An Atomistic Description of Dealloying

Abstract

Wedescribe the microscopic details of porosity formation during dealloying asilluminated by a kinetic Monte Carlo model incorporating site coordination-dependentsurface diffusion of all alloy components, and site coordination-dependent dissolutionof the less-noble atoms. Our simulation model reproduces the entirerange of phenomena associated with selective dissolution. These phenomena includecomposition and geometric restrictions on dealloying (parting limits), a composition-dependentcritical potential, a passivation regime, a regime of steady-state dissolutionflux, and porosity formation. We find that an intrinsic criticalpotential exists as a well-defined threshold potential separating surface passivationand porosity formation behaviors, but this intrinsic critical potential typicallysits at values well below the experimental measurements of theempirical critical potential. Finally, by detailed examination of the temperaturedependence of the dissolution flux, and also of the typesof surface sites contributing to the dissolution flux, we predictthat the binding energy of a terrace atom may bestraightforwardly extracted from analysis of experimental polarization curves. ©2004 TheElectrochemical Society. All rights reserved.