Nanoparticle size evaluation of catalysts by EXAFS: Advantages and limitations

Abstract

In this article we determine particle size of nanocatalysts using the first-shell

Biosynthesis and Characterization of Copper Nanoparticles Using Shewanella oneidensis: Application for Click Chemistry

“…However, 9.6 and 9 Cu atoms were determined to be coordinated at 2.54 and 5.29 Å, respectively; slightly lower than noted in the ideal structure of 12 Cu atoms in both shells. It is possible that this reduced coordination is caused by the nanoparticulate nature of the materials in this study …”

Effect of the Pt Precursor and Loading on the Structural Parameters and Catalytic Properties of Pt/Al2O3

“…[a] Average Pt particle diameter obtained by EXAFS correlation; [b] Average Pt particle diameter obtained by HAADF‐STEM analysis; TOF’: Turn‐over frequency based on Pt nanoparticle perimeter; [c] WGSR at 300 °C.…”

“…Therefore, it is reasonable to consider that there may have been a change in the morphology of the platinum NPs, depending on the Pt precursor used. For instance, the coordination number for the first coordination shell is not sufficient to characterize the complex morphology of Pt NPs, [8] since there is a strong effect [a] Average Pt particle diameter obtained by EXAFS correlation; [44] [b] Average Pt particle diameter obtained by HAADF-STEM analysis; TOF': Turn-over frequency based on Pt nanoparticle perimeter; [c] WGSR at 300°C.…”

Air Regeneration of Ethanol-Laden Pellet NaY-SiO2 and Pt/NaY-SiO2: Effects of Air Flow Rate on Pt Morphology and Regeneration Efficiency

“…The average Pt particle size on NaY-SiO 2 determined by the use of first-shell Pt-Pt coordination number (CN Pt-Pt ) of EXAFS measurements [37] is 1.3 and 3.3 nm, respectively, for fresh Pt/NaY-SiO 2 and PtR (LF) , while that determined from TEM images is about 1.5 and 3.8 nm, respectively (Figure 9a,c). The larger Pt particle size determined by TEM could be because: (1) the coupling between CN and the relative Debye-Waller factor (∆σ) of EXAFS equation causes the inherent uncertainty of coordination numbers (CN) estimation; and (2) Pt clusters with sizes less than 1 nm are difficult to resolve by TEM [38].…”

“…Because the formation of these oxidic species decreases Pt-Pt contributions, we are unable to estimate Pt particle size by the use of the correlation of CN Pt-Pt with particle size reported in literature [37]. However, it is shown in TEM images that the average Pt particle size of PtR (HF) is close to that of fresh Pt/NaY-SiO 2 (Figure 9a,b), suggesting that only few or no Pt clusters were aggregated in high flow regeneration.…”