Sonochemical assisted synthesis of manganese–nickel molybdate/reduced graphene oxide nanohybrid for energy storage

Abstract

Abstract In the present study, manganese-nickel molybdate was synthesized using an ultrasonic assisted method for the first time. The hybrid of reduced graphene oxide (RGO) with manganese-nickel molybdate was also prepared. The structure of nanohybrid was characterized by Raman spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and inductively coupled plasma optical emission spectrometry (ICP-OES). Field emission scanning electron microscopy images showed that the manganese-nickel molybdate has the nanorod morphology. In addition, transmission electron microscopy images confirmed the presence of reduced RGO nanosheets in the nanohybrid. From ICP-OES, the nanohybrid formula was obtained as Mn0.63Ni0.37MoO4-RGO. Some electrodes with different RGO weight ratios were also prepared on nickel foam (NF) plates. Cyclic voltammetry studies showed that nanohybrid has typical faradaic redox behavior in 2 M KOH. Additionally, galvanostatic investigations showed that Mn0.67Ni0.37MoO4- RGO (60 wt %) nanohybrid can provide the high specific capacity of 161.1 mA h g−1 at 2 A g−1, which is higher than that for MnMoO4-RGO and NiMoO4-RGO nanohybrids. Furthermore, the electrode based on Mn0.67Ni0.37MoO4 provided higher specific capacity than that for MnMoO4 or NiMoO4. Owing to the synergistic effect of both Mn and Ni elements with RGO in nanohybrid, the Mn0.67Ni0.37MoO4-RGO showed the high energy density of 87 W h kg−1 at 1080 W kg−1 and the power density of 8640 W kg−1 at 9.6 W h kg−1. The electrode provided the cyclic stability about 92% of its initial capacity after 2000 cycles at 50 mV s−1. Our results showed the successful synthesis of manganese-nickel molybdate/RGO nanohybrid for the potential use in energy storage systems.