Compact amperometric solid-electrolyte sensor for detection of NO2 in ppb range

A solid-state amperometric sensor for NO2 was designed by attaching a Na+ conductor (NASICON) based device with an NaNO2 layer deposited on the counter electrode. With the sensing electrode being polarized at a constant potential relative to the reference Au electrode, electric current flowing through the device under exposure to NO2 was measured as the sensing signal. The current response was almost linear to the NO2 concentration in the range from 10 ppb to 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 O2. A sensing mechanism is proposed from the sensing characteristics obtained.