Hydrogen Solubility and Atomic Structure of Graphene Supported Pd Nanoclusters

Abstract

We investigated the atomic structure of graphene supported Pd nanoclusters and their interaction with hydrogen up to atmospheric pressures at room temperature by surface X-ray diffraction and scanning tunneling microscopy. We find that Ir seeded Pd nanocluster superlattices with 1.2 nm cluster diameters can be grown on the graphene/Ir(111) moiré template with high structural perfection. The superlattice clusters are anchored through the rehybridized graphene to the Ir support, which superimposes a 2.0% inplane compression onto the clusters. During hydrogen exposure at 10 mbar pressure and room temperature, a significant part of the clusters gets unpinned from the superlattice. The clusters in registry undergo an out-of-plane expansion only, whereas the detached clusters expand in in- and out-of-plane directions. The formation of a hydrogen rich PdH x α′ phase was not observed. After exposure to 1 bar, the majority of the clusters are unpinned from superlattice sites, due to their surface interaction with hydrogen and possible spill over to the graphene support. Only minor sintering was observed, which is more pronounced for the unpinned clusters. The results give evidence that ultrasmall Pd clusters on graphene are a stable hydrogen storage system with reduced hydrogen storage hysteresis and maintain a large surface area for hydrogen chemisorption.

Adsorption of Lanthanide Atoms on Graphene: Similar, Yet Different

“…The understanding and quantum-chemical prediction of adsorption behavior of different atoms (in particular, metals) on graphene and graphene-based systems is of paramount importance for many advanced technologies, since it opens a way to fine-tuning of electronic, magnetic, and other properties of these nanomaterials. − While, therefore, it is natural that a large number of published reports address the interactions of different atoms with both defect-free (pristine) and defect-containing graphene, very few systematic theoretical studies can be found, − which comprise broad series of chemical elements.…”

The synchrotron radiation source PETRA III and its future ultra-low-emittance upgrade PETRA IV

“…With this, it makes an important contribution to solving the grand societal challenges, e.g. in human health [21,22], energy [23,24], mobility, information, and earth and environment and ranges from fundamental science [1-3, 25, 26] to industrial applications [9,[27][28][29][30]. A key strength is to perform experiments in situ and under working conditions, giving insight into processes, e.g.…”

Supported Metal Nanohydrides for Hydrogen Storage

“…However, this mechanism has been analyzed in detail for the case of Pd nanoparticles supported on graphene by performing accurate atomistic dynamical simulations, and its validity has been questioned, because of the existence of large spillover barriers. , Sizable barriers have also been predicted from calculations for other supported transition metal clusters. − Palladium is, in fact, a promising metal for applications related to hydrogen storage because it can absorb large amounts of hydrogen in the form of palladium hydrides . For this reason, the adsorption of hydrogen on free Pd nanoclusters − and on various types of carbon materials functionalized with palladium has been investigated. ,,− …”

“…One of the advantages of GDY and BGDY over other carbon materials for the purposes of gas storage is the lower weight. One reason for choosing palladium is that experiments by Contescu and coworkers ,,− and others , reported an enhancement of hydrogen storage when doping carbon materials with Pd. A second reason is that we have previously performed calculations to study the effect of this dopant on different carbon materials − ,, and have analyzed the hydrogen spillover process. , For this purpose, we perform accurate calculations using the formalism of density functional theory (DFT) .…”