Three-dimensional (3D) O, N-codoped activated carbon aerogels with ultramicropores were prepared via oxidation polymerization, freeze-drying, and carbonization/activation of aniline and sodium alginate. All the O, N-codoped activated carbon aerogels exhibit 3D interconnected hierarchical porous network structures with high specific surface areas (1337-1695 m(2) g(-1)), ultramicropores (0.52-0.54 nm), and rich O (12.68-18.48%) and N (1.18-3.59%) doping. A typical 3D O, N-codoped activated carbon aerogel (ACA700) obtained at the activation of 700 A degrees C exhibits excellent electrochemical performance. When ACA700 is utilized as electrode materials for supercapacitor, the highest specific capacitance of 342 F g(-1) at a current density of 2 A g(-1) in 3 M H2SO4 electrolyte is achieved. Furthermore, ACA700//ACA700 all-solid-state supercapacitor device displays acceptable energy density (3.8 Wh kg(-1)) at a power density of 246.0 W kg(-1), extraordinary coulombic efficiency (95.8%), and good rate capability. Therefore, the sustainable 3D O, N-codoped activated carbon aerogels with ultramicropores demonstrate tremendous potential for energy storage devices.