Functionalized porous carbon with three-dimensional (3D) interconnected pore structure has been successfully synthesized through direct heat-treatment of KOH-soaked soybeans. Benefiting from heteroatoms (N, O) doping, interconnected porous carbon framework with high surface area as well as high packing density (up to 1.1gcm−3), the as-obtained porous carbon material exhibits high volumetric capacitance of 468Fcm−3, good rate capability and excellent cycling stability (91% of capacitance retention after 10,000 cycles) in 6M KOH electolyte. More importantly, the as-assembled symmetric supercapacitor delivers high volumetric energy density of 28.6WhL−1 in 1M Na2SO4 aqueous solution.