Dealloying in Pt-based nanoalloys as a way to synthesize bimetallic nanoparticles: Atomistic simulations

Abstract

Dealloying is already being used as a method for manufacturing structured binary and multicomponent metal nanoparticles. In such a process, one of the metals, e.g. the less noble one, is selectively removed from the alloy, while the atoms of the more noble metal diffuse and reorganize into a particular structure, e.g. a porous structure or a core–shell structure. Usually, dealloying is provided by an electrochemical method. Binary Ni–Pt and Cu–Pt nanoparticles with an initial number of atoms N = 3000, equiatomic composition and uniform distributions of components over the volume were chosen as objects of atomistic simulations. In the course of simulation, Ni or Cu atoms, respectively, were gradually removed until 1200 atoms were removed. For the removal, at each step of the iterative process, an atom with the smallest absolute value of the potential energy was selected. The simulation was carried out using two alternative simulation methods (molecular dynamics (MD) and Monte Carlo (MC)). An integrated approach to the simulations allows us to increase the reliability of the results and to prevent the appearance of artifacts. The interatomic interaction in the simulated systems was described by the many-particle Gupta potential (tight-binding potential). A drop in energy was observed for Cu–Pt nanoparticles, while for the Ni–Pt nanoalloy, the MD method predicts a similar behavior, but the MC method predicts an increase in the energy of the nanoclusters after the removal of 400 atoms. Analysis of the structure showed that, at this moment, active pore formation begins in the Ni–Pt nanoparticles, both in the surface layers and in their central regions.