Density Functional Theory Studies On The Diffusion/Reaction In Nano-and Microscale Interfacial Systems

Under the new situation of national demand and industrial upgrading,vigorously developing green chemical engineering technology is an inevitable requirement for building a modern economic system and a fundamental strategy for solving environmental pollution problems.Interface regulation and strengthening is an important way to develop green chemical engineering,and has gradually become an active frontier of modern chemical engineering.At present,the understanding of nano-and microscale interface characteristics and mechanism of action is not deep enough.The difficulty lies in the lack of quantitative models.To this end,this thesis addresses the nano-and microscale interface system,using quantum and statistical(or both)density functional theory(DFT),to investigate the interrelationships between molecular diffusion,reactions and surface/interface properties of the nano-and microscale interface system at the molecular level.Based on this,we can obtain the regulatory measures to provide the microscopic mechanism and theoretical basis for strengthening the diffusion/reaction of modern chemical engineering.The main contents of the thesis are summarized as follows:(1)Aluminum ion batteries are an active frontier for the development of new energy materials,and their performance is limited by the ion intercalation and diffusion properties in energy materials.At present,the diffusion mechanism of ions in different types of new energy materials is still unclear.This paper focuses on the intercalation/deintercalation of aluminum ions in rutile TiO2,anatase TiO2,and TiO2(B)materials.First-principles DFT calculations are used to predict the crystal structure changes,stable intercalation sites,intercalation voltages,ion diffusion paths,and energy barriers of aluminum ions embedded in TiO2 materials.The relationship between the electrochemical performance of TiO2 materials and the process of aluminum ion intercalation was analyzed at the atomic scale.Based on this,possible modification methods are proposed,which provides a theoretical reference for the development and modification design of host materials for rechargeable aqueous aluminum ion batteries.(2)Improving the selectivity and the conversion rate of reaction is an important part of the development of green chemistry.Most slow reactions occur in solution,and the solvent has an important effect on the reaction rate,equilibrium,and even the reaction mechanism.At present,the selection of benign solvents is mainly based on experience or trial and error.Theoretical models that can reveal the solvent effect mechanism and provide solvent screening are still lacking.To address this challenge,this thesis uses quantum mechanics combined with statistical mechanics models,coupling quantum DFT and statistical DFT to construct multi-scale reaction density functional theory(RxDFT).In the framework of RxDFT,quantum DFT treats the intrinsic reaction in terms of the electron density while classical DFT deals with the liquid environment via the local molecular density.The coupling between the systems of two length scales is based on the microscopic interaction between the reaction system and the solvent.Subsequently,RxDFT was further extended to the water-phase reaction and the organic-phase reaction in the confined system and interface system,and the mechanism of the solvent on several important chemical reactions in chemical engineering was successfully described.The development of multi-scale RxDFT provides a feasible model for the selection of benign reaction solvents and the study of the mechanism of solvation effect and provides a successful case for the study of material-level mesoscale.(3)The coupling of molecular diffusion and reaction in the interfacial system is the key to improving the efficiency of the interface reaction.At present,there is no suitable microscopic model to describe the mechanism of interface reaction-diffusion coupling.Based on this,this thesis further expands the RxDFT.By incorporating the dynamic DFT with chemical reaction collision theory and quantum DFT,the multi-scale dynamic response density functional theory(DRxDFT)is developed.The proposed theory is supposed to provide a new approach towards the investigation of reaction-diffusion coupling in interfacial systems.DRxDFT combines two theories individually for the systems at different length scales,and in particular classical dynamic DFT treats the diffusion kinetics of reactant/product molecule species,while chemical reaction collision theory together with quantum DFT deals with chemical reactions.By employing the DRxDFT,the irreversible bimolecular model reaction A+2B->2C was preliminarily studied.The effects of interfacial adsorption capacity,molecular diffusion rate,temperature,initial reactant concentration,reaction energy barrier on the reaction conversion rate were systematically explored.Through this study,the commonalities and characteristics of the interface reaction mechanism are summarized to provide solid support and theoretical guidance for the optimization of the interface reaction processes and the design and development of catalysts with improved performance.The innovations of this thesis are summarized as follows.The diffusion kinetics of aluminum ions in different crystalline TiO2 materials was studied.The potential of different crystalline forms as electrode materials was evaluated for the first time in terms of electrochemical performance.The multi-scale RxDFT was developed and extended to the aqueous phase,organic phase,confinement reaction and interface reaction,revealing the liquid phase reaction mechanism and solvation effect.The DRxDFT is further developed to provide a microscopic theoretical model for molecular diffusion-reaction coupling in the interface reaction system,and preliminary studies of the effects of the reaction conditions such as interface adsorption capacity,molecular diffusion capacity,temperature,initial reactant concentration,reaction energy barrier on the reaction conversion rate.Based on this,some commonalities and characteristics of the interface reaction mechanism are summarized.