Hierarchical porous polystyrene-based activated carbon spheres for CO₂ capture

It is rather essential to design porous carbon adsorbents with high CO₂ capture performance for improving global warming and climate change. Activated carbon spheres with high specific surface area and hierarchical porous texture were prepared from polystyrene-based macroreticular resin spheres due to their low ash and mechanical stability by air pre-oxidization and steam activation. The as-prepared carbon spheres had a specific surface area of 1274.95 m² g^-1, total pore volume of 1.09 cm³ g^-1 and micropore volume of 0.47 cm³ g^-1. Moreover, these carbon spheres showed a hierarchical porous texture composed of ultrafine micropores (0.5-1 nm), micropores (1-2 nm), mesopores (10-50 nm) and macropores (50-100 nm). A CO₂ adsorption capacity of 2.82 mmol g^-1 for carbon spheres can be obtained at 30 °C and 1 atm. Further, after introducing nitrogen-containing functional groups by gaseous ammonia at 600 °C, these carbon spheres (NPSRCSs) exhibited a high CO₂ adsorption capacity of 3.2 mmol g^-1. In addition, excellent cyclic stability, low hygroscopicity and regenerability temperature suggested these carbon spheres were favorable for CO₂ capture.