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• Aminated and three-dimensional reduced graphene oxide aerogels were prepared. • They were modified with polyethyleneimine and studied for CO 2 capture. • The optimal sample captured well CO 2 at 400 ppm and 20 °C. • At CO 2 concentrations >2000 ppm, the CO 2 capturing capacity was enhanced at 50 °C. Amine-functionalized sorbents are promising materials for direct air capture (DAC). Reduced graphene oxide (rGO) aerogels have higher electrical and heat conductivities than commonly studied aminated silica. These properties could jointly enhance the productivity of an associated CO 2 separation process. In this study, three-dimensional (3D) rGO aerogels were fabricated, modified with polyethyleneimine (PEI) at various mass ratios, and applied successfully as a CO 2 adsorbent at different temperatures and pressures. The structure, morphology, and chemical properties of the aminated composite aerogels based on PEI-rGO were comparably characterized using elemental analysis, thermogravimetric analysis, and scanning electron microscopy. The CO 2 uptake performance of the PEI-rGO aerogels was assessed by analysis of the adsorption isotherms at 20 and 50 °C. The optimized PEI-rGO-71 (referring to 71 wt% PEI to the sample) exhibited the highest CO 2 uptake across the tested CO 2 pressure range (0.03–101 kPa), reaching 0.61 mmol CO 2 /g at the partial pressure of CO 2 in ambient air (0.04 kPa). It showed a superior CO 2 capture capacity compared to previously reported amine-modified graphene-based sorbents at ambient CO 2 concentration.
Ai et al. (Wed,) studied this question.