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 CeO 2 in the detection of gases - acetone and NO - in an oxygen containing envi ronment. However, in such gas mixture chemical reactions may take place at and near the hot sensor surface, changing the composition of the gas enviro nment. The effect of CeO2 - its catalytic activity - was studied in the oxi dation of acetone and NO during their detection. For this purpose, a partic ular experimental set-up was planned and built: a special, flow type quartz microreactor connected to a mass spectrometer, offering the possibility fo r simultaneous resistance measurement and analysis of the near sensor gas c omposition. The sensor was operated both in self- and oven-heated mode betw een 20-900 degreesC. The maximum sensitivity of CeO2 was found between 350- 450 degreesC for both gases. While acetone causes a well measurable resista nce 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 forma tion of CO2. Surprisingly, the same surface led to the reduction of NO. (C) 2000 Elsevier Science B.V. All rights reserved.