Electrocatalytic system for the synthesis of carbonates and use thereof

Abstract

The present application relates to a kind of for synthesizing carbonate electrocatalytic system and its application.The electrocatalytic system includes working electrode, counter electrode, reference electrode, electrolyte and reaction device;The working electrode includes first catalyst and gas diffusion layer;Second catalyst and solvent are included in the electrolyte;The preparation method of the first catalyst includes the following steps: (1) ion liquid monomer, divinylbenzene are mixed with initiator in solvent, and polymerization reaction is carried out, to obtain polyionic liquid precursor;(2) polyionic liquid precursor is calcined, to obtain the first catalyst;Second catalyst includes palladium carbon material;The solvent includes C1-C2 alcohol.The present application is designed by electrocatalytic system, obtains a kind of in-situ self-optimizing deposition system, breaks the static limitation of traditional pre-catalyst.

Description

Technical Field

[0001] This invention relates to the field of energy materials and electrochemistry, and in particular to an electrocatalytic system for the synthesis of carbonates and its applications. Background Technology

[0002] As a major greenhouse gas, excessive accumulation of CO2 has caused severe environmental problems. However, CO2 is also an abundant, inexpensive, and non-toxic renewable C1 resource, making its transformation into high-value-added chemicals of great significance. Carbonates are core raw materials for industries such as power battery electrolytes and polycarbonates, and developing their green synthesis technology is crucial for the new energy and information technology industries.

[0003] The direct synthesis of carbonates from CO2 and lower alcohols is the mainstream resource utilization route. Thermal synthesis techniques suffer from thermodynamic disadvantages and demanding reaction conditions, while electrocatalysis can overcome these thermodynamic barriers and aligns with the dual-carbon trend. However, existing electrocatalytic systems face core bottlenecks: numerous hydrogen evolution side reactions, low catalytic selectivity, and traditional methods rely on pre-supported catalysts, which suffer from active site aggregation, weak catalytic interface bonding, and inability to adapt to dynamic reaction changes, resulting in generally low Faraday efficiencies. Metal-free carbon-based catalysts are ideal supports due to their high specific surface area and conductivity, but pure carbon materials have weak CO2 adsorption and activation capabilities. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide an electrocatalytic system for the synthesis of carbonates and its applications. Through the design of the electrocatalytic system, an in-situ self-optimizing deposition system is obtained, overcoming the static limitations of traditional pre-prepared catalysts. It eliminates the need for pre-prepared cathode metal catalysts, dynamically releasing Pd active species during the reaction via palladium-on-carbon material. These species are then targeted and self-assembled on the PIL-NC surface to form an optimal catalytic interface, achieving real-time adaptation of catalytic performance. This solves both the problems of active site aggregation and interfacial bonding, significantly suppresses hydrogen evolution side reactions, and greatly improves the synthesis efficiency and stability of dimethyl carbonate, providing a novel technical pathway for the efficient resource utilization of CO2.

[0005] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides an electrocatalytic system for synthesizing carbonates, the electrocatalytic system comprising a working electrode, a counter electrode, a reference electrode, an electrolyte, and a reaction apparatus; the working electrode comprising a first catalyst and a gas diffusion layer; and the electrolyte comprising a second catalyst and a solvent. The first catalyst is a polyionic liquid-based nitrogen-doped carbon material; The second catalyst comprises palladium on carbon; the solvent comprises C1-C2 alcohols.

[0006] In this invention, the palladium-on-carbon material serves a dual function as both a carbonylation catalyst and an in-situ deposited Pd metal source. Polyionic liquids (PILs) possess advantages such as high thermal stability and designable structure; heteroatom doping improves their electronic structure and surface activity. The first catalyst is a PIL-based nitrogen-doped carbon material (PIL-NC), providing abundant CO2 activation sites. During constant-potential electrolysis, a reduction potential is applied to the cathode to drive the in-situ carbonylation reaction. Simultaneously, the second catalyst, while catalyzing carbonate synthesis, releases Pd species under the reduction potential. These Pd species are specifically captured, deposited, and self-assembled by the nitrogen-doped sites on the PIL-NC surface to form a PIL-NC-Pd composite catalytic interface. This in-situ constructed active interface, together with the gas diffusion layer, constitutes an electrode material with highly efficient catalytic performance. Through the synergistic effect of the in-situ constructed electrode material and the system, the electrochemical reaction of CO2 and lower alcohols to synthesize carbonates is catalyzed, achieving dynamic self-optimization of catalytic performance.

[0007] During constant-potential electrolysis, the Pd element is released in situ from the palladium-on-carbon material and captured and deposited by nitrogen-doped sites on the PIL-NC surface, thereby self-assembling to form a PIL-NC-Pd composite catalytic interface, resulting in a new electrode material deposited in situ. This composite catalytic interface forms the core catalytic layer of the electrode material.

[0008] Preferably, the first catalyst is obtained by calcining the polymerization of an ionic liquid monomer with divinylbenzene.

[0009] Preferably, the ionic liquid monomer comprises any one or a combination of at least two of 1-vinyl-3-methylimidazolium bromide (VimBr), 1-vinyl-3-methylimidazolium dicyandiamide (VimCN), 1-vinyl-3-methylimidazolium tetrafluoroborate (VimBF4), or 1-vinyl-3-methylimidazolium hexafluorophosphate (VimPF6).

[0010] In this invention, PVimBr-NC-1 has the highest pyrrole nitrogen content, which can generate stronger interfacial interactions with Pd, effectively promoting the conversion of CO2 to CO intermediates, thereby significantly improving the catalytic generation performance of DMC.

[0011] Preferably, the molar ratio of the ionic liquid monomer to divinylbenzene is (1-10):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1, etc.

[0012] Preferably, the preparation method of the first catalyst includes the following steps: (1) The ionic liquid monomer, divinylbenzene and initiator are mixed in a solvent and polymerized to obtain a polyionic liquid precursor; (2) The polyionic liquid precursor was calcined to obtain the first catalyst.

[0013] Preferably, the step (1) of mixing the ionic liquid monomer, divinylbenzene and initiator in a solvent is as follows: dissolve the ionic liquid monomer and divinylbenzene in a solvent, and then add the initiator.

[0014] Preferably, the initiator comprises azobisisobutyronitrile.

[0015] Preferably, the polymerization reaction in step (1) is carried out under nitrogen protection.

[0016] Preferably, the polymerization reaction time in step (1) is 20-28 h, for example, it can be 21 h, 22 h, 23 h, 24 h, 25 h, 26 h or 27 h.

[0017] Preferably, the polymerization reaction temperature in step (1) is 60-80℃, for example, it can be 65℃, 68℃, 70℃, 73℃ or 75℃.

[0018] Preferably, the polymerization reaction in step (1) is followed by a post-processing step, wherein the post-processing method includes centrifugation, washing, and vacuum drying.

[0019] Preferably, the vacuum drying temperature is 50-70°C, for example, it can be 55°C, 58°C, 60°C, 63°C or 65°C.

[0020] Preferably, the vacuum drying time is 10-14 h, for example, it can be 11 h, 11.5 h, 12 h, 12.5 h or 13 h.

[0021] Preferably, the solvent used for washing includes any one or a combination of at least two of methanol, ethanol, or deionized water, with ethanol being more preferred.

[0022] Preferably, the solvent in step (1) includes any one or a combination of at least two of methanol, ethanol or acetonitrile.

[0023] Preferably, the calcination is carried out under argon protection.

[0024] Preferably, the calcination is carried out in a corundum boat.

[0025] Preferably, the calcination temperature is 800-1000℃, for example, it can be 850℃, 880℃, 900℃, 930℃ or 950℃.

[0026] Preferably, the calcination time is 1-10 h, for example, it can be 2 h, 4 h, 5 h, 6 h or 8 h, etc.

[0027] Preferably, the preparation method of the first catalyst includes the following steps: (1) Dissolve 8-12 mmol (e.g., 9 mmol, 9.5 mmol, 10 mmol, 10.5 mmol or 11 mmol, etc.) of ionic liquid monomer and 1-12 mmol (e.g., 2 mmol, 4 mmol, 6 mmol, 8 mmol or 10 mmol, etc.) of divinylbenzene in 40-60 mL (e.g., 45 mL, 48 mL, 50 mL, 53 mL or 55 mL, etc.), purge with nitrogen gas to replace the gas and stir for 0.4-0.6 h (e.g., 0.45 h, 0.48 h, 0.5 h, 0.53 h or 0.55 h, etc.); add azobisisobutyronitrile as an initiator to carry out a polymerization reaction to obtain a polyionic liquid precursor; (2) The polyionic liquid precursor was calcined to obtain the first catalyst.

[0028] Preferably, the working electrode includes a cathode.

[0029] Preferably, the method for preparing the working electrode includes the following steps: The first catalyst is dispersed in a solvent, a binder is added to obtain a dispersion, and the dispersion is coated onto a gas diffusion layer to obtain the working electrode.

[0030] Preferably, the mass concentration of the first catalyst in the dispersion is 5-10 mg / mL, for example, it can be 6 mg / mL, 7 mg / mL, 7.5 mg / mL, 8 mg / mL or 9 mg / mL, etc.

[0031] Preferably, the process of coating the dispersion onto the gas diffusion layer further includes a post-processing step, wherein the post-processing method includes drying.

[0032] Preferably, the drying temperature is 10-40℃, for example, it can be 15℃, 20℃, 25℃, 30℃ or 35℃, etc.

[0033] Preferably, the drying time is 10-14 hours. For example, it can be 11 hours, 11.5 hours, 12 hours, 12.5 hours, or 13 hours.

[0034] Preferably, the binder comprises a Nafion 117 dispersion.

[0035] Preferably, the coating method includes drop coating.

[0036] Preferably, the solvent in which the first catalyst is dispersed includes any one or a combination of at least two of acetone, ethanol, isopropanol, or deionized water, with isopropanol being more preferred.

[0037] Preferably, the ratio of the volume of the Nafion 117 dispersion to the mass of the first catalyst is 10-100 μL / mg, for example, it can be 20 μL / mg, 30 μL / mg, 40 μL / mg, 50 μL / mg, 60 μL / mg or 80 μL / mg, and more preferably 10-50 μL / mg.

[0038] Preferably, the gas diffusion layer comprises any one or a combination of at least two of carbon fiber paper, carbon fiber woven fabric, or carbon black paper, with carbon fiber paper being more preferred.

[0039] Preferably, the amount of the first catalyst on the gas diffusion layer is 0.1-10 mg / cm³. 2 For example, it could be 0.5 mg / cm³. 2 1 mg / cm 2 2 mg / cm 2 4 mg / cm 2 5 mg / cm 2 6 mg / cm 2 Or 8 mg / cm 2 Further optimization was performed using 0.5-2 mg / cm³. 2 .

[0040] Preferably, the palladium-carbon material is prepared by loading a palladium compound onto a carbon-based material.

[0041] Preferably, the carbon-based material includes any one or a combination of at least two of activated carbon, carbon nanotubes, or carbon black, with activated carbon being more preferred.

[0042] In this invention, activated carbon-supported Pd material enables slow and controllable dissolution of Pd under an electric field, with a dissolution rate significantly lower than that of carbon black and carbon nanotube-supported systems. Thanks to the strong metal-support interaction and pore confinement effect between activated carbon and Pd, Pd is not easily lost rapidly but dissolves gradually in a mild manner, which is more conducive to maintaining stable catalytic active centers and thus improving the stability of the electrocatalytic reaction.

[0043] Preferably, the palladium compound includes any one or a combination of at least two of palladium chloride, palladium acetate, or palladium nitrate.

[0044] Preferably, the mass fraction of Pd in ​​the palladium-carbon material is 5%-20%, for example, it can be 8%, 10%, 12%, 14%, 16% or 18%, etc.

[0045] Preferably, the electrolyte further includes an electrolyte.

[0046] Preferably, the electrolyte comprises any one or a combination of at least two of sodium bromide, potassium bromide, tetrabutylammonium bromide, tetrabutylammonium iodide, or tetrabutylammonium chloride.

[0047] In this invention, sodium bromide has a high charge density and excellent ionic radius adaptability, allowing it to exist stably in the methanol system and efficiently participate in interfacial ion transport, thus maintaining the Br content. - The stable operation of the Br2 redox cycle provides a stable electrolyte environment for the electrocatalytic synthesis of DMC from CO2.

[0048] Preferably, the C1-C2 alcohols include methanol and / or ethanol.

[0049] In this invention, low-carbon alcohol solvents (such as methanol and ethanol) serve both as solvents for the electrolyte and as reactants for the synthesis of carbonates.

[0050] Preferably, the concentration of the electrolyte in the electrolyte solution is 0.1-10 M, for example, it can be 2 M, 4 M, 5 M, 6 M or 8 M, etc.

[0051] Preferably, the mass ratio of the second catalyst to the volume of the electrolyte is 0.1-10 mg / mL, for example, it can be 2 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL or 8 mg / mL, etc.

[0052] Preferably, the reaction device is a single electrolytic cell or an H-type electrolytic cell, and more preferably a single electrolytic cell.

[0053] Preferably, the counter electrode comprises a glassy carbon counter electrode.

[0054] Preferably, the reference electrode comprises an Ag / AgCl reference electrode.

[0055] Preferably, the carbonate comprises dimethyl carbonate and / or diethyl carbonate.

[0056] In a second aspect, the present invention provides a method for synthesizing carbonates, the method comprising the following steps: passing carbon dioxide into an electrocatalytic system as described in the first aspect to carry out an electrolytic reaction to obtain the carbonates.

[0057] Preferably, the potential of the electrolysis reaction is -1.2 to -3.0 V vs Ag / AgCl, for example, it can be -1.3 V, -1.4 V, -1.5 V, -1.6 V, -1.7 V, -1.8 V, -1.9 V, 2.0 V, 2.3 V, 2.5 V or 2.8 V, etc.

[0058] Preferably, the temperature of the electrolysis reaction is 25-30°C, for example, it can be 26°C, 27°C, 27.5°C, 28°C or 29°C.

[0059] Preferably, the electrolysis reaction time is 0.1-100 h, for example, it can be 1 h, 2 h, 3 h, 3.5 h, 4 h, 5 h, 6 h, 20 h, 40 h, 50 h, 60 h or 80 h, and more preferably 1-6 h.

[0060] Preferably, the pressure of the electrolysis reaction is 90-110 kPa, for example, it can be 95 kPa, 100 kPa, 101.325 kPa, 105 kPa or 108 kPa.

[0061] Preferably, the electrolysis reaction includes a constant potential electrolysis reaction.

[0062] Compared with the prior art, the present invention has at least the following beneficial effects: (1) PIL-NC material was prepared by using polyionic liquid as a precursor. Its abundant nitrogen doping sites can specifically capture Pd active species, provide a targeted substrate for in-situ self-optimized deposition, promote CO2 adsorption and activation, and significantly inhibit hydrogen evolution side reaction.

[0063] (2) This invention innovatively constructs an in-situ self-optimizing deposition system, which does not require the pre-preparation of cathode metal catalysts. The palladium carbon material has the dual role of carbonylation catalyst and Pd metal source and can realize Pd release-targeted capture-self-assembly optimization in one step. The process is simplified, the operation is controllable, and the economy is outstanding.

[0064] (3) The PIL-NC-Pd composite catalytic interface formed in situ dynamically adapts to the reaction environment, avoids the aggregation of Pd particles, has a tight interface bond, stable catalytic performance, and the Faraday efficiency of carbonate is above 75%.

[0065] (4) The reaction is carried out at room temperature and pressure, with mild conditions and low energy consumption. It is compatible with a variety of supporting electrolytes and low-carbon alcohol raw materials, providing an efficient and green technical path for the utilization of CO2 resources. Attached Figure Description

[0066] Figure 1 This is a schematic diagram of the self-optimized in-situ deposition process of Pd on the PvimBr-NC electrode.

[0067] Figure 2 This is a transmission electron microscope (TEM)-energy dispersive spectroscopy (EDS) image of PvimBr-NC-Pd. Detailed Implementation

[0068] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0069] The sources of some of the raw materials used in the following examples are as follows: The palladium-supported activated carbon material was purchased from Sigma, item number 205699.

[0070] The Nafion 117 dispersion was purchased from Sigma, catalog number 70160.

[0071] The palladium supported on carbon nanotubes was purchased from Sigma, grade 755131.

[0072] The palladium-supported carbon black was purchased from Sigma, grade 940321.

[0073] Preparation Example 1 A first catalyst, the preparation method of the first catalyst comprising the following steps: (1) Dissolve 10 mmol of 1-vinyl-3-methylimidazolium bromide and 10 mmol of divinylbenzene in 50 mL of acetonitrile, stir at 25 °C for 0.5 h, then add 1 mmol of azobisisobutyronitrile as an initiator, replace the air with N2 using the Schlenk technique, heat to 70 °C and react for 24 h, centrifuge to separate the solvent, and obtain the crude polyionic liquid product. Wash repeatedly with water and ethanol 3 times, and vacuum dry at 50 °C for 24 h to obtain a white powdery polyionic liquid precursor. (2) The polyionic liquid precursor was placed in a corundum boat and calcined at 900°C using high-purity Ar as a protective gas to obtain the first catalyst (PVimBr-NC-1).

[0074] Preparation Example 2 A first catalyst, the preparation method of the first catalyst comprising the following steps: (1) Dissolve 10 mmol of 1-vinyl-3-methylimidazolium bromide and 1 mmol of divinylbenzene in 50 mL of methanol, stir at 25 °C for 0.5 h, then add 1 mmol of azobisisobutyronitrile as an initiator, replace the air with N2 using the Schlenk technique, heat to 70 °C and react for 24 h, centrifuge to separate the solvent to obtain the crude polyionic liquid product, wash repeatedly with water and ethanol 3 times, and vacuum dry at 50 °C for 24 h to obtain a white powdery polyionic liquid precursor; (2) The polyionic liquid precursor was placed in a corundum boat and calcined at 900°C using high-purity Ar as a protective gas to obtain the first catalyst (PVimBr-NC-10).

[0075] Preparation Example 3 A first catalyst, the preparation method of the first catalyst comprising the following steps: (1) Dissolve 10 mmol of 1-vinyl-3-methylimidazolium dicyandiamide salt and 10 mmol of divinylbenzene in 50 mL of acetonitrile, stir at 25 °C for 0.5 h, then add 1 mmol of azobisisobutyronitrile as an initiator, replace the air with N2 using the Schlenk technique, heat to 70 °C and react for 24 h, centrifuge to separate the solvent, and obtain the crude polyionic liquid product. Wash repeatedly with water and ethanol 3 times, and vacuum dry at 50 °C for 24 h to obtain a white powdery polyionic liquid precursor. (2) The polyionic liquid precursor was placed in a corundum boat and calcined at 900°C using high-purity Ar as a protective gas to obtain the first catalyst (PVimCN-NC-1).

[0076] Preparation Example 4 A first catalyst, the preparation method of the first catalyst comprising the following steps: (1) 10 mmol of 1-vinyl-3-methylimidazolium tetrafluoroborate and 10 mmol of divinylbenzene were dissolved in 50 mL of acetonitrile and stirred at 25 °C for 0.5 h. Then 1 mmol of azobisisobutyronitrile was added as an initiator. The air was replaced with N2 using the Schlenk technique and the temperature was raised to 70 °C for 24 h. The solvent was separated by centrifugation to obtain the crude polyionic liquid product. The product was washed three times with water and ethanol and dried under vacuum at 50 °C for 24 h to obtain a white powdery polyionic liquid precursor. (2) The polyionic liquid precursor was placed in a corundum boat and calcined at 900°C using high-purity Ar as a protective gas to obtain the first catalyst (PVimBF4-NC-1).

[0077] Preparation Example 5 A first catalyst, the preparation method of the first catalyst comprising the following steps: (1) Dissolve 10 mmol of 1-vinyl-3-methylimidazolium hexafluorophosphate and 10 mmol of divinylbenzene in 50 mL of acetonitrile, stir at 25 °C for 0.5 h, then add 1 mmol of azobisisobutyronitrile as an initiator, replace the air with N2 using the Schlenk technique, heat to 70 °C and react for 24 h, centrifuge to separate the solvent, and obtain the crude polyionic liquid product. Wash repeatedly with water and ethanol 3 times, and vacuum dry at 50 °C for 24 h to obtain a white powdery polyionic liquid precursor. (2) The polyionic liquid precursor was placed in a corundum boat and calcined at 900°C using high-purity Ar as a protective gas to obtain the first catalyst (PVimPF6-NC-1).

[0078] Example 1 A method for synthesizing a carbonate, the method comprising the following steps: (1) Construction of the electrocatalytic system: The electrocatalytic system is a three-electrode single electrolytic cell system. The three electrodes include a working electrode, a glassy carbon counter electrode, and an Ag / AgCl reference electrode. The electrolyte is a 0.1 M sodium bromide / methanol solution with a volume of 10 mL. 60 mg of activated carbon-supported palladium material (10 wt% Pd) is added to the electrolyte as a metal precursor.

[0079] 1.5 mg of PVimBr-NC-1 catalyst was dispersed together with 10 μL of Nafion 117 dispersion (5 wt%) in 0.5 mL of isopropanol and sonicated for 30 min to ensure uniform dispersion. The dispersion was then uniformly drop-coated onto the surface of the carbon fiber paper gas diffusion layer and allowed to stand at 25 °C for 12 h. The catalyst loading at each electrode was 1 mg / cm³. 2 .

[0080] (2) Electrolysis reaction CO2 gas was introduced into the electrocatalytic system for 0.5 h to saturate the electrolyte. Then, the electrocatalytic synthesis of carbonates was initiated in a sealed electrolytic cell. During electrolysis, palladium in the palladium-on-carbon material was released in situ and self-assembled on the PVimBr-NC surface to form a PVimBr-NC-Pd composite catalytic interface. The electrolysis potential was -2.0 V vs. Ag / AgCl, the electrolysis time was 1 h, and the electrolysis temperature was 25 °C. The liquid product was analyzed by gas chromatography (GC, Agilent 8890), and the Faraday efficiency of dimethyl carbonate was 75.3%.

[0081] Example 2 A method for synthesizing a carbonate, differing from Example 1 only in that PVimBr-NC-1 in the electrode material is replaced with the same mass of PVimCN-NC-1, and the Faraday efficiency of the dimethyl carbonate is 72.8%.

[0082] Example 3 A method for synthesizing a carbonate, differing from Example 1 only in that PVimBr-NC-1 in the electrode material is replaced with the same mass of PVimBF4-NC-1, and the Faraday efficiency of the dimethyl carbonate is 71.7%.

[0083] Example 4 A method for synthesizing carbonate, differing from Example 1 only in that PVimBr-NC-1 in the electrode material is replaced with the same mass of PVimPF6-NC-1, and the Faraday efficiency of dimethyl carbonate is 69.9%.

[0084] Example 5 A method for synthesizing carbonates differs from Example 1 only in that the palladium supported on activated carbon is replaced with palladium supported on carbon nanotubes of the same mass, and the Faraday efficiency of dimethyl carbonate is 26.4%.

[0085] Example 6 A method for synthesizing carbonates differs from Example 1 only in that the palladium supported on activated carbon is replaced with the same mass of palladium supported on carbon black, and the Faraday efficiency of dimethyl carbonate is 21.2%.

[0086] Example 7 A method for synthesizing carbonates differs from Example 1 only in that the 0.1 M sodium bromide / methanol electrolyte is replaced with the same amount of 0.1 M potassium bromide / methanol solution, and the Faraday efficiency of dimethyl carbonate is 69.4%.

[0087] Example 8 A method for synthesizing carbonates differs from Example 1 only in that the 0.1 M sodium bromide / methanol solution is replaced with the same amount of 0.1 M tetrabutylammonium chloride / methanol solution, and the Faraday efficiency of dimethyl carbonate is 33.4%.

[0088] Example 9 A method for synthesizing carbonates differs from Example 1 only in that the 0.1 M sodium bromide / methanol solution is replaced with the same amount of 0.1 M tetrabutylammonium bromide / methanol solution, and the Faraday efficiency of dimethyl carbonate is 40.4%.

[0089] Example 10 A method for synthesizing carbonates differs from Example 1 only in that the 0.1 M sodium bromide / methanol electrolyte is replaced with the same amount of 0.1 M tetrabutylammonium iodide / methanol solution, and the Faraday efficiency of dimethyl carbonate is 35.4%.

[0090] Example 11 A method for synthesizing carbonates, differing from Example 1 only in that the electrolysis time is 6 h and the Faraday efficiency of dimethyl carbonate is 76.2%.

[0091] Example 12 A method for synthesizing carbonates differs from Example 1 only in that the 0.1 M sodium bromide / methanol solution is replaced with the same amount of 0.1 M sodium bromide / ethanol solution, and the Faraday efficiency of diethyl carbonate is 49.2%.

[0092] Comparative Example 1 A method for synthesizing carbonates differs from Example 1 only in that no palladium material supported on activated carbon is added, and no dimethyl carbonate is detected.

[0093] PVimBr-NC-1 and Pd-PVimBr-NC-1 were systematically characterized. Figure 1 The self-optimized in-situ deposition process of Pd on the PVimBr-NC electrode was demonstrated, and it was shown that PVimBr-NC-1 was formed by plate-like accumulation. Figure 1 Elemental analysis (EA) showed the presence of nitrogen, as detailed in Table 1. Figure 2 Transmission electron microscopy showed that Pd was uniformly deposited on PVimBr-NC-1 after the reaction to form Pd-PVimBr-NC-1.

[0094] Table 1 The test results show that: (1) As can be seen from Examples 1-13, the present invention has obtained an in-situ self-optimized deposition system by designing the electrocatalytic system, which breaks through the static limitations of traditional pre-made catalysts and improves the Faraday efficiency of carbonate synthesis.

[0095] (2) By comparing Example 1 with Examples 2-4, 5-6, 7-11 and 12, it can be seen that the present invention further improves the Faraday efficiency of carbonate by further limiting the types of the first and second catalysts and electrolytes, as well as the electrolysis time.

[0096] (3) As can be seen from Example 1 and Comparative Example 1, carbonate compounds cannot be synthesized without using a combination of polyionic liquid-based nitrogen-doped carbon materials and palladium carbon materials as catalysts.

[0097] In summary, this invention, through the design of an electrocatalytic system, yields an in-situ self-optimizing deposition system, overcoming the static limitations of traditional pre-prepared catalysts.

[0098] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An electrocatalytic system for synthesizing carbonates, characterized in that, The electrocatalytic system includes a working electrode, a counter electrode, a reference electrode, an electrolyte, and a reaction device; the working electrode includes a first catalyst and a gas diffusion layer; the electrolyte includes a second catalyst and a solvent; The first catalyst is a polyionic liquid-based nitrogen-doped carbon material; The second catalyst comprises palladium on carbon; the solvent comprises C1-C2 alcohols.

2. The electrocatalytic system according to claim 1, characterized in that, The first catalyst was obtained by polymerizing an ionic liquid monomer with divinylbenzene and then calcining it. Preferably, the ionic liquid monomer comprises any one or a combination of at least two of 1-vinyl-3-methylimidazolium bromide, 1-vinyl-3-methylimidazolium dicyandiamide, 1-vinyl-3-methylimidazolium tetrafluoroborate, or 1-vinyl-3-methylimidazolium hexafluorophosphate. Preferably, the molar ratio of the ionic liquid monomer to divinylbenzene is (1-10):

1.

3. The electrocatalytic system according to claim 1 or 2, characterized in that, The preparation method of the first catalyst includes the following steps: (1) The ionic liquid monomer, divinylbenzene and initiator are mixed in a solvent and polymerized to obtain a polyionic liquid precursor; (2) The polyionic liquid precursor was calcined to obtain the first catalyst; Preferably, the step (1) of mixing the ionic liquid monomer, divinylbenzene and initiator in a solvent is as follows: dissolving the ionic liquid monomer and divinylbenzene in a solvent, and then adding the initiator; Preferably, the initiator comprises azobisisobutyronitrile; Preferably, the polymerization reaction in step (1) is carried out under nitrogen protection; Preferably, the polymerization reaction in step (1) takes 20-28 hours; Preferably, the polymerization reaction in step (1) is carried out at a temperature of 60-80°C; Preferably, the polymerization reaction in step (1) further includes a post-processing step, wherein the post-processing method includes centrifugation, washing, and vacuum drying; Preferably, the vacuum drying temperature is 50-70°C; Preferably, the vacuum drying time is 10-14 h; Preferably, the solvent used for washing includes any one or a combination of at least two of methanol, ethanol, or deionized water; Preferably, the solvent in step (1) includes any one or a combination of at least two of methanol, ethanol or acetonitrile.

4. The electrocatalytic system according to any one of claims 1-3, characterized in that, The calcination temperature is 800-1000℃; Preferably, the calcination time is 1-10 h.

5. The electrocatalytic system according to any one of claims 1-4, characterized in that, The working electrode includes a cathode; Preferably, the method for preparing the working electrode includes the following steps: The first catalyst is dispersed in a solvent, a binder is added to obtain a dispersion, and the dispersion is coated onto a gas diffusion layer to obtain the working electrode. Preferably, the binder comprises a Nafion 117 dispersion; Preferably, the coating method includes drop coating; Preferably, the solvent in which the first catalyst is dispersed includes any one or a combination of at least two of acetone, ethanol, isopropanol or deionized water; Preferably, the volume ratio of the Nafion 117 dispersion to the mass ratio of the first catalyst is 10-100 μL / mg; Preferably, the gas diffusion layer comprises any one or a combination of at least two of carbon fiber paper, carbon fiber woven fabric, or carbon black paper; Preferably, the amount of the first catalyst on the gas diffusion layer is 0.1-10 mg / cm³. 2 .

6. The electrocatalytic system according to claims 1-5, characterized in that, The palladium-on-carbon material is prepared by loading a palladium compound onto a carbon-based material. Preferably, the carbon-based material includes any one or a combination of at least two of activated carbon, carbon nanotubes, or carbon black; Preferably, the palladium compound includes any one or a combination of at least two of palladium chloride, palladium acetate, or palladium nitrate; Preferably, the mass fraction of Pd in ​​the palladium-on-carbon material is 5%-20%.

7. The electrocatalytic system according to any one of claims 1-6, characterized in that, The electrolyte also includes an electrolyte; Preferably, the electrolyte comprises any one or a combination of at least two of sodium bromide, potassium bromide, tetrabutylammonium bromide, tetrabutylammonium iodide, or tetrabutylammonium chloride; Preferably, the C1-C2 alcohols include methanol and / or ethanol; Preferably, the concentration of the electrolyte in the electrolyte solution is 0.1-10 M; Preferably, the mass ratio of the second catalyst to the volume of the electrolyte is 0.1-10 mg / mL; Preferably, the reaction apparatus is a single electrolytic cell or an H-type electrolytic cell; Preferably, the counter electrode comprises a glassy carbon counter electrode; Preferably, the reference electrode comprises an Ag / AgCl reference electrode.

8. A method for synthesizing carbonates, characterized in that, The synthesis method includes the following steps: passing carbon dioxide into the electrocatalytic system as described in any one of claims 1-7 to carry out an electrolysis reaction to obtain the carbonate.

9. The synthesis method according to claim 8, characterized in that, The electrolysis reaction has a potential of -1.2 to -3.0 Vvs Ag / AgCl.

10. The synthesis method according to any one of claims 8 or 9, characterized in that, The temperature of the electrolysis reaction is 25-30℃; Preferably, the electrolysis reaction takes 1-6 hours.

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