Abstract
We have obtained nanocrystalline hydrate and alpha phase of nickel molybdate by a hydrothermal technique. On the basis of the obtained cyclic voltammetry data, we have evaluated the contribution of faradaic and non-faradaic processes to the total capacitance of molybdates under study. It was found that the specific capacitance of hydrate NiMoO4·H2O is 621 F/g at a scan rate of 1 mV / s and the specific capacitance of the α-NiMoO4 is 281 F/g. Cathodes for hybrid supercapacitors were formed on the basis of the obtained nickel molybdates. As a result of electrochemical studies, it was found that the specific capacitance of hybrid supercapacitor based on NiMoO4·H2O/C was 256 F/g at the current of 0.2 A/g, while the specific energy was 80 W h/kg and specific power – 304 W/kg and these results are higher below in the α-NiMoO4 /C-based hybrid supercapacitor.
Highlights
Among the binary metal oxides used as electrodes in energy-storage devices, nanocrystalline nickel molybdate (NiMoO4) is competitive due to its high electrochemical activity resulting from the reversible redox Ni2+ / Ni3+ reaction [1] and the crystal structure of the spinel type, which can provide efficient charge storage and high ion diffusion rate due to its three-dimensional network [2]
Electrodes were formed for a hybrid supercapacitor (HSC), in which the obtained nickel molybdates were used as cathodes and activated carbon [7] was used as the anode
Cyclic voltammograms (CVs) of electrodes based on hydrothermally obtained nickel molybdates are presented in Fig. 1 а, b
Summary
Among the binary metal oxides used as electrodes in energy-storage devices, nanocrystalline nickel molybdate (NiMoO4) is competitive due to its high electrochemical activity resulting from the reversible redox Ni2+ / Ni3+ reaction [1] and the crystal structure of the spinel type, which can provide efficient charge storage and high ion diffusion rate due to its three-dimensional network [2]. The α phase can be converted to the β phase when heated to temperature of 650 oC, which is unstable and turns into the α phase when the temperature decreases [4] It is known [5] that the hydrated structure of molybdate can provide better electrochemical parameters compared to the pure phase due to low crystallinity and higher specific surface area. This article presents the results of electrochemical studies of nanocrystalline nickel molybdates obtained by the hydrothermal method
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