Tuning the Redox Properties of the Nanostructured CoMoO4 Electrode: Effects of Surfactant Content and Synthesis Temperature.

A systematic study was performed to examine the effects of surfactant content and synthesis temperature on the morphologies and the redox properties of cobalt molybdate (CoMoO4 ). The results revealed that varying the concentration of surfactant (F127) varies the morphology from nanorods to nanospheres and nanoneedles. A concentration of metal-to-surfactant ratio of 1:1 outperformed that of 1:0.5 and 1:2 ratios in specific capacitance, energy density and cycling stability. The surfactant at the optimised ratio significantly influenced the morphology and particle size of the CoMoO4 material and acted as a template, whereas increasing the synthetic temperature did not contribute much to the energy storage. An asymmetric supercapacitor was fabricated based on CoMoO4 as the positive electrode and activated carbon as the negative electrode in 2 m NaOH electrolyte. The CoMoO4 material synthesised at 300 °C in the presence of F127 (1:1) showed a specific capacitance of 79 F g-1 and an energy density of 21 W h kg-1 when tested as a hybrid device. This suggests that the redox activity and its storage capability depend on the surfactant content as well as its self-assembly behaviour. CoMoO4 showed excellent cycling stability retaining over 75 % of its initial capacitance after 2000 cycles, which makes it a very promising candidate for large-scale energy-storage applications.