Physisorption of biodegradable choline-based ionic liquids (CBILs) and their aqueous solutions on 2D titanium carbide (MXene) nanosheets as promising media in energy storage systems

MXenes alongside ionic liquid electrolytes have been promising in energy storage systems. The nanoscopic structure of two biodegradable choline-based ionic liquids (CBILs) and their water mixtures were investigated near the MXene surface using quantum mechanics calculations and molecular dynamics simulations. Quantum mechanics calculations showed that the anion-cation interactions in the choline salicylate ([CH][SA]) are weaker than that for choline beta-alaninate ([CH][beta-Ala]), therefore, [SA]- tends to interact more with the MXene surface compared to [beta-Ala]- . Simulation results indicated that the ionic liquids aggregate in the vicinity of the MXene surface to form a dense layer with significantly different properties compared to bulk. Applying moisture to CBIL systems reduces the ion population in the first layer and also their structural correlations. Furthermore, there is a competition between water molecules and choline cations for interaction with anions. The presence of water molecules also increases the dynamics of hydrogen bonds, ion pairs, and ion cages. Perception of the nano-scale behavior of these unique classes of ionic liquids on MXenes could be beneficial for energy storage systems like batteries and electric double-layer capacitors.

Automated summary

MXenes combined with ionic liquid electrolytes have shown great promise in energy storage systems. The nanoscopic structure of biodegradable choline-based ionic liquids (CBILs) and their water mixtures near the MXene surface was studied through quantum mechanics calculations and molecular dynamics simulations. The results revealed that the interaction between the anion and cation in CBILs affects their behavior on the MXene surface, and the presence of water molecules alters the dynamics and structural correlations of the system. Understanding the nano-scale behavior of these unique ionic liquids on MXenes has potential applications in energy storage systems.