In Situ UV-Visible Optical Spectroscopy Study of Nanoporous Gold Formation By Electrolytic Dealloying

Chacko, Joel; Corsi, John S.; Welborn, Samuel S.; Detsi, Eric

doi:10.1149/ma2020-01482718mtgabs

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“…Yet several interesting aspects of dealloyed materials are still subject of contemporary research, such as the structural stability and coarsening behavior of the ensuing nanoporous structures or their mechanical properties . A broad variety of in situ methods have been utilized to study the dealloying process itself, ranging from dilatometry, resistometry, magnetometry, UV–vis spectroscopy, transmission X-ray microscopy (XTM), X-ray diffraction (XRD), − and Raman spectroscopy to real-space imaging techniques such as scanning tunneling microscopy and transmission electron microscopy (TEM) . While microscopic techniques, in general, allow the extraction of size information for the nanoporous structures, they suffer from the disadvantage of averaging over a limited sample area only.…”

Section: Introductionmentioning

confidence: 99%

In Situ Study of Nanoporosity Evolution during Dealloying AgAu and CoPd by Grazing-Incidence Small-Angle X-ray Scattering

et al. 2022

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Electrochemical dealloying has become a standard technique to produce nanoporous network structures of various noble metals, exploiting the selective dissolution of one component from an alloy. While achieving nanoporosity during dealloying has been intensively studied for the prime example of nanoporous Au from a AgAu alloy, dealloying from other noble-metal alloys has been rarely investigated in the scientific literature. Here, we study the evolution of nanoporosity in the electrochemical dealloying process for both CoPd and AgAu alloys using a combination of in situ grazing-incidence small-angle X-ray scattering (GISAXS), kinetic Monte Carlo (KMC) simulations, and scanning transmission electron microscopy (STEM). When comparing dealloying kinetics, we find a more rapid progression of the dealloying front for CoPd and also a considerably slower coarsening of the nanoporous structure for Pd in relation to Au. We argue that our findings are natural consequences of the effectively higher dealloying potential and the higher interatomic binding energy for the CoPd alloy. Our results corroborate the understanding of electrochemical dealloying on the basis of two rate equations for dissolution and surface diffusion and suggest the general applicability of this dealloying mechanism to binary alloys. The present study contributes to the future tailoring of structural size in nanoporous metals for improved chemical surface activity.

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