Chapter 2: Enhancing Charge Transport Kinetics in Cobalt Molybdenum Oxide Nanorods via Iron-Doping for High-Performance Supercapacitors

The rapid advancements in the field of energy storage have rendered the supercapacitor as an integral element in moving towards sustainable energy systems. However, the commercial success of such energy storage systems is dependent on the production of electrode materials having both high conductivity and electrochemical stability. This chapter highlights the design and preparation of iron-doped cobalt molybdenum oxide (CoMoO₄) nanorods (NRs) as a potential solution for energy storage applications. The formation of NRs is carried out via a simple hydrothermal route, where the presence of iron (Fe) in the compound serves as a mediator in controlling the internal architecture for fast ion and electron transport. The NRs' crystallinity was verified using X-ray diffraction (XRD), while their characteristic vibrational modes were characterized through Raman spectroscopy. Scanning electron microscopy (SEM) was used to demonstrate the even dispersion of the iron in the CoMoO₄ NRs, while EDX was used to confirm that the different elements were uniformly distributed in the NRs. From all the materials tested, the 6% Fe-CoMoO₄ NRs had the most optimal electrochemical properties. Cyclic voltammetry performed at a 5 mVs^-1 sweep rate produced a high specific capacitance of 2068 F g^-1, while the galvanostatic charge-discharge tests completed at a test current of 3 A g^-1 also yielded a value of 2160 F g^-1. Using electrochemical impedance spectroscopy, a very low charge transfer resistance of 4.02 Ω was observed, which is significantly lower than that of the pure CoMoO₄ NRs, which had a charge transfer resistance of 9.72 Ω. The 6% Fe-CoMoO₄ NRs exhibited an energy density of 79.44 Wh kg⁻¹ at 750 W kg⁻¹ power and retained 87.13% capacitance over 3000 cycles. These results demonstrate that Fe-CoMoO₄ NRs are excellent candidates for integration into next-generation energy storage systems.