Non-equilibrium Interface and Surface Dynamics

The Importance of Understanding Nanoscale Morphology and Topology to Make Advanced Catalysts for Energy Technologies

Jonah Erlebacher

Johns Hopkins University

In this talk, we will discuss the nanoscale morphology and topology of nanoporous metals from both a simulation and experimental viewpoint. These materials are formed from bulk alloys via a pattern forming instability during electrochemical etching in which the etch rate of one alloy component competes with surface diffusion of the remaining alloy components. The final surface morphology, topology, and composition is governed by tortuous diffusion pathways along the metal/electrolyte interface and can be tuned by control of such diffusion. Morphology and topology play an important role in using these materials as high surface area catalysts. Morphology tells us information about the polyfacetted nature of these porous materials, vital information when the reactivity depends on surface crystallographic orientation. Topology tells us about the stability of these materials during coarsening, which we demonstrate is controlled by Rayleigh instabilities that decrease the topological genus via ligament pinch-off processes. Kinetic Monte Carlo simulations give us insight into the details of these microscopic diffusion pathways, in particular how to stymie them and engineer stable, high performance nanostructured electrocatalysts.