Sensing characteristics and surface reaction mechanism of alcohol sensors based on doped SnO2
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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 oC. 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 ( ), 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.
Abstract
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 oC. 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 ( ), 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.