Inducing Porosity on Hollow Nanoparticles by Hypervelocity Impacts

The large surface-to-volume ratio of hollow palladium nanoparticles (hNPs) offers room to improve their hydrogen storage capacity as well as their catalytic activity. However, a less explored possibility is to use, in addition, the internal cavity. Here we explore, through classical molecular dynamics, the possibility of boring channels across the hNP wall by collision with solid Pd nanoprojectiles at high velocities, as well as their resilience to maintain their spherical geometry. We choose a stable hNP with an inner diameter of 13 nm and an outer diameter of 15 nm. The projectiles are Pd NPs of 1.5, 2.4, and 3.0 nm, respectively. We consider collision speeds between 3 and 15 km/s, with an impact parameter between 0 to 7 nm. Four different regimes, as a function of kinetic energy and impact parameter of the projectile, are found. For low speeds, the projectile is not able to penetrate the target and only creates surface craters. For a narrow range of intermediate speeds, the projectile enters the target...