EP0137911A1 - Process for manufacturing a depassivating layer and depassivating layer on an electrode for an electrochemical cell - Google Patents

Process for manufacturing a depassivating layer and depassivating layer on an electrode for an electrochemical cell Download PDF

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EP0137911A1
EP0137911A1 EP84107073A EP84107073A EP0137911A1 EP 0137911 A1 EP0137911 A1 EP 0137911A1 EP 84107073 A EP84107073 A EP 84107073A EP 84107073 A EP84107073 A EP 84107073A EP 0137911 A1 EP0137911 A1 EP 0137911A1
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depassivation
layer
substrate
noble metal
layer according
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EP0137911B1 (en
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Eric Killer
Günther Georg Anton Dr. Dipl.-Chem. Scherer
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BBC Brown Boveri AG Switzerland
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/28—Processes for applying liquids or other fluent materials performed by transfer from the surfaces of elements carrying the liquid or other fluent material, e.g. brushes, pads, rollers
    • 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
    • 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 is based on a method for producing a depassivation layer according to the preamble of claim 1 and on a depassivation layer according to the preamble of claim 2.
  • Electrodes The requirements placed on the electrodes of electrochemical cells are diverse and in some cases divergent, so that these electrodes usually have to be constructed from composite materials in order to be able to meet all conditions to some extent. This applies in particular to electrodes (anodes) that have to work under oxidizing conditions. Normally, a corrosion-resistant carrier material serving as a substrate is used for such electrodes, which in turn is provided with one or more additional layers of other components. If solid electrolytes are used for the construction of the electrochemical cell, the substrate is built up from porous, liquid and gas permeable material.
  • titanium is particularly suitable as a substrate for anodes in technical electrolysis processes.
  • the titanium substrate is coated with a specific electrocatalyst.
  • the electrocatalyst / titanium substrate interface is particularly critical for the functioning of the electrode.
  • the titanium substrate must be completely covered, since otherwise a non-conductive cover layer of essentially TiO 2 is formed under anodic conditions.
  • an intermediate layer is often applied, which consists of a stable and conductive material in the anodic potential range. Precious metals, especially platinum, are used for this.
  • This intermediate layer must be continuous, its thickness can be 0.1-1 nm.
  • Such electrodes provided with intermediate layers and electrocatalysts are known (A.
  • Nidola "Technological Impact of Metallic Oxides as Anodes", in “Electrodes of Conductive Metallic Oxides", Part B, page 627, editor: S. Trasatti, ELSEVIER, Amsterdam, 1981; PCS Hayfield, WR Jacob, "Platinum / Iridium-coated titanium anodes in brine electrolysis", in “Modern Chlor-Alkali Technology", page 103, Editor: MOCoulter, Ellis Horwood Ltd., Chichester 1980, Th. Comninellis, E. Plattner , Journal of Applied Electrochemistry, 12, 399/1982).
  • the protection of the carrier material is now of particular importance if the electrocatalyst is not applied as a microscopically coherent layer, but in the form of a porous powder-binder mixture which does not completely cover the substrate due to the porous structure.
  • the non-passivating intermediate layer becomes more important if the titanium substrate is not a solid workpiece, but rather one porous substrate, for example a sintered titanium foil acts as it is used in solid electrolyte cells.
  • porous titanium substrates are of great importance insofar as methods such as those used for planar and solid electrodes are out of the question in this case. This problem is exacerbated because, for economic reasons, only small amounts of noble metal 0.1 mg / cm 2 should be applied, but this is difficult with a relatively undefined surface, such as that of a porous substrate.
  • the invention is based on the object of specifying a method by means of which the surface of a porous body can be deliberately provided with a depassivation layer which has improved properties and a high stability and long service life with a minimal noble metal content.
  • 1 schematically shows the manufacturing method for producing a depassivation layer using a simplified device.
  • 1 is the sheet-like substrate, for example in the form of a porous plate or foil made of titanium (longitudinal section).
  • Figure 2 shows an elastic roll which can advantageously consist of "Teflon" (polytetrafluoroethylene).
  • 3 is a sheet-like, flexible solution carrier which is said to be porous and absorbent in order to be able to absorb the metal salt solution. It is connected in the form of a felt or paper between the substrate 1 and the roll 2. In the rolling process indicated by arrows, 3 releases a thin layer of the metal salt solution onto the surface of 1.
  • the porous substrate 1 which is composed of individual grains with cavities in between.
  • 4 is the at least partially connected depassivation layer in film form, which is a submicroscopically fine, homogeneous mixture of electronically conductive suboxides and oxides of the substrate and that from the applied metal salt solution contains precious metals or metals in metallic and / or oxidic form.
  • a porous sintered titanium plate as substrate (1) was provided with a depassivation layer (4) which contained platinum.
  • a depassivation layer (4) which contained platinum.
  • a aqueous 5 ⁇ 10 -2 N H2PtCl6 solution prepared.
  • the coating was carried out by means of an elastic roll (2) made of "Teflon” and a solution carrier (3) in the form of a chromatography paper. Coating was carried out a total of 5 times, the amount applied being determined gravimetrically in each case.
  • the coated titanium plate was then dried and subjected to a chemo-thermal treatment in the form of an annealing in air at 450 ° C. for 30 minutes.
  • the amount of platinum applied was determined to be 0.1 mg / cm 2 .
  • a porous sintered titanium foil as substrate (1) was coated in an analogous manner as in Example I.
  • the metal salt solution consisted of a 5 ⁇ 10 -2 N solution of the formula H 2 M c C 16 , where M c was a mixture of Pt and Ir in an atomic weight ratio of 70:30.
  • the amount of noble metal was determined to be 0.05 mg / cm 2 .
  • the substrates coated according to Examples I and II were tested as current collectors on the anode side of solid electrolyte cells and, despite the fact that the noble metal content was ten times lower, gave the same cell voltages as electrodes produced by conventional methods (electroplating, vapor deposition).
  • Depassivation layers of various types and compositions can be created using the new method.
  • All precious metals can generally be applied using a metal salt solution, both individually and in mixtures.
  • other metals which are not precious metals, are added.
  • noble metal oxides in particular the platinum metal groups
  • the finished depassivation layer can also contain gold and another component in the form of a metal or its oxide, in particular SnO 2 .
  • An essential part of the depassivation layer consists of an electrically conductive sub-oxide or oxide of the substrate, or mixtures thereof, generated on the surface during the chemo-thermal treatment.
  • All of the components listed form a submicroscopically fine, homogeneous mixture, whereby the individual components can have a dimension that goes down to close to the atomic range. This ensures an at least partially coherent film of the depassivation layer, which has optimal chemical and physical properties. In this way, the noble metal content of the depassivation layer can be kept to a minimum without accepting disadvantages, which has a favorable effect on the economy of the system.

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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)
  • Cell Electrode Carriers And Collectors (AREA)

Abstract

Eine Depassivierungsschicht wird auf einer Elektrode für eine elektrochemische Zelle dadurch hergestellt, daß eine die aufzubringenden Elemente enthaltende Metallsalzlösung durch Abrollen einer elastischen Rolle (2) unter Zwischenschaltung eines Lösungsträgers (3) in Form von Filz oder Papier in einer oder mehreren Schichten auf das zu beschichtende Substrat (1) in Form einer porösen Platte aufgebracht, anschliessend getrocknet und an Luft einer chemo-thermischen Behandlung (Tempern bei 450 °C) unterzogen wird. Auf diese Weise können gute Depassivierungsschichten mit verhältnismäßig geringem Edelmetallgehalt erzeugt werden. Die in homogener Filmform wenigstens teilweise zusammenhängende Depassivierungsschicht enthält als feinverteiltes submikroskopisches Gemenge neben Edelmetallen/Edelmetalloxyden und elektronisch leitende Suboxyde/Oxyde des Substrats (1) und kann noch weitere Komponenten wie SnO2 enthalten.A depassivation layer is produced on an electrode for an electrochemical cell in that a metal salt solution containing the elements to be applied by unrolling an elastic roller (2) with the interposition of a solution carrier (3) in the form of felt or paper in one or more layers on the surface to be coated Substrate (1) is applied in the form of a porous plate, then dried and subjected to a chemo-thermal treatment (tempering at 450 ° C.) in air. In this way, good depassivation layers with a relatively low precious metal content can be produced. The depassivation layer, which is at least partially coherent in homogeneous film form, contains a finely divided submicroscopic mixture in addition to noble metals / noble metal oxides and electronically conductive suboxides / oxides of the substrate (1) and can also contain further components such as SnO2.

Description

Die Erfindung geht aus von einem Verfahren zur Herstellung einer Depassivierungsschicht nach der Gattung des Oberbegriffs des Anspruchs 1 und von einer Depassivierungsschicht nach der Gattung des Oberbegriffs des Anspruchs 2.The invention is based on a method for producing a depassivation layer according to the preamble of claim 1 and on a depassivation layer according to the preamble of claim 2.

Die an die Elektroden elektrochemischer Zellen gestellten Anforderungen sind vielfältig und zum Teil divergierend, so dass diese Elektroden meist aus Verbundwerkstoffen aufgebaut werden müssen, um allen Bedingungen einigermassen gerecht werden zu können. Dies gilt insbesondere für Elektroden (Anoden), die unter oxydierenden Bedingungen arbeiten müssen. Normalerweise wird für derartige Elektroden ein als Substrat dienendes, korrosionsbeständiges Trägermaterial verwendet, das seinerseits mit einer oder mehreren zusätzlichen Schichten anderer Komponenten versehen ist. Im Falle der Verwendung von Feststoffelektrolyten für den Aufbau der elektrochemischen Zelle wird das Substrat aus porösem, flüssigkeits- und gasdurchlässigem Material aufgebaut.The requirements placed on the electrodes of electrochemical cells are diverse and in some cases divergent, so that these electrodes usually have to be constructed from composite materials in order to be able to meet all conditions to some extent. This applies in particular to electrodes (anodes) that have to work under oxidizing conditions. Normally, a corrosion-resistant carrier material serving as a substrate is used for such electrodes, which in turn is provided with one or more additional layers of other components. If solid electrolytes are used for the construction of the electrochemical cell, the substrate is built up from porous, liquid and gas permeable material.

Titan ist wegen seiner Korrosionsbeständigkeit als Substrat für Anoden bei technischen Elektrolyseprozessen besonders geeignet. Dabei wird je nach Elektrodenreaktion das Titansubstrat mit einem spezifischen Elektrokatalysator beschichtet. Besonders kritisch für die Funktion der Elektrode ist die Grenzfläche Elektrokatalysator/Titansubstrat. Das Titansubstrat muss vollständig bedeckt sein, da sich sonst unter anodischen Bedingungen eine nichtleitende Deckschicht von im wesentlichen Ti02 ausbildet. Um diese Deckschichtbildung zu verhindern, wird vielfach eine Zwischenschicht aufgebracht, die aus einem im anodischen Potentialbereich stabilen und leitfähigen Material besteht. Dafür werden Edelmetalle, im besonderen Platin verwendet. Diese Zwischenschicht muss zusammenhängend sein, ihre Dicke kann 0,1-1 nm betragen. Derartige, mit Zwischenschichten und Elektrokatalysatoren versehene Elektroden sind bekannt (A. Nidola, "Technological Impact of Metallic Oxides as Anodes", in "Electrodes of Conductive Metallic Oxides", Part B, page 627, Editor: S. Trasatti, ELSEVIER, Amsterdam, 1981; P.C.S.Hayfield, W.R.Jacob, "Platinum/ Iridium-coated titanium anodes in brine electrolysis", in "Modern Chlor-Alkali Technology", page 103, Editor: M.O.Coulter, Ellis Horwood Ltd., Chichester 1980, Th. Comninellis, E.Plattner, Journal of Applied Electrochemistry, 12, 399/1982).Because of its corrosion resistance, titanium is particularly suitable as a substrate for anodes in technical electrolysis processes. Depending on the electrode reaction, the titanium substrate is coated with a specific electrocatalyst. The electrocatalyst / titanium substrate interface is particularly critical for the functioning of the electrode. The titanium substrate must be completely covered, since otherwise a non-conductive cover layer of essentially TiO 2 is formed under anodic conditions. In order to prevent this cover layer formation, an intermediate layer is often applied, which consists of a stable and conductive material in the anodic potential range. Precious metals, especially platinum, are used for this. This intermediate layer must be continuous, its thickness can be 0.1-1 nm. Such electrodes provided with intermediate layers and electrocatalysts are known (A. Nidola, "Technological Impact of Metallic Oxides as Anodes", in "Electrodes of Conductive Metallic Oxides", Part B, page 627, editor: S. Trasatti, ELSEVIER, Amsterdam, 1981; PCS Hayfield, WR Jacob, "Platinum / Iridium-coated titanium anodes in brine electrolysis", in "Modern Chlor-Alkali Technology", page 103, Editor: MOCoulter, Ellis Horwood Ltd., Chichester 1980, Th. Comninellis, E. Plattner , Journal of Applied Electrochemistry, 12, 399/1982).

Der Schutz des Trägermaterials (Titansubstrat) ist nun von besonderer Wichtigkeit, wenn der Elektrokatalysator nicht als mikroskopisch zusammenhängende Schicht, sondern in Form eines porösen Pulver-Binder-Gemisches aufgebracht ist, das das Substrat aufgrund der porösen Struktur nicht vollständig bedeckt. Ausserdem gewinnt die nichtpassivierende Zwischenschicht an Bedeutung, wenn es sich bei dem Titansubstrat nicht um ein massives Werkstück, sondern um ein poröses Substrat, z.B. eine gesinterte Titanfolie handelt wie sie bei Feststoffelektrolyt-Zellen Verwendung findet. (Siehe zum Beispiel: B.V.Tilak, P.W.T.Lu, J.E.Coleman, S.Srinivasan, "The Electrolytic Production of Hydrogen", in Comprehensive Treatise of Electrochemistry, Volume 2, Edited by: J.O.M.Bockris, Brian E. Conway, Ernest Yeager, Ralph E. White, Plenum Press, N.Y. 1981).The protection of the carrier material (titanium substrate) is now of particular importance if the electrocatalyst is not applied as a microscopically coherent layer, but in the form of a porous powder-binder mixture which does not completely cover the substrate due to the porous structure. In addition, the non-passivating intermediate layer becomes more important if the titanium substrate is not a solid workpiece, but rather one porous substrate, for example a sintered titanium foil acts as it is used in solid electrolyte cells. (See for example: BVTilak, PWTLu, JEColeman, S.Srinivasan, "The Electrolytic Production of Hydrogen", in Comprehensive Treatise of Electrochemistry, Volume 2, Edited by: JOMBockris, Brian E. Conway, Ernest Yeager, Ralph E. White, Plenum Press, NY 1981).

Der Beschichtungstechnik bei porösen Titansubstraten kommt insofern eine wesentliche Bedeutung zu, als Methoden, wie sie bei planaren und massiven Elektroden angewendet werden, in diesem Fall nicht in Frage kommen. Dieses Problem wird noch erschwert, da man aus wirtschaftlichen Gründen möglichst nur kleine Mengen Edelmetall 0,1 mg/cm2 aufbringen möchte, dies aber bei einer relativ undefinierten Fläche, wie der eines porösen Substrats, schwierig ist.The coating technique for porous titanium substrates is of great importance insofar as methods such as those used for planar and solid electrodes are out of the question in this case. This problem is exacerbated because, for economic reasons, only small amounts of noble metal 0.1 mg / cm 2 should be applied, but this is difficult with a relatively undefined surface, such as that of a porous substrate.

Bisher wendete man folgende Verfahren an:

  • - Galvanische Abscheidung: Diese Methode erfordert eine umfangreiche Vorbehandlung des Substrats, welche unter anderem im Entfetten, Aetzen, Waschen, Trocknen, Wägen vor und nach dem galvanischen Abscheiden etc. besteht. Die elektrochemische Abscheidung von kleinen Mengen eines Edelmetalls oder einer Mischung bei rauhen oder porösen Proben ist ausserdem schwierig, da keine gleichmässige Verteilung der Platinkeime erzielt wird. Zusätzlich wird Edelmetall im Inneren einer porösen Probe abgeschieden, wo es keine Depassivierungsfunktion erfüllt.
  • - Aufdampfen: Aufdampfen kleiner Mengen eines Edelmetalls oder Edelmetalgemisches ist schwierig und der Aufdampfprozess relativ teuer.
  • - Aufpinseln oder Aufsprühen einer Lösung und anschliessende thermische Behandlung: Diese Methoden werden bei planaren Elektroden angewandt. Für poröse Elektroden sind sie jedoch ungeeignet, da ein wesentlicher Teil der Lösung in das Innere des porösen Substrats eindringt und damit für die Depassivierung verloren ist.
So far, the following procedures have been used:
  • - Galvanic deposition: This method requires extensive pretreatment of the substrate, which includes degreasing, etching, washing, drying, weighing before and after galvanic deposition, etc. The electrochemical deposition of small amounts of a noble metal or a mixture in the case of rough or porous samples is also difficult since the platinum nuclei are not evenly distributed. In addition, precious metal is deposited inside a porous sample, where it has no depassivation function.
  • - Evaporation: Evaporation of small amounts of a precious metal or noble Mixing metals is difficult and the evaporation process is relatively expensive.
  • - Brushing or spraying on a solution and subsequent thermal treatment: These methods are used for planar electrodes. However, they are unsuitable for porous electrodes, since a substantial part of the solution penetrates into the interior of the porous substrate and is therefore lost for the depassivation.

Es besteht daher das Bedürfnis nach neuen preisgünstigen Depassivierungsschichten und einem kostensenkenden Verfahren zu deren Herstellung.There is therefore a need for new, inexpensive depassivation layers and a cost-reducing method for their production.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren anzugeben, mit dessen Hilfe die Oberfläche eines porösen Körpers gezielt mit einer Depassivierungsschicht versehen werden kann, welche bei minimalem Edelmetallgehalt verbesserte Eigenschaften sowie eine hohe Stabilität und Lebensdauer aufweist.The invention is based on the object of specifying a method by means of which the surface of a porous body can be deliberately provided with a depassivation layer which has improved properties and a high stability and long service life with a minimal noble metal content.

Diese Aufgabe wird durch die im kennzeichnenden Teil des Anspruchs 1 und des Anspruchs 2 angegebenen Merkmale gelöst.This object is achieved by the features specified in the characterizing part of claim 1 and claim 2.

Die Erfindung wird anhand der nachfolgenden, durch Figuren näher erläuterten Ausführungsbeispiele beschrieben.The invention is described on the basis of the following exemplary embodiments which are explained in more detail by means of figures.

Dabei zeigt:

  • Fig. 1 das Verfahren anhand eines vereinfachenden Schemas,
  • Fig. 2 einen Querschnitt durch Substrat und Depassivierungsschicht.
It shows:
  • 1 shows the method using a simplifying scheme,
  • Fig. 2 shows a cross section through the substrate and depassivation layer.

In Fig. l ist das Herstellungsverfahren zur Erzeugung einer Depassivierungsschicht anhand einer vereinfachten Vorrichtung schematisch dargestellt. 1 ist das flächenförmige Substrat, beispielsweise in Form einer porösen Platte oder Folie aus Titan (Längsschnitt). 2 stellt eine elastische Rolle dar, welche vorteilhafterweise aus "Teflon" (Polytetrafluoräthylen) bestehen kann. 3 ist ein flächenförmiger biegsamer Lösungsträger, welcher porös und saugfähig sein soll, um die Metallsalzlösung aufnehmen zu können. Er wird in Form eines Filzes oder Papiers zwischen das Substrat 1 und die Rolle 2 geschaltet. Bei dem durch Pfeile angedeuteten Abrollvorgang gibt 3 eine dünne Schicht der Metallsalzlösung an die Oberfläche von 1 ab.1 schematically shows the manufacturing method for producing a depassivation layer using a simplified device. 1 is the sheet-like substrate, for example in the form of a porous plate or foil made of titanium (longitudinal section). Figure 2 shows an elastic roll which can advantageously consist of "Teflon" (polytetrafluoroethylene). 3 is a sheet-like, flexible solution carrier which is said to be porous and absorbent in order to be able to absorb the metal salt solution. It is connected in the form of a felt or paper between the substrate 1 and the roll 2. In the rolling process indicated by arrows, 3 releases a thin layer of the metal salt solution onto the surface of 1.

Fig. 2 zeigt einen Querschnitt durch das aus einzelnen Körnern mit dazwischenliegenden Hohlräumen aufgebaute poröse Substrat 1. 4 ist die mindestens teilweise zusammenhängende Depassivierungsschicht in Filmform, welche ein submikroskopisch feines, homogenes Gemenge von elektronisch leitenden Suboxyden und Oxyden des Substrats sowie die aus der aufgebrachten Metallsalzlösung stammenden Edelmetalle bzw. Metalle in metallischer und/oder oxydischer Form enthält.2 shows a cross section through the porous substrate 1, which is composed of individual grains with cavities in between. 4 is the at least partially connected depassivation layer in film form, which is a submicroscopically fine, homogeneous mixture of electronically conductive suboxides and oxides of the substrate and that from the applied metal salt solution contains precious metals or metals in metallic and / or oxidic form.

Ausführungsbeispiel I:Embodiment I:

Siehe Figuren 1 und 2!See Figures 1 and 2!

Eine poröse gesinterte Titanplatte als Substrat (1) wurde mit einer Depassivierungsschicht (4) versehen, welche Platin enthielt. Zu diesem Zweck wurde zunächst eine wässerige 5·10-2N H2PtCl6-Lösung hergestellt. Die Beschichtung erfolgte mittels einer elastischen Rolle (2) aus "Teflon" und eines Lösungsträgers (3) in Form eines Chromatographiepapiers. Es wurde insgesamt 5 x durch Abrollen beschichtet, wobei die aufgetragene Menge jeweils gravimetrisch bestimmt wurde. Daraufhin wurde die beschichtete Titanplatte getrocknet und einer chemo-thermischen Behandlung in Form eines Temperns während 30 min bei 450°C an Luft unterzogen. Die aufgetragene Platinmenge wurde mit 0,1 mg/cm2 bestimmt.A porous sintered titanium plate as substrate (1) was provided with a depassivation layer (4) which contained platinum. For this purpose, a aqueous 5 · 10 -2 N H2PtCl6 solution prepared. The coating was carried out by means of an elastic roll (2) made of "Teflon" and a solution carrier (3) in the form of a chromatography paper. Coating was carried out a total of 5 times, the amount applied being determined gravimetrically in each case. The coated titanium plate was then dried and subjected to a chemo-thermal treatment in the form of an annealing in air at 450 ° C. for 30 minutes. The amount of platinum applied was determined to be 0.1 mg / cm 2 .

Ausführungsbeispiel II:Working example II:

Eine poröse gesinterte Titanfolie als Substrat (1) wurde in analoger Weise gemäss Beispiel I beschichtet. Die Metallsalzlösung bestand aus einer 5·10-2N-Lösung der Formel H2Mc C16, wobei Mc eine Mischung von Pt und Ir im Atomgewichtsverhältnis 70:30 darstellte. Die Edelmetallmenge wurde zu 0,05 mg/cm2 bestimmt.A porous sintered titanium foil as substrate (1) was coated in an analogous manner as in Example I. The metal salt solution consisted of a 5 × 10 -2 N solution of the formula H 2 M c C 16 , where M c was a mixture of Pt and Ir in an atomic weight ratio of 70:30. The amount of noble metal was determined to be 0.05 mg / cm 2 .

Die nach Beispiel I und II beschichteten Substrate wurden als Stromkollektoren auf der Anodenseite von Feststoffelektrolytzellen geprüft und ergaben trotz um eine Zehnerpotenz geringerem Edelmetallgehalt gleiche Zellenspannungen wie nach herkömmlichen Verfahren (Galvanik, Aufdampfen) hergestellte Elektroden.The substrates coated according to Examples I and II were tested as current collectors on the anode side of solid electrolyte cells and, despite the fact that the noble metal content was ten times lower, gave the same cell voltages as electrodes produced by conventional methods (electroplating, vapor deposition).

Die Erfindung ist nicht auf die Ausführungsbeispiele beschränkt. Es können nach dem neuen Verfahren Depassivierungsschichten vielfältiger Art und Zusammensetzung erzeugt werden. Ausser Ti eignen sich Zr, Ta, Nb als Substratmaterialien. Alle Edelmetalle können grundsätzlich über eine Metallsalzlösung aufgetragen werden, sowohl einzeln als in Mischungen. Desgleichen können weitere Metalle, die nicht Edelmetalle sind, zugegeben werden. Die fertige Depassivierungsschicht kann neben Edelmetallen, Edelmetalloxyden (insbesondere der Platinmetallgruppen) auch Gold und eine weitere Komponente in Form eines Metalls oder dessen Oxyd, insbesondere Sn02 enthalten. Ein wesentlicher Teil der Depassivierungsschicht besteht aus einem bei der chemo-thermischen Behandlung auf der Oberfläche erzeugten elektrisch leitenden Suboxyd oder Oxyd des Substrats, bzw. Mischungen derselben. Alle angeführten Bestandteile bilden ein submikroskopisch feines, homgenes Gemenge, wobei die einzelnen Komponenten eine Dimension aufweisen können, die bis nahe an den atomaren Bereich heruntergeht. Dadurch wird ein mindestens teilweise zusammenhängender Film der Depassivierungsschicht gewährleistet, welcher optimale chemische und physikalische Eigenschaften besitzt. Der Edelmetallgehalt der Depassivierungsschicht kann auf diese Weise ohne Inkaufnahme von Nachteilen minimal gehalten werden, was sich günstig auf die Wirtschaftlichkeit der Anlage auswirkt.The invention is not restricted to the exemplary embodiments. Depassivation layers of various types and compositions can be created using the new method. In addition to Ti, Zr, Ta, Nb are suitable as substrate materials. All precious metals can generally be applied using a metal salt solution, both individually and in mixtures. Likewise, other metals, which are not precious metals, are added. In addition to noble metals, noble metal oxides (in particular the platinum metal groups), the finished depassivation layer can also contain gold and another component in the form of a metal or its oxide, in particular SnO 2 . An essential part of the depassivation layer consists of an electrically conductive sub-oxide or oxide of the substrate, or mixtures thereof, generated on the surface during the chemo-thermal treatment. All of the components listed form a submicroscopically fine, homogeneous mixture, whereby the individual components can have a dimension that goes down to close to the atomic range. This ensures an at least partially coherent film of the depassivation layer, which has optimal chemical and physical properties. In this way, the noble metal content of the depassivation layer can be kept to a minimum without accepting disadvantages, which has a favorable effect on the economy of the system.

Claims (8)

l. Verfahren zur Herstellung einer Depassivierungsschicht auf einer Elektrode einer elektrochemischen Zelle, wobei mindestens ein Edelmetall oder mindestens ein Edelmetall und ein weiteres Metall auf ein flächenförmiges Substrat aus mindestens einem der Elemente Titan, Zirkon, Tantal, Niob aufgebracht wird, dadurch gekennzeichnet, dass eine Metallsalzlösung, welche das oder die aufzubringenden Metalle enthält, mittels einer elastischen Rolle (2) und eines zwischen das Substrat (1) und die Rolle (2) geschalteten porösen, saugfähigen Lösungsträgers (3) in dünner Schicht auf das Substrat (1) durch ein- oder mehrmaliges Abrollen aufgebracht, getrocknet und durch eine chemo-thermische Behandlung in metallische und/oder oxydische Form übergeführt wird, wobei gleichzeitig die Oberfläche des Substrats (1) mindestens teilweise zu einem entsprechenden elektronisch leitenden Suboxyd und/oder Oxyd oxydiert wird und auf diese Weise eine aus einem submikroskopisch feinen homogenen Gemenge bestehende Depassivierungsschicht (4) in mindestens teilweise zusammenhängender Filmform gebildet wird.l. Method for producing a depassivation layer on an electrode of an electrochemical cell, wherein at least one noble metal or at least one noble metal and another metal is applied to a sheet-like substrate made of at least one of the elements titanium, zirconium, tantalum, niobium, characterized in that a metal salt solution, which contains the metal or metals to be applied, by means of an elastic roller (2) and a porous, absorbent solution carrier (3) connected between the substrate (1) and the roller (2) in a thin layer onto or onto the substrate (1) repeated unrolling applied, dried and converted into metallic and / or oxidic form by a chemo-thermal treatment, at the same time the surface of the substrate (1) being at least partially oxidized to a corresponding electronically conductive suboxide and / or oxide and in this way a De consists of a submicroscopically fine homogeneous mixture passivation layer (4) is formed in at least partially coherent film form. 2. Depassivierungsschicht (4) auf einer für eine elektrochemische Zelle bestimmten Elektrode, welche aus einem flächenförmigen Substrat (1) aus mindestens einem der Elemente Titan, Zirkon, Tantal, Niob aufgebaut ist, dadurch gekennzeichnet, dass sie aus einer mindestens teilweise zusammenhängenden Oberflächenschicht in Filmform besteht, welche ein submikroskopisch feines, homogenes Gemenge von elektronisch leitenden Suboxyden und/oder Oxyden des Substrats (1) und mindestens einem Edelmetall und/oder Edelmetalloxyd enthält.2. Depassivation layer (4) on an electrode intended for an electrochemical cell, which is composed of a sheet-like substrate (1) made of at least one of the elements titanium, zirconium, tantalum, niobium, characterized in that it consists of an at least partially coherent surface layer in Film form exists which contains a submicroscopically fine, homogeneous mixture of electronically conductive suboxides and / or oxides of the substrate (1) and at least one noble metal and / or noble metal oxide. 3. Depassivierungsschicht nach Anspruch 2, dadurch gekennzeichnet, dass das Edelmetall und/oder Edelmetalloxyd mindestens ein Platinmetall oder Gold enthält.3. Depassivation layer according to claim 2, characterized in that the noble metal and / or noble metal oxide contains at least one platinum metal or gold. 4. Depassivierungsschicht nach Anspruch 3, dadurch gekennzeichnet, dass das Edelmetall mindestens eines der Metalle Platin, Iridium, Ruthenium ist.4. Depassivation layer according to claim 3, characterized in that the noble metal is at least one of the metals platinum, iridium, ruthenium. 5. Depassivierungsschicht nach Anspruch 3, dadurch gekennzeichnet, dass das Edelmetalloxyd mindestens ein Oxyd oder Suboxyd mindestens eines der Elemente Platin, Iridium, Ruthenium ist.5. Depassivation layer according to claim 3, characterized in that the noble metal oxide is at least one oxide or suboxide of at least one of the elements platinum, iridium, ruthenium. 6. Depassivierungsschicht nach Anspruch 2, dadurch gekennzeichnet, dass das Edelmetall aus Gold besteht.6. depassivation layer according to claim 2, characterized in that the noble metal consists of gold. 7. Depassivierungsschicht nach Anspruch 2, dadurch gekennzeichnet, dass die Oberflächenschicht mindestens noch eine weitere zusätzliche metallische und/oder oxydische Komponente enthält.7. Depassivation layer according to claim 2, characterized in that the surface layer contains at least one further additional metallic and / or oxidic component. 8. Depassivierungsschicht nach Anspruch 7, dadurch gekennzeichnet, dass die zusätzliche Komponente aus Zinnoxyd besteht.8. Depassivation layer according to claim 7, characterized in that the additional component consists of tin oxide.
EP84107073A 1983-06-28 1984-06-20 Process for manufacturing a depassivating layer and depassivating layer on an electrode for an electrochemical cell Expired EP0137911B1 (en)

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US3933616A (en) * 1967-02-10 1976-01-20 Chemnor Corporation Coating of protected electrocatalytic material on an electrode
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JPS6022074B2 (en) * 1982-08-26 1985-05-30 ペルメレツク電極株式会社 Durable electrolytic electrode and its manufacturing method

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US3443055A (en) * 1966-01-14 1969-05-06 Ross M Gwynn Laminated metal electrodes and method for producing the same
DE2846576A1 (en) * 1978-10-26 1980-06-04 Basf Ag Production of coated strip material - has viscous coating deposited on tape and passed through control gap with second tape to produce two coated tapes
DE3004080A1 (en) * 1980-02-05 1981-08-13 Sigri Elektrographit Gmbh, 8901 Meitingen METHOD FOR COATING A POROUS ELECTRODE

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