Sensing of hydrocarbons with tin oxide sensors: possible reaction path as revealed by consumption measurements

The catalytic conversion of methane, propane and toluene by palladium-doped tin oxide sensors was measured in dry and humid conditions for several temperatures between 200 and 400 °C. To distinguish between the consumption caused by the sensitive material and the consumption caused by the transducer, additional measurements were performed with substrates equipped with electrodes and heater only. For all gases, the presence of humidity decreases both consumption and sensor signal. For methane and propane, no consumption by the substrate and electrodes/heater was found and the sensor signals are, in comparison with toluene, low. In humid conditions, there is a direct correlation between the consumption by the sensitive material and the sensor signal towards toluene. In dry conditions, this correlation is more complex and indicates a more complex interaction path.