One-pot in situ activation of agricultural plastic waste into hierarchical porous carbon for high-performance supercapacitors

Abstract

The escalating plastic pollution and the urgent demand for high-performance electrode materials for supercapacitors have become two critical global challenges. Herein, we report a green and efficient one-pot in situ activation strategy to upcycle waste agricultural plastic films into hierarchical porous carbon nanomaterials (PCNs) using potassium citrate as a bifunctional template and activator. This strategy integrates carbonization, pore formation, and activation into a single step, avoiding the use of corrosive acids, alkalis, or toxic solvents, and only requires water-based post-purification, which is in line with the principles of green chemistry. The optimized PCN-700 exhibits a well-defined hierarchical porous structure with a high specific surface area of 1131.9 m² g⁻¹ and a moderate defect density. When employed as an electrode material for supercapacitors, PCN-700 achieves an outstanding specific capacitance of 276.3 F g⁻¹ at 0.5 A g⁻¹. The symmetric supercapacitor (SC) based on PCN-700 electrodes delivers an energy density of 47.9 Wh kg⁻¹ at 510.1 W kg⁻¹, and retains an energy density of 36.9 Wh kg⁻¹ even when the power density is boosted to an ultrahigh level of 5209.4 W kg⁻¹. Moreover, the device demonstrates excellent long-term cycling stability, maintaining 88.9% of its initial capacitance with a coulombic efficiency of 99.8% after 10 000 consecutive charge–discharge cycles at a relatively high current density of 5 A g⁻¹. Practical application validation demonstrates that two assembled SC coin cells can successfully lit a 2 V LED and sustain its stable illumination for 80 s. This work not only offers a sustainable route to valorize non-recyclable plastics but also develops low-cost, high-performance porous carbons for advanced energy storage, achieving synergistic gains for environmental protection and energy storage advancement.