A method for electro-synthesis of carbonates from carbon dioxide and a low-carbon alcohol

Abstract

The application discloses a method for synthesizing carbonic acid ester by electrocatalytic conversion of carbon dioxide and methanol. The method uses nitrogen-containing polyionic liquid as a precursor, designs and prepares a novel nitrogen-containing polyionic liquid-based functionalized nitrogen-doped carbon nanotube material as a first catalyst, the first catalyst and a gas diffusion layer are made into a cathode material, and a polyionic liquid-based nitrogen-doped carbon nanotube material loaded with palladium is used as a second catalyst for electrolyte reaction. The overall electrocatalytic system comprises the above electrode material, the second catalyst, the reaction electrolyte and the reaction device, wherein the low-carbon alcohol (methanol, ethanol) is used as both the electrolyte solvent and the reactant, and the constant potential electrolysis reaction is carried out in the electrolysis cell reaction device through the synergistic effect of the electrode material, the second catalyst and the electrolyte to synthesize carbonic acid ester. The method for directly synthesizing carbonic acid ester by electrocatalysis of CO2 uses the novel nitrogen-containing polyionic liquid-based nitrogen-doped carbon nanotube catalytic material as the main body of the first catalyst and the second catalyst, the system is simplified, the preparation is convenient, the synthesis is efficient, and the process of electro-synthesizing organic carbonic acid ester from CO2 and low-carbon alcohol under mild conditions is promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of energy materials and electrochemistry, and relates to a construction method of a catalytic system for electrocatalytic CO2 preparation of carbonates, a functionalized carbon nanotube catalytic material prepared from a nitrogen-containing ionic liquid as a precursor, a nitrogen-containing polyionic liquid-based nitrogen-doped carbon nanotube material loaded with palladium, and a new type of electrochemical reaction system for CO2 synthesis of carbonates, so as to realize efficient and mild electrochemical synthesis of carbonates from CO2. BACKGROUND

[0002] CO2 is the main component of greenhouse gases, and its continuous accumulation due to the consumption of fossil fuels has brought about many environmental and social problems. At the same time, CO2 is a renewable C1 resource that is abundant in reserves, widely available, non-toxic, harmless and inexpensive. Its resource utilization can realize the conversion of inorganic carbon to high-value-added chemicals. However, the current method for large-scale treatment of CO2 is mainly absorption capture and storage (CCS), and the C1 resource cannot be effectively utilized. Among them, the synthesis of carbonates by replacing traditional toxic carbonyl sources with CO2 as a starting material is an important direction for the resource utilization of CO2.

[0003] Carbonates are classic chemicals and chemical products, and are also an important component of battery electrolytes, supporting frontier industries such as power batteries, electronic chemicals and polycarbonates, and thus promoting the rapid development of downstream electronic appliances, automobile industry, aerospace, energy information field. The direct synthesis of carbonates from CO2 and low-carbon alcohols has become a research hotspot in the field of CO2 chemical low-carbon energy in recent years due to the advantages of low-cost and easily available low-carbon alcohols, which can be selected from coal-based and do not depend on petroleum resources, and the "one-step" convenient synthesis. Commonly used catalysts for the thermal synthesis of carbonates from CO2 and low-carbon alcohols include alkali metal carbonates, metal-organic framework materials, supported metal catalysts, metal oxide catalysts, ionic liquid catalysts, etc., but there are problems such as thermodynamic disadvantage, high kinetic energy barrier, harsh reaction conditions, etc. The use of electrocatalytic process to prepare carbonates from CO2 and low-carbon alcohols can effectively overcome the thermodynamic barrier, improve the reaction efficiency, and alleviate the reaction conditions, which is in line with the development trend of green energy driving traditional chemical industry to help carbon reduction.

[0004] Currently, there are many problems in the electrocatalytic process of synthesizing carbonates from CO2, such as more hydrogen evolution by-products, and the compatibility of the catalytic system needs to be improved. By introducing new efficient and green catalytic materials, improving the compatibility and catalytic performance of the first catalyst and the second catalyst, and then realizing the new process of synthesizing carbonates from CO2 under mild conditions, it has important scientific significance and industrial significance. Metal-free carbon-based catalysts are ideal materials for electrocatalytic CO2 conversion due to their dimensional and nano-structural diversity. Higher specific surface area, excellent electrical conductivity and chemical stability can all promote the electrocatalytic performance of CO2, but pure carbon materials have weak adsorption capacity for CO2 molecules, resulting in poor catalytic activity. Heteroatom-doped carbon materials can effectively improve the electrocatalytic performance of carbon-based catalysts by adjusting the electronic structure and surface properties, and can provide CO2 activation sites. Polyionic liquid has low vapor pressure, high thermal stability and structural designability, and can directly prepare heteroatom-doped carbon materials with high yield by high-temperature carbonization of ionic liquid containing heteroatoms. Therefore, by using polyionic liquid as a precursor to prepare carbon materials, it is expected to realize efficient catalysis of CO2 to synthesize carbonates. SUMMARY

[0005] The purpose of the present application is to provide a method for electrocatalytic conversion of carbon dioxide to prepare carbonates.

[0006] The first purpose of the present application is to provide a method for preparing polyionic liquid-based nitrogen-doped carbon nanotube material using polyionic liquid as a precursor, comprising the following steps:

[0007] 1) Dissolve 10 mmol of vinyl ionic liquid monomer and divinylbenzene into 50 mL of solvent, replace the gas with nitrogen and stir for 0.5 h.

[0008] 2) Add azobisisobutyronitrile as an initiator, raise to 70℃, and polymerize for 24 h.

[0009] 3) After the reaction is completed, the crude product in the above system is centrifuged at a certain speed, washed and dried to obtain a polyionic liquid precursor.

[0010] 4) Mix the polyionic liquid precursor and carbon nanotubes and place them in a corundum boat, use high-purity Ar as a protective gas, and high-temperature calcine to obtain polyionic liquid-based nitrogen-doped carbon nanotube material.

[0011] The vinyl-containing ionic liquid in the above preparation method includes 2-methyl-6-vinylpyridine bromide, 2-methyl-6-vinylpyridine dicyanamide, 2-methyl-6-vinylpyridine tetrafluoroborate, and 2-methyl-6-vinylpyridine 2,4-dihydroxypyrimidine-5-carboxylate;

[0012] The molar ratio of the vinyl-containing ionic liquid monomer and divinylbenzene is 1:1-10:1, and specifically can be 1:1;

[0013] The solvent includes one or more of methanol, ethanol, and acetonitrile, and specifically can be methanol.

[0014] The washing solvent is one or more of methanol, ethanol, and deionized water, and specifically can be deionized water.

[0015] The drying temperature is 40-100°C, and the time is 10-48h, and specifically can be 100°C and 10h.

[0016] The second object of the present application is to provide an electrode material comprising the above-mentioned poly-ionic liquid-based nitrogen-doped carbon nanotube material and a gas diffusion layer.

[0017] The above-mentioned electrode material, a method for preparing the electrode material, comprises the following steps:

[0018] The poly-ionic liquid-based nitrogen-doped carbon nanotube material is dispersed in a solvent, and Nafion 117 dispersion liquid is added as a binder to obtain a dispersion liquid; the dispersion liquid is dropped onto the gas diffusion layer to obtain the electrode material.

[0019] In the above-mentioned electrode material, the solvent is selected from at least one of acetone, ethanol, isopropanol, and deionized water, and specifically can be isopropanol.

[0020] The catalyst ratio of the Nafion 117 dispersion liquid to the poly-ionic liquid-based nitrogen-doped carbon nanotube material is 10-100μL:1mg, and specifically can be 10μL:1mg.

[0021] In the above-mentioned electrode material, the gas diffusion layer can be selected from at least one of carbon fiber paper, carbon fiber woven cloth, and carbon black paper, and specifically can be carbon fiber paper.

[0022] In the above-mentioned electrode material, the amount of the poly-ionic liquid-based nitrogen-doped carbon material on the gas diffusion layer can be 0.1-10mg / cm 2 , and specifically can be 1mg / cm 2 .

[0023] The third object of the present application is to provide a method for loading a poly-ionic liquid-based nitrogen-doped carbon nanotube material with a palladium catalyst material, comprising the following steps:

[0024] 1) The poly-ionic liquid-based nitrogen-doped carbon material is stirred in a 10% nitric acid solution for 4h under reflux, and the heating temperature is 80°C; after the reflux is completed, the material is washed with deionized water until it is neutral.

[0025] 2) Dissolve the palladium compound in 10% hydrochloric acid solution, and move into the treated polyionic liquid-based nitrogen-doped carbon material, and stir for 2h.

[0026] 3) Dissolve sodium borohydride in deionized water, and add to the solution of step (2), and stir for 2h,

[0027] 4) Centrifuge, wash and dry the product to obtain the palladium / carbon material.

[0028] In the above polyionic liquid-based nitrogen-doped carbon nanotube material loaded palladium catalytic material, the palladium compound is one of palladium chloride and sodium tetrachloropalladate (II) ;

[0029] The mass fraction of palladium is 1% to 20%, and specifically can be 10%;

[0030] The molar ratio of sodium borohydride to palladium is 1:1 to 10:1, and specifically can be 1:1;

[0031] The washing solvent is one or more of methanol, ethanol and deionized water, and specifically can be methanol;

[0032] The drying temperature is 40 to 100 DEG C, and the time is 10 to 48h, and specifically can be 100 DEG C and 10h.

[0033] The fourth object of the present application is to provide an electrochemical catalytic system, which comprises the above-mentioned electrode material, a second catalyst, a reaction electrolyte and a reaction device.

[0034] In the above electrochemical system, the reaction electrolyte comprises an electrolyte and a reaction solvent, the electrolyte is selected from at least one of tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylammonium chloride, sodium bromide and potassium bromide, and the reaction solvent is selected from at least one of methanol and ethanol.

[0035] The concentration of the reaction electrolyte is 0.1 to 10M; specifically, it can be 1M tetrabutylammonium bromide / methanol solution;

[0036] The ratio of the second catalyst to the electrolyte is 1 to 100mg:10mL;

[0037] The reaction device is a single cell or an H-type electrolytic cell.

[0038] The fifth object of the present application is to provide the application of the above-mentioned electrode material and catalytic material or the above-mentioned electrochemical catalytic system in the electrocatalytic conversion of carbon dioxide to synthesize carbonates.

[0039] The sixth object of the present application is to provide a method for electrocatalytic conversion of carbon dioxide to carbonates, which is prepared by using carbon dioxide and electrolyte solvent as raw materials, and by using the electrode material, the palladium catalytic material supported by the nitrogen-doped carbon nanotube material prepared by using the nitrogen-containing polyionic liquid as precursor, and the electrolyte to perform constant potential electrolysis reaction in the electrolytic cell device to synthesize carbonates.

[0040] In the above method, the electrolyte is at least one selected from tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylammonium chloride, sodium bromide and potassium bromide, and the electrolyte solvent is at least one selected from methanol and ethanol, and specifically, tetrabutylammonium bromide methanol solution;

[0041] In the above method, the reaction device is a single electrolytic cell or an H-type electrolytic cell system, and specifically, a single electrolytic cell;

[0042] The potential of the electrolysis reaction can be -0.5 to -3 V vs.Ag / Ag + , and specifically, -1.5 V vs.Ag / Ag +

[0043] The electrolysis reaction time can be 0.1 to 100 h, and specifically, 50 h.

[0044] The reaction product includes dimethyl carbonate and diethyl carbonate.

[0045] The advantages and effects of the present application are as follows:

[0046] (1) The carbon nanotube catalytic material prepared by using the nitrogen-containing polyionic liquid as precursor is prepared by using the polyionic liquid as a template agent and a directing agent, which is beneficial to construct different carbon-nitrogen microstructures, provide adsorption sites at the catalytic interface, promote the adsorption and activation conversion of CO2, and inhibit the hydrogen evolution side reaction.

[0047] (2) The method is simple, and has good economy, controllability, operability and performance stability, and promotes the synthesis of carbonates under mild conditions.

[0048] (3) The palladium catalytic material supported by the carbon nanotube prepared by using the nitrogen-containing polyionic liquid as precursor can promote the dispersion of the catalytic site, prevent the agglomeration of the catalyst, improve the performance of the catalytic material, and promote the compatibility of the system, and exhibits excellent performance in the process of converting CO2 into carbonates. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 The scanning electron microscope (SEM) image of NCNT-PVCN-1

[0050] Figure 2 The scanning electron microscope-energy spectrum analysis (EDS Mapping) image of Pd / NCNT-PVCN-1 DETAILED DESCRIPTION

[0051] The technical solutions of the present application are further illustrated by the specific embodiments below. However, the present application is not limited to the following examples.

[0052] Example 1 Preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material

[0053] The preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material is taken as an example, with a molar ratio of 2-methyl-6-vinylpyridine dicyanamide salt to divinylbenzene being 1:1.

[0054] First, 10 mmol of 2-methyl-6-vinylpyridine dicyanamide salt and 10 mmol of divinylbenzene were dissolved in 50 mL of solvent, stirred at room temperature for 0.5 h, then 1 mmol of azobisisobutyronitrile was added as an initiator, the air was replaced with N2 by Schlenk technology, the temperature was raised to 70°C, and the reaction was carried out for 24 h. The solvent was separated by centrifugation, the crude product of polyionic liquid was washed with water and ethanol for 3 times, and dried at 50°C under vacuum for 24 h to obtain a white powder of polyionic liquid precursor. 0.3 g of polyionic liquid precursor and 0.2 g of carbon nanotubes were mixed and placed in a corundum boat, high-purity Ar was used as the protective gas, and the mixture was calcined at 800°C to obtain polyionic liquid-based nitrogen-doped carbon nanotube material (NCNT-PVCN-1).

[0055] The NCNT-PVCN-1 was systematically characterized, and the scanning electron microscope (SEM) image showed that the NCNT-PVCN-1 was composed of sheet-shaped particles stacked together. Figure 1 Elemental analysis (EA) showed the presence of nitrogen element, and the results are shown in the following table.

[0056]

[0057] Example 2 Preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material

[0058] The preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material is taken as an example, with a molar ratio of 2-methyl-6-vinylpyridine dicyanamide salt to divinylbenzene being 10:1.

[0059] Firstly, 10 mmol 2-methyl-6-vinylpyridine dicyanamide salt and 1 mmol divinylbenzene were dissolved in 50 mL solvent, stirred at room temperature for 0.5 h, then 1 mmol azobisisobutyronitrile was added as an initiator, air was replaced by N2 through Schlenk technology, the temperature was raised to 70°C, and the reaction was carried out for 24 h. The solvent was separated by centrifugation, and the crude product of polyionic liquid was obtained. The product was washed with water and ethanol for 3 times, and dried at 50°C under vacuum for 24 h to obtain white powder polyionic liquid precursor. 0.3 g of polyionic liquid precursor and 0.2 g of carbon nanotubes were mixed and placed in a corundum boat, high-purity Ar was used as protective gas, and the mixture was calcined at 800°C to obtain polyionic liquid-based nitrogen-doped carbon nanotube material (NCNT-PVCN-10).

[0060] Example 3 Preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material

[0061] The preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material with a molar ratio of 2-methyl-6-vinylpyridine bromide salt to divinylbenzene of 1:1 is taken as an example.

[0062] Firstly, 10 mmol 2-methyl-6-vinylpyridine bromide salt and 10 mmol divinylbenzene were dissolved in 50 mL solvent, stirred at room temperature for 0.5 h, then 1 mmol azobisisobutyronitrile was added as an initiator, air was replaced by N2 through Schlenk technology, the temperature was raised to 70°C, and the reaction was carried out for 24 h. The solvent was separated by centrifugation, and the crude product of polyionic liquid was obtained. The product was washed with water and ethanol for 3 times, and dried at 50°C under vacuum for 24 h to obtain white powder polyionic liquid precursor. 0.3 g of polyionic liquid precursor and 0.2 g of carbon nanotubes were mixed and placed in a corundum boat, high-purity Ar was used as protective gas, and the mixture was calcined at 800°C to obtain polyionic liquid-based nitrogen-doped carbon nanotube material (NCNT-PVBr-1).

[0063] Example 4 Preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material

[0064] The preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material with a molar ratio of 2-methyl-6-vinylpyridine tetrafluoroborate to divinylbenzene of 1:1 is taken as an example.

[0065] First, 10 mmol of 2-methyl-6-vinylpyridine tetrafluoroborate and 10 mmol of divinylbenzene were dissolved in 50 mL of solvent, stirred at room temperature for 0.5 h, then 1 mmol of azobisisobutyronitrile was added as an initiator, the air was replaced by N2 by Schlenk technique, the temperature was raised to 70°C and reacted for 24 h, the solvent was separated by centrifugation, the crude product of polyionic liquid was obtained, washed with water and ethanol for 3 times, and dried at 50°C under vacuum for 24 h to obtain white powder of polyionic liquid precursor. 0.3 g of polyionic liquid precursor and 0.2 g of carbon nanotubes were mixed and placed in a corundum boat, high-purity Ar was used as protective gas, and calcination was carried out at 800°C to obtain polyionic liquid-based nitrogen-doped carbon nanotube material (NCNT-PVBF4-1).

[0066] Example 5 Preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material

[0067] The preparation of polyionic liquid-based nitrogen-doped carbon nanotube catalytic material was taken as an example with a molar ratio of 2-methyl-6-vinylpyridine 2,4-dihydroxypyrimidine-5-carboxylate and divinylbenzene being 1:1.

[0068] First, 10 mmol of 2-methyl-6-vinylpyridine tetrafluoroborate and 10 mmol of divinylbenzene were dissolved in 50 mL of solvent, stirred at room temperature for 0.5 h, then 1 mmol of azobisisobutyronitrile was added as an initiator, the air was replaced by N2 by Schlenk technique, the temperature was raised to 70°C and reacted for 24 h, the solvent was separated by centrifugation, the crude product of polyionic liquid was obtained, washed with water and ethanol for 3 times, and dried at 50°C under vacuum for 24 h to obtain white powder of polyionic liquid precursor. 0.3 g of polyionic liquid precursor and 0.2 g of carbon nanotubes were mixed and placed in a corundum boat, high-purity Ar was used as protective gas, and calcination was carried out at 800°C to obtain polyionic liquid-based nitrogen-doped carbon nanotube material (NCNT-PVBF4-1).

[0069] Example 6 Method for preparing nitrogen-containing polyionic liquid-doped carbon material loaded Pd catalytic material

[0070] Firstly, 0.5 g of NCNT-PVCN-1 was placed in 50 mL of 10% nitric acid solution, heated to 80°C and stirred to reflux for 4 h. After reflux, it was washed with deionized water until neutral. 5 mg of palladium chloride was dissolved in 1 mL of hydrochloric acid solution, diluted with 20 mL of water, and then added to the treated NCNT-PVCN-1 solution. After stirring for 2 h, 150 mg of sodium borohydride was dissolved in 10 mL of water and slowly added to the solution. After stirring for 2 h, the solution was centrifuged, washed with deionized water until neutral, and vacuum dried at 60°C for 12 h to obtain Pd / NCNT-PVCN-1.

[0071] The same method was used to prepare Pd / NCNT-PVCN-1, Pd / NCNT-PVBr-1, Pd / NCNT-PVBF4-1, and Pd / NCNT-PVPym)-1.

[0072] The NCNT-PVCN-1 was characterized by scanning electron microscopy (SEM), which showed that Pd / NCNT-PVCN-1 was composed of nanoparticles accumulated on the surface of the catalyst. Figure 2 The elemental distribution map (EDS Mapping) showed that the Pd element was uniformly distributed on the surface of the catalyst. Figure 2

[0073] Example 7: Application of electrode material and second catalyst in CO2 electrocatalytic synthesis of carbonates

[0074] The NCNT-PVCN-1 and gas diffusion layer were used as electrode materials, and Pd / NCNT-PCN-1-1 was used as a second catalyst to construct an electro-synthesis system.

[0075] To prepare the working electrode, 1.5 mg of NCNT-PCN-1 catalyst was dispersed in 10 μL of Nafion 117 dispersion solution (5 wt%) and 0.5 mL of isopropyl alcohol, and ultrasonicated for 30 min to make it uniformly dispersed. The dispersion was uniformly dropped onto the surface of the gas diffusion layer carbon fiber paper, and left to stand at room temperature for 12 h. The loading amount of catalyst on each electrode was 1 mg / cm 2 .

[0076] The electrolysis experiment was carried out at 25°C. The electrolysis cell device used was a three-electrode single cell system, which included the above working electrode, a glassy carbon counter electrode, and an Ag / Ag + reference electrode. The electrolyte was 0.1 M tetrabutylammonium bromide / methanol solution, and the amount of electrolyte used was 10 mL. 50 mg of Pd / NCNT-PVCN-1 catalyst was added as a second catalyst. First, CO2 gas was introduced for 0.5 h to saturate the electrolyte, and then the electrolysis cell was sealed to start the electrocatalytic synthesis of carbonates. The potential range was -2.0 V vs. Ag / Ag​+ The electrolysis time was 1 h. The liquid product was analyzed by gas chromatography (GC, Agilent 8890), and the faradaic efficiency of dimethyl carbonate was 59.3%.

[0077] Example 8 Application of electrode material and second catalyst in CO2 electrocatalytic synthesis of carbonate system

[0078] The difference from Example 7 is that NCNT-PVCN-1 in the electrode material is replaced by NCNT-PVBr-1, and Pd / NCNT-PVCN-1 in the second catalyst is replaced by Pd / NCNT-PVBr-1. The faradaic efficiency of dimethyl carbonate is 55.8%.

[0079] Example 9 Application of electrode material and second catalyst in CO2 electrocatalytic synthesis of carbonate system

[0080] The difference from Example 7 is that NCNT-PVCN-1 in the electrode material is replaced by NCNT-PVBF4-1, and Pd / NCNT-PVCN-1 in the second catalyst is replaced by Pd / NCNT-PVBF4-1. The faradaic efficiency of dimethyl carbonate is 51.7%.

[0081] Example 10 Application of electrode material and second catalyst in CO2 electrocatalytic synthesis of carbonate system

[0082] The difference from Example 7 is that NCNT-PVCN-1 in the electrode material is replaced by NCNT-PVPymAc-1, and Pd / NCNT-PVCN-1 in the second catalyst is replaced by Pd / NCNT-PVPymAc-1. The faradaic efficiency of dimethyl carbonate is 49.9%.

[0083] Example 11 Application of potassium bromide as electrolyte in CO2 electrocatalytic synthesis of carbonate system

[0084] The difference from Example 7 is that the electrolyte used is 0.1M potassium bromide / methanol, and other conditions remain unchanged. The faradaic efficiency of dimethyl carbonate is 60.4%.

[0085] Example 12 Application of extending the electrolysis time to 6h in CO2 electrocatalytic synthesis of carbonate system

[0086] The difference from Example 7 is that the electrolysis reaction time is extended to 6h, and other conditions remain unchanged. The faradaic efficiency of dimethyl carbonate is 66.2%.

[0087] Example 13 Application of using ethanol as solvent in CO2 electrocatalytic synthesis of carbonate system

[0088] The difference from Example 7 is that the electrolyte used is 0.1 M tetrabutylammonium bromide in ethanol, and the other conditions are the same, and the faradaic efficiency of diethyl carbonate is 39.2%.

[0089] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any modification, equivalent replacement, improvement, etc. made by any person skilled in the art within the technical scope disclosed by the present application should be included in the protection scope of the present application.

Claims

1. A method for synthesizing carbonate esters by electrocatalytic reaction using CO2 as raw material, characterized in that: The method comprises the following steps: using a polyionic liquid-based nitrogen-doped carbon nanotube material as a first catalyst, the first catalyst and a gas diffusion layer forming an electrode material, adding a second catalyst into an electrolyte, wherein the second catalyst is a polyionic liquid-based nitrogen-doped carbon nanotube material loaded with palladium, and the ratio of the second catalyst to the electrolyte is 1 to 100 mg:10 mL; the electrolyte comprises a supporting electrolyte and an electrolyte solvent, wherein the supporting electrolyte is selected from at least one of tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylammonium chloride, sodium bromide and potassium bromide; methanol or ethanol serves as both an electrolyte solvent and a reactant; and a constant potential electrolysis reaction is performed in an electrolytic cell reaction device through the action of the electrode material, the second catalyst and the electrolyte to synthesize carbonate; and the potential of the electrolysis reaction is -0.5 to -3 V vs. Ag / Ag. + ; The electrolysis reaction time is 0.1 to 100 h; The synthesis method of the first catalyst is: 1) dissolving a vinyl-containing ionic liquid monomer and divinylbenzene in a solvent, introducing nitrogen to replace the gas and stirring; 2) Add azobisisobutyronitrile as an initiator, raise the temperature to 70°C, and conduct polymerization for 24 hours; 3) After the reaction is completed, the crude product in the above system is centrifuged, washed, and dried to obtain a polyionic liquid precursor; 4) mixing the polyionic liquid precursor and the carbon nanotubes in a corundum boat, using high-purity argon as a protective gas, and calcining at a high temperature to obtain a polyionic liquid-based nitrogen-doped carbon nanotube material; The vinyl-containing ionic liquid monomers include 2-methyl-6-vinylpyridine dicyanamide, 2-methyl-6-vinylpyridine bromide, and 2-methyl-6-vinylpyridine tetrafluoroborate; The molar ratio of the vinyl-containing ionic liquid monomer to divinylbenzene is 1:1 to 10:

1.

2. The method according to claim 1, characterized in that: Step 1) of the synthesis method of the first catalyst is: dissolving 10 mmol of vinyl-containing ionic liquid monomer and divinylbenzene in 50 mL of solvent, introducing nitrogen to replace the gas and stirring for 0.5 h; Step 1) The solvent includes one or more of methanol, ethanol, and acetonitrile; Step 3) The washing solvent is one or more of methanol, ethanol and deionized water; Step 3) The drying temperature is 40-100°C and the drying time is 10-48 hours.

3. An electrode material comprising the polyionic liquid-based nitrogen-doped carbon nanotube material according to claim 1 and a gas diffusion layer.

4. The electrode material according to claim 3, characterized in that The method for preparing the electrode material comprises the following steps: Dispersing the polyionic liquid-based nitrogen-doped carbon nanotube material in a solvent, adding Nafion 117 dispersion as a binder to obtain a dispersion, and applying the dispersion dropwise onto the gas diffusion layer to obtain the electrode material; The solvent is selected from at least one of acetone, ethanol, isopropanol and deionized water; The catalyst ratio of the Nafion 117 dispersion to the polyionic liquid-based nitrogen-doped carbon material is 10-100 μL:1 mg; In the electrode material, the gas diffusion layer is selected from at least one of carbon fiber paper, carbon fiber woven cloth and carbon black paper; On the gas diffusion layer, the amount of the polyionic liquid-based nitrogen-doped carbon nanotube material is 0.1-10 mg / cm 2 .

5. The second catalyst used in the method for synthesizing carbonate according to claim 1, wherein the second catalyst is a polyionic liquid-based nitrogen-doped carbon nanotube material supported on palladium, characterized in that: The preparation method of the second catalyst comprises the following steps: 1) stirring and refluxing the polyionic liquid-based nitrogen-doped carbon nanotube material of claim 1 in a 10% nitric acid solution for 4 h at a heating temperature of 80° C., and washing with deionized water until neutral after the reflux; 2) dissolving the palladium compound in a 10% hydrochloric acid solution, adding the polyionic liquid-based nitrogen-doped carbon nanotube material treated in step 1), and stirring and impregnating for 2 hours; 3) Dissolve sodium borohydride in deionized water, add to the solution in step 2), and stir to reduce for 2 h; 4) Centrifuging, washing, and drying the above product to obtain polyionic liquid-based nitrogen-doped carbon nanotube material loaded with palladium.

6. The second catalyst used in the method for synthesizing carbonate according to claim 5, characterized in that: The palladium compound is one of palladium chloride and sodium tetrachloropalladate (II); The palladium mass fraction is 1% to 20%; The molar ratio of sodium borohydride to palladium is 1:1 to 10:1; The washing solvent is one or more of methanol, ethanol and deionized water; The drying temperature is 40-100° C., and the drying time is 10-48 h.

7. An electrocatalytic system for synthesizing carbonates using CO2 as a raw material through an electrocatalytic reaction, comprising the electrode material of claim 3 or 4, the second catalyst of claim 5 or 6, a reaction electrolyte, and a reaction apparatus; the reaction electrolyte comprises a supporting electrolyte and an electrolyte solvent, the supporting electrolyte being selected from at least one of tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylammonium chloride, sodium bromide, and potassium bromide, and the electrolyte solvent being selected from at least one of methanol and ethanol; The concentration of the reaction electrolyte is 0.1 to 10 M; The ratio of the second catalyst to the electrolyte is 1-100 mg:10 mL; The reaction device is one of a single cell and an H-type electrolytic cell.

8. Use of the electrode material according to claim 3 or 4, the second catalyst according to claim 5 or 6, and the electrocatalytic system according to claim 7 in the electrocatalytic synthesis of organic carbonates from carbon dioxide.

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