The present invention relates to a method for preparing lithium hydroxide, comprising subjecting an aqueous composition (A), comprising lithium sulfate and sodium sulfate, to bipolar membrane electrodialysis; said step of bipolar membrane electrodialysis comprises processing in an electrodialyser comprising at least one electrodialysis cell (200) comprising a first compartment (220), supplied with water and delimited between a first bipolar membrane (250) and an anionic central membrane (230), and a second compartment (210), supplied with said aqueous composition (A) and delimited between said anionic central membrane (230) and a second bipolar membrane (240), then recovering, from said at least one electrodialysis cell (200), an aqueous composition (B) comprising lithium hydroxide and sodium sulfate, and subjecting it to a crystallisation step in order to prepare a salt.

A self-cleaning CO.sub.2 reduction strategy is proposed herein including alternating operation and regeneration of the CO.sub.2 electrolysis system. The strategy includes application of short and periodic reductions in applied voltage, thereby avoiding saturation and prevention of carbonate salt formation.

A water electrolyzer includes an electrochemical cell including an anode and a cathode, an electrolyte solution, a heater, a voltage applicator, and a controller. The heater heats the electrolyte solution. The voltage applicator applies a voltage between the anode and the cathode. The electrochemical cell includes nickel. In startup of the water electrolyzer, the controller causes the heater to increase the temperature of the electrolyte solution by heating and causes the voltage applicator to start application of a voltage when the temperature of the electrolyte solution is less than a predetermined threshold value.

A method of reducing a gaseous compound, for example, nitrogen or carbon dioxide, the method comprising the steps of subjecting the gaseous compound to plasma forming conditions to form a plasma; contacting the plasma with water or an electrolyte at a plasma-water or electrolyte-water interface, thereby to provide a dissolved plasma derived species; and electrocatalytically reducing said dissolved plasma derived species to provide a reduced compound. The plasma may for example be generated by a combination of glow discharge and spark discharge in a configuration of a pin-to-liquid with no enclosure, pin-to-liquid with nozzle enclosure, or a pin-to-liquid with a column bubbler enclosure. A catalyst, such as transition metal, maybe added, advantageously in the form of a nano structured catalyst.

A method of reducing a gaseous compound, for example, nitrogen or carbon dioxide, the method comprising the steps of subjecting the gaseous compound to plasma forming conditions to form a plasma; contacting the plasma with water or an electrolyte at a plasma-water or electrolyte-water interface, thereby to provide a dissolved plasma derived species; and electrocatalytically reducing said dissolved plasma derived species to provide a reduced compound. The plasma may for example be generated by a combination of glow discharge and spark discharge in a configuration of a pin-to-liquid with no enclosure, pin-to-liquid with nozzle enclosure, or a pin-to-liquid with a column bubbler enclosure. A catalyst, such as transition metal, maybe added, advantageously in the form of a nano structured catalyst.

A method of operating an electrochemical cell including introducing an aqueous solution into the electrochemical cell, applying a current across an anode and a cathode to produce a product, monitoring the voltage, dissolved hydrogen, or a condition of the aqueous solution, and applying the current in a pulsed waveform responsive to one of the measured parameters is disclosed. An electrochemical system including an electrochemical cell including an anode and a cathode, a source of an aqueous solution having an outlet fluidly connectable to the electrochemical cell, a sensor for measuring a parameter, and a controller configured to cause the anode and the cathode to apply the current in a pulsed waveform responsive to the parameter measurement is disclosed. Methods of suppressing accumulation of hydrogen gas within the electrochemical cell are also disclosed. Methods of facilitating operation of an electrochemical cell are also disclosed.

A water electrolyzer includes an electrochemical cell including an anode and a cathode, an electrolyte solution, a voltage applicator, and a controller. The voltage applicator applies a voltage between the anode and the cathode. The electrochemical cell includes nickel. In the shutdown of the water electrolyzer, the controller causes the voltage applicator to apply the voltage at least when the temperature of the electrolyte solution is equal to or more than a predetermined threshold value.

A neutralization cell is provided which may be used to increase a pH level of a chlorine solution. The neutralization cell includes a neutralization anode, a neutralization cathode, an inlet, and an outlet. The neutralization anode and the neutralization cathode are positioned to divide the neutralization cell into a middle area between the neutralization anode and the neutralization cathode, an anode area on a side of the neutralization anode furthest from the neutralization cathode, and a cathode area on a side of the neutralization cathode furthest from the neutralization anode. The inlet directs the chlorine solution into the neutralization cell by directing an incoming flow of the chlorine solution into the anode area. The outlet directs the chlorine solution out of the neutralization cell by directing an outgoing flow of the chlorine solution from the cathode area.

Systems and methods for electrochemical hydrogen looping cells are described. Generating a pH swing can expedite carbon dioxide capture from oceanwater. Many embodiments implement electrochemical hydrogen looping cells that simultaneously produce acid via anodic hydrogen oxidation and base via cathodic hydrogen evolution to generate a pH change.

Systems and methods for electrochemical hydrogen looping cells are described. Generating a pH swing can expedite carbon dioxide capture from oceanwater. Many embodiments implement electrochemical hydrogen looping cells that simultaneously produce acid via anodic hydrogen oxidation and base via cathodic hydrogen evolution to generate a pH change.