Superfine bismuth nano-cluster catalyst as well as preparation method and application thereof

Abstract

The invention discloses a superfine bismuth nano-cluster catalyst and a preparation method and application thereof, and belongs to the technical field of electrochemical catalysts.The preparation method comprises the steps that BiCl3 and activated carbon are added into methyl alcohol to be subjected to ultrasonic dispersion, and then a solution is removed through rotary evaporation; calcining the solid for the first time to obtain a product marked as Bi NPs / AC; the Bi NPs / AC is calcined for the second time, and the obtained product is marked as Bi NCs / AC. The preparation method of the superfine bismuth nano-cluster catalyst is short in time consumption, the use of organic solvents is reduced, the preparation method is efficient and environmentally friendly, and gram-grade products can be prepared on a large scale; the superfine bismuth nano-cluster catalyst is applied to an electrochemical reduction CO2 reaction and shows excellent formate generation activity in a traditional H-type electrolytic cell and a flow-type electrolytic cell, and when reaction gas is changed into diluted CO2 gas to simulate industrial flue gas, the performance of the catalyst for electrochemical reduction of CO2 is still maintained at a high level.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalyst technology, specifically relating to an ultrafine bismuth nanocluster catalyst, its preparation method, and its application. Background Technology

[0002] Excessive consumption of fossil fuels has led to a continuous rise in atmospheric carbon dioxide (CO2) concentrations, triggering global climate problems and a growing energy crisis. Electrochemical reduction of CO2 driven by renewable electricity offers a promising pathway to convert CO2 into value-added chemicals or fuels. This method establishes a carbon-neutral energy cycle and helps address energy storage issues. Flue gas, the largest source of CO2 emissions from fossil fuel combustion, typically contains only 5-30% CO2, with nitrogen (N2) as its main component. However, capturing and concentrating CO2 from flue gas is extremely energy-intensive and costly. Therefore, directly utilizing the low concentration of CO2 in flue gas for efficient conversion is more economically feasible. Furthermore, the single-pass conversion efficiency (SPCE) of CO2, which determines the cost of product separation, is typically below 10%, far below the standard for industrial applications.

[0003] Among the various products of electrochemical CO2 reduction, formic acid / formate salts have attracted widespread attention due to their highest added value per kilowatt-hour of electrical energy input. Formic acid / formate salts are in liquid / solid form at room temperature, making them easier to transport. Furthermore, formic acid has been widely used as a major building block in fuel cells and hydrogen storage. Numerous studies have demonstrated that p-block metals such as tin (Sn), indium (In), bismuth (Bi), and lead (Pb) exhibit superior performance in selectively reducing CO2 to formate salts. Among these, bismuth is a promising candidate material for practical applications due to its non-toxicity and low cost. However, bismuth-based materials remain unsatisfactory in terms of the activity, stability, and selectivity of formic acid, particularly at high Faradaic efficiencies (>90%) and high current densities (>200 mA·cm⁻¹). -2 The performance under these conditions may be due to limited exposure of active sites and structural changes that may occur during catalysis.

[0004] To optimize the electrochemical CO2 reduction performance of bismuth-based catalysts, an effective strategy is to reduce the size of bismuth nanoparticles (NPs). This not only increases the surface area and exposes more active sites but also alters the electronic states and number of low-coordination sites on the surface atoms, especially at corners and edges. Ultrafine metal nanoclusters (NCs) fill the gap between single atoms and large nanoparticles, providing catalytically active sites with neighboring metal atoms while maintaining high atom utilization efficiency. This makes them highly attractive for various catalytic reactions. Despite their potential benefits, precisely controlling the size of bismuth-based catalysts, from nanoparticles to ultrafine nanoclusters, remains a significant challenge because the hydrolysis of bismuth precursors and the low surface energy of bismuth atoms readily lead to aggregation. To address these challenges, researchers have explored the feasibility of loading metal catalysts onto suitable supports to isolate small-sized catalysts and prevent the migration and merging of metal atoms during preparation and electrochemistry. This approach allows for the customization of electronic and geometric structures to optimize catalytic performance. Carbon materials are often considered ideal electrocatalyst supports due to their high surface area, good electrical conductivity, and excellent chemical stability. Furthermore, bismuth atoms can be stabilized on carbon supports by forming covalent bonds without introducing additional heteroatoms at the anchor sites. When ultrasmall bismuth nanoclusters are supported by carbon supports, the interaction between the metal and the support can be further enhanced, thereby improving stability. Summary of the Invention

[0005] Technical problems to be solved: In order to address the technical problems of the continuous rise in atmospheric CO2 concentration, which leads to global climate problems and an increasingly serious energy crisis, the process of capturing and concentrating CO2 from flue gas is very energy-intensive and costly, and the unsatisfactory activity, stability and selectivity of bismuth-based materials in formic acid, this application proposes an ultrafine bismuth nanocluster catalyst, its preparation method and application.

[0006] Technical solution

[0007] A method for preparing an ultrafine bismuth nanocluster catalyst, comprising the following steps:

[0008] Step a: Add 60-90 mg BiCl3 and 200 mg activated carbon to 20 mL of methanol by mass-volume ratio, disperse by ultrasonication for 15 min, and then remove the solution by rotary evaporation;

[0009] Step b: The solid remaining after removing the solution in step a undergoes a first calcination at a temperature of 400℃ and a heating rate of 5℃·min. -1 Calcination for 2 hours, under Ar / H2 = 95:5 atmosphere protection, the product is labeled as Bi NPs / AC;

[0010] Step c: The Bi NPs / AC is calcined a second time at 500℃ for 2 hours, with a heating rate of 5℃·min. -1 The product obtained by calcination under an atmosphere of Ar / H2 = 95:5 was labeled as BiNCs / AC.

[0011] As a preferred technical solution of this application: the ultrasonic dispersion frequency in step a is 60kHz.

[0012] As a preferred technical solution of this application: the rotation process parameter in step a is 100 r / min.

[0013] As a preferred technical solution of this application: the amount of BiCl3 used in step a is 75mg.

[0014] An ultrafine bismuth nanocluster catalyst prepared by any of the above preparation methods.

[0015] This application also discloses the application of an ultrafine bismuth nanocluster catalyst in the electrochemical reduction of CO2 to formate.

[0016] Explanation of the principle of this application: Carbon materials are often regarded as ideal electrocatalyst support materials due to their high surface area, good conductivity and excellent chemical stability. Bismuth atoms can be stabilized on the carbon support by forming covalent bonds without the need to introduce additional heteroatoms at the anchor site. This isolates small-sized catalysts and prevents the migration and merging of metal atoms during preparation and electrochemistry. When ultra-small bismuth nanoclusters are supported by carbon supports, the interaction between the metal and the support can be further enhanced, thereby improving stability. It is possible to customize the electronic and geometric structures, thereby optimizing catalytic performance and solving the technical defects of hydrolysis of bismuth precursors and the tendency of bismuth atoms to agglomerate due to low surface energy. Attached Figure Description

[0017] Figure 1 This is a process flow diagram for this application;

[0018] Figure 2 XRD patterns of the BiNCs / AC and BiNPs / AC structures prepared in Example 1 of this application;

[0019] Figure 3 TEM image of BiNCs / AC prepared in Example 1 of this application;

[0020] Figure 4 HAADF-STEM image of BiNCs / AC prepared in Example 1 of this application;

[0021] Figure 5 The particle size distribution diagram of BiNCs / AC prepared in Example 1 of this application;

[0022] Figure 6 EDX mapping image of BiNCs / AC prepared in Example 1 of this application;

[0023] Figure 7 X-ray photoelectron spectra of BiNCs / AC and BiNPs / AC prepared in Example 1 of this application;

[0024] Figure 8 Linear sweep voltammetric curve of the electrochemical reduction of CO2 by BiNCs / AC prepared in Example 1 of this application in an H-type electrolytic cell, with 0.5M KHCO3 solution as the electrolyte;

[0025] Figure 9 The formate Faraday efficiency diagram of the electrochemical reduction of CO2 by BiNCs / AC prepared in Example 1 of this application in an H-type electrolyzer;

[0026] Figure 10 The partial current density diagram of formate prepared by BiNCs / AC in Example 1 of this application under different applied potentials during the electrochemical reduction of CO2 in an H-type electrolytic cell;

[0027] Figure 11 The graph shows the long-term electrolytic stability of BiNCs / AC prepared in Example 1 of this application during the electrochemical reduction of CO2 in an H-type electrolyzer at -0.8V.

[0028] Figure 12 A comparison of the cathode energy efficiency and long-term stability of the BiNCs / AC catalyst prepared in Example 1 of this application in the electrochemical reduction of CO2 in an H-type electrolyzer with other catalysts reported in the literature.

[0029] Figure 13 The images shown are gram-scale batch preparations of BiNCs / AC prepared in Example 1 of this application, where (a) is a gram-scale batch preparation photograph, (b) is a linear sweep voltammetric curve of electrochemical reduction of CO2 in an H-type electrolyzer, and (c) is a Faraday efficiency graph of formate.

[0030] Figure 14 The linear sweep voltammetric curve of BiNCs / AC prepared in Example 1 of this application for the electrochemical reduction of CO2 in a flow electrolyzer, with the electrolyte being a 1.0 M KOH solution;

[0031] Figure 15 The Faraday efficiency diagram of the electrochemical reduction of CO2 formate by BiNCs / AC prepared in Example 1 of this application in a flow electrolyzer.

[0032] Figure 16The single-pass conversion efficiency of electrochemical reduction of CO2 by BiNCs / AC prepared in Example 1 of this application under different current densities and CO2 feed concentrations in a flow electrolyzer.

[0033] Figure 17 Long-term stability test of BiNCs / AC prepared in Example 1 of this application for electrochemical reduction of CO2 in a flow electrolyzer under different CO2 feed concentrations;

[0034] Figure 18 The Faraday efficiency diagram of the electrochemical reduction of CO2 formate by BiNCs / AC prepared in Example 1 of this application in a flow electrolyzer using simulated O2-free flue gas (15 vol% CO2, 0.3 vol% SO2, 0.005% NO2, N2 as the balance gas).

[0035] Beneficial effects:

[0036] 1. The ultrafine bismuth nanoclusters provided by this invention fill the gap between single atoms and large nanoparticles, and can provide catalytically active sites with adjacent metal atoms while maintaining high atomic utilization efficiency;

[0037] 2. Since bismuth salts are easily hydrolyzed and the surface energy of bismuth atoms is low, making them prone to aggregation, most traditional bismuth-based catalysts are nanoparticles with large size and few active sites in electrocatalytic reactions.

[0038] 3. This invention uses a simple two-step calcination method to prepare ultrafine bismuth nanoclusters with a size of about 2 nm, which effectively increases the surface area of ​​the catalyst and exposes more active sites;

[0039] 4. The preparation method of the ultrafine bismuth nanocluster catalyst provided by the present invention is time-saving, reduces the use of organic solvents, is highly efficient and environmentally friendly, and can also prepare gram-level products on a large scale.

[0040] 5. The ultrafine bismuth nanocluster catalyst provided by this invention exhibits excellent formate formation activity in both traditional H-type electrolyzers and flow electrolyzers when applied to the electrochemical reduction of CO2.

[0041] 6. When the reaction gas of the ultrafine bismuth nanocluster catalyst provided by the present invention is changed to diluted CO2 gas to imitate industrial flue gas, the performance of the catalyst in electrochemically reducing CO2 remains at a high level and is almost unaffected by the CO2 concentration. Detailed Implementation

[0042] This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiment.

[0043] Example 1:

[0044] A method for preparing an ultrafine bismuth nanocluster catalyst, comprising the following steps:

[0045] Step a: Add 75 mg BiCl3 and 200 mg activated carbon to 20 mL methanol by mass-volume ratio, disperse by ultrasonication for 15 min, and then remove the solution by rotary evaporation;

[0046] Step b: The solid remaining after removing the solution in step a undergoes a first calcination at a temperature of 400℃ and a heating rate of 5℃·min. -1 Calcination for 2 hours, under Ar / H2 = 95:5 atmosphere protection, the product is labeled as Bi NPs / AC;

[0047] Step c: The Bi NPs / AC is calcined a second time at 500℃ for 2 hours, with a heating rate of 5℃·min. -1 The product obtained by calcination under an atmosphere of Ar / H2 = 95:5 was labeled as BiNCs / AC.

[0048] Example 2:

[0049] A method for preparing an ultrafine bismuth nanocluster catalyst, comprising the following steps:

[0050] Step a: Add 60 mg BiCl3 and 200 mg activated carbon to 20 mL methanol by mass-volume ratio, disperse by ultrasonication for 15 min, and then remove the solution by rotary evaporation;

[0051] Step b involves the first calcination of the solid remaining after solution removal in step a, at a temperature of 400℃ and a heating rate of 5℃·min. -1 Calcination for 2 hours, under Ar / H2 = 95:5 atmosphere protection, the product is labeled as Bi NPs / AC;

[0052] Step c, the Bi NPs / AC is calcined a second time at 500°C for 2 hours, with a heating rate of 5°C / min. -1 The product obtained by calcination under an atmosphere of Ar / H2 = 95:5 was labeled as BiNCs / AC.

[0053] Example 3:

[0054] A method for preparing an ultrafine bismuth nanocluster catalyst, comprising the following steps:

[0055] Step a: Add 90 mg BiCl3 and 200 mg activated carbon to 20 mL methanol by mass-volume ratio, disperse by ultrasonication for 15 min, and then remove the solution by rotary evaporation;

[0056] Step b involves the first calcination of the solid remaining after solution removal in step a, at a temperature of 400℃ and a heating rate of 5℃·min. -1 Calcination for 2 hours, under Ar / H2 = 95:5 atmosphere protection, the product is labeled as Bi NPs / AC;

[0057] Step c, the Bi NPs / AC is calcined a second time at 500°C for 2 hours, with a heating rate of 5°C / min. -1 The product obtained by calcination under an atmosphere of Ar / H2 = 95:5 was labeled as BiNCs / AC.

[0058] In summary, the ultrafine bismuth nanocluster catalyst prepared by this invention can confine the size of bismuth particles to around 2 nm and can be prepared in large-scale batches. The prepared BiNCs / AC catalyst can efficiently reduce CO2 to formate. In an H-type electrolyzer, the formate exhibits the highest Faradaic efficiency of 98.8% at -0.8 V, and the catalyst can operate continuously for 60 hours. When using low-concentration CO2 (15-30 vol% CO2) as the reactant, in a flow electrolyzer, when the current density exceeds the industrial requirement of 200 mA / cm², [further details are needed]. -2 Under these conditions, the BiNCs / AC catalyst still maintains good performance in the electrochemical reduction of CO2 to formate and excellent single-pass conversion efficiency. When using simulated industrial flue gas (without O2) as the reaction feedstock, the performance of CO2 electrochemical conversion to formate is not affected by other impurity gases.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an ultrafine bismuth nanocluster catalyst, characterized in that, The specific steps are as follows: Step a: Add 60-90 mg BiCl3 and 200 mg activated carbon to 20 mL of methanol by mass-volume ratio, disperse by ultrasonication for 15 min, and then remove the solution by rotary evaporation; Step b: The solid remaining after removing the solution in step a undergoes a first calcination at a temperature of 400℃ and a heating rate of 5℃·min. -1 Calcination for 2 hours, under Ar / H2 = 95:5 atmosphere protection, the product is labeled as Bi NPs / AC; Step c: The Bi NPs / AC is calcined a second time at 500℃ for 2 hours, with a heating rate of 5℃·min. -1 The product was calcined under an Ar / H2 = 95:5 atmosphere and labeled as Bi NCs / AC.

2. The ultrafine bismuth nanocluster catalyst according to claim 1, characterized in that: In step a, the ultrasonic dispersion frequency is 40-80kHz.

3. The ultrafine bismuth nanocluster catalyst according to claim 1, characterized in that: The rotation process parameters in step a are 80-120 r / min.

4. The ultrafine bismuth nanocluster catalyst according to claim 1, characterized in that: In step a, the amount of BiCl3 used is 75 mg.

5. An ultrafine bismuth nanocluster catalyst prepared by any one of the preparation methods described in claims 1-4.

6. The application of the ultrafine bismuth nanocluster catalyst of claim 5 in the electrochemical reduction of CO2 to formate.

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