A team of researchers at Harvard University has created a novel hydrogen fuel cell that keeps running even after its fuel supply is exhausted. The solid-oxide fuel cell (SOFC) converts hydrogen into electricity, and it can also store electrochemical energy like a battery. This allows the fuel cell to produce power for a short time after it has run out of hydrogen.
In a press statement, associate professor of materials science at the Harvard School of Engineering and Applied Sciences (SEAS) Shriram Ramanathan said: “This thin-film SOFC takes advantage of recent advances in low-temperature operation to incorporate a new and more versatile material. Vanadium oxide (VOx) at the anode behaves as a multifunctional material, allowing the fuel cell to both generate and store energy.”
The team’s findings were published in the journal Nano Letters in June, where they theorized that their hydrogen fuel cell would be useful in small-scale, portable energy applications, where a very compact and lightweight power supply is essential. “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.”
Thin-film SOFCs traditionally use platinum for the electrodes (the two “poles” known as the anode and the cathode) which, allows the cell to generate power for only about 15 seconds before the electrochemical reaction peters out. The Harvard team used a bilayer of platinum and VOx for their anode, which can continue operating without fuel for up to 14 times longer.
“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.”
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 within two years.