Abstract: It is described a novel type of electrode suitable for use as an anode for oxygen evolution from electrolytes containing sulphuric acid, or sulphates, in the presence of manganese, in electrometallurgical processes for the production of zinc, copper, nickel and cobalt and galvanic processes for the deposition of chromium, nickel and noble metals. The anode of the invention comprises a titanium substrate provided with an electrocatalytic coating for oxygen evolution made of iridium and bismuth oxides. In an alternative embodiment of the invention the coating comprises doping agents selected from the groups IV A, V A and V B, particularly tin and/or antimony.

Abstract: A new electrocatalytic coating to be applied onto a titanium matrix, suitable for oxygen evolution from acid electrolytes containing manganese and fluorides, comprising:a) an external coating for oxygen evolution at controlled potential, immune to manganese electrochemical precipitation and capable of promoting the spontaneous removal of the same during operation, consisting of ruthenium and iridium as the major components (60-85%), tin and cobalt (2-10%) and titanium and tantalum at intermediate concentrations with respect to the previous groups of components.b) an optional interlayer acting as an electroconductive system and protecting the titanium matrix against corrosion caused by fluorides, made of titanium and tantalum as the major components (<95%) and iridium (>5%) as the minor component.At least part of the above elements are in the form of oxides.

Abstract: The invention discloses a new electrode suitable for use as an anode for oxygen evolution from electrolytes containing fluorides or fluoride-complex anions even in high concentrations.The anode of the invention comprises a titanium substrate provided with a protective interlayer resistant to the aggressive action of fluorides, and an electrocatalytic coating for oxygen evolution.The protective interlayer is made of tungsten, oxides or oxyfluorides, optionally containing metals of the platinum group in minor quantities, metallo-ceramic compounds and intermetallic compounds either per se or as mixed oxides.

Abstract: A process for the electrolytic recovery of metals from solutions containing metal ions and fluorides and/or anionic flurocomplexes in diaphragmless cells wherein the deposition of the metals at the cathodes and the oxygen evolution at the anodes is effected, the improvement comprising the use of insoluble anodes made of sintered powders of doped tin dioxide optionally provided with coating of zirconyl phosphate and metal oxides which prevents the deposition of metal oxides on the anode surface and catalyze the oxygen evolution reaction.

Abstract: The present invention relates to metal anodes for oxygen evolution from solutions containing fluorides or artionic fluorocomplexes such as tetrafluoroborates and hexafluorosilicates, the anodes having a metal substrate or matrix selected in the group comprising nickel-copper alloys with a copper content in the range of 2.5 and 30% by weight, tungsten or tantalum, niobium or titanium, combinations thereof or alloys of the same with palladium, nickel or yttrium. The anodes further comprise electrocatalytic compounds for oxygen evolution dispersed in the metal matrix. In the case of nickel- copper alloys, useful electrocatalytic compounds are cerium or tin dioxides, with suitable additives, while for tungsten, cobalt added with nickel, iron, copper or palladium may be used.

Abstract: An electrode comprising a gas permeable and liquid permeable coating bonded to an ion exchange membrane, said coating comprising low overvoltage electrocatalytic particles, more electroconductive electrolyte resistant particles and an electrolyte resistant binder compatible with the membrane to bond the particles thereto, the electrode coating being provided with a plurality of pores with a pore size of at least 0.1 microns.Effective porosity is imparted to the layer of particles by means of a sacrificial, pore-forming agent and by leaching out such agent after the particles have been bonded together and the layer formed is in its desired thickness, preferably after it has been deposited upon the membrane.Surface resistivity of the layer is reduced and the layer is effectively reinforced by incorporating electroconductive particles which often have a higher overvoltage than the electrocatalytic particles and also have high electroconductivity.

Abstract: An electrode comprising a gas permeable and liquid permeable coating bonded to an ion exchange membrane, said coating comprising low overvoltage electrocatalytic particles, more electroconductive electrolyte resistant particles and an electrolyte resistant binder compatible with the membrane to bond the particles thereto, the electrode coating being provided with a plurality of pores with a pore size of at least 0.1 microns.Effective porosity is imparted to the layer of particles by means of a sacrificial, pore-forming agent and by leaching out such agent after the particles have been bonded together and the layer formed is in its desired thickness, preferably after it has been deposited upon the membrane.Surface resistivity of the layer is reduced and the layer is effectively reinforced by incorporating electroconductive particles which often have a higher overvoltage than the electrocatalytic particles and also have high electroconductivity.

Abstract: The present invention concerns electrodes for use in electrochemical processes, particularly as cathodes for hydrogen evolution in cells for the electrolysis of alkali metal halides, the electrodes comprising an electrocatalytic ceramic coating obtained by thermal deposition. Elements of the groups IB, IIB, IIIA, IVA, VA, V B; VI A; VI B and VIII are added to the solutions or dispersion of precursor compounds of electrocatalytic ceramic materials, the solutions or dispersions being thermally decomposed to obtain the coating.The surface of the doped coating thus obtained is substantially immune to poisoning by metal impurities, when the electrode according to the present invention is used as cathode in poisoned alkali solutions.

Abstract: The present invention concerns a method for preparing electrodes for use in electrochemical processes, said electrodes being constituted by a conductive support whereto an electrocatalytic coating is applied by galvanic deposition from a galvanic plating bath which additionally contains the groups IB, IIB, IIIA, IVA, VA, VB, VIB, VIII Of the periodic table.The electrodes of the invention, obtainable according to the method of the invention, when used as cathodes in membrane or diaphragm chlor-alkali cells, exhibit low hydrogen overvoltages, constant with time, and are substantially immune to poisoning by iron, mercury or other metal impurities present in the alkaline solutions.

Abstract: In a process for the electrolysis of alkali metal chloride conducted in a cell comprising a porous, gas and liquid permeable anode and a porous, gas and liquid permeable cathode separated by an ion exchange polymeric membrane impervious to the hydrodynamic flow, wherein the electrodes are in contact or in any way close to the membrane surface in order to reduce the interelectrodic gap, the insertion of a thin porous sheet, fluid permeable and highly hydrophilic, between the membrane and the cathode surfaces, allows for the considerable reduction of the cell voltage.

Abstract: An anode comprising an electroconductive substrate, whose external surface at least is selected from the group consisting of vanadium, niobium, tantalum and tungsten, alloys of said metals with each other and alloys of said metals with at least one metal selected from the group consisting of metals of groups IIIB and IV of the Periodic Table, lanthanides, actinides, the external surface having a corrosion resistant electrocatalytic coating of at least one member of the group consisting of noble metals and alloys thereof, noble metal oxides and non-noble metal oxieds, characterized in that the coating also contains at least one compound of an element selected from the group consisting of arsenic, antimony, bismuth, tin, for metal recovery from acid solutions based on fluodide-containing complex anions and an electrochemical cell.

Abstract: A gas and electrolyte permeable metal layer is bonded to an ion-permeable membrane by electroless deposition to produce a permeable metal deposit upon the membrane or diaphragm. Advantageously, the membrane surface to be coated is pretreated with an amphoteric material. Thereafter, the treated surface is treated to deposit the coating. Typical metals deposited include platinum group metals, iron group metals, such as nickel, cobalt and others including gold and silver. The coatings are very thin, rarely in excess of about 50 to 100 microns.The coated membrane may be installed in an electrolytic cell used for producing chlorine and alkali by electrolysis of alkali metal chloride with the coating serving as one electrode and another opposed electrode on or adjacent to the opposite side of the membrane. It may also be used in water electrolysis and for other purposes.The coatings may be thickened by depositing other coatings of the same or different composition by suitable coating techniques.

Abstract: The present invention concerns a method for preparing electrodes for use in electrochemical processes, said electrodes being constituted by a conductive support whereto an electrocatalytic coating is applied by galvanic deposition from a galvanic plating bath which additionally contains the groups IB, IIB, IIIA, IVA, VA, VIA, VIB, VIII of the periodic table.The electrodes of the invention, obtainable according to the method of the invention, when used as cathodes in membrane or diaphragm chlor-alkali cells, exhibit low hydrogen overvoltages, constant with time, and are substantially immune to poisoning by iron, mercury or other metal impurities present in the alkaline solutions.

Abstract: Halogen is produced by electrolyzing an aqueous halide in a specially designed cell. The cell comprises an anolyte chamber and a catholyte chamber separated by a permeable membrane or diaphragm, notably an ion exchange (generally cation exchange) polymer. At least one electrode comprises at least two sections. One section comprises a gas and electrolyte permeable layer, sheet or mat having a catalytic surface, i.e. one having a low overvoltage, (low hydrogen overvoltage if the cathode and low halogen overvoltage if the anode). This layer is spaced from the membrane by a second portion comprising an electroconductive resiliently compressible layer or mat, which is in contact with the membrane on one side thereof, the other side thereof being in contact with the main cathode.This second or spacer section advantageously has an electrode surface having a higher overvoltage than the first electrode surface. Preferably the cathode has the above construction.

Abstract: Anodes made of lead or lead alloys, used for the evolution of oxygen from sulphuric acid solutions, particularly in metal electrowinning processes, are made more catalytic by treating them in an oxidizing bath of hydrated molten salts, in particular comprising highly oxidizing persalts or nitrates, of cobalt, iron and nickel.After treatment, the anodes exhibit an extraordinary low oxygen overvoltage and allow a considerable saving of energy in comparison with untreated anodes.

Abstract: Anodes made of lead or lead alloys, used for the evolution of oxygen from sulphuric acid solutions, particularly in metal electrowinning processes, are made more catalytic by treating them in an oxidizing bath of hydrated molten salts, in particular comprising highly oxidizing persalts or nitrates, of cobalt, iron and nickel.After treatment, the anodes exhibit an extraordinary low oxygen overvoltage and allow a considerable saving of energy in comparison with untreated anodes.

Abstract: A cell is provided having an anode and cathode separated by an ion permeable membrane or diaphragm wherein an electrode layer is bonded to or otherwise embedded in on at least one and usually to both sides of the membrane. Polarity is imparted to a bonded or embedded electrode by pressing a crinkled resiliently compressible fabric against the membrane carrying the electrode layer. This fabric is substantially coextensive with the electrode layer and is constructed so that when compressed it exerts a substantially uniform elastic reaction pressure against the membrane carrying the electrode layer or a pliable foraminous sheet, i.e. screen, interposed between the membrane carrying the electrode layer and the resiliently compressible fabric. The resiliently compressible fabric has the ability of also transmitting pressure laterally so that pressure applied may distribute across the entire area of the layer and tendency to have local areas of too low of too high pressure is minimized or reduced.

Abstract: A process for preparing an electroconductive metal coating on a substrate wherein precursor compounds capable of decomposing to form an electroconductive coating are subjected to localized high intensive heat, followed by rapid cooling, while maintaining the bulk of the substrate and/or the surrounding atmosphere at a lower temperature.The process is particularly suited for preparing valve metal substrates coated with mixed oxides comprising at least one metal belonging to the platinum group and a valve metal. Such can be utilized as dimensionally stable anodes in electrolytic processes. The process is moreover useful for applying oxides coating on metal and non-metal substrates of different kinds, such as ceramics, glass, plastics and polymeric organic supports.

Abstract: Halogen is produced by electrolyzing an aqueous halide in a specially designed cell. The cell comprises an anolyte chamber and a catholyte chamber separated by a permeable membrane or diaphragm, notably an ion exchange (generally cation exchange) polymer. At least one electrode comprises at least two sections. One section comprises a gas and electrolyte permeable layer, sheet or mat having a catalytic surface, i.e. one having a low overvoltage, (low hydrogen overvoltage if the cathode and low halogen overvoltage if the anode). This layer is spaced from the membrane by a second section comprising a thin intermediate electroconductive layer, screen or coating which is in contact with the membrane on one side thereof, the other side thereof being in contact with the main cathode.This second or spacer section advantageously has an electrode surface having a higher overvoltage than the first electrode surface. Preferably the cathode has the above construction.

Abstract: A gas and electrolyte permeable metal layer is bonded to an ion-permeable membrane by electroless deposition to produce a permeable metal deposit upon the membrane or diaphragm. Advantageously, the membrane surface to be coated is pretreated with an amphoteric material. Thereafter, the treated surface is treated to deposit the coating. Typical metals deposited include platinum group metals, iron group metals, such as nickel, cobalt and others including gold and silver. The coatings are very thin, rarely in excess of about 50 to 100 microns.The coated membrane may be installed in an electrolytic cell used for producing chlorine and alkali by electrolysis of alkali metal chloride with the coating serving as one electrode and another opposed electrode on or adjacent to the opposite side of the membrane. It may also be used in water electrolysis and for other purposes.The coatings may be thickened by depositing other coatings of the same or different composition by suitable coating techniques.