Electrolysis cell of alkali solutions

Patent metadata

Field	Value
Publication number	US-11208728-B2
Application number	US-201414902376-A
Country	US
Kind code	B2
Filing date	Jul 15, 2014
Priority date	Jul 17, 2013
Publication date	Dec 28, 2021
Grant date	Dec 28, 2021

Abstract

The invention relates to an electrochemical cell partitioned by a cation-exchange membrane suitable for production of high purity hydrogen and oxygen by electrolysis of alkaline solutions comprising a cathode in form of porous web including a platinum or palladium catalyst. The cell can be used as an element of a modular filter-press electrolyzer.

First claim

The invention claimed is:

1. An electrolysis cell comprising:
a cation-exchange membrane,
an anodic compartment,
a cathodic compartment partitioned by the cation-exchange membrane, and
an electrolyte consisting of an aqueous solution of caustic soda comprising 8-45% by weight of concentration,
said anodic compartment consisting of a liquid chamber delimited by an anodic wall and by said cation-exchange membrane and filled with the electrolyte,
said anodic compartment containing an anode suitable for oxygen evolution, the anode comprising a nickel mesh activated with a thin layer of catalyst containing a mixture of oxides of lanthanum, cobalt and nickel assembled in direct contact with said cation-exchange membrane, said anodic compartment further comprising a feeding inlet and a discharging outlet for discharging the electrolyte,
said cathodic compartment delimited by a cathodic wall and by said cation-exchange membrane, said cathodic compartment containing a gas-diffusion cathode suitable for hydrogen evolution,
the gas-diffusion cathode comprising a carbon cloth having a hydrophilic layer consisting of 20% by weight of a catalytically-activated layer consisting of platinum and/or palladium, supported on high surface area carbon black, soaked with sulphonated perfluorinated ionomer dispersion and deposited upon the carbon cloth, and in direct contact with said cation-exchange membrane, and
said gas-diffusion cathode further comprising an external hydrophobic layer suitable for facilitating the release of hydrogen to the cathodic compartment, the hydrophobic layer being a mixture of low surface area carbon black and polytetrafluoroethylene (PTFE) in a 1:1 weight proportion,
wherein a purity of product hydrogen determined in terms of concentration of oxygen in a dried cathodic product ranges between 0.1-1 ppm of O 2 .

2. The electrolysis cell according to claim 1 wherein said cation-exchange membrane is a non-reinforced monolayer sulphonic membrane.

3. The electrolysis cell according to claim 1 , wherein said catalytically-activated layer of said hydrophilic layer of the gas-diffusion cathode contains platinum.

4. The electrolysis cell according to claim 1 , wherein said gas-diffusion cathode and said cathodic wall are put in electrical contact by means of a current collector consisting of a porous metal structure comprising distributed points of electrical contacts, wherein the porous metal structure is a nickel or steel foam.

5. The electrolysis cell according to claim 1 , wherein said anode suitable for oxygen evolution and said anodic wall are put in electrical contact by means of a current collector consisting of a porous metal structure, wherein the porous metal structure is a nickel or steel foam or mat.

6. An electrolyzer of alkali solutions consisting of a modular arrangement of plural electrolysis cells according to claim 1 , electrically connected through said anodic and cathodic walls according to a bipolar or monopolar configuration.

7. A process of electrolysis in the electrolysis cell according to claim 1 comprising the steps of:
feeding the electrolyte consisting of the aqueous solution of caustic soda comprising 8-45% by weight of concentration to said anodic and cathodic compartments;
connecting said cathodic compartment to a negative pole and said anodic compartment to a positive pole of a power unit, with subsequent supply of direct electrical current;
carrying out cathodic evolution of hydrogen within said catalytically-activated layer and discharging said hydrogen from said cathodic compartment;
carrying out evolution of oxygen on a surface of said anode; and
obtaining the purity of product hydrogen determined in terms of concentration of oxygen in the dried cathodic product ranging between 0.1-1 ppm of O 2 .

8. The process according to claim 7 wherein the aqueous solution of caustic soda is 10 to 20% by weight concentration.

Assignees

• Industrie De Nora Spa

Inventors

• Krasovic Julia Lynne

Classifications

• Y02E60/36

  Hydrogen production from non-carbon containing sources, e.g. by water electrolysis · CPC title

• C25B11/081

  the element being a noble metal · CPC title

• C25B1/04 Primary

  by electrolysis of water · CPC title

• Y02P70/50

  Manufacturing or production processes characterised by the final manufactured product · CPC title

• C25B11/031

  Porous electrodes · CPC title