Enhanced ethanol sensors based on MOF-derived ZnO/Co3O4 bimetallic oxides with high selectivity and improved stability

ZnO/Co3O4 ethanol sensors based on metal-organic framework (MOF-74) were prepared by one-step hydrothermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and gas-sensitive tests were performed. The gas sensing test results show that MOF-derived ZnO/Co3O4 (ZnO/Co3O4-MOF1:2) has higher sensitivity, better selectivity, and lower operating temperature than ZnO/Co3O4 without MOF template (ZnO/Co3O4–N1:2). The response value of ZnO/Co3O4-MOF1:2–50 ppm ethanol gas can reach 19.75, which is 13 times higher than that of ZnO/Co3O4–N1:2. Moreover, ZnO/Co3O4-MOF1:2 has excellent selectivity, outstanding reproducibility and good stability. The limit of detection concentration is up to 500 ppb. The improved ethanol sensing performance of MOF-74-derived ZnO/Co3O4 is mainly due to the porous structure of MOF-74 with a large number of internal pores, which provides more active sites for the surface adsorption and desorption of gas molecules. In addition, the amount of surface-defective and adsorbed oxygen involved in the sensing reaction is significantly increased, leading to a larger change in resistance during the redox reaction and a higher final response.