Understanding Metal Nanofilms for Sustainable Energy Applications

An emerging class of renewable energy transducers uses graphene-based materials (1,2,3) in contact with a liquid to convert fluid movement into electrical energy. While achieving up to 30% conversion efficiencies (4), these transducers are difficult to scale and synthetically complex. Professor Franz Geiger’s group at Northwestern University discovered comparable energy harvest in nanofilms of zero-valent iron topped by its thermal oxide (Fe:FeOx). Such films can be deposited onto glass or polymer substrates in a single step by physical vapor deposition using an inexpensive Fe source. When exposed to air, a 3-5 nm oxide layer spontaneously forms and self-passivates. Since this FeOx layer is hypothesized to play a role in current generation, a detailed understanding of its composition under operating conditions is an important fist step toward elucidating the mechanism of energy harvest.