US20220178034A1 - Electrode for electrolysis, and method for producing electrode for electrolysis - Google Patents
Electrode for electrolysis, and method for producing electrode for electrolysis Download PDFInfo
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- US20220178034A1 US20220178034A1 US17/604,426 US202017604426A US2022178034A1 US 20220178034 A1 US20220178034 A1 US 20220178034A1 US 202017604426 A US202017604426 A US 202017604426A US 2022178034 A1 US2022178034 A1 US 2022178034A1
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- tantalum
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- 238000005868 electrolysis reaction Methods 0.000 title claims description 110
- 238000004519 manufacturing process Methods 0.000 title claims description 16
- 229910052715 tantalum Inorganic materials 0.000 claims abstract description 172
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims abstract description 172
- 239000003054 catalyst Substances 0.000 claims abstract description 147
- 239000002131 composite material Substances 0.000 claims abstract description 139
- 239000000758 substrate Substances 0.000 claims abstract description 116
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 70
- 229910052741 iridium Inorganic materials 0.000 claims abstract description 32
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 29
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910001936 tantalum oxide Inorganic materials 0.000 claims abstract description 28
- 239000000203 mixture Substances 0.000 claims abstract description 24
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000010936 titanium Substances 0.000 claims abstract description 16
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims description 71
- 238000010438 heat treatment Methods 0.000 claims description 39
- 230000015572 biosynthetic process Effects 0.000 claims description 27
- 238000010304 firing Methods 0.000 claims description 27
- 238000001035 drying Methods 0.000 claims description 19
- 239000000243 solution Substances 0.000 description 33
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 30
- 239000000460 chlorine Substances 0.000 description 30
- 229910052801 chlorine Inorganic materials 0.000 description 30
- 235000002639 sodium chloride Nutrition 0.000 description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 26
- 150000003839 salts Chemical class 0.000 description 20
- 239000000463 material Substances 0.000 description 14
- 238000012360 testing method Methods 0.000 description 14
- 238000000926 separation method Methods 0.000 description 11
- 239000002904 solvent Substances 0.000 description 11
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 8
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- 150000003058 platinum compounds Chemical class 0.000 description 8
- 150000003482 tantalum compounds Chemical class 0.000 description 8
- 238000007788 roughening Methods 0.000 description 7
- 239000011780 sodium chloride Substances 0.000 description 7
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 6
- 230000032683 aging Effects 0.000 description 5
- 150000002504 iridium compounds Chemical class 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- ZNQVEEAIQZEUHB-UHFFFAOYSA-N 2-ethoxyethanol Chemical compound CCOCCO ZNQVEEAIQZEUHB-UHFFFAOYSA-N 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 229910001069 Ti alloy Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 3
- 229910000457 iridium oxide Inorganic materials 0.000 description 3
- 230000003746 surface roughness Effects 0.000 description 3
- 239000008399 tap water Substances 0.000 description 3
- 235000020679 tap water Nutrition 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- DTGCGGQKWZIERO-UHFFFAOYSA-N [Cl].[Ta] Chemical compound [Cl].[Ta] DTGCGGQKWZIERO-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 235000006408 oxalic acid Nutrition 0.000 description 2
- CLSUSRZJUQMOHH-UHFFFAOYSA-L platinum dichloride Chemical compound Cl[Pt]Cl CLSUSRZJUQMOHH-UHFFFAOYSA-L 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 229910001252 Pd alloy Inorganic materials 0.000 description 1
- 229910000929 Ru alloy Inorganic materials 0.000 description 1
- 229910001362 Ta alloys Inorganic materials 0.000 description 1
- 229910000756 V alloy Inorganic materials 0.000 description 1
- ABAGVFOSGPMBFK-UHFFFAOYSA-N [Ti].[Ni].[Ru] Chemical compound [Ti].[Ni].[Ru] ABAGVFOSGPMBFK-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- UQZIWOQVLUASCR-UHFFFAOYSA-N alumane;titanium Chemical compound [AlH3].[Ti] UQZIWOQVLUASCR-UHFFFAOYSA-N 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- GSNZLGXNWYUHMI-UHFFFAOYSA-N iridium(3+);trinitrate Chemical compound [Ir+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O GSNZLGXNWYUHMI-UHFFFAOYSA-N 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- SJLOMQIUPFZJAN-UHFFFAOYSA-N oxorhodium Chemical compound [Rh]=O SJLOMQIUPFZJAN-UHFFFAOYSA-N 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229910003450 rhodium oxide Inorganic materials 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- VSSLEOGOUUKTNN-UHFFFAOYSA-N tantalum titanium Chemical compound [Ti].[Ta] VSSLEOGOUUKTNN-UHFFFAOYSA-N 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
- -1 titanium-aluminum-vanadium Chemical compound 0.000 description 1
- DANYXEHCMQHDNX-UHFFFAOYSA-K trichloroiridium Chemical compound Cl[Ir](Cl)Cl DANYXEHCMQHDNX-UHFFFAOYSA-K 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
- C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
- C25B11/061—Metal or alloy
- C25B11/063—Valve metal, e.g. titanium
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/24—Halogens or compounds thereof
- C25B1/26—Chlorine; Compounds thereof
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
- C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
- C25B11/031—Porous electrodes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/052—Electrodes comprising one or more electrocatalytic coatings on a substrate
- C25B11/053—Electrodes comprising one or more electrocatalytic coatings on a substrate characterised by multilayer electrocatalytic coatings
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
- C25B11/069—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of at least one single element and at least one compound; consisting of two or more compounds
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
- C25B11/081—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the element being a noble metal
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
- C25B11/093—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one noble metal or noble metal oxide and at least one non-noble metal oxide
Definitions
- the electrode for electrolysis is desired to be less likely to cause the separation of the composite layer, which contains Iridium serving as a catalyst, in order to increase the life-time of the electrode.
- FIG. 8 is a sectional view of an electrode for electrolysis according to a variation.
- the composite layer 4 has a bottom layer closest to the primary surface 21 of the electrically conductive substrate 2 .
- the bottom layer of the composite layer 4 is constituted by one tantalum layer 41 of the plurality of tantalum layers 41 .
- the composite layer 4 has a top layer furthest from the electrically conductive substrate 2 .
- the top layer of the composite layer 4 is constituted by one catalyst layer 42 of the plurality of catalyst layers 42 .
- one tantalum layer 41 (first tantalum layer 411 ) of the plurality of tantalum layers 41 constitutes the bottom layer that is closest to the first primary surface 21 of the electrically conductive substrate 2 .
- one catalyst layer 42 (fourth catalyst layer 424 , in the illustrated example) of the plurality of catalyst layers 42 constitutes the top layer that is furthest from the electrically conductive substrate 2 .
- the compound layer formation process includes forming the composite layer 4 on the intermediate layer 3 (see FIG. 3D ).
- the compound layer formation process includes a stacked body formation process and a firing process.
- the stacked body formation process includes performing a first prescribed number of times (four times, for example) of first steps and a second prescribed number of times (four times, for example) of second steps, where the first step and the second step are performed alternately, to form, on the intermediate layer 3 which is on the electrically conductive substrate 2 , a stacked body 400 (see FIG. 3C ) serving as a basis of the composite layer 4 .
- the first step includes applying a solution (hereinafter, referred to as “first solution”) containing a tantalum compound serving as a basis of the tantalum layer 41 , and subsequently performing, without natural drying, heat treatment (drying process) of heating and drying under a first condition, to form a first material layer 410 serving as a basis of one tantalum layer 41 of the plurality of tantalum layers 41 .
- the first solution is a solution obtained by dissolving the tantalum compound in a solvent (hereinafter, referred to as “first solvent”).
- the first solvent is a liquid of a mixture of ethylene glycol monoethyl ether, hydrochloric acid and ethanol, for example.
- the tantalum compound is for example tantalum chlorine, but is not limited thereto.
- the tantalum compound may be tantalum ethoxydo, for example.
- the metal concentration (tantalum concentration) of the first solution is 26 mg/L, for example.
- the application amount of the first solution is 1 ⁇ L/cm 2 , for example.
- the first condition includes a heat treatment temperature and a heat treatment time.
- the heat treatment temperature of the first condition falls within a range of 100° C. to 400° C. for example, and the heat treatment temperature may be 220° C. as an example.
- the heat treatment time of the first condition falls within a range of 5 minutes to 15 minutes for example, and the heat treatment time may be 10 minutes as an example.
- the second step includes applying a solution (hereinafter, referred to as “second solution”) containing a platinum compound and iridium compound serving as a basis of the catalyst layer 42 , and subsequently performing, without natural drying, heat treatment (drying process) of heating and drying under a second condition, to form a second material layer 420 serving as a basis of one catalyst layer 42 of the plurality of catalyst layers 42 .
- the second solution is a solution obtained by dissolving the platinum compound and the iridium compound in a solvent (hereinafter, referred to as “second solvent”).
- the second solvent is a liquid of a mixture of ethylene glycol monoethyl ether, hydrochloric acid and ethanol, for example.
- the platinum compound is for example hydrogen chloroplatinate, but is not limited thereto.
- the platinum compound may be platinum chloride, for example.
- the iridium compound is for example hydrogen chloroidiate, but is not limited thereto.
- the iridium compound may be iridium chloride, iridium nitrate, or the like, for example.
- the metal concentration (total of platinum concentration and iridium concentration) of the second solution is 26 mg/L, for example.
- the application amount of the second solution is 2 ⁇ L/cm 2 , for example.
- the second condition includes a heat treatment temperature and a heat treatment time.
- the heat treatment temperature of the second condition falls within a range of 100° C. to 400° C. for example, and the heat treatment temperature may be 220° C. as an example.
- the heat treatment time of the second condition falls within a range of 5 minutes to 15 minutes for example, and the heat treatment time may be 10 minutes as an example.
- the firing process includes performing thermal treatment of firing the stacked body 400 under a predetermined firing condition to form the composite layer 4 and a plurality of cracks (recesses 5 ) (see FIG. 3D ).
- the firing condition includes a firing temperature and a firing time.
- the firing temperature falls within a range of 500° C. to 700° C. for example, and the firing temperature may be 560° C. as an example.
- the firing time falls within a range of 10 minutes to 20 minutes for example, and the firing time may be 15 minutes as an example.
- the plurality of cracks (recesses 5 ) may have mutually different shapes.
- the crack may be formed along a thickness direction of the composite layer 4 or may be at least partially curved in the composite layer 4 .
- Example 2 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:1:6 and the number of layers is 20;
- Example 3 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:1:6 and the number of layers is 30;
- Example 4 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:3:6 and the number of layers is 10;
- Example 5 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:3:6 and the number of layers is 20;
- Example 6 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:3:6 and the number of layers is 30;
- Example 7 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:5:6 and the number of layers is 10;
- Example 8 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:5:6 and the number of layers is 20;
- Example 9 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:5:6 and the number of layers is 30.
- the durability test was conducted according to the accelerated test.
- two electrodes for electrolysis 1 were produced in a same condition and used as a pair of electrodes. Firstly, the pair of electrodes were immersed in salt water inside a tank for electrolytic cell for a durability test apparatus, and an electric current was supplied between the pair of electrodes to conduct an initial aging.
- the electric current was supplied between the pair of electrodes for total twelve minutes, where the polarity was reversed every time a predetermined time (3 minutes) elapses.
- the feature “the polarity is reversed” used herein indicates that the roles of the pair of electrodes, the anode or the cathode, are mutually interchanged.
- the feature “the polarity is reversed” indicates that an electrode (to be) used as the higher potential side electrode is changed from one of the pair of electrodes to the other thereof, such that one of the electrodes which has been used as the anode is to be used as the cathode, and vice verse.
- the horizontal axis of FIG. 4 indicates the durability test time (elapsed time) after the initial aging.
- the vertical axis of FIG. 4 indicates the chlorine concentration. It should be noted that the chlorine generated around the anode is to be used for the generation of hypochlorous acid. Thus, the chlorine concentration substantially reflects the amount of chlorine, which has been produced during a recent unit time.
- FIGS. 5A, 5B, 5C and 5D Based on FIGS. 5A, 5B, 5C and 5D , an inferred mechanism is described which can explain a reason why the electrode for electrolysis 1 according to the first embodiment has an improved durability.
- FIGS. 5A, 5B, 5C, and 5D are ordered according to the time series.
- respective sides of a plurality of (four) catalyst layers 42 that partially form an inner surface of the recess 5 , as well as the main surface 40 , of the composite layer 4 are in contact with the salt water.
- Each of the plurality of (four) catalyst layers 42 thus can contribute to the generation of the chlorine.
- FIG. 5B shows a state of the electrode for electrolysis 1 where a catalyst layer 42 (fourth catalyst layer 424 ) of the top layer shown in FIG. 5A is lost.
- a catalyst layer 42 fourth catalyst layer 424
- respective sides of a plurality of (three) catalyst layers 42 that partially form an inner surface of the recess 5 are in contact with the salt water.
- Each of the plurality of (three) catalyst layers 42 thus can contribute to the generation of the chlorine.
- FIG. 5C shows a state where the plurality of (three) catalyst layers 42 are partially lost in an in-plane direction, from the state shown in FIG. 5B .
- the in-plane direction is defined as a direction perpendicular to the thickness direction D 1 of the electrically conductive substrate 2 . That is, the in-plane direction is a direction along the first primary surface 21 of the electrically conductive substrate 2 .
- respective sides, closer to the recess 5 of the plurality of (three) catalyst layers 42 are in contact with the salt water.
- Each of the plurality of (three) catalyst layers 42 thus can contribute to the generation of the chlorine.
- FIG. 5D shows a state where a tantalum layer 41 (fourth tantalum layer 414 ) on a catalyst layer 42 (third catalyst layer 423 ), which is furthest from the electrically conductive substrate 2 , of the plurality of (three) catalyst layers 42 is partially lost along the in-plane direction, from the state shown in FIG. 5C .
- respective sides, closer to the recess 5 , of the plurality of (three) catalyst layers 42 , as well as a main surface of the third catalyst layer 423 closer to the fourth tantalum layer 414 are in contact with the salt water.
- Each of the plurality of (three) catalyst layers 42 thus can contribute to the generation of the chlorine.
- At least one of the catalyst layers 42 always can contribute to the generation of the chlorine, regardless of the change in the state thereof.
- the electrode for electrolysis 1 according to the first embodiment thus can have an improved durability.
- the electrode for electrolysis 1 according to the first embodiment includes the composite layer 4 alternating the plurality of tantalum layers 41 and the plurality of catalyst layers 42 one layer by one layer, which can contribute to suppress the separation of the composite layer 4 .
- the electrode for electrolysis 1 according to the first embodiment includes the composite layer 4 , which also can contribute to suppress the waste of the composite layer 4 in use.
- the electrode for electrolysis 1 according to the first embodiment includes the composite layer 4 , which also can contribute to suppress the cohesion of iridium.
- the electrode for electrolysis 1 according to the first embodiment has the plurality of recesses 5 , which can increase the area of the surface of the composite layer 4 contributing the generation of the chlorine, and can contribute to improve the chlorine generation efficiency.
- the electrode for electrolysis 1 a according to the second embodiment is substantially the same as the electrode for electrolysis 1 according to the first embodiment.
- the electrode for electrolysis 1 a according to the second embodiment differ from the electrode for electrolysis 1 according to the first embodiment in the depths of the recesses 5 .
- Components of the electrode for electrolysis 1 a according to the second embodiment similar to those of the electrode for electrolysis 1 according to the first embodiment are assigned same reference signs and explanation thereof may be omitted.
- Each of the plurality of recesses 5 of the electrode for electrolysis 1 a according to the second embodiment has a depth which is smaller than or equal to a distance L 3 between a main surface 40 of a composite layer 4 and a bottom layer (first tantalum layer 411 ) of the composite layer 4 . This can contribute to further suppression of the separation of the composite layer 4 according to the electrode for electrolysis 1 a according to the second embodiment.
- a method for producing the electrode for electrolysis 1 a according to the second embodiment is explained with reference to FIGS. 7A to 7E . It may be omitted the detailed explanation of some of processes, similar to those of the method for producing the electrode for electrolysis 1 according to the first embodiment.
- An electrically conductive substrate 2 is prepared firstly as shown in FIG. 7A , and a roughening process, an intermediate layer formation process, and a composite layer formation process are performed sequentially after the preparation.
- the compound layer formation process includes a first process, a second process, and a third process.
- the tantalum compound may be tantalum ethoxydo, for example.
- the solution may be obtained by dissolving pure tantalum in the solvent, for example, which can form the tantalum layer 41 as a layer made from tantalum, instead of a layer made from tantalum oxide.
- the metal concentration (tantalum concentration) of the solution is 26 mg/L, for example.
- the application amount of the solution is 1 ⁇ L/cm 2 , for example.
- the firing condition includes a firing temperature (first prescribed temperature) and a firing time.
- the firing temperature falls within a range of 500° C. to 700° C. for example, and the firing temperature may be 560° C. as an example.
- the firing time falls within a range of 10 minutes to 20 minutes for example, and the firing time may be 15 minutes as an example.
- the first step of the second process includes applying a second solution containing a platinum compound and iridium compound serving as a basis of a catalyst layer 42 , and subsequently performing, without natural drying, heat treatment (drying process) of heating and drying under a second condition to form a second material layer 420 serving as a basis of one catalyst layer 42 of the plurality of catalyst layers 42 .
- the second solution contains platinum and iridium.
- the second solution is applied to a layer (a tantalum layer 41 as a bottom layer, or a first material layer 410 described later, for example) exposed outside on a side of the first primary surface 21 of the electrically conductive substrate 2 .
- the second condition includes a heat treatment temperature and a heat treatment time.
- the heat treatment temperature (second prescribed temperature) of the second condition falls within a range of 100° C. to 400° C. for example, and the heat treatment temperature may be 220° C. as an example.
- the heat treatment time of the second condition falls within a range of 5 minutes to 15 minutes for example, and the heat treatment time may be 10 minutes as an example.
- the second step of the second process includes applying a first solution containing a tantalum compound serving as a basis of the tantalum layer 41 , and subsequently performing, without natural drying, heat treatment (drying process) of heating and drying under a first condition, to form a first material layer 410 serving as a basis of one tantalum layer 41 of the plurality of tantalum layers 41 .
- the first solution contains tantalum.
- the first solution is applied to a layer (a second material layer 420 ) exposed outside on a side of the first primary surface 21 of the electrically conductive substrate 2 .
- the first condition includes a heat treatment temperature and a heat treatment time.
- the heat treatment temperature (third prescribed temperature) of the first condition falls within a range of 100° C. to 400° C. for example, and the heat treatment temperature may be 220° C. as an example.
- the heat treatment time of the first condition falls within a range of 5 minutes to 15 minutes for example, and the heat treatment time may be 10 minutes as an example.
- the third process includes firing the stacked body 401 at a prescribed temperature (fourth prescribed temperature) to form the plurality of catalyst layers 42 and tantalum layers 41 , other than the tantalum layer 41 constituting the bottom layer, of the plurality of the tantalum layer 41 together with a plurality of cracks (recesses 5 ) recessed from a main surface 40 of the catalyst layer 42 .
- the main surface 40 is a surface away from the intermediate layer 3 (see FIG. 7E ).
- the first and second embodiments are only exemplary ones of various embodiments of the present disclosure.
- the exemplary embodiment may be readily modified in various manners depending on a design choice or any other factor, as long as the purpose of the present disclosure can be attained.
- the number of tantalum layers 41 and/or catalyst layers 42 of a composite layer 4 is not limited to four, but may be two, three, five or more.
- the number of tantalum layers 41 and the number of catalyst layers 42 in the composite layer 4 are not limited to be the same, but may be different from each other.
- thicknesses of a plurality of tantalum layers 41 are not limited to be the same, but may be different from each other. It is also possible that some of a plurality of tantalum layers 41 have the same thickness, and remaining of the plurality of tantalum layer 41 may have a thickness different therefrom.
- thicknesses of a plurality of catalyst layers 42 are not limited to be the same, but may be different from each other. It is also possible that some of a plurality of catalyst layers 42 have the same thickness, and remaining of the plurality of catalyst layer 42 may have a thickness different therefrom.
- a plurality of tantalum layers 41 are not limited to have the same composition, but may have different compositions.
- a plurality of catalyst layers 42 are not limited to have the same composition, but may have different compositions.
- each a plurality of catalyst layers 42 of a composite layer 4 is not limited to be a porous layer.
- at least one catalyst layer 42 which is other than a catalyst layer 42 constituting a top layer of a plurality of catalyst layers 42 , may be a porous layer, for example.
- each of a plurality of catalyst layers 42 of a composite layer 4 may be a non-porous layer.
- a plurality of recesses 5 may have the same shape.
- a method for producing such an electrode for electrolysis 1 may include an etching technique, a laser processing, or the like to form such a plurality of recesses 5 . These techniques/processing can provide a greater degree of freedom for the design of a layout and dimensions of the plurality of recesses 5 and can realize a higher reproductivity about the positions of the plurality of recesses 5 .
- the electrode for electrolysis 1 b has a plurality of recesses 5 recessed from a main surface 40 , away from an intermediate layer 3 , of a composite layer 4 , and a top layer of the composite layer 4 is constituted by a tantalum layer 41 .
- Components of the electrode for electrolysis 1 b similar to those of the electrode for electrolysis 1 are assigned same reference signs and explanation thereof may be omitted.
- each of the plurality of recesses 5 has a depth such that each of the plurality of recesses 5 is made to go completely through at least one catalyst layer 42 of the plurality of catalyst layers 42 .
- Each of the plurality of recesses 5 may preferably have a depth such that each of the plurality of recesses 5 is made to go completely through the plurality of catalyst layers 42 , which can contribute to improve the chlorine generation efficiency.
- a bottom layer of a composite layer 4 may be constituted by one tantalum layer 41 of a plurality of tantalum layers 41 and be directly on a primary surface 21 of an electrically conductive substrate 2 without an intermediate layer 3 interposed therebetween.
- a top layer, furthest from the electrically conductive substrate 2 , of the composite layer 4 may be constituted by one catalyst layer 42 of a plurality of catalyst layers 42 .
- An electrode for electrolysis ( 1 ; 1 a ) includes an electrically conductive substrate ( 2 ), an intermediate layer ( 3 ), and a composite layer ( 4 ).
- the electrically conductive substrate ( 2 ) contains at least titanium.
- the intermediate layer ( 3 ) is provided on a primary surface ( 21 ) of the electrically conductive substrate ( 2 ).
- the composite layer ( 4 ) is provided on the intermediate layer ( 3 ).
- the composite layer ( 4 ) includes a plurality of tantalum layers ( 41 ) and a plurality of catalyst layers ( 42 ). Each of the plurality of tantalum layers ( 41 ) is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum.
- Each of the plurality of catalyst layers ( 42 ) contains platinum and iridium.
- the plurality of tantalum layers ( 41 ) and the plurality of catalyst layers ( 42 ) are alternately stacked one layer by one layer in a thickness direction (D 1 ) of the electrically conductive substrate ( 2 ).
- a bottom layer of the composite layer ( 4 ) closest to the primary surface ( 21 ) of the electrically conductive substrate ( 2 ) is constituted by one tantalum layer ( 41 ) of the plurality of tantalum layers ( 41 ).
- a top layer of the composite layer ( 4 ) furthest from the electrically conductive substrate ( 2 ) is constituted by one catalyst layer ( 42 ) of the plurality of catalyst layers ( 42 ).
- the electrode for electrolysis ( 1 ; 1 a ) according to the first aspect is less likely to cause the separation of the composite layer ( 4 ).
- the electrode for electrolysis ( 1 ; 1 a ) according to a second aspect, which may be implemented in conjunction with the first aspect, the composite layer ( 4 ) has a main surface ( 40 ) away from the intermediate layer ( 3 ).
- the electrode for electrolysis ( 1 ; 1 a ) has a plurality of recesses ( 5 ) recessed from the main surface ( 40 ) of the composite layer ( 4 ).
- Each of the plurality of recesses ( 5 ) has a depth which is greater than a distance (L 1 ) between the main surface ( 40 ) of the composite layer ( 4 ) and a catalyst layer 42 (third catalyst layer 423 ), second furthest from the electrically conductive substrate ( 2 ), of the plurality of catalyst layers ( 42 ) and also is smaller than or equal to a distance (L 2 ) between the main surface ( 40 ) of the composite layer ( 4 ) and the intermediate layer ( 3 ).
- a catalyst layer (third catalyst layer 423 ) second furthest from the electrically conductive substrate ( 2 ), of the plurality of catalyst layers ( 42 ), also can contribute to the generation of the chlorine.
- the electrode for electrolysis ( 1 ; 1 a ) according to this aspect thus can contribute to improve the durability and also can achieve the efficient consumption of the catalyst layer ( 42 ) to improve the chlorine generation efficiency by adjusting at least one of the number of catalyst layers ( 42 ) and the percentage of iridium contained in each of the plurality of catalyst layers ( 42 ).
- the electrode for electrolysis ( 1 a ) according to a third aspect, which may be implemented in conjunction with the second aspect, the depth of each of the plurality of recesses ( 5 ) is smaller than or equal to a distance (L 3 ) between the main surface ( 40 ) and the bottom layer (first tantalum layer 411 ) of the composite layer ( 4 ).
- the electrode for electrolysis ( 1 a ) according to the third aspect is further less likely to cause the separation of the composite layer ( 4 ).
- each of the plurality of recesses ( 5 ) is a crack extending linearly in a plan view as seen in the thickness direction (D 1 ).
- a catalyst layer ( 42 ) farther from the electrically conductive substrate ( 2 ) tends to contribute to the generation of the chlorine and a catalyst layer ( 42 ) closer to the electrically conductive substrate ( 2 ) is less likely to be consumed. This can improve the durability of the electrode for electrolysis ( 1 ; 1 a ).
- each of the plurality of recesses ( 5 ) has a width (H 1 ) within a range of 0.3 ⁇ m to 3 ⁇ m.
- a percentage of S 2 with respect to S 1 +S 2 falls within a range of 5% to 50%, where S 1 denotes an area of the main surface ( 40 ) of the composite layer ( 4 ) in the plan view as seen in the thickness direction (D 1 ) of the electrically conductive substrate, and S 2 denotes a total area of opening areas of the plurality of recesses ( 5 ) in the main surface ( 40 ) of the composite layer ( 4 ) in the plan view as seen in the thickness direction (D 1 ) of the electrically conductive substrate.
- the electrode for electrolysis ( 1 ; 1 a ) according to a seventh aspect, which may be implemented in conjunction with the sixth aspect, at least one recess ( 5 ) of the plurality of recesses ( 5 ) is present in a 0.01 mm 2 square region in the plan view as seen in the thickness direction (D 1 ) of the electrically conductive substrate ( 2 ), a total length of each opening edge of the at least one recess ( 5 ) present in the 0.01 mm 2 square region being greater than or equal to 1 mm.
- each of the plurality of catalyst layers ( 42 ) is a porous layer.
- the electrode for electrolysis ( 1 ; 1 a ) according to the eighth aspect can have an improved durability.
- the reason that the electrode for electrolysis ( 1 ; 1 a ) according to the eighth aspect can have the improved durability may be inferred that each catalyst layer ( 42 ), other than a catalyst layer ( 42 ) that constitutes the top layer, of the plurality of catalyst layers ( 42 ) can easily contribute to generate the chlorine because the salt water is likely to infiltrate in an in-plane direction into the catalyst layer ( 42 ) through a side of this catalyst layer ( 42 ) exposed to the recess ( 5 ).
- the electrode for electrolysis ( 1 ; 1 a ) according to a ninth aspect, which may be implemented in conjunction with any one of the first to eighth aspects, the primary surface ( 21 ) of the electrically conductive substrate ( 2 ) is uneven.
- the electrode for electrolysis ( 1 ; 1 a ) according to the ninth aspect can improve the adhesion of the electrically conductive substrate ( 2 ) to the intermediate layer ( 3 ) and thus the composite layer ( 4 ) is less likely to be separated from the electrically conductive substrate ( 2 ).
- a method for producing an electrode for electrolysis ( 1 a ) according to a tenth aspect includes an intermediate layer formation process and a composite layer formation process.
- the intermediate layer formation process includes forming an intermediate layer ( 3 ) on a primary surface ( 21 ) of an electrically conductive substrate ( 2 ) containing titanium.
- the composite layer formation process includes forming a composite layer ( 4 ) on the intermediate layer ( 3 ).
- the composite layer ( 4 ) has a stacked structure alternating a plurality of tantalum layers ( 41 ) and a plurality of catalyst layers ( 42 ) one layer by one layer.
- Each of the plurality of tantalum layers ( 41 ) is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum.
- the composite layer formation process includes a first process, a second process, and a third process.
- the first process includes applying a solution containing tantalum onto the intermediate layer ( 3 ) and subsequently firing at a first prescribed temperature to form a tantalum layer ( 41 ), of the plurality of tantalum layers ( 41 ), that constitutes a bottom layer of the stacked structure.
- the second process includes repeating a first step and a second step to form a stacked body ( 401 ) serving as a basis of a remaining part, other than the tantalum layer ( 41 ) that constitutes the bottom layer, of the stacked structure.
- the third process includes firing the stacked body ( 401 ) at a fourth prescribed temperature, which is higher than each of the second prescribed temperature and the third prescribed temperature, to form the plurality of catalyst layers ( 42 ) and tantalum layers ( 41 ), other than the tantalum layer ( 41 ) that constitutes the bottom layer, of the plurality of tantalum layers ( 41 ) together with a plurality of cracks (recesses 5 ) recessed from a main surface ( 40 ) of the catalyst layer ( 42 ), the main surface ( 40 ) being a surface away from the intermediate layer ( 3 ).
- the method for producing the electrode for electrolysis ( 1 a ) according to the tenth aspect is less likely to cause the separation of the composite layer ( 4 ).
- the electrode for electrolysis ( 1 b ) according to the eleventh aspect is less likely to cause the separation of the composite layer ( 4 ).
- An electrode for electrolysis ( 1 ; 1 a ) includes an electrically conductive substrate ( 2 ), an intermediate layer ( 3 ), and a composite layer ( 4 ).
- the electrically conductive substrate ( 2 ) contains at least titanium.
- the intermediate layer ( 3 ) is provided on a primary surface ( 21 ) of the electrically conductive substrate ( 2 ).
- the composite layer ( 4 ) is provided on the intermediate layer ( 3 ).
- the composite layer ( 4 ) includes a plurality of tantalum layers ( 41 ) and a plurality of catalyst layers ( 42 ). Each of the plurality of tantalum layers ( 41 ) is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum.
- the electrode for electrolysis ( 1 ; 1 a ) according to the twelfth aspect is less likely to cause the separation of the composite layer ( 4 ).
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Abstract
An electrically conductive substrate contains at least titanium. An intermediate layer is provided on a primary surface of the electrically conductive substrate. A composite layer is provided on the intermediate layer. The composite layer includes tantalum layers and catalyst layers. Each of the catalyst layers contains platinum and iridium. Each of the tantalum layers is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum. The tantalum layers and the catalyst layers are alternately stacked one layer by one layer in a thickness direction of the electrically conductive substrate. A bottom layer of the composite layer closest to the primary surface of the electrically conductive substrate is constituted by one tantalum layer of the tantalum layers. A top layer of the composite layer furthest from the electrically conductive substrate is constituted by one catalyst layer of the catalyst layers.
Description
- The present disclosure relates generally to electrodes for electrolysis and methods for producing electrodes for electrolysis, and more particularly to an electrode for electrolysis and a method for producing an electrode for electrolysis adapted for use in electrolyzing salt water to generate chlorine.
- There has been known a technique for producing hypochlorous acid that includes electrolyzing diluted saline water, which is obtained by adding salt to tap water, to generate chlorine and reacting thus generated chlorine with water to produce the hypochlorous acid (see Patent Literature 1).
-
Patent Literature 1 discloses an electrode for electrolysis that includes: an electrode body made from titanium or titanium alloy; a titanium oxide layer provided on the electrode body; an intermediate oxide layer provided on the titanium oxide layer, the intermediate oxide layer being made of a composite that contains iridium oxide within a range of 3 to 30 mol % and tantalum oxide within a range of 70 to 97 mol % in metal conversion; and a composite body provided on the intermediate oxide layer, the composite body containing rhodium oxide within a range of 2 to 35 mol %, iridium oxide within a range of 30 to 80 mol %, tantalum oxide within a range of 6 to 35 mol %, and platinum within a range of 12 to 62 mol % in metal conversion. - The electrode for electrolysis is desired to be less likely to cause the separation of the composite layer, which contains Iridium serving as a catalyst, in order to increase the life-time of the electrode.
- Patent Literature 1: JP 2009-52069 A
- An object of the present disclosure is to provide an electrode for electrolysis and a method for producing an electrode for electrolysis, which are less likely to cause the separation of the composite layer.
- An electrode for electrolysis according to one aspect of the present disclosure includes an electrically conductive substrate, an intermediate layer, and a composite layer. The electrically conductive substrate contains at least titanium. The intermediate layer is provided on a primary surface of the electrically conductive substrate. The composite layer is provided on the intermediate layer. The composite layer includes a plurality of tantalum layers and a plurality of catalyst layers. Each of the plurality of tantalum layers is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum. Each of the plurality of catalyst layers contains platinum and iridium. In the composite layer, the plurality of tantalum layers and the plurality of catalyst layers are alternately stacked one layer by one layer in a thickness direction of the electrically conductive substrate. The composite layer has a bottom layer closest to the primary surface of the electrically conductive substrate, the bottom layer being constituted by one tantalum layer of the plurality of tantalum layers. The composite layer has a top layer furthest from the electrically conductive substrate, the top layer being constituted by one catalyst layer of the plurality of catalyst layers.
- A method for producing an electrode for electrolysis according to another aspect of the present disclosure includes an intermediate layer formation process and a composite layer formation process. The intermediate layer formation process includes forming an intermediate layer on a primary surface of an electrically conductive substrate containing titanium. The composite layer formation process includes forming a composite layer on the intermediate layer. The composite layer has a stacked structure alternating a plurality of tantalum layers and a plurality of catalyst layers one layer by one layer. Each of the plurality of tantalum layers is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum. Each of the plurality of catalyst layers contains platinum and iridium. The composite layer formation process includes a first process, a second process, and a third process. The first process includes applying a solution containing tantalum onto the intermediate layer and subsequently firing at a first prescribed temperature to form a tantalum layer, of the plurality of tantalum layers, that constitutes a bottom layer of the stacked structure. The second process includes repeating a first step and a second step to form a stacked body serving as a basis of a remaining part, other than the tantalum layer that constitutes the bottom layer, of the stacked structure. The first step includes applying a solution containing platinum and iridium and subsequently heating and drying at a second prescribed temperature to form a layer serving as a basis of one catalyst layer of the plurality of catalyst layers. The second step includes applying a solution containing tantalum and subsequently heating and drying at a third prescribed temperature to form a layer serving as a basis of one, but other than the tantalum layer that constitutes the bottom layer, of the plurality of tantalum layers. The third process includes firing the stacked body at a fourth prescribed temperature, which is higher than each of the second prescribed temperature and the third prescribed temperature, to form the plurality of catalyst layers and tantalum layers, other than the tantalum layer that constitutes the bottom layer, of the plurality of tantalum layers together with a plurality of cracks recessed from a main surface of the catalyst layer, the main surface being a surface away from the intermediate layer.
- An electrode for electrolysis according to yet another aspect of the present disclosure includes an electrically conductive substrate, an intermediate layer, and a composite layer. The electrically conductive substrate contains at least titanium. The intermediate layer is provided on a primary surface of the electrically conductive substrate. The composite layer is provided on the intermediate layer. The composite layer includes a plurality of tantalum layers and a plurality of catalyst layers. Each of the plurality of tantalum layers is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum. Each of the plurality of catalyst layers contains platinum and iridium. In the composite layer, the plurality of tantalum layers and the plurality of catalyst layers are alternately stacked one layer by one layer in a thickness direction of the electrically conductive substrate. The composite layer has a bottom layer closest to the primary surface of the electrically conductive substrate, the bottom layer being constituted by one tantalum layer of the plurality of tantalum layers. The composite layer has a top layer furthest from the electrically conductive substrate, the top layer being constituted by another one tantalum layer of the plurality of tantalum layers. The composite layer has a main surface away from the intermediate layer. The electrode for electrolysis has a plurality of recesses recessed from the main surface of the composite layer. Each of the plurality of recesses has a depth such that each of the plurality of recesses is made to go completely through at least one catalyst layer of the plurality of catalyst layers.
-
FIG. 1 is a sectional view of an electrode for electrolysis according to a first embodiment; -
FIG. 2 is a plan view of the electrode for electrolysis; -
FIGS. 3A to 3D are sectional views illustrating processes of a method for producing the electrode for electrolysis; -
FIG. 4 is a graph illustrating a result of a durability test for the electrode for electrolysis; -
FIGS. 5A to 5D are views of an inferred mechanism for illustrating that the electrode for electrolysis has an improved durability; -
FIG. 6 is a sectional view of an electrode for electrolysis according to a second embodiment; -
FIGS. 7A to 7E are sectional views illustrating processes of a method for producing the electrode for electrolysis; and -
FIG. 8 is a sectional view of an electrode for electrolysis according to a variation. - The
FIGS. 1, 2, 3A to 3D, 5A to 5D, 6, 7A to 7E, and 8 to be referred to in the following description of first and second embodiments and the like are all schematic representations. The ratio of the dimensions including thicknesses, of respective constituent elements illustrated on the drawings does not always reflect their actual dimensional ratio. - An electrode for
electrolysis 1 according to the first embodiment is explained with reference toFIGS. 1 to 3D . - The electrode for
electrolysis 1 may be an electrode adapted for use in the electrolysis of salt water to generate chlorine. The salt water may be saline water, for example. The electrode forelectrolysis 1 may be used for a system for electrolyzing the salt water. Such a system includes an anode and a cathode between which a DC voltage is to be applied from a power source. In this system, the electrode forelectrolysis 1 may be used as the anode. This system can electrolyze the saline water to generate chlorine, and can produce hypochlorous acid by reacting the generated chlorine with water. - The electrode for
electrolysis 1 includes an electricallyconductive substrate 2, anintermediate layer 3, and acomposite layer 4. - Components of the electrode for
electrolysis 1 will be explained more in detail. - (2.1) Electrically Conductive Substrate
- The electrically
conductive substrate 2 includes a primary surface 21 (hereinafter, also referred to as “firstprimary surface 21”), and a secondprimary surface 22 opposite to the firstprimary surface 21. The electricallyconductive substrate 2 has a plan shape (shape of the outline of the electricallyconductive substrate 2 as seen in a thickness direction D1 of the electrically conductive substrate 2) of a rectangle. The electricallyconductive substrate 2 has a thickness within a range of 100 μm to 2 mm for example, and the thickness may be 500 μm as an example. The electricallyconductive substrate 2 has a size in the plan view of 25 mm by 60 mm, for example. - The electrically
conductive substrate 2 contains at least titanium. The electricallyconductive substrate 2 is a titanium substrate, for example. The material of the electricallyconductive substrate 2 may be titanium or an alloy containing titanium as main component (hereinafter, referred to as “titanium alloy”). Examples of the titanium alloy includes titanium-palladium alloy, titanium-nickel-ruthenium alloy, titanium-tantalum alloy, titanium-aluminum alloy, titanium-aluminum-vanadium alloy, and the like. - The first
primary surface 21 of the electricallyconductive substrate 2 may preferably be uneven. This can contribute to increase the adhesion with respect to theintermediate layer 3. According to the electrode forelectrolysis 1 of the first embodiment, the firstprimary surface 21 of the electricallyconductive substrate 2 is roughened before theintermediate layer 3 is provided. In terms of the surface roughness of the firstprimary surface 21 of the electricallyconductive substrate 2, the arithmetic mean deviation of the roughness profile Ra thereof is 0.3 μm and the maximum height of the profile Rz is 3 μm, for example. The arithmetic mean deviation of the roughness profile Ra and the maximum height of the profile Rz are defined by the JIS B 0601-2001 (ISO 4287-1997) standard. The arithmetic mean deviation of the roughness profile Ra and the maximum height of the profile Rz can be determined based on the measurement result for the Cross-sectional Scanning Electron Microscope (SEM) Image, for example. - (2.2) Intermediate Layer
- The
intermediate layer 3 is provided on the firstprimary surface 21 of the electricallyconductive substrate 2. The electrode forelectrolysis 1 has a boundary face between the electricallyconductive substrate 2 and theintermediate layer 3. Theintermediate layer 3 has corrosion resistance to the salt water and the chlorine. Theintermediate layer 3 may preferably be made of material exhibiting corrosion resistance to the salt water and the chlorine superior to those of the electricallyconductive substrate 2. Theintermediate layer 3 may preferably be made of material having electrical conductivity and high electrical conduction property. This can contribute to increase the electrical conductivity of the electrode forelectrolysis 1. The material of theintermediate layer 3 may be transition metal or a mixture containing transition metal, for example. Examples of the material include: platinum; a mixture of tantalum, platinum and iridium; iridium; iridium oxide; nickel; and the like. A specific example of the material of theintermediate layer 3 is platinum. Theintermediate layer 3 has a thickness within a range of 0.3 μm to 5 μm for example, and the thickness may be 0.6 μm as an example. - (2.3) Composite Layer
- The
composite layer 4 is provided on theintermediate layer 3. The electrode forelectrolysis 1 has a boundary face between thecomposite layer 4 and theintermediate layer 3. Thecomposite layer 4 is provided on the electricallyconductive substrate 2 with theintermediate layer 3 interposed therebetween. - The
composite layer 4 includes a plurality of (four, in the illustrated example) tantalum layers 41, and a plurality of (four, in the illustrated example) catalyst layers 42. Each of the plurality of catalyst layers 42 contains platinum and iridium. Each of the plurality of catalyst layers 42 is constituted by a mixture of platinum and iridium. Each of the plurality of tantalum layers 41 is a layer made from tantalum oxide, but is not limited thereto. Alternatively, atantalum layer 41 may be a layer made from tantalum or a layer made from a mixture of tantalum oxide and tantalum (i.e., a layer including a mix of tantalum oxide and tantalum). In each of the plurality of catalyst layers 42, iridium is dispersed through platinum. Iridium serves as a catalyst for the generation reaction of chlorine. Thecomposite layer 4 has a platinum:iridium:tantalum molar ratio of 6-10:1-10:1-8, for example. The molar quantity of iridium may preferably be smaller or equal to the molar quantity of platinum. This can contribute to suppress the cohesion of iridium due to aging variation caused by the long time use of the electrode forelectrolysis 1. Thetantalum layer 41 is superior to thecatalyst layer 42 in the corrosion resistance and is resistant to structural change. Accordingly, atantalum layer 41 provided on acatalyst layer 42 can prevent thecatalyst layer 42 directly underneath from causing the elution of iridium. - The
composite layer 4 has a stacked structure alternating the plurality of tantalum layers 41 and the plurality of catalyst layers 42 one layer by one layer in the thickness direction D1 of the electricallyconductive substrate 2. Each of the plurality of tantalum layers 41 has a thickness within a range of 15 nm to 300 nm for example, and the thickness may be 100 nm as an example. Each of the plurality of catalyst layers 42 has a thickness within a range of 15 nm to 100 nm for example, and the thickness may be 50 nm as an example. - Hereinafter, for the convenience of the explanation, the four
tantalum layers 41 may be referred to as afirst tantalum layer 411, asecond tantalum layer 412, athird tantalum layer 413, and afourth tantalum layer 414, respectively, in the order from a side closer to the firstprimary surface 21 of the electricallyconductive substrate 2. The four catalyst layers 42 may be referred to afirst catalyst layer 421, asecond catalyst layer 422, athird catalyst layer 423, and afourth catalyst layer 424, respectively, in the order from the side closer to the firstprimary surface 21 of the electricallyconductive substrate 2. - In the
composite layer 4, thefirst tantalum layer 411, thefirst catalyst layer 421, thesecond tantalum layer 412, thesecond catalyst layer 422, thethird tantalum layer 413, thethird catalyst layer 423, thefourth tantalum layer 414, and thefourth catalyst layer 424 are arranged in this order from the side of the electricallyconductive substrate 2. - The
composite layer 4 has a bottom layer closest to theprimary surface 21 of the electricallyconductive substrate 2. The bottom layer of thecomposite layer 4 is constituted by onetantalum layer 41 of the plurality of tantalum layers 41. Thecomposite layer 4 has a top layer furthest from the electricallyconductive substrate 2. The top layer of thecomposite layer 4 is constituted by onecatalyst layer 42 of the plurality of catalyst layers 42. - In the
composite layer 4, one tantalum layer 41 (first tantalum layer 411) of the plurality of tantalum layers 41 constitutes the bottom layer that is closest to the firstprimary surface 21 of the electricallyconductive substrate 2. In thecomposite layer 4, one catalyst layer 42 (fourth catalyst layer 424, in the illustrated example) of the plurality of catalyst layers 42 constitutes the top layer that is furthest from the electricallyconductive substrate 2. - The electrode for
electrolysis 1 has a plurality ofrecesses 5 recessed from amain surface 40 that is a surface, away from theintermediate layer 3, of thecomposite layer 4. Each of the plurality ofrecesses 5 has a depth which is larger than a distance L1 and also smaller than or equal to a distance L2. The distance L1 is a distance between themain surface 40 of thecomposite layer 4 and a catalyst layer 42 (third catalyst layer 423), second furthest from the electricallyconductive substrate 2, of the plurality of catalyst layers 42. The distance L2 is a distance between themain surface 40 of thecomposite layer 4 and theintermediate layer 3. - Each of the plurality of
recesses 5 has a width H1 (seeFIG. 2 ), in the plan view as seen in the thickness direction D1 of the electricallyconductive substrate 2, that falls within a range of 0.1 μm to 10 μm, and the width may preferably fall within a range of 0.3 μm to 3 μm. The width H1 of therecess 5, in the plan view as seen in the thickness direction D1 of the electricallyconductive substrate 2, indicates an opening width of therecess 5 in a transverse direction (perpendicular to the longitudinal direction) thereof within themain surface 40 of thecomposite layer 4. - Moreover, a percentage of S2 with respect to S1+S2 falls within a range of 5% to 50% for example, where S1 denotes an area of the
main surface 40 of thecomposite layer 4 in the plan view as seen in the thickness direction D1 of the electricallyconductive substrate 2, and S2 denotes a total area of opening areas of the plurality ofrecesses 5 in themain surface 40 of thecomposite layer 4 in the plan view as seen in the thickness direction D1 of the electricallyconductive substrate 2. The percentage of S2 with respect to S1+S2 may preferably be 5% or more, which can contribute to improve the chlorine generation efficiency. The percentage of S2 with respect to S1+S2 may preferably be 50% or less, and may further preferably be 20% or less, which can contribute to suppress the separation of thecomposite layer 4. That is, the percentage of S2 with respect to S1+S2 may preferably fall within a range of 5% to 20%. In the electrode forelectrolysis 1, at least one recess of the plurality of recesses is present in a 0.01 mm2 square region in the plan view as seen in the thickness direction D1 of the electricallyconductive substrate 2. A total length of each opening edge of the at least one recess present in the 0.01 mm2 square region is greater than or equal to 1 mm. - An example of a method for producing the electrode for
electrolysis 1 is explained with reference toFIGS. 3A to 3D . - The method for producing the electrode for electrolysis includes preparing the electrically
conductive substrate 2 as shown inFIG. 3A . The method includes a roughening process, an intermediate layer formation process, and a composite layer formation process which are performed sequentially after the preparation. - The roughening process includes, for example, immersing the electrically
conductive substrate 2 in an oxalic acid aqueous solution to roughen the firstprimary surface 21 of the electricallyconductive substrate 2. The roughening process is optional and may be omitted. In terms of the surface roughness of the firstprimary surface 21 of the electricallyconductive substrate 2 after the roughening process, the arithmetic mean deviation of the roughness profile Ra thereof is 0.3 μm and the maximum height of the profile Rz thereof is 3 μm, for example. The arithmetic mean deviation of the roughness profile Ra and the maximum height of the profile Rz may be values measured with a surface roughness meter of Zygo Co. - The intermediate layer formation process includes forming the
intermediate layer 3 on the firstprimary surface 21 of the electrically conductive substrate 2 (seeFIG. 3B ). Theintermediate layer 3 is a platinum layer, for example. The intermediate layer formation process includes: applying a raw material solution, serving as a basis of theintermediate layer 3, onto the firstprimary surface 21 of the electricallyconductive substrate 2; performing natural drying; performing heat treatment; and firing, to form theintermediate layer 3. The raw material solution is a solution obtained by dissolving a platinum compound in a solvent. The solvent is a liquid of a mixture of ethylene glycol monoethyl ether, hydrochloric acid and ethanol, for example. The platinum compound is for example hydrogen chloroplatinate, but is not limited thereto. Alternatively, the platinum compound may be platinum chloride, for example. The formation method of theintermediate layer 3 is not limited to the above method, but may include vapor deposition, sputtering, CVD method, plating, and the like. - The compound layer formation process includes forming the
composite layer 4 on the intermediate layer 3 (seeFIG. 3D ). - The compound layer formation process includes a stacked body formation process and a firing process.
- The stacked body formation process includes performing a first prescribed number of times (four times, for example) of first steps and a second prescribed number of times (four times, for example) of second steps, where the first step and the second step are performed alternately, to form, on the
intermediate layer 3 which is on the electricallyconductive substrate 2, a stacked body 400 (seeFIG. 3C ) serving as a basis of thecomposite layer 4. - The first step includes applying a solution (hereinafter, referred to as “first solution”) containing a tantalum compound serving as a basis of the
tantalum layer 41, and subsequently performing, without natural drying, heat treatment (drying process) of heating and drying under a first condition, to form afirst material layer 410 serving as a basis of onetantalum layer 41 of the plurality of tantalum layers 41. The first solution is a solution obtained by dissolving the tantalum compound in a solvent (hereinafter, referred to as “first solvent”). The first solvent is a liquid of a mixture of ethylene glycol monoethyl ether, hydrochloric acid and ethanol, for example. The tantalum compound is for example tantalum chlorine, but is not limited thereto. Alternatively, the tantalum compound may be tantalum ethoxydo, for example. The metal concentration (tantalum concentration) of the first solution is 26 mg/L, for example. The application amount of the first solution is 1 μL/cm2, for example. The first condition includes a heat treatment temperature and a heat treatment time. The heat treatment temperature of the first condition falls within a range of 100° C. to 400° C. for example, and the heat treatment temperature may be 220° C. as an example. The heat treatment time of the first condition falls within a range of 5 minutes to 15 minutes for example, and the heat treatment time may be 10 minutes as an example. - The second step includes applying a solution (hereinafter, referred to as “second solution”) containing a platinum compound and iridium compound serving as a basis of the
catalyst layer 42, and subsequently performing, without natural drying, heat treatment (drying process) of heating and drying under a second condition, to form asecond material layer 420 serving as a basis of onecatalyst layer 42 of the plurality of catalyst layers 42. The second solution is a solution obtained by dissolving the platinum compound and the iridium compound in a solvent (hereinafter, referred to as “second solvent”). The second solvent is a liquid of a mixture of ethylene glycol monoethyl ether, hydrochloric acid and ethanol, for example. The platinum compound is for example hydrogen chloroplatinate, but is not limited thereto. Alternatively, the platinum compound may be platinum chloride, for example. The iridium compound is for example hydrogen chloroidiate, but is not limited thereto. Alternatively, the iridium compound may be iridium chloride, iridium nitrate, or the like, for example. The metal concentration (total of platinum concentration and iridium concentration) of the second solution is 26 mg/L, for example. The application amount of the second solution is 2 μL/cm2, for example. The second condition includes a heat treatment temperature and a heat treatment time. The heat treatment temperature of the second condition falls within a range of 100° C. to 400° C. for example, and the heat treatment temperature may be 220° C. as an example. The heat treatment time of the second condition falls within a range of 5 minutes to 15 minutes for example, and the heat treatment time may be 10 minutes as an example. - The firing process includes performing thermal treatment of firing the
stacked body 400 under a predetermined firing condition to form thecomposite layer 4 and a plurality of cracks (recesses 5) (seeFIG. 3D ). The firing condition includes a firing temperature and a firing time. The firing temperature falls within a range of 500° C. to 700° C. for example, and the firing temperature may be 560° C. as an example. The firing time falls within a range of 10 minutes to 20 minutes for example, and the firing time may be 15 minutes as an example. The plurality of cracks (recesses 5) may have mutually different shapes. The crack may be formed along a thickness direction of thecomposite layer 4 or may be at least partially curved in thecomposite layer 4. -
FIG. 4 is a graph that shows durability test results for the following nine examples, Examples 1 to 9. The nine examples have mutually different electrodes forelectrolysis 1 whose platinum (Pt):iridium (Ir):tantalum (Ta) molar ratio of thecomposite layers 4 and/or the number of layers (the total number of layers of thetantalum layer 41 and the catalyst layer 42) included in the stacked structures of thecomposite layers 4 are different from each other, where: - Example 1 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:1:6 and the number of layers is 10;
- Example 2 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:1:6 and the number of layers is 20;
- Example 3 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:1:6 and the number of layers is 30;
- Example 4 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:3:6 and the number of layers is 10;
- Example 5 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:3:6 and the number of layers is 20;
- Example 6 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:3:6 and the number of layers is 30;
- Example 7 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:5:6 and the number of layers is 10;
- Example 8 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:5:6 and the number of layers is 20; and
- Example 9 relates to a sample whose molar ratio of Pt:Ir:Ta is 8:5:6 and the number of layers is 30.
- The durability test was conducted according to the accelerated test. In the durability test for each example, two electrodes for
electrolysis 1 were produced in a same condition and used as a pair of electrodes. Firstly, the pair of electrodes were immersed in salt water inside a tank for electrolytic cell for a durability test apparatus, and an electric current was supplied between the pair of electrodes to conduct an initial aging. After the initial aging, an electric current was continuously provided for a certain duration of time between the pair of electrodes immersed in the salt water, subsequently the pair of electrodes were put and immersed in another salt water inside a tank for electrolytic cell for a chlorine concentration measurement, and then an electric current was provided for a predetermined time (3 minutes) between the pair of electrodes and (average) chlorine concentration around the electrode were measured, which were performed repeatedly. It should be noted that the tank for electrolytic cell for the durability test apparatus has an inlet and an outlet for the salt water. During the durability test, salt water was added to the tank such that the electrical conductivity of the salt water inside the tank for electrolytic cell for the durability test apparatus was maintained within a range of 1650±200 S/m. During the durability test, the tank for electrolytic cell for the durability test apparatus was continuously supplied with tap water with a flow rate of 2 L/min while discharging water therefrom. The salt water supplied in the tank for electrolyte cell for the durability test apparatus was obtained by dissolving common salt (sodium chloride) in tap water. The current value of the electric current supplied during the durability test was 400 mA. Moreover, the salt water inside the tank for electrolytic cell for the chlorine concentration measurement was obtained by dissolving 4.5 g of common salt (sodium chloride) in 800 mL of pure water. The current value of the electric current supplied during the chlorine concentration measurement was 400 mA. Furthermore, during the initial aging, the electric current was supplied between the pair of electrodes for total twelve minutes, where the polarity was reversed every time a predetermined time (3 minutes) elapses. The feature “the polarity is reversed” used herein indicates that the roles of the pair of electrodes, the anode or the cathode, are mutually interchanged. In other words, the feature “the polarity is reversed” indicates that an electrode (to be) used as the higher potential side electrode is changed from one of the pair of electrodes to the other thereof, such that one of the electrodes which has been used as the anode is to be used as the cathode, and vice verse. - The horizontal axis of
FIG. 4 indicates the durability test time (elapsed time) after the initial aging. The vertical axis ofFIG. 4 indicates the chlorine concentration. It should be noted that the chlorine generated around the anode is to be used for the generation of hypochlorous acid. Thus, the chlorine concentration substantially reflects the amount of chlorine, which has been produced during a recent unit time. - It can be understood from
FIG. 4 that the durability increases as an increase in the number of layers under the same platinum (Pt):iridium (Ir):tantalum (Ta) molar ratio. It can also be understood fromFIG. 4 that the durability increases as an increase in the percentage of iridium (Ir) under the same number of layers and the same platinum (Pt):tantalum (Ta) molar ratio. - Based on
FIGS. 5A, 5B, 5C and 5D , an inferred mechanism is described which can explain a reason why the electrode forelectrolysis 1 according to the first embodiment has an improved durability.FIGS. 5A, 5B, 5C, and 5D are ordered according to the time series. - According to the electrode for
electrolysis 1 in a state shown inFIG. 5A , respective sides of a plurality of (four) catalyst layers 42 that partially form an inner surface of therecess 5, as well as themain surface 40, of thecomposite layer 4 are in contact with the salt water. Each of the plurality of (four) catalyst layers 42 thus can contribute to the generation of the chlorine. -
FIG. 5B shows a state of the electrode forelectrolysis 1 where a catalyst layer 42 (fourth catalyst layer 424) of the top layer shown inFIG. 5A is lost. According to the state shown inFIG. 5B , respective sides of a plurality of (three) catalyst layers 42 that partially form an inner surface of therecess 5 are in contact with the salt water. Each of the plurality of (three) catalyst layers 42 thus can contribute to the generation of the chlorine. -
FIG. 5C shows a state where the plurality of (three) catalyst layers 42 are partially lost in an in-plane direction, from the state shown inFIG. 5B . The in-plane direction is defined as a direction perpendicular to the thickness direction D1 of the electricallyconductive substrate 2. That is, the in-plane direction is a direction along the firstprimary surface 21 of the electricallyconductive substrate 2. According to the state shown inFIG. 5C , respective sides, closer to therecess 5, of the plurality of (three) catalyst layers 42 are in contact with the salt water. Each of the plurality of (three) catalyst layers 42 thus can contribute to the generation of the chlorine. -
FIG. 5D shows a state where a tantalum layer 41 (fourth tantalum layer 414) on a catalyst layer 42 (third catalyst layer 423), which is furthest from the electricallyconductive substrate 2, of the plurality of (three) catalyst layers 42 is partially lost along the in-plane direction, from the state shown inFIG. 5C . According to the state shown inFIG. 5D , respective sides, closer to therecess 5, of the plurality of (three) catalyst layers 42, as well as a main surface of thethird catalyst layer 423 closer to thefourth tantalum layer 414, are in contact with the salt water. Each of the plurality of (three) catalyst layers 42 thus can contribute to the generation of the chlorine. - With the electrode for
electrolysis 1 according to the first embodiment, at least one of the catalyst layers 42 always can contribute to the generation of the chlorine, regardless of the change in the state thereof. The electrode forelectrolysis 1 according to the first embodiment thus can have an improved durability. - The electrode for
electrolysis 1 according to the first embodiment includes thecomposite layer 4 alternating the plurality of tantalum layers 41 and the plurality of catalyst layers 42 one layer by one layer, which can contribute to suppress the separation of thecomposite layer 4. The electrode forelectrolysis 1 according to the first embodiment includes thecomposite layer 4, which also can contribute to suppress the waste of thecomposite layer 4 in use. The electrode forelectrolysis 1 according to the first embodiment includes thecomposite layer 4, which also can contribute to suppress the cohesion of iridium. - The electrode for
electrolysis 1 according to the first embodiment has the plurality ofrecesses 5, which can increase the area of the surface of thecomposite layer 4 contributing the generation of the chlorine, and can contribute to improve the chlorine generation efficiency. - An electrode for
electrolysis 1 a according to the second embodiment is explained with reference toFIG. 6 . - The electrode for
electrolysis 1 a according to the second embodiment is substantially the same as the electrode forelectrolysis 1 according to the first embodiment. The electrode forelectrolysis 1 a according to the second embodiment differ from the electrode forelectrolysis 1 according to the first embodiment in the depths of therecesses 5. Components of the electrode forelectrolysis 1 a according to the second embodiment similar to those of the electrode forelectrolysis 1 according to the first embodiment are assigned same reference signs and explanation thereof may be omitted. - Each of the plurality of
recesses 5 of the electrode forelectrolysis 1 a according to the second embodiment has a depth which is smaller than or equal to a distance L3 between amain surface 40 of acomposite layer 4 and a bottom layer (first tantalum layer 411) of thecomposite layer 4. This can contribute to further suppression of the separation of thecomposite layer 4 according to the electrode forelectrolysis 1 a according to the second embodiment. - A method for producing the electrode for
electrolysis 1 a according to the second embodiment is explained with reference toFIGS. 7A to 7E . It may be omitted the detailed explanation of some of processes, similar to those of the method for producing the electrode forelectrolysis 1 according to the first embodiment. - An electrically
conductive substrate 2 is prepared firstly as shown inFIG. 7A , and a roughening process, an intermediate layer formation process, and a composite layer formation process are performed sequentially after the preparation. - The roughening process includes, for example, immersing the electrically
conductive substrate 2 in an oxalic acid aqueous solution to roughen a firstprimary surface 21 of the electricallyconductive substrate 2. The roughening process is optional and may be omitted. - The intermediate layer formation process includes forming an
intermediate layer 3 on the firstprimary surface 21 of the electrically conductive substrate 2 (seeFIG. 7B ). - The compound layer formation process includes forming a
composite layer 4 on the intermediate layer 3 (seeFIG. 7E ). - The compound layer formation process includes a first process, a second process, and a third process.
- The first process includes applying a solution containing tantalum, serving as a basis of a
tantalum layer 41, onto theintermediate layer 3, and subsequently performing a firing to form atantalum layer 41, constituting a bottom layer of a stacked structure of thecomposite layer 4, of a plurality of tantalum layer 41 (seeFIG. 7C ). The solution is obtained by dissolving a tantalum compound in a solvent, for example. The solution thus includes tantalum. The solvent is a liquid of a mixture of ethylene glycol monoethyl ether, hydrochloric acid and ethanol, for example. The tantalum compound is for example tantalum chlorine, but is not limited thereto. Alternatively, the tantalum compound may be tantalum ethoxydo, for example. Further alternatively, the solution may be obtained by dissolving pure tantalum in the solvent, for example, which can form thetantalum layer 41 as a layer made from tantalum, instead of a layer made from tantalum oxide. The metal concentration (tantalum concentration) of the solution is 26 mg/L, for example. The application amount of the solution is 1 μL/cm2, for example. The firing condition includes a firing temperature (first prescribed temperature) and a firing time. The firing temperature falls within a range of 500° C. to 700° C. for example, and the firing temperature may be 560° C. as an example. The firing time falls within a range of 10 minutes to 20 minutes for example, and the firing time may be 15 minutes as an example. - The second process includes a first prescribed number of times (e.g., four times) of first steps and a second prescribed number of times (e.g., three times) of second steps which are performed alternatively to form a
stacked body 401. Thestacked body 401 serves as a basis of a remaining part, other than thetantalum layer 41 constituting the bottom layer, of the stacked structure of the composite layer 4 (seeFIG. 7D ). - The first step of the second process includes applying a second solution containing a platinum compound and iridium compound serving as a basis of a
catalyst layer 42, and subsequently performing, without natural drying, heat treatment (drying process) of heating and drying under a second condition to form asecond material layer 420 serving as a basis of onecatalyst layer 42 of the plurality of catalyst layers 42. The second solution contains platinum and iridium. The second solution is applied to a layer (atantalum layer 41 as a bottom layer, or afirst material layer 410 described later, for example) exposed outside on a side of the firstprimary surface 21 of the electricallyconductive substrate 2. The second condition includes a heat treatment temperature and a heat treatment time. The heat treatment temperature (second prescribed temperature) of the second condition falls within a range of 100° C. to 400° C. for example, and the heat treatment temperature may be 220° C. as an example. The heat treatment time of the second condition falls within a range of 5 minutes to 15 minutes for example, and the heat treatment time may be 10 minutes as an example. - The second step of the second process includes applying a first solution containing a tantalum compound serving as a basis of the
tantalum layer 41, and subsequently performing, without natural drying, heat treatment (drying process) of heating and drying under a first condition, to form afirst material layer 410 serving as a basis of onetantalum layer 41 of the plurality of tantalum layers 41. The first solution contains tantalum. The first solution is applied to a layer (a second material layer 420) exposed outside on a side of the firstprimary surface 21 of the electricallyconductive substrate 2. The first condition includes a heat treatment temperature and a heat treatment time. The heat treatment temperature (third prescribed temperature) of the first condition falls within a range of 100° C. to 400° C. for example, and the heat treatment temperature may be 220° C. as an example. The heat treatment time of the first condition falls within a range of 5 minutes to 15 minutes for example, and the heat treatment time may be 10 minutes as an example. - The third process includes firing the
stacked body 401 at a prescribed temperature (fourth prescribed temperature) to form the plurality of catalyst layers 42 andtantalum layers 41, other than thetantalum layer 41 constituting the bottom layer, of the plurality of thetantalum layer 41 together with a plurality of cracks (recesses 5) recessed from amain surface 40 of thecatalyst layer 42. Themain surface 40 is a surface away from the intermediate layer 3 (seeFIG. 7E ). - The method for producing the electrode for
electrolysis 1 a according to the second embodiment can provide the electrode forelectrolysis 1 a, which is less likely to cause the separation of thecomposite layer 4. - The first and second embodiments are only exemplary ones of various embodiments of the present disclosure. The exemplary embodiment may be readily modified in various manners depending on a design choice or any other factor, as long as the purpose of the present disclosure can be attained.
- In a variation, a plan shape of an electrically
conductive substrate 2 is not limited to a rectangle, but may be a square for example. - In a variation, the number of tantalum layers 41 and/or catalyst layers 42 of a
composite layer 4 is not limited to four, but may be two, three, five or more. The number of tantalum layers 41 and the number of catalyst layers 42 in thecomposite layer 4 are not limited to be the same, but may be different from each other. - In a variation, thicknesses of a plurality of tantalum layers 41 are not limited to be the same, but may be different from each other. It is also possible that some of a plurality of tantalum layers 41 have the same thickness, and remaining of the plurality of
tantalum layer 41 may have a thickness different therefrom. - In a variation, thicknesses of a plurality of catalyst layers 42 are not limited to be the same, but may be different from each other. It is also possible that some of a plurality of catalyst layers 42 have the same thickness, and remaining of the plurality of
catalyst layer 42 may have a thickness different therefrom. - In a variation, a plurality of tantalum layers 41 are not limited to have the same composition, but may have different compositions. a plurality of catalyst layers 42 are not limited to have the same composition, but may have different compositions.
- In a variation, each a plurality of catalyst layers 42 of a
composite layer 4 is not limited to be a porous layer. Alternatively, at least onecatalyst layer 42, which is other than acatalyst layer 42 constituting a top layer of a plurality of catalyst layers 42, may be a porous layer, for example. - In a variation, each of a plurality of catalyst layers 42 of a
composite layer 4 may be a non-porous layer. - In a variation, a plurality of
recesses 5 may have the same shape. A method for producing such an electrode forelectrolysis 1 may include an etching technique, a laser processing, or the like to form such a plurality ofrecesses 5. These techniques/processing can provide a greater degree of freedom for the design of a layout and dimensions of the plurality ofrecesses 5 and can realize a higher reproductivity about the positions of the plurality ofrecesses 5. - In a variation of an electrode for
electrolysis 1 b shown inFIG. 8 , the electrode forelectrolysis 1 b has a plurality ofrecesses 5 recessed from amain surface 40, away from anintermediate layer 3, of acomposite layer 4, and a top layer of thecomposite layer 4 is constituted by atantalum layer 41. Components of the electrode forelectrolysis 1 b similar to those of the electrode forelectrolysis 1 are assigned same reference signs and explanation thereof may be omitted. According to the electrode forelectrolysis 1 b including thecomposite layer 4 of which top layer is constituted by thetantalum layer 41, each of the plurality ofrecesses 5 has a depth such that each of the plurality ofrecesses 5 is made to go completely through at least onecatalyst layer 42 of the plurality of catalyst layers 42. Each of the plurality ofrecesses 5 may preferably have a depth such that each of the plurality ofrecesses 5 is made to go completely through the plurality of catalyst layers 42, which can contribute to improve the chlorine generation efficiency. - In a variation, a bottom layer of a
composite layer 4 may be constituted by onetantalum layer 41 of a plurality of tantalum layers 41 and be directly on aprimary surface 21 of an electricallyconductive substrate 2 without anintermediate layer 3 interposed therebetween. In this case, a top layer, furthest from the electricallyconductive substrate 2, of thecomposite layer 4 may be constituted by onecatalyst layer 42 of a plurality of catalyst layers 42. - (Recapitulation)
- As can be seen from the foregoing description of the first and second embodiments and the like, the present disclosure discloses the following aspects.
- An electrode for electrolysis (1; 1 a) according to a first aspect includes an electrically conductive substrate (2), an intermediate layer (3), and a composite layer (4). The electrically conductive substrate (2) contains at least titanium. The intermediate layer (3) is provided on a primary surface (21) of the electrically conductive substrate (2). The composite layer (4) is provided on the intermediate layer (3). The composite layer (4) includes a plurality of tantalum layers (41) and a plurality of catalyst layers (42). Each of the plurality of tantalum layers (41) is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum. Each of the plurality of catalyst layers (42) contains platinum and iridium. The plurality of tantalum layers (41) and the plurality of catalyst layers (42) are alternately stacked one layer by one layer in a thickness direction (D1) of the electrically conductive substrate (2). A bottom layer of the composite layer (4) closest to the primary surface (21) of the electrically conductive substrate (2) is constituted by one tantalum layer (41) of the plurality of tantalum layers (41). A top layer of the composite layer (4) furthest from the electrically conductive substrate (2) is constituted by one catalyst layer (42) of the plurality of catalyst layers (42).
- The electrode for electrolysis (1; 1 a) according to the first aspect is less likely to cause the separation of the composite layer (4).
- The electrode for electrolysis (1; 1 a) according to a second aspect, which may be implemented in conjunction with the first aspect, the composite layer (4) has a main surface (40) away from the intermediate layer (3). The electrode for electrolysis (1; 1 a) has a plurality of recesses (5) recessed from the main surface (40) of the composite layer (4). Each of the plurality of recesses (5) has a depth which is greater than a distance (L1) between the main surface (40) of the composite layer (4) and a catalyst layer 42 (third catalyst layer 423), second furthest from the electrically conductive substrate (2), of the plurality of catalyst layers (42) and also is smaller than or equal to a distance (L2) between the main surface (40) of the composite layer (4) and the intermediate layer (3).
- With the electrode for electrolysis (1; 1 a) according to the second aspect, a catalyst layer (third catalyst layer 423) second furthest from the electrically conductive substrate (2), of the plurality of catalyst layers (42), also can contribute to the generation of the chlorine. This allows the plurality of catalyst layers (42) to be gradually consumed from their sides constituting the plurality of recesses (5). The electrode for electrolysis (1; 1 a) according to this aspect thus can contribute to improve the durability and also can achieve the efficient consumption of the catalyst layer (42) to improve the chlorine generation efficiency by adjusting at least one of the number of catalyst layers (42) and the percentage of iridium contained in each of the plurality of catalyst layers (42).
- The electrode for electrolysis (1 a) according to a third aspect, which may be implemented in conjunction with the second aspect, the depth of each of the plurality of recesses (5) is smaller than or equal to a distance (L3) between the main surface (40) and the bottom layer (first tantalum layer 411) of the composite layer (4).
- The electrode for electrolysis (1 a) according to the third aspect is further less likely to cause the separation of the composite layer (4).
- The electrode for electrolysis (1; 1 a) according to a fourth aspect, which may be implemented in conjunction with the second or third aspect, each of the plurality of recesses (5) is a crack extending linearly in a plan view as seen in the thickness direction (D1).
- With the electrode for electrolysis (1; 1 a) according to the fourth aspect, a catalyst layer (42) farther from the electrically conductive substrate (2) tends to contribute to the generation of the chlorine and a catalyst layer (42) closer to the electrically conductive substrate (2) is less likely to be consumed. This can improve the durability of the electrode for electrolysis (1; 1 a).
- The electrode for electrolysis (1; 1 a) according to a fifth aspect, which may be implemented in conjunction with the fourth aspect, each of the plurality of recesses (5) has a width (H1) within a range of 0.3 μm to 3 μm.
- The electrode for electrolysis (1; 1 a) according to a sixth aspect, which may be implemented in conjunction with the fourth or fifth aspect, a percentage of S2 with respect to S1+S2 falls within a range of 5% to 50%, where S1 denotes an area of the main surface (40) of the composite layer (4) in the plan view as seen in the thickness direction (D1) of the electrically conductive substrate, and S2 denotes a total area of opening areas of the plurality of recesses (5) in the main surface (40) of the composite layer (4) in the plan view as seen in the thickness direction (D1) of the electrically conductive substrate.
- The electrode for electrolysis (1; 1 a) according to a seventh aspect, which may be implemented in conjunction with the sixth aspect, at least one recess (5) of the plurality of recesses (5) is present in a 0.01 mm2 square region in the plan view as seen in the thickness direction (D1) of the electrically conductive substrate (2), a total length of each opening edge of the at least one recess (5) present in the 0.01 mm2 square region being greater than or equal to 1 mm.
- The electrode for electrolysis (1; 1 a) according to an eighth aspect, which may be implemented in conjunction with any one of the first to seventh aspects, each of the plurality of catalyst layers (42) is a porous layer.
- The electrode for electrolysis (1; 1 a) according to the eighth aspect can have an improved durability. The reason that the electrode for electrolysis (1; 1 a) according to the eighth aspect can have the improved durability may be inferred that each catalyst layer (42), other than a catalyst layer (42) that constitutes the top layer, of the plurality of catalyst layers (42) can easily contribute to generate the chlorine because the salt water is likely to infiltrate in an in-plane direction into the catalyst layer (42) through a side of this catalyst layer (42) exposed to the recess (5).
- The electrode for electrolysis (1; 1 a) according to a ninth aspect, which may be implemented in conjunction with any one of the first to eighth aspects, the primary surface (21) of the electrically conductive substrate (2) is uneven.
- The electrode for electrolysis (1; 1 a) according to the ninth aspect can improve the adhesion of the electrically conductive substrate (2) to the intermediate layer (3) and thus the composite layer (4) is less likely to be separated from the electrically conductive substrate (2).
- A method for producing an electrode for electrolysis (1 a) according to a tenth aspect includes an intermediate layer formation process and a composite layer formation process. The intermediate layer formation process includes forming an intermediate layer (3) on a primary surface (21) of an electrically conductive substrate (2) containing titanium. The composite layer formation process includes forming a composite layer (4) on the intermediate layer (3). The composite layer (4) has a stacked structure alternating a plurality of tantalum layers (41) and a plurality of catalyst layers (42) one layer by one layer. Each of the plurality of tantalum layers (41) is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum. Each of the plurality of catalyst layers (42) contains platinum and iridium. The composite layer formation process includes a first process, a second process, and a third process. The first process includes applying a solution containing tantalum onto the intermediate layer (3) and subsequently firing at a first prescribed temperature to form a tantalum layer (41), of the plurality of tantalum layers (41), that constitutes a bottom layer of the stacked structure. The second process includes repeating a first step and a second step to form a stacked body (401) serving as a basis of a remaining part, other than the tantalum layer (41) that constitutes the bottom layer, of the stacked structure. The first step includes applying a solution containing platinum and iridium and subsequently heating and drying at a second prescribed temperature to form a layer (second material layer 420) serving as a basis of one catalyst layer (42) of the plurality of catalyst layers (42). The second step includes applying a solution containing tantalum and subsequently heating and drying at a third prescribed temperature to form a layer (first material layer 410) serving as a basis of one, but other than the tantalum layer (41) that constitutes the bottom layer, of the plurality of tantalum layers (41). The third process includes firing the stacked body (401) at a fourth prescribed temperature, which is higher than each of the second prescribed temperature and the third prescribed temperature, to form the plurality of catalyst layers (42) and tantalum layers (41), other than the tantalum layer (41) that constitutes the bottom layer, of the plurality of tantalum layers (41) together with a plurality of cracks (recesses 5) recessed from a main surface (40) of the catalyst layer (42), the main surface (40) being a surface away from the intermediate layer (3).
- The method for producing the electrode for electrolysis (1 a) according to the tenth aspect is less likely to cause the separation of the composite layer (4).
- An electrode for electrolysis (1 b) according to an eleventh aspect includes an electrically conductive substrate (2), an intermediate layer (3), and a composite layer (4). The electrically conductive substrate (2) contains at least titanium. The intermediate layer (3) is provided on a primary surface (21) of the electrically conductive substrate (2). The composite layer (4) is provided on the intermediate layer (3). The composite layer (4) includes a plurality of tantalum layers (41) and a plurality of catalyst layers (42). Each of the plurality of catalyst layers (42) contains platinum and iridium. Each of the plurality of tantalum layers (41) is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum. The plurality of tantalum layers (41) and the plurality of catalyst layers (42) are alternately stacked one layer by one layer in a thickness direction (D1) of the electrically conductive substrate (2). A bottom layer of the composite layer (4) closest to the primary surface (21) of the electrically conductive substrate (2) is constituted by one tantalum layer (41) of the plurality of tantalum layers (41). A top layer of the composite layer (4) furthest from the electrically conductive substrate (2) is constituted by another one tantalum layer (41) of the plurality of tantalum layers (41). The composite layer (4) has a main surface away from the intermediate layer (3). The electrode for electrolysis (1; 1 a) has a plurality of recesses (5) recessed from the main surface (40) of the composite layer (4). Each of the plurality of recesses (5) has a depth such that each of the plurality of recesses (5) is made to go completely through at least one catalyst layer (42) of the plurality of catalyst layers (42).
- The electrode for electrolysis (1 b) according to the eleventh aspect is less likely to cause the separation of the composite layer (4).
- An electrode for electrolysis (1; 1 a) according to a twelfth aspect includes an electrically conductive substrate (2), an intermediate layer (3), and a composite layer (4). The electrically conductive substrate (2) contains at least titanium. The intermediate layer (3) is provided on a primary surface (21) of the electrically conductive substrate (2). The composite layer (4) is provided on the intermediate layer (3). The composite layer (4) includes a plurality of tantalum layers (41) and a plurality of catalyst layers (42). Each of the plurality of tantalum layers (41) is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum. Each of the plurality of catalyst layers (42) contains platinum and iridium. The plurality of tantalum layers (41) and the plurality of catalyst layers (42) are alternately stacked one layer by one layer in a thickness direction (D1) of the electrically conductive substrate (2). A bottom layer of the composite layer (4) closest to the primary surface (21) of the electrically conductive substrate (2) is constituted by a tantalum layer (41). Atop layer of the composite layer (4) furthest from the electrically conductive substrate (2) is constituted by a catalyst layer (42).
- The electrode for electrolysis (1; 1 a) according to the twelfth aspect is less likely to cause the separation of the composite layer (4).
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- 1, 1 a, 1 b electrode for electrolysis
- 2 electrically conductive substrate
- 21 primary surface
- 3 intermediate layer
- 4 composite layer
- 40 main surface
- 41 tantalum layer
- 42 catalyst layer
- 5 recess
- 401 stacked body
- L1 distance
- L2 distance
- L3 distance
Claims (11)
1. An electrode for electrolysis, comprising:
an electrically conductive substrate containing at least titanium;
an intermediate layer on a primary surface of the electrically conductive substrate; and
a composite layer on the intermediate layer,
the composite layer including
a plurality of tantalum layers each of which is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum, and
a plurality of catalyst layers each of which contains platinum and iridium,
the plurality of tantalum layers and the plurality of catalyst layers being alternately stacked one layer by one layer in a thickness direction of the electrically conductive substrate,
a bottom layer of the composite layer closest to the primary surface of the electrically conductive substrate being constituted by one tantalum layer of the plurality of tantalum layers, and
a top layer of the composite layer furthest from the electrically conductive substrate being constituted by one catalyst layer of the plurality of catalyst layers.
2. The electrode for electrolysis of claim 1 , wherein
the composite layer has a main surface away from the intermediate layer,
the electrode for electrolysis has a plurality of recesses recessed from the main surface of the composite layer,
each of the plurality of recesses has a depth which is:
greater than a distance between the main surface of the composite layer and a catalyst layer, second furthest from the electrically conductive substrate, of the plurality of catalyst layers; and also
smaller than or equal to a distance between the main surface of the composite layer and the intermediate layer.
3. The electrode for electrolysis of claim 2 , wherein
the depth of each of the plurality of recesses is smaller than or equal to a distance between the main surface and the bottom layer of the composite layer.
4. The electrode for electrolysis of claim 2 , wherein
each of the plurality of recesses is a crack extending linearly in a plan view as seen in the thickness direction.
5. The electrode for electrolysis of claim 4 , wherein
each of the plurality of recesses has a width within a range of 0.3 μm to 3 μm.
6. The electrode for electrolysis of claim 4 , wherein
a percentage of S2 with respect to S1+S2 falls within a range of 5% to 50%, where S1 denotes an area of the main surface of the composite layer in the plan view as seen in the thickness direction of the electrically conductive substrate, and S2 denotes a total area of opening areas of the plurality of recesses in the main surface of the composite layer in the plan view as seen in the thickness direction of the electrically conductive substrate.
7. The electrode for electrolysis of claim 6 , wherein
at least one recess of the plurality of recesses is present in a 0.01 mm2 square region in the plan view as seen in the thickness direction of the electrically conductive substrate, a total length of each opening edge of the at least one recess present in the 0.01 mm2 square region being greater than or equal to 1 mm.
8. The electrode for electrolysis of claim 1 , wherein
each of the plurality of catalyst layers is a porous layer.
9. The electrode for electrolysis of claim 1 , wherein
the primary surface of the electrically conductive substrate is uneven.
10. A method for producing an electrode for electrolysis, comprising:
an intermediate layer formation process including forming an intermediate layer on a primary surface of an electrically conductive substrate containing titanium; and
a composite layer formation process including forming a composite layer on the intermediate layer, the composite layer having a stacked structure alternating a plurality of tantalum layers and a plurality of catalyst layers one layer by one layer,
each of the plurality of tantalum layers being made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum,
each of the plurality of catalyst layers containing platinum and iridium,
the composite layer formation process including a first process, a second process, and a third process,
the first process including applying a solution containing tantalum onto the intermediate layer and subsequently firing at a first prescribed temperature to form a tantalum layer, of the plurality of tantalum layers, that constitutes a bottom layer of the stacked structure,
the second process including repeating a first step and a second step to form a stacked body serving as a basis of a remaining part, other than the tantalum layer that constitutes the bottom layer, of the stacked structure,
the first step including applying a solution containing platinum and iridium and subsequently heating and drying at a second prescribed temperature to form a layer serving as a basis of one catalyst layer of the plurality of catalyst layers,
the second step including applying a solution containing tantalum and subsequently heating and drying at a third prescribed temperature to form a layer serving as a basis of one, but other than the tantalum layer that constitutes the bottom layer, of the plurality of tantalum layers,
the third process including firing the stacked body at a fourth prescribed temperature, which is higher than each of the second prescribed temperature and the third prescribed temperature, to form the plurality of catalyst layers and tantalum layers, other than the tantalum layer that constitutes the bottom layer, of the plurality of tantalum layers together with a plurality of cracks recessed from a main surface of the catalyst layer, the main surface being a surface away from the intermediate layer.
11. An electrode for electrolysis, comprising:
an electrically conductive substrate containing at least titanium;
an intermediate layer on a primary surface of the electrically conductive substrate; and
a composite layer on the intermediate layer,
the composite layer including
a plurality of tantalum layers each of which is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum, and
a plurality of catalyst layers each of which contains platinum and iridium,
the plurality of tantalum layers and the plurality of catalyst layers being alternately stacked one layer by one layer in a thickness direction of the electrically conductive substrate,
a bottom layer of the composite layer closest to the primary surface of the electrically conductive substrate being constituted by one tantalum layer of the plurality of tantalum layers,
a top layer of the composite layer furthest from the electrically conductive substrate being constituted by another one tantalum layer of the plurality of tantalum layers,
the composite layer having a main surface away from the intermediate layer,
the electrode for electrolysis having a plurality of recesses recessed from the main surface of the composite layer,
each of the plurality of recesses having a depth such that each of the plurality of recesses is made to go completely through at least one catalyst layer of the plurality of catalyst layers.
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PCT/JP2020/013021 WO2020217817A1 (en) | 2019-04-26 | 2020-03-24 | Electrode for electrolysis, and method for producing electrode for electrolysis |
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JP2931812B1 (en) * | 1998-04-24 | 1999-08-09 | ティーディーケイ株式会社 | Electrode for electrolysis and method for producing the same |
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