Electrode for oxygen evolution in industrial electrochemical processes

Abstract

The invention relates to a coating for anodes suitable for oxygen evolution in electrochemical processes, comprising one or more catalytic layers and an external layer. Such external layer having a composition based on tantalum oxides or tin oxides or zirconium oxides in an amount of 2 to 7 g/m 2 .

We claim: 
     
         1 - 9 . (canceled) 
     
     
         10 . Electrode for oxygen evolution in electrochemical processes comprising a valve metal substrate, a catalytic coating comprising a first layer of oxides of iridium and tantalum having a molar composition Ir 60-70%, Ta 30-40% referred to the metals and an external coating consisting of 2 to 7 g/m 2  of a single valve metal oxide. 
     
     
         11 . The electrode according to  claim 10  wherein said valve metal oxide is selected from the group consisting of tantalum oxide, tin oxide and zirconium oxide. 
     
     
         12 . The electrode according to  claim 11  wherein said external coating consists of 2.9 to 3.5 g/m 2  of a valve metal oxide selected between tantalum oxide, tin oxide and zirconium oxide. 
     
     
         13 . The electrode according to  claim 10  wherein said catalytic coating further comprises a second layer of oxides of iridium, tantalum and titanium having a molar composition Ir 76-84%, Ta 15-23%, Ti 0.2-1.3% referred to the metals interposed between said first catalytic layer and said external coating. 
     
     
         14 . The electrode according to  claim 10  wherein said catalytic coating has a specific loading of iridium of 5 to 50 g/m 2 . 
     
     
         15 . The electrode according to  claim 10  comprising an intermediate protective layer based on oxides of titanium or tantalum interposed between said substrate and said catalytic coating. 
     
     
         16 . The electrode according to  claim 15  wherein said catalytic coating has a specific loading of iridium of 8 to 15 g/m 2 . 
     
     
         17 . Method of manufacturing an electrode according to  claim 10  comprising the formation of said external coating by application and subsequent thermal decomposition of a solution containing a precursor of tantalum or tin or zirconium. 
     
     
         18 . Industrial electrochemical process comprising the anodic evolution of oxygen from an electrolytic bath on an electrode of according to  claim 10 .