Electrolysis of seawater to make hydrogen

The direct electrolysis of seawater to make hydrogen has been proven in a lab-scale demonstration.

There may be irony to be discovered within the ninth stanza of Samuel Taylor Coleridge’s poem, The Rime of the Historic Mariner:

“Water, water, in every single place,

And all of the boards did shrink,

Water, water, in every single place,

Nor any drop to drink.”

Simply as salty ocean water can’t quench the thirst of sailors, it additionally can’t satiate the water calls for of the rising hydrogen economic system. It is because the advanced composition of seawater renders it unusable for standard, large-scale water-splitting electrolysis, a course of that makes use of electrical energy to chemically convert water into hydrogen and oxygen.

Although considerable, seawater’s dissolved salts endure competing processes aside from water splitting inside the electrochemical cell, inflicting corrosion and facet reactions. Sodium chloride, the principle perpetrator, ranges from 34-37 elements per thousand in seawater and types corrosive chlorine gasoline and sodium hydroxide underneath electrolysis circumstances.

Chemical response by-product results that may happen underneath electrochemical circumstances are exacerbated by the co-existence of different dissolved alkali and alkaline earth and halogen salts, in addition to carbonates, borates, and sulfates, which end in comparable corrosive species. Whereas desalination pre-treatment can, in precept, resolve the challenges of dissolved salts, the extra vitality required makes this method economically unattractive.

Earlier makes an attempt to eradicate these deleterious chemical corrosion and response results by means of protecting coatings of electrocatalysts haven’t confirmed sufficiently efficient for a viable seawater electrolysis software.  

Regardless of the challenges, the direct electrolysis of seawater has not too long ago been achieved in a lab-scale demonstrator. The structure and constituents of the electrochemical cell, proven within the graphical illustration, achieved this feat utilizing an revolutionary, built-in, in-situ water purification membrane meeting.

The membrane is created from water-permeable polytetrafluoroethylene and is immersed in concentrated potassium hydroxide, which acts as a “self-dampening” electrolyte (SDE). This development facilitates the spontaneous and steady diffusion of pure water vapour from the much less salty seawater by means of the membrane, and collects it within the a lot saltier potassium hydroxide SDE, permitting it to be electrolytically break up into hydrogen and oxygen in separate cathode and anode chambers of the cell.

In a proof of idea, the system was in a position to run underneath real-world circumstances with out failure for over 3200 hours at 250 milliamperes per sq. centimeter and a couple of.1 volts with out side-reactions or corrosion issues.

This seawater electrolysis course of is a breakthrough which will kick off a myriad of software alternatives. To call just a few, by changing the seawater with industrial wastewater or lithium-rich water from battery recycling, the method can facilitate water remedy and lithium-collection, respectively, whereas producing hydrogen.

Now this is able to absolutely impress the Historic Mariner!

Reference: Heping Xie, et al., A membrane-based seawater electrolyser for hydrogen era, Nature (2022). DOI: 10.1038/s41586-022-05379-5

Characteristic picture credit score: Cristian Palmer on Unsplash