Microwave-assisted hydrothermal synthesis and electrochemical characterization of niobium pentoxide/carbon nanotubes composites

This study reports the fabrication of high mass loading (32 mg/cm2) electrodes of niobium pentoxide (Nb2O5) nanoparticles and carbon nanotubes (CNTs) using a facile procedure. The as-obtained Nb2O5 nanoparticles by microwave-assisted hydrothermal synthesis presented pseudohexagonal (TT) phase, and when exposed to the thermal treatment, the Nb2O5 nanoparticles changed to orthorhombic (T) phase. Distinct morphologies were obtained, which exhibited a specific surface area of 216 m2/g and 47 m2/g to pseudohexagonal and orthorhombic phases, respectively. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were performed in a three-electrode system using 1 M Li2SO4 as electrolyte with a potential window of 0–0.9 V (versus standard calomel electrode). Both materials showed capacitive behavior with a specific capacitance of 0.11 F/cm2 and 0.09 F/cm2 to nanocomposites CNT + TT-Nb2O5 and CNT + T-Nb2O5 at 2 mV/s, respectively. Thus, an efficient, simple, and promising process to produce electrodes for supercapacitors was demonstrated.