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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.

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somedave t1_iygu99w wrote

They didn't mention the electrolysis efficiency though.

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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."

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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.

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Latyon t1_iygfon0 wrote

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

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