| As a new type of solvent with the advantages of low vapor pressure,high chemical stability,and good designability,ionic liquids are widely used in many fields.However,there is a lack of in-depth investigation on the mechanism of ionic liquids and graphene oxide.In this paper,the mechanism of the interaction between anions and graphene oxide and the adsorption mechanism of ionic liquids on the graphene oxide surface were studied using a combination of quantum chemical calculations and molecular dynamics simulations.The main works are summarized as follows.（1）The adsorption mechanisms of different anions on the graphene oxide surface were investigated using density functional theory（DFT）calculations.The results show that the binding energy of anion and graphene oxide is stronger when the anion is on the hydroxyl side,and the order of the binding energy of anion and graphene oxide is:1-GO-[BF4]->1-GO-[B（CN）4]->1-GO-[PF6]->1-GO-[TF2N]->2-GO-[TF2N]->2-GO-[B（CN）4]->2-GO-[BF4]->2-GO-[PF6]-;Next,the non-covalent interactions between different anions and graphene oxide were investigated,and the calculation results showed that when the anion is on the hydroxyl side,the main forces between the anion and graphene oxide are hydrogen bonds,van der Waals interactions and other weak interactions,and when the anion is not on the hydroxyl side,the When the anion is not on the hydroxyl side,the major interaction force between the anion and graphene oxide is van der Waals interaction;according to the results of energy decomposition analysis,when the anion is on the hydroxyl side,the interaction energy of the system is dominated by the electrostatic interaction energy term,and when the anion is not on the hydroxyl side,van der Waals interaction plays a significant role.（2）The adsorption mechanisms of different ionic liquids on the graphene oxide surface were analyzed using DFT calculations.Firstly,the binding energy of the ionic liquids-graphene oxide configurations was studied.The binding energy of ionic liquid and graphene oxide is stronger when the ionic liquid is on the hydroxyl side;according to the results of the density of states study,the density of states changes significantly when the ionic liquid adsorbs on the graphene oxide surface,and its energy is partially transferred;the density of states of the ionic liquid-graphene oxide composite structure is relatively higher than that of the ionic liquid or graphene oxide Fermi energy negative migration,which indicates that the adsorption is accompanied by charge transfer from graphene oxide to the adsorbed ionic liquid;to verify this conclusion,the charge transfer was investigated and the calculation results showed that the total charge on the graphene oxide surface changed to positive charge after ionic liquid adsorption;the charge transfer between cations and anions is an important factor in ionic liquid adsorption;according to the ionic liquid and graphene oxide The analysis results of non-covalent interactions between ionic liquid and graphene oxide show that when the ionic liquid is on the hydroxyl side,the main forces between ionic liquid and graphene oxide are hydrogen bonds,van der Waals interactions and other weak interactions;when the ionic liquid is not on the hydroxyl side,van der Waals interactions between ionic liquid and graphene oxide play a key role in the adsorption process.（3）Molecular dynamics（MD）simulations were used to study the diffusion properties and interaction energies of different ionic liquid-graphene oxide systems at different layer spacings.The calculated results show that the diffusion rate of anions in the ionic liquid-graphene oxide systems increases with increasing layer spacing,while the interaction between graphene oxide and anions decreases subsequently. |
