Particle size effect of hydrogen-induced lattice expansion of palladium nanoclusters

Abstract

In situ synchrotron x-ray diffraction experiments on bare palladium nanoclusters prepared by inert-gas aggregation and size selected ͑1.7-6.0 nm͒ show significant changes in lattice parameter upon hydrogen loading and a narrowing of the miscibility gap, as the cluster size decreases. The results show that the miscibility gap is open for all cluster sizes studied, in contrast to previous literature results from surfactantencapsulated palladium clusters. We interpret these results by showing that the nature of the surface is critical in the hydrogenation behavior of the nanoclusters.

Inhibitive effect of Pt on Pd-hydride formation of Pd@Pt core-shell electrocatalysts: An in situ EXAFS and XRD study

“…In comparison, the fully mixed/alloy catalyst has a N(PdePt):N(P-dePd) ratio of 1.2. Such interfacial mixing has previously been reported by Liu et al [38], who investigated Pt@Pd and Pd@Pt catalyst particles with a narrow particle size distribution and Pt:Pd ratio of 1:1, enabling a detailed model of the extent of interfacial mixing to be proposed based on the analysis of their EXAFS data.…”

Localized Surface Plasmons Shed Light on Nanoscale Metal Hydrides

“…110 ppm H for the nanodisks, which is two to three orders of magnitude larger than for, e.g., the commonly used X-ray diffraction (XRD) technique. [ 6 ] Further, we note that the presented methods can easily be applied to study thermodynamics but also kinetics of other bulk or surface modifi cations on metallic nanoparticles of interest in materials-and nanoscience. The latter may include: (i) the characterization of inherent (e.g.…”

“…Furthermore, the typical experimental methods used in the fi eld today, e.g. volumetric, [ 4 ] gravimetric, [ 5 ] X-ray diffraction, [ 6 ] and nuclear reaction analysis [ 7 ] techniques are often complicated, too slow to resolve fast kinetics and they require large amounts of sample material. The latter is problematic in two ways: i) it amplifi es the inhomogeneous particle size distribution problem and ii) it may give rise to local temperature and/or concentration gradients altering the measured thermodynamics and kinetics.…”

X-ray scattering characterisation of nanoparticles

“…Suleiman and Pundt et al [216][217][218] and Ingham et al [219] studied the effect of hydrogen pressure on Pd nanoparticles less than 10 nm in diameter. Pd forms two distinct hydride phases, with a so-called 'miscibility gap' between the maximum concentration of hydrogen in the low-concentration (α) phase and the minimum concentration of hydrogen in the highconcentration (β) phase.…”

“…Suleiman et al, who measured surfactant-coated and polymer-encapsulated Pd nanoparticles 4.8 nm in size, [216] observed that the phase transition occurred at higher hydrogen pressures and was much more pronounced for the surfactant-coated particles. Ingham et al measured uncoated particles formed by a physical deposition method 1.7-6.1 nm in diameter, [219] and observed that while the behaviour of the β-phase with nanoparticle size was the same for uncoated and coated particles, the behaviour of the α-phase was noticeably different, resulting in a closure of the miscibility gap at non-zero sizes for surfactant-coated particles, while the gap remained open for all sizes of uncoated particles (see Figure 11). Kaszkur and intensity in the X-ray scattering patterns.…”