Zn Modification of Co3O4 Nanofibers: Effect on Structure and Conductivity

To overcome the low conductance issue of cobalt oxide nanofibers, we have synthesized cobalt oxide-based nanofibers with zinc (Co3O4/Zn) by the method of electrospinning. The structure of materials in this work were characterized extensively using X-ray diffraction, an X-ray fluorescence method, electron microscopy, and infrared and Raman spectroscopy. Nanofibers are shown to have a diameter of approximately 150 nm and consist of crystallites with an average size of about 20 nm. It has been found that the adding of zinc can significantly increase the conductivity of nanofibers: at a zinc concentration of about 15%, the conductivity increases by more than 4 orders of magnitude compared to cobalt oxide nanofibers without zinc and remains of p-type. We have shown that composite consists of ZnxCo3-xO4 and ZnO structures. Additionally, electron paramagnetic resonance (EPR) spectroscopy was conducted to identify the paramagnetic defects in the composites. Findings from the EPR spectroscopy were combined with the aforementioned characterization techniques to illuminate the mechanism of conductivity enhancement. The correlation between the concentration of paramagnetic cobalt atoms in an octahedral environment and the conductivity of Co3O4/ Zn composites indicates that the change in conductivity is associated with a change in the concentration of acceptor levels in the ZnxCo3-xO4 structure. Our results suggest that synthesis of nanofibers with zinc by electrospinning could be a promising method to construct high conductivity cobalt oxide-based nanofibers for environmental applications.