A halogen-modified bismuth nanoelectrocatalytic electrode synthesized in situ, its preparation method and application

Abstract

This invention discloses an in-situ synthetic halogen-modified bismuth nano-electrocatalytic electrode, its preparation method, and its application. The method involves first preparing basic bismuth nitrate via a simple hydrolysis method, then grafting halogen atoms onto the surface of the basic bismuth nitrate through a water bath treatment to synthesize a precursor. Finally, in-situ reduction under ECR conditions forms the halogen-modified bismuth-based nano-electrocatalytic electrode. The preparation method of this invention is simple, the reaction is relatively mild, and energy consumption is low. The prepared halogen-modified bismuth nanocatalytic material can effectively suppress the competing reaction for hydrogen evolution and increase the current density, thus exhibiting good electrocatalytic performance in reducing carbon dioxide to formic acid.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic reduction of carbon dioxide, specifically relating to an in-situ synthesized halogen-modified bismuth nanoelectrocatalytic electrode, its preparation method, and its application. Background Technology

[0002] Since the Industrial Revolution, the exploitation of fossil fuels has led to a year-on-year increase in CO2 concentration in the Earth's atmosphere. This has triggered a series of environmental problems, such as global warming, rising sea levels, and glacial melting. To reduce CO2 concentration or convert it into economically valuable chemicals, various technologies have been proposed. Among them, electrochemical CO2 reduction (CO2RR) can convert CO2 into valuable liquid chemicals or fuels, making it an effective technology for achieving carbon neutrality and peak carbon emissions. In the past decade, different catalysts have been developed to convert CO2 into various gaseous or liquid products via CO2RR, such as carbon monoxide, formic acid, ethylene, ethanol, and n-propanol. Among liquid products, formic acid has attracted considerable attention due to its economic feasibility and high hydrogen capacity.

[0003] In recent years, transition metal-based electrocatalysts, such as tin (Sn), indium (In), bismuth (Bi), and lead (Pb), have been extensively studied as typical catalysts for the electrocatalytic reduction of CO2 to formic acid because they exhibit strong adsorption of key intermediates in formic acid formation and inhibit the competitive hydrogen evolution reaction. Among them, bismuth-based nanocatalysts have attracted much attention from researchers due to their high selectivity in the electrochemical reduction of CO2 to formic acid over a wide potential window, as well as their relatively abundant reserves, non-toxicity, and low cost. To continuously improve the performance of bismuth-based catalysts, researchers have adopted various control strategies, such as controlling the morphology of bismuth nanomaterials and introducing defects, to give bismuth-based nanomaterials abundant active sites, such as edges, defects, grain boundaries, and high-index facets.

[0004] Studies have found that halide ions can anchor to Bi atoms by substituting hydroxyl groups on the surface, achieving surface halogenation of basic bismuth nitrate. This promotes local charge separation and activates hydroxyl groups, which is beneficial for the adsorption of CO2 molecules and protons, thus accelerating the photocatalytic CO2 conversion process. However, there are currently no reports on the surface halogenation of bismuth-based nanomaterials and its application in electrochemical CO2 reduction. Therefore, it is necessary to investigate the impact of surface halogenation using halide anions on the performance of electrochemical CO2 reduction. Summary of the Invention

[0005] The purpose of this invention is to provide an in-situ synthesized halogen-modified bismuth nano-electrocatalytic electrode, its preparation method, and its application. The precursor is synthesized by surface halogenation of basic bismuth nitrate nanoflowers in a water bath. The precursor is then reduced in situ under electrocatalytic CO2 reduction conditions to form an electrocatalytic electrode with halogen-modified bismuth nano-catalytic material. It exhibits good electrocatalytic reduction performance of CO2 to formic acid and has good application prospects.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A halogen-modified bismuth nano-electrocatalytic electrode synthesized in situ, the synthesis method of which includes the following steps:

[0008] 1) Dissolve 0.01-200 mmol Bi(NO3)3∙5H2O and 0.01-200 mmol hexadecyltrimethylammonium bromide (CTAB) in 6-600 mL of deionized water and stir vigorously for 30 minutes to obtain solution A; dissolve 0.005-0.05 mol of alkali metal hydroxide in 4-400 mL of ethanol and stir vigorously for 30 minutes to obtain solution B; quickly pour solution B into solution A and stir vigorously for 10-1000 minutes to obtain solution C; transfer solution C to a water bath at 50-90℃ and stir vigorously for 1-10 hours. After cooling to room temperature, centrifuge to collect the product, wash twice each with ethanol and deionized water, and then dry at 40-60℃ overnight to obtain basic bismuth nitrate powder;

[0009] 2) Dissolve 0.01-200 mmol / L of the metal halide in 5-500 mL of deionized water and stir for 3-300 minutes to obtain solution D; add 1-100 mg of the basic bismuth nitrate powder obtained in step 1) to solution D, stir at room temperature in the dark for 1-24 hours, then wash repeatedly with deionized water, and finally dry at 40-60℃ for 15 hours to obtain the precursor powder BON-X (X is a halogen).

[0010] 3) The precursor powder BON-X obtained in step 3) is uniformly dispersed in an organic solvent and ultrasonicated in an ice-water bath for 0.5-20 hours to obtain an electrode slurry. The obtained electrode slurry is drop-coated in small amounts multiple times onto the center of the side of the carbon paper loaded with the microporous carbon layer. After drying, it is used as the working electrode and electrolyzed under ECR conditions to synthesize an electrocatalytic electrode with halogen-modified bismuth nanocatalytic material in situ.

[0011] Further, the alkali metal hydroxide mentioned in step 1) includes Bi6O6(OH3)(NO3)3·1.5H2O or Bi6O5(OH3)(NO3)·3H2O.

[0012] Further, the metal halide mentioned in step 2) includes any one of sodium fluoride, sodium iodide, sodium bromide, potassium fluoride, potassium iodide, and potassium bromide.

[0013] Further, the organic solvent mentioned in step 3) is an ethanol solution containing 5 vol% Nafion.

[0014] Further, the concentration of the electrode slurry in step 3) is 1-50 mg / ml.

[0015] Furthermore, in step 3), the amount of electrode paste dropped onto the carbon paper is 100-1000 μL / cm. 2 .

[0016] Further, in step 3), during electrolysis, a 5-500 mL H-type electrolytic cell is selected, and a 0.5 M KHCO3 solution is used as the electrolyte solution (and the electrolyte in the cathode cell should be in a CO2 saturated state). A three-electrode system is constructed using a platinum sheet electrode as the counter electrode and a saturated Ag / AgCl electrode as the reference electrode, and constant current is applied at 5-150 mA for 5-60 min.

[0017] The halogen-modified bismuth nanoelectrocatalytic electrode exhibits excellent electrocatalytic reduction performance of CO2 to formic acid and can be applied to the electrocatalytic reduction of carbon dioxide to formic acid.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] (1) In this invention, basic bismuth nitrate was prepared by simple hydrolysis using alkali metal hydroxide as precipitant and CTAB as directing agent and surfactant. Halogen atoms were then grafted onto the surface of basic bismuth nitrate by water bath treatment to obtain BON-X precursor. Then, an electrocatalytic electrode with halogen-modified bismuth nanocatalytic material was synthesized by in-situ electroreduction under ECR conditions. The preparation method is simple, the reaction is relatively mild, the process is convenient, and the time is short.

[0020] (2) The halogen-modified bismuth nanocatalyst material prepared by the present invention exhibits good catalytic activity for electrocatalytic reduction of CO2 to formic acid and high single selectivity, and has good application prospects. Attached Figure Description

[0021] Figure 1 The XRD patterns of the precursor powders prepared in Examples 1-4 are shown.

[0022] Figure 2 The graph shows a comparison of linear sweep voltammetry (LSV) curves of the electrocatalytic electrodes prepared in Examples 1-4 in a CO2-saturated 0.5M KHCO3 electrolyte.

[0023] Figure 3The Faradaic efficiency (FE) of the formic acid product obtained by electrocatalytic electrodes prepared in Examples 1-4 after electrolysis at different potentials for 1 hour is shown. HCOOH Comparison chart. Detailed Implementation

[0024] A halogen-modified bismuth nano-electrocatalytic electrode synthesized in situ, the synthesis method of which includes the following steps:

[0025] 1) Dissolve 0.01-200 mmol Bi(NO3)3∙5H2O and 0.01-200 mmol hexadecyltrimethylammonium bromide (CTAB) in 6-600 mL of deionized water and stir vigorously for 30 minutes to obtain solution A; dissolve 0.005-0.05 mol of alkali metal hydroxide in 4-400 mL of ethanol and stir vigorously for 30 minutes to obtain solution B; quickly pour solution B into solution A and stir vigorously for 10-1000 minutes to obtain solution C; transfer solution C to a water bath at 50-90℃ and stir vigorously for 1-10 hours. After cooling to room temperature, centrifuge to collect the product, wash twice each with ethanol and deionized water, and then dry at 40-60℃ overnight to obtain basic bismuth nitrate powder;

[0026] 2) Dissolve 0.01-200 mmol / L of the metal halide in 5-500 mL of deionized water and stir for 3-300 minutes to obtain solution D; add 1-100 mg of the basic bismuth nitrate powder obtained in step 1) to solution D, stir at room temperature in the dark for 1-24 hours, then wash repeatedly with deionized water, and finally dry at 40-60℃ for 15 hours to obtain the precursor powder BON-X (X is a halogen).

[0027] 3) The precursor powder BON-X obtained in step 3) is uniformly dispersed in an ethanol solution containing 5 vol% Nafion, and sonicated in an ice-water bath for 0.5-20 hours to obtain an electrode slurry with a concentration of 1-50 mg / ml; the obtained electrode slurry is then diluted at a concentration of 100-1000 μL / cm³. 2 The amount of material was repeatedly dripped onto the center of the side of carbon paper supported by the microporous carbon layer. After drying, it was used as the working electrode. A three-electrode system was constructed with a platinum sheet electrode as the counter electrode and a saturated Ag / AgCl electrode as the reference electrode. In a 5-500 mL H-type electrolytic cell, 0.5 M KHCO3 solution was used as the electrolyte solution (the electrolyte in the cathode cell should be CO2 saturated). The electrocatalytic electrode with halogen-modified bismuth nanocatalytic material was synthesized in situ under a constant current of 5-150 mA for 5-60 min.

[0028] The alkali metal hydroxide mentioned in step 1) includes Bi6O6(OH3)(NO3)3·1.5H2O or Bi6O5(OH3)(NO3)·3H2O.

[0029] The metal halide mentioned in step 2) includes any one of sodium fluoride, sodium iodide, sodium bromide, potassium fluoride, potassium iodide, and potassium bromide.

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] The preparation of the BON electrocatalytic electrode includes the following steps:

[0033] (1) Dissolve 4 mmol Bi(NO3)3∙5H2O and 2 mmol CTAB in 200 mL of deionized water and stir vigorously for 30 minutes to obtain solution A; dissolve 0.1 mol urea in 100 mL of ethanol and stir vigorously for 30 minutes to obtain solution B; quickly pour solution B into solution A and stir vigorously for 30 minutes to obtain solution C; transfer solution C to a 75°C water bath and stir vigorously for 10 hours. After cooling to room temperature, centrifuge to collect the product, wash twice with ethanol and deionized water alternately, and dry at 45°C overnight to obtain basic bismuth nitrate powder.

[0034] (2) Disperse 20 mg of the obtained basic bismuth nitrate powder evenly into 4 mL of ethanol solution containing 5 vol% Nafion, and sonicate in an ice-water bath for 4 hours to obtain an electrode slurry; use a pipette to drop small amounts of the obtained electrode slurry onto the center of the side of the carbon paper loaded with the microporous carbon layer, with a drop volume of 100 μL / cm. 2 After drying, a working electrode was prepared, and a three-electrode system was constructed using a platinum sheet electrode as the counter electrode and a saturated Ag / AgCl electrode as the reference electrode. In a 100 mL H-type electrolytic cell, a 0.5 M KHCO3 solution was used as the electrolyte solution (the electrolyte in the cathode cell should be in a CO2 saturated state), and constant current electrolysis was performed at 150 mA for 1 h to synthesize an electrocatalytic electrode with BON catalytic material in situ.

[0035] Example 2

[0036] The preparation of the BON-Cl electrocatalytic electrode includes the following steps:

[0037] (1) Dissolve 4 mmol Bi(NO3)3∙5H2O and 2 mmol CTAB in 200 mL of deionized water and stir vigorously for 30 minutes to obtain solution A; dissolve 0.1 mol urea in 100 mL of ethanol and stir vigorously for 30 minutes to obtain solution B; quickly pour solution B into solution A and stir vigorously for 30 minutes to obtain solution C; transfer solution C to a 75°C water bath and stir vigorously for 10 hours. After cooling to room temperature, centrifuge to collect the product, wash twice with ethanol and deionized water alternately, and dry at 45°C overnight to obtain basic bismuth nitrate powder.

[0038] (2) Dissolve 8 mmol NaCl in 100 mL of deionized water and stir for 30 minutes to obtain solution D; add 100 mg of basic bismuth nitrate powder obtained in step (1) to solution D, stir at room temperature in the dark for 24 hours, then wash repeatedly with deionized water, and finally dry at 45°C for 15 hours to obtain BON-Cl precursor powder.

[0039] (3) Disperse 20 mg of the obtained BON-Cl precursor powder evenly into 4 mL of ethanol solution containing 5 vol% Nafion, and sonicate in an ice-water bath for 4 hours to obtain an electrode slurry; use a pipette to drop small amounts of the obtained electrode slurry onto the center of the side of the carbon paper loaded with the microporous carbon layer, with a drop volume of 100 μL / cm. 2 After drying, a working electrode was prepared, and a three-electrode system was constructed using a platinum sheet electrode as the counter electrode and a saturated Ag / AgCl electrode as the reference electrode. In a 100 mL H-type electrolytic cell, a 0.5 M KHCO3 solution was used as the electrolyte solution (the electrolyte in the cathode cell should be in a CO2 saturated state), and constant current electrolysis was performed at 150 mA for 1 h to synthesize an electrocatalytic electrode with BON-Cl catalytic material in situ.

[0040] Example 3

[0041] The preparation of the BON-I electrocatalytic electrode includes the following steps:

[0042] (1) Dissolve 4 mmol Bi(NO3)3∙5H2O and 2 mmol CTAB in 200 mL of deionized water and stir vigorously for 30 minutes to obtain solution A; dissolve 0.1 mol urea in 100 mL of ethanol and stir vigorously for 30 minutes to obtain solution B; quickly pour solution B into solution A and stir vigorously for 30 minutes to obtain solution C; transfer solution C to an 85℃ water bath and stir vigorously for 10 hours. After cooling to room temperature, centrifuge to collect the product, wash twice with ethanol and deionized water alternately, and dry at 45℃ overnight to obtain basic bismuth nitrate powder.

[0043] (2) Dissolve 8 mmol KI in 100 mL of deionized water and stir for 30 minutes to obtain solution D; add 100 mg of basic bismuth nitrate powder obtained in step (1) to solution D, stir at room temperature in the dark for 24 hours, then wash repeatedly with deionized water, and finally dry at 45°C for 15 hours to obtain BON-I precursor powder.

[0044] (3) Disperse 20 mg of the obtained BON-I precursor powder evenly into 4 mL of ethanol solution containing 5 vol% Nafion, and sonicate in an ice-water bath for 4 hours to obtain an electrode slurry; use a pipette to drop the obtained electrode slurry onto the center of the side of the carbon paper loaded with the microporous carbon layer in small amounts and multiple times, with a drop volume of 100 μL / cm. 2 After drying, a working electrode was prepared, and a three-electrode system was constructed using a platinum sheet electrode as the counter electrode and a saturated Ag / AgCl electrode as the reference electrode. In a 100 mL H-type electrolytic cell, a 0.5 M KHCO3 solution was used as the electrolyte solution (the electrolyte in the cathode cell should be CO2 saturated), and constant current electrolysis was performed at 150 mA for 1 h to synthesize an electrocatalytic electrode with BON-I catalytic material in situ.

[0045] Example 4

[0046] The preparation of the BON-F electrocatalytic electrode includes the following steps:

[0047] (1) Dissolve 4 mmol Bi(NO3)3∙5H2O and 2 mmol CTAB in 200 mL of deionized water and stir vigorously for 30 minutes to obtain solution A; dissolve 0.1 mol urea in 100 mL of ethanol and stir vigorously for 30 minutes to obtain solution B; quickly pour solution B into solution A and stir vigorously for 30 minutes to obtain solution C; transfer solution C to a 75°C water bath and stir vigorously for 5 hours. After cooling to room temperature, centrifuge to collect the product, wash twice with ethanol and deionized water alternately, and dry at 45°C overnight to obtain basic bismuth nitrate powder.

[0048] (2) Dissolve 8 mmol NaF in 100 mL of deionized water and stir for 30 minutes to obtain solution D; add 100 mg of basic bismuth nitrate powder obtained in step (1) to solution D, stir at room temperature in the dark for 24 hours, then wash repeatedly with deionized water, and finally dry at 45°C for 15 hours to obtain BON-F precursor powder.

[0049] (3) Disperse 20 mg of the obtained BON-F precursor powder evenly into 4 mL of ethanol solution containing 5 vol% Nafion, and sonicate in an ice-water bath for 4 hours to obtain an electrode slurry; use a pipette to drop small amounts of the obtained electrode slurry onto the center of the side of the carbon paper loaded with the microporous carbon layer, with a drop volume of 100 μL / cm. 2 After drying, a working electrode was prepared, and a three-electrode system was constructed using a platinum sheet electrode as the counter electrode and a saturated Ag / AgCl electrode as the reference electrode. In a 100 mL H-type electrolytic cell, a 0.5 M KHCO3 solution was used as the electrolyte solution (the electrolyte in the cathode cell should be in a CO2 saturated state), and constant current electrolysis was performed at 150 mA for 1 h to synthesize an electrocatalytic electrode with BON-F catalytic material in situ.

[0050] Figure 1 The XRD patterns of the precursor powders prepared in Examples 1-4 are shown in the figures. As can be seen from the spectra of the BON, BON-I, and BON-Cl precursors, diffraction peaks attributed to Bi6O6(OH3)(NO3)3·1.5H2O (PDF#53-1038) and Bi6O5(OH3)(NO3)·3H2O (PDF#48-0575) can be observed. The BON-Cl precursor spectrum also shows diffraction peaks attributed to BiOCl (PDF#06-0249), while the BON-F precursor XRD pattern only contains diffraction peaks attributed to BiOF (PDF#86-1648) and Bi6O6(OH3)(NO3)3·1.5H2O (PDF#53-1038). In summary, this indicates that the samples do not contain other impurities.

[0051] Application Examples

[0052] Electrochemical tests of the catalyst were performed using an electrochemical workstation, and the products of electrocatalytic CO2 reduction were detected using nuclear magnetic resonance hydrogen spectroscopy and gas chromatography.

[0053] The electrolyte solution used was 0.5M KHCO3 solution, the test temperature was 25℃, and the test system was a three-electrode system. The electrolytic cell was an H-type electrolytic cell, the platinum sheet electrode was the counter electrode, and the saturated Ag / AgCl electrode was the reference electrode. All potentials in the test results were adjusted to the potential relative to the reversible hydrogen electrode (vs. RHE). The linear sweep voltammetry (LSV) test scan rate was 3mV / s. Before the test, the working electrode was subjected to 20 cycles of cyclic voltammetry scan at a scan rate of 50mV / s. After one LSV test, the catalyst was electrolyzed at different potentials in constant potential mode for 1 hour. During the electrolysis process, gaseous products were collected and detected by chromatography. After the electrolysis was completed, the electrolyte in the cathode cell was collected for NMR analysis.

[0054] Figure 2 The figures show a comparison of the LSV curves of the electrocatalytic electrodes obtained in Examples 1-4 in a CO2-saturated 0.5 M KHCO3 cathode electrolyte. As can be seen from the figures, within the test potential range, the reduction current density of the BON-Cl electrocatalytic electrode is significantly greater than that of the BON, BON-I, and BON-F electrocatalytic electrodes.

[0055] Figure 3 The graph shows a comparison of the Faradaic efficiencies of the electrocatalytic electrodes obtained in Examples 1-4 for the electrocatalytic reduction of CO2 to formic acid (test potential range: -0.87V vs. RHE ~ -1.27V vs. RHE). As can be seen from the graph, within the test range, the Faradaic efficiency of the BON-Cl electrocatalytic electrode for formic acid remains consistently above 90%, and its Faradaic efficiency at high potentials is significantly better than other catalysts. In contrast, the Faradaic efficiencies of the BON, BON-I, and BON-F electrocatalytic electrodes all decrease significantly with increasing potential. This indicates that the BON, BON-Cl, BON-I, and BON-F electrocatalytic electrodes all exhibit good performance in the electrocatalytic reduction of carbon dioxide to formic acid, with the BON-Cl electrocatalytic electrode showing the best catalytic performance.

[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0057] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions of each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for in-situ synthesis of halogen-modified bismuth nano-electrocatalytic electrodes, characterized in that, Includes the following steps: 1) Dissolve 0.01-200 mmol Bi(NO3)3∙5H2O and 0.01-200 mmol CTAB in 6-600 mL of deionized water and stir vigorously for 30 minutes to obtain solution A; dissolve 0.005-0.05 mol of alkali metal hydroxide in 4-400 mL of ethanol and stir vigorously for 30 minutes to obtain solution B; quickly pour solution B into solution A and stir vigorously for 10-1000 minutes to obtain solution C; transfer solution C to a water bath at 50-90℃ and stir vigorously for 1-10 hours. After cooling to room temperature, centrifuge to collect the product, wash twice each with ethanol and deionized water, and then dry at 40-60℃ overnight to obtain basic bismuth nitrate powder; 2) Dissolve 0.01-200 mmol / L of metal halide in 5-500 mL of deionized water and stir for 3-300 minutes to obtain solution D; add 1-100 mg of basic bismuth nitrate powder obtained in step 1) to solution D, stir at room temperature in the dark for 1-24 hours, then wash repeatedly with deionized water, and finally dry at 40-60℃ for 15 hours to obtain precursor powder; 3) Disperse the precursor powder obtained in step 2) uniformly in an organic solvent and sonicate in an ice-water bath for 0.5-20 hours to obtain an electrode slurry; drop the obtained electrode slurry onto the center of the side of the carbon paper loaded with the microporous carbon layer in small amounts and multiple times, and after drying, use it as a working electrode for electrolysis under ECR conditions to synthesize an electrocatalytic electrode with halogen-modified bismuth nanocatalytic material in situ. The metal halide mentioned in step 2) is sodium chloride; Step 3) During electrolysis, a 0.5M KHCO3 solution is used as the electrolyte solution. A three-electrode system is constructed using a platinum sheet electrode as the counter electrode and a saturated Ag / AgCl electrode as the reference electrode. The system is treated with a constant current at 5-150 mA for 5-60 min.

2. The method for in-situ synthesis of halogen-modified bismuth nano-electrocatalytic electrodes according to claim 1, characterized in that, The basic bismuth nitrate obtained in step 1) includes Bi6O6(OH)3(NO3)3·1.5H2O or Bi6O5(OH)3(NO3)5·3H2O.

3. The method for in-situ synthesis of halogen-modified bismuth nano-electrocatalytic electrodes according to claim 1, characterized in that, The organic solvent mentioned in step 3) is an ethanol solution containing 5 vol% Nafion.

4. The method for in-situ synthesis of halogen-modified bismuth nano-electrocatalytic electrodes according to claim 1, characterized in that, The concentration of the electrode paste mentioned in step 3) is 1-50 mg / ml; its drop-coating amount on carbon paper is 100-1000 μL / cm. 2 .

5. A halogen-modified bismuth nanoelectrocatalytic electrode prepared by the method described in claim 1.

6. The application of the halogen-modified bismuth nanoelectrocatalytic electrode as described in claim 5 in the electrocatalytic reduction of carbon dioxide to formic acid.

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