Preparation of reduced graphene oxide/Co₃O₄ composites and sensing performance to toluene at low temperature

Although the gas sensing properties of p-type semiconductors (such as Co₃O₄) generally are lower than those of n-type oxide semiconductors, high quality gas sensors can still be designed by various modified methods due to their distinctive surface reactivity. In the work, the rGO/Co₃O₄ composites with different formulations have been successfully synthesized by a facile hydrothermal reaction. The morphology, structure and composition of as-prepared composites were characterized by XRD, FESEM, Raman, TG, XPS spectrum and BET analysis, respectively. The sensing tests indicate that the 5 wt% rGO composite to toluene not only exhibits the highest response and excellent selectivity, but also has linear response in concentration lower 5 ppm, indicating the composite is a promising sensing material for detection of toluene. Furthermore, the mechanism of rGO enhanced composite gas sensing is also discussed in detail, which is attributed to rGO action in composite and the formation of p-p isotype heterojunction at the interface between rGO and Co₃O₄.