EP0359876A1 - Electrode pour la production d'oxygène et son procédé de préparation - Google Patents

Electrode pour la production d'oxygène et son procédé de préparation Download PDF

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Publication number
EP0359876A1
EP0359876A1 EP88308703A EP88308703A EP0359876A1 EP 0359876 A1 EP0359876 A1 EP 0359876A1 EP 88308703 A EP88308703 A EP 88308703A EP 88308703 A EP88308703 A EP 88308703A EP 0359876 A1 EP0359876 A1 EP 0359876A1
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EP
European Patent Office
Prior art keywords
iridium
tantalum
electrode
coating
oxide
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP88308703A
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German (de)
English (en)
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EP0359876B1 (fr
Inventor
Hiroyuki Nakada
Yukio Kawashima
Kazuhide Ohe
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TDK Corp
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TDK Corp
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Publication date
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Priority to DE8888308703T priority Critical patent/DE3872237T2/de
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Publication of EP0359876B1 publication Critical patent/EP0359876B1/fr
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/02—Electrodes; Connections 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
    • C25B11/04—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 present invention relates to a novel oxygen-generating electrode and to a method for the preparation thereof. More particularly, the invention relates to an electrode which has an excellent durability and low oxygen overvoltage for generating oxygen by the electrolytic oxidation of an aqueous solution at an anode, as well as to a method for the preparation thereof.
  • Conventional metallic electrodes widely used in the electrolytic industry include those prepared by providing a coating layer of a platinum group metal or an oxide thereof on an electroconductive substrate made of titanium metal.
  • known electrodes used as anodes for producing chlorine by the electrolysis of brine include those prepared by providing a titanium substrate with a coating layer formed from an oxide mixture of ruthenium and titanium, or an oxide mixture of ruthenium and tin (see, for example, Japanese Patent Publications 46-21884, 48-3954 and 50-11330).
  • oxygen-generating electrolytic processes require electrodes which are different from the electrodes successfully used in the electrolytic processes accompanied by the generation of chlorine.
  • an electrode for the chlorine-generating electrolysis such as the above mentioned titanium-based electrode having a coating layer of an oxide mixture of ruthenium and titanium or ruthenium and tin
  • the electrolysis must be discontinued due to the rapid corrosion of the electrode.
  • the electrodes must be specialized for the particular electrolytic processes.
  • the electrodes most widely used in oxygen-generating electrolysis are lead-based electrodes and soluble zinc anodes, although other known and usable electrodes include iridium oxide and platinum-based electrodes, iridium oxide and tin oxide-based electrodes and platinum-plated titanium electrodes.
  • An electrode having an intermediate layer provided as mentioned above is not as effective as desired when the electrode is used in an electrolytic process at a high current density because the electroconductivity of the intermediate layer is usually lower than the overcoating layer.
  • Japanese Patent Kokai 56-123388 and 56-123389 disclose an electrode having an undercoating layer containing iridium oxide and tantalum oxide on an electroconductive metal substrate and an overcoating layer of lead dioxide.
  • the undercoating layer in this electrode serves merely to improve the adhesion between the substrate surface and the overcoating layer of lead dioxide to exhibit some effectiveness in preventing corrosion due to pin holes.
  • disadvantages are caused because of the insufficient effect of preventing formation of titanium oxide and the unavoidable contamination of the electrolyte solution with lead.
  • the electrode of the present invention suitable for use in an oxygen-generating electrolytic process is an integral body composed of:
  • the electrode of the invention has a basic structure in which an electroconductive substrate of a metal such as titanium is provided with an undercoating layer formed of a binary oxide mixture composed of iridium oxide and tantalum oxide and an overcoating layer of iridium oxide.
  • an undercoating layer of a mixed oxide can be formed by coating the substrate surface with a coating solution containing an iridium compound and a tantalum compound each of which decomposes on heating to form the respective oxides, followed by a heat treatment in an oxidizing atmosphere to convert the thermally decomposable compounds into the respective metal oxides.
  • the metal from which the electroconductive substrate is formed examples include so-called valve metals such as titanium, tantalum, zirconium and niobium as well as alloys of these metals, of which titanium is preferred in the invention.
  • the substrate shaped from these metals or alloys in an appropriate form of electrode is first provided as mentioned above with an undercoating layer of the binary oxide mixture.
  • suitable thermally decomposable compounds of iridium and tantalum include chloroiridic acid H2IrCl6.6H2O and tantalum halides and tantalum alkoxides, e.
  • the coating solution can be prepared by dissolving these compounds in a suitable organic solvent such as butyl alcohol in a proportion to give a mixed-oxide coating layer in which the molar proportions of iridium and tantalum calculated as metals are in the ranges from 50% to 90% for iridium and from 50% to 10% for tantalum or preferably, from 50% to 70% for iridium and from 50% to 30% for tantalum.
  • a suitable organic solvent such as butyl alcohol
  • the undercoating layer is less effective in providing protection of the substrate surface and adhesion between the substrate surface and the undercoating layer may be somewhat decreased in addition to the disadvantage of a decreased electroconductivity of the coating layer per se .
  • the substrate coated with the coating solution is dried and subjected to heat treatment at a temperature in the range from 400 to 500°C in an oxidizing atmosphere containing oxygen, such as air, for a length of time of 1 to 30 minutes.
  • an oxidizing atmosphere containing oxygen such as air
  • the thickness or coating amount of the undercoating layer is not particularly limited but it should be at least 0.2 mg/cm2 calculated as iridium metal. When the coating amount is too small, insufficient protection of the substrate surface is obtained. If necessary, the cycle of coating with the coating solution and heat treatment to effect thermal oxidative decomposition of the metal compounds is repeated several times until the coating amount of the oxide mixture has reached the above mentioned preferred range.
  • the undercoating layer composed of the binary oxide mixture of iridium oxide and tantalum oxide is formed in the above described manner, the undercoating layer is further coated with an overcoating layer of iridium oxide.
  • a coating layer of iridium oxide can be formed by coating the surface with a coating solution prepared by dissolving a thermally decomposable iridium compound in an organic solvent followed by a heat treatment in an oxidizing atmosphere.
  • the coating amount of the overcoating layer should be in the range from 0.05 to 3 mg/cm2 calculated as iridium metal.
  • the coating amount of the overcoating layer is too small, a disadvantage is that the consumption of the electrode in the electrolytic process is increased to effect the durability of the electrode.
  • an adverse influence is that the adhesive strength of the active electrode film is decreased together with an eventual increase in the anode potential within a short time in the course of the electrolytic process.
  • the procedure for providing the overcoating layer of iridium oxide is similar to the process for forming the binary mixed-oxide undercoating layer of iridium and tantalum oxides.
  • a thermally decomposable iridium compound such as chloroiridic acid is dissolved in an organic solvent and the substrate provided with the undercoating layer of iridium and tantalum oxides is coated with the solution, dried and subjected to a heat treatment at a temperature in the range from 400 to 550°C in an oxidizing atmosphere.
  • the cycle of coating with the solution of the iridium compound and heat treatment may be repeated several times until the coating amount has reached the desired range mentioned above.
  • a first coating solution was prepared by dissolving chloroiridic acid H2IrCl6 ⁇ 6H2O and tantalum pentabutoxide Ta(OC4H9)5 in n-butyl alcohol each in such an amount that the molar ratio of iridium to tantalum as metals was 60:40 and the total concentration thereof corresponded to 80 g of the metals per liter.
  • An electrode substrate made of titanium metal after an etching treatment using a hot aqueous solution of oxalic acid was coated by brushing with the coating solution prepared above and, after drying, subjected to a heat treatment at 450 °C in an electric oven into which air was blown.
  • the coating layer of mixed oxide thus formed on the substrate surface had a thickness corresponding to a coating amount of about 0.1 mg/cm2 calculated as metals. This procedure of coating with the coating solution, drying and a heat treatment in air was repeated 2 to 10 times to prepare five undercoated electrode bodies having different coating amounts of the mixed oxides of iridium and tantalum.
  • a second coating solution was prepared by dissolving chloroiridic acid in n-butyl alcohol in such an amount that the concentration of the compound as iridium metal was 60 g/liter.
  • Each of the electrode bodies having an undercoat­ing layer of a mixture of iridium and tantalum oxides formed by twice to 8 times repetition of the procedure of coating with the first coating solution, drying and a heat treatment as well as a fresh titanium-made electrode substrate was coated with the second coating solution by brushing and, after drying, subjected to a heat treatment at 450 °C in an electric oven into which air was blown.
  • Each of the thus prepared coated electrodes No. 1 to No. 6 was used as the anode for electrolysis of a 1 mole/liter aqueous solution of sulfuric acid at 60 °C with a platinum electrode as the cathode at a current density of 150 A/dm2 continuously over a length of time up to 3000 hours under monitoring of the cell voltage.
  • the figure of the accompanying drawing is a graph showing the change in the cell voltage for each electrode in the lapse of time.
  • the single-coated electrodes, i.e. No. 1 and No. 6 failed to serve for continued elec­trolysis already after about 1500 hours due to the increase of the cell voltage, which was initially about 5 volts, to exceed 10 volts.
  • the dually coated electrodes i.e. No. 2 to No. 5, could serve to continue the electrolysis even after about 3000 hours with little increase in the cell voltage.
  • the electrodes No. 1 to No. 5 were subjected to the measurement of the oxygen overvoltage by the potential scanning method in a 1 mole/liter aqueous solution of sulfuric acid at 30 °C with a current density of 20 A/dm2. The results were: 440 mV, 430 mV, 430 mV, 410 mV and 380 mV for the electrodes No. 1 to No. 5, respectively.
  • Electrode No. 7 Five titanium-made electrode substrates were coated each with the second coating solution of tantalum penta­butoxide alone prepared in Example 1 (electrode No. 7) or one of the above prepared coating solutions of iridium:tan­talum molar ratio of 20:80 (electrode No. 8), 50:50 (elec­trode No. 9) 60:40 (electrode No. 10) and 70:30 (electrode No. 11) followed by drying and a heat treatment at 500 °C in an electric oven into which air was blown. This proce­dure of coating with the coating solution, drying and heat treatment was repeated five times.
  • Each of the electrode bodies No. 7 to No. 11 was further coated with the second coating solution prepared in Example 1 followed by drying and a heat treatment at 500 °C in an electric oven into which air was blown. This pro­cedure of coating with the second coating solution, drying and a heat treatment was repeated five times.
  • Each of the thus prepared coated electrodes No. 7 to No. 11 was used as the anode for electrolysis of a 1 mole/liter aqueous solution of sulfuric acid at 60 °C with a platinum electrode as the cathode at a current density of 200 A/dm2 continuously over a length of time up to 1000 hours under monitoring of the cell voltage.
  • the results were that the electrodes No. 9, No. 10 and No. 11 could serve to continue the electrolysis over 1000 hours while the electrolysis could no longer be continued after 200 hours and 400 hours of continued electrolysis with the electrodes No. 7 and No. 8, respectively.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Prevention Of Electric Corrosion (AREA)
  • Chemically Coating (AREA)
  • Electrolytic Production Of Metals (AREA)
EP88308703A 1987-03-24 1988-09-20 Electrode pour la production d'oxygène et son procédé de préparation Expired - Lifetime EP0359876B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE8888308703T DE3872237T2 (de) 1988-09-20 1988-09-20 Elektrode fuer die entwicklung von sauerstoff und deren herstellungsverfahren.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP62068084A JPS63235493A (ja) 1987-03-24 1987-03-24 酸素発生用電極及びその製造方法
CA000576559A CA1327339C (fr) 1987-03-24 1988-09-06 Electrode a oxygene et methode de preparation connexe

Publications (2)

Publication Number Publication Date
EP0359876A1 true EP0359876A1 (fr) 1990-03-28
EP0359876B1 EP0359876B1 (fr) 1992-06-17

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EP88308703A Expired - Lifetime EP0359876B1 (fr) 1987-03-24 1988-09-20 Electrode pour la production d'oxygène et son procédé de préparation

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EP (1) EP0359876B1 (fr)
JP (1) JPS63235493A (fr)
CA (1) CA1327339C (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2239260A (en) * 1989-12-22 1991-06-26 Tdk Corp Oxygen-generating electrolysis electrode and method for the preparation thereof
EP0867527A1 (fr) * 1997-02-27 1998-09-30 Aragonesas Industrias Y Energia, S.A. Electrode à recouvrement catalytique pour des procesus électrochimiques et procédé de fabrication de celle-ci

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2616024B2 (ja) * 1989-07-14 1997-06-04 日本鋼管株式会社 電極損傷度合いの小さい電気亜鉛系めっき鋼板の製造方法
JPH0499294A (ja) * 1990-08-09 1992-03-31 Daiso Co Ltd 酸素発生用陽極及びその製法
KR100196094B1 (ko) 1992-03-11 1999-06-15 사토 히로시 산소발생전극
US6217729B1 (en) * 1999-04-08 2001-04-17 United States Filter Corporation Anode formulation and methods of manufacture
KR102305334B1 (ko) * 2019-10-04 2021-09-28 주식회사 웨스코일렉트로드 아연도금장치의 양극판
CN114272920B (zh) * 2021-11-22 2023-10-03 广东省科学院资源利用与稀土开发研究所 一种有机污染物降解用复合氧化物涂层电极及其制备方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2099019A (en) * 1981-05-19 1982-12-01 Permelec Electrode Ltd Electrolytic electrode having high durability
GB2134544A (en) * 1983-01-31 1984-08-15 Permelec Electrode Ltd Electrolysis electrodes
EP0243302A1 (fr) * 1986-04-17 1987-10-28 Eltech Systems Corporation Eléctrode contenant du platine métallique comme catalyseur dans une pellicule superficielle et son application

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2099019A (en) * 1981-05-19 1982-12-01 Permelec Electrode Ltd Electrolytic electrode having high durability
GB2134544A (en) * 1983-01-31 1984-08-15 Permelec Electrode Ltd Electrolysis electrodes
EP0243302A1 (fr) * 1986-04-17 1987-10-28 Eltech Systems Corporation Eléctrode contenant du platine métallique comme catalyseur dans une pellicule superficielle et son application

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, vol. 5, no. 204 (C-85)[876], 24th December 1981; & JP-A-56 123 388 (ASAHI KASEI KOGYO K.K.) 28-09-1981 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2239260A (en) * 1989-12-22 1991-06-26 Tdk Corp Oxygen-generating electrolysis electrode and method for the preparation thereof
GB2239260B (en) * 1989-12-22 1994-02-16 Tdk Corp Oxygen-generating electrode and method for the preparation thereof
EP0867527A1 (fr) * 1997-02-27 1998-09-30 Aragonesas Industrias Y Energia, S.A. Electrode à recouvrement catalytique pour des procesus électrochimiques et procédé de fabrication de celle-ci

Also Published As

Publication number Publication date
EP0359876B1 (fr) 1992-06-17
JPH0327635B2 (fr) 1991-04-16
JPS63235493A (ja) 1988-09-30
CA1327339C (fr) 1994-03-01

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