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: A halogen, such as chlorine, is generated by electrolysis of an aqueous solution of an alkali metal halide such as sodium chloride, in a cell having anolyte and catholyte chambers separated by a solid polymer electrolyte in the form of a stable, selectively cation permeable, ion exchange membrane. One or more catalytic electrodes including at least one thermally stablized, reduced oxide of a platinum group metal are bonded to the surface of the membrane. An aqueous brine solution is brought into contact with the anode and water or an aqueous NaOH solution is brought into contact with the cathode. The brine is electrolyzed to produce chlorine at the anode and hydrogen and caustic at the cathode. The cell membrane preferably has an anion rejecting cathode side barrier layer which rejects hydroxyl ions to block back migration of caustic to the anode thereby enhancing the cathode current efficiency of the cell and of the process.

Abstract: A unitary membrane-electrode assembly includes an electrode structure with multiple layers having different overvoltages for the desired electrochemical reaction. In the preferred arrangement the layer attached to the membrane has the higher overvoltage thereby preferentially locating the reaction zone a small but controlled distance away from the electrode membraneinterface. In a NaCl brine electrolysis process the use of a dual layer electrode as the cathode is particularly useful because it eliminates formation of concentrated caustic at the membrane surface. As a result, back migration of OH.sup.- ions is reduced and cathodic current efficiency is increased.

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: The present invention provides an electrode having a coating made of electrocatalytic ceramic materials on substantially incompatible metal substrates, by resorting to the use of an anchoring pre-coating or interlayer, applied over the metal substrate advantageously by galvanic electrodeposition, said pre-coating generally consisting of an inert metallic matrix containing particles of a ceramic material which preferably is compatible or even isomorphous with respect to the ceramic material constituting the superficial or external electrocatalytic coating.Adhesion to the metal substrate and electrical conductivity through the coating result thereby greatly improved.Further, the electrolysis of sodium chloride in cells provided with the electrode of the present invention is more efficient and less problematic.

Abstract: The present invention provides an electrode having a coating made of electrocatalytic ceramic materials on substantially incompatible metal substrates, by resorting to the use of an anchoring pre-coating or interlayer, applied over the metal substrate advantageously by galvanic electrodeposition, said pre-coating generally consisting of an inert metallic matrix containing particles of a ceramic material which preferably is compatible or even isomorphous with respect to the ceramic material constituting the superficial or external electrocatalytic coating.Adhesion to the metal substrate and electrical conductivity through the coating result thereby greatly improved.Further, the electrolysis of sodium chloride in cells provided with the electrode of the present invention is more efficient and less problematic.

Abstract: The invention is a monopolar electrochemical cell assembly of the type having two end members and at least one electrode unit positioned between said end members, said unit at least having:two substantially parallel, substantially planar electrode components spaced from each other;a sealing means around the perimeter of the unit; anda means to distribute electrical energy to each of said electrode components, said distributing means comprising:an electrically conductive, substantially rigid, planar electric current transmission element disposed in the space between said spaced electrode components said transmission element co-extensive with and extending beyond the perimeter of said electrode components and having a metallic electrical connection means attached to it suitable for conducting electrical current in or out of said transmission element;said transmission element being electrically and mechanically connected to each of said electrode components at a plurality of points spaced throughout the entire s

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: Shunt currents which flow between the electrodes of adjacent cells through the moving conductive fluid and the fluid pool in the manifold of a bipolar cell assembly are minimized by introducing the conductive fluid at the top of an elongated outlet manifold. This results in cascaded flow which interrupts the current path. Shunt currents between the fluid manifold walls of the conductive bipolar elements in the series connected electrochemical cell assemblies are minimized by insulating the manifold walls with insulating, elastomeric sealing grommets. This prevents current flow between the manifold walls through the electrically conductive fluid in the manifold and provides an edgeseal between bipolar plates.The instant invention relates to a process and apparatus for electrochemical cell assemblies and more particularly, for reducing shunt current in series connected bipolar assemblies.

Abstract: Anodes having a substantially impermeable coating or surface, obtained by moulding under pressure and heat an electrocatalytic layer consisting of a mixture of powders of an electrocatalytic material and inert thermoplastic resin on a conductive body or substrate, consisting of a mixture of powders of graphite and inert resin, resist surprisingly well to the electrochemical attack and offer significant advantages over the much more expensive activated titanium anodes.

Abstract: A bipolar diaphragm or membrane electrolyzer comprising a housing containing an end anode element, an end cathode element and a plurality of bipolar elements with their major dimensions lying in a substantially vertical plane and comprised of a bipolar wall separating the anode compartment and the cathode compartment and vertical foraminous electrodes parallel positioned a certain distance from the bipolar wall, diaphragms or membranes separating the anodes and cathodes, a series of baffles distributed along the entire width of the electrode compartment and extending from the bipolar wall to the foraminous electrode to form a series of vertical flow channels extending over a large portion of the height of the wall, the said baffles being alternately inclined one way and the other way with respect to the vertical plane normal to the bipolar wall plane and spaced from one another whereby the ratio of the electrode surface intercepted by the edges of two baffles laterally defining a vertical flow channel to the

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: 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: An electrolysis cell comprising a housing containing a plurality of alternating anode units and cathode units and an ion permeable membrane sheet disposed therebetween and having bonded to opposite sides of the membrane sheet a porous anode and a porous cathode, said cathode units comprising a pair of spaced foraminous electrical current cathode distributors of the same polarity forming a space for catholyte therebetween and means for flowing aqueous electrolyte through the catholyte space of the cathode unit and means for removing electrolysis products, the anode units comprising a pair of spaced foraminous electrical current anode distributors forming a space for anolyte therebetween, means for flowing aqueous halide solution through the said anolyte space and means for removing electrolysis products therefrom and means for uniformly compressing the units and membranes together whereby the current distributors are in firm electrical contact with their respective electrodes and to a novel method of generatin

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 or too high pressure is minimized or reduced.

Abstract: A process and an apparatus for producing alkali metal hypohalite by passing an alkali metal brine solution through the anode compartment of an electrolytic cell in which the anode compartment and the cathode compartment are separated by a fluid impervious, anion-permeable membrane, providing an aqueous support catholyte into the cathode compartment, impressing an electric potential across the anode and cathode to evolve halogen at the anode and hydrogen at the cathode and recovering alkali metal hypohalite from the anode compartment.

Abstract: Mass transfer to the surface of a substantially horizontal, foraminous gas-evolving electrode, suspended in the electrolyte pool over a co-operating electrode, is improved by inducing a vigorous multiple recirculation motion of the electrolyte to and from the interelectrodic gap through the openings in the foraminous electrode exploiting the gas lift of evolved gas bubbles by means of a multiplicity of baffles, alternatively slanting one way and the opposite with respect to the vertical axis, and defining, with their lower edges, an alternating series of large and small areas over the foraminous electrode surface; electrodes and cells incorporating the hydrodynamic means to effect recirculation are also disclosed.

Abstract: Cationic membranes permeable to ions but fluid impermeable comprising a partly sufonated terpolymer of styrene, divinylbenzene and at least one member of the group consisting of 2-vinylpyridine, 4-vinylpyridine and acrylic acid, the degree of sulfonation varying through the membrane cross-section from a maximum at the anodic surface to a minimum at the cathodic surface, their preparation, their use in electrolysis cells and electrochemical processes.

Abstract: Porous and electrolyte permeable composite diaphragms for electrolysis cells comprising a chemically inert, fibrous porous matrix or substrate impregnated with a copolymer of divinylbenzene and at least one member of the group consisting of 2-vinylpyridine and 4-vinylpyridine, method of electrolysis of an electrolyte using the said diaphragms and an electrolysis cell containing said diaphragms.

Abstract: A method of reducing ferric ions in a sulfuric acid ilmenite leach solution to ferrous ions comprising circulating a sulfuric acid ilmenite leach catholyte solution through the cathodic compartment of an electrolysis cell separated by a fluid-impervious anion exchange membrane from the anodic compartment, circulating a ferrous sulfate anolyte solution through the anodic compartment of the electrolysis cell and impressing an electrolysis current across the cell to reduce the ferric ions in the catholyte to ferrous ions and to oxidize a portion of the ferrous ions to ferric ions in the anolyte to prevent oxygen evolution in the anodic compartment and to an off-peak method of electrolysis operation to reduce energy consumption and to reduce or eliminate ferrous sulfate by-product.