Tin dioxide-based gas sensors for SO2 detection:: a chemical interpretation of the increase in sensitivity obtained after a primary detection

This paper deals with the study of the adsorption of sulfur dioxide on tin dioxide surfaces. First, using the method proposed by Walling, we studied surface acidity in order to show the effects of sulfur dioxide treatment. The results obtained were compared with those of a previous infrared analyses on sulfate formed during SO2 treatment. At the same time, we also studied the effects of tin dioxide hydration. We demonstrated that sulfur dioxide is adsorbed to form sulfate groups on basic OH groups. This was performed by blocking the acidic and basic sites of the tin dioxide surface via the use of ammonia and boron trifluoride acid, respectively. The analysis of the results obtained have enabled us to propose a reactional mechanism for the formation of sulfate groups and the increase in surface acidity depending on experimental conditions. (C) 1997 Elsevier Science S.A. All rights reserved.