Device for electrolyzing carbon dioxide and electrolysis method

Abstract

The invention relates to the technical field of electrochemical catalysis, in particular to a device for electrolyzing carbon dioxide and an electrolysis method. Through combination of a conductive substrate, a silver-based catalyst loaded on the conductive substrate, an anion exchange membrane, an aqueous solution containing sodium salt in an anode chamber and a cation exchange membrane between a cathode and an anode, the electrolytic efficiency is greatly improved, a byproduct sodium carbonate can be produced, the sodium carbonate market is wider, and the economic value can be effectively improved; in addition, the electrolysis device provided by the invention is simple in structure and low in cost, so that the overall cost is reduced. Wherein the anion exchange membrane and the cation exchange membrane are used at the same time, the silver-based catalyst layer is separated from H < + > in the catholyte through the anion exchange membrane, the hydrogen evolution side reaction is greatly reduced, and the electrolysis efficiency is improved; the cation exchange membrane transmembrane provides sodium ions, and sodium carbonate is co-produced.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical catalysis, and in particular to a device and a method for electrolyzing carbon dioxide. Background Art

[0002] As global climate change and environmental pollution become increasingly serious, reducing carbon dioxide (CO2) emissions has become a global focus. Electrochemical conversion of CO2 to organic matter is an effective way to reduce carbon emissions, among which electrocatalytic CO2 to carbon monoxide (CO) is currently the most mature electrocatalytic CO2 reduction technology.

[0003] Existing electrolysis devices generally use a certain concentration of potassium hydroxide aqueous solution as an electrolyte. When an electric current is applied while water is supplied to the anode, the water decomposes into hydrogen ions and electrons and produces oxygen. The electrons move to the cathode through an external wire, and the hydrogen ions move to the cathode through an ion selective membrane. In this case, the moving electrons react with the carbon dioxide and water supplied to the cathode, thereby decomposing into carbon monoxide and hydroxide ions (OH - ), and the generated hydroxide ions react with the hydrogen ions (H + ) reacts to produce water and is electrically neutral. The electrochemical decomposition reaction of carbon dioxide is completed by the above process. In this case, water supplied together with carbon dioxide reacts with mobile electrons in a manner separate from the carbon monoxide production reaction to be electrolyzed to produce hydrogen and simultaneously produce hydroxide ions. The reaction between water and electrons and the carbon monoxide production reaction can be said to be a competitive reaction. When a cation conductive membrane is used as an ion selective membrane, potassium ions (K + ) ions are transported through the membrane to the cathode, where K + The ions react with the carbon dioxide at the cathode and precipitate a salt such as potassium carbonate (K2CO3).

[0004] However, the existing electrocatalytic CO2 technology for producing CO still has some problems, such as low electrocatalytic efficiency, which limits its large-scale application. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect of low electrocatalytic efficiency of the battery device in the prior art, thereby providing a device and an electrolysis method for electrolyzing carbon dioxide.

[0006] To this end, the present application provides a device for electrolyzing carbon dioxide, comprising an anode chamber and a cathode chamber separated by a cation exchange membrane, wherein an anode chamber is provided with an anode, and a cathode chamber is provided with a cathode, wherein the cathode chamber comprises a cathode gas chamber and a cathode liquid chamber separated by the cathode, wherein the anode chamber has an aqueous solution containing a sodium salt, and the cathode comprises an anion exchange membrane and a silver-based catalyst layer located on one side of the anion exchange membrane, wherein one side of the silver-based catalyst layer on the cathode is close to the cathode gas chamber, and one side of the anion exchange membrane is close to the cathode liquid chamber; the silver-based catalyst layer comprises a conductive substrate and a silver-based catalyst loaded on the conductive substrate.

[0007] Furthermore, the silver loading on the cathode is 0.1-2 mg / cm 2 .

[0008] Furthermore, the conductive substrate includes one or more of carbon paper and carbon cloth; and / or the thickness of the conductive substrate is 10-500 μm; and / or the thickness of the anion exchange membrane is 20-100 μm; and / or the anion exchange membrane includes a chitosan anion exchange membrane, a polysulfone anion exchange membrane, a phenyl ether anion exchange membrane or a fluoroethylene anion exchange membrane; and / or the cation exchange membrane includes a perfluorosulfonic acid membrane.

[0009] For example, the perfluorosulfonic acid membrane cation exchange membrane may be one or more of DuPont's N2030, N115, and N117.

[0010] Furthermore, the preparation method of the cathode comprises the following steps:

[0011] The preparation method of the cathode comprises the following steps:

[0012] preparing a silver-based catalyst slurry;

[0013] The silver-based catalyst slurry is coated on a conductive substrate, dried, and combined with an anion exchange membrane to produce a cathode.

[0014] Furthermore, the silver-based catalyst slurry includes silver, a perfluorosulfonic acid-based polymer dispersion, isopropyl alcohol and water.

[0015] Furthermore, based on the total mass of the silver-based catalyst slurry, the silver-based catalyst slurry includes 0.1wt%-0.15wt% of silver, 1wt%-5wt% of a perfluorosulfonic acid-based polymer dispersion, 1wt%-5wt% of isopropanol, and the remainder is water; preferably, the solid content of the perfluorosulfonic acid-based polymer dispersion is 1-10%.

[0016] Furthermore, the conductive substrate and the anion exchange membrane are combined together by hot pressing.

[0017] Furthermore, the hot pressing temperature is 80-150° C. and the pressure is 0.8-2 MPa.

[0018] Perfluorosulfonic acid polymer, referred to as nafion.

[0019] Furthermore, the mass percentage of the aqueous solution containing sodium salt is 5-30%; and / or the aqueous solution containing sodium salt includes one or more of sodium sulfate aqueous solution and sodium chloride aqueous solution.

[0020] Furthermore, the cathode liquid chamber contains a sodium bicarbonate aqueous solution; optionally, the mass percentage of the sodium bicarbonate aqueous solution is 5-30%.

[0021] The present application also provides an electrolysis method, which uses any of the above-mentioned devices for electrolyzing carbon dioxide to electrolyze carbon dioxide.

[0022] Furthermore, the electrolysis process includes introducing carbon dioxide into the cathode chamber; preferably, the pressure in the cathode chamber is 0.8 to 1.2 atmospheres, and the introduction time is 0.5 to 2 hours; preferably, the introduction flow rate of carbon dioxide is 10 to 30 L / h.

[0023] Furthermore, the current density of the electrolysis is 1000-1500A / m 2 , voltage is 2~5V, time is 0.5~2 hours.

[0024] The main chemical and electrochemical reactions involved in the present invention are:

[0025] Cathode reaction: CO2+H2O+2e - →CO+2OH - ;

[0026] CO2+2Na + +2OH - →Na2CO3+2H2O;

[0027] Anode reaction: 4OH - -4e - →2H2O+O2.

[0028] The technical solution of the present invention has the following advantages:

[0029] 1. The device for electrolyzing carbon dioxide provided by the present invention comprises an anode chamber and a cathode chamber separated by a cation exchange membrane, wherein an anode chamber is provided with an anode, and a cathode chamber is provided with a cathode, wherein the cathode chamber comprises a cathode gas chamber and a cathode liquid chamber separated by a cathode, wherein the anode chamber has an aqueous solution containing sodium salt, and the cathode comprises an anion exchange membrane and a silver-based catalyst layer located on one side of the anion exchange membrane, wherein the silver-based catalyst layer on the cathode is close to the cathode gas chamber, and the anion exchange membrane is close to the cathode liquid chamber; wherein the silver-based catalyst layer comprises a conductive substrate and a silver-based catalyst supported on the conductive substrate. The electrolysis efficiency is greatly improved by combining a conductive substrate and a silver-based catalyst supported on a conductive substrate, an anion exchange membrane, an aqueous solution containing sodium salt in the anode chamber, and a cation exchange membrane separating the cathode and the anode, and sodium carbonate can be produced as a byproduct, so the sodium carbonate market is wider, and the economic value can be effectively improved. In addition, the electrolysis device provided by the present invention has a simple structure and low cost, thereby reducing the overall cost. Among them, an anion exchange membrane and a cation exchange membrane are used at the same time, and the silver-based catalyst layer is separated from the H in the cathode liquid by the anion exchange membrane. + The barrier greatly reduces the side reaction of hydrogen evolution and improves the efficiency of electrolysis. The cation exchange membrane provides sodium ions across the membrane to co-produce sodium carbonate.

[0030] 2. The device for electrolyzing carbon dioxide provided by the present invention, the silver-based catalyst slurry includes 0.1wt%-0.15wt% of silver, 1wt%-5wt% of a perfluorosulfonic acid-based polymer dispersion, 1wt%-5wt% of isopropanol, and the rest is water. The electrolysis efficiency can be further improved by using the silver-based catalyst slurry with the above composition and content.

[0031] 3. In the device for electrolyzing carbon dioxide provided by the present invention, the aqueous solution containing sodium salt comprises one or more of an aqueous sodium sulfate solution and an aqueous sodium chloride solution, and in particular, the use of a sodium sulfate solution can further improve the electrolysis efficiency and the yield of sodium carbonate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 is a schematic diagram of a device for electrolyzing carbon dioxide provided in Example 1;

[0034] Figure numerals: 1, anode chamber, 2, anode; 3, cathode gas chamber, 4, cathode liquid chamber; 5, cathode; 6, silver-based catalyst layer; 7, anion exchange membrane; 8, power supply; 9, cation exchange membrane. DETAILED DESCRIPTION

[0035] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0036] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0037] Example 1

[0038] This embodiment provides a device for electrolyzing carbon dioxide, such as Figure 1 As shown, it includes an anode chamber 1, an anode 2 in the anode chamber, a cathode chamber and a cathode 5 in the cathode chamber, and a cation exchange membrane 9 is arranged between the anode chamber and the cathode chamber, and the anode chamber and the cathode chamber are separated by the cation exchange membrane. The cathode chamber includes a cathode gas chamber 3 and a cathode liquid chamber 4 separated by the cathode. The cathode 5 includes an anion exchange membrane 7 and a silver-based catalyst layer 6 located on one side of the anion exchange membrane 7. The silver-based catalyst layer 6 is close to the cathode gas chamber 3, and one side of the anion exchange membrane 7 is close to the cathode liquid chamber 4. There is an aqueous solution containing sodium salt in the anode chamber, which is a sodium sulfate solution in this embodiment. The anode 2 and the cathode 5 are electrically connected to a power supply 8 respectively.

[0039] The cation exchange membrane used in this embodiment is Nafion 117 (perfluorosulfonic acid ion membrane 117, purchased from DuPont, with a thickness of 220 μm), and the anode is a coated titanium anode (DSA electrode, purchased from De Nora), with a size of 10 cm (length) × 10 cm (width). The preparation method of the cathode includes the following steps: 10 mg of silver powder, 0.5 g of nafion solution (5% water dispersion by mass), and 0.5 g of isopropanol are mixed, water is added to a total weight of 10 g, and ultrasonication is performed for 30 minutes to obtain a slurry, and the slurry is evenly sprayed to 10 cm 2 The carbon cloth (thickness 500 μm) was dried at room temperature and then hot pressed together with an anion exchange membrane (manufacturer: Dioxide Materials, brand: Sustainion X37-50, thickness 50 μm) at a temperature of 100°C and a pressure of 1 MPa to obtain a silver loading of 1 mg / cm 2The cathode has a size of 10 cm (length) × 10 cm (width).

[0040] The electrolysis was carried out using the electrolysis device as follows: 0.5L of a 10% Na2SO4 aqueous solution at 25°C was introduced into the anode chamber, 0.5L of a 10% NaHCO3 aqueous solution at 25°C was introduced into the cathode chamber, and CO2 was continuously introduced into the cathode gas chamber at a flow rate of 20L / h for electrolysis. The voltage of the electrolysis reaction was controlled to be 3V, and the current density was 1000A / m 2 , the electrolysis time is 1 hour. Under the action of the cathode, CO2 is electrolyzed into organic matter (including CO and formic acid). CO2 is introduced and the CO produced in the cathode chamber is discharged at the same time to maintain the pressure in the cathode chamber at 1 atmosphere, and the continuous introduction time is 1 hour. The oxygen produced by anode electrolysis is discharged through the anode exhaust port. The sodium ions in the sodium sulfate solution in the anode chamber pass through the cation exchange membrane and move to the cathode liquid chamber, where they react with carbon dioxide and precipitate sodium carbonate. After the electrolysis is completed, the cathode liquid in the cathode liquid chamber is collected, and the cathode liquid is subjected to a conventional cooling crystallization method to obtain a sodium carbonate product.

[0041] Example 2

[0042] This embodiment provides an electrolysis method, using the same device for electrolyzing carbon dioxide as in embodiment 1, and the only difference from embodiment 1 is the preparation method of the cathode. The preparation method of the cathode in this embodiment includes the following steps: 15 mg of silver powder, 0.1 g of nafion solution (a water dispersion with a mass percentage of 5%), and 0.1 g of isopropanol are mixed, water is added to a total weight of 10 g, and ultrasonication is performed for 30 minutes to obtain a slurry, and the slurry is evenly sprayed to 10 cm 2 The carbon cloth (thickness 100 μm) was dried at room temperature and then hot pressed together with an anion exchange membrane (manufacturer: Dioxide Materials, brand: SustainionX37-50, thickness 50 μm) at a temperature of 120°C and a pressure of 1.5 MPa to obtain a silver loading of 1.5 mg / cm 2 The cathode has a size of 10 cm (length) × 10 cm (width).

[0043] Example 3

[0044] This embodiment provides an electrolysis method, using the same device for electrolyzing carbon dioxide as in Embodiment 1, the only difference from Embodiment 1 being that the mass percentage of the sodium sulfate solution is 6 wt %.

[0045] Example 4

[0046] This embodiment provides an electrolysis method, using the same device for electrolyzing carbon dioxide as in Embodiment 1, the only difference from Embodiment 1 being that the mass percentage of the sodium sulfate solution is 30 wt%.

[0047] Example 5

[0048] This embodiment provides an electrolysis method, using the same device for electrolyzing carbon dioxide as in Embodiment 1, the only difference from Embodiment 1 being that the cation exchange membrane is different. The cation exchange membrane used in this embodiment is Nafion 115 (perfluorosulfonic acid ion membrane 115, purchased from DuPont).

[0049] Example 6

[0050] This embodiment provides an electrolysis method, using the same device for electrolyzing carbon dioxide as in embodiment 1, the only difference from embodiment 1 is the electrolysis reaction conditions. The voltage of the electrolysis reaction in this embodiment is 5V, and the current density is 1500A / m 2 , the electrolysis time is 0.5 hours.

[0051] Example 7

[0052] This embodiment provides a device and method for electrolyzing carbon dioxide. The only difference from Embodiment 1 is that the type of electrolyte in the anode chamber is different. The electrolyte in this embodiment is a sodium chloride solution with a mass percentage of 10%. The rest is the same as Embodiment 1.

[0053] Comparative Example 1

[0054] This embodiment provides a device and method for electrolyzing carbon dioxide, which differs from the embodiment 1 only in that the cathode is different. The cathode of this embodiment does not use an anion exchange membrane, and the rest is the same as the embodiment 1. The preparation method of the cathode of this comparative example comprises the following steps: 10 mg of silver powder, 0.5 g of nafion solution (a water dispersion with a mass percentage of 5%), and 0.5 g of isopropanol are mixed, water is added to a total weight of 10 g, and ultrasonication is performed for 30 minutes to obtain a slurry, and the slurry is evenly sprayed to 10 cm 2 Carbon cloth (thickness 500 μm) was applied and dried at room temperature to obtain a silver loading of 1 mg / cm 2 cathode.

[0055] Comparative Example 2

[0056] This embodiment provides a device and method for electrolyzing carbon dioxide, which differs from the embodiment 1 only in that the cathode is different. The cathode of this embodiment does not use a conductive substrate, and the rest is the same as the embodiment 1. The preparation method of the cathode of this comparative example comprises the following steps: 10 mg of silver powder, 0.5 g of nafion solution (a water dispersion with a mass percentage of 5%), and 0.5 g of isopropanol are mixed, water is added to a total weight of 10 g, and ultrasonication is performed for 30 minutes to obtain a slurry, and the slurry is evenly sprayed to 10 cm 2 The anion exchange membrane (manufacturer: Dioxide Materials, brand: SustainionX37-50, thickness 50 μm) was dried at room temperature to obtain a silver loading of 1 mg / cm 2 cathode.

[0057] Test Case

[0058] Before the cathode liquid prepared in each embodiment and comparative example was cooled and crystallized, the content of sodium carbonate was determined by acid-base titration, and the yield was calculated.

[0059] The gas composition in the exhaust pipeline was measured by gas chromatography (GC) analysis, and the CO Faraday efficiency was calculated: the gas produced by the cathode was collected by a gas bag for 5 minutes, passed into a gas chromatograph, and the percentage of CO generated in the gas phase was tested, and then multiplied by the total amount of gas passed to obtain the molar number of CO.

[0060] CO Faraday efficiency = nZF / It

[0061] n represents the number of moles of CO generated, and the unit is mole (mol).

[0062] Z represents the number of electrons transferred per mole of substance in the electrochemical reaction (change in valence) and has no units.

[0063] F is the Faraday constant, which has a value of approximately 96485 coulombs / mole.

[0064] I is the input current, the unit is A.

[0065] t is time in seconds, and the results are shown below.

[0066] The content of sodium formate impurity in the cathode liquid is qualitatively and quantitatively analyzed by liquid chromatography, and the yield is calculated. The liquid chromatography method includes: taking 5 ml of cathode liquid, adding 50 ml of 10% phosphoric acid to acidify it, mixing it evenly, injecting it into a liquid phase vial with a needle, and running the instrument until the result is generated.

[0067] Table 1 Test results

[0068]

[0069] It can be seen from the above table that, compared with Comparative Examples 1 and 2, the embodiments of the present invention can significantly improve the CO Faraday efficiency and efficiently co-produce sodium carbonate.

[0070] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A device for electrolyzing carbon dioxide, characterized in that: The invention comprises an anode chamber and a cathode chamber separated by a cation exchange membrane, wherein an anode is arranged in the anode chamber, a cathode is arranged in the cathode chamber, the cathode chamber comprises a cathode gas chamber and a cathode liquid chamber separated by the cathode, an aqueous solution containing a sodium salt is arranged in the anode chamber, the cathode comprises an anion exchange membrane and a silver-based catalyst layer located on one side of the anion exchange membrane, the silver-based catalyst layer on the cathode is close to the cathode gas chamber, and the anion exchange membrane is close to the cathode liquid chamber; the silver-based catalyst layer comprises a conductive substrate and a silver-based catalyst loaded on the conductive substrate.

2. The device for electrolyzing carbon dioxide according to claim 1, characterized in that: The silver loading on the cathode is 0.1-2 mg / cm 2 .

3. The device for electrolyzing carbon dioxide according to claim 1 or 2, characterized in that: The conductive substrate includes one or more of carbon paper and carbon cloth; and / or the thickness of the conductive substrate is 10-500 μm; and / or the thickness of the anion exchange membrane is 20-100 μm; and / or the anion exchange membrane includes a chitosan anion exchange membrane, a polysulfone anion exchange membrane, a phenyl ether anion exchange membrane or a fluoroethylene anion exchange membrane; and / or the cation exchange membrane includes a perfluorosulfonic acid membrane.

4. The device for electrolyzing carbon dioxide according to any one of claims 1 to 3, characterized in that: The preparation method of the cathode comprises the following steps: preparing a silver-based catalyst slurry; The silver-based catalyst slurry is coated on a conductive substrate, dried, and combined with an anion exchange membrane to produce a cathode.

5. The device for electrolyzing carbon dioxide according to claim 4, characterized in that: The silver-based catalyst slurry comprises silver, a perfluorosulfonic acid-based polymer dispersion, isopropanol and water; preferably, based on the total mass of the silver-based catalyst slurry, the silver-based catalyst slurry comprises 0.1wt%-0.15wt% of silver, 1wt%-5wt% of a perfluorosulfonic acid-based polymer dispersion, 1wt%-5wt% of isopropanol, and the remainder is water; preferably, the solid content of the perfluorosulfonic acid-based polymer dispersion is 1-10%.

6. The device for electrolyzing carbon dioxide according to any one of claims 1 to 5, characterized in that: The mass percentage of the aqueous solution containing sodium salt is 5-30%; and / or the aqueous solution containing sodium salt includes one or more of sodium sulfate aqueous solution and sodium chloride aqueous solution.

7. The device for electrolyzing carbon dioxide according to any one of claims 1 to 6, characterized in that: The cathode liquid chamber contains a sodium bicarbonate aqueous solution; optionally, the mass percentage of the sodium bicarbonate aqueous solution is 5-30%.

8. A method for electrolyzing carbon dioxide, characterized in that: Carbon dioxide is electrolyzed using the device for electrolyzing carbon dioxide described in any one of claims 1 to 7.

9. The method for electrolyzing carbon dioxide according to claim 8, characterized in that: The electrolysis process includes introducing carbon dioxide into the cathode chamber; preferably, the pressure of the cathode chamber is 0.8 to 1.2 atmospheres, and the introduction time is 0.5 to 2 hours; preferably, the introduction flow rate of carbon dioxide is 10 to 30 L / h.

10. The method for electrolyzing carbon dioxide according to claim 9, characterized in that: The current density of the electrolysis is 1000-1500A / m 2 , voltage is 2~5V, time is 0.5~2 hours.

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