Nitrogen-doped nanoporous carbons derived from lignin for high CO₂ capacity

In this paper, nitrogen (N)-doped ultra-porous carbon derived from lignin is synthesized through hydrothermal carbonization, KOH activation, and post-doping process for CO₂ adsorption. The specific surface areas of obtained N-doped porous carbons range from 247 to 3064 m²/g due to a successful KOH activation. N-containing groups of 0.62–1.17 wt% including pyridinic N, pyridone N, pyridine-N-oxide are found on the surface of porous carbon. N-doped porous carbon achieves the maximum CO₂ adsorption capacity of 13.6 mmol/g at 25 °C up to 10 atm and high stability over 10 adsorption/desorption cycles. As confirmed by enthalpy calculation with the Clausius–Clapeyron equation, an adsorption heat of N-doped porous carbon is higher than non-doped porous carbon, indicating a role of N functionalities for enhanced CO₂ adsorption capability. The overall results suggest that this carbon has high CO₂ capture capacity and can be easily regenerated and reused without any clear loss of CO₂ adsorption capacity.