Egg Albumin-Assisted Hydrothermal Synthesis of CoO Quasi-Cubes as Superior Electrode Material for Supercapacitors with Excellent Performances.

Novel CoO quasi-cubes with layered structure were obtained via two-step synthetic procedures. The precursors were initially prepared via hydrothermal reaction in the presence of egg albumin, and then the precursors were directly annealed at 300 °C in air to be converted into pure CoO powders. It was found that the size and morphology of final CoO products were greatly influenced by the amount of egg albumin and hydrothermal durations, respectively. Such layered CoO cubes possessed a mesoporous nature with a mean pore size of 5.58 nm and total specific surface area of 80.3 m/g. A three-electrode system and 2 M of KOH aqueous electrolyte were employed to evaluate the electrochemical properties of these CoO cubes. The results indicated that a specific capacitance of 754 F g at 1 A g was achieved. In addition, the CoO cubes-modified electrode exhibited an excellent rate performance of 77% at 10 A g and superior cycling durability with 86.7% capacitance retention during 4000 repeated charge-discharge process at 5 A g. Such high electrochemical performances suggest that these mesoporous CoO quasi-cubes can serve as an important electrode material for the next-generation advanced supercapacitors in the future.