A compact solid-state amperometric sensor for detection of NO2 in ppb range

A compact, solid-state, amperometric NO2 sensor was fabricated using a small Na+ conductor (NASICON) plate and an NaNO2 layer deposited on the counter electrode. With the sensing electrode polarized at a constant potential relative to the reference Au electrode coated with an inorganic adhesive, electric current flowing through the device under exposure to NO2 was measured as a sensing signal. The current response was almost linear with NO2 concentration in the range 10 ppb-1 ppm at 150 degrees C. The 90% response time to even 20 ppb NO2, was ca. 60 s. The NO2 sensitivity was hardly affected by the coexistence of CO2, H2O and O-2. Furthermore, the device could be operated rather stably during the test period of ca. 30 days except for several days in the early stage. A sensing mechanism is proposed on the basis of the sensing characteristics obtained. (C) 1998 Elsevier Science S.A. All rights reserved.