Controlling the Formation of Rodlike V2O5 Nanocrystals on Reduced Graphene Oxide for High-Performance Supercapacitors
Vanadium pentoxide (V2O5) has attracted much attention for energy storage application due to its high faradaic activity and stable crystal structures, which make it promising electrode materials for supercapacitors. However, the low electronic conductivity and small lithium ion diffusion coefficient of V2O5 limit its practical applications. To overcome these limitations, a facile and efficient method is here demonstrated for the fabrication of V2O5/reduced graphene oxide (rGO) nanocomposites as electrode materials for supercapacitors. With this method, the reduction of graphene oxide can be achieved in a cost-effective and envi-ronmentally friendly solvent, without the addition of any other toxic reducing agent. Importantly, this solvent can control the forma-tion of the uniform rod-like V2O5 nanocrystals on the surface of rGO. Compared to pure V2O5 microspheres, the V2O5/rGO nano-composite materials exhibited higher specific capacitance of 537 F g-1 at a current density of 1 A g-1 in neutral aqueous electrolytes, higher energy density of 74.58 Wh Kg-1 at a power density of 500 W kg-1 and better stability even after 1000 charge/discharge cy-cles. Their excellent performances can be attributed to the synergistic effect of rGO and rod-like V2O5 nanocrystals. Such impres-sive results may promote new opportunities for these electrode materials in high energy density storage systems.
Available from: Ganesh Kumar Veerasubramani
- "Among these materials, RuO 2 possess a higher specific capacitance of about 720 F/g and due to its high cost, the commercial application of this material becomes limited . Likewise, V 2 O 5 possess high specific capacitance but due to its low electronic conductivity and poor stability in aqueous electrode limits for its usage . However, due to the urgent needs in the high energy requirements and the need for energy storage devices, the researchers have focused on the development of novel materials for pseudocapacitor applications. "
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ABSTRACT: In this study, we demonstrated the formation of nanoarchitectures of nest like Ni3S2 grown directly on Ni foam by a one pot hydrothermal route and used it as a binder free electrode for high performance supercapacitors. The formation of Ni3S2 on the Ni foam is confirmed by the X-ray diffraction analysis. Field emission scanning electron microscope study revealed the formation of nest like Ni3S2 grown on the Ni foam has been obtained by the hydrothermal method. A plausible mechanism for the formation of Ni3S2 phase is discussed. The electrochemical properties of the as prepared Ni3S2/Ni electrodes are studied using cyclic voltammetry (CV), galvanostatic charge–discharge analysis and electrochemical impedance spectroscopy (EIS) studies. The CV study revealed the presence of redox peaks suggesting the pseudocapacitive nature of the prepared Ni3S2/Ni electrode. Galvanostatic charge–discharge analysis showed a maximum specific capacitance of 1293 F/g was achieved for the Ni3S2/Ni electrodes at a constant current density of about 5 mA/cm2. Further, EIS results (such as Nyquist and Bode plots) confirmed the pseudocapacitive nature of the Ni3S2/Ni electrode. The experimental results suggested the design of hierarchical nanostructures of Ni3S2 grown on Ni foam as a binder free electrode material will be an ideal candidate for supercapacitor applications.
Available from: Dongliang Chao
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ABSTRACT: This article provides an overview of solution-based methods for the controllable synthesis of metal oxides and their applications for electrochemical energy storage. Typical solution synthesis strategies are summarized and the detailed chemical reactions are elaborated for several common nanostructured transition metal oxides and their composites. The merits and demerits of these synthesis methods and some important considerations are discussed in association with their electrochemical performance. We also propose the basic guideline for designing advanced nanostructure electrode materials, and the future research trend in the development of high power and energy density electrochemical energy storage devices.
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ABSTRACT: Unlike other crystalline metal oxides amenable to templating by the Combined Assemblies of Soft and Hard chemistries (CASH) method, vanadium oxide nanostructures templated by poly(ethylene oxide-b-1,4-butadiene-b-ethylene oxide) (OBO) triblock copolymers are not preserved upon high temperature calcination in argon. Triconstituent cooperative assembly of the phenolic resin oligomer (resol) and an OBO triblock in a VOCl3 precursor solution enhances the carbon yield and can prevent break-out crystallization of the vanadia during calcination. However, the calcination environment significantly influences the observed mesoporous morphology in these composite thin films. Use of an argon atmosphere in this processing protocol leads to nearly complete loss of carbon-vanadium oxide thin film mesostructure, due to carbothermal reduction of vanadium oxide. This reduction mechanism also explains why the CASH method is not more generally successful for the fabrication of ordered mesoporous vanadia. Carbonization under a nitrogen atmosphere at temperatures up to 800 °C instead enables formation of a block copolymer-templated mesoporous structure, which apparently stems from the formation of a minor fraction of a stabilizing vanadium oxynitride. Thus, judicious selection of the inert gas for template removal is critical for the synthesis of well-defined, mesoporous vanadia-carbon composite films. This resol-assisted assembly method may generally apply to the fabrication of other mesoporous materials, wherein inorganic framework crystallization is problematic due to kinetically competitive carbothermal reduction processes.
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