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Dosimeter-Type NOx Sensing Properties of KMnO4 and Its Electrical Conductivity during Temperature Programmed Desorption
Zentrum für Energietechnik, Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95440 Bayreuth, Germany
Ford Research and Advanced Engineering, Dearborn, MI 48124, USA
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
* Author to whom correspondence should be addressed.
Received: 28 February 2013; in revised form: 22 March 2013 / Accepted: 25 March 2013 / Published: 2 April 2013
Abstract: An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release.
Keywords: NOx dosimeter; lean NOx trap (LNT); precious metal free NOx storage catalyst (NSC); electrical TPD; accumulating sensing principle; low ppm-level NOx detection; in-situ catalyst loading state monitoring; ammonia SCR; three-way catalyst (TWC)
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Groß, A.; Kremling, M.; Marr, I.; Kubinski, D.J.; Visser, J.H.; Tuller, H.L.; Moos, R. Dosimeter-Type NOx Sensing Properties of KMnO4 and Its Electrical Conductivity during Temperature Programmed Desorption. Sensors 2013, 13, 4428-4449.
Groß A, Kremling M, Marr I, Kubinski DJ, Visser JH, Tuller HL, Moos R. Dosimeter-Type NOx Sensing Properties of KMnO4 and Its Electrical Conductivity during Temperature Programmed Desorption. Sensors. 2013; 13(4):4428-4449.
Groß, Andrea; Kremling, Michael; Marr, Isabella; Kubinski, David J.; Visser, Jacobus H.; Tuller, Harry L.; Moos, Ralf. 2013. "Dosimeter-Type NOx Sensing Properties of KMnO4 and Its Electrical Conductivity during Temperature Programmed Desorption." Sensors 13, no. 4: 4428-4449.