Activation-self-activation strategy for one-step preparation of Platycladus orientalis leaves based N-O-S self-doping hierarchical porous carbon for high-performance supercapacitor

Development of new carbon materials with hierarchically porous structure and heteroatoms doping for commercial supercapacitor electrodes remain many challenges, due to the complex process routes, harsh process conditions and use of various chemical reagents which are harmful to the environment. Herein, Platycladus orientalis leaves (POL) based sponge-like N-O-S self-doping hierarchical porous carbon was facile prepared by one-step activation-self-activation technique, using natural bio-mineral of calcium oxalate in POL as self-activator, and a small amount of KHCO 3 as exogenous activator. Under the very mild activating condition of low temperature (650 ℃) and low concentration of activator (the mass ratio of KHCO 3 and POL is 0.5:1), the obtained POL-derived sponge-like carbon (POL-650–0.5) possesses high-surface area (1001.4 m 2 g −1 ), developed graded pore structure, and rich ternary heteroatom (2.83 at% for N, 12.72 at% for O and 0.38 at% for S). Benefitting from its interconnected hierarchical porous microstructure and rich active sites, the POL-650–0.5 exhibits an outstanding capacitive performance of 308.5 F g −1 (0.5 A g −1 ) and fine capacity retention of 77.8 % at 30 A g −1 . Moreover, the POL-650–0.5 based symmetrical device possesses a senior energy density of 17.5 Wh kg −1 in 6 M KOH electrolyte at 162.5 W kg −1 , conspicuous cyclicability (92.1 % capacity retention and 100 % Coulomb efficiency even after 10,000 cycles at 5 A g −1 ). This work provides a span-new mild synthesis pathway for high-value utilization of POL resources to facile prepare tri-heteroatoms self-doping carbon with graded pore structure for supercapacitor. • N/O/S self-doping hierarchical porous carbon is prepared by a facile and mild craft. • This work provides a way for high-value utilization of Platycladus orientalis leaves. • The obtained carbon products exhibit excellent electrochemical performance.