Relationship between ethanol gas sensitivity and surface catalytic property of tin oxide sensors modified with acidic or basic oxides

A semiconductor gas sensor using SnO2 was loaded with acidic or basic oxide s (5 wt.%) to investigate ethanol-gas sensing properties and related cataly tic properties. The sensitivity to ethanol gas at 300 degrees C increased t remendously with an addition of a basic oxide (e.g., La2O3), while it hardl y changed with that of an acidic oxide (WO,). It turned out that the additi on of the basic metal oxide to SnO2 brought about enhancement of catalytic activity not only for the dehydrogenation of ethanol gas to CH3CHO but also for the consecutive oxidation of CH3CHO to CO2. On the other hand, the aci dic metal oxide enhanced only the dehydration reaction, showing even an adv erse effect on the consecutive oxidation. Based on these results, it was co ncluded that the enhancement of the catalytic oxidation activity to an appr opriate level could be a reason for the high sensitivity to ethanol gas for the sensors loaded with basic oxides, particularly one loaded with La2O3. (C) 2000 Elsevier Science B.V. All rights reserved.