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TurretLauncher OP t1_iygf57r wrote

Abstract

Electrochemical saline water electrolysis using renewable energy as input is a highly desirable and sustainable method for the mass production of green hydrogen; however, its practical viability is seriously challenged by insufficient durability because of the electrode side reactions and corrosion issues arising from the complex components of seawater. Although catalyst engineering using polyanion coatings to suppress corrosion by chloride ions or creating highly selective electrocatalysts has been extensively exploited with modest success, it is still far from satisfactory for practical applications. Indirect seawater splitting by using a pre-desalination process can avoid side-reaction and corrosion problems, but it requires additional energy input, making it economically less attractive. In addition, the independent bulky desalination system makes seawater electrolysis systems less flexible in terms of size.

Here we propose a direct seawater electrolysis method for hydrogen production that radically addresses the side-reaction and corrosion problems. A demonstration system was stably operated at a current density of 250 milliamperes per square centimetre for over 3,200 hours under practical application conditions without failure. This strategy realizes efficient, size-flexible and scalable direct seawater electrolysis in a way similar to freshwater splitting without a notable increase in operation cost, and has high potential for practical application. Importantly, this configuration and mechanism promises further applications in simultaneous water-based effluent treatment and resource recovery and hydrogen generation in one step.

https://www.nature.com/articles/s41586-022-05379-5

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Ann_not_a_cult_er t1_iygz015 wrote

What about if they used hydrogen powered ICE engines to pump sea water to areas that need water, use R.O. to clean it, and use the brine in electrolysis to create the hydrogen thus lowering the cost and waste of desal plants?

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StandardSudden1283 t1_iyh0ihh wrote

2nd law of thermodynamics.

You'll never get more out of electrolysis than it requires

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Black_Moons t1_iyh9lmp wrote

This. If you use an IEC engine to burn hydrogen... you end up with: WATER!

You can't extract energy from turning water into something that gets turned back into water, because you ended up with the exact same substance you started with.

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LucyEleanor t1_iyir4d1 wrote

Plus lose alot of energy to heat.

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Black_Moons t1_iyj886d wrote

Yep. Electrolysis is very inefficient. But even if you made it 100% efficient, and somehow made an IEC engine 100% efficient, you'd still only be making an energy storage system at best.

Realistically, the above two systems are like, 60% and 30% efficient at best? So your talking 18% overall. Not really worth doing until we have so much renewable energy that what to do with all the extra between the hours of X and Y becomes an issue.

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LucyEleanor t1_iyj90yp wrote

We can make hydrogen fuel cell systems smaller and lighter than normal ice's though, so atleast they have their use in drones.

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ledow t1_iyjjd6o wrote

Hydrogen needs to be stored at 10,000 psi to come anywhere NEAR the energy density of a conventional fuel.

Though you can get more energy per kilo of hydrogen, you can't do that without basically compressing it to enormous pressures or taking up a ton of room, or using up lots of chemicals and energy to lock it into other substances (which add to the mass).

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LucyEleanor t1_iyjjhkb wrote

Well drones do use mini scuba tank guys full of compressed h2. Idk the psi tho

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[deleted] t1_iykisj3 wrote

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Black_Moons t1_iykond6 wrote

that is a really inefficient way of storing energy. about 18% efficiency after electrolysis and internal combustion engine.

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[deleted] t1_iykstc9 wrote

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Black_Moons t1_iykx3l8 wrote

Reshape heavy energy consumer industry like cement plants, aluminum smelters, ammonia production, etc to run during peak hours only, by giving them better per-hour pricing so instead of drawing power 24/7 and requiring baseload generation, they can run off peak hour renewables and enjoy lower costs of energy. They will have to increase facility size to compensate for lower productivity however.

Also, redox flow batteries arnt half bad..

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sillypicture t1_iyh2fb9 wrote

Every intermediate process introduces inefficiencies.

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KiwasiGames t1_iyhai42 wrote

You will always get less energy out of electrolysis in hydrogen than you put in as electricity. That’s how thermodynamics works. There is always waste energy in the form of heat.

So you won’t be saving any energy here.

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Hob_O_Rarison t1_iyi29q4 wrote

But you can turn solar energy into packagable, transferable fuel that can be stored and moved around.

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starmartyr t1_iyjo56g wrote

You might not be able to save energy, but not all energy has the same economic value. This has the potential to use cheap clean energy to move energy to places where it is not easily available. This is similar to our problem with water shortages. We don't have a shortage of water, we have a problem getting the water we need to the places that need it.

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KiwasiGames t1_iykyk90 wrote

While this is true in general terms, its not true for the post I was responding to.

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emote_control t1_iyjb3le wrote

You'd be better off just putting hydrogen farms in the ocean and shipping the products inland, given the energy density of hydrogen compared to sea water per unit mass. Much less wasted energy. For remote places with a plentiful renewable energy source but little clean water, it could be useful.

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