of Bi2S3 is approximately 6.8 nm.

[0052] The bismuth sulfide nanosheets prepared in Example 1 were used for the electrocatalytic reduction of CO2 to prepare formate. The specific steps are as follows:

[0053] (1) Bismuth sulfide nanosheets were dispersed in anhydrous ethanol, a small amount of Nafion solution was added, and after ultrasonic dispersion, they were drop-coated onto hydrophobic carbon paper and dried to serve as the negative electrode with a loading of 1 mg·cm⁻¹. -2 A platinum mesh is used as the anode, and a saturated calomel electrode is used as the reference electrode.

[0054] (2) During the electrochemical test, 0.5 mol / L potassium bicarbonate was used as the electrolyte. CO2 gas was continuously introduced during the test to form a saturated solution. The electrochemical reduction of CO2 to prepare formate was carried out at a voltage of -0.55 to -1.25 V. During the test, gas products were detected by online gas chromatography.

[0055] (3) After the reaction is complete, the electrolyte is collected and the liquid phase products are detected by nuclear magnetic resonance hydrogen spectroscopy.

[0056] Depend on Figure 7 It can be seen that after 1 hour of catalytic reaction, the characteristic peak of the reduction product formic acid appeared in the 1H NMR spectrum, and there were no other product peaks.

[0057] Depend on Figure 8 It can be seen that the Faradaic efficiency of formic acid remains above 90% over a wide voltage window, which is at a high level. The highest Faradaic efficiency reaches 98.6%, indicating that the prepared catalyst has excellent selectivity for the synthesis of formic acid.

[0058] The electrochemical (time-current) test of the electrocatalytic CO2 reduction is as follows: Figure 9 As shown, by Figure 9 It can be seen that at a voltage of -0.8V, the catalyst can achieve an energy density of approximately -30mA·cm⁻¹. -2 The catalyst operated stably for over 200 hours at the CO2 reduction current density, and the formic acid Faraday efficiency remained stable at over 90%, indicating that the prepared catalyst has good electrocatalytic stability.

[0059] Therefore, the characterization results show that bismuth oxide was completely sulfided into bismuth sulfide nanosheets, indicating that our method can prepare bismuth sulfide nanosheets simply and efficiently, and has excellent electrocatalytic CO2 reduction performance.

[0060] Examples 2-4

[0061] The difference from Example 1 is that the mass of bismuth nitrate in step (1) is changed to 2g, 3g and 6g respectively, while the rest is the same as in Example 1.

[0062] The products obtained in Examples 2-4 showed obvious formic acid characteristic peaks after testing, and no characteristic peaks of other products, indicating that the prepared catalyst has good selectivity for the synthesis of formic acid.

[0063] Examples 5-7

[0064] The difference from Example 1 is that the vulcanization reaction time in step (4) is changed to 30 min, 50 min and 60 min respectively, while the rest is the same as in Example 1.

[0065] The products obtained in Examples 5-7 showed obvious formic acid characteristic peaks after testing, and no characteristic peaks of other products, indicating that the prepared catalyst has good selectivity for the synthesis of formic acid.

[0066] Examples 8-10

[0067] The difference from Example 1 is that the argon flow rate in step (4) is changed to 200 sccm, 800 sccm and 1000 sccm respectively, while the rest is the same as in Example 1.

[0068] The products obtained in Examples 8-10 showed obvious formic acid characteristic peaks after testing, and no characteristic peaks of other products, indicating that the prepared catalyst has good selectivity for the synthesis of formic acid.

[0069] Examples 11-13

[0070] The difference from Example 1 is that the vulcanization temperature in step (4) is changed to 600°C, 620°C and 680°C respectively, while the rest is the same as Example 1.

[0071] The products obtained in Examples 11-13 showed obvious formic acid characteristic peaks after testing, and no characteristic peaks of other products, indicating that the prepared catalyst has good selectivity for the synthesis of formic acid.

[0072] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A high-temperature gas-phase sulfidation method for preparing a two-dimensional bismuth sulfide catalyst, characterized in that, The method includes the following steps: (1) Powdering of substance A to obtain uniformly sized powder of substance A; dissolving bismuth salt in solvent A to prepare a homogeneous bismuth salt solution; Substance A is a substance with a melting point higher than the decomposition temperature of bismuth salt, which does not react with bismuth salt and is insoluble in solvent A; the bismuth salt is a bismuth salt that can decompose at high temperatures; solvent A is a solvent that can dissolve bismuth salt but does not dissolve substance A. Substance A is sodium chloride, potassium chloride, sodium sulfate, or potassium sulfate; solvent A is ethylene glycol, ethanol, or isopropanol. (2) Mix the powder of substance A with the bismuth salt solution and stir evenly to obtain a mixture; then dry the mixture to remove solvent A and obtain a mixed powder; the mass ratio of bismuth salt to substance A is 1~3:10; (3) The mixed powder is annealed to decompose the bismuth salt into bismuth oxide, and a mixed powder of bismuth oxide and substance A is obtained; the annealing temperature is 500~600℃. (4) Place the mixed powder of bismuth oxide and substance A into the lower temperature zone of a closed heating environment under vacuum to atmospheric pressure; place the sulfur powder into the upper temperature zone of the heating environment; raise the temperature of the lower temperature zone to 600-700℃ and the temperature of the upper temperature zone to 100-150℃ respectively under a continuous inert gas flow of 200-600 sccm; then carry the sulfur vapor obtained in the upper temperature zone to the lower temperature zone through the continuous inert gas flow, and carry out a high-temperature sulfidation reaction in the lower temperature zone for at least 30 min; after the reaction is completed, cool naturally to room temperature, stop the gas flow, completely wash away substance A, and dry to obtain bismuth sulfide nanosheet powder.

2. The high-temperature gas-phase sulfidation method for preparing a two-dimensional bismuth sulfide catalyst according to claim 1, characterized in that, In step (1), the bismuth salt is bismuth nitrate or bismuth acetate.

3. The high-temperature gas-phase sulfidation method for preparing a two-dimensional bismuth sulfide catalyst according to claim 1, characterized in that, In step (1), the powdering process is performed by ball milling for 2 to 10 hours.

4. The high-temperature gas-phase sulfidation method for preparing a two-dimensional bismuth sulfide catalyst according to claim 1, characterized in that, In step (1), the size of substance A powder is 5~30µm.

5. The high-temperature gas-phase sulfidation method for preparing a two-dimensional bismuth sulfide catalyst according to claim 1, characterized in that, In step (2), the mixing and stirring time is 0.5~3h; the drying process is: vacuum drying at 60~90℃ for 5~12h.

6. The high-temperature gas-phase sulfidation method for preparing a two-dimensional bismuth sulfide catalyst according to claim 1, characterized in that, In step (3), the annealing time is at least 30 minutes.

7. The high-temperature gas-phase sulfidation method for preparing a two-dimensional bismuth sulfide catalyst according to claim 1, characterized in that, In step (4), the inert gas used is argon or nitrogen.

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