A method for electrocatalytic conversion of carbon dioxide to ethylene using copper-based catalyst precursors driven by surface amidation.

Abstract

This invention discloses a method for the electrocatalytic conversion of carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation. The invention employs a precursor engineering strategy, reacting copper salts with dicyandiamide in a sodium hydroxide solution, and precisely controlling the temperature and pH to prepare a nitrogen-modified copper oxide precursor. This precursor is then reconstructed in situ under electrocatalytic reduction conditions into an oxide-derived copper (OD copper) active structure with abundant grain boundaries and defects, simultaneously achieving the coexistence of lattice-doped nitrogen and interfacial amidated nitrogen. The preparation method involves precisely designing the precursor grain size, defect density, and nitrogen species distribution by controlling the type of copper source, segmented reaction temperature control, heating / cooling rates, and pH value, thereby indirectly controlling the particle size, grain boundary density, and nitrogen doping depth of the final OD copper active phase.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials, and in particular to a method for electrocatalytically converting carbon dioxide into ethylene using a copper-based catalyst precursor driven by surface amidation. Background Technology

[0002] Utilizing clean electricity generated from renewable energy sources such as solar and wind power to drive carbon dioxide reduction reactions, converting it into high-value-added fuels and chemicals, is a cutting-edge strategy for simultaneously achieving carbon cycling and energy storage. Among the many reduction products, multi-carbon products such as ethylene and ethanol have attracted considerable attention due to their high energy density and market demand. However, the electrocatalytic reduction of CO2 to C... 2+ The product still faces significant challenges: complex reaction pathways, difficulty in controlling product selectivity, severe competitive hydrogen evolution reactions, and structural instability of the catalyst under reaction conditions.

[0003] Copper is currently recognized as the only metallic element capable of efficiently converting CO2 into multi-carbon products. To improve its performance, researchers have developed various strategies, such as constructing nanostructures, creating defects, introducing dopant atoms, or performing surface modifications. For example, hollow or porous structures are prepared to increase specific surface area and CO2 adsorption capacity; or nitrogen is introduced to modulate the electronic state of copper. However, most existing technologies focus on single-dimensional regulation, and these methods often fail to achieve synergistic promotion of CO2 activation, key intermediate stabilization, and CC coupling steps. In particular, current understanding and utilization of nitrogen species are usually limited to the static level of electron donors or structural stabilizers, failing to fully utilize their potential to dynamically evolve into key reaction intermediates during the reaction process, thus limiting further improvements in catalytic performance.

[0004] Therefore, developing a novel catalytic material capable of synergistically controlling the bulk electronic structure of the catalyst and the interfacial reaction microenvironment at the atomic scale, and capable of forming active intermediate bridges in situ during the reaction, is crucial for overcoming current limitations in CO2-to-C2 catalysts. 2+ The bottlenecks in activity and selectivity of the transformation are crucial. Summary of the Invention

[0005] This invention addresses the problems of high CC coupling energy barrier, severe competitive hydrogen evolution, and easy instability of catalyst structure in electrocatalytic CO2 reduction by providing a method for electrocatalytically converting carbon dioxide into ethylene using surface amidation to drive a copper-based catalyst precursor.

[0006] In this invention, a nitrogen-coordinated copper oxide precursor is first synthesized via a wet chemical method, and a specific nitrogen species distribution is pre-constructed within it. Subsequently, under electrocatalytic reduction conditions, this precursor is reconstructed in situ into an oxide-derived copper (OD copper) active structure with a bulk-interface nitrogen synergistic effect. This design achieves indirect but decisive control over the particle size, grain boundary density, nitrogen doping depth, and surface functional group morphology of the final active phase of the catalyst—OD copper. Through a unique bulk-interface nitrogen synergistic engineering design, the catalyst simultaneously constructs lattice-doped nitrogen and surface-functionalized nitrogen within the copper matrix. This structure not only stabilizes the valence state of active copper but also dynamically evolves into an amide bond intermediate under electroreduction conditions, providing a crucial coupling bridge for CO2-derived intermediates, thereby efficiently driving the generation of multi-carbon products.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention achieves precise design of the precursor structure through temperature-pH synergistic regulation and copper source selection: 1. Precise temperature control in stages This invention divides the reaction process into three stages: coordination activation, lattice doping, and structure solidification. Each stage is independently optimized through precise heating / cooling rates: Low-temperature coordination activation stage (0-35℃, heating rate 1-2℃ / min): Slow heating ensures uniform adsorption of the cyano group (-C≡N) at the dicyandiamide end onto the copper hydroxyl oxide surface, preventing rapid hydrolysis or self-polymerization of dicyandiamide; Isothermal doping reaction stage (holding temperature for 1-3 hours): Within this core temperature window, the coordinated dicyandiamide undergoes chemical reconstruction: the nitrogen-terminus of the cyano group reacts with Cu… 2+ Strong coordination-induced electron transfer will transfer some Cu 2+ In-situ reduction to Cu with higher catalytic activity + To form a stable ≡N-Cu + -OH interface structure; simultaneously, reactive nitrogen species (such as NH4+) generated from the decomposition of dicyandiamide. 2- Nitrogen (-N) begins to diffuse into the interior of the copper lattice, achieving lattice doping. If the holding time is insufficient, nitrogen will only remain on the surface; if it is too long, it may lead to excessive nitriding on the surface, forming a passivation layer. During the cooling and curing stage (cooling rate 1-2℃ / min), the temperature is controlled and slowly lowered to maintain the metastable nitrogen-doped structure formed at high temperature (such as a specific Cu-N coordination configuration), preventing rapid cooling from causing uneven lattice stress.

[0008] 2. Synergistic regulation of pH value This invention maintains the pH of the reaction system between 11 and 13. This pH range has a dual effect: it allows copper ions to be converted into Cu(OH)4. 2-The presence of these forms facilitates the subsequent formation of defect-rich OD copper precursors. The effect on dicyandiamide is to ensure its deprotonated or neutral form, with the cyano group exhibiting the strongest nucleophilicity, effectively competing for coordination sites on the copper surface and forming stable chemical bonds. If the pH is too low (<10), dicyandiamide is protonated and deactivated; if the pH is too high (>13), OH... - Excessive competitive coordination inhibits dicyandiamide adsorption. Maintaining pH during the isothermal doping stage achieves an optimal match between thermodynamic energy supply and nucleophilic reaction environment, ensuring a balance between effective dicyandiamide coordination and moderate decomposition, thus achieving optimal nitrogen doping efficiency.

[0009] This invention achieves precise control over the grain size, defect density, and nitrogen species distribution of precursors through the synergistic regulation of temperature and pH. These precursor characteristics directly determine their reconstruction behavior under electroreduction conditions and the structure of the final OD copper active phase.

[0010] A method for preparing a surface-amidated copper-based catalyst precursor includes the following steps: adding a copper salt to an aqueous sodium hydroxide solution, heating and stirring under segmented temperature control, then adding dicyandiamide, continuing stirring to allow the dicyandiamide to coordinate with copper species, separating the solid from the reaction solution, drying to obtain a nitrogen-modified copper oxide precursor material, using the nitrogen-modified copper oxide precursor material as a catalyst for electrocatalytic CO2 reduction to ethylene; the nitrogen-modified copper oxide precursor material is reconstructed in situ under electrocatalytic CO2 reduction conditions into an oxide-derived copper (OD copper) active structure with a bulk-interface nitrogen synergistic effect.

[0011] This invention employs a precursor engineering strategy, reacting copper salts with dicyandiamide in a sodium hydroxide solution and precisely controlling the temperature and pH to prepare a nitrogen-modified copper oxide precursor. This precursor is then reconstructed in situ under electrocatalytic reduction conditions into an oxide-derived copper (OD copper) active structure with abundant grain boundaries and defects, simultaneously achieving the coexistence of lattice-doped nitrogen and interfacial amidated nitrogen. The preparation method involves precisely designing the precursor grain size, defect density, and nitrogen species distribution by controlling the type of copper source, segmented reaction temperature control, heating / cooling rates, and pH value, thereby indirectly controlling the particle size, grain boundary density, and nitrogen doping depth of the final OD copper active phase. During electrocatalysis, interfacial nitrogen species and reaction intermediates form dynamic amide bonds (-NH-C=O) in situ, giving the electrocatalytic interface a reversible surface amidation effect. These dynamic amide bonds are not static modification groups, but rather act as efficient "molecular bridges." By stabilizing the *CO intermediate and providing a novel, lower-barrier CC coupling pathway, they actively guide the reaction toward ethylene, resulting in a significant improvement in electrocatalytic performance.

[0012] Preferably, the copper salt is selected from one or more of the following: copper chloride (CuCl2·2H2O), copper nitrate (Cu(NO3)2·3H2O), copper acetate (Cu(CH3COO)2·H2O), and copper sulfate (CuSO4·5H2O), wherein the ratio of the copper salt to the sodium hydroxide aqueous solution is 0.02-0.06 mol:1000 mL. More preferably, the copper salt is copper chloride (CuCl2·2H2O), and the concentration of the copper salt solution is 0.02-0.06 mol / L. The molar ratio of the copper salt to dicyandiamide is 1:0.5-3.

[0013] Preferably, the mixture is heated to 33-37°C at a heating rate of 1-2°C / min and stirred. More preferably, the heating temperature is 35°C. The coordination reaction temperature is 33-37°C, and the coordination reaction time is 2-5 hours. The cyano groups of dicyandiamide are uniformly adsorbed onto the surface of copper species. The temperature is controlled at 35°C and maintained for 1-3 hours, causing chemical reconstruction of the dicyandiamide, with some of the nitrogen-terminated cyano groups coordinating with copper to form ≡N-Cu. + -OH interface structure, while active nitrogen species diffuse into the copper lattice to achieve bulk doping; cooling rate is controlled at 1-2℃ / min to maintain metastable nitrogen-doped structure.

[0014] Preferably, the concentration of the sodium hydroxide solution is 0.05-0.1 mol / L.

[0015] Preferably, the ratio of dicyandiamide to sodium hydroxide aqueous solution is 0.02-0.12 mol: 1000 mL. More preferably, the concentration of the dicyandiamide solution is 0.02-0.12 mol / L.

[0016] Preferably, centrifugal separation is used for separation, and the solid after centrifugation is washed with water 1-3 times and with alcohol 1-3 times; drying is carried out by vacuum freeze drying.

[0017] This invention also provides the application of the catalytic material prepared by the method for preparing the surface-amidated copper-based catalyst in the electrocatalytic production of ethylene from CO2. During the in-situ reconstruction of the nitrogen-modified copper oxide precursor into the OD copper active phase under electrocatalytic CO2 reduction conditions, copper oxide species are electrochemically reduced to metallic copper, accompanied by oxygen release, resulting in grain boundaries and defects. The initial morphology disintegrates and reassembles into nanoparticle aggregates. The pre-doped nitrogen species in the precursor migrate and rearrange, ultimately forming a bulk-interface synergistic structure where lattice-doped nitrogen and interfacial amidated nitrogen coexist.

[0018] The product directly obtained by the preparation method described in this invention is a nitrogen-modified copper oxide precursor, rather than the final active phase. In the initial stage of the electrocatalytic CO2 reduction reaction (the first 5-10 minutes after energization), this precursor undergoes in-situ electrochemical reconstruction at the reduction potential. During this reconstruction, the pre-doped nitrogen species in the precursor undergo dynamic migration and rearrangement, ultimately forming lattice-doped nitrogen (stabilizing the copper valence state and regulating the electronic structure) and interfacial amidated nitrogen (forming ≡N-Cu). + The invention achieves indirect control of the final OD copper active phase by precisely controlling the precursor structure: the precursor grain size determines the OD copper grain size, the precursor nitrogen distribution pattern determines the ratio of lattice nitrogen to interface nitrogen in OD copper, and the precursor defect density affects the number of OD copper grain boundaries.

[0019] Therefore, the beneficial effects of the present invention are as follows: The introduction of dicyandiamide precursors constructs a synergistic system of bulk lattice nitrogen doping and interfacial amidation nitrogen modification on copper-based catalysts. This unique "bulk-interfacial nitrogen synergy" engineering can fundamentally regulate the electronic state of active copper sites, stabilize their valence states required for catalysis, and optimize the adsorption behavior of key reaction intermediates. During electrocatalysis, surface nitrogen can react with intermediates such as COOH generated from CO2 reduction, forming dynamic amide bonds (-NH-C=O) in situ. These amide bonds, as key active bridging species, not only stabilize reaction intermediates but also provide novel, lower-barrier C / C coupling pathways for adjacent CO intermediates, directly guiding the reaction towards multi-carbon products. Simultaneously, the stabilizing effect of lattice nitrogen enhances the structural durability of the catalyst during long-term operation. The cyanamide-modified copper electrocatalytic material of this invention can efficiently and selectively convert CO2 into high-value C. 2+ The product effectively suppresses the competing hydrogen evolution reaction, achieving a simultaneous improvement in catalytic activity, selectivity, and stability. Experimental results show that the catalytic material of this invention exhibits performance at 600 mA·cm⁻¹. -2 Under certain conditions, electrocatalytic CO2 reduction of C 2+ The product's Faraday efficiency exceeded 80%, and the surface-amidated copper-based catalyst showed better electrocatalytic CO2 reduction of C2 compared to unmodified copper. 2+ The Faraday efficiency of the product was improved by about 31%. Attached Figure Description

[0020] Figure 1 This is an SEM image of the electrocatalytic material sample from Example 2.

[0021] Figure 2 This is a SEM image of the electrocatalytic material sample after the reaction in Example 2.

[0022] Figure 3These are XRD patterns of the electrocatalytic material sample before and after the reaction in Example 2.

[0023] Figure 4 These are the FTIR spectra of the electrocatalytic material sample and the dicyandiamide drug from Example 2.

[0024] Figure 5 This is the XPS N1s spectrum of the electrocatalytic material sample from Example 2. Figure 6 This is the TG-MS image of the electrocatalytic material sample from Example 2. Figure 7 These are XPS Cu LMM spectra of the electrocatalytic material sample before and after the reaction in Example 2.

[0025] Figure 8 SEM images of the electrocatalytic material sample in Comparative Example 1 Figure 9 The images show the FTIR spectra of the electrocatalytic material sample and the cyanamide drug in Comparative Example 2. Detailed Implementation

[0026] The technical solution of the present invention will be further described below through specific embodiments.

[0027] In this invention, unless otherwise specified, all raw materials and equipment used are commercially available or commonly used in the art. The methods described in the examples, unless otherwise specified, are conventional methods in the art. Unless otherwise indicated, all parts are by weight, temperatures are expressed in °C or at ambient temperature, and pressures are at or near atmospheric pressure. Various variations and combinations of reaction conditions (e.g., component concentrations, required solvents, solvent mixtures, temperature, pressure, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the method exist, requiring only reasonable routine experiments to optimize such method conditions.

[0028] Example A method for preparing a bulk-interfacial nitrogen-synergistic engineered copper catalyst includes the following steps: Add copper salt to an aqueous solution of sodium hydroxide and heat to 35°C while stirring to dissolve; In this invention, copper salt is a general term for all salts whose cation is copper ion, wherein the oxidation state of copper ion is +2. Copper chloride dihydrate is preferred. The concentration of copper salt is 0.02-0.06 mol / L. The cyanamide is selected from dicyandiamide, and the concentration of the dicyandiamide solution is 0.02-0.12 mol / L. The concentration of sodium hydroxide solution is 0.05-0.1 mol / L. After adding sodium hydroxide, the mixture is stirred for 0.5-1 h. The solid is separated from the above reaction solution and dried to obtain the product. The separation process employed centrifugation, followed by 1-3 water washes and 1-3 alcohol washes with the resulting solids. Drying was performed using vacuum freeze-drying at -50°C. The product was a bulk-interfacial nitrogen-co-engineered copper-based catalyst precursor.

[0029] It should be noted that the product directly obtained by the preparation method described in this invention is a bulk-interfacial nitrogen-coordinated engineered copper-based precursor material. In the initial stage of the electrocatalytic CO2 reduction reaction (typically the first 5-10 minutes after energization), this precursor undergoes in-situ electrochemical reconstruction at the reduction potential, reducing copper oxide species to metallic copper, accompanied by significant morphological evolution, ultimately forming an oxide-derived copper (OD copper) active structure with abundant grain boundaries, defect sites, and specific nitrogen species distribution (e.g., Figure 2 (As shown). Therefore, this invention indirectly but decisively controls the structural characteristics and catalytic performance of the final active phase by precisely regulating the chemical composition and microstructure of the precursor.

[0030] This invention also provides the application of the catalytic material prepared by the method of preparing the bulk-interface nitrogen-synergistic engineered copper-based catalyst in the electrocatalytic generation of multi-carbon products from carbon dioxide. The introduction of dicyandiamide constructs a unique "lattice nitrogen-surface dynamic nitrogen" synergistic structure on the copper matrix. This nitrogen-engineered surface can not only effectively capture and activate CO2 molecules, but its surface amine species can also react with key intermediates such as *COOH generated during CO2 reduction, constructing dynamic amide bond active bridges in situ. This amide bond, as a key reaction site, can significantly stabilize C1 intermediates and greatly reduce the C-C coupling barrier by providing new reaction channels, thereby directionally guiding the reaction pathway towards the generation of multi-carbon products. Simultaneously, the lattice-doped nitrogen atoms stabilize the copper valence state of the catalytic active center through strong electronic effects, effectively suppressing catalyst deactivation and reconstruction during operation. The bulk-interface nitrogen-synergistic engineered copper electrocatalytic material of this invention can efficiently suppress competitive hydrogen evolution reaction and highly selectively convert CO2 into ethylene, achieving a comprehensive improvement in catalytic performance.

[0031] Example 1 A method for preparing a material using surface amidation-driven electrocatalytic conversion of carbon dioxide to ethylene from a copper-based catalyst precursor comprises the following steps: Weigh 160 mg of sodium hydroxide and prepare a 50 mL aqueous solution, which is then poured into a beaker; then weigh 341 mg of copper chloride dihydrate and add it to the solution, stirring until homogeneous. The heating rate is controlled while continuously stirring at 35 °C; weigh 168.16 mg of dicyandiamide and add it to the solution. After stirring continuously for 0.5 h, continue stirring at 35 °C for 2 h, then stop stirring. The precipitate obtained after washing twice with distilled water and once with ethanol by centrifugation is dried in a vacuum freeze dryer at -50 °C to obtain a bulk-interfacial nitrogen-synergistic engineered copper-based catalyst precursor.

[0032] Example 2 A method for preparing a material using surface amidation-driven electrocatalytic conversion of carbon dioxide to ethylene from a copper-based catalyst precursor comprises the following steps: Weigh 160 mg of sodium hydroxide and prepare a 50 mL aqueous solution, which is then poured into a beaker; then weigh 341 mg of copper chloride dihydrate and add it to the solution, stirring until homogeneous. The heating rate is controlled while continuously stirring at 35 °C; weigh 336.32 mg of dicyandiamide and add it to the solution. After stirring continuously for 0.5 h, continue stirring at 35 °C for 2 h, then stop stirring. The precipitate obtained after washing twice with distilled water and once with ethanol by centrifugation is dried in a vacuum freeze dryer at -50 °C to obtain a bulk-interfacial nitrogen-synergistic engineered copper-based catalyst precursor.

[0033] The materials prepared in this embodiment were analyzed. Figure 1 and Figure 2 SEM results showed that the synthesized precursor was nanowire-shaped CuO, and after electroreduction, based on the SEM images before and after the reaction, and Figure 3 The XRD pattern shows that its morphology has been significantly reconstructed, the nanowire structure has disappeared, and it has been transformed into an irregular aggregate of copper particles. Figure 4 The FTIR spectrum showed that the synthesized precursor lacked cyanamide bonds, indicating that the cyano group (-C≡N) of dicyandiamide participated in the reaction during synthesis. The nitrogen-terminus of the cyano group coordinated to the copper surface, initiating electron transfer and causing the C≡N bond to break, thus breaking the Cu bond. 2+ After accepting ≡N electrons, it is reduced to Cu. + A new absorption peak is observed at 533 cm⁻¹, which is characteristic of the Cu-N vibration. Figure 5 XPS N1s spectral analysis showed that the terminal cyano group (≡N) of dicyandiamide coordinated with copper to form a Cu-N bond. After the reaction, the Cu-N bond shifted through... Figure 6 Thermogravimetric-mass spectrometry (TG-MS) analysis showed that 16 (NH2) was detected at approximately 175 °C. + ) and 17 (NH3) + These signals originate from the decomposition of nitrogenous substances within the material itself, clearly revealing the abundance of nitrogen-containing groups (such as -NH2) on the material surface. These groups can serve as potential Lewis base sites for activating CO2 and provide the necessary conditions for the formation of amide bonds during the electrocatalytic CO2 process; thus proving that the catalyst has a bulk-interfacial nitrogen synergistic effect. Figure 7 The Cu Auger spectrum showed that after a period of electrocatalytic testing, the valence state of Cu in the material remained unchanged, indicating that the active species were not simply surface modified during synthesis, but rather that the terminal cyano group (≡N) in dicyandiamide acted as a strong coordinating site with Cu. 2+Strong coordination occurs, which allows it to remain stable under reaction conditions.

[0034] Example 3 A method for preparing a material using surface amidation-driven electrocatalytic conversion of carbon dioxide to ethylene from a copper-based catalyst precursor comprises the following steps: Weigh 160 mg of sodium hydroxide and prepare a 50 mL aqueous solution, which is then poured into a beaker; weigh 341 mg of copper chloride dihydrate and add it to the solution, stirring until homogeneous; control the heating rate and continuously stir at 35 °C; weigh 504.48 mg of dicyandiamide and add it to the above solution. After continuous stirring for 0.5 h, continue stirring at 35 °C for 2 h, then stop stirring. The precipitate obtained after washing twice with distilled water and once with ethanol by centrifugation is dried in a vacuum freeze dryer at -50 °C to obtain a bulk-interfacial nitrogen-synergistic engineered copper-based catalyst precursor.

[0035] Example 4 A method for preparing a material using surface amidation-driven electrocatalytic conversion of carbon dioxide to ethylene from a copper-based catalyst precursor comprises the following steps: Weigh 160 mg of sodium hydroxide and prepare a 50 mL aqueous solution, which is then poured into a beaker; then weigh 499 mg of CuSO4·5H2O and add it to the solution, stirring until homogeneous. The heating rate is controlled while continuously stirring at 35 °C; weigh 504.48 mg of dicyandiamide and add it to the solution. After stirring continuously for 0.5 h, continue stirring at 35 °C for 2 h, then stop stirring. The precipitate obtained after washing twice with distilled water and once with ethanol by centrifugation is dried in a vacuum freeze dryer at -50 °C to obtain a bulk-interfacial nitrogen-synergistic engineered copper-based catalyst precursor.

[0036] Example 5 A method for preparing a material using surface amidation-driven electrocatalytic conversion of carbon dioxide to ethylene from a copper-based catalyst precursor comprises the following steps: Weigh 160 mg of sodium hydroxide and prepare a 50 mL aqueous solution, which is then poured into a beaker; then weigh 399 mg of Cu(CH3COO)3·H2O and add it to the solution, stirring until homogeneous. The heating rate is controlled while continuously stirring at 35 °C; weigh 504.48 mg of dicyandiamide and add it to the solution. After stirring continuously for 0.5 h, continue stirring at 35 °C for 2 h, then stop stirring. The precipitate obtained after washing twice with distilled water and once with ethanol by centrifugation is dried in a vacuum freeze dryer at -50 °C to obtain a bulk-interfacial nitrogen-synergistic engineered copper-based catalyst precursor.

[0037] Comparative Example Comparative Example 1 Pure copper is not modified with dicyandiamide. Specifically: Weigh 160 mg of sodium hydroxide and prepare 50 mL of sodium hydroxide aqueous solution, which is then poured into a beaker. Next, weigh 341 mg of copper chloride dihydrate and add it to the solution, stirring until homogeneous. Control the heating rate and stir continuously at 35 °C. Add 4 mL of hydrazine hydrate to the solution and continue stirring at 35 °C for 2 h. Stop stirring and wash the precipitate twice with distilled water and once with ethanol. Dry the precipitate in a vacuum freeze dryer at -50 °C to obtain pure copper without cyanamide modification.

[0038] SEM analysis was performed on the material prepared in Comparative Example 1, such as... Figure 8 As shown, the morphology is an irregular aggregate of copper particles.

[0039] Comparative Example 2 A method for preparing a surface-modified copper-based catalyst includes the following steps: Weigh 160 mg of sodium hydroxide and prepare a 50 mL sodium hydroxide aqueous solution, which is then poured into a beaker; then weigh 341 mg of copper chloride dihydrate and add it to the solution, stirring constantly at 35 °C; weigh 504.48 mg of cyanamide and add it to the above solution. After stirring continuously for 0.5 h, continue stirring at 35 °C for 2 h, then stop stirring. The precipitate obtained after washing twice with distilled water and once with ethanol by centrifugation is dried in a vacuum freeze dryer at -50 °C to obtain the cyanamide-modified copper-based catalyst.

[0040] The materials prepared in this embodiment were analyzed, and... Figure 9 FTIR characterization analysis showed that the cyanamide bond remained intact after cyanamide modification, indicating that the molecular structure remained largely unchanged, forming a relatively static capping layer that mainly provided electronic effects and might slightly modulate the adsorption energy of intermediates, but could not create new reaction pathways. In contrast, the dicyandiamide molecule underwent terminal -C≡N cleavage during synthesis, resulting in a surface chemical reaction that "grafted" it onto the catalyst surface, forming a highly directional, rigid structure with an active hydroxyl group at the end (≡N-Cu). + The -OH group can directly undergo reversible covalent amidation with the reaction intermediate during the reaction process, creating a completely new and more efficient reaction pathway.

[0041] Comparative Example 3 By adding melamine to modify the copper-based catalyst, it was found that melamine could not be successfully modified during the synthesis process. This is because no additional reducing agent was added during the synthesis process, making melamine more likely to react with Cu in the solution. 2+ A bulk reaction occurs, therefore, due to melamine's rigid symmetrical structure, poor solubility and reactivity in the system, and its reaction with Cu... 2+Its tendency to form bulk coordination polymers makes it impossible to perform effective and controllable chemical modification on copper surfaces.

[0042] Application Examples / Performance Testing The catalyst materials of each embodiment and comparative example were used for electrocatalysis, and the specific operation steps are as follows: Weigh 10 mg of material into a vial, add 960 μL of isopropanol and 40 μL of Nafion solution (Nafion solution mass fraction is 5%), mix, and sonicate for 2 hours to completely disperse the catalyst and obtain a uniform catalyst ink.

[0043] 300 μL of the prepared catalyst ink was evenly spread onto 1 cm × 3 cm carbon paper and dried. This dried paper was then used as the working electrode, with a platinum sheet as the anode and an Ag / AgCl electrode as the reference electrode. Catalytic performance testing was conducted using a Wuhan KOST CS2350H electrochemical workstation in a flow cell with a three-electrode system. The electrolyte was a 0.5 mol / L KOH aqueous solution. The electrochemical workstation applied a 600 mA cm⁻¹ pressure. -2 The current was first applied for 10 minutes to successfully activate the material precursor, transforming it from the CuO species into the active Cu phase. After the current stabilized, the product was collected for 15 seconds and introduced into the gas phase. The Faraday efficiency was calculated based on the peak area concentration of the gaseous product. The results are shown in the table below. As can be seen from the table above, the electrocatalyst material prepared in the optimal Example 2 of this invention is a copper-based catalyst supported on dicyandiamide. Its electrocatalytic performance can be stably tested for 2 hours, with an ethylene Faradaic efficiency of 79.56% and an ethylene current density of 477.36 mA cm⁻¹. -2 In Comparative Example 1, the electrocatalyst was unmodified cuprous oxide, with an ethylene Faradaic efficiency of 38.14% and an ethylene current density of 228.84 mA cm⁻¹. -2 In addition, the choice of different copper sources has a significant impact on the OD copper particle size and nitrogen doping depth: SO4 in copper sulfate 2- It has a weak coordination ability with copper ions, a fast precipitation rate, and easily forms large particles (>200 nm). CH3COO - It can act as a mild ligand to regulate the release rate of copper ions, generating OD copper particles with uniform particle size (approximately 100-150 nm). Copper chloride, due to its Cl... -The presence of [a specific substance] can form a Cu-Cl coordination intermediate in the early stages of the reaction, slowing down the copper precipitation rate and facilitating the formation of smaller OD copper particles (approximately 50-80 nm). Therefore, this invention first constructs an OD copper precursor with controllable particle size and abundant defects by controlling precipitation conditions (temperature, pH, and copper source type), and then achieves directional nitrogen doping and modification through the in-situ reaction of dicyandiamide. If commercial copper powder or large-particle copper oxide is used directly, it is difficult to achieve uniform nitrogen doping, and the surface modification layer is prone to detachment, making it impossible to form a stable dynamic amide bond intermediate.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for electrocatalytically converting carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation, characterized in that, Includes the following steps: Copper salts were added to an aqueous sodium hydroxide solution, heated to dissolve and stirred. Dicyandiamide was then added and stirred continuously to allow the dicyandiamide to undergo a coordination reaction with the copper species. The solid was separated from the reaction solution and dried to obtain the nitrogen-modified copper oxide precursor material. Nitrogen-modified copper oxide precursor material was used as a catalyst for electrocatalytic reduction of CO2 to ethylene. The nitrogen-modified copper oxide precursor material is reconstructed in situ under electrocatalytic CO2 reduction conditions into an oxide-derived copper active structure with a bulk-interface nitrogen synergistic effect.

2. The method for electrocatalytic conversion of carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation according to claim 1, characterized in that, The sodium hydroxide concentration in the sodium hydroxide aqueous solution is 0.05-0.1 mol / L.

3. The method for electrocatalytic conversion of carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation according to claim 1, characterized in that, The copper salt is selected from one or more of the following: copper chloride, copper nitrate, copper acetate, and copper sulfate. The ratio of the amount of copper salt to the aqueous sodium hydroxide solution is 0.02-0.06 mol: 1000 mL.

4. The method for electrocatalytic conversion of carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation according to claim 1, characterized in that, The ratio of dicyandiamide to sodium hydroxide aqueous solution is 0.02-0.12 mol: 1000 mL.

5. The method for electrocatalytic conversion of carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation according to claim 1, characterized in that, Heat to 33~37℃ at a heating rate of 1-2℃ / min to dissolve and stir.

6. The method for electrocatalytic conversion of carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation according to claim 1, characterized in that, The coordination reaction temperature is 33~37℃, and the coordination reaction time is 2-5 hours.

7. The method for electrocatalytic conversion of carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation according to claim 1, characterized in that, The molar ratio of the copper salt to dicyandiamide is 1:0.5-3.

8. The method for electrocatalytic conversion of carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation according to claim 1, characterized in that, The separation is carried out by centrifugation. After centrifugation, the solid is washed with water 1-3 times and with alcohol 1-3 times.

9. The method for electrocatalytic conversion of carbon dioxide to ethylene using a copper-based catalyst precursor driven by surface amidation according to claim 1, characterized in that, Vacuum freeze drying is used for drying.

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