Method for preparing formate through carbonate electroreduction and application of formate

Abstract

The invention discloses a method for preparing formate through carbonate electroreduction and application of the formate. The method comprises the following steps: 1) assembling a three-electrode system by using an electrode loaded with a tin-based oxygen-containing compound as a working electrode, an Ag / AgCl electrode or Hg / HgO electrode as a reference electrode, a platinum electrode as a counter electrode and a carbonate solution as an electrolyte, and filling the electrolyte into a gas diffusion electrochemical reaction tank; and 2) introducing oxygen-containing gas into the gas diffusion electrochemical reaction tank, electrifying to sequentially carry out local reduction of the tin-based oxygen-containing compound, electroreduction of carbonate and regeneration of the tin-based oxygen-containing compound, and circulating in sequence. The method for preparing formate through carbonate electroreduction has the advantages of being easy to operate, simple in equipment, reliable in principle, low in cost, high in stability and the like, and is suitable for large-scale industrial application.

Description

Technical Field

[0001] The invention relates to the technical field of electrocatalysis, and in particular to a method for preparing formate by utilizing carbonate electroreduction and application thereof. Background Art

[0002] With the large-scale use of fossil fuels, atmospheric carbon dioxide (CO 2 ) content is increasing, causing environmental problems such as global warming and ocean acidification, threatening human survival and ecological stability. Studies have shown that relying solely on nature’s own “carbon cycle” can no longer effectively control CO in the atmosphere. 2 The rise in carbon content urgently requires artificial "carbon cycle" to achieve the sustainable development goal of "carbon neutrality". 2 Conversion into fuels or high value-added chemicals is becoming an important technical component of the artificial "carbon cycle" (O'BRIEN CP, et al. 2 electrolyzers[J].Chemical Reviews,2024,124(7):3648-3693.). However, using existing methods to perform CO 2 During reduction, due to the large amount of CO 2 During the reaction, carbonate (CO 3 2- It is usually considered to be an electrochemically inert substance), which will seriously affect the conversion efficiency of carbon and energy (Vass, A., et al. Anode catalysts in CO 2 electrolysis: challenges and untapped opportunities.ACS Catal.2022,12(2),1037-1051.). In addition, direct reduction of gaseous CO 2 The systems are often complex in structure and have poor stability, which greatly limits their practical applications.

[0003] Therefore, it is of great significance to develop a method for reducing carbonate to formate with simple operation, simple equipment, reliable principle, low cost and high stability. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing formate by utilizing carbonate electroreduction and application thereof.

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

[0006] A method for preparing formate by carbonate electroreduction comprises the following steps:

[0007] 1) Assembling a three-electrode system by using an electrode loaded with a tin-based oxygen-containing compound as a working electrode, an Ag / AgCl electrode or a Hg / HgO electrode as a reference electrode, a platinum electrode as a counter electrode, and a carbonate solution as an electrolyte, and loading the electrolyte into a gas diffusion electrochemical reaction cell;

[0008] 2) introducing an oxygen-containing gas into a gas diffusion electrochemical reaction cell, then applying power in the potential range of -0.8V to 0V (relative to the reversible hydrogen electrode RHE) to perform local reduction of tin-based oxygen-containing compounds, then adjusting the potential in the potential range of -1.0V to -0.8V to perform electroreduction of carbonates, and then adjusting the potential in the potential range of -0.4V to 0.4V to perform regeneration of tin-based oxygen-containing compounds, and repeating the cycle.

[0009] Preferably, the tin-based oxygen-containing compound in step 1) is tin dioxide (SnO 2 ), tin oxide (SnO), tin hydroxide (Sn(OH) 4 ), stannous hydroxide (Sn(OH) 2 ) at least one of.

[0010] Preferably, the electrode loaded with a tin-based oxygen-containing compound in step 1) is a carbon electrode loaded with a tin-based oxygen-containing compound.

[0011] Preferably, the solute in the carbonate solution in step 1) is potassium carbonate (K 2 CO 3 ), sodium carbonate (Na 2 CO 3 )、Lithium carbonate (Li 2 CO 3 ) at least one of.

[0012] Preferably, the pH value of the carbonate solution in step 1) is 8 to 14. The carbonate solution is energized in the potential range of -0.8V to 0V to perform local reduction of the tin-based oxygen-containing compound, so that a large number of oxygen vacancies are exposed on the surface of the tin-based oxygen-containing compound, thereby achieving the reduction of CO in the carbonate solution. 3 2- Adsorption of ions.

[0013] Further preferably, the pH value of the carbonate solution in step 1) is 8.3-13.

[0014] Preferably, the volume percentage content of oxygen in the oxygen-containing gas in step 2) is 0.001% to 25%.

[0015] Further preferably, the oxygen-containing gas in step 2) is air.

[0016] Preferably, the local reduction time of the tin-based oxygen-containing compound in step 2) is 0.001s to 100s.

[0017] Preferably, the time for the electro-reduction of the carbonate in step 2) is 0.001s to 100s.

[0018] Further preferably, the time for the electro-reduction of the carbonate in step 2) is 5s to 40s.

[0019] Preferably, the regeneration time of the tin-based oxygen-containing compound in step 2) is 0.001s to 100s.

[0020] Further preferably, the regeneration time of the tin-based oxygen-containing compound in step 2) is 0.001s to 20s.

[0021] Preferably, the number of cycles in step 2) is ≥ 1.

[0022] A method for preparing formate by electroreduction of carbonate as described above is used for preparing formic acid.

[0023] Principle of the present invention: The present invention adopts a step potential method, firstly, the power is turned on in the potential range of -0.8V to 0V to carry out local reduction of the tin-based oxygen-containing compound, so that a large number of oxygen vacancies are exposed on the surface of the tin-based oxygen-containing compound, thereby realizing the reduction of CO in the carbonate solution. 3 2- ions, and then the potential was adjusted in the potential range of -1.0V to -0.8V to adsorb CO on tin-based oxygen-containing compounds. 3 2- ions are electroreduced to CO and HCOO - ions (tin-based oxygen-containing compounds will also be reduced), and then the potential is adjusted in the potential range of -0.4V to 0.4V to regenerate the tin-based oxygen-containing compounds, oxidize the deeply reduced tin-based oxygen-containing compounds into stable tin-based oxygen-containing compounds, and promote CO 3 2- Ions migrate to the double layer (tin-based oxygen-containing compounds will undergo irreversible structural damage when reduced at negative potential for a long time, and need to be oxidized at positive potential to maintain stability, and CO 3 2- The ions are negatively charged, and long-term application of negative reduction potential will cause CO 3 2- The ions are expelled from the double layer by Coulomb repulsion and cannot be adsorbed on the surface of the locally reduced tin-based oxygen-containing compound).

[0024] The beneficial effects of the present invention are as follows: the method for preparing formate by utilizing carbonate electroreduction of the present invention has the advantages of simple operation, simple equipment, reliable principle, low cost, high stability, etc., and is suitable for large-scale industrial application.

[0025] Specifically:

[0026] 1) The method for preparing formate by utilizing carbonate electroreduction of the present invention can 3 2- It is converted into carbon monoxide (CO) and formic acid (HCOOH) with high economic added value, with extremely high product selectivity and performance stability, and has great value in the fields of carbon emission reduction and renewable energy utilization;

[0027] 2) The method for preparing formate by carbonate electroreduction of the present invention has low cost and high stability, can be used to prepare formic acid, and is suitable for large-scale industrial application;

[0028] 3) The method of preparing formate by carbonate electroreduction of the present invention realizes a technical closed loop of carbon dioxide capture and reuse. Gaseous carbon dioxide can be directly collected by an alkaline solution without directly participating in a reduction reaction and without requiring a special reaction device, and the structure of the reaction device is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The surface of SnO2 with different oxygen vacancy contents is subjected to CO 3 2- The adsorption energy variation trend diagram.

[0030] Figure 2 This is the in situ Raman thermogram of cyclic voltammetry of potassium carbonate solution.

[0031] Figure 3 This is the chronoamperometric in situ Raman thermogram of potassium carbonate solution.

[0032] Figure 4 Schematic diagram of the step potential method in the embodiment.

[0033] Figure 5 Graph showing the electro-reduction effect of carbonate in the examples. DETAILED DESCRIPTION

[0034] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0035] Example:

[0036] A method for preparing formate by electroreduction of carbonate, comprising the following steps:

[0037] 1) Disperse tin dioxide with anhydrous ethanol to prepare a slurry with a mass fraction of 0.63%, and then coat the slurry on the surface of a carbon paper electrode and dry it to prepare a carbon paper electrode loaded with tin dioxide (the loading amount of tin dioxide is 0.004 g / cm 2), a carbon paper electrode loaded with tin dioxide is used as a working electrode, a Hg / HgO electrode is used as a reference electrode, a platinum electrode is used as a counter electrode, and a 0.5 mol / L potassium carbonate aqueous solution (pH value is 12.1, and sufficient Ar gas is introduced) is used as an electrolyte to assemble a three-electrode system, and the electrolyte is loaded into a gas diffusion electrochemical reaction cell (the atmosphere can be controlled);

[0038] 2) Air was continuously introduced into the gas diffusion electrochemical reaction cell, and then the potential was controlled to -0.7 V (relative to the reversible hydrogen electrode RHE) for 30 s (local reduction of tin dioxide to form SnOCO 3 ), and then adjust the potential to -1.0 V for 20 s (CO 3 2- ions are electroreduced to CO and HCOO - ions), then adjust the potential to 0 V for 10 s (regeneration of tin dioxide), and repeat this cycle, with the number of cycles ≥ 1.

[0039] Test part:

[0040] 1) Theoretical calculation of the surface effects of SnO2 with different oxygen vacancy contents on CO 3 2- The adsorption energy variation trend diagram is shown in Figure 1 shown.

[0041] Depend on Figure 1 It can be seen that: with the SnO 2 The oxygen vacancies on the surface increase, which is conducive to CO 3 2- The adsorption capacity is also greatly enhanced.

[0042] 2) The three-electrode system in this embodiment was placed in an in-situ Raman reaction cell for in-situ Raman observation. Cyclic voltammetry was used during the test. The voltage position was from 1.21 V to -0.99 V, and the cycle was 1 cycle. The scan rate was 100 mV / s. The in-situ Raman thermal map was as follows: Figure 2 (The bluer the color in the figure, the weaker the signal at that location, and the redder the color, the stronger the signal at that location).

[0043] Depend on Figure 2 It can be seen that: in potassium carbonate aqueous solution, when the voltage drops to -0.29V, SnO 2 @634cm -1 The signal begins to weaken, and SnO x -CO 3 @74 / 99cm -1 The signal increases rapidly until -0.82V and both signals disappear together, revealing that CO 3 2-In alkaline environment, SnO x The adsorption voltage range of the surface.

[0044] 3) The three-electrode system in this embodiment was placed in an in-situ Raman reaction cell for in-situ Raman observation. During the test, the chronoamperometry was used, and the potential was controlled at -0.69 V and -0.74 V for 100 s. The obtained in-situ Raman thermal image is shown in FIG. Figure 3 (a is the in-situ Raman thermal map corresponding to a potential of -0.69 V, and b is the in-situ Raman thermal map corresponding to a potential of -0.74 V; the bluer the color in the figure, the weaker the signal at that location, and the redder the color, the stronger the signal at that location).

[0045] Depend on Figure 3 It can be seen that the potential of -0.69V and -0.74V in potassium carbonate aqueous solution can achieve the tin-based oxide to CO 3 2- The adsorption is faster with lower potential and slower with higher potential. When the potential is -0.69V, CO 3 2- The adsorption was completed in about 10 seconds and lasted for more than 100 seconds. When the potential was -0.74 V, CO 3 2- The adsorption was completed around 3 s but could only last around 70 s, revealing that CO 3 2- In alkaline environment, SnO x Surface adsorption characteristics.

[0046] 4) The schematic diagram of the step potential method in this embodiment is as follows Figure 4 shown.

[0047] Depend on Figure 4 It can be seen that the adsorption potential can reduce the tin-based oxygen-containing compounds to a suitable oxidation state to complete the CO 3 2- The reduction potential can make the adsorbed CO 3 2- The open circuit potential can oxidize the deeply reduced tin-based oxygen-containing compounds to a stable state and promote the CO 3 2- Migrate to the double layer.

[0048] 5) The three-electrode system in this embodiment is connected to a gas chromatograph for real-time gas product detection, the gas flow rate is controlled to 25 mL / min, and the electrolyte is extracted after the reaction and the ions in the solution are detected using high performance liquid chromatography. The electroreduction effect diagram of the obtained carbonate is as shown in FIG. Figure 5(a is the test result of gaseous products of electro-reduction under air atmosphere, b is the test result of gaseous products of electro-reduction under argon atmosphere, and c is the test result of liquid products under two atmosphere environments).

[0049] Depend on Figure 5 It can be seen that:

[0050] a) In air atmosphere, tin-based oxygen-containing compounds can achieve spontaneous oxidation and then reduction to adsorb CO 3 2- , to achieve the CO 3 2- Continuous adsorption and reduction of ions to produce CO and HCOO - , and has high selectivity, and no H is produced in the reaction 2 ;

[0051] b) Under argon atmosphere, tin-based oxygen-containing compounds can only achieve CO in the early stage of the reaction. 3 2- Adsorption and reduction of CO and HCOO - However, since there is no oxygen in the reaction system, the tin-based oxygen-containing compounds cannot spontaneously oxidize, and thus cannot continuously achieve CO 3 2- Adsorption and reduction of CO and HCOO - , resulting in the late product being only H 2 ;

[0052] In summary, the present invention can realize the continuous catalytic reaction of tin-based oxygen-containing compounds with CO based on the step potential method and atmosphere control. 3 2- Reduction produces CO and HCOO - , suitable for large-scale industrial applications.

[0053] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing formate by electroreduction of carbonate, characterized in that: The following steps are involved: 1) Assembling a three-electrode system by using an electrode loaded with a tin-based oxygen-containing compound as a working electrode, an Ag / AgCl electrode or a Hg / HgO electrode as a reference electrode, a platinum electrode as a counter electrode, and a carbonate solution as an electrolyte, and loading the electrolyte into a gas diffusion electrochemical reaction cell; 2) introducing oxygen-containing gas into the gas diffusion electrochemical reaction cell, then applying power in the potential range of -0.8V to 0V to perform local reduction of tin-based oxygen-containing compounds, then adjusting the potential in the potential range of -1.0V to -0.8V to perform electro-reduction of carbonates, then adjusting the potential in the potential range of -0.4V to 0.4V to perform regeneration of tin-based oxygen-containing compounds, and repeating the cycle.

2. The method for preparing formate by carbonate electroreduction according to claim 1, characterized in that: In step 1), the tin-based oxygen-containing compound is at least one of tin dioxide, stannous oxide, tin hydroxide and stannous hydroxide.

3. The method for preparing formate by carbonate electroreduction according to claim 1 or 2, characterized in that: Step 1) The solute in the carbonate solution is at least one of potassium carbonate, sodium carbonate and lithium carbonate.

4. The method for preparing formate by carbonate electroreduction according to claim 1 or 2, characterized in that: Step 1) The pH value of the carbonate solution is 8-14.

5. The method for preparing formate by carbonate electroreduction according to claim 1, characterized in that: Step 2) The volume percentage content of oxygen in the oxygen-containing gas is 0.001% to 25%.

6. The method for preparing formate by carbonate electroreduction according to claim 1 or 5, characterized in that: Step 2) The local reduction time of the tin-based oxygen-containing compound is 0.001s to 100s.

7. The method for preparing formate by carbonate electroreduction according to claim 1 or 5, characterized in that: Step 2) The time for the electroreduction of the carbonate is 0.001s to 100s.

8. The method for preparing formate by carbonate electroreduction according to claim 1 or 5, characterized in that: Step 2) The regeneration time of the tin-based oxygen-containing compound is 0.001s to 100s.

9. The method for preparing formate by carbonate electroreduction according to claim 1 or 5, characterized in that: The number of cycles in step 2) is ≥ 1.

10. Use of the method for preparing formate by carbonate electroreduction as claimed in any one of claims 1 to 9 for preparing formic acid.

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