Materials scientists at Harvard have created a fuel cell that not only produces energy but also stores it, opening up new possibilities in hydrogen fuel cell technologies. The solid-oxide fuel cell (SOFC) converts hydrogen into electricity, and could have an impact on small-scale portable energy applications.

The thin-film SOFC benefited from recent advances in low-temperature operations, which enabled the integration of versatile materials, said lead researcher Shriram Ramantham. The star of the new cell is vanadium oxide, a multifuncional material that allows the fuel cell to multitask as both an energy generator and storage medium.

The new fuel cell uses a bilayer of platinum and vanadium oxide for the anode, which allows the cell to continue operating without fuel for up to 14 times as long as the thin-film SOFCs that use platinum only for the electrodes. In the case of the latter, when the platinum-anode SOFC runs out of fuel, it will continue to generate power for only about 15 seconds before it fizzles out. With the new fuel cell, the scientists have managed to increase that to three minutes, 30 seconds at a current density of 0.2 mA/cm2.

That length of time could be increased with further improvements to the composition of the vanadium oxide-platinum anode. It should happen fairly soon, and this type of fuel cell could be available for applications testing within two years. The researchers say that one field that could benefit from the new fuel cell is micro aerial vehicles, although fuel cells for powering vehicles are already a reality.

The researchers observed and confirmed a few chemical phenomena that possibly explains the extended power of the cell. The first of these is the oxidation of the vanadium ions. Another one is the storage of hydrogen within the vanadium oxide crystal lattice, which is then gradually released and oxidized at the anode. Finally, they noticed that the concentration of oxygen ions differs from the anode to the cathode, which could mean oxygen anions (negatively-charged ions) also get oxidized as in a concentration cell.

Details about the research appeared in the journal Nano Letters.

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