Copper-based core-shell structure catalyst as well as preparation method and application thereof

Abstract

The invention relates to the field of electrocatalytic reduction of carbon dioxide, and particularly provides a copper-based core-shell structure catalyst as well as a preparation method and application thereof. The catalyst is of a core-shell structure, the core of the core-shell structure is cuprous oxide, the shell of the core-shell structure is carbon, the shell is of a porous structure, and a gap is formed between the core and the shell. The method comprises the following steps: step 1, preparing a cuprous oxide core; 2, coating the surface of the inner core with silicon dioxide; 3, coating the surface of silicon dioxide with porous carbon to form a shell; and 4, etching the silicon dioxide to form the copper-based core-shell structure catalyst. The material is used for producing ethylene through electrocatalytic reduction of carbon dioxide, the reaction is carried out at a cathode of an electrocatalytic device, and the material is loaded on the surface of the cathode. According to the structure disclosed by the invention, through the combined action of local enrichment, field enhancement, reaction path regulation and control and structural stability, the proportion of C2H4 in an electro-catalysis carbon dioxide reduction product is increased, namely, the yield of C2H4 is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrocatalytic reduction of carbon dioxide, in particular, a copper-based core-shell structure catalyst, and a preparation method and application thereof. BACKGROUND

[0002] Ethylene (C2H4) is one of the most basic and important raw materials in modern chemical industry, which is widely used in polyethylene plastics, ethylene oxide, ethanol, pharmaceutical intermediates and other fields. The global annual demand has always been in the order of hundreds of millions of tons and is showing a sustained growth trend. The traditional preparation methods of ethylene mainly include steam cracking, petroleum cracking and methane dry reforming, etc. They are generally high in energy consumption and large in carbon emissions. In recent years, with the continuous rise of carbon dioxide concentration in the atmosphere, the resource utilization of CO2 has become a research hotspot. Because it can be carried out at room temperature and pressure, electrocatalytic reduction of CO2 (CO2RR) to prepare ethylene is considered as a very promising green route for preparing ethylene, which provides a new technical route for solving greenhouse gas emissions and high-value chemical preparation.

[0003] The catalyst system for electrocatalytic reduction of CO2 includes noble metals (such as Au, Ag), non-noble metals (such as Sn, Bi, Zn), transition metal oxides, and metal-organic frameworks (MOFs) and carbon-based composites which have developed rapidly in recent years. Among them, copper and its oxides, especially cuprous oxide, are the only metal catalysts that have been proven to be able to realize C-C coupling and generate multi-carbon products under electrocatalytic conditions. Compared with transition metal oxides, copper-based catalysts have a unique CO intermediate adsorption energy, which can stabilize CO* and OCCO* and other key intermediates on the surface, so that they will neither be easily desorbed as CO like Au and Ag, nor be excessively hydrogenated to generate methane like Ni and Fe. At the same time, copper often forms Cu + / Cu 0 coexistence structure in the reaction process, which effectively improves the activation ability of CO2 and the coverage of CO*, thereby providing favorable conditions for the generation of multi-carbon products.

[0004] However, due to the strong stability of CO2 molecules, complex reaction path, and high coupling degree of electrode interface process, the electrocatalytic reduction of CO2 often produces multiple products including CO, HCOOH, CH4, ethanol, acetic acid, ethylene, etc., and the distribution of which is jointly influenced by factors such as catalyst structure, potential, local pH, surface intermediate coverage, etc. In most catalytic systems, the yield of ethylene is usually low, and the C2H4 faradic efficiency is generally within a few tens of percentage points, which is difficult to meet the industrialization demand. For the generation of ethylene, C-C coupling is the most critical step, and this process depends on the encounter of two CO* on the catalyst surface and the formation of OCCO* intermediate, which has high requirements for the surface CO* coverage, adsorption energy, migration ability, and interface electric field distribution. Although copper or cuprous oxide is the only catalytic material that can realize C-C coupling at present, due to the moderate adsorption energy of CO* on the copper surface, the migration ability of CO* is limited, the strength of C-C coupling is low, and the local reaction environment makes it difficult for reaction intermediates to enrich on the surface, etc., which inhibits the further generation of ethylene.

[0005] In summary, the existing catalysts cannot meet the demand of high ethylene yield in products. SUMMARY

[0006] The present application aims at the deficiencies in the prior art, and provides a copper-based core-shell structure catalyst, a preparation method and application thereof, so as to solve the problem that the catalysts in the prior art cannot meet the demand of high ethylene yield in products.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: The present application provides a copper-based core-shell structure catalyst, the material is a core-shell structure, the inner core of the core-shell structure is cuprous oxide, the outer shell of the core-shell structure is carbon, the outer shell is a porous structure, and there is a gap between the inner core and the outer shell.

[0008] Further, the thickness of the gap between the inner core and the outer shell is 15-25 nm, the size of the inner core of the material is 150-1000 nm, and the size of the outer shell of the material is 30-50 nm.

[0009] The present application also provides a preparation method of a copper-based core-shell structure catalyst, which comprises the following steps: Step 1, preparing a cuprous oxide inner core; Step 2, coating silica on the surface of the inner core; Step 3, coating porous carbon on the surface of the silica to form an outer shell; Step 4, etching the silica to form a copper-based core-shell structure catalyst.

[0010] Further, step 1 comprises the following steps: adding sodium hydroxide into the mixed solution of copper sulfate pentahydrate and trisodium citrate, stirring, then adding ascorbic acid, standing at room temperature, centrifuging, washing, and vacuum drying the obtained precipitate to obtain the inner core.

[0011] Further, in step S1, the molar ratio of copper sulfate pentahydrate, trisodium citrate, sodium hydroxide and ascorbic acid is 3:1:12.5:1.5.

[0012] Further, step 2 comprises dispersing the inner core into a mixed solution of anhydrous ethanol and water, stirring, then adding a mixed solution of tetraethyl orthosilicate and ethanol, subsequently adding sodium hydroxide solution dropwise, and after reaction, centrifuging, washing, and vacuum drying the obtained precipitate to obtain the inner core coated with silicon dioxide.

[0013] Further, step 3 comprises dispersing the inner core coated with silicon dioxide into a buffer solution, adding dopamine hydrochloride, stirring, centrifuging, washing, vacuum drying the obtained precipitate, and annealing in an inert atmosphere to obtain the outer shell.

[0014] Further, step 4 comprises dispersing the product of step 3 into an etching solution to etch away the silicon dioxide, and after etching, centrifuging, washing, and vacuum drying to obtain the copper-based core-shell structure catalyst.

[0015] The application also proposes an application of the copper-based core-shell structure catalyst, which is used for electrocatalytic reduction of carbon dioxide to produce ethylene, and the reaction is carried out on the cathode of an electrocatalytic device, and the material is loaded on the surface of the cathode.

[0016] Further, the reaction cell of the electrocatalytic device is placed in an ultrasonic water tank, and the water bath ultrasonic is carried out at the same time of the electro-reduction reaction.

[0017] Compared with the prior art, the application has the following beneficial effects: The inner core and the outer shell of the copper-based core-shell structure catalyst of the application have a cavity. On the one hand, the porous carbon shell enriches CO2 and CO through micropore confinement and surface functional groups, so that a high CO2 and CO concentration is formed in the cavity, thereby maintaining a high CO* coverage on the surface of the inner core and promoting the coupling of CO* and CO*. On the other hand, the cavity serves as an isolation layer for the electrolyte, so that a capacitance is formed between the negatively charged inner core and the conductive carbon shell, and a strong and highly non-uniform local electric field is generated in the cavity; not only does this strengthen the polarization and activation of CO2 and reduce the energy barrier for the conversion of CO2 into COOH*, but it also selectively stabilizes the CO* and OCCO* intermediates with larger dipole moments through the direction and gradient of the electric field, thereby inhibiting the hydrogenation path of CHO* and H* and improving the selectivity of ethylene. The tangential component of the electric field improves the surface mobility of CO*, making it more likely to meet and undergo C-C coupling. In addition, the porous carbon shell provides a high-conductivity channel and structural confinement, which makes the Cu+ / Cu 0 The catalyst is kept, the activity decline caused by reconstitution or agglomeration is reduced, and the product C2H4 is helped to quickly discharge through the micro-flow channel, so as to avoid blocking the active site. The faraday efficiency of the catalyst for producing ethylene reaches 63%, and the stability is good.

[0018] Firstly, the cuprous oxide core is prepared by a coprecipitation method, and the core structure effectively improves the generation concentration of the intermediate CO, laying a foundation for the CO2 electro-reduction reaction; then, the inner core is coated with silicon dioxide, and a coating layer is formed on the surface of the silicon dioxide through in-situ polymerization reaction by using hydrochloric acid dopamine as a precursor; finally, a CO2 electro-reduction catalyst with a core-shell structure is successfully prepared through pyrolysis and etching processes. The catalyst further enriches the intermediate CO on the surface of cuprous oxide through the porous carbon shell, and at the same time, the cavity structure formed by etching avoids covering the active sites by the porous carbon shell, so that the catalytic stability is significantly enhanced. Meanwhile, a low-temperature water bath ultrasonic is used in the preparation and use process to enhance dispersion, reduce concentration difference, enhance material exchange, discharge desorbed ethylene in time, maintain high CO* coverage, and finally improve the ethylene yield. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The XRD result of the product obtained by the preparation method of the copper-based core-shell structure catalyst provided in Embodiment 2 of the present application; Figure 2 The TEM result of the product obtained by the preparation method of the copper-based core-shell structure catalyst provided in Embodiment 2 of the present application; Figure 3 The CO2 electro-reduction result of the product obtained by the preparation method of the copper-based core-shell structure catalyst provided in Embodiment 2 of the present application in 1 mol / L potassium hydroxide aqueous solution; Figure 4 The stability test result of the product obtained by the preparation method of the copper-based core-shell structure catalyst provided in Embodiment 2 of the present application. DETAILED DESCRIPTION

[0020] In order to make the implementation process of the present application clearer, the following will be described in detail in combination with the drawings.

[0021] Embodiment 1: The present application provides a copper-based core-shell structure catalyst, the material is a core-shell structure, there is a gap between the inner core and the outer shell, the material of the inner core is copper or cuprous oxide, the material of the outer shell is carbon, and the outer shell is a porous structure. The thickness of the gap between the inner core and the outer shell is 15-25 nm, the size of the inner core is 150-1000 nm, and the size of the outer shell is 30-50 nm.

[0022] The process of electrocatalytic reduction of CO2 is mainly on the Cu+ / Cu 0 The reaction occurs at the active site. At the start of the reaction, CO2 molecules enter the cavity through the porous channels of the outer shell, where they are adsorbed and activated under the polarization of the local electric field, forming key intermediates such as COOH* and CO*. Due to the confinement effect of the cavity and the enrichment capacity of the porous carbon shell for CO, a high coverage of CO* forms on the core surface, promoting the migration and coupling of CO* to generate the multi-carbon intermediate OCCO*. Subsequently, the CC-coupling intermediate undergoes multiple proton and electron transfer reactions, gradually transforming into C2H containing CC bonds. x O* species are generated, ultimately producing C2H4. Simultaneously, the porous carbon shell maintains rapid electron transport during the reaction and provides an electric field penetration, local pH regulation, and microfluidic environment, allowing the product C2H4 to quickly exit the cavity, avoiding blockage of the reaction sites and ensuring continuous and efficient generation of multi-carbon products.

[0023] Specifically, on the one hand, the cavity between the core and the shell has a confinement effect. The porous carbon shell enriches CO2 and CO through adsorption and confinement, thereby increasing the coverage of key intermediates on the core surface. The micropores on the shell surface enrich CO2 through π-π interactions, oxygen / nitrogen functional groups on the surface, and the micropore confinement effect, making the local CO2 concentration in the cavity higher than that in the external solution, thus enhancing the adsorption and activation of CO2 on the Cu2O surface. At the same time, the porous carbon shell retains the CO generated in the core in the cavity gaps, preventing CO from rapidly diffusing into the electrolyte, resulting in high CO partial pressure and high CO* coverage in the chamber. The increased CO* coverage is the core of CC coupling; the formation of ethylene depends on the meeting of two CO* on the surface to form the OCCO* intermediate; high coverage and moderate surface mobility increase the probability of CO* contact with CO*, thereby promoting the formation of C2H4. The internal cavity of the outer shell also results in a relatively higher pH level within the chamber. A higher pH inhibits the hydrogen evolution reaction and weakens the excessive hydrogenation pathway of CO*, reducing the CH4 generated from CO*, thus reducing reactions competing with ethylene formation. Furthermore, the cavity structure spatially separates the porous carbon shell from the core, preventing the carbon shell from adhering closely to and obscuring the active sites on the core surface during synthesis or reaction. This ensures that the catalytic surface is fully exposed to the electrolyte and reactants, which is beneficial for ethylene formation.

[0024] On the other hand, a capacitor is formed between the core and the shell. The core, Cu2O, is a semiconductor, partially negatively charged at the reduction potential, while the shell, porous carbon, is a conductor. The cavity between them, filled with electrolyte, constitutes a stable microcapacitor. An enhanced local electric field is formed inside the capacitor cavity, causing the electric field lines to concentrate in the cavity region, creating a strong and highly non-uniform local electric field. The electric field radially points from the shell towards the core, exhibiting a significant enhancement effect. Simultaneously, a transverse electric field component caused by the resistance gradient and curvature exists along the tangential direction on the surface, forming a large electric field gradient at the cavity boundary. The combined effect of the direction and gradient preferentially stabilizes CO* and OCCO* with larger dipole moments, while suppressing the hydrogenation intermediates CHO* and H* with smaller dipole moments, thereby reducing the hydrogenation pathway from CO* to CH4. Simultaneously, the tangential electric field enhances the migration of CO* on the core surface, making it easier for them to meet and form the CC coupling intermediate OCCO*, improving the selectivity of ethylene formation. In addition, the enhanced electric field has a stronger polarizing effect on CO2 molecules entering the cavity, which improves their adsorption and bending activation ability, thereby reducing the energy barrier for CO2 to convert into COOH* and promoting the activation process of CO2.

[0025] On the other hand, the porous carbon shell in the core-shell structure not only serves as a physical protective layer but also plays a role in regulating the electronic structure under electrochemical conditions. Firstly, due to the good conductivity of porous carbon, the shell surface can accumulate negative charges under an applied bias voltage, thereby enhancing the local electric field on the outside and making CO2 activation and intermediate polarization more efficient. Simultaneously, the shell provides a stable and continuous electron transport channel for the core, allowing electrons to be injected into active sites more quickly and uniformly, avoiding side reactions induced by uneven electron supply. Furthermore, the confinement and buffering effect of the porous carbon shell maintains the Cu content in the core. + The stability of Cu is improved, inhibiting its complete transformation into metallic Cu under strong reduction potentials, thereby reducing the activity loss caused by Cu nanoagglomeration and phase transition. The spatial isolation of the shell also slows down structural reconstruction, allowing Cu... + / Cu 0 The interface remains stable, further ensuring the ability to control intermediate states required for product generation.

[0026] Example 2: The preparation method of the copper-based core-shell structured catalyst described in Example 1 is as follows: Step 1: Prepare the cuprous oxide core; Sodium hydroxide was added to a mixture of copper sulfate pentahydrate and trisodium citrate, and after stirring, ascorbic acid was added. The mixture was allowed to stand at room temperature, centrifuged, washed, and the precipitate was dried under vacuum to obtain the core. The molar ratio of copper sulfate pentahydrate, trisodium citrate, sodium hydroxide, and ascorbic acid was 3:1:12.5:1.5; this ensured complete copper ion complexation, sufficient precipitation of the precursor, and stable and controllable reduction kinetics, thereby enabling controllable adjustment of the core particle size, crystal face exposure, and oxidation state.

[0027] Specifically, 1.6 mmol of copper sulfate pentahydrate and 0.5 mmol of trisodium citrate were dispersed in 80 mL of deionized water. Trisodium citrate, acting as a multidentate complexing agent, can react with Cu... 2+ A stable complex is formed, reducing the activity of free copper ions and thus regulating the nucleation rate, avoiding coarse and uneven particles caused by rapid precipitation. Simultaneously, citrate ions act as a crystal-facet-selective adsorbent, promoting the formation of regular morphologies. After stirring for 15 min, 20 mL of 1.25 M sodium hydroxide was added to the above solution. Adding excess sodium hydroxide rapidly generates the Cu(OH)₂ precursor, raising the pH and providing a uniform reaction environment for subsequent directional reduction. After stirring again for 15 min, 50 mL of 0.03 M ascorbic acid was added to the solution. Ascorbic acid is a mild reducing agent, selectively reducing Cu(OH)₂ to Cu. + It is further converted into Cu2O, avoiding the formation of metallic Cu or other impurity phases. Stir for another 3 minutes, let the mixed solution stand at room temperature for 1 hour, take the precipitate, centrifuge and wash it, and then vacuum dry the precipitate to obtain cuprous oxide nuclei.

[0028] Step 2: Coat the surface of the core with silicon dioxide; The kernel was dispersed in a mixture of anhydrous ethanol and water, stirred, and then a mixture of tetraethyl orthosilicate and ethanol was added. Subsequently, sodium hydroxide solution was added dropwise. After the reaction, the kernel was centrifuged, washed, and vacuum dried to obtain a precipitate coated with silica.

[0029] Specifically, 50 mg of Cu₂O obtained in step 2 was dispersed in a mixture of 50 mL anhydrous ethanol and 10 mL water, with a volume ratio of 5:1. The mixture was stirred for 10 min. Ethanol lowers the dielectric constant of the system and increases the volatility of the solvent, which helps improve the dispersibility of Cu₂O in the solution. The addition of a small amount of water provides the necessary moisture for the hydrolysis of tetraethyl orthosilicate, allowing the hydrolysis-condensation reaction to proceed uniformly under mild conditions. The volume ratio of tetraethyl orthosilicate to ethanol was 9:125. Premixing tetraethyl orthosilicate and ethanol ensures that the tetraethyl orthosilicate is sufficiently diluted, which reduces the hydrolysis rate and prevents the rapid nucleation of silica sol and spontaneous aggregation in the solution. This ensures that SiO₂ selectively forms a film on the Cu₂O surface rather than forming independent particles. 36 μL of tetraethyl orthosilicate and 500 μL of ethanol were mixed and added to the above solution, then stirred for 15 min. Subsequently, 1 mL of 0.1 M sodium hydroxide solution was added dropwise to the above solution at a rate of 0.2 mL per minute. This slow, constant introduction of alkalinity controlled the hydrolysis kinetics of tetraethyl orthosilicate, ensuring uniform, thin, and dense deposition of SiO2 and preventing the formation of a rough or uneven coating layer. The reaction was allowed to proceed at room temperature for 12 h, allowing the tetraethyl orthosilicate to fully hydrolyze, condense, and deposit on the core surface. After centrifugation and washing, the resulting precipitate was vacuum dried to obtain silica-coated cuprous oxide.

[0030] Step 3: Coat the surface of silica with porous carbon to form a shell; Dopamine was used to self-polymerize on the surface of SiO2-coated Cu2O and then annealed to form a carbon shell. The silica-coated core was dispersed in a buffer solution, dopamine hydrochloride was added, and the mixture was stirred, centrifuged, washed, and the precipitate was vacuum dried. After annealing in an inert atmosphere and natural cooling, the outer shell was obtained.

[0031] Specifically, 100 mg of silica-coated cuprous oxide obtained in step 2 was dispersed in 100 mL of buffer solution containing 0.1 mol / L tris(hydroxymethyl)aminomethane. The buffer solution also provided ionic strength to stabilize particle dispersion and prevent aggregation. 50 mg of dopamine hydrochloride was added, with a mass ratio of silica-coated cuprous oxide to dopamine hydrochloride of 2:1. This ensured a sufficiently thick and continuous polydopamine layer on the surface while avoiding excessive dopamine that could lead to self-aggregation of particles in the solution. The carbon layer formed in situ on the particle surface. The mixture was stirred for 24 h, centrifuged, washed, and the resulting precipitate was vacuum dried. Finally, it was annealed at 400 °C for 2 hours under a nitrogen atmosphere at a heating rate of 5 °C / min. After natural cooling, the powder was collected. The polydopamine was uniformly carbonized to form a stable N-doped carbon shell, while rapid heating was avoided to prevent carbon layer cracking, cavity collapse, or excessive reduction of Cu₂O to metallic Cu. The above-mentioned temperature can achieve carbonization without destroying the core structure, thereby obtaining a dense, conductive and porous carbon shell.

[0032] Step 4: Etch silicon dioxide to form a copper-based core-shell catalyst.

[0033] The product from step 3 was dispersed in an etching solution (2 mol / L sodium hydroxide solution) to etch away silicon dioxide. After etching, the product was centrifuged, washed, and vacuum dried to obtain a copper-based core-shell catalyst. Under alkaline conditions, SiO2 can quickly dissolve to form soluble silicates, while the carbon shell formed by polydopamine carbonization has good alkaline stability. The Cu2O core is also not easily corroded by alkali in a short time. That is, sodium hydroxide only etches the intermediate layer without damaging the core and shell. Using sodium hydroxide as an etchant not only cleanly removes SiO2, but its strong alkaline environment also has the following effects on the material interface: alkaline conditions further activate the nitrogen-containing functional groups on the carbon shell surface, improving the shell's CO2 affinity and conductivity; on the other hand, moderate alkaline etching introduces additional microporous structures into the carbon shell, improving the shell's gas permeability and CO2 and CO enrichment capacity. Simultaneously, a small amount of Cu-OH and Cu2O3 will form on the Cu2O surface under short-term alkaline treatment. + These sites help enhance the stability of CO2 adsorption and CO*, and promote CC coupling and ethylene generation.

[0034] To prevent cavity collapse and localized core dissolution, an ultrasonic bath is used during the etching process. The container holding the mixture is placed in an ultrasonic water bath, and the ultrasonic energy is transferred to the solution through the water medium. The ultrasonic power is 60-80W, and the frequency is 20-40kHz. This reduces particle aggregation and sedimentation, ensuring uniform dispersion of core-shell particles in the etching solution. This prevents excessively high sodium hydroxide concentrations in certain areas, which could lead to rapid etching and localized shell layer erosion or cavity collapse. Simultaneously, the microfluidics and cavitation effects induced by the acoustic field facilitate continuous contact between fresh etching solution and the SiO2 layer, as well as timely diffusion of etching products, improving mass exchange efficiency. Furthermore, to lower the temperature of the etching solution, an ice-water bath is used during the ultrasonic etching process. Initially, the solution is allowed to stand in the ultrasonic bath for 5-10 minutes to allow its temperature to decrease. As the ultrasound generates heat, the temperature rises, requiring frequent replacement of the low-temperature water in the ultrasonic bath during the process. This reduces the rate of side reactions involving SiO2 dissolution and Cu2O formation, ensuring complete removal of SiO2 without causing excessive corrosion to the carbon shell and Cu2O core in a short period. The low temperature also prevents the Cu2O core from being locally dissolved or transformed into unevenly sized Cu particles, thus ensuring the Cu... + / Cu 0 The proportion of active sites is improved. Low temperature slows down the chemical reaction rate, and ultrasonic uniform stirring eliminates local concentration and temperature gradients, thereby enabling the control of etching rate and spatial uniformity, thus maintaining the integrity of the cavity structure and the continuity of the carbon shell, forming a core, cavity, and shell structure.

[0035] The XRD and SEM characterization results of the prepared catalyst are as follows: Figure 1 and Figure 2 As shown. Figure 1 and Figure 2 Characterization results show that the prepared catalyst has a hollow structure of carbon-coated cuprous oxide. The catalyst was loaded onto carbon paper, which served as the cathode of the electrocatalytic device. The structure of the electrochemical reaction apparatus is common knowledge to those skilled in the art and will not be described in detail in this application. Figure 3 The image shows the selectivity distribution of carbon dioxide electroreduction products of the prepared catalyst in a 1 mol / L potassium hydroxide aqueous solution system and a flow electrolyzer (to improve mass transport efficiency and reduce system resistance). The selectivity of multi-carbon products exhibits regular fluctuations with changing current density, reaching a maximum at 600 mA / cm². -2 At the specified current density, the yield of ethylene reached a maximum of 63%. Figure 4 The results of the long-term stability test curve of the catalyst show that after 23 hours of continuous electrolysis, the selectivity of the catalyst for multi-carbon products did not decrease significantly and remained stable. In other words, the high ethylene yield is stable during the electrolysis process and can effectively improve the ethylene yield.

[0036] Example 3: The difference from Example 1 is that this example only performs step 1, that is, the prepared cuprous oxide is directly used as a catalyst for the electrocatalytic reduction of carbon dioxide to produce ethylene.

[0037] Example 4: The difference from Example 1 is that this example only performs steps 1 and 3, that is, it does not coat the outside of the core with silicon dioxide, nor does it etch the silicon dioxide. In this way, the catalyst obtained does not have a cavity structure in the middle, and the outer shell is in direct contact with the core, as a comparison.

[0038] Example 5: The difference from Example 1 is that the amount of tetraethyl orthosilicate was increased to 72 μL, which improved the deposition amount and thickness of silica. With all other conditions unchanged, a carbon-coated copper oxide catalyst with a larger cavity structure was obtained.

[0039] The catalysts obtained in Examples 3-5 were subjected to carbon dioxide electroreduction tests. The test results are shown in Table 1. The ethylene yield was less than 63% of that in Example 1.

[0040] Table 1. Comparison of ethylene products in the multi-carbon products of the catalysts prepared in Examples 3-5.

[0041] Example 6: This application also proposes an application of the above-mentioned copper-based core-shell structure catalyst, which is used for the electrocatalytic reduction of carbon dioxide to produce ethylene. The reaction takes place at the cathode of the electrocatalytic device, and the material is loaded on the cathode surface.

[0042] In the electrocatalytic reduction process, the electrolytic cell is placed in an ultrasonic water bath for ultrasonic treatment. The ultrasonic power is 60-80W, and the frequency is 40kHz. The electrolyte temperature is maintained at 10-20℃ during the ultrasonic process. The ultrasound generates acoustic microfluidics within the pores and cavities of the outer shell, forming a continuous microflow. These microflows and localized microjets create a pressure difference at each cavity opening. This accelerates the removal of C2H4 desorbed from the core surface through the pores in the carbon shell, preventing localized accumulation of C2H4 and high-pressure blockage within the cavities. Furthermore, it also facilitates the removal of H2 and OH groups. - Soluble salts are added to prevent deposits or gas blockage on the inner wall of the shell and at the pores. Simultaneously, ultrasonically driven convection continuously transports fresh CO2 and CO to the interface, reducing concentration polarization and maintaining a high CO and high pH environment within the cavity. This increases CO* coverage, making CC coupling more likely to occur. This dual approach of enhancing CC coupling and promoting ethylene discharge contributes to improving ethylene yield.

[0043] Using catalyst-loaded carbon paper as the cathode, the gas and liquid flow rates and liquid level are adjusted to maintain pressure balance between the gas and liquid phases on the cathode side, meaning the gas and liquid pressures are equal. The liquid level in the liquid reservoir of the electrolytic cell is adjusted to be level with the carbon paper, ensuring that the static pressure of the electrolyte at the carbon paper is not significantly higher than the gas pressure, and maintaining a gas-liquid pressure difference of less than 5-10 mbar. Gas and liquid flow in from the bottom and out from the top to reduce bubble accumulation and liquid entry into the porous layer. This prevents unreacted CO2 from penetrating the carbon paper and entering the anode chamber due to excessively high gas pressure, thus avoiding cross-contamination of gaseous products. It also prevents the electrolyte from flooding the carbon paper due to excessively high liquid pressure, which could block the CO2 transport channels. This maintains a consistently high CO2 supply and a stable three-phase interface on the catalyst surface, thereby maintaining a high local CO2 concentration and CO* coverage, enhancing CC coupling, suppressing proton excess and hydrogen evolution competition caused by flooding, and ultimately significantly improving the selectivity and Faraday efficiency of ethylene.

[0044] Furthermore, before use, a polytetrafluoroethylene (PTFE) dispersion containing 20-30 wt% is sprayed onto the back of the carbon paper (gas side) and baked at 340-360℃ for 40-50 minutes to form a highly hydrophobic microporous layer, serving as a stable gas diffusion channel. On the front of the carbon paper (electrolyte side), a Nafion aqueous dispersion is sprayed to maintain moderate hydrophilicity. This allows CO2 to diffuse continuously and in high flux from the back to the catalyst layer, while preventing electrolyte backflow into the deeper layers of the carbon paper and subsequent flooding. The catalyst layer is fully wetted by the electrolyte, maintaining good ion conduction and electrochemical reaction interface stability. This keeps the local CO2 concentration and CO* coverage at a high level, promoting CC coupling and inhibiting excessive proton transport and hydrogen evolution reactions, thereby improving ethylene selectivity and Faraday efficiency.

[0045] The carbon paper, with a pore size of 80-250 μm, has a microporous layer pre-coated on its catalyst-supported surface. This microporous layer, composed of a mixture of carbon black and 5-20 wt% polytetrafluoroethylene (PTFE), has a pore size of 20-60 μm, and the total thickness of the carbon paper is 200-300 μm. This prevents CO2 from dissipating or having its transport restricted over excessively long paths. In this way, the large pores are used for rapid and continuous CO2 delivery, while the small pores act as a reaction interface, ensuring sufficient contact between CO2 and the electrolyte and electrons near the catalyst sites. Even if the electrolyte partially penetrates, it will only wet a small number of micropores, without clogging the large pore channels, thus avoiding severe flooding. This synergistic effect of high-throughput gas delivery and a stable reaction interface maintains consistently high levels of local CO2 concentration and CO* coverage, which is beneficial for CC coupling and improves the selectivity and yield of ethylene.

[0046] To more clearly illustrate the application process, the following is a specific usage method of a catalytic device. This is not a limitation on the application method, but merely an example; the application method of this application is applicable to any electrocatalytic device. Specifically, during use, carbon dioxide gas needs to be introduced into the electrolytic cell, and gaseous products are collected from the system. The carbon paper supporting the catalyst serves as the cathode, nickel foam as the anode, and an Ag / AgCl electrode as the reference electrode. During use, these are connected to the corresponding electrodes on the electrochemical workstation: the cathode is connected to the WE port, the anode to the CE port, and the reference electrode to the RE port. An anion exchange membrane is used to separate the cathode and anode; otherwise, oxygen will be produced at the anode, and hydrogen will be produced in a side reaction at the cathode, posing a risk of explosion. During electrolysis, carbon dioxide gas is introduced into the electrolytic cell through the inlet to participate in the reaction. After the reaction, the products are discharged from the outlet, dehydrated by a dryer, and then the composition and concentration of the gaseous products are qualitatively and quantitatively analyzed using a gas chromatograph.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A copper-based core-shell structured catalyst, wherein the material is a core-shell structure, the core of the core-shell structure is cuprous oxide, and the outer shell of the core-shell structure is carbon, characterized in that... The outer shell has a porous structure, and there is a gap between the core and the outer shell.

2. The copper-based core-shell structured catalyst according to claim 1, characterized in that, The thickness of the gap between the core and the shell is 15-25 nm, the core size of the material is 150-1000 nm, and the shell size of the material is 30-50 nm.

3. A method for preparing a copper-based core-shell structured catalyst, characterized in that, The method includes the following steps: Step 1: Prepare the cuprous oxide core; Step 2: Coat the surface of the core with silicon dioxide; Step 3: Coat the surface of the silica with porous carbon to form a shell; Step 4: Etch the silicon dioxide to form a copper-based core-shell structure catalyst.

4. The method for preparing a copper-based core-shell structure according to claim 3, characterized in that, Step 1 includes the following steps: adding sodium hydroxide to a mixture of copper sulfate pentahydrate and trisodium citrate, stirring, then adding ascorbic acid, allowing it to stand at room temperature, centrifuging, washing, and vacuum drying the resulting precipitate to obtain the core.

5. The method for preparing the copper-based core-shell structured catalyst according to claim 4, characterized in that, In step S1, the molar ratio of copper sulfate pentahydrate, trisodium citrate, sodium hydroxide, and ascorbic acid is 3:1:12.5:1.

5.

6. The method for preparing the copper-based core-shell structured catalyst according to claim 5, characterized in that, Step 2 includes dispersing the core into a mixture of anhydrous ethanol and water, stirring, adding a mixture of tetraethyl orthosilicate and ethanol, then adding sodium hydroxide solution dropwise, reacting, centrifuging, washing, and vacuum drying the resulting precipitate to obtain the core coated with silica.

7. The method for preparing the copper-based core-shell structured catalyst according to claim 6, characterized in that, Step 3 includes dispersing the silica-coated core into a buffer solution, adding dopamine hydrochloride, stirring, centrifuging, washing, vacuum drying the resulting precipitate, annealing in an inert atmosphere, and naturally cooling to obtain the outer shell.

8. The method for preparing the copper-based core-shell structured catalyst according to claim 7, characterized in that, Step 4 includes dispersing the product of step 3 into an etching solution to etch away the silicon dioxide. After etching, the product is centrifuged, washed, and vacuum dried to obtain the copper-based core-shell structure catalyst.

9. The application of a copper-based core-shell structured catalyst, characterized in that, The copper-based core-shell structured catalyst as described in claim 1 or 2 is used for the electrocatalytic reduction of carbon dioxide to produce ethylene, wherein the reaction is carried out at the cathode of the electrocatalytic device, and the material is loaded on the cathode surface.

10. The application of the copper-based core-shell structured catalyst according to claim 9, characterized in that, The reaction tank of the electrocatalytic device is placed in an ultrasonic water bath, and the electroreduction reaction is carried out simultaneously with water bath ultrasound.

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