Size-Dependent Synthesis of Hollow Co <sub>3</sub> O <sub>4</sub> Nanocubes Derived from Co-Fe PBA as Battery-Type Electrode Materials for Hybrid Supercapacitors
Zhiling Peng, Wenqi Wang, Heming Zhao, Juncheng Qi, Huifang Zhang, Chungui Zhou, Bing Yan, Zepeng Zhang
Abstract
Hollow nanostructures with enlarged surface areas are highly attractive electrode materials for supercapacitors. In this work, the size-dependent synthesis of hollow Co 3 O 4 nanocubes via a facile ionic exchange reaction between Co-Fe Prussian blue analogues (PBAs) and alkali solution is reported. By adjusting the concentration of sodium citrate to control the reaction kinetics during nucleation and growth, four different sizes of Co-Fe PBAs were synthesized. It was also found that a Co-Fe PBA of about 140 nm can be easily converted into a well-defined internal hollow structure, while Co-Fe PBAs with smaller or larger sizes are challenged in generating a hollow structure. Benefitting from the inner voids and thin shell architecture, the derived hollow Co 3 O 4 nanocubes exhibit a high specific capacity of 296.6C cm −2 at 2 mA cm −2 , and a rate capability of 64.5% when the current density is increased to 60 mA cm −2 . Furthermore, a hybrid supercapacitor (HSC) was fabricated with hollow Co 3 O 4 nanocubes as the cathode and activated carbon as the anode, respectively. The HSC provided a maximum energy density of 14.1 Wh kg −1 at 464.7 W kg −1 . Moreover, it retained the excellent cycling stability of 85.7% of the original capacity over 5000 continuous charging and discharging processes.