Green formic acid co-production method based on electro-catalysis synergistic conversion of carbon dioxide and carbon-containing small molecules

Abstract

The invention discloses a green formic acid co-production method based on electro-catalysis synergistic conversion of carbon dioxide and carbon-containing small molecules, and belongs to the technical field of new energy conversion and carbon resource utilization. According to the method, a paired electro-catalysis system is constructed; an iron / cobalt bimetal organic framework catalyst is adopted as an anode, so that high-selectivity electro-oxidation of ethylene glycol is realized to generate formic acid; a bismuth-based metal organic framework catalyst is adopted as a cathode, efficient electroreduction of carbon dioxide is achieved, formic acid is also generated, and therefore a high-added-value product is co-produced in a single system in a synergetic mode. Compared with a traditional electrolyzed water system, the method has the advantages that carbon-containing small molecules are used for replacing high-energy-consumption oxygen evolution reaction (OER), the electrolysis energy consumption is remarkably reduced, and meanwhile, the Faraday efficiency and the product selectivity are improved. According to the technical path, capture and resource conversion of CO2 are achieved, high-value utilization of typical carbon-containing organic waste liquid is promoted, and a sustainable, economical and efficient solution is provided for renewable energy-driven green chemical industry, carbon neutralization and clean energy development.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy conversion and carbon resource utilization, and specifically relates to a green co-production method of formic acid based on electrocatalytic synergistic conversion of carbon dioxide and carbon-containing small molecules. Background Art

[0002] With the large-scale consumption of fossil energy and the continued growth of greenhouse gas emissions, the world is facing an increasingly severe dual crisis of environment and energy. Carbon dioxide (CO2), as the main greenhouse gas, its high concentration emissions are considered a key factor in climate change. Therefore, the capture and high-value conversion of CO2 has become one of the core paths to achieve carbon reduction goals. At the same time, industrial waste liquids and by-product organic small molecules (such as ethylene glycol and glycerol) exist in large quantities. Traditional treatment methods usually involve high-energy consumption thermochemical oxidation or direct emissions, resulting in resource waste and environmental burden.

[0003] Electrocatalytic technology, as a clean conversion method that can be coupled with renewable energy, has recently demonstrated great potential in the CO2 reduction reaction (CO2RR) and small molecule oxidation reaction (AOR). However, existing electrolysis systems generally use the water oxidation reaction (OER) as the anodic reaction, whose high overpotential and low product added value severely restrict overall energy efficiency and economic viability. Furthermore, most CO2RR systems suffer from poor selectivity, high energy consumption, and complex product distribution, making them difficult to meet the needs of industrial development.

[0004] To this end, a paired electrocatalytic reaction system was constructed, replacing OER with controlled electrooxidation of small organic molecules at the anode while simultaneously achieving highly selective CO2 reduction at the cathode, co-producing a unified target product. This not only helps reduce system energy consumption and improve product purity, but also enables the coordinated utilization of carbon-containing resources, in line with the development direction of green chemical industry and circular economy. Therefore, the development of an electrocatalytic system for the synergistic conversion of CO2 and carbon-containing small molecules and the green co-production of formic acid has important research value and application prospects. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for the electrocatalytic oxidation of ethylene glycol coupled with the reduction of carbon dioxide to produce formic acid. CoBDC-Fc / NF is used at the anode to oxidize ethylene glycol to produce formic acid, while Bi-MOF is used at the cathode to reduce carbon dioxide to produce formic acid.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for co-producing formic acid by electrocatalytic oxidation of ethylene glycol coupled with reduction of carbon dioxide, comprising the following steps:

[0008] The anode uses an iron / cobalt bimetallic organic framework as an ethylene glycol electro-oxidation catalyst, and the cathode uses a bismuth metal organic framework as a carbon dioxide reduction electro-catalyst; the electrolyte in the anode chamber is a 1M KOH aqueous solution containing 1M ethylene glycol, and the electrolyte in the cathode chamber is a 1M KOH aqueous solution. Electrolysis is carried out simultaneously at the cathode and anode to achieve ethylene glycol oxidation coupled with carbon dioxide reduction to produce formic acid.

[0009] The method for preparing the iron / cobalt bimetallic organic framework comprises the following steps:

[0010] (1) ultrasonically cleaning the nickel foam in acetone, hydrochloric acid, and ethanol in sequence, and then ultrasonically cleaning the nickel foam with deionized water until the surface is completely cleaned to obtain a clean nickel foam;

[0011] (2) Weighing cobalt metal salt and terephthalic acid, dissolving them in an organic solvent, stirring until completely dissolved, to form solution A; weighing 1,1′-ferrocenedicarboxylic acid, dissolving it in an organic solvent, stirring until completely dissolved, to form solution B;

[0012] (3) Solution A and Solution B are fully mixed, and a sodium hydroxide aqueous solution is added to obtain Solution C;

[0013] (4) Transfer solution C to the inner lining of a hydrothermal reactor and place the clean nickel foam therein;

[0014] (5) placing the inner lining of the hydrothermal kettle in a suitable steel jacket of the hydrothermal kettle and placing it in an oven for hydrothermal reaction; after the steel jacket is naturally cooled, taking out the nickel foam and washing it with deionized water and anhydrous ethanol, and then vacuum drying it at 60° C. to obtain the iron / cobalt bimetallic organic framework.

[0015] Wherein, the cleaning time in step (1) is 10-20 minutes, preferably 15 minutes; the hydrochloric acid concentration is 2-4 mol / L, preferably 3 mol / L.

[0016] The cobalt metal salt described in step (2) is one of cobalt acetate, cobalt nitrate or cobalt chloride, preferably cobalt nitrate; the organic solvent is one or more of methanol, ethanol, n-butanol, n-hexane and N,N-dimethylformamide, preferably N,N-dimethylformamide.

[0017] The molar ratio of terephthalic acid to 1,1′-ferrocenedicarboxylic acid in step (3) is 7-9:1-3, preferably 8.5:1.5.

[0018] The concentration of the sodium hydroxide aqueous solution described in step (3) is 0.4mmol / L.

[0019] The temperature of the hydrothermal reaction in step (4) is 80°C-120°C, preferably 100°C.

[0020] The hydrothermal reaction time in step (4) is 12-18 hours, preferably 15 hours.

[0021] The method for preparing the bismuth metal organic framework comprises the following steps:

[0022] S1. Weigh 750 mg of 1,3,5-benzenetricarboxylic acid, 150 mg of bismuth nitrate, and 25 mg of cetyltrimethylammonium bromide, and dissolve them in deionized water to obtain a solution;

[0023] S2. Ultrasonicate the solution obtained in S1, then wash with deionized water and dry to obtain a bismuth metal-organic framework.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention utilizes a hydrothermal method to prepare an iron-cobalt bimetallic organic framework as a highly selective anode catalyst for the oxidation of ethylene glycol to produce formic acid; and utilizes an ultrasonic method to prepare a bismuth-based metal organic framework as a cathode catalyst for the reduction of carbon dioxide to produce formic acid, thereby achieving the purpose of efficient co-production of formic acid by coupling anode and cathode.

[0026] (2) In a three-electrode H-type electrolytic cell, the iron-cobalt bimetallic organic framework (BOF) can achieve a Faradaic efficiency of 93% due to the synergistic effect of the bimetallic elements, and the Faradaic efficiency of formic acid remains above 85% over ten cycles. As a cathode catalyst for the reduction of carbon dioxide to formic acid, the bismuth-based MOF can maintain a Faradaic efficiency of over 93% for 10 hours. Furthermore, the two catalysts mentioned above are assembled into a two-electrode catalytic system as the anode and cathode, respectively, which can achieve high-efficiency formic acid production at a lower reaction voltage.

[0027] (3) The present invention is based on cobalt / iron-based metal organic framework materials and completes the preparation of MOFs materials in one step through a simple hydrothermal synthesis method. The preparation steps are concise and easy to operate. The resulting product is high in purity and does not require tedious post-processing, thereby improving the production efficiency of the product. In addition, the ethylene glycol electrooxidation catalyst of the iron / cobalt bimetallic organic framework obtained by the present invention has a stable structure, rich pores, and a large number of active sites, and exhibits excellent electrocatalytic activity and stability in the ethylene glycol electrooxidation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the present invention for achieving the co-production of formic acid by coupling anodic ethylene glycol oxidation with cathode carbon dioxide reduction;

[0029] Figure 2 Electrochemical polarization curves of the iron / cobalt bimetallic organic framework prepared in basic example 1 of the present invention in alkaline electrolytes with and without ethylene glycol;

[0030] Figure 3 Graph showing the Faradaic efficiency of formic acid production and the yield of formic acid at different potentials for the iron / cobalt bimetallic organic framework prepared in Basic Example 1 of the present invention;

[0031] Figure 4 is the X-ray diffraction pattern of the iron / cobalt bimetallic organic framework ethylene glycol electrooxidation catalyst CoBDC0.85-Fc0.15 / NF prepared in Basic Example 1;

[0032] Figure 5 This is a scanning electron microscope image of the iron / cobalt bimetallic organic framework ethylene glycol electrooxidation catalyst CoBDC0.85-Fc0.15 / NF prepared in Basic Example 1

[0033] Figure 6 The organic framework ethylene glycol electrooxidation catalysts CoBDC0.85-Fc0.15 / NF and CoBDC / NF prepared in Basic Example 1 and Comparative Example 1;

[0034] Figure 7 Electrochemical polarization curves of the iron / cobalt bimetallic organic frameworks prepared in Basic Example 1, Basic Example 2, Basic Example 3, and Comparative Example 1;

[0035] Figure 8 This is a Faradaic efficiency diagram of the iron / cobalt bimetallic organic framework ethylene glycol electrooxidation catalyst CoBDC0.85-Fc0.15 / NF prepared in Basic Example 1, subjected to 10 cycles of electrolysis in an alkaline electrolyte to which 1 M ethylene glycol was added;

[0036] Figure 9 This is the LSV curve of carbon dioxide reduction by the iron / cobalt bimetallic organic framework prepared in Basic Example 4;

[0037] Figure 10 is a Faradaic efficiency diagram for carbon dioxide reduction of the iron / cobalt bimetallic organic framework prepared in Basic Example 4;

[0038] Figure 11 is an LSV diagram of the production of formic acid by coupling electrooxidation of ethylene glycol and carbon dioxide in Example 1;

[0039] Figure 12 This is the Faradaic efficiency diagram for the coupled electrooxidation of ethylene glycol and carbon dioxide to produce formic acid. DETAILED DESCRIPTION

[0040] To facilitate understanding of the present invention by those skilled in the art, specific embodiments of the present invention are described below with reference to the accompanying drawings. The experimental methods described in the examples are conventional methods unless otherwise specified. The reagents and materials described are commercially available unless otherwise specified.

[0041] It should be noted that in the following examples and comparative examples, for the convenience of recording, the MOFs material is named CoBDCxFcy / NF, where x and y are the molar ratios of terephthalic acid and 1,1′-ferrocenedicarboxylic acid.

[0042] Basic Example 1 Preparation Method of Iron / Cobalt Bimetallic Organic Framework

[0043] The steps include:

[0044] (1) Cut the nickel foam into appropriate sizes and ultrasonically clean it in acetone, hydrochloric acid, and ethanol for 15 min respectively. After completion, continue ultrasonic cleaning with deionized water until the surface is completely cleaned.

[0045] (2) Weigh cobalt nitrate hexahydrate (1 mmol), dissolve it in N,N-dimethylformamide (4.5 mL), and stir until completely dissolved to form solution A; weigh 1,1′-ferrocenedicarboxylic acid (0.15 mmol) and terephthalic acid (0.85 mmol) and dissolve them in N,N-dimethylformamide (7.5 mL), and stir until completely dissolved to form solution B;

[0046] (3) Solution A and Solution B were thoroughly mixed, and 0.4 mmol / L sodium hydroxide aqueous solution (1 mL) was added to obtain Solution C;

[0047] (4) moving solution C to the inner lining of a hydrothermal kettle and placing a piece of the nickel foam cleaned in step (1) therein;

[0048] (5) The inner lining of the hydrothermal reactor was placed in a suitable hydrothermal reactor steel jacket and placed in an oven for hydrothermal reaction at 100°C for 15 hours. After the steel jacket was cooled naturally, the nickel foam was taken out and washed with deionized water and anhydrous ethanol several times, and then placed in a vacuum oven at 60°C for overnight drying to obtain the iron / cobalt bimetallic organic framework CoBDC0.85-Fc0.15 / NF.

[0049] Basic Example 2 Preparation Method of Iron / Cobalt Bimetallic Organic Framework

[0050] The steps include:

[0051] (1) Cut the nickel foam into appropriate sizes and ultrasonically clean it in acetone, hydrochloric acid, and ethanol for 15 min respectively. After completion, continue ultrasonic cleaning with deionized water until the surface is completely cleaned.

[0052] (2) Weigh cobalt nitrate hexahydrate (1 mmol), dissolve it in N,N-dimethylformamide (4.5 mL), and stir until completely dissolved to form solution A; weigh 1,1′-ferrocenedicarboxylic acid (0.2 mmol) and terephthalic acid (0.8 mmol) and dissolve them in N,N-dimethylformamide (7.5 mL), and stir until completely dissolved to form solution B;

[0053] (3) Solution A and Solution B were thoroughly mixed, and 0.4 mmol / L sodium hydroxide aqueous solution (1 mL) was added to obtain Solution C;

[0054] (4) moving solution C to the inner lining of a hydrothermal kettle and placing a piece of the nickel foam cleaned in step (1) therein;

[0055] (5) The inner lining of the hydrothermal autoclave was placed in a suitable hydrothermal autoclave steel jacket and placed in an oven for hydrothermal reaction at 100°C for 15 hours. After the steel jacket was cooled naturally, the nickel foam was taken out and washed with deionized water and anhydrous ethanol several times, and then placed in a vacuum oven at 60°C for overnight drying to obtain the iron / cobalt bimetallic organic framework CoBDC0.8-Fc0.2 / NF.

[0056] Basic Example 3 Preparation Method of Iron / Cobalt Bimetallic Organic Framework

[0057] (1) Cut the nickel foam into appropriate sizes and ultrasonically clean it in acetone, hydrochloric acid, and ethanol for 15 min respectively. After completion, continue ultrasonic cleaning with deionized water until the surface is completely cleaned.

[0058] (2) Weigh cobalt nitrate hexahydrate (1 mmol), dissolve it in N,N-dimethylformamide (4.5 mL), and stir until completely dissolved to form solution A; weigh 1,1′-ferrocenedicarboxylic acid (0.1 mmol) and terephthalic acid (0.9 mmol) and dissolve them in N,N-dimethylformamide (7.5 mL), and stir until completely dissolved to form solution B;

[0059] (3) Solution A and Solution B were thoroughly mixed, and 0.4 mmol / L sodium hydroxide aqueous solution (1 mL) was added to obtain Solution C;

[0060] (4) moving solution C to the inner lining of a hydrothermal kettle and placing a piece of the nickel foam cleaned in step (1) therein;

[0061] (4) The inner lining of the hydrothermal reactor was placed in a suitable hydrothermal reactor steel jacket, and the reaction was carried out in an oven at 100°C for 15 hours. After the steel jacket was cooled naturally, the nickel foam was taken out and washed with deionized water and anhydrous ethanol several times, and then dried in a vacuum oven at 60°C overnight to obtain the iron / cobalt bimetallic organic framework CoBDC0.9-Fc0.1 / NF.

[0062] Basic Example 4 Preparation Method of Bismuth Metal-Organic Framework

[0063] The steps include:

[0064] S1. Weigh 750 mg of 1,3,5-benzenetricarboxylic acid, 150 mg of bismuth nitrate, and 25 mg of cetyltrimethylammonium bromide, and dissolve them in deionized water to obtain a solution;

[0065] S2. Ultrasonicate the solution obtained in S1, then wash with deionized water and dry to obtain a bismuth metal-organic framework.

[0066] Comparative Example 1

[0067] S1. Cut the nickel foam into appropriate sizes and ultrasonically clean it in acetone, hydrochloric acid, and ethanol for 15 minutes respectively. After completion, continue ultrasonic cleaning with deionized water until the surface is completely cleaned.

[0068] S2. Weigh cobalt nitrate hexahydrate (1 mmol), dissolve it in N,N-dimethylformamide (4.5 mL), and stir until completely dissolved to form solution A; weigh terephthalic acid (1 mmol) and dissolve it in N,N-dimethylformamide (7.5 mL), and stir until completely dissolved to form solution B;

[0069] S3. Solution A and solution B were thoroughly mixed, and 0.4 mmol / L sodium hydroxide aqueous solution (1 mL) was added;

[0070] S4, transfer the solution obtained in S3 to the inner lining of a hydrothermal reactor, and place a piece of the cleaned nickel foam obtained in S1 therein;

[0071] S5. Place the hydrothermal autoclave lining in a suitable hydrothermal autoclave steel jacket and place it in an oven for hydrothermal reaction at 100°C for 15 hours. After the steel jacket is naturally cooled, remove the nickel foam, wash it with deionized water and anhydrous ethanol several times, and then dry it in a vacuum oven at 60°C overnight to obtain the ethylene glycol electrooxidation catalyst CoBDC / NF.

[0072] Example 1 A method for the electrocatalytic oxidation of ethylene glycol coupled with the reduction of carbon dioxide to produce formic acid

[0073] The specific steps are:

[0074] The anode uses an iron / cobalt bimetallic organic framework as an ethylene glycol electro-oxidation catalyst, and the cathode uses a bismuth metal organic framework as a carbon dioxide reduction electro-catalyst; the anode chamber electrolyte is a 1M KOH aqueous solution containing 1M ethylene glycol, and the cathode chamber electrolyte is a 1M KOH aqueous solution, which couples the oxidation of ethylene glycol with the reduction of carbon dioxide to produce formic acid.

[0075] The catalysts prepared in Example 1 and Comparative Example 1 were used as the anode of the electrolytic cell, and the catalyst prepared in Example 4 was used as the cathode of the electrolytic cell. The effective area of the catalytic electrode was 1 cm -2 The LSV scan rate was 5 mV / s; the LSV and Faraday efficiency of the flow cell were specifically tested.

[0076] The test results are:

[0077] according to Figure 2 From the electrochemical polarization curves of the catalyst prepared in Basic Example 1 in alkaline electrolytes with and without ethylene glycol, it can be seen that the addition of ethylene glycol can effectively reduce the reaction potential and increase the current density of the reaction.

[0078] according to Figure 3 As shown, in a wide voltage range, the catalyst prepared in Basic Example 1 has a high formic acid Faradaic efficiency and excellent formic acid yield.

[0079] according to Figure 4 It can be seen that the catalyst prepared in Basic Example 1 corresponds to CoBDC-Fc, and the two strong peaks in this spectrum correspond to the nickel foam substrate.

[0080] according to Figure 5 It can be seen that CoBDC0.85-Fc0.15 / NF presents a uniform flake structure, which enables the catalyst to better adsorb ethylene glycol molecules and increase the catalyst activity.

[0081] according to Figure 6 As shown in the figure, CoBDC0.85-Fc0.15 / NF has a larger specific surface area than CoBDC / NF, which will be more conducive to the adsorption and desorption of reaction raw materials and products.

[0082] according to Figure 7 It can be seen that when the catalysts of Basic Example 1, Basic Example 2, Basic Example 3 and Comparative Example 1 are used as anodes, respectively, in an alkaline electrolyte with the same amount of ethylene glycol added, the catalyst of Example 1 has excellent ethylene glycol electrooxidation performance.

[0083] according to Figure 8 It can be seen that the Fe / Co bimetallic organic framework ethylene glycol electro-oxidation catalyst CoBDC0.85-Fc0.15 / NF prepared in Basic Example 1 did not exhibit a decrease in Radic efficiency after 10 cycles of electrolysis in an alkaline electrolyte to which 1 M ethylene glycol was added, indicating that the catalyst has excellent stability.

[0084] according to Figure 9 It can be seen that Bi-MOF has a large current density.

[0085] according to Figure 10 It can be seen that the catalyst prepared in Basic Example 4 can achieve high Faradaic efficiency production of formic acid in a wide reaction range.

[0086] according to Figure 11 It can be seen that Example 1 can effectively reduce the voltage in the LSV for producing formic acid by coupling ethylene glycol electrooxidation and carbon dioxide;

[0087] according to Figure 12 It can be seen that the electrocatalytic oxidation of ethylene glycol coupled with the reduction of carbon dioxide to produce formic acid in Example 1 can achieve a Faradaic efficiency of up to 187%.

[0088] Obviously, the described embodiments are only individual embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

Claims

1. A green co-production method for formic acid based on electrocatalytic synergistic conversion of carbon dioxide and carbon-containing small molecules, characterized by: The specific steps are: The anode uses an iron / cobalt bimetallic organic framework as an ethylene glycol electro-oxidation catalyst, and the cathode uses a bismuth metal organic framework as a carbon dioxide reduction electro-catalyst; the electrolyte in the anode chamber is a KOH aqueous solution containing ethylene glycol, and the electrolyte in the cathode chamber is a KOH aqueous solution. Electrolysis is carried out simultaneously at the cathode and anode to achieve ethylene glycol oxidation coupled with carbon dioxide reduction to produce formic acid.

2. The method according to claim 1, wherein: The method for preparing the iron / cobalt bimetallic organic framework comprises the following steps: (1) ultrasonically cleaning the nickel foam in acetone, hydrochloric acid, and ethanol in sequence, and then ultrasonically cleaning the nickel foam with deionized water until the surface is completely cleaned to obtain a clean nickel foam; (2) Weighing cobalt metal salt and terephthalic acid, dissolving them in an organic solvent, stirring until completely dissolved, to form solution A; weighing 1,1′-ferrocenedicarboxylic acid, dissolving it in an organic solvent, stirring until completely dissolved, to form solution B; (3) Solution A and Solution B are fully mixed, and a sodium hydroxide aqueous solution is added to obtain Solution C; (4) Transfer solution C to the inner lining of a hydrothermal reactor and place the clean nickel foam therein; (5) placing the inner lining of the hydrothermal kettle in a suitable steel jacket of the hydrothermal kettle and placing it in an oven for hydrothermal reaction; after the steel jacket is naturally cooled, taking out the nickel foam and washing it with deionized water and anhydrous ethanol, and then vacuum drying it at 60° C. to obtain the iron / cobalt bimetallic organic framework.

3. The method according to claim 2, wherein: The cleaning time in step (1) is 10-20 minutes; the hydrochloric acid concentration is 2-4 mol / L.

4. The method according to claim 2, wherein: The cobalt metal salt described in step (2) is one of cobalt acetate, cobalt nitrate or cobalt chloride; and the organic solvent is one or more of methanol, ethanol, n-butanol, n-hexane and N,N-dimethylformamide.

5. The method according to claim 4, characterized in that: The cobalt metal salt described in step (2) is cobalt nitrate; and the organic solvent is N,N-dimethylformamide.

6. The method according to claim 2, wherein: The molar ratio of terephthalic acid to 1,1′-ferrocenedicarboxylic acid in step (3) is 7-9:1-3.

7. The method according to claim 6, characterized in that: The molar ratio of terephthalic acid to 1,1′-ferrocenedicarboxylic acid in step (3) is 8.5:1.

5.

8. The method according to claim 2, wherein: The concentration of the sodium hydroxide aqueous solution described in step (3) is 0.4mmol / L.

9. The method according to claim 2, wherein: The temperature of the hydrothermal reaction in step (4) is 80° C.-120° C., and the time is 12-18 hours.

10. The method according to claim 1, wherein: The method for preparing the bismuth metal organic framework comprises the following steps: S1. Weigh 750 mg of 1,3,5-benzenetricarboxylic acid, 150 mg of bismuth nitrate, and 25 mg of cetyltrimethylammonium bromide, and dissolve them in deionized water to obtain a solution; S2. Ultrasonicate the solution obtained in S1, then wash with deionized water and dry to obtain a bismuth metal-organic framework.

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