U.S. patent application number 15/666973 was filed with the patent office on 2018-04-12 for gas diffusion layer and electrochemical hydrogen pump.
The applicant listed for this patent is Panasonic Intellectual Property Management Co., Ltd.. Invention is credited to KUNIHIRO UKAI, YUUICHI YAKUMARU.
Application Number | 20180100243 15/666973 |
Document ID | / |
Family ID | 59558306 |
Filed Date | 2018-04-12 |
United States Patent
Application |
20180100243 |
Kind Code |
A1 |
YAKUMARU; YUUICHI ; et
al. |
April 12, 2018 |
GAS DIFFUSION LAYER AND ELECTROCHEMICAL HYDROGEN PUMP
Abstract
A gas diffusion layer includes sheet materials laminated to each
other and each having a gas diffusion portion in which
through-holes are provided to allow a gas to pass therethrough, and
a manifold hole which is provided in a region other than that of
the gas diffusion portion and through which the gas passes.
Inventors: |
YAKUMARU; YUUICHI; (Osaka,
JP) ; UKAI; KUNIHIRO; (Nara, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Intellectual Property Management Co., Ltd. |
Osaka |
|
JP |
|
|
Family ID: |
59558306 |
Appl. No.: |
15/666973 |
Filed: |
August 2, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 8/242 20130101;
C25B 9/10 20130101; H01M 8/0681 20130101; Y02E 60/50 20130101; F04B
35/04 20130101; H01M 8/0271 20130101; C25B 1/02 20130101; H01M
8/04089 20130101; C25B 15/08 20130101; H01M 8/023 20130101; H01M
8/0245 20130101 |
International
Class: |
C25B 15/08 20060101
C25B015/08; C25B 1/02 20060101 C25B001/02; C25B 9/10 20060101
C25B009/10; F04B 35/04 20060101 F04B035/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 7, 2016 |
JP |
2016-198956 |
Claims
1. A gas diffusion layer comprising: sheet materials laminated to
each other and each including a gas diffusion portion in which
through-holes are provided to allow a gas to pass therethrough, and
at least one manifold hole which is provided in a region other than
that of the gas diffusion portion and through which the gas
passes.
2. The gas diffusion layer according to claim 1, wherein the sheet
materials further include a sealing portion provided in a region
not surrounding the manifold hole and outside the gas diffusion
portion and at least one alignment portion which aligns adjacent
sheet materials with each other, and the at least one alignment
portion is provided outside the sealing portion.
3. The gas diffusion layer according to claim 2, wherein the at
least one alignment portion is provided between the sealing portion
and the manifold hole.
4. The gas diffusion layer according to claim 3, wherein the at
least one alignment portion is provided at a side closer to the
sealing portion than to the manifold hole.
5. The gas diffusion layer according to claim 4, wherein the at
least one alignment portion is provided around the periphery of the
sealing portion.
6. The gas diffusion layer according to claim 2, wherein the number
of the at least one alignment portion is two or more, and the
alignment portions are provided at positions which face each other
with the gas diffusion portion interposed therebetween.
7. The gas diffusion layer according to claim 1, wherein at least
one of the sheet materials includes at least one communication path
communicating between the through-holes.
8. The gas diffusion layer according to claim 7, wherein one of the
sheet materials which are located most outside has a small number
of the communication paths as compared to that of each of the other
sheet materials.
9. The gas diffusion layer according to claim 1, wherein the sheet
materials which are adjacent to each other are adhered to each
other.
10. The gas diffusion layer according to claim 7, wherein the
communication path communicates between through-holes provided in
the same sheet material adjacent to the sheet material in which the
communication path is provided.
11. The gas diffusion layer according to claim 7, wherein the
communication path communicates between through-holes provided in
different sheet materials each adjacent to the sheet material in
which the communication path is provided.
12. An electrochemical hydrogen pump comprising: an electrolyte
membrane having a pair of main surfaces; a cathode catalyst layer
provided on one main surface of the electrolyte membrane; an anode
catalyst layer provided on the other main surface of the
electrolyte membrane; a cathode gas diffusion layer provided on the
cathode catalyst layer; an anode gas diffusion layer provided on
the anode catalyst layer; a first plate including a gas flow path
through which an anode gas flows; a second plate including a gas
flow path through which a cathode gas flows; and a voltage
application device applying a voltage between the cathode catalyst
layer and the anode catalyst layer, wherein the anode gas diffusion
layer is the gas diffusion layer according to claim 1.
13. The electrochemical hydrogen pump according to claim 12,
wherein the communication path communicates between a through-hole
of the sheet materials located above a vertical line to the gas
flow path of the first plate and a through-hole of the sheet
materials located above a vertical line to a portion at which no
gas flow path of the first plate is provided.
Description
BACKGROUND
1. Technical Field
[0001] The present disclosure relates to a gas diffusion layer and
an electrochemical hydrogen pump.
2. Description of the Related Art
[0002] In recent years, in consideration of environmental issues,
such as global warming, and energy issues, such as depletion of
petroleum resources, as a clean alternative energy source instead
of fossil fuels, attention has been paid on a hydrogen gas. When a
hydrogen gas is combusted, water is only emitted, and carbon
dioxide, nitrogen oxide, and the like, each of which causes global
warming, are not emitted; hence, a hydrogen gas is expected as
clean energy. As a device using a hydrogen gas as a fuel, for
example, fuel cells may be mentioned, and for automobile power
sources and household power generation, fuel cells have been
increasingly developed and also have been spread. In addition, in a
coming hydrogen society, besides a technique of manufacturing a
hydrogen gas, technical development in terms of storage of a
hydrogen gas at a high density, transportation of a small volume of
hydrogen at a low cost, and usage thereof has been required.
Furthermore, in order to promote the spread of fuel cells,
infrastructure of fuel supply is also required to be organized.
Accordingly, various proposals have been made for purification to
obtain a high purity hydrogen gas and for pressure rising
thereof.
[0003] For example, Japanese Patent No. 4733380 has disclosed that
as shown in FIG. 12, a support member 30 for an electrolyte
membrane of a high differential pressure electrochemical cell is
used as a gas diffusion layer which is in contact with the
electrolyte membrane. That is, in one surface of the support member
30, a plurality of rectangular recess portions is formed, and in
the other surface, a plurality of rhombic recess portions is
formed. In addition, an overlapping portion of the two types of
recess portions forms a triangle through-hole 31 through which a
fluid passes. Accordingly, clogging of a fluid flow path which may
occur in a related mesh type gas diffusion layer may be suppressed,
and in addition, a rigidity can be secured which can withstand the
difference in pressure between a high pressure side and a low
pressure side of the electrochemical cell. Accordingly, since being
supported by the support member 30, the electrolyte membrane can be
suppressed from being deformed to a point of rupture.
SUMMARY
[0004] However, Japanese Patent No. 4733380 has not described a
manifold which supplies a gas from the outside, and hence, from
this document, the way of supplying a gas to the support member 30
has not been known.
[0005] In consideration of the situation described above, one
non-limiting and exemplary embodiment provides a gas diffusion
layer including sheet materials in each of which a manifold hole
for supplying a gas to a gas diffusion portion is provided.
[0006] In one general aspect, the techniques disclosed here feature
a gas diffusion layer comprising: sheet materials laminated to each
other and each of which include a gas diffusion portion having
through-holes through which a gas passes and a manifold hole which
is provided in a region other than that of the gas diffusion
portion and through which the gas passes.
[0007] According to one aspect of the present disclosure, a gas
diffusion layer including sheet materials in each of which a
manifold hole for supplying a gas to a gas diffusion portion is
provided can be obtained.
[0008] Additional benefits and advantages of the disclosed
embodiments will become apparent from the specification and
drawings. The benefits and/or advantages may be individually
obtained by the various embodiments and features of the
specification and drawings, which need not all be provided in order
to obtain one or more of such benefits and/or advantages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a view showing one example of a sheet material of
a gas diffusion layer of a first embodiment;
[0010] FIG. 2A is a view showing one example of a gas diffusion
layer of a second embodiment;
[0011] FIG. 2B is a view showing one example of the gas diffusion
layer of the second embodiment;
[0012] FIG. 3A is a view showing one example of the gas diffusion
layer of the second embodiment;
[0013] FIG. 3B is a view showing one example of the gas diffusion
layer of the second embodiment;
[0014] FIG. 4A is a view showing one example of a gas diffusion
layer of a third embodiment;
[0015] FIG. 4B is a view showing one example of a gas diffusion
layer of a modified example of the third embodiment;
[0016] FIG. 5A is a view showing one example of a sheet material of
the gas diffusion layer of the third embodiment;
[0017] FIG. 5B is a view showing one example of the sheet material
of the gas diffusion layer of the third embodiment;
[0018] FIG. 5C is a view showing one example of the sheet material
of the gas diffusion layer of the third embodiment;
[0019] FIG. 6 is a view showing one example of a gas diffusion
layer of a first example of the third embodiment;
[0020] FIG. 7 is a view showing one example of a gas diffusion
layer of a third example of the third embodiment;
[0021] FIG. 8 is a view showing one example of a gas diffusion
layer of a fourth example of the third embodiment;
[0022] FIG. 9 is a view showing one example of an electrochemical
hydrogen pump of a fourth embodiment;
[0023] FIG. 10 is a view showing one example of the electrochemical
hydrogen pump of the fourth embodiment;
[0024] FIG. 11 is a view showing one example of a gas diffusion
layer of an electrochemical hydrogen pump of an example of the
fourth embodiment; and
[0025] FIG. 12 is a view showing one example of a related gas
diffusion layer.
DETAILED DESCRIPTION
First Embodiment
[0026] For example, in an electrochemical hydrogen pump to obtain a
high pressure hydrogen gas, in order to prevent a gas to be
supplied to a solid molecular membrane (electrolyte membrane) from
leaking to the outside, gaskets or the like are provided at two
sides of a membrane electrode assembly (hereinafter referred to as
"MEA") (electrolyte membrane-gas diffusion layer-catalyst layer)
and are then integrally assembled with the MEA in advance.
Electrically conductive separator plates are disposed outside the
MEA's in order to mechanically fix the MEA's and to electrically
connect between adjacent MEA's in series. In a portion of the
separator plate in contact with the gas diffusion layer of the MEA,
a gas flow path which supplies a gas to the MEA and carries out an
excess gas from the MEA is formed. Although this gas flow path may
be formed separately from the separator plate, a groove-shaped gas
flow path is generally formed in a surface layer of the separator
plate.
[0027] In this case, for example, when the MEA's and the separator
plates are alternately overlapped with and laminated to each other,
in order to supply an appropriate amount of a gas to the gas flow
path of each separator plate, the separator plates are required to
be formed so that fluid paths are branched from an appropriate
conduit path, and front ends of the branched fluid paths are
connected to the gas flow paths of the separator plates. The
conduit path as described above is called a manifold.
[0028] Accordingly, a gas diffusion layer of a first aspect of the
present disclosure comprises sheet materials laminated to each
other and each including a gas diffusion portion in which
through-holes are provided to allow a gas to pass therethrough, and
at least one manifold hole which is provided in a region other than
that of the gas diffusion portion and through which the gas
passes.
[0029] As described above, since the gas diffusion layer of the MEA
is formed of a laminate of the sheet materials, and since the
manifold holes are provided in appropriate positions of the sheet
materials, for example, when the MEA's and the separator plates are
alternately overlapped with and laminated to each other, a gas
supply to the separator plates is appropriately performed. That is,
when the MEA's and the separator plates are alternately overlapped
with and laminated to each other, the gas diffusion portion of the
sheet material and the gas flow path of the separator plate are
disposed to face each other, and the manifold hole of the sheet
material and a manifold hole of the separator plate are disposed to
face each other, so that the manifold can be easily formed.
Accordingly, the gas flow path of each separator plate communicates
with the manifold, an appropriate amount of a gas can be supplied
to the gas flow path of the separator plate.
[0030] Hereinafter, with reference to the attached drawings, a
particular example of the first embodiment will be described.
[0031] The following particular example shows one example of the
first embodiment. Hence, as long as the numerical value, the shape,
the material, the constituent element, the arrangement position of
the constituent element, the connection mode thereof, and the like
described below are not described in the claims, the first
embodiment is not limited thereto (the same thing can also be said
for the other embodiments). In addition, among the following
constituent elements, a constituent element not described in the
independent claim showing a topmost concept will be described as an
arbitrary constituent element. In addition, in the drawings,
description of an element designated by the same reference numeral
may be omitted in some cases. In addition, in order to facilitate
the understanding of the drawings, the constituent elements are
schematically drawn, and hence, the shape, the dimensional ratio,
and the like may be not accurate in some cases.
[Device Structure]
[0032] FIG. 1 is a view showing one example of a sheet material of
a gas diffusion layer of the first embodiment.
[0033] In the example shown in FIG. 1, a sheet material 22 includes
a gas diffusion portion 24 and manifold holes 25.
[0034] In the gas diffusion portion 24, through-holes through which
a gas passes are provided. One example of the structure of the gas
diffusion portion 24 will be described in a third embodiment. The
manifold holes 25 are each provided in a region other than that of
the gas diffusion portion 24 and are each an opening through which
a gas passes. As long as being the opening as described above, the
manifold hole 25 may have any shape. For example, in FIG. 1,
although having a rectangular shape, the manifold hole 25 may have
a round shape. In addition, in FIG. 1, although the manifold holes
25 are provided at the two sides of the gas diffusion portion 24,
the arrangement is not limited thereto.
[0035] In this embodiment, the gas diffusion layer includes a
plurality of sheet materials 22. In addition, the sheet materials
22 are laminated to each other. For example, the sheet materials 22
may be integrally bonded to each other by welding, adhesion,
brazing, or the like. Main surfaces of the sheet materials in a
laminated state may be surface-bonded to each other by diffusion
bonding or the like. In this case, sealing of the manifold hole 25
at the bonding surface of the sheet material 22 is no required. One
example of the structure of the gas diffusion layer will be
described in a second embodiment.
[0036] As described above, since the gas diffusion layer of the MEA
is formed by the laminate of the sheet materials 22, and the
manifold holes 25 are provided in the sheet materials 22 at
appropriate positions, for example, when the MEA's and the
separator plates are alternately overlapped with and laminated to
each other, a gas supply to the separator plates is appropriately
performed. That is, when the MEA's and the separator plates are
alternately overlapped with and laminated to each other, the gas
diffusion portions 24 of the sheet materials 22 and the gas flow
paths of the separator plates are disposed to face each other, and
the manifold holes 25 of the sheet materials 22 and the manifold
holes of the separator plates are disposed to face each other, so
that the manifold can be easily formed. Accordingly, since the gas
flow paths of the separator plates communicate with the manifold,
an appropriate amount of a gas from the manifold can be supplied to
the gas flow paths of the separator plates.
Second Embodiment
[0037] As described above, the gas diffusion layer of the first
embodiment s formed of the laminate of the sheet materials having
the manifold holes.
[0038] In this case, fine through-holes are provided in the gas
diffusion portion of the sheet material, and when the sheet
materials are laminated to each other, in order to suppress the
displacement between the through-holes of the gas diffusion
portions, the sheet materials (gas diffusion portions) are required
to be aligned with each other at a high accuracy. Hence, a device
(alignment portion) performing a highly accurate alignment is
necessarily provided at an appropriate position of the sheet
material. In addition, in order to prevent a gas in the gas
diffusion portion from leaking to the outside, a sealing portion is
required to be provided at an appropriate position of the sheet
material.
[0039] Accordingly, intensive research how to provide the alignment
portion, the sealing portion, and the manifold hole in the sheet
material was carried out, and as a result, the following knowledge
was obtained. In addition, in the following description, as the
alignment portion, although an alignment hole will be described by
way of example, the alignment portion is not limited thereto (for
example, see FIGS. 3A and 3B).
[0040] First, the positional relationship among the alignment
portion, the sealing portion, and the manifold hole was
investigated.
[0041] The alignment hole is required to be provided outside a
region surrounded by the sealing portion. The reason for this is
that when the alignment hole is provided in the region surrounded
by the sealing portion, the alignment hole may function as a gas
leak path in some cases.
[0042] According to a gas diffusion layer of a second aspect of the
present disclosure, in the gas diffusion layer of the first aspect,
the sheet materials may further include a sealing portion provided
in a region not surrounding the manifold hole and outside the
periphery of the gas diffusion portion and at least one alignment
portion which aligns adjacent sheet materials with each other, and
the at least one alignment portion may be provided outside the
sealing portion.
[0043] In addition, in a region defined by an imaginary line drawn
in parallel to the sealing portion so as to pass through the
alignment hole, in order to exclude factors generating stress
concentration as much as possible when an exterior force is applied
to the sheet material, any process may be not performed on the
sheet material other than the gas diffusion portion. The reason for
this will be described below.
[0044] For example, before and after the alignment of the sheet
materials is performed, when an alignment pin is inserted into and
withdrawn from the alignment holes, an exterior force may be
applied to the sheet materials in some cases. In this case, when
the hole is provided in a part of a sheet material having a uniform
cross-section, the stress is increased (stress concentration) as
compared to that in the other part. Hence, in this case, in-plane
variation in strain of the sheet material is generated by the
stress concentration. As a result, if the manifold hole is present
in the region defined by the imaginary line, compared to the case
in which the manifold hole is present outside the region described
above, the in-plane variation in strain of the sheet material is
generated at a side close to the gas diffusion portion, and hence,
it is believed that the gas diffusion portion is seriously
adversely influenced. For example, by the in-plane variation in
strain of the sheet material, displacement of the through-holes of
the gas diffusion portion may arise in some cases.
[0045] In addition, fine flashes generated when the manifold hole
is formed in the sheet material are also required to be taken into
consideration. That is, when the manifold hole is present in the
region defined by the imaginary line, compared to the case in which
the manifold hole is present outside the region described above,
the fine flashes described above are generated at a side close to
the gas diffusion portion, and hence, it is believed that the gas
diffusion portion is seriously adversely influenced. For example,
by the fine flashes of the manifold hole, a desired horizontal
level of the gas diffusion portion of the sheet material may be
difficult to maintain in some cases.
[0046] That is, a gas diffusion layer of a third aspect of the
present disclosure was devised by the knowledge described above. In
the gas diffusion layer of the second aspect, the sheet materials
may further include a sealing portion provided in a region not
surrounding the manifold hole and outside the periphery of the gas
diffusion portion and at least one alignment portion which aligns
adjacent sheet materials with each other, and the at least one
alignment portion may be provided between the sealing portion and
the manifold hole.
[0047] Next, an optimum positional relationship between the
alignment hole and the sealing portion was investigated.
[0048] When the alignment hole is formed as close as possible to
the gas diffusion portion, since the distance between the alignment
hole and the gas diffusion portion can be minimized, influence
factors of the strain generated between the alignment hole and the
gas diffusion portion can be reduced. As a result, the displacement
of the through-holes of the gas diffusion portion can be
appropriately suppressed.
[0049] That is, the alignment hole may be formed in the vicinity of
the periphery of the sealing portion so as to be as close as
possible to the gas diffusion portion.
[0050] That is, a gas diffusion layer of a fourth aspect of the
present disclosure was devised based on the knowledge described
above, and in the gas diffusion layer of the third aspect, the at
least one alignment portion may be provided at a side closer to the
sealing portion than to the manifold hole. In addition, according a
gas diffusion layer of a fifth aspect of the present disclosure, in
the gas diffusion layer of the fourth aspect, the at least one
alignment portion may be provided around the periphery of the
sealing portion.
[0051] Furthermore, according to a gas diffusion layer of a sixth
aspect of the present disclosure, in the gas diffusion layer of one
of the second to the fifth aspects, the number of the at least one
alignment portion may be two or more, and the alignment portions
may be provided at positions which face each other with the gas
diffusion portion interposed therebetween.
[0052] According to the structure as described above, for example,
when an alignment pin is inserted into and withdrawn from the
alignment holes, since an exterior force working on the sheet
material is uniformly applied to the plane of the sheet material,
compared to the case in which alignment portions are not provided
at positions facing each other with the gas diffusion portion
interposed therebetween, the in-plane variation in stress
distribution of the sheet material can be suppressed.
[0053] As described above, according to the gas diffusion layer of
this aspect, when the sheet materials are laminated to each other,
in order to suppress the displacement between the through-holes of
the gas diffusion portions, the sheet materials can be aligned at a
high accurate.
[Device Structure]
[0054] FIGS. 2A, 2B, 3A, and 3B are views each showing one example
of the gas diffusion layer of the second embodiment. FIG. 2B is a
cross-sectional view of a gas diffusion layer 20 of FIG. 2A taken
along the line IIB-IIB. FIG. 3B is a cross-sectional view of a gas
diffusion layer 20 of FIG. 3A taken along the line IIIB-IIIB.
[0055] As shown in FIGS. 2A and 3A, the gas diffusion layer 20
includes sheet materials 22. In addition, in FIGS. 2A and 3A,
although the sheet materials 22 are drawn so as to be separated
from each other for the convenience, as described above, those
sheet materials 22 are integrally bonded to each other by welding,
adhesion, brazing, or the like.
[0056] The sheet material 22 includes a sealing portion 27. The
sealing portion 27 is provided in a region not surrounding a
manifold hole 25 and outside the periphery of a gas diffusion
portion 24 of the sheet material 22. In particular, as shown in
FIGS. 2A and 3A, the sealing portion 27 is provided for the topmost
sheet material 22. Accordingly, the gas diffusion layer 20 is
formed so as not to allow a gas in the gas diffusion portion 24 to
leak to the outside. In addition, because of the integral bonding
between the sheet materials 22, the sealing portion 27 is not
required to be provided for bonding portions between sheet
materials 22 located at a lower side.
[0057] The sealing portion 27 may have any structure as long as the
gas diffusion portion 24 is sealed so as not to allow a gas therein
to leak to the outside. As the sealing portion 27, for example, an
0 ring may be mentioned by way of example. In addition, an outer
circumference shape of the sealing portion 27 surrounding the gas
diffusion portion 24 may be either rectangular or round.
[0058] The sheet materials 22 each include at least one alignment
portion 26. The alignment portion 26 functions to align adjacent
sheet materials 22 with each other. The alignment portion 26 may
have any structure as long as adjacent sheet materials 22 can be
aligned with each other. As the alignment portion 26, an alignment
hole 26A shown in FIGS. 2A and 2B or an alignment protrusion 26B
shown in FIGS. 3A and 3B may be used.
[0059] In this case, the alignment portion 26 is required to be
provided in a region other than that surrounded by the sealing
portion 27. The reason for this is that when the alignment portion
26 is provided in the region surrounded by the sealing portion 27,
the alignment portion 26 may function as a gas leak path in some
cases.
[0060] In addition, the alignment portion 26 is provided between
the sealing portion 27 and the manifold hole 25. In this example,
the alignment portion 26 is provided around the periphery of the
sealing portion 27. In particular, four alignment portions 26 are
provided in the vicinities of four corners of a rectangular sealing
portion 27. The reason for this is as follows.
[0061] For example, before and after the alignment of the sheet
materials 22 is performed, when an alignment pin is inserted into
or withdrawn from the alignment holes 26A, an exterior force may be
applied to the sheet materials 22 in some cases. In this case, when
the hole is formed in a part of the sheet material 22 having a
uniform cross-section, the stress is increased as compared to that
in the other part (stress concentration). Accordingly, in this
case, the in-plane variation in strain of the sheet material 22 is
generated by the stress concentration. Hence, if the manifold hole
is present in a region defined by an imaginary line 100 obtained by
connection between the alignment holes 26A, compared to the case in
which the manifold hole 25 is present outside the region described
above, the in-plane variation in strain of the sheet materials 22
occurs at a side close to the gas diffusion portion 24, and as a
result, it is believed that the gas diffusion portion 24 is
seriously adversely influenced. For example, by the in-plane
variation in strain of the sheet material 22, displacement of the
through-holes of the gas diffusion portion 24 may occur in some
cases.
[0062] In addition, fine flashes generated when the manifold hole
25 is formed in the sheet material 22 are also required to be taken
into consideration. That is, if the manifold hole is present in the
region defined by the imaginary line 100, compared to the case in
which the manifold hole 25 is present outside the region described
above, since the above fine flashes are generated at a side close
to the gas diffusion portion 24, it is believed that the gas
diffusion portion 24 is seriously adversely influenced. For
example, by the fine flashes of the manifold hole 25, a desired
horizontal level of the gas diffusion portion 24 of the sheet
material 22 may be difficult to maintain in some cases.
[0063] Furthermore, when the alignment portion 26 is placed as
close as possible to the gas diffusion portion 24, since the
distance between the alignment portion 26 and the gas diffusion
portion 24 can be minimized, influence factors of the strain
generated between the alignment portion 26 and the gas diffusion
portion 24 can be reduced. As a result, the displacement of the
through-holes of the gas diffusion portion 24 can be appropriately
suppressed.
[0064] That is, the alignment portion 26 may be provided in the
vicinity of the periphery of the sealing portion 27 so as to be as
close as possible to the gas diffusion portion 24.
[0065] In addition, the sheet material 22 has a plurality of
alignment portions 26, and the alignment portions 26 are disposed
at positions facing each other with the gas diffusion portion 24
interposed therebetween. In particular, in a plan view of the gas
diffusion portion 24, when an X axis and a Y axis are drawn through
the center of the gas diffusion portion 24 so as to be orthogonal
to each other, an alignment portion 26 present in the first
quadrant and an alignment portion 26 present in the third quadrant
are located at opposite positions with respect to the center
described above. An alignment portion 26 present in the second
quadrant and an alignment portion 26 present in the fourth quadrant
are located at opposite positions with respect to the center
described above.
[0066] As described above, for example, when an alignment pin is
inserted into or withdrawn from the alignment holes 26A, since an
external force working on the sheet material 22 is uniformly
applied to the plane thereof, compared to the case in which the
alignment portions 26 are not provided at positions facing each
other with the gas diffusion portion 24 interposed therebetween,
the in-plane variation in stress distribution of the sheet material
22 can be suppressed.
[0067] As described above, in the gas diffusion layer 20 of this
embodiment, when the sheet materials 22 are laminated to each
other, in order to suppress the displacement between the
through-holes of the gas diffusion layer 20, the sheet materials 22
can be aligned with each other at a high accuracy.
[0068] In addition, except for the features described above, the
gas diffusion layer 20 of this embodiment may be formed in a manner
similar to that of the gas diffusion layer 20 of the first
embodiment.
Third Embodiment
[0069] The probability that the diffusion of a gas flowing through
a gas diffusion layer is non-uniformed has been intensively
investigated, and the following knowledge was obtained.
[0070] When flow directions of a gas in a gas diffusion layer are
parallel to each other in one direction as disclosed in Japanese
Patent No. 4733380, the diffusion of a gas flowing through the gas
diffusion layer may be non-uniformed in some cases.
[0071] For example, in the support member 30 disclosed in Japanese
Patent No. 4733380, when the structure is formed so that a gas
flows into the through-hole 31 of the support member 30 through a
gas flow path of an appropriate flow path member, a gas is not
allowed to flow into a through-holes 31 located above a vertical
line to a portion at which no gas flow path of the flow path member
is provided. Hence, in this case, the gas diffusion in the support
member 30 is non-uniformed, and by the non-uniformity of the gas
diffusion as described above, an increase in reaction overvoltage
of an electrochemical cell, that is, an increase in consumption
electric power, may occur in some cases.
[0072] Accordingly, in order to obtain a uniform gas diffusion in
the gas diffusion layer as compared to that in the past, the
present inventors finally found an idea to provide at least one
communication path communicating between through-holes in the gas
diffusion layer.
[0073] That is, according to a gas diffusion layer of a seventh
aspect of the present disclosure, in any one of the gas diffusion
layers of the first to the sixth aspects, at least one of the sheet
materials may include a communication path communicating between
through-holes of a sheet material adjacent thereto, the
through-holes thereof being apart from the other through-holes and
not communicated with each other.
[0074] According to the structure described above, as the gas
diffusion layer of this aspect, a gas diffusion layer in which the
gas diffusivity is taken into consideration as compared to that in
the past can be obtained. That is, since the sheet material of the
gas diffusion layer has a communication path, a gas passing into
the gas diffusion layer from an appropriate flow path member can be
supplied not only in one direction but also in an arbitrary
direction. Accordingly, when sheet materials having different
arrangement patterns of the communication paths are laminated to
each other, the direction of a gas flow in the gas diffusion layer
can be arbitrarily set. As a result, the gas diffusivity in the gas
diffusion layer is improved.
[0075] In addition, for example, when the structure in which a gas
is allowed to flow into a through-hole of a gas diffusion layer
through a gas flow path of an appropriate flow path member is used,
if the sheet material has no communication path described above, a
gas is not allowed to flow into a through-hole of the gas diffusion
layer located above the vertical line to the portion at which no
gas flow path of the flow path member is provided, and the gas
diffusion in the gas diffusion layer may be non-uniformed in some
cases. However, in the gas diffusion layer of this aspect, through
the communication path described above, since a gas is also allowed
to flow into the through-hole of the gas diffusion layer as
described above, the gas diffusion can be suppressed from being
non-uniformed.
[0076] In addition, according to a gas diffusion layer of an eighth
aspect of the present disclosure, in the gas diffusion layer of the
seventh aspect of the present disclosure, one of the sheet
materials which are located most outside may have a small number of
the communication paths as compared to that of each of the other
sheet materials. One of the sheet materials which are located most
outside contacts a catalyst layer.
[0077] According to the structure described above, the uniformity
of the gas diffusion is improved. Since the shape of the
through-hole is different from that of the communication path, the
open areas thereof are also different from each other. When the
open area of the through-hole is different from that of the
communication path, the fluid resistances thereof are different
from each other, and the degrees of easiness of gas flow are also
different from each other, so that the gas diffusion may be
non-uniformed thereby. However, when the number of the
communication paths is decreased, a gas may be more uniformly
supplied from the outermost sheet material to the entire region of
the catalyst layer in contact therewith.
[0078] In addition, according to a gas diffusion layer of a ninth
aspect of the present disclosure, in the gas diffusion layer of any
one of the first to the eighth aspects of the present disclosure,
among the sheet materials, adjacent sheet materials may be adhered
to each other.
[0079] According to the structure described above, even under the
conditions in which a high pressure is applied to the gas diffusion
layer, the displacement between the sheet materials of the laminate
is suppressed, and the probability of decreasing the gas
diffusivity due to the displacement between the through-holes of
adjacent sheet materials can be reduced.
[0080] In addition, according to a gas diffusion layer of a tenth
aspect of the present disclosure, in the gas diffusion layer of the
seventh or the eighth aspect of the present disclosure, the
communication path may communicate between through-holes provided
in the same sheet material which is adjacent to the sheet material
in which the communication path is provided.
[0081] According to the structure described above, compared to the
case in which no communication path is provided in the adjacent
sheet material, a gas can be uniformly diffused.
[0082] In addition, according to a gas diffusion layer of an
eleventh aspect of the present disclosure, in the gas diffusion
layer of any one of the seventh, the eighth, and the tenth aspects
of the present disclosure, the communication path may communicate
between through-holes provided in different sheet materials
adjacent to the sheet material in which the communication path is
provided.
[0083] According to the structure described above, compared to the
case in which no communication path is provided in the adjacent
sheet material, a gas can be uniformly diffused.
[Device Structure]
[0084] FIG. 4A is a view showing one example of a cross-section of
the gas diffusion layer of the third embodiment. In FIG. 4A, a
cross-section of the gas diffusion portion 24 of the gas diffusion
layer 20 is shown.
[0085] FIGS. 5A, 5B, and 5C are views each showing one example of
the sheet material of the gas diffusion layer of the first
embodiment. In FIGS. 5A, 5B, and 5C, a plan view of the gas
diffusion portion 24 of the sheet material 22 is shown.
[0086] As shown in FIG. 4A, the gas diffusion layer 20 includes
sheet materials 22 each having through-holes 21 through which a gas
passes. The through-hole 21 is separated from the other
through-holes 21 in the same sheet material 22 so as not to
communicate therewith. In addition, at least one sheet material 22
of the gas diffusion layer 20 includes a communication path 23
communicating between through-holes 21 provided in the same sheet
material 22 which are separated from the other through-holes 21 and
which are not communicated with each other. As long as the gas
diffusion layer 20 includes the sheet materials 22 each having the
through-holes 21, and at least one sheet material 22 of the gas
diffusion layer 20 includes the communication path 23 communicating
between the through-holes 21, any structure may be used.
[0087] According to the example shown in FIG. 4A, in the gas
diffusion layer 20, the through-holes 21 and pairs of end portions
of the communication paths 23 collectively form a gas flow path
(hereinafter, referred to as the "standard gas flow path")
extending in a direction penetrating the gas diffusion layer 20,
and the communication path 23 forms a gas flow path which is
branched from the standard gas flow path and which extends in a
direction parallel to the main surface of the gas diffusion layer
20 to an adjacent standard gas flow path. Accordingly, in a sheet
material 22 adjacent to the sheet material 22 in which the
communication path 23 is provided, the communication path 23
communicates between the through-holes 21 which are separated from
the other through-holes 21 and which are not communicated with each
other. In addition, another example of the gas diffusion layer 20
will be described in a modified example.
[0088] When the gas diffusion layer 20 is viewed in plan, for
example, as shown in FIG. 5A, in a metal-plate gas diffusion
portion 24a forming the sheet material 22 of the gas diffusion
layer 20, through-holes 21A may be formed at regular pitches in a
longitudinal direction and a lateral direction to have a matrix
shape (lattice shape). The through-hole 21A may have any shape. The
through-hole 21A may be, for example, a round hole having a
diameter of approximately several tens of micrometers (such as
approximately 50 .mu.m). As a material of the metal plate, although
for example, stainless steel, titanium, or the like may be used,
the material is not limited thereto. In addition, the metal plate
of FIG. 5A does not include the communication path described above.
FIG. 5A is a plan view obtained when one main surface of a metal
sheet forming the gas diffusion portion 24A is viewed in plan.
[0089] In addition, as shown in FIG. 5B, in a metal-plate gas
diffusion portion 24B forming the sheet material 22 of the gas
diffusion layer 20, through-holes 21B may be formed at regular
pitches in a longitudinal direction and a lateral direction. The
through-hole 21B may have any structure. The through-hole 21B may
be, for example, a round hole having a diameter of approximately
several tens of micrometers (such as approximately 50 .mu.m). As a
material of the metal plate, although for example, stainless steel,
titanium, or the like may be used, the material is not limited
thereto. FIG. 5B is a plan view obtained when one main surface of a
metal sheet forming the gas diffusion portion 24B is viewed in
plan.
[0090] In the example shown in FIG. 5B, when the centers of
adjacent through-holes 21B are connected to each other, the
through-holes 21B are arranged in a longitudinal direction and a
lateral direction so as to form a rhombus S shown by a two-dot
chain line. In this example, a communication path 23B is formed so
as to have an opening along an oblique line formed between centers
PB of adjacent rhombuses S. In addition, it may be said that the
communication path 23B extends in a direction parallel to a first
direction in which the through-holes 21B are connected to each
other without intersecting the communication path 23B. In addition,
it may also be said that the communication path 23B is formed so as
to have an opening along the centers (PB) of straight lines between
adjacent through-holes 21B having a longer distance (between
adjacent through-holes 21B arranged in a longitudinal direction and
a lateral direction) among the through-holes 21B adjacent in a
direction different from the first direction. In addition, for
example, when the gas diffusion portion 24B and the gas diffusion
portion 24A are laminated to each other, the through-holes 21B and
the communication paths 23B are arranged so that the through-holes
21A and the through-holes 21B are overlapped with each other, and
so that the through-holes 21A are overlapped with the pairs of end
portions of the communication paths 23B. Hence, in this case, the
communication path 23B can communicate between the through-holes
21A.
[0091] The communication path 23B may have any shape. For example,
when the through-hole 21B is a round hole having a diameter of
approximately several tens of micrometers (such as approximately 50
.mu.m), the communication path 23B may be a slit having a width of
approximately several tens of micrometers (such as approximately 50
.mu.m).
[0092] In addition, as shown in FIG. 5C, in a metal-plate gas
diffusion portion 24C forming the sheet material 22 of the gas
diffusion layer 20, through-holes 21C may be formed. The
through-holes 21C may have any shape. The through-hole 21C may be,
for example, a round hole having a diameter of approximately
several tens of micrometers (such as approximately 50 .mu.m). As a
material of the metal plate, although for example, stainless steel,
titanium, or the like may be used, the material is not limited
thereto, FIG. 5C is a plan view obtained when one main surface of a
metal sheet forming the gas diffusion portion 24C is viewed in
plan.
[0093] In the example shown in FIG. 5C, the through-holes 21C are
arranged in a longitudinal direction and a lateral direction so
that when the centers of adjacent through-holes 21C are connected
to each other without intersecting communication paths 23C, an
oblique straight line L shown by a two-dot chain line is formed. In
this example, the communication path 23C is formed so as to have an
opening along a line between two intermediate points PC which are
obtained by equally dividing a straight line between adjacent
through-holes 21C in a lateral direction. In addition, for example,
when the gas diffusion portion 24A and the gas diffusion portion
24C are laminated to each other, the through-holes 21C and the
communication paths 23C are arranged so that the through-holes 21A
and the through-holes 21C are overlapped with each other, and so
that the through-holes 21A are also overlapped with the pairs of
end portions of the communication paths 23C. Hence, in this case,
the communication path 23C can communicate between the
through-holes 21A.
[0094] The communication path 23C may have any shape. For example,
when the through-hole 210 is a round hole having a diameter of
approximately several tens of micrometers (such as approximately 50
.mu.m), the communication path 23C may be a slit having a width of
approximately several tens of micrometers (such as approximately 50
.mu.m).
[0095] Accordingly, the gas diffusion layer 20 of this embodiment
can uniformly diffuse a gas as compared to that in the past. That
is, since the gas diffusion layer 20 includes the communication
paths 23, a gas passing in the gas diffusion layer 20 can be
supplied not only in one direction but also in an arbitrary
direction. As a result, when sheet materials 22 having different
arrangement patterns of the communication paths 23 is laminated to
form the gas diffusion layer 20, the direction of a gas flow in the
gas diffusion layer 20 can be arbitrarily set. Hence, the gas
diffusivity in the gas diffusion layer 20 is improved.
[0096] In addition, the combination between the sheet materials 22
having different arrangement patterns of the communication paths 23
is not particularly limited. For example, a metal plate having a
different arrangement pattern from that of the gas diffusion
portion 24C may be a metal plate in which the position of the
communication path 23C is shifted in a lateral direction or a metal
plate including the gas diffusion portion 24B.
[0097] In addition, for example, in the case in which a gas is
allowed to flow into the through-hole 21 of the gas diffusion layer
20 through a gas flow path of a flow path member not shown in the
figure, if the gas diffusion layer 20 does not include the
communication path described above, a gas is not allowed to flow
into the through-hole 21 of the gas diffusion layer 20 located
above the vertical line to the portion at which no gas flow path of
the flow path member is provided, and the gas diffusion in the gas
diffusion layer 20 may be non-uniformed in some cases. However, in
the gas diffusion layer 20 of this embodiment, since a gas can be
allowed to flow into the through-hole 21 of the gas diffusion layer
20 through the communication path 23 as described above, the gas
diffusion can be suppressed from being non-uniformed.
[0098] In addition, the gas diffusion portion 24B and the gas
diffusion portion 24C shown in FIGS. 5B and 5C, respectively, are
configured as described below. First, the through-holes and the
communication paths are provided in the same main surface of the
sheet material. In addition, the open area of the through-hole and
the open area of the communication path in the same main surface of
the sheet material are different from each other. In particular,
the open area of the communication path in the same main surface of
the sheet material is larger than the open area of the
through-hole. In addition, the number of the through-holes in the
same main surface of the sheet material is different from that of
the communication paths. In particular, the number of the
through-holes in the same main surface of the sheet material is
larger than that of the communication paths.
[0099] In addition, the gas diffusion layer 20 of this embodiment
may be formed in a manner similar to that of the gas diffusion
layer 20 of the first or the second embodiment except for the
features described above.
[0100] In addition, the shapes and the dimensions of the
through-hole 21 and the communication path 23 are described by way
of example and are not limited to those shown in this example.
Modified Example
[0101] FIG. 4B is a view showing one example of a gas diffusion
layer of a modified example of the first embodiment. FIG. 4B shows
a cross-section of a gas diffusion portion 24 of a gas diffusion
layer 20.
[0102] As shown in FIG. 4B, the gas diffusion layer 20 includes
sheet materials 22 having through-holes 21 through which a gas
passes. In addition, at least one sheet material 22 of the gas
diffusion layer 20 includes a communication path 23 communicating
between the through-holes 21.
[0103] In the example shown in FIG. 4B, in a gas flow path
extending in a step wise manner (hereinafter, referred to as the
"step-wise gas flow path"), through-holes 21 each forming a through
path which extends in a direction penetrating the gas diffusion
layer 20 and communication paths 23 communicating between the
through paths of the step-wise gas flow path are provided in the
gas diffusion layer 20. Accordingly, the communication path 23
communicates between the through-holes 21 of the sheet materials 22
adjacent to the sheet material 22 in which the communication path
23 is provided.
[0104] In addition, in a plan view of the gas diffusion layer 20,
since the metal plate-made gas diffusion portion forming the sheet
material 22 of the gas diffusion layer 20 is similar to that of the
third embodiment, description thereof is omitted.
[0105] As described above, the gas diffusion layer 20 of this
modified example can uniformly diffuse a gas as compared to that in
the past. Since details of the effect and advantage of the gas
diffusion layer 20 of this modified example are similar to those of
the gas diffusion layer 20 of the third embodiment, description
thereof is omitted.
[0106] The gas diffusion layer 20 of this modified example may be
formed in a manner similar to that of the gas diffusion layer 20 of
the third embodiment except for the features described above.
First Example
[0107] FIG. 6 is a view showing one example of a gas diffusion
layer of a first example of the third embodiment. FIG. 6 shows a
cross-section of a gas diffusion portion 24 of a gas diffusion
layer 20.
[0108] According to the gas diffusion layer 20 of this example, in
the gas diffusion layer 20 of the third embodiment or the modified
example thereof, the number of communication paths of a sheet
material 22 (hereinafter, referred to as the "contact sheet
material 22" in some cases) of the gas diffusion layer 20 in
contact with a catalyst layer 3A is smaller than that of each of
the other layers. In addition, in FIG. 6, although an example in
which the contact sheet material 22 is provided in the gas
diffusion layer 20 of FIG. 4A is shown, the contact sheet material
22 as described above may also be provided in the gas diffusion
layer 20 of FIG. 4B.
[0109] For example, a metal plate forming the contact sheet
material 22 may be the metal plate of FIG. 5A including no
communication paths but is not limited thereto. In addition, a
metal sheet different from the contact sheet material 22 may be at
least one of the gas diffusion portion 24B of FIG. 5B and the gas
diffusion portion 24C of FIG. 5C but is not limited thereto. In
addition, as shown in FIGS. 5A to 5C, the area of a region in which
no openings are formed is larger than the open area of the
through-holes in the metal sheet. Hence, in the region of the main
surface of the outermost sheet material of the gas diffusion layer
which is in contact with the catalyst layer, the area in which no
openings are formed is larger than the open area of the
through-holes.
[0110] As the number of the communication paths 23 of the sheet
material 22 of the gas diffusion layer 20 is decreased, a contact
area between the anode catalyst layer 3A and the sheet material 22
is increased. Hence, the contact area between the contact sheet
material 22 and the anode catalyst layer 3A is increased as
compared to the case in which the anode catalyst layer 3A is in
contact with another layer, and hence, a contact resistance between
the contact sheet material 22 and the anode catalyst layer 3A can
be decreased.
[0111] In addition, when the number of the communication paths 23
of the sheet material 22 of the gas diffusion layer 20 is
increased, the variation in in-plane fluid resistance of this sheet
material 22 tends to increase. For example, when a region including
a large number of communication paths and a region including a
smaller number of communication paths than that described above are
simultaneously present in the surface of the sheet material 22,
since the open area of the communication path 23 is larger than
that of the through-hole 21, the fluid resistance of the former
region is lower than that of the latter region. Accordingly, a gas
is more easily allowed to flow in the former region than in the
latter region. Hence, if a sheet material 22 having a large number
of communication paths 23 is in contact with the catalyst layer 3A,
a uniform supply of a gas over the entire region of the catalyst
layer 3A from the gas diffusion layer 20 may be disturbed in some
cases. However, in the gas diffusion layer 20 of this example,
since the contact sheet material 22 having a small number of
communication paths 23 is in contact with the anode catalyst layer
3A, the probability described above can be reduced.
[0112] The gas diffusion layer 20 of this example may be formed in
a manner similar to that of the third embodiment or the modified
example thereof except for the features described above.
Second Example
[0113] According to a gas diffusion layer 20 of this example, in
the gas diffusion layer 20 of one of the first embodiment, the
second embodiment, the third embodiment, the modified example of
the third embodiment, and the first example of the third
embodiment, adjacent sheet material 22 of the gas diffusion layer
20 are adhered to each other. For example, metal plates forming the
adjacent sheet materials 22 are welded to each other by sintering,
and hence the adjacent sheet materials 22 are appropriately adhered
to each other.
[0114] The gas diffusion layer 20 of this example may be formed in
a manner similar to that of one of the first embodiment, the second
embodiment, the third embodiment, the modified example of the third
embodiment, and the first example of the third embodiment except
for the features described above.
Third Example
[0115] FIG. 7 is a view showing one example of a gas diffusion
layer of a third example of the third embodiment.
[0116] According to a gas diffusion layer 20 of this example, in
the gas diffusion layer 20 of one of the third embodiment, the
modified example of the third embodiment, and the first example of
the third embodiment, the communication path 23 communicates
between a through-hole 21LD and a through-hole 21RD provided in the
same sheet material 22D adjacent to the sheet material 22 in which
the communication path 23 is provided. That is, the communication
path 23 communicates between the left through-hole 21LD and the
right through-hole 21RD present in the same sheet material 22D
located under the sheet material 22 in which the communication path
23 is provided. In addition, the through-hole 21LD and the
through-hole 21RD are shifted from each other by the length of the
communication path 23 in a direction parallel to the main surface
of the gas diffusion layer 20.
[0117] In addition, as shown in FIG. 7, a sheet material 22U
provided on the sheet material 22 in which the communication path
23 is provided may include a through-hole 21U right above the
through-hole 21LD. In this case, the communication path 23
communicates between the through-hole 21U and the through-hole
21RD. In addition, the sheet material 22U located on the sheet
material 22 in which the communication path 23 is provided may
include a through-hole (not shown) located right above the
through-hole 21RD. In this case, the communication path 23
communicates between the through-hole located as described above
and the through-hole 21LD.
[0118] Since the gas diffusion layer 20 includes the communication
path 23, a gas passing in the gas diffusion layer 20 can be
supplied not only in a direction penetrating the gas diffusion
layer 20 but also in a direction parallel to the main surface of
the gas diffusion layer 20. Hence, the gas diffusivity in the gas
diffusion layer 20 is improved.
[0119] The gas diffusion layer 20 of this example may be formed in
a manner similar to that of the third embodiment, the modified
example of the third embodiment, and the first example of the third
embodiment except for the features described above.
Fourth Example
[0120] FIG. 8 is a view showing one example of a gas diffusion
layer of a fourth example of the third embodiment.
[0121] According to a gas diffusion layer 20 of this example, in
the gas diffusion layer 20 of one of the third embodiment, the
modified example of the third embodiment, and the first and the
third examples of the third embodiment, the communication path 23
communicates between a through-hole 21U and a through-hole 21D
provided, respectively, in a sheet material 22U and a sheet
material 22D different therefrom, each of which is adjacent to a
sheet material 22 in which the communication path 23 is provided.
That is, the through-hole 21U of the sheet material 22U located on
the sheet material 22 in which the communication path 23 is
provided and the through-hole 21D of the sheet material 22D located
thereunder communicate with each other. In addition, the
through-hole 21D and the through-hole 21U are shifted from each
other by the length of the communication path 23 in a direction
parallel to the main surface of the gas diffusion layer 20.
[0122] Since the gas diffusion layer 20 includes the communication
path 23, a gas passing in the gas diffusion layer 20 can be
supplied not only in a direction penetrating the gas diffusion
layer 20 but also in a direction parallel to the main surface of
the gas diffusion layer 20. Hence, the gas diffusivity in the gas
diffusion layer 20 is improved.
[0123] The gas diffusion layer 20 of this example may be formed in
a manner similar to that of the third embodiment, the modified
example of the third embodiment, and the first and the third
examples of the third embodiment except for the features described
above.
Fourth Embodiment
[0124] An electrochemical hydrogen pump of a fourth embodiment
includes an electrolyte membrane having a pair of main surfaces, a
cathode catalyst layer provided on one main surface of the
electrolyte membrane, an anode catalyst layer provided on the other
main surface of the electrolyte membrane, a cathode gas diffusion
layer provided on the cathode catalyst layer, an anode gas
diffusion layer provided on the anode catalyst layer, a first plate
including a gas flow path through which an anode gas flows, a
second plate including a gas flow path through which a cathode gas
flows, and a voltage application device applying a voltage between
the cathode catalyst layer and the anode catalyst layer. In
addition, the anode gas diffusion layer includes the gas diffusion
layer of one of the first embodiment, the second embodiment, the
modified example of the third embodiment, and the first to the
fourth examples of the third embodiment.
[0125] Accordingly, when the anode gas diffusion layer of the
electrochemical hydrogen pump of this embodiment is formed by
laminating sheet materials, in order to suppress the displacement
between through-holes of the anode diffusion layer, a highly
accurate alignment can be performed between the sheet materials. In
addition, the anode gas diffusion layer can secure a rigidity which
withstands the press of the electrolyte membrane at a high pressure
and can also uniformly diffuse an anode gas as compared to that in
the past. That is, since the anode gas diffusion layer includes
communication paths, an anode gas passing in the anode gas
diffusion layer from the first plate can be supplied not only in
one direction but also in an arbitrary direction. Hence, layers
having different arrangement patterns of the communication paths
are laminated in the anode gas diffusion layer, the flow direction
of the anode gas in the anode gas diffusion layer can be
arbitrarily set. Accordingly, since the diffusivity of the anode
gas in the anode gas diffusion layer is improved, an increase in
reaction overvoltage of the electrochemical hydrogen pump can be
suppressed. As a result, an increase in reaction resistance
(reaction overvoltage) generated when hydrogen in the anode gas is
dissociated into protons and electrons, that is, an increase in
consumption electric power required for a hydrogen compression
operation of the electrochemical hydrogen pump, can be suppressed
as compared to that in the past.
[0126] In addition, according to an electrochemical hydrogen pump
of one aspect of the present disclosure, in the electrochemical
hydrogen pump of the above fourth embodiment, the communication
path may communicate between a through-hole of the sheet material
located above a vertical line to the gas flow path of the first
plate and a through-hole of the sheet material located above a
vertical line to a portion of the first plate in which no gas flow
path is provided.
[0127] By the structure as described above, since a gas flowing
through the through-hole of the sheet material located above the
vertical line to the gas flow path is allowed to flow into the
through-hole of the sheet material located above the vertical line
to the portion of the first plate in which no gas flow path is
provided through the communication path, the uniformity of the gas
diffusion is improved.
[Device Structure]
[0128] FIGS. 9 and 10 are views each showing one example of an
electrochemical hydrogen pump of the fourth embodiment.
[0129] An electrochemical hydrogen pump 16 includes an electrolyte
membrane 4, a cathode catalyst layer 3C, an anode catalyst layer
3A, a cathode gas diffusion layer 2C, an anode gas diffusion layer
2A, a first plate 1A, a second plate 1C, and a voltage application
device 13.
[0130] As shown in FIG. 10, the electrolyte membrane 4 has a pair
of main surfaces 4U and 4D. The one main surface 4U of the
electrolyte membrane 4 is an upper surface (front surface), and the
other main surface 4D of the electrolyte membrane 4 is a lower
surface (rear surface).
[0131] The electrolyte membrane 4 is a proton conductive high
molecular weight membrane capable of transmitting protons
(H.sup.+). Any membrane may be used for the electrolyte membrane 4
as long as being a proton conductive high molecular weight
membrane. For example, as the electrolyte membrane 4, a fluorinated
high molecular weight electrolyte membrane may be mentioned. In
particular, for example, Nafion (registered trade name,
manufactured by E.I. du Pont) or Aciplex (trade name, manufactured
by Asahi Kasei Corporation) may be used.
[0132] The cathode catalyst layer 3C is provided on the one main
surface 4U of the electrolyte membrane 4. The cathode catalyst
layer 3C contains, for example, platinum as a catalyst metal but is
not limited thereto.
[0133] The anode catalyst layer 3A is provided on the other main
surface 4D of the electrolyte membrane 4. The anode catalyst layer
3A contains, for example, RuIrFeO.sub.x as a catalyst metal but is
not limited thereto.
[0134] In addition, as a catalyst preparation method for the
cathode catalyst layer 3C and the anode catalyst layer 3A, various
methods may be mentioned and are not particularly limited. For
example, as a carrier of the catalyst, an electrically conductive
porous substance powder or a carbon-based powder may be mentioned.
As the carbon-based powder, for example, a powder of graphite,
carbon black, active carbon having an electrically conductivity, or
the like may be mentioned. A method for supporting a catalyst
metal, such as platinum, on a carrier of carbon or the like is not
particularly limited. For example, a method, such as a powder
mixing or liquid phase mixing, may be used. As the latter liquid
phase mixing, for example, there may be mentioned a method in which
a carrier, such as carbon, is dispersed in a catalyst component
colloid solution so that the catalyst component is adsorbed on the
carrier. In addition, an active-oxygen removing material is used as
a carrier if necessary, and a catalyst metal, such as platinum, can
be supported thereon by a method similar to that described above.
The supporting state of the catalyst metal, such as platinum, on
the carrier is not particularly limited. For example, after being
formed into fine particles, the catalyst metal may be highly
dispersedly supported on the carrier.
[0135] The cathode gas diffusion layer 2C is provided on the
cathode catalyst layer 3C. In addition, the cathode gas diffusion
layer 2C may be a single sheet instead of a laminate formed of a
plurality of sheets as is the following anode gas diffusion layer
2A. As the cathode gas diffusion layer 2C, for example, there may
be used a sheet-shaped layer of high modulus graphitized carbon
fibers or a porous body formed by performing platinum plating on
the surface of a titanium powder sintered body. In addition, in the
case in which the above graphitized carbon fibers are used, when
carbon fibers are heat-treated, for example, at 2,000.degree. C. or
more, graphite crystals are grown, so that graphite fibers are
obtained.
[0136] The anode gas diffusion layer 2A is provided on the anode
catalyst layer 3A. The anode gas diffusion layer 2A is required to
have a rigidity which withstands the press of the electrolyte
membrane 4 at a high pressure. Any material may be used as the
anode gas diffusion layer 2A as long as having a rigidity which
withstands the press of the electrolyte membrane 4 at a high
pressure. In this embodiment, the anode gas diffusion layer 2A
includes a gas diffusion layer 20. In this gas diffusion layer 20,
when sheet materials 22 of the gas diffusion layer 20 are each
formed, for example, from a metal plate as described above, a
rigidity which withstands the press of the electrolyte membrane 4
at a high pressure can be secured. In addition, since the gas
diffusion layer 20 is similar to the gas diffusion layer 20 of one
of the first embodiment, the second embodiment, the modified
example of the third embodiment, and the first to the fourth
examples of the first embodiment, detailed description will be
omitted.
[0137] As described above, an MEA 15 includes the electrolyte
membrane 4, the cathode catalyst layer 3C and the anode catalyst
layer 3A provided on the main surfaces 4U and 4D of the electrolyte
membrane 4, respectively, the cathode gas diffusion layer 2C
provided on the upper surface of the cathode catalyst layer 3C, and
the anode gas diffusion layer 2A provided on the lower surface of
the anode catalyst layer 3A. In addition, those layers are bonded
to each other in a laminated state.
[0138] In the first plate 1A (separator plate), a gas flow path 14A
through which an anode gas flows is provided. That is, the first
plate 1A is a member supplying an anode gas to the anode gas
diffusion layer 2A. In particular, in a plan view of the first
plate 1A, for example, a serpentine-shaped gas flow path 14A
communicating with a manifold not shown is formed, and a region in
which this gas flow path 14A is formed is disposed so as to be in
contact with the lower surface of the anode gas diffusion layer
2A.
[0139] In addition, when being dried, the electrolyte membrane 4 is
liable to be broken besides an increase in membrane resistance (IR
loss) and an increase in reaction resistance (reaction overvoltage)
by dissociation of hydrogen into protons and electrons, and hence,
the anode gas contains at least a hydrogen gas and water molecules
(water steam). As the anode gas, for example, there may be
mentioned a reformed gas containing hydrogen or a
hydrogen-containing gas generated by water electrolysis.
[0140] In the second plate 1C (separator plate), a gas flow path
14C through which a cathode gas flows is provided. That is, in the
gas flow path 14C of the second plate 1C, a cathode gas flows from
the cathode gas diffusion layer 2C. In particular, in a plan view
of the second plate 1C, for example, a serpentine-shaped gas flow
path 14C communicating with a manifold not shown is formed, and a
region in which this gas flow path 14C is formed is disposed so as
to be in contact with the upper surface of the cathode gas
diffusion layer 2C. As the cathode gas, for example, a high purity
hydrogen gas may be mentioned.
[0141] In addition, since the lower and the upper surfaces of the
MEA 15 are sandwiched with the first plate 1A and the second plate
1C, respectively, a single cell of the electrochemical hydrogen
pump 16 is obtained.
[0142] The voltage application device 13 applies a voltage between
the cathode catalyst layer 3C and the anode catalyst layer 3A. In
particular, a plus terminal of the voltage application device 13 is
connected to the electrically conductive first plate 1A, and a
minus terminal of the voltage application device 13 is connected to
the electrically conductive second plate 1C. The voltage
application device 13 may have any structure as long as a voltage
can be applied between the cathode catalyst layer 3C and the anode
catalyst layer 3A.
[0143] In this case, the cathode gas diffusion layer 2C and the
anode gas diffusion layer 2A are electricity feeding bodies of the
cathode and the anode of the MEA 15. That is, the cathode gas
diffusion layer 2C functions to feed electricity between the second
plate 1C and the cathode catalyst layer 3C, and the anode gas
diffusion layer 2A functions to feed electricity between the first
plate 1A and the anode catalyst layer 3A.
[0144] In addition, the cathode gas diffusion layer 2C also
functions to diffuse a gas between the gas flow path 14C of the
second plate 1C and the cathode catalyst layer 3C, and the anode
gas diffusion layer 2A also functions to diffuse a gas between the
gas flow path 14A of the first plate 1A and the anode catalyst
layer 3A. For example, the anode gas flowing through the gas flow
path 14A of the first plate 1A diffuses to the surface of the anode
catalyst layer 3A through the anode gas diffusion layer 2A.
[0145] In addition, if necessary, a cooling device is provided for
the single cell of the electrochemical hydrogen pump 16, and by
laminating at least two cells, a stack structure may be formed from
a plurality of single cells.
[0146] As shown in FIG. 9, the electrochemical hydrogen pump 16
includes an anode chamber 8 and a cathode chamber 7.
[0147] The inside of the anode chamber 8 communicates with an anode
inlet pipe 11 and also communicates with the gas flow path 14A of
the first plate 1A through a fluid flow path not shown (such as a
pipe or a manifold). Accordingly, the anode gas flowing into the
anode chamber 8 through the anode inlet pipe 11 is supplied to the
gas flow path 14A of the first plate 1A.
[0148] The inside of the cathode chamber 7 communicates with a
cathode outlet pipe 12 and also communicates with the gas flow path
14C of the second plate 1C through a fluid flow path not shown
(such as a pipe or a manifold). Accordingly, after flowing into the
cathode chamber 7 through the gas flow path 14C of the second plate
1C, the cathode gas (hydrogen gas) passing through the MEA 15 is
then supplied to the cathode outlet pipe 12. In addition, an on-off
valve 9 (such as an electromagnetic valve) is provided for the
cathode outlet pipe 12, and since the on-off valve 9 is
appropriately opened or closed, the cathode gas is stored in a high
pressure hydrogen tank 10. Accordingly, the cathode gas as
described above is used, for example, as a fuel of a hydrogen-using
apparatus (such as a fuel cell vehicle).
[0149] Accordingly, in the anode gas diffusion layer 2A of this
embodiment, when the sheet materials 22 are laminated to each
other, in order to suppress the displacement between the
through-holes 21 of the anode gas diffusion layer 2A, the sheet
materials 22 can be aligned with each other at a high accuracy. In
addition, the anode gas diffusion layer 2A can secure a rigidity
which withstands the press of the electrolyte membrane 4 at a high
pressure and can also uniformly diffuse an anode gas as compared to
that in the past. That is, since the anode gas diffusion layer 2A
includes the communication paths 23, the anode gas passing through
the anode gas diffusion layer 2A from the first plate 1A can be
supplied not only in one direction but also in an arbitrary
direction. Hence, when layers having different arrangement patterns
of the communication paths 23 are laminated in the anode gas
diffusion layer 2A, the direction of the gas flow in the anode gas
diffusion layer 2A can be arbitrarily set. As a result, since the
diffusivity of the anode gas in the anode gas diffusion layer 2A is
improved, the increase in reaction overvoltage of the
electrochemical hydrogen pump 16 can be suppressed. Accordingly,
the increase in reaction resistance (reaction overvoltage)
generated when hydrogen in the anode gas is dissociated into
protons and electrons, that is, the increase in consumption
electric power required for a hydrogen compression operation of the
electrochemical hydrogen pump 16, can be suppressed as compared to
that in the past.
[Operation]
[0150] Hereinafter, an operation of the electrochemical hydrogen
pump of the embodiment will be described with reference to FIGS. 9
and 10. In addition, the following operation may be partially or
fully performed by a control program of a controller not shown in
the figure. Any controller may be used as long as having a control
function. The controller includes, for example, a computing circuit
and a storage circuit storing a control program. As the computing
circuit, for example, an MPU and/or a CPU may be mentioned. As the
storage circuit, for example, a memory may be mentioned. The
controller may be formed of a single controller performing a
centralized control or may be formed of a plurality of controllers
performing a decentralized control in cooperation with each
other.
[0151] First, by the voltage application device 13, a voltage is
applied between the anode and the cathode of the MEA 15.
[0152] Next, when the anode gas is supplied into the anode chamber
8 through the anode inlet pipe 11, electrons are dissociated from
hydrogen in the anode gas on the anode, so that protons (H.sup.+)
are generated (Formula (1)). The electrons thus dissociated are
transferred to the cathode through the voltage application device
13.
[0153] On the other hand, protons pass through the electrolyte
membrane 4 together with water molecules and are brought into
contact with the cathode. On the cathode, a reduction reaction is
performed by the protons passing through the electrolyte membrane 4
and electrons from the cathode gas diffusion layer 2C, so that the
cathode gas (hydrogen gas) is generated (Formula (2)).
[0154] Accordingly, gas purification of an anode gas containing
impurities, such as a CO.sub.2 gas, can be performed at a high
efficiency. That is, the impurities, such as a CO.sub.2 gas, are
removed by the MEA 15. In addition, the anode gas may contain a CO
gas as an impurity in some cases. In this case, since a CO gas
degrades the catalyst activity of the anode catalyst layer 3A and
the like, a CO gas is preferably removed by a CO remover not shown
in the figure (such as a modifier or a CO selective oxidizer).
[0155] In addition, when the on-off valve 9 is closed, the pressure
of the cathode gas in the cathode chamber 7 is increased, and the
gas pressure of the cathode becomes high. In particular, the
relationship among a gas pressure P1 of the anode, a gas pressure
P2 of the cathode, and a voltage E of the voltage application
device 13 can be shown by the following formula (3).
Anode: H.sub.2(low pressure).fwdarw.2H.sup.++2e.sup.- (1)
Cathode: 2H.sup.++2e.sup.-.fwdarw.H.sub.2(high pressure) (2)
E=(RT/2F)In(P2/P1)+ir (3)
[0156] In the formula (3), R represents the gas constant (8.3145
J/Kmol), T represents a temperature (K) of the MEA 15, F represents
Faraday's constant (96,485 C/mol), P2 represents the gas pressure
of the cathode, P1 represents the gas pressure of the anode, i
represents the current density (A/cm.sup.2), and r represents a
cell resistance (.OMEGA.cm.sup.2).
[0157] From the formula (3), it is easily understood that by an
increase in voltage E of the voltage application device 13, the gas
pressure P2 of the cathode can be increased.
[0158] Accordingly, in the electrochemical hydrogen pump 16 of this
embodiment, when the on-off valve 9 is closed, and the voltage E of
the voltage application device 13 is increased, the cathode gas
pressure in the cathode chamber 7 is increased. In addition, when
the cathode gas pressure reaches a predetermined pressure or more,
the on-off valve 9 is opened, so that the cathode gas in the
cathode chamber 7 is filled in the high pressure hydrogen tank 10
through the cathode outlet pipe 12. On the other hand, when the
cathode gas pressure in the cathode chamber 7 reaches less than the
predetermined pressure, the on-off valve 9 is closed, so that the
cathode chamber 7 and the high pressure hydrogen tank 10 are
disconnected to each other. Hence, the cathode gas in the high
pressure hydrogen tank 10 is suppressed from flowing back to the
cathode chamber 7.
[0159] As described above, by the electrochemical hydrogen pump 16,
the cathode gas (hydrogen gas) is pressurized to a desired target
pressure and is filled in the high pressure hydrogen tank 10.
Example
[0160] FIG. 11 is a view showing one example of the gas diffusion
layer of the electrochemical hydrogen pump of an example of the
fourth embodiment.
[0161] According to an electrochemical hydrogen pump 16 of this
example, in the electrochemical hydrogen pump 16 of the fourth
embodiment, a communication path 23 communicates between a
through-hole 21D of a gas diffusion layer 20 located above a
vertical line to a gas flow path 14A of a first plate 1A and a
through-hole 21U of a gas diffusion layer 20 located above a
vertical line to a portion (hereinafter, referred to as the "lib
LB") at which the gas flow path 14A of the first plate 1A is not
provided. In addition, the through-hole 21D and the through-hole
21U are shifted from each other by the length of the communication
path 23 in a direction parallel to the main surface of the gas
diffusion layer 20.
[0162] In this example, the structure is formed so that an anode
gas is allowed to flow into the through-hole 21D of the gas
diffusion layer 20 through the gas flow path 14A of the first plate
1A. Hence, when the communication path described above is not
formed in the gas diffusion layer 20, the anode gas is not allowed
to flow through the through-hole 21U of the gas diffusion layer 20
located above the vertical line to the lib LB in which the gas flow
path 14A of the first plate 1A is not provided, and the diffusion
of the anode gas in the gas diffusion layer 20 may be non-uniformed
in some cases.
[0163] For example, when the lateral dimension of the lib LB of the
first plate 1A is approximately several hundreds of micrometers
(such as approximately 500 .mu.m), in order to prevent the fracture
of the electrolyte membrane 4 by a high pressure, the through-holes
21D and 21U are each required to have a diameter of approximately
several tens of micrometers (such as approximately 50 .mu.m). In
this case, when the communication path is not provided in the gas
diffusion layer 20, the anode gas is not allowed to flow through
the through-hole 21U located above the vertical line to the lib
LB.
[0164] Hence, in this example, by the structure described above,
since the anode gas is also allowed to flow into the through-hole
21U of the gas diffusion layer 20 through the communication path 23
of the gas diffusion layer 20, the diffusion of the anode gas is
suppressed from being non-uniformed.
[0165] The electrochemical hydrogen pump 16 of this example may be
formed in a manner similar to that of the electrochemical hydrogen
pump 16 of the fourth embodiment except for the features described
above. In addition, the shapes and the dimensions of the
through-holes 21 and the lib LB are shown by way of example and are
not limited to those of this example.
[0166] In addition, as long as not conflicted with each other, the
first embodiment, the second embodiment, the third embodiment, the
modified example of the third embodiment, the first to the fourth
examples of the third embodiment, the fourth embodiment, and the
example of the fourth embodiment may be performed in
combination.
[0167] In addition, from the above description, it is apparent to a
person skilled in the art that many improvements of the present
disclosure and other embodiments thereof are to be performed.
Hence, it is to be understood that the above description has been
described by way of example in order to suggest the best mode of
carrying out the present disclosure to a person skilled in the art.
In addition, the structures and/or the functions disclosed in the
present disclosure can be modified and changed without departing
from the sprit and the scope thereof.
[0168] According to one aspect of the present disclosure, for
example, a gas diffusion layer can be obtained in which a manifold
hole supplying a gas to a gas diffusion portion is provided in each
sheet material. Hence, the one aspect of the present disclosure may
be applied, for example, to an electrochemical hydrogen pump.
* * * * *