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Understanding Solid-Gas Reaction Mechanisms by Operando Soft X-ray Absorption Spectroscopy at Ambient Pressure: On the Importance of Surface Hydroxides in SnO 2 Heterogeneous Catalysts and Sensors

30 Pages Posted: 22 Jan 2020 Sneak Peek Status: Review Complete

See all articles by Luca Braglia

Luca Braglia

Total Administrative Services Corporation (TASC) - Istituto Officina dei Materiali

Martina Fracchia

University of Pavia - Dipartimento di Chimica

Paolo Ghigna

University of Pavia - Dipartimento di Chimica

Alessandro Minguzzi

University of Milan - Dipartimento di Chimica

Daniela Meroni

University of Milan - Dipartimento di Chimica

Raju Edla

Total Administrative Services Corporation (TASC) - Istituto Officina dei Materiali

Matthias Vandichel

University of Limerick - Bernal Institute

Elisabet Ahlberg

University of Gothenburg - Department of Chemistry and Molecular Biology

Piero Torelli

Total Administrative Services Corporation (TASC) - Istituto Officina dei Materiali

More...

Abstract

Ambient pressure operando soft X-ray absorption spectroscopy (soft-XAS) was applied to study the reactivity of hydroxylated SnO2 nanoparticles towards reducing gases. H2 was first used as a test case, showing that gas phase and surface states can be simultaneously probed: soft-XAS at the O K-edge gains sensitivity towards the gas phase, while at the Sn M4,-edges tin surface states are explicitly probed. Results obtained by flowing hydrocarbons (CH4 and CH3CHCH2) unequivocally show that these gases react with surface hydroxyl groups to produce water without producing carbon oxides, and release electrons that localize on Sn to eventually form SnO. The partially reduced SnO2-x layer at the surface of SnO2 is readily reoxidised to SnO2 by treating the sample with O2 at mild temperatures (> 200 °C), revealing the nature of “electron sponge” of tin oxide. The experiments, combined with DFT calculations, allowed hypothesizing a mechanism for dissociative hydrocarbon adsorption on SnO2, involving direct reduction of Sn sites at the surface via cleavage of C-H bonds, and the formation of methoxy- and/or methyl-tin species at the surface.

Keywords: operando soft-XAS, catalysis, mechanisms of surface reactions, DFT, hydrocarbon adsorbtion

Suggested Citation

Braglia, Luca and Fracchia, Martina and Ghigna, Paolo and Minguzzi, Alessandro and Meroni, Daniela and Edla, Raju and Vandichel, Matthias and Ahlberg, Elisabet and Torelli, Piero, Understanding Solid-Gas Reaction Mechanisms by Operando Soft X-ray Absorption Spectroscopy at Ambient Pressure: On the Importance of Surface Hydroxides in SnO 2 Heterogeneous Catalysts and Sensors. Available at SSRN: https://ssrn.com/abstract=3520956 or http://dx.doi.org/10.2139/ssrn.3520956
This is a paper under consideration at Cell Press and has not been peer-reviewed.

Luca Braglia

Total Administrative Services Corporation (TASC) - Istituto Officina dei Materiali ( email )

Italy

Martina Fracchia

University of Pavia - Dipartimento di Chimica ( email )

Italy

Paolo Ghigna (Contact Author)

University of Pavia - Dipartimento di Chimica

Italy

Alessandro Minguzzi

University of Milan - Dipartimento di Chimica ( email )

Italy

Daniela Meroni

University of Milan - Dipartimento di Chimica ( email )

Italy

Raju Edla

Total Administrative Services Corporation (TASC) - Istituto Officina dei Materiali ( email )

Italy

Matthias Vandichel

University of Limerick - Bernal Institute ( email )

Ireland

Elisabet Ahlberg

University of Gothenburg - Department of Chemistry and Molecular Biology ( email )

Medicinaregatan 9 C
PO Box 462
Göteborg, SE405 30
Sweden

Piero Torelli

Total Administrative Services Corporation (TASC) - Istituto Officina dei Materiali ( email )

Italy

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