A Role of Activators for Efficient CO₂ Affinity on Polyacrylonitrile-Based Porous Carbon Materials

Herein, we investigated polyacrylonitrile (PAN)-based porous activated carbon sorbents as an efficient candidate for CO₂ capture. In this research, an easy and an economical method of chemical activation and carbonization was used to generate activated PAN precursor (PAN-C) adsorbents. The influence of various activators including NaOH, KOH, K₂CO₃, and KNO₃ on the textural features of PAN-C and their CO₂ adsorption performance under different temperatures was examined. Among the investigated adsorbents, PANC-NaOH and PANC-KOH exhibited high specific surface areas (2,012 and 3,072 m² g^-1), with high microporosity (0.82 and 1.15 cm³ g^-1) and large amounts of carbon and nitrogen moieties. The PAN-C activated with NaOH and KOH showed maximum CO₂ uptakes of 257 and 246 mg g^-1 at 273 K and 163 and 155 mg g^-1 at 298 K, 1 bar, respectively, which was much higher as compared to the inactivated PAN-C precursor (8.9 mg g^-1 at 273 K and 1 bar). The heat of adsorption (Q _st) was in the range 10.81-39.26 kJ mol^-1, indicating the physisorption nature of the CO₂ adsorption process. The PAN-C-based activated adsorbents demonstrated good regeneration ability over repeated adsorption cycles. The current study offers a facile two-step fabrication method to generate efficient activated porous carbon materials from inexpensive and readily available PAN for use as CO₂ adsorbents in environmental applications.