Electrolysis cell of alkali solutions

Patent metadata

Field	Value
Publication number	US-10968526-B2
Application number	US-201314436314-A
Country	US
Kind code	B2
Filing date	Oct 15, 2013
Priority date	Oct 16, 2012
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

The invention relates to an electrolysis cell of alkali solutions partitioned by an ion-exchange membrane into an anodic compartment in which an alkaline electrolyte is circulated and a cathodic compartment consisting of a gas chamber; the cathodic compartment contains a gas-diffusion cathode in whose interior an electrolyte film coming from the anodic compartment percolates.

First claim

The invention claimed is:

1. A cell for electrolysis of alkaline solutions comprising:
a cation-exchange membrane partitioning the cell into:
an anodic compartment,
a cathodic compartment, and
an alkaline electrolyte consisting of an aqueous solution of caustic soda comprising 10-45% 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 alkaline 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 mixtures of oxides of lanthanum, cobalt and nickel assembled in direct contact with said cation-exchange membrane, the anodic compartment further comprising a feeding inlet and a discharging outlet for discharging the alkaline electrolyte,
said cathodic compartment consisting of a gas chamber delimited by a cathodic wall and by said cation-exchange membrane,
said cathodic compartment containing a gas-diffusion cathode,
said gas-diffusion cathode comprising a carbon cloth having a hydrophilic layer consisting of 20% by weight of a catalytically-activated layer consisting of a platinum, palladium, rhodium or iridium 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,
said gas-diffusion cathode further comprising an external hydrophobic layer suitable for facilitating the release of hydrogen to the gas chamber, the hydrophobic layer being a mixture of low surface area carbon black and polytetrafluoroethylene (PTFE) in a 1:1 weight proportion, and
said gas-diffusion cathode being suitable for the percolation of an electrolyte film coming from the anodic compartment.

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

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

4. The 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 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. The cell according to claim 1 wherein said anode suitable for oxygen evolution consists of a substrate made of a nickel or steel mesh or expanded or punched sheet, optionally activated with a catalytic coating.

7. An electrolyzer of alkaline solutions consisting of a modular arrangement of cells electrically connected through anodic and cathodic walls according to a bipolar or monopolar configuration, each cell comprising:
an anodic compartment,
a cathodic compartment,
a cation-exchange membrane between the anodic compartment and the cathodic compartment, and
an alkaline electrolyte consisting of an aqueous solution of caustic soda comprising 10-45% 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 alkaline 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, the anodic compartment further comprising a feeding inlet and a discharging outlet for discharging the alkaline electrolyte,
said cathodic compartment consisting of a gas chamber delimited by a cathodic wall and by said cation-exchange membrane,
said cathodic compartment containing a gas-diffusion cathode,
said gas-diffusion cathode comprising a carbon cloth having a hydrophilic layer consisting of 20% by weight of a catalytically-activated layer consisting of a platinum, palladium, rhodium or iridium 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,
said gas-diffusion cathode further comprising an external hydrophobic layer suitable for facilitating the release of hydrogen to the gas chamber, the hydrophobic layer being a mixture of low surface area carbon black and polytetrafluoroethylene (PTFE) in a 1:1 weight proportion, and
said gas-diffusion cathode being suitable for the percolation of an electrolyte film coming from the anodic compartment.

8. A process of electrolysis in the cell according to claim 1 comprising the steps of:
feeding the alkaline electrolyte consisting of the aqueous solution of caustic soda comprising 10-45% by weight of concentration to said anodic compartment, with percolation of the electrolyte film inside said gas-diffusion cathode;
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;
conducting cathodic evolution of hydrogen within said electrolyte film and discharge of said hydrogen from said cathodic compartment;
conducting evolution of oxygen on a surface of said anode; and
withdrawing exhaust electrolyte containing dissolved oxygen from said anodic compartment.

Assignees

• Industrie De Nora Spa

Inventors

• Iacopetti Luciano
• Antozzi Antonio Lorenzo

Classifications

• Y02E60/36

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

• C25B1/02

  Hydrogen or oxygen · CPC title

• C25B9/23 Primary

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

• C25B1/04

  by electrolysis of water · CPC title

• C25B11/031

  Porous electrodes · CPC title