Electrode for electrolytic evolution of gas

Patent metadata

Field	Value
Publication number	US-2021404076-A1
Application number	US-201917292885-A
Country	US
Kind code	A1
Filing date	Dec 3, 2019
Priority date	Dec 3, 2018
Publication date	Dec 30, 2021
Grant date	—

Abstract

An electrode for evolution of gas in electrolytic processes having a substrate of valve metal and a catalytic coating having two layers. A first layer having oxides of valve metal, ruthenium and iridium and a second layer having one or more metals chosen from amongst elements of the platinum group.

First claim

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, obtained from precursors containing said iridium, ruthenium and tin in the form of organometallic complexes, 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, wherein said platinum-free first precursor solution contains said iridium, ruthenium and tin in the form of organometallic complexes, 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 claim 1 , 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 claim 1 , 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 claim 1 , 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 claim 1 , 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 claim 1 , 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 claim 1 , 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 claim 1 , 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 claim 1 , comprising the following steps:
applying to a valve metal substrate a platinum-free first solution comprising a mixture of iridium, ruthenium and tin, subsequently drying at 50-60° C. and carrying out decomposition of said first solution by heat treatment at 400-650° C. for a time of 5 to 30 minutes, wherein said first solution contains said iridium, ruthenium and tin in the form of organometallic complexes; repeating the previous step until a desired specific load of noble metal is reached; applying a tin-free second catalytic solution containing platinum and subsequently drying at 50-60° C. and carrying out decomposition of said second solution by heat treatment at 400-650° C. for a time of 5 to 30 minutes; repeating the previous step 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 . (canceled)

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 claim 1 .

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 .

16 . The electrode according to claim 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.

17 . The electrode according to claim 2 , 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.

18 . The electrode according to claim 2 , 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.

19 . The electrode according to claim 2 , 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.

20 . The electrode according to claim 2 , wherein said first catalytic layer also contains titanium oxides in molar percentage Ti=30-40% referred to the metal element.

21 . The electrode according to claim 2 , 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.

Assignees

• Industrie De Nora Spa

Inventors

• Gargiulo Alice
• Hayashida Toshikazu

Classifications

• C25B9/23

  comprising ion-exchange membranes in or on which electrode material is embedded · CPC title

• C25B11/081

  the element being a noble metal · CPC title

• C25B11/093 Primary

  at least one noble metal or noble metal oxide and at least one non-noble metal oxide · CPC title

• C25B11/097

  comprising two or more noble metals or noble metal alloys · CPC title

• C25B1/46 Primary

  in diaphragm cells · CPC title