# US 5,705,534 A · Method for the preparation of cation exchange membranes doped with insoluble metal salts

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- Number: US 5,705,534 A
- Document ID: US5705534A
- Status: Granted
- Kind: A
- Application number: 08/657,953
- Filed: 1996-06-04
- Granted: 1998-01-06
- Earliest claimed: 1995-09-22
- Assignees: National Power PLC
- Inventors: Vincent F. D'Agostino; Graham Edward Cooley; John Michael Newton; Karel Bouchal
- Web page: https://patentgrep.com/patent/US5705534A

## CPC

- C08J 5/225: {containing fluorine}
- H01M 8/0289: Means for holding the electrolyte (solid polymer electrolytes H01M8/1018)
- H01M 50/409: Separators, membranes or diaphragms characterised by the material
- C08J 2327/12: containing fluorine atoms
- H01M 8/188: {by recharging of redox couples containing fluids; Redox flow type batteries}
- Y02E 60/10: Energy storage using batteries
- Y02E 60/50: Fuel cells
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A method of preparing a modified cation exchange membrane in which a sulfide of silver, tungsten, molybdenum or a mixture thereof is deposited within the polymer matrix, which method comprises the steps of: i) forming within the polymer matrix of the membrane a complex of silver, tungsten, molybdenum or a mixture thereof with a water soluble compound containing an --SH group; and ii) converting the complex formed in step (i) into the insoluble sulfide of silver, tungsten, molybdenum or a mixture thereof.

## Claims

### Claim 1

A method of preparing a modified cation exchange membrane having a polymer matrix and a sulfide of silver, tungsten, molybdenum or a mixture thereof deposited within the polymer matrix, which method comprises the steps of:
i) forming within the polymer matrix of the membrane a complex of silver, tungsten, molybdenum or a mixture thereof with a water soluble compound containing an --SH group; and
ii) converting the complex formed in the step (i) into the insoluble sulfide of silver, tungsten, molybdenum or a mixture thereof.

### Claim 2 (depends on 1)

A method as claimed in claim 1 wherein the complex in step (i) is formed by contacting the cation exchange membrane with a water soluble salt of silver, tungsten, molybdenum, or a mixture thereof, or a solution of a chelate of tungsten or molybdenum, or a mixture thereof, and subsequently contacting the membrane with an aqueous solution of a water soluble compound containing an --SH group.

### Claim 3 (depends on 2)

A method as claimed in claim 2 wherein the water soluble salt is silver nitrate.

### Claim 4 (depends on 2)

A method as claimed in claim 2 wherein the chelate of tungsten or molybdenum is formed with 8-hydroxyquinoline, toluene-3,4-dithiol or benzoin .alpha.-oxime.

### Claim 5 (depends on 1)

A method as claimed in claim 1 wherein the water soluble compound used in step (i) is isothiourea, mercaptomethanol, 2-mercaptoethanol, 3-mercaptopropanol, 3-mercaptobutanol, 4-mercaptobutanol, thioformamide, thioacetamide, thiobenzamide, mercaptoacetic acid, 3-mercaptopropanoic acid or 4-mercaptobutanecarboxylic acid.

### Claim 6 (depends on 1)

A method as claimed in claim 1 wherein the membrane is dehydrated prior to step (i).

### Claim 7 (depends on 1)

A method as claimed in claim 1 wherein the complex formed in step (i) is a silver complex and the conversion in step (ii) to the insoluble sulfide is effected by alkaline hydrolysis.

### Claim 8 (depends on 7)

A method as claimed in claim 7 wherein the alkaline hydrolysis is effected using sodium hydroxide or potassium hydroxide.

### Claim 9 (depends on 1)

A method as claimed in claim 1 wherein the complex formed in step (i) is a tungsten or molybdenum complex and the conversion in step (ii) to the insoluble sulfide is effected by heat treatment.

### Claim 10 (depends on 9)

A method as claimed in claim 9 wherein the heat treatment is carried out at a temperature of 200.degree. C. or above.