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

SnO₂/Co₃O₄nanofibers(NFs)are synthesized by using a homopolar electrospinning system with double jets of positive polarity electric fields.The morphology and structure of SnO₂/Co₃O₄hetero-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/Co₃O₄NFs 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,Sn O₂has the disadvantages of high optimal operating temperature and poor reproducibility.Comparing with Sn O₂,the optimal operating temperature of SnO₂/Co₃O₄NFs is reduced from 350℃to 250℃,which may be related to the catalysis of Co₂O₂.The response of SnO₂/Co₃O₄to 100-ppm ethanol at 250℃is 50.9,9 times higher than that of pure Sn O₂,which may be attributed to the p–n heterojunction between the n-type Sn O₂crystalline grain and the p-type Co₂O₂crystalline grain.The nanoscale p–n heterojunction promotes the electron migration and forms an interface barrier.The synergy effects between Sn O₂and Co₂O₂,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.