Method for efficiently preparing C2 + product through CO2 electrochemical reduction

Abstract

The invention discloses a method for efficiently preparing a C2 + product through CO2 electrochemical reduction, which comprises the following specific steps: by taking foamy copper as a working electrode, a platinum sheet as a counter electrode, Ag / AgCl as a reference electrode and a KCl aqueous solution as an electrolyte, carrying out CO2 aeration on the electrolyte to saturate the electrolyte and continuously introducing CO2 gas into the electrolyte, and alternately applying an oxidation potential Ea and a reduction potential Ec to the reaction system, and carrying out CO2 electrochemical reduction reaction. The method for efficiently preparing the C2 + product through CO2 electrochemical reduction is simple in step and easy to implement, a complex electrocatalyst does not need to be prepared, the oxidation reaction and the reduction reaction are alternately conducted on the surface of foamy copper in the reaction process, the morphology can be kept unchanged after a certain reaction stage is reached, and therefore the time for preparing the C2 + product can be greatly prolonged, and the method is suitable for industrial production. And moreover, the C2 + product selectivity is high, and high C2 + product selectivity and long-term stability can be realized at the same time under the industrial-grade current density.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrolytic production of organic compounds, and particularly relates to a method for efficiently preparing C 2+ products through CO2 electrochemical reduction. BACKGROUND

[0002] Under the background of global energy crisis and increasingly serious greenhouse effect, electrocatalytic reduction of carbon dioxide (CO2RR) as a technology for converting CO2 into high-value chemicals and fuels has attracted widespread attention. CO2RR technology not only helps to alleviate greenhouse gas emissions, but also provides a new way for renewable energy storage. Among the various chemicals produced by CO2RR, C 2+ compounds (such as ethylene, ethanol, acetic acid, etc.) are highly valued due to their high energy density and market value.

[0003] In CO2RR, copper is the only single-component catalyst that can reduce CO2 to C 2+ products. Due to its suitable CO binding energy and natural abundance, copper has become the focus of research. However, most current research focuses on the modification of Cu-based catalysts to improve the selectivity and stability of C 2+ products, which often involves complex synthesis processes. In addition, traditional electrolysis methods may cause deactivation of Cu δ+ active species during long-term operation, and when operated at industrial current density, traditional constant potential electrolysis may also face problems such as insufficient CO2 supply and carbonate precipitation. These problems limit the industrialization process of CO2RR technology.

[0004] The application provides a new electrocatalytic mode, which is simple and easy to implement, can improve the selectivity of C 2+ products in CO2 electrochemical reduction, and can be stably operated for a long time, providing a feasible solution for the industrialization of CO2RR technology. SUMMARY

[0005] The application solves the technical problem that existing CO2 electro-reduction technology cannot simultaneously achieve high C 2+ product selectivity and long-term stability at industrial current density, and provides a method for efficiently preparing C 2+ products through CO2 electrochemical reduction, which is simple in process and excellent in performance.

[0006] The application provides a method for efficiently preparing C 2+The method for producing the product is as follows: taking foamed copper as the working electrode, platinum sheet as the counter electrode, Ag / AgCl as the reference electrode, and KCl aqueous solution as the electrolyte, the electrolyte is saturated by CO2 aeration and CO2 gas is continuously introduced into the electrolyte, and the reaction system is alternately applied with oxidation potential E a and reduction potential E c to carry out the electrochemical reduction of CO2.

[0007] According to the above scheme, the pore density of the foamed copper is 10-200 PPI (pores per inch), preferably 80-150 PPI. The three-dimensional porous structure of the foamed copper can provide a large specific surface area and excellent mass transfer performance while ensuring structural strength, which is the key to achieving high current density and high selectivity. The size of the foamed copper can be adjusted according to the size of the electrolytic cell, and the typical size is 1 cm x 1 cm with a thickness of 0.5-10 mm.

[0008] According to the above scheme, the foamed copper needs to be cleaned before use (to remove surface oxides and organic impurities), and the specific method is as follows: immerse the foamed copper in a hydrochloric acid (HCl) or nitric acid (HNO3) aqueous solution with a concentration of 0.05-3.0 mol / L, ultrasonic treatment at room temperature for 5-30 minutes, then rinse thoroughly with deionized water or ultrapure water, and finally dry with high-purity nitrogen or argon. The preferred acid concentration is 0.1 mol / L, and the preferred ultrasonic treatment time is 10 minutes. This pretreatment process can effectively activate the surface of the foamed copper and ensure the activity and reproducibility of the subsequent electrocatalytic reaction.

[0009] According to the above scheme, the concentration of the KCl aqueous solution is 0.1-6.0 mol / L, preferably 2.0 mol / L. This concentration range can provide sufficient ionic conductivity to support amperometric current density, while ensuring that the Cl - concentration in the electrolyte can effectively regulate the microenvironment at the electrode interface and promote C-C coupling reactions.

[0010] According to the above scheme, the flow rate of CO2 gas introduced into the electrolyte is 10-200 sccm, preferably 20 sccm. This flow rate range can ensure the continuous saturation of CO2 in the electrolyte, providing sufficient reactants for high current density reactions, and avoiding excessive gas flow that causes disturbance or electrolyte splashing on the electrode surface.

[0011] According to the above scheme, the oxidation potential E a is -0.38 V to +0.12 V (relative to the Ag / AgCl reference electrode), the time t a for applying the oxidation potential E a is 5-15 seconds, preferably 10 seconds. The E aThe potential range is selected above the initial potential of CO2 reduction, aiming to avoid CO2 reduction reaction in the anodic pulse stage, while inducing moderate electrochemical oxidation / reconstruction of copper species to generate high-activity Cu δ+ species, and promoting specific adsorption and rearrangement of ions in the double layer. a The time range is set based on the kinetics requirement of catalyst interface reconstruction and ion migration, too short will not work, too long may lead to excessive oxidation or reduced efficiency of the catalyst.

[0012] According to the above scheme, the reduction potential E c is -1.78~-1.38V (vs. Ag / AgCl reference electrode), the reduction potential E c is applied for a time t c of 5~15 seconds, preferably 10 seconds. The potential range Ec is the key to achieve 200~400mA / cm 2 industrial current density, ensuring that the CO2 reduction reaction proceeds at a high rate. c The time range needs to be matched with t a , both to ensure sufficient product generation in a single cycle, and to avoid excessive coverage or deactivation of active sites on the catalyst surface due to too long reduction time, so as to maintain high selectivity of the reaction.

[0013] Preferably, Ea=-0.18V, Ec=-1.78V, t a =t c =10s.

[0014] According to the above scheme, the CO2 electrochemical reduction reaction time is 0.5~100 hours. Under the optimized pulse parameters, the system can be stably operated for more than 20 hours without significant performance degradation, showing excellent stability.

[0015] According to the above scheme, the CO2 electrochemical reduction reaction C 2+ product selectivity is 50~70%. Under the optimal pulse parameter combination (Ea=-0.18V, Ec=-1.78V, t a =t c =10s), the C 2+ product Faraday efficiency can exceed 60%, and the highest can reach 63%, which is significantly better than the constant potential electrolysis under the same conditions.

[0016] The core principle of the present application is to use pulse electrolysis strategy, by alternating the application of oxidation potential (Ea) and reduction potential (Ec), to dynamically regulate the phase structure and interface microenvironment of the foam copper catalyst surface, thereby realizing the conversion of CO2 to C 2+efficient and stable transformation of products. In the stage of applying the oxidation potential Ea (-0.38~+0.12V), the surface of the foamed copper is moderately electrochemically oxidized, part of the metal copper (Cu 0 ) is oxidized into copper (Cu δ+ ) in an oxidized state, mainly Cu + ), and a Cu / Cu2O composite interface is formed in situ on the surface of the catalyst. This process not only regenerates the active species essential for C-C coupling, but also drives the reconstruction of the double electric layer, causing the enrichment of Cl - and other anions in the interface and pushing protons (H + ) away from the electrode surface, thus creating a preliminary condition for the subsequent reduction stage. In the stage of applying the reduction potential Ec (-1.78~-1.38V), the CO2 reduction reaction proceeds at a high speed. The pre-formed Cu δ+ species are partially reduced and strongly interact with the newly generated CO intermediates; at the same time, the enrichment of Cl - in the interface and the locally elevated pH value cooperate to significantly stabilize the adsorption of the CO intermediate and greatly reduce the energy barrier of C-C coupling, thus efficiently guiding the reaction path to C 2+ products such as ethylene and ethanol, and effectively inhibiting the hydrogen evolution side reaction. In the initial stage of the reaction (within 5 minutes), under the action of the pulse potential, the surface of the foamed copper rapidly undergoes dynamic reconstruction, forming a kind of "coral-like" nanostructure rich in Cu 0 / Cu + interface and oxygen vacancies. Once this structure is formed, it tends to be stable, providing a solid guarantee for the subsequent long-term continuous reaction.

[0017] The method for efficiently preparing C 2+ products by electrochemical reduction of CO2 provided by the present application has the advantages that the steps are simple and easy to implement, and a complex electrocatalyst does not need to be prepared. The surface of the foamed copper alternately undergoes oxidation and reduction reactions during the electrochemical reduction of CO2, and the morphology remains unchanged after a certain reaction stage, so that the preparation time of C 2+ products can be greatly extended, and the selectivity of C 2+ products is high, and high C 2+ product selectivity and long-term stability can be realized simultaneously at an industrial current density. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the pulse current response curve of Example 1 of the present application under pulse conditions (Ea=-0.18V, Ec=-1.78V, t a =t c =10s) with time; Figure 2Example 1 was performed under pulsed conditions (Ea = -0.18V, Ec = -1.78V, t...). a =t c A magnified view of the current density within the first 200 seconds of the time window (=10s); Figure 3 Example 1 was performed under pulsed conditions (Ea = -0.18V, Ec = -1.78V, t...). a =t c =10s) C 2+ Product Faraday efficiency distribution diagram; Figure 4 The images are scanning electron microscope (SEM) images of the copper foam (CF) material in Example 1 before (a, b), after 5 min (c) and 4300 s (d) of pulsed electrochemical reduction of CO2. Figure 5 The images shown are transmission electron microscope (TEM) images (a), high-resolution transmission electron microscope (HRTEM) images (b), and selected area electron diffraction (SAED) images (c) of the copper foam material after electrochemical reduction of CO2 in Example 1. Figure 6 The X-ray diffraction (XRD) comparison images of the copper foam material in Example 1 before (a) and after (b) electrochemical reduction of CO2 are shown. Figure 7 The above are comparison images of X-ray photoelectron spectroscopy (XPS) of Cu 2p (a), Cu LMM (b), O 1s (c), and Cl 2p (d) of the copper foam material in Example 1 before electrochemical reduction of CO2 and after different pulse reaction times. Figure 8 This is a comparison of the Raman spectra of the copper foam material in Example 1 before and after electrochemical reduction of CO2; Figure 9 Example 2 was performed under pulsed conditions (Ea = -0.18V, Ec = -1.78V, t...). a =t c The pulse current response curves as a function of time at 5s (a) and C 2+ Product Faraday efficiency distribution diagram (b); Figure 10 Example 3 was performed under pulsed conditions (Ea = -0.18V, Ec = -1.78V, t...). a =t c The pulse current response curves as a function of time at 15s (a) and C 2+ Product Faraday efficiency distribution diagram (b); Figure 11 Example 4 was performed under pulsed conditions (Ea = -0.18V, Ec = -1.78V, t...). a =12s,tc =8s)under pulse conditions (Ea=-0.18V, Ec=-1.78V, t 2+ =14s, t a =6s)under pulse conditions (Ea=-0.18V, Ec=-1.78V, t c =14s, t 2+ =6s)under pulse conditions (Ea=-0.18V, Ec=-1.78V, t Figure 12 =8s)under pulse conditions (Ea=-0.18V, Ec=-1.78V, t

[0019] To make the skilled in the art better understand the technical solutions of the present application, the present application will be described in further detail below with reference to the drawings.

[0020] The foam copper used in the embodiment of the present application has a size of 1cmx1cmx1.5mm and a pore density of 90-110PPI. Before use, the foam copper is subjected to cleaning treatment, and the specific method is as follows: the foam copper is immersed in a 0.1mol / L HCl solution, and is subjected to ultrasonic treatment at 20℃ for 10 minutes, with an ultrasonic power of 40Hz, then is washed with deionized water for three times, and finally is dried with high-purity nitrogen gas for use.

[0021] Example 1 A method for efficiently preparing C 2+ The specific steps are as follows: a Shanghai Chenhua electrochemical workstation (CHI 760E) is selected, the temperature during the experiment is 20℃, a standard three-electrode system is adopted, the foam copper is used as the working electrode, the platinum sheet is used as the counter electrode, the Ag / AgCl is used as the reference electrode, the 2mol / L KCl aqueous solution is used as the electrolyte, the electrolyte is subjected to CO2 aeration in an H-type electrolysis cell for 30 minutes to make it saturated, and the CO2 gas is continuously introduced into the electrolyte at a flow rate of 20sccm, and the oxidation potential E a =-0.18V and the reduction potential E c =-1.78V (all relative to Ag / AgCl) are alternately applied to the reaction system, the pulse cycle is 20s, the anodic pulse time t a =10s, the cathodic pulse time t c =10s, and the CO2 electrochemical reduction reaction lasts for 4300s.

[0022] Figure 1 The pulse current-time response curve under the conditions of the present embodiment (Ea=-0.18V, Ec=-1.78V, t a =t c =10s) experiences 215 pulse cycles, the anodic current stably approaches zero, and the cathodic reduction current density is always higher than 300mA / cm​2 , which meets the industrial current density standard.

[0023] Figure 2 The local magnification diagram of current density in the 200s time window before the reaction of this embodiment clearly shows the stable and periodic fluctuation of the current signal in the pulse electrolysis process, and the cathode reduction current density is stably maintained at about 318mA / cm 2 , which proves that the method of this embodiment can achieve excellent potential-current pulse response stability under industrial current density.

[0024] Figure 3 The C 2+ product (C2H4, C2H5OH, CH3CH2CH2OH) Faraday efficiency comparison chart, the total C 2+ The product selectivity reaches 63%, among which the Faraday efficiency of ethylene (C2H4), ethanol (C2H5OH) and n-propanol (CH3CH2CH2OH) is 34%, 23% and 6% respectively, which shows that the method of this embodiment can achieve outstanding product selectivity under high current density. It shows that through the optimization of the pulse parameter combination, the unification of high reaction rate and high selectivity is successfully realized, which provides a reliable technical scheme for the industrial application of CO2 electro-reduction technology.

[0025] The scanning electron microscope images of the foam copper before and after the electrochemical reduction of CO2 in this embodiment are as shown in Figure 4 , wherein (a) and (b) are the morphologies of the foam copper surface before the electrochemical reduction of CO2 under different magnifications, showing that the surface is relatively smooth, and the existing depression is caused by slight acid etching in the pretreatment stage. (c) and (d) are the surface morphologies after 5min and 4300s of electrochemical reduction of CO2. It can be observed that after 5min of reaction, the foam copper surface forms a dense and accumulated coral-like nanoparticle structure, which indicates that the foam copper surface undergoes structure reconstruction and active phase regeneration during the pulse electro-catalysis process, and the foam copper surface morphology tends to be stable after 5min of reaction. This unique coral-like structure provides a larger specific surface area and more active sites, which is beneficial to the occurrence of C-C coupling reaction.

[0026] The transmission electron microscope images of the foam copper after the electrochemical reduction of CO2 in this embodiment are as shown in Figure 5The TEM image (a) shows that the catalyst presents a stacked block coral-like morphology, which is closely related to the periodic reduction and redeposition process in the pulse process. The high-resolution TEM image (b) shows clear lattice fringes of 0.24 nm and 0.30 nm, which are attributed to the (111) and (110) crystal planes of Cu2O, respectively. The lattice fringe of 0.21 nm is detected, which is attributed to the (111) crystal plane of metallic Cu. These results confirm that the pulse electrochemical environment successfully induces Cu 0 / Cu + The synergistic construction of dual active sites. The corresponding selected area electron diffraction image (c) further confirms this conclusion, and the diffraction rings can be attributed to the (111), (110) crystal planes of Cu2O and the (111) crystal plane of Cu. These results collectively confirm that the pulse electrochemical environment successfully induces Cu 0 / Cu + The synergistic construction of dual active sites. This unique coral-like stacked structure not only significantly increases the exposure ratio of high-index crystal planes, improves the specific surface area of the catalyst, but also constructs a three-dimensional mass transfer channel. At the same time, the Cu 0 / Cu + The electronic transfer effect at the interface can optimize the adsorption strength of the CO intermediate, and the two aspects synergistically promote the selectivity of the C-C coupling path.

[0027] The X-ray diffraction comparison chart of the foam copper before and after the electrochemical reduction of CO2 in this embodiment is shown in Figure 6 , wherein (a) is the foam copper before the reaction, and (b) is the foam copper after the reaction. By comparing the X-ray diffraction charts before and after the reaction, it can be seen that there is no significant difference between them, and they are consistent with the diffraction peaks of the standard substance Cu (PDF #01-089-2838). Specifically, the three main peaks at 43.316°, 50.448° and 74.125° correspond to the (111), (200) and (220) crystal planes of Cu, respectively. The appearance of these peaks confirms the crystal structure of the catalyst. Although the catalyst has undergone a pulse electrochemical reduction process, the bulk phase of the catalyst remains stable and does not change significantly. This result shows that the coral-like nanostructure formed in the pulse electrolysis process is mainly a surface reconstruction based on the basic crystal structure of metallic copper, rather than a change in the bulk phase structure.

[0028] The X-ray photoelectron spectroscopy comparison chart of the foam copper before and after the electrochemical reduction of CO2 in this embodiment is shown in Figure 7 . (a) is the Cu 2p high-resolution XPS spectrum, which shows that the catalysts before and after the reaction have Cu 3 / 2 at about 934 eV (Cu 2p 1 / 2 ) and about 954 eV (Cu2p 2+The characteristic peaks of the species are mainly due to air oxidation on the material surface. Further precise valence state analysis of the catalyst after the reaction using Cu LMM Auger electron spectroscopy (b) revealed Cu valence states at approximately 913 eV, 916 eV, and 918 eV, respectively. 0 Cu + Cu 2+ The triple characteristic peaks confirm that pulse modulation can effectively induce Cu + The formation of active sites optimizes the Cu content on the catalyst surface. 0 / Cu + The proportion. The fine 1s spectra (c) of O2 before and after the reaction of copper foam show that the oxygen species in the catalyst are mainly lattice oxygen (O2). Ⅰ (approximately 532 eV) and hydroxyl / surface adsorbed oxygen (O Ⅲ It exists in the form of approximately 533 eV. Quantitative analysis shows that O on the catalyst surface after the reaction... Ⅰ The relative content increased significantly by approximately 18% compared to before the reaction, directly demonstrating that pulse treatment induced the reconstruction and enrichment of metal oxides. Furthermore, (d) shows a comparison of the Cl 2p spectra before and after the reaction of the copper foam; it can be seen that the Cl 2p spectrum of the copper foam after the reaction exhibits similarities to that before the reaction in the 198-200 eV range. - The highly species-matched characteristic peaks indicate that, under the pulsed strategy in this embodiment, the Cl in the electrolyte... - It can stably reside on the catalyst surface in ionic form. Cl - The residence of the substance, through synergistic effect with the pulse potential, optimizes the interfacial double-layer structure and reaction microenvironment, thereby jointly enhancing the CO2RR production of C. 2+ The performance of the product.

[0029] The Raman spectra of the copper foam before and after electrochemical reduction of CO2 in this embodiment are shown in the figure below. Figure 8 As shown, at approximately 144cm -1 The sharp peak observed at 450-700 cm⁻¹ belongs to the symmetric stretching vibration mode of Cu₂O, while the peak at 450-700 cm⁻¹ belongs to the symmetric stretching vibration mode of Cu₂O. -1 The bimodal range is related to Cu x Jahn-Teller distortion correlation was observed in the O species. Cu2O characteristic peaks were also detected in the CF sample that had not undergone the pulse reaction, attributed to its auto-oxidation process in air.

[0030] Example 2 A method for the efficient preparation of C by electrochemical reduction of CO2 2+ The method for producing the product is basically the same as that in Example 1, except for the setting of the pulse time parameter: the anode pulse time t is set... a With cathode pulse time t cAll pulses were adjusted to 5 seconds, meaning the total pulse period was 10 seconds, and the CO2 electrochemical reduction reaction lasted for 4300 seconds.

[0031] The electrochemical response and product selectivity test results under the conditions of this embodiment are as follows: Figure 9 As shown in (a) and (b), (a) is the pulse current versus time response curve. After 215 pulse cycles, the anode current stabilizes and approaches zero, while the cathode reduction current density remains stable at approximately 273 mA / cm² in each cycle. 2 (b) shows the product analysis results. Under this short pulse period, C 2+ The overall Faradaic efficiency of the products dropped sharply to 11%, with hydrogen (H2) and carbon monoxide (CO) being the main products, while the Faradaic efficiencies of the target products ethylene, ethanol, and n-propanol were 4%, 6%, and 1%, respectively. Compared with Example 1 (t a =t c =10s) 63% of C 2+ Compared to the efficiency comparison, the performance degradation is significant. This indicates that the pulse duration is too short to provide sufficient energy for the Cu on the catalyst surface to become active. δ+ The sufficient generation of species and the adsorption of *CO intermediates coupled with CC provide the necessary reaction time window, causing the reaction pathway to mainly remain at the stage of generating C1 products or undergoing hydrogen evolution reaction.

[0032] Example 3 A method for the efficient preparation of C by electrochemical reduction of CO2 2+ The method for producing the product is basically the same as that in Example 1, except for the setting of the pulse time parameter: the anode pulse time t is set... a With cathode pulse time t c The pulse duration is extended to 15 seconds, resulting in a total pulse period of 30 seconds. The CO2 electrochemical reduction reaction continues for 4300 seconds.

[0033] The electrochemical response and product selectivity test results under the conditions of this embodiment are as follows: Figure 10 As shown in (a) and (b), (a) is the pulse current versus time response curve. After 215 pulse cycles, the anode current stabilizes and approaches zero, while the cathode reduction current density remains stable at approximately 327 mA / cm² in each cycle. 2 (b) shows the product selectivity analysis results, indicating that C 2+ The overall Faradaic efficiency of the product was 54%, with selectivities of 30%, 20%, and 4% for ethylene, ethanol, and n-propanol, respectively. Compared to Example 1, C 2+The selectivity decreased by approximately 9%. This result indicates that while the excessively long pulse time ensures sufficient reaction progress within each half-cycle, it may lead to excessive oxidation of the catalyst surface during the anodic stage, which to some extent hinders charge transfer and reactant contact; meanwhile, during the cathodic stage, the excessively long reduction time may promote the occurrence of side reactions.

[0034] Example 4 A method for the efficient preparation of C by electrochemical reduction of CO2 2+ The method for producing the product is basically the same as that in Example 1, except that the pulse time ratio is adjusted: the total pulse period is kept at 20s, but the anode pulse time t is adjusted. a Adjusted to 12s, cathode pulse time t c The time was adjusted accordingly to 8 seconds, and the CO2 electrochemical reduction reaction continued for 4300 seconds.

[0035] The electrochemical response and product selectivity test results under the conditions of this embodiment are as follows: Figure 11 As shown in (a) and (b), (a) is the pulse current versus time response curve, showing that the system operates smoothly. After 215 pulse cycles, the anode current stabilizes and approaches zero, while the cathode reduction current density remains stable at approximately 332 mA / cm² in each cycle. 2 (b) shows the product selectivity analysis results, C 2+ The overall Faraday efficiency of the product reached 61%, slightly lower than that under the symmetric pulse condition in Example 1 (t a =t c The efficiency was 63% at t=10s. The Faraday efficiencies of the main products ethylene, ethanol, and n-propanol were 32%, 23%, and 6%, respectively. This result indicates that appropriately extending the anode time (t=10s) can improve efficiency. a A period of 12 seconds may be beneficial for the more complete generation or stabilization of Cu within a single cycle. δ+ Active species, and an 8s cathode pulse time (t) c It can still effectively drive CO2 reduction and CC coupling, thus achieving selective micro-optimization.

[0036] Example 5 A method for the efficient preparation of C by electrochemical reduction of CO2 2+ The method for producing the product is basically the same as that in Example 1, except that the pulse time ratio is adjusted: the total pulse period is kept at 20s, but the anode pulse time t is adjusted. a Further extended to 14s, cathode pulse time t c The time was shortened to 6 seconds, while the CO2 electrochemical reduction reaction lasted for 4300 seconds.

[0037] The electrochemical response and product selectivity test results under the conditions of this embodiment are as follows: Figure 12As shown in (a) and (b), (a) is the pulse current versus time response curve. After 215 pulse cycles, the anode current stabilizes and approaches zero, while the cathode reduction current density remains stable at approximately 314 mA / cm² in each cycle. 2 (b) shows the product selectivity analysis results, C 2+ The overall Faraday efficiency of the product was 58%, 5% lower than that of Example 1. The selectivities for ethylene, ethanol, and n-propanol were 32%, 22%, and 4%, respectively. These results, along with those of Example 4, indicate that with a total cycle of 20 s and an anode time t... a Within the range of 10s to 14s, moderately extend t. a , correspondingly shorten t c This allows C to maintain a high current density while keeping it low. 2+ The product selectivity remained stable in the high range of 58-63%. This is likely due to the long anode time ensuring sufficient oxidation state species (Cu) on the catalyst surface. + The full generation of CO2 and the optimization of the interface structure are achieved, while the shorter but sufficiently strong cathode pulses are efficiently focused on the reduction and coupling steps of CO2, reducing the side reactions that may occur during long cathode times.

[0038] This invention, by adjusting the electrochemical reduction reaction conditions, enables the formation of a stable Cu-rich layer on the surface of copper foam in situ during the initial stage of the reaction (approximately 5 minutes). 0 / Cu + The coral-like nanostructure at the interface, once formed, allows the system to enter a stable operating state, not only for C 2+ The Faraday efficiency of the product is significantly improved (compared to only 45% under optimal potentiostatic electrolysis). More importantly, this method endows the system with excellent resistance to deactivation, maintaining high selectivity and a efficiency exceeding 300 mA / cm². 2 Under industrial-grade current density conditions, the method can operate stably for a long time through routine maintenance such as periodic electrolyte replacement, demonstrating that the method of the present invention has great potential to meet the requirements of long-term continuous operation in industrial applications.

[0039] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A highly efficient method for the electrochemical reduction of CO2 to prepare C 2+ The method for producing the product is characterized by, The specific steps are as follows: using copper foam as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, KCl aqueous solution as the electrolyte, the electrolyte is saturated with CO2 and CO2 gas is continuously introduced into the electrolyte, and an oxidation potential E is alternately applied to the reaction system. a and reduction potential E c CO2 undergoes an electrochemical reduction reaction.

2. The method for efficient CO2 electrochemical reduction preparation according to claim 1 2+ The method for producing the product is characterized by, The pore density of the copper foam is 10~200 PPI.

3. The method for efficient preparation of C by CO2 electrochemical reduction according to claim 1 2+ The method for producing the product is characterized by, The foamed copper needs to be cleaned before use. The specific method is as follows: Immerse the foamed copper in a hydrochloric acid or nitric acid aqueous solution with a concentration of 0.05~3.0mol / L, sonicate it at room temperature for 5~30 minutes, then rinse it thoroughly with deionized water or ultrapure water, and finally blow it dry with high-purity nitrogen or argon gas for later use.

4. The method for efficient preparation of C by CO2 electrochemical reduction according to claim 1 2+ The method for producing the product is characterized by, The concentration of the KCl aqueous solution is 0.1~6.0 mol / L.

5. The method for efficient preparation of C by CO2 electrochemical reduction according to claim 1 2+ The method for producing the product is characterized by, The flow rate of CO2 gas introduced into the electrolyte is 10~200 sccm.

6. The method for efficient preparation of C by electrochemical reduction of CO2 according to claim 1 2+ The method for producing the product is characterized by, The oxidation potential E a An oxidation potential E is applied, ranging from -0.38V to +0.12V. a Time t a It lasts for 5 to 15 seconds.

7. The method for efficient preparation of C by CO2 electrochemical reduction according to claim 1 2+ The method for producing the product is characterized by, The reduction potential E c The voltage is -1.78 to -1.38V, and a reduction potential E is applied. c Time t c It lasts for 5 to 15 seconds.

8. The method for efficient preparation of C by CO2 electrochemical reduction according to claim 6 or 7 2+ The method for producing the product is characterized by, Ea=-0.18V,Ec=-1.78V,t a =t c =10s。 9. The method for efficient preparation of C by electrochemical reduction of CO2 according to claim 1 2+ The method for producing the product is characterized by, The electrochemical reduction reaction time of CO2 is 0.5 to 100 hours.

10. The method for efficient preparation of C by CO2 electrochemical reduction according to claim 1 2+ The method for producing the product is characterized by, CO2 electrochemical reduction reaction C 2+ The product selectivity is 50-70%.

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