A natural polymer structure-induced copper-based material and a preparation method and application thereof
A three-step electrochemical method was used to prepare a self-supporting copper catalytic electrode induced by the structure of natural polymers, which solved the problem of selectively producing multiple carbon products from carbon dioxide reduction at high current densities. This method enabled the preparation of highly selective and stable ethanol and improved the catalytic performance of copper-based materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF CHEM CHINESE ACAD OF SCI
- Filing Date
- 2022-09-15
- Publication Date
- 2026-06-19
AI Technical Summary
In the existing technology, it is difficult to efficiently reduce carbon dioxide to selectively prepare highly selective multi-carbon products, especially ethanol, at high current densities, due to insufficient activity and stability of copper-based catalysts.
A three-step electrochemical method was used to prepare a self-supporting copper catalytic electrode induced by natural polymer structure. A copper-based precursor was synthesized on a carbon fiber substrate, and the self-supporting copper catalytic electrode was generated in situ under carbon dioxide electroreduction. The chelating and structure-inducing effects of natural polymers such as chitin, chitosan or chitosan oligosaccharide were utilized to improve catalytic activity and selectivity of target products.
It achieves highly selective ethanol production at high current density with good catalytic stability, low cost, good reproducibility, and environmental friendliness, and significantly improves the Faraday efficiency and stability of the catalyst.
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Figure CN117737753B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of green chemistry technology, specifically relating to a copper-based material induced by the structure of a natural polymer, its preparation method, and its application in the electrochemical reduction of carbon dioxide to prepare multi-carbon products. Background Technology
[0002] Electrochemical carbon dioxide reduction can effectively utilize renewable energy to convert carbon dioxide into high-value-added chemicals, and its green and sustainable development has attracted widespread attention. However, how to achieve efficient reduction of carbon dioxide to highly selective multi-carbon products at high current densities has always been a key research focus and challenge in this field.
[0003] Among the various products generated from the reduction of carbon dioxide, ethanol is a valuable and highly useful chemical raw material with wide applications in the chemical industry, medical and health fields, food industry, and agricultural production. Currently, the known Faraday efficiencies of electrocatalysts for the reduction of carbon dioxide to polyols are generally below 45%, with current densities less than 200 mA / cm², and they are generally accompanied by the formation of multiple multi-carbon products. Therefore, preparing highly selective, efficient, and stable electrocatalysts remains a significant challenge. Copper-based materials exhibit good catalytic activity for the formation of multi-carbon products, but their selectivity is usually not outstanding. Therefore, a copper-based catalytic material can be designed to improve the reaction activity and the selectivity of the target product by adjusting the surface electronic structure of the catalyst and its interaction with reaction intermediates through lattice strain. Summary of the Invention
[0004] This invention is the first to utilize a three-step electrochemical method to prepare a self-supporting copper catalytic electrode induced by the structure of a natural polymer, and uses it as a cathode electrode for the electrocatalytic reduction of carbon dioxide to prepare multi-carbon products. It exhibits high catalytic activity, ethanol selectivity and stability, and has superior performance.
[0005] The technical solution adopted in this invention is as follows:
[0006] This invention provides a method for preparing a self-supporting copper catalytic electrode induced by a natural polymer structure.
[0007] The method for preparing a self-supporting copper catalytic electrode induced by natural polymer structure provided by the present invention includes the following steps: in the presence of a natural polymer, a copper-based precursor is synthesized on a carbon fiber substrate by an electrochemical method, and then a self-supporting copper catalytic electrode is generated in situ in a potassium hydroxide solution or a potassium bicarbonate solution under a carbon dioxide electroreduction environment.
[0008] The natural polymers include chitin, chitosan, or chitosan oligosaccharides. The chitosan may be low-viscosity chitosan (viscosity range 100-200 mPa·s), medium-viscosity chitosan (viscosity range 200-400 mPa·s), or high-viscosity chitosan (viscosity range >400 mPa·s).
[0009] The salts used in the electrochemical synthesis of copper-based precursors are copper chloride, copper sulfate, copper nitrate, or copper acetylacetone.
[0010] Furthermore, the above preparation method specifically includes the following steps:
[0011] a) Prepare a suspension of natural polymer and copper salt, stir at room temperature for more than 6 hours, then centrifuge, wash and dry to obtain a copper ion-natural polymer chelate.
[0012] b) The copper ion-natural polymer chelate obtained in step a) is drop-coated onto a carbon fiber substrate (such as hydrophobic carbon paper) as a working electrode and treated with a constant current method to obtain copper nanoparticles reduced to zero valence on the carbon fiber substrate.
[0013] c) Using the carbon fiber substrate processed in step b) as the working electrode, constant potential mode electrodeposition is performed to obtain a copper-based precursor.
[0014] d) The precursor obtained in step c) is dried and used as the working electrode. A mercury-mercury oxide electrode is selected as the reference electrode and a nickel mesh electrode is selected as the counter electrode. Carbon dioxide electrochemical reduction is carried out in a flow electrolytic cell. The electrolyte is potassium hydroxide solution or potassium bicarbonate solution. Finally, a self-supporting copper catalytic electrode induced by natural polymer is obtained.
[0015] In step a) of the above method, the concentration of natural polymer in the suspension can be 5 to 20 g / L (specifically, 10 g / L), and the concentration of copper ions in the suspension is 0.005 to 0.15 mol / L.
[0016] Step b) of the above method specifically includes: drop-coating the copper ion-natural polymer obtained in step a) onto a carbon fiber substrate (such as hydrophobic carbon paper) as the working electrode, using a silver-silver chloride electrode as the reference electrode, and a platinum mesh electrode as the counter electrode. The electrode is placed in a carbon dioxide-saturated KHCO3 solution and electrolyzed in a constant current mode to obtain copper nanoparticles reduced to the zero valence state on the carbon fiber substrate.
[0017] The concentration of the KHCO3 solution is 0.1 to 5 mol per liter (specifically, 1 mol per liter).
[0018] The constant current mode has a current density of -100 to -500 mA and an electrolysis time of 1000 to 3000 seconds.
[0019] The above method step c) specifically includes: using the carbon fiber substrate treated in step b) as the working electrode, the silver-silver chloride electrode as the reference electrode, and the platinum mesh electrode as the counter electrode, and placing it in a copper ion-containing solution or a copper ion-acid solution, constant potential mode electrodeposition can be performed at multiple potentials to obtain different precursors.
[0020] The copper ion concentration in the copper ion-containing solution or copper ion-acid solution is 0.005–0.15 mol / L, and the hydrogen ion concentration is 0–1 mol / L. The reduction potential set for the constant potential mode electrodeposition is -1.1 to -1.6 V (relative to the silver / silver chloride reference electrode), and the electrodeposition time is 200–1000 seconds (e.g., 600 seconds).
[0021] In step d) of the above method, the concentration of the potassium hydroxide solution is 0.1–5 mol / L (specifically, 1 mol / L). The concentration of the potassium bicarbonate solution is 0.1–5 mol / L.
[0022] In step d) of the above method, the conditions for the electrochemical reduction of carbon dioxide are: -100 to -1000 mA in constant current mode, and micron rod copper catalyst can be obtained within one minute, with no limit on the specific reaction time.
[0023] The self-supporting copper catalytic electrode prepared by the above method is also within the scope of protection of this invention.
[0024] This invention also protects the use of the above-mentioned self-supporting copper catalytic electrode in the preparation of electrode materials.
[0025] Preferably, the self-supporting copper catalytic electrode is used as a cathode electrode for the electrocatalytic reduction of carbon dioxide to prepare multi-carbon products.
[0026] This invention also protects a method for preparing multi-carbon products by electrocatalytic reduction of carbon dioxide.
[0027] The method involves using the self-supporting copper catalytic electrode as the working electrode, the mercury-mercury oxide electrode as the reference electrode, and the platinum electrode as the counter electrode in an electrocatalytic carbon dioxide conversion system, employing a constant current mode in a saturated CO2 electrolyte to perform electrocatalytic CO2 conversion and obtain multi-carbon products.
[0028] The electrolyte is a potassium hydroxide solution or a potassium bicarbonate solution; the concentration of the potassium hydroxide solution or potassium bicarbonate solution is 0.1 to 5 mol per liter (specifically, 1 mol per liter).
[0029] The current density in the constant current mode is -100 to -1000 mA.
[0030] The multi-carbon products include PrOH, EtOH, CH3COOH, and C2H4.
[0031] Compared with the prior art, the present invention has the following beneficial effects:
[0032] The preparation method of this invention is a three-step electrochemical method. The preparation method of the catalytic material is simple, low-cost, highly reproducible, and environmentally friendly. The preparation method provided by this invention is unique and ingenious, utilizing the chelating and structural induction effects of natural polymers on copper ions, offering a new approach for synthesizing highly active electrode materials for the conversion of carbon dioxide to multi-carbon products. The self-supporting copper catalytic electrode synthesized by this method can achieve high ethanol selectivity at high current densities and exhibits high catalytic stability. Attached Figure Description
[0033] To illustrate the core solutions of the embodiments of the present invention and the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0034] Figure 1 A scanning electron microscope image of the self-supporting copper precursor prepared in Example 1;
[0035] Figure 2 This is a scanning electron microscope image of the self-supporting copper material prepared in Example 1;
[0036] Figure 3 X-ray diffraction pattern of the self-supporting copper material prepared in Example 1;
[0037] Figure 4 The elemental distribution diagram is shown for the self-supporting copper material prepared in Example 1.
[0038] Figure 5 Scanning electron microscope image of the low-viscosity chitosan-induced low-concentration copper ion self-supporting copper material prepared in Example 2;
[0039] Figure 6 This is a scanning electron microscope image of the low-viscosity chitosan-induced high-concentration copper ion self-supporting copper material prepared in Example 3;
[0040] Figure 7 This is a scanning electron microscope image of the self-supporting copper material with low concentration of copper ions induced by medium viscosity chitosan prepared in Example 4.
[0041] Figure 8 This is a scanning electron microscope image of the self-supporting copper material with high concentration of copper ions induced by medium viscosity chitosan prepared in Example 5.
[0042] Figure 9Scanning electron microscope image of the self-supporting copper material with low concentration of copper ions induced by high viscosity chitosan prepared in Example 6;
[0043] Figure 10 Scanning electron microscope image of the high-viscosity chitosan-induced high-concentration copper ion self-supporting copper material prepared in Example 7;
[0044] Figure 11 The graph shows the carbon dioxide electrochemical reduction performance of the self-supporting copper material prepared in Example 1.
[0045] Figure 12 The graph shows the performance stability of the self-supporting copper material prepared in Example 1 in catalyzing the conversion of carbon dioxide into multi-carbon products. The test current was -900 mA per square centimeter. Detailed Implementation
[0046] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments. Unless otherwise specified, the methods described are conventional methods. Unless otherwise specified, the raw materials are all available from publicly available commercial sources.
[0047] Example 1:
[0048] a. Prepare 30 mL of a 0.015 mol / L copper chloride solution, disperse 0.2 g of low-viscosity chitosan (100-200 mPa·s) in the solution, stir at room temperature for more than 6 hours, then centrifuge, wash, and dry to obtain a copper ion-chitosan chelate.
[0049] b. Prepare a 1 mol / L potassium bicarbonate solution, and saturate it with carbon dioxide. Drop-coat a copper ion-chitosan chelate (2.5 mg / cm²) onto hydrophobic carbon paper as the working electrode. Select a silver-silver chloride electrode as the reference electrode and a platinum mesh electrode as the counter electrode. Perform constant current mode electrodeposition at -100 mA for 1000 seconds in the above solution to obtain copper nanoparticles reduced to the zero valence state on the hydrophobic carbon paper.
[0050] c. Prepare a solution containing 0.015 mol / L copper chloride and 0.2 mol / L hydrochloric acid. Place the carbon paper from step b in this solution as the working electrode, select a silver-silver chloride electrode as the reference electrode, and a platinum mesh electrode as the counter electrode. Perform constant potential mode electrodeposition for 600 seconds at potentials ranging from -1.1 V to -1.6 V to obtain different precursors on the hydrophobic carbon paper.
[0051] Figure 1 This is a scanning electron microscope (SEM) image of a self-supporting copper precursor obtained by potentiostatic electrodeposition using a constant potential of -1.1 volts.
[0052] d. The precursor obtained in step c is dried and used as the working electrode. A mercury-mercury oxide electrode is selected as the reference electrode and a nickel mesh electrode is selected as the counter electrode. Electrochemical reduction of carbon dioxide is carried out in a flow electrolytic cell (constant current -500 mA). The electrolyte is a 1 mol / L potassium hydroxide solution. Finally, a chitosan-induced self-supporting copper catalytic electrode is obtained on hydrophobic carbon paper.
[0053] The self-supporting copper precursor obtained by electrodeposition under the above-mentioned constant potential condition of -1.1V was processed in step d. The resulting scanning electron microscope image, X-ray diffraction pattern, and elemental distribution map of the self-supporting copper catalytic electrode are shown in the figure. Figure 2-4 .
[0054] Example 2:
[0055] By changing the copper chloride concentration in Example 1 to 0.005 mol / L, a self-supporting copper material with low viscosity chitosan-induced low concentration of copper ions can be obtained. See the scanning electron microscope image for details. Figure 5 .
[0056] Example 3:
[0057] By changing the copper chloride concentration in Example 1 to 0.15 mol / L, a self-supporting copper material with a high concentration of copper ions induced by low viscosity chitosan can be obtained. See the scanning electron microscope image for details. Figure 6 .
[0058] Example 4:
[0059] By replacing the low-viscosity chitosan in Example 2 with medium-viscosity chitosan (200-400 mPa·s), a self-supporting copper material with low concentration of copper ions induced by medium-viscosity chitosan can be obtained. See the scanning electron microscope image for details. Figure 7 .
[0060] Example 5:
[0061] By replacing the chitosan in Example 3 with medium-viscosity chitosan, a self-supporting copper material with a high concentration of copper ions induced by medium-viscosity chitosan can be obtained. See the scanning electron microscope image for details. Figure 8 .
[0062] Example 6:
[0063] Replacing the chitosan in Example 2 with high-viscosity chitosan (>400 mPa·s) ultimately yields a self-supporting copper material with low concentration of copper ions induced by high-viscosity chitosan. See the scanning electron microscope image for details. Figure 9 .
[0064] Example 7:
[0065] Replacing the chitosan in Example 3 with high-viscosity chitosan ultimately yields a self-supporting copper material with a high concentration of copper ions induced by high-viscosity chitosan. See the scanning electron microscope image for details. Figure 10 .
[0066] Example 8:
[0067] The electrochemical reduction performance of the self-supporting copper catalyst induced by the natural polymer structure of this invention was tested using a three-electrode system (constant current method): the reference electrode was a mercury-mercury oxide electrode, the counter electrode was a platinum mesh electrode, and the working electrode was the self-supporting copper material finally prepared in Examples 1-7. The tests were conducted in a flow electrolyzer with a 1 mol / L potassium hydroxide solution as the electrolyte, and carbon dioxide (flow rate 50 mL / min) circulating in the gas chamber. The optimal electrochemical reduction performance of the self-supporting copper catalyst in Example 1 is described in [reference needed]. Figure 11 .from Figure 11 It can be seen that the distribution of carbon dioxide reduction products changes significantly with the change of current. At 800 mA / cm² (-0.80 V vs RHE), the Faraday efficiency of alcohols reaches 54.7%, with a partial current density of 437.6 mA / cm². At 900 mA / cm² (-0.87 V vs RHE), C… 2+ The products (including PrOH, EtOH, CH3COOH, C2H4) have a Faradaic efficiency of 88.2%, of which alcohols account for 51.4%.
[0068] Example 9:
[0069] The catalytic stability of the self-supporting copper material in Example 1 was tested using the carbon dioxide reduction testing apparatus described in Example 8. Stability testing was conducted at 900 mA / cm², and the voltage and C values were obtained. 2+ For Faraday efficiency, see the curves of alcohol Faraday efficiency versus time. Figure 12 .from Figure 12 It can be seen that after 24 hours of testing, the self-supporting copper material can maintain its catalytic activity well.
[0070] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.
Claims
1. A method for preparing a self-supporting copper catalytic electrode induced by a natural polymer structure, comprising the following steps: a) Prepare a suspension of natural polymer and copper salt, stir at room temperature for more than 6 hours, then centrifuge, wash and dry to obtain a copper ion-natural polymer chelate. b) The copper ion-natural polymer obtained in step a) was drop-coated onto a carbon fiber substrate as a working electrode and treated with a constant current method to obtain copper nanoparticles reduced to zero valence on the carbon fiber substrate. c) Using the carbon fiber substrate treated in step b) as the working electrode, place it in a copper ion solution or a copper ion-acid solution and perform constant potential mode electrodeposition to obtain a copper-based precursor. d) The precursor obtained in step c) is dried and used as the working electrode. A mercury-mercury oxide electrode is selected as the reference electrode and a nickel mesh electrode is selected as the counter electrode. Carbon dioxide electrochemical reduction is carried out in a flow electrolytic cell. The electrolyte is potassium hydroxide solution or potassium bicarbonate solution, and finally a self-supporting copper catalytic electrode is obtained. The natural polymers include chitin, chitosan, or chitooligosaccharides; The copper-based precursor is copper nanoparticles coated with a natural polymer. The salt used in the copper ion-containing solution or copper ion-acid solution is copper chloride, copper sulfate, copper nitrate, or copper acetylacetonate.
2. The preparation method according to claim 1, characterized in that: In step a), the concentration of natural polymer in the suspension is 5-20 g / L, and the concentration of copper ions in the suspension is 0.005-0.15 mol / L. Step b) specifically includes: drop-coating the copper ion-natural polymer obtained in step a) onto a carbon fiber substrate as a working electrode, using a silver-silver chloride electrode as a reference electrode and a platinum mesh electrode as a counter electrode, placing it in a carbon dioxide-saturated KHCO3 solution, and performing electrolysis treatment in constant current mode to obtain copper nanoparticles reduced to zero valence state on the carbon fiber substrate. The concentration of the KHCO3 solution is 0.1 to 5 mol per liter; The constant current mode has a current of -100 to -500 mA and an electrolysis time of 1000 to 3000 seconds.
3. The production method according to claim 1 or 2, characterized by: Step c) specifically includes: using the carbon fiber substrate treated in step b) as the working electrode, the silver-silver chloride electrode as the reference electrode, and the platinum mesh electrode as the counter electrode, placing it in a copper ion-containing solution or a copper ion-acid solution, and performing constant potential mode electrodeposition to obtain the precursor. Wherein, the copper ion concentration in the copper ion-containing solution or copper ion-acid solution is 0.005~0.15 mol / L, and the hydrogen ion concentration is 0~1 mol / L; the reduction potential set for the constant potential mode electrodeposition is -1.1 to -1.6 V, and the electrodeposition time in the constant potential mode is 200~1000 seconds.
4. The production method according to claim 1 or 2, characterized by: In step d), the concentration of the potassium hydroxide solution is 1 mole per liter; The conditions for the electrochemical reduction of carbon dioxide are: -100 to -1000 mA in constant current mode, and micron-sized copper catalyst can be obtained within one minute.
5. The self-supporting copper catalytic electrode prepared by the method according to any one of claims 1-4.
6. The application of the self-supporting copper catalytic electrode according to claim 5 in the preparation of electrode materials.
7. Use according to claim 6, characterized in that: The self-supporting copper catalytic electrode is used as a cathode electrode for the electrocatalytic reduction of carbon dioxide to prepare multi-carbon products.
8. A method for preparing multi-carbon products by electrocatalytic reduction of carbon dioxide, comprising the following steps: in an electrocatalytic carbon dioxide conversion system, using the self-supporting copper catalytic electrode as described in claim 5 as the working electrode, a mercury-mercury oxide electrode as the reference electrode, and a platinum electrode as the counter electrode, electrocatalytic CO2 conversion is carried out in a constant current mode in a saturated CO2 electrolyte to obtain multi-carbon products.
9. The method of claim 8, wherein: The electrolyte is a potassium hydroxide solution or a potassium bicarbonate solution; the concentration of the potassium hydroxide solution or potassium bicarbonate solution is 0.1~5 mol per liter; The current in the constant current mode is -100 to -1000 mA; The multi-carbon products include PrOH, EtOH, CH3COOH, and C2H4.