Amino acid modified copper-based catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electro-catalytic materials and carbon dioxide emission reduction and resource utilization, and particularly relates to an amino acid modified copper-based catalyst and a preparation method and application thereof. According to the catalyst, the surface of cuprous oxide with an orthorhombic-section semi-cube shape is modified through L-cysteine, and a composite structure with a special interface microenvironment is formed. Sulfydryl in L-cysteine and copper species on the surface of cuprous oxide can form a strong coordination effect, water decomposition and * CO protonation are promoted, the surface structure is stabilized, asymmetric coupling is facilitated, meanwhile, amino can provide an electron-rich environment, capture of carbon dioxide is enhanced, and the selectivity and stability of ethylene prepared through electro-catalysis carbon dioxide reduction are cooperatively regulated and controlled.

Description

Technical Field

[0001] This invention belongs to the technical field of electrocatalytic materials and carbon dioxide emission reduction and resource utilization, specifically relating to an amino acid-modified copper-based catalyst for electrocatalytic carbon dioxide to ethylene production, its preparation method, and its application. Background Technology

[0002] The rapid development of modern industry and the accelerating pace of global industrialization are inseparable from the massive consumption of fossil fuels. Consequently, the concentration of carbon dioxide (CO2) emitted into the atmosphere from the combustion of fossil fuels is rising daily, and the resulting greenhouse effect has become a global challenge. CO2 is a cheap, non-toxic, and abundant carbon resource. Converting it into valuable chemicals has the dual significance of rational carbon resource utilization and environmental protection. Therefore, developing efficient carbon capture, utilization, and storage (CFS) technologies is of paramount importance. Among numerous CFS technologies, electrocatalytic carbon dioxide reduction reaction (CO2RR) technology can utilize electricity generated from renewable energy sources such as wind or solar power to convert CO2 into high-value products such as formic acid (HCOOH) and ethylene (C2H4) under relatively mild reaction conditions, realizing the resource utilization of CO2. It can also store intermittent electrical energy in the form of chemical energy, representing a clean, energy-saving, green, and sustainable technological path.

[0003] Among the various known electrocatalyst materials, copper (Cu)-based catalysts have attracted widespread attention due to their ability to efficiently reduce CO2 to multi-carbon products. Copper oxides, such as cuprous oxide (Cu2O), are inexpensive, widely available, and exhibit certain catalytic activity for CO2 reduction, making them a subject of extensive research. Generally, the morphology and surface chemical state of a catalyst play a crucial role in its catalytic activity and selectivity. During the electrocatalytic CO2 reduction process, Cu2O is reduced in situ to metallic Cu, and its initial morphology and structure are difficult to maintain, leading to poor catalyst stability and unsatisfactory product selectivity.

[0004] Therefore, it is of great significance to develop a Cu-based electrocatalyst with high stability and the ability to effectively control product selectivity. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an amino acid-modified copper-based catalyst with unique morphology, high stability, and high selectivity. This catalyst uses amino acids as surface modifiers to modify Cu2O, regulating its surface electronic structure, improving CO2 capture and adsorption, and achieving highly selective generation of C2H4. Another purpose of this invention is to provide a simple preparation method for an amino acid-modified copper-based catalyst with highly controllable operating conditions. A further purpose is to provide an application of this amino acid-modified copper-based catalyst. Finally, a method for electrocatalytically producing ethylene from carbon dioxide is also provided.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an amino acid-modified copper-based catalyst, the catalyst being composed of Cu2O with a cubic or rhombic semi-cubic morphology and natural amino acids modified on the surface of Cu2O.

[0008] Preferably, the natural amino acid is L-cysteine, glycine, or lysine.

[0009] Preferably, the natural amino acid is L-cysteine. L-cysteine ​​(L-cys) is a natural amino acid containing a thiol group (-SH) and an amino group (-NH2). Its thiol group has a strong interaction with Cu species and can act as a surface modifier to stabilize nanoparticles and regulate their surface electronic structure. At the same time, the amino functional group can provide an electron-rich environment to promote the adsorption and activation of CO2, which is beneficial to CO2 capture.

[0010] Secondly, the present invention provides a method for preparing an amino acid-modified copper-based catalyst, wherein amino acids are added to a cuprous oxide suspension with an orthorhombic semi-cubic morphology, so that the amino acids are fully modified on the surface of the cuprous oxide, and the product after the reaction is collected, which is the amino acid-modified copper-based catalyst.

[0011] Preferably, the preparation method of the cuprous oxide suspension with an orthorhombic semi-cubic morphology is as follows: an alkaline solution is added to a copper salt solution to adjust the pH of the reaction system to 9.0-11.0 to obtain a mixed solution; a reducing agent is added to the mixed solution and the reaction is stirred to obtain the cuprous oxide suspension.

[0012] Preferably, the copper salt is copper sulfate pentahydrate, copper chloride dihydrate, or copper nitrate.

[0013] Preferably, the alkaline solution is a sodium hydroxide solution with a concentration of 0.1-0.5M.

[0014] Preferably, the reducing agent is glucose or ascorbic acid solution.

[0015] Preferably, an alkaline solution is added to the copper salt solution, and the reaction is carried out at a stirring speed of 400-800 rpm. The pH value of the reaction system is adjusted to 9.0-11.0 to obtain a mixed solution. A reducing agent is added to the mixed solution, and the reaction is carried out at a stirring speed of 400-800 rpm to obtain a cuprous oxide suspension.

[0016] Preferably, an alkaline solution is added dropwise to a copper salt solution at a rate of 2-6 ml / min, and the reaction is stirred at a rate of 400-800 rpm to adjust the pH of the reaction system to 9.0-11.0 to obtain a mixed solution; a reducing agent is added dropwise to the mixed solution at a rate of 2-4 ml / min, and the reaction is stirred at a rate of 500-1000 rpm to obtain a cuprous oxide suspension.

[0017] Preferably, the amino acid is L-cysteine, glycine, or lysine, and the loading method to fully modify the cuprous oxide surface with amino acids is ultrasonic stirring at room temperature, oil bath heating and stirring, or hydrothermal loading.

[0018] Preferably, the molar ratio of copper salt to amino acid is 5-20:1. More preferably, the molar ratio of copper salt to amino acid is 5-10:1.

[0019] Preferably, the present invention provides an amino acid-modified Cu-based catalyst for the electrocatalytic production of C2H4 from CO2, and the preparation method of the catalyst is as follows:

[0020] (1) Dissolve the soluble copper salt in deionized water and stir until homogeneous to form a divalent copper solution;

[0021] (2) Add an alkaline solution to the divalent copper solution in step (1), react with stirring, adjust the pH value of the reaction system, and obtain a mixed solution;

[0022] (3) Add a reducing agent to the mixed solution in step (2) and react with stirring. Divalent copper is reduced to monovalent copper to obtain an orange-yellow Cu2O suspension. Continue stirring until the solution color no longer changes significantly to ensure that the reaction proceeds fully.

[0023] (4) Add amino acids to the Cu2O suspension obtained in step (3), disperse by ultrasonication, stir the reaction to fully modify the surface of Cu2O with amino acids, and obtain the product after the reaction is completed.

[0024] (5) The product after the reaction in step (4) is centrifuged, washed and dried to obtain the amino acid-modified Cu-based catalyst.

[0025] Preferably, in step (1), the soluble copper salt is copper sulfate pentahydrate, copper chloride dihydrate, or copper nitrate, and the solution concentration is 0.5-5 mM.

[0026] Preferably, in step (2), the alkaline solution is a sodium hydroxide solution with a concentration of 0.1-0.5M, which is added slowly and evenly using a syringe pump at a rate of 2-6 ml / min to adjust the pH of the reaction system to 9.0-11.0. The stirring speed is 400-800 rpm and the stirring is carried out at room temperature.

[0027] Preferably, in step (3), the reducing agent is a reducing agent such as glucose or ascorbic acid solution, and the molar ratio of copper salt to reducing agent is 1:(1-4); the reducing agent is added slowly and evenly using an injection pump at a rate of 2-4 ml / min, and the stirring speed is 600-1000 rpm, and the stirring is carried out at a temperature of 25-60℃ for 1-3 hours.

[0028] Preferably, in step (4), the amino acids are L-cys, glycine (Gly) and lysine (Lys), and the molar ratio of the amino acids to the soluble copper salt in step (1) is (1-10):20; the ultrasonic time is 30-60 min, the stirring speed is 500-1000 rpm, and the reaction is carried out at room temperature for 1-3 h.

[0029] Preferably, the centrifugation speed in step (5) is 5000-10000 rpm; the impurities are removed by washing with ethanol and deionized water three times each; the drying is vacuum drying, which is carried out in a vacuum drying oven for 4-12 hours at a temperature of 50-80℃.

[0030] Thirdly, the present invention provides the application of the above-mentioned catalyst in the preparation of an electrode for electrocatalytic carbon dioxide to ethylene production.

[0031] A catalyst ink is prepared by mixing an amino acid-modified copper-based catalyst with a perfluorosulfonic acid polymer; the catalyst ink is then coated onto the surface of an electrode substrate to obtain a copper-based catalytic electrode.

[0032] Fourthly, the present invention provides a method for electrocatalytically producing ethylene from carbon dioxide, wherein the above-mentioned catalyst is mixed with a perfluorosulfonic acid type polymer to form a catalyst ink; the catalyst ink is coated on the surface of an electrode substrate to obtain a copper-based catalytic electrode; the copper-based catalytic electrode is used as the working electrode, a platinum mesh or platinum sheet is used as the counter electrode, and a silver-silver chloride electrode or a saturated calomel electrode is used as the reference electrode to form a three-electrode system for reducing carbon dioxide to produce ethylene.

[0033] Preferably, this invention provides an application of a Cu-based catalyst for the electroreduction of CO2 to C2H4. The aforementioned amino acid-modified copper-based catalyst, i.e., amino acid-modified Cu2O catalyst particles, are uniformly dispersed in an appropriate amount of ethanol, and an appropriate amount of Nafion (a perfluorosulfonic acid polymer) is added to prepare a catalyst ink. After ultrasonic dispersion, the ink is drop-coated onto the surface of an electrode substrate until the catalyst loading reaches 0.5-3 mg / cm³. 2A Cu-based catalytic electrode was obtained. The Cu-based catalytic electrode was made into a working electrode, and a platinum mesh or platinum sheet was used as the counter electrode, while a silver-silver chloride electrode or a saturated calomel electrode was used as the reference electrode, forming a three-electrode system. A negative potential was applied through an electrochemical workstation, and CO2 was reduced to carbon-containing economic products such as HCOOH and C2H4 in an H cell or a flow cell using acidic, neutral, or alkaline solutions as electrolytes.

[0034] Preferably, the catalyst loading is 0.6-2 mg / cm³. 2 .

[0035] Preferably, the electrode substrate is carbon cloth, carbon paper, gas working electrode, etc.

[0036] Preferably, the CO2 electroreduction conversion system uses a flow cell electrolyzer with a platinum mesh as the counter electrode and a silver-silver chloride electrode as the reference electrode. The cathode and anode chambers use a 0.1-1M neutral potassium bicarbonate (KHCO3) solution or an alkaline potassium hydroxide (KOH) solution as the electrolyte. A proton exchange membrane (PEM) or anion exchange membrane (AEM) separates the cathode and anode chambers. High-purity CO2 gas is continuously introduced at a flow rate of 10-40 mL / min. A peristaltic pump ensures gas-liquid contact. The electrocatalytic CO2 reduction reaction is performed using an electrochemical workstation in constant potential or constant current mode to generate products. The device is connected to an online gas chromatograph (GC) to support the analysis of the gaseous products. Under suitable potential or current conditions, this Cu-based catalyst can efficiently reduce CO2 to C2H4.

[0037] Invention Principle: This invention modifies the surface of cuprous oxide with an orthorhombic semi-cubic morphology using L-cysteine, forming a composite structure with a unique interfacial microenvironment. The thiol group in L-cysteine ​​forms a strong coordination interaction with copper species on the cuprous oxide surface, promoting water splitting and *CO protonation, stabilizing the surface structure, and facilitating asymmetric coupling. Simultaneously, the amino group provides an electron-rich environment, enhancing carbon dioxide capture and synergistically regulating the selectivity and stability of electrocatalytic carbon dioxide reduction to ethylene.

[0038] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0039] 1. High Ethylene Selectivity: This invention utilizes an amino acid-modified Cu-based catalyst. By adjusting the feed ratio, rotation speed at different nucleation stages, and feed rate, a unique orthorhombic semi-cubic structure Cu₂O is obtained. The L-cys groups in the amino acids provide an electron-rich environment through the amino groups, promoting CO₂ adsorption and activation, and capturing CO₂. Simultaneously, the thiol groups strongly coordinate with copper species on the Cu₂O surface to form Cu-S, promoting water decomposition and CO protonation, which facilitates subsequent asymmetric coupling and synergistically catalyzes the reduction of CO₂ to C₂H₄. This catalyst exhibits a high C₂H₄ Faradaic efficiency of over 60% in neutral or alkaline electrolytes, superior to traditional Cu-based catalysts.

[0040] 2. Long-term stability: In this invention, L-cys is used to modify Cu2O, and its rhombic semi-cubic structure is stabilized through the strong coordination of Cu-S. It can still maintain a high C2H4 Faraday efficiency in a test of up to 50 hours, which is better than the rhombic semi-cubic Cu2O without L-cys modification.

[0041] 3. High industrialization potential: The L-cys-modified orthorhombic semi-cubic Cu2O catalyst of this invention can achieve an industrial current density (>-0.25 A / cm²) in a flow cell. 2 Its high C2H4 selectivity has the potential for industrial-scale application. Attached Figure Description

[0042] Figure 1 These are scanning electron microscope images of Comparative Examples 1, 2, 3 and 1 of the present invention; wherein, (a) is BC-Cu2O, (b) is B-GR-Cu2O, (c) is LS-Cu2O and (d) is L-GR-Cu2O.

[0043] Figure 2 Comparison of the Faraday efficiency of electrocatalytic reduction of CO2 to C2H4 at a current density of -250 mA / cm² for Comparative Examples 1, 2, 3, and 1.

[0044] Figure 3 This is a comparison of the Faraday efficiency of three electrodes with different amino acid types in Example 3 for the electrocatalytic reduction of CO2 to C2H4 at a current density of -200 mA / cm².

[0045] Figure 4 This is a comparison of the Faraday efficiency of three electrodes with different reaction speeds of 400 / 600, 500 / 700, and 800 / 1000 rpm in Example 2 at a current density of -200 mA / cm² for the electrocatalytic reduction of CO2 to C2H4.

[0046] Figure 5This is a comparison of the selectivity of three electrodes for electrocatalytic reduction of CO2 to C2H4 at potentials of -1.2V vs. RHE under different loading modes of L-cys in Example 4.

[0047] Figure 6 This is a comparison of the selectivity of three electrodes in the electrocatalytic reduction of CO2 to C2H4 at a potential of -1.2V vs. RHE when the Cu2O:L-cys molar ratio is 20:1, 10:1, and 5:1 in Example 5.

[0048] Figure 7 This is a comparison of the long-term stability of L-cys modified Cu2O catalysts with different proportions in Comparative Example 1, Comparative Example 2, Example 1, and Example 5 of this invention at -1.2V vs. RHE potential. Detailed Implementation

[0049] The technical solution of the present invention will be further described below through specific embodiments. The scope of protection of the present invention includes the following embodiments but is not limited to them. Any changes related to the present invention are within the scope of protection.

[0050] The pharmaceutical products used in the following examples and comparative examples are all commercially available pharmaceutical products. In the following examples, L-cys-modified rhombic semi-cubic Cu2O, rhombic semi-cubic Cu2O modified with different types of amino acids, L-cys-modified Cu2O, rhombic semi-cubic Cu2O with different L-cys loading methods, and rhombic semi-cubic Cu2O modified with different proportions of L-cys are all amino acid-modified copper-based catalysts of the present invention.

[0051] Example 1

[0052] This embodiment provides the preparation of an L-cys-modified rhombic semi-cubic Cu2O electrode:

[0053] (1-1) Dissolve 2 mmol of copper chloride dihydrate in 500 ml of deionized water and stir well. The solution is light blue.

[0054] (1-2) Use a syringe pump to add 30 ml of 0.3 M sodium hydroxide solution dropwise at a rate of 3 ml / min, adjust the pH of the reaction system to about 9.5, and generate a light blue flocculent precipitate. Control the rotation speed to 500 rpm and carry out the reaction at room temperature.

[0055] (1-3) Use a syringe pump to add 20 ml of 0.2 M ascorbic acid solution at a constant rate of 2 ml / min. Divalent copper is reduced to monovalent copper, and the solution color turns orange-yellow or brown-yellow. Control the rotation speed to maintain 700 rpm and react at 50℃ for 1 h.

[0056] (1-4) After the reaction, the mixed solution was cooled to room temperature, 0.2 mmol of L-cys powder was added, and the mixture was ultrasonically dispersed at 40 W for 30 min. Then, the mixture was stirred at room temperature for 2 h to allow L-cys to be fully modified on Cu2O particles.

[0057] (1-5) The solid product after centrifugation reaction was washed three times each with ethanol and deionized water at a speed of 8000 rpm to remove impurities. It was then placed in a vacuum drying oven and dried at 60°C for 12 h to obtain L-cys modified rhombic semi-cubic Cu2O particles, which are amino acid modified copper-based catalysts.

[0058] (1-6) Take 100 mg of L-cys-modified rhombic semi-cubic Cu2O particles, disperse them in 4 ml of ethanol, add 100 μL of Nafion to prepare a catalyst ink, ultrasonically disperse the prepared catalyst ink for 1 h, and then drop-coat it onto a surface with an area of ​​1.5 x 1.5 cm. 2 On the gas diffusion electrode, the catalyst loading weight is 1.0 mg / cm³. 2 An L-cys-modified rhombic semi-cubic Cu2O electrode was obtained, denoted as L-GR-Cu2O.

[0059] Comparative Example 1

[0060] This comparative example provides the preparation of a cubic Cu2O catalyst electrode without amino acid modification:

[0061] (2-1) Dissolve 1 mmol of copper acetate in 500 ml of deionized water and stir well. The solution is light blue.

[0062] (2-2) Add 30 ml of 0.3 M sodium hydroxide solution dropwise to form a light blue flocculent precipitate. Keep the rotation speed at 500 rpm and carry out the reaction at room temperature.

[0063] (2-3) Add 20 ml of 0.2 M ascorbic acid solution dropwise over 10 min. Divalent copper is reduced to monovalent copper, and the solution color turns brownish-yellow. React at room temperature for 3 h.

[0064] (2-4) The solid product after centrifugation reaction was washed three times each with ethanol and deionized water at a speed of 8000 rpm to remove impurities. It was then placed in a vacuum drying oven and dried at 60°C for 12 h to obtain cubic Cu2O particles.

[0065] (2-5) Take 50 mg of cubic Cu2O particles, disperse them in 2 ml of ethanol, add 50 μL of Nafion to prepare a catalyst ink, and then ultrasonically disperse the catalyst ink for 1 h before drop-coating it onto a surface with an area of ​​1.5 x 1.5 cm. 2On the gas diffusion electrode, the catalyst loading weight is 1.0 mg / cm³. 2 A cubic Cu2O particle electrode without amino acid modification was obtained, denoted as BC-Cu2O.

[0066] Comparative Example 2

[0067] This comparative example provides the preparation of an orthorhombic semi-cubic Cu2O catalyst electrode without amino acid modification:

[0068] The specific method is the same as steps (1-1) to (1-3) in Example 1, without subsequent L-cys modification. The dried rhombic semi-cubic Cu2O particles are ground, 50 mg is taken, dispersed in 2 ml of ethanol, 50 μL of Nafion is added, and the mixture is sonicated for 1 h to prepare catalyst ink. 92.2 μL of catalyst ink is then drop-coated onto an area of ​​1.5 x 1.5 cm using a pipette. 2 On the gas diffusion electrode, the catalyst loading weight is 1.0 mg / cm³. 2 An unmodified rhombic semi-cubic Cu2O electrode, denoted as B-GR-Cu2O, was obtained.

[0069] Comparative Example 3

[0070] This comparative example provides the preparation of an L-cys-modified spherical Cu2O electrode:

[0071] (3-1) Dissolve 1 mmol of copper acetate in 100 ml of deionized water, stir well, add to a three-necked flask placed in a water bath, place a rotor, connect the inlet to nitrogen gas, connect the outlet to a bubbler to pass through the waste liquid bottle, seal the main port with a rubber stopper, turn on the nitrogen switch, adjust the flow rate and bubble for 10 minutes to displace the air in the container and form nitrogen protection, set the speed to 500 rpm;

[0072] (3-2) Dissolve 3.4g of sodium hydroxide in 20ml of deoxygenated water (pre-bubbled with nitrogen to remove deionized water). Add the prepared solution to a three-necked flask using a syringe, heat to 60℃ and react for 10min. A yellow-brown precipitate will gradually form.

[0073] (3-2) Dissolve 0.54g of glucose in 30ml of deoxygenated water (purged with nitrogen), add the prepared solution to a three-necked flask using a syringe, and react for 30min. The precipitate changes from yellow-brown to dark brown.

[0074] (3-3) Dissolve 0.2 mmol of L-cys powder in 20 ml of deoxygenated water and add it to a three-necked flask using a syringe. Stir and react for 3 h to modify the surface of Cu2O with L-cys.

[0075] (3-4) After the reaction is complete, stop heating and wait for the mixed solution to cool to room temperature. Then, filter under continuous nitrogen purging to obtain solid product. Place it in a vacuum drying oven and dry at 60°C for 12 hours to obtain L-cys modified spherical Cu2O particles.

[0076] (3-5) Take 50 mg of L-cys-modified spherical Cu2O particles, disperse them in 2 ml of ethanol, add 50 μL of Nafion to prepare a catalyst ink, ultrasonically disperse the prepared catalyst ink for 1 h, and then drop-coat it onto a surface with an area of ​​1.5 x 1.5 cm. 2 On the gas diffusion electrode, the catalyst loading weight is 1.0 mg / cm³. 2 L-cys-modified spherical Cu2O electrodes were obtained, denoted as LS-Cu2O.

[0077] SEM images of the catalytic electrodes prepared in Comparative Examples 1, 2, and 3 and Example 1 are shown below. Figure 1 , Figure 1 In (a), the cubic Cu2O catalyst electrode BC-Cu2O without amino acid modification is obtained without nucleation stage. The Cu2O particles obtained by controlling the rotation speed and feeding rate are cubic in shape, with an average particle size of 50 nm, and are easy to agglomerate. Figure 1 (b) in the figure is the Cu2O catalytic electrode B-GR-Cu2O without L-cys modification. By controlling the raw material input ratio, the rotation speed of different nucleation stages and the feeding speed, it exhibits a unique rhombic semi-cubic morphology with an average particle size of about 120 nm, but the particle size is not uniform. Figure 1 (c) is the L-cys modified Cu2O electrode LS-Cu2O, which has an approximately spherical morphology and an average particle size of about 400 nm. It is relatively uniform in size but prone to agglomeration. Figure 1 (d) in the image represents the L-GR-Cu2O electrode modified with L-cys, exhibiting a unique rhombic semi-cubic morphology. The amino and thiol groups in L-cys synergistically catalyze CO2 reduction, with an average particle size of approximately 150 nm. Figure 1 It can be seen that L-GR-Cu2O has the advantages of large specific surface area, uniform dispersion, and uniform size.

[0078] Application of Cu-based catalyst electrode for electroreduction of CO2 to C2H4: The performance of the Cu-based catalytic electrode was tested in a flow electrolyzer. Catalytic electrodes prepared in Examples 1, 1, 2, and 3 were used as working electrodes, a platinum mesh as the counter electrode, and a silver-silver chloride electrode as the reference electrode. The cathode electrolyte was 1M KHCO3, and the anolyte was 1M KOH. The cathode and anolyte chambers were separated by an ion-exchange membrane. High-purity CO2 was introduced at a flow rate of 30 sccm, and the downstream end was connected to an online gas chromatograph. Constant current testing was performed at a current density of -250 mA / cm² using an electrochemical workstation. The gaseous products generated by the reaction were measured and analyzed by online GC, and the liquid products were analyzed by 1H NMR spectroscopy. After electrolysis for 25 min, the Faraday efficiency of the main gaseous product C2H4 was calculated based on the amount of C2H4 detected by online GC. Results are shown below. Figure 2 Electrodes prepared from BC-Cu2O, B-GR-Cu2O, LS-Cu2O, and L-GR-Cu2O exhibited Faradaic efficiencies of 20.74%, 33.37%, 36.84%, and 61.22% for C2H4 at a current density of -250 mA / cm², respectively. Figure 1 , Figure 2 The results show that L-cys-modified Cu2O and L-GR-Cu2O, by adjusting the raw material input ratio and precisely controlling the dripping rate of the reducing agent using an injection pump at different nucleation stages, and adjusting the rotation speed at each reaction stage, produced a uniform rhombic semi-cubic morphology with 26 faces, 24 vertices, and 48 edges. The amino groups in the modified L-cys provide an electron-rich environment, promoting CO2 adsorption and activation, facilitating CO2 capture. The thiol groups also strongly coordinate with Cu species on the Cu2O surface to form Cu-S, promoting water decomposition, promoting *CO protonation, stabilizing the rhombic semi-cubic structure, providing more adsorption sites and reactive sites for the reaction, which is beneficial for subsequent asymmetric coupling. Compared with the cubic Cu2O and the unmodified rhombic semi-cubic Cu2O, the cubic Cu2O showed higher selectivity for C2H4.

[0079] Example 2

[0080] This invention provides the preparation and application of orthorhombic semi-cubic Cu2O electrodes modified with different types of amino acids. The specific steps are as follows:

[0081] 1) Preparation of rhombic semi-cubic Cu2O electrodes modified with different types of amino acids:

[0082] The steps (1-1) to (1-3) in Example 1 are basically the same, except that 0.2 mmol L-cys in step (1-4) is replaced with 0.3 mmol L-cys, Gly and Lys. The subsequent centrifugation, washing, drying and electrode preparation processes are the same as in Example 1, and rhombic half-cubic Cu2O electrodes modified with L-cys, Gly and Lys are obtained respectively, denoted as L-cys-Cu2O, Gly-Cu2O and Lys-Cu2O.

[0083] 2) Application of rhombic semi-cubic Cu2O electrodes modified with different types of amino acids: Constant current testing was performed at a current density of -200 mA / cm², using the same equipment and procedure as in Example 1. Online GC was used for product content measurement and analysis. After electrolysis for 25 min, the results are shown in […]. Figure 3 The Faradaic efficiencies of gaseous C2H4 produced by Cu2O electrodes modified with three different amino acids—L-cys-Cu2O, Gly-Cu2O, and Lys-Cu2O—were 51.27%, 35.06%, and 22.16%, respectively. Compared to Gly and Lys, L-cys, due to the synergistic regulatory effect of its thiol and amino functional groups, exhibits a stronger advantage in improving the electrocatalytic performance of Cu2O in the production of C2H4 from CO2.

[0084] Example 3

[0085] This invention provides the preparation and application of L-cys-modified Cu2O electrodes prepared with different fractional reaction speeds. The specific steps are as follows:

[0086] 1) Preparation of L-cys-modified Cu2O electrodes at different reaction speeds: 2 mmol of copper chloride dihydrate was dissolved in 500 ml of deionized water and stirred until homogeneous, resulting in a light blue solution. 30 ml of 0.3 M sodium hydroxide solution was added dropwise at a rate of 3 ml / min using a syringe pump, producing a light blue flocculent precipitate. The reaction was carried out at room temperature with the reaction speed controlled at 400, 500, and 800 rpm. 20 ml of 0.2 M ascorbic acid solution was added dropwise at a rate of 2 ml / min using a syringe pump, resulting in an orange-yellow or brownish-yellow color. The reaction was carried out at 600 and 700 rpm. The reaction was carried out at 0.00-1000 rpm at 50℃ for 1 h. After the reaction was completed, the solution was allowed to cool naturally to room temperature, and 0.2 mmol of L-cys was added. The mixture was sonicated for 30 min to completely disperse the L-cys in the solution. The reaction was continued at 500 rpm at room temperature for 2 h. After the L-cys was fully modified, the solid product was separated by centrifugation at 8000 rpm and washed three times each with ethanol and deionized water to remove impurities. The product was then dried in a vacuum drying oven at 60℃ for 12 h to obtain L-cys-modified rhombic semi-cubic Cu2O particles prepared by different fractional reaction speeds. 50 mg of L-cys-modified Cu2O particles were taken and dispersed in 2 ml of ethanol. 50 μL of Nafion was added to prepare a catalyst ink. After sonication for 1 h, the ink was drop-coated onto a 1.5 x 1.5 cm² area. 2 On the gas diffusion electrode, the catalyst loading weight is 1.0 mg / cm³. 2 L-cys-modified Cu2O electrodes prepared with different fractional reaction speeds were obtained.

[0087] 2) Applications of L-cys-modified Cu2O electrodes with different reaction speeds:

[0088] The performance of the three Cu2O electrodes described above was tested in a flow electrolytic cell. A platinum mesh was used as the counter electrode, and a silver-silver chloride electrode was used as the reference electrode. The cathode electrolyte was 1M KHCO3, and the anolyte was 1M KOH. The cathode and anolyte chambers were separated by an ion-exchange membrane. High-purity CO2 was introduced at a flow rate of 30 sccm. A constant current test was performed using an electrochemical workstation with a current density of -200 mA / cm². The product content was measured and analyzed using online GC. After electrolysis for 25 min, the GC test results were obtained and recorded. Figure 4 The Faraday efficiencies of C2H4 were 40.71%, 53.44%, and 43.48%, respectively. From... Figure 4 The results show that the best performance is achieved when the reaction speeds of the front and rear stages are 500 and 700 rpm, respectively.

[0089] Example 4

[0090] This invention provides the preparation and application of rhombic semi-cubic Cu2O electrodes with different L-cys loading methods. The specific steps are as follows:

[0091] Fabrication of rhombohedral semi-cubic Cu2O electrodes with different L-cys loading methods:

[0092] 1) Preparation of L-cys-modified Cu2O electrode loaded with ultrasonic stirring at room temperature

[0093] 2 mmol of copper chloride dihydrate was dissolved in 500 ml of deionized water and stirred until homogeneous, resulting in a light blue solution. 30 ml of 0.3 M sodium hydroxide solution was added dropwise at a rate of 3 ml / min using a syringe pump, producing a light blue flocculent precipitate. The reaction was carried out at room temperature with the stirring speed maintained at 500 rpm. 20 ml of 0.2 M ascorbic acid solution was then added dropwise at a rate of 2 ml / min, resulting in an orange-yellow or brownish-yellow color. The reaction was carried out at 50°C for 1 h with the stirring speed maintained at 700 rpm. After the solution cooled naturally to room temperature, 0.2 mmol of L-cys was added, and the mixture was sonicated at 40 W for 30 min to ensure complete dispersion. The mixture was stirred continuously at 500 rpm for 2 h at room temperature until fully modified with L-cys. The solid product was then centrifuged at 8000 rpm and washed three times each with ethanol and deionized water to remove impurities. The product was then dried in a vacuum drying oven at 60°C for 12 h, yielding ultrasonically stirred Cu₂O particles modified with L-cys.

[0094] 2) Preparation of L-cys-modified Cu2O electrode by oil bath heating

[0095] 2 mmol of copper chloride dihydrate was dissolved in 500 ml of deionized water and stirred until homogeneous, resulting in a light blue solution. 30 ml of 0.3 M sodium hydroxide solution was added dropwise at a rate of 3 ml / min using a syringe pump, producing a light blue flocculent precipitate. The reaction was carried out at room temperature with the stirring speed maintained at 500 rpm. 20 ml of 0.2 M ascorbic acid solution was then added dropwise at a rate of 2 ml / min using a syringe pump, resulting in an orange-yellow or brownish-yellow color. The reaction was carried out at 50°C for 1 h with the stirring speed maintained at 700 rpm. 0.2 mmol of L-cys was added, and the reaction was continued at 50°C with stirring at 500 rpm for 2 h. After sufficient L-cys modification, the solid product was separated by centrifugation at 8000 rpm and washed three times each with ethanol and deionized water to remove impurities. The product was then dried in a vacuum drying oven at 60°C for 12 h, yielding L-cys-modified Cu₂O particles heated in an oil bath.

[0096] 3) Preparation of hydrothermally loaded L-cys modified Cu2O electrode

[0097] 2 mmol of copper chloride dihydrate was dissolved in 500 ml of deionized water and stirred until homogeneous, resulting in a light blue solution. 20 ml of 0.2 M ascorbic acid solution was added dropwise at a rate of 2 ml / min using a syringe pump, causing the color to change to orange-yellow or brownish-yellow. The reaction was carried out at 50°C for 3 h while maintaining the rotation speed at 700 rpm. The solid product was centrifuged at 8000 rpm, washed three times each with ethanol and deionized water, and then dried in a vacuum oven at 60°C for 12 h. The dried solid product was ground, dissolved in 20 ml of deionized water, and 0.2 mmol of L-cys powder was added. The solution was transferred to a 50 ml reaction vessel and placed in a forced-air drying oven for hydrothermal reaction at 120°C. Heating was stopped after 12 h, and the reaction vessel was allowed to cool naturally to room temperature. The solid product was then centrifuged, washed three times with ethanol and deionized water, and then dried in a vacuum oven at 60°C for 12 h to obtain hydrothermally loaded L-cys-modified Cu₂O particles.

[0098] Applications of rhombic semi-cubic Cu2O electrodes with different L-cys loading methods:

[0099] Take 50 mg of each of the three types of L-cys-modified Cu2O particles mentioned above, disperse them in 2 ml of ethanol, add 50 μL of Nafion to prepare a catalyst ink, ultrasonically disperse for 1 h, and then drop-coat it onto a surface with an area of ​​1.5 x 1.5 cm. 2 On the gas diffusion electrode, the catalyst loading weight is 1.0 mg / cm³. 2 Performance testing was conducted in a flow cell using the same equipment and procedures as in Example 1. A constant potential test was performed by applying a potential of -1.2V vs. RHE using an electrochemical workstation. Product content was measured and analyzed using online GC. After electrolysis for 25 minutes, the GC test results were obtained and recorded. Figure 5 The Faraday efficiencies of the gaseous product C2H4 of Cu2O electrodes under three loading methods—ultrasonic room temperature stirring, oil bath heating, and hydrothermal heating—were 60.06%, 39.12%, and 48.56%, respectively, with ultrasonic room temperature stirring exhibiting the best performance.

[0100] Example 5

[0101] This invention provides the preparation and application of rhombic semi-cubic Cu2O electrodes modified with different proportions of L-cys. The specific steps are as follows:

[0102] 1) Preparation of rhombic semi-cubic Cu2O electrodes modified with different proportions of L-cys:

[0103] Dissolve 2 mmol of copper chloride dihydrate in 500 ml of deionized water and stir until homogeneous; the solution turns pale blue. Add 30 ml of 0.3 M sodium hydroxide solution dropwise at a rate of 3 ml / min using a syringe pump, forming a pale blue flocculent precipitate. Maintain the pump speed at 500 rpm and allow the reaction to proceed at room temperature. Add 20 ml of 0.2 M ascorbic acid solution dropwise at a rate of 2 ml / min using a syringe pump; the color changes to orange-yellow or brownish-yellow. Maintain the pump speed at 700 rpm and allow the reaction to proceed at 50°C for 1 hour. After the solution cools naturally to room temperature, add 0.1 mmol of sodium hydroxide solution to each solution. L-cys (0.1 mmol, 0.2 mmol, and 0.4 mmol, respectively, with molar ratios of Cu:L-cys of 20:1, 10:1, and 5:1, respectively) were dissolved in water and ultrasonicated at 40 W for 30 min to ensure complete dispersion. The mixture was stirred continuously at 500 rpm for 2 h at room temperature until L-cys modification was complete. The solid product was then centrifuged at 8000 rpm and washed three times each with ethanol and deionized water to remove impurities. The product was then dried in a vacuum oven at 60 °C for 12 h to obtain rhombic semi-cubic Cu₂O particles modified with different proportions of L-cys. 50 mg of each L-cys-modified rhombic semi-cubic Cu₂O particle was dispersed in 2 ml of ethanol, and 50 μL of Nafion was added to prepare a catalyst ink. After ultrasonic dispersion for 1 h, the ink was drop-coated onto a 1.5 x 1.5 cm² area. 2 On the gas diffusion electrode, the catalyst loading weight is 1.0 mg / cm³. 2 Different proportions of L-cys modified rhombic semi-cubic Cu2O electrodes were obtained.

[0104] 2) Application of L-cys-modified rhombic semi-cubic Cu₂O electrodes with different proportions: The performance of the three Cu-based catalytic electrodes with different proportions was tested in a flow electrolyzer. The operation steps were the same as in Example 1. A constant potential test was performed by applying a potential of -1.2V vs. RHE using an electrochemical workstation. The product content was measured and analyzed using online GC. After electrolysis for 25 min, the GC test results were obtained and recorded. Figure 4 The Faraday efficiencies of the gaseous product C2H4 at three electrodes with Cu2O:L-cys molar ratios of 20:1, 10:1, and 5:1 were 39.08%, 60.06%, and 46.36%, respectively. From... Figure 6 The results show that the selectivity of the target product C2H4 of the L-cys modified rhombic semi-cubic Cu2O electrode exhibits a volcanic trend of first increasing and then decreasing due to the change in the molar ratio of Cu2O to L-cys. The best performance is shown when the molar ratio of Cu2O to L-cys is 10:1.

[0105] Three different proportions of L-cys-modified Cu-based catalysts from Comparative Example 1, Comparative Example 2, Example 1, and Example 5 were selected. Long-term current-time (it) tests were conducted at a constant potential of -1.2 V vs. RHE. The gas-phase products were analyzed using online GC, and the long-term stability was recorded. Results are shown below. Figure 7 Compared with Comparative Examples 1 and 2, the performance degradation was only maintained for 8h and 12h respectively. The three Cu-based catalysts in Example 5 were able to maintain for 24h, 45h and 36h respectively with the C2H4 Faradaic efficiency degradation not exceeding 20%. Among them, Example 1 still had 50.5% C2H4 Faradaic efficiency after 50h, indicating that the thiol group in L-cys can stabilize the semi-cubic structure of the catalyst through Cu-S bond and has strong long-term stability.

[0106] The above results fully demonstrate that by adjusting the raw material input ratio and precisely controlling the dripping rate of the reducing agent and the reaction stirring speed through an injection pump at different stages of nucleation, the morphology of Cu2O rhombohedral semi-cubic shape can be effectively regulated. Furthermore, the L-cys in the modified amino acids can have their thiol groups strongly coordinated with Cu species on the Cu2O surface to form Cu-S, promoting water decomposition and *CO protonation, stabilizing the surface structure. At the same time, the amino groups can provide an electron-rich environment, enhancing CO2 capture, synergistically regulating the local microenvironment of the reaction, and promoting asymmetric coupling. Using ultrasonic stirring at room temperature can ensure sufficient L-cys loading without denaturing the amino acids due to high temperatures, and can also prevent agglomeration, maintain particle size uniformity, and increase specific surface area, thereby significantly improving the selectivity and stability of electrocatalytic CO2 reduction to C2H4.

Claims

1. An amino acid-modified copper-based catalyst, characterized in that, The catalyst consists of Cu2O with a rhombohedral semi-cubic morphology and natural amino acids modified on the surface of Cu2O, wherein the natural amino acid is L-cysteine.

2. A method for preparing the amino acid-modified copper-based catalyst according to claim 1, characterized in that, Amino acids were added to a cuprous oxide suspension with a rhombohedral semi-cubic morphology. The amino acids were then loaded by ultrasonic stirring at room temperature to fully modify the surface of the cuprous oxide. The reaction product was collected and became the amino acid-modified copper-based catalyst.

3. The method for preparing the amino acid-modified copper-based catalyst according to claim 2, characterized in that, The preparation method of cuprous oxide suspension with an orthorhombic semi-cubic morphology is as follows: add an alkaline solution to a copper salt solution, adjust the pH of the reaction system to 9.0-11.0 to obtain a mixed solution; add a reducing agent to the mixed solution and stir the reaction to obtain cuprous oxide suspension.

4. The method for preparing the amino acid-modified copper-based catalyst according to claim 3, characterized in that, The copper salt is copper sulfate pentahydrate, copper chloride dihydrate, or copper nitrate; or, the alkaline solution is sodium hydroxide solution; or, the reducing agent is glucose or ascorbic acid solution.

5. The method for preparing the amino acid-modified copper-based catalyst according to claim 3, characterized in that, An alkaline solution is added to a copper salt solution, and the reaction is carried out at a stirring speed of 400-800 rpm. The pH value of the reaction system is adjusted to 9.0-11.0 to obtain a mixed solution. A reducing agent is added to the mixed solution, and the reaction is carried out at a stirring speed of 400-800 rpm to obtain a cuprous oxide suspension.

6. The method for preparing the amino acid-modified copper-based catalyst according to claim 5, characterized in that, The method for adding an alkaline solution to a copper salt solution is to add the alkaline solution dropwise at a rate of 2-6 ml / min. The method for adding a reducing agent to a mixed solution is to add the reducing agent solution dropwise at a rate of 2-4 ml / min.

7. The method for preparing the amino acid-modified copper-based catalyst according to claim 3, characterized in that, The molar ratio of copper salt to amino acid is 5-20:

1.

8. The use of the catalyst of claim 1 in the preparation of an electrode for electrocatalytic carbon dioxide to ethylene production.

9. The application according to claim 8, characterized in that, A catalyst ink is prepared by mixing an amino acid-modified copper-based catalyst with a perfluorosulfonic acid polymer; the catalyst ink is then coated onto the surface of an electrode substrate to obtain a copper-based catalytic electrode.

10. A method for electrocatalytically producing ethylene from carbon dioxide, characterized in that, The catalyst of claim 1 is mixed with a perfluorosulfonic acid polymer to prepare a catalyst ink; the catalyst ink is coated on the surface of an electrode substrate to obtain a copper-based catalytic electrode; the copper-based catalytic electrode is used as the working electrode, a platinum mesh or platinum sheet is used as the counter electrode, and a silver-silver chloride electrode or a saturated calomel electrode is used as the reference electrode to form a three-electrode system to reduce carbon dioxide and produce ethylene.

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