Reaction analysis on sensing electrode of amperometric NO2 sensor based onsodium ion conductor by using chronopotentiometry

Galvanostatic chronopotentiometry was performed to identify the reaction pr oducts formed on the sensing electrode of an amperometric NO2 sensor based on NASICON (Nat conductor). It was indicated that the products after the se nsing operation at 150 or 200 degreesC were different, depending on the atm osphere, NaNO2 and NaNO3 were formed in the NO2-containing air, while NaOx (presumably Na2O2) was formed in the NO2-free air. It is concluded that NaO x is formed through the cathodic reaction of O-2, while NaNO2 is formed as a primary product of the cathodic reaction of NO2. It is also concluded tha t NaNO3 is formed as a secondary product of the chemical reaction between N aOx and NaNO2 in dry condition, although the reaction between NaO, and gase ous NO2 also takes place in the humid condition as another root for NaNO3 f ormation. (C) 2001 Elsevier Science B.V. All rights reserved.