Using gas chromatographic analyses, the effects of additives (PdCl2, Al2O3, and La2O3) on the alcohol-sensing properties of SnO2-based sensor elements were investigated. Also, the decomposition products of the alcohol gases and their decomposition steps at the surface of the SnO2-based powder elements were analyzed. Ethanol was catalytically oxidized by the SnO2-based powders. With the PdCl2-doped SnO2, the C-C bond clea vage product, methane, was produced. This seems to be related with the significant promotional role of PdCl2-doping in the sensing of ethanol, especially at temperatures below 300 degrees C. With the La2O3-doped SnO2, relatively large amounts of CO and CO2 were produced, resulting in an enhanced sensitivity. On the other hand, with the Al2O3-doped SnO2, selective dehydration, which consumes the less adsorbed oxygen species (O-ads(-)), seems to degrade the sensitivity. When exposed to methanol, the SnO2-based sensors showed oxidation products consisting of CO, CO2 and H2O and sensing characteristics similar to those seen with ethanol.

Keywords: gas sensor; snob alcohol sensing; gas chromatography; reaction step; dopant