Detection of xylene from C/Co3O4 nanocomposites synthesized from double-template using g-C3N4/ZIF-67

Gas sensors based on MOS materials have the advantages of high sensitivity, adjustable components, low cost and easy integration. MOF-derived MOS materials possess high porosity, which has the potential to detect VOC gases. And the introduction of carbon materials is an effective means to improve the gas-sensing performance due to the adsorption and activation effects. In this paper, C/Co3O4 nanocomposites were synthesized from double-template using g-C3N4/ZIF-67 precursor and applied to xylene sensors. The characterization results show that graphitized carbon species/dots were successfully introduced into the surface of Co3O4 nanoparticles, and XPS results confirmed the increase of chemisorbed oxygen. The density functional theory calculations also show that the existence of carbon species could enhance the adsorption of xylene and oxygen, as well as the obvious activation of oxygen (increased O-O bond length). The effects of adsorption and activation, structural advantages and surface electronic structure modulation lead to a significant improvement in the xylene-sensing properties of the composites. The response of C/Co3O4 to 100 ppm xylene is 17.62, which is 3.2 times higher than that of pure Co3O4. Meanwhile, the sensor has a low detection limit (1 ppm), short response time (7 s) and good stability. This work provides a feasible method to improve the performance of xylene sensor and has reference value for the effect of carbon materials on gas-sensing behavior.