Facile one-step synthesis of cork-derived hierarchical porous carbons with P, N, and O heteroatoms for high-performance supercapacitor electrodes

High-performance electrodes of activated carbons (PNOACs) with P, N, and O heteroatoms were prepared through a simple one-step phosphoric acid activation method without the need for any dopants or post-treatment. In the preparation procedure, cork biomass material from Quercus variabilis was used as the precursor, and phosphoric acid was used as both the phosphoric resource and the activation agent. The pore structure, morphology, and physicochemical properties of the as-prepared carbons were investigated. In addition, the electrochemical performances of the PNOACs were evaluated using three-electrode and two-electrode systems (symmetric supercapacitor, AS). The results indicated that cork is promising as a low-cost and environmental-friendly precursor for producing high-performance supercapacitors electrode. Furthermore, galvanostatic charge–discharge analysis revealed a specific capacitance of 206 F g−1 at a current density of 0.5 A g−1, which can be attributed to the excellent hierarchical pore structure (micro-, meso-, and macropores) and suitable pore size distribution of the PNOACs. The specific surface area and total pore volume as high as 515.80 m2 g−1 and 0.29 cm3 g−1 were obtained, respectively. The presence of heteroatoms, namely N (0.81–1.07%), P (0.52–2.06%), and O (15.87–19.18%) content, on the carbon surface resulted in a considerable enhancement in the capacitive performance. Furthermore, a PNOAC sample, prepared at 600 °C with a mass ratio of 1:1, exhibited high long-term cycling stability (84.5%) and an energy density of 15.03 W h kg−1. Therefore, cork is highly promising as an electrode material for supercapacitors to attain exceptional electrochemical performance, as well as provide a new possibility for the utilization and valorization of high-value cork waste.