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Hierarchical tubular structures composed of Co3O4 hollow nanoparticles and carbon nanotubes (CNTs) have been synthesized by an efficient multi-step route. Starting from polymer-cobalt acetate (Co(Ac)2) composite nanofibers, uniform polymer-Co(Ac)2@zeolitic imidazolate framework-67 (ZIF-67) core-shell nanofibers are first synthesized via partial phase transformation with 2-methylimidazole in ethanol. After the selective dissolution of polymer-Co(Ac)2 cores, the resulting ZIF-67 tubular structures can be converted into hierarchical CNTs/Co-carbon hybrids by annealing in Ar/H2 atmosphere. Finally, the hierarchical CNT/Co3O4 microtubes are obtained by a subsequent thermal treatment in air. Impressively, the as-prepared nanocomposite delivers a high reversible capacity of 1281 mAh g−1 at 0.1 A g−1 with exceptional rate capability and long cycle life over 200 cycles as an anode material for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A simple and versatile method for general synthesis of uniform one-dimensional (1D) M xCo3− xS4 (M=Ni, Mn, Zn) hollow tubular structures (HTSs), using soft polymeric nanofibers as a template, is described. Fibrous core-shell polymer@M-Co acetate hydroxide precursors with a controllable molar ratio of M/Co are first prepared, followed by a sulfidation process to obtain core-shell polymer@M xCo3− xS4 composite nanofibers. The as-made M xCo3− xS4 HTSs have a high surface area and exhibit exceptional electrochemical performance as electrode materials for hybrid supercapacitors. For example, the MnCo2S4 HTS electrode can deliver specific capacitance of 1094 F g−1 at 10 A g−1, and the cycling stability is remarkable, with only about 6 % loss over 20 000 cycles. [ABSTRACT FROM AUTHOR]