Upcycled Polystyrene-Based Composite Films with gCN and Fe-gCN Functional Fillers for High-Performance Supercapacitor Electrodes

High Resolution Image Download MS PowerPoint Slide To address the growing challenges of plastic waste management and sustainable resource utilization, this study explores the upcycling of recycled polystyrene (PS) packaging into functional materials for energy storage applications. Graphitic carbon nitride (gCN) and iron-doped gCN (Fe-gCN) were incorporated as functional fillers to enhance the electrochemical performance of the resulting composites while simultaneously promoting the valorization of plastic waste into high-value electrode materials. This approach demonstrates a sustainable pathway for converting post-consumer polymer waste into advanced materials suitable for supercapacitor applications. The incorporation of gCN and Fe-gCN into polystyrene (PS) resulted in flexible thin composite layers exhibiting a remarkable enhancement in dielectric constant values; a 42% increase in dielectric constant was recorded for gCN/PS and a 50% increase for Fe-gCN/PS with only 0.7 wt % filler loading. In addition to dielectric enhancement, a considerable improvement in electrical conductivity was also observed, highlighting the potential of these composites for advanced energy storage applications. The gCN/PS and Fe-gCN/PS composite layers were developed on a graphite pencil electrode by a simple solution dipping method for electrochemical evaluations. SEM analysis revealed that gCN and Fe-gCN modify the microstructure of the PS surface, facilitating more efficient charge transfer across the electrode surface, as demonstrated by electrochemical impedance spectroscopy. Charge transfer resistance values have been substantially reduced from 4412 Ω for pure PS to 700 Ω for 0.7% gCN/PS and 91 Ω for 0.7% Fe-gCN/PS. The incorporation of only 0.7 wt % functional fillers into recycled PS results in a remarkable enhancement in specific capacitance. Maximum specific capacitance values of 110 F g −1 and 150 F g −1 at 30 A g −1 were achieved for 0.7% gCN/PS and 0.7% Fe-gCN/PS, respectively. Moreover, the 0.7% Fe-gCN/PS composite delivers a high energy density of 83.3 Wh kg −1 at a high power density of 29.9 kW kg −1 . In addition, this composite exhibited excellent cycling stability, retaining 89% of its initial capacitance over 1000 charge−discharge cycles. These findings demonstrate the strong potential of upcycled PS-based composites incorporating gCN and Fe-gCN as cost-effective and sustainable electrode materials for next-generation supercapacitor applications.