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1. WO2020115028 - ÉLECTRODE POUR L'ÉVOLUTION ÉLECTROLYTIQUE D'UN GAZ

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

CLAI MS

1. An electrode for gas evolution in electrolytic processes comprising a valve metal substrate and a coating comprising a first catalytic layer formed on said substrate containing a mixture of iridium, ruthenium, tin and platinum or their oxides or combinations thereof and a second catalytic layer formed on said first catalytic layer containing platinum and tin or their oxides or combinations thereof, wherein said tin of the said second catalytic layer is present in a decreasing concentration from the interface with said first catalytic layer and wherein said platinum of the said first catalytic layer is present in a decreasing concentration from the interface with said second catalytic layer.

2. An electrode for gas evolution in electrolytic processes comprising a valve metal substrate and a coating comprising a first catalytic layer formed on said substrate containing a mixture of iridium, ruthenium, tin and platinum or their oxides or combinations thereof and a second catalytic layer formed on said first catalytic layer containing platinum and tin or their oxides or combinations thereof, wherein said first layer is obtained from a platinum-free first precursor solution comprising a mixture of iridium, ruthenium and tin, applied said substrate and subjected to a heat treatment, and wherein said second catalytic layer is obtained from a tin-free second catalytic composition containing platinum, applied said substrate and subjected to a heat treatment.

3. The electrode according to one of claims 1 or 2, wherein said second catalytic layer contains Pt = 48-96% in the form of metal, or its oxides, in molar percentage referred to the metal element.

4. The electrode according to one of claims 1 to 3, wherein said second catalytic layer contains Pd = 0-24% or Rh = 0-24%, in the form of metal, or their oxides, or combinations thereof, in the form of metals or their oxides in molar percentage referred to the metal elements.

5. The electrode according to one of claims 1 to 4, wherein said second catalytic layer contains Sn = 4-12% in the form of metal or its oxides, in average molar percentage referred to the metal element.

6. The electrode according to any one of the preceding claims, wherein said iridium, ruthenium and tin oxides of said first catalytic layer are present in molar percentages Ru = 24-34%, Ir = 3-13%, Sn = 30-70% referring to the metal elements.

7. The electrode according to any one of the preceding claims, wherein said first catalytic layer also contains titanium oxides in molar percentage Ti = 30-40% referred to the metal element.

8. The electrode according to any one of the preceding claims, wherein said first catalytic layer contains Pt = 3-10% in the form of metal or its oxides, in average molar percentage referred to the metal element.

9. The electrode according to any one of the preceding claims, wherein the valve metal substrate is selected from the group consisting of titanium, tantalum, zirconium, niobium, tungsten, aluminium, silicon, or their alloys.

10. A method for the production of an electrode as defined in one of the previous claims, comprising the following steps:

- application to a valve metal substrate of a platinum-free first solution comprising a mixture of iridium, ruthenium and tin, subsequent drying at 50- 60 °C and decomposition of said first solution by heat treatment at 400-650 °C for a time of 5 to 30 minutes;

- repetition of stage a) until a desired specific load of noble metal is reached;

- application of a tin-free second catalytic solution containing platinum and subsequent drying at 50-60 °C and decomposition of said second solution by heat treatment at 400-650 °C for a time of 5 to 30 minutes;

- repetition of stage c) until a desired specific load of noble metal is reached.

11. The method according to claim 10, wherein the temperature of said thermal decomposition in steps a) and c) is between 480 and 550 °C.

12. The method according to one of claims 10 or 11 , wherein said first solution contains said iridium, ruthenium and tin in the form of organometallic complexes.

13. A cell for the electrolysis of solutions of alkaline chlorides comprising an anodic compartment and a cathodic compartment wherein the anodic compartment is equipped with the electrode according to any one of claims 1 to 8.

14. A cell for electrolysis according to claim 13 wherein said anodic compartment and said cathodic compartment are separated by a diaphragm or an ion-exchange membrane.

15. An electrolyzer for the production of chlorine and alkali from alkali chloride solutions comprising a modular arrangement of cells, wherein each cell is the cell according to claim 13.