Synthesis And Electrochemical Properties Of Nickel And Cobalt Based Oxide Nanofibers

Supercapacitors have drawn intense research attention for applications in many aspects.Electrode materials play an important role in the performance of supercapacitors.Transition metals are considered the most promising candidate due to its excellent electrochemical properties.The NiO,NiO/CA,Co3O4/WP,Co3O4/P and NiO/Co3O4 omposites have been fabricated by electrospinning process.The structure and morphology of the samples were characterized by XRD,TG-DSC,TEM,SEM and N2 adsorption-desorption etc.Electrochemical properties were characterized by cyclic voltammetry,galvanostatic charge/discharge measurements,and electrochemical impedance spectroscopy.The results indicated that the NiO nanofibers had well crystalline,and comprised of many NiO sheets.The specific capacitance was 148 F·g-1 at the current densities of 5 mA·cm-2.The nanofibers modified by citric acid were hollow tube and displayed superior capacitive performance with large capacitance(336 F·g-1),which was 2.5 times of NiO electrodes,The electrochemical impedance spectroscopy showed that the NiO/CA nanofiber had lower charge-transfer resistance.After the addition of P123,the Co3O4 nanofibers(Co3O4/P)have the regular shape,and the grain size is smaller than that of the Co304 nanofibers without P123(C03O4/WP),so the specific surface area of the Co3O4/P electrode is bigger than C03o4/WP On the other hand,due to the small size of Co3O4/P,the active material and the conductive agent could contact with each other closely,which can increase the electrical conductivity of electrode.The nanofibers displayed superior capacitive performance with large capacitance(401 F·g-1),which were 2.2 times of Co3O4 electrodes without P123.The internal resistance Rs of Co3O4/P nanofibers is 0.45? and the Rct is 0.20?.Furthermore,the Co3O4/P nanofibers showed excellent cyclic performance after 1000 cycles.The NiO/Co3O4 nanofibers with different mass ratio and different additive were examined.After the addition of P123 and CA,the nanofibers have the regular shape,and the conductive agent could contact with each other closely.The internal resistance Rs of nanofibers is 0.45?and the Rct is 0.21?.The specific capacitance was 788 F g'1 at the current densities of 5 mA·cm-2.Furthermore,the nanofibers showed excellent cyclic performance,the capacitance decreases only 7%of the initial capacitance after 1000 cycles.