Imagine a clock that still runs after the electriocity is cut off during a storm or a lamp that continues to shine during a power outage.
Materials scientists at Harvard have demonstrated a clean energy generation with a solid-oxide fuel cell (SOFC) that converts hydrogen into electricity but can also store electrochemical energy like a battery.
This power “on-age” during an outage was developped by a professor, a a post-doctoral fellow and Iranian graduate student Kian Kerman at the Harvard School of Engineering and Applied Sciences (SEAS).
The principal investigator, Shriram Ramanathan, associate professor of materials science at SEAS, said, “Vanadium oxide (VOx) at the anode behaves as a multifunctional material, allowing the fuel cell to both generate and store energy.”
The finding, which appeared online in the journal Nano Letters in June, 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.
“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 life span significantly.”
Ramanathan, Van Over-meere and Kerman 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 electrochemical reaction peters out.
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. 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 life span.
“There are three reactions that potentially take place within the cell due to this vanadium oxide anode,” says Ramanathan. 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 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 within two years.