Solid-state amperometric sensor based on a sodium ion conductor for detection of total NOx in an atmospheric environment

An Na+ conductor-based amperometric sensor was designed for the detection o f total NOx (NO + NO2) in air. An original amperometric device, attached wi th a layer of NaNO2 on the counter electrode (Au) was sensitive to NO2, but insensitive to NO. In order to make the device sensitive to NO, the sensin g electrode (Au) was covered with double layers of catalysts to oxidize NO to NO2, i.e., WO3 and Pt (0.5 wt %)-loaded SiO2. At the sensing electrode p otential fixed at -150 mV vs. the reference electrode (Au), the current res ponse was proportional to the concentration of NO2 or NO up to 1 ppm at 150 degrees C. In addition, the proportionality constants (sensitivity) were a lmost the same to NO and NO2. The current responses were hardly affected by the coexistence of CO 2 and H2O. The NOx sensing mechanism of the present sensor was briefly discussed. (C) 1999 The Electrochemical Society. S1099-0 062(99)02-046-5. All rights reserved.