Method for improving efficiency of preparing formic acid from tin phthalocyanine molecules through electro-catalysis of carbon dioxide

Abstract

The invention discloses a method for improving the efficiency of preparing formic acid from tin phthalocyanine molecules through electrocatalysis of carbon dioxide, belongs to the technical field of energy catalysis, and is specifically realized by loading SnPc molecules on carbon nanotubes with the diameter of 50-80nm. By exploring the influence of the shape curvature of the carrier on the active site of the SnPc molecule, the carbon nanotube with the diameter of 50-80nm is specifically selected as the optimal carrier of SnPc, so that the Faraday efficiency of preparing formic acid by electro-catalysis of carbon dioxide by the tin phthalocyanine molecule is improved to the maximum extent, and meanwhile, the excellent catalytic stability is shown; and the SnPc molecular catalyst is used for the first time for electrically reducing a pure formic acid solution in a solid electrolyte reaction tank. The preparation method is simple, controllable, easy to implement and suitable for large-scale production and application.

Description

Technical Field

[0001] The invention belongs to the technical field of energy catalysis, and in particular relates to a method for improving the efficiency of preparing formic acid by electrocatalysis of carbon dioxide by tin phthalocyanine molecules. Background Art

[0002] As carbon dioxide (CO2) levels rise due to the burning of fossil fuels, environmental pollution, energy crisis and other problems are becoming increasingly serious, and the urgent need to solve this problem has pushed CO2 conversion technology to the forefront of sustainable innovation. Electrochemical CO2 reduction (CO2RR) technology uses renewable electricity to convert CO2 into valuable products, providing a direct way to reduce carbon emissions while producing chemicals and fuels necessary for industry. Compared with other products, formic acid has a higher energy density and can be used as a hydrogen storage material and fuel cell fuel; at the same time, formic acid is also a raw material for the production of many drugs and organic syntheses, and there is a very large industrial demand. The wide industrial relevance of formic acid makes CO2 to formic acid conversion technology a high-impact solution to environmental problems and industrial needs.

[0003] Among the known studies, there have been many studies on catalysts for the electrocatalytic production of formic acid from CO2, mainly focusing on bismuth-based materials and alloys of other metals. Despite its potential, bulk metal catalysts have the problem of low atomic utilization. Single-atom catalysts (SACs) have attracted considerable attention due to their highest atomic efficiency, clear active sites and high catalytic selectivity. Tin phthalocyanine (SnPc) is a molecular catalyst that is loaded on a carbon carrier with good conductivity to construct a single-atom catalyst. It is one of the few single-atom catalysts currently studied that can convert CO2 into formic acid, and maintains good performance (Faraday efficiency value FE>80%). However, if you want to improve the catalytic performance of SnPc-based single-atom catalysts, you need to further optimize them. Traditional methods for optimizing catalytic activity generally design new structures or change functional groups, which are costly and time-consuming. Therefore, the present invention hopes to create a more effective catalyst without cumbersome chemical modification. Summary of the invention

[0004] In view of the cumbersome problem of traditional chemical modification methods, the present invention provides a method for improving the efficiency of preparing formic acid from carbon dioxide by electrocatalysis of tin phthalocyanine molecules. By specifically using carbon nanotubes with a diameter of 50 to 80 nm as the carrier of SnPc, high selectivity of carbon dioxide reduction to formic acid is achieved, showing high Faraday efficiency and excellent catalytic stability. The method is simple, easy to implement, and suitable for large-scale production and application.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for improving the efficiency of preparing formic acid by electrocatalyzing carbon dioxide using tin phthalocyanine molecules is achieved by loading SnPc molecules on carbon nanotubes with a diameter of 50 to 80 nm.

[0007] Furthermore, the method specifically comprises the following steps:

[0008] Step 1, dispersing carbon nanotubes with a diameter of 50 to 80 nm in an organic solvent, and continuously stirring to obtain a mixed solution A with a concentration of 0.75 to 1.33 mg / mL;

[0009] Step 2, dissolving SnPc molecules in an organic solvent, and obtaining a mixed solution B with a concentration of 0.75-1.33 mg / mL by ultrasonication;

[0010] Step 3, according to the volume ratio of mixed solution B: mixed solution A = 1:3-10, the mixed solution B is added to the mixed solution A, and the mixture is continuously stirred to obtain a mixed solution C;

[0011] Step 4: After the mixed solution C is filtered, washed and dried in sequence, a single atom catalyst of SnPc molecules supported by carbon nanotubes is obtained.

[0012] Furthermore, the organic solvent in step 1 and step 2 is N,N-dimethylformamide (DMF) solution.

[0013] Furthermore, the stirring speed of step 1 is 500-600 rpm.

[0014] Furthermore, the ultrasonication time in step 2 is 20 to 40 minutes.

[0015] Furthermore, in step 3, the mixed solution B is slowly dripped into the mixed solution A which is kept in a stirring state.

[0016] Furthermore, the continuous stirring time in step 3 is 20 to 30 hours.

[0017] Furthermore, the drying conditions of step 4 are: vacuum drying at 50-80° C. for 20-30 hours.

[0018] Furthermore, before preparing the mixed solution A in step 1, the method further includes the steps of washing and drying the carbon nanotubes.

[0019] The present invention also provides a carbon dioxide electroreduction formic acid device, which uses the gas diffusion layer loaded with the single-atom catalyst as a working electrode.

[0020] Furthermore, the carbon dioxide electroreduction formic acid device is implemented based on a flow-through electrolytic cell or a solid electrolyte reaction cell.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention proposes a method for improving the efficiency of electrocatalytic carbon dioxide preparation of formic acid by tin phthalocyanine molecules. By exploring the influence of the carrier shape curvature on the active sites of the SnPc molecular catalyst, carbon nanotubes with a diameter of 50 to 80 nm are specifically selected as the best carrier of SnPc to maximize the Faraday efficiency of electrocatalytic carbon dioxide preparation of formic acid by tin phthalocyanine molecules. The Faraday efficiency can be maintained at more than 80% at a current density of 300 milliamperes per square centimeter in a flow-type electrolytic cell, and the partial current density of formic acid reaches -216 milliamperes per square centimeter. At the same time, it exhibits excellent catalytic stability, realizing the first use of SnPc molecular catalysts in solid electrolyte reaction cells for the electroreduction preparation of pure formic acid solution.

[0023] 2. Compared with the cumbersome and high-cost traditional chemical modification methods, the preparation method of the present invention is simple, controllable, easy to implement, and suitable for large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 Element distribution energy spectra of single atom catalysts of carbon nanotubes with diameters of 4-6 nm, 20-30 nm, and 50-80 nm and graphene-supported SnPc molecular catalysts prepared in Example 1 of the present invention (respectively denoted as SnPc / CNT(4-6), SnPc / CNT(20-30), SnPc / CNT(50-80), and SnPc / G catalysts);

[0026] Figure 2 X-ray photoelectron spectra of SnPc / CNT (4-6), SnPc / CNT (20-30), SnPc / CNT (50-80) and SnPc / G catalysts prepared in Example 1 of the present invention;

[0027] Figure 3 The Faraday efficiencies of the products of the SnPc / CNT(4-6), SnPc / CNT(20-30), SnPc / CNT(50-80) and SnPc / G catalysts prepared in Example 1 of the present invention at different current densities in the electroreduction reaction of carbon dioxide in a flow-type electrolyzer; wherein (a) is the SnPc / CNT(4-6) catalyst; (b) is the SnPc / CNT(20-30) catalyst; (c) is the SnPc / G catalyst; and (d) is the SnPc / CNT(50-80) catalyst;

[0028] Figure 4 A graph showing the variation of formate partial current with cathode potential in the electroreduction reaction of carbon dioxide catalyzed by SnPc / CNT(4-6), SnPc / CNT(20-30), SnPc / CNT(50-80) and SnPc / G catalysts prepared in Example 1 of the present invention in a flow-type electrolytic cell;

[0029] Figure 5 The cathode potential-time curve and the Faraday efficiency variation with time of the constant current stability test of the SnPc / CNT (50-80) catalyst prepared in Example 1 of the present invention for catalyzing the carbon dioxide electroreduction reaction in a flow-type electrolyzer;

[0030] Figure 6 The Tafel slopes of SnPc / CNT (4-6), SnPc / CNT (20-30), SnPc / CNT (50-80) and SnPc / G catalysts prepared in Example 1 of the present invention tested in a flow-type electrolytic cell;

[0031] Figure 7 This is a schematic diagram of a solid electrolyte reaction cell used in Example 3 of the present invention;

[0032] Figure 8 The cathode potential-time curve and the Faraday efficiency variation with time obtained by the constant current stability test of the SnPc / CNT (50-80) catalyst prepared in Example 1 of the present invention catalyzing the carbon dioxide electroreduction reaction in a solid electrolyte reaction cell. DETAILED DESCRIPTION

[0033] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.

[0034] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0035] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably adopts analytically pure materials or materials with conventional purity requirements in the field of atomic layer deposition.

[0036] All raw materials and process steps of the present invention, their brands or abbreviations are conventional brands or abbreviations in the art, and each brand or abbreviation is clear and definite in the field of its related use. Those skilled in the art can purchase them from the market or prepare them by conventional methods, or implement them with corresponding equipment according to the brands, abbreviations and corresponding uses.

[0037] The present invention will be further described below in conjunction with embodiments:

[0038] Example 1

[0039] In order to explore the effect of the curvature of the support shape on the active sites of the SnPc molecular catalyst and the Faraday efficiency of carbon dioxide in preparing formic acid, this example prepared single-atom catalysts of SnPc molecular catalysts supported by carbon nanotubes of different diameters and graphene, which specifically included the following steps:

[0040] Step 1, dissolving carbon nanotubes and graphene with diameters of 4-6 nm, 20-30 nm, and 50-80 nm in hydrochloric acid respectively under stirring at room temperature, wherein the mass of the carbon nanotubes or graphene is 30 mg, the concentration of hydrochloric acid is 5 mol / L, the volume is 40 mL, ultrasonic treatment is performed for 5 min to uniformly disperse the carbon nanotubes or graphene in the hydrochloric acid, and the obtained mixed solution is magnetically stirred for more than 10 hours; then the obtained mixed solution is filtered and separated to obtain a solid material, and water filter paper is selected for filtration, and deionized water is added after filtering the hydrochloric acid until all the solid materials are covered, and after filtering the deionized water, the above filtration step is repeated three times, and vacuum drying is performed at 60° C. overnight to obtain carbon nanotubes and graphene with diameters of 4-6 nm, 20-30 nm, and 50-80 nm after washing and drying;

[0041] Step 2, dispersing the carbon nanotubes and graphene with diameters of 4-6 nm, 20-30 nm, and 50-80 nm obtained in step 1 into DMF solvent respectively, stirring continuously at room temperature at a stirring speed of 500 rpm to obtain a mixed solution A, wherein the mass of the carbon nanotubes or graphene is 30 mg, and the volume of the DMF solvent is 30 mL;

[0042] Step 3, dissolve 3 mg of SnPc molecules in 3 mL of DMF solution at room temperature, and ultrasonicate for 20 min to obtain a mixed solution B;

[0043] Step 4: Keeping the mixed solution A in a stirring state, slowly dripping the mixed solution B until the mixed solution A and the mixed solution B are completely mixed to obtain a mixed solution C, and continue stirring for 24 hours;

[0044] Step 5, the mixed solution C obtained in step 5 is filtered and separated, and after filtering the DMF solution, anhydrous ethanol is added until all solid materials are covered. After filtering the anhydrous ethanol, the above filtration step is repeated three times, and the mixture is dried in a vacuum oven at 60°C overnight to obtain carbon nanotubes with diameters of 4-6 nm, 20-30 nm, and 50-80 nm and single-atom catalysts of graphene-loaded SnPc molecules, which are respectively recorded as SnPc / CNT(4-6), SnPc / CNT(20-30), SnPc / CNT(50-80) and SnPc / G catalysts.

[0045] The SnPc / CNT (4-6), SnPc / CNT (20-30), SnPc / CNT (50-80) and SnPc / G catalysts prepared in this example are characterized below.

[0046] Figure 1 The element distribution energy spectra of SnPc / CNT(4-6), SnPc / CNT(20-30), SnPc / CNT(50-80) and SnPc / G catalysts prepared in this embodiment show that the Sn element, N element and C element involved in SnPc / CNT(4-6), SnPc / CNT(20-30), SnPc / CNT(50-80) and SnPc / G catalysts are uniformly distributed in the materials, indicating that the preparation method can synthesize single-atom catalysts with uniform loading of SnPc molecular catalysts.

[0047] Figure 2 The X-ray photoelectron energy spectrum of SnPc / CNT(4-6), SnPc / CNT(20-30), SnPc / CNT(50-80) and SnPc / G catalysts prepared in this embodiment shows that as the curvature of the carrier shape decreases (the curvature of the carrier shape of SnPc / CNT(4-6), SnPc / CNT(20-30), SnPc / CNT(50-80) and SnPc / G catalysts gradually decreases), the distortion degree of the carrier decreases, the stronger the electronic adsorption of the carrier on the Sn atom, the valence of the Sn atom gradually increases, and the Sn in SnPc / G shows the highest binding energy, while the Sn atom binding energy in SnPc / CNT(4-6) is the lowest. This shows that the curvature of the carrier shape will interact with the SnPc molecular catalyst, affecting the electronegativity of the Sn single atom active site, and thus affecting the activity of the single atom catalyst.

[0048] Example 2

[0049] The catalytic performance of SnPc / CNT (4-6), SnPc / CNT (20-30), SnPc / CNT (50-80) and SnPc / G catalysts prepared in Example 1 for the electroreduction reaction of carbon dioxide was tested using a three-electrode flow-through electrolytic cell.

[0050] Specifically, in a three-electrode flow-type electrolytic cell, a gas diffusion layer loaded with SnPc / CNT (4-6), SnPc / CNT (20-30), SnPc / CNT (50-80) and SnPc / G catalysts prepared in Example 1 was used as a working electrode, nickel foam was used as a counter electrode, a silver / silver chloride electrode was used as a reference electrode, a 0.5 mol / L potassium bicarbonate solution was used as a cathode electrolyte, and a 1 mol / L potassium hydroxide solution was used as an anode electrolyte. The carbon dioxide electroreduction performance test was carried out in a three-electrode flow-type electrolytic cell. During the test, the flow rate of carbon dioxide was maintained at 30 sccm, and the flow rate of the electrolyte was maintained at 60 mL / min. The test adopted a constant current method, and the applied current density range was -10 to -800 mA cm -2 The gas phase products of the reaction were detected by gas chromatography, and the liquid phase products were detected by anion chromatography. The coulomb amount corresponding to the product concentration was calculated, and the catalytic selectivity, activity and other data were obtained based on the total coulomb amount recorded by the electrochemical workstation.

[0051] Figure 3 The Faraday efficiencies of the products of the SnPc / CNT (4-6), SnPc / CNT (20-30), SnPc / CNT (50-80) and SnPc / G catalysts prepared in Example 1 at different current densities in the carbon dioxide electroreduction reaction in a flow-type electrolyzer, wherein: Figure 3 (a) is SnPc / CNT (4-6) catalyst, Figure 3 (b) is SnPc / CNT (20-30) catalyst, Figure 3 (c) is SnPc / G catalyst, Figure 3 (d) is SnPc / CNT (50-80) catalyst; Figure 4 The graph of the formate partial current versus cathode potential of the SnPc / CNT (4-6), SnPc / CNT (20-30), SnPc / CNT (50-80) and SnPc / G catalysts prepared in Example 1 in the flow-type electrolytic cell catalyzing the carbon dioxide electroreduction reaction. Figure 3 It can be seen that compared with the planar graphene, the bent carbon nanotubes can bring better catalytic performance to SnPc, almost at full current density (-50 to -300 mA cm -2 ), HCOO prepared by SnPc / CNT(4-6), SnPc / CNT(20-30), SnPc / CNT(50-80) based on carbon nanotubes -The Faraday efficiency is higher than that of SnPc / G based on graphene, indicating that the curved support induces local strain to enhance the electroreduction efficiency. However, when the study focused on SnPc / CNT(4-6), SnPc / CNT(20-30), and SnPc / CNT(50-80) based on all carbon nanotubes, it was found that as the size of the carbon nanotubes decreased, the performance of the catalyst also gradually decreased. Specifically, the highest formic acid Faraday efficiency of SnPc / CNT(50-80) reached 85%, but as the size of the carbon nanotubes decreased, the highest formic acid Faraday efficiency of SnPc / CNT(20-30) dropped to 82%. After further reducing the size, the highest formic acid Faraday efficiency of SnPc / CNT(4-6) was only 59%. On the other hand, when the current density reached -200mA cm -2 and -300mA cm -2 When the current density increases, the formic acid Faradaic efficiency of SnPc / CNT (50-80) can maintain 75% and 72%, while with the increase of current density, the formic acid Faradaic efficiency of SnPc / CNT (20-30) is only 20% and 4% at the same current density, and SnPc / CNT (4-6) is even lower, only 11% and 1%. This performance difference is Figure 4 The comparison is more obvious. The maximum partial current density of formate in SnPc / CNT (50-80) is -216 mA cm -2 , while the highest bias current density of SnPc / CNT (20-30) and SnPc / CNT (4-6) is only -73mAcm -2 and -46mA cm -2 , SnPc / G is the lowest, only -27mA cm -2 Therefore, it can be considered that although the curved support-induced local strain greatly increases the electroreduction efficiency of the SnPc molecular catalyst, the greater the degree of distortion, the better. Excessive distortion will lead to reduced catalytic activity. Therefore, the present invention specifically selects carbon nanotubes with a diameter of 50 to 80 nm as the best carrier of SnPc to maximize the Faradaic efficiency of the electrocatalytic carbon dioxide preparation of formic acid by tin phthalocyanine molecules.

[0052] Figure 5The cathode potential-time curve and Faraday efficiency change over time of the constant current stability test of the SnPc / CNT (50-80) catalyst prepared in Example 1 for the electroreduction reaction of carbon dioxide in a flow-type electrolyzer show that the performance of the SnPc / CNT (50-80) catalyst in catalyzing the conversion of formic acid can be maintained for more than 15 hours. The traditional method of improving the activity of SnPc by axial coordination (Journal of the American Chemical Society 145.13(2023):7242-7251.) is less than 100mAcm -2 It only ran for 8 h at a current density of , which shows that the method of the present invention can significantly improve the catalytic stability.

[0053] Figure 6 The Tafel slopes of SnPc / CNT (4-6), SnPc / CNT (20-30), SnPc / CNT (50-80) and SnPc / G catalysts prepared in Example 1 tested in a flow-type electrolytic cell. The Tafel slope can be used to reflect the speed of the reaction kinetics. The lower the Tafel slope, the faster the kinetic process. Figure 6 As shown, compared with SnPc / CNT (4-6), SnPc / CNT (20-30) and SnPc / G catalysts, SnPc / CNT (50-80) has the lowest Tafel slope of only 96 mV, proving that the active sites on the carbon nanotube support with a diameter of 50 to 80 nm can exhibit the best catalytic activity.

[0054] Example 3

[0055] The SnPc / CNT (50-80) catalyst prepared in Example 1 was tested for its catalytic stability in the carbon dioxide electroreduction reaction using a solid electrolyte reaction cell.

[0056] Specifically, in Figure 7 In the solid electrolyte reaction cell shown, the gas diffusion electrode loaded with the SnPc / CNT (50-80) catalyst prepared in Example 1 is used as the working electrode, the titanium mesh loaded with iridium oxide is used as the counter electrode, and the 0.5 mol / L sulfuric acid solution is used as the electrolyte of the anode. The flow rate is 20 mL / min, and the middle layer is carried out with deionized water to carry out pure formic acid (HCOOH) solution at a flow rate of 0.8 mL / min. During the test, the carbon dioxide flow rate is maintained at 30 sccm. The test adopts the constant current method, and the applied current density is 33 mA cm -2 , the total current is 100mA. The gas phase products of the reaction are detected by gas chromatography, and the liquid phase products are detected by anion chromatography. The coulomb amount corresponding to the product concentration is calculated, and the catalytic selectivity, activity and other data are obtained based on the total coulomb amount recorded by the electrochemical workstation.

[0057] In such Figure 7 In the solid electrolyte reaction cell shown, the cathode electrode for reducing CO2 is provided by humidified CO2 gas to promote the mass transfer of CO2, while the anode side is circulated by 0.5 mol / L sulfuric acid solution for oxygen evolution reaction. When CO2 is reduced by SnPc / CNT (50-80) catalyst, the negatively charged formate generated under the drive of the electric field flows through the anion exchange membrane to the middle solid electrolyte channel. At the same time, the protons generated by the oxygen evolution reaction on the anode side can pass through the proton exchange membrane to compensate the charge. Depending on the type of the intermediate solid ion conductive electrolyte, the formic acid product can be formed by ion recombination at the left or right interface between the middle channel and the membrane, and diffused through liquid water. The formed liquid product can be quickly released by a slow flow of deionized water to prepare a pure HCOOH solution.

[0058] Figure 8 The cathode potential-time curve and the Faraday efficiency variation with time graph obtained from the constant current stability test of the SnPc / CNT (50-80) catalyst prepared in Example 1 for catalyzing the electroreduction reaction of carbon dioxide in a solid electrolyte reaction cell show that the performance of the SnPc / CNT (50-80) catalyst in electrocatalyzing the conversion of carbon dioxide to formic acid can be stably maintained for more than 15 hours at a total current of 100 mA. This is also the first attempt of SnPc molecular catalyst in a solid electrolyte reaction cell, which is a good start.

[0059] Example 4

[0060] In this embodiment, a SnPc / CNT (50-80) catalyst was prepared. The preparation process was different from that in Example 1 except that the mass of the carbon nanotubes in step 2 was adjusted to 9 mg and the volume of the DMF solvent was adjusted to 9 mL; the other steps remained unchanged.

[0061] Example 5

[0062] In this embodiment, a SnPc / CNT (50-80) catalyst is prepared. The preparation process is different from that in Example 1, except that the continuous stirring time of the mixed solution C obtained in step 4 is adjusted to 30 hours; the other steps remain unchanged.

[0063] The above is that the present invention explores the performance of SnPc molecular catalysts loaded on carriers of different sizes in the production of formic acid by CO2 electroreduction, clarifies that carbon nanotubes with a diameter of 50 to 80 nm have the best performance, and makes a pioneering use of the invention in a solid electrolyte reaction cell. The preparation method and application are introduced in detail. The principle and implementation mode of the present invention are explained by using specific examples in this article. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the text of the claims, or if they include equivalent structural elements that are not substantially different from the text of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for improving the efficiency of preparing formic acid by electrocatalysis of carbon dioxide using tin phthalocyanine molecules, characterized in that: This is achieved by loading SnPc molecules on carbon nanotubes with a diameter of 50 to 80 nm.

2. The method for improving the efficiency of preparing formic acid by electrocatalysis of carbon dioxide using tin phthalocyanine molecules according to claim 1, characterized in that: The method specifically comprises the following steps: Step 1, dispersing carbon nanotubes with a diameter of 50 to 80 nm in an organic solvent, and continuously stirring to obtain a mixed solution A with a concentration of 0.75 to 1.33 mg / mL; Step 2, dissolving SnPc molecules in an organic solvent, and obtaining a mixed solution B with a concentration of 0.75-1.33 mg / mL by ultrasonication; Step 3, according to the volume ratio of mixed solution B: mixed solution A = 1:3-10, the mixed solution B is added to the mixed solution A, and the mixture is continuously stirred to obtain a mixed solution C; Step 4: After the mixed solution C is filtered, washed and dried in sequence, a single atom catalyst of SnPc molecules supported by carbon nanotubes is obtained.

3. The method for improving the efficiency of preparing formic acid by electrocatalysis of carbon dioxide using tin phthalocyanine molecules according to claim 2, characterized in that: The continuous stirring time of step 3 is 20 to 30 hours.

4. The method for improving the efficiency of preparing formic acid by electrocatalysis of carbon dioxide using tin phthalocyanine molecules according to claim 2, characterized in that: In step 3, the mixed solution B is slowly dripped into the mixed solution A which is kept in a stirring state.

5. The method for improving the efficiency of preparing formic acid by electrocatalysis of carbon dioxide using tin phthalocyanine molecules according to claim 2, characterized in that: The organic solvent in step 1 and step 2 is N,N-dimethylformamide solution.

6. The method for improving the efficiency of preparing formic acid by electrocatalysis of carbon dioxide using tin phthalocyanine molecules according to claim 2, characterized in that: The drying conditions of step 4 are: vacuum drying at 50-80° C. for 20-30 hours.

7. A carbon dioxide electroreduction formic acid device, characterized in that: The gas diffusion layer of the single-atom catalyst loaded with SnPc molecules loaded on the carbon nanotubes obtained by the method of any one of claims 2 to 6 is used as the working electrode.

8. The carbon dioxide electroreduction formic acid device according to claim 7, characterized in that: It is realized based on a flow-through electrolytic cell or a solid electrolyte reaction cell.

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