Leveraging bidirectional synergy of nano-plastics and copper ions to prepare biochar-based energy storage materials with enhanced metal dispersion.

Carbon/metal compound composites offer significant performance and stability advantages for supercapacitor electrodes. However, conventional strategies struggle to concurrently achieve high metal content and dispersion within the carbon skeleton, both critically affecting energy storage performance and cycling stability. Separately, spent biochar adsorbents pose secondary pollution risks if improperly disposed of. To address these issues, the copper ion loading capacity of nanoplastics is enhanced by investigating the bidirectional promotive effect between nanoplastics and copper ions in aqueous systems: copper ions on the nanoplastics surface will promote their thermal oxidative decomposition. Meanwhile, the oxygen-containing functional groups generated by thermal oxidative decomposition strengthen the interaction between nanoplastics and copper ions, enabling higher copper ion loading on their surfaces, and forming a positive feedback loop. Subsequent co-processing of the nanoplastic system with biochar via nano-micro hybrid scale pyrolysis and activation ultimately yielded the carbon/copper oxide composite (CPC/CuOx), possessing a high specific surface area while concurrently achieving high metal dispersion and high metal content. As a supercapacitor electrode, CPC/CuOx delivered a high specific capacitance of 744 F·g-1 at 0.5 A·g-1 and maintained 80% capacitance retention after 10, 000 cycles. Therefore, this novel approach facilitates high-performance carbon/metal composites and provides a route to convert spent adsorbents into energy materials, mitigating leakage risks after environmental remediation.