Hydrogen Separation Membrane and Fuel Cell, and Manufacturing Method Therefor

US 2007 248 874A1

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A method of manufacturing a hydrogen separation membrane comprises the steps of forming an intermediate layer suitable for controlling oxidation of a hydrogen permeable metal layer on the surface of the hydrogen permeable metal layer on the surface of the hydrogen permeable metal used as a substrate; and attaching a catalytic metal in a granular form on the surface of the intermediate layer. This method can be used to manufacture a hydrogen separation membrane in which the quantity of catalytic metal used is controlled.

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Claims

1. A method of manufacturing a hydrogen separation membrane, the manufacturing method comprising the steps of:
(a) forming an oxidation control layer for controlling oxidation of a hydrogen permeable metal layer on a surface thereof; the oxidation control layer being formed tungsten trioxide (WO3), molybdenum trioxide (MoO3), a ceramic perovskite, or a ceramic pyrochlore, the hydrogen permeable metal layer being used as a substrate, and
(b) attaching catalytic metal having dissociation and bonding reactions of hydrogen activity in a granular form on a surface of the oxidation control layer.

Show 2 dependent claims

4. A method of manufacturing a hydrogen separation membrane, the manufacturing method comprising the steps of:
(a) forming an oxidation control layer for controlling oxidation of a hydrogen permeable metal layer used as a substrate on a surface thereof;
(b) attaching catalytic metal having dissociation and bonding reactions of hydrogen activity in a granular form on a surface of the oxidation control layer; and
(c) forming irregularly a surface of the formed oxidation control layer, and
wherein in the step (b), the catalytic metal having dissociation and bonding reactions of hydrogen activity is caused to attach in a granular form to a surface of the irregular oxidation control layer.

Show 4 dependent claims

9. A hydrogen separation membrane comprising:
a hydrogen permeable metal layer as a substrate;
an oxidation control layer formed on a surface of the hydrogen permeable metal layer for controlling oxidation thereof, the oxidation control layer being formed by tungsten trioxide (WO3), molybdenum trioxide (MoO3), a ceramic perovskite, or a ceramic pyrochlore; and
a hydrogen dissociation bonding activity layer formed by attaching a catalytic metal with hydrogen dissociation and bonding reaction activity in a granular form on a surface of the oxidation control layer.

Show dependent claim

Description

TECHNICAL FIELD

The present invention relates to a hydrogen separation membrane for controlling the use of a catalytic metal for activating hydrogen dissociation and bonding, a fuel cell, and a manufacturing method therefor.

BACKGROUND ART

Conventionally, the hydrogen separation membrane described in JAPANESE PATENT LAID-OPEN GAZETTE No. 7-185277 described below, for example, is known as a hydrogen separation membrane having a function to separate only hydrogen from a hydrogen-rich gas used in a fuel cell or the like. For the hydrogen separation membrane indicated in this literature, a hydrogen permeable metal layer (vanadium (V)) is used as the substrate, and both sides thereof are coated with a metal diffusion control layer. Also, the surfaces of such metal diffusion control layers are coated with palladium (Pd) as a catalytic metal in a membrane form, and the catalytic metal activates and promotes dissociation and bonding of hydrogen (hereinafter the catalytic metal is referred to as a hydrogen dissociation and bonding catalytic metal).

The palladium (Pd) used as the hydrogen dissociation and bonding catalytic metal in the hydrogen dissociation membrane described above is expensive, so there is a demand to control the quantity of palladium (Pd) used as much as possible.

The problem described above is not limited to only palladium (Pd), but also concerns other metals used in hydrogen dissociation and bonding catalytic metal.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a hydrogen separation membrane for controlling the quantity of hydrogen dissociation and bonding catalytic metal used, and a fuel cell, and a manufacturing method therefor, taking into consideration the above-mentioned problem.

In order to attain at least part of the above and the other related objects, the present invention is directed to a method of manufacturing a hydrogen separation membrane. The manufacturing method comprises the steps of: (a) forming an oxidation control layer for controlling oxidation of a hydrogen permeable metal layer used as a substrate on a surface thereof, and (b) attaching catalytic metal having dissociation and bonding reactions of hydrogen activity in a granular form on a surface of the oxidation control layer.

According to the above-mentioned manufacturing method for a hydrogen separation membrane, a catalytic metal is attached in a granular form, so it is possible to increase the surface area of the active interface of the catalytic metal over the case where a conventional catalytic metal is formed in a membrane form. Consequently, if the surface area of the active interface is set to the same size as that of the active interface in the case where the catalytic metal is formed in a membrane form, for example, it is possible to control the quantity of catalytic metal used better than in the case where the catalytic metal is formed in a membrane form.

In the above-mentioned manufacturing method, the catalytic metal attached in the step (b) may be a hydrogen permeable metal.

Also, the above-mentioned manufacturing method may further comprise the step of: (c) a process is further provided for contouring the surface of the formed above-mentioned oxidation control layer. In the step (b), the catalytic metal having dissociation and bonding reactions of hydrogen activity may be caused to attach in a granular form to a surface of the irregular oxidation control layer.

If this is done, catalytic metal is made to attach to the irregular oxidation control layer in a granular form, so the surface area of the active interface of the catalytic metal can be increased over the case where the catalytic metal is formed in a membrane form along the surface of the irregular oxidation control layer. Consequently, if the surface area of the active interface is set to the same size as that of the active interface of the catalytic metal in the case where catalytic metal is formed in a membrane form along the surface of the irregular oxidation control layer, for example, it is possible to control the quantity of catalytic metal used better than in the case where the catalytic metal is formed in a membrane form.

If the above-mentioned oxidation control layer is handled as mentioned below, it can be formed irregularly.

That is, in accordance with one preferable application of the above-mentioned manufacturing method, in the step (a), the oxidation control layer is formed amorphously, and in the step (c), a surface of the oxidation control layer is formed irregularly by crystallizing the amorphous oxidation control layer.

If this is done, the amorphous oxidation control layer can be formed irregularly using the physical changes that occur during crystallization.

Also, in accordance with another preferable application of the above-mentioned manufacturing method, in the step (a), the oxidation control layer is formed by a metal oxide whose oxidation is incomplete, and in the step (c), the oxidation control layer is formed irregularly by oxidizing the oxidation control layer made from the metal oxide whose oxidation is incomplete.

If this is done, the oxidation control layer formed from metal oxide whose oxidation is incomplete can be formed irregularly using the physical changes that occur during oxidation.

In accordance with further another preferable application of the above-mentioned manufacturing method, in the step (a), the oxidation control layer is formed with pure metal, and in the step (c), the oxidation control layer is formed irregularly by oxidizing the oxidation control layer made from the pure metal.

If this is done, the oxidation control layer made from pure metal can be formed irregularly using the physical changes that occur during oxidation.

In order to attain at least part of the above and the other related objects, the present invention is directed to a method of manufacturing a fuel cell. The manufacturing method comprises the manufacturing method comprising the steps of: manufacturing the above-mentioned hydrogen separation membrane; and (d) forming an electrolyte layer having proton conductivity on a surface of the hydrogen separation membrane.

According to the manufacturing method for the above-mentioned fuel cell, a hydrogen separation membrane is used which can control the quantity of the above-mentioned catalytic metal used, so it is possible to control the cost of manufacturing a fuel cell.

In order to attain at least part of the above and the other related objects, the present invention is directed to a hydrogen separation membrane. The hydrogen separation membrane comprises a hydrogen permeable metal layer as a substrate; an oxidation control layer formed on a surface of the hydrogen permeable metal layer for controlling oxidation thereof; and a hydrogen dissociation bonding activity layer formed by attaching a catalytic metal with hydrogen dissociation and bonding reaction activity in a granular form on a surface of the oxidation control layer.

According to the above-mentioned hydrogen separation membrane, catalytic metal is attached in a granular form, so the surface area of the active interface of the catalytic metal can be increased more than in the case where a conventional catalytic metal is made in a membrane form. Consequently, if the surface area of the active interface is set to the same size as that of the active interface of the catalytic metal in the case where catalytic metal is formed in a membrane form, for example, it is possible to control the quantity of catalytic metal used better than in the case where the catalytic metal is formed in a membrane form.

In order to attain at least part of the above and the other related objects, the present invention is directed to a fuel cell. The fuel cell comprises the above-mentioned hydrogen separation membrane; and an electrolyte layer formed on a surface of the hydrogen separation membrane and having proton conductivity.

According to the above-mentioned fuel cell, a hydrogen separation membrane is used which can control the quantity of the above-mentioned catalytic metal used, so it is possible to control the cost of manufacturing a fuel cell.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flowchart showing the process for manufacturing a hydrogen separation membrane of Embodiment 1 of the present invention.

FIG. 2 is a flowchart showing the process for manufacturing a hydrogen separation membrane of Embodiment 2 of the present invention.

FIG. 3 is a view for explaining a hydrogen separation membrane when hydrogen dissociation and bonding catalytic metal is coated in a membrane form along a surface of an irregular oxidation control layer 125 in a conventional example.

FIG. 4 is a flowchart showing the process for manufacturing a hydrogen separation membrane of Embodiment 3 of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Modes for carrying out the present invention are described below based on embodiments in the below sequence.

A. Embodiment 1

  • A1. Manufacturing Method for a Hydrogen Separation Membrane
  • A2. Effects of the Embodiment
B. Embodiment 2

  • B1. Manufacturing Method for a Hydrogen Separation Membrane
  • B2. Effects of the Embodiment
C. Embodiment 3

  • C1. Manufacturing Method for a Hydrogen Separation Membrane
  • C2. Effects of the Embodiment
D. Variants
A. Embodiment 1

A1. Manufacturing Method for a Hydrogen Separation Membrane

FIG. 1 is a flowchart showing the process for manufacturing a hydrogen separation membrane in Embodiment 1 of the present invention. Components and so forth formed in each process are illustrated in the flowchart.

A method for manufacturing a hydrogen separation membrane is described below as Embodiment 1 of the present invention using the flowchart shown in FIG. 1.

First, a hydrogen permeable metal layer 100 is prepared as a substrate. Hydrogen selectively passes through the hydrogen permeable metal layer 100 (step S100). Also, in the present embodiment, vanadium (V) is used as the hydrogen permeable metal layer 100 whose thickness is about 50 μm. The thickness may be arbitrarily set according to the use of the hydrogen separation membrane to be produced.

Next, an oxidation retardant for controlling oxidation of the hydrogen permeable metal layer 100, which is the substrate, is coated evenly on both sides thereof, forming an oxidation control layer 110 (step S120). An agent that allows hydrogen to pass through readily is used as the oxidation retardant. For example, tungsten trioxide (WO3), molybdenum trioxide (MoO3), a barium cerate (BaCeO3) or a strontium cerate (SrCeO3) ceramic perovskite (hereinafter, referred to as perovskite) (ABO3), or Sm2Zr2O7 or other ceramic pyrochlore (hereinafter referred to as pyrochlore) (A2B2O7) may be used. Also, the coating of the oxidation retardant is carried out with a PVD method such as ion plating or sputtering, for example. It is desirable to apply the coating at a temperature of about 300 to 500° C. such that the oxidation retardant does not become amorphous. In the present embodiment, the thickness of the oxidation control layer 110 is about 100 nm. This thickness may be set arbitrarily according to the use of the hydrogen separation membrane to be produced. The oxidation control layer 110 has a function to control metal diffusion which can occur between vanadium (V) and a hydrogen dissociation and bonding catalytic metal 120 described below.

Continuing, the hydrogen dissociation and bonding catalytic metal 120 is coated in a granular form on the surface of the oxidation control layer 110 (step S140). A noble metal such as palladium (Pd) or ruthenium (Ru), for example, is used for the hydrogen dissociation and bonding catalytic metal 120. Granular surfaces that do not contact the oxidation control layer 110 in the hydrogen dissociation and bonding catalytic metal 120 in a granular form become active interfaces in which hydrogen dissociation and bonding becomes active. Also, the coating of the hydrogen dissociation and bonding catalytic metal 120 is carried out with a PVD or other such method. As shown in step S140, it is desirable for the size of the grains in the coating to be 20 nm or less so that they do not bond and become a membrane.

A hydrogen separation membrane 10 is thus produced.

A2. Effects of the Embodiment

According to the manufacturing method for a hydrogen separation membrane of the present embodiment as described above, the hydrogen dissociation and bonding catalytic metal 120 is coated in a granular form on the surface of the oxidation control layer 110 which is formed evenly (step S140). If this is done, granular surfaces not contacting the oxidation control layer 110 in the hydrogen dissociation and bonding catalytic metal 120 become active interfaces, so it is possible to make the surface area of the active interface larger than in a case where the hydrogen dissociation and bonding catalytic metal 120 is formed in a membrane form. Consequently, in the case where the surface area of the active interface of the hydrogen dissociation and bonding catalytic metal 120 is set to the same size as the surface area of the active interface in the case where the hydrogen dissociation and bonding catalytic metal 120 is formed in a membrane form, for example, it is possible to control the quantity of hydrogen dissociation and bonding catalytic metal 120 used better than in the case where the hydrogen dissociation and bonding catalytic metal 120 is formed in a membrane form.

B. Embodiment 2

Next, Embodiment 2 of the present invention is described. This manufacturing method for a hydrogen separation membrane of the present embodiment is different from the manufacturing method for a hydrogen separation membrane of Embodiment 1 in the below points. Specifically, in Embodiment 1, the oxidation control layer 110 is formed evenly on both surfaces of the hydrogen permeable metal layer 100, and the hydrogen dissociation and bonding catalytic metal 120 is coated on the formed oxidation control layer 110, but in the present embodiment, the oxidation control layer is formed irregularly, and hydrogen dissociation and bonding catalytic metal is coated on the irregular oxidation control layer. The present embodiment is described therefore below focused on the process representing the points different from Embodiment 1.

B1. Manufacturing Method for a Hydrogen Separation Membrane

FIG. 2 is a flowchart showing the process for manufacturing a hydrogen separation membrane in Embodiment 2 of the present invention. Components and so forth formed in each process different from Embodiment 1 are illustrated in the flowchart.

First, the hydrogen permeable metal layer 100 is prepared as the substrate as in Embodiment 1 (step S100).

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