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

Abstract

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.