Novel low temperature synthesis and electrochemical characterization of mesoporous nickel cobaltite-reduced graphene oxide (RGO) composite for supercapacitor application

• Mesoporous nickel cobaltite-graphene composite was prepared by combustion method.
• Rapid and low temperature compound formation was demonstrated
• Prepared materials demonstrate high crystallinity and porous morphology.
• High specific capacity of 662.3 C/g was exhibited by the composite material.
• Symmetrical supercapacitor fabricated offered 169.6 C/g specific capacity.

A simple low temperature method was formulated for the synthesis of mesoporous nickel cobaltite and graphene-nickel cobaltite composite nanoparticles. Self-combustion of urea-nitrate complexant yields high crystalline single phase NiCo2O4 nanoparticles. As expected, graphene prevents the agglomeration of the nanoparticles and restacking of graphene sheets were avoided mutually. FTIR analysis reveals the successful reduction of RGO and composite formation. Qualitative analysis of RGO was obtained from Raman spectrum, which further confirms the composite formation. Chemical purity of the compound was evaluated from XPS studies. Nickel and cobalt ions were found to be in the mixed oxidation state typical of NiCo2O4. Porous morphology of the prepared samples was observed from the FESEM images. BET analysis reveals the significant increase in the specific surface area and mesopores distribution in the composite. Gn-NiCo demonstrates excellent capacitive performance. High specific capacity of 662.3 Cg−1 was determined for Gn-NiCo against 485.5 Cg−1 exhibited by bare nickel cobaltite at 5 mV/s scan rate. Composite material also shows excellent rate characteristics and long cycling stability. This superior performance can be attributed to the porous morphology and high electrical conductivity of graphene sheets. Symmetrical capacitor fabricated using Gn-NiCo electrode material operates within 0–0.8 V potential window. Specific capacity of 169.6 Cg−1 was obtained in the real capacitor mode. Gn-NiCo prepared by combustion technique is a promising electrode material for supercapacitor applications.