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Characterization of the sensitive material for a resistive NOx gas dosimeter by DRIFT spectroscopy

Title data

Schönauer-Kamin, Daniela ; Marr, Isabella ; Zehentbauer, Melanie ; Zängle, Clara ; Moos, Ralf:
Characterization of the sensitive material for a resistive NOx gas dosimeter by DRIFT spectroscopy.
In: Sensors and Actuators B: Chemical. Vol. 320 (October 2020) . - No. 128568.
ISSN 0925-4005
DOI: https://doi.org/10.1016/j.snb.2020.128568

Abstract in another language

Resistive NOx gas dosimeters measure continuously the integrated NOx concentration, i.e., the NOx dose. The impedance of potassium-manganese based NOx storage catalyst films decrease at 350 °C linearly with the NOx dose. The slope of the signal is proportional to the actual NOx concentration. The dosimeter principle is based on the sorption of NOx on the sensitive material. During NOx absence, the sensor signal remains constant, i.e. no desorption occurs. When a certain sorption state is reached, the sorbed species has to be desorbed thermally. To study the sorption processes on the NOx storage material, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) was used. Different material compositions were investigated by DRIFTS on powdered catalysts and operando DRIFTS on NOx dosimeters themselves. On Al2O3 (catalyst support) no NOx sorbs. Manganese addition (Mn-Al2O3) leads to few detectable nitrites on Aluminum-sites during NOx exposure. On Potassium-loaded alumina (K-Al2O3), nitrites and nitrates form. The comparison of NO2 and NO proves that NO2 is sorbed directly as nitrate species and NO cannot be strongly sorbed as nitrate on K-Al2O3. The complete material composition K/Mn-Al2O3 shows strong nitrate bands during NO and NO2 exposure. An interplay of potassium and manganese when forming nitrates was found. Operando DRIFTS confirms the direct relation between formed nitrates and complex impedance. Furthermore, it is proven that during thermal regeneration, sorbed nitrites and nitrates desorb completely and the sensor signal returns to its initial value. On the whole, the sorption behavior of the powders and the dosimeter behavior can be explained.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Functional Materials > Chair Functional Materials - Univ.-Prof. Dr.-Ing. Ralf Moos
Profile Fields > Advanced Fields > Advanced Materials
Research Institutions > Research Centres > Bayreuth Center for Material Science and Engineering - BayMAT
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 04 Sep 2020 07:33
Last Modified: 04 Sep 2020 07:33
URI: https://eref.uni-bayreuth.de/id/eprint/56791