Augmenting the performance of thermally deoxygenated graphite oxide supercapacitor electrodes using 6 M KOH electrolyte with K3Fe(CN)6 redox additive

Abstract

This study focuses on enhancing the performance of thermally deoxygenated graphite oxide (TDGO) supercapacitor electrodes by incorporating a redox additive viz., 0.03 M K₃Fe(CN)₆ in 6 M KOH. Characterization of the prepared TDGO was conducted through XRD, Raman, XPS, FESEM and BET surface area analysis, revealing incomplete deoxygenation and the presence of oxygen functional groups. TDGO exhibits a maximum significant surface area of 288.3 m² g⁻¹ with an average pore diameter of 2.4 nm. The I_D/I_G ratio of 0.98 suggests the prevalence of structural defects dominating the sp² graphitic structure. FESEM images reveal exfoliated irregular layers in TDGO. In a three-electrode configuration, the optimized system achieves an areal specific capacitance (C_sp) of 817 F cm⁻² at 1 A g⁻¹, a 2.5-fold increase compared to 6 M KOH alone. The [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻ redox couple in the electrolyte alters the charge storage mechanism from surface-controlled to diffusion-controlled pseudocapacitance. A symmetric TDGO300 supercapacitor in the KOH/K₃Fe(CN)₆ redox electrolyte system exhibits a C_sp of 414.6 F cm⁻², delivering an energy density of 17.4 W h kg⁻¹ at a power density of 235 W kg⁻¹. Notably, the TDGO300 supercapacitor retains 97.4% of its initial capacitance after 2000 continuous charge–discharge cycles. This work establishes a straightforward strategy to significantly improve the capacitive performance of TDGO supercapacitors by leveraging redox additives, showcasing their potential for advanced energy storage applications.