Recycling polyvinyl chloride plastics into hard carbon: influence of functional groups on structural and electrochemical properties

The global surge in polyvinyl chloride (PVC) waste demands urgent technological solutions that address both environmental persistence and resource recovery. Here, we present a triple-functionalization strategy that converts chlorinated plastic waste into high-performance sodium-ion battery anodes through molecular-level control of carbon architectures. Sequential dichlorination, sulfonation, and N-doping collaboratively reconfigure precursor reactivity, steering pyrolysis toward hierarchically porous hard carbon with tailored defect chemistry. Sulfonic groups stabilize 3D carbon skeletons during carbonization, enabling closed-pore formation with an average diameter of ~2.55 nm while N-doping expands interlayer spacing (0.382 nm) and creates adsorption-active pyrrolic-N sites. This defect-engineered synergy delivers unprecedented sodium storage metrics: 355 mAh g−1 reversible capacity at 0.1 A g−1 (95.4% of graphite’s Li-ion capacity), a capacity retention of 216 mAh g−1 after 1000 cycles at 1.0 A g−1 (70.1% capacity retention), and 188 mAh g−1 even at a high current density of 5.0 A g−1. Operando analyses reveal a potential-dependent storage hierarchy: surface-dominated adsorption transitions to intercalation/filling-dominated behavior with defect-buffered structural integrity. The process simultaneously achieves 25% carbon yield from PVC and avoids toxic dioxin emissions, establishing a scalable prototype for sustainable energy storage systems.