Unveiling a paradigm shift in supercapacitor dynamics: γ-Al2O3-infused ZnO nanorods with redox-active K4Fe(CN)6 alkaline electrolytes

Abstract

The rapid charge-discharge capability, high specific energy, and extended cyclic stability required of supercapacitors (SCs) depend heavily on electrode materials with exceptional electrical conductivity, large surface area, and tunable morphology. In this study, we present a novel approach to enhance the electrochemical capabilities of zinc oxide (ZnO) via γ-Al2O3 doping. The material's inherent stability, porosity, and large surface area are investigated through appropriate techniques. Results demonstrate that the hydrothermal technique, incorporating γ-Al2O3 into ZnO can transform ZnO nanoflakes into significantly elongated nanorods. The electrochemical evaluation in a redox-active electrolyte comprising 2 M KOH and 0.2 M potassium ferrocyanide (PFC) reveals a remarkable specific capacity of 267 C/g, at a current density of 3 A/g. The fabricated asymmetric coin cell (ACC) reveals an energy density of 23.52 Wh/kg, a power density of 1.5 kW/kg at 3 A/g, a coulombic efficiency (CE) of 98.9 %, and a capacity retention of 88.9 % after 9000 charge-discharge cycles. These findings highlight the significant potential of γ-Al2O3-doped ZnO as a superior electrode material for SCs. Moreover, this work underscores the effectiveness of PFC in reducing charge transfer resistance and promoting diffusion-controlled charge storage mechanisms, thereby enhancing the overall electrochemical performance. © 2024 Elsevier B.V.