Porous structure, device, and method for producing porous structure

Abstract

A porous structure according to the present invention is produced by heat-treating a polymer structure. The porous structure has a periodic structure in which flow paths, the inner walls of which are formed by minimal curved surfaces, are repeated periodically.　A method for producing a porous structure according to the present invention comprises: a step for molding a polymer structure serving as a prototype of the porous structure by photolithography using a photo-resin as a starting material; and a step for heat-treating the polymer structure.　The problem to be solved by the present invention is to provide a porous structure capable of obtaining good flow path performance.

Description

Porous structure, device, and method for manufacturing porous structure

[0001] The present invention relates to a porous structure, a device, and a method for manufacturing a porous structure.

[0002] In devices that use porous structures as flow channels (e.g., gas diffusion layers), the channel performance affects the performance and output of the device, so porous structures that can provide good channel performance are desired.

[0003] WO2023 / 230378A1

[0004] The problem to be solved by the present invention is to provide a porous structure that can provide good flow path performance.

[0005] [1] A porous structure according to one aspect of the present invention is a porous structure produced by heat-treating a polymer structure, the porous structure having, at least in part, a periodic structure in which flow paths whose inner walls are formed by minimal curved surfaces are periodically repeated.

[0006] [2] A porous structure according to one aspect of the present invention is the porous structure according to the above [1], further comprising pores communicating with the flow paths.

[0007] [3] A porous structure according to one aspect of the present invention is the porous structure described in [2] above, wherein the pores are formed so that the pore diameter increases in the direction in which the bubbles are discharged.

[0008] [4] A porous structure according to one aspect of the present invention is the porous structure described in the above [2] or [3], wherein the pores are formed so as to satisfy the following conditional expression:

[0009] Pb-Pl>2γcosθ / rp where, Pb: pressure of the bubble, Pl: pressure of the liquid, γ: surface tension, θ: contact angle in the liquid phase, and rp: radius of the hole.

[0010] [5] A porous structure according to one aspect of the present invention is the porous structure described in any one of [1] to [4] above, wherein the polymer structure is formed by stereolithography using a photoresin as a starting material.

[0011] [6] A porous structure according to one aspect of the present invention is the porous structure according to any one of the above [1] to [5], wherein the polymer structure is a gel structure.

[0012] [7] A porous structure according to one aspect of the present invention is the porous structure according to any one of the above [1] to [6], which contains carbon as a constituent material.

[0013] [8] A porous structure according to one aspect of the present invention is the porous structure according to the above [7], further comprising an inorganic material as a constituent material.

[0014] [9] A porous structure according to one aspect of the present invention is the porous structure according to the above [8], wherein the inorganic material contains a metal.

[0015]

[10] A porous structure according to one aspect of the present invention is the porous structure according to the above [9], wherein the carbon is contained as an impurity, and the carbon content is 0.1 wt % or more and 5 wt % or less.

[0016]

[11] A porous structure according to one aspect of the present invention is the porous structure according to the above [9] or

[10] , wherein the carbon is contained as a metal carbide, and the carbon content is 3 wt % or more and 40 wt % or less.

[0017]

[12] A porous structure according to one aspect of the present invention is the porous structure according to any one of the above [1] to

[11] , wherein the porosity is 20% or more and 99% or less.

[0018]

[13] A porous structure according to one aspect of the present invention is the porous structure according to any one of the above [1] to

[12] , wherein the surface roughness Ra of the inner wall is 50 μm or less.

[0019]

[14] A porous structure according to one aspect of the present invention is the porous structure according to any one of [1] to

[13] above, wherein the periodic structure is a TPMS (triply periodic minimal surface) structure.

[0020]

[15] A porous structure according to one aspect of the present invention is the porous structure according to the above

[14] , wherein the periodic structure is a gyroid structure.

[0021]

[16] An apparatus according to one aspect of the present invention is an apparatus comprising the porous structure described in any one of [1] to

[15] above.

[0022]

[17] An apparatus according to one aspect of the present invention is the apparatus according to the above

[16] , comprising the porous structure as a gas diffusion layer of an electrolysis cell.

[0023]

[18] The device according to one aspect of the present invention is the device according to the above

[16] , which comprises the porous structure as a gas diffusion layer or a proton transport layer of a fuel cell.

[0024]

[19] A method for producing a porous structure according to one aspect of the present invention includes the steps of: using a photoresin as a starting material to form a polymer structure that serves as a prototype of the porous structure by stereolithography; and heat-treating the polymer structure.

[0025]

[20] A method for producing a porous structure according to one aspect of the present invention is the method for producing a porous structure according to the above

[19] , wherein the polymer structure contains an inorganic material.

[0026]

[21] A method for producing a porous structure according to one aspect of the present invention is the method for producing a porous structure according to the above

[20] , wherein the inorganic material contains a metal or a metal ion.

[0027]

[22] In the method for producing a porous structure according to one aspect of the present invention, the step of heat treating includes a firing step in the method for producing a porous structure according to the above item

[21] .

[0028]

[23] In the method for producing a porous structure according to one aspect of the present invention, the step of heat treating further includes a reduction step subsequent to the firing step.

[0029]

[24] A method for producing a porous structure according to one aspect of the present invention is the method for producing a porous structure according to any one of the above

[19] to

[23] , wherein the polymer structure has a periodic structure in which flow paths whose inner walls are formed by minimal curved surfaces are periodically repeated.

[0030]

[25] A method for producing a porous structure according to one aspect of the present invention is the method for producing a porous structure according to any one of the above items

[19] to

[24] , wherein the polymer structure is a gel structure.

[0031] FIG. 1 is a schematic cross-sectional view of a water electrolysis device using the porous structure according to the present embodiment. FIG. 2 is a view showing an example of the three-dimensional structure of the porous structure according to the present embodiment. FIG. 3 is a view showing a conditional formula satisfied by the porous structure according to the present embodiment. FIG. 4 is a view showing an example of a manufacturing process for the porous structure according to the present embodiment. FIG. 5 is a view showing an example of a manufacturing method for the porous structure according to the present embodiment. FIG. 6 is a schematic cross-sectional view of a fuel cell using the porous structure according to the present embodiment. FIG. 7 is a view showing another example of a manufacturing process for the porous structure according to the present embodiment. FIG. 8 is a view showing another example of a manufacturing method for the porous structure according to the present embodiment. FIG. 9 is a view showing another example of a manufacturing process for the porous structure according to the present embodiment. FIG. 10 is a view showing another example of a manufacturing method for the porous structure according to the present embodiment. FIG. 11 is an overview photograph of the porous structures of Samples 1 to 3 according to the examples. FIG. 12 is a view showing the size etc. of each sample produced. FIG. 13 is an optical microscope photograph of Sample 1 according to the example. FIG. 14 is an optical microscope photograph of Sample 2 according to the example. FIG. 15 is an optical microscope photograph of Sample 3 according to the example. FIG. 16 is an optical microscope photograph of Sample 4 according to the example. FIG. 17 is a view showing the results of measuring the surface roughness of each sample according to the examples.

[0032] Hereinafter, each embodiment will be described with reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or redundant description of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art.

[0033] The porous structure 1 according to this embodiment can be used in a device in which a fluid (gas, liquid, etc.) passes through the porous structure, and a portion of the fluid transfers heat or causes a surface reaction on the surface of the porous structure 1. Specifically, the porous structure 1 can be used, for example, as an electrode of an electrochemical device (e.g., an electrode of a lithium ion battery), a current collector of an electrochemical device (e.g., a current collector of a lithium metal battery), a gas diffusion layer or electrode of a fuel cell, a catalytic device, an electrolysis device (electrolysis of carbon dioxide, electrolysis of saline solution, etc.), a heat sink, a wick of a vapor chamber, a catalyst or catalyst support material of various sensors, etc. An example of a device using the porous structure 1 will be described below. <First Embodiment>

[0034] (Water Electrolysis Apparatus) FIG. 1 is a schematic cross-sectional view showing the general configuration of a water electrolysis apparatus 100 using a porous structure 1 according to this embodiment. As shown in FIG. 1 , the water electrolysis apparatus 100 has a water electrolysis cell 10. The water electrolysis cell 10 includes an anode 3A composed of a porous structure 1A and an anode catalyst layer 2A, and a cathode 3C composed of a porous structure 1C and a cathode catalyst layer 2C. In the water electrolysis cell 10, the porous structures 1 (1A, 1C) function as gas diffusion layers (GDLs). The structure of the porous structure 1 will be described later.

[0035] An electrolyte membrane 4 is disposed between the anode 3A and the cathode 3C. Separators 5A and 5C are disposed on the outside of the anode 3A and the cathode 3C, respectively, and a voltage is applied from a power source 6 to the anode 3A and the cathode 3C via the separators 5A and 5C. Gaskets 7 and 8 are disposed between the separator 5A and the electrolyte membrane 4, and between the separator 5C and the electrolyte membrane 4, respectively.

[0036] Water (HO) is supplied to the water electrolysis cell 10 from a water supply unit 9a. Oxygen (O) generated at the anode 3A is exhausted from an oxygen exhaust unit 9b, and hydrogen (H) generated at the cathode 3C is exhausted from a hydrogen exhaust unit 9c. Although Fig. 1 shows an example in which the water electrolysis device 100 has one water electrolysis cell 10, the water electrolysis device 100 may have a plurality of stacked water electrolysis cells 10.

[0037] (Porous Structure) Next, the porous structure 1 (1A, 1C) will be described.

[0038] 2 is a schematic diagram showing the three-dimensional structure of the porous structure 1, illustrating a cut-out portion of the porous structure 1. The three-dimensional data of this porous structure 1 is created by three-dimensional CAD (Computer Aided Design).

[0039] As shown in FIG. 2 , the porous structure 1 has an internal structure 1c composed of a large number of pores 1a through which gas generated in the water electrolysis cell 10 can pass and flow paths 1b communicating with the pores 1a. The internal structure 1c is formed so that the inner walls of the flow paths 1b form minimal curved surfaces. Unit cells including the internal structure 1c form a periodic structure (e.g., a triple periodic minimal surface (TPMS) structure, such as a gyroid structure or a Schwarz P structure) in which the unit cells are continuously and periodically repeated three-dimensionally within the porous structure 1. This facilitates the release of bubbles adhering to the inner walls of the porous structure 1 and makes it difficult for bubbles to become trapped (adhered) within the porous structure 1. As a result, the efficiency of bubble transport through the porous structure 1 can be improved. The periodic structure may be formed in at least a portion of the porous structure 1.

[0040] By repeating the unit cell in the porous structure a predetermined number of times, a porous structure of a desired size can be produced. For example, if the size of the finally obtained porous structure is 10 mm and the unit cell is a cube with a side length of 0.1 mm, the number of unit cell repetitions may be set to 100. In this case, the number of repetitions may be set taking into consideration the effects of expansion and contraction during heat treatment.

[0041] For example, if there is a 50% shrinkage during the heat treatment, the number of repetitions may be doubled to 200. Conversely, if there is a 100% expansion during the heat treatment, the number of repetitions may be halved to 50.

[0042] Alternatively, the size of the unit cells may be adjusted to accommodate expansion or contraction during heat treatment, rather than the number of unit cell repetitions. For example, if there is a 50% contraction during heat treatment, the size of the unit cells may be doubled. Conversely, if there is a 100% expansion during heat treatment, the size of the unit cells may be halved.

[0043] Alternatively, the number of repetitions of the unit cells and the size of the unit cells may be combined and appropriately adjusted to accommodate expansion and contraction during heat treatment. For example, the number of repetitions of the unit cells and / or the size of the unit cells may be adjusted in consideration of the expansion characteristics of each region of the porous structure (e.g., the central region or the peripheral region).

[0044] In this way, by setting the number of repetitions of the unit cells in the porous structure, it is possible to produce a porous structure of a desired size. However, the number of repetitions is not limited to this and may be set appropriately according to requirements.

[0045] 2, the internal structure 1c of the porous structure 1 is formed so that its size (pore diameter and flow path width) increases in the direction in which the fluid (air bubbles) are discharged. That is, the internal structure 1c is formed so that the pore diameter d2 on the fluid (air bubble) discharge side (separator side) is larger than the pore diameter d1 on the fluid (air bubble) supply side (electrolyte membrane side). This allows air bubbles trapped inside the porous structure 1 to be smoothly discharged to the outside, improving the flow path performance of the porous structure. As a result, the performance of the device (e.g., electrochemical device) can be improved.

[0046] Furthermore, if the pore size (diameter) of the pores 1a is too small, the resistance to the fluid increases, slowing the fluid supply speed. Furthermore, if the pore size of the pores 1a is too large, it becomes difficult to increase the contact surface between the bubbles and the porous structure, the size of the bubbles required for the bubbles to escape increases, and it takes a long time for the bubbles to escape. Therefore, the pore size of the pores 1a is preferably formed to be 1 μm or more and 100 μm or less. The lower limit of the pore size is more preferably 10 μm or more. Specifically, the pore size of the pores 1a included in the first and second layers of the periodic structure, counting from the fluid supply side of the porous structure 1, is preferably 20 μm or more and 30 μm or less.

[0047] The diameter of the holes 1a is preferably set to satisfy the conditional expression shown in Fig. 3. When the diameter of the holes 1a satisfies the conditional expression shown in Fig. 3, bubbles can easily pass through the holes 1a. This can increase the efficiency of discharging bubbles from the porous structure 1.

[0048] Furthermore, if the porosity of the porous structure 1 is too small, the pressure loss of the fluid flowing inside the porous structure 1 increases, while if it is too large, the mechanical strength of the porous structure 1 decreases. Therefore, the porosity is preferably 20% or more and 99% or less. Furthermore, the porosity is more preferably 80% or more and 95% or less.

[0049] Furthermore, if the wall thickness of the porous structure 1 is too small, the mechanical strength of the porous structure 1 decreases, and if it is too large, the size of the porous structure 1 becomes too large. Therefore, the wall thickness may be 10 μm or more and 500 μm or less. More preferably, it is 50 μm or more and 200 μm or less. However, this does not apply when a larger or smaller size porous structure 1 is produced.

[0050] Furthermore, if the surface roughness Ra of the porous structure 1 is too large, the pressure loss of the fluid flowing inside the porous structure 1 increases, so the surface roughness Ra is preferably 50 μm or less. The surface roughness Ra is more preferably 5 μm or less, and even more preferably 1 μm or less.

[0051] The porous structure may be made of a material selected from the group consisting of carbon, inorganic materials, metals, metal alloys, metal carbides, oxides, nitrides, and composite materials containing any of these. The composite material may have a core-shell structure.

[0052] Examples of materials constituting the porous structure include lithium (Li), sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), sulfur (S), potassium (K), calcium (Ca), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), arsenic (As), strontium (Sr), yttrium (Y), and zirconium (Z). r), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), indium (In), tin (Sn), (Sb), barium (Ba), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg), titanium (Ti), lead (Pb), bismuth (Bi), polonium (Po), neodymium (Nd), and ytterbium (Yb) may also be used.

[0053] If the content of carbon (C) as an impurity in the porous structure 1 is too low, the mechanical properties will be reduced, and if it is too high, the electrical conductivity and thermal conductivity will be reduced, affecting the performance of the device (electrochemical device). Therefore, the content of carbon as an impurity is preferably 0.1 wt% to 5 wt%, more preferably 0.1 wt% to 1%, or 1 wt% to 5 wt%. In this way, by including carbon as an impurity in the porous structure 1, it is possible to increase the mechanical strength while maintaining the electrical conductivity and thermal conductivity.

[0054] When carbon (C) is contained as a metal carbide (e.g., tungsten carbide (WC), titanium carbide (TiC), etc.), the carbon content is preferably 3 wt % or more and 40 wt % or less, and more preferably 6 wt % or more and 20 wt % or less.

[0055] (Method for manufacturing porous structure) First, a general flow of the manufacturing process of the porous structure 1 will be described.

[0056] 4A to 4C are diagrams showing an example of a manufacturing process for the porous structure 1. As shown in Fig. 4A, first, a photoresin solution, which is a homogeneous solution of a photosensitive binder, is prepared as a starting material (Fig. 4A).

[0057] Next, a three-dimensional organogel structure that will serve as a prototype (template) of the porous structure 1 is 3D printed (additive manufacturing) in the photoresin solution by photolithography (FIG. 4B). A polymer gel network is formed inside this organogel. Examples of photolithography methods that can be used include DLP (Digital Light Processing) and SLA (Stereolithography Apparatus). UV-curable resin (photoradical polymerization) can be used as the photoresin.

[0058] Next, the organogel is converted into a hydrogel, and metal precursors (metal ions) are incorporated into the three-dimensional structure of the hydrogel by swelling (FIG. 4(C)).

[0059] Next, the three-dimensional structure of the hydrogel containing the metal precursor (metal ion) is baked to obtain a three-dimensional structure made of metal oxide (FIG. 4(D)).

[0060] Then, by reducing the fired three-dimensional structure made of metal oxide, a porous structure 1 made of a desired metal or alloy is obtained (FIG. 4(E)).

[0061] In this way, the porous structure 1 is obtained by firing and reducing the hydrogel structure containing the metal precursor.

[0062] Next, a method for producing the porous structure 1 will be specifically described.

[0063] FIG. 5 is a flowchart showing an example of a method for manufacturing the porous structure 1.

[0064] [Preparation of Photoresin Solution] As shown in FIG. 5, first, a photoresin solution (photocurable resin solution) to be used for stereolithography is prepared (see step S1 in FIG. 5 / FIG. 4(A)).

[0065] Specifically, for example, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-ylphenyl)-butan-1-one (Irgacure 379; iGM Resins), bis[4-(dimethylamino)phenyl]methanone (Michler's ketone; Sigma-Aldrich), and 1-(phenyldiazenyl)naphthalen-2-ol (Sudan I; Sigma-Aldrich) are added to DMF (Sigma-Aldrich, >99.9%) and stirred. This solution is then added to a mixture of DMF and PEGda Mn = 575 (Sigma-Aldrich), and the resulting mixture is used as a photoresin solution.

[0066] Next, the photoresin solution is molded into a three-dimensional organogel structure by stereolithography (see step S2 in FIG. 5 / FIG. 4(B)). This three-dimensional structure corresponds to the three-dimensional structure of the porous structure 1 and serves as a scaffold for introducing a metal precursor in a subsequent step (step S4).

[0067] Specifically, for example, based on the three-dimensional data of the porous structure 1 described in Fig. 2, a DLP 3D printer with a wavelength of 405 nm is used to mold a photoresin solution into an organogel (gel structure) having a three-dimensional structure corresponding to the porous structure 1. Here, the gel structure is a polymer structure containing a solvent.

[0068] [Conversion of Organogel to Hydrogel] Next, the organogel is converted to a hydrogel by solvent exchange (see step S3 in FIG. 5 / FIG. 4(C)). This removes the DMF (photoresin component) remaining in the three-dimensional structure, allowing the metal precursor to be uniformly distributed when it is introduced in the subsequent step (step S4).

[0069] Specifically, for example, a 3D-printed organogel is immersed in DMF on a hot plate at 70°C for 1 hour. After the first DMF rinse, the DMF is decanted, and the organogel is again immersed in fresh DMF at 70°C for 1 hour. The organogel is then immersed in deionized water at 70°C for 1 hour, followed by fresh deionized water at 70°C for 1 hour, converting the 3D structure from organogel to hydrogel. This hydrogel is also a gel structure (polymer structure).

[0070] [Introduction of Metal Precursor] Next, the hydrogel is swelled in a metal salt solution to introduce a metal precursor (metal ion) into the three-dimensional structure (gel structure) of the hydrogel (step S4 in FIG. 5 / FIG. 4(C)).

[0071] Specifically, for example, a 2M solution of copper nitrate, nickel nitrate, iron nitrate, cobalt nitrate, silver nitrate, chromium nitrate, or ammonium metatungstate is prepared in deionized water, and the three-dimensional hydrogel structure is immersed in the desired metal salt solution at 70°C for 24 hours or at 70°C for 2 weeks (in the case of a tungsten-nickel alloy).This causes metal ions to precipitate in the three-dimensional hydrogel structure.

[0072] The metal precursor (metal ion) may be mixed in advance with the photoresin solution in step S1. In this case, the organogel in step S2 already contains the metal precursor, and step S4 may be omitted.

[0073] [Baking] Next, the three-dimensional hydrogel structure (gel structure) containing the metal precursor (metal ion) is baked to remove the gel component (step S5). After baking, the three-dimensional structure is composed of metal oxide (see FIG. 4(D)).

[0074] Specifically, for example, a three-dimensional structure of hydrogel containing a metal precursor (metal ion) is baked in an air stream under low pressure.

[0075] [Reduction] Then, the fired three-dimensional structure (metal oxide structure) made of metal oxide is reduced (step S6).

[0076] Specifically, the fired three-dimensional structure is then heated in forming gas at a flow rate of 150 sccm, a pressure of approximately 22 Torr, and a rate of 3°C per minute to 900°C or 700°C (for Cu and Ag), and then isothermally maintained for 6 hours for reduction, thereby obtaining a porous structure 1 made of the desired metal or alloy (see FIG. 4(E)).

[0077] When an attempt is made to increase the porosity of a porous structure using conventional manufacturing methods, the sintering of the metal powders is weak, resulting in very low mechanical strength and high surface roughness. On the other hand, according to the manufacturing method of the porous structure 1 according to the present embodiment, the final porous structure 1 contains carbon as an impurity, so that the porosity can be increased without decreasing the mechanical strength, and the surface roughness can also be reduced.

[0078] As shown in Fig. 7, a porous structure 1 made of a composite material of carbon and reduced metal or carbide (a mixture of metal and carbon) can be produced by heat-treating a hydrogel (gel structure) containing metal ions in a vacuum without firing it. That is, as shown in Fig. 8, a porous structure 1 made of a mixture of metal and carbon can be produced by carrying out a step (step S51) of heat-treating the hydrogel (gel structure) after the step (S4) of introducing a metal precursor into the hydrogel.

[0079] 9, the porous structure 1 made of carbon can be produced by heat-treating the organogel (gel structure) in a vacuum. That is, as shown in FIG. 10, the porous structure 1 made of carbon can be produced by performing a step (step S31) of heat-treating the organogel (gel structure) after a step (step S4) of molding a three-dimensional structure (gel structure) of the organogel by stereolithography 3D printing.

[0080] Furthermore, although an example in which a gel structure (a polymer structure containing a solvent) is used as the polymer structure has been described, a polymer structure containing no solvent may also be used. That is, the porous structure 1 may be produced by heat-treating a polymer structure containing no solvent. <Second Embodiment> Next, a second embodiment will be described, which is an example in which the porous structure 1 is used in a fuel cell. Components similar to those in the first embodiment are designated by the same reference numerals, and duplicated explanations will be omitted.

[0081] Fig. 6 is a diagram showing an example of a schematic configuration of a fuel cell 200 according to a second embodiment. As shown in Fig. 6, the fuel cell 200 has a fuel cell 20. The fuel cell 20 includes a fuel electrode (anode) 13A composed of a porous structure 1A and an anode catalyst layer 2A, and an oxygen electrode (cathode) 13C composed of a porous structure 1C and a cathode catalyst layer 2C. In the fuel cell 20, the porous structure 1 (1A, 1C) functions as a porous transport layer (PTL) or a gas diffusion layer.

[0082] An electrolyte membrane 4 is disposed between the fuel electrode 13A and the oxygen electrode 13C. A separator 5A and a separator 5C are disposed on the outer sides of the fuel electrode 13A and the oxygen electrode 13C, respectively. Gaskets 7 and 8 are disposed between the separator 5A and the electrolyte membrane 4, and between the separator 5C and the electrolyte membrane 4, respectively.

[0083] Hydrogen is supplied to the fuel cell 20 from a hydrogen supply unit 120, and oxygen is supplied from an oxygen supply unit 121. Water (HO) produced by the reaction between the hydrogen ions that have moved from the fuel electrode 13A to the oxygen electrode 13C and the oxygen ions is discharged from a discharge unit 119. Note that while Fig. 6 shows an example in which the fuel cell 200 has one fuel cell 20, the fuel cell 200 may have a plurality of stacked fuel cell units 20.

[0084] In this way, the fuel cell according to the second embodiment uses the porous structure 1, which has excellent gas (gas bubble) permeability, as the porous transport layer of the fuel cell 20, and can therefore improve the reaction efficiency of the oxidation-reduction reaction occurring in the fuel cell 20. <Example> Next, an example of the porous structure 1 will be described.

[0085] (Fabricated Samples) In this example, the porous structures of Samples 1 to 3 have a gyroid structure, and the porous structure of Sample 4 has a Schwarz P structure.

[0086] Figure 11 is a photograph showing the appearance of the porous structures of Samples 1 to 3. Figure 12 shows the size (L × W × H), mass (g), density (g / cm) of each sample. ３ ), porosity (%), and wall thickness (μm).

[0087] Figures 13 to 16 are optical microscope photographs of Samples 1 to 4. The optical microscope photograph of Figure 13 (Sample 1) was taken under the following conditions: lens: HR-2500E, wide-range: 140x, H field of view: 2304.86 μm, resolution: 1.13 μm. The optical microscope photograph of Figure 14 (Sample 2) was taken under the following conditions: lens: HR-2500E, wide-range: 140x, H field of view: 2304.86 μm, resolution: 1.13 μm. The optical microscope photograph of Figure 15 (Sample 3) was taken under the following conditions: lens: HR-2500E, wide-range: 140x, H field of view: 2304.86 μm, resolution: 1.13 μm. The optical microscope photograph of FIG. 18 (Sample 4) was taken under the following conditions: lens: HR-2500E, wide-range: 80x, H field of view: 3660.95 μm, resolution: 1.79 μm.

[0088] (Fabrication Method) First, CAD data for the porous structures of Samples 1 to 4 was designed. Next, based on this CAD data, a photocurable gel solution containing PEGda (Polyethylene Glycol Diacrylate) (Mn 700) and DMSO (Dimethyl sulfoxide) was used to create a 3D gel structure using a stereolithography 3D printer. This 3D structure was immersed in water to perform solvent exchange, producing a 3D structure containing water (gel structure). This gel structure was then immersed in a copper ion solution to allow copper ions to penetrate, producing a gel structure containing copper ions. Subsequently, the 3D copper structures with gyrode structures (Samples 1 to 3) were fabricated through calcination in air and reduction in forming gas (see Figure 11).

[0089] (Evaluation Method) After each sample was prepared, its length (L), width (W), and height (H) were measured using a micrometer, its wall thickness was measured using a digital microscope, and its mass was measured using an electronic balance. From these measurements, the density was calculated from (mass) / (length x width x height). The relative density of the sample was calculated by dividing the calculated density by the density of pure copper = 8.96 g / cm. 3 The porosity was calculated from 1 - (relative density). A digital microscope (Hirox Digital Microscope HRX-01) was used to observe the microstructure and measure the surface roughness Ra.

[0090] (Evaluation Results) Figure 17 shows the surface roughness measurement results for each sample. Surface roughness measurements were performed over an arbitrarily selected range of 130 μm. The subnumbers in the sample numbers indicate measurement results at different locations on the same sample. As shown in Figure 17, the arithmetic mean roughness (Ra) of each sample (porous structure) in this example was confirmed to range from 0.5 to 3.3 μm. Furthermore, the maximum height roughness (Rz) of each sample was confirmed to range from 1.5 to 11.2 μm. Furthermore, the 10-point mean roughness (RzJIS) of each sample was confirmed to range from 1.0 to 9.6 μm. As described above, the present invention is not limited to the above-described embodiments. The components can be modified and embodied within the scope of the present invention. Various inventions can be realized by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all of the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined.

Claims

1. A porous structure produced by heat-treating a polymer structure, at least in part of which has a periodic structure in which flow channels whose inner walls are formed by minimal curved surfaces are periodically repeated.

2. The porous structure according to claim 1, further comprising pores communicating with the flow paths.

3. The porous structure according to claim 2, wherein the pores are formed so that the pore diameter increases in the direction in which the bubbles are discharged.

4. The porous structure according to claim 2, wherein the pores are formed so as to satisfy the following condition: Pb - Pl > 2γ cos θ / rp, where Pb: pressure of bubbles, Pl: pressure of liquid, γ: surface tension, θ: contact angle in the liquid phase, and rp: radius of pore.

5. The porous structure according to any one of claims 1 to 4, wherein the polymer structure is formed by stereolithography using a photoresin as a starting material.

6. The porous structure according to claim 5, wherein the polymer structure is a gel structure.

7. The porous structure according to claim 1, which contains carbon as a constituent material.

8. The porous structure according to claim 7, further comprising an inorganic material as a constituent material.

9. The porous structure of claim 8, wherein the inorganic material comprises a metal.

10. The porous structure according to claim 9, wherein the carbon is contained as an impurity, and the carbon content is 0.1 wt % or more and 5 wt % or less.

11. The porous structure according to claim 9 or 10, wherein the carbon is contained as a metal carbide, and the carbon content is 3 wt % or more and 40 wt % or less.

12. The porous structure according to claim 1, having a porosity of 20% or more and 99% or less.

13. The porous structure according to claim 1, wherein the surface roughness Ra of the inner wall is 50 μm or less.

14. The porous structure according to claim 1, wherein the periodic structure is a TPMS (Triply Periodic Minimal Surface) structure.

15. The porous structure according to claim 14, wherein the periodic structure is a gyroid structure.

16. A device comprising the porous structure of claim 1.

17. The device according to claim 16, comprising the porous structure as a gas diffusion layer in an electrolysis cell.

18. The device according to claim 16, comprising the porous structure as a gas diffusion layer or a proton transport layer of a fuel cell.

19. A method for manufacturing a porous structure, comprising: a step of molding a polymer structure that serves as a prototype of the porous structure by stereolithography using a photoresin as a starting material; and a step of heat-treating the polymer structure.

20. The method for producing a porous structure according to claim 19, wherein the polymer structure comprises an inorganic material.

21. The method for producing a porous structure according to claim 20, wherein the inorganic material contains a metal or metal ions.

22. The method for producing a porous structure according to claim 21, wherein the heat treatment step includes a firing step.

23. The method for producing a porous structure according to claim 22, wherein the heat treatment step further includes a reduction step after the firing step.

24. The method for producing a porous structure according to any one of claims 19 to 23, wherein the polymer structure has a periodic structure in which flow paths whose inner walls are formed by minimal curved surfaces are periodically repeated.

25. The method for producing a porous structure according to claim 24, wherein the polymer structure is a gel structure.

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