Typha orientalis leaves derived P-doped hierarchical porous carbon electrode and carbon/MnO2 composite electrode for high-performance asymmetric supercapacitor

Sustainable biomass-derived carbon used as electrode features the concept of green chemistry. Herein, Typha orientalis leaves, which show tunable porous structure with high phosphorus content, were used as precursor to prepare P-doped hierarchical porous carbon material and then acted as negative electrode for supercapacitor. Different with the traditional activation methods, the biomass was pretreated by ZnCl2 then activated with KOH (Zn-K-ATC). Owing to the hierarchical porous structure, large specific surface area (1975 m2 g−1) and pseudocapacitance provided by P self-doping, Zn-K-ATC had a high specific capacitance of 324 F g−1 at 1 A g−1 in 1 M KOH. Zn-K-ATC was further used as support to grow MnO2 (Zn-K-ATC/MnO2) as the positive electrode material with a specific capacitance of 384 F g−1 at 1 A g−1 in 1 M Na2SO4. The assembled Zn-K-ATC/MnO2//Zn-K-ATC asymmetric supercapacitor device had a voltage window of 2 V with a high energy density of 46 Wh kg−1 at 1000 W kg−1. This work gives a systematic research and complete inspection on the preparation of supercapacitor from biomass-derived materials, which expects to provide a valuable method for the preparation of green, low-cost, high-performance supercapacitor materials. [Display omitted] •P self-doped hierarchical porous carbon was prepared from Typha orientalis leaves.•ZnCl2 pretreatment can make the material have better structure and performance.•The porous carbon exhibits excellent electrochemical performance.•An asymmetric supercapacitor device was fabricated using porous carbon and C/MnO2.•The device has a high energy density of 46 Wh kg−1 at 1000 W kg−1.