Rational design of multi-shelled CoO/Co9S8 hollow microspheres for high-performance hybrid supercapacitors

Hollow structures with complex interiors are promising to endow electroactive materials with fascinating physical properties, such as low mass density, large surface area and high permeability. Meanwhile, the construction of hollow structures with binary chemical compositions could further enhance the resultant electrochemical properties. Herein, we reported a designed synthesis of multi-shelled CoO/Co9S8 hollow microspheres by calcining a hollow microsphere precursor with S powder in argon gas (Ar). The inherent characteristic of cobalt(II) mono-oxide can benefit the electrochemical activity, while the cobalt sulfide component could improve the electrical conductivity of this cobalt-based composite material. These multi-shelled hollow structures are proved to possess a porous texture with a relatively large specific surface area (SSA = 43.1 m(2) g(-1)), which could provide more active sites for electrochemical reactions. As a result, the as-prepared multi-shelled CoO/Co9S8 hollow microspheres exhibit an enhanced specific capacitance and excellent rate performance when evaluated as electrode materials for hybrid supercapacitors.