Hydrothermal synthesis of hierarchical CoO/SnO₂ nanostructures for ethanol gas sensor

In this work, ethanol gas sensor with high performance was fabricated successfully with hierarchical CoO/SnO₂ heterojunction by two-steps hydrothermal method. The response value of CoO/SnO₂ sensor is up to 145 at 250 °C when exposed to 100 ppm ethanol gas, which is much higher than that (13.5) of SnO₂ sensor. These good sensing performances mainly attribute to the formation of the CoO/SnO₂ heterojunction, which makes great variation of resistance in air and ethanol gas. Thus, the combination of n-type SnO₂ and p-type CoO provides an effective strategy to design new ethanol gas sensors. The unique nanostructure also played an important role in detecting ethanol, due to its contribution in facilitating the transport rate of the ethanol gas molecules. Also, we provide a general two-step strategy for designing the heterojunction based on the SnO₂ nanostructure.