Enhanced room temperature sensing of Co3O4-intercalated reduced graphene oxide based gas sensors

The room temperature gas sensing properties of the Co3O4 intercalated reduced graphene oxide (rGO) based thick film semiconductor sensors were investigated. The Co3O4–rGO composite based sensors showed a much higher response to NO2 at room temperature compared to the rGO based sensors. However, with an increase in the rGO concentration from 5 wt% to 30 wt%, the response showed a decreasing tendency. The sensor response to NO2 was not fully recovered within the measurement time (∼20 min) due to the much strong adsorption of NO2 at the defective sites of rGO. In contrast, the sensors using rGO showed a fast response and full recovery to methanol. This has been proposed to be exclusively due to the interaction of methanol with the sp2 bonding of the carbon. Similarly, with Co3O4 intercalated rGO, the response was significantly enhanced and the response/recovery time was within 1–2 min. Two possible reasons have been discussed including the increased surface area of the rGO thick film by the intercalation of Co3O4 nanocrystals and the Co3+-carbon coupling effect for the rapid response.