U.S. patent application number 15/065170 was filed with the patent office on 2016-06-30 for electrode unit, electrolytic cell comprising electrode unit, electrolytic device and method of manufacturing electrode of electrode unit.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. The applicant listed for this patent is KABUSHIKI KAISHA TOSHIBA. Invention is credited to Wu MEI, Katsuyuki NAITO, Hideo OOTA, Norihiro TOMIMATSU, Ryosuke YAGI, Masahiro YOKOTA, Norihiro YOSHINAGA.
Application Number | 20160186335 15/065170 |
Document ID | / |
Family ID | 55532850 |
Filed Date | 2016-06-30 |
United States Patent
Application |
20160186335 |
Kind Code |
A1 |
NAITO; Katsuyuki ; et
al. |
June 30, 2016 |
ELECTRODE UNIT, ELECTROLYTIC CELL COMPRISING ELECTRODE UNIT,
ELECTROLYTIC DEVICE AND METHOD OF MANUFACTURING ELECTRODE OF
ELECTRODE UNIT
Abstract
According to one embodiment, an electrode unit of an
electrolytic device includes a first electrode including a first
surface, a second surface located on a side opposite to the first
surface, and a plurality of through-holes opening on the first
surface and the second surface, a second electrode opposed to the
first surface of the first electrode, and a porous membrane
containing an inorganic oxide and provided on the first surface of
the first electrode to cover the first surface and the
through-holes.
Inventors: |
NAITO; Katsuyuki; (Tokyo,
JP) ; YOSHINAGA; Norihiro; (Kawasaki, JP) ;
MEI; Wu; (Yokohama, JP) ; TOMIMATSU; Norihiro;
(Mitaka, JP) ; YAGI; Ryosuke; (Yokohama, JP)
; YOKOTA; Masahiro; (Fukaya, JP) ; OOTA;
Hideo; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOSHIBA |
Minato-ku |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Minato-ku
JP
|
Family ID: |
55532850 |
Appl. No.: |
15/065170 |
Filed: |
March 9, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2015/056388 |
Mar 4, 2015 |
|
|
|
15065170 |
|
|
|
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Current U.S.
Class: |
204/252 ;
204/283; 216/17 |
Current CPC
Class: |
C25B 11/0405 20130101;
C25B 11/0452 20130101; C25B 1/26 20130101; C25B 11/03 20130101;
C25B 9/08 20130101; C02F 1/46109 20130101; C02F 2001/46161
20130101; C02F 2201/46115 20130101; C02F 1/4674 20130101; C02F
2001/46157 20130101; C25B 13/04 20130101; C25B 11/0415 20130101;
C25B 13/02 20130101 |
International
Class: |
C25B 9/08 20060101
C25B009/08; C25B 11/03 20060101 C25B011/03; C25B 13/02 20060101
C25B013/02; C25B 11/04 20060101 C25B011/04; C25B 1/26 20060101
C25B001/26; C25B 13/04 20060101 C25B013/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 19, 2014 |
JP |
2014-191992 |
Claims
1. An electrode unit comprising: a first electrode comprising a
first surface, a second surface located on a side opposite to the
first surface, and a plurality of through-holes opening on the
first surface and the second surface; a second electrode opposed to
the first surface of the first electrode; and a porous membrane
containing inorganic oxide, provided on the first surface of the
first electrode to cover the first surface and the
through-holes.
2. The electrode unit of claim 1, wherein an opening area of the
through-holes on the first surface is 0.01 to 4 mm.sup.2.
3. The electrode unit of claim 2, wherein the first electrode
comprises a plurality of first holes opening on the first surface,
and a plurality of second holes opening on the second surface, the
second holes having a dimension greater than a dimension of the
first holes, and one second hole communicates with a plurality of
first holes to form the through holes.
4. The electrode unit of claim 3, wherein an opening area of the
second holes on the second surface is 1 to 1600 mm.sup.2.
5. The electrode unit of claim 3, wherein a number density of the
first holes per unit area is greater than a number density of the
second holes per unit area.
6. The electrode unit of claim 3, wherein the first holes have a
tapered or curved surface which widens towards the first surface
side.
7. The electrode unit of claim 1, further comprising a diaphragm
which is provided between the porous membrane and the second
electrode, and transmits at least one of an ion and liquid.
8. The electrode unit of claim 1, wherein the second electrode has
a porous configuration including a plurality of through-holes.
9. The electrode unit of claim 1, wherein the inorganic oxide of
the porous membrane is at least one selected from titanium oxide,
aluminum oxide, zirconium oxide and zircon.
10. The electrode unit of claim 1, wherein the inorganic oxide of
the porous membrane is at least one selected from titanium oxide,
silicon oxide, aluminum oxide, zirconium oxide, tungsten oxide,
zircon and zeolite.
11. The electrode unit of claim 1, wherein the porous membrane has
irregular pores in a plane and in a three-dimensional manner.
12. The electrode unit of claim 1, wherein the porous membrane is
provided such that a pore dimension of a surface on the first
electrode side is different from a pore dimension of a surface on
the second electrode side.
13. The electrode unit of claim 1, wherein the porous membrane
comprises a first area which is in contact with the first surface
of the first electrode, and a second area which covers the
through-holes, and an imperforate membrane or a porous membrane
having a pore-dimension less than a dimension of a surface pore of
the second area is further provided on a surface of the first
area.
14. The electrode unit of claim 1, wherein the porous membrane
covers a part of or an entire part of a wall surface defining the
through-holes of the first electrode.
15. The electrode unit of claim 1, wherein a space for inputting an
electrolyte, or a holder for holding an electrolyte is provided
between the first electrode and the second electrode.
16. An electrolytic cell comprising: an electrolytic chamber; and
the electrode unit of claim 1, provided in the electrolytic
chamber.
17. An electrolytic device comprising: an electrolytic cell
comprising an electrolytic chamber; the electrode unit of claim 1,
provided in the electrolytic chamber; and a power supply which
applies voltage to the first and second electrodes of the electrode
unit.
18. The electrolytic device of claim 17, wherein the electrode unit
electrolyzes an electrolyte containing a chloride ion.
19. A method of manufacturing an electrode used for an electrode
unit, the method comprising: forming a plurality of through-holes
on an electrode matrix; forming a preprocessing membrane by
applying a solution containing at least one of an inorganic oxide
particle and a precursor to the electrode matrix; and forming a
porous membrane having a large number of pores by burning the
preprocessing membrane.
20. A method of manufacturing an electrode used for an electrode
unit, the method comprising: forming a plurality of through-holes
on an electrode matrix; applying an organic substance to the
through-holes and one of surfaces of the electrode matrix; forming
a preprocessing membrane by applying a solution containing at least
one of an inorganic oxide particle and a precursor to the other
surface of the electrode matrix; and forming a porous membrane
having a large number of pores by burning the preprocessing
membrane after removing the organic substance or without removing
the organic substance.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation Application of PCT
Application No. PCT/JP2015/056388, filed Mar. 4, 2015 and based
upon and claiming the benefit of priority from Japanese Patent
Application No. 2014-191992, filed Sep. 19, 2014, the entire
contents of all of which are incorporated herein by reference.
FIELD
[0002] Embodiments described herein relate generally to an
electrode unit, an electrolytic cell comprising an electrode unit,
an electrolytic device and a method of manufacturing an electrode
for an electrode unit.
BACKGROUND
[0003] In recent years, an electrolytic device for electrolyzing
water and producing an electrolyzed aqueous solution which has
various functions, such as an ionized alkaline solution, an ozone
solution or aqueous hypochlorous acid has been provided. This
electrolytic device comprises an electrolytic cell, and an
electrode unit provided in the electrolytic cell.
[0004] For example, an electrolytic device comprising a
three-chamber electrolytic cell is proposed. The electrolytic cell
is divided into three chambers, specifically, an intermediate
chamber and anode and cathode chambers located on both sides of the
intermediate chamber, by cation- and anion-exchange membranes
included in an electrode unit. The electrode unit comprises an
anode and a cathode. The anode and the cathode of the electrode
unit are provided in the anode and cathode chambers, respectively.
As the electrodes, an electrode having a porous configuration is
used. A large number of through-holes are formed on the matrix made
of a metal plate by applying expanding, etching or punching.
[0005] In this type of electrolytic device, for example, a salt
water is supplied to the intermediate chamber, and water is
supplied to the anode and cathode chambers. The salt water in the
intermediate chamber is electrolyzed by the cathode and the anode.
In this manner, aqueous hypochlorous acid is produced from the
gaseous chlorine produced by the anode. Aqueous sodium hydroxide is
produced in the cathode chamber. The produced aqueous hypochlorous
acid is used as a disinfectant. The aqueous sodium hydroxide is
used as a cleaning solution.
[0006] In the three-chamber electrolytic cell, the anion-exchange
membrane is degraded easily by chlorine or hypochlorous acid. When
an electrode having a porous configuration adheres tightly to an
ion-exchange membrane (electrolyte membrane), stress is easily
concentrated on the edge portion of the pores of the electrode.
Thus, a diaphragm formed of, for example, a thin electrolyte
membrane which is weak mechanically, deteriorates easily. In
consideration of this factor, the following technique is suggested.
Nonwoven fabric having overlaps or slits is inserted between an
electrode having a porous configuration and an electrolyte membrane
to reduce the degradation of the electrode by chlorine.
[0007] An electrode unit in which a porous inorganic oxide membrane
is formed in a flat valve electrode by sol-gel is known.
[0008] However, the electrolytic device having the above structure
cannot avoid degradation of the electrode unit when operated for a
very long time.
[0009] Embodiments described herein aim to provide an electrode
unit, an electrolytic device and a method of manufacturing an
electrode for an electrode unit, enabling the electrolytic
performance to be maintained for a long time and allowing long-life
operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a cross-sectional view showing an electrolytic
device according to a first embodiment.
[0011] FIG. 2 is an exploded perspective view showing an electrode
unit of the electrolytic device according to the first
embodiment.
[0012] FIG. 3A is a cross-sectional view in which an electrode and
a porous membrane of the electrode unit are enlarged.
[0013] FIG. 3B is a cross-sectional view in which the electrode and
the porous membrane of the electrode unit are enlarged.
[0014] FIG. 3C is a cross-sectional view schematically showing the
porous membrane formed by a multilayer film.
[0015] FIG. 3D is a cross-sectional view schematically showing the
porous membrane formed by an inorganic oxide film having irregular
pores in a plane or in a three-dimensional manner.
[0016] FIG. 4 is a cross-sectional view showing the electrode unit
according to a first modification example.
[0017] FIG. 5 is a cross-sectional view showing the electrode and
the porous membrane of the electrode unit according to a second
modification example.
[0018] FIG. 6 is a perspective view showing an electrolytic device
according to a second embodiment.
[0019] FIG. 7 is an exploded perspective view showing an electrode
unit of the electrolytic device according to the second
embodiment.
[0020] FIG. 8 is a cross-sectional view showing the electrode unit
according to the second embodiment.
[0021] FIG. 9 is a cross-sectional view showing a process for
manufacturing an electrode for the electrode unit according to the
second embodiment.
[0022] FIG. 10 is a cross-sectional view showing a process for
manufacturing the electrode and a porous membrane.
[0023] FIG. 11 is a cross-sectional view showing the electrode unit
according to a third modification example.
[0024] FIG. 12 is a cross-sectional view of an electrolytic device
according to a third embodiment.
[0025] FIG. 13 is a cross-sectional view of an electrolytic device
according to a fourth embodiment.
[0026] FIG. 14 is a cross-sectional view showing an electrode unit
according to a fourth modification example.
DETAILED DESCRIPTION
[0027] Various embodiments will be described in detail with
reference to drawings. In general, according to one embodiment, an
electrolytic device comprises an electrode unit. The electrode unit
comprises: a first electrode comprising a first surface, a second
surface located on a side opposite to the first surface, and a
plurality of through-holes opening on the first surface and the
second surface; a second electrode opposed to the first surface of
the first electrode; and a porous membrane containing inorganic
oxide, provided on the first surface of the first electrode to
cover the first surface and the through-holes.
[0028] Structures common in embodiments are denoted by the same
reference numbers or symbols. Overlapping explanations are omitted.
Each figure is an exemplary diagram of an embodiment to prompt
understanding of the embodiment. The shapes, dimensions or ratios
in the drawings may differ from those of the actual device.
However, they may be appropriately changed in consideration of the
explanation below and known art. For example, the drawings show
that electrodes are provided on a plane surface. However, the
electrodes may be bent or cylindrical in accordance with the shape
of the electrode unit.
First Embodiment
[0029] FIG. 1 schematically shows an electrolytic device according
to a first embodiment. An electrolytic device 10 comprises, for
example, a two-chamber electrolytic cell 11 comprising an electrode
unit 12.
[0030] The electrolytic cell 11 is formed in the shape of a flat
and rectangular box. The electrolytic cell 11 is divided into two
chambers, specifically, an anode chamber 16 and a cathode chamber
18, by a diving wall 14 and the electrode unit 12.
[0031] The electrode unit 12 comprises a first electrode (anode) 20
located in the anode chamber 16, a second electrode (a
counterelectrode, a cathode) 22 located in the cathode chamber 18,
and a porous membrane 24 provided between the first and second
electrodes.
[0032] The electrolytic device 10 comprises a power supply 30 which
applies voltage to the first and second electrodes 20 and 22 of the
electrode unit 12, ammeter 32, a voltmeter 34 and a control device
36 which controls these elements. A flow channel for liquid may be
provided in the anode chamber 16 and the cathode chamber 18. For
example, a pipe or a pump for supplying liquid from outside or
discharging liquid may be connected to the anode chamber 16 and the
cathode chamber 18. A porous spacer may be provided between the
electrode unit 12 and the anode chamber 16 or the cathode chamber
18.
[0033] Now, this specification explains the electrode unit 12 in
detail. FIG. 2 is an exploded perspective view of the electrode
unit.
[0034] As shown in FIG. 1 and FIG. 2, the first electrode 20 has a
porous configuration in which a large number of through-holes 13
are formed on a matrix 21 made of, for example, a rectangular metal
plate. The plate-like matrix 21 comprises a first surface 21a, and
a second surface 21b facing and substantially parallel to the first
surface 21a. The interval between the first surface 21a and the
second surface 21b, in other words, the thickness of the plate, is
defined as T1. The first surface 21a faces the porous membrane 24.
The second surface 21b faces the anode chamber 16.
[0035] A large number of through-holes 13 are formed on the whole
surface of the first electrode 20. The through-holes 13 open on the
first surface 21a and the second surface 21b. In the present
embodiment, each through-hole 13 is formed by a tapered wall
surface or a curved wall surface such that the opening dimension on
the first surface 21a side is greater than that on the second
surface 21b side. Each through-hole 13 may take a variety of forms
such as a square, a rectangle, a rhomboid, a circle or an ellipse.
The vertexes of a square, a rectangle or a rhomboid may be rounded.
The through-holes 13 need not be aligned regularly and may be
arranged randomly.
[0036] For the matrix 21 of the first electrode 20, valve metal
such as titanium, chromium, aluminum or an alloy thereof, or
conductive metal may be used. Of these materials, titanium is
preferable. An electrocatalyst (catalytic layer) is preferably
formed on the first and second surfaces 21a and 21b of the first
electrode 20 depending on the electrolytic reaction. In the case of
the anode, as the catalyst, a noble metal catalyst such as platinum
or an oxide catalyst such as iridium oxide is preferably used. The
amount of electrocatalyst per unit area on one surface of the first
electrode may differ from that on the other surface of the first
electrode. In this manner, for example, a side reaction may be
prevented. The surface roughness of the matrix 21 is preferably
0.01 to 3 .mu.m. When the surface roughness is equal to or less
than 0.01 .mu.m, the actual surface area of the electrode is
reduced. When the surface roughness is equal to or greater than 3
.mu.m, the stress applied to the porous membrane is easily
concentrated on the convex portion of the electrode. The surface
roughness of the matrix 21 is more preferably 0.02 to 2 .mu.m, and
is further preferably 0.03 to 1 .mu.m.
[0037] As shown in FIG. 1 and FIG. 2, in the present embodiment,
the second electrode (counterelectrode) 22 is structured in the
same manner as the first electrode 20. The second electrode 22 has
a porous configuration in which a large number of through-holes 15
are formed on a matrix 23 made of, for example, a rectangular metal
plate. The matrix 23 comprises a first surface 23a, and a second
surface 23b facing and substantially parallel to the first surface
23a. The first surface 23a faces the porous membrane 24. The second
surface 23b faces the cathode chamber 18.
[0038] The continuous porous membrane 24 is formed on the first
surface 21a of the first electrode 20 and covers the whole first
surface 21a and the through holes 13. In the present embodiment,
the porous membrane 24 is formed in a rectangular shape so as to
have dimensions substantially equal to those of the first electrode
20. The porous membrane 24 is interposed between the first surface
21a of the first electrode 20 and the first surface 23a of the
second electrode 22. The second electrode 22 may not come into
direct contact with the porous membrane 24. Alternatively, another
structure may be provided between the second electrode 22 and the
porous membrane 24.
[0039] As the porous membrane 24, a uniform inorganic oxide porous
membrane containing an inorganic oxide which is chemically stable
is used. Various materials may be used for the inorganic oxide. For
example, titanium oxide, silicon oxide, aluminum oxide, niobium
oxide, zirconium oxide, tantalum oxide, nickel oxide, tungsten
oxide, zircon or zeolite may be used. Of these materials, titanium
oxide, zirconium oxide, silicon oxide and aluminum oxide are
preferably used. Hydroxide, alkoxide, oxyhalide or hydrate may be
contained in the inorganic oxide. When the inorganic oxide is
prepared by the hydrolysis of metal halide or metal alkoxide, a
composite thereof may be easily obtained depending on the
temperature of the subsequent treatment.
[0040] When using the first electrode 20 for the anode, titanium
oxide, aluminum oxide, zirconium oxide and zircon are preferable as
the inorganic oxide for the porous membrane 24, since these
materials easily have a positive zeta potential in an acidic region
and therefore exhibit an anion-exchange function. When using the
first electrode 20 for the cathode, titanium oxide, aluminum oxide,
zirconium oxide, silicon oxide, tungsten oxide, zircon and zeolite
are preferable as the inorganic oxide for the porous membrane 24,
since these materials easily have a negative zeta potential in an
alkaline region and therefore exhibit a cation-exchange
function.
[0041] As schematically shown in FIG. 3D, the porous membrane 24
containing an inorganic oxide may be formed to have irregular pores
in a plane and in a three-dimensional manner through application of
nanoparticles or sol-gel. In this case, the porous membrane 24 is
resistant to bending, etc. The porous membrane 24 may contain
polymers in addition to the inorganic oxide. Polymers add
flexibility to the membrane. As the polymers, a halogen atom may be
preferably substituted on a main chain which is chemically stable.
For example, polyvinylidene chloride, polyvinylidene fluoride and
Teflon (registered trademark) are preferable. Of these materials,
Teflon is particularly preferable. Apart from these materials, as
the polymers, polyethylene and an engineering plastics such as
polyimide or polyphenylenesulfide may be employed.
[0042] As shown in FIG. 3A, the pore dimension of the porous
membrane 24 may be formed such that the opening dimension on the
first electrode 20 side is different from that on the second
electrode 22 side. When the opening dimension of each pore on the
second electrode 22 side is made greater than that on the first
electrode 20 side, ion transfer can be further facilitated, and
moreover, the concentration of stress applied by the through-hole
13 of the first electrode 20 can be reduced. The structure in which
the opening dimension on the second electrode 22 side is great
facilitates ion transfer caused by diffusion. When the first
electrode 20 is used for the anode, a positive potential is
applied. Therefore, even when the opening dimension on the first
electrode 20 side is less, anions are easily drawn to the first
electrode 20. If the pore dimension on the first electrode 20 side
is great, the produced chlorine or hypochlorous acid is easily
diffused to the porous membrane 24 side.
[0043] The pore dimension on the surface of the porous membrane 24
can be measured by a high-resolution scanning electron microscope
(SEM). The pores inside the porous membrane can be measured by
cross-sectional SEM observation.
[0044] As schematically shown in FIG. 3B, the porous membrane 24
comprises a first area 24a which covers the portion of the first
surface 21a of the first electrode 20, and a second area 24b which
covers the opening of the through-hole 13. Normally, it is
difficult to discharge gas such as the produced chlorine in the
portion of the first surface 21a of the first electrode 20. Thus,
the electrode unit 12 is easily degraded. To solve this problem, as
described above, the pores on the surface of the first area 24a may
be eliminated, in other words, no pore may be formed.
Alternatively, the dimension of each pore on the surface of the
first area 24a may be made less than that on the second area 24b.
This structure inhibits an electrolytic reaction in an area which
is in contact with the first area 24a. Thus, the degradation of the
electrode unit 12 can be prevented. To form the first area 24a so
as to have no pore, or to reduce the pore dimension, as shown in
FIG. 3B, a thin imperforate membrane 29a or a porous membrane 29b
having a less pore-dimension may be formed on the first surface 21a
of the first electrode 20 by screen printing, etc. It should be
noted that, in this case, the reactive area of the first electrode
20 is small. Therefore, it is necessary to cause a sufficient
reaction in an electrode area where gas is easily discharged. A
side reaction can be reduced by covering the surface (second
surface 21b) opposite to the porous membrane 24 of the first
electrode 20 with an electrical insulating membrane.
[0045] As shown in FIG. 3C, for the porous membrane 24, a
multilayer film including a plurality of porous membranes 28a and
28b having different pore-dimensions may be used. In this case, the
pore dimension of the porous membrane 28b located on the second
electrode 22 side may be made greater than that of the porous
membrane 28a located on the first electrode 20 side. This structure
can further facilitate ion transfer and reduce the concentration of
stress applied by the through-hole of the electrode.
[0046] The first electrode 20, the porous membrane 24 and the
second electrode 22 having the above structures are brought into
contact with each other by pressing them in a state where the
porous membrane 24 is interposed between the first electrode 20 and
the second electrode 22. In this manner, the electrode unit 12 is
obtained.
[0047] As shown in FIG. 1, the electrode unit 12 is provided in the
electrolytic cell 11 and is attached to the dividing wall 14. The
electrolytic cell 11 is divided into the anode chamber 16 and the
cathode chamber 18 by the dividing wall 14 and the electrode unit
12. Thus, the electrode unit 12 is provided in the electrolytic
cell 11 such that the alignment direction of the structural members
is, for example, the horizontal direction. The first electrode 20
of the electrode unit 12 faces the anode chamber 16. The second
electrode 22 faces the cathode chamber 18.
[0048] In the electrolytic device 10, the two poles of the power
supply 30 are electrically connected to the first electrode 20 and
the second electrode 22. The power supply 30 applies voltage to the
first and second electrodes 20 and 22 under control of the control
device 36. The voltmeter 34 is electrically connected to the first
electrode 20 and the second electrode 22 and detects the voltage
applied to the electrode unit 12. The detected data is supplied to
the control device 36. The ammeter 32 is connected to the voltage
application circuit of the electrode unit 12 and detects the
current flowing in the electrode unit 12. The detected data is
supplied to the control device 36. The control device 36 controls
the application of voltage or load for the electrode unit 12 by the
power supply 30 based on the detected data in accordance with the
program stored in the memory. The electrolytic device 10 applies
voltage or load between the first electrode 20 and the second
electrode 22 in a state where the substance for reaction is
supplied to the anode chamber 16 and the cathode chamber 18. In
this manner, the electrochemical reaction for electrolysis is
advanced. The electrolytic device 10 of the present embodiment
preferably electrolyzes an electrolyte containing chloride
ions.
[0049] According to the electrolytic device and the electrode unit
having the above structure, the porous membrane 24 containing an
inorganic oxide which is chemically stable is formed to cover the
first surface of the first electrode 20 and the through-holes. With
this structure, the distance between the first electrode 20 and the
second electrode 22 can be maintained as constant as possible.
Thus, the flow of liquid can be uniform. The electrolytic reaction
can occur uniformly at the interfaces between electrodes. Because
of the uniform electrolytic reaction, the catalysts and the
electrode metals deteriorate uniformly. In addition, an inorganic
oxide which is chemically stable is used. Thus, the life duration
of the electrode unit can be significantly prolonged. Since the
electrolytic reaction occurs uniformly, the reaction efficiency of
the electrolytic device can be improved, and further, the
deterioration of the electrodes can be inhibited.
[0050] In the first electrode 20 having a porous configuration, the
through-holes are formed with a tapered or curved surface which
enlarges towards the first surface side. With this structure, the
contact angle between the opening of each through-hole and the
porous membrane 24 is made as an obtuse angle, thereby reducing the
concentration of stress on the porous membrane 24.
[0051] With the above structures, it is possible to obtain a
long-life electrode unit which can maintain the electrolytic
performance for a long time, and an electrolytic device comprising
the electrode unit.
[0052] In the first embodiment, the second electrode 22 has a
porous configuration with a large number of through-holes. However,
the second electrode 22 is not limited to this configuration. For
example, a plate-like electrode without a through-hole may be
employed.
[0053] FIG. 4 shows the electrode unit according to a first
modification example. As shown in this figure, the electrode unit
12 may comprise a diaphragm 26 which transmits at least one of ions
and liquid. For example, the diaphragm 26 is formed in a
rectangular shape so as to have dimensions substantially equal to
those of the first electrode 20, and is interposed between the
porous membrane 24 and the first surface 23a of the second
electrode 22. The diaphragm 26 adheres tightly to the porous
membrane 24, and further adheres tightly to the whole first surface
23a of the second electrode 22.
[0054] For the diaphragm 26, various electrolyte membranes and
porous membranes having nano-pores may be used. A usable example of
the electrolyte membranes is a polyelectrolyte membrane such as a
cation-exchange solid polyelectrolyte membrane, more specifically,
a cation-exchange membrane, or an anion-exchange membrane, or a
hydrocarbon-series membrane. Usable examples of the cation-exchange
membrane are Nafion (registered trademark of E. I. du Pont de
Nemours and Company) 112, 115 and 117, Flemion (registered
trademark of Asahi Glass Co., Ltd.), Aciplex (registered trademark
of Asahi Glass Co., Ltd.), and GORE-SELECT (registered trademark of
W.L. Gore & Associates, Inc.). A usable example of the
anion-exchange membrane is A201 manufactured by Tokuyama
Corporation. Usable examples of the porous membranes having
nano-pores are porous ceramic such as porous glass, porous alumina,
porous titania and porous zeolite, and porous polymers such as
porous polyethylen, porous propylene and porous teflon. With the
diaphragm 26 described above, the ion selectivity can be
improved.
[0055] FIG. 5 shows a part of the electrode unit according to a
second modification example. As shown in FIG. 5(a) and FIG. 5(b),
the porous membrane 24 of the electrode unit 12 may be present on
the wall surface defining the through-holes 15 of the first
electrode 20 (in other words, on the sidewall surface of the
through-holes). In other words, the porous membrane 24 may be
formed so as to cover the first surface 21a of the first electrode
20 and a part of or the entire part of the wall surface of at least
one through-hole 15. When the porous membrane 24 is formed in this
manner, the bond between the first electrode 20 and the porous
membrane 24 is strengthened. The porous membrane 24 is difficult to
remove even with a thermal cycle, etc.
[0056] Now, this specification explains an electrode unit and an
electrolytic device according to another embodiment. Note that in
the other embodiments described below, the same referential numbers
and symbols are given to the same structural elements as the above
first embodiment, and the detailed explanations thereof are
omitted. The elements different from those of the first embodiment
are mainly discussed in detail.
Second Embodiment
[0057] FIG. 6 is a cross-sectional view schematically showing an
electrolytic device according to a second embodiment. FIG. 7 is an
exploded perspective view of an electrode unit. FIG. 8 is a
cross-sectional view of the electrode unit. In the second
embodiment, a first electrode 20 of an electrode unit 12 has a
porous configuration, and through-holes are formed such that the
opening dimension on the first surface 21a side differs from that
on the second surface 21b side.
[0058] As shown in FIG. 6 to FIG. 8, the first electrode 20 has a
porous configuration in which a large number of through-holes are
formed on a matrix 21 made of, for example, a rectangular metal
plate. The matrix 21 comprises the first surface 21a, and the
second surface 21b facing and substantially parallel to the first
surface 21a. The interval between the first surface 21a and the
second surface 21b, in other words, the thickness of the plate, is
defined as T1. The first surface 21a faces a porous membrane 24.
The second surface 21b faces an anode chamber 16.
[0059] A plurality of first holes 40 are formed on the first
surface 21a of the matrix 21 and open on the first surface 21a.
Moreover, a plurality of second holes 42 are formed on the second
surface 21b and open on the second surface 21b. Each first hole 40
communicates with the second hole 42 facing the first hole 40.
Thus, a through-hole penetrating the matrix 21 is formed. The first
holes 40 made on the porous membrane 24 side have an opening
dimension (R1) which is less than the opening dimension (R2) of the
second holes 42. Further, the first holes 40 are greater in number
than the second holes 42. The opening area of the second holes 42
is greater than that of the first holes 40. The depth of the first
holes 40 is T2, and the depth of the second holes 42 is T3. The
holes are formed such that T2+T3=T1. In the present embodiment, the
holes are formed such that T2<T3.
[0060] The second holes 42 are formed in, for example, a
rectangular shape and are arranged in a matrix on the second
surface 21b. The circumferential wall which defines each second
hole 42 may be formed to have a tapered surface 42a or a curved
surface so that the dimension enlarges from the bottom of the hole
to the opening, in other words, to the second surface side. The
interval between adjacent second holes 42, that is, the width of a
linear portion of the electrode, is set to W2. Note that the second
holes 42 are not limited to a rectangular shape, and may take
various other forms. Moreover, the second holes 42 need not be
aligned regularly and may be arranged randomly.
[0061] The first holes 40 are formed in, for example, a rectangular
shape and are arranged in a matrix on the first surface 21a. The
circumferential wall which defines each first hole 40 may be formed
to have a tapered or curved surface so that the dimension enlarges
from the bottom of the hole to the opening, in other words, to the
first surface 21a. In this embodiment, a plurality of, for example,
nine first holes 40 are provided to face one second hole 42. The
nine first holes 40 communicate with the second hole 42 and form
the through-holes penetrating the matrix 21 together with the
second hole 42. Interval W1 between adjacent first holes 40 is set
so as to be less than interval W2 between second holes 42. With
this structure, the number density of the first holes 40 on the
first surface 21a is sufficiently greater than that of the second
holes 42 on the second surface 21b. Other elements such as the
matrix 21 and the catalytic layer of the first electrode 20 have
the same structures as the first embodiment.
[0062] The opening dimension of the first holes 40 is preferably
less in order to make the pressure uniform. However, the first
holes 40 need to be large to the extent that substance diffusion
can be prevented. In the case of a square, the dimension of each
side of the opening is preferably 0.1 to 2 mm, and is more
preferably 0.3 to 1 mm. The opening may take a variety of forms
such as a square, a rectangle, a rhomboid, a circle and an ellipse,
while the opening area is preferably 0.01 to 4 mm.sup.2 in the same
manner as the above square. The opening area is more preferably 0.1
to 1.5 mm.sup.2. The opening area is further preferably 0.2 to 1
mm.sup.2. The ratio of the opening area to the electrode area
including the opening (in other words, the opening ratio) is
preferably 0.05 to 0.5, and is more preferably 0.1 to 0.4, and is
further preferably 0.15 to 0.3. If the opening ratio is excessively
less, outgassing is difficult. If the opening ratio is excessively
great, electrode reaction is inhibited.
[0063] Note that the first holes 40 are not limited to a
rectangular shape, and may take other forms. Moreover, the first
holes 40 need not be aligned regularly and may be arranged
randomly. Furthermore, all the first holes 40 may not necessarily
communicate with the second holes 42. Some first holes 40 may not
communicate with second holes 42. Thus, some first holes 40 may not
communicate with the anode chamber 16. For example, the first holes
40 may be formed in a rectangular shape extending from the vicinity
of one end of the electrode to the vicinity of the other end of the
electrode. In these first holes 40, a plurality of opening portions
communicating with the second holes 42 may be arranged at
intervals. Only a part of each first hole 40 may communicate with
the second holes. The first holes which do not communicate with the
second holes can increase the electrode area.
[0064] Preferably, 85% or more of all of the first holes 40 have an
opening area of 0.01 to 4 mm.sup.2. More preferably, 90% or more,
and further preferably, 95% ore more of all of the first holes 40
have an opening area of 0.01 to 4 mm.sup.2.
[0065] Various shapes may be employed for each second hole 42, such
as a square, a rectangle, a rhomboid, a circle or an ellipse. The
opening dimension of each second hole 42 is preferably great in
order to facilitate outgassing. However, if the opening dimension
is great, the electrical resistance is increased. Therefore, the
second holes 42 cannot be significantly enlarged. In the case of a
square, the dimension of each side of the opening is preferably 1
to 40 mm, and is more preferably 2 to 20 mm. The opening may take a
variety of forms such as a square, a rectangle, a rhomboid, a
circle and an ellipse, while the opening area is preferably 1 to
1600 mm.sup.2 in the same manner as the above square. The opening
area of the second holes 42 is more preferably 4 to 900 mm.sup.2,
and is further preferably 9 to 400 mm.sup.2. For example, the
opening may be shaped in a rectangle or an ellipse which is long in
one direction so as to connect an end and the other end of the
electrode.
[0066] The porous membrane 24 containing an inorganic oxide is
formed on the first surface 21a of the first electrode 20 so as to
cover the whole first surface 21a and the first holes 40. The
porous membrane 24 employs the same porous membrane as the first
embodiment described above.
[0067] In the second embodiment, as shown in FIG. 6 to FIG. 8, a
second electrode (counterelectrode) 22 is structured in the same
manner as the first electrode 20. The second electrode 22 has a
porous configuration in which a large number of through-holes are
formed on a matrix 23 made of, for example, a rectangular metal
plate. The matrix 23 comprises a first surface 23a, and a second
surface 23b facing and substantially parallel to the first surface
23a. The first surface 23a faces a diaphragm 26. The second surface
23b faces a cathode chamber 18.
[0068] A plurality of first holes 44 are formed on the first
surface 23a of the matrix 23 and open on the first surface 23a.
Further, a plurality of second holes 46 are formed on the second
surface 23b and open on the second surface 23b. The opening
dimension of the first holes 44 made on the diaphragm 26 side is
less than that of the second holes 46. Further, the first holes 44
are greater in number than the second holes 46. The depth of the
first holes 44 is less than that of the second holes 46.
[0069] A plurality of, for example, nine first holes 44 are
provided to face one second hole 46. The nine first holes 44
communicate with the second hole 46 and form the through-holes
penetrating the matrix 23 together with the second hole 46. The
interval between adjacent first holes 44 is set so as to be less
than the interval between the second holes 46. With this structure,
the number density of the first holes 44 on the first surface 23a
is sufficiently greater than that of the second holes 46 on the
second surface 23b.
[0070] The first electrode 20, the porous membrane 24 and the
second electrode 22 having the above structures are brought into
contact with each other by pressing them in a state where the
porous membrane 24 is interposed between the first electrode 20 and
the second electrode 22. In this manner, the electrode unit 12 is
obtained. In the present embodiment, an electrolytic device 10
preferably electrolyzes an electrolyte containing chloride
ions.
[0071] This specification explains an example of a method of
manufacturing the first electrode 20 and the porous membrane 24
having the above structures. The first electrode 20 can be
manufactured by, for example, an etching method using a mask. As
shown in FIG. 9(a) and FIG. 9(b), the flat matrix 21 is prepared.
Resist films 50a and 50b are applied to the first and second
surfaces 21a and 21b of the matrix 21. As shown in FIG. 9(c), the
resist films 50a and 50b are exposed, using an optical mask (not
shown). Thus, masks 52a and 52b for etching are prepared. As shown
in FIG. 9(d), wet etching is applied to the first and second
surfaces 21a and 21b of the matrix 21 via the masks 52a and 52b
with solution. In this manner, a plurality of first holes 40 and a
plurality of second holes 42 are formed. Subsequently, the first
electrode 20 is obtained by removing the masks 52a and 52b.
[0072] The shape of the tapered or curved surface of the first and
second holes 40 and 42 can be controlled based on the material of
the matrix 21 and etching conditions. The depth of the first holes
40 is T2, and the depth of the second holes 42 is T3. As stated
above, the first and second holes are formed such that T2<T3. In
etching, both surfaces of the matrix 21 may be etched at the same
time, or may be etched separately. The type of etching is not
limited to wet etching. For example, dry etching may be employed.
Apart from etching, the first electrode 20 may be manufactured by,
for example, an expanding method, a punching method or a processing
method using a laser or precision cutting.
[0073] Subsequently, the porous membrane 24 is formed on the first
surface 21a of the first electrode 20. As shown in FIG. 9(e), a
preprocessing film 24c is manufactured by applying a solution
containing inorganic oxide particles and/or inorganic oxide
precursors to the first surface 21a. Subsequently, as shown in FIG.
9(f), the preprocessing film 24c is subjected to sintering to
manufacture the porous membrane 24 having a large number of
pores.
[0074] For example, the solution containing inorganic oxide
precursors is prepared by dissolving metal alkoxide in alcohol,
adding a solvent having a high boiling point such as glycerin to
achieve a porous configuration, or blending an organic substance
such as fatty acid which is easily oxidized to be carbon dioxide at
the time of sintering. To cover the pores of the electrode, the
viscosity of the solution is preferably increased by adding a small
amount of water and partially hydrolyzing metal alkoxide.
Alternatively, a dispersion liquid containing inorganic oxide
particles may be applied. Alternatively, they may be combined with
each other.
[0075] As a method of applying the solution containing inorganic
oxide particles and/or inorganic oxide precursors, for example,
brush or spray application is preferable, as it is simple and easy.
In the process for applying sintering to the preprocessing film 24c
and preparing pores, the sintering temperature is preferably 150 to
600.degree. C.
[0076] In the above process for manufacturing the porous membrane
24, as shown in FIG. 10(a), the first and second holes 40 and 42 of
the first electrode 20 may be covered by an organic substance 55
before preparing the preprocessing film. Subsequently, the
preprocessing film 24c may be formed on the first surface 21a of
the first electrode 20 as shown in FIG. 10(b). Subsequently, as
shown in FIG. 10(c), the organic substance 55 is removed, and the
preprocessing film 24c is burned. Thus, the porous membrane 24 is
formed. Alternatively, the preprocessing film 24c may be burned
while the organic substance 55 is left.
[0077] In the above manufacturing process, the through-holes of the
electrode can be covered certainly when the solution containing
inorganic oxide particles and/or inorganic oxide precursors is
applied. Further, the film thickness of the inorganic oxide can be
made constant such that the film can be flat.
[0078] In the second embodiment, the other structures of the
electrode unit 12 and the electrolytic device 10 are the same as
those of the first embodiment described above. According to the
second embodiment, in a manner similar to that of the first
embodiment, it is possible to obtain a long-life electrode unit
which can maintain the electrolytic performance for a long time, an
electrolytic device comprising the electrode unit, and a method of
manufacturing an electrode.
[0079] According to the second embodiment, in the first electrode
20, the dimension of the first holes 40 formed on the first surface
21a on the porous membrane 24 side is made less than that of the
second holes 42. The number density of the first holes 40 is made
great. This structure allows the reduction in the concentration of
stress applied from the first electrode 20 side to the porous
membrane 24. As a continuous membrane, the porous membrane 24 is
brought into contact with the whole first surface 21a of the first
electrode 20. Thus, the holes of the first electrode 20 are covered
by the porous membrane 24. The distance between the first electrode
20 and the diaphragm 26 can be easily maintained equally over the
whole surface. In this manner, it is possible to prevent occurrence
of distribution in the film thickness of the porous membrane 24 and
maintain the film thickness of the porous membrane 24 equally. This
structure enables the electrolytic reaction to be caused uniformly,
thereby improving the reaction efficiency of the electrolytic
device and preventing the degradation of the electrolyte
membrane.
[0080] FIG. 11 shows the electrode unit according to a third
modification example. As shown in this figure, in the above second
embodiment, the electrode unit 12 may comprise the diaphragm 26
which transmits at least one of ions and liquid. For example, the
diaphragm 26 is formed in a rectangular shape so as to have
dimensions substantially equal to those of the first electrode 20,
and is interposed between the porous membrane 24 and the first
surface 23a of the second electrode 22. The diaphragm 26 adheres
tightly to the porous membrane 24, and further adheres tightly to
the whole first surface 23a of the second electrode 22. As the
diaphragm 26, a diaphragm similar to that of the first modification
example may be used.
Third Embodiment
[0081] FIG. 12 is a cross-sectional view showing an electrolytic
device according to a third embodiment. In the third embodiment, an
electrolytic cell 11 of an electrolytic device 10 is structured as
a one-chamber electrolytic cell comprising only one electrolytic
chamber 17. An electrode unit 12 is provided in the electrolytic
chamber 17. For example, a pipe or a pump for supplying an
electrolyte from outside or discharging an electrolyte may be
connected to the electrolytic chamber 17.
[0082] In the one-chamber electrolytic cell 11, a second electrode
(counterelectrode) 22 of the electrode unit 12 preferably has a
porous configuration in a manner similar to that of the first
electrode 20. The porous configuration enables the electrode area
to be increased.
Fourth Embodiment
[0083] FIG. 13 is a cross-sectional view showing an electrolytic
device according to a fourth embodiment.
[0084] As shown in FIG. 13, an electrolytic device 10 comprises a
three-chamber electrolytic cell 11 and an electrode unit 12. The
electrolytic cell 11 is formed in the shape of a flat and
rectangular box. The electrolytic cell 11 is divided into three
chambers, specifically, an anode chamber 16, a cathode chamber 18
and an intermediate chamber 19 formed between the electrodes, by a
dividing wall 14 and the electrode unit 12.
[0085] The electrode unit 12 comprises a first electrode (anode) 20
located in the anode chamber 16, a second electrode (a
counterelectrode, a cathode) 22 located in the cathode chamber 18,
a porous membrane 24 formed on a first surface 21a of the first
electrode 20, and a porous membrane 27 formed on a first surface
23a of the second electrode 22. The first electrode 20 and the
second electrode 22 face each other across an intervening space
such that they are parallel to each other. The intermediate chamber
(electrolyte chamber) 19 which stores an electrolyte is formed
between the porous membranes 24 and 27 of the first and second
electrodes 20 and 22. A holder 25 which holds an electrolyte may be
provided in the intermediate chamber 19. The first and second
electrodes 20 and 22 may be connected to each other by a plurality
of insulating bridges 60.
[0086] The electrolytic device 10 comprises a power supply 30 which
applies voltage to the first and second electrodes 20 and 22 of the
electrode unit 12, an ammeter 32, a voltmeter 34 and a control
device 36 which controls these elements. A flow channel for liquid
may be provided in the anode chamber 16 and the cathode chamber 18.
For example, a pipe or a pump for supplying liquid from outside or
discharging liquid may be connected to the anode chamber 16 and the
cathode chamber 18. A porous spacer may be provided between the
electrode unit 12 and the anode chamber 16 or the cathode chamber
18 depending on the case.
[0087] In the electrode unit 12, the first and second electrodes 20
and 22 are formed to have a porous configuration similar to that of
the second embodiment. The continuous porous membrane 24 is formed
in, for example, a rectangular shape so as to have dimensions
substantially equal to those of the first electrode 20, and faces
the whole first surface 21a. The continuous porous membrane 27 is
formed in, for example, a rectangular shape so as to have
dimensions substantially equal to those of the second electrode 22,
and faces the whole first surface 23a. As these porous membranes 24
and 27, porous membranes similar to those of the first embodiment
may be used. Various materials may be used for the porous membranes
24 and 27.
[0088] The porous membranes 24 and 27 may also function as
diaphragms as long as they are inorganic oxide films having
irregular pores in a plane or in a three-dimensional manner. The
porous membranes 24 and 27 may be multilayer films of a plurality
of porous membranes having different pore-dimensions.
[0089] In the fourth embodiment having the above structures,
effects similar to those of the first embodiment can be obtained.
It is possible to obtain a long-life electrode unit and
electrolytic device having a high reaction efficiency.
[0090] FIG. 14 shows the electrode unit according to a fourth
modification example. As shown in this figure, the electrode unit
12 may comprise diaphragms 26a and 26b which transmit at least one
of ions and liquid. The diaphragm 26a is formed in, for example, a
rectangular shape so as to have dimensions substantially equal to
those of the first electrode 20, and faces the first surface 21a of
the first electrode 20. The porous membrane 24 is interposed
between the first surface 21a of the first electrode 20 and the
diaphragm 26a, and adheres tightly to the first electrode 20 and
the diaphragm 26a.
[0091] The diaphragm 26b is formed in, for example, a rectangular
shape so as to have dimensions substantially equal to those of the
second electrode 22, and faces the first surface 23a of the second
electrode 22. The porous membrane 27 is interposed between the
first surface 23a of the second electrode 22 and the diaphragm 26b,
and adheres tightly to the second electrode 22 and the diaphragm
26b.
[0092] For the diaphragms 26a and 26b, various electrolyte
membranes and porous membranes having nano-pores may be used. A
usable example of the electrolyte membranes is a polyelectrolyte
membrane such as a cation-exchange solid polyelectrolyte membrane,
more specifically, a cation-exchange membrane, or an anion-exchange
membrane, or a hydrocarbon-series membrane. Usable examples of the
cation-exchange membrane are Nafion (registered trademark of E. I.
du Pont de Nemours and Company) 112, 115 and 117, Flemion
(registered trademark of Asahi Glass Co., Ltd.), Aciplex
(registered trademark of Asahi Glass Co.,
[0093] Ltd.), and GORE-SELECT (registered trademark of W. L. Gore
& Associates, Inc.). A usable example of the anion-exchange
membrane is A201 manufactured by Tokuyama Corporation. Usable
examples of the porous membranes having nano-pores are porous
ceramic such as porous glass, porous alumina and porous titanium,
and porous polymers such as porous polyethylene, porous propylene
and porous teflon.
[0094] Now, various examples and comparative examples are
described.
EXAMPLE 1
[0095] For the electrode matrix 21, a flat titanium plate having a
plate thickness (T1) of 0.5 mm is employed. This titanium plate is
etched as shown in FIG. 9. In this manner, the electrode 20 shown
in FIG. 6 and FIG. 7 is manufactured. In the electrode, the
thickness (T2) of the area including the small first holes 40 (in
other words, the depth of the first holes) is 0.15 mm. The
thickness (T3) of the area including the large second holes 42 (in
other words, the depth of the second holes) is 0.35 mm. Each first
hole 40 has a square shape. The dimension (R1) of each side is 0.57
mm. Each second hole 42 has a square shape. While the vertexes of
the square are rounded, the dimension (R2) of each side of the
square which can be obtained by extrapolating the linear potion is
2 mm. The width (W1) of the linear portion formed between adjacent
first holes 40 is 0.1 mm. The width (W2) of the broad linear
portion formed between adjacent second holes 42 is 1.0 mm.
[0096] This etched electrode matrix 21 is processed in 10 wt % of
an oxalic acid solution at 80.degree. C. for an hour. A solution
adjusted by adding 1-butanol to iridium chloride (IrCl3.nH2O) so as
to obtain 0.25M (Ir) is applied to the first surface 21a of the
electrode matrix 21. Subsequently, drying and burning are applied.
In this case, drying is performed at 80.degree. C. for 10 minutes,
and burning is performed at 450.degree. C. for 10 minutes. The
above application, drying and burning are repeated five times. The
electrode matrix made through this process is cut out such that the
reactive electrode area can be 3 cm.times.4 cm. In this manner, the
first electrode (anode) 20 is manufactured.
[0097] Ethanol and diethanolamine are added to titanium (IV)
tetraisopropoxide under ice bath. An aqueous solution of ethanol is
added drop by drop while stirring it. Thus, sol is prepared. The
thin film is made porous by thermal processing. Polyethylene glycol
(molecular weight: 5000) for increasing the viscosity of the sol is
added to the sol cooled to a room temperature. The first surface
21a of the electrode 20 is coated with a brush. The coated film is
burned at 500.degree. C. for 7 minutes. Coating and burning are
repeated at three times. Subsequently, burning is performed at
500.degree. C. for an hour. Thus, the porous membrane 24 formed of
titanium oxide is obtained.
[0098] In the above process for manufacturing the electrode,
instead of preparing iridium oxide, platinum is sputtered to obtain
the second electrode (the counterelectrode, the cathode) 22. In the
same way as above, the porous membrane 27 formed by a titanium
oxide film is prepared on the second electrode 22.
[0099] The electrode unit 12 shown in FIG. 13 is manufactured,
using the above first and second electrodes 20 and 22. As the
holder 25 which holds the electrolyte, porous polystyrene having a
thickness of 5 mm is used. The first and second electrodes, the
porous membranes, the dividing wall and the porous polystyrene are
laid to overlap each other and are secured by a silicone sealant
and screws. In this manner, the electrode unit 12 is obtained. The
electrolyte device 10 shown in FIG. 13 is manufactured, using this
electrode unit 12.
[0100] The anode and cathode chambers 16 and 18 of the electrolytic
cell 11 are each formed from a vinyl-chloride container in which a
straight flow channel is formed. The control device 36, the power
supply 30, the voltmeter 34 and the ammeter 32 are provided. A pipe
and a pump for supplying water to the anode and cathode chambers 16
and 18 are connected to the electrolytic cell 11. Further, a
saturated salt water tank, a pipe and a pump for circulating a
saturated salt water to the holder (porous polystyrene) 25 of the
electrode unit 12 are connected to the electrode unit.
[0101] The electrolytic device 10 is operated for electrolysis at a
voltage of 4 V and a current of 1.5 A. Aqueous hypochlorous acid is
produced on the first electrode (anode) 20 side, and aqueous sodium
hydroxide is produced on the second electrode (cathode) 22 side.
Even after continuous operation for 1000 hours, no substantial rise
in voltage or change in product concentration is observed. Thus, a
stable electrolytic treatment can be carried out.
EXAMPLE 2
[0102] The electrolytic device 10 is manufactured in the same
manner as in Example 1 except that A201 of Tokuyama Corporation,
which is an anion-exchange membrane, is employed as the diaphragm
26a, and Nafion 117 is provided as the diaphragm 26b between the
porous membrane 24 or 27 and the holder 25 which holds an
electrolyte.
[0103] The electrolytic device 10 is operated for electrolysis at a
voltage of 5.2 V and a current of 1.5 A. Aqueous hypochlorous acid
is produced on the first electrode (anode) 20 side, and aqueous
sodium hydroxide is produced on the second electrode (cathode) 22
side. In Example 2, the concentration of sodium chloride contained
in the aqueous hypochlorous acid is decreased in comparison with
Example 1. Even after continuous operation for 1000 hours, no
substantial rise in voltage or change in product concentration is
observed. Thus, the electrolytic treatment is stable.
EXAMPLE 3
[0104] The electrolytic device 10 is manufactured in the same
manner as in Example 1 except that tetraethoxysilane is employed
instead of titanium (IV) tetraisopropoxide.
[0105] This electrolytic device is operated for electrolysis at a
voltage of 4.3 V and a current of 1.5 A. Aqueous hypochlorous acid
is produced on the first electrode (anode) 20 side, and aqueous
sodium hydroxide is produced on the second electrode (cathode) 22
side. Even after continuous operation for 1000 hours, no
substantial rise in voltage or change in product concentration is
observed. Thus, a stable electrolytic treatment can be carried
out.
EXAMPLE 4
[0106] The electrolytic device 10 is manufactured in the same
manner as in Example 1 except that aluminum triisopropoxide is
employed instead of titanium (IV) tetraisopropoxide.
[0107] This electrolytic device is operated for electrolysis at a
voltage of 4.0 V and a current of 1.5 A. Aqueous hypochlorous acid
is produced on the first electrode (anode) 20 side, and aqueous
sodium hydroxide is produced on the second electrode (cathode) 22
side. Even after continuous operation for 1000 hours, no
substantial rise in voltage or change in product concentration is
observed. Thus, a stable electrolytic treatment can be carried
out.
EXAMPLE 5
[0108] The electrolytic device 10 is manufactured in the same
manner as in Example 1 except that zirconium (IV) tetraisopropoxide
is employed instead of titanium (IV) tetraisopropoxide.
[0109] This electrolytic device is operated for electrolysis at a
voltage of 4.2 V and a current of 1.5 A. Aqueous hypochlorous acid
is produced on the first electrode (anode) 20 side, and aqueous
sodium hydroxide is produced on the second electrode (cathode) 22
side. Even after continuous operation for 1000 hours, no
substantial rise in voltage or change in product concentration is
observed. Thus, a stable electrolytic treatment can be carried
out.
EXAMPLE 6
[0110] The first and second electrodes are manufactured in the same
manner as in Example 1. In the same manner as in Example 1, the
porous membrane 24 formed of titanium oxide is prepared on the
first electrode 20. They are laid to overlap each other, using a
silicone sealant and screws. Thus, the electrode unit 12 is
obtained.
[0111] The electrolytic device 10 shown in FIG. 12 is manufactured,
using this electrode unit 12. The control device 36, the power
supply 30, the voltmeter 34 and the ammeter 32 are provided. A pipe
and a pump for supplying a salt water to the electrolytic chamber
17 are provided. The electrolytic device 10 is operated for
electrolysis at a voltage of 3.7 V and a current of 1.5 A. Thus, a
sodium hypochlorite solution is produced. Even after continuous
operation for 1000 hours, no substantial rise in voltage or change
in product concentration is observed. Thus, a stable electrolytic
treatment can be carried out.
EXAMPLE 7
[0112] The first and second electrodes 20 and 22 are manufactured
in the same manner as in Example 1. Spin coating is applied to the
second surface 21b of the first electrode 20 with an ethyl acetate
solution of PMMA to fill the second holes 42 and 46 of the
electrode with PMMA. An aqueous dispersion containing titanium
oxide nanoparticles having a grain size of 50 nm is applied to the
first surface 21a of the first electrode 20 by screen printing.
After provisional sintering at 100.degree. C., the PMMA is removed
by ethyl acetate. Subsequently, burning is performed at 450.degree.
C. Then, the electrode is put into water. Titanium tetrachloride is
added drop by drop. After the electrode is left at room temperature
for five hours, it is rinsed in water and burned at 450.degree. C.
Thus, the porous membrane 24 formed of titanium oxide is
obtained.
[0113] In the above process for manufacturing the electrode,
instead of preparing iridium oxide, platinum is sputtered to obtain
the second electrode (cathode) 22. In the same way as above, the
porous membrane 27 formed by a titanium oxide film is prepared on
the second electrode 22.
[0114] The electrode unit 12 shown in FIG. 13 is manufactured,
using the above first and second electrodes 20 and 22. As the
holder 25 which holds the electrolyte, porous polystyrene having a
thickness of 5 mm is used. The first and second electrodes, the
porous membranes, the diving wall and the porous polystyrene are
laid to overlap each other and are secured by a silicone sealant
and screws. In this manner, the electrode unit 12 is obtained. The
electrolytic device 10 shown in FIG. 13 is manufactured, using this
electrode unit 12.
[0115] The anode and cathode chambers 16 and 18 of the electrolytic
cell 11 are each formed from a vinyl-chloride container in which a
straight flow channel is formed. The control device 36, the power
supply 30, the voltmeter 34 and the ammeter 32 are provided. A pipe
and a pump for supplying tap water to the anode and cathode
chambers 16 and 18 are connected to the electrolytic cell 11.
Further, a saturated salt water tank, a pipe and a pump for
circulating a saturated salt water to the holder (porous
polystyrene) 25 of the electrode unit 12 are connected to the
electrode unit.
[0116] The electrolytic device 10 is operated for electrolysis at a
voltage of 4 V and a current of 1.5 A. Aqueous hypochlorous acid is
produced on the first electrode (anode) 20 side, and aqueous sodium
hydroxide is produced on the second electrode (cathode) 22 side.
Even after continuous operation for 1000 hours, no substantial rise
in voltage or change in product concentration is observed. Thus, a
stable electrolytic treatment can be carried out.
EXAMPLE 8
[0117] The first and second electrodes are manufactured in the same
manner as in Example 1. An aqueous dispersion containing titanium
oxide nanoparticles having a grain size of 50 nm is applied to
fabric formed of polyvinylidene chloride fibers with a thickness of
200 .mu.m by dip coating and arranged on the first surface of the
first electrode. After burning is performed at 150.degree. C., the
electrode is put into water. Titanium tetrachloride is added drop
by drop. After the electrode is left at room temperature for five
hours, it is rinsed in water and burned at 150.degree. C. Thus, the
porous membrane 24 containing titanium oxide is obtained.
[0118] In the above process for manufacturing the electrode,
instead of preparing iridium oxide, platinum is sputtered to obtain
the second electrode (cathode) 22. In the same way as above, the
porous membrane 27 containing a titanium oxide film is prepared on
the second electrode 22.
[0119] The electrode unit 12 shown in FIG. 14 is manufactured,
using the above first and second electrodes. A201 of Tokuyama
Corporation, which is an anion-exchange membrane, is employed as
the diaphragm 26a. Nafion 117 is employed as the diaphragm 26b. As
the holder 25 which holds the electrolyte, porous polystyrene
having a thickness of 5 mm is used. They are laid to overlap each
other and are bonded together by a silicone sealant and screws.
Thus, the electrode unit 12 is obtained. The electrolytic device is
manufactured, using this electrode unit 12.
[0120] The anode and cathode chambers 16 and 18 of the electrolytic
cell 11 are each formed from a vinyl-chloride container in which a
straight flow channel is formed. The control device 36, the power
supply 30, the voltmeter 34 and the ammeter 32 are provided. A pipe
and a pump for supplying tap water to the anode and cathode
chambers 16 and 18 are connected to the electrolytic cell 11.
Further, a saturated salt water tank, a pipe and a pump for
circulating a saturated salt water to the holder (porous
polystyrene) 25 of the electrode unit 12 are connected to the
electrode unit.
[0121] The electrolytic device 10 is operated for electrolysis at a
voltage of 5.5 V and a current of 1.5 A. Aqueous hypochlorous acid
is produced on the first electrode (anode) 20 side, and aqueous
sodium hydroxide is produced on the second electrode (cathode) 22
side. Even after continuous operation for 1000 hours, no
substantial rise in voltage or change in product concentration is
observed. Thus, a stable electrolytic treatment can be carried
out.
EXAMPLE 9
[0122] The first and second electrodes are manufactured in the same
manner as in Example 1. A hydrophilic Teflon-coated filter is put
into water. Then, titanium tetrachloride is added drop by drop.
After the electrode is left at 50.degree. C. for two hours, it is
rinsed in water and burned at 250.degree. C. Thus, the porous
membrane 24 containing titanium oxide is obtained.
[0123] In the above process for manufacturing the electrode,
instead of preparing iridium oxide, platinum is sputtered to obtain
the second electrode (cathode) 22. In the same way as above, the
porous membrane 27 containing titanium oxide is prepared on the
second electrode 22.
[0124] The electrode unit 12 shown in FIG. 14 is manufactured,
using the above first and second electrodes. A201 of Tokuyama
Corporation, which is an anion-exchange membrane, is employed as
the diaphragm 26a. Nafion 117 is employed as the diaphragm 26b. As
the holder 25 which holds the electrolyte, porous polystyrene
having a thickness of 5 mm is used. They are laid to overlap each
other and are bonded together by a silicone sealant and screws.
Thus, the electrode unit 12 is obtained. The electrolytic device is
manufactured, using this electrode unit 12.
[0125] The anode and cathode chambers 16 and 18 of the electrolytic
cell 11 are each formed from a vinyl-chloride container in which a
straight flow channel is formed. The control device 36, the power
supply 30, the voltmeter 34 and the ammeter 32 are provided. A pipe
and a pump for supplying tap water to the anode and cathode
chambers 16 and 18 are connected to the electrolytic cell 11.
Further, a saturated salt water tank, a pipe and a pump for
circulating a saturated salt water to the holder (porous
polystyrene) 25 of the electrode unit 12 are connected to the
electrode unit.
[0126] The electrolytic device 10 is operated for electrolysis at a
voltage of 5.7 V and a current of 1.5 A. Aqueous hypochlorous acid
is produced on the first electrode (anode) 20 side, and aqueous
sodium hydroxide is produced on the second electrode (cathode) 22
side. Even after continuous operation for 1000 hours, no
substantial rise in voltage or change in product concentration is
observed. Thus, a stable electrolytic treatment can be carried
out.
EXAMPLE 10
[0127] For the electrode matrix 21, a flat titanium plate having a
plate thickness (T1) of 0.5 mm is employed. This titanium plate is
etched as shown in FIG. 9. In this manner, an electrode is
manufactured. In the electrode, the thickness (T2) of the area
including the small first holes 40 (in other words, the depth of
the first holes) is 0.15 mm. The thickness (T3) of the area
including the large second holes 42 (in other words, the depth of
the second holes) is 0.35 mm. The first holes 40 have a rhomboid
shape. The dimension of the longer diagonal line is 0.69 mm. The
dimension of the shorter diagonal line is 0.4 mm. The second holes
42 have a rhomboid shape. The dimension of the longer diagonal line
is 6.1 mm. The dimension of the shorter diagonal line is 3.5 mm.
The width (W1) of the linear portion formed between adjacent first
holes 40 is 0.15 mm. The width (W2) of the broad linear portion
formed between adjacent second holes 42 is 1 mm. The other
structures are the same as those of Example 1. On these conditions,
the electrode unit 12 and the electrolytic device 10 are
manufactured.
[0128] The electrolytic device 10 is operated for electrolysis at a
voltage of 5.3 V and a current of 1.5 A. Aqueous hypochlorous acid
is produced on the anode 20 side, and aqueous sodium hydroxide is
produced on the cathode 22 side. Even after continuous operation
for 1000 hours, no substantial rise in voltage or change in product
concentration is observed. Thus, a stable electrolytic treatment
can be carried out.
COMPARATIVE EXAMPLE 1
[0129] An electrolytic device is manufactured in the same manner as
in Example 1 except that a porous polystyrene membrane is employed
instead of the continuous inorganic porous membrane. This
electrolytic device is operated for electrolysis at a voltage of 4
V and a current of 1.5 A. Aqueous hypochlorous acid is produced on
the anode side, and aqueous sodium hydroxide is produced on the
cathode side. After continuous operation for 1000 hours, a
significant rise in voltage and a decrease in product concentration
are observed. Thus, it is found that this device lacks a long-term
stability.
COMPARATIVE EXAMPLE 2
[0130] An electrode unit and an electrolytic device are
manufactured in the same manner as in Example 7 without coating
with PMMA. In this electrode unit, the through-holes are not
covered by an inorganic porous membrane.
[0131] This electrolytic device is operated for electrolysis at a
voltage of 3.5 V and a current of 1.5 A. Aqueous hypochlorous acid
is produced on the anode side, and aqueous sodium hydroxide is
produced on the cathode side. A great amount of salt is contained
in the aqueous hypochlorous acid.
[0132] The present invention is not limited to the embodiments
described above but the constituent elements of the invention can
be modified in various manners without departing from the spirit
and scope of the invention. Various aspects of the invention can
also be extracted from any appropriate combination of a plurality
of constituent elements disclosed in the embodiments. Some
constituent elements may be deleted from all of the constituent
elements disclosed in the embodiments. The constituent elements
described in different embodiments may be combined arbitrarily.
[0133] For example, the first electrode and the second electrode
are not limited to rectangular shapes, but various other forms may
be selected. The first and second holes of the first electrode are
not limited to rectangular shapes, and may have various other
shapes such as a circular or elliptical shape. Further, the
material of each structural member is not limited to that employed
in the embodiments or examples discussed, but various other
materials may be selected as needed. The electrolytic cell of the
electrolytic device is not limited to one- to three-chamber
electrolytic cells, and may be applied to any types of electrolytic
cells using electrodes in general. The electrolytes and products
are not limited to salt or hypochlorous acid, and may be developed
into various electrolytes and products.
* * * * *