Synthesis and improved electrochemical performances of nano β-NiMoO4–CoMoO4·xH2O composites for asymmetric supercapacitors

Abstract

Nano-sized β-NiMoO₄–CoMoO₄·xH₂O composites were synthesized by a solution combustion synthesis (SCS) technique. The effect of weight ratio of transition metal on the electrochemical capacitive performance of the nanocomposites was investigated by cyclic voltammetry and galvanostatic charge–discharge methods. The NiMoO₄–CoMoO₄·xH₂O nanocomposite with weight ratio of 3 : 1 (Ni : Co) exhibits enhanced capacitive behaviour relative to other composites and delivered a maximum specific capacitance of 1472 Fg⁻¹ at a current density of 5 mAcm⁻². The enhancement in specific capacitance is due to the small particle size, uniform size distribution, high surface area and high weight fraction of Ni. The synergistic effect of nickel and cobalt improves the electrochemical behaviour relative to pure nickel and cobalt molybdates. A full cell was fabricated using the β-NiMoO₄–CoMoO₄·xH₂O nanocomposite (3 : 1) and activated carbon (AC) as a positive and negative electrode, respectively. The cell delivered high capacitance (80 Fg⁻¹) and energy density (28 Wh kg⁻¹) and good cycling stability up to 1000 cycles.