TW202003100A - Hydrogen permeable membrane and method for producing same - Google Patents

Abstract

This hydrogen permeable membrane comprises an alloy film which contains Pd and Cu. This alloy film is an electrolytic plating film and has a BCC structure; and the Pd:Cu ratio (atomic ratio) in this alloy film is from 4:6 to 6:4.

Description

Hydrogen penetrating membrane and manufacturing method thereof

The invention relates to a hydrogen penetrating membrane and a manufacturing method thereof.

In order to obtain a material of high-purity hydrogen, a hydrogen-penetrating membrane that selectively penetrates hydrogen has been proposed. Hydrogen penetrating membranes are known to include Pd alloy membranes. The Pd alloy film is known as a PdCu alloy film.

Regarding a PdCu alloy film for a hydrogen penetrating membrane, Patent Document 1 (Japanese Unexamined Patent Publication No. 2008-81765) has disclosed a palladium alloy plating solution containing a specific palladium complex and a hydrogen separation membrane formed from the plating solution . Patent Document 1 describes that as a specific example, an alloy film is formed using a plating solution containing palladium chloride, copper nitrate, aspartic acid, dipotassium citrate, and dipotassium hydrogen phosphate.

In addition, Non-Patent Document 1 (Fabrication of Electrolytic PdCu Alloy Coating Films for Hydrogen Permeable Membranes, Surface Technology Association's 125th Lecture Conference Highlights, page 141) has described the following point: After the electrolytic PdCu coating film is formed on SUS304 , The point of peeling off the PdCu film; the obtained PdCu film is a film of Pd 63wt%-Cu 37wt%, which is a point of view that is very close to the alloy ratio Pd 60wt%-Cu 40wt% with hydrogen permeability; When confirming the crystallinity of the PdCu film before and after the heat treatment, only the α phase was confirmed before the heat treatment, but the viewpoint of the β phase formation after the heat treatment; and in view of the hydrogen permeability of the PdCu alloy film due to the mixture of the α phase and the β phase In order to obtain the effect, it is considered that the obtained PdCu alloy film has a function as a hydrogen penetrating film.

However, whether it is Patent Document 1 or Non-Patent Document 1, there is no description as to whether the obtained PdCu alloy film actually functions as a hydrogen penetrating film. Moreover, according to the inventor's opinion, even if a PdCu alloy film is formed by electroplating, and a heat treatment is performed as described in Non-Patent Document 1 to form a β phase (body-centered cubic phase), it is still not available as a hydrogen penetrating film Full hydrogen penetration performance.

Therefore, an object of the present invention is to provide a hydrogen permeable film that has sufficient hydrogen permeation performance and utilizes a PdCu alloy film, and a method for manufacturing the same.

In order to solve the above-mentioned problems, the present invention includes the following matters.

(1) A hydrogen penetrating film including an alloy film containing Pd and Cu, characterized in that the alloy film is a plated film and has a BCC structure; and the Pd:Cu ratio (atomic ratio) of the alloy film is 6: 4~4:6.

(2) The hydrogen permeable film as described in (1) above, wherein the film thickness of the alloy film is 1 to 100 μm.

(3) A method for manufacturing a hydrogen penetrating membrane, characterized by comprising: a step of manufacturing an alloy film containing Pd and Cu; and a step of changing at least a part of the crystal structure of the alloy film to a BCC structure in the presence of non-oxygen After the step of changing to the BCC structure, the step of treating the alloy film with oxygen under heating conditions; and the step of treating the alloy film with reducing gas after the step of oxygen treatment.

(4) The manufacturing method as described in (3) above, wherein the step of forming the alloy film includes a step of forming the alloy film by electroplating.

(5) The manufacturing method according to the above (3) or (4), wherein the step of changing to the BCC structure includes a step of heat-treating the alloy film under reduced pressure.

(6) The production method according to any one of (3) to (5) above, wherein the reducing gas contains hydrogen.

(7) The manufacturing method as described in any one of (3) to (6) above, wherein after the step of treating with oxygen, a step of changing the environment containing the alloy film to a reduced pressure state is further provided; In addition, the step of treating with the reducing gas is a step of introducing the reducing gas into the environment including the alloy film after the step of reducing the pressure to the reduced pressure state.

(8) The production method according to any one of (3) to (7) above, wherein the step of treating with reducing gas is carried out under heating conditions.

(9) The production method described in any one of (3) to (8) above, further comprising after the step of treating with a reducing gas, depressurizing the environment containing the alloy film to make it again The step of becoming a reduced pressure state; the step of cooling the aforementioned alloy film after the aforementioned step of becoming the reduced pressure state again; and the step of returning the environment containing the aforementioned alloy film to atmospheric pressure after the aforementioned cooling step.

According to the present invention, there is provided a hydrogen penetrating film having sufficient hydrogen penetrating performance and using a PdCu alloy film, and a method for manufacturing the same.

[Figure 1] An SEM photograph of an alloy film.

[Figure 2] This shows the X-ray diffraction intensity spectrum of the alloy film.

Fig. 3 shows the results of the indentation test of the alloy film.

1: Manufacturing method of hydrogen penetrating membrane

The manufacturing method of the hydrogen permeable membrane of the embodiment of the present invention includes: a step of manufacturing an alloy film containing Pd and Cu (step S1); and changing at least a part of the crystal structure of the alloy film to BCC in the absence of oxygen ( body-centered cubic (body-centered cubic lattice) structure step (step S2); after the step of changing to BCC structure, the step of treating the alloy film with oxygen under heating conditions (step S3); and the step of treating with oxygen After the step, the aforementioned alloy film is treated with a reducing gas (step S4).

It is generally considered that in order to improve the hydrogen penetration performance of the Pd alloy film, a part of the crystal structure must be a BCC structure. However, in the case of the PdCu alloy film, only a part of the crystal structure is changed to the BCC structure system, and sufficient hydrogen penetration performance cannot be obtained. In this regard, according to the present invention, by changing a part of the crystal structure to a BCC structure in the absence of oxygen, the alloy film is treated with oxygen under heating conditions, and further treated with a reducing gas, thereby improving the PdCu alloy film Hydrogen penetration performance.

Hereinafter, each step will be described in detail.

Step 1: Film formation of alloy film

An alloy film containing Pd and Cu is produced. In this embodiment, the alloy film is produced by electroplating using PdCu plating solution.

That is, first, a PdCu plating solution is prepared.

For the PdCu plating solution, for example, a plating solution containing a palladium ion supply source such as dichlorotetramine palladium, a copper ion supply source such as copper sulfate, and additives such as polyphosphate can be used.

Next, using the prepared PdCu plating solution, an alloy film containing Pd and Cu is deposited on the conductive substrate by electroplating.

The bath temperature at the time of plating is, for example, 20 to 80°C, preferably 30 to 70°C, and more preferably 40 to 60°C.

The current density is, for example, 0.5 to 3.0 A/dm ² , and ideally 1.0 to 2.0 A/dm ² .

The thickness of the alloy film is, for example, 1 to 100 μm, preferably 3 to 30 μm, and more preferably 5 to 20 μm.

In addition, the electroplating is performed under the condition that the Pd:Cu ratio (atomic ratio) of the obtained alloy film is 4:6 to 6:4, and it is ideally performed under the condition of 4.5:5.5 to 5.5:4.5.

In addition, when a material with low adhesion to the alloy film (for example, SUS304) is used as the substrate, the alloy film can be peeled from the substrate after the alloy film is formed. As a result, the alloy film alone can be used as a hydrogen permeable film.

However, depending on the application, the laminate of the base material and the alloy film may be used as a hydrogen separation membrane without peeling the alloy film from the base material.

Step 2: Transformation of crystal structure

The alloy film formed in step S1 is generally FCC (face-centered cubic; face-centered cubic) structure. Therefore, at least a part of the crystal structure of the alloy film is changed to the BCC structure in the absence of oxygen. Specifically, the alloy film is heat-treated using a high vacuum electric furnace under reduced pressure. By performing heat treatment under reduced pressure, at least a part of the crystal structure of the alloy film can be changed to the BCC structure.

The heat treatment temperature at this time is, for example, preferably 300°C or higher, and more preferably 400°C or higher. In addition, the upper limit of the heat treatment temperature is, for example, 600°C or lower, and ideally 500°C or lower.

The heat treatment time is, for example, 10 minutes to 10 hours, preferably 20 minutes to 5 hours, and more preferably 30 minutes to 3 hours.

In addition, in this specification, the reduced pressure state refers to, for example, a state of 100 Pa or less, preferably a state of 50 Pa or less, and more preferably a state of 10 Pa or less.

Step 3: Oxygen treatment

Next, the alloy film is treated with oxygen under heating conditions.

Specifically, the alloy film is placed under the same temperature and pressure conditions as in step S2, and an oxygen-containing gas (ideally air) is introduced into an environment containing the alloy film, that is, a high vacuum electric furnace. Oxygen is introduced, for example, to return the pressure to atmospheric pressure.

Step 4: Treatment with reducing gas

Next, the heating state is maintained, and the environment including the alloy film is decompressed again to become a decompressed state.

Next, a reducing gas is introduced into the environment containing the alloy film. The reducing gas is introduced, for example, until the pressure returns to atmospheric pressure.

As the reducing gas, for example, hydrogen, green gas (3% hydrogen + argon), etc. can be used, and it is desirable to use hydrogen.

Step 5: Cool

After cooling the alloy film, take it out of the high vacuum electric furnace. Thereby, the hydrogen permeable membrane of this embodiment can be obtained.

In addition, the PdCu alloy film has the property of storing hydrogen under low temperature conditions (about 300° C. or lower). Therefore, if only cooling is performed after step S4, the alloy film may store hydrogen. After absorbing hydrogen, the membrane may become hard and fragile. In order to prevent the alloy film from absorbing hydrogen, it is desirable to depressurize the high vacuum electric furnace again before cooling to a decompressed state. Then, after cooling under reduced pressure, the pressure is returned to atmospheric pressure. After that, the alloy film is taken out. By adopting such a procedure, hydrogen storage during cooling can be prevented.

2: Hydrogen penetrating membrane

The hydrogen penetrating membrane of this embodiment has the alloy membrane obtained by the above method. The alloy film can be used alone as a hydrogen penetrating film, or the alloy film can be used as a hydrogen penetrating film in combination with other materials.

In addition, the alloy film obtained by the above method has a BCC structure, and the Pd:Cu ratio (atomic ratio) is 4:6 to 6:4.

Whether or not the alloy film has a BCC structure can be confirmed by X-ray diffraction, for example. Specifically, in the presence of the BCC structure, in X-ray diffraction using CuKα rays, the peak exists at the position of the diffraction angle 2θ=43±0.5. On the other hand, in the presence of the FCC structure, in X-ray diffraction using CuKα rays, the peak exists at the position of the diffraction angle 2θ=42±0.5.

In the above alloy film, it is desirable that in X-ray diffraction using a hydrogen penetrating film of CuKα rays, the peak intensity of the peak appearing at the position of the diffraction angle 2θ=43±0.5 is higher than that at the diffraction angle 2θ The peak intensity at the position of =42±0.5 is large.

As described above, according to the present embodiment, after the crystal structure of the alloy film is changed (step S2), by performing oxygen treatment under heating conditions (step S3) and treatment using reducing gas (step S4), A PdCu alloy film with high hydrogen penetration performance is obtained.

According to this embodiment, an alloy film having a hydrogen penetration property of, for example, 3 to 20 mL/min/cm ² can be obtained, and ideally an alloy film having a hydrogen penetration property of 5 to 20 mL/min/cm ² . In addition, the hydrogen penetration performance here means the value measured at 450 degreeC and a differential pressure of 1 atm.

In addition, in the present embodiment, an example of producing an alloy film by electroplating has been described in step 1 (production of alloy film). However, even in the case where the alloy film is produced by rolling instead of electroplating, by performing the processes of steps S2 to S4, a high hydrogen penetration performance can still be obtained.

However, ideally, the alloy film used in the hydrogen penetrating film of this embodiment is preferably an electroplated film. The hydrogen penetration performance depends on the thickness of the hydrogen penetration film. The thinner the film thickness, the higher the hydrogen penetration performance. In the case of using the PdCu plating solution of the present embodiment, the thin film can be produced more stably than the rolling method. In addition, when the PdCu plating solution of the present embodiment is used, an alloy film with a denser and finer crystal structure can be obtained than the rolling method, and as a result, an alloy film with excellent durability can be obtained.

Whether it is a plated film can be confirmed by observing an SEM photograph of the alloy film cross section, for example. That is, if it is an electroplated film, the crystal grain size observed in its cross section will be smaller than that obtained by the rolling method or the like. For example, when the cross-section of the alloy film is observed from a 20,000-times SEM photograph, if the circumference of the largest crystal grain in the field of view of 5 μm×5 μm is 4 μm or less, it can be inferred that the alloy film is a plated film. In the case of a film obtained by the calendering method or the like, the "perimeter of the largest crystal grain" generally exceeds 4 μm.

In addition, in the present embodiment, an example in which the crystal structure is changed to the BCC structure by performing heat treatment under a reduced pressure state has been described in step S2. However, as long as it is in the presence of non-oxygen, it does not necessarily have to be in a reduced pressure state. For example, even if heat treatment is performed in the presence of a reducing gas (such as argon and 3% hydrogen), the crystal structure can be changed to a BCC structure.

[Experiment example]

Next, in order to explain the present invention in more detail, examples of experiments conducted by the applicant will be described.

[Research on Hydrogen Permeability]

(Example 1)

Step S1: film formation of alloy film

Prepare PdCu plating solution. As the PdCu plating solution, a plating solution containing dichlorotetramine palladium (Pd concentration 8 g/L), copper sulfate (Cu concentration 3 g/L), and polyphosphate was prepared.

Prepare SUS304 as the base material. The prepared PdCu plating solution is used for electroplating on the prepared substrate to precipitate the PdCu alloy film. After precipitation, the PdCu alloy film was peeled from the substrate.

The conditions of electroplating are as follows.

Bath temperature: 50℃

Current density: 1.5A/dm ²

The Pd:Cu atomic ratio of the obtained alloy film was measured by EPMA (Electron Probe Micro Analyzer) to obtain 5:5.

The film thickness of the alloy film is 10 μm.

Step S2: Heat treatment under reduced pressure

Next, the obtained alloy film is placed in a high vacuum electric furnace. The pressure in the furnace is reduced, and the alloy film is heated. The heating temperature is 450°C and the heating time is 1 hour.

Next, after cooling to room temperature, the pressure was returned to atmospheric pressure, and the alloy film was taken out from the high vacuum electric furnace.

Step S3: Oxygen treatment under high temperature

Next, the alloy film was installed in the hydrogen penetration amount measuring device. The environment of the alloy film is reduced again. In addition, the alloy film was heated at 450°C. Next, air was introduced into the hydrogen penetration amount measuring device to return the pressure to atmospheric pressure. That is, the oxygen treatment at a high temperature is performed.

Step S4: Treatment with hydrogen gas (hydrogen penetration test)

Next, the heating state is maintained, and the inside of the hydrogen penetration amount measuring device is again brought into a reduced pressure state. After the pressure is reduced, hydrogen is introduced into the hydrogen penetration measuring device to return the pressure to atmospheric pressure.

At this time, the heating state was maintained, a hydrogen penetration test was performed, and the hydrogen penetration performance of the alloy film was measured. The hydrogen penetration test was carried out by the following procedure. In the hydrogen penetration amount measuring device, an alloy film is arranged in advance to separate the primary space and the secondary space. Hydrogen was supplied to the primary space so that the differential pressure between the primary space and the secondary space was 1 atm. Next, the amount of hydrogen flowing from the primary space through the alloy film to the secondary space was measured.

(Comparative example 1)

By the same method as in Example 1, a PdCu plating solution was used on the substrate to form an alloy film.

However, the process after the heat treatment in the reduced pressure state (steps S2 and S3) is not performed, and the formed alloy film is directly put into the hydrogen penetration amount measuring device. After the inside of the hydrogen penetration amount measuring device is decompressed, a hydrogen penetration test is performed while introducing hydrogen into the device at room temperature, and the hydrogen penetration performance is measured (step S4).

(Comparative example 2)

By the same method as in Example 1, a PdCu plating solution was used on the substrate to form an alloy film (step S1). In the same manner as in Example 1, the obtained alloy film was put into a high-vacuum electric furnace, and heat treatment was performed under reduced pressure (step S2). However, unlike Example 1, a hydrogen penetration test (step S4) was performed without performing oxygen treatment at a high temperature (step S3). That is, after step S2, the alloy film taken out from the high-vacuum electric furnace was set in a hydrogen penetration amount measuring device, the inside of the device was reduced in pressure, and after heating at 450°C, hydrogen was introduced into the device to conduct a hydrogen penetration test , To measure the hydrogen penetration performance.

(Example 2)

A PdCu alloy film (thickness: 10 μm) produced by the rolling method is prepared. The prepared PdCu alloy film was subjected to the same treatment as in Example 1 (steps S1 to S4), and a hydrogen penetration test was performed.

(Comparative example 3)

In the same manner as in Example 2, a PdCu alloy film (thickness: 10 μm) prepared by the rolling method was prepared. However, in the same manner as in Comparative Example 1, after the heat treatment under reduced pressure (steps S2 and S3), a hydrogen penetration test was performed at room temperature, and the hydrogen penetration performance was measured.

(Comparative example 4)

In the same manner as in Example 2, a PdCu alloy film (thickness: 10 μm) produced by the rolling method was prepared. After that, it was treated in the same manner as in Comparative Example 2 to perform a hydrogen penetration test. That is, the obtained alloy film is subjected to a heat treatment under reduced pressure (step S2). Cool to room temperature under reduced pressure continuously. After cooling, return the pressure to atmospheric pressure and remove the alloy film from the high vacuum electric furnace. After that, the alloy film was moved to a hydrogen penetration amount measuring device, and the inside of the device was reduced in pressure, without performing oxygen treatment at a high temperature (step S3), heating at 450°C, and performing a hydrogen penetration test (step S4) ).

(Example 3)

By the same procedure as in Example 1, the hydrogen penetration amount of the alloy film was measured. However, the heating temperature at the time of hydrogen penetration measurement is 300°C instead of 450°C.

The results of the hydrogen penetration tests of Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 1.

As shown in Table 1, in Comparative Example 1 and Comparative Example 3, the hydrogen penetration amount was 0. That is, it can be seen that the alloy film does not have hydrogen penetration performance without performing heat treatment under reduced pressure. In addition, in Comparative Examples 2 and 4, the hydrogen penetration amount (mL/min/cm ² ) was 2.30 and 2.21, respectively. It was confirmed that by performing heat treatment under reduced pressure, the alloy film can be given hydrogen permeability. However, the amount of hydrogen penetration is still small, and hydrogen penetration performance that can be used as a hydrogen penetration membrane (for example, 3 mL/min/cm ² or more) cannot be obtained.

On the other hand, in Examples 1 to 3, the hydrogen penetration amount is significantly improved compared to Comparative Examples 2 and 4, and has a hydrogen penetration performance that can be used as a hydrogen penetration membrane, for example, 3 mL/min/cm ² or more . That is, after the heat treatment in the reduced pressure state, by performing the oxygen treatment in the heated state and the treatment using the reducing gas, the amount of hydrogen penetration is higher than that in the case where only the heat treatment in the reduced pressure state is performed. Significantly improved.

[Study on Surface State]

The alloy films of Comparative Examples 1 and 3 (after step S1 and before step S4), Comparative Example 2 (after step S2 and before step S4) and Examples 1 and 2 (after step S4) were observed by SEM photograph . In addition, in Example 1, after oxygen treatment in a high-temperature state and before treatment with hydrogen (between steps S3 and S4), the surface state was also observed by SEM photographs. The SEM photograph is shown in Figure 1. As shown in FIG. 1, Comparative Examples 1 and 2 differ greatly from Example 1 in the surface state. That is, it can be seen that by performing oxygen treatment under heating conditions, the heating state is maintained while the pressure is reduced again, and then hydrogen is introduced to return to atmospheric pressure, thereby changing the structure of the alloy film.

[Research on crystal structure]

Next, the alloy films of Comparative Example 1 (after step S1 and before step S4) and Comparative Example 2 (after step S2 and before step S4) were subjected to X-ray diffraction intensity spectrum measurement. The measurement result is shown in Fig. 2. As shown in FIG. 2, in Comparative Example 1, only the peak of the FCC structure was observed (A in the figure). That is, it can be known that the alloy film before the heat treatment in the reduced pressure state has an FCC structure. On the other hand, Comparative Example 2 mainly showed the peak of the BCC structure (B in the figure), and the peak of the FCC structure was also slightly observed. Specifically, in Comparative Example 2, the peak intensity of the peak of the BCC structure at the diffraction angle 2θ=43±0.5 is much larger than the peak intensity of the peak of the FCC structure at the diffraction angle 2θ=42±0.5. That is, it can be seen that the crystal structure of the alloy film of Comparative Example 2 is mainly a BCC structure, and is slightly mixed with the FCC structure.

From the results of the X-ray diffraction intensity spectrum, it can be seen that by subjecting the alloy film to heat treatment under reduced pressure, at least a part of the crystal structure changes from the FCC structure to the BCC structure. However, even in Comparative Example 2 with a BCC structure, as shown in Table 1, sufficient hydrogen penetration performance could not be obtained. That is, it can be understood that only changing the crystal structure to the BCC structure cannot achieve the desired hydrogen penetration performance.

[Research on mechanical properties]

Under the same conditions as in Example 1, a PdCu plating solution was used to form a PdCu alloy film with a thickness of 5 μm and 10 μm by electroplating. After the plating, the alloy film was peeled from the substrate.

In addition, by the rolling method, PdCu alloy films with film thicknesses of 5 μm and 10 μm were prepared.

Each alloy film is supported by a supporting member having a circular unsupported area. Next, at the center of the unsupported area, the rod-shaped jig was pressed vertically against the alloy film, and the relationship between the displacement of the alloy film and the force (test force) received by the rod-shaped jig until the alloy film was broken was measured.

The test results are shown in Figure 3. Each spectrum in FIG. 3 corresponds to the following conditions.

Spectrum A: Electroplating 5μm

Spectrum B: Electroplating 10μm

Spectrum C: calendered film 5μm

Spectrum D: Rolled film 10μm

As shown in FIG. 3, the displacement and test force of the alloy film formed by electroplating under the same conditions as in Example 1 until the film is pierced are larger than those obtained by the rolling method .

That is, it can be seen that the alloy film obtained by electroplating is more flexible than the rolled film and has excellent durability.

Claims (9)

A hydrogen penetrating film including an alloy film containing Pd and Cu, characterized in that the alloy film is an electroplated film and has a BCC structure (body-centered-cubic; body-centered cubic lattice); and the Pd of the alloy film : The Cu ratio (atomic ratio) is 6:4 to 4:6. The hydrogen permeable membrane as described in item 1 of the patent application range, wherein the film thickness of the aforementioned alloy membrane is 1 to 100 μm. A method for manufacturing a hydrogen penetrating membrane, characterized by comprising: a step of manufacturing an alloy film containing Pd and Cu; a step of changing at least a part of the crystal structure of the alloy film to a BCC structure in the presence of non-oxygen; After the step of changing to the BCC structure, the step of treating the alloy film with oxygen under heating conditions; and the step of treating the alloy film with reducing gas after the step of oxygen treatment. The manufacturing method described in Item 3 of the patent application range, wherein the step of forming the alloy film includes the step of forming the alloy film by electroplating. The manufacturing method described in item 3 or 4 of the patent application range, wherein the step of changing to the BCC structure includes a step of heat-treating the alloy film under reduced pressure. The manufacturing method as described in any one of items 3 to 5 of the patent application range, wherein the reducing gas contains hydrogen. The manufacturing method as described in any one of items 3 to 6 of the patent application scope, wherein after the step of oxygen treatment, the step of changing the environment containing the alloy film to a reduced pressure state is further provided; and The step of reducing gas treatment includes the step of introducing the reducing gas into the environment containing the alloy film after the step of reducing the pressure to the reduced pressure. The manufacturing method as described in any one of the items 3 to 7 of the patent application scope, wherein the step of treating with the reducing gas is performed under heating conditions. The manufacturing method as described in any one of the items 3 to 8 of the patent application scope, further comprising after the step of treating with the reducing gas, depressurizing the environment containing the alloy film to make it again reduced The step of pressing the state; the step of cooling the alloy film after the step of becoming the reduced pressure state again; and the step of returning the environment containing the alloy film to atmospheric pressure after the step of cooling.

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