Porous composite

Abstract

The porous composite is provided with a substrate having a first main surface and a nickel layer provided on at least a portion of the first main surface, the substrate being made of a nickel porous body having a three-dimensional mesh structure or a nickel mesh structure, and the nickel layer has an arithmetic mean height Sa defined in ISO 25178 of 5 µm or less.

Description

[Technical field]

[0001] The present disclosure relates to porous composites. [Background technology]

[0002] Hydrogen is attracting attention as a highly efficient clean energy source because it is suitable for storage and transportation and has a small environmental impact. Most hydrogen is produced by steam reforming of fossil fuels, but hydrogen production by water electrolysis is becoming increasingly important from the perspective of reducing the environmental impact. Because water electrolysis involves the consumption of electricity, various improvements to the water electrolysis method have been attempted in order to realize a highly efficient hydrogen production system.

[0003] In recent years, AEM (Anion Exchange Membrane) type water electrolysis using anion exchange membranes has been attracting attention (for example, Patent Document 1). Compared with currently mainstream alkaline water electrolysis and PEM (Polymer Electrolyte Membrane) type water electrolysis, the advantages of AEM type water electrolysis are that it can increase the current density compared to alkaline water electrolysis, the equipment can be made more compact, and it does not require a precious metal catalyst that is essential for PEM type water electrolysis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-26413 Summary of the Invention

[0005] The composite porous body of the present disclosure is A substrate having a first major surface; a nickel layer provided on at least a portion of the first main surface, The substrate is made of a nickel porous body having a three-dimensional network structure or a nickel mesh structure, The nickel layer has an arithmetic mean height Sa, as defined in ISO 25178, of 5 μm or less, making it a porous composite. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view of an example of a porous composite according to the first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a typical example of the configuration of a nickel porous body. [Diagram 3] FIG. 3 is an enlarged schematic view showing a cross section of the nickel porous body shown in FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view of the skeleton 11 shown in FIG. 3 taken along line IV-IV. [Diagram 5] FIG. 5 is a diagram showing an example of an SEM image of a cross section of the porous composite of the first embodiment. [Figure 6] FIG. 6 is a diagram that shows a schematic SEM image of a cross section of a nickel mesh structure. [Figure 7] FIG. 7 is a diagram showing an example of an SEM image of a cross section of the nickel layer of the porous composite of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [Problem that this disclosure aims to solve] In AEM-type water electrolysis, an anion exchange membrane and an electrode made of a conductive porous body are arranged next to each other. If the surface of the porous body is rough, the protrusions on the surface of the porous body may pierce the anion exchange membrane, causing a micro-short circuit, or through holes may form in the anion exchange membrane, causing cross-leakage of oxygen and hydrogen. To avoid this problem, a method of thickening the anion exchange membrane is considered. However, thickening the anion exchange membrane increases the resistance of the water electrolysis cell, which increases the voltage during water electrolysis and increases power consumption. For this reason, there is a demand for a technology that can provide electrodes with reduced surface roughness to prevent problems with the anion exchange membrane.

[0008] [Effects of this disclosure] According to the present disclosure, it is possible to provide a porous composite that is used as an electrode for an AEM type water electrolysis device and has reduced surface roughness.

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) The porous composite of the present disclosure comprises: A substrate having a first major surface; a nickel layer provided on at least a portion of the first main surface, The substrate is made of a nickel porous body having a three-dimensional network structure or a nickel mesh structure, The nickel layer has an arithmetic mean height Sa, as defined in ISO 25178, of 5 μm or less, making it a porous composite.

[0010] According to the present disclosure, it is possible to provide a porous composite material having reduced surface roughness and used as an electrode for an AEM-type water electrolysis device. In the present disclosure, ISO 25178 is, more specifically, ISO 25178-2:2012.

[0011] (2) In the above (1), the nickel layer has a plurality of pores therein, The nickel layer may have an average opening size of 0.1 μm or more and 50 μm or less.

[0012] This improves the smoothness of the surface of the nickel layer, making it less likely to pierce the anion exchange membrane.

[0013] (3) In the above (1) or (2), the average thickness of the nickel layer may be 0.5 μm or more and 100 μm or less.

[0014] This allows the strength of the nickel layer itself to be maintained in an AEM-type water electrolysis device using the porous composite as an electrode. In addition, material transport of the electrolyte and generated gases between the substrate part of the porous composite and the anion exchange membrane becomes smooth, improving the electrolysis efficiency of the AEM-type water electrolysis device.

[0015] (4) In any of (1) to (3) above, The nickel layer has a plurality of pores therein, The nickel layer may have a porosity of 40% or more and 75% or less.

[0016] As a result, in an AEM-type water electrolysis device using a porous composite as an electrode, material transport of the electrolyte, generated gas, and the like is smoother between the substrate part of the porous composite and the anion exchange membrane, improving the electrolysis efficiency of the AEM-type water electrolysis device.

[0017] (5) In any one of the above (1) to (4), the average thickness of the porous composite may be 50 μm or more and 500 μm or less.

[0018] As a result, in an AEM type water electrolysis device using a porous composite as an electrode, material transport such as electrolyte and gas within the electrolysis cell becomes smoother, the electrolysis device can be made smaller, and the uniformity of material transport within the electrolysis cell is improved, thereby improving the electrolysis efficiency of the AEM type water electrolysis device.

[0019] (6) In any one of the above (1) to (5), the average opening diameter of the substrate may be 50 μm or more and 800 μm or less.

[0020] According to this, in an AEM type water electrolysis device using a porous composite as an electrode, the transport of materials such as electrolyte and gas within the electrolysis cell becomes smoother, improving the electrolysis efficiency of the AEM type water electrolysis device.

[0021] (7) In any one of the above (1) to (6), the cross-sectional porosity of the substrate may be 50% or more and 95% or less.

[0022] According to this, in an AEM type water electrolysis device using a porous composite as an electrode, the transport of materials such as electrolyte and gas within the electrolysis cell becomes smoother, improving the electrolysis efficiency of the AEM type water electrolysis device.

[0023] [Details of the embodiment of the present disclosure] Specific examples of the porous composite of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. In addition, the dimensional relationships of the length, width, thickness, depth, etc. are appropriately changed for clarity and simplification of the drawings, and do not necessarily represent the actual dimensional relationships.

[0024] In the present disclosure, an expression in the form "A~B" means greater than or equal to A and less than or equal to B. When no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0025] In the present disclosure, when one or more numerical values ​​are listed as the lower limit and the upper limit of a numerical range, the combination of any one numerical value listed in the lower limit and any one numerical value listed in the upper limit is also disclosed.

[0026] [Embodiment 1: Porous Composite] A porous composite according to one embodiment of the present disclosure (hereinafter also referred to as "embodiment 1") comprises: A substrate having a first major surface; a nickel layer provided on at least a portion of the first main surface, The substrate is made of a nickel porous body having a three-dimensional network structure or a nickel mesh structure, The nickel layer has an arithmetic mean height Sa, as defined in ISO 25178, of 5 μm or less, making it a porous composite.

[0027] In the porous composite of embodiment 1, the nickel layer has an arithmetic mean height Sa of 5 μm or less as specified in ISO 25178, and surface irregularities are reduced. When the porous composite is used in an application involving contact with an anion exchange membrane, such as AEM-type water electrolysis, the arithmetic mean height Sa of the nickel layer is 5 μm or less, and thus protrusions on the surface of the porous composite are prevented from piercing the anion exchange membrane, and defects such as micro-short circuits and cross-leaks of oxygen and hydrogen due to through-holes formed in the anion exchange membrane are prevented.

[0028] Furthermore, by making the arithmetic mean height Sa of the nickel layer 5 μm or less, the protrusions on the surface of the porous composite are prevented from piercing the anion exchange membrane, which contributes to making the anion exchange membrane thinner and ultimately leads to improved electrolysis efficiency.

[0029] AEM-type water electrolysis includes the CCM method, in which a catalyst is applied to an anion exchange membrane, and the CCS method, in which a catalyst is applied to an electrode made of a conductive porous body. In the CCS method, increasing the contact area between the catalyst and the anion exchange membrane that contributes to the electrolysis reaction contributes to improving electrolysis performance.

[0030] In the porous composite of embodiment 1, the arithmetic mean height Sa of the nickel layer is 5 μm or less, and therefore when a catalyst is applied to the nickel layer to form a catalyst layer, the surface unevenness of the catalyst layer is reduced. Therefore, when the porous composite of embodiment 1 is used in AEM-type water electrolysis of the CCS method with the nickel layer applied with a catalyst, it is possible to increase the contact area between the catalyst and the anion exchange membrane.

[0031] <Porous composite structure> As shown in FIG. 1, a porous composite 30 of the first embodiment includes a substrate 5 having a first main surface 1 and a nickel layer 20 provided on at least a portion of the first main surface 1 .

[0032] The lower limit of the average thickness of the porous composite may be 50 μm or more, 100 μm or more, or 150 μm or more from the viewpoint of smooth substance transport in an electrolysis cell in an AEM-type water electrolysis device using the porous composite as an electrode. The upper limit of the average thickness of the porous composite may be 500 μm or less, 400 μm or less, or 300 μm or less from the viewpoint of miniaturizing the electrolysis device and improving the uniformity of substance transport in the electrolysis cell. The average thickness of the porous composite may 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.

[0033] In the present disclosure, the average thickness of the porous composite is measured by the following method. The thickness is measured at any five points of the porous composite using a commercially available digital thickness gauge (Teclock Corporation). The average of the thicknesses at the five points is calculated. In the present disclosure, the average corresponds to the average thickness of the porous composite.

[0034] <Base material> In the porous composite 30 of the first embodiment, the substrate 5 is made of a nickel porous body 10 having a three-dimensional network structure or a nickel 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 as a whole.

[0035] <Porous nickel> Fig. 2 is a diagram illustrating a typical configuration example of the nickel porous body 10. Fig. 3 is an enlarged schematic diagram showing a cross section of the nickel porous body 10 shown in Fig. 2. As shown in Fig. 3, the nickel porous body 10 has a skeleton 11 with a three-dimensional network structure. Pores 14 are formed inside the nickel porous body 10 by the skeleton 11 with the three-dimensional network structure.

[0036] The skeleton 11 of the nickel porous body 10 is composed of a skeleton main body 12, and the inside 13 of the skeleton 11 is hollow. At least some of the pores 14 formed by the skeleton 11 are interconnected pores that communicate with adjacent pores 14.

[0037] The nickel porous body 10 may contain 80% by mass or more of nickel. In the present disclosure, the composition of the nickel porous body 10 means the composition of the skeletal body 12. That is, the skeletal body 12 of the nickel porous body 10 can also be expressed as containing 80% by mass or more of nickel. The nickel porous body 10 may contain other components other than nickel. The other components may be at least one selected from the group consisting of iron, cobalt, chromium, phosphorus, boron, and carbon. The total content of the 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 the other components in the nickel porous body 10 is measured by ICP (Inductively Coupled Plasma) emission spectrometry.

[0038] Fig. 4 shows a schematic diagram of a cross section of the skeleton 11 shown in Fig. 3 along line IV-IV. The cross-sectional shape of the skeleton 11 can be modeled as a triangle with a hollow center (interior 13 of the skeleton).

[0039] <Nickel mesh structure> The nickel mesh structure may be a woven fabric, a nonwoven fabric, a punched sheet, or the like. The nickel mesh structure may contain 80% by mass or more of nickel. The nickel mesh structure may contain other components other than nickel. The other components may be at least one selected from the group consisting of iron, cobalt, chromium, phosphorus, boron, and carbon. The total content of the other components in the nickel mesh structure may be 0.1% by mass or more and 20% by mass or less. The total content of the other components in the nickel mesh structure is measured by ICP atomic emission spectrometry.

[0040] <Average opening diameter of substrate> In an AEM type water electrolysis device using the porous composite as an electrode, the average opening diameter of the substrate 5 may be 50 μm or more and 800 μm or less, 100 μm or more and 700 μm or less, or 150 μm or more and 600 μm or less, from the viewpoint of improving the efficiency of substance transport of the electrolyte, gas, etc. in the substrate and smoothing the substance transport in the electrolysis cell.

[0041] In the present disclosure, when the substrate 5 is a nickel porous body, the average opening diameter of the substrate 5 is measured by the following procedure. Step A1: The porous composite 30 is cut along an imaginary plane parallel to the normal line of the main surface to expose a cross section of the substrate 5 along the normal line of the main surface.

[0042] Step A2: A cross section of the substrate 5 is observed using a scanning electron microscope (SEM) at an appropriate magnification that allows the opening structure of the substrate 5 to be photographed within the field of view, to obtain an SEM image of the cross section of the substrate 5. The boundary between the substrate 5 and the nickel layer 20 can be confirmed in the SEM image. The position of the boundary corresponds to the position of the first main surface 1 of the substrate 5.

[0043] Step A3: In the SEM image of the cross section of the substrate 5, draw three imaginary straight lines that divide the substrate into four equal parts in the thickness direction. The imaginary straight lines are designated as imaginary straight lines L1, L2, and L3, in that order from the nickel layer side. The lengths of the imaginary straight lines L1, L2, and L3 are the lengths that cross the field of view.

[0044] Step A4: For each of the imaginary lines L1, L2, and L3, measure the number of pores N1 (pieces) that the imaginary lines cross and the total length of the pores LT (μm). Calculate LT (μm) / N1 (pieces) for each of the three imaginary lines. Calculate the average A1 of LT (μm) / N1 (pieces) for the three imaginary lines.

[0045] Step A5: Obtain SEM images of step A2 at three non-overlapping locations, and perform steps A3 and A4 based on each SEM image to calculate an average A1. Calculate an average A2 of the three averages A1. In the present disclosure, the average A2 corresponds to the average opening diameter of the substrate 5.

[0046] FIG. 5 is an example of an SEM image of a cross section of the porous composite of embodiment 1. In FIG. 5, the line LS1 indicates the first main surface of the substrate 5, and the line LS2 indicates the second main surface of the substrate 5. In FIG. 5, the virtual lines L1, L2, and L3 are shown as white lines. In FIG. 5, the number of pores crossed by the virtual line L1 is 14, and the total length of the pores is 1727 μm. The number of pores crossed by the virtual line L2 is 12, and the total length of the pores is 1701 μm. The number of pores crossed by the virtual line L3 is 14, and the total length of the pores is 1815 μm. Based on these, the average opening diameter of the substrate 5 shown in FIG. 5 is calculated to be 131.1 μm. In FIG. 5, the pores correspond to the area sandwiched between the arrows and the area sandwiched between the arrows and the outer edge of the measurement area. The length of the pores corresponds to the length of the black straight line on the virtual line. The hollow space inside the skeleton 11 is not measured as a porosity.

[0047] It has been confirmed that, for the same porous composite, even if the measurement area is changed when the average opening diameter of the substrate is measured, there is almost no variation in the measurement results. Since the substrate is in a sheet form, the cross-sectional SEM image may show some waviness at the boundary between the substrate 5 and the nickel layer 20. In such a case, the straight line LS1 shown in the cross-sectional SEM image does not exactly coincide with the boundary between the substrate 5 and the nickel layer 20, but it has been confirmed that as long as the straight line LS1 is located approximately at the boundary between the substrate 5 and the nickel layer 20, there is almost no effect on the measurement result of the average opening diameter of the substrate 5.

[0048] In the present disclosure, when the substrate 5 is a nickel mesh structure, the average opening diameter of the substrate 5 is measured by the following procedure. The porous composite 30 is cut along a virtual plane parallel to the normal line of the main surface to expose a cross section of the substrate 5 along the normal line of the main surface. The cross section of the substrate 5 is observed using a scanning electron microscope at an appropriate magnification that allows the opening structure of the substrate 5 to be photographed within the field of view to obtain an SEM image of the cross section of the substrate 5. FIG. 6 is a diagram that shows a schematic SEM image of the cross section of a nickel mesh structure.

[0049] In the SEM image of the cross section of the nickel mesh structure, a single imaginary straight line L61 is drawn across the thickest part of the cross section of the metal wire 16 that constitutes the mesh. The number N1 (pieces) of pores 14 that the imaginary line crosses and the total length LT (μm) of the pores 14 are measured, and LT (μm) / N1 (pieces) is calculated.

[0050] SEM images of the cross section of the nickel mesh structure are obtained at three non-overlapping positions, and LT (μm) / N1 (pieces) is calculated based on each SEM image by the above procedure. The average of the three LT (μm) / N1 (pieces) is calculated. In the present disclosure, the average corresponds to the average opening diameter of the substrate 5.

[0051] It has been confirmed that, for the same porous composite, the average opening diameter of the substrate is measured with varying measurement areas, with almost no variation in the measurement results.

[0052] <Cross-sectional porosity of substrate> The lower limit of the cross-sectional porosity of the substrate 5 may be 50% or more, 55% or more, or 65% or more from the viewpoint of reducing pressure loss in the porous composite 30 and smoothing material transport of the electrolyte, gas, and the like in the electrolysis cell and improving the electrolysis efficiency of the AEM water electrolysis device. The upper limit of the cross-sectional porosity of the substrate 5 may be 95% or less, 85% or less, or 75% or less from the viewpoint of ensuring an appropriate compressive strength. The cross-sectional porosity of the substrate 5 may be 50% or more and 95% or less, 55% or more and 85% or less, or 65% or more and 75% or less.

[0053] In the present disclosure, the cross-sectional porosity of the substrate 5 is measured by the following procedure. Step B1: The porous composite 30 is cut along an imaginary plane parallel to the normal line of the main surface to expose a cross section of the substrate 5 along the normal line of the main surface.

[0054] Step B2: The cross section of the substrate 5 is observed with a scanning electron microscope at an appropriate magnification that allows the porous structure of the substrate 5 to be photographed, and an SEM image is obtained.

[0055] Step B3: In the SEM image of the cross section of the substrate 5, a rectangular measurement area is provided that includes an area large enough to measure the cross-sectional porosity of the substrate 5. Using image processing software, the percentage (S1 / SA)×100 of the area S1 of the pores relative to the area SA of the entire measurement area is calculated.

[0056] Step B4: Obtain SEM images in step B2 at three non-overlapping locations, and perform step B3 based on each SEM image to determine the percentage (S1 / SA) x 100. Calculate the average of the three percentages (S1 / SA) x 100. In the present disclosure, this average corresponds to the cross-sectional porosity of the substrate 5.

[0057] It has been confirmed that for the same porous composite, the cross-sectional porosity of the substrate is measured with varying measurement areas with almost no variation in the measurement results.

[0058] <Average thickness of substrate> The average thickness of the substrate 5 may 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 a cross section of the substrate 5 is obtained by the same method as steps A1 and A2 of the method for measuring the average opening diameter 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 points. The average of the distances at the five points is calculated. In the present disclosure, the average corresponds to the average thickness of the substrate 5.

[0059] It has been confirmed that, for the same porous composite, even when the measurement of the average thickness of the above-mentioned substrate is performed by changing the measurement area, there is almost no variation in the measurement results.

[0060] <Nickel layer> In the porous composite 30 of the first embodiment, the surface of the nickel layer 20 is the surface to which a catalyst is applied when the porous composite 30 is used in CCS-type AEM-type water electrolysis. In Fig. 1, the nickel layer 20 is provided on the entire surface of the first main surface 1, but this is not limited thereto. When the porous composite 30 is used in CCS-type AEM-type water electrolysis in a state in which a catalyst is applied to the nickel layer 20, the region where the nickel layer 20 is provided may be part of the first main surface 1 as long as the catalyst can be present in the region facing the anion exchange membrane.

[0061] The nickel layer 20 may contain 80% by mass or more of nickel. The nickel layer 20 may contain other components other than nickel. The other components may be at least one selected from the group consisting of iron, cobalt, chromium, phosphorus, boron, and carbon. The total content of the other components in the nickel layer 20 may be 0.01% by mass or more and 20% by mass or less. The content of the other components in the nickel layer 20 is measured by ICP atomic emission spectrometry.

[0062] The nickel layer 20 may be made of a sintered nickel body.

[0063] <Arithmetic mean height Sa of nickel layer> The upper limit of the arithmetic mean height Sa of the nickel layer 20 as specified in ISO 25178 is 5 μm or less, may be 4 μm or less, or may be 3 μm or less. The lower limit of the arithmetic mean height Sa of the nickel layer 20 is not particularly limited, and may be 0 μm or more, or may be 0.5 μm or more from the viewpoint of manufacturing. The arithmetic mean height Sa of the nickel layer 20 may 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 convex part on the surface of the porous composite may be stuck into the anion exchange membrane. In addition, if deep holes exist on the surface of the nickel layer 20 and a catalyst is applied to the nickel layer, the catalyst buried in the deep holes may not function, resulting in a loss of the catalyst. In addition, holes may be formed in the catalyst layer itself formed by applying a catalyst to the nickel layer, and the perforated part may not function as a catalyst.

[0064] In the present disclosure, the arithmetic mean height Sa defined in ISO 25178 is measured by the following procedure. The surface of the nickel layer 20 is observed with a laser microscope at an appropriate magnification that allows the uneven structure of the surface to be observed. The measurement area is the entire field of view. The surface of the nickel layer 20 is the main surface of the nickel layer 20 opposite to the main surface facing the first main surface 1 of the substrate 5, and is shown as the third main surface 3 in FIG. 1. The arithmetic mean height Sa defined in ISO 25178 of the measurement area is measured. For the measurement, a laser microscope "VK-X3000" (trademark) manufactured by Keyence Corporation is used. The arithmetic mean height Sa is measured in three measurement areas that do not overlap each other. The average of the arithmetic mean heights Sa of the three measurement areas is calculated. In the present disclosure, the average corresponds to the arithmetic mean height Sa of the nickel layer 20.

[0065] It has been confirmed that, for the same porous composite, even when the measurement of the arithmetic mean height Sa of the nickel layer is performed by changing the measurement area, there is almost no variation in the measurement results.

[0066] <Average opening diameter of nickel layer> In the porous composite 30 of the first embodiment, the nickel layer 20 may have a plurality of pores therein. 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 smoothing the transport of substances such as electrolyte and gas in an electrolysis cell in an AEM-type water electrolysis device using the porous composite as an electrode. 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 from the viewpoint of improving the smoothness of the surface of the nickel layer, suppressing the protrusions on the surface of the porous composite from piercing the opposing anion exchange membrane, and maintaining the smoothness of the surface of the catalyst layer formed by applying it to the nickel layer. 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.

[0067] In the present disclosure, the average opening size of the nickel layer 20 is measured by the following procedure. Step C1: The porous composite 30 is cut along an imaginary plane parallel to the normal to the main surface to expose a cross section of the nickel layer 20 along the normal to the main surface.

[0068] Step C2: Observe the cross section of the nickel layer 20 using an SEM at an appropriate magnification that allows the opening structure of the nickel layer 20 to be photographed within the field of view, and obtain 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 position of the boundary corresponds to the position of the first main surface 1 of the substrate 5.

[0069] Step C3: Draw three imaginary lines that divide the nickel layer into four equal parts in the thickness direction in the SEM image of the cross section of the nickel layer 20. The imaginary lines are designated as imaginary line L11, imaginary line L12, and imaginary line L13, in that order from the substrate side.

[0070] Step C4: For each of the imaginary lines L11, L12, and L13, measure the number of pores N11 (pieces) that the imaginary lines cross and the total length of the pores LT1 (μm). Calculate LT1 (μm) / N11 (pieces) for each of the three imaginary lines. Calculate the average A11 of LT1 (μm) / N11 (pieces) for the three imaginary lines.

[0071] Step C5: Obtain SEM images of step C2 at three non-overlapping locations, and perform steps C3 and C4 based on each SEM image to calculate the average A11. Calculate the average A12 of the three averages A11. In the present disclosure, the average A12 corresponds to the average opening diameter of the nickel layer 20.

[0072] FIG. 7 is an example of an SEM image of a cross section of the nickel layer of the porous composite of embodiment 1. In FIG. 7, the line LS3 indicates the surface of the nickel layer, and the line LS4 indicates the boundary between the substrate 5 and the nickel layer. In FIG. 7, the virtual lines L11, L12, and L13 are shown as white lines. In FIG. 7, the number of pores crossed by the virtual line L13 is 7, and the total length of the pores is 18.4 μm. Similarly, the number of pores crossed by the virtual line L12 is 7, and the total length of the pores is 22.4 μm. The number of pores crossed by the virtual line L11 is 12, and the total length of the pores is 35.2 μm. Based on these, the average opening diameter of the nickel layer 20 shown in FIG. 7 is calculated to be 2.9 μm. In FIG. 7, the pores correspond to the area sandwiched between the arrows and the area sandwiched between the arrows and the outer edge of the measurement area. The length of the pores corresponds to the length of the black line on the virtual line.

[0073] It has been confirmed that, for the same porous composite, the average opening diameter of the nickel layer is measured with varying measurement areas, with almost no variation in the measurement results.

[0074] <Porosity of nickel layer> In the porous composite 30 of the first embodiment, the nickel layer 20 may have a plurality of pores therein. The lower limit of the porosity of the nickel layer 20 may be 40% or more, 45% or more, or 55% or more from the viewpoint of smoothing the material transport of the electrolyte and the generated gas between the base material portion of the porous composite and the anion exchange membrane in an AEM type water electrolysis device using the porous composite as an electrode and improving the electrolysis efficiency of the AEM type water electrolysis device. The upper limit of the porosity of the nickel layer 20 may be 75% or less, 70% or less, or 65% or less in order to provide an appropriate resistance to compression. 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.

[0075] In the present disclosure, the porosity of the nickel layer 20 is measured by the following procedure. Step D1: The porous composite 30 is cut along an imaginary plane parallel to the normal line of the main surface to expose a cross section of the nickel layer 20 along the normal line of the main surface.

[0076] Step D2: The cross section of the nickel layer 20 is observed using a scanning electron microscope at an appropriate magnification that allows the pores in the nickel layer 20 to be photographed, and an SEM image is obtained.

[0077] Step D3: In the SEM of the cross section of the nickel layer 20, a rectangular measurement area including an area large enough to measure the porosity of the nickel layer 20 is provided. Using image processing software, the percentage (S11 / SA1)×100 of the pore area S11 to the total area SA1 of each measurement area is calculated.

[0078] Step D4: Obtain SEM images of step D2 at three non-overlapping locations, and perform step D3 based on each SEM image to determine the percentage (S11 / SA1) x 100. Calculate the average of the three percentages (S11 / SA1) x 100. In the present disclosure, this average corresponds to the porosity of the nickel layer 20.

[0079] It has been confirmed that, for the same porous composite, even when the measurement of the porosity of the nickel layer is performed by changing the measurement area, there is almost no variation in the measurement results.

[0080] <Average thickness of nickel layer> The lower limit of the average thickness of the nickel layer 20 may 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 maintaining the strength of the nickel layer itself. The upper limit of the average thickness of the nickel layer 20 may be 100 μm or less, 90 μm or less, or 80 μm or less from the viewpoint of smoothing the transport of substances such as the electrolyte and the generated gas between the substrate portion of the porous composite and the anion exchange membrane. The average thickness of the nickel layer 20 may 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.

[0081] The method for measuring the average thickness of the nickel layer 20 is as follows. An SEM image of a cross section of the nickel layer 20 is obtained by the same method as steps C1 and C2 of the method for measuring the average opening size 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 points. The average of the distances at the five points is calculated. In the present disclosure, the average corresponds to the average thickness of the nickel layer 20.

[0082] It has been confirmed that, for the same porous composite, the measurement of the average thickness of the nickel layer is performed with different measurement areas, and there is almost no variation in the measurement results.

[0083] <Method of manufacturing porous composite> A description will be given of an example of a method for producing the porous composite of embodiment 1. The method for producing the porous composite can include a step of preparing a substrate material, a step of preparing a nickel microporous sheet, a step of performing roll pressing on the substrate material and the nickel microporous sheet in a laminated state to obtain a laminate, and a step of heating the laminate to obtain a porous composite.

[0084] <Process of preparing substrate material> As a substrate material, a nickel porous body or a nickel mesh structure having a three-dimensional network structure is prepared. The nickel porous body or the nickel mesh structure is used in a sheet shape as a whole.

[0085] The average pore size of the nickel porous body may be 50 μm or more and 5000 μm or less, 100 μm or more and 1000 μm or less, or 200 μm or more and 700 μm or less.

[0086] The average pore diameter of a nickel porous body is defined by the following formula [1]: In formula [1], nc is the average number of pores per inch (25.4 mm = 25,400 μm) obtained by observing at least 10 fields of view of the main surface of the nickel porous body using a microscope or the like. Average pore diameter = 25400μm / nc Equation [1] The number of pores is measured in accordance with the method for determining the number of pores (cell count) of soft foamed materials specified in JIS K6400-1:2004, Appendix 1 (reference).

[0087] As the nickel porous body, for example, "Nickel Celmet" (trademark) manufactured by Sumitomo Electric Industries, Ltd. can be prepared.

[0088] The nickel mesh structure may be prepared, for example, by plain weaving nickel wires.

[0089] <Step of preparing nickel microporous sheet> The nickel microporous sheet can be prepared by the following procedure. Nickel powder, a binder, and pure water are mixed to obtain a slurry. The slurry is applied to a support. For example, a polytetrafluoroethylene (PTFE) sheet can be used as the support. The slurry applied to the support is dried and then peeled off from the sheet to obtain a nickel green sheet. The drying conditions can be, for example, 30 minutes at 80°C in the atmosphere.

[0090] The nickel green sheet is sintered to obtain a nickel microporous sheet. The sintering conditions can be, for example, 10 minutes at 900°C in a hydrogen atmosphere. The thickness of the nickel microporous sheet can be, for example, 0.5 μm or more and 100 μm or less.

[0091] <Step of obtaining laminate> Next, the substrate material and the nickel microporous sheet are laminated together and roll pressed to obtain a laminate. The conditions for roll pressing may be set to an appropriate roll gap based on the thicknesses of the substrate material and the nickel microporous sheet. For example, the roll gap may be set to about 80% of the desired thickness of the porous composite.

[0092] <Step of obtaining porous composite> Next, the laminate is heated to obtain a porous composite. The heating conditions can be, for example, 900°C for 10 minutes in a hydrogen atmosphere. This allows a porous composite in which the substrate and the nickel microporous sheet are bonded to each other to be obtained. EXAMPLES

[0093] The present embodiment will be described more specifically with reference to examples, although the present embodiment is not limited to these examples.

[0094] [Sample 1 to Sample 18] <Preparation of porous composite> <Process of preparing substrate material> As the substrate material, a nickel porous body having a three-dimensional mesh structure (nickel content 99.9% by mass, referred to as "Ni porous body" in Table 1) or a nickel mesh structure (nickel content 99.9% by mass, referred to as "Ni mesh structure" in Table 1) was prepared. The type of substrate material used in each sample, the average pore size of the substrate material, and the thickness of the substrate material are as shown in Table 1.

[0095] <Step of preparing nickel microporous sheet> Nickel powder, a binder, and pure water were mixed to obtain a slurry. The average particle size of the nickel powder used in each sample is as shown in Table 1. The average particle size of the nickel powder is a value 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 the nickel powder to the binder was nickel powder:binder=95:5 on a dry mass basis. Pure water was added to the mixture of nickel powder and binder to obtain a slurry.

[0096] The slurry was applied to a support made of a PTFE sheet. An applicator was used for application. The slurry applied to the support was dried and then peeled off from the sheet to obtain a nickel green sheet. The drying conditions were 80°C in air for 30 minutes.

[0097] The nickel green sheet was roll-pressed as necessary and then sintered to obtain a nickel microporous sheet. The sintering conditions were 900°C for 10 minutes in a hydrogen atmosphere. The thickness of the nickel microporous sheet for each sample is as shown in the "Thickness of nickel microporous sheet" column in Table 1.

[0098] <Step of obtaining laminate> Next, the substrate material and the nickel microporous sheet were laminated together and roll pressed to obtain a laminate. The roll gap during roll pressing for each sample was as shown in the "Roll Gap" column in Table 1.

[0099] <Step of obtaining porous composite> The laminate was then heated at 900° C. for 10 minutes in a hydrogen atmosphere to obtain a porous composite.

[0100] [Table 1]

[0101] [Measurement of porous composites] For each sample of composite porous body, the average opening diameter of the substrate, the cross-sectional porosity of the substrate, the arithmetic mean height Sa of the nickel layer as defined in ISO 25178, the average opening 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. The specific measurement method is as described in the first embodiment. The results are shown in Table 2.

[0102] [Table 2]

[0103] [evaluation] The composite porous bodies of Samples 1 to 9, 11 to 13, and 15 to 18 have nickel layers with an arithmetic mean height Sa of 5 μm or less as defined in ISO 25178, and thus correspond to Examples. The composite porous bodies of Samples 10 and 14 have nickel layers with an arithmetic mean height Sa of more than 5 μm as defined in ISO 25178, and thus correspond to Comparative Examples.

[0104] The composite porous bodies of Samples 1 to 9, Samples 11 to 13, and Samples 15 to 18 have an arithmetic mean height Sa of 5 μm or less, and the surface irregularities are reduced. Therefore, when the composite porous bodies of Samples 1 to 9, Samples 11 to 13, and Samples 15 to 18 are used in applications involving contact with an anion exchange membrane, the protrusions on the surface of the porous composite are prevented from piercing the anion exchange membrane, and defects such as micro-short circuits and through-holes formed in the anion exchange membrane that cause cross-leakage of oxygen and hydrogen are prevented. Furthermore, when a catalyst is applied to the nickel layer of the composite porous bodies of Samples 1 to 9, Samples 11 to 13, and Samples 15 to 18 to form a catalyst layer, the surface irregularities of the catalyst layer are also reduced. Therefore, when the porous composites of Samples 1 to 9, Samples 11 to 13, and Samples 15 to 18 are used as electrodes in a CCS-type AEM water electrolysis device with a catalyst applied to the nickel layer, it is possible to increase the contact area between the catalyst and the anion exchange membrane, and the electrolysis performance of the AEM water electrolysis device is improved.

[0105] Although the embodiments and examples of the present disclosure have been described above, it is intended from the outset that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is indicated by the claims, not by the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope. [Explanation of symbols]

[0106] 1 first main surface, 2 second main surface, 3 third main surface, 5 substrate, 10 nickel porous body, 11 skeleton, 12 skeleton main body, 13 inside of skeleton, 14 pore portion, 16 metal wire, 20 nickel layer, 30 porous composite.

Claims

1. a substrate having a first major surface; a nickel layer provided on at least a portion of the first main surface, the substrate is made of a nickel porous body having a three-dimensional network structure or a nickel mesh structure, The porous composite, wherein the nickel layer has an arithmetic mean height Sa defined in ISO 25178 of 5 μm or less.

2. the nickel layer has a plurality of pores therein, 2. The porous composite according to claim 1, wherein the nickel layer has an average pore size of 0.1 μm or more and 50 μm or less.

3. 3. The porous composite according to claim 1, wherein the nickel layer has an average thickness of 0.5 μm or more and 100 μm or less.

4. the nickel layer has a plurality of pores therein, 3. The porous composite according to claim 1, wherein the porosity of the nickel layer is 40% or more and 75% or less.

5. 3. The porous composite according to claim 1, wherein the average thickness of the porous composite is 50 μm or more and 500 μm or less.

6. 3. The porous composite according to claim 1, wherein the substrate has an average pore size of 50 μm or more and 800 μm or less.

7. 3. The porous composite according to claim 1, wherein the cross-sectional porosity of the substrate is 50% or more and 95% or less.

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