Nitrogen-rich hollow carbon microspheres with tunable shell thicknesses for enhanced CO2 adsorption.

Nitrogen-rich hollow carbon microspheres were successfully synthesized using resorcinol and formaldehyde as carbon sources, tetraethylenepentamine (TEPA) as a catalyst, and nitrogen source, with SiO2 microspheres as a hollow template. The hollow carbon microspheres were prepared by adding varying amounts of SiO₂ hollow templates to a fixed amount of TEPA. The shell thickness increased as the amount of SiO₂ template decreased and the shell thicknesses of AHMCS-2(1), AHMCS-2(3), and AHMCS-2(5) were 28.5 nm, 17.3 nm, and 12.7 nm, respectively. The activated hollow carbon microspheres (AHMCS-2(1), AHMCS-2(3) and AHMCS-2(5)) contained 4.66%, 5.05%, and 3.27% nitrogen, respectively. Due to the sufficient activation process, the specific surface area and microporous volume of hollow carbon microspheres are greatly increased compared to solid carbon microspheres, therefore, their CO₂ adsorption performance is superior as well. As the shell layer thickens, the specific surface area and micropore volume of the activated hollow carbon microspheres increased, among which AHMCS-2(1) showed the largest specific surface area and micropore volume of 1146 m²/g and 0.45 cm³/g, respectively. Similarly, the CO₂ adsorption capacity of activated hollow carbon microspheres increased with the increasing thickness of the shell layer, and that of AHMCS-2(1) reached 5.54 mmol/g at 0 °C. High specific surface area, high micropore volume, high nitrogen content, and small micropore pore size are favorable for CO₂ adsorption by carbon microspheres. The hollow carbon microspheres exhibit high CO₂ dynamic adsorption capacity, excellent selective adsorption, and good cyclic stability. Highlights: Nitrogen-rich hollow carbon microspheres with different shell layer thicknesses were prepared using the template method. The thicker shell thickness retains more micropores and nitrogen content. The nitrogen-rich hollow carbon microspheres have high CO₂ adsorption performance due to large specific surface area and high nitrogen content. The effect of activation process on the nitrogen-rich hollow carbon microspheres with different shell thicknesses is investigated. [ABSTRACT FROM AUTHOR]