EP0707095B1 - Electrode for electrochemical processes and use thereof - Google Patents

Electrode for electrochemical processes and use thereof Download PDF

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Publication number
EP0707095B1
EP0707095B1 EP95202666A EP95202666A EP0707095B1 EP 0707095 B1 EP0707095 B1 EP 0707095B1 EP 95202666 A EP95202666 A EP 95202666A EP 95202666 A EP95202666 A EP 95202666A EP 0707095 B1 EP0707095 B1 EP 0707095B1
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Prior art keywords
coating
platinum
electrode
iridium
oxide
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German (de)
French (fr)
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EP0707095A1 (en
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Alessandra Pastacaldi
Francesco Posar
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Solvay SA
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Solvay SA
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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
    • C25B11/04—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 invention relates to electrochemical processes, in particular to electrolysis processes.
  • It relates more particularly to an electrode usable in such processes.
  • Important parameters of industrial electrolysis processes are, on the one hand, the potentials of electrochemical reactions at the electrodes and, on the other hand, the current efficiency at the electrodes.
  • the difficulty in achieving acceptable current yields is particularly present in the electrolysis processes of the salts of alkali metals in aqueous solution, the reaction at the anode being accompanied usually of parasitic oxygen formation.
  • This difficulty is particularly present in chlorine manufacturing processes by electrolysis of aqueous solutions of alkali metal chloride (in particular sodium).
  • anodes comprising, on an electroconductive substrate, a coating of oxide of ruthenium and tin oxide, combined with platinum, platinum oxide or iridium oxide.
  • anode whose coating consists of a mixture of 14 mol% platinum, 6 mol% iridium and 80 mol% tin.
  • iridium and tin are in the form of oxides.
  • the invention therefore relates to an electrode for an electrochemical process, comprising, on an electroconductive substrate, a coating including from 12 to 17% by weight of platinum, from 30 to 40% by weight of iridium oxide and from 43 to 58% by weight of tin oxide.
  • the substrate must be made of a material electroconductive, inert under the electrolysis conditions at which the electrode is intended. Notwithstanding this condition, the electrode substrate according to the invention is not critical and its constitution does not constitute the object of the invention.
  • the substrate can advantageously be in a metal selected from titanium, tantalum, zirconium, vanadium, niobium and tungsten or an alloy of these metals.
  • the substrate profile is not critical and does not constitute the object of the invention, the most suitable profile depending on the destination of the electrode and must therefore be determined in each particular case.
  • the substrate of the electrode according to the invention may be a plate solid or openwork, rigid or flexible, a wire, a lattice of intertwined wires or a stack of beads.
  • the coating must be present on the substrate in an amount sufficient to cover a substantial part of the substrate and to catalyze the electrochemical reaction for which the electrode is intended.
  • the optimum amount of coating will therefore depend on the electrochemical reaction for which the electrode is intended and it can be determined in each particular case by routine laboratory work.
  • it is desirable that the coating is present on the substrate in an amount at least equal to 1 g (preferably 5 g) per m 2 of the surface of the substrate to which it is applied.
  • 1 g preferably 5 g
  • thickness of the coating on the substrate there is, in principle, no upper limit to the thickness of the coating on the substrate, in practice there is no point in it exceeding 20 g per m 2 of the aforementioned surface of the substrate, thicknesses of 8 to 12 g / m 2 being specially recommended.
  • platinum, iridium oxide and the tin oxide are preferably distributed homogeneously in the coating.
  • this expression is meant that the relative concentrations of platinum, iridium oxide and tin oxide are substantially identical in all coating points or that they do not diverge more 5% (preferably 1%) between any two points of the coating.
  • any suitable means may be used to apply the coating on the substrate.
  • One recommended way is to apply on the substrate a coating of thermally decomposable platinum compounds, iridium and tin and then subject the coating to treatment thermal in an oxidizing atmosphere, so as to decompose the compounds thermally decomposable and to form the coating.
  • Heat-decomposable compounds can be any compound which, heated in an atmosphere oxidizing, release platinum or platinum oxide, iridium dioxide and tin dioxide. They can for example be selected from the nitrates, sulfates, phosphates, halides and acid salts carboxylic.
  • heat-decomposable compounds above can be used in the solid state, for example in the state a powder, or in a liquid state, for example in the form of molten salts, suspensions or solutions.
  • the heat treatment consists, by definition, by heating the coating to a sufficient temperature in controlled oxidizing atmosphere to decompose thermally decomposable compounds and coprecipitate platinum or platinum oxide, iridium oxide and tin oxide.
  • the oxidizing atmosphere can consist of atmospheric air, enriched air or pure oxygen. We prefer to use atmospheric air.
  • the choice of thermally decomposable compounds and the temperature of the heat treatment are interdependent.
  • the choice of thermally decomposable compounds is notably influenced by the permissible temperature for heat treatment, so as to prevent it from damaging the substrate.
  • the thermally decomposable compounds are selected from the halides and these are used at the state dissolved in an organic solvent.
  • Chlorides are preferred, in particular especially iridium tetrachloride, tin tetrachloride and acid hexachloroplatinic
  • the organic solvent is advantageously selected from alcohols, preferably aliphatic alcohols such as methanol, ethanol and isopropanol, for example.
  • temperatures from 100 to 1000 ° C are suitable in the majority of cases, those of 200 to 750 ° C being specially recommended.
  • an iridium oxide content greater than 8% (preferably at least equal to 25%) of the weight of the coating allows to substantially increase the overvoltage of discharge of oxygen anions, when the electrode is used as an anode in an electrolysis process of an aqueous solution an alkali metal salt, in particular sodium chloride.
  • the platinum content of the coating is at least 10% (from preferably at least 12%) by weight.
  • This embodiment of the electrode has the additional advantage of having lower overvoltage at electrochemical discharge of chloride anions and it is therefore specially adapted to serve as an anode in processes electrolytic production of chlorine.
  • the electrode coating can consist exclusively of platinum, iridium oxide and tin oxide, or it may include a or several additional compounds, different from platinum, oxide iridium and tin oxide. In general it is preferred that the coating of the electrode according to the invention consists essentially of platinum, iridium oxide and tin oxide.
  • the coating of the electrode essentially consists of 12 to 17% by weight of platinum, from 30 to 40% by weight of iridium oxide and from 43 to 58% by weight of oxide of tin.
  • the electrode according to this embodiment of the invention especially suitable as an anode for the production of chlorine by electrolysis of aqueous solutions of alkali metal chloride.
  • the invention therefore also relates to the use of the electrode according to the invention as an anode in the electrolysis processes of the salts of alkali metals in aqueous solution, especially for the production of chlorine by electrolysis of aqueous metal chloride solutions alkaline. It especially concerns the use of the electrode according to the invention as an anode for the production of chlorine by electrolysis of a aqueous sodium chloride solution.
  • electrodes were prepared comprising a titanium substrate and a coating of platinum, iridium oxide and tin oxide on the substrate.
  • the substrate consisted of a lattice in the form of a disc of approximately 100 cm 2 in area and the coating was applied to the entire area of the disc.
  • three separate organic solutions were first prepared, namely a solution of hexachloroplatinic acid in isopropanol (30 g of hexachloroplatinic acid per liter of solution), a solution of iridium tetrachloride in isopropanol (20 g iridium tetrachloride per liter of solution) and a solution of tin tetrachloride in isopropanol (23 g tin tetrachloride per liter of solution).
  • the three solutions were then mixed in adequate proportions to form the coating and it was then applied to the disc in ten successive layers. After each layer of plaster, the disc and the plaster were heated in atmospheric air, at a temperature of 450 ° C for one hour.
  • the electrodes obtained as described above were used as anodes in a laboratory electrolysis cell, the cathode of which consisted of a 100 cm 2 nickel disc, separated from the anode by a membrane of the NAFION brand. ® (DU PONT), selectively permeable to cations.
  • the distance between the anode and the cathode was set at 1 mm.
  • an appreciably saturated aqueous solution of sodium chloride was electrolysed at 85 ° C., under an anodic current density of 3.5 kA / m 2 .
  • the anode chamber of the cell was continuously supplied with the sodium chloride solution, so as to produce, in the cathode chamber, an aqueous solution of approximately 32% by weight of hydroxide. sodium.
  • chlorine was produced at the anode and hydrogen was produced at the cathode.
  • the oxygen content in the gas collected at the anode was measured. The results of the measurements were plotted on the diagram of the appended drawing. On this diagram, the abscissa scale represents time, expressed in days, and the ordinate scale represents the oxygen content in the gas produced at the anode (expressed in% by weight of gas).

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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)
  • Electrolytic Production Of Metals (AREA)
  • Primary Cells (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Secondary Cells (AREA)
  • Chemically Coating (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Inert Electrodes (AREA)

Abstract

A novel electrode, for electrochemical processes, consists of an electrically conductive substrate bearing a coating of platinum, iridium oxide and tin oxide with an iridium oxide content of more than 8 (pref. at least 25) wt.%. Pref. the coating comprises (by wt.) 12-17% platinum, 30-40% iridium oxide and 53-58% tin oxide.

Description

L'invention concerne les procédés électrochimiques, en particulier les procédés d'électrolyse.The invention relates to electrochemical processes, in particular to electrolysis processes.

Elle concerne plus particulièrement une électrode utilisable dans de tels procédés.It relates more particularly to an electrode usable in such processes.

Des paramètres importants des procédés d'électrolyse industriels sont, d'une part, les potentiels des réactions électrochimiques aux électrodes et, d'autre part, le rendement de courant aux électrodes.Important parameters of industrial electrolysis processes are, on the one hand, the potentials of electrochemical reactions at the electrodes and, on the other hand, the current efficiency at the electrodes.

La difficulté de réaliser des rendements de courant acceptables est particulièrement présente dans les procédés d'électrolyse des sels des métaux alcalins en solution aqueuse, la réaction à l'anode s'accompagnant habituellement d'une formation parasite d'oxygène. Cette difficulté est particulièrement présente dans les procédés de fabrication de chlore par électrolyse de solutions aqueuses de chlorure de métal alcalin (en particulier de sodium).The difficulty in achieving acceptable current yields is particularly present in the electrolysis processes of the salts of alkali metals in aqueous solution, the reaction at the anode being accompanied usually of parasitic oxygen formation. This difficulty is particularly present in chlorine manufacturing processes by electrolysis of aqueous solutions of alkali metal chloride (in particular sodium).

Le moyen utilisé pour réduire la production parasite d'oxygène dans les procédés d'électrolyse consiste à faire usage d'anodes présentant une surtension élevée à l'oxydation des anions d'oxygène. A cet effet, dans la demande de brevet européen EP-A-0153586, on propose des anodes comprenant, sur un substrat électroconducteur, un revêtement d'oxyde de ruthénium et d'oxyde d'étain, associés à du platine, de l'oxyde de platine ou de l'oxyde d'iridium. On cite par ailleurs une anode dont le revêtement consiste en un mélange de 14 % molaire de platine, de 6 % molaire d'iridium et de 80 % molaire d'étain. Dans ce revêtement connu, l'iridium et l'étain sont à l'état d'oxydes.The means used to reduce the parasitic production of oxygen in the electrolysis process consists in making use of anodes having a high overvoltage at the oxidation of oxygen anions. To this end, in the European patent application EP-A-0153586, anodes are proposed comprising, on an electroconductive substrate, a coating of oxide of ruthenium and tin oxide, combined with platinum, platinum oxide or iridium oxide. We also cite an anode whose coating consists of a mixture of 14 mol% platinum, 6 mol% iridium and 80 mol% tin. In this known coating, iridium and tin are in the form of oxides.

En ce qui concerne le revêtement connu précité de platine, d'oxyde d'iridium et d'oxyde d'étain, on a maintenant trouvé qu'en modifiant de manière appropriée ses teneurs relatives en platine, oxyde d'iridium et oxyde d'étain, il était possible d'augmenter de manière sensible et inattendue la surtension à l'oxydation des anions d'oxygène et, par voie de conséquence, d'améliorer le rendement de courant anodique dans les procédés d'électrolyse des sels de métaux alcalins en solution aqueuse.As regards the aforementioned known coating of platinum, oxide of iridium and tin oxide, we have now found that by modifying its relative contents of platinum, iridium oxide and tin oxide it was possible to increase significantly and unexpected the overvoltage to the oxidation of oxygen anions and, by way of consequently, to improve the anode current efficiency in the processes for the electrolysis of alkali metal salts in aqueous solution.

L'invention concerne dès lors une électrode pour procédé électrochimique, comprenant, sur un substrat électroconducteur, un revêtement comprenant de 12 à 17 % en poids de platine, de 30 à 40 % en poids d'oxyde d'iridium et de 43 à 58 % en poids d'oxyde d'étain.The invention therefore relates to an electrode for an electrochemical process, comprising, on an electroconductive substrate, a coating including from 12 to 17% by weight of platinum, from 30 to 40% by weight of iridium oxide and from 43 to 58% by weight of tin oxide.

Dans l'électrode selon l'invention, le substrat doit être en un matériau électroconducteur, inerte dans les conditions d'électrolyse auxquelles l'électrode est destinée. Nonobstant cette condition, le substrat de l'électrode selon l'invention n'est pas critique et sa constitution ne constitue pas l'objet de l'invention. A titre d'exemple, le substrat peut avantageusement être en un métal sélectionné parmi le titane, le tantale, le zirconium, le vanadium, le niobium et le tungstène ou en un alliage de ces métaux.In the electrode according to the invention, the substrate must be made of a material electroconductive, inert under the electrolysis conditions at which the electrode is intended. Notwithstanding this condition, the electrode substrate according to the invention is not critical and its constitution does not constitute the object of the invention. For example, the substrate can advantageously be in a metal selected from titanium, tantalum, zirconium, vanadium, niobium and tungsten or an alloy of these metals.

Le profil du substrat n'est pas critique et ne constitue pas l'objet de l'invention, le profil le plus adéquat dépendant de la destination de l'électrode et devant dès lors être déterminé dans chaque cas particulier. A titre d'exemple, le substrat de l'électrode selon l'invention peut être une plaque pleine ou ajourée, rigide ou flexible, un fil, un treillis de fils entrelacés ou un empilage de billes.The substrate profile is not critical and does not constitute the object of the invention, the most suitable profile depending on the destination of the electrode and must therefore be determined in each particular case. As for example, the substrate of the electrode according to the invention may be a plate solid or openwork, rigid or flexible, a wire, a lattice of intertwined wires or a stack of beads.

Le revêtement doit être présent sur le substrat en une quantité suffisante pour couvrir une partie substantielle du substrat et catalyser la réaction électrochimique à laquelle l'électrode est destinée. La quantité optimum de revêtement va dès lors dépendre de la réaction électrochimique à laquelle on destine l'électrode et elle peut être déterminée dans chaque cas particulier par un travail de routine au laboratoire. En pratique, il est souhaitable que le revêtement soit présent sur le substrat en une quantité au moins égale à 1 g (de préférence à 5 g) par m2 de la surface du substrat sur laquelle il est appliqué. Bien qu'il n'existe pas, en principe, de limite supérieure à l'épaisseur du revêtement sur le substrat, en pratique il n'y a pas intérêt à ce qu'il excède 20 g par m2 de la surface précitée du substrat, les épaisseurs de 8 à 12 g/m2 étant spécialement recommandées.The coating must be present on the substrate in an amount sufficient to cover a substantial part of the substrate and to catalyze the electrochemical reaction for which the electrode is intended. The optimum amount of coating will therefore depend on the electrochemical reaction for which the electrode is intended and it can be determined in each particular case by routine laboratory work. In practice, it is desirable that the coating is present on the substrate in an amount at least equal to 1 g (preferably 5 g) per m 2 of the surface of the substrate to which it is applied. Although there is, in principle, no upper limit to the thickness of the coating on the substrate, in practice there is no point in it exceeding 20 g per m 2 of the aforementioned surface of the substrate, thicknesses of 8 to 12 g / m 2 being specially recommended.

Dans l'électrode selon l'invention, le platine, l'oxyde d'iridium et l'oxyde d'étain sont de préférence répartis de manière homogène dans le revêtement. On entend par cette expression, que les concentrations relatives de platine, d'oxyde d'iridium et d'oxyde d'étain sont sensiblement identiques en tous points de revêtement ou qu'elles ne divergent pas de plus de 5 % (de préférence 1 %) entre deux points quelconque du revêtement.In the electrode according to the invention, platinum, iridium oxide and the tin oxide are preferably distributed homogeneously in the coating. By this expression is meant that the relative concentrations of platinum, iridium oxide and tin oxide are substantially identical in all coating points or that they do not diverge more 5% (preferably 1%) between any two points of the coating.

Tous moyens appropriés peuvent être utilisés pour appliquer le revêtement sur le substrat. Un moyen recommandé consiste à appliquer sur le substrat un enduit de composés thermodécomposables du platine, de l'iridium et de l'étain et à soumettre ensuite l'enduit à un traitement thermique en atmosphère oxydante, de manière à décomposer les composés thermodécomposables et à former le revêtement. Les composés thermodécomposables peuvent être tous composés qui, chauffés en atmosphère oxydante, libèrent du platine ou de l'oxyde de platine, du dioxyde d'iridium et du dioxyde d'étain. Ils peuvent par exemple être sélectionnés parmi les nitrates, les sulfates, les phosphates, les halogénures et les sels d'acides carboxyliques. Pour constituer l'enduit, les composés thermodécomposables précités peuvent être mis en oeuvre à l'état solide, par exemple à l'état d'une poudre, ou à l'état liquide, par exemple sous la forme de sels fondus, de suspensions ou de solutions. Le traitement thermique consiste, par définition, en un chauffage de l'enduit à une température suffisante en atmosphère oxydante contrôlée pour décomposer les composés thermodécomposables et coprécipiter du platine ou de l'oxyde de platine, de l'oxyde d'iridium et de l'oxyde d'étain. L'atmosphère oxydante peut consister en de l'air atmosphérique, de l'air enrichi ou de l'oxygène pur. On préfère utiliser l'air atmosphérique. Le choix des composés thermodécomposables et la température du traitement thermique sont interdépendants. Le choix des composés thermodécomposables est notamment influencé par la température admissible pour le traitement thermique, de manière à éviter que celui-ci endommage le substrat. Dans une forme d'exécution avantageuse de l'invention, les composés thermodécomposables sont sélectionnés parmi les halogénures et ceux-ci sont mis en oeuvre à l'état dissous dans un solvant organique. Les chlorures sont préférés, en particulier le tétrachlorure d'iridium, le tétrachlorure d'étain et l'acide hexachloroplatinique, et le solvant organique est avantageusement sélectionné parmi les alcools, de préférence les alcools aliphatiques tels que le méthanol, l'éthanol et l'isopropanol, par exemple. Pour l'exécution du traitement thermique, les températures de 100 à 1 000 °C conviennent dans la majorité des cas, celles de 200 à 750 °C étant spécialement recommandées. Dans la mise en oeuvre de cette forme d'exécution de l'invention, il est généralement recommandé d'appliquer plusieurs couches successives de la solution organique des composés thermodécomposables sur le substrat et de soumettre chaque couche individuellement au traitement thermique défini plus haut. Any suitable means may be used to apply the coating on the substrate. One recommended way is to apply on the substrate a coating of thermally decomposable platinum compounds, iridium and tin and then subject the coating to treatment thermal in an oxidizing atmosphere, so as to decompose the compounds thermally decomposable and to form the coating. Heat-decomposable compounds can be any compound which, heated in an atmosphere oxidizing, release platinum or platinum oxide, iridium dioxide and tin dioxide. They can for example be selected from the nitrates, sulfates, phosphates, halides and acid salts carboxylic. To make the plaster, heat-decomposable compounds above can be used in the solid state, for example in the state a powder, or in a liquid state, for example in the form of molten salts, suspensions or solutions. The heat treatment consists, by definition, by heating the coating to a sufficient temperature in controlled oxidizing atmosphere to decompose thermally decomposable compounds and coprecipitate platinum or platinum oxide, iridium oxide and tin oxide. The oxidizing atmosphere can consist of atmospheric air, enriched air or pure oxygen. We prefer to use atmospheric air. The choice of thermally decomposable compounds and the temperature of the heat treatment are interdependent. The choice of thermally decomposable compounds is notably influenced by the permissible temperature for heat treatment, so as to prevent it from damaging the substrate. In a form advantageous implementation of the invention, the thermally decomposable compounds are selected from the halides and these are used at the state dissolved in an organic solvent. Chlorides are preferred, in particular especially iridium tetrachloride, tin tetrachloride and acid hexachloroplatinic, and the organic solvent is advantageously selected from alcohols, preferably aliphatic alcohols such as methanol, ethanol and isopropanol, for example. For the execution of heat treatment, temperatures from 100 to 1000 ° C are suitable in the majority of cases, those of 200 to 750 ° C being specially recommended. In the implementation of this embodiment of the invention, it is generally recommended to apply several successive coats of the organic solution of the thermally decomposable compounds on the substrate and subject each layer individually to heat treatment defined above.

La sélection d'une teneur en oxyde d'iridium supérieure à 8 % (de préférence au moins égale à 25 %) du poids du revêtement permet d'augmenter de manière substantielle la surtension de décharge des anions oxygène, lorsque l'électrode est utilisée comme anode dans un procédé d'électrolyse d'une solution aqueuse d'un sel de métal alcalin, en particulier de chlorure de sodium.The selection of an iridium oxide content greater than 8% (preferably at least equal to 25%) of the weight of the coating allows to substantially increase the overvoltage of discharge of oxygen anions, when the electrode is used as an anode in an electrolysis process of an aqueous solution an alkali metal salt, in particular sodium chloride.

Dans une forme de réalisation particulière de l'électrode la teneur en platine du revêtement est d'au moins 10 % (de préférence d'au moins 12 %) en poids. Cette forme de réalisation de l'électrode possède l'avantage supplémentaire de présenter une plus faible surtension à la décharge électrochimique des anions chlorure et elle est de ce fait spécialement adaptée à servir d'anode dans les procédés de fabrication électrolytique de chlore.In a particular embodiment of the electrode the platinum content of the coating is at least 10% (from preferably at least 12%) by weight. This embodiment of the electrode has the additional advantage of having lower overvoltage at electrochemical discharge of chloride anions and it is therefore specially adapted to serve as an anode in processes electrolytic production of chlorine.

Le revêtement de l'électrode peut être constitué exclusivement de platine, d'oxyde d'iridium et d'oxyde d'étain, ou bien il peut comprendre un ou plusieurs composés additionnels, différents du platine, de l'oxyde d'iridium et de l'oxyde d'étain. En général on préfère que le revêtement de l'électrode selon l'invention soit essentiellement constitué de platine, d'oxyde d'iridium et d'oxyde d'étain.The electrode coating can consist exclusively of platinum, iridium oxide and tin oxide, or it may include a or several additional compounds, different from platinum, oxide iridium and tin oxide. In general it is preferred that the coating of the electrode according to the invention consists essentially of platinum, iridium oxide and tin oxide.

Selon une forme de réalisation préférée de l'invention, le revêtement de l'électrode est essentiellement constitué de 12 à 17 % en poids de platine, de 30 à 40 % en poids d'oxyde d'iridium et de 43 à 58 % en poids d'oxyde d'étain. L'électrode conforme à cette forme de réalisation de l'invention convient spécialement bien comme anode pour la production de chlore par électrolyse des solutions aqueuses de chlorure des métaux alcalins.According to a preferred embodiment of the invention, the coating of the electrode essentially consists of 12 to 17% by weight of platinum, from 30 to 40% by weight of iridium oxide and from 43 to 58% by weight of oxide of tin. The electrode according to this embodiment of the invention especially suitable as an anode for the production of chlorine by electrolysis of aqueous solutions of alkali metal chloride.

L'invention concerne dès lors également l'utilisation de l'électrode selon l'invention comme anode dans les procédés d'électrolyse des sels des métaux alcalins en solution aqueuse, spécialement pour la production de chlore par électrolyse des solutions aqueuses de chlorure des métaux alcalins. Elle concerne tout spécialement l'utilisation de l'électrode selon l'invention comme anode pour la production de chlore par électrolyse d'une solution aqueuse de chlorure de sodium.The invention therefore also relates to the use of the electrode according to the invention as an anode in the electrolysis processes of the salts of alkali metals in aqueous solution, especially for the production of chlorine by electrolysis of aqueous metal chloride solutions alkaline. It especially concerns the use of the electrode according to the invention as an anode for the production of chlorine by electrolysis of a aqueous sodium chloride solution.

L'intérêt de l'invention va ressortir de la description des exemples suivants, en référence à la figure unique du dessin annexé qui est un diagramme fournissant les performances comparées d'une électrode selon l'invention et d'une électrode antérieure à l'invention.The advantage of the invention will emerge from the description of the examples following, with reference to the single figure of the accompanying drawing which is a diagram providing the comparative performances of an electrode according to the invention and an electrode prior to the invention.

Dans les exemples dont la description suit, on a préparé des électrodes comprenant un substrat en titane et un revêtement de platine, d'oxyde d'iridium et d'oxyde d'étain sur le substrat. Le substrat a consisté en un treillis ayant la forme d'un disque d'environ 100 cm2 de superficie et le revêtement a été appliqué sur la totalité de la superficie du disque. Pour former le revêtement, on a d'abord préparé trois solutions organiques distinctes, à savoir une solution d'acide hexachloroplatinique dans de l'isopropanol (30 g d'acide hexachloroplatinique par litre de solution), une solution de tétrachlorure d'iridium dans de l'isopropanol (20 g de tétrachlorure d'iridium par litre de solution) et une solution de tétrachlorure d'étain dans de l'isopropanol (23 g de tétrachlorure d'étain par litre de solution). Les trois solutions ont ensuite été mélangées en proportions adéquates pour constituer l'enduit et celui-ci a ensuite été appliqué sur le disque en dix couches successsives. A l'issue de chaque couche d'enduit, le disque et l'enduit ont été chauffés dans l'air atmosphérique, à la température de 450 °C pendant une heure.In the examples whose description follows, electrodes were prepared comprising a titanium substrate and a coating of platinum, iridium oxide and tin oxide on the substrate. The substrate consisted of a lattice in the form of a disc of approximately 100 cm 2 in area and the coating was applied to the entire area of the disc. To form the coating, three separate organic solutions were first prepared, namely a solution of hexachloroplatinic acid in isopropanol (30 g of hexachloroplatinic acid per liter of solution), a solution of iridium tetrachloride in isopropanol (20 g iridium tetrachloride per liter of solution) and a solution of tin tetrachloride in isopropanol (23 g tin tetrachloride per liter of solution). The three solutions were then mixed in adequate proportions to form the coating and it was then applied to the disc in ten successive layers. After each layer of plaster, the disc and the plaster were heated in atmospheric air, at a temperature of 450 ° C for one hour.

Les électrodes obtenues de la manière exposée ci-dessus ont été utilisées comme anodes dans une cellule d'électrolyse de laboratoire, dont la cathode a consisté en un disque en nickel de 100 cm2, séparé de l'anode par une membrane de marque NAFION® (DU PONT), sélectivement perméable aux cations. La distance entre l'anode et la cathode a été fixée à 1 mm. Pour évaluer les performances de l'anode, on a procédé à l'électrolyse d'une solution aqueuse sensiblement saturée de chlorure de sodium à 85 °C, sous une densité de courant anodique de 3,5 kA/m2. A cet effet, pendant l'électrolyse, on a alimenté la chambre anodique de la cellule en permanence avec la solution de chlorure de sodium, de manière à produire, dans la chambre cathodique, une solution aqueuse de 32 % en poids environ d'hydroxyde de sodium. On a de la sorte produit du chlore à l'anode et de l'hydrogène à la cathode. Pour évaluer les performances de l'anode, on a mesuré la teneur en oxygène dans le gaz recueilli à l'anode. Les résultats des mesures ont été portés sur le diagramme du dessin annexé. Sur ce diagramme, l'échelle des abscisses représente le temps, exprimé en jours, et l'échelle des ordonnées représente la teneur en oxygène dans le gaz produit à l'anode (exprimée en % en poids de gaz).The electrodes obtained as described above were used as anodes in a laboratory electrolysis cell, the cathode of which consisted of a 100 cm 2 nickel disc, separated from the anode by a membrane of the NAFION brand. ® (DU PONT), selectively permeable to cations. The distance between the anode and the cathode was set at 1 mm. To evaluate the performance of the anode, an appreciably saturated aqueous solution of sodium chloride was electrolysed at 85 ° C., under an anodic current density of 3.5 kA / m 2 . For this purpose, during the electrolysis, the anode chamber of the cell was continuously supplied with the sodium chloride solution, so as to produce, in the cathode chamber, an aqueous solution of approximately 32% by weight of hydroxide. sodium. In this way, chlorine was produced at the anode and hydrogen was produced at the cathode. To assess the performance of the anode, the oxygen content in the gas collected at the anode was measured. The results of the measurements were plotted on the diagram of the appended drawing. On this diagram, the abscissa scale represents time, expressed in days, and the ordinate scale represents the oxygen content in the gas produced at the anode (expressed in% by weight of gas).

Exemple 1 (de référence)Example 1 (for reference)

Dans cet exemple, les solutions d'acide hexachloroplatinique, de tétrachlorure d'iridium et de tétrachlorure d'étain ont été mélangées en proportions adéquates pour qu'à l'issue du traitement thermique, le revêtement présente la composition pondérale suivante, qui est celle de l'électrode utilisée à l'exemple 13 de la demande de brevet EP-A-0153586 citée plus haut :

  • platine : 17 %,
  • dioxyde d'iridium : 8 %,
  • dioxyde d'étain : 75 %.
    • In this example, the solutions of hexachloroplatinic acid, iridium tetrachloride and tin tetrachloride were mixed in adequate proportions so that, after the heat treatment, the coating has the following composition by weight, which is that of the electrode used in Example 13 of patent application EP-A-0153586 cited above:
  • platinum: 17%,
  • iridium dioxide: 8%,
  • tin dioxide: 75%.

    • L'évolution au cours du temps de la teneur en oxygène dans le gaz recueilli a l'anode est représentée par les symboles ▪ au diagramme du dessin.The evolution over time of the oxygen content in the gas collected at the anode is represented by the symbols ▪ in the diagram of the drawing.

    Exemple 2 (conforme à l'invention)Example 2 (according to the invention)

    Dans cet exemple, les solutions d'acide hexachloroplatinique, de tétrachlorure d'iridium et de tétrachlorure d'étain ont été mélangées en proportions adéquates pour qu'à l'issue du traitement thermique, le revêtement présente la composition pondérale suivante, conforme à l'invention :

  • platine : 15 %,
  • dioxyde d'iridium : 35 %,
  • dioxyde d'étain : 50 %.
    • In this example, the solutions of hexachloroplatinic acid, iridium tetrachloride and tin tetrachloride were mixed in suitable proportions so that, after the heat treatment, the coating has the following composition by weight, in accordance with l invention:
  • platinum: 15%,
  • iridium dioxide: 35%,
  • tin dioxide: 50%.

    • L'évolution au cours du temps de la teneur en oxygène dans le gaz recueilli a l'anode est représentée par les symboles + au diagramme du dessin.The evolution over time of the oxygen content in the gas collected at the anode is represented by the symbols + in the diagram of the drawing.

    Une comparaison des résultats des exemples 1 et 2 au diagramme du dessin fait immédiatement apparaítre le progrès apporté par l'invention.A comparison of the results of examples 1 and 2 with the diagram of drawing immediately shows the progress made by the invention.

    Claims (6)

    1. Electrode for an electrochemical process, comprising, on an electrically conductive substrate, a coating comprising from 12 to 17% by weight of platinum, from 30 to 40% by weight of iridium oxide and from 43 to 58% by weight of tin oxide.
    2. Electrode according to Claim 1, characterized in that the coating consists essentially of platinum, iridium oxide and tin oxide.
    3. Electrode according to any one of Claims 1 or 2, characterized in that the substrate is made of a metal selected from titanium, tantalum, zirconium vanadium, niobium and tungsten, or made of an alloy of these metals.
    4. Use of the electrode according to any one of Claims 1 to 3 as the anode in a process for electrolyzing an alkali metal salt in aqueous solution.
    5. Use according to Claim 4, for producing chlorine, the alkali metal salt being a chloride.
    6. Use according to Claim 5, in which the alkali metal is sodium.
    EP95202666A 1994-10-11 1995-10-04 Electrode for electrochemical processes and use thereof Expired - Lifetime EP0707095B1 (en)

    Applications Claiming Priority (2)

    Application Number Priority Date Filing Date Title
    ITMI942070A IT1270649B (en) 1994-10-11 1994-10-11 ELECTRODE FOR AN ELECTROCHEMICAL PROCEDURE AND USE OF THE ELECTRODE
    ITMI942070 1994-10-11

    Publications (2)

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    EP0707095A1 EP0707095A1 (en) 1996-04-17
    EP0707095B1 true EP0707095B1 (en) 1999-03-31

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    EP (1) EP0707095B1 (en)
    JP (1) JP3943151B2 (en)
    AT (1) ATE178367T1 (en)
    BR (1) BR9504362A (en)
    CA (1) CA2160221C (en)
    DE (1) DE69508689T2 (en)
    DK (1) DK0707095T3 (en)
    ES (1) ES2131758T3 (en)
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    FR2716207B1 (en) * 1994-02-15 1996-05-31 Rhone Poulenc Chimie Electroactive material, its preparation and its use for obtaining cathode elements.
    US5989396A (en) * 1997-04-02 1999-11-23 Eltech Systems Corporation Electrode and electrolytic cell containing same
    US6271131B1 (en) * 1998-08-26 2001-08-07 Micron Technology, Inc. Methods for forming rhodium-containing layers such as platinum-rhodium barrier layers
    US6284655B1 (en) 1998-09-03 2001-09-04 Micron Technology, Inc. Method for producing low carbon/oxygen conductive layers
    US6239028B1 (en) * 1998-09-03 2001-05-29 Micron Technology, Inc. Methods for forming iridium-containing films on substrates
    US6323081B1 (en) 1998-09-03 2001-11-27 Micron Technology, Inc. Diffusion barrier layers and methods of forming same
    US6329286B1 (en) 1999-04-27 2001-12-11 Micron Technology, Inc. Methods for forming conformal iridium layers on substrates
    US6660631B1 (en) * 2000-08-31 2003-12-09 Micron Technology, Inc. Devices containing platinum-iridium films and methods of preparing such films and devices
    JP4476759B2 (en) 2004-09-17 2010-06-09 多摩化学工業株式会社 Method for producing electrode for electrolysis, and method for producing aqueous quaternary ammonium hydroxide solution using this electrode for electrolysis
    KR20190022333A (en) * 2017-08-23 2019-03-06 주식회사 엘지화학 Anode for electrolysis and preparation method thereof
    WO2022103102A1 (en) 2020-11-12 2022-05-19 주식회사 엘지화학 Electrode for electrolysis

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    DE3460087D1 (en) * 1983-03-11 1986-05-22 Bbc Brown Boveri & Cie Catalyst for the coating of anodes, and its manufacturing process
    JPS60162787A (en) * 1984-01-31 1985-08-24 Tdk Corp Electrode for electrolysis
    JPH0633489B2 (en) * 1984-08-17 1994-05-02 ティーディーケイ株式会社 Electrode for dilute salt water electrolysis
    JPS62243790A (en) * 1986-04-15 1987-10-24 Osaka Soda Co Ltd Anode for electrolysis
    JP2885913B2 (en) * 1990-09-04 1999-04-26 ペルメレック電極株式会社 Anode for chromium plating and method for producing the same

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    CA2160221C (en) 2007-02-20
    BR9504362A (en) 1997-09-02
    DK0707095T3 (en) 1999-10-18
    EP0707095A1 (en) 1996-04-17
    PL310881A1 (en) 1996-04-15
    JP3943151B2 (en) 2007-07-11
    DE69508689T2 (en) 1999-09-30
    CA2160221A1 (en) 1996-04-12
    US5679225A (en) 1997-10-21
    JPH08176876A (en) 1996-07-09
    PL178811B1 (en) 2000-06-30
    DE69508689D1 (en) 1999-05-06
    ITMI942070A0 (en) 1994-10-11
    ATE178367T1 (en) 1999-04-15
    ITMI942070A1 (en) 1996-04-11
    IT1270649B (en) 1997-05-07
    ES2131758T3 (en) 1999-08-01

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