Shape-Dependent Hydrogen-Storage Properties in Pd Nanocrystals: Which Does Hydrogen Prefer, Octahedron (111) or Cube (100)?

Abstract

Pd octahedrons and cubes enclosed by {111} and {100} facets, respectively, have been synthesized for investigation of the shape effect on hydrogen-absorption properties. Hydrogen-storage properties were investigated using in situ powder X-ray diffraction, in situ solid-state (2)H NMR and hydrogen pressure-composition isotherm measurements. With these measurements, it was found that the exposed facets do not affect hydrogen-storage capacity; however, they significantly affect the absorption speed, with octahedral nanocrystals showing the faster response. The heat of adsorption of hydrogen and the hydrogen diffusion pathway were suggested to be dominant factors for hydrogen-absorption speed. Furthermore, in situ solid-state (2)H NMR detected for the first time the state of (2)H in a solid-solution (Pd + H) phase of Pd nanocrystals at rt.

Morphology control of K2O promoter on Hägg carbide (χ-Fe5C2) under Fischer–Tropsch synthesis condition

“…Particle shape is an important factor in determining the chemical and physical properties of a particular nanostructure, because the intrinsic properties are strongly correlated with their morphologies [19]. For example, Pd nanoparticles exposed on the {1 1 1} facet exhibit rapid kinetics for hydrogen storage [19] and are more active for CO oxidation [20], compared with the cubes with the {1 0 0} facets.…”

An analytical description for the elastic compression of metallic polyhedral nanoparticles

“…12,13 The shape of nanoparticles could affect their physical and chemical properties, like catalyst activity in hydrogen evolution reaction 14 and oxygen reduction reaction, 15 hydrogen storage, 16 and sensor's sensitivity. 17 The mechanical properties of nanoparticles also depend on their shapes.…”

“…[12][13][14][15][16][17] For such a complex polyhedral structure, it is in fact a challenge to describe its elastic compression analytically. In the present paper, combining finite element calculations and scaling analysis, we generalize the analytical load-indent depth relation for face-centered cubic (fcc) polyhedral particles.…”

Novel hydrogen storage properties of palladium nanocrystals activated by a pentagonal cyclic twinned structure

“…To investigate the properties of the Pd PCT structure, we first carried out hydrogen storage experiments. To avoid any possible surface and size effects during hydriding and dehydriding [30][31][32][33], icosahedral Pd NCs and octahedral Pd NCs with similar sizes (around 40 nm) were synthesized according to the reported methods and chosen as representatives of the PCT and SC structures [34,35], because both of them are enclosed only by {111} facets (see the Experimental section, and Figs. S1 and S2 in the Electronic Supplementary Material (ESM) for details).…”

“…However, the results suggest that the difference between the hydrogen retention abilities of the icosahedral Pd NCs and octahedral Pd NCs is not caused by Pd-I interactions, but is only magnified with the help of I -. The magnification effect also overcomes the common problem whereby studies of the phase transition process of Pd in hydrogen storage are largely restricted to in situ characterization techniques [30,33].…”