Electrolytic ion diffusion properties and their effects on charge storage potentials of pseudocapacitive Co3O4 electrode film

In this report, we have employed an electrodeposition approach under three-electrode configuration to fabricate Co3O4 electrode film and investigated the effect of electrolytic Na+ and K+ from KOH, NaOH, and Na2SO4 aqueous electrolytes, on its charge storage characteristics. The microstructural studies validated the formation of stable phases and cubic crystal structure. The film grew with slightly dense sphere-shaped nanostructure and large surface area and is composed of corresponding elements, as revealed from microstructural studies. The charge storage measurements on fabricated Co3O4 film electrode were carried out extensively under three-electrode mode. The electrode's performance was found to be dependent on ion diffusion nature of the electrolytes and hence displayed optimum specific capacitance/capacity of 240 Fg(-1)/46.6mAh g(-1) in Na2SO4 compared to in NaOH due to multiple redox peaks, with better ion diffusion in KOH due to smaller Na+ ions, constituting relatively low solution resistance with faster ion kinetic and transport. The study unveiled that the performance of Co3O4 electrode in aqueous electrolyte is dependent on the electrolyte's ionic strengths, mobility and diffusion, and pH.