SnO2 : Bi2O3 based CO sensor: Laser-Raman, temperature programmed desorption and X-ray photoelectron spectroscopic studies

The sensitivity and selectivity of tin oxide (SnO2) based gas sensors towar ds carbon monoxide (CO) was improved by doping the base material with Bi2O3 and Sb2O3. Laser-Raman studies of the compound confirm the formation of bi smuth stannate (Bi2Sn2O7) above 800 degrees C, which seems to be acting as a molecular sieve allowing only CO gas to react with the sensor surface, th ereby imparting selectivity to the sensor. The chemisorption of oxygen on S nO2:Bi2O3 was investigated over a wide range of temperatures from room temp erature to 800 degrees C by means of Temperature Programmed Desorption (TPD ) and X-ray Photoelectron Spectroscopic (XPS) studies which were carried ou t to establish the exact chemical species present on the sensor surface bef ore and after the reaction. (C) 1999 Elsevier Science S.A. All rights reser ved.