Single-Crystalline Fe2O3 on Reduced Graphene Oxide as an Anode Material for All-Solid-State Supercapacitors

Research often focuses on improving cathode materials to boost the energy density of charge storage devices to levels comparable to batteries, while anode materials have been less frequently explored. This work presents the iron oxide/reduced graphene oxide (Fe2O3/rGO) composite synthesis by a one-pot hydrothermal method for possible utilization as an anode material in battery applications. The crystalline Fe2O3 nanoparticles were allowed to grow over two-dimensional (2D) rGO sheets as a growth template using the hydrophilic groups as nucleation centers. The unique structure of Fe2O3/rGO composites significantly enhances ion transport efficiency, optimizing active materials’ utilization and thus improving overall performance in energy storage applications. The optimized Fe2O3/rGO-3h composite electrode demonstrates an excellent specific capacity of 233 mAh g–1 at a current density of 2 A g–1. The flexible ASSC device shows a high capacity of 41 mAh g–1 at a current density of 1 A g–1 with an energy density of 27.8 Wh kg–1 at a power density of 750 W kg–1. Furthermore, cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) curves of flexible devices remained stable upon bending up to 180° and during series or parallel connections. A laboratory prototype of a CR-2032 coin-type ultracapacitor can power a blue, red, green, and yellow LED to run continuously on just one charge. Further, density functional theory (DFT) was employed to investigate the charge transfer, electronic structure, and binding interactions of Fe2O3/rGO composites, elucidating their potential as high-performance anode materials for supercapacitors. This work unlocks an avenue for designing and fabricating Fe2O3/rGO composites as promising anode materials by utilizing rGO as a template for the next generation of supercapacitors with improved energy storage performance.