Supercapacitive performance of Fe-doped nickel molybdate/rGO hybrids: The effect of rGO

Abstract

Hydrated nickel molybdate (HNMO) is considered one of the fascinating materials for various applications due to its porous structure, low synthesis cost, good specific surface area, and abundant features. Nonetheless, the primal HNMO suffers from an inferior electrical conductivity, hence a poor supercapacitive property. For solving this drawback, we synthesize Fe-doped HNMO/rGO rod-like nanostructure hybrids (FNMG) using a one-pot hydrothermal route where our special emphasis is placed on investigating their supercapacitive performance. The powders with different rGO contents were studied and compared. Considering the data obtained from FTIR and Raman spectroscopy, XRD, FESEM, and HRTEM, rGO is firmly linked to Fe-doped HNMO via electrostatic interaction, exhibiting a preferable supercapacitive ability among the various compounds of the HNMO family. The supercapacitive properties of the electrodes were studied by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS) tests. Among the mentioned electrodes, the one containing 15 mg mL−1 graphene oxide (GO) suspension (FNMG15) possesses the best electrochemical performance with a capacity of 1189 F g−1 at 1 A g−1 current density, and in a 2 M KOH electrolyte, notably higher than that with 20 mg mL−1 GO (around 19.5%), and 5 mg mL−1 GO (around 44%). Meanwhile, cyclic stability and rate performance of the FNMG15 sample were reached to 86% and 71%, respectively. Eventually, a two-electrode asymmetric energy storage device (FNMG15//AC) was fabricated. It shows a specific capacitance of 182.7 F g−1, a maximum energy density of 65.03 Wh kg−1 at a power density of 686.5 W kg−1, and cycling stability of 83.2% after 1000 cycles. The resulting data imply that the FNMG15 has an excellent capability for electrochemical energy storage devices.