Electronic Structure Sensitivity to Hydration in Smectite Clays Unveiled by Near-Ambient Pressure X-ray Photoelectron Spectroscopy
Résumé
Utilizing Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) under pressures up to 10 mbar, this study investigates the hydration behaviors of two swelling (negatively charged) smectite clays, specifically hydroxyhectorite and hydroxysaponite, under the influence of counterions, Cs + , Na + and Sr 2+ which differ in size and affinity for water. NAP-XPS reveals differences in the electronic structures of hydroxyhectorite and hydroxysaponite, which are related to the location of cation substitution within the negatively charged phyllosilicate layers. Importantly, this study provides atomic-scale insights into the interactions between water and these clays, focusing on changes in the counterion core-level binding energies due to hydration. We discuss the fact that the binding energy shift due to hydration results from the combination of two components: a physical component related to a change in the electrostatic potential (calculated after molecular dynamics simulation), and a chemical component related to a change in charge transfer between ligands and counterion, due to the replacement of phyllosilicate oxygen atoms with water molecules (as suggested by quantum chemistry calculations). These insights-critical for understanding the electronic structure of swelling smectites-open promising avenues for future research into the hydration mechanisms of other nanostructured minerals using NAP-XPS.
Mots clés
Clays smectites water soft X-rays synchrotron radiation near ambient pressure X-ray photoelectron spectroscopy electronic structure core-ionization spectroscopy binding energy shifts molecular dynamics DFT quantum chemistry
Clays
smectites
water
soft X-rays
synchrotron radiation
near ambient pressure
X-ray photoelectron spectroscopy
electronic structure
core-ionization spectroscopy
binding energy shifts
molecular dynamics
DFT quantum chemistry
Domaines
ChimieOrigine | Fichiers produits par l'(les) auteur(s) |
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