Oxidation Rate and Crystallinity Dynamics of Silver Nanoparticles at High Temperatures

Reactive molecular dynamics (MD) is used to investigate the oxidation kinetics of silver nanoparticles (AgNPs) at temperature ranges of 600–900 K by employing a ReaxFF force field. Oxidation of metallic AgNPs leads to a core–shell structure with a silver oxide layer formed at the nanoparticle surface. Higher temperatures and smaller particle sizes result in faster loss of the fcc crystallinity of the Ag core. The (100) facet is more prone to oxidation than the (111) facet, in agreement with previous experiments and computational works. The fraction of the Ag+ ions present in the oxide layer increases with decreasing particle size, indicating that smaller particles have the potential to release more Ag+ ions in water, consistent with ion-selective electrode experiments. A reaction-limited model is applied to quantify the oxidation rate of nanosilver at various temperatures. Higher temperatures lead to faster oxidation. In addition, small particles (dp ≤ 6 nm) exhibit lower activation energies, indicating that they are more prone to oxidation than larger ones, consistent with experiments of Al nanoparticles, revealing decreasing activation energy with decreasing particle size.