Method of making an electrode having a coating containing a platinum metal oxide thereon

Abstract

A method of making an electrode for use in an electrolytic process. The electrode has a core of a film-forming metal and a layer having at least a part of the outside portion of the thickness thereof of an electrolyte resistant and electrolysis product resistant material, which material contains as the material effective for carrying out electrolysis at least one oxide of at least one platinum metal taken from the group consisting of platinum, iridium, rhodium palladium, ruthenium and osmium. The method comprises forming the platinum metal on the core and then oxidizing it, forming the oxide and then applying it to the core, or forming the oxide directly on the core, for example, by heating a solution of a salt of the metal or electrolysis.

What is claimed is: 
     
       1. A method of making an electrode comprising forming on at least part of the surface of a core of a film-forming metal a layer containing at least one platinum metal taken from the group consisting of platinum, iridium, rhodium, palladium, ruthenium, rhenium and osmium, and alloys of these metals, the amount of platinum metal being sufficient, when converted to the oxide thereof, to be effective for carrying out electrolysis, and subjecting the layer to oxidizing conditions which are sufficient to oxidize the metal of said layer until the layer is oxidized to a depth of at least about 0.054 micron. 
     
     
       2. A method as claimed in claim 1 in which the core metal is a metal taken from the group consisting of titanium, tantalum, zirconium and niobium and alloys of said metals. 
     
     
       3. A method as claimed in claim 2 comprising oxidizing said core metal for forming an oxide layer on said core metal prior to applying the oxide of the platinum metal. 
     
     
       4. A method as claimed in claim 3 in which the oxide layer is formed on the core metal thermally. 
     
     
       5. A method as claimed in claim 1 in which the step of subjecting the layer to oxidizing conditions comprises applying to it a melt of an oxidizing salt. 
     
     
       6. A method as claimed in claim 5 in which the core is titanium, the metal of the layer is platinum, and the step of subjecting the layer to oxidizing conditions comprises immersing the core having the layer of platinum thereon into a melt of a material taken from the group consisting of sodium nitrate and potassium nitrate. 
     
     
       7. A method as claimed in claim 5 in which the core is zirconium, the metal of the layer is an alloy of platinum and palladium, and the step of subjecting the layer to oxidizing conditions comprises immersing the core having the layer thereon into a melt of a material taken from the group consisting of sodium nitrate and potassium nitrate. 
     
     
       8. A method as claimed in claim 5 in which the core is niobium, the metal of the layer is palladium, and the step of subjecting the layer to oxidizing conditions comprises immersing the core having the layer thereon into a melt of a material taken from the group consisting of sodium nitrate and potassium nitrate. 
     
     
       9. A method as claimed in claim 1 in which the platinum metal is taken from the group consisting of ruthenium and palladium, and the step of subjecting the layer to oxidizing conditions comprises heating it in an oxygen containing atmosphere. 
     
     
       10. A method as claimed in claim 9 in which the core is titanium and the metal is ruthenium, and the step of heating in an oxygen containing atmosphere comprises heating in an oxygen containing atmosphere having a partial pressure of oxygen substantially equal to that of air. 
     
     
       11. A method as claimed in claim 9 in which the core is tantalum and the metal is ruthenium, and the step of heating in a oxygen containing atmosphere comprises heating in air. 
     
     
       12. A method as claimed in claim 11 in which the step of forming the metal layer comprises applying to the core a solution of a salt which when heated will form on the core the metal, and then heating the core to form the metal. 
     
     
       13. A method as claimed in claim 1 in which the step of subjecting the layer to oxidizing conditions comprises heating it in an oxygen containing atmosphere which has a partial pressure of oxygen greater than the partial oxygen pressure of atmospheric air. 
     
     
       14. A method as claimed in claim 13 in which the core is titanium with 4% molybdenum, the step of forming the metal layer comprises applying to the core a solution of a salt of platinum which will form platinum when heated, and then heating the core to form platinum, and the step of heating in an oxygen containing atmosphere comprises heating in oxygen at a pressure of 8-15 atmospheres. 
     
     
       15. A method of making an electrode comprising forming a material containing as a substance effective to carry out electrolysis at least one oxide of a platinum metal taken from the group consisting of platinum, iridium, rhodium, palladium, ruthenium, rhenium and osmium, and alloys of these metals, and applying the material to at least a part of the surface of a core of a film-forming metal to form a layer on said part of the surface of the core, which layer is at least 0.054 micron thick. 
     
     
       16. A method as claimed in claim 15 in which the core metal is a metal taken from the group consisting of titanium, tantalum, zirconium and niobium and alloys of said metals. 
     
     
       17. A method as claimed in claim 16 comprising oxidizing said core metal for forming an oxide layer on said core metal prior to applying the oxide of the platinum metal. 
     
     
       18. A method as claimed in claim 17 in which the oxide layer is formed on the core metal thermally. 
     
     
       19. A method as claimed in claim 15 in which the step of forming the material comprises melting a platinum metal oxide under pressure, and the step of applying the material to the core comprises applying the molten oxide to the core and then cooling the thus-coated core. 
     
     
       20. A method as claimed in claim 15 in which the step of forming the material comprises preparing a hot melt of the platinum metal oxide, and the step of applying the material to the core comprises spraying the hot melt onto the core. 
     
     
       21. A method as claimed in claim 15 in which the step of forming the material comprises forming a dispersion of the platinum metal oxide in a liquid carrier which is a liquid which can be evaporated without leaving any residue, and the step of applying the material to the core comprises contacting the core and the dispersion. 
     
     
       22. A method as claimed in claim 21 in which the step of applying the material comprises spraying the dispersion onto the core. 
     
     
       23. A method as claimed in claim 21 in which the step of applying the material comprises brushing the dispersion onto the core. 
     
     
       24. A method as claimed in claim 21 in which the step of applying the material comprises dipping the core into the dispersion. 
     
     
       25. A method as claimed in claim 21 in which the core is titanium and the dispersion is a dispersion of platinum oxide. 
     
     
       26. A method as claimed in claim 21 in which the core is niobium and the dispersion is a dispersion of rhodium oxide and iridium oxide. 
     
     
       27. A method as claimed in claim 21 which further comprises, after the dispersion is applied to the core, applying pressure to the dispersion for adhering the dispersion to the core. 
     
     
       28. A method as claimed in claim 15 in which the step of forming the material comprises preparing a plasma of the platinum metal oxide, and the step of applying the material to the core comprises spraying the plasma onto the core. 
     
     
       29. A method as claimed in claim 28 in which the core is titanium and the oxide is platinum dioxide. 
     
     
       30. A method as claimed in claim 15 in which the step of forming the material comprises preparing a dispersion of a platinum metal oxide and an oxide of a metal other than platinum in a liquid carrier which is evaporated without leaving any residue, and the step of applying the material to the core comprises contacting the core and the dispersion. 
     
     
       31. A method as claimed in claim 30 in which the core is 4% molybdenum and the balance titanium, and the platinum metal oxide is platinum oxide and the oxide of a metal other than platinum is manganese dioxide. 
     
     
       32. A method as claimed in claim 30 in which the core is titanium and the platinum metal oxide is platinum oxide and the oxide of a metal other than platinum is silicon dioxide. 
     
     
       33. A method of making an electrode comprising forming a solution of a material containing a salt of at least one platinum metal taken from the group consisting of platinum, iridium, rhodium, palladium, ruthenium, rhenium and osmium, the amount of platinum metal salt being sufficient, when converted to the oxide of the platinum metal, to be effective for carrying out electrolysis, contacting at least part of the surface of a core of a film forming metal with the solution, and subjecting the solution to conditions for causing a layer to be formed on the part of the surface of the core which contains, as a material effective for carrying out electrolysis, the oxide of the platinum metal, said step of contacting comprising contacting said surface of said core with sufficient solution for forming, during the subjecting of the solution to said conditions, a layer which is at least 0.054 micron thick. 
     
     
       34. A method as claimed in claim 33 in which the core metal is a metal taken from the group consisting of titanium, tantalum, zirconium and niobium and alloys of said metals. 
     
     
       35. A method as claimed in claim 34 comprising forming an oxide layer on said core metal prior to applying the oxide of the platinum metal. 
     
     
       36. A method as claimed in claim 35 in which the oxide layer is formed on the core metal thermally. 
     
     
       37. A method as claimed in claim 33 in which the step of forming the solution comprises forming a solution containing a salt of the platinum metal in an organic carrier, the step of contacting the surface of the core with the solution comprises coating the part of the surface of the core with the solution, and the step of subjecting the solution to conditions for causing the layer to be formed comprises heating the coated core in air to directly deposit the oxide of the platinum metal. 
     
     
       38. A method as claimed in claim 37 in which the core is titanium, and the platinum metal is palladium. 
     
     
       39. A method as claimed in claim 37 in which the core is tungsten and the platinum metal is ruthenium. 
     
     
       40. A method as claimed in claim 37 in which the core is tantalum and the platinum metals are palladium and iridium. .[.41. A method as claimed in claim 33 in which the step of forming the solution comprises forming an electrolyte of a salt of the platinum metal, the step of contacting the surface of the core with the solution comprises inserting the core into the solution, and the step of subjecting the solution to conditions for causing the layer to be formed comprises carrying out electrolysis using the immersed core as an electrode in the electrolyte..]. .[.42. A method as claimed in claim 41 in which the core is a metal taken from the group consisting of titanium and tantalum and the platinum metal is platinum..]. 
     
     
        3. A method as claimed in claim 33 in which the step of forming the solution comprises forming a solution of a salt of the platinum metal and the salt of a metal other than a platinum metal in an organic carrier, the step of contacting the surface of the core with the solution, and the step of subjecting the solution to conditions for causing the layer to be formed comprises heating the coated core in air to deposit directly the oxide of the platinum metal and the oxide of the metal other than the 
     
     
        platinum metal. 44. A method as claimed in claim 43 in which the core is titanium and the platinum metal is iridium and the metal other than 
     
     
        platinum metal is manganese. 45. A method as claimed in claim 43 in which the core is titanium and the platinum metal is platinum and the metal other than platinum metal is chromium.