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New insights into the electrochemistry of magnesium molybdate hierarchical architectures for high performance sodium devices

Abstract

Magnesium molybdate (MgMoO4), which possesses synergistic features combining both hierarchical platelike nanomaterials and porous architectures, has been successfully synthesized through a facile combustion synthesis at a low temperature. The hierarchical architecture is characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), scanning transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses. The as-obtained MgMoO4 nanoplates showed a porous structure with a pore-size distribution ranging from 50 to 70 nm. This porosity provides an electron transport pathway and enhanced surface reaction kinetics. The binding energies measured for Mg 2p, Mo 3d, 3p and O 1s are consistent with the literature, and with the metal ions being present as M (II) and M (VI) states, respectively. This indicates that the oxidation states of the metal cations are as-expected. The electrochemical behaviour of MgMoO4 was investigated using aqueous (NaOH) and non-aqueous solvents (NaClO4 in EC: DMC: FEC) for supercapacitor and battery applications. The sodium-ion capacitor involves ion absorption and insertion into the MgMoO4 electrodes resulting in superior power and energy densities. However, the cycling stability was found to be stable only for an aqueous system. The formation of a solid electrolyte surface layer restricted the reversible capacity of the MgMoO4 in the sodium-battery. Nevertheless, it does offer some promise as an anode material for storing energy with high rate performance and excellent capacity retention. Detailed comparative analyses of various electrolytes in storage devices such as hybrid sodium-ion capacitors, sodium-ion batteries is vital for integration of hierarchically structured materials into practical applications. The reaction mechanisms are postulated.

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Publication details

The article was received on 11 May 2018, accepted on 12 Jun 2018 and first published on 12 Jun 2018


Article type: Paper
DOI: 10.1039/C8NR03824D
Citation: Nanoscale, 2018, Accepted Manuscript
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    New insights into the electrochemistry of magnesium molybdate hierarchical architectures for high performance sodium devices

    M. Meenakshi, D. Mitchell, A. R. Munnangi, A. J. Barlow and M. Fichtner, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR03824D

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