Length Absence of Spillover of Hydrogen Adsorbed on Small Palladium Clusters Anchored to Graphene Vacancies
Experimental evidence exists for the enhancement of the hydrogen storage capacity of porous carbons when these materials are doped with metal nanoparticles. One of the most studied dopants is palladium. Dissociation of the hydrogen molecules and spillover of the H atoms towards the carbon substrate...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | Universidad del País Vasco |
| Repositorio: | Addi. Archivo Digital para la Docencia y la Investigación |
| OAI Identifier: | oai:addi.ehu.eus:10810/52536 |
| Acceso en línea: | http://hdl.handle.net/10810/52536 |
| Access Level: | acceso abierto |
| Palabra clave: | hydrogen spillover hydrogen adsorption hydrogen storage graphene vacancies hydrogenated palladium Ab initio molecular dynamics activated carbon-fibers storage capacity adsorption nanotubes dissociation simulation surfaces spheres atoms |
| Sumario: | Experimental evidence exists for the enhancement of the hydrogen storage capacity of porous carbons when these materials are doped with metal nanoparticles. One of the most studied dopants is palladium. Dissociation of the hydrogen molecules and spillover of the H atoms towards the carbon substrate has been advocated as the reason for the enhancement of the storage capacity. We have investigated this mechanism by performing ab initio density functional molecular dynamics (AIMD) simulations of the deposition of molecular hydrogen on Pd6 clusters anchored on graphene vacancies. The clusters are initially near-saturated with atomic and molecular hydrogen. This condition would facilitate the occurrence of spillover, since our energy calculations based on density functional theory indicate that migration of preadsorbed H atoms towards the graphene substrate becomes exothermic on Pd clusters with high hydrogen coverages. However, AIMD simulations show that the H atoms prefer to intercalate and absorb within the Pd cluster rather than migrate to the carbon substrate. These results reveal that high activation barriers exist preventing the spillover of hydrogen from the anchored Pd clusters to the carbon substrate. |
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