Preparation method of ZnFe single atom supported Cu nanoparticle for CO2 electro-reduction

Abstract

The application belongs to the technical field of electrochemical method for reducing CO2, and particularly relates to a preparation method of ZnFe single-atom supported Cu nanoparticles for CO2 electro-reduction, which comprises the following steps: (1) synthesizing ZnFe single-atom catalyst; (2) preparing ZnFe single-atom catalyst supported Cu nanoparticles. The ZnFe single-atom catalyst is compounded with Cu nanoparticles to realize series catalysis, which can further promote the generation of multi-carbon products on the basis of Cu nanoparticles; in the CO2 electro-reduction reaction, the CO selectivity of the ZnFe single-atom catalyst is very high, CO2 is first reduced into CO on the surface of the ZnFe single-atom catalyst, and CO is adsorbed and gathered on the surface of the Cu nanoparticles to be further reduced into alcohol and olefin.

Description

Technical Field

[0001] This invention relates to the field of electrochemical CO2 reduction technology, specifically to a method for preparing ZnFe single-atom-supported Cu nanoparticles for CO2 electroreduction. Background Technology

[0002] With global warming, we are experiencing a series of catastrophic climate events, including droughts, forest fires, and rising sea levels, and the global average temperature is rising at an unprecedented rate. Related research indicates that even if the Earth's current CO2 concentration does not increase further, it would take nearly 1,000 years to eliminate it on its own. Converting CO2 into usable renewable energy can not only reduce the concentration of carbon dioxide in the environment but also convert carbon dioxide into renewable energy sources.

[0003] Electrochemical reduction of carbon dioxide can not only address the greenhouse effect but also convert it into usable energy in a green and environmentally friendly way. In the field of electrocatalytic carbon dioxide reduction, copper is currently the only metal electrode capable of reducing carbon dioxide to polyols, acids, and alkenes independently. Furthermore, copper is abundant and inexpensive, making it more suitable for industrial production. Copper also possesses SERS enhancement capabilities, allowing for surface-enhanced Raman spectroscopy studies to investigate the reaction pathway of CO2 electroreduction. However, copper electrodes face serious problems such as excessively high overpotential, low product selectivity, and hydrogen evolution reaction. Introducing another catalyst that primarily produces carbon monoxide in CO2 electroreduction to achieve tandem catalysis and improve the efficiency of the CO2 electroreduction reaction has attracted considerable attention from researchers. Single-atom catalysts exhibit high CO selectivity in CO2 electroreduction and possess a single and abundant number of single-atom active sites, providing a highly efficient catalytic medium for CO2 electroreduction. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing ZnFe single-atom supported Cu nanoparticles for CO2 electroreduction. This invention achieves tandem catalysis by combining ZnFe single-atom catalysts and Cu nanoparticles, thereby further improving the selectivity of multi-carbon products during CO2 electroreduction and providing a highly efficient catalytic mediator for CO2 electroreduction catalyst design and active site research.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a method for preparing ZnFe single-atom-supported Cu nanoparticles for CO2 electroreduction, specifically comprising the following steps:

[0006] (1) Synthesis of ZnFe single-atom catalyst: Zinc chloride, potassium chloride and ferric chloride were dissolved in ultrapure water, then frozen into a solid state and freeze-dried to obtain a salt template; o-phenylenediamine precursor was dissolved in ethanol, ultrasonically dispersed and added to the above salt template and ground for 20-40 min; ammonium persulfate was dissolved in ultrapure water, ultrasonically dispersed and added to the above material and ground for 20-40 min; after standing for 10-15 h, it was treated in a muffle furnace at 170-230℃ for 1-3 h; then heat-treated in a tube furnace at 750-850℃ in a hydrogen / argon atmosphere for 1-3 h, cooled and taken out, acid washed with dilute hydrochloric acid solution, and then washed with water, alcohol and dried to obtain ZnFe single-atom catalyst;

[0007] (2) Preparation of ZnFe single-atom catalyst supported on Cu nanoparticles: ZnFe single-atom catalyst was added to ultrapure water, Cu nanoparticles were added to ethanol, and the two were sonicated for 20-40 min respectively. Then, Nafion solution was added and sonicated for 20-40 min to obtain ZnFe single-atom catalyst supported on Cu nanoparticles.

[0008] In a preferred embodiment of the present invention, in step (1), the mass ratio of the precursor o-phenylenediamine, zinc chloride, potassium chloride, ferric chloride, and ammonium persulfate is 1:(6-10):(6-10):(2-4):(2-4), the volume ratio of ethanol to ultrapure water is 1:(4-10), and the concentration of o-phenylenediamine dissolved in ethanol is 80-120 g / L; in step (2), the concentration of ZnFe single-atom catalyst is 1.5-2.5 mg / mL, the concentration of Cu nanoparticles is 3.5-4.5 mg / mL, the mass ratio of ZnFe single-atom catalyst to Cu nanoparticles is 1:(2-5), and the volume ratio of Nafion solution, ultrapure water, and ethanol is 1:(8-12):(8-12).

[0009] To achieve the above objectives, the second technical solution of the present invention is: a ZnFe single-atom-loaded Cu nanoparticle for CO2 electroreduction.

[0010] To achieve the above objectives, the third technical solution of the present invention is: an application of ZnFe single-atom-supported Cu nanoparticles in CO2 electroreduction, comprising the following steps:

[0011] (1) Clamping carbon paper in platinum electrode clamp: First, clean the platinum electrode clamp of a certain width in water with ultrasonic cleaning, dry the platinum sheet with nitrogen gas, and clamp the carbon paper in the platinum electrode clamp so that the exposed length of the carbon paper is 0.5-2 times the width of the platinum electrode clamp.

[0012] (2) Coat ZnFe single-atom-supported Cu nanoparticles uniformly onto the carbon paper exposed in step (1): at a ratio of 15-25 μL / cm 2Apply the ink evenly to the carbon paper and then dry it.

[0013] (3) Add equal amounts of 0.05-0.15M KHCO3 solution to the cathode chamber and anode chamber of the electrolytic cell until the liquid surface can just completely submerge the exposed carbon paper. Pass CO2 gas into the cathode chamber until the electrolyte is saturated. Place the carbon paper between the platinum electrode clips coated with ZnFe single-atom-loaded Cu nanoparticles obtained in step (2) in the cathode chamber of the electrolytic cell.

[0014] (4) Place a platinum sheet as the counter electrode in the anode chamber of the electrolytic cell, place a calomel electrode as the reference electrode in the cathode chamber of the electrolytic cell, and connect the electrolytic cell tested by the electrochemical workstation to the gas chromatograph in order to obtain the product results of the CO2 reduction process.

[0015] (5) First, the catalyst surface is activated by cyclic voltammetry (CV). Then, the products of CO2 reduction reaction of the catalyst are tested at different potentials. The Faraday efficiency (FE) of each product is calculated based on the concentration of each product and the current under constant potential test conditions.

[0016] In a preferred embodiment of the present invention, in step (1), both sides of the carbon paper are hydrophobically treated, and the catalyst is coated on the front side of the carbon paper modified with carbon black.

[0017] In a preferred embodiment of the present invention, in step (3), the anode chamber and the cathode chamber are separated by a Nafion proton exchange membrane.

[0018] In a preferred embodiment of the present invention, in step (3), the front side of the carbon paper coated with the catalyst is placed in the electrolytic cell facing the direction of CO2 gas output, so that CO2 can be more easily adsorbed on the catalyst surface.

[0019] In a preferred embodiment of the present invention, in step (4), gas chromatography uses high-purity nitrogen (purity ≥99.99%) as the carrier gas, and thermal conductivity detector (TCD) and flame ionization detector (FID) detect H2 and other carbon-containing gaseous products, respectively.

[0020] In a preferred embodiment of the present invention, the cyclic voltammetry (CV) potential range set in step (5) is intended to desorb and remove impurities on the catalyst surface without causing catalyst reconstruction.

[0021] In a preferred embodiment of the present invention, the products of the CO2 electroreduction reaction of the catalyst in step (5) are compared four times at different potentials to make the results more convincing.

[0022] In a preferred embodiment of the present invention, the Faraday efficiency (FE) of various products in step (5) is calculated according to the formula FE = Igas / I total ×100%.

[0023] ZnFe single-atom catalysts possess abundant pores, facilitating their integration with Cu nanoparticle loading for tandem catalyst construction. In the CO2 electroreduction reaction, ZnFe single-atom catalysts exhibit high CO selectivity. CO2 is first reduced to CO on the ZnFe single-atom catalyst surface, and CO then adsorbs and aggregates on the Cu nanoparticle surface for further reduction to alcohols and alkenes. However, the adsorption capacity of Cu nanoparticles for CO is limited, and the atomic distance between Cu nanoparticles and ZnFe single atoms affects CO adsorption and desorption, thus impacting the electrocatalytic CO2 reduction performance. Therefore, it is necessary to regulate the mass ratio of ZnFe single-atom catalysts to Cu nanoparticles and the atomic distance between them to ensure that all CO generated on the ZnFe single-atom catalyst surface is adsorbed and aggregated on the Cu nanoparticle surface, promoting CO coupling. This invention designs a catalyst preparation process based on the mass ratio of ZnFe single atoms to Cu nanoparticles and the atomic distance between them, including exploring conditions such as the thickness of the remaining carbon skeleton after calcination of different thicknesses of organic layers, and the potential and time for electrodeposition on the ZnFe single-atom surface.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The ZnFe single-atom catalyst obtained by this invention has relatively single and abundant catalytic sites, and its surface has a layered honeycomb structure. There is a strong interaction between ZnFe single atoms and Cu nanoparticles, which makes Cu nanoparticles tightly bound around ZnFe single atoms. The prepared catalyst is suitable for CO2 electroreduction reaction.

[0026] 2. This invention combines ZnFe single-atom catalyst with Cu nanoparticles to achieve tandem catalysis, which can further promote the generation of multi-carbon products based on Cu nanoparticles. In the CO2 electroreduction reaction, the ZnFe single-atom catalyst has high CO selectivity. CO2 is first reduced to CO on the surface of ZnFe single-atom catalyst, and CO is adsorbed and aggregated on the surface of Cu nanoparticles for further reduction to alcohols and alkenes, etc.

[0027] 3. This invention can utilize the SERS enhancement capability of Cu to study the intermediates and intermediate products generated by CO2 electroreduction using in-situ surface-enhanced Raman spectroscopy to derive the reaction pathway, providing information to guide catalyst design;

[0028] 4. The catalyst design strategy of this invention has high versatility. It is not only applicable to ordinary single-atom catalysts and Cu nanoparticle composites, but also to other metal and non-metal materials that mainly produce CO and Cu nanoparticle composites to achieve tandem catalysis, providing a guide for the rational design of catalysts.

[0029] 5. This invention can further investigate the deeper relationship between single-atom catalysts and Cu nanoparticles, such as the effect of atomic-level regulation of interatomic spacing on the CO2 electroreduction reaction, elucidating the mechanism and structure-activity relationship of the CO2 electroreduction reaction at the molecular level, and further guiding the rational design of catalysts. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of the ZnFe single-atom catalyst synthesized in Example 1;

[0031] Figure 2 This is a transmission electron microscope image of the ZnFe single-atom catalyst synthesized in Example 1;

[0032] Figure 3 This is a scanning electron microscope image of Cu nanoparticles supported on the ZnFe single-atom catalyst constructed in Example 1;

[0033] Figure 4 This is a graph showing the CO2 electroreduction performance of Cu nanoparticles supported on a ZnFe single-atom catalyst in Example 1.

[0034] Figure 5 This is a scanning electron microscope image of Cu nanoparticles supported on the ZnFe single-atom catalyst constructed in Example 2;

[0035] Figure 6 This is a graph showing the CO2 electroreduction performance of Cu nanoparticles supported on a ZnFe single-atom catalyst in Example 2.

[0036] Figure 7 This is a comparison chart of the performance of Fe single atoms and ZnFe single atoms in CO2 electroreduction. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in more detail below with reference to the accompanying drawings and specific embodiments. However, the scope of protection of this invention is not limited to these embodiments. The same reference numerals throughout the text always represent the same elements, and similar reference numerals represent similar elements.

[0038] A method for preparing ZnFe single-atom-supported Cu nanoparticles for CO2 electroreduction includes the following steps:

[0039] (1) Synthesis of ZnFe single-atom catalyst: Zinc chloride, potassium chloride and ferric chloride were dissolved in ultrapure water, then frozen into a solid state and freeze-dried to obtain a salt template; o-phenylenediamine precursor was dissolved in ethanol, ultrasonically dispersed and added to the above salt template and ground for 20-40 min; ammonium persulfate was dissolved in ultrapure water, ultrasonically dispersed and added to the above material and ground for 20-40 min; after standing for 10-15 h, it was treated in a muffle furnace at 170-230℃ for 1-3 h; then heat-treated in a tube furnace at 750-850℃ in a hydrogen / argon atmosphere for 1-3 h, cooled and taken out, acid washed with dilute hydrochloric acid solution, and then washed with water, alcohol and dried to obtain ZnFe single-atom catalyst;

[0040] (2) Preparation of ZnFe single-atom catalyst supported on Cu nanoparticles: ZnFe single-atom catalyst was added to ultrapure water, Cu nanoparticles were added to ethanol, and the two were sonicated for 20-40 min respectively. Then, Nafion solution was added and sonicated for 20-40 min to obtain ZnFe single-atom catalyst supported on Cu nanoparticles.

[0041] In step (1), the mass ratio of the precursor o-phenylenediamine, zinc chloride, potassium chloride, ferric chloride, and ammonium persulfate is 1:(6-10):(6-10):(2-4):(2-4), the volume ratio of ethanol to ultrapure water is 1:(4-10), and the concentration of o-phenylenediamine dissolved in ethanol is 80-120 g / L. In step (2), the concentration of ZnFe single-atom catalyst is 1.5-2.5 mg / mL, the concentration of Cu nanoparticles is 3.5-4.5 mg / mL, the mass ratio of ZnFe single-atom catalyst to Cu nanoparticles is 1:(2-5), and the volume ratio of Nafion solution, ultrapure water, and ethanol is 1:(8-12):(8-12).

[0042] A ZnFe single-atom-loaded Cu nanoparticle prepared by the method described above.

[0043] For example, the application of ZnFe single-atom-supported Cu nanoparticles in CO2 electroreduction includes the following steps:

[0044] (1) Clamping carbon paper in platinum electrode clamp: First, clean the platinum electrode clamp of a certain width in water with ultrasonic cleaning, dry the platinum sheet with nitrogen gas, and clamp the carbon paper in the platinum electrode clamp so that the exposed length of the carbon paper is 0.5-2 times the width of the platinum electrode clamp.

[0045] (2) Coat ZnFe single-atom-supported Cu nanoparticles uniformly onto the carbon paper exposed in step (1): at a ratio of 15-25 μL / cm 2 Apply the ink evenly to the carbon paper and then dry it.

[0046] (3) Add equal amounts of 0.05-0.15M KHCO3 solution to the cathode chamber and anode chamber of the electrolytic cell until the liquid surface can just completely submerge the exposed carbon paper. Pass CO2 gas into the cathode chamber until the electrolyte is saturated. Place the carbon paper between the platinum electrode clips coated with ZnFe single-atom-loaded Cu nanoparticles obtained in step (2) in the cathode chamber of the electrolytic cell.

[0047] (4) Place a platinum sheet as the counter electrode in the anode chamber of the electrolytic cell, place a calomel electrode as the reference electrode in the cathode chamber of the electrolytic cell, and connect the electrolytic cell tested by the electrochemical workstation to the gas chromatograph in order to obtain the product results of the CO2 reduction process.

[0048] (5) First, the catalyst surface is activated by cyclic voltammetry (CV). Then, the products of CO2 reduction reaction of the catalyst are tested at different potentials. The Faraday efficiency (FE) of each product is calculated based on the concentration of each product and the current under constant potential test conditions.

[0049] In step (1), both sides of the carbon paper are hydrophobically treated, and the catalyst is coated on the front side of the carbon paper modified with carbon black.

[0050] In step (3), the anode chamber and the cathode chamber are separated by a proton exchange membrane, Nafion.

[0051] In step (3), the front of the carbon paper coated with the catalyst is placed in the electrolytic cell facing the direction of CO2 gas output, so that CO2 can be more easily adsorbed on the catalyst surface.

[0052] In step (4), gas chromatography uses high-purity nitrogen with a purity of ≥99.99% as the carrier gas, and a thermal conductivity detector and a hydrogen flame ionization detector detect H2 and other carbon-containing gaseous products, respectively.

[0053] In step (5), the cyclic voltammetry potential range is set so that impurities on the catalyst surface are desorbed and removed, but the catalyst is not reconstructed.

[0054] The formula for calculating the Faraday efficiency of each product in step (5) is FE = I gas / I total ×100%.

[0055] Example 1

[0056] A method for preparing ZnFe single-atom-supported Cu nanoparticles for CO2 electroreduction, the specific steps of which are as follows:

[0057] (1) Synthesis of ZnFe single-atom catalyst: Zinc chloride: potassium chloride: ferric chloride were dispersed in ultrapure water at a mass ratio of 2:2:1 to form an aqueous solution with a mass concentration of 80 g / L. After freezing into a solid state, the solution was freeze-dried to obtain a eutectic salt template. o-phenylenediamine, eutectic salt, and ammonium persulfate were weighed at a mass ratio of 1:2:12. o-phenylenediamine was used as a precursor and dissolved in ethanol to form a 100 g / L o-phenylenediamine solution. After ultrasonic mixing, the solution was added to the above salt template and the grinding time was controlled at 20 min until the mixture was homogeneous. Ammonium persulfate was dissolved in ultrapure water to form a 500 g / L ammonium persulfate solution. After ultrasonic dispersion, the above material was added and the mixture was ground for another 30 min. After drying, the solution was placed in a muffle furnace and heated to 110 °C at a rate of 7 °C / min for 3 h to dehydrate it. After cooling to room temperature, the solution was placed in a tube furnace and pyrolyzed at 800 °C at a rate of 6 °C / min for 3 h under a hydrogen / argon atmosphere. After cooling to room temperature, the solution was stirred with 0.5 mol / L hydrochloric acid aqueous solution at 75 °C for 3 h, centrifuged, washed with ultrapure water, and dried at 60 °C for 24 h to obtain a ZnFe single-atom catalyst.

[0058] (2) Preparation of ZnFe single-atom catalyst supported on Cu nanoparticles: 1 mg of ZnFe single-atom catalyst was added to a 2 mL glass reagent bottle, 500 μL of water was added, the bottle was sealed, and sonicated at room temperature for 30 min. 2 mg of Cu nanoparticles were added to a 2 mL glass reagent bottle, 500 μL of ethanol was added, the bottle was sealed, and sonicated at room temperature for 30 min. The entire aqueous solution of ZnFe single-atom catalyst was added to the glass reagent bottle containing the Cu nanoparticle ethanol solution, and then 50 μL of Nafion solution was added. The mixture was then sonicated at room temperature for another 30 min.

[0059] The ZnFe single-atom-supported Cu nanoparticles prepared by the above method are used for CO2 electroreduction, including the following steps:

[0060] (1) Clamp the carbon paper in the platinum electrode clamp: First, clean the platinum electrode clamp with a width of 1cm in water with ultrasonic cleaning, dry the platinum sheet with nitrogen gas, and clamp the carbon paper in the platinum electrode clamp so that the exposed length of the carbon paper is 1cm.

[0061] (2) ZnFe single-atom-supported Cu nanoparticles were uniformly coated on a 1×1 cm² substrate. 2 On the carbon paper: Each carbon paper has a catalyst loading of 1 mg. A total of 350 μL of solution is dropped onto the carbon paper. Take 20 μL of solution at a time and spread it evenly on the carbon paper. Dry it under an infrared drying lamp. After one drying is completed, the next coating is applied until the corresponding loading is reached.

[0062] (3) Add 30 mL of 0.1 M KHCO3 solution to each of the two chambers of the H-type electrolytic cell, and pass CO2 gas through at a flow rate of 30 mL / min for 30 min to saturate the electrolyte. Place the platinum electrode clip with carbon paper coated with ink obtained in step (2) into the cathode chamber of the H-type electrolytic cell.

[0063] (4) Place a platinum sheet as the counter electrode in the anode chamber of the H-type electrolytic cell, place a calomel electrode as the reference electrode in the cathode chamber of the H-type electrolytic cell, and connect the electrolytic cell tested by the electrochemical workstation to the gas chromatograph in order to obtain the product results of the CO2 reduction process.

[0064] (5) First, the catalyst surface is activated by cyclic voltammetry (CV). Then, the products of the CO2 reduction reaction of the catalyst (CO, CH4, C2H4, H2) are tested four times at different potentials. The Faraday efficiency (FE) of each product is calculated based on the concentrations of CO, CH4, C2H4, H2 and the current under constant potential test conditions.

[0065] Figure 1 The image shows a scanning electron microscope (SEM) image of the synthesized ZnFe single-atom catalyst. It can be seen that the ZnFe single-atom catalyst has a honeycomb morphology with many pores on the surface. The diameter of the pores is much larger than that of Cu nanoparticles, which facilitates the loading of Cu nanoparticles. The surface is relatively rough, which increases the specific surface area of ​​the catalyst and facilitates the adsorption of CO2.

[0066] Figure 2 The image shows a transmission electron microscope (TEM) image of the synthesized ZnFe single-atom catalyst. It can be seen that there are no obvious nanoparticles on the catalyst surface, indicating that ZnFe atoms do not aggregate in the catalyst.

[0067] Figure 3 The image shows a scanning electron microscope (SEM) image of the ZnFe single-atom catalyst and Cu nanoparticle loading in Example 1 with a mass ratio of 1:2. It can be seen that the Cu nanoparticles are evenly distributed on the surface of the ZnFe single-atom catalyst, and there is a certain interaction between the two.

[0068] Figure 4 The graph shows the performance of CO2 electroreduction reaction in Example 1 when the mass ratio of ZnFe single-atom catalyst to Cu nanoparticles is 1:2. As the applied potential becomes more negative, the selectivity of CO decreases, while the selectivity of C2H4 and CH4 increases, and the current density also increases.

[0069] Example 2

[0070] A method for preparing ZnFe single-atom-supported Cu nanoparticles for CO2 electroreduction, the specific steps of which are as follows:

[0071] (1) Synthesis of ZnFe single-atom catalyst: Zinc chloride: potassium chloride: ferric chloride were dispersed in ultrapure water at a mass ratio of 2:2:1 to form an aqueous solution with a mass concentration of 80 g / L. After freezing into a solid state, the solution was freeze-dried to obtain a eutectic salt template. o-phenylenediamine, eutectic salt, and ammonium persulfate were weighed at a mass ratio of 1:2:12. o-phenylenediamine was used as a precursor and dissolved in ethanol to form a 100 g / L o-phenylenediamine solution. After ultrasonic mixing, the solution was added to the above salt template and the grinding time was controlled at 20 min until the mixture was homogeneous. Ammonium persulfate was dissolved in ultrapure water to form a 500 g / L ammonium persulfate solution. After ultrasonic dispersion, the above material was added and the mixture was ground for another 30 min. After drying, the solution was placed in a muffle furnace and heated to 110 °C at a rate of 7 °C / min for 3 h to dehydrate it. After cooling to room temperature, the solution was placed in a tube furnace and pyrolyzed at 800 °C at a rate of 6 °C / min for 3 h under a hydrogen / argon atmosphere. After cooling to room temperature, the solution was stirred with 0.5 mol / L hydrochloric acid aqueous solution at 75 °C for 3 h, centrifuged, washed with ultrapure water, and dried at 60 °C for 24 h to obtain a ZnFe single-atom catalyst.

[0072] (2) Preparation of ZnFe single-atom catalyst supported on Cu nanoparticles: 1 mg of ZnFe single-atom catalyst and 500 μL of water were added to a 2 mL glass reagent bottle, and 5 mg of Cu nanoparticles and 500 μL of ethanol were added to another 2 mL glass reagent bottle. After sonication for 30 min, the entire aqueous solution of ZnFe single-atom catalyst was added to the glass reagent bottle containing the Cu nanoparticle ethanol solution, and 50 μL of Nafion solution was added. After sonication for 30 min, the solution was sonicated again.

[0073] The ZnFe single-atom-supported Cu nanoparticles prepared by the above method are used for CO2 electroreduction, including the following steps:

[0074] (1) Clamp the carbon paper in the platinum electrode clamp: First, clean the platinum electrode clamp with a width of 1cm in water with ultrasonic cleaning, dry the platinum sheet with nitrogen gas, and clamp the carbon paper in the platinum electrode clamp so that the exposed length of the carbon paper is 1cm.

[0075] (2) ZnFe single-atom-supported Cu nanoparticles were uniformly coated on a 1×1 cm² substrate. 2 On the carbon paper: the catalyst loading of each carbon paper is 1 mg, and a total of 175 μL of solution is dropped on. Take 20 μL of solution at a time and spread it evenly on the carbon paper. Dry it under an infrared drying lamp. After one drying is completed, the next coating is applied until the corresponding loading is reached.

[0076] (3) Add 30 mL of 0.1 M KHCO3 solution to each of the two chambers of the H-type electrolytic cell, and pass CO2 gas through at a flow rate of 30 mL / min for 30 min to saturate the electrolyte. Place the platinum electrode clip with carbon paper coated with ZnFe single atom-loaded Cu nanoparticles obtained in step (2) into the cathode chamber of the H-type electrolytic cell.

[0077] (4) Place a platinum sheet as the counter electrode in the anode chamber of the H-type electrolytic cell, place a calomel electrode as the reference electrode in the cathode chamber of the H-type electrolytic cell, and connect the electrolytic cell tested by the electrochemical workstation to the gas chromatograph in order to obtain the product results of the CO2 reduction process.

[0078] (5) First, the catalyst surface is activated by cyclic voltammetry (CV). Then, the products of the CO2 reduction reaction of the catalyst (CO, CH4, C2H4, H2) are tested four times at different potentials. The Faraday efficiency (FE) of each product is calculated based on the concentrations of CO, CH4, C2H4, H2 and the current under constant potential test conditions.

[0079] Figure 5 The image shows a scanning electron microscope (SEM) image of the ZnFe single-atom catalyst and Cu nanoparticle loading ratio of 1:5 in Example 2. It can be seen that the Cu nanoparticles are evenly distributed on the surface of the ZnFe single-atom catalyst, and the loading of Cu nanoparticles is significantly increased, indicating that there is a certain interaction between the two.

[0080] Figure 6 The graph shows the CO2 electroreduction reaction performance of the ZnFe single-atom catalyst and Cu nanoparticle loading mass ratio of 1:5 in Example 2. As the applied potential becomes more negative, the selectivity of CO decreases, while the selectivity of C2H4 and CH4 increases. The increase in the selectivity of CH4 is very significant, and the current density also increases.

[0081] Comparative Example 1

[0082] Synthesis of Fe single-atom catalyst: Potassium chloride and ferric chloride were dissolved in ultrapure water, frozen into a solid state, and then freeze-dried. o-Phenylenediamine, as a precursor, was dissolved in ethanol solution, ultrasonically dispersed, and then added to the above salt template, and ground until homogeneous. Ammonium persulfate was dissolved in 1M dilute hydrochloric acid solution, ultrasonically dispersed, and then added to the above materials, with further grinding for 30 min. After standing for 12 h, it was treated in a muffle furnace at 200℃ for 2 h. Subsequently, it was heat-treated in a tube furnace under a hydrogen / argon atmosphere at 800℃ for 2 h, cooled, and removed. After acid washing with dilute hydrochloric acid solution, it was washed with water, alcohol, and dried to obtain the Fe single-atom catalyst. It was used for electrocatalytic CO2 reduction reaction according to the method in Example 1.

[0083] Figure 7This is a performance comparison chart of Fe single-atom catalysts and ZnFe single-atom catalysts for CO2 electroreduction. As can be seen from the chart, the Fe single-atom catalyst has a lower selectivity for CO production in the electrocatalytic CO2 reduction reaction. Therefore, the effect of Fe single-atom catalysts loaded with Cu nanoparticles for CO2 electroreduction is much worse than that of ZnFe single-atom catalysts.

[0084] The addition of Zn can enhance the interaction between Zn and Fe, optimize the charge distribution of the N and C atoms coordinated around it, and increase the selectivity of ZnFe single atoms for CO electroreduction to produce CO; at the same time, Cu nanoparticles can couple around the ZnFe active sites to rapidly convert CO into multi-carbon products.

[0085] The above embodiments are merely optimized implementations of the present invention, used to illustrate the principles and effects of the present invention, and are not intended to limit the present invention. It should be noted that any modifications made to the above embodiments by those skilled in the art without departing from the spirit and scope of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing ZnFe single-atom supported Cu nanoparticles for CO2 electroreduction, characterized in that, The method comprises the following steps: (1) Synthesis of ZnFe single-atom catalyst: Dissolve zinc chloride, potassium chloride and iron chloride in ultrapure water, then freeze into solid state and then freeze-dry to obtain a salt template; Dissolve the precursor o-phenylenediamine in ethanol, ultrasonic dispersion, then add the above-mentioned salt template and grind for 20-40 min; Take ammonium persulfate dissolved in ultrapure water, ultrasonic dispersion, then add the above-mentioned material and continue to grind for 20-40 min; After standing for 10-15 h, treat in a muffle furnace at 170-230 DEG C for 1-3 h; Then heat treat in a tube furnace at 750-850 DEG C in a hydrogen / argon atmosphere for 1-3 h, after cooling, take out and acid wash with dilute hydrochloric acid solution, then wash with water, alcohol, dry to obtain the ZnFe single-atom catalyst; (2) Preparation of ZnFe single-atom catalyst loaded with Cu nanoparticles: Add the ZnFe single-atom catalyst to ultrapure water, add Cu nanoparticles to ethanol, ultrasonic dispersion for 20-40 min respectively, then mix the two, then add Nafion solution and ultrasonic dispersion for 20-40 min to obtain the ZnFe single-atom catalyst loaded with Cu nanoparticles; The mass ratio of the precursor o-phenylenediamine, zinc chloride, potassium chloride, iron chloride and ammonium persulfate is 1:(6-10):(6-10):(2-4):(2-4), the concentration of the ZnFe single-atom catalyst is 1.5-2.5 mg / mL, the concentration of the Cu nanoparticles is 3.5-4.5 mg / mL, and the mass ratio of the ZnFe single-atom catalyst to the Cu nanoparticles is 1:(2-5).

2. The production method according to claim 1, wherein The volume ratio of ethanol to ultrapure water in the step (1) is 1:(4-10), and the concentration of o-phenylenediamine dissolved in ethanol is 80-120 g / L; The volume ratio of the Nafion solution to ultrapure water to ethanol in the step (2) is 1:(8-12):(8-12).

3. A ZnFe single-atom loaded with Cu nanoparticles prepared by the preparation method of claim 1 or 2.

4. The use of ZnFe single atom supported Cu nanoparticles for the electroreduction of CO2 according to claim 3, characterized in that, The method comprises the following steps: (1) Clamping carbon paper in platinum electrode clamp: First, ultrasonic clean a certain width of platinum electrode in water, blow dry the platinum sheet with nitrogen, clamp the carbon paper in the platinum electrode clamp so that the length of the exposed carbon paper is 0.5-2 times the width of the platinum electrode clamp; (2) ZnFe monatomic Cu nanoparticles are uniformly coated on the exposed carbon paper in step (1): 15-25 μL / cm 2 ZnFe monatomic Cu nanoparticles are uniformly coated on the carbon paper; (3) Add equal amount of KHCO3 solution with a concentration of 0.05-0.15 M to the cathode chamber and the anode chamber of the electrolytic cell respectively until the liquid surface completely covers the exposed carbon paper, introduce CO2 gas into the electrolyte in the cathode chamber until saturation, and place the platinum electrode clamp with the ZnFe single-atom loaded with Cu nanoparticles obtained in step (2) clamping the carbon paper in the cathode chamber of the electrolytic cell; (4) Place the platinum sheet as a counter electrode in the anode chamber of the electrolytic cell, place the calomel electrode as a reference electrode in the cathode chamber of the electrolytic cell, and connect the electrolytic cell tested by the electrochemical workstation with a gas chromatograph to obtain the product results of the CO2 reduction process. (5) The catalyst surface is activated by cyclic voltammetry, then the products of CO2 reduction reaction at different potentials are tested, and the Faraday efficiency of various products is calculated according to the concentration of various products and the current under constant potential test conditions.

5. The use according to claim 4, wherein the compound is ###0002### In the step (1), the front and back surfaces of the carbon paper are subjected to hydrophobic treatment, and the catalyst is coated on the front surface of the carbon paper modified with carbon black.

6. The use according to claim 4, wherein the compound is ###0003### In the step (3), the front surface of the carbon paper coated with the catalyst is placed in the electrolytic cell and faces the direction of CO2 gas outlet.

7. The use according to claim 4, wherein the compound is ###0002### In the step (3), the anode chamber and the cathode chamber are separated by a Nafion proton exchange membrane.

8. The use according to claim 4, wherein the compound is ###0002### In the step (4), the gas chromatograph uses high-purity nitrogen with a purity of ≥99.99% as the carrier gas, and the thermal conductivity detector and the hydrogen flame ionization detector are used to detect H2 and other carbon-containing gas phase products, respectively.

9. The use according to claim 4, wherein the compound is ###0003### In the step (5), the cyclic voltammetry potential range is set to remove impurities on the surface of the catalyst without causing the catalyst to be reconstructed.

10. The use according to claim 4, wherein the compound is ###00010### or a pharmaceutically acceptable salt thereof. The formula for calculating the Faraday efficiency of various products in step (5) is FE = I gas / I total x 100%.

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