表界面反应与扩散耦合的跨尺度研究

The reaction-diffusion process is of unique importance to chemical engineering, catalysis, material science, bioengineering and others. It is also one of the cores to chemical engineering principles, heat transfer, mass transfer, momentum transfer and reaction engineering. When it comes to the surface or interface, accurate measurement and direct characterization of a reaction-diffusion coupled process are very challenging. A complete understanding of the fundamental mechanism requires (a) a model which is representative of structural and chemical properties and their spatial and temporal distributions; (b) a method which can describe simultaneously reaction and diffusion coupled mechanisms. It is only through manipulating surface and interface structures between molecule/atom and bulk material, can solutions be achieved to significantly advance chemical engineering and related disciplines to transmit and benefit from the emerging development of interdisciplinary multiscale researches. In this project, we propose to develop a reactive force field based model to describe the multiscale structural factors and the reaction-diffusion coupled processes. By studying two selected reactions of theoretical importance and application potential, we plan to investigate how surface/interface properties affect the reaction and diffusion mechanisms simultaneously. We plan to seek the fundamental understandings from electronic and atomic/molecular levels, and reveal the compromised nature between reaction and diffusion mechanisms. With the understanding of structural, chemical, thermo and dynamic properties of the system, their spatial and temporal distributions, we shall be able to predict properties such as reaction pathway and energy barrier, reaction products and their yield, adsorption and diffusion selectivities, and provide fundamental understanding to process control and designing optimization. The theoretical framework developed under this project shall be especially useful in designing better surface/interface structure for new catalytic materials and providing general guideline to systems of interest in other research fields.

反应-扩散过程在化工、催化、材料和生物领域普遍存在，在化学工程的核心“三传一反”中占据重要地位，是优化反应工艺的核心问题。受限空间内通过实验测定与控制反应-扩散过程异常困难，需要建立同时考虑化学反应和扩散耦合的模型，准确描述表界面上控制机制竞争与协调导致的界面现象，其瓶颈为界面处反应的量子力学的不连续性描述与受限条件下扩散传递的分子动力学连续性描述的耦合问题。本项目结合量化计算和经典分子模拟，采用反应力场和过渡态理论，以氨基酸水溶液在TiO2材料表面的吸附与分解和Rh催化CO还原NO气固催化反应为代表，以“揭示机制”和“调控优化”为核心，用一套参数同时描述流体在表界面的吸附、扩散、反应耦合行为，从电子和原子/分子两个层面阐明表界面结构对反应和扩散性能的影响，探究控制机制之间竞争与协调在时空尺度演变的本质，建立反应—扩散耦合的跨尺度模型，为开发创新工艺提供理论指导。

反应-扩散（Reaction-Diffusion, RD）是化工过程、分离、催化反应等动力学过程中最重要和最基本的过程之一，在化学工程的核心“三传一反”中占据重要地位，对化工过程中反应分子的微观传递行为及催化剂内部发生的化学反应的深入研究有助于化工反应器和催化剂及化工过程的设计。本项目针对 “反应器微元及微反应系统中介质、材料及表界面结构的形成机理与反应的定向调控”这一关键科学问题，应用反应力场与过渡态理论，结合量化计算和经典分子模拟方法，以金属铑（Rh）催化CO还原NO、小分子在石墨烯及C3N4表界面上扩散与反应、TiO2表面氨基酸水溶液的吸附与分解为依托，围绕表界面结构、反应与扩散耦合来展开研究，预测反应路径、反应产物的成分和结构间的相互影响，建立从表界面到流体体相的反应-扩散模型。. 基于DFT的Rh(100)和Rh(111)表面NO–CO反应体系kMC模型构建，考察了在不同环境条件下的稳态平均覆盖度、表面特征构型、产物转化频率、选择性等性质及各基元步骤对于总反应的速率控制度、生成路径选择性的选择控制度。此结果对于设计高效、经济、环保的下一代催化剂具有重要意义。.研究了小分子在石墨烯和C3N4表界面上的迁移和反应活性。考察了褶皱对石墨烯穿透性能的影响、石墨烯/铜界面对水分子分解的影响。褶皱的存在可以提高石墨烯的穿透性能，并且穿透性会随着曲率的变大而增强，凹面相对于凸面会更有利于氧原子穿越。石墨烯/铜界面可以促进水分子的分解。为石墨烯在膜分离及催化提供了理论依据。. 研究了水在二氧化钛和贵金属表面的行为。界面水的行为可能完全不同，离解，化学吸附或表现出疏水性相互作用，这取决于与之接触的固体表面的类型。我们发现，近地表水分子的行为可能会显着影响界面处的流体性质，反之，界面水会诱导基质的结构和化学变化。 可以通过对基底施加压缩晶格应变来控制金属表面上的低迁移率第一吸附水层，这是由界面分子的细微堆积变化介导的。通过调整晶格应变，揭示TiO2表面如何影响润湿性转变。.