Electrode with electrocatalytic surface

Claim 2

In an electrode for use in electrocatalytic processes comprising a base of a film-forming metal with an operative electrocatalytic outer surface formed as an integral surface film of the film-forming metal base incorporating therein a platinum-group metal or compound thereof as electrocatalyst, the improvement comprising said electrocatalytic outer surface is formed by a surface treatment by applying to the surface of the film-forming metal base at least one layer of a solution of at least one thermodecomposable compound which consists essentially of a platinum-group metal compound, drying and heating each applied layer to decompose said compound in a similar manner to methods known per se for the formation of platinum-group metal and platinum-group metal oxide coatings, wherein said solution contains a halide agent which attacks the film-forming metal base and converts metal from the base into ions which are converted into a compound of the film-forming metal during the heating step, and wherein the concentration of said halide agent in the solution, the concentration of the platinum-group metal compound(s) in the solution, the drying, the heating and the number of applied layers are such that during the heating of each layer including the last layer, the electrocatalyst formed from the decomposed platinum-group metal compound is incorporated fully in a simultaneously-formed surface film of film-forming metal compound grown up from the base as a result of said halide agent attacking the film-forming metal base thereby forming an electrolytic outer surface, said outer surface being the surface film of film-forming metal compound integral with and wholly containing the electrocatalyst formed from the decomposed platinum-group metal compound.

Claim 3

The electrode of claim 1, wherein the surface film of the film-forming metal base consists of oxide.

Claim 4

The electrode of claim 1, wherein the surface film of the film-forming metal base consists of one of a carbide, nitride, hydride and boride.

Claim 5

The electrode of claim 1, 2 or 3, wherein the electrode base is sheet-like and the surface film contains up to 0.5 g/m 2 , as metal, of the electrocatalyst per projected surface area of the electrode base.

Claim 6

The electrode of claim 1, 2 or 3, wherein said film contains at least one of iridium, rhodium and oxides or iridium and rhodium.

Claim 7

The electrode of claim 1, 2 or 3, wherein said film contains (a) at least one of iridium and rhodium and (b) ruthenium as metals or oxides in a metal weight ratio (a):(b) of from 4:1 to 1:4.

Claim 8

The electrode of claim 1, 2 or 3, wherein the electrode base is formed of particles.

Claim 9

In a method of forming an electrode for use in electrolytic processes comprising a base of film-forming metal with an operative electrocatalytic outer surface formed as an integral surface film of the film-forming metal base incorporating therein a platinum-group metal or compound thereof as electrocatalyst, the improvement comprising forming said electrocatalytic outer surface by a surface treatment by applying to the surface of the film-forming metal base at least one layer of a solution of at least one thermodecomposable compound which consists essentially of a platinum-group metal compound, drying and heating each applied layer to decompose said compound in a manner similar to methods known per se for the formation of platinum-group metal and platinum-metal oxide coatings, wherein said solution contains a halide agent which attacks the film-forming metal base and converts metal from the base into ions which are converted into a compound of the film-forming metal during the heating step, and wherein the concentration of said halide agent in the solution, the concentration of the platinum-group metal compound(s) in the solution, the drying, the heating and the number of applied layers are such that during the heating of each layer including the last layer, the electrocatalyst formed from the decomposed platinum-group metal compound is incorporated fully in a simultaneously-formed surface film of film-forming metal compound grown up from the base as a result of said halide agent attacking the film-forming metal base thereby forming an electrocatalytic outer surface, said outer surface being the surface film of film-forming metal compound integral with and wholly containing the electrocatalyst formed from the decomposed platinum-group metal compound.

Claim 10

In a method of forming an electrode for use in electrolytic processes comprising a base of film-forming metal with an operative electrocatalytic outer surface formed as an integral surface film of the film-forming metal base incorporating therein a platinum-group metal or compound thereof as electrocatalyst, the improvement comprising forming said electrocatalytic outer surface by a surface treatment by applying to the surface of the film-forming metal base at least one layer of a solution of at least one thermodecomposable compound which consists essentially of a platinum-group metal compound, drying and heating each applied layer to decompose said compound in a manner similar to methods known per se for the formation of platinum-group metal and platinum-metal oxide coatings, wherein said solution contains a halide agent which attacks the film-forming metal base and converts metal from the base into ions which are converted into a compound of the film-forming metal during the heating step, and wherein the concentration of said halide agent in the solution, the concentration of the platinum-group metal compound(s) in the solution, the drying, the heating and the number of applied layers are such that during the heating of each layer including the last layer, the electrocatalyst formed from the decomposed platinum-group metal compound is incorporated fully in a simultaneously-formed surface film of film-forming metal compound grown up from the base as a result of said halide agent attacking the film-forming metal base thereby forming an electrocatalytic outer surface, said outer surface being the surface film of film-forming metal compound integral with and wholly containing the electrocatalyst formed from the decomposed platinum-group metal compound.

Claim 11

The method of claim 8, wherein the electrode base is sheet-like and each applied layer of the solution contains up to 0.2 g/m 2 as metal of at least one of an iridium, rhodium and ruthenium compound per projected surface area of the electrode base.

Claim 12

The method of claim 8, wherein the solution contains compound of (a) at least one of iridium and rhodium and (b) ruthenium in a metal weight ratio (a):(b) of from 4:1 to 1:4.

Claim 13

The method of claim 9, wherein from 2 to 5 layers of the solution are applied, each followed by heating to between about 400° C. to 600° C. for about 5 to 15 minutes, the final layer possibly being heated for a longer period.

Claim 14

The method of claim 11, wherein the final surface film contains up to 0.5 g/m 2 as metal of the electrocatalyst per projected surface area of the electrode base.

Claim 15

The method of claim 8, wherein the solution contains said agent and said platinum-group metal compound in a molar ratio from 1:1 to 100:1.

Claim 16

The method of claim 13, wherein said molar ratio is selected between 3:1 and 30:1.

Claim 17

The method of claim 8, 9, 10, 11, 12, 13 or 14, wherein the heating is carried out in air to form a surface film of film-forming metal oxide.

Claim 18

The method of claim 8, 9, 10, 11, 12, 13 or 14, wherein the heating is carried out in one of a carbon, nitrogen, hydrogen and boron-containing non-oxidizing atmosphere to form a surface film selected from a film-forming metal carbide, nitride, hydride and boride.

Claim 19

In the production of an electrode for use in electrolytic processes, a method of activating the surface of a film-forming metal comprising applying to the surface of the film-forming metal at least one layer of a solution of at least one thermodecomposable compound which consists essentially of a platinum group metal compound, drying and heating each applied layer to decompose said compound, the improvement comprising said method is a surface treatment wherein a surface film of a compound of the film-forming metal which is electrocatalytic and electroconductive is formed by application of a solution containing a halide agent which attacks the film-forming metal surface and converts metal from the surface into ions which are converted into the compound of the film-forming metal during the heating step, wherein the concentration of said halide agent in the solution, the concentration of the platinum-group metal compound in the solution, the drying, the heating and the number of applied layers are such that during the heating of each layer including the last layer, the electrocatalyst formed from the decomposed platinum-group metal compound is incorporated fully in a simultaneously formed surface film of film-forming metal compound grown up from the film-forming metal as a result of said halide agent attacking the film-forming metal thereby forming an electrocatalytic outer surface, said outer surface being the surface film of film-forming metal compound integral with and wholly containing the electrocatalyst formed from the decomposed platinum-group metal compound.

Claim 20

In the production of an electrode for use in electrolytic processes, a method of activating the surface of a film-forming metal comprising applying to the surface of the film-forming metal at least one layer of a solution of at least one thermodecomposable compound which consists essentially of a platinum group metal compound, drying and heating each applied layer to decompose said compound, the improvement comprising said method is a surface treatment wherein a surface film of a compound of the film-forming metal which is electrocatalytic and electroconductive is formed by application of a solution containing a halide agent which attacks the film-forming metal surface and converts metal from the surface into ions which are converted into the compound of the film-forming metal during the heating step, wherein the concentration of said halide agent in the solution, the concentration of the platinum-group metal compound in the solution, the drying, the heating and the number of applied layers are such that during the heating of each layer including the last layer, the electrocatalyst formed from the decomposed platinum-group metal compound is incorporated fully in a simultaneously formed surface film of film-forming metal compound grown up from the film-forming metal as a result of said halide agent attacking the film-forming metal thereby forming an electrocatalytic outer surface, said outer surface being the surface film of film-forming metal compound integral with and wholly containing the electrocatalyst formed from the decomposed platinum-group metal compound.

Claim 21

The method of claim 17, wherein the film-forming metal is in particulate form.

Claim 22

The method of claim 18, wherein the drying step is carried out in at least two separate stages to drive off all solvent from the particulate film-forming metal.

Claim 23

The method of claim 18 or 19, wherein the heating is carried out in air to form a surface film of film-forming metal oxide on the particles.

Claim 24

The method of claim 18 or 19, wherein the heating is carried out in one of a carbon, nitrogen, hydrogen and boron-containing non-oxidizing atmosphere to form a surface film selected from a film-forming metal carbide, nitride, hydride and boride on the particles.

Claim 25

The method of claim 17, 18 or 19, wherein the solution contains compounds of (a) at least one of iridium and rhodium and (b) ruthenium in a metal weight ratio (a):(b) of from 4:1 to 1:4.

Claim 26

The method of claim 18 or 19, comprising the further step of applying the surface-activated particles onto a conductive support.

Claim 27

In an electrode for use in electrolytic processes comprising particles of film-forming metal having an electrocatalytic surface formed by applying to the film-forming metal particles at least one layer of a solution of at least one thermodecomposable compound which consists essentially of a platinum-group metal compound, drying and heating each applied layer to decompose said compound, the improvement comprising a surface film of a compound of the film-forming metal which is electrocatalytic and electroconductive is formed on the particles by a surface treatment by applying a solution containing a halide agent which attacks the film-forming metal surface of the particles and converts metal from the surface into ions which are converted into the compound of the film-forming metal during the heating step, and wherein the concentration of said agent in the solution, the concentration of the platinum-group metal compound(s) in the solution, the drying, the heating and the number of applied layers are such that during the heating of each layer including the last one, the electrocatalyst formed from the decomposed platinum group metal compound is incorporated fully in a simultaneously-formed surface film of film-forming metal compound grown up on the surface of the particles as a result of said halide agent attacking the film-forming metal particles thereby forming an electrocatalytic outer surface, said outer surface being the surface film of film-forming metal compound integral with and wholly containing the electrocatalyst formed from the decomposed platinum-group metal compound.

Claim 28

In an electrode for use in electrolytic processes comprising particles of film-forming metal having an electrocatalytic surface formed by applying to the film-forming metal particles at least one layer of a solution of at least one thermodecomposable compound which consists essentially of a platinum-group metal compound, drying and heating each applied layer to decompose said compound, the improvement comprising a surface film of a compound of the film-forming metal which is electrocatalytic and electroconductive is formed on the particles by a surface treatment by applying a solution containing a halide agent which attacks the film-forming metal surface of the particles and converts metal from the surface into ions which are converted into the compound of the film-forming metal during the heating step, and wherein the concentration of said agent in the solution, the concentration of the platinum-group metal compound(s) in the solution, the drying, the heating and the number of applied layers are such that during the heating of each layer including the last one, the electrocatalyst formed from the decomposed platinum group metal compound is incorporated fully in a simultaneously-formed surface film of film-forming metal compound grown up on the surface of the particles as a result of said halide agent attacking the film-forming metal particles thereby forming an electrocatalytic outer surface, said outer surface being the surface film of film-forming metal compound integral with and wholly containing the electrocatalyst formed from the decomposed platinum-group metal compound.

Claim 29

The electrode of claim 24, wherein the surface film of the film-forming metal particles consists of oxide.

Claim 30

The electrode of claim 24, wherein the surface film of the film-forming metal particles consists of one of a carbide, nitride, hydride and boride.

Claim 31

The electrode of claim 24, 25 or 26, wherein said surface film of the particles contains (a) at least one of iridium and rhodium and (b) ruthenium as metals or oxides in a metal weight ratio (a):(b) of from 4:1 to 1:4.

Claim 32

The electrode of claim 24, 25, or 26, wherein said particles are supported on a conductive support.

Claim 33

The electrode of claim 24, 25, or 26, wherein said particles are associated with a current feeder.

Claim 34

In an electrode for use in electrolytic processes comprising a base of film-forming metal with an operative electrocatalytic outer surface formed as an integral surface film of the film-forming metal base incorporating therein a platinum group metal or compound thereof as electrocatalyst, the improvement comprising said electrocatalytic outer surface is formed by a surface treatment by applying to the surface of the film-forming metal base at least one layer of a solution of at least one thermodecomposable compound which consists essentially of a platinum-group metal compound, drying and heating each applied layer to decompose said compound, wherein said solution contains a halide agent which attacks the film-forming metal base and converts metal from the base into ions which are converted into a film-forming metal compound during the heating step, and wherein the concentration of said halide agent in the solution and the concentration of said platinum-group metal compound in the solution and the drying and the heat procedure and the number of applied layers of the solution are such that during the heating of each layer, including the last layer, the electrocatalytic surface thus formed is an integral film of decomposed platinum-group metal compound and film-forming metal compound wherein the film-forming metal compound in the electrocatalytic surface is provided by a surface film grown up from the film-forming metal base as a result of said halide agent attacking the film-forming metal base and said decomposed platinum-group metal compound is fully incorporated in said surface film grown up from the film-forming metal base whereby the electrocatalytic material formed from the decomposed platinum-group metal compound is an integral part of said surface film.

Claim 35

In an electrode for use in electrolytic processes comprising a base of film-forming metal with an operative electrocatalytic outer surface formed as an integral surface film of the film-forming metal base incorporating therein a platinum group metal or compound thereof as electrocatalyst, the improvement comprising said electrocatalytic outer surface is formed by a surface treatment by applying to the surface of the film-forming metal base at least one layer of a solution of at least one thermodecomposable compound which consists essentially of a platinum-group metal compound, drying and heating each applied layer to decompose said compound, wherein said solution contains a halide agent which attacks the film-forming metal base and converts metal from the base into ions which are converted into a film-forming metal compound during the heating step, and wherein the concentration of said halide agent in the solution and the concentration of said platinum-group metal compound in the solution and the drying and the heat procedure and the number of applied layers of the solution are such that during the heating of each layer, including the last layer, the electrocatalytic surface thus formed is an integral film of decomposed platinum-group metal compound and film-forming metal compound wherein the film-forming metal compound in the electrocatalytic surface is provided by a surface film grown up from the film-forming metal base as a result of said halide agent attacking the film-forming metal base and said decomposed platinum-group metal compound is fully incorporated in said surface film grown up from the film-forming metal base whereby the electrocatalytic material formed from the decomposed platinum-group metal compound is an integral part of said surface film.