Preparation method and application of bismuth hydroxide ultrathin nanotube catalyst
The synthesis of bismuth hydroxide ultra-thin nanotube catalysts by solvent thermal method solved the problems of high overpotential, insufficient selectivity and poor stability in the existing electrocatalytic carbon dioxide reduction technology, and realized the selectivity of CO2 at high current density into high value-added formic acid (salt) products, significantly improving the stability and Faraday efficiency of the catalyst.
Patent Information
- Application Number
- CN202510347455.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-24
- Publication Date
- 2025-06-24
AI Technical Summary
The existing electrocatalytic carbon dioxide reduction technology has problems such as high overpotentials, insufficient product selectivity and poor stability at high current density, making it difficult to effectively improve activity and current density.
The ultra-thin nanotube catalyst of bismuth hydroxide was synthesized by solvothermal method. By adding amphiphilic polymer, bismuth source and ligand to the alcohol-water mixed solvent, the precipitation rate of bismuth salt was controlled to achieve the controllable growth of bismuth hydroxide into a hollow tubular structure with a nanoscale thickness.
The prepared bismuth hydroxide ultra-thin nanotube catalyst has nano-sized ultra-thin tube walls and unique hollow structures, which significantly improves the specific surface area and mass transfer efficiency, and realizes the selective conversion of CO2 at high current density into high value-added formic acid (salt) products, and its stability and Faraday efficiency are significantly better than commercial catalysts.
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Figure CN120191963A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of electrocatalytic reduction of carbon dioxide, and specifically relates to a preparation method of bismuth hydroxide ultrathin nanotube catalysts and their application in the field of carbon dioxide electroreduction. Background Art
[0002] Electrocatalytic carbon dioxide (CO2) reduction (ECR) is an important technology for efficiently accommodating renewable energy, achieving carbon neutrality, and producing high-value chemicals under mild conditions. However, current ECR technologies still suffer from problems such as high overpotential, insufficient product selectivity at high current densities, and poor stability. Developing catalysts with a large number of active sites and excellent mass transfer characteristics can effectively improve ECR activity and current density, thereby effectively overcoming the above limitations.
[0003] The process of ECR to produce formic acid (salt) has advantages such as low overpotential, high selectivity, and high product added value, and is a more promising branch in current ECR technologies. Metallic bismuth (Bi) and its compounds are abundant in reserves, non-toxic, and have low hydrogen evolution activity. Their p orbitals are conducive to adsorbing and activating oxygen atoms in CO2 molecules, making them ideal catalysts for ECR to produce formic acid (salt).
[0004] Research shows that compared with commercial catalysts with scales in the tens of nanometers or even micrometers, ultrathin structure catalysts with nanoscale thickness can provide a higher specific surface area and more sufficient gas-liquid interface contact, effectively improving the ECR current density at the same overpotential and suppressing hydrogen evolution from the dimensions of the number of active sites and carbon dioxide mass transfer efficiency, thus achieving efficient and stable production of formic acid (salt). Summary of the Invention
[0005] The technical problem to be solved by the present invention is to obtain an ultrathin structure ECR catalyst with nanoscale thickness. For this purpose, the present invention provides a method for synthesizing bismuth hydroxide ultrathin nanotube catalysts by a solvothermal method with simple process and low cost, which can achieve the selective conversion of CO2 into formic acid (salt) products with higher added value at high current densities.
[0006] To solve the above problems, the present invention adopts the following technical solutions:
[0007] A preparation method of bismuth hydroxide ultrathin nanotubes, comprising:
[0008] 1) Dissolve an amphiphilic polymer, such as polyether P123, polyether F127, etc., in an alcohol-water mixed solvent by stirring until completely dissolved and clarified to obtain a mixed solution;
[0009] 2) Add a bismuth source and a ligand to the mixed solution obtained in step 1), wherein the bismuth source is a compound containing trivalent bismuth ions, and the ligand is a water-soluble amine, such as Bi(NO3)3·5H2O and hexamethylenetetramine, and stir to obtain a suspension;
[0010] 3) Add a polyol with a volume 5 - 10 times that of the suspension, such as ethylene glycol, to the suspension, and stir to obtain a sol with increased viscosity and re - uniformly dispersed solute; stop stirring and let the sol stand still.
[0011] 4) Transfer the sol to a container for heating reaction, wash the product after the reaction ends, and dry to obtain white bismuth hydroxide ultrathin nanotube powder.
[0012] In some specific embodiments of the present invention, bismuth nitrate is used as the bismuth source, hexamethylenetetramine is used as the ligand, and polyether P123 self - assembles in a mixed solution of ethylene glycol, ethanol, and water to obtain a sol with uniformly dispersed precursors, thereby effectively controlling the precipitation rate of bismuth salts. In the subsequent solvothermal reaction, bismuth hydroxide is finally controllably grown into a hollow tubular structure with a nanoscale thickness. The prepared bismuth hydroxide ultrathin nanotubes have nanoscale ultrathin tube walls and a unique hollow structure, with a tube diameter of 4 - 7 nm and a tube wall thickness of only 0.5 - 2 nm. They have a large specific surface area and a potential gas - liquid interface, and are ideal catalysts for the production of formic acid (salt) by ECR.
[0013] Preferably, in the above step 1), the amphiphilic polymer is polyether P123 or polyether F127, and the concentration of the amphiphilic polymer in the prepared mixed solution is 100 - 200 mg / mL.
[0014] Further, the volume fraction of water in the alcohol - water mixed solvent in the above step 1) is less than or equal to 25%. Preferably, the alcohol - water mixed solvent is a mixed solvent of ethanol and deionized water, and the volume ratio of ethanol to deionized water is 3:1 to 5:1.
[0015] Preferably, in step 1), the mixed solution is stirred for 10 - 60 min to completely dissolve the amphiphilic polymer.
[0016] Further, in step 2), the molar concentration of the bismuth source (calculated as bismuth ions) is 0.1 - 0.2 mol / L, and the molar ratio of the bismuth source to the ligand (calculated as amino groups) is 1:2 to 1:4, such as about 1:3, to coordinate bismuth ions with amino groups and achieve controllable hydrolysis. The stirring time of the suspension is 10 - 60 min.
[0017] Preferably, in step 3), add ethylene glycol with a volume 5 - 10 times that of the suspension to the suspension, stir for 30 - 120 min, and the stirring temperature is 10 - 30 °C; the standing time of the sol is 36 - 120 h, and the standing temperature is 10 - 30 °C.
[0018] Further, the container used in step 4) is airtight, its volume is more than 1.5 times the volume of the sol, the heating temperature is 150 - 200 °C, and the heating time is 1 - 3 h.
[0019] Further, after the reaction in step 4) is completed, the product is washed with ethanol and deionized water. The number of washing times is more than 3 times. After each washing, the product is collected by centrifugation. The solvent for the first washing is ethanol, and the solvents for subsequent washings are ethanol and / or deionized water.
[0020] Preferably, the drying temperature in step 4) is 10 - 60 °C.
[0021] The present invention further provides a catalytic electrode for electrocatalytic reduction of carbon dioxide. The bismuth hydroxide ultrathin nanotubes are loaded on the catalytic electrode, and it can be prepared by the following method: Disperse the bismuth hydroxide ultrathin nanotubes in an alcohol (such as ethanol) or an alcohol - water mixed solvent, and then mix an ion - exchange resin dispersion, such as Nafion or PiperION dispersion, to improve the surface hydrophilic - hydrophobic property and ion conduction performance. After ultrasonic treatment, a uniform catalyst solution is obtained; Take the catalyst solution and drop - coat it on the hydrophobic side of the gas diffusion layer (GDL) or the surface of a porous self - supporting structure, such as hydrophobic carbon paper, carbon cloth, or copper foam. After uniformly drop - coating, it is dried.
[0022] Test the performance of the prepared catalytic electrode for electro - reduction of carbon dioxide in a flow - through electrolytic cell. The flow - through electrolytic cell includes an anodic chamber, a cathodic chamber, a cathodic gas chamber, and an ion - exchange membrane. The anodic electrolyte and the cathodic electrolyte circulate in the anodic chamber and the cathodic chamber respectively, and their components are potassium bicarbonate solution; The catalytic electrode serves as the cathode. The side loaded with the catalyst contacts the cathodic electrolyte, and the other side contacts the flowing carbon dioxide gas in the cathodic gas chamber. The test results show that the catalytic electrode of the present invention has excellent ECR performance.
[0023] Compared with the prior art, the present invention has the following beneficial effects:
[0024] 1. The bismuth hydroxide ultrathin nanotube catalyst has the characteristics of low cost and simple synthesis method;
[0025] 2. The prepared bismuth hydroxide ultrathin nanotube catalyst has a nanoscale ultrathin tube wall and a unique hollow structure, and its specific surface area and mass transfer efficiency are significantly superior to commercial catalysts;
[0026] 3. The bismuth hydroxide ultrathin nanotube electrode material prepared by this method has an extremely wide current density range for electrocatalytic reduction of CO2 to formic acid (salt) and high Faraday efficiency. Specifically, within a current density of 1000 mA cm -2 It can maintain a formic acid (salt) Faraday efficiency of more than 95%, which is significantly superior to commercial catalysts. Description of the Drawings
[0027] Figure 1 is the transmission electron microscope image of the bismuth hydroxide ultrathin nanotubes prepared in the embodiment of the present invention.
[0028] Figure 2 is the X-ray diffraction pattern of the bismuth hydroxide ultrathin nanotubes prepared in the embodiments of the present invention.
[0029] Figure 3 is the thermogravimetric analysis data of the bismuth hydroxide ultrathin nanotubes prepared in the embodiments of the present invention in a nitrogen atmosphere, where (a) is the weight loss curve; (b) is the heat flow curve.
[0030] Figure 4 is the Faraday efficiency of the catalytic product formate in the bismuth hydroxide ultrathin nanotube catalytic electrode prepared in the embodiments of the present invention in a 0.5 mol / L potassium bicarbonate solution at different current densities. Detailed implementation manners
[0031] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings through embodiments.
[0032] In this embodiment, a bismuth hydroxide ultrathin nanotube catalyst was prepared and its performance for electrocatalytic reduction of carbon dioxide was studied.
[0033] 1. Synthesize the bismuth hydroxide ultrathin nanotube catalyst, and the specific method is as follows:
[0034] Dissolve 600 mg of polyether P123 in a mixed solution of 3.6 mL of ethanol and 0.9 mL of deionized water by stirring until the solution becomes completely clear; add 250 mg of Bi(NO3)3·5H2O and 60 mg of hexamethylenetetramine to the mixed solution and stir for 10 min to obtain a suspension; add 30 mL of ethylene glycol to the suspension and stir for 30 min to obtain a sol; stop stirring and let the sol stand at room temperature for 72 h; transfer the sol to a reaction kettle with a polytetrafluoroethylene liner and heat it in an oven at 180 °C for 2 h; after the reaction, wash the product with ethanol, centrifuge it, and then wash the product three times repeatedly with ethanol and deionized water, and dry it to obtain a white bismuth hydroxide ultrathin nanotube catalyst powder.
[0035] 2. Prepare the bismuth hydroxide ultrathin nanotube catalytic electrode by the drop-coating method, and the specific method is as follows:
[0036] Disperse 5 mg of bismuth hydroxide ultrathin nanotubes in 1 mL of ethanol solution, and then mix 0.01 mL of Nafion (5 wt%) solution, and ultrasonically treat it at a power of 35 W for 30 min to obtain a uniform catalyst solution. Take 0.2 mL of the catalyst slurry and drop-coat it on the surface of the carbon paper (CFP, 1×1 cm 2 ), and uniformly drop-coat it until dry under an infrared lamp.
[0037] 3. Test the performance of the prepared electrode for electroreduction of carbon dioxide in a flow-through electrolytic cell, and the specific method is as follows:
[0038] A three - electrode test system was adopted. The prepared bismuth hydroxide ultrathin nanotube catalytic electrode was used as the cathode, and the effective area of the cathode was 0.5×0.5 cm 2 , a platinum sheet or a titanium felt loaded with nano - iridium dioxide was used as the anode, and a mercury - mercuric oxide electrode was used as the reference electrode. The anode electrolyte and the cathode electrolyte were both 0.5 mol / L potassium bicarbonate solution, which circulated in the cathode chamber and the anode chamber respectively, and CO2 gas was introduced from the back of the cathode.
[0039] Figure 1 The transmission electron microscope image of the bismuth hydroxide ultrathin nanotubes prepared in the example is shown. It can be seen that the material is a typical hollow tubular structure, the tube diameter is about 5 nm, and the tube wall thickness is only about 1 nm, with a large specific surface area and a large number of potential gas - liquid interfaces.
[0040] Figure 2 is the X - ray diffraction pattern of the bismuth hydroxide ultrathin nanotubes prepared in the example.
[0041] Figure 3 is the thermogravimetric analysis data of the bismuth hydroxide ultrathin nanotubes prepared in the example in a nitrogen atmosphere. The weight loss law and the weight loss ratio conform to the reaction properties and stoichiometric relationship of bismuth hydroxide losing water.
[0042] Figure 4 is the Faraday efficiency of the bismuth hydroxide ultrathin nanotube catalytic electrode prepared in the example for producing formic acid (salt) at different current densities in a flow cell. It can be seen that the Faraday efficiency of formic acid (salt) is above 95% in a wide current density range up to 1000 mAcm -2 and below, showing excellent ECR performance.
[0043] The above embodiments describe 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 by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the principle of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.
Claims
1. A method for preparing bismuth hydroxide ultrathin nanotubes, comprising: 1) stirring and dissolving the amphiphilic polymer in an alcohol-water mixed solvent until a clear mixed solution is obtained; 2) adding a bismuth source and a ligand to the mixed solution obtained in step 1), wherein the bismuth source is a compound containing trivalent bismuth ions and the ligand is a water-soluble amine, and stirring to obtain a suspension; 3) Add 5-10 times the volume of polyol to the suspension, stir to obtain a sol with increased viscosity and redispersed solute, stop stirring and let the sol stand; 4) The sol is transferred to a container and heated for reaction. After the reaction is completed, the product is washed and dried to obtain white bismuth hydroxide ultra-thin nanotube powder.
2. The preparation method according to claim 1, characterized in that In step 1), the amphiphilic polymer is selected from polyether P123 and polyether F127, and its concentration in the mixed solution is 100-200 mg / mL; the volume proportion of water in the alcohol-water mixed solvent is less than or equal to 25%.
3. The preparation method according to claim 1, characterized in that: In step 2), the bismuth source is bismuth nitrate, and the ligand is hexamethylenetetramine.
4. The preparation method according to claim 1, characterized in that: The molar concentration of the bismuth source added in step 2) is 0.1-0.2 mol / L in terms of bismuth ions, and the molar ratio of the bismuth source in terms of bismuth ions and the ligand in terms of amino groups is 1:2 to 1:
4.
5. The preparation method according to claim 1, characterized in that: In step 3), the polyol is ethylene glycol, the stirring time is 30-120 min, and the stirring temperature is 10-30° C.; the standing time of the sol is 36-120 h, and the standing temperature is 10-30° C.
6. The preparation method according to claim 1, characterized in that: In step 4), the heating reaction temperature is 150-200° C. and the heating time is 1-3 h.
7. The bismuth hydroxide ultra-thin nanotubes obtained by the preparation method according to any one of claims 1 to 6 have nanometer-level ultra-thin tube walls and hollow structures, the nanotube diameter is 4-7 nm, and the tube wall thickness is 0.5-2 nm.
8. Use of the bismuth hydroxide ultrathin nanotubes according to claim 7 as a catalyst for electrocatalytic reduction of carbon dioxide.
9. A catalytic electrode for electrocatalytic reduction of carbon dioxide, characterized in that: The catalytic electrode is loaded with the bismuth hydroxide ultra-thin nanotubes described in claim 7 as a catalyst.
10. A method for electrocatalytic reduction of carbon dioxide, using a flowing electrolytic cell, wherein the flowing electrolytic cell comprises an anode chamber, a cathode chamber and a cathode gas chamber, wherein an anolyte and a cathode electrolyte circulate in the anode chamber and the cathode chamber respectively; characterized in that: The catalytic electrode according to claim 9 is used as the cathode, and one side of the catalytic electrode carrying the bismuth hydroxide ultra-thin nanotube catalyst is in contact with the cathode electrolyte, and the other side is in contact with the flowing carbon dioxide gas in the cathode gas chamber.