SnO2/Co3O4 nanofibers using double jets electrospinning as low operating temperature gas sensor

Abstract

SnO2/Co3O4 nanofibers (NFs) are synthesized by using a homopolar electrospinning system with double jets of positive polarity electric fields. The morphology and structure of SnO2/Co3O4 hetero-nanofibers are characterized by using field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectrometer (XPS). The analyses of SnO2/Co3O4 NFs by EDS and HRTEM show that the cobalt and tin exist on one nanofiber, which is related to the homopolar electrospinning and the crystallization during sintering. As a typical n-type semiconductor, SnO2 has the disadvantages of high optimal operating temperature and poor reproducibility. Comparing with SnO2, the optimal operating temperature of SnO2/Co3O4 NFs is reduced from 350°C to 250°C, which may be related to the catalysis of Co3O4. The response of SnO2/Co3O4 to 100-ppm ethanol at 250°C is 50.9, 9 times higher than that of pure SnO2, which may be attributed to the p–n heterojunction between the n-type SnO2 crystalline grain and the p-type Co3O4 crystalline grain. The nanoscale p–n heterojunction promotes the electron migration and forms an interface barrier. The synergy effects between SnO2 and Co3O4, the crystalline grain p–n heterojunction, the existence of nanofibers and the large specific surface area all jointly contribute to the improved gas sensing performance.