Sustainable mechanochemical production of amino graphene for enhanced electrothermal carbon dioxide capture

Graphene-based materials are particularly attractive for electrothermal swing adsorption (ETSA)-driven CO2 capture because of their exceptional electrical and thermal conductivities. However, the intrinsic chemical inertness of pristine graphene hinders preferential CO2 binding from gas mixtures, yielding low adsorption capacity and poor selectivity. In addition, the scalable production of functional graphene for industrial-level CO2 capture remains a critical challenge. Herein, polyamine-assisted mechanochemistry (PAME) is demonstrated as an impactful and scalable approach for producing ultrathin graphene nanosheet-polyethyleneimine (GNs-PEI) composites. Density functional theory (DFT) calculations reveal strong binding interactions of 0.183 J/m2 between graphite and polyamine, which facilitate simultaneous exfoliation and functionalization during the PAME process. The yielded GNs-PEI exhibits a high aspect ratio of 201 and an amine content of approximately 38.23 wt%. The GNs-PEI exhibited a CO2 adsorption capacity of up to 4.77–3.44 mmol/g and a selectivity of 386 − 122 under simulated flue gas conditions (CO2/N2 ratio of 15/85) at 25–55 ℃, respectively. Furthermore, GNs-PEI achieved dynamic CO2 capacities of 3.06–3.62 mmol/g (dry) and 3.37–4.21 mmol/g (85% RH) at 25 and 50 ℃, suitable for industrial post-combustion capture. Also, the GNs-PEI demonstrated wonderful cyclic stability, retaining over 88.8% of its initial adsorption capacity after 50 temperature-swing adsorption-desorption cycles. Under a simulated ETSA process, GNs-PEI foam showed a prominent heating rate of 1.43 ℃/s at an applied bias of 8 V.