Theoretical Studies On Solvated Electron Morphology And Interfacial Behavior

The solvated electron is formed by injection of an excess electron,then solvation and relaxation in solutions.Due to its excellent reducibility,the solvated electron has been widely used in various reactions in the fields of biochemistry,energy,catalysis and radiation.Now,researchers have been able to capture,measure or calculate its morphology,energy and spectral characteristics or properties accurately.However,its particularness and participation in reaction processes need to be further studied because of its unique state and properties.Studying its important role and mechanism in typical chemical reactions,elucidating the important reaction intermediates involved and the importance of the solution environment are important for us to fully understand the specific reaction processes and unique reaction phenomena.In this paper,based on density function theory and ab initio molecular dynamics simulation,we study the electron presolvation phenomenon in general complexes and interfacial electron behaviors of representative reactions in which solvated electrons participate.The main conclusions and innovations are as follows:1.Electron Presolvation in Tetrahydrofuran-Incorporated Supramolecular Sodium Entities:Alkali metal atoms can repopulate their valence electrons towards solvation due to impact from solvents or microsuiroundings and provide the remaining alkali metal cations for coordinating with a variety of specific solvents,forming various electron-expanded complexes or solvated ionic pairs with special interaction.Taking Na(THF)n(n=1-6,THF=tetrahydrofuran)and Na2@THF complexes as typical representatives,density functional theory calculations are carried out to explore the solvation of sodium atom and its dimer in THF and characterize their complexes as the solvent-incorporated supramolecular entities and particularly valence electron presolvation due to their interaction with solvent THF.Compared with strongly bound valance electron of alkali metal atoms,THF coordination enables Na or Na2 electrons to exhibit much more active states(i.e.the presolvated states),electrons distribute in the frames of the generally structured metal cation complexes distortedly and diffusely.Furthermore,the degree of electron diffusion and the polarity of the Na-Na bond are proportional to the coordination number(n)and the coordination number difference(Δn)between two Na centers in Na2@THF.The unique properties of such entities are also discussed.This work offers a theoretical support to the supramolecular entities formed by alkali-metal atoms or their dimers with ligands containing O or N and uncovers the unique electron presolvation phenomena and also enriches our understanding of the novel metal atom complexes.2.Proton-Coupled Electron Transfer Initiated by Sodium Cluster Ionization at Liquid Surface:Hydrogen evolution reaction(HER)between sodium(Na)and water has always been used in chemical theory and experiment teaching as a classical displacement reaction.Although studies have confirmed the fact that solvated electrons are involved in the reaction process,the mechanism has not been clearly revealed.Here,we simulate the solvation process of a single Na or a metallic Na cluster in aqueous solution by hybrid functional-based ab initio molecular dynamics method,especially to elucidate the interfacial electron dynamics behavior.Results show that Na is highly ionized through H2O solvation in aqueous solutions and generates a unique pre-solvated electron(epre-).For the small-sized Na8 cluster located at the vacuum-liquid interface,Na atoms at Na8 bottom vertex are solvated and Na8 is ionized internally.Moreover,Na8 HOMO electrons are pre-solvated and penetrate below the surface.Notably,H2O reorganization near the surface and subsequent HER by proton-coupled electron transfer are triggered by Na8 solvation or its internal electron polarization.This is the first time that the microscopic dynamics mechanism of Na and H2O reaction is studied by ab initio molecular dynamics simulation and also provides a theoretical basis for HER with the participation of epre-which deepens our attention and understanding of redox reactions involving solvated electrons.3.Ab Initio Molecular Dynamics Study on Electron Behavior at Na(100)/H2O Interface:The electron transfer behavior at metal/water interface will play a very important role in the research of photocatalysis and redox reactions.Our previous studies on the interaction between Na atom,Na2 molecule,small-sized Na8 cluster and THF or H2O have laid a foundation for us to carry out the research of the larger system of Na/H2O interface in this work.Our dynamics simulation results have shown that H2O presolvation effect influences surface Na atoms obviously,and the interaction between Na and H2O results in significant deformation and polarization of surface electrons.Moreover,the tight and uniform arrangement of surface Na atoms at the solid-liquid interface is also adjusted.This phenomenon is particularly evident in the simulation of stepped metal surface/H2O interface.This work makes us have a fuller knowledge and understanding of the solid-liquid interface and will provide empirical and theoretical reference for solid-liquid interface study represented by metal/water.