Core-niobium pentoxide carbon-shell nanoparticles decorating multiwalled carbon nanotubes as electrode for electrochemical capacitors

We report here a method to produce nanostructured and porous electrodes by electrospraying niobium pentoxide nanoparticles onto entangled spaghetti-like multiwalled carbon nanotubes. The novel niobium pentoxide and carbon nanotubes composite material exhibits promising electrode properties for the aqueous-based electro-chemical capacitors. Monoclinic and orthorhombic niobium pentoxide nanoparticles are partially covered with a thin carbon layer and anchored onto carbon nanotubes. Not only does this electrode material possess the excellent, well-known characteristics associated with carbon nanotubes (large voltage window and chemical stability), but it also has pseudocapacitive properties due to niobium pentoxide nanoparticles. This approach improves the electrical conductivity and chemical stability and also avoids reaggregation and deactivation of niobium pentoxide nanoparticles. These nanostructured carbon nanotubes and niobium pentoxide composite electrodes are characterized by ex-situ techniques, such as scanning and transmission electron microscopy, Raman, X-ray photoelectron spectroscopy, and X-ray diffraction. In-situ studies are performed on cyclic voltanunetry, galvanostatic (re)charge/discharge curves, and electrochemical impedance spectroscopy techniques. Our results show that carbon nanotubes and niobium pentoxide composite has outstanding electrochemical properties, including high specific capacitance (similar to 320 F g(-1)), long lifespan (more than 100,000 charge and discharge cycles), and high energy and power densities.