Electrode for electrolysis cell
The invention relates to an electrode formulation comprising a catalytic layer containing tin, ruthenium, iridium, palladium and niobium oxides applied to a titanium or other valve metal substrate. A protective layer based on titanium oxide modified with oxides of other elements such as tantalum, niobium or bismuth may be interposed between the substrate and the catalytic layer. The thus obtained electrode is suitable for use as an anode in electrolysis cells for chlorine production.
1. Electrode suitable for operating as an anode in electrolysis cells comprising a valve metal substrate and an external catalytic layer containing oxides of tin, ruthenium, iridium, palladium and niobium in a Sn 50-70%, Ru 5-20%, Ir 5-20%, Pd 1-10%, Nb 0.5-5% elementary molar ratio.
2. The electrode according to claim 1 , comprising a protective layer containing TiO 2 interposed between the valve metal substrate and the external catalytic layer.
3. The electrode according to claim 2 , wherein the protective layer containing TiO 2 is added with tantalum, niobium or bismuth oxides in an overall elementary molar ratio of 0.5 to 3%.
4. A method for manufacturing an electrode, comprising:
applying multiple coats of a precursor solution containing Sn, Ir and Ru hydroxyacetochloride complexes, at least one Pd soluble species and at least one Nb soluble species to a valve metal substrate; and
executing after each coat a thermal treatment at a maximum temperature of 400° C. to 480° C. for a duration of 15 to 30 minutes.
5. The method according to claim 4 , wherein the at least one Pd soluble species comprises one or more of Pd(NO 3 ) 2 previously dissolved in a nitric acid aqueous solution and PdCl 2 previously dissolved in ethanol, and the at least one Nb soluble species is NbCl 5 previously dissolved in butanol.
6. A method for manufacturing an electrode, comprising:
applying multiple coats of a first hydroalcoholic solution containing a titanium hydroxyacetochloride complex and at least one salt of titanium, niobium or bismuth to a valve metal substrate with execution after each coat of a thermal treatment at a maximum temperature of 400 to 480° C. for a duration of 15 to 30 minutes; and
applying multiple coats of a second hydroalcoholic solution containing Sn, Ir and Ru hydroxyacetochloride complexes, at least one Pd soluble species and at least one Nb soluble species with execution after each coat of a thermal treatment at a maximum temperature of 400 to 480° C. for a duration of 15 to 30 minutes.
7. The method according to claim 6 , wherein the first hydroalcoholic solution is prepared by dissolution of BiCl 3 in an acetic solution of a titanium hydroxyacetochloride complex and subsequent addition of NbCl 5 dissolved in butanol.
8. The method according to claim 6 , wherein the first hydroalcoholic solution is prepared by addition of TaCl 5 dissolved in butanol to an acetic solution of a titanium hydroxyacetochloride complex.
9. An electrolysis cell comprising a cathodic compartment containing a cathode and an anodic compartment containing an anode separated by a membrane or diaphragm, the anodic compartment being fed with an alkali chloride brine, wherein the anode of the anodic compartment comprises an electrode comprising a valve metal substrate and an external catalytic layer containing oxides of tin, ruthenium, iridium, palladium and niobium in a Sn 50-70%, Ru 5-20%, Ir 5-20%, Pd 1-10%, Nb 0.5-5% elementary molar ratio.
10. The electrolysis cell of claim 9 , wherein an electrical potential difference is applied between the anode and the cathode of the cell and chorine is evolved on the surface of the anode of the anodic compartment to produce produce chlorine and alkali.