Separator and electrochemical cell comprising same

Abstract

The present invention relates to a separator in which an anode catalyst layer is coated on one surface of a porous substrate, and an electrochemical cell comprising same, the separator allowing ions to smoothly move through pores of the porous substrate and exhibiting low overpotential due to having the anode catalyst layer coated on one surface thereof.

Description

Separator and electrochemical cell containing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0116359, filed September 1, 2023, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to a separator and an electrochemical cell including the same.

[0006]

[0007] Carbon dioxide is a greenhouse gas that causes global warming and must be reduced. Known methods for reducing carbon dioxide include capture, chemical conversion, and electrochemical conversion. Among these, electrochemical conversion allows for precise control of the composition of other synthetic gases, offering greater economic benefits than simply removing carbon dioxide. Furthermore, electrolysis of carbon dioxide with water can yield carbon monoxide, ethylene, methane, formic acid, formate, various hydrocarbons, and organic compounds such as aldehydes and alcohols.

[0008] The process of electrochemically decomposing and converting carbon dioxide using an electrochemical cell is as follows. When water is supplied to the anode and an electric current is applied, the water decomposes to produce oxygen gas, while simultaneously generating hydrogen ions and electrons. These electrons then move to the cathode through an external conductor. Carbon dioxide and water vapor are supplied to the cathode, which react with the electrons transferred from the anode to decompose into carbon monoxide and hydroxide ions. The generated hydroxide ions move to the anode through a membrane, where they are oxidized to produce oxygen gas, water, and electrons. Through this process, the electrochemical decomposition reaction of carbon dioxide proceeds.

[0009] Meanwhile, ionic membranes such as Nafion membranes are widely used as membranes applied to electrochemical cells. However, Nafion membranes are expensive and, as cation exchange membranes, have the disadvantage of limited usability under certain pH conditions. Specifically, when Nafion membranes are used in basic or neutral electrolyte conditions used in carbon dioxide electrolysis, the performance of the electrochemical cell deteriorates, such as slow ion permeation rates and high overvoltages. Meanwhile, anion exchange membranes that are compatible with basic electrolytes are more expensive than Nafion membranes, making them uneconomical for mass production and commercialization. Therefore, there is a need to develop membranes that have performance equivalent to or superior to ionic exchange membranes such as cation exchange membranes or anion exchange membranes, but at a lower cost.

[0010]

[0011] The present invention has been devised to solve the problems of the above-mentioned prior art, and aims to provide a separation membrane having performance equivalent to or superior to that of a conventional ion exchange membrane by using an inexpensive porous substrate as a separation membrane material and coating an anode catalyst layer on one surface of the porous substrate.

[0012] In addition, the present invention aims to provide an electrochemical cell including the above-described separator.

[0013]

[0014] To solve the above problems, the present invention provides a separator and an electrochemical cell including the same.

[0015] (1) The present invention provides a separation membrane comprising a porous substrate and an anode catalyst layer, wherein the anode catalyst layer comprises metal particles and a binder, and the anode catalyst layer is coated on one side of the porous substrate.

[0016] (2) The present invention provides a separation membrane in which the pores of the porous substrate in the above (1) have an average diameter of 10 nm or more and 500 nm or less.

[0017] (3) The present invention provides a separation membrane in which the porosity of the porous substrate in (1) or (2) is 50% by volume or more and 95% by volume or less.

[0018] (4) The present invention provides a separation membrane according to any one of the above (1) to (3), wherein the thickness of the porous substrate is 10 ㎛ or more and 500 ㎛ or less.

[0019] (5) The present invention provides a separation membrane in any one of the above (1) to (4), wherein the porous substrate is at least one selected from the group consisting of polyethersulfone, polytetrafluoroethylene, polyethylene, polypropylene, polyethylene terephthalate, polyester, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethylenenaphthalene, polyvinylidene fluoride, cellulose acetate, and nylon.

[0020] (6) In any one of the above (1) to (5), the content per unit area of ​​the oxidation catalyst in the anode catalyst layer is 0.1 mg / cm 2More than 3mg / cm 2 A separation membrane is provided as follows.

[0021] (7) The present invention provides a separation membrane according to any one of the above (1) to (6), wherein the thickness of the anode catalyst layer is 1 µm or more and 30 µm or less.

[0022] (8) In any one of the above (1) to (7), the metal particles have an average particle diameter (D) of the primary particles. SEM ) provides a separation membrane having a thickness of 20 nm or more and 30 nm or less.

[0023] (9) In any one of the above (1) to (8), the metal particles have an average particle diameter (D) of secondary particles. 50 ) provides a separation membrane having a thickness of 100 nm or more and 2,000 nm or less.

[0024] (10) The present invention provides an electrochemical cell comprising a separator and a cathode of any one of (1) to (9), wherein the cathode is in contact with the other surface of the separator on which the anode catalyst layer is not coated.

[0025] (11) The present invention provides an electrochemical cell in which, in the above (10), the cathode has a cathode catalyst layer coated on one side of the gas diffusion layer.

[0026] (12) The present invention provides a method for manufacturing an electrochemical cell, comprising the steps of: a step (S10) of manufacturing a separator by coating an anode catalyst layer on one side of a porous substrate; and a step (S20) of arranging a cathode so that the anode catalyst layer is in contact with the other side of the separator on which the anode catalyst layer is not coated, wherein the anode catalyst layer includes metal particles and a binder.

[0027] (13) The present invention provides a method for manufacturing an electrochemical cell, wherein in the above (12), the step S10 comprises a step (S11) of preparing an anode catalyst ink by mixing metal particles, a binder, and a solvent, a step (S12) of applying the anode catalyst ink to a transfer film to prepare an anode catalyst layer, and a step (S13) of coating the anode catalyst layer by transferring the anode catalyst layer to one side of a porous substrate.

[0028]

[0029] The separation membrane of the present invention has the advantage of high carbon dioxide conversion rate and low overvoltage due to smooth ion permeation even under basic or neutral electrolyte conditions by using a porous substrate.

[0030] In addition, the separation membrane of the present invention has the advantage of being suitable for mass production because it is cheaper than an ion exchange membrane.

[0031]

[0032] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0033] The terms and words used in this specification should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0034] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0035] In this specification, it should be understood that the terms “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0036] In this specification, "primary particle" means the smallest particle unit that can be distinguished as a single lump when observing metal particles through a scanning electron microscope (SEM), and may be composed of multiple crystal grains. The average particle diameter (D) of the primary particle SEM ) can be measured using scanning electron microscope images.

[0037] In this specification, "average particle diameter (D SEM )" means the arithmetic mean value calculated after measuring the particle diameters of primary particles observed in a scanning electron microscope image. Specifically, the average particle diameter can be measured by measuring the length of the diameter of primary particles observed in a scanning electron microscope image and then calculating the arithmetic mean value of the length.

[0038] In this specification, "secondary particle" means a secondary structure formed by the aggregation of multiple primary particles. The average particle diameter (D) of the secondary particles 50 ) can be measured using a particle size analyzer.

[0039] In this specification, "average particle diameter (D 50)" means the particle size at the 50% point of the volume cumulative distribution according to particle size. The above average particle size is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Malvern Panlytical, Zetasizer) and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, and calculating the particle size distribution, and calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to particle size in the measuring device, thereby obtaining D 50 can be measured.

[0040] In this specification, "average diameter" refers to the average diameter measured by the BET (Brunauer-Emmett-Teller Analysis) method. For example, the average diameter of the pores of a porous substrate can be measured by the BET method, which measures the specific surface area of ​​the sample surface, pore size, and distribution by adsorbing the measurement target to a gas.

[0041] In this specification, "porosity" refers to the volume ratio of pores (small holes or empty spaces) of a porous material, and for example, the porosity can be derived by measuring the density, weight, and volume of a material and calculating them inversely using them. Specifically, the volume of the membrane can be derived from the thickness and area of ​​the manufactured membrane, and the density of the membrane can be derived using the weight of the membrane and the calculated volume of the membrane. Next, the packing density of the membrane can be calculated using the density of the material itself without pores included in the membrane and the calculated density of the membrane, and then the porosity volume% can be derived using Equation 1 below.

[0042] [Formula 1]

[0043] Porosity (vol%) = (1-packing density) × 100

[0044] In this specification, “content per unit area” is measured by multiplying the weight ratio of the target material in the catalyst layer by the difference in weight between the porous substrate coated with the catalyst layer and the porous substrate before coating, divided by the area of ​​one side of the porous substrate.

[0045] In this specification, the "separation membrane" is applied to an electrochemical device such as carbon dioxide electrolysis, water electrolysis, or fuel cell, and generates hydrogen ions (H + ) or hydroxide ions (OH - ) refers to a membrane that can transmit anions such as hydroxide ions. For example, the membrane may be a porous substrate having pores through which hydroxide ions can pass.

[0046] In this specification, the term "porous substrate" refers to a substrate having a plurality of pores formed therein, through which gas or liquid can pass. The pores refer to regions within the porous substrate where no constituent material of the porous substrate exists, and the shape of the pores may be not only spherical, but also polyhedral or amorphous, having length, width, and height determined by intersection of straight or curved elements. For example, the porous substrate may be in the form of a sheet, and an electrolyte containing ions can pass through the pores of the porous substrate.

[0047] In this specification, "cathode" may mean an electrode where a reduction reaction of a reactant occurs in an electrochemical device such as carbon dioxide electrolysis, water electrolysis, or a fuel cell.

[0048] In this specification, "anode" may mean an electrode where an oxidation reaction of a reactant occurs in an electrochemical device such as carbon dioxide electrolysis, water electrolysis, or a fuel cell.

[0049] As used herein, the term "electrochemical cell" refers to a device comprising a cathode, an anode, and a separator disposed between the cathode and the anode. The electrochemical cell may be applied to an electrochemical conversion device capable of producing useful chemicals through electrochemical conversion, such as an electrochemical device such as carbon dioxide electrolysis, water electrolysis, or a fuel cell.

[0050]

[0051] membrane

[0052] The present invention provides a separation membrane.

[0053] According to one embodiment of the present invention, the separation membrane includes a porous substrate and an anode catalyst layer, the anode catalyst layer includes metal particles and a binder, and the anode catalyst layer may be coated on one surface of the porous substrate.

[0054] The separator of the present invention is characterized by including a porous substrate having pores through which ions generated from a cathode can move. In this case, the porous substrate may be in the form of a sheet on which an anode catalyst layer can be coated in a flat shape on one surface of the substrate. In the separator of the present invention, ions generated from the cathode reach the anode catalyst layer through the pores of the separator in a state of being contained in the electrolyte, so that the ions can smoothly reach the anode catalyst layer according to the movement of the electrolyte even without using an ion exchange membrane.

[0055] Compared to a case where the anode catalyst layer is coated on a separate substrate rather than a separator, the separator of the present invention can lower the overvoltage of the electrode by reducing the interfacial resistance between the separator and the anode catalyst layer since the anode catalyst layer is coated on one side of the porous substrate. In addition, since the hydroxide ions generated at the cathode can immediately meet the anode catalyst layer coated on one side of the porous substrate after passing through the separator, there is an advantage in that the movement distance of the ions can be shortened, thereby improving the performance of the electrode. On the other hand, in the case of a separator in which the cathode catalyst layer is coated on one side of the porous substrate and the anode catalyst layer is not coated on the other side, unlike the separator of the present invention, the ions that pass through the separator may float in the electrolyte without immediately meeting the anode catalyst layer, and thus the effect of improving the performance of the electrode may not be exhibited. In addition, when the cathode catalyst layer is coated on one surface of the porous substrate and the cathode catalyst particles are attached to one surface of the porous substrate, the resistance may increase as the catalyst particles hinder the movement of hydroxide ions to the anode through the separator, and as a result, the overvoltage of the electrochemical cell may increase. Meanwhile, the separator is characterized in that the other surface of the porous substrate is not coated with the cathode catalyst layer. When the cathode catalyst layer is coated on the other surface of the porous substrate, the thickness of the separator may increase, which may increase the resistance due to the separator, and as a result, problems such as an increase in the overvoltage may occur. That is, the separator is characterized in that no material, including the cathode catalyst layer, is coated or attached to the other surface of the porous substrate on which the anode catalyst layer is not coated, and only the constituent materials and pores of the porous substrate exist.

[0056] The metal particles included in the anode catalyst layer of the present invention may be metal particles including one or more elements selected from the group consisting of Ir, Pt, Au, Pd, Ag, Rh, Ru, Ni, Al, Mo, Cr, Cu, Ti, W, and Ta, and the listed elements may act as a catalyst for an oxidation reaction in the anode catalyst layer to lower the activation energy of the oxidation reaction of water. Specifically, the metal particles may be in the form of IrO(OH) attached to the surface of a TiO2 support, and iridium in the metal particles may act as a catalyst for the oxidation reaction of water and hydroxide ions in the anode to promote the generation of oxygen gas.

[0057] One surface of the porous substrate of the present invention is coated with an anode catalyst layer, but the internal pores of the porous substrate may not be filled with metal particles constituting the anode catalyst layer. Since the internal pores of the porous substrate of the present invention are not filled with metal particles, the risk of metal particles reaching the cathode during operation of the electrochemical cell, thereby causing the loss of function of the electrochemical cell, can be prevented. In addition, since the internal pores of the porous substrate are not filled with metal particles, ions can smoothly move through the pores, thereby improving the performance of the electrochemical cell.

[0058] In addition, the anode catalyst layer of the present invention includes a binder. The binder is attached to the surface of the metal particles to prevent aggregation between the metal particles, thereby enabling the metal particles to be evenly distributed within the anode catalyst layer. In addition, the binder functions as an adhesive to prevent the metal particles from detaching from one side of the porous substrate. Specifically, the binder may be an ionomer such as Nafion, Sustainion, or Aemion, and the ionomer is attached to the surface of the metal particles within the anode catalyst layer to prevent aggregation between the metal particles, and at the same time, connects the metal particles to one side of the porous substrate, thereby preventing the metal particles from detaching from one side of the porous substrate.

[0059]

[0060] According to one embodiment of the present invention, the pores of the porous substrate may have an average diameter of 10 nm or more and 500 nm or less, and specifically, the average diameter of the pores may be 10 nm or more, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, 100 nm or more, 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more, 160 nm or more, 170 nm or more, 180 nm or more, 190 nm or more, or 200 nm or more, and also 500 nm or less, 490 nm or less, 480 nm or less, 470 nm or less, 460 nm or less, 450 nm or less, 440 nm or less, 430 nm or less, 420 nm or less, It may be 410 nm or less, 400 nm or less, 390 nm or less, 380 nm or less, 370 nm or less, 360 nm or less, 350 nm or less, 340 nm or less, 330 nm or less, 320 nm or less, 310 nm or less, or 300 nm or less. When the average diameter of the pores of the porous substrate satisfies the above range, ions generated at the cathode can smoothly move through the pores of the separator. Therefore, the carbon dioxide conversion rate of the electrochemical cell including the separator increases, so that the performance of the electrochemical cell can be improved. In addition, when the average diameter of the pores satisfies the above range, the mechanical properties of the separator are superior compared to when the pore diameter is excessively large, so that the electrochemical cell including the separator can be stably operated.

[0061]

[0062] According to one embodiment of the present invention, the porosity of the porous substrate may be 15% by volume or more and 95% by volume or less, and specifically, the porosity may be 15% by volume or more, 20% by volume or more, 25% by volume or more, 30% by volume or more, 35% by volume or more, 40% by volume or more, 45% by volume or more, 50% by volume or more, 55% by volume or more, 60% by volume or more, 65% by volume or more, and further may be 95% by volume or less, 90% by volume or less, 85% by volume or less, 80% by volume or less, 77% by volume or less, 75% by volume or less, 70% by volume or less, and 69% by volume or less. The above porosity refers to the ratio of the volume of pores to the total volume of the porous substrate. When the porosity of the porous substrate satisfies the above range, sufficient pores exist within the porous substrate, allowing ions to move smoothly through the pores, thereby improving the performance of the electrochemical cell including the separator. In addition, when the porosity of the porous substrate satisfies the above range, the mechanical properties of the separator are excellent, allowing the electrochemical cell including the separator to be stably operated.

[0063]

[0064] According to one embodiment of the present invention, the thickness of the porous substrate may be 10 ㎛ or more and 500 ㎛ or less, and specifically, the thickness of the porous substrate may be 10 ㎛ or more, 50 ㎛ or more, 100 ㎛ or more, 125 ㎛ or more, 150 ㎛ or more, 200 ㎛ or more, 220 ㎛ or more, or 250 ㎛ or more, and further may be 500 ㎛ or less, 450 ㎛ or less, 400 ㎛ or less, 350 ㎛ or less, 300 ㎛ or less, or 250 ㎛ or less. When the thickness of the porous substrate satisfies the above range, the resistance of the separator is lowered compared to a case where the separator is excessively thick, and thus the performance of the electrode may be improved. In addition, compared to a case where the thickness of the separator is excessively thin, the mechanical properties of the separator are excellent, and thus an electrochemical cell including the separator may be stably operated.

[0065]

[0066] According to one embodiment of the present invention, the porous substrate may be at least one selected from the group consisting of polyethersulfone, polytetrafluoroethylene, polyethylene, polypropylene, polyethylene terephthalate, polyester, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethylenenaphthalene, polyvinylidene fluoride, cellulose acetate, and nylon. The porous substrate listed above contains a large number of pores within the substrate, so that ions generated at the anode can move to the cathode through the pores, and has the advantage of being cheaper than ion exchange membranes. Specifically, the porous substrate may be polyethersulfone, and polyethersulfone contains sufficient pores within the substrate, so that hydroxide ions generated at the anode can smoothly move to the cathode through the pores. Additionally, polyethersulfone has the advantage of being suitable for mass production due to its low price compared to ion exchange membranes such as Nafion and Aemion.

[0067]

[0068] According to one embodiment of the present invention, the content per unit area of ​​the oxidation catalyst in the anode catalyst layer is 0.1 mg / cm 2 More than 3.0 mg / cm 2 It may be less than or equal to, and specifically, the content per unit area of ​​the oxidation catalyst is 0.1 mg / cm 2 Above, 0.2 mg / cm 2 Above, 0.3 mg / cm 2 Above, 0.4 mg / cm 2 Above, 0.5 mg / cm 2 Above, 0.6 mg / cm 2 Above, 0.7 mg / cm 2 Above, 0.8 mg / cm 2 Above, 0.9 mg / cm 2 Above, 1.0 mg / cm 2 or more than 1.1 mg / cm 2 It may be more than 3.0 mg / cm 2 Below, 2.9 mg / cm 2 Below, 2.8 mg / cm 2 Below, 2.7 mg / cm 2 Below, 2.6 mg / cm 2 Below 2.5 mg / cm 2 Below, 2.4 mg / cm 2 Below, 2.3 mg / cm 2 Below 2.2 mg / cm 2 Below, 2.1 mg / cm 2 Below 2.0 mg / cm 2 Below, 1.9 mg / cm 2 Below, 1.8 mg / cm 2 Below, 1.7 mg / cm 2 Below, 1.6 mg / cm 2 Below 1.5 mg / cm 2 Below, 1.4 mg / cm 2 Below, 1.3 mg / cm 2 Below, 1.2 mg / cm 2 Below, 1.1 mg / cm 2 Below 1.0 mg / cm 2Below 0.9 mg / cm 2 Below 0.8 mg / cm 2 Below 0.7 mg / cm 2 It may be as follows. The oxidation catalyst may include one or more elements selected from the group consisting of Ir, Pt, Au, Pd, Ag, Rh, Ru, Ni, Al, Mo, Cr, Cu, Ti, W and Ta included in the metal particles of the present invention as described above, and the oxidation catalyst may act as a catalyst for the oxidation reaction in the anode catalyst layer to reduce the activation energy of the oxidation reaction of water. When the content per unit area of ​​the oxidation catalyst in the anode catalyst layer satisfies the above range, the oxidation reaction of water and hydroxide ions can sufficiently occur in the anode catalyst layer. As a result, the number of electrons moving to the cathode through the conductor increases, so that the carbon dioxide reduction reaction at the cathode can be further promoted. In addition, the degree of improvement in electrode performance relative to the cost of the oxidation catalyst introduced in the above range is high, so that it can be economical. Specifically, according to one embodiment of the present invention, the metal particles may be in the form of IrO(OH) attached to the surface of a TiO2 support, and the content per unit area of ​​iridium, which is an oxidation catalyst in the anode catalyst layer, is 0.1 mg / cm 2 More than 3.0 mg / cm 2 It may be as follows. When the content of iridium in the anode catalyst layer is as above, the oxidation reaction of water can sufficiently occur in the anode catalyst layer, and the carbon dioxide reduction reaction at the cathode can be further promoted.

[0069]

[0070] According to one embodiment of the present invention, the thickness of the anode catalyst layer may be 1 ㎛ or more and 50 ㎛ or less, and specifically, the thickness of the anode catalyst layer may be 1 ㎛ or more, 5 ㎛ or more, 10 ㎛ or more, 15 ㎛ or more, or 20 ㎛ or more, and may also be 50 ㎛ or less, 45 ㎛ or less, 40 ㎛ or less, 35 ㎛ or less, 30 ㎛ or less, 25 ㎛ or less, 20 ㎛ or less, or 15 ㎛ or less. When the thickness of the anode catalyst layer satisfies the above range, the mechanical properties of the electrode catalyst layer may be excellent, and at the same time, the resistance of the separator may be low because the catalyst layer is not excessively thick. In addition, since the anode catalyst layer may sufficiently contain metal particles, the oxidation reaction of water and the oxidation reaction of hydroxide ions may be actively performed in the anode catalyst layer, and as a result, the carbon dioxide conversion reaction at the cathode may be further promoted.

[0071]

[0072] According to one embodiment of the present invention, the metal particles have an average particle diameter (D) of primary particles SEM ) may be 20 nm or more and 30 nm or less, and specifically, the average particle diameter of the primary particles may be 20 nm or more, 21 nm or more, 22 nm or more, 23 nm or more, 24 nm or more, or 25 nm or more, and may also be 30 nm or less, 29 nm or less, 28 nm or less, 27 nm or less, or 26 nm or less. The average particle diameter of the primary particles (D SEM) satisfies the above range, the specific surface area of ​​the primary particle is high, so that the oxidation reaction of hydroxide ions and water can actively occur on the surface of the metal particle. As a result, the amount of electrons moving to the cathode through the conductor increases, so that the carbon dioxide reduction reaction at the cathode can be further promoted. Specifically, the primary particle may be formed of a crystal grain or multiple crystal grains in which one or more particles having IrO(OH) attached to the surface of a TiO2 support are aggregated, and the average particle diameter of the crystal grain or multiple crystal grains may be 20 nm or more and 30 nm or less. Iridium, which is an oxidation catalyst, can actively promote the oxidation reaction of water and hydroxide ions on the surface of the primary particle having the above average particle diameter.

[0073]

[0074] According to one embodiment of the present invention, the metal particles have an average particle diameter (D) of secondary particles 50 ) may be 100 nm or more and 2,000 nm or less, and specifically, the average particle diameter of the secondary particles may be 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, 500 nm or more, or 600 nm or more, and may also be 2,000 nm or less, 1,900 nm or less, 1,800 nm or less, 1,700 nm or less, 1,600 nm or less, 1,500 nm or less, 1,400 nm or less, 1,300 nm or less, 1,200 nm or less, 1,100 nm or less, 1,000 nm or less, 900 nm or less, 800 nm or less, or 700 nm or less. The average particle diameter (D) of the secondary particles 50) satisfies the above range, the specific surface area of ​​the secondary particles is high, so that the oxidation reaction of hydroxide ions and water can actively occur on the surface of the metal particles. In addition, since the average particle diameter of the secondary particles is sufficiently large, pores for the hydroxide ions or water particles to penetrate into the interior of the secondary particles can be sufficiently formed on the surface of the secondary particles, and as a result, the oxidation reaction of hydroxide ions or water particles can also actively occur not only on the surface of the secondary particles but also inside the secondary particles. As a result, the amount of electrons moving to the cathode through the conductor increases, so that the carbon dioxide reduction reaction at the cathode can be further promoted. Specifically, the secondary particles may be in the form of a secondary structure in which one or more particles having IrO(OH) attached to the surface of a TiO2 support are aggregated or primary particles composed of multiple crystal grains are again aggregated, and the average particle diameter of the secondary structure may be 100 nm or more and 2,000 nm or less. Iridium, which is an oxidation catalyst, can actively promote the oxidation reaction of water and hydroxide ions on the surface and inside of secondary particles having the above average particle diameter.

[0075]

[0076] electrochemical cell

[0077] The present invention provides an electrochemical cell including the above-described separator.

[0078] According to one embodiment of the present invention, the electrochemical cell may include the separator and the cathode, and the cathode may be in contact with the other surface of the separator on which the anode catalyst layer is not coated.

[0079] The above-described separator may be in the form of an anode catalyst layer coated on one side of a porous substrate, and the anode catalyst layer may include metal particles and a binder. In addition, the other side of the separator on which the anode catalyst layer is not coated, that is, the other side of the porous substrate, may be in contact with a cathode. Therefore, in the electrochemical cell of the present invention, the anode catalyst layer coated on one side of the porous substrate may be an anode, and the cathode may be a gas diffusion layer coated with a cathode catalyst layer, or a substrate separate from the porous substrate and the gas diffusion layer may be coated with a cathode catalyst layer. That is, the electrochemical cell of the present invention is characterized in that the other side of the porous substrate is not coated with a cathode catalyst layer. This is because, when a cathode catalyst layer is coated on the other side of the porous substrate, cathode catalyst particles may impede the movement of hydroxide ions to the anode, which may increase resistance, and as a result, may increase overvoltage. Additionally, the cathode catalyst layer may include a catalyst for a carbon dioxide reduction reaction comprising one or more elements selected from the group consisting of Ag, Au, Zn, In, Cu, Ni, Pt, Pd, Ti, Fe, Ga, and Sn.

[0080] According to one embodiment of the present invention, the electrochemical cell may be a cell that electrolyzes carbon dioxide and water vapor to convert them into carbon monoxide and hydroxide ions, and the electrochemical cell can be utilized in all electrochemical conversion devices that can produce useful chemical substances through electrochemical conversion, such as fuel cells and water electrolysis devices, in addition to carbon dioxide electrolysis devices. Specifically, the carbon dioxide electrolysis process is as follows. In the anode catalyst layer coated on one surface of the porous substrate, an oxidation reaction of water occurs to generate oxygen gas, hydrogen ions, and electrons, and the generated electrons are transferred to the cathode through a conductor. In the cathode, carbon dioxide and water vapor supplied from the gas diffusion layer react with electrons transferred from the anode catalyst layer to decompose into carbon monoxide and hydroxide ions, and the generated hydroxide ions, while being contained in the electrolyte, pass through the porous substrate of the separation membrane and move to the anode catalyst layer. Subsequently, in the anode catalyst layer, the hydroxide ions are oxidized to generate oxygen gas, water, and electrons. In the electrochemical cell of the present invention, an electrochemical decomposition reaction of carbon dioxide proceeds through the above process.

[0081] According to one embodiment of the present invention, the cathode may have a cathode catalyst layer coated on one side of the gas diffusion layer. Specifically, unlike the anode, the cathode catalyst layer may not be coated on one side of the porous substrate, but may be coated on one side of the gas diffusion layer and be in contact with the other side of the porous substrate. In the electrochemical cell of the present invention, the cathode catalyst layer is coated on one side of the gas diffusion layer, not the other side of the porous substrate, and is in contact with the other side of the porous substrate. Therefore, compared to when the cathode catalyst layer is coated on the other side of the separator, the thickness of the separator is thinner, thereby reducing the resistance of the separator. In addition, compared to when the cathode catalyst layer is coated on a separate substrate from the gas diffusion layer, the interfacial resistance between the gas diffusion layer and the cathode catalyst layer can be reduced, and since no separate substrate is required, the structure of the electrochemical cell can also be simplified.

[0082]

[0083] Electrochemical cell manufacturing method

[0084] The present invention provides a method for manufacturing the above-described electrochemical cell.

[0085] According to one embodiment of the present invention, the method for manufacturing an electrochemical cell includes a step (S10) of manufacturing a separator by coating an anode catalyst layer on one side of a porous substrate, and a step (S20) of arranging a cathode so that the anode catalyst layer is in contact with the other side of the separator on which the anode catalyst layer is not coated in step S10, and the anode catalyst layer may include metal particles and a binder.

[0086] The above step S10 is a step for manufacturing the separator of the present invention described above, and may be a step for coating an anode catalyst layer including the metal particles and a binder on one side of a porous substrate. The metal particles included in the anode catalyst layer may be metal particles including one or more elements selected from the group consisting of Ir, Pt, Au, Pd, Ag, Rh, Ru, Ni, Al, Mo, Cr, Cu, Ti, W, and Ta, and the listed elements may act as a catalyst for the oxidation reaction in the anode catalyst layer to lower the activation energy of the oxidation reaction of water and hydroxide ions. The separator manufactured through the above step S10 has an advantage in that the interfacial resistance between the separator and the anode catalyst layer is reduced because the anode catalyst layer is coated on one side of the porous substrate, thereby lowering the overvoltage of the electrode. In addition, since the hydroxide ions generated at the cathode can meet the anode catalyst layer immediately after penetrating the porous substrate, the migration distance of the ions is shortened, thereby improving the performance of the electrode.

[0087] The above step S20 is a step of arranging the cathode so that it is in contact with the other surface of the separator on which the anode catalyst layer is not coated, and the cathode may be a gas diffusion layer or a substrate separate from the porous substrate and the gas diffusion layer in which the cathode catalyst layer is coated. That is, the electrochemical cell manufacturing method of the present invention is characterized in that the other surface of the porous substrate is not coated with a cathode catalyst layer. This is because, if the cathode catalyst layer is coated on the other surface of the porous substrate, the cathode catalyst particles may impede the movement of hydroxide ions to the anode, which may increase the resistance. In addition, if the cathode catalyst layer is coated on the other surface, the thickness of the separator may increase, which may increase the resistance due to the separator, and as a result, problems such as an increase in overvoltage may occur. Specifically, the cathode may be in the form of a cathode catalyst layer coated on one surface of a gas diffusion layer, and the cathode catalyst layer may include a catalyst for a carbon dioxide reduction reaction including one or more elements selected from the group consisting of Ag, Au, Zn, In, Cu, Ni, Pt, Pd, Ti, Fe, Ga, and Sn.

[0088]

[0089] According to one embodiment of the present invention, the step S10 may include a step of preparing an anode catalyst ink by mixing metal particles, a binder, and a solvent (S11), a step of applying the anode catalyst ink to a transfer film to prepare an anode catalyst layer (S12), and a step of coating the anode catalyst layer by transferring the anode catalyst layer to one side of a porous substrate (S13). The step S10 may be a step of preparing a separator by performing coating in a manner of preparing an anode catalyst layer on a transfer film and then transferring the anode catalyst layer to one side of a porous substrate. Specifically, in the step S11, after mixing metal particles, a binder, and a solvent to prepare an anode catalyst ink, in the step S12, the catalyst ink is applied to a transfer film separate from the porous substrate and dried to prepare a solid anode catalyst layer. Next, in step S13, the anode catalyst layer formed on the transfer film is transferred to one side of a porous substrate, thereby manufacturing a separator having the anode catalyst layer coated on one side of the porous substrate. Compared to a method of directly applying the anode catalyst ink to one side of the porous substrate and coating, when coating is performed by transfer as in steps S11 to S13, there is an advantage in that the problem of the substrate swelling due to moisture can be prevented since the liquid catalyst ink is applied to one side of the porous substrate. In addition, since the solid anode catalyst layer is transferred to one side of the porous substrate, the problem of the liquid catalyst ink penetrating into the pores of the porous substrate and then reaching the cathode, thereby losing the function of the electrochemical cell, can be prevented, thereby enabling the safe manufacture of an electrochemical cell. That is, when manufacturing a separation membrane according to steps S11 to S13, since a solid anode catalyst layer is coated on a porous substrate, there is an advantage in that the porous substrate does not swell due to moisture and the liquid anode catalyst ink does not penetrate into the pores.

[0090]

[0091] Hereinafter, the present invention will be described in more detail with examples and experimental examples to specifically explain the present invention. However, the present invention is not limited to these examples and experimental examples. The examples according to the present invention can be modified in various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more fully explain the present invention to those of average skill in the art.

[0092]

[0093] Examples and Comparative Examples

[0094] Example 1

[0095] An anode catalyst ink was prepared by mixing 1 g of metal particles (TiO2 with IrO(OH) attached) with 4.6 mL of a solution containing 1-propanol, ultrapure water, and Nafion binder in a weight ratio of 3.3:0.42:075, respectively. The anode catalyst ink was applied to a PTFE transfer film using a bar coating device and then dried to prepare an anode catalyst layer. Subsequently, the PTFE film coated with the anode catalyst layer was laminated onto a polyethersulfone porous substrate having an average pore diameter of 200 nm, a porosity of 77% by volume, and a thickness of 150 μm, and then transferred using a press. After the transfer, the PTFE film was removed, and a separator was prepared in which the anode catalyst layer was coated on one surface of the polyethersulfone porous substrate. The iridium content per unit area in the anode catalyst layer was 0.4 mg / cm 2 , and the thickness of the anode catalyst layer was 10 ㎛. In addition, the average particle diameter (D) of the primary particles of the metal particles in the anode catalyst layer SEM ) is 25 nm, and the average particle diameter of the secondary particles (D 50 ) was 600 nm.

[0096] Example 2

[0097] The conditions were the same as those of Example 1, but instead of the polyethersulfone porous substrate, cellulose acetate (thickness: 125 μm, porosity: 69% by volume, average pore diameter: 200 nm) was used to manufacture a membrane with an anode catalyst layer coated on one side.

[0098] Example 3

[0099] Other conditions are the same as in Example 1, but the content per unit area of ​​iridium in the anode catalyst layer is 0.4 mg / cm 2 Instead, 0.7 mg / cm 2 A separator with an anode catalyst layer coated on one side was manufactured by adjusting the

[0100] Example 4

[0101] The conditions were the same as those of Example 1, but instead of the polyethersulfone porous substrate, a Zirfon220 membrane (thickness: 220 μm, porosity: 55% by volume, average pore diameter: 150 nm) was used to manufacture a membrane with an anode catalyst layer coated on one side.

[0102]

[0103] Comparative Example 1

[0104] The same polyethersulfone porous substrate used in the above example was used as a separator. However, unlike Example 1, the polyethersulfone porous substrate was not coated with an anode catalyst layer, and a titanium mesh substrate coated with iridium particles was used as the anode, and the anode was positioned so as to be in contact with one surface of the separator.

[0105] Comparative Example 2

[0106] The conditions for Example 1 were the same, but instead of the polyethersulfone porous substrate, a Nafion membrane, which is a cation exchange membrane, was used to manufacture a membrane with an anode catalyst layer coated on one side.

[0107] Comparative Example 3

[0108] The conditions for Example 1 were the same, but instead of the polyethersulfone porous substrate, an anion exchange membrane, an Amyon membrane, was used to manufacture a membrane coated with an anode catalyst layer on one side.

[0109] Comparative Example 4

[0110] The conditions for Example 1 were the same, but instead of the anode catalyst layer, a cathode catalyst layer containing Ag particles was coated on one side of a polyethersulfone porous substrate to manufacture a separator in which the cathode catalyst layer was coated on one side of the porous substrate.

[0111] Comparative Example 5

[0112] The conditions for Example 1 were the same, but a cathode catalyst layer including Ag particles was coated on the other side of a polyethersulfone porous substrate not coated with an anode catalyst layer, thereby manufacturing a separator in which an anode catalyst layer and a cathode catalyst layer were coated on each side of the porous substrate.

[0113] Comparative Example 6

[0114] The conditions were the same as those in Example 1, but a separation membrane was manufactured using a polyethersulfone porous substrate having a porosity of 19.0% by volume.

[0115]

[0116] Experimental example

[0117] (1) Manufacturing of electrochemical cells

[0118] Cathode catalyst ink containing Ag particles was applied at a pressure of 25 cm 2A cathode was manufactured by coating one side of a gas diffusion layer (JNT30-A6P (JNTG Co.)) having an area of ​​120°C with an ultrasonic spray coater. In the case of Examples 2 and 3, the cathode was placed in contact with the other side of the separator on which the anode catalyst layer was not coated, thereby manufacturing an electrochemical cell. In the case of Comparative Example 1, the cathode was placed in contact with the other side of the separator on which the anode was not in contact, and in the case of Comparative Examples 4 and 5, the anode of Comparative Example 1 was placed in contact with the other side of the separator on which the cathode catalyst layer was not coated, thereby manufacturing an electrochemical cell.

[0119]

[0120] (2) Evaluation of electrochemical performance according to current density

[0121] The reaction was carried out for 30 minutes using the above electrochemical cell, and 0.5 M CsHCO3 was supplied as an electrolyte to the anode at a temperature of 40°C at a rate of 25 mL / min, and humidified carbon dioxide was supplied to the cathode at a temperature of 40°C at a rate of 200 mL / min. Using a VSP Potentiostat (BioLogic Co.), the currents were 100, 200, and 300 mA / cm 2 The current density was applied for 30 minutes, and a reaction voltage of 1 to 4 V was applied to measure the overvoltage, carbon dioxide conversion rate, and faradaic efficiency for the product.

[0122] The above overvoltage measurement was performed using a VSP Potentiostat (BioLogic). An 80 A booster was installed, and current corresponding to a large area was applied. The current application rates were 100, 200, and 300 mA / cm, respectively. 2 After maintaining it for a certain period of time, the voltage at the point where 15 minutes had elapsed was recorded.

[0123] The conversion rate of the above carbon dioxide was calculated as the ratio of carbon monoxide produced to the amount of carbon dioxide gas injected per hour, and the Faraday efficiency was measured by analyzing the gas composition in the exhaust line through GC (Gas Chromatography). The Faraday efficiency was calculated using the following equation.

[0124] [Mathematical Formula 1]

[0125]

[0126]

[0127] In the above mathematical expression 1, Q is the flow rate in the discharge line, F is the Faraday constant, p is the pressure, T is the measured temperature, and R is the ideal gas constant. The total current (i total ) is the value of the total current applied over time, and the current for the product (i product ) is the volume of gas measured through GC analysis (V product ) is the value calculated from.

[0128]

[0129] Discrimination performance Example 1 Example 2 Example 3 Example 4 Comparative example 1100 mA / cm 2 Overvoltage (V) -2.559-2.500-2.52-2.62-2.84CO Faradaic efficiency (%) 97.09100.0095.8499.5699H2Faraday efficiency (%) 9.551.0110.360.790.25CO2 conversion rate (%) 9.59.869.229.749.96200 mA / cm 2 Overvoltage (V) -2.679-2.640-2.68-2.82-3.111CO Faradaic efficiency (%) 100 100.00 92.3 195.18 95.46H2 Faradaic efficiency (%) 4.13 0.25 020.7 0.23CO2 Conversion rate (%) 21.19 18.78 17.76 18.62 19.22 300 mA / cm 2Overvoltage (V) -2.785-2.9-2.85-2.99-3.301COFaraday efficiency (%)94.9895.8492.0092.5892.55H2Faraday efficiency (%)2.770.63.011.150.36CO2 conversion rate (%)27.8726.6325.3027.1727.95

[0130] Discrimination performance comparison example 2 Comparison example 3 Comparison example 4 Comparison example 5 Comparison example 6100 mA / cm 2 Overvoltage (V) -2.873-2.585-3.753- (>5 V)- (>5 V)CO Faradaic efficiency (%) 64.9110.2678.69--H2 Faradaic efficiency (%) 38.5893.9610.22--CO2 conversion rate (%) 3.718.897.57--200 mA / cm 2 Overvoltage (V) -3.028-2.759---CO Faradaic efficiency (%) 61.814.73---H2 Faradaic efficiency (%) 38.4990.18---CO2 conversion rate (%) 7.4117.07---300 mA / cm 2 Overvoltage (V) -3.103-2.888---CO Faradaic efficiency (%) 66.912.91---H2 Faradaic efficiency (%) 32.3386.34---CO2 conversion rate (%) 9.3324.51---

[0131] As shown in Tables 1 and 2 above, in the case of the electrochemical cells of Examples 1 to 4 using a separator in which an anode catalyst layer was coated on one side of a porous substrate, the overvoltage was lower than that of the electrochemical cell of the comparative example at all current densities, and furthermore, as the current density increased, the overvoltage of the examples was significantly lower than that of the comparative example. In particular, in the case of the electrochemical cells of Comparative Examples 4 to 6 in which a cathode catalyst layer was coated on one side of a porous substrate, the overvoltage exceeded 5 V, which is the limit of the measuring device, and thus measurement was impossible. In addition, not only the overvoltage but also the carbon dioxide conversion rate and the faradaic efficiency of the product could not be measured. In the case of Comparative Example 4 in which a cathode catalyst layer was coated on one side of a porous substrate, the cathode catalyst particles hindered the movement of hydroxide ions through the separator, which increased the resistance of the separator, resulting in a significantly high overvoltage. In addition, in the case of Comparative Example 5, in which an anode catalyst layer and a cathode catalyst layer were coated on each side of the porous substrate, in addition to the resistance increasing effect of the cathode catalyst particles, the thickness of the separator was thicker than in the example, so that the resistance increased further, and as a result, the overvoltage was high enough to exceed 5 V at all current densities.

[0132] In addition, in the case of Comparative Example 6, the porosity was outside the scope of the present invention, and as in Comparative Example 5, the overvoltage was so high as to exceed 5 V at all current densities that measurement was impossible.

[0133] In addition, when comparing the electrochemical cells of Examples 1 and 2 in which the anode catalyst layer was coated on one side of the porous substrate and Comparative Example 1 in which the separator was not coated with the anode catalyst layer on one side of the porous substrate, the electrochemical cells of Examples 1 and 2 were found to have lower overvoltages at all current densities. In the case of Comparative Example 1 in which the anode catalyst layer was not coated on the separator, the resistance may increase as the anode and the separator become separated during operation of the electrochemical cell, resulting in a higher overvoltage compared to the Examples. From this, it can be confirmed that the separator of the present invention lowers the overvoltage by reducing the interfacial resistance between the separator and the anode by coating the anode catalyst layer on one side of the porous substrate.

[0134] Meanwhile, when comparing the electrochemical cells of Comparative Examples 2 and 3 using commonly used Nafion and Amyon membranes with the electrochemical cells of Examples 1 and 2, it can be confirmed that the electrochemical cell using the membrane of the Examples not only has a low overvoltage but also a high carbon dioxide conversion rate. This is because, unlike ion exchange membranes, the separator of the present invention has pores, so that the hydroxide ions generated at the cathode can quickly move to the anode through the pores while being contained in the electrolyte. Therefore, it can be confirmed that the separator of the present invention enables the production of an electrochemical cell having a low overvoltage and an excellent carbon dioxide conversion rate compared to ionic separators such as conventional Nafion and Amyon. In addition, since a porous substrate that is less expensive than the ionic separator is used, there is also an economic advantage, and thus, it has the advantage of being suitable for mass production.

[0135] From these results, it can be confirmed that the separator of the present invention allows hydroxide ions generated at the cathode to move smoothly through the pores of the porous substrate, and since the anode catalyst layer is coated on one surface of the separator, the interfacial resistance between the anode and the separator is also low, and thus it is possible to manufacture an electrochemical cell with low overvoltage and excellent electrode performance using the separator of the present invention.

Claims

1. Containing a porous substrate and an anode catalyst layer, The above anode catalyst layer comprises metal particles and a binder, A separation membrane in which the anode catalyst layer is coated on one side of the porous substrate.

2. In paragraph 1, A separation membrane in which the pores of the above porous substrate have an average diameter of 10 nm or more and 500 nm or less.

3. In paragraph 1, A separation membrane in which the porosity of the above porous substrate is 50% by volume or more and 95% by volume or less.

4. In paragraph 1, A separation membrane wherein the thickness of the porous substrate is 10 ㎛ or more and 500 ㎛ or less.

5. In paragraph 1, A membrane in which the porous substrate is at least one selected from the group consisting of polyethersulfone, polytetrafluoroethylene, polyethylene, polypropylene, polyethylene terephthalate, polyester, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethylenenaphthalene, polyvinylidene fluoride, cellulose acetate, and nylon.

6. In paragraph 1, The content per unit area of ​​the oxidation catalyst in the above anode catalyst layer is 0.1 mg / cm 2 More than 3.0 mg / cm 2 A membrane that is as follows.

7. In paragraph 1, A separation membrane having a thickness of the anode catalyst layer of 1 ㎛ or more and 30 ㎛ or less.

8. In paragraph 1, The above metal particles have an average particle diameter (D) of primary particles SEM ) is a separation membrane having a thickness of 20 nm or more and 30 nm or less.

9. In paragraph 1, The above metal particles have an average particle diameter (D) of secondary particles 50 ) is a separation membrane having a thickness of 100 nm or more and 2,000 nm or less.

10. Including the separator and cathode of paragraph 1, An electrochemical cell wherein the cathode is in contact with the other surface of the separator on which the anode catalyst layer is not coated.

11. In paragraph 10, The above cathode is an electrochemical cell in which a cathode catalyst layer is coated on one side of a gas diffusion layer.

12. A step (S10) of manufacturing a separation membrane by coating an anode catalyst layer on one side of a porous substrate; and Including a step (S20) of arranging the cathode so that the anode catalyst layer is in contact with the other surface of the uncoated separator in the step S10; A method for manufacturing an electrochemical cell, wherein the anode catalyst layer comprises metal particles and a binder.

13. In paragraph 12, The above step S10 is a step (S11) of preparing an anode catalyst ink by mixing metal particles, a binder, and a solvent; A step (S12) of manufacturing an anode catalyst layer by applying the above anode catalyst ink to a transfer film; and An electrochemical cell manufacturing method comprising a step (S13) of coating an anode catalyst layer by transferring the anode catalyst layer to one side of a porous substrate.

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