Surface strain, oxidation effect, and reconstruction of spherical and faceted Ag and Pd nanoparticles

Abstract

Surface strain plays a crucial role in enhancing the performance of nanocatalysts. In this work, the distribution of atomic strain and stress in three different structures (bulk, surface, and nanoparticle) of Ag and Pd was investigated. The atomic strain and stress in bulk structures approach 0 %, while the first atomic layer of surface structures exhibits a significant tensile state. For faceted nanoparticles, the compressive strain is localized along the edges and vertices of the surface, as well as in the inner core region, while tensile strain is observed on the surface facet. The Laplace pressure experienced by spherical nanoparticles of different sizes increases with decreasing radius, induces compressive atomic strain and stress both on the surface and within the interior of nanoparticles. After oxidation, tensile atomic strain and stress are induced in the oxidized surface regions, with the magnitudes increasing proportionally to the oxidation degree. We also developed an energy-dependence diagram for the structural reconstruction of faceted nanoparticles, revealing that the process is driven by surface reconstruction and atomic strain, with a strong dependence on both energy and temperature. These founds in this contribution provide a theoretical basis and insight for the future design of noble metal nanocatalysts.