Chemical reactions in the detection of acetone and NO by a CeO2 thin film

This work presents an attempt to apply the undoped n-type semiconductor CeO2 in the detection of gases — acetone and NO — in an oxygen containing environment. However, in such gas mixture chemical reactions may take place at and near the hot sensor surface, changing the composition of the gas environment. The effect of CeO2 — its catalytic activity — was studied in the oxidation of acetone and NO during their detection. For this purpose, a particular experimental set-up was planned and built: a special, flow type quartz microreactor connected to a mass spectrometer, offering the possibility for simultaneous resistance measurement and analysis of the near sensor gas composition. The sensor was operated both in self- and oven-heated mode between 20–900°C. The maximum sensitivity of CeO2 was found between 350–450°C for both gases. While acetone causes a well measurable resistance change, the signal due to NO is quite small. The CeO2 surface proved to be catalytically active in the oxidation of acetone resulting in the formation of CO2. Surprisingly, the same surface led to the reduction of NO.