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 m(2)/g and 0.45 cm(3)/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 degrees 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.