Interactions of Hydrogen with Pd@MOF Composites.

Physisorption and chemisorption of hydrogen on solid-state materials are two fundamentally different interactions, both of which display advantages and drawbacks for hydrogen storage. It has been hypothesised that their combination by merging two classes of materials showing different sorption behaviour towards hydrogen in the same composite may synergistically combine their desirable properties. As representatives of such composites, palladium nanoparticles, nanoclusters, and single atoms have been encapsulated in a metal-organic framework matrix, embedded, or immobilised in its pores, respectively. In this minireview, we review advances on the understanding and potential applications of the combination of Pd with metal-organic framework matrices through the analysis of the nanocomposite materials' interaction with hydrogen and sorption properties.

Investigation of the local structure of nanosized rhodium hydride.

The local structure and the thermal stability of small and well-dispersed RhHx nanoparticles (average size of 1.4 nm) were studied by in situ X-ray Absorption Spectroscopy. The RhHx nanoparticles are stable at room temperature and undergo a structural transition from hydride (fcc) to metal phase (fcc) with a shrinking of the lattice volume due to the desorption of hydrogen. This phase transition occurs in the temperature range of 150-180 °C, in good agreement with the results from thermo-desorption spectroscopy. Above 180 °C, the desorbed nanoparticles undertake important coalescence. In situ transmission electron microscopy performed up to 300 °C proves that this process cannot be only thermal, thus it may be ascribed to a X-ray beam effect.