Carbon-layer-coated palladium-doped copper-based electro-catalytic material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electro-catalytic materials, in particular to a carbon-layer-coated palladium-doped copper-based electro-catalytic material and a preparation method and application thereof.The preparation method comprises the following steps that a copper source compound, a palladium source compound and trimesic acid are mixed in a solvent to be subjected to a hydrothermal reaction, and a precursor is obtained; the precursor is subjected to air atmosphere pyrolysis and hydrogen atmosphere pyrolysis, and the palladium-doped copper-based electro-catalysis material coated with the carbon layer is obtained. The method is simple and convenient, the cost is low, the prepared electro-catalysis material is a copper-based catalyst in a composite morphology, the prepared electro-catalysis material is used as a cathode material for electro-catalysis of carbon dioxide, the selectivity of a C2 product reduced by CO2 can be effectively improved, the Faraday efficiency of ethylene and ethanol is nearly doubled, meanwhile, the stable catalytic performance of the material is kept, and the method is suitable for industrial production. And the application of the copper-based electro-catalysis material in the field of electro-catalysis of carbon dioxide is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic materials, and in particular to a carbon-layer-coated palladium-doped copper-based electrocatalytic material, a preparation method thereof, and an application thereof. Background Art

[0002] The excessive dependence on fossil fuels and the excessive emission of CO2 gas have led to a sharp rise in the concentration of CO2 in the atmosphere, seriously threatening the sustainable development of human society. Therefore, exploring and developing CO2 resource conversion technologies can not only accelerate the utilization of clean energy and reduce the dependence on fossil energy, but also be of great significance to environmental protection and economic development. The electrochemical CO2 reduction reaction shows good application prospects due to its mild reaction conditions, product diversity, and the availability of renewable power resources. Among many products, the electrocatalytic CO2 reaction products (such as ethylene, ethanol, and acetic acid) have attracted much attention due to their high economic value and research value. However, this reaction still faces challenges such as low selectivity and poor stability, which limit its practical industrial application. Therefore, designing and developing efficient electrocatalytic CO2 reaction catalysts to improve the selectivity and stability of C2 products has important research value.

[0003] Among many catalytic materials, copper is considered an efficient CO2 reduction active site due to its special electronic structure, which can promote the C-C coupling reaction to achieve the generation of C2 products. However, there is still great room for improvement in the selectivity and stability of specific products at a single copper site. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a carbon-layer-coated palladium-doped copper-based electrocatalytic material, a preparation method thereof, and an application thereof, which have high product selectivity.

[0005] To achieve the above object, the present invention provides a preparation method of a carbon-layer-coated palladium-doped copper-based electrocatalytic material, comprising the following steps:

[0006] Mixing a copper source compound, a palladium source compound, and trimesic acid in a solvent for hydrothermal reaction to obtain a precursor;

[0007] The precursor is pyrolyzed in an air atmosphere and then in a hydrogen atmosphere to obtain a carbon-layer-coated palladium-doped copper-based electrocatalytic material.

[0008] Optionally, the copper source compound includes one or more of copper nitrate, copper chloride, and copper acetate;

[0009] The palladium source compound includes one or more of palladium nitrate and palladium chloride.

[0010] Optionally, the solvent includes one or more of n-butanol and methanol.

[0011] Optionally, the molar ratio of the copper source compound to the palladium source compound is 10:1 - 20:1;

[0012] The molar ratio of the copper source compound to the trimesic acid is 1:1 - 1:5.

[0013] Optionally, the temperature of the hydrothermal reaction is 120 - 140 °C;

[0014] The time of the hydrothermal reaction is 3 - 5 h.

[0015] Optionally, the heating rate of the pyrolysis in air atmosphere is 10 - 15 °C·min -1 ;

[0016] The temperature of the pyrolysis in air atmosphere is 250 - 350 °C;

[0017] The time of the pyrolysis in air atmosphere is 2 - 3 h.

[0018] Optionally, the heating rate of the pyrolysis in hydrogen atmosphere is 5 - 15 °C·min -1 ;

[0019] The temperature of the pyrolysis in hydrogen atmosphere is 250 - 350 °C;

[0020] The time of the pyrolysis in hydrogen atmosphere is 2 - 3 h;

[0021] In the hydrogen atmosphere, the volume content of hydrogen is more than 10%.

[0022] The present invention provides a carbon-coated palladium-doped copper-based electrocatalytic material, comprising: a Pd-Cu composite material, and a carbon coating layer coated on the outside of the Pd-Cu composite material.

[0023] Optionally, the carbon coating layer is a porous carbon layer.

[0024] The present invention provides the application of the carbon-coated palladium-doped copper-based electrocatalytic material prepared by the above preparation method or the above carbon-coated palladium-doped copper-based electrocatalytic material in the preparation of the cathode material of an electrocatalytic carbon dioxide battery.

[0025] Compared with the prior art, the present invention provides a method for preparing a carbon-layer-coated palladium-doped copper-based electrocatalytic material, comprising the following steps: mixing a copper source compound, a palladium source compound, and trimesic acid in a solvent for hydrothermal reaction to obtain a precursor; pyrolyzing the precursor in an air atmosphere and then in a hydrogen atmosphere to obtain the carbon-layer-coated palladium-doped copper-based electrocatalytic material. This method is simple and low-cost. The prepared electrocatalytic material is a copper-based catalyst with a composite morphology. When used as the cathode material for electrocatalytic carbon dioxide, it can effectively improve the selectivity of C2 products in CO2 reduction, nearly doubling the Faraday efficiency of ethylene and ethanol. Meanwhile, the material maintains stable catalytic performance, significantly improving the application of copper-based electrocatalytic materials in the field of electrocatalytic carbon dioxide. Description of the Drawings

[0026] Figure 1 Transmission electron microscopy (TEM) images of the carbon-layer-uniformly-coated palladium-doped copper-based electrocatalytic material prepared in Example 1 at 200 nm and 5 nm;

[0027] Figure 2 Energy-dispersive spectroscopy (EDS) analysis diagram of the carbon-layer-uniformly-coated palladium-doped copper-based electrocatalytic material prepared in Example 1;

[0028] Figure 3 X-ray diffraction patterns of the electrocatalytic materials prepared in Example 1 and Comparative Example 3;

[0029] Figure 4 Analysis results of the Faraday efficiency and current density of the electrocatalytic materials prepared in Example 1 and Comparative Example 3;

[0030] Figure 5 X-ray photoelectron spectroscopy diagrams of the electrocatalytic materials prepared in Example 1 and Comparative Example 3, where (a) is the Cu 2p X-ray photoelectron spectroscopy diagram of the electrocatalytic material prepared in Example 1, (b) is the C1s X-ray photoelectron spectroscopy diagram of the electrocatalytic material prepared in Example 1, (c) is the Pd 3d X-ray photoelectron spectroscopy diagram of the electrocatalytic material prepared in Example 1, (d) is the Cu 2p X-ray photoelectron spectroscopy diagram of the electrocatalytic material prepared in Comparative Example 3, and (e) is the C1s X-ray photoelectron spectroscopy diagram of the electrocatalytic material prepared in Comparative Example 3. Detailed Description of the Invention

[0031] The present invention provides a method for preparing a carbon-layer-coated palladium-doped copper-based electrocatalytic material, comprising the following steps:

[0032] Mixing a copper source compound, a palladium source compound, and trimesic acid in a solvent for hydrothermal reaction to obtain a precursor;

[0033] The precursor is pyrolyzed in an air atmosphere and then in a hydrogen atmosphere to obtain a palladium-doped copper-based electrocatalytic material coated with a carbon layer.

[0034] In the present invention, the morphology of the Cu-based material is effectively regulated by doping with noble metal palladium and coating with a uniform carbon layer. Through the screening of a series of noble metals (Ag, Pt), it is found that palladium (Pd) can provide an appropriate amount of *H for the formation of the key intermediate *CHO due to its special hydrogen storage characteristics. Its synergistic effect with copper sites can reduce the adsorption energy for the formation of the key intermediate, thereby improving the selectivity of C2 products. In addition, a uniformly coated carbon layer structure is introduced through pyrolysis to prevent the reconstruction of reactive metals during the electrocatalysis of CO2, and at the same time, the electronic structure of metal active sites is changed, thereby optimizing the adsorption energy of key intermediates in CO2 reduction.

[0035] In addition, the present invention regulates the morphology of the copper-based catalytic material by adjusting the types of doped metals and the synthesis process of the precursor, improving the selectivity for C2 products from 57.9% when Pd is not doped to 80.2%. The Faraday efficiencies of ethylene and ethanol are significantly improved, and the current density is also significantly increased, significantly improving the application of copper-based materials in the field of electrocatalytic carbon dioxide.

[0036] The copper source compound can be a copper-containing compound that can be dissolved in a solvent, preferably including one or more of copper nitrate, copper chloride, and copper acetate, and more preferably copper nitrate.

[0037] The palladium source compound can be a palladium-containing compound that can be dissolved in a solvent, preferably including one or more of palladium nitrate and palladium chloride, and more preferably palladium nitrate.

[0038] The molar ratio of the copper source compound to the palladium source compound is preferably 10:1 - 20:1, more preferably 10:1 - 15:1. In some embodiments of the present application, the molar ratio of the copper source compound to the palladium source compound is 13:1.

[0039] In the present invention, palladium elements are doped into the copper catalyst, which can improve the selectivity of C2 compounds, including the selectivity of ethylene and ethanol, during the electrocatalysis of carbon dioxide.

[0040] In the present invention, trimesic acid is used as the carbon source for the reaction. At the same time, trimesic acid coordinates with Cu, and a porous carbon coating layer can be formed after pyrolysis in an air atmosphere, improving the conductivity of the material and increasing the current density of the battery during the electrocatalysis of carbon dioxide.

[0041] The molar ratio of the copper source compound to the trimesic acid is preferably 1:1 - 1:5, more preferably 1:1.5 - 1:4. In some embodiments of the present application, the molar ratio of the copper source compound to the trimesic acid is 1:1.8, 1:2 or 1:4, or a range value with any of the above values as the upper or lower limit.

[0042] The solvent for the reaction preferably includes one or more of n-butanol and methanol.

[0043] Among them, the volume ratio of the n-butanol to the methanol is preferably 1:1.

[0044] The dosage ratio of the n-butanol to the copper source compound is preferably 20 - 40 mL:0.5 g, more preferably 20 - 30 mL:0.5 g. In some embodiments of the present application, the dosage ratio of the n-butanol to the copper source compound is 20 mL∶0.5 g.

[0045] The temperature of the hydrothermal reaction is preferably 120 - 140 °C, more preferably 130 - 140 °C. In some embodiments of the present application, the temperature of the hydrothermal reaction is 140 °C.

[0046] The time of the hydrothermal reaction is preferably 3 - 5 h, more preferably 3 - 4 h, and even more preferably 3 h.

[0047] In some embodiments of the present invention, the preparation of the precursor includes the following steps:

[0048] Dissolve copper nitrate, palladium nitrate and trimesic acid in a mixed solution of n-butanol and methanol, carry out hydrothermal reaction, and then obtain the precursor material by separating the precipitate, washing and drying.

[0049] The present invention has no special limitation on the solvent for the washing, and general poor solvents can be used, including but not limited to methanol, etc.

[0050] The present invention has no special limitation on the drying, and appropriate temperature parameters can be selected for drying according to the properties of the product. Preferably, the drying temperature is 40 - 70 °C, more preferably 60 °C.

[0051] The drying can be a drying method well known to those skilled in the art. To ensure the stability of the product, the present invention preferably uses vacuum drying.

[0052] Then pyrolyze the precursor in an air atmosphere to form Pd doping on Cu, and at the same time form a carbon coating layer on the outermost layer of the material. It should be noted that after pyrolysis in an air atmosphere, the Cu element exists in the form of copper oxide and is reduced to Cu during the subsequent pyrolysis process in a hydrogen atmosphere.

[0053] The heating rate of the pyrolysis in the air atmosphere is preferably 10-15 °C·min -1 , more preferably 10-12 °C·min -1 , in some embodiments of the present invention, the heating rate of the pyrolysis in the air atmosphere is 10 °C·min -1 or 15 °C·min -1 .

[0054] The temperature of the pyrolysis in the air atmosphere is preferably 250-350 °C, more preferably 300-350 °C. In some embodiments of the present invention, the temperature of the pyrolysis in the air atmosphere is 250 °C or 350 °C.

[0055] The time of the pyrolysis in the air atmosphere is preferably 2-3 h, more preferably 2-2.5 h. In some embodiments of the present invention, the time is 2 h.

[0056] After the pyrolysis in the air atmosphere, the system is naturally cooled, and then the pyrolysis in the hydrogen atmosphere is carried out. It should be noted that the pyrolysis in the hydrogen atmosphere must be carried out after the pyrolysis in the air atmosphere.

[0057] The heating rate of the pyrolysis in the hydrogen atmosphere is preferably 5-15 °C·min -1 , more preferably 5-12 °C·min -1 , in some embodiments of the present invention, the heating rate of the pyrolysis in the hydrogen atmosphere is 5 °C·min -1 or 10 °C·min -1 .

[0058] The temperature of the pyrolysis in the hydrogen atmosphere is preferably 250-350 °C, more preferably 250-300 °C. In some embodiments of the present invention, the temperature of the pyrolysis in the air atmosphere is 250 °C or 350 °C.

[0059] The time of the pyrolysis in the hydrogen atmosphere is preferably 2-3 h, more preferably 2-2.5 h. In some embodiments of the present invention, the time is 2 h.

[0060] In the hydrogen atmosphere, the volume content of hydrogen is preferably more than 10%, more preferably 10%.

[0061] In some embodiments of the present invention, the hydrogen atmosphere is an argon atmosphere containing 10% hydrogen.

[0062] After the pyrolysis in the hydrogen atmosphere is completed, the system is naturally cooled to obtain the carbon-layer-coated palladium-doped copper-based electrocatalytic material.

[0063] The present invention also provides a carbon-layer-coated palladium-doped copper-based electrocatalytic material, comprising: a Pd-Cu composite material, and a carbon coating layer coated outside the Pd-Cu composite material.

[0064] The Pd-Cu composite material is palladium-doped copper material, wherein the doping amount of palladium is preferably 1%-5%, more preferably 1%-3%, and in some embodiments, the doping amount of palladium is 2%.

[0065] The carbon coating layer is a porous carbon layer, which uniformly coats the surface of the Pd-Cu composite material. The thickness of the carbon coating layer is preferably 2-4 nm, and in some embodiments, the thickness of the carbon coating layer is 2.5 nm.

[0066] The morphology of the carbon-coated palladium-doped copper-based electrocatalytic material is nanoparticles, and the particle size of the nanoparticles is preferably 100-500 nm, and in some embodiments, the particle size of the nanoparticles is 200 nm.

[0067] The carbon coating layer can uniformly coat the entire surface of the Pd-Cu composite material to form a core-shell structure.

[0068] In the present invention, a carbon material coating layer is introduced into the electrocatalytic material. Due to its low cost and environmental friendliness, the carbon material can form efficient active sites in cooperation with transition metals, which can improve the conductivity and stability of the material. The presence of the carbon layer can also change the electronic structure of the metal active sites, thereby optimizing the adsorption energy of key intermediates in the electrocatalytic CO2 reaction. At the same time, the use of the carbon layer can prevent the reconstruction of the metal during the reaction, which helps to improve the selectivity of CO2 reduction to produce C2 products. The analysis tests of Faraday efficiency and current density show that when the carbon-coated palladium-doped copper-based electrocatalytic material provided by the present invention is used as a working electrode in the electrocatalytic carbon dioxide reaction, the Faraday efficiencies of ethylene and ethanol are significantly improved, and the current density is also significantly increased.

[0069] Based on this, the present invention provides the application of the carbon-coated palladium-doped copper-based electrocatalytic material prepared by the above preparation method or the above carbon-coated palladium-doped copper-based electrocatalytic material in the preparation of the cathode material of an electrocatalytic carbon dioxide battery.

[0070] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0071] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0072] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description of this invention and the examples are only exemplary.

[0073] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0074] To further illustrate this invention, the following will be described in detail in combination with examples. However, it should be understood that these descriptions are only to further illustrate the features and advantages of this invention, rather than a limitation on the claims of the invention.

[0075] There is no particular limitation on the sources of all raw materials of this invention, and they can be purchased on the market or prepared according to the conventional methods well-known to those skilled in the art.

[0076] "Room temperature" in the examples of this invention refers to "25 ± 3 °C".

[0077] Example 1

[0078] Dissolve 0.5 g of copper nitrate and 1 g of benzene-1,3,5-tricarboxylic acid in 20 mL of methanol and 20 mL of n-butanol, add 500 microliters of palladium nitrate solution (Pd 4% - 5%, mass fraction), and then stir at high speed for more than 30 min until the drugs are completely dissolved. Then transfer the solution to a 100 mL hydrothermal reactor, react at 140 °C for 3 hours, and then cool naturally. After the reaction, collect the product by centrifugation, wash it twice with methanol, and finally dry it overnight under vacuum at 60 °C. After drying, heat the powder in an air atmosphere at a heating rate of 10 °C·min - -1 to 350 °C, pyrolyze for 2 hours, and then cool naturally. Then continue to heat it in an argon atmosphere containing 10% hydrogen at a heating rate of 5 °C·min - -1 to 250 °C, pyrolyze for 2 hours, and then cool naturally to obtain a palladium-doped copper-based electrocatalytic material with a uniformly carbon-coated layer.

[0079] Comparative Example 1

[0080] Dissolve 0.5 g of copper nitrate and 1 g of trimesic acid in 20 mL of methanol and 20 mL of n-butanol, add 500 μL of silver nitrate (Ag 4%-5%, mass fraction) solution, and stir at high speed for more than 30 min until the drugs are completely dissolved. Then transfer the solution to a 100 mL hydrothermal reactor, react at 140 °C for 3 hours, and then cool down naturally. After the reaction is completed, collect the product by centrifugation, wash it twice with methanol, and finally dry it overnight under vacuum at 60 °C. After drying, heat the powder in an air atmosphere at a heating rate of 10 °C·min - 1 to 350 °C, pyrolyze for 2 hours, and then cool down naturally. Then continue to heat it in an argon atmosphere containing 10% hydrogen at a heating rate of 5 °C·min - 1 to 250 °C, pyrolyze for 2 hours, and then cool down naturally to obtain a silver-doped copper-based electrocatalytic material with a uniformly carbon-coated layer.

[0081] Comparative Example 2

[0082] Dissolve 0.5 g of copper nitrate and 1 g of trimesic acid in 20 mL of methanol and 20 mL of n-butanol, add 500 μL of platinum nitrate (Pt 4%-5%, mass fraction) solution, and stir at high speed for more than 30 min until the drugs are completely dissolved. Then transfer the solution to a 100 mL hydrothermal reactor, react at 140 °C for 3 hours, and then cool down naturally. After the reaction is completed, collect the product by centrifugation, wash it twice with methanol, and finally dry it overnight under vacuum at 60 °C. After drying, heat the powder in an air atmosphere at a heating rate of 10 °C·min - 1 to 350 °C, pyrolyze for 2 hours, and then cool down naturally. Then continue to heat it in an argon atmosphere containing 10% hydrogen at a heating rate of 5 °C·min 1 to 250 °C, pyrolyze for 2 hours, and then cool down naturally to obtain a platinum-doped copper-based electrocatalytic material with a uniformly carbon-coated layer.

[0083] Comparative Example 3

[0084] Dissolve 0.5 g of copper nitrate and 1 g of trimesic acid in 20 mL of methanol and 20 mL of n-butanol, stir at high speed for more than 30 min until the drugs are completely dissolved. Then transfer the solution to a 100 mL hydrothermal reactor, react at 140 °C for 3 hours, and then cool down naturally. After the reaction is completed, collect the product by centrifugation, wash it twice with methanol, and finally dry it overnight under vacuum at 60 °C. After drying, heat the powder in an air atmosphere at a heating rate of 10 °C·min - 1 to 350 °C, pyrolyze for 2 hours, and then cool down naturally. Then continue to heat it in an argon atmosphere containing 10% hydrogen at a heating rate of 5 °C·min - 1 to 250 °C, pyrolyze for 2 hours, and then cool down naturally to obtain a copper-based electrocatalytic material with a uniformly carbon-coated layer.

[0085] Comparative Example 4

[0086] Dissolve 0.5 g of copper nitrate and 1 g of trimesic acid in 20 mL of methanol and 20 mL of n-butanol, add 500 μL of palladium nitrate (Pd 4%-5%, mass fraction) solution, and stir at high speed for more than 30 min until the drugs are completely dissolved. Then transfer the solution to a 100 mL hydrothermal reactor, react at 140 °C for 3 hours, and then cool naturally. After the reaction, collect the product by centrifugation, wash it twice with methanol, and finally dry it overnight under vacuum at 60 °C. After drying, heat the powder in an air atmosphere at a heating rate of 10 °C·min - ^-1 to 350 °C, pyrolyze for 2 hours, and then cool naturally to obtain a palladium-doped copper oxide electrocatalytic material with a uniformly carbon-coated layer.

[0087] Comparative Example 5

[0088] Dissolve 0.5 g of copper nitrate and 1 g of trimesic acid in 20 mL of methanol and 20 mL of n-butanol, add 500 μL of palladium nitrate (Pd 4%-5%, mass fraction) solution, and stir at high speed for more than 30 min until the drugs are completely dissolved. Then transfer the solution to a 100 mL hydrothermal reactor, react at 140 °C for 3 hours, and then cool naturally. After the reaction, collect the product by centrifugation, wash it twice with methanol, and finally dry it overnight under vacuum at 60 °C. After drying, heat the powder in an air atmosphere at a heating rate of 10 °C·min - ^-1 to 850 °C, pyrolyze for 2 hours, and then cool naturally. Then continue to heat in an argon atmosphere containing 10% hydrogen at a heating rate of 5 °C·min - ^-1 to 250 °C, pyrolyze for 2 hours, and then cool naturally to obtain a palladium-doped copper-based electrocatalytic material.

[0089] Performance Test

[0090] (1) Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) analysis

[0091] The transmission electron microscopy (TEM) images of the palladium-doped copper-based electrocatalytic material with a uniformly carbon-coated layer prepared in Example 1 at 200 nm and 5 nm are shown in Figure 1 , and it can be seen from Figure 1 that the material has a granular structure; at the edge of the metal particles, a uniform porous carbon layer structure can be observed, and its thickness is about 2.5 nm. The energy dispersive spectroscopy (EDS) analysis is shown in Figure 2 , and it can be seen from Figure 2 that the material contains elements C, Cu, and Pd, and the elements are uniformly distributed.

[0092] (2) X-ray diffraction

[0093] The X-ray diffraction patterns of the electrocatalytic materials prepared in Example 1 and Comparative Example 3 are shown in Figure 3 , where the upper line is the X-ray diffraction pattern of the palladium-doped copper-based electrocatalytic material with a uniformly coated carbon layer prepared in Example 1, and the lower line is the X-ray diffraction pattern of the copper-based electrocatalytic material with a uniformly coated carbon layer prepared in Comparative Example 3. It can be seen that there are obvious diffraction peaks of the Cu material, and by magnifying, a broad peak belonging to the (002) crystal plane of the carbon material can be seen. Among them, the X-ray diffraction pattern of the electrocatalytic material prepared in Example 1 does not show the diffraction peaks of the doped element Pb material, indicating that the Pb element is uniformly doped and dispersed in the material.

[0094] (3) Analysis of Faraday efficiency and current density

[0095] Weigh 0.005 g of the electrocatalytic materials prepared in Example 1 and Comparative Example 3 respectively, then add 470 μL of isopropanol and 30 μL of Nafion (perfluorosulfonic acid resin), ultrasonicate them, and after uniform dispersion, uniformly coat them on the surface of a 0.5×1.5 cm carbon paper and dry at room temperature. The dried carbon paper is used as the working electrode for standby.

[0096] The test system is a three-electrode system of a flow electrolytic cell, which consists of a working electrode, a reference electrode and a counter electrode. The reference electrode is Ag / AgCl (saturated KCl solution), the counter electrode is a commercial platinum sheet, and the working electrode is the prepared carbon paper.

[0097] The electrolyte is 50 mL of 0.5 mol / L potassium hydroxide solution, and CO2 is introduced at a flow rate of 15 mL / min; linear sweep voltammetry (LSV) tests are carried out on a CHI 660 electrochemical workstation, and the scanning window is -0.6 to -2.5 V; the potentiostatic electrolysis experiment is carried out on a CHI 660 electrochemical workstation, the voltage setting range is -1.6 V to -2.4 V, and the duration is 2 h. After the reaction starts, it enters the gas chromatograph, and samples are taken every 12 min; after the reaction ends, the liquid in the cathode chamber is taken for nuclear magnetic resonance testing to determine the liquid-phase products.

[0098] The analysis results of the Faraday efficiency and current density of the electrocatalytic materials prepared in Example 1 and Comparative Examples 1-5 are shown in Figure 4 , where (a) is the analysis curve of the Faraday efficiency and current density of the electrocatalytic material prepared in Example 1, and (b)-(f) are the analysis curves of the Faraday efficiency and current density of the electrocatalytic materials prepared in Comparative Examples 1-5. It can be seen that the Faraday efficiency of the C2 product in Example 1 is increased to 80.2%, the Faraday efficiencies of ethylene and ethanol are significantly increased, and the current density is also significantly increased.

[0099] (4) X-ray photoelectron spectroscopy analysis

[0100] X-ray photoelectron spectroscopy diagrams of the electrocatalytic materials prepared in Example 1 and Comparative Example 3, where (a) is the Cu 2p X-ray photoelectron spectroscopy diagram of the electrocatalytic material in Example 1, (b) is the C1s X-ray photoelectron spectroscopy diagram of the electrocatalytic material in Example 1, (c) is the X-ray photoelectron spectroscopy diagram of Pd 3d of the electrocatalytic material in Example 1, (d) is the Cu 2p X-ray photoelectron spectroscopy diagram of the electrocatalytic material in Comparative Example 3, and (e) is the C1s X-ray photoelectron spectroscopy diagram of the electrocatalytic material in Comparative Example 3. It can be seen that Pd doping has no obvious effect on the state of Cu metal and the composition of the carbon layer in the electrocatalytic material.

[0101] Example 2

[0102] Dissolve 0.5 g of copper nitrate and 2 g of trimesic acid in 20 mL of methanol and 20 mL of n-butanol, add 1000 microliters of palladium nitrate solution (Pd 4%-5%, mass fraction), and stir at high speed for more than 30 min until the drugs are completely dissolved. Then transfer the solution to a 100 mL hydrothermal reactor, react at 140 °C for 3 hours, and then cool naturally. After the reaction is completed, collect the product by centrifugation, wash it twice with methanol, and finally dry it overnight under vacuum at 60 °C. After drying, heat the powder in an air atmosphere at a heating rate of 10 °C·min - -1 to 350 °C, pyrolyze for 2 hours, and then cool naturally. Then continue to heat in an argon atmosphere containing 10% hydrogen at a heating rate of 5 °C·min - -1 to 250 °C, pyrolyze for 2 hours, and then cool naturally to obtain a palladium-doped copper-based electrocatalytic material with a uniformly coated carbon layer.

[0103] The morphology of the prepared material is the same as that in Example 1, which is a granular structure. The material contains elements C, Cu, and Pd, and each element is uniformly distributed. The performance test results show that the Faraday efficiency of C2 products is increased to 79.52%, the Faraday efficiencies of ethylene and ethanol are significantly increased, and the current density is also significantly increased.

[0104] Example 3

[0105] Dissolve 0.5 g of copper nitrate and 1 g of trimesic acid in 20 mL of methanol and 20 mL of n-butanol, add 500 microliters of palladium nitrate solution (Pd 4%-5%, mass fraction), and stir at high speed for more than 30 min until the drugs are completely dissolved. Then transfer the solution to a 100 mL hydrothermal reactor, react at 140 °C for 3 hours, and then cool naturally. After the reaction is completed, collect the product by centrifugation, wash it twice with methanol, and finally dry it overnight under vacuum at 60 °C. After drying, heat the powder in an air atmosphere at a heating rate of 15 °C·min - -1 to 250 °C, pyrolyze for 3 hours, and then cool naturally. Then continue to heat in an argon atmosphere containing 10% hydrogen at a heating rate of 10 °C·min- Heat it to 350 °C at a heating rate of 1, and after pyrolysis for 3 hours, naturally cool it to obtain a palladium-doped copper-based electrocatalytic material with a uniformly carbon-coated layer.

[0106] The morphology of the prepared material is the same as that in Example 1, which is a granular structure. The material contains elements C, Cu, and Pd, and each element is uniformly distributed. The performance test results show that the Faraday efficiency of C2 products is increased to 81.24%, the Faraday efficiencies of ethylene and ethanol are significantly increased, and the current density is also significantly increased.

[0107] Combined with the foregoing content, it can be seen that in the embodiments of the present invention, the noble metal Pd is incorporated into the copper-based catalyst by hydrothermal and pyrolysis methods to construct a specific morphology, demonstrating its influence on the catalytic mechanism of the catalytic material in the process of carbon dioxide reduction. Among them, the palladium element has the most obvious improvement on C2 products. Its synergistic effect with copper sites can reduce the adsorption energy for the formation of key intermediates, thereby improving the selectivity of C2 products. In addition, a uniformly carbon-coated layer structure is introduced by pyrolysis to prevent the reconstruction of reactive metals during the electrocatalytic CO2 process, and at the same time change the electronic structure of metal active sites, thereby optimizing the adsorption energy of key intermediates in CO2 reduction.

[0108] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a carbon-coated palladium-doped copper-based electrocatalytic material, comprising the following steps: Mix a copper source compound, a palladium source compound, and trimesic acid in a solvent and perform a hydrothermal reaction to obtain a precursor; The precursor is pyrolyzed in an air atmosphere and then in a hydrogen atmosphere to obtain a carbon-coated palladium-doped copper-based electrocatalytic material.

2. The preparation method according to claim 1, characterized in that, The copper source compound includes one or more of copper nitrate, copper chloride, and copper acetate; The palladium source compound includes one or more of palladium nitrate and palladium chloride.

3. The preparation method according to claim 1, wherein The solvent includes one or more of n-butanol and methanol.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the copper source compound to the palladium source compound is 10:1 - 20:1; The molar ratio of the copper source compound to trimesic acid is 1:1 - 1:

5.

5. The preparation method according to claim 1, characterized in that, According to the preparation method described in claim 1, characterized in that the temperature of the hydrothermal reaction is 120 - 140 °C; The time of the hydrothermal reaction is 3 - 5 h.

6. The preparation method according to claim 1, characterized in that, The heating rate of the pyrolysis in the air atmosphere is 10-15 °C·min -1 ; The temperature of the pyrolysis in the air atmosphere is 250 - 350 °C; The time of the pyrolysis in the air atmosphere is 2 - 3 h.

7. The preparation method according to claim 1, characterized in that, The heating rate of the pyrolysis in a hydrogen atmosphere is 5-15 °C·min -1 ; The temperature of the pyrolysis in the hydrogen atmosphere is 250 - 350 °C; The time of the pyrolysis in the hydrogen atmosphere is 2 - 3 h; In the hydrogen atmosphere, the volume content of hydrogen is more than 10%.

8. A carbon-layer-coated palladium-doped copper-based electrocatalytic material, characterized in that Includes: A Pd-Cu composite material, and a carbon coating layer coated on the outside of the Pd-Cu composite material.

9. The carbon layer-coated palladium-doped copper-based electrocatalytic material according to claim 8, wherein The carbon coating layer is a porous carbon layer.

10. The application of the carbon-coated palladium-doped copper-based electrocatalytic material prepared by the preparation method described in any one of claims 1 to 7 or the carbon-coated palladium-doped copper-based electrocatalytic material described in any one of claims 8 to 9 in the preparation of the cathode material of an electrocatalytic carbon dioxide battery.

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