Interface-enhanced CO(2) capture via the synthetic effects of a nanomaterial-supported ionic liquid thin film

Ionic liquids (ILs) are effective CO(2) capture media and recent experimental evidence has demonstrated that the addition of two-dimensional (2D) nanomaterials into ILs can effectively improve their CO(2) capturing capability. However, an in-depth mechanism on how 2D nanomaterials enhance CO(2) absorption is poorly documented. In this study, the adsorption of CO(2) by a representative IL, namely 1-ethyl-3-methyl-imidazole-tetrafluoroborate ([EMIM][BF(4)]), coated on graphene (GRA, the prototype 2D nanomaterial) and nitrogenized graphene (C(3)N) was investigated by molecular dynamics simulations. The influence of the IL film thickness on the amount of CO(2) adsorption was systematically analyzed. Our data clearly indicate that at the IL-gas interface the CO(2) accumulation is significantly enhanced. In contrast, at the IL-GRA and IL-C(3)N interfaces, only slight enhancement was observed for CO(2) accumulation. Quantitative calculations of the adsorption-free energy for CO(2) inside the IL film further support the simulation results. Our present results also reveal that the sub-nanometer IL film possesses a considerably high CO(2) capture efficiency because of the formation of the reduced bulk IL region. Moreover, the nanomaterial substrate surfaces can effectively accelerate the diffusion of CO(2), which is beneficial for the CO(2) mass transfer. In general, our theoretical study provides a deep microscopic understanding of the CO(2) capture by nanomaterials and IL composites. These results could benefit the design and fabrication of a high-performance CO(2) capture and storage medium through the synthetic effects of ILs and nanomaterials.