Nitrogen-doped layered porous carbon has been successfully fabricated from the biomass of porcine bladders via carbonization and KOH activation. The effects of KOH dosage on the structure, composition and capacitive property of carbon were investigated by a variety of means (SEM, HRTEM, XRD, Raman, XPS, BET and electrochemical test). Owing to the unique layered structure and rich heteroatom content of porcine bladders, the sample obtained at a KOH/carbon mass ratio of 2 were endowed with appropriate pore structure, large specific surface area (1881.7 m(2) g(-1)) and high nitrogen content (5.38%). Meanwhile, the sample exhibits the best electrochemical performance in 6 M KOH electrolyte, including high specific capacitance (322.5 F g(-1) at a current density of 0.5 A g(-1)), desirable rate capability (79% capacitance retention when current density increases from 0.5 to 10 A g(-1)) and superior cycling stability (96% capacitance retention after 5000 cycles). Furthermore, the symmetric supercapacitor assembled with this carbon electrode can deliver 10.9 Wh kg(-1) energy density at 0.15 kW kg(-1) power density, and maintain 95% capacitance after 5000 cycles. The prominent performance of this material suggests its promising application in supercapacitor electrode. (C) 2019 Elsevier Inc. All rights reserved.