N/S co-doped carbon with balanced micro-mesoporosity for ultra-stable supercapacitors

The accelerating demand for sustainable, high-rate, and durable energy storage underscores the need for carbon electrodes that simultaneously offer balanced micro–mesoporosity for rapid ion transport and robust heteroatom functionalities for enhanced interfacial chemistry. In the present work, we convert bitumen asphaltenes and recycled cellulose acetate into N/S co-doped hierarchical carbons via ammonium persulfate-assisted co‑carbonization and KOH activation. The optimized carbon combines an ultrahigh specific surface area of 3527 m 2 g −1 , balanced micro–mesoporosity, and uniformly distributed electroactive N/S species (pyridinic/pyrrolic N, C S, SO x ), enhancing conductivity and pseudocapacitance. In three-electrode tests, the electrode delivered 382.5 F g −1 at 0.5 A g −1 with 74% retention at 10 A g −1 . The symmetric aqueous device achieved a specific capacitance of 288.2 F g −1 at 0.5 A g −1 , energy densities of 10.01 Wh kg −1 at 257.4 W kg −1 and 5.42 Wh kg −1 at 6728.3 W kg −1 , and 108.7% capacitance retention after 10,000 cycles at 5 A g −1 . This study advances sustainable energy storage by enabling low-cost, high-performance supercapacitors and promoting solid-waste recycling.