Preparation and performance of tubular nanoflaky (Ni, Co, Mn) oxides with hierarchical mesoporous structure

The nickel cobalt manganese oxide (NCMO/CNT) with hierarchical tubular nanoflaky structure is intentionally designed and synthesized via a facile method by using carbon nanotube (CNT) as a backbone template, then the nickel cobalt manganese oxide with nanosheet-like nanotube structure (NCMONST) is synthesized after removed successfully the CNT templates. The morphology, structure and physicochemical properties of the NCMONST samples are characterized by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and nitrogen adsorption-desorption isotherms. The results reveal that the NCMO shell with a thickness of 0.2 μm grows uniformly on the surface of the CNT with a diameter of 0.1 μm. After calcined NCMO/CNT in air, the mesoporous NCMONST is successfully obtained. The as-prepared NCMONST maintains the tubular and sheets-like structure of NCMO/CNT, and possesses a high specific surface area of 134.1 m2 g−1, large pore volume of 0.609 cm3 g−1 and broad pore-size distribution. The electrochemical results show that the NCMONST exhibits a high specific capacitance of 680 F g−1 at 1 A g−1, excellent rate capability of 38% at 20 A g−1 and good capacity retention of 88% after 1000 cycles. Therefore, the transition metal oxide with porous structure is a promising electrode candidate for the application of supercapacitors.