Mechanism of biomass activation and ammonia modification for nitrogen-doped porous carbon materials

The effect of chemical activation and NH3 modification on activated carbons (ACs) was explored via two contrasting bamboo pyrolysis strategies involving either two steps (activation followed by nitrogen doping in NH3 atmosphere) or one step (activation in NH3 atmosphere) with several chemical activating reagents (KOH, K2CO3, and KOH + K2CO3). The ACs produced by the two-step method showed relatively smaller specific surface areas (similar to 90% micropores) and lower nitrogen contents. From the one-step method, the ACs had larger pore diameters with about 90% small mesopores (2-3.5 nm). Due to a promotion effect with the KOH + K(2)CO(3 )combination, the AC attained the greatest surface area (2417 m(2) g(-1)) and highest nitrogen content (3.89 wt%), endowing the highest capacitance (175 F g(-1)). The balance between surface area and nitrogen content recommends KOH + K(2)CO(3 )activation via the one-step method as the best choice for achieving both greener production process and better pore structure.