Highly porous cobalt oxide-decorated carbon nanofibers fabricated from starch as free-standing electrodes for supercapacitors

Hybrid supercapacitor with improved energy density was prepared by electrospinning using biopolymer, and a simple dip-coating method. Through the optimization of the dip-coating time and post-heat treatment process, carbon nanofiber with highly porous structure and Co3O4 particles formed on the surface was successfully fabricated. It was found that Co3O4/C nanofibers dipped for one hour exhibited a highly porous microstructure with a specific surface area of 964 m(2)/g, and this was mainly composed of pores with an average diameter of 2.4 nm. These characteristics contributed to superior electrochemical properties of hybrid nanofibers, among which a 137 F/g specific capacitance was achieved with a very stable cycle life (91% retention after 5,000 cycles). The combination of porous carbon nanofiber derived by optimized calcination process of Co precursor and redox reaction from the Co3O4 provided a synergistic effect for enhanced specific capacitance of the hybrid supercapacitor.