Synthesis of nanostructured metal oxides and sulfides for high performance energy devices.

Abstract

In the last few decades, energy crises enforced scientists and researchers to search for the new nanostructured materials that may have a potential for energy harvesting and storage devices. Energy storage have earned a key position in energy devices due to its viability as compared to energy harvesting devices. Metal oxide and sulfides nanostructured materials have an enormous potential for energy devices owing to their high electrochemical performance and excellent stability. In the current study, hydrothermal method has been employed for the synthesis of Ce2Zr2O7, CeO2, Y2Zr2O7, PbS, CeS2, MnS and nanocomposite of Ce2Zr2O7/PbS, CeO2/CeS2 and Y2Zr2O7/MnS materials. The synthesized nanostructured materials have been characterized to find their applications in supercapacitor devices. Structural and morphological studies have confirmed the purity and the clear morphology of the materials. Electrochemical study using three-electrode system demonstrates that metal sulfide has higher specific capacitance than metal oxide but metal oxide reveals superiority in the cyclic stability. Therefore, due to synergistic effect, the nanocomposite of metal oxide and sulfide gain the conductivity of the sulfide and the stability of the oxide. As a result, the nanocomposites depict the better electrochemical performance in a sense of capacitance retention and cyclic stability with good rate capability. Specific capacitance (Csp), energy density (E) and power density (P) of the nanostructured electrode using Ni foam as a substrate have been measured with threeelectrode system by cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) techniques. The Csp and E of Ce2Zr2O7/PbS, CeO2/CeS2, Y2Zr2O7/MnS are 219, 420, 221 F/g and 6.7, 21.2, 10 Wh/kg at a constant applied current density of 1 A/g, respectively. The Csp of Ce2Zr2O7/PbS, CeO2/CeS2, Y2Zr2O7/MnS nanocomposites electrode after 1000 successive CV cycles are 116, 700, 261 F/g, correspondingly. The iii electrode consisting of SrZrO3 nanorods exhibits remarkably high Csp of 1225 F/g and 65 Wh/kg energy density. The excellent results of SrZrO3 nanorods are owing to its high specific surface area, small pore size and unique morphology. Cyclic stability analysis reveals an excellent stability of the studied electrodes due to their unique morphologies and conductive nature of the substrate (Ni foam). Csp remains constant in Ce2Zr2O7/PbS, while in case of CeO2/CeS2 and Y2Zr2O7/MnS, the Csp increases continuously up to 1000 successive CV cycles. The SrZrO3 nanorods shows high cyclic stability up to 1000 cycles. Above studies, suggest a significant promise of aforementioned materials for their use in future generation supercapacitors electrodes.