Theoretical Study On The Interaction Mechanism Between Ionic Liquids And Different Two-dimensional Material

Ionic liquids（ILs）have the characteristics of designability,good conductivity,and low volatility.Two-dimensional（2D）materials can maintain the structural integrity when non-covalently doping by ILs.They are ideal liquids as electrolytes and solvent for exfoliation of two-dimensional materials.Investigating the interfacial interactions between ILs and 2D materials is crucial for optimizing the performance of batteries,supercapacitors,and optoelectronic nanodevices.The main research contents of the paper are as follows:（1）Density functional theory（DFT）calculations have been performed to investigate the interfacial interactions of ionic liquids（ILs）on theα-andβ-phases of phosphorene（P）and arsenene（As）.Nine representative ILs based on the combinations of 1-ethyl-3-methylimidazolium（[EMIM]⁺）,N-methylpyridinium（[MPI]⁺）,and Tetramethylammoni-um（[TMA]⁺）cations paired to tetrafluoroborate（[BF₄]^-）,trifluoromethanesulfonate（[TFO]^-）,and chloridion（Cl^-）anions were used as adsorbates on the P and As nanosheets with different phases to explore the effect of IL adsorption on the electronic and optical properties of 2D materials.The calculated structure,adsorption energy,and charge transfer suggest that the interaction between ILs and P and As nanosheets is dominated by noncovalent forces,and the most stable adsorption structures are characterized by the simultaneous interaction of the cation and anion with the surface,irrespective of the types of ILs and surfaces.Furthermore,the IL adsorption leads to the larger change in the electronic properties ofβ-phase P and As than those of theirα-phase counterparts,which demonstrates that the adsorption properties are not only related to the chemical elements,but also closely related to the phase structures.The present results provide insight into the further applications of ILs and phosphorene（arsenene）hybrid materials.（2）Using the same calculation method,the interfacial interaction mechanism between the above nine ionic liquids and MoXY（X,Y=O,S,Se,Te）nanosheets were investigated.The results show that the adsorption energy and charge transfer amount of the Janus MoXY are significantly different from their parent materials when the electronegativity difference between two sides is large,while the adsorption energy and charge transfer of Janus MoXY with less polarity are similar to those of the parent material.The effects of ionic liquids adsorption on the electronic and optical properties of different MoXY nanosheets can be divided into the following five categories（ILs/MoOS means ILs adsorbed on the S-side,ILs/MoSO denotes ILs adsorbed on the O-side）:（1）When nine kinds of ionic liquids adsorbed on MoOS and MoOSenanosheets,the band gaps of the systems did not change;（2）the adsorption of ILs containing[Cl]^-led to the obvious changes of electronic and optical properties of MoSeO,MoTeS,and MoTeSenanosheets;（3）the adsorption of ILs containing[MPI]⁺resulted in significant changes in the electronic and optical properties of MoTe₂,MoSTe,and MoSeTenanosheets;（4）the adsorption of ILs containing[MPI]⁺or[Cl]^-led to obvious changes in the electronic and optical properties of MoSe₂and MoSSenanosheets;（5）the adsorption of ILs containing[TFO]^-or Cl^-led to obvious change in the electronic and optical properties of MoO₂,MoSO₂,MoS₂,and MoSeS nanosheets.Our calculated results can provide a theoretical basis for the potential applications of Mo-based 2D metal oxides,sulfides,and corresponding Janus materials in the fields of energy,electronics,optoelectronics,and catalysis.