NOx adsorption onto dehydroxylated or hydroxylated tin dioxide surface. Application to SnO2-based sensors

SnO2-based sensors present strong interactions with NOx-containing atmosphe res. For this reason, it is fundamental to identify the nature of the adsor bed species resulting from the interaction of NO and NO2 with the tin oxide surface. This aspect has been studied in literature by Temperature Program med Desorption (TPD). To state more precisely structures of adsorbed specie s, we Link TPD with Diffuse Reflectance Fourier Transform Spectroscopy (DRI FTS). Concerning NO2 adsorption, DRIFTS experiments indicate the formation of monodentate nitrate species at room temperature. By increasing the tempe rature, a conversion of adsorbed species is observed. The nature of surface groups is discussed. In the presence of hydroxyl groups (two different OH groups are evidenced), the formation of hydrogeno nitrates is detected. (C) 2000 Elsevier Science S.A. All rights reserved.