Dosimeter-Type NO(x) Sensing Properties of KMnO(4) and Its Electrical Conductivity during Temperature Programmed Desorption

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