New fuel cell keeps going after the hydrogen runs out

Jun 29, 2012
Shriram Ramanathan's laboratory setup for testing solid-oxide fuel cells. The fuel cell is hidden under the circular component at the top, which pins it down to create a tight seal with the hydrogen fuel entering from below. Two needles connect with the electrodes to measure the electricity produced. Credit: Caroline Perry, Harvard SEAS

Imagine a kerosene lamp that continued to shine after the fuel was spent, or an electric stove that could remain hot during a power outage.

Materials scientists at Harvard have demonstrated an equivalent feat in clean energy generation with a solid-oxide (SOFC) that converts hydrogen into electricity but can also store like a battery. This fuel cell can continue to produce power for a short time after its fuel has run out.

"This thin-film SOFC takes advantage of recent advances in low-temperature operation to incorporate a new and more versatile material," explains principal investigator Shriram Ramanathan, Associate Professor of Materials Science at the Harvard School of Engineering and Applied Sciences (SEAS). "Vanadium oxide (VOx) at the behaves as a multifunctional material, allowing the fuel cell to both generate and store energy."

The finding, which appears online in the journal Nano Letters, will be most important for small-scale, portable energy applications, where a very compact and lightweight power supply is essential and the fuel supply may be interrupted.

New fuel cell keeps going after the hydrogen runs out
Left: Each dark speck within the nine white circles at left is a tiny fuel cell. An AA battery is shown for size comparison. Right: One of the nine circles is magnified in this image, showing the wrinkled surface of the electrochemical membrane. Credit: Left: Caroline Perry, SEAS Communications. Right: Quentin Van Overmeere, Harvard SEAS.

"Unmanned aerial vehicles, for instance, would really benefit from this," says lead author Quentin Van Overmeere, a postdoctoral fellow at SEAS. "When it's impossible to refuel in the field, an extra boost of stored energy could extend the device's lifespan significantly."

Ramanathan, Van Overmeere, and their coauthor Kian Kerman (a graduate student at SEAS) typically work on thin-film SOFCs that use platinum for the electrodes (the two "poles" known as the anode and the cathode). But when a platinum-anode SOFC runs out of fuel, it can continue to generate power for only about 15 seconds before the peters out.

New fuel cell keeps going after the hydrogen runs out
Three possible mechanisms (left to right) can explain the operation of the vanadium oxide / platinum fuel cell after its fuel has been spent. The illustration represents a simplified cross-section of the SOFC: the top layer is the cathode (made of porous platinum), the middle layer is the electrolyte (yttria-stabilized zirconia, YSZ), and the bottom layer is the VOx anode. During normal operation, the hydrogen fuel would be at the bottom of this diagram. Credit: Quentin Van Overmeere, Harvard SEAS

The new SOFC uses a bilayer of platinum and VOx for the anode, which allows the cell to continue operating without fuel for up to 14 times as long (3 minutes, 30 seconds, at a current density of 0.2 mA/cm2). This early result is only a "proof of concept," according to Ramanathan, and his team predicts that future improvements to the composition of the VOx-platinum anode will further extend the cell's lifespan.

During normal operation, the amount of power produced by the new device is comparable to that produced by a platinum-anode SOFC. Meanwhile, the special nanostructured VOx layer sets up various chemical reactions that continue after the hydrogen fuel has run out.

"There are three reactions that potentially take place within the cell due to this vanadium oxide anode," says Ramanathan. "The first is the oxidation of vanadium ions, which we verified through XPS (X-ray photoelectron spectroscopy). The second is the storage of hydrogen within the VOx crystal lattice, which is gradually released and oxidized at the anode. And the third phenomenon we might see is that the concentration of oxygen ions differs from the anode to the cathode, so we may also have oxygen anions being oxidized, as in a concentration cell."

All three of those reactions are capable of feeding electrons into a circuit, but it is currently unclear exactly what allows the new fuel cell to keep running. Ramanathan's team has so far determined experimentally and quantitatively that at least two of three possible mechanisms are simultaneously at work.

Ramanathan and his colleagues estimate that a more advanced fuel cell of this type, capable of producing power without fuel for a longer period of time, will be available for applications testing (e.g., in micro-air vehicles) within 2 years.

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User comments : 11

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SatanLover
1.8 / 5 (5) Jun 29, 2012
well this is interesting. what if we can create fuel cells that keep going forever by injecting new bacteria every time it runs dry?
KingDWS
not rated yet Jun 29, 2012
That's a loww temp sofc. Low temp means 400 to maybe 800 degrees C. About all you'd get is fried bacteria. Yummy time for lunch :-)
warmonger
5 / 5 (2) Jun 30, 2012
Kind of interesting but I really don't see the point. The energy being used to run the thing after the fuel is used up came from the fuel anyway.

Or if you're going to tell me that this is an efficient way to store energy in the cell, then what do we need the fuel for? Just find a way of using this technique to store all of the energy and you can get rid of the fuel.
antialias_physorg
3 / 5 (4) Jun 30, 2012
well this is interesting. what if we can create fuel cells that keep going forever by injecting new bacteria every time it runs dry?

Wow, what a great idea. Next you're going to invent a car that can keep going if we occasionally fill it up with gas. You, sir, are a genius.
SatanLover
1.8 / 5 (5) Jun 30, 2012
well this is interesting. what if we can create fuel cells that keep going forever by injecting new bacteria every time it runs dry?

Wow, what a great idea. Next you're going to invent a car that can keep going if we occasionally fill it up with gas. You, sir, are a genius.


No i am saying that the waste the bacteria leave behind can become food for the new injected bacteria. You only inject a few bacteria not a whole tank full of bacteria.

Sir you are an idiot, congratulations.
antialias_physorg
1 / 5 (1) Jun 30, 2012

No i am saying that the waste the bacteria leave behind can become food for the new injected bacteria.

I'll explain this in very simple terms so that even you can understand it - because obviously you're not even reading what you write yourself:

Bacetria leave WASTE. The reason WASTE is WASTE is because the bacteria have extracte anything useful (to them) from it. It is therefore of no more use to the bacteria in any way and cannot be used by them for food (you know: because it's WASTE)

Get it?
SatanLover
3 / 5 (4) Jun 30, 2012

Bacetria leave WASTE. The reason WASTE is WASTE is because the bacteria have extracte anything useful (to them) from it. It is therefore of no more use to the bacteria in any way and cannot be used by them for food (you know: because it's WASTE)


And this waste becomes food for a different bacteria.

GET IT?

Don't be a freaking retard please cause i thought better of you ;)
Aloken
not rated yet Jul 02, 2012
And this waste becomes food for a different bacteria.

GET IT?

Don't be a freaking retard please cause i thought better of you ;)


Even if that worked you're just replacing hydrogen with bacteria, it's still fuel (except harder to use because you have to change it instead of just adding more). Also you'd need a tank full of different types of bacteria to keep it running for extended periods of time, so you imagined a device that has to swap to a different type of fuel every so often just to work and thought it was a good idea. Really?
antialias_physorg
not rated yet Jul 02, 2012
And this waste becomes food for a different bacteria.

As I said in my first post. You have just (re)invented the idea of adding fuel to keep something going. That isn't really new. I think the cavemen who first thought about throwing a log on the fire came up with that one (or possible the first organism that thought about sticking food into it's mouth).
AtlasT
1 / 5 (1) Jul 02, 2012
Cold fusion will wipe out all this useless research. Actually it would do it before twenty years already, if the physicists wouldn't prohibit it as a single man just for the sake of their own research.
SatanLover
not rated yet Jul 03, 2012

And this waste becomes food for a different bacteria.

As I said in my first post. You have just (re)invented the idea of adding fuel to keep something going. That isn't really new. I think the cavemen who first thought about throwing a log on the fire came up with that one (or possible the first organism that thought about sticking food into it's mouth).

I am sorry but you just went double retarded.

Do you understand what bacteria do? Right they grow and consume and reproduce. Fuel doesnt grow consume and reproduce. capiche? What happened to you dude? Why did you just become double retarded?