Preparation and electrochemical properties of ultra-high specific surface area N-doped biomass-porous carbon

•The ultra-high specific surface area carbons were prepared from food waste soybean dregs.•The as-prepared carbon material showed a high specific surface area up to 2004.21 m2 g−1.•The as-obtained samples exhibited high specific capacitance with 175.8 F g−1 at 0.5 A g−1. Plant-based porous carbon materials are considered as one of the most promising electrode materials for manufacturing supercapacitors (SCs) due to their low-cost and natural abundance. In this work, the N-doped biomass-porous carbons with the ultra-high specific surface area were prepared from food waste soybean dregs via a very simple carbonization method. Field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) displayed the as-prepared samples with a large number of micro- and nanostructures. By optimizing the additive amount of urea and carbonization temperature, the as-prepared carbon material showed a high specific surface area up to 2004.21 m2 g−1. The cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests had been used to investigate the electrochemical performance of samples. The as-obtained samples exhibited a reasonable specific capacitance of 175.8 F•g−1 at 0.5 A•g−1 and good capacitance retention of 84.1% from 0.5 to 4 A•g−1.