Extension of Rietveld Refinement for Benchtop Powder XRD Analysis of Ultrasmall Supported Nanoparticles

Abstract

We present a method for characterizing ultrasmall (<2 nm) supported crystallites with benchtop XRD. Central to the method is an understanding of the intensity effects at play; these intensity effects and their corrections are discussed in depth. Background subtraction�long considered one of the main barriers to ultrasmall crystal characterization�is solved by correcting the diffractogram of a separately measured support for the relevant intensity effects. Rietveld refinement is demonstrated to be an adequate analysis method for the general characterization of simple nanosystems. A 4.8% Pt/SiO 2 sample (1.3 nm, volume-weighted average) is used as a case study; it is found that the Pt spontaneously oxidizes under ambient conditions and consists of a metallic core surrounded by a PtO 2 shell. Both phases have average dimensions smaller than 1 nm. The XRD results also suggest lattice expansion of the Pt core as compared to bulk Pt.

Insights into size effects of Pt/Al2O3 catalysts on hydrogen production from methylcyclohexane dehydrogenation

“…1 shows the XRD patterns of as-calcined Pt/Al 2 O 3 samples. Only the feature peaks of γ-alumina are observed while those associated with bulk PtO 2 (33.9°2θ) or bulk Pt (39.8°2θ) are not detected, 29,30 indicating the absence of Pt or PtO 2 nanoparticles or their sizes are less than the detection limit (around 2-3 nm), which further corroborates the high dispersion of Pt on the Al 2 O 3 support.…”

The preparation of silica supported, dilute limit PdAu alloys via simultaneous strong electrostatic adsorption

“…With the high intensity detector employed, careful background subtraction and peak fitting allows the identification of nanocrystalline features even smaller than 1 nm. 27 The Pd-only sample exhibits discernable broad peaks (Fig. 2b, bottom) which can be fit as 1 nm Pd 2 O particles.…”

Stabilizing Lattice Oxygen in a P2-Na0.67Mn0.5Fe0.5O2 Cathode via an Integrated Strategy for High-Performance Na-Ion Batteries

“…A diffractometer (XRD, Rigaku SmartLab, Japan, Cu Kα) was used for the XRD test and in situ XRD to characterize the crystal structure of the cathode material samples with a 10° min –1 scan rate and a 0.01° step width. The Rietveld method was used to obtain the refined lattice parameters by Fullprof software. , The neutron powder diffraction experiment was carried out with a wavelength of 1.479 Å on PKU-HIPD at the China Advanced Research Reactor (CARR). A scanning electron microscope (Hitachi SU8010, Japan) connected to an EDS detector was applied to observe the morphology, element distribution, and composition of the samples.…”

“…The Rietveld method was used to obtain the refined lattice parameters by Fullprof software. 35,36 The neutron powder diffraction experiment was carried out with a wavelength of 1.479 Å on PKU-HIPD at the China Advanced Research Reactor (CARR). A scanning electron microscope (Hitachi SU8010, Japan) connected to an EDS detector was applied to observe the morphology, element distribution, and composition of the samples.…”