Eltech Systems Corporation

Diamond Shamrock Corporation

Diamond Shamrock Technologies S.a.

Diamond Shamrock Chemicals Company

Henri B Beer

Jean M Hinden

Jeries I Bishara

Vittorio De Nora

Michael Katz

Thinh Trong Nguyen

Mark R Honard

Joseph K Walker, Jr

Jean-Marie Fresnel

Frans A Van Den Keybus

William A Kovatch

Lucovicus F Suykerbuyk

Theo L Muller

Franz A Van Den Keybus

Dirk Arnouts

An electrode for use in electrolytic processes having a substrate of film-forming metal comprises an electrocatalyst incorporated in an integral surface film of the film-forming metal oxide grown from the substrate. The electrocatalyst incorporated in the integral surface film comprises two superimposed layers, a first layer comprising platinum metal and a second layer comprising an oxide of iridium, rhodium, palladium or ruthenium, the first platinum containing layer being next to the substrate and the second iridium, rhodium, palladium or ruthenium oxide containing layer being at the outer surface of the integral surface film of the film-forming metal oxide. The electrode comprising the two superimposed layers may be further coated with another electrochemically active catalytic outer layer in which case said superimposed layers serve as the electrode underlayer. The electrode is particularly useful as an oxygen evolving anode in high speed electroplating (electrogalvanizing).

Electrode with a platinum metal catalyst in surface film and its use

The precipitation or deposition of particles from a solution in a cell (61) which an electric field is applied between an anode (65,67,68) and a cathode (66), typically an electrolysis cell for the co-precipitation of mixed oxides but also cells for electrodeposition or the electrophoretic deposition of colloidal particles, is controlled by measuring the pH of the solution in the cell using a probe (72) shielded in a tube (73) from the migrating electric current and from gas bubbles. The pH of the solution is then adjusted to a selected value as a function of the measured pH, e.g. by varying the electrolysis current or by bubbling in acid vapor, air or base vapor.

Fine, uniform particles, and precipitation or depositing of particles

A porous high surface area composite electroconductive catalytic material, particularly as electrocatalyst for electrolysis electrodes, comprises a porous pre-formed matrix which is a catalytic mixed crystal material of at least one platinum group metal oxide and at least one valve metal oxide throughout which a subsequently-added additional catalyst preferably consisting of at least one platinum group metal and/or oxide is dispersed by chemideposition in an oxidizing or reducing atmosphere preferably followed by an annealing post heat treatment. The porous matrix may be ruthenium-titanium oxide and the additional catalyst advantageously comprises at least two oxides of ruthenium, rhodium, palladium and iridium, other combinations being possible.

Composite catalytic material particularly for electrolysis electrodes

Narrow gap electrolysis cells

An electrode having a lead base and a catalyst is manufactured by (a) compressing titanium sponge particles so as to consolidate them to a coherent porous layer, (b) applying the catalyst to the titanium sponge particles, and (c) fixing the layer of consolidated sponge particles to the lead base. The catalyst is formed on the titanium sponge particles before or after their consolidation to a coherent layer. This layer may be produced and fixed to the base in a single compressing and fixing step combining (a) and (c). Oxygen is anodically evolved at a reduced, stable potential by means of this electrode, so that it can be usefully applied as an anode in processes for electrowinning metals from acid electrolytes.

Manufacture of electrodes with lead base

A method of making a catalytic lead-based oxygen-evolving anode comprises catalytically activating titanium sponge particles larger than 300 microns by impregnating with a solution containing Mn and Ru compounds, in amounts corresponding to Mn/Ru in an atomic ratio between 70/30 and 90/10, and thermally converting the compounds to an electrocatalyst comprising Mn and Ru in oxide form. Catalytic Ti sponge particles with up to 3 wt % Ru are thus produced, which are then uniformly distributed on the surface of a lead anode base in an amount greater than 400 g/m.sup.2, pressed, and partly embedded, thereby firmly anchoring and electrically connecting them to the lead anode base. The catalytic lead-based anode thus produced operates with oxygen evolution on the catalytic particles at a reduced potential at which the lead base remains electrochemically inactive. It thereby operates with significant energy savings over an extended service life.

Method of making a catalytic lead-based oxygen evolving anode

An electrode for use in electrolytic processes comprises a base of film-forming metal such as titanium with an operative outer electrocatalytic surface which is an integral surface film of a compound of the titanium base, usually the oxide, incorporating a platinum-group metal electrocatalyst, preferably iridium, rhodium, palladium and/or ruthenium as metal or oxide. The surface film is formed by the application of a dilute solution of a thermodecomposable iridium, rhodium and/or ruthenium compound containing an agent such as HCl which attacks the titanium base and converts metal from the base into ions which are converted to the compound in a subsequent heating step. The concentrations of this agent and of the thermodecomposable compound and the number of applied layers are such that during heating the electrocatalyst formed from the decomposed compound is incorporated fully in the surface film formed from the base. The base is usually in sheet form, but may also be a powder.

Electrode with electrocatalytic surface

Metals such as lead, silver, copper, calcium, antimony, cadmium, nickel and zinc are electroplated onto a film-forming metal substrate from the group of aluminium, titanium, zirconium, niobium, molybdenum, tungsten, tantalum and alloys thereof, using an etching/electroplating solution comprising ions of the metal(s) to be plated, optionally alkali metal ions, aluminium halide and an aromatic hydrocarbon. Surface oxide is removed from the film-forming metal substrate by reaction with the aluminium halide and the metal(s) in solution to form soluble complexes, this possibly being assisted by anodization. This is followed by cathodically connecting the substrate and passing current to electroplate the metal(s) onto the oxide-free surface, directly in the same etching/electroplating solution.

Electroplating film-forming metals in non-aqueous electrolyte

An electrode for use in an electrolytic process is provided with a mixed oxide interface between a titanium base and an outer coating. The mixed oxide is formed at said interface by means of titanium from the base and noble metal from a solution containing a predetermined amount of HCl which attacks the titanium base surface. Slow drying provides a metal chloride mixture which is thermally converted to said mixed oxide of titanium and noble metal in a given ratio, whereby to protect the titanium base from oxidation. An outer coating of manganese dioxide or lead dioxide is electroplated on the mixed oxide layer so as to provide an inexpensive electrode with improved resistance to oxidation. This electrode can be used for various processes where a high resistance to oxidation is required, e.g. as a manganese dioxide anode in a metal electrowinning process or as a lead dioxide anode for electroflotation or organic oxidation reactions.

Dimensionally stable coated electrode for electrolytic process,

An anode with a base of lead or lead alloy is provided with catalytic particles of titanium which comprise a very small amount of platinum group metal or an oxide thereof. These catalytic particles are partly embedded, anchored and electrically connected to the base, so that oxygen is evolved on these particles at a reduced potential at which the underlying lead or lead alloy of the base remains electrochemically inactive, and the anode base thereby serves only as a stable conductive support to the catalytic particles. Operation of this anode at a reduced potential provides energy savings. It may be used more particularly in cells for electrowinning metals with a higher degree of purity at a reduced energy cost with respect to conventional cells equipped with anodes consisting of lead or a lead alloy.

Anode with lead base and method of making same

An electrode for use in electrolytic processes comprises a substrate of film-forming metal such as titanium having a porous electrocatalytic coating comprising at least one platinum-group metal and/or oxide thereof possibly mixed with other metal oxides, in an amount of at least about 2 g/m.sup.2 of the platinum-group metal(s) per projected surface area of the substrate. Below the coating is a preformed barrier layer constituted by a surface oxide film grown up from the substrate. This preformed barrier layer has rhodium and/or iridium as metal or compound incorporated in the surface oxide film during formation thereof in an amount of up to 1 g/m.sup.2 (as metal) per projected surface area of the substrate.

Coated metal electrode with improved barrier layer

In the production of electrolytic manganese dioxide, the anodically-deposited product is removed by cathodically polarizing the electrode, possibly assisted by impact or vibration. Typically, the current is reversed periodically when the deposit is about 100-1500.mu. thick and shortly after current reversal, the product peels off as flake-like particles which can easily be ground to form a battery de-polarizer. An apparatus for use in carrying out the removal of the desired product from electrodes is disclosed and illustrated.

Production of electrolytic manganese dioxide

A method of making an electrode for use in an electrolytic process. The electrode has a core of a film-forming metal and a layer having at least a part of the outside portion of the thickness thereof of an electrolyte resistant and electrolysis product resistant material, which material contains as the material effective for carrying out electrolysis at least one oxide of at least one platinum metal taken from the group consisting of platinum, iridium, rhodium, palladium, ruthenium and osmium. The method comprises forming the platinum metal on the core and then oxidizing it, forming the oxide and then applying it to the core, or forming the oxide directly on the core, for example, by heating a solution of a salt of the metal or electrolysis.

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Heide Kalmthout, Belgium

Henri B Beer