A method for efficiently electrocatalytically reducing carbon dioxide to carbon monoxide using an electrolyte

Abstract

The application discloses a method for realizing high-efficiency electrocatalytic reduction of carbon dioxide into carbon monoxide by using an electrolyte. + The method comprises the following steps: taking a metal sheet as a working electrode, Ag / Ag + Taking an inert electrode as a counter electrode, taking an ionic liquid / acetonitrile solution as a cathode electrolyte, taking a proton acid solution as an anode electrolyte, taking carbon dioxide as a reactant, performing constant-potential electrolysis, and obtaining carbon monoxide; the metal sheet is a non-noble metal sheet, including copper, iron, nickel, cobalt, titanium and alloys thereof; the cation of the ionic liquid is imidazole, pyridine or quaternary ammonium salt, and the anion is tetrafluoroborate or hexafluorophosphate. The electrode material adopted by the application is a cheap and easily available commercial metal sheet, the reaction has high repeatability, the reaction current density is large, the carbon monoxide Faraday efficiency is high, the solvent is green, the reaction condition is mild, and the operation is simple.

Description

Technical Field

[0001] This invention relates to a method for achieving efficient electrocatalytic reduction of carbon dioxide to carbon monoxide using an electrolyte, belonging to the field of electrocatalysis. Background Technology

[0002] Excessive atmospheric carbon dioxide concentration is a major cause of global warming, making the electrochemical conversion of carbon dioxide into other carbon-containing compounds highly significant. Carbon monoxide is an important raw material for synthesizing a series of basic organic chemical products and intermediates, and it is also in high demand in several fields such as the metallurgical industry. Therefore, reducing carbon dioxide to carbon monoxide via electrochemical methods has broad application prospects.

[0003] However, the electrode materials, i.e., catalysts, used for the electrocatalytic reduction of carbon dioxide to carbon monoxide typically require careful design. Therefore, due to cost factors, reproducibility is relatively low, hindering large-scale utilization. Using common commercial metal electrodes can overcome this problem; these are inexpensive, readily available, highly stable, and can be used on a large scale.

[0004] Ionic liquid electrolytes can facilitate the efficient reduction of carbon dioxide to carbon monoxide. However, currently used ionic liquid matrix electrolytes still need improvement in terms of carbon monoxide selectivity and current density. Therefore, it is essential to design a novel ionic liquid electrolyte that delivers higher current density and carbon monoxide selectivity. Summary of the Invention

[0005] The purpose of this invention is to provide a highly efficient electrocatalytic method for reducing carbon dioxide to carbon monoxide, using common non-precious metal sheets as electrode materials to electro-reduce carbon dioxide to prepare carbon monoxide.

[0006] The method for electrocatalytic reduction of carbon dioxide to carbon monoxide provided by this invention includes the following steps:

[0007] At room temperature and normal pressure, using a metal sheet as the working electrode, Ag / Ag + Using an inert electrode as the reference electrode and an ionic liquid / acetonitrile solution as the cathode electrolyte and a protic acid solution as the anode electrolyte, carbon dioxide is used as the reactant. The mixture is electrolyzed at a constant potential to produce carbon monoxide.

[0008] The metal sheet is a non-precious metal sheet, including copper, iron, nickel, cobalt, titanium and their alloys, such as cobalt-nickel alloy. Before use, it is ultrasonically treated in acetone and then wiped dry.

[0009] In the above method, the cation of the ionic liquid can be an imidazole, pyridine, or quaternary ammonium salt, preferably an imidazole, and the anion can be tetrafluoroborate or hexafluorophosphate, preferably tetrafluoroborate.

[0010] The ionic liquid is preferably 1-butyl-3-methylimidazolium tetrafluoroborate and / or 1-dodecyl-3-methylimidazolium tetrafluoroborate, more preferably a mixture of 1-butyl-3-methylimidazolium tetrafluoroborate and 1-dodecyl-3-methylimidazolium tetrafluoroborate, with a molar ratio of 1 to 4:1 to 4, such as 1:4, 2:3, 3:2 or 4:1.

[0011] In the ionic liquid / acetonitrile solution, the molar concentration of the ionic liquid is 0.1 to 1 M, preferably 0.1 to 0.5 M, and more preferably 0.5 M.

[0012] In the above method, the protic acid solution is a sulfuric acid solution, a hydrochloric acid solution, or a nitric acid solution.

[0013] In the above method, the potential for constant potential electrolysis is -2.0V to 3.0V vs. Ag / Ag. + ;

[0014] The constant potential electrolysis time is 15 to 120 minutes;

[0015] The constant potential electrolysis is carried out in an H-type electrolytic cell.

[0016] The electrode material used in this invention is a cheap and readily available commercial metal sheet. It has the advantages of high reaction repeatability, high reaction current density, high carbon monoxide Faraday efficiency, green solvent, mild reaction conditions, and simple operation. Attached Figure Description

[0017] Figure 1 X-ray diffraction patterns of commercial copper foil, iron foil, cobalt-nickel alloy and titanium foil.

[0018] Figure 2 The diagram shows the structures of two imidazole ionic liquids. Detailed Implementation

[0019] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0020] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0021] The method for efficiently reducing carbon dioxide to carbon monoxide with non-precious metals provided by this invention includes the following steps:

[0022] 1) Preparation of ionic liquid electrolyte:

[0023] Two ionic liquids were mixed thoroughly in acetonitrile in a certain proportion to obtain an initial solution. The cations of the two ionic liquids have different alkyl chain lengths, with one alkyl chain having a chain length ≤ 6 and the other having a chain length > 6.

[0024] 2) Electrode preparation:

[0025] The cathode is a commercially available non-precious metal sheet, and the anode is an inert electrode. The electrode sheet is ultrasonicated in acetone for 20 minutes and then wiped dry before use.

[0026] In step 1), the ionic liquid cation can be imidazole, pyridine, quaternary ammonium salt, etc., and the anion can be tetrafluoroborate or hexafluorophosphate, specifically 1-butyl-3-methylimidazolium tetrafluoroborate (C4mimBF4) or 1-dodecyl-3-methylimidazolium tetrafluoroborate (C4mimBF4). 12 mimBF4);

[0027] In the initial solution, the total concentration of the two ionic liquids, expressed in terms of molar concentration, can be 0.1–1 M.

[0028] Example 1:

[0029] 1. Electrolyte preparation: Prepare 30 mL of acetonitrile ionic liquid solution, wherein the ionic liquids C4mimBF4 and C... 12 The concentrations of mimBF4 were 0.3 M and 0.2 M, respectively.

[0030] 2. Electrode treatment: Place copper foil, iron foil, cobalt-nickel alloy and titanium foil in acetone and sonicate for 20 minutes. After wiping dry, they can be used as working electrodes.

[0031] The X-ray diffraction patterns of the commercial copper foil, iron foil, cobalt-nickel alloy, and titanium foil used are as follows: Figure 1 As shown, the metal sheet exhibits good crystallization.

[0032] 3. Electrocatalysis: using a metal electrode as the working electrode and a platinum electrode as the counter electrode, Ag / Ag + Using the above solution as the reference electrode and 0.5M sulfuric acid as the anolyte, an H-type electrolytic cell was used at -2.5V Ag / Ag + Electrolysis was performed at the potential for 2 hours. The gaseous and liquid products after the reaction were analyzed by gas chromatography and nuclear magnetic resonance, respectively. The current density and product Faraday efficiency at different potentials were calculated, and the results are shown in Table 1.

[0033] To use C4mimBF4 / MeCN and C alone 12 The above electrolysis experiment was conducted using mimBF4 / MeCN as the cathode electrolyte, and the results are shown in Table 1.

[0034] Table 1 shows the electrode performance at -2.5V vs. Ag / Ag in Examples 1 and 2. + Reaction results in different electrolytes under different conditions

[0035]

[0036]

[0037] Example 2:

[0038] 1. Electrolyte preparation: Prepare 30 mL of acetonitrile ionic liquid solution, wherein the ionic liquids C4mimBF4 and C... 12 The total concentration of mimBF4 was 0.5 M.

[0039] 2. Electrode treatment: Place the copper foil in acetone and sonicate for 20 minutes. After wiping it dry, it is ready for use.

[0040] 3. Electrocatalysis: using copper foil as the working electrode and platinum electrode as the counter electrode, Ag / Ag + Using the above solution as the reference electrode and 0.5M sulfuric acid as the anolyte, an H-type electrolytic cell was used at -2.5V Ag / Ag + Electrolysis was performed at the potential for 2 hours. The gaseous and liquid products after the reaction were analyzed by gas chromatography and nuclear magnetic resonance, respectively. The current density and product Faraday efficiency at different potentials were calculated, and the results are shown in Table 1.

[0041] As can be seen from the data in Table 1, different electrodes in ternary mixed electrolytes (0.1–0.4 M C4mimBF4 / ... 12 Both mimBF4 and MeCN exhibit the highest current density and the highest CO Faradaic efficiency, indicating that this electrolyte can effectively improve the reaction rate and product selectivity of electrocatalytic CO2 reduction.

Claims

1. A method for the electrocatalytic reduction of carbon dioxide to carbon monoxide, comprising the following steps: At room temperature and normal pressure, using a metal sheet as the working electrode, Ag / Ag + Using an inert electrode as the reference electrode and an ionic liquid / acetonitrile solution as the cathode electrolyte and a protic acid solution as the anode electrolyte, carbon dioxide is used as the reactant. The mixture is electrolyzed at a constant potential to produce carbon monoxide. The metal sheet is a non-precious metal sheet, selected from copper, iron, nickel, cobalt, titanium, and cobalt-nickel alloys; The cation of the ionic liquid is an imidazole.

2. The method according to claim 1, characterized in that: The anion of the ionic liquid is tetrafluoroborate or hexafluorophosphate.

3. The method according to claim 2, characterized in that: The ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate and / or 1-dodecyl-3-methylimidazolium tetrafluoroborate.

4. The method according to claim 2 or 3, characterized in that: In the ionic liquid / acetonitrile solution, the molar concentration of the ionic liquid is 0.1~1 M.

5. The method according to claim 2 or 3, characterized in that: The constant potential electrolysis is -2.0 V to 3.0 V vs. Ag / Ag + .

6. The method according to claim 2 or 3, characterized in that: The constant potential electrolysis time is 15~120 minutes.

7. The method according to claim 2 or 3, characterized in that: The constant potential electrolysis is carried out in an H-type electrolytic cell.

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