Metal-free core-shell structured N-doped carbon/carbon heterojunction for efficient CO2 capture

N-doped carbon/carbon heterojunction holds huge potential for efficient CO 2 capture. Here, a series of site-specific N-doped core-shell carbon spheres with carbon/carbon heterojunction were successfully prepared by carbonization of polypyrrole coated hypercrosslinked polystyrene spheres, followed by chemical activation with KOH. These activated carbon spheres possessed large specific surface area (2080 m 2  g −1 ) and abundant micropores (0.45 cm 3  g −1 ). Despite their low nitrogen content (0.96 wt%), the CO 2 adsorption capacities of activated samples reached 3.69 and 5.80 mmol g −1 measured at 298 and 273 K, respectively, under atmospheric pressure (1 bar). More significantly, the N-doped carbon/carbon heterojunction contributes to a stronger and denser CO 2 packing in this system.