Energy conversion via metal nanolayers

Mavis D. Boamah, Emilie H. Lozier, Jeongmin Kim, Paul E. Ohno, Catherine E. Walker, Thomas F. Miller, Franz M. Geiger*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Current approaches for electric power generation from nanoscale 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. Nanolayers 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 nanooverlayer that forms spontaneously in air and then self-terminates. Indeed, experiments suggest a role for intraoxide 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.

Original languageEnglish (US)
Pages (from-to)16210-16215
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number33
StatePublished - Aug 13 2019


  • Electron transfer
  • Energy conversion
  • Inorganic nanomaterials
  • Solid–liquid interface
  • Sustainability

ASJC Scopus subject areas

  • General


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