Preparation of three-dimensional carbon microtube/carbon nanotube composites and their application in supercapacitor

Carbon microtubes (CMTs) were prepared by the carbonization of poplar catkins according to their natural microtubular structure. The CMTs were then used as the substrate for growing carbon nanotubes (CNTs) by chemical vapor deposition. The prepared three-dimensional CMT/CNT composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. Two-electrode supercapacitor cells constructed with the CMT/CNT showed a specific capacitance of 77 F·g ^-1 with 1 mol·L ^-1 Li ₂SO ₄ electrolyte, which is much higher than that for CMTs (23 F·g ^-1).