Gradual “OH−-incursion” outside-inside strategy in construction of 3D flower-like Co3O4-CNT>N-PEGm hierarchical microspheres for supercapacitors

Abstract

We have synthesized a novel dodecyl benzene sulfate (DBS)-intercalated 3D flower-like α-Co(OH)2-CNT>N-PEGm hierarchical microsphere composites as the precursor by a gradual “OH−-incursion” with an outside-inside strategy, in which the incorporating CNT>N-PEGm were modified by Nitrene Chemistry with the methoxypolyethylene glycol (mPEG). Based on the sintering process, the Co3O4-CNT>N-PEGm composites exhibit close function of CNT>N-PEGm with Co3O4 nanostructures, due to the coordination bonds formed between the lone pair of electrons on ether-oxygen groups of the polymer chains on the CNTs surface and cobalt ions. Moreover, the as-prepared Co3O4-CNT>N-PEGm can provide a range of hierarchical mesoporous as short ion-diffusion channels in the Co3O4 nanosheets at the exterior of the composites, meanwhile the CNT>N-PEGms provide electron transport channels to improve the electron transport in the interior of Co3O4 microspheres. Hence, the high specific capacitance value of 1513.2 F g−1 at a current density of 0.5 A g−1 was achieved for Co3O4-CNT>N-PEGm in 6 M KOH solution. Furthermore, an asymmetric supercapacitor fabricated with Co3O4-CNT>N-PEGm as positive electrode material and active carbon as negative electrode material showed an excellent capacitance of 119.9 F g−1 at a current density of 0.5 A g−1 and an energy density of 42.6 Wh kg−1 at the power density of 400 kW kg−1.