Carbon dioxide electrolysis device and carbon dioxide electrolysis method

Abstract

The present application relates to the field of carbon dioxide electrolysis, and specifically provides a carbon dioxide electrolysis device and a carbon dioxide electrolysis method. The electrolysis device includes an electrolytic cell with a two-cavity structure, and the electrolysis cell includes a cathode plate, a cathode electrode, a cathode liquid flow plate, a diaphragm, an anode electrode and an anode plate arranged in sequence relative to each other; one side of the cathode electrode is close to the cathode plate, and both are respectively provided with openings to form a first feed channel and a first discharge channel in the cathode electrode and the cathode plate, a first cavity for the circulation of cathode electrolyte is formed between the cathode electrode and the diaphragm, and a second cavity for the circulation of anode electrolyte is formed between the anode plate and the anode electrode; a gas-liquid mixer is connected to the first feed channel for gas-liquid mixing to form a multiphase flow. The electrolysis device of the present application can be implemented stably for a long time under conditions not lower than the current density of the gas diffusion type electrode.

Description

Technical Field

[0001] The present application relates to the field of carbon dioxide electrolysis, and in particular, to a carbon dioxide electrolysis device and a carbon dioxide electrolysis method. Background Art

[0002] Carbon dioxide emission reduction technologies are attracting increasing attention, among which carbon dioxide electroreduction is widely considered to be one of the most promising technologies.

[0003] In carbon dioxide electrolysis, gas diffusion electrodes are often used to promote the mass transfer rate of the reaction and thus accelerate the reaction rate. Existing research and industrial practice on carbon dioxide reduction mostly use gas diffusion electrodes to promote the mass transfer of carbon dioxide to support industrial-grade current density. However, in fact, gas diffusion electrodes were originally designed for hydrogen fuel cells, water electrolysis devices, etc. to promote the mass transfer of substances such as hydrogen and water, and were not designed for carbon dioxide electrolysis devices. Since the electrode potential of the carbon dioxide reduction reaction is relatively high and requires a large amount of contact with the electrolyte, the gas diffusion electrode cannot be used at its designed current density (>10kA / m 2 ) and its long-term stable operation current density is less than 1kA / m 2 , the current density is too small, resulting in low energy efficiency and increased costs after scale-up.

[0004] Furthermore, due to the porous structure of gas diffusion electrodes, strict control of the gas-liquid phase equilibrium, electrolyte pH, and concentration is required during operation to prevent carbonate / bicarbonate precipitation or electrolyte blocking of gas mass transfer channels, leading to electrode deactivation. This significantly increases operating costs. Consequently, gas diffusion electrodes face challenges in achieving designed activity, low actual activity, high operating costs, and cumbersome operation during carbon dioxide electrolysis, significantly limiting their use.

[0005] Therefore, it is necessary to develop a carbon dioxide electrolysis device and electrolysis method that can replace the gas diffusion type electrode. Summary of the Invention

[0006] Considering the aforementioned drawbacks of gas diffusion electrodes, which result in low actual activity, high operating costs, and cumbersome operation, the inventors of this application have provided a novel carbon dioxide electrolysis device and electrolysis method. This electrolysis device replaces gas diffusion electrodes by introducing multiphase flow combined with pressure control, enabling the present invention to be operated stably and for extended periods of time at current densities no lower than those of gas diffusion electrodes.

[0007] In a first aspect, the present application provides a carbon dioxide electrolysis device, comprising an electrolysis cell, wherein the electrolysis cell has a two-chamber structure, including a cathode plate, a cathode electrode, a cathode liquid flow plate, a diaphragm, an anode electrode, and an anode plate, which are arranged opposite to each other in sequence;

[0008] One side of the cathode electrode is in close contact with the cathode plate, and both are provided with openings to form a first feed channel and a first discharge channel in the cathode electrode and the cathode plate respectively;

[0009] The cathode liquid flow plate has a hollow flow channel to form a first cavity for cathode electrolyte to flow between the cathode plate and the diaphragm;

[0010] One side of the anode electrode is fixed to the anode plate, and a groove is provided on the side of the anode plate facing the anode electrode to form a second cavity for the circulation of the anolyte between the anode plate and the anode electrode, and the anode plate is provided with an opening for forming a second feed channel and a second discharge channel;

[0011] The first feed channel is connected to a gas-liquid mixer for mixing carbon dioxide gas with cathode electrolyte to form a multiphase flow.

[0012] In a second aspect, the present application provides a method for electrolyzing carbon dioxide, which is performed in the carbon dioxide electrolysis device and comprises:

[0013] 1) The carbon dioxide gas and the cathode electrolyte enter the gas-liquid mixer for gas-liquid mixing to form a multiphase flow;

[0014] 2) The multiphase flow enters the first cavity of the electrolytic cell, and the anolyte enters the second cavity of the electrolytic cell. When the electrolysis power supply is turned on, the carbon dioxide in the multiphase flow undergoes a reduction reaction in the first cavity, and the anolyte undergoes an oxidation reaction in the second cavity.

[0015] This application combines multiphase flow technology and can regulate pressure to enhance carbon dioxide mass transfer and replenish the carbon dioxide consumed in the reaction. This fundamentally avoids the "flooding" phenomenon and pore blockage problems associated with gas diffusion electrodes while ensuring effective mass transfer. The electrolysis device of this application has high operational stability. Furthermore, the electrolysis method of this application does not require strict gas-liquid phase pressure balancing, is simple to operate, and has low operating and maintenance costs.

[0016] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of an electrolytic cell (not installed) according to one embodiment of the present application;

[0018] Figure 2 This is a cross-sectional schematic diagram of an electrolytic cell according to one embodiment of the present application;

[0019] Figure 3 A schematic diagram of an electrolysis device according to one embodiment of the present application;

[0020] Figure 4 This is a schematic diagram of a gas-liquid mixer according to one embodiment of the present application;

[0021] Figure 5 This is a schematic diagram of the flow channel structure of a cathode liquid flow plate according to one embodiment of the present application;

[0022] Figure 6 This is a schematic diagram of the flow channel structure of a cathode liquid flow plate according to another embodiment of the present application;

[0023] Figure 7 This is a relationship diagram of the device operating time, voltage and product selectivity in Example 1.

[0024] Description of Reference Numerals

[0025] 100: electrolytic cell; 1: cathode plate; 2: cathode electrode; 3: cathode liquid flow plate;

[0026] 4: diaphragm; 5: anode electrode; 6: anode plate; 7-1: first sealing ring;

[0027] 7-2: Second sealing ring; 8: Gas-liquid mixer; 9: Cathode pump;

[0028] 10: Carbon dioxide flow controller; 11: Cathode back pressure valve;

[0029] 12: Anode pump; 13: Anode back pressure valve;

[0030] a: first feed channel; a-1: first feed port;

[0031] b: first discharge channel; b-1: first discharge port;

[0032] c: second feed channel; c-1: second feed port;

[0033] d: second discharge channel; d-1: second discharge port. DETAILED DESCRIPTION

[0034] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this application, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0036] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] There are three main deficiencies in the use of gas diffusion electrodes in carbon dioxide reduction electrolysis devices:

[0039] First, the electrode potential of the carbon dioxide reduction reaction is high, and the electrode needs to be in contact with the electrolyte in large quantities. At a large current density (>2kA / m 2 ) The hydrophobicity of the gas diffusion electrode will decrease rapidly, causing the electrolyte to block the gas pores and cause "flooding", thereby reducing the activity of carbon dioxide reduction and the selectivity of products (such as formic acid, CO, etc.); for example, if the current density is large (2kA / m 2 If the reaction is run for more than 2 h, the product (e.g., CO) selectivity will decrease significantly and cannot be restored, and the electrode will be irreversibly damaged.

[0040] Second, in a conventional three-chamber electrolysis device (comprising a cathode liquid chamber, a cathode gas chamber, and an anode liquid chamber), a gas diffusion electrode is used to separate the cathode liquid chamber from the cathode gas chamber. Due to its porous structure, the gas-liquid equilibrium must be strictly controlled. Otherwise, the liquid phase will enter the gas chamber due to excessive pressure, causing the liquid to block the gas transmission channels and thus cause electrode inactivation.

[0041] Third, the carbon dioxide reduction process will generate hydroxide on the electrode surface / in the pores, causing the local pH to increase. The hydroxide will absorb carbon dioxide to generate carbonate / bicarbonate with lower solubility, which can easily precipitate and block the pores of the gas diffusion electrode and the gas phase flow channel, affecting the normal operation of the device. Therefore, the type, pH and concentration of the electrolyte must be strictly controlled to avoid the precipitation of carbonate / bicarbonate. If carbonate / bicarbonate precipitation occurs, the device must be disassembled and thoroughly cleaned, which will greatly increase operating costs.

[0042] Based on the above-mentioned problems, the present application provides a carbon dioxide electrolysis device and electrolysis method.

[0043] The present application provides a carbon dioxide electrolysis device, comprising an electrolytic cell 100, wherein the electrolytic cell 100 has a two-cavity structure. Figure 1 and Figure 2 As shown, the electrolytic cell 100 includes a cathode plate 1, a cathode electrode 2, a cathode liquid flow plate 3, a diaphragm 4, an anode electrode 5 and an anode plate 6 which are arranged opposite to each other in sequence.

[0044] In the electrolytic cell 100, one side of the cathode electrode 2 is in close contact with the cathode plate 1 to prevent a gas diffusion zone between the two. The cathode electrode 2 and the cathode plate 1 are each provided with openings, thereby forming a first feed channel a and a first discharge channel b of the electrolytic cell 100 within the cathode electrode 2 and the cathode plate 1, respectively. The cathode liquid flow plate 3 has a hollowed-out flow channel to form a first cavity (catholyte chamber) between the cathode plate 1 and the diaphragm 4 for the circulation of the cathode electrolyte (multiphase flow).

[0045] In the electrolytic cell 100, one side of the anode electrode 5 is fixed on the anode plate 6, and a groove is provided on the side of the anode plate 6 facing the anode electrode 5 to form a second cavity (anolyte chamber) for the circulation of the anode electrolyte between the anode plate 6 and the anode electrode 5, and the anode plate 6 is provided with an opening for forming a second feed channel c and a second discharge channel d.

[0046] In the present application, one side of the cathode electrode 2 is in close contact with the cathode plate 1 , so that only the side of the cathode electrode 2 facing the cathode liquid flow plate 3 contacts with carbon dioxide and undergoes a reduction reaction.

[0047] In the present application, the material of the cathode plate 1 can be selected from metal or alloy materials that can serve as current collectors, wherein the metal can be selected from at least one of copper, titanium, aluminum, nickel, silver and iron, and the alloy material can be selected from at least one of brass, bronze, nickel silver, stainless steel, titanium alloy and Hastelloy alloy.

[0048] The cathode plate 1 may be provided with a current collecting joint, which is connected to an external circuit via the current collecting joint.

[0049] In the present application, the cathode electrode 2 has a cathode catalyst that can promote the reduction of carbon dioxide to generate carbon-containing compounds. Preferably, the cathode electrode 2 is selected from a metal sheet electrode or a supported conductive sheet electrode.

[0050] Optionally, the metal in the metal sheet is selected from one or more of tin (Sn), silver (Ag), copper (Cu), gold (Au), lead (Pb), bismuth (Bi) and indium (In).

[0051] Alternatively, the supported conductive sheet electrode comprises a conductive substrate and a metal or metal oxide supported thereon, wherein the metal is selected from one or more of tin, silver, copper, gold, lead, bismuth, and indium; the metal oxide is selected from one or more of tin oxide, silver oxide, copper oxide, gold oxide, lead oxide, bismuth oxide, and indium oxide; and the conductive substrate is selected from a carbon substrate (such as carbon felt), a tin substrate, a silver substrate, a copper substrate, a titanium substrate, or an iron substrate. In the supported conductive sheet, when the conductive substrate is the aforementioned metal substrate, the metal supported on the substrate is preferably different from the metal of the substrate.

[0052] As used herein, "the metals selected from "two or more" include a simple mixture of two or more metals or an alloy formed through a specific forming process (including heating). For example, "the metals may be selected from two of tin, silver, and copper" means that the metals may be a simple mixture of any two of "tin, silver, and copper" or an alloy formed from any two of "tin, silver, and copper."

[0053] In the present application, the flow channel of the cathode liquid flow plate 3 is a hollow structure, so that the multiphase flow can simultaneously contact the cathode electrode 2 and the diaphragm 4 while flowing in the flow channel. The flow channel of the cathode liquid flow plate 3 can be various shapes used in microchannel reactors, such as serpentine flow channels, straight flow channels, etc. The cross-section of the flow channel can be rectangular, trapezoidal, curved, etc., and is preferably rectangular.

[0054] In some embodiments, the flow channel of the cathode liquid flow plate 3 is a single serpentine flow channel, multiple serpentine flow channels or multiple straight parallel flow channels, and the width of the flow channel is 0.5 to 5 mm, for example, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm.

[0055] Furthermore, the flow channel of the cathode liquid flow plate 3 is a single serpentine flow channel or a multi-serpentine flow channel. The serpentine flow channel can increase the area utilization rate. A single serpentine flow channel means that the flow channel is a single flow channel (no bifurcation) and is distributed in a serpentine shape (such as Figure 5As shown, black lines represent flow channels. The number of channels of the multi-serpentine flow channels can be 2 to 8, for example, 2, 3, 4, 5, 6, 7, or 8, and the serpentine flow channels can be distributed in parallel.

[0056] In one embodiment, the multiple serpentine flow channels are arranged in parallel and have a tree-like distribution. Figure 6 As shown (black lines represent flow channels), tree-type distribution means that the inlet and outlet of the flow channel are also provided with tree-like distribution channels. A single stream of fluid is distributed to each serpentine flow channel through the tree-like channel, and then the logistics are converged into a single stream of fluid through the tree-like flow channel and flow out of the reactor.

[0057] In some embodiments, the cathode liquid flow plate 3 has a thickness of 0.5 to 5 mm. To reduce electrical resistance and improve energy efficiency, the thickness of the cathode liquid flow plate 3 is preferably no greater than 3 mm, for example, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm. According to a specific embodiment, the thickness of the cathode liquid flow plate 3 is equal to the depth of the flow channel in the cathode liquid flow plate 3, that is, both sides of the entire cathode liquid flow plate 3 are planar structures.

[0058] The cathode liquid flow plate 3 can be made of various insulating inert polymer materials. Optionally, the cathode liquid flow plate 3 is made of polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK) or chlorinated polyvinyl chloride (CPVC).

[0059] In the present application, one side of the anode electrode 5 faces the flow channel of the anode plate 6 , so that the anode electrolyte flows in the second cavity in a manner of contacting the anode electrode 5 .

[0060] The anode electrode 5 has a catalyst material that can promote the oxidation reaction of water in the anolyte to produce products such as oxygen. In some embodiments, the anode electrode 5 is selected from metal felt, foamed metal, foamed metal loaded with an anode catalyst, or metal felt loaded with an anode catalyst. The anode catalyst can be a metal and / or a metal oxide. The metal is, for example, one or more of titanium (Ti), platinum (Pt), palladium (Pd), iridium (Ir), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru) and rhodium (Rh). The metal oxide is, for example, at least one of iridium oxide (IrO2), nickel oxide, cobalt oxide, tin oxide, indium oxide, rhodium oxide, ruthenium oxide and iron oxide.

[0061] Optionally, the anode catalyst is selected from one or more of titanium, platinum, palladium, nickel, iridium oxide, nickel oxide, cobalt oxide, tin oxide, indium oxide, rhodium oxide, ruthenium oxide and iron oxide.

[0062] Furthermore, the anode electrode 5 is selected from titanium felt, titanium foam, nickel foam, titanium felt loaded with iridium oxide, titanium foam loaded with iridium oxide, or titanium felt loaded with nickel oxide.

[0063] In the present application, the flow channel formed by the grooves in the anode plate 6 can be a serpentine flow channel or a straight parallel flow channel. In some embodiments, the flow channel formed by the grooves in the anode plate 6 is a single serpentine flow channel, multiple serpentine flow channels, or multiple straight parallel flow channels, and the width of the flow channel is 0.5 to 3 mm (e.g., 1 mm, 2 mm, 2.5 mm, 3 mm), and the depth of the flow channel is 0.5 to 5 mm (e.g., 1 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, 5 mm).

[0064] The material of the anode plate 6 can be selected from various metals or carbon materials that can serve as current collectors, wherein the metal can be selected from one or more of titanium, copper, silver, gold, iron, nickel, titanium alloy, stainless steel and Hastelloy, and the carbon material can be selected from graphite and / or carbon black.

[0065] The anode plate 6 may be provided with a current collecting joint, which is connected to an external circuit through the current collecting joint.

[0066] In one embodiment, one side of the anode plate 6 has a recess, the recess has a flow channel formed by the groove, and the anode electrode 5 is fixed in the recess to form the second cavity with the anode plate 6 .

[0067] In the present application, the diaphragm 4 may be an ion exchange membrane or an ion exchange membrane loaded with an anode catalyst. The ion exchange membrane may be, for example, DuPont's Nafion XL membrane or Nafion 115 membrane. The anode catalyst is as described above.

[0068] The ion exchange membrane loaded with the anode catalyst is a membrane loaded with the anode catalyst on one side of the membrane, and the side of the membrane loaded with the catalyst faces the anode electrode 5 .

[0069] In order to maintain pressure balance on both sides of the diaphragm 4 and support the membrane, it is preferred that the diaphragm 4 is in close contact with the anode electrode 5 .

[0070] According to one embodiment, the electrolytic cell 100 further includes a first sealing ring 7-1 and a second sealing ring 7-2, wherein the first sealing ring 7-1 is used to seal the first cavity to prevent multiphase flow from flowing out from the four sides of the first cavity (other parts except the inlet and outlet), and the second sealing ring 7-2 is used to seal the second cavity to prevent the anode electrolyte from flowing out from the four sides of the second cavity (other parts except the inlet and outlet).

[0071] In a specific embodiment, sealing areas are left on the edges of the cathode plate 1 on the side facing the cathode electrode 2, the anode plate 6 on the side facing the anode electrode 5, and both sides of the cathode liquid flow plate 3, so that the first sealing ring 7-1 is attached to the sealing area to achieve sealing between the cathode plate 1, cathode electrode 2, cathode liquid flow plate 3 and diaphragm 4, and the second sealing ring 7-2 is attached to the sealing area to achieve sealing between the anode plate 6, anode electrode 5 and diaphragm 4. The first sealing ring 7-1 and the second sealing ring 7-2 can be rubber sealing rings, and the sealing areas of the cathode plate 1 and anode plate 6 can each be provided with a groove for accommodating the sealing ring.

[0072] like Figure 3 As shown, the first feed channel a of the electrolytic cell 100 is connected to a gas-liquid mixer 8. The gas-liquid mixer 8 is used to mix carbon dioxide gas with the cathode electrolyte to form a multiphase flow. Specifically, the outlet of the gas-liquid mixer 8 is connected to the first feed channel a to deliver the multiphase flow to the first chamber of the electrolytic cell 100.

[0073] The gas-liquid mixer 8 can be selected from various multiphase flow generating devices. Figure 4 As shown, the gas-liquid mixer 8 is a three-way gas-liquid mixer, wherein cathode electrolyte and carbon dioxide gas flow from two branch pipes and then enter the main pipe to mix and form a multiphase flow (bubble flow).

[0074] Alternatively, as Figure 3 As shown, the two feed ports of the gas-liquid mixer 8 are connected to a cathode pump 9 and a carbon dioxide flow controller 10 respectively.

[0075] In the present application, the anolyte can enter the second cavity of the electrolytic cell 100 through the second feed channel c. Figure 3 As shown, the second feed channel c is connected to an anode pump 12 .

[0076] In the present application, the reaction products and the like in the first cavity can be sent out of the electrolytic cell 100 through the first discharge channel b. The reaction products and the like in the second cavity can be sent out of the electrolytic cell 100 through the second discharge channel d.

[0077] like Figure 3 As shown, optionally, the first discharge channel b is connected to a cathode back pressure valve 11, and the second discharge channel d is connected to an anode back pressure valve 13, and the reaction pressure in the electrolytic cell 100 is adjusted by the cathode back pressure valve 11 and the anode back pressure valve 13.

[0078] In the present application, the electrolysis device may further include a gas-liquid separation device and a reactant recovery device to achieve the collection of products and the recycling of the electrolyte. The specific selections are well known in the art and will not be described in detail here.

[0079] In the present application, the electrolysis device may be connected to an external power source so that current flows between the anode electrode 5 and the cathode electrode 2 .

[0080] According to a specific embodiment, in the electrolysis device, in the electrolysis cell 100, the cathode plate 1, the cathode electrode 2, the cathode liquid flow plate 3, the diaphragm 4, the anode electrode 5 and the anode plate 6 are fixed by fasteners (not shown) to form a compact structure, and the first sealing ring 7-1 (rubber sealing ring) is used to achieve the sealing between the cathode plate 1, the cathode electrode 2, the cathode liquid flow plate 3 and the diaphragm 4, and the second sealing ring 7-2 (rubber sealing ring) is used to achieve the sealing between the anode plate 6, the anode electrode 5 and the diaphragm 4; The carbon flow controller 10 and the cathode pump 9 are connected to the two feed pipes of the three-way gas-liquid mixer via pipes. The outlet of the mixer is connected to the first feed port a-1 of the electrolytic cell 100, and the anode pump 12 is connected to the second feed port c-1 of the electrolytic cell 100. The cathode backpressure valve 11 is connected to the first discharge port b-1 of the electrolytic cell 100, and the anode backpressure valve 13 is connected to the second discharge port d-1 of the electrolytic cell 100. The reaction pressure in the electrolytic cell 100 is adjusted by the cathode backpressure valve 11 and the anode backpressure valve 13. In the following examples, unless otherwise specified, the electrolysis apparatus used is as shown in this specific embodiment.

[0081] The present application also provides a method for electrolyzing carbon dioxide, which is performed in the above-mentioned carbon dioxide electrolysis device and comprises:

[0082] 1) The carbon dioxide gas and the cathode electrolyte enter the gas-liquid mixer 8 for gas-liquid mixing to form a multiphase flow;

[0083] 2) The multiphase flow enters the first cavity of the electrolytic cell 100, and the anolyte enters the second cavity of the electrolytic cell 100. When the electrolysis power supply is turned on, the carbon dioxide in the multiphase flow undergoes a reduction reaction in the first cavity, and the anolyte undergoes an oxidation reaction in the second cavity.

[0084] The electrolysis method of the present application can be constant current electrolysis or constant voltage electrolysis. The current density set by the constant current electrolysis is preferably not less than 1kA / m 2 , more preferably greater than 1kA / m 2 , for example 2kA / m 2 , 3kA / m 2 , 4kA / m 2 , 5kA / m 2 .

[0085] In the present application, the anolyte and catholyte may be the same or different. In some embodiments, the catholyte is an aqueous solution of a first electrolyte, and the anolyte is an aqueous solution of water, an acid, or a second electrolyte. The first and second electrolytes may be the same or different and each independently be a soluble salt or base.

[0086] The soluble salt is selected from at least one of carbonate, bicarbonate, phosphate, hydrogen phosphate, hydrochloride, acetate, perchlorate, sulfate and formates. The cation in the soluble salt can be a metal ion (e.g., K + 、Na + 、Li + 、Cs + ).

[0087] The alkali is selected from alkali metal hydroxides and / or ammonia water. The alkali metal hydroxides are, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.

[0088] The acid is at least one of a sulfuric acid aqueous solution, a perchloric acid aqueous solution and hydrochloric acid.

[0089] In some embodiments, the concentration of the solute in the cathode electrolyte and the anode electrolyte can be 0.1 to 10 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, or 4 mol / L. The solute refers to the first electrolyte, the second electrolyte, an alkali metal hydroxide, an acid, or the like. For example, when the electrolyte is an aqueous solution of sodium hydroxide (NaOH), the concentration of the solute refers to the content of NaOH; when the electrolyte is hydrochloric acid, the concentration of the solute refers to the content of hydrogen chloride (HCl); and when the electrolyte is an aqueous solution of potassium bicarbonate (KHCO3), the concentration of the solute refers to the content of KHCO3.

[0090] In the method of the present application, carbon dioxide undergoes a reduction reaction in the first chamber near the cathode electrode 2, thereby producing carbon-containing compounds such as carbon monoxide, formic acid, methane, ethane, ethylene, methanol, and ethanol. The specific products produced are related to the electrode material. The anode electrode 5 can oxidize water to produce oxygen (O2) and hydrogen ions, or can oxidize hydroxide ions (OH-) to produce water and oxygen.

[0091] In the method of the present application, the flow rate of the cathode electrolyte in a single flow channel can be 5 to 100 mL / min, for example, 10 mL / min, 15 mL / min, 20 mL / min, 25 mL / min, 30 mL / min, 35 mL / min, 40 mL / min, 45 mL / min, 50 mL / min, and 100 mL / min.

[0092] In the method of the present application, the flow rate of carbon dioxide gas in a single flow channel can be 5 to 1000 sccm, for example, 10 sccm, 50 sccm, 100 sccm, 150 sccm, 200 sccm, 220 sccm, 250 sccm, 300 sccm, 320 sccm, 350 sccm, 370 sccm, 380 sccm, 400 sccm, 450 sccm, 480 sccm, 500 sccm, and 1000 sccm.

[0093] In the method of the present application, the flow rate of the anolyte in a single flow channel can be 20 to 500 mL / min, for example, 20 mL / min, 25 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, 80 mL / min, 120 mL / min, 150 mL / min, 200 mL / min, 300 mL / min, 400 mL / min, and 500 mL / min.

[0094] In this application, a single flow rate refers to the flow rate within a single flow channel. For example, when the flow channel on the cathode liquid flow plate 3 is a single serpentine flow channel, the single flow rate refers to the flow rate within that flow channel. When the flow channels on the cathode liquid flow plate 3 are four serpentine flow channels, the flow rate within a single flow channel refers to the flow rate within each serpentine flow channel. In the following embodiments, flow rate refers to the total flow rate. When there is only one flow channel, the single flow rate is the total flow rate. When there are multiple flow channels, the total flow rate refers to the sum of the flow rates of each flow channel.

[0095] In the method of the present application, the reaction pressure in the electrolytic cell 100 can be 1 to 50 bar, for example, 2 bar, 5 bar, 6 bar, 7 bar, 8 bar, 9 bar, 10 bar, 15 bar, 20 bar, 25 bar, 30 bar, 35 bar, 40 bar, 45 bar, 50 bar. Preferably, the reaction pressure is 5 to 30 bar.

[0096] The method of the present application is a continuous operation method, which uses a gas-liquid mixer to mix carbon dioxide and cathode electrolyte to form a multiphase flow (bubble flow) containing a large number of carbon dioxide microbubbles. The bubble flow enters the first cavity of the electrolytic cell and undergoes a reduction reaction near the cathode electrode. During the flow, the carbon dioxide gas in the bubbles continuously dissolves in the electrolyte to replenish the carbon dioxide consumed by the reaction and maintain the carbon dioxide concentration in the bubbles. In addition, the use of bubble flow can increase the contact area between the carbon dioxide gas and the electrolyte, and by pressurizing the electrolyte, the solubility of carbon dioxide in the electrolyte can be further increased, which is beneficial to the mass transfer of carbon dioxide to the electrode surface and can support a higher current density. The method of the present application makes the current density of the carbon dioxide reaction at 2kA / m 2 The above can achieve higher reaction efficiency and ensure long-term stable operation of the device.

[0097] The present application is described below with reference to embodiments, which are only used to explain the present application and are not used to limit the present application.

[0098] In the following embodiments, unless otherwise specified, the carbon dioxide electrolysis method is as follows: cathode electrolyte is pumped into a three-way gas-liquid mixer via a cathode pump 9, and carbon dioxide gas is sent into the three-way gas-liquid mixer, where the two are mixed to generate a multiphase flow. The multiphase flow passes through the first feed channel a, through the cathode plate 1 and the cathode electrode 2, and enters the cathode liquid flow plate 3 to participate in the carbon dioxide reduction reaction. The resulting reduction product leaves the electrolytic cell 100 along with the electrolyte through the first discharge channel b, and undergoes gas-liquid separation to obtain a gas stream and a liquid stream.

[0099] The anode electrolyte is pressurized by the anode pump 12 and enters the second feed channel c to pass through the anode plate 6 and enter its flow channel. The water in the electrolyte undergoes electron transfer on the surface of the anode electrode 2 and is oxidized into oxygen. The generated oxygen leaves the electrolytic cell 100 along with the electrolyte through the second discharge channel d.

[0100] The gas stream obtained by the gas phase separation is subjected to a gas chromatograph to determine the product concentration therein, and the liquid stream is subjected to a liquid chromatograph to determine the product concentration therein, and then the partial current corresponding to the product is calculated. The partial current / total current is the Faraday efficiency (i.e., selectivity) of the product.

[0101] Unless otherwise specified, the membrane 4 is a Nafion XL ion exchange membrane produced by DuPont, with a thickness of 27.94 μm.

[0102] Example 1

[0103] In the electrolytic cell 100 , the cathode plate 1 is made of copper and has a size of 90 mm×90 mm×20 mm.

[0104] The cathode electrode 2 is a metal tin sheet with a size of 55 mm×55 mm×0.1 mm; the area of ​​the diaphragm 4 is consistent with that of the cathode electrode 2 .

[0105] The anode electrode 5 is a titanium felt loaded with iridium oxide (iridium oxide loading is 1 mg / cm 2 ), the electrode size is 50mm×50mm×0.4mm.

[0106] Anode plate 6 is made of titanium and measures 90 mm x 90 mm x 20 mm. It has a groove and a flow channel. The groove dimensions are the same as those of anode electrode 5, allowing anode electrode 5 to fit into the groove and contact the flow channel surface. The flow channel is a single serpentine flow channel with a width of 2 mm, a depth of 1.5 mm, and a length of 0.85 m.

[0107] The cathode liquid flow plate 3 is made of PMMA, with a thickness of 1.5 mm (channel depth), a single serpentine channel, a channel length of 1.6 m, a channel width of 1 mm, and a channel area of ​​50 mm×50 mm.

[0108] The cathode electrolyte is a KHCO3 aqueous solution with a concentration of 1 mol / L, and the anolyte is a 0.1 mol / L H2SO4 aqueous solution.

[0109] The cathode electrolyte flow rate is 30 mL / min, the carbon dioxide gas flow rate is 200 sccm, the anolyte flow rate is 40 mL / min, the pressure in the device is controlled at 8 bar, a constant current reaction is used, and the current density is set to 2 kA / m 2 (Total current 3.2A), during the reaction operation, the voltage and formic acid, hydrogen, carbon monoxide selectivity (Faraday efficiency) change with the device operation time as shown in the following results. Figure 7 shown.

[0110] Depend on Figure 7 It can be seen that in this embodiment, when the current density is set to 2kA / m 2 Under the conditions of high current density, the device maintained a formic acid selectivity of about 80% during an electrolysis time of more than 200 hours, and the device voltage was stable at around 5.2V, indicating that the electrolysis device can operate stably for a long time at high current density.

[0111] Example 2

[0112] Carbon dioxide was electrolyzed according to the method of Example 1, except that the anolyte was a KHCO3 aqueous solution with a concentration of 1 mol / L, and the current density was set to 5 kA / m 2 (Total current 8A). During the reaction operation, the formic acid selectivity (Faraday efficiency) at different times is shown in Table 1.

[0113] Table 1

[0114] Running time (h) 2 4 6 8 10 Formic acid selectivity (%) 71.2 71.0 71.2 70.9 70.6 Device voltage (V) 6.54 6.56 6.57 6.65 6.63

[0115] As can be seen from Table 1, in this embodiment, the current density is set to 5kA / m 2 The selectivity of formic acid can reach more than 70% under the condition of 100 nm, and the device voltage is about 6.5V.

[0116] Example 3

[0117] In the electrolytic cell 100, the cathode electrode 2 is adjusted to a metallic silver sheet, and the diaphragm 4 is adjusted to a Nafion 115 membrane loaded with iridium oxide (iridium oxide is loaded on the side of the membrane facing the anode electrode 5, with a loading of 1 mg / cm 2 ), the anode electrode 5 is adjusted to titanium felt, and the rest is the same as in Example 1.

[0118] The cathode electrolyte is a KHCO3 aqueous solution with a concentration of 2 mol / L, and the anode electrolyte is pure water.

[0119] The cathode electrolyte flow rate is 15 mL / min, the carbon dioxide gas flow rate is 200 sccm, the anolyte flow rate is 80 mL / min, the pressure in the device is controlled at 8 bar, a constant current reaction is used, and the current density is set to 2 kA / m 2 (Total current 3.2 A). During the reaction operation, the CO selectivity (Faraday efficiency) results at different times are shown in Table 2.

[0120] Table 2

[0121] Running time (h) 2 4 6 8 10 CO selectivity (%) 71.6 71.8 70.9 71.1 70.8 Device voltage (V) 4.48 4.51 4.53 4.50 4.52

[0122] As can be seen from Table 2, in this embodiment, the current density is set to 2kA / m 2 When the CO selectivity reaches over 70%, the device voltage is about 4.5V.

[0123] Example 4

[0124] In the electrolytic cell 100 , the cathode plate 1 is made of copper and has a size of 160 mm×130 mm×20 mm.

[0125] The cathode electrode 2 is a metal tin sheet with a size of 120 mm×90 mm×0.1 mm; the area of ​​the diaphragm 4 is consistent with that of the cathode electrode 2 .

[0126] The anode electrode 5 is titanium felt loaded with iridium oxide (same as in Example 1), and the electrode size is 120 mm×90 mm×0.4 mm.

[0127] Anode plate 6 is made of titanium and measures 160 mm x 130 mm x 20 mm. It has grooves and flow channels. The groove dimensions are identical to those of anode electrode 5, allowing the anode electrode 5 to fit into the grooves and contact the flow channel surfaces. The flow channels consist of three parallel serpentine channels, 2 mm wide and 1 mm deep, with each channel measuring 1.1 m long.

[0128] The cathode liquid flow plate 3 is made of PMMA with a thickness of 1.5 mm (channel depth) and uses four parallel serpentine channels with a tree-shaped distribution ( Figure 6 As shown, there are 4 serpentine flow channels in total), a single serpentine flow channel is 1.7m long, 1mm wide, and the flow channel area is 120mm×90mm.

[0129] The cathode electrolyte is a KHCO3 aqueous solution with a concentration of 1 mol / L, and the anolyte is a sulfuric acid aqueous solution with a concentration of 0.5 mol / L.

[0130] The cathode electrolyte flow rate is 80 mL / min, the carbon dioxide gas flow rate is 1000 sccm, the anolyte flow rate is 150 mL / min, the pressure in the device is controlled at 8 bar, a constant current reaction is used, and the current density is set to 3 kA / m 2 (Total current 20A). During the reaction operation, the formic acid selectivity (Faraday efficiency) results at different times are shown in Table 3.

[0131] Table 3

[0132] Running time (h) 2 4 6 8 10 Formic acid selectivity (%) 86.2 85.5 85.7 85.2 84.8 Device voltage (V) 5.48 5.46 5.52 5.53 5.51

[0133] As can be seen from Table 3, in this embodiment, the current density is set to 3kA / m 2 The formic acid selectivity can reach more than 80%, and the device voltage is about 5.5V.

[0134] From the above, we can see that this application is at 2kA / m 2 At the set current density of 2kA / m, the device operates stably for more than 200h and maintains about 80% formic acid selectivity, which can achieve long-term stable operation of the device. 2 At the set current density, the device has a CO selectivity of over 70% after 10 hours of operation, which is higher than the existing gas diffusion electrode electrolysis device, which also requires a higher device voltage.

[0135] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0136] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make several modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the appended claims, and the specification and drawings may be used to interpret the claims.

Claims

1. A carbon dioxide electrolysis device, characterized in that: The electrolytic cell (100) comprises an electrolytic cell (100), wherein the electrolytic cell (100) has a two-cavity structure and comprises a cathode plate (1), a cathode electrode (2), a cathode liquid flow plate (3), a diaphragm (4), an anode electrode (5), and an anode plate (6) which are arranged opposite to each other in sequence; One side of the cathode electrode (2) is in close contact with the cathode plate (1), and both are provided with openings, so as to form a first feed channel (a) and a first discharge channel (b) in the cathode electrode (2) and the cathode plate (1); the cathode liquid flow plate (3) has a hollow flow channel, so as to form a first cavity for the cathode electrolyte to flow between the cathode plate (1) and the diaphragm (4); One side of the anode electrode (5) is fixed on the anode plate (6), and a groove is provided on a side of the anode plate (6) facing the anode electrode (5) to form a second cavity for the circulation of anolyte between the anode plate (6) and the anode electrode (5), and the anode plate (6) is provided with an opening for forming a second feed channel (c) and a second discharge channel (d); The first feed channel (a) is connected to a gas-liquid mixer (8) for mixing carbon dioxide gas with cathode electrolyte to form a multiphase flow; The cathode electrode (2) is selected from a metal sheet electrode or a loaded conductive sheet electrode; The flow rate of the cathode electrolyte in a single flow channel is 5 to 100 mL / min, and the flow rate of carbon dioxide in a single flow channel is 5 to 1000 sccm; The reaction pressure in the electrolytic cell is 1 to 50 bar.

2. The carbon dioxide electrolysis device according to claim 1, characterized in that The metal in the metal foil electrode is selected from one or more of tin, silver, copper, gold, lead, bismuth and indium.

3. The carbon dioxide electrolysis device according to claim 1, characterized in that The loaded conductive sheet electrode comprises a conductive substrate and a metal or metal oxide loaded thereon, wherein the metal is selected from one or more of tin, silver, copper, gold, lead, bismuth and indium; the metal oxide is selected from one or more of tin oxide, silver oxide, copper oxide, gold oxide, lead oxide, bismuth oxide and indium oxide; and the conductive substrate is selected from a carbon substrate, a tin substrate, a silver substrate, a copper substrate, a titanium substrate or an iron substrate.

4. The carbon dioxide electrolysis device according to claim 1, characterized in that The thickness of the cathode liquid flow plate (3) is 0.5-5 mm, the flow channel of the cathode liquid flow plate (3) is a single serpentine flow channel, multiple serpentine flow channels or multiple straight parallel flow channels, and the width of the flow channel is 0.5-5 mm.

5. The carbon dioxide electrolysis device according to claim 4, characterized in that The cathode liquid flow plate (3) is made of polymethyl methacrylate, polytetrafluoroethylene, polyetheretherketone or chlorinated polyvinyl chloride.

6. The carbon dioxide electrolysis device according to claim 1, characterized in that The anode electrode (5) is selected from metal felt, foamed metal, foamed metal loaded with anode catalyst, or metal felt loaded with anode catalyst.

7. The carbon dioxide electrolysis device according to claim 6, characterized in that The anode catalyst is selected from one or more of titanium, platinum, palladium, nickel, iridium oxide, nickel oxide, cobalt oxide, tin oxide, indium oxide, rhodium oxide, ruthenium oxide and iron oxide.

8. The carbon dioxide electrolysis device according to claim 6, characterized in that The anode electrode (5) is selected from titanium felt, titanium foam, nickel foam, titanium felt loaded with iridium oxide, titanium foam loaded with iridium oxide, or titanium felt loaded with nickel oxide.

9. The carbon dioxide electrolysis device according to claim 1, characterized in that: The flow channel formed by the grooves in the anode plate (6) is a single serpentine flow channel, multiple serpentine flow channels or multiple straight parallel flow channels, the width of the flow channel is 0.5-3 mm, and the depth of the flow channel is 0.5-5 mm.

10. The carbon dioxide electrolysis device according to claim 1, characterized in that: The diaphragm (4) is an ion exchange diaphragm or an ion exchange diaphragm loaded with an anode catalyst.

11. The carbon dioxide electrolysis device according to claim 10, characterized in that: The anode catalyst is selected from one or more of titanium, platinum, palladium, nickel, iron, cobalt, ruthenium, rhodium, iridium, iridium oxide, nickel oxide, cobalt oxide, tin oxide, indium oxide, rhodium oxide, ruthenium oxide and iron oxide.

12. The carbon dioxide electrolysis device according to claim 10, characterized in that The diaphragm (4) is in close contact with the anode electrode (5).

13. The carbon dioxide electrolysis device according to claim 1, characterized in that The electrolytic cell (100) further includes a first sealing ring (7-1) and a second sealing ring (7-2), wherein the first sealing ring (7-1) is used to seal the first cavity to prevent multiphase flow from flowing out from around the first cavity, and the second sealing ring (7-2) is used to seal the second cavity to prevent anode electrolyte from flowing out from around the first cavity.

14. The carbon dioxide electrolysis device according to claim 1, characterized in that The gas-liquid mixer (8) is a three-way gas-liquid mixer, and the two feed ports of the gas-liquid mixer (8) are respectively connected to a cathode pump (9) and a carbon dioxide flow controller (10).

15. The carbon dioxide electrolysis device according to claim 1, characterized in that The second feed channel (c) is connected to an anode pump (12); The first discharge channel (b) is connected to a cathode back pressure valve (11), and the second discharge channel (d) is connected to an anode back pressure valve (13).

16. A method for electrolysis of carbon dioxide, characterized in that: The method is carried out in the carbon dioxide electrolysis device according to any one of claims 1 to 15, comprising: 1) Carbon dioxide gas and cathode electrolyte enter the gas-liquid mixer (8) for gas-liquid mixing to form a multiphase flow; 2) the multiphase flow enters the first cavity of the electrolytic cell (100), and the anolyte enters the second cavity of the electrolytic cell (100); when the electrolysis power supply is turned on, the carbon dioxide in the multiphase flow undergoes a reduction reaction in the first cavity, and the anolyte undergoes an oxidation reaction in the second cavity; In step 2), the reaction pressure is 1 to 50 bar.

17. The electrolysis method according to claim 16, characterized in that In step 2), the reaction pressure is 5 to 30 bar.

18. The electrolysis method according to any one of claims 16 to 17, characterized in that: The cathode electrolyte is an aqueous solution of a first electrolyte, and the anode electrolyte is an aqueous solution of water, an acid, or a second electrolyte; The first electrolyte and the second electrolyte are the same or different and are each independently a soluble salt or a base, wherein the soluble salt is selected from at least one of carbonate, bicarbonate, phosphate, hydrogen phosphate, hydrochloride, acetate, perchlorate, sulfate and formates; and the base is selected from alkali metal hydroxide and / or ammonia water. The acid is at least one of a sulfuric acid aqueous solution, a perchloric acid aqueous solution and hydrochloric acid.

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