Peroxymonosulfate Activation by N-doped 3D Graphene from Spent Lithium-Ion Batteries for Organic Pollutants Degradation: an Insight into the Degradation Mechanism

The large-scale retirement of lithium-ion batteries (LIBs) has raised increasing concerns about recycling spent graphite with low value-added. However, it remains challenging to design a low energy consumption and high value-added approach for upcycling spent graphite. This study proposes a novel recycling strategy involving the reconstruction of porous architectures through nitrogen-doped graphene using NH3·H2O to enhance the deactivation resistance of rhodamine B (RhB) degradation via peroxymonosulfate (PMS) activation. Spent graphite with defects and polar functional groups were used as the feed materials. Specifically, the prepared defective nitrogen-doped graphene can efficiently activate the PMS under a broad pH range and a real water matrix. The analytical and density functional theory calculation results suggested that graphite N plays the dominant role in activating PMS with the formation of reactive oxygen species. The quenching, electron paramagnetic resonance and electrochemical results indicated that the singlet oxygen plays a dominant role, while the free radicals of superoxide radical, sulfate radical and hydroxyl radical work together during the degradation of RhB into CO2 and H2O through demethylation, chromophore cleavage, opening-ring and mineralization. This study proposes a promising strategy for upcycling spent graphite from spent LIBs into environmental functional materials with potential application in effluent treatment.