Defective carbon nanotube forest grown on stainless steel encapsulated in MnO2 nanosheets for supercapacitors

Abstract

MnO2 nanorods coated carbon nanotubes forest composite were synthesized on stainless steel substrate (SS). The annealed carbon nanotubes with high defect density showed the advantage for efficient electron transfer, demonstrating a good platform for fabrication of composite electrode materials of high performance. Initially, multiwall carbon nanotubes (CNTs) were grown on SS by chemical vapor deposition (CVD) method without the addition of external metal catalyst and followed by annealing at 500 °C for 2 h to obtain eligible defect density on CNT forest surface. Then MnO2 nanostructures were electrodeposited for various time intervals to control favorable morphology and excellent capacitance performance. The obtained nanocomposite materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman analysis. Cyclic voltammetry (CV), galvanostatic charge-discharge and Ac Impedance tests were also carried out to evaluate its capacitive property. The MnO2-800/O-CNTs nanocomposite exhibited high capacitance of 531 F g−1 at a current density of 1 A g−1 and 398 F g−1 at a current density of 10 A g−1. After 1000 cycles, the capacity retention is still maintained at 95.7%, suggesting potential applications for fabrication of high performance energy storage devices.