# Carbon Spheres as CO\({}_{2}\) Sorbents
## 4 Discussion
They fabricated two types of carbon honeycomb structures: standard type A, which involved phenolic resin as the liquid precursor, and type B, which involved the same phenolic resin but containing cobalt acetate dissolved at 1 wt.%. Both kinds of samples were carbonized in nitrogen at a high temperature and then activated in CO\({}_{2}\). For samples of type A, only micropores (no mesopores at all) were formed and their volume increased as a result of the deepening of pores formed during carbonization. No pore broadening was observed for these samples. The introduction of a metallic catalyst (cobalt) in the precursor resin changed the pore structure dramatically (samples B). The pore structure on carbonization remained the same as that of the carbon without the catalyst (samples A). The difference between type A and B appeared upon activation. A bimodal pore size distribution was observed for samples B. Despite micropores of the same size range as in samples A, large meso and macropores were formed in samples B. In both kinds of samples, A and B, the micropore volume increase took place because of pore deepening, rather than pore broadening. According to [PERSON] et al. [48], the adsorption in pores depended on the applied pressure. With an increase of adsorption pressure, bigger and bigger pores govern the adsorption, nonetheless researchers state that at the atmospheric pressure, adsorption is contributed to by the narrow micropores (below 0.6 nm) with high adsorption potential. To use the whole adsorption potential of bigger micropores, higher fugacity of adsorbent is required. Hence, the higher pressure must be applied. Investigation of [PERSON] et al. [49] showed that the adsorption of CO\({}_{2}\) molecules in the 0.3 nm slit pores, due to the similar size of CO\({}_{2}\) molecules, was very poor. In contrast, the highest CO\({}_{2}\) adsorption was noticed in the 0.4 nm pores. Furthermore, strong decrease of the stabilization energy of CO\({}_{2}\) molecules in pores larger than 0.4 nm was noticed. With an increase of pore size, the interactions between CO\({}_{2}\) molecules and carbon pores were more and more weak. To summarize, the presence of micropores below 0.7 nm is one of the essential traits for a good CO\({}_{2}\) adsorbent. Comparing the samples modified with potassium oxalate, the 7:1 weight ratio is an optimum one value, and there is no benefit to employ more. According to the analysis of the obtained results, the adsorption properties of nanocarbon materials towards carbon dioxide increased with both increasing specific surface area and porosity (Figures 11 and 12). The presence of potassium on the surface of the samples had a positive effect on the CO\({}_{2}\) adsorption (Figure 13), however the presence of surface oxygen had no apparent effect on adsorption. Surprisingly, the presence of surface nitrogen decreased the ability to adsorb carbon dioxide (Figure 14). Figure 11: Relation between specific surface area and CO\({}_{2}\) uptake at 0 \({}^{\circ}\)C.  
Figure 12: Relation between the total pore volume of the samples and CO\({}_{2}\) uptake at 0 \({}^{\circ}\)C.