Faculty Colloquium - Facet-Selective and Flow-Through Electrochemistry with Metal Nanowires

Presenter: Professor Benjamin Wiley (Duke University, Department of Chemistry)

Abstract:  Metal nanowires are metal sticks tens of nanometers wide and tens of micrometers long. Why metal nanowires grow in isotropic solutions when their crystal structures have cubic symmetry has been a mystery for nearly 20 years. Researchers have hypothesized that organic additives, usually called capping agents, direct anisotropic growth of nanowires by adsorbing to the sides of nanowires while leaving the ends open to atomic addition. I will show measurements with single-crystal electrodes can be used to test this capping agent hypothesis. The evidence suggests the capping agent hypothesis is wrong for at least two different nanowire syntheses.

In the second half of my talk, I will show how a three-dimensional network of nanowires can be used to achieve unprecedented rates of electrochemical conversion. Achieving a high rate of electrochemical conversion requires the use of flow-through porous electrodes, but the types of flow-through electrodes that are commercially available has not changed in ~40 years. A Cu nanowire electrode reduced Cu ions at a single-pass conversion of 75% at a flow rate 278 times greater than for carbon paper. For the intramolecular cyclization of 2,2′-bis(bromomethyl)-1,1′-biphenyl to 9,10-dihydrophenanthrene, the maximum productivity of the Cu nanowire electrode was 4 times higher than that of carbon paper. These results demonstrate the ability of nanowire electrodes to improve the productivity of electrosynthesis.