Effect of the Electrolyte on the Production of Graphene Oxide by Electrochemical Exfoliation from Discharged Batteries

Graphene derivatives are known for their exceptional properties and are essential for commercial applications, ranging from electronics to energy storage and generation. This study investigates the effect of different acidic electrolytes (sulfuric acid (H2SO4), hydrochloric acid (HCl), and nitric acid (HNO3)) on the synthesis of graphene oxide (GO) via electrochemical exfoliation. Characterization techniques confirm that all exfoliated samples contain a mixture of GO and reduced graphene oxide (rGO). X-ray diffraction reveals that HNO3 promotes the highest GO formation, as indicated by a sharp peak at 2θ = 11.6°, suggesting increased interlayer spacing. X-ray photoelectron spectroscopy shows a higher oxygen content (greater carbon-to-oxygen (C/O) ratio), confirming a greater presence of oxygenated groups in HNO3-treated samples. Raman spectroscopy differentiates GO and rGO through characteristic bands. Ultraviolet-visible absorption spectroscopy further supports these findings, as the HNO₃-treated sample exhibits a strong absorption band at 262 nm, indicating partial restoration of electronic conjugation, while the 300 nm band is absent in H2SO4-treated samples, confirming smaller amount oxygenated groups. Scanning electron microscopy reveals morphological changes, with stacked GO layers and incomplete exfoliation. No single-layer graphene was observed. These results highlight how electrolyte choice significantly affects GO structure and composition, guiding its optimization for applications in energy storage, electronics, and materials science.