Doped copper-based catalytic electrode and preparation method and application thereof

Abstract

The application provides a doped copper-based catalytic electrode and a preparation method and application thereof, the doped copper-based catalytic electrode comprises a porous carbon base, nitrogen species and copper species, the content of the porous carbon base in terms of carbon element is 60wt%-90wt% based on the weight of the doped copper-based catalytic electrode, the content of the copper species in terms of copper element is 5wt%-25wt%, and the content of the nitrogen species in terms of nitrogen element is 5wt%-15wt%. The preparation method of the doped copper-based catalytic electrode comprises the following steps: (1) pretreating petroleum coke; (2) activating the pretreated petroleum coke; (3) preparing a nitrogen-doped carbon electrode by taking the activated petroleum coke as a base material; and (4) introducing copper to the nitrogen-doped carbon electrode by an electrochemical deposition method to obtain the doped copper-based catalytic electrode. The problems of low catalytic activity, poor stability and difficulty in large-scale use of existing electrochemical catalytic materials are solved.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis and relates to an electrode material and its preparation method, particularly to a doped copper-based catalytic electrode for electrocatalytic reduction of carbon dioxide to methane and its preparation method. Background Technology

[0002] Carbon dioxide, as the most common greenhouse gas, is continuously released due to the excessive consumption of traditional fossil fuels, leading to energy and environmental problems such as global warming. Electrochemical methods can convert carbon dioxide into high-value chemicals and organic fuels, effectively alleviating the energy crisis. However, due to the diversity of products and the complexity of the reactions involved, competing hydrogen evolution reactions and product selectivity remain major challenges. The rational design and preparation of advanced catalytic materials are key to achieving efficient and stable carbon dioxide conversion.

[0003] Compared to other metals, copper surfaces possess moderate CO* adsorption capacity and relatively weak H* adsorption capacity, thus enabling them to catalyze the electroreduction of carbon dioxide to hydrocarbons and multi-carbon products. Due to the complexity of the reaction, achieving the desired performance using single-component materials is often challenging; however, combining several materials to construct nanocomposites is expected to yield superior catalytic properties. Carbon materials, due to their high specific surface area and excellent electrochemical stability, have proven to be suitable components for combining with metals, metal oxides, and metal hydroxides for carbon dioxide electroreduction, providing unique properties due to electronic interactions, interfacial effects, and synergistic effects. This allows for the regulation of the adsorption of carbon dioxide electroreduction reaction intermediates and their distribution on the catalyst surface, providing an effective method to promote hydrocarbon formation.

[0004] Patent CN 112830468 A uses nitrogen-doped carbon materials as precursors and heat-treats them in an ammonia atmosphere to obtain carbon materials rich in carbon topological defects. These materials exhibit highly efficient carbon dioxide electroreduction catalytic activity, high selectivity for carbon monoxide, and high stability. Patent CN 108914153 A synthesizes copper chloride / polyvinylpyrrolidone / polyacrylonitrile nanofiber membranes using electrospinning technology. After a series of post-treatment processes, a porous nitrogen-doped carbon nanofiber electrocatalyst with copper nanoparticles supported on it and a certain mechanical strength is obtained. Patent CN 117285029 A discloses a method for preparing boron and nitrogen co-doped hollow carbon nanosphere catalysts. The catalyst, obtained by reacting 3-hydroxyphenylboronic acid, ammonia, oleic acid, and formaldehyde solution, presents as hollow spheres with a particle size of 100-300 nm, uniformly distributed, and exhibits high specific surface area and high electrochemical activity. It demonstrates excellent activity and high reproducibility in the carbon dioxide reduction reaction. However, the proton competition reaction that occurs in solution currently greatly affects the Faraday efficiency, and the electrocatalyst used and the applied electrode potential also have a huge impact on the final reduction product, becoming a bottleneck for the further development of this technology. Summary of the Invention

[0005] Loading metals onto carbon-based materials can enhance their catalytic activity; however, the active sites of metals directly loaded onto carbon-based catalysts are prone to detachment, resulting in poor stability. To address these shortcomings, this invention aims to provide a doped copper-based catalytic electrode, its preparation method, and its applications, thereby solving the problems of low catalytic activity, poor stability, and difficulty in large-scale application of existing electrochemical catalytic materials. Introducing nitrogen into a carbon support can affect the carbon lattice, charge density, and structural defects, thereby modulating the electronic structure of the loaded metal and achieving a unique synergistic effect.

[0006] The present invention first provides a doped copper-based catalytic electrode, which comprises a porous carbon matrix, nitrogen species, and copper species. Based on the weight of the doped copper-based catalytic electrode, the porous carbon matrix contains 60 wt% to 90 wt% carbon, preferably 65 wt% to 80 wt%; the copper species contains 5 wt% to 25 wt% copper, preferably 10 wt% to 20 wt%; and the nitrogen species contains 5 wt% to 15 wt% nitrogen, preferably 5 wt% to 10 wt%.

[0007] Furthermore, in the above-mentioned doped copper-based catalytic electrode, the nitrogen species include pyrrole nitrogen, pyridine nitrogen, and graphitic nitrogen, wherein the content of pyrrole nitrogen is 20%–50%, preferably 30%–45%; and the content of pyridine nitrogen is 10%–40%, preferably 20%–30%. The nitrogen species are distributed on a porous carbon matrix.

[0008] Furthermore, in the above-mentioned doped copper-based catalytic electrode, the copper species is Cu(Cu) 0 Cu2O (Cu + ) and CuO (Cu 2+ A mixture of copper species distributed on a porous carbon matrix.

[0009] Furthermore, in the above-mentioned doped copper-based catalytic electrode, the Cu in the surface copper species... 2+ The content is 40%–90%, more preferably 45%–80%; Cu 0 The content is 10% to 50%, more preferably 15% to 45%.

[0010] Furthermore, in the above-mentioned doped copper-based catalytic electrode, the copper species are nanoparticles with a particle size of 100–400 nm.

[0011] Another aspect of the present invention provides a method for preparing a doped copper-based catalytic electrode, the method comprising the following steps:

[0012] (1) Petroleum coke is pretreated by contacting it with nitrogen-containing compounds, and then separated and dried to obtain pretreated petroleum coke.

[0013] (2) Under the presence of an activator, the pretreated petroleum coke obtained in step (1) is activated and then washed and dried to obtain nitrogen-doped carbon material.

[0014] (3) A nitrogen-doped carbon electrode is prepared using the nitrogen-doped carbon material obtained in step (2) as a substrate;

[0015] (4) Copper is introduced onto the nitrogen-doped carbon electrode obtained in step (3) by electrochemical deposition to obtain a doped copper-based catalytic electrode.

[0016] Furthermore, as a specific embodiment, the pretreatment reaction temperature in step (1) is 120–220°C, preferably 150–200°C; the pretreatment reaction time is 6–24 h, preferably 10–18 h; the drying temperature is 20–120°C, preferably 40–105°C; and the drying time is 1–24 h, preferably 6–18 h. The separation can be performed using any of the existing liquid-solid two-phase separation methods in the art, preferably centrifugal separation.

[0017] Furthermore, as a specific embodiment, the nitrogen-containing compound in step (1) is selected from one or more of ethylenediamine, N-methylpyrrolidone, N,N-dimethylformamide, triethylamine, ammonia solution, formamide, and acetamide, preferably formamide.

[0018] Furthermore, as a specific embodiment, the volume-to-mass ratio of the nitrogen-containing compound (by volume) to the petroleum coke (by mass) in step (1) is 8:1 to 2:1 (mL / g), preferably 5:1 to 3:1 (mL / g).

[0019] Furthermore, as a specific embodiment, the volatile matter content of the petroleum coke in step (1) is not higher than 10 wt%, preferably not higher than 8 wt%, such as 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, etc.; the particle size of the petroleum coke is 10-500 μm, preferably 30-300 μm. The petroleum coke is a product obtained from the thermal processing of petroleum feedstock, such as a solid product obtained from the production process of a delayed coking unit.

[0020] Furthermore, as a specific implementation, the activation process in step (2) is as follows: under the presence of an inert atmosphere, the pretreated petroleum coke obtained in step (1) and the activator are heated to perform activation treatment; the activation treatment conditions are as follows: the activation treatment temperature is 700-1100℃, preferably 750-900℃; the activation treatment time is 30-200min, preferably 50-100min. The inert atmosphere can be selected from one or more of nitrogen, helium, and argon.

[0021] Furthermore, as a specific embodiment, in a more preferred case, the activation treatment in step (2) is further included in a pre-activation treatment, the pre-activation treatment temperature is 150-300℃, preferably 180-280℃, and the pre-activation treatment time is 5-200min, preferably 30-100min.

[0022] Furthermore, as a specific embodiment, the activator in step (2) is an alkaline activator, which is usually at least one of the following: hydroxide containing alkali metal elements, salt containing alkali metal elements, hydroxide containing alkaline earth metal elements, and salt containing alkaline earth metal elements; the specific activator can be selected from one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, potassium carbonate, and potassium bicarbonate, preferably potassium hydroxide.

[0023] Furthermore, as a specific implementation, the mass ratio of the pretreated petroleum coke to the activator obtained in step (1) of step (2) is 1:0.2 to 1:2, preferably 1:0.6 to 1:1.

[0024] Furthermore, as a specific embodiment, in a more preferred case, a modifier is introduced during the activation process in step (2). The modifier is an organic compound containing both amino and hydroxyl groups. This compound can be an amino acid containing hydroxyl groups, specifically selected from one or more of serine, threonine, and tyrosine. Introducing a modifier containing both amino and hydroxyl groups during the petroleum coke activation process can form uniform metal nucleation sites on the carbon material surface, creating favorable conditions for the subsequent successful deposition of copper nanoparticles. It can also enhance the interaction between the carbon matrix and the metal. The mass ratio of the modifier to the pretreated petroleum coke obtained in step (1) is 2:1 to 0.5:1, preferably 1:1 to 0.6:1.

[0025] Furthermore, as a specific implementation method, the water washing described in step (2) generally requires washing with water until the pH value of the filtrate is neutral. Specifically, at least one of deionized water, distilled water, and ultrapure water can be used for washing.

[0026] Furthermore, as a specific implementation, the drying temperature in step (2) is 20-120°C, preferably 40-100°C; the drying time is 1-24h, preferably 4-12h.

[0027] Furthermore, as a specific implementation, the size of the nitrogen-doped carbon material obtained in step (2) is adjusted to 10-20 μm, and then the nitrogen-doped carbon electrode is prepared. The size can usually be adjusted by ball milling. Specifically, it can be placed in a ball milling jar and milled for 1-3 hours at a milling speed of 100-150 rpm.

[0028] Furthermore, as a specific implementation, the nitrogen-doped carbon electrode can be prepared in step (3) using any one or more of the existing electrode preparation methods, such as at least one of the wet coating method, dry coating method, electrostatic spraying method, etc.

[0029] Furthermore, as a specific implementation, the preparation process of the nitrogen-doped carbon electrode in step (3) is as follows: the nitrogen-doped carbon material, conductive agent and binder obtained in step (2) are mixed evenly and then coated evenly on the current collector. After the slurry is fully dried, it is rolled to obtain a porous carbon electrode.

[0030] Furthermore, as a specific implementation method, in the preparation process of nitrogen-doped carbon electrodes, the conductive agent can be at least one of conductive carbon black, graphene, carbon nanotubes, and conductive graphite.

[0031] Furthermore, as a specific embodiment, in the fabrication process of the nitrogen-doped carbon electrode, the binder can be selected from at least one of polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyvinylidene fluoride (PVDF).

[0032] Furthermore, as a specific embodiment, in the fabrication process of the nitrogen-doped carbon electrode, the current collector can be selected from at least one of glassy carbon electrode, carbon paper, carbon cloth, copper foil, titanium sheet, and stainless steel mesh.

[0033] Furthermore, in the above-mentioned method for preparing the working electrode, the ratio of nitrogen-doped carbon material, conductive agent, and binder in the nitrogen-doped carbon electrode preparation process is 7-9:0.5-2:0.5-2.

[0034] Furthermore, as a specific embodiment, in the preparation process of the nitrogen-doped carbon electrode, the loading amount of the slurry mixture uniformly coated on the current collector is generally controlled to be 0.5–2.0 mg / cm³. 2 .

[0035] Furthermore, as a specific implementation method, the electrochemical deposition method in step (4) includes the following steps:

[0036] (4.1) Under mixed conditions, copper precursor, inorganic acid, organic compound containing polyhydroxyl group and water are mixed to obtain electrolyte solution;

[0037] (4.2) Under the protection of an inert atmosphere, copper nanoparticles are grown on the surface of a nitrogen-doped carbon electrode using a three-electrode system under constant potential conditions. The proportion of copper species in different valence states in the copper nanoparticles is controlled by adjusting the deposition charge. After deposition, the copper nanoparticles are washed and dried to obtain a nitrogen-doped copper-based catalytic electrode.

[0038] Furthermore, as a specific embodiment, the copper precursor mentioned in step (4.1) is a copper salt, which can be selected from one or more of copper chloride, copper sulfate, copper nitrate, and copper acetate, wherein the concentration of copper ions in the electrolyte solution is 0.01 to 0.1 mol / L, preferably 0.02 to 0.06 mol / L.

[0039] Furthermore, as a specific embodiment, the inorganic acid mentioned in step (4.1) is preferably one or more of hydrochloric acid, sulfuric acid, and nitric acid, wherein the concentration of the inorganic acid in the electrolyte solution is 0.1 to 1 mol / L, preferably 0.2 to 0.6 mol / L.

[0040] Furthermore, as a specific embodiment, the organic compound containing multiple hydroxyl groups mentioned in step (4.1) is an organic compound containing three or more hydroxyl groups, preferably an organic compound containing four or more hydroxyl groups, and can be selected from carbohydrate compounds, more specifically, one or more of glucose, fructose, lactose, and maltose, with a mass ratio of 0.5:1 to 4:1 to copper salt, preferably 1:1 to 2.5:1. The addition of hydroxyl-rich carbohydrates forms a suitable hydroxyl-covered environment on the surface of the copper species, optimizing the surface structure and reactivity of the catalytic electrode, providing effective sites for the *CO intermediate, and inhibiting the hydrogen evolution reaction to a certain extent, thus achieving high selectivity for methane.

[0041] Furthermore, as a specific implementation, in the three-electrode system described in step (4.2), the working electrode is the nitrogen-doped carbon electrode obtained in step (3), the counter electrode can be at least one of graphite electrode and platinum wire electrode, preferably a graphite electrode, and the reference electrode is at least one of silver / silver chloride electrode, saturated calomel electrode, and mercury / mercury oxide electrode, preferably a silver / silver chloride electrode.

[0042] Furthermore, as a specific implementation, the inert atmosphere mentioned in step (4.2) can be nitrogen and / or an inert gas, and the inert gas can be one or more of helium, neon, argon, krypton, and xenon.

[0043] Furthermore, as a specific implementation, the constant voltage is -0.1V to -1.4V (vs. RHE), preferably -0.5V to -1.0V (vs. RHE).

[0044] Furthermore, as a specific implementation method, the deposition time is 60–900 s, preferably 120–540 s.

[0045] Furthermore, as a specific implementation method, the deposition temperature is 20–40°C.

[0046] Furthermore, as a specific implementation method, the washing is generally performed using ethanol.

[0047] Furthermore, as a specific embodiment, the drying temperature is 40–80°C, preferably dried under vacuum conditions.

[0048] The third aspect of the present invention provides the application of the doped copper-based catalytic electrode described in the first aspect of the present invention and / or the doped copper-based catalytic electrode obtained by the preparation method described in the second aspect of the present invention in the electrocatalytic reduction of carbon dioxide to methane.

[0049] Compared with the prior art, the doped copper-based catalytic electrode, its preparation method, and its application provided by the present invention have the following beneficial effects:

[0050] 1. This invention first pretreats petroleum coke by introducing nitrogen species, which provides a local environment to activate CO2 molecules and enhances the interaction between the porous carbon electrode and copper nanoparticles. This suppresses the occurrence of hydrogen evolution side reactions and improves the adsorption of *CO intermediates, which are key intermediates for deep CO2 reduction and can enhance the formation of hydrocarbon products on the copper surface. Furthermore, the abundant pyrrole N in the copper-based catalytic electrode is more conducive to the formation of bridged *CO, thus making methane the dominant product.

[0051] 2. This invention selects copper nanoparticles with high electrochemical activity as the active material and porous carbon with high specific surface area as the matrix. The active material and the support are combined through an electrochemical process, and the synergistic effect between the two is utilized to effectively electroreduc carbon dioxide into methane.

[0052] 3. In the process of petroleum coke activation treatment, this invention introduces an organic compound containing both amino and hydroxyl groups as a modifier, which forms uniform metal nanocrystal nucleation sites on the surface of a porous carbon matrix, enabling copper nanoparticles to be successfully deposited on the carbon matrix; at the same time, it further enhances the interaction between the carbon support and the metal.

[0053] 4. The method of this invention utilizes electrodeposition to load copper nanoparticles onto a nitrogen-doped porous carbon electrode. The process is easily controlled and can form a continuous, uniform, and fully covered metal layer. The uniform distribution of active sites and good interfacial contact enhance the activity of carbon dioxide electroreduction to methane. During deposition, the introduction of hydroxyl-rich organic compounds into the electrolyte creates a suitable hydroxyl-covered environment on the surface of the copper nanoparticles, providing effective sites for the *CO intermediate and simultaneously inhibiting the hydrogen evolution reaction to a certain extent, thus achieving high selectivity for methane.

[0054] 5. The copper-based catalytic electrode provided by this invention can achieve high methane selectivity, activity, and stability; its methane Faradaic efficiency is as high as 55.3%, and its current density can reach 14.9 mA / cm². 2 It also has good stability.

[0055] 6. In the preparation method of the doped copper-based catalytic electrode for the electroreduction of carbon dioxide to methane described in this invention, petroleum coke is used as the raw material for preparing the porous carbon matrix, which provides a new method for utilizing petroleum coke and realizes the resource utilization of petroleum coke. Attached Figure Description

[0056] Figure 1 These are the XRD diffraction patterns of the catalytic electrodes provided in Examples 1, 5 and Comparative Example 1 of this invention.

[0057] Figure 2This is the XPS N 1s spectrum of the catalytic electrode provided in Example 1 of the present invention.

[0058] Figure 3 These are XPS Cu 2p spectra of the catalytic electrodes provided in Examples 1, 5 and Comparative Example 1 of this invention.

[0059] Figure 4 This is a schematic diagram of the Faraday efficiency of the catalytic electrodes provided in Examples 1-5 and Comparative Examples 1-4 of the present invention for the electrocatalytic reduction of carbon dioxide into gaseous products, including four products: hydrogen, carbon monoxide, methane, and ethylene, with an applied potential of -1.0V (vs. RHE).

[0060] Figure 5 This is a schematic diagram of the Faraday efficiency of the catalytic electrode provided in Embodiment 1 of the present invention for the electrocatalytic reduction of carbon dioxide into gaseous products, including four products: hydrogen, carbon monoxide, methane, and ethylene, with an applied potential of -0.8 to 1.2 V (vs. RHE).

[0061] Figure 6 This is a schematic diagram illustrating the stability of the catalytic electrode with excellent methane Faradaic efficiency provided in Example 1 of the present invention for electrocatalytic carbon dioxide reduction reaction. The test data includes the methane Faradaic efficiency and current density at a voltage of -1.0V (vs. RHE). Detailed Implementation

[0062] The embodiments of the present invention will be described in further detail below with reference to examples. These examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0063] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0064] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0065] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0066] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0067] In the context of this invention, all numerical values ​​of parameters (e.g., quantity or condition) should be understood to be modified by the term “about” in all cases, regardless of whether “about” actually appears before the numerical value.

[0068] In the context of this invention, "substantially" means that deviations that are acceptable or considered reasonable to those skilled in the art are permitted, such as deviations within ±5%, ±2%, ±1%, ±0.5%, or ±0.1%.

[0069] Unless otherwise specified, all percentages, parts, ratios, etc., mentioned in this instruction manual are based on weight, and pressures are gauge pressures. Room temperature mentioned in this instruction manual refers to 25°C.

[0070] In the context of this invention, any two or more embodiments or aspects of this invention can be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of this invention.

[0071] In this paper, X-ray diffraction data were obtained using a Panalytical X'Pert Pro X-ray powder diffractometer under the following conditions: Cu Kα, l = 0.15406 nm, 40 kV / 40 mA, scan range: 5–70°, step size: 0.02°. X-ray electron spectroscopy data were obtained using a Shimadzu AXIS SPURA+ instrument under the following conditions: Al Kα photoelectron source, E = 1486.6 eV. All binding energies were corrected for contaminated carbon (C 1s 284.8 eV).

[0072] Example 1

[0073] Weigh 10g of petroleum coke powder and add it to 50mL of formamide. After stirring for 30min, transfer the mixture to a polytetrafluoroethylene liner, place it in a reaction vessel, and react at 180℃ for 12h. After centrifugation, dry the solid product at 80℃ for 12h to obtain pretreated petroleum coke.

[0074] Weigh 3.64g of pretreated petroleum coke, 2.72g of potassium hydroxide, and 3.64g of tyrosine, mix and grind them into powder. Under a nitrogen atmosphere, heat to 250℃ and hold for 30min. Then adjust the temperature to 900℃ and hold for 90min. After cooling to room temperature, filter and wash the activated product with deionized water until the pH of the filtrate is neutral. Dry the solid product at 105℃ for 12h to obtain nitrogen-doped porous carbon.

[0075] Nitrogen-doped porous carbon was ball-milled in a ball mill jar for 1 hour at a speed of 150 rpm. Subsequently, porous carbon, conductive carbon black, and PTFE were mixed at a mass ratio of 8:1:1 and stirred for 30 minutes to obtain a slurry mixture. This slurry mixture was then uniformly coated onto a titanium sheet with a loading of 1 mg / cm³. 2 After the slurry has dried sufficiently, it is placed on a two-roll mill for rolling to obtain porous carbon electrode sheets, which are then cut into rectangles of 1cm × 1.5cm.

[0076] 0.96 g of copper sulfate and 2.16 g of glucose were weighed and added to 100 mL of deionized water. Then, 0.06 mol of sulfuric acid was added dropwise to the solution, and the mixture was stirred for 30 min to form a homogeneous electrolyte solution. Nitrogen gas was introduced into the electrolyte at 25 °C. A porous carbon electrode sheet was used as the working electrode, a graphite electrode as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode. Deposition was performed at -0.8 V (vs. RHE) for 300 s. After deposition, the electrode was rinsed with ethanol and dried in a vacuum drying oven at 80 °C to obtain a copper-based electrode. In this copper-based electrode, the carbon support content was 63.1 wt%, the copper species content was 20.2 wt%, and the nitrogen species content was 7.9 wt%. The copper species were a mixture of Cu, Cu₂O, and CuO, wherein Cu… 2+ The proportion was 78%, of which Cu 0 The proportion is 19%; the nitrogen species is a mixture of pyrrole N, pyridine N and graphite N, wherein the proportion of pyrrole N is 46% and the proportion of pyridine N is 27%.

[0077] Example 2

[0078] Weigh 10g of petroleum coke powder and add it to 50mL of formamide. After stirring for 30min, transfer the mixture to a polytetrafluoroethylene liner, place it in a reaction vessel, and react at 180℃ for 12h. After centrifugation, dry the solid product at 80℃ for 12h to obtain pretreated petroleum coke.

[0079] Weigh 3.64g of pretreated petroleum coke, 2.72g of potassium hydroxide, and 3.64g of tyrosine, mix and grind them into powder. Under a nitrogen atmosphere, adjust the temperature to 900℃ and maintain it for 90min. After cooling to room temperature, filter and wash the activated product with deionized water until the pH of the filtrate is neutral. Dry the solid product at 105℃ for 12h to obtain nitrogen-doped porous carbon.

[0080] Nitrogen-doped porous carbon was ball-milled in a ball mill jar for 1 hour at a speed of 150 rpm. Subsequently, porous carbon, conductive carbon black, and PTFE were mixed at a mass ratio of 8:1:1 and stirred for 30 minutes to obtain a slurry mixture. This slurry mixture was then uniformly coated onto a titanium sheet with a loading of 1 mg / cm³. 2 After the slurry has dried sufficiently, it is placed on a two-roll mill for rolling to obtain porous carbon electrode sheets, which are then cut into rectangles of 1cm × 1.5cm.

[0081] 0.96 g of copper sulfate and 2.16 g of glucose were weighed and added to 100 mL of deionized water. Then, 0.06 mol of sulfuric acid was added dropwise to the solution, and the mixture was stirred for 30 min to form a homogeneous electrolyte solution. Nitrogen gas was introduced into the electrolyte at 25 °C. A porous carbon electrode sheet was used as the working electrode, a graphite electrode as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode. Deposition was performed at -0.8 V (vs. RHE) for 300 s. After deposition, the electrode was rinsed with ethanol and dried in a vacuum drying oven at 80 °C to obtain a copper-based electrode. In this copper-based electrode, the carbon support content was 72.8 wt%, the copper species content was 10.9 wt%, and the nitrogen species content was 6.4 wt%. The copper species were a mixture of Cu, Cu₂O, and CuO, wherein Cu… 2+ The proportion was 65%, of which Cu 0 The proportion of pyrrole N is 31%; the nitrogen species is a mixture of pyrrole N, pyridine N and graphite N, wherein pyrrole N accounts for 33% and pyridine N accounts for 31%.

[0082] Example 3

[0083] Weigh 10g of petroleum coke powder and add it to 30mL of N,N-dimethylformamide. After stirring for 30min, transfer the mixture to a polytetrafluoroethylene liner, place it in a reaction vessel, and react at 150℃ for 18h. After centrifugation, dry the solid product at 60℃ for 18h to obtain pretreated petroleum coke.

[0084] Weigh 3.85g of pretreated petroleum coke, 3.85g of potassium hydroxide, and 2.30g of serine, mix and grind them into powder. Under a nitrogen atmosphere, heat to 180℃ and hold for 100min. Then adjust the temperature to 800℃ and hold for 60min. After cooling to room temperature, filter and wash the activated product with deionized water until the pH of the filtrate is neutral. Dry the solid product at 80℃ for 8h to obtain nitrogen-doped porous carbon.

[0085] Nitrogen-doped porous carbon material was ball-milled in a ball mill jar for 3 hours at a speed of 100 rpm. Subsequently, porous carbon, carbon nanotubes, and PVDF were mixed at a mass ratio of 8:1:1 and stirred for 30 minutes to obtain a slurry mixture. This slurry mixture was then uniformly coated onto a glassy carbon electrode with a loading of 0.5 mg / cm³. 2 After the slurry has dried sufficiently, it is placed on a two-roll mill for rolling to obtain porous carbon electrode sheets, which are then cut into rectangles of 1cm × 1.5cm.

[0086] Weigh 0.54 g of copper chloride and 0.72 g of fructose and add them to 100 mL of deionized water. Then, add 0.04 mol of hydrochloric acid dropwise to the solution and stir for 60 min to form a homogeneous electrolyte solution. Argon gas is introduced into the electrolyte at 30 °C. Using a porous carbon electrode sheet as the working electrode, a graphite electrode as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, deposition is performed at -0.5 V (vs. RHE) for 540 s. After deposition, the electrode is rinsed with ethanol and dried in a vacuum drying oven at 60 °C to obtain a copper-based electrode. In this copper-based electrode, the carbon support content is 69.5 wt%, the copper species content is 17.2 wt%, and the nitrogen species content is 7.6 wt%. The copper species is a mixture of Cu, Cu₂O, and CuO, wherein Cu... 2+ The proportion was 74%, of which Cu 0 The proportion of is 21%; the nitrogen species is a mixture of pyrrole N, pyridine N and graphite N, wherein the proportion of pyrrole N is 39% and the proportion of pyridine N is 26%.

[0087] Example 4

[0088] Weigh 10g of petroleum coke powder and add it to 40mL of a mixture of N,N-dimethylformamide and formamide (volume ratio 1:1). After stirring for 30min, transfer the mixture to a polytetrafluoroethylene liner, load it into a reaction vessel, and react at 200℃ for 10h. After centrifugation, dry the solid product at 100℃ for 6h to obtain pretreated petroleum coke.

[0089] Weigh 4.26g of pretreated petroleum coke, 2.56g of potassium hydroxide, and 3.18g of threonine, mix and grind them into powder. Under a nitrogen atmosphere, heat to 280℃ and hold for 60min. Then adjust the temperature to 750℃ and hold for 100min. After cooling to room temperature, filter and wash the activated product with deionized water until the pH of the filtrate is neutral. Dry the solid product at 100℃ to obtain nitrogen-doped porous carbon.

[0090] Nitrogen-doped porous carbon material was ball-milled in a ball mill jar for 2 hours at a speed of 120 rpm. Subsequently, porous carbon, graphene, and PVA were mixed at a mass ratio of 7:1.5:1.5 and stirred for 30 minutes to obtain a slurry mixture. This slurry mixture was then uniformly coated onto a titanium sheet with a loading of 2 mg / cm³. 2 After the slurry has dried sufficiently, it is placed on a two-roll mill for rolling to obtain porous carbon electrode sheets, which are then cut into rectangles of 1cm × 1.5cm.

[0091] Weigh 0.48 g of copper nitrate trihydrate and 0.90 g of fructose and add them to 100 mL of deionized water. Then, add 0.02 mol of nitric acid dropwise to the solution and stir for 60 min to form a homogeneous electrolyte solution. At 40 °C, helium gas is introduced into the electrolyte. Using a porous carbon electrode sheet as the working electrode, a graphite electrode as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, deposition is performed at -1.0 V (vs. RHE) for 120 s. After deposition, the electrode is rinsed with ethanol and dried in a vacuum drying oven at 70 °C to obtain a copper-based electrode. In this copper-based electrode, the carbon support content is 71.2 wt%, the copper species content is 13.6 wt%, and the nitrogen species content is 8.5 wt%. The copper species are a mixture of Cu, Cu₂O, and CuO, wherein Cu… 2+ The proportion was 69%, of which Cu 0 The proportion of is 24%; the nitrogen species is a mixture of pyrrole N, pyridine N and graphite N, wherein the proportion of pyrrole N is 41% and the proportion of pyridine N is 22%.

[0092] Example 5

[0093] Weigh 10g of petroleum coke powder and add it to 50mL of formamide. After stirring for 30min, transfer the mixture to a polytetrafluoroethylene liner, place it in a reaction vessel, and react at 180℃ for 12h. After centrifugation, dry the solid product at 80℃ for 12h to obtain pretreated petroleum coke.

[0094] Weigh 3.64g of pretreated petroleum coke and 2.72g of potassium hydroxide, mix and grind them into powder. Under a nitrogen atmosphere, adjust the temperature to 900℃ and maintain it for 90min. After cooling to room temperature, filter and wash the activated product with deionized water until the pH of the filtrate is neutral. Dry the solid product at 105℃ for 12h to obtain nitrogen-doped porous carbon.

[0095] Nitrogen-doped porous carbon material was ball-milled in a ball mill jar for 1 hour at a milling speed of 150 rpm. Subsequently, porous carbon, conductive carbon black, and PTFE were mixed at a mass ratio of 8:1:1 and stirred for 30 minutes to obtain a slurry mixture. This slurry mixture was then uniformly coated onto a titanium sheet with a loading of 1 mg / cm³. 2After the slurry has dried sufficiently, it is placed on a two-roll mill for rolling to obtain nitrogen-doped porous carbon electrode sheets, which are then cut into rectangles of 1cm × 1.5cm.

[0096] 0.96 g of copper sulfate and 2.16 g of glucose were weighed and added to 100 mL of deionized water. Then, 0.06 mol of sulfuric acid was added dropwise to the solution, and the mixture was stirred for 30 min to form a homogeneous electrolyte solution. Nitrogen gas was introduced into the electrolyte at 25 °C. A porous carbon electrode sheet was used as the working electrode, a graphite electrode as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode. Deposition was performed at -0.8 V (vs. RHE) for 300 s. After deposition, the electrode was rinsed with ethanol and dried in a vacuum drying oven at 80 °C to obtain a copper-based electrode. In this copper-based electrode, the carbon support content was 76.0 wt%, the copper species content was 7.6 wt%, and the nitrogen species content was 8.9 wt%. The copper species were a mixture of Cu, Cu₂O, and CuO, wherein Cu… 2+ The proportion was 54%, of which Cu 0 The proportion of is 41%; the nitrogen species is a mixture of pyrrole N, pyridine N and graphite N, wherein the proportion of pyrrole N is 28% and the proportion of pyridine N is 50%.

[0097] Comparative Example 1

[0098] Weigh 3.64g of petroleum coke powder, 2.72g of potassium hydroxide, and 3.64g of tyrosine, mix and grind them into powder. Under a nitrogen atmosphere, heat to 250℃ and hold for 30min. Then adjust the temperature to 900℃ and hold for 90min. After cooling to room temperature, filter and wash the activated product with deionized water until the pH of the filtrate is neutral. Dry the solid product at 105℃ for 12h to obtain porous carbon.

[0099] Porous carbon was placed in a ball mill jar and ball-milled for 1 hour at a speed of 150 rpm. Subsequently, porous carbon, conductive carbon black, and PTFE were mixed at a mass ratio of 8:1:1 and stirred for 30 minutes to obtain a slurry mixture. This slurry mixture was then uniformly coated onto a titanium sheet with a loading of 1 mg / cm³. 2 After the slurry has dried sufficiently, it is placed on a two-roll mill for rolling to obtain porous carbon electrode sheets, which are then cut into rectangles of 1cm × 1.5cm.

[0100] 0.96 g of copper sulfate and 2.16 g of glucose were weighed and added to 100 mL of deionized water. Then, 0.06 mol of sulfuric acid was added dropwise to the solution, and the mixture was stirred for 30 min to form a homogeneous electrolyte solution. Nitrogen gas was bubbled into the electrolyte at 25 °C. A porous carbon electrode was used as the working electrode, a graphite electrode as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode. Deposition was performed at -0.8 V (vs. RHE) for 300 s. After deposition, the electrode was rinsed with ethanol and dried in a vacuum drying oven at 80 °C to obtain a copper-based electrode. In this copper-based electrode, the carbon support content was 75.0 wt%, and the copper species content was 14.5 wt%, wherein the copper species was a mixture of Cu, Cu₂O, and CuO, wherein Cu… 2+ The proportion was 45%, of which Cu 0 The proportion was 13%.

[0101] Comparative Example 2

[0102] Weigh 10g of petroleum coke powder and add it to 30mL of N,N-dimethylformamide. After stirring for 30min, transfer the mixture to a polytetrafluoroethylene liner, place it in a reaction vessel, and react at 150℃ for 18h. After centrifugation, dry the solid product at 60℃ for 18h to obtain pretreated petroleum coke.

[0103] Weigh 3.85g of pretreated petroleum coke, 3.85g of potassium hydroxide, and 2.30g of serine, mix and grind them into powder. Under a nitrogen atmosphere, heat to 180℃ and hold for 100min. Then adjust the temperature to 800℃ and hold for 60min. After cooling to room temperature, filter and wash the activated product with deionized water until the pH of the filtrate is neutral. Dry the solid product at 80℃ for 8h to obtain nitrogen-doped porous carbon.

[0104] Nitrogen-doped porous carbon material was ball-milled in a ball mill jar for 3 hours at a speed of 100 rpm. Subsequently, porous carbon, carbon nanotubes, and PVDF were mixed at a mass ratio of 8:1:1 and stirred for 30 minutes to obtain a slurry mixture. This slurry mixture was then uniformly coated onto a glassy carbon electrode with a loading of 0.5 mg / cm³. 2 After the slurry has dried sufficiently, it is placed on a two-roll mill for rolling to obtain porous carbon electrode sheets, which are then cut into rectangles of 1cm × 1.5cm.

[0105] 0.54 g of copper chloride was weighed and added to 100 mL of deionized water. Then, 0.04 mol of hydrochloric acid was added dropwise to the solution, and the mixture was stirred for 60 min to form a homogeneous electrolyte solution. Argon gas was introduced into the electrolyte at 30 °C. A porous carbon electrode was used as the working electrode, a graphite electrode as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode. Deposition was performed at -0.5 V (vs. RHE) for 540 s. After deposition, the electrode was rinsed with ethanol and dried in a vacuum drying oven at 60 °C to obtain a copper-based electrode. In this copper-based electrode, the carbon support content was 76.3 wt%, the copper species content was 13.1 wt%, and the nitrogen species content was 7.1 wt%. The copper species were a mixture of Cu, Cu₂O, and CuO, wherein Cu… 2+ The proportion was 64%, of which Cu 0 The proportion is 17%; the nitrogen species is a mixture of pyrrole N, pyridine N and graphite N, wherein the proportion of pyrrole N is 36% and the proportion of pyridine N is 27%.

[0106] Comparative Example 3

[0107] Weigh 10g of petroleum coke powder and add it to 40mL of a mixture of N,N-dimethylformamide and formamide (volume ratio 1:1). After stirring for 30min, transfer the mixture to a polytetrafluoroethylene liner, load it into a reaction vessel, and react at 200℃ for 10h. After centrifugation, dry the solid product at 100℃ for 6h to obtain pretreated petroleum coke.

[0108] Weigh 4.26g of pretreated petroleum coke, 2.56g of potassium hydroxide, and 3.18g of glycine, mix and grind them into powder. Under a nitrogen atmosphere, heat to 280℃ and hold for 60min. Then adjust the temperature to 750℃ and hold for 100min. After cooling to room temperature, filter and wash the activated product with deionized water until the pH of the filtrate is neutral. Dry the solid product at 100℃ to obtain nitrogen-doped porous carbon.

[0109] Nitrogen-doped porous carbon material was ball-milled in a ball mill jar for 2 hours at a speed of 120 rpm. Subsequently, porous carbon, graphene, and PVA were mixed at a mass ratio of 7:1.5:1.5 and stirred for 30 minutes to obtain a slurry mixture. This slurry mixture was then uniformly coated onto a titanium sheet with a loading of 2 mg / cm³. 2 After the slurry has dried sufficiently, it is placed on a two-roll mill for rolling to obtain porous carbon electrode sheets, which are then cut into rectangles of 1cm × 1.5cm.

[0110] Weigh 0.48 g of copper nitrate trihydrate and 0.90 g of fructose and add them to 100 mL of deionized water. Then, add 0.02 mol of nitric acid dropwise to the solution and stir for 60 min to form a homogeneous electrolyte solution. At 40 °C, helium gas is introduced into the electrolyte. Using a porous carbon electrode sheet as the working electrode, a graphite electrode as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, deposition is performed at -1.0 V (vs. RHE) for 120 s. After deposition, the electrode is rinsed with ethanol and dried in a vacuum drying oven at 70 °C to obtain a copper-based electrode. In this copper-based electrode, the carbon support content is 78.7 wt%, the copper species content is 8.8 wt%, and the nitrogen species content is 5.13 wt%. The copper species is a mixture of Cu, Cu₂O, and CuO, wherein Cu... 2+ The proportion was 46%, of which Cu 0 The proportion is 35%; the nitrogen species is a mixture of pyrrole N, pyridine N and graphite N, wherein the proportion of pyrrole N is 24% and the proportion of pyridine N is 20%.

[0111] Comparative Example 4

[0112] Weigh 10g of petroleum coke powder and add it to 50mL of formamide. After stirring for 30min, transfer the mixture to a polytetrafluoroethylene liner, place it in a reaction vessel, and react at 180℃ for 12h. After centrifugation, dry the solid product at 80℃ for 12h to obtain pretreated petroleum coke.

[0113] Weigh 3.64g of pretreated petroleum coke and 2.72g of potassium hydroxide, mix and grind them into powder. Under a nitrogen atmosphere, heat to 900℃ and hold for 120min. After cooling to room temperature, filter and wash the activated product with deionized water until the pH of the filtrate is neutral. Dry the solid product at 105℃ for 12h to obtain nitrogen-doped porous carbon.

[0114] Nitrogen-doped porous carbon material was ball-milled in a ball mill jar for 1 hour at a milling speed of 150 rpm. Subsequently, porous carbon, conductive carbon black, and PTFE were mixed at a mass ratio of 8:1:1 and stirred for 30 minutes to obtain a slurry mixture. This slurry mixture was then uniformly coated onto a titanium sheet with a loading of 1 mg / cm³. 2 After the slurry has dried sufficiently, it is placed on a two-roll mill for rolling to obtain nitrogen-doped porous carbon electrode sheets, which are then cut into rectangles of 1cm × 1.5cm.

[0115] 0.96 g of copper sulfate and 2.16 g of citric acid were weighed and added to 100 mL of deionized water. Then, 0.06 mol of sulfuric acid was added dropwise to the solution, and the mixture was stirred for 30 min to form a homogeneous electrolyte solution. Nitrogen gas was introduced into the electrolyte at 25 °C. A porous carbon electrode sheet was used as the working electrode, a graphite electrode as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode. Deposition was performed at -0.8 V (vs. RHE) for 300 s. After deposition, the electrode was rinsed with ethanol and dried in a vacuum drying oven at 80 °C to obtain a copper-based electrode. In this copper-based electrode, the carbon support content was 82.4 wt%, the copper species content was 4.0 wt%, and the nitrogen species content was 4.3 wt%. The copper species were a mixture of Cu, Cu₂O, and CuO, wherein Cu… 2+ The proportion was 47%, of which Cu 0 The proportion of is 22%; the nitrogen species is a mixture of pyrrole N, pyridine N and graphite N, wherein the proportion of pyrrole N is 31% and the proportion of pyridine N is 21%.

[0116] Electrochemical performance testing of copper-based catalytic electrodes:

[0117] A series of electrocatalytic carbon dioxide reduction tests were conducted in an H-type electrolytic cell separated by a proton exchange membrane. High-purity carbon dioxide gas was introduced at a flow rate of 20 sccm / mL at the cathode side and high-purity argon gas at a flow rate of 20 sccm / mL at the anode side. A three-electrode system was used, employing 0.5 M KHCO3 solution as the electrolyte, a silver / silver chloride electrode as the reference electrode, a platinum wire electrode as the counter electrode, and a copper-based electrode as the working electrode. Cyclic voltammetry, linear sweep voltammetry, and chronoamperometry at potentials of -0.8 to -1.2 V (vs. RHE) were performed on the catalyst using an electrochemical workstation. Gas chromatography was used for qualitative and quantitative analysis of the gaseous products. The test results are as follows: Figure 4 , 5 The data are shown in Tables 1 and 2. Table 1 shows the Faraday efficiency data of the catalytic electrodes provided in Examples 1-5 and Comparative Examples 1-4 for the electrocatalytic reduction of carbon dioxide into gaseous products, including hydrogen, carbon monoxide, methane, and ethylene, with an applied potential of -1.0V (vs. RHE). Figure 4 Table 2 shows the Faraday efficiency data of the catalytic electrode provided in Example 1 of this invention for the electrocatalytic reduction of carbon dioxide into gaseous products, including four products: hydrogen, carbon monoxide, methane, and ethylene, with an applied potential of -0.8 to 1.2 V (vs. RHE). Figure 5 .

[0118] Table 1

[0119]

[0120]

[0121] Table 2

[0122]

[0123] like Figure 4 As shown, at a potential of -1.0V (vs. RHE), the catalytic electrode provided in Example 1 exhibited the best methane Faradaic efficiency, while the catalytic electrode provided in Example 5, which did not add any modifier during the preparation of nitrogen-doped porous carbon, showed poor performance with a methane Faradaic efficiency of only 15.4%. This confirms the feasibility of modifying nitrogen-doped porous carbon by introducing a modifier in this invention, providing favorable conditions for the subsequent electrodeposition process. Furthermore, the catalytic electrode provided in Comparative Example 1, which was not nitrogen-doped before petroleum coke activation, showed a significant difference in the distribution of its reduction products compared to Example 1, reflecting the activation effect of nitrogen doping on CO2 molecules. It also inhibits the occurrence of hydrogen evolution side reactions, improves the adsorption of *CO intermediates, and increases the formation of hydrocarbon products on the surface of the catalytic electrode. The catalytic electrode provided in Comparative Example 2, which did not have hydroxyl-containing compounds added to the electrolyte during deposition, also showed a significant difference in electrochemical performance compared to Example 3. This indicates that introducing hydroxyl-rich compounds into the deposition electrolyte can provide a certain degree of hydroxyl coverage on the surface of copper species, thereby providing effective sites for *CO intermediates.

[0124] Figure 5 As can be seen, with the increase of the applied potential, the selectivity of hydrocarbons exhibits a process of first increasing and then decreasing, with the CO selectivity gradually decreasing. This is mainly because CO has a shorter reaction pathway and a lower overpotential. However, with the increase of current density (overpotential), the adsorbed CO will further undergo hydrogenation to form hydrocarbons. The catalyst provided in Example 1 exhibits unique product selectivity characteristics, achieving a methane Faradaic efficiency of 55.3% at a potential of -1.0V (vs. RHE), while the H2 selectivity is only 21.6%.

Claims

1. A doped copper-based catalytic electrode, the doped copper-based catalytic electrode comprising a porous carbon matrix, nitrogen species, and copper species, wherein, based on the weight of the doped copper-based catalytic electrode, the porous carbon matrix comprises 60 wt% to 90 wt% of carbon, preferably 65 wt% to 80 wt%; the copper species comprises 5 wt% to 25 wt% of copper, preferably 10 wt% to 20 wt%; and the nitrogen species comprises 5 wt% to 15 wt% of nitrogen, preferably 5 wt% to 10 wt%.

2. The doped copper-based catalytic electrode according to claim 1, wherein, The nitrogen species include pyrrole nitrogen, pyridine nitrogen and graphitic nitrogen, wherein the content of pyrrole nitrogen is 20% to 50%, preferably 30% to 45%; and the content of pyridine nitrogen is 10% to 40%, preferably 20% to 30%.

3. The doped copper-based catalytic electrode according to claim 1, wherein, The copper species is Cu (Cu 0 Cu2O (Cu + ) and CuO (Cu 2+ A mixture of copper species distributed on a porous carbon matrix.

4. The doped copper-based catalytic electrode according to claim 1, wherein, Cu in surface copper species 2+ The content is 40%–90%, preferably 45%–80%; Cu 0 The content is 10% to 50%, preferably 15% to 45%.

5. A method for preparing a doped copper-based catalytic electrode, the method comprising the following steps: (1) Petroleum coke is pretreated by contacting it with nitrogen-containing compounds, and then separated and dried to obtain pretreated petroleum coke. (2) Under the presence of an activator, the pretreated petroleum coke obtained in step (1) is activated and then washed and dried to obtain nitrogen-doped carbon material; (3) Prepare nitrogen-doped carbon electrodes using the nitrogen-doped carbon material obtained in step (2) as a substrate; (4) Copper is introduced onto the nitrogen-doped carbon electrode obtained in step (3) by electrochemical deposition to obtain a doped copper-based catalytic electrode.

6. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, The pretreatment reaction temperature in step (1) is 120-220℃, preferably 150-200℃.

7. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, The nitrogen-containing compound in step (1) is selected from one or more of ethylenediamine, N-methylpyrrolidone, N,N-dimethylformamide, triethylamine, ammonia solution, formamide, and acetamide, preferably formamide.

8. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, The volume-to-mass ratio of the nitrogen-containing compound to the petroleum coke in step (1) is 8:1 to 2:1, preferably 5:1 to 3:

1.

9. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, The activation process in step (2) is as follows: Under the condition of an inert atmosphere, the pretreated petroleum coke and activator obtained in step (1) are heated to activate the petroleum coke and activator. The activation conditions are as follows: the activation temperature is 700-1100℃, preferably 750-900℃; the inert atmosphere is selected from one or more of nitrogen, helium and argon.

10. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, Before the activation treatment in step (2), there is a pre-activation treatment, the temperature of which is 150-300℃, preferably 180-280℃.

11. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, The activator in step (2) is an alkaline activator, which is at least one of the following: hydroxide containing alkali metal elements, salt containing alkali metal elements, hydroxide containing alkaline earth metal elements, and salt containing alkaline earth metal elements; the specific activator is selected from one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, potassium carbonate, and potassium bicarbonate, preferably potassium hydroxide.

12. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, The mass ratio of the pretreated petroleum coke to the activator obtained in step (1) in step (2) is 1:0.2 to 1:2, preferably 1:0.6 to 1:

1.

13. The method for preparing the doped copper-based catalytic electrode according to claim 5 or 9, wherein, In the activation process of step (2), a modifier is introduced. The modifier is an organic compound containing both amino and hydroxyl groups. The compound containing both amino and hydroxyl groups is an amino acid containing hydroxyl groups, selected from one or more of serine, threonine, and tyrosine.

14. The method for preparing the doped copper-based catalytic electrode according to claim 13, wherein, The mass ratio of the modifier to the pretreated petroleum coke obtained in step (1) is 2:1 to 0.5:1, preferably 1:1 to 0.6:

1.

15. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, In step (3), the nitrogen-doped carbon electrode is prepared by at least one of the following methods: wet coating, dry coating, and electrostatic spraying.

16. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, The preparation process of nitrogen-doped carbon electrode in step (3) is as follows: the nitrogen-doped carbon material, conductive agent and binder obtained in step (2) are mixed evenly and then coated evenly on the current collector. After the slurry is fully dried, it is rolled to obtain a porous carbon electrode.

17. The method for preparing the doped copper-based catalytic electrode according to claim 16, wherein, The conductive agent is at least one of conductive carbon black, graphene, carbon nanotubes, and conductive graphite; the binder is at least one of polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), hydroxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyvinylidene fluoride (PVDF); the current collector is at least one of glassy carbon electrode, carbon paper, carbon cloth, copper foil, titanium sheet, and stainless steel mesh.

18. The method for preparing the doped copper-based catalytic electrode according to claim 16, wherein, The ratio of nitrogen-doped carbon material, conductive agent, and binder is 7–9:0.5–2:0.5–2.

19. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, The electrochemical deposition method in step (4) includes the following steps: (4.1) Under mixed conditions, copper precursor, inorganic acid, organic compound containing polyhydroxyl group and water are mixed to obtain electrolyte solution; (4.2) Under the protection of an inert atmosphere, copper nanoparticles are grown on the surface of a nitrogen-doped carbon electrode using a three-electrode system under constant potential conditions. The proportion of copper species in different valence states in the copper nanoparticles is controlled by adjusting the deposition charge. After deposition, the copper nanoparticles are washed and dried to obtain a nitrogen-doped copper-based catalytic electrode.

20. The method for preparing the doped copper-based catalytic electrode according to claim 19, wherein, The copper precursor in step (4.1) is a copper salt, which is selected from one or more of copper chloride, copper sulfate, copper nitrate, and copper acetate. The concentration of copper ions in the electrolyte solution is 0.01 to 0.1 mol / L, preferably 0.02 to 0.06 mol / L.

21. The method for preparing the doped copper-based catalytic electrode according to claim 19, wherein, The inorganic acid in step (4.1) is preferably one or more of hydrochloric acid, sulfuric acid, and nitric acid, wherein the concentration of the inorganic acid in the electrolyte solution is 0.1 to 1 mol / L, preferably 0.2 to 0.6 mol / L.

22. The method for preparing the doped copper-based catalytic electrode according to claim 19, wherein, The organic compound containing multiple hydroxyl groups mentioned in step (4.1) is an organic compound containing three or more hydroxyl groups, preferably an organic compound containing four or more hydroxyl groups, selected from carbohydrate compounds, specifically one or more of glucose, fructose, lactose, and maltose, and its mass ratio with copper salt is 0.5:1 to 4:1, preferably 1:1 to 2.5:

1.

23. The method for preparing the doped copper-based catalytic electrode according to claim 19, wherein, In the three-electrode system of step (4.2), the working electrode is the nitrogen-doped carbon electrode obtained in step (3), the counter electrode is at least one of graphite electrode and platinum wire electrode, preferably graphite electrode, and the reference electrode is at least one of silver / silver chloride electrode, saturated calomel electrode and mercury / mercury oxide electrode, preferably silver / silver chloride electrode.

24. The method for preparing the doped copper-based catalytic electrode according to claim 19, wherein, The constant voltage is -0.1 V to -1.4 V (vs. RHE), preferably -0.5 V to -1.0 V (vs. RHE).

25. The method for preparing the doped copper-based catalytic electrode according to claim 5, wherein, The deposition time is 60–900 s, preferably 120–540 s; the deposition temperature is 20–40 °C.

26. The doped copper-based catalytic electrode according to any one of claims 1-4 and / or the doped copper-based catalytic electrode obtained by the preparation method according to any one of claims 5-25 is used in the electrocatalytic reduction of carbon dioxide to methane.

Images