The selective adsorption mechanism of CO2 from biomass pyrolysis gas on N-doped carbon materials with an electric field: A first-principles study

Renewable biomass resources can be efficiently converted into fuels, materials, or chemicals by pyrolysis. The selective adsorption of CO2 from the biomass pyrolysis gas is beneficial for its further utilization. Herein, density functional theory (DFT) was employed to reveal the adsorption mechanism of CO2 in pyrolysis gases by the graphite-N-, pyridine-N-, and pyrrole-N-doped graphene models. The impacts of the electric field and the in-fluence of other biomass pyrolysis gas components on CO2 adsorption were particularly explored. The results show that the three graphite-N atoms doped graphene (3N-G) can achieve chemical adsorption of CO2 with the electric field. While physical adsorption occurs when CO2 adsorbs on the surface of the other graphene models regardless of the electric field. In addition, H2, CO, CH4, and C2H4 are physically adsorbed on 3N-G, and their adsorption is not affected by the electric field. The co-adsorption of CO2 with H2, CO, CH4, and C2H4 on 3N-G with an electric field indicates that CO2 is chemisorbed and other gas molecules are physisorbed. In summary, 3N-G can achieve selective adsorption of CO2 when the electric field is adopted. The present work lays a foundation for the separation and purification of biomass pyrolysis gas components and CO2 capture.