Self-templated synthesis of N-doped CoSe2/C double-shelled dodecahedra for high-performance supercapacitors

Transition metal chalcogenides have attracted increasing attentions as electrode materials for energy storage devices. Their electrochemical properties are largely determined by morphologies and structures. In this paper, we reported the fabrication of CoSe2/C dodecahedra with tunable interior structures, such as solid, yolk-shell, and double-shell structured interiors. Dodecahedron-shaped cobalt-organic frameworks are used as the sacrificial template, in which the cobalt species react with selenium to in situ form CoSe2 nanoparticles. Moreover, the organic framework is converted into nitrogen-doped carbon framework. The controllable preparation of CoSe2/C composite with diversified interior structures can be realized by a temperature determined annealing process in argon atmosphere. In particular, the unusual double-shell structured composites with non-spherical shells and heterogeneous intervals are formed. The possible formation mechanism of the structure is proposed. As electrode materials for supercapacitors, the double-shelled CoSe2/C composites exhibit high capacitance, good rate capability and long-term cycling stability.