Enhanced room temperature NH3 sensing of rGO/Co3O4 nanocomposites

Cobalt oxide decorated reduced graphene oxide (rGO/Co3O4) nanocomposites (NC's) based gas sensors exhibited p-type semiconducting behavior. The rGO/Co3O4 NC's were prepared by the solvothermal technique at 180 °C for 8 h. SEM revealed that the Co3O4 NP's are distributed over and between the rGO sheets. The energy band gap and gas sensing performances had changed when the amount of Co3O4 NP's used to decorate the rGO. The gas sensing ability of the rGO/Co3O4 NC's exhibited good sensitivity. The rGO/Co3O4 NC's showed higher sensor responses gas than does the rGO based gas sensor at room temperature; while the Co3O4 based gas sensor was unable to detect the NH3. The decoration of rGO with Co3O4 nanoparticles (NP's) led to the formation of Co–C bridges which permitted the exchange of charge carriers from Co3O4 NP's to rGO sheets thus increasing the number of sites at which the gas reaction can occur. This leads to the sensor response of rGO/Co3O4 NC's to increase rapidly from 20 to 40 ppm of NH3. In addition, the signal of 25% rGO/Co3O4 NC's showed excellent sensitivity (1.78%) with the fastest response time (351 s) being at 20 ppm of NH3. Therefore, the results in this research work demonstrated that the rGO/Co3O4 NC's can be developed to achieve high performance gas sensor for NH3 at room temperature. (a) The response curve and (b) the response time and recovery time of rGO and rGO/Co3O4 NC’s toward 20 ppm of NH3 at room temperature. [Display omitted] •Density of Co3O4 NP's distributed on rGO sheets increases when the weight ratio of Co3O4 NP's increases.•NH3 sensors of rGO/Co3O4 NC's have higher responses than Co3O4 or rGO only gas sensor at room temperature.•Signal of 25% rGO/Co3O4 NC's shows excellent sensitivity with the fastest response time being at 20 ppm.•The rGO/Co3O4 NC's can be used to achieve or high performance in a NH3 gas sensor.•Sensor response of 80 wt% exhibits extreme rapid increase which never fully recovers to baseline values.