Vertically aligned mixed V 2O 5-TiO 2 nanotube arrays for supercapacitor applications
ABSTRACT Highly ordered mixed V 2O 5-TiO 2 nanotubes can be formed by self-organizing anodization of Ti-V alloys with vanadium content of up to 18 at%. In the resulting oxide nanotube arrays, the vanadium is electrochemically switchable leading to a specific capacitance that can reach up to 220 F g -1 and an energy density of 19.56 Wh kg -1 with perfect reversibility and long-term stability. Thus these mixed oxide nanotubes may be considered as a promising candidate for supercapacitors. © 2011 The Royal Society of Chemistry.
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ABSTRACT: The fabrication of self-organized VO(2) nanotubular/nanoporous layers is demonstrated by self-organizing anodization, followed by a suitable heat treatment. These VO(2) layers show a reversible metal to insulator transition (MIT) at 70 and 44 °C, when heating and cooling, respectively.Advanced Materials 02/2012; 24(12):1571-5. · 14.83 Impact Factor
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ABSTRACT: High specific capacitance per area is a critical requirement for a practical supercapacitor electrode, and needs a combination of high mass-loading of the electrochemically active material per area, and high utilization efficiency of this material. However, pursuing high mass-loading on conventional electrodes usually leads to an increase in “dead” material which is not accessible to the electrolyte in the supercapacitor, and thus prevents high utilization efficiencies of the material being realized. Here we show that this antagonism can be overcome by incorporating the electrochemically active material in a mesoporous hierarchical architecture. Fabrication of ternary ordered hierarchical Co3O4@Ni-Co-O nanosheet-nanorod arrays—involving the growth of densely aligned slim Ni-Co-O nanorods (diameter <20 nm) on Co3O4 microsheets which had been previously loaded on macroporous nickel foam—gives a material with excellent electrochemical performance as a supercapacitor electrode. At a current density of 5 mA/cm2, the electrodes have both high mass loading per area (12 mg/cm2) and high efficiency of 2098 F/g, giving specific capacitances per area as high as ∼25 F/cm2. When the current density was increased from 5 to 30 mA/cm2, 72% of the specific capacitance was retained and, furthermore, no significant decrease in capacitance was observed over 1000 charge/discharge cycles. The combination of these merits makes the composite material an excellent candidate for practical application as a supercapacitor electrode and, more generally, highlights the increased efficacies of materials which can result from fabricating mesoporous hierarchical structures at the nanoscale.Nano Research 5(5). · 7.39 Impact Factor
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ABSTRACT: The present work demonstrates that morphology of TiO2-WO 3 composite nanotubes formed by alloy anodization can be tuned by controlling applied voltages and time. Distinctive tube morphology can be formed by applying a voltage of more than 80 V. Nanotube diameter and length have a linear relationship with the anodization voltage with a current efficiency of almost 100 %. Furthermore, compared to pure TiO2, the composite nanotubes show a very uniform tube diameter along the tube axis even at the extended anodization time. © 2012 Springer Science+Business Media Dordrecht.Journal of Applied Electrochemistry 43(1). · 1.84 Impact Factor