[Invention Title]

SEPARATION MEMBRANE, HYDROGEN SEPARATION MEMBRANE INCLUDING SEPARATION MEMBRANE, AND DEVICE INCLUDING HYDROGEN SEPARATION MEMBRANE

[Technical Field]

A separation membrane, a hydrogen separation membrane including the same, and a hydrogen separation device including the hydrogen separation membrane are disclosed.

[Background Art]

Recently, hydrogen has been in the spotlight as a clean energy source. As a separation membrane for selectively separating hydrogen from hydrogen- containing gases, various metal/metal alloys, silica/zeolite ceramics, metal ceramic composites (cermet), carbon-based polymer separation membranes, and the like are known. Among them, representatively, a Pd-based alloy separation membrane is commercially used (Chemical Reviews, 107, 4078- 4110, 2007).

However, the Pd-based alloy is a noble metal and is expensive, and hydrogen separation performance of the alloy is improved by only about 2 to 3 times. Representative Pd-based alloys include Pd-Ag23, Pd-Cu40, and the like (Platinum Metals Rev., 21 , 44-50, 1977).

Research on Group 5 metals such as vanadium (V), niobium (Nb), and tantalum (Ta) is being actively undertaken as an alternative for the conventional Pd-based alloy separation membrane. These metals have larger affinity for hydrogen than the Pd, and thus have excellent hydrogen-containing capability, an excellent hydrogen diffusion characteristic through a small lattice of a body- centered cubic (BCC) lattice structure, and in general, about 10 to 100 times the hydrogen permeability of the Pd-based alloys (J. Membr. Sci., 362, 12-28, 2010). However, these metals have no hydrogen dissociation characteristics by themselves, and coating the metals with a metal catalyst layer of Pd and the like having hydrogen dissociation performance is required. When the catalyst layer is coated, hydrogen permeation performance of a separation membrane may be deteriorated during operation at a high temperature due to formation of intermetallic phases by mutual diffusion between the metals.

[Disclosure]

[Technical Problem]

One embodiment provides a separation membrane without performance degradation during long-time operation at a high temperature.

Another embodiment provides a hydrogen separation membrane including the separation membrane.

Yet another embodiment provides a hydrogen separation device including the hydrogen separation membrane.

Still another embodiment provides a method of manufacturing the separation membrane.

[Technical Solution]

In one embodiment, a separation membrane includes a metal layer including at least one kind of Group 5 element, a non-porous metal oxide layer that is stacked on the surface of the metal layer and includes at least one selected from AI ₂ O ₃ , Si0 ₂ , Hf0 ₂ , Zr0 ₂ , Ti0 ₂ , and a combination thereof, and metal catalyst layer that is stacked on the non-porous metal oxide layer and has hydrogen dissociation performance, wherein the non-porous metal oxide layer suppresses formation of an intermetallic phase by mutual diffusion between the metal layer including the Group 5 element and the metal catalyst layer, and has permeability for hydrogen atoms separated from the metal catalyst layer.

The non-porous metal oxide layer may have a thickness of less than about 15 nm, for example greater than or equal to about 0.5 nm and less than or equal to about 10 nm.

The non-porous metal oxide layer may consist of Al ₂ 03.

The non-porous metal oxide layer may have porosity of less than about 1 volume%.

The non-porous metal oxide layer may be stacked on one side or both sides of the metal layer including the Group 5 element.

The metal catalyst layer may include at least one selected from Pd, Ni, Pt, Fe, Cu, Mo, Ir, Ru, Rh, or a mixture of two or more thereof.

The Group 5 element may be V, Nb, or Ta.

The metal layer including the Group 5 element may further include at least one kind of Group 4-based transition metal being capable of forming a body-centered cubic (bcc) structure along with the Group 5 element.

The Group 4-based transition metal being capable of forming a bcc structure along with the Group 5 element may be Ti, Zr, or Hf. The metal catalyst layer may have a thickness of about 100 nm to about 1000 nm.

The separation membrane may have a thickness of about 10 m to about 1000 ivn.

In another embodiment, a hydrogen separation membrane including the separation membrane is provided.

The hydrogen separation membrane may be operated at a temperature of about 300 °C to about 600 °C.

The hydrogen separation membrane may be operated at a hydrogen pressure of greater than or equal to about 1 atm.

The hydrogen separation membrane may have hydrogen permeability of about 1.0 x 10 ^"8 to about 3.0 x 10 ^'7 mol/m*s*Pa ¹ ' ² at about 300 °C to about 600 °C.

In another embodiment, a method of manufacturing the hydrogen separation membrane includes

preparing a metal layer including at least one kind of a Group 5-based metal,

stacking a non-porous metal oxide layer including ,at least one selected from Al ₂ 0 ₃ , S1O2, Hf0 ₂ , VO2, and T1O2 on the surface of the metal layer in a thickness of less than about 15 nm, and

stacking a catalyst layer including at least one selected from Pd, Ni, Pt, Fe, Cu, Mo, Ir, Ru, Rh, or a mixture of two or more thereof on the metal oxide layer.

The non-porous metal oxide layer may be stacked using an ALD (atomic layer deposition) deposition apparatus or by sputtering. In yet another embodiment, a hydrogen separation device including the hydrogen separation membrane is provided.

The hydrogen separation device includes the hydrogen separation membrane according to the embodiment, a chamber equipped with a supplier for a mixed gas including hydrogen gas, and a discharge chamber equipped with a discharger for separated hydrogen gas, wherein the hydrogen separation membrane contacts the chamber on one surface of the hydrogen separation membrane, and contacts the discharge chamber on the other surface.

In one embodiment, the hydrogen separation membrane may be formed in a tubular shape, a cylindrical chamber barrier rib having a larger diameter than that of the tubular hydrogen separation membrane may be formed at the outside of the hydrogen separation membrane, a space between the chamber barrier rib and the hydrogen separation membrane may be formed as the chamber, and the inside of the tubular hydrogen separation membrane may be formed as the discharge chamber where hydrogen is discharged.

[Advantageous Effects]

An intermetallic phase due to the mutual diffusion between a metallic layer including a Group V element and a metallic catalyst layer is not formed in the separation membrane according to an embodiment, even when used in a high temperature. Accordingly, a hydrogen separation membrane of which the performance is not deteriorated when being used in a high temperature for a long period can be obtained.

[Description of Drawings]

FIG. 1 is a schematic view showing a cross-section of a separation membrane according to one embodiment in a thickness direction.

FIG. 2 is a schematic view showing a mechanism through which hydrogen gas is separated with a conventional separation membrane including a metal catalyst layer on both surfaces of the separation membrane.

FIG. 3 is a graph showing hydrogen permeability measurements of a conventional hydrogen separation membrane respectively forming a 150 nm- thick Pd layer or a 100 nm-thick Ni layer on both sides of a vanadium foil, which are measured at 400 °C for 1 hour.

FIG. 4 is a graph showing hydrogen permeability measurements of hydrogen separation membranes manufactured by forming a 150 nm-thick metal catalyst layer on both sides of each of 80 nm, 130 nm, and 250 nm-thick vanadium foils, which are measured at 400 °C for 15 hours.

FIG. 5 is a graph showing hydrogen permeability measurements of hydrogen separation membranes manufactured by respectively forming each of 0.5 nm, 1 nm, 1.5 nm, 2 nm, and 3 nm-thick alumina (Al ₂ 0 ₃ ) layers on the vanadium foil by using an ALD (atomic layer deposition) apparatus and the vanadium separation membrane itself having no alumina layer, which are measured at 400 °C for 1 hour.

FIG. 6 is a SEM photograph showing that a 4.0 nm-thick alumina layer is uniformly coated on a vanadium foil by using an ALD (atomic layer deposition) apparatus.

FIG. 7 is a TEM photograph showing the cross-section of a separation membrane manufactured by coating an about 5.0 nm-thick alumina layer on a vanadium foil by using an ALD (atomic layer deposition) apparatus and forming a Pd catalyst layer thereon.

FIG. 8 is a graph showing hydrogen permeability measurements of a separation membrane manufactured by respectively forming each alumina layer having various thicknesses on a vanadium foil by using RF sputtering and a Pd catalyst layer thereon and a vanadium separation membrane itself having no alumina layer, which are measured at 400 °C for greater than or equal to 4 hours.

FIG. 9 is a schematic view showing a hydrogen separation device according to one embodiment.

FIG. 10 is a schematic view showing a hydrogen separation device including a tubular separation membrane according to another embodiment. [Best Mode]

This disclosure will be described more fully hereinafter in the following detailed description, in which some but not all embodiments of this disclosure are described. However, this disclosure may be embodied in many different forms, and is not construed as limited to the exemplary embodiments set forth herein.

As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of this disclosure. The size and thickness of each constituent element as shown in the drawings are randomly indicated for better understanding and ease of description, and this disclosure is not necessarily limited to as shown. The size and thickness of each constituent element as shown in the drawings are exaggeratedly indicated for better understanding and ease of description, and this disclosure is not necessarily limited to as shown.

In one embodiment, a separation membrane includes a metal layer including at least one kind of Group 5 element and a non-porous metal oxide layer that is stacked on the surface of the metal layer and includes at least one selected from Al ₂ 0 ₃ , S1O2, Hf0 ₂ , Zr02, Ti0 ₂ , and a combination thereof, and a metal catalyst layer that is stacked on the non-porous metal oxide layer and has hydrogen dissociation performance, wherein the non-porous metal oxide layer suppresses formation of an intermetallic phase by mutual diffusion between the metal layer including the Group 5 element and the metal catalyst layer, and has permeability for hydrogen atoms separated from the metal catalyst layer.

The non-porous metal oxide layer may be stacked on one side or both sides of the metal layer including the Group 5 element.

Researches on a separation membrane including Group 5-based metals have been actively undertaken as an alternative for the Pd-based separation membrane having both hydrogen dissociation performance and hydrogen permeation performance. The Group 5-based metals such as vanadium (V), niobium (Nb), or tantalum (Ta) have larger hydrogen affinity and thus hydrogen- containing capability than Pd-based metals, and have excellent hydrogen diffusion characteristics through a small lattice of the body-centered cubic structure to provide higher hydrogen permeation performance of about 10-100 times that of Pd-based metals (J. Membr. Sci., 362, 12-28 (2010)). However, these Group 5-based metals have no hydrogen dissociation characteristics by themselves, so one surface or both surfaces need to be coated with a Pd-based metal catalyst layer in a predetermined thickness. FIG. 2 schematically shows a hydrogen separation membrane including the Pd-based catalyst layer on both surfaces of a Group 5-based metal layer and a mechanism through which hydrogen is dissociated, permeated, and recombined through the hydrogen separation membrane.

A separation membrane 10 manufactured by coating a catalyst layer 12 including a Pd-based metal on the surface of a metal layer 11 including a Group 5-based metal has a problem of constantly deteriorating hydrogen permeation performance, since an intermetalic phase is formed due to mutual diffusion of metals between the metal layer and the catalyst layer at a temperature of greater than or equal to about 350 °C.

Specifically, as shown in FIG. 3, hydrogen permeability of a separation membrane manufactured by respectively forming a 150 nm-thick Pd layer or a 100 nm-thick Ni layer on both sides of a 250 nm-thick vanadium foil is rapidly deteriorated at 400 °C as time passes. In particular, a separation membrane having a Ni-V-Ni structure tends to show a rapid decrease of hydrogen permeability within one hour. The Pd-V-Pd separation membrane seems to show less decrease of hydrogen permeability in FIG. 3, but shows a constant decrease as time passes as shown in FIG. 4.

However, the embodiment of the present invention may provide a separation membrane capable of suppressing an intermetalic phase due to mutual diffusion between the metal layer including a Group 5 element and a metal catalyst layer having hydrogen dissociation performance, and thus operating for a long time by laminating a non-porous thin metal oxide layer transmitting hydrogen atoms separated from the metal catalyst layer as well as preventing mutual diffusion between the metal layer including the Group 5 element and the metal catalyst layer on one surface or both surfaces of the metal layer including a Group 5 element.

As shown from the post-described example, a separation membrane including a Group 5-based metal and coated with a non-porous thin metal oxide layer may maintain high hydrogen permeation performance at a high temperature of greater than or equal to about 300 °C, for example, greater than or equal to about 350 °C, and specifically, greater than or equal to about 400 °C, and thus operates at a high temperature and pressure for a long time, when a catalyst layer having hydrogen dissociation performance is laminated thereon.

The non-porous metal oxide layer may include at least one selected from AI2O3, Si0 ₂ , Hf0 ₂ , Zr0 ₂ , ΤΊΟ2, and a combination thereof, and is a non- porous uniform thin film.

Herein, "non-porous" refers to having porosity of less than about 1 volume%.

In an exemplary embodiment, the separation membrane may have a non-porous dense film structure having porosity of less than about 0.5 volume%, and specifically about 0 %.

The non-porous metal oxide layer may be stacked on the metal layer at a thin thickness of less than about 15 nm, for example greater than or equal to about 0.5 nm and less than or equal to about 10 nm.

The non-porous metal oxide layer may be laminated on the metal layer including the Group 5 element in a conventional method of sputtering, chemical vapor deposition (CVD), and the like, but for example, an ALD (atomic layer deposition) apparatus may be used to from a uniform and dense layer having a thickness within the range. However, any method may be adopted, as long as the metal oxide layer is uniformly and densely formed to have a thickness within the range on the metal layer.

The Group 5 element may be V (vanadium), Nb (niobium), or Ta

(tantalum).

The metal layer including the Group 5 element may further include a Group 4-based metal, for example, Ti (titanium), Zr (zirconium), or Hf (hafnium) being capable of having a body-centered cubic (bcc) structure, along with the Group 5 element.

The metal such as Ti, Zr, or Hf and the like may maintain ductility of an alloy when alloying with a Group 5-based metal. It is known that hydrogen embrittlement fractures more easily occur as the metal hardness is increased, and that the hardness and the ductility generally have an inversely proportional relationship. Accordingly, it is understood that the hydrogen embrittlement fractures are suppressed when the ductility is maintained by decreasing the alloy hardness. The Ti, Zr, or Hf may be included in an amount of greater than or equal to about 40 atom%, for example, greater than or equal to about 50 atom%, and specifically greater than or equal to about 60 atom% in the metal layer. These elements of the Ti, Zr, or Hf and the like are less expensive than the Group 5-based element, and may be included in a larger amount than the Group 5-based element. For example, even though these elements may be included in an amount of greater than or equal to about 80 atom%, for example, greater than or equal to about 85 atom%, and specifically greater than or equal to about 89 atom%, hydrogen embrittlement fractures are suppressed by not deteriorating hydrogen permeation performance of the Group 5 element but maintaining ductility of an alloy. The Group 5-based element may be included in the remaining amount in an alloy, after a metal is included within the range for maintaining ductility of the alloy.

The metal catalyst layer having hydrogen dissociation performance may include Pd, Ni, Pt, Fe, Cu, Mo, Ir, Ru, Rh, or a mixture of two or more thereof.

In an exemplary embodiment, the catalyst layer may include Pd, Pt, or

Ni.

The catalyst layer may have a thickness of about 100 nm to about 1000 nm.

The separation membrane may have a total thickness of about 10 m to about 1000 pm.

The separation membrane including the non-porous metal oxide layer and the metal catalyst layer on the surface may be operated without deterioration of hydrogen permeation performance for a long time at a high temperature of greater than or equal to about 300 °C, for example, greater than or equal to about 350 °C, and for example, greater than or equal to about 400 °C under a hydrogen pressure of greater than or equal to about 1 atm.

Accordingly, in another embodiment, a hydrogen separation membrane including the separation membrane is provided.

According to the embodiment, a hydrogen separation membrane 1 as shown in FIG. 1 as an exemplary embodiment has a structure in which a non- porous thin metal oxide layer 3 made of alumina is coated on both surfaces of a vanadium metal layer 2, and a Pd-based catalyst layer 4 is respectively coated on the metal oxide layers.

The hydrogen separation membrane 1 is prevented from forming an intermetallic phase due to mutual diffusion between the metal layer and the catalyst layer when operated at a high temperature under a high pressure for a long time, since the non-porous metal oxide layer 2 is present between the vanadium metal layer 2 and the Pd-based catalyst layer 3.

In the drawing, the non-porous metal oxide layer 3 is formed on both surfaces of the vanadium metal layer 2, but the non-porous metal oxide layer 3 may be formed on one surface of the metal layer 2.

The hydrogen separation membrane may be operated at a temperature of about 300 °C to about 600 °C.

The hydrogen separation membrane may be operated at a hydrogen pressure of greater than or equal to about 1 atm.

In general, when a hydrogen separation membrane is operated at less than or equal to about 250 °C, a mutual diffusion problem is reported not to occur between the metal layer including the Group 5 element and the metal catalyst layer. However, the hydrogen separation membrane does not have high hydrogen permeability within the temperature range, but needs to be operated at a high temperature ranging from about 300 °C to about 600 °C under a high pressure of greater than or equal to about 1 atm to more efficiently separate hydrogen.

According to the embodiment, a hydrogen separation membrane is suppressed from formation of the intermetalic phase due to mutual diffusion between a metal layer including the Group 5 element and a metal catalyst layer having hydrogen dissociation performance within a temperature range of about 300 °C to about 600 °C in which the intermetalic phase is generally formed, and thus may have no deterioration of hydrogen permeability when operated at a high temperature under a high pressure for a long time.

For example, the hydrogen separation membrane may have hydrogen permeability of about 1.0 x 10 ^"8 to about 3.0 x 10 ^"7 mol/m*s*Pa ^1/2 at about 300 °C to about 600 °C.

The hydrogen permeability may be calculated according to the following equation.

[Equation 1]

Permeability = Solubility (S) * Diffusion Coefficient (D)

The hydrogen separation membrane may have a thickness ranging from about 10 μιη to about 1000 pm, and specifically, about 20 pm to about 200 pm. When the hydrogen separation membrane has a thickness within the range, the hydrogen separation membrane may have appropriate permeability for a separation membrane.

The hydrogen separation membrane may be applied in a technical field for selectively permeating and separating only H2 gas out of a gas mixture including H ₂ , CO2, CO, and the like that is produced through steam reformation, coal gasification, WGS (water gas shift) reaction, and the like. For example, the hydrogen separation membrane may be applied to a high purity hydrogen generator, a hydrogen regenerator for a fuel cell, a separation membrane for separating hydrogen out of a mixed gas in a gasification combined thermal power plant, a separation membrane for separation of H ₂ /C0 ₂ , and the like.

The separated hydrogen may be used for generating electric power as a clean energy source or as a chemical raw material (NH ₄ , an olefin, and the like) or for purifying petroleum. Meanwhile, after removing the hydrogen, a residual gas consists of a C0 ₂ component in a high concentration. Accordingly, the C0 ₂ rich gas may be selectively collected and stored to remove C0 ₂ therein.

According to another embodiment, a method of manufacturing the hydrogen separation membrane is provided. The manufacturing method may include:

preparing a metal layer including at least one kind of Group 5-based metal;

stacking a non-porous metal oxide layer including at least one selected from Al ₂ 0 ₃ , Si0 ₂ , Hf0 ₂ , V0 ₂ and Ti0 ₂ on a surface of the metal layer at a thickness of less than about 15 nm; and

stacking a metal catalyst layer including at least one selected from Pd,

Ni, Pt, Fe, Cu, Mo, Ir, Ru, Rh, or a mixture of two or more thereof on the metal oxide layer.

As aforementioned, the stacking step of the non-porous metal oxide layer on a surface of the metal layer may be performed by sputtering, chemical vapor deposition (CVD), and the like, and an atomic layer deposition (ALD) apparatus may be used to manufacture a thinner and more uniform dense membrane according to an exemplary embodiment.

The ALD (atomic layer deposition) apparatus proceeds a reaction of adsorbing a precursor forming the metal oxide layer as an atomic unit on the metal layer including a Group 5 element, and thus uniformly forms one atomic layer per cycle on the metal layer

Accordingly, the ALD apparatus may stack the non-porous metal oxide layer on the metal layer, so that a final product, a metal oxide layer, may have a thickness of less than or equal to nanometers (nm). In addition, the metal oxide layer may be formed to have a uniform thickness on the metal layer, even when the surface of the metal layer is defective or non-uniform.

As shown in the following examples, the ALD apparatus may manufacture a thin metal oxide layer having a thickness of less than or equal to 1 nm by adjusting the cycle number. Specifically, when an Al ₂ 0 ₃ oxide layer is deposited on a vanadium foil by using the ALD apparatus in Example 1 , an about 1 nm-thick metal oxide layer is obtained at the 9 ^th cycle, and thus, for example, an about 0.5 nm-thick metal oxide layer, which has a thickness of less than 1 nm, can be obtained by decreasing the cycle number to less than 9 cycles.

FIG. 6 is a SEM photograph showing a 5 nm-thick AI2O3 layer coated on the surface of vanadium by using the ALD deposition apparatus in Example 1. The thin Al ₂ 0 ₃ layer is uniformly coated. In addition, the metal oxide layer is a non-porous dense thin film unlike a vanadium (V) or Pd layer as shown in the TEM photograph of FIG. 7.

Each of 0.5 nm, 1 nm, 1.5 nm, 2 nm, and 3 nm-thick alumina layers is formed on a 250 pm-thick vanadium metal layer in the ALD method, and then an about 100 nm-thick Pd catalyst layer is formed thereon, and hydrogen permeability results of separation membranes are provided in FIG. 5. As shown in the drawing, initial hydrogen permeability of the separation membrane is very high at 7 x 10 ^"8 mol/m ^* s ^* Pa ^1/2 . However, the separation membrane shows a gradual decrease of hydrogen permeation performance as time passes. As for the 3 nm-thick alumina layer, hydrogen permeability becomes a little lower at 3 x10 ^"8 mol/m ^* s*Pa ^1/2 , but is very stably maintained. In addition, the 1.5 nm and 2 nm thick alumina layers respectively show hydrogen permeability of about 9 x 10 ^~8 mol/m ^* s*Pa ^{1 2} and about 5 x 10 ^"8 mol/m ^* s ^* Pa ^1/2 and no permeability change for one hour, and stably maintain hydrogen permeability when tested for 12 hours.

In addition, another embodiment provides a hydrogen separation device including the hydrogen separation membrane according to the embodiment, a chamber equipped with a supplier for a mixed gas including hydrogen gas, and a discharge chamber equipped with a discharger for separated hydrogen gas.

The hydrogen separation membrane contacts the chamber on one surface of the hydrogen separation membrane, and contacts the discharge chamber on the other surface.

FIG. 9 is a schematic view showing the hydrogen separation device 20 according to one embodiment. When a mixed gas including hydrogen gas is introduced into a chamber 22 through a supplier 21 of the mixed gas including hydrogen gas, only hydrogen gas of the mixed gas is selectively separated into a discharge chamber 24 through a hydrogen separation membrane 23. The separated hydrogen gas may be recovered through a discharge unit 25. The hydrogen separation device 20 may further include a means 26 for recovering the remaining gas from which the hydrogen gas is separated. The hydrogen separation device 20 is shown in a simplified form for better comprehension and easy description, and may further include additional constitutional components according to its use.

FIG. 10 is a schematic view showing another embodiment in which the hydrogen separation device 30 is formed in a tubular shape. The hydrogen separation device 30 includes a tubular shaped hydrogen separation membrane 33, and a large cylindrical chamber barrier rib 36 having a larger diameter than the tubular shaped hydrogen separation membrane is formed outside of the hydrogen separation membrane 33. A space between the chamber barrier rib 36 and the hydrogen separation membrane is provided as a chamber 32, and the inside of the tubular shaped hydrogen separation membrane 33 is provided as a discharge chamber 34 for discharging hydrogen. The chamber 32 may further include a supply unit (not shown) for a mixed gas including hydrogen gas and a recovery unit (not shown) for recovering the remaining gas from which hydrogen gas is separated. In addition, a discharge unit (not shown) may be further included for discharging the separated hydrogen gas into the discharge chamber 34.

In addition, according to another embodiment, when including the tubular shaped hydrogen separation membrane 33, the mixed gas is supplied to the inside of the tubular shaped hydrogen separation membrane 33, and hydrogen from the mixed gas is passed through the tubular shaped hydrogen separation membrane 33 and separated to the outside of the tubular shaped hydrogen separation membrane 33 to discharge hydrogen, contrary to the case shown in FIG. 10. In addition, according to another embodiment, when including the tubular shaped hydrogen separation membrane 33, the mixed gas is supplied to the inside of the tubular shaped hydrogen separation membrane 33, and hydrogen from the mixed gas is passed through the tubular shaped hydrogen separation membrane 33 and separated to the outside of the tubular shaped hydrogen separation membrane 33 to discharge hydrogen, contrary to the case shown in FIG. 10.

Hereinafter, the embodiments are illustrated in more detail with reference to examples. However, they are exemplary examples of the present invention, and this disclosure is not limited thereto.

[Mode for Invention]

Example 1 : Manufacture of V-AhOg-Pd Separation Membrane using ALP

In order to form an alumina (AI2O3) thin film on a 250 pm-thick vanadium metal layer in an ALD method, an AI2O3 atomic layer is formed by flowing TMA (trimethyl aluminum, AI(CH ₃ )3) as a precursor along with H ₂ 0 through a surface chemical reaction in a 300 °C ALD (atomic layer deposition) apparatus (D100 ALD, NCD Co., Ltd.) chamber. Subsequently, the Al ₂ 0 ₃ atomic layer is purged to remove a non-reactant, by which the process is defined as one cycle. When the thickness of the layer deposited by repeating the cycle is measured, the layer is 1 nm thick at the 9th cycle. When the temperature is lower, the rate of forming a layer is higher. The layer may have a desired thickness by controlling the cycle number, and thus, samples respectively coated with each of 0.5 nm, 1 nm, 1.5 nm, 2 nm, and 3 nm-thick AI2O3 layers are manufactured.

FIG. 6 is a SEM photograph showing a sample including an about 5 nm- thick AI2O3 layer on the surface of a vanadium foil. The Al ₂ 0 ₃ layer is coated to be uniform and thin.

In addition, a 150 nm-thick Pd thin film is coated on the V-Al ₂ 0 ₃ layer. The coating is performed by a magnetron sputtering system using a 2 inch Pd target (SHS-2M4-400, Samhanparkmak Vacuum Co., Ltd.). The vanadium thin membrane sample coated with the Al ₂ 0 ₃ layer is mounted on a sputter substrate, and the chamber is highly vacuumed (to less than or equal to 3 x 10 ^"5 torr). Subsequently, an argon (Ar) gas flows at 20 seem into the chamber until the pressure of the chamber becomes 2 x 10 ^"3 torr. Then, a 150 nm-thick Pd layer is deposited for 10 minutes by applying 100 W of power with an RF gun.

FIG. 7 is a TEM (transmission electron microscope) result showing the cross-section of a membrane obtained by forming an about 5 nm-thick Al ₂ 0 ₃ layer in an ALD method and depositing a 150 nm-thick Pd layer thereon, and the AI2O3 layer shows no crystallinity, unlike a Pd or V metal showing a metal lattice, referring to the drawing. Accordingly, the Al ₂ 0 ₃ layer is amorphous and dense.

Example 2: Manufacture of V-AlgOs-Pd Separation Membrane by Sputtering

A separation membrane is manufactured by depositing an Al ₂ 0 ₃ layer on a vanadium foil in a reactive sputtering method using an Al target.

Specifically, a 250 pm-thick vanadium foil is washed on the surface and mounted on a magnetron sputtering system (SHS-2M4-400, Samhanparkmak Vacuum Co., LTD.) as a sputterer depositing on a 6-inch Si wafer, and a DC gun is fixed at power of 60 W (voltage of 280-310 V, current of 0.2 A) to set an Al deposition condition at room temperature. Subsequently, Al ₂ 0 ₃ is deposited by flowing 0 ₂ at 5-10 seem under an argon (Ar) gas atmosphere of 50 seem until a ratio of 0 ₂ /Ar reaches 20 %. When the Al ₂ 0 ₃ is deposited for 20 minutes, the Al ₂ 0 ₃ is deposited to be about 30 nm thick, and when the Al ₂ 0 ₃ is deposited for 10 minutes, the Al ₂ 0 ₃ is deposited to be about 20 nm thick. When the Al ₂ 0 ₃ is deposited for 10 minutes after adjusting a ratio of the0 ₂ /Ar to be 10 %, the Al ₂ 0 ₃ is deposited to be about 5 nm thick. When the deposition time is reduced to 5 minutes, the Al ₂ 0 ₃ is deposited to be about 7 nm thick. When the oxygen partial pressure is reduced to 5 %, the amount of oxygen is insufficient, and thus an Al-rich metal phase is formed, showing a shiny silver appearance. When the deposition time is reduced, the deposition thickness decreases in proportion to time.

The method is adopted to respectively form each of 7 nm, 10 nm, 15 nm, 20 nm, and 30 nm-thick alumina layers on a 250 pm-thick vanadium metal layer, and then a 100 nm-thick Pd catalyst layer is respectively formed thereon, manufacturing a separation membrane.

Experimental Example: Evaluation of Hydrogen Permeation Characteristics

Hydrogen permeability of the hydrogen separation membranes according to Examples 1 and 2 is measured. As for a control group, a hydrogen separation membrane is manufactured by forming only a 150 nm- thick Pd catalyst layer on the 250 pm-thick vanadium foil without depositing Al ₂ 0 ₃ in an example.

The hydrogen permeability is measured by using self-developed hydrogen permeability equipment. First, the separation membrane samples according to Examples 1 and 2 are manufactured into disk-shaped separation membrane samples having a diameter of 12 mm, and are then mounted in the chamber of the hydrogen permeability equipment, and the chamber is evacuated. When the chamber is in a low vacuum condition of 10 ^"3 torr, a heating jacket is slowly heated up to 400 °C. When the temperature of 400 °C is stabilized, the amount of hydrogen flowing out through a mass flow meter (MFM) after applying a hydrogen partial pressure of 8 atm at an inlet and maintaining 1 atm at an outlet is measured.

Permeability of the separation membrane according to Example 1 is measured for about 1 hour, and the results are provided in FIG. 5. Permeability of the separation membrane according to Example 2 is measured for greater than or equal to about 4 hours, and the results are provided in FIG. 8.

As shown from FIG. 5, the control group forming only a Pd catalyst layer on a vanadium foil without coating AI2O3 shows sharply deteriorated hydrogen permeability as soon as a hydrogen partial pressure is applied thereto, and completely loses hydrogen permeation performance after about one hour. On the other hand, when AI ₂ O ₃ is coated to be 1 nm thick on a vanadium foil, initial hydrogen permeability is very high, at about 7 x 10 ^"8 mol/m*s ^* Pa ^{1 2} . However, the separation membrane shows gradually deteriorated hydrogen permeation performance as time passes. When a 3 nm-thick alumina layer is formed, hydrogen permeability becomes a little lower at about 3 x 10-10 ^"8 mol/m ^* s ^* Pa ^1/2 , but is very stably maintained. In addition, for the 1.5 nm and 2 nm-thick alumina layers, hydrogen permeability is respectively about 9 x 10 ^"8 mol/m*s ^* Pa ^1/2 and about 5 x 10 ^"8 mol/m*s ^* Pa ^1/2 which are stably maintained for a long time, that is, for one hour.

The separation membrane according to Example 2 shows initial hydrogen permeability of about 3 x 10 ^"8 to about 2 x 10 ^"9 mol/m*s*Pa ^{1 2} as shown in FIG. 8, and almost no permeability change when measured for 4 hours. In particular, a 7 nm-thick Al ₂ 0 ₃ sample deposited under a condition of 0 ₂ /Ar = 10 % for 5 minutes shows the highest permeability, and the permeability decreases when the 5 minutes is cut down to 3 minutes. An Al ₂ 0 ₃ layer formed in a deposition method shows hydrogen permeability and secures even stable long-term permeability, even though the AI2O3 layer formed in a deposition method is thicker than an AI2O3 layer formed in the ALD method. Accordingly, the AI2O3 layer formed in a sputtering method turns out to be less dense than the Al ₂ 0 ₃ layer formed in the ALD method.

While this disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.