Fe-Ni alloy film and method for producing the same

Abstract

To provide an electrode that exhibits an excellent effect.SOLUTION: There is provided an Fe-Ni alloy film containing Fe and Ni, in which multiple holes are formed on the surface of the alloy film in the depth direction from an opening, and nanoparticles are dispersed on the surface of the holes. A composition of Fe-Ni composing the alloy film is different from that of Fe-Ni composing the nanoparticles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an Fe—Ni alloy film and a method for producing the same, a laminate in which the alloy film is formed on a substrate, and a battery including the laminate. [Background technology]

[0002] Nanoporous anodic oxide films formed by the anodization of transition metals have a large surface area, and therefore, electrodes (especially oxygen evolution reaction (OER) electrodes) equipped with these films have been actively studied for their application to secondary batteries, electrochemical capacitors, and water electrolysis. In particular, anodic oxide films of iron (Fe) and Fe alloys, which are based on inexpensive and abundant Fe, have attracted considerable attention as they can be used as electrodes for water splitting applications suitable for low-cost mass production (Non-Patent Documents 1-3).

[0003] It is known that the composition of oxide films produced by anodization is strongly dependent on the composition of the base material from which they are made. Therefore, when using an anodized film as an electrode, it is essential to control the metal composition of the raw material used for anodization. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Fan et al.NATURE COMMUNICATIONS,2018,9,1809 [Non-patent document 2] Yu et al.RSC Advances,2012,2,12177 [Non-patent document 3] In Situ Activation of Anodized Ni-Fe Alloys for the Oxygen Evolution Reaction in Alkaline Media,ACS Appl.EenergyMater.2020,3,12316-12326 Summary of the Invention [Problem to be solved by the invention]

[0005] The anodic oxide film produced by the conventional technology has a problem in that it does not exhibit a fully satisfactory electrochemical effect when used as an electrode. Therefore, an object of the present invention is to provide an electrode that exhibits excellent electrochemical effect. [Means for solving the problem]

[0006] The present inventors adopted a Ni-Fe alloy plating film as the metal to be anodized, and after careful consideration of its composition, analyzed electrodes containing the anodized film. As a result, they found that a treated film obtained by anodizing and heat-treating an alloy film having a specific composition ratio exhibits extremely excellent electrochemical effects. The present disclosure is an invention completed based on this finding, and broadly includes the following aspects of the invention.

[0007] Item 1 An Fe-Ni alloy film containing Fe and Ni, a plurality of holes are formed on the surface of the alloy film in a depth direction from the opening portion, Furthermore, nanoparticles are present in a dispersed state on the surfaces of the pores, the Fe—Ni composition constituting the alloy film is different from the Fe—Ni composition constituting the nanoparticles; Fe-Ni alloy film.

[0008] Item 2. The Fe—Ni alloy film according to item 1, wherein the pores have an average pore size of 5 to 100 nm.

[0009] Item 3. The Fe—Ni alloy film according to item 1 or 2, wherein the nanoparticles have an average particle size of 10 to 50 nm.

[0010] Item 4. The Fe—Ni alloy film according to any one of Items 1 to 3, wherein the content of the Ni component constituting the alloy film is lower than the content of the Ni component constituting the nanoparticles.

[0011] Item 5: A method for producing an Fe—Ni alloy film according to any one of items 1 to 4, (1) anodizing an alloy film containing Fe and Ni; and (2) heat-treating the anodized film obtained in step 1; A method for producing an Fe—Ni alloy film, comprising:

[0012] Item 6. The manufacturing method according to item 5, wherein the alloy film containing Fe and Ni that is anodized contains 30 atomic percent (at %) or more of iron.

[0013] Item 7: A laminate comprising an alloy film containing Fe and Ni according to any one of items 1 to 4 above formed on a substrate.

[0014] Item 8. The laminate according to item 7, which is used for an electrode.

[0015] Item 9. A battery comprising the laminate according to item 7. [Effects of the Invention]

[0016] According to the present invention, an electrode that exhibits excellent electrochemical effects can be provided, more specifically, an electrode that exhibits excellent OER effects can be provided. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 shows an SEM image of the Fe—Ni alloy film of the present invention and its schematic diagram. [Figure 2] FIG. 2 is a diagram showing the results of a comparison based on Ni composition in Experimental Example 1. [Figure 3] FIG. 3 is a diagram showing the results of a comparison between the alloy film manufacturing methods in Experimental Example 1. [Figure 4] FIG. 4 is a diagram showing the results of Fe and Ni distribution in Experimental Example 1. [Figure 5] FIG. 5 is a diagram showing the results of the film thickness of the Fe—Ni alloy film in Experimental Example 1. [Figure 6] FIG. 6 shows the results of the OER activity evaluation in Experimental Example 1. [Figure 7] FIG. 7 is a diagram showing the results of Experimental Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described below. In the following, unless otherwise specified, the symbol "to" indicating a numerical range does not mean "less than" or "exceeding," but rather "greater than or equal to or less than." In other words, "A to B" means "greater than or equal to A and less than or equal to B," and both A and B are included.

[0019] In this specification, the expression "comprise" or "contain" a certain component includes the component in question, and may further include other components.

[0020] The Fe-Ni alloy film of the present invention contains Fe and Ni. In addition to Fe and Ni, other metal components may be contained within the range that does not impair the effects of the present invention. Examples of such metal components include Mn, Co, Mo, W, and Cr.

[0021] A plurality of holes are formed on the surface of the Fe-Ni alloy film in the depth direction from the opening. The specific number of the holes is not particularly limited as long as the effects of the present invention can be achieved. For example, the number of holes is usually 1 x 10 per surface area of ​​the Fe-Ni alloy film (the surface area is the area of ​​the horizontal surface of the Fe-Ni alloy film excluding the surface area of ​​the holes). 9 ~3x10 12 pieces / cm 2 The holes are formed at a ratio of about 1.2x10 9 ~2.5x10 12 pieces / cm 2 Approximately, more preferably 1.3x10 9 ~2.2x10 12 pieces / cm 2 Approximately, most preferably 1.5x10 9 ~2x10 12 pieces / cm 2 That's about it.

[0022] The average pore size of the pores is not particularly limited as long as the effects of the present invention are achieved. The average pore size of such pores can usually be about 5 to 100 nm. From the viewpoint of further improving electrode performance, the average pore size of the pores is preferably about 30 to 80 nm, more preferably about 40 to 60 nm. By setting the average pore size to 30 nm or more, it is expected that when the Fe—Ni alloy film is applied to an electrode, deterioration of electrode performance due to inhibition of bubble detachment during OER will not occur. Furthermore, by setting the average pore size to 60 nm or less, it is expected that when the Fe—Ni alloy film is applied to an electrode, a sufficient electrode surface area can be obtained. The average pore size can be calculated by measuring, for example, SEM images of sample surfaces observed with a scanning electron microscope (SEM, JEOL Ltd. JSM-6700F) and cross-sectional images of oxide films observed with a scanning transmission electron microscope (STEM, JEOL Ltd. JEM-2100F) using a length measurement function of image processing software.

[0023] The Fe-Ni alloy film further contains nanoparticles dispersed on the surfaces of the pores. The number of such nanoparticles present on the surfaces of the pores is not particularly limited as long as the effects of the present invention are achieved. Typically, the number is 6 x 10 9 ~1.5x10 14 pieces / cm 2 The surface of the hole may be present in a proportion of about 8x10 9 ~1.45x10 14 pieces / cm 2 A ratio of about 1x10 10 ~1.4x10 14 pieces / cm 2 The surface of the pores may be present in a proportion of about 100%.

[0024] The average particle size of the nanoparticles is not particularly limited as long as the effects of the present invention can be achieved. The average particle size of the nanoparticles can usually be about 10 to 50 nm. More preferably, the average particle size of the nanoparticles can be about 10 to 40 nm. The average particle size can be calculated by measuring the length of an elemental mapping image of Fe and Ni in a cross section of an oxide film obtained by EDS analysis using a scanning transmission electron microscope (STEM, JEOL Ltd. JEM-2100F) using a length measurement function of image processing software.

[0025] The Fe-Ni composition of the alloy film is different from the Fe-Ni composition of the nanoparticles. More specifically, the mass ratio of the Ni component in the Fe-Ni composition of the alloy film to the Ni component in the Fe-Ni composition of the nanoparticles is 1:1 to 1:5. This mass ratio is a measurement value measured using the same measuring equipment and conditions as in the measurement method in the Examples described below.

[0026] The thickness of the Fe-Ni alloy film is not particularly limited as long as the effects of the present invention are exhibited. It can usually be about 0.2 to 30 μm. The thickness of the Fe-Ni alloy film is more preferably about 0.3 to 20 μm, and most preferably about 1 to 17 μm. The above values ​​are measured using the same measuring equipment and under the same conditions as those used in the Examples described below.

[0027] A schematic diagram and a typical example of an SEM image of the Fe—Ni alloy film of the present invention are shown in FIG. 1. As shown, the porous film has a plurality of pores formed on the surface of the porous film from the opening in the depth direction. Furthermore, a plurality of pores are present on the surface of the alloy film (upper part of the figure), and the pores are arranged in a comb-like pattern from the opening in the depth direction (lower part of the figure). Furthermore, the pores are roughly linear, with almost no branching.

[0028] In the schematic diagram of the alloy film shown in FIG. 1(a), nanoparticles are present in a dispersed state on the surface of the pores, as shown in black.

[0029] The content of the Ni component constituting the Fe—Ni alloy film is preferably lower than the content of the Ni component constituting the nanoparticles. That is, the content of the Fe component constituting the Fe—Ni alloy film is preferably higher than the content of the Fe component constituting the nanoparticles. In the Fe—Ni alloy film, Ni oxide has high catalytic activity in electrochemical reactions, while Fe oxide has high electrical conductivity. Therefore, when the Fe—Ni alloy film with high electrical conductivity contains nanoparticles with high catalytic activity, an electrode containing the alloy film can exhibit excellent electrochemical activity, particularly OER activity.

[0030] As described above, the content of the Ni component constituting the nanoparticles dispersed in the Fe—Ni alloy film of the present invention is preferably higher (Ni-rich) than the content of the Ni component constituting the Fe—Ni alloy film. That is, the content of the Fe component constituting the Fe—Ni alloy film is preferably higher (Fe-rich) than the content of the Fe component constituting the nanoparticles. While composite oxides of Fe and Ni have excellent electrochemical reaction activity (especially for OER), the addition of Ni inevitably reduces their electrical conductivity. Therefore, with the structure of a uniform porous Ni—Fe film as disclosed in Non-Patent Document 3, it is difficult to achieve both improved electrode reaction activity and maintained electrical conductivity.

[0031] The Fe-Ni alloy film of the present invention has both high electrical conductivity due to its high Fe content and high catalytic activity in electrochemical reactions due to the high Ni content of the nanoparticles dispersed in the Fe-Ni alloy film, making it possible to achieve both improved electrode reaction activity and maintenance of electrical conductivity. Therefore, by applying the Fe-Ni alloy film of the present invention to an electrode, it is possible to exhibit excellent electrocatalytic activity, particularly OER activity.

[0032] The method for producing the Fe—Ni alloy film includes the following steps 1 and 2.

[0033] Step 1: A step of anodizing an alloy film containing Fe and Ni.

[0034] Step 2: A step of heat treating the anodized film obtained in step 1.

[0035] The Fe content in the alloy film containing Fe and Ni used in step 1 is not particularly limited as long as the effects of the present invention are achieved. For example, an alloy film containing about 30 at% or more of iron can be used. More preferably, the alloy film contains about 50 at% or more of iron, and most preferably, an alloy film containing about 55 at% or more of iron. By setting the iron content to 55 at% or more, it is expected that a columnar pore structure oriented perpendicular to the substrate can be generated, which is beneficial for the mass transfer of reactants and products inside the pores.

[0036] The alloy film used as the production raw material in step 1 above can be produced by a known method. Examples include alloy films produced by wet film-forming methods, mechanical alloying methods, and vapor phase deposition methods. Among these, alloy films produced by wet film-forming methods are preferred. These alloy production methods, unlike the melting and casting method, which is a common alloy production method, do not include high-temperature processes in the production process, which suppresses the coarsening of crystal grains. As a result, it is presumed that the fine nanocrystalline grain structure of the alloy film is inherited by the porous structure, thereby realizing the generation of nanoparticles on the pore surfaces.

[0037] A wide variety of known electrolytic solutions can be used as the electrolytic solution used in the anodizing treatment in step 1. Examples include an ethylene glycol solution containing water, ammonium fluoride, sodium fluoride, or the like at a concentration of about 0.05 to 3 moles per liter (mol / L). More specifically, examples include an ethylene glycol solution containing ammonium fluoride at a concentration of about 0.05 to 3 mol / L, sodium fluoride at a concentration of about 0.1 to 2 mol / L, and water at a concentration of about 0.1 to 3 mol / L.

[0038] Known conditions can be adopted for the anodizing treatment in the above step 1. For example, the treatment can be performed at a voltage of about 5 to 80 V for about 20 to 3600 seconds.

[0039] The heat treatment conditions in step 2 can be those of known methods. Specifically, the heat treatment can be carried out in an atmosphere of an inert gas such as nitrogen or argon, the air, or a vacuum. Of these, it is preferable to carry out the heat treatment in a nitrogen atmosphere. The heat treatment time can usually be about 5 to 300 minutes, preferably about 30 to 120 minutes, and most preferably about 30 to 60 minutes.

[0040] The heat treatment temperature in step 2 can also be determined by a known method. Specifically, the temperature is about 573 to 873 K, more preferably about 623 to 773 K, and most preferably about 623 to 723 K. By setting the temperature at 573 K or higher, the crystallinity of the film is improved, and the conductivity is expected to be improved. Furthermore, by setting the temperature at 873 K or lower, the collapse of the porous structure due to the heat treatment can be suppressed, and a high surface area can be maintained.

[0041] The above-described alloy film containing Fe and Ni can be used to form a laminate together with a substrate. That is, the laminate of the present invention can be formed by forming the above-described alloy film on a substrate. Specifically, the laminate can be produced by forming the alloy film on the substrate by an Fe-Ni plating method or the like, followed by anodizing and heat treatment. Specific conditions can be as described above.

[0042] The material of the substrate is not particularly limited as long as it can exhibit the effects of the present invention. Specific examples include copper (Cu), nickel (Ni), aluminum (Al), carbon (C), and alumina ceramics. Among these, Cu and Ni are preferred. Furthermore, the thickness of the substrate is also not particularly limited as long as it can exhibit the effects of the present invention. Specific examples include a thickness of about 1 to 100,000 μm. A thickness of about 100 to 5,000 μm is more preferred.

[0043] The laminate contains the Fe—Ni alloy film of the present invention, and therefore can be suitably used as an electrode. That is, the electrode of the present invention includes the laminate.

[0044] The electrode of the present invention can be used in a variety of applications. Specific examples include electrodes installed in water electrolytic cells for hydrogen production, electrodes installed in metal-air secondary batteries, electrodes installed in wet surface treatment electrolytic cells, electrodes installed in fuel cells, and electrodes installed in supercapacitors. Among these, electrodes used as electrodes exhibiting the OER electrode effect, such as electrodes installed in water electrolytic cells for hydrogen production, electrodes installed in metal-air secondary batteries, and electrodes installed in wet surface treatment electrolytic cells, are preferred.

[0045] The various characteristics, such as properties, structures, and functions, described for each embodiment of the present invention above can be combined as appropriate to specify the aspects included in the present invention. In other words, the present invention can include all inventions of the aspects of each characteristic that can be combined as disclosed in this specification. [Example]

[0046] The following examples are provided to explain the present invention in more detail, but it goes without saying that the present invention is not limited to the examples shown below.

[0047] (Experimental Example 1) 1. Preparation of Fe-Ni alloy plating film Using a Cu substrate as the working electrode and a pure iron plate as the counter electrode, constant current electroplating was performed under various conditions in the baths shown in Table 1 (citric acid bath: for low Ni composition) or Table 2 (malonic acid bath: for medium to high Ni composition) to produce Fe-Ni alloy plating films with different Ni compositions on the substrate. The plating time was 10 minutes unless otherwise specified.

[0048] The values ​​of each compound in the table are expressed in mol / L, and the manufacturers of each compound are Nacalai Tesque for diammonium hydrogen citrate, malonic acid, and saccharin sodium, and Fujifilm Wako Pure Chemical Industries for the others.

[0049] The plating film thickness and composition were determined by fluorescent X-ray FP method (SEA6000VX manufactured by Hitachi High-Tech Science).

[0050] [Table 1]

[0051] [Table 2]

[0052] 2. Anodizing The Fe-Ni alloy plating film prepared in step 1 above was anodized in an ethylene glycol electrolyte containing 0.1 mol / L ammonium fluoride and 0.5 mol / L distilled water. The bath temperature was 20°C, and anodization was carried out at a low voltage of 40 V. The electrolysis time is shown in Table 3 below.

[0053] [Table 3]

[0054] 3.Heat treatment The anodized film prepared in step 2 above was heat-treated in an alumina tubular heat treatment furnace at a predetermined temperature for 30 minutes. During the heat treatment, nitrogen or argon gas with a purity of 99.999% was passed through the furnace at a flow rate of 100 mL / min to create an inert gas atmosphere. The heating and cooling rates up to the predetermined temperature were controlled at 2.5 K / min. These Fe-Ni alloy films are essentially composed of Fe, Ni, and O, but may contain other components as long as the effects of the present invention are not impaired, as described above.

[0055] (Comparative Example) As a comparative example, a melt-cast Fe—Ni alloy plate (manufactured by Nilaco Corporation) containing 42% Ni was anodized and heat-treated in the same manner as Samples 1-10.

[0056] The longitudinal cross-sections of the oxide films thus produced were observed using a scanning transmission electron microscope (STEM, JEOL JEM-2100F) in the usual manner. Thin film specimens for STEM longitudinal cross-section observation were processed using an ion slicer (JEOL EM-09100IS). Cross-sections of some specimens were observed using a focused ion beam processing and observation system (FIB, JEOL JIB-4000) in the usual manner.

[0057] (Comparison by Ni composition) Figure 2 shows a STEM dark-field image (A) and a STEM-EDS elemental mapping analysis image (B) of the film after heat treatment. The heat treatment was carried out at 673 K. In the STEM-EDS elemental mapping analysis image (B), red indicates Fe and green indicates Ni.

[0058] From the results of the STEM dark-field image in (A), it was not possible to determine that multiple holes were formed in the depth direction from the opening under the plating conditions (79 at% Ni) of Sample 10. Furthermore, it became clear that multiple holes were formed in the depth direction from the opening under the plating conditions (5 at% Ni) of Sample 1, the plating conditions (10 at% Ni) of Sample 2, and the plating conditions (68 at% Ni) of Sample 9.

[0059] The average pore diameter of these pores was approximately 25 nm for the plating conditions of Sample 1 (5 at% Ni) and approximately 35 nm for the plating conditions of Sample 2 (10 at% Ni). This average pore diameter was calculated based on the area per pore obtained by filling in the pores in the images taken by SEM surface observation using the image processing software ImageJ and using the software's particle analysis function. In addition, for some samples, the pore diameter was calculated from the results of measuring the diameter in TEM cross-sectional observation images using ImageJ.

[0060] Furthermore, from the STEM-EDS elemental mapping analysis image shown in Figure 2(B), it was not possible to determine that multiple pores extending from the opening in the depth direction contained Fe as the main component and that nanoparticles containing Ni as the main component were dispersed within the pores under the plating conditions for Sample 1. In contrast, under the plating conditions for Sample 2, it was confirmed that multiple pores extending from the opening in the depth direction contained Fe as the main component and that nanoparticles containing Ni as the main component were dispersed within the pores.

[0061] The average particle size of the nanoparticles containing Ni as the main component was approximately 20 nm under the plating conditions for Sample 2. This average particle size was calculated by measuring the particle size of the nanoparticles in the STEM-EDS image using the image processing software ImageJ.

[0062] (Comparison by alloy film manufacturing method) Figure 3 shows the results of STEM dark-field images (grayscale) and STEM-EDS elemental mapping analysis (color) of an alloy-plated film produced under the plating conditions of Sample 6 (42 at% Ni) and subjected to anodization and heat treatment at 673 K as described above, and of a film of the alloy of Comparative Example 1 similarly subjected to anodization and heat treatment. In Sample 6 (B), the STEM dark-field image confirmed that multiple pores were formed in the depth direction from the opening, and the multiple pores in the depth direction from the opening contained Fe as a primary component, and STEM-EDS elemental mapping analysis confirmed the presence of nanoparticles primarily composed of Ni therein. On the other hand, in the comparative example (A), although multiple pores were confirmed to be formed in the depth direction from the opening, the presence of nanoparticles primarily composed of Ni was not confirmed.

[0063] Therefore, by using a plated film as the alloy film subjected to anodization and heat treatment, a film was produced in which multiple holes were formed in the depth direction from the opening and, further, nanoparticles were present in a dispersed state on the surface of the holes.

[0064] (Fe and Ni distribution) Figure 4(A) shows the results of STEM-EDS elemental mapping analysis of an alloy-plated film produced under the plating conditions of Sample 6 (42 at% Ni) and subjected to anodization and heat treatment at 673 K as described above. As above, red and green indicate Fe and Ni, respectively. These results show that the main component of the multiple pores (pore walls) extending from the openings in the depth direction is Fe, and that the main component of the nanoparticles dispersed therein is Ni.

[0065] The results were also examined by STEM-EDS elemental mapping analysis of the alloy-plated films produced under the plating conditions of Samples 3, 5, 6, and 9, which were subjected to anodization and heat treatment at 673 K as described above. Figure 4(B) shows the results. Specifically, the local composition was extracted using the extraction function of the EDS mapping software attached to the JEOL JEM2100F transmission electron microscope used, and the Fe and Ni ratios were calculated. These results revealed that, under all plating conditions, the Ni content in the nanoparticles was greater than that in the pore walls. It was also revealed that an Fe-Ni alloy film containing 70 at% Ni or less, i.e., 30 at% or more of Fe, subjected to anodization and heat treatment at 673 K, is preferable.

[0066] (Fe-Ni alloy film thickness) Figure 5(A) shows a STEM dark-field image of a film produced by anodizing and heat-treating an Fe-Ni alloy plated film produced under the plating conditions of Sample 6 (42 at% Ni), Figure 5(B) shows the results of STEM-EDS elemental mapping analysis, and Figure 5(C) shows a STEM dark-field image of the entire film. The enlarged upper part of (C) corresponds to (A) and (B), and it can be seen that a Cu substrate is present in the lower part of (C).

[0067] In addition, in the film after the above heat treatment, the distance from the Cu substrate to the top of the film, that is, the film thickness after the above heat treatment, was 16.2 μm.

[0068] (OER activity evaluation) OER activity tests were performed on Fe-Ni alloy film samples prepared by anodizing and heat treatment using the alloy plating films prepared under the conditions of Samples 2 and 6. The alloy films were fabricated on 0.3 mm-thick pure copper substrates. The OER activity tests were performed using a Biologic VSP electrochemical measurement system, as shown in the schematic diagram of Figure 6(A). The reference electrode (RE) was Hg / HgO (0.1 mol / L KOH), the counter electrode (CE) was a platinum wire, and the sweep rate was 10 mV / s. The electrolyte used was an oxygen-saturated 0.1 mol / L KOH solution. Prior to the experiment, the dissolved oxygen concentration in the electrolyte was saturated by passing 99.995% oxygen gas through the solution for approximately 15 minutes. Anodic polarization curves were obtained using a three-electrode electrochemical cell with a platinum wire counter electrode and a mercury / mercury oxide reference electrode. As a comparative example, a melt-rolled Fe—Ni alloy plate (manufactured by Nilaco Corporation) containing 42 at% Ni was used instead of the alloy film produced under the conditions of Sample 2 or 6. The results are shown in FIG.

[0069] The results shown in Figure 6 reveal that the electrode containing the anodized and heat-treated alloy film, which was produced under the same plating conditions as Samples 2 and 6, exhibits an improved OER current compared to the electrode containing the anodized and heat-treated alloy film of the comparative example. This result is thought to be due to the fact that, although the comparative example electrode forms a porous film by anodization and heat treatment as shown in Figure 3, nanoparticles primarily composed of Ni are not dispersed.

[0070] (Experimental Example 2) In addition, the above-mentioned heat treatment temperature was examined for anodized alloy-plated films produced under the plating conditions of Sample 6 (42 at% Ni) at 573 K, 873 K, and 1073 K. Figure 7(A) shows a STEM dark-field image, Figure 7(B) shows the STEM-EDS elemental mapping analysis results, and Figure 7(C) shows a FIB SIM image. After heat treatment at 573 K, the formation of a porous phase was confirmed in the STEM dark-field image, and the clear separation of the Fe and Ni phases was also confirmed in the STEM-EDS elemental mapping analysis results. Furthermore, after heat treatment at 1073 K, the formation of a porous film was not confirmed. This is likely due to the high heat treatment temperature. Furthermore, as shown in the SIM image in Figure 7(C), after heat treatment at 873 K, most of the porous layer of the oxide film disappeared, but the porous structure remained near the surface.

[0071] (Experimental Example 3) The Cu substrate used in Experimental Example 1 was replaced with a Ni substrate, and an Fe-Ni alloy plating film was produced under specified plating conditions. The resulting alloy film was subjected to anodization and heat treatment, resulting in a structure similar to that produced on a Cu substrate (data not shown).

Claims

1. An Fe—Ni alloy film containing Fe and Ni, a plurality of holes are formed on the surface of the alloy film in a depth direction from the opening portion, Furthermore, nanoparticles are present in a dispersed state on the surfaces of the pores, A laminate in which an Fe—Ni alloy film is formed on a substrate, the Fe—Ni composition of which is different from the Fe—Ni composition of which the nanoparticles are made.

2. 2. The laminate according to claim 1, wherein the pores have an average pore size of 5 to 100 nm.

3. 3. The laminate according to claim 1, wherein the nanoparticles have an average particle size of 10 to 50 nm.

4. 4. The laminate according to claim 1, wherein the content of the Ni component constituting the alloy film is lower than the content of the Ni component constituting the nanoparticles.

5. A method for producing the laminate according to any one of claims 1 to 4, (1) a step of anodizing an alloy film containing Fe and Ni formed on a substrate; and (2) heat-treating the anodized film obtained in step 1; The method for producing an Fe—Ni alloy film comprises:

6. 6. The manufacturing method according to claim 5, wherein the alloy film containing Fe and Ni that is subjected to the anodizing treatment contains iron in an amount of 30 atomic percent (at %) or more.

7. The laminate according to claim 1, which is used for an electrode.

8. A battery comprising the laminate according to claim 1.

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