Researchers create hydrogen fuel from seawater

Researchers create hydrogen fuel from seawater
A prototype device used solar energy to create hydrogen fuel from seawater. Credit: H. Dai, Yun Kuang, Michael Kenney

Stanford researchers have devised a way to generate hydrogen fuel using solar power, electrodes and saltwater from San Francisco Bay.

The findings, published March 18 in Proceedings of the National Academy of Sciences, demonstrate a new way of separating hydrogen and oxygen gas from via electricity. Existing water-splitting methods rely on highly purified water, which is a precious resource and costly to produce.

Theoretically, to power cities and cars, "you need so much hydrogen it is not conceivable to use purified water," said Hongjie Dai, J.G. Jackson and C.J. Wood professor in chemistry at Stanford and co-senior author on the paper. "We barely have enough water for our current needs in California."

Hydrogen is an appealing option for fuel because it doesn't emit carbon dioxide, Dai said. Burning hydrogen produces only water and should ease worsening climate change problems.

Dai said his lab showed proof-of-concept with a demo, but the researchers will leave it up to manufacturers to scale and mass produce the design.

Tackling corrosion

As a concept, splitting water into hydrogen and oxygen with electricity—called electrolysis—is a simple and old idea: a connects to two electrodes placed in water. When power turns on, hydrogen gas bubbles out of the negative end—called the cathode—and breathable oxygen emerges at the positive end—the anode.

But negatively charged chloride in seawater salt can corrode the positive end, limiting the system's lifespan. Dai and his team wanted to find a way to stop those seawater components from breaking down the submerged anodes.

The researchers discovered that if they coated the anode with layers that were rich in , the layers repelled chloride and slowed down the decay of the underlying metal.

They layered nickel-iron hydroxide on top of nickel sulfide, which covers a nickel foam core. The nickel foam acts as a conductor—transporting electricity from the power source—and the nickel-iron hydroxide sparks the electrolysis, separating water into oxygen and hydrogen. During electrolysis, the nickel sulfide evolves into a negatively charged layer that protects the anode. Just as the negative ends of two magnets push against one another, the negatively charged layer repels chloride and prevents it from reaching the core metal.

Without the negatively charged coating, the anode only works for around 12 hours in seawater, according to Michael Kenney, a graduate student in the Dai lab and co-lead author on the paper. "The whole electrode falls apart into a crumble," Kenney said. "But with this layer, it is able to go more than a thousand hours."

Previous studies attempting to split seawater for hydrogen fuel had run low amounts of electric current, because corrosion occurs at higher currents. But Dai, Kenney and their colleagues were able to conduct up to 10 times more electricity through their multi-layer device, which helps it generate hydrogen from seawater at a faster rate.

"I think we set a record on the current to split seawater," Dai said.

The team members conducted most of their tests in controlled laboratory conditions, where they could regulate the amount of electricity entering the system. But they also designed a solar-powered demonstration machine that produced and oxygen gas from seawater collected from San Francisco Bay.

And without the risk of corrosion from salts, the device matched current technologies that use purified water. "The impressive thing about this study was that we were able to operate at electrical currents that are the same as what is used in industry today," Kenney said.

Surprisingly simple

Looking back, Dai and Kenney can see the simplicity of their design. "If we had a crystal ball three years ago, it would have been done in a month," Dai said. But now that the basic recipe is figured out for electrolysis with seawater, the new method will open doors for increasing the availability of powered by solar or wind energy.

In the future, the technology could be used for purposes beyond generating energy. Since the process also produces breathable oxygen, divers or submarines could bring devices into the ocean and generate oxygen down below without having to surface for air.

In terms of transferring the technology, "one could just use these elements in existing electrolyzer systems and that could be pretty quick," Dai said. "It's not like starting from zero—it's more like starting from 80 or 90 percent."


Explore further

A step closer to sustainable energy from seawater

More information: Yun Kuang el al., "Solar-driven, highly sustained splitting of seawater into hydrogen and oxygen fuels," PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1900556116
Citation: Researchers create hydrogen fuel from seawater (2019, March 18) retrieved 24 April 2019 from https://phys.org/news/2019-03-hydrogen-fuel-seawater.html
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Mar 18, 2019
Introduce "Pumped Hydro" to Oceans. Let Ships carry Cement Blocks into shallow Sea Waters and align them one above the other for "Forever" Electricity production!
Excess electricity is used to pump a large quantity of water uphill into a holding pond. Later, the water is allowed to flow downhill below, spinning turbine blades to generate electricity along the way. No Reservoir is needed below in this case.

Mar 18, 2019
Well, they've improved on the corrosion problem, but what about bio-fouling ??

Mar 18, 2019
More, 5 units of energy in to get 3 out. Pointless.

Mar 19, 2019
Well, they've improved on the corrosion problem, but what about bio-fouling ??

Since the anode lasts only 1000 hours (roughly 42 days) before needing to be replaced I wouldn't worry too much about bio fouling.

Mar 19, 2019
More, 5 units of energy in to get 3 out. Pointless.

You're confused. Hydrogen is about storing energy, not magically creating it out of nothing.

Mar 19, 2019
You're confused. Hydrogen is about storing energy, not magically creating it out of nothing.

I think he's referring to the inherent loss in using hydrogen as a storage medium.
Although it's worse than 3/5...it's more like 3 units in - one unit out. (at least in the automotive sector).
In mass power storage or used for heating applications it might be slightly better. But the loss is still pretty high compared to using batteries as storage.

i think only when one goes to really large storage units or when the storage time is long (using power from summer to use in winter - i.e. when sorage concerns outweigh efficiency) is there a real market for hydrogen.

Mar 19, 2019
I'll also point out that when it's free power from the sky, it's a bit easier to justify.

Mar 19, 2019
I think he's referring to the inherent loss in using hydrogen as a storage medium.

You're right, I'm used to encountering people who think of hydrogen as a fuel and not a battery. And you're right, it's not a very efficient battery. But part of its promise that gets forgotten is the "cleanliness", of its cycle, which counts for something, and is part of why seeing advances like this are still interesting. If it could lead to the type of scaling up that you mention then its a worthwhile endeavor.

Mar 19, 2019
I'll also point out that when it's free power from the sky, it's a bit easier to justify.

Da Schitts, the "meat" loving, knob gobbler, brays.
Is that how you justify, all the ass pummelling you get from trolling men's toilets?
It's free.
LMAO.

Mar 19, 2019
I'll also point out that when it's free power from the sky, it's a bit easier to justify.

Still: Powerplants for that free power have to be built and cost a bit of money.
If you can get x amount of usable energy from what you build or 3x the amount for the same cost then I'd always go for the 3x unless there are extenuating circumstances.

Mar 20, 2019
Well, they've improved on the corrosion problem, but what about bio-fouling ??

Since the anode lasts only 1000 hours (roughly 42 days) before needing to be replaced I wouldn't worry too much about bio fouling.

A sustainable solution would be useful for Deep Sea Hydrogen Storage,

Diagram -
https://scottishs...rage.jpg

Blog post - "Off-Shore Electricity from Wind, Solar and Hydrogen Power"
https://scottishs...n-power/

Mar 20, 2019
Theoretically, to power cities and cars, "you need so much hydrogen it is not conceivable to use purified water," said Hongjie Dai, J.G. Jackson and C.J. Wood professor in chemistry in Stanford's School of Humanities and Sciences and co-senior author on the paper. "We barely have enough water for our current needs in California."

California could transmit electrical power north to Canada, where they have plenty of fresh water, produce the hydrogen by electrolysis and pipe the hydrogen south back to California.

There is no global shortage of fresh water but admittedly, many places do indeed suffer very significant local shortages of fresh water which I do not make light of and so I praise California highly for their extensive water supply network.

Mar 20, 2019
A sustainable solution would be useful for Deep Sea Hydrogen Storage,

Diagram -
https://scottishs...rage.jpg

Or indeed for sea surface storage of hydrogen in pressurised tanks as energy storage for floating wind farms.

Mar 20, 2019
@betterexists

Using the sea as the lower reservoir for pumped storage was pioneered in Okinawa, years ago.
https://en.wikipe..._Station

That method has been adopted elsewhere and is also the default variant of my Strathdearn Pumped Storage Hydro scheme
https://scottishs...cotland/
though there are fresh water variants of Strathdearn PSH too.

What's impractical I think would be to construct an artificial upper reservoir at sea as betterexists seems to suggest.

Mar 20, 2019
A sustainable solution would be useful for Deep Sea Hydrogen Storage,

Diagram -
https://scottishs...rage.jpg

Or indeed for sea surface storage of hydrogen in pressurised tanks as energy storage for floating wind farms.

Failing that one could always ship the freshwater in or catch rainwater and use that to top up a custom electrolyte solution.

So there is no doubt in my mind that a good solution to producing hydrogen fuel from seawater would be very useful but perhaps it would be deployed in a slightly different way to that imagined by the researchers at Stanford.

Good work.

Mar 20, 2019
I'll also point out that when it's free power from the sky, it's a bit easier to justify.


However, you have to take into account what else you might have accomplished with that "free" power from the sky. And also how accurate the use of the word "free" is. I recently looked long and hard at a solar power array for my house. I did not find a single free option.
And then you have to decide what to do with the electricity once you have it. I can choose to put kwh into my Tesla battery, or I can store less than half that amount of energy in hydrogen. So even if I can convince myself that the solar power is free, its still not unlimited - it must be budgeted. If I choose hydrogen, I have less energy left to budget. I already started with not quite enough, so its not hard to see where that ends up....

Mar 23, 2019
For me the best option for hydrogen storage of energy would also include the fresh water generation by capturing the water created when the hydrogen is burned back to water. That way we would combine water desalination to energy storage. That should improve the combined efficiency, when there is not separate water desalination needing energy.

Mar 26, 2019
If they are running high current than the layers of the electrodes must also be preventing the system from producing chlorine gas.

I'm a bit curious about what effect the calcium and magnesium ions in the water have on the electrodes too.

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