Long-term atomistic simulation of hydrogen absorption in palladium nanocubes using a diffusive molecular dynamics method
Understanding the transport of hydrogen within metallic nanomaterials is crucial for the advancement of energy storage and the mitigation of hydrogen embrittlement. Using nanosized palladium particles as a model, recent experimental studies have revealed several interesting phenomena that occur over long time periods. The time scale of these phenomena is beyond the capability of established atomistic models such as molecular dynamics. In this work, we present the application of a new approach, referred to as diffusive molecular dynamics (DMD), to the simulation of long-term diffusive mass transport at the atomic scale. Specifically, we simulate the absorption of hydrogen by palladium nanocubes with edge lengths in the range of 4 nm and 16 nm. We find that the absorption process is dominated by the initiation and propagation of an atomistically sharp α/β Pd-H phase boundary, with thickness in the range of 0.2 to 1.0 nm, which separates an α phase core from a β phase shell. The evolution of phase boundary and the resulting local lattice deformation are described in this paper in detail. The effects of size on both equilibrium and kinetic properties are also assessed.
© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. Received 1 December 2017, Revised 24 January 2018, Accepted 25 January 2018, Available online 19 February 2018. The authors gratefully acknowledge the support of the Institute for Critical Technologies and Applied Sciences (ICTAS) at Virginia Tech through a Junior Faculty Collaboration (JFC) project, the Ministerio de Economía y Competitividad of Spain under grant number DPI2015-66534-R, and the U. S. Army Research Laboratory (ARL) through the Materials in Extreme Dynamic Environments (MEDE) Collaborative Research Alliance (CRA) under Award Number W911NF-11-R-0001.