Porous transport layer and water electrolysis system comprising same

Abstract

The present invention relates to a porous transport layer and a water electrolysis system comprising same. The porous transport layer according to the present invention may comprise a porous layer including a fluorine-based resin region in a part of one or both surfaces of the porous layer.

Description

Porous diffusion membrane and water electrolysis system including the same

[0001] The present invention relates to a porous diffusion membrane and a water electrolysis system including the same according to embodiments of the present invention.

[0002] Water electrolysis technology converts electrical energy generated from environmentally friendly energy sources into high-energy-density hydrogen or carbon compound gases. Specifically, water electrolysis technology produces hydrogen by electrolyzing water through electrochemical electrolysis. Efficient electrode catalysts are required for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water electrolysis. The core of hydrogen production through water electrolysis is the technology to produce hydrogen and oxygen through the electrolysis of water. However, because the water electrolysis reaction proceeds in an aqueous solution, gases of different phases may be generated that do not separate from the electrode surface (see Figure 2a). These unseparated gases can adhere to the electrode, reducing the surface area of ​​the electrode and the active sites for the gas production catalytic reaction, thereby reducing efficiency.

[0003] Typically, in a water electrolysis system (e.g., anion exchange membrane water electrolysis (AEMWE) cell), hydrogen and oxygen are generated through the electrolysis of water, so a liquid phase (e.g., water or electrolyte) and a gaseous phase (e.g., hydrogen or oxygen) exist inside the cell. During this process, the hydrogen / oxygen gas as products can accumulate between the catalyst layer (MEA) and the porous transport layer (PTL). If gas bubbles accumulate between the catalyst layer (MEA) and the porous transport layer (PTL), the area where the reactants (e.g., water, electrolyte) come into contact with the catalyst decreases (i.e., the catalyst inactive area increases), which can cause overpotential and reduce the water electrolysis efficiency.

[0004] Accordingly, according to one embodiment, the present invention provides a porous diffusion membrane capable of improving cell efficiency by rapidly removing hydrogen / oxygen gases, which are products inside the cell, from the catalyst layer (i.e., MEA) in order to solve the mentioned problem.

[0005] According to one embodiment, the present invention provides a method for manufacturing a porous diffusion membrane according to embodiments of the present invention.

[0006] According to one embodiment, the present invention provides a water electrolysis system comprising a porous substrate diffusion membrane; and a membrane electrode assembly; according to embodiments of the present invention.

[0007] However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0008] According to embodiments, the porous diffusion membrane may include a porous membrane including a fluorine-based resin region on a portion of one or both sides of the porous membrane;

[0009] According to one embodiment, the porous membrane may include a single layer or multiple layers, and at least one of the multiple layers of the porous membrane may include a fluorine-based resin region.

[0010] According to one embodiment, the porous membrane may include a lower layer; and an upper layer having a fluorine-based resin region on the lower layer.

[0011] According to one embodiment, the porous membrane may be a foam, woven fabric, felt or nonwoven fabric comprising at least one of a metal, an oxide, an alloy, a polymer, silicon, glass, quartz and a carbon-based material.

[0012] According to one embodiment, the thickness of the porous membrane may be 50 μm (micrometers) to 1000 μm (micrometers), and the porosity may be 70% or more.

[0013] According to one embodiment, the fluorine resin region may have a pattern in the form of a polygon, a band, a line, a circle, an ellipse, a dot, or a mesh.

[0014] According to one embodiment, the fluorinated resin region may include a fluorinated resin including at least one or more of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer resin (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE / CTFE), ethylene-chlorotrifluoroethylene resin (ECTFE), fluorinated ethylene-propylene copolymer, perfluoroalkoxy polymer, and polychlorotrifluoroethylene, or a combination thereof.

[0015] According to one embodiment, the fluorine-based resin region may have a thickness of 40 μm (micrometers) to 800 μm (micrometers), and the fluorine-based resin region may be greater than 0% to 90% based on the area of ​​one surface of the porous membrane.

[0016] According to one embodiment, the fluorine-based resin region may be heat-treated at a temperature of 350° C. to 450° C. after coating the fluorine-based resin on the porous membrane.

[0017] In one embodiment, the fluorine resin region may have a porosity of 70% or greater.

[0018] According to one embodiment, the fluorine-based resin region may have a surface contact angle for hydrogen or oxygen of 20 degrees (°) or less and a surface contact angle for water of 100 degrees (°) or more, and a region of the porous membrane where the fluorine-based resin region is not formed may have a surface contact angle for hydrogen or oxygen of 100 degrees (°) or more and a surface contact angle for water of 10 degrees (°) or less.

[0019] According to embodiments, a water electrolysis system may include: an electrolyte membrane; a membrane electrode assembly including a catalyst layer on both sides of the electrolyte membrane; and a porous diffusion membrane of claim 1 on one or both sides of the membrane electrode assembly.

[0020] According to one embodiment, the surface of the porous diffusion membrane facing the membrane electrode assembly may be free of a fluorine-based resin region.

[0021] According to one embodiment, the electrolysis system may be an anion exchange membrane electrolysis system.

[0022] According to one embodiment, the present invention provides a porous diffusion membrane and a water electrolysis system including the same, which can rapidly remove hydrogen / oxygen gases, which are products inside the cell, from a catalyst layer (i.e., MEA), thereby reducing overpotential (e.g., ohmic overpotential, mass transport overpotential) and improving water electrolysis efficiency.

[0023] FIG. 1 is an exemplary diagram showing the configuration of a porous diffusion membrane (10) according to embodiments of the present invention.

[0024] FIG. 2a and FIG. 2b are schematic diagrams of gas diffusion occurring on the surface of an MEA according to one embodiment, and relate to FIG. 2a (conventional porous diffusion membrane (PTL)) and FIG. 2b (porous diffusion membrane (10) of the present invention).

[0025] FIG. 3 is an exemplary diagram illustrating the configuration of a water electrolysis system (i.e., a single cell for driving AEMWE) according to embodiments of the present invention.

[0026] Figure 4 illustrates an example process of a method for manufacturing a porous diffusion membrane (10) according to one embodiment.

[0027] FIG. 5 shows an SEM image of a porous diffusion membrane (hereinafter, Janus PTL) having a PTFE coating film formed thereon according to one embodiment.

[0028] FIG. 6 shows the porosity of Janus PTL and Pristine PTL according to one embodiment.

[0029] Figure 7 shows SEM images of Janus PTLs before and after PTFE coating and annealing according to one embodiment, nickel foam (left) and SUS foam (right) PTLs.

[0030] FIG. 8 illustrates patterns of PTFE coating films in Janus PTL according to one embodiment, which are circle, octagon, triangle, and stripe patterns.

[0031] FIG. 9 shows the wettability of Janus PTL to water according to one embodiment, the back side (top) and the front side (formation surface of PTFE coating film, PTFE / Ni)) (bottom).

[0032] FIG. 10 illustrates the static contact angle of Janus PTL and Pristine PTL according to one embodiment.

[0033] FIG. 11 illustrates the dynamic contact angle of Janus PTL and Pristine PTL according to one embodiment.

[0034] FIG. 12 shows, according to one embodiment, the gas permeability in water of Janus PTL and Pristine PTL, including a gas permeation image (top) and a schematic diagram of the gas permeation phenomenon (bottom).

[0035] Figure 13 shows the gas permeability of Janus PTL according to one embodiment, PTFE / Ni surface (top) and Ni surface (left).

[0036] FIG. 14 shows the water permeability of Janus PTL and Pristine PTL according to one embodiment, Pristine PTL (left) and Janus PTL (right), and a schematic diagram of the water permeation phenomenon (bottom).

[0037] FIG. 15a illustrates the growth of gas bubbles coming out through the Janus PTL and the Pristine PTL according to one embodiment.

[0038] Figure 15b illustrates the internal / external pressure difference using the size of the gas bubbles coming out through the Janus PTL and the Pristine PTL, according to one embodiment.

[0039] FIG. 15c shows the BPP (Bubble point pressure) according to the structure, type, and thickness of the PTL in Janus PTL, according to one embodiment.

[0040] FIG. 16a illustrates bubble adhesion of Pristine PTL according to one embodiment.

[0041] FIG. 16b illustrates bubble adhesion of Janus PTL according to one embodiment.

[0042] FIG. 16c shows BPP, which is the force at which a gas bubble is absorbed divided by the contact area, in Janus PTL and Pristine PTL, according to one embodiment.

[0043] FIG. 17a is a polarization curve of an AEMWE electrolysis voltage / current graph according to one embodiment.

[0044] Figure 17b is a result of AEMWE electrolysis impedance resistance measurement (EIS) according to one embodiment.

[0045] Figure 18a is a performance evaluation (generality test) of PTL (Fixed Pt / C(HER) / NiFe(OER) electrocatalysts) in AEMWE according to one embodiment.

[0046] Figure 18b is a performance evaluation (generality test) of an OER electrocatalyst (Fixed NF to 500 μm) in AEMWE according to one embodiment.

[0047] FIG. 19 is a schematic diagram and image of bubble movement within an AEMWE cell, according to one embodiment.

[0048] FIG. 20 is an LSV curve of an AEMWE cell of a 3-Stack cell according to one embodiment.

[0049] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. In describing the present invention, if a detailed description of a related known function or configuration is determined to unnecessarily obscure the gist of the present invention, such detailed description will be omitted. In addition, the terms used in this specification are terms used to appropriately express preferred embodiments of the present invention, and these may vary depending on the intention of the user or operator, or the customs of the field to which the present invention belongs. Therefore, the definitions of these terms should be determined based on the contents throughout this specification. The same reference numerals presented in each drawing represent the same elements.

[0050] Throughout the specification, when we say that an element is "on" another element, this includes not only cases where the element is in contact with the other element, but also cases where another element exists between the two elements.

[0051] Throughout the specification, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components.

[0052] In this document, phrases such as "A or B," "at least one of A and B," "at least one of A or B," "A, B, or C," "at least one of A, B, and C," and "at least one of A, B, or C" can each include any one of the items listed together with the corresponding phrase, or all possible combinations thereof. Terms such as "first," "second," or "first" or "second" may be used merely to distinguish the corresponding element from other corresponding elements and do not limit the corresponding elements in any other respect (e.g., importance or order). For example, suitable results may be achieved even if the described techniques are performed in a different order than the described method, and / or the described elements are combined or combined in a different form than the described method, or are replaced or substituted by other elements or equivalents. Therefore, other implementations, other embodiments, and equivalents of the claims are also within the scope of the following claims.

[0053] Hereinafter, the porous diffusion membrane of the present invention and the electrolysis system including the same will be described in detail with reference to examples and drawings. However, the present invention is not limited to these examples and drawings.

[0054] FIG. 1 is an exemplary diagram showing the configuration of a porous diffusion membrane (10) according to embodiments of the present invention. In FIG. 1, the porous diffusion membrane (10) includes a porous membrane (110) and may include a fluorine-based resin region (120) on a portion of one or both sides of the porous membrane (110).

[0055] According to one embodiment, the porous membrane (110) may include a single layer or multiple layers, and when the porous membrane (110) is multiple layers, at least one of the multiple layers may include a fluorine-based resin region (120). In some embodiments, all of the multiple layers may include a fluorine-based resin region (120).

[0056] According to one embodiment, the porous membrane (110) may include a lower layer (110a) and an upper layer (110b) disposed on the lower layer (110a) and having a fluorine-based resin region (120). At least a portion of one surface of the upper layer (110b) may include the fluorine-based resin region (120).

[0057] According to one embodiment, the thickness of the porous membrane (110) may be about 300 nm or more; about 500 nm or more; about 1 μm (micrometer) or more; about 5 μm (micrometer) or more; about 10 μm (micrometer) or more; about 100 μm (micrometer) or more; about 500 μm (micrometer) or more; about 1000 μm (micrometer) or more; about 2,000 μm (micrometer) or more; about 10 μm (micrometer) to about 3,000 μm (micrometer); about 100 μm (micrometer) to about 3,000 μm (micrometer); about 1,000 μm (micrometer) to about 3,000 μm (micrometer); or about 10 μm (micrometer) to 2,000 μm (micrometer). The above thickness may be the thickness of one membrane or the entire thickness of the porous membrane (110). When the mentioned thickness range is applied, the performance and efficiency of the membrane electrode assembly (e.g., water electrolysis system) can be improved.

[0058] According to one embodiment, the porous membrane (110) can be a film or sheet having a porosity of about 50% or more; about 60% or more; about 70% or more; about 80% or more; or about 90% or more. In some embodiments, the porous membrane (110) can be applied without limitation as long as it is a porous membrane applicable to a porous diffusion membrane in a water electrolysis system or a fuel cell, and the porous membrane (110) can include at least one or more of a metal, an alloy, stainless steel, an organic polymer, silicon, glass, quartz, and a carbon-based material (e.g., graphene, graphite, carbon black, carbon, carbon nanotubes, or activated carbon), or a combination thereof. According to one embodiment, the porous membrane (110) can be a foam, a felt, a non-woven fabric, a mesh, a paper, a woven fabric, or the like. For example, the porous membrane (110) may be a three-dimensional porous film or sheet having a regular or irregular pore network. More specifically, it may be nickel felt, nickel foam, or SUS foam.

[0059] According to one embodiment, the size of the pores in the porous membrane (110) may be 0.01 μm (micrometer) to 800 μm (micrometer).

[0060] According to one embodiment, the surface of the porous membrane (110) may be a flat surface, have surface roughness due to derived or concave protrusions, or be textured.

[0061] According to one embodiment, the fluorine-based resin region (120) is formed on at least a portion of the porous membrane (110). Referring to FIG. 2b, the fluorine-based resin region (120) promotes the diffusion of gases (hydrogen and oxygen) generated from the catalyst layer and provides superhydrophobic and aerophilic properties, and a portion of the porous membrane (110) on which the fluorine-based resin region (120) is not formed exhibits hydrophilic and aerophobic properties, has good wettability to water, and can smoothly supply water used for the reaction. This can prevent an increase in the inactive area due to gas bubbles on the catalyst layer by quickly removing gases, and can improve the catalytic efficiency. That is, the fluorine-based resin region (120) can implement a porous diffusion membrane having "Janus wettability".

[0062] According to one embodiment, the fluorine-based resin region (120) is formed in various shapes on the surface of the porous membrane (110), and the fluorine-based resin region (120) may be formed in a pattern in the shape of a polygon, a band, a line, a circle, an oval, a dot, or a mesh. In some embodiments, the fluorine-based resin region (120) may be formed in a pattern in the shape of a band, a circle, a polygon, or a line in a specific area. In some embodiments, the fluorine-based resin region (120) may be formed in a limited or dispersed manner in a specific area.

[0063] According to one embodiment, the fluorine-based resin region (120) may include a fluorine-based resin including at least one or more of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer resin (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE / CTFE), ethylene-chlorotrifluoroethylene resin (ECTFE), fluorinated ethylene-propylene copolymer, perfluoroalkoxy polymer, and polychlorotrifluoroethylene, or a combination thereof. Preferably, the fluorine-based resin may be PTFE. The fluorine-based resin may have superhydrophobicity, thermal stability, and / or chemical stability.

[0064] According to one embodiment, the molecular weight (number average molecular weight) of the fluorinated resin may be 1,000,000 to 15,000,000 g / mol; 2,000,000 to 15,000,000 g / mol; 3,000,000 to 10,000,000 g / mol; or 4,000,000 to 5,000,000 g / mol. By applying these molecular weight ranges, coating can be well performed on porous films of various materials or structures, and surface properties that can promote gas diffusion can be provided.

[0065] According to one embodiment, the thickness of the fluorine resin region (120) may be 40 μm (micrometers) to 800 μm (micrometers); 40 μm (micrometers) to 600 μm (micrometers); 40 μm (micrometers) to 500 μm (micrometers); 60 μm (micrometers) to 200 μm (micrometers); or 50 μm (micrometers) to 100 μm (micrometers). By applying the mentioned thickness range, diffusion of gas generated in the catalyst layer can be accelerated, and catalyst efficiency can be improved.

[0066] According to one embodiment, the area of ​​the fluorine-based resin region (120) may be from more than 0% to less than 100%; from 10% to less than 100%; from 30% to 90%; from 30% to 80%; or from 30% to 50%, based on the area of ​​one side of the porous membrane. Preferably, it may be from 30% to 60%. By applying the mentioned range, a porous diffusion membrane capable of rapidly removing gas generated in a catalyst layer at low pressure and smoothly supplying water into the catalyst layer can be provided.

[0067] According to one embodiment, the fluorine-based resin region (120) may be heat-treated at a temperature of 50° C. to 300° C.; 70° C. to 280° C.; 100° C. to 250° C.; 150° C. to 250° C. or 200° C. to 250° C., and then at a temperature of 100° C. to 400° C.; 150° C. to 450° C.; 200° C. to 450° C.; 250° C. to 450° C.; 300° C. to 400° C. or preferably 350° C. to 450° C. and for 1 minute to 30 minutes; 5 minutes to 20 minutes; or 5 minutes to 10 minutes after forming a coating film of the fluorine-based resin on the porous membrane (110). After heat treatment by the mentioned process, a coating film can be stably formed on a porous film in the fluorine resin region, and rapid gas diffusion can be induced.

[0068] According to one embodiment, the fluorine-based resin region (120) may have a surface contact angle with respect to a gas (e.g., hydrogen, oxygen, or air) of 20 degrees (°) or less; 15 degrees or less; 10 degrees or less; or 9 degrees or less, and the fluorine-based resin region (120) may have a surface contact angle with respect to water of 100 degrees or more; 120 degrees or more; or 140 degrees or more. This can improve the efficiency of the membrane electrode assembly by rapidly discharging a gas (e.g., hydrogen or oxygen) generated from the catalyst layer due to the surface energy or surface properties of the porous membrane (110).

[0069] According to one embodiment, FIGS. 2A and 2B illustrate the flow of gas bubbles between a catalyst layer and a porous diffusion membrane, wherein in FIG. 2A, a conventional porous diffusion membrane (Conventional PTL) is applied in which a fluorine-based resin region (120) is not formed. In FIG. 2A, it can be seen that the gas generated from the electrocatalyst on the surface of the MEA cannot easily escape but accumulates between the porous diffusion membranes, and an inactive catalyst region is formed by the gas bubbles. In FIG. 2B, a porous diffusion membrane (i.e., Janus PTL) in which a fluorine-based resin region (120) is formed is applied, and hydrogen and oxygen gases generated from the electrocatalyst on the surface of the MEA can easily escape through the porous diffusion membrane, thereby improving the overall water electrolysis efficiency.

[0070] In one embodiment, the fluorine resin region (120) may have the same porosity as the porous membrane (110) or may have a porosity of 60% or more; 70% or more; 80% or more or 90% or more. This porosity may be related to the pore area based on the total area of ​​the fluorine resin region (120).

[0071] According to one embodiment, the fluorine-based resin region (120) on one surface of the porous membrane (110) (e.g., the upper layer (110a) of FIG. 1) may have a surface contact angle for hydrogen or oxygen of about 20 degrees (°) or less; about 15 degrees or less; about 10 degrees or less; about 5 degrees or less; about 2 degrees or less; or about 0 degrees or less, and a surface contact angle for water of about 100 degrees or more; about 120 degrees or more; about 140 degrees or more; or about 150 degrees or more. The region of the porous membrane where the fluorine-based resin region (120) is not formed may have a surface contact angle for hydrogen or oxygen of about 100 degrees or more; about 120 degrees or more; about 140 degrees or more; or about 150 degrees or more, and a surface contact angle for water of about 20 degrees or less; about 15 degrees or less; about 10 degrees or less; about 5 degrees or less; It may be about 2 degrees or less; or about 0 degrees or less.

[0072] According to one embodiment, the present invention may provide a method for manufacturing a porous diffusion membrane (e.g., the porous diffusion membrane (10) of FIG. 1). The method may include a step of preparing a porous membrane; a step of coating a fluorine-based resin on the porous membrane; and a step of performing a heat treatment after the coating step.

[0073] According to one embodiment, the step of preparing a porous membrane may prepare a porous membrane (110) applicable to the porous diffusion membrane (10) mentioned in the description of the porous diffusion membrane (10) of FIG. 1.

[0074] According to one embodiment, the coating step may be performed using a coating solution containing 20 wt% or more; 30 wt% or more; 40 wt% or more; 50 wt% or more or 60 wt% or more of a fluorinated resin. Any solvent capable of dissolving or dispersing the fluorinated resin may be used without limitation as the coating solution. The coating step may utilize spin coating, spray coating, or the like. According to one embodiment, the coating step may be performed after forming a mask on a porous film according to a desired portion or a desired pattern shape.

[0075] According to one embodiment, the coating step may be performed after preheating the porous membrane at a temperature of 50° C. to 300° C.; 70° C. to 280° C.; 100° C. to 250° C.; 150° C. to 250° C. or 200° C. to 250° C.

[0076] According to one embodiment, the heat treatment step may be performed at a temperature of 100°C to 400°C; 150°C to 450°C; 200°C to 450°C; 250°C to 450°C; 300°C to 400°C; or preferably 350°C to 450°C for 1 minute to 30 minutes; 5 minutes to 20 minutes; or 5 minutes to 10 minutes, and the atmosphere in the heat treatment (e.g., annealing) may include an inert gas, oxygen, or the like. Through this heat treatment, the fluorine-based resin film may be mechanically interlocked and agglomerated to form a stable coating film. The heat treatment step may be performed at a higher temperature than the coating step.

[0077] In one embodiment, the porous diffusion membrane of the present invention may be applied to a fuel cell or a water electrolysis system. In one embodiment, the porous diffusion membrane may be bonded to a membrane electrode assembly and applied to a fuel cell or a water electrolysis system.

[0078] According to one embodiment, FIG. 3 illustrates a configuration of a water electrolysis system (200) according to embodiments of the present invention, wherein the water electrolysis system (200) may include a membrane electrode assembly (MEA; Membrane Electrode Assembly) 210, a porous diffusion layer (PTL; porous transport layer) 210a, 210b, a gasket (230a, 230b), a bipolar plate (240a, 240b), and an end plate (250a, 250b). In FIG. 3, the water electrolysis system (200) may correspond to a single cell configuration of the water electrolysis system. The membrane electrode assembly (210, MEA; Membrane Electrode Assembly), gasket (230a, 230b), bipolar plate (240a, 240b), and end plate (250a, 250b) may have a configuration known in the technical field of the present invention, and are not specifically mentioned in this document.

[0079] According to one embodiment, the membrane electrode assembly (210) includes a membrane (i.e., an electrolyte membrane) and a catalyst layer on both sides of the membrane, and may include a porous diffusion layer (210a, 210b) (e.g., a porous diffusion membrane (10)) according to embodiments of the present invention on one or both sides of the membrane electrode assembly (210).

[0080] According to one embodiment, the porous diffusion layer (210a, 210b) may not include a fluorine-based resin region (120) on the side facing the membrane electrode assembly (210), and may include a fluorine-based resin region on the side of the porous diffusion layer (210a, 210b) that does not contact the membrane electrode assembly (210). That is, the side of the porous diffusion layer (210a, 210b) facing or in contact with the membrane electrode assembly (210) may be free of the fluorine-based resin region (120).

[0081] According to one embodiment, the catalyst layer may be applied without limitation to any electrode catalyst applicable to a fuel cell or water electrolysis system, and may be, for example, a platinum catalyst.

[0082]

[0083] *According to the 57th embodiment, the electrolyte membrane can be applied without limitation as long as it is applicable to a membrane electrode assembly of a fuel cell or a water electrolysis system, and for example, the electrolyte membrane can be an anion exchange membrane in a water electrolysis system.

[0084] According to one embodiment, the water electrolysis system is an anion exchange membrane water electrolysis system (AEMWE), and the porous diffusion layer (210a, 210b) may be a porous diffusion membrane for anisotropic mass transport that can rapidly remove hydrogen / oxygen gases from the MEA by introducing a fluorine-based resin region (120).

[0085] Hereinafter, the present invention will be described in more detail by way of examples and comparative examples.

[0086] However, the following examples are only intended to illustrate the present invention, and the content of the present invention is not limited to the following examples.

[0087] Example 1: Preparation of Janus PTL

[0088] Janus PTL was manufactured according to the process shown in Fig. 4.

[0089] After preparing Pristine PTL (NF (nickel foam) with a thickness of 0.5 mm by washing and drying), a part of the Pristine PTL was masked considering the area requiring PTFE coating, and heated on a hot plate at 250°C (degree Celsius) for 10 minutes. Next, PTFE coating was performed on only one side (i.e., the area excluding the masking) by spraying 60 wt% PTFE dispersion spray (air pressure: 1 bar, using an airbrush with a nozzle size of 0.3 mm) from a height of 15 cm for 30 seconds. Next, heat treatment was performed at 380°C (degree Celsius) for 10 minutes.

[0090] Figure 5 shows an SEM image of the Janus PTL. Examining the coated surface (top), back (bottom), and side (cross-section) in the SEM image, it can be seen that only one side is well coated with PTFE. The thickness of the PTFE film is approximately 150 μm (micrometers) to 200 μm (micrometers).

[0091] Figure 6 shows a porosimetry analysis to confirm changes in the pore size of PTL. As shown in Figure 6, the pore size was slightly reduced by PTFE coating, but the overall distribution was not significantly affected. Furthermore, the porosity values ​​were similar (Pristine PTL: 79.94%, Janus PTL: 78.09%). This confirms that the chemical modification of Pristine PTL occurred without significantly affecting its physical structure.

[0092] Example 2

[0093] Janus PTL was manufactured using a PTFE coating process using NF, nickel felt, and SUS foam of 1.6 mm thickness, each in the same manner as in Example 1.

[0094] Fig. 7 shows SEM images of PTFE-coated PTLs (nickel foam (left) and SUSU foam (right)) of different structures or materials. It can be seen from Fig. 7 that PTFE coating is possible on various pristine PTL materials and structures when the coating process of the present invention is used.

[0095] Example 3

[0096] Large area (225 cm 2 ), 100 cm 2 and 25 cm 2 Janus PTL was manufactured using the same process as Example 1 using Pristine PTL (NF (nickel foam) with a thickness of 0.5 mm). It was confirmed that a PTFE coating film was formed on the surface of all Pristine PTLs. The area of ​​the PTFE coating film corresponds to about 50% to 60% of the area of ​​one side of the Pristine PTL.

[0097] Example 4

[0098] Janus PTLs having PTFE coating films of various shapes were fabricated by changing the shape of the mask. The coating process was performed in the same manner as in Example 1. As shown in Fig. 8, coating films having circular, octagonal, triangular, or striped patterns can be fabricated on the pristine PTL.

[0099] The properties of Janus PTL and Pristine PTL of the examples were evaluated. Unless otherwise specified, the properties correspond to Janus PTL and Pristine PTL of Example 1.

[0100] (1) Wettability

[0101] Confirming the underwater properties of Janus PTL

[0102] Looking at Figure 9, when Janus PTL (Example 1) is placed in water, it can be seen that the coated side (Janus NF) has a silvery, shiny gas layer that does not get wet with water, whereas the back side (NF) is wet with water.

[0103] X-ray analysis further confirmed the presence of an internal gas film within the PTFE-coated parts of the Janus PTL.

[0104] Static contact angle analysis of Janus PTL

[0105] Looking at Figure 10, it can be seen that the PTFE coated side shows superhydrophobic and aerophilic properties, while the uncoated Ni foam side shows hydrophilic and aerophobic properties by allowing water to permeate and showing a high contact angle for gas.

[0106] Dynamic contact angle analysis of Pristine PTL and Janus PTL

[0107] Looking at Figure 11, in the case of Pristine PTL, capillary rise is observed on both sides due to its hydrophilicity, with water being drawn to the surface. In the case of Janus PTL, water is seen being pushed downwards on the PTFE-coated portion, and capillary rise is observed on the back of the coating.

[0108] Through this, it can be confirmed that PTFE is well coated on only one side and that a gas film is formed by PTFE.

[0109] (2) Water and air permeability of Pristine PTL and Janus PTL

[0110] Comparison of gas permeability in water

[0111] Looking at Fig. 12, it can be confirmed that in the case of Pristine PTL, gas bubbles are not permeated but are pushed out. However, in the case of Janus PTL, it can be confirmed that gas is permeated from Ni (back of coating) to PTFE / Ni (coating side). The drawing below in Fig. 12 is a schematic diagram of the gas permeation phenomenon, and it can be confirmed that in the case of Pristine PTL, due to its hydrophilic characteristics, capillary pressure acts in the direction of pushing out bubbles. In the case of Janus PTL, it can be confirmed that a channel is formed when the film (gas film) and gas bubble come into contact, and permeation occurs due to the difference in Laplace pressure.

[0112] In Fig. 13, it can be confirmed that there is no penetration in the opposite direction (PTFE / Ni to Ni direction) from Janus PTL (left).

[0113] In Fig. 13, after removing the gas film in the Janus PTL (right), it can be confirmed that no permeation occurs when a bubble is injected in the same direction as the left (Pristine PTL) in Fig. 13. This confirms that the permeability of the bubble gas is created by the gas film.

[0114] Confirmation of water permeability of two substances,

[0115] In Fig. 14, it can be seen that Pristine PTL (left) moves well in both directions, while Janus PTL (right) only transmits in the PTFE / Ni to Ni direction. Water permeability of NF is greater than that of Janus NF.

[0116] For a more quantitative analysis, BPP (bubble point pressure) measurements were performed. Although not shown in the drawing, the BPP of Pristine PTL and Janus PTL was defined as the point at which gas bubbles were visible, and different behaviors were observed in the growth of the gas bubbles. This can be confirmed in Fig. 15a. In Fig. 15a, in the case of Pristine PTL (NF), the gas bubbles grew discontinuously, but in the case of Janus PTL, the bubbles grew continuously. (BPP measurement conditions in Fig. 15a: Syringe size: 1 mL, Compression speed: 0.2 μl / s)

[0117] In Fig. 15b, the size of the gas bubbles released to the outside can be used to graphically represent the internal / external pressure difference. In the case of Pristine NF (nickel foam), bubbles are discharged at a high pressure of approximately 1000 Pa, while in the case of Janus NF, bubbles are discharged at a low pressure of approximately 60 Pa. Furthermore, bubbles are discharged discontinuously in Pristine NF, while those in Janus NF are discharged continuously.

[0118] In Fig. 15c, PTFE coating was also performed on PTLs made of different structures and materials (i.e., Example 2), and BPP could be measured. It can be confirmed that BPP decreases regardless of the material and pore structure. The SUS foam was coated under 10 wt% PTFE and 110°C annealing conditions.

[0119] Figures 16a to 16c show measurements of bubble adhesion at BPP (bubble point pressure). The measurement conditions are "Needle size: 20 gage, Approach / retraction speed: 10 μm / s, and Bubble diameter: 1 mm."

[0120] In the bubble adhesion measurement for pristine NF in Fig. 16a, it can be confirmed that even when compressed, bubbles are not absorbed and slight adhesion is observed.

[0121] In Fig. 16b, it can be confirmed that gas bubbles are absorbed when a force (compression) exceeding a certain force is applied to the Janus NF in bubble adhesion.

[0122] In Fig. 16c, the force at which a gas bubble is absorbed is divided by the contact area and compared with the previously described BPP. The fact that the Janus NF has a similar pressure value supports that the BPP value was measured well.

[0123] AEMWE water electrolysis voltage / current graph (polarization curve)

[0124] In Fig. 17a, NiFe was used as the OER catalyst and Pt / C was used as the HER catalyst as the catalyst layer for electrolysis operation, and it can be confirmed that the electrolysis performance of Janus PTL was improved compared to Pristine PTL.

[0125] AEMWE Electrolysis Impedance Resistance (EIS) Measurement

[0126] 0.5 A / cm in Fig. 17b 2 When the impedance resistance is measured under the conditions, R mass It was confirmed that the resistance was reduced. While two semi-circles appeared in Pristine PTL, the second semi-circle was almost absent in Janus PTL, which confirms that Janus PTL has excellent mass transport as an impedance resistance (R1: Activation loss, R3: Mass transport resistance in Figure 17b).

[0127] Performance evaluation at AEMWE

[0128] Figure 18a shows the performance evaluation according to PTL ((Fixed Pt / C(HER) / NiFe(OER) electrocatalysts). Figure 18b shows the performance evaluation according to OER electrocatalyst (Fixed NF to 500 μm).

[0129] When the HER catalyst Pt / C and the OER catalyst NiFe were fixed, performance improvement was observed in all cases when the PTL was used as SUS foam, Ni felt, and 1.5 mm thick Ni foam (Fig. 18a).

[0130] In electrolysis, when the HER catalyst was fixed to Pt / C and the OER catalyst was used as IrO2, NiCo LDH, or NiFe, performance improvement could be observed in all cases (Fig. 18b).

[0131] That is, it can be confirmed that it is universally applicable regardless of the type of catalyst or PTL in the water electrolysis cell.

[0132] In Fig. 19, for the Pristine PTL (top), bubble escaping is observed at all locations and is discontinuous. For the Janus PTL (bottom), most bubble escaping occurs in the PTFE-coated portion, and bubbles are observed to emerge continuously.

[0133] Results of application to a 3-stack cell using HER catalyst Pt / C and OER catalyst NiFe.

[0134] We previously confirmed an increase in performance in single cells, and when this is applied to large-area stack cells, we can also confirm an improvement in efficiency.

[0135] According to one embodiment, the present invention can easily manufacture a porous transport layer (PTL) having Janus wettability by spray coating a fluorinated resin (i.e., PTFE). The fluorinated resin (i.e., PTFE) coating can be applied to a large area of ​​PTL, and can be coated on nickel (Ni) or stainless steel (SUS), etc., and the design of the coating can be freely formed in various shapes (circular, striped, etc.). In the case of a PTL after coating with a fluorinated resin (i.e., PTFE), the bubble point pressure (BPP) at which bubbles penetrate in water is reduced, which can be applied to an anion exchange membrane water electrolysis cell (AEMWE) to improve water electrolysis efficiency.

[0136] According to one embodiment, the present invention can reduce mass transportation overpotential and ohmic overpotential through a fluororesin (i.e., PTFE) coating. That is, when a PTL having Janus wettability is applied to an AEMWE, the generated gases (oxygen, hydrogen) can be quickly removed, thereby improving efficiency.

[0137] Although the embodiments described above have been described with limited examples and drawings, those skilled in the art will recognize that various modifications and variations are possible based on the above teachings. For example, appropriate results can be achieved even if the described techniques are performed in a different order than described, and / or the described components are combined or combined in a different manner than described, or are replaced or substituted with other components or equivalents. Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the following claims.

Claims

1. A porous membrane comprising a fluorine resin region on one side or part of both sides of the porous membrane; A porous diffusion membrane for a membrane electrode assembly, comprising:

2. In paragraph 1, The above porous membrane is, Containing a single layer or multiple layers, A porous diffusion membrane, wherein at least one of the multiple layers of the porous membrane includes a fluorine-based resin region.

3. In paragraph 1, The above porous membrane is, A lower layer; and an upper layer having a fluorine-based resin region on the lower layer; A porous diffusion membrane comprising:

4. In paragraph 1, The above porous membrane is, A porous diffusion membrane, which is a foam, woven fabric, felt or nonwoven fabric containing at least one or more of metal, oxide, alloy, polymer, silicon, glass, quartz and carbon-based materials.

5. In paragraph 1, A porous diffusion membrane, wherein the thickness of the porous membrane is 50 ㎛ (micrometer) to 1000 ㎛ (micrometer) and the porosity is 70% or more.

6. In paragraph 1, The above fluorine resin region is, Having a pattern in the form of a polygon, band, line, circle, oval, dot or mesh, Porous diffusion membrane.

7. In paragraph 1, The above fluorine resin region is, A porous diffusion membrane comprising a fluorinated resin comprising at least one or more of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer resin (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE / CTFE), ethylene-chlorotrifluoroethylene resin (ECTFE), fluorinated ethylene-propylene copolymer, perfluoro alkoxy polymer, and polychlorotrifluoroethylene, or a combination thereof.

8. In paragraph 1, The above fluorine resin region has a thickness of 40 ㎛ (micrometer) to 800 ㎛ (micrometer), A porous diffusion membrane, wherein the fluorine resin region is greater than 0% to 90% of the area of one side of the porous membrane.

9. In paragraph 1, The above fluorine resin region is, A porous diffusion membrane, which is heat-treated at a temperature of 350°C to 450°C after coating a fluorine-based resin on the porous membrane.

10. In paragraph 1, A porous diffusion membrane, wherein the above fluorine resin region has a porosity of 70% or more.

11. In paragraph 1, The above fluorine resin region is, The surface contact angle for hydrogen or oxygen is 20 degrees (°) or less, The surface contact angle with water is greater than 100 degrees (°), The region of the porous membrane where the above fluorine resin region is not formed is, The surface contact angle for hydrogen or oxygen is greater than 100 degrees (°), A porous diffusion membrane having a surface contact angle with water of 10 degrees (°) or less.

12. An electrolyte membrane; and a membrane electrode assembly including catalyst layers on both sides of the electrolyte membrane; and A porous diffusion film of claim 1 on one or both sides of the membrane electrode assembly; A water electrolysis system comprising:

13. In paragraph 12, A water electrolysis system, wherein the surface of the porous diffusion membrane facing the membrane electrode assembly is a fluorine-based resin region free.

14. In paragraph 12, The above electrolysis system is an anion exchange membrane electrolysis system.

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