Enhancement of Lewis Acidity of Cr-Doped Nanocrystalline SnO2 : Effect on Surface NH3 Oxidation and Sensory Detection Pattern

Alexey V Garshev; Vladimir K Ivanov; Alina A Krotova; Darya G Filatova; Elizaveta A Konstantinova; Daniil O Naberezhnyi; Nikolay O Khmelevsky; Artem V Marikutsa; Pavel A Kots; Andrey V Smirnov; Marina N Rumyantseva; Alexander M Gaskov; Valeriy V Krivetskiy

doi:10.1002/cphc.201900192

Enhancement of Lewis Acidity of Cr-Doped Nanocrystalline SnO₂ : Effect on Surface NH₃ Oxidation and Sensory Detection Pattern

Chemphyschem. 2019 Aug 5;20(15):1985-1996. doi: 10.1002/cphc.201900192. Epub 2019 Jul 5.

Authors

Affiliations

¹ Department of Chemistry, M. V. Lomonosov Moscow State University, 1/3 Leninskie Gory, 119991, Moscow, Russia.
² Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 31 Leninsky pr., Moscow, 119991, Russia.
³ Department of Physics, M. V. Lomonosov Moscow State University, 1/2 Leninskie Gory, 119991, Moscow, Russia.
⁴ National Research Center Kurchatov Institute, Kurchatov Square 1, 123182, Moscow, Russia.
⁵ Department of Nano-, Bio-, Information Technology and Cognitive Science, Moscow Institute of Physics and Technology, Institutskij 9, 141701, Dolgoprudny, Moscow Region, Russia.
⁶ Faculty of Materials Science, M. V. Lomonosov Moscow State University, Leninskie Gory 1 bd. 73, 119991, Moscow, Russia.
⁷ LISM, Moscow State Technological University Stankin, 127055, Moscow, Russia.

PMID: 31190363
DOI: 10.1002/cphc.201900192

Abstract

Understanding ammonia oxidation over metal oxide surfaces is crucial for improving its detection with resistive type gas sensors. Formation of NO_x during this process makes sensor response and calibration unstable. Cr-doping of nanocrystalline metal oxides has been reported to suppress NO₂ sensitivity and improve response towards NH₃ , however the exact mechanism of such chromium action remained unknown. Herein, by using EPR spectroscopy we demonstrate formation of Cr(VI) lattice defects on the surface of nanocrystalline Cr-doped SnO₂ . Enhancement of Cr-doped SnO₂ surface acidity and ammonia adsorption as a result has been revealed by using in situ IR spectroscopy. Moreover, a decrease in concentration of free electrons in the conduction band has been shown as a result of substitutional Cr(III) defects formation. Weaker NO_x chemisorption during ammonia oxidation over SnO₂ surface after Cr doping has been found with the use of mass-spectrometry assisted NH₃ thermo-programmed desorption. The given example of surface acidity adjustment and electronic configuration by means of doping may find use in the design of new gas-sensing metal oxide materials.

Keywords: ammonia; doping; metal oxide; semiconductors; sensors.

Publication types

Research Support, Non-U.S. Gov't

Abstract

Publication types

Grants and funding