WO1997043465A1 - Anode a longevite amelioree et son procede de fabrication - Google Patents
Anode a longevite amelioree et son procede de fabrication Download PDFInfo
- Publication number
- WO1997043465A1 WO1997043465A1 PCT/FR1997/000836 FR9700836W WO9743465A1 WO 1997043465 A1 WO1997043465 A1 WO 1997043465A1 FR 9700836 W FR9700836 W FR 9700836W WO 9743465 A1 WO9743465 A1 WO 9743465A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- ircl
- substrate
- anode
- thermal decomposition
- temperature
- Prior art date
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Classifications
-
- 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
Definitions
- the subject of the present invention is an improved longevity anode for use in electrochemical processes. It also relates to the method of manufacturing this anode.
- Electrochemical processes have many applications in very varied sectors of activity such as mineral and organic electrosynthesis, electrometallurgy, depollution, electrodialysis, cathodic protection, treatment of polluted soils.
- the anodes commonly used for such applications are characterized by a stable geometry resulting from a high chemical and electrochemical inertia and by a constant potential during very long periods of use reaching, or even exceeding, two to three years.
- These electrodes known as DSA (Dimensionally Stable Anodes) have already shown their good electrochemical performance as an anode for the release of chlorine and / or oxygen.
- DSA Dissionally Stable Anodes
- These anodes consist of a metal of the “valve” type such as Ti, Ta, Nb, Zr, Sn and their alloys, covered with a layer of an electrocata ⁇ lytic material composed of oxides of precious metals such as Ir0 2.
- valve metal oxides such as Sn0 2 , Ti0 2 or Ta z 0 5 .
- valve metal is understood to mean a metal which is covered with a thin layer of protective oxide when it is oxidized (passivation) and which lets the current pass only under a cathodic potential.
- the chlorine electrodes used in industrial processes consist of a titanium substrate covered with a mixture of oxides including Ru0 2 which gives the material its electrocatalytic properties.
- Ru0 2 which gives the material its electrocatalytic properties.
- the anodes covered with Ru0 2 specific for the industrial production of chlorine have poor performance as an anode for the release of oxygen in an acid medium.
- the anodes intended for the release of oxygen, in particular in an acidic electrolytic medium, currently marketed consist of a titanium substrate covered with a layer of at least one metal oxide than, for example, iridium oxide. .
- Mixtures of these precursors are also used when it is desired to deposit layers of mixed catalytic oxides.
- the precursor or mixture of precursors is applied in the form of a solution in an alcoholic solvent, preferably in a mixture of ethanol and isopropanol.
- the precursor solution is deposited on the surface of the valve metal, for example with a brush, by spraying, by nebulization or by any other process known in the art.
- the solvent is then evaporated by steaming and the electrode undergoes a heat treatment in air at the decomposition temperature of the precursor to form the corresponding metal oxide.
- an electrode comprising a metal base "valve", in particular in titanium, on which is deposited a coating made of tantalum oxide and iridium oxide.
- This coating is applied by thermal decomposition, at a temperature between 350 ° and 600 ° C., of a tantalum oxide precursor and of an iridium oxide precursor, such as TaCl 5 respectively. and IrCl 3 .
- a Ti0 2 layer is formed on the titanium substrate which is protected by an electrocatalytic oxide such as an iridium oxide and / or a tantalum oxide, thus leading to a passivation of the anode. The lifespan of such an anode is therefore not satisfactory.
- tantalum substrate solves this problem because of its excellent resistance to chemical corrosion and its electrochemical stability.
- the tantalum substrate has already been described, no method allows satisfactory electrocatalytic deposits of iridium oxide to be produced on tantalum.
- the dissociation temperatures of IrCl 3 and H 2 IrCl 6 which are the usual precursors of Ir0 2 , are higher than the tantalum oxidation temperature. Therefore, the formation of tantalum oxide on the tantalum substrate appears before the formation of the catalytic oxide Ir0 2 , which decreases the performance of these electrodes.
- Test A which is an accelerated test for measuring the life of the anodes, consists in carrying out the electrolysis of a concentrated sulfuric acid solution using the anode to be tested, under a current density. 25 to 50 times greater than the current density applied in industrial processes. The lifetimes of the anodes under these conditions are therefore shorter than the lifetimes under normal operating conditions, which facilitates comparative study with a view to optimizing the conditions for preparing the anodes.
- This test A is carried out as follows. In a cylindrical double-walled glass cell with a capacity of 200 ml, electro ⁇ lysis is carried out of a sulfuric acid solution at 30% by mass, the temperature of which is regulated at 80 ° C., and which is stirred continuously by a magnetic stirrer.
- the anode has a rectangular shape (100 mm x 10 mm x 1 mm) and is inserted into heat-shrink tubing. Once the sheath is in place, a small circular opening of 0.20 cm 2 is cut out with a punch in the sheath. This in order to define precisely and reproducibly the area of the active surface of the anode.
- the distance between the two electrodes is 3 cm ( ⁇ 0.2 cm).
- the gases released by the electrolysis of water are channeled separately to cooling tubes to limit the vesicular entrainment of sulfuric acid and avoid the risk of explosion.
- the current density is then kept constant at this value and the potential difference between the anode and the cathode is recorded.
- the surface mass of Ir0 2 is defined as being the mass of electrocatalytic oxide Ir0 2 deposited as a coating per unit area of substrate.
- the normalized service life ⁇ is thus expressed in hm 2 .g "1 .
- a graphical representation of the potential difference U between the anode and the cathode measured during the test described above as a function of time is given in Figure 1.
- the potential difference U gradually increases from time 0 to time t 0 , t 0 indicating the moment when the anodic current density working temperature reaches the desired constant value of 50 kA.m "2.
- the potential difference is then constant until time t ,, the anode thus experiences normal operation between t Q and t 1 ( then after time t lr the potential difference increases indicating a deterioration of the anode
- the value of the potential difference U f U 0 + 2 (V) is reached at time t :.
- the lifetime of the anode deduced from this curve is therefore equal to t f -t c .
- the anodes which are the subject of the present invention have a normalized service life as measured by this test, clearly greater than that of the anodes currently used, as will emerge from the examples given below.
- the subject of the present invention is an anode with improved longevity, characterized in that it has a standardized service life of at least 14 hm 2 .g “1 , preferably greater than 20 hm 2 .g “ 1 , and more preferential ⁇ LEMENT still greater than 25 hm 2 .g “1 , as measured by test A above and that it consists of a substrate of at least one metal compound having an external surface in tantalum, the external surface being covered of an electrocatalytic coating of iridium oxide.
- the substrate used for the anode according to the invention can consist solely of tantalum. However, in order to limit the manufacturing costs, this substrate may consist of at least one metallic compound other than tantalum covered with a layer of tantalum.
- the metallic compounds other than tantalum commonly used are chosen from copper, nickel, titanium, their alloys, steel or stainless steel.
- the substrate does not consist solely of tantalum, it comprises an outer layer of tantalum.
- This tantalum layer can be applied by any known method such as by vacuum deposition, sputtering, ionic deposition, deposition from a reactive atmosphere, by co-lamination or by electrochemical means as described in French patent application no. 95 07158 not yet published in the name of the Applicant Company.
- This tantalum layer has a thickness of between 10 ⁇ m and 500 ⁇ m, preferably between 20 ⁇ m and 200 ⁇ m, more preferably between 20 ⁇ m and 100 ⁇ m.
- the substrate used can be in the form of a plate, a hollow cylinder, a spherical particle or the like, depending on the applications envisaged for the anode.
- the coating of iridium oxide covering the substrate is such that the surface mass of iridium oxide is greater than 4 gm " '', preferably less than
- the present invention also relates to a method for manufacturing an anode as defined above, characterized in that the electrocatalytic coating of iridium oxide is produced in several layers by the thermal decomposition of iridium tetrachloride IrCl 4 previously applied as a coating on the substrate.
- the Applicant Company has had the merit of finding that by using such a mode of formation of the electrocatalyst coating, the anode does not undergo deactivation.
- This thermal decomposition is carried out at a temperature below about 500 ° C, preferably below 475 ° C, and more preferably still between about 350 and 450 ° C.
- the thermal decomposition is firstly carried out at a temperature of between approximately 350 ° C. and 400 ° C. , more preferably around 350 ° C, then the temperature can be increased to about 500 ° C, preferably up to 475 ° C and even more preferably between about 350 ° C and 450 ° C.
- the first layers are obtained by thermal decomposition of a solution of IrCl 4 at a temperature between about 350 ° C and 400 ° C, more preferably about 350 ° C then the following layers are obtained with a temperature of thermal decomposition which has been increased and which is less than approximately 500 ° C.
- the precursor IrCl 4 is deposited on the substrate in the form of a solution in an organic solvent making it possible to lower the temperature of thermal decomposition of IrCl 4 in oxide Ir0 2 .
- the solvent having this characteristic is chosen an alcoholic solvent, for example an aliphatic alcohol, C j -C , such as methanol, ethanol, propanol, 1 isopropanol, butanol 1, butanol 2, 1 isobutanol or tert. -butanol, or a mixture thereof.
- a mixture of isopropanol and ethanol or isopropanol and 1-butanol is used.
- the solvent is evaporated off before carrying out the heat treatment in the air.
- the method of the present invention comprises the successive steps of:
- step (b) deposition of the iridium oxide layer by application to the substrate of the solution of IrCl 4 in an organic solvent, evaporation of the solvent and thermal decomposition of IrCl 4 ;
- step (a) above for preparing the substrate cleaning is preferably carried out using a surfactant.
- Sandblasting increases the surface specific substrate and chemical pickling eliminates the insulating oxide layer which would have formed on the tantalum surface of the electrode.
- Step (b) comprising the successive operations of applying the IrCl 4 solution, evaporating the solvent and thermal decomposition is repeated as many times as necessary to obtain the desired surface mass of oxide d 'iridium.
- the surface mass of iridium oxide is preferably from 5 to 20 g / m /, of course, it can be greater, but this is disadvantageous from an economic point of view.
- Step (b) is repeated at least 3 times, preferably at least 5 times.
- the application of the precursor solution is carried out for example with a brush, or by immersion, or by any other process known in the art, such as by spraying, nebulization, etc.
- the solvent can be evaporated in particular by steaming at the evaporation temperature of the solvent used.
- the thermal decomposition of the precursor is carried out in an oven, in the air.
- the thermal decomposition of the precursor is carried out at a temperature between about 350 and 400 D C, more preferably about 350 ° C. Then for the following layers, preferably from the third layer, the thermal decomposition temperature is increased, it is less than about 500 ° C, preferably less than 475 ° C and more preferably still between about 350 and 450 ° vs.
- the final heat treatment step (c) is carried out at a temperature below about 550 ° C, preferably below 525 ° C and more preferably still between around 450 and 500 ° C.
- ASTM grade 4 titanium containing 500 ppm of iron and 400 ppm of oxygen;
- ASTM grade 7 alloy of titanium and palladium of formula TiO, 2Pd% m / m;
- NF T40 titanium containing 100 ppm of iron and 100 ppm of oxygen
- - NF TD12ZE titanium alloy with formula Til2Mo6Zr4, 5Sn;
- NF TA6V4 (UNS R56320): titanium alloy of formula Ti6A14V;
- AISI 316L stainless steel of grade NF Z2 CND 17-12.
- a support metal plate of 100 mm X 10 mm X 1 mm is used as substrate for the anode.
- This plate is degreased with chloroform and then subjected to sandblasting under a pressure of 5 bar with 1 corundum (particle size: 125 ⁇ m).
- the plate is then rinsed in a tank of osmosis water under ultrasound for 10 minutes, subjected to a chemical pickling using hydrochloric or hydrofluoric acid then is rinsed.
- a precursor solution is applied by immersion or with a brush.
- the plate thus coated is steamed at 80 ° C for 5 minutes and then calcined in air in an oven at a temperature T x for 5 minutes.
- n being the number of layers of the precursor solution which must be applied in order to obtain the desired areal mass of lr0 2 .
- the plate is calcined in air for two hours at a temperature T 2 .
- the anodes thus prepared are subjected to test A as described above, whereby their service life and their standardized service life are determined.
- the number n of layers of the precursor solution applied as well as the corresponding surface mass of lr0 2 are indicated in Table I below, which also reports the results of test A.
- Comparative Example 1 was repeated, except that the substrate used was titanium NFT40 and that the chemical etching step was carried out using 37% hydrochloric acid at boiling point.
- Comparative Example 1 was repeated except that the substrates used were titanium alloys as indicated in Table I below.
- the chemical pickling was carried out using hydrochloric acid of concentration 37% and 36% respectively.
- Example 5 Manufacture of Ta / Ir0 2 anodes
- Anodes having a tantalum substrate covered with lr0 2 were manufactured using tantalum plates of purity greater than 99.9%, in accordance with the general procedure of Example 1 with the following specifications:
- the chemical etching step was carried out using 40% hydrofluoric acid at 25 ° C for one minute;
- Example 6 Manufacture of Ta / Ir0 2 anodes [substrate: AISI 316 L (UNS S31603) coated with Ta, precursor: IrCl 4 ].
- Example 5 is repeated, except that a stainless steel plate (316 L) covered with a tantalum layer is used, the thickness of which is indicated in brackets in the following Table II. All the anodes made in this example include 10 layers of precursor solution.
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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)
- Battery Electrode And Active Subsutance (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE69703163T DE69703163T2 (de) | 1996-05-13 | 1997-05-12 | Anode mit verbesserter lebensdauer und deren herstellungsverfahren |
EP97924074A EP0925387B1 (fr) | 1996-05-13 | 1997-05-12 | Anode a longevite amelioree et son procede de fabrication |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR96/05916 | 1996-05-13 | ||
FR9605916A FR2748495B1 (fr) | 1996-05-13 | 1996-05-13 | Anode a longevite amelioree et son procede de fabrication |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1997043465A1 true WO1997043465A1 (fr) | 1997-11-20 |
Family
ID=9492070
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FR1997/000836 WO1997043465A1 (fr) | 1996-05-13 | 1997-05-12 | Anode a longevite amelioree et son procede de fabrication |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0925387B1 (fr) |
DE (1) | DE69703163T2 (fr) |
ES (1) | ES2152673T3 (fr) |
FR (1) | FR2748495B1 (fr) |
WO (1) | WO1997043465A1 (fr) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN114787423A (zh) * | 2019-12-13 | 2022-07-22 | 松下知识产权经营株式会社 | 电解电极 |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2811339B1 (fr) * | 2000-07-07 | 2003-08-29 | Electricite De France | Procede de preparation de materiaux metalliques pour leur utilisation comme electrodes |
FR2811338B1 (fr) * | 2000-11-10 | 2003-02-14 | Electricite De France | Procede de preparation de materiaux metalliques pour leur utilisation comme electrodes |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4257856A (en) * | 1979-10-17 | 1981-03-24 | Bell Telephone Laboratories, Incorporated | Electrolytic process useful for the electrolysis of water |
EP0383470A2 (fr) * | 1989-02-14 | 1990-08-22 | Imperial Chemical Industries Plc | Procédé électrolytique |
EP0384194A2 (fr) * | 1989-02-18 | 1990-08-29 | Bayer Ag | Anodes dimensionnellement stables et leur utilisation pour la production de dichromates alcalins et d'acide chromique |
JPH0533177A (ja) * | 1991-02-04 | 1993-02-09 | Daiso Co Ltd | 酸素発生用陽極の製法 |
-
1996
- 1996-05-13 FR FR9605916A patent/FR2748495B1/fr not_active Expired - Fee Related
-
1997
- 1997-05-12 EP EP97924074A patent/EP0925387B1/fr not_active Expired - Lifetime
- 1997-05-12 DE DE69703163T patent/DE69703163T2/de not_active Expired - Lifetime
- 1997-05-12 ES ES97924074T patent/ES2152673T3/es not_active Expired - Lifetime
- 1997-05-12 WO PCT/FR1997/000836 patent/WO1997043465A1/fr active IP Right Grant
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4257856A (en) * | 1979-10-17 | 1981-03-24 | Bell Telephone Laboratories, Incorporated | Electrolytic process useful for the electrolysis of water |
EP0383470A2 (fr) * | 1989-02-14 | 1990-08-22 | Imperial Chemical Industries Plc | Procédé électrolytique |
EP0384194A2 (fr) * | 1989-02-18 | 1990-08-29 | Bayer Ag | Anodes dimensionnellement stables et leur utilisation pour la production de dichromates alcalins et d'acide chromique |
JPH0533177A (ja) * | 1991-02-04 | 1993-02-09 | Daiso Co Ltd | 酸素発生用陽極の製法 |
Non-Patent Citations (1)
Title |
---|
DATABASE WPI Section Ch Week 9311, Derwent World Patents Index; Class E36, AN 93-089086, XP002022091 * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN114787423A (zh) * | 2019-12-13 | 2022-07-22 | 松下知识产权经营株式会社 | 电解电极 |
Also Published As
Publication number | Publication date |
---|---|
FR2748495A1 (fr) | 1997-11-14 |
ES2152673T3 (es) | 2001-02-01 |
DE69703163D1 (de) | 2000-10-26 |
EP0925387B1 (fr) | 2000-09-20 |
EP0925387A1 (fr) | 1999-06-30 |
DE69703163T2 (de) | 2001-05-17 |
FR2748495B1 (fr) | 1998-07-17 |
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