CO sensing performance in micro-arc oxidized TiO2 films for air quality control

Porous TiO2 films were prepared by the micro-arc oxidation (MAO) of Ti plates, and their CO sensing properties at low concentrations (5–100 ppm) were investigated as an application for an air quality control sensor. The obtained rutile films exhibited the maximum CO gas response at 350 °C, which is typical for semiconductor-type gas sensors, and the Ra/Rg was ∼1.6 for 10 ppm CO (Ra: resistance in air, Rg: resistance in a sample gas). The magnitude of the gas response increased almost linearly with increasing the CO concentration from 5 to 100 ppm. The CO sensing performance of the TiO2 sensor in the presence of humidity was investigated and compared with that of a SnO2 sensor.