Recycling spent dry cells into rGO/MnO2 nanocomposites for advanced supercapacitor electrodes

Abstract

Electronic waste (e-waste) poses a pressing environmental challenge, with improper disposal leading to pollution, resource depletion, and ecosystem damage. In this study, we demonstrate a sustainable strategy to repurpose e-waste into high-performance supercapacitor materials. A reduced graphene oxide/manganese dioxide (rGO/MnO₂) nanocomposite was synthesized entirely from spent dry cells through a cost-effective process. Structural and morphological analyses confirmed a porous nanostructure with a large accessible surface area, enabling efficient charge storage, rapid ion transport, and favorable electrochemical reversibility. Electrochemical testing in 1 M KOH revealed excellent performance, with a specific capacitance of 532 F g⁻¹ at 1 A g⁻¹, an energy density of 36.22 Wh kg⁻¹ at a power density of 350 W kg⁻¹, and 80% capacitance retention after 1500 cycles. Kinetic analysis indicated a hybrid charge storage mechanism involving both capacitive and diffusion-controlled contributions, with capacitive behavior becoming more dominant at higher scan rates. Impedance measurements further confirmed low charge-transfer resistance and rapid ion diffusion. This sustainable approach for converting e-waste into advanced supercapacitor electrodes demonstrates the potential of hybrid charge storage mechanisms in delivering fast, reversible, and durable energy storage.