Tetragonal pencil-like VO2(R) as electrode materials for high-performance redox activities

Pencil-like tetragonal vanadium dioxide has been synthesized via one-step hydrothermal treatment. The compounds were analyzed through X-ray powder diffraction; scanning electron microscope and X-ray photoelectron spectroscopy (XPS). The optical properties of the as-synthesized material were studied by UV-visible diffuse reflection spectroscopy and room temperature photoluminescence. Thin films of VO2(R) deposited on ITO substrates were electrochemically characterized by cyclic voltammetry (CV). The voltammograms show a reversible redox behavior with a doping/dedoping process corresponding to reversible cation intercalation/de-intercalation into the crystal lattice of the pencil. This process is easier in propylene carbonate than in aqueous solvent. It is also easier for the small Li+ cation than larger ones, Na+ and K+. This is attributed to a probable presence of one tunnel cavities in the structure of VO2(R). The good electrochemical property of the VO2(R) is attributed to its unique ultralong nanopencils structure with a good structural stability.