Metallic Porous Body

Abstract

a porous metal body having a skeleton with a three-dimensional mesh structure, the porous metal body being in the form of a sheet including a first main surface and a second main surface opposite the first main surface, the porous metal body comprising a first porous metal body layer including the first main surface, the first porous metal body layer including a first region sandwiched between a virtual surface S11 which is 0.01 mm away from the first main surface toward the first porous metal body layer and a virtual surface S12 which is 0.10 mm away from the first main surface toward the first porous metal body layer, the aperture ratio A1 of the first region being 40% or less, the aperture ratio being measured by observing a cross section of the porous metal body taken along a normal to the first main surface with a scanning electron microscope, the transmitted light area ratio of the first main surface being 2% or less, and the transmitted light area ratio being measured by observing the first main surface with a microscope while irradiating the porous metal body with light from the second main surface side.

Description

[Technical field]

[0001] The present disclosure relates to a porous metal body. [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 burden on the environment. 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, it allows the equipment to 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 metal porous body of the present disclosure is A metal porous body having a skeleton with a three-dimensional network structure, The metal porous body is in a sheet shape including a first main surface and a second main surface opposite to the first main surface, the metal porous body includes a first metal porous body layer including the first main surface, the first metal porous body layer includes a first region between an imaginary plane S11 that is 0.01 mm away from the first main surface toward the first metal porous body layer side, and an imaginary plane S12 that is 0.10 mm away from the first main surface toward the first metal porous body layer side, The aperture ratio A1 of the first region is 40% or less, The aperture ratio is measured by observing a cross section of the metal porous body taken along a normal line of the first main surface with a scanning electron microscope; The light transmitting area ratio of the first main surface is 2% or less, The light transmittance area ratio is measured by observing the first main surface with a microscope while irradiating the metal porous body with light from the second main surface side. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram illustrating a typical example of the configuration of the metallic porous body according to the first embodiment. [Diagram 2] FIG. 2 is an enlarged schematic view showing a cross section of the skeleton 11 of the porous metal body 10 shown in FIG. [Diagram 3] FIG. 3 is a schematic cross-sectional view of the skeleton 11 shown in FIG. 2 taken along line III-III. [Figure 4] FIG. 4 is a cross-sectional view of an example of a porous metal body according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [Problem that this disclosure aims to solve] In AEM-type water electrolysis, the electrodes in contact with the electrolyte membrane must be smooth to prevent damage to the electrolyte membrane. There are two types of methods: the CCM method, in which a catalyst is applied to the AEM membrane, and the CCS method, in which a catalyst is applied to an electrode made of a conductive porous body such as a porous metal. In the CCS method, increasing the contact area between the catalyst and the electrolyte membrane that contributes to the electrolysis reaction contributes to improving the electric field performance. For this reason, there is a demand for porous metal bodies that can be coated with more catalyst on their surface.

[0008] Therefore, an object of the present disclosure is to provide a porous metal body that has an improved surface smoothness to prevent damage to an electrolyte membrane and that allows a larger amount of catalyst to be applied to the surface.

[0009] [Effects of this disclosure] According to the present disclosure, it is possible to provide a porous metal body that has an improved surface smoothness, suppresses damage to an electrolyte membrane, and allows a larger amount of catalyst to be applied to the surface.

[0010] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) The metal porous body of the present disclosure is A metal porous body having a skeleton with a three-dimensional network structure, The metal porous body is in a sheet shape including a first main surface and a second main surface opposite to the first main surface, the metal porous body includes a first metal porous body layer including the first main surface, the first metal porous body layer includes a first region between an imaginary plane S11 that is 0.01 mm away from the first main surface toward the first metal porous body layer side, and an imaginary plane S12 that is 0.10 mm away from the first main surface toward the first metal porous body layer side, The aperture ratio A1 of the first region is 40% or less, The aperture ratio is measured by observing a cross section of the metal porous body taken along a normal line of the first main surface with a scanning electron microscope; The light transmitting area ratio of the first main surface is 2% or less, The light transmittance area ratio is measured by observing the first main surface with a microscope while irradiating the metal porous body with light from the second main surface side.

[0011] According to the present disclosure, it is possible to provide a porous metal body that has an improved surface smoothness, suppresses damage to an electrolyte membrane, and allows a larger amount of catalyst to be applied to the surface.

[0012] (2) In the above (1), the metal porous body includes a second metal porous body layer provided in contact with a main surface opposite to the first main surface of the first metal porous body layer, the second metal porous body layer includes a second region sandwiched between a first interface between the first metal porous body layer and the second metal porous body layer and a virtual plane S13 that is 0.01 mm away from the first interface toward the second metal porous body layer; The aperture ratio A2 of the second region may be the same as or larger than the aperture ratio A1.

[0013] This makes it possible to reduce pressure loss in the porous metal body. When the porous metal body is used in an AEM water electrolysis device, the generated gas can be easily removed by the liquid flow.

[0014] (3) In the above (2), the ratio A2 / A1 of the opening rate A2 to the opening rate A1 may be 1.0 or more and 4.0 or less, thereby making it possible to reduce pressure loss in the porous metal body.

[0015] (4) In the above (2) or (3), the metal porous body includes a third metal porous body layer provided in contact with a fourth main surface of the second metal porous body layer opposite to a third main surface in contact with the first metal porous body layer, the third metal porous body layer includes a third region sandwiched between a second interface between the second metal porous body layer and the third metal porous body layer and a virtual plane S14 that is 0.01 mm away from the second interface toward the third metal porous body layer; The aperture ratio A3 of the third region may be the same as or larger than the aperture ratio A1.

[0016] This makes it possible to reduce pressure loss in the porous metal body. When the porous metal body is used in an AEM water electrolysis device, the generated gas can be easily removed by the liquid flow.

[0017] (5) In the above (4), a ratio A3 / A1 of the opening ratio A3 to the opening ratio A1 may be 1.0 or more and 4.0 or less, thereby making it possible to reduce pressure loss in the porous metal body.

[0018] (6) In any of (1) to (5) above, the first major surface includes a first opening defined by the skeleton; the first opening is an opening through which light passes when the metal porous body is irradiated with light from the second main surface side, the first opening includes a second opening, The second opening has a circle equivalent diameter of 35 μm or less, The percentage (N2 / N1)×100 of the number N2 of the second openings to the number N1 of the first openings may be 50% or more.

[0019] This further increases the amount of catalyst that can be applied to the surface of the metal porous body.

[0020] (7) In any of (1) to (6) above, the first major surface includes a first opening defined by the skeleton; the first opening is an opening through which light passes when the metal porous body is irradiated with light from the second main surface side, The upper limit of the equivalent circle diameter of the first opening may be 60 μm or less.

[0021] This further increases the amount of catalyst that can be applied to the surface of the metal porous body.

[0022] [Details of the embodiment of the present disclosure] Specific examples of the metal porous body of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference symbols represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0023] 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.

[0024] 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.

[0025] [Embodiment 1: Porous metal body] The metal porous body according to one embodiment of the present disclosure is A metal porous body having a skeleton with a three-dimensional network structure, The metal porous body is in a sheet shape including a first main surface and a second main surface opposite to the first main surface, the metal porous body includes a first metal porous body layer including the first main surface, the first metal porous body layer includes a first region between an imaginary surface S11 that is 0.01 mm away from the first main surface toward the first metal porous body layer side, and an imaginary surface S12 that is 0.10 mm away from the first main surface toward the first metal porous body layer side; The aperture ratio A1 of the first region is 40% or less, The aperture ratio is measured by observing a cross section of the metal porous body taken along a normal line to the first main surface with a scanning electron microscope; The light transmitting area ratio of the first main surface is 2% or less, The light transmittance area ratio is measured by observing the first main surface of the porous metal body under a microscope while irradiating the porous metal body with light from the second main surface side.

[0026] <Structure of porous metal body> Fig. 1 is a diagram illustrating a typical configuration example of a metal porous body according to embodiment 1. Fig. 2 is an enlarged schematic diagram of a cross section of a skeleton 11 of a metal porous body 10 shown in Fig. 1. Fig. 3 is a schematic diagram of a cross section taken along line III-III of the skeleton 11 shown in Fig. 2. Fig. 4 is a cross-sectional view of an example of a metal porous body according to embodiment 1.

[0027] The metal porous body 10 has a skeleton 11 with a three-dimensional mesh structure. The metal porous body 10 has a sheet-like appearance including a first main surface 1 and a second main surface 2 opposite to the first main surface 1. Pores 14 are formed inside the metal porous body 10 by the skeleton 11 with the three-dimensional mesh structure.

[0028] The skeleton 11 of the metal porous body 10 is composed of a skeleton main body 12 made of metal, and the inside 13 of the skeleton is hollow. Furthermore, at least some of the pores 14 formed by the skeleton 11 are interconnected pores that communicate with adjacent pores 14.

[0029] As shown in FIG. 3, the cross-sectional shape of the skeleton 11 can be modeled as a triangle with a hollow center (interior 13 of the skeleton).

[0030] The first main surface of the metal porous body can consist of only the skeleton 11 of the three-dimensional mesh structure, or can consist of the skeleton 11 of the three-dimensional mesh structure and pores 14. On the first main surface of the metal porous body, there is no filler that fills the pores 14, or no coating material that covers the skeleton 11 and the pores 14.

[0031] In the metal porous body 10 of the first embodiment, the composition of the skeleton is not particularly limited and may be appropriately selected depending on the application. Examples of the skeleton composition include nickel, nickel-chromium, nickel-cobalt, nickel-tin, copper, and aluminum.

[0032] The thickness of the metal porous body 10 of the first embodiment is not particularly limited and is appropriately selected depending on the application. The thickness of the metal porous body 10 may be, for example, 0.1 mm or more and 10 mm or less, or 0.1 mm or more and 5 mm or less. The thickness of the metal porous body 10 can be measured, for example, by a digital thickness gauge.

[0033] <First metal porous layer> 4, the porous metal body 10 of the first embodiment includes a first porous metal body layer 5 including a first main surface 1. The first porous metal body layer 5 includes a first region 15 sandwiched between an imaginary surface S11 that is 0.01 mm away from the first main surface 1 toward the first porous metal body layer 5 side, and an imaginary surface S12 that is 0.10 mm away from the first main surface 1 toward the first porous metal body layer 5 side. The first region 15 includes the imaginary surface S11 and the imaginary surface S12.

[0034] <Aperture ratio A1 of the first area> The aperture ratio A1 of the first region of the metal porous body 10 of the first embodiment is 40% or less. This increases the smoothness of the first main surface of the metal porous body, and when the metal porous body is used as an electrode in an AEM-type water electrolysis device and the first main surface is arranged in contact with the electrolyte membrane, damage to the electrolyte membrane can be suppressed. In addition, when a catalyst is sprayed onto the first main surface, the catalyst is easily retained on the first main surface, and a larger amount of catalyst can be applied to the first main surface. The upper limit of the aperture ratio A1 of the first region may be 38% or less, 36% or less, or 30% or less, from the viewpoint of increasing the amount of catalyst applied to the first main surface. The lower limit of the aperture ratio A1 of the first region is not particularly limited, and may be, for example, 20% or more, 25% or more, or 27% or more. The aperture ratio A1 of the first region may be 20% or more and 40% or less, 20% or more and 38% or less, 25% or more and 36% or less, or 27% or more and 30% or less.

[0035] In the present disclosure, the aperture ratio A1 of the first region is measured by observing a cross section of the metal porous body along the normal line to the first main surface thereof with a scanning electron microscope. Specifically, the measurement is performed in the following manner.

[0036] Step A1: The metal porous body is cut along an imaginary plane parallel to the normal line of the first main surface to expose a cross section along the normal line of the first main surface.

[0037] Step A2: Observe the cross section of the metal porous body using a scanning electron microscope to obtain an observation image. The observation magnification is appropriately set depending on the size of the measurement field of the scanning electron microscope and the size of the pores 14. For example, the observation magnification can be 100 times.

[0038] Step A3: On the cross section of the metal porous body in the observed image, draw an imaginary line L0 that is 0.01 mm away from the first main surface, an imaginary line L1 that is 0.05 mm away from the first main surface, and an imaginary line L2 that is 0.10 mm away from the first main surface. The length of each of the imaginary lines L0, L1, and L2 is set to a length that crosses at least 10 pores 14. For example, when the observation magnification is 100 times, the length of each of the imaginary lines L0, L1, and L2 can be 1 mm or more.

[0039] Step A4: For each of the imaginary straight lines L0, L1, and L2, calculate a percentage P1 (P1 = (LP / LT) x 100) of the total length LP of the pores 14 crossed by the imaginary straight lines relative to the length LT of the imaginary straight lines. Calculate the percentage P1 for each of the imaginary straight lines L0, L1, and L2. Calculate the average P11 of the three calculated percentages P1. In the present disclosure, the average P11 corresponds to the opening ratio A1 of the first region.

[0040] <Light transmittance area ratio of the first principal surface> The light transmission area ratio of the first main surface of the metal porous body 10 of the first embodiment is 2% or less. According to this, when the catalyst is sprayed onto the first main surface, the catalyst is easily retained on the first main surface, and a larger amount of catalyst can be applied to the first main surface. The upper limit of the light transmission area ratio of the first main surface may be 1.9% or less, 1.8% or less, 1.7% or less, 1.5% or less, 1.0% or less, or 0.8% or less, from the viewpoint of increasing the amount of catalyst applied to the first main surface. The lower limit of the light transmission area ratio of the first main surface may be 0% or more. The light transmission area ratio of the first main surface may be 0% or more and 2% or less, 0% or more and 1.9% or less, 0% or more and 1.8% or less, 0% or more and 1.7% or less, 0% or more and 1.5% or less, 0% or more and 1.0% or less, or 0% or more and 0.8% or less.

[0041] In the present disclosure, the light transmittance area ratio of the first principal surface is measured by observing the first principal surface with a microscope while irradiating the metal porous body with light from the second principal surface side. Specifically, the measurement is performed by the following procedure.

[0042] Step B1: While irradiating the metal porous body with light from the second main surface side, the first main surface is observed with a microscope to obtain an observation image. The observation magnification is appropriately set according to the size of the measurement field of the microscope. For example, the observation magnification can be 10 to 1000 times. The size of the observation image is, for example, rectangular, and each of its length and width may be 10 times or more longer than the maximum opening diameter of the pores if pores are present in the first main surface. The microscope used is a "VHX-7000" (trademark) manufactured by KEYENCE Corporation.

[0043] Step B2: The observed image is binarized using the image processing software attached to the microscope to obtain a binarized image. The brightness threshold value for binarization can be determined appropriately depending on the state of the image to be used. For example, when there are 256 gradations, the central value of 128 can be used.

[0044] In the binarized image, areas through which light is passing are displayed in white. The percentage of the area S1 of the area through which light is passing relative to the area S of the entire binarized image is calculated as (S1 / S) x 100.

[0045] Step B3: Obtain the observation images of step B1 at three non-overlapping locations, and perform step B2 based on each observation image to obtain a percentage (S1 / S) x 100. Calculate the average of the percentages (S1 / S) x 100 of the three observation images. In the present disclosure, the average of the percentages (S1 / S) x 100 of the three observation images corresponds to the transmitted light area ratio of the first principal surface.

[0046] <Circle equivalent diameter of first opening> The first main surface of the porous metal body 10 of the embodiment 1 may include a first opening defined by a skeleton. The first opening is an opening through which light passes when the porous metal body is irradiated with light from the second main surface side.

[0047] The upper limit of the circle-equivalent diameter of the first opening may be 60 μm or less, 55 μm or less, or 50 μm or less, from the viewpoint of improving the smoothness of the first main surface and from the viewpoint of increasing the amount of catalyst applied to the first main surface. The lower limit of the circle-equivalent diameter of the first opening is not particularly limited, but may be, for example, 1 μm or more. The circle-equivalent diameter of the first opening may be 1 μm or more and 60 μm or less, 3 μm or more and 55 μm or less, or 5 μm or more and 50 μm or less. According to this, when the catalyst is sprayed toward the first main surface, the catalyst forms a catalyst layer on the first main surface and is easily retained on the first main surface, and more catalyst can be applied to the first main surface.

[0048] In the present disclosure, the upper limit of the equivalent circle diameter of the first opening is measured by the following procedure.

[0049] Step C1: Identify the areas through which light passes on the first main surface by the same method as steps B1 and B2 of the method for measuring the light transmission area ratio of the first main surface. Each of the areas through which light passes corresponds to a first opening.

[0050] Step C2: For each of the first openings identified in step C1, the circle-equivalent diameter is obtained using image processing. Specifically, the contour length CL and area S of each of the first openings are obtained, and the circle-equivalent diameter r is calculated from r = 2 × S / CL. In the observed image, the circle-equivalent diameter of the largest first opening is identified.

[0051] Step C3: Obtain the observation images of step B1 at three non-overlapping positions, and perform steps C1 and C2 based on each observation image to identify the circle equivalent diameter of the largest first opening. In the present disclosure, the circle equivalent diameter r of the largest first opening among the three observation images corresponds to the upper limit of the circle equivalent diameter of the first opening.

[0052] <Percentage of the number of second openings N2 to the number of first openings N1 (N2 / N1) x 100> The first main surface of the metal porous body 10 of embodiment 1 includes a first opening, which includes a second opening, the second opening has a circle equivalent diameter of 35 μm or less, and the percentage (N2 / N1)×100 of the number N2 of the second openings to the number N1 of the first openings may be 50% or more.

[0053] The lower limit of the percentage (N2 / N1)×100 may be 50% or more, 51% or more, 53% or more, 55% or more, or 60% or more, from the viewpoint of reducing the pressure loss of the metal porous body and facilitating the transport of the electrolyte to the catalyst-coated layer on the first main surface and the discharge of the gas generated in the catalyst-coated layer. The upper limit of the percentage (N2 / N1)×100 is not particularly limited, but may be, for example, 100% or less, 90% or less, 80% or less, or 75% or less. The percentage (N2 / N1)×100 may be 50% or more and 100% or less, 51% or more and 90% or less, 53% or more and 80% or less, 55% or more and 75% or less, or 60% or more and 75% or less.

[0054] In the present disclosure, the percentage (N2 / N1)×100 is measured by the following procedure.

[0055] Step D1: Determine the equivalent circle diameter for each of the first openings using the same method as steps C1 and C2 in the method for measuring the upper limit of the equivalent circle diameter of the first openings. Openings with an equivalent circle diameter of 35 μm or less correspond to the second openings.

[0056] Step D2: In the entire observation image, the number n1 of first openings (regardless of the circle equivalent diameter) and the number n2 of second openings with a circle equivalent diameter of 35 μm or less are counted, and the percentage (n2 / n1)×100 is calculated.

[0057] Step D3: Obtain the observation images of step B1 at three non-overlapping locations, and perform steps D1 and D2 based on each observation image to calculate the percentage (n2 / n1) × 100. In the present disclosure, the average of the percentages (n2 / n1) × 100 of the three observation images corresponds to the percentage (N2 / N1) × 100 of the number N2 of second openings relative to the number N1 of first openings.

[0058] <Second metal porous layer> 4, the metal porous body 10 of the first embodiment includes a second metal porous body layer 6 provided in contact with the main surface opposite to the first main surface 1 of the first porous metal layer 5, and the second porous metal layer 6 may include a second region 16 sandwiched between a first interface 8 between the first porous metal layer 5 and the second porous metal layer 6 and an imaginary plane S13 that is 0.01 mm away from the first interface 8 toward the second porous metal layer 6. The second region 16 does not include the third main surface 3 of the second porous metal layer 6 on the first porous metal layer 5 side, but includes the imaginary plane S13.

[0059] <Aperture ratio A2 of the second area> The aperture ratio A2 of the second region of the porous metal body 10 of the first embodiment may be the same as or larger than the aperture ratio A1 of the first region.

[0060] The lower limit of the ratio A2 / A1 of the aperture ratio A2 to the aperture ratio A1 may be 1.0 or more, 1.2 or more, or 1.5 or more, from the viewpoint of reducing the pressure loss of the metal porous body and facilitating the transport of the electrolyte to the catalyst coating layer on the first main surface and the discharge of the gas generated in the catalyst coating layer. The upper limit of the ratio A2 / A1 may be 4.0 or less, 3.0 or less, or 2.7 or less, from the viewpoint of balancing the catalyst coating amount on the first main surface with the electrolyte transport and gas discharge on the second main surface. The ratio A2 / A1 may be 1.0 or more and 4.0 or less, 1.2 or more and 3.0 or less, or 1.5 or more and 2.7 or less.

[0061] The aperture ratio A2 may be, for example, 25% or more and 80% or less, 35% or more and 75% or less, or 40% or more and 70% or less.

[0062] In the present disclosure, the aperture ratio A2 of the second region is measured by observing a cross section of the metal porous body along the normal line to the first main surface thereof with a scanning electron microscope. Specifically, the measurement is performed in the following manner.

[0063] Step E1: An observation image of the cross section of the porous metal body is obtained by the same method as steps A1 and A2 in the method for measuring the opening ratio A1 of the first region.

[0064] Step E2: Draw an imaginary line L3 that is 0.003 mm away from the first interface, an imaginary line L4 that is 0.006 mm away from the first interface, and an imaginary line L5 that is 0.01 mm away from the first interface on the cross section of the second porous metal layer in the observed image. The lengths of the imaginary lines L3, L4, and L5 are each set to a length that crosses at least 10 pores 14.

[0065] Step E3: For each of the imaginary lines L3, L4, and L5, calculate a percentage P2 (P2 = (LP / LT) x 100) of the total length LP of the pores 14 crossed by the imaginary lines relative to the length LT of the imaginary lines. Calculate the percentage P2 for each of the imaginary lines L3, L4, and L5. Calculate the average P22 of the three calculated percentages P2. In the present disclosure, the average P22 corresponds to the opening ratio A2 of the second region.

[0066] <Third metal porous layer> 4, the metal porous body 10 of the first embodiment includes a third metal porous body layer 7 provided in contact with the fourth main surface 4 of the second metal porous body layer 6 opposite to the third main surface 3 in contact with the first porous metal layer 5, and the third metal porous body layer 7 may include a third region 17 sandwiched between a second interface 9 between the second metal porous body layer 6 and the third metal porous body layer 7 and an imaginary plane S14 that is 0.01 mm away from the second interface 9 toward the third metal porous body layer 7. The third region does not include the main surface of the third metal porous body layer 7 on the second metal porous body layer 6 side, but includes the imaginary plane S14.

[0067] The aperture ratio A3 of the third region of the metal porous body 10 of the first embodiment may be the same as or larger than the aperture ratio A1.

[0068] The lower limit of the ratio A3 / A1 of the aperture ratio A3 to the aperture ratio A1 may be 1.0 or more, 1.2 or more, or 1.5 or more from the viewpoint of reducing the pressure loss of the metal porous body. The upper limit of the ratio A3 / A1 may be 4.0 or less, 3.3 or less, or 3.0 or less from the viewpoint of balancing the catalyst coating amount on the first main surface with the electrolyte transport and gas discharge on the second main surface. The ratio A3 / A1 may be 1.0 or more and 4.0 or less, 1.0 or more and 3.3 or less, or 1.0 or more and 3.0 or less.

[0069] The aperture ratio A3 of the third region of the porous metal body 10 of the first embodiment may be the same as or larger than the aperture ratio A2.

[0070] The lower limit of the ratio A3 / A2 of the aperture ratio A3 to the aperture ratio A2 may be 1.0 or more, 1.2 or more, or 1.5 or more from the viewpoint of reducing the pressure loss of the metal porous body. The upper limit of the ratio A3 / A2 may be 4.0 or less, 3.3 or less, or 3.0 or less from the viewpoint of balancing the catalyst coating amount on the first main surface with the electrolyte transport and gas discharge on the second main surface. The ratio A3 / A2 may be 1.0 or more and 4.0 or less, 1.0 or more and 3.3 or less, or 1.0 or more and 3.0 or less.

[0071] The aperture ratio A3 may be, for example, 30% or more and 95% or less, 35% or more and 90% or less, or 45% or more and 90% or less.

[0072] In the present disclosure, the aperture ratio A3 of the third region is measured by observing a cross section of the metal porous body along the normal line to the first main surface thereof with a scanning electron microscope. Specifically, the measurement is performed in the following manner.

[0073] Step F1: An observation image of the cross section of the porous metal body is obtained by the same method as steps A1 and A2 in the method for measuring the opening ratio A1 of the first region.

[0074] Step F2: Draw an imaginary line L6 that is 0.003 mm away from the second interface, an imaginary line L7 that is 0.006 mm away from the second interface, and an imaginary line L8 that is 0.01 mm away from the second interface on the cross section of the third porous metal layer in the observed image. The lengths of the imaginary lines L6, L7, and L8 are each set to a length that crosses at least 10 pores 14.

[0075] Step F3: For each of the imaginary lines L6, L7, and L8, calculate a percentage P3 (P3 = (LP / LT) x 100) of the total length LP of the pores 14 crossed by the imaginary lines relative to the length LT of the imaginary lines. Calculate the percentage P3 for each of the imaginary lines L6, L7, and L8. Calculate the average P33 of the three calculated percentages P3. In the present disclosure, the average P33 corresponds to the opening ratio A3 of the third region.

[0076] <Method of manufacturing porous metal body> The manufacturing method of the metal porous body of embodiment 1 can include a first step of preparing a metal porous body material having a skeleton with a three-dimensional mesh structure, and a second step of obtaining a metal porous body by performing a two-stage press on the metal porous body material.

[0077] ≪First step≫ A metal porous material having a three-dimensional mesh-like structure is prepared. The metal porous material is used in a sheet-like shape as a whole. The average pore size of the metal porous material may be appropriately selected depending on the application of the metal porous body 10. For example, the average pore size of the metal porous material 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.

[0078] The average pore size of a porous metal material is defined by the following formula [1]: In formula [1], nc is the average number of pores 14 per inch (25.4 mm = 25,400 μm) when the main surface of the porous metal material is observed in at least 10 fields of view using a microscope or the like. Average pore diameter = 25400μm / nc Equation [1] The number of pores 14 is measured in accordance with the method for determining the number of pores (cell number) of a soft foamed material according to JIS K6400-1:2004, Appendix 1 (reference).

[0079] Two or more sheets of the porous metal material having different average pore diameters may be prepared.

[0080] Examples of the porous metal material that can be used include "Aluminum Celmet" (trademark) manufactured by Sumitomo Electric Industries, Ltd., and copper or nickel "Celmet" (trademark).

[0081] ≪Second process≫ Next, the porous metal material is subjected to a two-stage press to obtain a porous metal body. Specifically, the porous metal material is pressed in the thickness direction using a roll press. In the first stage of pressing, the material is pressed to 1.5 to 2.0 times the final thickness of the desired porous metal layer, and in the second stage of pressing, the material is pressed to the desired thickness. At this time, the pressing pressure, pressing speed, and number of pressings may be selected according to the size and properties of the porous metal material. For example, in the case of a sample having a width of 10 cm, pressing can be performed at a linear pressure of 10 kN and a speed of 10 cm / min.

[0082] When two or more sheets of porous metal material are prepared in the first step, the first step of pressing may be performed separately for each porous metal material. In addition, the first step of pressing may be performed simultaneously in a laminated state in which two or more sheets of porous metal material are stacked so that their main surfaces face each other. In addition, for example, the porous metal material that has been subjected to the first step of pressing and the unpressed porous metal material may be stacked and the second step of pressing may be performed in a laminated state. The order, timing, and number of pressings may be adjusted according to the final desired structure, but it is preferable to press one or more times in a laminated state in the end. By the two-step pressing, the opposing main surfaces of two or more porous metal materials are directly bonded to each other, and a porous metal material in which two or more porous metal materials are integrated can be obtained. It is presumed that at the interface between the two porous metal materials facing each other, at least a part of the skeletons of both porous metal materials are entangled, thereby bonding the two porous metal materials. In the obtained porous metal body, no adhesive or the like is present at the interface between the two opposing sheets of porous metal body material.

[0083] The inventors have discovered that by performing two-stage pressing, a metal porous body of embodiment 1 can be obtained in which the opening ratio A1 of the first region is 40% or less and the transmitted light area ratio of the first main surface is 2% or less. EXAMPLES

[0084] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0085] [Preparation of porous metal bodies] A sheet-shaped metal porous material made of nickel having a three-dimensional mesh-like structure was prepared. For each sample, one, two or three sheets of the metal porous material (first metal porous material, second metal porous material, third metal porous material) were prepared. The average pore size and thickness of the metal porous material prepared for each sample are as shown in Table 1.

[0086] Next, the metal porous body material was pressed to obtain a metal porous body. For samples in which two or three sheets of metal porous body materials were prepared, the metal porous body materials were laminated so that the main surfaces of the metal porous body materials faced each other to obtain a laminate, and then pressed. When three sheets of metal porous body materials were used, the first metal porous body material, the second metal porous body material, and the third metal porous body material were laminated in the above order, and pressed.

[0087] The pressing was performed in the thickness direction of the metal porous material using a roll press. The overall thickness of the metal porous material after the first pressing step and the overall thickness of the metal porous material after the second pressing step are shown in the "First Step" and "Second Step" columns of "Pressing" in Table 1, respectively. Samples marked with "-" in the "Second Step" column in Table 1 did not undergo the second pressing step.

[0088] [Table 1]

[0089] [Measurement of porous metal bodies] For each sample's metal porous body, the thicknesses of the first metal porous body layer corresponding to the first metal porous body material, the second metal porous body layer corresponding to the second metal porous body material, and the third metal porous body layer corresponding to the third metal porous body material were measured. The measurement was carried out by observing the cross-section of the metal porous body under a microscope at a magnification of 100 times. For each of the first metal porous body layer, the second metal porous body layer, and the third metal porous body layer, the thicknesses at three locations were measured, and their average was calculated, which was taken as the thickness of each of the first metal porous body layer, the second metal porous body layer, and the third metal porous body layer. The results are shown in the columns of "First Metal Porous Body Layer", "Second Metal Porous Body Layer", and "Third Metal Porous Body Layer" in Table 2. Furthermore, the thickness of the entire laminate is also shown in the "Laminate" column of Table 2.

[0090]

Table 2

[0091] For each sample's metal porous body, the porosity A1 of the first region, the porosity A2 of the second region, the porosity A3 of the third region, the light transmission area ratio of the first main surface, the upper limit of the equivalent circle diameter of the first opening, and the percentage (N2 / N1)×100 of the number N2 of the second opening with respect to the number N1 of the first opening were measured. The specific measurement method is as described in Embodiment 1. Furthermore, based on the measurement results, A2 / A1 and A3 / A1 were calculated. The results are shown in Table 3.

[0092]

Table 3

[0093] [Evaluation of Metal Porous Body] <AEM-Type Water Electrolysis Catalyst Coating> The amount of catalyst that could be applied to the surface of each sample was evaluated. The specific evaluation method is as follows. A catalyst ink was applied to the first main surface of each sample. A commercially available platinum-supported carbon powder, which is a catalyst for AEM-type water electrolysis, was used as the catalyst contained in the catalyst ink. The catalyst ink was prepared by mixing platinum-supported carbon powder and a 10 wt% polytetrafluoroethylene (PTFE) dispersion solution (solvent: pure water) at a ratio that would result in a concentration that could be applied. The percentage of the area of ​​the catalyst region relative to the area of ​​the entire field of view (hereinafter also referred to as the "catalyst region percentage") was measured using SEM-EDX. The results are shown in the "AEM-type water electrolysis catalyst application" column in Table 4. The larger the catalyst region percentage value, the greater the amount of catalyst that can be applied to the surface of the metal porous body.

[0094] <Pressure loss> For each sample, the pressure loss was evaluated when air was passed through the metal porous body. The specific evaluation method is as follows. A measurement sample with a diameter of 25 mm was prepared for each sample. The sample was tightly fixed in a pipe with an inner diameter of 25 mm, and air was allowed to flow through the pipe to measure the pressure loss when the air flowed perpendicular to the main surface of the measurement sample. The difference with the blank was taken, and when the air flow velocity was 1 m / s, a pressure loss of 15 kPa or less was evaluated as "A", and a pressure loss of more than 15 Pa was evaluated as "B". The evaluations are shown in the "Pressure Loss" column in Table 4.

[0095] [Table 4]

[0096] [Consideration] The metal porous bodies of Samples 1 to 12 were obtained by carrying out two-stage pressing and correspond to Examples, whereas the metal porous bodies of Samples 101 to 106 were obtained by carrying out only the first stage pressing and correspond to Comparative Examples.

[0097] It was confirmed that the porous metal bodies of Samples 1 to 12 had an aperture ratio A1 of 40% or less, which was smaller than the aperture ratio A1 of the porous metal bodies of Samples 101 to 106. This shows that the porous metal bodies of Samples 1 to 12 have smooth surfaces and can suppress damage to the electrolyte membrane.

[0098] It was confirmed that the porous metal bodies of Samples 1 to 12 had a larger amount of catalyst that could be applied to the surface of the porous metal body than the porous metal bodies of Samples 101 to 106.

[0099] It was confirmed that the metal porous bodies of Samples 1 to 12 had smaller pressure loss than the metal porous bodies of Samples 101 to 104. This shows that the metal porous bodies of Samples 1 to 12 can smoothly pass the electrolytic solution used in AEM-type water electrolysis and gases such as oxygen and hydrogen that are generated.

[0100] From the above, it is presumed that when the porous metal bodies of Samples 1 to 12 are used as electrodes in an AEM-type water electrolysis device, damage to the electrolyte membrane can be suppressed, which in turn leads to a thinner electrolyte membrane and improved electrolysis performance. In addition, when the porous metal bodies of Samples 1 to 12 are used as electrodes in an AEM-type water electrolysis device, particularly using the CCS method, it is presumed that the amount of catalyst on the surface can be increased, further improving electrolysis performance.

[0101] Furthermore, the metal porous body disclosed herein is believed to be effective not only as an electrode for an AEM water electrolysis device, but also in other applications where surface smoothness, porosity, and electrical conductivity are simultaneously required, and it is presumed that the body will also be effective as a current collector for an anode-supported solid oxide fuel cell, for example.

[0102] 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]

[0103] 1 first main surface, 2 second main surface, 3 third main surface, 4 fourth main surface, 5 first porous metal layer, 6 second porous metal layer, 7 third porous metal layer, 8 first interface, 9 second interface, 10 porous metal, 11 skeleton, 12 skeleton main body, 13 interior of skeleton, 14 pore portion, 15 first region, 16 second region, 17 third region.

Claims

1. A porous metal body having a skeleton with a three-dimensional network structure, the metal porous body is in a sheet shape including a first main surface and a second main surface opposite to the first main surface, the porous metal body includes a first porous metal body layer including the first main surface, the first metal porous body layer includes a first region sandwiched between an imaginary surface S11 that is 0.01 mm away from the first main surface toward the first metal porous body layer side, and an imaginary surface S12 that is 0.10 mm away from the first main surface toward the first metal porous body layer side, The aperture ratio A1 of the first region is 40% or less, the aperture ratio is measured by observing a cross section of the metal porous body taken along a normal to the first main surface with a scanning electron microscope; the transmitted light area ratio of the first main surface is 2% or less; The metal porous body, wherein the light transmittance area ratio is measured by irradiating the metal porous body with light from the second main surface side and observing the first main surface with a microscope.

2. the metal porous body includes a second metal porous body layer provided in contact with a main surface opposite to the first main surface of the first metal porous body layer, the second metal porous body layer includes a second region sandwiched between a first interface between the first metal porous body layer and the second metal porous body layer and an imaginary plane S13 that is 0.01 mm away from the first interface toward the second metal porous body layer, The metal porous body according to claim 1 , wherein the aperture ratio A2 of the second region is equal to or greater than the aperture ratio A1.

3. The porous metal body according to claim 2 , wherein a ratio A2 / A1 of the opening ratio A2 to the opening ratio A1 is 1.0 or more and 4.0 or less.

4. the metal porous body includes a third metal porous body layer provided in contact with a fourth main surface of the second metal porous body layer opposite to a third main surface that is in contact with the first metal porous body layer, the third metal porous body layer includes a third region sandwiched between a second interface between the second metal porous body layer and the third metal porous body layer and an imaginary plane S14 that is 0.01 mm away from the second interface toward the third metal porous body layer; 4. The metal porous body according to claim 2, wherein the aperture ratio A3 of the third region is equal to or greater than the aperture ratio A1.

5. The porous metal body according to claim 4 , wherein a ratio A3 / A1 of the opening ratio A3 to the opening ratio A1 is 1.0 or more and 4.0 or less.

6. the first major surface includes a first opening defined by the skeleton; the first opening is an opening through which light passes when the metal porous body is irradiated with light from the second main surface side, the first opening includes a second opening; The second opening has an equivalent circle diameter of 35 μm or less, 3. The metal porous body according to claim 1, wherein the percentage (N2 / N1) x 100 of the number N2 of the second openings to the number N1 of the first openings is 50% or more.

7. the first major surface includes a first opening defined by the skeleton; the first opening is an opening through which light passes when the metal porous body is irradiated with light from the second main surface side, The metal porous body according to claim 1 or 2, wherein the upper limit of the equivalent circle diameter of the first openings is 60 μm or less.

Images