Dosimeter-Type NO[subscript x] Sensing Properties of KMnO[subscript 4] and Its Electrical Conductivity during Temperature Programmed Desorption

Abstract

An impedimetric NO[subscript x] dosimeter based on the NO[subscript x] sorption material KMnO[subscript 4] is proposed. In addition to its application as a low level NO[subscript x] dosimeter, KMnO[subscript 4] shows potential as a precious metal free lean NO[subscript x] trap material (LNT) for NO[subscript x] storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO[subscript 2] exposure can be detected electrically as instantaneous values at 380 °C by progressive NO[subscript x] accumulation in the KMnO[subscript 4] based sensitive layer. The linear NO[subscript x] sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NO[subscript x] sorption-dependent conductivity of the KMnO[subscript 4]-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NO[subscript x] loading amount increases proportionally to the NO[subscript x] exposure time at sorption temperature. The cumulated NO[subscript x] exposure, as well as the corresponding NO[subscript x] loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NO[subscript x] concentration information from the signal derivative or (2) during the short-term thermal NO[subscript x] release.