Porous member, manufacturing method thereof, and electrochemical cell having same

Abstract

A cell assembly of an electrochemical cell includes an ion exchange member, a cathode disposed on one side of the ion exchange member, and an anode disposed on the other side of the ion exchange member. Each of the cathode and the anode includes a catalyst layer and a porous member. The porous member includes a first porous layer having first pores of a first scale, and a second porous layer disposed between the first porous layer and the catalyst layer. The second porous layer has second pores of a second scale smaller than the first scale. The second porous layer of at least one of the cathode or the anode includes a hydrophobic region and a hydrophilic region adjacent to each other along the plane direction.

Description

Porous member, method for manufacturing same, and electrochemical cell having the same

[0001] The present invention relates to an electrochemical cell, and more particularly, to a porous member, a method for manufacturing the same, and an electrochemical cell having the same.

[0002] Representative examples of electrochemical cells include fuel cells and water electrolysis cells. Fuel cells generate electricity through the electrochemical reaction of hydrogen and oxygen. Water electrolysis cells electrolyze water to produce hydrogen and oxygen. Fuel cell cells include a porous material that functions as a gas diffusion layer, while water electrolysis cells include a porous material that functions as a transport layer.

[0003] The present invention aims to provide a porous member capable of improving the performance of an electrochemical cell by increasing the reaction rate and lowering the material transfer resistance, a method for manufacturing the same, and an electrochemical cell having the same.

[0004] A porous member according to one embodiment includes a first porous layer having first pores of a first scale, and a second porous layer having second pores of a second scale smaller than the first scale and located on one surface of the first porous layer. The second porous layer includes a hydrophobic region and a hydrophilic region adjacent to each other along the surface direction.

[0005] The first scale of the first pores may be micrometer scale, and the second scale of the second pores may be nanometer scale. The thickness of the first porous layer may be greater than the thickness of the second porous layer.

[0006] The first porous layer may be hydrophobic, and the area occupied by the hydrophilic region in the second porous layer may be smaller than the area occupied by the hydrophobic region. The first porous layer may include a plurality of carbon fibers coated with a hydrophobic polymer layer. The hydrophilic region of the second porous layer may include a plurality of carbon powders. The hydrophobic region of the second porous layer may include a plurality of carbon powders coated with a hydrophobic polymer layer.

[0007] On the other hand, the first porous layer may have hydrophilicity, and the area occupied by the hydrophobic region in the second porous layer may be smaller than the area occupied by the hydrophilic region. The first porous layer may include at least one of a plurality of carbon fibers, a plurality of titanium fibers, a plurality of titanium powders, and a nickel porous body. The hydrophilic region of the second porous layer may include a plurality of carbon powders. The hydrophobic region of the second porous layer may include a plurality of carbon powders coated with a hydrophobic polymer layer.

[0008] Either the hydrophobic region or the hydrophilic region can form a pattern of a preset shape. The depth of either the hydrophobic region or the hydrophilic region can be equal to or less than the thickness of the second porous layer.

[0009] A method for manufacturing a porous member according to one embodiment includes the steps of (i) forming a first porous layer having micrometer-scale pores and either hydrophobicity or hydrophilicity, (ii) forming a second porous layer having nanometer-scale pores and hydrophobicity, (iii) preparing an exposure mask having a plurality of holes formed therein, positioning the exposure mask over the second porous layer, and (iv) irradiating a plasma beam through the plurality of holes to the second porous layer to modify a portion of the second porous layer into a hydrophilic region.

[0010] The method for manufacturing a porous member may further include a process of applying a NaOH solution to a hydrophilic region, drying the region to precipitate NaOH, and washing the hydrophilic region with pure water and then drying the region.

[0011] An electrochemical cell according to one embodiment includes a cell assembly and a pair of separators positioned on opposite sides of the cell assembly. The cell assembly includes an ion exchange member, a cathode positioned on one side of the ion exchange member, and an anode positioned on the other side of a membrane. Each of the cathode and the anode includes a catalyst layer and a porous member. The porous member includes a first porous layer having first pores of a first scale, and a second porous layer positioned between the first porous layer and the catalyst layer. The second porous layer has second pores of a second scale smaller than the first scale. The second porous layer belonging to at least one of the cathode and the anode includes a hydrophobic region and a hydrophilic region adjacent to each other along a plane direction.

[0012] The first scale of the first pores may be micrometer scale, and the second scale of the second pores may be nanometer scale. The thickness of the first porous layer may be greater than the thickness of the second porous layer.

[0013] The electrochemical cell may be a low-temperature fuel cell cell. The ion exchange member may be any one of a cation exchange membrane, an anion exchange membrane, and a liquid electrolyte. When the ion exchange member is a cation exchange membrane, the hydrophobic region and the hydrophilic region may be located at the cathode. When the ion exchange member is an anion exchange membrane, the hydrophobic region and the hydrophilic region may be located at the cathode and the anode. When the ion exchange member is a liquid electrolyte, the hydrophobic region and the hydrophilic region may be located at either the cathode or the anode.

[0014] The first porous layer may have hydrophobic properties, and the area occupied by the hydrophilic region in the second porous layer where the hydrophobic region and the hydrophilic region are located may be smaller than the area occupied by the hydrophobic region. The depth of the hydrophilic region may be equal to or smaller than the thickness of the second porous layer. The depth of the hydrophobic region may be equal to the thickness of the second porous layer.

[0015] Alternatively, the electrochemical cell may be a water electrolysis cell. The ion exchange member may be a cation exchange membrane. The hydrophobic region and the hydrophilic region may be located at the anode. The first porous layer may be hydrophilic, and the area occupied by the hydrophobic region in the second porous layer belonging to the anode may be smaller than the area occupied by the hydrophilic region.

[0016] Alternatively, the ion exchange member may be either an anion exchange membrane or a liquid electrolyte. The hydrophobic and hydrophilic regions may be located at the cathode and anode electrodes. The first porous layer may be hydrophilic, and the area occupied by the hydrophobic region in the second porous layer may be smaller than the area occupied by the hydrophilic region.

[0017] The fuel cell of this embodiment can increase the reaction rate by continuously supplying oxidant and continuously discharging water, and can improve power density by lowering the transfer resistance between oxidant and water. Furthermore, the water electrolysis cell of this embodiment can increase the reaction rate by continuously supplying water and continuously discharging bubbles (oxygen or hydrogen bubbles), and can improve hydrogen production efficiency by lowering the transfer resistance between water and bubbles.

[0018] Figure 1 is a schematic cross-sectional view of an electrochemical cell according to the first embodiment.

[0019] FIG. 2 is a schematic perspective view showing a porous member of the cathode electrode of the fuel cell shown in FIG. 1.

[0020] Figure 3 is a schematic cross-sectional view of the porous member illustrated in Figure 2.

[0021] Figure 4 is a schematic diagram showing pores inside the porous member illustrated in Figure 3.

[0022] Figure 5 is a graph showing the required water pressure according to pore size.

[0023] Figure 6 is a schematic diagram of the porous member shown in Figure 3.

[0024] Figure 7 is a schematic diagram for explaining the movement of water and oxidant in the second porous layer illustrated in Figure 4.

[0025] Figures 8 and 9 are schematic diagrams showing a modified example of the second porous layer illustrated in Figure 2.

[0026] Fig. 10 is a schematic diagram showing a modified example of the porous member illustrated in Fig. 3.

[0027] Figure 11 is a graph showing the performance evaluation results for three fuel cell cells.

[0028] Fig. 12 is a schematic cross-sectional view of an electrochemical cell according to the second embodiment.

[0029] Fig. 13 is a schematic cross-sectional view of an electrochemical cell according to the third embodiment.

[0030] Fig. 14 is a schematic cross-sectional view of an electrochemical cell according to the fourth embodiment.

[0031] Fig. 15 is a schematic perspective view showing a porous member of the anode electrode of the electrolysis cell illustrated in Fig. 14.

[0032] Figure 16 is a schematic cross-sectional view of the porous member illustrated in Figure 15.

[0033] Figure 17 is a schematic diagram showing pores inside the porous member illustrated in Figure 16.

[0034] Figure 18 is a schematic diagram of the porous member shown in Figure 16.

[0035] Figure 19 is a schematic diagram for explaining the movement of water and oxygen bubbles in the second porous layer illustrated in Figure 17.

[0036] Fig. 20 is a schematic cross-sectional view of an electrochemical cell according to the fifth embodiment.

[0037] Fig. 21 is a schematic perspective view showing a porous member of the cathode electrode of the electrolysis cell illustrated in Fig. 20.

[0038] Fig. 22 is a schematic cross-sectional view of the porous member illustrated in Fig. 21.

[0039] Fig. 23 is a flowchart showing a method for manufacturing a porous member according to one embodiment.

[0040] Figures 24 to 26 are schematic perspective views illustrating a manufacturing process of a porous member according to one embodiment.

[0041] Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0042] Figure 1 is a schematic cross-sectional view of an electrochemical cell according to the first embodiment.

[0043] Referring to Fig. 1, the electrochemical cell of the present embodiment is composed of a fuel cell cell (100). The fuel cell cell (100) may be a low-temperature fuel cell cell having an operating temperature of approximately 300°C or less, but is not limited to this example.

[0044] A typical fuel cell system consists of a stack comprising multiple fuel cell cells, an oxidizer supply unit that supplies oxidizer to the stack, and a fuel supply unit that supplies fuel to the stack. The oxidizer supply unit may be comprised of an air pump, and the fuel supply unit may be comprised of a fuel tank and a fuel pump.

[0045] A fuel cell cell (100) may include a cell assembly (110) and a separator (120) positioned on both sides of the cell assembly (110). The separator (120) may be referred to as a bipolar plate and is made of a conductor. The cell assembly (110) may include an ion exchange member (10), a cathode electrode (20) positioned on one side of the ion exchange member (10), and an anode electrode (30) positioned on the other side of the ion exchange member (10).

[0046] The ion exchange member (10) may be composed of a cation exchange membrane. The cathode (20) may be referred to as an air electrode or an oxygen electrode, and the anode (30) may be referred to as a fuel electrode. The cathode (20) may include a catalyst layer (21) and a porous member (25), and the anode (30) may include a catalyst layer (31) and a porous member (35).

[0047] The catalyst layer (21, 31) may be positioned between the ion exchange member (10) and the porous member (25, 35). The porous member (25, 35) may be referred to as a gas diffusion layer. The porous member (25, 35) may be composed of a first porous layer (26, 36) for supporting the catalyst layer (21, 31) and a second porous layer (27, 37) for enhancing the gas diffusion effect. The second porous layer (27, 37) may be positioned to be in contact with the catalyst layer (21, 31).

[0048] An oxidizing agent passage (121) is positioned on one side of the separator (120) facing the cathode (20) so that an oxidizing agent (e.g., air) can be supplied to the cathode (20). A fuel passage (122) is positioned on one side of the separator (120) facing the anode (30) so that a fuel (e.g., methanol, ethanol, natural gas, hydrogen reformed gas, etc.) can be supplied to the anode (30).

[0049] When an oxidant and fuel are supplied to the cell assembly (110), a reduction reaction of the oxidant occurs in the catalyst layer (21) of the cathode (20), and an oxidation reaction of the fuel occurs in the catalyst layer (31) of the anode (30). Electricity is generated by this electrochemical reaction, and water is generated as a side effect in the catalyst layer (21) of the cathode (20).

[0050] The ion exchange member (10) needs to be sufficiently hydrated to ensure high proton conductivity. On the other hand, an excessive amount of water in the catalyst layer (21) and porous member (25) of the cathode (20) may impede the oxidant from accessing the catalyst layer (21), thereby reducing the reaction rate in the catalyst layer (21) and increasing the transfer loss of the oxidant. If the cathode (20) is not properly managed with water, the power density will decrease.

[0051] Fig. 2 is a schematic perspective view showing a porous member of the cathode electrode of the fuel cell cell illustrated in Fig. 1. Fig. 3 is a schematic cross-sectional view of the porous member illustrated in Fig. 2.

[0052] Referring to FIGS. 1 to 3, the porous member (25) of the cathode (20) may be formed of a laminated structure of a first porous layer (26) and a second porous layer (27) having different pore scales. The first porous layer (26) may have first pores of a first scale, and the second porous layer (27) may have second pores of a second scale smaller than the first scale.

[0053] The first scale may be a micrometer scale, and the second scale may be a nanometer scale. Throughout the specification, the micrometer scale means a size of 1 μm or more and less than 1,000 μm, and the nanometer scale means a size of 1 nm or more and less than 1,000 nm. For example, the average size of the first pores of the first porous layer (26) may be approximately several tens of micrometers, and the average size of the second pores of the second porous layer (27) may be approximately several tens of nanometers.

[0054] The first porous layer (26) may have a first thickness suitable for supporting the catalyst layer (21), and the second porous layer (27) may have a second thickness smaller than the first thickness. The first porous layer (26) may be referred to as a gas diffusion backing layer. The second porous layer (27) may be referred to as a micro porous layer.

[0055] Fig. 4 is a schematic diagram showing the pores inside the porous member illustrated in Fig. 3. Fig. 5 is a graph showing the required water pressure according to the pore size.

[0056] Referring to Fig. 4, water generated in the catalyst layer of the cathode is discharged through the second pores (P2) of the second porous layer and the first pores (P1) of the first porous layer connected thereto. Since the first pores (P1) are tens of micrometers in size and the second pores (P2) are tens of nanometers in size, a pore gradient structure is created within the porous member.

[0057] When a droplet exists across a first pore (P1) and a second pore (P2), the contact angle of the droplet is the same in the first pore (P1) and the second pore (P2). However, the curvature of the droplet surface in the second pore (P2) is greater than the curvature of the droplet surface in the first pore (P1), and the water pressure in the second pore (P2) is greater than the water pressure in the first pore (P1). The pressure (P) required to remove water from the pore can be expressed by the following mathematical equation.

[0058]

[0059] Here, γ is the surface tension of water, θ is the contact angle of water, and d represents the size (diameter) of the pores.

[0060] Referring to Figures 4 and 5, the nanometer-sized second pores (P2) act as a higher capillary barrier during the water discharge process, and the smaller the pore size, the greater the pressure (P) required to remove water. This capillary barrier is beneficial for maintaining a high hydration degree of the ion exchange member, but if the hydration of the ion exchange member is excessive, water flooding may occur, which may degrade the performance of the fuel cell.

[0061] Figure 6 is a schematic diagram of the porous member shown in Figure 3.

[0062] Referring to FIGS. 2, 3, and 6, the entire first porous layer (26) can be hydrophobic. For example, the first porous layer (26) can include a plurality of carbon fibers (261) and a hydrophobic polymer layer (262) coated on the surface of each of the plurality of carbon fibers (261). The carbon fibers (261) can be rod-shaped, and the hydrophobic polymer layer (262) can include polytetrafluoroethylene (PTFE), but is not limited to these examples.

[0063] The second porous layer (27) may include a hydrophobic region (27A) and a hydrophilic region (27B) adjacent to each other along the planar direction. Throughout the specification, the planar direction means a direction parallel to the main surface (upper and lower surfaces based on FIG. 3) of the porous member (25) and a direction orthogonal to the thickness direction of the porous member (25). In FIG. 3, the planar direction is indicated as D1, and the thickness direction is indicated as D2. The hydrophilic region (27B) may occupy a part of the second porous layer (27), and the hydrophobic region (27A) may occupy the remainder of the second porous layer (27).

[0064] The hydrophobic region (27A) may include a plurality of carbon powders (271) and a hydrophobic polymer layer (272) coated on the surface of each of the plurality of carbon powders (271). The hydrophilic region (27B) may include a plurality of carbon powders (271). The carbon powders (271) may be spherical. The hydrophobic polymer layer (272) may include PTFE, but is not limited to this example. The second porous layer (27) may be divided into a hydrophobic region (27A) and a hydrophilic region (27B) depending on the presence or absence of the hydrophobic polymer layer (272).

[0065] Figure 7 is a schematic diagram for explaining the movement of water and oxidant in the second porous layer illustrated in Figure 4.

[0066] Referring to Fig. 7, the hydrophobic region (27A) repels water, allowing the oxidizing agent to pass through more easily than water. On the other hand, the hydrophilic region (27B) easily retains water, allowing water to pass through more easily than the oxidizing agent. In other words, in the second porous layer (27), the hydrophobic region (27A) can function as a movement path for the oxidizing agent, and the hydrophilic region (27B) can function as a movement path for water.

[0067] Referring to FIGS. 2, 3, and 7, the second porous layer (27) can spatially separate the movement (supply) path of the oxidizer and the movement (discharge) path of water by means of the adjacent hydrophobic region (27A) and hydrophilic region (27B) along the surface direction. Accordingly, the porous member (25) can continuously supply the oxidizer by using the hydrophobic region (27A) and continuously discharge water by using the hydrophilic region (27B).

[0068] Assuming that the entire second porous layer is a hydrophobic region, the pressure required to remove water (P) increases due to the nanometer-scale pore size and hydrophobicity, making water discharge difficult. On the other hand, the hydrophilic region (27B) of the second porous layer (27) can lower the pressure required (P) and facilitate water discharge due to the characteristic that the water contact angle is smaller than 90° despite the nanometer-scale pore size.

[0069] Either the hydrophobic region (27A) or the hydrophilic region (27B), for example, the hydrophilic region (27B), may be formed of a plurality of dot patterns as shown in Fig. 2, and may be formed of various patterns other than the dot pattern. Figs. 8 and 9 are schematic diagrams showing variations of the second porous layer illustrated in Fig. 2.

[0070] Referring to Fig. 8, either the hydrophobic region (27A) or the hydrophilic region (27B), for example, the hydrophilic region (27B), may be formed of a plurality of line patterns. Referring to Fig. 9, either the hydrophobic region (27A) or the hydrophilic region (27B), for example, the hydrophilic region (27B), may be formed of a plurality of cross patterns. The shapes of the hydrophobic region (27A) and the hydrophilic region (27B) are not limited to the examples illustrated.

[0071] The area occupied by the hydrophilic region (27B) in the second porous layer (27) may be smaller than the area occupied by the hydrophobic region (27A), but is not limited to this example. In a fuel cell, the porous member fundamentally functions to transfer oxidants toward the catalyst layer. Therefore, if the area of ​​the hydrophilic region is smaller than the area of ​​the hydrophobic region, the efficiency of oxidant supply can be increased while securing a water discharge path.

[0072] The depth of the hydrophobic region (27A) may be equal to the thickness of the second porous layer (27), and the depth of the hydrophilic region (27B) may be equal to or less than the thickness of the second porous layer (27). FIG. 3 illustrates a case where the depth of the hydrophobic region (27A) and the depth of the hydrophilic region (27B) are equal to the thickness of the second porous layer (27).

[0073] Fig. 10 is a schematic diagram showing a modified example of the porous member illustrated in Fig. 3.

[0074] Referring to Fig. 10, the depth of the hydrophilic region (27B) may be smaller than the thickness of the second porous layer (27). At this time, the hydrophilic region (27B) is located on the surface of the second porous layer (27), and the hydrophobic region (27C) may be located between the first porous layer (26) and the hydrophilic region (27B). That is, the second porous layer (27) may include a mixed region (27D) in which the hydrophilic region (27B) and the hydrophobic region (27C) face each other along the thickness direction, and a hydrophobic region (27A) other than the mixed region (27D).

[0075] Even if the hydrophilic region (27B) occupies a portion of the second porous layer (27) along the thickness direction, water drawn to the hydrophilic region (27B) can move along the hydrophilic region (27B) to the first porous layer (26) through the hydrophobic region (27D) due to the property of maintaining the direction of movement. In other words, the porous member (25) illustrated in FIG. 3 and the porous member (25) illustrated in FIG. 10 can perform the same function of discharging water.

[0076] Referring again to FIG. 1, the porous member (35) of the anode (30) may be formed of a laminated structure of a third porous layer (36) and a fourth porous layer (37) having different pore scales. The third porous layer (36) may have the same configuration as the first porous layer (26) of the cathode (20). The fourth porous layer (37) may have the same configuration as the second porous layer (27) of the cathode (20) except that there is no hydrophilic region.

[0077] Figure 11 is a graph showing the performance evaluation results for three fuel cell cells. Table 1 below shows the characteristics of the three fuel cell cells.

[0078] Shape of the hydrophilic region of the second porous layer of the cathode electrode Area ratio occupied by the hydrophilic region in the second porous layer Comparative example Entire hydrophobic region--Example 1 Including hydrophilic region and hydrophobic region Multiple dot patterns Approximately 10% Example 2 Including hydrophilic region and hydrophobic region Multiple line patterns Approximately 25%

[0079] Referring to FIG. 11, it can be confirmed that both the current density and the power density are increased in the fuel cell cells of Examples 1 and 2 compared to the fuel cell cell of the comparative example. In addition, it can be confirmed that the current density and the power density are further increased in the fuel cell cell of Example 2, which has a larger area of ​​the hydrophilic region than the fuel cell cell of Example 1. The fuel cell cell (100) of the present embodiment can increase the reaction speed by continuously supplying an oxidant and continuously discharging water, and can improve the power density by lowering the transfer resistance of the oxidant and water.

[0080] Fig. 12 is a schematic cross-sectional view of an electrochemical cell according to a second embodiment. The electrochemical cell of the second embodiment has the same or similar configuration as the first embodiment described above, except for the following details.

[0081] Referring to Fig. 12, in the fuel cell cell (100A) of the present embodiment, the ion exchange member (10) may be composed of an anion exchange membrane. In this case, an oxidant and water may be supplied to the cathode (20), and fuel may be supplied to the anode (30). When the oxidant, water, and fuel are supplied to the cell assembly (110), electricity is generated by an electrochemical reaction, water is discharged from the cathode (20), and water is also discharged from the anode (30).

[0082] In the present embodiment, the hydrophobic region (27A, 37A) and the hydrophilic region (27B, 37B) can be located in both the cathode electrode (20) and the anode electrode (30). That is, the porous member (25, 35) of each of the cathode electrode (20) and the anode electrode (30) can include a first porous layer (26, 36) and a second porous layer (27, 37), and the second porous layer (27, 37) can include a hydrophobic region (27A, 37A) and a hydrophilic region (27B, 37B) adjacent along the plane direction. The porous member (25, 35) has the same configuration as the porous member of the cathode electrode described in the first embodiment described above.

[0083] In the second porous layer (27) of the cathode (20), the hydrophobic region (27A) can function as a movement path for the oxidant, and the hydrophilic region (27B) can function as a movement path for water. In the second porous layer (37) of the anode (30), the hydrophobic region (37A) can function as a movement path for the fuel, and the hydrophobic region (37B) can function as a movement path for the water.

[0084] Fig. 13 is a schematic cross-sectional view of an electrochemical cell according to a third embodiment. The electrochemical cell of the third embodiment has the same or similar configuration as the first embodiment described above, except for the following details.

[0085] Referring to Fig. 13, in the fuel cell cell (100B) of the present embodiment, the ion exchange member (10) may be composed of a liquid electrolyte. In this case, the cell assembly (110) may have a structure capable of containing the liquid electrolyte in a hermetic state. In the present embodiment, the hydrophobic region and the hydrophilic region may be located on either the cathode electrode (20) or the anode electrode (30).

[0086] For example, if the low-temperature fuel cell cell (100B) using a liquid electrolyte is a phosphoric acid fuel cell, the hydrophobic region and the hydrophilic region may be located at the cathode electrode (20) from which water is discharged. On the other hand, if the low-temperature fuel cell cell (100B) using a liquid electrolyte is an alkaline fuel cell, the hydrophobic region and the hydrophilic region may be located at the anode electrode (30) from which water is discharged. For convenience, FIG. 13 illustrates an alkaline fuel cell in which the hydrophobic region (37A) and the hydrophilic region (37B) are located at the anode electrode (30) as an example.

[0087] Fig. 14 is a schematic cross-sectional view of an electrochemical cell according to the fourth embodiment.

[0088] Referring to Fig. 14, the electrochemical cell of the present embodiment is composed of a water electrolysis cell (200). The water electrolysis cell (200) may be a low-temperature water electrolysis cell having an operating temperature of approximately 120°C or less, but is not limited to this example. The water electrolysis cell (200) produces hydrogen and oxygen through the electrolysis of water. The water electrolysis cell (200) of the present embodiment may be a polymer electrolyte water electrolysis cell using a cation exchange membrane.

[0089] The electrolysis cell (200) may include a cell assembly (210) and a separator (220) positioned on both sides of the cell assembly (210). The separator (220) may be referred to as a bipolar plate and is made of a conductor. The cell assembly (210) may include an ion exchange member (40), a cathode electrode (50) positioned on one side of the ion exchange member (40), and an anode electrode (60) positioned on the other side of the ion exchange member (40). The ion exchange member (40) may be composed of a cation exchange membrane.

[0090] The cathode electrode (50) may include a catalyst layer (51) and a porous member (55), and the anode electrode (60) may include a catalyst layer (61) and a porous member (65). The catalyst layers (51, 61) may be positioned between the ion exchange member (40) and the porous member (55, 65). The porous member (55, 65) may be referred to as a porous transport layer. The porous member (55, 65) may be composed of a first porous layer (56, 66) for supporting the catalyst layer (51, 61), and a second porous layer (57, 67) for enhancing the transport effect of water and bubbles. The second porous layer (57, 67) may be positioned to be in contact with the catalyst layer (51, 61).

[0091] A first flow path (221) may be positioned on one side of the separator (220) facing the cathode (50), and a second flow path (222) may be positioned on one side of the separator (220) facing the anode (60). When liquid water is supplied to the inlet of the first flow path (221) and the inlet of the second flow path (222), hydrogen is generated in the catalyst layer (51) of the cathode (50) and oxygen is generated in the catalyst layer (61) of the anode (60) through an electrochemical reaction.

[0092] Hydrogen can move to the first flow path (221) through the porous member (55) and be discharged together with liquid water through the outlet of the first flow path (221). Oxygen can move to the second flow path (222) through the porous member (65) and be discharged together with liquid water through the outlet of the second flow path (222). The porous members (55, 65) allow liquid water supplied from the separator (220) to be transferred to the catalyst layer (51, 61) and at the same time allow bubbles (hydrogen bubbles or oxygen bubbles) generated in the catalyst layer (51, 61) to be discharged toward the separator (220).

[0093] In a typical polymer electrolyte water electrolysis cell, oxygen bubbles generated in the catalyst layer of the anode electrode mainly block the porous member, hindering water transfer, and increasing the reaction rate and water transfer resistance, thereby reducing hydrogen production efficiency.

[0094] Fig. 15 is a schematic perspective view showing a porous member of the anode electrode of the electrolysis cell illustrated in Fig. 14. Fig. 16 is a schematic cross-sectional view of the porous member illustrated in Fig. 15.

[0095] Referring to FIGS. 14 to 16, the porous member (65) of the anode (60) may be formed of a laminated structure of a first porous layer (66) and a second porous layer (67) having different pore scales. The first porous layer (66) may have first pores of a first scale, and the second porous layer (67) may have second pores of a second scale smaller than the first scale.

[0096] The first scale may be a micrometer scale, and the second scale may be a nanometer scale. For example, the average size of the first pores of the first porous layer (66) may be approximately tens of micrometers, and the average size of the second pores of the second porous layer (67) may be approximately tens of nanometers. The first porous layer (66) may have a first thickness suitable for supporting the catalyst layer (61), and the second porous layer (67) may have a second thickness smaller than the first thickness.

[0097] Figure 17 is a schematic diagram showing pores inside the porous member illustrated in Figure 16.

[0098] Referring to Fig. 17, oxygen bubbles generated in the catalyst layer of the anode are discharged through the second pores (P2) of the second porous layer and the first pores (P1) of the first porous layer connected thereto. Since the first pores (P1) are tens of micrometers in size and the second pores (P2) are tens of nanometers in size, a pore gradient structure is created within the porous member.

[0099] The pressure (P) required to remove bubbles from the pores can be expressed by the aforementioned mathematical formula 1. However, in this case, θ in mathematical formula 1 represents the contact angle of the bubbles. The nanometer-sized second pores (P2) act as a higher capillary barrier in the process of removing the pores, and the pressure (P) required to remove the bubbles increases as the pore size decreases.

[0100] Figure 18 is a schematic diagram of the porous member shown in Figure 16.

[0101] Referring to FIGS. 15, 16, and 18, the entire first porous layer (66) can implement hydrophilicity. For example, the first porous layer (66) can include at least one of a plurality of carbon fibers (661), a plurality of titanium fibers, a plurality of titanium powders, and a nickel porous body (foam). The carbon fibers (661) can be rod-shaped. The second porous layer (67) can include a hydrophobic region (67A) and a hydrophilic region (67B) adjacent to each other along the plane direction. The hydrophilic region (67B) can occupy a part of the second porous layer (67), and the hydrophobic region (67A) can occupy the remainder of the second porous layer (67).

[0102] The hydrophobic region (67A) may include a plurality of carbon powders (671) and a hydrophobic polymer layer (672) coated on the surface of each of the plurality of carbon powders (671). The hydrophilic region (67B) may include a plurality of carbon powders (671). The carbon powders (671) may be spherical. The hydrophobic polymer layer (672) may include PTFE, but is not limited to this example. The second porous layer (67) may be divided into a hydrophobic region (67A) and a hydrophilic region (67B) depending on the presence or absence of the hydrophobic polymer layer (672).

[0103] Figure 19 is a schematic diagram for explaining the movement of water and oxygen bubbles in the second porous layer shown in Figure 18.

[0104] Referring to Fig. 19, the hydrophilic region (67B) easily absorbs water and thus allows water to pass through it. On the other hand, the hydrophobic region (67A) repels water and thus allows oxygen bubbles to pass through it more easily than water. In other words, in the second porous layer (67), the hydrophilic region (67B) can function as a path for water movement, and the hydrophobic region (67A) can function as a path for oxygen bubbles movement.

[0105] Referring to FIGS. 15, 16, and 19, the second porous layer (67) can spatially separate the water movement (supply) path and the oxygen bubble movement (discharge) path by means of the adjacent hydrophilic region (67B) and hydrophobic region (67A) along the surface direction. Accordingly, the porous member (65) of the anode electrode (60) can continuously supply water using the hydrophilic region (67B) and continuously discharge oxygen bubbles using the hydrophobic region (67A).

[0106] Assuming that the entire second porous layer is a hydrophilic region, the pressure required to remove oxygen bubbles (P) increases due to the nanometer-scale pore size and hydrophilicity, making it difficult for the oxygen bubbles to be discharged smoothly. On the other hand, the hydrophobic region (67A) of the second porous layer (67) can lower the pressure required for oxygen bubbles (P) due to its hydrophobicity that repels water despite its nanometer-scale pore size, thereby facilitating the discharge of oxygen bubbles.

[0107] Either the hydrophobic region (67A) or the hydrophilic region (67B), for example, the hydrophilic region (67B), may be formed of a plurality of dot patterns as shown in FIG. 13, and may be formed of various patterns such as a plurality of line patterns or cross patterns in addition to the dot pattern.

[0108] The area occupied by the hydrophobic region (67A) in the second porous layer (67) may be smaller than the area occupied by the hydrophilic region (67B), but is not limited to this example. In the water electrolysis cell (200), the porous member (65) basically functions to transfer water toward the catalyst layer (61), so when the area of ​​the hydrophobic region (67A) is smaller than the area of ​​the hydrophilic region (67B), the water supply efficiency can be increased while securing a discharge path for oxygen bubbles.

[0109] The depth of the hydrophilic region (67B) may be equal to or less than the thickness of the second porous layer (67), and the depth of the hydrophobic region (67A) may be equal to the thickness of the second porous layer (67). FIG. 14 illustrates a case where the depth of the hydrophilic region (67B) and the depth of the hydrophobic region (67A) are equal to the thickness of the second porous layer (67).

[0110] Referring again to FIG. 14, the porous member (55) of the cathode (50) may be formed of a laminated structure of a third porous layer (56) and a fourth porous layer (57) having different pore scales. The third porous layer (56) may have the same configuration as the first porous layer (66) of the anode (60). The fourth porous layer (57) may have the same configuration as the second porous layer (67) of the anode (60) except that there is no hydrophobic region.

[0111] The water electrolysis cell (200) of the present embodiment can increase the reaction rate by continuously supplying water and continuously discharging oxygen bubbles, and can improve hydrogen production efficiency by lowering the transfer resistance of water and oxygen bubbles.

[0112] Fig. 20 is a schematic cross-sectional view of an electrochemical cell according to the fifth embodiment.

[0113] Referring to Fig. 20, the electrochemical cell of the present embodiment is composed of a water electrolysis cell (200A). The water electrolysis cell (200A) of the present embodiment may be a water electrolysis cell using an anion exchange membrane or an alkaline water electrolysis cell using a liquid electrolyte.

[0114] The electrolysis cell (200A) of the present embodiment has the same or similar configuration as the electrolysis cell of the second embodiment described above, except that the ion exchange member (70) is composed of either an anion exchange membrane or a liquid electrolyte, and the second porous layers (57, 67) of the cathode electrode (50) and the anode electrode (60) include hydrophobic regions (57A, 67A) and hydrophilic regions (57B, 67B) that are adjacent to each other along the surface direction. However, when the ion exchange member (70) is a liquid electrolyte, the cell assembly (210) may have a structure capable of containing the liquid electrolyte in a hermetic state.

[0115] In a typical anion exchange membrane electrolysis cell or alkaline electrolysis cell, hydrogen bubbles generated from the catalyst layer of the cathode and oxygen bubbles generated from the catalyst layer of the anode mainly block the porous member, hindering water transfer, and increasing the reaction rate and water transfer resistance, thereby reducing hydrogen production efficiency.

[0116] Fig. 21 is a schematic perspective view showing a porous member of the cathode electrode of the electrolysis cell illustrated in Fig. 20. Fig. 22 is a schematic cross-sectional view of the porous member illustrated in Fig. 21.

[0117] Referring to FIGS. 20 to 22, the porous member (55) of the cathode (50) may be formed of a laminated structure of a first porous layer (56) and a second porous layer (57) having different pore scales. The first porous layer (56) may have the same configuration as the first porous layer of the anode described in the fourth embodiment. The second porous layer (57) may have the same configuration as the second porous layer of the anode described in the fifth embodiment.

[0118] The second porous layer (57) may include a hydrophobic region (57A) and a hydrophilic region (57B) adjacent to each other along the surface direction. In the second porous layer (57), the hydrophilic region (57B) may function as a movement path of water toward the catalyst layer (51) of the cathode (50), and the hydrophobic region (57A) may function as a movement path of hydrogen bubbles generated in the catalyst layer (51) of the cathode (50).

[0119] The second porous layer (57) can spatially separate the water movement (supply) path and the hydrogen bubble movement (discharge) path by means of the adjacent hydrophilic region (57B) and hydrophobic region (57A) along the surface direction. Therefore, the porous member (55) of the cathode electrode (50) can continuously supply water using the hydrophilic region (57B) and continuously discharge hydrogen bubbles using the hydrophobic region (57A).

[0120] The electrolysis cell (300A) of the present embodiment can increase the reaction rate by continuously supplying water and continuously discharging hydrogen bubbles and oxygen bubbles, and can improve hydrogen production efficiency by lowering the transfer resistance of water, hydrogen bubbles, and oxygen bubbles.

[0121] Fig. 23 is a flowchart showing a method for manufacturing a porous member according to one embodiment.

[0122] Referring to FIG. 23, a method for manufacturing a porous member according to the present embodiment may include the steps of creating a first porous layer having first pores of a first scale (S10), creating a second porous layer having second pores of a second scale smaller than the first scale and implementing hydrophobicity (S20), placing an exposure mask having a plurality of holes formed therein on the second porous layer (S30), and irradiating a plasma beam to the second porous layer through the plurality of holes to modify a portion of the second porous layer into a hydrophilic region (S40).

[0123] Figures 24 to 26 are schematic perspective views illustrating a manufacturing process of a porous member according to one embodiment.

[0124] Referring to FIG. 24, the first porous layer (410) may include a plurality of carbon fibers and a hydrophobic polymer layer coated on the surface of each of the plurality of carbon fibers. The first porous layer (410) may implement hydrophobicity. On the other hand, the first porous layer (420) may include at least one of a plurality of carbon fibers, a plurality of titanium fibers, a plurality of titanium powders, and a nickel porous body. The first porous layer (420) may implement hydrophilicity. The former first porous layer (410) may be applied to a fuel cell cell, and the latter first porous layer (420) may be applied to a water electrolysis cell.

[0125] The second porous layer (430) may include a plurality of carbon powders and a hydrophobic polymer layer coated on the surface of each of the plurality of carbon powders. The second porous layer (430) may implement hydrophobicity. The second porous layer (430) may be laminated on the first porous layer (410, 420) or the second porous layer (430) may be formed on the first porous layer (410, 420) to form the porous member (400).

[0126] A plurality of holes (501) may be positioned in the exposure mask (500). The plurality of holes (501) may be formed in various shapes, such as circular, rod-shaped, or cross-shaped, and the size of the holes (501) may be adjusted in various ways depending on the area of ​​the hydrophilic region to be modified.

[0127] Referring to FIGS. 25 and 26, an exposure mask (500) can be laminated on the second porous layer (430) so as to be in contact with the second porous layer (430) (see FIG. 22). A portion of the second porous layer (430) facing the plurality of holes (501) is exposed, and the remainder is covered by the exposure mask (500). The porous member (400) and the exposure mask (500) can be moved to a plasma chamber (600), and plasma discharge can occur in the plasma chamber (600). Through this process, a plasma beam can be irradiated to the second porous layer (430) through the plurality of holes (501).

[0128] Since the plasma beam has a shallow penetration depth, selective irradiation of the second porous layer (430) is possible. The plasma beam can remove the hydrophobic polymer layer to reveal the carbon powder. Therefore, the portion of the second porous layer (430) irradiated with the plasma beam can be modified into a hydrophilic region (430B). That is, the second porous layer (430) can be composed of a hydrophobic region and a hydrophilic region modified by the plasma beam. The plasma beam can be generated in various gas atmospheres such as air, oxygen, or nitrogen, and the modification characteristics can be controlled by appropriately adjusting the discharge intensity, gas flow rate, treatment time, etc.

[0129] The porous member (400) and the exposure mask (500) can be taken out from the plasma chamber (600), and the porous member (400) and the exposure mask (500) can be separated. Since the second porous layer that implements hydrophobicity is a commercialized product, it may be a simpler method to modify a portion of the hydrophobic second porous layer into a hydrophilic layer rather than modifying a portion of the hydrophilic second porous layer into a hydrophobic layer.

[0130] Additionally, the second porous layer (430) can be immersed in a NaOH solution, removed, and left in the air at room temperature for approximately one day. This allows the hydrophobic polymer layer to be further removed from the hydrophilic region (430B), and NaOH to precipitate from the hydrophilic region (430B). Subsequently, the hydrophilic region (430B) can be washed with pure water and dried. The hydrophilic region (430B) that has undergone this process can permanently realize hydrophilicity.

[0131] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. A first porous layer having a first pore of a first scale; and A second porous layer is located on one surface of the first porous layer and includes a second porous layer having second pores of a second scale smaller than the first scale, The second porous layer is a porous member including a hydrophobic region and a hydrophilic region adjacent to each other along the plane direction.

2. In paragraph 1, The first scale of the above first pore is a micrometer scale, The second scale of the second pore is a nanometer scale, A porous member wherein the thickness of the first porous layer is greater than the thickness of the second porous layer.

3. In paragraph 1, The above first porous layer has hydrophobicity, A porous member in which the area occupied by the hydrophilic region in the second porous layer is smaller than the area occupied by the hydrophobic region.

4. In paragraph 3, The first porous layer comprises a plurality of carbon fibers coated with a hydrophobic polymer layer, The hydrophilic region of the second porous layer comprises a plurality of carbon powders, A porous member in which the hydrophobic region of the second porous layer comprises a plurality of carbon powders coated with a hydrophobic polymer layer.

5. In paragraph 1, The above first porous layer has hydrophilicity, A porous member in which the area occupied by the hydrophobic region in the second porous layer is smaller than the area occupied by the hydrophilic region.

6. In paragraph 5, The first porous layer comprises at least one of a plurality of carbon fibers, a plurality of titanium fibers, a plurality of titanium powders, and a nickel porous body, The hydrophilic region of the second porous layer comprises a plurality of carbon powders, A porous member in which the hydrophobic region of the second porous layer comprises a plurality of carbon powders coated with a hydrophobic polymer layer.

7. In paragraph 1, Either the hydrophobic region or the hydrophilic region forms a pattern of a preset shape, A porous member in which the depth of one of the hydrophobic region and the hydrophilic region is equal to or less than the thickness of the second porous layer.

8. Create a first porous layer having micrometer-scale pores and either hydrophobic or hydrophilic properties; A second porous layer having nanometer-scale pores and hydrophobicity is created; An exposure mask having a plurality of holes formed therein is prepared, and the exposure mask is placed on the second porous layer; A method for manufacturing a porous member, wherein a plasma beam is irradiated to the second porous layer through the plurality of holes to modify a portion of the second porous layer into a hydrophilic region.

9. In paragraph 8, A method for manufacturing a porous member further comprising the steps of applying a NaOH solution to the hydrophilic region, drying the hydrophilic region to precipitate NaOH, and washing the hydrophilic region with pure water and then drying the hydrophilic region.

10. A cell assembly including an ion exchange member, a cathode electrode positioned on one side of the ion exchange member, and an anode electrode positioned on the other side of the ion exchange member; and comprising a pair of separators positioned on both sides of the above cell assembly, Each of the above cathode and anode electrodes includes a catalyst layer and a porous member, The above porous member is, a first porous layer having first pores of a first scale; and A second porous layer is positioned between the first porous layer and the catalyst layer, and includes a second porous layer having second pores of a second scale smaller than the first scale, An electrochemical cell wherein the second porous layer belonging to at least one of the cathode and the anode electrodes includes a hydrophobic region and a hydrophilic region adjacent to each other along the plane direction.

11. In paragraph 10, The first scale of the above first pore is a micrometer scale, The second scale of the second pore is a nanometer scale, An electrochemical cell wherein the thickness of the first porous layer is greater than the thickness of the second porous layer.

12. In paragraph 10, The above electrochemical cell is an electrochemical cell that is a low-temperature fuel cell cell.

13. In paragraph 12, The above ion exchange member is one of a cation exchange membrane, an anion exchange membrane, and a liquid electrolyte, When the ion exchange member is a cation exchange membrane, the hydrophobic region and the hydrophilic region are located at the cathode, When the ion exchange member is an anion exchange membrane, the hydrophobic region and the hydrophilic region are located at the cathode and the anode, An electrochemical cell wherein the hydrophobic region and the hydrophilic region are located at one of the cathode and the anode when the ion exchange member is a liquid electrolyte.

14. In paragraph 13, The above first porous layer has hydrophobicity, An electrochemical cell in which the area occupied by the hydrophilic region in the second porous layer where the hydrophobic region and the hydrophilic region are located is smaller than the area occupied by the hydrophobic region.

15. In paragraph 14, An electrochemical cell in which the depth of the hydrophilic region is equal to or less than the thickness of the second porous layer, and the depth of the hydrophobic region is equal to the thickness of the second porous layer.

16. In paragraph 10, The above electrochemical cell is an electrochemical cell that is a water electrolysis cell.

17. In paragraph 16, The above ion exchange member is a cation exchange membrane, An electrochemical cell wherein the hydrophobic region and the hydrophilic region are located at the anode electrode.

18. In paragraph 17, The above first porous layer has hydrophilicity, An electrochemical cell in which the area occupied by the hydrophobic region in the second porous layer belonging to the anode electrode is smaller than the area occupied by the hydrophilic region.

19. In paragraph 16, The above ion exchange member is either an anion exchange membrane or a liquid electrolyte, An electrochemical cell in which the hydrophobic region and the hydrophilic region are located at the cathode and the anode.

20. In paragraph 19, The above first porous layer has hydrophilicity, An electrochemical cell in which the area occupied by the hydrophobic region in the second porous layer is smaller than the area occupied by the hydrophilic region.

Images