A method for quantifying the area ratio and area of ​​different contact regions between a porous transport layer and a catalyst layer and its application

Abstract

The present invention provides a method and application for quantifying the area ratio and area of ​​different contact areas between a porous transport layer and a catalyst layer, and relates to the technical field of proton exchange membrane electrolyzers. The quantification method disclosed in the present invention is: by measuring the surface of the CL, a two-dimensional contour image and a three-dimensional contour image are obtained, and the CL is customized into three parts according to the three-dimensional contour image: an uncontact area, a boundary area, and a contact area, and then the pixel ratio of the three parts is obtained according to the two-dimensional contour image; the above method is used to quantify the area ratio of different contact areas between the PTL and the CL, and there is a linear relationship between the obtained boundary area ratio and the electrochemical performance of the proton exchange membrane electrolyzer, which can provide certain guidance for improving the electrochemical performance of the proton exchange membrane electrolyzer; in addition, the quantified area ratio can also provide technical inspiration for the structural design and material screening of the PTL.

Description

Technical Field

[0001] This invention relates to the field of proton exchange membrane electrolyzer technology, and more specifically, to a method and its application for quantifying the area ratio and area of ​​different contact regions between the porous transport layer and the catalyst layer. Background Technology

[0002] Proton exchange membranes (PEMs) possess high ion transport performance, good stability and corrosion resistance, and can effectively remove impurity ions from water to produce pure, pollution-free water, thus finding widespread application in water electrolysis. As the core component of a PEM water electrolysis hydrogen production device, the proton exchange membrane electrolyzer (PEMEC) is assembled from components such as a catalyst-coated proton exchange membrane (CCM), a porous transport layer (PTL), bipolar plates (BP), end plates, sealing gaskets, and a frame, all tightly connected by applying a certain pre-tightening force. Within the internal structure of the PEM electrolyzer, the interface between the PTL and the catalyst layer (CL) is the primary site of electrochemical reactions, and these reactions are highly complex. Effective catalytic activity sites require simultaneous electron / proton conduction and water vapor transport. The matching and assembly method of the components at the PTL-CL interface significantly affect the expression of the catalytic layer's reactive sites, thereby impacting catalyst utilization. Therefore, the study and characterization of the PTL-CL interface are crucial.

[0003] Studies have reported that the catalyst utilization rate at the PTL and CL interface varies depending on water and gas transport and assembly conditions. The highest catalyst utilization rate is observed in regions with electronic conductors, active catalysts, proton supports, and unrestricted water and gas transport. Therefore, quantifying the effective contact area ratio between the PTL and CL is crucial for PTL structural design and material selection. However, commonly used PTL structures contain pores of varying sizes, and the surface of PTLs is generally rough, making it difficult to measure the area ratio of different contact regions at the PTL and CL interface. Summary of the Invention

[0004] The main objective of this invention is to provide a method and its application for quantifying the area ratio and area of ​​different contact regions between the porous transport layer and the catalyst layer, so as to solve the problem in the prior art that it is difficult to quantify the effective contact area ratio of the PTL and CL interfaces.

[0005] To achieve the above objective, according to a first aspect of the present invention, a method for quantifying the area ratio of different contact regions between a porous transport layer and a catalyst layer is provided, the method comprising the following steps:

[0006] S1, Measure the CL surface disassembled from PEMEC to obtain two-dimensional contour images and three-dimensional contour images;

[0007] S2. Divide the 3D contour image into regions, classifying the CL surface in the 3D contour image into contact regions, boundary regions, and non-contact regions according to height from low to high. The percentages of the maximum height of the contact region, boundary region, and non-contact region relative to the maximum height of the CL surface are x, x+y, and x+y+z, respectively; x is 10%-20%, y is 30%-40%, and z is 50%; additionally, x+y = 50%.

[0008] S3, determine the pixels of the regions divided in the above three-dimensional contour image, and segment the above two-dimensional contour image according to the determined pixels to obtain the number of pixels of the contact area, boundary area and non-contact area in the two-dimensional contour image; calculate the ratio of the number of pixels of the contact area, boundary area and non-contact area in the two-dimensional contour image to the total number of pixels in the two-dimensional contour image; that is, the area ratio of the contact area, boundary area and non-contact area.

[0009] The above method first divides the CL surface region into contact, boundary, and non-contact regions using a three-dimensional contour image. In the contact region, the PTL material is in contact with the catalyst in the CL, and this region exhibits varying catalyst utilization rates due to the influence of water and gas transport and assembly conditions. In the boundary region, electron, proton, water, and gas transport are unrestricted, resulting in good catalyst utilization. In the non-contact region, the CL permeates through the pores of the PTL, leading to low catalyst utilization. This division allows for the establishment of a linear relationship between the area of ​​the boundary region and the electrochemical performance of the PEMEC, guiding the structural design of the PTL. By identifying the pixels in each region on the three-dimensional contour image, the number of pixels in each region can be counted on the two-dimensional contour image. The ratio of the number of pixels in each region to the total number of pixels in the two-dimensional contour image represents the area proportion of each region. The boundary region area proportion calculated by this method shows high linearity with the electrochemical performance of the PEMEC.

[0010] Furthermore, in S2, x is 20% and y is 30%.

[0011] By optimizing the method of dividing each region on the three-dimensional contour image, the linearity between the obtained boundary region area and the electrochemical performance of PEMEC approaches 1, which can more accurately guide the structural design of PTL or the selection of materials.

[0012] Furthermore, in S1, a shape laser microscope or an X-ray tomography scanner is used to obtain two-dimensional contour images and three-dimensional contour images.

[0013] Furthermore, in S3, Photoshop or ImageJ software is used to determine the number of pixels in the divided regions of the 3D contour image and to count the number of pixels in the contact areas, boundary areas, and non-contact areas of the 2D contour image. These software programs are readily available and easy to install; they are commonly used graphics analysis and processing software and can conveniently count the number of pixels in the contact areas, boundary areas, and non-contact areas.

[0014] According to a second aspect of the present invention, a method for quantifying the area of ​​different contact regions between a porous transport layer and a catalyst layer is provided, comprising the following steps:

[0015] (1) Quantify the area ratio of different contact regions between the porous transport layer and the catalyst layer;

[0016] (2) The surface area of ​​different contact areas is calculated using the following formula:

[0017] S i =A×a×k

[0018] Among them, S i The area to be measured;

[0019] A is the projected area of ​​CL obtained from the two-dimensional contour image;

[0020] 'a' represents the area percentage of the region to be measured.

[0021] k is the ratio of the surface area of ​​CL to its projected area in the two-dimensional contour image;

[0022] The above step (1) is measured using the method of quantifying the area ratio of different contact areas between the porous transport layer and the catalyst layer according to the first aspect of the present invention.

[0023] Furthermore, k is measured by shape laser microscopy.

[0024] According to a third aspect of the present invention, an application is provided in improving the electrochemical performance of a proton exchange membrane electrolyzer by the method described above for quantifying the area ratio of different contact regions between the porous transport layer and the catalyst layer, the proton exchange membrane electrolyzer comprising a CL and a porous transport layer connected thereto.

[0025] Since there is a linear relationship between the boundary region area ratio measured in the first aspect of the present invention and the boundary region area measured in the second aspect of the present invention, the method of quantifying the different contact area areas of the porous transport layer and the catalyst layer in the second aspect of the present invention can also be used to improve the electrochemical performance of proton exchange membrane electrolyzers.

[0026] Furthermore, the electrochemical performance of the proton exchange membrane electrolyzer is improved by increasing the area ratio of the aforementioned boundary region.

[0027] Furthermore, the area ratio of the boundary region can be increased by designing the structure of the porous transport layer.

[0028] By applying the technical solution of this invention, two-dimensional and three-dimensional contour images are obtained by measuring the surface of the CL (continuum exchange membrane) electrolyzer. The surface is divided into non-contact areas, boundary areas, and contact areas based on the height in the three-dimensional contour image. Then, the pixel points are determined. The area ratio of different regions is obtained by the determined pixel points in the two-dimensional contour image. This method is simple, and the obtained boundary area ratio has a linear relationship with the electrochemical performance of the proton exchange membrane electrolyzer. It can be used to guide the structural design and material selection of porous transport layers. Attached Figure Description

[0029] Figure 1 This is a surface topography diagram of CL in Example 1;

[0030] Figure 2 (a) is a three-dimensional contour image of the CL surface in Example 1, and (b) is a diagram showing the division of different contact areas on the three-dimensional contour image of the CL surface in Example 1.

[0031] Figure 3 (a) is a two-dimensional contour image of the CL surface in Example 1; (b) is an image of the non-contact area, (c) the boundary area, and (d) the contact area segmented from the two-dimensional contour image of the CL surface in Example 1.

[0032] Figure 4 This is a polarization curve diagram of PEMEC1-PEMEC5 in the embodiment;

[0033] Figure 5 The following are (a) area-potential diagrams of the uncontacted region, (b) area-potential diagrams of the boundary region, and (c) area-potential diagrams of the contact region for different CLs in Examples 1-5.

[0034] The above figures include the following descriptions: 1. Example 1; 2. Example 2; 3. Example 3; 4. Example 4; 5. Example 5. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0036] As described in the background section of this invention, PEMEC includes components such as CCM, PTL, and bipolar plates. Since the PTL has a porous structure, some areas of the CL in the CCM permeate through the pores of the PTL after being compressed. However, the conductivity of CL is much lower than that of the PTL, resulting in the lowest catalyst utilization rate in the non-contact areas of the PTL and CL. In the areas where the PTL and CL are in complete contact, the catalyst utilization rate is also affected by water and gas transport and assembly conditions. In both the non-contact and fully contact areas, the catalyst utilization rate is lower than that in the boundary areas. Therefore, it is necessary to provide a quantitative method for the area ratio of different contact areas to guide the structural design and material selection of the PTL. However, existing PTLs generally have pores with different diameters, and the surface of the PTL is rough and uneven. When in contact with CL, uneven indentations are formed on its surface, further increasing the difficulty of quantifying the contact area ratio of different regions of the PTL and CL.

[0037] To address the aforementioned technical problems, in a typical embodiment of the present invention, a method for quantifying the area ratio of different contact regions between the porous transport layer and the catalyst layer is provided. This method includes the following steps:

[0038] S1, Measure the CL surface disassembled from PEMEC to obtain two-dimensional contour images and three-dimensional contour images;

[0039] S2, the three-dimensional contour image is divided into regions, and the CL surface in the three-dimensional contour image is divided into contact regions, boundary regions, and non-contact regions according to the height from low to high; wherein, the percentage of the maximum height of the contact region, boundary region, and non-contact region to the maximum height of the CL surface is x, x+y, and x+y+z respectively; where x is 10%-20%, y is 30%-40%, z is 50%, and x+y = 50%;

[0040] S3, determine the pixels of the regions divided in the above three-dimensional contour image, and segment the above two-dimensional contour image according to the determined pixels to obtain the number of pixels of the contact area, boundary area and non-contact area in the two-dimensional contour image; calculate the ratio of the number of pixels of the contact area, boundary area and non-contact area in the two-dimensional contour image to the total number of pixels in the two-dimensional contour image; that is, the area ratio of the contact area, boundary area and non-contact area.

[0041] In the description of this invention, the term "different contact areas" refers to contact areas, boundary areas, and non-contact areas.

[0042] In the description of this invention, the term "area ratio" refers to the ratio of the surface area of ​​the area to be measured to the surface area of ​​the CL.

[0043] In the description of this invention, the term "height" refers to a dimension that gradually increases in value along the direction from CL toward PTL.

[0044] In the description of this invention, the term "maximum height" refers to the maximum dimension of the CL along the direction from the CL toward the PTL.

[0045] This invention obtains the true surface morphology of a CL (Clean-Layered Component) under pressure by measuring the surface of a CL disassembled from a PEMEC. Two-dimensional and three-dimensional contour images of the CL surface can be directly obtained using the equipment. The three-dimensional contour image divides the CL into contact, boundary, and non-contact regions, while the two-dimensional contour image allows for the statistical analysis of pixels in each region, thus obtaining the area proportion of each region. Furthermore, the area proportion of the boundary region obtained by the quantification method according to this invention has a linear relationship with the electrochemical performance of the PEMEC, which can be used to guide the structural design and material selection of a PTL (Potentially Transmitted Tolerant Light).

[0046] In a preferred embodiment of the present invention, in S2, x is 20% and y is 30%.

[0047] By optimizing the region division method, the linear fit between the area ratio of the obtained boundary region and the electrochemical performance of PEMEC is higher.

[0048] Typically, but not limitingly, in S1, two-dimensional and three-dimensional contour images are obtained using a shape laser microscope or an X-ray tomography scanner.

[0049] Typically, but not exclusively, in S3, Photoshop or ImageJ software is used to determine the number of pixels in the divided regions of a 3D contour image and to count the number of pixels in the contact, boundary, and non-contact areas of a 2D contour image. These are commonly used graphics analysis and processing software programs, easy to operate. Other software with image processing capabilities can also be used to count the number of pixels.

[0050] In the description of this invention, the term "pixel" refers to the smallest unit that constitutes an image. In a three-dimensional contour image, the color of pixels in different regions can be obtained based on the height. Then, in a two-dimensional contour image, the number of pixels is counted based on the color corresponding to different regions.

[0051] In a typical embodiment of the present invention, a method for quantifying the area of ​​different contact regions between a porous transport layer and a catalyst layer is provided, comprising the following steps:

[0052] (1) Quantify the area ratio of different contact regions between the porous transport layer and the catalyst layer;

[0053] (2) The surface area of ​​different contact areas is calculated using the following formula:

[0054] S i =A×a×k

[0055] Among them, S i The area to be measured;

[0056] A is the projected area of ​​CL obtained from the two-dimensional contour image;

[0057] 'a' represents the area percentage of the region to be measured.

[0058] k is the ratio of the surface area of ​​CL to its projected area in the two-dimensional contour image;

[0059] The above step (1) was measured using the method of quantifying the area ratio of different contact areas between the porous transport layer and the catalyst layer in the above typical embodiments of the present invention.

[0060] Typical, but not limiting, k is measured by shape laser microscopy.

[0061] In another typical embodiment of the present invention, an application is provided in improving the electrochemical performance of a proton exchange membrane electrolyzer by the above-described method for quantifying the area ratio of different contact regions between the porous transport layer and the catalyst layer, the proton exchange membrane electrolyzer comprising a CL and a porous transport layer connected thereto.

[0062] Since the area ratio of different contact regions between the porous transport layer and the catalyst layer is linearly related to their area, the method of quantifying the area of ​​different contact regions between the porous transport layer and the catalyst layer in the above typical embodiments can also be applied to improve the electrochemical performance of proton exchange membrane electrolyzers.

[0063] In a preferred embodiment of the present invention, the electrochemical performance of the proton exchange membrane electrolyzer is improved by increasing the area ratio of the boundary region.

[0064] In a preferred embodiment of the present invention, the boundary region area ratio is increased by optimizing the structure of the PTL.

[0065] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0066] Building different PTLs:

[0067] Laser etching technology was used to etch sintered titanium (Kunshan Xuanzuan Electronic Technology Co., Ltd., with a filtration accuracy of 20μm) with a thickness of 0.5mm for different durations, resulting in PTL1, PTL2, and PTL3 with different surface roughnesses. The specific etching conditions are as follows:

[0068] PTL1: Etching time is 0 min;

[0069] PTL2: Etching time is 80 min;

[0070] PTL3: Etching time is 40 min;

[0071] PTL4: PTL with a thickness of 0.5 mm (Shanghai Zhizhen New Energy Co., Ltd., with a particle size of 20-30 μm);

[0072] PTL5: Etching time is 60 min;

[0073] Assemble PEMEC:

[0074] (1) An anode catalyst slurry is prepared from water, anode catalyst powder, Nafion solution and organic solvent; a cathode catalyst slurry is prepared from water, cathode catalyst powder, Nafion solution and organic solvent;

[0075] (2) The two slurries were dispersed by ball milling;

[0076] (3) The dispersed anode catalyst slurry and cathode catalyst slurry are coated on both sides of polytetrafluoroethylene (PTFE) respectively, and then hot-pressed at 120℃ and 4MPa for 5min;

[0077] (4) The anodic catalyst layer and cathode catalyst layer formed on both sides of PTFE are transferred onto the proton exchange membrane to obtain a catalyst-coated membrane (CCM);

[0078] (5) Finally, the CCM, the sintered titanium porous transport layer of the anode, the carbon paper of the cathode gas diffusion layer, and the anode and cathode sealing gaskets are assembled together by a torque of 2 N·m to obtain PEMEC.

[0079] PEMEC1, PEMEC2, PEMEC3, PEMEC4, and PEMEC5 are assembled from PTL1, PTL2, PTL3, PTL4, and PTL5, respectively.

[0080] The electrochemical performance of PEMEC1-5 was tested separately. The test methods and results are described below.

[0081] Example 1

[0082] An embodiment of the method for quantifying the area ratio of different contact regions between a porous transport layer and a catalyst layer according to the present invention, wherein the method described in Embodiment 1 includes the following steps:

[0083] S1. The surface of the CL (anode side) of the CCM disassembled from the PEMEC1 after performance testing was measured using a shape laser microscope (LM, Keyence VK-X1100, Japan) to obtain the CL surface topography map, two-dimensional contour image and three-dimensional contour image; Figure 1 This is a surface topography diagram of CL;

[0084] S2, the three-dimensional contour image is divided into regions, and the CL surface in the three-dimensional contour image is divided into contact region, boundary region and non-contact region according to the height from low to high; among them, the percentage of the maximum height of the contact region, boundary region and non-contact region to the maximum height of the CL surface is 20%, 50% and 100% respectively. Figure 2 (a) is a three-dimensional contour image of the CL surface. Figure 2 (b) is a diagram showing the division of different contact areas on the CL surface;

[0085] S3, determine the pixels of the regions divided in the above three-dimensional contour image; and segment the above two-dimensional contour image based on the determined pixels. Figure 3 (a) is a two-dimensional contour image of the CL surface. Figure 3 (b) is an image of the non-contact region segmented from a two-dimensional contour image of the CL surface. Figure 3 (c) is an image of the boundary region segmented on the two-dimensional contour image of the CL surface. Figure 3 (d) is the contact area image segmented on the two-dimensional contour image of the CL surface; the number of pixels in the contact area, boundary area and non-contact area on the two-dimensional contour image is counted using Photoshop software, and the ratio of the number of pixels in the three areas to the total number of pixels in the two-dimensional contour image is obtained respectively; that is, the area ratio of the non-contact area, boundary area and contact area.

[0086] Then, the area of ​​the boundary region is calculated based on its area ratio. The calculation method is as follows:

[0087] S=A×a×k

[0088] Where S is the area of ​​the boundary region;

[0089] A is the projected area of ​​CL obtained from the two-dimensional contour image;

[0090] 'a' represents the area percentage of the boundary region;

[0091] k is the ratio of the surface area of ​​CL to its projected area in a two-dimensional contour image, measured by a shape laser microscope.

[0092] In this embodiment, A is 0.376 mm. 2a is 27.9%, k is 1.252; the calculated S1 is 0.131 mm. 2 .

[0093] Examples 2-5

[0094] Examples 2-5 illustrate the method of quantifying the area ratio of different contact regions between the porous transport layer and the catalyst layer according to the present invention. The only difference from Example 1 is the type of PEMEC: PEMEC2 in Example 2, PEMEC3 in Example 3, PEMEC4 in Example 4, and PEMEC5 in Example 5.

[0095] Calculated:

[0096] In Example 2, the area ratio 'a' of the boundary region is 30.9%, and A is 0.376 mm. 2 k is 1.269 and S is 0.147 mm. 2 ;

[0097] In Example 3, the area ratio 'a' of the boundary region is 39.6%, and A is 0.376 mm. 2 k is 1.371, and S is 0.204 mm. 2 ;

[0098] In Example 4, the area ratio 'a' of the boundary region is 36.8%, and A is 0.376 mm. 2 k is 1.408, and S is 0.195 mm. 2 ;

[0099] In Example 5, the area ratio 'a' of the boundary region is 36.3%, and A is 0.376 mm. 2 k is 1.296, and S is 0.177 mm. 2 .

[0100] Performance testing

[0101] The electrochemical performance of PEMEC1, PEMEC2, PEMEC3, PEMEC4, and PEMEC5 was tested:

[0102] Polarization curves: recorded for current densities ranging from 0.025 A / cm². 2 Up to 4A / cm 2 The voltage value of the electrolytic cell under the specified conditions was maintained for 2 minutes at each current density step. To prevent passivation failure of the electrolytic cell under high voltage conditions, the upper limit of the safe voltage was set to 3V.

[0103] Figure 4The figure shows the polarization curves of PEMEC1-PEMEC5. As can be seen from the figure, the electrochemical performance of PEMEC is better as the area of ​​the boundary region increases.

[0104] Figure 5 Examples 1-5 show the following area-potential diagrams for different contact regions: (a) uncontacted region area-potential diagram, (b) boundary region area-potential diagram, and (c) contact region area-potential diagram (current density 4 A·cm). -2 As shown in the figure, there is a linear relationship between the area of ​​the CL boundary region and the electrochemical performance of PEMEC.

[0105] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for quantifying the area ratio of different contact regions between a porous transport layer and a catalyst layer, characterized in that, Includes the following steps: S1, Measure the surface of CL disassembled from the proton exchange membrane electrolyzer to obtain two-dimensional contour images and three-dimensional contour images; S2, the three-dimensional contour image is divided into regions, and the CL surface in the three-dimensional contour image is divided into contact regions, boundary regions, and non-contact regions according to the height from low to high; the percentage of the maximum height of the contact region, the boundary region, and the non-contact region relative to the maximum height of the CL surface is x, x+y, and x+y+z, respectively; where x is 10%-20%, y is 30%-40%, z is 50%, and x+y = 50%; S3, determine the pixels of the regions divided in the three-dimensional contour image, and segment the two-dimensional contour image according to the determined pixels to obtain the number of pixels of the contact area, the boundary area, and the non-contact area on the two-dimensional contour image; Calculate the ratio of the number of pixels in the contact area, the boundary area, and the non-contact area in the two-dimensional contour image to the total number of pixels in the two-dimensional contour image, respectively. That is, the area ratio of the contact area, the boundary area, and the non-contact area.

2. The method for quantifying the area ratio of different contact regions between the porous transport layer and the catalyst layer according to claim 1, characterized in that, In S2, x is 20% and y is 30%.

3. The method for quantifying the area ratio of different contact regions between the porous transport layer and the catalyst layer according to claim 1, characterized in that, In step S1, the two-dimensional contour image and the three-dimensional contour image are obtained using a shape laser microscope or an X-ray tomography scanner; and / or, in step S3, Photoshop software or ImageJ software is used to determine the pixel points of the regions divided in the three-dimensional contour image and to count the number of pixels in the contact area, the boundary area, and the non-contact area in the two-dimensional contour image.

4. A method for quantifying the contact area of ​​different regions between a porous transport layer and a catalyst layer, characterized in that, The method includes: (1) Quantify the area ratio of different contact regions between the porous transport layer and the catalyst layer; (2) The surface area of ​​different contact areas is calculated using the following formula: S i =A×a×k Wherein, the S i The area to be measured; A is the projected area of ​​CL obtained from the two-dimensional contour image; 'a' represents the area percentage of the region to be measured. The value of k is the ratio of the surface area of ​​the CL to its projected area in the two-dimensional contour image; In step (1), the method for quantifying the area ratio of different contact regions between the porous transport layer and the catalyst layer is the method described in any one of claims 1 to 3.

5. The method for quantifying the contact area of ​​different regions between the porous transport layer and the catalyst layer according to claim 4, characterized in that, The value of k is measured by a shape laser microscope.

6. The application of a method for quantifying the area ratio of different contact regions between the porous transport layer and the catalyst layer according to any one of claims 1 to 3 in improving the electrochemical performance of a proton exchange membrane electrolyzer, characterized in that, The proton exchange membrane electrolyzer includes a CL and a porous transport layer connected to the CL.

7. The application according to claim 6, characterized in that, The electrochemical performance of the proton exchange membrane electrolyzer is improved by increasing the area ratio of the boundary region.

8. The application according to claim 7, characterized in that, The area ratio of the boundary region is increased by designing the structure of the porous transmission layer.

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