Detailed understanding of how gas sensors work
Metal oxide semiconductors, such as SnO2, are important materials for gas sensor applications due to their high sensitivity and easy fabrication. Their basic mode of operation is based on detecting changes in electrical conductivity caused by the adsorption of target molecules on the surface of the semiconductor. SnO2 is the most commonly used material for such metal oxide gas sensors. However, despite its technical relevance and numerous mechanistic studies, it has not yet been possible to gain a detailed understanding of its function at the molecular level.
A detailed understanding of the functioning of gas sensors is the basis for the development of improved gas sensors. In order to elucidate the functioning of gas sensors at the molecular level, the development of operando techniques, which relate the sensor response directly under operating conditions to the structural changes, is of crucial importance. It has been shown that due to the complexity of metal oxide gas sensors only a suitable combination of such operando techniques can elucidate their functioning and the underlying reaction mechanism. In the article recently published in the Angewandte, we present a new operando spectroscopic approach which for the first time combines resistance measurements with three spectroscopic techniques (UV-Vis, Raman, IR) in one experimental setup and allows to link the sensor response with the oxygen vacancy concentration in the metal oxide, the type of adsorbates and the gas phase composition. As shown in the figure, the sensor resistance is directly correlated with the number of oxygen vacancies on the surface and the type of surface species, especially acetate and hydroxy species
More information:
Elger, Ann-Kathrin; Hess, Christian (2019): Angewandte Chemie, DOI: 10.1002/anie.201908871
