Electrode for electrolytic evolution of gas

Abstract

An electrode for gas evolution in electrolytic processes comprising a catalytic coating containing oxides of tin, ruthenium, titanium and one or more elements selected from the group consisting of niobium, tantalum and tungsten applied to a metallic substrate, and a method for its preparation.

1 . An electrode for gas evolution in electrolytic processes comprising a metal substrate and a catalytic coating said catalytic coating comprising tin, ruthenium, titanium and one or more elements selected from the group consisting of niobium, tantalum, tungsten wherein tin is 10-20%, ruthenium is 25-45%, titanium is 20-40%, and one or more elements selected from the group consisting of niobium, tantalum, tungsten is 10-20% in the form of metals or their oxides in percentage by weight referred to the elements. 
     
     
         2 . The electrode according to  claim 1  wherein said one or more elements selected from the group consisting of niobium, tantalum, tungsten is tantalum. 
     
     
         3 . The electrode according to  claim 1  wherein the titanium of said catalytic coating is present in the form of oxide in the rutile form. 
     
     
         4 . The electrode according to  claim 1  wherein the catalytic coating has a ruthenium load comprised between 2.2 and 9 g/m 2 . 
     
     
         5 . A method for the production of an electrode as defined in  claim 1 , comprising the following steps:
 a) applying to a metal substrate a solution comprising the precursors of ruthenium, tin, titanium and one or more elements selected from the group consisting of niobium, tantalum, tungsten, subsequent drying at 50-60° C. and thermal decomposition at 450-600° C. for a time of 5 to 30 minutes until reaching a specific load of ruthenium comprised between 0.4 and 1.2 g/m 2 ;   b) repeating step a) until obtaining a catalytic coating with a specific load of ruthenium comprised between 2.2 and 9 g/m 2 ;   c) thermally treating at 450-600° C. for a time of 50 to 200 minutes.   
     
     
         6 . A cell for the electrolysis of alkaline chloride solutions and/or for electro-chlorination comprising an anodic compartment and a cathodic compartment wherein the anodic compartment is equipped with the electrode according to  claim 1 . 
     
     
         7 . The cell for electrolysis and/or for electro-chlorination according to  claim 6  wherein said anodic compartment and said cathodic compartment are separated by a diaphragm or an ion exchange membrane. 
     
     
         8 . An electrolyzer for the production of chlorine and alkali starting from alkali chloride solutions comprising a modular arrangement of cells according to  claim 7 .