Waste-to-sensor: Repurposing spent Li-ion battery graphite into reduced graphene oxide for electrochemical detection of ascorbic acid

Spent lithium-ion batteries (S-LIBs) are typically discarded in landfills after their lifecycle ends, despite containing valuable materials like graphite. While much research focuses on extracting precious metals from the cathode, this study explores the recycling, recovery, and reuse of spent graphite, converting it into reduced graphene oxide (rGO) for electrochemical sensing. The rGO material demonstrated excellent sensitivity to ascorbic acid (AA) in a concentration range of 1 mM to 100 mM at pH 7.6, offering a cost-effective solution for AA detection. The recovered graphite (RG) from S-LIBs and commercial graphite (CG) was first converted into graphene oxide (R-GO, C-GO) and then reduced (R-rGO, C-rGO). This material underwent extensive structural characterization using techniques such as powder X-ray diffraction (PXRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, field-emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). Electrochemical performance was evaluated through cyclic voltammetry (CV), differential pulse voltammetry (DPV). This study underscores the "waste-to-wealth" concept and supports circular economy principles by transforming electronic waste into a valuable resource. The LOD and LOQ for both the material R-rGO and C-rGO were calculated as 3.055 mM, 10.18 mM, and 3.41 mM, 11.36 mM, respectively. The rGO-based sensor not only promotes sustainable recycling but also offers a low-cost, high-performance solution for ascorbic acid detection, with potential applications in food quality monitoring, medical diagnostics, and the cosmetic industry.