It's one of those reactions that depends on concentration and acidity, basically not going to be a concern for seawater electrolysis. Making chlorine gas is a pretty involved process, the NaCl salt has to be highly pure, etc.
> "In all cell processes, the filtered brine is heated and passed through a bed of salt in a saturator in order to increase its salt concentration before feeding it to the electrolyzers. In some plants, the brine feed is acidified to improve the cell current efficiency. The acidification reduces the alkalinity, which would otherwise react with the chlorine in the anolyte compartment, forming chlorate."
At neutral-alkaline pH with seawater you can get hypochlorite (ClO-), basically relatively weak chlorine bleach formation at 0.5-1%, this is used when seawater is used for industrial cooling systems (see nuclear power plants etc.):
> "A more realistic picture of the problems DSS faces can be gained from on-site hypochlorite generators, a technology established since the early 1970s for industrial water cooling systems. There, low concentrated hypochlorite is used to avoid the growth of marine organisms as they tend to foul equipment and worsen heat transfer. The hypochlorite is formed by direct oxidation of Cl- from the filtered seawater feed. The electrolysers are one compartment cells made of titanium, and the electrodes are comprised of a titanium core with a precious metal oxide coating (Ru, Ir, Pt)."
source: Hausmann et al. (2021). Is direct seawater splitting economically meaningful? (sci-hub)
Hydrogen from seawater directly seems pretty speculative, be interesting if it works, you could have hydrogen production at sea maybe. Scale might be an issue (giant barges with solar panels making hydrogen for fueling shipping?)
Yea it produces chlorine. Nuclear subs need to use reverse osmosis first to get around that problem when they want to produce Oxygen from seawater. https://www.youtube.com/watch?v=g3Ud6mHdhlQ
There is a proposed method to sequester carbon and reduce ocean acidification by doing this process, extracting the Hydrogen and Chlorine (or hydrochloric acid) for industrial purposes, and releasing the sodium hydroxide to absorb dissolved CO2 (carbonic acid) into sodium carbonate.
It was mind blowing for me at the time! Subsequent approaches to accelerated silicate weathering like Project Vesta dropped the chemical component and just used mechanical crushing of rocks to accelerate weathering. The all-mechanical approach is less complicated and energy intensive.
If you're extracting chlorine to react it with rock it probably makes more sense to just react the rock directly. But if you can use the chlorine industrially it makes more sense not to involve the mining and transport of rock. There's currently a significant industry of chlorine and HCl production that isn't linked to a carbon sequestration process that we can supplant.
One could also release the chlorine into the atmosphere to destroy atmospheric methane. Elemental chlorine in sunlight is rapidly (within minutes) broken down into chlorine atoms. These atoms, being free radicals, efficiently extract hydrogen from methane molecules, starting a chain of reactions that converts the remaining fragment to CO2 and water.
You'd need a hell of a lot of chlorine to compensate for current methane injection, though.
No , cholrine radicals will also deplete ozone layer ,
Besides I don't think releasing highly reactive gases at any concentration into the atmosphere is a good idea, there can be other effects we haven't studied well enough.
Methane is present throughout the troposphere -- it has an atmospheric lifetime of something over a decade and becomes well mixed. You'd want to release the chlorine in a sufficiently dilute and dispersed form that it didn't overwhelm the methane in the air it which it was released.
Needs massive energy input which would come from where? Also, massive amounts of toxic chemicals. Use biology to solve climate change by growing biomass (bio CCS) in the form of kelp, diatoms, and other high growth life (maybe GMO) to sink to the bottom of the ocean.
> But if they manage to get H2 from it then the sodium, oxygen, and chlorine have to bind into something else than usual I guess.
It's the same electrolysis process used today in swimming pools to generate chlorine. The hydrogen evaporates, the chlorine ends up in the water, and the chemical reaction ends up producing the same salt it started with. You don't have to add salt[0] and the chlorine pretty quickly evaporates and breaks down in sunlight if you don't put cyanuric acid in the water to bind it.
Mostly it could be ignored, though if the chlorine level got high enough it would kill the organic things.
[0] except for losses due to other reasons than chlorine generation
I only played vanilla, but my pool at home with salt system has taught me that. It uses a 48v cell with 3000 ppm salt to create chlorine to sanitize the pool water. Many pools now days use this kind of system rather than chlorine tablets or whatever.
Doesn't brine electrolysis also produce chlorine, or has Factorio fed me some horseshit?