The nano-composite of Co-doped g-C3N4 and ZnO sensors for the rapid detection of BTEX gases: stability studies and gas sensing mechanism

In the present study, the nano-composite of Co-doped g-C3N4 and ZnO (Co–C3N4/ZnO) sensor was successfully prepared by using solid-phase precursor synthesis method. The crystalline phases were analyzed by X-ray diffraction (XRD), the microstructure of Co–C3N4/ZnO sensor was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the chemical bonding states were analyzed by X-ray photoelectron spectroscopy (XPS). The gas sensing performance of Co–C3N4/ZnO sensor was systematically studied and compared with other sensors at the operating temperature of 200–370 °C, and the highest response was observed at 370 °C. Interestingly, Co–C3N4/ZnO sensor exhibited better response to o-xylene, m-xylene and p-xylene compared with other BTEX gases tested in this study; especially about 11 times higher response was observed against p-xylene compared with pure ZnO sensor at 370 °C. In addition, this sensor showed good stability and repeatability even after 14 weeks with a response/recovery time of 2 s/2 s. The improved gas sensing performance of this sensor was attributed to the formation of more active sites and more number of active oxygen species on the surface of ZnO. Based on these results, it could be ideal to explore Co–C3N4/ZnO sensor for the rapid detection of BTEX gases, specifically for p-xylene, in the surrounding environment.