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TurretLauncher OP t1_iygf57r wrote


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.


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?


StandardSudden1283 t1_iyh0ihh wrote

2nd law of thermodynamics.

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


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.


LucyEleanor t1_iyir4d1 wrote

Plus lose alot of energy to heat.


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.


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.


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).


LucyEleanor t1_iyjjhkb wrote

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


[deleted] t1_iykisj3 wrote



Black_Moons t1_iykond6 wrote

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


[deleted] t1_iykstc9 wrote



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..


sillypicture t1_iyh2fb9 wrote

Every intermediate process introduces inefficiencies.


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.


Hob_O_Rarison t1_iyi29q4 wrote

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


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.


KiwasiGames t1_iykyk90 wrote

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


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.


TurretLauncher OP t1_iygfdfl wrote

The team assembled a device and put it to use on Shenzhen Bay seawater (an inlet north of Hong Kong and Macau). And, by nearly every reasonable performance measure, it worked well.

It maintained performance even after 3,200 hours of use, and electron microscopy of the membrane after use indicated that the pores remained unblocked at this point. The KOH used for the system wasn't completely pure, so it contained low levels of the ions found in seawater. But those levels didn't increase over time, confirming that the system kept the seawater out of the electrolysis chamber. Power-wise, the system used about as much as a standard electrolyzer, confirming that the water purification wasn't exacting any energetic cost.

The KOH solution also was self-balancing, with water diffusion into the device slowing if its internal solution became too dilute. If it gets too concentrated, the efficiency of electrolysis drops, so the elimination of water slows down.

The authors estimate their device would handle pressures down to about 75 meters of seawater. The temperature at those depths might be limiting, however, as the diffusion rate of water across the membrane was six times higher at 30° C than it is at 0° C.

Even with all that good news, there are options for improving performance. Various salts beyond KOH are suitable, and some may perform better. The researchers also found that incorporating KOH into a hydrogel around the electrodes boosted hydrogen production. Finally, it's possible that altering the material or structure of the electrodes used in the water splitting could boost things further.

Finally, the team suggested that this might be useful for things in addition to hydrogen production. Instead of seawater, they immersed one of the devices into a dilute lithium solution and found that 200 hours of operation increased the lithium concentrations by more than 40-fold due to water moving into the device. There are plenty of other contexts, like purifying contaminated water, where this sort of concentration ability could be useful.


somedave t1_iygu99w wrote

They didn't mention the electrolysis efficiency though.


tminus7700 t1_iykl7q5 wrote

That is key. From what I have read this is NOT a hydrogen producing device, but an enhanced reverse osmosis device. That provides water to a conventional electrolytic cell. You could just electrolysis sea water directly. You will get hydrogen and chlorine. I don't know which would be more energy efficient. The chlorine would also be a useful product.

Besides hydrogen is not close to the fuel of the future.

>Water electrolysis has not yet been implemented on a large scale >Only four per cent of all hydrogen produced worldwide are the result of water electrolysis. As the electrodes used in the process are not efficient enough, large-scale application is not profitable. **To date, hydrogen has been mainly obtained from fossil fuels, with large CO2 volumes being released in the process,**says Wolfgang Schuhmann. "If we succeeded in obtaining hydrogen by using electrolysis instead, it would be a huge step towards climate-friendly energy conversion. For this purpose, we could utilise surplus electricity, for example generated by wind power."


somedave t1_iylpjbl wrote

A bit of chlorine would be useful, as would sodium and other metals, but realistically we'd want orders of magnitude more hydrogen if we were going to use it to replace fossil fuels.


Latyon t1_iygfon0 wrote

This is radical. My science brain is positively engorged with vibrant thought.


NoConversation9358 t1_iygkcpa wrote

Can't you do that with an extension cord and some wire strippers?


KiwasiGames t1_iyha5dq wrote

The basic problem is that the sea water will corrode your electrodes (ie the exposed extension cord wire). On any sort of scale, electrodes become a huge cost and downtime factor. As a result most electrolysis plants use clean water.

Improved electrodes that are resistant to seawater corrosion means that we don’t need to use potable water to produce hydrogen. This is a big deal (if the tech ends up being scalable).


dejco t1_iyhhm2z wrote

You could use graphite.


baggier t1_iyk3dha wrote

then the graphite overpotentials mean you use more voltage and less efficiency


sonoma95436 t1_iygqcim wrote

We did this in school You need a dc source. 2 test tubes A lantern battery or a dc power supply wire textures and salted water. Hydrogen will form in one tube, twice the hydrogen as oxygen in the other as its h20. Using graphite rods in the water prevents most corrosion. This is old stuff.


bigb1 t1_iyh3twq wrote

H2O means you have 2 Hydrogen and 1 Oxygen.


sonoma95436 t1_iyhao82 wrote

Yes left out the word. 2 atoms hydrogen 1 oxygen.


tornpentacle t1_iyh0h6f wrote

This is a repost; the journal article itself was posted earlier.


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nmagod t1_iygg3ij wrote

I genuinely feel like we hear about this "new revolutionary electrolysis method" every year, and then it goes away until the next one.


VitaminPb t1_iygoei3 wrote

I am unclear if this scales with input power (doubtful) or requires increased processing volume to scale. Also, what is the rate of the electrolysis in terms of liters per minute or hour?


Boomape1956 t1_iyiwfi2 wrote

It’s called a salt water chlorinator. I have one for my pool.


Likeyoueasilyamused t1_iyjc4jx wrote

Good news everybody, we've discovered a reason and a way for big corporations to destroy earth's oceans. Ta ta.


HRamos_3 t1_iyhhz8h wrote

Is said new device electric? Cause I'm fairly sure electrolysis has been known for a while now...


thraupidae t1_iyiy6f6 wrote

Electrolysis needs to be done with pure water to not destroy the device eventually. This is different because it appears to be sustainable and stable in seawater. The test said that after 3200 hours the membrane was still fine. Probes for electrolysis would be fried well before that.


Azreken t1_iyi3a4v wrote

I’m calling it now that an advanced version of this type of tech is what’s being used in the UAP that pilots have been witnessing on the coasts the last few years.

Whether alien or not, idk, but it’s gotta be some kind of device that pulls hydrogen directly from water and uses it as fuel since they keep dipping into the water.


IsildursBane20 t1_iyi991x wrote

I made this 20 years ago with a battery, what’s so special ?


JamesTheMannequin t1_iygm2vd wrote

Why not a device that simply removes the Oxygen, leaving Hydrogen as a byproduct?

Edit: It was a joke, guys. Sheesh.


Spike_Spiegel t1_iygpuxa wrote

Perhaps a thermonuclear fission-fusion type device? Of say..2000 megatons?


tornpentacle t1_iyh0z1p wrote

I don't mean to sound abrasive, but it might be wise to check the rules before commenting