DEPARTMENT OF
PHYSICAL CHEMISTRY
Physikalische Chemie - Direktor: Prof. Dr. Martin Wolf
Informal Seminar
Host: Y. Tong

Friday, December 20, 2019, 2:00 pm
PC Seminar Room, G 2.06, Faradayweg 4
Prof. Franz Geiger
Northwestern University
Energy Conversion via Metal Nanolayers
Current approaches for electric power generation from nano scale conducting or semiconducting layers in contact with moving aqueous droplets are promising as they show efficiencies of around 30%, yet even the most successful ones pose challenges regarding fabrication and scaling. Here, we report stable, all inorganic single-element structures synthesized in a single step that generate electrical current when alternating salinity gradients flow along its surface in a liquid flow cell. Nano layers of iron, vanadium, or nickel, 10 to 30 nm thin, produce open-circuit potentials of several tens of millivolt and current densities of several microA cm−2 at aqueous flow velocities of just a few cm s−1. The principle of operation is strongly sensitive to charge-carrier motion in the thermal oxide nano overlayer that forms spontaneously in air and then self-terminates. Indeed, experiments suggest a role for intra oxide electron transfer for Fe, V, and Ni nanolayers, as their thermal oxides contain several metal-oxidation states, whereas controls using Al or Cr nanolayers, which self-terminate with oxides that are redox inactive under the experimental conditions, exhibit dramatically diminished performance. The nanolayers are shown to generate electrical current in various modes of application with moving liquids, including sliding liquid droplets, salinity gradients in a flowing liquid, and in the oscillatory motion of a liquid without a salinity gradient.