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 of total NOx (NO + NO2) in air. An original amperometric device, attached with 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 sensing 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 potential fixed at -150 mV vs. the reference electrode (Au), the current response was proportional to the concentration of NO2 or NO up to 1 ppm at 150 degrees C. In addition, the proportionality constants (sensitivity) were almost 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. S1099-0062(99)02-046-5. All rights reserved.