# US 12,000,056 B2 · Tandem electrolysis cell > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,000,056 B2 - Document ID: US12000056B2 - Status: Granted - Kind: B2 - Application number: 16/933,790 - Filed: 2020-07-20 - Published: 2021-12-23 - Granted: 2024-06-04 - Earliest claimed: 2020-06-18 - Assignees: Saudi Arabian Oil Company - Applicants: Saudi Arabian Oil Company - Inventors: Ahmad D. Hammad; Bandar A. Fadhel - Web page: https://patentgrep.com/patent/US12000056B2 ## CPC - C25B 1/46: in diaphragm cells - B01D 53/265: {by refrigeration (condensation)} - C25B 1/04: by electrolysis of water - C25B 1/55: Photoelectrolysis - C25B 9/21: two or more diaphragms - C25B 9/23: comprising ion-exchange membranes in or on which electrode material is embedded - C25B 9/60: Constructional parts of cells - C25B 9/65: Means for supplying current; Electrode connections; Electric inter-cell connections - C25B 9/70: Assemblies comprising two or more cells - C25B 13/08: based on organic materials - C25B 15/02: Process control or regulation - C25B 15/025: of electrolyte parameters - C25B 15/029: Concentration - C25B 15/031: pH - C25B 15/08: Supplying or removing reactants or electrolytes; Regeneration of electrolytes - E03B 3/28: from humid air (condensing of vapours in general B01D5/00; dehumidification of air for air-conditioning F24F3/14) - H02S 40/38: Energy storage means, e.g. batteries, structurally associated with PV modules - H02S 40/425: {using a gaseous or a liquid coolant, e.g. air flow ventilation, water circulation} - Y02E 10/50: Photovoltaic [PV] energy - Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis - Y02E 70/30: Systems combining energy storage with energy generation of non-fossil origin - C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B) - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - E03B: INSTALLATIONS OR METHODS FOR OBTAINING, COLLECTING, OR DISTRIBUTING WATER (drilling wells, obtaining fluids in general from wells E21B; pipe-line systems in general F17D) - H02S: GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES (obtaining electrical energy from radioactive sources G21H1/12; light sensitive inorganic semiconductor devices H10F; light sensitive organic semiconductor devices H10K30/00; thermoelectric devices H10N10/00; pyroelectric devices H10N15/00) - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A system and methods for electrolysis of saline solutions are provided. An exemplary system provides a tandem electrolysis cell. The tandem electrolysis cell includes a common enclosure that has two chambers. A first chamber is separated from a second chamber by a cation selective membrane. A common anode and a first cathode (cathode A) are disposed in the first chamber. The first cathode and the common anode are configured to electrolyze a saline solution to hydrogen and oxygen. A second cathode (cathode B) is disposed in the second chamber. The second cathode and the common anode are configured to electrolyze a brine solution in the first chamber to form chlorine and water in the second chamber to form hydrogen and hydroxide ions. ## Claims ### Claim 1 A tandem electrolysis cell, comprising: a common enclosure comprising two chambers, wherein a first chamber is separated from a second chamber by a cation selective membrane; a common anode disposed in the first chamber, wherein the common anode is operated continuously; a first cathode (cathode A) disposed in the first chamber, wherein the first cathode and the common anode are configured to electrolyze a saline solution to hydrogen and oxygen, during a first stage of operation; a second cathode (cathode B) disposed in the second chamber, wherein the second cathode and the common anode are configured to electrolyze a brine solution in the first chamber to form chlorine and water in the second chamber to form hydrogen and hydroxide ions, during a second stage of operation; a controller to open valves, during the first stage of operation, and close valves, during the second stage of operation on: a saline inlet port on the first chamber; an alkali inlet port on the first chamber; a first hydrogen outlet port proximate to cathode A on the first chamber; and an oxygen outlet port proximate to the common anode on the first chamber, the oxygen outlet port being attached to the first chamber; and the controller to open valves, during the second stage of operation, and close valves, during the first stage of operation on: a water inlet port on the second chamber; an alkali outlet port on the second chamber; a second hydrogen outlet port on the second chamber; and a chlorine outlet port proximate to the common anode on the first chamber, the chlorine outlet port being attached to the first chamber, wherein the common anode is positioned between cathode A and cathode B, and between the oxygen outlet port and the chlorine outlet port. ### Claim 2 (depends on 1) The tandem electrolysis cell of claim 1, wherein the enclosure comprises a corrosion resistant inner surface. ### Claim 3 (depends on 2) The tandem electrolysis cell of claim 2, wherein the corrosion resistant inner surface is glass. ### Claim 4 (depends on 1) The tandem electrolysis cell of claim 1, wherein the enclosure comprises a ceramic. ### Claim 5 (depends on 1) The tandem electrolysis cell of claim 1, wherein the first chamber comprises a gas barrier, wherein cathode A is on a first side of the gas barrier and the common anode is on a second side of the gas barrier, wherein the gas barrier extends below cathode A and the common anode, and wherein an opening below the gas barrier allows liquid flow between cathode A and the common anode. ### Claim 6 (depends on 5) The tandem electrolysis cell of claim 5, wherein the saline inlet port is proximate to cathode A on the first side of the gas barrier. ### Claim 7 (depends on 5) The tandem electrolysis cell of claim 5, wherein the alkali inlet port is proximate to cathode A on the first side of the gas barrier. ### Claim 8 (depends on 5) The tandem electrolysis cell of claim 5, wherein the first hydrogen outlet port proximate to cathode A is on the first side of the gas barrier, wherein the first hydrogen outlet port is on a top surface of the enclosure. ### Claim 9 (depends on 5) The tandem electrolysis cell of claim 5, wherein the oxygen outlet port proximate to the common anode is on the second side of the gas barrier, wherein the oxygen outlet port is on a top surface of the enclosure. ### Claim 10 (depends on 5) The tandem electrolysis cell of claim 5, wherein the chlorine outlet port proximate to the common anode on the second side of the gas barrier, wherein the chlorine removal port is on a top surface of the enclosure. ### Claim 11 (depends on 1) The tandem electrolysis cell of claim 1, wherein the cation selective membrane is a sodium permeable membrane. ### Claim 12 (depends on 11) The tandem electrolysis cell of claim 11, wherein the sodium permeable membrane comprises sulfonated tetrafluoroethylene or polyvinylidene fluoride copolymers or both. ### Claim 13 A system for electrolyzing seawater, comprising: a tandem electrolysis cell, comprising: a common enclosure comprising two chambers, wherein a first chamber is separated from a second chamber by a cation selective membrane; a common anode disposed in the first chamber, wherein the common anode is operated continuously; a first cathode (cathode A) disposed in the first chamber, wherein the first cathode and the common anode are configured to electrolyze a saline solution to hydrogen and oxygen in a first electrolysis reaction; a second cathode (cathode B) disposed in the second chamber, wherein the second cathode and the common anode are configured to electrolyze a brine solution in the first chamber to form chlorine and water in the second chamber to form hydrogen and hydroxide ions in a second electrolysis reaction, wherein the common anode is positioned between cathode A and cathode B; a controller to open valves, during the first electrolysis reaction, and close valves, during the second electrolysis on: a saline inlet port on the first chamber; an alkali inlet port on the first chamber; a first hydrogen outlet port proximate to cathode A on the first chamber; and an oxygen outlet port proximate to the common anode on the first chamber, the oxygen outlet port attached to in the first chamber; and the controller to open valves, during the second electrolysis reaction, and close valves, during the first electrolysis reaction on: a water inlet port on the second chamber; an alkali outlet port on the second chamber; a second hydrogen outlet port on the second chamber; and a chlorine outlet port proximate to the common anode on the first chamber, the chlorine outlet port attached to the first chamber, wherein the common anode is positioned between the oxygen outlet port and the chlorine outlet port; and an atmospheric water producer, wherein the atmospheric water producer comprises: a solar panel to generate electricity; a battery to store the electricity, wherein the battery powers the tandem electrolysis cell; a cooling system powered by the battery, wherein the cooling system harvests atmospheric moisture; and a water storage tank to collect the harvested atmospheric moisture, wherein the water storage tank provides the water to the second chamber. ### Claim 14 (depends on 13) The system of claim 13, comprising a sodium hydroxide storage tank to store sodium hydroxide produced during operation of the second chamber for use during operation of the first chamber, the sodium hydroxide storage tank being connected to the alkali inlet port on the first chamber. ### Claim 15 (depends on 13) The system of claim 13, comprising a first power supply to provide power to cathode A and the common anode. ### Claim 16 (depends on 15) The system of claim 15, comprising a second power supply to provide power to cathode B and the common anode. ### Claim 17 (depends on 13) The system of claim 13, comprising an ion sensor in the first chamber. ### Claim 18 (depends on 17) The system of claim 17, wherein the ion sensor is a sodium electrode. ### Claim 19 (depends on 13) The system of claim 13, comprising an ion sensor in the second chamber. ### Claim 20 (depends on 19) The system of claim 19, wherein the ion sensor is a pH electrode. ### Claim 21 (depends on 13) The system of claim 13, comprising a level sensor in the first chamber, or a level sensor in the second chamber, or both. ### Claim 22 (depends on 13) The system of claim 13, wherein the controller comprises a processor and a data store, wherein the data store comprises instructions to direct the processor to: determine if a sodium ion concentration in the first chamber is above a threshold, and, if so: turn off a first power supply providing power to cathode A and the common anode; and turn on a second power supply to provide power to cathode B and the common anode; and determine if a pH in the second chamber is below a threshold, and, if so: turn off a second power supply providing power to cathode B and the common anode; and turn on a first power supply to provide power to cathode A and the common anode. ### Claim 23 (depends on 22) The system of claim 22, wherein the data store comprises instructions to direct the processor to: close valves for the first electrolysis reaction after turning off the first power supply; and open valves for the second electrolysis reaction prior to turning on the second power supply. ### Claim 24 (depends on 22) The system of claim 22, wherein the data store comprises instructions to direct the processor to: close valves for the second electrolysis reaction after turning off the second power supply; and open valves for the first electrolysis reaction prior to turning on the first power supply. ### Claim 25 A method for using a tandem electrolysis cell (TEC) to form hydrogen, oxygen, chlorine, and sodium hydroxide, comprising: determining if a sodium ion concentration in a first chamber of the TEC is below a threshold, and, if so, opening valves on: a saline inlet port on the first chamber; an alkali inlet port on the first chamber; a first hydrogen outlet port proximate to a first cathode (cathode A) on the first chamber; and an oxygen outlet port proximate to a common anode on the first chamber, the oxygen outlet port being attached to the first chamber; and closing valves on: a water inlet port on a second chamber; an alkali outlet port on the second chamber; a second hydrogen outlet port on the second chamber; and a chlorine outlet port proximate to the common anode on the first chamber, the chlorine outlet port being attached to the first chamber; and while the sodium ion concentration remains below the threshold, iterating: flowing saline water into a half-cell of the first chamber comprising cathode A; forming hydrogen at cathode A and oxygen at the common anode; and monitoring the sodium ion concentration in the first chamber; and determining if a pH in the second chamber of the TEC is below a threshold, and, if so, opening valves on: the water inlet port on the second chamber; the alkali outlet port on the second chamber; the second hydrogen outlet port on the second chamber; and the chlorine outlet port proximate to the common anode on the first chamber; and closing valves on: the saline inlet port on the first chamber; the alkali inlet port on the first chamber; the first hydrogen outlet port proximate to cathode A on the first chamber; and the oxygen outlet port proximate to the common anode on the first chamber; and while the pH remains below the threshold, iterating: flowing fresh water into a half-cell of a second chamber comprising a second cathode (cathode B); forming hydrogen and hydroxide ions at cathode B and oxygen at the common anode; and monitoring the pH in the first chamber, wherein the common anode is positioned between cathode A and cathode B, and between the oxygen outlet port and the chlorine outlet port. ### Claim 26 (depends on 25) The method of claim 25, comprising, when the sodium ion concentration exceeds the threshold in the first chamber: powering off a first power supply that supplies power to cathode A and the common anode; and powering on a second power supplies that supplies power to cathode B and the common anode. ### Claim 27 (depends on 25) The method of claim 25, comprising, when the pH drops below the threshold in the second chamber: powering off a second power supply that supplies power to cathode B and the common anode; and powering on a first power supplies that supplies power to cathode A and the common anode.