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Direct in situ spectroscopic evidence of the crucial role played by surface oxygen vacancies in the O2-sensing mechanism of SnO2

DOI: 10.1039/D2SC01738E DOI Help

Authors: Stefan Kucharski (University College London; Research Complex at Harwell) , Pilar Ferrer (Diamond Light Source) , Federica Venturini (Diamond Light Source) , Georg Held (Diamond Light Source) , Alex S. Walton (University of Manchester) , Conor Byrne (University of Manchester) , James A. Covington (University of Warwick) , Sai Kiran Ayyala (University of Warwick) , Andrew Beale (University College London; Research Complex at Harwell) , Chris Blackman (University College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemical Science , VOL 121

State: Published (Approved)
Published: May 2022
Diamond Proposal Number(s): 25766

Open Access Open Access

Abstract: Conductometric gas sensors (CGS) provide a reproducible gas response at a low cost but their operation mechanisms are still not fully understood. In this paper, we elucidate the nature of interactions between SnO2, a common gas-sensitive material, and O2, a ubiquitous gas central to the detection mechanisms of CGS. Using synchrotron radiation, we investigated a working SnO2 sensor under operando conditions via near-ambient pressure (NAP) XPS with simultaneous resistance measurements, and created a depth profile of the variable near-surface stoichiometry of SnO2−x as a function of O2 pressure. Our results reveal a correlation between the dynamically changing surface oxygen vacancies and the resistance response in SnO2-based CGS. While oxygen adsorbates were observed in this study we conclude that these are an intermediary in oxygen transport between the gas phase and the lattice, and that surface oxygen vacancies, not the observed oxygen adsorbates, are central to response generation in SnO2-based gas sensors.

Subject Areas: Chemistry, Materials

Instruments: B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS

Added On: 12/05/2022 10:07


Discipline Tags:

Chemistry Materials Science Inorganic Chemistry

Technical Tags:

Spectroscopy X-ray Photoelectron Spectroscopy (XPS)