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

SnO 2 /Co 3 O 4 nanofibers (NFs) are synthesized by using a homopolar electrospinning system with double jets of positive polarity electric fields. The morphology and structure of SnO 2 /Co 3 O 4 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 SnO 2 /Co 3 O 4 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, SnO 2 has the disadvantages of high optimal operating temperature and poor reproducibility. Comparing with SnO 2 , the optimal operating temperature of SnO 2 /Co 3 O 4 NFs is reduced from 350°C to 250°C, which may be related to the catalysis of Co 3 O 4 . The response of SnO 2 /Co 3 O 4 to 100-ppm ethanol at 250°C is 50.9, 9 times higher than that of pure SnO 2 , which may be attributed to the p–n heterojunction between the n-type SnO 2 crystalline grain and the p-type Co 3 O 4 crystalline grain. The nanoscale p–n heterojunction promotes the electron migration and forms an interface barrier. The synergy effects between SnO 2 and Co 3 O 4 , 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.