Graphene Oxide Concentration Engineering: Unlocking Superior Performance in Hydrothermally Synthesized Supercapacitors

This study explores the controlled synthesis and electrochemical performance of reduced graphene oxide (rGO) thin films, prepared through hydrothermal reduction of graphene oxide (GO) at varying concentrations (0.25‐1 mg/mL) at 100 °C for 4 h. Structural analysis using XRD, FT‐IR, Raman spectroscopy, and XPS confirmed the progressive restoration of the sp 2 carbon network and reduction of oxygen functional groups with increasing GO concentration. FE‐SEM images displayed a distinctive crumpled and wrinkled surface morphology, providing an enlarged effective surface area conducive to electrolyte accessibility and ion diffusion. Electrochemical evaluations through cyclic voltammetry (CV) and galvanostatic charge‐discharge (GCD) techniques highlighted the films exceptional pseudocapacitive behavior, with specific capacitance values significantly rising from 227.4 F g⁻¹ for rGO 0.25 to 426.7 F g⁻¹ for rGO 1 at a scan rate of 10 mV s⁻¹. Furthermore, the rGO 1 electrode demonstrated good cyclic stability, retaining ∼68% of its initial capacitance after 5000 CV cycles. These findings highlight the pivotal influence of GO concentration in optimizing the electrochemical performance of rGO thin films, affirming their potential as high‐performance materials for advanced energy storage applications, including next‐generation supercapacitors.