Facile synthesis of inherently nitrogen-doped PAN-derived microporous carbons activated with NaNH2 for selective CO2 adsorption and separation

초록

N-doped porous carbons (PCs) are extensively researched for CO2 capture and separation under flue gas conditions, but their complex and expensive preparation methods hinder widespread industrial use. Herein, we present a direct approach for synthesizing N-doped PCs by utilizing polyacrylonitrile (PAN) and NaNH2 as precursors, without the need for any solvents. The utilization of NaNH2 as both a porogen and nitrogen supply during carbonization is primarily responsible for the formation of the well-developed pore structure and high specific surface area of N-doped PCs. The optimized sample "PN-3" demonstrated excellent textural features with an excellent specific surface area (SSA) of 2490 m(2)/g, a pore volume of 2.0559 cm(3)/g, a well-defined pore size distribution (PSD), and abundant micropores (<1 nm). In addition, PN-3 has the highest pyrrolic nitrogen content (similar to 40.1 at.%), resulting in a significant capacity for CO2 adsorption (7.15 mmol/g at 273 K/1bar, 4.56 mmol/g at 298 K/1 bar, 26.2 mmol/g at 298 K/ 40 bar). Furthermore, it exhibits an outstanding CO2/N-2 selectivity (similar to 102) based on the ideal adsorbed solution theory (IAST) at 273 K, surpassing the performance of most of previously reported biomass and polymer-derived N-doped carbons in terms of CO2 adsorption and separation. In addition, the adsorption process is characterized by a modest heat of adsorption (39.10 kJ/mol) and a steady cyclic pattern of CO2 adsorption-desorption under flue gas settings (15 % CO2 and 85 % N-2). This indicates that the adsorption is mostly governed by physisorption, which allows for an energy-efficient regeneration process. In summary, this study showcases the successful production of highly PCs that can effectively adsorb CO2, enlightening the way toward establishment of a cost-effective and facile synthetic protocol for achieving CO2 capture/separation at the commercial scale.

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