DE2213083A1 - Electrodes for electrochemical processes - Google Patents

Description

Folder 22829 - Dr ₀ P / hr Case HBo 23700

IMPBRIAL CHMIOAL IKDUSIßlBS London, Great Britain

"Electrodes for electrochemical decay"

Priority? 18o March 1971, & r «eeterit« xmien

The invention relates to electrodes for electrochemical processes and in particular to electrodes where there is a support part made of a forming material which has a coating which effectively prevents the transmission of an electrical current from the support part to an electrolyte and the is resistant to electrochemical attack ο

Eb is known to be oxides of platinum group metals as Bel & g * use on electrodes of the type mentioned, well as a » high internal resistance to electrochemical dissolution in various corrosive media they still have

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are effective with regard to the discharge of ions from a ^s Slektrolyteno Di "present invention now proposes improved electrodes against which have deposits which aug oxides of the platinum metal group consist The electrodes geaiäss of the invention are particularly useful as anodes aetallelektroyee in cells for the alkali ** They are particularly useful in cells with flowing mercury cathodes, because the electrodes are highly resistant to damage from short-circuit contact with the cathode, as sometimes occurs even with normal work in these cells. The electrodes can, however, also be used in other electrochemical processes be, a generally other electrolytic process with sheet metal catalyze, for example in fuel cells, for sheet metal synthesis and for the cathodiaohen Schute »

According to the present invention, an electrode Jtur Proposed use in electrochemical processes, which consists of a carrier part made of a film-forming metal or a film-forming alloy; which has a coating, which consists of a layer of a mixture of the oxide or the Oxide VQO of at least one platinum group metal into a © Ratio of 20 to 80 (rew «- # and a transforming metal oxide exists, with another layer on top of this layer a film-forming metal oxide is attached *.

In a preferred embodiment of the electrode, the ratio of the metal oxides of the platinum group to the film-forming metal oxide in the layer of this mixture is not less than 1.1, but is less than 2: 1, based on the weight

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A transforming metal is one of the metals titanium, zirconium, biob, tantalum and tungsten _c The support part of the electrode is preferably made of titanium or a titanium alloy with anodic polarization properties similar to those of titanium.

Under the grid or oxides of at least one metal of the platinum group, the oxide is tow "dxe oxides of at least" one of the metals ruthenium, rhodium, palladium, osmitai,. Understood iridium and platinum.

In a preferred embodiment of the electrode according to FIG According to the invention, the layer of this mixture consists of rmthenium diocide and titanium dioxide and the layer applied to it consists of titanium dioxide.

The preventive form of axis guidance but production of the layer of mixed oxides on the backing part is as follows Sin covering is composed of a paint composition a compound of at least one platinum group metal that can be decomposed by the action of heat and an organic compound that is decomposable by the action of heat, a film-forming compound Metal in an organic carrier liquid, these "paints, if desired - a reducing agent, such as Linalool, is applied to the carrier part, the application is made duroh evaporation of the carrier- » liquid dried and the covering is then in an oxidizing atmosphere, for example in air to a temperature '

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for τοπ at least 35O ⁰ G and voraugaireise within the range of 400 to 55O ⁰ C received in order to in this way the compounds of the metals of the platinum group and the fila-forming. The metal can then be converted into oxides of these metals. Further applications of the paint composition can then be applied to the carrier provided with the coating, then dried and heated in the same way in order to increase the thickness of the mixed oxide layer to a desired extent. For example, in the case of electrodes which are used as anodes in carbon silver cathode cells in the electrolysis of alkali metal chloride solutions, this coating is applied to a thickness within the range of 10 to 15 g / m of the coating surface of the carrier part. However, this thickness is in no way critical. Thicker or thinner coatings can also be used, and the thickness is generally selected with regard to the wear and tear of the electrode to which it is subject during use in the cell and it is also dependent on, among other things, the Current density set under which the electrode works.

The preferred method for forming the surrounding layer of the film-forming metal oxide consists in applying a coating of a heat-absorbable organic compound of the film-forming metal in an organic carrier liquid to the mixed oxide layer, whereupon the coating is dried by evaporating the carrier liquid and then in an oxidizing agent Atmosphere, for example air, is heated in order to convert the organic compound of the film-forming metal into the oxide of this metal. The preferred thickness of this overlying layer of the filamentary metal oxide lies within the range from 2 to 10 g / m 2 of the surface provided with the covering. The desired strength

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The coating can be adjusted by adjusting the viscous si did the topping composition by Euaats of more; or less of the organic carrier liquid and / or duroh repeated application of thin layers of the covering material Settlement are preserved · Each order is dried and β rhi t Et, so as to make the top covering the desired Build strength. ;

They decompose organic compounds of the filabild ketals by the action of heat, which are used for the formation of the “overlying coating” of the film-forming metal oxide as described in the previous section, and especially the alkyl titanates, the alkyl halotitanates, in which the halogen There is chlorine, bromine or fluorine (also known as titanium alkexides and alkoxi ^ halides) and the corresponding alkyl compounds of other film-forming metals the alkyl titanate and Ealotiteaate, inabeeoMere those in which the alkyl groups each contain 2 to 4 carbon atoms. Coverings of these preferred compounds, dl "are applied by means of an organic carrier liquid are preferably dried at a temperature of 100 to 200 ⁰ C and then in an oxidizing atmosphere at 250 to 800 ⁰ O, preferably at 350 to 550 ⁰ O, heated - to convert the litanate compounds into titanium dioxide,

Any of the duroh heat exposure »replaceable Connections of the fumbildenden hotalle, which in the

gaggenen Abtat »listed, can auoh la den A * eti * ioh ~ by means of »amm« i8et * ungen be applied »welehe sur the underlayer of mixed oxides on the electrode? £ g # r *

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part can be used. The alkyl * titanates and the alkyl halotitanates, the halogen being composed of OhIor, There is bromine or fluorine, preferably and especially those in which the alkyl groups each contain 2 to 4 carbon atoms. The compounds which can be decomposed by the action of heat the platinum group metals used in the manufacture of these paint / paint compositions preferably the halides such as ruthenium trichloride, halogen acid complexes such as hexachloroplatinic acid or resinates of these metals. The preferred platinum group metal compound is ruthenite sodium chloride.

The invention is explained in more detail in the following examples », without being limited to this.

example ι

A titanium sheet strip 34 cm long, 6 mm wide and 1 mm thick was etched in oxalic acid solution, washed, dried and then eyed with a mixture containing 4.3 g of partially hydrated euthenium triochloride, 12.0 g of n-pentanol and 6.4 g of tet * Contained abutyl orthotitanate. The paint coating was dried at 180 ⁰ O and then 15 Hinuten long värmebehandelto in air at 45O ⁰ C Total six Auftragssohichten this paint were applied, each order and was dried heated in the same manner as on the titanium Upper * fläohe one surface layer τοη wad 14 g / m au give the final coating of 60% and 40% titanium dioxide Rutheniuirdioiid _r beaogen the Oewioht, bestando This coating of mixed oxides was then painted with a mixture of 5 β Tetrabutylerthotitanat in 5 g of n-pentanol. This mandate was likewise dried at "180 ⁰ C and then heat treated for 15 minutes i" air at 45O ⁰ C. In particular, there were three toppings

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of this second coat of paint applied to any topping

* I

dried and heat-treated in the same way to give ep a coating of 4 g / m 2 of titanium dioxide on the coating of the mixed oxide layer ₀

Studied of these is provided with the cover strip cut off was and as anodes but Cfalorherstellung aua ohloridsolelögungen 'which 21 »5 5 * sodium chloride, a pH value of 2 to 3 and a temperature of 6S ⁰ C besäßeο The samples were at a low overpotential (50 mV at a current density of 3 kA / m) and they also exhibit excellent resistance to damage when they come into contact with the amalgam cathode in a mercury * electrolytic cell for sodium chloride solution

Example 2

His anode, whose working surface had a G-iHterform "was built up from titanium strips and it had a projected surface of 0.1 m", This anode was etched in oxalic acid solution for 16 hours "washed and dried" The anode grid was then coated with a coating of paint sprayed, which consisted of 6O _f 5 g of ruthenium trichloride and 90.0 g of tetra-n ^ butylprthotitanate in 500g of n-pentanol. The order was dried in an oven at 130 ⁰ C and then in a layer of, composition of 60 Gtew, - i ^ u O ₂ and 40 Ö9w _f - $> TIQ ₂ by Brhiteen in air for 20 minutes in an "oven * of 450 C. Another five layers of the same paint composition were then sprayed onto the anode. Each layer was dried and then heat-treated in air exactly like the first layer. Then an outer layer consisting of titanium dioxide alone was applied to the anode by placing three coverings on a coating material

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aenaeteung, which consists of 25 g titanate consisted of 75 g of n-pentanol. Every job was 180 ⁰ C and then 20 minutes in air at 450 ⁰ O would be treated. The total amount of deposited on the titanium grid

Oxide was then 32 g / m projected surface «,

The eo coated anode was then turned into a Qtieokslberkathodenselle sub Elektrolyeieren - introduced by latriumchloridaole, namely as BreatB for a graphite anode o Jffaohdem the arrangement satisfactorily 6 months old an anode plug of up to 900 amperes had worked Wear or damage to the anode detected.

Example ?

2 A titanium mesh anode with a projected surface area of 0.1 a was provided with a coating according to Example 2 with the modification that the paint material composition used for the eraten seohe coating consisted of 55 g of ruthenium trichloride and 101 g of tetra-n-butyl orthotitanate in 300 g of nP «atanol a sublayer on the titanium lattice of the combined content of 55 wt. -4> ¹ ^ ⁰ P ^and ^ öewo- ^ TiOg ° The outer layer of titanium dioxide alone was then applied as shown in Example 2 ^! Deole used and it also showed no wear or damage after 6 months of use with an anode power supply up to 900 amps.

Claims ι 209839/1 125

Claims (1)

PATENT CLAIMS Electrode for electrochemical processes, characterized in that it consists of a carrier part and a film-forming part Metal or metal alloy and they have a coating made of a mixture of the oxide or oxides Clay at least one platinum group metal in a lot from 20 tie 80 wt. £ and one film-forming «! Metal oxide "consists, where there is another rail above this layer a film-forming metal oxide is attached. 2 »Electrode according to claim 1, characterized in that the ratio of the metal oxides of the platinum group to the metal oxide of the film-forming metal in the layer of this mixture is not less than 1: 1 and less than 2: 1, based on weight, _o 3o electrode naoh one of the preceding claims, characterized marked that the! Dräger part is made of titanium or a titanium alloy consists of what anodic polarization property which are similar to those of titanium. 4o electrode according to one of the preceding claims, characterized in that the layer of the mixture of ßuthenium »dioxide lind titanium dioxide and attached thereto a layer of titanium dioxide is _n 5. Electrode according to one of the preceding Anaprüohe, thereby 2 within the range of 10 to 15 g / m of the occupied upper * marked that the GwICHTsraenge der Sohioht H ^ r Mleohung within the B
area is. 2 0 9 8 3 9/1125 - ίο - 6. Electrode naoh one of the Toraogehends »claims ·, thereby marked that that weight of the top sohidht within of the range »from 2» ie 10 g / m 2 of the covered surface. 7 ° Process for the production of an electrode according to Ansproeh 1, characterized by the following working hole » (1) On a carrier part made of a film-forming metal or metal alloy, at least one coating made of a substance composition is applied, consisting of a compound τοη at least tinea metal of the platinum group and an organic compound of a film-forming metal in an organic * carrier liquid which can be eroded by heat Each job is dried by evaporation of the carrier liquid and then each job is ^{heat-treated in an oxidising atmosphere at a temperature of at least 35O 0} C in order to convert the compounds of the metals of the platinum group and the transforming metal into oxide of these metals, (2) Application to this layer of mixed oxides on the Carrier part τοη at least one covering from a duroh heat » Effect of a resetable organic compound in a film The metal is dissolved in an organic carrier liquid and dried of the coating by evaporation of the carrier liquid and Srhitaen each coating in an oxidizing atmosphere to the organic compound of the film-forming metal in the oxide of this Transferring metal? 8. The method according to claim 7, characterized in that the carrier part consists of titanium or a titanium alloy, the anodic «polarization properties similar to those τοη Titan beeitato 209839/1 125 9 »Method according to one of claims 7 and 8, characterized marked that at work it chrltt (1) the StoffjraiMua * Meetting contains a reducing agent. 10, method according to one of claims 7 to 9 »daduröh marked, daee with the work ride (1) caused by the action of heat ^ replaceable compound of at least one of the metals the platinum group consists of Hutheniumtriehlorid. 11 ο method Naeh one of Anepriiohe 7 to 10, characterized in that the temperature to which the coating is heated in an oxidizing atmosphere at Arbeitseohritt (1) is within dee range of 400 "to, 55O ⁰ C. 1 2 ₀ method according to any one of claims 7 bia 11, characterized in that when Arbeitesohritt (1) the Anssahl the linings of the force applied to the! Eragerteil dried and heated composition IGT sufficient tua a layer of the mixed oxides zn result, the 10 bie 15 g / m of the covered surface of the beam part is _o 13. The method according to any one of claims 7 to 12, characterized in that in step (1) the organic compound of a metal which can be converted by heat is an alkyl titanate or an alkyl halotitanate, the halogen consisting of chlorine, bromine or fluorine _{or the like} 14, the method according to claim 13 _f, characterized in that the alkyl groups of the AXkyltitaaate or Alkylhaloti-tanata ie Contain 2 to 4 carbon atoms? 15, the method according to any one of claims 7 to 14, characterized 209839/1125 characterized in that the proportions of the metal compounds of the Platinum group and the metal compound of the film-forming metals » in the material composition of the work step (1) such be selected that the ratio of metal oxides to the Platinum group sum metal oxide of the film-forming metal in the 3ohioht of the mixed oxides in step (1) not less than 1: 1 but less than 2: 1, based on the 'weight, iso 16 method according to one of claims 7 to 15 »thereby gekennaeiohnet that the total amount of topping, the over the The mixed oxide layer is sufficient to add a layer of the metal oxide to be formed in step (2) give, which is 2 to 10 g / m of the covered surface o 17 * Method according to one of claims 7 to 16, daduroh characterized in that in step (2) the organic connection of a filabildendea Metal is an alkyl titanate or an alkyl halotitanate, wherein the halogen consists of chlorine, bromine or fluorine, 18 »The method according to claim 17, characterized in that the alkyl groups of the alkyl titanate or alkyl halotitanate depending Containing 2 to 4 carbon atoms » 19o method according to claim 17 or 18, characterized in that in step (2) each order at 100 bie 200 C is dried in an oxidizing atmosphere 2oo method of claim 19, daduroh in that is heat treated in Arbeltsechritt (2) after drying each order at 350 to 55O ⁰ C in an oxidizing atmosphere. 209839/1 125 21 ο Use of the electrode according to Anepruoh 1 to 6 Anode in aintr line · with «intr K» thodtn from fll, * 8eend «a Qutok» silver ear chlor-alkali electrolysis. 2098 39/1125