Electrocatalytic composition for oxygen-depolarised cathode
AssigneeDe Nora Electtrodi S.p.A.
InventorsGian Nicola Martelli, Fulvio Federico
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Abstract
An oxygen-depolarised cathode for aqueous hydrchloric acid electrolysis membrane cells is described, the cathode being in contact with the membrane and capable of preventing the release of hydrogen into oxygen even at the highest current densities. Hydrochloric acid may also be of technical grade with a concentration limited to 15%, whereas the operating temperature must not exceed 60° C. The cathode contains a mixture of rhodium sulphide and a metal of the platinum group applied in a single layer or alternatively applied separately in two distinct layers.
Claims22
An oxygen-depolarised cathode for hydrochloric acid electrolysis membrane cells, comprising an inert conductive substrate and a set of catalysts, said set comprising rhodium sulphide and at least one metal of the platinum group.
The cathode of the preceding claims characterised in that said rhodium sulphide and said at least one metal of the platinum group are mixed in a catalytic layer.
The cathode of the preceding claims, characterised in that at least one of the catalytic layers comprises an inert polymeric binder.
The cathode of the preceding claims, characterized in that said at least one metal of the platinum group is selected from the group comprising platinum, iridium and palladium.
The cathode of the preceding claims, characterised in that the particles of said rhodium sulphide have an average size ranging within 10 and 100 nanometres.
The cathode of the preceding claims, characterised in that the particles of said at least one metal of the platinum group have an average size ranging within 200 and 500 nanometres.
The cathode of the preceding claims, characterised in that the load of said rhodium sulphide ranges within 0.5 and 1 mg/cm2 given as metal.
The cathode of the preceding claims, characterised in that said at least one metal of the platinum group is contained in quantity ranging between 1 and 20% by weight of the load of said rhodium sulphide.
A hydrochloric acid electrolysis cell divided by at least one ion exchange membrane in at least one cathodic compartment and at least one anodic compartment said at least one anodic compartment comprising connections for the feeding of aqueous hydrochloric acid and the withdrawal of the residual acid and of the product chlorine, said at least one cathodic compartment comprising connections for the feeding of oxygen or an oxygen-containing gas and for the withdrawal of residual oxygen and reaction water, characterised in that said at least one cathodic compartment comprises at least one cathode of the preceding claims.
The process of claims from 17 to 19 characterised in that said hydrochloric acid has a concentration not exceeding 15%.
The process of claims from 17 to 20 characterised in that the operating temperature does not exceed 60° C.
The process of claims from 17 to 21 characterised in that said residual oxygen extracted from said cathodic compartment is substantially free of hydrogen.
Dependencies are inferred from the claim text.