Biomass-derived nitrogen-doped porous carbon with superior capacitive performance and high CO2 capture capacity

Nitrogen-doped porous carbon is synthesised through a low-cost approach that utilise water chestnut as a carbon source and melamine as a nitrogen source through potassium hydroxide (KOH) activation for 2 h at 600 °C-900 °C. The obtained samples exhibit predominant characteristics with highly developed micropores, an ultralarge specific surface area (3401 m2 g−1) and a high nitrogen content (4.89 at.%). These characteristics endow nitrogen-doped porous carbon with a high specific capacity of 346 F g−1 and a high energy density of 22.4 W h kg−1 at 0.5 A g−1 in 6 mol dm−3 KOH. It also exhibits an excellent cycling stability with a retention of nearly 97.6% capacity after 5000 cycles at 1 A g−1. In addition, the unique pore structure and high nitrogen content of porous carbon provide an important contribution to CO2 adsorption capacity, which can reach up to 6.0 mmol g−1 (at 0 °C and 1 bar) and 4.7 mmol g−1 (at 25 °C and 1 bar), and to high CO2/N2 selectivity. Results show that the synthesised porous carbon exhibit considerable potential in electrochemical energy storage and solid adsorption.