A polymer and copper co-doped coal-based composite material and its preparation method and application
By using polymer and copper co-doped coal-based composite materials as electrocatalysts, the problems of slow catalytic kinetics and hydrogen evolution during the ethylene overpotential process are solved, and efficient ethylene selectivity and current density are achieved.
Patent Information
- Application Number
- CN202310367865.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-07
- Publication Date
- 2025-05-02
- Estimated Expiration
- 2043-04-07
AI Technical Summary
Traditional polycrystalline copper catalysts have slow catalytic kinetics during the ethylene overpotential process, resulting in less ethylene selectivity and current density, and serious hydrogen evolution problems.
Co-doped coal-based composite materials are used as electrocatalysts. Through the adjustment of the porous structure of the coal-based material and the polymer layer, the crystallinity of copper is reduced, the hydrogen evolution property of the catalyst is suppressed, and the selectivity of ethylene is improved.
The ethylene activity of the catalyst is significantly improved, the ethylene Faraday efficiency can reach up to 62%, the current density of the ethylene part can reach up to 142.4mA/cm2, and the electrochemical performance is excellent.
Smart Images
Figure CN116377507B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of inorganic nanomaterials and electrochemistry, and relates to a coal-based material, and in particular to a polymer and copper co-doped coal-based composite material, and a preparation method and application thereof. Background Art
[0002] The rapid development of modern industry has intensified the use of traditional fossil fuels by humans. The large amount of CO2 produced has destroyed the originally stable carbon cycle in nature, leading to serious ecological problems. Therefore, the CO2 problem needs to be solved urgently. Using CO2 as a base material to produce high-value-added chemicals or fuels is a very promising strategy to reduce or even get rid of human dependence on fossil fuels and achieve rapid decarbonization. Compared with traditional thermal catalytic CO2 hydrogenation technology, electrocatalytic CO2 reduction (ECR) technology driven by renewable energy is particularly promising because it can not only operate at room temperature and pressure, but also obtain a variety of reduction products, such as CO, formic acid, methane, ethylene and ethanol. In particular, the preparation of ethylene products by ECR has attracted widespread attention from researchers because ethylene is one of the most important basic raw materials in the chemical industry.
[0003] The conversion of CO2 to ethylene on the electrode surface undergoes a multi-step proton-coupled electron transfer (PCET) process, so this places extremely high demands on the activity and stability of the catalyst. Currently, compared with other materials, copper exhibits ethylene activity because it has suitable adsorption energy for key ethylene intermediates such as *CO and *CO*CHO. However, the catalytic kinetics of traditional polycrystalline copper are slow, which makes their ethylene overpotential high and the hydrogen evolution problem serious. Therefore, the ethylene selectivity and current density of polycrystalline copper catalysts are relatively small. Summary of the invention
[0004] One of the purposes of the present invention is to provide a method for preparing a polymer and copper co-doped coal-based composite material, the synthesis steps of which are simple and controllable and the cost is low.
[0005] The second object of the present invention is to provide a polymer and copper co-doped coal-based composite material prepared by the above preparation method, which can reduce the crystallinity of copper, inhibit the hydrogen evolution of the catalyst, and improve the selectivity of ethylene.
[0006] The third object of the present invention is to provide the application of the above polymer and copper co-doped coal-based composite material.
[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0008] In one aspect, the present invention provides a method for preparing a polymer and copper co-doped coal-based composite material, comprising the following steps:
[0009] (1) Coal powder and potassium hydroxide were weighed in a mass ratio of 1:3, and deionized water and ethanol were added; the mixture was heated to 80°C and stirred vigorously until the solvent was completely evaporated; the mixture was placed in a vacuum oven at 80°C for 12 hours;
[0010] (2) placing the dry powder obtained in step (1) into a tube furnace, heating it to 600-900° C. in an inert atmosphere, and keeping the temperature for 30 min, and then naturally cooling it to room temperature; acid washing, filtering, washing, and drying to obtain porous coal;
[0011] (3) Weigh porous coal, polymer, surfactant and copper salt in a mass ratio of 0.1 g: 0.5 g: 1 g: 2 mmol, add deionized water and ethanol, heat the mixture to 40-80 ° C and stir vigorously for 30 min; add sodium hydroxide to the mixture, continue stirring for 30 min, then add ascorbic acid, and continue stirring for 30 min; the polymer is one or more of polytetrafluoroethylene, fluorinated ethylene propylene copolymer, polyaniline, phenolic resin, polyacrylonitrile; the surfactant is one or more of polyoxyethylene alkyl ether, sodium dodecylbenzene sulfonate, anhydrous sorbitan fatty acid ester, hexadecyltrimethylammonium bromide, polysorbate and dodecylamine acetate; the copper salt is one or more of copper nitrate, copper sulfate, copper citrate, copper acetate, copper acetylacetonate, basic copper carbonate and copper chloride;
[0012] (4) The precipitate obtained in step (3) is centrifuged and washed three times with water, and the obtained solid is placed in an oven and dried for 12 hours.
[0013] Preferably, in step (1), the coal powder is anthracite coal powder.
[0014] Preferably, in step (2), the calcination temperature is 750°C.
[0015] Preferably, in step (3), the polymer is polytetrafluoroethylene, the surfactant is polyoxyethylene alkyl ether, and the copper salt is copper nitrate; in this case, the catalytic performance is optimal.
[0016] Preferably, in step (3), the heating temperature is 55°C.
[0017] Preferably, in step (3), the mass ratio of the sodium hydroxide to the copper salt is 6-7:1, and the mass ratio of the ascorbic acid to the copper salt is 0.01-2 g:2 mmol.
[0018] More preferably, in step (3), the mass ratio of the sodium hydroxide to the copper salt is 6.25:1, and the mass ratio of the ascorbic acid to the copper salt is 0.05 g:2 mmol.
[0019] Preferably, in step (1), the volume ratio of deionized water to ethanol is 1:1; and in step (3), the volume ratio of deionized water to ethanol is 8-9:1.
[0020] In a second aspect, the present invention also provides a polymer and copper co-doped coal-based composite material prepared by the above preparation method.
[0021] In a third aspect, the present invention also provides the use of the above polymer and copper co-doped coal-based composite material in the electrocatalytic reduction of carbon dioxide to produce ethylene.
[0022] The polymer and copper co-doped coal-based composite material can be used as a cathode catalyst for electrocatalytic reduction of carbon dioxide. The method is as follows: 10 mg of the prepared polymer and copper co-doped coal-based composite material is weighed into a sample tube, and then 20 μL of perfluorosulfonic acid-polytetrafluoroethylene copolymer and 980 μL of isopropanol are added, and ultrasonic treatment is performed for 60 minutes to form a well-dispersed black solution, and then the solution is dropped on carbon paper or a gas diffusion layer and dried to prepare a working electrode.
[0023] Compared with the existing technology, the present invention has the following beneficial effects:
[0024] (1) The raw materials used in the present invention, such as coal, copper salt and polymer, are widely available and inexpensive, and are suitable for large-scale production.
[0025] (2) The coal used in the present invention has a robust carbon skeleton, a stable structure, good electrical conductivity, and a rich pore structure. Loading copper species on the coal carrier can reduce the crystallinity of copper, thereby significantly increasing the number of copper active sites of the catalyst and improving the ethylene activity of the catalyst. In addition, the coal carrier can also prevent the migration and loss of copper species during the electrochemical process, thereby improving the stability of the catalyst.
[0026] (3) The present invention loads a layer of polymer on the surface of the coal-based catalyst, which can effectively adjust the microenvironment of the catalyst surface, reduce the proton concentration near the copper active site, and thus inhibit the hydrogen evolution of the catalyst and improve the selectivity of ethylene.
[0027] (4) The polymer and copper co-doped coal-based composite material prepared by the present invention has excellent ethylene activity, and its ethylene Faraday efficiency can reach up to 62%, and the maximum ethylene partial current density can reach 142.4 mA / cm 2 , excellent electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 This is the nitrogen adsorption and desorption isotherm of porous coal.
[0029] Figure 2 This is a transmission electron microscope image of the polymer and copper co-doped coal-based composite material prepared in Example 1 of the present invention.
[0030] Figure 3 This is the carbon dioxide adsorption isotherm of the polymer and copper co-doped coal-based composite material prepared in Example 1 of the present invention.
[0031] Figure 4 This is a water contact angle diagram of the polymer and copper co-doped coal-based composite material prepared in Example 1 of the present invention.
[0032] Figure 5 This is the cyclic voltammetry curve of the polymer and copper co-doped coal-based composite material prepared in Example 1 of the present invention in a carbon dioxide atmosphere.
[0033] Figure 6 This is a diagram of the ethylene Faraday efficiency of the polymer and copper co-doped coal-based composite materials prepared in Examples 1-5 of the present invention at different potentials.
[0034] Figure 7 Graphs showing ethylene current density at different potentials for the polymer and copper co-doped coal-based composite materials prepared in Examples 1-5 of the present invention. DETAILED DESCRIPTION
[0035] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0036] The present invention uses coal as a raw material, and the coal can be one or more of lignite, long flame coal, non-caking coal, weakly caking coal, medium caking coal, gas coal, gas-fat coal, fat coal, coking coal, lean coal, lean lean coal, lean coal and anthracite. Among them, anthracite has the best effect. The following examples are illustrated by selecting anthracite as a raw material.
[0037] Put large particles of anthracite into a ball mill and grind them at 400 rpm for two hours to obtain anthracite powder.
[0038] Example 1
[0039] Weigh 0.3g of anthracite coal powder and 0.9g of potassium hydroxide, add 5mL of deionized water and 5mL of ethanol; heat the mixture to 80℃ and stir vigorously until the solvent is completely volatilized; put the mixture into a vacuum oven at 80℃ for 12h; put the obtained dry powder into a tube furnace, heat it to 750℃ in a nitrogen atmosphere, and keep it warm for 30min, then cool it naturally to room temperature; after acid washing, filtration, washing and drying, porous coal is obtained. Weigh 0.1g of porous coal, 0.5g of polytetrafluoroethylene, 1g of polyoxyethylene alkyl ether and 2mmol of copper nitrate, add 45mL of deionized water and 5mL of ethanol, heat the mixture to 55℃ and stir vigorously for 30min; add 0.5g of sodium hydroxide to the mixture; add 0.05g of ascorbic acid after 30min, and continue stirring for 30min; centrifuge the obtained precipitate, wash it with water three times, and put the obtained solid into an oven to dry for 12h.
[0040] Figure 1 It is the nitrogen adsorption-desorption isotherm of porous coal. When the relative pressure of porous coal is <0.1, the nitrogen adsorption amount of porous coal increases rapidly, indicating that porous coal has rich microporous structure, which is conducive to anchoring metal active sites on porous coal.
[0041] The polymer and copper co-doped coal-based composite material prepared in this example was placed under a transmission electron microscope (TEM) for observation. Figure 2 As shown, it can be seen that the surface of the coal matrix is covered with a large amount of Cu species and polytetrafluoroethylene, which indicates that the Cu species and polytetrafluoroethylene are successfully loaded onto the coal matrix. This composite structure provides a large number of active sites for carbon dioxide reduction.
[0042] Example 2
[0043] Weigh 0.3g of anthracite coal powder and 0.9g of potassium hydroxide, add 5mL of deionized water and 5mL of ethanol; heat the mixture to 80℃ and stir vigorously until the solvent is completely volatilized; put the mixture into a vacuum oven at 80℃ for 12h; put the obtained dry powder into a tube furnace, heat it to 750℃ in a nitrogen atmosphere, and keep it warm for 30min, then cool it naturally to room temperature; after acid washing, filtration, washing and drying, porous coal is obtained. Weigh 0.1g of porous coal, 0.5g of polyaniline, 1g of polyoxyethylene alkyl ether and 2mmol of copper nitrate, add 45mL of deionized water and 5mL of ethanol, heat the mixture to 55℃ and stir vigorously for 30min; add 0.5g of sodium hydroxide to the mixture; add 0.05g of ascorbic acid after 30min, and continue stirring for 30min; centrifuge the obtained precipitate, wash it with water three times, and put the obtained solid into an oven to dry for 12h.
[0044] Example 3
[0045] Weigh 0.3g of anthracite coal powder and 0.9g of potassium hydroxide, add 5mL of deionized water and 5mL of ethanol; heat the mixture to 80℃ and stir vigorously until the solvent is completely volatilized; put the mixture into a vacuum oven at 80℃ for 12h; put the obtained dry powder into a tube furnace, heat it to 750℃ in a nitrogen atmosphere, and keep it warm for 30min, then cool it naturally to room temperature; after acid washing, filtration, washing and drying, porous coal is obtained. Weigh 0.1g of porous coal, 0.5g of polytetrafluoroethylene, 1g of hexadecyltrimethylammonium bromide and 2mmol of copper nitrate, add 45mL of deionized water and 5mL of ethanol, heat the mixture to 55℃ and stir vigorously for 30min; add 0.5g of sodium hydroxide to the mixture; add 0.05g of ascorbic acid after 30min, and continue stirring for 30min; centrifuge the obtained precipitate, wash it with water three times, and put the obtained solid into an oven to dry for 12h.
[0046] Example 4
[0047] Weigh 0.3g of anthracite coal powder and 0.9g of potassium hydroxide, add 5mL of deionized water and 5mL of ethanol; heat the mixture to 80℃ and stir vigorously until the solvent is completely volatilized; put the mixture into a vacuum oven at 80℃ for 12h; put the obtained dry powder into a tube furnace, heat it to 750℃ in a nitrogen atmosphere, and keep it warm for 30min, then cool it naturally to room temperature; after acid washing, filtration, washing and drying, porous coal is obtained. Weigh 0.1g of porous coal, 0.5g of polytetrafluoroethylene, 1g of polyoxyethylene alkyl ether and 2mmol of copper acetylacetonate, add 45mL of deionized water and 5mL of ethanol, heat the mixture to 55℃ and stir vigorously for 30min; add 0.5g of sodium hydroxide to the mixture; add 0.05g of ascorbic acid after 30min, and continue stirring for 30min; centrifuge the obtained precipitate, wash it with water three times, and put the obtained solid into an oven to dry for 12h.
[0048] Example 5
[0049] Weigh 0.3g of anthracite coal powder and 0.9g of potassium hydroxide, add 5mL of deionized water and 5mL of ethanol; heat the mixture to 80℃ and stir vigorously until the solvent is completely volatilized; put the mixture into a vacuum oven at 80℃ for 12h; put the obtained dry powder into a tube furnace, heat it to 750℃ in a nitrogen atmosphere, and keep it warm for 30min, then cool it naturally to room temperature; after acid washing, filtration, washing and drying, porous coal is obtained. Weigh 0.1g of porous coal, 0.5g of polytetrafluoroethylene, 1g of polyoxyethylene alkyl ether and 2mmol of copper nitrate, add 45mL of deionized water and 5mL of ethanol, heat the mixture to 55℃ and stir vigorously for 30min; add 0.5g of sodium hydroxide to the mixture; add 2g of ascorbic acid after 30min, and continue stirring for 30min; centrifuge the obtained precipitate, wash it with water three times, and put the obtained solid into an oven to dry for 12h.
[0050] The polymer and copper co-doped coal-based composite materials prepared in Examples 1-5 were characterized and tested according to the following scheme.
[0051] (1) Carbon dioxide adsorption isotherm
[0052] like Figure 3 As shown in Figure 1, the coal-based composite material prepared in Example 1 can adsorb up to 3.85 cm2 of carbon dioxide at room temperature and pressure. 3 This indicates that the porous coal matrix and Cu species of coal-based materials are conducive to the adsorption of carbon dioxide, which in turn can provide sufficient reaction substrates for Cu active sites, thereby promoting the carbon dioxide reduction reaction.
[0053] (2) Water contact angle
[0054] like Figure 4 As shown, the water contact angle of the coal-based composite material prepared in Example 1 is 141°, indicating that the surface of the material is hydrophobic. This shows that the polytetrafluoroethylene polymer on the surface of the coal-based composite material can effectively reduce the proton concentration on the surface of the material, which is conducive to inhibiting the hydrogen evolution performance of the material and then improving the selectivity of the ethylene product.
[0055] (3) Catalytic performance test
[0056] 10 mg of the prepared coal-based composite material was weighed into a sample tube, followed by the addition of 20 μL of perfluorosulfonic acid-polytetrafluoroethylene copolymer and 980 μL of isopropanol, and ultrasonic treatment was performed for 60 min to form a well-dispersed black solution, which was then dropped onto carbon paper or a gas diffusion layer and air-dried to prepare a working electrode. In addition, a platinum sheet and an Ag / AgCl electrode were used as a counter electrode and a reference electrode, respectively.
[0057] like Figure 5 As shown, the current density of Example 1 increases rapidly after the potential is less than -0.5 V, which indicates that the polymer and copper co-doped coal-based composite material prepared by the present invention can efficiently electrocatalyze the reduction of carbon dioxide.
[0058] Depend on Figure 6 It can be seen that the ethylene Faraday efficiency of the coal-based material obtained in Example 1 gradually increases with the negative shift of the potential, wherein it reaches a maximum ethylene Faraday efficiency of 62% at a potential of -0.92V, which indicates that the prepared coal-based material has excellent ethylene selectivity. Changing the types of polymers, surfactants and copper salts causes a slight decrease in the Faraday efficiency of ethylene, but it can also be maintained at around 50%. Changing the amount of ascorbic acid, the ethylene Faraday efficiency of Example 5 is significantly reduced, because the amount of ascorbic acid can adjust the ratio of the generated copper oxide and cuprous oxide. When the amount of ascorbic acid is low, the proportion of copper oxide in the final product is high, and when the amount of ascorbic acid is high, the proportion of cuprous oxide in the final product is high. This shows that the amount of ascorbic acid will significantly affect the degree of reduction of copper species, thereby affecting the selectivity of the ethylene product.
[0059] Depend on Figure 7 It can be seen that as the potential shifts negatively, the current density of the ethylene part of each example gradually increases. Among them, Example 1 reaches an industrial-grade current density of 142.4 mA / cm at a potential of -0.92 V. 2 , indicating that Example 1 has outstanding ethylene activity. In addition, the ethylene partial current density of Example 1 is greater than that of other examples at each potential, which also reflects the excellent catalytic activity of Example 1.
[0060] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.
Claims
1. A method for preparing a polymer and copper co-doped coal-based composite material, characterized in that: The following steps are involved: (1) Weigh coal powder and potassium hydroxide in a mass ratio of 1:3, add deionized water and ethanol; heat the mixture to 80°C and stir vigorously until the solvent is completely evaporated; place the mixture in a vacuum oven at 80°C for 12 hours; (2) placing the dry powder obtained in step (1) into a tube furnace, heating it to 600-900°C in an inert atmosphere, and keeping it at this temperature for 30 minutes, and then naturally cooling it to room temperature; acid washing, filtering, washing, and drying are performed to obtain porous coal; (3) Weigh porous coal, polymer, surfactant and copper salt in a ratio of 0.1 g: 0.5 g: 1 g: 2 mmol, add deionized water and ethanol, heat the mixture to 40-80 ° C and stir vigorously for 30 min; add sodium hydroxide to the mixture, continue stirring for 30 min, then add ascorbic acid, and continue stirring for 30 min; the polymer is one or two of polytetrafluoroethylene and polyaniline; the surfactant is one or more of polyoxyethylene alkyl ether, sodium dodecylbenzene sulfonate, anhydrous sorbitan fatty acid ester, hexadecyltrimethylammonium bromide, polysorbate and dodecylamine acetate; the copper salt is one or more of copper nitrate, copper sulfate, copper citrate, copper acetate, copper acetylacetonate, basic copper carbonate and copper chloride; (4) The precipitate obtained in step (3) is centrifuged and washed three times with water. The obtained solid is placed in an oven and dried for 12 hours.
2. The method for preparing a polymer and copper co-doped coal-based composite material according to claim 1, characterized in that: In step (1), the coal powder is anthracite coal powder.
3. The method for preparing a polymer and copper co-doped coal-based composite material according to claim 1, characterized in that: In step (2), the heating temperature is 750°C.
4. The method for preparing a polymer and copper co-doped coal-based composite material according to claim 1, characterized in that: In step (3), the polymer is polytetrafluoroethylene, the surfactant is polyoxyethylene alkyl ether, and the copper salt is copper nitrate.
5. The method for preparing a polymer and copper co-doped coal-based composite material according to claim 1, characterized in that: In step (3), the heating temperature is 55°C.
6. The method for preparing a polymer and copper co-doped coal-based composite material according to claim 1, characterized in that: In step (3), the ratio of the ascorbic acid to the copper salt is 0.01-2 g: 2 mmol.
7. The method for preparing a polymer and copper co-doped coal-based composite material according to claim 1, characterized in that: In step (3), the ratio of ascorbic acid to copper salt is 0.05 g:2 mmol.
8. The method for preparing a polymer and copper co-doped coal-based composite material according to claim 1, characterized in that: In step (1), the volume ratio of deionized water to ethanol is 1:1; in step (3), the volume ratio of deionized water to ethanol is 8-9:
1.
9. A polymer and copper co-doped coal-based composite material prepared by the preparation method according to any one of claims 1 to 8.
10. Use of the polymer and copper co-doped coal-based composite material according to claim 9 in the preparation of ethylene by electrocatalytic reduction of carbon dioxide.