Highlight on H-Bond Interaction-Associated Multiple Ion Layer Formation of an Imidazolium-Based Ionic Liquid on a Potential-Bias Surface: Molecular Dynamics Simulations

M Armstrong and N Chiangraeng and M Jitvisate and S Rimjaem and P Nimmanpipug, JOURNAL OF PHYSICAL CHEMISTRY C, 126, 20644-20657 (2022).

DOI: 10.1021/acs.jpcc.2c06057

Multiple ion layer formation associated with molecular orientation alteration and hydrogen bonding in a supercapacitor model with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C2mimNtF2) as a room temperature ionic liquid (RTIL) electrolyte has been investigated using potential-bias classical molecular dynamics (CMD) simulations. A 50-ion pair model was used to observe the molecular ion layer formation of C2mimNtF2 of the simulated electrified graphite electrode. After applying the potential bias, multiple layers of C2mim+ and NtF2- formed and became more pronounced. An orientation analysis indicated that the higher potential differences play a significant role in C2mim+, especially near the negative surface. The pi-pi stacking interaction between C2mim+ rings and graphene electrodes was clearly perceived. Principal component analysis (PCA) was introduced to address the characteristics of the layer formation, respectively, to the potential bias applied to the simulated model. PCA scores from the applied potential (OLE = 0.0, 1.0, 2.0, 3.0, and 4.0 V) were used to group the characteristics of the atom pairing associated with the number of H-bonds between H atoms in the C2mim+ cation and all atoms in the NtF2- anion.

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