Preparation method and application of Bi-based catalyst
By modulating the electronic structure of Bi through solvothermal and in-situ electroreduction methods with Sb doping, a Bi-Sb interfacial catalyst was prepared, which solved the problem of low formate formation efficiency of Bi-based catalysts under high current density and realized an efficient and stable CO2 electroreduction process for formate production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-03-10
AI Technical Summary
Existing Bi-based catalysts exhibit low formate formation efficiency, insufficient selectivity, and inadequate stability at high current densities, making it difficult to meet industrial requirements.
Bi-based catalysts were prepared by using a solvothermal and in-situ electroreduction method with Sb doping modification to control the electronic structure of Bi and form a Bi-Sb interface to promote the reduction of CO2 to formate.
Bi-based catalysts exhibit excellent formate selectivity and stability at high current densities, achieving a Faraday efficiency of 95%, which significantly improves catalyst activity and production efficiency while reducing production costs.
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Figure CN121629449A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrocatalytic carbon dioxide reduction technology, and relates to a method for preparing a Bi-based catalyst and its application. Background Technology
[0002] Among various CO2 conversion technologies, electrochemical reduction has attracted widespread attention due to its advantages such as mild reaction conditions and compatibility with renewable energy. Formate, as a major product of CO2 electroreduction, has broad application potential in fields such as chemical engineering, energy, and agriculture, for example, as fuel for fuel cells and precursors for organic synthesis. However, there is still a significant shortage of catalysts for electrocatalytic CO2 reduction (CO2R) to formate, which seriously restricts the practical application of this technology.
[0003] Among various CO2 reduction catalysts, bismuth (Bi)-based materials are considered promising catalysts for formate synthesis due to their advantages such as low cost, environmental friendliness, and abundant reserves. However, existing Bi-based catalysts still face problems such as low product selectivity, insufficient catalytic activity, and poor stability, making it difficult to meet the requirements of continuous industrial production. Their performance degrades rapidly, requiring frequent replacement or replenishment of the catalyst, which not only increases production costs but also exacerbates the complexity of the process. Especially under high current density operating conditions, the selectivity and activity limitations of Bi-based catalysts become even more prominent, leading to a significant reduction in formate formation efficiency.
[0004] Therefore, it is necessary to provide a method for preparing Bi-based catalysts and their applications, so that the prepared Bi-based catalysts maintain excellent formate selectivity at high current densities. Summary of the Invention
[0005] To overcome the problems in the prior art, this invention introduces a strategy of Sb doping modification and uses a combination of solvothermal and in-situ electroreduction methods to prepare a series of Bi-based catalysts. By controlling the electronic structure of Bi with Sb, the limitations of its selectivity and catalytic activity are broken, thereby effectively improving the selectivity of Bi-based catalysts under high current density conditions.
[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a method for preparing a Bi-based catalyst, the method comprising the following steps: (1) After mixing Bi salt and Sb salt, a mixed powder is obtained and used as a reaction precursor.
[0007] (2) Dissolve the mixed powder from step (1) in a mixed solution of N,N-dimethylformamide and potassium hydroxide.
[0008] (3) Add sodium borohydride to the solution in step (2).
[0009] (4) After stirring the mixed solution from step (3) evenly, place it in a hydrothermal reactor for reaction.
[0010] (5) Wash the powder obtained in step (4) and then centrifuge and dry it.
[0011] (6) The obtained powder is formulated into a catalytic ink, sprayed onto the surface of a hydrophobic electrode, and reduced under a constant current density to obtain a catalyst.
[0012] Preferably, the Bi salt described in this invention is one of BiCl3, Bi2(SO4)3, and BiNO3; the antimony salt is one of SbCl3, Sb2(SO4)3, and SbNO3.
[0013] Preferably, the molar ratio of Bi salt to Sb in this invention is 0 to 2.
[0014] Preferably, the amount of N,N-dimethylformamide added in this invention is sufficient to completely dissolve the mixed powder, and the amount of potassium hydroxide used is such that the pH of the solution is 9-14; Preferably, the molar ratio of sodium borohydride to the salt precursor in this invention is 0.5 to 3.
[0015] Preferably, in step (4) of the present invention, the solvothermal reaction temperature is 80~200℃ and the reaction time is 8~24 h.
[0016] Preferably, the washing method in step (5) of the present invention is as follows: the precipitate is washed by centrifugation three times each with water and ethanol; the drying conditions are: vacuum drying, temperature not lower than 60°C, and drying time not lower than 24 h.
[0017] The specific process of step (6) is as follows: S1: The powder obtained in step (5) is dispersed in a mixture of isopropanol and perfluorosulfonic acid resin solution. After ultrasonic dispersion, a catalytic ink is formed. The catalytic ink is sprayed onto the surface of a hydrophobic electrode (hydrophobic carbon paper) and allowed to dry naturally to obtain the working electrode. In the mixture, the volume ratio of isopropanol to perfluorosulfonic acid resin solution is 19:1, the mass percentage concentration of the perfluorosulfonic acid resin solution is 5%, and the amount of catalytic ink loaded on the hydrophobic carbon paper is 0.8~1.2 mg / cm³. 2 The ultrasonic frequency was 40 kHz, and the ultrasonic dispersion time was 1~1.5 seconds. S2: In a three-electrode system (using iridium oxide as the counter electrode, silver chloride as the reference electrode, and KOH solution as the electrolyte), a cathode current is applied to the working electrode obtained in step (S1) to obtain the Bi-based catalyst; the applied cathode current density is 100~700 mA cm⁻¹. -2 The restoration time is 5~30 min.
[0018] In another aspect, the present invention proposes the application of the above-mentioned Bi-based catalyst in the electroreduction of carbon dioxide to prepare formate.
[0019] The beneficial effects of this invention are: 1. The Bi-based catalyst prepared by this invention exhibits excellent formate selectivity under high current density conditions, reaching 600 mA / cm². 2 At that time, the formate's Faradaic efficiency (FE) reached 95%, far exceeding that of pure Bi at 200 mA / cm². 2 85% at that time.
[0020] 2. The preparation method of this invention for Sb-modified Bi-based catalysts is beneficial for promoting the activation of CO2 molecules by Bi. At the same time, Sb can reduce the water dissociation energy barrier, and finally, further hydrogenation reaction is carried out at the Bi-Sb interface to generate *OCHO intermediate, which significantly improves the formate formation efficiency.
[0021] 4. The preparation method of this invention is simple and effectively improves the catalytic efficiency and stability of the catalyst, which is conducive to reducing production costs and improving production efficiency. It has high value for industrial application and is expected to promote the technology of CO2 electrochemical reduction to prepare formate from the laboratory to industrial production. Attached Figure Description
[0022] Figure 1 Here is an electron microscope image of the catalyst of Example 1 of the present invention; Figure 2 The XRD patterns are of the catalysts in Examples 1-5 and Comparative Examples 1 and 2 of this invention. Figure 3 The above are XPS diagrams of the catalysts in Examples 1-5 and Comparative Examples 1 and 2 of the present invention, wherein Figure (a) is the Bi 4f diagram of the catalyst and Figure (b) is the Sb 3d diagram of the catalyst. Figure 4 The graph shows the Faraday efficiency of the catalysts in Examples 1 and Comparative Examples 1 and 2 of this invention for the catalytic reduction of CO2 to formate as a function of current density. Figure 5 The catalysts used in Examples 1-5 and Comparative Examples 1 and 2 of this invention were tested at a current density of 600 mA / cm². 2 A comparison of the Faraday efficiency of catalytic CO2 reduction to formate production. Detailed Implementation
[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described. Example 1
[0024] In this embodiment, the Bi-based catalyst was prepared according to the following method: (1) Accurately weigh 2 mmol of BiCl3, 1.5 mmol of SbCl3, and 0.72 g of NaOH and dissolve them in 80 mL of N,N-dimethylformamide. Stir until completely dissolved.
[0025] (2) Add 1 mmol of sodium borohydride to the above solution quickly to obtain a black solution after preliminary reduction.
[0026] (3) Transfer the solution to a stainless steel autoclave lined with polytetrafluoroethylene, seal it, and place it in an oven. Heat at 140°C for 12 h. After the reaction is complete, allow it to cool naturally to room temperature. Pour the reaction solution into a centrifuge tube and centrifuge at 8000 r / min for 10 min. Collect the blackish-gray precipitate and wash it three times each with deionized water and anhydrous ethanol under the same centrifugation conditions. Transfer the washed precipitate to a petri dish, place it in a vacuum drying oven, and dry it at 60°C for at least 24 h. Grind the dried precipitate to obtain the original powder.
[0027] (4) Weigh 10 mg of the original powder, add it to 950 μL of isopropanol and 50 μL of 5% Nafion solution, and place it in an ultrasonic instrument to disperse it ultrasonically at a frequency of 40 kHz for 1 h to obtain a uniform catalytic ink. Use a micro-spray gun to uniformly spray the catalytic ink onto hydrophobic carbon paper and let it dry naturally (the amount of catalytic ink loaded on the hydrophobic carbon paper is 1 mg / cm). 2 ), to obtain the working electrode.
[0028] (5) The hydrophobic carbon paper loaded with the Bi-based precursor was placed in 1.0 M KOH electrolyte as the working electrode and connected to an electrochemical workstation (CH1140C). Iridium oxide was used as the counter electrode and silver chloride as the reference electrode. The electrochemical workstation was started and subjected to a constant 600 mA / cm² test. 2 Current reduction yields the final Bi-based catalyst, denoted as Bi2Sb. 1.5 . Example 2
[0029] In this embodiment, the Bi-based catalyst was prepared according to the following method: (1) Accurately weigh 2 mmol of BiCl3, 0.6 mmol of SbCl3, and 0.72 g of NaOH and dissolve them in 80 mL of N,N-dimethylformamide. Stir until completely dissolved.
[0030] (2) Add 1 mmol of sodium borohydride to the above solution quickly to obtain a black solution after preliminary reduction.
[0031] (3) Transfer the solution to a stainless steel autoclave lined with polytetrafluoroethylene, seal it, and place it in an oven. Heat at 140°C for 12 h. After the reaction is complete, allow it to cool naturally to room temperature. Pour the reaction solution into a centrifuge tube and centrifuge at 8000 r / min for 10 min. Collect the blackish-gray precipitate and wash it three times each with deionized water and anhydrous ethanol under the same centrifugation conditions. Transfer the washed precipitate to a petri dish, place it in a vacuum drying oven, and dry it at 60°C for at least 24 h. Grind the dried precipitate to obtain the original powder.
[0032] (4) Weigh 10 mg of the original powder, add it to 950 μL of isopropanol and 50 μL of 5% Nafion solution, and place it in an ultrasonic instrument to disperse it ultrasonically at a frequency of 40 kHz for 1 h to obtain a uniform catalytic ink. Use a micro-spray gun to uniformly spray the catalytic ink onto hydrophobic carbon paper and let it dry naturally (the amount of catalytic ink loaded on the hydrophobic carbon paper is 1 mg / cm). 2 ), to obtain the working electrode.
[0033] (5) The hydrophobic carbon paper loaded with the Bi-based precursor was placed in 1.0 M KOH electrolyte as the working electrode and connected to an electrochemical workstation (CH1140C). Iridium oxide was used as the counter electrode, and silver chloride was used as the reference electrode. The electrochemical workstation was started and a constant 600 mA / cm² was applied. 2 Current reduction yields the final Bi-based catalyst, denoted as Bi2Sb. 0.6 . Example 3
[0034] In this embodiment, the Bi-based catalyst was prepared according to the following method: (1) Accurately weigh 2 mmol of BiCl3, 0.9 mmol of SbCl3, and 0.72 g of NaOH and dissolve them in 80 mL of N,N-dimethylformamide. Stir until completely dissolved.
[0035] (2) Add 1 mmol of sodium borohydride to the above solution quickly to obtain a black solution after preliminary reduction.
[0036] (3) Transfer the solution to a stainless steel autoclave lined with polytetrafluoroethylene, seal it, and place it in an oven. Heat at 140°C for 12 h. After the reaction is complete, allow it to cool naturally to room temperature. Pour the reaction solution into a centrifuge tube and centrifuge at 8000 r / min for 10 min. Collect the blackish-gray precipitate and wash it three times each with deionized water and anhydrous ethanol under the same centrifugation conditions. Transfer the washed precipitate to a petri dish, place it in a vacuum drying oven, and dry it at 60°C for at least 24 h. Grind the dried precipitate to obtain the original powder.
[0037] (4) Weigh 10 mg of the original powder, add it to 950 μL of isopropanol and 50 μL of 5% Nafion solution, and place it in an ultrasonic instrument to disperse it ultrasonically at a frequency of 40 kHz for 1 h to obtain a uniform catalytic ink. Use a micro-spray gun to uniformly spray the catalytic ink onto hydrophobic carbon paper and let it dry naturally (the amount of catalytic ink loaded on the hydrophobic carbon paper is 1 mg / cm). 2 ), to obtain the working electrode.
[0038] (5) The hydrophobic carbon paper loaded with the Bi-based precursor was placed in 1.0 M KOH electrolyte as the working electrode and connected to an electrochemical workstation (CH1140C). Iridium oxide was used as the counter electrode and silver chloride as the reference electrode. The electrochemical workstation was started and subjected to a constant 600 mA / cm² test. 2 Current reduction yields the final Bi-based catalyst, denoted as Bi2Sb. 0.9 . Example 4
[0039] In this embodiment, the Bi-based catalyst was prepared according to the following method: (1) Accurately weigh 2 mmol of BiCl3, 1.2 mmol of SbCl3, and 0.72 g of NaOH and dissolve them in 80 mL of N,N-dimethylformamide. Stir until completely dissolved.
[0040] (2) Add 1 mmol of sodium borohydride to the above solution quickly to obtain a black solution after preliminary reduction.
[0041] (3) Transfer the solution to a stainless steel autoclave lined with polytetrafluoroethylene, seal it, and place it in an oven. Heat at 140°C for 12 h. After the reaction is complete, allow it to cool naturally to room temperature. Pour the reaction solution into a centrifuge tube and centrifuge at 8000 r / min for 10 min. Collect the blackish-gray precipitate and wash it three times each with deionized water and anhydrous ethanol under the same centrifugation conditions. Transfer the washed precipitate to a petri dish, place it in a vacuum drying oven, and dry it at 60°C for at least 24 h. Grind the dried precipitate to obtain the original powder.
[0042] (4) Weigh 10 mg of the original powder, add it to 950 μL of isopropanol and 50 μL of 5% Nafion solution, and place it in an ultrasonic instrument to disperse it ultrasonically at a frequency of 40 kHz for 1 h to obtain a uniform catalytic ink. Use a micro-spray gun to uniformly spray the catalytic ink onto hydrophobic carbon paper and let it dry naturally (the amount of catalytic ink loaded on the hydrophobic carbon paper is 1 mg / cm). 2 ), to obtain the working electrode.
[0043] (5) The hydrophobic carbon paper loaded with the Bi-based precursor was placed in 1.0 M KOH electrolyte as the working electrode and connected to an electrochemical workstation (CH1140C). Iridium oxide was used as the counter electrode and silver chloride as the reference electrode. The electrochemical workstation was started and subjected to a constant 600 mA / cm² test. 2 Current reduction yields the final Bi-based catalyst, denoted as Bi2Sb. 1.2 . Example 5
[0044] In this embodiment, the Bi-based catalyst was prepared according to the following method: (1) Accurately weigh 2 mmol of BiCl3, 2 mmol of SbCl3, and 0.72 g of NaOH and dissolve them in 80 mL of N,N-dimethylformamide. Stir until completely dissolved.
[0045] (2) Add 1 mmol of sodium borohydride to the above solution quickly to obtain a black solution after preliminary reduction.
[0046] (3) Transfer the solution to a stainless steel autoclave lined with polytetrafluoroethylene, seal it, and place it in an oven. Heat at 140°C for 12 h. After the reaction is complete, allow it to cool naturally to room temperature. Pour the reaction solution into a centrifuge tube and centrifuge at 8000 r / min for 10 min. Collect the blackish-gray precipitate and wash it three times each with deionized water and anhydrous ethanol under the same centrifugation conditions. Transfer the washed precipitate to a petri dish, place it in a vacuum drying oven, and dry it at 60°C for at least 24 h. Grind the dried precipitate to obtain the original powder.
[0047] (4) Weigh 10 mg of the original powder, add it to 950 μL of isopropanol and 50 μL of 5% Nafion solution, and place it in an ultrasonic instrument to disperse it ultrasonically at a frequency of 40 kHz for 1 h to obtain a uniform catalytic ink. Use a micro-spray gun to uniformly spray the catalytic ink onto hydrophobic carbon paper and let it dry naturally (the amount of catalytic ink loaded on the hydrophobic carbon paper is 1 mg / cm). 2 ), to obtain the working electrode.
[0048] (5) The hydrophobic carbon paper loaded with the Bi-based precursor was placed in 1.0 M KOH electrolyte as the working electrode and connected to an electrochemical workstation (CH1140C). Iridium oxide was used as the counter electrode, and silver chloride was used as the reference electrode. The electrochemical workstation was started and a constant 600 mA / cm² was applied. 2 The final Bi-based catalyst, denoted as Bi2Sb2, is obtained by electric current reduction.
[0049] Comparative Example 1 The catalyst in this comparative example was prepared using the same method as in Example 1, except that SbCl3 was not introduced, and the final catalyst was denoted as Bi.
[0050] Comparative Example 2 The catalyst in this comparative example was prepared using the same method as in Example 1, except that BiCl3 was not introduced, and the final catalyst was denoted as Sb.
[0051] Electrocatalytic performance testing of the catalyst: Using the above-described example as the working electrode, iridium oxide as the counter electrode, and silver chloride as the reference electrode, the anode and cathode chambers were separated by anion exchange membranes, and a self-made flow electrolytic cell was used. CO2 gas (flow rate 50 sccm) was introduced into the cathode chamber, and the electrolyte was 1.0 M KOH solution at a flow rate of 10 mL / min; the electrolyte in the anode chamber was 1.0 M KOH solution. CO2 gas was continuously introduced into the electrolyte until it reached saturation. Different potentials or current densities were applied using an electrochemical workstation, and the Faradaic efficiency (FE) and current density of formate under different conditions were determined using analytical methods such as gas chromatography and nuclear magnetic resonance. During the test, the product distribution and current changes at different reaction times were recorded to evaluate the selectivity and activity of the catalyst.
[0052] pass Figure 1 It can be seen that the Bi₂Sb₂ catalyst mainly exhibits aggregated granular form, showing the corresponding lattices of metallic Bi and Sb. However, the Bi and Sb elements are not uniformly distributed, but exhibit phase segregation, indicating that alloying has not occurred. Figure 2 Further analysis revealed that without Sb modification, the material primarily exhibited pure Bi metal; after Sb modification, the Bi lattice broadened, but it still retained the metallic phase, while also displaying a weak metallic Sb phase, further confirming that phase separation was the main process. Figure 3 It can be observed that Sb doping has a certain impact on the electronic structure of Bi, with electrons mainly transferring from Sb to Bi. Figure 4 Experimental results show that this regulatory effect significantly improves the catalytic performance of Bi, with pure Bi exhibiting the best performance at 200 mA / cm². 2 The formate Faraday efficiency was maintained at 85%, while after the introduction of Sb, Bi2Sb...1.5 The catalyst's current density was increased to 600 mA / cm². 2 At this point, the formate Faraday efficiency can still be maintained at 95%. Figure 5 Further investigation revealed that Sb doping exhibits a volcano-like relationship in regulating the Faraday efficiency of formate, with the optimal effect observed at a Bi:Sb molar ratio of 1:2. This catalyst design and regulation strategy significantly enhances the catalytic performance of traditional Bi-based catalysts, providing new ideas and methodologies for future application.
Claims
1. A method for preparing a Bi-based catalyst, characterized by: The preparation method comprises the following steps: (1) mixing Bi salt and Sb salt to obtain a mixed powder as a reaction precursor; (2) dissolving the mixed powder of step (1) into a mixed solution of N, N-dimethylformamide and potassium hydroxide; (3) adding sodium borohydride into the solution of step (2); (4) stirring the mixed solution of step (3) uniformly and then placing it into an autoclave for reaction; (5) washing the powder obtained in step (4) and then centrifugally drying; (6) preparing the obtained powder into catalytic ink, spraying the catalytic ink onto the surface of a hydrophobic electrode, and obtaining a catalyst after reduction under a constant current density.
2. The method of claim 1, wherein: The Bi salt is one of BiCl3, Bi2(SO4)3 and BiNO3; and the Sb salt is one of SbCl3, Sb2(SO4)3 and SbNO3.
3. The method of claim 1, wherein: The molar ratio of the Bi salt to the Sb is 0-2.
4. The method of claim 1, wherein: The amount of potassium hydroxide is such that the pH of the solution is 9-14.
5. The method of claim 1, wherein: The molar ratio of sodium borohydride to the salt precursor is 0.5-3.
6. The method of claim 1, wherein: The temperature of the solvent thermal reaction in step (4) is 80-200 ℃, and the reaction time is 8-24 h.
7. The method of claim 1, wherein: In step (5), the washing method is that the precipitated substance is centrifugally washed with water and ethanol each for three times; and the drying condition is vacuum drying at a temperature not lower than 60 ℃ for a time not less than 24 h.
8. The method of claim 1, wherein: The specific process of step (6) is as follows: S1: dispersing the powder obtained in step (5) into a mixed solution of isopropyl alcohol and perfluorosulfonic acid resin solution, ultrasonically dispersing to form catalytic ink, spraying the catalytic ink onto the surface of a hydrophobic electrode and naturally drying to obtain a working electrode; S2: in a three-electrode system, a cathode current is applied to the working electrode obtained in the step (S1), and the cathode current density is 100-700 mA cm -2 The reduction time is 5-30 min, and a Bi-based catalyst is obtained.
9. Use of a Bi-based catalyst produced according to the process of any one of claims 1 to 8, characterized in that: The Bi-based catalyst is used to catalyze the electro-reduction of carbon dioxide to prepare formate.