Preparation method of bismuth-doped hollow nanospheres electrode and application thereof in formic acid production
By using bismuth-doped porous hollow carbon nanosphere electrodes, the problem of high CO2 activation energy barrier was solved, the rate and efficiency of CO2 reduction to formic acid were improved, and efficient CO2 resource utilization was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTH CHINA ELECTRIC POWER UNIV
- Filing Date
- 2023-03-24
- Publication Date
- 2026-05-19
AI Technical Summary
In existing electrocatalytic CO2 reduction technologies, the CO2 activation energy barrier is high and the reaction activity is poor, resulting in a low rate of formic acid production.
By employing bismuth-doped porous hollow carbon nanosphere electrodes, the local concentration and activation efficiency of CO2 are improved, the activation energy barrier is reduced, and the formic acid production rate is enhanced by controlling the pore structure and the amount of metallic bismuth doping.
Under mild conditions, CO2 reduction to formic acid was achieved with high efficiency and high yield, with a formic acid production rate of up to 613 mol L⁻¹ h⁻¹ g⁻¹. The material has a stable structure and is easy to apply in industrial applications.
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Figure CN116288502B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical technology, specifically relating to a method for preparing a bismuth-doped porous hollow carbon nanosphere electrode and its application in the electroreduction of CO2 to produce formic acid. Background Technology
[0002] The extensive use of fossil fuels has not only led to a continuous increase in atmospheric CO2 emissions, causing environmental problems, but also triggered an energy crisis due to the over-exploitation of fossil fuels. Converting CO2 into fuel or valuable carbon-containing feedstocks is an effective way to utilize CO2, reducing atmospheric CO2 levels and mitigating the greenhouse effect, while also providing a new approach to solving the problem of energy regeneration. CO2 is a linear molecule with a zero dipole moment, and its standard enthalpy of formation is -398.38 kJ / mol. -1 CO2 is the final product of many chemical or biological combustion reactions. Its molecules are in a state of minimum energy, making them very stable and inert. Currently, CO2 conversion methods include chemical conversion, catalytic hydrogenation, photocatalytic reduction, and electrochemical reduction. Electrochemical methods offer mild reaction conditions, typically operating at room temperature and pressure; they can be powered by renewable energy sources (wind, solar, tidal, etc.); the equipment is simple; and the selectivity and activity of the reduction products can be easily adjusted by controlling reaction conditions, making it an effective way to convert CO2 into valuable compounds. Electrocatalytic reduction of CO2 to formic acid is achieved through a two-electron transfer process, avoiding the poor product selectivity problems caused by multi-electron transfer processes. Sn-supported redox graphene electrodes exhibit high selectivity for formic acid production through electroreduction (ACS Catalysis, 2021, 11, 3310-3318). However, current electrocatalytic reduction of CO2 to formic acid still faces challenges such as a high CO2 activation energy barrier and poor CO2 reactivity, resulting in a low formic acid production rate. To address the shortcomings of existing electrocatalytic CO2 technologies, this invention provides a method for preparing bismuth-doped porous hollow carbon nanosphere electrodes and an application in the electroreduction of CO2 to produce formic acid. By utilizing the local confinement effect of the hollow cavities of the carbon spheres, the CO2 concentration on the surface of the active sites of metallic bismuth is increased, thereby lowering the CO2 activation barrier, increasing the rate of CO2 reduction to formic acid, and reducing the concentration of CO2 in the atmosphere to achieve its resource recovery. Summary of the Invention
[0003] This invention addresses the shortcomings of existing electrocatalytic CO2 reduction technologies by providing a novel electrocatalytic electrode preparation method for the efficient and high-yield reduction of CO2 to formic acid under mild conditions, and its application in the electrocatalytic reduction of CO2 to formic acid. To achieve the above objectives, the technical solution provided by this invention is as follows:
[0004] A method for preparing a bismuth-doped porous hollow carbon nanosphere electrode, characterized in that:
[0005] Step 1: Preparation of bismuth-containing precursor microspheres: Under room temperature conditions, a certain mass of propyl orthosilicate was added to a mixed solution of ethanol and water. Ammonia was added under stirring. After stirring at room temperature, 0.05~1.0g of bismuth nitrate, resorcinol and formaldehyde were added to the mixed solution respectively. The mixture was stirred continuously, filtered and separated, and washed with high-purity water and ethanol respectively. The bismuth-containing precursor microspheres were then dried.
[0006] Step 2: Preparation of bismuth-doped porous carbon nanospheres: A certain mass of bismuth-containing precursor microsphere powders was placed in a quartz boat and calcined in a tube furnace. To maintain the uniform pore structure of the carbon material, the temperature was raised to 5~10 ℃ min. -1 The material was kept at 800-1000 ℃ for 4 h to ensure complete carbonization. The calcination was carried out in an argon atmosphere and cooled to room temperature to obtain black powder bismuth-doped porous carbon nanospheres.
[0007] Step 3: Preparation of bismuth-doped porous hollow carbon nanospheres: A certain mass of black powder bismuth-doped porous carbon nanospheres is added to a concentrated NaOH solution and stirred continuously. The mixture is then filtered and washed with water until neutral. This process is repeated multiple times. The resulting black powder catalyst is then dried under vacuum for later use.
[0008] Step 4: Preparation of bismuth-doped porous hollow carbon nanosphere electrode: The bismuth-doped porous hollow carbon nanosphere catalyst was added to a mixed solution of high-purity water and Nafion. After ultrasonic mixing, the suspension was dropped onto carbon cloth and dried at room temperature to serve as the working electrode.
[0009] Preferably, step 1 further includes the following: adding ammonia water under stirring conditions, stirring at room temperature for 15 minutes, then adding 0.05~1.0 g of bismuth nitrate, resorcinol, and formaldehyde to the mixed solution, stirring continuously for 24 hours, filtering and separating, washing three times with high-purity water and ethanol respectively, and drying at 80℃ to obtain bismuth precursor microspheres, wherein the volume ratio of ethanol:high-purity water:ammonia water is 70:10:3, the molar ratio of propyl orthosilicate:resorcinol:formaldehyde is 25~30:5~13:40~50, bismuth nitrate is the bismuth source for the synthesis catalyst, and the amount of bismuth doping in the catalyst material is obtained by controlling the amount added. Propyl orthosilicate, resorcinol, and formaldehyde are precursors of silicon and carbon, and carbon-coated silica nanospheres of different sizes and thicknesses can be obtained by controlling the amount of propyl orthosilicate, resorcinol, and formaldehyde added.
[0010] Preferably, a certain mass of black powder is added to 10 mol L -1 The mixture was stirred continuously in a concentrated NaOH solution for 72 h. A strong alkaline solution was used to etch away the silica generated during the reaction, yielding hollow carbon nanospheres. These nanospheres were then filtered, washed with water until neutral, and this process was repeated three times. The resulting black powder catalyst was then vacuum-dried at 120 °C for later use.
[0011] Preferably, step 4 further includes the following: In order to obtain electrode materials with different catalyst layer thicknesses, 3~10 mg of bismuth-doped porous hollow carbon nanosphere catalyst is added to a mixed solution of 2.85 mL of high-purity water and 0.15 mL of 5 wt% Nafion to ensure that the catalyst is evenly dispersed in the solution. After ultrasonic mixing for 30 min, the suspension is dropped onto carbon cloth or carbon paper and dried at room temperature to serve as the working electrode.
[0012] This invention also discloses a bismuth-doped porous hollow carbon nanosphere electrode, which is obtained by the above-mentioned method for preparing bismuth-doped porous hollow carbon nanosphere electrodes; characterized in that: the carbon spheres on the electrode surface are prepared by a room temperature solvent stirring method, and the electrode is prepared by bismuth-doped porous hollow carbon nanospheres with a diameter in the range of 100 nm-200 nm and a surface pore size in the range of 2-5 nm.
[0013] This invention also discloses a method for the electrochemical reduction of CO2 to produce formic acid. This method uses the aforementioned bismuth-doped porous hollow carbon nanosphere electrode as the working electrode, a platinum sheet as the anode, and a silver / silver chloride electrode as the reference electrode. CO2 is reduced electrochemically under an applied voltage of -0.8 to -1.4 V or 10 to 50 mA cm⁻¹. -2 Apply current, 1~3 L h -1 The process involves electrochemical reduction of carbon dioxide under specific flow conditions. This electrochemical reduction of CO2 is carried out in a closed dual-cell reactor, with the two cells separated by a Nafion 117 proton exchange membrane. Potassium bicarbonate, potassium hydroxide, and sodium sulfate are used as supporting electrolytes. Bismuth-doped porous hollow carbon nanospheres are used as cathodes, and platinum sheet electrodes are used as anodes. CO2 is introduced into the solution before the reaction begins and is continuously aerated during the reaction. Beneficial effects
[0014] Bismuth-doped porous hollow carbon nanospheres possess the advantages of porous carbon walls and hollow nanocavities. The hollow carbon sphere structure has a higher electrochemical active area, providing more reactive sites. The porous carbon walls with controllable pore sizes provide an effective pathway for CO2 mass transfer, while the hollow nanospheres can act as confined spaces to enrich CO2, increasing local CO2 concentration and enhancing CO2-activated formic acid production, with a formic acid production rate reaching 613 mol L⁻¹. -1 h -1 g -1 .
[0015] The preparation process of bismuth-doped porous hollow carbon nanospheres is simple, easy to operate, has mild reaction conditions, stable material structure, long service life, and stable and reliable CO2 reduction to produce formic acid, making it easy to realize industrial application. Attached Figure Description
[0016] Figure 1 This is a scanning electron microscope image of bismuth-doped porous hollow carbon nanospheres.
[0017] Figure 2 This is a transmission electron microscope (TEM) image of bismuth-doped porous hollow carbon nanospheres.
[0018] Figure 3 The image shows the crystal structure of the bismuth-doped porous hollow carbon nanospheres prepared in Example 1. Figure 4 Bismuth-doped porous hollow carbon nanospheres prepared in Example 1 were subjected to 0.1 mol L⁻¹ -1 The rate of electroreduction of CO2 to formic acid in potassium bicarbonate electrolyte varies with the applied voltage.
[0019] Figure 5 The image shows the crystal structure of the bismuth-doped porous hollow carbon nanospheres prepared in Example 2.
[0020] Figure 6 Aberration-corrected electron microscopy image of the bismuth-doped porous hollow carbon nanospheres prepared in Example 2.
[0021] Figure 7 Bismuth-doped porous hollow carbon nanospheres prepared in Example 2 were subjected to 1 mol L... -1 CO2 was continuously electroreduced in potassium hydroxide electrolyte to produce formic acid for 4 hours. Implementation
[0022] The embodiments of the present invention will be described below with reference to the accompanying drawings, but the present invention is not limited to the following embodiments.
[0023] A method for preparing a bismuth-doped porous hollow carbon nanosphere electrode, characterized in that:
[0024] Step 1: Preparation of bismuth-containing precursor microspheres: Under room temperature conditions, a certain mass of propyl orthosilicate is added to a mixed solution of ethanol and water. Ammonia is added under stirring. After stirring at room temperature, 0.05~1.0 g of bismuth nitrate, resorcinol, and formaldehyde are added to the mixed solution respectively. The mixture is stirred continuously, filtered, and washed with high-purity water and ethanol respectively, and dried to obtain bismuth-containing precursor microspheres. Step 1 further includes the following: Ammonia is added under stirring. After stirring at room temperature for 15 minutes, 0.05~1.0 g of bismuth nitrate, resorcinol, and formaldehyde are added to the mixed solution respectively. The mixture is stirred continuously for 24 hours, filtered, and washed three times with high-purity water and ethanol respectively. The mixture is dried at 80℃ to obtain bismuth-containing precursor microspheres. The volume ratio of ethanol:high-purity water:ammonia is 70:10:3, and the molar ratio of propyl orthosilicate:resorcinol:formaldehyde is 25~30:5~13:40~50.
[0025] Step 2: Preparation of bismuth-doped porous carbon nanospheres: A certain mass of bismuth-containing precursor microsphere powders was placed in a quartz boat and calcined in a tube furnace at 5~10 ℃ min. -1 The temperature was increased rapidly, and the mixture was calcined at 800-1000℃ in an argon atmosphere. After cooling to room temperature, black bismuth-doped porous carbon nanospheres were obtained.
[0026] Step 3: Preparation of bismuth-doped porous hollow carbon nanospheres: A certain mass of black bismuth-doped porous carbon nanospheres was added to a concentrated NaOH solution and stirred continuously. The mixture was then filtered, washed with water until neutral, and this process was repeated several times. The resulting black powder catalyst was then vacuum-dried for later use. The catalyst morphology is shown in the attached figure. Figure 1 As shown, the catalyst is spherical and composed of attached... Figure 2 As shown, the prepared catalyst has a hollow nanosphere structure; preferably, a certain mass of black powder is added to 10 mol L... -1 The catalyst was stirred continuously in a concentrated NaOH solution for 72 h, then filtered and washed with water until neutral. This process was repeated three times. The resulting black powder catalyst was dried under vacuum at 120 °C for later use.
[0027] Step 4: Preparation of bismuth-doped porous hollow carbon nanosphere electrode: The bismuth-doped porous hollow carbon nanosphere catalyst was added to a mixed solution of high-purity water and Nafion. After ultrasonic mixing, the suspension was dropped onto carbon cloth and dried at room temperature to serve as the working electrode. Step 4 further includes the following: 3-10 mg of bismuth-doped porous hollow carbon nanosphere catalyst was added to a mixed solution of 2.85 mL of high-purity water and 0.15 mL of 5 wt% Nafion. After ultrasonic mixing for 30 min, the suspension was dropped onto carbon cloth and dried at room temperature to serve as the working electrode.
[0028] This invention discloses a bismuth-doped porous hollow carbon nanosphere electrode, which is obtained by the above-mentioned method for preparing bismuth-doped porous hollow carbon nanosphere electrodes. The carbon spheres on the electrode surface are prepared by a room temperature solvent stirring method, and the electrodes are prepared by bismuth-doped porous hollow carbon nanospheres with a diameter range of 100 nm-200 nm and a surface pore size range of 2-5 nm. Example
[0029] This invention provides a method for preparing bismuth-doped hollow carbon nanospheres, specifically implemented according to the following steps:
[0030] ① Propyl orthosilicate was added to a mixed solution of ethanol and water, and ammonia was added under stirring. After stirring at room temperature for 15 minutes, 0.5 g of bismuth nitrate, resorcinol and formaldehyde were added to the mixed solution respectively. The mixture was stirred for 24 hours, filtered and separated, washed three times with high-purity water and ethanol respectively, and dried at 80℃ to obtain bismuth precursor microspheres. The volume ratio of ethanol:high-purity water:ammonia was 70:10:3, and the molar ratio of propyl orthosilicate:resorcinol:formaldehyde was 29:11:45.
[0031] ② A certain mass of bismuth-containing precursor microsphere powders was placed in a quartz boat and calcined in a tube furnace at 10 °C for 1 min. -1 The temperature was increased rapidly, and the mixture was calcined at 900 °C for 4 hours in an argon atmosphere. After cooling to room temperature, black bismuth-doped porous carbon nanospheres were obtained.
[0032] ③ A certain mass of bismuth-doped porous carbon nanospheres was added to 10 mol L -1 The mixture was continuously stirred in a concentrated NaOH solution for 72 h, then filtered and washed with water until neutral. This process was repeated three times. The resulting black powdered bismuth-doped porous hollow carbon nanosphere catalyst was dried under vacuum at 120 °C.
[0033] ④ Add 10 mg of bismuth-doped porous hollow carbon nanosphere catalyst to a mixed solution of 2.85 mL of high-purity water and 0.15 mL of 5 wt% Nafion. After ultrasonic mixing for 30 min, drop the suspension onto carbon cloth and dry it at room temperature to use it as the working electrode.
[0034] The bismuth-doped hollow carbon nanospheres obtained by controlling the addition amounts of metallic bismuth, propyl orthosilicate, resorcinol, and formaldehyde have a diameter of approximately 120 nm, a carbon layer thickness of approximately 20 nm, and a metallic bismuth content of 1.06 wt%. The hollow cavity of the carbon nanospheres can serve as a nanoreactor to improve the CO2 reaction rate; the appropriate carbon layer thickness ensures the structural integrity of the hollow carbon spheres and effectively shortens the mass transfer layer thickness between the reactant CO2 and the product formic acid, reducing mass transfer resistance and increasing the mass transfer efficiency of CO2 and formic acid; the metallic bismuth doping amount of 1.06 wt% can form bismuth oxide metal oxides such as... Figure 3 As shown, an appropriate amount of bismuth doping ensures that bismuth oxide particles are uniformly distributed on the surface of carbon spheres, providing more CO2 reactive sites.
[0035] The bismuth-doped hollow carbon nanosphere electrode obtained by the above method is applied to the electroreduction of CO2 to produce formic acid, and is specifically implemented according to the following steps:
[0036] The electrocatalytic reduction of CO2 was carried out in a closed dual-cell reactor, with the two cells separated by a Nafion 117 proton exchange membrane, using a 0.1 mol L⁻¹ feedstock. -1Potassium bicarbonate was used as the supporting electrolyte. A bismuth-doped porous hollow carbon nanosphere electrode was used as the cathode, and a platinum sheet electrode as the anode. CO2 was introduced into the solution before the reaction began, and continuous aeration was maintained during the reaction to keep the solution CO2 saturated. At 1.5 L / h... -1 Under carbon dioxide flow conditions, the voltage is adjusted between -0.8 and -1.4 V to carry out the electrochemical reduction of carbon dioxide, and the generated gaseous products are collected using a gas collection device. Figure 4 The graph shows the change in formic acid concentration with applied voltage. The formic acid concentration initially increases and then decreases with a negative shift in applied voltage. The highest formic acid concentration of 568.1 mmol / L is achieved when the applied voltage is -1.1 V. -1 h -1 g -1 . Example
[0037] This invention provides a method for preparing bismuth-doped hollow carbon nanospheres, specifically implemented according to the following steps:
[0038] ① Propyl orthosilicate was added to a mixed solution of ethanol and water, and ammonia was added under stirring. After stirring at room temperature for 15 minutes, 0.15 g of bismuth nitrate, resorcinol and formaldehyde were added to the mixed solution respectively. The mixture was stirred for 24 hours, filtered and separated, washed three times with high-purity water and ethanol respectively, and dried at 80℃ to obtain bismuth precursor microspheres. The volume ratio of ethanol:high-purity water:ammonia was 70:10:3, and the molar ratio of propyl orthosilicate:resorcinol:formaldehyde was 29:11:45.
[0039] ② A certain mass of bismuth-containing precursor microsphere powders was placed in a quartz boat and calcined in a tube furnace at 10 °C for 1 min. -1 The temperature was increased rapidly, and the mixture was calcined at 900 °C for 4 hours in an argon atmosphere. After cooling to room temperature, black bismuth-doped porous carbon nanospheres were obtained.
[0040] ③ A certain mass of bismuth-doped porous carbon nanospheres was added to 10 mol L -1 The mixture was continuously stirred in a concentrated NaOH solution for 72 h, then filtered and washed with water until neutral. This process was repeated three times. The resulting black powdered bismuth-doped porous hollow carbon nanosphere catalyst was dried under vacuum at 120 °C.
[0041] ④ Add 10 mg of bismuth-doped porous hollow carbon nanosphere catalyst to 2.85 mL of high-purity water and 0.15 mL of 5wt% Nafion. After ultrasonic mixing for 30 min, drop the suspension onto carbon cloth and dry it at room temperature to use as the working electrode.
[0042] The bismuth-doped hollow carbon nanospheres obtained by controlling the addition amounts of bismuth, propyl orthosilicate, resorcinol, and formaldehyde have a diameter of approximately 120 nm, a carbon layer thickness of approximately 20 nm, and a bismuth content of 0.25 wt%. The hollow cavity of the carbon nanospheres can serve as a nanoreactor to improve the CO2 reaction rate; the appropriate carbon layer thickness ensures the structural integrity of the hollow carbon spheres and effectively shortens the mass transfer layer thickness between the reactant CO2 and the product formic acid, reducing mass transfer resistance and increasing the mass transfer efficiency of CO2 and formic acid; when the bismuth nitrate addition amount is 0.15 g, the obtained catalytic material has a bismuth doping content of 0.25 wt%. Figure 5 The crystal structure diagram shown does not contain peaks for metallic bismuth and bismuth oxide. Figure 6 Aberration-corrected electron microscopy revealed that metallic bismuth was distributed in the hollow carbon spheres in the form of single atoms. Single-atom bismuth can avoid the aggregation of metallic bismuth to form metal particles and has high dispersibility. At the same time, single-atom bismuth has high atomic utilization and unsaturated coordination structure, which can provide more active sites for CO2 reaction.
[0043] This invention also provides a method for applying bismuth-doped hollow carbon nanospheres to the electroreduction of CO2 to produce formic acid, specifically implemented according to the following steps:
[0044] The electrocatalytic reduction of CO2 was carried out in a closed dual-cell reactor, with the two cells separated by a Nafion 117 proton exchange membrane, using 1 mol L⁻¹ water. -1 Potassium hydroxide was used as the supporting electrolyte. A bismuth-doped porous hollow carbon nanosphere electrode was used as the cathode, and a platinum sheet electrode as the anode. CO2 was introduced into the solution before the reaction began to saturate the reaction solution with CO2. After the reaction started, the CO2 aeration pipeline was connected to the cathode plate, and the aeration rate was 2.0 L / h. -1 Under the condition of carbon dioxide flow rate, the applied current is adjusted to 20 mA cm⁻¹. -2 An electrochemical reduction of CO2 was carried out. The electrolyte was kept in a flowing state during the reaction at a flow rate of 3 mL / min. -1 .from Figure 7 It can be seen that the formic acid yield can reach 613 mol L during the continuous 4-hour electroreduction of CO2. -1 h -1 g -1 The formic acid-producing faradaic efficiency reached 100%.
[0045] The preparation process of bismuth-doped porous hollow carbon nanospheres is simple. The hollow carbon sphere structure has a higher electrochemical active area, providing more reactive sites. The porous carbon walls with controllable pore size provide an effective pathway for CO2 mass transfer, and the hollow nanospheres can act as confined spaces to enrich CO2, increase the local CO2 concentration, and enhance CO2 activation formic acid production. By controlling the amount of bismuth nitrate added, the doping amount and bismuth doping morphology can be adjusted. Under optimized conditions, the formic acid production rate can reach 613 mol / L. -1 h -1 g -1 .
[0046] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.
Claims
1. A method for preparing a bismuth-doped porous hollow carbon nanosphere electrode, characterized in that: Step 1: Preparation of bismuth-containing precursor microspheres: Under room temperature conditions, a certain mass of propyl orthosilicate was added to a mixed solution of ethanol and water. Ammonia was added under stirring. After stirring at room temperature, bismuth nitrate, resorcinol and formaldehyde were added to the mixed solution respectively. The mixture was stirred continuously, filtered and separated, and washed with high-purity water and ethanol respectively and dried to obtain bismuth-containing precursor microspheres. Step 2: Preparation of bismuth-doped porous carbon nanospheres: A certain mass of bismuth-containing precursor microsphere powder was placed in a quartz boat and calcined in a tube furnace at 5~10 ℃ min. -1 The temperature was increased rapidly, and the mixture was calcined at 800-1000 °C for 4-6 hours in an argon atmosphere. After cooling to room temperature, black bismuth-doped porous carbon nanospheres were obtained. Step 3: Preparation of bismuth-doped porous hollow carbon nanospheres: A certain mass of black powder bismuth-doped porous carbon nanospheres is added to a concentrated NaOH solution and stirred continuously. The mixture is then filtered and washed with water until neutral. This process is repeated multiple times. The resulting black powder catalyst is then dried under vacuum for later use. Step 4: Preparation of bismuth-doped porous hollow carbon nanosphere electrode: The bismuth-doped porous hollow carbon nanosphere catalyst was added to a mixed solution of high-purity water and Nafion. After ultrasonic mixing, the suspension was dropped onto carbon cloth and dried at room temperature to serve as the working electrode.
2. The method for preparing bismuth-doped porous hollow carbon nanosphere electrodes according to claim 1, characterized in that: Step 1 further includes the following: adding ammonia water under stirring conditions, stirring at room temperature for 15 minutes, then adding 0.05~1.0 g of bismuth nitrate, resorcinol and formaldehyde to the mixed solution, stirring continuously for 24 hours, filtering and separating, washing three times with high-purity water and ethanol respectively, and drying at 80℃ to obtain bismuth precursor microspheres, wherein the volume ratio of ethanol:high-purity water:ammonia water is 70:10:3, and the molar ratio of propyl orthosilicate:resorcinol:formaldehyde is 25~30:5~13:40~50.
3. The method for preparing the bismuth-doped porous hollow carbon nanosphere electrode according to claim 1, characterized in that: Step 4 further includes the following: 3-10 mg of bismuth-doped porous hollow carbon nanosphere catalyst is added to a mixed solution of 2.85 mL of high-purity water and 0.15 mL of 5 wt% Nafion. After ultrasonic mixing for 30 min, the suspension is dropped onto carbon cloth and dried at room temperature to serve as the working electrode.
4. A bismuth-doped porous hollow carbon nanosphere electrode, wherein the electrode is obtained by the preparation method of the bismuth-doped porous hollow carbon nanosphere electrode according to claim 1; characterized in that: The electrode surface carbon spheres were prepared by a room temperature solvent stirring method. The electrodes were made of bismuth-doped porous hollow carbon nanospheres with a diameter range of 100 nm to 200 nm and a surface pore size range of 2 to 5 nm.
5. The application method of electroreduction of CO2 to produce formic acid, characterized by: This method uses the bismuth-doped porous hollow carbon nanosphere electrode as described in claim 4 as the working electrode, a platinum sheet as the anode, and a silver / silver chloride electrode as the reference electrode. CO2 is reduced electrochemically under an applied voltage of -0.8 to -1.4 V or 10 to 50 mA cm⁻¹. -2 Apply current, 1~3 L h -1 The process involves electrochemical reduction of carbon dioxide under specific carbon dioxide flow conditions. This electrochemical reduction of CO2 is carried out in a closed dual-cell reactor, with the two cells separated by a Nafion 117 proton exchange membrane. Potassium bicarbonate, potassium hydroxide, and sodium sulfate are used as supporting electrolytes. CO2 is introduced into the solution before the reaction begins and is continuously aerated during the reaction.