A method for a single-chamber electrolysis system for electrocatalytic production of formic acid

Abstract

The present invention discloses a method for an electrocatalytic production of formic acid in a single-chamber electrolysis system, belonging to the field of electrocatalysis. The cathode electrode and the anode electrode of the present invention are arranged in the single-chamber electrolysis system. The anode electrode is a self-supporting electrode loaded with a nickel-based layered double hydroxide catalyst, and the cathode electrode is a gas diffusion electrode sprayed with a copper-based, bismuth-based, tin-based or indium-based metal or alloy catalyst. In the examples provided by the present invention, a nickel foam electrode with electrochemically activated surface-grown NiV layered double hydroxide is used as the anode electrode for catalyzing the oxidation of glycerol to produce formic acid, and conductive carbon black loaded with Bi nanoparticles is sprayed onto the gas diffusion electrode as the cathode electrode for catalyzing the electrochemical reduction of CO2 to produce formic acid. The present invention realizes the simultaneous production of formic acid at the cathode and the anode in the single-chamber electrolysis system, greatly improves the energy efficiency of formic acid production, reduces the cost of the electrochemical reactor, and improves the stability of the reaction device. The scaled-up single-chamber electrolysis system provides a new idea for the industrial-scale production of formic acid.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalysis, and particularly relates to a method for a single-chamber electrolysis system for electrocatalytic production of formic acid. Background Art

[0002] Since the Industrial Revolution, the productivity of human society has been greatly improved due to the use of fossil fuels. However, the sharp increase in CO2 emissions has caused a series of problems such as global warming. Over the past century or so, the CO2 content in the atmosphere has increased from 280 ppm to 420 ppm, the temperature has increased by 1.4 °C, and the sea level has continued to rise. Therefore, it is urgent to mitigate climate change through CO2 capture, storage, and utilization technologies. Electrochemical CO2 reduction driven by renewable electricity can effectively convert CO2 into fuels and chemicals, realize the storage of intermittent electricity, and close the anthropogenic carbon cycle, becoming a very promising CO2 utilization technology. Among the products of electrochemical CO2 reduction, formic acid is considered the most suitable product for industrial scale production. Formic acid is an important raw material for pharmaceutical processing and chemical products, and is also a liquid fuel for a commonly used proton exchange membrane fuel cell. At the same time, it can store hydrogen in liquid form. There are methods such as sodium formate method, methanol carbonylation method, formamide method, and carbon dioxide hydrogenation for industrial preparation of formic acid. Traditional industrial preparation methods often require high temperature and high pressure, and the process is cumbersome and time-consuming. In contrast, the preparation of formic acid / formate by electrochemical CO2 reduction has mild conditions and a controllable process, which is a very promising technology. At present, a large number of studies have designed and developed high-performance catalysts for catalytic CO2 reduction to prepare formic acid / formate. Catalysts such as copper-based, bismuth-based, tin-based, and indium-based catalysts have shown excellent formic acid product selectivity and catalytic activity. And how to further improve the overall efficiency of the formic acid electrolysis system for electroreduction of CO2 has become the research focus of formic acid scale production.

[0003] Traditional electrochemical CO2 reduction technology includes the CO2 reduction reaction at the cathode and the oxygen evolution reaction at the anode. However, due to the slow kinetics of the oxygen evolution reaction, nearly 90% of the electrical energy in electrochemical CO2 reduction technology is consumed at the anode oxygen evolution reaction end, and the value-added of the oxygen product of the oxygen evolution reaction is low, reducing the energy efficiency of the entire electrolysis system. Therefore, finding a thermodynamically more favorable reaction to replace the oxygen evolution reaction is expected to reduce the overall energy consumption of the electrolysis system. For example, introducing reducing molecules such as hydrazine hydrate, methanol, ethanol, urea, glycerol, benzyl alcohol, etc. into the electrolyte system can significantly reduce the oxidation potential of the anodic reaction. Among them, organic oxidation can obtain chemicals such as formic acid and acetic acid, and the value-added of the anode products will also be significantly improved. Therefore, coupling the organic oxidation reaction with the electrochemical CO2 reduction reaction is expected to reduce the energy consumption of the electrolysis system and obtain high-value-added anode products. Current studies have shown that coupling the electrochemical CO2 reduction reaction with the urea oxidation reaction, glycerol oxidation reaction, and glucose oxidation reaction can significantly reduce the energy consumption and obtain high-value-added multi-carbon products at the same time. However, the products of the coupled organic oxidation reaction are often different and complex from the electrochemical CO2 reduction products, and the cost of subsequent product separation will be higher. The crossover of the cathode and anode products will also disrupt the reaction equilibrium. How to design the cathode and anode reactions to obtain the same carbon products will be the focus of future research.

[0004] Comparing the electrochemical CO2 reduction products with the organic oxidation reaction products, formic acid is the only product that can be generated with high selectivity at both the cathode and the anode. When the cathode and anode products are both formic acid, the ion exchange membrane used to separate the cathode and anode products in traditional electrochemical CO2 reduction technology can be discarded, thus enabling the electrolysis process to be carried out in a single-chamber electrolysis system. This single-chamber electrolysis system has a smaller internal resistance and can drive the cathode and anode reactions with lower energy consumption to obtain a high-concentration single product, reducing the cost of product separation. At the same time, discarding the ion exchange membrane can reduce the cost of the electrochemical reactor and improve its stability; the single-chamber electrolysis system can reduce the amount of electrolyte used, further reducing the cost of the electrolysis system. Based on this, there is an urgent need for an electrolysis system that can improve the formic acid yield, improve the energy efficiency, and reduce the electrolysis cost. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for a single-chamber electrolysis system for electrocatalytic production of formic acid.

[0006] The specific technical solutions adopted by the present invention are as follows:

[0007] Based on a single-chamber electrolysis system, a self-supporting electrode loaded with an anode material catalyst is used as the anode electrode, a gas diffusion electrode sprayed with a cathode material catalyst is used as the cathode electrode, and an aqueous potassium hydroxide solution containing glycerol is used as the electrolyte. An electric current is applied to the cathode electrode to carry out an electrolysis reaction to prepare formic acid; the side of the cathode electrode sprayed with the catalyst layer is in direct contact with the electrolyte, and carbon dioxide gas is introduced into the back of the cathode electrode.

[0008] In the present invention, the single-chamber electrolysis system does not use an ion exchange membrane, and the cathode and anode materials are arranged in a single-chamber electrochemical reactor (i.e., the single-chamber electrolysis system).

[0009] Preferably, the above anode material catalyst is a nickel-based layered double hydroxide.

[0010] Preferably, the material of the above self-supporting electrode is one of carbon paper, carbon cloth, nickel foam or copper foam.

[0011] Preferably, the above cathode electrode uses a gas diffusion electrode sprayed with a cathode material catalyst.

[0012] Furthermore, the above cathode material catalyst is one of copper-based, bismuth-based, tin-based and indium-based metal catalysts, or an alloy catalyst composed of at least two of copper-based, bismuth-based, tin-based and indium-based metal groups.

[0013] Even further, the above bismuth-based metal catalyst uses Bi / C nanoparticles.

[0014] Preferably, the above electrolyte is a 0.5-10 mol / L potassium hydroxide (KOH) solution containing 0.01-0.5 mol / L glycerol.

[0015] Preferably, the effective electrode areas of the above anode electrode and cathode electrode are both 1-100 cm 2 。

[0016] Preferably, the electrolyte inlet and outlet of the above single-chamber electrolysis system are respectively connected to a liquid storage tank and a peristaltic pump through pipelines, and the peristaltic pump is connected to the liquid storage tank through a pipeline to realize electrolyte circulation and control the flow rate.

[0017] Preferably, the flow rate of the above electrolyte is controlled by a peristaltic pump to be 10-40 mL / min.

[0018] Preferably, the flow rate of the above carbon dioxide gas (CO2) is controlled by a mass flowmeter to be 20-40 mL / min.

[0019] Preferably, the above current intensity is 100-500 mAcm -2 。

[0020] Preferably, an external power supply is used to control and record the voltage between the cathode electrode and the anode electrode (i.e., the cell voltage) during the above electrolysis process. The gaseous products of the CO2 reduction reaction are detected by an on-line gas chromatograph, and the liquid products in the single-chamber electrochemical reactor are detected by 1 1H nuclear magnetic resonance spectroscopy; the main products generated at the cathode and the anode are both formic acid.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Replacing the oxygen evolution reaction with the glycerol oxidation reaction can significantly reduce the anodic oxidation potential and the energy input of the electrolysis system;

[0023] (2) The products of the electrochemical CO2 reduction and glycerol oxidation are both formic acid, enabling efficient electrochemical preparation of formic acid;

[0024] (3) The single-chamber electrolysis system can reduce the voltage consumption caused by the ion exchange membrane, improve the stability of the electrochemical reactor, reduce the loss of the electrolyte, and lower the cost of product separation, thereby realizing low-cost electrolytic preparation of formic acid;

[0025] (4) When the single-chamber electrolysis system is scaled up to 10 cm 2 it can still maintain an energy efficiency of producing 10 mmol of formic acid per watt-hour of electrical energy, showing the potential for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of a single-chamber electrolysis system for electrocatalytic production of formic acid provided by the present invention;

[0027] Figure 2 is a microscopic morphology diagram of the anode electrode provided in Example 1;

[0028] Figure 3 is a microscopic morphology diagram of the cathode electrode provided in Example 1;

[0029] Figure 4 is the 1H NMR spectrum of the electrolyte in Example 1;

[0030] Figure 5 is a graph of the molar amount of formic acid produced per watt-hour of electrical energy at different current densities in Example 1;

[0031] Figure 6 is a graph of the molar amount of formic acid produced per watt-hour of electrical energy at different effective electrode areas;

[0032] Figure 7 is a schematic diagram of a two-chamber electrolysis system provided in Comparative Example 1;

[0033] Figure 8Graph of the amount of formic acid produced per watt-hour of electrical energy at different current densities in Comparative Example 1;

[0034] Figure 9 Schematic diagram of a traditional two-chamber electrolysis system provided in Comparative Example 2;

[0035] Figure 10 Graph of the amount of formic acid produced per watt-hour of electrical energy at different current densities in Comparative Example 2. Detailed implementation manners

[0036] The present invention will be further described and explained below in conjunction with the accompanying drawings and specific implementation manners. The technical features of each implementation manner in the present invention can be combined correspondingly without conflict.

[0037] As Figure 1 shown, two reactions of electrochemical CO2 reduction and glycerol oxidation are coupled in a single-chamber electrolysis system. On the cathode side, CO2 is introduced into the gas chamber and diffused through the diffusion layer of the gas diffusion electrode to the catalytic side to undergo the CO2 reduction reaction. The gas products and the remaining CO2 diffuse back into the gas chamber and enter the gas chromatograph for on-line detection. On the anode side, the anode catalyst directly catalyzes the oxidation of glycerol in the electrolyte. The electrolyte is controlled by a peristaltic pump to be introduced from the lower opening of the electrolyte plate, pass through the electrolyte chamber, and flow out from the upper opening, while contacting the cathode and anode electrodes and participating in the catalytic reactions of the cathode and anode. The electrolyte inlet and outlet are respectively connected to the liquid storage tank and the peristaltic pump through silica gel tubes, and the peristaltic pump is connected to the liquid storage tank through silica gel tubes to realize the electrolyte circulation and control the flow rate. In the single-chamber electrolysis system, the anode electrode catalyzes the oxidation of glycerol to produce formic acid, and the cathode electrode catalyzes the reduction of CO2 to produce formic acid, and the same liquid-phase product is obtained on the cathode and anode.

[0038] Example 1

[0039] This example provides a single-chamber electrolysis system coupling electrochemical CO2 reduction and glycerol oxidation reactions, and the effective areas of the cathode electrode and the anode electrode are 2 cm 2 and are applied to the preparation of formic acid at different current densities as follows:

[0040] 1. Preparation of the anode electrode:

[0041] (1) Immerse the nickel foam with a size of 3 cm × 3 cm in a 2 mol / L hydrochloric acid aqueous solution for 20 - 30 min, and then rinse with deionized water to remove surface impurities to obtain the hydrochloric acid-treated nickel foam;

[0042] (2) Dissolve NiCl2·6H2O, VCl3, NH4Cl and urea in 80 mL of aqueous solution to obtain a precursor solution. The concentrations of NiCl2·6H2O, VCl3, NH4Cl and urea in the above precursor solution are 30 mmol / L, 10 mmol / L, 37.5 mmol / L and 62.5 mmol / L respectively. After uniform dispersion, add the nickel foam treated with the above hydrochloric acid, place it in a reaction kettle and keep it at 120 °C for 12 h;

[0043] (3) After the reaction kettle cools down, take out the reacted nickel foam, rinse it 3 times with deionized water and absolute ethanol respectively, and then dry it in vacuum at 40 °C to obtain a nickel foam electrode material with a NiV layered double hydroxide grown on its surface;

[0044] (4) Electrochemically activate the above nickel foam electrode material with NiV layered double hydroxide grown on its surface in 1 mol / L KOH electrolyte to obtain an anode electrode (1.6 V vs. reversible hydrogen electrode, 6000 s).

[0045] As Figure 2 shown in the microscopic morphology diagram, the NiV layered double hydroxide presents a flaky structure and is evenly distributed, indicating that the obtained anode electrode is a nickel foam electrode material with a NiV layered double hydroxide grown on its surface by electrochemical activation.

[0046] 2. Preparation of the cathode electrode:

[0047] (1) Add BiCl3, C6H5O7Na3·2H2O and 0.2 g of conductive carbon black (XC-72) to 200 mL of water, so that the concentrations of BiCl3 and C6H5O7Na3·2H2O are 2.5 mmol / L and 40 mmol / L respectively, and ultrasonically disperse them evenly to obtain a dispersion;

[0048] (2) Add 50 mL of an ethanol solution of sodium borohydride (0.1 mol / L) dropwise to the above dispersion, stir for 30 min to fully reduce Bi 3+ , collect the precipitate by centrifugation with a centrifuge, wash it 3 times with deionized water and absolute ethanol respectively, and then dry it in vacuum at 60 °C to obtain XC-72 loaded with Bi nanoparticles (Bi / C nanoparticles);

[0049] (3) Disperse 7 mg of Bi / C nanoparticles in a mixed solution containing 840 μL of absolute ethanol (C2H5OH), 560 μL of H2O and 28 μL of Nafion membrane solution, ultrasonically disperse it evenly, and spray the uniform Bi / C nanoparticle dispersion on the gas diffusion electrode with a spray gun to obtain a cathode electrode;

[0050] As Figure 3As shown in the microscopic morphology diagram, the obtained cathode electrode is a gas diffusion electrode sprayed with Bi / C nanoparticles with a size of 40 - 60 nm.

[0051] 3. Electrolysis reaction:

[0052] Using the above electrochemically activated nickel foam electrode with a surface-grown NiV layered double hydroxide as the anode material, the gas diffusion electrode sprayed with Bi / C nanoparticles as the cathode material, and a 1 mol / L KOH aqueous solution containing 0.5 mol / L glycerol as the electrolyte to form a single-chamber electrolysis system. The side of the gas diffusion electrode sprayed with the catalyst layer is in direct contact with the electrolyte, and a certain volume of the electrolyte is circulated by a peristaltic pump, with the flow rate of the electrolyte controlled at 20 mL / min; CO2 is continuously introduced into the back of the gas diffusion electrode at a flow rate of 40 mL / min; the geometric area with electrode activity during the reaction of the cathode electrode and the anode electrode is set to 2 cm 2 ; Chronopotentiometry is used for the electrolysis reaction, and the current densities are set to 100, 200, 300, 400, and 500 mA cm -2 .

[0053] During the electrolysis process, an external power supply is used to control and record the voltage (i.e., cell voltage) between the cathode electrode and the anode electrode; an on-line gas chromatograph is used to detect the gas-phase products of the CO2 reduction reaction; 1 1H nuclear magnetic resonance spectroscopy is used to detect the liquid-phase products in the single-chamber electrolysis system.

[0054] As Figure 4 shown by the 1H NMR results, formic acid is the only liquid-phase product when the working current of 100 mA cm -2 is applied to the single-chamber electrolysis system. As Figure 5 shown, the energy efficiency of the single-chamber electrolysis system for producing formic acid decreases with the increase of the applied current intensity, and the molar amount of formic acid produced per watt-hour of electric energy reaches a maximum of 12 mmol at a current density of 100 mA cm -2 .

[0055] Example 2

[0056] This example provides a single-chamber electrolysis system for coupling electrochemical CO2 reduction and glycerol oxidation reactions, with the effective area of the cathode electrode and the anode electrode being 10 cm 2 and applied to the preparation of formic acid at a current density of 100 mA cm -2 as follows:

[0057] 1. Preparation of the anode electrode:

[0058] (1) Immerse nickel foam with a size of 4 cm × 4 cm into 2 mol / L hydrochloric acid aqueous solution for 20 - 30 min, and then rinse it with deionized water to remove surface impurities, obtaining nickel foam treated with hydrochloric acid;

[0059] (2) Dissolve NiCl₂·6H₂O, VCl₃, NH₄Cl and urea in 80 mL aqueous solution to obtain a precursor solution. The concentrations of NiCl₂·6H₂O, VCl₃, NH₄Cl and urea in the above precursor solution are 30 mmol / L, 10 mmol / L, 37.5 mmol / L and 62.5 mmol / L respectively. After uniform dispersion, add the nickel foam treated with hydrochloric acid above, and place it in a reaction kettle to maintain at 120 °C for 12 h;

[0060] (3) After the reaction kettle cools down, take out the reacted nickel foam and rinse it 3 times with deionized water and absolute ethanol respectively, and then dry it in vacuum at 40 °C to obtain a nickel foam electrode material with a NiV layered double hydroxide grown on the surface;

[0061] (4) Electrochemically activate the above nickel foam electrode material with a NiV layered double hydroxide grown on the surface in 1 mol / L KOH electrolyte to obtain an anode electrode (1.6 V vs. reversible hydrogen electrode, 6000 s).

[0062] 2. Preparation of the cathode electrode:

[0063] (1) Add BiCl₃, C₆H₅O₇Na₃·2H₂O and 0.2 g of conductive carbon black (XC - 72) to 200 mL of water, so that the concentrations of BiCl₃ and C₆H₅O₇Na₃·2H₂O are 2.5 mmol / L and 40 mmol / L respectively, and disperse them evenly by ultrasonic to obtain a dispersion;

[0064] (2) In the above dispersion, dropwise add 50 mL of ethanol solution of sodium borohydride (0.1 mol / L), and stir for 30 min to fully reduce Bi 3+ , centrifuge and collect the precipitate with a centrifuge, wash it 3 times with deionized water and absolute ethanol respectively, and then dry it in vacuum at 60 °C to obtain XC - 72 loaded with Bi nanoparticles (Bi / C nanoparticles);

[0065] (3) Disperse 18 mg of Bi / C nanoparticles in a mixed solution containing 2.16 mL of absolute ethanol (C₂H₅OH), 1.44 mL of H₂O and 72 μL of Nafion membrane solution, disperse it evenly by ultrasonic, and spray the uniform Bi / C nanoparticle dispersion on the gas diffusion electrode with a spray gun to obtain a cathode electrode;

[0066] 3. Electrolysis reaction:

[0067] The nickel foam electrode with an electrochemically activated surface grown with NiV layered double hydroxide is used as the anode material, the gas diffusion electrode sprayed with Bi / C nanoparticles is used as the cathode material, and an aqueous solution of 1 mol / L KOH containing 0.5 mol / L glycerol is used as the electrolyte to form a single-chamber electrolysis system. The side of the gas diffusion electrode sprayed with the catalyst layer is in direct contact with the electrolyte, and a certain volume of the electrolyte is circulated by a peristaltic pump. The flow rate of the electrolyte is controlled by the peristaltic pump to be 20 mL / min; CO2 is continuously introduced into the back of the gas diffusion electrode, and the flow rate is controlled to be 40 mL / min; the geometric area with electrode activity during the reaction of the cathode electrode and the anode electrode is set to 10 cm 2 ; Chronopotentiometry is used for electrolysis, and the current density is set to 100 mA cm -2 .

[0068] During the electrolysis process, an external power supply is used to control and record the voltage between the cathode electrode and the anode electrode (i.e., the cell voltage); an online gas chromatograph is used to detect the gas-phase products of the CO2 reduction reaction; 1 1H nuclear magnetic resonance spectroscopy is used to detect the liquid-phase products in the single-chamber electrolysis system.

[0069] As Figure 6 shown, in the single-chamber electrolysis system, the effective electrode areas are (i.e., the geometric areas with electrode activity during the reaction) 2 cm 2 and 10 cm 2 . The production yield diagrams of catalytic electrochemically reducing CO2 and oxidizing glycerol to prepare formic acid show that after enlarging the effective electrode area (10 cm 2 ), the single-chamber electrolysis system still maintains a high energy efficiency for producing formic acid and has the potential for large-scale production of formic acid.

[0070] Example 3

[0071] This example provides a single-chamber electrolysis system for coupling the electrochemical CO2 reduction and glycerol oxidation reactions. The effective areas of the cathode electrode and the anode electrode are 100 cm 2 and are applied to the preparation of formic acid at a current density of 100 mA cm -2 as follows:

[0072] 1. Preparation of the anode electrode:

[0073] (1) Immerse a nickel foam with a size of 11 cm × 11 cm in a 2 mol / L hydrochloric acid aqueous solution for 20 - 30 min, and then rinse with deionized water to remove surface impurities to obtain hydrochloric acid-treated nickel foam;

[0074] (2) Dissolve NiCl2·6H2O, VCl3, NH4Cl, and urea in 80 mL of aqueous solution to obtain a precursor solution. The concentrations of NiCl2·6H2O, VCl3, NH4Cl, and urea in the above precursor solution are 30 mmol / L, 10 mmol / L, 37.5 mmol / L, and 62.5 mmol / L, respectively. After uniform dispersion, add the above foam nickel treated with hydrochloric acid, place it in a reaction kettle, and maintain it at 120 °C for 12 h;

[0075] (3) After the reaction kettle cools down, take out the reacted foam nickel, rinse it 3 times with deionized water and absolute ethanol respectively, and then vacuum dry it at 40 °C to obtain a foam nickel electrode material with a NiV layered double hydroxide grown on the surface;

[0076] (4) Electrochemically activate the above foam nickel electrode material with a NiV layered double hydroxide grown on the surface in a 1 mol / L KOH electrolyte to obtain an anode electrode (1.6 V vs. reversible hydrogen electrode, 6000 s).

[0077] 2. Preparation of the cathode electrode:

[0078] (1) Add BiCl3, C6H5O7Na3·2H2O, and 0.2 g of conductive carbon black (XC-72) to 200 mL of water, so that the concentrations of BiCl3 and C6H5O7Na3·2H2O are 2.5 mmol / L and 40 mmol / L respectively, and ultrasonically disperse them evenly to obtain a dispersion;

[0079] (2) Drop 50 mL of an ethanol solution of sodium borohydride (0.1 mol / L) into the above dispersion, stir for 30 min to fully reduce Bi 3+ , centrifuge and collect the precipitate with a centrifuge, wash it 3 times with deionized water and absolute ethanol respectively, and then vacuum dry it at 60 °C to obtain XC-72 loaded with Bi nanoparticles (Bi / C nanoparticles);

[0080] (3) Disperse 135 mg of Bi / C nanoparticles in a mixed solution containing 16.2 mL of absolute ethanol (C2H5OH), 10.8 mL of H2O, and 540 μL of Nafion membrane solution, ultrasonically disperse it evenly, and spray the uniform Bi / C nanoparticle dispersion on the gas diffusion electrode with a spray gun to obtain a cathode electrode;

[0081] 3. Electrolysis reaction:

[0082] The nickel foam electrode with electrochemically activated surface-grown NiV layered double hydroxide is used as the anode material, the gas diffusion electrode sprayed with Bi / C nanoparticles is used as the cathode material, and an aqueous solution of 1 mol / L KOH containing 0.5 mol / L glycerol is used as the electrolyte to form a single-chamber electrolysis system. The side of the gas diffusion electrode sprayed with the catalyst layer is in direct contact with the electrolyte. A certain volume of the electrolyte is circulated by a peristaltic pump, and the flow rate of the electrolyte is controlled by the peristaltic pump to be 20 mL / min; CO2 is continuously introduced into the back of the gas diffusion electrode, and the flow rate is controlled to be 40 mL / min; the geometric area of the cathode and anode electrodes with electrode activity during the reaction is set to 100 cm 2 ; Chronopotentiometry is used for electrolysis, and the current density is set to 100 mAcm -2 .

[0083] During the electrolysis process, an external power supply is used to control and record the voltage between the cathode and anode electrodes (i.e., the cell voltage); an on-line gas chromatograph is used to detect the gas-phase products of the CO2 reduction reaction; 1 1H nuclear magnetic resonance spectroscopy is used to detect the liquid-phase products in the single-chamber electrolysis system.

[0084] A single-chamber electrolysis system for coupling electrochemical CO2 reduction and glycerol oxidation provided in this example can achieve the catalytic electrochemical CO2 reduction and glycerol oxidation to prepare formic acid when the effective area of the electrode is 100 cm 2 .

[0085] Comparative Example 1

[0086] This comparative example provides a method for catalytically electrochemically reducing CO2 and oxidizing glycerol to prepare formic acid in a two-chamber electrolysis system, which is as follows:

[0087] The nickel foam electrode with electrochemically activated surface-grown NiV layered double hydroxide prepared in Example 1 is used as the anode material, and the gas diffusion electrode sprayed with Bi / C nanoparticles is used as the cathode material; both the anode electrolyte and the cathode electrolyte are aqueous solutions of 1 mol / L KOH containing 0.5 mol / L glycerol; the cathode and anode electrolytes are separated by an anion exchange membrane (as Figure 7 shown); the side of the gas diffusion electrode sprayed with the catalyst layer is in direct contact with the electrolyte. Two peristaltic pumps are used to control equal volumes of the cathode and anode electrolytes, and the flow rates of the cathode and anode electrolytes circulated in the cathode and anode electrolyte chambers are controlled by the peristaltic pumps to be 20 mL / min; CO2 is continuously introduced into the back of the gas diffusion electrode, and the flow rate is controlled to be 40 mL / min; Chronopotentiometry is used for electrolysis, and the current densities are set to 100, 200, 300, 400, and 500 mAcm -2, an electrolysis reaction is carried out. During the electrolysis process, an external power supply is used to control and record the voltage between the cathode electrode and the anode electrode (i.e., the cell voltage); an online gas chromatography is used to detect the gaseous products of the CO2 reduction reaction; 1 1H nuclear magnetic resonance spectroscopy is used to detect the liquid-phase products in the cathode electrolyte and the anode electrolyte.

[0088] As Figure 8 shown, the molar amount of formic acid produced per watt-hour of electrical energy in the two-compartment electrolysis system decreases with the increase of the current density. When tested at a current density of 100 mA cm -2 , the energy efficiency reaches a maximum value of 8 mmol, which is lower than the molar amount of formic acid produced per watt-hour of electrical energy of 12 mmol in the single-compartment electrolysis system of Example 1 at a current density of 100 mA cm -2 .

[0089] Comparative Example 2

[0090] This comparative example provides a method for catalytic electrochemically reducing CO2 and oxygen evolution reaction to prepare formic acid in a traditional two-compartment electrolysis system, which is as follows:

[0091] The foam nickel electrode with electrochemically activated surface-grown NiV layered double hydroxide prepared in Example 1 is used as the anode material, and the gas diffusion electrode sprayed with Bi / C nanoparticles is used as the cathode material; both the anode electrolyte and the cathode electrolyte are 1 mol / L KOH aqueous solution; the cathode and anode electrolytes are separated by an anion exchange membrane (as Figure 9 shown); the side of the gas diffusion electrode sprayed with the catalyst layer is in direct contact with the electrolyte. Equal volumes of the cathode and anode electrolytes are respectively controlled by peristaltic pumps to circulate in the cathode and anode electrolyte chambers, and two peristaltic pumps are used to control the flow rates of the cathode and anode electrolytes to be 20 mL / min; CO2 is continuously introduced into the back of the gas diffusion electrode, and the flow rate is controlled to be 40 mL / min; chronopotentiometry is used for electrolysis, and the current density is set to 100, 200, 300, 400, and 500 mA cm -2 , and an electrolysis reaction is carried out; during the electrolysis process, an external power supply is used to control and record the voltage between the cathode electrode and the anode electrode (i.e., the cell voltage); an online gas chromatography is used to detect the gaseous products of the CO2 reduction reaction; 1 1H nuclear magnetic resonance spectroscopy is used to detect the liquid-phase products in the cathode electrolyte.

[0092] As Figure 10 shown, the molar amount of formic acid produced per watt-hour of electrical energy in the two-compartment electrolysis system where only formic acid is electrocatalytically reduced from CO2 at the cathode is significantly reduced, and the energy efficiency reaches a maximum value of 6 mmol when tested at a current density of 100 mA cm -2 .

[0093] Comparing Example 1 with Comparative Examples 1 and 2 proves that the single-chamber electrolysis system coupling electrochemical CO2 reduction and glycerol oxidation reaction can significantly improve the energy efficiency of electrocatalytic formic acid production.

[0094] The present invention realizes the simultaneous production of formic acid at the cathode and anode in a single-chamber electrolysis system, greatly improving the energy efficiency of formic acid production, reducing the cost of the electrochemical reactor, and enhancing the stability of the reaction device. The scaled-up single-chamber electrolysis system provides a new idea for the industrial-scale production of formic acid.

[0095] The above-described embodiments are only a preferred solution of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for a single-chamber electrolysis system for electrocatalytic production of formic acid, characterized in that, The details are as follows: Based on a single-chamber electrolysis system, a self-supporting electrode loaded with an anode material catalyst is used as the anode electrode, a gas diffusion electrode sprayed with a cathode material catalyst is used as the cathode electrode, and an aqueous potassium hydroxide solution containing glycerol is used as the electrolyte. An electric current is applied to the cathode electrode to carry out an electrolysis reaction to prepare formic acid. The side of the cathode electrode sprayed with the catalyst layer is in direct contact with the electrolyte, and carbon dioxide gas is introduced into the back of the cathode electrode. The self-supporting electrode is made of one of carbon paper, carbon cloth, nickel foam or copper foam. The anode material catalyst is nickel-based layered double hydroxide. The cathode electrode uses a gas diffusion electrode sprayed with a cathode material catalyst. The cathode material catalyst is one of copper-based, bismuth-based, tin-based and indium-based metal catalysts, or an alloy catalyst composed of at least two of copper-based, bismuth-based, tin-based and indium-based metal groups.

2. The method for a single-chamber electrolysis system for electrocatalytic production of formic acid according to claim 1, characterized in that, The nickel-based layered double hydroxide is NiV layered double hydroxide.

3. The method for a single-chamber electrolysis system for electrocatalytic production of formic acid according to claim 1, characterized in that, The bismuth-based metal catalyst is Bi / C nanoparticles.

4. The method for a single-chamber electrolysis system for electrocatalytic production of formic acid according to claim 1, characterized in that, The electrolyte is a 0.5 - 10 mol / L potassium hydroxide solution containing 0.01 - 0.5 mol / L glycerol.

5. The method for a single-chamber electrolysis system for electrocatalytic production of formic acid according to claim 1, characterized in that, The effective electrode areas of the anode electrode and the cathode electrode are both 1 to 100 cm 2 .

6. The method for a single-chamber electrolysis system for electrocatalytic production of formic acid according to claim 1, characterized in that, The electrolyte inlet and outlet in the single-chamber electrolysis system are respectively connected to a liquid storage tank and a peristaltic pump through pipelines. The peristaltic pump is connected to the liquid storage tank through a pipeline to realize electrolyte circulation and control the flow rate. The flow rate of the electrolyte is controlled by the peristaltic pump to be 10 - 40 mL / min. The flow rate of the carbon dioxide gas is controlled by a mass flowmeter to be 20 - 40 mL / min.

7. The method for a single-chamber electrolysis system for electrocatalytic production of formic acid according to claim 1, characterized in that, The intensity of the current is 100~500 mA·cm -2 .

8. The method for a single-chamber electrolysis system for electrocatalytic production of formic acid according to claim 1, characterized in that, The electrolysis process uses an external power supply to control and record the voltage between the cathode electrode and the anode electrode.

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