Abstract
Nickel and its alloys are often used in the form of nanostructured materials, e.g., as catalysts for hydrogenation reactions, for hydrogen-storage applications, and as battery materials. This study focuses on subsurface hydride (NiHx) formation in Ni nanoparticles. The pressure at which hydrogen is incorporated within the nanoparticle surface is probed using grand canonical Monte Carlo (GCMC) simulations. An important observation is that the Ni nanoparticle size can have a significant effect on the hydride formation. Unlike bulk Ni, which forms the hydride phase at very high H-2 pressures, subsurface NiHx can form at significantly lower pressures with 2.7-9.1 nm particles. The (1 1 1) and (100) facets and facet edges of these nanoparticles possess remarkably different H incorporation characteristics compared to the nanoparticle core. The easier H-absorption in Ni nanoparticles is explained in terms of a nucleation-and-growth process, which begins at the facet edges and proceeds towards the interior of the nanoparticle. The NiHx and Ni phases co-exist in nanoparticle systems, which is not observed in bulk Ni. A computational characterization approach is used to gain insights into the layer-by-layer H incorpo-ration, which can be valuable for devising material preparation strategies for adsorption-based hydrogen storage and catalysis.
NSTL
Elsevier