Apparent inverse Gibbs-Thomson effect in dealloyed nanoporous nanoparticles

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• The Gibbs-Thomson effect describes how nanoscale curvature lowers the electrochemical potential for nanoparticle dissolution.
• This effect predicts a decrease in dissolution potential proportional to the inverse of the nanoparticle radius (1/r).

Purpose of the Study:

• To investigate the electrochemical dissolution behavior of alloy nanoparticles, considering selective dissolution and nanoporosity evolution.
• To determine if the Gibbs-Thomson effect holds true for alloy nanoparticles undergoing dealloying.

Main Methods:

• Kinetic Monte Carlo (KMC) simulations were employed to model the dissolution process.
• The simulations focused on the interplay between selective dissolution of less noble components and the evolution of nanoporosity.

Main Results:

• Alloy nanoparticles require a higher electrochemical potential for complete dissolution compared to bulk materials, an effect that increases with decreasing particle size (empirically as 1/r).
• Selective dissolution of the less noble component is followed by surface passivation due to the increased mobility of the more noble atoms.
• Complete dealloying and nanoporosity evolution depend on the persistence of surface passivation layer fluctuations, enabling dissolution through percolating networks of the less noble component.

Conclusions:

• The dissolution of alloy nanoparticles is governed by kinetic factors, leading to a reversal of the typical Gibbs-Thomson effect.
• Surface passivation and the resulting percolation of dissolution pathways are critical for understanding dealloying in alloy nanoparticles.