Synthesis of Novel Vanadium Oxide Nanotubes and Nanofibers
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Synthesis of Novel Vanadium Oxide Nanotubes and Nanofibers Samuel T. Lutta, Hong Dong, Peter Y. Zavalij, and M. Stanley Whittingham*
Chemistry Department and the Institute for Materials Research, State University of NewYork at Binghamton, Binghamton, NewYork 13902-6016, U.S.A. ABSTRACT We are exploring the synthesis and properties of structured vanadium oxides mainly nanotubes and nanorods. Nanotubes initially formed with surfactant templates have been readily exchanged with simple cations without change of the basal-plane structure. These compounds contain δ-like vanadium oxide layers with the vanadium in VO6 octahedra. This structure is particularly suitable for redox reactions. In this paper we report on synthesis of vanadium oxide, (NH4)xV2O5-δ·nH2O rods using organic polymer as template. This compound has been synthesized by sol-gel reaction and subsequent hydrothermal treatment. TGA, SEM, XRD and FTIR were used to characterize this compound. Thermal analysis of this compound shows that the fibrous morphology is maintained when it is heated in nitrogen and oxygen above 300 °C. However, in both cases the size of the fibers decreases. Performance of this compound as cathode material in secondary electrolyte has been investigated using LiPF6 as electrolyte. A capacity of 140 mAh/g was obtained which remained fairly constant with up to at least 10 cycles. We also investigated electrochemical behavior of thermal products. INTRODUCTION There has been much recent interest in preparing new vanadium oxides owing to their promise as cathodes and anodes in secondary lithium batteries and electrochromic devices [1-2]. Also the catalytic behavior of vanadium oxides make these materials viable candidates as heterogeneous catalysts [3]. The physical and chemical properties of substances might well be altered when they are prepared on a nanoscopic scale and thus this phenomenon opens up a completely new perspective for material design that benefits from the introduction of particle size as a new, powerful parameter [4]. Thus fabrication of vanadium oxides in nanostructured form and with anisotropic morphology appears to be a particularly attractive goal. The first successful approach to make a tubular vanadium oxide was use of carbon nanotubes as a template [5]; it was found possible to coat crystalline layers of V2O5-structures on the external surfaces of the carbon nanotubes. Recently, new type of vanadium oxide nanotubes was obtained by a soft-chemistry synthesis involving amines with long alkyl chains as molecular, structure directing template [6]. This material consisted of scrolls of vanadium oxide layers within which the alkyl amines were embedded. The structure of the double-sheet layer in this material is similar to BaV7O16·nH2O [7]. In our attempts to make structured vanadium oxides, we have developed a new method to make novel vanadium oxide tubes and nanorods using an organic polymer as template. The synthetic approach involved sol-gel and hydrothermal techniques. This method allows us to *
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