Synthesis and characterization of graphene/binary metal molybdate (graphene/Zn_1-xNi_xMoO₄) nanocomposite for supercapacitors

A novel graphene/binary metal molybdate (Zn_1-xNi_xMoO₄) is synthesized via a facile and simple microwave synthesis route (x = 0.0, 0.2, 0.4, 0.6, 0.8). Electrochemical studies are performed for all the samples to study their charge storage mechanism and frequency dependence in a three-electrode set up with 2m KOH electrolyte solution. Among the samples, Zn_0.6Ni_0.4MoO₄ shows better electrochemical performance which is combined with graphene so as to obtain graphene/Zn_1-xNi_xMoO₄ (x = 0.4) nanocomposite. XRD and Raman analyses have confirmed formation of complexation of graphene/binary metal molybdate nanocomposite. TEM morphological profile illustrates little aggregation and interconnected layers of graphene interspersed with rice-like grains of binary metal molybdate. Graphene/Zn_1-xNi_xMoO₄ (x = 0.4) exhibits good energy density and power density of 62.3 Wh kg^-1 and 448.5 W kg^-1 respectively with a specific capacitance of 555.5 F g^-1 at 1 A g^-1. The electrode material with good cyclic stability of 85% even after 5000 charge/discharge cycles may be explored as a novel option for supercapacitors. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)