Fabrication of porous nanosheet-based Co 3 O 4 hollow nanocubes for electrochemical capacitors with high rate capability

<p>Well-defined hierarchical Co3O4 hollow nanocubes with uniform porous structures and high specific surface area have been synthesized by Cu2O template-assisted method combing a post-calcination process in air. Results show that the obtained hollow Co3O4 nanocubes are porous in their shells, which are built up of many interlaced ultrathin nanosheets (similar to 5 nm in thickness). Both nanosheet networks and porous interconnections within hollow nanocubes can facilitate the transportation of electrons and electrolyte ions, and accordingly result in high electrochemical performances. As is expected, these Co3O4 nanocubes exhibit a specific capacitance (404.9 F g(-1) at a charge-discharge current density of 0.5 A g(-1)), excellent rate capability (87.8% capacity retention at 20 A g(-1)), and good cycling stability (about 5% lose after 2000 cycles). Moreover, the assembled asymmetric systems using activated carbon as negative electrode can output a high energy density of 21.8 W h kg(-1) at power density of 0.4 kW kg(-1); even maintain 51.8% at a high power density of 8 kW kg(-1), further showing high rate capability. (C) 2015 Elsevier Ltd. All rights reserved.</p>