Abstract: The invention concerns a diaphragm chlor-alkali electrolysis cell comprising a cover, a conductive base for supporting the anodes and a cathode in the form of a box provided with internal wall, external wall and tubular fingers made of a mesh or perforated sheet covered with a porous diaphragm. One or more copper sheets for electric current distribution are fixed to the cathode external walls. The connection between the copper sheets and the cathode external walls is made by means of bolts with the interposition of a conductive and deformable element provided with residual elasticity under compression. The weldings for the assembling of the cathode walls are free from internal stresses.

Abstract: Bipolar plate made of a composite material for use in a filter-press electrolyzer. Said plate comprises a central portion (6) which is electrically conductive and is obtained by heat-pressing of a mixture of graphite or conductive carbon and a thermoplastic polymer powder resistance to corrosion and two terminal portions (7,8) containing the distribution holes (2,3,4,5) for the inlet of the fresh electrolytes and for the outlet of the exhausted electrolytes and electrolysis products. Said terminal portions are integral with the central portion and are obtained during said heat-pressing from a mixture of graphite or conductive carbon and said thermoplastic polymer powder with a ratio between said powders lower than that of the central portion. Said mixture of the terminal portions may further contain also a non-conductive compound powder, in which case the mixture may also be free from graphite or conductive carbon powder.

Abstract: The present invention refers to an electrochemical cell or stack of cells comprising two end-plates (7), bipolar plates (1) made of metal or metal alloy, gas permeable metal distributors (2), metal current collectors(3), gasket frames (4) provided with channels for feeding the gaseous reactants and discharging the excess reactants and condensates, a couple of gas diffusion electrodes, (5), an ion-exchange membrane (6), wherein said current conductors provide for a highly distributed segmented contact area on the electrode surface without isolated peaks and have an extremely smooth surface without asperities and at the same time porous and permeable to the gas flow.

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: The present invention describes an improved electrode suitable for application in solid polymer electrolyte fuel cells, comprising a thin, porous, planar, conductive substrate having one side coated with a pre-layer consisting of conductive carbon having a low surface area mixed to a first hydrophobic agent, to which is applied a catalytic layer consisting of platinum supported on conductive carbon with a high surface area, mixed to a second hydrophobic agent. The hydrophobic degree of the applied layers are suitably adjusted to obtain the best exploitation of the catalyst and to improve the water balance of the process.

Abstract: The invention discloses a novel structure for an expandable anode to be used in diaphragm cells. This new structure comprises a conductor bar in the form of a copper core provided with a titanium layer having a first and a second pair of flexible expanders fixed thereto. The welding points of the second pair of expanders are positioned orthogonally with respect to the welding points of the first pair of expanders along the circumference of the conductor bar. Also the anode surfaces are connected by welding points to the pairs of expanders. The anode of the invention may be both a new anode and a conventional existing anode having only a first pair of expanders whereto the second pair of expanders is attached. With the device of the present invention the ohmic drop between the conductor bar and the anode surface is substantially decreased and further there is no risk of damaging the interface between the copper core and the titanium coating by an excessive thermal stress, due to the welding procedures.

Abstract: A reactivation method for an electrolyzer for the production of sodium hydrochlorite and chlorate, equipped with interleaved plates acting as anodes and cathodes, wherein at least the anode plates are provided with foraminous sheets having an electrocatalytic coating and a planar profile, said sheets being applied to the anode plates by means of a multiplicity of connection points.

Abstract: A gas diffusion electrode comprising an electrically conductive web provided on at least one side thereof with a coating containing a rhodium--rhodium oxide catalyst on a carbon black support and a method for the preparation of the rhodium--rhodium oxide catalyst.

Abstract: The invention concerns membrane electrolyzers suitable for processes such as water or hydrogen halides electrolysis, as well as electrochemical generators fed with gases containing hydrogen and oxygen for direct conversion into electric energy. These apparatuses generally consist of a filter-press assembly of conductive bipolar plates (2), electrodes (4), sealing gaskets (5) membranes (6) and internal longitudinal ducts for feeding the reactants and withdrawing the products and residual reactants. The invention is directed to the method for repairing said electrolyzers or generators when an elementary cell is malfunctioning. This method comprises making at least two perforations in the peripheral area of the bipolar plates (2) and/or gaskets (5) of the malfunctioning cell to reach distribution channels (9, 11) which connect the compartments containing the electrodes (4) with said longitudinal ducts.

Abstract: The invention concerns an improved electrode particularly useful for electrochemical processes forming gaseous products. The electrode is made of a composite structure comprising a shaped sheet having a profile of the "venetian blind" type, which provides for ensuring the necessary stiffness and improved local fluodynamics, and a mesh having the same "venetian blind" profile, provided with an electrocatalytic coating. The mesh is fixed by spot welding to the sheet in order to have the two profiles substantially coincident.

Abstract: The invention concerns an improved electrode particularly useful for electrochemical processes forming gaseous products. The electrode is made of a composite structure comprising a shaped sheet having a profile of the "venetian blind" type, which provides for ensuring the necessary stiffness and improved local fluodynamics, and a mesh having the same "venetian blind" profile, provided with an electrocatalytic coating. The mesh is fixed by spot welding to the sheet in order to have the two profiles substantially coincident.

Abstract: The invention concerns an improved electrode particularly useful for electrochemical processes forming gaseous products. The electrode is made of a composite structure comprising a shaped sheet having a profile of the "venetian blind" type, which provides for ensuring the necessary stiffness and improved local fluodynamics, and a mesh having the same "venetian blind" profile, provided with an electrocatalytic coating. The mesh is fixed by spot welding to the sheet in order to have the two profiles substantially coincident.

Abstract: The improved method for the production of chlorine from aqueous solutions of hydrochloric acid in a membrane electrolysis cell comprises a cathode compartment equipped with a gas diffusion cathode fed with air or enriched air or oxygen and an anodic compartment with an anode provided with an electrocatalytic coating for chlorine evolution. Said anode compartment is fed with an aqueous solution of hydrochloric acid having a maximum concentration of 20% and a maximum temperature of 60.degree. C., and containing an oxidizing compound having a redox potential of at least 0 Volts NHE and preferably 0.3-0.6 Volts NHE. A suitable oxidizing compound is trivalent iron in concentrations comprised in the range of 100-10,000 ppm. Both the anodic and cathodic compartment of the cell and their internal structures are made of titanium or alloys thereof, such as 0.2%. titanium-palladium.