U.S. patent application number 13/322492 was filed with the patent office on 2012-05-24 for gas diffusion electrode equipped ion exchange membrane electrolyzer.
This patent application is currently assigned to CHLORINE ENGINEERS CORP., LTD.. Invention is credited to Kiyohito Asaumi, Mitsuharu Hamamori, Yukinori Iguchi.
Application Number | 20120125782 13/322492 |
Document ID | / |
Family ID | 43222412 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120125782 |
Kind Code |
A1 |
Asaumi; Kiyohito ; et
al. |
May 24, 2012 |
GAS DIFFUSION ELECTRODE EQUIPPED ION EXCHANGE MEMBRANE
ELECTROLYZER
Abstract
Provided is a gas diffusion electrode equipped ion exchange
membrane electrolyzer including an anode, an ion-exchange membrane,
and a cathode chamber in which a gas diffusion electrode is
disposed, wherein in a cathode gas chamber formed between a back
plate of the cathode chamber and one side of the gas diffusion
electrode opposite to the electrolytic surface, a gas-permeable
elastic member is disposed between the gas diffusion electrode and
the back plate, and the elastic member forms a conductive
connection between the gas diffusion electrode and the back plate
by making contact with corrosion-resistant conductive layers formed
on the surfaces of a plurality of conductive members which are
joined to the back plate.
Inventors: |
Asaumi; Kiyohito;
(Tamano-shi, JP) ; Iguchi; Yukinori; (Tamano-shi,
JP) ; Hamamori; Mitsuharu; (Nagoya-shi, JP) |
Assignee: |
CHLORINE ENGINEERS CORP.,
LTD.
Chuo-ku, Tokyo
JP
KANEKA CORPORATION
Osaka-shi, Osaka
JP
TOAGOSEI CO. LTD.
Minato-ku, Tokyo
JP
|
Family ID: |
43222412 |
Appl. No.: |
13/322492 |
Filed: |
May 24, 2010 |
PCT Filed: |
May 24, 2010 |
PCT NO: |
PCT/JP2010/003470 |
371 Date: |
January 20, 2012 |
Current U.S.
Class: |
205/510 ;
204/282; 205/622 |
Current CPC
Class: |
C25B 9/65 20210101; C25B
9/19 20210101 |
Class at
Publication: |
205/510 ;
204/282; 205/622 |
International
Class: |
C25B 11/00 20060101
C25B011/00; C25B 1/26 20060101 C25B001/26; C25B 1/16 20060101
C25B001/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 26, 2009 |
JP |
2009-126622 |
Claims
1. A gas diffusion electrode equipped ion exchange membrane
electrolyzer having an anode, an ion exchange membrane, and a
cathode chamber in which a gas diffusion electrode is disposed,
characterized in that in a cathode gas chamber formed between a
back plate of the cathode chamber and one side of the gas diffusion
electrode opposite to the electrolytic surface, a gas-permeable
elastic member is disposed between the gas diffusion electrode and
the back plate, and the elastic member forms a conductive
connection between the gas diffusion electrode and the back plate
by making contact with corrosion-resistant conductive layers formed
on the surfaces of a plurality of conductive members which are
joined to the back plate.
2. The gas diffusion electrode equipped ion exchange membrane
electrolyzer according to claim 1, characterized in that the
conductive member has a silver or platinum group metal-containing
corrosion-resistant conductive layer on a foil or plate made of
nickel or a nickel alloy.
3. The gas diffusion electrode equipped ion exchange membrane
electrolyzer according to claim 1, characterized in that the
conductive member is obtained by integrating the silver or platinum
group metal-containing corrosion-resistant conductive layer by
means of plating, cladding or baking coating.
4. The gas diffusion electrode equipped ion exchange membrane
electrolyzer according to claim 1, characterized in that a part of
or the entire conductive member is joined to the back plate.
5. The gas diffusion electrode equipped ion exchange membrane
electrolyzer according to claim 1, characterized in that the
elastic member forms a corrosion-resistant conductive layer on a
conductive contacting surface or the entire surface thereof.
6. A manufacturing method of an alkali metal hydroxide aqueous
solution, comprising: providing a gas diffusion electrode equipped
ion exchange membrane electrolyzer having an anode, an ion exchange
membrane, and a cathode chamber in which a gas diffusion electrode
is disposed, characterized in that, in a cathode gas chamber formed
between a back plate of the cathode chamber and one side of the gas
diffusion electrode opposite to the electrolytic surface, a
gas-permeable elastic member is disposed between the gas diffusion
electrode and the back plate, and the elastic member forms a
conductive connection between the gas diffusion electrode and the
back plate by making contact with corrosion-resistant conductive
layers formed on the surfaces of a plurality of conductive members
which are joined to the back plate; and using the gas diffusion
electrode to manufacture an alkali metal hydroxide aqueous
solution.
7. a manufacturing method of chlorine, comprising: providing a gas
diffusion electrode equipped ion exchange membrane electrolyzer
having an anode, an ion exchange membrane, and a cathode chamber in
which a gas diffusion electrode is disposed, characterized in that,
in a cathode gas chamber formed between a back plate of the cathode
chamber and one side of the gas diffusion electrode opposite to the
electrolytic surface, a gas-permeable elastic member is disposed
between the gas diffusion electrode and the back plate, and the
elastic member forms a conductive connection between the gas
diffusion electrode and the back plate by making contact with
corrosion-resistant conductive layers formed on the surfaces of a
plurality of conductive members which are joined to the back plate;
and using the gas diffusion electrode to manufacture chlorine.
Description
TECHNICAL FIELD
[0001] The present invention relates to a gas diffusion electrode
equipped ion exchange membrane electrolyzer for use in electrolysis
of an alkali metal chloride aqueous solution such as brine and,
more particularly, to a gas diffusion electrode equipped ion
exchange membrane electrolyzer suitably applied to a two-chamber
type gas diffusion electrode equipped ion exchange membrane
electrolyzer.
BACKGROUND ART
[0002] A gas diffusion electrode equipped ion exchange membrane
electrolyzer provided with a gas diffusion electrode is utilized as
a means for reducing electrolysis voltage by causing a reaction
with a gas introduced from outside at the gas diffusion
electrode.
[0003] In a gas diffusion electrode equipped ion exchange membrane
electrolyzer for alkali metal chloride aqueous solution wherein the
gas diffusion electrode is used as a cathode, an alkali chloride
aqueous solution is supplied to an anode chamber so as to generate
a chlorine gas at an anode. On the other hand, an oxygen-containing
gas is supplied to a cathode chamber, whereby at the gas diffusion
electrode, the oxygen is reduced, and further, an alkali metal
hydroxide aqueous solution is generated.
[0004] An electrolyte cannot be made to flow over the entire
surface of the gas diffusion electrode unless a state where the gas
diffusion electrode is brought into firm and uniform contact to the
ion exchange membrane is maintained. If not, a current cannot be
made to flow uniformly through the electrolytic surface of the gas
diffusion electrode.
[0005] To cope with this, there has been proposed an ion exchange
membrane electrolyzer in which a gas-permeable elastic member is
disposed between a cathode chamber at the back of the gas diffusion
electrode and a back plate so as to bring the gas diffusion
electrode into firm contact with the ion exchange membrane and to
ensure electrical conduction between the back plate of the cathode
chamber and gas diffusion electrode.
[0006] Since the alkali metal hydroxide aqueous solution and oxygen
exist in the cathode chamber, an oxidizing environment is formed
along the inner wall surface of the cathode chamber. Therefore, the
cathode chamber is made of nickel, a nickel alloy, or the like.
However, under such an environment, a passivation film is formed on
the surface of the nickel or nickel alloy due to oxidation.
[0007] Although progression of metal corrosion can be restrained by
the passivation film formed on the nickel or nickel alloy, a large
conduction resistance is generated by the passivation film in a
conducting circuit through which a current is made to flow by the
contact of the elastic member with the back plate of the cathode
chamber and the gas diffusion electrode.
[0008] To prevent a reduction in the conductivity due to the
passivation film, there has been proposed a configuration in which
silver plating is applied to the back plate of the cathode chamber
and elastic member so as to prevent an increase in the conduction
resistance (refer to e.g., Patent Document 1).
Citation List
Patent Document
[0009] Patent Document 1: JP-A-2006-322018
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0010] Although to prevent a reduction in the conductivity and
prevent an increase in the conduction resistance by applying silver
plating to the back plate of the cathode chamber and elastic member
is an effective means for preventing an increase in the voltage of
the gas diffusion electrode equipped ion exchange membrane
electrolyzer, it has not been possible to avoid the increase in the
voltage of the electrolyzer under a long duration of
electrolysis.
[0011] An object of the present invention is to provide a gas
diffusion electrode equipped ion exchange membrane electrolyzer
capable of preventing an increase in the voltage of the
electrolyzer due to an increase in the conduction resistance in the
conducting circuit from the gas diffusion electrode to the back
plate of the cathode chamber so as to perform a lower voltage
operation which is one of the features of the gas diffusion
electrode equipped ion exchange membrane electrolyzer for a long
period of time.
Means for Solving the Problems
[0012] According to the present invention, there is provided a gas
diffusion electrode equipped ion exchange membrane electrolyzer
having an anode, an ion exchange membrane, and a cathode chamber in
which a gas diffusion electrode is disposed, characterized in that
in a cathode gas chamber formed between a back plate of the cathode
chamber and one side of the gas diffusion electrode opposite to the
electrolytic surface, a gas-permeable elastic member is disposed
between the gas diffusion electrode and the back plate, and the
elastic member forms a conductive connection between the gas
diffusion electrode and the back plate by making contact with
corrosion-resistant conductive layers formed on the surfaces of a
plurality of conductive members which are joined to the back
plate.
[0013] The conductive member has a silver or platinum group
metal-containing corrosion-resistant conductive layer on a foil or
plate made of nickel or a nickel alloy.
[0014] The conductive member is obtained by integrating the silver
or platinum group metal-containing corrosion-resistant conductive
layer by means of plating, cladding or baking coating.
[0015] A part of or the entire conductive member is joined to the
back plate.
[0016] The elastic member forms a corrosion-resistant conductive
layer on a conductive contacting surface or the entire surface
thereof.
Advantages of the Invention
[0017] The gas diffusion electrode equipped ion exchange membrane
electrolyzer according to the present invention has a configuration
in which the plurality of conductive members on the surface of each
of which the corrosion-resistant conductive layer is formed are
disposed on the surfaces contacting the elastic member and back
plate of the cathode chamber for electrical conduction to the gas
diffusion electrode. As a result, there can be provided a gas
diffusion electrode equipped ion exchange membrane electrolyzer in
which characteristics of the contact portion with the elastic
member for electrical conduction to the gas diffusion electrode are
stable, and the voltage of the electrolyzer can stably be kept at a
lower level for a long period of time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a cross-sectional view for explaining an
embodiment of a gas diffusion electrode equipped ion exchange
membrane electrolyzer according to the present invention.
[0019] FIG. 2 is an exploded perspective view for explaining the
embodiment of the gas diffusion electrode equipped ion exchange
membrane electrolyzer according to the present invention.
[0020] FIGS. 3A and 3B are views for explaining the embodiment of
the gas diffusion electrode equipped ion exchange membrane
electrolyzer according to the present invention, which illustrate
the conductive member, and in which FIG. 3A illustrates an example
in which conductive members each having a comparatively large area
are mounted to the back plate, and FIG. 3B illustrates an example
in which a large number of conductive members each having a
comparatively small area are mounted to the back plate.
[0021] FIG. 4 is a view for explaining Example and Comparative
Example of the gas diffusion electrode equipped ion exchange
membrane electrolyzer according to the present invention.
[0022] FIG. 5 is a view for explaining the embodiment of the gas
diffusion electrode equipped ion exchange membrane electrolyzer
according to the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0023] It has been found that partial separation of a coating layer
of a material excellent in conductivity such as silver formed on
the conduction contacting surface of a back plate of a cathode
chamber of a gas diffusion electrode equipped ion exchange membrane
electrolyzer is caused by an occurrence of portions different in
electrochemical characteristics due to unevenness in the film
thickness occurring in the coating layer formed by plating or the
like.
[0024] That is, the back plate of the cathode chamber is surrounded
by a cathode chamber frame, so that it is not possible to avoid an
occurrence of a phenomenon in which unevenness occurs in the flow
of a plating solution in a plating tank, causing formation of
portions different in characteristics such as film thickness. Thus,
when electrolysis is performed for a long period of time, a problem
such as film separation from the back plate may occur.
[0025] In the present invention, a problem caused by directly
plating a conductive layer to the back plate is solved as follows.
That is, a plurality of conductive members made of a planar metal
foil or metal plate formed by plating a corrosion-resistant
conductive layer made of silver or platinum-group metal to the
surface thereof are joined to the back plate so as to make the
characteristics of the contacting portion to an elastic member
uniform, thereby allowing prevention of a phenomenon such as
separation of the corrosion-resistant conductive layer contacting
the elastic member.
[0026] An embodiment of the present invention will be described
with reference to the accompanying drawings.
[0027] FIG. 1 is a cross-sectional view for explaining an
embodiment of a gas diffusion electrode equipped ion exchange
membrane electrolyzer according to the present invention.
[0028] The following description is made taking a gas diffusion
electrode equipped ion exchange membrane electrolyzer for use in
electrolysis of brine, in which a single anode chamber and a single
cathode chamber are stacked through an ion exchange membrane.
[0029] FIG. 1 is a cross-sectional view obtained by cutting the gas
diffusion electrode equipped ion exchange membrane electrolyzer
along a plane orthogonal to an electrode surface.
[0030] A gas diffusion electrode equipped ion exchange membrane
electrolyzer 1 has a configuration called a two-chamber type gas
diffusion electrode equipped ion exchange membrane electrolyzer, in
which an anode chamber 20 and a cathode chamber 30 provided therein
are separated by an ion exchange membrane 10.
[0031] The anode chamber 20 has an anode 211 and is filled with
brine as an anolyte 213. An anolyte inlet 215 is formed at the
lower portion of the anode chamber 20.
[0032] An outlet 217 for anolyte whose concentration has been
decreased by electrolysis and gas is formed at the upper portion of
the anode chamber, and an anode chamber frame 219 is stacked to the
ion exchange membrane 10 through an anode chamber side gasket
221.
[0033] The cathode chamber 30 is provided on the opposite side to
the anode chamber 20 with respect to the ion exchange membrane 10,
and a gas diffusion electrode 313 is provided in the cathode
chamber.
[0034] A liquid retaining member 311 is disposed between a cathode
chamber inner space 301 including the gas diffusion electrode 313
and ion exchange membrane 10.
[0035] On one side of the gas diffusion electrode 313 opposite to
the liquid retaining member 311 side, an elastic member 330 which
is made of a wire rod and which has inside thereof a space through
which a gas can be passed is disposed.
[0036] The elastic member 330 brings the gas diffusion electrode
313 and liquid retaining member 311 into firm contact with the ion
exchange membrane 10 side to forma cathode gas chamber 317 within
the cathode chamber and makes contact with corrosion-resistant
conductive layers 341 formed on the surfaces of a plurality of
conductive members 340 which are joined to the back plate 327 of
the cathode chamber 30 to form a conducting circuit between the gas
diffusion electrode 313 and back plate 327.
[0037] When an alkali metal chloride aqueous solution is supplied
to the anode chamber 20 of the gas diffusion electrode equipped ion
exchange membrane electrolyzer 1 according to the present invention
and then current is applied between the anode 211 and gas diffusion
electrode 313 while an oxygen-containing gas is supplied to the
cathode gas chamber 317 of the cathode chamber 30 through an oxygen
inlet 319, the gas diffusion electrode 313 is supplied with the
fluid content of an alkali metal hydroxide aqueous solution from
the liquid retaining member 311 as well as supplied with the
oxygen-containing gas from the cathode gas chamber 317 side,
resulting in progress of a generating reaction of the alkali metal
hydroxide aqueous solution in the gas diffusion electrode 313.
[0038] The generated alkali metal hydroxide aqueous solution is
transferred to the liquid retaining member 311 according to the
concentration gradient and absorbed/retained by the liquid
retaining member 311, as well as flows down along the inside of the
liquid retaining member 311 and gas chamber side of the gas
diffusion electrode 313 to be discharged from a cathode gas chamber
outlet 321.
[0039] Since a high concentration oxygen, a water vapor, and mist
of the alkali metal hydroxide aqueous solution exist in the cathode
gas chamber 317, and temperature of the cathode gas chamber 317
reaches about 90.degree. C., the cathode chamber is made of nickel,
a nickel alloy, or the like. Further, the elastic member is made of
a metal material having a high corrosion resistance and a high
conductivity, such as nickel or a high nickel alloy.
[0040] In a conventional gas diffusion electrode equipped ion
exchange membrane electrolyzer, a metal having a satisfactory
corrosion resistance, such as nickel or a nickel alloy, used as a
material of the cathode gas chamber 317 is oxidized at its surface
in the presence of a high concentration oxygen to form a
passivation film, impeding electrical conduction, which leads to an
increase in the voltage of the electrolyzer.
[0041] To cope with this, in the gas diffusion electrode equipped
ion exchange membrane electrolyzer according to the present
invention, a plurality of planar conductive members 340 each having
a corrosion-resistant conductive layer 341 on the surface thereof
are disposed on the back plate 327 of the cathode chamber 30.
[0042] Each planar conductive member 340 has the
corrosion-resistant conductive layer 341 whose surface
characteristics are made uniform by plating, cladding, or baking
coating, so that even if the area of the back plate 327 is
increased, a surface having uniform characteristics can be obtained
in any position.
[0043] As a result, in a long period operation, an increase in a
contact resistance does not occur at the contacting surfaces of the
elastic member 330 forming the conducting circuit between the gas
diffusion electrode 313 and back plate 327 due to existence of the
corrosion-resistant conductive layers 341, allowing prevention of
an increase in the voltage of the electrolyzer.
[0044] As the planar conductive member, it is preferable to use the
same material as that of the back plate of the cathode chamber,
i.e., a nickel material, the thickness thereof preferably being 0.1
mm to 1.0 mm. The corrosion-resistant conductive layer maybe formed
of a metal such as silver or platinum group metal and it is
particularly preferable to use silver having a satisfactory
conductivity. The corrosion-resistant conductive layer can be
formed by plating, cladding, baking, or the like.
[0045] The thickness of the corrosion-resistant conductive layer is
preferably set to 0.5 .mu.m or more. When the thickness falls below
0.5 .mu.m, sufficient characteristics cannot be obtained. On the
other hand, the larger the thickness, the more excellent the
corrosion resistance and the like become; however, a thickness of
about 5 .mu.m will suffice.
[0046] It is preferable that the planar conductive member is formed
in a size of 60 mm.times.56 mm to 1220 mm.times.500 mm. When the
size is smaller than 60 mm.times.56 mm, the number of the planar
conductive members to be installed is increased to increase the
number of spot welding points, which may result in a degradation of
the uniformity. On the other hand, when the size is larger than
1220 mm.times.500 mm, nonuniformity is likely to occur unfavorably
when the corrosion-resistant conductive layer is formed by plating
or the like.
[0047] FIG. 2 is a view for explaining the embodiment of the gas
diffusion electrode equipped ion exchange membrane electrolyzer
according to the present invention and more specifically, an
exploded perspective view for explaining the elastic member and
conductive member.
[0048] The plurality of conductive members 340 are joined to the
back plate 327 of a cathode chamber frame 323. In the illustrative
example, 12 conductive members 340 are disposed.
[0049] The elastic member 330 is disposed such that one surface
thereof contacts the conductive members 340 and the other surface
thereof contacts one surface of the gas diffusion electrode
opposite to the electrolytic surface.
[0050] In the example of FIG. 2, the elastic member 330 has eight
unit elastic members 333a, 333b, 333c, 333d, 333e, 333f, 333g, and
333h mounted to an elastic member frame 331, each of which is
constituted by a hollow spring coil forming a gas passage and is
disposed so as to uniformly press the gas diffusion electrode and
to allow uniform electrical conduction between the gas diffusion
electrode and back plate.
[0051] The use of the plurality of unit elastic members can allow
the pressure and current distribution uniformly applied to the gas
diffusion electrode even when the electrolysis area of the gas
diffusion electrode is increased. Further, the number of the unit
elastic members 333a to 333h forming the elastic member 330 and the
number of the conductive members may appropriately be set in
accordance with the size of the electrolysis area or magnitude of
the application current density.
[0052] FIG. 3 is a view for explaining the embodiment of the gas
diffusion electrode equipped ion exchange membrane electrolyzer
according to the present invention, which illustrates the
conductive member.
[0053] In the example of FIG. 3A, conductive members 340 each
having a comparatively large area are mounted to the back plate by
a method such as spot welding performed at joining portions 343 and
the corrosion-resistant conductive layers 341 formed on the
conductive members 340 are disposed on the gas diffusion electrode
side.
[0054] In the example of FIG. 3B, a large number of conductive
members 340 each having a smaller area than the conductive members
of FIG. 3A are mounted to the back plate 327 and joined thereto at
the joining portions 343, and corrosion-resistant conductive layers
341 are formed respectively on the surface of the mounted
conductive members.
[0055] The mounting of a large number of the small-area conductive
members 340 allows stable electrical conduction between the back
plate and gas diffusion electrode for a long period of time.
[0056] Hereinafter, the present invention will be described based
on Examples and Comparative Examples.
EXAMPLE
Example 1
[0057] An ion exchange membrane (anode ion exchange membrane F-8020
made by Asahi Glass Co., Ltd) was disposed in an electrolyzer
having an effective electrolysis area of 56 mm (height).times.60 mm
(width) so as to contact an anode for brine electrolysis (JP202R
made by Permelec Electrode Ltd.). On the opposite side of the anode
of the ion exchange membrane, a carbon fiber fabric (made by
Zoltek) having a thickness of 0.4 mm that covers the electrolytic
surface was stacked as a liquid retaining member, and further a
liquid-permeable gas diffusion electrode (Permelec Electrode Ltd.)
was stacked on the liquid retaining member.
[0058] A nickel wire coil obtained by winding a nickel wire having
a wire diameter of 0.17 mm in a coil shape having a winding
diameter of 6 mm was disposed on one side of the gas diffusion
electrode opposite to the electrolytic surface.
[0059] A conductive member made of a nickel foil (NW2201) of 56 mm
(H).times.60 mm (W).times.0.2 mm (T) having one surface that has
been subjected to silver plating was joined to the back plate of
the cathode chamber of the cathode chamber frame by spot welding at
six points.
[0060] A voltage measurement terminal was attached to the gas
diffusion electrode, and the electrolyzer was operated for 17 days
with the current density kept at 3 kA/m.sup.2, electrolysis
temperature kept at 87.degree. C. to 89.degree. C., and aqueous
sodium hydroxide concentration kept at 30 mass % to 33 mass %.
[0061] A potential difference between the gas diffusion electrode
and back plate, i.e., voltage drop was measured. The measurement
result is shown in FIG. 4. A voltage was not increased but kept at
an initial voltage of 0.001 V, that is, operation of the
electrolyzer was stable for 17 days.
Example 2
[0062] An ion exchange membrane (anode ion exchange membrane
"Aciplex" F-4403 made by Asahi Kasei Chemicals Corporation) was
disposed in an electrolyzer having an effective electrolysis area
of 620 mm (width).times.1220 mm (height) so as to contact an anode
for brine electrolysis (JP202R made by Permelec Electrode Ltd.). On
the opposite side of the anode of the ion exchange membrane, a
carbon fiber fabric (made by Zoltek) having a thickness of 0.4 mm
that covers the electrolytic surface was stacked as a liquid
retaining member, and further a liquid-permeable gas diffusion
electrode (Permelec Electrode Ltd.) was stacked on the liquid
retaining member.
[0063] Four nickel wire coils each obtained by winding a nickel
wire having a wire diameter of 0.17 mm in a coil shape having a
winding diameter of 6 mm were disposed on one surface of the gas
diffusion electrode opposite to the electrolytic surface.
[0064] Two conductive members each made of a nickel foil (NW2201)
of 1160 mm (H).times.310 mm (W).times.0.2 mm (T) having one surface
that has been subjected to silver plating of a 10 .mu.m thickness
were each joined to the back plate of the cathode chamber of the
cathode chamber frame by spot welding at 144 points.
[0065] Thus obtained electrolyzer was used to perform electrolysis
with the current density kept at 3 kA/m.sup.2, electrolysis
temperature kept at 75.degree. C. to 85.degree. C., and aqueous
sodium hydroxide concentration kept at 30 mass % to 34 mass %.
[0066] As illustrated in FIG. 5 showing a trend in the voltage of
the electrolyzer, an increase in the voltage was not observed.
[0067] When the electrolyzer was disassembled after the total
operation period of 500 days, no abnormality was observed in the
silver plated conductive member.
Comparative Example 1
[0068] An electrolyzer produced in the same manner as Example 1
except that the silver plating was not applied to the conductive
member was used to perform electrolysis under the same conditions
as those in Example 1, and a potential difference between the gas
diffusion electrode and back plate of the cathode chamber was
measured in the same manner as Example 1. As illustrated in FIG. 4
showing the measurement result, the potential difference was
increased with time.
[0069] Further, when the electrolyzer was disassembled after stop
of the operation, the nickel foil used as the conducting member was
turned black due to formation of a passivation film.
Comparative Example 2
[0070] Electrolysis was performed in the same manner as Example 2
except that an electrolyzer has a cathode chamber in which the
conductive member was not provided and silver plating of a 10 .mu.m
center thickness was applied to the back plate, and a trend in the
voltage of the electrolyzer was measured.
[0071] A 200 mV voltage increase was observed after 300 days
operation. Further, when the electrolyzer was disassembled after
stop of the operation, the silver plating at substantially all the
conducting portions of the silver plating layer of the back plate
contacting the elastic member were separated to expose the nickel
material as the underlayer, and further, the nickel material as the
underlayer was turned black due to formation of a passivation
film.
INDUSTRIAL APPLICABILITY
[0072] The gas diffusion electrode equipped ion exchange membrane
electrolyzer according to the present invention has a configuration
in which the plurality of conductive members on the surface of each
of which the corrosion-resistant conductive layer is formed are
disposed on the surfaces contacting the elastic member and back
plate of the cathode chamber for electrical conduction to the gas
diffusion electrode. As a result, there can be provided a gas
diffusion electrode equipped ion exchange membrane electrolyzer in
which characteristics of the contact portion with the elastic
member for electrical conduction to the gas diffusion electrode are
stable, no separation of the corrosion-resistant conductive layer
from the surface of the conductive member occurs, voltage drop
between the gas diffusion electrode and back plate is small, and
performance can be made stable for a long period of time.
EXPLANATION OF SYMBOLS
[0073] 1: Gas diffusion electrode equipped ion exchange membrane
electrolyzer
[0074] 10: Ion exchange membrane
[0075] 20: Anode chamber
[0076] 30: Cathode chamber
[0077] 211: Anode
[0078] 213: Anolyte
[0079] 215: Anolyte inlet
[0080] 217: Anolyte and gas outlet
[0081] 219: Anode chamber frame
[0082] 221: Anode chamber side gasket
[0083] 301: Cathode chamber inner space
[0084] 311: Liquid retaining member
[0085] 313: Gas diffusion electrode
[0086] 317: Cathode gas chamber
[0087] 319: Oxygen inlet
[0088] 321: Cathode gas chamber outlet
[0089] 323: Cathode chamber frame
[0090] 325: Cathode chamber side gasket
[0091] 327: Back plate
[0092] 330: Elastic member
[0093] 331: Elastic member frame
[0094] 333a, 333b, 333c, 333d, 333e, 333f, 333g, 333h: Unit elastic
member
[0095] 340: Conductive member
[0096] 341: Corrosion-resistant conductive layer
[0097] 343: Joining portion
* * * * *