Cuxsny-nc nanosheet catalyst for co2 electroreduction to formate salt and preparation method and application thereof

Abstract

This invention relates to the field of gas catalyst technology. To address the problem of poor performance of existing catalysts in terms of high current density and Faradaic efficiency for formate, a Cu-based method for the electroreduction of formate from CO2 is proposed. x Sn y -NC nanosheet catalysts, their preparation methods, and applications. The specific preparation method involves ultrasonically dispersing copper and tin salts with melamine in anhydrous methanol, reacting the mixture with stirring, followed by hydrothermal treatment, and then cooling, separation, and drying to obtain Cu. x Sn y - Melamine precursor; then the precursor is calcined at high temperature to obtain Cu x Sn y -NC catalyst. This catalyst is used for the electrochemical reduction of carbon dioxide to formate, optimizing the adsorption energy for the key intermediate *OCHO, suppressing the hydrogen evolution side reaction, and achieving highly selective production of formate with a Faraday efficiency of approximately 94% and a partial current density exceeding 250 mA / cm². 2 It is simple to prepare, low in cost, and has the potential for industrial application.

Description

Technical Field

[0001] This invention relates to the field of gas catalyst technology, specifically to a Cu-based method for the electroreduction of formate from CO2. x Sn y -NC nanosheet catalysts, their preparation methods, and applications. Background Technology

[0002] To achieve effective coupling between carbon dioxide resource utilization and renewable energy storage, current research is focused on optimizing electrochemical carbon dioxide reduction systems at multiple scales. At the catalyst level, constructing atomically dispersed active sites, regulating surface charge distribution, and designing multi-level composite structures can significantly improve reaction activity and target product selectivity. At the reaction interface level, fine-tuning the electrode surface microenvironment, such as optimizing local carbon dioxide concentration and stabilizing interface pH, can effectively promote reaction mass transfer and suppress side reactions. At the system integration level, developing novel membrane electrode assemblies, optimizing flow field structures, and designing intelligent control systems compatible with fluctuating renewable energy sources are key to improving energy conversion efficiency and device operational stability. These synergistic optimization strategies are collectively driving the development of carbon dioxide electroreduction technology towards high efficiency, stability, and scalability.

[0003] With the continuous development of electrochemical carbon dioxide reduction technology, various catalyst systems for converting CO2 into formate have been proposed in existing technologies. However, these schemes still have many shortcomings in terms of structural design and process implementation. For example, CN116103673A discloses a method for in-situ growth of SnO2 nanosheets on the surface of copper foam and the construction of Bi-SnO2 modified electrodes by electrodeposition of Bi. This process is cumbersome, involving multiple hydrothermal and electrodeposition steps, and under high current density conditions, the CO content of the byproduct exceeds 10%, the formate Faraday efficiency is only 85.1%, and the current density is 87.5 mA cm⁻¹. -2 It is difficult to meet industrial-grade current density (200 mA cm⁻¹). -2 To address the requirement for high selectivity, CN105854864A proposes a carbon-supported tin indium oxide catalyst, SnxIn. (1-x) O (1.5+0.5x)The preparation of CuSn / C requires high-temperature, high-pressure organic solvents, resulting in high toxicity, high energy consumption, and poor environmental friendliness. Furthermore, it fails to achieve high Faradaic efficiency at industrial current densities, limiting its large-scale application. Although CN120174411A discloses the application of a CuSn alloy catalyst in electrocatalytic CO2 reduction, it still has certain limitations: in terms of synthesis, this method employs a multi-step carbonization combined with ball milling process to construct CuSn co-doped porous carbon materials, which is a lengthy process. Multiple high-temperature treatments and mechanical mixing easily lead to high energy consumption and poor structural controllability. In addition, this method does not clearly report the specific products of CO2 electrocatalytic conversion and lacks verification of catalytic performance under high current density conditions, thus limiting its application potential in practical industrial-grade electrode preparation. The CuSn / NC diatomic catalyst disclosed in "Design and Electrochemical CO2 / O2 Reduction Performance Study of Carbon-Supported CuSn Diatomic and PtZn Alloy Catalysts" can achieve the electrochemical reduction of carbon dioxide, but it is limited to generating CO, which has low economic value, and the preparation process is complex with high temperatures and a current density of only 15 mA cm⁻¹. -2 These issues severely limit the feasibility and economic viability of this catalyst in industrial applications.

[0004] In summary, existing catalysts do not perform ideally in terms of high current density and Faraday efficiency for formate, making it difficult to achieve highly selective yield of the target product. Therefore, designing and developing novel, highly efficient electrode materials is key to achieving breakthroughs in CO2 electrocatalytic reduction technology and advancing its practical application. Summary of the Invention

[0005] This invention addresses the low current density and poor product selectivity in the production of formate via catalysts during the electrochemical reduction of carbon dioxide, and provides a copper-tin composite Cu... x Sn y The application of NC catalysts in the electrochemical reduction of carbon dioxide can effectively enhance catalytic activity and increase the formate fractional current density.

[0006] To achieve the above objectives, a first aspect of the present invention provides a copper-tin composite two-dimensional sheet-like catalyst, wherein the catalyst is composed of Cu x Sn y -NC, where the ratio of y to x is 1 to 9.

[0007] A second aspect of this invention provides a method for preparing a copper-tin composite two-dimensional sheet catalyst, comprising:

[0008] Step 1: Copper and tin salts were ultrasonically dispersed with melamine in anhydrous methanol, and then subjected to a hydrothermal reaction. After the hydrothermal reaction, the mixture was cooled, separated, and dried to obtain Cu. x Sn y- Melamine precursor;

[0009] Step 2: The obtained Cu x Sn y The melamine precursor was placed in a tube furnace and subjected to high-temperature calcination to obtain Cu. x Sn y -NC catalyst, where the ratio of y to x is 1 to 9.

[0010] Preferably, in step 1,

[0011] The copper salt is one or more of copper nitrate, copper chloride, copper sulfate, copper acetylacetonate, or copper acetate;

[0012] Tin salts are one or more of tin chloride and tin sulfate.

[0013] Preferably, the molar ratio of tin salt to copper salt is 1 to 9;

[0014] The total amount of the copper and tin salts mixed together was in a molar ratio of 1:2.7 to melamine.

[0015] Preferably, the hydrothermal reaction in step 1 is carried out at a temperature of 160°C for 6 to 12 hours.

[0016] Preferably, the calcination temperature in step 2 is 560℃, the heating rate is 1℃ / min to 10℃ / min, and the calcination time is 1 h to 3 h.

[0017] A third aspect of the present invention provides the application of the copper-tin composite two-dimensional sheet catalyst as described above in the electrochemical reduction of carbon dioxide.

[0018] Preferably, in the electrochemical reduction of carbon dioxide, Cu x Sn y -NC catalyst is used as the working electrode in the cathode reduction of carbon dioxide reaction system.

[0019] Preferably, in the cathode reduction carbon dioxide reaction system, the solute of the catholyte is selected from one or more of KOH, KHCO3, KCl, K2SO4, NaOH, NaHCO3, NaCl and Na2SO4;

[0020] Preferably, the molar concentration of the solute in the catholyte is 0.1~1.0 mol / L;

[0021] The current density for the electrochemical reduction of carbon dioxide is -50 to -500 mA / cm². 2 .

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. Cu in this invention xSn y The -NC bimetallic composite catalyst exhibits high selectivity in the electroreduction of CO2, achieving a formate Faraday efficiency of 94%, significantly outperforming existing technologies. The catalyst is produced through a mild hydrothermal-calcination process involving metal sources (copper chloride and tin chloride) and melamine, forming a two-dimensional layered nitrogen-doped carbon matrix. The metal sources coordinate with the nitrogen-doped carbon matrix, providing abundant active sites that allow for ample contact with the electrolyte and CO2. By controlling the ratio of copper to tin, highly efficient and selective formate production is achieved. The preparation method is simple, low-cost, environmentally friendly, and demonstrates excellent catalytic performance, showing potential for industrial application.

[0024] 2. In this invention, the synergistic effect between Cu and Sn induces a unique electronic microenvironment on the catalyst surface, in which the electronic structure of the active sites and the adsorption behavior of key reaction intermediates can be precisely controlled. When Cu groups are introduced into Sn, due to the difference in electronegativity between Cu and Sn, electrons are partially transferred from Sn to Cu, resulting in an electron-deficient state at the Sn sites. This rearrangement of electronic structure optimizes the adsorption energy of the key CO2 reduction intermediate *OCHO (bidentate) at the Sn active center: it enhances both the activation and adsorption of CO2 and promotes the conversion of the intermediate to formate, thereby significantly reducing the reaction energy barrier of this pathway. At the same time, Cu doping synergistically modulates the proton transport pathway on the catalyst surface, and the formed Cu-Sn synergistic interface changes the adsorption free energy of hydrogen intermediates on the surface, making it unfavorable for the binding of hydrogen atoms and the desorption of hydrogen molecules, effectively suppressing the competing side reaction of hydrogen evolution. This means that more proton-electron pairs can be efficiently used in the CO2 reduction pathway. Therefore, by constructing such atomically interacting Cu and Sn active centers, this invention successfully achieved a high reaction rate (split density) while significantly directing the product selectivity towards formate. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0026] In the attached diagram:

[0027] Figure 1 The image shows the X-ray diffraction pattern of the Cu1Sn2-NC catalyst prepared in Example 1.

[0028] Figure 2 The image shows a transmission electron microscope (TEM) image of the Cu1Sn2-NC catalyst prepared in Example 1.

[0029] Figure 3 Cu with different copper-tin molar ratios x Sn y- Faraday efficiency diagram of NC catalyst for electrocatalytic carbon dioxide products. Detailed Implementation

[0030] The following combination Figures 1-3 The preferred embodiments of the present invention are described herein. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0031] Raw materials and reagents: All raw materials used in this invention were purchased from the market.

[0032] A copper-tin composite two-dimensional sheet catalyst, composed of Cu x Sn y -NC, where the ratio of y to x is 1 to 9.

[0033] A method for preparing a copper-tin composite two-dimensional sheet catalyst, comprising:

[0034] Step 1: Copper and tin salts were ultrasonically dispersed with melamine in anhydrous methanol. After stirring for half an hour, a hydrothermal reaction was carried out at 160°C for 6-12 hours. After the hydrothermal reaction, the mixture was cooled, separated, and dried to obtain Cu. x Sn y - Melamine precursor. The separation method is one or more of centrifugation or filtration. The drying method is one or more of vacuum drying or freeze drying.

[0035] The copper salt is one or more of copper nitrate, copper chloride, copper sulfate, copper acetylacetonate, or copper acetate; the tin salt is one or more of tin chloride and tin sulfate. The molar ratio of copper salt to tin salt is 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, or 1:9.

[0036] Furthermore, the total amount of the copper and tin salts mixed together has a molar ratio of 1:2.7 to melamine.

[0037] When the molar ratio of copper salt to tin salt is 1:3 (pure tin), the Faraday efficiency of formate in the electrochemical reduction reaction of carbon dioxide is above 85%, and the partial current density of formate is above 250 mA / cm². 2 above.

[0038] Preferably, when the molar ratio of copper salt to tin salt is 1:2, the Faraday efficiency of formate in the electrochemical reduction reaction of carbon dioxide is above 90%, and the partial current density of formate is above 270 mA / cm². 2 above.

[0039] Step 2: Add Cu x Sn yThe melamine precursor was placed in a tube furnace and heated to 560°C at a heating rate of 1°C / min to 10°C / min for 1 to 3 hours to obtain Cu. x Sn y -NC catalyst, where the ratio of y to x is 1 to 9.

[0040] Example 1: This example provides a method for preparing a Cu1Sn2-NC catalyst, including:

[0041] Step 1: 2.24 mmol CuCl2·2H2O, 4.48 mmol SnCl4·5H2O, and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Cu1Sn2-melamine precursor.

[0042] Step 2: The obtained Cu1Sn2-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, and then cooled to room temperature by a programmed process to obtain the target catalyst Cu1Sn2-NC catalyst.

[0043] CO2 electrocatalytic reduction activity test:

[0044] The Cu1Sn2-NC catalyst obtained in this embodiment was dispersed on carbon paper for electrocatalytic reduction reaction testing to observe the catalytic activity. Using the Cu1Sn2-NC catalyst as the working electrode, CO2 was reduced under constant current with an applied current density of -300 mA / cm². 2 The reaction time was 300 s, the CO2 flow rate was 20 mL / min, the catholyte was a 1.0 mol / L KOH solution saturated with CO2, the anolyte was a 1.0 mol / L KOH solution, and the counter electrode was nickel foam. Hydrogen, carbon monoxide and formate were obtained, with the formate having a Faraday efficiency of 94%.

[0045] The X-ray diffraction pattern of the Cu1Sn2-NC catalyst prepared in Example 1 is shown below. Figure 1 As shown in the spectrum, no diffraction peaks of other impurities were detected, proving that the synthesized product has high purity. The transmission electron microscope (TEM) image is shown below. Figure 2 As shown, the Cu1Sn2-NC catalyst has a two-dimensional layered structure.

[0046] Comparative Example 1: 6.72 mmol SnCl4·5H2O and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Sn-melamine precursor. Finally, the Sn-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, followed by a programmed cooling to room temperature to obtain the catalyst Sn-NC.

[0047] Analysis of the experimental results showed that the Faraday current efficiency of H2 in Comparative Example 1 was 10.2%, which was higher than the 1.7% Faraday current efficiency of H2 in Example 1. This indicates that as the tin content gradually increases, the hydrogen evolution reaction intensifies, the current flowing to the electrochemical reduction of CO2 is weakened, leading to a decrease in the Faraday efficiency of formate.

[0048] Example 2: This example provides a method for preparing a Cu1Sn1-NC catalyst, specifically including the following steps:

[0049] Step 1: 3.36 mmol CuCl2·2H2O, 3.36 mmol SnCl4·5H2O, and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Cu1Sn1-melamine precursor.

[0050] Step 2: Finally, the Cu1Sn1-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain the Cu1Sn1-NC catalyst.

[0051] CO2 electrocatalytic reduction activity test:

[0052] The Cu1Sn1-NC catalyst obtained in this embodiment was dispersed on carbon paper for electrocatalytic reduction reaction testing to observe the catalytic activity. Using the Cu1Sn1-NC catalyst as the working electrode, CO2 was reduced under constant current with an applied current density of -300 mA / cm². 2The reaction time was 300 s, the CO2 flow rate was 20 mL / min, the catholyte was a 1.0 mol / L KOH solution saturated with CO2, the anolyte was a 1.0 mol / L KOH solution, and the counter electrode was nickel foam. Hydrogen, carbon monoxide and formate were obtained, with the formate having a Faraday efficiency of 77.5%.

[0053] Example 3: This example provides a method for preparing a Cu1Sn3-NC catalyst, specifically including the following steps:

[0054] Step 1: 1.68 mmol CuCl2·2H2O, 5.04 mmol SnCl4·5H2O, and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene (PTFE) and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Cu1Sn3-melamine precursor.

[0055] Step 2: Finally, the Cu1Sn3-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain the Cu1Sn3-NC catalyst.

[0056] CO2 electrocatalytic reduction activity test:

[0057] The Cu1Sn3-NC catalyst obtained in this embodiment was dispersed on carbon paper for electrocatalytic reduction reaction testing to observe the catalytic activity. Using the Cu1Sn3-NC catalyst as the working electrode, CO2 was reduced under constant current with an applied current density of -300 mA / cm². 2 The reaction time was 300 s, the CO2 flow rate was 20 mL / min, the catholyte was a 1.0 mol / L KOH solution saturated with CO2, the anolyte was a 1.0 mol / L KOH solution, and the counter electrode was nickel foam. Hydrogen, carbon monoxide and formate were obtained, with the formate having a Faraday efficiency of 90.1%.

[0058] Example 4: This example provides a method for preparing a Cu1Sn4-NC catalyst, specifically including the following steps:

[0059] Step 1: 1.34 mmol CuCl2·2H2O, 6.72 mmol SnCl4·5H2O, and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene (PTFE) and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Cu1Sn4-melamine precursor.

[0060] Step 2: Finally, the Cu1Sn4-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain the Cu1Sn4-NC catalyst.

[0061] CO2 electrocatalytic reduction activity test: The Cu1Sn4-NC catalyst obtained in this example was dispersed on carbon paper for electrocatalytic reduction reaction test to observe the catalytic activity of the catalyst. Using the Cu1Sn4-NC catalyst as the working electrode, CO2 was reduced under constant current with an applied current density of -300 mA / cm². 2 The reaction time was 300 s, the CO2 flow rate was 20 mL / min, the catholyte was a 1.0 mol / L KOH solution saturated with CO2, the anolyte was a 1.0 mol / L KOH solution, and the counter electrode was nickel foam. Hydrogen, carbon monoxide and formate were obtained, with the formate having a Faraday efficiency of 89.8%.

[0062] Example 5: This example provides a method for preparing a Cu1Sn5-NC catalyst, specifically including the following steps:

[0063] Step 1: 1.12 mmol CuCl2·2H2O, 5.6 mmol SnCl4·5H2O, and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Cu1Sn5-melamine precursor.

[0064] Step 2: Finally, the Cu1Sn5-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain the Cu1Sn5-NC catalyst.

[0065] CO2 electrocatalytic reduction activity test:

[0066] The Cu1Sn5-NC catalyst obtained in this embodiment was dispersed on carbon paper for electrocatalytic reduction reaction testing to observe the catalytic activity. Using the Cu1Sn5-NC catalyst as the working electrode, CO2 was reduced under constant current with an applied current density of -300 mA / cm². 2 The reaction time was 300 s, the CO2 flow rate was 20 mL / min, the catholyte was a 1.0 mol / L KOH solution saturated with CO2, the anolyte was a 1.0 mol / L KOH solution, and the counter electrode was nickel foam. Hydrogen, carbon monoxide and formate were obtained, with the formate having a Faraday efficiency of 88.2%.

[0067] Example 6: This example provides a method for preparing a Cu1Sn6-NC catalyst, specifically including the following steps:

[0068] Step 1: 0.96 mmol CuCl2·2H2O, 5.76 mmol SnCl4·5H2O, and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene (PTFE) and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Cu1Sn6-melamine precursor.

[0069] Step 2: Finally, the Cu1Sn6-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain the Cu1Sn6-NC catalyst.

[0070] CO2 electrocatalytic reduction activity test:

[0071] The Cu1Sn6-NC catalyst obtained in this embodiment was dispersed on carbon paper for electrocatalytic reduction reaction testing to observe the catalytic activity. Using the Cu1Sn6-NC catalyst as the working electrode, CO2 was reduced under constant current with an applied current density of -300 mA / cm². 2 The reaction time was 300 s, the CO2 flow rate was 20 mL / min, the catholyte was a 1.0 mol / L KOH solution saturated with CO2, the anolyte was a 1.0 mol / L KOH solution, and the counter electrode was nickel foam. Hydrogen, carbon monoxide and formate were obtained, with the formate having a Faraday efficiency of 88.1%.

[0072] Example 7: This example provides a method for preparing a Cu1Sn7-NC catalyst, specifically including the following steps:

[0073] Step 1: 0.84 mmol CuCl2·2H2O, 5.88 mmol SnCl4·5H2O, and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Cu1Sn7-melamine precursor.

[0074] Step 2: Finally, the Cu1Sn7-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain the Cu1Sn7-NC catalyst.

[0075] CO2 electrocatalytic reduction activity test:

[0076] The Cu1Sn7-NC catalyst obtained in this embodiment was dispersed on carbon paper for electrocatalytic reduction reaction testing to observe the catalytic activity. Using the Cu1Sn7-NC catalyst as the working electrode, CO2 was reduced under constant current with an applied current density of -300 mA / cm². 2 The reaction time was 300 s, the CO2 flow rate was 20 mL / min, the catholyte was a 1.0 mol / L KOH solution saturated with CO2, the anolyte was a 1.0 mol / L KOH solution, and the counter electrode was nickel foam. Hydrogen, carbon monoxide and formate were obtained, with the formate having a Faraday efficiency of 88.7%.

[0077] Example 8: This example provides a method for preparing a Cu1Sn8-NC catalyst, specifically including the following steps:

[0078] Step 1: 0.75 mmol CuCl2·2H2O, 5.97 mmol SnCl4·5H2O, and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene (PTFE) and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Cu1Sn8-melamine precursor.

[0079] Step 2: Finally, the Cu1Sn8-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain the Cu1Sn8-NC catalyst.

[0080] CO2 electrocatalytic reduction activity test:

[0081] The Cu1Sn8-NC catalyst obtained in this embodiment was dispersed on carbon paper for electrocatalytic reduction reaction testing to observe the catalytic activity. Using the Cu1Sn8-NC catalyst as the working electrode, CO2 was reduced under constant current with an applied current density of -300 mA / cm². 2 The reaction time was 300 s, the CO2 flow rate was 20 mL / min, the catholyte was a 1.0 mol / L KOH solution saturated with CO2, the anolyte was a 1.0 mol / L KOH solution, and the counter electrode was nickel foam. Hydrogen, carbon monoxide and formate were obtained, with the formate having a Faraday efficiency of 87.9%.

[0082] Example 9: This example provides a method for preparing a Cu1Sn9-NC catalyst, specifically including the following steps:

[0083] Step 1: 0.672 mmol CuCl2·2H2O, 6.048 mmol SnCl4·5H2O, and 17.84 mmol melamine were co-dispersed in 60 mL anhydrous methanol at room temperature and mechanically stirred for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene (PTFE) and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and freeze-dried for 6 hours to obtain the Cu1Sn9-melamine precursor.

[0084] Step 2: Finally, the Cu1Sn9-melamine precursor was placed in a tube furnace and calcined at 560 °C for 2.5 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain the Cu1Sn9-NC catalyst.

[0085] CO2 electrocatalytic reduction activity test:

[0086] The Cu1Sn9-NC catalyst obtained in this embodiment was dispersed on carbon paper for electrocatalytic reduction reaction testing to observe the catalytic activity. Using the Cu1Sn9-NC catalyst as the working electrode, CO2 was reduced under constant current with an applied current density of -300 mA / cm². 2 The reaction time was 300 s, the CO2 flow rate was 20 mL / min, the catholyte was a 1.0 mol / L KOH solution saturated with CO2, the anolyte was a 1.0 mol / L KOH solution, and the counter electrode was nickel foam. Hydrogen, carbon monoxide and formate were obtained, with the formate having a Faraday efficiency of 88.5%.

[0087] The Faraday efficiency of the electroreduction of carbon dioxide to hydrogen, carbon monoxide, and formate for different molar ratios of copper and tin salts is as follows: Figure 3 As shown, from Figure 3 It can be seen that when the molar ratio of copper salt to tin salt is 1:2, the formate has the highest Faraday efficiency, which is 94%.

[0088] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A Cu-based method for the electroreduction of formate by CO2 x Sn y The method for preparing NC nanosheet catalysts is characterized by, include: Step 1: Ultrasonic dispersion of copper and tin salts with melamine in anhydrous methanol, mixed and then hydrothermally reacted; after hydrothermal reaction, cooling, separation, and freeze-drying for 6 hours, Cu x Sn y - melamine precursor; Step 2: The obtained Cu x Sn y The melamine precursor was placed in a tube furnace and subjected to high-temperature calcination under a nitrogen atmosphere to obtain Cu. x Sn y -NC catalyst, where the ratio of y to x is 1 to 9.

2. The Cu-based method for the electroreduction of formate by CO2 according to claim 1 x Sn y The method for preparing NC nanosheet catalysts is characterized by, In step 1, The copper salt is one or more of copper nitrate, copper chloride, copper sulfate, copper acetylacetonate, or copper acetate; Tin salts are one or more of tin chloride and tin sulfate.

3. The Cu-based method for the electroreduction of formate by CO2 according to claim 2 x Sn y The method for preparing NC nanosheet catalysts is characterized by, The molar ratio of tin salts to copper salts is 1 to 9; The total amount of the copper and tin salts mixed together was in a molar ratio of 1:2.7 to melamine.

4. The Cu-based method for the electroreduction of formate by CO2 according to claim 3. x Sn y The method for preparing NC nanosheet catalysts is characterized by, In step 1, the hydrothermal reaction temperature is 160℃ and the time is 6~12 h.

5. The Cu-based method for the electroreduction of formate by CO2 according to claim 4. x Sn y The method for preparing NC nanosheet catalysts is characterized by, The calcination temperature in step 2 is 560℃, the heating rate is 1℃ / min to 10℃ / min, and the calcination time is 1 h to 3 h.

6. Cu prepared by the method according to any one of claims 1-5 x Sn y The application of NC nanosheet catalysts in the electrochemical reduction of carbon dioxide is characterized by... In the cathodic reduction of carbon dioxide reaction system, the solute of the catholy solution is selected from one or more of KOH, KHCO3, KCl, K2SO4, NaOH, NaHCO3, NaCl and Na2SO4, and the CO2 flow rate is 20 mL / min.

7. The application according to claim 6, characterized in that, In the electrochemical reduction of carbon dioxide, Cu x Sn y -NC catalyst is used as the working electrode in the cathode reduction of carbon dioxide reaction system.

8. The application according to claim 7, characterized in that, The molar concentration of the solute in the catholyte is 0.1~1.0 mol / L; The current density for the electrochemical reduction of carbon dioxide is -50 to -500 mA / cm². 2 .

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