Tailored Carbon Nanocomposites for Efficient CO₂ Capture

CO₂ capture by adsorption on proper solid materials appears to be a promising approach, due to its low energy requirements and ease of implementation. This study aimed to prepare efficient materials for CO₂ capture based on composites of nanocarbon and reduced graphene oxide, using graphite, L-ascorbic acid, and glycine as precursors. The materials were characterized by XRD, low-temperature N₂ adsorption, FTIR, Raman, and XPS spectroscopies, along with SEM and TEM. The CO₂ adsorption capacities, heats of adsorption, and selectivity were determined. A hierarchical porous structure was found for NC-LAA, NC/RGO-LAA, and NC/RGO-Gly. At 273 K and 100 kPa, the adsorption capacities for NC-LAA and NC-Gly reached 2.6 mmol/g and 2.5 mmol/g, respectively, while for the composites, the capacities were 1.7 mmol/g for NC/RGO-Gly and 3.5 mmol/g for NC/RGO-LAA. The adsorption ability of the glycine-derived materials is related to the presence of nitrogen-containing functional groups. The heats of adsorption for NC-LAA, NC-Gly, and NC/RGO-Gly reveal chemisorption with CO₂. Except for chemisorption, the NC/RGO-LAA material shows a sustained physical adsorption up to higher CO₂ coverage. The best adsorption of CO₂, observed for NC/RGO-LAA, is connected with the synergy between carbon dots and RGO. This composition ensures both sufficient oxygen surface functionalization and a proper hierarchical porous structure.