Plasma-Modified N/O-Doped Porous Carbon for CO2 Capture: An Experimental and Theoretical Study

N/O-codoped porous carbon was prepared for CO2 capture through biomass hydrothermal carbonization and nonthermal plasma treatment. Density functional theory (DFT) calculations were used to understand the microcosmic insights into the effects of heteroatoms on CO2 capture. The results reveal that air plasma treatment can introduce N and O functional groups into porous carbon with a negligible change of the textural properties. Both nitrogen and oxygen doping can enhance the CO2 adsorption performance of porous carbon. The maximum CO2 capture capacity of heteroatom-doped porous carbon is 37.42 mg/g under the simulated flue gas condition. Compared with oxygen doping, nitrogen doping is more favorable for CO2 capture by porous carbon. Kinetic analysis indicates that the high adsorption rate is responsible for the good CO2 capture ability of porous carbon. The adsorption kinetics of the CO2 molecule on a porous carbon surface can be well predicted by the Bangham adsorption model. DFT calculations further indicate that CO2 adsorption in porous carbon is controlled by the physisorption mechanism. The nitrogen-doped carbon surface shows stronger affinity to CO2 than the oxygen-doped carbon surface. Nitrogen/oxygen codoping is more favorable for CO2 capture by porous carbon than nitrogen or oxygen doping.