Nitrogen-doped activated carbons with high performances for CO2 adsorption

Nitrogen-doped activated carbons (NACs) were produced from Brazil nut shells (BNS) using a concurrent procedure of KOH-activation and N-doping using melamine (MM), hexamethylenetetramine (HMTA), or tetramethylamonium hydroxide (TMAOH). N2 physisorption results demonstrated the materials have SBET values ranging from 1755 to 2562 m² g−1. The XPS analysis evidenced that all NACs showed relative N-surface composition from 6.40% to 17.1%. Raman spectra and SEM images proved the N-doping caused a great damage to the surface of the materials. Low-pressure CO2 adsorption results demonstrated that qe values ranged from 4.16 to 5.30 mmol g−1. Amongst NACs, the material AC2MM showed the lowest SBET value (1755 m² g−1), the highest N surface content (17.1%), and the highest CO2 qe values (5.30 mmol g−1 at 273 K and 1.0 bar, and 22.60 mmol g−1 at 298 K and 45 bar). Thus, the results evidence that N-doping tends to contribute more for CO2 adsorption than extremely high surface area values.