Monitoring Morphology and Hydrogen Coverage of Nanometric Pt/γ‐Al₂O₃ Particles by In Situ HERFD–XANES and Quantum Simulations

Abstract

Platinum nanoclusters highly dispersed on γ-alumina are widely used as heterogeneous catalysts. To understand the chemical interplay between the Pt nanoparticles, the support, and the reductive atmosphere, we performed X-ray absorption near edge structure (XANES) in situ experiments recorded in high energy resolution fluorescence detection (HERFD) mode. Spectra are assigned by comparison with simulated XANES spectra on models obtained by molecular dynamics (DFT-MD). We propose platinum cluster morphologies and quantify the hydrogen coverages compatible with XANES spectra recorded at variable hydrogen pressures and temperatures. Using cutting-edge methodologies to assign XANES spectra, this work gives unequalled atomic insights into the characterization of supported nanoclusters.

Solving the Structure and Dynamics of Metal Nanoparticles by Combining X-Ray Absorption Fine Structure Spectroscopy and Atomistic Structure Simulations

“…Analysis based on constructing 3D NP structure models is especially attractive for XANES because path-by-path approaches are not applicable in this spectral region. Like EXAFS, XANES data can also be used to validate DFTgenerated 3D structure models (135,136). Likewise, the influence of atomic thermal motion on XANES spectra can be modeled by MD simulations (111,137).…”

High‐Energy Resolution Fluorescence Detected X‐Ray Absorption Spectroscopy: A Powerful New Structural Tool in Environmental Biogeochemistry Sciences

“…As an example, we present on Supplemental Fig. S5 HERFD and conventional XANES spectra acquired simultaneously on the same sample position, a Pt/Al 2 O 3 catalyst powder (Gorczyca et al, 2014). The increase of the intense peak after the edge (the so-called white line) seems characteristic of the oxidation of the Pt with the beam.…”

Dehydrogenation mechanisms of methyl-cyclohexane on γ-Al2O3 supported Pt13: Impact of cluster ductility

“…[1][2][3][4] In particular, the level of complexity of these systems rises due to the ductility of the metallic nano-clusters or in other words, their reconstruction induced by their environment (temperature, pressure, support, adsorbed intermediates…) as it has been highlighted by previous theoretical [5][6][7][8][9][10][11] and experimental studies. [1][2][3]12] It can be underlined that such a ductility is sometimes called "fluxionality", [11] although the latter more precisely refers to a process that in the end does not change the structure of the considered compound, as originally defined by Cotton. [13] Among others, platinum based nano-clusters supported on alumina (γ-Al 2 O 3 ) are well known to be active catalysts in naphtha reforming catalytic processes, [14] and light alkane non-oxidative dehydrogenation.…”