Hydrogen Storage in Palladium Hollow Nanoparticles

Abstract

The potential and properties of palladium hollow nano particles (hNPs) as a possible H storage material are explored by means of classical molecular dynamics (MD) simulations. First, we study the stability of pure Pd hNPs for different sizes and thicknesses, obtaining good agreement with experimental results for nanometer size Pd hNP. Next we add, every 100 fs, single H atoms into the NP cavity. During the first stages of the simulation, our results show hydride formation on the inner surface, similar to what has been observed in experiments on Pd surfaces and NPs. Formation of the Pd hydride decreases the absorption rate, and H gas is formed inside the cavity. The maximum H gas pressure that is reached is of 7 GPa, before fractures appear in the hNP, and consequently the hNP breaks up. We obtain a maximum H/Pd ratio of 1.21 when H is introduced only inside the cavity. However, when H is deposited both on the inside and outside surfaces, this ratio reaches 1.70, which is 25% larger than previous reports. Beyond this ratio, the hNP breaks up, and the H gas is ejected from the hNP cavity.