Porous composite

Abstract

A porous composite body having: a base material having a first main face and a nickel layer provided to at least a part of the first main face, the base material being composed of a nickel mesh structure or a nickel porous body having a three-dimensional network structure, and the arithmetic mean height Sa of the nickel layer as defined by ISO 25178 being 5 μm or less.

Description

Technical Field

[0001] This invention relates to a porous composite. Background Technology

[0002] Hydrogen has garnered attention as a highly efficient and clean energy source due to its suitability for storage and transportation and its low environmental impact. While most hydrogen is produced through steam reforming of fossil fuels, the importance of hydrogen production via water electrolysis is increasingly recognized from the perspective of reducing environmental impact. Since water electrolysis consumes electricity, various improvements are being explored to achieve highly efficient hydrogen production systems.

[0003] In recent years, AEM (Anion Exchange Membrane) type water electrolysis using anion exchange membranes has attracted much attention (e.g., Patent Document 1). Compared with the currently mainstream alkaline water electrolysis and PEM (Polymer Electrolyte Membrane) type water electrolysis, AEM type water electrolysis has the advantages of increasing current density and making the device more compact compared to alkaline water electrolysis, and it does not require the precious metal catalyst necessary in PEM type water electrolysis.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2022-26413 Summary of the Invention

[0007] The composite porous body of the present invention is a porous composite having:

[0008] The substrate having the first main surface, and

[0009] A nickel layer disposed on at least a portion of the aforementioned first main surface,

[0010] The aforementioned substrate is composed of a nickel mesh structure or a nickel porous body with a three-dimensional mesh structure.

[0011] The arithmetic mean height Sa of the aforementioned nickel layer, as specified in ISO 25178, is less than 5 μm. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view of an example of the porous composite of Embodiment 1.

[0013] Figure 2 This is a diagram illustrating a representative structural example of a nickel porous body.

[0014] Figure 3 It is Figure 2 The diagram shows an enlarged cross-section of a nickel porous body.

[0015] Figure 4 yes Figure 3 A schematic diagram of the cross-section along line IV-IV of the skeleton 11 shown.

[0016] Figure 5 This is an example of a SEM image showing a cross-section of the porous composite of Embodiment 1.

[0017] Figure 6 This is a schematic SEM image showing a cross-section of a nickel mesh structure.

[0018] Figure 7 This is an example of a SEM image showing a cross-section of the nickel layer of the porous composite of Embodiment 1. Detailed Implementation

[0019] [The problem this invention aims to solve]

[0020] In AEM-type water electrolysis, the anion exchange membrane is positioned adjacent to an electrode composed of a conductive porous body. If the surface of the porous body is rough, the protrusions on the surface can penetrate the anion exchange membrane, potentially causing micro-short circuits or through-holes in the membrane leading to cross-leakage of oxygen and hydrogen. To avoid this problem, thickening the anion exchange membrane could be considered. However, thickening the anion exchange membrane increases the resistance of the water electrolysis cell, leading to a rise in voltage during electrolysis and thus increasing power consumption. Therefore, to avoid the problems associated with the anion exchange membrane, a technology is needed to provide electrodes with reduced surface roughness.

[0021] [Effects of the Invention]

[0022] According to the present invention, a porous composite material with reduced surface roughness can be provided for use as an electrode in an AEM-type water electrolysis device.

[0023] [Detailed Description of Implementation]

[0024] First, embodiments of the present invention will be described.

[0025] (1) The porous composite of the present invention has the following characteristics:

[0026] The substrate having the first main surface, and

[0027] A nickel layer disposed on at least a portion of the aforementioned first main surface,

[0028] The aforementioned substrate is composed of a nickel mesh structure or a nickel porous body with a three-dimensional mesh structure.

[0029] The arithmetic mean height Sa of the aforementioned nickel layer, as specified in ISO 25178, is less than 5 μm.

[0030] According to the present invention, a porous composite material with reduced surface roughness can be provided for use as an electrode in an AEM-type water electrolysis device. In this invention, ISO 25178 is more specifically ISO 25178-2:2012.

[0031] (2) In (1) above, the nickel layer has multiple pores inside.

[0032] The average opening diameter of the aforementioned nickel layer can be greater than 0.1 μm and less than 50 μm.

[0033] As a result, the smoothness of the nickel layer surface is improved, making it less likely to penetrate the anion exchange membrane.

[0034] (3) In (1) or (2) above, the average thickness of the nickel layer may be more than 0.5 μm and less than 100 μm.

[0035] Therefore, in the AEM-type water electrolysis device that uses the porous composite as an electrode, the strength of the nickel layer itself is maintained. Furthermore, the transport of substances such as electrolyte and generated gases becomes smoother between the substrate portion of the porous composite and the anion exchange membrane, thus improving the electrolysis efficiency of the AEM-type water electrolysis device.

[0036] (4) In any of the above (1) to (3),

[0037] The aforementioned nickel layer has multiple pores inside.

[0038] The porosity of the aforementioned nickel layer can be above 40% and below 75%.

[0039] Therefore, in the AEM-type water electrolysis device that uses a porous composite as an electrode, the transport of substances such as electrolyte and generated gas becomes smoother between the substrate portion of the porous composite and the anion exchange membrane, thereby improving the electrolysis efficiency of the AEM-type water electrolysis device.

[0040] (5) In any of (1) to (4) above, the average thickness of the porous composite can be more than 50 μm and less than 500 μm.

[0041] Therefore, in the AEM-type water electrolysis device that uses porous composites as electrodes, the transport of electrolytes, gases, and other substances in the electrolysis cell becomes smoother, and the miniaturization of the electrolysis device and the uniformity of substance transport in the electrolysis cell improve the electrolysis efficiency of the AEM-type water electrolysis device.

[0042] (6) In any of (1) to (5) above, the average opening diameter of the substrate may be 50 μm or more and 800 μm or less.

[0043] Therefore, in the AEM-type water electrolysis device that uses porous composites as electrodes, the transport of electrolytes, gases, and other substances in the electrolytic cell becomes smoother, and the electrolysis efficiency of the AEM-type water electrolysis device is improved.

[0044] (7) In any of (1) to (6) above, the cross-sectional porosity of the substrate can be 50% or more and 95% or less.

[0045] Therefore, in the AEM-type water electrolysis device that uses porous composites as electrodes, the transport of electrolytes, gases, and other substances in the electrolytic cell becomes smoother, and the electrolysis efficiency of the AEM-type water electrolysis device is improved.

[0046] [Detailed Description of Embodiments of the Invention]

[0047] Specific examples of the porous composite of the present invention will be described below with reference to the accompanying drawings. In the drawings of the present invention, the same reference numerals denote the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately modified for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0048] In this invention, the form "A~B" indicates A above and B below. When there is no unit recorded at A but only at B, the unit of A is the same as the unit of B.

[0049] In this invention, when more than one value is recorded as the lower limit and the upper limit of the numerical range, a combination of any value recorded at the lower limit and any value recorded at the upper limit is also disclosed.

[0050] [Implementation Method 1: Porous Composite]

[0051] One embodiment of the present invention (hereinafter also referred to as "Embodiment 1") has a porous composite comprising:

[0052] The substrate having the first main surface, and

[0053] A nickel layer disposed on at least a portion of the first main surface,

[0054] The substrate is composed of a nickel mesh structure or a nickel porous body with a three-dimensional mesh structure.

[0055] The arithmetic mean height Sa of the nickel layer, as specified in ISO 25178, is less than 5 μm.

[0056] In the porous composite of Embodiment 1, the arithmetic mean height Sa of the nickel layer, as specified in ISO 25178, is 5 μm or less, thus reducing surface unevenness. Because the arithmetic mean height Sa of the nickel layer is 5 μm or less, when the porous composite is used in applications involving contact with anion exchange membranes, such as AEM-type water electrolysis, it can prevent protrusions on the surface of the porous composite from penetrating the anion exchange membrane, thereby suppressing adverse conditions such as micro-short circuits or the formation of through-holes on the anion exchange membrane leading to cross-leakage of oxygen and hydrogen.

[0057] Furthermore, since the arithmetic mean height Sa of the nickel layer is less than 5 μm, it can suppress the protrusions on the surface of the porous composite from penetrating the anion exchange membrane, which helps to thin the anion exchange membrane and thus helps to improve the electrolysis efficiency.

[0058] AEM-type water electrolysis includes two methods: CCM (Catalyst Coating) where the catalyst is coated on an anion exchange membrane, and CCS (Catalyst Coating) where the catalyst is coated on an electrode made of conductive porous material. In the CCS method, increasing the contact area between the catalyst and the anion exchange membrane, which facilitates the electrolysis reaction, helps to improve electrolysis performance.

[0059] In the porous composite of Embodiment 1, since the arithmetic mean height Sa of the nickel layer is less than 5 μm, the surface roughness of the catalyst layer is reduced when a catalyst is coated on the nickel layer to form a catalyst layer. Therefore, when the porous composite of Embodiment 1 is used in CCS-type AEM water electrolysis with the catalyst coated on the nickel layer, the contact area between the catalyst and the anion exchange membrane can be increased.

[0060] <Structure of porous composites>

[0061] like Figure 1 As shown, the porous composite 30 of Embodiment 1 has: a substrate 5 having a first main surface 1, and a nickel layer 20 disposed on at least a portion of the first main surface 1.

[0062] From the viewpoint of ensuring smooth material transport within the electrolytic cell in an AEM-type water electrolysis device that uses porous composites as electrodes, the lower limit of the average thickness of the porous composite can be 50 μm or more, 100 μm or more, or 150 μm or more. From the viewpoint of miniaturizing the electrolysis device and improving the uniformity of material transport within the electrolytic cell, the upper limit of the average thickness of the porous composite can be 500 μm or less, 400 μm or less, or 300 μm or less. The average thickness of the porous composite can be 50 μm or more and 500 μm or less, 100 μm or more and 400 μm or less, or 150 μm or more and 300 μm or less.

[0063] In this invention, the average thickness of the porous composite is determined by the following method: The thickness is measured at any five locations on the porous composite using a commercially available digital thickness gauge (manufactured by Tokuro Co., Ltd., Japan). The average thickness at the five locations is calculated. In this invention, this average value corresponds to the average thickness of the porous composite.

[0064] <Substrate>

[0065] In the porous composite 30 of Embodiment 1, the substrate 5 is composed of a nickel mesh structure or a nickel porous body 10 with a three-dimensional mesh structure. The substrate 5 has a sheet-like appearance including a first main surface 1 and a second main surface 2 opposite to the first main surface 1.

[0066] <<Nickel Porous Materials>>

[0067] Figure 2 This is a diagram illustrating a representative structural example of nickel porous body 10. Figure 3 It is Figure 2 The diagram shows an enlarged cross-section of the nickel porous body 10. Figure 3 As shown, the nickel porous body 10 has a three-dimensional network structure framework 11. Through the three-dimensional network structure framework 11, pores 14 are formed inside the nickel porous body 10.

[0068] The framework 11 of the nickel porous body 10 is composed of a framework body 12, and the interior 13 of the framework 11 is hollow. At least a portion of the pore portions 14 formed by the framework 11 are communicating pores that communicate with adjacent pore portions 14.

[0069] The nickel porous body 10 may contain 80% by mass or more of nickel. In this invention, the composition of the nickel porous body 10 refers to the composition of the framework body 12. That is, it can also be stated that the framework body 12 of the nickel porous body 10 contains 80% by mass or more of nickel. The nickel porous body 10 may contain other components besides nickel. Other components may be at least one selected from iron, cobalt, chromium, phosphorus, boron, and carbon. The total content of other components in the nickel porous body 10 may be 0.1% by mass or more and 20% by mass or less. The total content of other components in the nickel porous body 10 is determined by ICP (Inductively Coupled Plasma) emission spectroscopy.

[0070] Figure 3 A schematic diagram of the cross-section along line IV-IV of the skeleton 11 shown is as follows: Figure 4 As shown. The cross-sectional shape of the skeleton 11 can be modeled as a hollow triangle in the central part (the interior 13 of the skeleton).

[0071] <<Nickel Mesh Structure>>

[0072] As a nickel mesh structure, it can be made of woven fabric, non-woven fabric, stamped sheet, etc. The nickel mesh structure can contain more than 80% by mass of nickel. The nickel mesh structure can contain other components besides nickel. These other components can be at least one selected from iron, cobalt, chromium, phosphorus, boron, and carbon. The total content of other components in the nickel mesh structure can be more than 0.1% by mass and less than 20% by mass. The total content of other components in the nickel mesh structure is determined by ICP emission spectroscopy.

[0073] <<Average aperture diameter of the substrate>>

[0074] From the viewpoint of improving the material transport efficiency of electrolyte, gas, etc. in the substrate and ensuring smooth material transport in the electrolytic cell in the AEM-type water electrolysis device that uses porous composites as electrodes, the average opening diameter of the substrate 5 can be 50 μm or more and 800 μm or less, or 100 μm or more and 700 μm or less, or 150 μm or more and 600 μm or less.

[0075] In this invention, when the substrate 5 is a nickel porous body, the average opening diameter of the substrate 5 is determined by the following steps.

[0076] Step A1: Cut the porous composite 30 along a virtual plane parallel to the normal of the main surface to expose the cross section of the substrate 5 along the normal of the main surface.

[0077] Step A2: Using a scanning electron microscope (SEM), observe the cross-section of substrate 5 at an appropriate magnification that allows for imaging of the opening structure within the field of view, and obtain an SEM image of the cross-section of substrate 5. The boundary between substrate 5 and nickel layer 20 can be confirmed in the SEM image. The location of this boundary corresponds to the location of the first principal surface 1 of substrate 5.

[0078] Step A3: In the SEM image of the cross-section of substrate 5, draw three virtual straight lines that divide the substrate into four equal parts along its thickness direction. Designate these virtual straight lines, starting from the nickel layer side, as virtual line L1, virtual line L2, and virtual line L3. The lengths of each of the virtual straight lines L1, L2, and L3 are the lengths spanning the field of view.

[0079] Step A4: On each of the virtual lines L1, L2, and L3, measure the number N1 (pores) crossed by the virtual line and the total length LT (μm) of the pores. Calculate LT (μm) / N1 (pores) for each of the three virtual lines. Calculate the average value A1 of LT (μm) / N1 (pores) for the three virtual lines.

[0080] Step A5: Obtain SEM images from step A2 at three non-overlapping locations. Perform steps A3 and A4 based on each SEM image, and calculate the average value A1. Calculate the average value A2 of the three average values ​​A1. In this invention, this average value A2 corresponds to the average opening diameter of the substrate 5.

[0081] Figure 5 This is an example of a SEM image of a cross-section of the porous composite of Embodiment 1. Figure 5 In the diagram, straight line LS1 represents the first main surface of substrate 5, and straight line LS2 represents the second main surface of substrate 5. Figure 5 In the diagram, virtual lines L1, L2, and L3 are represented by white lines. Figure 5 In the diagram, virtual line L1 traverses 14 pores, with a total length of 1727 μm. Virtual line L2 traverses 12 pores, with a total length of 1701 μm. Virtual line L3 traverses 14 pores, with a total length of 1815 μm. Based on these... Figure 5 The average aperture diameter of substrate 5 shown is calculated to be 131.1 μm. Figure 5 In the diagram, the pore portion corresponds to the area enclosed by the arrow and the area bounded by the arrow and the outer edge of the measurement area. The length of the pore portion corresponds to the length of the black line on the virtual line. The hollow interior of the skeleton 11 is not measured as a pore portion.

[0082] It has been confirmed that for the same porous composite, even when the measurement area is changed to measure the average aperture diameter of the substrate, the measurement results show almost no deviation. Since the substrate is sheet-like, the boundary between the substrate 5 and the nickel layer 20 may sometimes exhibit slight undulations in the cross-sectional SEM image. In this case, although the straight line LS1 shown in the cross-sectional SEM image does not precisely coincide with the boundary between the substrate 5 and the nickel layer 20, it has been confirmed that as long as the straight line LS1 is approximately located on the boundary between the substrate 5 and the nickel layer 20, it has almost no impact on the measurement results of the average aperture diameter of the substrate 5.

[0083] In this invention, when the substrate 5 is a nickel mesh structure, the average opening diameter of the substrate 5 is determined by the following steps: The porous composite 30 is cut along a virtual plane parallel to the normal of the main surface, exposing the cross-section of the substrate 5 along the normal of the main surface. Using a scanning electron microscope, the cross-section of the substrate 5 is observed at an appropriate magnification that allows the opening structure of the substrate 5 to be photographed within the field of view, thereby obtaining an SEM image of the cross-section of the substrate 5. Figure 6 This is a schematic SEM image showing a cross-section of a nickel mesh structure.

[0084] In the SEM image of the cross-section of the nickel mesh structure, draw a virtual straight line L61 that crosses the thickest part of the cross-section of the metal wire 16 that constitutes the mesh. Measure the number N1 (pores) of the pores 14 that the virtual straight line crosses and the total length LT (μm) of the pores 14, and calculate LT (μm) / N1 (pores).

[0085] SEM images of the cross-section of the nickel mesh structure were acquired at three non-overlapping locations. Based on each SEM image, LT(μm) / N1(pieces) was calculated using the steps described above. The average value of the three LT(μm) / N1(pieces) values ​​was calculated. In this invention, this average value corresponds to the average aperture diameter of the substrate 5.

[0086] It has been confirmed that for the same porous composite, even when the average opening diameter of the substrate is measured in a different measurement area, the measurement results show almost no deviation.

[0087] <<Cross-sectional porosity of the substrate>>

[0088] From the perspective of reducing the pressure loss of the porous composite 30, and from the perspective of ensuring smooth transport of electrolyte, gas, and other substances within the electrolytic cell and improving the electrolysis efficiency of the AEM-type water electrolysis device, the lower limit of the cross-sectional porosity of the substrate 5 can be 50% or more, 55% or more, or 65% or more. From the perspective of ensuring appropriate compressive strength, the upper limit of the cross-sectional porosity of the substrate 5 can be 95% or less, 85% or less, or 75% or less. The cross-sectional porosity of the substrate 5 can be 50% or more and 95% or less, 55% or more and 85% or less, or 65% or more and 75% or less.

[0089] In this invention, the cross-sectional porosity of the substrate 5 is determined by the following steps.

[0090] Step B1: Cut the porous composite 30 along a virtual plane parallel to the normal of the main surface to expose the cross section of the substrate 5 along the normal of the main surface.

[0091] Step B2: Using a scanning electron microscope, observe the cross-section of substrate 5 at an appropriate magnification that allows for imaging of the porous structure of substrate 5, and obtain SEM images.

[0092] Step B3: In the SEM image of the cross-section of substrate 5, set a rectangular measurement area that is large enough to measure the porosity of the cross-section of substrate 5. Use image processing software to calculate the percentage of the area S1 of the pores relative to the area SA of the entire measurement area (S1 / SA) × 100.

[0093] Step B4: Obtain SEM images from step B2 at three non-overlapping locations. Based on each SEM image, perform step B3 to calculate the percentage (S1 / SA) × 100. Calculate the average of the three percentages (S1 / SA) × 100. In this invention, this average value corresponds to the cross-sectional porosity of the substrate 5.

[0094] It has been confirmed that for the same porous composite, even when the measurement area is changed to measure the cross-sectional porosity of the above-mentioned substrate, the measurement results show almost no deviation.

[0095] <<Average thickness of substrate>>

[0096] The average thickness of the substrate 5 can be, for example, 0.04 mm or more and 0.5 mm or less, or 0.1 mm or more and 0.3 mm or less. The method for measuring the average thickness of the substrate 5 is as follows: An SEM image of the cross-section of the substrate 5 is obtained using the same method as steps A1 and A2 of the method for measuring the average aperture of the substrate 5. In the SEM image, the distance from the first main surface 1 to the second main surface 2 of the substrate 5 is measured at any five locations. The average value of the five distances is calculated. In this invention, this average value corresponds to the average thickness of the substrate 5.

[0097] It has been confirmed that for the same porous composite, even when the average thickness of the substrate is measured in different measurement areas, the measurement results show almost no deviation.

[0098] <Nickel layer>

[0099] In the porous composite 30 of Embodiment 1, the surface of the nickel layer 20 is the surface coated with a catalyst when the porous composite 30 is used in AEM-type water electrolysis in a CCS manner. Figure 1 In this process, the nickel layer 20 is disposed on the entire surface of the first main surface 1, but is not limited thereto. When the porous composite 30 is used for AEM-type water electrolysis in the CCS method with a catalyst coated on the nickel layer 20, the area where the nickel layer 20 is disposed can also be part of the first main surface 1, as long as the catalyst can be present in the region opposite to the anion exchange membrane.

[0100] The nickel layer 20 may contain more than 80% by mass of nickel. The nickel layer 20 may contain other components besides nickel. These other components may be at least one selected from iron, cobalt, chromium, phosphorus, boron, and carbon. The total content of the other components in the nickel layer 20 may be more than 0.01% by mass and less than 20% by mass. The content of the other components in the nickel layer 20 is determined by ICP emission spectroscopy.

[0101] The nickel layer 20 can be composed of a nickel sintered body.

[0102] <<Arithmetic Mean Height Sa of Nickel Layer>>

[0103] The arithmetic mean height Sa of the nickel layer 20, as specified in ISO 25178, has an upper limit of 5 μm or less, but can also be 4 μm or less, or 3 μm or less. There is no particular limitation on the lower limit of the arithmetic mean height Sa of the nickel layer 20; it can be 0 μm or more, or from a manufacturing point of view, 0.5 μm or more. The arithmetic mean height Sa of the nickel layer 20 can be 0 μm or more and 5 μm or less, 0 μm or more and 4 μm or less, or 0.5 μm or more and 5 μm or less. If the arithmetic mean height Sa of the nickel layer 20 exceeds 5 μm, the protrusions on the surface of the porous composite may penetrate the anion exchange membrane. Furthermore, the surface of the nickel layer 20 contains deep pores; when a catalyst is coated on the nickel layer, the catalyst embedded in these deep pores may not function, leading to catalyst loss. Additionally, the catalyst layer itself formed by coating the catalyst on the nickel layer may contain pores, and the open portions may not function as catalysts.

[0104] In this invention, the arithmetic mean height Sa, as specified in ISO 25178, is determined through the following steps. A laser microscope is used to observe the surface of the nickel layer 20 at an appropriate magnification that allows observation of the surface unevenness. The measurement area is set to the entire field of view. The surface of the nickel layer 20 refers to the main surface of the nickel layer 20 opposite to the main surface 1 of the substrate 5. Figure 1 The third principal surface 3 is represented in the diagram. The arithmetic mean height Sa of this measurement area is measured according to ISO 25178. The measurement is performed using a Keyence VK-X3000 laser microscope (trademark). The arithmetic mean height Sa is measured in three non-overlapping measurement areas. The average value of the arithmetic mean height Sa of the three measurement areas is calculated. In this invention, this average value corresponds to the arithmetic mean height Sa of the nickel layer 20.

[0105] It has been confirmed that for the same porous composite, even when the measurement area is changed to measure the arithmetic mean height Sa of the nickel layer, the measurement results show almost no deviation.

[0106] <<Average aperture of the nickel layer>>

[0107] In the porous composite 30 of Embodiment 1, the nickel layer 20 may have multiple pores inside. From the viewpoint of ensuring smooth transport of electrolyte, gas, and other substances in the electrolytic cell in an AEM-type water electrolysis apparatus where the porous composite is used as an electrode, the lower limit of the average opening diameter of the nickel layer 20 may be 0.1 μm or more, 1 μm or more, or 2 μm or more. From the viewpoint of improving the smoothness of the nickel layer surface, suppressing the protrusions on the porous composite surface from penetrating the opposing anion exchange membrane, and maintaining the surface smoothness of the catalyst layer formed on the nickel layer, the upper limit of the average opening diameter of the nickel layer 20 may be 50 μm or less, 25 μm or less, or 10 μm or less. The average opening diameter of the nickel layer 20 may be 0.1 μm or more and 50 μm or less, 1 μm or more and 25 μm or less, or 2 μm or more and 10 μm or less.

[0108] In this invention, the average opening diameter of the nickel layer 20 is determined by the following steps.

[0109] Step C1: Cut the porous composite 30 along a virtual plane parallel to the normal of the main surface to expose the cross section of the nickel layer 20 along the normal of the main surface.

[0110] Step C2: Using a SEM, observe the cross-section of the nickel layer 20 at an appropriate magnification to capture images of the open structure within the field of view, obtaining an SEM image of the cross-section of the nickel layer 20. The boundary between the substrate 5 and the nickel layer 20 can be confirmed in the SEM image. The location of this boundary corresponds to the location of the first main surface 1 of the substrate 5.

[0111] Step C3: In the SEM image of the cross-section of nickel layer 20, draw three virtual straight lines that divide the nickel layer into four equal parts along its thickness direction. Designate these virtual straight lines sequentially as virtual line L11, virtual line L12, and virtual line L13, starting from the substrate side.

[0112] Step C4: On each of the virtual lines L11, L12, and L13, measure the number of pores N11 (pores) crossed by the virtual line and the total length of the pores LT1 (μm). Calculate LT1 (μm) / N11 (pores) for each of the three virtual lines. Calculate the average value A11 of LT1 (μm) / N11 (pores) for the three virtual lines.

[0113] Step C5: Obtain SEM images from step C2 at three non-overlapping locations. Perform steps C3 and C4 based on each SEM image to calculate the average value A11. Calculate the average value A12 of the three average values ​​A11. In this invention, this average value A12 corresponds to the average aperture diameter of the nickel layer 20.

[0114] Figure 7This is an example of a SEM image of a cross-section of the nickel layer in the porous composite of Embodiment 1. Figure 7 In the diagram, straight line LS3 represents the surface of the nickel layer, and straight line LS4 represents the boundary between the substrate 5 and the nickel layer. Figure 7 In the diagram, virtual lines L11, L12, and L13 are represented by white lines. Figure 7 In the diagram, virtual line L13 traverses 7 pores, with a total length of 18.4 μm. Similarly, virtual line L12 traverses 7 pores, with a total length of 22.4 μm. Virtual line L11 traverses 12 pores, with a total length of 35.2 μm. Based on these... Figure 7 The average aperture of the nickel layer 20 shown is calculated to be 2.9 μm. Figure 7 In the diagram, the stomata correspond to the area enclosed by the arrow and the area bounded by the arrow and the outer edge of the measurement area. The length of the stomata corresponds to the length of the black line on the virtual line.

[0115] It has been confirmed that for the same porous composite, even when the average opening diameter of the nickel layer is measured in a different measurement area, the measurement results show almost no deviation.

[0116] <<Porosity of the Nickel Layer>>

[0117] In the porous composite 30 of Embodiment 1, the nickel layer 20 may have multiple pores internally. From the viewpoint of improving the electrolysis efficiency of the AEM-type water electrolysis device by ensuring smooth transport of substances such as electrolyte and generated gas between the substrate portion of the porous composite and the anion exchange membrane in an AEM-type water electrolysis device using the porous composite as an electrode, the lower limit of the porosity of the nickel layer 20 may be 40% or more, 45% or more, or 55% or more. To impart appropriate compressive strength, the upper limit of the porosity of the nickel layer 20 may be 75% or less, 70% or less, or 65% or less. The porosity of the nickel layer 20 may be 40% or more and 75% or less, 45% or more and 70% or less, or 55% or more and 65% or less.

[0118] In this invention, the porosity of the nickel layer 20 is determined by the following steps.

[0119] Step D1: Cut the porous composite 30 along a virtual plane parallel to the normal of the main surface to expose the cross section of the nickel layer 20 along the normal of the main surface.

[0120] Step D2: Using a scanning electron microscope, observe the cross-section of the nickel layer 20 at an appropriate magnification that allows for imaging of the pores in the nickel layer 20, and obtain SEM images.

[0121] Step D3: In the SEM of the cross-section of nickel layer 20, set up a rectangular measurement area that is large enough to measure the porosity of nickel layer 20. Use image processing software to calculate the percentage of the pore area S11 relative to the total area SA1 of each measurement area (S11 / SA1) × 100.

[0122] Step D4: Obtain SEM images from step D2 at three non-overlapping locations. Based on each SEM image, perform step D3 to calculate the percentage (S11 / SA1) × 100. Calculate the average of the three percentages (S11 / SA1) × 100. In this invention, this average value corresponds to the porosity of the nickel layer 20.

[0123] It has been confirmed that for the same porous composite, even when the measurement area is changed to measure the porosity of the nickel layer, the measurement results show almost no deviation.

[0124] <<Average thickness of nickel layer>>

[0125] From the viewpoint of maintaining the strength of the nickel layer itself, the lower limit of the average thickness of the nickel layer 20 can be 0.5 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, or 30 μm or more. From the viewpoint of facilitating the smooth transport of substances such as electrolyte and generated gases between the substrate portion of the porous composite and the anion exchange membrane, the upper limit of the average thickness of the nickel layer 20 can be 100 μm or less, 90 μm or less, or 80 μm or less. The average thickness of the nickel layer 20 can be 0.5 μm or more and 100 μm or less, 5 μm or more and 100 μm or less, 10 μm or more and 100 μm or less, 20 μm or more and 90 μm or less, or 30 μm or more and 80 μm or less.

[0126] The method for determining the average thickness of the nickel layer 20 is as follows. An SEM image of the cross-section of the nickel layer 20 is obtained using the same method as steps C1 and C2 in the method for determining the average aperture of the nickel layer 20. In the SEM image, the distance from the surface of the nickel layer 20 to the boundary between the nickel layer 20 and the substrate 5 is measured at any five locations. The average value of the distances at the five locations is calculated. In this invention, this average value corresponds to the average thickness of the nickel layer 20.

[0127] It has been confirmed that for the same porous composite, even when the measurement area is changed to measure the average thickness of the nickel layer, the measurement results show almost no deviation.

[0128] <Manufacturing Method of Porous Composites>

[0129] An example of a method for manufacturing a porous composite according to Embodiment 1 will be described. The method for manufacturing a porous composite may include: a step of preparing a substrate material, a step of preparing a nickel microporous sheet, a step of rolling the substrate material and the nickel microporous sheet in a stacked state to obtain a laminate, and a step of heating the laminate to obtain a porous composite.

[0130] <<Preparation of Substrate Materials>>

[0131] As the substrate material, prepare a nickel mesh structure or a nickel porous body with a three-dimensional mesh structure. Use a nickel porous body or nickel mesh structure that is entirely sheet-like.

[0132] The average pore size of nickel porous bodies can be above 50 μm and below 5000 μm, above 100 μm and below 1000 μm, or above 200 μm and below 700 μm.

[0133] The average pore size of the nickel porous body is defined by the following formula [1]. In formula [1], nc is the number obtained by averaging the number of pores per inch (25.4 mm = 25400 μm) by observing at least 10 fields of view on the main surface of the nickel porous body with a microscope or the like.

[0134]

[0135] Furthermore, the number of pores was determined according to the method for determining the number of pores (cell count) of flexible foamed materials in Appendix 1 (reference) of JIS K6400-1:2004.

[0136] As a nickel porous material, for example, "Nickel Celmet" (trademark) manufactured by Sumitomo Electric Industries, Ltd. can be prepared.

[0137] As a nickel mesh structure, for example, a material made by plain weaving nickel wire can be prepared.

[0138] <<Process for Preparing Nickel Microporous Sheets>>

[0139] Nickel microporous sheets can be prepared by the following steps: Nickel powder, binder, and pure water are mixed to obtain a slurry. The slurry is then coated onto a support. For example, a polytetrafluoroethylene (PTFE) sheet can be used as the support. After drying the slurry coated on the support, it is peeled off from the sheet to obtain a green nickel sheet. Drying conditions can be, for example, at atmospheric temperature and 80°C for 30 minutes.

[0140] Nickel microporous sheets are obtained by sintering nickel green sheets. Sintering conditions can be, for example, at 900°C for 10 minutes in a hydrogen atmosphere. The thickness of the nickel microporous sheets can be, for example, 0.5 μm or more and 100 μm or less.

[0141] <<Processes for Obtaining the Stacked Body>>

[0142] Next, the substrate material and the nickel microporous sheet are stacked and rolled to obtain a laminate. The rolling conditions can be set with an appropriate roller gap based on the thickness of the substrate material and the nickel microporous sheet. For example, the roller gap can be set to about 80% of the desired thickness of the porous composite.

[0143] <<Processes for Obtaining Porous Composites>>

[0144] Next, a porous composite is obtained by heating the laminate. Heating conditions, for example, can be at 900°C for 10 minutes in a hydrogen atmosphere. This yields a porous composite material bonded to a nickel microporous sheet.

[0145] Example

[0146] This embodiment will be described in more detail through examples. However, this embodiment is not limited to these examples.

[0147] [Sample 1 to Sample 18]

[0148] <Fabrication of Porous Complexes>

[0149] <<Preparation of Substrate Materials>>

[0150] As substrate materials, nickel porous bodies (99.9% by mass nickel content, denoted as "Ni porous bodies" in Table 1) or nickel mesh structures (99.9% by mass nickel content, denoted as "Ni mesh structures" in Table 1) with three-dimensional network structures were prepared. The types of substrate materials used in each sample, the average pore size of the substrate materials, and the thickness of the substrate materials are shown in Table 1.

[0151] <<Process for Preparing Nickel Microporous Sheets>>

[0152] Nickel powder, binder, and pure water were mixed to obtain a slurry. The average particle size of the nickel powder used in each sample is shown in Table 1. The average particle size of the nickel powder was measured by the Fisher sub-sieve sizer method. Polyvinyl alcohol 500 (trademark) manufactured by Kishida Chemical Co., Ltd. was used as the binder. The mixing ratio of nickel powder to binder was set to nickel powder:binder = 95:5 based on the mass at the time of drying. Pure water was added to the mixture of nickel powder and binder to obtain the slurry.

[0153] The slurry is applied to a support made of PTFE sheet. A coater is used for coating. After the slurry applied to the support is dried, it is peeled off from the sheet to obtain a green nickel sheet. The drying conditions are atmospheric drying at 80°C for 30 minutes.

[0154] As needed, the nickel green sheets were rolled and then sintered to obtain nickel microporous sheets. The sintering conditions were 900°C for 10 minutes in a hydrogen atmosphere. The thickness of the nickel microporous sheets for each sample is shown in the "Nickel Microporous Sheet Thickness" column of Table 1.

[0155] <<Processes for Obtaining the Stacked Body>>

[0156] Next, the substrate material and the nickel microporous sheet were stacked and rolled to obtain a laminate. The roller gap during rolling for each sample is shown in the "Roller Gap" column of Table 1.

[0157] <<Processes for Obtaining Porous Composites>>

[0158] Next, a porous composite was obtained by heating the laminate. The heating conditions were 900°C for 10 minutes in a hydrogen atmosphere.

[0159] [Table 1]

[0160]

[0161] [Determination of porous complexes]

[0162] For each sample's composite porous body, the average aperture diameter of the substrate, the cross-sectional porosity of the substrate, the arithmetic mean height Sa of the nickel layer as specified in ISO 25178, the average aperture diameter of the nickel layer, the average thickness of the nickel layer, the porosity of the nickel layer, and the average thickness of the porous composite were measured. Specific measurement methods are as described in Embodiment 1. The results are shown in Table 2.

[0163] [Table 2]

[0164]

[0165] [evaluate]

[0166] The composite porous bodies of samples 1-9, 11-13, and 15-18, whose arithmetic mean height Sa of the nickel layer as specified in ISO 25178 is less than 5 μm, are equivalent to the Examples. The composite porous bodies of samples 10 and 14, whose arithmetic mean height Sa of the nickel layer as specified in ISO 25178 exceeds 5 μm, are equivalent to the Comparative Examples.

[0167] The composite porous bodies of samples 1-9, 11-13, and 15-18 have an arithmetic mean height Sa of less than 5 μm, and their surface unevenness is reduced. Therefore, when these composite porous bodies are used in applications involving contact with anion exchange membranes, it is possible to prevent protrusions on the surface of the porous composite from penetrating the anion exchange membrane, thereby suppressing adverse conditions such as micro-short circuits or the formation of through-holes in the anion exchange membrane leading to cross-leakage of oxygen and hydrogen. Furthermore, when a catalyst is coated onto the nickel layer of the composite porous bodies of samples 1-9, 11-13, and 15-18 to form a catalyst layer, the surface unevenness of the catalyst layer is also reduced. Therefore, when the porous composites of samples 1 to 9, 11 to 13, and 15 to 18 are used as electrodes in an AEM-type water electrolysis device with catalyst coated on their nickel layers, the contact area between the catalyst and the anion exchange membrane can be increased, thereby improving the electrolysis performance of the AEM-type water electrolysis device.

[0168] The embodiments and examples of the present invention have been described above, but it is assumed from the outset that the above embodiments and examples can be appropriately combined or modified.

[0169] The embodiments and examples disclosed herein are exemplary in all respects and should not be considered limiting. The scope of the invention is set forth not by the above embodiments and examples, but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0170] Explanation of reference numerals in the attached figures

[0171] 1: First main surface; 2: Second main surface; 3: Third main surface; 5: Substrate; 10: Nickel porous body; 11: Skeleton; 12: Main body of skeleton; 13: Interior of skeleton; 14: Porous part; 16: Metal wire; 20: Nickel layer; 30: Porous composite.

Claims

1. A porous composite having: The substrate having the first main surface, and A nickel layer disposed on at least a portion of the first main surface, The substrate is composed of a nickel mesh structure or a nickel porous body with a three-dimensional mesh structure. The arithmetic mean height Sa of the nickel layer, as specified in ISO 25178, is less than 5 μm.

2. The porous composite according to claim 1, wherein, The nickel layer has multiple pores inside. The average aperture of the nickel layer is greater than 0.1 μm and less than 50 μm.

3. The porous composite according to claim 1 or claim 2, wherein, The average thickness of the nickel layer is greater than 0.5 μm and less than 100 μm.

4. The porous composite according to any one of claims 1 to 3, wherein, The nickel layer has multiple pores inside. The porosity of the nickel layer is above 40% and below 75%.

5. The porous composite according to any one of claims 1 to 4, wherein, The average thickness of the porous composite is greater than 50 μm and less than 500 μm.

6. The porous composite according to any one of claims 1 to 5, wherein, The average opening diameter of the substrate is greater than 50 μm and less than 800 μm.

7. The porous composite according to any one of claims 1 to 6, wherein, The cross-sectional porosity of the substrate is above 50% and below 95%.

Images