SnO 2:Bi 2O 3 based CO sensor: Laser-Raman, temperature programmed desorption and X-ray photoelectron spectroscopic studies

Abstract

The sensitivity and selectivity of tin oxide (SnO 2) based gas sensors towards carbon monoxide (CO) was improved by doping the base material with Bi 2O 3 and Sb 2O 3. Laser-Raman studies of the compound confirm the formation of bismuth stannate (Bi 2Sn 2O 7) above 800°C, which seems to be acting as a molecular sieve allowing only CO gas to react with the sensor surface, thereby imparting selectivity to the sensor. The chemisorption of oxygen on SnO 2:Bi 2O 3 was investigated over a wide range of temperatures from room temperature to 800°C by means of Temperature Programmed Desorption (TPD) and X-ray Photoelectron Spectroscopic (XPS) studies which were carried out to establish the exact chemical species present on the sensor surface before and after the reaction.