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EP0215381B1 - Procédé de fabrication d'électrodes - Google Patents

Procédé de fabrication d'électrodes Download PDF

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Publication number
EP0215381B1
EP0215381B1 EP86112216A EP86112216A EP0215381B1 EP 0215381 B1 EP0215381 B1 EP 0215381B1 EP 86112216 A EP86112216 A EP 86112216A EP 86112216 A EP86112216 A EP 86112216A EP 0215381 B1 EP0215381 B1 EP 0215381B1
Authority
EP
European Patent Office
Prior art keywords
nickel
bath
deposition
iron
molar ratio
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP86112216A
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German (de)
English (en)
Other versions
EP0215381A1 (fr
Inventor
Hans Dr. Roos
Dieter Dr. Schlaefer
Knut Dr. Bittler
Richard Dr. Schiedermaier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
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Filing date
Publication date
Application filed by BASF SE filed Critical BASF SE
Publication of EP0215381A1 publication Critical patent/EP0215381A1/fr
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Publication of EP0215381B1 publication Critical patent/EP0215381B1/fr
Expired legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
    • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
    • 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

Definitions

  • the present invention relates to a method for producing electrodes consisting of an electrically conductive base body and an electrochemically active boron-containing nickel layer applied thereon, which has been obtained by electroless deposition from a bath containing Ni (II) salts and complexing agents by reduction with sodium boranate can be used, for example, as an H 2 -generating cathode in electrolysis processes, in particular in chlor-alkali electrolysis.
  • iron cathodes In the electrolysis of aqueous alkali metal chloride solutions, iron cathodes are generally used today in the diaphragm process and nickel cathodes, in which the hydrogen is deposited, are used in the membrane process.
  • nickel cathodes In the electrolysis of aqueous alkali metal chloride solutions, iron cathodes are generally used today in the diaphragm process and nickel cathodes, in which the hydrogen is deposited, are used in the membrane process.
  • nickel cathodes in the membrane process is preferable because there are greater demands on the purity of the electrolyte. If a cathode is in the de-energized state, corrosion always occurs with the iron; this leads to the deposition of iron hydroxide, which can settle on the membrane as an undesirable precipitate. This precipitation then causes a significant deterioration in the membrane properties, which essentially leads to an increase in energy consumption due to destruction of the membrane.
  • nickel cathodes are also associated with another important advantage. Energy consumption is a key economic factor in an electrolysis process. If nickel is now used as the cathode material for H 2 deposition instead of iron, the cell voltage required for electrolysis is reduced, since the hydrogen deposition potential on nickel is significantly lower than on iron. Thus, much less energy is used to carry out the electrolysis when using nickel cathodes.
  • DE-A-32 18 429 a coating that is done with the help of plasma spraying technology.
  • a layer of pure nickel is first sprayed on, which is then coated with a nickel / aluminum or nickel / zinc mixture.
  • Leaching of the AI or Zn is said to produce so-called Raney nickel, as is known as a hydrogenation catalyst from organic chemistry.
  • the residual porosity of plasma-sprayed layers remains problematic with this coating process. As is generally known in thermal spraying, this residual porosity is process-related and cannot be avoided. This results in a corresponding susceptibility to corrosion if the electrode base body in the electrolysis cell is not loaded cathodically or is not stored in an inert gas atmosphere.
  • plasma spraying is a very complex process, because during the coating process, a complicated sequence of movements has to be carried out either with the plasma spray gun or the cathode, which often weighs several tons.
  • the plasma spraying process is a relatively expensive coating method due to the extensive but necessary use of noble gas.
  • the aluminum or zinc In an additional step, the aluminum or zinc must be removed from this spray layer.
  • the aluminum or zinc When stored in the air, there is a risk that the reactivity and structure of the Raney nickel will be changed by oxidation; a fact known from organic chemistry where Raney nickel is usually stored in non-aqueous solvents to preserve activity.
  • the aluminum or zinc components are removed, additional continuous pores are created which further increase the susceptibility to corrosion mentioned above.
  • an active layer is deposited electrolytically on the electrode base body.
  • particles of nickel-aluminum alloy are built into the electrolytically deposited layer. These particles in the layer are then removed by removing the alloyed components e.g. AI activated, as is also described in the above-cited DE-A-32 18 429.
  • electrolytically deposited layers mostly have a crystalline structure over a wide range. This is for creating reactive surfaces, e.g. required at Raney nickel, not desired. Rather, the most reactive surfaces are achieved through amorphous structures.
  • DE-A-30 47 636 claims an active layer consisting of various metal components and a leachable metal or metal oxide additive. These layers become electro lytically applied to the cathode body. This naturally brings with it the same deposition problems as the process described in US 4,302,322.
  • DE-B-26 30 398 proposes, in addition to various other possibilities, to produce at least one surface of the electrode from a metal alloy with a low hydrogen overvoltage.
  • nickel, cobalt or iron should be alloyed with titanium, molybdenum, tungsten, magnesium, niobium or tantalum and bound in a non-stoichiometric manner.
  • the production takes place essentially by melting or sintering the components in the appropriate proportions.
  • the alloy is then applied to the cathode body by plasma spraying, sputtering, vacuum evaporation or explosive plating of the corresponding powder mixture.
  • the components can also be deposited electrolytically or by decomposing salts of the elements.
  • the deposited layer is then optionally subjected to a heat treatment in a neutral or reducing atmosphere.
  • these aqueous bath solutions also contain, in dissolved form, buffer substances, complexing agents, accelerators and stabilizers and, if appropriate, catalysts.
  • the nickel plating takes place at temperatures of 50 to 95 ° C.
  • the layers produced in the electroless nickel plating for the purpose of corrosion protection are not suitable, for example, for the nickel plating of base bodies in the context of the production of electrodes, since these layers have different requirements, for example with regard to electrochemical-catalytic activity, in contrast to surface gloss, surface hardness and the like.
  • DE-OS 2 706 577 therefore describes a method for producing a steel base body provided with a nickel coating, which is used as a cathode for chlor-alkali electrolysis.
  • the deposition takes place from an aqueous nickel (II) salt bath which contains a reducing agent, for example sodium hypophosphite, sodium borohydride, sodium dithionite or, in particular, hydrazine hydrate.
  • the baths also contain complexing agents such as ammonia, ethylenediamine, citric acid or glycolic acid.
  • the deposition temperatures are somewhat lower than in the processes of electroplating described above, namely 20 to 70 ° C, with temperatures of 30 to 40 ° C being preferred.
  • FR-A-2 218 137 describes a process for the preparation of catalysts for the cathodic hydrogen evolution in alkaline electrolytes which consists in the fact that nickel, cobalt, or iron ions, preferably in divalent form, from aqueous solution in the presence of a Complexing agent for the metal ion with water-soluble boranates or borazanes at a temperature below 60 ° C and a concentration of free metal ions below 10- 10 mol / 1 are deposited to form X-ray amorphous boron deposits.
  • the present invention was therefore based on the object of providing a method for producing electrodes, consisting of an electrically conductive base body with an electrochemically active nickel layer deposited thereon, which by electroless deposition from a bath containing nickel (11) salts and complexing agents by reduction with Sodium boranate has been obtained, in which on the one hand electrochemically active electrodes are obtained in a reproducible manner and on the other hand an undesired decomposition of the bath during the deposition is largely avoided.
  • the bath has a molar ratio of complexing agent: nickel salt from 80 to 200, a molar ratio of sodium boranate: nickel salt from 0.7 to 4.0 and a content of hydroxides of sodium, potassium and alkaline earth metals, which are more basic than ammonia, from 10 to 400 mmol / 1 and has a nickel salt content of 10 to 80 mmol / l.
  • the baths according to the invention contain a large excess of complexing agents corresponding to a molar ratio of complexing agent: nickel salt of 80-200.
  • Ammonia is a particularly preferred complexing agent, but other known complexing agents such as citric acid, amines and the like are also suitable.
  • the concentration of free nickel ions in the bath corresponds to the equilibria
  • hydroxides of sodium and potassium come into consideration as hydroxides which are more basic than ammonia, but the hydroxides of the alkaline earth metals are also suitable.
  • the hydroxide concentration in the bath should be 10 to 400 mmol / l.
  • Another essential characteristic of the process according to the invention is a high molar ratio of sodium boranate to nickel salt in the bath.
  • This high molar ratio apparently creates a special surface structure of the deposited nickel layer, to which a particularly low hydrogen deposition potential of less than 1100 mV can be attributed, which is even lower than the hydrogen deposition potential of pure nickel, which, even if its surface e.g. has been artificially enlarged by sandblasting, is between 1280 and 1300 mV.
  • Nickel borides can be formed during electroless nickel plating. As can be seen from the equation, such a side reaction, particularly at higher boranate concentrations (as is present in the coating according to the invention and also possible due to the high degree of complexation of Ni 2+ by large excesses of NHs without self-decomposition of the solution), will take place to an increased extent. This also favors the incorporation of boron into the nickel layer; the boron content is 6-30% by weight, depending on the reaction.
  • the nickel layer produced under the conditions according to the invention is X-ray amorphous, which obviously has a favorable effect on achieving high activity.
  • Suitable nickel salts are salts whose anion reacts with the sodium boranate. Nickel chloride or nickel sulfate is particularly suitable. The nickel salts should advantageously be used in amounts such that the bath contains from 10 to 80 mmol / l of nickel salt.
  • the temperatures during the coating are expediently kept below 30 ° C., preferably at temperatures of 20 to 25 ° C.
  • This ratio should be> 500 cm 2/1 bath solution.
  • metal ions can be added to the bath, for example salts of cobalt, aluminum, zinc, chromium, copper, palladium or platinum.
  • the content of these additives should be selected in the range of 500 ppb - 50 ppm.
  • bodies made of electrically conductive materials are suitable as the basic body.
  • iron or iron-containing alloys, steel, but also graphite or nickel itself are particularly suitable.
  • the amorphous active nickel layers according to the invention passivate easily due to their amorphous structure, i.e. they easily coat with an oxide skin when exposed to atmospheric oxygen or oxygen dissolved in an aqueous medium.
  • the inactivation of the nickel layer deposited according to the invention - in contrast e.g. to other nickel layers, which have been created by removing a component again develop their full catalytic activity if, for example, can be used as the cathode in chlor-alkali electrolysis, which is noticeable by a sharp reduction in the hydrogen separation potential.
  • the catalyst is activated as follows:
  • the hydrogen separation potentials measured in the following examples were determined at a current density of 1.5 kA / m 2 and 20 ° C. against the normal hydrogen electrode.
  • the molar ratio of complexing agent: nickel salt is approximately 123 and the molar ratio of sodium boranate: nickel salt is approximately 1.0.
  • the grid is removed from the bath, washed with water and the hydrogen separation potential is determined to be 1075 mV.
  • Example 1 b Three iron grids (ST 12/03), each with an area of 240 cm 2, are coated as described in Example 1 a), immersed in 10% strength by weight sodium hydroxide solution for 24 hours and, after placing a diaphragm made of asbestos 1.5 Baked for hours at a temperature of 350 ° C.
  • the thickness of the active layer at the start of the experiment is 2.5 - 3 ⁇ m.
  • the determination of the nickel concentration Tration in the diaphragm solution provides values that are below the analysis accuracy ( ⁇ 100 ppb) and the optical findings after removal of the cathodes also show no noticeable nickel removal.
  • Example 1a A sandblasted, polished and untreated nickel sheet is degreased with acetone, for 5 minutes in conc. HCI pickled, blown dry with nitrogen and then electrolessly coated with a nickel layer as described in Example 1a.
  • HCI pickled, blown dry with nitrogen and then electrolessly coated with a nickel layer as described in Example 1a.
  • the H 2 deposition potentials are compared to those potentials that are obtained with non-coated, but similarly pretreated nickel sheets: From Examples 1a) and 1e) it can be seen that the H 2 deposition potential of the cathodes coated according to the invention, at about 1060-1075 mV, is significantly below the deposition potential of nickel, which, depending on the pretreatment, according to Example 1 e) 1300 and 1525, respectively mV is.
  • Example 1d shows that the deposition potential of a cathode coated according to the invention rises sharply with increasing time after storage in saline solution, but that the initial potential can again be approximately reached after cathodic loading. This fact can also be found in Example 1e), which is included as a parallel example to Example 1b), since the H 2 deposition voltage cannot be measured in the cathode described here because of the diaphragm applied.
  • the cathode is rinsed with water and the H 2 deposition potential is determined to be 1290 mV.
  • Each iron grate (ST 12/03) with the dimensions 1 x 12 cm (surface 48.6 cm 2 ) is pretreated as described in Example 1a), weighed, and for 20 hours in 0.064 l of a still bath at a temperature of 20 ° C immersed, the each 2 g NaBH 4/1 contains.
  • the ammonia and nickel salt content is varied according to the values given in the table.
  • the cathodes are rinsed with water, blown dry with nitrogen and weighed again to determine the amount of nickel deposited.
  • nickel is spontaneously deposited in the bath at low molar ratios of ammonia to nickel salt.
  • the nickel nuclei deposited in the bath compete with the iron lattice to be coated, ie in other words that practically no nickel is deposited on the iron lattice.
  • Only in experiment d ie with a molar ratio of NH 3 : nickel salt of 88, is the deposition of the nickel in the bath itself strongly suppressed, but very little nickel is deposited on the lattice with 1.6 mg Ni / g lattice.
  • the amount of nickel deposited on the grid can be greatly increased by adding NaOH.
  • the nickel chloride content of the bath can be seen from the following table, as can the molar ratio of NHs (complexing agent): Ni.
  • the electrodes are removed from the bath, rinsed with water, stored in 10% strength by weight NaOH for 24 hours and then heat-treated at 360 ° C. for 1.5 hours. After 60 minutes of cathodic loading at 2 kA / m 2 , the following H 2 separation potentials listed in the table are measured:
  • Iron grids are coated in accordance with Example 1a) and aftertreated in accordance with Example 1c), with no stirring or stirring during the coating.
  • Iron grids are coated in accordance with example 1a) and aftertreated in accordance with example 1c), different temperatures as indicated in the table being maintained during the coating.
  • Each iron grate is immersed in a bath, as described in Example 1 a), to which copper has been added in the amount specified in the table. After 20 hours of coating time, the grids are rinsed with water, blown dry with nitrogen and weighed.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Chemically Coating (AREA)

Claims (6)

1. Procédé de fabrication d'électrodes consistant en un support électriquement conducteur sur lequel a été déposée une couche de nickel contenant du bore, électrochimiquement active, cette couche ayant été obtenue par un dépôt sans courant dans un bain contenant des sels de nickel(II) et des formateurs de complexes par réduction avec du boranate de sodium, caractérisé en ce que le bain présente un rapport molaire des formateurs de complexes au sel de nickel de 80 à 200, un rapport molaire du boranate de sodium au sel de nickel de 0,7 à 4,0, une teneur en hydroxydes de sodium, potassium et métaux alcalino- terreux, qui sont plus fortement basiques que l'ammoniac, de 10 à 400 millimoles par litre et une teneur en sels de nickel de 10 à 80 millimoles par litre.
2. Procédé suivant la revendication 1, caractérisé en ce que le bain présente une température allant jusqu'à 30°C.
3. Procédé suivant les revendications 1 et 2, caractérisé en ce que le bain présente une température de 20 à 25°C.
4. Procédé suivant les revendications 1 à 3, caractérisé en ce que le bain n'est pas agité.
5. Procédé suivant les revendications 1 à 4, caractérisé en ce que le bain contient, en des quantités de 500 ppb à 50 ppm, des ions des métaux suivants: cobalt, aluminium, zinc, chrome, cuivre, palladium, platine.
6. Utilisation du procédé suivant les revendications 1 à 5 pour la fabrication de cathodes pour l'électrolyse à l'alcali-chlore.
EP86112216A 1985-09-14 1986-09-04 Procédé de fabrication d'électrodes Expired EP0215381B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3532866 1985-09-14
DE19853532866 DE3532866A1 (de) 1985-09-14 1985-09-14 Verfahren zur herstellung von elektroden

Publications (2)

Publication Number Publication Date
EP0215381A1 EP0215381A1 (fr) 1987-03-25
EP0215381B1 true EP0215381B1 (fr) 1989-11-23

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EP86112216A Expired EP0215381B1 (fr) 1985-09-14 1986-09-04 Procédé de fabrication d'électrodes

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DE (2) DE3532866A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007043333A1 (fr) * 2005-10-07 2007-04-19 Nippon Mining & Metals Co., Ltd. Solution de nickelage autocatalytique
US11482607B2 (en) * 2018-12-05 2022-10-25 Mitsubishi Electric Corporation Semiconductor device and method for manufacturing semiconductor device

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2307852C3 (de) * 1973-02-17 1975-12-11 Deutsche Automobilgesellschaft Mbh, 3000 Hannover Luft- und Lagerbeständige Katalysatoren für die kathodische Wasserstoffentwicklung

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Publication number Publication date
DE3532866A1 (de) 1987-03-26
DE3667076D1 (en) 1989-12-28
EP0215381A1 (fr) 1987-03-25

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